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Biomedical subjects

B Laurent

Publications and source records attributed to B Laurent.

At least 55 records · Page 3Linked to original sources
PubMed1999

Electrical stimulation of motor cortex for pain control: a combined PET-scan and electrophysiological study.

Although electrical stimulation of the precentral gyrus (MCS) is emerging as a promising technique for pain control, its mechanisms of action remain obscure, and its application largely empirical. Using positron emission tomography (PET) we studied regional changes in cerebral flood flow (rCBF) in 10 patients undergoing motor cortex stimulation for pain control, seven of whom also underwent somatosensory evoked potentials and nociceptive spinal reflex recordings. The most significant MCS-related increase in rCBF concerned the ventral-lateral thalamus, probably reflecting cortico-thalamic connections from motor areas. CBF increases were also observed in medial thalamus, anterior cingulate/orbitofrontal cortex, anterior insula and upper brainstem; conversely, no significant CBF changes appeared in motor areas beneath the stimulating electrode. Somatosensory evoked potentials from SI remained stable during MCS, and no rCBF changes were observed in somatosensory cortex during the procedure. Our results suggest that descending axons, rather than apical dendrites, are primarily activated by MCS, and highlight the thalamus as the key structure mediating functional MCS effects. A model of MCS action is proposed, whereby activation of thalamic nuclei directly connected with motor and premotor cortices would entail a cascade of synaptic events in pain-related structures receiving afferents from these nuclei, including the medial thalamus, anterior cingulate and upper brainstem. MCS could influence the affective-emotional component of chronic pain by way of cingulate/orbitofrontal activation, and lead to descending inhibition of pain impulses by activation of the brainstem, also suggested by attenuation of spinal flexion reflexes. In contrast, the hypothesis of somatosensory cortex activation by MCS could not be confirmed by our results.

Adult↗
PubMed1999

Haemodynamic brain responses to acute pain in humans: sensory and attentional networks.

Turning attention towards or away from a painful heat stimulus is known to modify both the subjective intensity of pain and the cortical evoked potentials to noxious stimuli. Using PET, we investigated in 12 volunteers whether pain-related regional cerebral blood flow (rCBF) changes were also modulated by attention. High (mean 46.6 degrees C) or low (mean 39 degrees C) intensity thermal stimuli were applied to the hand under three attentional conditions: (i) attention directed towards the stimuli, (ii) attention diverted from the stimuli, and (iii) no task. Only the insular/second somatosensory cortices were found to respond whatever the attentional context and might, therefore, subserve the sensory-discriminative dimension of pain (intensity coding). In parallel, other rCBF changes previously described as 'pain-related' appeared to depend essentially on the attentional context. Attention to the thermal stimulus involved a large network which was primarily right-sided, including prefrontal, posterior parietal, anterior cingulate cortices and thalamus. Anterior cingulate activity was not found to pertain to the intensity coding network but rather to the attentional neural activity triggered by pain. The attentional network disclosed in this study could be further subdivided into a non-specific arousal component, involving thalamic and upper brainstem regions, and a selective attention and orientating component including prefrontal, posterior parietal and cingulate cortices. A further effect observed in response to high intensity stimuli was a rCBF decrease within the somatosensory cortex ipsilateral to stimulation, which was considered to reflect contrast enhancing and/or anticipation processes. Attentional processes could possibly explain part of the variability observed in previous PET reports and should therefore be considered in further studies on pain in both normal subjects and patients with chronic pain.

Acoustic Stimulation↗
PubMed1999

Membranoproliferative glomerulonephritis with subendothelial deposits (type 1) associated with hepatitis G virus infection in a renal transplant recipient.

BACKGROUND: Infection with hepatitis B virus (HBV) or hepatitis C virus (HCV) is a well-known etiology for membranoproliferative glomerulonephritis (MPGN) with subendothelial deposits (MPGN type 1). MATERIAL AND METHODS: The newly discovered hepatitis G virus (HGV) is currently under active investigation. We report the first case of de novo MPGN type 1 associated with HGV infection in a young male renal transplant recipient who manifested glomerulonephritis (GN) with proteinuria 7 years after transplant, and whose original disease was chronic obstructive pyelonephritis secondary to nephrolithiasis. RESULTS: Serum markers for HBV and HCV infections were negative. HGV infection was detected by specific double-nested reverse transcriptase-polymerase chain reaction (RT-PCR) in sera (positive HGV viremia) 2.5 years after renal transplantation. By specific in situ RT-PCR, the presence of the HGV genome was detected in peripheral blood mononuclear cells and in the kidney biopsy (glomeruli and tubules), but not in the liver. CONCLUSION: This report adds new information on the role of HGV infection in the occurrence of de novo GN (MPGN type 1) in renal transplantation.

Adult↗
PubMed1999

Precentral cortex stimulation for the treatment of central neuropathic pain: results of a prospective study in a 20-patient series.

The authors report a series of 23 patients with central neuropathic pain who were treated with the recently developed technique of precentral cortex stimulation (PCS). Of the 20 patients with a follow-up of more than 1 year (mean of 23 months) 25% had an excellent, 35% a good and 15% a fair relief of pain. In 25% the method failed. On the basis of these findings and the literature data (127 reported cases), the authors advocate PCS in patients with severe and medically refractory poststroke pain.

Adult↗
PubMed1999

[Serratus anterior muscle flap: indications and sequelae. 26 cases and review of the literature].

The authors report their experience of the use of the serratus anterior flap. Between 1992 and 1997, this flap was used for 14 head and neck and 11 limb and 1 intra-thoracic reconstructions. Twelve patients were examined for functional evaluation of the donor site. When only 2 or 3 slips are raised donor site morbidity is limited to moderate winging of the scapula with no functional disorders. Because of its thinness, and the length and diameter of the vascular pedicle, the serratus anterior flap is our favourite option for small wounds of the distal limb or composite and large defects in association with flaps of the subscapular system.

Adolescent↗
PubMed1998

[Early diagnosis of Alzheimer's disease].

The diagnosis of dementia of Alzheimer type (DTA) in the early stage of the disease may be possible with the development of specialized memory consultations. After this diagnosis, we can inform family and even the patient in some cases, monitor the progression of disease, give or not treatment, and help family for daily life management (money, car driving, administration papers, etc.). The first step is to analyse the memory complaints of the patient and if possible of his family. The difficulties in everyday life are more informative than an anxious complaint of memory and some IADL deficiency appear early: difficulty to use phone, drugs, transports or checks. The patient examination by a practitioner or a neurologist has to be complete, even if normal in most of the cases. The practitioner has to explore without specific material, the main cognitive domain: the "5 words test" illustrates a useful memory tool, analysing two types of recall. We also must observe writing, digit span, naming and verbal fluency. The examination by a psychologist using standardized batteries of tests must always be driven by this clinical exploration using common scales like MMS or ADAS. In very early DTA, we may observe a cognitive decline limited to some aspects of memory (free long term recall, cued recall, working memory...) with a decline of the most controlled attentional tasks. An isolated memory disorder has to be identified either as onset of DTA or as an aging related cognitive decline (ARCD): the difference is qualitative and may appear only on repeated exams by experimented psychologist.

Aged↗
PubMed1998

A randomized prospective study comparing low-dose OKT3 to low-dose ATG for the treatment of acute steroid-resistant rejection episodes in kidney transplant recipients.

Acute steroid-resistant rejection episodes in kidney allograft recipients require treatment with antilymphocyte antibodies. Monoclonal anti-CD3 and polyclonal antilymphocyte antibodies have been widely used but seldom compared. Recent data have suggested that these antibodies could be used at reduced doses without jeopardizing their efficacy. In this study, we randomized renal transplant recipients who encountered a first acute steroid-resistant rejection episode to low-dose ATG or low-dose OKT3 treatment. Sixty patients were enrolled in the study. They received prophylactic immunosuppression with cyclosporin, azathioprine, and prednisolone. Treatment of biopsy-proven rejection consisted of a 10-day course of either ATG (n = 31) or OKT3 (n = 29). The total ATG dose was 484 +/- 110 mg, i.e., 0.75 mg/kg per day. The total OKT3 dose was 32 +/- 4 mg, i.e., 0.05 mg/kg per day. We compared reversion of rejection, side effects, immunodepression, and graft function. Reversion of rejection was similar in the two groups, although we noted a trend in favor of ATG. Results were 3% vs 10% early graft failures, 13% vs 23% overall graft failures, 28% vs 38% 3-month actuarial incidence of rebound rejection, and 89% vs 81% 1-year graft survival rate in the ATG and OKT3 groups, respectively. Tolerance was worse in the OKT3 group due to the first-dose syndrome. Infections and cancers occurred with the same frequency. ATG resulted in a deeper and longer decrease in peripheral lymphocyte subsets. Graft function was similar in the two groups. We conclude that low-dose ATG and low-dose OKT3 are equally effective in reversing steroid-resistant acute rejection. Tolerance was better with ATG, which also gave a more potent and longlasting immunodepression. The use of reduced doses of ATG and OKT3 did not appear to lessen their efficacy.

Adult↗
PubMed1998

Aggressive treatment with complete remission in primary diffuse leptomeningeal gliomatosis--a case report.

Primary leptomeningeal gliomatosis is rare, and the diffuse form (PLDG) is even more unusual. The following report is an example. A 17 year-old man developed a syndrome characterized by extensive basal and chronic spinal meningitis. Routine biological tests showed elevated levels of CSF proteins, and moderate mononuclear pleocytosis, with no direct evidence of neoplasia, leading to a diagnosis of chronic meningitis. A second meningeal biopsy, guided by MRI and performed in the left frontal region, led to the specific diagnosis of primary diffuse leptomeningeal gliomatosis. Treatment including ventricular and lumbar shunting, a course of cortico-spinal radiation, and three courses of an eight-drug systemic chemotherapy with intrathecal methotrexate lead to complete remission over 15 months. We believe that this is the first report of such a remission in the literature.

Adolescent↗
PubMed1998

Allodynia after lateral-medullary (Wallenberg) infarct. A PET study.

We used PET to study regional cerebral blood flow (rCBF) changes in nine patients with unilateral central pain after a lateral medullary infarct (Wallenberg's syndrome). All patients presented, on the abnormal side, a combination of hypaesthesia to noxious and thermal stimuli and allodynia to rubbing of the skin with a cold object (i.e. abnormal pain to innocuous stimulation). The rCBF responses during allodynia were compared with those obtained during stimulation of the normal side using (i) a cold non-noxious stimulus identical to that applied to the painful side, and (ii) an electrical high-frequency stimulus at painful ranges. Statistical analysis disclosed two abnormal patterns of rCBF change during allodynia. First, there is a quantitative change whereby the blood flow response was out of proportion with the actual intensity of the stimulus, i.e. the pattern of activation by innocuous rubbing of the skin was in our patients identical to that previously reported in response to painful stimuli in normal subjects. This pattern concerned primarily the contralateral thalamus in its lateral half and the primary and somatosensory areas, as well as inferior parietal [Brodmann area (BA) 39/40], anterior insular (BA 6) and medial prefrontal (BA 10) cortices. Thalamic over-activity may reflect abnormal transduction and amplification of sensory inputs after spinothalamic deafferentation. This might be responsible for both increased rCBF in multiple cortical targets and the perceived shift of stimulus intensity from innocuous to painful ranges. The second abnormality associated with allodynic sensation was qualitative. It concerned exclusively the contralateral cingulate gyrus, which did not exhibit the usual pain-related rCBF increase reported in normal subjects. This abnormal cingulate response may account for the peculiar response of lateral medullary infarct patients to allodynic pain, which is not simply perceived as an exaggerated pain sensation, but as a new, strange and extremely unpleasant feeling, not previously experienced by the patients.

Adult↗
PubMed1998

Advantage of antithymocyte globulin induction in sensitized kidney recipients: a randomized prospective study comparing induction with and without antithymocyte globulin.

BACKGROUND: Sensitized kidney allograft recipients require special management to improve their outcome. One strategy is heavy immunosuppression with antilymphocyte antibodies. Controversy continues about the actual advantage of induction protocols whilst infections and cancers are a constant risk. In addition, little is known about how to handle sensitized patients with low levels of sensitization. METHODS: In this study, we randomized sensitized renal transplant recipients, who received prophylactic treatment with or without antithymocyte globulin (ATG), in addition to a standard triple regimen consisting of cyclosporin, steroids and azathioprine at ATG discontinuation. The induction treatment consisted of a low-dose ATG course over 10 days. Randomization was stratified on the maximum PRA, according to the five following classes: 5% < PRA < or = 20%, 20% < PRA < or = 40%, 40% < PRA < or = 60%, 60% < PRA < or = 80% and 80% < PRA < or = 100%. RESULTS: Eighty nine patients were enrolled: 47 patients received ATG and 42 did not. ATG induction lowered the incidence of biopsy-proven acute rejection episodes from 64 to 38%, increased 1 year graft survival from 76 to 89% and was associated with a higher 1 year inulin clearance (37+/-15 vs 49+/-18 ml/min). ATG-associated side effects were restricted to leucopenia and thrombocytopenia, whereas bacterial and viral infections, gammopathies and cancers did not occur more frequently. ATG induction benefited all sensitized patients, and not only the hypersensitized patients. CONCLUSIONS: We conclude that ATG induction is beneficial for all sensitized patients, regardless of their level of sensitization, with regard to acute rejection episodes, graft survival and graft function. Low-dose ATG is sufficient and prevents additional complications.

Adult↗
PubMed1998

[Consensus statement of an interdisciplinary group of French experts on modalities of diagnosis and medical treatment of Alzheimer's disease at a treatable stage].

A group of French expert met on the 7th and 8th of February 1998 in order to establish a consensus attitude for Alzheimer's disease diagnosis and treatment. Members were drawn from primary care, geriatrics, neurology and psychiatry. They used the consensus statement of the American Association for Geriatrics, the Alzheimer's Association and the American Geriatrics Society published in JAMA, in October 1997 as a source of data for further consideration. Alzheimer's disease in the most common etiology of dementia. Main clinical features are cognitive impairment and psycho-behavioral disorders. Diagnosis must be one of inclusion and not exclusion. It is based on interviews of informants and family members and office-based clinical assessment. After a physical examination, cognitive function must be evaluated using the Mini-Mental State Examination. A laboratory evaluation should include a complete blood cell count, blood chemistry and determination of thyroid-stimulating hormone. In addition, noncontrast computed tomography head scans are adequate in most cases. Available pharmacologic treatments are not curative but are given to improve quality of life and enhance cognition and behavior. Two cholinesterases inhibitors, tacrine and donepezil, are the only agents officially authorized for treatment of the cognitive impairment in Alzheimer's disease. Mood and behaviour disorder also have to be treated by both pharmacologic and nonpharmacologic strategies. Only pharmacologic treatments will be detailed here. The consensus statements established by this group of experts will be reevaluated each year, considering the new available data on Alzheimer's disease.

Aged↗
PubMed1998

[Memory and dementia].

Memory impairment in ageing is clearly different from Alzheimer's disease. Many papers dealed with the modifications of the different cognitive sections of memory at different stages of Alzheimer's progression: the early involvement of working and episodic memories, those later of semantic and retrograde memories and the lasting saving of implicit memory must be know by clinicians to better understand the target of symptomatic therapy and to differentiate Alzheimer from others degenerative dementias. Above all, these progress authorize an early diagnostic of "possible Alzheimer" at a pre-dementia stage facing to isolated memory complaint. The amnesic profile of others dementias is different and the qualitative approach of testing become essential for the categorization of dementias at early stages with an isolated progressive memory disorder.

Alzheimer Disease↗
PubMed1997

Association and dissociation between laser-evoked potentials and pain perception.

We investigated the relation between the subjective sensation of pain and two different components of the laser evoked potential, namely the vertex response (N220-P350) and an earlier lateralized response (middle-latency NP160). Brain responses to laser stimuli were obtained in 15 subjects under attentive and distractive conditions. Although stimulus intensity was kept constant, it was perceived as significantly higher when subjects attended the stimulation. There was a positive correlation between subjective intensity perception and the amplitude of the vertex potential, but no correlation existed with the middle-latency component. While laser vertex potentials may reflect attentional/perceptual mechanisms that determine subjective experience, the NP160 behaves as a pre-perceptual sensory response that should be advantageous in the assessment of early cortical pain processing.

Adult↗
PubMed1997

Buspirone, a 5-hydroxytryptamine1A agonist, is active in cerebellar ataxia. Results of a double-blind drug placebo study in patients with cerebellar cortical atrophy.

OBJECTIVE: To establish the antiataxic effect of buspirone hydrochloride, a serotonergic 5-hydroxytryptamine1A (5-HT1A) agonist, in a homogenous group of patients characterized by the same well-defined single condition, cerebellar cortical atrophy. SETTING: University ataxia research center. METHODS: Double-blind randomized study of buspirone vs placebo during a 4-month period. PATIENTS: Nineteen patients met the inclusion criteria; all completed the study. Of these 19 patients, 9 were treated with placebo and 10 were treated with the drug. MAIN OUTCOME MEASURES: A semiquantitative scale for kinetic and static ("postural") cerebellar functions; quantitative clinical measurements measuring time in standard tests that evaluated stance, speech, writing, and drawing; and posturographic analysis of the sway path and sway area of the center-of-foot pressure. The primary end point was improvement of the posttherapeutic change of one of the semiquantitative ataxic scores. The secondary end points were modification of the changes of quantitative measures--clinical or posturographic. RESULTS: In intention-to-treat analysis, a significant improvement of the primary end point, ie, the posttherapeutic change of the ataxic kinetic score, was shown. Among secondary end points, the maximum time of standing with feet together also was significantly improved. CONCLUSIONS: Buspirone is active in cerebellar ataxia of patients with cerebellar atrophy. These results confirm the data suggested by open-label studies with buspirone. However, the effect is partial and not clinically major. These pharmacological results might be due to serotonergic mechanisms and confirm a possible link between cerebellar ataxia and the metabolism of serotonin.

Adult↗
PubMed1997

Positron emission tomography during motor cortex stimulation for pain control.

We studied regional changes in cerebral flood flow (rCBF) in 9 patients undergoing motor cortex stimulation (MCS) for pain control. Significant increase in rCBF was observed in the lateral thalamus ipsilateral to MCS probably reflecting corticothalamic connections from motor/premotor areas. Subsignificant increases were observed in the anterior cingulate, left insula and upper brainstem. Mean rCBF in the anterior cingulate increased during MCS in patients with good analgesic efficacy, while it decreased in those with poor clinical outcome; conversely, thalamic rCBF increased in the two groups, albeit to a greater extent in patients with good clinical results. Our results support a model of MCS action whereby activation of thalamic nuclei directly connected with motor and premotor cortices would entail a cascade of synaptic events in other pain-related structures, including the anterior cingulate and the periaqueductal gray. MCS could influence the affective-emotional component of chronic pain by way of cingulate activation, and lead to descending inhibition of pain impulses by activation of the brainstem. Such effects may be obtained only if thalamic activation reaches a 'threshold' level, below which the analgesic cascade would not be successfully triggered.

Adult↗
PubMed1996

RSC, an essential, abundant chromatin-remodeling complex.

A novel 15-subunit complex with the capacity to remodel the structure of chromatin, termed RSC, has been isolated from S. cerevisiae on the basis of homology to the SWI/SNF complex. At least three RSC subunits are related to SWI/SNF polypeptides: Sth1p, Rsc6p, and Rsc8p are significantly similar to Swi2/Snf2p, Swp73p, and Swi3p, respectively, and were identified by mass spectrometric and sequence analysis of peptide fragments. Like SWI/SNF, RSC exhibits a DNA-dependent ATPase activity stimulated by both free and nucleosomal DNA and a capacity to perturb nucleosome structure. RSC is, however, at least 10-fold more abundant than SWI/SNF complex and is essential for mitotic growth. Contrary to a report for SWII/SNF complex, no association of RSC (nor of SWI/SNF complex) with RNA polymerase II holoenzyme was detected.

Acetyltransferases↗
PubMed1996

Pre-Main-Sequence Star Candidates in the Bar of the Large Magellanic Cloud

Candidate pre-main-sequence stars were observed in the bar of the Large Magellanic Cloud during the search for dark matter in the galactic halo. Seven blue stars of apparent visual magnitude 15 to 17 had irregular photometric variations and hydrogen emission lines in their optical spectra, which suggested that these stars are pre-main-sequence stars of about 10 solar masses. These stars are slightly more massive and definitely more luminous than are Herbig AeBe pre-main-sequence stars in our own galaxy. Continued observations of these very young stars from another galaxy, which are probably at the pre-hydrogen-burning stage, should provide important clues about early stages of star formation.

Journal Article↗