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Biomedical subjects

F E Wilson

Publications and source records attributed to F E Wilson.

At least 37 records · Page 2Linked to original sources
PubMed1987

Origins and regional distribution of blood flow to the respiratory muscles in conscious sheep.

The blood flow to the portions of the diaphragm (sternal, costal, and crural) and to the external and internal intercostal muscles was measured, using radio-labelled microspheres, in 12 young sheep breathing quietly. We calculated total blood flow and oxygen uptake of the diaphragm (VO2di). We also determined the proportion of diaphragmatic and intercostal muscle blood flow that arose from the descending aorta. Diaphragmatic blood flow (Qdi) was 0.62 +/- 0.04% of cardiac output (mean +/- SEM). VO2di was 1.53 +/- 0.15 ml X min-1 X 100 g-1, and was linearly related to Qdi. When standardized for weight Qdi was 28.3 +/- 1.5 ml X min-1 X 100 g-1, significantly greater than both external intercostal muscle blood flow (18.9 +/- 2.6 ml X min-1 X 100 g-1; P less than 0.05), and internal intercostal muscle blood flow (11.4 +/- 1.4 ml X min-1 X 100 g-1; P less than 0.01). Blood flow to the costal portion of the diaphragm was significantly less than blood flow to the crural portions. There was no difference between flow to these portions and to the sternal portion of the diaphragm. The blood supplying the dorsal-most regions of the diaphragm arose predominantly from the descending aorta. The results suggest that the crural portions work at a higher rate than the costal portions under resting conditions.

Animals↗
PubMed1986

Testosterone sensitivity of the seminal sacs of tree sparrows (Spizella arborea) in different reproductive states.

Testosterone sensitivity of the seminal sacs of castrated tree sparrows from each of three reproductive states was evaluated by measuring the change in seminal-sac mass per unit change in the logarithm of replacement or plasma testosterone. Birds were exposed to exogenous testosterone for 38 days. Replacement doses less than 0.17 mumol or plasma concentrations less than about 0.7 nmol/l did not induce seminal-sac growth in photosensitive castrated birds held on short days, in photosensitive castrated birds transferred from short to long days, or in photorefractory castrated birds retained on long days. Higher replacement doses or plasma concentrations, however, stimulated log dose-dependent growth of the seminal sacs in castrated birds from all three reproductive states. The change in seminal-sac mass per unit change in the logarithm of the dose of replacement testosterone was less (P = 0.0495) in photosensitive castrated birds held on short days than in photosensitive castrated birds transferred to long days. A more critical test of sensitivity (i.e. the change in seminal-sac mass per unit change in the logarithm of mean plasma testosterone concentration) indicated, however, that sensitivity of the seminal sacs to testosterone is independent of reproductive state. That result, when considered in the context of the plasma testosterone profile of intact males during a simulated reproductive cycle, argues that the seminal sacs of sexually quiescent (photosensitive or photorefractory) tree sparrows are small not because of their insensitivity to androgens, but because of a deficiency of circulating androgens.

Animals↗
PubMed1986

A testosterone-independent reduction in net photoperiodic drive triggers photorefractoriness in male tree sparrows (Spizella arborea).

An experiment was performed to determine whether photorefractoriness in male tree sparrows is triggered by a testosterone-independent reduction in net photoperiodic drive or by a photoperiod-induced hypersensitivity of the hypothalamic-pituitary axis to testosterone negative feedback. Photosensitive male tree sparrows were transferred from 8 h light:16 h darkness (8L:16D) to 20L:4D. Birds were castrated bilaterally on day 28 of photostimulation. Beginning on day 33 and weekly thereafter until day 54, birds were given replacement testosterone (0-1.49 mumol) in s.c. polydimethylsiloxane capsules. Plasma samples collected on days 36, 43, 50 and 57 were assayed for LH. Plasma LH concentrations in birds without replacement testosterone were regarded as reflecting net photoperiodic drive in the absence of testosterone feedback, and the slopes of curves relating the logarithm of plasma LH concentration to dose of replacement testosterone were taken as quantitative measures of testosterone feedback sensitivity. The results showed that a testosterone-independent reduction in net photoperiodic drive beginning between days 43 and 50 preceded any change in sensitivity to testosterone negative feedback. Such results provide compelling evidence that a testosterone-independent mechanism triggers the photorefractory state in male tree sparrows.

Animals↗
PubMed1985

Purification of a DNA primase activity from the yeast Saccharomyces cerevisiae. Primase can be separated from DNA polymerase I.

A primase activity which permits DNA synthesis by yeast DNA polymerase I on a single-stranded circular phi X174 or M13 DNA or on poly(dT)n has been extensively purified by fractionation of a yeast enzyme extract which supports in vitro replication of the yeast 2-microns plasmid DNA (Kojo, H., Greenberg, B. D., and Sugino, A. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 7261-7265). Most of this DNA primase activity was separated from DNA polymerase activity, although a small amount remained associated with DNA polymerase I. The primase, active as a monomer, has a molecular weight of about 60,000. The primase synthesizes oligoribonucleotides of discrete size, mainly eight or nine nucleotides, in the presence of single-stranded template DNA and ribonucleoside 5'-triphosphates; it utilizes deoxyribonucleoside 5'-triphosphates as substrate with 10-fold lower efficiency. Product size, chromatographic properties, alpha-amanitin resistance, and molecular weight of the primase activity distinguish it from RNA polymerases I, II, and III. The DNA products synthesized by both primase and DNA polymerase I on a single-stranded DNA template were 200-500 nucleotides long and covalently linked to oligoribonucleotides at their 5'-ends. Addition of yeast single-stranded DNA-binding protein (Arendes, J., Kim, K. C., and Sugino, A. (1983) Proc. Natl. Acad. Sci. U.S. A. 80, 673-677) stimulated the DNA synthesis 2-3-fold.

Bacteriophage phi X 174↗
PubMed1985

Androgen feedback-dependent and -independent control of photoinduced LH secretion in male tree sparrows (Spizella arborea).

Photoperiodic control of gonadotrophin secretion in male tree sparrows was studied by examining changes in plasma LH in castrated birds retained on short daylengths and in castrated birds transferred to long daylengths. Plasma LH concentrations were markedly higher in photostimulated birds than in non-photostimulated birds throughout the 25-day experiment, and implantation of the antiandrogen cyproterone (free alcohol), which should have blocked the action of castration-resistant androgens, did not increase plasma LH in either group. Such results, obtained from birds in which testosterone feedback was inoperative, indicate that the gonadostimulatory effect of long daylengths in intact males must be mediated, at least in part, by an androgen feedback-independent mechanism. To determine whether changes in testosterone feedback facilitate gonadotrophin secretion during photostimulation, two feedback performance characteristics (i.e. set point (minimum concentration of testosterone that suppresses plasma LH) and sensitivity (change in plasma LH per unit change in testosterone)) were quantified by evaluating plasma LH responses of non-photostimulated castrated birds and of photostimulated castrated birds to replacement testosterone (0-4.16 mumol). The data indicate that, in addition to stimulating LH secretion by an androgen feedback-independent mechanism, long daylengths reduce feedback inhibition of LH secretion by increasing the putative set point and decreasing the sensitivity of the testosterone feedback mechanism. The feedback-independent effect is the predominant effect of photostimulation on LH secretion in male tree sparrows.

Animals↗
PubMed1985

An androgen-independent mechanism maintains photorefractoriness in male tree sparrows (Spizella arborea).

A series of experiments was performed to clarify whether photorefractoriness in male tree sparrows is maintained by an androgen-dependent mechanism. Castration did not raise plasma LH in photorefractory males held under a daily photoperiod of 20 h light:4 h darkness (20L:4D). Castrated photorefractory males were implanted with the antiandrogen cyproterone or injected s.c. with the antiandrogen flutamide to determine whether androgens which may be resistant to castration inhibit LH secretion. Neither cyproterone nor flutamide raised plasma LH above values found in castrated control birds. Castrated photorefractory males were treated with testosterone to determine whether plasma LH in photorefractory males is androgen-suppressible. Concentrations of plasma LH were independent of plasma testosterone over a wide range of concentrations. The lack of LH response to castration, to castration coupled with antiandrogen therapy, and to castration coupled with testosterone replacement argues that photorefractoriness in male tree sparrows is maintained by an androgen-independent mechanism.

Animals↗
PubMed1984

Antecedents of periventricular haemorrhage in infants weighing 1250 g or less at birth.

Fifty infants who weighed 1250 g or less at birth were studied with serial real time cerebral ultrasound to evaluate the temporal relation of various perinatal factors to the onset and progression of periventricular haemorrhage (PVH). The significant antecedents of PVH were severe bruising at birth, low birthweight, short gestation, ratio of arterial oxygen pressure (PaO2) to fractional inspired oxygen (FiO2), and haematocrit on admission, hyaline membrane disease, assisted ventilation, pneumothorax, administration of tubocurarine, hypercapnia, hypoxaemia, and hypotension. Case control studies, in which infants with PVH at 26 weeks' and 28 weeks' gestation were compared with matched infants without PVH, confirmed that the antecedents identified were independent of gestational influences. A multivariate discriminant analysis for the antecedents of PVH showed that hyaline membrane disease, hypercapnia, and short gestation correctly classified presence or absence of PVH in 78% of the study group. A similar analysis comparing infants with germinal layer haemorrhage or intraventricular haemorrhage with those who developed intracerebral extension of haemorrhage showed that three factors found on admission (hypothermia, a low PaO2:FiO2 ratio, and severe bruising) combined to classify correctly 90% of the haemorrhages. Our data suggest that prevention of perinatal trauma and asphyxia as well as respiratory illness, especially hyaline membrane disease, and stabilisation of blood gas tensions, blood pressure, and haematocrit within the physiological range, are likely to be the most effective ways of preventing PVH in extremely preterm infants.

Birth Injuries↗
PubMed1983

Computerised nutritional data management in neonatal intensive care.

We report a minicomputer based recording, reporting, and research system for patient data management in the neonatal intensive care unit (NICU). It is moderately priced, transportable, and independent of a central computer. It requires only a desk top and standard power supply, and successfully meets the medical documentation, communication, and research needs of the NICU. The first phase of programme development has enabled us to process growth and nutritional data from infants on complex parenteral and enteral nutrition. The system is well suited to medical users and provides a practical interactive data management system with many potential applications in the NICU.

Australia↗
PubMed1982

Detailed physical mapping of the ribosomal RNA genes of Bacillus subtilis.

Characterization of patterns of ribosomal RNA (rRNA) homology with restriction digests of Bacillus subtilis 168 chromosomal DNA and with cloned DNA sequences has resulted in the construction of a physical map of the rRNA gene sets. There are two types of gene sets which differ in the size of "spacer" DNA sequences separating the 16S and 23S rRNA determinants. It was estimated that there are ten rRNA gene sets on the B. subtilis chromosome.

Bacillus subtilis↗
PubMed1981

Genetic mapping of a linked cluster of ribosomal ribonucleic acid genes in Bacillus subtilis.

A ribosomal ribonucleic acid gene set consisting of genes for 16S, 23S, 5S, and 4S ribonucleic acid species has been genetically mapped to a position between the markers recG13 and abrB74 on the Bacillus subtilis chromosome and designated rrnA. A ribosomal mutation, ksgA, was found to be linked to rrnA. This places rrnA in a region of the chromosome where ribosome-related genes occur but that is not directly adjacent to the major cluster of ribosome-related markers.

Bacillus subtilis↗
PubMed1981

Acute respiratory failure secondary to polymyxin-B inhalation.

A patient with asthma was given aerosol treatment with a solution containing 25 mg of polymyxin-B, and 0.7 ml of isoetherine diluted in 2 ml of isotonic saline. After a few inhalations, he had a severe, near-fatal asthmatic reaction requiring resuscitation, intubation, and mechanical ventilation. The reaction was attributed to the polymyxin-B and occurred despite the patient's receiving maintenance prednisone, 80 mg per day, and the concomitant administration of isoetherine. Possible mechanisms include: (1) bronchial irritant effect or reflex bronchoconstriction, (2) type I (IgE mediated) allergic reaction, or (3) direct histamine release induced by polymyxin, a basic polypeptide known to cause histamine release.

Acute Disease↗