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R A Fraser

Publications and source records attributed to R A Fraser.

At least 19 recordsLinked to original sources
PubMed2000

Promoter-targeted selection and isolation of neural progenitor cells from the adult human ventricular zone.

Adult humans, like their nonhuman mammalian counterparts, harbor persistent neural progenitor cells in the forebrain ventricular lining. In the absence of adequate surface markers, however, these cells have proven difficult to isolate for study. We have previously identified and selected neural progenitor cells from both the fetal and adult rodent ventricular zone (VZ), by sorting forebrain cells transfected with plasmid DNA encoding the gene for green fluorescent protein driven by the early neuronal promoter for Talpha1 tubulin (P/Talpha1:hGFP). We have now extended this approach by purifying both P/Talpha1:hGFP tubulin-defined neuronal progenitors, as well as potentially less committed E/nestin:hGFP-defined neural progenitor cells, from the adult human VZ. The ventricular wall of the temporal horn of the lateral ventricle was dissected from temporal lobes obtained from four adult patients undergoing therapeutic lobectomy. These samples were dissociated, and the cultured cells transduced with either P/Talpha1:hGFP or E/nestin:EGFP plasmid DNA. A week later, the cells were redissociated, selected via fluorescence-activated cell sorting (FACS) on the basis of neural promoter-driven GFP expression, and replated. The majority of these cells expressed the early neuronal protein betaIII-tubulin upon FACS; within the week thereafter, most matured as morphologically evident neurons that coexpressed betaIII-tubulin and microtubule-associated protein (MAP)-2. Many of these neurons had incorporated bromodeoxyuridine in vitro in the days before FACS, indicating their mitogenesis in vitro. Thus, the use of fluorescent transgenes under the control of early neural promoters permits the enrichment of neuronal progenitor cells from the adult human ventricular zone. The specific acquisition, in both purity and number, of residual neural progenitor cells from the adult human brain may now permit hitherto unfeasible studies of both their biology and practical application.

Adult↗
PubMed2000

In vitro neurogenesis by progenitor cells isolated from the adult human hippocampus.

Neurogenesis persists in the adult mammalian hippocampus. To identify and isolate neuronal progenitor cells of the adult human hippocampus, we transfected ventricular zone-free dissociates of surgically-excised dentate gyrus with DNA encoding humanized green fluorescent protein (hGFP), placed under the control of either the nestin enhancer (E/nestin) or the Talpha1 tubulin promoter (P/Talpha1), two regulatory regions that direct transcription in neural progenitor cells. The resultant P/Talpha1:hGFP+ and E/nestin:enhanced (E)GFP+ cells expressed betaIII-tubulin or microtubule-associated protein-2; many incorporated bromodeoxyuridine, indicating their genesis in vitro. Using fluorescence-activated cell sorting, the E/nestin:EGFP+ and P/Talpha1:hGFP+ cells were isolated to near purity, and matured antigenically and physiologically as neurons. Thus, the adult human hippocampus contains mitotically competent neuronal progenitors that can be selectively extracted. The isolation of these cells may provide a cellular substrate for re-populating the damaged or degenerated adult hippocampus.

Adult↗
PubMed2000

Delayed epistaxis resulting from external carotid artery injury requiring embolization: a rare complication of transsphenoidal surgery: case report.

OBJECTIVE AND IMPORTANCE: Delayed epistaxis resulting from trauma to branches of the external carotid artery is an infrequent but potentially serious complication of transsphenoidal surgery. We report two cases of severe, delayed epistaxis in patients who had undergone transsphenoidal surgery. In both cases, noninvasive treatment failed, necessitating endovascular intervention. CLINICAL PRESENTATION: The first patient, a 52-year-old woman with a prolactinoma, underwent a second transsphenoidal resection 18 months after the first surgery. She was readmitted on postoperative Day 15 with massive epistaxis. The second patient, a 40-year-old woman, had undergone two transsphenoidal surgeries, 14 years apart, for an adrenocorticotropic hormone-secreting adenoma. She was readmitted with massive epistaxis on postoperative Day 17. INTERVENTION: Both patients were initially treated with nasal balloon packing but experienced recurrent hemorrhage when the balloon was deflated, necessitating referral to the interventional radiology department for embolization. At arteriography, the first patient was found to have a pseudoaneurysm of the medial branch of the left internal maxillary artery, which was subsequently embolized. Arteriography in the second patient revealed an abnormally dilated midline branch of the right internal maxillary artery in the nasal septum; this vessel was occluded at arteriography. CONCLUSION: Delayed massive epistaxis is a rare but significant complication of transsphenoidal surgery. Injury to branches of the external carotid artery, along with injury to the internal carotid artery, should be suspected in patients who present with delayed epistaxis after transsphenoidal surgery. Angiography performed in patients with refractory bleeding should include selective external carotid injections. Epistaxis that is refractory to anterior and posterior nasal packing may be effectively treated with endovascular embolization.

Adult↗
PubMed1999

Identification, isolation, and promoter-defined separation of mitotic oligodendrocyte progenitor cells from the adult human subcortical white matter.

Previous studies have suggested the persistence of oligodendrocyte progenitor cells in the adult mammalian subcortical white matter. To identify oligodendrocyte progenitors in the adult human subcortical white matter, we transfected dissociates of capsular white matter with plasmid DNA bearing the gene for green fluorescence protein (hGFP), placed under the control of the human early promoter (P2) for the oligodendrocytic protein cyclic nucleotide phosphodiesterase (P/hCNP2). Within 4 d after transfection with P/hCNP2:hGFP, a discrete population of small, bipolar cells were noted to express GFP. These cells were A2B5-positive (A2B5(+)), incorporated bromodeoxyuridine in vitro, and constituted <0.5% of all cells. Using fluorescence-activated cell sorting (FACS), the P/hCNP2-driven GFP(+) cells were then isolated and enriched to near-purity. In the weeks after FACS, most P/hCNP2:hGFP-sorted cells matured as morphologically and antigenically characteristic oligodendrocytes. Thus, the human subcortical white matter harbors mitotically competent progenitor cells, which give rise primarily to oligodendrocytes in vitro. By using fluorescent transgenes of GFP expressed under the control of an early oligodendrocytic promoter, these oligodendrocyte progenitor cells may be extracted and purified from adult human white matter in sufficient numbers for implantation and cell-based therapy.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1998

The putative cofactor TIF1alpha is a protein kinase that is hyperphosphorylated upon interaction with liganded nuclear receptors.

Ligand-induced gene activation by nuclear receptors (NRs) is a complex process requiring dissociation of corepressors and recruitment of coactivators. The putative transcriptional intermediary factor TIF1alpha has been previously characterized as a nuclear protein that interacts directly with the AF-2 ligand-dependent activating domain present in the ligand-binding domain of numerous steroid and nonsteroid receptors, including the estrogen (ERalpha) and retinoid X (RXRalpha) receptors. We report here that TIF1alpha is both a phosphoprotein and a protein kinase. TIF1alpha coexpressed in COS-1 cells with RXRalpha or ERalpha is phosphorylated and becomes hyperphosphorylated upon ligand treatment. This hyperphosphorylation requires the binding of TIF1alpha to transcriptionally active NRs since it is prevented by mutations either in the core (alpha-helix 12 of the ligand-binding domain) of the AF-2 activating domains of RXRalpha and ERalpha or in the NR box of TIF1alpha that are known to prevent TIF1alpha-NR interactions. Thus, TIF1alpha is a phosphoprotein that undergoes ligand-dependent hyperphosphorylation as a consequence of nuclear receptor binding. We further show that purified recombinant TIF1alpha possesses intrinsic kinase activity and that, in addition to autophosphorylation, TIF1alpha selectively phosphorylates the transcription factors TFIIEalpha, TAFII28, and TAFII55 in vitro. These latter results raise the possibility that TIF1alpha may act, at least in part, by phosphorylating and modifying the activity of components of the transcriptional machinery.

Animals↗
PubMed1998

Fibroblast growth factor-2/brain-derived neurotrophic factor-associated maturation of new neurons generated from adult human subependymal cells.

The adult mammalian forebrain harbors neuronal precursor cells in the subependymal zone (SZ). Neuronal progenitors also persist in the adult human SZ and have been cultured from epileptic temporal lobe. In the present study, we sought to identify these neural progenitors in situ, and to direct their expansion and neuronal differentiation in vitro. We prepared explants of adult human SZ, obtained from temporal lobe resections of refractory epileptics. The resultant cultures were treated with fibroblast growth factor-2 (FGF-2) for a week, with concurrent exposure to [3H]thymidine, then switched to media containing brain-derived neurotrophic factor (BDNF) for up to 2 months. Sporadic neuronal outgrowth, verified antigenically and physiologically, was observed from SZ cultures regardless of FGF-2/BDNF treatment; however, only FGF-2/BDNF-treated cultures exhibited profuse outgrowth, and these displayed neuronal survival as long as 9 weeks in vitro. In addition, cortical cultures derived from two brains generated microtubule-associated protein-2+ neurons, which incorporated [3H]thymidine and exhibited significant calcium increments to depolarization. In histological sections of the subependyma, both uncommitted and restricted progenitors, defined respectively by musashi and Hu protein expression, were identified. Thus, the adult human subependyma harbors neural progenitors, which are able to give rise to neurons whose numbers can be supported for prolonged periods in vitro.

Adult↗
PubMed1998

Neural stem and progenitor cells: a strategy for gene therapy and brain repair.

The damaged adult mammalian brain is incapable of significant structural self-repair. Although varying degrees of recovery from injury are possible, this is largely because of synaptic and functional plasticity rather than the frank regeneration of neural tissues. The lack of structural plasticity of the adult brain is partly because of its inability to generate new neurons, a limitation that has severely hindered the development of therapies for neurological injury or degeneration. However, a variety of experimental studies, as well as moderately successful clinical engraftment of fetal tissue into the adult parkinsonian brain, suggests that cell replacement is evolving as a valuable treatment modality. Neural stem cells, which are the self-renewing precursors of neurons and glia, have been isolated from both the embryonic and adult mammalian central nervous system. In the adult human brain, both neuronal and oligodendroglial precursors have been identified, and methods for their harvest and enrichment have been established. Neural precursors have several characteristics that make them ideal vectors for brain repair. They may be clonally expanded in tissue culture, providing a renewable supply of material for transplantation. Moreover, progenitors are ideal for genetic manipulation and may be engineered to express exogenous genes for neurotransmitters, neurotrophic factors, and metabolic enzymes. Thus, the persistence of neuronal precursors in the adult mammalian brain may permit us to design novel and effective strategies for central nervous system repair, by which we may yet challenge the irreparability of the structurally damaged adult nervous system.

Animals↗
PubMed1998

Phase II study of dexverapamil plus anthracycline in patients with metastatic breast cancer who have progressed on the same anthracycline regimen.

The purpose of this study is to evaluate whether metastatic breast cancer that has progressed on an anthracycline-containing drug regimen will subsequently respond to that identical regimen if dexverapamil, a modulator of P-glycoprotein-mediated drug resistance, is given concomitantly. Eligible patients received 180 mg/m2 dexverapamil every 6 h for 15 doses with the anthracycline administered 30 min after the seventh dose. Blood for dexverapamil levels was drawn before and 30 min after this dose. When possible, biopsies were obtained to measure mdr-1 expression by reverse transcription-PCR and by image cytometry. Of the 21 patients entered onto the trial, 20 were evaluable for response. There were two partial responses (10%) that both lasted for 6 months, and two additional patients had stable disease. Seven patients had asymptomatic cardiotoxicity consisting of hypotension (24%), bradycardia (5%), or prolongation of the P-R interval (14%). Two patients developed acute congestive heart failure, one on dexverapamil and one 10 days after stopping it. Dexverapamil did not seem to increase anthracycline toxicity. The median trough dexverapamil plus norverapamil level on day 3 was 1110 ng/ml (range, 186-3385 ng/ml), and the median peak level was 2164 ng/ml (range, 964-8382 ng/ml). There was poor correlation between reverse transcription-PCR and image cytometry for the level of mdr-1 expression. Because dexverapamil has been shown to affect doxorubicin pharmacokinetics subsequent to the initiation of this trial, it cannot be concluded that the responses seen were necessarily due to P-glycoprotein inhibition. Additional studies are necessary to determine whether mdr-1 modulators can reverse clinical drug resistance in breast cancer patients. The intrinsic cardiotoxicity of dexverapamil makes it less suitable for such studies than several other available agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

The XPB subunit of repair/transcription factor TFIIH directly interacts with SUG1, a subunit of the 26S proteasome and putative transcription factor.

Mutations in the basal transcription initiation/DNA repair factor TFIIH are responsible for three human disorders: xeroderma pigmentosum (XP), cockayne syndrome (CS) and trichothiodystrophy (TTD). The non-repair features of CS and TTD are thought to be due to a partial inactivation of the transcription function of the complex. To search for proteins whose interaction with TFIIH subunits is disturbed by mutations in patients we used the yeast two-hybrid system and report the isolation of a novel XPB interacting protein, SUG1. The interaction was validated in vivo and in vitro in the following manner. (i) SUG1 interacts with XPB but not with the other core TFIIH subunits in the two-hybrid assay. (ii) Physical interaction is observed in a baculovirus co-expression system. (iii) In fibroblasts under non-overexpression conditions a portion of SUG1 is bound to the TFIIH holocomplex as deduced from co-purification, immunopurification and nickel-chelate affinity chromatography using functional tagged TFIIH. Furthermore, overexpression of SUG1 in normal fibroblasts induced arrest of transcription and a chromatin collapse in vivo. Interestingly, the interaction was diminished with a mutant form of XPB, thus providing a potential link with the clinical features of XP-B patients. Since SUG1 is an integral component of the 26S proteasome and may be part of the mediator, our findings disclose a SUG1-dependent link between TFIIH and the cellular machinery involved in protein modelling/degradation.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1997

SUG1, a putative transcriptional mediator and subunit of the PA700 proteasome regulatory complex, is a DNA helicase.

Yeast SUG1 was originally characterized as a transcriptional mediator for the GAL4 transactivator. A similar role in vertebrates was suggested by the ligand-enhanced interaction between mammalian homologues of yeast SUG1 and the ligand-dependent activating domain (AF-2) of nuclear receptors. SUG1 was also shown to be a component of the PA700 regulatory complex of the 26 S proteasome and a member of a large family of putative ATPases. However, no catalytic function has yet been attributed to SUG1. We show here that SUG1 is a 3'-5' DNA helicase whose activity is dependent on an intact ATP binding domain. The sedimentation heterogeneity of mammalian SUG1 suggests that it may be associated with distinct protein complexes and therefore play multiple roles.

Adenosine Triphosphatases↗
PubMed1996

Long-term survivors of glioblastoma multiforme: clinical and molecular characteristics.

Long term survival is rare in patients with glioblastoma multiforme (GBM). To determine if the tumors of patients with long survivals constitute a subgroup of patients with identifiable molecular genetic characteristics, we studied the p53 gene and Epidermal Growth Factor Receptor (EGF-R) expression in long-term survivors of GBM. A review of the Tumor Registry of Memorial Hospital for Cancer and Allied Diseases documented that 521 patients were treated for GBM between 1954 and 1987 and that 12 patients had seven-year or longer survivals. Six additional long-term survivors were identified from other institutions. After pathological re-examination, the diagnosis of 8 of these 18 (44%) tumors was changed to other histologic tumor types. Using immunohistochemical analysis, 4 of 10 confirmed malignant gliomas had over-expression of p53. Polymerase chain reaction/single-strand conformational polymorphism (PCR/SSCP) analysis and sequence analysis of these 4 tumors showed no p53 mutations in exons 5-8, the region where most mutations have been reported in human malignancies. Immunohistochemical analysis for EGF-R was performed on the tumors of the 10 long-term survivors. EGF-R over-expression was identified in 4 (40%), which is consistent with previous reported studies for GBM in general. These findings suggest that there is a subset of GBM defined by the accumulation of wild-type p53 and that the over-expression of EGF-R does not preclude long-term survival. The seven-year survival rate for confirmed GBM in patients from the Memorial Hospital Tumor Registry was at least 1%.

Adult↗
PubMed1995

Functional interactions between retinoic acid receptor-related orphan nuclear receptor (ROR alpha) and the retinoic acid receptors in the regulation of the gamma F-crystallin promoter.

We have previously demonstrated that an everted repeat of the hexamer PuGGTCA located within the gamma F-crystallin promoter mediates activation of the murine gamma F-crystallin gene by retinoic acid and thyroid hormone receptors. Here, we show that the recently identified retinoic acid receptor-related orphan nuclear receptor (ROR alpha) is expressed in the murine lens and activates the gamma F-crystallin promoter. In contrast to the retinoic acid and thyroid hormone receptors, activation of the gamma F-crystallin promoter by ROR alpha requires binding to the single 3' half-site and spacer sequences of gamma F-crystallin hormone response element (gamma F-HRE). We further demonstrate that ROR alpha-dependent activation is repressed by the competitive binding of retinoic acid receptor/retinoid X receptor heterodimers to the gamma F-HRE in the absence of all-trans-retinoic acid. These studies suggest that the interplay of retinoid receptors and ROR alpha on the gamma F-HRE may constitute an important mechanism regulating gamma F-crystallin gene expression in the murine lens.

Animals↗
PubMed1993

Expression of parathyroid hormone-related peptide gene in the rat hypothalamus.

1. Parathyroid hormone-related peptide (PTHrP), originally isolated from human malignant tumors, is present in a variety of normal mammalian tissues, including the brain. 2. The expression and translation of the PTHrP gene within the rat hypothalamus was demonstrated in this study by the specific hybridization of a 1.8 kb mRNA product with a PTHrP cDNA probe and by the crossreactivity of rat hypothalamic extracts in a PTHrP radioimmunoassay. 3. These results suggest roles for PTHrP in neural or hypophysiotropic regulation.

Animals↗
PubMed1993

Growth hormone receptor gene expression in sex-linked dwarf Leghorn chickens: evidence against a gene deletion.

GH receptor (GHR) mRNA has been identified in peripheral (liver and muscle) and central (brain and hypothalamus) tissues of sex-linked dwarf (SLD) Leghorn chickens. Total RNA was extracted from the tissues of immature (1 week, 4 week), pubertal (16 week) and adult (> 24 weeks) SLD and K (the normally growing strain) Leghorn chickens. In both groups and all tissues, an mRNA moiety of 4.4 kb hybridized with cRNA probes derived from the rabbit hepatic GHR sequence. An additional low-abundance transcript of 2.8 kb was also identified in some tissues. An age-related increase in expression was observed in K and SLD hepatic GHR mRNA, suggesting normal regulation of SLD GHR gene transcription. Amplification of cDNA from K and SLD tissues in the presence of oligonucleotide primers coding for the intracellular or extracellular domains of the chicken GHR generated electrophoretically separable fragments of expected size. Restriction enzyme digestion of the products with EcoRI, BstNI, HaeIII, NcoI or BamHI produced smaller moieties of expected sizes in both strains. These results demonstrate that, in contrast to broiler SLDs, a GHR gene deletion is not responsible for the GHR dysfunction in Leghorn SLDs. Although the actual defect in GHR gene expression in SLD Leghorns remains to be identified, this study demonstrates that sex-linked dwarfism, like Laron dwarfism, is due to a heterogeneity of lesions.

Animals↗
PubMed1993

Chimeric chickens and their use in manipulation of the chicken genome.

Germline chimeric chickens can be made by injecting dispersed cells from Stage X blastoderms into recipient embryos at an equivalent stage of development. Colonization of the chimera by donor-derived cells is facilitated when the recipient embryo is compromised by exposure to irradiation prior to injection of the donor cells. Donor cells can be genetically manipulated by lipofection-mediated gene transfer before they are introduced into the recipient. The genetic modification is expressed in the ectoderm, mesoderm, and endoderm of the chimera after incubation for 96 h. Donor cells can also be cultured as dispersed cells in a monolayer or as whole-embryo explants for at least 48 h before transfer into recipients and retain the ability to enter both somatic and germline tissues in the resulting chimera. A strategy is proposed for the production of transgenic chickens using lipofection-mediated gene transfer to blastoderm cells isolated from Stage X embryos, which are subsequently injected into compromised recipients to yield a germline chimera.

Animals↗