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.     

Thermography as a predictive tool for laser treatment of port-wine stains

The argon laser, which has been proven both useful and safe for port-wine stain therapy, interacts with the hemoglobin of the vessels. In a percentage of cases, this treatment is still inefficient, and there is a lack of correlation between these bad results and clinical or histologic criteria. Thermography, which explores the vascularization of the port-wine stain, leads us to consider port-wine stains from a physical point of view. This very simple test shows no correlation with the clinical parameters of port-wine stain but is closely related to the results obtained with laser therapy. It seems to be a good criterion to estimate the argon laser treatment prognosis.     

Metabolic,physiological and kinetic aspects of the alcoholic fermentation of whey permeate by Kluyveromyces fragilis NRRL 665 and Kluyveromyces lactis NCYC 571

Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l^?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l^?1 h^?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l^?1 was possible with a maximum specific growth rate of 0.276 h^?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l^?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h^?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h^?1 resulted in a productivity of 22 g l^?1 h^?1 at 22 g ethanol l^?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l^?1 h^?1 at 45 g product l^?1 was attained at a dilution rate of 0.2 h^?1, with an initial lactose concentration of 95 g l^?1.     

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.     

What makes wild rabbits drink?

Wild rabbits Oryctolagus cuniculus (L) introduced to Australia over a century ago successfully colonized diverse environments in a large part of the continent varying from arid desert, alps, to lush grasslands and coastline where water and salt may be either abundant or very scarce. Wild rabbits caught in Northern Victoria were studied under laboratory conditions, where they adapted to dry pelleted food and drank regularly water and a cafeteria of electrolyte solutions offered. Intracerebroventricular (IVT) infusion of angiotensin II (AII) in doses 10, 50 and 500 ng/h did not increase their water drinking, but increased salt appetite, although it was delayed one or more days after the beginning of AII infusion. IVT infusion of AII 500 ng/h for one day caused a halving in water intake and a tenfold increase in sodium excretion. These were followed by compensatory changes in water and 0.5 M NaCl intake on the consecutive days. IVT infusion of AII 50 ng/h for one day induced an increased urinary sodium excretion, a negative sodium balance which was not followed by an increased salt appetite. IVT infusion of AII 10 ng/h for five days caused a progressive increase in sodium excretion and salt appetite which were significant on the fourth day of infusion and both remained eight-ten times greater than control levels for three days after the cessation of infusion. Water intake was unchanged. IVT infusion of 0.3 M Na-CSF for two days reduced water and food intake, and caused a negative sodium balance on the second day of infusion which was not followed by increase in salt appetite.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of IIIGlc of the phosphoenolpyruvate-glucose phosphotransferase system in inducer exclusion in Escherichia coli.

The phosphoenolpyruvate-D-glucose phosphotransferase system of Enterobacteriaceae is thought to regulate the synthesis and activity of a number of catabolite uptake systems, including those for maltose, lactose, and glycerol, via the phosphorylation state of one of its components, IIIGlc. We have investigated the proposal by Kornberg and co-workers (FEBS Lett. 117(Suppl.):K28-K36, 1980) that not IIIGlc, but an unknown protein, the product of the iex gene, is responsible for the exclusion of the above-mentioned compounds from the cell. The iex mutant HK738 of Escherichia coli contains normal amounts of IIIGlc as measured by specific antibodies, in contrast to crr mutants that lack IIIGlc. The IIIGlc of the iex strain functions normally in glucose and methyl alpha-glucoside transport, and the specific activity in in vitro phosphorylation is approximately 60% of that of the parent. The IIIGlc activity of the iex strain is, however, heat labile, in contrast to the parental IIIGlc, suggesting that the mutant contains an altered IIIGlc. This is supported by the observation that IIIGlc from the iex strain cannot bind to the lactose carrier. Thus it cannot inhibit the carrier, and this explains why the uptake of non-phosphotransferase system compounds in an iex strain is resistant to phosphotransferase system sugars. The introduction of a plasmid containing a wild-type crr+ allele into the iex strain restores the iex phenotype to that of the iex+ parent. The IIIGlc produced from the plasmid in the iex strain is heat stable and binds normally to the lactose carrier. These results lead to the conclusion that the iex mutation is most likely allelic with crr and results in an altered, temperature-sensitive IIIGlc that is still able to function D-glucose and methyl alpha-glucoside uptake and phosphorylation and in the activation of adenylate cyclase, but is unable to bind to and inhibit the lactose carrier.     

Binding of 5-methoxypsoralen to human serum low density lipoproteins

5-methoxypsoralen (5-MOP) binds to human serum low density lipoproteins (LDL) according to a two-step process. Scatchard analysis of the first step yields K = 1.4 × 10⁵ M^?1 and 4 binding sites. It involves the LDL apoprotein. The second step corresponds to a solubilization, in the lipidic core, of ? 45 molecules of 5MOP per LDL molecule. It is accompanied by a large blue shift of the 5MOP fluorescence. The ability of LDL to bind 5MOP and to carry it into various cells may explain some biological effects sometimes encountered during PUVA therapy.