Ultrastructural and biochemical enzymatic properties of right ventricular muscles during hindlimb suspension in rats

As a result of exposure to microgravitational forces, the body fluids are shifted from lower part of the body to upper part with a volume of about 2 liters. Many reports on the hemodynamic, humoral, and other biomedical aspects of the body exposed by weightlessness have been reported. A 45 degree head-down tail suspension was introduced to examine ultrastructure and biochemical analyses on the right and left ventricles in rats. Increases in oxydative enzyme activities and relatively increase in m-CK(mitochondrial creatine kinase) were recognized in the right ventricle after suspension for 2 weeks. Mitochondrial volume and density of mitochondrial cristae were also increased. Direct measurement of right ventricular systolic pressure of suspended rats were significantly higher (28.99 +/- 3.11 mmHg) than that of control rats (20.99 +/- 2.94 mmHg), (p < 0.01).     

Effect of irradiation on glycosaminoglycans content in rat tissue

Glycosaminoglycan (GAGs) fractions were determined in tissues (skin, liver, lungs, aortic wall) and blood serum of rats irradiated with a single dose of 500 R. An increase of total GAGs as well as changes in the fractions were found in the tissues and urine of exposed rats.     

Effects of prenatal gamma-irradiation on the astrocyte proliferation in response to injury in the brain of 6-day-old rat

Pregnant Wistar rats were exposed to a single 1.0 Gy dose of gamma rays on gestational days 13, 15, 17 or 19 (E13, E15, E17 and E19, respectively). A mechanical injury was made in the cerebral hemisphere of their 6 day-old male offsprings. The injured rats were injected with [3H]thymidine on day 1 or 2 after injury and killed 4 h after the injection. Brain sections were immunostained for glial fibrillary acidic protein (GFAP) or S-100beta protein, subjected to autoradiography and examined microscopically to record proliferating astrocytes. The intensity of astrocyte proliferation in response to injury showed a gradual decrease from the level maximal in brains irradiated on E13 to minimal in those irradiated on E19. The changes were regarded as being related to the stage of prenatal development when irradiation of the brain was performed.     

Semicircular canal function following a flight aboard biosatellite "Cosmos-936"

The nystagmic reflex, latent period, total and mean number of events, and their duration were measured in the rats flown for 18.5 days aboard the biosatellite Cosmos-936 under the conditions of weightlessness and artificial gravity. The studies demonstrated that prolonged weightlessness did not influence the receptor formations and centers of semi-circular canals. A long exposure to artificial gravity brought about a decrease in reactivity and sensitivity of semi-circular canals. The mechanisms of these phenomena are discussed.     

Changes of the antiheparin activity of the blood plasma and lymph in dogs after total irradiation

An increase was demonstrated of the antiheparin activity in the blood of rats after their total exposure to 200, 500 and 800 R and dogs exposed to 400 R. In the rats the increase of the antiheparin activity was directly dependent of the exposure used. The antiheparin activity increased up to 180 min after the exposure. In the irradiated dogs, there was also a strong increase in the antiheparin activity with a certain decrease 24 hrs after irradiation. A secondary increase was observed on the 7th, 10th and 13th days of the experiment. In the lymph of the irradiated dogs, the increase of the antiheparin activity was steeper than that in the blood itself. The results achieved could serve as a starting point for further investigations to answer the question of possible using these changes for diagnostic estimation of the biological degree of the radiation damage under different conditions.     

Changes in dialysis units'' quality improvement practices from 1994 to 1996

We studied the effect of gravity on cerebral cortical blood flow (CBF), mean arterial blood pressure (BPa) and heart rate in six rabbits exposed to parabolic flights. The CBF was obtained using a laser-Doppler probe fixed on to a cranial window. Before weightlessness, the animals were exposed to chest-to-back directed acceleration (1.8-2.0 g). The CBF values were expressed as a percentage of CBFo (mean CBF during 60 s before the 1st parabola). Propranolol (1 mg x kg[-1] i.v.) was given after the 11th parabola and pentobarbital (12-15 mg x kg[-1] i.v.) after the 16th parabola. Before the administration of the drugs, CBF increased (P < 0.01) during hypergravity [i.e. maximal CBF 151 (SD 64)% CBFo. Simultaneously BPa increased [maximal BPa, 119 (SD 11) mmHg (P < 0.01)]. At the onset of weightlessness, CBF and BPa reached maximal values [194 (SD 96)% CBFo (P < 0.01) and 127 (SD 19) mmHg, (P < 0.01) respectively]. The microgravity-induced increase in CBF was transient since CBF returned to its baseline value after 8 (SD 2) s of microgravity. After propranolol administration, CBF was not statistically different during hypergravity but an elevation of CBF was still observed in weightlessness. The increases in CBF and BPa also persisted during weightlessness after pentobarbital administration. These data would indicate that CBF of nonanesthetized rabbits increases during the first seconds of weightlessness and demonstrate the involvement of rapid active regulatory mechanisms since CBF returned to control values within 8 (SD 2) s. We concluded that this elevation in blood flow was not related to stress because it persisted after the administration of propranolol and pentobarbital.     

Controlled multiplex PCR of enterotoxigenic Clostridium perfringens strains in food samples

Developing rats between 5 and 44 days of age as well as rats about 2 months old were anesthetized with urethane. Spontaneous activities and muscle potentials to sciatic stimuli were recorded from their exposed medial gastrocnemius muscles using concentric electrodes. Neostigmine of 0.12-0.40 mg/kg was injected into the contralateral muscles. Regardless of age, spontaneous activities were not observed and muscle potentials were evoked by single stimuli primarily in a biphasic wave (main component) before the drug treatment. Developmental differences were revealed in the presence of the drug. 1) Spontaneous activities were detected only in single spikes around postnatal 10 days. Single or double spikes were often found in rats of about two weeks. Burst discharges such as seen in adult rats were observed immediately before weaning. 2) In rats of 2 weeks or so, one or more components were observed obscurely following the main component of muscle potentials, which appeared definitely at the preweaning period. 3) When double shocks with the interval of 2 sec were delivered in the presence of the drug, the second potential was greatly depressed in rats older than two weeks as well as in adult rats. The potential was only slightly reduced in rats around 10 days. Thus, an adult pattern as to impulse transmission was observed immediately before weaning. These alterations would, at least in part, reflect the maturation of acetylcholine receptors at neuromuscular junctions.     

Characterisation of the gene encoding adenylosuccinate lyase of Plasmodium falciparum

Pregnant Wistar rats were exposed to a single 1.0 Gy dose of gamma-irradiation on gestational day 13, 15, 17 or 19. Thirty-day-old male offspring received a mechanical lesion in the left cerebral hemisphere. One, 2 or 4 days after the injury the rats were injected with [3H]thymidine and sacrificed 4 h after the injection. Thereafter, brain sections were immunostained for GFAP or S100 beta protein, subjected to autoradiography and examined microscopically to record immunopositive astrocytes labelled with [3H]thymidine. Statistically significant elevation of the reactive astrocyte proliferation was revealed on the 2nd day following injury in brains irradiated on gestational day 15. The results represent the first in vivo evidence that a low-dose prenatal gamma-irradiation can induce a long-term increase in the ability of astroglia to proliferate in response to injury.     

Effect of weightlessness and centrifugation on red cell survival in rats subjected to space flight

Rats were flown aboard the Soviet biosatellite Cosmos 936 for 18.5 d during August, 1977. Five rats were subjected to near-weightless space flight, as with Cosmos 782, and five rats were subjected to a 1-G force via an on-board centrifuge. These rats and three control groups were injected with 2-14C glycine 19 d preflight. The flight rats were recovered from orbit after 18.5 d of space flight. Erythrocyte hemolysis and lifespan were evaluated in the five groups of rats by quantitation of radioactive carbon monoxide exhaled in the breath which arises from the breakdown of the previously labeled hemoglobin. The results support our previous findings wherein hemolysis was found to increase as a result of weightless space flight. A comparison to the centrifuged animals indicates that artificial gravity attenuates the effect of weightlessness on hemolysis and appears to normalize the hemolytic rate in the early postflight period.     

Effects of prenatal gamma-irradiation on postnatal astrogliogenesis in the hippocampal formation of rat

Female Wistar rats were exposed to a single 1.0 Gy dose of gamma radiation on gestational days 13, 15, 17 or 19 (E13, E15, E17 and E19, respectively). Their 8- and 16-day old male offsprings were injected with 3H-thymidine and sacrificed 4 h after the injection. Brain sections were immunostained for S100beta protein and subjected to autoradiography. Thereafter, the dorsal part of the hippocampal formation was examined microscopically and numbers and locations of proliferating astrocytes were recorded. Following prenatal irradiation, the intensity of astrocyte proliferation was considerably reduced, especially in the region of dentate gyrus. The reduction showed regular trend of changes being much stronger in brains irradiated on E19 than in those irradiated on E13. The changes, therefore, were related to the stage of brain development at which the irradiation was performed. A possible role of neuronal regulatory influence on the postnatal development of glial cells was discussed.     

贵冶失重秤控制品质优化

通过分析失重秤的系统组成及工作原理,针对失重秤实际生产中的使用情况、从多个方面分析了影响失重秤控制品质的因素。比如:失重仓重上下限、干矿仓料位、加料阀伸缩节、失重仓流态化、称重传感器、控制参数、螺旋磨损等,并对这些因素进行系统归类,按类别制定相应的控制措施,进而分步逐项实施,从而优化了失重秤的控制品质。最后,根据整个优化过程,摸索出了解决失重秤波动的一套方法,为今后失重秤的稳定高效运行奠定良好的基础。     

Effect of carbon disulfide on cholesterol content in rat tissue

The effect of chronic intoxication of rats with CS2 on the level of cholesterol in the body tissues was studied. Prolonged exposure to CS2 vapour results in the increased level of cholesterol in serum. It was interesting to find out whether accumulation of cholesterol occurs subsequently in the body tissues. Studies were performed on male Wistar albino rats exposed to CS2 vapour at concentration 0.8--1 mg/1 during 13 months. The level of cholesterol in the blood, aorta wall, muscles, liver and adipose tissue was estimated after 4, 10 and 13 months of intoxication. Chronic exposure of rats to CS2 vapour causes: (a) loss of body weight about 30 per cent after 10 months of intoxication; (b) increase of concentration of free and esterified cholesterol in the aorta wall about 20 and 63 per cent, whereas in the skeletal muscles about 40 and 80 per cent, after 10 and 13 months of exposure respectively; (c) no changes of the level of cholesterol in the liver. On the base of the results obtained in this study it was concluded, that prolonged exposure to CS2 contributed to accumulation of cholesterol only in some tissues. Changes we found are probably the result of quantitative shift in the redistribution of cholesterol among the tissues.     

Solution structures of DNA.RNA hybrids with purine-rich and pyrimidine-rich strands: comparison with the homologous DNA and RNA duplexes

The effects of two different duration space-flights on the extent of atrophy, fiber type composition, and myosin heavy chain (MHC) content of rat soleus muscles were compared. Adult male Fisher rats (n=12) were aboard flight STS-57 and exposed to 10 days of microgravity and adult ovariectomized female Spraque-Dawley rats (n=12) were aboard flight STS-62 for 14 days. Soleus muscles were bilaterally removed from the flight and control animals and frozen for subsequent analyses. Muscle wet weights, fiber types (I, IC, IIC, and IIA), cross-sectional area, and MHC content were determined. Although a significant difference was found between the soleus wet weights of the two ground-based control groups, they were similar with regard to MHC content (ca 90% MHCI and ca 10% MHCIIa) and fiber type composition. Unloading of the muscles caused slow-to-fast transformations which included a decrease in the percentage of type I fibers and MHCI, an increase in fibers classified as type IC, and the expression of two fast myosin heavy chains not found in the control rat soleus muscles (MHCIId and MHCIIb). Although the amount of atrophy (ca 26%) and the extent of slow-to-fast transformation (decrease in the percentage of MHCI from 90% to 82.5%) in the soleus muscles were similar between the two spaceflights, the percentages of the fast MHCs differed. After 14 days of spaceflight, the percentage of MHCIIa was significantly lower and the percentages of MHCIId and MHCIIb were significantly higher than the corresponding MHC content of the soleus muscles from the 10-day animals. Indeed, MHCIId became the predominant fast MHC after 14 days in space. These data suggest fast-to-faster transformations continued during the longer spaceflight.     

Malnutrition in elderly people

The goal of the work was to study female tolerance of g-loads before and after simulated weightlessness, and evaluate the effectiveness of countermeasures and anti-g means proposed for space flight. Centrifuge with a 7.25 m arm was used for 29 runs of 8 female subjects. The subjects were exposed to the transverse loads (+GX) at 8.2 g on a special regimen with the total run time of 9 min to simulate the ballistic descent from orbit in a SOYUZ-TM vehicle. Baseline tolerance of the females to transverse loads up to +8GX was good and satisfactory. Following 120 days of bed rest without the countermeasures or the anti-g suit g-tolerance was significantly lowered as evidenced by visual disorders in 67% of cases and exaggerated, if compared with the pre-hypokinesia levels, heart and respiration rates, i.e. 20% and 23.5%, respectively. The countermeasures and anti-g suit Centaur maintained g-tolerance at essentially the baseline level and precluded visual disorders. Results of the study speak in favor of the countermeasures and anti-g means used by the females in simulated long-duration weightlessness which can be recommended for the final phase of extended space mission.     

An experimental model of acute encephalopathy after total body irradiation in the rat: effect of liposome-entrapped Cu/Zn superoxide dismutase

PURPOSE: To develop an experimental model of acute encephalopathy following total body irradiation in rats and to define the therapeutic effect of liposome-entrapped Cu/Zn superoxide dismutase. METHODS AND MATERIALS: A total of 120 4-month-old rats received 4.5 Gy total body irradiation (TBI) while 120 rats received sham irradiation. A behavioral study based on a conditioning test of negative reinforcement, the one-way avoidance test, was performed 5 hours before irradiation and repeated the following days. Subcutaneous treatment was started 1 hour after irradiation and repeated daily for 2 weeks. In both the irradiated and sham group, three subgroups were defined according to the treatment received: liposome-entrapped Cu/Zn superoxide dismutase (0.5 mg/kg), liposomes only, normal saline. RESULTS: This work comprised two consecutive studies. In study A (90 rats) the one-way avoidance test was administered daily from day 0 to day 4 with a recall session at day 14. In study B (validation phase in 150 rats) the behavioral test was performed only from day 0 to day 6. Before irradiation, all rats showed a similar behavioral response. Study A (6 groups of 15 rats): Following TBI, irradiated rats treated with liposomes only or saline demonstrated a significant delay in learning the one-way avoidance test in comparison with sham-irradiated rats (0.05 < p <0.001 depending upon the day of evaluation and the subgroup type). In contrast, irradiated rats treated with liposome-entrapped Cu/Zn superoxide dismutase did not differ from sham-irradiated rats. Study B (6 groups of 25 rats): The results were the same as those in study A, demonstrating a significant delay in the learning of the test in the liposome and saline-treated irradiated rats in comparison with sham-irradiated rats (0.02 < p < 0.001). The irradiated rats, treated with liposome-entrapped Cu/Zn superoxide dismutase did not differ from the sham-irradiated controls. CONCLUSION: This study indicates that a relatively low dose of total body irradiation induces a substantial acute learning dysfunction in the rat. This effect is prevented by the administration of liposome-entrapped Cu/Zn superoxide dismutase.     

Effect of bodyweight on the rate of glucose uptake by isolated rat muscles

The uptake of glucose by isolated extensor digitorum longus muscles was measured in rats of 78-350 g bodyweight. The rate of uptake per unit weight of muscle fell as the weight of the animal increased. It is concluded that in metabolic studies with isolated rat skelatal muscles, only muscles from weight-matched rats should be compared.     

Xenobiotic-enhanced expression of cytochromes P450 2E1 and 2B in primary cultured rat hepatocytes

The purpose of this investigation was to determine whether long-term, heavy resistance training would cause adaptations in rat skeletal muscle structure and function. Ten male Wistar rats (3 weeks old) were trained to climb a 40-cm vertical ladder (4 days/week) while carrying progressively heavier loads secured to their tails. After 26 weeks of training the rats were capable of lifting up to 800 g or 140% of their individual body mass for four sets of 12-15 repetitions per session. No difference in body mass was observed between the trained rats and age-matched sedentary control rats. Absolute and relative heart mass were greater in trained rats than control rats. When expressed relative to body mass, the mass of the extensor digitorum longus (EDL) and soleus muscles was greater in trained rats than control rats. No difference in absolute muscle mass or maximum force-producing capacity was evident in either the EDL or soleus muscles after training, although both muscles exhibited an increased resistance to fatigue. Individual fibre hypertrophy was evident in all four skeletal muscles investigated, i.e. EDL, soleus, plantaris and rectus femoris muscles of trained rats, but muscle fibre type proportions within each of the muscles tested remained unchanged. Despite an increased ability of the rats to lift progressively heavier loads, this heavy resistance training model did not induce gross muscle hypertrophy nor did it increase the force-producing capacity of the EDL or soleus muscles.     

Radiographic verification of implant abutment seating

This study was designed to identify the mechanisms underlying the reduction in food intake in rats. Measurements were made of the release of cholecystokinin (CCK) stimulated by potassium chloride in the hypothalamus after (a) gamma irradiation (60Co), (b) treatment with the CCK-A and CCK-B antagonists L-364,718 and L-365,260 with and without radiation, (c) bilateral abdominal vagotomy, and (d) vagotomy with and without radiation and with and without L-364,718. The concentrations of CCK in hypothalamus perfusate were measured by a radioimmunoassay. Exposure of rats to 1, 3, 5 and 10 Gy (1 Gy/min) increased release of CCK in the hypothalamus in a manner that was dependent on dose. A dose of 5 Gy was chosen for further studies. Intraperitoneal (i.p.) administration of 10, 20 and 50 microg/kg of L-364,718 did not induce significant changes in release of CCK in sham-irradiated animals. However, the drug decreased the release of CCK induced by radiation in a dose-dependent manner. In contrast to L-364,718, 20-50 microg/kg of L-365,260 decreased the release of CCK in the hypothalamus in sham-irradiated animals but did not decrease release of CCK induced by exposure to radiation. Vagotomy produced an insignificant reduction in release of CCK compared to that in sham-irradiated controls. However, vagotomy decreased release of CCK in irradiated rats compared to the irradiated rats without vagotomy. Vagotomy and i.p. administration of 10, 20 and 50 microg/kg of L-364,718 decreased release of CCK in irradiated rats compared to that in irradiated rats without vagotomy. However, i.p. administration of 10, 20 and 50 microg/kg of L-364,718 did not induce significant decreases in release of CCK in the hypothalamus of vagotomized and irradiated animals compared to those in rats that were vagotomized and irradiated but not treated with L-364,718. These results demonstrate that radiation increases the release of CCK in the hypothalamus, and that this effect is inhibited by vagotomy and the administration of a CCK-A receptor antagonist. A CCK-A receptor antagonist may be used to mitigate a radiation-induced deficit in food intake.     

Chronic activation of protein kinase C in soleus muscles and other tissues of insulin-resistant type II diabetic Goto-Kakizaki (GK), obese/aged, and obese/Zucker rats. A mechanism for inhibiting glycogen synthesis

We examined the possibility that protein kinase C (PKC) is chronically activated and may contribute to impaired glycogen synthesis and insulin resistance in soleus muscles of hyperinsulinemic type II diabetic Goto-Kakizaki (GK) rats. Relative to nondiabetic controls, PKC enzyme activity and levels of immunoreactive PKC-alpha, beta, epsilon, and delta were increased in membrane fractions and decreased cytosolic fractions of GK soleus muscles. In addition, PKC-theta levels were decreased in both membrane and cytosol fractios, whereas PKC-zeta levels were not changed in either fraction in GK soleus muscles. These increases in membrane PKC (alpha, beta, epsilon, and delta) could not be accounted for by alterations in PKC mRNA or total PKC levels but were associated with increases in membrane diacylglycerol (DAG) and therefore appeared to reflect translocative activation of PKC. In evaluation of potential causes for persistent PKC activation, membrane PKC levels were decreased in soleus muscles of hyperglycemic streptozotocin (STZ)-induced diabetic rats; thus, a role for simple hyperglycemia as a cause of PKC activation in GK rats was not evident in the STZ model. In support of the possibility that hyperinsulinemia contributed to PKC activation in GK soleus muscles, we found that DAG levels were increased, and PKC was translocated, in soleus muscles of both (1) normoglycemic hyperinsulinemic obese/aged rats and (2) mildly hyperglycemic hyperinsulinemic obese/Zucker rats. In keeping with the possibility that PKC activation may contribute to impaired glycogen synthase activation in GK muscles, phorbol esters inhibited, and a PKC inhibitor, RO 31-8220, increased insulin effects on glycogen synthesis in soleus muscles incubated in vitro. Our findings suggested that: (1) hyperinsulinemia, as observed in type II diabetic GK rats and certain genetic and nongenetic forms of obesity in rats, is associated with persistent translocation and activation of PKC in soleus muscles, and (2) this persistent PKC activation may contribute to impaired glycogen synthesis and insulin resistance.     

Recovery of muscle functions in rats following prolonged movement restraint

Experiments were carried out to measure time and force parameters of isometric contractions and structural parameters of muscles of hind limbs of rats which were exposed to hypokinesia for 130 days and then were kept under surveillance for 3 months. During recovery certain functions of the contractile system returned to the normal. At the same time M. soleus displayed persistent changes that were indicative of atrophic developments. Unlike M. soleus where delayed contraction (due to an increase in the time of relaxation) was followed by losses in force, fast muscles (M. ext. digit. longus and M. plantaris) showed recovery of force parameters. They also exhibited delayed contraction due to an increase in the time of tension development and half-relaxation. These differences are associated with dissimilar function and structure of muscular fibers. On the whole, the pattern of recovery of the motor functions reflects responses to an increased load of the neuromuscular system of animals which are kept in large cages after prolonged hypokinesia.