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At least 73 records · Page 4Linked to original sources
PubMed1980

[Postmortem changes in the ultrastructure, cytoplasmic proteins and nuclear chromatin of rabbit nerve cells].

Changes in the set of water soluble cytoplasmic and chromatin proteins have been studied in the rabbit neocortex, cerebral trunk, liver and muscles by means of electrophoresis in polyacryl gel with sodium dodecisulfate, 12 and 24 h after the animals are decapitated, when the material is kept in cold and at room temperature. Ultrastructure of pyramidal neurons in layer V of the rabbit sensomotor cortex has also been studied immediately after death and after 24 hours' preservation of the material at 4 degrees C and at room temperature. It has been stated that the ultrastructural changes in the nucleus and in the set of chromatin proteins in the cerebral cells are rather small even 24 h after death. Cytoplasmic structure and spectrum of the cytoplasmic proteins undergo much greater changes. Chromatin proteins of the cerebral cell nuclei, especially those of the neocortex, much better withstand the postmortem proteolysis than the cells in the liver and muscles, and cytoplasmic proteins of the cerebral cells are less stable than in other tissues. A possibility to perform analogous investigations in section material of the human brain and possible mechanisms of adaptive character on unequal stability of proteins in various tissue cells are discussed.

Animals↗
PubMed1977

Postmortem changes in stereological parameters of cerebral capillaries.

The present study investigated the influence of different postmortem times on stereological parameters of capillaries in the cerebral cortex. For the human investigation different brain regions of two 77 and 79 year-old subjects were examined. The animal experiment, carried out on 10 male cats, allowed a comparison between intravitam deep-frozen cerebral cortex and tissue obtained after decapitation. The parameters were diameter Di, volume fraction VVi, surface-to-volume ratio Si/Vi, mean minimal distance between capillary centers of gravity deltaAB, length per unit cortex volume LVi, and number of fragments per measuring field Ni, AT. Neither the cat experiment nor the human investigation yielded a noteworthy change of the capillary diameter in the postmortem cortical tissue. Nevertheless, a significantly enlarged mean minimal distance between capillaries in the cat cerebral cortex shortly after decapitation (30 sec) suggests the formation of edema which then regresses. Furthermore the experiment revealed that 22 hours after death there is a significantly (p less than 0.01) diminished volume fraction and length per unit cortex volume with an augmented surface-to-volume ratio. These changes are thought to be a consequence of water loss. In contrast to the animal experiment the human cerebral capillaries showed no changes in stereological parameters at two different postmortem times. These results encourage continuation of further stereological investigations on human brains obtained at autopsy and may contribute to the understanding of the aging process in the human cerebral cortex.

Aged↗
PubMed1997

[Correlation between ear canal resonance and tympanic membrane impedance in relation to age and body mass and postmortem changes].

The human temporal bone preparation is an acknowledged model for research of the physical processes affecting the outer ear canal and eardrum. Changes affecting the oscillation and resonance behavior of the tympanic membrane and ear canal between death and temporal bone preparation presently exist in only a few studies. Since the influence of age and physique, as well as the width of ear canal on the ear canal resonance may be important, we prepared two separate studies to analyze these questions. The goal of our first test series involved children and was devised to determine if changes in the outer auditory canal resonances differed according to age. In so doing, canal resonance was recorded with a real ear measurement system. Further, we recorded middle ear pressure, impedance of the tympanic membrane, ear canal volume, height, weight and surface of the body, head and ear size. We found a significant decrease in the resonance frequency of the outer ear which was age-dependent and was 2.75 kHz in the 7-year-old child. In a separate study we wanted to know if results found in the postmortem temporal bone reflected in vivo relationships. A tympanometer and real ear measurement system was used to test the resonance behavior of the auditory canal as well as the vibration of the eardrum in dependence on temperature and the time after death for 9 h. We then proved the absence of significant changes in the auditory canal and eardrum oscillation in this time period before possible postmortem changes occurred. Our findings show that the method of bone preservation after its preparation is decisive for the validity of measurements in the isolated human temporal bone.

Acoustic Impedance Tests↗
PubMed1981

[Postmortem changes in the perilymphatic lactate and pyruvate concentrations of guinea pigs. (author's transl)].

Lactate and pyruvate of perilymph (PL) were studied 30, 60, and 120 min postmortem. During this period the mean lactate concentration of scala tympani and scala vestibuli increased from 4.8 mmol/l found intravitally to 17.8 and 15.1 mmol/l, respectively, whereas pyruvate decreased from an average of 0.33 to 0.10 mmol/l (fig. 1). These inverse changes of concentration yield postmortem lactate/pyruvate quotients which are more than one order of magnitude higher than the quotients found intravitally (Table 1). In comparative tests of blood samples carried out 30, 60, and 120 min after the sampling (Fig.1), the lactate increase was found to be markedly lower than in postmortem PL. The substantial metabolite changes in PL seem to be caused by glycolytic activity of all cochlear structures that are in direct contact with PL. The decrease of pyruvate level is probably due to a shift of the lactate-pyruvate equilibrium (lactate dehydrogenase system) in PL. The blood vessels in the perilymphatic space can be neglected as postmortem metabolite source of PL.

Animals↗