Proliferation of lamellar whorls in arcuate neurons of the hypothalamus of male rats treated with estradiol benzoate or cyproterone acetate

Summary The arcuate nucleus of the hypothalamus (AH) of male rats which had been treated either with estradiol benzoate (E²B) or cyproterone acetate (CPA) was examined ultrastructurally for the presence of whorls of endoplasmic reticulum. The incidence of whorl containing neurons (WCN) was 2–4 times higher in the AH of animals treated for 2–3 weeks with E²B or for 2 weeks with CPA than in the AH of oil treated controls. CPA is a powerful anti-androgen while E²B acts both peripherally and centrally to limit testosterone production. These findings, together with previous evidence that whorls proliferate in AH of male rats deprived of androgen by morphine treatment or castration, suggest that steroid feedback (androgen alone or both androgen and estrogen) plays an important role in AH whorl proliferation. The possibility that WCN may be LH-RH containing neurons is suggested by the close correspondence between the number and location of WCN within AH as determined in this study and the distribution of LH-RH containing cells reported by others.The authors are indebted to Schering AG for supplying cyproterone acetate for this study. This work was supported by grants DA-00259, NS-09156 and MH-14677 from U.S.P.H.S.Research Scientist Development Award MH-38894Research Scientist Development Award MH-70180     

Purification and properties of the arginine-specific carbamoyl-phosphate synthase from Saccharomyces cerevisiae.

The arginine-specific carbamoyl-phosphate synthase of yeast was stabilized sufficiently to allow partial purification of the enzyme (30- to 40-fold). The synthase (mol. wt 115000) comprised two unequal subunits: a heavy subunit (mol. wt 80000) capable of catalysing synthesis of carbamoyl phosphate with ammonia as a nitrogen donor and a light subunit conferring upon the holoenzyme the ability to utilize glutamine. The enzyme had unusually high affinity for ATP (Km = 0.2 mM) and atypical negative cooperativity for glutamine binding ([S]0.5 = 0.25 mM). Glutamine activity was not modulated by possible effectors such as arginine, ornithine or N-acetylglutamate. Thus, although the yeast arginine enzyme physically and functionally resembles the single enteric synthase, the systems differ substantially both in kinetic properties and in regulation of activity.     

Results of 12 years' treatment of chronic renal failure by dialysis and transplantation.

The survival of 305 patients with chronic renal failure treated at the Vancouver General Hospital by centre and home peritoneal dialysis, centre and home hemodialysis and cadaver renal transplantation over a 12-year period was analysed. There was decreasing survival with age except in patients undergoing home dialysis. Hypertension and analgesic nephropathy as primary causes of renal disease were associated with a poor prognosis. Hence age and diagnosis appear to be two of the main determinants of survival. Cardiovascular disease was the commonest cause of death but seven deaths were due to dialysis dementia. The results compare favourably with other published statistics.     

Associations of like and unlike polysaccharides: Mechanism and specificity in galactomannans,interacting bacterial polysaccharides,and related systems

Chiroptical, rheological, and n.m.r.-relaxation evidence is presented, to identify interactions of two types between different polysaccharides: (1) mutual exclusion of incompatible molecules, with consequent increase in the effective concentration of both; and (2) energetically favourable association of structurally and sterically regular chain-segments. β-1,4-linked plant polysaccharides interact by association of unsubstituted backbone regions, either with like chians, or with sterically compatible, unlike molecules. Extracellular polysaccharides (xanthans) of Xanthomonas plant pathogens maintain their ordered native conformation in solution, and this accounts for their industrially valuable, rheological peculiarities. These materials bind strongly to the plant glycans. Random-coil bacterial gums show no such interactions, although dextran enhances autogelation of galactomannans by exclusion. Extracellular polysaccharides from Arthrobacter species also have ordered native conformations in solution, but do not share the specific interactions of xanthan. Native xanthan shows marked specificity in its interactions with plant glycans, indicating a possible biological role in host-pathogen recognition.     

Undescribed toxin in pseudomembranous colitis.

A girl aged 12 developed pseudomembranous colitis after a short course of oral penicillin. She had no history of adverse reaction to penicillin before or after the illness. No pathogenic bacteria, mycoplasmas, or viruses were found in her faeces, but they did contain a toxin. Toxin was also found in four of five other patients with pseudomembranous colitis but not in six specimens obtained from patients with diarrhoea caused by other disorders. Further studies may show that pseudomembranous colitis is caused by a bacterial toxin.     

Insulin-activated protein kinases phosphorylate a pseudosubstrate synthetic peptide inhibitor of the p70 S6 kinase

p70 S6 kinase, a major insulin-mitogen-activated ribosomal S6 protein kinase in mammalian cells, is activated by phosphorylation of multiple Ser/Thr residues on the enzyme polypeptide. A synthetic peptide, corresponding to a 37-residue segment from the carboxyl-terminal tail of the kinase which resembles the sequence phosphorylated in S6, acts as a competitive inhibitor of p70 S6 kinase without itself being phosphorylated by the enzyme. This synthetic peptide is phosphorylated by an array of protein kinases which are rapidly activated by insulin. Thus, these sequences of p70 S6 kinase constitute a potential autoinhibitory pseudosubstrate site, whose phosphorylation is catalyzed by candidate upstream-activating protein kinases.     

Growth modulation by epidermal growth factor (EGF) in human colonic carcinoma cells: constitutive expression of the human EGF gene

The functional role of epidermal growth factor (EGF) in epithelium-derived human colonic carcinoma cells was investigated by transfection with plasmid pUCDS3, which contained synthetic human EGF encoding sequences, into two human colonic carcinoma cell types with dissimilar phenotypic properties: the moderately differentiated and growth factor-responsive Moser and the highly metastatic KM12SM cells. The Moser cells exhibited a proliferative response to treatment with exogenous EGF, while the KM12SM cells did not. The constitutive expression of the human EGF gene in these colonic carcinoma cell types resulted in elevated expression of EGF mRNA, with concurrent production and secretion of a large amount of EGF, and downmodulation of transforming growth factor-alpha (TGF-alpha) secretion. Growth stimulation and down-modulation of both high and low affinity EGF receptors were observed in the EGF-transfected Moser clones. Results of experiments using anti-EGF and anti-EGF-receptor antibody to block the proliferation of EGF-transfected Moser clones suggested that autocrine stimulatory mechanisms involving both EGF and TGF-alpha were operative in these cells. By comparison, a growth-inhibitory effect, with no apparent EGF receptor modulation, was observed in the EGF-transfected KM12SM clones. Both the parental and EGF-transfected KM12SM clones possessed fewer EGF receptors than the Moser cells, and anti-EGF or anti-EGF-receptor antibody did not affect the cells' growth properties. These results suggested that the mechanisms of growth inhibition in the EGF-transfected KM12SM clones were non-autocrine or intracellular in nature. Thus, constitutive expression of the human EGF gene in two phenotypically different, epithelium-derived human colonic carcinoma cells resulted in divergent altered growth characteristics.     

Oviposition by the African migratory locust, Locusta migratoria migratorioides, in a crop environment in South Africa

Oviposition by the African migratory locust, Locusta migratoria migratorioides (Orthoptera: Acrididae), was studied in maize and wheat crops on the Orange Free State Highveld. Maize was shown to be the most important oviposition habitat with peak laying taking place in autumn and early winter when highest pod densities were recorded. Laying was mainly concentrated along the middle of the crop interrows in maize and within clearings in the wheat crop. Despite the uniform layout of these crops, the distribution of egg pods was found to be aggregated. Non-reproductive behaviour, such as locust aggregation, basking and feeding, as well as environmental factors appeared to influence the distribution of egg pods in these crops. Secondary selection for optinum soil moisture and compaction on the laying site enhanced the aggregation of pods.     

Purification and characterisation of the insulin-stimulated protein kinase from rabbit skeletal muscle; close similarity to S6 kinase II.

The insulin-stimulated protein kinase (ISPK) was purified over 50,000-fold from extracts of rabbit skeletal muscle by a procedure involving chromatography on phosphocellulose, fractionation with ammonium sulphate, and further chromatography on DEAE-cellulose, phenyl-Superose, Mono S and Mono Q. About 10 micrograms enzyme was isolated from 800 g muscle (one rabbit) in four days with an overall recovery of 5%. The purified enzyme showed a single protein-staining band of apparent molecular mass 91 kDa when analysed by SDS/polyacrylamide gel electrophoresis. The ISPK comigrated during SDS/polyacrylamide gel electrophoresis with the enzyme S6 kinase II from Xenopus eggs, and was recognised in immunoblotting and immunoprecipitation experiments by antibodies raised against S6 kinase II. The substrate specificities of ISPK and S6 kinase II were also very similar and like S6 kinase II, ISPK that had been inactivated by protein phosphatase 2A could be reactivated by incubation with mitogen-activated protein kinase and MgATP. ISPK was distinct from an insulin-stimulated 70-kDa S6 kinase from rat liver in both substrate specificity and immunological cross reactivity. It is concluded that ISPK is closely related in structure to S6 kinase II and may be a mammalian equivalent of this enzyme. The possibility that ISPK is involved in mediating a number of the actions of insulin is discussed.