Antibiotic penetration through the blood-brain barrier in rats and the effect on this process of proteolytic enzymes]

Penetration of penicillin, ampicillin, oxacillin, tetracycline, streptomycin and gentamycin through the hemato-encephalic barrier in rats and effect of proteolytic enzymes on the above process were studied comparatively. The levels of penetration to the brain were highest for ampicillin, then followed penicillin, tetracycline, oxacillin, streptomycin and gentamycin. Preliminary intramuscular administration of trypsin and chimotrypsin (10 mg/kg) to the animals had no effect on permeability of the hemato-encephalic barrier for the antibiotics tested, except penicillin. Higher levels of the antibiotics in the brain tissue may be explained by higher antibiotic blood levels under the effect of proteolytic enzymes.     

Antibiotic interaction with proteolytic enzymes]

The effect of penicillin, tetracycline, aminoglucozide antibiotics and streptomycin on BAEE-esterase activity of trypsin was studied. It was found that benzylpenicillin in amounts of 50, 100 and 300 mg, ampicillin in an amount of 25 mg, methicillin in an amount of 12 mg and tetracycline in an amount of 2.5 mg as calculated per 1 mg of trypsin had no effect in vitro on the esterase activity of the enzyme. Neomycin, kanamycin and streptomycin in amounts of 5, 10, 100 or 300 mg per 1 mg of trypsin catalyzed splitting of BAEE by trypsin. When the antibiotics were added to the bile, its esterase activity increased. Preliminary intramuscular administration of trypsin and kanamycin to the rats had no effect on the ampicillin levels in the blood serum and brain and did not affect the permeability of the hemato-encephalic barrier as compared to the use of trypsin alone.     

Intracellular distribution of tetracyclines in rat hepatocytes

Distribution of tetracyclines, such as oxytetracycline, morphocycline, tetracycline, doxicycline and methacycline in the liver cells of rats was studied. The ratio of the subcellular structures, i. e. nuclei, mitochondria and microsomes and the liquid phase containing the drugs in the dissolved state in the system studied was close to the natural ratio of the hepatocyte organoids and cytoplasm. Distribution of tetracyclines in the subcellular fractions was not uniform. The nuclei did not absorb the drugs. The role of microsomes in drug absorption was insignificant. The mitochondria bound the highest amounts of the drugs and defined the characteristics of their intracellular distribution. The amounts of the drugs in the active form remaining in the cytoplasm after their contact with organoids were low. At the same time there was observed a a definite activating effect of the cytoplasm components on the antibiotics contained in it.     

Efficient use of a combination of ampicillin and chymotrypsin]

The effect of chimotripsin on the level and duration of the ampicillin concentration increase in rats, as well as the effect of the enzyme on the in vitro antibiotic detection in the blood serum and organ homogenates of the animals was studied. It was found that rational combined use of ampicillin and chimotripsin required the enzyme administration not later than 1 hour before the antibiotic injection. Chimotripsin provided increased ampicillin levels in the blood serum and liver of the rats for at least 5 hours and in the kidneys and lungs for at least 4 hours. The enzyme present in the rats for 2 hours had no effect on determination of ampicillin activity in vitro in the presence of the blood serum and organ homogenates of the animals.     

Study of the effect of tetracycline carboxamide derivatives on the cardiovascular and urinary systems]

The effect of tetracycline carboxamide derivatives, such as morphocycline, glycocycline and reverin on the cardio-vascular and urinary systems was studied on 24 rabbits using clinico-physiological and pathomorphological methods. The experiment was accounted for 7 days. When the drugs were administered in doses of 5 mg/kg, the changes in the indices of hemodynamics, respiration and bioelectric activity of the myocardium were rather of the same type. They were evident from decreased arterial pressure, slower rate of the pulse and respiration, lower voltage of peaks R and T, prolongation of intervals T--P and R--P, shifts in segment S--T from the isoelectric line. The changes took place by the 2nd and 5th minutes after the drug administration. Beginning from the 10th minute the hemodynamic indices returned to the initial values. By the level of the drugs effect on the above indices the antibiotics may be arranged in the following order: morphocycline, glycocycline and reverin. No effect of the antibiotics on the urinary system was noted.     

Effect of exogenous serotonin on intragastric pH and its influence on serum gastrin levels in rats.

The effect of various doses of serotonin on the serum gastrin levels and intragastric pH in rats, was studied. After serotonin administration of 10 mg/kg i.p., a significant increase in serum gastrin levels was noted, as well as a strong increase in the intragastric pH. It was also observed that a lower dose, 5 mg/kg i.p., significantly increased serum gastrin levels, while intragastric pH was not affected, remaining at baseline values throughout the study. These results suggest that the increase observed in serum gastrin levels after administration of exogenous serotonin is not mediated by increase in intragastric pH.     

Interaction between diazepam and oral antidiabetic agents on serum glucose,insulin and chromium levels in rats

This study was undertaken to investigate the effect of diazepam in the presence and absence of glibenclamide, metformin or their combination on serum levels of glucose, insulin and chromium in rats. Results indicated that diazepam (10 mg/kg i.p.) induced marked hyperglycaemic effects in hyperglycaemic rats. This effect was associated with significant reductions in serum chromium levels and insignificant reduction in serum insulin levels. Diazepam-induced hyperglycaemia was counter-acted by concurrent administration of glibenclamide (5 mg/kg orally), metformin (500 mg/kg orally) or their combination. The effect of diazepam on serum chromium level was counteracted partially by administration of glibenclamide and augmented in the presence of metformin or its combination with glibenclamide. It is concluded that the diazepam-induced hyperglycaemia, as well as the hypoglycaemic effect of glibenclamide, might be related to changes in serum chromium levels.     

Induction of acute respiratory distress syndrome in rats by lipopolysaccharide and its effect on oxidative stress and antioxidant status in lung

Acute lung injury (ALI) or its severe form, acute respiratory distress syndrome (ARDS) is an important cause of mortality in the human population. Despite significant advances made, the mortality associated with ALI remains unchanged. The objective of the present study was to evaluate the role of oxidative stress, alveolar antioxidant status and multiple organ injury in ARDS induced by lipopolysaccharide (LPS) in rats. Rats were divided into 4 groups, group I control rats were given saline intraperitoneally, whereas groups II, III and IV (LPS-treated) rats received an intraperitoneal injection of LPS (10 mg/kg body weight) and sacrificed after various time intervals. In LPS-treated rats, we observed increased levels of oxidative products, decreased levels of antioxidants in lung tissues and increased levels of serum marker enzymes, suggesting multiple organ injury. Bronchoalveolar lavage fluid (BALF) neutrophil content and protein concentration in LPS-treated rats were significantly elevated in a time-dependent manner. Histological studies revealed neutrophil influx and diffused alveolar damage in LPS-administered rats. These results clearly suggested that increased oxidant levels led to oxidative stress, antioxidant deficiency attenuating lung inflammation and tissue damage. LPS administration resulted in multiple organ failure, leading to increased mortality.     

Elevated daytime rat pineal and serum melatonin levels induced by isoproterenol are depressed by swimming

Isoproterenol (1 mg/kg) was subcutaneously injected into adult male rats during the day to stimulate pineal N-acetyltransferase (NAT) activity and pineal and serum melatonin levels. Two hours after isoproterenol administration when levels of each of these variables had increased significantly, the experimental animals swam for 10 min in 22 degrees C water. At 15 min after swimming onset, pineal and serum melatonin levels were highly significantly depressed compared to those in control animals that did not swim. The high NAT level was not influenced by swimming. In a second study, isoproterenol injected rats swam for either 1, 3, 6 or 10 min and were sampled 15 min after the onset of swimming. The reduction in the elevated pineal melatonin in these animals was correlated with the length of the swim, i.e., as the duration of swim increased the percent reduction in pineal melatonin also increased. Neither pineal NAT nor hydroxyindole-O-methyltransferase (HIOMT) activities were influenced by swimming. The results suggest that elevated pineal and serum melatonin induced by isoproterenol can be depressed with no effect on the activity of the enzymes which convert serotonin to melatonin.     

Effect of some antibiotics on the resistance of white mice to staphylococcal toxin]

Penicillin and streptomycin in experimental staphylococcal intoxication had different effects on the disease depending on the period of their use. Penicillin injections prior to administration of the toxin increased significantly the resistance of the animals to it, while with the use of streptomycin there was only a tendency to its increase. The use of both antibiotics against the background of the intoxication had a reverse effect: there was a tendency to a decreased animal resistance to a greater extent with the use of streptomycin. The use of tetracycline hydrochloride had no effect on the animal resistance to the staphylococcal toxin.     

Stability of enzymes inactivating aminoglycoside antibiotics

Stability of aminoglycoside phosphotransferases, adenylyltransferases and acetyltransferases isolated from various sources was studied. The enzymes were characterized by different substrate profiles. They were stored at a temperature of -10 degrees C in the form of frozen solutions or at a temperature of 4 degrees C in the lyophilized form. It was shown that lyophilization markedly increased the stability of the enzymes inactivating aminoglycoside antibiotics. Aminoglycoside phosphotransferases and adenylyltransferases with streptomycin as substrate were less stable than aminoglycoside phosphotransferases with neomycin as substrate. Aminoglycoside acetyltransferases from Streptomyces fradiae 918 producing neomycin were least stable among the enzymes studied. Lyophilized enzymes as a possible stabilizer of ATP added to the preparations had no significant effect on their stability during storage.     

Effect of the physiological activity of Clostridium cells on their sensitivity to antibiotics]

Actively multiplicating cells of C1. perfringens proved to be more sensitive to 7-chlor-7-desoxylincomycin and rifampicin than the cells in the phase of the population dying. The bactericidal effect of the antibiotics on Clostridia vegetating at a temperature range within 37--4degrees was studied. Determination of the content of higher fatty acids in the cultivation medium with the method of gas chromatography showed that the metabolic processes in the bacterial cells went on at a temperature of 4degrees. Sensitivity of Clostridia to antibiotics at 20 and 4degrees lowered. However, all antibiotics inhibited the cell viability under such conditions. The inhibitors of the intracellular protein synthesis, i. e. rifampicin, 7-chlor-7-desoxylincomycin and morphocycline proved to be most active. The effect of beta-lactame antibiotics, i. e. cephaloridine and benzylpenicillin was reliable though lower.     

Pancreatic islet-cell viability, functionality and oxidative status remain unaffected at pharmacological concentrations of commonly used antibiotics in vitro

Environmental factors such as diet, physical activity, drugs, pollution and life style play an important role in the progression and/or precipitation of diseases like diabetes, hypertension, obesity and cardiovascular disorders. Indiscriminate use of antibiotics to combat infectious diseases is one of the commonest forms of misuse of drugs. Antibiotics seem to have a correlation with diabetes and pancreatic function. There are controversial reports about the effect of antibiotics on the pancreatic islets; some suggesting their harmless action, some depicting a beneficial role and others indicating deleterious effect. Moreover, use of antibiotics is mandatory during islet isolation and cultivation to reduce incidences of microbial contamination. It is likely that antibiotic treatment may adversely affect islet viability and its functioning leading to failure of islet transplantation. The presentin vitro study was undertaken to examine the effect of commonly used antibiotics such as gentamycin, penicillin, streptomycin, tetracycline, neomycin, erythromycin and chloramphenicol on islet viability, its functioning and induction of oxidative stress if any. The viability and insulin production data showed that none of the antibiotics used in the present study affect the viability and the functioning of the islets at their pharmacological concentrations. Free radical levels measured in terms of melonyldialdehyde (MDA), nitric oxide (NO) and reduced glutathione (GSH) reveal that except for a marginal increase in lipid peroxidation with tetracycline and slight increase in NO levels with streptomycin, none of these antibiotics affect the oxidative status of the cells. Antioxidant enzymes such as superoxide dismutase and catalase remain unaffected after this treatment. Our results reveal the innocuous nature of the antibiotics used at pharmacological concentrations, suggesting their safety whenever prescribed to combat infections and also during islet isolation procedures.     

Role of antibiotics in lipid peroxidation.

Alterations in the levels of lipid peroxides, superoxide dismutase, catalase, glutathione, free fatty acid and serum ceruloplasmin were studied in rats fed with high fat cholesterol diet administered different antibiotics, viz. ampicillin, tetracycline, streptomycin, chloramphenicol and cephalosporin. The concentrations of lipid peroxides, glutathione, free fatty acid decreased in most of the tissues, except in tetracycline, streptomycin and cephalosporin treated rats. The changes observed in the activities of superoxide dismutase and catalase in the liver and kidney of these antibiotics administered groups also are in accordance with the changes in lipid peroxides. The results show that the tetracycline is hepatotoxic and nephrotoxic, while cephalosporin and streptomycin are nephrotoxic.     

Effect of parathyroid hormone on the increase in serum glucose and insulin levels after a glucose load to thyroparathyroidectomized rats.

Thyroparathyroidectomy (TPTX) caused a significant increase in serum glucose and a corresponding fall in serum calcium in both fed and fasted rats. The increase in serum glucose, induced by TPTX, was markedly potentiated by a single intraperitoneal administration of calcium (2 mg/100 g BW) which caused a significant elevation of serum calcium in thyroparathyroidectomized rats. Parathyroid hormone (PTH; 20 U/100 g BW) administered subcutaneously to thyroparathyroidectomized rats, caused a significant decrease in serum glucose (0.1 g/100 g BW) to sham-operated rats significantly increased both serum glucose and insulin. The rise of serum glucose produced by a glucose load was markedly potentiated by TPTX, but the increase in serum insulin was not promoted significantly. The administration of PTH decreased both serum glucose and insulin levels increased by a glucose load to thyroparathyroidectomized rats, in a dose-dependent manner. The administration of calcitonin (80 MRC mU/100 g BW) significantly prevented the effect of PTH to decrease serum glucose after a glucose load to thyroparathyroidectomized rats, and calcitonin increased serum insulin. These results suggest that the effect of PTH on serum glucose does not involve insulin secretion.     

Opposing actions of dehydroepiandrosterone and corticosterone in rats.

The purpose of this study was to determine the impact of dehydroepiandrosterone (DHEA) and corticosterone (CORT) treatment, using implants as a route of administration, on specific hormones, metabolites, and enzymes involved in energy metabolism. Sixty male Sprague-Dawley rats, 325 g initial weight, were implanted subcutaneously for 3 weeks with time-release pellets containing either DHEA or CORT at doses of 0, 10, 25, 50, or 100 mg in this 2 x 5 factorial experiment. In general, body weights and food intakes decreased as the level of steroid hormones increased. In contrast to DHEA treatment, rats receiving the 50- and 100-mg doses of CORT had lighter thymus glands and spleens and heavier epididymal and retroperitoneal fat pads than their controls. Rats treated with 100 mg of DHEA had lowered serum levels of triglycerides and lipid hydroperoxides whereas rats treated with 100 mg of CORT had higher levels of these blood lipids compared to their respective controls. In contrast to DHEA treatment, there was a dose-dependent increase in liver lipid content and the specific activities of the hepatic lipogenic enzymes glucose-6-phosphate dehydrogenase, malic enzyme, and fatty acid synthase in response to CORT treatment. Rats treated with 100 mg of DHEA had higher serum levels of IGF-1 than control rats. Conversely, rats treated with 100 mg of CORT had lower serum levels of IGF-1 and higher serum levels of testosterone, progesterone, and insulin than their controls. These data demonstrate the lipogenic actions of corticosterone in rats. Conversely, DHEA treatment reduced serum and hepatic lipids. Furthermore, these data suggest that using implants instead of bolus injections of steroids may be a more physiological approach for studying the influence of these steroids on lipid metabolism.     

Adaptation of siblings of female rats given ethanol effect of N-acetyl-L-cysteine

Summary Ethanol administration to female rats before and during pregnancy resulted in decreased number of litters and increased activities of serum GOT, GPT and ALP. The hepatotoxicity of ethanol was indicated by the histological alterations both in the mother and siblings. There was increased levels of tissue lipids in mother and litters born to alcoholic rats. The concentration of TBARS in the liver and kidney were significantly increased in alcohol treated rats and their litters. The activities of the anti-peroxidative enzymes SOD and CAT were decreased on alcohol treatment in female rats. The glutathione content in liver and kidney decreased significantly in litters born to alcoholic rats.We have observed that the treatment with N-acetylcysteine offers protection against the toxic effect of alcohol in female rats during pregnancy and litters born to them. In N-acetylcysteine treated rats the number of litters as well as the average birth weight were close to that of control animals. Nacetylcysteine decreases the activities of serum GOT, GPT and ALP in female rats. We have also observed decreased levels of tissue lipids in mother and litters born to alcoholic rats given N-acetylcysteine when compared to alcoholic rats. The levels of TBARS in liver, kidney were also decreased both in mother and litter born to alcohol + N-acetylcysteine, while the activities of SOD and CAT were increased in liver of alcoholic rats given N-acetylcysteine when compared to alcoholic rats. Histopathological studies also showed the protective effect of N-acetylcysteine in both mother and litter in liver and kidney against alcoholic induced toxicity.     

Comparative study of the interaction of cephalosporins with blood serum proteins and organ homogenates

Interaction of 7 semisynthetic antibiotics (cephaloridine, cephalexin, cephradine, cephazolin, cephalotin, cephacetrile and cephapirin) with proteins of human, bovine and rabbit blood serum, as well as organ and tissue homogenates of rats was studied comparatively. The study showed that binding of the cephalosporins by the blood serum depended on both the chemical structure of the antibiotic and the species affiliation of the protein substrate. The binding lvels of cephazolin and cephalotin by the blood serum proteins (except bovine serum) were the highest, while the binding level of cephaloridine was the lowest. A significant decrease in the values of binding by the serum proteins of the drugs with high percentage of binding was observed when the drug concentrations in solution were increased. Binding of the cephalosporins by the blood serum proteins was in most cases completely reversible. The activity of the cephalosporins decreased in the presence of the rat organ and tissue homogenates. The levels of the activity decrease as compared to the theoretical ones were the highest with the use of cephalotin, cephacetrile and cephapirin. The lowest values of detection of these antibiotics were noted on their incubation with the liver, kidneys and lungs.     

Comparative study of the distribution of semisynthetic cephalosporins in the body of rats]

Distribution of 6 cephalosporin antibiotics, i. e. cephaloridin, cephalotin, cephradin cephacetryl, cephazolin and cephapyrin for parenteral use was studied comparatively on rats. The studies showed that all the above cephalosporins were well absorbed into the blood after intramuscular administration. The highest serum levels were achieved with the use of cephozolin. Still, its levels in the animal organs were mainly not higher and sometimes even lower than those provided by the other antibiotics. The highest levels of cephalosporins were detected in the kidneys. Cephalotin, cephapyrin and cephacetryl differed by the character of their distribution in the rats from the other 3 antibiotics: the levels of cephalotin and cephapyrin in the heart, spleen and muscles were lower than those of the other cephalosporins; sometimes they were even not detected in these organs; cephacetryl was not found in these organs. The levels of these 3 antibiotics in the kidneys were lower than those of the other cephalosporins. Cephalotin, cephacetryl and sometimes cephapyrin were not detected in the rat liver. None of the cephalosporins was found in the brain tissue.     

Effect of estrogens on β-hydroxy-β-methylglutaryl coenzyme a reductase activity and cholesterol levels

The effect of estrogens on hepatic β-hydroxy-β-methylglutaryl coenzyme A reductase activity and cholesterol in serum and liver of ovarietcomized rats on normal diet, 2% cholestyramine diet or 2% cholesterol diet was investigated. Estrogen administration to ovariectomized rats on normal diet resulted in increased reductase activity and was correlated with decreased serum cholesterol and increased liver cholesterol levels wlth mestranol (ME), ethinyl estradiol (EE) and estradiol benzoate (EB, 250 μg) but increased serum and liver cholesterol levels with 25 μg and 100 μg EB administration. The increased stimulation of reductase activity by estrogen administration was absolished when rats were fed a 2% cholesterol diet. Cholestyramine feeding markedly increased reductase activity in livers of ovariectomized rats. These studies show that estrogens are not absolutely required for the stimulation of reductase activity and therefore is consistent with the model in which cholesterol functions as a feedback repressor of reductase activity.