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Biomedical subjects

A Laurent

Publications and source records attributed to A Laurent.

At least 91 records · Page 5Linked to original sources
PubMed1994

15-Desmethyl FK-506 and 15,31-desmethyl FK-506 from human liver microsomes: isolation, identification (by fast atom bombardment mass spectrometry and NMR), and evaluation of in vitro immunosuppressive activity.

15-Desmethyl FK-506 and 15,31-desmethyl FK-506 metabolites extracted from incubated human liver microsomes were separated by normal and reversed-phase HPLC. The metabolites were identified by fast atom bombardment/mass spectrometry and nuclear magnetic resonance spectroscopy. The in vitro 50% inhibitory concentration, tested against bidirectional mixed lymphocyte reactions, was 325 mg/L for 15,31-desmethyl FK-506 and 4 mg/L for 15-desmethyl FK-506, indicating that these products of FK-506 demethylation retain in vitro immunosuppressive activity.

Chromatography, High Pressure Liquid↗
PubMed1994

[Radiosurgical irradiation of 49 cerebral arteriovenous malformations using linear accelerator].

During 1990 we treated 49 cases of arterio-veinous malformations (AVMs) using radiosurgery. We employed 15 MV X-Ray minibeams of a Saturne 43 Linac, eight additional collimators, 6-20 mm, the O Betti armchair and the Talairach stereotactic frame. Irradiation consisted of delivering 25 Gy at the periphery of the nidus corresponding to the 60-70% peripheral isodose range. We used the "Associated Target Methodology" and the three-dimensional treatment planning system Artemis-3D, both of which have been developed in our radiotherapy department. In December 1992, 44 out of 49 patients who had been treated were available for analysis with a 2-3-year follow-up. The overall obliteration rate was 33/44 (75%). According to the number of isocenters the obliteration rate was: 22/26 (85%) for one isocenter. In 18 multi-isocenters irradiation cases overall obliteration rate was 11/18 (61%). Two isocenters were used in nine of these 18 cases, the obliteration rate was 6/9; while when three isocenters were used it was 2/4 and in five cases of four isocenters irradiation the obliteration rate was 3/5. Obliteration rate for lesions < or = 4200 mm3 was 31/37 (84%). For greater volumes (5500 mm3 to 19000 mm3; median 9200 mm3) the obliteration rate was 2/7 whereas three others were partially (75 to 90%) obliterated and two remained inchanged. Before radiosurgery 21 cases received other treatment (mostly embolizations), the obliteration rate in this group was 15/21 (71.5%) while in previously untreated AVMs it was 18/23 (78%). A control arteriography was performed between 6 to 18 months after radiosurgery in 44 patients; three others refused the arteriography but are alive and well; two others had palliative irradiation, one of whom is dead. Out of 28 AVMs checked between 6 to 12 months 17/28 were obliterated (61%). In four cases, epilepsy was the first symptom; one has not suffered a further crisis whereas three others experienced a decrease in the number of crises. Two patients had recurrence of bleeding four and six months after irradiation (recurrence rate 2/44 = 5%). There were no lasting neurological consequences.

Adolescent↗
PubMed1994

[Specific reactivity to serotonin of afferent vessels in human pharyngolaryngeal carcinoma. Methodology and initial results].

This work describes an experimental protocol studying action of Serotonin (5-HT) on vessels feeding human pharyngolaryngeal carcinoma. Right and left superior laryngeal arteries were obtained during total (pharyngo)laryngectomy. As tumor growth is asymmetrical, tumor and opposite side arteries were considered as tumor (T) and control (C) vessels, respectively. (T) and (C) vessels were cut in 3 mm rings and suspended in organ chambers for pharmacological studies. Preliminary results (2 tumors, 7 tumoral rings and 5 control rings) indicate that 5-HT induces specific vasoconstriction in (T) arteries feeding human pharyngolaryngeal carcinoma.

Arteries↗
PubMed1994

[Early pediatric-psychiatric management of suicide attempts in adolescents].

The authors describe an experience of early intervention by child psychiatrists in adolescents attending an emergency care pediatrics unit for suicide attempts. The two main aspects of this intervention are: 1) a former interview between the child psychiatrist and the suicidal adolescent taking place within the emergency care pediatrics unit; 2) a systematic few days hospitalization of the suicidal adolescent in a child-adolescent psychiatric unit allowing early therapy for both the adolescent and his/her parents. Based on preliminary results the authors believe that early child psychiatrist intervention provides an improvement in the care of suicidal adolescents, especially to prevent recurrent suicide attempts, as compared with conventional care with delayed child psychiatrist participation.

Adolescent↗
PubMed1994

The first epidemic of dengue hemorrhagic fever in French Guiana.

From July 1991 to October 1992, an outbreak of dengue spread into the main urban areas of French Guiana, where 90% of the country's 114,808 inhabitants live. In mid-July 1991 dengue-2 virus was identified as being responsible for most cases, while dengue-1 virus was rarely isolated and circulated at a low level. The number of dengue cases during this period was unknown because there was no clinically based dengue surveillance system. The only available data were for the number of suspected cases as indicated by the number of patients for whom blood samples were submitted to a laboratory for dengue diagnosis. Eight hundred forty-seven of the 2,948 suspected cases were diagnosed in the laboratory as dengue cases. Six fatal cases were reported. This outbreak was marked by the appearance of the first clinical cases of dengue hemorrhagic fever (DHF) in French Guiana. Forty cases met the World Health Organization definition of clinical DHF: 32 were grade II, seven were grade III, and one was grade IV and fatal. Eighteen cases were confirmed in the laboratory and 12 were probable; there was no proof of the dengue etiology for the remaining patients.

Antibodies, Viral↗
PubMed1993

Biodegradable starch microspheres for cerebral arterial embolization.

RATIONALE AND OBJECTIVES: Various materials have been used to perform intracerebral and cervical arterial embolization for head and neck tumors and vascular malformations. This preliminary prospective study was designed to analyze the clinical and histopathologic consequences of arterial embolization into the brain using biodegradable starch microspheres. METHODS: A new arterial embolization procedure which ensured the integrity of the common and internal carotid arteries, without modifying the arterial flow, was designed. The procedure allowed for cerebral arterial microembolization in 20 Sprague-Dawley rats. Various amounts of biodegradable starch microspheres (Spherex) were introduced into the brain via the left external carotid artery. RESULTS AND CONCLUSIONS: Clinical and histopathologic results suggested that: 1) consequences of cerebral embolization using biodegradable starch microspheres are related to the amount of material embolized; and 2) Spherex microspheres behave differently from degradable microspheres in the brain. Despite the rapid biodegradability of the material, permanent damage from ischemia to the brain was noted.

Animals↗
PubMed1993

Herpes simplex virus ICP0 and ICP4 immediate early proteins strongly enhance expression of a retrovirus harboured by a leptomeningeal cell line from a patient with multiple sclerosis.

A leptomeningeal cell line (LM7) harbouring an unknown retrovirus was recently isolated from the cerebrospinal fluid of a patient with multiple sclerosis. However, spontaneous expression of the LM7 retrovirus in this primary culture is quite low. We present results showing that in vitro infection of LM7 cells with herpes simplex virus type 1 (HSV-1), but not that of control cells, results in (i) potent stimulation of the specific reverse transcriptase (RT) activity detected in the culture supernatant and (ii) co-expression of both typical HSV-1 virions and abundant retrovirus-like particles. Transfection of LM7 cells with plasmids expressing HSV-1 immediate early (IE) ICP0 and ICP4 proteins produced a similar enhancement of RT activity in culture supernatants with retrovirus-like particles being identifiable by electron microscopy. These effects were not observed with a plasmid expressing ICP27 or with the parental plasmid in LM7 cells, nor with any of these four plasmids in control cells. These results show that HSV IE trans-activating proteins strongly enhance the expression of the latent retrovirus present in LM7 cells. The possible role in vivo of herpesviruses as 'triggering' cofactors in the retrovirus hypothesis for multiple sclerosis aetiology is also discussed.

Arachnoid↗
PubMed1993

[Family violence and adolescence].

Intrafamilial violence represents a vast topic, even if one limits the subject to the nuclear family. Indeed it includes violence from parents to the child, violence between brothers and sisters, conjugal violence and violence exercised by the child to his parents. Although one can differentiate the types of violence (physical, sexual, and psychological), they often coexist within the same family. Adolescence favors the onset or the reactivation of familial violence; this violence often has repercussion on the psychological equilibrium of the adolescent. Very little is written about parents abused by one of their children (usually an adolescent). This phenomenon is relatively unrecognized and its frequency probably under-estimated. It points to a distortion in parent to child relationship. Therapeutic and/or socio-educational approach must be directed toward both the victim and the aggressor.

Adolescent↗
PubMed1993

[Effects of the stimulation of the subthalamic nucleus in Parkinson disease].

In Parkinson's disease, experimental studies favour a neuronal hyperactivity of the subthalamic nucleus. We carried out a subthalamic nucleus electrical stimulation in a patient aged 51, suffering for 8 years from a severe akineto-rigid form of Parkinson's disease, complicated with an on-off effect. Stereotaxic surgery was done under local anaesthesia on one side. Within the theoretical target, a 130 Hz stimulation induced akinesia alleviation mainly on the contralateral limbs. No abnormal movement was noticed. Then a long-term quadripolar DBS Medtronic electrode was inserted in that area. The study of the effects of chronic stimulation is in progress to determine the best temporal and electrical stimulation variables.

Electric Stimulation Therapy↗
PubMed1992

Relationship between symptoms rated with the Positive and Negative Syndrome Scale and brain measures in schizophrenia.

The Positive and Negative Syndrome Scale (PANSS) was used to rate clinical symptoms in 42 inpatients with schizophrenia before they were examined by computed tomography. Significantly higher mean size of lateral and third ventricles, and higher mean cortical atrophy were found in schizophrenic patients compared with healthy control subjects. Ventricular enlargement and cortical atrophy were significantly related to low scores on the Composite subscale of the PANSS. Positive correlations were observed mainly with negative items such as blunted affect, emotional withdrawal, difficulties in abstract thinking, passive-apathetic social withdrawal, and lack of spontaneity of conversation. Additional positive correlations were observed with two items from the General Psychopathology subscale (mannerisms and disorientation). Inverse correlations were found with most positive items. These results suggest a relationship between brain structural abnormalities and the symptomatology of schizophrenia recorded with PANSS.

Adult↗
PubMed1991

Cerebrotendinous xanthomatosis: treatments with simvastatin, lovastatin, and chenodeoxycholic acid in 3 siblings.

We report 3 sisters treated for cerebrotendinous xanthomatosis. We treated one, with a severe neurologic form of the illness, with chenodeoxycholic acid, then lovastatin and simvastatin. These drugs had different efficacy and tolerance, but induced no clinical improvement. Her sisters, without neurologic symptoms, received chenodeoxycholic acid, which normalized the cholestanol level. Optimal treatment of this illness must begin before there is significant clinical symptomatology.

Adult↗
PubMed1991

[Research in interventional imaging].

Interventional Imaging research has two objectives: developing new materials for atraumatic percutaneous and image-guided access to pathologies and organs, and their treatment tools. This represents a new field of research of Biomedical Engineering, which is at the cross-point of medical and engineering techniques. It requires a major input from industrial firms.

Radiology, Interventional↗
PubMed1991

[Stereotaxic irradiation of 46 cerebral angiomas. Analysis of the angiographic results 2 and a half years after treatment].

Between May 1986 and March 1987, 46 small and medium sized cerebral arteriovenous malformations (AVM) were treated by radiosurgery in Paris. The stereotaxic coordinates of the lesions were determined according to the method of J. Talairach and the total radiation dose was delivered on spherical or ovoid target volumes with minibeams of 18 MV photons, using the technique developed by Osvaldo Betti. A review of the cases was undertaken in december 89. Twenty-one patients had previously been treated by embolization and/or surgery (46.6%). During the 25 to 40 months follow-up there were only 2 recurrences of bleeding (4.3). Control arteriography was performed in 38 cases (38/46 = 82.6%). There were thirteen cases of total disappearance of the AVM (13/36 = 34.2%), 17 incomplete obliterations (44.7%) and 9 (23%) arteriographies failed to show any radiological improvement. Eight patients had no arteriographic follow-up: 2 of them experienced a recurrence of bleeding and died before the planned arteriography, 1 was lost to follow-up and 5 patients refused control arteriography. A multidisciplinary team is needed to study the shape, the volume, the hemodynamic features of the AVM and the dosimetry in order to attain the best definition of the target volume and of the dose distribution. It seems that when the target volume included the nidus and the venous collector, follow-up arteriography results were satisfactory. Even though the optimum dose is yet to be determined, our results imply that a dose distribution allowing for 25 grays at the periphery of the AVM (isodose 70%) seems sufficient provided that the target volume is included within the 25.00 Gy isodose curve.

Adolescent↗
PubMed1991

Cellular mechanism of metformin action.

Activation of the insulin receptor tyrosine kinase and tyrosine phosphorylation of intracellular substrates are important steps in insulin signalling. In order to elucidate the cellular mechanism of action of metformin (NN'dimethylbiguanide) we have focused towards the effects of metformin on the insulin receptor kinase, the phosphorylation cascade and the biological effect of insulin. Since annexins (lipocortins) have been recently recognized as substrates of several tyrosine kinases we have investigated the effect of metformin on phosphorylation of annexins after insulin stimulation or microinjection of pp60c-src kinase in Xenopus laevis oocytes. Insulin induced in oocytes progression through the cell cycle from late G2 to M phase (maturation). Microinjection of pp60c-src kinase or treatment with metformin potentiates both the rate and the level of insulin-induced oocyte maturation. In oocytes prelabeled with 32P orthophosphate metformin potentiates insulin induced phosphorylation of annexins. It is concluded that annexins are substrates of the phosphorylation cascade initiated by insulin which is synergistic to the action of pp60c-src kinase and that this early phosphorylation events correlate well with the enhanced biological effect of insulin during metformin treatment.

Animals↗
PubMed1990

Production and characterization of human monoclonal antibodies against core protein p25 and transmembrane glycoprotein gp41 of HIV-1.

With a view to obtaining human monoclonal antibodies against HIV-1 antigens we used the Epstein-Barr virus immortalization technique to induce lymphoblastoid cell lines from peripheral blood lymphocytes of 10 people who were seropositive for HIV-1 and had no clinical symptoms. A number of polyclonal lines were obtained which synthesized antibodies against most of the major proteins and glycoproteins of HIV-1. Three stable clones were characterized for class, secretion characteristics and specificity. Two of these clones produce antibodies which react with gp41, and the third reacts with p25. One of the anti-gp41 antibodies was found to have neutralizing activity.

Amino Acid Sequence↗
PubMed1989

Melanin in the inner ear. An experimental study with control and kanamycin-intoxicated colored guinea-pigs.

Following several studies on the effects of kanamycin toxicity on the inner ears of guinea pigs, we have studied the importance of melanin in this phenomenon. Transmission electron microscopy showed that, under the influence of kanamycin, the intermediate strial cells developed a secretory aspect similar to that seen in skin melanocytes. This aspect as yet has never been described for the inner ear cells. A planimetric, morphometric method was also used to determine the strial cell melanin status in control animals. Additional findings in the study confirmed an increase in the number of melanosomes during kanamycin poisoning. Statistical data are discussed.

Animals↗