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Biomedical subjects

M Wittmann

Publications and source records attributed to M Wittmann.

At least 55 records · Page 3Linked to original sources
PubMed1999

Time perception and temporal processing levels of the brain.

A classification is presented to structure divergent empirical findings on temporal mechanisms of the brain. Proceeding from our time experiences of simultaneity, nonsimultaneity, temporal order, duration, and the subjective present, a classification of thresholds is established that marks distinct processes involved in time perception and the temporal control of movements. On the basis of this classification, evidence has been collected that suggests that perception and action share common timing mechanisms. Furthermore, brain structures involved in temporal aspects of behavior on different time scales have been identified--namely, the cerebellum, the basal ganglia, and circumscribed cortical regions. Another question under debate concerns the representational mode in which time is represented in the brain; models suggest neuronal oscillations or interval-based mechanisms.

Animals↗
PubMed1999

[How, when and what can we learn? Temporal and spatial characteristics of sensorimotor coordination].

On the basis of an account on elementary processes of spatio-temporal control of movements and on findings on motor learning, we propose in this article the employment of test and training procedures for motor skills in the training of surgeons. Elementary temporal and spatial factors of motor performance control underly the very precise complex motor behaviour of the activity of a surgeon. An established diagnosis of individual competence in this domain could help the doctors' decisions on whether to take up surgery. Training devices could improve the efficiency of the surgeons' motor functions. The inclusion of knowledge of motor abilities and learning processes could complement the present-day training of surgeons.

Clinical Competence↗
PubMed1990

The influence of psychotropic drugs and releasing hormones on anterior pituitary hormone secretion in healthy subjects and depressed patients.

Pharmacoendocrinological studies have shown that psychotropic drugs with different actions have different effects on anterior pituitary hormone secretion in man. Substances with different effects on the central nervous system are characterized by a different pharmacoendocrinological profile. Studies with various receptor blockers have shown varying influences on the DMI-induced growth hormone, prolactin, and ACTH/cortisol secretion. Growth hormone stimulation was shown to be mediated by alpha 2-receptors and inhibited by beta-receptors. Investigations in male and female endogenous depressive patients demonstrated a significantly blunted growth hormone response to DMI compared with age- and sex-matched healthy subjects. A comparative study in male endogenous depressive patients showed a significantly diminished growth hormone stimulation both after DMI and after growth hormone-releasing hormone compared to healthy male subjects. In further tests a simultaneous application of four releasing hormones (GHRH, CRH, GnRH, TRH) was used. These investigations showed a significantly lower GH stimulation in endogenous depressive patients compared with age- and sex-matched healthy subjects, but not in neurotic depressive or schizophrenic patients. Cortisol stimulation was similar in all groups of patients and healthy subjects. TSH stimulation was significantly lower in endogenous depressive and schizophrenic patients than in healthy subjects. Somatomedin-C concentrations were significantly elevated in endogenous depressed patients compared with healthy subjects. The blunted growth hormone response in endogenous depression could be explained by inhibitory influences such as increased somatomedin-C concentrations or a hyperactivity of central beta-adrenergic-receptors.

Depressive Disorder↗
PubMed1989

[Observations of the birth and suckling behavior of goats].

50 goats of several breeds and crossbreeds as well as their kids were observed. The experiment involved 388 hours of observation over 62 days. The average duration of pregnancy was 151.2 days. In addition to physical characteristics and labored mobility, a tendency toward isolation and characteristic vocalization were noted. The period from onset of birth to the first delivery averaged less than 20 min. Subsequent to delivery the doe arose immediately, followed by the kid in an average of 21 min. Initial suckling by the kids occurred on average 42 min after birth. After an initially high frequency of suckling cycles, the cycle in the following weeks was reduced to 1 to 2 times an hour in the case of a single kid birth, while twins suckled more often. Out of 5,562 observations, only 1% were true cases of suckling from another doe.

Animals↗
PubMed1988

[Simultaneous intra- and extrauterine pregnancy].

A report on a case of simultaneous intrauterine and extrauterine pregnancy associated with right-sided tubal pregnancy and rupture in the eighth week of pregnancy and spontaneous parturition in the 42nd week. The incidence rate and aetiological factors, as well as diagnostic possibilities and differential diagnostic considerations are presented.

Adult↗
PubMed1986

Effect of receptor blockers (methysergide, propranolol, phentolamine, yohimbine and prazosin) on desimipramine-induced pituitary hormone stimulation in humans--I. Growth hormone.

In this report the effects of various receptor blockers on desimipramine (DMI)-induced growth hormone (GH) secretion in healthy male subjects are presented. Each trial consisted of two administrations: one of DMI i.v. alone and one of DMI i.v. in combination with the respective receptor blocker: methysergide (serotonin (5-HT) receptor blocker), propranolol (beta receptor blocker), phentolamine (alpha-1/alpha-2 receptor blocker), yohimbine (alpha-2 greater than alpha-1 receptor blocker), and prazosin (alpha-1 receptor blocker). DMI-induced GH stimulation was not significantly different after DMI i.v. alone (n = 12) than after three days' pretreatment with 12 mg methysergide p.o. in another group of subjects (n = 12). Following combined administration of DMI and propranolol (15 mg i.v.), GH secretion was significantly increased by 25 mg DMI (p less than 0.05) and 50 mg DMI (incomplete block design, n = 18). GH secretion was significantly lower (p less than 0.01) after DMI in combination with 60 mg phentolamine i.v. compared to that after administration of DMI alone in the same group (n = 12). Following 10 mg yohimbine i.v. in combination with DMI (n = 6), the DMI-induced GH increase was also significantly less (p less than 0.05) than that after DMI alone. The DMI-induced GH increase following DMI plus 1 mg prazosin p.o. (n = 12) was comparable to that after DMI alone. The results indicate that the GH-stimulating effect of DMI is primarily related to the ability of DMI to inhibit noradrenaline (NA) reuptake. Should serotonergic receptors be involved in the DMI-induced GH secretion at all, they transmit a positive stimulus. The alpha-1 receptors are most likely not (or not essentially) involved, whereas alpha-2 receptors affect the DMI-induced secretion positively, and beta receptors have an inhibitory effect.

Adolescent↗
PubMed1986

Effects of receptor blockers (methysergide, propranolol, phentolamine, yohimbine and prazosin) on desimipramine-induced pituitary hormone stimulation in humans--II. Prolactin.

In this report the effects of various receptor blockers on desimipramine (DMI)-induced prolactin (PRL) secretion in healthy male subjects are presented. Each trial consisted of two administrations: one of DMI i.v. alone and one of DMI i.v. in combination with the respective receptor blocker: methysergide (serotonin (5-HT) receptor blocker), propranolol (beta receptor blocker), phentolamine (alpha-1/alpha-2 receptor blocker), yohimbine (alpha-2 greater than alpha-1 receptor blocker), and prazosin (alpha-1 receptor blocker). Following administration of methysergide (12 mg p.o., n = 12), a significantly lower (p less than 0.01) DMI-induced PRL secretion compared to DMI alone in another group of subjects (n = 12) was observed. Combined administration with propranolol (15 mg i.v.) significantly enhanced the DMI-induced PRL secretion compared to DMI 50 mg i.v. alone (n = 18, incomplete block design) (p less than 0.01). Neither combined administration with phentolamine (60 mg i.v., n = 12), yohimbine (10 mg i.v., n = 6), nor prazosin (1 mg p.o., n = 12) significantly influenced the DMI-induced PRL secretion compared to DMI alone in the same subjects. The results of the present study, especially the inhibitory effect on DMI-induced PRL secretion of methysergide, indicate that the primarily noradrenaline (NA) and lesser serotonin (5-HT) reuptake inhibiting antidepressant DMI stimulates PRL secretion via 5-HT neurons. Furthermore, the significantly enhanced PRL release following combined administration of DMI and propranolol suggests that a noradrenergic inhibitory effect also may be involved in the transmission of the PRL stimulus.

Blood Glucose↗
PubMed1986

Effects of receptor blockers (methysergide, propranolol, phentolamine, yohimbine and prazosin) on desimipramine-induced pituitary hormone stimulation in humans--III. Hypothalamo-pituitary-adrenocortical axis.

In this report the effects of various receptor blockers on the desimipramine (DMI)-induced cortisol (ACTH) secretion in healthy male subjects are presented. Each trial consisted of two administrations: one of DMI i.v. alone and one of DMI i.v. in combination with the respective receptor blocker, i.e. methysergide (serotonin (5-HT) receptor blocker), propranolol (beta receptor blocker), phentolamine (alpha-1/alpha-2 receptor blocker), yohimbine (alpha-2 greater than alpha-1 receptor blocker), and prazosin (alpha-1 receptor blocker). In addition, the effect of prazosin on DMI-induced ACTH stimulation was examined. DMI-induced cortisol stimulation was not significantly different after DMI alone (n = 12) from that after three days pretreatment with methysergide (12 mg p.o.) in another group of subjects (n = 12). Neither the combination of DMI plus propranolol (15 mg i.v. n = 18, incomplete block design) nor that of DMI plus phentolamine (60 mg i.v. n = 12) had a significant influence on DMI-induced cortisol secretion. Following combined administration with yohimbine (10 mg i.v.), cortisol secretion was higher compared to that after DMI alone in the same group (n = 6). DMI-induced cortisol secretion was significantly lower (p less than 0.01) following combined administration with prazosin (1 mg p.o. n = 12), as was DMI-induced ACTH secretion (p less than 0.05) in these subjects. The findings of these trials, especially those of the prazosin trial, indicate that DMI-induced stimulation of cortisol and ACTH secretion is attributable to the noradrenaline (NA) reuptake inhibiting effect of DMI, and that the stimulus is transmitted with the aid of noradrenergic alpha-1 receptors. Alpha-2 receptors possibly exert a negative influence on this effect.

Blood Glucose↗
PubMed1985

Dose-dependent growth hormone, prolactin and cortisol stimulation after i.v. administration of desimipramine in human subjects.

In previous studies it was shown that the tricyclic antidepressant desimipramine (DMI) had different stimulatory effects on growth hormone (GH), prolactin (PRL), ACTH and cortisol secretion in healthy subjects, depending on the mode of administration. The present study examined the effects following i.v. administration of placebo and DMI (5, 15, 25, 50 and 75 mg) on GH, PRL and cortisol secretion in male subjects (n = 6). This primarily noradrenergic and secondarily serotonergic reuptake-inhibiting substance was found to stimulate the secretion of GH, PRL and cortisol in a dose-dependent manner. Compared to placebo, significant increases occurred in GH (p less than 0.05) and in PRL (p less than 0.05) from a dose of DMI 25 mg on, and in cortisol (p less than 0.05) from 15 mg on. The results indicate that, in addition to the dose, the method of administration influenced the effects of DMI on the three hormones.

Adolescent↗
PubMed1984

Effects of psychotropic drugs (desimipramine, chlorimipramine, sulpiride and diazepam) on the human HPA axis.

The effects of acute administration of different psychotropic drugs on the human hypothalamic pituitary adrenal (HPA) axis were examined in six groups consisting of six healthy male subjects each, compared to placebo. Desimipramine (DMI) (50 mg IV) significantly stimulated ACTH secretion. DMI (25 and 50 mg IV) and chlorimipramine (CI) (25 mg IV) significantly stimulated cortisol, whereas neither sulpiride (100 mg IV) nor diazepam (10 mg IV) significantly affected secretion of cortisol, as compared to placebo. Since DMI primarily inhibits norepinephrine (NE) uptake and CI primarily that of serotonin (5-HT), whereas sulpiride is a dopamine(DA)-receptor blocker and diazepam a GABA-agonistic benzodiazepine derivative, NE and 5-HT uptake-inhibiting antidepressants seem to influence the HPA axis via the central nervous system.

Adolescent↗
PubMed1983

[Palliative intrabronchial laser treatment of malignant bronchial stenosis using the fiberbronchoscope].

During a period of 15 months we performed a laser therapy of bronchi stenosis due to malignant tumors in 28 patients. We used a Neodym-YAG-Laser (MBB-AT, Munich), guided through a fiberbronchoscope (Olympus BF-1 TR). 59% of total-stenoses and 83% of the partly occluded bronchi could be opened sufficiently. During a follow-up period of 12 months (mean 4.7 m) 83% of the bronchi remained open. According to our experience, fractional tissue removal is the method of choice rather than all-at-once coagulation since tissue edema may cause bronchial occlusion 1 to 3 days after treatment. We think, if surgical treatment is ruled out, intrabronchial laser coagulation is an alternative with little impairment of the patient to prevent hypoventilation and repair functional conditions.

Adenocarcinoma↗