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Biomedical subjects

A Laurent

Publications and source records attributed to A Laurent.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1986

Endovascular treatment with isobutyl cyano acrylate in patients with arteriovenous malformation of the brain. Indications, results and complications.

Between December 1984 and May 1986 67 patients with arteriovenous malformation (AVM) of the brain have been treated with endovascular occlusion using isobutyl-cyano-acrylate at the Lariboisière Hospital. Six patients were completely cured, i.e. with complete occlusion of the malformation. In 21, reduction of the size of the AVM was obtained, permitting surgery or radiation therapy not considered possible before endovascular intervention. In 33 cases a partial cure was achieved, but additional embolization is needed. In 3 cases the treatment was interrupted. Four patients died. The overall frequency of complications was in this material around 10 per cent.

Bucrylate↗
PubMed1986

[LAV type II: a second retrovirus associated with AIDS in West Africa].

A second retrovirus, named LAV-II, has been isolated from two West-African patients with AIDS. By its genomic sequences and its proteins, this virus is different from the LAV-I/HTLV-III, isolated from U.S.A., Europe and Central Africa. It differs also from STLV-III, isolated from Rhesus Macaques with AIDS, but displays an antigenic relationship with the latter virus, at the level of its external envelope protein. The tropism of LAV-II for T4 lymphocytes and the induction of cytopathic effect in infected cells are similar to those of LAV-I.

Acquired Immunodeficiency Syndrome↗
PubMed1985

The density of myelinated fibres is related to the fascicle diameter in human superficial peroneal nerve. Statistical study of 41 normal samples.

The density of myelinated fibres in the superficial peroneal nerve was studied in 41 samples from 24 control human subjects. Photographic montages of the whole nerve fascicle were made from semithin and ultrathin transverse sections and used for a statistical analysis of sampling procedures, range of variations and relations between density and other variables. The results indicate that the spatial distribution of myelinated fibres within a nerve is often non-uniform. Therefore, it was not possible to define a statistically valid sampling system. The study of relations between variables shows the lack of any correlation between density and age and a considerable variation in the density. In contrast, there is a strong positive linear correlation between the surface area of the nerve fascicle and its content of myelinated fibres. That is, the fibre density of a given normal nerve is related to its diameter and can be predicted within a narrow range of error. We propose the term "derived density" for this value, and its application as a tool in the diagnosis of peripheral neuropathies is now being studied.

Adolescent↗
PubMed1981

[Thyroïd cyst, parathyroïd adenoma and lithium therapy (author's transl)].

A forty years old woman had euthyroidïd functions three years ago, with normal scintiscanning. Under treatment with Lithium, she developed a clinical and biological hypothyroidïdism. A "cold" nodule was fund on the scintiscanning. Hypercalcemia and hypophosphoremia were fortuitously discovered prior to operation. A single parathyroididïd adenoma was excised from the left inferior gland. Incidence of Lithium in the appraisal of the thyroïd cyst and the parathyroïd adenoma is discussed.

Adenoma↗