Reduction in postprandial energy expenditure during pregnancy.

Energy expenditure was measured during pregnancy in seven primigravid women at 12-15, 25-28, and 34-36 weeks and after the cessation of lactation. On each occasion the resting metabolic rate and the increase in metabolic rate after ingestion of a liquid test meal were measured by indirect calorimetry. In absolute terms the resting metabolic rate increased steadily during pregnancy but when expressed per unit of body weight no change was found. The energetic response to a mixed constituent meal was significantly reduced by 28% in the middle trimester of pregnancy. These findings suggest a possible maternal adaptation to increase energetic efficiency at a time when the energy demands of the fetus are high.     

Secretion of the sweet-tasting plant protein thaumatin byBacillus subtilis

Summary With the -amylase promoter and ribosome binding site,Bacillis subtilis was used to express the sweet plant protein thaumatin II cDNA fused in the correct reading frame to the -amylase leader peptide. The r-thaumatin was purified from the medium on a S-Sepharose column and detected with western blots by sheep -thaumatin antibodies. The r-thaumatin and authentic thaumatin were the same size when reduced by 2-ME and the same size when not reduced.     

High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans

We compared male-reproductive-tract polypeptides of Drosophila melanogaster and D. simulans by using two-dimensional gel electrophoresis. Approximately 64% of male-reproductive-tract polypeptides were identical between two randomly chosen isofemale lines from these two species, compared with 83% identity for third-instar imaginal wing-disc polypeptides. Qualitatively similar differences were found between reproductive tracts and imaginal discs when D. sechellia was compared with D. melanogaster and with D. simulans. When genic polymorphism was taken into account, approximately 10% of male- reproductive-tract polypeptides were apparently fixed for different alleles between D. melanogaster and D. simulans; this proportion is the same as that found for soluble enzymes by one-dimensional gel electrophoresis. Strikingly, approximately 20% of male-reproductive- tract polypeptides of either D. melanogaster or D. simulans had no detectable homologue in the other species. We propose that proteins of the Drosophila male reproductive tract may have diverged more extensively between species than have other types of proteins and that much of this divergence may involve large changes in levels of polypeptide expression.      

Secretion of the sweet-tasting plant protein thaumatin byStreptomyces lividans

Summary To produce and direct the export inStreptomyces lividans of the sweet plant protein thaumatin, thaumatin II cDNA was fused in the correct reading frame to the -galactosidase leader peptide, under the control of the -galactosidase promoter and ribosome binding site. The export of the recombinant thaumatin may allow the correct formation of the thaumatin disulfide bonds. The recombinant thaumatin was purified from the medium on an S-Sepharose column and detected with western blots by sheep -thaumatin antibodies. The recombinant thaumatin was the same size as authentic thaumatin and changed position on an acrylamide gel in response to reduction by 2-mercaptoethanol in the same manner.     

Effects of fish oil on VLDL triglyceride kinetics in humans

Dietary n-3 fatty acids (FAs) found in fish oils markedly lower plasma triglyceride (TG) and very low density lipoprotein (VLDL) levels in both normal and hypertriglyceridemic subjects. The present study examined the mechanism of this effect. Ten subjects with widely different plasma triglyceride levels (82 to 1002 mg/dl) were fed metabolically controlled diets containing 20% fat. The control diet contained a blend of cocoa butter and peanut oil (P/S = 0.8). The test diet contained fish oil (P/S = 1.1) and provided 10-17 g of n-3 FAs per day (depending on calorie intake). After 3 to 5 weeks of each diet, the kinetics of VLDL-TG were determined over a 48-h period after the injection of [3H]glycerol. The fish oil diet reduced the VLDL-TG synthetic rate from 23 +/- 14.3 (mean +/- SD) to 12.6 +/- 7.5 mg/h per kg ideal weight (P less than 0.005) and increased the fractional catabolic rate (FCR) for VLDL-TG from 0.23 +/- 0.12 to 0.38 +/- 0.16 h -1 (P less than 0.005). At the same time, there was a 66% reduction of plasma triglyceride levels, resulting largely from a 78% decrease in VLDL-TG levels (398 +/- 317 to 87 +/- 77 mg/dl; P less than 0.005). There was a strong correlation (r = 0.83; P less than 0.01) between the change in synthetic rates and pool sizes, but there was no correlation (r = 0.24; NS) between changes in FCRs and pool sizes. The VLDL cholesterol: triglyceride ratio increased during the n-3 diet suggesting that smaller VLDL particles were present. These particles would be expected to leave the VLDL fraction more rapidly than larger particles producing a higher FCR. We conclude that the hypotriglyceridemic effect of fish oil appears to be caused primarily by an inhibition of very low density lipoprotein-triglyceride synthesis, but an additional, independent effect upon VLDL catabolism cannot be ruled out.     

Microelectrode studies of the active Na transport pathway of frog skin

When the outer surface of short-circuited frog skin was penetrated with microelectrodes, stable negative potentials that averaged near -100 mV were recorded consistently, confirming the results of Nagel (W. Nagel. 1975. Abstracts of the 5th International Biophysics Congress, Copenhagen. P-147.). The appearance of these stable potentials, V(O), concurrent with the observations that (a) a high resistance outer barrier R(O) accounting for approximately 75 percent or more of the transcellular resistance of control skins had been penetrated and that (b) 10(-5) M amiloride and reduced [Na] outside caused the values of V(O) to increase towards means value near -130 mV while the values of percent R(O) increased to more than 90 percent. It was of relationships were the same as the values of E(1) observed in studies of the current-voltage relationships were the same as the values of E’(1) defined as the values of voltage at the inner barrier when the V(O) of the outer barrier was reduced to zero by voltage clamping of the skins. Accordingly, these data are interpreted to mean that the values of E(1), approximately 130 mV, represent the E(Na) of the sodium pump at the inner barrier. 2,4-DNP was observed to decrease the values of transepithelial voltage less than E(1) the V(O) was negative. These data can be interpreted with a simple electrical equivalent circuit of the active sodium transport pathway of the frog skin that includes the idea that the outer membrane behaves as an electrical rectifier for ion transport.     

Some factors affecting phosphate transport in a perfused rat heart preparation.

Pi uptake by a perfused rat heart preparation did not require the presence of any other permeant anion, but was markedly dependent on the extracellular Na+ concentration and accelerated when tissue oxygenation was inadequate. Pi efflux was also independent of other permeant anions, but apparently varied with the intracellular Na+ concentration. Cardiac Pi efflux was not sensitive to a number of inhibitors that clock Cl- movement in heart and other tissues. Both uptake and efflux apparently proceed via a reversible electroneutral co-transport system linked to the transmembrane Na+ gradient. Pi uptake was independent of cardiac work load, but the efflux rate was sharply accelerated after an increase in aortic pressure development, with a slow return towards basal values during sustained periods of high work output. An inverted biphasic effect on the efflux rate was observed after a reduction in cardiac work load. Mild hypoxia and respiratory and metabolic acidosis each resulted in a transient acceleration of Pi efflux followed by a return towards basal values during prolonged exposure to the stimulus, whereas respiratory and metabolic alkalosis produced a similar but inverted response. The origin of these phasic effects on Pi efflux remains to be identified at present.     

Interaction between high-density lipoprotein subpopulations in apo B-free and abetalipoproteinemic plasma.

Two populations of high-density lipoprotein (HDL) particles exist in human plasma. Both contain apolipoprotein (apo) A-I, but only one contains apo A-II: Lp(AI w AII) and Lp(AI w/o AII). To study the extent of interaction between these particles, apo B-free plasma prepared by the selective removal of apo B-containing lipoproteins (LpB) from the plasma of three normolipidemic (NL) subjects and whole plasma from two patients with abetalipoproteinemia (ABL) were incubated at 37 degrees C for 24 h. Apo B-free plasma samples were used to avoid lipid-exchange between HDL and LpB. Lp(AI w AII) and Lp(AI w/o AII) were isolated from each apo B-free plasma sample before and after incubation and their protein and lipid contents quantified. Before incubation, ABL plasma had reduced levels of Lp(AI w AII) and Lp(AI w/o AII), (40% and 70% of normals, respectively). Compared to the HDL of apo B-free NL plasma, ABL HDL had higher relative contents of free cholesterol, phospholipid and total lipid, and contained more particles with apparent hydrated Stokes diameter in the 9.2-17.0 nm region. These differences were particularly pronounced in particles without apo A-II. Despite their differences, the total cholesterol contents of Lp(AI w AII) increased, while that of Lp(AI w/o AII) decreased in all five plasma samples and the amount of apo A-I in Lp(AI w AII) increased by 6-8 mg/dl in four during the incubation. These compositional changes were accompanied by a relative reduction of particles in the 7.0-8.2 nm Stokes diameter size region and an increase of particles in the 9.2-11.2 nm region. These data are consistent with intravascular modulation between HDL particles with and without apo A-II. The observed increase in apo A-II-associated cholesterol and apo A-I, could involve either the transfer of cholesterol and apo A-I from particles without apo A-II to those with A-II, or the transfer of apo A-II from Lp(AI w AII) to Lp(AI w/o AII). The exact mechanism and direction of the transfer remain to be determined.