Biomedical subjects

D Wietelmann

Publications and source records attributed to D Wietelmann.

3 recordsLinked to original sources

PubMed1998

[Brain stem glioma].

Brain-stem gliomas occur mainly in childhood and are localized in the mesencephalon, pons and medulla oblongata. Diagnosis is a domain of MRI, requiring T2, T1 and KM. CT shows hemorrhage and calcification well. The criteria are the primary site, size, tumor growth, brain-stem enlargement, delineation, intralesional structure, exophytic components and enhancement. Secondary criteria are herniation, hydrocephalus and liquorgenic seeding. In CT glioma are hypodense, in MRI hyperintense in T2 and hypointense in T1. Enhancement is seen in 25-60% and does not allow differentiation of tumor vs nontumor or gradings. Factors influencing poor outcome are high grade, a short history, cranial nerve involvement, severe brain-stem enlargement, pontine site, diffuse growth and recurrency. The 5-year-survival rate is 30% (after radiation: focal tumors 85%, diffuse 20%). Most frequent are symptoms of brain pressure, cerebellum, cranial nerves and pyramidal tract. There is no agreement on whether biopsy is necessary or not. A diagnosis of tumor is highly suggestive if classical MRI findings fit the clinical history.

Adolescent↗

PubMed1989

Distribution of recurrent inhibition in the cat forelimb.

This chapter reviews experiments on the distribution of recurrent pathways from motor axon collaterals to alpha motoneurones in the brachial enlargement of the cat. In anaesthetized cats intracellular recording from identified forelimb motoneurones was used to reveal the pattern of recurrent inhibition or excitation following stimulation of muscle nerves. The recurrent connections of the motor nuclei acting on the elbow follow the tight mechanical agonism of the muscles involved. Extensive bidirectional recurrent inhibitory connections were found between motor nuclei innervating elbow and wrist muscles. It is suggested that one group of these connections supports the organization of limb extension, the other group organization of limb flexion. The supinator and the pronator teres motornuclei have identical recurrent connections. Co-convergence from elbow flexor and extensor motornuclei in one and the same motoneurone is frequent. It is suggested that this pattern may serve the stabilization of the radio-ulnar plane. Neither homonymous nor heteronymous recurrent actions were observed in the radial motornuclei acting on the digits, which suggests a lack of recurrent axon collaterals in these nuclei. These results draw attention to the fact that recurrent inhibition is not evenly distributed between all limb motor nuclei.

Animals↗

PubMed1988

Recurrent inhibition in the cat distal forelimb.

The pattern of recurrent pathways from motor axon collaterals to motoneurones has been investigated in the spinal cord of anaesthetized cats with intracellular techniques. Only recurrent inhibitory postsynaptic potentials (RIPSPs) were observed so far. They were very pronounced between the mechanical synergists acting at the elbow. The triceps muscles received substantial effects also from the extensor carpi ulnaris (ECU) and from palmar-located medialis (M) and ulnaris (Ul) muscles. The effects were much smaller in the motor nuclei acting on the wrist (ECU, EC radialis (ECR]. The motor nuclei to the muscles acting on the phalanges (extensor digitorum communis and lateralis, extensor indicis proprius, and abductor pollicis longus (EDC, EDL, EIP, APL] neither received nor emitted any recurrent effects, which may indicate a lack of the recurrent system in these distal motor nuclei. A comparison of the recurrent pattern with the distribution of monosynaptic excitation from large muscles spindle afferents (Ia) shows that there is a partial overlap of both systems only at the elbow joint.

Action Potentials↗