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Biomedical subjects

V Lemaire

Publications and source records attributed to V Lemaire.

At least 19 recordsLinked to original sources
PubMed2006

Motherhood-induced memory improvement persists across lifespan in rats but is abolished by a gestational stress.

Motherhood modifies the biology and behavior of the female, a process which prepares the mother's cognitive systems that are needed for nurturance. It has recently been shown that motherhood enhances hippocampal-mediated spatial learning and synaptic plasticity. Deleterious and long-term effects of a stress experienced during gestation have been demonstrated on progeny. Surprisingly little is known about the effect of such stress on mothers. Here, we investigated the effect of gestational stress on the adaptive changes due to motherhood. Female rats were mated and stressed during the last week of gestation. Two weeks after weaning, they were submitted to behavioral tests or electrophysiological study. A group of females were then kept for 16 months after motherhood experience to study the long-term effect of gestational stress and motherhood on memory when they were 22 months old. We confirm that a single motherhood experience selectively increases hippocampal-mediated spatial memory during the entire lifespan of female rats and protects them from age-associated memory impairments. However, we demonstrate that a stressful experience during gestation totally abolishes the positive effects of motherhood both on spatial memory and on hippocampal synaptic plasticity (long-term potentiation). Environmental factors that induce biological vulnerability have negative effects even for fundamental biological behaviors.

Animals↗
PubMed2005

Primary stenting for the acute treatment of carotid artery dissection.

OBJECTIVES: To review and evaluate our experience with carotid artery stenting in the acute treatment of carotid artery dissection (CAD). PATIENTS AND METHODS: Reviewing the charts of our hospital between 2000 and 2001, we found two consecutive patients who benefited from primary stenting for the acute treatment of spontaneous extracranial internal CAD. RESULTS: Primary stenting of the internal carotid artery was successful in both cases without any post-operative complications. Clinical and US duplex scan follow-up confirmed the absence of neurological symptoms and the patency of the internal carotid artery with complete disappearance of the dissection at 36 and 42 months after the procedure, respectively. CONCLUSION: Despite the small number of patients, primary stenting for acute CAD seems to be safe and effective.

Acute Disease↗
PubMed2005

Pregnenolone sulfate enhances neurogenesis and PSA-NCAM in young and aged hippocampus.

Age-dependent cognitive impairments have been correlated with functional and structural modifications in the hippocampal formation. In particular, the brain endogenous steroid pregnenolone-sulfate (Preg-S) is a cognitive enhancer whose hippocampal levels have been linked physiologically to cognitive performance in senescent animals. However, the mechanism of its actions remains unknown. Because neurogenesis is sensitive to hormonal influences, we examined the effect of Preg-S on neurogenesis, a novel form of plasticity, in young and old rats. We demonstrate that in vivo infusion of Preg-S stimulates neurogenesis and the expression of the polysialylated forms of NCAM, PSA-NCAM, in the dentate gyrus of 3- and 20-month-old rats. These influences on hippocampal plasticity are mediated by the modulation of the gamma-aminobutyric acid receptor complex A (GABA(A)) receptors present on hippocampal neuroblasts. In vitro, Preg-S stimulates the division of adult-derived spheres suggesting a direct influence on progenitors. These data provide evidence that neurosteroids represent one of the local secreted signals controlling hippocampal neurogenesis. Thus, therapies which stimulate neurosteroidogenesis could preserve hippocampal plasticity and prevent the appearance of age-related cognitive disturbances.

Age Factors↗
PubMed2004

Tip of the greater horn of the hyoid bone: a landmark for cervical surgery.

The purpose of this study was to assess the relevance of the tip of the greater horn of the hyoid bone (THB) in the localization of the carotid bifurcation, the superior thyroid and lingual arteries, and the hypoglossal and superior laryngeal nerves. Measurements of these structures with respect to the THB were also made. Thirty perfusion-fixed human cadavers (60 specimens) were studied. Sharp measurements were made along two orthogonal axes crossing exactly on the THB. The vertical axis was parallel to the craniocaudal axis of the body. Taking the THB as a landmark, the five structures were identified in all the specimens. The mean value, standard deviation, and range of measurements for each structure studied are given in the text. This study shows the THB to be a useful landmark which is an aid to locating the aforementioned structures with confidence, and concludes that knowledge of this landmark would be beneficial for the surgeon dealing with the mid neck area.

Aged↗
PubMed2004

Environmentally induced long-term structural changes: cues for functional orientation and vulnerabilities.

Environmental challenges profoundly modify phenotypes and disrupt inherent developmental programs both at functional and structural levels. As an example, we have studied the impact of these environmental influences on adult neurogenesis in the dentate gyrus. Neurogenesis results from an inherent program, participates to hippocampal network organization and, as a consequence, to the various functional abilities depending on this region, including memories. In preclinical studies of aging we have shown that phenotypes vulnerable to the development of spatial memory disorders are characterized by lower hippocampal neurogenesis. We have hypothesized that these interindividual variations in functional expression of neurogenesis in senescent subjects could be predicted early in life. Indeed, a behavioral response (novelty-induced locomotor reactivity) and a biological trait (hypothalamo-pituitary-adrenal axis activity), which are predictive of cognitive impairments later in life, are related to neurogenesis in young adult rats. This suggests that subjects starting off with an impaired neurogenesis, here rats that are high reactive to stress, are predisposed for the development of age-related cognitive disorders. We have further shown that these inter-individual differences result from early deleterious life events. Indeed, prenatal stress orients neurogenesis in pathological ways for the entire life, and precipitates age-related cognitive impairments. Altogether these data suggest first that hippocampal neurogenesis plays a pivotal role in environmentally-induced vulnerability to the development of pathological aging, and second that environmental challenges and life events orient structural developments, leading to different phenotypes.

Animals↗
PubMed2004

Combined reconstruction of the diabetic foot including revascularization and free-tissue transfer.

Diabetic patients, presenting with both peripheral vascular disease and large soft-tissue defects, are too often treated by primary amputation. A combined revascularization and free-tissue transfer procedure can extend limb salvage in these patients. The authors report their experience over 4 years with 19 diabetic patients with peripheral vascular disease and large soft-tissue defects of the foot requiring free-tissue transfer. Although there was a 100 percent flap survival, early local wound problems occurred in three patients (16.6 percent). The recurrence rate was about 18.7 percent, but no complementary flap procedures were mandatory. With a mean follow-up of 38 months (range: 23 to 55 months), the limb salvage rate was 94.4 percent. Although there was one limb loss and one patient with ambulation difficulties, 16 patients (84.2 percent) were fully rehabilitated and were able to function independently. Despite a rather small series, this study confirms that in selected diabetic patients, a combined approach of vascular and reconstructive surgeons can reduce the limb amputation rate with acceptable complication rates. This combined approach offers major benefits to these patients, especially stable coverage and preservation of ambulation, and should always be considered before amputation.

Adult↗
PubMed2003

Structural modeling of drug release from biodegradable porous matrices based on a combined diffusion/erosion process.

Biodegradable, porous microspheres exhibit a wide range of release profiles. We propose in this paper a unifying approach based on the dual action of diffusion and erosion to establish which mechanisms are responsible for the variety of release kinetics observed during in vitro experiments. Our modeling procedure leads to the partitioning of the matrix into multiple, identical elements, thus simplifying significantly the mathematical and numerical treatment of the problem. The model equations cannot be solved analytically, since the domain contains a moving interface, and must therefore be solved numerically, using specific methods designed for that purpose. Our model confirms the major role that the relative dominance between diffusion and erosion plays in the release kinetics. In particular, the velocity of erosion, the effective diffusion coefficient of the drug molecule in the wetted polymer, the average pore length, and the initial pore diameter are sensitive parameters, whereas the porosity and the effective diffusion coefficient of the drug in the solvent-filled pores is seen to have little influence, if any, on the release kinetics. The model is confirmed by using release data from biodegradable microspheres with different ratios of low and high molecular weight PLA. Excellent goodness of fit is achieved by varying two parameters for all types of experimental kinetics: from the typical square root of time profile to zero-order kinetics to concave release curves. We are also able to predict, by interpolation, release curves from microspheres made of intermediate, untested ratios of PLA by using a relation between two model parameters.

Biocompatible Materials↗
PubMed2003

[Free flap pedicle loss: clinical study on 8 cases].

The authors report on 8 cases of free flaps with vascular pedicle disruption that were encountered between postoperative days 8 to 18. In one case, the inflow disappeared 18 months after the transfer without any trouble. This resulted in 2 partial and one complete flap losses. The 4 other flaps survived completely. This complete survival is related to the angiogenesis process coming from the surrounding tissues. The most obvious causal factor responsible for the 2 partial losses was the coverage of large, non viable areas, such as a prosthetic material and bone deprived of periosteum. The only causal factor that could be assessed in the case of total necrosis was the presence of an immunosuppressive treatment. Variables participating in the installation of an adequate angiogenic response are then discussed in accordance to this experience and to the literature. Limited contact with viable tissue, ischemia-reperfusion or drugs limiting the angiogenesis seems to promote failure when the pedicle is quickly disrupted. Hypoxia seems to be the most important cellular mechanism promoting the angiogenesis in this context.

Aged↗
PubMed2003

A low rate of trisomy 21 in twin-pregnancies: a cytogenetics retrospective study of 278 cases.

From January 1st 1990 until December 31st 2001, we collected 19686 prenatal diagnosis (on amniocentesis and chorius villus sampling). Five hundred twelve samples (2.6%) concerned 278 twin pregnancies. The most frequent indications were maternal age > or = 35 years (108/278 = 38.8%), medically assisted procreation (34/278 = 12.3%), positive ultrasound (20/278 = 7.2%). Chromosome abnormalities were found in eight twin-pregnancies (2.9%): five with only one fetus affected [47,XX,+ 18; 45,XX,t( 13;14); 47,XYY; 47,XXX; 45,XX, t(13;14)], two with both fetuses showing the same chromosomal abnormality [inv(11)(q21q25); 47,XX,+ 18] and one with only one fetus tested [47,XX,+ 18]. In total, we found eight autosomal abnormalities, four inherited balanced rearrangements (two robertsonian translocations and two paracentric inversions of chromosome 11) and four trisomies 18. We also observed two sex chromosome abnormalities interesting only one of the two fetuses. Surprisingly, we did no detect any Down Syndrome among this population. The frequency of Down Syndrome was significantly (p < 0.05) lower in our population of twin pregnancies (0.0%) as compared to the observed incidence in singleton pregnancies during the same period (163/19162 = 0.9%).

Adult↗
PubMed2002

[Arterial revascularization with free tissue transfer for salvage of ischemic limbs with extensive tissue loss: an alternative to amputation].

Severe limb ischemia is a common problem encountered in medical practice. Aggressive attempts at revascularization have extended the limits of limb salvage. However, in certain cases, extended tissue loss compromises the healing process. It often results in amputation despite bypass graft patency. Microvascular free tissue transfer combined with arterial revascularization allows healing of these wounds and limb preservation. This combined approach is the ultimate alternative to amputation.

Amputation, Surgical↗
PubMed2002

[Deep vein thrombosis in a burn patient].

Association between deep venous thrombosis (DVT) and pulmonary embolism is probably an underestimated problem in the thermally injured patients. However, those patients display important risk factors according to Virchow's triad. This article reports on three unrecognised DVT's accompanying burns which were characterized by absence of healing or edema. The pathophysiology of this issue is then discussed with respect to the specific area of the thermally injured patient. It is our belief that local inflammatory phenomenon play a major part in the genesis of DVT associated with chronic non-healing burns.

Adult↗
PubMed2001

Long term neurodevelopmental and behavioral effects of perinatal life events in rats.

Modern neurosciences are now able to open new avenues concerning an experimental approach to clinical neurosciences and psychiatry. Detection and prediction of potential vulnerabilities such as behavioral disturbances and neurodegenerative diseases, are urgent tasks leading to prevention that must be encouraged in parallel to the enormous efforts displayed for treatments. Besides possible genetic origins of diseases, environmental factors are now coming under scrutiny, and especially deleterious and challenging life events and stress occurring during prenatal and postnatal critical periods may orient brain functions towards deleterious developments. The hypothesis that will be examined is that early events might be at the origin of pathological transformations and symptoms after long periods of apparent normal abilities and behavioral homeostasis. We used models of prenatal stress and postnatal manipulations such as cross-fostering. It will be demonstrated that such events induce long-term changes, cognitive and emotional modifications appearing first, when offspring are adults, followed by cognitive defects later in life. Increased sensitivity of the hypothalamic pituitary-adrenal axis (HPA), the endocrine system controlling the secretion of stress hormones (corticoids), appears to be a major element of pathogenesis. HPA axis dysfunction appears very early after birth (3 days) and lasts for months. Cumulative exposure to high levels of hormones seems to be detrimental for some brain regions, especially the hippocampus and major neurotransmitter systems such as dopamine neurons. We evidenced that neuronal modifications in hippocampal region are correlated with behavioral and cognitive defects, relating environment, stress in early life, hormonal changes, long-term neuropathological processes and impaired cognition in aging. Moreover appears in offspring, when adults, a proneness to engage in drug dependence. These data emphasize the need to consider early environmental life events as etiological factors for delayed neuropsychiatric disturbances, neurodegenerative defects included. Moreover, they strengthen the interest for a longitudinal approach to promote experimental psychopathology.

Journal Article↗
PubMed2001

Thyrolingual trunk arising from the common carotid artery: a case report.

During a cadaver dissection in the anatomy department of the University of Liege, Belgium, an anatomic variation of the superior thyroid and lingual arteries was observed on the right side in a 68-year-old woman. Both arteries arose from a common trunk located 30 mm beneath the carotid bifurcation. After a 5.2 mm course, the thyrolingual trunk divided into superior thyroid and lingual arteries which followed an unusual course towards their respective organs. Knowledge of this anomaly is important for those who are involved with neck surgery and anatomy.

Aged↗
PubMed2001

Bilateral case of superficial ulnar artery originating from axillary artery.

During the dissection of an 86-year-old male human cadaver, superficial ulnar arteries were found in both upper limbs. These arteries branched from the axillary arteries. In the left arm, the artery crossed ventral to the medial root of the median nerve before running towards the medial part of the arm. The persistence of the median artery was noted. In the right arm, the ulnar artery had a common origin with the subscapular artery. It crossed anterior to the lateral root of the median nerve and then, in the arm, ran alongside the anterolateral aspect of the median nerve, near the biceps brachii muscle, which was supplied by this superficial ulnar artery. Then the artery crossed the median nerve and the brachial artery. The embryology, incidence and clinical relevance of this anatomical variation are discussed. So this was a rare case where the ulnar arteries originated from the axillary artery on both sides, but then followed different courses in the arm and, on the right side, the superficial ulnar artery partly supplied the biceps brachii muscle.

Aged↗
PubMed2001

Numerical bifurcation analysis of delay differential equations arising from physiological modeling.

This paper has a dual purpose. First, we describe numerical methods for continuation and bifurcation analysis of steady state solutions and periodic solutions of systems of delay differential equations with an arbitrary number of fixed, discrete delays. Second, we demonstrate how these methods can be used to obtain insight into complex biological regulatory systems in which interactions occur with time delays: for this, we consider a system of two equations for the plasma glucose and insulin concentrations in a diabetic patient subject to a system of external assistance. The model has two delays: the technological delay of the external system, and the physiological delay of the patient's liver. We compute stability of the steady state solution as a function of two parameters, compare with analytical results and compute several branches of periodic solutions and their stability. These numerical results allow to infer two categories of diabetic patients for which the external system has different efficiency.

Blood Glucose↗
PubMed2001

[Pneumomediastinum in children].

Pneumomediastinum in children is diagnosed in two circumstances: cervical subcutaneous emphysema or radiological findings. The predominant symptoms are dyspnoea, stabbing chest pain, sore throat and dysphagia. Traumatic injuries and pulmonary diseases such as asthma are the most common causes of pneumomediastinum. It may rarely result from iatrogenic manoeuvres or acidocetosis. Spontaneous mediastinal emphysema is seldom reported in children. Chest X-ray films are essential investigations. The treatment is directed towards the underlying cause, with conservative management being sufficient in most cases. However, the risk of surveying of pneumothorax or tension pneumomediastinum justifies close clinical follow-up in a specialised care unit. The onset of these pathologies necessitates a more aggressive therapy by aspiration through percutaneous catheter placed in the mediastinum.

Asthma↗