Exercise,agonistic behaviour and food acquisition in Arctic charr,Salvelinus alpinus

Synopsis Although swimming is energetically costly, a number of studies on salmonid species have demonstrated increased growth rates in fishes forced to swim for prolonged periods at moderate speeds (typically 1–2 body lengths per sec). This suggests that additional energetic costs of swimming are more than met by alternative compensatory gains. The mechanisms underlying such effects are not fully understood. In this paper, we describe an experiment designed to examine one possible mechanism, namely a swimming-induced inhibition of aggression, with consequent beneficial effects on growth. The study used Arctic charr,Salvelinus alpinus, a species for which a positive relationship between exercise and growth has been clearly established. Using direct behavioural observations on small groups, we demonstrate that individuals displaying high levels of aggressive behaviour are able to monopolise access to food and that enforced swimming at a moderate speed (1 body length per sec) reduces the incidence of aggression although not the degree of monopolisation of food shown by aggressive individuals. These results suggest that the enhanced growth rates accompanying enforced swimming may reflect lower energetic costs of reduced aggressive activity rather than improved access to food by subordinates.     

Protein exporter function and in vitro ATPase activity are correlated in ABC-domain mutants of HlyB

The Escherichia coli toxin exporter HlyB comprises an integral membrane domain fused to a cytoplasmic domain of the ATP-binding casette (ABC) super-family, and it directs translocation of the 110kDa haemolysin protein out of the bacterial cell without using an N-terminal secretion signal peptide. We have exploited the ability to purify the soluble HlyB ABC domain as a fusion with glutathione S-transferase to obtain a direct correlation of the in vivo export of protein by HlyB with the degree of ATP binding and hydrolysis measured in vitro. Mutations in residues that are invariant or highly conserved in the ATP-binding fold and glycine-rich linker peptide of prokaryotic and eukaryotic ABC transporters caused a complete less of both HlyB exporter function and ATPase activity in proteins still able to bind ATP effectively and undergo ATP-induced conformational change. Mutation of less-conserved residues caused reduced export and ATP hydrolysis, but not ATP binding, whereas substitutions of poorly conserved residues did not impair activity either in vivo or in vitro. The data show that protein export by HlyB has an absolute requirement for the hydrolysis of ATP bound by its cytoplasmic domain and indicate that comparable mutations that disable other prokaryotic and eukaryotic ABC transporters also cause a specific loss of enzymatic activity.     

Characterization of the high affinity heparin binding site of the Alzheimer's disease βA4 amyloid precursor protein (APP) and its enhancement by zinc(II)

The Alzheimer's disease βA4 amyloid precursor protein (APP) has been shown to be involved in a diverse set of biological protein precursor-like proteins (APLP1 and APLP2) belong to a superfamily of proteins that are probably functionally related. In order to characterize the cell adhesion properties of APP the brain specific isoform APP₆₉₅ was purified and used to assess the binding to herparin, a structural and functional analogue of the glycosaminoglycan heparan sulfate. We show that APP binds in a time dependent and saturable manner to heparin. The salt concentration of 620 mM at which APP elutes from heparin Sepharose is greater than physiological. Tha apparent equilibrium constant for dissociation was determined to be 300 pM for APP binding to heparin Sepharose. A high affinity heparin binding site was identified within a region conversed in rodent and human APP, APLP1 and APLP2. This binding site was located between residues 316-337 of APP₆₉₅ which is within the carbohydrate domain of APP. We also demonstrate an interaction between this heparin binding site and the zinc(II) binding site which is conserved in all members of the APP superfamily. We show by using an automated surface plasmon resonance biosensor (BIAcore, Pharmacia) that the affinity for heparin is increased two- to four-fold in the presence of micromolar zinc(II). The identification of zinc-enhanced binding of APP to heparin sulfate side chains of proteoglycans offers a molecular link between zinc(II), as a putative environmental toxin for Alzheimer's disease, and aggregation of amyloid βA4 protein.     

Biomass production from the green algae Chlorella vulgaris and Ankistrodesmus braunii cultured heterotrophically

Summary Ankistrodesmus braunii and Chlorella vulgaris were cultured heterotrophically under various operating conditions. The maximum rate of biomass production was 900 and 900 mg L^-1 d^-1 by C. vulgaris and 1000 and 700 mg L^-1 d^-1 by A. braunii in the light and dark, respectively. This indicates that these algae could produce in excess of 1530 dry weight tonnes ha^-1 y^-1 which is 10–20 times higher than the maximum production levels in the literature.     

Serum indole-3-acetic acid in control subjects and newly abstinent alcoholics after an oral loading with L-tryptophan: a preliminary study using liquid chromatography with amperometric detection

Described in this paper is a rapid, isocratic assay for serum indole-3-acetic acid (IAA). The sample preparation involves only protein precipitation using sulfosalicylic acid, and the sensitivity of amperometric detection is in the picogram range. The chromatographic analysis time is approximately 4 min. The devised method was used for a longitudinal study of IAA levels in serum samples from control subjects and newly abstinent alcoholics. Dietary variations were eliminated by administering a 2.0-g loading dose of L-Trp to all subjects investigated. The results are presented in the form of cumulative frequency polygons. Preliminary data indicate no differences in IAA levels between newly abstinent alcoholics and control subjects.     

Decreased UDP-GlcNAc:Glycopeptideβ-2-N-Acetylglucosaminyltransferase II activity in a ricin-resistant mutant of baby hamster kidney (BHK) cells

The ricin-resistant mutant baby hamster kidney (BHK) cell line RIC^R21 is unable to make the sialylated bi- or triantennary complexN-glycans found in wild type cells and accumulates instead non-bisected hybrid structures containing three Man residues and one or two sialylated antennae (Hugheset al 1983, Carbohydr Res 120215-34). Specific assays forN-acetylglucosaminyltransferases I, II, III and IV were applied to Triton X-100 extracts of wild type BHK, RIC^R14 and RIC^R21 cells. It was shown that RIC^R21 cell extracts had a decreasedN-acetylglucosaminyltransferase II specific activity (17 to 27% of wild type values). It is suggested that in wild type cellsN-acetylglucosaminyltransferase II action proceeds quickly, leading to complexN-glycan synthesis, while in RIC^R21 cells potential substrates forN-acetylglucosaminyltransferase II move into the trans-Golgi compartment before the transferase can act, thereby leading to hybrid structures.     

Interrelationships of dietary protein level,aflatoxin B1 metabolism,and hepatic microsomal epoxide hydrase activity

In a continuation of studies on protein intake and aflatoxin B₁ (AFB₁) metabolism, weanling rats were fed semipurified diets containing either 20% casein or 5% casein for two weeks to determine the effect of dietary protein level on hepatic microsomal epoxide hydrase activity and AFB₁ metabolism in an effort to evaluate the role of protein intake on the formation and degradation of the reactive metabolite of AFB₁. Styrene oxide was used as substrate for epoxide hydrase since the hypothetical AFB₁ 2,3-epoxide (AFB-epox) cannot be synthesized because of its lability. Two groups of animals were fed 20% casein diets; one was fed ad libitum and the second was pair fed to the 5% casein group in order to control the effects of total feed intake. The depression of epoxide hydrase activities caused by the 5% casein diets was approximately equivalent to that previously seen with hepatic microsomal mixed function oxidase (MFO) activities with the identical protocol. Similarly, the metabolism of AFB₁ to AFQ₁ and AFM₁ was depressed by the 5% casein diets, with an increase in the production of chromatographically more polar material. The relationship of the MFO and epoxide hydrase activities to AFB₁ metabolism and formation of macromolecular adducts is discussed.     

Site of production of an oviposition-deterring pheromone component in Rhagoletis pomonella flies

Using behavioural and electrophysiological assay techniques, we identified the posterior half of the midgut as being a principal site of production of a major component of the oviposition-deterring, fruit-marking pheromone of female Rhagoletis pomonella flies. Following secretion into, and accumulation in, the gut lumen, this component is released, together with other gut contents, in the marking trail deposited during dragging of the ovipositor on the fruit surface after egg-laying, as well as in the faeces. Other components of the pheromone may be produced elsewhere.     

The modulation of membrane fluidity by hydrogenation processes. III. The hydrogenation of biomembranes of spinach chloroplasts and a study of the effect of this on photosynthetic electron transport

A method is reported for the in situ modification of the lipids of isolated spinach chloroplast membranes. The technique is based on a direct hydrogenation of the lipid double bonds in the presence of the catalyst, chlorotris(triphenylphosphine)rhodium (I). The pattern of hydrogenation achieved suggests that the catalyst distributes amongst all of the membranes. The polyunsaturated lipids within the membranes are hydrogenated at a faster rate and at an earlier stage than are the monoenoic lipids.Whilst addition of the catalyst to the chloroplast causes an initial 10–20% decrease in Hill activity, saturation of up to 40% of the double bonds present can be accomplished without causing further significant alterations in photosynthetic electron transport processes or marked morphological changes of the chloroplast structure as observed in the electron microscope.     

Time course of osmotic adaptation and gill energetics of rainbow trout (Salmo gairdneri R.) following abrupt changes in external salinity

Summary The physiological and biochemical responses of rainbow trout (mean weight 250 g) to abrupt increases in salinity have been investigated. An initial crisis period lasting about 30 h was characterized by an increase in plasma and muscle ions, a rapid gill dehydration and a pronounced acidosis following a transient alkalosis. Mortality was low during this period. During the following days, gradual changes resulted in new steady state levels for most parameters examined.Analysis of adenylate pool (ATP, ATP/ADP ratio and energy charge) in the gills demonstrated an increased energy demand exhibiting two phases (4 h and 3 days), and a return to freshwater values. The gill respiration rate was constant during 3 days in sea water and decreased slightly later on. It was not influenced during the reverse transfer of seawater adapted fish into fresh water at the level of either isolated gills or perfused heads.