Inhibition of the pancreatic microsome enzyme release phenomenon by inhibitors of signal peptidase activity

The protease-sensitive release of α-amylase from rat pancreatic microsomes, incubated at 37°C, was inhibited by protease inhibitors which have been reported to inhibit signal peptidase activity. Protease inhibitors which did not affect signal peptidase activity also failed to inhibit amylase release from microsomes. Although the observed amylase release was in the opposite direction to enzyme secretion and involved fully-synthesised proteins, rather than nascent peptides, it is proposed that the enzyme release phenomenon reported from this laboratory (Pearce et al. (1978) Biochem. J. 176, 611–614) is related to the protein transporting mechanism involved in secretion.     

Subpopulations of splenic T and B lymphocytes producing and regulating leukocyte adherence inhibition factor

Picryl chloride induces contact hypersensitivity in mice, accompanied by spleen cell sensitization that is demonstrable in vitro by specific antigen-induced formation of leukocyte adherence inhibition factor (LAIF). This cellular activity was detected only up to 7 days after sensitization; thereafter the spleen cells appeared to be unreactive with the antigen. The cells were still normally reactive with the mitogen concanavalin A. Antigen reactivity of such “late” cells was restored by passage through a glass-bead column (provided resulting nonadherent cells were reconstituted with normal macrophages), and the restored reactivity was again suppressed by the eluted glass-bead-adherent cells. Suppression was antigen specific. Separation of T and B lymphocytes by affinity chromatography, after glass-bead treatment of sensitized spleen cells, showed that two subpopulations of B cells—those responsible for producing LAIF as well as those suppressing LAIF production by T cells—were glassbead adherent. This was extended by showing directly with anti-Thy-1.2 serum that B cells producing LAIF and suppressor T cells were glass adherent. Thus two suppressive cell populations, and the B cell producing LAIF, were glass adherent while the T-cell LAIF producer was not. Tests for adoptive transfer of cutaneous hypersensitivity in vivo demonstrated the relevance of many of the above observations to conditions in the whole animal. “Late” spleen cells from sensitized mice could not transfer hypersensitivity but this property was restored by glass-bead passage. The eluted adherent cells suppressed transfer. Both adoptive transfer and its suppression were antigen specific.     

Density, distribution and mobility of surface anions on a normal/transformed cell pair

The distribution and mobility of cell surface anions was investigated on low passage cultures of secondary BALB/c embryonic fibroblasts and their SV40-transformed counterparts (VLM cells) using polycationized ferritin (PCF) as a label. While the absolute number of anions/nm² of membrane was equivalent on the two cell types, the topographical distribution and mobility of these anions was strikingly different. After pulse-labeling with PCF at 37 °C, anions on BALB/c fibroblasts occurred in large piled-up clusters separated by extensive areas of membrane ( = 0.47 μm) free of negative charges. Labeling at 4 °C reduced the degree of “piling up” within the clusters, but the intercluster spacing was maintained indicating that the anions have short-range mobility in the membrane and can be cross-linked into a tight lattice at 37 °C. These anions do not, however, demonstrate any long-range mobility during a 20 min post-label incubation in PBS. In contrast, anions on VLM cells are inherently present in a random configuration of microclusters and single anions with relatively small ( = 0.09 μm) intervening areas of low charge density. Short-range mobility of surface anions is not displayed, presumably as a result of the inter-site distance, but long-range mobility is indicated by the formation of large site clusters following a 20 min incubation in PBS after pulse-labeling. Very mild proteolysis of BALB/c fibroblasts induces a change in the topography of surface anions toward the random configuration typical of VLM cells. These data are discussed in relation to altered social interactions between tumor cells which may be influenced by cell-cell adhesion characteristics.     

A technique for quantitating enzyme histochemistry in adjuvant arthritic joints. II. Acid phosphatase

Synopsis This paper reports on the incorporation of acid phosphatase histochemistry with a quantitative technique designed to measure the percentage of histochemically-localized enzyme-reactive cells found in adjuvant arthritic articular cartilage, synovial membrane and bone marrow. With the data presented and the comparisons made, this incorporation is validated and adjuvant arthritic acid phosphatase lesions established. In addition to discussing the importance of the histochemical data and its relationship with intra-articular lysosomes, the applicability of the reactive cell values to drug inhibition studies is discussed.     

Distribution and movement of toxaphene in anaerobic saline marsh soils

The biological oxygen demand (BOD) of filtered water from Lake Wingra, Wisconsin is significantly higher in the littoral zone than in the pelagial zone. Laboratory experiments indicate that BOD is not influenced by water temperature at the time of sampling or by enrichment with nitrate or ammonia. Rather, enrichment with macrophyte leachate sharply increases BOD, and enrichment with phosphate produces a small but significant increase in BOD. We conclude that high BOD in littoral waters of the lake is an indication of production of labile organic matter in the water by dense beds of the macrophyte Myriophyllum spicatum.     

Critical problems with extraction of ATP for bioluminescence assay of plankton biomass

Recovery of ATP by boiling tris extraction was 90–95 percent greater in 1 liter grab samples than in concentrated net samples. ATP losses were attributed to insulating effects promoted by accumulation of detritus on filters. A series of extractions over a concentration range of whole or size-segregated plankters and cultured algae was made to determine volume of water to be filtered for optimum extraction efficiency. Accuracy of ATP assays was optimized by: (i) using large diameter (i.e. 47 mm) acetate filters; (2) limiting sample volume filtered to 50 ml when particulate organic carbon (POC) exceeded 0.4 mg l^–1; and (3) performing extractions in boiling tris maintained initially on a laboratory hot plate at 400°C as opposed to hot water bath at 100°C.Additional problems were encountered in using published cellular carbon: ATP ratios for conversion of ATP data to biomass as carbon. Ratios of POC: ATP in cultures of sheathed blue-green algae reached 550 : i, while non-sheathed forms yielded ratios near values previously reported for plankton communities. Difficulties in applying a uniform conversion factor may be expected in plankton communities containing significant volumes of sheathed blue-greens.     

Effect of temperature on locomotor activity in the goldfish (Carassius auratus) and the bluegill (Lepomis macrochirus): Presence of an ‘activity well’ in the region of the final preferendum

Goldfish (Carassius auratus) and bluegill sunfish (Lepomis macrochirus) were placed in aquaria where their locomotor activity was monitored by photocells, and tested at various acclimation temperatures over a range encompassing their final thermal preferenda. Activity was pooled over 24-hour periods to eliminate any circadian rhythm effects. Both species exhibited an activity well of reduced locomotor activity in the region of the final preferendum. Goldfish, tested either singly or in groups of 2–5 individuals, exhibited a social-interaction effect which became more pronounced at higher temperatures. These results are discussed in relation to a thermokinetic interpretation of thermo-regulatory behavior in fishes, and to the correspondence between thermal preferenda and thermal optima.     

Thermoregulatory behavior of the bluespotted sunfish,Enneacanthus Gloriousus

Twenty bluespotted sunfish, Enneacanthus gloriosus, were individually tested for thermoregulatory behavior in an electronic shuttlebox. The first fishes of this genus to be tested for thermoregulatory behavior, these individuals were captured near the northern limit of their zoogeographic range, in northeastern Pennsylvania. The mean final preferendum from pooled data of all 20 fish was 28.5°C; there were no significant differences between day and night.     

Effects of Cerulenin upon the Syntheses of Lipid and Protein and upon the Formation of Respiratory Enzymes in Adapting, Lipid-Limited Saccharomyces cerevisiae

When bakers' yeast cells were grown anaerobically in a medium supplemented with Tween 80 and ergosterol, exposure during aeration to the fatty acid synthesis inhibitor, cerulenin, had little effect upon respiratory adaptation, the induction of enzymes of electron transport, or the in vivo incorporation of [(14)C]leucine into mitochondrial membranes. These lipid-supplemented cells were apparently able to undergo normal respiratory adaptation utilizing endogenous lipids alone. The level of cerulenin used (2 mug/ml) inhibited the in vivo incorporation of [(14)C]acetate into mitochondrial membrane lipids by 96%. If, however, the cells were deprived of exogenous lipid during anaerobic growth, subsequent exposure to cerulenin severely reduced their capacity to undergo respiratory adaptation, to form enzymes of electron transport, and to incorporate amino acid into both total cell and mitochondrial membrane proteins. This cerulenin-mediated inhibition of enzyme formation and of protein synthesis was nearly completely reversed by the addition of exogenous lipid during the aeration of the cells. In lipid-limited cells, chloramphenicol also had dramatic inhibitory effects, both alone (75%) and together with cerulenin (85%), upon total cell and mitochondrial membrane [(14)C]leucine incorporation. This marked chloramphenicol-mediated inhibition was also largely reversed by exogenous lipid. It is concluded that, in lipid-limited cells, either cerulenin or chloramphenicol may prevent the emergence of a pattern of lipids required for normal levels of protein synthetic activity. The effect of cerulenin upon the formation of mitochondrial inner membrane enzymes thus appears to reflect a nonspecific effect of this antilipogenic antibiotic upon total cell protein synthesis.     

SPECIAL PAPER: THE PLASTOCHRON INDEX: A REVIEW AFTER TWO DECADES OF USE

The plastochron index provides a morphological time scale which has proved more reliable than chronological age in studies relating morphological and physiological development of a whole plant or plant organ. Since its inception in 1957, the index has been utilized in a variety of investigations from leaf ontogeny in cottonwood trees to rhizoid cluster initiation in algae. The plastochron index has been extensively used in studies involving source and sink relationships, leaf anatomy, cell differentiation, and primary vascularization. It has been used in investigations of hormonal regulation of plant growth and in studies of the effects of various environmental factors on developmental processes in crops. This paper reviews some of the literature from 1957 to present concerning the development and use of the plastochron index.