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Biomedical subjects

G F Walter

Publications and source records attributed to G F Walter.

At least 55 records · Page 3Linked to original sources
PubMed1994

Skeletal muscle glycogen content in patients with cirrhosis.

We investigated stable cirrhotic patients for muscle glycogen content. Muscle biopsy samples were taken of 14 patients after overnight fasting. Electron microscopy showed normal intracellular distribution of glycogen (n = 8). Muscle glycogen concentration was 16.5 +/- 7.1 gm/kg wet muscle weight (normal range, 10 to 20 gm/kg). Basal, early postabsorptive, exercise-induced and insulin-induced respiratory quotients as well as insulin sensitivity (euglycemic clamp technique, 7.2 pmol insulin/kg body weight/min) and glucose tolerance were assessed. The glucose disposal rate was 23.0 +/- 10.1 mumol/kg/min (mean +/- S.D.), indicating moderate insulin resistance in these patients. We found no association between basal muscle glycogen content and basal or postprandial respiratory quotient, insulin sensitivity, nutritional status or glucose tolerance. However, there was a positive correlation between muscle glycogen content and exercise, as well as insulin-induced respiratory quotient (r = 0.651, p < 0.03 and r = 0.587, p < 0.03, respectively). We conclude that postabsorptive muscle glycogen stores, which are effectively maintained in patients with cirrhosis, are one determinant of exercise-induced and insulin-induced whole body fuel metabolism in these patients.

Adult↗
PubMed1994

[Regeneration of peripheral nerves after interposition of acellular muscle into larger defects].

Peripheral nerve grafting is an established procedure in reconstructive surgery. Nerve grafts, however, are only available to a limited extent and patients are faced with neurologic deficits at the donor areas. Pretreated skeletal muscle has been proposed as an alternative grafting material. In nine adult Sprague-Dawley rats, a 2 cm gap of the sciatic nerve is grafted with a M. gracilis segment which has been pretreated through repeated freezing and thawing. Regeneration is evaluated after six weeks postoperatively. The results are compared to nine conventional nerve grafts. Regeneration was evident in all grafts. Histologically, the muscle grafts revealed a high proportion of connective tissue, a good vascularisation but an inferior degree of myelinisation. Morphometrically, the muscle grafts proved to be inferior according to axon counts and myelinisation. Muscle grafts provide a substrate comparable to peripheral nerves regarding the tubular architecture based on laminin. There are however no viable Schwann cells within these substitutes, which makes them inferior compared to conventional nerve grafts for peripheral nerve repair. These results are discussed with respect to further experiments concerning allogeneic nerve grafting and peripheral nerve preservation.

Animals↗
PubMed1993

Neuromuscular hamartoma (benign "Triton" tumour) in a mouse.

Histological examination of a 22-month-old CD-1 mouse revealed a threefold enlargement of the right trigeminal ganglion. This change was due to the presence of well-differentiated striated muscle fibers intermingling with nerves and ganglion cells. The number of ganglionic Schwann cells was also increased as demonstrated by their positive S-100 protein staining. In addition, slight interstitial mononuclear cell infiltration and fibrosis were observed. The myocytes, which stained positive for myoglobin and desmin, and the proliferated Schwann cells did not show any signs of cellular or nuclear atypia. The lesion was diagnosed as "neuromuscular hamartoma (benign "Triton" tumor)" reflecting the capability of either Schwann cells or neural crest derived precursor cells to differentiate into various other cell types.

Animals↗
PubMed1993

Immunohistochemical detection of female sex hormone receptors in meningiomas: correlation with clinical and histological features.

Sixty-one meningiomas from 60 patients were screened for estrogen receptors and progesterone receptors (PgR) with monoclonal antibodies in an immunohistochemical assay. In addition, 43 of the cases were evaluated for tumor size and peritumoral edema, as seen on computed tomographic scans and magnetic resonance images. Sixty-one percent of the tumors contained significant amounts of PgR, whereas no estrogen receptor-positive tumor was observed. Thirteen percent of all tumors were classified as nonbenign variants (atypical and anaplastic meningiomas) and were more frequently found in male patients (P < 0.05). Nonbenign tumors more frequently showed an absence of PgR (P < 0.05), and there was a tendency for PgR-negative tumors to be larger than PgR-positive ones. No correlation was found between PgR status and edema. It is concluded that PgR status in meningiomas is related to tumor differentiation and may be of prognostic value with regard to biological behavior and clinical outcome.

Adolescent↗
PubMed1992

Primitive neuroectodermal tumors after prophylactic central nervous system irradiation in children. Association with an activated K-ras gene.

Three patients had supratentorial malignant brain tumors 7 to 9 years after prophylactic central nervous system (CNS) treatment for acute lymphocytic leukemia or malignant T-cell lymphoma. Therapy was administered at the age of 3 to 8 years and included cranial irradiation (total dose, 1800 to 2400 cGy) and intrathecal methotrexate. The brain tumors had histologic and immunohistochemical features of primitive neuroectodermal tumors (PNET), including neuroblastic rosettes, rhythmic arrangement of tumor cells, and immunohistochemical expression of glial, and in one patient neuronal, marker proteins. Using polymerase chain reaction-mediated DNA amplification from paraffin-embedded tissues and subsequent DNA sequence analysis, an activating point mutation was detected in the K-ras protooncogene in one tumor. This mutation was a G to A transition in position 2 of codon 12, substituting aspartate (GAT) for glycine (GGT). This type of mutation has not been observed before in human brain tumors, but it is frequent in radiation-induced murine lymphomas. These observations suggest that PNET can be induced after completion of the embryonal and fetal development of the human CNS. Oncogene-activating point mutations may represent a pathogenetic mechanism involved in the genesis of radiation-induced brain tumors.

Aspartic Acid↗
PubMed1992

Down syndrome complicated by brain tumors: case report and review of the literature.

This report concerns a 24-year-old male patient with Down syndrome, complicated by a benign but true neoplastic lesion of a differentiated papilloma of the choroid plexus which simultaneously displayed a dysgenetic character. A review of the literature revealed a lack of single case reports of Down syndrome with brain tumors, which may reflect chance occurrence; however, the brain tumors in Down syndrome patients are characterized by their dysontogenetic or dysgenetic character.

Adult↗
PubMed1992

Arterial hypertension and neurovascular compression at the ventrolateral medulla. A comparative microanatomical and pathological study.

Intraoperative observations and animal experiments suggest that neurovascular compression at the left ventrolateral medulla is a possible etiological factor in essential hypertension. In pursuing this hypothesis, the authors examined the neurovascular relations in the posterior cranial fossa of 24 patients with essential hypertension, of 10 with renal hypertension, and of 21 normotensive control patients. Artificial perfusion of the vessels and microsurgical investigations during autopsy identified the vascular relations at the brain stem and at the root entry zone of the caudal cranial nerves. There was no evidence of neurovascular compression at the ventrolateral medulla on the left side in any patient from the control group or among those with renal hypertension. Two normotensive patients had neurovascular compression at the right ventrolateral medulla by the posterior inferior cerebellar artery. In contrast, all patients with essential hypertension had definite neurovascular compression at the left ventrolateral medulla. Additional compression of the right side was seen in three of these patients. Based on the anatomical appearance, it was possible to define three distinct types of neurovascular compression at the ventrolateral medulla. Common to all three types is the compression of the medulla oblongata at its rostral part just caudal to the pontomedullary junction and lateral to the olive in the retro-olivary sulcus. Comparative histopathological study of the microsurgically examined brain-stem specimens revealed no differences between patients with essential hypertension, those with renal hypertension, and normal controls. There was a structural integrity at the site of neurovascular compression at the ventrolateral medulla. The microanatomical findings of this study show that neurovascular relations at the ventrolateral medulla in essential hypertension give rise to pulsatile compression on the left. This supports Jannetta's hypothesis of neurovascular compression at the left ventrolateral medulla as an etiology of essential hypertension.

Adult↗
PubMed1992

[Apparent contradictory findings in the immunohistochemical detection of hormone production in hypophyseal adenoma].

In some cases of pituitary adenomas, the immunohistochemical proof of a hormone production does not correspond with the clinical findings. False negative results are caused by different functional stages of the adenoma cells when hormone granules are largely released. Then, the intracellular content of hormone granules lies under the immunohistochemical demonstrability although clinical findings show high serum values of the hormone in question. Especially in prolactinomas, sparsely granulated forms are not rare. In these cases, the proof of a hormone production is possible by means of immuno-electronmicroscopy. Preoperative application of a bromocriptine therapy may falsify the results too. False positive results may occur in "plurihormonal" adenomas. True plurihormonal adenomas--especially the combinations GH/PRL and FSH/LH--exist but frequently reported combinations of several hormones should be seen with care. Often, the operatively removed tissue is cut into small pieces not only containing adenomatous tissue but also parts of the neighbouring normal pituitary gland with a production of several or even all hormones investigated. By use of GFAP or S-100 protein for the detection of folliculostellate cells, adenomatous and normal pituitary tissue can be differed. Folliculostellate cells can only be found in normal pituitary but not in adenomas.

Adenoma↗
PubMed1991

Regeneration of autologous and allogenic nerve grafts in a rat genetic model: preliminary report.

The authors report observations concerning rejection and regeneration processes of allogenic peripheral neural tissue, depending on different genetic mismatches in a rat model. Five groups representing different rat strains (n = 100) were subjected to orthotopic grafting of 2.5-cm segments of sciatic nerve. Combinations represented different genetic barriers, including the Major Histocompatibility Complex (MHC), a non-MHC, a subgroup (A) of the MHC, a group representing MHC plus non-MHC, and an autologous control group. Animals were examined after one, two, and 12 weeks; additional evaluations in some of the experimental groups were done at six and eight weeks. Regeneration in varying degrees was evident in all groups at 12 weeks.

Animals↗
PubMed1991

[Systemic lupus erythematosus (SLE) with panniculitis and rhabdomyolysis].

In systemic lupus erythematosus as a multi-system disease the involvement of skeletal muscle has been described as a rather mild polymyositis, myopathy or inclusion-body myositis. Here we present a patient with a severe lupus presenting with a fulminant myositis with rhabdomyolysis and panniculitis.

Adult↗
PubMed1990

Brain neurotransmitter changes in three patients who had a fatal hyperthermia syndrome.

The authors examined the autopsied brains from three patients who had a fatal hyperthermia syndrome. There was marked hypothalamic noradrenaline depletion in all three patients, severe brain choline acetyltransferase deficiency with nucleus basalis cell loss in two patients, and mild to moderate brain choline acetyltransferase loss in one patient. Striatal dopamine metabolite/dopamine ratio was below normal in two patients and not elevated, as would be expected after short-term neuroleptic administration, in the third. This suggests that reduced capability (aggravated by the cholinergic deficit) of the nigrostriatal dopamine system to respond adequately to stress and/or neuroleptic-induced receptor blockade may be important in the development and course of fatal hyperthermia syndrome.

Adolescent↗
PubMed1990

Brain edema, autoregulation, and calcium antagonism. An experimental study with nimodipine.

We investigated the effects of the calcium entry blocker nimodipine on cerebral autoregulation, BBB, and vasogenic edema in animal experiments. In the first series of rats, ICBF was measured with H2 clearance using a balanced multiwire surface electrode. Variations in blood pressure (SAP), which was measured via femoral catheter, were induced by infusion of norfenefrine (pressure increase) and by hemorrhage (pressure decrease). The effect of SAP on the cerebral microcirculation was evaluated. In control animals receiving nimodipine, a typical autoregulation plateau was found. In rats treated with nimodipine infusion (12-14 micrograms/kg/min), 1CBF was considerably elevated at all blood pressure levels above 50 mm Hg, and in the steep 1CBF/SAP correlation, the autoregulation plateau was almost suspended. In a second series of randomized rats, the effect of nimodipine on BBB was investigated after Evans blue infusion. When a SAP of 180 mm Hg systolic was maintained for 6 min, a diffuse Evans blue staining was seen in 70% of the nimodipine animals (break-through of BBB). In the third series of rats, the effect of nimodipine on cold injury edema was investigated. Nimodipine (1 mg i.p.) considerably decreased the SAP; Edema formation measured by water and Na+ content 24 hr after trauma was then reduced. However, if the decrease in SAP was in part prevented by norfenefrine application, the rats receiving nimodipine developed significantly more edema. Brain water and sodium contents were markedly increased in both hemispheres. The results indicate an interference of nimodipine with cerebral autoregulation, and a BBB disruption may occur at lower SAP. If the BBB is impaired, nimodipine may considerably intensify edema formation. Nimodipine and similar calcium entry blockers should therefore only be used with caution in acute brain damage.

Animals↗
PubMed1990

[Adverse effects of cyclosporin A with special reference to the peripheral nervous system].

Since the introduction of Cyclosporine A (CsA) in 1972, several studies have focused on its effects on experimental autologous peripheral nerve transplants. Although several studies have reported neurotoxicity of CsA in the central nervous system, no such data exist regarding the peripheral nervous system. The present study focuses on the effects of CsA in the therapeutic and toxic doses on axon regeneration, particularly the rate and quality of axon regeneration. Autologous nerve transplantation was performed in Lewis rats and axon regeneration evaluated clinically (motor function, body weight), electroneurographically and histologically. In transplanted nerves, even high doses of CsA (30 mg/kg bodyweight) did not lead to delayed or impaired axon regeneration. Long-term application in normal peripheral nerves did however cause axon degeneration with edema and vacuolisation of myelin sheaths, retraction of myelin sheaths from the node of Ranvier, and marked enhancement of the Schmidt-Lantermann incisures. As neurological side effects such as tremor and paresthesia have been reported under application of CsA in man, the above data might be of clinical relevance.

Animals↗
PubMed1989

Temporal evolution of electroencephalographic abnormalities in Creutzfeldt-Jakob disease.

Frequent serial EEG investigations of three patients with neuropathologically confirmed Creutzfeldt-Jakob disease lasting 13, 24 and 68 weeks revealed typical periodic activity of short duration with stereotyped bilateral sharp waves at the 7th, 8th, and 12th week, respectively, after the onset of symptoms. During the later stages, there were several deviations from this typical pattern. However, periodic activity was preceded between the 3rd and 9th week by intermittent localized or lateralized delta rhythms, which gradually changed into periodic activity. This early temporal evolution of EEG abnormalities may be helpful in the early diagnosis of Creutzfeldt-Jakob disease when accompanied by other investigations to exclude other causes of intermittent delta rhythms.

Aged↗
PubMed1989

Serial computed tomography findings in Creutzfeldt-Jakob disease.

Serial CT investigations of 3 patients with histologically confirmed Creutzfeldt-Jakob disease revealed persisting slight brain atrophy to progressive extreme atrophy corresponding to the absolute, not the individual duration of illness. No correlation was observed between CT findings and the patients' condition or electroencephalographic results. In one case with a duration of about 16 months and a terminal brain weight of 750 g a massive bilateral, later unilateral subdural hygroma appeared which probably was caused by retraction of the brain showing an enormous atrophy.

Atrophy↗