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Biomedical subjects

M D Mann

Publications and source records attributed to M D Mann.

At least 19 recordsLinked to original sources
PubMed1995

Habitat-related variations in brain and body size of pocket gophers.

Cranial capacities were measured in two sets of genetically-related pocket gophers, one from desert shrubland, the other from an irrigated alfalfa field. The two sets differed in sex ratio and in age structure, but both showed the strong sexual dimorphism characteristic of pocket gophers. After sorting by trapping site, sex and suture score (age), the covariations between brain weight, body length and cranial basilar length were calculated. The brains of the alfalfa field animals followed the same somatic scaling relations as those of the desert shrubland animals, all the differences in brain weight being explained fully by the sexual dimorphism in the somatic variables. The slopes defined by the means of brain and body weights of females and of males from the two sites were nearly equal, and were the same as the trajectories calculated from a geometric model based on the statistical characteristics of the samples. It is argued that these slopes define how much brain size must increase to serve a body of increased size, with no change in life style. The differences in age structure between males from the two sites provided evidence of a mechanism by which sexual dimorphism might develop and be enhanced in a nutritionally-enriched environment.

Age Distribution↗
PubMed1994

Isotope bone scanning for acute osteomyelitis and septic arthritis in children.

We prospectively studied 86 children to assess the value and accuracy of isotope bone scanning in the diagnosis of suspected acute haematogenous osteomyelitis and septic arthritis. The patients were scanned because of difficulty in localising the exact site of the pathology. Characteristic scan appearances were found. In osteomyelitis there was increased or decreased uptake extending beyond the confines of the joint capsule; in septic arthritis there was increased or decreased uptake on either side of the joint line, but largely limited to and uniform within the joint capsule. The bone-scan images were correlated with the final diagnosis in 34 sites of septic arthritis and in 62 sites of osteomyelitis. The overall accuracy of the bone scans was 81%. The predictive value for a positive scan to be correct was 100% for a cold scan and 82% for a hot scan. The main reason for a false-positive scan was contiguous soft-tissue infection. The predictive value for a negative scan to be correct was 63%. One reason for a false-negative scan was that the patient was in the transitional phase from cold to hot.

Adolescent↗
PubMed1992

Brain size/body length relations among myomorph rodents.

The relation between cranial volume and body length was examined in 45 species of myomorph rodents to determine how accurately the former can be estimated from the latter. On average within species, cranial capacity was directly proportional to body length (proportional to the cube root of body weight). On average across species, cranial capacity was directly proportional to the square of body length (proportional to the two-thirds power of body weight). Geometric similarity held within species, but the differences in habitus among species within the same genus generated genus slopes that differed from those defined by strict geometric similarity. It was found that cranial capacity could be estimated as accurately from body length as from body weight, and that body length was better if any differences in habitus were involved (because body length is relatively insensitive to habitus). Therefore, body length (or some strong correlate thereof) may serve well as the primary variable in brain paleoallometry.

Animals↗
PubMed1992

Relation between brain and body growth in allied rats.

Cranial volumes were measured from museum specimens of wild-caught and laboratory-born Allied rats from eastern Australia. The relation of these volumes to body weight and body length, and also to age at death in the laboratory-reared sample, was determined. Growth of both brain and body was rapid during the first three postnatal months and slowed markedly over the next month, but appeared to continue at a very slow rate throughout life. In particular, the major surge in brain growth occurred in the first three postnatal weeks. Modified Gompertzian growth functions describe the pattern of growth quite well, though the nature of the data precluded highly sensitive fits. Three features were clear: 1) the rate of slowing of growth was about the same for all variables, 2) growth appeared to continue throughout the life of the animal, and 3) the trajectory of brain growth led that of body growth by about four days. The pattern of growth in Allied rats is similar to that of laboratory rats and probably to those in other murids.

Animals↗
PubMed1991

Dietary manipulation for treating infants with prolonged dehydrating diarrhoea: a comparison of four different formulae.

Dietary manipulation is often the first step in the treatment of infants with persistent acute dehydrating diarrhoea. This usually entails elimination of lactose, but other disaccharides or whole protein may be causing the disease. Serial elimination of these takes time and it may be preferable to use a whole protein and disaccharide-free formula as the first feed change. This study assessed the effect on stool weight of a change from cow's milk formula feeds to one of four different formulae in infants with severe diarrhoea persisting after 3 days in hospital. Two feeds were lactose-free soy formulae containing sucrose, one was disaccharide-free soy formula and one a disaccharide-free protein hydrolysate. Regardless of which feed the infants received, diarrhoea resolved in approximately 50% following the change in diet. Comparing those who got better with those who did not, the former were generally better nourished and had an initial lower stool output, but it was impossible to predict on clinical grounds which individual would respond to the removal of cow's milk. The results suggest that elimination of lactose in infants with persistent severe diarrhoea will benefit a significant number in the early stage of the disease. As there is no additional benefit from eliminating sucrose or whole protein at this stage, the cheapest available lactose-free formula should be used initially.

Diarrhea, Infantile↗
PubMed1990

The pattern of childhood poisoning in the western Cape.

An analysis of poisoning cases treated at the Red Cross War Memorial Children's Hospital during 1987 and of calls received on the poisons line is presented. Treatment of 1,116 children was undertaken and 922 telephone calls were logged. Of the patients treated, 60% had ingested a drug and 30% had drunk paraffin. The high prevalence of paraffin poisoning in the western Cape is examined. Constant vigilance must be maintained if childhood poisoning is to be prevented.

Child↗
PubMed1990

Dosimetry of swallowed non absorbed 99mTc radiopharmaceuticals in pediatric patients.

A calculation is presented which derives the absorbed dose experienced by pediatric patients of different ages who swallow a non absorbable 99mTc compound. All previous models assume sudden movement of radionuclide from one compartment of the gastrointestinal tract to another. The present model is novel in considering continuous distal motion through the gut and so more closely approximates the physiologic situation. Published S values are used to derive absorbed doses. The resulting calculated absorbed doses are comparable to, or lower than, those previously published and these differences are most marked in the large gut, which remains the critical organ.

Child↗
PubMed1990

Effect of loperamide on stool output and duration of acute infectious diarrhea in infants.

This study was designed to assess the effect of loperamide, given to infants in higher than recommended doses, on the severity and duration of acute diarrhea. Thirty infants with acute diarrhea and dehydration were given loperamide (0.8 mg/kg/day), in addition to standard fluid therapy, for 48 hours after admission to the hospital. The stool output in grams per kilograms of body weight per day and the duration of diarrhea in these infants were compared with those in 30 matched control infants receiving only standard fluid therapy. Two infants given loperamide had to be withdrawn from the trial because ileus developed in one and the other had persistent severe vomiting. In four other infants receiving loperamide, drowsiness developed but resolved rapidly on discontinuation of the drug. Infants receiving loperamide had a shorter duration of diarrhea (median 2.5 vs 6.0 days) and lower daily stool output than the control subjects had. The study confirmed the efficacy of loperamide in reducing the duration and severity of diarrhea but raised doubts regarding its safety in the treatment of young infants.

Administration, Oral↗
PubMed1990

Factors influencing the duration of acute diarrheal disease in infancy.

The majority of episodes of acute infectious diarrhea in infancy are of relatively short duration. Prolongation of the diarrhea presents problems in management, deterioration of the infant's nutritional status, and an increased mortality. As part of a prospective study of the etiology of acute infectious diarrhea, some factors associated with the probability (more or less) of having self-limiting disease have been identified. The well-nourished infant over 6 months of age is more likely to have self-limiting disease, whereas this outcome is least likely in the very young infant under 3 months of age, particularly if underweight for age. With the exception of Shigella, bacterial enteropathogens (Campylobacter fetus jejuni, Salmonella B, and certain enteropathogenic Escherichia coli types) were also associated with a decreased likelihood of self-limiting disease. Rotavirus infection was associated with self-limiting disease except in the infant under 3 months of age, where the probability of self-limiting disease was decreased.

Acute Disease↗
PubMed1990

Absorption and retention in acute diarrhoea.

15N-yeast protein absorption, nitrogen and fat retention and stool reducing substances and lactate were measured in 6 infants who had acute diarrhoea and 15 who had had severe diarrhoea for 4 d. The results were compared with those of previously reported infants, who had had diarrhoea for 8 d. The infants were fed a full cream cows' milk, soy based or low lactose formula. In all cases the losses of nitrogen and energy in stool rose as stool weight increased. In severe diarrhoea, the losses of nutrients in stool were so great that oral feeds did not provide adequate nitrogen and energy. The smallest loss of nitrogen and fat were found in infants who had had diarrhoea for 4 d and who were fed a soy based formula.

Analysis of Variance↗
PubMed1990

Pulmonary ventilation and perfusion abnormalities and ventilation perfusion imbalance in children with pulmonary atresia or extreme tetralogy of Fallot.

Xenon-133 lung ventilation and perfusion scans were done preoperatively after cardiac catheterization and cineangiocardiography in 19 children; 6 had pulmonary atresia with an intact ventricular septum and hypoplastic right ventricle, 4 pulmonary atresia with associated complex univentricular heart, and 9 extreme Tetralogy of Fallot. The four patients with discrepancies in the sizes of the left and right pulmonary arteries on angiography had marked asymmetry of pulmonary perfusion and ventilation-perfusion imbalance on scintigraphy. Similar degrees of asymmetry and imbalance were present in 6 of the 15 children with equal-size pulmonary vessels. Asymmetry of pulmonary perfusion and ventilation-perfusion imbalance were associated with a poor prognosis.

Child↗
PubMed1989

Sensory nerve crush and regeneration and the receptive fields and response properties of neurons in the primary somatosensory cerebral cortex of cats.

Extracellular recordings were made of activity evoked in neurons of the forepaw focus of somatosensory cerebral cortex by electrical stimulation of each paw in control cats and cats that had undergone crush injury of all cutaneous sensory nerves to the contralateral forepaw 31 to 63 days previously. Neurons responding only to stimulation of the contralateral forepaw were classified as sa; neurons responding to stimulation of both forepaws were classified as sb; neurons responding to stimulation of both contralateral paws were classified as sc; and neurons responding to stimulation of at least three paws were classified as m. The ratio sa:sb:sc:m neurons was 46:3:0:0 in control cats and 104:15:3:26 in cats that had undergone nerve crush 1-2 months prior to study. sa neurons from experimental cats had depth distributions similar to those in controls and responded to contralateral forepaw stimulation with more spikes per discharge, longer latency, and higher threshold than sa neurons in control cats. m neurons from experimental cats were distributed deeper in the cortex than sa neurons, and, when compared to experimental sa neurons, they responded with longer latency and poorer frequency-following ability; however, the number of spikes per discharge and threshold were not significantly different. The appearance of wide-field neurons in this tissue may be explained in terms of strengthening of previously sub-threshold inputs to neurons in the somatosensory system. If the neurons in sensory cortex play a requisite role in cutaneous sensations and if changes similar to those reported here occur and persist in human cortex after nerve crush, then "complete" recovery of sensation in such patients may occur against a background of changed cortical neuronal responsiveness.

Action Potentials↗
PubMed1988

Response of severe infantile diarrhoea to soya-based feeds.

Ongoing acute diarrhoea in infancy may respond to a change from a cows' milk to a soya-based formula. This is usually ascribed to the change in carbohydrate content of the feed but the ideal carbohydrate composition of the soya feed is uncertain. Twenty infants with severe watery diarrhoea persisting 2 days after initial rehydration and refeeding with a cows' milk formula were randomly allocated to one of two soya-based formulas. In one the carbohydrate was a mixture of sucrose and glucose polymers and in the other all the carbohydrate glucose polymers. No advantage was noted for either formula. Approximately 50% of each group responded to dietary change. The prompt cessation of diarrhoea and the disappearance of evidence of carbohydrate malabsorption suggests the response is due to the removal of lactose from the diet. Those infants that did not respond had evidence of continuing carbohydrate malabsorption and were not simply lactose-intolerant. The pathogenesis of this carbohydrate malabsorption and the possible relationship to small-bowel bacterial overgrowth requires further investigation.

Body Weight↗
PubMed1988

Enteropathogens associated with acute infantile diarrhoea in Cape Town.

The results of a year-long controlled study on the causation of acute infectious diarrhoea in infants are reported. Campylobacter fetus subspecies jejuni, rotavirus and certain enteropathogenic Escherichia coli (EPEC) types were identified as the most common enteropathogens. Shigella, Salmonella group B and Yersinia enterocolitica were significant but less common pathogens. Campylobacter, rotavirus, the significant EPEC types and Shigella infections were more frequent in the warm summer and autumn months. This only partially accounts for the marked summer peak of diarrhoea, since at this time the percentage of cases of undetermined causation is highest (61%). Over the year an identifiable cause of the diarrhoea was found in 49% of the patients studied. A specific EPEC type, 0126:K71(B16), appeared to vary in pathogenicity on a seasonal basis. Multiple enteropathogens occurred relatively frequently.

Campylobacter↗