Anti-thirst action of propranolol

A reduction of the thirst was observed one hour after intramuscolar injection of 0.3 mg/kg propranolol in the rat; this effect was not observed with higher doses. According to work hypotheses, small doses could act blocking renal beta-adrenergic receptors: the stopped renin emission reduces angiotensin production that is the basic factor of thirst. The AA hypothesize that the lack of the effect in response to higher doses of propranolol can be explained through a different action of this drug which antagonizes the first one.     

Variations in plasma protein components during extracorporeal circulation

In this research we have determined the behaviour of proteic plasmatic pattern and some enzymes during extracorporeal circulation and we noted a constant increase of albumin and of the ratio Alb/Glob. We observed also variations of some enzymes. Our opinion according other AA. is that this changes are determined principally by the large dose of heparin necessary during the C.E.C.     

The identification of the periodic behaviour in an epidemic model

In this paper we study a method for the identification of the unknown parameter of the periodic function and also the first component of the state vector, in a mathematical model which describes the evolution of some diseases with an oro-fecal transmission.To solve the identification problem we use a numerical method to integrate the differential equations system, which reproduces the stability properties of the above mentioned continuous system.The numerical methods which we propose can be applied also to a spatial semi discretization of the reaction-diffusion model which is a diffusive generalization of the system that we consider in this paper.Finally, through an analysis on both the continuous and the discrete system we also obtain a necessary condition on the experimental data in order that a periodic trajectory of the system exists.Work supported by: Progetto Finalizzato Controllo Malattie da Infezione-CNR and by Ministero Pubblica Istruzione     

Met-enkephalin immunoreactivity in blood platelets

Picogram amounts (50–150 pg/mg protein) of immunoreactive met-enkephalin material (met-enkephalin in IR) were detected by radioimmunoassay in human, rat and rabbit platelets. Characterization of this material by thin-layer chromatography, gel filtration chromatography and high-pressure liquid chromatography indicated that it behaves identically with synthetic met-enkephalin. No high molecular weight met-enkephalin IR could be detected in the platelet extracts, even after trypsin hydrolysis, using two antisera which are able to recognize some of the putative met-enkephalin precursors present in the adrenal gland or striatum. $\text{In vitro}$, thrombin released platelet met-enkephalin in IR concomitantly with 5-hydroxytryptamine (5-HT), suggesting a common subcellular localization, i.e. the 5-HT storing organelles, for met-enkephalin IR and the amine. $\text{In vivo}$, platelet met-enkephalin IR in the Sprague-Dawley rat was affected neither by adrenalectomy nor by hypophysectomy. Thirteen- and 18-week-old spontaneous hypertensive rats (SHR) had lower platelet concentrations of met-enkephalin in IR than age matched normotensive Wistar-Kyoto rats.     

The stereochemistry of matricin and 4-epimatricin,proazulene sesquiterpene lactones from Artemisia arborescens

An investigation of Artemisia arborescens afforded, in addition to the known compounds matricin, artabsin and artemetin, the new guaianolide 4-epimatricin. The stereostructures of 4-epimatricin and matricin were assigned on the basis of spectroscopic evidence.     

Separation of mannosylretinylphosphate from dolichylmannosylphosphate by chromatography on columns of DEAE-sephacel

A one-step column chromatographic procedure on DEAE-Sephacel allows the separation of mannosylretinylphosphate from dolichylmannosylphosphate with minimal breakdown of the mannosylretinylphosphate. Using this procedure, subcellular fractions of rat liver were shown to be active in synthesizing both mannolipids from GDP-[¹⁴C]mannose in the absence or presence of exogenous retinylphosphate.     

Effect of temperature on the stability and activity of crystalline ox liver nuclear and mitochondrial glutamate dehydrogenases

A study on the response of the stability and activity of crystalline ox liver nuclear and mitochondrial glutamate dehydrogenases to temperature variations has been carried out. The thermodynamic properties of the heat inactivation process and of the reaction with the substrates glutamate and α-ketoglutarate have been investigated. The heat inactivation of nuclear glutamate dehydrogenase proceeds at a faster rate than that of the mitochondrial enzyme in the temperature range 40–51 °C; the enthalpy of activation of the inactivation process is higher and the entropy is almost double, compared to the values of mitochondrial glutamate dehydrogenase. The effect of temperature on the maximal velocity shows that, with both glutamate and α-ketoglutarate, the enthalpy of activation with nuclear glutamate dehydrogenase is double and the decrease in entropy almost half of the values of the mitochondrial enzyme. The variation of the apparent K_m with temperature shows a decrease of the affinity of both enzymes for glutamate, with no major difference in the thermodynamic properties of the reaction. With α-ketoglutarate, on the other hand, the affinity of nuclear glutamate dehydrogenase decreased, whereas that of the mitochondrial enzyme increased with temperature. The process is therefore exothermic with the former enzyme, endothermic with the latter; furthermore, it occurs with a decrease in enthropy with nuclear glutamate dehydrogenase, but with a large increase with the mitochondrial enzyme. The studies on the effect of temperature on the activity were carried out in the range 20–44 °C.     

Time-dependent phosphorescence anisotropy measurements of the slow rotational motions of proteins in viscous solution

A method of monitoring slow rotational motions of proteins from the decay of the intrinsic phosphorescence is described. The phosphorescence is excited with a 10-μsec pulse of vertically polarized light from an air gap lamp, and the anisotropy was computed as a function of time from the simultaneously detected vertically and horizontally polarized components of the emission. The approach is illustrated with time-dependent measurements of the anisotropy of the tryptophan phosphorescence of Staphylococcus aureus nuclease, bovine carbonic anhydrase, and liver alcohol dehydrogenase in glycerol-phosphate buffer between ?90 and ?70°C. The temperature- and molecular-weight dependence of the exponential decays in the anisotropy indicate that overall rotation of the proteins is at the origin of the depolarization. The potential of the approach as a probe of the slow rotational motions of proteins in membranes and other macromolecular complexes is stressed.