Search PubMed⌕ Search

Biomedical subjects

J Marc

Publications and source records attributed to J Marc.

At least 19 recordsLinked to original sources
PubMed2005

Etidronate does not suppress periprosthetic bone loss following cemented hip arthroplasty.

Periprosthetic bone loss after arthroplasty may threaten prosthesis survival. The current study investigated the effect of etidronate therapy on periprosthetic, contralateral hip, and spine bone mineral density (BMD) in a one-year, prospective, randomized, double-blind study on 46 patients after cemented hip arthroplasty. BMD was measured with dual-energy X-ray absorptiometry (DXA). There were no significant differences between mean BMD measurements of the etidronate and placebo groups, with the exception of the mean percent change in the spine at six months and 12 months and in Gruen zone 3 at six months; in all three cases, the etidronate group had significantly greater mean values. These findings suggest that cyclic etidronate therapy has no significant effect in suppressing periprosthetic bone loss following cemented hip arthroplasty.

Absorptiometry, Photon↗
PubMed2003

Putative microtubule-associated proteins from the Arabidopsis genome.

Plant microtubule-associated proteins (MAPs) are important in modulating the function of the microtubule cytoskeleton. Various plant MAPs have already been described. However, because of the complexity of the plant microtubule cytoskeleton and its responses to developmental and environmental stimuli, there are undoubtedly many more MAPs to be discovered. We have used a literature search and the BLAST protein comparison program to identify which model MAPs from other taxa have close homologues in Arabidopsis thaliana. The search revealed Arabidopsis homologues of 14 model MAPs, with E values (numbers of proteins that will match the model protein merely by chance) of <1 x 10(-10) and homologous domains spanning 98-599 amino acid residues, representing 57.1-97.0% of the model MAP sequence, as well as 22.5-72.8% amino acid identities and 76.3-96.2% conservation of secondary structure in the homologous domain. All of the Arabidopsis homologues have either a full cDNA clone or an expressed sequence tag in the GenBank database and therefore are expressed. The proteins are likely to regulate a variety of functions, including tubulin folding, microtubule nucleation and polymerisation dynamics, microtubule-dependent cell cycle control, organisation of microtubule arrays, interaction of microtubules with plasma-membrane-associated protein complexes, and interactions with various other proteins. The exact functions of these putative MAPs in the plant cell remain to be elucidated empirically. The identification of these putative MAPs opens new avenues for the investigation of the complexities of the plant microtubule cytoskeleton.

Amino Acid Sequence↗
PubMed2002

Sequence variations in the osteoprotegerin gene promoter in patients with postmenopausal osteoporosis.

Osteoprotegerin (OPG) is a recently discovered member of the TNF receptor superfamily that acts as an important paracrine regulator of bone remodeling. OPG knockout mice develop severe osteoporosis, whereas administration of OPG can prevent ovariectomy-induced bone loss. These findings implicate a role for OPG in the development of osteoporosis. In the present study, we screened the OPG gene promoter for sequence variations and examined their association with bone mineral density (BMD) in 103 osteoporotic postmenopausal women. Single-strand conformation polymorphism analysis followed by DNA sequencing revealed a presence of four nucleotide substitutions: 209 G-->A, 245 T-->G, 889 C-->T, and 950 T-->C. The frequencies of genotypes were as follows: GG (89.3%), GA (10.7%) for 209 G-->A polymorphism; TT (89.3%), TG (10.7%) for 245 T-->G polymorphism; and TT (25.2%), TC (53.4%), CC (21.4%) for 950 T-->C polymorphism. Substitution 889 C-->T was found in only two patients. Statistically significant association of genotypes with BMD at the lumbar spine (P = 0.005) was observed for 209 G-->A and 245 T-->G polymorphisms. Haplotype GATG was associated with lower BMD as compared with GGTT haplotype. Our results suggest that 209 G-->A and 245 T-->G polymorphisms in the OPG gene promoter may contribute to the genetic regulation of BMD.

Aged↗
PubMed2001

Codon 325 sequence polymorphism of the estrogen receptor alpha gene and bone mineral density in postmenopausal women.

Estrogen receptor alpha (ER alpha) encoding gene is one of the candidate genes to be involved in the development of osteoporosis. Until now correlation between three ER gene polymorphisms (identified with PvuII, XbaI and BstUI) and bone mineral density (BMD) have been investigated. The results of these studies are contradictory. Thus the aim of our work was to search for new, yet unknown, and probably more informative polymorphism(s) of the ER alpha gene. For detection of mutations the whole coding region of the ER alpha gene was screened systematically. In a group of 85 late postmenopausal women all of the eight exons were amplified by polymerase chain reaction (PCR) and fragments were further analyzed by single-stranded conformation polymorphism (SSCP) analysis. Mutations were confirmed by direct DNA sequencing. In the whole coding region of the ER alpha gene two silent mutations in codon 87 and 325, respectively, were found. The silent mutation in codon 85 of exon 1 (GCG-->GCC; A87A) was described previously, as BstUI polymorphism. On the other side, the silent mutation in codon 325 (CCC-->CCG; P325P), located in exon 4, has not been analyzed so far in correlation with BMD. According to the distribution of genotypes CC:CG:GG=49.4:41.2:9.4, we can affirm the existence of genetic polymorphism in codon 325 in our population of late postmenopausal women. The mean femoral neck BMD, but not the lumbar spine BMD, was significantly lower (P=0.029) in the homozygous GG-women with CCG/CCG codon 325 as compared to the homozygous CC-women with the normal codon CCC/CCC. Our results suggest that codon 325 sequence polymorphism of the ER alpha gene might be one of the factors associated with low femoral neck BMD.

Aged↗
PubMed2001

A gamma-tubulin antibody against a plant peptide sequence localises to cell division-specific microtubule arrays and organelles in plants.

Gamma tubulin (gamma-tubulin) is involved in microtubule initiation in the eukaryotes. In animal cells it is localised to centrosomes and to other, non-centrosomal sites of microtubule initiation. In addition, cytoplasmic complexes containing gamma-tubulin (gamma-TuRCs; gamma-somes) have been described, which are multiprotein complexes involved in microtubule initiation. Most localisations of gamma-tubulin in plants have previously been achieved using an antibody directed towards a conserved peptide sequence found in animal cells, showing co-localisation with all microtubule arrays throughout the cell cycle. Because different antibodies may give various patterns of subcellular localisation, in the present study we raised a polyclonal antibody ('Hayley') to the plant peptide sequence EDFATQGGDRKDVFFY (bold letters indicate plant-specific amino acids) to further investigate the subcellular distribution in plants. Immunoblotting using wheat root tip protein extracts revealed a 58 kDagamma-tubulin-like peptide as has been described before. Immunofluorescence microscopy of wheat root-tip cells, however, revealed localisation of gamma-tubulin to a subset of mitotic microtubule arrays and the cytokinetic phragmoplast, but not to interphase cortical arrays or the preprophase band of microtubules. This lack of labelling may be caused by a restriction of antibody access during interphase, but more likely by a cell division-specific conformational change in the gamma-tubulin molecule. Our antibody also gave an organelle-like labelling, not described before, which may represent storage forms or precursors of gamma-tubulin, perhaps related to plastid-based microtubule initiation in hepatics and hornworts.

Amino Acid Sequence↗
PubMed2001

A 90-kD phospholipase D from tobacco binds to microtubules and the plasma membrane.

The organization of microtubule arrays in the plant cell cortex involves interactions with the plasma membrane, presumably through protein bridges. We have used immunochemistry and monoclonal antibody 6G5 against a candidate bridge protein, a 90-kD tubulin binding protein (p90) from tobacco BY-2 membranes, to characterize the protein and isolate the corresponding gene. Screening an Arabidopsis cDNA expression library with the antibody 6G5 produced a partial clone encoding phospholipase D (PLD), and a full-length gene was obtained by sequencing a corresponding expressed sequence tag clone. The predicted protein of 857 amino acids contains the active sites of a phospholipid-metabolizing enzyme and a Ca(2+)-dependent lipid binding domain and is identical to Arabidopsis PLD delta. Two amino acid sequences obtained by Edman degradation of the tobacco p90 are identical to corresponding segments of a PLD sequence from tobacco. Moreover, immunoprecipitation using the antibody 6G5 and tobacco BY-2 protein extracts gave significant PLD activity, and PLD activity of tobacco BY-2 membrane proteins was enriched 6.7-fold by tubulin-affinity chromatography. In a cosedimentation assay, p90 bound and decorated microtubules. In immunofluorescence microscopy of intact tobacco BY-2 cells or lysed protoplasts, p90 colocalized with cortical microtubules, and taxol-induced microtubule bundling was accompanied by corresponding reorganization of p90. Labeling of p90 remained along the plasma membrane when microtubules were depolymerized, although detergent extraction abolished the labeling. Therefore, p90 is a specialized PLD that associates with membranes and microtubules, possibly conveying hormonal and environmental signals to the microtubule cytoskeleton.

Amino Acid Sequence↗
PubMed2001

Optimization of single-stranded conformation polymorphism (SSCP) analysis for screening for the estrogen receptor-alpha gene polymorphism P325P.

Since there are no theoretical models for single-stranded conformation polymorphism (SSCP) analysis, conditions for detecting specific mutation must be found experimentally. Previously, a time-consuming (22 hours) SSCP method was used for the detection of polymorphism in codon 325 (CCC to CCG; P325P) in exon 4 of estrogen receptor-alpha gene. The aim of our work was to study different gel loading buffers, additives to polyacrylamide gel, voltages, running times and temperatures of electrophoresis, in order to develop a better and faster SSCP analysis for screening of P325P polymorphism. Our results show that a low ionic strength gel loading buffer and 10% addition of glycerol to the 8% polyacrylamide gel (37:1) are essential for the good separation of mutated and wild-type single stranded conformers of exon 4. The most suitable conditions for electrophoresis were 300 V, 5 h and 22 degrees C. We concluded that a much faster SSCP analysis for sreening of P325P polymorphism of estrogen receptor-alpha gene was developed. Although our final result could be applied only to the detection of the described genetic polymorphism, we hope that the results of our study will be helpful to analysts using SSCP analysis in their mutation screening programs.

Codon↗
PubMed2001

Control of brittleness in butyl-methylmethacrylate resin embedding mixtures to facilitate their use in immunofluorescence microscopy.

Butyl-methylmethacrylate resin mixtures were tested for brittleness-inducing factors in polymerised resin using a rapid quantitative scoring technique. The major source of brittleness was identified as the reducing agent dithiothreitol, which is commonly included in resin mixtures at 10 mM, to protect against tissue oxidation. Lowering the dithiothreitol content to 5 mM substantially reduced brittleness. Changing the 4:1 ratio of butyl- to methylmethacrylate to 9:1 or 3:2, and reducing the concentration of the catalyst, benzoin ethyl ether, to 0.25% also reduced dithiothreitol-induced brittleness. Polymerisation at temperatures close to 0 degrees C increased dithiothreitol-induced brittleness, but this was controlled in the 4:1 and 9:1 resin mixtures by lowering the catalyst concentration from 0.5 to 0.25%. Degassing the resin mixture with nitrogen gas prior to polymerisation did not reduce brittleness. Immunolabelled onion roots which were embedded using the 3:2 resin mixture ratio, 5 mM dithiothreitol and the 0.25% catalyst concentration, showed excellent preservation of cortical microtubule arrays.

Dithiothreitol↗
PubMed2000

Association of vitamin D receptor gene polymorphism with bone mineral density in Slovenian postmenopausal women.

Osteoporosis is a common bone disease which affects one in three women after the 60th year of life and is a major cause of morbidity in older people. To identify patients with osteoporosis, measurement of bone mineral density (BMD) is recommended. The association of BMD with vitamin D receptor (VDR) genotype in Slovenian postmenopausal women was studied. We determined VDR genotype in 102 late postmenopausal women aged 47-77 years. BMD measurements were performed at the level of the lumbar spine (L2-L4) by dual X-ray absorptiometry. Our data show significantly lower BMD in BB women compared to those with bb genotype. The relative distribution of VDR genotypes and alleles in the Slovenian population was 18.6:57.8:23.6% for BB:Bb:bb, respectively. The results are consistent with those of a previous study which found an excellent correlation between BB VDR genotype and low BMD. The data were derived from a relatively small, but ethnically homogeneous population of the same socioeconomic status, with very similar dietary and physical activity habits. Dietary habits in particular seem to be important because of the relatively low calcium intake which may enhance the phenotypic expression of VDR gene polymorphisms.

Aged↗
PubMed1999

VDR genotype and response to etidronate therapy in late postmenopausal women.

Twenty-four late postmenopausal women with osteoporosis were studied. The patients were separated in three subgroups according to the BsmI polymorphism of the vitamin D receptor (VDR) gene: BB (n = 8), Bb (n = 10) and bb (n = 6). They did not differ in age (mean ages were 66.0 years, 65.9 years and 63.9 years, respectively), years after menopause (18.7 years, 18.1 years and 18.4 years) or body weight (64.9 kg, 65.3 kg and 63.8 kg), the variables known to be associated with bone mineral density (BMD). The results show that the response to antiresorptive bisphosphonate therapy in combination with calcium supplementation is modified by VDR genotype. The lumbar spine BMD increased significantly faster in the BB and Bb groups (7.3% and 7.0%, respectively) compared with the bb group (2.5%) during 1 year of cyclic etidronate therapy (400 mg/day) and calcium supplementation (1000 mg/day). The biochemical marker of bone resorption (urinary hydroxyproline excretion) as well as the bone formation marker (serum levels of osteocalcin) decreased during the treatment. With respect to VDR genotype, a significantly higher decrease in osteocalcin level was observed in bb as compared with BB subjects. We conclude that the VDR genotype is involved in an individual's response to cyclic etidronate therapy with calcium supplementation.

Aged↗
PubMed1998

A GFP-MAP4 reporter gene for visualizing cortical microtubule rearrangements in living epidermal cells

Microtubules influence morphogenesis by forming distinct geometrical arrays in the cell cortex, which in turn affect the deposition of cellulose microfibrils. Although many chemical and physical factors affect microtubule orientation, it is unclear how cortical microtubules in elongating cells maintain their ordered transverse arrays and how they reorganize into new geometries. To visualize these reorientations in living cells, we constructed a microtubule reporter gene by fusing the microtubule binding domain of the mammalian microtubule-associated protein 4 (MAP4) gene with the green fluorescent protein (GFP) gene, and transient expression of the recombinant protein in epidermal cells of fava bean was induced. The reporter protein decorates microtubules in vivo and binds to microtubules in vitro. Confocal microscopy and time-course analysis of labeled cortical arrays along the outer epidermal wall revealed the lengthening, shortening, and movement of microtubules; localized microtubule reorientations; and global microtubule reorganizations. The global microtubule orientation in some cells fluctuates about the transverse axis and may be a result of a cyclic self-correcting mechanism to maintain a net transverse orientation during cellular elongation.

Journal Article↗
PubMed1995

A gamma-tubulin that associates specifically with centrioles in HeLa cells and the basal body complex in Chlamydomonas.

gamma-Tubulin is a putative component of microtubule initiating material. To further explore its subcellular distribution in plant and animal cells, we have raised a polyclonal antibody, Rb27, directed towards a conserved region (EEFATEGTDRKDVFFY) of the gamma-tubulin molecule. Immunoblotting of cell protein extracts with Rb27 reveals a polypeptide band of M(r) 49 kD in HeLa and a 58 kD band in Chlamydomonas. Although these polypeptides are comparable in size to forms of gamma-tubulin detected previously in mammalian and plant protein extracts by other antibodies to gamma-tubulin, by immunofluorescence microscopy Rb27 gives localization patterns not previously seen. It localizes specifically with the centrioles in HeLa cells and with the basal body complex in Chlamydomonas. Other gamma-tubulin antibodies label pericentriolar material. Because of the similarities in the size of the polypeptides recognized by our and other gamma-tubulin antibodies, and a restricted co-localization with known microtubule-organizing centres in evolutionarily distant organisms, we propose that Rb27 recognizes a novel conserved gamma-tubulin isotype.

Amino Acid Sequence↗
PubMed1995

[A case of a dizygotic twin pregnancy where superfetation seems indisputable].

A case of superfoetation is presented. Difference of age (3 weeks) between twins was established by ultrasound at 10 weeks, and persisted through subsequent echographic surveillance up to delivery at 39 of amenorrhea with twin 39 and 36 weeks old. Only three publications in recent international literature are related to superfoetation. An attempt is made to try to understand superfoetation and to clearly differentiate it from superovulation.

Adult↗
PubMed1994

Neurovascular complications of cocaine.

Use of cocaine in the USA, has reached epidemic proportions since 1983, when "crack" was introduced, its higher potency compared with cocaine HCl has been associated with a tremendous increase in the incidence of strokes. This study reports our experience with 55 cases of neurovascular events (25 ischemic and 30 hemorrhagic) related to cocaine use in 54 patients. Only 15 patients had other risk factors for stroke. Twenty six patients smoked "crack", 10 snorted cocaine and 12 injected it intravenously. Strokes occurred within 3 h of cocaine use in 15 patients with infarcts and 17 with hemorrhages. Ten infarcts occurred after an overnight binge. Of the hemorrhage group 9 were subarachnoid, 16 intracerebral (8 basal ganglia, 7 hemispheric and one brain stem) and 5 intraventricular. Computerized tomography (CT) showed an aneurysm of the anterior communicating artery, as well as one of the vein of Galen. Four aneurysms and 3 AVMs were identified on angiography. CT revealed 15 infarcts; it was normal in 7 patients with pure motor hemiparesis and in 3 with findings consistent with anterior spinal artery infarction. Several mechanisms may be responsible for the cerebrovascular complications. A sudden rise in systemic arterial pressure may cause hemorrhages, frequently in association with an underlying aneurysm or AVM. Vasospasm, arteritis, myocardial infarction with cardiac arrhythmias and increased platelet aggregation may provoke infarcts.

Adult↗
PubMed1994

Brainstem toxoplasmosis in patients with acquired immunodeficiency syndrome.

Brainstem involvement by Toxoplasma gondii is probably more common than other opportunistic infections, although it has not received adequate attention. Identification of toxoplasmosis is essential, as this condition responds to treatment with a significant increase in life expectancy. During the past 4 years, 366 AIDS patients with central nervous system toxoplasmosis diagnosed by biopsy or improvement following empirical treatment were evaluated. Among them, 8 (7 men, 1 woman; aged 25-55 yr) presented with signs of brainstem dysfunction. Six patients presented with an oculomotor nerve palsy and contralateral hemiplegia; 1 had an additional ipsilateral rubral tremor. The seventh patient had complete external ophthalmoplegia and the eighth had Parinaud's syndrome. Computed tomography revealed enhancing lesions in the brainstem of all patients. Seven responded to treatment with pyrimethamine and sulfadiazine.

AIDS-Related Opportunistic Infections↗
PubMed1993

A gamma-tubulin-related protein associated with the microtubule arrays of higher plants in a cell cycle-dependent manner.

An antibody specific for a conserved gamma-tubulin peptide identifies a plant polypeptide of 58 kDa. gamma-Tubulin antibody affinity purified from this polypeptide recognizes the centrosome in mammalian cells. Using immunofluorescence microscopy, we determined the distribution of this gamma-tubulin-related polypeptide during the complex changes in microtubule arrays that occur throughout the plant cell cycle. We report a punctate association of gamma-tubulin-related polypeptide with the cortical microtubule array and the preprophase band. As cells enter prophase, gamma-tubulin-related polypeptide accumulates around the nucleus and forms a polar cap from which early spindle microtubules radiate. During metaphase and anaphase, gamma-tubulin-related polypeptide preferentially associates with kinetochore fibers and eventually accumulates at the poles. In telophase, localization occurs over the phragmoplast. gamma-Tubulin-related polypeptide appears to be excluded from the plus ends of microtubules at the metaphase plate and cell plate. Its distribution during the cell cycle may be significant in light of differences in the behavior and organization of plant microtubules. The identification of gamma-tubulin-related polypeptide could help characterize microtubule organizing centers in these organisms.

Amino Acid Sequence↗
PubMed1983

Chondroid chordoma. Electron-microscopic study of two cases.

Chondroid chordoma is an unusual tumor composed of an admixture of chondromatous and chordomatous tissue usually located in the spheno-occipital region. This tumor shares many of the clinical and histologic features of classic chordoma and chondrosarcoma and has been shown to have a better prognosis than either of these lesions. To the best of our knowledge, no ultrastructural studies have been performed in the 26 cases of chondroid chordoma published previously. We document the ultrastructural features of two examples of chondroid chordoma. Certain features such as prominent and dilated rough endoplasmic reticulum, intracytoplasmic glycogen aggregates, and abundant fibrillogranular matrix are common to chordoma, chondrosarcoma, and chondroid chordoma. The presence of well-formed tonofilament desmosome complexes as well as complexes composed of alternating profiles of rough endoplasmic reticulum and mitochondria were seen only in chordoma and chondroid chordoma, but not in cartilaginous tumors. Of particular interest was the finding of crystalline, tubular structures within the rough endoplasmic reticulum of both cases of chondroid chordoma, a finding not described previously. The distinction of chondroid chordoma from classical chordoma is said to be a difficult one at the light-microscopic level, and we suggest that these intraergastoplasmic tubular structures might constitute an extremely helpful differential marker.

Adult↗