Operation Everest II: metabolic and hormonal responses to incremental exercise to exhaustion.

The reasons for the reduced exercise capacities observed at high altitudes are not completely known. Substrate availability or accumulations of lactate and ammonium could have significant roles. As part of Operation Everest II, peak oxygen uptakes were determined in five normal male volunteers with use of progressively increasing cycling work loads at ambient barometric pressures of 760, 380, and 282 Torr. Decrements from sea level (SL) to 380 and 282 Torr occurred in peak power output (19 and 47%), time to exhaustion (19 and 48%), and oxygen uptake (41 and 61%), respectively. Arterial saturations after exhaustive exercise were decreased to 63% at 380 Torr and 39% at 282 Torr. At 380 and 282 Torr, postexercise plasma concentrations of glucose and free fatty acids were not increased, whereas plasma glycerol concentrations were decreased relative to SL (145 +/- 24 microM at 380 Torr and 77 +/- 10 microM at 282 Torr vs. 213 +/- 24 microM at SL). Preexercise plasma insulin concentrations were elevated at both 380 and 282 Torr (87 +/- 16 pM at 380 Torr and 85 +/- 18 pM at 282 Torr vs. 41 +/- 30 pM at SL). In general, postexercise concentrations of plasma catecholamines were decreased at altitude compared with SL. Preexercise lactate and ammonium concentrations were not different at any simulated altitude. From these data neither substrate availability nor metabolic product accumulation limited exercise capacity at extreme simulated altitude.     

PHENOTYPIC PLASTICITY IN THE SAILFIN MOLLY,POECILIA LATIPINNA (PISCES: POECILIIDAE). II. LABORATORY EXPERIMENT

Field studies indicate that the influence of environmental factors on growth rate and size and age at maturity in sailfin mollies (Poecilia latipinna) is inconsistent over time and suggest that the marked interdemic variation in male body size in this species is the result of genetic variation. However, the role of specific environmental factors in generating phenotypic variation must be studied under controlled conditions unattainable in nature. We raised newborn sailfin mollies from four populations in laboratory aquaria under all possible combinations of two temperatures, three salinities, and two food levels to examine explicitly the influence of these environmental factors. Males were much less susceptible than females to temperature variation and were generally less plastic than females in terms of all three traits. Members of both sexes matured at larger sizes and at later ages in less saline and in cooler environments. Food levels were not sufficiently different to affect the traits we studied. The effects of temperature and salinity were not synergistic. Males from different populations exhibited different average ages and sizes at maturity, but females did not. The magnitudes of the effects we found were not substantial enough to account for the consistent interdemic differences in male and female body size that have been observed previously. Our results also indicate that no single environmental factor is solely responsible for the environmental effects observed in field experiments on growth and development. These studies, together with other work, indicate that the strongest sources of interdemic variation are genetic differences in males and differences in postmaturation growth and survivorship in females.     

Bacterial yields on methanol,methylamine, formaldehyde,and formate

Several bacteria utilizing C₁-compounds as sole carbon sources were grown on these substrates in continuous culture. The molar yield values (g of cell dry wt/mol of substrate utilized) of bacteria which utilize C₁-compounds via the ribulose monophosphate pathway were between 15.7 to 17.3 when grown on methanol; while the molar yield values of bacteria which use the serine pathway for the assimilation of C₁-compounds varied between 9.8 and 13.1. The molar yield values of different bacteria which use the serine pathway decreased as the oxidation levels of the C₁-growth substrates increased. On formaldehyde the values were between 7.2 to 9.6, whereas on formate the values varied from 3.3 to 6.9. It appears that bacteria utilize C_l-compounds more efficiently via the ribulose monophosphate pathway than via the serine pathway. The oxidation step from methanol to formaldehyde (and from methylamine to formaldehyde) in the bacteria studied may be energy yielding. A comparison has been made between the experimental yield values obtained and theoretical values.     

Metabolic interrelations of hydroxy-substituted ether-linked glycerolipids in the pink portion of the rabbit harderian gland.

The pink portion of the rabbit harderian gland is known to contain a preponderance of ether-linked glycerolipids consisting primarily of 1-(O-acyl)hydroxyalkyl-2,3-diacyl-sn-glycerols and smaller amounts of 1-alkyl-2,3-diacyl-sn-glycerols. In the present study, we have used a combination of chemical, enzymatic, and chromatographic techniques to identify two minor lipid components in the gland as 1-hydroxyalkyl-2-acyl-sn-glycerols and 1-hydroxyalkyl-2,3-diacyl-sn-glycerols. The long-chain acyl groups occurring in the 1-hydroxyalkyl-2-acyl-sn-glycerols and 1-hydroxyalkyl-2,3-diacyl-sn-glycerols are almost exclusively hexadecanoic acid, whereas the 1-(O-acyl)hydroxyalkyl-2,3-diacyl-sn-glycerols have a ratio of hexadecanoic acid to octadecanoic acid of $\text{2}\text{1}$. The 1-(O-acyl) hydroxyalkyl-2,3-diacyl-sn-glycerols and the 1-hydroxyalkyl-2,3-diacyl-sn-glycerols also contain a short-chain acyl moiety identified as 3-methylbutanoic acid (isovaleric acid). This acid was found to occupy the 3-position of the glycerol backbone in these lipid classes.Metabolic experiments demonstrate that 3-methylbutanoic acid in the lipids of the gland is derived from the catabolism of l-leucine. Pulse-chase data show a precursor-product relation between the 1-hydroxyalkyl-2,3-diacyl-sn-glycerols and 1-(O-acyl-hydroxyalkyl-2,3-diacyl-sn-glycerols and rule out direct hydroxylation of 1-alkyl-2,3-diacyl-sn-glycerols as a possible biosynthetic route to the 1-(O-acyl)hydroxyalkyl-2,3-diacyl-sn-glycerols.Characterization of the alkyl and acyl groups and the positional distributions of the acyl moieties in combination with the metabolic information indicated the acylation sequence involved in the formation of 1-(O-acyl)hydroxyalkyl-2,3-diacyl-sn-glycerol is 1-hydroxyalkyl-2-acyl-sn-glycerols → 1-hydroxyalkyl-2,3-diacyl-sn-glycerols → 1-(O-acyl)hydroxyalkyl-2,3-diacyl-sn-glycerols. The data also suggest that hydroxylation of the alkyl side-chain occurs before or at the alkylacylglycerol stage.     

Secretion of proteins and antibody fragments from transiently transfected endothelial progenitor cells

In neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and amyotrophic lateral sclerosis, neuroinflammation can lead to blood‐brain barrier (BBB) breakdown. After intravenous or intra‐arterial injection into mice, endothelial progenitor cells (EPCs) home to the damaged BBB to promote neurovascular repair. Autologous EPCs transfected to express specific therapeutic proteins offer an innovative therapeutic option. Here, we demonstrate that EPC transfection by electroporation with plasmids encoding the reporter protein GFP or an anti‐β‐amyloid antibody fragment (Fab) leads to secretion of each protein. We also demonstrate the secreted anti‐β‐amyloid Fab protein functions in β‐amyloid aggregate solubilization.     

Key Ecological Function Peaks at the Land–Ocean Transition Zone When Vertebrate Scavengers Concentrate on Ocean Beaches

Ecosystems - Ecotones can form hot spots of biodiversity by containing species from multiple ecosystems. Because biodiversity is often linked to ecological function, we posit that rates of key...     

Fatty acid activation and utilization by Alistipes finegoldii,a representative Bacteroidetes resident of the human gut microbiome

Members of the Bacteroidetes phylum, represented by Alistipes finegoldii, are prominent anerobic, Gram-negative inhabitants of the gut microbiome. The lipid biosynthetic pathways were analyzed using bioinformatic analyses, lipidomics, metabolic labeling and biochemistry to characterize exogenous fatty acid metabolism. A. finegoldii only produced the saturated fatty acids. The most abundant lipids were phosphatidylethanolamine (PE) and sulfonolipid (SL). Neither phosphatidylglycerol nor cardiolipin are present. PE synthesis is initiated by the PlsX/PlsY/PlsC pathway, whereas the SL pathway is related to sphingolipid biosynthesis. A. finegoldii incorporated medium-chain fatty acids (≤14 carbons) into PE and SL after their elongation, whereas long-chain fatty acids (≥16 carbons) were not elongated. Fatty acids >16 carbons were primarily incorporated into the 2-position of phosphatidylethanolamine at the PlsC step, the only biosynthetic enzyme that utilizes long-chain acyl-ACP. The ability to assimilate a broad-spectrum of fatty acid chain lengths present in the gut environment is due to the expression of two acyl-acyl carrier protein (ACP) synthetases. Acyl-ACP synthetase 1 had a substrate preference for medium-chain fatty acids and synthetase 2 had a substrate preference for long-chain fatty acids. This unique combination of synthetases allows A. finegoldii to utilize both the medium- and long-chain fatty acid nutrients available in the gut environment to assemble its membrane lipids.