Effects of temperature on nutrient self‐selection in the silverfish Lepisma saccharina

Nutrient self‐selection represents an important behaviour that has been measured across many taxa. Despite the amount of research on this phenomenon, few studies report the evaluation of the effects of environmental variables such as temperature on nutrient selection by animals. In the present study, the nutrient selections of the silverfish Lepisma saccharina L. are measured across a range of temperatures (10, 15, 20, 25, 30 and 35 °C) using feeding arenas with three nutrient choices: carbohydrate (sucrose), protein (casein) and fat (lard). An overall preference for carbohydrates is shown across the range of temperatures, followed by protein, and then fat. However, the proportional consumption of each dietary component changes with temperature; the proportional carbohydrate consumption decreases dramatically with increasing temperature (>94% of the diet at 15 °C but <58% at 30 °C), whereas the proportional protein and lipid consumption increases with increasing temperature up to 30 °C. Changes in nutrient selection with temperature may be related to the dietary requirements of the insect at different temperatures.     

Release of an ice-active substance by Antarctic sea ice diatoms

Interstitial water from the diatom-rich ice platelet layer in McMurdo Sound, Antarctica contains a macromolecular, ice-active substance (IAS) that, at in situ concentrations, causes dense pitting on the basal surfaces of growing ice platelets. In this respect, it resembles several fish antifreezes that also cause pitting on ice surfaces, but unlike the antifreezes, it does not lower the freezing point. The IAS appeared to be released by diatoms, as extracts from the diatoms contained IAS, while seawater from a diatom-free area did not. No evidence of IAS was found in several species of temperate water diatoms. The ice-pitting activity of the IAS was destroyed by proteases and by incubation at 40° C, but not by periodate oxidation, or by incubation with galactosidase or endonuclease. Thus, activity appears to arise from a protein or protein component, and not from carbohydrate or nucleic acids. Potential roles of the IAS in the sea ice community are discussed.     

CL 277,082: a novel inhibitor of ACAT-catalyzed cholesterol esterification and cholesterol absorption

CL 277,082 (I) was found to be a potent inhibitor of acyl CoA:cholesterol acyltransferase (ACAT, EC 2.3.1.26) in microsomes from a variety of tissues with IC50 values of 0.14 microM for intestinal mucosal microsomes, 0.74 microM for liver, and 1.18 microM for rat adrenal. I was also shown to inhibit ACAT in cultured smooth muscle cells (IC50 = 0.8 microM) and was found to be specific in inhibiting cholesterol esterification since it did not inhibit fatty acid incorporation into triglycerides or phospholipids. Also, other cholesterol esterifying enzymes such as lecithin:cholesterol acyltransferase (LCAT) and pancreatic cholesterol esterase were not inhibited by I, nor was esterification of retinol by acyl CoA:retinol acyltransferase (ARAT) from intestinal mucosal microsomes inhibited. I was a potent inhibitor of cholesterol absorption in cholesterol-fed rats by markedly inhibiting increases in liver and serum cholesterol concentration (ED50 = 5.2 mg/kg per day) while increasing the excretion of neutral 14C-labeled sterol in the feces.     

Ultrastructure of the lipid sac wall in the Antarctic notothenioid fish Pleuragramma antarcticum

Summary Electron microscopy indicates that the intermuscular lipid sac walls of Pleuragramma antarcticum consist of several white adipocytes arranged circumferentially around a large lipid droplet. Since sac walls are cellular, the lipid may be available for metabolism in addition to its obvious role in buoyancy.     

The Distribution of Enzymes Which Synthesize Nicotinamide Adenine Dinucleotide and Nicotinamide Adenine Dinucleotide Phosphate in Monkey, Rabbit, and Ground Squirrel Retinas

The activity of adenosinetriphosphate:nicotinamide adenylyltransferase (EC 2.7.7.1) was measured in all the layers of monkey, rabbit, and ground squirrel retinas. Nicotinamide adenine dinucleotide (NAD) kinase (EC 2.7.1.23) distribution was measured in monkey and rabbit retinas. An attempt was made to measure NAD synthetase (EC 6.3.5.1), but the activities in the retinal layers were too low to produce a reliable increment in the levels of endogenous NAD. In monkey retina the adenylyl transferase was highest by far in the outer and inner nuclear layers, lower and variable in ganglion cell and fiber layers, and almost absent elsewhere. Rabbit retina differed in that activity was nearly absent in the outer nuclear layer, whereas in the ground squirrel outer nuclear layer activity was double that of the inner nuclear layer. The species differences suggest that adenylyl transferase is almost absent from cone cell nuclei and high in rod cell nuclei. NAD kinase distribution in monkey retina was almost the mirror image of that of adenylyl transferase.