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Biomedical subjects

A Laurent

Publications and source records attributed to A Laurent.

At least 19 recordsLinked to original sources
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↗
PubMed1988

Maitotoxin triggers the cortical reaction and phosphatidylinositol-4,5-bisphosphate breakdown in amphibian oocytes.

Maitotoxin, a potent marine toxin extracted from peredinians, was found to mimic fertilization in Xenopus oocytes and to trigger the breakdown of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2, the precursor of inositol 1,4,5-trisphosphate], an increase of intracellular pCa and the cortical reaction, including the exocytosis of cortical granules and a wave-like propagation of contraction in the animal hemisphere. All these effects of maitotoxin required the presence of external calcium. Moreover, the toxin considerably increased Ca2+ influx in amphibian oocytes arrested at first meiotic prophase, due to the permanent activation of voltage-dependent Ca2+ channels. Nevertheless it is doubtful that maitotoxin acts primarily as a Ca2+ ionophore or at the level of Ca2+ channels. Indeed no stimulation of Ca2+ uptake was observed in metaphase-II-arrested oocytes, although maitotoxin readily triggered the breakdown of PtdIns(4,5)P2 as well as the cortical reaction in such cells. On the other hand, PtdIns(4,5)P2 breakdown was not reduced in oocytes microinjected with EGTA, although the calcium chelator prevented the oocytes from undergoing the cortical reaction. Taken together, these findings support the view that the toxin might act primarily by increasing PtdIns(4,5)P2 phosphodiesterase activity.

Animals↗
PubMed1988

Involvement of a calcium-phospholipid-dependent protein kinase in the maturation of Xenopus laevis oocytes.

It has been described that phosphorylation, and dephosphorylation, of specific proteins is associated with key events of the cell cycle and is likely to be due to activation of kinase(s). From our results, the presence of calcium-phospholipid-dependent protein kinase (PKC) was clearly demonstrated in both the cytosolic and particulate fractions of immature Xenopus laevis oocytes and in the cytosolic fraction of mature oocytes. However, it was less active in metaphase II- than in prophase I-arrested oocytes. The enzyme was partially purified by DEAE-cellulose and phenyl-Sepharose chromatography. It was activated in vitro by the tumor-promoting phorbol ester, 12-O-tetradecanoyl phorbol 13-acetate (TPA) as already described for PKC from other tissues. On the other hand, a calcium-phospholipid-independent histone kinase activity 4-fold higher in metaphase II- than in prophase I-arrested oocytes was detected. The possible role of PKC and phospholipid-independent histone kinase in the maturation process is discussed.

Animals↗
PubMed1988

Treatment of a recurrent traumatic carotid-cavernous fistula: vertebro-basilar approach after surgical occlusion of the internal carotid artery.

A case of a post-traumatic carotid-cavernous fistula treated by endovascular approach through the vertebrobasilar system is reported. The 16 year old female patient was hurt in a car accident. The instantly-occurring carotid-cavernous fistula was treated with a Fogarty catheter, the internal carotid artery being occluded during this procedure. Ten years later the fistula recurred with a predominantly cortical venous drainage. The fistula was closed with two detachable balloons by an endovascular approach from the vertebrobasilar system via the posterior communicating artery. The small residual fistula, fed by the external artery was occluded by a venous approach via the internal jugular.

Adult↗
PubMed1988

[Van Bogaert's cerebrotendinous xanthomatosis. A study of 3 cases].

The authors report three observations of cerebro-tendinous xanthomatosis (CTX). The three patients presented tendinous xanthoma and cataract. The neurologic disorders were different in each case. The first one, a 43 years old woman suffered from dementia, ataxia and pseudobulbar palsy: CT scan showed cerebellar hypodense lesions. After the apparition of bulbar signs ans cachexia she died at 45. The second patient, a 39 years old man had an ataxia and mild psychiatric disorders. He was stabilized with a treatment of chenodesoxycholic acid. The third one, a 49 years old women suffered only from tendinous xanthoma, cataract, and had no neurological disorder. His plasmatic cholestanol level was high. CTX is a recessive deficit of the hepatic 26 hydroxylase with deposits of abnormal metabolites in tendons, crystalline lenses and central nervous system. Reviewing the 44 observations of CTX in the literature, the authors define the genetical, clinical, biochemical and therapeutical aspects of CTX, and underline the necessity of a early diagnosis with cholestanol dosage, before the apparition of neurological disorders and the short terminal phase. CTX is a rare but fortunately treatable neurolipidosis.

Adult↗
PubMed1987

Further evidence for a central stimulatory action of catecholamines on adrenocorticotropin release in the rat.

Catecholamines may stimulate ACTH secretion during stress. To investigate the nature and site of such an action, plasma ACTH was measured in four groups of unanesthetized adult female rats with an indwelling carotid cannula. Sequential 300-microliter blood samples were taken 60 min, 30 min, and immediately before an intracerebroventricular (icv) infusion of 2.5 microliter adrenaline or noradrenaline and 5, 15, 45, 60, and 120 min after the infusion. The four groups were: 1) intact rats; 2) rats infused 7 days after undergoing a discrete bilateral lesion of the ventral noradrenergic ascending bundle caused by 6-hydroxydopamine, which depleted their hypothalamic adrenaline and noradrenaline levels by 90% and 80%, respectively; 3) rats infused 30 min after pretreatment via the icv route with either prazosin or propranolol; and 4) rats infused 16 and 2 h after two successive intracarotid injections of an anti-rCRH-41 serum. In another group, the effects of icv catecholamine administration were compared with those of an intracerebral (ic) microinfusion close to a single paraventricular nucleus (PVN). Finally, in two additional groups blood was sampled at the above-mentioned times before and after a 2-min ether inhalation by intact rats or prazosin- and/or propranolol-pretreated rats. In the intact rats (group 1), a stress-like stimulatory dose response was noted after both adrenaline and noradrenaline infusions, with a half-maximal effect at concentrations of about 0.6 nmol and a maximal effect at 2.7 nmol or more. At maximally effective doses, adrenaline was significantly more active than noradrenaline. In the rats with ventral noradrenergic ascending bundle lesions (group 2), 2.7 nM adrenaline or noradrenaline stimulated ACTH release as in the controls without lesions. In group 3, prazosin blocked the ACTH responses to both adrenaline and noradrenaline, whereas propranolol only blocked the response to adrenaline. In group 4, i.e. rats pretreated with an anti-rCRH-41 serum, the amplitude of the ACTH surge after icv adrenaline or noradrenaline infusion was halved. A unilateral ic catecholamine microinfusion next to the PVN (half the icv dose given in group 1) led to a rapid ACTH release that peaked at half the response measured in the icv infused rats. Ether stress-induced ACTH release was decreased by 50-60% after icv pretreatment with 1 or 10 micrograms prazosin, 1 or 6.5 micrograms propranolol, or a combined dose comprising 1 microgram of both. The following conclusions were reached.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗
PubMed1987

[Arteriovenous malformations in the region of the ampulla of Galen. Anatomical and clinical aspects and the course of endovascular treatment (1979-1986). Apropos of 10 cases].

Technological progress has resulted in embolization being adapted as treatment of choice for arteriovenous malformations in the region of Galen's ampulla. To ensure recovery it is essential to conduct treatment at an early stage, to adapt it to the morphologic type of malformation and to investigate possible associated thrombosis requiring anticoagulant therapy. A shunt operation may be necessary if hydrocephalus fails to regress.

Adult↗
PubMed1986

Endovascular treatment of vertebral arteriovenous fistulas in twenty-two patients.

Twenty-two cases of vertebral arteriovenous fistulas treated by embolization are reported. Although such fistulas are usually asymptomatic they may be occasionally responsible for tinnitus. Neurologic complications are exceptional. Spontaneous fistulas have been found predominantly in the C1-C2 region (9 of 13 cases), while post-traumatic fistulas were located in the C5-C6 region and were often iatrogenic in origin (7 of 9 cases). In 17 cases embolization caused definitive closure of the fistula, while the vertebral artery remained patent. In three patients it was also necessary to close the vertebral artery in order to occlude the fistula. In two instances, endovascular management failed to obliterate the fistula. At present, endovascular treatment is the simplest and one of the least aggressive therapeutic approaches to vertebral arteriovenous fistulas.

Angioplasty, Balloon↗