Mechanism of action of somatostatin.

The chain of events leading to the manifestation of the biological action of somatostatin are described. Internalization is mediated by cytoskeletal proteins in the presence of calmodulin. Transduction of the somatostatin message at the membrane level takes place through inhibition of cyclic AMP accumulation and blockade of cytosol calcium increases.

G-protein distribution in canine cardiac sarcoplasmic reticulum and sarcolemma: comparison to rabbit skeletal muscle membranes and to brain and erythrocyte G-proteins.

Herein we describe the distribution of G-proteins in canine cardiac sarcolemma (SL) and sarcoplasmic reticulum (SR) and in rabbit skeletal muscle SL, T-tubules, and junctional and longitudinal SR in comparison to G-proteins of human erythrocyte and bovine brain. G-proteins were unequivocally present in cardiac SL and SR and in skeletal T-tubules. Both cardiac fractions had two substrates specifically ADP-ribosylated by cholera toxin migrating on a sodium dodecyl sulfate-polyacrylamide gel at about 42 and 45 kDa.

Inhibitory regulation of adenylyl cyclases. Evidence inconsistent with beta gamma-complexes of Gi proteins mediating hormonal effects by interfering with activation of Gs.

The possible effect of cholera toxin (CTX) on hormonal inhibition of adenylyl cyclase in somatostatin (SST)-sensitive GH3 cells was quantitatively evaluated. The toxin treatment employed led to an essentially complete ADP ribosylation of all alpha s subunits of the stimulatory regulatory component (Gs) of the system and to ca. 5- to 7-fold increases in the activity measured, yet it failed to affect the inhibitory action of SST regardless of whether analyzed in terms of degree of inhibition (ca.

Formation of ion-translocating oligomers by nigericin.

At pH 4.0, greater than 10(-7) M nigericin was found capable of conducting net charge transfer across bimolecular lecithin membranes, with a stoichiometry of three uncharged ionophore moieties per cation. At neutral or alkaline pH, nigericin catalyzed the transfer of net charge through dimer forms.

Postnatal development of brain TRH, serum TSH and thyroid hormones in the male and female rat.

The postnatal development of immunoreactive TRH in the central nervous system (CNS), serum TSH and thyroid hormones was studied in both male and female normal rats. While in most structures of the CNS, TRH increased until day 20-30, serum TSH values peaked at day 15 as did T4. Significant differences were also obtained between both sexes in these parameters.

Postnatal development of calmodulin and calmodulin-dependent phosphodiesterase in different regions of the rat central nervous system.

We have studied the concentration of calmodulin and phosphodiesterase (cAMP high Km) in five different parts of the rat central nervous system (hemispheres, cerebellum, diencephalon, brain stem and spinal cord) during postnatal development (5, 10, 15, 20, 30 and 45 days after birth). The concentration of the enzyme and its regulatory protein were independent, so that no correlation could be established between them. In most structures, calmodulin concentration tended to decrease with age, while phosphodiesterase increased or remained at similar values during the time studied.

Effect of isometamidium on infections by Trypanosoma vivax and T. evansi in experimentally-infected animals.

Assays dealing with the therapeutic and prophylactic activity of isometamidium on experimental infections by Trypanosoma vivax and T. evansi were carried out. The drug was found to be highly effective against T.

Bilateral incipient germ cell tumours of the testis in the incomplete testicular feminization syndrome.

The presence of bilateral incipient germ cell tumours in the testes of two cases of the incomplete testicular feminization syndrome (TFS) is reported and found to resemble that occurring in the testes of infertile men. Both the nature and nomenclature of the lesion is discussed, as is its relevance in the early diagnosis and improved therapy of testicular tumours, which occur frequently in TFS. Suggestions are made for a more complete postpubertal surveillance in these patients, including assay of tumour markers and bilateral biopsies in cases of complete TFS.