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Biomedical subjects

G Fischer

Publications and source records attributed to G Fischer.

At least 469 records · Page 26Linked to original sources
PubMed1986

[Exclusion of an arteriovenous malformation of the left olfactory groove using endo-orbital ligation of the ethmoidal arteries].

A case history of a 59 year old male patient having an intra frontal cerebral hematoma due to a ruptured olfactory groove arteriovenous malformation (AVM) is reported. Following the operative removal of the hematoma, the patient improved steadily and the risk of a recurrent bleeding was considered. A total thrombosis of the AVM was achieved by a two step bilateral transorbital ligation of both anterior and posterior ethmoidal arteries, with no further intracranial approach. The simplicity of this technic is pointed out and its application in other pathological conditions-such as basilar meningiomas in which embolization is hazardous--is suggested. The authors more recently experienced the beneficial effect of transorbital ligation of ethmoidal arteries prior to removal of a highly vascular supra-sellar meningioma.

Arteries↗
PubMed1986

Effects of long-term administration of propyldazine on blood pressure and counter-regulatory systems in conscious hypertensive dogs.

The counter-regulatory effects in response to blood pressure reduction by propyldazine were studied in conscious dogs with bilateral cellophane perinephritis hypertension. During a 22-day period of chronic treatment, the initial increase in heart rate, plasma renin activity, angiotensin II, aldosterone, and vasopressin, which indicate counter-regulation to the drug induced decrease in blood pressure, vanished. On the fifth day of treatment another, presumably cellular mechanism, had taken over the restitution of blood pressure and thereby led to tolerance towards the action of further propyldazine administration. Seven days after the end of chronic treatment a renewed propyldazine administration did not produce the same effects as obtained with the first administration; after 28 days the hypotensive effect of propyldazine was identical to the one observed before treatment.

Animals↗
PubMed1985

The refolding of urea-denatured ribonuclease A is catalyzed by peptidyl-prolyl cis-trans isomerase.

The refolding of urea-denatured ribonuclease A was measured at 0.31-3.1 mol . l-1 urea in the presence of various concentrations of peptidyl-prolyl cis-trans isomerase isolated from pig kidney. The rate of the slow CT-phase in the refolding reaction was found to be sensitive to this enzyme. A rate enhancement proportional to the isomerase activity has been observed. The activity of the enzyme was assayed with Glt-Ala-Ala-Pro-Phe-4-nitroanilide. The catalytic activity of the isomerase against unfolded ribonuclease is suppressed after preincubation of the enzyme with 0.001 mol . l-1 Cu2+, 0.01 mol . l-1 H+ and by heat inactivation. The results indicate the involvement of the cis/trans interconversion of proline peptide bonds during the refolding of ribonuclease A.

Amino Acid Isomerases↗
PubMed1985

Cultured astrocytes form a syncytium after maturation.

The formation of functional gap junctions between astrocytes was investigated during differentiation of these cells in culture. Precursor cells of GFA (glial fibrillary acidic) protein-positive astrocytes were cultured in a chemically defined medium as a homogeneous population. These cells were rarely coupled to one neighbour, as revealed by electrical and dye coupling and never formed a large syncytium, as investigated by injection and spread of Lucifer Yellow. Differentiation with respect to GFA protein accumulation can be induced in these cells by culturing in horse serum-containing medium. The formation of functional junctions developed within 2 weeks in about 20% of the cells. Coupled cells formed a large syncytium. When the astrocytes were co-cultured with primary cerebellar cells (consisting predominantly of small neurons) after the switch to serum-containing medium the percentage of coupled astrocytes increased to about 65%. Again the coupled cells formed a large syncytium. Since no physical contact was possible between the astrocyte cultures and the primary cerebellar cells the stimulation of coupling had to be signalized by soluble factor(s).

Animals↗
PubMed1985

[Somatosensory evoked potentials in intraspinal tumors].

SEPs have been recorded in 15 patients with spinal cord tumors (mostly ependymomas) and in 5 patients with cord compression due to meningiomas (3 cas), neuromas (1 case) or neurosarcoma (1 cas). All the patients have been operated on so that precise informations were available on the histology and the location of the tumor. SEPs were monitored during surgery in 8 patients. The main conclusions of this study are as follows: There was a good correlation between the somatosensory troubles for touch, vibration sense and joint position sense, and SEPs abnormalities, however, SEPs may be clearly abnormal in the absence of any somatosensory deficit when the dorsal columns are compressed and not infiltrated by the tumor. In the latter situation the reverse dissociation (i.e., normal SEPs with somatosensory troubles) may be observed. The possibility of a dissociation between normal N11 and N13 cervical components and absent P14 far field components (non-cephalic reference) has been confirmed in 6 patients with cervicomedullary tumors. In 3 of them, this dissociation was found to be reversible and early SEPs returned to normal after surgery. Peroperative monitoring of scalp SEPs recorded with a non-cephalic reference electrode allowed the detection of transient SEP abnormalities related with a traction on the dorsal columns of the cord. SEP monitoring is recommended for any surgical removal of tumor that needs a posterior myelotomy.

Adult↗
PubMed1985

Effects of N-nitrosomorpholine and phenobarbital on UDP-glucuronyltransferase in putative preneoplastic foci of rat liver.

Effects of initiators and promoters of hepatocarcinogenesis on UDP-glucuronyltransferase and arylhydrocarbon hydroxylase were investigated in foci of altered hepatocytes. A single administration of N-nitrosomorpholine (75 mg/kg, 24 h after partial hepatectomy) was used for initiation and chronic administration of phenobarbital (0.1% in tap water) for promotion. Histological evidence indicated that ATPase-negative, gamma-glutamyltranspeptidase-positive, and UDP-glucuronyltransferase-positive foci were highly correlated. Based on this evidence ATPase-negative foci were used as a guide to monitor early lesions and to microdissect lyophilized foci and extra-focal tissue. It was found that treatment with N-nitrosomorpholine led to a permanent increase of UDP-glucuronyltransferase activity in foci tissue (3- to 5-fold, detected 180 and 330 days after initiation). In contrast, arylhydrocarbon hydroxylase activity was decreased by 50%. Administration of phenobarbital further increased UDP-glucuronyltransferase activity in focal tissue (up to 9-fold, compared with control liver). However, this further increase of enzyme activity by phenobarbital was reversible. The results suggest that (i) initiation by chemical carcinogens leads to permanent alterations of drug metabolizing enzymes, consistent with increased toxin-resistance of initiated hepatocytes, and (ii) chronic administration of phenobarbital markedly enhances gene expression of UDP-glucuronyltransferase in initiated hepatocytes.

Adenosine Triphosphatases↗
PubMed1985

Glycosaminoglycans of rat cerebellum: I. Quantitative analysis of the main constituents at postnatal day 6.

Isolated glycosaminoglycans (GAGs) were quantified biochemically in the cerebella of 6-day-old rats. 14C-Labeled hyaluronic acid (HA) and chondroitin-4-sulfate (C-4-S), added prior to isolation of GAGs from tissue, served as internal standards to allow correction for unknown losses during the purification procedure and exact quantification of GAGs in the intact tissue. Three main constituents--HA, chondroitin sulfate (CS), and heparan sulfate (HS)--were found at concentrations of 1.82, 1.52, and 0.76 micrograms/mg protein amounting to 44%, 37%, and 19% of the total GAG fraction, respectively. Incorporation of [3H]glucosamine precursor into GAGs was higher for HS (56% of incorporated precursor) and lower for HA (29%) and CS (15%). The specific activities of individual GAGs were 64.7 nCi/micrograms for HS, 14.2 for HA, and 8.3 for CS.

Acetic Anhydrides↗
PubMed1985

Glycosaminoglycans of rat cerebellum: II. A developmental study.

Total and individual glycosaminoglycans (GAGs) were determined in rat cerebellum in tissue explants at various postnatal ages. The major constituents of GAGs were chondroitin sulfate (CS), hyaluronic acid (HA), and heparan sulfate (HS). Dermatan sulfate (DS) and keratan sulfate (KS) could not be detected and therefore each amounts to less than 5% of all GAGs at all ages studied. HA was the prominent GAG during postnatal development and only a minor constituent at adult ages, whereas CS was the predominant GAG in adulthood. HS remained relatively constant throughout development. The incorporation of [3H]glucosamine into individual GAGs was highest for HS at postnatal day 6, whereas HA showed intermediate and CS the lowest levels of incorporation during the first postnatal week. All major GAGs showed the lowest incorporation values at adult ages.

Age Factors↗
PubMed1985

Intramedullary sarcoidosis of the cervical spinal cord.

A 26-year-old male with a history of pulmonary sarcoidosis showed clinical, myelographic and intra-operative evidence of a C5-C6 spinal cord tumour, which was diagnosed by biopsy as a pure intramedullary granuloma. Among the 29 published cases of histologically proven cord sarcoidosis, only five presented with pure parenchymatous infiltration without meningeal involvement. Corticosteroids are the most useful therapy, and surgery is indicated only for minimal biopsy when the parenchyma is invaded.

Adult↗
PubMed1985

Treatment of cerebrospinal fluid rhinorrhea by percutaneous lumboperitoneal shunting: review of 15 cases.

Fifteen patients with recalcitrant cerebrospinal fluid (CSF) fistula underwent the insertion of a lumboperitoneal shunt. The shunt consists of a two-piece Silastic tube and has been used in a population of 150 patients with communicating hydrocephalus, persistent postoperative meningocele, and benign intracranial hypertension. The spinal catheter is introduced subcutaneously and no flushing device is used. We studied three groups: 9 patients had a history of head trauma, and 7 of these had undergone one or several ineffective direct approaches to the dural leak. Four patients presented with a presumably congenital fistula. Two patients had persistent rhinorrhea due to previous intracranial procedures. Indium-111 cisternography was performed in 10 patients before lumboperitonel (LP) shunting and failed in 2 of those to document the site of leakage. Twelve patients showed cessation of rhinorrhea after LP shunting. In 4 of these, shunt-related complications responded to shunt removal with no further recurrence of rhinorrhea. Two patients underwent revision of the shunt. In 3 patients, the LP shunt failed to control the CSF leak and further intracranial procedures were indicated. The LP shunt provides an attractive and technically simple solution when direct methods of treatment have failed. Additionally, LP shunting should be considered as a primary mode of treatment in elderly patients or when impairment of CSF dynamics is documented by radionuclide cisternography and computed tomographic scanning. When an LP shunt is ineffective, shunt function should be checked by isotopic studies before additional surgery is performed.

Adult↗
PubMed1985

[The cause of growth processes].

Transformation of fundamental ideas of physics into the biology has created biodynamics. In this paper, biodynamics has brought into a greater frame of physics and biology, and so stand out the connections at heart between both branches of knowledge. By the help of the idea of force, it will be possible to develop a bio-technics out of the bio-science, similar the developing of technics out of the physics.

Biomechanical Phenomena↗