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Biomedical subjects

V Ng

Publications and source records attributed to V Ng.

At least 55 records · Page 3Linked to original sources
PubMed1996

DNA strand breaks and poly (ADP-ribose) polymerase activation induced by crystalline nickel subsulfide in MRC-5 lung fibroblast cells.

Nickel compounds are potent carcinogens. Their carcinogenicity is believed to be associated with their solubility and cellular uptake. In the present study, we assessed the in vitro genotoxic effect of a water-insoluble nickel compound, crystalline nickel subsulfide (alpha-Ni3S2) on human embryo lung fibroblast cell line (MRC-5 cells). DNA strand breaks was evaluated using single cell gel electrophoresis, or comet assay. The alpha-Ni3S2 induction of poly (ADP-ribose) polymerase (PADPRP), a nuclear enzyme associated with DNA damage and repair was also studied. Hydrogen peroxide (H2O2) was used as a reference compound. A dose-response relationship was found between alpha-Ni2S2 concentrations (2.5 micrograms/cm2 to 20 micrograms/cm2) and the comet tail length. The increase of PADPRP activity of alpha-Ni2S2 treated MRC-5 cells was also significant and dose-dependent within the concentration range of 2.5 micrograms/ cm2 to 10 micrograms/cm2. Close associations have been found between the comet length and PADPRP level for H2O2 (r = 0.98) and alpha-Ni3S2 (r = 0.97). These results clearly suggest that alpha-Ni3S2 is a potent agent in inducing DNA strand breaks, which may be closely related to its carcinogenic effects. Data from the present study also suggest that both comet assay and PADPRP determination are sensitive techniques for quantitative evaluation of DNA damage induced by nickel compounds.

Carcinogens↗
PubMed1995

Influence of molecular characteristics on clinical outcome in human immunodeficiency virus-associated non-Hodgkin's lymphoma: identification of a subgroup with favorable clinical outcome.

The relationship between clinical and molecular characteristics of 45 treated individuals with histologically-documented human immunodeficiency virus (HIV)-associated B-cell non-Hodgkin's lymphoma was examined to determine whether differences in molecular features of lymphoma were associated with differences in clinical outcome. Tissue specimens from these tumors were evaluated for evidence of Ig heavy-chain gene rearrangements using both Southern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR). Lymphomas were also evaluated for the presence of Epstein-Barr virus (EBV) DNA sequences and c-myc gene rearrangements. Twenty-five lymphomas were characterized as polyclonal and 20 as monoclonal. PCR amplification of expressed Ig variable (V)-region genes confirmed polyclonality in three extensively studied polyclonal lymphomas. The median CD4 count was significantly higher in the group with polyclonal disease (277/microL) than in the group with monoclonal disease (123/microL), P = .04. The complete response rate to therapy was significantly higher in patients with polyclonal disease (78%) and CD4 greater than 200/microL (81%) than in those with monoclonal disease (31%) and CD4 less than 200/microL (33%). CD4 count, clonality, and presence of EBV DNA sequences were the most important predictors of survival. Both Kaplan-Meier and Cox proportional hazards analyses showed a markedly prolonged survival in those patients with both CD4 > or = 200/microL and polyclonal disease. Histologically the polyclonal lymphomas were high grade in appearance and contained prominent macrophages. All seven surviving patients were in this group. Median survival for those individuals whose tumors contained EBV sequences was only 3.2 months (range, 0.4 to 19.5), whereas those with EBV- tumors survived for a median of 9.0 months (range, 0.7 to 65.2), P = .0007. These data indicate that molecular features of HIV-associated lymphomas may be important predictors of clinical outcome. These characteristics define a distinct subset of patients with polyclonal EBV- tumors and CD4 counts greater than 200/microL that appear to have a less aggressive clinical course.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Prevalence of hepatitis C virus sequence variants in South-East Asia.

The nature and distribution of hepatitis C virus (HCV) genotypic variants present in south-east Asia have not been extensively investigated. We analysed HCV RNA obtained from 67 clinical serum samples from Singapore, Thailand, Indonesia, the Philippines and South Korea. All samples were amplified by semi-nested RT-PCR and the nucleotide sequence determined for four regions within the E1, E2/NS1, NS4 and NS5 genes. Each isolate had a unique nucleotide and deduced amino acid sequence, consistent with the genetic heterogeneity of this virus. There was remarkably little amino acid sequence variation between isolates of the same genotype, apart from variable domains within putative envelope glycoproteins that are likely to be under immune pressure. All isolates could be classified according to the currently recognized genotypes of HCV, with the exception of one Singapore isolate that defined a new group 3 subtype. The 1b genotype, which predominates in Japan, was the most widely distributed genotype and accounted for 58% of all isolates sequenced. Regional variations in HCV genotype distribution were observed, with type 3a being found almost exclusively in Thailand. By contrast, the 1a genotype, which predominates in the USA was the most prevalent genotype in the Philippines. Genotype 1a was found less commonly among the Thai isolates, presumably having been introduced from the West in stored blood products or by sporadic transmission. The significant prevalence of HCV types 2 and 3 restates the need for variant genotypes to be included in immunodiagnostic and vaccine development strategies. This study reveals that the 1b genotype of HCV, previously found to be the major variant present in east Asia, also predominantes in the south-east Asian region, and may be the major HCV type found worldwide.

Amino Acid Sequence↗
PubMed1993

A non-lymphoma idiotype is indicative and predictive for B cell malignancies in AIDS.

The 1F7 idiotype previously defined (J Immunol 147:933;1991 and Eur J Immunol 22:1749;1992) is expressed on antibodies reactive to different proteins of HIV (gp41, p24, gp120). Since serum levels of 1F7 (IgM or IgG) are significantly higher in patients with HIV lymphoma as opposed to HIV-infected individuals, normal controls and non-HIV lymphoma patients, we hypothesized the B-cell neoplasms were the source of the idiotype. However, immunohistochemistry on cryostat sections revealed no 1F7 idiotype signal on neoplastic B-cells nor tumor infiltrative T-cells (n = 8). Interestingly, reactive lymphocytosis adjacent to tumor masses and reactive follicular hyperplastic controls (n = 5) exhibited significant 1F7 reactivity. The reactivity appeared in paracortical and perifollicular lymphoid regions, predominantly regions of B, T and antigen presenting cells in lymph nodes or tonsils. A survey of electrophoretically defined paraproteins with anti-HIV specificities derived from HIV-infected patients showed no Western blot reactivity with the 1F7 anti-idiotypic antibody. Therefore, the idiotype does not appear to be a direct product of B-cell neoplasia or abnormal B-cell proliferation, but is produced by B cell clones responding to HIV infection. This high level of serum 1F7 reactivity could be an important clue in the pathogenesis of HIV lymphomas and confers a highly predictive serological test for HIV lymphoma.

Animals↗
PubMed1993

Update on laboratory tests for the diagnosis of pulmonary disease in HIV-1-infected individuals.

Various diagnostic tests, both specific and nonspecific, are available in the clinical laboratories for diagnosing human immunodeficiency virus-1 (HIV-1) infection and associated respiratory pathogens. Pneumocystis carinii pneumonia remains the most common pulmonary disease in HIV-1-infected individuals and there have been no significant advances in the laboratory diagnosis of the pathogen beyond the traditional microscopic examination of specimens. In contrast, the greatest revolution in laboratory diagnostic testing has been for mycobacteria, with major advances resulting in significant reduction in the time necessary for isolation and identification to the species level. The application of the polymerase chain reaction for the identification of a variety of pulmonary pathogens observed in HIV-1 infected individuals is discussed.

Enzyme-Linked Immunosorbent Assay↗
PubMed1992

Toxoplasma gondii pneumonitis in patients infected with the human immunodeficiency virus.

Pulmonary toxoplasmosis is a rarely recognized opportunistic infection in immunocompromised patients. A few case reports have described pulmonary toxoplasmosis in human immunodeficiency virus-infected patients in association with Toxoplasma gondii central nervous system disease. We encountered six cases of pulmonary toxoplasmosis in human immunodeficiency virus-infected patients who presented with a protracted febrile illness, respiratory symptoms, and an abnormal chest roentgenogram in the absence of neurologic findings. No clinical or roentgenographic features distinguished T gondii pneumonitis from more common opportunistic pulmonary infections. As the acquired immunodeficiency syndrome epidemic progresses, the presenting illnesses have evolved. Toxoplasma gondii must be considered a potential cause of pulmonary disease during the evaluation of human immunodeficiency virus-infected patients with respiratory symptoms.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Computer-assisted assessment of human sperm morphology: usefulness in predicting fertilizing capacity of human spermatozoa.

OBJECTIVE: The usefulness of sperm morphology to predict the outcome of human sperm fertilizing capacity was examined. DESIGN, SETTING, PATIENTS: Semen samples from 50 male patients attending the infertility clinic of a tertiary referral institution were studied. MAIN OUTCOME MEASURES: Sperm morphology was classified both by visual assessment and computer-assisted image analysis. In addition, morphometric analysis of the spermatozoa was measured by the morphologizer. Multivariate discriminant analysis was used to evaluate the usefulness of these morphology parameters for predicting the outcome of the zona-free hamster oocyte sperm penetration assay. RESULTS: The manually derived percent of spermatozoa with normal and small head were selected to be of discriminating value in predicting the outcome of the zona-free hamster oocyte penetration test. The accuracy of correctly classifying the outcome of zona-free hamster oocyte penetration test by these two parameters in combination was 84%, whereas assessment of sperm morphology with morphometric analysis by the morphologizer selected a total of eight variables, which together predicted sperm fertilizing capacity with 74% accuracy. Addition of the morphologizer-derived parameters to those derived manually did not significantly improve the predictive value. CONCLUSION: We conclude that the results of the zona-free hamster egg penetration test could be predicted using manual assessment of sperm morphology and computer-assisted morphometric analysis did not add further information.

Animals↗
PubMed1991

Prognostic variables in patients with diffuse large-cell lymphoma treated with MACOP-B.

One hundred twenty-six patients with diffuse large-cell lymphoma were treated with methotrexate with leucovorin, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin (MACOP-B) between April 1981 and June 1986. Univariate and multivariate analyses were performed using overall survival as of September 1989 as the end point. Four independent negative predictors of survival were identified: presence of B symptoms; more than two involved lymph node sites; more than one extranodal site (variables related to tumor burden), and age older than 60, a variable related to the patient's ability to tolerate treatment. Each variable contributed the same relative risk of dying and, accordingly, this simple predictive formula was developed empirically: (4-N) x 30 = the approximate percentage of chance of survival at 5 years. "N" is the number of predictive variables present. The same four predictors were also found to be significant by multivariate analysis when only those patients achieving a complete response were analyzed.

Adolescent↗
PubMed1991

Computer-assisted assessment of human sperm morphology: comparison with visual assessment.

OBJECTIVE: Sperm morphology classification was analyzed by the computer-assisted semen analysis equipped with the Morphologizer II (Cryo Resources Ltd., New York, NY) was compared with the traditional manual method. DESIGN, SETTING, PATIENTS: Fifty stained semen smears from men attending the infertility clinic of a tertiary referral institution were studied. MAIN OUTCOME MEASURES: Sperm head morphology was classified by the two methods into the following forms: normal, small oval, big oval, taper, and amorphous. RESULTS: Overall, the classifications of mean percent normal, small, and amorphous head forms were similar in the two methods. However, the differences between paired values obtained by the two methods were highly variable (range from -20% to +20%). The large differences between the methods were related to the large coefficients of variations present when classifying abnormal sperm morphology even by the same experienced technician. Only the percent normal spermatozoa could be classified by both methods with acceptable precision. In contrast, the variations in the morphometric analyses between the different semen smears were very small. CONCLUSIONS: There was no advantage of the morphologizer over the manual method in sperm morphology classification. The clinical value of morphometric parameters of spermatozoa has to be defined.

Humans↗
PubMed1990

Diet and histologic types of benign breast disease defined by subsequent risk of breast cancer.

The authors investigated the relation between diet and histologic types of benign breast disease defined by subsequent risk of breast cancer in a case-control study of volunteers who entered the Vancouver Center of the Canadian National Breast Screening Study between 1983 and 1985. Proliferative benign breast disease (n = 124) was inversely associated with vitamin A supplementation (vitamin A user vs. nonuser, odds ratio (OR) = 0.5) and frequent green vegetable consumption (frequent vs. rare consumption, OR = 0.3), whereas severe atypias and borderline carcinoma in situ (n = 32) were directly associated with frequent meat fats consumption (frequent vs. rare consumption, OR = 3.2) with no association with vitamin A or vegetable consumption. No dietary relations were found for histologic types of benign breast disease at no increased risk for subsequent breast cancer (n = 274). The implications of these findings in relation to the etiology of breast cancer are discussed.

Breast Neoplasms↗
PubMed1984

Nitrosation by alkyl nitrites. Catalysis by inorganic salts.

Isobutyl nitrite is an effective nitrosating agent at acidic, neutral and basic pH in the presence of species arising from phosphate ion. The reaction is first-order in isobutyl nitrite and amine. In the reaction of isobutyl nitrite with sulfanilamide, the pH dependence reflects the change in concentration of the various protonated forms of phosphate, with H3PO4 and H2PO4- most strongly affecting the rate. In the reaction of isobutyl nitrite with dipropylamine, the pH dependence also reflects the change in the concentration of unprotonated amine.

Catalysis↗
PubMedDate not supplied

The accuracy of sperm concentration determination by the automated CellSoft semen analyzer before and after discontinuous Percoll gradient centrifugation.

The automated CellSoft semen analyzer identifies human spermatozoa on the basis of user-defined values for cell size and luminosity. Previous studies have shown that the non-sperm particles usually present in seminal plasma would interfere with the computerized determination of sperm concentration by the CellSoft system. Therefore, an effective method to separate the sperm from non-sperm particles would be desirable to obtain accurate determination of sperm concentration. In the present study, sperm concentrations in 72 semen samples before and after discontinuous Percoll gradient centrifugation were determined by the automated CellSoft system and the results compared with those obtained with the routine procedure using the haemocytomer according to the World Health Organization laboratory manual. The computerized measurement caused a significant overestimation when the sperm concentration in semen was less than 80 x 10(6)/ml. Processing of human semen sample by the simple two-layer discontinuous Percoll gradient centrifugation removed the majority of non-sperm particles and the overestimation by the automated CellSoft system became significant only when the sperm concentration in the final Percoll sperm preparation was less than 10 x 10(6)/ml. These findings indicate that the automated CellSoft semen analyzer has to be improved to allow for the correction of non-sperm particles in seminal plasma or processed sperm samples before it can be used to provide sufficiently accurate sperm concentration results for routine laboratory service or research purposes.

Cell Separation↗
PubMedDate not supplied

Profiles of sperm morphology and motility after discontinuous multiple-step Percoll density gradient centrifugation.

Morphology and motility are important parameters for assessing the fertilizing capacity of spermatozoa. This investigation reports a systematic study on the profiles of these parameters after percoll gradient centrifugation. Spermatozoa from normal human semen were fractionated by discontinuous Percoll gradients (30%, 45%, 75%, 90%). Spermatozoa washed with Earle's balanced salt solution were used as a control. After centrifugation, sperm morphology was evaluated according to strict criteria; motility was assessed by a computer-assisted semen analysis system. The results showed that the percentage of spermatozoa with normal morphology increased, while those with severe morphological defects decreased, as the density of Percoll increased. The percentages of motile spermatozoa and hyperactivated spermatozoa, and the velocity and amplitude of lateral head displacement of the spermatozoa were significantly higher in the 75% and 90% Percoll fractions than that in the 30% and 45% ones, and in the control. These results demonstrated that Percoll density gradient centrifugation enriched spermatozoa in terms of morphology and motility.

Cell Separation↗