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Biomedical subjects

C Lebrun

Publications and source records attributed to C Lebrun.

At least 91 records · Page 5Linked to original sources
PubMed1989

Experimental dissociation of memory systems in mice: behavioral and neurochemical aspects.

Evidence for different types of memory in mice may lead to development of animal models for human memory disorders and provides informations on neurobiological systems underlying these processes. Series of experiments in mice, using a 8-arm radial maze with or without cholinergic drugs or chronic alcohol consumption supply arguments for multiple memory stores and for cholinergic influence greatest for short-term system. Studies of differential cholinergic activation following training militate for dissociation in time of hippocampal and cortical cholinergic pathways. Age-related memory involvement seems to be associated with an attenuation of central cholinergic activation. Several problems inherent to sensitivity and selectivity of the tasks remain in discussion.

Animals↗
PubMed1989

[Joint lesions of the first column of thumb].

Lesions involving the thumb from the interphalangeal joint to the trapezo-metacarpal (TM) joint are very frequently the result of sports injuries. The authors discuss the most frequent lesions: 1) Dislocations of the metacarpo-phalangeal (MP) joint of the thumb which can be reduced in almost every case by means of well conducted orthopaedic manoeuvres. 2) Sprains of the MP joint of the thumb, very common lesions the severity of which must not be underestimated and which always require surgical treatment in the serious lesions, regardless of the compartment involved (radial or ulnar). 3) Bennett's fractures or fracture-dislocations of the TM joint; when neglected inadequately treated, these lesions lead to disabling post-traumatic arthritis of the TM joint. A poor result of treatment for any one of these three lesions always compromises opposition of the thumb and/or the strength of pollico-digital grip.

Fractures, Bone↗
PubMed1988

[2 cases of early "siliconitis" (silicone synovitis)].

Two cases of early silicone synovitis, 12 and 18 months after surgery for partial scaphoid implant arthroplasty (Swanson design) are reported. None of the implants had been fixed by Kirschner wire or sutured to the radius or an other carpal bone. Both implants had been immobilized for six weeks. Initially the result in both cases was good. Pain and loss of range of movement gradually increased, and a large erosive osteolytic defect of the radius was seen on the X-ray after 12 months for the first case and 18 months for the second one. Surgical revision consisted of implant removal, synovectomy with a proximal row carpectomy in the first case and a soft tissue interposition arthroplasty for the second one. The histologic examination showed a foreign body reaction with birefringent material in multinucleated giant cells. All reports about this type of silicone implant complication emphasises the role of compression forces and micro-fragmentation of the silicone. Should we continue to perform partial scaphoid implant arthroplasty from whom microparticles are creating a severe foreign body reaction?

Adult↗
PubMed1987

Hypertonic saline mimics the effects of vasopressin on inhibitory avoidance in the rat.

Rats tested in a step-through inhibitory avoidance task were administered hypertonic saline (2 ml of 0.25. 0.5, and 1.0 M intraperitoneally) or arginine vasopressin (1.0, 2.0, and 4.0 micrograms) injected subcutaneously (sc) after the training trial where the rats received a mild footshock (0.2 mA, 3 s). Both hypertonic saline and vasopressin produced significant increases in latency to reenter 24 h later. These treatments failed to increase reentry latencies in animals that received the same procedure but no shock. The facilitation of inhibitory avoidance produced by hypertonic saline was reversed by sc administration of 25 micrograms of the vasopressor (V-1) vasopressin antagonist, dPtyr(Me)AVP. The results suggest that the endogenous release of vasopressin can be behaviorally significant in situations of acute homeostatic challenge.

Animals↗
PubMed1987

[10 congenital trigger fingers. Apropos of a case report].

Ten congenital triggers fingers have been treated on a 3 years old girl after correction of congenital bilateral club feet. Such a case, without any other congenital malformation seems to be unique in the French literature and only found twice in the English one. This child in spite of a normal growth and good psychomotor development, presents an unusual face, with a mouth a little bit too small, but her karyotype is normal. No trismus and no microstomia were found to enable this case to be classified in a specific syndrome. The right diagnosis may be a non evolutive arthrogryposis of the extremities. Dividing the ten proximal pulleys (A1) let 10 voluminous nodules pass through and allowed full range of motion in nine out of ten fingers. A remaining flexion deformity of the proximal interphalangeal joint needed an anterior arthrolysis, the final result was good.

Abnormalities, Multiple↗
PubMed1987

Central cardiovascular actions of vasopressin in the rat.

Arginine vasopressin (AVP) containing neurones and pathways have been localized in various cardiovascular control centers of the central nervous system in rats. AVP influences cardiovascular regulation when injected into various areas of the central nervous system. The blood pressure increases in response to central AVP injections were shown to be initiated by stimulation of central V1-AVP receptors and mediated by stimulation of sympathetic outflow to the periphery. On the other hand, AVP has also been shown to attenuate the pressor responses to electrical stimulation of the mesencephalic reticular formation when injected into the brain ventricular system. In addition, AVP can participate in cardiovascular regulation by modulating baroreceptor reflex sensitivity. We have shown that in rats peripheral (hormonal) AVP can sensitize the heart rate component of the baroreceptor reflex by acting on V2-AVP receptors accessible from the blood, while at the same time central (neuronal) AVP can attenuate the baroreceptor reflex through brain V1-AVP receptors that cannot be reached from the blood. Binding and functional studies favour the existence of V1-AVP receptors in the central nervous system, whereas evidence for central V2-AVP receptors is still scarce. The role of AVP in hypertension remains controversial, but recent evidence suggests that a discordance between the various central and peripheral cardiovascular actions of AVP, rather than its hormonal vasopressor effects, may contribute to the pathogenesis of hypertension.

Animals↗
PubMed1986

[Antihypertensive action and inhibition of tissue conversion enzyme by ramipril, perindopril and enalapril in the spontaneously hypertensive rat (SHRSP)].

Ramipril and perindopril, the active diacids of two new converting enzyme (CE) inhibitors proved to possess a similar inhibitory potency against rat plasma CE in vitro. These diacid compounds were more active than enalaprilic acid or captopril. In stroke-prone spontaneously hypertensive rats (SHRSP) chronic oral treatment for two weeks with enalapril (30 mg/kg per day), ramipril or perindopril (each 1 mg/kg per day) normalized blood pressure. The CE inhibitor-induced changes in parameters of the plasma renin-angiotensin system (angiotensin I, angiotensin II, PRC, CE activity) followed the expected pattern, but were not quantitatively related to the antihypertensive action of the three inhibitors. Four weeks of oral equi-dose treatment with the three CE inhibitors (10 mg/kg per day) inhibited tissue CE activity in various organs including kidney, heart, vascular wall and brain. Ramipril and perindopril lowered blood pressure and tissue CE activity more potently than enalapril. These results confirm the hypothesis that CE inhibition in tissue with subsequent local reduction of ANG II synthesis may contribute to the antihypertensive mechanisms of CE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1985

Vasopressin pressor antagonist injected centrally reverses behavioral effects of peripheral injection of vasopressin, but only at doses that reverse increase in blood pressure.

Previous work in rats (Ader, R. and De Wied, D., Psychon. Sci., 29 (1972) 46-48) has established that subcutaneously (s.c.) injected arginine vasopressin (AVP) prolongs extinction of active avoidance and that this effect could be prevented by pretreatment with the vasopressin antagonist analog [1-deaminopenicillamine, 2-(O-methyl)tyrosine]-beta-arginine vasopressin (dPtyr(Me)AVP). The purpose of the present study was to determine if peripherally administered AVP acts via a peripheral blood pressure effect or by a direct action in the central nervous system. We therefore tested the effects of the antagonist injected intracerebroventricularly (i.c.v.) on the prolongation of active avoidance and on blood pressure effects of s.c. injected AVP. The antagonist (i.c.v.) blocked the behavioral effects of systemically injected AVP only at dose sufficient to block the peripherally mediated pressor response of systemically administered AVP. The results show that peripherally injected AVP acts on peripheral systems and support our hypothesis that the peripheral visceral action of AVP contributed significantly to its behavioral action.

Animals↗
PubMed1985

Arginine vasopressin, stress, and memory.

Arginine vasopressin (AVP) has been shown to have several non-renal actions including the potentiation of learned avoidance behavior in rats and improvement in cognitive functioning in humans. Research in our laboratory has confirmed these behavioral effects in rats using both peripheral and central injection of AVP. We have begun to examine the physiological basis for these effects. Peripheral administration of a vasopressor AVP antagonist reversed the prolongation of extinction produced by peripherally administered AVP in both active and passive avoidance, but also reversed the aversive unconditioned effects of AVP. However, central administration of the vasopressor AVP antagonist reversed peripheral effects of AVP only at doses shown to act peripherally to reverse vasopressor effects of AVP. An osmotic stress in doses known to liberate endogenous AVP mimicked the behavioral effects of exogenously administered AVP, and this stress effect was reversed by the AVP antagonist. These results support our hypothesis of separate but parallel AVP systems in the pituitary and brain with a role in behavioral adaptation to certain types of stress.

Animals↗
PubMed1984

Behavioral effects of peripheral administration of arginine vasopressin: a review of our search for a mode of action and a hypothesis.

In this review we present data summarizing our studies concerning the mechanism of action for the behavioral effects of peripheral arginine vasopressin (AVP) administration. We have demonstrated a clear performance improvement in a one trial appetitive task designed to measure the memory-learning process. This behavioral effect is blocked by peptide analogs which block the pressor response to AVP. From these data, and from other data obtained in aversively motivated tasks, we hypothesize that peripheral AVP injections induce effects of physiological-endocrinological origin and that these peripheral signals (e.g. vasopressor actions) alert and arouse the animal, thus helping to improve its association of environmental events. This hypothesis is similar to that proposed by others regarding peripheral hormones and memory and still leaves open the possibility that vasopressin in the brain acts independently of the above proposed action for peripherally derived vasopressin.

Animals↗
PubMed1982

Changes in the number of germ cells in the gonads of the rainbow trout (Salmo gairdneri) during the first 10 post-hatching weeks.

The number of germ cells in fry gonads was determined from histological sections sampled periodically over a 10-week post-hatching period. Several successive types of germ cells were identified: primordial germ cells (PGC), two kinds of gonocytes (G1 and G2) and all the stages of female meiotic prophase. The mean diameters are shown in table 1. The number of germ cells increased regularly from 47 +/- 35 (SD) after hatching (PGC) to 166 +/- 25 at 2 post-hatching weeks (G1). At 5 post-hatching weeks, two groups of fish could be distinguished by the number of their germ cells (G2) - one group had less than 926 cells and the other more than 1 577 - and by their gonadal morphology (Filiform or with an enlarged anterior part due to germ cell concentration). At 6 post-hatching weeks, the ovary differentiated with organization of the ovarian lamellae and the appearance of oocytes in meiotic prophase (4 out of 10 trout). The gonads of the other fish stayed at the indifferent stage. The number of germ cells was significantly higher in female-type gonads (6 335 +/- 3 558) than in indifferent gonads (1 696 +/- 467). The situation was the same at 8 to 10 weeks.

Animals↗
PubMed1981

[Domiciliary care of pathological pregnancies by midwives. Comparative controlled study on 996 women (author's transl)].

In order to evaluate the effectiveness of domiciliary care of pathological pregnancies by midwives a comparative study was carried out on two groups of pregnant women, the one group being treated by this new method of caring fort them, the other by traditional care. There was random selection for the two groups. The results of this comparative controlled study show that when midwives care for these patients at home once a pathological condition has become established premature labour and admission to hospital is not avoided. A more preventive attitude developed. This implies that they intervene very early in pregnancy as soon as risk factors for pathological conditions appear without waiting for the pathological conditions themselves to develop.

Adult↗
PubMedDate not supplied

Central injections of arginine vasopressin prolong extinction of active avoidance.

Behavioral and physiological effects of arginine vasopressin (AVP) were examined following intracerebroventricular (ICV) injection in the rat. ICV injections prolonged extinction of active avoidance at doses of 1.0 and 10.0 ng/rat and this effect was blocked by peripheral injection of the vasopressor antagonist of vasopressin [dPtyr(Me)AVP] at a dose of 30 micrograms/kg (SC). However, 1.0 ng of AVP ICV failed to alter systemic blood pressure and also failed to produce taste aversions in a one or two bottle test. Results suggest that central AVP has a central action independent of systemic changes in blood pressure, but that the receptor mediating this action is functionally similar to the AVP V1 (vasopressor) receptor.

Animals↗
PubMedDate not supplied

A comparison of the working memory performances of young and aged mice combined with parallel measures of testing and drug-induced activations of septo-hippocampal and nbm-cortical cholinergic neurones.

The spatial working memory performances of young (2 months) and aged (24-26 months) mice of the C57BL/6 strain were compared using a delayed nonmatching to place (DNMTP) protocol in an automated 8-arm radial maze. The aged mice were observed to exhibit a selective and interference-related memory deficit. Parallel neurochemical analysis of the activity of septo-hippocampal and nbm-cortical cholinergic neurones in vivo was conducted using measures of sodium-dependent high-affinity choline uptake. Results showed that whereas the level of cholinergic activity in both brain regions varied less than 10% between young and aged mice in quiet conditions (basal) the activation usually observed at 30-sec posttest (+20-25%) in young mice was greatly attenuated in the frontal cortex and almost totally absent in the hippocampus of aged mice. In view of these results a complementary experiment was carried out in order to test the intrinsic ability of septo-hippocampal cholinergic neurones to activate using acute injection of scopolamine (1 mg/kg IP 20 min) to both young and aged mice in quiet conditions. The drug injection resulted in a very large (+70%) increase in hippocampal high-affinity choline uptake and with amplitudes which did not vary significantly between young and aged subjects. These observations attest to a relatively well-preserved state of central cholinergic neurones and an intact capacity to activate normally when challenged pharmacologically in aged mice. The results strongly suggest that the loss of cholinergic activation and associated memory deficit in aged mice might rather be related to a hypofunction of phasically active transsynaptic processes which normally mediate the activation of these cholinergic pathways during memory testing.

Age Factors↗