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Biomedical subjects

G F Walter

Publications and source records attributed to G F Walter.

At least 73 records · Page 4Linked to original sources
PubMed1989

Complement-derived polypeptide C3adesArg as a mediator of inflammation at the blood-brain barrier in a new experimental cat model.

The effect of the complement-derived polypeptide C3adesArg as a mediator of inflammation in the central nervous system was examined. Twenty-five anesthetized cats received 4 mg of this polypeptide by intraventricular injection, 20 cats who served as controls received saline. Cerebrospinal fluid (CSF) was sampled 3 h after intraventricular injection and the brains were removed. For assessment of the permeability of the blood-brain barrier the CSF penetration of four antibiotics, which were given intravenously was measured. Five control animals were employed for each antibiotic (tobramycin, ampicillin, imipenem, fosfomycin), whereas six C3adesArg-treated animals were used for each antibiotic and seven for tobramycin. Besides CSF levels of glucose, the prostanoids 6-keto-prostaglandin F1 alpha, thromboxane B2 and prostaglandin E2 were measured. The morphological examinations in the CSF sediments and histological brain sections in the C3adesArg-treated animals disclosed a distinct inflammation with leptomeningeal and perivascular infiltration of polymorphonuclear granulocytes compared to normal findings in the controls. The CSF/serum ratios of all of the antibiotics were markedly elevated compared to controls, indicating a blood-brain barrier disruption. The levels of all prostanoids were significantly higher in the treatment group than in the control group, whereas the glucose levels were lower. These findings are in accordance with a granulocytic meningitis as seen in some infections at the acute stage. It is concluded that C3adesArg acts as a mediator of inflammation in the central nervous system.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Cellular mechanisms of rejection and regeneration in peripheral nerve allografts.

A model of rejection and regeneration of peripheral nerve allografts in rats is presented. A 2.5-cm segment of 28 right sciatic nerves was transplanted orthotopically from LEW.1W to DA and from DA to LEW.1W. With a microsurgical technique, proximal and distal coaptations were performed. In an autologous control group the same surgical procedure was applied. Evaluation included clinical estimation of motor recovery and macroscopic appearance of the graft, electrophysiological examination, conventional histology, and immunohistology. The latter concentrated on demonstration of monomorphic and polymorphic determinants of MHC class I and II antigens and of macrophages. By functional, electrophysiological, and histological parameters it was demonstrated that after rejection a certain degree of regeneration took place in the allografts. Both rejection and subsequent regeneration were studied in detail by immunohistology. During the course of Wallerian degeneration MHC class I expression on myelin sheaths could be demonstrated. When the rejection response occurred, additional MHC class II expression on myelin sheaths and on vascular endothelial was observed. Recipient specific class I-positive macrophages were infiltrating the graft from the epineurium and the coaptation sites, and were later present at the sites of myelin degradation. At 6 weeks postoperatively donor-specific MHC products were no longer detectable, but recipient-specific Schwann cells were present in the allograft tissue. We conclude that a rejection response renders a peripheral nerve allograft acellular but does not destroy the nerve architecture, still enabling it to function as an axon conduit. The regeneration in the rejected allograft however lacks the positive neurotropic and -trophic influence physiologically provided by viable Schwann cells.

Animals↗
PubMed1988

The influence of nimodipine on cerebral blood flow autoregulation and blood-brain barrier.

Twenty anesthetized rats were randomly assigned to a nimodipine-treated group or a control group of 10 rats each. Local cerebral blood flow (lCBF) was measured by means of a surface electrode using the hydrogen clearance technique. Systemic arterial pressure (SAP) was varied with administration of norfenefrine or by hemorrhage in order to obtain SAP/cerebral blood flow (CBF) curves under different conditions. In the control group, a typical autoregulation curve was obtained with an lCBF plateau between 70 and 120 mm Hg SAP. The nimodipine-treated animals, however, showed only a slight diminution in the slope of the curve but no real plateau, indicating impairment of CBF autoregulation. In another series, 20 anesthetized rats were randomly assigned to a treatment group or a control group of 10 animals each. Intravenous Evans blue dye was used as a tracer for blood-brain barrier (BBB) function. In both groups, SAP was raised to a level of 180 mm Hg with administration of norfenefrine for 6 minutes. Extravasation of significantly more Evans blue dye was observed in the nimodipine group than in the control group, indicating impairment of the BBB. It is concluded that nimodipine may impair CBF autoregulation, allowing damage to the BBB under hypertensive conditions.

Animals↗
PubMed1988

[Nerve regeneration in autologous and allogeneic transplant of the sciatic nerve of the rat with and without immunosuppression by cyclosporin A].

The following experimental studies show different stages of regeneration and rejection in autologous and allogenic nerve grafts in 162 rats with and without immunosuppression with Cyclosporin A. Allografts were used in congenic rats differing only in major histocompatibility complex (MHC). Nerve regeneration was studied in autologous grafts with and without treatment with Cy A and with toxic doses of Cy A. No difference in nerve regeneration was seen in these groups. Allografts were transplanted between congenic rats type LEW 1 A and 1 U and vice versa with and without treatment with Cy A. Various degrees of rejection from slight to moderate were seen. Without Cy A-treatment, nerve grafts were totally destroyed after four weeks. With Cy A, nerve grafting resulted in complete regeneration.

Animals↗
PubMed1987

Unusual EEG findings in a case of Creutzfeldt-Jakob disease.

A case is reported of histopathologically verified Creutzfeldt-Jakob disease of long duration (more than 3 years) with some clinical peculiarities. The prominent peculiarity was a nearly normal EEG during repeated examinations, even in the terminal stage.

Adult↗
PubMed1986

[Fatal eosinophilic meningoencephalitis following lacquer poisoning. Case report and differential diagnostic considerations].

The authors report about a 43-year-old male patient, who suffered from an acute toxic brain injury. Twelve days prior to death, after sealing his floor, he experienced progressively increasing headache without fever; the CSF examination disclosed marked eosinophilia. The clinical and pathomorphological features of his illness are discussed and together with the various possible etiologies of eosinophilia in the CSF.

Adult↗
PubMed1986

[Cranial computed tomography in maple syrup urine disease].

Cranial computed tomography in the initial stage of the intermediate phenotype of maple syrup urine disease (MSUD) demonstrates diffuse, symmetric hypodensities in white and grey matter, which show a complete return to normal after early introduction of an adequate protein-restrictive diet. If diagnosis of this disease is missed or delayed, progressive global (end-stage) atrophy will take place over several years. A decrease in density values correlates well with the total cerebral lipid and water content (closely related to myelinisation), whereas progression and grade of atrophy show a relationship with the severity of pathological white and grey matter changes that are not demonstrable with computed tomography but can be proven histologically. Analysis of both morphological parameters corresponds well with clinical-neurological outcome and therapeutic success.

Brain↗
PubMed1985

Carcinomatous meningeosis as exclusive metastasizing pattern in a malignant thymoma.

In a 57-year-old male patient meningitic symptoms occurred. CSF cytology exhibited carcinoma cells, thus establishing the diagnosis of carcinomatous meningeosis. The primary site of the tumor or metastases were not detected intra vitam. The autopsy revealed a malignant thymoma with an exclusive metastatic participation of the leptomeninges except for some few regional lymph nodes. Cerebral metastases of malignant thymoma is an extremely rare condition.

Brain↗
PubMed1984

Immunohistochemistry of folliculo-stellate cells in normal human adenohypophyses and in pituitary adenomas.

Presence and distribution of S-100 protein (S-100), neuron-specific enolase (NSE), cytokeratin polypeptides, glial fibrillary acidic protein (GFAP), vimentin, actin, lysozyme and pituitary hormones (prolactin, hGH, ACTH, beta-FSH, beta-LH, beta-TSH, alpha subunit) in folliculo-stellate cells (FSC) were studied in seven normal human pituitary glands and 28 pituitary adenomas using peroxidase-antiperoxidase and the avidin-biotin immunohistochemical techniques. Approximately 5% of the cells of the adenohypophysis were agranular, non-hormone-producing FSC most of which showed a conspicuous and strong reaction with S-100 antibodies but some were, in addition, GFAP- and vimentin-positive. In contrast to endocrine cells (EC), FSC were not decorated by antibodies to NSE or cytokeratins. In addition to supportive functions, these cells, due to their close special relationship to EC, seem to have transport and other metabolic functions yet to be elucidated. By their S-100 reactivity and their distribution FSC are comparable to glial cells of the central and Schwann and satellite cells of the peripheral nervous system (PNS) as well as to supportive cells in neuroendocrine organs and related tumors (e.g., pheochromocytomas, paragangliomas, carcinoids). With one exception, S-100 reactive FSC were not found in pituitary adenomas. The immunohistochemical demonstration of S-100 protein in pituitary tissue is, therefore, a reliable aid in the discrimination between adenomas and normal pituitary tissue, particularly in small and poorly preserved specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1984

Immunohistochemical demonstration of cytokeratins in endocrine cells of the human pituitary gland and in pituitary adenomas.

Ten non-neoplastic pituitary glands and 22 pituitary adenomas producing different hormones were studied by immunofluorescence microscopy as well as peroxidase-antiperoxidase and biotin-avidin techniques on frozen sections and formalin-fixed, paraffin-embedded material using antibodies to cytokeratin, vimentin, GFAP, neurofilament protein and different pituitary hormones. The endocrine cells in non-neoplastic pituitary glands as well as in most pituitary adenomas were cytokeratin-positive. The cytoplasmic cytokeratin distribution patterns of non-neoplastic and tumor cells were similar and typical of the type of hormone produced: GH-producing normal cells showed a paranuclear condensation of cytokeratin-reactive intermediate filaments; this accumulation was even further accentuated in GH-producing adenomas resulting in fibrous bodies (Kovacs and Horvath 1978) decorated by cytokeratin antibodies. Prolactin-producing cells showed a less intense cytoplasmic cytokeratin-specific staining with focal paranuclear accentuation in non-neoplastic as well as in neoplastic glands. ACTH-producing cells in normal pituitary glands as well as in adenomas exhibited a strong and more uniform cytoplasmic cytokeratin staining. The cytokeratin reactivity in glycoprotein hormone-producing cells of non-neoplastic tissue and adenomas was weak. Vimentin and GFAP reactivity was confined to agranular folliculo-stellate cells. The specific and different distribution patterns of cytokeratins in pituitary cells can, therefore, provide an (indirect) indication to the production of a specific hormone if immunocytochemistry fails to demonstrate hormone production.

Adenoma↗
PubMed1984

The effects of carbon dioxide- and neodymium-YAG lasers on the central and peripheral nervous systems, and cerebral blood vessels.

The morphological reaction of brain and peripheral nerve tissue and of cerebral blood vessels to the application of two types of laser-beams is described. Lasers as cutting instruments produce smoother cut surfaces and provoke less bleeding than conventional techniques. There is almost no focal oedema. Their effects are limited to clearly determinable zones. Scar formation after laser cutting is minimised. With defocused laser-beams a photo-coagulation of tumours, for example, highly vascularised tumours or pituitary adenomas, is possible. Small arteries may be cut without bleeding. Peripheral nerves cut by use of lasers do not develop neuromas. The results of the laser technique are compared with those of conventional methods.

Animals↗
PubMed1984

CT diagnosis of thrombosis of dural sinuses in childhood.

This paper describes the CT findings in five cases of cerebral and cerebellar sinovenous occlusion. Characteristic CT findings are the visualisation of the thrombosed sinuses and veins, known as the "filled triangle" and the "cord sign" on the control scan, and the "empty triangle" with tentorial and gyral enhancement after contrast enhancement. The high incidence of thrombosed internal cerebral veins and superior cerebellar veins with sinus thrombosis in children is remarkable. CT with both control and contrast enhanced scans will probably provide the correct diagnosis in the majority of cases.

Child, Preschool↗
PubMed1983

Mitochondrial reaction in skeletal muscle to induced activity.

The purpose of the present study was to investigate the structure of muscle mitochondria for a possible early response to electrically induced short- and medium-term activity. Rats were anesthetized with Na-pentobarbital. Both parts of the triceps surae muscle were stimulated by direct electrical impulses for periods between 2 and 60 min. Biopsies were taken and prepared for histological, enzyme-histochemical, and electron-microscopic examinations. Enzyme histochemistry demonstrated an increase of oxidative activity and an increase of RNA by NADH-tetrazolium reductase and modified Gomori's trichrome staining or acridine orange-induced fluorescence, respectively. These changes appeared especially within type I fibers, as shown by ATPase reactions, and corresponded to an increase in number and size of muscle mitochondria, followed by alterations of the mitochondrial structure. The mitochondria reacted immediately to the electrical stimulation of the muscle, and the degree of alteration depended on the duration of the experiments. These results suggest that mitochondria have a certain capacity for adapting rapidly to changes in the energy metabolism. Beginning energetic decompensation may be responsible for the alterations of the mitochondrial structure.

Animals↗