Biomedical subjects

J M Meyer

Publications and source records attributed to J M Meyer.

At least 55 records · Page 3Linked to original sources

PubMed2000

Protein undernutrition-induced bone loss is associated with decreased IGF-I levels and estrogen deficiency.

Protein undernutrition is a known factor in the pathogenesis of osteoporotic fracture in the elderly, but the mechanisms of bone loss resulting from this deficiency are still poorly understood. We investigated the effects of four isocaloric diets with varying levels of protein content (15, 7.5, 5, and 2.5% casein) on areal bone mineral density (BMD), bone ultimate strength, histomorphometry, biochemical markers of bone remodeling, plasma IGF-I, and sex hormone status in adult female rats. After 16 weeks on a 2.5% casein diet, BMD was significantly decreased at skeletal sites containing trabecular or cortical bone. Plasma IGF-I was decreased by 29-34% and no estrus sign in vaginal smear was observed. To investigate the roles of estrogen deficiency and protein undernutrition, the same protocol was used in ovariectomized (OVX) or sham-operated (SHAM) rats, pair-fed isocaloric diets containing either 15 or 2.5% casein. Trabecular BMD was decreased by either manipulation, with effects appearing to be additive. Cortical BMD was decreased only in rats on a low-protein diet. This was accompanied by an increased urinary deoxypyridinoline excretion without any change in osteocalcin levels, suggesting an uncoupling between resorption and formation. Isocaloric protein undernutrition decreased bone mineral mass and strength. This effect might be related to decreased plasma IGF-I and/or estrogen deficiency with a consequent imbalance in bone remodeling.

Animals↗

PubMed2000

[Predictive malignancy factors in thyroid nodular disease].

Nodular thyroid pathology is frequent and remains a controversial issue when it comes to establishing an ideal endocrine surgical strategy. We studied clinical and complementary data predictive of malignancy using a large retrospective analysis of 366 cases operated for nodular pathology of the thyroid gland between January 1995 and December 1997 in our Head and Neck Surgery Unit of the Pasteur Hospital in Nice, France. The incidence of malignancy was 12.8% with the usual histologic findings (83% of well-differentiated tumors: 70% papillary, 13% vesicular, 9% medullar, 6% oncocytic and 2% anaplastic). Statistical analysis did not conclude on the predictive value of several items in terms of their relationship to high risk of malignancy (p > 0.05): size of nodules, signs of local compression, biological findings, presence of calcifications, mixed ultrasound aspect, no hypoechogenic halo, scintigraphic aspect. This retrospective work did however identify items predictive of malignancy when appearing in patients with nodular thyroid disease: male sex (odds ratio 2.4; 95%CI [1.17-4.88]; p=0.13), age (less than 40 yr or more than 70yr) (p=0.003), hard nodule consistency (odds ratio 7.40; 95%CI [3.99-13.52], p<0.001), invasion of lymphatic nodes noted prior to surgery (p=0.031), hyperechogenicity on ultrasound exam (p=0.013). We were able to confirm the highly negative predictive value (92%) of fine needle aspiration, emphasizing its value in endocrine thyroid nodular disease diagnosis.

Adolescent↗

PubMed1999

The ferripyoverdine receptor FpvA of Pseudomonas aeruginosa PAO1 recognizes the ferripyoverdines of P. aeruginosa PAO1 and P. fluorescens ATCC 13525.

FpvA, the ferripyoverdine outer membrane receptor of Pseudomonas aeruginosa ATCC 15692 (PAO1 strain), is not specific to the pyoverdine produced by PAO1, but is also able to recognize the structurally different (ferri)pyoverdine of P. fluorescens ATCC 13525. The specificity of FpvA was assessed by iron uptake competitions using the wild-type strains P. aeruginosa ATCC 15692 and P. fluorescens ATCC 13525 and their respective ferripyoverdines, and by fpvA gene complementation of a FpvA-deficient mutant of P. aeruginosa ATCC 15692. The receptor mutant was able to utilize none of the two pyoverdines, while the same but fpvA-complemented mutant recovered simultaneously the ability to incorporate iron thanks to each of the two siderophores. The broad specificity of recognition of FpvA is viewed as an advantage for the strain in iron competition. Moreover, it allows an interesting approach for the understanding of the recognition mechanism between a (ferri)pyoverdine and its cognate outer membrane receptor.

Bacterial Outer Membrane Proteins↗

PubMed1999

The new selective estrogen receptor modulator MDL 103,323 increases bone mineral density and bone strength in adult ovariectomized rats.

Selective estrogen receptor modulators (SERMs) can prevent the bone loss induced by ovariectomy (OVX), but it is not established whether they can increase bone mass and strength in a curative protocol in ovariectomized osteopenic animals. We investigated the influence of a SERM of the new generation, MDL 103,323, on areal bone mineral density (BMD), as measured by dual-energy X-ray absorptiometry, bone strength and remodeling in OVX osteopenic rats. Nine weeks after OVX, 8-month-old rats were divided into six groups of 10 animals. MDL 103,323 was given by gavage at doses of 0.01, 0.1 or 0.6 mg/kg body weight, 5 days a week. The effect of MDL 103,323 was compared with that of the bisphosphonate pamidronate (APD), which was injected subcutaneously at a dose of 1.6 mmol/kg body weight for 5 days every 4 weeks. Lumbar spine (LS), femoral neck (FN), proximal tibia (PT) and midshaft tibia (MT) BMD, bone strength, and proximal tibia histomorphometry, serum osteocalcin, urinary total deoxypyridinoline and serum insulin-like growth factor I (IGF-I) were measured. After 16 weeks of treatment, BMD changes (means +/- SEM) were -11.4 +/- 2. 2, +4.0 +/- 2.1 and +6.4 +/- 1.0% respectively in OVX controls, in rats treated with 0.1 mg/kg MDL 103,323 (p<0.05) and in APD-treated rats (p<0.02) at the level of LS; -0.4 +/- 1.1, +6.7 +/- 1.4, +7.2 +/- 1.8% (p<0.01 and NS) at the level of FN; and -2.6 +/- 1.2%, +5.8 +/- 1.2, +6.9 +/- 1.4% (p<0.03 and 0.01) at the level of PT. MDL 103, 323-treated animals had a higher trabecular bone volume, a higher number of trabeculae and smaller intertrabecular spaces compared with OVX controls. Vertebral body ultimate strength was 186 +/- 13, 292 +/- 16, 249 +/- 23 N (p<0.05) in OVX controls, MDL 103, 323-treated rats and APD-treated rats, respectively. The administration of 0.6 mg/kg of MDL 103,323 did not further increase BMD or bone strength, indicating a bell-shaped dose-response curve. MDL 103,323 lowered plasma osteocalcin concentration and urinary deoxypyridinoline excretion. In rats treated with 0.1 mg/kg MDL 103, 323, plasma IGF-I was increased as compared with OVX controls (664 +/- 36 ng/ml vs 527 +/- 39 ng/ml, p<0.05). In conclusion, these results indicate that this new SERM positively influences BMD and lumbar spine bone strength in estrogen-deficient rats.

Analysis of Variance↗

PubMed1999

Initial aspects of mineralization at the dentino-enamel junction in embryonic mouse incisor in vivo and in vitro: a tem comparative study.

The frontier between the enamel organ and the dental papilla, the future dentino-enamel junction, undergoes coordinated modifications. The mineralization of the extracellular matrix starts within the predentine, which is a prerequisite for the formation of the first enamel crystallites in vivo. We investigated the dentino-enamel junction using the embryonic mouse incisor as a model. Our data showed that the notion of the dentino-enamel junction should not be restricted to the thin interface classically described. A temporo-spatial survey from the epithelio-mesenchymal junction to the dentino-enamel junction delineated a clear sequence of events characterized by the early deposition of electron-dense granules, followed by the appearance of patches of stippled material at the dentino-enamel junction. The first tiny enamel crystallites appeared in the vicinity of this material which presented a well-ordered alignment. The comparison of data obtained in vivo on 17-, 18-, 19-d-old embryonic incisors with those obtained in vitro using 15-d-old embryonic incisors cultured for 7 d emphasizes the relevance of this sequence. Helicoidal growing crystals were observed in cultured tooth germs but never in vivo.

Amelogenesis↗

PubMed1999

Comparative study of the physical properties of a polyacid-modified composite resin and a resin-modified glass ionomer cement.

OBJECTIVES: The physical properties of the resin-modified composite resin Dyract (Detrey Dentsply) and the resin-modified glass ionomer cement Fuji II LC (GC) were compared, and the effect of water sorption on these properties was studied. METHODS: Compressive, diametral compressive and flexural strengths were measured using specimens aged up to three months. The Vickers hardness and the water erosion were also determined. The specimens were stored at 37 degrees C under five different conditions, chosen to vary the water sorption of the samples. The results were analyzed using a multi-factor analysis of variance. RESULTS: Dry specimens of Dyract and Fuji II LC showed similar properties. However, the two materials behaved differently when stored in presence of water. In contrast to Fuji II LC, Dyract showed very little expansion for the first 24 h (1.5 +/- 0.3 and 0.03 +/- 0.01%, respectively), leached small quantities of ions and retained its mechanical strength. Those differences are related to their chemical composition. Fuji II LC is hydrophilic, as it contains polyHEMA. In the presence of water, Fuji II LC behaves like a hydrogel, but the network resulting from the copolymerization of acidic and UDMA monomers is less hydrophilic, and the effect of water on Dyract is retarded. SIGNIFICANCE: The significant properties of Dyract are determined by its composite character. This certainly represents some advantages, for instance, a higher mechanical strength, a better protection against initial dehydration and subsequent water effects. However, Dyract shows some disadvantages over Fuji II LC, like a lower amount of fluoride release or the interference of oxygen during polymerization.

Absorption↗

PubMed1999

Effect of water on the physical properties of resin-modified glass ionomer cements.

OBJECTIVES: Resin-modified glass ionomer cements (GIC) are available for clinical use as restorative materials or as liners and bases. This work was conducted to study the effect of water sorption on the physical properties of several resin-modified GIC, by changing the samples' storage conditions. METHODS: The water sorption, the flexural strength, the flexural elastic modulus, the Vickers hardness and the dimensional changes of five resin-modified GICs were measured using specimens aged for 24 h to 3 mon. The specimens were stored at 37 degrees C, either in a dry environment (A), immersed in water (B), stored in a humid environment (C), stored in a humid environment for 1 h and then immersed in water (D), or immersed in water and subsequently dried (B + A). An analysis of variance was used to compare the results. RESULTS: The resin-modified GIC absorb during the first 24 h large amounts of water (114-172 mg/cm3) compared to the conventional GIC (30-63 mg/cm3). Water alters the physical properties of resin-modified GICs: With regard to dry specimens, a decrease in the flexural strength of 20 to 80% was observed for samples immersed in water. Decreases in their flexural elastic modulus (50 to 80%) and in their hardness (approximately 50%) were also observed. Water sorption also provoked an expansion in volume of the immersed specimens, ranging from 3.4 to 11.3% after 24 h. SIGNIFICANCE: The flexural strength and Vickers hardness of the resin-modified GICs are sensitive to the water contained in the tested specimens. A correlation was established between the decrease in their physical properties and the water uptake. However, it should not be concluded that these materials are not adequate for use in applications in direct contact with oral fluids. Probably, resin-modified GIC placed in oral cavities would not be affected to the same extent as in in vitro tests. In an oral environment, the constituents of saliva will certainly decrease the rate of water sorption and will hence delay its effects.

Absorption↗

PubMed1999

Epilepsy and seizure occurrence in a population-based sample of Virginian twins and their families.

Epilepsy and seizure occurrence was assessed in a large, population-based sample of Virginian twins and their families. Medical history information on twins and their relatives was collected by questionnaire and used to estimate prevalence of seizures and epilepsy for this sample. Health history information was available on 16,634 twins and their families. Lifetime prevalence of a history of seizures ranged from < 1 to 5%. Concordance rates were larger in monozygotic (MZ) than dizygotic (DZ) pairs overall, however, significant differences between the zygosities were only noted for Caucasian twins. To facilitate interpretation of results, the sample was partitioned into two age groups: 16-35 years and > 35 years of age. In the first age category of twins, significant differences were observed for the following seizure types; epilepsy (0.30 and 0.13, p <0.03), febrile seizures (0.39 and 0.12, p <0.001), and other convulsions/seizures (0.28 and 0.01, p < 0.001). While for twins in the second age category, only the comparison for febrile seizures (0.42 and 0.14, p < 0.001) resulted in a significant difference between zygosities. A family history of seizures was reported in 215 (35.1%) of the 613 seizure positive probands. Increased risk of seizures (1.88-4.64) among relatives of affected versus unaffected individuals was also observed.

Adolescent↗

PubMed1999

Revised structures of the pyoverdins from Pseudomonas putida CFBP 2461 and from Pseudomonas fluorescens CFBP 2392.

Several suggestions for structures of the siderophores (pyoverdins) from Pseudomonas spp. can be found in the literature which are based on a FAB mass spectrometric analysis only. Availability of two original strains of two Pseudomonas spp. allowed to re-investigate the structure of their pyoverdins. In both cases the amino acid sequence had to be corrected. In addition, D- and L-amino acids could be identified and located in the peptide chain. The knowledge of the correct structures is important in view of an ongoing study to establish relationships between the nature of the peptide chains of pyoverdins and their recognition by outer membrane proteins.

Amino Acid Sequence↗

PubMed1999

Genetic and social determinants of initiation and age at onset of smoking in Australian twins.

Retrospective data on age at onset of smoking, reported by 3810 adult Australian twin pairs, were analyzed to determine the role of genetic and environmental factors in the onset of smoking. Results of nonmetric multidimensional scaling supported a two-process model in which different etiologic factors determined which individuals were at risk of becoming smokers and the age at onset of smoking in those who were at risk. Parametric model-fitting confirmed this difference. For female twins and younger male twins (aged 30 years or less), the onset of smoking was strongly influenced by genetic factors, with shared and nonshared environmental effects having a more modest impact. For older male twins, shared environmental influences on onset of smoking were very important, and the influence of genetic predisposition was slight. The age at which smoking onset occurred, however, was influenced by both genetic and nonshared environmental effects, but not by shared environmental effects, in both sexes and both cohorts.

Adolescent↗

PubMed1999

In-vitro synergy of paromomycin with metronidazole alone or metronidazole plus hydroxymetronidazole against Helicobacter pylori.

The in-vitro activities of paromomycin and metronidazole alone or paromomycin and metronidazole plus hydroxymetronidazole (2:1 ratio) were studied against 19 Helicobacter pylori isolates using an in-vitro chequerboard technique. Partial synergy was demonstrated for the majority of isolates (11/19) for both combinations tested. When hydroxymetronidazole was added to the parent compound, the number of metronidazole-sensitive isolates demonstrating synergy increased to 5/12, compared with 1/12 for the combination that did not include the metabolite. In metronidazole-resistant isolates there was a shift from an additive effect to partial synergy for the combination containing hydroxymetronidazole. The in-vitro activity of paromomycin and the synergic effect that is achieved in combination with metronidazole and hydroxymetronidazole render paromomycin suitable for further investigation as a treatment option for H. pylori infection.

Anti-Bacterial Agents↗

PubMed1999

Uptake of pyocin S3 occurs through the outer membrane ferripyoverdine type II receptor of Pseudomonas aeruginosa.

Pyocin S3 was found to kill exclusively Pseudomonas aeruginosa isolates producing type II pyoverdine (exemplified by strain ATCC 27853). Killing was specifically inhibited by addition of type II ferripyoverdine. All Tn5 mutants resistant to pyocin S3 were defective for pyoverdine-mediated iron uptake and failed to produce an 85-kDa iron-repressed outer membrane protein. We conclude that this protein is probably the type II ferripyoverdine receptor that is used by pyocin S3 to gain entry into the cell.

Bacterial Outer Membrane Proteins↗

PubMed1999

The pvc gene cluster of Pseudomonas aeruginosa: role in synthesis of the pyoverdine chromophore and regulation by PtxR and PvdS.

A putative operon of four genes implicated in the synthesis of the chromophore moiety of the Pseudomonas aeruginosa siderophore pyoverdine, dubbed pvcABCD (where pvc stands for pyoverdine chromophore), was cloned and sequenced. Mutational inactivation of the pvc genes abrogated pyoverdine biosynthesis, consistent with their involvement in the biosynthesis of this siderophore. pvcABCD expression was negatively regulated by iron and positively regulated by both PvdS, the alternate sigma factor required for pyoverdine biosynthesis, and PtxR, a LysR family activator previously implicated in exotoxin A regulation.

Bacterial Proteins↗

PubMed1999

Imaging appearances of Sister Mary Joseph nodule.

Sister Mary Joseph nodules are metastatic deposits in the periumbilical area. The purpose of this review is to demonstrate umbilical anatomy, discuss modes of metastatic spread, the various imaging appearances and their relevance to the radiologist.

Adult↗

PubMed1999

Tobacco, alcohol and drug use in eight- to sixteen-year-old twins: the Virginia Twin Study of Adolescent Behavioral Development.

OBJECTIVE: This study reports prevalences of lifetime and current alcohol, tobacco and drug use in adolescents; examines associations between substance use and a number of putative risk factors; and estimates the contribution of genetic, shared and unique environmental influences on substance use. METHOD: Substance use data were collected using the Child and Adolescent Psychiatric Assessment on a population sample of 1,412 male and female monozygotic and dizygotic twin pairs, aged 8 through 16, from the Virginia Twin Study of Adolescent Behavioral Development. RESULTS: Heritabilities were estimated to be 84% and 82% for liability to lifetime and current tobacco use, respectively. For alcohol use the role of genes and environment varied according to the context of reporting. Liability to lifetime alcohol use was estimated to be under environmental control, with 71% of the variation shared by members of a twin pair and 29% unique to individual twins. Lifetime alcohol use without the permission of a parent or guardian and current use of alcohol were predominantly explained by genetic factors (h2 = 72% and 74%). The role of genetic factors increased and that of unique environmental factors decreased with increasing severity of alcohol use. Lifetime use of any drug showed a heritability of 45%, with the shared environment accounting for 47% of the variation. Shared environmental factors explained most of the variation in marijuana use. CONCLUSIONS: Genetic factors explained a significant proportion of the variation in the use of tobacco, alcohol and other drugs. Shared environmental factors contributed significantly to lifetime alcohol use and other drug use.

Adolescent↗

PubMed1999

HLA-DRB1 genotype influences risk for and severity of rheumatoid arthritis.

OBJECTIVE: To examine how HLA-DRB1 genotypes influence rheumatoid arthritis (RA) risk and clinical severity. METHODS: We performed polymerase chain reaction based DRB1 and tumor necrosis factor (TNF) genotyping of 309 Caucasian RA and 283 Caucasian control subjects. For risk analyses, we grouped the DRB1 alleles encoding each specific shared epitope: *0401 alone, *0404 with *0102, *0405 with *0408 and *0101, and *1001 alone. For estimates of RA outcome, we retrospectively obtained data regarding ARA classification criteria, age of disease onset and disease duration, number of slow acting antirheumatic drugs (SAARD) used, and rheumatoid factor (RF). RESULTS: Homozygous shared-epitope DRB1 genotypes, compound heterozygous genotypes, and simple heterozygous genotypes all conferred elevated relative risk (RR) for RA (RR 4.3, 11.7, and 3.5, respectively). However, compound heterozygous genotypes conferred more risk than either simple heterozygous genotype (RR 3.3, p = 0.004) or homozygous genotype (RR 2.8, p = 0.036). There was a trend toward more compound heterozygous genotypes in the male RA group than in the female RA group (p < 0.1), and male sex was associated with higher frequency of rheumatoid nodules (56 vs 35% for female RA). RA outcome was estimated by number of SAARD used; mean SAARD used was higher in male than in female RA (p < 0.01) and higher in genotypes containing one or 2 shared epitope DRB1 alleles than in those negative for shared epitope DRB1 alleles (p < 0.05). Analyses also suggested that shared epitope DRB1 genotype significantly influenced the occurrence of seropositive RA. Seropositive RA fraction was related to either number of shared epitope alleles (0, 1, or 2) represented in the DRB1 genotype, or, alternatively, to the combination of sex with shared epitope DRB1 genotype. The presence of one or 2 shared epitope DRB alleles influenced the occurrence of high titer seropositive RA as defined by sheep cell agglutination test (p < 0.01). TNFab microsatellite markers and TNF promoter polymorphisms did not influence SAARD number, seropositive RA, or high titer seropositive RA. CONCLUSION: Not all shared epitope DRB1 genotypes conferred the same relative risk, and the male RA group tended to have more compound heterozygous genotypes and more severe RA as indicated by rheumatoid nodules and SAARD usage. DRB1 genotypes with one or 2 shared epitope DRB1 alleles influenced the RA outcome as estimated by numbers of SAARD used and RF.

Alleles↗

PubMed1999

[Chronic sinusitis in patients infected by HIV: therapeutic strategies].

Chronic sinus pathology is a frequently encountered disease in HIV infected patients. The responsible bacterial agents and management are yet to be settled. The authors report the results of a retrospective study led in the unit of Head and Neck Surgery of the University Hospital of Nice. 25 patients where HIV holders and had a sinus pathology which had lasted more than 6 weeks, despite one or several antimicrobial drug administrations. Clinical and CT scan data are detailed as well as pathology results of the samples harvested during sinus surgery (bacteria free 32%, Pseudomonas aeruginosa 32%, Streptococcus pneumoniae 16%, Staphylococcus aureus 16%, Hemophilus influenzae 16%, anaerobic agents 16% and Toxoplasma gondii 4%). All patients underwent surgery (antral puncture with maxillary sinus drainage 17, functional endoscopic sinus surgery 8). Results where gathered at 4 months with 76% of relapse (100% in patients with less than 200/mm3 CD4 cells). In conclusion empiric antimicrobial drug therapy will be expected to be also effective on Pseudomonas aeruginosa, the surgical management being most often deceiving and leading to relapse especially when considering the frequency of bilateral morbidity and the level of CD4 cell below 200/mm3.

Adult↗

PubMed1999

Initial features of the inner dental epithelium histo-morphogenesis in the first lower molar in mouse.

First lower molar development in the mouse was investigated from the cap to early bell stage using histology, morphometry, TEM and 3D reconstructions. This period was characterized by the histogenesis of the enamel organ (EO), folding of the epithelio-mesenchymal junction and growth of the tooth. The histogenesis of the EO and appearance of the enamel knot (EK) were initiated at the early cap stage (ED14). From ED14 to ED15, the anterior and posterior extension of the EK was very prominent whilst the length of the enamel organ did not substantially change. The EK appeared as a dynamic and transitory histological structure including dying and replacement cells. At ED16, the folding of the IDE, which extended over the anterior two thirds of the molar, was the first sign of cuspidogenesis. It was accompanied by a local remodeling of the basement membrane (BM): IDE cells involved in this folding transitorily lost contact with the BM which formed a loop in the mesenchyme. During this period, the growth of the lower M1 along the antero-posterior axis was restricted to the posterior part of the molar. Histogenesis occurred in the whole EO, whilst initial cuspidogenesis was limited to the anterior part of the tooth. Distinct cell populations were thus involved in different contemporary processes leading to changes in the cell density in the mesenchyme, in the mitotic activity, in cell-shape, and cell-matrix interactions in the IDE, and remodeling of the BM where both epithelium and mesenchyme might participate.

Animals↗