The effect of different gas mixtures under increased pressure on the self-stimulation reaction of rabbits]

Self-stimulation of rabbits in heliox at high pressure was decreased. That effect was potentiated by rapid compression. Addition of 2% or 6% nitrogen to heliox exerted no influence on the self-stimulation behavior.     

The pulmonary hemodynamics changes under experimental myocardial ischemia in rabbits following increased arterial pressure

In acute experiments in anesthetized rabbits, changes of the pulmonary hemodynamics following myocardial ischemia in the region of the descendent left coronary artery were studied in control animals and after the infusion of adrenaline and phenylephrine. The pulmonary artery pressure was increased following infusion of these drugs; however, it decreased to normal level in the condition of myocardial ischemia. Meanwhile the pulmonary vascular resistance was elevated to the same level in both cases. Following adrenaline infusion, the pulmonary artery blood flow and venous return increased and, in the condition of myocardial ischemia, they decreased to normal level, but the left atrial pressure was decreased. Following phenylephrine infusion, the pulmonary artery blood flow and venous return did not change and, in the condition of myocardial ischemia, these parameters decreased lower than normal level but the left atrial pressure was elevated. Thus we concluded that equal values of the pulmonary artery pressure in both cases were caused by changes of different character in the left atrial pressure. The differences of the changes character and values of the pulmonary artery flow under experimental myocardial ischemia following the infusion of adrenaline and phenylephrine were caused by different shifts of the venous return.     

Changes in pain sensitivity under increased atmospheric pressure]

It has been established that augmentation of air pressure from 0.1 to 1.1 MPa (with 0.1 MPa intervals) was accompanied in rats with the development of progressive analgesia which was measured according to the threshold of vocalization in the test of electrical stimulation of the tail. The highest analgesic response arose at 0.7-1.1 MPa. All the animals might be divided into two groups: group 1-72% of the animals with a 200% increase of the threshold, group 2--animals with such an increase by 15%. The augmentation of the pressure of heliox (79.1% of helium, 20.9% of oxygen) also caused analgesia, but not so strong. In patients pain thresholds to the mechanical nociceptive stimulation also increased by about 43-67% and 95-100% under the influence of increased air pressure of 0.4 and 0.7 MPa, respectively. In group 1 patients (67%) pain threshold increased by 50-100%, in group 2 by 15-25%. Pretreatment with naloxone (1 mg/kg), atropine (1 mg/kg), yohimbine (1 mg/kg), parachloramphetamine (5 mg/kg) and prasosin (1 mg/kg) decreased hyperbaric analgesia in rats by 41-56, 41-56, 17-19, 17-19%, respectively. The role of increased partial pressure of nitrogen in hyperbaric analgesia and possible neurochemical mechanisms of its realization are discussed.     

Met-enkephalin restores self-stimulation behavior in rabbits after destruction of the hypothalamic nuclei]

Contralateral lesions of ventromedial and lateral hypothalamic nuclei inhibited hypothalamic self-stimulation in rabbits. Intracerebroventricular injection of metenkephalin evoked the restoration of self-stimulation behavior.     

The effect of neurotropic substances on the self-stimulation reaction at the thalamic level]

The effect of d-amphetamine, cocaine, caffeine, morphine, imipramine, phenobarbital, LSD-25, benactyzine, meprobamate, diazepam, chloridiazepoxide on the lateral hypothalamic self-stimulation of rats was investigated. D-amphetamine, cocaine, caffeine, morphine, imipramine decreased the threshold of selfstimulation. Meprobamate, diazepam, chlordiazepoxide failed to influence this index, but increase the intensity of self-stimulation during the threshold, the optimum and more than the optimum cirrent intensity. Benactyzine, LSD-25, phenobarbital decreased the threshold and increased the frequency of self-stimulation during all the current intensities. A comparative study of the above results showed the agents of the first group to exert a direct stimulating action on the positive reinforcement system. Tranquillizers activated this system due to their depressive action on the negative reinforcement system. Benactyzine, LSD-25, phenobarbital activated the system and depressed the system of negative reinforcement.     

Effect of the "memory peptide" ACTH 5-10 on the self-stimulation reaction of rabbits

Experiments on rabbits were made to study variation in the frequency of the self-stimulation reaction from the lateral hypothalamus under the effect of the corticotropin fragment ACTH5-10. Intraperitoneal administration of the peptide in a dose of 50 micrograms/kg that causes the improved training in different behavioral models produces no significant effect on the mechanism of intracranial positive reinforcement. Intraventricular injection of 5 microliters of 0.9% NaCl leads to a short-term suppression of the self-stimulation reaction. Administration of 50 pcM/kg ACTH5-10 in the same volume of physiological saline completely abolishes the inhibitory action of the intraventricular injection itself.     

Enzymic chemical reaction under microgravity environment in space

In recent years, some papers have reported synergism in the biological effects of space radiation and microgravity. However, there is no direct evidence for these phenomena. As one possible mechanism, we investigated whether DNA ligation in the final step of DSBs repair of DNA molecules induced by radiation is depressed by microgravity. Therefore, we have scheduled the space experiments of the effects of microgravity on repair activity of T4 DNA ligase for DSBs prepared with digestion of a restriction enzyme (Sma I) to plasmid DNA. As another possible mechanism, the high mutation frequency may be induced from abnormal base-incorporation during DNA replication under microgravity. Using the Taq polymerase and polymerase III, we have also scheduled whether mutation frequency is affected by microgravity during DNA replication for a damaged DNA base induced by an alkylating agent (N-methyl-N-nitrosourea, MNU).     

A comparison of the self-stimulation reaction and of conditioned place preference with fenamine administration in rats]

The reinforcing properties of different doses of amphetamine (1 and 5 mg/kg) were examined using two variants of self-stimulation reaction (in the Skinner box and locomotor self-stimulation in a shuttle box) and place preference test. Amphetamine in dose of 1 mg/kg increased the frequency of self-stimulation in the Skinner box and prolonged the time of rat staying in active zone of a shuttle box to a greater degree than 5 mg/kg of the drug. On the contrary, the aversive phase of self-stimulation, determined by a coefficient of "disagreement", grew higher after 5 mg/kg amphetamine than following 1 mg/kg. The study of effects by place preference test revealed the other regularity: the most positive reinforcing properties possessed the drug in a dose of 5 mg/kg. Thus, there are dissociation between the two doses of amphetamine (1 and 5 mg/kg) in their action on different physiological conditioned responses. The mechanisms of this dissociation are discussed.     

Cyclic analogs of ACTH fragments in self-stimulation and grooming behavior in rabbits

In present study new cyclic fragments of ACTH EHFRWGKPVG--NH2 and KHFRWG--NH2 were investigated in organization of self-stimulation and grooming behaviour in rabbits. Intracerebroventricular injections of EHFRWGPVG--NH2 in doses of 0.1-2.5 g evoked significant increases of self-stimulation and in doses of 4-5 g suppressed self-stimulation in rabbits. The effect of other fragments KHFRWG--NH2 on self-stimulation was not statistically significant. Both fragments induced excessive grooming behaviour in rabbits. The effects of these fragments persisted of 48-72 hours.     

Response of rabbits to pyrogen in a helox environment

1. 1.|The effectiveness of a gas environment consisting of 80% helium and 20% oxygen (Helox) in reducing a rabbit's fever due to an i.v. injection of endotoxin was found to be dependent on the amount of pyrogen injected.

2. 2.|When a relatively large dose of pyrogen was injected, the helox environment used in these experiments reduced the mean maximum temperature reached during the fever from 41.5 to 40.5°C, but the helox did not significantly alter the change in temperature from baseline levels prior to the injection (a 1.4°C increase in air and a 1.1°C increase in helox).

3. 3.|When a relatively low dose of pyrogen was injected, the helox environment increased the change in temperature from baseline at peak fever, but did not produce a significant change in the actual temperatures attained during the fever.

Enhanced heterologous protein production in Pichia pastoris under increased air pressure

Pichia pastoris is a widely used host for the production of heterologous proteins. In this case, high cell densities are needed and oxygen is a major limiting factor. The increased air pressure could be used to improve the oxygen solubility in the medium and to reach the high oxygen demand of methanol metabolism. In this study, two P. pastoris strains producing two different recombinant proteins, one intracellular (β‐galactosidase) and other extracellular (frutalin), were used to investigate the effect of increased air pressure on yeast growth in glycerol and heterologous protein production, using the methanol AOX1‐inducible system. Experiments were carried out in a stainless steel bioreactor under total air pressure of 1 bar and 5 bar. The use of an air pressure raise of up to 5 bar proved to be applicable for P. pastoris cultivation. Moreover, no effects on the kinetic growth parameters and methanol utilization (Mut) phenotype of strains were found, while an increase in recombinant β‐galactosidase‐specific activity (ninefold) and recombinant frutalin production was observed. Furthermore, the air pressure raise led to a reduction in the secreted protease specific activity. This work shows for the first time that the application of an air pressure of 5 bar may be used as a strategy to decrease protease secretion and improve recombinant protein production in P. pastoris. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1040–1047, 2014     

Effect of helium-oxygen pressure on dopamine detected in vivo in the striatum of hamsters

Free-moving hamsters chronically implanted in the striatum with carbon multifiber electrodes selective to dopamine were compressed in a helium-oxygen breathing mixture to 81 bars. Under these conditions, there was an increase in the electrochemical responses recorded from the carbon electrode by differential pulse voltammetry, which occurred during the compression and disappeared when the animals returned to the surface. This change was related to an increase in extracellular dopamine levels induced by the increase in pressure of the helium-oxygen mixture.