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Biomedical subjects

G King

Publications and source records attributed to G King.

At least 91 records · Page 5Linked to original sources
PubMed1996

An Mll-AF9 fusion gene made by homologous recombination causes acute leukemia in chimeric mice: a method to create fusion oncogenes.

Homologous recombination in embryonal stem cells has been used to produce a fusion oncogene, thereby mimicking chromosomal translocations that frequently result in formation of tumor-specific fusion oncogenes in human malignancies. AF9 sequences were fused into the mouse Mll gene so that expression of the Mll-AF9 fusion gene occurred from endogenous Mll transcription control elements, as in t(9;11) found in human leukemias. Chimeric mice carrying the fusion gene developed tumors, which were restricted to acute myeloid leukemias despite the widespread activity of the Mll promoter. Onset of perceptible disease was preceded by expansion of ES cell derivatives in peripheral blood. This novel use of homologous recombination formally proves that chromosomal translocations contribute to malignancy and provides a general strategy to create fusion oncogenes for studying their role in tumorigenesis.

Acute Disease↗
PubMed1996

Restriction by EcoKI is enhanced by co-operative interactions between target sequences and is dependent on DEAD box motifs.

One subunit of both type I and type III restriction and modification enzymes contains motifs characteristic of DEAD box proteins, which implies that these enzymes may be DNA helicases. This subunit is essential for restriction, but not modification. The current model for restriction by both types of enzyme postulates that DNA cutting is stimulated when two enzyme complexes bound to neighbouring target sequences meet as the consequence of ATP-dependent DNA translocation. For type I enzymes, this model is supported by in vitro experiments, but the predicted co-operative interactions between targets have not been detected by assays that monitor restriction in vivo. The experiments reported here clearly establish the required synergistic effect but, in contrast to earlier experiments, they use Escherichia coli K-12 strains deficient in the restriction alleviation function associated with the Rac prophage. In bacteria with elevated levels of EcoKI the co-operative interactions are obscured, consistent with co-operation between free enzyme and that bound at target sites. We have made changes in three of the motifs characteristic of DEAD box proteins, including motif III, which in RecG is implicated in the migration of Holliday junctions. Conservative changes in each of the three motifs impair restriction.

Amino Acid Sequence↗
PubMed1996

Polymerized cyclomaltoheptaose (beta-cyclodextrin, beta-CDn) inclusion complex formation with chlorogenic acid: solvent effects on thermochemistry and enthalpy-entropy compensation.

The inclusion of chlorogenic acid (CA) by epichlorohydrin-polymerized cyclomaltoheptaose (beta-cyclodextrin, beta-CDn) was studied with regard to temperature, solvent, and water activity aH2O approximately mole fraction = XH2O = 0.8-1 using MeOH as the diluent; 0.1 M sodium phosphate buffer). We discovered that the extreme convex curvature in K (the apparent stability constant) as a function of temperature was nearly eliminated at the lowest XH2O. The latter finding argues that this unusual CD behavior in aqueous media was due to perturbations in beta-CD's spatial organization in the polymeric matrix with temperature. Related to this we found, from the dependence of K on XH2O (K = K'XzH2O), that the beta-CDn.CA complex's stoichiometric coefficient, z, for water, varied between 5 and 8, depending on the temperature of the solution (K' = 400-800 M-1; T approximately 295-315 K). Our determinations of z were similar to those reported previously for beta-CD.(+)-limonene (z approximately 7), soluble beta-CD.CA (z approximately 6) or obtained by molecular dynamics calculations for beta-CD.CA reported herein (z approximately 5). However, beta-CDn.CA's z values did show a significant positive correlation with temperature not evident in equivalent solution experiments. Calculations of delta H and delta S at various XH2O values show linear enthalpy-entropy compensation (delta H plotted against delta S) but with a slope (Tc = theta delta H/theta delta S approximately 228 K) significantly less than Tc values determined from either standard aqueous thermodynamic experiments (Tc approximately 305 K on either beta-CD or beta-CDn) or variable XH2O (Tc approximately 272 K) experiments. To the best of our knowledge, this is the smallest Tc value detected in a multitude of CD.guest studies. This evident solvent effect on Tc strongly argues that the chemical part process of inclusion complex formation involves changes in the solvation of the beta-CDn's binding site.

Carbohydrate Conformation↗
PubMed1996

Particle sizes of purified kappa-casein: metal effect and correspondence with predicted three-dimensional molecular models.

kappa-Casein as purified from bovine milk exhibits a rather unique disulfide bonding pattern as revealed by SDS-PAGE. The disulfide-bonded caseins present range from dimer to octamer and above and preparations contain about 10% monomer. All of these heterogenous polymers, however, self-associated into nearly spherical uniform particles with an average radius of 8.9 nm as revealed by negatively stained transmission electron micrographs. Evidence is presented that multivalent cations play a role in the stabilization of these spherical particles. Treatment with EDTA causes disruption of the kappa-casein particles and leads to a broder size distribution as judged by electron microscopy and dynamic light scattering. The size and shape of the particles are in accord with earlier proposed 3D models for kappa-casein that actually predicted participation of divalent cations in the structure.

Amino Acids↗
PubMed1996

Intraperitoneal cell movement during abdominal carbon dioxide insufflation and laparoscopy. An in vivo model.

PURPOSE: Possible mechanisms of movement of malignant cells within the peritoneal cavity during CO2 insufflation and laparoscopy involve direct transfer via laparoscopic instruments or dispersion of cells by CO2 or water vapor. An in vivo model has been developed to study these mechanisms. METHODS: Laparoscopy was performed on an animal model (domestic white pig). Cells derived from colorectal cancer cell line Lim 1215 were injected to lie free within the peritoneal cavity. A polycarbonate filter system with a 5-micron pore diameter was used to examine CO2 expelled from the peritoneal cavity, during laparoscopy and manipulation of abdominal viscera, for malignant cells. Laparoscopic instruments and laparoscopic ports were washed independently, and fluid was centrifuged and examined for malignant cells. RESULTS: Malignant cells were identified on 1 of 30 filters used to examine exhaust carbon dioxide. Malignant cells also were identified from 2 of 10 washings from laparoscopic ports and from 4 of 10 washings of laparoscopic instruments. CONCLUSIONS: These results suggest that movement of cells throughout the peritoneal cavity during laparoscopy is via contaminated instruments, but local cell movement by dispersion possibly within water vapor from the port may also occur.

Animals↗
PubMed1996

The movement of mucosal cells of the gallbladder within the peritoneal cavity during laparoscopic cholecystectomy.

BACKGROUND: Tumor dissemination to trocar sites following the removal of a gallbladder malignancy by laparoscopic cholecystectomy is well documented. The mode of transfer of malignant cells to those sites remains unclear. METHODS: The appearance and movement of gallbladder mucosal cells within the peritoneal cavity during laparoscopic cholecystectomy was prospectively studied in 15 patients. The appearance of cells on laparoscopic instruments, laparoscopic working ports, and also within a 5-microm polycarbonate filter, filtering exhaust carbon dioxide and attached to one of the main working ports, was noted. RESULTS: Four out of 15 gallbladders were perforated during cholecystectomy. Operative choledochography was performed in 11 of the 15 cases. Glandular cells were found on instruments at the end of the procedure in six cases. Cells were also found in two of the 15 polycarbonate filters and on the laparoscopic ports in two of the 15 cases. CONCLUSION: These findings suggest that cellular contamination of the peritoneal cavity is frequent during laparoscopic cholecystectomy. This may occur when the gallbladder wall is macroscopically breached or when operative choledochography is performed, or by microperforation due to the application of crushing laparoscopic graspers to the gallbladder wall. Glandular cells adhere to instruments in 40% of the operative procedures and may be the main source of dissemination of malignant cells through the peritoneal cavity.

Cholecystectomy, Laparoscopic↗
PubMed1996

Substance use, coping, and safer sex practices among adolescents with hemophilia and human immunodeficiency virus. The Hemophilia Behavioral Intervention Evaluative Project Committee.

PURPOSE: To examine the use of alcohol and other drugs (AOD) to cope with the human immunodeficiency virus (HIV), the use of AOD before or during sex by 306 adolescent males with HIV and hemophilia, and its association with safer sex practices. METHODS: A survey instrument was administered to adolescents at 11 sites of the Hemophilia Behavioral Intervention Evaluative Project. Survey questions focused on knowledge of sexual activity, safer sex practices, AOD use, attitudinal and behavioral influences of parents, peers and sex partners, communication patterns, and perceived facilitators and barriers to practicing safer sex. RESULTS: A total of 68% of all respondents reported using condoms every time they had heterosexual sex. Respondents who did not use AOD to cope were more likely than AOD copers to report that they disclose their HIV status to all sex partners, talk to all of their sex partners about safer sex, find the use of condoms more enjoyable, and have sex partners who approved of their use of condoms. Condom use was not related to the use of AOD to cope or the use of AOD with the most recent female sex partner. CONCLUSIONS: The use of AOD to cope with HIV and its use before or during sex was negatively associated with certain safer sex attitudes and practices. AOD use may help facilitate HIV transmission among adolescents with HIV and/or hemophilia.

Adaptation, Psychological↗
PubMed1996

Adhesion molecule interactions in human glomerulonephritis: importance of the tubulointerstitium.

Infiltration of leukocytes into glomerular and interstitial regions of the kidney is a key event in the pathogenesis of human glomerulonephritis. This process is mediated by specific adhesion molecules, some of which are expressed in a coordinated fashion following endothelial cell activation. We have assessed the pattern of expression of the selectins (E, P and L), and the counter-receptors (LFA-1 and ICAM-1, and VLA-4 and VCAM-1 in 119 renal biopsies using sequential sections, and have correlated this with the degree of histological damage (tubular atrophy and interstitial fibrosis) and the intensity of the macrophage infiltrate. Sections were stained with the monoclonal antibodies using a standard alkaline phosphatase anti-alkaline phosphatase (APAAP) technique. There were strong correlations between the following: (1) expression of LFA-1, VLA-4, and L-selectin in the periglomerular region, interstitium and in focal interstitial infiltrates and the presence of macrophages in these regions; (2) de novo tubular expression of ICAM-1 and VCAM-1; (3) staining for ICAM-1 and VCAM-1 on focal cellular infiltrates within the interstitium; and (4) staining for E- and P-selectin on extraglomerular endothelium. These are also strongly correlated with the degree of chronic histological damage. There was, however, no correlation between glomerular expression of adhesion molecules or glomerular macrophage infiltration and chronic histological damage. Although expression of VCAM-1 by the glomerular mesangium was strongly correlated with the presence of cells staining for VLA-4 within the glomerulus, glomerular expression of adhesion molecules correlated poorly with their expression in other sites. These results show that coordinated up-regulation of adhesion molecule expression in the tubulointerstitium is associated with interstitial fibrosis and tubular atrophy and may contribute, therefore, to the progression of renal disease.

Biopsy↗
PubMed1996

Maintaining safer sex behaviours in HIV-infected adolescents with haemophilia. The Hemophilia Behavioral Evaluative Intervention Project Committee.

Adolescents with haemophilia comprise 44% of the reported AIDS cases in teenagers. Unprotected sexual intercourse among this group increases the risk of HIV transmission. Understanding the influences which others may have on the sexual behaviour of adolescents with HIV and haemophilia may lead to the development of effective risk reduction strategies. An evaluative instrument, administered to 307 HIV-infected adolescents with haemophilia, assessed their behavioural stage of change (Prochaska & DiClemente), attitudes, beliefs and behaviours about safer sex practices. The influence of parents, peers and sexual partners on sexual behaviour was compared between (1) those who were sexually experienced and (2) and those who were sexually inexperienced. Barriers and facilitators to practising safer sex were identified. Although parents influenced the sexual behaviour of both groups, this influence was significantly greater in the sexually inactive group. Fewer than 20% reported that their peers impacted their decisions about sexual behaviour. Eighty-six per cent of the sexually active indicated that partners significantly impacted their sexual decisions, while 60% of the sexually inactive indicated that future partners would affect their decisions about sex. Most participants agreed that disclosure of HIV status before intercourse was desirable, but only 31% of the sexually active said they told every partner. Fear of rejection or a negative reaction from the partner, and lack of communication skills were the greatest barriers to disclosure of HIV status and practising safer sex. This study indicates that behavioural interventions for both groups should focus on developing communication skills and self-efficacy. Interventions should include the key influences for each group--parents for the sexually inactive and partners for the sexually active.

Adolescent↗
PubMed1996

Computer model of a bovine type I collagen microfibril.

Collagens are a family of structural proteins of the extracellular matrix. The fibril-forming collagens are the major structural proteins of skin, cartilage, bone, blood vessel walls and internal organs. In addition to biological function, the collagens provide natural structural frameworks that are utilized in the medical, food and leather industries. Many schemes for the organization of type I collagen into triple helices, microfibrils and fibrils have been proposed during the past 30 years. Here, the development of a molecular model of a bovine type I collagen "Smith' microfibril is described. In cross-section, this model exhibits a symmetrical, pentagonal grouping of five triple helices. The model comprises 15 polypeptide chains having 315 residues each. This model is large enough to allow a comparison of its gross structural features with images of stained collagen obtained by electron microscopy, yet small enough to be manipulated on a minicomputer or work-station. The model is useful for (among others) studies of structure-function relationships in collagen, exploring folding pathways, predicting the efficacy of potential crosslinking agents or chemical modifications, and designing synthetic collagen-like materials or modifications for specific applications.

Amino Acid Sequence↗
PubMed1996

Expression of bcl-2 and p53 in Merkel cell carcinoma. An immunohistochemical study.

Bcl-2 is a protooncogene thought to play a role in oncogenesis by inhibiting programmed cell death. It may interact with p53, a tumor-suppressor gene which induces apoptosis in certain circumstances. We have studied these gene products by immunohistochemistry in 15 cases of Merkel cell carcinoma, a tumor characterised by prominent apoptosis. Five cases showed moderate/strong staining for p53, with moderate/strong bcl-2 staining in 10 patients. In seven cases abundance of p53 and bcl-2 expression was mutually exclusive. Two patients died within 1 year of diagnosis and six had nodal recurrences. Gene expression and survival appear unrelated. The role of Bcl-2 and p53 in tumorigenesis is complicated and may be inter-related with other genes known to be involved in programmed cell death.

Aged↗
PubMed1996

Immunocytochemistry of mucosal changes in patients infected with the intestinal nematode Strongyloides stercoralis.

AIM: To investigate the immunopathological changes in duodenal tissues induced by strongyloidiasis and to relate these to degrees of clinical severity. METHODS: Tissues taken from 21 patients showing mild, moderate or severe symptoms of strongyloidiasis, and from non-infected controls, were sectioned and stained immunocytochemically for IgA, secretory component (SC) and HLA-DR. Immunopathology was assessed by changes in numbers, intensity and distribution of stained cells. RESULTS: Parasitised individuals showed villous atrophy and crypt hyperplasia. There was notable infiltration of the lamina propria by IgA positive plasma cells and of the epithelium by intraepithelial lymphocytes. Infection was also associated with increased expression of SC and decreased expression of HLA-DR in epithelial cells. Changes in all parameters correlated with degree of clinical severity. CONCLUSIONS: Profound mucosal changes are induced by strongyloidiasis. Some are analogous to those seen in coeliac disease, but others seem quite unusual. It is likely that these changes are functionally related to the immunopathophysiological consequences of infection seen in patients with severe disease.

Adult↗
PubMed1996

A therapist's guide to children's self-esteem.

The term self-esteem is frequently used by occupational therapists and other health care professionals who work with children. There are differing interpretations as to what this term actually means. In this article, we use Susan Harter's model of self-esteem to define the nature of self-esteem and apply it to clinical practice. We outline the developmental characteristics important to consider when addressing the self-esteem of young children, such as the findings that young children's self-esteem is often more related to their perceptions of parental acceptance than perceptions of competence and that children are generally unable to accurately verbalize their level of self-esteem until 8 years of age. Specific implications for occupational therapy evaluation include whether the use of self-report or observer-report measures is preferable and whether self-esteem or self-concept should be measured. We discuss when to address self-esteem and which dimensions of self-esteem should be treated. The dimensions of self-esteem that are identified as low during the evaluation and that the child perceives to be important are addressed. The reevaluation issue of what specifically should be measured after intervention is also discussed. For example, it is recommended that the reevaluation instrument be sensitive to the domains of self-concept targeted for intervention.

Child↗
PubMed1996

Issues of disclosure and condom use in adolescents with hemophilia and HIV. Hemophilia Behavioral Evaluative Intervention Project Staff.

PURPOSE: To examine the patterns, facilitators, and barriers to disclosure of HIV seropositivity in an adolescent population and to determine the relationship between disclosure and condom use. BACKGROUND: In recent years, public health efforts have focused on methods to prevent the transmission of the Human Immunodeficiency Virus (HIV). These efforts have included safer sex education, skill building and self-efficacy training, behavioral change techniques, and encouragement of serostatus disclosure to sexual partners. In 1990, the Centers for Disease Control and Prevention (CDC) funded 10 hemophilia treatment centers to develop and implement a theory-based behavioral intervention to prevent the sexual transmission of HIV. METHODS: A baseline survey, focusing on barriers to safer sex, the influence of parents, peers, and sexual partners, alcohol and drug use, and communication and disclosure patterns, was administered to 321 young males (ages 12 to 25) with hemophilia and HIV. RESULTS: Fifty-eight percent of the sexually experienced adolescents did not disclose their HIV status to their most recent sexual partners (i.e., nondisclosers) compared to 42 percent who reported that either they informed their partners or their partners already knew their HIV status (i.e., disclosers). There was no correlation between disclosure and condom use. The most significant predictor of disclosure was the perception that peers would disclose their HIV status. CONCLUSION: The results suggest that disclosure does not necessarily facilitate condom use in this population. This conclusion may have implications for future public health efforts in HIV prevention. Rather than focusing primarily on the promotion of serostatus disclosure, behavioral interventions should emphasize the practice of safer sex, utilizing peer educators and support networks.

Adolescent↗
PubMed1996

Immunocytochemical demonstration that human duodenal Brunner's glands may participate in intestinal defence.

The immunocytochemical demonstration of IgA and IgM in some secretory units of human Brunner's glands, associated with the presence of secretory component in all secretory cells, indicates the possibility that these glands assist the function of the intestinal crypts in transporting immunoglobulins into the gut lumen. In addition, the presence of muramidase (lysozyme) in the cells of the secretory units suggests that Brunner's glands continuously secrete bactericidal enzyme, thus reinforcing the function of the Paneth cells as contributors to nonspecific defence (innate immunity) in the intestinal tract.

Brunner Glands↗
PubMed1995

The human gp39 promoter. Two distinct nuclear factors of activated T cell protein-binding elements contribute independently to transcriptional activation.

gp39, a cytokine expressed on the surface of activated T cells, is essential for T cell-dependent antibody responses in vivo. We cloned and sequenced 1.2 kilobases of the 5' flank region of the human gp39 gene promoter and determined its transcription start site. When used in reporter gene assays, this DNA segment conferred promoter activity in response to T cell activation. gp39 promoter function in transfectants was inhibited by cyclosporin A, as is expression of the endogenous gp39 gene in T-lineage cells. At least 0.5 kilobase of the 5' flank region was required for promoter activity. Two putative binding sites for the NF-AT family of transcriptional activator proteins were identified at -259 to -265 and -62 to -69 with respect to the transcription start site. Both sites contributed significantly and independently to promoter activity in response to T cell activation. Additionally, when incubated in vitro with nuclear protein purified from activated human CD4 T cells, both of these sites preferentially bound the NF-AT family member, NF-ATp. These results suggest that NF-ATp, via binding to at least two cis-elements, is essential for the induction of gp39 gene expression in response to T cell activation.

Base Sequence↗
PubMed1995

Genetic strategy for analyzing specificity of dimer formation: Escherichia coli cyclic AMP receptor protein mutant altered in its dimerization specificity.

Many transcriptional regulators function in homo- or heterodimeric combinations. The same protein can carry out distinct regulatory functions depending on the partner with which it associates. Here, we describe a mutant of the Escherichia coli cAMP receptor protein (CRP) that has an altered dimerization specificity; that is, mutant/mutant homodimers form preferentially over wild-type/mutant heterodimers. CRP dimerization involves the formation of a parallel coiled-coil structure, and our CRP mutant bears an amino acid substitution affecting the first "d" position residue within the alpha-helix that mediates CRP dimerization. The genetic strategy we used to isolate this CRP altered dimerization specificity (ADS) mutant is generalizable and could be utilized to isolate ADS mutants of other dimeric transcriptional regulators.

Amino Acid Sequence↗