阿可的窩 Yi-Juai

Epigenetics
(節錄自維基 by陳怡睿)
In biology, the term epigenetics refers to heritable changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the underlying DNA sequence. These changes may remain through cell divisions for the remainder of the cell's life and may also last for multiple generations. However, there is no change in the underlying DNA sequence of the organism; instead, non-genetic factors cause the organism's genes to behave (or "express themselves") differently. The best example of epigenetic changes in eukaryotic biology is the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo which in turn become fully differentiated cells. In other words, a single fertilized egg cell - the zygote - changes into the many cell types including neurons, muscle cells, epithelium, blood vessels et cetera as it continues to divide. It does so by activating some genes while inhibiting others.
Etymology and definitions
Epigenetics (as in "epigenetic landscape") was coined by C. H. Waddington in 1942 as a portmanteau of the words genetics and epigenesis. Epigenesis is an older word to describe the differentiation of cells from their initial totipotent state in embryonic development. When Waddington coined the term the physical nature of genes and their role in heredity was not known; he used it as a conceptual model of how genes might interact with their surroundings to produce a phenotype.
Robin Holliday defined epigenetics as "the study of the mechanisms of temporal and spatial control of gene activity during the development of complex organisms." Thus epigenetic can be used to describe any aspect other than DNA sequence that influences the development of an organism.
The modern usage of the word is more narrow, referring to heritable traits (over rounds of cell division and sometimes transgenerationally) that do not involve changes to the underlying DNA sequence. The Greek prefix epi- in epigenetics implies features that are "on top of" or "in addition to" genetics; thus epigenetic traits exist on top of or in addition to the traditional molecular basis for inheritance.
Molecular basis of epigenetics
The molecular basis of epigenetics is complex. It involves modifications of the activation of certain genes, but not the basic structure of DNA. Additionally, the chromatin proteins associated with DNA may be activated or silenced. What this means is that every cell in your body has the same instruction manual, but different cell types are using different chapters. For example, your neurons contain the DNA instructions to make your fingernails, but for these and most other cells in the body, the necessary genes are turned off. Epigenetic changes are preserved when cells divide. Most epigenetic changes only occur within the course of one individual organism's lifetime, but some epigenetic changes are inherited from one generation to the next. Specific epigenetic processes include paramutation, bookmarking, imprinting, gene silencing, X chromosome inactivation, position effect, reprogramming, transvection, maternal effects, the progress of carcinogenesis, many effects of teratogens, regulation of histone modifications and heterochromatin, and technical limitations affecting parthenogenesis and cloning.
Epigenetic research uses a wide range of molecular biologic techniques to further our understanding of epigenetic phenomena, including chromatin immunoprecipitation (together with its large-scale variants ChIP-on-chip and ChIP-seq), fluorescent in situ hybridization, methylation-sensitive restriction enzymes, DNA adenine methyltransferase identification (DamID) and bisulfite sequencing. Furthermore, the use of bioinformatic methods is playing an increasing role (computational epigenetics).
Mechanisms
Several types of epigenetic inheritance systems may play a role in what has become known as cell memory:
DNA methylation and chromatin remodeling
Because the phenotype of a cell or individual is affected by which of its genes are transcribed, heritable transcription states can give rise to epigenetic effects. There are several layers of regulation of gene expression. One way that genes are regulated is through the remodeling of chromatin. Chromatin is the complex of DNA and the histone proteins with which it associates. Histone proteins are little spheres that DNA wraps around. If the way that DNA is wrapped around the histones changes, gene expression can change as well. Chromatin remodeling is initiated by one of two things:
1. The first way is post translational modification of the amino acids that make up histone proteins.
2. The second way is the addition of methyl groups to the DNA, at CpG sites, to convert cytosine to 5-methylcytosine.
The way that the cells stay differentiated in the case of DNA methylation is more clear to us than it is in the case of histone shape. Basically, certain enzymes (such as Dnmt1) "prefer" the methylated cytosine. If this enzyme comes to a "hemimethylated" portion of DNA (DNA where only one strand contains the methylcytosine, and the other side still contains cytosine) the enzyme will methylate the other half.
Although modifications occur throughout the histone sequence, the unstructured termini of histones (called histone tails) are particularly highly modified. These modifications include acetylation, methylation and ubiquitylation. Acetylation is the most highly studied of these modifications. For example, acetylation of the K14 and K9 lysines of the tail of histone H3 by histone acetyltransferase enzymes (HATs) is generally correlated with transcriptional competence.
One mode of thinking is that this tendency of acetylation to be associated with "active" transcription is biophysical in nature. Because lysine normally has a positive charge on the nitrogen at its end, lysine can bind the negatively charged phosphates of the DNA backbone and prevent them from repelling each other. The acetylation event converts the positively charged amine group on the side chain into a neutral amide linkage. This removes the positive charge causing the DNA to repel itself. When this occurs, complexes like SWI/SNF and other transcriptional factors can bind to the DNA, thus opening it up and exposing it to enzymes like RNA polymerase so transcription of the gene can occur.
In addition, the positively charged tails of histone proteins from one nucleosome may interact with the histone proteins on a neighboring nucleosome, causing them to pack closely. Lysine acetylation may interfere with these interactions, causing the chromatin structure to open up.
Lysine acetylation may also act as a beacon to recruit other activating chromatin modifying enzymes (and basal transcription machinery as well). Indeed, the bromodomain—a protein segment (domain) that specifically binds acetyl-lysine—is found in many enzymes that help activate transcription including the SWI/SNF complex (on the protein polybromo). It may be that acetylation acts in this and the previous way to aid in transcriptional activation.
The idea that modifications act as docking modules for related factors is borne out by histone methylation as well. Methylation of lysine 9 of histone H3 has long been associated with constitutively transcriptionally silent chromatin (constitutive heterochromatin). It has been determined that a chromodomain (a domain that specifically binds methyl-lysine) in the transcriptionally repressive protein HP1 recruits HP1 to K9 methylated regions. One example that seems to refute the biophysical model for acetylation is that tri-methylation of histone H3 at lysine 4 is strongly associated with (and required for full) transcriptional activation. Tri-methylation in this case would introduce a fixed positive charge on the tail.
It should be emphasized that differing histone modifications are likely to function in differing ways; acetylation at one position is likely to function differently than acetylation at another position. Also, multiple modifications may occur at the same time, and these modifications may work together to change the behavior of the nucleosome. The idea that multiple dynamic modifications regulate gene transcription in a systematic and reproducible way is called the histone code.
DNA methylation frequently occurs in repeated sequences, and may help to suppress 'junk DNA': Because 5-methylcytosine is chemically very similar to thymidine, CpG sites are frequently mutated and become rare in the genome, except at CpG islands where they remain unmethylated. Epigenetic changes of this type thus have the potential to direct increased frequencies of permanent genetic mutation. DNA methylation patterns are known to be established and modified in response to environmental factors by a complex interplay of at least three independent DNA methyltransferases, DNMT1, DNMT3A and DNMT3B, the loss of any of which is lethal in mice. DNMT1 is the most abundant methyltransferase in somatic cells, localizes to replication foci, has a 10–40-fold preference for hemimethylated DNA and interacts with the proliferating cell nuclear antigen (PCNA). By preferentially modifying hemimethylated DNA, DNMT1 transfers patterns of methylation to a newly synthesized strand after DNA replication, and therefore is often referred to as the ‘maintenance' methyltransferase. DNMT1 is essential for proper embryonic development, imprinting and X-inactivation.
Chromosomal regions can adopt stable and heritable alternative states resulting in bistable gene expression without changes to the DNA sequence. Epigenetic control is often associated with alternative covalent modifications of histones. The stability and heritability of states of larger chromosomal regions are often thought to involve positive feedback where modified nucleosomes recruit enzymes that similarly modify nearby nucleosomes. A simplified stochastic model for this type of epigenetics is found here.
Because DNA methylation and chromatin remodeling play such a central role in many types of epigenic inheritance, the word "epigenetics" is sometimes used as a synonym for these processes. However, this can be misleading. Chromatin remodeling is not always inherited, and not all epigenetic inheritance involves chromatin remodeling.
It has been suggested that the histone code could be mediated by the effect of small RNAs. The recent discovery and characterization of a vast array of small (21- to 26-nt), non-coding RNAs suggests that there is an RNA component, possibly involved in epigenetic gene regulation. Small interfering RNAs can modulate transcriptional gene expression via epigenetic modulation of targeted promoters.
RNA transcripts and their encoded proteins
Sometimes a gene, after being turned on, transcribes a product that (either directly or indirectly) maintains the activity of that gene. For example, Hnf4 and MyoD enhance the transcription of many liver- and muscle-specific genes, respectively, including their own, through the transcription factor activity of the proteins they encode. Other epigenetic changes are mediated by the production of different splice forms of RNA, or by formation of double-stranded RNA (RNAi). Descendants of the cell in which the gene was turned on will inherit this activity, even if the original stimulus for gene-activation is no longer present. These genes are most often turned on or off by signal transduction, although in some systems where syncytia or gap junctions are important, RNA may spread directly to other cells or nuclei by diffusion. A large amount of RNA and protein is contributed to the zygote by the mother during oogenesis or via nurse cells, resulting in maternal effect phenotypes. A smaller quantity of sperm RNA is transmitted from the father, but there is recent evidence that this epigenetic information can lead to visible changes in several generations of offspring.
Prions
Prions are infectious forms of proteins. Proteins generally fold into discrete units which perform distinct cellular functions, but some proteins are also capable of forming an infectious conformational state known as a prion. Although often viewed in the context of infectious disease, prions are more loosely defined by their ability to catalytically convert other native state versions of the same protein to an infectious conformational state. It is in this latter sense that they can be viewed as epigenetic agents capable of inducing a phenotypic change without a modification of the genome.
Fungal prions are considered epigenetic because the infectious phenotype caused by the prion can be inherited without modification of the genome. PSI+ and URE3, discovered in yeast in 1965 and 1971, are the two best studied of this type of prion. Prions can have a phenotypic effect through the sequestration of protein in aggregates, thereby reducing that protein's activity. In PSI+ cells, the loss of the Sup35 protein (which is involved in termination of translation) causes ribosomes to have a higher rate of read-through of stop codons, an effect which results in suppression of nonsense mutations in other genes. The ability of Sup35 to form prions may be a conserved trait. It could confer an adaptive advantage by giving cells the ability to switch into a PSI+ state and express dormant genetic features normally terminated by premature stop codon mutations.
Structural inheritance systems
 
In ciliates such as Tetrahymena and Paramecium, genetically identical cells show heritable differences in the patterns of ciliary rows on their cell surface. Experimentally altered patterns can be transmitted to daughter cells. It seems existing structures act as templates for new structures. The mechanisms of such inheritance are unclear, but reasons exist to assume that multicellular organisms also use existing cell structures to assemble new ones.[28]
Functions and consequences
Development
Somatic epigenetic inheritance, particularly through DNA methylation and chromatin remodeling, is very important in the development of multicellular eukaryotic organisms. The genome sequence is static (with some notable exceptions), but cells differentiate in many different types, which perform different functions, and respond differently to the environment and intercellular signalling. Thus, as individuals develop, morphogens activate or silence genes in an epigenetically heritable fashion, giving cells a "memory". In mammals, most cells terminally differentiate, with only stem cells retaining the ability to differentiate into several cell types ("totipotency" and "multipotency"). In mammals, some stem cells continue producing new differentiated cells throughout life, but mammals are not able to respond to loss of some tissues, for example, the inability to regenerate limbs, which some other animals are capable of. Unlike animals, plant cells do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. While plants do utilise many of the same epigenetic mechanisms as animals, such as chromatin remodeling, it has been hypothesised that plant cells do not have "memories", resetting their gene expression patterns at each cell division using positional information from the environment and surrounding cells to determine their fate.
Medicine
Epigenetics has many and varied potential medical applications. Congenital genetic disease is well understood, and it is also clear that epigenetics can play a role, for example, in the case of Angelman syndrome and Prader-Willi syndrome. These are normal genetic diseases caused by gene deletions, but are unusually common because individuals are essentially hemizygous because of genomic imprinting, and therefore a single gene knock out is sufficient to cause the disease, where most cases would require both copies to be knocked out.
Evolution
Although epigenetics in multicellular organisms is generally thought to be a mechanism involved in differentiation, with epigenetic patterns "reset" when organisms reproduce, there have been some observations of transgenerational epigenetic inheritance (e.g., the phenomenon of paramutation observed in maize). Although most of these multigenerational epigenetic traits are gradually lost over several generations, the possibility remains that multigenerational epigenetics could be another aspect to evolution and adaptation. These effects may require enhancements to the standard conceptual framework of the modern evolutionary synthesis.
Epigenetic features may play a role in short-term adaptation of species by allowing for reversible phenotype variability. The modification of epigenetic features associated with a region of DNA allows organisms, on a multigenerational time scale, to switch between phenotypes that express and repress that particular gene. Whereas the DNA sequence of the region is not mutated, this change is reversible. It has also been speculated that organisms may take advantage of differential mutation rates associated with epigenetic features to control the mutation rates of particular genes.
Epigenetic changes have also been observed to occur in response to environmental exposure—for example, mice given some dietary supplements have epigenetic changes affecting expression of the agouti gene, which affects their fur color, weight, and propensity to develop cancer.
Epigenetic effects in humans
Genomic imprinting and related disorders
Some human disorders are associated with genomic imprinting, a phenomenon in mammals where the father and mother contribute different epigenetic patterns for specific genomic loci in their germ cells. The most well-known case of imprinting in human disorders is that of Angelman syndrome and Prader-Willi syndrome—both can be produced by the same genetic mutation, chromosome 15q partial deletion, and the particular syndrome that will develop depends on whether the mutation is inherited from the child's mother or from their father. This is due to the presence of genomic imprinting in the region. Beckwith-Wiedemann syndrome is also associated with genomic imprinting, often caused by abnormalities in maternal genomic imprinting of a region on chromosome 11.
Transgenerational epigenetic observations
Marcus Pembrey and colleagues also observed that the paternal (but not maternal) grandsons of Swedish boys who were exposed to famine in the 19th century were less likely to die of cardiovascular disease; if food was plentiful then diabetes mortality in the grandchildren increased, suggesting that this was a transgenerational epigenetic inheritance.
Cancer and developmental abnormalities
A variety of compounds are considered as epigenetic carcinogens—they result in an increased incidence of tumors, but they do not show mutagen activity (toxic compounds or pathogens that cause tumors incident to increased regeneration should also be excluded). Examples include diethylstilbestrol, arsenite, hexachlorobenzene, and nickel compounds.
Many teratogens exert specific effects on the fetus by epigenetic mechanisms. While epigenetic effects may preserve the effect of a teratogen such as diethylstilbestrol throughout the life of an affected child, the possibility of birth defects resulting from exposure of fathers or in second and succeeding generations of offspring has generally been rejected on theoretical grounds and for lack of evidence. However, a range of male-mediated abnormalities have been demonstrated, and more are likely to exist. FDA label information for Vidaza(tm), a formulation of 5-azacitidine (an unmethylatable analog of cytidine that causes hypomethylation when incorporated into DNA) states that "men should be advised not to father a child" while using the drug, citing evidence in treated male mice of reduced fertility, increased embryo loss, and abnormal embryo development. In rats, endocrine differences were observed in offspring of males exposed to morphine. In mice, second generation effects of diethylstilbesterol have been described occurring by epigenetic mechanisms.
Epigenetics in microorganisms
Bacteria make widespread use of postreplicative DNA methylation for the epigenetic control of DNA-protein interactions. Bacteria make use of DNA adenine methylation (rather than DNA cytosine methylation) as an epigenetic signal. DNA adenine methylation is important in bacteria virulence in organisms such as Escherichia coli, Salmonella, Vibrio, Yersinia, Haemophilus, and Brucella. In Alphaproteobacteria, methylation of adenine regulates the cell cycle and couples gene transcription to DNA replication. In Gammaproteobacteria, adenine methylation provides signals for DNA replication, chromosome segregation, mismatch repair, packaging of bacteriophage, transposase activity and regulation of gene expression.
The yeast prion PSI is generated by a conformational change of a translation termination factor, which is then inherited by daughter cells. This can provide a survival advantage under adverse conditions. This is an example of epigenetic regulation enabling unicellular organisms to respond rapidly to environmental stress. Prions can be viewed as epigenetic agents capable of inducing a phenotypic change without modification of the genome.

DNA methylation
(節錄自維基 by陳怡睿)
DNA methylation is a type of chemical modification of DNA that can be inherited and subsequently removed without changing the original DNA sequence. As such, it is part of the epigenetic code and is also the most well characterized epigenetic mechanism.
DNA methylation involves the addition of a methyl group to DNA — for example, to the number 5 carbon of the cytosine pyrimidine ring — in this case with the specific effect of reducing gene expression. DNA methylation at the 5 position of cytosine has been found in every vertebrate examined. In adult somatic tissues, DNA methylation typically occurs in a CpG dinucleotide context; non-CpG methylation is prevalent in embryonic stem cells.
In plants, cytosines are methylated both symmetrically (CpG or CpNpG) and asymmetrically (CpNpNp), where N can be any nucleotide but guanine. Some organisms, such as fruit flies, exhibit virtually no DNA methylation.
Research has suggested that long term memories in humans may be stored via DNA methylation.
In mammals
DNA methylation is essential for normal development and is associated with a number of key processes including imprinting, X-chromosome inactivation, suppression of repetitive elements and carcinogenesis.
Between 60-90% of all CpGs are methylated in mammals. Unmethylated CpGs are grouped in clusters called "CpG islands" that are present in the 5' regulatory regions of many genes. In many disease processes such as cancer, gene promoter CpG islands acquire abnormal hypermethylation, which results in heritable transcriptional silencing. DNA methylation may impact the transcription of genes in two ways. First, the methylation of DNA may itself physically impede the binding of transcriptional proteins to the gene and secondly, and likely more important, methylated DNA may be bound by proteins known as methyl-CpG-binding domain proteins (MBDs). MBD proteins then recruit additional proteins to the locus, such as histone deacetylases and other chromatin remodelling proteins that can modify histones, thereby forming compact, inactive chromatin termed silent chromatin. This link between DNA methylation and chromatin structure is very important. In particular, loss of methyl-CpG-binding protein 2 (MeCP2) has been implicated in Rett syndrome and methyl-CpG binding domain protein 2 (MBD2) mediates the transcriptional silencing of hypermethylated genes in cancer.
DNA Methyltransferases
In mammalian cells, DNA methylation occurs mainly at the C5 position of CpG dinucleodtides and carried out by two general classes of enzymatic activities - maintenance methylation and de novo methylation.
Maintenance methylation activity is necessary to preserve DNA methylation after every cellular DNA replication cycle. Without the DNA methyltransferase, the replication machinery itself would produce daughter strands that are unmethylated and overtime would lead to passive demethylation. DNMT1 is the proposed maintenance methyltransferase that is responsible for copying DNA methylation patterns to the daughter strands during DNA replication. Mouse models with both copies of DNMT1 deleted are embryonic lethal at approximately day 9, due to the requirement of DNMT1 activity for development in mammalian cells.
It is thought that DNMT3a and DNMT3b are the de novo methyltransferases that set up DNA methylation patterns early in development. DNMT3L is a protein that is homologous to the other DNMT3s but has no catalytic activity. Instead, DNMT3L assists the de novo methyltransferases by increasing their ability to bind to DNA and stimulating their activity. Finally, DNMT2 (TRDMT1) has been identified as a DNA methyltransferase homolog, containing all 10 sequence motifs common to all DNA methyltransferases; however, DNMT2 (TRDMT1) does not methylate DNA but instead methylates cytosine-38 in the anticodon loop of aspartic acid transfer RNA.
Since many tumor suppressor genes are silenced by DNA methylation during carcinogenesis, there have been attempts to re-express these genes by inhibiting the DNMTs. 5-aza-2'-deoxycytidine (decitabine) is a nucleoside analog that inhibits DNMTs by trapping them in a covalent complex on DNA by preventing the β-elimination step of catalysis, thus resulting in the enzymes' degradation. However, for decitabine to be active, it must be incorporated into the genome of the cell, but this can cause mutations in the daughter cells if the cell does not die. Additionally, decitabine is toxic to the bone marrow, which limits the size of its therapeutic window. These pitfalls have led to the development of antisense RNA therapies that target the DNMTs by degrading their mRNAs and preventing their translation. However, it is currently unclear if targeting DNMT1 alone is sufficient to reactivate tumor suppressor genes silenced by DNA methylation.
In plants
Significant progress has been made in understanding DNA methylation in plants, specifically in the model plant, Arabidopsis thaliana. Whereas in mammals methylation mainly occurs on the cytosine in a CpG context, in plants the cytosine can be methylated in the CpG, CpNpG, and CpNpN context, where N represents any nucleotide but guanine.
The principal Arabidopsis DNA methyltransferase enzymes, which transfer and covalently attach methyl groups onto DNA, are DRM2, MET1, and CMT3. Both the DRM2 and MET1 proteins share significant homology to the mammalian methyltransferases DNMT3 and DNMT1, respectively, whereas the CMT3 protein is unique to the plant kingdom. There are currently two classes of DNA methyltransferases: 1) the de-novo class, or enzymes that create new methylation marks on the DNA, and 2) a maintenance class that recognizes the methylation marks on the parental strand of DNA and transfers new methylation to the daughters strands after DNA replication. DRM2 is the only enzyme that has been implicated as a de-novo DNA methyltransferase. DRM2 has also been shown, along with MET1 and CMT3 to be involved in maintaining methylation marks through DNA replication. Currently, it is not clear how the cell determines the locations of de-novo DNA methylation, but evidence suggests that for many, though not all locations, RNA-directed DNA methylation (RdDM) is involved. In RdDM, specific RNA transcripts are produced from a genomic DNA template, and this RNA forms secondary structures called double-stranded RNA molecules. The double-stranded RNAs, through either the small interfering RNA (siRNA) or microRNA (miRNA) pathways, direct de-novo DNA methylation of the original genomic location that produced the RNA. This sort of mechanism is thought to be important in cellular defense against RNA viruses and/or transposons both of which often form a double-stranded RNA that can be mutagenic to the host genome. By methylating their genomic locations, through a still-poorly-understood mechanism, they are shut off and are no longer active in the cell, protecting the genome from their mutagenic effect.
In fungi
Many fungi apparently have low levels (0.1 to 0.5%) of cytosine methylation while other fungi have as much as 5% of the genome methylated. This value seems to vary both among species and among isolates of the same species. There is also evidence that DNA methylation may be involved in state-specific control of gene expression in fungi.
Although brewers yeast (Saccharomyces) and fission yeast (Schizosaccharomyces) have very little DNA methylation, the model filamentous fungus Neurospora crassa has a well characterized methylation system. Several genes control methylation in Neurospora and mutation of the DNA methyl transferase, dim-2, eliminates all DNA methylation in Neurospora but does not affect growth or sexual reproduction. While the Neurospora genome has very little repeated DNA, half of the methylation occurs in repeated DNA including transposon relics and centromeric DNA.The ability to evaluate other important phenomena in a DNA methylase deficient genetic background makes Neurospora and important system in which to study DNA methylation.
In bacteria
Adenine or cytosine methylation is part of the restriction modification system of many bacteria, in which DNAs are methylated periodically throughout the genome. A methylase is the enzyme that recognizes a specific sequence and methylates one of the bases in or near that sequence. Foreign DNAs (which are not methylated in this manner) that are introduced into the cell are degraded by sequence-specific restriction enzymes. Bacterial genomic DNA is not recognized by these restriction enzymes. The methylation of native DNA acts as a sort of primitive immune system, allowing the bacteria to protect themselves from infection by bacteriophage. These restriction enzymes are the basis of restriction fragment length polymorphism (RFLP) testing, used to detect DNA polymorphisms.

衛生署放寬具殺菌作用漱口水管理方式，從只能在藥局、牙科診所販售的「指示用藥」，改為「乙類成藥」，民眾可在一般商店買到。
衛生署放寬的是含
Chlorhexidine gluconate、Cetylpyridinium
chloride兩種殺菌成分漱口水。藥政處表示，過去，Chlorhexidine gluconate
濃度超過0.1%、Cetylpyridinium
chloride濃度超過0.045%的漱口水，都是以指示用藥管理，一般商店可購得的漱口水，就算含上述兩種殺菌成分，濃度也相當低，以一般商品管理，
有些漱口水則是標榜含氟，可以預防蛀牙。

這星期一,在太源院區看診的時候,患者家屬問說: "聽說你們醫院有更好的設備,結果和一般診所沒有太大的差別,診所醫師說一定要你們才能夠做的治療,原以為是全自動的檢查與治療機器,沒想到你們也沒用特殊工具,一下就治好了..."
這個問題其實有兩大原因.首先,太源院區為本院的復健與身心治療院區,患者的組成與一般情況不同,所需要的支援與耐心勢必要比較多.因為在這裡,我們有對於身心障礙方面的專家,所以在治療上,我們沒有後顧之憂.而診所在這方面就有其結構上的不足,醫師無法放心治療,當然會將患者轉出來.
另外,診所比較注重時效,而有身心障礙問題的患者,每次看診所需的時間和花費的精神,以效益來說是不划算的.我們在這個院區所提供的治療,就是以患者的狀態為主要考量,進一步評估與治療,所需要的時間自然更多,相對的也更能夠解決問題.
這裡要跟大家澄清的觀念是:

英研究：上網查病況 愈查愈擔心






更新日期:2008/12/02 11:03

資料來源: 維基百科 整理: 陳怡睿
ELISA
    Enzyme-Linked ImmunoSorbent Assay, also called ELISA, is a biochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample. The ELISA has been used as a diagnostic tool in medicine and plant pathology, as well as a quality control check in various industries. In simple terms, in ELISA an unknown amount of antigen is affixed to a surface, and then a specific antibody is washed over the surface so that it can bind to the antigen. This antibody is linked to an enzyme, and in the final step a substance is added that the enzyme can convert to some detectable signal. Thus in the case of fluorescence ELISA, when light of the appropriate wavelength is shone upon the sample, any antigen/antibody complexes will fluoresce so that the amount of antigen in the sample can be inferred through the magnitude of the fluorescence.
    Performing an ELISA involves at least one antibody with specificity for a particular antigen. The sample with an unknown amount of antigen is immobilized on a solid support (usually a polystyrene microtiter plate) either non-specifically (via adsorption to the surface) or specifically (via capture by another antibody specific to the same antigen, in a "sandwich" ELISA). After the antigen is immobilized the detection antibody is added, forming a complex with the antigen. The detection antibody can be covalently linked to an enzyme, or can itself be detected by a secondary antibody which is linked to an enzyme through bioconjugation. Between each step the plate is typically washed with a mild detergent solution to remove any proteins or antibodies that are not specifically bound. After the final wash step the plate is developed by adding an enzymatic substrate to produce a visible signal, which indicates the quantity of antigen in the sample. Older ELISAs utilize chromogenic substrates, though newer assays employ fluorogenic substrates enabling much higher sensitivity.
Applications
    Because the ELISA can be performed to evaluate either the presence of antigen or the presence of antibody in a sample, it is a useful tool both for determining serum antibody concentrations (such as with the HIV test or West Nile Virus) and also for detecting the presence of antigen. It has also found applications in the food industry in detecting potential food allergens such as milk, peanuts, walnuts, almonds, and eggs. ELISA can also be used in toxicology as a rapid presumptive screen for certain classes of drugs.
    The ELISA test was the first screening test commonly employed for HIV. It has a high sensitivity. In an ELISA test, a person's serum is diluted 400-fold and applied to a plate to which HIV antigens have been attached. If antibodies to HIV are present in the serum, they may bind to these HIV antigens. The plate is then washed to remove all other components of the serum. A specially prepared "secondary antibody" is then applied to the plate, followed by another wash. This secondary antibody is chemically linked in advance to an enzyme. Thus the plate will contain enzyme in proportion to the amount of secondary antibody bound to the plate. A substrate for the enzyme is applied, and catalysis by the enzyme leads to a change in color or fluorescence. ELISA results are reported as a number; the most controversial aspect of this test is determining the "cut-off" point between a positive and negative result.
One method of determining a cut-off point is by comparison with a known standard. For example, if an ELISA test will be used in workplace drug screening, a cut-off concentration (e.g., 50 ng/mL of drug) will be established and a sample will be prepared that contains that concentration of analyte. Unknowns that generate a signal that is stronger than the known sample are called "positive"; those that generate weaker signal are called "negative."
Types
"Indirect" ELISA
The steps of the general, "indirect," ELISA for determining serum antibody concentrations are:
Apply a sample of known antigen of known concentration to a surface, often the well of a microtiter plate. The antigen is fixed to the surface to render it immobile. Simple adsorption of the protein to the plastic surface is usually sufficient. These samples of known antigen concentrations will constitute a standard curve used to calculate antigen concentrations of unknown samples. Note that the antigen itself may be an antibody.
A concentrated solution of non-interacting protein, such as bovine serum albumin (BSA) or casein, is added to all plate wells. This step is known as blocking, because the serum proteins block non-specific adsorption of other proteins to the plate.
The plate wells or other surface are then coated with serum samples of unknown antigen concentration, diluted into the same buffer used for the antigen standards. Since antigen immobilization in this step is due to non-specific adsorption, it is important for the total protein concentration to be similar to that of the antigen standards.
The plate is washed, and a detection antibody specific to the antigen of interest is applied to all plate wells. This antibody will only bind to immobilized antigen on the well surface, not to other serum proteins or the blocking proteins.
Secondary antibodies, which will bind to any remaining detection antibodies, are added to the wells. These secondary antibodies are conjugated to the substrate-specific enzyme. This step may be skipped if the detection antibody is conjugated to an enzyme.
Wash the plate, so that excess unbound enzyme-antibody conjugates are removed.
Apply a substrate which is converted by the enzyme to elicit a chromogenic or fluorogenic or electrochemical signal.
View/quantify the result using a spectrophotometer, spectrofluorometer, or other optical/electrochemical device.
    The enzyme acts as an amplifier; even if only few enzyme-linked antibodies remain bound, the enzyme molecules will produce many signal molecules. A major disadvantage of the indirect ELISA is that the method of antigen immobilization is non-specific; any proteins in the sample will stick to the microtiter plate well, so small concentrations of analyte in serum must compete with other serum proteins when binding to the well surface. The sandwich ELISA provides a solution to this problem.
    ELISA may be run in a qualitative or quantitative format. Qualitative results provide a simple positive or negative result for a sample. The cutoff between positive and negative is determined by the analyst and may be statistical. Two or three times the standard deviation is often used to distinguish positive and negative samples. In quantitative ELISA, the optical density or fluorescent units of the sample is interpolated into a standard curve, which is typically a serial dilution of the target.
Sandwich ELISA
    A less-common variant of this technique, called "sandwich" ELISA, is used to detect sample antigen. The steps are as follows:
Prepare a surface to which a known quantity of capture antibody is bound.
Block any non specific binding sites on the surface.
Apply the antigen-containing sample to the plate.
Wash the plate, so that unbound antigen is removed.
Apply primary antibodies that bind specifically to the antigen.
Apply enzyme-linked secondary antibodies which are specific to the primary antibodies.
Wash the plate, so that the unbound antibody-enzyme conjugates are removed.
Apply a chemical which is converted by the enzyme into a color or fluorescent or electrochemical signal.
Measure the absorbance or fluorescence or electrochemical signal (e.g., current) of the plate wells to determine the presence and quantity of antigen.
    The image to the right includes the use of a secondary antibody conjugated to an enzyme, though technically this is not necessary if the primary antibody is conjugated to an enzyme. However, use of a secondary-antibody conjugate avoids the expensive process of creating enzyme-linked antibodies for every antigen one might want to detect. By using an enzyme-linked antibody that binds the Fc region of other antibodies, this same enzyme-linked antibody can be used in a variety of situations. The major advantage of a sandwich ELISA is the ability to use crude or impure samples and still selectively bind any antigen that may be present. Without the first layer of "capture" antibody, any proteins in the sample (including serum proteins) may competitively adsorb to the plate surface, lowering the quantity of antigen immobilized.
Competitive ELISA
    A third use of ELISA is through competitive binding. The steps for this ELISA are somewhat different than the first two examples:
Unlabeled antibody is incubated in the presence of its antigen.
These bound antibody/antigen complexes are then added to an antigen coated well.
The plate is washed, so that unbound antibody is removed. (The more antigen in the sample, the less antibody will be able to bind to the antigen in the well, hence "competition.")
The secondary antibody, specific to the primary antibody is added. This second antibody is coupled to the enzyme.
A substrate is added, and remaining enzymes elicit a chromogenic or fluorescent signal.
    For competitive ELISA, the higher the original antigen concentration, the weaker the eventual signal.
Note that some competitive ELISA kits include enzyme-linked antigen rather than enzyme-linked antibody. The labeled antigen competes for primary antibody binding sites with your sample antigen (unlabeled). The more antigen in the sample, the less labeled antigen is retained in the well and the weaker the signal.
ELISA Reverse method & device (ELISA-R m&d)
    A newer technique uses a solid phase made up of an immunosorbent polystyrene rod with 4-12 protruding ogives. The entire device is immersed in a test tube containing the collected sample and the following steps (washing, incubation in conjugate and incubation in chromogenous) are carried out by dipping the ogives in microwells of standard microplates pre-filled with reagents.
Advantages:
The ogives can each be sensitized to a different reagent, allowing the simultaneous detection of different antibodies and different antigens for multi-target assays;
The sample volume can be increased to improve the test sensitivity in clinical (saliva, urine), food (bulk milk, pooled eggs) and environmental (water) samples;
One ogive is left unsensitized to measure the non-specific reactions of the sample;
The use of laboratory supplies for dispensing sample aliquots, washing solution and reagents in microwells is not required, facilitating ready-to-use lab-kits and on-site kits.
Radioimmunoassay
    Radioimmunoassay (RIA) is a scientific method used to test antigens (for example, hormone levels in the blood) without the need to use a bioassay. It was developed by Rosalyn Yalow and Solomon Aaron Berson in the 1950s. In 1977, Rosalyn Sussman Yalow received the Nobel Prize in Medicine for the development of the RIA for insulin: the precise measurement of minute amounts of such a hormone was considered a breakthrough in endocrinology.
    Although the RIA technique is extremely sensitive and extremely specific, it requires a sophisticated apparatus and is costly. It also requires special precautions, since radioactive substances are used. Therefore, today it has been largely supplanted by the ELISA method, where the antigen-antibody reaction is measured using colorometric signals instead of a radioactive signal.
    To perform a radioimmunoassay, a known quantity of an antigen is made radioactive, frequently by labeling it with gamma-radioactive isotopes of iodine attached to tyrosine. This radiolabeled antigen is then mixed with a known amount of antibody for that antigen, and as a result, the two chemically bind to one another. Then, a sample of serum from a patient containing an unknown quantity of that same antigen is added. This causes the unlabeled (or "cold") antigen from the serum to compete with the radiolabeled antigen for antibody binding sites.
    As the concentration of "cold" antigen is increased, more of it binds to the antibody, displacing the radiolabeled variant, and reducing the ratio of antibody-bound radiolabeled antigen to free radiolabeled antigen. The bound antigens are then separated from the unbound ones, and the radioactivity of the free antigen remaining in the supernatant is measured. A binding curve can then be plotted, and the exact amount of antigen in the patient's serum can be determined.
    With this technique, separating bound from unbound antigen is crucial. Initially, the method of separation employed was the use of a second "anti-antibody" directed against the first for precipitation and centrifugation. The use of charcoal suspension for precipitation was extended but replaced later by Drs. Werner and Acebedo at Columbia University for RIA of T3 and T4. An ultramicro RIA for human TSH was published in BBRC (1975) by Drs. Acebedo, Hayek et al.
Applications
    The technique of radioimmunoassay has revolutionized research and clinical practice in many areas, e.g., blood banking, diagnosis of allergies,  and endocrinology.

子宮頸癌疫苗 14歲前打效果最好
2008-11-27
記者王昶閔／台北報導
女性在越年輕時施打子宮頸癌疫苗，產生的抗體濃度越高。研究顯示，女性在10至14歲間接種疫苗，會比15至25歲再打，所產生的人類乳突病毒（HPV）抗體至少高2倍。醫師表示，抗體濃度比較高，理論上防癌效果更好。
台大醫院婦產部主治醫師鄭文芳表示，子宮頸癌是由HPV引起，可以透過疫苗預防，目前台灣上市的兩種子宮頸癌疫苗，衛生署分別核准用於10到25歲女性與9至26歲，對於人類乳突病毒（HPV）第十六、十八型病毒引發的子宮頸癌癌前病變，都有至少5年的保護效果。
他表示，約有8成5的HPV是透過性行為傳染，疫苗最好在未發生性行為前施打，且越早施打疫苗，抗體濃度越高，如果是在10歲到14歲間施打的話，到了15歲時的抗體濃度，會比15歲時施打來得高。
鄭文芳表示，抗體濃度越高，保護力就越好，HPV若感染到細胞，只要一個半小時就能完全控制細胞，使細胞幫助病毒複製，速度相當快，所以擁有足夠的抗體濃度很重要。
鄭文芳不願評論哪家的疫苗比較好，他只表示，理想的子宮頸癌疫苗應該具有保護效果好、保護型別多、抗體能快速中和病毒、抗體能持久隨時應付所需4大條件。
他表示，全球有7成的子宮頸癌是第十六及十八型HPV引起，其餘是其他病毒型或原因引起，所以施打疫苗後，若有性行為者，目前建議還是每年要做抹片。

蛀牙引發蜂窩性組織炎 阿嬤差點送掉老命

88歲老阿嬤差點為1顆牙送命！ （記者徐夏蓮攝）

記者徐夏蓮／台中報導

中市一名88歲老阿嬤，只剩4顆牙齒，沒想到上月其中1顆發炎疼痛，她懶得看醫師，自行吃止痛藥止痛，竟因此引發蜂窩性組織炎，並進而引發壞死性筋膜炎，送醫急救住院1個月才撿回老命。

中山醫學大學口腔醫學研究中心口腔顎面外科蔡樂霖昨天指出，這位88歲阿嬤有糖尿病史，她上月發現右下後排牙齒腫痛，她心想牙齒痛沒什麼，吃止痛藥止痛就好
了，沒想到牙痛依舊，還發炎產生膿瘍，細菌竟從她的牙齒到骨膜，再從骨膜流竄到組織筋膜間隙、顳肌，害阿嬤蜂窩性組織炎，並進而引發壞死性筋膜炎，差點為
此送掉老命。

蔡樂霖醫師說，這位阿嬤因為發燒腫痛到無法進食，家人嚇得馬上將她送去掛急診，要不是馬上開刀處理，阿嬤真的是性命垂危，住院1個月，上週六才終於平安出院回家。

蔡樂霖指出，大家都說「牙痛不是病，痛起來真要人命」，事實上，牙痛不僅是病，它痛起來也確實會要人命，幾年前他就診治過1位才50多歲的婦人，因有糖尿病、自體免疫疾病，為了1顆蛀牙沒醫治，整個後腦潰爛最後死亡。

他
表示，牙疾不好好治療，口腔內的細菌形成膿瘍，約1週就可併發蜂窩性組織炎，膿液沒去處，一定會往人體組織間隙流竄，往上跑到鼻竇、臉頰，往下跑到頸部，
有人因此爛穿成洞狀，也有人因此造成呼吸道腫脹壓迫到患者呼吸功能，還有跑到肺部的，上了年紀的民眾，或有糖尿病、免疫功能低下、長期服用類固醇的民眾，
更是不要小看牙齒的疾病！

Content : 您好！請問如有糖尿病，是一定不能做人工植牙嗎?? 完全沒機會能做嗎??~~~3Q~~~
Ans: (by Dr.陳怡睿)
 
關於糖尿病的問題 主要的影響是傷口的癒合
而不受控制的糖尿病 和牙周問題的相關性早已被確認
但是在對糖分控制良好且健康無礙的患者進行植牙手術仍然可行
不過必須注意以下幾點:
1. 患者有無傷口延遲癒合或感染不癒的情況
2. 口腔內的牙周問題是否獲得完善的處理與控制
--> 包括: 牙結石的清除 口腔衛生的維護 殘根的拔除 肉芽組織的清除...
3. 最好不要立即植牙 約需等一個月
4. 植牙最好以二階段方式施行 原則上時間比一般情況要再延長一至二個月
5. 和內科醫師做進一步的確認
請至牙醫師處直接詢問並進行檢查是最好的方式

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