The effect of pregnancy on mineralo- and gluco-corticoid secretion in the sheep

1. The peripheral blood concentrations of aldosterone, corticosterone and cortisol were measured during pregnancy in conscious, undisturbed sheep. 2. Aldosterone levels did not change during pregnancy and the mean pregnant value, 1-2 s.d. 1-4 ng/100 ml(n = 12) was not significantly different from the non-pregnant value, 2-1 s.d. 1-7 (n = 16). 3. Cortisol levels likewise were unchanged by pregnancy-non-pregnant values were 0-56 s.d. 0-50 mug/100 ml (n = 12) compared with 0-46 s.d. 0-40 mug/100 ml (n = 16) in pregnant sheep. 4. Sheep of 110-140 days gestation had a 400 mmol greater total exchangeable sodium than non-pregnant sheep. Plasma volume and plasma renin concentration tended to be elevated near to term. 5. Very high aldosterone secretion rates and peripheral blood levels could be produced in pregnant sheep by stress, intravenous ACTH or angiotensin II infusions, and by sodium deficiency. It is suggested that the pregnant sheep may show increased sensitivity in contrast to non-pregnant sheep to these stimuli and the enlarged size of their adrenals may be a contributing factor.

Heteropolypeptides from poly-alpha-cyanoglycine and hydrogen cyanide: a model for the origin of proteins

Poly-alpha-cyanoglycine, a homopolymer synthesized from the N-carboxyanhydride of alpha-cyanoglycine, is converted by cumulative reaction of hydrogen cyanide to heteropolypeptides that can be hydrolyzed to protein amino acids, including glycine, alanine, valine, aspartic acid, and glutamic acid. These results are consistent with the hypothesis that the original heteropolypeptides on the earth arose spontaneously from hydrogen cyanide and water without the intervening formation of alpha-amino acids.

Highly asymmetric transcription by RNA polymerase containing phage-SP01-induced polypeptides and a new host protein

An RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) has been purified from phage-SP01-infected Bacillus subtilis that copies RNA almost exclusively from the heavy strand of native SP01 DNA, the DNA strand from which "middle" and "late" classes of RNA are copied in vivo. Hybridization-competition established that this RNA polymerase termed enzyme A, preferentially synthesizes middle RNA in vitro. Enzyme A contains beta',beta, alpha, and two newly identified host polypeptides, variation of (21,500 daltons) and omega (11,000 daltons). All of these polypeptides are associated with highly purified RNA polymerase from uninfected bacteria. In addition, enzyme A contains phage-induced subunits of 26,000, 24,000, and 13,500 daltons. Enzyme A lacks sigma polypeptide, and strand-selective transcription by this enzyme is resistant to anti-sigma antibody. A reconstitution experiment strongly suggests that the host variation of protein is required in addition to a phage-induced subunit(s) (or an unidentified phage-induced modification) for strand-selective transcription of SP01 middle genes in vitro.

Localization and characterization of the hippuricase activity of group B streptococci

Studies are presented on the isolation, localization, and characterization of hippuricase activity of group B streptococci. Washed, intact cells, live or heat killed at 56 C, exhibited hydrolysis of hippuric acid, but cell-free filtrates of the organism did not. Excellent hippuricase activity was recoverable from supernatant fluids of mechanically disrupted cells, and evidence suggests that it exists largely intracellularly. Characteristics of the hippuricase preparation are consistent with the view that the biologically active principle is an enzyme. A quantitative microtiter technique has been developed which is useful in titrating enzymatic activity and antibody neutralization. Sera from rabbits immunized with filtered preparations neutralized hippuricase activity.

Action spectra and adaptation properties of carp photoreceptors

The mass photoreceptor response of the isolated carp retina was studied after immersing the tissue in aspartate-Ringer solution. Two electro-retinogram components were isolated by differential depth recording: a fast cornea-negative wave, arising in the receptor layer, and a slow, cornea-negative wave arising at some level proximal to the photoreceptors. Only the fast component was investigated further. In complete dark adaptation, its action spectrum peaked near 540 nm and indicated input from both porphyropsin-containing rods (lambda(max) approximately 525 nm) and cones with longer wavelength sensitivity. Under photopic conditions a broad action spectrum, lambda(max) approximately 580 nm was seen. In the presence of chromatic backgrounds, the photopic curve could be fractionated into three components whose action spectra agreed reasonably well with the spectral characteristics of blue, green, and red cone pigments of the goldfish. In parallel studies, the carp rod pigment was studied in situ by transmission densitometry. The reduction in optical density after a full bleach averaged 0.28 at its lambda(max) 525 nm. In the isolated retina no regeneration of rod pigment occurred within 2 h after bleaching. The bleaching power of background fields used in adaptation experiments was determined directly. Both rods and cones generated increment threshold functions with slopes of +1 on log-log coordinates over a 3-4 log range of background intensities. Background fields which bleached less than 0.5% rod pigment nevertheless diminished photoreceptor sensitivity. The degree and rate of recovery of receptor sensitivity after exposure to a background field was a function of the total flux (I x t) of the field. Rod saturation, i.e. the abolition of rod voltages, occurred after approximately 12% of rod pigment was bleached. In light-adapted retinas bathed in normal Ringer solution, a small test flash elicited a larger response in the presence of an annular background field than when it fell upon a dark retina. The enhancement was not observed in aspartate-treated retinas.

A proposed method to interrupt gastrointestinal bleeding: preliminary report

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Ionic, histological and vascular factors in the reaction of the sheep's parotid to high and low mineralocorticoid status

1. The blood capillaries from the alveolar areas of the sheep's parotid gland drain into a sinusoidal portal venous system which is in close relation to the striated intralobular ducts.2. The alveoli of the gland are surrounded by a mesh of muscular processes of myoepithelial cells: there are no myoepithelial structures in relation to the ducts.3. In close relation to the alveoli are nerve fibres, some containing noradrenaline and some with cholinesterase at their cellular contact area. Stimulation of the cervical sympathetic trunk for 1-2 min (or intra-arterial injection of noradrenaline) causes expulsion from each gland of a regular amount of saliva without changing the long term appearance rate of saliva. Stimulation of the secretomotor nerve (or acetylcholine I.A.) causes an increase in saliva production.4. It is proposed that the saliva which appears due to sympathetic stimulation is expelled from the alveoli by contraction of the myoepithelial network and is little changed during its rapid transit through the duct system.5. The results indicate that the alveolar cells react to increasing aldosterone status by increasing concentration of K(+) in alveolar fluid with inverse change of Na(+) in alveolar secretion over a wide range of flow rates.6. No histological evidence of innervation of the intralobular striated ducts by sympathetic or secretomotor nerves was obtained.7. The secretory ducts appear to be the site of exchange of HCO(3) (-) and phosphate, Na(+) and K(+), and for enrichment of SCN(-) and I(-) in the alveolar fluid.8. During stimulation of the secretomotor nerve supply, the gland, whether in adrenally insufficient or in hyperaldosterone status, shows the initial transient of discharge of K(+) into saliva and blood and then maintains K(+) intake from plasma as near to output in saliva as does the gland in the replete animal with basal aldosterone status.