Oligo(A) and double-stranded segments in polyadenylated and non-polyadenylated RNA from cytoplasm and nuclei of chick embryo

Chick embryonic RNA was fractionated by affinity chromatography on oligo(dT)-cellulose and poly(U)-Sepharose into three classes: poly(A)+RNA containing poly(A) segments of 100 and more residues, poly(A)-oligo(A)+RNA containing oligo(A) segments of about 25 residues, and poly(A)-oligo(A)-RNA which bound to neither of the beds used and which contained double-stranded segments of 300 and more base pairs. These three classes of RNA were found in cytoplasmic as well as in heterogeneous nuclear RNA. Double-stranded segments in hnRNA, unlike those in cytoplasmic RNA, were intermolecular in nature; this may explain the occurrence of "giant" molecules in hnRNA.     

Incidence of non-cholera vibrios in Hungary.

In the period 1971 to 1976, 200 non-cholera vibrio (NCV) strains were isolated in Hungary; 18 of the cultures were derived from 34 729 faecal and 182 from 237 surface water samples. Ninety-two strains belonged to the Heiberg-Smith group I and 108 to group II. Two strains failed to give the string test and 3 were pteridine resistant. The strains were classified into 48 serotypes according to Smith's system. Faecal NCV strains belonged to serotypes 46 and 328; these serotypes did not occur in water. Of the 18 faecal strains 13 were isolated from 18 048 persons who had travelled in cholera-infected areas, and 5 strains from persons who had never left Hungary (2 from 4559 patients with diarrhoea and 3 from 6061 healthy individuals). These data indicate that although NCV are present in the environment, they play an insignificant role in enteric infections in Hungary.     

Comparison of agar gel precipitation and complement fixation test for the detection of Brucella ovis infection.

Blood samples from 710 sheep raised in 20 different farms were examined for Brucella ovis antibodies. Thirty samples were positive with complement fixation, 35 samples with precipitation, and 58 samples with both tests. It has been concluded that the gel precipitation technique is adequate for screening but for individual testing both methods should be used simultaneously.     

Intracellular oxygen tension and energy metabolism in the cat brain cortex during haemorrhagic shock.

The changes in intracellular oxygen tension and energy metabolism of the cat brain cortex were studied by surface fluororeflectometry during haemorrhagic shock. The results may be summarized as follows. (a) Intracellular oxygen tension, i.e. the maximum cortical NAD reduction obtained during nitrogen gas inhalation decreased gradually during the hypovolaemic phase of shock and finally, the brain cortex became ischaemic. (b) Partial uncoupling of the cerebrocortical mitochondrial respiration and oxidative phosphorylation appeared in the very early period of bleeding, as indicated by the overshot of the cortical NAD/NADH redox state towards oxidation subsequent to the cessation of nitrogen gas inhalation. Partial uncoupling of mitochondrial respiration and oxidative phosphorylation became more pronounced during the later phases of bleeding, finally, the mitochondrial electron transport stopped. In line with these changes the frequency and the amplitude of ECoG decreased gradually and markedly during the hypovolaemic phase of shock. (c) Microcirculation and energy metabolism of the cat brain cortex were severely and irreversibly damaged during the hypovolaemic phase of shock. This was clearly shown by the fact that in the majority of experiments the nitrogen anoxia after reinfusion failed to bring about changes in the cortical NAD/NADH redox state and the ECoG changes occurred during bleeding did not improve after reinfusion. It is concluded that the early disturbances of cerebrocortical energy metabolism play an important role in the development of neural and vascular lesions of the brain that occur during haemorrhagic shock.     

Effect of renal vasodilatation on intrarenal blood flow distribution

Total renal blood flow (TRBF) and its intrarenal and intracortical distribution were measured before and during renal vasodilatation induced by acetylcholine infusion using the 133Xe washout, 86Rb uptake and radioactive microspheres distribution techniques. A good agreement was observed between TRBF calculated from 133Xe washout and measured with the electromagnetic flowmeter (FM). 86Rb-TRBF was lower than FM-TRBF and, due to the progressive reduction of renal 86Rb uptake, the difference increased with the increase of flow. With the alteration of TRBF the intrarenal distribution of 86Rb uptake did, however, not change significantly and, accordingly there was no redistribution of RBF either between the cortex and medulla, or among the individual cortical zones. The intracortical distribution of labelled microspheres showed, however, moderate flow dependent changes: with the rise of TRBF, due probably to the reduction of the steric hindrance, the estimated fractional perfusion of the inner cortical zones increased. The sum of the per cent 86Rb content of the innermost cortical zone (C4) and of the medulla exceeded the per cent microsphere content of zone C4. It is concluded that the medulla is perfused not exclusively with blood flowing from the juxtamedullar glomeruli. The regional flow values obtained from the 133Xe curves are not comparable with the results obtained by other methods and cannot be attributed to well defined areas of the kidney.     

Experimental studies on the mechanism of the nitroglycerin effect.

The regional decrease of the speed and extent of the contraction and the relaxation of the canine myocardium induced by coronary ligation was enhanced by intravenously administered nitroglycerin (GTN), simultaneously with the decrease of the left ventricular pressure, while the increase of myocardial fiber length caused by that procedure was partly abolished. The above changes could be reproduced by GTN applied directly onto the ischaemic myocardial surface even before the decrease of the left ventricular pressure. These changes induced by GTN might play a role in the decrease or abolishment of regional asynergic wall motion.     

Species differences in the effect of isoproterenol and pindolol on renin release in vitro.

The effects of selective beta adrenergic receptor stimulation with isoproterenol (3 X 10(-8) M) and of beta adrenergic blockade with pindolol (3 X 10(-5) M) on the renin release in vitro were investigated in incubated canine and rat kidney slices. Bioassay was used to measure the renin content of the tissue samples and incubation media; renin content in the canine incubation medium was measured also by radioimmunoassay. Isoproterenol in a concentration of 3 X 10(-8) M brought about a significant increase in the renin content of the incubation media as well as the tissue slices obtained from canine kidney, however, there was no change in these parameters under similar conditions if rat kidneys were incubated. Pindolol, on the other hand, in a concentration of 3 X 10(-5) M caused a significant decrease in the renin release from as well as in the renin content of the rat kidney slices, while canine kidney slices failed to respond to the same dose of the drug. The differences between the two species is suggested to be due to the differences in basal renin levels.     

Intravenous perfusion of adrenaline and adaptation to muscular exercise in man]

Eleven normal subjects underwent epinephrine perfusions (1.9; 6.1; 11.8 ng/min) during a short (20 min) and mild (50% VO2 max) exercise. VO2 was not modified by epinephrine perfusion, while heart rate ventrilation and plasmatic lactate were increased proportionally to epinephrine doses.     

The membrane valve: A consequence of asymmetrical inhibition of membrane carriers. I. Equilibrating transport systems

Facilitated membrane transport systems act as valves, or rectifiers, when the substrate affinities on the two sides of the membrane differ substantially, i.e. when the system is strongly asymmetric. The asymmetry may be intrinsic or imposed by a reversible competitive inhibitor acting on only one side of the membrane. Under non-equilibrium conditions such systems allow net movements of substrate to proceed faster, sometimes much faster, in one direction than the other, though the final equilibrium is unaffected. Obligatory exchange systems may also function as valves when inhibited unsymmetrically, permitting exchange to occur more rapidly with one distribution of substrates than with the reversed distribution. Here, unequal flux rates do not depend on unequal concentrations of the substrate on either side of the membrane, but may also occur with equal concentrations, provided the affinities of the two substrates differ.The kinetic theory leading to these conclusions is given here, and it is shown how individual parameters of a carrier system affect the efficiency, or tightness, of the valve. In addition, simple kinetic tests for the operation of a valve are outlined. Examples are cited of transport systems having inhibitor-binding sites on only one surface of the cell membrane, which could function normally as valves. Systems implicated are glucose transport in various cells, the ADP-ATP exchanger of mitochondria, the anion transporter of erythrocytes, and the Na⁺-K⁺ pump.     

Relationship of photocarotenogenesis to other behavioural and regulatory responses inPhycomyces

The effect of light on carotene accumulation was studied by analyzing the -carotene content of 4--old mycelia continuously exposed to illumination of different intensities. The wild-type, mutants defective in phototropism, mutants defective in carotene regulation, and newpic mutants specifically defective for photocarotenogenesis were examined. The results indicate that photocarotenogenesis depends on a single sensory pathway which shares its earlier steps (governed by genesmadA andmadB) with the sensory pathway for phototropism. It shares its later steps (probably governed by genescarA andpicB) with one of the pathways for carotene regulation, and includes at least one specific step (governed by genepicA) not known to be involved in other responses.