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Biomedical subjects

M Mayr

Publications and source records attributed to M Mayr.

At least 19 recordsLinked to original sources
PubMed1995

Rapid adaptation to eccentric exercise-induced muscle damage.

This study examined eccentric exercise-induced muscle damage and rapid adaptation. Twenty-two male subjects performed 70 eccentric actions with the knee extensors. Group A (n = 11) and group B (n = 11) repeated the same exercise 4 and 13 days after the initial bout, respectively. Criterion measures included muscle soreness, muscle force generation (vertical jump height on a Kistler platform), and plasma levels of creatine kinase (CK), slow-twitch skeletal (cardiac beta-type) myosin heavy chains (MHC), and cardiac troponin I. Subjects were tested pre-exercise and up to day 4 following each bout. The initial exercise resulted in an increase in CK and MHC, a decrement in muscle force, and delayed onset muscle soreness in all participants. CK and MHC release correlated closely (rho = 0.73, p = 0.0001), both did not correlate with the decrement in muscle force generation after exercise. Because cardiac troponin I could not be detected in all samples, which excluded a protein release from the heart (cardiac beta-type MHC), this finding provides evidence for a injury of slow-twitch skeletal muscle fibers in response to eccentric contractions. Repetition of the initial eccentric exercise bout after 13 days (group B) did not cause muscle soreness, a decrement in muscle reaction force with vertical jump or significant changes in plasma MHC and CK concentrations, whereas in case of repetition after 4 days (group A) only the significant increases in CK and MHC were abolished. The decrement in reaction force with vertical jump did not differ significantly from that after the initial exercise session, but perceived muscle soreness was less pronounced.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1995

Effects of inotropic stimulation on energy metabolism and systolic function of ischemic right ventricle.

This study determined whether dobutamine enhances regional systolic function in the ischemic right ventricle (RV) at the cost of adverse effects on regional energy metabolism. Seventeen alpha-chloralose-anesthetized, open-chest pigs were studied under four conditions: 1) control; 2) dobutamine infusion (mean dose 9 micrograms.kg-1.min-1); 3) RV ischemia (45 +/- 5% reduction in RV free wall blood flow for 100 min); and 4) continued ischemia with dobutamine. Regional RV free wall high-energy phosphate metabolites were measured by 31P nuclear magnetic resonance (NMR) spectroscopy or by high-speed drill biopsies of the RV free wall. Regional RV free wall substrate and O2 consumption were measured using coronary venous blood sampling. Global RV systolic function was assessed by the maximal first derivative of RV pressure (dP/dtmax), and regional RV free wall systolic function was assessed by systolic segment shortening in the ischemic zone. Right coronary artery constriction caused markedly depressed regional RV systolic function, net lactate production, and coronary venous acidosis. Surprisingly, high-energy phosphates were unchanged compared with control. Addition of dobutamine caused a further decline in coronary venous pH and continued lactate production but did not reduce high-energy phosphates. While dobutamine markedly enhanced global RV systolic function (RV dP/dtmax 201 +/- 19% of control), systolic shortening in the ischemic RV free wall remained severely depressed (47 +/- 18% of control) despite dobutamine. The mechanism of high-energy phosphate preservation is likely due to diminished consumption of ATP in the hypocontractile ischemic region.

Animals↗
PubMed1993

EEG mapping investigations of psychomotor and music perception brain dysfunction in untreated schizophrenic patients.

Twenty-six untreated schizophrenic inpatients and 34 control persons were investigated using 16-channel EEG mapping during resting, manumotor and music perception tasks. Power values of activation tasks were each referenced to a separate, immediately preceding resting condition, using conventional delta, theta, alpha and 2 beta frequency bands. Results in delta and alpha bands, which maximally separated the two groups, are reported only for space reasons. Results indicated a "nonreactivity" (in all frequency bands) on the two activation paradigms in schizophrenic patients as a group. Major gender effects were obtained in normal persons, but not signs of nonreactivity comparable to patients. Subdividing patients exclusively by means of their EEG changes on activation produced meaningful clinical subgroups of "positive/negative" schizophrenics. This latter finding could contribute towards clinical utility of EEG mapping in psychiatry.

Adult↗
PubMed1989

Different anisotropies of movement direction in upper and lower layers of the cat's area 18 and their implications for global optic flow processing.

Cells in Area 18 of awake and behaving cats were tested for directional preference with a large visual noise pattern. Upper and lower layer cells were found to exhibit different anisotropies for movement direction, offset by 90 degrees. These findings could reflect different functions for the global mapping and processing of optic flow field in upper and lower layers.

Animals↗
PubMed1987

Myocardial metabolism of free fatty acids. Studies with 14C-labeled substrates in humans.

Free fatty acids are considered to be the major energy source for the myocardium. To investigate the metabolic fate of this substrate in humans, 24 subjects underwent coronary sinus and arterial catheterization. 13 subjects were healthy volunteers and 11 subjects had symptoms of ischemic heart disease. [1-14C]oleate or [1-14C]palmitate bound to albumin was infused at a constant rate of 25 microCi/h. Oxidation was determined by measuring the 14CO2 production. The data demonstrated that a high percentage (84 +/- 17%) of the palmitate and oleate extracted by the myocardium underwent rapid oxidation. A highly significant correlation was present between the arterial level and the amount oxidized (r = 0.82, P less than 0.001 for palmitate; r = 0.77, P less than 0.001 for oleate). The isotope extraction ratio was greater than the chemical extraction ratio. This difference of 6 +/- 2 nmol/ml of blood in the young normal subjects was significantly less than the 12 +/- 4 nmol/ml observed in the ischemic heart disease patients (P less than 0.001).

Adolescent↗
PubMed1985

Differences in direction specificity of receptive fields in upper and lower layers of the cat's prestriate area 18.

Direction specificity was measured for neurons in area 18 (A18) in penetrations approximately perpendicular to the layers in awake cats. A majority of lower layer cells (below 1.0 mm) preferred stimuli moving at rather orthogonal directions with respect to the preferred directions of the neurons in the upper layers (0-1.0 mm). The results suggest more functional autonomy of the corresponding cortical layers.

Animals↗
PubMed1984

Single cell activity in area 18 of the cat's visual cortex during optokinetic nystagmus.

Single cell activity was recorded in area 18 during optokinetic nystagmus (OKN) in awake cats. The search coil technique was used to record the horizontal and vertical eye movements. Cells showing direction specific responses to a moving large area random dot pattern (70%) were tested with different velocities in the preferred and in the null-direction. Their response characteristics can be classified according to the two phases of the OKN. 41% responded specifically to the retinal slip velocity, having their response optimum at different values between 2 and 100 degrees/s. Additionally, in 60% of all tested cells the resetting saccades of the OKN were correlated with brief activity bursts of 39 ms latency on the average. These results are discussed in terms of two concepts: the classic concept of a corollary discharge from the oculomotor system and the concept of a gating function of the reticular system on thalamic and cortical transmission.

Animals↗
PubMed1978

[Specific glucocorticoid receptor activity in the lungs and concentration of corticosteroids in the plasma of newborn rabbits during the first hours of life (author's transl)].

Nine pure-bred albino New Zealand white rabbits were delivered on the 30th day of gestation (term 31 days) by Caesarean section. The concentration of dexamethasone binding receptors in the cytosol and nucleus of the lungs as well as the total plasma corticosteroid levels were measured in the newborns before the first breath, after 30 min, 1, 2, 4, 6 and 24 h after birth. The level of plasma corticosteroids increased after birth while the concentration of the receptors in the cytosol and nucleus decreased but was still present after 24 h as well as in the lungs of adult animals. A temporary increase in the concentration of the nuclear receptors after 1 and 2 h is explained by the translocation and binding of the abundantly produced steroid-receptor-complex to the nucleus. The stress of hypo- and hyperthermia on the newborns showed variable behaviour with respect to receptor activity. However, the relationship between the corticosteroid levels in the plasma and the concentrations of the receptors in the cytosol and the nucleus of the lungs was similar as in fetuses kept under "physiological" conditions. It may be concluded from these results that in the rabbit the specific glucocorticoid receptor activity in the lungs decreases after birth but is present throughout life.

Adrenal Cortex Hormones↗
PubMed1970

[Rib osteomas].

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Adolescent↗