Catecholamines in fetal pig plasma and the response to acute hypoxia and chronic fetal decapitation

Summary Dopamine, norepinephrine and epinephrine were measured by radioenzymatic assay in blood plasma samples drawn from the umbilical arteries of 30 anaesthetised Landrace pig fetuses. Just prior to term, the concentrations of dopamine (0.46±0.14 ng·ml^–1) and norepinephrine (1.74±0.60 ng·mg^–1) were lower than earlier in gestation, whereas epinephrine concentrations at term (0.80±0.31 ng·ml^–1) were similar to those at mid-gestation, intervening stages of gestation having higher levels of plasma epinephrine. Fetal hypoxia was induced by clamping the umbilical cord for 2 min and the catecholamines determined in arterial blood samples immediately thereafter, then again 3 min after removal of the clamp. Inconsistent effects of cord clamping on catecholamine levels were seen at 55 days, but thereafter, in all but one instance, the hormone levels were increased. Fetuses near term tended to respond less than fetuses at 75 and 96 days gestation (term=114±1 day). Catecholamines were also present in the circulation of fetuses decapitated at 42 days gestation and studied at 109±1 days. The average concentrations of dopamine (1.12±0.27 ng·ml^–1) and norepinephrine (8.23±3.04 ng·ml^–1) were greater than in intact fetuses, the plasma epinephrine levels being comparable to, or slightly higher than, those in intact fetuses. The results demonstrate that catecholamines are present in the circulation of the intact and decapitated pig fetus and that the actual concentrations and the type of response to umbilical cord clamping are dependent on gestation age.     

Genetic studies among Kanet and Koli of Kinnar district in Himachal Pradesh,India

Data are presented on serological and electrophoretic variants of 18 systems of red cells in 228 individuals belonging to a scheduled tribe (Kanet) and a scheduled caste (Koli) of Kinnar district in Himachal Pradesh, India. Differences in gene frequencies clearly indicate biological distinction in the local population. The possible cause of this genetic heterogeneity is discussed.     

Ultrastructure of arterioles in the cat brain

Summary A total of 110 arterioles were examined in the brains of cats; different sites were studied including the cortex, putamen, pons and crus cerebri. No internal elastic laminae were seen in the subendothelial space, although occasional fragments of elastic material were present in the larger arterioles. The media was composed of one, two or three layers of smooth muscle cells which interlocked in such a way that the vessel wall thickness was constant. Numerous tight junctions were seen between adjacent smooth muscle cells and between the endothelium and smooth muscle cells. Apart from the usual cell organelles, the smooth muscle cells of arterioles had numerous dense patches on the cell surface. The structure of the adventitia varied according to the diameter of the vessel and the site in the brain; it contained adventitial cells, bundles of collagen fibres and nerve fibres. Innervation of arterioles was more constant in the brain stem than in the cortex. Metarterioles had less specialised, atypical smooth muscle cells, a discontinuous media and numerous, extensive myoendothelial tight junctions; they were not innervated by nerve fibres. The diameter of metarterioles was less than 10 m whereas that of arterioles was 10–45 m. The possible functional aspects of arteriolar innervation are discussed.     

Effects of synthetic ovine CRF on ACTH, cortisol and blood pressure in sheep

Intravenously administered synthetic ovine CRF at doses of 0.1, 1.0 and 10.0 micrograms/kg increased plasma ACTH and cortisol concentrations in a dose-dependent fashion in unanesthetized sheep. In two unanesthetized sheep, aortic blood pressure remained relatively unaffected after the intravenous administration of CRF at 5 and 20 micrograms/kg. These results suggest that peripherally administered ovine synthetic CRF specifically stimulates the sheep pituitary-adrenal axis. Unlike other species receiving intravenous synthetic ovine CRF, sheep did not show hypotensive effects.     

Drug-Induced Changes in Blood Pressure Lead to Changes in Extracellular Concentrations of Epinephrine, Dihydroxyphenylacetic Acid, and 5-Hydroxyindoleacetic Acid in the Rostral Ventrolateral Medulla of the Rat

Neurochemical changes in the extracellular fluid of the rostral ventrolateral medulla (RVLM) were produced by changes in arterial blood pressure. Blood pressure was raised or lowered with systemic infusions of phenylephrine or nitroprusside and neurochemicals were recovered from RVLM by in vivo microdialysis. A dialysis probe 300 microns in diameter and 500 microns in length was stereotaxically implanted in the RVLM of the urethane-anesthetized rat. Sterile physiological Ringer's solution was perfused at a rate of 1.5 microliter/min. The perfusate was collected under ice-cold conditions every 15 min for the assay of epinephrine, dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA), ascorbic acid, and uric acid. After stable baseline neurochemical concentrations were achieved, animals were infused with phenylephrine or nitroprusside intravenously to raise or lower the blood pressure. Increasing blood pressure 50 mm Hg above the baseline value by phenylephrine led to a significant reduction in heart rate and a reduction in extracellular epinephrine and DOPAC concentrations. The 5-HIAA concentration was increased during the hypertensive drug infusion. There were no changes in the concentrations of ascorbic acid or uric acid. Hypotension produced by nitroprusside (-20 mm Hg) led to neurochemical changes which were the reciprocal of those seen during hypertension. During hypotension, heart rate increased as did the extracellular fluid epinephrine concentration. The 5-HIAA concentration fell with hypotension and remained depressed following the nitroprusside infusion. Ascorbic acid and uric acid concentrations did not change during hypotension but ascorbic acid did increase after the nitroprusside infusion stopped. These data provide direct evidence that epinephrine release in RVLM is linked to changes in systemic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiovascular and renal effects of eel and rat atrial natriuretic peptide in rainbow trout,Salmo gairdneri

Summary The renal and in vitro vascular effects of atrial natriuretic peptides have been examined in seveal species of fish. However, comparatively few investigations have described the effects of these peptides on the cardiovascular system in vivo. In the present experiments the dorsal aorta and urinary bladder were cannulated and the effects of atrial natriuretic peptides from rat and eel were monitored in conscious trout during bolus injection or continuous atrial natriuretic peptide infusion. The results show that the initial pressor effect of atrial natriuretic peptides is independent of environmental salinity adaptation (fresh or seawater) and the chemical form of atrial natriuretic peptide injected, but it is affected by the rate of atrial natriuretic peptide administration. This pressor response, and the accompanying diuresis, are mediated through -adrenergic activation. Continuous infusion of either rat or eel atrial natriuretic peptide produces a steady fall in mean arterial blood pressure, which is temporally preceded by an increase in heart rate and a decrease in pulse pressure. Diuresis induced by atrial natriuretic peptides is only partially sustained during continuous infusion. Propranolol partially blocks the increase induced in heart rate by atrial natriuretic peptides, but does not affect either pulse pressure or mean arterial pressure. Propranolol significantly increases urine flow in saline-infused animals but has no apparent effect on animals subjected to infusions of atrial natriuretic peptides. These results indicate that there are multiple foci for the action of atrial natriuretic peptides in trout and that in many instances the effects of atrial natriuretic peptides are mediated through secondary effector systems.Abbreviations ANP atrial natriuretic peptide - bw body weight - PBS phosphate-buffered saline     

Morphologic differentiation of colon carcinoma cell lines HT-29 and HT-29KM in rotating-wall vessels

Summary A new low shear stress microcarrier culture system has been developed at NASA’s Johnson Space Center that permits three-dimensional tissue culture. Two established human colon adenocarcinoma cell lines, HT-29, an undifferentiated, and HT-29KM, a stable, moderately differentiated subline of HT-29, were grown in new tissue culture bioreactors called Rotating-Wall Vessels (RWVs). RWVs are used in conjunction with multicellular cocultivation to develop a unique in vitro tissue modeling system. Cells were cultivated on Cytodex-3 microcarrier beads, with and without mixed normal human colonic fibroblasts, which served as the mesenchymal layer. Culture of the tumor lines in the absence of fibroblasts produced spheroidlike growth and minimal differentiation. In contrast, when tumor lines were co-cultivated with normal colonic fibroblasts, initial growth was confined to the fibroblast population until the microcarriers were covered. The tumor cells then commenced proliferation at an accelerated rate, organizing themselves into three-dimensional tissue masses that achieved 1.0- to 1.5-cm diameters. The masses displayed glandular structures, apical and internal glandular microvilli, tight intercellular junctions, desmosomes, cellular polarity, sinusoid development, internalized mucin, and structural organization akin to normal colon crypt development. Differentiated samples were subjected to transmission and scanning electron microscopy and histologic analysis, revealing embryoniclike mesenchymal cells lining the areas around the growth matrices. Necrosis was minimal throughout the tissue masses. These data suggest that the RWV affords a new model for investigation and isolation of growth, regulatory, and structural processes within neoplastic and normal tissue.     

Oxygen uptake of carp,Cyprinus carpio,swimming in normoxic and hypoxic water

Synopsis Oxygen uptake (V_{o 2}) was measured in carp of approximately 40 cm length swimming at controlled variable oxygen tensions (P_{o 2}). At P_{o 2}> 120 mm Hg V_{o 2} increased with an increase in swimming speed from 5.6 to 11.3 cm · sec^–1. Extrapolation of V_{o 2} to zero activity at P_{o 2} = 140 mm Hg revealed a standard O₂ uptake of 36.7 ml O₂ · kg^–1 · h^–1 at 20° C. At the lowest swimming speed (5.6 cm · s^–1) the oxygen uptake increased when the water P_{o 2} was reduced. A near doubling in V_{o 2} was seen at P_{o 2} = 70 mm Hg compared to 140 mm Hg. At higher swimming speeds in hypoxic water V_{o 2} decreased relative to the values at low swimming speeds. As a result the slope of the lines expressing log V_{o 2} as a function of swimming speed decreased from positive to negative values with decreasing P_{o 2} of the water. pH of blood from the caudal vein drawn before and at termination of swimming at P_{o 2} = 70 mm Hg and 100 mm Hg did not show any decrease in relation to rest values at P_{o 2} = 140 mm Hg. Blood lactate concentration did not increase during swimming at these tensions.     

Enzymes Related to Monoamine Transmitter Metabolism in Brain Microvessels

The activities of tyrosine hydroxylase, aromatic L-aminoacid decarboxylase, monoamine oxidase, and catechol-O-methyltransferase were measured in microvessel (capillaries and venules), parenchymal arterioles, and pial vessels from rat brains, and the decarboxylase activity was compared in brain microvessels from rabbit, cat, dog, pig, cow, baboon, and man. Cranial sympathectomy was performed to estimate the neuronal contribution to the enzyme activities. All vascular regions had substantial activities of the various enzymes studied. The activity of aromatic L-aminoacid decarboxylase in cerebral microvessels was high in rat, dog, pig, cow, and man; intermediate in rabbit and cat; and low in baboon. In addition to this enzyme, cerebral microvessels also contained tyrosine hydroxylase and monoamine oxidase. Aromatic aminoacid decarboxylase and monoamine oxidase serve an enzymatic barrier function at the microvascular level, whereas the main function of tyrosine hydroxylase is probably to synthesize monoamines within nerve terminals that remain in close association with microvessels under the conditions used for preparation of the microvascular fraction. In larger intracerebral and pial vessels monoamine oxidase was present both in the wall itself and in perivascular sympathetic nerves; the remaining two enzymes had a primarily neuronal localization. The latter types of vessels also contained catechol-O-methyltransferase in their walls.     

A review of some physiological and toxicological responses of freshwater fish to acid stress

Synopsis Data relating to the specific effect of low pH on growth of freshwater fishes are ambiguous. Reproductive failure resulting from acid stress appears to be related to an upset in calcium metabolism and to faulty deposition of protein in developing oocytes. It appears that the ’no effect‘ level of pH depression for successful reproduction is around 6.5. Data on behaviorial responses of freshwater fish to acid stress and CO₂ are described. Most fish appear to be indifferent to pH within the range of approximately 10.5 to 5.5 and between 7.4 and 4.5 CO₂ appears to be the main directive factor. In cases of severe acid stress alteration of gill membranes and/or coagulation of gill mucus occurs and death due to hypoxia may result from a lengthening of the water-blood diffusion distance. Several reports agree that acid stress causes an upset of electrolyte homeostasis in fish but effects of low pH on osmotic permeability are largely lacking. Most hatcheryreared salmonids can tolerate pH 5.0 indefinitely but below this level the homeostatic electrolyte and osmotic regulatory mechanisms become inadequate. When fish are subjected to debilitating acid stress blood pH decreases possibly as the result of flux of H⁺ ions across gill membranes into the blood. This could change transepithelial potential and allow a blood, to-water diffusion of Na⁺ ions down an electrochemical gradient. Lowered ambient pH may interfere with gill calcium levels increasing permeability to both H⁺ and Na⁺ ions or an acidemia may occur as the result of a decrease in the excretion of metabolically produced H⁺ ions and CO₂. When the capacity of the buffer mechanisms is exceeded the blood pH drops and the capacity of hemoglobin to transport oxygen is decreased.