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Biomedical subjects

M Carey

Publications and source records attributed to M Carey.

At least 73 records · Page 4Linked to original sources
PubMed1998

Compensatory energetic relationships between upstream activators and the RNA polymerase II general transcription machinery.

Activation of RNA polymerase II transcription in vivo and in vitro is synergistic with respect to increasing numbers of activator binding sites or increasing concentrations of activator. The Epstein-Barr virus ZEBRA protein manifests both forms of synergy during activation of genes involved in the viral lytic cycle. The synergy has an underlying mechanistic basis that we and others have proposed is founded largely on the energetic contributions of (i) upstream ZEBRA binding to its sites, (ii) the general pol II machinery binding to the core promoter, and (iii) interactions between ZEBRA and the general machinery. We hypothesize that these interactions form a network for which a minimum stability must be attained to activate transcription. One prediction of this model is that the energetic contributions should be reciprocal, such that a strong core promoter linked to a weak upstream promoter would be functionally analogous to a weak core linked to a strong upstream promoter. We tested this view by measuring the transcriptional response after systematically altering the upstream and core promoters. Our data provide strong qualitative support for this hypothesis and provide a theoretical basis for analyzing Epstein-Barr virus gene regulation.

Binding Sites↗
PubMed1998

Bone mass and structure at the hip in men and women over the age of 60 years.

Bone mass and structure at the proximal femur are important predictors of hip fracture. The aims of this study were to compare in a large sample of elderly men and women the precision of measurements of bone mass and structure at multiple sites at the proximal femur, to examine their interrelationships, to establish their relationships with age and body size, and to examine criteria for defining geometric and architectural variables in bone structure. Women (n = 336) and men (n = 141) over the age of 60 years were studied cross-sectionally. Bone mineral density (BMD) and content (BMC) at the proximal femur were measured in duplicate by dual-energy X-ray absorptiometry (DXA). Shaft and total upper femur (hip) sites in addition to femoral neck, Ward's triangle and trochanter were measured. Structural variables, measured from radiographs and from DXA images, including cortical thickness at calcar femorale, lateral cotex and midfemur, width of the femur and medulla, Singh grade, hip and femoral axis length, femoral head and neck width and the center of mass of the femoral neck. BMD and BMC had high reproducibility and there were significant differences in reproducibility across sites. Among sites, total upper femur and shaft had the highest reproducibility. Duplicate measurements substantially improved reliability of the measurement and are recommended when the value is close to a diagnostic level or when it will be used to establish rates of change. Reproducibility of structural variables was also high except for the lateral cortex, center of mass and Singh grade. Variance due to measurement error did not change with either age or gender. Women were significantly different from men, after controlling for differences in body size, in all variables except Singh grade and medulla width. BMD and BMC were negatively related to age and positively to body size. Structural variables examined in relation to age and body size fell into two categories. The first comprised variables that were not age-related but were body-size-related suggesting that they could be classified as geometric variables. The second comprised variables that were both body-size-related and age-related, suggesting that they could be classified as architectural variables. Using these criteria, calcar and lateral cortex were architectural variables, whereas shaft width, hip and femoral axis length, femoral head and neck width, and center of mass were geometric in both men and women. In women, shaft cortex width and medulla width were age-related, whereas in men they were not. Singh grade showed no consistent pattern with age or body size in women and men.

Absorptiometry, Photon↗
PubMed1998

Changes in performance, muscle metabolites, enzymes and fibre types after short sprint training.

In contrast to endurance training, little research has been carried out to investigate the effects of short (< 10 s) sprint training on performance, muscle metabolism and fibre types. Nine fit male subjects performed a mean of 16 outdoor sprint running training sessions over 6 weeks. Distances sprinted were 30-80 m at 90-100% maximum speed and between 20 and 40 sprints were performed in each session. Endurance (maximal oxygen consumption; VO2max), sprint (10 m and 40 m times), sustained sprint (supramaximal treadmill run) and repeated sprint (6 x 40 m sprints, 24 s recovery between each) performance tests were performed before and after training. Muscle biopsy samples (vastus lateralis) were also taken to examine changes in metabolites, enzyme activities and fibre types. After training, significant improvements were seen in 40 m time (P < 0.01), supramaximal treadmill run time (P < 0.05), repeated sprint performance (P < 0.05) and VO2max (P < 0.01). Resting muscle concentrations of ATP and phosphocreatine did not change. Phosphorylase activity increased (P < 0.025), citrate synthase activity decreased (P < 0.01), but no significant changes were recorded in myokinase and phosphofructokinase activities. The proportion of type II muscle fibres increased significantly (P < 0.05). These results demonstrate that 6 weeks of short sprint training can improve endurance, sprint and repeated sprint ability in fit subjects. Increases in the proportion of type II muscle fibres are also possible with this type of training.

Adult↗
PubMed1998

Central neurocytoma: a correlative clinicopathologic and radiologic analysis.

BACKGROUND: Central neurocytoma was described as a well differentiated tumor of neuronal origin, distinct from ganglion cell tumors and neuroblastoma. An initially perceived benign biologic behavior has been questioned by subsequent reports of anaplastic and recurrent tumors. We report six cases of central neurocytoma, with variable clinical and pathologic features that stimulate discussion on the management of these tumors. METHODS: Of the 95 oligodendrogliomas treated in our institution in the last 40 years, three tumors were reclassified as central neurocytomas on histologic reappraisal. Three additional cases prospectively diagnosed as central neurocytomas are reported. The clinical, pathologic, and radiologic features are reviewed. RESULTS: Early recurrence, not related to malignant histologic features, was noted in two patients who had not received postoperative radiotherapy. Anaplastic histologic changes were not accompanied by malignant biologic behavior in another patient. Neither patient with recurrent tumor was controlled by radiotherapy alone. Chemotherapy with carboplatin reduced tumor size temporarily in one of these patients. CONCLUSION: An entirely benign nature for this tumor is questioned and it appears that there may be malignant variants. Surgery should aim for maximum possible excision, as the location of the tumor allows. The role of postoperative radiotherapy remains controversial and may be considered in cases of subtotal excision of tumors with anaplastic histologic features. Chemotherapy may be of benefit in cases recurring despite surgery and radiotherapy.

Adolescent↗
PubMed1998

Pre-emptive glycopyrrolate 0.2 mg and bradycardia during gynaecological laparoscopy with mivacurium.

In a prospective, randomized, double-blind, placebo-controlled trial, the effect of pre-emptive glycopyrrolate 0.2 mg given intravenously on the incidence of bradycardia in patients undergoing elective gynaecological laparoscopy with mivacurium neuromuscular blockade was investigated. Seven out of 32 (21.6%) control patients developed bradycardia (heart rate < 50 min-1), compared with 3 of 31 (9.6%) patients receiving glycopyrrolate (P = 0.4). Glycopyrrolate 0.2 mg, given immediately before induction in gynaecological laparoscopy with mivacurium, did not significantly reduce the incidence of intraoperative bradycardia.

Adult↗
PubMed1997

Protease footprinting analysis of ternary complex formation by human TFIIA.

Transcription factor (TF) IIA performs two important regulatory functions during RNA polymerase II transcription: it is required for efficient binding of TFIID to a core promoter and it mediates the effects of upstream activators, both through direct interaction with the TATA box binding protein (TBP). To begin studying how TFIIA mediates these effects, we used a highly sensitive protease footprinting methodology to identify surfaces of human TFIIA participating in TFIIA x TBP x TATA ternary complex formation. Chymotrypsin and proteinase K cleavage patterns of TFIIA bearing a 32P-end-labeled gamma subunit revealed that amino acids 59-73 were protected from cleavage both in the context of an immobilized ternary complex and in a binary complex with TBP alone. In contrast, amino acids 341-367 in the beta portion of a 32P-labeled alpha-beta subunit were protected in the ternary but not in the binary complex, implying that those residues interact with promoter DNA. The regions of human TFIIA identified by protease footprinting are homologous to and encompass the yeast TFIIA residues that contact TBP and DNA in the recently solved crystal structure of the yeast ternary complex. The conservation of the regions and residues mediating complex formation implies that yeast and human TFIIA employ the same mechanism to stabilize the binding of TFIID to a core promoter.

Binding Sites↗
PubMed1997

A phase II study of leuprolide in advanced/recurrent endometrial cancer.

In order to determine the efficacy and toxicity of the gonadotrophin-releasing hormone agonist Leuprolide in the management of patients with recurrent or metastatic endometrial cancer, we performed a phase II study. Patients were included if there was clinical or radiological documentation of bidimensionally measurable recurrent or metastatic endometrial cancer that was deemed incurable. Treatment was 7.5 mg i.m. every 28 days, and was to continue for at least 2 courses until evidence of disease progression, patient requested withdrawal, or unacceptable toxicity. Twenty-five patients received Leuprolide for recurrent or metastatic endometrial cancer. The median age at study entry was 62 years, and the median time from initial diagnosis to first course of Leuprolide was 25 months. Six patients had received no systemic or radiotherapy prior to study entry, and 2 of these had not previously undergone hysterectomy. Fifteen patients received prior pelvic radiotherapy and 3 patients received prior whole abdominal radiotherapy. Nine of the 25 patients had received prior progestational agents, and 2 had received prior systemic chemotherapy. There were no responders, 8 patients had stable disease for a median 5 months (range 1-8), 14 patients progressed on therapy, and 3 patients were not evaluable for response due to receiving only 1 treatment. One patient experienced a grade 3 toxicity that was possibly attributable to Leuprolide (deep venous thrombosis). The median survival from study entry was 6 months. Twelve patients received progesterone after discontinuing this study, and none responded. Leuprolide does not appear to be a clinically active agent in the treatment of recurrent or metastatic endometrial cancer.

Adult↗
PubMed1997

Recruitment of the putative transcription-repair coupling factor CSB/ERCC6 to RNA polymerase II elongation complexes.

Cockayne's syndrome (CS) is a disease characterized by developmental and growth defects, sunlight sensitivity, and a defect in transcription-coupled nucleotide excision repair. The two principle proteins involved in CS, CSA and CSB/ERCC6, have been hypothesized to bind RNA polymerase II (Pol II) and link transcription to DNA repair. We have tested CSA and CSB in assays designed to determine their role in transcription-coupled repair. Using a unique oligo(dC)-tailed DNA template, we provide biochemical evidence that CSB/ERCC6 interacts with Pol II molecules engaged in ternary complexes containing DNA and nascent RNA. CSB is a DNA-activated ATPase, and hydrolysis of the ATP beta-gamma phosphoanhydride bond is required for the formation of a stable Pol II-CSB-DNA-RNA complex. Unlike CSB, CSA does not directly bind Pol II.

Adenosine Triphosphatases↗
PubMed1996

Yeast HMG proteins NHP6A/B potentiate promoter-specific transcriptional activation in vivo and assembly of preinitiation complexes in vitro.

Nonhistone proteins 6A and 6B (NHP6A/B) are nonsequence-specific DNA-binding proteins from Saccharomyces cerevisiae that are related structurally and functionally to the mammalian high mobility group proteins 1 and 2. These DNA architectural proteins distort DNA structure severely and have been shown to promote assembly of specialized recombination complexes. Here we show that the yeast NHP6A/B proteins are required for the induction of a subset of genes transcribed by RNA polymerase II (pol II). Activation of the CUP1, CYC1, GAL1, and DDR2 genes was decreased or abolished completely in the delta nhp6A/B strain. No significant change in basal expression was observed for any of the 10 genes examined. Analysis of chimeric gene constructs localized the regions dependent on NHP6A/B to be primarily at the core promoters, although the GAL1 UAS also requires NHP6A/B for activity. In vitro, NHP6A stimulated transcription by pol II at the GAL1 promoter three- to fivefold above the level of activation by GAL4-VP16 alone. Gel mobility shift assays showed that NHP6A promotes the formation of a complex with TBP and TFIIA at the TATA box that has enhanced affinity for TFIIB.

Fungal Proteins↗
PubMed1996

Assembly of the isomerized TFIIA--TFIID--TATA ternary complex is necessary and sufficient for gene activation.

The prevailing view of eukaryotic gene activation poses that activators stimulate transcription by recruiting limiting components of the general transcription machinery to a core promoter. In one such model case, activation by the Epstein-Barr virus ZEBRA protein correlated closely with recruitment of the general transcription factors TFIIA and TFIID (the DA complex) as measured by DNase I footprinting and gel mobility shift assays. We now report that simple recruitment is not sufficient for full-level activation. An additional concentration-independent, rate-limiting step is activator-mediated isomerization of the DA complex characterized by an extended TFIID footprint. The isomerized complex supports both binding of TFIIB in gel mobility shift assays and activated transcription in heat-treated nuclear extracts, even after removal of ZEBRA. Surprisingly, the regulatory phenomenon of synergy was manifested only when the concentration of TFIID was limiting. When the DA complex was saturating, transcription was not synergistic, as indicated by the ability of a single activator to induce isomerization effectively and turn on a gene. On the basis of these observations, we propose a new biochemical model for eukaryotic gene activation and synergy.

DNA-Binding Proteins↗