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Biomedical subjects

E Koenig

Publications and source records attributed to E Koenig.

At least 73 records · Page 4Linked to original sources
PubMed1981

Aftereffects of vestibular and optokinetic stimulation and their interaction.

In humans the influence of prior vestibular stimulation (3, 6, 9, 12, and 18 degrees/second2 for 10 seconds) and subsequent whole-field optokinetic stimulation (30, 60, 90, 120, and 180 degrees/second for 1 minute) or the presentation of a stationary pattern on after-nystagmus (AN) was studied. For comparison, pure vestibular and pure optokinetic stimuli also were employed. The presentation of a stationary pattern resulted in suppression of vestibular nystagmus, which recovered after the termination of fixation. Fixation during the period of AN I did not inhibit an AN II. During the combinations of vestibular and optokinetic stimuli when the elicited vestibular (VN) and optokinetic nystagmus (OKN) had the same direction, there was a weak AN I toward the direction of the preceding VN and OKN, and a strong AN II toward the opposite side. When VN had been opposite to the subsequent OKN, there was a strong AN I toward the direction of OKN; AN II toward the opposite direction was small or mostly absent. Thus, AN was always stronger into the direction opposite to the previously elicited VN, indicating that the vestibular afference is the predominant input to the VAN II-integrator.

Acceleration↗
PubMed1980

The preparation of a sarcolemmal fraction from evacuated muscle slices.

A novel procedure is described for preparing a plasma membrane fraction from skeletal muscle (e.i., sarcolemma). The procedure entails evacuating the myoplasm from muscle slices as a preliminary step to homogenization and fractionation. The evacuated muscle slices are composed of a stroma-containing sarcolemma, which is then homogenized and fractionated, utilizing a sequence of differential and discontinuous sucrose density gradient centrifugations. On the basis of electron microscopy, selective enzyme markers and alpha-bungarotoxin binding in innervated and denervated muscles, the fraction most enriched with sarcolemma is recovered from the 0.5/0.7 M interface of a discontinuous sucrose gradient.

Acetylcholine↗
PubMed1980

Effects of denervation on the composition and synthesis of sarcolemmal proteins.

In vitro synthesis of proteins and changes in polypeptide composition of sarcolemma were studied in innervated and denervated extensor digitorum longus muscle of the rat. A technique of evacuating myoplasm from muscle slices was used as a preliminary step in the preparation of three membrane fractions, M, H and S, containing sarcolemma. On the basis of findings from the previous study and the present investigation, it was concluded that the M fraction was most enriched with extrajunctional sarcolemma. In vitro incorporation of [3H]leucine into membrane proteins of the M fraction showed an apparent linear increase in the rate of protein synthesis from 1-10 days after denervation. The relative increase at 10 days was 137% greater than that of innervated controls. Fractions H and S showed a smaller relative increase. Polypeptide composition of M, H and S fractions based on SDS gel electrophoresis of innervated and denervated muscle, showed qualitative and quantitative changes. The most striking difference was a nominal 29 000 component in M that constituted a disproportionately large peak. Following 10 days of denervation the M fraction underwent significant compositional changes in its electrophoretic profile, the most dramatic of which was a large reduction in the proportion of the 19 000 component. The denervation-induced compositional change is discussed in light of known alterations in the chloride conductance of the muscle plasmalemma.

Animals↗
PubMed1979

Ribosomal RNA in Mauthner axon: implications for a protein synthesizing machinery in the myelinated axon.

RNA was extracted from myelin-free Mauthner axons of the goldfish on a microscale and fractionated by microelectrophoresis. Microextracts showed the presence of nominal 26 SE, 18 SE, 5 SE and 4 SE components, which co-migrated with rRNA from fish brain. In addition, a non-ribosomal 15 SE component was present in axon microextracts, but not in RNA extracts of fish brain or of myelin sheath from Mauthner axon, indicating an unusual enrichment of a putative mRNA class. Evidence was presented to support the contention that axonal rRNA was not due to contamination from the myelin sheath. Possible reasons for the lack of ultrastructural evidence for axoplasmic ribosomes are discussed.

Animals↗
PubMed1978

Identification of locally synthesized proteins in proximal stump axons of the neurotomized hypoglossal nerve.

Analysis of radioactively labeled proteins was carried out on microsamples of myelin-free axons isolated from neurotomized and normal hypoglossal nerves of the rabbit after in vitro incubation with [3H]leucine. Major radioactive peaks in axonal endings of the proximal stump 18 h after neurotomy, identified by autoradiography of microelectrophoregrams, had apparent molecular weights of 52,000d, 41,000d and 18,000d. This autoradiographic pattern differed from that of axons of untransected nerve in: (1) not having a prominent 100,000d component present in the latter; and (2) having a novel 41,000d component not present in the latter. Labeling of axonal proteins in the proximal stump in vivo resulted in no apparent retrograde transport during the 5 h studied. Autoradiographic analysis of labeled proteins released by nerves into the medium during in vitro incubation revealed a major radioactive peak with an apparent molecular weight of 77,000d. Attempts to demonstrate uptake of the 77,000d component by unlabeled axons in vitro and in vivo were unsuccessful. The hypothesis was advanced that the 52,000d protein may be neurofilament protein, and the possible significance of the 41,000d component was discussed in the contexts of the pathology of the traumatized proximal stump, and of the antecedent events leading to axonal outgrowth.

Animals↗
PubMed1977

Isolation of non-myelin plasma membranes unique to white matter.

A procedure is described for isolating two membrane fractions from rabbit spinal-cord white matter enriched with 5'-nucleotidase, a nonspecific plasma membrane marker, 2',3'-cyclic nucleotide phosphohydrolase, an oligodendroglial plasma membrane marker, and acetylcholinesterase, an axonal plasma membrane marker. While the two membrane fractions exhibited similar enrichments with respect to cyclic nucleotide phosphohydrolase, enrichments of 5'-nucleotidase and acetylcholinesterase were significantly greater in the heavier membrane fraction. Selected enzyme markers for cyto- and mitochondrial membranes were not detected. Moreover, gray matter did not yield homologous membrane fractions in the gradient when subjected to the identical procedure, indicating that the two membrane fractions were unique to white matter. While electronmicroscopic examination revealed that both membrane fractions were comtaminated with myelin, the heavier fraction was least contaminated and exhibited a fair degree of homogeneity with respect to single membrane vesicular profiles. It was concluded that both membrane fractions were enriched with oligodendroglial and axonal plasma membranes, with the heavier fraction containing significantly more axolemma.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗