The nature of the cytosolic activators of the adrenal steroid 21-hydroxylation system

The steroid 21-hydroxylase activity present in the microsomes of bovine adrenals is stimulated by components of the cytosol. The nature of these activators has been examined by two procedures. The first consisted of treating cytosol with increasing amounts of acetone. When the concentration of the organic solvent reached 50%, a precipitate, presumably proteinaceous, formed. The portion of the precipitate that was redissolvable in 0.05 m potassium phosphate buffer, pH 7.2, contained 7–15% of the stimulatory activity originally present in the cytosol. When the acetone concentration was raised to 90%, another active material precipitated. It was identified as oxidized glutathione (GSSG) and it accounted for about 5% of the activity in the cytosol. In an attempt to avoid the harmful effects of acetone, the second procedure employed only gel filtration and ion exchange resin chromatography. By these means the cytosol was separated into 11 protein fractions and a small molecular weight material. Forty six percent of the proteins and the same fraction of the stimulatory activity present in the original cytosol were recovered. Because all 11 protein fractions contained some stimulatory activity, the results suggested that the protein constituents of these fractions were relatively nonspecific. Yet, of the several known proteins which were tested for activity (bovine serum albumin, ovalbumin, human γ-globulin, bovine pancreatic ribonuclease, and pig insulin) only bovine serum albumin proved to be active. An additional 8% of the stimulatory activity of the cytosol was present in the fraction containing the low molecular weight components and this was all attributable to its GSSG content.     

On the existence of non-cycling germinative cells in human epidermis in vivo and cell cycle aspects of psoriasis

Abstract. This report deals with the controversies of whether all germinative epidermal cells in human epidermis are in the cycling state and whether stimulated hyperproliferation of psoriatic epidermis is due to a shortening of the cell cycle time or to a recruitment of non-cycling germinative epidermal cells. Experiments were performed on human subjects in vivo . Continuous infusion of [³H]thymidine for 8½ days indicated that 40% of germinative epidermal cells reside in the non-cycling state. Proliferative stimulation by tape stripping indicated recruitment of non-cycling (G₀) germinative epidermal cells in both normal and psoriatic skin, and a prolongation (rather than a shortening) of cell cycle traverse in activated psoriatic epidermal cells.     

ACTH4–10 affects behavior but not plasma corticosterone levels in a conditioned taste aversion situation

Rats injected with LiCl after they consumed a sweetened milk solution subsequently avoided the milk. ACTH4--10 injection prior to a retention test for the aversion augmented the behavioral measure of the aversion. Rats consuming milk paired earlier with LiCl showed elevated plasma levels of corticosterone. The augmented avoidance response in ACTH4--10 injected rats was not paralleled by an augmented pituitary-adrenal response.     

Ultrastructure and some other properties of inverted thyroid follicles in suspension culture

Separated thyroid follicles in suspension culture invert in 5% serum. In some, the inversion is not complete in that a small normal follicle persists completely in the interior of an inverted follicle. In inverted follicles the lumens are distended and electron lucent. The bounding epithelial cells are stretched, have relatively few microvilli on the surface toward the medium but they have bundles of oriented microfilaments usually located near the lumen. The cells are connected together by tight junctions. When inverted follicles are punctured, the lumen shrinks, the cells retract and become cuboidal and microvilli reappear. Microfilaments persist at the luminal surface but no longer in oriented bundles. No appreciable extracellular matrix is present at the basal cell surface in contact with the lumen, but matrix is occasionally observed between cells. Since bundles of microfilaments like stress fibers are observed in the cells in suspension culture, the presence of stress fibers in cells in monolayer culture is probably not dependent on attachment but might be a reflection of the spreading of the attached cells.     

Subspecies differences in hormonal and behavioral responses after group formation in squirrel monkeys

The behavioral and hormonal responses of squirrel monkeys of the Bolivian and Guyanese subspecies were compared after a group formation procedure. Two groups of each subspecies, consisting of five females and three males (later reduced to two) were observed daily during the week of group formation and for nine weeks following removal of a single male from each group. Measures of plasma cortisol were examined in the females after the initial group formation and after the groups were reduced by one male. The levels of plasma testosterone were assessed in all the males during the initial week of group formation. Linear dominance hierarchies were determined both within and across the sexes in both subspecies. The frequency and directionality of low-level aggressive interactions indicated that females of the Bolivian subspecies were dominant to the males, while the males of the Guyanese subspecies ranked over all the females. Additionally, the Bolivian squirrel monkey females showed an elevation of plasma cortisol on the day of group formation, which declined 48 hr later, then reelevated after the groups were reduced by one male and declined gradually over a nine-week period. Guyanese females showed little change in cortisol levels during both periods. This suggests fundamental hormonal, as well as behavioral, differences between the two subspecies. The change in plasma testosterone levels in the males during the initial week of group formation was positively correlated with social status. Furthermore, differences in the dynamics within individual groups for each subspecies were reflected by the levels of plasma cortisol of the female members.     

Gas exchange through the jelly capsule of the terrestrial eggs of the frog,Pseudophryne bibroni

Summary The terrestrial eggs of the Australian frog,Pseudophryne bibroni, increase in diameter during development by absorbing water from the substrate into the perivitelline space. This decreases the thickness of the jelly capsule and increases its effective surface area, both effects joining to increase the O₂ conductance of the capsule in parallel with the rate of O₂ consumption. PerivitellineP _{O 2}, calculated from capsule morphology and metabolic rate, and confirmed with micro-O₂-electrodes, remains high and constant (17–19 kPa) throughout the 39 day incubation period at 12°C. The increase in conductance is essential for adequate oxygenation of late embryos. Eggs incubated on substrates of 0 and –25 kPa matric tension (bracketing field conditions) take up disparate amounts of water but show similar conductance.     

Respiration and heat production by the inflorescence of Philodendron selloum Koch

During a 2-d sequence of anthesis, the spadices of the thermogenic arum lily, Philodendron selloum, regulated maximum temperature within a small range (37–44°C) by reversible thermal inhibition of respiratory heat production. This response protects the inflorescence and the attracted insects from thermal damage. Heat production by whole spadices, measured by O₂ respirometry, equalled heat loss, measured by gradient layer calorimetry, which confirmed the heat equivalence of O₂ consumption (20.4 J ml^-1). This also indicated that there was no net phosphorylation during thermogenesis, heat production being the primary function of high rates of respiration. The sterile male florets consumed about 30 ml g^-1 h^-1 and the average 124-g spadix produced about 7 W to maintain a 30°C difference between spadix and ambient temperature. Most of the energy for thermogenesis is present in the florets before anthesis. Despite high respiratory rates, thermogenesis is an energetically inexpensive component of the reproductive process.     

Protein carboxyl-methylation: Role in exocytosis and chemotaxis

The enzyme, protein carboxyl-methylase adds methyl groups to the free carboxyl groups of proteins resulting in the neutralization of their negative charges. This reaction may affect both the structure and the function of these proteins. Protein carboxyl-methylation has been implicated in exocytosis and in chemotaxis. The enzymes involved in the turnover of carboxyl-methylated proteins are described and criteria to evaluate the role of these enzymes in exocytosis and chemotaxis are discussed.     

Enhanced release of striatal dopamine following medial hypothalamic damage in rats

Rats given bilateral lesions of the medial hypothalamus, using either direct or radio frequency current, and killed 2 hours later showed a significant elevation in striatal concentration of homovanillic acid (HVA), while striatal dopamine (DA) was unaltered. After unilateral damage the elevated HVA was seen only in the hemisphere ipsilateral to the lesion. In rats killed 2 days after such damage, the striatal HVA did not differ from controls. The elevation of HVA, suggesting an enhanced release of striatal DA, is associated with a resistance to the cataleptic action of the DA receptor blocking agent droperidol. The present findings suggest that medial hypothalamic lesions can increase neurotransmission within brain DA neurons, and that this neurochemical event may account for at least some of the short-term behavioral effects of these lesions. The relationship of these brain events to the long-term behavioral effects of the lesion remains an important issue for future research.