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Biomedical subjects

R G White

Publications and source records attributed to R G White.

At least 55 records · Page 3Linked to original sources
PubMed1989

Advanced abdominal pregnancy--a review of 23 cases.

Twenty-three cases of advanced abdominal pregnancy were managed at Harare Hospital, Zimbabwe, over a 10 year period. The incidence was 1 in 9500 total deliveries and 1 in 60 ectopic pregnancies. There were no maternal deaths but perinatal mortality was 83%. Of the 5 liveborn infants, 4 had pressure deformities and 3 were small for gestational age. There was one neonatal death due to pulmonary hypoplasia. Diagnosis is difficult and is often first suggested by failed induction of labour in a case of presumed intrauterine death. Abnormal presentation of the fetus, displacement of the cervix and anaemia were the most common clinical features. At operation, haemorrhagic shock occurred more frequently when attempts were made to remove the placenta. However, the average post-operative stay of patients who had placental tissue left was 22.4 days compared with 8.3 days for those who had the placenta removed. It is recommended that the placenta be removed only if its entire blood supply can be ligated. Partial removal of the placenta is the most hazardous procedure and should not be undertaken.

Female↗
PubMed1989

Localization of cutaneous lesions in digital images.

Digital imaging could potentially provide a rapid, objective, and quantitative means of detecting changes in important skin conditions, especially the dysplasic nevus syndrome. Image analysis techniques can be applied to digital images to automate the search for changes in moles or other features. Consistent determination of lesion boundaries, perimeter, and area in digital images is a vital first step in this process. In this paper, we show how bilaterally symmetric Laplacian-of-a-Gaussian filters can be used to recover the borders of selected lesions while remaining robust with respect to factors such as the camera point spread function and additive noise. Tests on real and synthetic images demonstrate that lesion borders, area, and perimeter can be obtained with a high degree of reliability. Boundaries are routinely found to within +/- 0.2 pixels, and area and perimeter measurements vary by less than 10% when imaging spot targets and actual cutaneous lesions under a realistic range of experimental conditions.

Dysplastic Nevus Syndrome↗
PubMed1988

Platelet-activating factor induces glycogen degradation in fetal rabbit lung in utero.

The role of platelet-activating factor (PAF, 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in initiating glycogen breakdown in the fetal rabbit lung was assessed by intraperitoneal administration of this potent ether-linked glycerophospholipid. Forty-five min after in utero injection of PAF (2.5 X 10(-7) mol), fetal pulmonary and hepatic glycogen concentrations were reduced from 326 to 256 and from 9.8 to 6.6 micrograms of glycogen/mg protein, respectively. Glycolytic activity was similarly increased as judged by an elevation of lactate (2-fold) in lung, liver, and plasma upon PAF injection. These actions of PAF were dose- and time-dependent. The glycogenolytic response did not occur when an equimolar dose of the inactive enantiomer, D-PAF was injected. Pretreatment of the fetus with a specific PAF receptor antagonist, SRI-63-441, prevented the PAF response. We have previously demonstrated (Hoffman, D. R., Truong, C. T., and Johnston, J. M. (1986) Biochim. Biophys. Acta 879, 88-96) that PAF biosynthesis and PAF concentrations increase significantly on day 24 of fetal rabbit lung development. A concurrent decrease in pulmonary glycogen concentration at this point of gestation is potentially reflective of the PAF-induced action. Thus, these observations would suggest a role for PAF in the normal physiology of fetal lung maturation.

Animals↗
PubMed1988

Energy expenditure and protein turnover in three species of wallabies (Marsupialia: Macropodidae).

Relationships between basal and fed metabolic rates and whole-body protein turnover rates were examined in three species of wallabies, the red-necked pademelon (Thylogale thetis), parma wallaby (Macropus parma) and tammar wallaby (M. eugenii). There were no significant differences among wallaby species in basal metabolic rate (BMR) which was 30% below eutherian mammals. However, the fed metabolic rate of the tammar was lower than that of the other two species (P less than 0.05), as was the protein turnover rate (P less than 0.01) which is consistent with its lower voluntary feed intake and with its lower maintenance nitrogen requirement. Protein turnover rates in the wallabies were 23-47% lower than in eutherian mammals. Similarly, protein synthesis made a lower contribution to fed metabolic rates in the wallabies (7-8%) than in eutherians (17-25%). Thus, compared with several eutherian species, macropodid marsupials have low rates of both energy and protein metabolism, but within the macropodids there is not necessarily a close link between basal metabolic rate and whole-body protein turnover.

Animals↗
PubMed1988

Glucose turnover and defense of blood glucose levels in Arctic fox (Alopex lagopus).

1. Glucose utilization was assessed in fed and fasted arctic fox, maintained on a diet similar in composition to food available in the wild. 2. Fasted (24 hr) glucose concentration was not significantly different from the fed level (134 mg/dl). 3. Fasting was associated with a significant reduction in glucose space, pool size, total entry rate, and irreversible loss which suggests a decline in gluconeogenesis. 4. Glucose recycling was not significantly different between the fed and fasted states. 5. We suggest that, in the arctic fox, the mechanism for defending blood glucose levels during fasting is based on restricting blood glucose to tissues with a high glucose dependency.

Animals↗
PubMed1988

Effect of basic and nonbasic amino acid substitutions on transport induced by simian virus 40 T-antigen synthetic peptide nuclear transport signals.

A previous study demonstrated the ability of a synthetic peptide homologous to the simian virus 40 T-antigen nuclear transport signal to induce the nuclear transport of carrier proteins and the dependence of peptide-induced transport on a positive charge at the lysine corresponding to amino acid 128 of T antigen. In this investigation synthetic peptides were utilized to examine the effect on transport of amino acid substitutions within the T-antigen nuclear transport signal. Nuclear transport was evaluated by immunofluorescence after microinjection of protein-peptide conjugates into the cytoplasm of mammalian cells. Substitution of other basic amino acids at position 128 revealed a hierarchy for nuclear transport. The rate of nuclear transport was most rapid when a lysine was at position 128 followed in descending order by arginine, D-lysine, ornithine, and p-aminophenylalanine. Peptide-induced nuclear transport was dependent upon a positively charged amino acid at positions 128 and 129, since substitutions of neutral asparagines at these positions abolished transport. However, partial transport was observed with the peptide having an asparagine at position 128 when a high number of peptides were conjugated to the carrier protein.

Amino Acids↗
PubMed1988

Analytical procedures for estimating milk intake and yield in steady-state and nonsteady-state systems.

A tracer method for determining milk intake, introduced earlier, was based on the transfer of tritiated water from a lactating female to a nuring offspring via milk. The analysis of the tracer data assumed a steady state system, i.e., the total body water of the offspring was assumed to be constant over the measurement period. This paper discusses the potential errors in the milk intake estimates in applications where steady-state does not exist. Three analytical procedures are considered and include the application of 1) steady state equations for a nonsteady-state system, 2) analytical solutions to nonsteady-state equations, and 3) a computer modeling program, SAAM-27. The application of steady-state equations is the simplest procedure and may yield acceptable estimates if the growth rate of the nuring offspring is low. The analytical solution procedure yields acceptable estimates at high growth rates of the nursing offspring but becomes unacceptable at low growth rates. The SAAM program requires sophisticated computer hardware and programming; however, the procedure yields the best estimates of milk intake in applications ranging from steady-state to high growth rates.

Animals↗
PubMed1986

Gravitropism in higher plant shoots. IV. Further studies on participation of ethylene.

Ethylene at 1.0 and 10.0 cubic centimeters per cubic meter decreased the rate of gravitropic bending in stems of cocklebur (Xanthium strumarium L.) and tomato (Lycopersicon esculentum Mill), but 0.1 cubic centimeter per cubic meter ethylene had little effect. Treating cocklebur plants with 1.0 millimolar aminoethoxyvinylglycine (AVG) (ethylene synthesis inhibitor) delayed stem bending compared with controls, but adding 0.1 cubic centimeter per cubic meter ethylene in the surrounding atmosphere (or applying 0.1% ethephon solution) partially restored the rate of bending of AVG-treated plants. Ethylene increases in bending stems, and AVG inhibits this. Virtually all newly synthesized ethylene appeared in bottom halves of horizontal stems, where ethylene concentrations were as much as 100 times those in upright stems or in top halves of horizontal stems. This was especially true when horizontal stems were physically restrained from bending. Ethylene might promote cell elongation in bottom tissues of a horizontal stem or indicate other factors there (e.g. a large amount of 'functioning' auxin). Or top and bottom tissues may become differentially sensitive to ethylene. Auxin applied to one side of a vertical stem caused extreme bending away from that side; gibberellic acid, kinetin, and abscisic acid were without effect. Acidic ethephon solutions applied to one side of young seedlings of cocklebur, tomato, sunflower (Helianthus annuus L.), and soybean (Glycine max [L.] Merr.) caused bending away from that side, but neutral ethephon solutions did not cause bending. Buffered or unbuffered acid (HCl) caused similar bending. Neutral ethephon solutions produced typical ethylene symptoms (i.e. epinasty, inhibition of stem elongation). HCl or acidic ethephon applied to the top of horizontal stems caused downward bending, but these substances applied to the bottom of such stems inhibited growth and upward bending--an unexpected result.

Dose-Response Relationship, Drug↗
PubMed1986

Validation of doubly labeled water method using a ruminant.

CO2 production (CDP, ml CO2 . g-1 . h-1) by captive caribou and reindeer (Rangifer tarandus) was measured using the doubly labeled water method (3H2O and H2(18)O) and compared with CO2 expiration rates (VCO2), adjusted for CO2 losses in CH4 and urine, as determined by open-circuit respirometry. CDP calculated from samples of blood or urine from a reindeer in winter was 1-3% higher than the adjusted VCO2. Differences between values derived by the two methods of 5-20% were found in summer trials with caribou. None of these differences were statistically significant (P greater than 0.05). Differences in summer could in part be explained by the net deposition of 3H, 18O, and unlabeled CO2 in antlers and other growing tissues. Total body water volumes calculated from 3H2O dilution were up to 15% higher than those calculated from H2(18)O dilution. The doubly labeled water method appears to be a reasonably accurate method for measuring CDP by caribou and reindeer in winter when growth rates are low, but the method may overestimate CDP by rapidly growing and/or fattening animals.

Animals↗
PubMed1986

Typhoid fever in pregnancy. Case report and review of the literature.

The clinical details of two cases of typhoid fever in pregnancy are described. The first patient contracted the disease in the third trimester, with successful outcome for both mother and baby. The second patient became infected in the first trimester, with the complication of underlying cardiac disease. This resulted in typhoid endocarditis contributing to fetal loss. A survey of the literature is presented and treatment recommendations outlined.

Abortion, Spontaneous↗
PubMed1984

Modes of thermal protection in newborn muskoxen (Ovibos moschatus).

The muskoxen (Ovibos moschatus), a native of Greenland and the Canadian North West Territories, give birth in late April, and the newborn calves are known to tolerate an ambient temperature (Ta) of -35 degrees C. At birth the calves weigh about 8 kg, increasing in weight with 0.6 kg . day-1 for the first 30 days. With a deep body temperature (DBT) of 39.5 degrees C (range 37.7-41.3 degrees C) the newborn calves are consequently able to maintain a thermogradient of at least 70 degrees C between body core and the environment. The calves use primarily two modes of thermal protection: High metabolic heat production and prime fur insulation. Metabolic rate was about 3.5 W . kg-1 at thermoneutrality in calves aged from 8 h to 7 days. Lower critical temperature at this age was about -7 degrees C and a drop in Ta to -30 degrees C increased metabolism to about 5.3 W . kg-1. Upper critical temperature at age 4-7 days is as low as 20 degrees C, while it in calves aged only 18-24 h appears to be even lower. The calves possess great amounts of brown adipose tissue (BAT) at birth. Mitochondria from the BAT deposits were isolated and found to be in an extremely loose-coupled state with a great capacity for thermogenesis. Skeletal muscle contained very few mitochondria and is hardly employed in aerobic non-shivering thermogenesis. Calves shiver visibly while drying just after birth, but are normally not seen shivering thereafter. The conductance value for the dry pelt of newborn calves averaged 3.2 W . m-2 . 0 degrees C-1 (n = 4). Wetting of the pelt with ice-water at a Ta of 3 degrees C increased conductance to 8.8 W . m-2 . 0 degrees C-1. The conductance of the pelt was also influenced by wind, being 10 W . m-2 . C-1 at a wind-speed of 10 m . sec-1. The legs of the newborn calves are heavily furred and countercurrent circulation is not present, subcutaneous temperature just above the hooves being +29.8 degrees C at Ta of -24 degrees C as compared to 37.5 degrees C on the back. The newborn calves could cope with a Ta of -30 degrees C without apparent problems under experimental conditions, but they suffered hypothermia when exposed to a Ta of -33 degrees C in combination with wind of 10 m . sec-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1982

Autologous x-irradiated tumour cells and percutaneous BCG in operable lung cancer.

To determine the value of specific immunotherapy with adjuvant BCG in operable lung cancer, the immunological and clinical results of serial postoperative injections of autologous irradiated tumour cells and BCG were compared with those of a single preoperative injection of BCG in two randomly selected groups of patients undergoing resection of their tumours. There was a significant rise in tuberculin skin reactivity from seven weeks to 11 months after operation in the treated group. Actuarial curves for survival and freedom from tumour recurrence and median survival times showed an advantage for the treated patients who had stage I tumours, but these differences were significant only at the levels p = 0.07 - 0.09. Survival and duration of freedom from tumour recurrence was greater in autograft-treated patients whose skin responded to a weak test dose of dinitrochlorobenzene (DNCB) after sensitisation with 2% DNCB than in control DNCB-positive patients (p = 0.02). There were no significant differences in the actual proportion of patients from each group surviving at two years. The results show that this form of specific immunotherapy with adjuvant may have a beneficial effect in patients with stage I tumours and those who become sensitised to 2% DNCB after the first exposure.

Aged↗