The biology and energetics of the potato aphid Macrosiphum euphorbiae, living in galls of the apple aphids Dysaphis devecta and Aphis pomi

A non-gall-forming aphid, Macrosiphum euphorbiae, was reared within the galls of Dysaphis devecta and Aphis pomi which had been induced in apple seedlings. Similar aphids were also reared on ungalled seedling leaves of a similar age and also on mature leaves and in old galls.There is a weak positive linear relationship between lipid content and pre-reproductive adult dry weight, but aphids living on young galled or ungalled plant tissue have 30% lipid compared to 11% for aphids living on old plant tissue. Adult aphids gradually decline in weight, losing between 24% and 38% of their pre-reproductive biomass before death. The energy content of this loss subsidieses reproduction. Reproduction of aphids feeding in old galls or on mature leaves was negligible, but on younger tissues average fecundity was 31, there being little difference between aphids living on galled and ungalled tissue. There is no simple relationship between pre-reproductive adult embryo content and fecundity.The principal factor mediating honeydew production was aphid size and this factor overrides any variation caused by different feeding sites. Honeydew production averaged 0.43 mg during a life of 30 days. Aphids successfully completing their life cycle have a life-time energy consumption of 30.58 joules of which 18% is lost as heat during respiration (R), 30% is contained in honeydew (F+U), 1% is contained in exuviae (Pe). Larval growth accounts for 17% (Pg), and adult reproduction for 34% (Pr).The P/C ratio for M. euphorbiae is 53% and is broadly comparable with aphids living on herbaceous plants.

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Résumé Un puceron ne formant pas de galles, Macrosiphum euphorbiae, a été élevé dans des galles de Dysaphis devecta et Aphis pomi formées sur semis de pommiers. D'autres M. euphorbiae ont été élevés sur feuilles sans galles du même âge provenent de semis identiques, sur feuilles mûres et sur vieilles galles.Il y a une faible relation positive linéaire entre la teneur en lipides et le poids sec des adultes avant la reproduction, mais les pucerons élevés sur tissus végétaux jeunes avec ou sans galles contiennent 30% de lipides contre 11% pour ceux élevés sur tissus âgés. Le poids des pucerons adultes diminue progressivement, la perte avant la mort se situant entre 24 et 38% de la biomasse avant la reproduction. Le contenu énergétique de ces pertes alimente la reproduction. La reproduction de pucerons consommant les vieilles galles ou les feuilles mûres était négligeable, mais sur jeunes tissus la fécondité moyenne était de 31-avec peu de différences entre pucerons sur galles ou feuilles-. Il n'y a pas de corrélation simple entre le contenu en embryon des adultes avant la reproduction et la fécondité.Le principal paramètre conditionnant la production de miellat est la taille du puceron; ce paramètre surpasse toute variation provoquée par les divers lieux d'alimentation. La production moyenne de miellat est de 0,43-mg pendant une vie de 30 jours. Les pucerons accomplissant leur cycle avec succès utilisent pendant leur vie 30,58 joules, dont 18% sont dissipés sous forme de chaleur pendant la respiration (R); le contenu du miellat (F+U) correspond à 30%, et 1% est contenu dans l'exuvie (Pe). La croissance larvaire (Pg) utilise 17%, et l'activité reproductrice des adultes (Pr) 34% de l'énergie. Le rapport P/C-53% pour M. euphorbiae-est globalement comparable à celui des pucerons vivant sur plantes herbacées.

     

Potassium and ventilation during incremental exercise in trained and untrained men.

The present investigation was undertaken to examine the relationship between plasma potassium (K+) and ventilation (VE) during incremental exercise. Blood lactate (La-) was also measured, and its relationship with VE was similarly examined. Eight endurance-trained triathletes (ET) and eight active but untrained men (UT) performed an incremental cycling test to volitional fatigue. Maximal oxygen uptake (VO2max) and oxygen uptake (VO2) at lactate threshold (LT) were higher (P < 0.05) in ET (VO2max 4.60 +/- 0.10 l/min, LT 2.77 +/- 0.85 l/min) than in UT (VO2max 3.79 +/- 0.11 l/min, LT 1.94 +/- 0.60 l/min). There were significant (P < 0.05) correlations between VE and K+ (UT 0.87, ET 0.77) and between VE and La- (UT 0.88, ET 0.85). In ET compared with UT, VE was lower (P < 0.05) at 330 W, K+ was lower at 300 and 330 W, and La- was lower at all work loads > 90 W. These results suggest that K+ may make an important contribution to the regulation of ventilation during incremental exercise and that endurance training attenuates the K+ response to that exercise.     

Protection of Respiratory Chain Enzymes from Ischaemic Damage in Adult Rat Brain Slices

The effect of aglycaemic hypoxia (AH) on the activity of the mitochondrial respiratory chain complexes was measured in superfused adult cortical brain slices. After 15 min of AH the activity of complex II–III was significantly reduced (by 45%) with no change in complex I or IV. Following 30 min of reperfusion the activities of complex II–III and IV were significantly reduced (by 45% and 20% respectively). These reductions in enzyme activity were abolished by removing the external calcium or by the addition of Nω-nitro-l-arginine (LNNA) or an analogue of superoxide dismutase (SOD) manganese [III] tetrakis 4-benzoic acid porphyrin (Mn-TBAP). These data suggest that a reactive oxygen species (ROS) such as peroxynitrite is involved in the reduction of mitochondrial complex activities following AH.     

The acyclic CB1R inverse agonist taranabant mediates weight loss by increasing energy expenditure and decreasing caloric intake

Cannabinoid 1 receptor (CB1R) inverse agonists are emerging as a potential obesity therapy. However, the physiological mechanisms by which these agents modulate human energy balance are incompletely elucidated. Here, we describe a comprehensive clinical research study of taranabant, a structurally novel acyclic CB1R inverse agonist. Positron emission tomography imaging using the selective CB1R tracer [(18)F]MK-9470 confirmed central nervous system receptor occupancy levels ( approximately 10%-40%) associated with energy balance/weight-loss effects in animals. In a 12-week weight-loss study, taranabant induced statistically significant weight loss compared to placebo in obese subjects over the entire range of evaluated doses (0.5, 2, 4, and 6 mg once per day) (p < 0.001). Taranabant treatment was associated with dose-related increased incidence of clinical adverse events, including mild to moderate gastrointestinal and psychiatric effects. Mechanism-of-action studies suggest that engagement of the CB1R by taranabant leads to weight loss by reducing food intake and increasing energy expenditure and fat oxidation.     

Integrin-independent tyrosine phosphorylation of p125(fak) in human platelets stimulated by collagen

Collagen fibers or a glycoprotein VI-specific collagen-related peptide (CRP-XL) stimulated tyrosine phosphorylation of the focal adhesion kinase, p125(fak) (FAK), in human platelets. An integrin alpha(2)beta(1)-specific triple-helical peptide ligand, containing the sequence GFOGER (single-letter nomenclature, O = Hyp) was without effect. Antibodies to the alpha(2) and beta(1) integrin subunits did not inhibit platelet FAK tyrosine phosphorylation caused by either collagen fibers or CRP-XL. Tyrosine phosphorylation of FAK caused by CRP-XL or thrombin, but not that caused by collagen fibers, was partially inhibited by GR144053F, an antagonist of integrin alpha(IIb)beta(3). The intracellular Ca(2+) chelator, BAPTA, and the protein kinase C inhibitor, Ro31-8220, were each highly effective inhibitors of the FAK tyrosine phosphorylation caused by collagen or CRP-XL. These data suggest that, in human platelets, 1) occupation or clustering of the integrin alpha(2)beta(1) is neither sufficient nor necessary for activation of FAK, 2) the fibrinogen receptor alpha(IIb)beta(3) is not required for activation of FAK by collagen fibers, and 3) both intracellular Ca(2+) and protein kinase C activity are essential intermediaries of FAK activation.     

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

Two unusual budding bacteria isolated from a swimming pool

S ly , L.I. & H argreaves , M.H. 1984. Two unusual budding bacteria isolated from a swimming pool. Journal of Applied Bacteriology 56 , 479–486.
Two unusual strains of budding bacteria were isolated on a Millipore Pseudomonas Count Water Tester during routine monitoring of Pseudomonas aeruginosa counts in a swimming pool. The first isolate has been identified as Blastobacter sp. It was a yellow-pigmented, Gram negative rod-shaped organism with a polar holdfast by which it attached to solid surfaces or other cells to form rosettes. The cells reproduced by asymmetric division or budding at the free pole of the cell, producing motile daughter cells with a single polar flagellum. The second isolate, which has not yet been identified, was a red-pigmented, Gram negative rod-shaped organism which produced one or more buds at each pole of the cell. Cell division appears to occur by both binary fission and by budding. Both organisms were strict aerobes, catalase and oxidase positive and did not produce acid from glucose in Hugh and Leifson medium.