Anomeric and other substrate specificity studies with myo-inositol-1-P synthase

L-myo-Inositol-1-phosphate synthase has been found to have at least a 5-fold preference for the beta-anomer of its natural substrate D-Glc-6-P. The alpha-anomer appears to be an inhibitor of the reaction and may be converted to product as well. As well as showing an enzymatic preference for the equatorial C-1 hydroxyl of D-Glc-6-P, our results suggest that it is the pyranose form of D-Glc-6-P that binds to the enzyme and that ring-opening is an enzymatic step. We have also found D-2-dGlc-6-P, D-2-F-2-dGlc-6-P, and D-Man-6-P each to be both competitive inhibitors and substrates that are converted to inositol phosphates by the synthase. D-Allose-6-P is a weak inhibitor of the enzyme, but not a substrate. D-Gal-6-P is neither substrate nor inhibitor. Thus the specificity of the synthase with respect to single position epimers of D-Glc-6-P increases in the order C1 less than C2 much less than C3 less than C4.     

Grooming and touching behaviour in captive ring-tailed lemurs (Lemur catta L.)

The distribution of grooming and touching behaviours was recorded in a group of captive ring-tailed lemurs. Grooming was found to be performed chiefly by older, higher ranking animals; touching (i.e., “reach out and touch” behaviour) was directed primarily by younger, low ranking animals to older, high ranking individuals. It is suggested that such touching is a submissive gesture in this species.     

Gastrointestinal pH measurement in rats: influence of the microbial flora, diet and fasting

The pH of the rat intestinal tract was decreased by the presence of a microbial flora, but its influence in the forestomach is less clear. Stomach pH values varied according to the amount of food present at the time of measurement. Fasting increased the pH of the gastrointestinal tract in conventional rats but had little effect in germfree rats. In the conventional rat, feeding a purified diet compared with a commercial diet resulted in a lower pH in the forestomach and a higher pH in the caecal contents. Magnesium trisilicate promoted gastric emptying in conventional rats and its antacid effect was observed only in the caecum and colon.     

Alkali sensitivity in plasmid-bearing strains of Escherichia coli

Introduction of the ColV,I-K94 plasmid into any of four strains of Escherichia coli gave derivatives which grew less well than the parent at alkaline pH. The alkali sensitivity of the 1829 derivative resulted from the presence of the plasmid rather than from its introduction into a less alkali tolerant variant. Of two other ColV plasmids tested, one (ColV-K30) conferred substantial alkali sensitivity whereas the other (ColV-41) had little effect. Of several other plasmids examined, R124-F2 (which confers derepressed transfer properties) resembled ColV,I-K94 in its effect on alkali sensitivity and ColV-K98 produced a marked effect. The other plasmids (F lac , R124 itself, R1 and R483ColIa) had only a small effect. For ColV plasmids, it appears to be the presence of transfer and colicin components together which leads to the reduced tolerance to alkaline pHs.     

Immunity in cryptococcosis: An overview

Cryptococcosis is an often fatal opportunistic fungal infection. Despite efforts to elucidate the role of immunity in host defense against the disease, much remains to be learned. The purpose of this brief review is to provide the reader with an overview of the history of research concerned with host immunity in cryptococcosis. Both humoral and cell-mediated studies are included. An effort has been made to present the reader with a comprehensive list of references in the hope of encouraging additional reading and research in this important area.     

A chronic implant for recording of cochlear potentials in primates

A new technique for the continuous recording of peripheral bioelectrical activity in the auditory system of primates is described. Because of basic differences in the anatomy of the temporal bone, the approach to the round window of the cochlea is more difficult in most primates than in lower animals. A relatively simple surgical approach, which made possible the placement of an electrode into the perilymph of the inner ear via the well-demarcated horizontal semicircular canal was therefore developed and is described in detail. The bared tip of a Teflon-coated wire was cemented into the canal opening with carboxylate cement, and the wire attached to a permanent electrical connector on the skull. Cochlear microphonic and action potentials of 50 to 100 μV amplitude were thus recorded on a continuing basis at the same time that behavioral studies of primate auditory acuity were conducted.