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M Langmeier

Publications and source records attributed to M Langmeier.

64 records · Page 4Linked to original sources
PubMed1980

Changes in some parameters of the presynaptic bag in synapses of the somatosensory cortex of the rat brain after repetitive electrical stimulation prolonging self-sustained after-discharges. An electron microscopic morphometric study.

The sensorimotor area of the rat cerebral cortex was subjected to repeated electrical stimulation at 10 min intervals; this progressively prolonged the duration of self-sustained after-discharges (SSAD). Ten minutes after the third SSAD ended, the animals' brains were perfused with fixing fluid. The homotopic area of the contralateral hemisphere was examined electron microscopically. In type I synapses in the second cortical layer we determined A) the mean areas of sections of the presynaptic bag, B) the length of the active zone of the presynaptic bag, C) the mean total number of agranular synaptic vesicles per 0.01 micron2 area of the presynaptic bag in the experimental and control rats. In the experimental animals value A) rose by 34%, value B) by 14%, value C) by 95% and value D) by 52%. The differences are all statistically significant. Findings A) and B) are most likely evidence of ionic shifts, while findings C) and D) testify to the increase in the number of synaptic vesicles in the whole presynaptic bag and also to their redistribution towards the synaptic cleft. The possibility that findings C) and D) are the morphological correlate of increased synaptic transmission during experimental treatment leading to the kindling phenomenon cannot be ruled out.

Animals↗
PubMed1980

Changes in the length and width of the postsynaptic density, the width of the intersynaptic density and the synaptic cleft in the cerebral cortex synapses of rats exposed to prolonged aerogenic hypoxia during early ontogenesis. An electron microscopic morphometric study.

Infant rats, together with the female, were exposed daily from birth to the age of 17 days (except for the 6th, 7th, 13th and 14th day) to a simulated attitude of 7,000 m. On the 18th day, 20 hours after the last exposure to hypoxia, the animals were perfused. In each of 118 synapses from the two control animals and 162 synapses from the two experimental animals (type I synapses, second cortical layer of the somatosensory cortex, impregnated with phosphotungstic acid), we measured A) the maximal thickness of the postsynaptic density and B) the minimal thickness of the postsynaptic density, C) estimated the thickness of the postsynaptic density and measured D) the distance between the pre- and the postsynaptic density, E) the thickness of the intersynaptic density and F) the length of the postsynaptic dense projection. In the experimental animals we found value A) to be 25% lower, value B) 28% lower, value C) 30% lower, value D) 5% lower, value E) 2.5% lower and value F) 17% higher than in the controls. The differences are statistically significant (evaluated by a t-test). It was found that, under our experimental hypobaric conditions, the maturation of synapses is retarded or modified.

Animals↗
PubMed1977

Postnatal changes in the DNA content of mouse cerebral hemispheres.

Changes in the wet weight of the cerebral hemispheres and in their DNA content and concentration were studied in CBA mice (non-SPF, Velaz, Prague) aged from 1 to 270 days. It was found that hemisphere wet weight rose by 350% between the 1st and 14th day and by a further 11% between the 14th and 180th day. In the next three months it remained stable. The total DNA content rose by 30% between the 1st and 2nd day and by 45% between the 1st and 10th day; changes between the 10th and 180th day were non-significant, but a decrease of 16% occurred by the 270th day. Between the 1st and 2nd day the DNA concentration did not alter, or rose non-significantly (+20%). Towards the end of the 2nd postnatal week it fell exponentially (-75%). Changes in the DNA content and concentration indicate that the rate of cell proliferation in mouse cerebral hemispheres is highest on the first two days after birth, while the general chemical composition of the hemisphere develops fastest between the 2nd and 14th day. The constancy of the DNA content between the 10th and 180th day implies that cell division in the hemispheres of adolescent and adult mice primarily reflects renewal of the non-neuronal cell population.

Animals↗
PubMedDate not supplied

Localization of the origin of self-sustained afterdischarges (SSADs) in the rat: I. The spike-and-wave type of SSAD.

The genesis of the thalamocortical self-sustained afterdischarge (SSAD) composed of spike-and-wave (S + W) rhythm was studied in adult male albino rats. Under control conditions, rhythmic electrical stimulation of the specific somatosensory nucleus of the thalamus always elicited type S + W SSAD. An electrolytic lesion of the nonspecific thalamic nuclei did not prevent generation of type S + W SSAD, while stimulation of the ventrobasal complex evoked both type S + W SSAD and another type of SSAD composed of large waves with superimposed fast activity. Elimination of the cortex (by suction or spreading depression) ipsilateral to the stimulated thalamus completely suppressed any possibility of the formation of type S + W SSAD; elimination of the contralateral cortex did not affect it. Our results suggest that the cortex is the decisive factor in the genesis of S + W rhythm, while the thalamus markedly influences the conditions of its formation.

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