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Biomedical subjects

V Maier

Publications and source records attributed to V Maier.

17 recordsLinked to original sources
PubMed1992

Dilatory and inotropic effects of corticotropin-releasing factor (CRF) on the isolated heart. Effects on atrial natriuretic peptide (ANP) release.

The effects of CRF administration on cardiac performance, coronary flow and ANP release were investigated in the rat heart. Isolated hearts were perfused at a constant filling pressure according to working heart model with a Krebs-Henseleit solution containing glucose and insulin, saturated with a gas mixture containing 95% O2 and 5% CO2. Administration of CRF via a cannula into the left atrium elicited a prolonged increase in the coronary flow rate and a transient increase in the aortic pressure resulting in an overall increase in the pressure-volume work. The oxygen consumption, after the administration of CRF, increased in accordance with the cardiac effort. No changes were observed in the spontaneous heart rate. Furthermore, administration of CRF induced a short-term increase of ANP release into the coronary perfusate. Our experiments suggest that administration of CRF produces a prolonged dilatory effect on the coronary arteries while producing a transient positive inotropic effect and a transient increase of ANP release on the isolated rat heart.

Animals↗
PubMed1992

Contribution of postprandial amino acid levels to stimulation of insulin, glucagon, and pancreatic polypeptide in humans.

The present study was designed to examine the contribution of the postprandial increase of plasma amino acids after ingestion of a protein-rich meal to the rise of the three pancreatic hormones insulin, glucagon, and pancreatic polypeptide (PP). A mixed amino acid solution was designed, which permitted a fairly close imitation of the arterial plasma pattern of the 21 amino acids that rise after ingestion of a 200-g porcine steak meal. In 10 healthy subjects the intravenous infusion of this mixed amino acid solution at a rate of 10 g/h elicited a rise of the 21 amino acids examined that correlated well with the postprandial increase (r = 0.89, p < 0.001). The maximal rise of plasma insulin (64 +/- 5 pmol/L) and glucagon (630 +/- 21 ng/L) was not significantly different from the postprandial increase of these two hormones (49 +/- 4 pmol/L and 780 +/- 28 ng/L, respectively). PP levels rose by 316 +/- 33 ng/L postprandially, which was clearly above the increase of 112 +/- 13 ng/L during intravenous amino acids (p < 0.01). In conclusion, the present data demonstrate that the postprandial rise of amino acid levels in arterialized venous plasma can account for most if not all of the postprandial increase of insulin and glucagon during the ingestion of a protein-rich meal. In contrast, only 35% of postprandial PP levels can be ascribed to the rise of plasma amino acids. In contrast to the effect of carbohydrate-rich meals, an enteric augmentation of insulin release seems to be of minor and possibly of no importance during ingestion of protein-rich meals.

Adult↗
PubMed1991

Periodic hypersomnia: case report with biochemical and EEG findings.

We report on a 23-year-old patient with periodic hypersomnia. Electroencephalographic (EEG) background activity for this individual was slightly slowed in the EEG during an episode of hypersomnia, and intermittent slow activity was found in addition. Usual laboratory parameters were normal; however, leucine-enkephalin was markedly elevated in the plasma at that time, whereas free cysteine could not be demonstrated. Clinical findings were normal in the following years, and the EEG background activity returned to normal; leucine-enkephalin and cysteine also returned to normal values.

Adult↗
PubMed1991

Comparison of neural activity in the supplementary motor area and in the primary motor cortex in monkeys.

Neuronal activity recorded from the primary motor cortex (MI) and from the supplementary motor area (SMA) was compared in two monkeys trained to perform conditioned arm movements. A handle had to be held in a central waiting position until a visual go and cueing signal indicated to the monkey to move the handle either to a medial or to a lateral target zone (choice reaction time paradigm). Unit and representative electromyographic data were analyzed in relation either to the go signal or to movement onset. In 240 penetrations, 431 SMA neurons and 353 MI neurons were found with activity related to the task. The majority of neurons (303 in MI, 290 in SMA) displayed activity changes after the go signal and before movement onset. Of these "short-lead neurons", 71% in MI and 41% in SMA were clearly related to movement execution. The distribution of lead times in MI and SMA neurons was completely overlapping without any statistical difference among subgroups. The remaining neurons were as well related to the go signal as to movement onset, or were better related to the visual go signal. The response latencies to this signal were not statistically different in SMA and MI neurons. Activity changes during the waiting period was observed more frequently in SMA (47%) than in MI (32%); modulations restricted to the waiting period occurred in 14% of SMA neurons, but were exceptional in MI neurons (3%). It is concluded from these experiments that a surprisingly large proportion of SMA neurons have "MI-like" properties, in that they are temporally recruited together with MI neurons, with similar patterns of discharges during the task. This then suggests that the two interconnected areas operate in parallel. A population of SMA neurons is involved in some processing that is not as predominantly expressed in MI. This activity could relate to sensory, timing, or other higher-order aspects of response preparation, and/or motor functions such as postural stabilization.

Animals↗
PubMed1991

Effect of CCK on food intake in man: physiological or pharmacological effect?

The present study was designed to determine in humans the dose of CCK which suppresses food intake. 18 male subjects received in randomized order either i.v. saline or Thr28 Nle31 CCK 25-33 (CCK-9) at 100 or 500 pmol/kgh, respectively. In addition, 7 subjects received CCK together with the opiate receptor antagonist naloxone to examine if activation of endogenous opioids might interfere with the potential satiating effect of CCK. Food intake during saline was 32 +/- 2 sandwiches (mean +/- SEM), during CCK-9 100 pmol/kgh 28 +/- 2 (n.s.) and only 12 +/- 3 during CCK-9 500 pmol/kgh (p less than 0.01). The respective water intake was 730 +/- 70 ml, 590 +/- 60 ml (n.s.) and 320 +/- 50 ml (p less than 0.01). Naloxone further reduced food and water intake during high but not low dose CCK or saline. During saline postprandial insulin levels rose by 49 +/- 6 microU/ml within 45 min which was attenuated during low dose (23 +/- 6 microU/ml; p less than 0.01) and high dose CCK-9 (1 +/- 1 microU/ml; p less than 0.001). Plasma glucagon did not change in control or CCK experiments. The postprandial rise of pancreatic polypeptide was attenuated during high dose CCK. Naloxone had no effect on the hormonal response except for a prolonged reduction of insulin and glucose levels following high dose CCK + naloxone. Plasma CCK levels rose by 5.4 pmol/l in controls but by 55 and 255 pmol/l during the low and high dose CCK infusion, respectively. These data demonstrate that suppression of food intake in man by i.v. CCK is a pharmacological rather than a physiological effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Ultrastructural localization of prolactin-like antigenic determinants in neurosecretory cells in the brain of the honeybee (Apis mellifica).

With two different antisera to human prolactin (hPRL), the ultrastructural localization of PRL-like material in the bee brain is examined by means of the protein-A-gold method at the electron microscopical level. Labelling is found in electron-dense granules of medium size (150-200 nm in diameter) for the first time in insects. Such granules are distributed in the cytoplasm of the neurosecretory cells, their axons and their axon-terminals. The electron-dense granule is one criterion for identifying a neurosecretory cell. In the honeybee, hPRL-like material may serve as an old neurohormone with respect to its evolution.

Animals↗
PubMed1979

D-Trp8-D-Cys14-somatostatin--demonstration of its differential suppressive activity in juvenile diabetics.

In 8 insulin-dependent diabetics, the effect of D-Trp8-D-Cys14-somatostatin on blood glucose, growth hormone, and glucagon levels as well as on insulin requirements from an artificial endocrine pancreas was studied during a balanced meal. The somatostatin analogue was infused at a rate of 25 microgram/h preceeded by a bolus injection of 25 microgram 30 minutes before ingestion of the meal. At this dose the analogue had no effect on glucagon levels and insulin requirements from the artificial pancreas. On the other hand, there was a significant lowering effect on fasting blood glucose levels, possibly indicating a direct inhibition of hepatic glucose production. Furthermore, there might be a slight effect on growth hormone levels, as was demonstrated by a rebound increase after termination of analogue infusion.

Adolescent↗
PubMed1979

Influence of insulin infusion kinetics of an artificial beta cell on blood glucose control in insulin-dependent diabetics.

The influence of different control modes for insulin infusion with an artificial beta cell was examined in 41 insulin-dependent diabetics. In 21 Patients, oral glucose tolerance tests were performed with control modes characterized either by low dynamic and high static gain (type I, 10 patients) or high dynamic and low static gain (type III, 11 patients). The change from type I to type III control mode effected an increase of initial insulin infusion rates (91 +/- 59 to 313 +/- 81 mU/min 10-20 min after glucose ingestion) and a decrease of infusion rates during the following phase of the 3-hour observation period (28.2 +/- 4.2 to 18.1 +/- 2.8 U) in patients whose blood glucose curves were completely normalized. Suppression of plasma glucagon levels, observed in 5 healthy control subjects, was not fully restored to normal in these patients. In another 20 insulin-dependent diabetics, daily insulin requirements form the artificial beta cell were determined by employing two control modes (types II and III) comparable in static control but different in dynamic control. Gain of dynamic control, especially in the range of falling glucose levels, was higher in type III control mode (15 patients) than in type II mode (5 patients). These insulin requirements were compared to the insulin doses necessary for subcutaneous treatment. While intravenous insulin requirements were much higher when type II control mode was employed (78.2 +/- 10.2%), during application of type III mode, intravenous insulin requirements were only 10.8 +/- 5.5% higher than subcutaneous doses. We conclude from these data that early increases in insulin infusion rates followed by a rapid decrease seem to reduce insulin requirements after glucose ingestion. A high-gain dynamic control is the basis for this insulin infusion profile.

Adolescent↗
PubMed1979

The effect of three days of blood glucose normalization by means of an "artificial endocrine pancreas" on the concentrations of growth hormone, glucagon, and cortisol in juvenile diabetics.

Glucagon, growth hormone, and cortisol secretion was studied in seven male insulin-dependent diabetics under conventional subcutaneous insulin therapy and after three days of blood glucose normalization attained by the artificial endocrine pancreas (Biostator-GCIIS). The diurnal hormonal profiles under the two types of therapy were compared. Six healthy male students served as control group. A three-day period of blood glucose normalization in insulin-dependent diabetic can restore glucagon secretion to normal. Growth hormone secretion is decreased but not completely normalised. Cortisol secretion is slightly decreased. It is concluded that prolonged normoglycemia achieved by means of an artificial endocrine pancreas may completely control endocrine abnormalities in insulin-dependent diabetics.

Adult↗
PubMed1978

Transmitter mediated arginine vasopressin release from superfused hypothalamus and pituitary gland.

The study was designed to investigate the effect of various neurotransmitters on the hypothalamus and pituitary gland to determine the sites of their action. Superfused isolated rat hypothalami and pituitary glands demonstrated basal secretion of arginine vasopressin (AVP) and repeated response to stimulation thus showing the viability of the preparation. Acetylcholine and histamine stimulated the release of AVP at the hypothalamic and pituitary levels; dopamine and norepinephrine released AVP in a dose related manner only from the hypothalamus; angiotensin II released AVP in the same fashion only from the pituitary gland. AVP secretion stimulated by dopamine and norepinephrine may represent synaptic inputs which are localized at the hypothalamus and must be distinguished from the site of action at the pituitary gland of angiotensin II.

Acetylcholine↗
PubMed1977

Insulin release from collagenase-isolated islets of rat pancreas in the presence of cyclic AMP and somatostatin.

In order to study the role of cyclic AMP in the inhibition by somatostatin of glucose-induced insulin release, the effect of somatostatin on the potentiation by dibutyryl-cyclic AMP (db-cAMP) of insulin release from isolated pancreatic islets of rats was examined. Isolated islets were obtained from the rat pancreas by the collagenase method. Ten islets were incubated for periods of 30 min in Krebs-Ringer bicarbonate buffer containg albumin and glucose 2.0 mg/ml in the presence or absence of somatostatin (1 microgram/ml or 100 ng/ml) and/or db-cAMP 1 mM. Glucose-induced insulin release was reduced by somatostatin in concentrations of 1 microgram/ml. Somatostatin in a concentration of 100 ng/ml significantly abolished the potentiation by db-cAMP of insulin release (p less than 0;01), in spite of exerting no inhibition of glucose-induced insulin release. However, in the presence of theophylline 5 mM, somatostatin 100 ng/ml did not show that inhibitory effect on the potentiated insulin release.

Animals↗
PubMed1977

Improved method and its clinical application of a radioimmunoassay of arginine vasopressin in human serum.

A sensitive and specific double-antibody radioimmunoassay for measuring circulating levels of arginine vasopressin in human serum is described. It is possible to detect arginine vasopressin levels of 1 microU/ml serum without extraction procedure. Normal subjects were found to have 5.7 +/- 4.4 microU/ml after a dehydration period of 12 hours. Water loading diminished arginine vasopressin concentrations while dehydration increased it. Application of furosemide over a period of 14 days brought forth constant but not significant decreases. Subjects suffering from psychogenic polydipsia showed normal levels in spite of drinking 8-12 liters of water per day. Patients suffering from liver cirrhosis with ascites showed significantly higher arginine vasopressin levels, approaching normal values, when ascites was under control.

Arginine Vasopressin↗
PubMed1975

Interactions of concanavalin A with isolated pancreatic islets.

Pancreatic islets of mice were isolated by the collagenase method. After a preincubation period of 20 min they were incubated in Krebs-Ringer-albumin buffer in the presence of glucose. Concanavalin A (2 mg/ml) inhibits the glucose-induced release of insulin; this same property is shown by Concanavalin A bound to nonphagocytosable beads of Sephrose at lower concentrations (0.4 mg/ml). In pancreatic islets stimulated by tolbutamide, glibenclamide or arginine the secretion of insulin is not inhibited in the presence of Concanavalin A. The incorporation of tritiated leucine is not influenced by Concanavalin A. Since desialized pancreatic islets react in the same way the glucose-induced secretion of insulin appears to be a membrane-dependent process.

Animals↗
PubMedDate not supplied

Glucagon as a non species-specific regulator of the glycaemia in honeybee (Apis mellifica).

It is known that hormones which exist in vertebrates are very old in respect to evolution. The presence of insulin and glucagon in insects had already been suggested in the early sixties. In this study honeybees are living in an "artificial hive" in the German laboratory under exactly standardized conditions. In the French laboratory standardized conditions yielded because only emerging worker bees were used i.e. those which were just slipping from the honeycomb alveoli. It seemed of interest to introduce an in vivo model in which one animal is punctured at tergum III in order to gain 1 microliter hemolymph using a glass capillary tube . *For the first time it is possible to puncture one animal three times. The main sugars in the hemolymph were silylated* and determined by gas chromatography in the German resp. by nano thin layer chromatography in the French laboratory. 0-500 ng porcine glucagon resp. the same amount of purified bee glucagon were injected to the animals and the action on carbohydrates observed during 2 hours. Similar to the action of glucagon in vertebrates, carbohydrate metabolism although completely different, appears to be regulated in part in this invertebrate stem. It is concluded that glucagon may represent a key hormone for degradation of the glycogen stores.

Acclimatization↗