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J Leung

Publications and source records attributed to J Leung.

At least 73 records · Page 4Linked to original sources
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

Tardive dystonia and diffuse idiopathic skeletal hyperostosis.

Tardive dystonia is a late side effect of long term neuroleptic treatment. A Chinese woman with tardive dystonia in the form of retrocollis for ten years showed radiological evidence of diffuse idiopathic skeletal hyperostosis (DISH) in the cervical spine. This association has not been previously reported in the literature. It is postulated that the retrocollis led to an abnormal stress of the cervical spine where excessive bone formation occurred. Hence tardive dystonia may act as a risk factor for DISH in patients who have an ossifying diathesis.

Antipsychotic Agents↗
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↗
PubMed1989

'Mangoism'.

Explore the source record for details and available documents.

Carotenoids↗
PubMed1989

Computer-assisted image analysis of sperm concentration in human semen before and after swim-up separation: comparison with assessment by haemocytometer.

Evaluation of male fertility is based predominantly on results from semen analysis and determination of the sperm concentration is one of the main parameters of the analysis. The availability of a fully automated videomicrographic digital image analyser would offer both an objective and rapid method for determination of the sperm concentration. In the present study the sperm concentration in 327 semen samples was determined by haemocytometer according to the World Health Organization guidelines, and also by a computer-assisted digital image analyser system. Results were classified according to the routine procedure (haemocytometer) before statistical analyses. The computerized measurements caused a shift to the right in the frequency distribution of sperm concentration. Sperm concentrations were more often overestimated significantly (P less than 0.001) by the computerized measurements in semen samples with concentrations up to 80.0 x 10(6)/ml. This overestimation seemed to be caused by the presence of particles in seminal plasma that were recognized incorrectly as sperm by the computer program. The computerized digital image analyser gave an average sperm concentration of 2.2 +/- 0.6 x 10(6)/ml (mean +/- SEM) in 17 azoospermic semen samples while the routine procedure did not detect the presence of sperm cells. After removing the seminal plasma by washing and centrifugation with culture medium, and using the swim-up procedure to harvest motile sperm, the computerized measurements showed comparable results with the routine procedure for those sperm preparations (n = 44) with sperm concentrations greater than 5.0 x 10(6)/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1987

Extensive microheterogeneity of serine tRNA genes from Drosophila melanogaster.

The nucleotide sequences of nine genes corresponding to tRNA(Ser)4 or tRNA(Ser)7 of Drosophila melanogaster were determined. Eight of the genes compose the major tRNA(Ser)4,7 cluster at 12DE on the X chromosome, while the other is from 23E on the left arm of chromosome 2. Among the eight X-linked genes, five different, interrelated, classes of sequence were found. Four of the eight genes correspond to tRNA(Ser)4 and tRNA(Ser)7 (which are 96% homologous), two appear to result from single crossovers between tRNA(Ser)4 and tRNA(Ser)7 genes, one is an apparent double crossover product, and the last differs from a tRNA(Ser)4 gene by a single C to T transition at position 50. The single autosomal gene corresponds to tRNA(Ser)7. Comparison of a pair of genes corresponding to tRNA(Ser)4 from D. melanogaster and Drosophila simulans showed that, while gene flanking sequences may diverge considerably by accumulation of point changes, gene sequences are maintained intact. Our data indicate that recombination occurs between non-allelic tRNA(Ser) genes, and suggest that at least some recombinational events may be intergenic conversions.

Animals↗
PubMed1987

Nonrandom chromosomal aberrations and clonal chromosomal evolution in acute leukemia associated with Down's syndrome.

Nine Down's syndrome (DS) children, four with acute leukemia, one with acute leukemia as well as rhabdomyosarcoma, and four with other hematologic disorders, were analyzed for constitutional and acquired chromosomal aberrations. Acquired clonal chromosomal aberrations were identified only in the acute leukemia cases, and four of the five acute leukemia demonstrated numerical and/or structural aberrations involving chromosomes #8, #19, and #21. Of the 11 aneuploid stem cell lines identified in the five acute leukemia cases, trisomy 21, trisomy 8, trisomy 19, and tetrasomy or pentasomy 21 was found in 11, seven, four, and two lines, respectively. The frequent appearance of multiple stem cell lines with common and/or overlapping chromosomal aberrations in acute leukemia cases demonstrates the existence of genomic instability and heterogeneity of the neoplastic cell population, which results from clonal chromosomal evolution. Furthermore, trisomy 19 was identified only with the concurrent presence of trisomy 8, suggesting that the nondisjunction of chromosome #19 probably occurred after that of #8. Trisomy 21 was observed in every aneuploid stem cell line and, in one case, trisomy 21 was maintained in the bone marrow leukemic cells but not in the orbital rhabdomyosarcoma cells, indicating that this constitutional chromosomal aberration is probably crucial for and predisposed to the development of acute leukemia in DS patients. The association of acquired clonal chromosomal aberrations, especially those involving chromosomes #8, #19, and #21, with DS acute leukemia strongly suggests the clinical implication of cytogenetic analysis in the diagnosis of acute leukemia development in DS patients.

Acute Disease↗
PubMed1985

Drosophila melanogaster tRNAVal3b genes and their allogenes.

Drosophila tRNAVal3b genes have been analyzed with respect to their nucleotide sequence and in vitro transcription efficiency. Plasmid pDt78R contains a single tRNA gene derived from the major tRNAVal3b gene cluster at chromosome band 84D. Its sequence corresponds to that of the tRNAVal3b. Two other plasmids, pDt41R and pDt48, each contain a tRNAVal3b-like gene from the minor tRNAVal3b gene cluster at chromosome bands 90BC. They contain the expected CAC anticodon, but their sequence differs from the tRNA at four positions. In homologous cell-free extracts, the tRNAVal3b variant genes in pDt41R and pDt48 are transcribed an order of magnitude more efficiently than the tRNAVal3b gene in pDt78R. However, the variant genes do not appear to contribute significantly to the in vivo tRNA pool [Larsen et al.: Mol. Gen. Genet. 185 (1982) 390-396]. We propose the term allogenes to describe families of related DNA sequences that may code for variant forms of a standard tRNA isoaccepting species.

Chromosome Mapping↗
PubMed1978

Transformation of human embryo cells with the use of cell-free extracts of a human rhabdomyosarcoma cell line (HUS-2): brief communication.

Cell-free extracts of the human rhabdomyosarcoma cell line HUS-2 caused the transformation of human embryo fibroblasts. This transformation included morphologic alteration, karyotypic change, and an increase in culture longevity. With the use of sex markers, multiple karyotypes confirmed that the human embryo fibroblasts were transformed, and the use of cell-free material further suggested the presence of a transforming virus. RNA-dependent DNA polymerase activity in a particle with a specific gravity of 1.16 g/cm3 indicated the presence of an RNA type C virus. Evidence also suggested that the known mammalian type C viruses, routine cytopathic effect-inducing viruses, or mycoplasma were not the agents responsible for the transformation. That both the donor (HUS-2) and converted (HUE-T) cell lines cross-reacted with antisera prepared against HUE-T indicated a common antigen arising in the process of conversion of HUS-2 cells to HUE-T cells.

Animals↗
PubMed1975

Longitudinal impedance of single frog muscle fibers.

The longitudinal impedance of single skeletal muscle fibers has been measured from1 to 10,000 Hz in an oil gap apparatus which forces current to flow longitudinally down the fiber. The impedance observed is purely resistive in some fibers from the semitendinosus muscle and in two fibers from the sartorius muscle. In other fibers from the semitendinosus muscle a small phase shift is observed. The mean value of the maximum phase shift observed from all fibers is 1.07 degrees. The artifacts associated with the apparatus and method are examined theoretically and it is shown that one of the likely artifacts could account for the small phase observed. It is concluded that the longitudinal impedance of skeletal muscle fibers is essentially resistive and that little, if any, longitudinal current crosses the membranes of the sarcoplasmic reticulum.

Animals↗
PubMed1974

Longitudinal impedance of skinned frog muscle fibers.

Longitudinal impedance of skinned muscle fibers was measured with extracellular electrodes and an oil gap method in which a central longitudinal section of fiber is insulated by oil while the ends of the fiber are bathed in conducting pools of relaxing solution. Intact single fibers were isolated from frog semitendinosus muscle and the sarcolemma removed either by mechanical or chemical methods. Stray capacitance across the oil gap was measured after each experiment and its admittance subtracted from the admittance of the fiber and oil gap. Effects of impedance at the ends of the fiber were eliminated by measuring the impedance with two lengths of fiber in the oil gap and subtracting the impedance at the shorter length from that at the longer length. Longitudinal impedance so determined for mechanically and chemically skinned fibers exhibited zero phase shift from 1 to 10,000 Hz, i.e., the longitudinal impedance of skinned fibers is purely resistive. If we assume that our skinned fibers are a model of the sarcoplasm of muscle, we conclude that the equivalent circuit of the sarcoplasm is a resistor.

Animals↗