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.     

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.     

Inactivation of mitochondrial carbamoyl phosphate synthetase induced by ascorbate, oxygen, and Fe3+ in the presence of acetylglutamate: protection by ATP and HCO3- and lack of inactivation of ornithine transcarbamylase

Of the two mitochondrial enzymes of the urea cycle, carbamoyl phosphate synthetase (CPS) was and ornithine transcarbamylase (OTC) was not inactivated by the Fe3+-oxygen-ascorbate model system for mixed-function oxidation [R. L. Levine, (1983) J. Biol. Chem. 258, 11828-11833]. The susceptibility of OTC was not increased by its substrates, products, or inhibitors, whereas that of CPS was markedly increased by acetylglutamate (its allosteric activator) when ATP was absent. Thus, acetylglutamate binds in the absence of ATP and exposes to oxidation essential groups of the enzyme. We estimate for this binding a KD value of 1.6 mM, which greatly exceeds the KD values (less than 10 microM) determined in the presence of ATP and bicarbonate. ATP, and even more, mixtures of ATP and bicarbonate protected CPS from inactivation. Acetylglutamate exposes the site for the ATP molecule that yields Pi, and it appears that ATP protects by binding at this site. Experiments of limited proteolysis with elastase suggest that oxidation prevents this binding of ATP and show that it accelerates cleavage of CPS by the protease, thus supporting the idea that oxidation may precede proteolysis. Trypsin, chymotrypsin, and papain also hydrolyze the oxidized enzyme considerably faster than the native enzyme. Our results also support the idea that oxidative inactivation is site specific and requires sites on the enzyme for Me2+ and, possibly, for a nucleotide.     

Limited proteolysis reveals low-affinity binding of N-acetyl-L-glutamate to rat-liver carbamoyl-phosphate synthetase (ammonia)

Carbamoyl-phosphate synthetase was inactivated by elastase with first-order kinetics, and N-acetyl-L-glutamate speeded inactivation. From the dependence of the t1/2 value for inactivation on the concentration of acetylglutamate we estimate a Kd value for binding of the activator of 0.365 mM, which is approximately 600 times greater than in the presence of ATP, HCO3-, K+ and Mg2+. K+ and Mg2+ are not required for binding with low affinity, and in the absence of ATP they do not appear to increase the affinity for acetylglutamate. In the presence of acetylglutamate, mixtures of ATP, K+ and Mg2+ protect the enzyme from inactivation. ADP or AdoPP[NH]P partly replaced ATP in protecting the enzyme and thus binding of the nucleotide without further reaction is enough for protection. Two partial activities of the enzyme were inactivated by elastase to the same extent as the overall reaction, and thus elastase affects some property of the enzyme which is essential for catalysis. With other proteinases tested, inactivation was also accelerated by acetylglutamate and was slowed by mixtures of ATP, K+, Mg2+ and acetylglutamate, suggesting that changes in the accessibility of susceptible bonds are responsible for the changes in the degree of inactivation. It is concluded that elastase attacks at or close to the binding sites for ATP, and that exposure of the binding site for the ATP molecule that yields Pi (ATPA) upon binding of acetylglutamate causes the acceleration of the proteolytic inactivation.     

Bacterial Metabolism of 2,6-Xylenol

Strain DM1, a Mycobacterium sp. that utilizes 2,6-xylenol, 2,3,6-trimethylphenol, and o-cresol as sources of carbon and energy, was isolated. Intact cells of Mycobacterium strain DM1 grown with 2,6-xylenol cooxidized 2,4,6-trimethylphenol to 2,4,6-trimethylresorcinol. 4-Chloro-3,5-dimethylphenol prevents 2,6-xylenol from being totally degraded; it was quantitatively converted to 2,6-dimethylhydroquinone by resting cells. 2,6-Dimethylhydroquinone, citraconate, and an unidentified metabolite were detected as products of 2,6-xylenol oxidation in cells that were partially inactivated by EDTA. Under oxygen limitation, 2,6-dimethylhy-droquinone, citraconate, and an unidentified metabolite were released during 2,6-xylenol turnover by resting cells. Cell extracts of 2,6-xylenol-grown cells contained a 2,6-dimethylhydroquinone-converting enzyme. When supplemented with NADH, cell extracts catalyzed the reduction of 2,6-dimethyl-3-hydroxyquinone to 2,6-dimethyl-3-hydroxyhydroquinone. Since a citraconase was also demonstrated in cell extracts, a new metabolic pathway with 2,6-dimethyl-3-hydroxyhydroquinone as the ring fission substrate is proposed.     

A method for the quantitation of intestinal metaplasia of the stomach by morphometry

A novel method to quantitate the extent of intestinal metaplasia in gastrectomy specimens is presented. Morphometric measurements of histochemically labeled mucin-producing goblet cells were done in three selected gastrectomies (one having a peptic ulcer, one with adenocarcinoma of the intestinal type, and one with adenocarcinoma of the diffuse type). The sectioning of the gastrectomy specimens was standardized. The results indicated that the intestinal metaplasia was significantly higher in the specimen with adenocarcinoma of the intestinal type (as compared to the other two specimens), both along the lesser and greater curvatures as well as in the fundic area. These quantitative results confirm nonquantitative reports based on subjective visual impressions. This quantitative histochemical method for measuring the actual length as well as the topographical distribution of intestinal metaplasia in resected stomachs will be used in future studies of intestinal metaplasia with the aim of disclosing possible differences among populations with disparate incidences of gastric carcinoma.     

Sex-specific response of the vasopressin-reacting neurons of the paraventricular nucleus of the rat hypothalamus following chronic administration of met-enkephalin.

Using the peroxidase-antiperoxidase immunocytochemical technique, a morphometric study of the magnocellular neurons of the Paraventricular nucleus of the rat hypothalamus, reactive to specific anti-vasopressin rabbit serum, was made. Following systemic and chronic administration of met-enkephalin the number of immunoreactive neurons was higher, especially in females. Additionally, in the females, it was possible to observe an increase in the immunoreactivity and the presence of well-stained fibres. These findings suggest, especially in females, a blockage in the release of vasopressin, facilitating its immunocytochemical visualization.