Essential function of linoleic acid esterified in acylglucosylceramide and acylceramide in maintaining the epidermal water permeability barrier. Evidence from feeding studies with oleate, linoleate, arachidonate, columbinate and alpha-linolenate

Essential fatty acid-deficient rats were supplemented with 300 mg per day of pure fatty acid esters: oleate (O), linoleate (L), arachidonate (A), and columbinate (C) for 10 days. During this period, the rats in groups L, A, and C all showed a decrease in their initially high trans-epidermal water loss, a classical essential fatty acid-deficiency symptom, to a level seen in non-deficient rats (group N). The trans-epidermal water loss in rats of group O was unaffected by the supplementation. Fatty acid composition of two epidermal sphingolipids, acylglucosylceramide and acylceramide, from the skin were determined. The results indicate that re-establishment of a low trans-epidermal water loss was associated with incorporation of linolenate into the two epidermal sphingolipids. Supplementation with columbinate resulted in relatively high amounts of this fatty acid in the investigated epidermal sphingolipids. Analysis of pooled skin specimens from a previous study in which weanling rats were fed a fat-free diet and supplemented orally with pure alpha-linolenate for 13 weeks (Hansen, H.S. and Jensen, B. (1983) Lipids 18, 682-690) revealed very little polyunsaturated fatty acid in the two sphingolipids. These rats showed increased evaporation which was comparable to that of essential fatty acid-deficient rats. We interpret these results as strong evidence for a very specific and essential function of linoleic acid in maintaining the integrity of the epidermal water permeability barrier. This function of linoleate is independent of its role as precursor for arachidonate and icosanoids.     

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.     

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.     

Retention of bone cell viability in mouse calvarial explants after cryopreservation

Newborn mouse calvaria, cyropreserved at -196 degrees C in serum-free medium containing dimethyl-sulfoxide, were compared to unpreserved explants for bone cell viability by [3H]thymidine uptake. Other explants were studied using autoradiography to compare the histological appearance of the cryopreserved and control unpreserved explant sites of cellular localization of [3H]thymidine. After short-term cryopreservation, calvarial bone cells, including less differentiated osteoprogenitor cells, survived as indicated by their incorporation of the DNA precursor. With culture continuing for up to 24 hr after thawing and in the continuous presence of [3H]thymidine, additional labeled thymidine was incorporated, indicating that the proliferative ability of explant cells persists after cryopreservation. Cryopreserved bone explants did not, however, incorporate the same amount of labeled thymidine as did controls at each time point studied. These events, as measured quantitatively and observed by autoradiography of the tissue, indicate that newborn calvarial bone cell proliferation in vitro continues after cryopreservation. The large surface:mass ratio of the tissue and its proportionate volume of calcified matrix apparently permits it to behave as an isolated cell population with regard to the diffusion of the cryoprotectant and thermal conductivity, thus permitting the retention of explant viability.     

DIFFERENTIAL INCORPORATION OF [3H]LYSINE INTO VISUAL CORTEX PROTEIN FRACTIONS DURING FIRST EXPOSURE TO LIGHT

—A resolution of the enhancement of protein synthesis in the visual cortex of rats during first exposure to light (Richardson and Rose , 1972) was achieved by polyacrylamide gel electrophoresis using a double-labelling technique. Differential incorporation of lysine was established between exposed and control animals in two fractions of the soluble proteins and seven fractions of the insoluble proteins. This suggests that exposure to a new experience of this type involves a specific effect on protein synthesis, rather than a general stimulation across all fractions.