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Biomedical subjects

W Gibson

Publications and source records attributed to W Gibson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Comparison between African-American and white women in their beliefs about breast cancer and their health locus of control.

The purpose of this study was to examine the health beliefs of African-American and white women about breast cancer and locus of control, using the health belief model and the health locus of control construct. The Health Screening Questionnaire, developed by Sugarek, Deyo, and Holmes, was used to collect self-report data about health beliefs related to breast cancer and health locus of control. Participants included 197 white and 152 African-American women, between the ages of 19 and 93, recruited from various settings in central Florida. Significant differences were found between the two groups on all of the health beliefs about cancer items. The African-American women were significantly more likely to believe in chance, or to depend on powerful others for their health. Perceived susceptibility to cancer, doubts about the value of early diagnosis, and beliefs about the seriousness of breast cancer all were significantly associated with powerful other scores among African-American women. There was no relation between health beliefs and years of education for African-American women, but for white women, those with the least education were more likely to believe that death was inevitable with a cancer diagnosis. These results add to the information needed for the development of effective programs aimed at increasing breast cancer screening among African-American women.

Adult↗
PubMed1999

Genetic exchange in the trypanosomatidae.

The only trypanosomatid so far proved to undergo genetic exchange is Trypanosoma brucei, for which hybrid production after co-transmission of different parental strains through the tsetse fly vector has been demonstrated experimentally. Analogous mating experiments have been attempted with other Trypanosoma and Leishmania species, so far without success. However, natural Leishmania hybrids, with a combination of the molecular characters of two sympatric species, have been described amongst both New and Old World isolates. Typical homozygotic and heterozygotic banding patterns for isoenzyme and deoxyribonucleic acid markers have also been demonstrated amongst naturally-occurring T. cruzi isolates. The mechanism of genetic exchange in T. brucei remains unclear, although it appears to be a true sexual process involving meiosis. However, no haploid stage has been observed, and intermediates in the process are still a matter for conjecture. The frequency of sex in trypanosomes in nature is also a matter for speculation and controversy, with conflicting results arising from population genetics analysis. Experimental findings for T. brucei are discussed in the first section of this review, together with laboratory evidence of genetic exchange in other species. The second section covers population genetics analysis of the large body of data from field isolates of Leishmania and Trypanosoma species. The final discussion attempts to put the evidence from experimental and population genetics into its biological context.

Animals↗
PubMed1999

The molecular evolution of trypanosomes.

The absence of a fossil record has meant that the evolution of protozoa has remained largely a matter for speculation. Recent advances in molecular biology and phylogenetic analysis, however, are allowing the 'history written in the genes' to be interpreted. Here, Jamie Stevens and Wendy Gibson review progress in reconstruction of trypanosome phylogeny based on molecular data from rRNA and protein-coding genes.

Africa↗
PubMed1999

Congenital insensitivity to pain with anhidrosis: novel mutations in the TRKA (NTRK1) gene encoding a high-affinity receptor for nerve growth factor.

Congenital insensitivity to pain with anhidrosis (CIPA) is characterized by recurrent episodes of unexplained fever, anhidrosis (inability to sweat), absence of reaction to noxious stimuli, self-mutilating behavior, and mental retardation. Human TRKA encodes a high-affinity tyrosine kinase receptor for nerve growth factor (NGF), a member of the neurotrophin family that induces neurite outgrowth and promotes survival of embryonic sensory and sympathetic neurons. We have recently demonstrated that TRKA is responsible for CIPA by identifying three mutations in a region encoding the intracellular tyrosine kinase domain of TRKA in one Ecuadorian and three Japanese families. We have developed a comprehensive strategy to screen for TRKA mutations, on the basis of the gene's structure and organization. Here we report 11 novel mutations, in seven affected families. These are six missense mutations, two frameshift mutations, one nonsense mutation, and two splice-site mutations. Mendelian inheritance of the mutations is confirmed in six families for which parent samples are available. Two mutations are linked, on the same chromosome, to Arg85Ser and to His598Tyr;Gly607Val, hence, they probably represent double and triple mutations. The mutations are distributed in an extracellular domain, involved in NGF binding, as well as the intracellular signal-transduction domain. These data suggest that TRKA defects cause CIPA in various ethnic groups.

Base Sequence↗
PubMed1999

Phosphorylation of simian cytomegalovirus assembly protein precursor (pAPNG.5) and proteinase precursor (pAPNG1): multiple attachment sites identified, including two adjacent serines in a casein kinase II consensus sequence.

The assembly protein precursor (pAP) of cytomegalovirus (CMV), and its homologs in other herpesviruses, functions at several key steps during the process of capsid formation. This protein, and the genetically related maturational proteinase, is distinguished from the other capsid proteins by posttranslational modifications, including phosphorylation. The objective of this study was to identify sites at which pAP is phosphorylated so that the functional significance of this modification and the enzyme(s) responsible for it can be determined. In the work reported here, we used peptide mapping, mass spectrometry, and site-directed mutagenesis to identify two sets of pAP phosphorylation sites. One is a casein kinase II (CKII) consensus sequence that contains two adjacent serines, both of which are phosphorylated. The other site(s) is in a different domain of the protein, is phosphorylated less frequently than the CKII site, does not require preceding CKII-site phosphorylation, and causes an electrophoretic mobility shift when phosphorylated. Transfection/expression assays for proteolytic activity showed no gross effect of CKII-site phosphorylation on the enzymatic activity of the proteinase or on the substrate behavior of pAP. Evidence is presented that both the CKII sites and the secondary sites are phosphorylated in virus-infected cells and plasmid-transfected cells, indicating that these modifications can be made by a cellular enzyme(s). Apparent compartmental differences in phosphorylation of the CKII-site (cytoplasmic) and secondary-site (nuclear) serines suggest the involvement of more that one enzyme in these modifications.

Amino Acid Sequence↗
PubMed1999

Capsid structure of simian cytomegalovirus from cryoelectron microscopy: evidence for tegument attachment sites.

We have used cryoelectron microscopy and image reconstruction to study B-capsids recovered from both the nuclear and the cytoplasmic fractions of cells infected with simian cytomegalovirus (SCMV). SCMV, a representative betaherpesvirus, could thus be compared with the previously described B-capsids of the alphaherpesviruses, herpes simplex virus type 1 (HSV-1) and equine herpesvirus 1 (EHV-1), and of channel catfish virus, an evolutionarily remote herpesvirus. Nuclear B-capsid architecture is generally conserved with SCMV, but it is 4% larger in inner radius than HSV-1, implying that its approximately 30% larger genome should be packed more tightly. Isolated SCMV B-capsids retain a relatively well preserved inner shell (or "small core") of scaffolding-assembly protein, whose radial-density profile indicates that this protein is approximately 16-nm long and consists of two domains connected by a low-density linker. As with HSV-1, the hexons but not the pentons of the major capsid protein (151 kDa) bind the smallest capsid protein (approximately 8 kDa). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed cytoplasmic B-capsid preparations to contain proteins similar in molecular weight to the basic phosphoprotein (approximately 119 kDa) and the matrix proteins (65 to 70 kDa). Micrographs revealed that these particles had variable amounts of surface-adherent material not present on nuclear B-capsids that we take to be tegument proteins. Cytoplasmic B-capsids were classified accordingly as lightly, moderately, or heavily tegumented. By comparing the three corresponding density maps with each other and with the nuclear B-capsid, two interactions were identified between putative tegument proteins and the capsid surface. One is between the major capsid protein and a protein estimated by electron microscopy to be 50 to 60 kDa; the other involves an elongated molecule estimated to be 100 to 120 kDa that is anchored on the triplexes, most likely on its dimer subunits. Candidates for the proteins bound at these sites are discussed. This first visualization of such linkages makes a step towards understanding the organization and functional rationale of the herpesvirus tegument.

Capsid↗
PubMed1999

Cochlear implantation in children with large vestibular aqueduct syndrome.

OBJECTIVE: This study describes the effectiveness of a multielectrode cochlear implant prosthesis (Cochlear; Cochlear Pty., Lane Cove, Australia) for providing hearing to children with deafness caused by large vestibular aqueduct syndrome (LVAS). STUDY DESIGN: The study design was a retrospective study. SETTING: All the children attended The Children's Cochlear Implant Center (NSW), which is a specialist center that provides audiologic testing, speech therapy, habilitation, and medical assistance for children with cochlear implants. PATIENTS: Ten children were studied who had profound hearing loss and radiologic evidence of a vestibular aqueduct larger than 2 mm in width in its intraosseous portion. INTERVENTION: The children received a multielectrode (Cochlear) cochlear implant prosthesis, and the associated programming of the device and habitation were performed postoperatively. No significant problems were encountered at any of the surgeries, although there was an initial gush of perilymph when the otic capsule was opened in 7 ears. MAIN OUTCOME MEASURES: Postoperative audiologic performance at six monthly intervals and school performance were assessed. RESULTS: The postoperative auditory performance was improved in all children. At 6 months, their average BKB score had increased from 31% to 79%; average word score, from 8% to 43%; and average phoneme score, from 38% to 70%. The older children were able to continue their education in their usual setting with less reliance on hearing support staff. CONCLUSION: Children with a deteriorating hearing loss caused by LVAS can derive considerable benefit from a cochlear implant.

Child↗
PubMed1998

beta-D-glucosyl-hydroxymethyluracil is a conserved DNA modification in kinetoplastid protozoans and is abundant in their telomeres.

The unusual DNA base beta-D-glucosyl-hydroxymethyluracil, called "J, " replaces approximately 0.5-1% of Thy in DNA of African trypanosomes but has not been found in other organisms thus far. In Trypanosoma brucei, J is located predominantly in repetitive DNA, and its presence correlates with the silencing of telomeric genes. Using antibodies specific for J, we have developed sensitive assays to screen for J in a range of organisms and have found that J is not limited to trypanosomes that undergo antigenic variation but is conserved among Kinetoplastida. In all kinetoplastids tested, including the human pathogens Leishmania donovani and Trypanosoma cruzi, J was found to be abundantly present in the (GGGTTA)n telomere repeats. Outside Kinetoplastida, J was found only in Diplonema, a small phagotrophic marine flagellate, in which we also identified 5-MeCyt. Fractionation of Diplonema DNA showed that the two modifications are present in a common genome compartment, which suggests that they may have a similar function. Dinoflagellates appear to contain small amounts of modified bases that may be analogs of J. The evolutionary conservation of J in kinetoplastid protozoans suggests that it has a general function, repression of transcription or recombination, or a combination of both. T. brucei may have recruited J for the control of genes involved in antigenic variation.

Animals↗
PubMed1998

Cytomegalovirus assembly protein precursor and proteinase precursor contain two nuclear localization signals that mediate their own nuclear translocation and that of the major capsid protein.

The cytomegalovirus (CMV) assembly protein precursor (pAP) interacts with the major capsid protein (MCP), and this interaction is required for nuclear translocation of the MCP, which otherwise remains in the cytoplasm of transfected cells (L. J. Wood et al., J. Virol. 71:179-190, 1997). We have interpreted this finding to indicate that the CMV MCP lacks its own nuclear localization signal (NLS) and utilizes the pAP as an NLS-bearing escort into the nucleus. The CMV pAP amino acid sequence has two clusters of basic residues (e.g., KRRRER [NLS1] and KARKRLK [NLS2], for simian CMV) that resemble the simian virus 40 large-T-antigen NLS (D. Kalderon et al., Cell 39:499-509, 1984) and one of these (NLS1) has a counterpart in the pAP homologs of other herpesviruses. The work described here establishes that NLS1 and NLS2 are mutually independent NLS that can act (i) in cis to translocate pAP and the related proteinase precursor (pNP1) into the nucleus and (ii) in trans to transport MCP into the nucleus. By using combinations of NLS mutants and carboxy-terminal deletion constructs, we demonstrated a self-interaction of pAP and cytoplasmic interactions of pAP with pNP1 and of pNP1 with itself. The relevance of these findings to early steps in capsid assembly, the mechanism of MCP nuclear transport, and the possible cytoplasmic formation of protocapsomeric substructures is discussed.

Amino Acid Sequence↗
PubMed1997

Folate-based inhibitors of thymidylate synthase: synthesis and antitumor activity of gamma-linked sterically hindered dipeptide analogues of 2-desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583).

In an effort to synthesize inhibitors of thymidylate synthase (TS) that do not undergo polyglutamation, a series of gamma-linked sterically hindered dipeptide analogues of 2-desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583) was prepared. A methyl, ethyl, or propargyl group was incorporated into the gamma-glutamyl amide bond of gamma-linked L,L dipeptide derivatives of ICI 198583, such as ICI 198583-gamma-L-Glu. In addition, steric bulk was introduced on either side of the gamma-glutamyl bond of ICI 198583-gamma-L-Glu or ICI 198583-gamma-L-Ala. The resulting dipeptide analogues, e.g., ICI 198583-gamma-MeGlu and ICI 198583-gamma-Aib, were apparently stable to in vivo hydrolysis but poorer inhibitors of TS and L1210 cell growth. However, introduction of 7-Me, 2'-F substitution into the quinazoline nucleus gave significant improvement in the inhibitory activity against thymidylate synthase. Compounds 28-30, the 7-Me, 2'-F derivatives of ICI 198583-gamma-MeGlu, ICI 198583-gamma-EtGlu, and ICI 198583-gamma-PgGlu, respectively, were potent inhibitors of TS (K(iapp) = 0.21-1.1 nM) and L1210 cell growth (IC50 = 0.05-0.34 microM) and were similar to that seen with the most potent gamma-linked L,D dipeptide derivatives of ICI 198583 previously synthesized. Furthermore, the low cross-resistance ratios for the L1210:R(D1694)/L1210 cell line indicated that 28-30 do not undergo polyglutamation.

Animals↗
PubMed1997

Assemblin homolog of herpes simplex virus type 1 retains proteolytic activity when expressed as a recombinant two-chain enzyme.

The herpes simplex virus type 1 (HSV) maturational proteinase is synthesized as a precursor that undergoes two autoproteolytic cleavages; one at its (M)aturational site, which eliminates its carboxyl "tail," and a second at its (R)elease site, which separates the amino proteolytic half of the precursor from its nonproteolytic carboxyl half. In cytomegalovirus (CMV) the proteolytic half of the precursor, called assemblin, undergoes a third cleavage at an (I)nternal site that converts it from a single-chain to a two-chain enzyme that retains activity. The HSV assemblin homolog has no I site and therefore does not form a counterpart two-chain enzyme. In the work reported here we have cloned and expressed HSV sequences that encode mimics of the An and Ac subunits of two-chain CMV assemblin. We show that when these HSV sequences are coexpressed in eukaryotic cells, the resulting subunits associate spontaneously to form an active two-chain enzyme. We also show that the two-chain HSV enzyme, like the natural one-chain form, retains its marked preference for HSV over CMV substrates, and that intertypic recombinant two-chain assemblin (e.g., HSV An/CMV Ac) does not form because the cross-species subunits do not interact. We conclude from these results that (i) there are not intrinsic structural differences in the HSV assemblin homolog that preclude its functioning as a CMV-like two-chain enzyme, (ii) the substrate selectivity shown by the single-chain HSV enzyme was not noticeably relaxed in the HSV two-chain mimic, and (iii) the interactive domains, through which the An and Ac portions of the single-chain enzymes associate, differ between HSV and CMV.

Amino Acid Sequence↗
PubMed1997

Kinetoplast DNA minicircles are inherited from both parents in genetic crosses of Trypanosoma brucei.

In the order Kinetoplastida, genetic exchange has been demonstrated only in the genus Trypanosoma. Analysis of kinetoplast DNA (kDNA) in genetic crosses of T. brucei has shown that whereas maxicircles are inherited uniparentally, minicircles are inherited from both parents. This result was confirmed for a new cross of T. b. brucei and T. b. rhodesiense by restriction enzyme digestion and Southern analysis of purified kDNA. By hybridisation with small minicircle-derived probes, we could demonstrate the presence of particular parental minicircles in the kDNA of hybrid progeny clones. All hybrid clones had inherited two minicircles from one parent despite two of the four clones having maxicircles from the other parent. The results suggest that rather than small-scale exchange of minicircles between parental networks, gross breakdown and reassembly of the minicircle network occurs during genetic exchange.

Animals↗
PubMed1997

Human cytomegalovirus capsid assembly protein precursor (pUL80.5) interacts with itself and with the major capsid protein (pUL86) through two different domains.

We have used the yeast GAL4 two-hybrid system to examine interactions between the human cytomegalovirus (HCMV) major capsid protein (MCP, encoded by UL86) and the precursor assembly protein (pAP, encoded by UL80.5 and cleaved at its carboxyl end to yield AP) and found that (i) the pAP interacts with the MCP through residues located within the carboxy-terminal 21 amino acids of the pAP, called the carboxyl conserved domain (CCD); (ii) the pAP interacts with itself through a separate region, called the amino conserved domain (ACD), located between amino acids His34 and Arg52 near the amino end of the molecule; (iii) the simian CMV (SCMV) pAP and AP can interact with or replace their HCMV counterparts in these interactions, whereas the herpes simplex virus pAP and AP homologs cannot; and (iv) the HCMV and SCMV maturational proteinase precursors (ACpra, encoded by UL80a and APNG1, respectively) can interact with the pAP and MCP. The ACD and CCD amino acid sequences are highly conserved among members of the betaherpesvirus group and appear to have counterparts in the alpha- and gammaherpesvirus pAP homologs. Deleting the ACD from the HCMV pAP, or substituting Ala for a conserved Leu in the ACD, eliminated detectable pAP self-interaction and also substantially reduced MCP binding in the two-hybrid assay. This finding indicates that the pAP self-interaction influences the pAP-MCP interaction. Immunofluorescence studies corroborated the pAP-MCP interaction detected in the GAL4 two-hybrid experiments and showed that nuclear transport of the MCP was mediated by pAP but not AP. We conclude that the pAP interacts with the MCP, that this interaction is mediated by the CCD and is influenced by pAP self-interaction, and that one function of the pAP-MCP interaction may be to provide a controlled mechanism for transporting the MCP into the nucleus.

Amino Acid Sequence↗