Biomedical subjects

J Huang

Publications and source records attributed to J Huang.

At least 19 recordsLinked to original sources

PubMed1999

Kaposi's sarcoma and non-Hodgkin's lymphoma incidence trends in AIDS Clinical Trial Group study participants.

Combination therapy with protease inhibitors and nucleoside analogues dramatically suppresses plasma HIV-1 RNA and delays progression to AIDS, but the impact on HIV-associated malignancy remains to be established. We therefore examined incidence trends of Kaposi's sarcoma and non-Hodgkin's lymphoma in patients with advanced HIV infection in nine AIDS Clinical Trial Group studies of antiviral therapies for HIV and cytomegalovirus infections. Among a total of 6587 patients enrolled between November 1987 and February 1997, there were 280 cases of Kaposi's sarcoma and 68 cases of non-Hodgkin's lymphoma. Incidence rates per 100 person-years of both malignancies declined in concert with decreases in mortality, but the decreases in Kaposi's sarcoma were more profound and consistent than the decreases in non-Hodgkin's lymphoma. These data suggest that current therapies have ameliorated the incidence of Kaposi's sarcoma, but may not have had an equal effect on non-Hodgkin's lymphoma.

AIDS-Related Opportunistic Infections↗

PubMed1999

Neuronal protection in stroke by an sLex-glycosylated complement inhibitory protein.

Glycoprotein adhesion receptors such as selectins contribute to tissue injury in stroke. Ischemic neurons strongly expressed C1q, which may target them for complement-mediated attack or C1qRp-mediated clearance. A hybrid molecule was used to simultaneously inhibit both complement activation and selectin-mediated adhesion. The extracellular domain of soluble complement receptor-1 (sCR1) was sialyl Lewis x glycosylated (sCR1sLex) to inhibit complement activation and endothelial-platelet-leukocyte interactions. sCR1 and sCR1sLex colocalized to ischemic cerebral microvessels and C1q-expressing neurons, inhibited neutrophil and platelet accumulation, and reduced cerebral infarct volumes. Additional benefit was conferred by sialyl Lewis x glycosylation of the unmodified parent sCR1 molecule.

Animals↗

PubMed1999

c-Src association with and phosphorylation of p58gag, a membrane- and microfilament-associated retroviral Gag-like protein in a xenotransplantable rat mammary tumor.

The retroviral Gag-like protein p58gag expressed in a highly metastatic ascites rat mammary adenocarcinoma has been implicated in cell surface changes contributing to xenotransplantability. p58gag is present in the cells in a plasma membrane- and microfilament-associated signal transduction particle containing Src and is phosphorylated on tyrosine. Overlay analyses and affinity chromatography with glutathione S-transferase (GST) fusion proteins of Src homology-3 (SH3) domains showed direct binding of the Src but not the Crk SH3 domain to p58gag. This association was confirmed by co-immunoprecipitation of partially purified p58gag from ascites cell lysates with platelet Src. Further, a GST-p58gag fusion protein bound full length c-Src from either platelets or c-Src-expressing insect cells. The GST-p58gag fusion protein, but not GST, was phosphorylated by platelet or insect cell-expressed c-Src, but not by a kinase negative c-Src variant. The binding of GST-p58gag to c-Src was almost completely abolished by a 50-fold excess of the GST-SH3 domain of Src, and a parallel decrease in tyrosine phosphorylation of p58gag was observed. These results demonstrate that p58gag is tyrosine-phosphorylated as a consequence of its specific association with c-Src via its SH3 domain. These observations suggest a mechanism by which Gag proteins may contribute to retroviral maturation or pathogenesis through binding and relocalization of SH3 domain-containing proteins such as Src-like tyrosine kinases to sites of association of microfilaments with the plasma membrane.

Adenocarcinoma↗

PubMed1999

Activation of the phagocyte NADPH oxidase protein p47(phox). Phosphorylation controls SH3 domain-dependent binding to p22(phox).

Activation of phagocyte NADPH oxidase requires interaction between p47(phox) and p22(phox). p47(phox) in resting phagocytes does not bind p22(phox). Phosphorylation of serines in the p47(phox) C terminus enables binding to the p22(phox) C terminus by inducing a conformational change in p47(phox) that unmasks the SH3A domain. We report that an arginine/lysine-rich region in the p47(phox) C terminus binds the p47(phox) SH3 domains expressed in tandem (SH3AB) but does not bind the individual N-terminal SH3A and C-terminal SH3B domains. Peptides matching amino acids 301-320 and 314-335 of the p47(phox) arginine/lysine-rich region block the p47(phox) SH3AB/p22(phox) C-terminal and p47(phox) SH3AB/p47(phox) C-terminal binding and inhibit NADPH oxidase activity in vitro. Peptides with phosphoserines substituted for serines 310 and 328 do not block binding and are poor inhibitors of oxidase activity. Mutated full-length p47(phox) with aspartic acid substitutions to mimic the effects of phosphorylations at serines 310 and 328 bind the p22(phox) proline-rich region in contrast to wild-type p47(phox). We conclude that the p47(phox) SH3A domain-binding site is blocked by an interaction between the p47(phox) SH3AB domains and the C-terminal arginine/lysine-rich region. Phosphorylation of serines in the p47(phox) C terminus disrupts this interaction leading to exposure of the SH3A domain, binding to p22(phox), and activation of the NADPH oxidase.

Amino Acid Sequence↗

PubMed1999

Immunization with amyloid-beta attenuates Alzheimer-disease-like pathology in the PDAPP mouse.

Amyloid-beta peptide (Abeta) seems to have a central role in the neuropathology of Alzheimer's disease (AD). Familial forms of the disease have been linked to mutations in the amyloid precursor protein (APP) and the presenilin genes. Disease-linked mutations in these genes result in increased production of the 42-amino-acid form of the peptide (Abeta42), which is the predominant form found in the amyloid plaques of Alzheimer's disease. The PDAPP transgenic mouse, which overexpresses mutant human APP (in which the amino acid at position 717 is phenylalanine instead of the normal valine), progressively develops many of the neuropathological hallmarks of Alzheimer's disease in an age- and brain-region-dependent manner. In the present study, transgenic animals were immunized with Abeta42, either before the onset of AD-type neuropathologies (at 6 weeks of age) or at an older age (11 months), when amyloid-beta deposition and several of the subsequent neuropathological changes were well established. We report that immunization of the young animals essentially prevented the development of beta-amyloid-plaque formation, neuritic dystrophy and astrogliosis. Treatment of the older animals also markedly reduced the extent and progression of these AD-like neuropathologies. Our results raise the possibility that immunization with amyloid-beta may be effective in preventing and treating Alzheimer's disease.

Alzheimer Disease↗

PubMed1999

Targeted inhibition of intrinsic coagulation limits cerebral injury in stroke without increasing intracerebral hemorrhage.

Agents that restore vascular patency in stroke also increase the risk of intracerebral hemorrhage (ICH). As Factor IXa is a key intermediary in the intrinsic pathway of coagulation, targeted inhibition of Factor IXa-dependent coagulation might inhibit microvascular thrombosis in stroke without impairing extrinsic hemostatic mechanisms that limit ICH. A competitive inhibitor of native Factor IXa for assembly into the intrinsic Factor X activation complex, Factor IXai, was prepared by covalent modification of the Factor IXa active site. In a modified cephalin clotting time assay, in vivo administration of Factor IXai caused a dose-dependent increase in time to clot formation (3.6-fold increase at the 300 micrograms/kg dose compared with vehicle-treated control animals, P < 0.05). Mice given Factor IXai and subjected to middle cerebral artery occlusion and reperfusion demonstrated reduced microvascular fibrin accumulation by immunoblotting and immunostaining, reduced 111In-labeled platelet deposition (42% decrease, P < 0.05), increased cerebral perfusion (2.6-fold increase in ipsilateral blood flow by laser doppler, P < 0.05), and smaller cerebral infarcts than vehicle-treated controls (70% reduction, P < 0.05) based on triphenyl tetrazolium chloride staining of serial cerebral sections. At therapeutically effective doses, Factor IXai was not associated with increased ICH, as opposed to tissue plasminogen activator (tPA) or heparin, both of which significantly increased ICH. Factor IXai was cerebroprotective even when given after the onset of stroke, indicating that microvascular thrombosis continues to evolve (and may be inhibited) even after primary occlusion of a major cerebrovascular tributary.

Animals↗

PubMed1999

A novel form of rhodopsin kinase from chicken retina and pineal gland.

The G protein-coupled receptor kinases (GRKs) are important enzymes in the desensitization of activated G protein-coupled receptors (GPCR). Seven members of the GRK family have been identified to date. Among these enzymes, GRK1 is involved in phototransduction and is the most specialized kinase of the family. GRK1 phosphorylates photoactivated rhodopsin (Rho*), initiating steps in its deactivation. In this study, we found that chicken retina and pineal gland express a novel form of GRK that has sequence features characteristic of GRK1. However, unlike bovine GRK1 which is farnesylated, chicken GRK1 contains a consensus sequence for geranylgeranylation. Peptides corresponding to the C-terminal sequence of chicken GRK1 are geranylgeranylated by a cytosolic extract of chicken liver. Based on results of molecular cloning and immunolocalization, it appears that both rod and cone photoreceptors express this novel GRK1. These data indicate a larger sequence diversity of photoreceptor GRKs than anticipated previously.

Amino Acid Sequence↗

PubMed1999

Effect of time of 7E3 administration on rt-PA-induced reperfusion: study in a canine model of thrombus-based occlusion-reperfusion.

Chimeric version of the murine monoclonal antibody, 7E3 has been proposed for the early restoration of coronary artery patency during thrombolytic therapy. We determined the optimal time for administration of 7E3 during recombinant tissue plasminogen activator (rt-PA)-induced thrombolysis using a canine model of coronary artery thrombosis. After 30 min of thrombotic occlusion, microspheres were injected to assess regional myocardial blood flow, followed by a 90-min rt-PA infusion. Dogs were randomized to three groups wherein 7E3 (0.8 mg kg(-1), i.v.) was administered either 5 min before rt-PA (Group I), at the first evidence of thrombolysis (Group II), or after the completion of rt-PA infusion (Group III). Hemodynamic parameters were monitored for 6 h after which infarct size was estimated. Time to occlusion/reperfusion was similar in all groups. In the rt-PA alone group, 78% arteries reoccluded after 60 min of reperfusion. The incidence of reocclusion was lower in Groups II (25%, P = 0.04) and III (0%. P < 0.01). All arteries (100%) were patent at the end of the protocol in Group III vs 50% remaining patent in Group I (P = 0.01). Arterial patency was maintained longer in Group III (301 min, n = 10), compared with Groups I (124 min, n = 5) and II (124 min, n = 6). Arterial flow was greater in Group III (82%) compared with Groups I (27%) and II (35%) (P < 0.01). Regional myocardial blood flow and infarct size were similar in all groups. The data indicate that the time of administration of 7E3 in conjunction with rt-PA-induced thrombolysis influences patency status. The experimental results suggest that in the absence of aspirin and heparin, optimal thrombolysis is obtained when 7E3 is administered after the completion of rt-PA infusion regimen.

Animals↗

PubMed1999

Colorectal carcinoma among ethnic Chinese in Singapore: trends in incidence rate by anatomic subsite from 1968 to 1992.

BACKGROUND: Recent epidemiologic studies have suggested that the anatomic distribution of colorectal carcinoma may have undergone a distal to proximal shift over several decades, which has been attributed variously to environmental and genetic factors as well as preventive intervention. METHODS: Trends in subsite distribution and the incidence rate of colorectal carcinoma among Chinese in Singapore between 1968 and 1992 were explored using data from the Singapore Cancer Registry (n = 10,489). Age-standardized incidence rates were computed and compared further using age-period-cohort models by subsite and gender. RESULTS: The proportion of lesions in the distal colon was found to have increased from 23.2% to 24.4% whereas that for the proximal colon and rectum were fairly consistent over the past 25 years. Our results also showed that age-standardized rates have doubled in proximal lesions (2-3% annually) and more than doubled in distal lesions (3-4% annually) whereas rates in rectal carcinoma have shown a slight increase or stability over time. The patterns of change in all subsite tumors could be attributed to a significant birth cohort effect. CONCLUSIONS: The results of the current study suggest that incidence rates have increased rapidly with no distal to proximal shift observed among ethnic Chinese in Singapore over the past 25 years. The pattern of change differs from findings reported in high incidence countries such as the U. S. and parts of Europe, suggesting that the preventive intervention and early diagnostic capabilities that may have played an important role in these countries have had less effect in Asia. The rapid overall increase in the incidence rate of colon carcinoma supports the role of dietary and other environmental factors as possible risk factors.

Adult↗

PubMed1999

Involvement of caspases in proteolytic cleavage of Alzheimer's amyloid-beta precursor protein and amyloidogenic A beta peptide formation.

The amyloid-beta precursor protein (APP) is directly and efficiently cleaved by caspases during apoptosis, resulting in elevated amyloid-beta (A beta) peptide formation. The predominant site of caspase-mediated proteolysis is within the cytoplasmic tail of APP, and cleavage at this site occurs in hippocampal neurons in vivo following acute excitotoxic or ischemic brain injury. Caspase-3 is the predominant caspase involved in APP cleavage, consistent with its marked elevation in dying neurons of Alzheimer's disease brains and colocalization of its APP cleavage product with A beta in senile plaques. Caspases thus appear to play a dual role in proteolytic processing of APP and the resulting propensity for A beta peptide formation, as well as in the ultimate apoptotic death of neurons in Alzheimer's disease.

Acute Disease↗

PubMed1999

Incidence, evolution, and spatial distribution of functional reentry during ventricular fibrillation in pigs.

Functional reentry has been hypothesized to be an underlying mechanism of ventricular fibrillation (VF); however, its contribution to activation patterns during fully developed VF is unclear. We applied new quantitative pattern analysis techniques to mapping data acquired from a 21 x 24 unipolar electrode array (2-mm spacing) located on the ventricular epicardium of 7 open-chest, unsupported pigs. Data epochs 4 seconds long beginning 1, 10, 20, 30, and 40 seconds after electrical induction were analyzed. Reentrant circuits were automatically identified and quantified. We found that 2.3% of activation pathways could unambiguously be classified as reentrant. From scaling analysis, an additional 28% of the pathways may also have been reentrant. Reentry was short-lived with 1.5+/-1.5 (mean+/-SD) complete cycles per circuit. The fraction of reentrant pathways, number of cycles per circuit, cycle duration, and area and perimeter of the cores all increased significantly as VF progressed. Core drift speed decreased significantly. Neither the orientation of the cores nor the direction of drift was well predicted by the epicardial fiber orientation (r2=0.108 and 0.138, respectively, by linear regression). Reentrant circuits were clustered in regions of the epicardium. We conclude the following: (1) Epicardial reentry is relatively uncommon and short-lived during VF, suggesting either that sustained reentry is transmural or that mechanisms governing sustained reentry are relatively unimportant to the dynamics of VF. (2) Reentrant circuits become more common, larger, and longer-lived as VF progresses, which may explain a recently observed increase in VF organization during the first minute of VF. (3) The conditions necessary to induce and sustain reentry are distributed nonuniformly.

Animals↗

PubMed1999

The disappearance of cyclin B at the end of mitosis is regulated spatially in Drosophila cells.

We have followed the behaviour of a cyclin B-green fluorescent protein (GFP) fusion protein in living Drosophila embryos in order to study how the localization and destruction of cyclin B is regulated in space and time. We show that the fusion protein accumulates at centrosomes in interphase, in the nucleus in prophase, on the mitotic spindle in prometaphase and on the microtubules that overlap in the middle of the spindle in metaphase. In cellularized embryos, toward the end of metaphase, the spindle-associated cyclin B-GFP disappears from the spindle in a wave that starts at the spindle poles and spreads to the spindle equator; when the cyclin B-GFP on the spindle is almost undetectable, the chromosomes enter anaphase, and any remaining cytoplasmic cyclin B-GFP then disappears over the next few minutes. The endogenous cyclin B protein appears to behave in a similar manner. These findings suggest that the inactivation of cyclin B is regulated spatially in Drosophila cells. We show that the anaphase-promoting complex/cyclosome (APC/C) specifically interacts with microtubules in embryo extracts, but it is not confined to the spindle in mitosis, suggesting that the spatially regulated disappearance of cyclin B may reflect the spatially regulated activation of the APC/C.

Animals↗

PubMed1999

The conformational and dynamic basis for ligand binding reactivity in hemoglobin Ypsilanti (beta 99 asp-->Tyr): origin of the quaternary enhancement effect.

Hemoglobin Ypsilanti (HbY) is a stable tetrameric hemoglobin that binds oxygen with little or no cooperativity and with high affinity [Doyle, M. L., et al. (1992) Proteins: Struct., Funct., Genet. 14, 351-362]. It displays an especially large quaternary enhancement effect. An X-ray crystallographic study [Smith, F. R., et al. (1991) Proteins: Struct., Funct., Genet. 10, 81-91] of the carboxy derivative of this hemoglobin (COHbY) revealed a new quaternary structure that partially resembles the recently described R2 structure [Silva, M. M., et al. (1992) J. Biol. Chem. 267, 17248-17256]. Very little is known about either the solution phase conformations of the liganded and deoxy forms of HbY or the molecular basis for the large quaternary enhancement effect (Doyle et al., 1992). In this study, near-IR absorption, Soret-enhanced Raman, and UV (229 nm) resonance Raman spectroscopies are used to probe the liganded and deoxy derivatives of HbY in solution. Nanosecond time-resolved near-IR absorption measurements are used to expose the relaxation properties of the photoproduct of COHbY. Time-resolved (Soret band) absorption is used to generate the geminate and solvent phase ligand rebinding curves for photodissociated COHbY. The spectroscopic results indicate that COHbY has an R-like conformation with respect to both the proximal heme pocket and the hinge region of the alpha 1 beta 2 interface. The deoxy derivative of HbY has spectroscopic features that are very similar to those observed for species assigned to the deoxy R or half-liganded R conformations of human adult hemoglobin (HbA). The 10 ns to 100 micros relaxation properties of the photoproduct of COHbY are distinctly different from those of HbA in that for HbY, little if any tertiary or quaternary relaxation is observed. The near-absence of relaxation in the HbY photoproduct explains the differences in the geminate and solvent phase CO recombination between HbA and HbY. The impact of the conformational and relaxation properties of HbY on the geminate rebinding process forms the basis of a model that accounts for the large quaternary enhancement effect reported for HbY (Doyle et al., 1992). In addition, the spectroscopic data and the X-ray crystallographic results explain the slow relaxation for HbY and the near-absence of cooperative ligand binding for this protein based on the behavior of the penultimate tyrosines.

Adult↗

PubMed1999

IL-12 administered during Chlamydia psittaci lung infection in mice confers immediate and long-term protection and reduces macrophage inflammatory protein-2 level and neutrophil infiltration in lung tissue.

Protection against infections with the intracellular bacterium Chlamydia spp. requires Th1-polarized CD4+ T cell immunity. In BALB/c mouse lung infections, immediate innate and nascent Chlamydia-specific immune responses following intranasal inoculation of Chlamydia psittaci strain B577 were modulated by 7-day i.p. administration of murine rIL-12, the initiation cytokine for Th1 immunity. Treatment with IL-12 reduced the severity of chlamydial pneumonia, abolished mortality (37.5% in untreated mice), and significantly reduced numbers of chlamydial organisms in lungs. On day 4 after inoculation, the neutrophil:macrophage ratio in bronchointerstitial pneumonias was 1.96 in untreated mice and 0.51 in IL-12-treated mice. This immediate, IL-12-mediated shift in innate inflammatory phenotype was correlated with a significant reduction of lung concentrations of the neutrophil chemoattractant macrophage inflammatory protein (MIP)-2 (putative murine homologue of human IL-8), monocyte chemotactic protein-1, and TNF-alpha; and a reduction in MIP-1alpha and IFN-gamma, at high-dose infection only, and IL-12-independent IL-10 levels. Chlamydia-specific Ab titers and Ig isotype ratios indicated an IL-12-dependent Th1 shift. Recall responses of IL-12-primed mice to secondary chlamydial lung infection eliminated chlamydiae more effectively and generated a lung cytokine profile conducive to perpetuation of the Th1 memory population. These data support the hypothesis that genetic differences in endogenous IL-12 production and response pathways could determine disease outcomes characterized by poor chlamydial clearance and a purulent inflammatory infiltrate vs effective elimination of chlamydiae in a macrophage-dominated response.

Administration, Intranasal↗

PubMed1999

Temporary and partial inhibition of platelets by SM-20302 prevents coronary artery thrombosis in a chronic canine model.

We proposed that temporary and partial platelet inhibition by a GPIIb/IIIa receptor antagonist, SM-20302, would provide sustained antithrombotic efficacy in a chronic model of coronary artery thrombosis. Instrumented, conscious dogs received vehicle (Group I, n = 7), low dose SM-20302 (30 microg/kg bolus + 1 microg/kg/min infusion for 6 h) (Group II, n = 7), or high dose SM-20302 (100 microg/kg bolus + 1 microg/kg/min infusion for 6 h) (Group III, n = 7). Thrombosis was initiated by electrolytic injury to the circumflex coronary artery. Coronary blood flow was monitored for 6 h on day 1 and days 2-6. Platelet aggregation was performed in platelet-rich plasma prepared from citrated or heparinized blood. At 6 h, both doses of SM-20302 inhibited adenosine diphosphate-induced platelet aggregation completely (> 90%) in citrated platelet-rich plasma, but incompletely (57-59%) in heparinized platelet-rich plasma. Platelet reactivity returned to baseline values at 24 h. Control animals developed thrombotic occlusion on Day 1. Both doses of SM-20302 maintained vessel patency during the infusion period (Day 1) and the subsequent 5 days. Myocardial infarct size and mortality in the drug treated groups were reduced compared to the vehicle group. Thus, temporary inhibition of platelet reactivity by SM-20302 is associated with sustained prevention of primary thrombus formation, and reduction in infarct size and mortality.

Animals↗

PubMed1999

Maximum solubility of cholesterol in phosphatidylcholine and phosphatidylethanolamine bilayers.

In any lipid bilayer membrane, there is an upper limit on the cholesterol concentration that can be accommodated within the bilayer structure; excess cholesterol will precipitate as crystals of pure cholesterol monohydrate. This cholesterol solubility limit is a well-defined quantity. It is a first-order phase boundary in the phospholipid/cholesterol phase diagram. There are many different solubility limits in the literature, but no clear picture has emerged that can unify the disparate results. We have studied the effects that different sample preparation methods can have on the apparent experimental solubility limit. We find that artifactual demixing of cholesterol can occur during conventional sample preparation and that this demixed cholesterol may produce artifactual cholesterol crystals. Therefore, phospholipid/cholesterol suspensions which are prepared by conventional methods may manifest variable, falsely low cholesterol solubility limits. We have developed two novel preparative methods which are specifically designed to prevent demixing during sample preparation. For detection of the cholesterol crystals, X-ray diffraction has proven to be quantitative and highly sensitive. Experiments based on these methods yield reproducible and precise cholesterol solubility limits: 66 mol% for phosphatidylcholine (PC) bilayers and 51 mol% for phosphatidylethanolamine (PE) bilayers. We present evidence that these are true, equilibrium values. In contrast to the dramatic headgroup effect (PC vs. PE), acyl chain variations had no effect on the cholesterol solubility limit in four different PC/cholesterol mixtures.

Cholesterol↗

PubMed1999

Characterization of the surface proteins of influenza A (H5N1) viruses isolated from humans in 1997-1998.

Influenza A (H5N1) viruses infected humans in Hong Kong between May and December, 1997. Sixteen viruses, including 6 from fatal cases, were isolated during this outbreak. Molecular analysis of the surface proteins genes encoding the hemagglutinin (HA) and neuraminidase (NA) of these H5N1 isolates, of a subtype not previously known to infect humans, are presented. The 16 human H5 HA sequences contain multiple basic amino acids adjacent to the cleavage site, a motif associated with highly pathogenic avian influenza A viruses. The phylogenetic relationship among both avian and human H5 hemagglutinins indicates that the human isolates are related directly to isolates that circulated among chickens in the live poultry markets in Hong Kong prior to and during the outbreak in humans. HA sequences from the human isolates and a recent chicken isolate represent a separate clade, within which there are two subgroups that are distinguishable antigenically and by the presence of a potential glycosylation site. Likewise the N1 neuraminidases of the human H5 isolates represent a clade that is evolutionarily distinct from previously characterized N1 neuraminidases. The recent human H5N1 virus NA genes are avian-like, indicating direct introduction from an avian source rather than evolution of a human N1 NA. All of the 16 human NA genes encode a shortened stalk due to a 19-amino acid deletion, also found in the recent avian H5N1 isolates from Hong Kong. Two unique amino acids were identified in the N1 NAs of the recent human isolates; however, it is not known if these residues influence host range. Neither the HA nor the NA genes of the human H5N1 virus isolates show evidence of adaptive changes during the outbreak. Although analyses of the surface protein genes of the H5N1 viruses from this outbreak did not provide immediate answers regarding the molecular basis for virulence, the analyses provided clues to potentially important areas of the genes worth further investigation.

Adolescent↗

PubMed1999

High frequency of p16INK4A gene alterations in hepatocellular carcinoma.

The tumor suppressor gene p16 (CDKN2/MTS-1/INK4A) is an important component of the cell cycle and inactivation of the gene has been found in a variety of human cancers. In order to investigate the role of p16 gene in the tumorigenesis of hepatocellular carcinoma (HCC), 48 cases of HCC were analysed for p16 alterations by: methylation-specific PCR (MSP) to determine the methylation status of the p16 promoter region; comparative multiplex PCR to detect homozygous deletion; PCR-SSCP and DNA sequencing analysis to identify mutation of the p16 gene. We found high frequency of hypermethylation of the 5' CpG island of the p16 gene in 30 of 48 cases (62.5%) of HCC tumors. Moreover, homozygous deletion at p16 region were present in five of 48 cases (10.4%); and missense mutation were detected in three of 48 cases (6.3%). The overall frequency of p16 alterations, including homozygous deletion, mutation and hypermethylation, in HCC tumors was 70.8% (34 of 48 cases). These findings suggest that: (a) the inactivation of the p16 is a frequent event in HCC; (b) the p16 gene is inactivated by multiple mechanisms including homozygous deletion, promoter hypermethylation and point mutation; (c) the most common somatic alteration of the p16 gene in HCC is de novo hypermethylation of the 5' CpG island; and (d) in contrast to other studies, high frequency of genomic alterations are not uncommon in the 9p21 of the p16 gene. Our results strongly suggest that the p16 gene plays an important role in the pathogenesis of HCC.

Carcinoma, Hepatocellular↗