Beneficial effect of serum on the fertilizability of mouse oocytes matured in vitro

Mouse oocytes matured in vitro in chemically defined medium were not penetrated by spermatozoa. The time required for dissolution of the zona pellucida of such oocytes by alpha-chymotrypsin was much longer than that for ovulated oocytes. Addition of fetal calf serum to the medium for maturation of oocytes improved the incidence of sperm penetration and shortened the time of enzymic dissolution of the zona pellucida. These results suggest that the low rate of fertilization of oocytes matured in vitro is mainly due to qualitative changes of the zona pellucida, which could be overcome by a factor or factors in fetal calf serum.     

Cholesterol oxidation on fluorocarbon emulsion surface leads to the formation of 7-peroxycholesterol

Formation of biologically active oxidized derivatives of cholesterol as a result of its oxidation on the surface of fluorocarbon emulsions was studied. A single product of cholesterol oxidation, 7-peroxycholesterol, was found. It was shown that 7-peroxycholesterol and its derivative 7-keto-cholesterol inhibit the rosette formation between human T-lymphocytes and sheep erythrocytes. These substances exert a strong cytostatic action on the growth of procaryotic and eucaryotic cell cultures. Thus, oxidative modification of blood plasma components on the surface of fluorocarbon emulsion particles with the formation of highly active compounds must be taken into account when using the fluorocarbon emulsions in medicine.     

Effect of armin on synaptic transmission in frog neuromuscular preparations

The action of armin, an organophosphorus inhibitor of cholinesterases, on synaptic transmission parameters was studied by means of intracellular registration of end plate potentials and currents (EPP and EPC) in the frog. On 10-minute exposure the increase in the temporary parameters became manifest provided the drug was administered at a concentration of 10(-6) g/ml and over. EPC reversal potential and cholinoreceptor sensitivity to armin did not change substantially. At a concentration of 10-(-8) g/ml armin exerted a potentiating effect on the frequency of miniature EPP and quantum composition of EPP, while that effect was not related to armin anticholinesterase activity. The presynaptic acetylcholine release was suppressed by high concentration of armin (10(-5) g/ml). Under the conditions cited there was a decrease in the depot of the available transmitter quanta in nerve terminals.     

The effect of proprioceptive training on neuromuscular function in patients with patellar pain

Eight patients with patellar pain underwent knee proprioceptive training. The maximal knee extension torque associated with the Vastus Lateralis EMG signal increased (p 0.001 and 0.039). Although muscle balance was not improved, all the patients improved their clinical scores.     

The effect of Ptilotus plant tissue on pH of in vitro media

Changes occur in the pH of in vitro nutrient media during preparation and over the culture period. The direction and extent of the changes depend upon the initial pH and the presence or type of gelling agent. Agar-based medium was progressively acidified in the presence of a living Ptilotus exaltatus explant. This was not a response to wounding and the rate of acidification could be maintained by frequent replacement of the medium. The rate appears to be pH dependent with an equilibrium occurring at pH4. The pH effect was not accounted for by K⁺ uptake.     

The effect of Eglin C on the function of human neutrophils in vitro

Eglin C is an inhibitor of polymorphonuclear leukocyte elastase and cathepsin G. Recently, it was suggested that Eglin C may inhibit bacterial clearance in an experimental animal model of pneumonia. Since the phagocytic-bactericidal activity of polymorphonuclear leukocytes is most important in the promotion of bacterial clearance, we determined the effect of Eglin C on a variety of functions of isolated human polymorphonuclear leukocytes such as phagocytic-bactericidal activity, superoxide production, degranulation and chemotaxis. Apart from a partial inhibition of superoxide production, which was shown to be due to a superoxide dismutase-like effect of Eglin C, there was no inhibition of polymorphonuclear leukocyte functions measured. Eglin C can therefore be considered as a protease inhibitor, which does not interfere with the phagocytic-bactericidal activity of human polymorphonuclear leukocytes.     

Effects of caffeine on neuromuscular function.

This double-blind, repeated-measures study examined the effects of caffeine on neuromuscular function. Eleven male volunteers [22.3 +/- 2.4 (SD) yr] came to the laboratory for control, placebo, and caffeine (6 mg/kg dose) trials. Each trial consisted of 10 x 1-ms stimulation of the tibial nerve to elicit maximal H reflexes of the soleus, four attempts at a maximal voluntary contraction (MVC) of the right knee extensors, six brief submaximal contractions, and a 50% MVC held to fatigue. Isometric force and surface electromyographic signals were recorded continuously. The degree of maximal voluntary activation was assessed with the twitch-interpolation technique. Single-unit recordings were made with tungsten microelectrodes during the submaximal contractions. Voluntary activation at MVC increased by 3.50 +/- 1.01 (SE) % (P < 0. 01), but there was no change in H-reflex amplitude, suggesting that caffeine increases maximal voluntary activation at a supraspinal level. Neither the force-EMG relationship nor motor unit firing rates were altered by caffeine. Subjects were able to hold a 50% MVC for an average of 66.1 s in the absence of caffeine. Time to fatigue (T(lim)) increased by 25.80 +/- 16.06% after caffeine administration (P < 0.05). There was no significant change in T(lim) from pretest to posttest in the control or placebo trials. The increase in T(lim) was associated with an attenuated decline in twitch amplitude, which would suggest that the mechanism is, at least in part, peripheral.     

Improved stability of Drosophila larval neuromuscular preparations in haemolymph-like physiological solutions

Neuromuscular preparations from third instar larvae of Drosophila are not well-maintained in commonly used physiological solutions: vacuoles form in the muscle fibers, and membrane potential declines. These problems may result from the NaK ratio and total divalent cation content of these physiological solutions being quite different from those of haemolymph. Accordingly haemolymph-like solutions, based upon ion measurements of major cations, were developed and tested. Haemolymph-like solutions maintained the membrane potential at a relatively constant level, and prolonged the physiological life of the preparations. Synaptic transmission was well-maintained in haemolymph-like solutions, but the excitatory synaptic potentials had a slower time course and summated more effectively with repetitive stimulation, than in standard Drosophila solutions. Voltage-clamp experiments suggest that these effects are linked to more pronounced activation of muscle fiber membrane conductances in standard solutions, rather than to differences in passive muscle membrane properties or changes in postsynaptic receptor channel kinetics. Calcium dependence of transmitter release was steep in both standard and haemolymph-like solutions, but higher external calcium concentrations were required for a given level of release in haemolymph-like solutions. Thus, haemolymph-like solutions allow for prolonged, stable recording of synaptic transmission.Abbreviations HL haemolymph-like     

Beneficial acclimation and the Bogert effect

Few studies have examined the extent to which phenotypic plasticity in a given trait might be influenced by behavioural responses to an environmental cue. Regulatory behaviour might eliminate environmental variation such that little selection for physiological change would take place. Here, to test this Bogert effect on acclimation, we use two life-stages of a kelp fly that inhabit the same habitat, but differ profoundly in their behaviour. We predicted that when denied opportunities for behavioural regulation, mobile, though brachypterous adults would show a performance advantage in most thermal environments following acclimation to their preferred temperature(s). By contrast, in the less mobile larvae, that have a broader thermal preference, beneficial acclimation would be more evident. Ordered factor anova with orthogonal polynomial contrasts revealed that adults recovered faster from chill coma following any one of six short-term temperature treatments if they had been acclimated at low temperature, whilst larvae showed beneficial acclimation.     

Effect of chromium ions on the function of neuromuscular junctions

It has been shown on neuro-muscular preparations of frog sartorius muscle that chromium ions in the concentrations 1-4 x 10(-6) g/ml strengthen spontaneous and evoked transmitter release. Cr3+ ions in the concentrations above 4 x 10(-6) g/ml decrease the membrane potential of muscle fibres, decrease the quantum content of the end plate potentials. Experiments on a single Ranvier node have shown that Cr3+ ions decrease the amplitude, increase the rate and duration of the action potential of a nerve fibre. It is concluded that chromium ions produce a pronounced effect on synaptic transmission, which differs significantly from the action of manganese, cobalt and nickel ions.