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Biomedical subjects

C Hamel

Publications and source records attributed to C Hamel.

At least 19 recordsLinked to original sources
PubMed2005

Response of strawberry to inoculation with arbuscular mycorrhizal fungi under very high soil phosphorus conditions.

A field study was done to assess the potential benefit of arbuscular mycorrhizal (AM) inoculation of elite strawberry plants on plant multiplication, under typical strawberry nursery conditions and, in particular, high soil P fertility (Mehlich-3 extractible P=498 mg kg(-1)). Commercially in vitro propagated elite plants of five cultivars ('Chambly,' 'Glooscap,' 'Joliette,' 'Kent,' and 'Sweet Charlie') were transplanted in noninoculated growth substrate or in substrate inoculated with Glomus intraradices or with a mixture of species (G. intraradices, Glomus mosseae, and Glomus etunicatum) at the acclimation stage and were grown for 6 weeks before transplantation in the field. We found that AM fungi can impact on plant productivity in a soil classified as excessively rich in P. Inoculated mother plants produced about 25% fewer daughter plants than the control in Chambly (P=0.03), and Glooscap produced about 50% more (P=0.008) daughter plants when inoculated with G. intraradices, while the productivity of other cultivars was not significantly decreased. Daughter plant shoot mass was not affected by treatments, but their roots had lower, higher, or similar mass, depending on the cultivar-inoculum combination. Root mass was unrelated to plant number. The average level of AM colonization of daughter plants produced by noninoculated mother plants did not exceed 2%, whereas plants produced from inoculated mothers had over 10% of their root length colonized 7 weeks after transplantation of mother plants and approximately 6% after 14 weeks (harvest), suggesting that the AM fungi brought into the field by inoculated mother plants had established and spread up to the daughter plants. The host or nonhost nature of the crop species preceding strawberry plant production (barley or buckwheat) had no effect on soil mycorrhizal potential, on mother plant productivity, or on daughter plant mycorrhizal development. Thus, in soil excessively rich in P, inoculation may be the only option for management of the symbiosis.

Biomass↗
PubMed2005

[Genetics of retinitis pigmentosa: metabolic classification and phenotype/genotype correlations].

Retinitis pigmentosa (RP, prevalence 1/4000) is a set of hereditary retinal dystrophies characterized by pigment deposits in fundus and progressive death of photoreceptors, always associated with the alteration of retinal pigment epithelium. Genetic heterogeneity of the typical nonsyndromic form (rod cone dystrophy) is extensive: 11 genes and one locus were reported for autosomal dominant RP, 17 genes and five loci for autosomal recessive RP, and two genes and two loci for X-linked RP. A survey of mutation screening reports in large series of patients indicates that the frequency of mutations for all cloned genes varies from 40% to 54% of cases in autosomal dominant RP, from 17% to 24% in autosomal recessive RP (excluding the USH2A gene for which the values remain uncertain) and from 61% to 89% in X-linked RP. Very few studies report on sporadic cases except for the two X-linked genes, RP2 and RPGR, which account for 29% of sporadic cases in males. Altogether, the two most frequently involved genes are RPGR (13% of all RP cases) and RHO (4%), an important consideration for molecular diagnosis. Finally, we roughly estimate that currently known genes do not represent more than 50% of RP cases, suggesting that many genes remain to be discovered. The known genes can be classified into metabolic groups according to the encoded protein: visual transduction, visual cycle, transcription factors, structural proteins, spliceosome complex and cellular traffic, indicating the high level of specialization of photoreceptors and of the retinal pigment epithelium. In parallel with this classification, genotype/phenotype correlations have been established that will help ophthalmologists to suspect particular genes, and thereby mechanisms. This approach will provide better informations to patients and will orient the choice of future therapies.

Genotype↗
PubMed2005

[Leber congenital amaurosis: comprehensive survey of genetic heterogeneity. A clinical definition update].

Leber congenital amaurosis (LCA) is the earliest and most severe form of all inherited retinal dystrophies, responsible for congenital blindness. Disease-associated mutations have been hitherto reported in seven genes. These genes are all expressed preferentially in the photoreceptor cells or the retinal pigment epithelium, but they are involved in strikingly different physiologic pathways, resulting in an unforeseeable pathophysiologic variety. This broad genetic and physiologic heterogeneity, which could greatly increase in the coming years, hinders molecular diagnosis in LCA patients. Genotyping is, however, required to establish genetically defined subgroups of patients ready for therapy. Here we report a comprehensive mutational analysis of all the known genes in 179 unrelated LCA patients, including 52 familial and 127 sporadic (27/127 consanguineous) cases. Mutations were identified in 47.5% of patients. GUCY2D accounted for by far the largest part of the LCA cases in our series (21.2%), followed by CRB1 (10%), RPE65 (6.1%), RPGRIP1 (4.5%), AIPL1 (3.4%), TULP1 (1.7%) and CRX (0.6%). The clinical history of all patients with mutations was carefully revisited in the search for phenotype variations. Genotype-phenotype correlations were found that made it possible to divide patients into two main groups. The first one includes patients whose symptoms fit the traditional definition of LCA, i.e., congenital or very early cone-rod dystrophy, while the second group gathers patients affected with severe yet progressive rod-cone dystrophy. In addition, objective ophthalmologic data subdivided each group into two subtypes. Based on these findings, we have drawn decisional flowcharts directing the molecular analysis of LCA genes in a given case. These flowcharts will hopefully lighten the onerous task of genotyping new patients, but only if the most precise clinical history since birth is available.

Animals↗
PubMed2005

[Hereditary macular dystrophies].

Hereditary macular dystrophies are degenerative diseases of the central area of the retina associating primary anomalies of the retinal pigment epithelium and sensory retina. These conditions, whose hallmark is a loss of visual acuity, are a major cause of blindness and affect patients at all ages. Macular dystrophies group diseases that are heterogenous at the genetic level, as well as at the clinical, histological and physiopathological levels. Monogenic macular dystrophies are rare autosomal dominant conditions, with the exception of Stargardt disease in its typical form, which is not only relatively frequent but is also inherited as an autosomal recessive trait. During the last few years, the molecular bases of these conditions have begun to be elucidated with the identification of several responsible genes. For some macular dystrophies, this new information has confirmed pre-existing hypotheses on their pathophysiology, but for others, the discovery of the disease gene has added further complexity to the disease process. Two contradictory concepts were particularly highlighted by these genetic studies. Several phenotypes previously described as different clinical entities were brought together by the identification of mutations in the same gene, and converselyome conditions that were clinically assigned the same name, often heterogeneous at the clinical level, appeared genetically and physiopathologically heterogeneous. In addition, it is worth noting that the monogenic macular dystrophy genes were often regarded as potential factors for susceptibility to age-related macular degenerations. However, to date, only ABCA4 mutations have been associated with a minority of this frequent multifactorial condition. The aim of this article is to give a progress report on the monogenic macular dystrophy genes and to review current knowledge concerning the pathophysiology of these conditions.

Humans↗
PubMed2004

Calcium supplementation on bone loss in postmenopausal women.

BACKGROUND: Although calcium is one the simplest and least expensive strategies for preventing osteoporotic fractures calcium supplementation is nevertheless not without controversy (Kanis 1989; Nordin 1990). The Food and Drug Administration in the US has permitted a bone health claim for calcium-rich foods, and the NIH in its Consensus Development Process approved a statement that high calcium intake reduces the risk of osteoporosis. OBJECTIVES: To assess the effects of calcium on bone density and fractures in postmenopausal women. SEARCH STRATEGY: We searched Cochrane Controlled Register, MEDLINE and EMBASE up to 2001, and examined citations of relevant articles and proceedings of international meetings. SELECTION CRITERIA: Trials that randomized postmenopausal women to calcium supplementation or usual calcium intake in the diet and reported bone mineral density of the total body, vertebral spine, hip, or forearm or recorded the number of fractures, and followed patients for at least one year were considered for inclusion. DATA COLLECTION AND ANALYSIS: Three independent reviewers assessed the methodologic quality and extracted data for each trial. For each bone density site (lumbar spine, total body, combined hip and combined forearm), we calculated the weighted mean difference in bone density between treatment and control groups using the percentage change from baseline. We constructed regression models in which the independent variables were year and dose, and the dependent variable was the effect size. This regression was used to determine the years across which pooling was appropriate. Heterogeneity was assessed. For each fracture analysis we calculated a risk ratio. MAIN RESULTS: Fifteen trials, representing 1806 participants, were included. Calcium was more effective than placebo in reducing rates of bone loss after two or more years of treatment. The pooled difference in percentage change from baseline was 2.05% (95% CI 0.24 to 3.86) for total body bone density, 1.66% (95% CI 0.92 to 2.39) for the lumbar spine at 2 years, 1.60% (95% CI 0.78 to 2.41) for the hip, and 1.91% (95% CI 0.33 to 3.50) for the distal radius. The relative risk of fractures of the vertebrae was 0.79 (95% CI 0.54 to 1.09); the relative risk for non-vertebral fractures was 0.86 (95% CI 0.43 to 1.72). REVIEWER'S CONCLUSIONS: Calcium supplementation alone has a small positive effect on bone density. The data show a trend toward reduction in vertebral fractures, but it is unclear if calcium reduces the incidence of non vertebral fractures.

Bone Density↗
PubMed2004

[Laparoscopic treatment for Crohn's disease].

AIM: Several studies have demonstrated the feasibility and safety of laparoscopic surgery for Crohn's disease. A trend towards less morbidity as compared to laparotomy has been suggested. However, problems noted early in the experience may have prevented the optimal benefit from having been conferred. Accordingly, the aim of this study was to evaluate perioperatively those patients. METHODS: All 51 patients with Crohn's disease who underwent an intestinal resection at Cleveland Clinic Florida between January 1997 and December 1998 were analyzed. RESULTS: Seventeen patients underwent laparoscopic treatment: there were no significant differences between the 2 groups as to age, gender, incidences of comorbidity, prior laparotomy, or the use of anti-inflammatory and immunosuppressive agents. Similarly, there were no significant differences between the 2 groups as to either surgical indication, intraoperative findings, or procedure performed. Moreover, there were no significant differences concerning total anesthetic time or surgical operative time, the incidence of intraoperative morbidity or need for enterolysis or stoma construction, use of intraoperative endoscopy, or need for transfusion. Significant differences were noted in the duration of patient controlled analgesic usage (3.1 days in the laparoscopic group vs 3.9 days, respectively; p = 0.03), the incidence of postoperative morbidity (7/17 patients in the laparoscopic group vs 27/34 patients: p = 0.01), and length of hospital stay (6.4 days in the laparoscopic group vs 9.6 days, respectively; p = 0.05). CONCLUSIONS: In this retrospective cohort comparative study, laparoscopic intestinal resection for Crohn's disease, when compared to laparotomy, was associated with a short duration of patient controlled analgesic usage, a lower incidence of postoperative morbidity and a shorter hospital stay, without significantly increased operative time.

Adult↗
PubMed2003

Arbuscular mycorrhiza colonization and development at suboptimal root zone temperature.

Temperature has a strong influence on the activity of living organisms. This study, involving two indoor experiments, evaluated the effects of root zone temperature (10, 15 and 23 degrees C) on the formation and development of arbuscular mycorrhizae (AM). In the first trial, greenhouse-grown sorghum [ Sorghum bicolor (L.) Moench] was either colonized by Glomus intraradices Schenck & Smith or left non-mycorrhizal. Root length, root and shoot weight and root colonization were measured after 5, 10 and 15 weeks of plant growth. Although suboptimal root zone temperatures reduced growth in both mycorrhizal and non-mycorrhizal plants, mycorrhizal plants were larger than non-mycorrhizal plants after 15 weeks at 15 and 23 degrees C. At suboptimal root zone temperatures, mycorrhizal inoculation sometimes slightly reduced root development. AM colonization was more affected than root growth at suboptimal root zone temperatures. Colonization was markedly reduced at 15 degrees C compared with 23 degrees C, and almost completely inhibited at 10 degrees C. The second experiment was conducted in vitro using transformed carrot ( Daucus carota L.) roots supporting G. intraradices. Mycelium length and spore number were measured weekly for 15 weeks. Spore metabolic activity (iodonitrotetrazolium reduction), root length and percentage root colonization were measured after 15 weeks. G. intraradices sporulation was reduced at temperatures below 23 degrees C, while spore metabolic activity was significantly reduced only at 10 degrees C. Root length and in particular percentage colonization were decreased at suboptimal temperatures. A negative interaction between AM hyphal growth and root growth resulting in reduced probability of contact at suboptimal root zone temperatures is proposed to explain the greater reduction observed in root colonization than in root and hyphal growth.

Cold Temperature↗
PubMed2003

Calcium supplementation on bone loss in postmenopausal women.

BACKGROUND: Although calcium is one the simplest and least expensive strategies for preventing osteoporotic fractures calcium supplementation is nevertheless not without controversy (Kanis 1989; Nordin 1990). The Food and Drug Administration in the US has permitted a bone health claim for calcium-rich foods, and the NIH in its Consensus Development Process approved a statement that high calcium intake reduces the risk of osteoporosis. OBJECTIVES: To assess the effects of calcium on bone density and fractures in postmenopausal women. SEARCH STRATEGY: We searched Cochrane Controlled Register, MEDLINE and EMBASE up to 2001, and examined citations of relevant articles and proceedings of international meetings. SELECTION CRITERIA: Trials that randomized postmenopausal women to calcium supplementation or usual calcium intake in the diet and reported bone mineral density of the total body, vertebral spine, hip, or forearm or recorded the number of fractures, and followed patients for at least one year were considered for inclusion. DATA COLLECTION AND ANALYSIS: Three independent reviewers assessed the methodologic quality and extracted data for each trial. For each bone density site (lumbar spine, total body, combined hip and combined forearm), we calculated the weighted mean difference in bone density between treatment and control groups using the percentage change from baseline. We constructed regression models in which the independent variables were year and dose, and the dependent variable was the effect size. This regression was used to determine the years across which pooling was appropriate. Heterogeneity was assessed. For each fracture analysis we calculated a risk ratio. MAIN RESULTS: Fifteen trials, representing 1806 participants, were included. Calcium was more effective than placebo in reducing rates of bone loss after two or more years of treatment. The pooled difference in percentage change from baseline was 2.05% (95% CI 0.24 to 3.86) for total body bone density, 1.66% (95% CI 0.92 to 2.39) for the lumbar spine at 2 years, 1.60% (95% CI 0.78 to 2.41) for the hip, and 1.91% (95% CI 0.33 to 3.50) for the distal radius. The relative risk of fractures of the vertebrae was 0.79 (95% CI 0.54 to 1.09); the relative risk for non-vertebral fractures was 0.86 (95% CI 0.43 to 1.72). REVIEWER'S CONCLUSIONS: Calcium supplementation alone has a small positive effect on bone density. The data show a trend toward reduction in vertebral fractures, but it is unclear if calcium reduces the incidence of non vertebral fractures.

Bone Density↗
PubMed2003

[Laparoscopic surgery for endoscopically irretrievable colonic polyps].

AIM: The vast majority of benign colorectal neoplasms can be safely removed by colonoscopic polypectomy; while peduncolated polyps can be easily endoscopically excised, the removal of sessile polyps may be more difficult. METHODS: Between January 1997 and December 1998, 12 patients underwent laparoscopic or laparoscopic-assisted colonic resection for treatment of endoscopically irretrievable colonic polyps; this group was compared to 12 patients who underwent a laparotomic approach for polyps in the same period of time and to 23 patients who previously underwent similar laparoscopic resections. RESULTS: There were no significant differences between laparoscopic and laparotomic groups. CONCLUSION: Laparoscopic or laparoscopic-assisted colonic resection for treatment of endoscopically irretrievable colonic polyps remains our preferred method of treating these lesions.

Aged↗
PubMed2002

Phosphorus-32 absorption and translocation to host plants by arbuscular mycorrhizal fungi at low root-zone temperature.

Arbuscular mycorrhizal (AM) mycelia persist in soil over winter. Functioning of the AM symbiosis very early in the spring when the soil temperature is low may be of ecological significance for perennial and biannual plants in cool climates. An indoor experiment was conducted to investigate the effects of low root-zone temperatures on 32P uptake by 10-week-old leek plants (Allium porrum L.) inoculated or not with the AM fungus Glomus intraradices Schenck & Smith. Plants were grown in a greenhouse at approximately 23 degrees C prior to exposing their roots to 23 degrees C, 15 degrees C or 0 degree C. Mycorrhizal colonization increased 32P activity of leek leaves at a root-zone temperature of 23 degrees C seven days after injection of 32P into the soil, whereas 14 days after injection, 32P increases were measured at both 23 degrees C and 15 degrees C. The lack of difference in 32P activity between AM and non-AM plants at 0 degree C, both 7 and 14 days after injection, suggests that the AM fungus is not functional at this low root-zone temperature.

Cold Temperature↗
PubMed2001

Restorative proctocolectomy with ileal pouch anal anastomosis in obese patients.

BACKGROUND: Obesity is a relative contraindication to performing restorative proctocolectomy. The aim of this study was to assess the morbidity and functional results after restorative proctocolectomy in obese patients as compared to a matched cohort of non-obese patients. METHODS: 334 patients who had restorative proctocolectomy were reviewed; obesity was defined as a body mass index (BMI) greater than or equal to 30 kg/m2. 31 obese patients were matched to 31 non-obese patients for age, gender, steroid use, and diagnosis. Operative time, length of hospitalization, and both perioperative (< 6 weeks) and long-term morbidity (> 6 weeks), especially sepsis, were evaluated. RESULTS: The BMI was significantly higher in the obese group (33.7 vs 23.2) (p < 0.0001), and no difference was found between the obese and non-obese groups relative to the matched parameters of age, gender, steroid use and diagnosis. There was no difference in the rate of mucosectomy performed between the obese and non-obese patients (9.6% vs 3.2%, p = NS). 16% of the obese patients underwent one stage restorative proctocolectomies as compared to 10% in the non-obese group. Operative time was longer in the obese group (229 min vs 196 min; p = 0.02), but overall hospital length of stay was similar (9.7 days vs 7.7 days; p = 0.13). Perioperative morbidity was higher in obese patients (32% vs 9.6%, p = 0.058). However, there was no statistical significance in long-term morbidity (23% vs 32%, p = 0.57) at a mean follow-up of 51 months in the obese group and 53 months in the non-obese group. Obese patients had more stomal complications (10 vs 0%) and incisional hernias (13 vs 3%) (p = NS). Overall the pelvic sepsis-rate was significantly higher in the obese group (16 vs 0%; p < 0.05). 60% of the obese patients who developed pelvic sepsis had pouch-anal anastomosis performed without proximal fecal diversion. Mean bowel movements/24 hours, pad use, nocturnal evacuation, accidents/24 hours and incontinence scores were not statistically significant between the groups. CONCLUSION: Obese patients have a higher rate of pelvic sepsis and peri-operative morbidity when compared to a matched non-obese cohort of patients; however, the functional outcome of restorative proctocolectomy in obese patients is not significantly different than in non-obese patients.

Adenomatous Polyposis Coli↗
PubMed2000

The fate and mobility of copper from chemical root control barriers in soil and leachate.

The use of copper (Cu)-treated containers is common horticultural practice, though the movement of this Cu to soil and water remains unexplored. Therefore, the fate and quantity of Cu migrating from the fabric of 10 in-ground Cu(OH)(2)-treated root control baskets was studied in the field. After 3 months, 29% of the initial Cu remained on the basket fabric, 71% of the Cu had been deposited in the soil, 0.2% was in the leaves and roots of the maple shrub (Acer ginnala) growing in the basket, and 0.004% was recovered in leachate from the baskets. Soluble Cu concentrations in leachate varied between 0.5 and 8.5 mg l(-1) and exceeded 1 mg l(-1) in 60% of samples. Mycorrhizal inoculation significantly increased the Cu concentration in A. ginnala leaves. Baskets containing no tree had significantly higher soil Cu and leached significantly more Cu over the 3-month period than treed baskets.

Journal Article↗
PubMed1999

[Cecum reservoir].

UNLABELLED: The choice of the best reconstruction technique following resection of either the stomach or the rectum remains a matter of discussion. While there is no problem in reconnecting intestinal segments, which do not serve as a reservoir, there are many different operation techniques to replace the stomach and rectum, producing significantly different functional results. The ileocecal segment offers an excellent intestinal reservoir combined with an antireflux mechanism, thus presenting an ideal replacement for the stomach. For replacement of the rectal reservoir as well, the ileocecal segment may be used in the first line of treatment. METHOD: The ileocecal segment was used in 20 patients following gastric resection and lymphadenectomy to reconstruct the intestinal passage between the esophagus and the duodenal stump (group A). In some further 44 patients (group B) the ileocecal segment was used to replace the rectum between the descending colon and the dentate line following resection for very low-grade rectal cancer. Mortality and morbidity were investigated in both groups. In group A quality of life, weight loss, dumping and reflux symptoms were evaluated. In group B continence, discrimination, defecation quality, urge and the patient satisfaction were investigated. All data were recorded prospectively. RESULTS: Early and late mortality were not different compared to other reconstruction types. In each group one patient died within 60 days postoperatively due to myocardial infarction. The morbidity following stomach replacement was 20%, following rectal replacement 4.6% during hospitalization and 13.8% during follow-up, respectively. One patient complained about heartburn, but endoscopically no pathology was detected in any patient. Three months postoperatively the patients' weight remained stable or started to increase. Three months following rectal replacement 87% of the patients were continent with further improvement over 2 years. Soiling mainly during the night remained over 2 years in 44%. 88% of the patients were completely satisfied 2 years postoperatively. CONCLUSION: The replacement of either the stomach or the rectum using the ileocecal segment with an adequate surgical technique is safe and produces excellent functional outcome regarding the reconstruction of the intestinal passage as well as the reservoir function of the primary organ. Furthermore, preservation of the duodenal passage after gastrectomy may prevent dysregulation of the endocrine and exocrine pancreatic hormones.

Anastomosis, Surgical↗
PubMed1999

Molecular analysis of the rhodopsin gene in southern France: identification of the first duplication responsible for retinitis pigmentosa, c.998999ins4.

PURPOSE: Mutations in the gene encoding rhodopsin, the visual pigment in rod photoreceptors, were shown to be the most common cause of autosomal retinitis pigmentosa (RP). In order to determine the prevalence of rhodopsin alterations in southern French populations, we examined 52 unrelated patients/families with autosomal dominant RP (adRP=29), RP simplex (6), or unclassified RP (17). METHODS: The full coding and flanking sequences of the rhodopsin (RHO) gene were scanned using an improved DGGE (denaturing gradient gel electrophoresis) assay, followed by sequencing of abnormal fragments. RESULTS: This study revealed three RHO mutations in patients with adRP (G106R, R135W, and c.998999ins4) and a number of frequent or rare polymorphisms. No disease-causing sequence variation was found in simplex and unclassified RP pedigrees. Mutation c.998999ins4 has not been previously reported, and appears as the first duplication identified so far in the RHO gene. This frameshift mutation, which is associated with a severe RP, alters the carboxy terminus and predicts a 353-amino acid mutant rhodopsin instead of 348. DISCUSSION: Our study demonstrates that rhodopsin mutations are responsible for only 10.3% of adRP in French populations living in the Mediterranean area in contrast to the 25-35% reported in other populations.

Adult↗
PubMed1997

Cloning of the genes encoding two murine and human cochlear unconventional type I myosins.

Several lines of evidence indicate a crucial role for unconventional myosins in the function of the sensory hair cells of the inner ear. We report here the characterization of the cDNAs encoding two unconventional type I myosins from a mouse cochlear cDNA library. The first cDNA encodes a putative protein named Myo1c, which is likely to be the murine orthologue of the bullfrog myosin I beta and which may be involved in the gating of the mechanotransduction channel of the sensory hair cells. This myosin belongs to the group of short-tailed myosins I, with its tail ending shortly after a polybasic, TH-1-like domain. The second cDNA encodes a novel type I myosin Myo1f which displays three regions: a head domain with the conserved ATP- and actin-binding sites, a neck domain with a single IQ motif, and a tail domain with the tripartite structure initially described in protozoan myosins I. The tail of Myo1f includes (1) a TH-1 region rich in basic residues, which may interact with anionic membrane phospholipids; (2) a TH-2 proline-rich region, expected to contain an ATP-insensitive actin-binding site; and (3) a SH-3 domain found in a variety of cytoskeletal and signaling proteins. Northern blot analysis indicated that the genes encoding Myo1c and Myo1f display a widespread tissue expression in the adult mouse. Myo1c and Myo1f were mapped by in situ hybridization to the chromosomal regions 11D-11E and 17B-17C, respectively. The human orthologuous genes MYO1C and MYO1F were also characterized, and mapped to the human chromosomal regions 17p18 and 19p13.2-19p13.3, respectively.

Amino Acid Sequence↗