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Biomedical subjects

J Wolff

Publications and source records attributed to J Wolff.

At least 181 records · Page 10Linked to original sources
PubMed1984

Calmodulin binds to both microtubule-associated protein 2 and tau proteins.

Calmodulin binding to microtubule-associated proteins (MAPs) was studied by using three experimental techniques: affinity chromatography, cross-linking, and equilibrium binding. 1) Calmodulin affinity chromatography: both MAP2 and tau proteins were bound to calmodulin affinity columns in the presence of calcium and released with ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), whereas tubulin was not bound. 2) Cross-linking 125I-calmodulin to whole MAPs and MAP2 by disuccinimidyl suberate: 125I-calmodulin was cross-linked to MAP2 and tau proteins showing an intense radioactivity band at 300,000 daltons and a diffuse band between 70,000 and 90,000 daltons. The cross-linking was calcium-dependent and was blocked by EGTA, trifluoperazine, or excess unlabeled calmodulin. 3) Equilibrium binding of 125I-calmodulin to MAP2 and tau using the Hummel-Dreyer technique on Sephadex G-100 columns: MAP2 and tau proteins bound 125I-calmodulin in a calcium-dependent manner and no binding occurred in the presence of EGTA. The apparent dissociation constant of calmodulin for MAP2 was 7 microM. The results indicate that calmodulin exerts its effect on microtubule assembly through the formation of a "Ca2+ X calmodulin X MAP2 or X tau" complex.

Animals↗
PubMed1984

Comparison of androgen biosynthesis in isolated leydig cells from rat and mouse testis: incubation and superfusion studies.

Production of testosterone by highly purified Leydig cells prepared from rat and mouse testes is compared. Testosterone formation is improved to a higher degree in rat (2.7-fold) than in mouse (1.7-fold) cells by collagenase treatment of the testis compared with mechanical isolation. Mouse Leydig cells respond to exogenous stimuli (choriogonadotropin, dibutyryl cyclic AMP) with 2.4-fold higher testosterone secretion than rat cells. A 1.7-fold increased conversion of androgen precursors to testosterone by mouse compared with rat Leydig cells is demonstrated in static incubations as well as in steady-state superfusion experiments and can be derived from enhanced androstenedione reduction and a less inhibitory effect of progesterone on this process in mouse Leydig cells.

Androgens↗
PubMed1984

Estimation of kinetic parameters of androgen-synthesizing enzyme activities in superfused Leydig cells from rat testes: difference between endogenous and exogenous substrates.

Kinetic parameters of 3 beta-hydroxysteroid dehydrogenase/isomerase, steroid-17 alpha-monooxygenase, and steroid-17,20-lyase activities were estimated under steady-state conditions. Purified Leydig cells from rat testes were superfused with pregnenolone, progesterone, or 17 alpha-hydroxyprogesterone. The Km values for both the monooxygenase- and the lyase-catalyzed reactions were by factors of five to ten higher if analyzed with the exogenously added substrate (0.98 and 0.65 microM, respectively) than if calculated from endogenous substrate derived from a precursor (0.10 and 0.13 microM, respectively). This discrepancy may be explained by different substrate partition between the intra- and extracellular spaces and by different substrate concentration at the active site of the respective enzyme, depending on whether the actual substrate is of exogenous or endogenous source.

3-Hydroxysteroid Dehydrogenases↗
PubMed1984

A carrier-free cell superfusion system for the study of androgen formation from precursor steroids by isolated rat testis Leydig cells under steady-state conditions.

A cell superfusion system is presented in which cells can be kept in suspension if there is an equilibrium between cell sedimentation velocity and superfusion medium flow velocity. Since the cross-section area of the central core increases gradually, theoretical considerations and experimental results demonstrate that single isolated cells as well as small cell aggregates are not able to leave the superfusion chamber. The whole apparatus is constructed from glass to avoid adsorption of steroids. As an application of the system, androgen formation from progestin precursors by isolated rat testis Leydig cells is shown. Under steady-state conditions, constant concentrations of substrates, intermediates, and products are measured in the collected effluent. In contrast to conventional cell incubation, constant testosterone formation rates and linearly increasing cumulative testosterone production are achieved.

Animals↗
PubMed1984

Bilateral torsion of the adnexa: a case report and a review of the world literature.

The 15th case of bilateral adnexal torsion, or the fifth case in which the bilateral adnexal torsion did not occur simultaneously, is presented. A review of the cases reported in the world literature reveals that fever (82%), nausea and/or vomiting (73%), and abdominal pain (93%) were the most common symptoms. Previous recurrent attacks of abdominal pain occurred in 53% of patients and may be the one finding that is highly suggestive of this entity. The adnexa were histologically normal in 50% of the specimens, with the remaining adnexal tissues manifesting evidence of tubal infection (ie, hydrosalpinx and pyosalpinx). The diagnosis was suspected preoperatively in only 38% of the cases.

Adnexal Diseases↗
PubMed1984

[Comparative study of oxygen tension in arterial blood and arterialized capillary blood in relation to the oxygen content of inspired air in healthy newborn infants].

The values of oxygen tension of arterial blood were compared with those of arterialized capillary blood in 65 healthy newborns. The latter ones always had a significantly lower level than the arterial ones. A sufficient correlation between paired values could be stated only under conditions of normal room air. With increasing FiO2 (0.4, 0.6, 1.0) the capillary oxygen tension remains behind the arterial one. Giving pure oxygen the capillary tension is nearly half of the arterial value.

Capillaries↗
PubMed1983

Calcium-independent activation of adenylate cyclase by calmodulin.

Adenylate cyclase of Bordetella pertussis is stimulated by calmodulin by two distinct interactions. At low activator concentrations (approximately equal to 1 nM) the process is Ca2+-dependent (i.e. inhibited by EGTA added before calmodulin). High activator concentrations (approximately equal to 0.1-10 microM) stimulate adenylate cyclase also in the presence of EGTA, an effect not accounted for by residual Ca2+ or low concentrations of Ca X calmodulin, which thus appears to be due to calcium-free calmodulin. Some calmodulin dose-response curves show both phases of stimulation, separated by a plateau of activity, and half-maximal activating concentrations differ by 100-300-fold. Both effects are on the V and not the Km for ATP and are not mimicked by 10(5)-fold greater concentrations of parvalbumin or by various polyanions. In addition, adenylate cyclase stimulation at high calmodulin concentrations is greater in the presence of EGTA than in its absence. This enhancement is also produced by 1,10-phenanthroline and 8-hydroxyquinoline but not by non-chelating isomers. These compounds are poor Ca2+ chelators, stimulate at any calmodulin concentration (unlike EGTA), and suggest regulation of this adenylate cyclase by a second metal ion.

Adenylyl Cyclases↗
PubMed1983

Iodide-induced thyrotoxicosis.

Iodide-induced thyrotoxicosis (IIT) occurs in patients with: 1) endemic goiter; 2) nonendemic goiter; 3) no previous thyroid disease. Iodine prophylaxis for endemic goiter caused transient increase of 0.01-0.04% over the basal incidence of hyperthyroidism peaking at 1-3 years and normalizing in 3-10 years despite continued iodide exposure. Elderly subjects with large nodular goiters of long standing are at greater risk. In nonendemic areas, iodine-containing drugs such as amiodarone, radiographic contrast media or iodochlorhydroxyquinoline are implicated in IIT more often than iodides. With nonendemic goiter, IIT occurs more commonly in women whereas, in the absence of preexisting thyroid disease, men are more often affected. In both groups, exophthalmos and antithyroid antibodies are absent, radioiodine uptake is low, there is no thyroid tenderness or pain, and the hyperthyroidism is self-limited (1-6 months) and should thus be treated conservatively. IIT occurs more frequently in areas of marginal iodine intake (Europe) than in the U.S. In view of the extensive exposure to iodine, it is a rare complication in this country. It is postulated that defective autoregulation of hormone biosynthesis may contribute to IIT.

Adolescent↗
PubMed1983

Two transitions of haemoglobin expression in Xenopus: from embryonic to larval and from larval to adult.

Electrophoretic analyses of haemoglobin and globin phenotypes in families of Xenopus borealis and Xenopus l. laevis revealed two developmental haemoglobin transitions during ontogeny. The first transition occurs at the developmental stage when tadpoles begin to feed. It is characterized by the decline of embryonic-specific globins in favour of novel, tadpole-specific globins (X. borealis) correlated to changes in the haemoglobin pattern. We suppose that this switch results from the replacement of a primitive, ventral blood island-dependent erythrocyte population by tadpole erythrocytes from other erythropoietic sites. Several other globin chains and haemoglobins are present in both young tadpoles and throughout larval life. The second, well-known transition occurs during metamorphosis, where all tadpole haemoglobins are replaced by adult haemoglobins composed of entirely different globin chains.

Aging↗
PubMed1983

Biphasic effect of pertussis vaccine on serum insulin in mice.

Administration of pertussis vaccine, consisting of whole, killed Bordetella pertussis organisms, causes hyperinsulinemia and enhanced secretion of insulin in response to a variety of secretagogues in rats and mice. In examining the time course and properties of this phenomenon, we discovered two distinct and separate effects of the bacteria on glucose and insulin levels in mice. First, a heat-stable (80 degrees C for 30 min) component causes a brief hyperinsulinemia which is +measureable by 1 h, maximal at 8 h, and ends in less than 48 h. This effect appears to be due to B. pertussis endotoxin, is mimicked by Escherichia coli endotoxin, and is associated with a transient, mild hypoglycemia. Second, there is a heat-labile component of the B. pertussis organism which induces a sustained (greater than 14 days), dose-dependent hyperinsulinemia which reaches a maximum at 5 to 7 days and has no associated hypoglycemia. The two effects are further distinguishable in that the early, endotoxin-induced hyperinsulinemia exhibits the normal suppressibility by exogenous epinephrine, whereas epinephrine markedly enhances the hyperinsulinemia occurring at 7 days. These two effects of B. pertussis appear to be mediated by different mechanisms and may be important in the well-recognized reactogenicity of pertussis vaccine in humans.

Animals↗