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Biomedical subjects

J Dietz

Publications and source records attributed to J Dietz.

At least 37 records · Page 2Linked to original sources
PubMed1991

Acute hypoxia-induced diuresis in rats.

Acute hypoxia elicits diuresis, natriuresis, and hypotension in many mammalian species, but the cause of this effect remains unclear. The present study, using chronically instrumented rats, was undertaken to assess a possible role of atrial natriuretic factor (ANF) in these hypoxic responses. Acute hypoxia (10.5% O2) increased urine output and sodium and potassium excretion. Systemic arterial blood pressure fell during acute hypoxia. Levels of ANF significantly increased with acute hypoxia. The plasma levels of ANF during acute hypoxia were similar to those found following bolus doses of exogenous ANF which are known to cause diuresis, natriuresis and a fall in blood pressure. Increased ANF levels may play a role in mediating physiologic responses to hypoxia in the rat.

Animals↗
PubMed1990

Differential regulation of two glucose transporters by chronic growth hormone treatment of cultured 3T3-F442A adipose cells.

New methods for the analysis of glucose transporters were used to analyze the molecular mechanisms involved in the insulin-antagonistic effects of growth hormone (GH), which is known as a diabetogenic hormone. The ability of GH to alter the number and mRNA levels of two different glucose transporters in cultured 3T3-F442A adipocytes was investigated using specific antibodies and cDNA probes. At concentrations of GH as low as 0.5 and 5 ng/ml and at incubation times as short as 4 h, GH decreased rates of 2-deoxyglucose uptake in 3T3-F442A adipocytes. 3-O-Methyl-D-glucose uptake was inhibited to an extent similar to that of 2-deoxyglucose uptake (60-80%) after a 24-h incubation with GH (500 ng/ml), indicating that GH inhibits glucose metabolism specifically at the step of glucose transport. To determine whether reduced rates of glucose transport might result from reduced numbers of glucose transporters, whole cell lysates were prepared from GH-treated cells and subjected to immunoblotting using antibodies that identify Glut 1 (HepG2/rat brain) and Glut 4 (muscle/adipose) transporters. GH caused a time- and dose-dependent decrease in the number of Glut 1 transporters in the cell. Northern and slot-blot analyses showed a GH-induced dose-dependent decrease in levels of Glut 1 mRNA. In contrast, levels of Glut 4 transporter and mRNA were unchanged by GH. These data suggest that GH regulates Glut 1 and Glut 4 transporters differentially and that it exerts its inhibitory effect on glucose uptake at least in part by decreasing the synthesis of Glut 1 transporters. These studies provide the first evidence that GH regulates a key gene in metabolic regulation and can interfere with gene expression.

Adipose Tissue↗
PubMed1982

Myoclonus and ocular oscillations induced by L-tryptophan.

A patient with chronic manic-depressive illness developed generalized myoclonus and spontaneous ocular oscillations after a single 2 gm dose of L-tryptophan. She had been pretreated with both a tricyclic antidepressant and a monoamine oxidase inhibitor. The involuntary movements gradually disappeared within 24 hours after the drugs were discontinued. Electrooculographic recording 7 hours after onset of the abnormal eye movements revealed square-wave jerks and hypometric voluntary saccades. Pursuit as well as optokinetic and vestibular slow phases were normal except for superimposition of the square-wave jerks. Repeat recording 24 hours later was entirely normal.

Adult↗
PubMed1982

Energy-dependent extrusion of cyclic 3',5'-adenosine-monophosphate. A drug-sensitive regulatory mechanism for the intracellular nucleotide concentration in rat erythrocytes.

In reticulocyte-rich suspensions of red blood cells from rats extrusion of cAMP as a regulatory mechanism of intracellular cAMP was investigated. In response to isoprenaline and/or the phosphodiesterase inhibitors Ro 20-1724 and rolipram extrusion of cAMP increases dependent on the concentration of the drugs and time of exposure. However, these drugs exert their effects on the extrusion of cAMP only indirectly, i.e. via increased intracellular levels of cAMP, since the respective EC50-values of the drugs for intracellular accumulation and extrusion of cAMP are identical (isoprenaline: approximately 50 nM; rolipram: approximately 1 microM; Ro 20-1724: 15 microM). The dependence of the rate of extrusion on intracellular levels of cAMP is characterized by a typical concentration-effect relationship from which a maximal capacity of cAMP extrusion of 3-6 nmol/10 min/10(9) cells and a half maximal effective intracellular cAMP concentration of 40-50 nmol/10(9) cells can be derived. This relationship has been inferred from either kinetic or steady-state approaches. At rapidly changing intracellular levels of cAMP an apparent time lag of extracellular cAMP accumulation is obligatorily conditioned by this relationship. Vasodilating drugs which lower the ATP content of the cells as well as the uncoupler of oxidative phosphorylation, FCCP, inhibit the extrusive process (papaverine greater than FCCP greater than dipyridamole greater than dilazep much greater than hexobendine greater than or equal to carbocromene) leading to a 3-5-fold increase of the intrato extracellular concentration gradient of cAMP. It is concluded that extrusion of cAMP is a saturable and energy-dependent process which regulates the intracellular cAMP concentration independent of the activities of adenylate cyclase and phosphodiesterase.

Adenosine Triphosphate↗
PubMed1981

Cystinuria in the maned wolf of South America.

Of 42 maned wolves in zoos or live-trapped in Brazil, 34 had excessive cystine in their urine. Renal clearance studies of five of the affected wolves revealed a variable defect for the reabsorption of cystine and dibasic amino acids. The renal tubular handling of other solutes including glucose, phosphate, sodium, potassium, and uric acid was considered normal. Urinary calculi composed of cystine were found in four wolves and proved fatal in three of them. With the exception of the high incidence in this species, this hereditary disease resembles the disorder described in dogs and humans.

Amino Acids↗
PubMed1981

[Experiences with the total endoprosthesis of the knee joint to Blauth (author's transl)].

Following a brief review of the differential indication for total prosthesis of the knee joint, the article reports on 136 implantations of the hinged prosthesis according to Blauth. In 94% of the cases the results were good and very good (n = 66) within an average follow-up examination period of 2 years. One of the main features of the success of the treatment is the relief from pain achieved with this prosthesis provided it functions well. Differentation of the treatment results according to the basic underlying disease (rheumatoid arthritis; pangonarthrosis) shows that good results were achieved particularly in relatively young rheumatic patients thanks to their co-operative capacity during the follow-up treatment period. The following relevant complications were seen among the 136 implantations: one early infection, three late infections, two deaths due to cardiovascular general complications, and one fatal case of sepsis as a result of a late infection. The rate of the aseptic loosenings was 1.5% only, and hence favourably low, as was evident from the follow-up examinations of the implanted knee joints. Lateralisation of the patella, which occurred in one-half of the cases, is attributed by us to an intraoperative weakening of the medial patella ligament (which acts as an auxiliary extension apparatus). We intend to counteract this in future via an additional lateral capsular discision. The follow-up study presented here confirms the efficiency of the Blauth model, as well as the generally valid indication criteria for total implantation of the knee joint.

Adult↗
PubMed1981

[Comments on coxa vara infantum with shearing of the epiphysis of the femoral head in Seckel's syndrome (author's transl)].

Seckel's syndrome, also known as bird-headed dwarf of Seckel or nanocephalic dwarf, occurs very rarely within the field of orthopaedic diseases. 20 cases only have been described in literature so far. The article gives a detailed explanation of the syndrome. In the two patients discussed here, the specifically orthopaedic aspect follows from an accompanying coxa vara infantum with shearing of the epiphysis of the femoral head. The article describes the pre-operative and post-operative clinical and roentgenological findings.

Dwarfism↗
PubMed1979

Inversal relationship between basal adenylcyclase activity and maximal degree of stimulation in membranes of red blood cells from rats.

The degree of stimulation of adenylcyclase activity, in membranes from immature red blood cells from rats, brought about by isoprenaline, guanylyl-imidodiphosphate and sodium fluoride is strongly dependent on the basal activity of the enzyme. The inversal relationship between basal activity and the maximal degree of stimulation by (--) isoprenaline, shows an apparent seasonal dependence.

Adenylyl Cyclases↗
PubMed1978

Direct characterization of beta-adrenoceptors in membranes of immature red blood cells from rats.

By means of the radioactive antagonist ligand (3H)(-) dihydroalprenolol (DHAP) specific binding sites were identified in membrane preparations from red blood cells from rats. These specific sites were characterized as beta-adrenoceptors because of the following reasons: Specific binding of DHAP (in contrast to unspecific binding) was dependent on temperature and time of incubation. Furthermore, specific binding of DHAP showed saturability, temperature-dependent reversibility and high affinity (KD-value of DHAP = 6.51 nM). Specific binding of DHAP was competitively inhibited by beta-adrenergic antagonists (pindolol greater than alprenolol greater than or equal to propranolol greater than practolol) and agonists (isoprenaline greater than adrenaline). The (-) enantiomers of pindolol and isoprenaline showed pronounced higher affinities for the receptor sites than the respective (+) enantiomers. The receptor density in the membrane preparations (pmoles/mg protein) was strongly dependent on the degree of reticulocytosis: The Bmax-values increased more than 4 to 5 fold without alteration of the respective KD-values when reticulocyte counts were enhanced from 3 to 80% treatment of the animals with increasing doses of acetyl phenylhydrazine.

Alprenolol↗
PubMed1978

Correlation between isoprenaline-stimulated synthesis of cyclic AMP and occurrence of beta-adrenoreceptors in immature erythrocytes from rats.

When increasing reticulocytosis (up to 80%) was induced in rats by treatment with acetyl-phenylhydrazine (up to 70 mg/kg on 3 consecutive days) synthesis of cAMP stimulated by isoprenaline in intact red blood cells and in the related membrane preparations increased up to 100-fold. At the same time the density of beta-adrenoreceptor sites (measured by ligand binding with (3H)(-)-dihydroalprenolol) in the related membrane preparations was only increased about 5-fold. There was however a linear correlation between the increase of isoprenaline-stimulated enzyme activity and the receptor density in membrane preparations. The results indicate that mature red cells contain beta-adrenoreceptor sites but little or not adenyl cyclase activity. Thus, during the maturation process of these cells, enzyme activity and receptor densities decrease at different speeds indicating a different turnover of these two entities of the cytoplasmic membrane.

Adenylyl Cyclases↗
PubMed1977

Effect of volume expansion and veratrine on salt gland secretion in the goose.

The influence of acute intravascular volume expansion on salt gland secretion of conscious, adult geese was investigated. The intravenous administration of 5% dextran in Krebs-bicarbonate-Ringer solution in an amount equivalent to 30% of the estimated blood volume caused a transient but highly significant increase in salt gland secretion independent of changes in plasma osmolality or sodium concentration. Intravenous veratrine (60 microng) caused a similar increase in salt gland secretion only when administered after the volume load. Intravenous 5% NaCl always caused a prolonged and significant increase in salt gland secretion which was not potentiated by veratrine. Volume expansion and hypertonic saline caused a significant tachycardia while veratrine caused a significant bradycardia. It is concluded that a volume component may contribute to the initiation of salt gland secretion in the goose and that the peripheral receptor involved is most likely vascular in origin.

Animals↗