Microbial contamination of hydrogel contact lenses

Bacterial contamination of contact lenses (CLs) may contribute to CL-related corneal infection and inflammation. This study reports CL biota over time during daily and extended wear. Microbial contamination of a 58% water, ionic hydrogel CL and a 38% water, non-ionic hydrogel CL was evaluated in an Australian and an Indian population. Fifty wearers were repeatedly sampled over 18 months. Overnight CL use did not alter the frequency of positive cultures, nor the spectrum of organisms compared with daily CL wear. There were no differences in type and frequency of CL contamination between the CL types. Positive cultures were more frequently recovered from the Indian population compared with the Australian population. Streptococcus spp. and Propionibacterium spp. were more frequently isolated from the Australian population. Fungi and Bacillus spp. were more frequently isolated from the Indian population. Normal CL biota alone cannot explain the increased rate of infection and inflammation in extended wear.     

Histidine Uptake in Strains of Neurospora crassa with Normal and Mutant Transport Systems

Kinetic parameters for three systems of active histidine uptake by germinated conidia of Neurospora crassa have been measured. Each system appears to follow typical Michaelis-Menten kinetics when studied separately from the other systems. Under the conditions studied, the general amino acid transport system was found to account for the major portion of histidine uptake from low concentrations. Three types of transport mutants with altered growth inhibition patterns were selected in a histidine auxotroph. Growth of one mutant, type bas(a), could be inhibited by the addition of methionine to a histidine-supplemented medium, and another type, neu(a), could be inhibited by the addition of arginine. These mutants were shown to be lacking active histidine uptake by the basic amino acid and neutral amino acid transport systems, respectively. Another type of double mutant (his-3, neu(r)) could be inhibited only by the addition of very high concentrations of methionine in the presence of arginine and histidine, and the mutation appeared to have altered the specificity of the neutral amino acid permease.     

Transduction of Methicillin Resistance in Staphylococcus aureus Dependent on an Unusual Specificity of the Recipient Strain

Resistance to methicillin was transduced by phage 80 or 53 from two naturally occurring methicillin-resistant strains of Staphylococcus aureus to methicillin-susceptible recipient strains at frequencies of 10⁻⁷ to 10⁻⁹. Ultraviolet irradiation of transducing phage and posttransductional incubation at 30 C were essential for useful frequencies of transduction. Effectiveness as a recipient for this transduction was highly specific. Strain NCTC 8325 (PS47) in its native state was an ineffective recipient but became effective after it had received by transduction one of several penicillinase plasmids. This acquired effectiveness was retained in most cases after elimination of the plasmid by ethidium bromide treatment. Like the donor strain, the progeny were heterogeneous in the degree of their resistance to methicillin, which was expressed by a higher proportion of cells as the temperature of incubation was lowered from 37 to 30 C. Separate transductants varied widely in the degree of resistance acquired by transduction. Methicillin resistance was stable in the donor and transductant strains. We favored the interpretation that methicillin resistance in our strains was determined by a single chromosomal gene, although the possibility that it was determined by two or more closely linked genes could not be excluded.     

The Potassium Content of Gonyaulax polyedra and Phase Changes in the Circadian Rhythm of Stimulated Bioluminescence by Short Exposures to Ethanol and Valinomycin

A circadian rhythm in the intracellular level of K⁺ in Gonyaulax polyedra is reported. When axenic cultures of Gonyaulax in continuous light (60-75 fot candles) are exposed for 4 hours to 0.1 or 0.2% ethanol, the subsequent free-running rhythm in stimulated bioluminescence is phase-shifted, the amount and direction of the shift being dependent on the time in the circadian cycle when cells are treated. The phase-response curve for ethanol closely resembles that for light in similarly maintained cells. When valinomycin (0.1 or 0.2 μg ml⁻¹) is present in addition to ethanol, the phase of the bioluminescence rhythm is returned to that of an untreated cell suspension. Valinomycin thus negates the effect of ethanol on phase. The intracellular K⁺ level immediately after treatment of a cell suspension for 4 hours with ethanol (0.1%) is about half that of untreated cells. If valinomycin (0.1 μg ml⁻¹) is also present during the 4-hour treatment, the intracellular K⁺ is only slightly lower than in untreated cells. Increasing the external concentration of K⁺ or Na⁺ for 4 hours has no effect on the rhythm of stimulated bioluminescence. These results are interpreted as support for the hypothesis that the mechanism by which circadian oscillations are generated involves changes in membrane properties.     

Absence of Circular Plasmid Deoxyribonucleic Acid Attributable to a Genetic Determinant for Methicillin Resistance in Staphylococcus aureus

Plasmid deoxyribonucleic acid was not detected by centrifugal analysis of lysates of penicillinase-negative strains of Staphylococcus aureus harboring a determinant of methicillin resistance derived from strain Villaluz. When these strains contained a penicillinase plasmid, the plasmid deoxyribonucleic acid of methicillin-resistant and methicillin-susceptible strains was indistinguishable by the methods employed. The results indicate that the genetic determinant for methicillin resistance in the strains examined was not associated with a circular plasmid comparable to those that have been shown to determine resistance to benzylpenicillin, tetracycline, and chloramphenicol in S. aureus.     

Preliminary crystallographic characterization of ricin agglutinin

The quaternary structure of ricin agglutinin (RCA) has been determined by x-ray crystallography. The refined structure of ricin proved to be a successful search model using the molecular replacement method of phase determination. RCA forms an elongated molecule of dimensions 120 Å × 60 Å × 40 Å with two A chains at the center and a B chain at each end. The A chains are covalently associated via a disulfide bridge between Cys 156 of both chains. Additional contacts at residues 114–115 stabilize the dimer interface. The covalent association of RCA A chains was confirmed by gel filtration under reducing and nonreducing conditions. Proteins 28:586–589, 1997. © 1997 Wiley-Liss, Inc.     

Semiochemical attractants for the beech leaf‐mining weevil,Orchestes fagi

The beech leaf‐mining weevil, Orchestes fagi L. (Curculionidae: Curculioninae: Rhamphini), a pest of European beech, Fagus sylvatica L. (Fagaceae), was recently discovered infesting American beech, Fagus grandifolia Ehrh., in Nova Scotia, Canada. Adult O. fagi feed on both young and mature leaves of beech as well as on other species (e.g., raspberry, Rubus spp.), but oviposition and larval feeding are restricted to beech. Females oviposit in young developing beech leaves at the time of bud burst. We characterized volatiles emitted from buds, leaves, and sapwood of American beech and examined their potential as attractants alone or when combined with other weevil pheromones for O. fagi. We predicted that adults would be attracted to volatiles emitted from beech leaves, especially those emitted from bursting beech buds. Gas chromatography/mass spectrometry (GC/MS) analyses of volatiles collected from buds at pre‐ and post‐budburst identified two diterpene hydrocarbons, 9‐geranyl‐p‐cymene ( 1 ) and 9‐geranyl‐α‐terpinene ( 2a ), that were emitted in large amounts at the time of bud burst. Compound 1 significantly increased mean catch of males and total O. fagi (but not females) on sticky traps compared with unbaited controls. Y‐tube bioassays confirmed attraction of male O. fagi to bursting beech buds and compound 1 . Attraction of male O. fagi to 1 , emitted in large quantities from American beech, is likely adaptive because both oviposition and mating of O. fagi coincide with budburst. Our data suggest that traps baited with 1 may be useful for monitoring the spread of O. fagi in North America.     

Attenuation of skeletal muscle atrophy via protease inhibition.

Skeletal muscle atrophy in response to a number of muscle wasting conditions, including disuse, involves the induction of increased protein breakdown, decreased protein synthesis, and likely a variable component of apoptosis. The increased activation of specific proteases in the atrophy process presents a number of potential therapeutic targets to reduce muscle atrophy via protease inhibition. In this study, mice were provided with food supplemented with the Bowman-Birk inhibitor (BBI), a serine protease inhibitor known to reduce the proteolytic activity of a number of proteases, such as chymotrypsin, trypsin, elastase, cathepsin G, and chymase. Mice fed the BBI diet were suspended for 3-14 days, and the muscle mass and function were then compared with those of the suspended mice on a normal diet. The results indicate that dietary supplementation with BBI significantly attenuates the normal loss of muscle mass and strength following unloading. Furthermore, the data reveal the existence of yet uncharacterized serine proteases that are important contributors to the evolution of disuse atrophy, since BBI inhibited serine protease activity that was elevated following hindlimb unloading and also slowed the loss of muscle fiber size. These results demonstrate that targeted reduction of protein degradation can limit the severity of muscle mass loss following hindlimb unloading. Thus BBI is a candidate therapeutic agent to minimize skeletal muscle atrophy and loss of strength associated with disuse, cachexia, sepsis, weightlessness, or the combination of age and inactivity.