Hypophyseal corticotropic activity during perinatal period: ontogenesis and regulation

1. In the fetal rat hypophysis, the "opio-melano-corticotropic" cells were immunocytologically revealed earlier in the pars distalis (day 16) than in the pars intermedia (day 17). At an early stage of embryonic development, some factors, possibly of nervous origin, could exert inductive influence on the differentiation and/or the increase in the number of immunoreactive cells. 2. Several forms of ACTH, characterized by their apparent molecular weight, bioactivity and immunoreactivity, can be observed when acid extracts are subjected to gel filtration on Sephadex G 50 fine columns. The ratios between these ACTH forms change during fetal development; the rise in bioactive ACTH content during the last days of gestation, is correlated with an increase of the "intermediate" and "little" molecular forms of ACTH and a parallel decrease of the "big" form. 3. The hypophyseal corticotropic activity is highest on days 18-19 of gestation. Between days 17 and 19, the cortico-stimulating activity is largely independent of the hypothalamus although the fetal hypothalamus shows light hypophyso-stimulating influence. In contrast, between days 19 and 21, the hypophyseal corticotropic activity is mostly under the hypothalamic control; the ACTH release is greatly reduced in its absence. 4. Circulating corticosteroids exert a negative feedback directly at the hypothalamic and pituitary levels. Such negative feedback could explain the decrease of the corticotropic activity of the pituitary during the last three days of gestation and the first postnatal days. 5. The fetus at the end of gestation, as the newborn, is responsive to stress; however, the extent of the pituitary response is weaker than in the adult.     

Characteristics of antimicrobial fibers prepared with wood periodate oxycellulose

A kind of antimicrobial fibers, a composite of Chitosan-Dialdehyde Cellulose (C-DAC) fibers, was prepared by using commercially elemental chlorine-free (ECF) bleached kraft softwood cellulose fibers oxidized by periodate and then further grafted by chitosan with different molecular weights. The characteristics of the C-DAC fibers and physical properties as well as antimicrobial activities of the handsheet made of C-DAC fibers were measured. The results show that the dry and rewet tensile indices, antimicrobial activity against Staphylococcus aureus and Escherichia coli, can be improved significantly as the molecular weight of grafted chitosan on the dialdehyde cellulose fibers decreases.     

Corticohypophysiotropic and corticotropic activity in adrenalectomized male and female rats after psychic stress

We show modifications in the hypothalamic CRF activity and plasma ACTH concentration in adult rats of both sexes, which were five day sham-operated or adrenalectomized and killed either under basal conditions or after a 3 min period or psychological stress. 1. Under basal conditions, the inhibition of the basal release of ACTH is suppressed in 5 day adrenalectomized rats and a sex difference appears: plasma ACTH concentration is twice as great in females than in males. 2. After a 3 min period of psychological stress, the usual increase in hypothalamic CRF activity observed in sham-operated rats, which seems to be sex-related, does not appear in adrenalectomized male or female rats. However, in adrenalectomized rats, the maximal increase in plasma ACTH concentration occurred more rapidly, with a rate 10 times as great in males and 4 times as great in females, than in sham-operated rats. Differences between the sexes in the maximal increase in plasma ACTH concentration remains 1,6 times as great in females than in males. 3. Our results confirm that corticosteroids exert: (1) a tonic feedback inhibition of the basal release of ACTH, (2) a fast feedback inhibition of the stress induced release of ACTH; the promote an increase in the hypothalamic CRF content. Relative intensity of these two inhibitory mechanisms seems to be sex-related.     

Effects of bilateral olfactory bulbectomy on the anterior pituitary corticotropic cell activity in male rats.

Bilateral olfactory bulbectomy (OB) has drastic biochemical and behavioral effects and is often associated with an increase in plasma corticosterone concentrations. This experiment examined the effects of OB on adrenocorticotropin (ACTH) and corticosterone release under basal and stress conditions and on proopiomelanocortin (POMC) gene expression. Bulbectomy potentiated hypophysal ACTH and adrenal corticosterone release induced by ether stress but had no effect on ACTH release under basal conditions, despite a significant increase of circulating corticosterone. POMC gene expression was stronger (+60%) in OB rats than in sham-operated rats. These results suggest that olfactory bulbectomy substantially altered the negative feed-back exerted by glucocorticoids on anterior pituitary corticotropic cells in the male rat.     

Telomerase activity coevolves with body mass not lifespan

In multicellular organisms, telomerase is required to maintain telomere length in the germline but is dispensable in the soma. Mice, for example, express telomerase in somatic and germline tissues, while humans express telomerase almost exclusively in the germline. As a result, when telomeres of human somatic cells reach a critical length the cells enter irreversible growth arrest called replicative senescence. Replicative senescence is believed to be an anticancer mechanism that limits cell proliferation. The difference between mice and humans led to the hypothesis that repression of telomerase in somatic cells has evolved as a tumor-suppressor adaptation in large, long-lived organisms. We tested whether regulation of telomerase activity coevolves with lifespan and body mass using comparative analysis of 15 rodent species with highly diverse lifespans and body masses. Here we show that telomerase activity does not coevolve with lifespan but instead coevolves with body mass: larger rodents repress telomerase activity in somatic cells. These results suggest that large body mass presents a greater risk of cancer than long lifespan, and large animals evolve repression of telomerase activity to mitigate that risk.     

Multiple unit activity recording in the corticotropic area of the deafferented hypothalamus and corticosteronemia in the pigeon.

10 Diurnal variations in both multiple unit activity and plasma corticosterone level were suppressed after complete neural isolation of the basal hypothalamus in the pigeon. 20 It is suggested that the circadian activity of the hypothalamic pituitary corticotropic unit partially depends upon the inhibiting influence from the hippocampic-septal structures.     

The adenylate cyclase-activating activity of cholera toxin is not associated with a nicotinamide--adenine dinucleotide glycohydrolase activity.

The NAD+ glycohydrolase activity of cholera-toxin samples can be separated from their adenylate cyclase-activating activity by polyacrylamide-gel electrophoresis and is inhibited by sodium dodecyl sulphate (which does not inhibit the action of toxin on cells), but not by antibodies to pure toxin. It is therefore probably not a true property of the toxin.     

Calcitonin gene-related peptide does not interact with sympathetic activity in myocardial ischemia

The aim of the present study was to assess whether calcitonin gene-related peptide (CGRP) modulates exocytotic norepinephrine release in ischemic myocardium. In isolated rat hearts subjected to 30 min of low flow ischemia, CGRP release increased 2.8-fold whereas stimulation-induced norepinephrine release decreased 4.1-fold. Pretreatment of rats with capsaicin almost completely depleted cardiac CGRP stores; however, suppression of norepinephrine release by 30 min of low flow ischemia was not affected. At normal flow, exogenous CGRP (5 micromol l-1) had no effect on norepinephrine release. These findings suggest that CGRP release from sensory neurons does not interact with the cardiac sympathetic system during myocardial ischemia.     

The Botrytis cinerea xylanase Xyn11A contributes to virulence with its necrotizing activity,not with its catalytic activity

Background  

The Botrytis cinerea xylanase Xyn11A has been previously shown to be required for full virulence of this organism despite its poor contribution to the secreted xylanase activity and the low xylan content of B. cinerea hosts. Intriguingly, xylanases from other fungi have been shown to have the property, independent of the xylan degrading activity, to induce necrosis when applied to plant tissues, so we decided to test the hypothesis that secreted Xyn11A contributes to virulence by promoting the necrosis of the plant tissue surrounding the infection, therefore facilitating the growth of this necrotroph.