Up-regulation of cerebral carbonic anhydrase by anoxic stress in piglets

The resuscitation of asphyxiated babies is associated with changes in cerebral protein synthesis that can influence the neurological outcome. Insufficient gas exchange results in rapid shifts in extracellular and intracellular pH. Carbonic anhydrase (CA) plays an important role in buffering acute changes in pH in the brain. We investigated whether asphyxia/re-ventilation influences the expression of cerebral CA isoforms (CA-II, CA-III and CA-IV) in anaesthetized newborn pigs. The cerebral cortex, hippocampus, cerebellum and retina were sampled, and prepared for either CA immunohistochemistry or CA immunoblotting from piglets subjected to asphyxia (10 min) followed by 2-4 h of re-ventilation, and also from normoxic controls. The CA immunoreactivity (IR) of all the isoforms studied was weak in the controls, apart from staining of a few oligodendrocytes in the subcortical white matter, some astrocytes in the superficial layer of the cerebral cortex, the cerebellar Purkinje cells and the retinal Müller cells that possessed moderate CA-II IR. However, asphyxia induced a marked increase in the CA IR of all isoforms in all the cerebral regions investigated and the retina after 4 h of survival. The pyramidal cells of the frontal cortex and hippocampus displayed the most conspicuous increase in CA IR. Immunoblotting confirmed increased levels of all the CA isoenzymes. We conclude that raised CA levels after asphyxia may contribute to the compensatory mechanisms that protect against the pathological changes in the neonatal CNS.     

Modification of the contractile activity of isolated rat atria by lectin-activated T-lymphocyte subsets

We had previously shown that human T-lymphocytes (ERFC) that had been activated for a short time with phytohemagglutinin (PHA) produced positive inotropic and chronotropic effects on spontaneously beating rat atria (Sterin-Borda, L., et al., Naunyn Scmiedeberg's Arch. Pharmacol. 324, 58, 1983). In this study, we first prepared T4-rich (T4) and T8-rich (T8) cells from ERFC by selective lysis with OKT4 and OKT8 monoclonal antibodies and rabbit complement. Then, we tested the effect of PHA-stimulated T4 (PHA-T4) and T8 (PHA-T8) on beating rat atria. PHA-T4 cells stimulated the tension and the frequency of contraction of isolated rat atria by a mechanism that involved the generation of the slow reacting substance of anaphylaxis (SRS-A), since both 10(-5) M nordihydroguaiaretic acid (NDGA) and 10(-7) M FPL-55712 were effective inhibitors. On the other hand, PHA-T8 cells decreased the tension of beating atria. Indomethacin (10(-6) M) could not block the depressor effect. Cell-free PHA-T4 supernatants reacted with the heart tissue similarly to whole PHA-T4 cells. Since NDGA or FPL-55712 treated organs did not respond to active PHA-T4 supernatants, the lipoxygenase system of the auricles seems to be required for the reaction and the active metabolites appear to derive mainly from the heart. Our results suggest that PHA-activated "helper/inducer" cells release soluble factors that can in turn trigger the lipoxygenase metabolic pathway of arachidonic acid in the heart, generating the active leukotrienes responsible for the positive inotropic and chronotropic effects.     

Prostacyclin (PGI2) and U-46619 stimulate coronary arteries from diabetic dogs and their action is influenced by inhibitors of prostaglandin biosynthesis

Isolated coronary arteries from diabetic dogs presented different contractile response to U-46619 to prostacyclin (PGI₂) and to arachidonic acid (AA) than those of normal dogs. The stimulatory effect of the synthetic endoperoxide analogue U-46619, was significantly higher in the diabetic condition than in preparations from normal animals. On the other hand, while PGI₂ evoked a dose-dependent relaxation of normal coronary arteries, diabetic vessels were not relaxed by low concentration of PGI₂ whereas higher ones produced a distinct constrictor effect. Additionally, inhibitors of prostaglandins and thromboxane (TX) biosynthesis such as corticosterone, indomethacin, acetylsalicylic acid, imidazole and L-8027, abolished the stimulatory effect of PGI₂ in coronary arteries from diabetic dogs. AA relaxed coronaries from normal dogs and constricted those from diabetic animals, this action being inhibited by imidazol and L-8027.The present results suggests that: a) coronary vessels from diabetic dogs are more reactive to an endoperoxide analogue than normal preparations and b) PGI₂ and AA probably contract diabetic coronary arteries via the participation of a TX like material. It is then plausible that this effect could be tentatively ascribed to the production of a prostaglandin constricting substance including als the probable generation of a TXA₂-like agonist.     

Ovarian hormones inhibit the release of prostacyclin-like material from isolated rat uterus

The influence of sex steroids on the production of prostacyclin (PGI₂) like material by the isolated rat uterus incubated in a buffer medium was explored by monitoring its ability to inhibit ADP-induced platelet aggregation. Chopped uterine strips from rats in natural estrus can generate an unstable substance that inhibits platelet aggregation and suggest to be prostacyclin. This capacity was significantly enhanced in preparations from spayed animals. The injection of 17-beta estradiol; progesterone or both diminished the production of the prostacyclin-like material by the uterus from ovariectomized rats. The already existing notion that ovarian steroids are able to regulate the synthesis of stable prostaglandins is discussed together with the present results suggesting in addition a depressive effect of sex hormones on the uterine PGI₂ synthetase system.     

Distribution of antibodies against beta-adrenoceptors in the course of human Trypanosoma cruzi infection.

We examined the possible role of altered humoral immunity in Chagas' disease by analyzing the effect of sera on the binding of radioligand to beta-adrenoceptors during the course of human Trypanosoma cruzi infection. We described two circulating IgG which bind with myocardial beta 1- and spleen cell beta 2-adrenoceptor. Both chagasic IgG against beta 1- and beta 2-adrenoceptors increased intracellular levels of cAMP, which could be blocked by specific beta 1- and beta 2-adrenoceptor antagonists. The IgG against the beta 1-adrenoceptor inhibited the action of norepinephrine on the contractility of atria. We also found differences in the distribution of beta 1- and beta 2-adrenoceptor antibodies in the course of infection. The anti-beta 2-adrenoceptor IgG appears during the acute stage, peaks on the group with less than 10 years of infection, and then decreases. The prevalence of anti-beta 1-adrenergic antibody is low in the acute stage, but it increases over time since infection, being higher in the group with more than 15 years of infection. The probable pathogenic role of both beta 1- and beta 2-adrenergic chagasic antibodies is discussed.     

Antilaminin IgG releases TXB2 through activation of the cholinergic system

Antilaminin IgG was bound to cholinergic muscarinic receptors of normal mice heart and released TXB2, simulating the biological effect of a cholinergic agonist. Antilaminin IgG interfered with the binding of the radiolabelled muscarinis antagonist (-)3H-QNB in a noncompetitive fashion. Following the interaction of the antibody with the cholinergic receptor, an increased production of TXB2 occurred. This effect required the activation of the muscarinic cholinergic system, because it was blunted by atropine and mimicked by acetylcholine.     

Involvement of nitric oxide synthase and protein kinase C activation on chagasic antibodies action upon cardiac contractility

We have already demonstrated the presence of antibodies in the sera of chagasic patients with the ability to interact with neurotransmitter receptors triggering several intracellular pathways of transduction signals. Here we show that, chagasic IgG induced protein kinase C (PKC) translocation to rat cardiac membranes and this effect was inhibited by muscarinic cholinergic blockers atropine and AF-DX 116 pointing to the participation of M₂ receptors in this effect. It was also able to stimulate nitric oxide synthase (NOS) activity and this action was blunted by phospholipase C (PLC) and PKC inhibitors indicating that the production of nitric oxide (NO) would be the consequence of the cascade of enzymatic pathways triggered by mAChR activation. PKC and NOS activities were involved in chagasic IgG negative inotropic actions on rat isolated myocardium as its effects were blunted by staurosporine and L-N-monomethyl arginine. Furthermore, low concentrations of chagasic IgG inhibited the cardiac mechanical action of carbachol in a non-competitive manner. These data suggested that PKC activation in myocardium by chagasic IgG would be involved in its physiological actions by modulating NOS activity. The participation of PKC-mediated phosphorylation of mAChR leading to receptor desensitization as one of the causes of dysautonomia is also discussed.     

Cholinoceptor activation subserving the effects of interferon gamma on the contractility of rat ileum

Recombinant rat interferon gamma stimulated the contractility of isolated rat ileum at doses of 4-12 units/ml. Muscarinic cholinoceptors were involved, as treatment of the tissue with atropine prevented the contractile response of the ileum. Furthermore, interferon gamma increased the affinity of carbachol for the cholinoceptors and did not change its maximum effect. Neurogenic pathways were also involved since pretreatment of ileum with hexamethonium, hemicholinium or tetrodotoxin impaired the contractile effect of interferon gamma. In contrast to the action of exogenous carbachol, the effects of interferon gamma are indirect. They appear to involve a G protein regulating phosphoinositide turnover and cytoskeletal structures since they could not be induced in ileum strips that were pretreated with pertussis toxin, phospholipase C inhibitors (2-nitro-carboxyphenyl, NN-diphenyl carbamate and neomycin), cytochalasine B or colchicine.     

Biomphalaria tenagophila potencial vector of Schistosoma mansoni in the Paraná River basin (Argentina and Paraguay)

Susceptibility and compatibility experiments were carried out with 700 Biomphalaria tenagophila from the Paraná River basin exposed to infection with Schistosoma mansoni. Individual infection was performed with 10 miracidia of SJ2 strain from the Paraiba valley (Brazil) originally infective to B. tenagophila. These snails were laboratory-breed progeny of B. tenagophila collected from six localities of Argentina and one from Paraguay. From Argentina: Rincón de Vences (7%) and Posadas (11%) became infected with S. mansoni and the calculation of Frandsen's index (TCP/100) shows that they were Class II poorly compatible. Those snails from Goya (22%), Maloyas (5%), and Berón de Astrada (3%) were Class III compatible to the S. mansoni. None of the 100 snails exposed from Caá-Catí became infected (Class 0 incompatible). Tested samples from Paraguay (Encarnación) were infected (20%) and compatible (Class III). It was also studied the persistence of the infection in 244 snails of the first generation (F1) of those that were susceptible from three places. It was demonstrated an increment of the susceptibility in the F1 from Maloyas (chi2 = 27.22; p = 0.0001) and Posadas (chi2 = 4.24; p = 0.04). The results point out the possibility that schistosomiasis might be able to spread into the Paraná River basin where B. tenagophila exists.