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Biomedical subjects

W Mayr

Publications and source records attributed to W Mayr.

90 records · Page 5Linked to original sources
PubMed1976

Number, location and severity of coronary arterial changes in steelhead trout (Salmo gairdnerii).

Steelhead trout (Salmo gairdnerii) were taken at three stages of sexual maturity to study their coronary arteries for arteriosclerotic lesions. At least 18 sections from the glutaraldehyde- and osmium-fixed arteries were obtained from each fish. Fish in the middle of the spawning migration and sexually mature fish at the spawning ground had lesions in about 20% of the arterial sections. These consisted of focal proliferations of smooth muscle cells projecting into the lumen through the broken elastic lamina with an intact endothelium around them. Sexually mature fish with patches of fungus on their head and back had twice as high a percentage of arterial sections with lesions as the first two groups of fish. Sexually immature fish were not studied. The lesions occurred approximately equally in all sizes of coronary arteries except for very small arteries. All lesions but one were focal; that lesion involved a third of the intima and the media. The lesions have no elastic lamina below the endothelium and seem to have no lipid.

Aging↗
PubMed1975

On the heterogeneity of linkage estimations between LA and four loci of the HL-A system,.

Three cases of crossing over between the LA and FOUR loci of HL-A system are presented in this note. Recombination fractions between those two loci are also calculated from familial data kindly provided by other European laboratories. It is suggested that differences found in maternal and paternal recombination frequency are due to the heterogeneity of estimates of each laboratory.

Child↗
PubMedDate not supplied

[Functional electrostimulation of paraplegic patients--1 year's practical application. Results in patients and experiences].

In October 1982 two patients suffering from paraplegia ware, world wide for the first time, implanted two 8-channel-stimulation-devices at the II. Surgical Clinics Vienna. Four electrodes were fixed to the nervus femoralis and the nervus gluteus inferior with the help of microsurgical techniques. The aim of the operation is to enable the paralysed patient to "stand up himself" and to "cover a short distance on crutches". They must learn to manipulate the implanted "more-channel-device" with their fingers, and to coordinate this with the supporting function and the balance function of their arms. The wheel-chair shall not and cannot be substituted with this method: Not without, but with wheel-chair and functional electrostimulation. A comprising training-programme for building up muscles, balance control and gait training was necessary. After 4 months muscle-force and endurance had increased 200%. The patients could stand up stimulatedly without help between parallel bars. At the rehabilitation center Bad Häring the first steps were done in March 1983 (= 5. month after operation). The greatest success was when a patient could get stimulatedly out of her car and do the through-swing-gait over a distance of 60 meters. After one year the muscle force was quadrupled, the endurance was increased 20-30 times, depending on the type of gait. Both patients are able to walk in the 4-P-gait or swing-through-gait on crutches over short distances without help from others. Riding a bicycle stimulatedly on even ground was demonstrated.

Adult↗
PubMedDate not supplied

Technology and long-term application of an epineural electrode.

An epineural electrode (ENE) was developed to achieve a controllable, progressive muscle contraction and reduce muscle fatigue during functional electrostimulation. In vitro studies of annular (torus-shaped) electrodes have been carried out to select adequate electrode materials and electrode diameters. We investigated the long-term stability of ENEs using different intensities of current (range: 0.8-1.2 mA) in sheep and rat experiments. Depending upon size and material, ENE tolerates anodic and cathodic impulses of up to 1 msec and 8 mA (peak current). ENEs were used during clinical application in four paraplegic patients (16 channel implants) for stimulation of lower extremities, and in nine quadruplegic patients (eight channel implants) for diaphragm pacing, for a total observation time of 37 patient years. The low rate of clinical complications, including no corrosion of the electrodes or significant loss of nerve fibers, seems related to the small dimensions of the electrode (less than 1 mm2).

Animals↗
PubMedDate not supplied

Computerized tomographic (CT) appearance of the myocardium after reversible and irreversible ischemic injury.

Computerized tomographic abnormalities have been observed within hours after coronary occlusion. It has not been determined whether these CT changes are always indicative of irreversible myocardial damage or whether they can be produced by reversible myocardial injury. Accordingly, in the current study, the circumflex coronary arteries of 16 dogs were occluded for 20 minutes (reversible injury) or 40 minutes (irreversible injury) and then reperfused. The animals were sacrificed 24 hours later. Ten minutes prior to sacrifice, eight of the dogs received contrast material intravenously. The electron microscopic changes in the 20-minute occlusion group consisted of reversible damage, while those in the 40-minute group were irreversible. Two of the animals in the 20-minute group showed slightly decreased X-ray density of the infarct in the absence of contrast media, but none showed contrast enhancement of the infarct in the presence of contrast media. All the animals in the 40-minute group showed decreased X-ray density, and all animals that received contrast media had contrast enhancement of the area of ischemic damage. The results of the current study suggest that the decreased X-ray density of the area of ischemic damage on CT scans is due to cellular edema and may be observed in reversible myocardial injury, while delayed contrast enhancement is only associated with, and is indicative of, irreversible myocardial injury.

Animals↗
PubMedDate not supplied

Laryngeal pacemaker: activity of the posterior cricoarytenoid muscle (PCM) and the diaphragm during respiration in sheep.

Electromyograms (EMG) of the PCM and the diaphragm were evaluated in 6 sedated female sheep. Corresponding pneumatograms were recorded simultaneously by means of thermocontrolled respiration flowmeter. Evidence was obtained on considerable intra- and inter-individual differences in the duration of respiratory cycles as well as PCM- and diaphragmatic activity. Most of the evaluated respiratory periods showed either a phase coincidence between the PCM and the diaphragm, or a leading edge of about 40-80 ms of the posticus muscle. Due to this minimal phase shift, the diaphragmatic myogram seems to be a valuable trigger for an external PCM stimulation unit in bilateral recurrent nerve palsy.

Animals↗
PubMedDate not supplied

Multichannel stimulation of phrenic nerves by epineural electrodes. Clinical experience and future developments.

Between 1983 and 1992, 23 patients with complete ventilatory insufficiency of differing etiologies were treated with an eight channel implant (Medimplant Inc., Vienna) for fatigue free stimulation of both phrenic nerves. Data for 15 patients with high spinal cord lesions (ages: 9-51 years) are summarized: 1) level of lesion: C0, 3 patients; C1/C2, 4; C2/C3, 8; 2) time between incident and implantation: 3-14 months; 3) diaphragm training: 1-22 months; 4) chronic pacing: 5-83 months; 5) tracheostomy closed: 7 patients; 6) living permanently at home: 13 patients; 7) respiratory rate per minute: 12-17; 8) duration of inspiration: 1.0-1.3 sec; 9) tidal volume: 7-20 ml/kg body weight; 10) volume per minute: 121-198 ml/kg body weight; 11) pH: 7.39-7.42; 12) pCO2: 22.9-38.6 mmHg; 13) pO2: 81.2-104.5 mmHg; and 14) died by December 1992, 4 patients. All currently available implants for phrenic pacing need an external power supply and radio control. The authors have developed and tested the first fully implantable device. Features of this implant include an electronic circuit based on the microcontroller MC68HC705C8; surface mounted technology (SMD); eight channels; constant current source adjustable to 5 mA in 256 steps, impulse duration: 100-1000 musec, stimulation frequency: 1-33 Hz; and minimum lifetime: 3 years. The implant is programmed via bidirectional radio transmission using an IBM compatible computer. The dimensions, including battery, eight electrode connectors, and antenna, are 67 x 48 x 13 mm. The implant weights 58 g. This new device may improve patients' safety and quality of life in the near future.

Adolescent↗