Biomedical subjects
Publications and source records attributed to G Mitchell.
A family is reported in which the index case presented with an acute form of maple syrup urine disease (MSUD), whereas two of her sisters and her father were found to have an almost asymptomatic form of the disease. It is proposed that the members of this family are compound heterozygotes for the classical deficient mutant gene and for a "variant" allele.
Five patients aged 7 to 21 months are described who developed attacks of coma after a short prodromal illness with diarrhea or vomiting or both. Four had concomitant hypoglycemia, and all had hypoketonemia, with excessive urinary excretion of medium-chain dicarboxylic acids, medium-chain (omega-1)-hydroxyacids, suberylglycine, hexanoylglycine, and octanoylcarnitine. All patients accumulated octanoic acid, decanoic acid, and cis-4-decenoic acid in plasma. Fibroblasts from three patients showed a decreased rate of octanoate oxidation (10%, 12%, and 29% of control values, respectively). These findings suggest a deficiency of medium-chain acyl-CoA dehydrogenase, most probably an autosomal recessive inherited metabolic disorder. Two of the patients died during an acute attack, and a third had severe neurologic sequelae; the two remaining patients recovered. Plasma free carnitine levels were low, but total carnitine was normal. The three surviving patients underwent a fasting test, which did not lead to hypoglycemia, although hypoketonemia, dicarboxylic aciduria, and excessive mobilization of fatty acids did occur. The surviving patients were maintained on frequent carbohydrate-enriched meals.
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Athetotic cerebral palsy was diagnosed in a 6-month-old boy with no history of perinatal trauma. Lesch-Nyhan syndrome (i.e., complete deficiency of hypoxanthine-guanine phosphoribosyltransferase [HGPRT] ) was diagnosed only when the boy began biting his lower lip at the age of 10 years. It is suggested, on the basis of this case and others like it in the literature, that the delayed onset or absence of self-mutilation in patients with Lesch-Nyhan syndrome may be more common than has been previously suspected. In all males said to have cerebral palsy, HGPRT deficiency must be ruled out, preferably by measuring the ratio of uric acid to creatinine in a random urine specimen.
Therapeutic guidelines have been obtained from a retrospective review of 41 patients affected with organic acidaemias, 16 patients with neonatal maple syrup urine disease (MSUD), 11 methylmalonic acidaemia, (MMA) seven propionic acidaemias (PA) and seven isovaleric acidaemias (IVA), and by comparing this personal series with similar reported cases. The emergency treatment of these organic acidurias in the neonate has to main goals: toxin removal and anabolism. Anabolism is always promoted by early diet therapy. The best method of toxin removal depends on the nature of the defect; peritoneal dialysis with exchange transfusions or multiple or prolonged exchange transfusions in MSUD and in PA, diuresis and exchange transfusions in MMA and glycine supplementation in IVA. Vitamin supplementation (thiamine 20 mg, biotin 10 mg, B12 2 mg and riboflavin 100 mg) should be tried in all cases although the neonatal forms of these defects are very rarely vitamin responsive. Additional treatments such as carnitine or insulin may prove to be useful.
Behavioral primatology is a subdiscipline of the research area referred to as primatology. Like primatology, behavioral primatology is an eclectic field of study made up of researchers from diverse basic disciplines having very different historical roots and employing extremely different methodologies biased by emphases and assumptions dictated by their histories. Psychologists, zoologists, anthropologists, and psychiatrists make up the majority of those currently active in behavioral primatology, but others, including those in veterinary science, are active in research in the area. Behavioral data can be useful to veterinary scientists and to those in comparative medicine and are interesting in their own right. Veterinarians and medical scientists may specialize in behavioral disorders. In addition, those not directly interested in behavior itself may still make use of behavioral indices of potential physiologic and morphologic abnormality. Often an animal may be inadvertently stressed by social and nonsocial environmental factors, and such stress effects may be first and best recognized by behavioral means. A recognition by those not in the behavioral sciences of the basic feral behavior of primates can go a long way toward prevention or alleviation of both behavioral and physical stress of primates in captivity. Studies of free-ranging but captive troops are sources of information almost as good as, and sometimes even better than, field studies. In addition, there is a growing realization that "natural experiments" on primates in zoos can be of value, especially since many species held in zoologic parks are those least well known in more traditional captive research settings. It must be recognized that the findings from research done on captive primates living in large field cages are not directly comparable to those derived from more directly invasive but more experimental laboratory settings. A comparative perspective on captive environments, as well as on species, is strongly recommended. Behavioral primatologists, and particularly psychologists, have long been interested in behavioral development in various species of primates. A recognition of the importance of the effects of early experience, of species differences in development, of sex differences in development, of differences in species-specific social structures and in the relative plasticity of these, and of differences in symptoms of behavioral abnormality can contribute to the arsenal of techniques that might be used to improve the well-being of the primates and can help in the selection of appropriate animal models of disorder in humans for those in comparative medicine.(ABSTRACT TRUNCATED AT 400 WORDS)
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The effect of adenosine on intraparenchymal cerebral blood flow was examined in conscious rabbits with the 133Xe clearance technique. Perivascular application of 10(-3) and 10(-4) M adenosine to hypothalamic blood vessels increased hypothalamic blood flow by approximately 50% (p less than 0.005). This vasodilatation was attenuated by the intrahypothalamic injection of the beta-adrenergic receptor antagonist propranolol, but was unaffected by alpha-adrenoreceptor blockade with phenoxybenzamine, or depression of neuronal activity with barbiturate. 2-Chloroadenosine, a stable analogue of adenosine, also increased hypothalamic blood flow by 50% (p less than 0.005), but this dilatation was unaffected by propranolol. These results suggest that adenosine increased hypothalamic blood flow at high concentrations by vascular receptor systems dependent on adenosine receptors and adrenergic receptors. Adenosine (10(-6) M) reduced hypothalamic blood flow by approximately 25% (p less than 0.005). This vasoconstriction was unaffected by adrenergic blockade with propranolol or phenoxybenzamine, or by inhibition of neuronal activity with barbiturate. The results suggest that adenosine decreases hypothalamic blood flow at low concentrations by stimulation of adenosine receptors associated with vascular smooth muscle.
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Carcasses of sheep from various areas in South Africa and South West Africa (Namibia) show a wet glistening appearance immediately after slaughter. The subcutaneous interstitial fluid of these sheep has a significantly lower protein concentration and colloid osmotic pressure and a significantly higher albumin/globulin ratio than that of normal sheep. These results imply the presence of an oedema and an increased capillary permeability to protein. They suggest that histamine, or an histamine-like substance, mediates the changes.
Angora goats may develop a characteristic ventral oedema of the subcutaneous tissue which is not unlike the 'wet-carcass syndrome' of sheep. The plasma of oedematous goats shows a lower total protein concentration, a lower colloid osmotic pressure and a lower albumin: globulin ratio than that of normal goats. Similarly, interstitial fluid of oedematous goats has a lower protein concentration, osmolality and colloid osmotic pressure than the fluid from normal but a similar albumin:globulin ratio. These results suggest that, unlike the 'wet-carcass syndrome' of sheep, the most likely explanation for the oedema is hypoproteinaemia which leads to filtration of fluid and an increased capillary permeability.