Mutant of Yeast Sensitive to 2,6-Diaminopurine

A mutant of yeast sensitive to growth inhibition by 2,6-diaminopurine (2,6-DAP) was analyzed genetically and found to be a double mutant. One gene, dap, conferred approximately 30% sensitivity to the analogue. The other, slw, potentiated the inhibition such that the double mutant dap slw was inhibited 90%. The mutation dap conferred concomitant sensitivity to a number of other purine analogues. The activity of a purine phosphoribosyltransferase with 2,6-DAP in a strain carrying dap was found to be three times higher than in the wild type. It is inferred that the mutation alters the properties of a purine phosphoribosyltransferase. A possible mechanism for the effect of slw is also discussed.     

A comparison of some hydrolytic and gas chromatographic procedures used in methylation analysis of the carbohydrate units of glycopeptides

The polysaccharide secreted by Klebsiella aerogenes type 54 strain A3 was isolated, methylated, the ester carboxyl-reduced, and the product partially hydrolyzed. The resulting, partially O-methylated oligosaccharides were reduced and ethylated, and the mixture of products was fractionated by l.c. The l.c. fractions containing per-O-alkylated oligosaccharide-alditols were analyzed by e.i.-m.s. Pure per-O-alkylated oligosaccharide-alditols were also analyzed by ¹H-n.m.r. spectroscopy. The products obtained by base-catalyzed degradation and subsequent ethylation of the per-O-methylated polysaccharide were fractionated by l.c. The main product isolated was analyzed by e.i.-m.s., c.i.-m.s., and ¹H-n.m.r. spectroscopy. The results of these studies, in conjunction with results of analytical methods commonly used in the elucidation of polysaccharide structures, unambiguously characterized the primary glycosyl structure of the polysaccharide. Base-labile substituents, previously reported to be present in the polysaccharide, were not studied. Structure 1 revises, and complements, previously reported structures.

     

Thermoregulatory, behavioral and seizure modulatory effects of AVP in the gerbil

Recent reports suggest that arginine vasopressin (AVP) may be an endogenous antipyretic peptide and a mediator of febrile convulsions [10,12]. The spontaneously seizing Mongolian gerbil was used to investigate the thermoregulatory, behavioral and seizure modulatory effects of AVP. Injection of AVP (1.0 and 5.0 μg IV and 0.01–1.0 mg/kg SC) caused dose-related falls in body temperature. Stereotypic scratching, terminated by a body shake, was observed after AVP (1.0–5.0 μg IV). However, such behavior was not observed after subcutaneous injection of AVP. AVP did not potentiate seizure induction in the gerbils but rather reduced the seizure incidence. The data demonstrate that AVP can reduce body temperature and cause specific behaviors, but it does not appear to play a role in the pathogenesis of seizures in the seizure sensitive strain of Mongolian gerbil.     

New mechanical aid to physiotherapy in cystic fibrosis.

The force of impact and frequency of percussion by physiotherapists and parents of children with cystic fibrosis were analysed on a special test rig and incorporated in a prototype percussor. In adult volunteers and cadavers a maximum intrathoracic pressure could be achieved by a critical frequency of mechanical percussion which was higher than that reached by physiotherapists and parents. Consequently the percussor was redesigned to operate at this optimum frequency. It was then discovered that if the percussor was pressed firmly enough against the chest, this maximum intrathoracic pressure could be indicated by quivering of the voice. In a continuing study of intrathoracic pressures obtained mechanically and manually the Salford percussor''s produced higher pressures than the physiotherapists'' and maintained them constantly, while the physiotherapists'' efforts and results varied from one to another. Hospital and domiciliary use of the percussor have shown it to help in the first stage of the physiotherapy routine for patients with cystic fibrosis. The percussor should enable adolescents and adults to treat themselves and encourage twice-daily and more effective chest treatments. It is easy to apply and its speed and efficiency should enable parents to improve the quality of their chest therapy for younger children at home. Its long-term benefits are difficult to assess because of the nature of the disease.     

Studies of the regulation of purine nucleotide catabolism.

Ehrlich ascites tumor cells containing radioactive ATP were incubated in vitro with a range of concentrations of 2-deoxyglucose in order to produce different rates of ATP catabolism. Concentrations of all radioactive products of ATP catabolism were measured, and apparent rates of adenylate deaminase and inosinate dehydrogenase and of adenylate and inosinate dephosphorylation were calculated. It was concluded that these processes were reggulated primarily by the rate of formation of substrate, and to a lesser extent in some cases, by substrate concentration. No evidence was obtained for regulation of these processes by the concentration of ATP. The deoxyglucose-induced catabolism of radioactive GTP was also studied. When ATP catabolism was induced by incubation with 2,4-dinitrophenol, time courses of accumulation of purine nucleoside monophosphates and rates of alternative pathways of their metabolism were quite different than when deoxyglucose was used.     

The emergence of neural activity and its role in the development of the enteric nervous system

The enteric nervous system (ENS) is a vital part of the autonomic nervous system that regulates many gastrointestinal functions, including motility and secretion. All neurons and glia of the ENS arise from neural crest-derived cells that migrate into the gastrointestinal tract during embryonic development. It has been known for many years that a subpopulation of the enteric neural crest-derived cells expresses pan-neuronal markers at early stages of ENS development. Recent studies have demonstrated that some enteric neurons exhibit electrical activity from as early as E11.5 in the mouse, with further maturation of activity during embryonic and postnatal development. This article discusses the maturation of electrophysiological and morphological properties of enteric neurons, the formation of synapses and synaptic activity, and the influence of neural activity on ENS development.