The mouse bioassay for the detection of estrogenic activity in rodent diets: III. Stimulation of uterine weight by dextrose, sucrose and corn starch

We have shown previously that mice fed the American Institute of Nutrition (AIN-76A) purified diet experience a significant increase in uterine:body weight (U:BW) ratios when compared to the U:BW ratios of mice fed a closed formula natural ingredient diet (Certified Rodent Chow #5002) for 7 days. The AIN-76A purified diet contains 5% corn oil and 65% carbohydrates with 50% of the carbohydrates coming from sucrose or dextrose and 15% from corn starch. The objective of this study was to determine whether the fat and carbohydrate content contributed to the unexpected uterine growth promoting activity observed in mice fed the AIN-76A diet. Estrogen bioassays were performed using CD-1 mice weaned at 15 days of age and assigned randomly to the negative control diet (Certified Rodent Chow #5002) or to the positive control diet (#5002) containing 4 or 6 ppb DES for comparison or to the test diets. The test diets were prepared by adding sucrose, dextrose, corn starch, corn oil or soybean oil to the #5002 negative control diet at 10% w/w concentration. Uterine:BW ratios were determined at 7 days post-feeding. The uterine weights and the U:BW ratios of mice fed the test diets containing dextrose, corn starch, or corn oil, were increased significantly (P less than 0.05) over those of mice fed the negative control diet. The uterine weights and U:BW ratios of mice fed the test diets containing sucrose or soybean oil also were increased over those of mice fed the negative control diet. These increases in uterine weights and U:BW ratios were similar to the increases in uterine weights and U:BW ratios of mice fed the positive control diet containing 4 ppb DES. It was concluded that the fats and carbohydrates caused preferential increases in uterine weights and in U:BW ratios and may account for the estrogen-like uterine growth promoting activity observed in mice fed the AIN-76A purified diet.     

Anaerobic glucose and serine metabolism in Staphylococcus epidermidis

Anaerobically grown Staphylococcus epidermidis fermented glucose with the production of lactate and trace amounts of acetate, formate and CO2. Isotopic and inhibitor studies, assays for key enzymes of different metabolic pathways, and fermentation balances, all indicated that glucose was metabolized principally via glycolysis and to a very limited extent by the hexose monophosphate oxidative pathway. Serine fermentation proceeded via deamination and dismutation yielding NH3 and equimolar amounts of lactate, acetate and CO2; small amounts of formate arose by the operation of pyruvate-formate lyase. Incorporation of 0.5% (w/v) glucose in the growth medium depressed serine metabolism by repressing the activities of serine dehydratase and pyruvate dehydrogenase but, conversely, enhanced the activities of phosphofructokinase and lactate dehydrogenase. Glucose-grown organisms at various stages of anaerobic batch growth showed an inverse relationship between the rates of fermentation of serine and glucose. L-Lactate dehydrogenase activity in crude extracts depended on fructose 1,6-bisphosphate, and fructose 1,6-bisphosphate aldolase was found to be a class I aldolase. Despite the presence of ribokinase, D-ribose-5-phosphate isomerase, transaldolase and transketolase, the organisms utilized ribose only after growth aerobically in basal medium, and then at a slow rate after an initial lag period.     

The regulation of transport of glucose and methyl α-glucoside in Pseudomonas aeruginosa

The methyl alpha-glucoside-transport system of Pseudomonas aeruginosa has been characterized with respect to its specificity, energy-dependence, kinetics and regulation. The uptake of glucose involved two components, one of which transported glucose (K(m)=8mum) and methyl alpha-glucoside (K(m)=2.8mm) whereas the other was more complex, involving the extracellular activity of glucose dehydrogenase. Mutants defective in this enzyme have been isolated and characterized. The methyl alpha-glucoside-glucose-transport system was repressed when the organism was grown in the absence of glucose; the induction of this transport system by glucose, and its activity once induced, were inhibited by products of citrate metabolism.     

A LIGHT- AND ELECTRON-MICROSCOPIC SURVEY OF ALGAL CELL WALLS. I. PHAEOPHYTA AND RHODOPHYTA

Dawes , Clinton J., Flora M. Scott , and E. Bowler . (U. California, Los Angeles.) A light- and electron-microscopic survey of algal cell walls. I. Phaeophyta and Rhodophyta. Amer. Jour. Bot. 48(10): 925–934. Illus. 1961.—An introductory survey of the structure of the cell walls of brown, red, and green algae, as seen under light and electron microscopes, has been completed. In the present paper (Part I) the structure of the thalli of the Phaeophyta and Rhodophyta is compared, and the occurrence of intercellular spaces, pitting, and microfibrillar patterns is discussed. A detailed comparison of the cell-wall structure and growth of a brown alga, Dictyota flabellata, and of a red alga, Helminthocladia californica, is also presented. In Dictyota, typical of the brown algae, the microfibrillar pattern in the apical cells and in the adjacent cells of the thallus tip is reticulate. In mature cells, the microfibrils are dominantly parallel in orientation. Pits, which are fields of closely set pores, are distinctive. The microfibrils in the pit areas are masked by non-fibrillar material. Helminthocladia, with a cell wall characteristic of the red algae, differs from Dictyota in that the microfibrillar pattern is reticulate at all ages of the cell and throughout the thallus. In the pit areas, the microfibrils are not masked by amorphous material. Pit connections, characteristic of the Florideae, can be divided into 2 major groups. Either the pit connection is an open channel between 2 adjacent cells, or it is composed of numerous plasmodesmata traversing a continuous, loose, microfibrillar wall. The techniques of the survey are emphasized in that fragmented cell walls were studied, and, also, chemically cleared material was constantly compared with fresh material under light and electron microscopes. It is concluded that the cell wall, as a taxonomic character, is of value only in delimiting the Phaeophyta and Rhodophyta.     

A fluorescent probe for a phosphonium ion efflux system in bacteria

Abstract The interaction of a fluorescent probe with three species of bacteria shows properties consistent with the probe acting as a substrate for an efflux system that can also transport phosphonium ions and related compounds.     

IN SITU UPTAKE KINETICS OF AMMONIUM AND PHOSPHATE AND CHEMICAL COMPOSITION OF THE RED SEAWEED GRACILARIA TIKVAHIAE1

The uptake kinetics of ammonium and phosphate by Gracilaria tikvahiae McLachlan were studied under field conditions. Seaweeds, pulse fed once a week for 6 h over a 4-week period, had maximum uptake rates of 19 μmol·g fwt^?1·h^?1 for ammonium and 0.28 μmol·g fwt^?1·h^?1 for phosphate. For both nutrients there was a positive linear correlation between uptake rate (v) and concentration (S) over the entire range of concentration tested. In a nutrient depletion experiment, the phosphate uptake curve determined over a wide range of concentrations consisted of two stages of saturation at low concentrations, and a linear phase at high concentrations. Ash free dry weight, chlorophyll a, phycoerythrin, and protein content were higher in pulse fed plants than in control plants receiving no nutrient additions, while the reverse held true for carbohydrate contents and the C/N ratios. The C/N ratio inversely correlated with ammonium and phosphate uptake rate as well as protein and phycoerythrin content, and positively with carbohydrate content.     

Responses of Spotted Hyenas to Lions Reflect Individual Differences in Behavior

Competition among mammalian carnivores can be particularly intense and can influence population dynamics at lower trophic levels. One strategy employed by carnivores to minimize potentially costly interspecific competition is avoidance of dominant species. Recent research has highlighted the importance of consistent individual differences in behavior (i.e. temperament traits) in understanding behavioral variation during predator–prey interactions and intraspecific interactions. However, the importance of such individual differences to interspecific competition has received little attention. Here, we examined the responses of spotted hyenas (Crocuta crocuta) to their primary competitors, African lions (Panthera leo), to (1) determine whether hyenas avoid lions and (2) evaluate the potential importance of individual differences in behavior during interspecific competition. Spotted hyenas and lions co‐occur throughout much of Africa and are vigorous competitors. Whereas lions sometimes kill hyenas and steal their food, lions also represent a source of food for hyenas via scavenging. Using audio playback experiments, we found that hyenas do not uniformly avoid potential encounters with lions. Indeed, we noted considerable variation among individuals in their responses to lion roars, and this variation reflected consistent individual differences in risk‐taking and vigilance tendencies. Individual differences in vigilance behavior were specific to interactions with lions. We conclude that individual differences in behavior have the potential to play an important role in determining the nature and outcome of interspecific competition.