Effects of 24-hour fast on cycling endurance time at two different intensities

Ten competitive cyclists were exercised to exhaustion to test the potential of a 24-h fast for increasing endurance. One group (n = 4) was tested at an initial intensity of 86% maximum O2 uptake (VO2max) (HI) and a second group (n = 6) at 79% VO2max (MI). Both groups repeated test rides in fasted and normal-diet conditions. Time to fatigue was designated at two points: fatigue 1 occurred when pedal frequency could not be maintained at the initial percent VO2max; fatigue 2 occurred when pedal frequency could not be maintained at a workload of approximately 65% VO2max. In both HI and MI the 24-h fast had no effect on resting muscle glycogen stores but significantly increased plasma free fatty acid (FFA) levels. Despite the increased FFA availability, time to fatigue was reduced in the fasted groups. Fatigue 1 and 2 times (mean +/- SE) for HI-fasted were 42.0 +/- 6.2 and 170.0 +/- 20.4 min, respectively, compared with those of the HI-normal diet of 115.3 +/- 25.6 and 201.0 +/- 14.8 min. Fatigue 1 and 2 times for MI-fasted were 142.0 +/- 19.6 and 167.5 +/- 10.5 min compared with those of the MI-normal diet of 191.3 +/- 25.0 and 214.3 +/- 18.9 min. The cause of fatigue at fatigue 1 was not readily apparent. Fatigue 2 in all groups seemed to be related to hypoglycemia as well as muscle glycogen depletion.     

A new Madia of sect. Anisocarpus (Compositae: Heliantheae) from Trinity County,California

A new annual species ofMadia sect.Anisocarpus,Madia doris-nilesiae, from the serpentine soils of western Trinity County, California is described, illustrated, and compared to the other annual members of the section. On the basis of floral and fruit morphologies the annual members of the section can be divided into two geographical units.Madia dorisnilesiae is unique in that it has a combination of these characters.     

Photoperiodic regulation of reproductive development in male prairie voles: influence of laboratory breeding

Two populations of male prairie voles, one derived from an outbred laboratory colony and the second consisting of F1 offspring of wild-trapped voles, were tested for responsiveness to photoperiod. Animals were reared from birth until 35 days of age either in 16L:8D or 8L:16D photoperiods. Short day lengths did not affect the reproductive apparatus of the laboratory-strain voles; however, offspring of wild-caught voles manifested arrested development of the reproductive system in short photoperiods. These results suggest that selection processes associated with laboratory husbandry can alter responsiveness to photoperiod; the use of wild-trapped animals or their F1 progeny is indicated in photoperiodism research.     

Microhabitat utilization by two leptodactylid frogs in the Andes of central Chile

Summary Some basic parameters of the life history of Alsodes montanus and Alsodes tumultuosus (Anura-Leptodactylidae), were studied from 1977 to 1980 by periodic field observations at Farellones and La Parva (33–34° south lat.; 2,700–3,000 m above sea level). Special attention was paid to strategies of resource partitioning in relation to gross features of the environment. The latter was unstable with a relative short period favorable for activity of the animals. Physical environmental differences between the first and second season of this study, resulted in a decrease in total number of active adults, a reduction in the duration of larval activity and a shift in microhabitat preferences of larvae.During the favorable season, October to May, adults of both species showed spatial and temporal segregation, related to different physical features of the environment; larvae did not show temporal segregation. Larvae of both species were found in seven different microhabitats; only in one of these did they show significant difference in microhabitat preference, A. tumultuosus was found more often in crevices. Microhabitat dimensions were more important than time and food resources in the separation of the niches of the two species. The segregation of niche dimensions, microhabitat, diel and annual activity and food were not complementary.Coexistence was therefore observed with the species tending to use different resources. When the same resource was used, it was not limiting.     

Nitrate Reductases from Wild-Type and nr(1)-Mutant Soybean (Glycine max [L.] Merr.) Leaves : I. Purification, Kinetics, and Physical Properties

NADH:nitrate reductase (EC 1.6.6.1) and NAD(P)H:nitrate reductase (EC 1.6.6.2) were purified from wild-type soybean (Glycine max [L.] Merr., cv Williams) and nr₁-mutant soybean plants. Purification included Blue Sepharose- and hydroxylapatite-column chromatography using acetone powders from fully expanded unifoliolate leaves as the enzyme source.

Two forms of constitutive nitrate reductase were sequentially eluted with NADPH and NADH from Blue Sepharose loaded with extract from wild-type plants grown on urea as sole nitrogen source. The form eluted with NADPH was designated c₁NR, and the form eluted with NADH was designated c₂NR. Nitrate-grown nr₁ mutant soybean plants yielded a NADH:nitrate reductase (designated iNR) when Blue Sepharose columns were eluted with NADH; NADPH failed to elute any NR form from Blue Sepharose loaded with this extract. Both c₁NR and c₂NR had similar pH optima of 6.5, sedimentation behavior (s_20,w of 5.5-6.0), and electrophoretic mobility. However, c₁NR was more active with NADPH than with NADH, while c₂NR preferred NADH as electron donor. Apparent Michaelis constants for nitrate were 5 millimolar (c₁NR) and 0.19 millimolar (c₂NR). The iNR from the mutant had a pH optimum of 7.5, s_20,w of 7.6, and was less mobile on polyacrylamide gels than c₁NR and c₂NR. The iNR preferred NADH over NADPH and had an apparent Michaelis constant of 0.13 millimolar for nitrate.

Thus, wild-type soybean contains two forms of constitutive nitrate reductase, both differing in their physical properties from nitrate reductases common in higher plants. The inducible nitrate reductase form present in soybeans, however, appears to be similar to most substrateinduced nitrate reductases found in higher plants.

     

Viral polypeptides detected by a complement-dependent neutralizing murine monoclonal antibody to human cytomegalovirus.

Murine monoclonal antibodies were produced which coimmunoprecipitated, under reducing conditions, 130,000- and 55,000-dalton (Da) polypeptides from cells infected with human cytomegalovirus (CMV) strain AD169. A 92,000-Da species, possibly a biosynthetic intermediate, was also detectable. One of the monoclonal antibodies, 15D8, neutralized CMV AD169 only in the presence of guinea pig complement. A second monoclonal antibody, 14E10, coimmunoprecipitated the 130,000- and 55,000-Da polypeptides but did not neutralize viral infectivity. By sequential immunoprecipitation, both monoclonal antibodies have been shown to recognize the same polypeptides. Monoclonal antibody 15D8 detected the 130,000- and 55,000-Da polypeptides in five of six clinical strains and three laboratory strains tested. The 14E10 monoclonal antibody detected the 130,000-Da protein in four of six CMV clinical isolates and in strain AD169 but did not immunoprecipitate any polypeptides from extracts of cells infected with either Towne or Davis laboratory strains. In kinetic studies, the synthesis of the 130,000-Da polypeptide preceded the appearance of the 55,000-Da polypeptide. In infected cells radiolabeled with a pulse of L-[35S]methionine, the isotope was initially detected in the 130,000-Da polypeptide but could be chased into the 55,000-Da polypeptide. These polypeptides exist in the intracellular and extracellular virus as disulfide-linked multimers. Extracellular virus contained a high-molecular-weight (greater than 200,000 Da) multimer composed entirely of 55,000-Da polypeptides. In extracts from infected cells an additional high-molecular-weight multimer was detected consisting of disulfide-linked 130,000-Da polypeptides.     

Differential modulation of the expression of axonal proteins by non-neuronal cells of the peripheral and central nervous system.

Axonal behavior during the formation of the neuronal network of the nervous system has been shown to be under environmental control. Hence, as a first step in a project aiming to elucidate the molecular basis of axonal functions, we have identified axonal proteins whose synthesis is subject to environmentally induced changes. Neurons from chicken embryonic dorsal root ganglia (DRG) were grown in a compartmental cell culture system that allows selective examination of axonal proteins. Non-neuronal cells of the peripheral or central nervous system were co-cultured with the DRG axons. The axonal proteins expressed under these different environmental conditions were examined by metabolic labeling and two-dimensional SDS-polyacrylamide gel electrophoresis. Computerized quantification revealed that 12 out of 400 axonal proteins responded to changes in the local axonal environment by a change in their relative abundance. Some proteins changed in response to both types of co-cultures whereas some changed specifically under the influence of either peripheral or central non-neuronal cells.     

Genes coding for 5S ribosomal RNA of the nematode Caenorhabditis elegans

We have identified a 1-kb genomic sequence that represents the major class of 5S rRNA genes in the nematode Caenorhabditis elegans. This 1-kb sequence is tandemly repeated 110 times in the haploid genome forming a single homogeneous gene family. Other nematode genomic sequences, distinct from the major 1-kb repeat class but homologous to it, may represent dispersed 5S rRNA genes or the ends of a gene cluster. One such fragment shows a restriction fragment length difference between two C. elegans strains. This should allow the genetic analysis of 5S rRNA-coding DNA (5S X rDNA) and its flanking regions in C. elegans.