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Biomedical subjects

B Gray

Publications and source records attributed to B Gray.

At least 19 recordsLinked to original sources
PubMed1999

Comparison of the rates of exchange of lead in the blood of newly born infants and their mothers with lead from their current environment.

Newly born infants (n = 15) were monitored for 6 months after birth or for longer periods to evaluate the changes in isotopic composition and lead concentration in infants as compared with that in women from the same population groups and to determine the clearance rates of lead from blood in the infants. These data represent the first published results for serial blood sampling in a relatively large cohort of newly born infants. Blood lead concentrations decrease from the cord to samples taken at 60 to 90 days and then increase by amounts varying from negligible to 166%. In spite of concern about individual susceptibility to lead pharmacokinetics, changes in isotopic ratio followed a smooth decrease over time for 9 of the 11 infants born to migrant parents, and the patterns of variation were quite reproducible. Data for 2 of 4 infants born to multigenerational Australian parents exhibited little change in isotopic ratio over time, and in the other two cases, the changes were attributed to diet. The rate of exchange (t1/2) for the migrant infants of lead in blood derived from the mother during pregnancy and the lead from the current environment was calculated by using a linear function and ranged from 65 to 131 (91+/-19, mean+/-SD) days. The half-lives for the exchange of skeletal and environmental lead for 7 of the 8 women before significant mobilization of lead from the maternal skeleton ranged from 50 to 66 (59+/-6) days. One explanation for the longer half-lives for infants as compared with the mothers may be the proportionally higher contribution of current environmental (Australian) lead in the infants at parturition. Exchanges of lead in infants are more complex than for the adults, reflecting inputs from sources such as maternal skeletal lead during breast feeding.

Adolescent↗
PubMed1998

Designed beta-sheet-forming peptide 33mers with potent human bactericidal/permeability increasing protein-like bactericidal and endotoxin neutralizing activities.

Novel peptide 33mers have been designed by incorporating beta-conformation stabilizing residues from the beta-sheet domains of alpha-chemokines and functionally important residues from the beta-sheet domain of human neutrophil bactericidal protein (B/PI). B/PI is known for its ability to kill bacteria and to neutralize the action of bacterial endotoxin (lipopolysaccharide, LPS) which can induce septic shock leading to eventual death. Here, the goal was to make short linear peptides which demonstrate good beta-sheet folding and maintain bioactivity as in native B/PI. A library of 24 peptide 33mers (betapep-1 to betapep-24) were synthesized with various amino acid substitutions. CD and NMR data acquired in aqueous solution indicate that betapep peptides form beta-sheet structure to varying degrees and self-associate as dimers and tetramers like the alpha-chemokines. Bactericidal activity toward Gram-negative Pseudomonas aeruginosa was tested, and betapep-19 was found to be only about 5-fold less potent (62% kill at 1.2 x 10(-7) M) than native B/PI (80% kill at 2.9 x 10(-8) M). At LPS neutralization, betapep-2 and -23 were found to be most active (66-78% effective at 1.2 x 10(-6) M), being only about 50-100-fold less active than B/PI (50% at 1.5 x 10(-8) M). In terms of structure-activity relations, beta-sheet structural stability correlates with the capacity to neutralize LPS, but not with bactericidal activity. Although a net positive charge is necessary for activity, it is not sufficient for optimal activity. Hydrophobic residues tend to influence activities indirectly by affecting structural stability. Furthermore, results show that sequentially and spatially related residues from the beta-sheet domain of native B/PI can be designed into short linear peptides which show good beta-sheet folding and retain much of the native activity. This research contributes to the development of solutions to the problem of multiple drug-resistant, opportunistic microorganisms like P. aeruginosa and of agents effective at neutralizing bacterial endotoxin.

Amino Acid Sequence↗
PubMed1998

Intravenous RMP-7 increases delivery of ganciclovir into rat brain tumors and enhances the effects of herpes simplex virus thymidine kinase gene therapy.

Herpes simplex virus thymidine kinase (HSV-tk) gene therapy for brain tumors depends on ganciclovir (GCV) and its transport across the blood-brain tumor barrier (BBTB). We examined whether RMP-7, the bradykinin analog and potent BBTB permeabilizer, could enhance the efficacy of GCV treatment of brain tumors by increasing the BBTB delivery of GCV. In vitro, a significant bystander cytocidal effect of GCV was shown in mixed HSV-tk-transduced (HSV-tk+) and control vector-transduced (HSV-tk-) C6 glioma cultures. A dose-dependent cytotoxic effect of GCV on untransformed C6 cells was also shown. In vivo, rats with 100% HSV-tk+ or 100% HSV-tk- intracerebral C6 gliomas were treated for 7 days with intravenous infusions of GCV alone or with GCV and RMP-7 (2.5 microg/kg/day). The growth of HSV-tk+ and HSV-tk- gliomas decreased with increasing doses of GCV. A high dosage (100 mg of GCV/kg/day) eradicated all HSV-tk- and HSV-tk+ tumors. An intermediate dosage (5 mg of GCV/kg/day) reduced the growth of HSV-tk- gliomas by 42% if given alone, and by 88% in combination with RMP-7. A low dosage (0.5 mg of GCV/kg/day) in combination with RMP-7 enhanced the regression of HSV-tk+ gliomas by 87% compared with GCV alone. Low-dose GCV was ineffective in HSV-tk- tumors. RMP-7 increased [3H] GCV tumoral uptake by 2.6- and 1.7-fold in the tumor center and periphery, respectively. We conclude that RMP-7 could be an important adjunctive treatment for suicide gene therapy of brain tumors, while an RMP-7/GCV combination may also have a significant antitumor effect in untransfected gliomas.

3T3 Cells↗
PubMed1998

In vitro selection for K562 cells with higher retrovirally mediated copy number of aldehyde dehydrogenase class-1 and higher resistance to 4-hydroperoxycyclophosphamide.

Previously, we have reported the successful expression of human aldehyde dehydrogenase class-1 (ALDH-1) in K562 leukemia cells using a retroviral vector and demonstrated low expression that resulted in up to three-fold increase in resistance to 4-hydroperoxycyclophosphamide (4-HC), an active derivative to cyclophosphamide. The purpose of this study was to investigate whether in vitro treatment with 4-HC will allow selection of K562 cells expressing higher levels of ALDH-1, and whether these selected cells are more resistant to 4-HC. Stably transfected or transduced K562 cells with retroviral pLXSN vector containing ALDH-1 cDNA (ALDH-1 cells) were treated repeatedly with 4-HC and then allowed to grow to confluence in liquid culture. Subsequently, the resistance to 4-HC of ALDH-1 cells treated once (ALDH-1+) or twice (ALDH-1++) with 4-HC was compared to ALDH-1 cells or wild-type K562 cells (WT cells). The results show significant increase in 4-HC resistance of ALDH-1+ (2- to 16-fold, p < 0.005) over ALDH-1 or WT cells. No difference was detected between ALDH-1+ and ALDH-1++. In addition, higher ALDH-1 mRNA and enzyme activity were found in ALDH-1+ compared to ALDH-1 cells. Southern analysis of DNA extracted from the different experimental groups demonstrated an eight-fold increase in ALDH-1 cDNA in ALDH-1+ versus the ALDH-1 cells. This was confirmed by sequential FISH analysis using biotin labeled pLXSN/ALDH-1 vector. Positive signals consistently localized to the centromeric region of chromosome 9 and the long arm of chromosome 17 were demonstrated only in the ALDH-1+ cells and represented a fusion product of multiple copies of the pLXSN/ALDH-1 vector. In summary, we have demonstrated that in vitro treatment with 4-HC results in the selection of K562 cells with multiple copies of ALDH-1 gene that are clustered in two main integration sites. These cells demonstrate significantly higher resistance to 4-HC when compared to previously untreated cells. Such successful in vitro selection could have significant implications for future cancer gene therapy protocols.

Aldehyde Dehydrogenase↗
PubMed1998

Retroviral vector-mediated gene transfer into keratocytes in vitro and in vivo.

PURPOSE: To determine the potential of somatic gene transfer as a technique for modulating corneal wound healing after superficial keratectomy. METHODS: The transduction of human and rabbit keratocytes with beta-galactosidase and herpes simplex virus thymidine kinase genes was performed. In vitro, human and rabbit keratocytes were transduced with retroviral vectors bearing beta-galactosidase or HStk (herpes simplex virus thymidine kinase) genes. In vivo, rabbit keratocytes were transduced by topical application of vector supernatant after a superficial keratectomy. In vitro and in vivo, expression of the beta-galactosidase gene was examined with histochemical staining. In vitro, ganciclovir cytotoxicity in HStk gene-transduced keratocytes and bystander effect in co-cultures of HStk(+) and HStk(-) keratocytes were measured by determining the degree of confluency of cells in 6-well plates after 10 days of incubation. Corneal haze in rabbits was measured after transduction with Hstk and subsequent treatment with topical ganciclovir. RESULTS: In vitro, both human and rabbit keratocytes were transduced successfully with both beta-galactosidase and HStk genes. Transduction efficiency was greater with human (22%) than with rabbit (16%) cells, and both HStk-transduced cell lines showed dose-dependent ganciclovir cytotoxicity and a significant bystander effect. In vivo, expression of beta-galactosidase within vimentin-positive corneal stromal cells confirmed transduction of keratocytes in the rabbit after superficial stromal keratectomy with an efficiency of 25% to 40%. Postoperative application of topical ganciclovir reduced corneal stromal haze in rabbits. CONCLUSIONS: The ability to genetically transduce stromal keratocytes provides a new strategy for understanding the important cellular and molecular events that influence corneal wound healing, thus offering a potential approach to decrease or prevent corneal haze and scarring after superficial keratectomy.

Animals↗
PubMed1998

Comparative in vitro activities of four new fluoroquinolones against Streptococcus pneumoniae determined by Etest.

Clinafloxacin, levofloxacin, sparfloxacin and trovafloxacin were tested by Etest against 188 Streptococcus pneumoniae isolates. Clinafloxacin and trovafloxacin were 2-4-fold more potent than sparfloxacin and 8-fold more than levofloxacin. Two isolates, both serotype 6, with high-level quinolone resistance (> or = 8 micrograms/ml) were detected. The Etest is a practical means for determining S. pneumoniae susceptibilities to new fluoroquinolones.

Anti-Infective Agents↗
PubMed1998

The use of video-imaging to assess the sub-lethal impact of plant secondary compounds on Schistosoma mansoni miracidia.

The study describes methods developed for using video-imaging technology to record and measure the velocity of Schistosoma mansoni miracidia. The efficacy of the classical bioassay procedure (a qualitative behavioural assay) was compared with that of the new quantitative protocol, for assessing the sub-lethal impact of a larvicidal dichloromethane extract of the seeds of Millettia thonningii on miracidia. The new technique confirmed the efficacy of the classical bioassay for rapid determination of the lethal and sub-lethal impact of larvicides but also provided quantitative information on sub-lethal impacts on miracidial velocity and shape.

Animals↗
PubMed1997

Induction and prevention of colonic inflammation in IL-2-deficient mice.

Gene-targeted mice deficient for IL-2 (IL-2 -/- mice) are free of apparent disease when maintained under germfree conditions but develop colitis and autoimmunity in a conventional environment. Here we show that colitis can be reproducibly induced in IL-2 -/- mice, but not in IL-2 +/+ mice, by i.p. immunization with Ag in CFA; thus enabling the systematic study of the immunopathogenesis of the colitis. We found that TNP-KLH or TNP-OVA had the most significant effect in inducing colitis, and while TNP-KLH immunization leads to the early appearance of activated T cells in the colons of both IL-2 -/- and IL-2 +/+ mice, only lamina propria cells of IL-2 -/- mice produced high amounts of INF-gamma. Moreover, both infiltrating colon CD4+ (69%) and CD8+ (6%) T cells secrete large amounts of IFN-gamma; however, only the depletion of CD4+ T cells leads to abrogation of the inflammation. In further analysis, we showed that the high IFN-gamma production is IL-12 driven, since colonic tissues of IL-2 -/- mice but not IL-2 +/+ mice show the presence of heterodimeric IL-12 and co-administration of anti-IL-12 with TNP-KLH completely prevented colitis and significantly reduced IFN-gamma production. Finally, we demonstrate that IL-2 -/- mice are deficient in their ability to induce Th2 responses after TNP-KLH challenge and that such immunization also leads to autoimmune-like phenomena in other organs of IL-2 -/- mice. These findings suggest that in the absence of IL-2 systemic administration of Ag induces primarily Th1 cells driven by overexpression of heterodimeric IL-12.

Animals↗
PubMed1997

Dysregulated intrathymic development in the IL-2-deficient mouse leads to colitis-inducing thymocytes.

Gene-targeted mice lacking the IL-2 gene (IL-2 -/- mice) develop various forms of autoimmunity as well as severe colitis, either spontaneously in a conventional environment or after immunization with 2,4,6-trinitrophenol (TNP)-conjugated keyhole limpet hemocyanin (KLH) in a specific pathogen-free environment. We show here that the induction of colitis with TNP-KLH induces a change in the thymocyte population characterized by decreased numbers of double positive (DP; CD4+CD8+) thymocytes (IL-2 +/+, 45.2 x 10(6) vs IL-2 -/-, 23.6 x 10(6)) and increased numbers of single positive (SP; CD4+CD8- or CD4-CD8+) thymocytes (IL-2 +/+, 5.3 x 10(6) vs IL-2 -/-, 20.9 x 10(6)). The latter also bear activation markers. In addition, thymocytes from TNP-KLH-immunized IL-2 -/- mice produce more IFN-gamma and less IL-4 than similarly immunized IL-2 +/+ mice. These defects in thymocyte maturation and lymphokine production are IL-12 driven, since they are prevented when immunized IL-2 -/- mice are coadministered with anti-lL-12. Furthermore, we demonstrate that IL-2 -/- mice exhibit decreased cortical apoptosis as determined by thymocyte numbers and detection of apoptotic cells in situ. Finally, we show that colitis-inducing thymocytes are generated in the immunized IL-2 -/- thymus, since IL-2 +/+ mice develop colitis following injection of small numbers of single positive thymocytes from immunized IL-2 -/- mice but not from IL-2 +/+ mice. Taken together, these data indicate that, in the absence of IL-2, thymocyte maturation is abnormally directed by IL-12 toward the generation of mature, activated Th1-type thymocytes that are capable of mediating colitis.

Animals↗
PubMed1997

Patient-physician pairing: does racial and ethnic congruity influence selection of a regular physician?

Many public and private sector efforts are devoted toward increasing the training of physicians from under-represented minority groups, yet little has been documented regarding the association between physicians' racial backgrounds and the patient populations they serve. To address this question, we use 1987 National Medical Expenditure Survey to examine the impact of race/ethnicity on the matching between physician and patients. Our results show that minority patients are significantly more likely to report having a minority physician as their regular doctor. We estimate that minority patients are five times as likely as non-minorities to report that their regular physician is a member of a racial/ethnic minority. This effect is especially pronounced among Hispanics who identify a Hispanic physician as their regular provider 19 times more often than non-minorities. After controlling for other socioeconomic factors, both these figures remain significant, but drop by approximately one-half. These results support the notion that minority patients tend to see minority physicians at a disproportional rate independent of other socio-economic factors.

Black or African American↗
PubMed1997

Out to tender--the nurses' role in awarding the contract for therapeutic bed/mattress hire.

AIM: A project group was established to award the contract for hire of therapeutic beds and mattresses for a large hospital Trust within the United Kingdom National Health Service (NHS). BACKGROUND: No structure existed for awarding or evaluating such a contract. Involving nurses in the process was intended to bring the decision-making nearer the patient. METHOD: The project group consisted of volunteers from a range of clinical nursing grades. They were highly motivated with an interest in pressure sore management. Expertise from NHS Supplies was also involved. RESULTS: The project group successfully awarded the contract, producing a robust operational tool through an objective process. Awareness was raised regarding control of expenditure and a commitment to education. Ongoing evaluation of the contract has also been the responsibility of this group. CONCLUSION: The project group achieved its aim of awarding a contract that best met the needs of the Trust and continues to monitor that contract. The systematic approach, comprehensive documentation and collaboration with NHS Supplies are felt to contribute to its success. Explicit criteria within the contract provides a clear framework for its monitoring and evaluation.

Beds↗
PubMed1997

In vitro activities of oral antimicrobial agents against penicillin-resistant Streptococcus pneumoniae: implications for outpatient treatment.

We tested 83 penicillin-intermediate (Peni) and 50 penicillin-resistant (Penr) isolates of Streptococcus pneumoniae against eight oral antimicrobials. Clarithromycin's MICs (minimal inhibitory concentration) were generally the same or one to two dilutions less than those of azithromycin. Seventy-two percent of Peni isolates were susceptible to clarithromycin and azithromycin, in contrast to 42% and 40%, respectively, of Penr isolates. Cefuroxime activity exceeded that of cefprozil, which exceeded that of cefaclor, in Peni isolates. For all three cephalosporins, MICs of 90% of isolates tested were > or = 3 dilutions higher for Penr isolates than for Peni isolates. Percentages of Peni isolates susceptible to clindamycin and tetracycline were 92% and 83%, respectively, and 78% and 82% for Penr. Only 49% of Peni isolates and 4% of Penr isolates were susceptible to trimethoprim-sulfamethoxazole. Azithromycin, clarithromycin, cefuroxime, cefprozil, clindamycin, and tetracycline may be useful in treating infections caused by Peni S pneumoniae, but Penr isolates are frequently resistant to both old and newer agents.

Administration, Oral↗
PubMed1997

Maternal smoking and medical expenditures for childhood respiratory illness.

OBJECTIVES: This study sought to assess the association between environmental tobacco smoke exposure from maternal smoking and health care expenditures for respiratory conditions among US children. METHODS: Multivariate analysis of the 1987 National Medical Expenditure Survey was undertaken with a sample that included 2624 children 5 years of age and under. RESULTS: After analysis that controlled for various sociodemographic factors associated with health care usage, respiratory-related health care expenditures among children whose mothers smoke were found to be significantly higher than those expenditures for children of nonsmoking mothers. Truncated regression techniques were used to estimate that maternal smoking was associated with increased health care expenditures averaging (in 1995 dollars) $120 per year for children aged 5 years and under and $175 per year for children aged 2 years and under. Our analysis indicates that passive smoking was associated with $661 million in annual medical expenditures in 1987, representing 19% of all expenditures for childhood respiratory conditions. CONCLUSIONS: Maternal smoking is associated with significantly increased child health expenditures and contributes significantly to the overall cost of medical care.

Child, Preschool↗
PubMed1997

Age distribution of lymphocytic choriomeningitis virus serum antibody in Birmingham, Alabama: evidence of a decreased risk of infection.

Lymphocytic choriomeningitis virus (LCMV) is an arenavirus that causes human disease ranging from a mild, flu-like illness to meningitis. Infections occur principally in and around the home due to contact with infected mice. Data on the incidence of LCMV infection in the United States are scarce but suggest that the risk of infection may have decreased over the past 30-40 years. To examine this hypothesis, sera from an age-stratified sample of hospital patients in Birmingham, Alabama were tested for LCMV antibody by ELISA. The overall prevalence of LCMV-specific IgG was 3.5% (56 of 1,600). The prevalence of antibody among those < 30 years of age was 0.3% (2 of 600), while the prevalence among those 30 years of age and older was 5.4% (P < 0.0001). Multiple logistic regression was used to identify risk factors for LCMV seropositivity. Age was positively associated (P < 0.0001) and socioeconomic status was negatively associated with a positive antibody test result (P < 0.03). These data are consistent with a decreased incidence of human LCMV infection in Birmingham over the past 30-40 years.

Adolescent↗
PubMed1997

Development of a reverse transcription-polymerase chain reaction assay for diagnosis of lymphocytic choriomeningitis virus infection and its use in a prospective surveillance study.

Lymphocytic choriomeningitis virus (LCMV), which is one of several arenaviruses that are pathogenic for humans, causes encephalitis and meningitis in man. In this study, single-stage and nested reverse transcription-polymerase chain reaction (RT-PCR) assays were developed that targeted the GPC and N genes of LCMV. Both assays detected < 1 TCID50 unit of LCMV. These assays were used to measure the incidence of LCMV infection by testing cerebrospinal fluid (CSF) samples with > or = 10 leukocytes/microl collected over 1 year from patients undergoing lumbar puncture for diagnostic reasons at two Birmingham hospitals. Samples were tested for the presence of LCMV RNA by using the RT- PCR assay and for LCMV-specific IgM antibody by using an ELISA assay. None of the specimens collected from 813 patients was positive by either assay. Although no cases of acute infection were detected, 4% (11/272) of serum collected from a subset of patients was positive for LCMV-specific IgG. A significantly greater rate of seropositivity was found among subjects over 60 years of age (9.4%; P < 0.025) than was found in younger subjects (2.4% at 30-59 years of age; 0% at < 30 years of age). These data suggest that serious central nervous system disease due to LCMV infection is not common in this population. The high rate of seropositivity in those over 60 years of age suggest that infection was once more common.

Adult↗
PubMed1996

Reciprocal regulation of mucosal surface IgA+ B cells by Ig receptor cross-linking and CD40 ligand.

In the present study, we analyze the role of Ig receptor cross-linking in T cell-dependent stimulation of both preswitch (surface IgM+ (sIgM+/sIgD+) B cells and postswitch (sIgA+) B cells. We demonstrate that purified sIgA+ B cells pretreated with anti-IgA-dextran at low concentrations (10 and 100 ng/ml) exhibited an increased response to activated T cells, whereas pretreatment with higher doses (1 and 10 micrograms/ml) led to a profound suppression of IgA secretion (> or = 90%). The suppressive effect of anti-IgA-dextran was accentuated in the presence of IL-2 and attenuated in the presence of IL-4. Anti-IgA-dextran pretreatment had no effect on sIgA+ B cell survival. sIgM+/sIgD+ B cells pretreated with anti-IgD-dextran or anti-IgM-dextran did not show significant inhibition. The increased susceptibility of sIgA+ B cells, but not of sIgM+/sIgD+ B cells, to Ig cross-linking-mediated suppression was confirmed in cross-linking studies with the same Ab (anti-kappa-dextran). Importantly, anti-IgA-dextran-mediated suppression could be reversed by stimulation of sIgA+ B cells with fibroblasts expressing CD40L; such a reversal required persistent exposure to cells expressing high levels of CD40L. These studies imply that Ig receptor cross-linking renders postswitch sIgA+ B cells unresponsive to subsequent stimulation via activated T cells, but this unresponsiveness is overcome by a persistent high level CD40L signal.

Animals↗