Search PubMed⌕ Search

Biomedical subjects

P Shaw

Publications and source records attributed to P Shaw.

At least 19 recordsLinked to original sources
PubMed2001

The Ph1 locus is needed to ensure specific somatic and meiotic centromere association.

The correct pairing and segregation of chromosomes during meiosis is essential for genetic stability and subsequent fertility. This is more difficult to achieve in polyploid species, such as wheat, because they possess more than one diploid set of similar chromosomes. In wheat, the Ph1 locus ensures correct homologue pairing and recombination. Although clustering of telomeres into a bouquet early in meiosis has been suggested to facilitate homologue pairing, centromeres associate in pairs in polyploid cereals early during floral development. We can now extend this observation to root development. Here we show that the Ph1 locus acts both meiotically and somatically by reducing non-homologous centromere associations. This has the effect of promoting true homologous association when centromeres are induced to associate. In fact, non-homologously associated centromeres separate at the beginning of meiosis in the presence, but not the absence, of Ph1. This permits the correction of homologue association during the telomere-bouquet stage in meiosis. We conclude that the Ph1 locus is not responsible for the induction of centromere association, but rather for its specificity.

Binding Sites↗
PubMed2001

KOJAK encodes a cellulose synthase-like protein required for root hair cell morphogenesis in Arabidopsis.

The cell wall is an important determinant of plant cell form. Here we define a class of Arabidopsis root hair mutants with defective cell walls. Plants homozygous for kojak (kjk) mutations initiate root hairs that rupture at their tip soon after initiation. The KJK gene was isolated by positional cloning, and its identity was confirmed by the molecular complementation of the Kjk(-) phenotype and the sequence of three kjk mutant alleles. KOJAK encodes a cellulose synthase-like protein, AtCSLD3. KOJAK/AtCSLD3 is the first member of this subfamily of proteins to be shown to have a function in cell growth. Subcellular localization of the KOJAK/AtCSLD3 protein using a GFP fusion shows that KOJAK/AtCSLD3 is located on the endoplasmic reticulum, indicating that KOJAK/AtCSLD3 is required for the synthesis of a noncellulosic wall polysaccharide. Consistent with the cell specific defect in the roots of kjk mutants, KOJAK/AtCSDL3 is preferentially expressed in hair cells of the epidermis. The Kjk(-) phenotype and the pattern of KOJAK/AtCSLD3 expression suggest that this gene acts early in the process of root hair outgrowth. These results suggest that KOJAK/AtCSLD3 is involved in the biosynthesis of beta-glucan-containing polysaccharides that are required during root hair elongation.

Amino Acid Sequence↗
PubMed2001

Changes in the demographics and perioperative care of stage IA(2)/IB(1) cervical cancer over the past 16 years.

OBJECTIVES: The aim of this study was to determine whether there have been any significant changes in the demographics and perioperative care of FIGO stage IA(2)/IB(1) cervical cancer over the past 16 years and, if so, to quantify them. METHODS: Since July 1984, all patients with FIGO stage IA(2)/IB(1) cervical cancer undergoing radical surgery by members of our division have been entered into a prospective database. Selection for surgery has been unchanged over the past 16 years. Since March 1994 and November 1996, one surgeon has performed radical vaginal trachelectomy and laparoscopic assisted radical vaginal hysterectomy, respectively. Statistical analysis used Spearman's correlation analysis, the proportional hazards regression model of Cox, and the Mantel-Hanzel test was performed. Due to the number of statistical analyses, statistical significance was defined as P < 0.01. RESULTS: Eight hundred sixty-four patients have undergone radical surgery (784 radical hysterectomy, 42 radical vaginal trachelectomy, 32 radical vaginal hysterectomy, 6 radical abdominal trachelectomy) for FIGO stage IA(2)/IB(1) carcinoma of the cervix by members of our division since 1984. There have been no changes in the median age (40 years), tumor size (2.0 cm), incidence of capillary lymphatic space involvement (47%), or positive pelvic lymph nodes (6%) over the past 16 years. The median Quetelet index (24.6), depth of tumor invasion (squamous cell carcinomas only) (6.0 mm), and proportion of patients with comorbid conditions (17%) have increased over time (P = 0.001, P = 0.003, and P < 0.001, respectively). Pathologically, there has been an increase in the proportion of adenocarcinomas (28%) and a decrease in the proportion of grade 3 tumors (28%) (P < 0.001 and P < 0.001, respectively). The median operating time (2.8 h), hospital stay (7.0 days), blood loss (600 cc), allogeneic blood transfusion (23%), postoperative infections (13%), and noninfectious complications (6%) have all decreased (P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, and P = 0.002, respectively). There has been no change in the incidence of positive surgical margins (3%), adjuvant radiation (13%), or recurrence-free survival (2 and 5 years, 94 and 90%, respectively) after a median follow-up of 45 months. CONCLUSION: Despite no substantive changes in the selection criteria for surgery and the small time interval studied (16 years), almost all indices of operative and postoperative morbidity analyzed have decreased significantly. These changes have occurred without an increase in the use of adjuvant radiation or decrease in recurrence-free survival. Although little progress has been made in the cure rates associated with surgical management of FIGO stage IA(2)/IB(1) cervical cancer during this time interval, it appears that the morbidity of surgery has decreased.

Adenocarcinoma↗
PubMed2001

A novel highly informative polyA microsatellite on the telomeric side of the INK4a/ARF locus.

The INK4a/ARF locus encodes two cell cycle-regulatory proteins, p16(INK4a)and p14(ARF). Inactivation of the p16(INK4a)(MTS1) tumor suppressor gene by mutations, promoter methylation or gene deletions is a common event in the development of many different human tumors. The present report describes a novel polyA mononucleotide repeat situated 7.2 kb on the telomeric side of the INK4a/ARF locus. This highly polymorphic microsatellite marker (heterozygote frequency: 0.78) proved to be efficient for p16 allele loss and microsatellite instability analyses in human colon cancer.

Adenocarcinoma↗
PubMed2001

Complex variant t(4;11) characterized by fluorescence in situ hybridization in infant acute lymphoblastic leukemia.

A 6-month-old girl was diagnosed with acute lymphoblastic leukemia (ALL). Chromosome analysis of bone marrow aspirate showed 46,XX,t(4;11)(q21;q23) with an atypical appearance of the 11p on the der(11) chromosome. FISH studies to fully characterize the translocation utilised 8 probes: whole chromosome painting probes for chromosome 11 and chromosome 4; separate chromosome 11 short arm and long arm paints; specific subtelomere probes from 11p, 11q, and 4q; MLL gene probe. Taken together, the results indicated a two-step abnormality: an initial standard t(4;11)(q21;q23), followed by another t(4;11)--this time, between the two derivative chromosomes. The MLL gene was split by the first translocation and its position altered by the second.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Methylation silencing and mutations of the p14ARF and p16INK4a genes in colon cancer.

The INK4a-ARF locus encodes two tumor suppressor proteins involved in cell-cycle regulation, p16INK4a and p14ARF, whose functions are inactivated in many human cancers. The aim of this study was to evaluate p14ARF and p16INK4a gene inactivation and its association with some clinocopathological parameters in colon cancer. The mutational and methylation status of the p14ARF and p16INK4a genes was analyzed in 60 primary colon carcinomas and 8 colon cancer cell lines. We have identified the first two reported mutations affecting exon 1beta of p14ARF in the HCT116 cell line and in one of the primary colon carcinomas. Both mutations occur within the N-terminal region of p14ARF, documented as important for nucleolar localization and interaction with Mdm2. Tumor-specific methylation of the p14ARF and p16INK4a genes was found in 33% and 32% of primary colon carcinomas, respectively. Methylation of the p14ARF was inversely correlated with p53 overexpression (p = 0.02). p14ARF and p16INK4a gene methylation was significantly more frequent in right-sided than in left-sided tumors (p = 0.02). Methylation of the p14ARF gene occurred more frequently in well-differentiated adenocarcinomas (p = 0.005), whereas the p16INK4a gene was more often methylated in poorly differentiated adenocarcinomas (p = 0.002). The present results underline the role of p14ARF and p16INK4a gene inactivation in the development of colon carcinoma. They suggest that the methylation profile of specific genes, in particular p14ARF and p16INK4a, might be related to biologically distinct subsets of colon carcinomas and possibly to different tumorigenic pathways.

Adaptor Proteins, Signal Transducing↗
PubMed2001

River basin-related genetic structuring in an endangered fish species, Chondrostoma lusitanicum, based on mtDNA sequencing and RFLP analysis.

Chondrostoma lusitanicum is a Portuguese endemic cyprinid with a restricted distribution and reduced numbers in some basins, justifying its status as a threatened species. We examined genetic population structure using samples from throughout its geographical range in Portugal, using sequencing of b cytochrome and restriction fragment length polymorphism analysis of the NADH subunits 5 and 6. There was reduced within-population genetic variability but considerable among-population differentiation, particularly marked between both the Mira and Arade basins in the extreme south and other populations. These results confirm phylogeographic relationships suggested by previous fragmentary allozyme studies for C. lusitanicum, and are in accordance with allozyme and mitochondrial DNA data on phylogeography of coexisting cyprinid species of the genus Leuciscus. The levels of genetic divergence revealed by sequence and RFLP data showed strongly concordant patterns: geographical genetic structuring, with the definition of three distinct groups, was observed. The high values of nucleotide divergence and pairwise sequence divergence of the Mira and Arade groups, when compared with all other samples, support a distinct taxonomic status probably at the species level. Results are also discussed in relation to conservation of this highly fragmented species, in terms of Evolutionary Significant Units and Management Units.

Analysis of Variance↗
PubMed2001

Increasing incidence of midterm and long-term complications after endovascular graft repair of abdominal aortic aneurysms: a note of caution based on a 9-year experience.

OBJECTIVE: To analyze the late complications after endovascular graft repair of elective abdominal aortic aneurysms (AAAs) at the authors' institution since November 1992. SUMMARY BACKGROUND DATA: Recently, the use of endovascular grafts for the treatment of AAAs has increased dramatically. However, there is little midterm or long-term proof of their efficacy. METHODS: During the past 9 years, 239 endovascular graft repairs were performed for nonruptured AAAs, many (86%) in high-risk patients or in those with complex anatomy. The grafts used were Montefiore (n = 97), Ancure/EVT (n = 14), Vanguard (n = 16), Talent (n = 47), Excluder (n = 20), AneuRx (n = 29), and Zenith (n = 16). All but the AneuRx and Ancure repairs were performed as part of a U.S. phase 1 or phase 2 clinical trial under a Food and Drug Administration investigational device exemption. Procedural outcomes and follow-up results were prospectively recorded. RESULTS: The major complication and death rates within 30 days of endovascular graft repair were 17.6% and 8.5%, respectively. The technical success rate with complete AAA exclusion was 88.7%. During follow-up to 75 months (mean +/- standard deviation, 15.7 +/- 6.3 months), 53 patients (22%) died of unrelated causes. Two AAAs treated with endovascular grafts ruptured and were surgically repaired, with one death. Other late complications included type 1 endoleak (n = 7), aortoduodenal fistula (n = 2), graft thrombosis/stenosis (n = 7), limb separation or fabric tear with a subsequent type 3 endoleak (n = 1), and a persistent type 2 endoleak (n = 13). Secondary intervention or surgery was required in 23 patients (10%). These included deployment of a second graft (n = 4), open AAA repair (n = 5), coil embolization (n = 6), extraanatomic bypass (n = 4), and stent placement (n = 3). CONCLUSION: With longer follow-up, complications occurred with increasing frequency. Although most could be managed with some form of endovascular reintervention, some complications resulted in a high death rate. Although endovascular graft repair is less invasive and sometimes effective in the long term, it is often not a definitive procedure. These findings mandate long-term surveillance and prospective studies to prove the effectiveness of endovascular graft repair.

Aged↗
PubMed2001

Subacute pulmonary granulomatous schistosomiasis: high resolution CT appearances--another cause of the halo sign.

A case of probable acute granulomatous pulmonary schistosomiasis is described with multiple focal opacities on chest radiography and widespread, but predominantly peribronchovascular, nodules with ground-glass halos on high resolution CT (HRCT). The HRCT appearances in early schistosomiasis have not been described previously. Although the features are not diagnostic and may be seen in other conditions, in the appropriate clinical context they may suggest pulmonary involvement in schistosomiasis. The features of pulmonary schistosomiasis in the different stages of infection are discussed. Pulmonary involvement should be suspected in patients with even minor respiratory symptoms when there is a history of exposure to fresh water in endemic areas.

Acute Disease↗
PubMed2001

Involvement of connexin 43 in meiotic maturation of bovine oocytes.

In ovarian follicles, cumulus cells provide the oocyte with small molecules that permit growth and control maturation. These nutrients reach the germinal cell through gap junction channels, which are present between the cumulus cells and the oocyte, and between the cumulus cells. In this study the involvement of intercellular communication mediated by gap junction channels on oocyte maturation of in vitro cultured bovine cumulus-oocyte complexes (COCs) was investigated. The stages of oocyte maturation were determined by Hoechst 33342 staining, which showed that 90% of COCs placed in the maturation medium for 24 h progress to the metaphase II stage. Bovine COC gap junction communication was disrupted initially using n-alkanols, which inhibit any passage through gap junctions. In the presence of 1-heptanol (3 mmol l(-1)) or octanol (3.0 mmol l(-1) and 0.3 mmol l(-1)), only 29% of the COCs reached metaphase II. Removal of the uncoupling agent was associated with restoration of oocyte maturation, indicating that treatment with n-alkanols was neither cytotoxic nor irreversible. Concentrations of connexin 43 (Cx43), the major gap junction protein expressed in the COCs, were decreased specifically using a recombinant adenovirus expressing the antisense Cx43 cDNA (Ad-asCx43). The efficacy of adenoviral infection was > 95% in cumulus cells evaluated after infection with recombinant adenoviruses expressing the green fluorescence protein. RT-PCR performed on total RNA isolated from Ad-asCx43-infected COCs showed that the rat Cx43 cDNA was transcribed. Western blot analysis revealed a three-fold decrease in Cx43 expression in COCs expressing the antisense RNA for Cx43. Injection of cumulus cells with Lucifer yellow demonstrated further that the resulting lower amount of Cx43 in infected COCs is associated with a two-fold decrease in the extent of coupling between cumulus cells. In addition, oocyte maturation was decreased by 50% in the infected COC cultures. These results indicate that Cx43-mediated communication between cumulus cells plays a crucial role in maturation of bovine oocytes.

Adenoviridae↗
PubMed2001

Native and artificial reticuloplasmins co-accumulate in distinct domains of the endoplasmic reticulum and in post-endoplasmic reticulum compartments.

We compared the subcellular distribution of native and artificial reticuloplasmins in endosperm, callus, and leaf tissues of transgenic rice (Oryza sativa) to determine the distribution of these proteins among endoplasmic reticulum (ER) and post-ER compartments. The native reticuloplasmin was calreticulin. The artificial reticuloplasmin was a recombinant single-chain antibody (scFv), expressed with an N-terminal signal peptide and the C-terminal KDEL sequence for retrieval to the ER (scFvT84.66-KDEL). We found that both molecules were distributed in the same manner. In endosperm, each accumulated in ER-derived prolamine protein bodies, but also in glutelin protein storage vacuoles, even though glutelins are known to pass through the Golgi apparatus en route to these organelles. This finding may suggest that similar mechanisms are involved in the sorting of reticuloplasmins and rice seed storage proteins. However, the presence of reticuloplasmins in protein storage vacuoles could also be due to simple dispersal into these compartments during protein storage vacuole biogenesis, before glutelin deposition. In callus and leaf mesophyll cells, both reticuloplasmins accumulated in ribosome-coated vesicles probably derived directly from the rough ER.

Calcium-Binding Proteins↗
PubMed2000

Physical map of 17p13 and the genes adjacent to p53.

Genetic lesions in the p53 tumor suppressor gene are the most frequently observed alterations in human cancers. Typically in tumors, one allele of the p53 gene is initially mutated, followed by deletion of the remaining wildtype allele. In human colon cancer, for example, approximately 70% of late stage tumors are hemizygous mutant p53. Since the precise gene environment surrounding the p53 gene is not known, the neighboring genes concomitantly lost with wildtype p53 deletion remain undetermined. A restriction enzyme map and clone array of 1.1 Mb surrounding the p53 gene were constructed using a combination of YAC, BAC, NotI linking, and NotI jumping clones. The resulting physical map and clone array include approximately 400 kb telomeric and 700 kb centromeric to the p53 gene. Sequence determination and analysis adjacent to NotI and AscI sites, indicative of CpG islands, allowed the rapid identification of numerous genes within the cloned region. Twenty-seven transcription units were identified, including 18 characterized genes. Limited analysis of primary human colon tumors, hemizygous for the p53 gene, indicates loss of the entire 1.1-Mb region upon deletion of wildtype p53.

Chromosomes, Artificial, Yeast↗
PubMed2000

The nucleus: a highly organized but dynamic structure.

The nucleus in plants and animals is a highly structured organelle containing several well-defined subregions or suborganelles. These include the nucleolus, interphase chromosome territories and coiled bodies. We have visualized transcription sites in plants at both light- and electron-microscopy level by the incorporation of BrUTP. In the nucleolus many dispersed foci are revealed within the dense fibrillar component, each of which probably corresponds to a single gene copy. In the nucleoplasm there are also many dispersed foci of transcription, but not enough to correspond to one site per transcribed gene. We have shown that in wheat, and probably many other plant species, interphase chromosome territories are organized in a very regular way, with all the chromosomes in the Rabl configuration, all the centromeres clustered at the nuclear membrane and all the telomeres located at the nuclear membrane on the opposite side of the nucleus. However, despite this regular, polarized structure, there is no sign of polarization of transcription sites, or of any preferred location for them with respect to chromosome territorial boundaries. The nucleus is also highly dynamic. As an example, we have shown by the use of a green fluorescent protein fusion to the spliceosomal protein U2B" that coiled bodies move and coalesce within the nucleus, and may act as transport structures within the nucleus and nucleolus.

Autoantigens↗
PubMed2000

Widely separated multiple transgene integration sites in wheat chromosomes are brought together at interphase.

We have investigated the organization of transgenes delivered by particle bombardment into the wheat genome, combining conventional molecular analysis with fluorescence in situ hybridization (FISH) and three-dimensional confocal microscopy. We selected a representative population of transformed wheat lines and carried out molecular and expression analysis. FISH on metaphase chromosomes showed that transgene integration sites were often separated by considerable lengths of genomic DNA (>1 Mbp), or could even be on opposite chromosome arms. Plants showing multiple integration sites on a single chromosome were selected for three-dimensional confocal analysis of interphase nuclei in root and embryo tissue sections. Confocal microscopy revealed that these sites lay in close physical proximity in the interphase nuclei. Our results clearly show that multiple transgenes physically separated by large intervening regions of endogenous DNA at metaphase can be brought together at interphase. This may reflect the original physical organization of the endogenous DNA at the moment of transformation, with DNA strand breaks introduced into several co-localized DNA loops by the intruding gold particles. Alternatively, the transgenes may be brought together after transformation, either by an ectopic homologous pairing mechanism, or by recruitment to a common transcription site.

Chromosome Mapping↗