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C Legrand

Publications and source records attributed to C Legrand.

At least 145 records · Page 8Linked to original sources
PubMed1988

Gelsolin immunoreactivity and development of the tectorial membrane in the cochlea of normal and hypothyroid rats.

Gelsolin was localized by immunocytochemistry in the developing cochlea of the rat. In normal animals, the protein appeared at 18 th day in utero in cells of the Kölliker's organ, which are involved in the secretion of the tectorial membrane. The Kölliker's organ cells were not immunoreactive after the first postnatal week, which is when they cease their secretory activity. Gelsolin immunoreactivity was similar in thyroid-deficient rats until the second postnatal week but, at this age, Kölliker's organ did not transform and its gelsolin immunoreactivity persisted, together with its secretory activity. As a result, the tectorial membrane was greatly distorted and out of contact with the hair cells, which dramatically impaired the mechanical properties of the organ of Corti. The developing cochlea thus provides an example of the involvement of gelsolin in a secretory process that is of importance in the development of hearing.

Animals↗
PubMed1988

Characterization of beta-adrenoceptors in myometrium of preparturient rats.

The purpose of this study was to characterize the beta-adrenoceptor subtypes in pregnant rat myometrial membrane fractions and to determine the concentration of beta 2-adrenoceptors in uterus during late pregnancy. Two methods are compared. A non-subtype-selective antagonist radioligand [3H]dihydroalprenolol ([3H]DHA) was used to label all of the beta-adrenoceptors. [3H]DHA bound to both beta 1- and beta 2-adrenoceptors with indistinguishable affinity (KD = 1.31 nM, Bmax = 174 fmol/mg protein). Computer modelling of competition curves of unlabeled selective antagonists or agonists was then required in order to determine reliably beta 1- and beta 2-adrenoceptor affinities and proportions: the beta 1-adrenoceptors represent 35.5% and the beta 2-adrenoceptors 64.5% of the entire beta-adrenoceptor population in rat gravid myometrium at term. The second approach utilized the radioligand [3H]hydroxybenzylisoproterenol ([3H]HBI) which is a very high-affinity beta-adrenoceptor agonist. The characteristics of the [3H]HBI binding sites are essentially those expected of beta 2-adrenoceptors, but the [3H]HBI binding sites represent only 34% of [3H]DHA binding sites and may represent the fraction of beta 2-adrenoceptors that mediate adenylate cyclase stimulation and uterine relaxation. Between 21 d 09 h and 22 d 09 h of gestation, the number of beta 2-adrenoceptors was constant (mean = 225.6 +/- 20.2 fmol/mg protein). At term, the number of [3H]HBI binding sites dropped (-75%) during the last 7 h of pregnancy, suggesting a reduced ability to elicit relaxation through beta-adrenoceptor activation in parturient myometrium of rat.

Animals↗
PubMed1987

Glucose homeostasis in magnesium-deficient rats.

Glucose homeostasis was studied in rats fed diets containing 750,200, or 100 mg/kg Mg for 6 to 8 weeks, from the age of 4 weeks. Weight gain of the rats receiving 200 and 100 mg/kg diets was decreased. This resulted from both a lower food intake and reduced effectiveness of the ingested food. Fed or fasting plasma glucose levels were similar in the three groups. During an intravenous glucose tolerance test, the rate of glucose disappearance was higher in Mg 100 rats than in controls. By contrast, during an oral glucose tolerance test, the rise in plasma glucose was greater and more sustained in Mg 100 rats. During both tests, the insulin response was markedly lower in Mg-deficient rats than in controls. This could be partially due to the reduced insulin content of the pancreas of these animals. The impairment of tolerance to oral glucose was corrected by 5 weeks on a high-Mg diet. After intravenous injection of insulin, the fall in plasma glucose levels was also slightly more pronounced in Mg 100 rats. During no test did we observe a significant difference between glucose or insulin responses in Mg 200 or Mg 750 rats. These results, thus, show that chronic Mg deficiency alters several parameters of glucose homeostasis in the rat.

Animals↗
PubMed1987

Rat myometrial adrenergic receptors in late pregnancy.

The myometrium of the rat has been found to contain both alpha 1- and beta-adrenergic receptors. To investigate the implication of these adrenergic receptors in uterine reactivity near term delivery, we have measured the number and the affinity of alpha 1-adrenergic antagonist [( 3H]prazosin: [3H]PRAZ)-binding sites and of very high affinity beta 2-adrenergic agonist [( 3H]hydroxybenzylisoproterenol: [3H]HBI)-binding sites in myometrial membranes throughout the last 5 days of pregnancy and at delivery. The number of specific binding sites was constant from Day 18 of pregnancy up to 6 h prior to birth. In the last 6 h of pregnancy, there was a sharp increase in the number of alpha 1-receptors (+70%, p less than 0.05). Simultaneously, the number of beta 2-receptors coupled to the adenylate cyclase system dropped (-75%; p less than 0.001). These results indicate that with the approach of parturition, there is a regulation of uterine reactivity by a modulation of the concentrations of myometrial adrenergic receptors during the last 6 h of gestation.

5'-Nucleotidase↗
PubMed1987

A variant of Glanzmann's thrombasthenia with abnormal glycoprotein IIb-IIIa complexes in the platelet membrane.

Patient C.M. presented platelet function defects symptomatic of Glanzmann's thrombasthenia. However, analysis of surface-labeled platelets by SDS-polyacrylamide gel electrophoresis revealed the usual presence of the major glycoproteins, including GP IIb and GP IIIa. Platelet fibrinogen was not detected. Analysis of Triton X-100 extracts of Ca2+-washed C.M. platelets by crossed immunoelectrophoresis (CIE) showed normal amounts of GP IIb-IIIa complexes. However, when samples were electrophoresed through an agarose gel containing 125I-fibrinogen, the usual binding of fibrinogen to GP IIb-IIIa did not occur. Furthermore, the GP IIb-IIIa complexes showed an increased sensitivity to dissociation with EDTA, either after Triton X-100 solubilization or in the intact platelet membrane. For example, after incubation with EDTA at room temperature, the patient's platelets bound little of the monoclonal antibodies AP-2 or T10 (anti-GP IIb-IIIa complex) although normally binding Tab (anti-GP IIb). Patient C.M. appears to represent a subgroup of thrombasthenia where platelets contain unstable GP IIb-IIIa complexes unable to support fibrinogen binding.

Adult↗
PubMed1987

Comparative effects of 6-hydroxydopamine and alpha-adrenoceptor antagonists on intrauterine migration and spacing of blastocysts in the rat.

Sympathetic nerve terminals were destroyed by administration of 6-hydroxydopamine (2 x 50 mg/kg) at 10:00 h on Days 4 and 5 of pregnancy in the rat. In the myometrium, this treatment markedly decreased noradrenaline concentrations (by 99%, P less than 0.001), demonstrating that myometrial noradrenaline is mainly originated from sympathetic nerves; therefore after 6-hydroxydopamine, the distribution and spacing of blastocysts remain unaffected throughout the uterus. Administration of phenoxybenzamine (2 x 6 mg/kg) in the morning of Days 4 and 5, or prazosin (4 x 3 mg/kg) from 12:00 h on Day 4 until 12:00 h on Day 5 disorganized the even distribution of blastocysts from the tubal end to the cervical end of the uterine horns. These results provide evidence that a noradrenergic transmission via action on myometrial post-synaptic alpha 1-adrenoceptors is involved as a regulatory mechanism of uterine motility for distribution and spacing of blastocysts in the rat uterus.

Animals↗
PubMed1986

Thyroid state and cholecalcin (calcium-binding protein) in cerebellum of the developing rat.

Cholecalcin (28,000 Da, vitamin D-dependent calcium-binding protein) is a marker of Purkinje cell development in the rat cerebellum from embryonic day 17 when these cells can first be distinguished. Specific antibodies raised against human cerebellar or rat renal cholecalcin were used in an immunocytochemical and quantitative study in altered thyroid states. The immunocytochemical staining was qualitatively similar in both normal and hypothyroid animals but clearly demonstrated the slowing of Purkinje cell development resulting from the lack of thyroxine. This effect was also reflected in quantitative studies which showed that the total cholecalcin per cerebellum was lower in thyroid-deficient rats. However, there was, in these animals, no specific reduction in cholecalcin level. Moreover, the response to thyroxine treatment indicated that the synthesis of cholecalcin occurred later and slower than that of the majority of cerebellar proteins and even after other more complex mechanisms of cerebellar cortex development (such as neurite outgrowth) have been induced. Thus, cholecalcin synthesis does not appear particularly sensitive to thyroid hormone level but might rather follow the increase in cell size induced by the hormone.

Animals↗
PubMed1986

Effects of hypothyroidism on postnatal development in the peripheral vestibular system.

The morphogenetic effects of congenital hypothyroidism on the development of rat vestibular receptor cells and ganglia were investigated by transmission electron microscopy. Vestibular ganglia are especially immature and characterized by an absence of a myelin sheath around the perikarya. The type I hair cells have a delayed development in their innervation. The last cells to differentiate and the last synaptic contacts to develop are the most affected. The most remarkable result of hypothyroidism is the persistent immaturity of the synaptic contacts.

Animals↗
PubMed1986

Immunocytochemical localisation of gelsolin in oligodendroglia of the developing rabbit central nervous system.

Antibodies raised against gelsolin of rabbit lung macrophages were used in an immunocytochemical study during development of the rabbit central nervous system. With the exception of a transient staining of the cerebellar Purkinje cells during the first postnatal week, gelsolin was found a new marker for oligodendrocytes, especially in developing animals. In the macrophages, gelsolin is involved in the control of locomotion, secretion and endocytosis. In the oligodendrocytes, which produce the myelin sheaths in the central nervous system, gelsolin could therefore be involved in the control of the complex motile events leading to myelin wrapping.

Animals↗
PubMed1986

A prospective randomized study comparing the efficacy of Timentin alone or in combination with amikacin in the treatment of febrile neutropenic patients.

One hundred febrile episodes in neutropenic (PMN less than 500/mm3) patients were treated with Timentin alone or in combination with amikacin. The overall response rate in 87 episodes was 82.9% with Timentin alone and 84.5% with the combination. Eleven out of 15 patients with septicaemia were cured by Timentin alone and 12 out of 13 by the combination, a response rate of 73.3% and 92.4% respectively (not-statistically significant P = 1.307). The rates of superinfection were low. Few side effects occurred. Timentin is a useful antibiotic in the treatment of febrile neutropenic patients and was, in this study, as effective alone as in combination with an aminoglycoside in the initial therapy.

Adolescent↗
PubMed1986

Evidence for a noradrenergic transmission in the control of parturition in the rat.

6-Hydroxydopamine, when injected at 14:00 h on Days 21 and 22 of pregnancy in the rat (2 X 50 mg/kg), markedly decreased plasma and uterine noradrenaline concentrations (-60% and -82% respectively; P less than 0.001). As a consequence of this treatment, there was severe disturbance in the distribution pattern of parturitions: 61% of rats had suppressed parturition and 31% of rats displayed a lengthened or interrupted labour. A bolus dose of prazosin (3 mg/kg) administered at 12:00 h on Day 22 completely blocked the normal process of parturition throughout the next 6 h, a result which is compatible with the half-life of the drug (2.9 +/- 0.8 h). Administration of phentolamine (3 mg/kg) at term induced a significant decrease of uterine activity (frequency X duration of bursts of spike potentials) as revealed by electromyographic recordings in vivo. These results suggest that noradrenaline released from sympathetic nerve terminals interacts with alpha-adrenoceptors located post-synaptically to improve the overall excitability of the myometrium at the onset of labour.

Animals↗
PubMed1985

Studies on platelets of patients with inherited platelet disorders suggest that collagen-induced fibrinogen binding to membrane receptors requires secreted ADP but not released alpha-granule proteins.

Collagen induces a saturable 125I-fibrinogen binding to normal human platelets. A role for secreted ADP in this process is supported by studies on 2 patients with the Chédiak-Higashi syndrome. Both collagen-induced nucleotide release and 125I-fibrinogen binding were strongly reduced while ADP-induced fibrinogen binding was normal. Platelets from 2 patients with the gray platelet syndrome bound normal amounts of 125I-fibrinogen in the presence of ADP or collagen despite the severe reduction of secretable alpha-granule proteins. Binding did not occur to collagen-stimulated type I thrombasthenic platelets which lacked GPIIb-IIIa complexes but was detected in amounts which correlated with the residual concentrations of GPIIb-IIIa in the platelets of a patient with type II disease. Our results allow us to propose that collagen-induced fibrinogen binding to normal platelets requires the presence of GPIIb-IIIa complexes and secreted ADP but proceeds independently of alpha-granule release.

Adenosine Diphosphate↗
PubMed1985

Characterization of alpha-adrenoceptors in myometrium of preparturient rats.

We describe three methods for the quantitative analysis of the alpha-adrenoceptor subtypes in preparturient rat myometrial membrane fractions. A non-subtype-selective antagonist radioligand. [3H]dihydroergocryptine ([3H]DHE), was used to label all of the alpha-receptors. [3H]DHE bound to both alpha 1- and alpha 2-receptors with indistinguishable affinity. Computer modelling of competition curves of unlabeled selective antagonists or agonists was then required in order to determine reliably alpha 1 and alpha 2 affinities and proportions: the alpha 1-receptors represent 45% and the alpha 2-receptors 55% of the entire alpha-receptor population in rat uterus. The second approach involved the administration of phenoxybenzamine (POB) that irreversibly blocks the alpha 1-adrenoceptors. Myometrial membranes obtained from rats 1 h after the administration of varying amounts of POB showed a dose-dependent reduction in specific [3H]DHE binding. This reduction was accompanied by a progressive increase of the value of the dissociation constant. Our data indicate that a dose of 1 mg of POB left the alpha 2-receptors intact while entirely blocking the alpha 1-receptors in rat myometrium. The third approach utilized the selective radioligand antagonists [3H]prazosin ([3H]PRAZ) and [3H]rauwolscine ([3H]RAUW). The results obtained with these radioligands confirmed our observations on the alpha-adrenoceptor subtypes in experiments with [3H]DHE. The results obtained with the 3 methods are in good agreement. Each approach appears valid and applicable to the characterization of alpha 1- and alpha 2-adrenoceptor subtypes in rat uterus, but the method using [3H]PRAZ and [3H]RAUW demonstrates more directly the presence of the two receptor subtypes.

Animals↗
PubMed1985

Evidence that a collagen derived octapeptide inhibits fibrinogen binding to platelets stimulated by collagen and not by ADP.

A synthetic octapeptide derived from type III collagen which specifically inhibits the activation and aggregation of platelets by collagen without affecting their adhesion was assayed on the collagen and ADP dependent fibrinogen binding to platelets. With 20 micrograms/ml collagen, the octapeptide (6 mM) inhibited by 68% the fibrinogen binding: this inhibition was correlated (p less than 0.01) to a decrease in the velocity of aggregation, suggesting that the fibrinogen binding might influence this parameter. The octapeptide did not affect the ADP-induced platelet aggregation and fibrinogen binding. This indicates that the octapeptide does not inhibit the binding of fibrinogen to its receptor directly, but interferes with some step(s) preceding the collagen-induced expression of the fibrinogen receptor.

Adenosine Diphosphate↗
PubMed1985

Characteristics of collagen-induced fibrinogen binding to human platelets.

Polymerized type I calf skin collagen induced a time-dependent specific binding of 125I-fibrinogen to washed human platelets. Binding occurred more rapidly in a shaken rather than in an unstirred system. It was linear in the range 0.05-0.3 microM added fibrinogen and was saturated at higher fibrinogen concentrations (more than 0.8 microM). Scatchard analysis showed a single population of binding sites (16530 +/- 5410 per platelet) with a Kd = 0.53 +/- 0.23 microM. Collagen-induced 125I-fibrinogen binding to platelets was completely inhibited by ADP antagonists such as creatine phosphate/creatine phosphokinase and AMP, and partially inhibited by pretreatment of the platelets with aspirin. With both normal and aspirin-treated platelets a close correlation was observed between the amount of 125I-fibrinogen bound and the extent of dense granule secretion. Our results confirm that fibrinogen becomes bound to platelet surface receptors during collagen-induced platelet aggregation and suggest that secreted ADP is an essential cofactor in this process.

Adenosine Diphosphate↗
PubMed1985

Con A-binding glycoproteins in the developing cerebellum of control and hypothyroid rats.

Concanavalin A (Con A)-binding glycoproteins were studied during the postnatal development of the cerebellum of control and hypothyroid rats. Only 4 glycoprotein bands have a transient behavior in control animals. They progressively increase until the 13th day and markedly decline between the 15th and the 18th postnatal day. In the cerebellum of hypothyroid rats, the level of these compounds is greatly reduced and the previous decrease observed in controls is not found again. This defect of Con A-binding glycoproteins mainly localized on the plasma membrane of parallel fibers might be related to the reduced synaptogenesis observed in the molecular layer of hypothyroid rats between parallel fibers and Purkinje cell dendritic spines.

Age Factors↗
PubMed1985

Corrective effects of thyroxine on cochlear abnormalities induced by congenital hypothyroidism in the rat. I. Morphological study.

In order to study the corrective effects of thyroxine on the cochlear abnormalities induced by congenital hypothyroidism, small doses of thyroxine were injected in propylthiouracil-treated rat pups for 2 consecutive days during selected periods of development (days 3 and 4, 6 and 7, 9 and 10, 12 and 13, 18 and 19). Some animals also received thyroid replacement therapy from days 12 to 17. Corrective effects of thyroxine on cochlear structures were observed using light microscopy and transmission electron microscopy. The corrective effects not only depended on the period of administration of the hormone, but also on the structure investigated within the organ of Corti. For a given structure, a period of maximal sensitivity to thyroxine exists which corresponds to the period of development during which that structure undergoes its main morphological changes (i.e. from 6 to 13 days for the inner sulcus epithelium, the first postnatal week for the tectorial membrane, from 6 to 10 days for the pillars and the tunnel of Corti, the second and probably a part of the third postnatal week for outer hair cell synaptogenesis).

Age Factors↗