Inactivation of cephalothin and cephaloridine by Staphylococcus aureus

Benner, Ernest J. (University of Washington School of Medicine, Seattle), John V. Bennett, Jean L. Brodie, and William M. M. Kirby. Inactivation of cephalothin and cephaloridine by Staphylococcus aureus. J. Bacteriol. 90:1599-1604. 1965.-Marked differences were observed in the susceptibility of penicillinase-producing staphylococci to cephalothin and cephaloridine. All of 100 strains of penicillin G-resistant Staphylococcus aureus, with the use of a large inoculum, were found to be susceptible to 2 mug/ml of cephalothin, whereas only 50% were susceptible to this concentration of cephaloridine, and 15% required 15 mug/ml or more for inhibition. In contrast, penicillin G-sensitive strains were more susceptible to cephaloridine and did not show the marked inoculum effect observed with the cephaloridine-resistant strains. These differences were due to a much greater destruction of cephaloridine than of cephalothin by staphylococcal penicillinase. Cephaloridine-resistant staphyloccoci were stronger penicillinase producers than were susceptible strains, and the resistant strains were found to inactivate cephaloridine by hydrolysis of the beta-lactam ring. In population studies, cephaloridine-resistant cells differed from methicillin-resistant cells in that they decreased in numbers as the drug concentration was increased, and the survivors in higher drug concentrations were no more resistant than was the parent strain. Treatment with acriflavine eliminated resistance of the cells to both penicillin G and cephaloridine. It was concluded that cephaloridine resistance was due to hydrolysis by penicillinase, and that this was related to the pyridine ring substitution in the cephalosporanic acid nucleus.     

Biological control ofOpuntia spp. byCactoblastis cactorum in the Leeward Islands (West Indies)

Résumé Les auteurs relatent les circonstances de l'introduction dans les ?les Leeward (Antilles), deCactoblastis cactorum (Berg.) (Lepid. Phycitidae) qui eut pour résultat la destruction spectaculaire de diversOpuntia, principalementO. triacantha. Introduit en 1957 dans l'?le Nevis,Cactoblastis s'est établi rapidement et, vers 1960, il produisit d'excellents résultats qui se sont maintenus par la suite. Des matériaux provenant de l'?le Nevis ont été introduits dans les ?les voisines de Montserrat et Antigua. Dans la première, lesOpuntia ont été rapidement détruits. mais faute de conditions culturales convenables, ils ont été remplacés par desAcacia sp. si bien que le bénéfice de l'opération est très faible. Dans l'?le d'Antigua, leCactoblastis s'est acclimaté mais, jusqu'à présent, la destruction desOpuntia n'est pas complète. LeCactoblastis s'est aussi répandu, accidentellement ou non, dans les ?les St. Kitts et U.S. Virgin. Les auteurs donnent la liste d'autres régions où l'introduction de cet insecte pourrait être envisagée. Les espècesDactylopius sp. aff.confusus (Ckll.) etD. opuntiae Ckll. (Hemiptera, Coccidae) ont aussi été introduites dans l'?le Nevis mais ne s'y sont pas maintenues. Les auteurs donnent des raisons possibles de cet échec.      

"Necking" behaviour in the giraffe

Previous references to "necking" behaviour, and the main features of the study area are briefly outlined.
"Necking" behaviour in giraffe takes place only in all male herds. When the animals are in a head to head posture the intensity is either high or low, but when animals take up a head to tail posture the actions are always of high intensity and appear to have greater sexual significance.
The significance of "necking" is discussed, and it is suggested that these ritualized actions form an important sexuo-social bonding mechanism whereby a hierarchy is created amongst the males, and movement between strictly bachelor and mixed herds helps to maintain contact between the sexes in this polygamous mammal.     

Role of Lipid in the Protection of Staphylococcus aureus Against Trichlorophenol in Mixed Culture

The sensitivities of Proteus mirabilis, Salmonella schottmuelleri, Aerobacter aerogenes, and Staphylococcus aureus to 2, 4, 6-trichlorophenol in sodium borate were studied. It was demonstrated that these gram-negative organisms can protect S. aureus from the effect of the phenol in mixed culture. There is a direct correlation between this protective effect and the quantity of total lipid extracted from the gram-negative organisms. The distribution coefficient between trichlorophenol and the lipid of the cells is related to the sensitivity and capacity to protect S. aureus in mixed culture. Hydrogen bonding between the cell's lipid and the phenolic compound is discussed as a possible mechanism which determines a cell's response to the inhibitor.     

Meeting announcements

The levels of individual free and conjugated ecdysteroids and ecdysteroid acids, labeled from [¹⁴C]cholesterol, in five different age groups of male Manduca sexta during pupal-adult development were determined by HPLC. Eight free ecdysteroids, eight ecdysteroid phosphates, and two ecdysteroid acids were identified. Newly ecdysed pupae contained predominantly 3-epiecdysteroids in each of the free, conjugated, and acidic ecdysteroid fractions. The titer of each ecdysteroid fraction rose sharply by day 4, and this was particularly noteworthy with respect to free ecdysone and 3-epi-20-hydroxyecdysonoic acid. This stage demonstrated high degrees of ecdysone biosynthesis, oxidative catabolism, and phosphorylation. As development proceeded to day 16, total ecdysteroid titer remained constant; a decreasing free ecdysteroid titer was accompanieid by increasing titers of both conjugates and acids resulting from the metabolic processes of hydroxylation, oxidation, epimerization, and phosphorylation. The predominant metabolites throughout development were 3-epi-20-hydroxyecdysonoic acid and the phosphate conjugates of 3-epi-20-hydroxyecdysone and 3-epi-20,26-dihydroxyecdysone. The ultimate inactivation of the ecdysteroids of M. sexta during pupal-adult development is possibly mediated by two pairs of metabolically-linked processes, one leading to a 3-epiecdysteroid acid, and the other to 3-epiecdysteroid phosphates.     

Cloned mouse melanocyte lines carrying the germline mutations albino and brown: complementation in culture

We have established two new immortal lines of mouse melanocytes, melan-b and melan-c, from mice homozygous for the brown (b) and albino (c) mutations respectively. Both lines were derived through differentiation in vitro of embryonic epidermal melanoblasts. The brown melanocytes are visibly brown by light microscopy, and centrifuged cell suspensions form brown pellets. The albino melanocytes form white pellets and contain abundant unpigmented premelanosomes as shown by transmission electron microscopy. Like normal, non-immortal melanocytes and like the immortal black melanocyte line melan-a, both lines show little or no growth in a standard, serum-supplemented medium, but proliferate well in the presence of 12-o-tetradecanoyl phorbol-13-acetate (TPA). Sustained growth of the albino cells also requires either keratinocyte feeder cells or 2-mercaptoethanol (2-ME). The modal chromosome numbers are 39 for melan-b and 40 (diploid) for melan-c. Neither line is tumorigenic in nude mice. Heterokaryons between the two lines can be constructed and form wild-type, black pigment. Melanocyte lines can now be reproducibly generated from mice of different strains, and provide tools for molecular studies of germline coat-colour mutations. These two lines provide elegant means to study the developmentally controlled expression of the two complementary genes, B and C, with black melanin pigment as a readily detectable natural marker.