The Effect of Recovery Medium on the Isolation of Staphylococcus aureus after Heat Treatment and after the Storage of Frozen or Dried Cells

The recovery of heated or dried cells of Staphylococcus aureus was best on media containing blood or sodium pyruvate. It is suggested that the catalase of S. aureus may be destroyed or its activity reduced by heating or drying and that one of the main reasons for the better recoveries on these media is that they are able to destroy peroxide. All media tested adequately supported the recovery of frozen cells.     

Staining Nerve Fibers with Methylene Blue. An Evaluation of Variables Used in An Immersion Technic

A study of the effects of osmotic pressure, pH, the presence of dextrose, acetate, pyruvate or lactate, and agents affecting cell permeability during supravital staining by methylene blue was made by means of an immersion technic. Mesentery and intestine of dogs and cats were used. Penetration of the dye was limited to the mesentery and more superficial layers of intestine. Conditions which facilitated the characteristic differentiation of of nerve fibers were: continuous oxygenation of the staining solution, pH about 5.6 stabilized by phosphate buffer, and the presence of small amounts of acetate and lactate. Young animals' tissue stained better than old. Methylene blue was a much more effective staining agent than less completely methylated thionins.     

The yeasts of British fresh sausage and minced beef

Three hundred and eighty three yeasts isolated from samples of unsulphited or sulphited sausages and skinless sausages and minced beef were characterized in detail.Debaryomyces hansenii was the most commonly isolated yeast from most samples followed byCandida zeylanoides andPichia membranaefaciens. The presence of sulphite in sausages did not appear to affect the numbers and range of yeasts present but did affect their relative proportions. A survey of one factory showed that meat intended for sausage production and equipment harboured the same range of yeasts that are found in the finished products.     

Behaviour of antioxidant defense system in the adaptive response to salt stress in Helianthus annuus L. cells

A relationship between the antioxidant defense system and salt tolerance in two types of sunflower calli differing in salt sensitivity was studied. No reduction in growth occurred in the NaCl-salt-adapted cell line (T) when grown on 175 mM NaCl but growth of the salt-stressed cell line (S) was reduced by 83%. Lipid peroxidation and protein oxidation increased during acute stress of salt stressed cells at 14 and 28 d of the experiment, while salt-adapted calli (T) remained similar to non-shocked (C) values. The antioxidant defense system of callus adapted to growth under NaCl responded differently to 175 mM of salt compared with the corresponding controls under shock treatment. Salt-adapted and salt-stressed calli showed a similar pattern in GSH content at day 14 but at day 28 in S calli, GSH content was increased 100% over the non-shocked calli, while T calli returned to the initial values. In the salt-stressed calli, a general decrease in all the antioxidant enzymes studied (except for glutathione reductase and dehydroascorbate reductase activities) was observed at day 28. Except for catalase, the antioxidant enzymes were elevated constitutively in adapted calli as compared to stressed cells, when both were grown in the absence of NaCl (time 0), and remained unaltered until 28 d after the beginning of the experiment. These results suggest the involvement of an enzymatic antioxidant defense system in the adaptive response to salt stress in Helianthus annuus L. cells.     

Avoidance of headwinds or exploitation of ground effect—why do birds fly low?

ABSTRACT Birds often fly close to the ground or water. Wind shear theory predicts that wind speeds decline with proximity to the substratum, so birds might be expected to fly lower when flying upwind than when flying downwind. We tested this prediction and found that the wind shear equation is valid at heights below 4 m, with wind speed over a smooth surface ～40% lower at a height of 0.08 m than at 4 m. Birds that fly close enough to smooth substrata can also benefit energetically from ground effect, where vortices generated by their flight interact with the ground or water. This suggests that birds should use ground effect more when flying upwind than when flying downwind. We determined the percent time spent flying in ground effect by 21 species of passerine and non‐passerine birds flying in sheltered coastal aquatic and nearby terrestrial areas of County Cork, Ireland. We found that use of ground effect was uncommon for passerines, but common for a variety of non‐passerine waterbirds. However, phylogenetic analysis indicates no linkage between phylogeny and incidence of ground effect use and it is probable that incidence of use is determined by ecology rather than phylogeny. Great Cormorants (Phalacrocorax carbo) used ground effect most frequently over water (59.4% of time in flight). Over land, Barn Swallows (Hirundo rustica) used ground effect most often (19.8% of time). Phylogenetic contrasts regression analysis showed no significant relationship between use of ground effect and either wing aspect ratio or wing loading for 18 of our focal species, though simple linear regression analysis indicated that birds with greater wing loading used ground effect slightly (but significantly) more often. We found that 95% of Great Cormorants flying upwind used ground effect whereas only 35% did so when flying downwind. Few Black‐headed Gulls (Chroicocephalus ridibundus) used ground effect (probably because they fly high to locate prey), but still showed greater use when flying upwind (25%) than downwind (2.5%). When flying upwind in ground effect at the wind speeds encountered in our study, the velocity for minimum power (V_mp) for Great Cormorants was exceeded, suggesting theoretical benefits of about 14.3%. Our study indicates that several species exploit both wind shear and ground effect to minimize energy expenditure during commuting and foraging, but that others do not, because of either complexity of habitat morphology or the demands of their foraging ecology.     

Orchids,bilateral symmetry and insect perception

The basic characteristics of orchids, possessing the greatest number of complex floral images of any Angiosperm family, are reviewed. Bilateral symmetry (zygomorphy) is shown by use of information theory techniques to give much greater possibilities for the transmission of visually mediated information than radial symmetry. The difference in information content is further enhanced by motion. The analysis is offered as evidence that the evolution of diversity in complex images, if effected by the unique behavioral specificity of pollinators known as “flower constancy”, is most economically explained by hypothesizing recognition and storage of the total image (“gestalt”) in the agents of natural selection.