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Laurent Thomas

Publications and source records attributed to Laurent Thomas.

9 recordsLinked to original sources
PubMed2025

Genome-wide association meta-regression identifies stem cell lineage orchestration as a key driver of acne risk.

Over 85% of the population experience acne at some point in their lives, with its severity spanning a quantitative spectrum, from mild, transient outbreaks to more persistent, severe forms of the condition. Moderate to severe disease poses a substantial global burden arising from both the physical and psychological impacts of this highly visible condition. The analytical approach taken in this study aimed to address the impact of variation in the dichotomisation of acne case control status, driven by ascertainment and study design, on effect size estimates across independent genetic association studies of acne. Through a fixed intercept meta-regression framework, we combined evidence genome-wide for association with acne across studies in which case-control status had been ascertained in different settings, allowing for different severity threshold definitions. Across a combined sample of 73,997 cases and 1,103,940 controls of European, South Asian and African American ancestry we identify genetic variation at 165 genomic loci that influence acne risk. There is evidence for both shared and ancestry specific components to the genetic susceptibility to acne and for sex differences in the magnitude of effect of risk alleles at three loci. We observe that common genetic variation explains 13.4% of acne heritability on the liability scale. Consistent with the hypothesis that genetic risk primarily operates at the level of individual pilosebaceous units, a polygenic score derived from this case-control study of acne susceptibility is associated with both self-reported and clinically assessed acne severity in adolescence, further strengthening the link between genetic risk and disease severity. Prioritisation of causal genes at the identified acne risk loci, provides genetic validation of the targets of established and emerging acne therapies, including retinoid treatments. The identified acne risk loci are enriched for genes encoding downstream effectors of RXRA signalling, including SOX9 and components of the WNT and p53 pathways. Illustrating that the control of stem cell lineage plasticity and cellular fate are important mechanisms through which genetic variation influences acne susceptibility within the pilosebaceous unit.

Journal Article↗
PubMed2005

Liquid mechanical behavior of mixed monolayers of amino and alkyl silanes by atomic force microscopy.

The adsorption of mixed terminally aminated organosilyl compounds with long-chain n-alkyltrichlorosilanes on silica substrates has been studied by FTIR and AFM to deposit and study DNA. By optimization of deposition conditions, the mixed monolayers were found to be well organized and homogeneous. The amino group was protected to obtain a reproducible grafting and then deprotected after the film formation. In addition, atomic force microscopy (AFM) studies in both dynamical modes, amplitude modulation and frequency modulation, reveal that the layer behaves as a fluid as measured by the tip-cantilever and has a smaller characteristic time than the tip-cantilever. For three amplitudes, the experimental frequency shifts have been modeled for a fluidlike layer crossed by the tip. Finally, we show that this new fluidlike monolayer is suitable for DNA deposition and AFM studies.

Microscopy, Atomic Force↗
PubMed2005

Occipital infarction revealed by quadranopsia following snakebite by Bothrops lanceolatus.

We report a case of snakebite in which envenomation was manifested through impairment of the visual field. The patient, a 46-year-old man, was bitten on the right thumb by Bothrops lanceolatus. Treatment with a specific equine antivenom (Bothrofav) was administered one hour after the bite. With the exception of fang marks, the results of a clinical examination, particularly the neurologic component, were normal. The day after the bite, the patient developed an inferior left lateral homonymous quadranopsia with macular epargne. T2 magnetic resonance imaging showed a right occipital infarction. His condition improved clinically and biologically. This observation of snakebite is the first in which envenomation was accompanied exclusively by an impairment of the visual field. Envenomation by B. lanceolatus is distinct in its incidence of significant thrombotic complications at a distance from the site of the bite.

Animals↗
PubMed2004

Urinary continence after salvage radiation therapy following radical prostatectomy, assessed by a self-administered questionnaire: a prospective study.

OBJECTIVE: To evaluate urinary continence after salvage radiotherapy following radical prostatectomy (RP) for clinically localized prostate cancer. PATIENTS AND METHODS: In all, 145 men had a retropubic RP in our department between 1992 and 2000. From this group, salvage radiotherapy with the dose of 65 Gy was given to 18 patients for a rising prostatic specific antigen (PSA) level. The mean (range) age at RP was 63 (50-72) years and the initial PSA level 14.95 (4.8-34) ng/mL. The radiotherapy was given at 46 (6-96) months after RP. A self-administered questionnaire about their urinary status was mailed to the patients before and 18 months after radiotherapy. The mean follow-up after radiotherapy was 34 (20-70) months. RESULTS: Before radiotherapy, 17 patients were continent (defining continence as no regular use of pads). After salvage radiotherapy, 16 men had had no change in their urinary status, even for the one patient using pads. One patient with stress urinary incontinence showed a slight worsening of his urinary status after radiotherapy. Another patient who was continent before radiotherapy developed urgency with no urinary leakage. Fourteen men stated that they were very satisfied or satisfied about their urinary status after radiotherapy and four were mildly satisfied. Nine would undergo radiotherapy again even with their present continence status and nine probably would. CONCLUSION: Using an anonymous self-administered questionnaire, salvage radiotherapy for a rising PSA level seems to be safe and does not worsen the continence achieved after RP in most patients.

Aged↗
PubMed2004

[Perirenal extension of a pelvic lymphocele after radical prostatectomy].

Lymphocele is a rare symptomatic complication of iliopelvic lymph node dissection during radical prostatectomy. The authors report a case of pelvic lymphocele with perirenal extension diagnosed 6 months after the operation and successfully treated by laparoscopic marsupialisation. The possibility of lymphocele must be considered in any patient presenting with abdominopelvic symptoms after iliopelvic lymph node dissection, even several months after the operation. The treatment of choice is laparoscopic marsupialisation, in the absence of infection.

Aged↗
PubMed2002

Multiple cerebral infarctions following a snakebite by Bothrops caribbaeus.

Bothrops caribbaeus, a species of the Bothrops complex, is found only in the island of Saint Lucia, West Indies. Snakebite from this pitviper is very rare. We report the case of a healthy 32-year-old Saint Lucian man who developed multiple cerebral infarctions following envenoming by this snake. This patient developed signs and symptoms very similar to those observed in patients envenomed by Bothrops lanceolatus, a snake found only in Martinique, the neighbor island of Saint Lucia. This clinical presentation differs dramatically from coagulopathies and systemic bleeding observed with the Central and South American bothropic envenomings. The exact mechanism of this thrombogenic phenomenon, leading to a unique envenoming syndrome, remains unknown.

Adult↗
PubMed2002

[Treatment of phimosis with locally applied 0.05% clobetasol propionate. Prospective study with 108 children].

OBJECTIVE: This study was designed to evaluate the efficacy of topical application of corticosteroid cream in the treatment of phimosis in children and to compare the results obtained with those reported in the literature. MATERIALS AND METHODS: In the context of a prospective study conducted between January 1997 and November 2001, 108 children with a mean age of 5.9 years, presenting with true phimosis preventing retraction of the foreskin, were treated by twice-daily application of 0.05% clobetasol propionate cream for 10 days. The results were evaluated at one month and then every six months by a urologist in the outpatients department. A second course of treatment identical to the first was proposed in the case of failure or partial efficacy. RESULTS: 96 children were evaluated with a mean follow-up of 14 months (range: 6 to 24 months). Seventy nine children (82%) are cured after a first course of treatment. In the remaining 17 children, 2 were treated by circumcision and 15 received a second course of treatment resulting in cure in another 9 cases. The final cure rate was therefore 92%. Among the six failures, 4 children were circumcised, corresponding to a total of 6 circumcisions out of this series of 96 cases of phimosis (6%). No local or systemic adverse effects related to steroid therapy were observed and no recurrence of phimosis was observed during the study. CONCLUSION: This study confirms the efficacy and safety of local steroid therapy in the treatment of phimosis in children. Surgical treatment of phimosis should therefore be reserved for failures of medical treatment and has now become much less frequent.

Administration, Topical↗