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Biomedical subjects

G George

Publications and source records attributed to G George.

At least 55 records · Page 3Linked to original sources
PubMed1983

Interactions of chrysotile and crocidolite asbestos with red blood cell membranes. Chrysotile binds to sialic acid.

Chrysotile and crocidolite are commonly used forms of asbestos. Hemolysis has been widely used as a test of membrane injury, and it has been shown previously that chrysotile causes rapid breakdown of red blood cells (RBCs), whereas crocidolite is only weakly hemolytic. A reasonable hypothesis set forth to explain the cytotoxic effects of chrysotile maintains that positively charged chrysotile fibers bind to negatively charged sialic acid residues on RBC membranes causing clustering of membrane proteins and increased cell permeability to Na and K ions. Our studies presented here provide two lines of evidence in direct support of this hypothesis. (a) Morphologic--Ultrastructural techniques showed that both chrysotile and crocidolite asbestos bind to and distort more than 85% of RBCs treated for 15 minutes. The distorting effects of chrysotile, but not crocidolite, were almost totally ablated by pretreating the cells with neuraminidase. In addition, gold-conjugated wheat germ agglutinin was used to label the distribution of sialic acid groups on RBC membranes. Pretreatment of the RBCs with chrysotile, but not crocidolite, reduced the number of gold-conjugated wheat germ agglutinin-labeled sites to less than 30% of the control level. (b) Biochemical--The thiobarbituric acid assay was used to determine the percentage of sialic acid that remained with the cell pellet after neuraminidase and/or asbestos treatment. Asbestos treatment alone caused no release of sialic acid from the cells. Neuraminidase treatment for 3.5 hours removed more than 80% of the sialic acid from cell surfaces. Chrysotile, but not crocidolite, asbestos prevented neuraminidase-mediated removal of sialic acid from RBCs. In addition, x-ray energy spectrometry of freeze-dried cells showed that RBCs distorted by chrysotile, but not by crocidolite, exhibited significant alterations in intracellular Na:K ratios. The morphologic and biochemical data strongly support the hypothesis that chrysotile asbestos binds to sialic acid groups on RBC membranes. Consequently, the sialic acid residues are redistributed on the surfaces of distorted cells which then are unable to maintain a normal Na:K balance with the surrounding medium.

Animals↗
PubMed1982

[Treatment of tumors in relation to the transverse portion of the vertebral artery].

Among 28 lesions, 22 tumors and 6 anteriovenous malformations, operated with control of the vertebral artery, 15 are located close to the transverse canal. Analysis of arteriographic datas from 20 cases of tumors related to the vertebral artery, points out the interest of the surgical control of this vessel, in the treatment of these tumors. This control is mainly indicated in case of hypervascularized tumors, or compression of the vertebral artery, especially if it is the dominant vessel or if it gives a radiculo-medullary branch. For this control, the lateral retro-jugular approach is used, and sometimes associated with other techniques: embolization, posterior approach, or anastomosis between carotid and vertebral artery about the lesion.

Arteriovenous Malformations↗
PubMed1982

[On the use of physostigmine in anesthesia and intensive care].

Physostigmine is an antidote in cases of overdosage with intravenous anaesthetics such as dehydrobenzperidol, benzodiazepines and ketamine. It is also useful in antagonizing drug induced comas of different origin particularly in cases of acute intoxication with tricyclic antidepressants and alcohol. We discuss our therapeutic observations in anaesthesiological and intensive care patients. We have not seen any side effects after physostigmine administration, but the possibility of undesired parasympathomimetic activity demands correct indication, well calculated dosage and continuous surveillance of the patient.

Aged↗
PubMed1981

[Cefotaxime in the treatment of severe infections due to multiresistant Gram-negative bacilli (author's transl)].

Cefotaxime was used to treat 33 patients with serious Gram-negative bacillary infections. The dosage varied between 1.5 g and 4 g/day in patients without renal failure. Eighteen patients had urinary tract infections, 6 had pulmonary infections and 10 had miscellaneous infections. Sixteen patients were also bacteremic. Twenty-five infections were due to pathogens resistant to ampicillin, cephalothin, gentamicin and/or tobramycin, in vitro. Fifteen infections had failed to resolve during ampicillin, cefazolin, gentamicin or tobramycin therapy. Thirty-two patients responded favourably (cure or improvement). Four patients developed superinfection with cefotaxime-resistant bacteria. One patient developed mild reversible renal insufficiency. Cefotaxime is a very active cephalosporin with potential use in serious multi-resistant enterobacteria infections.

Acinetobacter Infections↗
PubMed1981

Behavioural correlates of an experimental hippocampal epileptiform syndrome in rats.

Experiments are reported describing assessment of abnormal behaviour of rats in which a chronic epileptiform syndrome has been induced by the injection of tetanus toxin bilaterally into their hippocampi. The abnormal behaviour included hyper-reactivity to a novel environment, intermittent aggression on handling, and abnormally passive response to a strange rat introduced into their home cage. In animals with unilateral injection of toxin, electrical records from the hippocampi have been obtained. They illustrated bilaterally simultaneous discharges and also some independence between the two hippocampi. The discharges were accompanied by overt signs of complex partial seizures during the first few weeks of the syndrome but later occurred without motor signs. In this later stage the rats were somewhat resistant to the convulsant effects of pentylenetetrazol.

Aggression↗
PubMed1980

[The metabolism of halothane under the influence of thiopental, methohexital, etomidate, enflurane and disulfiram under clinical conditions (author's transl)].

The biotransformation of halothane is supposed to be the cause of the rare "halothane-hepatitis". Therefore an inhibition of the metabolism of Halothane is of some interest. We used bromide as a metabolite of Halothane and investigated the bromide level of the serum of patients after halothane anaesthesia by means of x-ray fluorescence spectrometry. The induction of anaesthesia with Thiopental, Methohexital and Etomidate had no influence on the bromide level. Likewise the influence of Enflurane on the metabolism of Halothane was not significant. An effective inhibitor in man is Disulfiram. The authors assume, that further information about the toxicity of Halothane metabolites can be gained through further studies of drugs like Disulfiram.

Adolescent↗
PubMed1977

Epileptiform syndrome in rats produced by injecting tetanus toxin into the hippocampus.

An epileptiform syndrome in rats produced by injecting small doses (a few (mouse)LD50) of tetanus toxin into the hippocampus is described. The animals had intermittent seizures, with at least a superficial resemblance to human epilepsy, for some weeks but they eventually recovered. They were hyperkinetic for several weeks after the injection of toxin, and showed intermittent aggressive behaviour. Control animals which received similar injections of tetanus toxin first neutralised with antitoxin did not have seizures, and their behaviour appeared normal. EEG recordings showed characteristic seizure activity. Histological examination of the site of injection showed very little morphological damage.

Animals↗