The interaction of amino-deuteromethylated melittin with phospholipid membranes studied by deuterium NMR

Melittin, deuteromethylated on each of the four amino groups (Gly-1 N alpha and Lys-7, 21, and 23 N epsilon), was prepared by reductive methylation using deuteroformaldehyde and NaBD3CN. Deuterium NMR spectra were obtained for the modified peptide (D-melittin) bound to phospholipid bilayers and erythrocyte ghosts. D-Melittin at 4 mol% (peptide:lipid) induced reversible transitions between extended bilayers and micelles at the phase-transition temperature in dimyristoylphosphatidylcholine (DMPC) bilayers. These changes in lipid morphology did not occur at 1 mol% D-melittin: DMPC and the peptide was highly motionally restricted in gel in gel-phase lipid.     

Differential regulation of macrophage CCAAT-enhancer binding protein isoforms by lipopolysaccharide and cytokines

The regulation of the C/EBP family in macrophages by LPS and cytokines is of potentially crucial importance in several pathophysiological conditions. The action of LPS and three cytokines on the expression of C/EBP mRNA, protein and functional DNA binding activity in the murine J774.2 cell line was therefore studied. Exposure of the cells to LPS, IL-1, IFN-gamma and TNF-alpha produced a reduction of C/EBP alpha mRNA levels and a corresponding increase in the expression of C/EBP beta and C/EBP delta. EMSA showed time-dependent changes in the DNA binding activity of individual C/EBP isoforms and demonstrated the participation of heterodimers between the different members in DNA-protein interactions. Additionally, mediator-specific changes in the kinetics and magnitude of C/EBP mRNA expression pattern and profile of DNA-protein interactions were observed. These studies provide novel insights into the potential mechanisms that may be responsible for the mediator-specific regulation of macrophage gene expression through the C/EBP family.     

A comparison of the composition and apolipoprotein content of the lipoproteins isolated from human and ferret (Mustela putorius furo L.) serum.

1. The lipoproteins isolated at densities of less than 1.006, 1.006-1.063 and 1.063-1.21 g/ml from human and ferret (Mustela putorius furo L.) serum were compared. 2. Ferret very low density lipoprotein contained proportionately less triglyceride and more phospholipid than human. 3. Ferret low density lipoprotein contained proportionately more triglyceride and less cholesterol than human. 4. High density lipoprotein was the major lipoprotein in ferret serum. 5. The gel electrophoretic patterns of lipoprotein apoproteins and the pattern of apoprotein solubility in tetramethylurea were similar for human and ferret fractions. 6. The ferret may provide a convenient animal for the study of serum lipoprotein structure, function and metabolism.     

Mechanism, temporal patterns, and magnitudes of the metabolic responses to the KATP channel agonist diazoxide

To assess the mechanism, temporal patterns, and magnitudes of the metabolic responses to the ATP-dependent potassium channel agonist diazoxide, neuroendocrine and metabolic responses to intravenous diazoxide (saline, 1.0 and 2.0 mg/kg) and oral diazoxide (placebo, 4.0 and 6.0 mg/kg) were assessed in healthy young adults. Intravenous diazoxide produced rapid, but transient, decrements (P = 0.0023) in plasma insulin (e.g., nadirs of 2.8 +/- 0.5 and 1.8 +/- 0.3 microU/ml compared with 7.0 +/- 1.0 microU/ml after saline at 4.0-7.5 min) and C-peptide (P = 0.0228) associated with dose-related increments in plasma glucose (P = 0.0044) and serum nonesterified fatty acids (P < 0.0001). After oral diazoxide, plasma insulin appeared to decline, as did C-peptide, again associated with dose-related increments in plasma glucose (P < 0.0001) and serum nonesterified fatty acids (P = 0.0141). Plasma glucagon, as well as cortisol and growth hormone, was not altered. Plasma epinephrine increased (P = 0.0215) slightly only after intravenous diazoxide. There were dose-related increments in plasma norepinephrine (P = 0.0038 and P = 0.0005, respectively), undoubtedly reflecting a compensatory sympathetic neural response to vasodilation produced by diazoxide, but these would not raise plasma glucose or serum nonesterified fatty acid levels. Thus selective suppression of insulin secretion, without stimulation of glucagon secretion, raised plasma glucose and serum nonesterified fatty acid concentrations. These findings define the temporal patterns and magnitudes of the metabolic responses to diazoxide and underscore the primacy of regulated insulin secretion in the physiological regulation of postabsorptive carbohydrate and lipid metabolism.     

Norepinephrine response to exercise at the same relative intensity before and after endurance exercise training

It is welldocumented that endurance exercise training results in a bluntednorepinephrine (NE) response to exercise of a given absolute exerciseintensity. However, it is not clear what effect traininghas on the catecholamine response to exercise of the same relativeintensity because previous studies have provided conflicting results.The purpose of the present study was, therefore, to determine thecatecholamine response to exercise of the same relative exerciseintensity before and after endurance exercise training. Six women andthree men [age 28 ± 8 (SD) yr] performed 10 wk oftraining. Maximal O₂ uptake(O_{2 max}) wasdetermined during treadmill exercise. Fifteen-minute treadmill exercisebouts were performed at 60, 65, 70, 75, 80, and 85% ofO_{2 max} before andafter training.O_{2 max} was increasedby 20% (from 39.2 ± 7.7 to 46.9 ± 8.1 ml · kg¹ · min¹;P < 0.05) in response to training.Plasma NE concentrations were higher(P < 0.05) during exercise at thesame relative intensity after, compared with before, training at65-85% ofO_{2 max.}Differences between heart rates and plasma epinephrine concentrationsafter, compared with before, training were not statisticallysignificant. These results provide evidence that the NE response toexercise is dependent on the absolute as well as the relative intensity of the exercise.     

Generation time of Acanthocyclops robustus in relation to food availability and temperature in a shallow eutrophic lake

The generation time of the predatory cyclopoid copepod Acanthocyclops robustus was estimated on 11 occasions during the years 1980 to 1982 in Alderfen Broad. In a multiple regression model, generation time was found to be uncorrelated with temperature, positively correlated (p < 0.05) with the densities of Bosmina longirostris and rotifers, and negatively correlated (p < 0.001) with the density of nauplii of the calanoid copepod Eudiaptomus gracilis. It is suggested that generation time was determined largely by the availability of calanoid nauplii as prey, even though these constituted only 2% of zooplankton standing biomass.