Evaluation of the silica microbead method for isolation of red beet protoplast plasma membrane sheets

The silica microbead procedure was utilized for the isolation of plasma membrane sheets from protoplasts of a higher plant, the red beet (Beta vulgaris L.). Membrane yields, as determined by recovery of an exogenous membrane marker were approx. 75%. The plasma membrane fraction contained the enzyme marker, pH 6.5, vanadate-sensitive, K+-stimulated, Mg2+-ATPase and small amounts of mitochondria, endoplasmic reticulum, and possibly tonoplast. The silica microbead procedure was also used for the isolation of intact vacuoles from microbead-coated protoplasts.     

The aggressive behaviour of individual male polecats (Mustela putorius, M. furo and hybrids) towards familiar and unfamiliar opponents

Experiments are described which were designed to investigate the significance of individual differences in aggressiveness between polecats and the relation between the familiarity of the opponent and the pattern and outcome of fighting.
The behaviour of Mustela putorius, M. furo and hybrids between the two species was investigated in an indoor arena of 16 m².
Two kinds of fighting between male polecats were recorded, "companion fighting" between cage mates, in which biting was inhibited and neither of the opponents became intimidated and "uninhibited fighting" between unfamiliar individuals from which a winner and loser generally emerged and a rank order formed.
Individual differences in aggressiveness were assessed by means of a scoring system which statistical analysis showed, generally, to be consistent for any one individual. The rank of an animal, however, was found not to be invariably related to its aggression score.
A number of other factors influencing fighting were investigated, the earlier introduction of one individual into the arena increases its chances of winning a fight; when offered a choice, male polecats fight strangers in preference to cage mates; and the separation of a group of cage mates for as little as 48 hours induces them to behave towards one another like strangers with the result that a rank order is formed. Factors which had no apparent effect on fighting between males were the weight of the individual or the presence of females.
The attributes of familiar and unfamiliar opponents are discussed in the light of these findings.     

The non-flavin redox center of the streptococcal NADH peroxidase. I. Thiol reactivity and redox behavior in the presence of urea

Unlike the 2-electron-reduced (EH2) forms of the flavoprotein disulfide reductases and mercuric reductase, the native EH2 form of the streptococcal NADH peroxidase is quite refractile toward chemical modification with thiol-specific reagents. In the presence of 1.3 M urea, however, the single thiol of the reduced enzyme reacts with phenylmercuric acetate with a t1/2 of 3 min. This modification abolishes the charge-transfer absorbance band at 540 nm and inactivates the enzyme; the latter effect is shown to be reversed with dithiothreitol. Alkylation of the streptococcal peroxidase with iodo[1-14C]acetamide under reducing conditions in the presence of 8 M guanidine hydrochloride allows the isolation of a single labeled tryptic peptide with the sequence: Gly-Asp-Phe-Ile-Ser-Phe-Leu-Ser-C*ys-Gly-Met-Gln-Leu-Tyr-Leu- Glu-Gly-Lys. This sequence is identical to that previously reported (Poole, L. B., and Claiborne, A. (1988) Biochem. Biophys. Res. Commun. 153, 261-266) for the cysteinyl peptide isolated from the NADH peroxidase labeled metabolically with [35S]cysteine. Careful examination of the physical properties of the streptococcal peroxidase in the presence of 1.3 M urea shows that, while catalytic activity and native structural features are largely retained, the relative potentials of flavin and non-flavin redox centers are dramatically affected. We propose that low concentrations of urea stabilize an intermediate state in the transition between native and denatured forms, which is responsible for the observed changes in both active-site thiol reactivity and in redox properties.     

Nisin stimulates oxygen consumption by Staphylococcus aureus and Escherichia coli.

Nisin stimulated oxygen consumption by nongrowing, glucose-metabolizing Staphylococcus aureus and Escherichia coli cells, indicating a protonophore mode of action. A similar stimulation in E. coli cells osmotically stressed to disrupt the outer cell membrane confirmed the cytoplasmic membrane as the site of nisin action and showed that nisin uptake was not prevented by the outer membrane.