Selectivity in plant food consumption in the lizard Liolaemus lutzae from southeastern Brazil

Selectivity in the consumption of plant matter from the natural habitat by the tropidurid lizard Liolaemus lutzae, endemic to the beach habitats of restingas of southeastern Brazil, and the differences in the qualitative properties of the plants consumed were studied in the Barra de MaricÝ restinga, Rio de Janeiro State. The diets of 180 lizards were analysed and the plant species present in the stomachs and their frequencies were recorded. Only four of the 19 species which occur on the beach (Phylloxerus portulacoides, Althernantera maritima, Ipomoea littoralis and I. pes-caprae) were consumed by the lizard and their frequencies in the stomachs differed from that of occurrence. Analysis of the composition of the leaves of the 13 most abundant plant species indicated that the plants consumed by the lizards had the highest contents of water, total nitrogen, total sugar and the lowest amount of gross fibres. Thus, it appears that L. lutzae is not a generalist herbivore, but feeds selectively on those plants in its environment that are most easily digested and assimilated. A seletividade no consumo de algumas entre as espécies vegetais ocorrentes no habitat de praia pelo lagarto tropidur¡deo Liolaemus lutzae e, as diferenças nas propriedades qualitativas presentes nas plantas consumidas em relação às demais plantas mais abundantes do habitat foram estudada na restinga da Barra de Maricá, Sudeste do Brasil. A dieta de 180 lagartos foi analisada tendo sido anotadas as espécies de plantas presentes no estômago e suas respectivas frequências. Apenas quatro entre as 19 espécies registradas na praia (Phylloxerus portulacoides, Althernantera maritima, Ipomoea littoralis and I. pes-caprae) foram consumidas por L. lutzae. As frequências destas na dieta do lagarto diferiram da frequência com que as plantas ocorrem no habitat. A análise da composição das folhas de 13 entre as espécies de plantas mais frequentes indicou que as plantas consumidas pelo lagarto possuem as mais elevadas proporçôes de água, nitrogênio total, açúcar total e a menor proporção de fibras. Aparentemente L. lutzae não é um herbivoro generalista mas seleciona no seu ambiente as plantas as quais são mais facilmente digeridas e assimiladas.     

Insulin-Like Peptides of the Cerebropleural Ganglion of the Mollusc Anodonta cygnea: Isolation, Purification, and Radioligand Analysis

Cerebropleural ganglia from 4000 individuals of the mollusc Anodonta cygnea were submitted to procedures developed for isolation of vertebrate pancreatic insulins: homogenization and extraction, stage-like isoelectrical sedimentation, and ion-exchange chromatography. As a result of purification of the obtained preparation, using high-effective liquid chromatography, there were identified 7 protein peaks differing by time of retention on the reverse-phase sorbent in acetonitryl gradient and designated as insulin-related peptides (IRP), IRP1-IRP7. The material was characterized by the peptide ability to inhibit specific binding of ¹²⁵I-insulin and of insulin-related factor-1 (¹²⁵I-IGF-1) by plasma membranes of the rat liver and brain. The IC₅₀ value of peptide concentration (nM) able to replace 50% of the labeled hormone bound with the receptor amounted in the insulin radioreceptor system for IRP1 to 330, for IRP3 to 130, for IRP4 to 17, for IRP5 to130, for IRP6 to 420 nM. Peptide IRP7 at a maximal concentration (10⁴ ng/ml) replaced less than 50% of labeled hormone, whereas in IRP2 no inhibitory ability was detected under these experimental conditions. The IC₅₀ value in the case of ¹²⁵I-IGF-1 amounted for IRP1, IRP4, and IRP5 to17, for IRP2 to 50, for IRP3 to 83, for IRP6 to 133 nM. IRP7 at a concentration of 10⁴ ng/ml replaced less than 50% of labeled hormone. The same high relative affinity of the peptide IRP4 (12% of activity of standard insulin and IGF-1) to both receptor types is revealed. The results of analysis in two types of hormonal test systems indicate the ability of the insulin-related peptides of the anodonta cerebropleural ganglion to interact with the vertebrate receptor of insulin and IGF-1. This gives grounds to suggest the presence of the metabolic and growth-stimulating properties in these peptides. For the first time, the IGF-1 activity is revealed in insulin-like molecules in invertebrates. Taking into account the chromatographically revealed differences of physicochemical characteristics of individual IRP as well as predominance of their IGF-1-binding properties, there is suggested another organization of the IRP receptor-binding domains in IPR of this mollusc species, as compared with mammalian insulins.     

Role of superoxide in radiation-killing of Escherichia coli and in thymine release from thymidine

The role of superoxide and hydroxyl radicals in gamma-radiation-killing of Escherichia coli K12 was studied in aerated suspensions supplemented with formate, phosphate, superoxide dismutase, catalase and saturated with nitrous oxide. Nitrous oxide, which converts e-aq to .OH, caused decreased radiosensitivity. On the other hand, formate, which results in conversion of .OH to .O2-, resulted in an increased radiosensitivity. The results implicated .O2- as a major cause of radiation-mediated cell-killing. The addition of the enzymes, superoxide dismutase or catalase to the E. coli suspensions prior to and during irradiation had no effect on cell survival, indicating that the biologically significant site of generation and action of .O2- is an intracellular one. Further studies were undertaken to examine the role of superoxide in DNA damage. The release of thymine from the DNA base, thymidine was studied as a result of gamma-irradiation and of chemically generated superoxide (using KO2 in dimethyl sulfoxide). Thymine was identified by HPLC and mass spectrometry. C-13 NMR analysis of the reaction mixture of thymidine with KO2 in dimethyl sulfoxide provided evidence for attack of .O2 at the ribosyl Cl' atom.     

Syrticola mediterraneus n. sp., a harpacticoid copepod from the Bay of Calvi,Corsica

Syrticola mediterraneus n. sp. belonging to the family Cylindropsyllidae Sars (sensu Lang, 1948) is described from the Bay of Calvi (Corsica). The species is closely related to (?) Notopontia galapagoensis Mielke, 1982 and Syrticola flandricus Willems & Claeys, 1982. The former species is now transferred to the genus Syrticola as Syrticola galapagoensis n. comb.     

Flash spectroscopy of purple membrane.

Flash spectroscopy data were obtained for purple membrane fragments at pH 5, 7, and 9 for seven temperatures from 5 degrees to 35 degrees C, at the magic angle for actinic versus measuring beam polarizations, at fifteen wavelengths from 380 to 700 nm, and for about five decades of time from 1 microsecond to completion of the photocycle. Signal-to-noise ratios are as high as 500. Systematic errors involving beam geometries, light scattering, absorption flattening, photoselection, temperature fluctuations, partial dark adaptation of the sample, unwanted actinic effects, and cooperativity were eliminated, compensated for, or are shown to be irrelevant for the conclusions. Using nonlinear least squares techniques, all data at one temperature and one pH were fitted to sums of exponential decays, which is the form required if the system obeys conventional first-order kinetics. The rate constants obtained have well behaved Arrhenius plots. Analysis of the residual errors of the fitting shows that seven exponentials are required to fit the data to the accuracy of the noise level.     

Central transmural venous pressure and plasma arginine vasopressin during negative pressure breathing in man

After overnight food and fluid restriction, 8 normal healthy males were examined in the upright sitting position before (prestudy), during and after (recovery) negative pressure breathing (NPB) with a pressure (P = difference between airway pressure and barometric pressure) of -9.6 +/- 0.5 to -10.4 +/- 0.4 mm Hg for 30 min. Plasma arginine vasopressin (pAVP) did not change significantly comparing prestudy with 10 and 30 min of NPB or comparing recovery with NPB at 10, 20 or 30 min. However, at 20 min of NBP, pAVP was slightly lower than at prestudy (p less than 0.05). Central venous pressure (CVP) decreased significantly during NPB, and central transmural venous pressure (CVP-P) increased significantly from -0.9 +/- 0.8 mm Hg to 3.8 +/- 0.7, 4.3 +/- 0.7 and 4.5 +/- 0.6 mm Hg (p less than 0.001) after 10, 20 and 30 min, respectively. Systolic, diastolic and mean arterial pressure and heart rate did not change significantly during NPB. Diuresis, natriuresis, kaliuresis, osmotic excretion and clearance were slightly increased during the recovery hour after NPB compared to prestudy, while urine osmolality decreased during NPB (n = 6). However, none of these changes were significant. There was no significant correlation between CVP-P and pAVP. In conclusion, -10 mm Hg NPB for 30 min in upright sitting subjects did not change pAVP consistently, while CVP-P was significantly increased and HR and arterial pressures were unchanged. This lends support to the concept that arterial baroreceptors and not cardiopulmonary mechanoreceptors are of importance in regulating AVP secretion in man.     

Degranulation and histamine release from murine mast cells sensitized with dengue virus-immune sera

Mice were immunized with dengue type 2 virus (DEN 2) under a schedule favoring the production of IgE antibody. The antibody obtained could sensitize peritoneal resident mast cells both in vitro and in vivo so that the sensitized cells were degranulated and released histamine on challenge with the DEN 2 antigen. It was also demonstrated that the antibody was cytophilic and heat-labile. The above observations suggest that the present experimental system can be used to detect anti-DEN 2 IgE antibody in mice.     

Cascade of autophosphorylation in the beta-subunit of the insulin receptor

Insulin stimulated autophosphorylation of the beta-subunit of the insulin receptor purified from Fao hepatoma cells or purified from Chinese hamster ovary (CHO/HIRC) or Swiss 3T3 (3T3/HIRC) cells transfected with the wild-type human insulin receptor cDNA. Autophosphorylation of the purified receptor occurred in at least two regions of the beta-subunit: the regulatory region containing Tyr-1146, Tyr-1150, and Tyr-1151, and the C-terminus containing Tyr-1316 and Tyr-1322. In the presence of antiphosphotyrosine antibody (alpha-PY), autophosphorylation of the purified receptor was inhibited nearly 80% during insulin stimulation. Tryptic peptide mapping showed that alpha-PY inhibited autophosphorylation of both tyrosyl residues in the C-terminus and one tyrosyl residue in the regulatory region, either Tyr-1150 or Tyr-1151. Thus, a bis-phosphorylated form of the regulatory region accumulated in the presence of alpha-PY, which contained Tyr(P)-1146 and either Tyr(P)-1150 or 1151. In intact Fao, CHO/HIRC, and 3T3/HIRC cells, insulin stimulated tyrosyl phosphorylation of the beta-subunit of the insulin receptor. Tryptic peptide mapping indicated that the regulatory region of the beta-subunit was mainly (greater than 80%) bis-phosphorylated; however, all three tyrosyl residues of the regulatory region were phosphorylated in about 20% of the receptors. As the phosphotransferase was activated by tris-phosphorylation but not bis-phosphorylation of the regulatory region of the beta-subunit (White et al.: Journal of Biological Chemistry 263:2969-2980, 1988), the extent of autophosphorylation in the regulatory region may play an important regulatory role during signal transmission in the intact cell.     

On the relationship between rate of ATP synthesis and H+ electrochemical gradient in rat-liver mitochondria

The relationship between rate of ATP synthesis, JATP, and value of the proton electrochemical gradient, delta mu H, has been analyzed in intact mitochondria. Onset of phosphorylation causes a depression of delta mu H of 1.5 kJ/mol. There is a close parallelism between inhibition of JATP and restoration of delta mu H to its state-4 value during titrations with oligomycin or atractyloside. Titrations with ionophores display the following features: (a) delta mu H can be depressed by 3-4 kJ/mol by valinomycin + K+ without affecting the rate of ATP synthesis; (b) uncouplers abolish JATP completely while depressing delta mu H by 3 kJ/mol; (c) complete abolition of ATP synthesis by inhibitors of electron transport is accompanied by a depression of delta mu H of only 1 kJ/mol. The results indicate that: (a) there is a close functional relationship between redox and ATPase H+ pumps, whereby inhibition of electron transfer is accompanied by simultaneous inhibition of the ATPase H+ pumps; and (b) uncoupling of oxidative phosphorylation is not due to depression of delta mu H per se. The consistence of the present data with either a chemiosmotic model where delta mu H is the sole and obligatory intermediate for energy coupling, or models where there is a direct transfer of energy between the two pumps is discussed.