Biomedical subjects

A George

Publications and source records attributed to A George.

At least 37 records · Page 2Linked to original sources

PubMed2001

Efficient presentation of both cytosolic and endogenous transmembrane protein antigens on MHC class II is dependent on cytoplasmic proteolysis.

Peptides from extracellular proteins presented on MHC class II are mostly generated and loaded in endolysosomal compartments, but the major pathways responsible for loading peptides from APC-endogenous sources on MHC class II are as yet unclear. In this study, we show that MHC class II molecules present peptides from proteins such as OVA or conalbumin introduced into the cytoplasm by hyperosmotic pinosome lysis, with efficiencies comparable to their presentation via extracellular fluid-phase endocytosis. This cytosolic presentation pathway is sensitive to proteasomal inhibitors, whereas the presentation of exogenous Ags taken up by endocytosis is not. Inhibitors of nonproteasomal cytosolic proteases can also inhibit MHC class II-restricted presentation of cytosolically delivered protein, without inhibiting MHC class I-restricted presentation from the same protein. Cytosolic processing of a soluble fusion protein containing the peptide epitope I-Ealpha(52-68) yields an epitope that is similar to the one generated during constitutive presentation of I-Ealpha as an endogenous transmembrane protein, but is subtly different from the one generated in the exogenous pathway. Constitutive MHC class II-mediated presentation of the endogenous transmembrane protein I-Ealpha is also specifically inhibited over time by inhibitors of cytosolic proteolysis. Thus, Ag processing in the cytoplasm appears to be essential for the efficient presentation of endogenous proteins, even transmembrane ones, on MHC class II, and the proteolytic pathways involved may differ from those used for MHC class I-mediated presentation.

Acetylcysteine↗

PubMed2001

Differentiation of embryonic mesenchymal cells to odontoblast-like cells by overexpression of dentin matrix protein 1.

Cells of the craniofacial skeleton are derived from a common mesenchymal progenitor. The regulatory factors that control their differentiation into various cell lineages are unknown. To investigate the biological function of dentin matrix protein 1 (DMP1), an extracellular matrix gene involved in calcified tissue formation, stable transgenic cell lines and adenovirally infected cells overexpressing DMP1 were generated. The findings in this paper demonstrate that overexpression of DMP1 in pluripotent and mesenchyme-derived cells such as C3H10T1/2, MC3T3-E1, and RPC-C2A can induce these cells to differentiate and form functional odontoblast-like cells. Functional differentiation of odontoblasts requires unique sets of genes being turned on and off in a growth- and differentiation-specific manner. The genes studied include transcription factors like core binding factor 1 (Cbfa1), bone morphogenetic protein 2 (BMP2), and BMP4; early markers for extracellular matrix deposition like alkaline phosphatase (ALP), osteopontin, osteonectin, and osteocalcin; and late markers like DMP2 and dentin sialoprotein (DSP) that are expressed by terminally differentiated odontoblasts and are responsible for the formation of tissue-specific dentin matrix. However, this differentiation pathway was limited to mesenchyme-derived cells only. Other cell lines tested by the adenoviral expression system failed to express odontoblast-phenotypic specific genes. An in vitro mineralized nodule formation assay demonstrated that overexpressed cells could differentiate and form a mineralized matrix. Furthermore, we also demonstrate that phosphorylation of Cbfa1 (osteoblast-specific transcription factor) was not required for the expression of odontoblast-specific genes, indicating the involvement of other unidentified odontoblast-specific transcription factors or coactivators. Cell lines that differentiate into odontoblast-like cells are useful tools for studying the mechanism involved in the terminal differentiation process of these postmitotic cells.

3T3 Cells↗

PubMed2001

Effect of aerobic exercise on behavioral and neuroendocrine responses to meta-chlorophenylpiperazine and to ipsapirone in untrained healthy subjects.

RATIONALE: Several clinical studies suggest antidepressive and anxiolytic effects of regular aerobic exercise. OBJECTIVES: The present study examines the effects of a 10-week protocol of moderate aerobic exercise (3-4 miles jogging 3 times per week) on central serotonergic receptor sensitivity. METHODS: Neuroendocrine challenges using oral doses of meta-chlorophenylpiperazine (m-CPP; 0.4 mg/kg), ipsapirone (0.3 mg/kg), and placebo were performed in 12 untrained healthy volunteers before and after 10 weeks of moderate aerobic exercise. RESULTS: Before training, administration of the non-selective serotonergic agonist m-CPP, which exerts a number of well-reproducible effects mainly via its action on 5-HT2C receptors, was associated with a significant increase of cortisol and prolactin (but not adrenaline or noradrenaline) in comparison with the placebo condition. After the 10-week training period, administration of m-CPP was followed by a blunted cortisol response which was not significantly increased in comparison to the placebo challenge. In contrast, the increases of cortisol observed after administration of the 5-HT1A agonist ipsapirone were of the same magnitude during the pre- and post-training challenge sessions. The behavioral response to ipsapirone and the mean maximal increases of plasma adrenaline and noradrenaline did not change during the training period. CONCLUSIONS: Regular aerobic exercise is associated with a blunted cortisol response to m-CPP, which might reflect a downregulation of central 5-HT2C receptors.

Adult↗

PubMed2001

Acute thrombocytopenic crisis following burns complicated by staphylococcal septicaemia.

The pathophysiological changes in a burn patient can at times manifest as severe complications, the management of which can be extremely challenging to the burn surgeon. A case report of an adult male with burns (18% total body surface area) who developed an acute unexpected thrombocytopenia crisis (2x10(9) l(-1)) on day 3 followed by disseminated intravascular coagulation is presented. The various etiological factors and possible mechanisms leading to thrombocytopenia in burns are discussed. Minor burns may present acute major complications in the presence of other thrombocytopenic factors like trauma and sepsis and thrombocytopenia by it self can be a good indicator of sub-clinical infection.

Adult↗

PubMed2001

Minor [correction of Mi1nor] burns and pneumatocoeles: a case report.

Minor burns in children need to be cautiously managed as they may manifest with life threatening complications especially in the presence of staphylococcal infection. A one and a half year old child with minor burns (12% TBSA), who developed large pneumatocoeles and peumomediastinum following Staphylococcus aureus pneumonia causing severe respiratory distress and needing ventilatory support is presented. Most of the pneumatocoeles were spontaneously absorbed over a period of 10 days while surgical interference was being contemplated. A conservative approach to pneumatocoeles as in non-burn patients may help prevent unnecessary surgery. An extensive English literature search (since 1966) did not reveal any report of pneumatocoeles in association with burns and therefore we believe this to be the first report of its kind.

Burns↗

PubMed2001

A comparative study of sialic acid-rich proteins in rat bone and dentin.

Four sialic acid-rich (SA-rich) proteins found in bone and dentin, osteopontin (OPN), bone sialoprotein (BSP), bone acidic glycoprotein-75 (BAG-75), and dentin matrix protein 1 (DMP1), share some common features. We used SDS-PAGE and Western immunoblots to analyze and compare SA-rich proteins in bone and dentin extracts from rats with a single chromatographic procedure. OPN was detected in dentin extracts, with a relative level less than one-seventieth of that in bone. Both bone and dentin BSP demonstrated an extremely broad distribution pattern, probably due to a high degree of heterogeneity in post-translational modifications. BAG-75 in both bone and dentin was detected as an 83 kDa band, dramatically distinct from that of DMPI. Using a polyclonal antibody raised against a purified bone 57 kDa protein (a portion of DMPI), we detected 150 kDa protein bands in bone fraction; the same bands were recognized by antirecombinant rat DMPI antibody. Bands from dentin migrating at about 150 kDa in earlier fractions and progressing to 200 kDa in later fractions showed a clear immunoreactivity to the anti-57 kDa antibody. We conclude that the majority of DMPI in rat bone is processed into fragments, whereas that in dentin remains intact.

Animals↗

PubMed2001

Inositol hexasulphate, a casein kinase inhibitor, alters the distribution of dentin matrix protein 1 in cultured embryonic mouse tooth germs.

Immunohistochemical studies using a polyclonal antibody, raised against the recombinant form of dentin matrix protein 1 (DMP1), show that DMP1 was detected mainly in odontoblasts in cultured mouse embryonic tooth germs. However, in restricted areas, DMP1 staining was also observed in secretory ameloblasts, in the stratum intermedium and stellate reticulum, but only when the odontoblasts located in front of them were unstained. When the embryonic tooth germs were cultured in the presence of inositol hexasulfate, a casein kinase I and II inhibitor, staining of odontoblasts was weak or nil, whereas, in contrast, ameloblasts and enamel organ were strongly immunolabelled, suggesting an enhanced translocation of DMP1 after secretion to the secretory ameloblasts and/or stratum intermedium and stellate reticulum. Moreover, DMP1--was shown to be a good substrate for gelatinase A (MMP-2), but not to gelatinase B (MMP- 9). We hypothesized that DMP1--or the sub-fractions cleaved by the MMP--could behave as diffusible signaling molecule (s) rather than as a true dentin extracellular matrix component.

Ameloblasts↗

PubMed2001

T cells in mice expressing a transgenic human TCR beta chain get positively selected but cannot be activated in the periphery by signaling through TCR.

TCR-CD3 complex-mediated signaling is crucial for both developmental selection and antigenic activation of T cells. We report that mice expressing a recombined human TCRbeta chain (Tg), which have normal development of T cells, mounted very weak responses to immunization with protein antigens as well as the HA307-319 peptide recognized by the human T cell clone HA1.7 from which the transgene is derived. An anti-CD3epsilon mAb triggered equivalent proliferation from Tg and non-Tg T cells, but an anti-human TCRbeta mAb induced proliferation poorly in Tg T cells in contrast to human T cells or HA1.7. In Tg mice, T cells expressing endogenous TCR were CD44(high), whereas most transgene-expressing T cells remained CD44(low), suggesting that transgene-expressing cells are not activated in the periphery to participate in immune responses. However, anti-human TCRbeta could induce some activation markers on T cells and cross-linking of the Tg TCR by plate-coated anti-human TCRbeta efficiently induced T cell proliferation. Human TCRbeta-mediated Tg T cell activation could be rescued by exogenous IL-2, as well as by the calcium ionophore A23187, but not by phorbol esters. Thus, this human TCRbeta chain functions efficiently for positive selection of mouse T cells, but not for their peripheral activation, probably because of a lack of oligomerization leading to defects in signaling for calcium flux and IL-2 induction. The data thus suggest an early point of separation of signaling pathways between positive selection and peripheral activation of T cells.

Animals↗

PubMed2001

Flavobacterium frigidarium sp. nov., an aerobic, psychrophilic, xylanolytic and laminarinolytic bacterium from Antarctica.

A psychrophilic, aerobic bacterium designated A2iT was isolated from marine sediment recovered from shallow waters surrounding Adelaide Island, Antarctica (67 degrees 34' S, 68 degrees 07' W). The organism exhibited xylanolytic and laminarinolytic activity and was halotolerant. Basic characterization showed that it was gram-negative, non-motile, yellow-pigmented (beta,beta-carotene-3,3'-diol) and positive for oxidase and catalase synthesis. Analysis of the 16S rDNA sequence suggests that the organism belongs to the Flexibacter-Cytophaga-Bacteroides phylum. On the basis of its 16S rDNA sequence, the bacterium is 96.8% similar to Flavobacterium columnare ATCC 43622--its closest relation. The genomic DNA G+C content was 35 mol%. Growth on xylan occurs optimally at 15 degrees C, though growth also occurs at 0 degrees C, and the doubling times are 9.6 and 34.8 h, respectively. The maximum growth temperature on xylan is at 24 degrees C. The bacterium is a neutrophile, growing across the pH range 5.6-8.4 and having an optimum at pH 7.5. Analysis of the 16S rDNA sequence, together with phenotypic characterization, suggests that the organism is a member of the genus Flavobacterium. DNA-DNA hybridization experiments have shown that it is a novel species; it is proposed, therefore, that the organism be designated as the type strain of Flavobacterium frigidarium sp. nov. (= ATCC 700810T = NCIMB 13737T).

Aerobiosis↗

PubMed2001

Cigar magazines: using tobacco to sell a lifestyle.

OBJECTIVE: To assess the content of two cigar "lifestyle" magazines, Cigar Aficionado and Smoke. DESIGN: Content analysis of cigar focused articles. SUBJECTS: Cigar focused articles (n = 353) from Cigar Aficionado and Smoke magazines. MAIN OUTCOME MEASURES: Primary focus; mention of health effects, environmental tobacco smoke, or scientific research; quotation and description of individuals; characteristics such as sex, age, ethnicity, smoking status, affiliation, and stance towards cigars; and overall image of cigars. RESULTS: Cigar business-focused articles were the largest category (40%, n = 143), followed by articles about cigar events (12%, n = 42). Notable were articles featuring cigar benefits to raise money for health charities. Celebrities were featured in 34% (n = 121) of articles and 96% (n = 271) favoured cigar use. Only four (1%) articles featured health effects of cigars as a primary focus. CONCLUSIONS: Cigar Aficionado and Smoke broke new ground in tobacco marketing by combining promotion of product, lifestyle, and industry in the same vehicle and linking the medium directly to product related events that extended its reach. The creation and marketing of new tobacco use sites challenges the increasing "isolation" of smokers, and positions cigar use as a socially welcome relief from restrictions. Public health advocates should anticipate and challenge other new tobacco marketing vehicles as communications technologies advance and public spaces for smoking shrink.

Advertising↗

PubMed2000

Ligation of CD27 on murine B cells responding to T-dependent and T-independent stimuli inhibits the generation of plasma cells.

B cells can be stimulated either allogenically with the Th cell clone D10G4.1 and bone marrow-derived dendritic cells or polyclonally with LPS to proliferate and undergo terminal differentiation to Ig-secreting plasma cells in vitro. The addition of anti-CD27 to such cultures inhibits Ig secretion, and inhibition is more marked in T-dependent cultures than in T-independent cultures. Both IgM and secondary isotypes are affected, and addition of anti-CD27 even 4 days after culture initiation inhibits Ig secretion. Anti-CD27 does not affect B cell proliferation or the acquisition of activation markers by B cells, and no marked loss of B cell viability is detected in cells cultured in the presence of anti-CD27, suggesting that the inhibition of Ig secretion is not due to inhibition of early activation events or to death of activated cells in vitro. However, the presence of anti-CD27 significantly inhibits the induction of Blimp-1 and J chain transcripts, which are turned on in cells committed to plasma cell differentiation. Furthermore, mice immunized under cover of anti-CD27 make less Ag-specific IgM and IgG, but have equivalent T cell responses when compared with control mice. These data suggest that ligation of CD27, a member of the TNFR family, on the B cell surface may prevent terminal differentiation of activated B cells into Ig-secreting plasma cells.

Animals↗

PubMed2000

Fractionation and characterization of oligomeric, protofibrillar and fibrillar forms of beta-amyloid peptide.

The beta-amyloid (Abeta) peptide, a major component of senile plaques in Alzheimer's disease brain, has been shown previously to undergo a process of polymerization to produce neurotoxic forms of amyloid. Recent literature has attempted to define precisely the form of Abeta responsible for its neurodegenerative properties. In the present study we describe a novel density-gradient centrifugation method for the isolation and characterization of structurally distinct polymerized forms of Abeta peptide. Fractions containing protofibrils, fibrils, sheet structures and low molecular mass oligomers were prepared. The fractionated forms of Abeta were characterized structurally by transmission electron microscopy. The effects on cell viability of these fractions was determined in the B12 neuronal cell line and hippocampal neurons. Marked effects on cell viability in the cells were found to correspond to the presence of protofibrillar and fibrillar structures, but not to monomeric peptide or sheet-like structures of polymerized Abeta. Biological activity correlated with a positive reaction in an immunoassay that specifically detects protofibrillar and fibrillar Abeta; those fractions that were immunoassay negative had no effect on cell viability. These data suggest that the effect of Abeta on cell viability is not confined to a single conformational form but that both fibrillar and protofibrillar species have the potential to be active in this assay.

Amyloid beta-Peptides↗

PubMed2000

Cloning and characterization of rat dentin matrix protein 1 (DMP1) gene and its 5'-upstream region.

Rat dentin matrix protein 1 (DMP1) is a highly acidic 58-kDa phosphoprotein, and DMP1 was the first gene to be cloned from the mineralized dentin matrix. It exists as a highly phosphorylated protein with a pI of 3 in the dentin matrix and, in that state, might have an important role in the mineralization process. The spatio-temporal distribution during development indicates that the expression of this gene is tightly regulated in the odontoblasts. It is now known that DMP1 is not unique to dentin but is present in other mineralized tissues like long bone, calvaria, and ameloblasts. To study the transcriptional regulation and the function of DMP1 in these tissues, a genomic clone with a functional promoter, introns, and exons was isolated. Sequence analysis showed that the rat DMP1 gene is comprised of six exons and five introns and spans approximately 13 kilobases (kb). Exon 1 contains the 5'-untranslated sequences. Exon 2 encodes a total of 18 amino acids including the 16 amino acids of the signal sequence. Exons 3-5 encode 16, 11, and 15 amino acids, respectively. Exon 6 contains 1.3 kb of the coding sequence with the RGD domain, stop codon, and the 3'-untranslated region (1.1 kb). We have mapped two transcription start sites within the DMP1 promoter that are 280 and 321 base pairs, respectively, from the ATG start codon. The location of functional elements within the 5'-upstream DMP1 DNA fragment was determined by cloning it into a luciferase reporter gene. Transient transfection and luciferase assays revealed that the 3 kb fragment has the ability to drive the luciferase gene. However, this promoter activity was restricted to MC3T3-E1 cells (an osteoblast cell lineage). The promoter was silent in Chinese hamster ovary cells (an epithelial cell lineage), indicating the necessity of tissue-specific factors to drive the transcription.

5' Untranslated Regions↗

PubMed2000

Disruption of T cell tolerance to self-immunoglobulin causes polyclonal B cell stimulation followed by inactivation of responding autoreactive T cells.

Scavenger receptor (SR)-specific delivery by maleylation of a ubiquitous self-protein, Ig, to SR-bearing APCs results in self-limiting induction of autoimmune effects in vivo. Immunization with maleyl-Ig breaks T cell tolerance to self-Ig and causes hypergammaglobulinemia, with increases in spleen weight and cellularity. The majority of splenic B cells show an activated phenotype upon maleyl-Ig immunization, leading to large-scale conversion to a CD138+ phenotype and to significant increases in CD138-expressing splenic plasma cells. The polyclonal B cell activation, hypergammaglobulinemia, and autoreactive Ig-specific T cell responses decline over a 2-mo period postimmunization. Following adoptive transfer, T cells from maleyl-Ig-immune mice taken at 2 wk postimmunization can induce hypergammaglobulinemia in the recipients, but those taken at 10 wk postimmunization cannot. Hypergammaglobulinemia in the adoptive transfer recipients is also transient and is followed by an inability to respond to fresh maleyl-Ig immunization, suggesting that the autoreactive Ig-specific T cells are inactivated peripherally following disruption of tolerance. Thus, although autoreactive T cell responses to a ubiquitous self-Ag, Ig, are induced by SR-mediated delivery to professional APCs in vivo resulting in autoimmune pathophysiological effects, they are effectively and rapidly turned off by inactivation of these activated Ig-specific T cells in vivo.

Animals↗

PubMed2000

Medulloblastoma in children--the Ottawa experience.

A retrospective review of 36 children diagnosed with medulloblastoma in the Ottawa area between 1974 and 1997 was completed (mean age 7.8+/-4.2 years, range 1.2-15.3 years). Via a suboccipital approach, complete tumor resection was achieved in 75% and subtotal resection (>90%) in 25%, without any operative mortality. The tumor was located in the vermis in 39% and in the cerebellar hemisphere in 11%; it occupied both locations in 50%. In 47% of the children a ventriculoperitoneal shunt was required. Postoperatively, craniospinal radiation at 3600 cGy with a boost to the posterior fossa was administered. Chemotherapy was used in 56%. The 1-year survival rate was 92%, and survival plateaued at 54% at 5 years. Children less than 3 years of age fared worse than those over 3 years old. While the male-to-female ratio was 1.6:1, there was no gender difference in survival. Chang's classification was used to grade the tumors. T stage did not have an impact on survival, but M stage did. No statistically significant difference in survival was found between the patients who had a total resection and those who had a subtotal resection. There was no difference in survival in terms of tumor location, hydrocephalus or ventriculoperitoneal shunt. Chemotherapy showed no survival benefit. The recurrence rate was 26%, and its timing followed Collin's law. Recurrence led to death within 1-9 months. GH deficiency was diagnosed in 5 patients and hypothyroidism in 4 patients. The mean follow-up time was 4.4+/-3.7 years, with a range of 2.5 months to 16.5 years. Fourteen patients died, 5 were lost to follow-up, and 7 were transferred to adult care without persistent disease. Ten children are presently being followed up by the Neuro-oncology Clinic. Four children continue to be followed through psychology services. Our results are comparable to those in larger series, and are similar to those of the Montreal Children's Hospital.

Adolescent↗

PubMed2000

Promotion of selective cell attachment by the RGD sequence in dentine matrix protein 1.

Dentine matrix protein 1 (DMP1) is an important component of the non-collagenous extracellular matrix of developing teeth and bones. Functions of DMP1 other than a putative role in the initiation of mineralization are largely unknown. A first report on the DNA and deduced amino acid sequence showed that DMP1 has a single Arg-Gly-Asp (RGD) sequence. Here, whether the RGD sequence functions as a cell-attachment domain was tested. Using site-directed mutagenesis, two mutant recombinant DMP1 proteins with specific alterations at the RGD site were created. In the first mutant protein the RGD sequence was altered to a RGE (RGE) sequence; in the second the RGD domain was deleted (DEL). Mutated proteins were confirmed to be DMP1 by partial protein sequencing and dot-blot analysis with an anti-DMP1 antibody. Attachment of RPC-C2A (dental pulp cells), MC3T3-E1 (calvarial cells) or CHO (Chinese hamster ovary cells) to non-tissue-culture plastic coated with either DMP1, RGE or DEL proteins was compared. Bovine serum albumin and fibronectin served as negative and positive controls, respectively. The RGD-containing native DMP1 protein effectively allowed cell attachment and spreading. The RGE and DEL proteins with the altered and deleted RGD sites were significantly less effective in promoting cell attachment than the recombinant DMP1. Both RPC-C2A pulp cells and MC3T3-E1 cells showed similar reductions in attachment to mutated proteins. Treatment of RPC-C2A cells with a RGD-containing peptide prior to plating on DMP1-coated chambers abolished DMP1-mediated cell attachment. In contrast to RPC-C2A and MC3T3-E1cells, CHO cells, which normally do not express DMP1, failed to attach to DMP1. These data demonstrate that DMP1 promotes cell attachment through the RGD domain and that the attachment is cell- and tissue-specific. A basis for these observations is proposed using computer-generated models of the polypeptides within the DMP1 protein containing the RGD, RGE or DEL sequences.

3T3 Cells↗

PubMed2000

Uterine rupture in a multiparous woman during labor induction with oral misoprostol.

A multigravida with gestational diabetes, mild pregnancy-induced hypertension and a previous curettage received four doses of misoprostol (100 microg) at three hourly intervals for induction of labor at term. Vaginal delivery of a live healthy baby occurred 1 h after the fourth dose. Hindwaters were bloodstained. Three hours later, she had excessive bleeding. Examination showed that the left lateral uterine wall had ruptured. She recovered after hysterectomy and blood transfusions.

Administration, Oral↗

PubMed2000

Liquid ammonia injury.

The toxic effects of a gas depend on the time of exposure, concentration and its chemical nature. Pressurized liquids and gases exert an additional cold thermal injury and this may complicate the clinical picture. A patient who had an accidental exposure to liquid ammonia over a prolonged period, manifesting in cutaneous, respiratory and ocular damage in addition to a severe cold thermal injury (frostbite) with a fatal outcome is presented. The patient had flaccid quadriparesis and episodes of bradycardia, which has not been reported previously. These manifestations raise the possibility of the systemic toxicity in patients with prolonged exposure to ammonia.

Accidents, Occupational↗