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Biomedical subjects

J R Jenkins

Publications and source records attributed to J R Jenkins.

At least 37 records · Page 2Linked to original sources
PubMed1996

Cost-effective evaluation and management of the acute abdomen.

1. Managed care gate-keeper financial responsibility must be balanced with specialist diagnostic and therapeutic responsibility to maximize cost effectiveness and quality of medical service. 2. Cost in health care is closely tied to length of stay and operating room time; extremes of patient age are associated with increased costs. 3. Through years of training and subsequent experience, surgeons are best qualified to direct work-up of patients with an acute abdomen, especially when the work-up requires costly imaging (e.g., CT scan, ultrasonography, angiography). 4. Cost is increased when the surgeon is not involved early in cases of acute abdomen. 5. Surgeons must be willing to enter the evaluation phase of the patient with an acute abdomen patient early and follow during the observation period to best reduce unnecessary laboratory work or tests. 6. Health care teams willing to implement pathways and then document the effect such pathways exert will be most successful in assessing new technologies' cost effectiveness.

Abdomen, Acute↗
PubMed1996

Pavlovian conditioning of agonistic behavior in male threespine stickleback (Gasterosteus aculeatus).

The red coloration of male stickleback (Gasterosteus aculeatus) possesses signal value in male-male interactions. Therefore, it was predicted that males would learn to associate a red signal more readily than a green signal with a conspecific rival in a Pavlovian conditioning experiment. Males were presented red and green signal lights where one signal was always paired with presentation of a rival (excitatory conditioned stimulus, CS+) and one signal was never paired with presentation of a rival (nonreinforced stimulus, CS-). Males learned the task rapidly, showing conditioned approach and zigzag responses, but CS+ vs. CS- differentiation persisted, even after a prolonged extinction period. In addition, there were no differences in learning rates between fish trained to the red signal as the CS+ and fish trained to the green signal as the CS+. The results suggest that, although males may rapidly learn about rivals, they are not predisposed to associated red (over green) with the appearance of a rival under the conditions of this experiment. Because males must establish and maintain territories in order to nest and mate, learning about neighboring rivals may be an adaptive mechanism by which males more effectively defend their territories and thereby increase their reproductive fitness.

Agonistic Behavior↗
PubMed1995

Transcriptional activation plays a role in the induction of apoptosis by transiently transfected wild-type p53.

The p53 tumor suppressor gene has been implicated in the induction of apoptosis in several cell systems. We have recently reported than transiently-transfected wt p53 is capable of inducing apoptosis in certain transformed cell lines. We demonstrated by quantitative analysis using flow cytometry that apoptosis was restricted to the population expressing wt, but not mutant, p53. In the present study we use this model system to analyse the functional domain of p53 in the induction of apoptosis. Several constructs expressing mutations or deletions in the C-terminal oligomerization domain, the N-terminal transactivation domain or the central DNA-binding domain were introduced into HeLa cells, and the ability of the expressed proteins to induce apoptosis was evaluated. All the functional domains were found to be necessary for the induction of apoptosis. In addition, cycloheximide and actinomycin D inhibited wt p53-induced apoptosis. We therefore conclude that p53 acts in this cell system, at least in part, as a transcriptional activator in the induction of apoptosis.

Apoptosis↗
PubMed1995

Oligomerisation of full length p53 contributes to the interaction with mdm2 but not HPV E6.

The tumour suppressor protein p53 normally functions as a tetramer in a defined conformational state. Mutations within p53 which contribute to cancer development frequently induce a conformational shift in the protein which correlates with loss of wild type growth suppressor functions. Both the cell encoded mdm2 protein and the human papillomavirus oncoprotein E6 can regulate p53 function and we have examined the interaction of these proteins with p53. The E6/p53 association is sensitive to conformational alterations in the p53 protein, although oligomerisation is not necessary for this interaction to occur. Analysis of C-terminal p53 truncations has indicated that the region between residues 327 and 347 may play a role in E6 binding. Since monomeric forms of p53 retain transcriptional and transformation suppressor activities, our results indicate that E6 targets p53 proteins which retain these wild type functions. Conversely, the interaction of p53 with mdm2 is not dependent on the conformation of the p53 protein but is significantly impaired by loss of quaternary structure. It is possible that mdm2 plays a role in mediating activities of p53 which, unlike transcriptional activation, depend on oligomerisation.

Base Sequence↗
PubMed1994

The relationship between serum p53 autoantibodies and characteristics of human breast cancer.

Sera from 182 newly diagnosed breast cancer patients were assayed for antibodies to p53 using an enzyme-linked immunosorbent assay (ELISA) method, and antibodies were detected in 48 (26%) compared with 1 out of 76 (1.3%) normal control volunteers (P = 0.0001). In breast cancer patients, autoantibodies were found in all stages of disease progression: carcinoma in situ, primary invasive breast cancer and in metastatic disease. In the subset of patients in whom sequential sera were assessed over a 6 month period, changes in the p53 antibody titres were observed. The presence of antibodies to p53 correlated positively with high histological grade (P = 0.0012) and a history of second primary cancer (six positive out of eight cases). The incidence of autoantibodies was lower in those patients with a first-degree relative with breast cancer (P = 0.046). Out of 68 patients, there was a significant correlation between positive p53 autoantibody status and the detection of p53 protein in the tissue sections by immunocytochemistry (P = 0.002). In the seronegative patients, positive p53 tumour staining was strongly associated with a family history of breast cancer (P = 0.009). The p53 protein overexpressed in heritable breast cancers may therefore be less immunogenic. The presence of p53 autoantibodies provides important additional information to immunochemistry and may identify patients with aggressive histological types of breast cancer.

Adult↗
PubMed1994

Human p53 directs DNA strand reassociation and is photolabelled by 8-azido ATP.

p53 is the most frequent known target for mutation in human cancer. Evidence suggests that p53 protein may be involved variously in transcription and cell cycle control, in DNA replication and in G1 checkpoint control following the cellular response to radiation induced DNA damage. p53 blocks DNA replication of the small DNA tumour virus, simian virus 40, by inhibiting unwinding of the viral origin of replication by the DNA helicase activity of the virally encoded large T antigen protein. Here we report the novel observation that human p53 protein can bind ATP and exhibits an intrinsic ATP stimulated DNA strand reassociation activity. Both activities map to the carboxyl terminal 128 amino acids of p53. Thus, in addition to any role in transcription, our results indicate that p53 is potentially capable of inhibiting mammalian replicative DNA synthesis by blocking the DNA strand separation step during replication origin recruitment. However, the ability of p53 to modulate the topological relationship between complementary nucleotide strands is also compatible with a direct role for p53 in other aspects of DNA synthesis, recombination or repair.

Adenosine Triphosphate↗
PubMed1993

Putative dehydrogenase tms1 suppresses growth arrest induced by a p53 tumour mutant in fission yeast.

Expression of a human tumour-derived p53 His 273 cDNA induced growth arrest in fission yeast Schizosaccharomyces pombe. Based on the p53-induced growth arrest, we cloned an extragenic suppressor, termed tms1, by complementation. The open reading frame of the tms1 gene corresponded to a protein of 347 amino acids with a calculated mass of 37380 Da. The transcriptional start site of the tms1 gene was mapped and, in addition, the corresponding cDNA was isolated and expressed in Escherichia coli. Recombinant tms1 protein served as an antigen to produce specific polyclonal antibodies to aid identification of the tms1-gene-product in total yeast lysates. Comparison of the deduced amino acid sequence of tms1 with available databases revealed significant similarity to dehydrogenases, suggesting that the tms1 protein itself might possess dehydrogenase activity.

Amino Acid Sequence↗
PubMed1993

Human cells express two differentially spliced forms of topoisomerase II beta mRNA.

Screening of a human B-cell cDNA library with a topoisomerase II beta gene-specific probe revealed the presence of two distinct forms of topoisomerase II beta cDNA. One form (designated topoisomerase II beta-1), representing the majority of the clones, would encode the topoisomerase II beta amino acid sequence reported recently [Jenkins, J.R. et al. (1992) Nucleic Acids Res., 20, 5587-5592]. The second form (designated topoisomerase II beta-2) would encode a protein containing an additional 5 amino acids inserted after Valine-23 of the topoisomerase II beta-1 protein sequence. The topoisomerase II beta-1 and beta-2 mRNAs were both widely expressed in human cell lines and tissues. Topoisomerase II beta-2 mRNA was expressed at a lower level than that of the beta-1 form, but the relative expression of the two forms varied in different cell types. Analysis of genomic DNA clones revealed that the two forms of topoisomerase II beta mRNA arose via differential splicing. These data indicate that in addition to the closely related topoisomerase II alpha and beta isozymes, there are two forms of topoisomerase II beta mRNA widely expressed in human cells.

Amino Acid Sequence↗
PubMed1993

The transforming and suppressor functions of p53 alleles: effects of mutations that disrupt phosphorylation, oligomerization and nuclear translocation.

Mutant p53 alleles that have a recessive phenotype in human tumors can, in cooperation with an activated H-ras gene, transform rat embryo fibroblasts (REFs). Mutant p53 proteins differ from wild type, and from each other in conformation, localization and transforming potential. Missense mutations in codons 143, 175 and 275 confer strong transforming potential. A serine 135 p53 mutant has an intermediate transforming potential, while the histidine codon 273 allele transforms weakly, if at all. In contrast to the wild type p53 gene, mutant p53 alleles with strong transforming ability cannot suppress the transformation of REFs by other oncogenes. The His273 allele retains partial suppressor function in this assay. The relevance of p53 oligomerization, phosphorylation and nuclear translocation to the transforming potential of mutant p53 and to wild type p53 suppressor function were examined. The inability of mutant p53 polypeptides to form homodimers correlates with loss of transforming function. Monomeric variants of wild type p53 protein, however, retain the ability to suppress focus formation. Phosphorylation of serine residues 315 and 392 is not required for the transforming function of mutant p53, nor is serine 315 required for suppressor function when these alleles are constitutively expressed in REF assays. Nuclear translocation-defective mutant and wild type p53 proteins retain transforming and suppressor function in REF assays.

Alleles↗
PubMed1993

Two approaches to reading instruction with children with disabilities: does program design make a difference?

This study examined the effects on reading achievement of variation in program design and tested the hypothesis this Distar Reading Mastery's (Engelmann & Bruner, 1988b) demonstrated effects with disadvantaged children in Project Follow Through can be generalized to children with disabilities. We compared the effects of two synthetic phonics reading programs, Direct Instruction (DI) Reading Mastery I and II and Addison Wesley's Meet the Superkids and The Superkids' Club, (Rowland, 1982a, 1982b) for 81 children in transitional kindergarten special education classes. No significant achievement differences were evident for the instructional program either at the end of the treatment year, or on follow-up testing 1 year later. However, among children who made advanced progress, the DI group showed larger reading gains.

Child↗
PubMed1993

Teaching phonological awareness to young children with learning disabilities.

This study examined the feasibility of teaching phonological manipulation skills to preschool children with disabilities. Forty-seven children, 4-6 years old, enrolled in a special education preschool, were randomly assigned to receive training in one of three categories of phonological tasks (rhyming, blending, and segmenting) or a control group. Results indicated that children were able to make significant progress in each experimental category, but that they demonstrated little or no generalization either within a category (e.g., from one type of blending task to another type of blending task) or between categories (e.g., from blending to segmenting). Although the children's level of cognitive development significantly predicted some learning outcomes, it did not appear to limit the learning of phonological tasks.

Awareness↗
PubMed1993

Human p53 binds DNA as a protein homodimer but monomeric variants retain full transcription transactivation activity.

Wild-type human p53 protein is able to self-associate and consists predominantly of homotetramers in solution. In earlier work we identified the protein sequence motifs involved in p53 quaternary structure and showed that while monomeric p53 protein retains tumour suppressor function, monomeric tumour mutant p53 lacks dominant transforming activity. In this report we use point mutated and truncated cDNA genes encoding self-association defective human p53 proteins to investigate the relationship between p53 protein quaternary structure and the associated activities of transcription transactivation and target specific DNA binding. We show that p53 binds to a target oligonucleotide as a protein homodimer and that p53 dimerisation is required for detectable DNA binding. We found no evidence for p53 tetramer: DNA complexes and we suggest that the quaternary structure status of p53 may regulate a DNA binding associated activity. Monomeric p53 proteins failed to bind DNA in these assays but exhibited increased transactivating activity. Thus, both transcription transactivation and tumour suppressor functions act independently of p53 protein self-association and DNA binding. We propose that our results validate the p53 dimerisation motif as a target for rational anticancer drug design. We predict that compounds able to block p53 dimer assembly would inhibit the dominant transforming activities of mutant p53 in tumours retaining expression of a mutant allele, while leaving intact the wild-type p53 associated activities of transcription transactivation and transformation suppression in unaffected tissue.

Base Sequence↗
PubMed1992

The E2 binding sites determine the efficiency of replication for the origin of human papillomavirus type 18.

Human papillomaviruses (HPV-s) have been shown to possess transforming and immortalizing activity for many different, mainly keratinocyte cell lines and they have been detected in 90% of anogenital cancer tissues, which suggests a causative role in the induction of anogenital and other tumours. We have exploited a quantitative assay to identify and characterize the origin of replication of the human papillomavirus type 18 (HPV-18), one of the most prevalent types in the high-risk HPV group. Replication of HPV origin fragments was studied transiently by cotransfection with a protein expression vector providing replication proteins E1 and E2. We have localized the HPV-18 origin to nucleotides 7767-119. This region contains three E2 binding sites and an essential A/T rich DNA region (nucleotides 9-35) that is partly homologous to the E1 binding site found in bovine papillomavirus type 1 (BPV-1) genome. At least one of the three E2 binding sites was absolutely required for origin function; addition of other E2 sites had cooperative stimulating effect. This is the first quantitative analysis of the E2 binding sites for papillomavirus replication.

Base Sequence↗
PubMed1992

Isolation of cDNA clones encoding the beta isozyme of human DNA topoisomerase II and localisation of the gene to chromosome 3p24.

Topoisomerases catalyse the interconversion of topological isomers of DNA and have key roles in nucleic acid metabolism. Human cells express two distinct type II topoisomerase isozymes, designated topoisomerase II alpha (170 kDa form) and topoisomerase II beta (180 kDa form). We have isolated cDNA clones encoding the beta isozyme from a human B-cell library. The proposed coding region for the topoisomerase II beta protein is 4,863 nucleotides long and would encode a polypeptide with a calculated M(r) of 182,705. The predicted topoisomerase II beta protein sequence shows striking similarity (72% identical residues) to that of the human alpha isozyme, and homology to topoisomerase II proteins from Drosophila, yeast and bacteria. Regions of greatest amino acid sequence divergence lie at the extreme N-terminus and over a C-terminal domain comprising approximately 25% of the total protein. We have quantified the level of topoisomerase II beta mRNA in a panel of human tumour cell lines of different origin using an RNase protection assay, and compared the level to that of topoisomerase II alpha mRNA. Topoisomerase II beta mRNA was expressed in haemopoietic, epithelial and fibroblast cell lines, although to different extents, with U937 cells (promonocytic leukaemia) showing a particularly high level. There was no obvious relationship in terms of level of expression between the topoisomerase II alpha and beta genes. We have localised the gene encoding topoisomerase II beta protein to chromosome 3p24 in the human genome.

Amino Acid Sequence↗
PubMed1992

Specialized instruction within general education: a case study of one elementary school.

This study examined how classroom teachers in one elementary school approached the problem of designing specialized instruction for students with reading problems. We asked 12 teachers to rate their confidence in designing effective interventions and then to diagnose a student's reading problem, select an intervention, and implement it. Teachers were moderately confident about their ability to design effective interventions; but some teachers expressed doubts about how to proceed. Their approach to intervention differed somewhat from that of special education resource teachers. Some teachers experienced considerable difficulty in implementing the interventions they selected.

Achievement↗
PubMed1992

A C-terminal alpha-helix plus basic region motif is the major structural determinant of p53 tetramerization.

The p53 gene product has been implicated in both human and animal tumorigenesis. p53 forms heterologous complexes with the transforming proteins encoded by several different DNA tumor viruses. p53 also assembles into stable homo-oligomers. We demonstrate that the major structural determinant for the tetramerization of p53 is an alpha-helical plus basic region motif near the C-terminus of the protein. A monomeric p53 mutant adopts a conformation distinct from both 'wild-type' and 'mutant' form as defined by PAb1620 and PAb240 monoclonal antibody recognition. Nevertheless, monomeric and dimeric mutant p53 proteins retain the ability to suppress SV40 origin-directed DNA replication in vivo. Thus, p53-p53 interaction and expression of the PAb1620 epitope is not a prerequisite for such activity. We present data suggesting that suppression of replication by p53 may occur by a mechanism that is independent of detectable p53-T antigen association.

Amino Acid Sequence↗