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Biomedical subjects

J Pelletier

Publications and source records attributed to J Pelletier.

At least 91 records · Page 5Linked to original sources
PubMed1997

Regulation of renal EGF receptor expression is normal in Denys-Drash syndrome.

In patients with Denys-Drash syndrome, mutations of the Wilms' tumor suppressor gene are associated with nephroblastomas and developmental abnormalities of the genital tract and renal glomerulus. Normally, the Wilms' tumor gene product (WT1) is expressed at high levels in visceral glomerular epithelial cells (VGEC) of the emerging fetal glomerulus. We demonstrate that WT1 could normally serve to suppress EGF receptor expression in VGEC, since immunoreactive EGF receptor is strikingly absent compared to epithelial cells of the emerging proximal and distal tubule, which lack WT1. When HEK293 cells were co-transfected with plasmids containing EGFR enhancer/promoter elements linked to a CAT reporter and plasmids containing WT1 cDNA, EGFR enhancer/promoter activity was suppressed by all wild-type WT1 isoforms, but not by deletion mutants of WT1 lacking normal zinc-finger or N-terminal domains. Surprisingly, plasmids expressing a Denys-Drash WT1 mutant (R394W) retained the ability to suppress EGFR promoter activity in this system. Furthermore, we found that immunoreactive EGFR was appropriately undetectable in glomeruli from a three-year-old girl with Denys-Drash syndrome and in sections of her Wilm's tumor. These data suggest that faulty suppression of EGFR cannot account for the abnormalities of glomerulogenesis seen in Denys-Drash patients.

Cell Line↗
PubMed1997

Gordona terrae central nervous system infection in an immunocompetent patient.

The bacterial genus Gordona includes seven species of mycolic acid-containing actinomycetes which are cultured from environmental sources and rarely from clinical samples. They have been implicated in primary pulmonary diseases, nosocomial wound infections, and central nervous system infections in two immunocompromised patients. We isolated Gordona terrae from the cerebrospinal fluid sample of an immunocompetent patient with meningitis and multiple brain abscesses and detected Gordona terrae DNA in the abscesses. The outcome was good at the 4-year follow-up, after prolonged treatment with trimethoprim-sulfamethoxazole. Phenotypic identification of this isolate was confirmed by analysis of the 16S rRNA gene sequence, which shared 100% homology with that of G. terrae reference strains. Physicians and clinical microbiologists must be aware of the occurrence of Gordona species infection not only among immunocompromised patients but among all patients. Accurate identification of Gordona species may be accomplished by molecular techniques.

Actinomycetales↗
PubMed1997

The murine Sim-2 gene product inhibits transcription by active repression and functional interference.

The Drosophila single-minded (Dsim) gene encodes a master regulatory protein involved in cell fate determination during midline development. This protein is a member of a rapidly expanding family of gene products possessing basic helix-loop-helix (bHLH) and hydrophobic PAS (designated a conserved region among PER, ARNT [aryl hydrocarbon receptor nuclear translocator] and SIM) protein association domains. Members of this family function as central transcriptional regulators in cellular differentiation and in the response to environmental stimuli such as xenobiotics and hypoxia. We have previously identified a murine member of this family, called mSim-2, showing sequence homology to the bHLH and PAS domains of Dsim. Immunoprecipitation experiments with recombinant proteins indicate that mSIM-2 associates with the arnt gene product. In the present work, by using fine-structure mapping we found that the HLH and PAS motifs of both proteins are required for optimal association. Forced expression of GAL4/mSIM-2 fusion constructs in mammalian cells demonstrated the presence of two separable repression domains within the carboxy terminus of mSIM-2. We found that mSIM-2 is capable of repressing ARNT-mediated transcriptional activation in a mammalian two-hybrid system. This effect (i) is dependent on the ability of mSIM-2 and ARNT to heterodimerize, (ii) is dependent on the presence of the mSIM-2 carboxy-terminal repression domain, and (iii) is not specific to the ARNT activation domain. These results suggest that mSIM-2 repression activity can dominantly override the activation potential of adjacent transcription factors. We also demonstrated that mSIM-2 can functionally interfere with hypoxia-inducible factor 1alpha (HIF-1alpha)/ARNT transcription complexes, providing a second mechanism by which mSIM-2 may inhibit transcription.

Animals↗
PubMed1997

The use of oral terbinafine (Lamisil) in children.

In an ongoing study of Lamisil in children, 21 patients have so far been enrolled and preliminary data are reported in this paper. Eighteen have tinea capitis and 1 has tinea corporis. So far, Trichophyton tonsurans has been identified in 17 and Trichophyton violaceum in 2. Lamisil has so far proved to be well tolerated, efficacious and cost-effective in a 2-week course in those children with a Trichophyton species. If Microsporum canis is isolated, a longer course is probably indicated. Lamisil has the distinct advantage of producing good results in a short time period, making patient compliance less of a problem.

Administration, Oral↗
PubMed1997

Achromatic visual backward masking of colored stimuli in type I diabetes.

On a visual backward masking task using color stimuli with an achromatic patterned mask, we compared the masking performances of 3 Type I diabetics with those of 9 participants in a control group. Analysis indicated that the diabetics show a marked decrement in performance with blue stimuli and a lesser decrement with red stimuli. Suggestions for further theoretical and parametric studies are discussed.

Adult↗
PubMed1997

A cytotoxic factor for glial cells: a new avenue of research for multiple sclerosis?

A novel retrovirus, provisionally called Multiple Sclerosis RetroVirus (MSRV), was recently described in multiple sclerosis (MS). We report here that monocyte/macrophage culture supernatants from MS patients containing reverse transcriptase activity secrete a cytotoxin which induces death of primary mouse cortical glial cells. This cytotoxin, which was also found in MS cerebrospinal fluid, specifically causes death of mouse immortalized astrocytes and oligodendrocytes in vitro and seems to be associated to MSRV-specific RNA. This toxic factor, called gliotoxin, is present only in active cases of MS and is a stable glycosylated protein of 17 kDa, in CSF as well as in monocyte/macrophage culture supernatants. Since this gliotoxin is highly toxic for glial cells, it may represent an initial pathogenic factor, leading to the neuropathological features of MS, like blood brain barrier disruption and demyelination.

Animals↗
PubMed1997

[Angiodysplasia of moya-moya type disclosed by choreic unvoluntary abnormal movements during oral contraception. Apropos of 2 cases].

Two seventeen year-old women, developed acute onset left choreic movements following two months and two weeks use of oral contraceptives. Left hemiparesia appeared a few days later, while involuntary movements discontinued. Cranial CT scan and MRI showed bilateral ischemic lesion in the frontal region for the first case and isolated lesion in the right centrum ovale for the second. Angiography showed nearly complete obstruction of the terminal portion of the internal carotid artery with an outline Moya-Moya network. After discontinuing oral contraceptives, there has been no relapse of neurologic dysfunction for more than three years for the first case and twelve months for the second one. The role of perfusion insufficiency in limb-shaking carotid transient ischemic attack is discussed and the possible relations between oral contraceptives, chorea and angiographic features resembling Moya-Moya disease are evaluated.

Adolescent↗
PubMed1997

[Acute myelopathies in young patients and multiple sclerosis. prospective study of 20 cases].

The risk of progression to multiple sclerosis (MS) after an episode of acute non compressive episode involving the spinal cord remains uncertain. A follow-up study was performed to determine the risk of early progression to MS in 20 patients presenting with clinically isolated lesions of the spinal cord, combined clinical evaluation, spinal and brain magnetic resonance imaging (MRI), visual, brainstem auditory and somatosensory evoked potentials (VEPs, BAEPs, SEPs), and cerebrospinal fluid (CSF) electrophoresis analysis. Spinal cord MRI demonstrated more lesions in cervical region (74 p. 100) than thoracic or lumbar regions (26 p. 100). Six patients (30 p. 100) had an initial brain MRI that was strongly suggestive of MS and 5 patients (25 p. 100) had only one MS-like abnormality. Eight patients (40 p. 100) had abnormal VEPs, 3 (15 p. 100) abnormal BAEPSs and only 44 p. 100 (8/18) abnormal SEPs. In contrast, CSF analysis showed oligoclonal bands (CSFOB) in 15/19 patients (79 p. 100). The diagnosis of MS was performed initially in 13 cases (65 p. 100) (clinically definite MS (CDMS) in 30 p. 100, laboratory-supported definite MS (LSDMS) in 61 p. 100 and clinically probable (CPMS) in one case). During the follow-up period (18 +/- 7 months), 8 patients (40 p. 100) presented one or more exacerbations and time to the first recurrence was 8 +/- 5 months. Seven of these 8 patients were initially treated by infusion of methylprednisolone. Among these patients, all of them had CSF OB and initial brain MRI was strongly suggestive of MS in 3 of them. During this follow-up period, brain MRI showed emergence of lesions in 4 cases with normal initial examination and 3 of them presented exacerbations. At the follow-up term, the diagnosis of MS was performed in 15 cases (75 p. 100) CDMs in 66 p. 100, LSDMS in 26 p. 100 and CPMS in one case). This confirms the predictive value of brain MRI and CSF OB for the diagnosis of MS in patients who present with clinically isolated acute syndrome of the spinal cord.

Acute Disease↗
PubMed1996

Identification of nuclear localization signals within the zinc fingers of the WT1 tumor suppressor gene product.

WT1 encodes a zinc finger protein with a key role in urogenital development that is inactivated in a subset of Wilms' tumors. This tumor suppressor gene product contains an amino-terminal dimerization domain required for trans-inhibition of wild-type WT1 activity by mutants defective for DNA binding. In the course of characterizing truncation mutants of WT1, we noted that the WT1 zinc fingers contain two functionally independent targeting signals required for nuclear localization of the protein. These novel signals lie within zinc fingers I and within zinc fingers II and III. We demonstrate that nuclear targeting of the WT1 homodimerization domain functionally antagonizes activity of the wild-type protein activity.

3T3 Cells↗
PubMed1996

PAX8-mediated activation of the wt1 tumor suppressor gene.

The developing renal system has long been exploited to study the regulation of gene expression during mesenchymal-epithelial transitions. Several transcription factors, including WT1 and PAX8, are expressed early in nephrogenesis and play a key role in this process. The expression of PAX8 occurs in the induced mesenchyme of the developing kidney prior to the upregulation of WT1 levels in the same cells. In this report, we assessed whether the Pax-8 gene product resides upstream of wt1 in a common regulatory pathway. Transfection studies, as well as gel-shift assays, indicate that PAX8 transactivates wt1 through elements within a 38 bp conserved motif, present in human and murine promoters. Two PAX8 isoforms, generated by alternative splicing at the C-terminus and previously thought to lack transactivation potential, were found to be capable of activating wt1 expression. We also demonstrate that the endogenous wt1 promoter can be upregulated by exogenously supplied PAX8, suggesting that a function of PAX8 during mesenchymal--epithelial cell transition in renal development is to induce wt1 gene expression.

3T3 Cells↗
PubMed1996

The sheep estrogen receptor: cloning and regulation of expression in the hypothalamo-pituitary axis.

We have prepared an ovine pituitary cDNA library, isolated a clone containing the full-coding sequence of estrogen receptor (ER) cDNA, and determined its primary structure. This cDNA encodes a protein of 596 amino acids which shows great homology to other mammalian ER sequences, the highest degree being 95% with the porcine receptor. Northern blot analysis of ovine pituitary RNA revealed a 6.3 kb transcript. This receptor was showed to bind a consensus ERE and to be transcriptionally activated by E2. Studies investigating the pattern of expression of the ovine ER mRNA were also carried out, using the reverse transcription/PCR technique. Expression of ER mRNA was analyzed in ram pituitary and hypothalamus after contrasted light regimen and castration. Results showed that the light regimen had no effect on ER mRNA expression whereas castration induced a slight (approximately 20%) but significant increase of ER mRNA expression at both the hypothalamic (P < 0.05) and pituitary (P < 0.01) levels, indicating a negative regulation of ER gene expression by testicular steroids. Since we have previously shown no variations in ER protein levels after castration, data suggest the activation of a complex pattern including both transcriptional and post-transcriptional regulatory mechanisms in the ram hypothalamo-pituitary axis.

Amino Acid Sequence↗
PubMed1996

The paired-box transcription factor, PAX2, positively modulates expression of the Wilms' tumor suppressor gene (WT1).

The Wilms' tumor suppressor gene, wt1, encodes a zinc finger protein which functions as a transcriptional regulator. Expression of the wt1 gene is developmentally regulated and restricted to a small set of tissues which include the fetal urogenital system, mesothelium, and spleen. In the developing kidney, induction of neprohogenesis by the ureter is accompanied by an increase in expression levels of the Pax-2 gene, a developmentally and spatially regulated paired-box member. This is followed by an increase in wt1 expression as mesenchymal cells condense and differentiate. In this report, we demonstrate that PAX2 isoforms are capable of transactivating the wt1 promoter. Deletion mutagenesis of the wt1 promoter identified an element responsible for mediating PAX2 responsiveness, located between nucleotides -33 and -71 relative to the first wt1 transcription start site. Consistent with its identity as a PAX responsive element, multimerization of this mofit upstream of a heterologous minimal promoter enhanced reporter activity when co-transfected with a Pax-2 expression vector. Finally, we demonstrate that PAX2 can stimulate expression of the endogenous wt1 gene. These results suggest that a role for PAX2 during mesenchyme-to-epithelium transition in renal development is to induce wt1 expression.

3T3 Cells↗
PubMed1996

Characterization of msim, a murine homologue of the Drosophila sim transcription factor.

Mutations in the Drosophila single-minded (sim) gene result in loss of precursor cells that give rise to midline cells of the embryonic central nervous system. During the course of an exon-trapping strategy aimed at identifying transcripts that contribute to the etiology and pathophysiology of Down syndrome, we identified a human exon from the Down syndrome critical region showing significant homology to the Drosophila sim gene. Using a cross-hybridization approach, we have isolated a murine homolog of the Drosophila sim gene, which we designated msim. Nucleotide and predicted amino acid sequence analyses of msim cDNA clones indicate that this gene encodes a member of the basic-helix-loop-helix class of transcription factors. The murine and Drosophila proteins share 88% residues within the basic-helix-loop-helix domain, with an overall homology of 92%. In addition, the N-terminal domain of MSIM contains two PAS dimerization motifs also featured in the Drosophila sim gene product, as well as a small number of other transcription factors. Northern blot analysis of adult murine tissues revealed that the msim gene produces a single mRNA species of approximately 4 kb expressed in a small number of tissues, with the highest levels in the kidneys and lower levels present in skeletal muscle, lung, testis, brain, and heart. In situ hybridization experiments demonstrate that msim is also expressed in early fetal development in the central nervous system and in cartilage primordia. The characteristics of the msim gene are consistent with its putative function as a transcriptional regulator.

Amino Acid Sequence↗
PubMed1996

Associations between subclinical paratuberculosis and milk production, milk components, and somatic cell counts in dairy herds.

OBJECTIVE: To determine associations between subclinical Mycobacterium paratuberculosis infection and milk production, milk components, and somatic cell counts of dairy cattle. DESIGN: Cross-sectional epidemiologic survey. ANIMALS: 23 dairy herds in Wisconsin containing 1,653 adult cows were studied. The herds had above average milk production and a history of bovine paratuberculosis in the herd within the previous 12 months. PROCEDURE: All adult cows in the herds were tested for paratuberculosis by use of an absorbed ELISA. Milk yield, fat, protein, and somatic cell count data were retrieved electronically from Dairy Herd Improvement Association records. RESULTS: 147 ELISA-positive and 1,506 ELISA-negative cows were identified. ELISA-positive cows had a mature-equivalent milk production of 376 kg (829 lb)/lactation less than that for ELISA-negative herdmates. Significant difference was not found in lactation average percent-ages of fat and protein, or somatic cell count linear score. When comparing ELISA-positive and -negative cow's current mature equivalent milk with all previous lactations, significant difference was found only from the immediate-preceding lactation. When this difference was examined by parity group, significant difference was confined to cows in the second lactation. CLINICAL IMPLICATIONS: Subclinical paratuberculosis infections, as determined by ELISA, are associated with a 4% reduction in milk yield and add to the already substantial costs of clinical M paratuberculosis infection in the dairy industry.

Analysis of Variance↗
PubMed1996

Epidemiologic study of on-farm management practices associated with prevalence of Mycobacterium paratuberculosis infections in dairy cattle.

OBJECTIVE: To use an on-farm recording form to quantity the effect of specific management practices on apparent prevalence of Mycobacterium paratuberculosis in dairy cattle herds. DESIGN: Epidemiologic survey. ANIMALS: 26 commercial Wisconsin dairy farms. PROCEDURES: An instrument was developed on the basis of literature review and expert interviews to quantify on-farm management practices associated with increased apparent prevalence of M paratuberculosis. On-farm visits were conducted to assess how specific management practices were conducted. Apparent prevalence of M paratuberculosis infection was measured for all animals > 20 months old on all farms, using a commercial ELISA. Regression analysis was used to identify management variables that were significantly associated with apparent prevalence of M paratuberculosis. RESULTS: Regression analysis (R2 = 0.90) identified that high scores for environmental conditions, newborn calf care, grower calf care, bred heifer care, and manure handling were significantly associated with M paratuberculosis apparent prevalence in Wisconsin dairy herds. CLINICAL IMPLICATIONS: Environmental conditions, newborn calf care, grower calf management, bred heifer management, and manure handling factors may serve as a prioritized checklist for instructing owners and managers where to place emphasis in changing management practices to limit M paratuberculosis prevalence. Likewise, the factors identified as having low association with apparent prevalence may be de-emphasized in control programs, allowing dairy managers to focus time and finances on more effective components of an M paratuberculosis control program.

Animal Husbandry↗
PubMed1996

A non-AUG translational initiation event generates novel WT1 isoforms.

The Wilms' tumor (WT) suppressor gene, WT1, is mutated in a small set of WTs and is essential for proper development of the urogenital system. The gene has three sites of transcriptional initiation and produces mRNA transcripts containing 5'-untranslated regions of more than 350 nucleotides. The mRNA, through two alternative splicing events, is predicted to direct the synthesis of four protein isoforms with molecular masses of 47-49 kDa. In this report, we identify and characterize novel WT1 protein isoforms having predicted molecular masses of 54-56 kDa. Mutational analysis of the murine wt1 mRNA demonstrates that the novel isoforms are the result of translation initiation at a CUG codon 204 bases upstream of and in frame with the initiator AUG. We show that these isoforms are present in both normal murine tissue and in WTs. Like WT1, the larger isoforms localize to the cell nucleus and are capable of mediating transcriptional repression. Our results indicate that regulation of WT1 gene expression is more complex than previously suspected and have important implications for normal and abnormal urogenital system development.

Amino Acid Sequence↗
PubMed1996

Age-related changes in carboxyl methylation of proteins in the kidney.

Age-related changes in the carboxyl methylation activities of L-isoaspartyl/D-aspartyl methyltransferase (PIMT) and C-terminal isoprenylcysteine methyltransferase (PPMT), as well as in the methylation levels of their major substrates, were studied in the soluble and brush border membrane (BBM) fractions of kidney cortex isolated from rats aged 3 weeks, and 2, 7 and 12 months. PIMT activity measured with ovalbumin, an exogenous substrate, decreased by 30% in the soluble fraction, while it increased by 37% in BBM of rats older than 2 months. In the soluble fraction, the affinity of PIMT for the universal methyl donor, S-adenosyl-L-methionine, was unaffected, while the apparent maximal velocity measured with ovalbumin was 30% lower in 7-month-old rats than in 3-week-old rats. However, the amount of PIMT measured by Western blotting with anti-PIMT antibodies in the soluble fraction was not affected by age. These results suggest that a reduction in the specific activity of PIMT in the soluble fraction occurs as a function of age. Stimulation of the methylation of total proteins by guanosine 5'-3-O-(thio) triphosphate (GTP gamma S) increased in the soluble fraction of rats older than 2 months, (30%) and decreased in BBM of rats older than 7 months (25%). The PIMT methylation of endogenous substrates of 48 and 61 kDa in the soluble fraction decreased by 40% in rats older than 2 months, but no significant difference was found for substrates in the BBM fraction as a function of age. On the other hand, the PPMT activity was stable from 3 weeks postnatal to adulthood. The C-terminal carboxyl methylation of the major PPMT substrates in BBM (22, 26, and 44 kDa) remained stable throughout development and in adults. The levels of carboxyl methylation of the 22 and 26 kDa substrates in BBM were GTP gamma S-dependent, but only the effect on the 22 kDa substrate was regulated by age. These data suggest that the activities of PIMT and PPMT are regulated differently during development and aging in the rat kidney cortex.

Aging↗