Biomedical subjects

J R Murphy

Publications and source records attributed to J R Murphy.

At least 73 records · Page 4Linked to original sources

PubMed1996

Isolation of Campylobacter species from Zambian patients with acute diarrhoea.

Four hundred and one consecutive diarrhoea patients and 101 adult patients without diarrhoea were enrolled for this study from a health centre in Lusaka. Campylobacter was isolated from 6% of patients with acute diarrhoea. However, non of these were seen in control group. Further studies are being carried out to determine the importance of Campylobacter species with other bacterial pathogens. It will also be interesting to see its impact and association with human immuno deficiency virus in this region.

Acute Disease↗

PubMed1995

Structures of the apo- and the metal ion-activated forms of the diphtheria tox repressor from Corynebacterium diphtheriae.

The diphtheria tox repressor (DtxR) of Corynebacterium diphtheriae plays a critical role in the regulation of diphtheria toxin expression and the control of other iron-sensitive genes. The crystal structures of apo-DtxR and of the metal ion-activated form of the repressor have been solved and used to identify motifs involved in DNA and metal ion binding. Residues involved in binding of the activated repressor to the diphtheria tox operator, glutamine 43, arginine 47, and arginine 50, were located and confirmed by site-directed mutagenesis. Previous biochemical and genetic data can be explained in terms of these structures. Conformational differences between apo- and Ni-DtxR are discussed with regard to the mechanism of action of this repressor.

Amino Acid Sequence↗

PubMed1995

Transition metal ion activation of DNA binding by the diphtheria tox repressor requires the formation of stable homodimers.

The diphtheria tox repressor (DtxR) is a transition metal ion-dependent regulatory element that controls the expression of diphtheria toxin and several genes involved in the synthesis of siderophores in Corynebacterium diphtheriae. In the presence of transition metal ions apo-DtxR becomes activated and specifically binds to its target DNA sequences. We demonstrate by glutaraldehyde cross-linking that monomeric apo-DtxR is in weak equilibrium with a dimeric form and that upon addition of activating metal ions to the reaction mixture a dimeric complex is stabilized. Addition of the DNA-binding-defective mutant apo-DtxR(delta 1-47) to apo-DtxR in the absence of transition metal ions inhibits conversion of the apo-repressor to its activated DNA-binding form. We also show that the binding of Ni2+ to both apo-DtxR and apo-DtxR(delta 1-47) is cooperative and that upon ion binding there is a conformational change in the environment of the indole ring moiety of Trp-104. For the wild-type repressor the consequences of this conformational change include a shift in equilibrium toward dimer formation and activation of target DNA binding by the repressor. We conclude that the formation of DtxR homodimers is mediated through a protein-protein interaction domain that is also activated on metal ion binding.

Apoproteins↗

PubMed1995

Targeting diphtheria toxin to growth factor receptors.

Biochemical, genetic and X-ray crystallographic analysis of diphtheria toxin have demonstrated that the native toxin is composed of three structural domains that function in an ordered fashion to intoxicate a eukoryotic cell. With the knowledge that, if delivered to the cytosol, a single molecule of the catalytic domain is lethal for the cell, we have used recombinant DNA methods to genetically replace the native toxin receptor binding domain with a series of growth factors. The resulting diphtheria toxin-related cytokine fusion proteins, or fusion toxins bind to their respective receptors, are internalized by receptor-mediated endocytosis, and efficiently eliminate target cell populations by the adenosine diphosphate ribosylation of elongation factor 2. Based upon the results of preclinical studies, DAB486IL-2, DAB389IL-2 and DAB389EGF have, or are in the process of being evaluated in Phase I/II clinical trials. To date, administration of the diphtheria toxin-based fusion proteins targeted toward the high affinity IL-2 receptor have been found to be safe, well tolerated, and capable of inducing remission in refractory hematologic malignancies.

Diphtheria Toxin↗

PubMed1995

Colonization factors of enterotoxigenic E. coli (ETEC) from residents of northern Egypt.

Infection caused by enterotoxigenic Escherichia coli (ETEC) poses a serious health problem to children in developing countries. Colonization of the small intestinal mucosa by ETEC strains is mediated by antigenically specific fimbriae, also known as colonization factor antigens (CFA). The importance of this study arises from reports that active and passive immunization with ETEC strains harboring CFAs induced protective immunity against diarrhea in animal models with preformed antibodies. In humans, ETEC containing CFA/I, II, III and IV have been identified. The aim of this study was to define CFAs of ETEC isolated in Alexandria, Egypt. One hundred and seven ETEC isolates from 132 human residents in Alexandria, Egypt were isolated during a birth cohort study. ETEC isolates were screened for heat labile (LT) and heat stable (ST) toxins using a 32P oligonucleotide hybridization probe and a GM1 ELISA. These isolates were examined using monoclonal antibodies against CFA/I, II, III, IV, and against the putative colonization antigens PCF0159 and PCF0166, CS 7 and CS 17. CFAs were found in 48% of ETEC strains. CFA/I was found in 18% of the strains, CFA/II in 10% and CFA/IV in 14%. CFA III was not found. All fifteen strains expressing CFA/IV expressed CS6 and produced ST. CFA/IV was not found in non-ST producing strains, while CFA/I was absent in ST-only producing strains.

Antigens, Bacterial↗

PubMed1995

Genetic construction and characterization of the diphtheria toxin-related interleukin 15 fusion protein DAB389 sIL-15.

A gene fusion encoding DAB389 sIL-15 was constructed in which the catalytic and transmembrane domains of native diphtheria toxin (DAB389) are genetically linked to the N-terminus of simian interleukin 15 (sIL-15). It was demonstrated that the cytotoxic action of DAB389 sIL-15 is mediated through the IL-15 receptor. Since toxicity may be blocked with chloroquine, it was concluded that following binding to the IL-15 receptor, the fusion toxin is internalized by receptor-mediated endocytosis and must pass through an acidic compartment in order to facilitate the delivery of the catalytic domain to the cytosol of target cells. As a non-toxic control, the ADP-ribosyltransferase defective mutant DA(E149S)B389 sIL-15 was constructed. It was demonstrated that both sIL-15 and DA(E149S)B389 sIL-15 stimulate protein and DNA synthesis in IL-15 receptor-positive CTLL-2 cells in vitro.

Amino Acid Sequence↗

PubMed1995

Variation in cancer risk estimates for exposure to powerline frequency electromagnetic fields: a meta-analysis comparing EMF measurement methods.

We used meta-analysis to synthesize the findings from eleven case-control studies on cancer risks in humans exposed to 50-60 Hertz powerline electromagnetic fields (EMFs). Pooled estimates of risk are derived for different EMF measurement methods and types of cancer. EMF measurement methods are classified as: wiring configuration codes, distance to power distribution equipment, spot measurements of magnetic fields, and calculated indices based on distance to power distribution equipment and historic load data. Pooled odds ratios depicting the risk of cancer by each measurement type are presented for all cancers combined, leukemia for all age groups and childhood leukemia. The wire code measurement technique was associated with a significantly increased risk for all three cancer types, while spot measures consistently showed non-significant odds ratios. Distance measures and the calculated indices produced risk estimates which were significant only for leukemia.

Adult↗

PubMed1995

Serum antibody to lipopolysaccharide antigens of Shigella species among U.S. military personnel deployed to Saudi Arabia and Kuwait during Operations Desert Shield and Desert Storm.

During Operations Desert Shield and Desert Storm, U.S. troops were at high risk of diarrheal disease due to Shigella spp., particularly Shigella sonnei. In order to better understand the serologic response to Shigella infection, 830 male U.S. combat troops were evaluated before and after the deployment to Saudi Arabia and Kuwait for immunoglobulin A (IgA) and IgG anti-Shigella lipopolysaccharide (LPS) (antibody to S. sonnei form I and Shigella flexneri serotypes 1a, 2a, and 3a) in serum. Just before deployment, 10.3% of the subjects were seropositive for IgA and 18.3% were positive for IgG anti-Shigella LPS. IgA and IgG anti-LPS antibody levels in serum prior to deployment were significantly associated with nonwhite race and ethnicity, birth outside the United States, and antibody to hepatitis A virus and Helicobacter pylori. During the deployment, which lasted for a mean of 131 days, 60% of the subjects reported at least one episode of diarrhea and 15% reported an episode of diarrhea with feverishness; also, 5.5% of the subjects exhibited IgA seroconversion to Shigella LPS and 14.0% exhibited IgG seroconversion. A significant association between the development of diarrheal symptoms and either positive predeployment anti-LPS antibody or seroconversion was not found. These data indicate that in this population of U.S. Desert Storm troops who were at high risk of Shigella infection, there was no apparent relation between IgA or IgG anti-Shigella LPS in serum and diarrheal disease.

Adolescent↗

PubMed1995

Molecular cloning, DNA sequence analysis, and characterization of the Corynebacterium diphtheriae dtxR homolog from Brevibacterium lactofermentum.

A homolog of the Corynebacterium diphtheriae dtxR gene was isolated from Brevibacterium lactofermentum. The product of the B. lactofermentum dtxR gene was immunoreactive with polyclonal anti-DtxR antibodies and functioned as an iron-activated repressor capable of regulating the expression of beta-galactosidase from a diphtheria tox promoter/operator transcriptional fusion in recombinant Escherichia coli. The extents of induction by increasing concentrations of the chelator 2,2'-dipyridyl were identical in cells expressing DtxR from either C. diphtheriae or B. lactofermentum.

Amino Acid Sequence↗

PubMed1995

Longitudinal measurement of anticardiolipin antibodies during normal pregnancy: a prospective study.

We have previously shown that elevation of anticardiolipin antibodies (aCL) at the first prenatal visit is associated with increased fetal loss in normal pregnancy. The variation in aCL levels during normal pregnancy has not been established. To examine this question we measured IgG, IgM and IgA aCL levels five times during pregnancy at weeks 5-15, 16-25, 26-35, 36-37 and at delivery. Data were analyzed to determine: (a) the within and between subject variability of aCL during pregnancy; (2) the temporal trend of aCL; and (3) the relation of serial measures of aCL with maternal complications of pregnancy. We divided our cohort of 354 subjects into two groups. Group A included those subjects with consistently normal levels of aCL and group B those subjects with at least one elevated level of aCL. In group A the within subject variability was relatively low (28-34%). In group B we found wide fluctuations in aCL levels and a within subject variability of 88-91%. Subjects in group B had no increase in maternal complications of pregnancy. The present data suggest that aCL may fluctuate significantly during normal pregnancy and there is little clinical value in measuring aCL on a serial basis during pregnancy.

Adolescent↗

PubMed1995

Effect of supplementation with an iron-fortified milk on incidence of diarrhea and respiratory infection in urban-resident infants.

To address the hypothesis that increased infectious morbidity is associated with iron supplementation, 783 randomly selected infants were provided with a powdered full fat cow's milk (non-fortified group) and 872 with a powdered acidified full fat cow's milk fortified with 15 mg of iron as ferrous sulfate (fortified group). All infants were followed from birth to 15 months of age with a monthly home visit by a nurse who recorded morbidity occurring during the previous 30 days. At 9 months of age, 15% of infants in each cohort were receiving breast milk only; data for these infants were segregated to make the third group. Episodes (mean +/- SD) of diarrhea/infant/year were 1.06 +/- 1.29, 1.14 +/- 1.37, and 0.82 +/- 1.04 for the fortified, non-fortified and breast-fed groups, respectively; the fortified and non-fortified bottle-fed groups had a very similar incidence of respiratory illness; 2.66 +/- 2.07 and 2.74 +/- 2.24 episodes/infant/year, respectively. The incidence of respiratory illness for both bottle-fed groups was significantly higher than that for the breast-fed group (2.22 +/- 1.84 respiratory episodes/infant/year). We conclude that for the infants the tested form of iron fortified milk, which is sufficient to lower iron deficiency anemia, does not result in an increased incidence of diarrhea or respiratory illness.

Analysis of Variance↗

PubMed1995

Campylobacter diarrhea in Alexandria, Egypt.

The role of Campylobacter as a cause of bacterial diarrhea in young children in Alexandria, Egypt was investigated. Stools or rectal swabs were collected from 880 children (mean age 9.8 months) presenting to a hospital with the primary complaint of diarrhea and from 1,079 well children (mean age 8.8 months) attending a vaccination clinic. Isolation of Campylobacter was significantly (p<0.0002) more frequent from cases (17.2%) than from controls (6.4%). Campylobacter was isolated from children presenting with diarrhea more frequently than Salmonella (3% isolation rate), Shigella (2% isolation rate), or other bacterial pathogens (1% isolatoin rate). Isolation of Campylobacter was significantly more frequent during the rainy season (p<0.0012). These results implicate Campylobacter as a major bacterial cause of diarrhea for which young children are brought for medical attention in Alexandria, Egypt.

Ambulatory Care Facilities↗

PubMed1995

Characteristics of Shigella sonnei infection of volunteers: signs, symptoms, immune responses, changes in selected cytokines and acute-phase substances.

Shigella sonnei infection resulting from oral administration of 500 colony-forming units was followed in 11 volunteers with the objective of studying the immune response and pathogenesis. Characterization of infection included recording of signs and symptoms, excretion of S. sonnei in stool, measurement of humoral tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma), C-reactive protein, IL-2 receptor, soluble CD8, antibody-antigen complexes, and endotoxin. Measurements were also made of the immune response including lymphocytes secreting antibody to S. sonnei O antigen and serum antibody to this antigen. Six of the volunteers developed typical shigellosis with excretion of bacteria in stool and systemic signs and symptoms, three excreted bacteria but did not show illness, and two showed no evidence of infection or illness. Shigellosis was characterized by excretion in stool of S. sonnei beginning on average 1.3 days after ingestion. Excretion of S. sonnei (mean of time of the first positive cultures) was followed in sequence by the onset of increases in TNF-alpha (10 hr), liquid stools (14 hr), fever and dysentery (18 hr), IFN-gamma (22 hr), and C-reactive protein (34 hr). A S. sonnei-specific immune response was demonstrated somewhat later, between days 4 and 7 postinfection by antibody-secreting cells, and between days 7 and 14 postinfection by humoral antibody. Shigellosis was not associated with increased humoral IL-1 beta, endotoxin, or antigen-antibody complexes.

Acute-Phase Proteins↗

PubMed1995

Educational and consultative functions, topics, and methods of hospital general tumor conferences.

The educational and consultative functions, topics, and methods of 20 hospital general tumor conferences in Colorado were studied over a three-year period. Methods used included questionnaires completed by hospital admitting staff members, by tumor conference directors, and by conference attendees. Workshops were held in which a multidisciplinary panel of physicians, nurses, and cancer registrars discussed the educational and patient-management aspects of tumor conferences with tumor conference directors. The study design included evaluation of the effects of providing certain teaching aids, including newsletters, Physician Data Query printouts, and tumor registry data on the functions, topics, and methods of the conferences. Although certain temporal trends were suggested, the handouts as employed added little of perceived effectiveness for the busy clinicians attending. The characteristics of the tumor conferences were analyzed according to hospital size, presence of one or more residency programs, and location (metropolitan or otherwise). One observation was that relatively few primary care physicians attended these tumor conferences, especially those in large hospitals, and approaches to meeting the needs of that group are discussed. The importance of the interpersonal skills of the tumor conference director in the effectiveness of the conference was very evident.

Colorado↗

PubMed1995

HIV-1 prevalence and risk factors among sexually transmitted disease clinic attenders in Trinidad.

OBJECTIVES: To study trends in prevalence and to ascertain risk factors for HIV-1 among sexually transmitted disease (STD) clinic attenders in Trinidad. DESIGN AND METHODS: Serial cross-sectional studies were conducted in 1987-1988 and 1990-1991 at a centralized STD clinic in Port of Spain. A case-control study was carried out to examine in greater detail the demographic and behavioral risk factors for HIV-1 among self-declared heterosexuals in this population. RESULTS: HIV-1 prevalence increased from 3.0% [95% confidence interval (CI), 2.3-3.9] in 1987-1988 to 13.6% (95% CI, 11.8-15.6) in 1990-1991. Age > or = 40 years [odds ratio (OR), 2.0; 95% CI, 1.4-2.8], urban residence (OR, 2.2; 95% CI, 1.6-3.0), and human T-lymphotropic virus-I seropositivity (OR, 3.1; 95% CI, 1.6-6.0) were significant risk factors for HIV-1 in 1990-1991. In the case-control analysis, significant independent risk factors for men included current genital ulcer disease (OR, 5.2; 95% CI, 2.2-12.5), current genital warts (OR, 3.9; 95% CI, 1.2-12.0), having ever had syphilis (OR, 3.2; 95% CI 1.6-6.1), and use of crack cocaine in the preceding 6 months (OR, 6.2; 95% CI, 2.7-14.2). Corresponding risk factors for women were commercial sex work (OR, 5.7; 95% CI, 1.3-25.7), initiation of sexual activity before age 14 years (OR, 4.8; 95% CI, 1.5-16.0), and past non-gonococcal cervicitis (OR, 4.1; 95% CI, 1.3-13.1). CONCLUSIONS: HIV-1 in this setting is primarily heterosexually transmitted in a milieu of unprotected sexual activity fuelled by a crack cocaine epidemic. Targeted interventions to prevent, detect and treat STD and crack cocaine addiction, as well as disrupt their adverse synergism, may substantially reduce HIV-1 transmission in this population.

Adult↗

PubMed1995

Attitudes of Colorado health professionals toward breast and cervical cancer screening in Hispanic women.

BACKGROUND: A variety of economic, cultural, and communication barriers appear to be involved in breast and cervical cancer screening among Hispanic women. These barriers include culture-based embarrassment both for mammography and for Pap smears and fear and hopelessness concerning a diagnosis of cancer. Cost and access barriers are shared by low-income women from various ethnic and racial groups, as is a purported lack of physician referral. Hispanic women may have the latter problem enhanced by a language barrier between physicians and patients when the physicians do not speak or understand Spanish. PURPOSE: The goal of this project, conducted by the Cancer Education Division of the University of Colorado Cancer Center, has been to determine the attitudes and practices among health care providers in areas of Colorado with relatively large Hispanic populations (concerning screening mammography, clinical breast examination, breast self-examination, and Pap testing) and to design interventions to address any deficiencies or problems recognized. These studies were coordinated with telephone surveys and focus groups involving Hispanic women, directed by E. Flores in the Department of Sociology of the University of Colorado at Boulder and by C. Chrvala at the Colorado Department of Health. METHODS: Data were collected from 520 primary care physicians, nurses, and allied health personnel in 11 Colorado counties through focus groups and mailed questionnaires. Responses were analyzed by considering a variety of demographic characteristics of the respondents and by stratifying the associated practices by percent of Hispanic patients. RESULTS: The physicians involved in the focus groups and responding to the questionnaires, as well as their associated nurses and other health care personnel, are generally familiar with the breast and cervical cancer-screening guidelines as developed and disseminated by several organizations, including the National Cancer Institute and the American Cancer Society. Major barriers to screening Hispanic women, as perceived by these health care providers, appear to be cost; lack of transportation, child care, and release from work; fear of diagnosis of cancer; patients considering the test unnecessary; discomfort; and embarrassment. The prompt use of colposcopy to evaluate patients whose Pap smears indicated dysplasia appeared less than optimal, especially among internists. CONCLUSIONS: Familiarity with guidelines for breast and cervical cancer screening is widespread among Colorado physicians and associated health care personnel, including those with high percentages of Hispanic patients in their practices. Increased continuing education efforts may be indicated concerning the application of colposcopy to the evaluation of women with abnormal Pap smears and concerning the application of computer technology to cancer-screening reminder systems. IMPLICATIONS: Educational approaches to primary care professionals may improve the effectiveness of breast and cervical cancer screening, although a variety of other approaches will also be necessary to decrease barriers to screening of Hispanic women.

Adult↗

PubMed1995

Treatment of travellers' diarrhoea: zaldaride compared with loperamide and placebo.

OBJECTIVE: To compare zaldaride maleate, a calmodulin inhibitor with gastrointestinal antisecretory properties, with loperamide and a placebo in the treatment of travellers' diarrhoea. DESIGN: Randomized, double-blind, double-dummy study. SETTING: Study clinic staffed by European residents on Nile cruise ships. PATIENTS: Tourists (n = 436) who acquired travellers' diarrhoea during the Nile cruise. INTERVENTIONS: (1) Zaldaride 20 mg four times daily, (2) zaldaride 2 x 20 mg as initial loading dose followed by three doses of 20 mg on the first day and four doses of 20 mg on the second day, (3) loperamide 2 x 2 mg loading dose following by a flexible dosage of 2 mg after each unformed stool (maximum of 16 mg daily), (4) placebo. MAIN OUTCOME MEASURES: Number of unformed stools, rate of improvement of patients with diarrhoea, rate of relief from diarrhoea. RESULTS: Among the 331 compliant and fully evaluated patients, the zaldaride with loading dose group showed no significant differences in cure rates from the loperamide group. For most parameters, zaldaride without a loading dose and the placebo resulted in significantly lower cure rates. CONCLUSIONS: A zaldaride regimen including a loading dose was shown to be well tolerated and as effective as loperamide.

Adolescent↗

PubMed1995

Diphtheria toxin-based receptor-specific chimaeric toxins as targeted therapies.

The results from the phase I/II studies of the intravenous administration of DAB486-IL-2 to patients with refractory haematological malignancies have now proven in principle the feasibility of fusion toxin therapy in man. Indeed, the cell-surface receptor-specific intoxication of neoplastic cells through the catalytic ADP-ribosylation of EF-2 is the prototype of a new class of biological response modifiers that may be generally applicable. In those circumstances where either the de novo expression or up-regulation of a cell-surface receptor can be associated with human disease [e.g. the up-regulation of the epidermal growth factor (EGF) receptor on breast cancer], it should be possible to construct genetically a DT-related/growth factor fusion protein to produce an experimental biological treatment of that malignancy. The EGF receptor-targeted fusion toxin DAB389-EGF has within the last year begun human phase I clinical trials. The pre-clinical development of DAB389-IL-7 has begun with the anticipation that this novel fusion toxin will be evaluated in the treatment of the acute leukaemias in which the IL-7R has been shown to be present.

Amino Acid Sequence↗