Effects of sulphuric acid exposure on the behaviour of largemouth bass,Micropterus salmoides

Synopsis Young-of-the-year largemouth bass,Micropterus salmoides, were exposed to four concentrations of sulphuric acid (pH levels 7.2, 6.1, 4.8, and 3.7) for 30 days, and the frequencies of feeding acts and activity bouts, and time budgets were recorded. Juveniles at pH 6.1 and at pH 4.8 performed the two feeding acts, bites and orientations, more often, and spent more time feeding than bass at pH 7.2. Bass at pH 3.7, however, reduced feeding, and spent a significantly larger portion of their time hovering in the water column. Frequencies of comfort and agonistic acts increased with a decline in pH. Alterations of behavioural repertoires of young-of-the-year largemouth bass were useful indicators of sulphuric acid exposure.     

Rapid determination of antimicrobial susceptibility patterns ofListeria monocytogenes isolates by the autobac AIS and MIC procedures

A total of 34 isolates ofListeria monocytogenes were tested against ampicillin, cephalothin, chloramphenicol, erythromycin, tetracycline, and penicillin-G using the Autobac 3-h AIS and the Autobac 5-h MIC procedures. The results were compared to susceptibility category interpretations and MICs determined using the Sceptor system. With the Sceptor System, all isolates were interpreted to be moderately susceptible to ampicillin and penicillin-G, and susceptible to the four other antibiotics. With the Autobac AIS, all isolates were interpreted to be susceptible to all the antibiotics except penicillin-G. All but one of the 34 isolates were interpreted to be resistant to penicillin-G with the Autobac AIS test. The remaining isolate was interpreted to be indeterminant. The Autobac AIS test was unsatisfactory for determining the susceptibility ofL. monocytogenes isolates to penicillin-G. The Autobac MIC results correlated well with the MIC results of the Sceptor system provided that the Autobac was programmed as though it were testing enterococci. The Autobac MIC reported penicillin-G MICs in units per milliliter and required the use of a conversion factor to obtain micrograms per milliliter, and did not allow for the testing of erythromycin. The Autobac MIC susceptibility category interpretations must not be used, as they were derived from an outdated susceptibility standard. The Autobac MIC test may be used if the limitations given above are observed.     

dam methylation and the initiation of DNA replication on oriC plasmids

Summary Plasmid DNA containing the replication origin of the Escherichia coli chromosome (oriC) has been shown to be inefficient as a template for DNA synthesis in vitro when isolated from dam mutants. here, we extend this study to hemimethylated oriC plasmids and to replication in dam-3 mutant enzyme extracts. The results show that: (1) hemimethylated oriC plasmids replicate with the same low efficiency as nonmethylated DNA; (2) DNA synthesis starts at oriC regardless of the methylated state of the template; (3) replication in dam-3 enzyme extracts is inefficient because this strain is deficient in DnaA protein; and (4) consistent with this observation, the copy number of the oriC plasmid pFH271 is reduced in the dam-3 mutant. However, we have found that low DnaA protein levels in dam-3 mutants are not sufficient to explain the reduced transformation efficiency of oriC plasmids. We suggest that there must exist in vivo inhibitory factors not present or present in low quantities in vitro which specifically recognize the hemimethylated or nonmethylated forms of the oric region.     

Vitamin K1 reduction in human liver. Location of the coumarin-drug-insensitive enzyme.

The protein kinase C inhibitor staurosporine influenced in different ways the functions of human neutrophils. Staurosporine prevented the enhanced protein phosphorylation in phorbol ester- and N-formylmethyionyl-leucylphenylalanine (fMLP)-stimulated cells, and was a powerful inhibitor of the respiratory burst induced by phorbol myristate acetate [IC50 (concentration causing 50% inhibition) 17 nM] and the chemotactic peptides fMLP and C5a (IC50 24 nM). It did not alter, however, the superoxide production by cell-free preparations of NADPH oxidase. Staurosporine had no effect on agonist-dependent changes in cytosolic free Ca2+ and exocytosis of specific and azurophil granules, and showed only a slight inhibition of the release of vitamin B12-binding protein induced by phorbol myristate acetate (decreased by 40% at 200 nM). On the other hand, staurosporine also exhibited neutrophil-activating properties: it induced the release of gelatinase (from secretory vesicles) and vitamin-B12-binding protein (from specific granules). These effects were protracted, concentration-dependent, insensitive to Ca2+ depletion, and strongly enhanced by cytochalasin B. Staurosporine, however, did not induce the release of beta-glucuronidase or elastase (from azurophil granules). Except for the sensitivity to cytochalasin B, these properties suggest a similarity between the exocytosis-inducing actions of staurosporine and PMA. The results obtained with staurosporine provide further evidence that different signal-transduction processes are involved in neutrophil activation, and suggest that protein phosphorylation is required for the induction of the respiratory burst, but not for exocytosis.