Inactivation of aminoglycosides by beta-lactams of the penicillin and cephalosporin groups

Interaction of carbenicillin with kanamycin, gentamicin, tobramycin, and amikacin, as well as that of cefotaxime with the same aminoglycosides were studied. It was shown that carbenicillin inactivated aminoglycosides in a patient's plasma, urine, rH 5.3-8.44, and in buffer solutions, pH 3.7, 7.5 and 9.25. The inactivation level was the least in acid media. The mechanism of the inactivation was elucidated: opening of the carbenicillin beta-lactam ring occurred at the start.     

Role and activity of jasmonates in plants under in vitro conditions

Jasmonates (JAs), such as jasmonic acid and its methyl ester, are lipid-derived compounds with signal functions in plant growth and development, as well as in responses to stress. JAs are widely distributed in plants as natural plant growth regulators. JAs do not work independently but work as a part of a complex signaling network with other phytohormones. They are deployed to induce response during wounding and are often used for elicitation and stimulation of secondary metabolites production in different in vitro culture systems. Application of JAs seems to be promising during different steps of the micropropagation system for different species. JAs stimulate proliferation rate of shoots, roots, callus and induce microtubers and bulblets formation. However, negative effects of JAs on the condition of plant tissues are also reported, e.g. leaf senescence, reduced growth and inhibited somatic embryogenesis. This review summarizes the current knowledge of the application and properties of jasmonates under in vitro conditions in terms of cell division, explant growth, proliferation ability, storage organ formation and stress response.

     

Antimicrobial activity of 2-aminophenoxazin-3-one under anaerobic conditions.

Potential toxicity of 2-aminophenoxazin-3-one to 20 bacterial species and two fungi and its inactivation under anaerobic conditions were investigated. Minimum inhibitory concentration for cellulolytic bacteria was in the range of 50-100 micrograms.mL-1, but at 100 micrograms.mL-1 of 2-aminophenoxazin-3-one, there was no effect on the growth of any of the noncellulolytic bacteria. Four noncellulolytic bacterial strains showed no inhibition of growth, even at 200 micrograms.mL-1 of this compound. Under anaerobic conditions and in the presence of cysteine, the long wavelength absorption band of this compound slowly shifted from about 434 to 320 nm, and its inhibitory effect on RNA synthesis was relieved after one-half of a generation time in cultures of cellulolytic ruminal bacteria. A similar shift of absorption band was observed in rumen fluid filtered through a 0.22-microns Millipore filter. It was concluded that protonation of 2-aminophenoxazin-3-one under anaerobic conditions present in the rumen would considerably reduce its potential toxicity to cellulolytic bacteria.     

Antimicrobial activity of piperacillin in vitro]

There was an increase in the resistance of clinical isolates to piperacillin as compared to that in 1987-1988. It was shown on the kinetic models that there was difference in the effect of the inhibitory and subinhibitory concentrations of the drug on microorganisms in various growth phases. No post-antibiotic action against Staphylococcus aureus and Pseudomonas aeruginosa and a slightly pronounced dose-dependent effect with respect to Escherichia coli were noted.     

Pyruvate metabolism in rice coleoptiles under anaerobiosis

Relative importance of ethanolic, lactate and alanine fermentation pathways was estimated in coleoptiles of rice seedlings (Oryza sativa L.) subjected to anoxic stress. The in vitro activities of alcohol dehydrogenase (ADH, EC 1.1.1.1), pyruvate decarboxylase (PDC, EC 4.1.1.1) and alanine aminotransferase (AlaAT, EC 2.6.1.2) in the coleoptiles increased in anoxia, whereas no significant increase was measured in lactate dehydrogenase (LDH, EC 1.1.1.27) activity. At 48 h, the ADH, PDC and AlaAT activities in anoxic coleoptiles were 62-, 15- and 7.6-fold greater, respectively, than those in the presence of oxygen. Ethanol and alanine in the coleoptiles accumulated rapidly under anoxia, increasing by 48 h, 57- and 5.6-fold compared with those in the presence of oxygen, respectively. However, lactate concentration did not increase and no initial burst of lactate production was detected. The relative ratio of carbon flux from pyruvate to ethanol, lactate and alanine in anoxic coleoptiles was estimated to be 92, 1 and 7% of the total carbon flux, respectively. These results suggest that the potential carbon flux from pyruvate to ethanol may be much greater than the potential flux from pyruvate to lactate and alanine in rice coleoptiles during anoxia.     

Glyco-optimization of aminoglycosides: new aminoglycosides as novel anti-infective agents

Glyco-optimization (OPopS) of aminoglycosides has been performed by replacing the existing sugar moiety with a variety of sugar derivatives. Glycosylation of the 6-position of nebramine provided a library of novel 4,6-linked aminoglycosides (AMGs). Among them, compounds 8b,g,i,l, and 8u with 2"-amino, 2",3"-diamino, 2",4"-diamino, 3",4"-diamino, 3"-amino groups, respectively, showed significant antimicrobial activity against Gram-(+) and -(-) bacteria. Several were particularly potent against Pseudomonus aeruginosa with MICs in the 1-2 microg/mL range.     

Comparative in vitro activity of moxalactam (LY127935), other beta-lactam antibiotics,and aminoglycosides

Moxalactam (LY127935), a novel beta-lactam antibiotic, was compared with semisynthetic penicillins, cephalosporins, and aminoglycosides by the agar dilution method against 5,317 recent clinical isolates of facultative and anaerobic bactria. At 0.5 μg/ml, moxalactam inhibited 90% of all Gram-negative bacilli tested except forPseudomonas aeruginosa (81% inhibited by 32 μg/ml) andAcinetobacter calcoaceticus (88% inhibited by 32 μg/ml). More than 90% ofBacteroides fragilis andStaphylococcus aureus were inhibited by 4 μg/ml and 8 μg/ml, respectively. Moxalactam was at least 16-fold more active by weight than cephalothin, cefamandole, and cefoxitin forEscherichia coli, Klebsiella pneumoniae, andEnterobacter species, and 2- to 4-fold more active than cefoxitin forB. fragilis. Moxalactam was 4-fold less active than cefamandole and cephalothin forS. aureus and 2- to 4-fold less active than piperacillin forP. aeruginosa. Moxalactam was as active or more active than the aminoglycosides for all facultative Gram-negative bacilli except forP. aeruginosa. Moxalactam was inhibitory (minimal inhibitory concentration <16 μg/ml) for 20/27 gentamicin-resistant isolates and 8/13 amikacin-resistant organisms. Moxalactam’s in vitro activity against Gram-negative bacilli is markedly superior to presently available cephalosporins and, except forP. aeruginosa, is comparable to the aminoglycosides.     

Lymphocytolytic activity of glucocorticoids in vitro: 51Cr release under equilibrium conditions.

Cytolytic activity of glucocorticoids in vitro is assessed by measuring radiochromium release from steroid-treated thymic lymphocytes under the equilibrium conditions provided by a continuous-labeling technique. Isotope release is a glucocorticoid-specific effect produced at physiological concentrations and is virtually abolished by inhibitors of RNA and protein synthesis. The relative lytic potencies of the steroids tested are comparable to those reported for glucocorticoids as measured by other methods. This procedure not only possesses the advantages typical of isotopic techniques in general, but, in addition, circumvents the problem of "spontaneous" label release associated with the pulse-labeling method. It is a useful alternative to the morphologic examination of cells or the estimation of cell viability for determination of glucocorticoid cytolytic activity.     

Phosphodiesterase activity of mouse sperm incubated under conditions that modulate fertilizing potential in vitro

Cyclic AMP has been implicated as a regulator of capacitation, but the control of its metabolism in sperm remains obscure. A recent study of mouse sperm has shown capacitation-related changes in the activities of both adenylate cyclase, which increased during incubation, and cyclic nucleotide phosphodiesterase, which decreased. The present study was conducted to extend these observations by measuring phosphodiesterase activity in sperm incubated in media with modified calcium and/or glucose content, conditions known to modulate fertilizing ability. Phosphodiesterase activity of sequential sperm samples, taken first when sperm are essentially uncapacitated and then when they are either partially or completely capacitated, decreased with time under all conditions, and in each case the greater fall in activity was seen in the medium that would support the greater change in fertilizing ability of the sperm population. Sperm washed by centrifugation to remove epididymal fluid also displayed a reduction in phosphodiesterase activity with time. The medium surrounding the sperm contained about half of the total phosphodiesterase activity, as well as 5′-nucleotidase and adenosine deaminase. The crude enzyme preparation showed complex kinetic behavior when assayed over a range of cAMP concentrations, but the reduction in activity with time was seen at all substrate levels. The observed changes in phosphodiesterase activity, together with the increased adenylate cyclase activity seen under these sperm incubation conditions, would increase cAMP availability with time, thus providing further evidence for a fundamental role for cAMP in controlling the events of capacitation.     

Antimicrobial activity in vitro of plumbagin isolated from Plumbago species

Plumbagin is a naturally occurring naphthoquinone isolated from roots of Plumbago scandens. The plant was collected at the Campus of Funda??o Oswaldo Cruz, Rio de Janeiro, Brazil. P. scandens is used as a traditional medicine for the treatment of several diseases. The antimicrobial activity of plumbagin was evaluated using the macrodilution method. The compound exhibited relatively specific activity against bacteria and yeast. The minimum inhibitory concentration test showed the growth inhibiton of Staphylococcus aureus at a concentration of 1.56 g/ml and of Candida albicans at a concentration of 0.78 g/ml. These results suggest the naphthoquinone plumbagin as a promising antimicrobial agent.     

Action of aminoglycosides on platelet aggregation in vitro

The authors tested the influence of gentamicin, spectinomycin dihydrostreptomycin on the ADP and epinephrine in vitro induced platelet aggregation. Our aim was to demonstrate if platelet aggregation in vitro had some influences by antibiotics. A reduction in platelet aggregability, strictly dependent from the used antibiotic dose was observed. We have studied platelet function thanks to Born's method, adding to PRP gradual therapeutics doses of antibiotics. The results showed a reduction of platelet function which was dose-depended, and, particularly, gentamicin seemed to be the most effective among aminoglycosides. An interference between these drugs and the ADP and epinephrine binding to specific platelet receptor sites is proposed.     

Antimicrobial activity of histidine-rich peptides is dependent on acidic conditions

Synthetic peptides composed of multiples of the consensus heparin-binding Cardin and Weintraub sequences AKKARA and ARKKAAKA are antimicrobial. Replacement of lysine and arginine by histidine in these peptides completely abrogates their antimicrobial and heparin-binding activities at neutral pH. However, the antibacterial activity against Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) as well as the fungus Candida albicans, was restored at acidic conditions (pH 5.5). Fluorescence microscopy and FACS analysis showed that the binding of the histidine-rich peptides to E. coli and Candida was significantly enhanced at pH 5.5. Likewise, fluorescence studies for assessment of membrane permeation as well as electron microscopy analysis of peptide-treated bacteria, paired with studies of peptide effects on liposomes, demonstrated that the peptides induce membrane lysis only at acidic pH. No discernible hemolysis was noted for the histidine-rich peptides. Similar pH-dependent antimicrobial activities were demonstrated for peptides derived from histidine-rich and heparin-binding regions of human kininogen and histidine-rich glycoprotein. The results demonstrate that the presence of an acidic environment is an important regulator of the activity of histidine-rich antimicrobial peptides.     

Antimicrobial activity of histidine-rich peptides is dependent on acidic conditions

Synthetic peptides composed of multiples of the consensus heparin-binding Cardin and Weintraub sequences AKKARA and ARKKAAKA are antimicrobial. Replacement of lysine and arginine by histidine in these peptides completely abrogates their antimicrobial and heparin-binding activities at neutral pH. However, the antibacterial activity against Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) as well as the fungus Candida albicans, was restored at acidic conditions (pH 5.5). Fluorescence microscopy and FACS analysis showed that the binding of the histidine-rich peptides to E. coli and Candida was significantly enhanced at pH 5.5. Likewise, fluorescence studies for assessment of membrane permeation as well as electron microscopy analysis of peptide-treated bacteria, paired with studies of peptide effects on liposomes, demonstrated that the peptides induce membrane lysis only at acidic pH. No discernible hemolysis was noted for the histidine-rich peptides. Similar pH-dependent antimicrobial activities were demonstrated for peptides derived from histidine-rich and heparin-binding regions of human kininogen and histidine-rich glycoprotein. The results demonstrate that the presence of an acidic environment is an important regulator of the activity of histidine-rich antimicrobial peptides.     

Antimicrobial activity of Brazilian propolis extracts against rumen bacteria in vitro

The antimicrobial activity of three Brazilian propolis extracts was evaluated on bacterial strains representing major rumen functional groups. The extracts were prepared using different concentrations of propolis and alcohol, resulting in different phenolic compositions. The propolis extracts inhibited the growth of Fibrobacter succinogenes S85, Ruminococcus flavefaciens FD-1, Ruminococcus albus 7, Butyrivibrio fibrisolvens D1, Prevotella albensis M384, Peptostreptococcus sp. D1, Clostridium aminophilum F and Streptococcus bovis Pearl11, while R. albus 20, Prevotella bryantii B₁4 and Ruminobacter amylophilus H18 were resistant to all the extracts. The inhibited strains showed also different sensitivity to propolis; the hyper-ammonia-producing bacteria (C. aminophilum F and Peptostreptococcus sp. D1) being the most sensitive. Inhibition of hyper-ammonia-producing bacteria by propolis would be beneficial to the animal. The extract containing the lowest amount of phenolic compounds (LLOS C3) showed the lowest antimicrobial activity against all the bacteria. The major phenolic compounds identified in the propolis extracts (naringenin, chrysin, caffeic acid, p-coumaric acid and Artepillin C) were also evaluated on four sensitive strains. Only naringenin showed inhibitory effect against all strains, suggesting that naringenin is one of the components participating to the antibacterial activity of propolis.