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Biomedical subjects

S Sylvester

Publications and source records attributed to S Sylvester.

12 recordsLinked to original sources
PubMed1998

Interlaboratory concordance of DNA sequence analysis to detect reverse transcriptase mutations in HIV-1 proviral DNA. ACTG Sequencing Working Group. AIDS Clinical Trials Group.

Thirteen laboratories evaluated the reproducibility of sequencing methods to detect drug resistance mutations in HIV-1 reverse transcriptase (RT). Blinded, cultured peripheral blood mononuclear cell pellets were distributed to each laboratory. Each laboratory used its preferred method for sequencing proviral DNA. Differences in protocols included: DNA purification; number of PCR amplifications; PCR product purification; sequence/location of PCR/sequencing primers; sequencing template; sequencing reaction label; sequencing polymerase; and use of manual versus automated methods to resolve sequencing reaction products. Five unknowns were evaluated. Thirteen laboratories submitted 39043 nucleotide assignments spanning codons 10-256 of HIV-1 RT. A consensus nucleotide assignment (defined as agreement among > or = 75% of laboratories) could be made in over 99% of nucleotide positions, and was more frequent in the three laboratory isolates. The overall rate of discrepant nucleotide assignments was 0.29%. A consensus nucleotide assignment could not be made at RT codon 41 in the clinical isolate tested. Clonal analysis revealed that this was due to the presence of a mixture of wild-type and mutant genotypes. These observations suggest that sequencing methodologies currently in use in ACTG laboratories to sequence HIV-1 RT yield highly concordant results for laboratory strains; however, more discrepancies among laboratories may occur when clinical isolates are tested.

Codon↗
PubMed1996

Male fetal progenitor cells persist in maternal blood for as long as 27 years postpartum.

Rare nucleated fetal cells circulate within maternal blood. Noninvasive prenatal diagnosis by isolation and genetic analysis of these cells is currently being undertaken. We sought to determine if genetic evidence existed for persistent circulation of fetal cells from prior pregnancies. Venous blood samples were obtained from 32 pregnant women and 8 nonpregnant women who had given birth to males 6 months to 27 years earlier. Mononuclear cells were sorted by flow cytometry using antibodies to CD antigens 3, 4, 5, 19, 23, 34, and 38. DNA within sorted cells, amplified by PCR for Y chromosome sequences, was considered predictive of a male fetus or evidence of persistent male fetal cells. In the 32 pregnancies, male DNA was detected in 13 of 19 women carrying a male fetus. In 4 of 13 pregnancies with female fetuses, male DNA was also detected. All of the 4 women had prior pregnancies; 2 of the 4 had prior males and the other 2 had terminations of pregnancy. In 6 of the 8 nonpregnant women, male DNA was detected in CD34+CD38+ cells, even in a woman who had her last son 27 years prior to blood sampling. Our data demonstrate the continued maternal circulation of fetal CD34+ or CD34+CD38+ cells from a prior pregnancy. The prolonged persistence of fetal progenitor cells may represent a human analogue of the microchimerism described in the mouse and may have significance in development of tolerance of the fetus. Pregnancy may thus establish a long-term, low-grade chimeric state in the human female.

ADP-ribosyl Cyclase↗
PubMed1995

Molecular responses to hyperoxia in vivo: relationship to increased tolerance in aged rats.

In this study, we have used the rat model of hyperoxia to examine the molecular responses to oxidative stress in lung. We show that in addition to the antioxidant enzyme manganese superoxide dismutase, expression of a variety of stress-responsive genes including heme oxygenase-1, c-fos, c-jun, CAAT-enhancer binding protein (C/EBP)-beta, and C/EBP-delta were increased after hyperoxia. Increased c-fos, c-jun, C/EBP-beta, and C/EBP-delta mRNA expression was correlated with increased DNA binding activity of the transcription factor complexes activator protein 1 and C/EBP in tissue lysates. Because oxidative damage plays an important role in the aging process and little is known about the susceptibility of aged rats to hyperoxia, we also examined the relative tolerance of old rats to hyperoxia. Surprisingly, we observed that aged rats exhibit greater tolerance to hyperoxic stress than young rats. Old rats exhibited decreased arterial oxygen tension when compared to young rats after hyperoxia exposure. This increased tolerance coincided with decreased albumin levels in bronchoalveolar lavage and the delayed onset of activation of transcription factors and expression of oxidative stress-inducible genes in old rats. Transcription factor and stress-response gene activation may serve as useful molecular markers for oxidant lung injury.

Aging↗
PubMed1989

Alternative positions in the second stage of labour: a randomized controlled trial.

A controlled clinical trial involving 151 primigravidae and 18 midwives assessed the acceptability and outcome of second-stage labour in upright positions. Women who had no specific antenatal preparation and preferences regarding labour positions were managed either conventionally (semi-recumbent and lateral), or encouraged to adopt upright positions (squatting, kneeling, sitting or standing) according to individual preference. Of the women allocated to the upright position 74% completed the second stage upright, with kneeling being the most favoured position, but squatting was, despite all assistance, too difficult to maintain. Adoption of upright positions resulted in a higher rate of intact perineums. There was a clinically apparent reduction of forceps deliveries in the upright group which influenced midwives' attitudes. Moving the parturient from recumbent to upright positions was often perceived to be beneficial when there was slow progress. Estimated blood loss was similar in the two groups, as was the condition of the newborn (Apgar score and umbilical artery pH). Alternative positions in the second stage of labour, in particular kneeling, are achievable even without specific birth aids and antenatal preparation. They appear safe, acceptable to most parturients and their midwives, and are easily integrated into modern labour ward practice; they may have clinical advantages which need further investigation.

Apgar Score↗
PubMed1980

Inherited, early onset, insulin-requiring diabetes mellitus of Keeshond dogs.

Spontaneous diabetes mellitus has been characterized in a line of nonobese purebred keeshond dogs as an insulin-requiring hereditary disorder with onset at between 2 and 6 mo of age. Diabetic dogs developed cataracts, became ketotic, hyperglycemic, hypercholesterolemic, lipemic, and hypoinsulinemic. Basal glucagon, cortisol, and T4 serum concentrations and responses to ACTH, TSH, and arginine were normal. Light microscopic studies of the pancreas by immunocytochemical procedures revealed the absence of islet B cells, the presence of A cells, and solitary B cells. Diabetic dogs had poor fecundity, and a single puberal diabetic male had poor semen quality and was unable to sire pups. Parents of diabetics and nondiabetic siblings were normal. This spontaneous form of diabetes mellitus, with similar lesions to the insulin-dependent diabetes of people, will be a valuable aid to comparative biomedical research of diabetes mellitus.

Animals↗
PubMed1976

Enzymatic sulfation of steroids: I. The enzymatic basis for the sex difference in cortisol sulfation by rat liver preparations.

Liver cytosols from female rats contained 6-8 times as much cortisol sulfotransferase activity as those from males. The reaction product, with both sexes, appeared to be cortisol-21 sulfate. Liver cytosols from male and female rats showed different substrate preferences when tested with cortisol, estradiol-17beta, testosterone, and dehydroepiandrosterone, suggesting that they contained different steroid sulfotransferases. Fractionation of cytosols from female rats on DEAE Sephadex A-50 columns resolved 3 steroid sulfotransferases, or families of steroid sulfotransferases (STI, STII, and STIII). These enzymes exhibited different substrate preferences. STI and STIII had the greatest preferences for cortisol, although none of the enzymes was restricted to the glucocorticoid. Fractionation of cytosols from males resolved 2 sulfotransferases which eluted at salt concentrations identical to STII and STIII from females. Study of the development of cortisol sulfotransferase activity with age showed little enzyme activity in rats of either sex at 2 days after birth. Enzyme activity developed in parallel in both sexes until 30 days after birth. Then the sulfotransferase activity began to rise in females and to drop in males. By day 50-55 both sexes attained adult enzyme levels. STII was the major enzyme in all immature animals. STIII was also present, but STI was absent. In male rats STIII activity began to rise by day 30. Soon after, STII activity began to drop. By day 55 adult male patterns developed. STI was the major enzyme in females by day 30. In ensuing days all 3 enzyme levels rose, until by day 50 adult enzyme patterns and levels were attained. The data suggest that the ovaries stimulated production of all 3 sulfotransferases and that the testes suppressed production of STII (and perhaps STI). Preliminary studies with gonadectomized rats supported the suppressive role of the testes, but suggested that the ovaries were not the only factor controlling sulfotransferase production in female rats.

Age Factors↗
PubMed1976

Enzymatic sulfation of steroids: II. The control of the hepatic cortisol sulfotransferase activity and of the individual hepatic steroid sulfotransferases of rats by gonads and gonadal hormones.

Ovariectomy has relatively little effect on hepatic cortisol sulfotransferase activity (HCSA) in female rats, diminishing it only 30%. On the other hand, castration more than doubles HCSA in males. HCSA is due to 3 steroid sulfotransferases, STI, STII, and STIII. Its dimunition in ovariectomized rats is due to decreased STI and STII. Castration of males results in elevation of STII. Thus, ovaries appear to stimulate STI and STII production and testes appear to inhibit production of STII and perhaps STI. Studies with testosterone and estradiol-17beta support a role for sex hormones as mediators of gonadal effects on HCSA, by stimulating or inhibiting production of the individual enzymes. Estradiol-17beta administration reverses the effect of ovariectomy on HCSA. Testosterone administration to intact or castrated females decreases HCSA by 60-70%, due to disappearance of all STI and most STII activity. Thus, androgen administration appears to suppress both STI and STII production. In intact males testosterone administration elevates HCSA 70-80% due to increased STIII. Estradiol-17beta administration to intact or castrated males elevates HCSA 9-10-fold. In intact animals this is due to elevated STI and STII but not STIII. In castrates all three enzymes are elevated by the estrogen.

Animals↗