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Biomedical subjects

C Michel

Publications and source records attributed to C Michel.

At least 397 records · Page 22Linked to original sources
PubMedDate not supplied

Marine animal biosynthetic constituents for cancer chemotherapy.

A fifteen year investigation of marine animal components as sources for new and potentially useful cancer chemotherapeutic drugs has led to our discovery of a number of such valuable substance. The especially productive Indian Ocean sea hare Dolabella auricularia has yielded (100 kg leads to or approximately 1 mg each) a series of very potent cell growth inhibitory substances designated dolastatins 1-9. The first member of this new series, dolastatin 1, may represent the most potent anticancer agent so far uncovered with, e.g., a curative response (33%) using a dose of 11 microgram/kg (T/C 240, to T/C 139 at 1.37 microgram/kg) in the National Cancer Institute's murine B16 melanoma. Structural elucidation of the new antineoplastic agents is underway, and recent progress is illustrated with peptide dolastatin 3 (P388 ED 50 2.7 x 10(-7) microgram/ml).

Animals↗
PubMedDate not supplied

Radical intermediates during the oxidation of nitropropanes. The formation of NO2 from 2-nitropropane, its reactivity with nucleosides, and implications for the genotoxicity of 2-nitropropane.

The chemistry of the nonenzymatic oxidation of the rat liver carcinogen, 2-nitropropane, and its anionic form, propane-2-nitronate, was investigated using pulse radiolysis and EPR/spin trapping with 3,5-dibromo-4-nitrosobenzenesulfonic acid as the trapping agent. The results suggest that, following initial oxidation to a secondary alkyl radical, propane-2-nitronate is effectively degraded in a peroxidative chain reaction with the intermediary formation of peroxyl and NO2.radicals. The latter radical was shown to react appreciably fast with ribonucleosides, deoxyribonucleosides, and guanosine nucleotides. It is proposed that nonenzymatic formation of NO2.radicals after enzymatic oxidation of propane-2-nitronate to the corresponding secondary alkyl radical accounts for the induction of DNA damage observed after exposure of rats to 2-nitropropane.

Free Radicals↗
PubMedDate not supplied

H-2 influence on the production of real but not of apparent H-2-specific antibodies induced by the association of syngeneic class I heavy chains with bovine beta 2-microglobulin.

Immunogenic properties of class I molecules resulting from the association of mouse class I heavy chains with a xenogeneic beta 2-microglobulin (beta 2-m) were investigated by studying the antibody response of mice of injections to syngeneic Con A lymphoblasts, induced in conditions allowing the replacement of endogenous beta 2-m by exogenously added bovine beta 2-m provided by fetal calf serum (FCS-Con A blasts). Lymphocytotoxic antibodies were regularly produced and according to their specificities they could be divided into two types: antibodies whose reactivity was (1) dependent on and (2) independent of the presence of bovine beta 2-m on target cells. Although both types displayed an H-2 dependent polymorphic reaction pattern, only antibodies recognizing class I molecules without bovine beta 2-m can be considered as real H-2-specific antibodies. The others are only apparent H-2-specific antibodies: their polymorphic reaction pattern is dependent both on the presence of bovine beta 2-m on the surface of target cells and on their H-2 haplotype. A comparison of the antibody response of mice with various H-2 haplotypes to injections of syngeneic FCS-Con A blasts showed no significant difference in the induction of bovine beta 2-m-dependent antibodies (apparent H-2-specific) among the mice from all strains tested (H-2b, H-2p, H-2q, and H-2s). Unexpectedly, for most strains more than 60% of the immunized mice produced also beta 2-m-independent antibodies (real H-2-specific), with the exception of H-2q mice, in which only 30% of sera were positive. The real H-2-specific antibody response is of two types: some mice (H-2p and H-2s) produced antibodies only reactive with allogeneic target cells whereas others (H-2b and H-2q) produced in addition antibodies that were reactive with syngeneic cells. Thus H-2 appears to play an important role in the induction and specificity of the lymphocytotoxic H-2-specific antibodies induced upon immunization with cells expressing syngeneic class I heavy chains associated with bovine beta 2-m.

Animals↗
PubMedDate not supplied

Kinetic investigations of the autoxidation of adrenalin.

Generation rates of superoxide anions (O2-) by autoxidizing adrenalin at pH 9.5 were determined in solutions containing either superoxide dismutase (0.85 M-1 S-1) or hydroxylamine (0.0185 M-1 S-1) as competitive scavengers. The rate constants of O2- with adrenalin and hydroxylamine were calculated for neutral and alkaline solutions. The respective values were for adrenalin: 5.6 X 10(4) M-1 S-1, pH 7.8; 7.0 X 10(3) M-1 S-1, pH 9.5--and for hydroxylamine 5.9 X 10(4) M-1 S-1, pH 7.8; 3.4 X 10(4) M-1 S-1, pH 9.5. The effects of various competitors and O2- sources on the rate constants were compared.

Epinephrine↗
PubMedDate not supplied

Radical functions in vivo: a critical review of current concepts and hypotheses.

Most of the basic knowledge about radical reactions comes from radiation chemical studies in vitro. In view of the rapidly increasing knowledge on radical reaction in vivo, it is important to reconcile the fundamental physico-chemical reaction characteristics of radicals with the need to explain their alleged biological effects. Severe problems in the understanding of their in vivo action remain unsolved. An example is phagocytosis, which seems to be a paradigm of a 'deleterious' radical process. The exact mechanism is not clear; so it is an open question whether the intruder is eventually killed by radicals (like OH) or by endproducts of radical reactions (like H2O2 and/or HOCl). It is even more difficult to understand signalling by radicals: owing to their chemical nature they are 'unspecifically' reacting species--they withdraw or add electrons--and thus their reactions are governed by redox-properties. Since all radicals have different redox characteristics and different molecular shapes, the usual key-and-keyhole picture for molecular interaction does not apply, as there, is no reactive site conceivable which has the property of reacting with radicals 'specifically. Our intent in this article is: (i) to briefly review some fundamental characteristics of in vitro radical reactions, (ii) to extrapolate from this to the conditions in vivo, and (iii) to discuss current hypotheses concerning the redox-regulation of cellular signalling. This leads us to the tentative conclusion that radicals per se must be tolerated by the cell and do not threaten its life, if they stay below a certain concentration limit. The main biological implication of radical-reactions seems to be that the cell derives signals from the balance of oxidative versus reductive processes and that radicals may interact with pathways of intra- and intercellular communication.

Animals↗
PubMedDate not supplied

[Late sequelae of childhood condylar process fractures and their therapeutic options].

The causes of TMJ ankylosis after collum mandibulae fractures in the early childhood are discussed and two different surgical treatment approaches are presented. In cases of unilateral involvement it often suffices to separate the ankylosed area while the rest of the joint is spared; where as in cases of pronounced bilateral ankyloses wide reactions with temporary implantation of bone cement are carried out.

Adult↗
PubMedDate not supplied

[Results after treatment of facial fractures with the Wurzburg titanium miniplate system].

The basic principles of anatomy and materials science, forming the foundation for the application of the Würzburg titanium miniplate system, are described in detail. Based on 252 midfacial fractures and 315 mandibular fractures treated with this Miniplate system between 1984 and 1987, the clinical results of using this system in traumatology are discussed.

Bone Plates↗
PubMedDate not supplied

[Treatment of midfacial fractures with bicoronal incisions].

During the period 1985 to 1987 twelve patients with central or centrolateral midfacial fractures were operated via a bicoronal approach at the university hospital for oro- and maxillofacial surgery in Wurzburg. All fractures were treated with the Wurzburg titanium mini-plates. Esthetic and functional results were very satisfactory, since this type of incision offers good access to the site of surgery without causing surgery induced scars in the visible area.

Adult↗
PubMedDate not supplied

[Value of the kidney revascularization in renovascular hypertension with kidney failure].

The effects of renal revascularization on blood pressure and renal function were evaluated in 8 hypertensive patients with renal impairment and renal artery stenosis in both kidneys (6 cases) or in a solitary kidney (2 cases). Mean age was 66 +/- 7 years. The mean duration of arterial hypertension was 13 +/- 8 years. In spite of treatment with 3 antihypertensive drugs (or more in 5 cases) blood pressure values ranged from 170-90 to 260-150 mmHg. Adding captopril (in 3 cases) or minoxidil (in 1 case) resulted in control of hypertension in 1 patient and further deterioration of renal function in 2. Two patients underwent surgery after failure of percutaneous transluminal angioplasty. There were 6 revascularizations and 2 nephrectomies with contralateral revascularization. One patient died post-operatively. In the remaining 7 patients, the hypertension was controlled with one or two drugs and the renal function remained stable or improved over a mean follow-up period of 2 years. We consider that these results warrant radiological exploration in all patients, even old, with renal impairment and drug-resistant hypertension. Renal revascularization must be performed as early as possible in view of the rapid degradation of renal function under medical treatment in these patients.

Acute Kidney Injury↗
PubMedDate not supplied

[Cerebral glucose metabolism in autistic children. Study and positron emission tomography].

Brain glucose metabolism was measured in 18 autistic children, using high resolution positron emission tomography (PET Scan), with fluorodeoxyglucose (FDG) as tracer. Measurements were performed on an ECAT III tomograph (CTI). Global brain glucose utilization in the autistic population was slightly more elevated than in young adult volunteers, particularly in frontal cortical regions, an observation previously reported for adult autists (Rumsey et al., 1985). However, mean brain glucose metabolism did not differ significantly from that of control children. Regional metabolic maps were also normal, although there was evidence for heterogeneities, particularly at the level of prefrontal and parieto-occipital association areas: 6 children showed a relative hyperfrontality whilst hypofrontality was found in 2 cases. These data suggest that PET might be useful for a better definition of subsets of autistic syndrome in children.

Adolescent↗
PubMedDate not supplied

Effects of morphine on urine flow in rats. Involvement of vasopressin.

The actions of morphine (1.25 to 20 mg/kg i.p.) were compared in several models of experimental polyuria: alcohol--or water--loaded rats and Brattleboro rats (i.e. animals with congenital lack of vasopressin). In normal rats (without load), morphine induced no change except at low dose. In water-loaded rats, the opiate exhibited its dose-related antidiuretic effect and increased Na+, urea and osmolality excretion. After inhibition of vasopressin secretion by alcohol load as well as in Brattleboro rats, morphine induced antidiuretic response for the higher doses and diuretic effects for the lower doses. The morphine --induced changes in urine flow were suppressed by naloxone in normal, water--and alcohol--loaded rats. These results indicate that morphine is able to induce diuretic or antidiuretic action according to the state of hydratation in conscious rats after peripheral administration. This property is due to an interference with opiate receptors without involvement of vasopressin secretion.

Animals↗