The ectoparasitization of Coleophora alticolella (Lepidoptera) in relation to its aititudinal distribution

Abstract. 1. The parasitization of the larvae of Coleophora alticolella . feeding on Juncus squarrosus , was investigated at a series of altitudes from 15 to 520m above sea-level in northern England during 1977 and 1978.
2. Six species of primary parasitoid and one hyperparasitoid were reared from this host. Five of the primary parasitoids were ectophagous; only two specimens of the endoparasitoid, Gonotypus melanostoma , were reared.
3. All of the parasitoid species were recorded at 15 m but fewer at sites of higher altitude. Only one species, Scambus brevicomis , was recorded above 305 m, and none above 395 m. The hyperparasitoid, Tetrastichus endemus, was present only at 15 m.
4. Percentage parasitization was highest at 15 m; it was reduced from 51% to only 2% between 215 and 305 m in 1978. There was an increase in host density over this altitudinal range.
5. Three species, Scambus brevicomis. Elachertus olivaceus and Euderus viridis , accounted for most of the parasitization, but their relative proportions vaned at different altitudes.
6. The sex-ratios of the parasitoids reared from Coleophora alticolella ranged from 3.2% females for Scambus brevicomis , which is considered to also use larger hosts, to 99.4% females for Elachertus olivaceus , which develops by thelytokous parthenogenesis.
7. Euderus viridis and Scambus brevicomis started to attack the Coleophora alticolella larvae at a later date at 245 m than at 15 m, but attack by Elachertus olivacats was not delayed at the higher site.     

Influence of increasing levels of β-glucanase on the productive value of barley diets for broiler chickens

The influence on the productive value of diets for broiler chickens based on barley harvested at two stages of ripeness, when including β-glucanase in increasing amounts, was evaluated in a production experiment over three weeks. Feed consumption and live weight increased (P < 0.001) and feed conversion was improved (P < 0.001) by including β-glucanase in the diets. Dry matter content of excreta increased significantly as a result of β-glucanase inclusion. Broiler chickens receiving diets based on barley harvested at combine ripeness were slightly heavier (P < 0.05) at three weeks than those fed on barley harvested at early yellow ripeness.     

Chronic exposure to inhaled anesthetics increases cholesterol content in Acholeplasma laidlawii

Acholeplasma laidlawii cells were grown in cholesterol-enriched medium and exposed continuously to either air (control), 4.0 vol.% halothane in air at 1 atm pressure (4% atm halothane), or 80% cyclopropane in oxygen for 24 h at 37°C. Cells grown in the presence of 4% atm halothane or 80% cyclopropane had approximately twice as much membrane cholesterol content/mg protein as the control cells. Cells grown in an anesthetic environment also tended to have a higher membrane cholesterol/phospholipid molar ratio compared to control cells. Membranes isolated from halothane-exposed cells grown in a cholesterol-enriched medium were more ordered at 37°C (measurements were made with no anesthetic present) than membranes from control cells grown in an identically enriched medium. This difference in membrane physical state between control and anesthetic-exposed cells decreased as the temperature decreased, and disappeared at approx. 23°C. Continuous exposure of A. laidlawii to 4% atm halothane or 80% cyclopropane for 24 h did not markedly affect membrane fatty acid composition, either in cells grown on an unsupplemented medium or in cells grown in a medium enriched in myristic, palmitic or stearic acids. These results further support the hypothesis that an increased membrane cholesterol content may play a role in the tolerance or dependence that develops after chronic exposure to anesthetic agents.     

Food sharing: a model of manipulation by harassment

Most analyses of food-sharing behavior invoke complex explanationssuch as indirect and delayed benefits for sharing via kin selectionand reciprocal altruism. However, food sharing can be a moregeneral phenomenon accounted for by more parsimonious, mutualisticexplanations. We propose a game theoretical model of a generalsharing situation in which food owners share because it is in their own self-interest—they avoid high costs associatedwith beggar harassment. When beggars harass, owners may benefitfrom sharing part of the food if their consumption rate islow relative to the rate of cost accrual. Our model predictsthat harassment can be a profitable strategy for beggars if they reap some direct benefits from harassing other than sharedfood (such as picking up scraps). Therefore, beggars may manipulatethe owner's fitness payoffs in such a way as to make sharingmutualistic.     

Synthesis by Enzymatic Catalysis VI—An Investigation of Chemical Modification of HRP by Fourier Transform Infra-Red Vibrational Spectroscopy

Horseradish peroxidase was chemically conjugated on its carbohydrate moieties with short aliphatic chains (C₈ and C₁₆). An analytical method using FT.IR spectroscopy was developed to analyze this alteration in enzyme structure. This method is non-destructive, and can be applied directly to samples of the reaction mixture. More general applications of this technique are described and discussed.     

Single-step,rapid separation of acidic and basic isoenzymes from commercial horseradish peroxidase

A simple and sensitive high-performance liquid chromatography method with electrochemical detector is described for the determination of free 3-methoxy-4-hydroxyphenylacetic acid (HVA) in human plasma. The method does not involve any extraction, is specific and reproducible, and has the potential to measure serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) simultaneously. The plasma concentration of free HVA in eight normal, healthy adult volunteers was 10.9 ± 4.6 (mean ± SD). In a preliminary study, in one schizophrenic patient the plasma HVA increased twofold after neuroleptic treatment.     

Peroxidase activity in human red cell: a biological model for excited state molecules generation.

The presence of enzymically generated triplet acetone in red cells and energy transfer to eosin, rose bengal and 9,10-dibromoanthracene-2-sulfonate was indicate by: (1) product distribution; (2) K_ET τ_o, similar to the 2-methylpropanal/peroxidase/O₂ system; (3) correlation between hemolysis, oxygen uptake and photon emission; (4) membrane protection by energy acceptors, and (5) by comparison of the 2-methylpropanal/peroxidase/O₂ system with 2-methylpropanal/red cells/membranes/O₂ and 2-methylpropanal/acid extractable protein from red cells membrane/O₂ systems, which have a high peroxidase activity.This is the first report of a biological system producing a photohemolysis effect in the dark.     

Neuron differentiation and axon growth in the developing wing of Drosophila melanogaster

Sensory neurons in the wing of Drosophila originate locally from epithelial cells and send their axons toward the base of the wing in two major bundles, the L1 and L3 nerves. We have estimated the birth times of a number of identified wing sensory neurons using an X-irradiation technique and have followed the appearance of their somata and axons by means of an immunohistochemical stain. These cells become immunoreactive and begin axon growth in a sequence which mirrors the sequence of their birth times. The earliest ones are born before pupariation and begin axonogenesis within 1 to 2 hr after the onset of metamorphosis; the last are born and differentiate some 12 to 14 hr later. The L1 and L3 nerves are formed in sections, with specific neurons pioneering defined stretches of the pathways during the period between 0 and 4 hr after pupariation (AP), and finally joining together around 12 hr AP. By 16 hr AP the adult complement of neurons is present and the adult peripheral nerve pattern has been established. Pathway establishment appears to be specified by multiple cues. In places where neurons differentiate in close proximity to one another, random filopodial exploration followed by axon growth to a neighboring neuron soma might be the major factor leading to pathway construction. In other locations, filopodial contact between neighboring somata does not appear to occur, and axon pathways joining neural neighbors by the most direct route are not established. We propose that in these cases additional factors, including veins which are already present at the time of axonogenesis, influence the growth of axons through non-neural tissues.     

Regulation of enzymes and isoenzymes of carbohydrate metabolism in the yeast Saccharomyces cerevisiae

An electrophoretic method has been devised to investigate the changes in the enzymes and isoenzymes of carbohydrate metabolism, upon adding glucose to derepressed yeast cell. (i) Of the glycolytic enzymes tested, enolase II, pyruvate kinase and pyruvate decarboxylase were markedly increased. This increase was accompanied by an overall increase in glycolytic activity and was prevented by cycloheximide, an inhibitor of protein synthesis. (ii) In contrast, respiratory activity decreased after adding glucose. This decrease was clearly shown to be the result of repression of respiratory enzymes. A rapid decrease within a few minutes of adding glucose, by analogy with the so-called ‘Crabtree effect’, was not observed in yeast. (iii) The gluconeogenic enzymes, fructose-1,6-bisphosphatase and malate dehydrogenase, which are inactivated after adding glucose, showed no significant changes in electrophoretic mobilities. Hence, there was no evidence of enzyme modifications, which were postulated as initiating degradation. However, it was possible to investigate cytoplasmic and mitochondrial malate dehydrogenase isoenzymes separately. Synthesis of the mitochondrial isoenzyme was repressed, whereas only cytoplasmic malate hydrogenase was subject to glucose inactivation.