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At least 55 records · Page 3Linked to original sources
PubMed1979

[Action of grisin on the variability of an Acinomyces griseus culture and the use of the same antibiotic as a selection agent in the selection of active variants].

The effect of grisin on survival and variation of Actinomyces griseus producin grisin was studied. The efficiency of various concentrations of grisin on induction of variation according to the feature of the antibiotic production was compared. A possibility of increasing the productivity of strain. VNIIGenetics-115 by the use of the mutations of resistance to grisin is shown.

Anti-Bacterial Agents↗
PubMed1977

Ionic selectivity, saturation and block in gramicidin A channels: I. Theory for the electrical properties of ion selective channels having two pairs of binding sites and multiple conductance states.

A model for the gramicidin A channel is proposed which extends existing models by adding a specific cationic binding site at each entrance to the channel. The binding of ions to these outer channel sites is assumed to shift the energy levels of the inner sites and barriers and thereby alter the channel conductance. The resulting properties are analyzed theoretically for the simplest case of two inner sites and a single energy barrier. This for-site model (two outer and two inner) predicts that the membrane potential at zero current (Uo) should be a Goldman-Hodgkin-Katz equation with concentration-dependent permeability ratios. The coefficients of the concentration-dependent terms are shown to be related to the peak energy shifts of the barrier and to the binding constants of the outer sites. The thory also predicts the channel conductance in symmetrical solutions to exhibit three limiting behaviors, from which the properties of the outer and inner sites can be characterized. In two-cation symmetrical mixtures the conductance as a function of mole fraction is shown to have a minimum, and the related phenomenon of inhibition and block exerted by one ion on the other is explained explicitly by the theory. These various phenomena, having ion interactions in a multiply occupied channel as a common physical basis, are all related (by the theory) through a set of measurable parameters describing the properties of the system.

Electric Conductivity↗
PubMed1978

Effect of selective and non-selective beta-adrenoreceptor blockade on calf blood flow in hypertensive patients.

1. Dose-response curves of isoprenaline were constructed in nine hypertensive patients before and after either propranolol or metoprolol. 2. The decrease of diastolic blood pressure and increase of heart rate with isoprenaline were significantly more inhibited by propranolol than by metoprolol. 3. The increase in calf blood flow with isoprenaline was significantly more depressed after propranolol than after metoprolol. 4. The results suggest that the response of the vessels in the limbs to sympathetic stimulation is much less affected after metoprolol than after propranolol.

Blood Pressure↗
PubMed1979

Selective adaptation to frequency-modulated tones: evidence for an information-processing channel selectively sensitive to frequency changes.

Exposure to an FM tone elevates FM threshold but not AM threshold. This holds for a wide range of frequency deviations (delta F = +/- 0.4 Hz- +/- 30 Hz at least) provided that modulation frequency is low (fm = 2 Hz), but if fm is somewhat higher (e.g., 8 Hz) the finding only holds for small frequency deviations. FM threshold can rise with time up to an adapting duration of at least 1200 s, through this buildup depends on frequency deviation. Exposure to an AM tone elevates AM threshold, but not FM threshold, over a wide range of modulation depths (at least m = 5%--50%). Quasi-FM (QFM) adapting tones resemble FM adapting tones in their effects upon FM and AM sensitivities, even though QFM and AM adapting tones have identical power spectra. Exposure to a pure tone produces no difference between FM and AM threshold elevations. These data can be explained if the human auditory pathway contains separate information-processing channels for AM and FM signals whose sensitivities do not overlap even with suprathreshold stimuli. We suppose that the FM channel (but not the AM channel) is sensitive to changing differences (or ratios) between signals from different sites along the basilar membrane.

Adaptation, Psychological↗
PubMed1978

Effects of selective and non-selective beta-adrenergic blockade on coronary dynamics in man assessed by rapid atrial pacing.

The effects on coronary dynamics of propranolol and atenolol were studied in 12 patients undergoing cardiac catheterisation for suspected coronary artery disease. Myocardial blood flow was measured using the coronary sinus continuous thermodilution technique. Data were obtained immediately after drug administration and during rapid atrial pacing. The immediate effects were similar for both drugs. A significant reduction in heart rate was accompanied by a small reduction in myocardial oxygen consumption. Changes in coronary sinus flow induced by rapid pacing were closely related to changes in tension-time index. This relation was not modified by propranolol or atenolol. Neither propranolol nor atenolol therefore has significant coronary vasoconstrictor properties. Cardioselectivity appears to be unimportant with respect to beta-adrenergic blockade and the coronary circulation.

Adult↗
PubMed1979

[A new therapeutic concept for the selection of liver cirrhotics with recurrent bleeding esophageal varices for selective shunt].

Analysis was made of almost 600 patients who received shunt operations between January 1, 1952 and January 1, 1975 because of liver cirrhosis and repeated bleeding from gastroesophageal varices. The emergency portosystemic shunt was abandoned owing to its 50% lethality; the portocaval shunt was also discontinued, because of an encephalopathy rate of 25%. The splenorenal shunt (Linton) and coronary-caval shunt (Gütgemann) gave comparatively satisfactory results. A more recent introduction was the mesocaval interposition shunt (Drapanas). We also developed new criteria of indication for a shunt operation: elective shunt, liver volume 1000--2500 ml, portal vein perfusion 15%--40%, avoidance of celiac trunk and hepatic artery stenosis. Using only the types of shunt operation and criteria of indication here recommended, lethality among 65 patients operated on between January 1, 1975 and July 1, 1978 was only 6%, delayed lethality only 3%. The rate of encephalopathy was reduced to 5%. The 5-year life expectancy should increase to more than 70%. Thus, support is provided for the proposed therapy concept and criteria for shunt indication.

Aged↗