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Biomedical subjects

T Wilson

Publications and source records attributed to T Wilson.

At least 19 recordsLinked to original sources
PubMed1992

A proposed function for spermine and spermidine: protection of replicating DNA against damage by singlet oxygen.

Like all aliphatic amines, the polyamines spermine and spermidine are physical quenchers of singlet molecular oxygen (1O2*). The rate constants of these processes were determined in vitro with photochemically generated 1O2* and the hydrocarbon rubrene as substrate, in pyridine. At millimolar concentration, spermine and spermidine should quench 1O2* in vivo and prevent it from damaging DNA. It is proposed that a biological function of polyamines is the protection of replicating DNA against oxidative damage.

DNA↗
PubMed1992

Spermine and spermidine protection of plasmid DNA against single-strand breaks induced by singlet oxygen.

Oxidative damage to DNA induced by singlet molecular oxygen (1O2*) includes single-strand breaks, which the biologically occurring 1O2* quenchers spermine and spermidine are shown to prevent. These polyamines at a physiological concentration (10 mM) reduce the percentage of the open circular form of pBR322 plasmid DNA, which is generated at the expense of the native supercoiled form when the plasmids are incubated with a chemical source of 1O2*, the water-soluble endoperoxide of 3,3'-(1,4-naphthylidene)dipropionate. Spermine and spermidine can be expected to protect DNA against other damaging effects of 1O2*.

DNA↗
PubMed1992

The effect of ellagic acid on xenobiotic metabolism by cytochrome P-450IIE1 and nitrosodimethylamine mutagenicity.

Ellagic acid (EA) is an inhibitor of the in vitro mutagenicity of N-nitrosodimethylamine (NDMA) in Salmonella typhimurium strain TA100 using pyrazole-induced rat liver 9000 x g supernatant (S-9). In order to understand this activity, the effect of EA on the metabolic hydroxylation of 4-nitrophenol, a substrate, as is NDMA, for cytochrome P-450IIE1 was studied using pyrazole induced rat S-9 and microsomal protein. It is shown that EA has an inhibitory effect on 4-nitrophenol hydroxylase with both enzyme preparations. This effect on cytochrome P-450IIE1 may be responsible, at least in part, for the inhibition of NDMA mutagenicity by EA.

Animals↗
PubMed1992

Surgical management of urethral strictures based on etiology. Where do urethral stents fit in?

Recent studies in the urologic literature indicate a renewed interest in the management of urethral stricture disease. Specifically, urologists are now treating all types of urethral strictures regardless of location, etiology, or extent with methods other than primary urethroplasty or direct vision internal urethrotomy (DVIU), i.e., balloon dilation or urethral stenting. To see which patients might best be managed by these new modalities, we reviewed our experience with urethral strictures at LAC-USC Medical Center.

Humans↗
PubMed1992

Serum concentrations of secretory IgA in pregnancies delivering at term or preterm.

Secretory component (SC) is a phospholipase A2 inhibitor possibly associated with pregnancy maintenance and in serum is bound either to IgA (sIgA) or IgM (sIgM). To determine if serum secretory component levels a) increase during pregnancy, b) fall as term approaches, c) are low in women who will deliver prematurely, serum sIgA was measured at "booking in" and related to weeks of gestation and length of gestation at subsequent noninduced delivery. Levels of sIgA increased during pregnancy; sIgA increased from a non-pregnant value of 1.6 nM +/- 0.2 (mean +/- SEM) to 2.8 nM +/- 0.3 at the end of the second trimester, then fell significantly between 31-34 weeks. Delivery before 37 weeks was associated with significantly reduced serum sIgA levels, particularly in women who delivered before 32 weeks and in whom sIgA concentrations were similar to those of nonpregnant women.

Female↗
PubMed1992

The impact of status asthmaticus practice guidelines on patient outcome and physician behavior.

This study assesses the effects of a status asthmaticus guideline on patient outcome and pediatrician behavior in a staff model health maintenance organization (HMO). The guidelines were drafted by an asthma specialist in the HMO and then discussed with key clinical personnel. A preprinted protocol order form was developed to help implement the guideline into clinical practice. The medical records of pediatric patients admitted to the hospital with status asthmaticus before (N = 67) and after (N = 59) guideline development and implementation were reviewed. This study demonstrates that locally developed, treatment-specific guidelines based on scientific evidence and combined with a staff consensus process and a user-friendly protocol form can influence physician behavior and patient outcome positively.

Adolescent↗
PubMed1992

Decreased inhibition by gravidin of arachidonate release from transformed compared to nontransformed cells.

1. Gravidin (a phospholipase A2 inhibitor) reduced the release of arachidonic acid from human lymphocytes by 51% at 10(-8) M. 2. Under normal culture conditions, nanomolar gravidin caused a significant reduction in the release of free arachidonic acid from human lymphocytes or nontransformed fibroblasts but in transformed cells, nanomolar gravidin was ineffective. 3. Inhibition of arachidonate release appeared to be related to rate of growth as inhibitory effects of gravidin on Jurkat cells and HL-29 cells could be observed if the cells were cultured under conditions where DNA synthesis was low. 4. The reported disparate effects of lipocortin on cell phospholipase A2 activity may be reconciled if DNA synthesis is investigated.

Arachidonic Acid↗
PubMed1992

A blue fluorescent protein from a yellow-emitting luminous bacterium.

Vibrio fischeri strain Y1 emits yellow light in vivo due to the participation of a yellow fluorescent protein (YFP) in the luciferase reaction. In this study it was found that the organism also produces a protein (referred to as Y1-BFP) emitting strong blue fluorescence. Its molecular weight, about 25 kDa, is the same as or very close to that of YFP. The fluorescence excitation and emission maxima of the purified Y1-BFP are at 416 and 461 nm, respectively, and the fluorescence lifetime is 12.5 ns at 2 degrees C. The molar extinction coefficient of Y1-BFP at 416 nm was estimated to be approx. 9500. With the homologous luciferase, Y1-BFP decreases the intensity and rate of decay in the in vitro reaction but has no effect on its emission spectrum (in contrast to YFP, which has a striking effect on the spectrum). With luciferase isolated from Vibrio harveyi, however, Y1-BFP causes a small blue-shift (approximately 10 nm) in the emission of the enzyme catalyzed reaction, whereas YFP has no effect on the emission spectrum.

Bacterial Proteins↗
PubMed1991

Gravidin, an endogenous inhibitor of phospholipase A2 activity, is a secretory component of IgA.

Gravidin, a phospholipase inhibitor characterised previously from amniotic fluid, was partially sequenced at the N-terminal and found to be identical to secretory component of human IgA. Inhibition of antiphospholipase activity was observed after incubation of gravidin with monoclonal antibody to human secretory component. Secretory component isolated from human saliva and breast milk was found to inhibit arachidonic acid release from human lymphocytes. It was concluded that gravidin is secretory component of IgA.

Amino Acid Sequence↗
PubMed1991

Effects of ranitidine, given t.d.s., on intragastric and oesophageal pH in patients with gastrooesophageal reflux.

The purpose of this study was to determine the effects of 150 mg ranitidine, 300 mg ranitidine or placebo, administered every 8 h, on gastro-oesophageal pH and heartburn parameters in reflux patients. Twelve symptomatic reflux patients received each of the three treatments in a randomized, double-blind, crossover fashion. Intragastric and oesophageal pH were monitored continuously for a 24 h period. Meals were standardized, consumed at set times and patients were allowed to recline and sleep from 23.00 hours until 06.00 hours only. The gastric record was analysed for the percentage of time that the pH was greater than or equal to 4. The oesophageal record was analysed for acid contact time (percentage time (%) pH less than or equal to 4.0) and reflux episode frequency. Finally, patients recorded each new episode of heartburn and graded daytime heartburn severity at the end of each hour. Ranitidine increased the median (%) time that the intragastric pH remained at or above 4, from 4.5 (placebo) to 33.9% (150 mg dose) and 33.3% (300 mg dose). Ranitidine dose-dependently reduced the median 24-hour oesophageal acid contact time from 13.3% (placebo) to 6.8% (150 mg dose) and 2.5% (300 mg dose). The 300 mg dose significantly reduced daytime heartburn episode frequency and severity while the 150 mg dose reduced heartburn severity only. We conclude that 150 and 300 mg doses of ranitidine administered every 8 h have major, sometimes dose-dependent effects on the objective parameters and symptoms of gastro-oesophageal reflux.

Adult↗
PubMed1991

Elevated 18-hydroxy-corticosterone in inbred salt-sensitive rats.

Rats susceptible to the hypertensive effect of dietary salt (SS/Jr) have excess 18-hydroxydeoxycorticosterone (18-OH-DOC) and 19-nor-DOC compared to control rats (SR/Jr). This may be caused by an abnormal adrenal 11 beta-hydroxylase, which catalyzes the 11 beta, 18, and 19-hydroxylations of DOC. A comparison of the urinary products of this enzyme including 18-OH-DOC, 19-nor-DOC, corticosterone (B), and 18-OH-B have not been described in the SS/Jr. Therefore, these steroid products were measured at 7 and 12 weeks of age in 36 weanling male and female, SS/Jr and SR/Jr (n = 9 in each group), on a low-salt diet. In both the male and female SS/Jr urinary free levels of 18-OH-DOC, 19-nor-DOC, and 18-OH-B were elevated, while B was not different at 6 and 10 weeks of age. The largest increases were in 18-OH-B levels, and these levels correlated with 18-OH-DOC and B but not 19-nor-DOC. The high degree of correlation between these steroids probably reflects their closely related dependence on adrenal 11 beta-hydroxylase biosynthesis.

18-Hydroxycorticosterone↗
PubMed1990

Aortic occlusion and vascular isolation allowing avascular hepatic resection.

Occlusion of the supraceliac abdominal aorta and hepatic vascular isolation were employed in a series of 15 patients as a definitive method to allow avascular hepatic resection. The series was compared with an earlier group of patients treated conventionally. In the avascular hepatic resection group there was no mortality; hypotension did not occur at the time of hepatic vascular isolation; rapid, accurate excision of the hepatic lesions could be achieved in a bloodless field; resection of midline lesions and those involving the great veins was possible; and "segmentectomies," or resections crossing segmental boundaries, could be performed where previously formal hepatic lobectomies were required. Concomitantly, the greatest amount of uninvolved hepatic parenchyma remained in situ. There was increased ease of operative management, reduced blood loss, and reduced operating time (mean, 2.8 hours).

Adult↗
PubMed1990

Phospholipases in human parturition.

Phospholipase A2 plays a major role in controlling PG synthesis. Regulation of the activity of this enzyme probably holds the key to the onset of labour. Both PLA2 and PLC can contribute to arachidonate release and PG production in cells, but PLA2 appears to be the main role of synthesis. Phospholipase A2 and PLC can be activated independently of each other; an influx of external calcium is required for PLA2 activation. It is suggested that PLC contributes to PG synthesis through product stimulation of protein kinase C which maintains a pool of free arachidonate by inhibiting reincorporation into the cell membrane. The regulatory role for lipocortin in phospholipase inhibition is controversial and unlikely to be relevant to the onset of labour.

Arachidonic Acids↗