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Biomedical subjects

A Leung

Publications and source records attributed to A Leung.

At least 127 records · Page 7Linked to original sources
PubMed1979

Analysis of genetic complementation by whole-cell microtechniques in fibroblast heterokaryons.

A whole-cell microtechnique for the determination of complementation of human metabolic disorders is presented. This procedure permits the isolation of individual multinucleate cells produced by cell fusion for the quantitative evaluation of complementation. Mutant fibroblasts with a deficiency of propionyl-CoA carboxylase activity (EC 6.4.1.3) that had been mapped to complementation groups pcc and bio were used to evaluate the microtechnique. Complementation was monitored by the determination of [14C]propionate incorporation into cellular macromolecules. Single cells or a small number of cells were isolated from plastic film dishes after radioactive incubation by cutting out the portion of the plastic film holding the desired cells. Isotope incorporation was linear in 10-50 unfused cells and in 10-50 fused normal cells containing five or more nuclei. There was also a direct correlation between the nuclear content of cells and the amount of isotope incorporated. Three pcc and two bio mutants were fused in pairwise combinations by means of polyethylene glycol and complementation was determined by isotope incorporation in sets of 50 multinucleate cells, each cell isolated individually. The results agreed with autoradiographic data for both complementing and noncomplementing strains. The method is quantitative and gives severalfold higher sensitivity than current procedures. The method can be applied to the complementation analysis of a wide variety of inherited disorders of intermediary metabolism.

Acyl Coenzyme A↗
PubMed1977

Arginine esterase and lysosomal hydrolases in liver from cystic fibrosis subjects.

The total activity and isoelectric focusing patterns of arginine esterase, cathepsin B1, and several lysosomal hydrolases were normal in liver from two patients with cystic fibrosis. No abnormalities were observed in values for pH optimum, Km, and Vmax for arginine esterase and cathepsin B1 in liver from cystic fibrosis patients compared to those values for liver from the control subject. Soybean trypsin inhibitor at concentrations up to 100 microgram/ml had no effect on liver arginine esterase or cathepsin B1.

Adolescent↗
PubMed1976

Simplified fluorometric assay for diphenylhydantoin in plasma.

The fluorometric benzophenone procedure for diphenylhydantoin has been simplified by eliminating the need for preliminary extraction of plasma with an organic solvent. Assays are done directly on 0.2 ml of plasma by treating it with alkaline permanganate to form benzophenone, extracting the benzophenone with heptane, and then shaking the heptane layer with sulfuric acid and measuring the fluorescence of the acid layer. The assay is highly reproducible, and adequately sensitive to detect 1 mug of the drug per milliliter of plasma. Fluorometric and gas-liquid chromatographic assays of 154 plasmas gave results that were not significantly different, even in the presence of phenobarbital, other barbiturates and anticonvulsant drugs, or of various tranquilizers and other commonly used drugs. The assay is rapid, the unit cost per assay low.

Chromatography, Gas↗
PubMedDate not supplied

Diagnostic value of sperm function tests and routine semen analyses in fertile and infertile men.

The results of routine semen analyses, the zona-free hamster oocyte penetration test, the hypoosmotic swelling test, and semen adenosine triphosphate levels were studied in 66 fertile and 130 infertile men. Multivariate discriminant analysis demonstrated that routine semen parameters including semen volume, sperm count, percent sperm motility, and percent normal spermatozoa in combination could predict the fertility of these patients with 70.4% accuracy. Of the three sperm function tests evaluated, the zona-free hamster oocyte penetration test and the hypoosmotic swelling test were selected by the multivariate discriminant analysis as variables capable of providing significant information on the fertility status of the patients. However, the addition of the results of these two tests to the routine semen analysis did not significantly improve the predictability of fertility. The overall correct prediction rate was 77.6% after incorporation of the results of these two sperm function tests. In this group of subjects, the presently available sperm function tests did not predict the fertility status of a patient with a high degree of accuracy.

Diagnostic Tests, Routine↗
PubMedDate not supplied

Suppression of defective-sporulation phenotypes by mutations in transcription factor genes of Bacillus subtilis.

Mutations in the Bacillus subtilis major RNA polymerase sigma factor gene (rpoD/crsA47) and a sensory receiver gene (spoOA/rvtA11) are potent intergenic suppressors of several stage 0 sporulation mutations (spoOB, OE, OF & OK). We show here that these suppressors also rescue temperature-sensitive sporulation phenotypes (Spots) caused by mutations in RNA polymerase, ribosomal protein, and protein synthesis elongation factor EF-G genes. The effects of the crsA and rvtA suppressors on RNA polymerase and ribosomal protein spots mutations are similar to those previously described for mutations in another intergenic suppressor gene rev. We have examined the effects of rvtA and crsA mutations on the expression of sporulation-associated membrane proteins, including flagellin and penicillin binding protein 5* (PBP 5*). Both suppressors restored sporulation and synthesis of PBP 5* in several spoO mutants. However, only rvtA restored flagellin synthesis in spoO suppressed backgrounds. The membrane protein phenotypes resulting from the presence of crsA or rvtA suppressors in spoO strains suggests that these suppressors function via distinct molecular mechanisms. The rvtA and crsA mutations are also able to block the ability of ethanol to induce spoO phenocopies at concentrations of ethanol which prevent sporulation in wild type cells. The effects of ethanol on sporulation-associated membrane protein synthesis in wild type and suppressor containing strains have been examined.

Bacillus subtilis↗
PubMedDate not supplied

Association of rheumatoid arthritis and primary osteoarthritis with changes in the glycosylation pattern of total serum IgG.

Rheumatoid arthritis (RA) is a widely prevalent (1-3%) chronic systemic disease thought to have an autoimmune component; both humoral and cellular mechanisms have been implicated. Primary osteoarthritis (OA) is considered to be distinct from rheumatoid arthritis, and here damage is thought to be secondary to cartilage degeneration. In rheumatoid arthritis, immune complexes are present that consist exclusively of immunoglobulin, implying that this is both the 'antibody' (rheumatoid factor [RF]) and the 'antigen' (most commonly IgG). Autoantigenic reactivity has been localized to the constant-region (C gamma 2) domains of IgG. There is no evidence for a polypeptide determinant but carbohydrate changes have been reported. We have therefore conducted a study, simultaneously in Oxford and Tokyo, to compare in detail the N-glycosylation pattern of serum IgG (Fig. 1) isolated from normal individuals and from patients with either primary osteoarthritis or rheumatoid arthritis. The results, which required an evaluation of the primary sequences of approximately 1,400 oligosaccharides from 46 IgG samples, indicate that: (1) IgG isolated from normal individuals, patients with RA and patients with OA contains different distributions of asparagine-linked bi-antennary complex-type oligosaccharide structures, (2) in neither disease is the IgG associated with novel oligosaccharide structures, but the observed differences are due to changes in the relative extent of galactosylation compared with normal individuals. This change results in a 'shift' in the population of IgG molecules towards those carrying complex oligosaccharides, one or both of whose arms terminate in N-acetylglucosamine. These two arthritides may therefore be glycosylation diseases, reflecting changes in the intracellular processing, or post-secretory degradation of N-linked oligosaccharides.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Paediatric palliative care: a lack of research-based evidence.

Providing the best possible care for the child and family is paramount to health professionals working in paediatric palliative care. However, there is little research which enables practitioners to question their current practice. There are concerns about conducting research on children receiving palliative care at such a sensitive time for the child and his/her family. These concerns must be considered against the growing demand for clear standards and guidelines for practice within health care. According to the Department of Health (DoH) there is no place within the modern healthcare system for the adoption of unproven theories or outdated care (DoH, 1998). While no-one would question the dedication and care being delivered to children and their families by well-trained staff, the lack of research is a cause for concern. A group of students undertaking a degree module in paediatric palliative care identified the lack of literature and research in this area and have undertaken a review of the available literature.

Child↗
PubMedDate not supplied

Reproductive aging in the Brown Norway rat is characterized by accelerated germ cell apoptosis and is not altered by luteinizing hormone replacement.

Reproductive aging in the male Brown Norway (BN) rat is characterized by decreased Leydig cell steroidogenesis associated with seminiferous tubule dysfunction. This could be a result of a combination of a primary testicular defect and a secondary hypothalamic pituitary dysfunction. In the present study, we determined in the BN rat whether germ cell loss occurred via apoptosis. We then defined the age of onset of Leydig cell dysfunction and germ cell loss and examined whether chronic luteinizing hormone (LH) replacement would delay or prevent reproductive aging. Plasma hormone levels, testicular sperm concentrations, and germ cell apoptosis were studied in 6, 9, 12, 15, 18, and 21-month-old BN rats. Beginning at 15 months, testicular weight, sperm concentration, total sperm counts, plasma testosterone, LH, and inhibin decreased, whereas the proportion of regressed testes and plasma follicle-stimulating hormone (FSH) levels increased with aging. Accelerated germ cell apoptosis involving spermatogonia, preleptotene and pachytene spermatocytes, and spermatids was evident in some tubules of the relatively normal testes from 21-month-old rats. In the regressed testes, complete cessation of spermatogenesis occurred. The apoptotic index was higher in the testes of old (21-month-old) rats in particular at stages XII-XIV when compared with younger animals. Chronic LH replacement (0.5 microg i.p. twice per day) administered to 15-month-old BN rats for 6 months did not alter plasma hormone levels, testes weight, sperm concentration or content, or the germ cell apoptotic index. In the control group, 3 out of 10 testes were regressed, whereas in the LH-replaced group, only 1 out of 12 testes was regressed. We show in this study that early reproductive aging in the BN rat began at around 15 months. Germ cell loss associated with aging occurs via apoptosis. Replacement therapy with LH for 6 months does not decrease or delay the testicular dysfunction associated with aging. It is unlikely that hypothalamic-pituitary dysregulation is the major cause of testicular aging.

Aging↗
PubMedDate not supplied

Long-term effects of triptolide on spermatogenesis, epididymal sperm function, and fertility in male rats.

Prior studies had suggested that triptolide, a diterpene triepoxide isolated from a Chinese medicinal plant, might be an attractive candidate as a post-testicular male contraceptive agent. Despite the promise that triptolide would not affect testis function, nagging concerns remained that a delayed onset of testicular effect might exist. The objectives of this study were to assess the effects of relatively longer treatment duration of triptolide on fertility, spermatogenesis, and epididymal sperm pathophysiology; and to evaluate the reversibility of these effects after the cessation of treatment. Adult male Sprague-Dawley rats were fed daily with either 30% gum acacia as a vehicle control (n = 12) or 100 microg/kg body weight (BW) of triptolide for 82 days (n = 12) followed by a recovery period of up to 14 weeks (n = 6). At the end of the treatment period, all rats treated with triptolide were sterile. Cauda epididymal sperm content decreased by 84.8% and sperm motility was reduced to zero. In addition, virtually all cauda epididymal sperm in the triptolide-treated group exhibited severe structural abnormalities. The most striking changes observed were head-tail separation, premature chromatin decondensation of sperm nuclei, a complete absence of the plasma membrane of the entire middle and principle pieces, disorganization of the mitochondrial sheath, and aggregation of many sperm tails. Longer treatment duration of triptolide also affected spermatogenesis, with marked variability in the response of individual animals. The degree of damage ranged from apparently normal-looking seminiferous tubules to flattened seminiferous epithelium lined by a single layer of cells consisting of Sertoli cells and a few spermatogonia. Affected tubules exhibited intraepithelial vacuoles of varying sizes, multinucleated giant cells, germ cell exfoliation, and tubular atrophy. Recovery occurred as early as 6 weeks after cessation of treatment. By 14 weeks, 4 out of 6 triptolide-treated males were fertile and the females that were impregnated by 3 out of 4 triptolide-treated male rats produced apparently normal litters. These results suggest that triptolide has 2 phenotypic effects on mature and maturing germ cells. The first action appears earlier and manifests mainly in epididymal sperm. The second action presumably is directly on germ cells in testis and causes a variable impairment of spermatogenesis that may not be completely reversible. It is unclear if the earlier effect is a delayed manifestation of subtle testicular injury or post-testicular action.

Animals↗
PubMedDate not supplied

Evaluation of human sperm hyperactivated motility and its relationship with the zona-free hamster oocyte sperm penetration assay.

The authors studied hyperactivated motility of human spermatozoa as a method of evaluating capacitation by examining its relationship to results of zona-free hamster oocyte sperm penetration assays (SPA) of semen samples from 50 men attending the infertility clinic. Hyperactivated motility was assessed in the seminal plasma and after swim-up preparation of spermatozoa at 1, 3, and 24 hours of incubation in capacitation media using a computer-assisted semen analysis system equipped with a hyperactivation module. Hyperactivated motility reached a peak at 1 hour and plateaued at 3 hours. The percentage of spermatozoa in seminal plasma with star-spin hyperactivated motility was significantly lower in the group showing no penetration in the SPA. The hyperactivated motility characteristics did not differ in the groups with positive or negative penetration. Correlation analysis failed to show any significant relationship between the hyperactivated motility parameters and SPA score. When the hyperactivated motility characteristics were compared in samples with normal and abnormal semen analyses, the total percentage of spermatozoa with hyperactivated motility and the percentage with star-spin at 3 hours were significantly lower in the group with abnormal semen analysis. The data indicate that lower hyperactivated motility of spermatozoa was found in patients with a score of zero for SPA and in patients with abnormal semen analysis. It was concluded that although no direct correlations were found between the results of SPA and hyperactivated motility, evaluating hyperactivated motility may still be useful as an early indicator of capacitation abnormalities of human spermatozoa not measured by SPA.

Animals↗
PubMedDate not supplied

Early effects of vasectomy on testicular structure and on germ cell and macrophage apoptosis in the hamster.

This study provides quantitative information on the early (up to 3 months) effects of vasectomy on apoptosis in the hamster testis. Groups of five adult male golden hamsters were either bilaterally vasectomized or sham-operated and sacrificed at intervals of 3, 6, and 12 weeks after surgery. In all three postvasectomy groups, testis weight and testicular and plasma testosterone (T) levels were not different from controls. Spermatogenic alterations, ranging from tubules with mild intraepithelial vacuoles to almost completely atrophied tubules, were detected in samples of 1 of 5 testes both at 3 and 12 weeks after vasectomy. Histometric analysis of testicular tissues at 3, 6, and 12 weeks in the postvasectomy groups showed no discernible effect of vasectomy on the absolute volumes of seminiferous tubules, tubular lumen, and total Leydig cells when compared to respective controls. In situ analysis of germ-cell apoptosis, characterized by 3'-end-labeling immunocytochemistry, revealed a significant increase (2.5-fold) in germ-cell apoptosis at stages XIII-I, involving primarily the dividing spermatocytes after 3 weeks of vasectomy. Apoptotic index was not changed from sham-operated animals at 6 and 12 weeks postvasectomy. Interestingly, a very high incidence of macrophage apoptosis was detected in the samples of three out of five testes in the 12 weeks postvasectomy group (39.3%) compared to that of controls (0.8%). These results demonstrate that vasectomy has little or no detrimental effect on the morphologic characteristics of the spermatogenesis or intratesticular concentrations of testosterone in the majority of the animals studied up to 12 weeks postsurgery, although vasectomy transiently (3 weeks postsurgery) activated germ-cell apoptosis, involving dividing spermatocytes at stages XIII-I.

Animals↗