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D Parry

Publications and source records attributed to D Parry.

At least 19 recordsLinked to original sources
PubMed2000

Cyclin D2 is essential for BCR-mediated proliferation and CD5 B cell development.

Progression into G(1) in B lymphocytes is regulated by cyclins D2 and D3, components of the cell cycle machinery currently believed to have overlapping and potentially redundant roles in cell cycle control. To study the specific role of cyclin D2 in B lymphocyte proliferation, we examined B cells from cyclin D2(-/-) mice and demonstrate a specific requirement for cyclin D2 in BCR- but not CD40- or lipopolysaccharide-induced proliferation. Furthermore, conventional B cell development proceeds normally in the mutant mice; however, the CD5 B cell compartment is dramatically reduced, suggesting that cyclin D2 is important in CD5 B cell development as well as antigen-dependent B cell clonal expansion.

Animals↗
PubMed1999

Reverse genetic analysis of Caenorhabditis elegans presenilins reveals redundant but unequal roles for sel-12 and hop-1 in Notch-pathway signaling.

Mutations in the human presenilin genes PS1 and PS2 cause early-onset Alzheimer's disease. Studies in Caenorhabditis elegans and in mice indicate that one function of presenilin genes is to facilitate Notch-pathway signaling. Notably, mutations in the C. elegans presenilin gene sel-12 reduce signaling through an activated version of the Notch receptor LIN-12. To investigate the function of a second C. elegans presenilin gene hop-1 and to examine possible genetic interactions between hop-1 and sel-12, we used a reverse genetic strategy to isolate deletion alleles of both loci. Animals bearing both hop-1 and sel-12 deletions displayed new phenotypes not observed in animals bearing either single deletion. These new phenotypes-germ-line proliferation defects, maternal-effect embryonic lethality, and somatic gonad defects-resemble those resulting from a reduction in signaling through the C. elegans Notch receptors GLP-1 and LIN-12. Thus SEL-12 and HOP-1 appear to function redundantly in promoting Notch-pathway signaling. Phenotypic analyses of hop-1 and sel-12 single and double mutant animals suggest that sel-12 provides more presenilin function than does hop-1.

Animals↗
PubMed1999

Cyclin E associates with BAF155 and BRG1, components of the mammalian SWI-SNF complex, and alters the ability of BRG1 to induce growth arrest.

SWI-SNF complexes have been implicated in transcriptional regulation by chromatin remodeling. We have identified an interaction between two components of the mammalian SWI-SNF complex and cyclin E, an essential cell cycle regulatory protein required for G1/S transition. BRG1 and BAF155, mammalian homologs of yeast SWI2 and SWI3, respectively, are found in cyclin E complexes and are phosphorylated by cyclin E-associated kinase activity. In this report, we show that overexpression of BRG1 causes growth arrest and induction of senescence-associated beta-galactosidase activity, which can be overcome by cyclin E. Our results suggest that cyclin E may modulate the activity of the SWI-SNF apparatus to maintain the chromatin in a transcriptionally permissive state.

Amino Acid Sequence↗
PubMed1999

Cyclin D-CDK subunit arrangement is dependent on the availability of competing INK4 and p21 class inhibitors.

The D-type cyclins and their major kinase partners CDK4 and CDK6 regulate G0-G1-S progression by contributing to the phosphorylation and inactivation of the retinoblastoma gene product, pRB. Assembly of active cyclin D-CDK complexes in response to mitogenic signals is negatively regulated by INK4 family members. Here we show that although all four INK4 proteins associate with CDK4 and CDK6 in vitro, only p16(INK4a) can form stable, binary complexes with both CDK4 and CDK6 in proliferating cells. The other INK4 family members form stable complexes with CDK6 but associate only transiently with CDK4. Conversely, CDK4 stably associates with both p21(CIP1) and p27(KIP1) in cyclin-containing complexes, suggesting that CDK4 is in equilibrium between INK4 and p21(CIP1)- or p27(KIP1)-bound states. In agreement with this hypothesis, overexpression of p21(CIP1) in 293 cells, where CDK4 is bound to p16(INK4a), stimulates the formation of ternary cyclin D-CDK4-p21(CIP1) complexes. These data suggest that members of the p21 family of proteins promote the association of D-type cyclins with CDKs by counteracting the effects of INK4 molecules.

Amino Acid Sequence↗
PubMed1998

Induction of labour for post term pregnancy: an observational study.

The aim of the study was to compare the 2 management protocols for postterm pregnancy; elective induction of labour at 42 weeks' gestation and continuing the pregnancy with fetal monitoring while awaiting spontaneous labour. A retrospective observational study compared a cohort of 360 pregnancies where labour was induced with 486 controls. All pregnancies were postterm (>294 days) by an early ultrasound scan. Induction of labour was achieved with either prostaglandin vaginal pessaries or gel or forewater rupture and Syntocinon infusion. The control group consisted of women with postterm pregnancies who were not induced routinely and who usually had twice weekly fetal assessment with cardiotocography and/or ultrasound. Women who had their labour induced differed from those who awaited spontaneous labour. Nulliparas (OR 1.54; 95% CI 1.24-1.83) and married women (OR 1.76; 95% CI 1.45-2.06) were more likely to have their labour induced. There was no association between the type of caregiver and induction of labour. Induction of labour was associated with a reduction in the incidence of normal vaginal delivery (OR 0.63, 95% CI 0.43-0.92) and an increased incidence of operative vaginal delivery (OR 1.46; 95% CI 1.34-2.01). There was no difference in the overall rate of Caesarean section. There was no difference in fetal or neonatal outcomes. Parity had a major influence on delivery outcomes from a policy of induction of labour. Nulliparas in the induced group had worse outcomes with only 43% achieving a normal vaginal delivery (OR 0.78, 95% CI 0.65-0.95). In contrast for multiparas, the induced group had better outcomes with less Caesarean sections (OR 0.88, 95% CI 0.81-0.96). This retrospective observational study of current clinical practice shows that induction of labour for postterm pregnancy appears to be favoured by nulliparous married women. It suggests that induction of labour may improve delivery outcomes for multigravas but has an adverse effect for nulliparas.

Cesarean Section↗
PubMed1998

Assessment of the effect of the oral iron chelator deferiprone on asymptomatic Plasmodium falciparum parasitemia in humans.

While the parenteral iron-chelating agent desferrioxamine B has anti-malarial activity in humans, the usefulness of an orally active chelator for this indication has not been investigated previously in vivo. We conducted a prospective, double-blind, placebo-controlled, cross-over trial of deferiprone (L1; CP20; 1,2-dimethyl-3-hydroxypyridin-4-one) in 25 adult Zambians with asymptomatic Plasmodium falciparum parasitemia. Deferiprone was administered daily for three or four days in divided doses of 75 or 100 mg/kg of body weight, dosages that are effective for treating iron overload. No reduction in asexual intra-erythrocytic parasites was observed during or after deferiprone treatment. The mean peak plasma concentration of deferiprone (108.9 +/- 24.9 micromol/L) achieved was within the range demonstrated to inhibit the growth of P. falciparum in vitro, but the systemic exposure as determined by the 24-hr plasma concentration-time curve would not be predicted inhibit growth in vivo. No evidence of deferiprone-associated hematological toxicity was noted in this short-term study of these subjects, all of whom had clinical evidence of normal body iron stores. Because of the risk of neutropenia and other adverse effects with higher doses or prolonged use of the chelator, additional trials of deferiprone as a sole anti-malarial agent would not seem to be justified. In contrast, further efforts are needed to develop other orally active iron-chelating agents specifically for their anti-malarial action.

Administration, Oral↗
PubMed1997

Accumulation of p16INK4a in mouse fibroblasts as a function of replicative senescence and not of retinoblastoma gene status.

Viral transformation of mouse and human fibroblasts has very different effects on the composition of cyclin-dependent kinase (Cdk) complexes. In human cells transformed by the large T-antigen of simian virus 40 (SV40 T-Ag) and human tumour cell lines that lack a functional retinoblastoma gene product (pRb) no cyclin D1-Cdk4 complexes can be detected because all the available Cdk4 is associated with the Cdk-inhibitor p16INK4a. In contrast, SV40-transformed mouse cells and fibroblasts from Rh1-nullizygous mouse embryos contain normal levels of cyclin D1-Cdk4 complexes. To investigate this species difference, we have compared the biochemical properties and expression of mouse p16INK4a with that of its human counterpart. There is a marked increase in p16 RNA and protein levels as primary embryo fibroblasts approach their finite lifespan in culture, but mouse p16 expression does not appear to be influenced by the status of pRb. Transformed or spontaneously immortalized mouse cells therefore do not achieve the very high levels of p16 characteristic of pRb-negative human cell lines. We suggest that these differences may be related to the different frequencies with which mouse and human cells can be immortalized in culture.

3T3 Cells↗
PubMed1997

Raf-induced proliferation or cell cycle arrest is determined by the level of Raf activity with arrest mediated by p21Cip1.

The Raf family of protein kinases display differences in their abilities to promote the entry of quiescent NIH 3T3 cells into the S phase of the cell cycle. Although conditional activation of deltaA-Raf:ER promoted cell cycle progression, activation of deltaRaf-1:ER and deltaB-Raf:ER elicited a G1 arrest that was not overcome by exogenously added growth factors. Activation of all three deltaRaf:ER kinases led to elevated expression of cyclin D1 and cyclin E and reduced expression of p27Kip1. However, activation of deltaB-Raf:ER and deltaRaf-1:ER induced the expression of p21Cip1, whereas activation of deltaA-Raf:ER did not. A catalytically potentiated form of deltaA-Raf:ER, generated by point mutation, strongly induced p21Cip1 expression and elicited cell cycle arrest similarly to deltaB-Raf:ER and deltaRaf-1:ER. These data suggested that the strength and duration of signaling by Raf kinases might influence the biological outcome of activation of this pathway. By titration of deltaB-Raf:ER activity we demonstrated that low levels of Raf activity led to activation of cyclin D1-cdk4 and cyclin E-cdk2 complexes and to cell cycle progression whereas higher Raf activity elicited cell cycle arrest correlating with p21Cip1 induction and inhibition of cyclin-cdk activity. Using green fluorescent protein-tagged forms of deltaRaf-1:ER in primary mouse embryo fibroblasts (MEFs) we demonstrated that p21Cip1 was induced by Raf in a p53-independent manner, leading to cell cycle arrest. By contrast, activation of Raf in p21Cip1(-/-) MEFs led to a robust mitogenic response that was similar to that observed in response to platelet-derived growth factor. These data indicate that, depending on the level of kinase activity, Raf can elicit either cell cycle progression or cell cycle arrest in mouse fibroblasts. The ability of Raf to elicit cell cycle arrest is strongly associated with its ability to induce the expression of the cyclin-dependent kinase inhibitor p21Cip1 in a manner that bears analogy to alpha-factor arrest in Saccharomyces cerevisiae. These data are consistent with a role for Raf kinases in both proliferation and differentiation of mammalian cells.

3T3 Cells↗
PubMed1997

Regulation and function of the cyclin-dependent kinase inhibitor p16CDKN2.

Many human tumours show perturbations of a pathway that includes the D-cyclins, their associated cyclin-dependent kinases, and specific kinase inhibitors. The focal point of this pathway is the product of the retinoblastoma tumour suppressor gene, pRb, which imposes a block on G1 phase progression. Thus, the major role of the cyclin D-dependent kinases is to overcome this block by initiating the phosphorylation of pRb. Excessive activity of this pathway is likely to lead to excessive cell proliferation. Conversely, accumulation of the inhibitors is associated with the cessation of cell division.

Carrier Proteins↗
PubMed1996

A study of the brightness of laryngoscope light.

We have measured the brightness (luminance) of the light spot produced by 105 Macintosh 3 laryngoscope blades (33 bulb, 72 fibrelight) using a Hagner photometer. An estimate of the minimum luminance required for laryngoscopy (circa. 100 cd.m-2), was determined using a laryngoscope adapted to provide a variable light output. Five (15%) of bulb blades and 24 (33%) of the fibrelight blades failed to meet this minimum level. A new bulb blade produced brighter lighting conditions (maximum 700 cd.m-2) than a new fibrelight blade (max. 500 cd.m-2). In total, 61 (84%) of the fibrelight blades and three (9%) of the bulb blades were found to provide a light spot that encompassed areas of luminance below 30 cd.m-2, which is a level for comfortable reading. The light spot from a mains-powered fibreoptic bronchoscope was found to be four times brighter (2000 cd.m-2) than a new battery-powered fibrelight laryngoscope.

Bronchoscopes↗
PubMed1996

Regulation of p16CDKN2 expression and its implications for cell immortalization and senescence.

p16CDKN2 specifically binds to and inhibits the cyclin-dependent kinases CDK4 and CDK6, which function as regulators of cell cycle progression in G1 by contributing to the phosphorylation of the retinoblastoma protein (pRB). Human cell lines lacking functional pRB contain high levels of p16 RNA and protein, suggesting a negative feedback loop by which pRB might regulate p16 expression in late G1. By a combination of nuclear run-on assays and promoter analyses in human fibroblasts expressing a temperature-sensitive simian virus 40 T antigen, we show that p16 transcription is affected by the status of pRB and define a region in the p16 promoter that is required for this response. However, the effect is not sufficient to account for the differences in p16 RNA levels between pRB-positive and -negative cells. Moreover, p16 RNA is extremely stable, and the levels do not change appreciably during the cell cycle. Primary human fibroblasts express very low levels of p16, but the RNA and protein accumulate in late-passage, senescent cells. The apparent overexpression of p16 in pRB-negative cell lines is therefore caused by at least two factors: loss of repression by pRB and an increase in the number of population doublings.

Base Sequence↗
PubMed1996

Temperature-sensitive mutants of p16CDKN2 associated with familial melanoma.

Altered expression or function of the p16CDKN2 tumor suppressor gene on chromosome 9p21 occurs in a wide range of human tumors, and mutations in the gene have been shown to segregate with familial predisposition to malignant melanoma. We have used a variety of assays to examine the functional properties of tumor-associated alleles, including eight premature termination mutants, eight missense mutants, and three isoforms of p16 initiated at different amino-terminal methionine codons. The amino- and carboxy-terminal domains of the protein, outside the ankyrin-like repeats, appeared to be dispensable, but the majority of the premature termination mutations led to loss of function. Of the missense mutations tested, four displayed clear loss of function whereas two behaved like the wild type under all conditions tested. The remaining two mutations, a G-to-W mutation at position 101 (Gl01W) and V126D, both of which are associated with familial melanoma, were found to be temperature sensitive for binding to Cdk4 and Cdk6 in vitro, for inhibiting cyclin D1-Cdk4 in a reconstituted pRb-kinase assay, and for increasing the proportion of G1-phase cells following transfection. These findings clarify previous disparities and argue strongly that p16CDKN2 is a bona fide tumor suppressor associated with familial melanoma.

Bone Neoplasms↗
PubMed1996

Pregnancy following a single lung transplant.

Successful pregnancy in a single lung transplant recipient has not been reported previously. The long term effect of pregnancy on graft function and management of deteriorating pulmonary function is not defined. This case describes the management, outcome, and problems encountered when a single lung transplant recipient developed a progressive deterioration in pulmonary function during pregnancy, attributed to accelerated obliterative bronchiolitis.

Adult↗
PubMed1996

Type of mutation in the neurofibromatosis type 2 gene (NF2) frequently determines severity of disease.

The gene predisposing to neurofibromatosis type 2 (NF2) on human chromosome 22 has revealed a wide variety of different mutations in NF2 individuals. These patients display a marked variability in clinical presentation, ranging from very severe disease with numerous tumors at a young age to a relatively mild condition much later in life. To investigate whether this phenotypic heterogeneity is determined by the type of mutation in NF2, we have collected clinical information on 111 NF2 cases from 73 different families on whom we have performed mutation screening in this gene. Sixty-seven individuals (56.2%) from 41 of these kindreds revealed 36 different putative disease-causing mutations. These include 26 proposed protein-truncating alterations (frameshift deletions/insertions and nonsense mutations), 6 splice-site mutations, 2 missense mutations, 1 base substitution in the 3' UTR of the NF2 cDNA, and a single 3-bp in-frame insertion. Seventeen of these mutations are novel, whereas the remaining 19 have been described previously in other NF2 individuals or sporadic tumors. When individuals harboring protein-truncating mutations are compared with cases with single codon alterations, a significant correlation (P < .001) with clinical outcome is observed. Twenty-four of 28 patients with mutations that cause premature truncation of the NF2 protein, schwannomin, present with severe phenotypes. In contrast, all 16 cases from three families with mutations that affect only a single amino acid have mild NF2. These data provide conclusive evidence that a phenotype/genotype correlation exists for certain NF2 mutations.

Adolescent↗
PubMed1995

Deletion and altered regulation of p16INK4a and p15INK4b in undifferentiated mouse skin tumors.

p16INK4a and p15INK4b are cell cycle regulators that specifically bind to and inhibit the cyclin D-dependent kinases, cdk4 and cdk6. Because these genes undergo frequent deletions and/or mutations in various human cancers, we examined the status and expression of the cognate mouse cdk inhibitors in a panel of 29 cell lines, as well as in 12 primary tumors, representing different stages of mouse skin carcinogenesis. Deletion of p16INK4a and/or p15INK4b was seen in 8 of 10 cell lines derived from spindle carcinomas, the most advanced stage of skin carcinogenesis. Five showed deletion of both genes, and three had independent deletions of p16INK4a or p15INK4b, but in those retaining p16INK4a, expression of the protein was not detected. By contrast, none of 19 more differentiated squamous cell lines exhibited such deletions. In several cases, primary tumor DNA was available, and two spindle tumors showed the same deletion pattern as observed in the corresponding cell lines. In apparent contrast, comparison of two clonally related squamous and spindle cell lines derived from a single carcinoma showed unusually high levels of p16INK4a and p15INK4b only in the invasive spindle cells. Therefore, deletion or altered regulation of p16INK4a and p15INK4b occur concomitantly with the loss of differentiation associated with the late spindle stage of tumor progression in mouse skin.

Animals↗