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Biomedical subjects

T Barth

Publications and source records attributed to T Barth.

At least 91 records · Page 5Linked to original sources
PubMed1980

The term intrinsic sensitivity and its application to the vasopressor action of noradrenaline and vasopressin in arteriosclerotic rats.

The intrinsic sensitivity, i.s., as the quotient of the maximum of the cumulative dose-response curve of an agonist in a pathologically or otherwise changed target object to the maximum of the cumulative dose-response curve of the agonists in the normal target object, has been used to characterize the reaction ability for vasoconstriction of the blood vessel system of the isolated perfused hind legs of arteriosclerotic rats (pretreatment with vitamin D2) on the injection of noradrenaline (NA), 8-lysine-vasopressin (LVP), and a vasopressin preparation with an admixture of oxytocin (VA), respectively. I.s. was found to be 0.80 to NA, 0.32 to LVP, but 1.27 to VA. That means that reaction ability for vasoconstriction of the blood vessel system of vitamin D2-pretreated arteriosclerotic rats is decreased for certain agonists but is increased for others. pD2 value of NA was found to be 4.69 in normal rats and 4.85 in vitamin D2-pretreated rats. The respective data were 5.80 and 6.32 for LVP and 3.58 and 3.88 for VA. Comparing EAm in normal rats, the relation of NA, LVP, VA, prostaglandin F2 alpha, and angiotensin II was about 1 : 1 : 06 : 0.25 : 0.15.

Animals↗
PubMed1979

Vasopressin analogs: sedative properties and passive avoidance behavior in rats.

The effects of several types of vasopressin analogs that are considered to be resistant to some of the physiologically significant enzymatic systems were investigated utilizing rats trained in a passive avoidance task. Enhancement of avoidance latencies was observed 2, 7 and 13 days after the single learning trial when deamino-carbavasopressins, triglycyl-8-lysine-vasopressin or its des-glycinamide derivative, and deamino-D-arginine-vasopressin were given shortly after the learning trial in the dose of 1 microgram s.c. (8-L-Arginine)deamino-6-carba-vasopressin and (8-L-ornithine)deamino-6-carba-vasopressin were also active in the dose of 0.1 microgram. Lysine vasopressin and its des-glycinamide derivative failed to enhance avoidance latencies in part of the experiments if doses of 0.3--3 micrograms were administered and 7 or 13 day intervals were used between the learning and the test trials. Enhancement of avoidance latencies was also observed, if some of the peptides were injected 20 min but not 120 or 180 min before the test trial. Marked depression of exploratory behavior of rats in an open field was found after s.c. injections of low doses (1--3 micrograms kg-1) of deamino-carba-vasopressins. Higher doses (10--30 micrograms kg-1) induced sleep-like immobility not accompanied by ataxia or catalepsy.

Animals↗
PubMed1979

Effect of deamino-dicarba-oxytocin and oxytocin on myoelectrical and mechanical activity of uterus, stomach and small intestine in dog.

In conscious dog deamino-dicarba-oxytocin strongly stimulated a spike activity in the uterus which was more prolonged than that after oxytocin. Both oxytocin and deamino-dicarba-oxytocin inhibited the tone and peristaltic contractions of stomach and small intestines in starving dogs, eliminated the spike discharges, reduced the basic electrical rhythm frequency of the stomach and accelerated the propagation velocity of the slow waves in the small intestine. Only oxytocin, but not its deamino-analogue, reduced the pulse frequency and inhibited the spontaneous contractions of muscle strips isolated from the guinea pig stomach and portal vein.

Action Potentials↗
PubMed1977

[Studies on the use of megestrol acetate for estrus synchronization in heifers].

Megestrol acetate has been tested for its applicability to synchronisation of oestrus in 463 mature heifers in the framework of preclinical and clinical experiments. Clinical tests and studies in the context of laboratory diagnostics have shown that 40 mg/die megestrol acetate, administered in two applications with twelve hours in-between and over 15 days, are necessary for maximum synchronisation effect. The resulting oestrus was found to be prolonged, with ovulations taking place within two or three days. Technological requirements in this context are discussed. Megestrol acetate is found to be suitable for oestrus synchronisation in heifer. Tests conducted under industrialised conditions have shown conception rates to be identical with those obtained by administration of chloromadinone acetate.

Animals↗
PubMed1976

Protracted milk-ejecting effect of some oxytocin analogues in rats.

Protracted effect of [2-0-methyltyrosine]-deamino-1-carba-oxytocin, [2-0-methyltyrosine]-oxytocin and its dimeric form was studied on the mammary gland of lactating rat in vivo. Biphasic course of biological response found for monomers and slow onset of response observed for dimer led to the assumption that the substances behaved like hormonogens.

Animals↗
PubMed1976

Specific antidiuretic effect of [Leu4, D-Arg8] vasotocin and [Mpr1, Leu4, D-Arg8] vasotocin. Comment on the idea of lipophilic properties and position 4.

[Leu4, D-Arg8] vasotocin (I) and [Mpr1, Leu4, D-Arg8] vasotocin (II) possess a considerable and very specific antidiuretic effect. In I, the change of configuration in position 8 caused an increase of the magnitude of the antidiuretic effect. In I, the change of configuration in position 8 caused by two orders and a decrease of the magnitude of the pressor effect by one order. I and II are the first vasotocin analogues reported to have a relatively high and specific antidiuretic effect.

Animals↗
PubMed1975

Vasopressin-sensitive kidney adenylate cyclase. Structural requirements for attachment to the receptor and enzyme activation: studies with vasopressin analogues.

Several vasopressin analogues were tested on pig kidney membranes for their ability to activate adenylate cyclase and to inhibit the binding of [8-lysine]vasopressin. Both the adenylate cyclase activation and hormonal binding were measured on the same enzyme preparation and under identical were measured on the same enzyme preparation and under identical experimental conditions. A preincubation period in the presence of hormone allowed the binding process to reach equilibrium. Peptide concentrations causing half-maximal adenylate cyclase activation (apparent Km) were, in the order of decreasing affinity:2.5 to 7.0 to 7.0 times 10-10 M [8-lysine] vasopressin, 3.1 to 4.0 times 10-9 M [8-arginine] vasopressin, 2.0 to 3.0 times 10-9 M [I,6-alpha-deaminocystathionine, 8-ornithine]vasopressin, 3.1 times 10-7 M des-9-glycineamide[8-lysine]vasopressin, 0.5 to 1.0 times 10-6 M[1,6-alpha-deaminocystathionine, 2-0-tert...

Adenylyl Cyclases↗
PubMed1975

Renal adenylate cyclase activation by amino acylated vasopressin and oxytocin.

Two series of neurohypophysial peptide amino-acylated derivatives were tested for their ability to activate plasma membrane adenylate cyclase prepared from pig or rat kidney. They were firstly [8-lysine]-vasopressin-related derivatives (Na-[Glycyl-Cys]1-[8-Lysine]-vasopressin and Na-[Glycyl-Glycyl-Cys51-[8-Lysine]-vasopressin) and secondly oxytocin-related derivatives (Na-[Glycyl-Cys-a1)-oxytocin, Na-[Leucyl-Glycyl-Glycyl--Cys]-oxytocin, and Na-[Glycyl-Cys]-[2-0methyl tyrosine]-oxtocin). The maximal adenylate cyclase activation induced by these peptides was lower than that induced by their respective parent hormones. After incubation of these analogues with plasma membranes obtained from the renal medulla, no significant release of parent hormones occurred. Good qualitative correlations were observed between relative antidiuretic activities measured in vivo and relative potencies in activating adenylate cyclase. It was concluded that direct action of peptides tested on the kidney is at least partly responsible for their antidiuretic activity in vivo.

Adenylyl Cyclases↗
PubMed1975

Activation of rat kidney adenylate cyclase by vasopressin analogues: lack of correlation with antidiuretic activity.

Vasopressin analogues with enhanced antidiuretic activity in vivo (deamino-[D-arg8]-vasopressin, deamino-6-carba-[Orn8]-vasopressin, deamino-6-carba-[Arg8]-vasopressin, and deamino-6-carba-[D-Arg8]-vasopressin) were tested for their ability to activate rat renal medullary adenylate cyclase and compared to the natural antidiuretic hormones [Arg8]- and [Lys8]-vasopressin. The enzyme preparation used did not inactivate the vasopressins or the analogues tested. The analogues activated adenylate cyclase. However, several of them were far less effective than expected on the basis of their very high in vivo antidiuretic activity. It was concluded that the enhanced in vivo activity reflects greater metabolic stability in vivo rather than enhanced affinity for the renal antidiuretic hormone receptor.

Adenylyl Cyclases↗
PubMed1975

Milk-ejecting and uterotonic activities of oxytocin analogues in rats.

The milk-ejecting activity of oxytocin analogues modified in the aminoterminal part of the molecule was determined in experiment on rats in vivo. As compared with oxytocin, the analogues did not have significantly higher milk-ejecting activity and there was no dissociation of the two basic oxytocin-like activities.

Animals↗