Variation in the diet of the viperine snake Natvix mama in relation to prey availability

The diet of the viperine snake was compared with food availability in the Ebro Delta, a wetland largely occupied by rice fields, in 1990 and 1991. Snake selection of prey type and size was studied seasonally and by snake group: males, females and immature snakes. Overall, feeding activity (percentage of individuals with prey and number of prey per stomach) increased with food availability. Diet analysis showed that viperine snakes mainly foraged on the green frog Rana perezi (adults and tadpoles) and the carp Cyprinus earpio. Conversely, viperine snakes rejected the mosquito fish Gambusia holbroki which is the most abundant species in autumn, when Natrix maura has a low feeding activity. Statistical comparisons between viperine snake diet and prey availability showed that males selected small carp, immature snakes selected tadpoles and, in spring, females selected frogs. The selection of small carp by males may reflect a sexual divergence of trophic niche related to sexual size dimorphism, as females are larger than males. As tadpoles are presumably easier to catch than fish, tadpole selection by immature individuals may reflect variance in capture abilities. In spring, the selection of frogs by females overlapped with vitellogenesis, suggesting that females compensate for the cost of reproduction by selecting green frogs, which have a greater biomass and higher energy content than fish. Carps eaten in spring were smaller than in summer. Moreover, in summer viperine snakes selected smaller carp than the available mean size. This divergent tendency between carp size selection and carp size availability reveals how seasonal diet shifts in prey size selection may be a response to an increase in prey size.     

A pertussis toxin-sensitive G-protein mediates some aspects of insulin action in BC3H-1 murine myocytes.

The involvement of G-proteins in the insulin signal transduction system has been studied in detail using the murine BC3H-1 myocyte system. Pertussis toxin (PT) treatment, previously shown to attenuate some of the metabolic effects of insulin in this cell line (Luttrell, L.M., Hewlett, E.L., Romero, G., and Rogol, A.D. (1988) J. Biol. Chem. 263, 6134-6141), abolished insulin-induced generation of diacylglycerol and inositolglycan mediators with no effects on either the autophosphorylation of the insulin receptor or the phosphorylation of the major endogenous substrates for insulin-stimulated tyrosine kinase activity (pp185 and pp42-45). In vitro ADP-ribosylation and immunoblotting studies suggest that the major PT substrate is a 40-kDa protein of the G alpha family. This protein band did not exhibit detectable tyrosine phosphorylation upon stimulation of either intact cells or cell membranes with insulin. In the presence of low concentrations of GTP, insulin treatment of isolated myocyte plasma membranes resulted in a small (30-40%) but significant stimulation of GTP hydrolysis. This effect was best observed in the presence of small concentrations of sodium dodecyl sulfate. The rate of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) binding to BC3H-1 membranes was also significantly increased in the presence of insulin. The effects of insulin on GTP hydrolysis and GTP gamma S binding were found to be dependent on the concentration of insulin. These effects were not detected in plasma membranes prepared from PT-pretreated BC3H-1 myocytes. In contrast, pretreatment with the B (inactive) subunit of PT did not alter the response of myocyte membranes to insulin. High affinity binding of [125I]iodoinsulin to myocyte plasma membranes was reduced by 60-70% in the presence of guanine nucleotides. Similar effects on insulin binding were produced by PT pretreatment of the cells. In contrast, adenine nucleotides had no effect on insulin binding. Scatchard analysis of the binding data showed that the observed effects of guanine nucleotides and PT on insulin binding resulted either from a reduction in the number of high affinity insulin binding sites or from a significant reduction of the affinity of insulin for its receptor. Low affinity binding sites did not appear to be affected by either guanine nucleotides nor PT pretreatment. These results provide substantial evidence suggestive of a noncovalent interaction between the insulin receptor and a regulatory G-protein system during the process of insulin signaling.     

Analysis of Immune Response Markers in Jorge Lobo's Disease Lesions Suggests the Occurrence of Mixed T Helper Responses with the Dominance of Regulatory T Cell Activity

Jorge Lobo’s disease (JLD) is a chronic infection that affects the skin and subcutaneous tissues. Its etiologic agent is the fungus Lacazia loboi. Lesions are classified as localized, multifocal, or disseminated, depending on their location. Early diagnosis and the surgical removal of lesions are the best therapeutic options currently available for JLD. The few studies that evaluate the immunological response of JLD patients show a predominance of Th2 response, as well as a high frequency of TGF-β and IL-10 positive cells in the lesions; however, the overall immunological status of the lesions in terms of their T cell phenotype has yet to be determined. Therefore, the objective of this study was to evaluate the pattern of Th1, Th2, Th17 and regulatory T cell (Treg) markers mRNA in JLD patients by means of real-time PCR. Biopsies of JLD lesions (N = 102) were classified according to their clinical and histopathological features and then analyzed using real-time PCR in order to determine the expression levels of TGF-β1, FoxP3, CTLA4, IKZF2, IL-10, T-bet, IFN-γ, GATA3, IL-4, IL-5, IL-13, IL-33, RORC, IL-17A, IL-17F, and IL-22 and to compare these levels to those of healthy control skin (N = 12). The results showed an increased expression of FoxP3, CTLA4, TGF-β1, IL-10, T-bet, IL-17F, and IL-17A in lesions, while GATA3 and IL-4 levels were found to be lower in diseased skin than in the control group. When the clinical forms were compared, TGF-β1 was found to be highly expressed in patients with a single localized lesion while IL-5 and IL-17A levels were higher in patients with multiple/disseminated lesions. These results demonstrate the occurrence of mixed T helper responses and suggest the dominance of regulatory T cell activity, which could inhibit Th-dependent protective responses to intracellular fungi such as L. loboi. Therefore, Tregs may play a key role in JLD pathogenesis.     

SuperSAGE analysis of the <Emphasis Type="Italic">Nicotiana attenuata</Emphasis> transcriptome after fatty acid-amino acid elicitation (FAC): identification of early mediators of insect responses

Background  

Plants trigger and tailor defense responses after perception of the oral secretions (OS) of attacking specialist lepidopteran larvae. Fatty acid-amino acid conjugates (FACs) in the OS of the Manduca sexta larvae are necessary and sufficient to elicit the herbivory-specific responses in Nicotiana attenuata, an annual wild tobacco species. How FACs are perceived and activate signal transduction mechanisms is unknown.     

Regulated nitrate transport in the cyanobacterium Anacystis nidulans.

Intracellular accumulation of nitrate, indicative of the operation of an active nitrate transport system, has been measured in intact cells of the cyanobacterium Anacystis nidulans. The ability of the cells to accumulate nitrate was effectively hindered by either ammonium addition or selective inhibition of CO2 fixation by DL-glyceraldehyde, with the effect of either compound being prevented by previously blocking ammonium assimilation. The results support the contention that nitrate utilization in cyanobacteria is regulated at the level of nitrate transport through the concerted action of ammonium assimilation and CO2 fixation.     

Glutathione content and GSH S-transferase activity in midgut gland of Procambarus clarkii. Sex differences, the effect of fasting, and their implications in cadmium toxicity

1. Glutathione content and GSH S-transferase activity in the midgut gland of Procambarus clarkii (P. c.) of different sex and body weight are presented. 2. Procambarus clarkii females' GSH concentration in the midgut gland decreases to a higher extent upon fasting, compared with males. 3. Procambarus clarkii females, both in control and fasting conditions, have a slightly higher GSH S-transferase activity than males. 4. Cadmium present in water only affects GSH content and GSH S-transferase activity (after 96 hr) in midgut gland, with cadmium chloride concentrations higher than 100 micrograms/l.