Distinct effects of the C-terminal octapeptide of cholecystokinin and of a cholera toxin pretreatment of the kinetics of rat pancreatic adenylate cyclase activity

(1) The kinetic parameters of rat pancreatic adenylate cyclase were evaluated, using GTP, p[NH]ppG or GTP gamma S as nucleotide activator, cholecystokinin as peptide hormone, and GDP beta S and dibutyryl cyclic GMP as inhibitors of guanosine triphosphate and CCK-8, respectively. The time courses of activation and the degree of activation at steady state (EA/ETOT) were compatible with a simple two-state model of activation-deactivation based on a pseudo-monomolecular activation process (rate constant kappa+1), and a deactivation process (rate constant kappa off) that included, depending on the activating nucleotide, the hydrolysis of GTP (rate constant kappa 2) and/or the dissociation of the intact nucleotide (rate constant kappa-1), so that EA/ETOT = kappa+1/(kappa+1 + kappa 2 + kappa-1). (2) The hormone CCK-8 increased the value of kappa+1 with GTP dose-dependently, from 0.2 to 10.9 min-1. The value of kappa-1 increased 0.01 to 0.3 min-1 but the value of kappa 2 was unaltered at 7 min-1, so that EA/ETOT increased 15-fold, from 4% to 61%. (3) A cholera toxin pretreatment at 30 micrograms/ml allowed also a large increase in EA/ETOT with GTP (up to 51%) but the underlying mechanism was different. It consisted of a 14-fold decrease in the kappa off value of the GTP-activated enzyme (from 7 min-1 to 0.5 min-1) that corresponded to a reduction in GTPase activity. When testing the system with p[NH]ppG, two added effects of the cholera toxin pretreatment were observed: a 4-fold increase in the value of kappa+1 (from 0.2 to 0.8 min-1) and the occurrence of a significant 0.3 min-1 value for kappa-1.

[Association of hyperlipidemia, acute pancreatitis and diabetic keto-acidosis. A case report (author's transl)]

A 32-year-old man was admitted semi-comatose with digestive troubles to the hospital. A diabetic keto-acidosis was discovered. The diabetes was known by the patient for one year and a half, but it was not treated. Furthermore the laboratory studies showed a hyperlipidemia (type V) and an increase in pancreatic enzymes. The hyperlipidemia disappeared with insulin therapy. The chronology of the facts was probably: a hyperlipidemia associated with the diabetes, responsible of an acute pancreatitis, which induced a keto-acidosis.

Dependent proximal loop colostomy: does it defunction the distal colon?

The operation of dependent proximal loop colostomy is described. This colostomy avoids the complications of prolapse and paracolostomy hernia and is easy to close. It appears clinically to totally defunction the distal colon; his ability was studied by means of a radioactive tracer. Ten patients were given chromium-51 by mouth and it was found that none of this spilled over into the distal loop. It is concluded that dependent proximal loop colostomies effectively defunction the distal colon.

[Maximum rate of sedimentation of a suspension placed in a viscosimeter with coaxial cylinders. Application to a number of pathological blood samples (author's transl)]

Erythrocyte sedimentation of normal and pathological human bloods at varying controlled shear rates has been measured. Erythrocyte sedimentation rate (ESR) was found to reach a maximum at a characteristic shear rate gamma c [gamma c less than .1 s-1 for normal bloods; gamma c greater than .1 s-1 for pathological bloods]. Records of viscosity versus shear rate exhibit a break near gamma c. Examples show that ESR is well correlated with viscometric data.

Genetic control of lysine permeases in Saccharomycopsis lipolytica

In order to obtain strains of Saccharomycopsis lipolytica impaired in the active transport of L-lysine, mutants resistant to a mixture of L-canavanine, L-4-5-transdehydrolysine and L-S-amino ethylcysteine, taken either all three or two by two, were isolated. These compounds were shown previously to be competitive inhibitors of L-lysine uptake. The resistance patterns and excretion capacity of the mutants were established. All mutants behaved as monogenic. Recombination tests indicated that four genes at least were involved. All mutants were impaired in both high and low affinity L-lysine transport systems. Several hypotheses on the functions of these genes are put forward and discussed.

Characterization of (Mg,Ca)-ATPase activity in rat pancreatic plasma membranes

1. Pancreatic plasma membranes containing a high adenylate cyclase activity and a low contamination by cytochrome c oxidase were isolated from the rat by sucrose density centrifugation. The preparation contained an (Mg,Ca)-ATPase of high activity with the following characteristics. 2. The ATPase activity was shown to have two apparent Km values for Mg-ATP (0.24 +/- 0.09 mM and 1.15 +/- 0.21 mM) and two apparent Km values for Ca-ATP (0.14 +/- 0.09 mM and 0.68 +/- 0.10 mM). Mg-GTP and Ca-GTP were also hydrolysed by the preparation. The phase transition temperature was 19.3 +/- 1.0 degrees C for the Mg-ATPase and 22.6 +/- 1.1 degrees C for the Ca-ATPase activities. 3. Three lines of evidence suggest that Mg-ATP and Ca-ATP were substrates for the same enzyme: Mg-dependent and Ca-dependent activities were not additive; the two activities showed the same pH optimum at 8.0; and the nonionic detergents Triton X-100, Triton X-305, Triton N-101, Lubrol P 12 A, and digitonin, produced a parallel solubilization of the two activities. 4. Enzyme activities were insensitive to potassium, sodium, ouabain, pancreozymin, carbamoyl-choline, secretin, concanavalin A, wheat germ agglutinin, and soybean lectin.

Dissociation of cyclic GMP synthesis from cholinergic-stimulated secretion of protein from rat exocrine pancreas

The phosphodiesterase inhibitors RO-201724/1 and 1-methyl-3-isobutylxanthine (MIX) stimulate a rapid increase in cyclic GMP content in rat pancreas; the latter agent also potentiates the stimulatory effect of carbachol on cyclic GMP synthesis. However, neither RO-201724/1 nor MIX alter basal secretion of 3H-labeled protein, nor do they affect the secretory response to carbachol used in either suboptimal or optimal concentrations. MIX as well does not alter the rate at which carbachol stimulates pancreatic enzyme release. The ability of carbachol to increase cyclic GMP synthesis is lost if extracellular calcium concentration is lowered to 0.05 mM; at this calcium concentration, however, the muscarinic agent still elicits a marked secretory effect. The dissociation between cyclic GMP synthesis and the secretory response suggests that the cyclic nucleotide does not play a major role in the stimulus--enzyme secretion coupling phenomenon of the exocrine pancreas.

Histological-venographic correlates in portal hypertension

Magnification hepatic wedge venography and manometry were evaluated in 40 patients with portal hypertension and in 6 normal individuals. Venography (alone or in combination with manometry) generally facilitated prediction of histology in cirrhosis, hepato-venular occlusive disease, periportal fibrosis, congenital hepatic fibrosis, and portal vein obstruction. The magnification wedge venograms demonstrated a number of histological features of cirrhosis that have not previously been described in vivo, including porto-hepatic vein shunts, micro- and macronodular regeneration, and obstructive changes which were more severe in hepatic than in portal veins.

Study of adenine aminohydrolase in the yeast, Schizosaccharomyces pombe

Observation of the growth of some adenineless mutants of Schizosaccharomyces pombe on six substituted purine analogs leads to the hypothesis that an enzyme is present which catalyzes the conversion of these analogs into hypoxanthine. The enzyme adenase (adenine aminohydrolase, EC 3.5.4.2) has been found to be active in cell-free extracts of S. pombe. Results are reported which are in agreement with the hypothesis that this enzyme is responsible for the in vivo utilization of 6-chloropurine. This evidence comes mainly from a study of adenine aminohydrolase in two mutants selected for partial inability to grow on 6-chloropurine.