Search PubMed⌕ Search

Biomedical subjects

M Oehmichen

Publications and source records attributed to M Oehmichen.

At least 127 records · Page 7Linked to original sources
PubMed1982

Enzyme activity in human mononuclear blood cells.

Two different kinds of mononuclear blood cell samples (mixed blood cell population consisting of lymphocytes, monocytes, and platelets; pure lymphocyte population) were tested for enzyme activity of mitochondrial malic enzyme, peptidase A, and alpha-fucosidase. None of the three enzymes was demonstrable in the pure lymphocyte preparation; the mixed cell population, however, exhibited a distinct enzyme activity. Positive reactivity is thus obviously dependent upon monocytes and/or platelets.

Blood Platelets↗
PubMed1982

Origin, proliferation, and fate of cerebrospinal fluid cells. A review on cerebrospinal fluid cell kinetics.

Four aspects of cytokinetic investigations of cerebrospinal fluid cells were reviewed: the origin of these cells, their ability to divide, their fate, and the alterations occurring under pathologic conditions. Animal experiments and in vitro reactions of human cerebrospinal fluid cells indicated that, under normal and pathologic conditions, blood lymphocytes and blood monocytes are capable of leaving the vascular system inside the subarachnoid space. When these cells are located extravascularily, they seldom divide in the subarachnoid space under normal conditions. Migration via lymphatic pathways is possible, at lest under pathologic conditions. Cell turnover, as a whole, is extremely low under normal conditions. It is markedly altered by meningeal inflammation and meningeal tumor cell dissemination. Diagnostic significance other than morphology cannot yet result from cytokinetic investigations of cerebrospinal fluid cytology; prognostic significance may be possible.

Animals↗
PubMed1982

Fatal nitrosamine poisoning.

A case is reported in which progressive liver symptoms with rise in bilirubin concentration, hemorrhagic diathesis, and signs of portal hypertension developed three years before death in liver coma. The pathologic and neuropathologic findings are described. The case was clarified after dimethylnitrosamine was demonstrated in food intended for the patient and after it was established that small amounts of nitrosamine could have been repeatedly ingested by the patient over a period of years. Comparable cases of human dimethylnitrosamine poisonings published in the literature are presented. The relatively typical morphologic alterations in the liver are described. Problems involved in the histological interpretation of such liver changes as well as the forensic conclusions to be drawn are discussed.

Adult↗
PubMed1982

Forensic significance of acetylcholine esterase histochemistry in organophosphate intoxication. Original investigations and review of the literature.

The reduction of acetylcholine esterase (AChE) activity or the complete blocking of AChE to be observed by histochemical demonstration of AChE in tissue after experimental and spontaneous (human) organophosphate intoxication (especially paraoxone = E600 and parathion = E605) should be interpreted as an indication of an in vivo inhibition of the cholinergic system. In animal experiments, a relationship was demonstrated between AChE activity and the applied dose of organophosphorous compounds. In addition, enzyme inhibition was observed in in vitro systems using AChE-containing mouse tissue sections pretreated with organophosphate solutions or with body fluids containing organophosphates. Examination of the concentration dependency indicated that the inhibiting solution must contain at least 0.15 microgram/ml paraoxone or 5 mg/ml parathion to block AChE in the section. Using the same in vitro system, a half-life of 6-7 min was established for the paraoxone inactivating enzyme in blood. The in vivo and in vitro inhibited AChE was reactivated by consecutive treatment of blocked sections with toxogonin. This possibility of reactivation therefore allows qualitative classifications of the AChE-inhibiting toxin to the alkylphosphates. The postmortem persistence of the AChE inhibitory effect was demonstrable for about a 2-month interval. Since the histochemically demonstrable activity of the enzyme AChE is more or less constant during a postmortem interval of at least 70h, the model of histochemical demonstration is a method which provides a morphological equivalent for acute organophosphate intoxication.

Acetylcholinesterase↗
PubMed1982

Are resting and/or reactive microglia macrophages?

According to recent submicroscopic, cytokinetics, and functional (particularly cytoimmunologic) investigations, no relationship exists between "resting" microglia (the small argyrophilic cells appearing in undamaged brain tissue, first described by Rio Hortega) and "reactive" microglia (the argyrophilic cells appearing under pathologic conditions). While "resting" microglia are apparently cells of neuro-ectodermal origin, all observations tend to indicate that "reactive" microglia are derived from extravasated blood monocytes and should be called brain macrophages. In the intact brain parenchyma, no macrophages are demonstrable. Free subarachnoidal cells in the cerebrospinal fluid (CSF), perivascular cells, and epiplexus and/or supraependymal cells in the CSF-containing spaces of the normal central nervous system are cells of the mononuclear phagocyte system and must be considered as CSF macrophages. According to rough estimates, the normal adult central nervous system contains a maximum of 280,000 CSF macrophages.

Animals↗
PubMed1982

Time-dependency of the lymphatic efflux of intracerebrally applied corpuscular tracers. Light and electron microscopic investigations.

Morphologic methods were used to investigate the rate at which intracerebrally injected corpuscular tracers (carbon, ferritin, and colloidal gold) appear in the cervical lymph nodes of rabbits. The survival intervals ranged from 3 minutes to 90 days. The lymph nodes were examined with light microscopy and sometimes also with electron microscopy. Ferritin was first detected in the deep paratracheal cervical lymph nodes 6 minutes after injection with electron microscopy and 10 minutes after injection with light microscopy. All tracers appeared first extracellularly in the sinuses of the lymph nodes; within 3 hours, however, they had been almost entirely incorporated, appearing then in the sinus lining cells as well as in the lymph node macrophages. In the following days, the tracer concentrated and accumulated in the macrophages. After 12 days, all tracer-bearing macrophages had already disappeared. The amount and distribution of tracer in the sinus lining cells, however, remained virtually unchanged during the entire 3-month observation period. The importance of these observations is discussed.

Animals↗
PubMed1981

Diagnostic significance of nerve cells in human CSF with particular reference to CSF cytology in the brain death syndrome.

Cytological examination of the cerebrospinal fluid (CSF) in 5 cases of the brain death syndrome treated on a respirator revealed the presence of nerve cells (mostly Purkinje cells), massive pleocytosis with many polymorphonuclear leukocytes, and numerous macrophages containing erythrocytes, leukocytes, lipid droplets, and hemosiderin. Portions of connective tissue with well preserved capillaries, and debris which could not be more closely identified, were also found. Neuropathological examination in 4 cases revealed progressive autolysis of brain tissue and displacement of the autolyzed tissue into the subarachnoid space of the spinal canal, partly due to tonsillar herniation. All five patients exhibited clinical signs of brain death and had been placed on respirators for various periods of time. The cytological findings in the CSF, together with the clinical signs of brain death, constitute an intravital morphological indication of brain tissue autolysis.

Autolysis↗
PubMed1980

Enzyme alterations in brain tissue during the early postmortal interval with reference to the histomorphology: review of the literature.

The state of research on enzyme alterations in brain tissue during the early postmortal interval is surveyed with special reference to the histomorphology; the questions currently discussed in the literature are given special consideration. The type of alterations appearing during the postmortal interval and their dependency on the length of the interval are described so that practically applicable conclusions may be drawn. The findings on enzyme alterations presented in the literature (enzymes of the oxidative metabolism, transmitter, enzymes) are compiled in tables. It could be shown that important structural alterations ascertainable with light microscopy and quantitative alterations in enzyme activity ascertainable with biochemical methods do not usually occur during a 6- to 8-h postmortal interval. Qualitative investigations (i.e., histoenzymatic studies) with longer postmortal intervals and with positive findings are applicable.

Animals↗
PubMed1980

Postmortal diffusion of plasma albumin in rat brain.

After i.v. injection of Evans blue solution (EB), the postmortal diffusion of plasma albumin and its relationship to the postmortal interval (0 to 48 h) were studied in rat brain. A decrease in intravascular plasma albumin with increasing evidence of the same fraction in relation to the length of the postmortal interval was observed via diffuse EB fluorescence in the perivascular, periventricular, and subpial neuropil. Stained nerve cells and single endothelial cells were found grouped around individual vessels, particularly in the region of the basis encephali. The EB-fluorescent cells proved to be hyperchromatic when subsequently stained with cresyl violet; the nerve cells therefore were considered dark neurons. EB-fluorescent dark neurons were also found around the lesion in experiments involving postmortal traumatic damage of cerebral tissue. Since all EB-fluorescent nerve cells proved to the dark neurons, but not all dark neurons exhibited EB fluorescence, it was concluded that dark neurons possess a capacity for intensifying the absorption of plasma albumin. No fluorescence was demonstrated in control studies of cerebral tissue in which EB had not been injected.

Animals↗
PubMed1980

Cytochemical markers for mononuclear phagocytes as demonstrated in reactive microglia and globoid cells.

Several cytochemical characteristics of mononuclear phagocytes which are used as identifying markers were studied in reactive microglia from traumatically damaged brain tissue of guinea pigs and humans as well as in globoid cells from a child with familial globoid cell leukodystrophy (Krabbes' disease). The following cytochemical methods were used: acid phosphatase, lysozyme, peroxidase, alpha-naphthyl acetate esterase, alpha-naphthyl butyrate esterase, adenosine triphosphatase, and the periodic acid-Schiff reaction (PAS reaction). Distinct activity of almost all enzymes and the PAS reaction were demonstrable in reactive microglia and globoid cells. Peroxidase however could not be demonstrated in globoid cells. The similarity of the cytochemical characteristics for mononuclear phagocytes, reactive microglia, and globoid cells tends to indicate a common identity for these cell types. The lack of peroxidase in globoid cells may be due to a final maturation and differentiation after the monocyte stage.

Animals↗