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Biomedical subjects

C Baker

Publications and source records attributed to C Baker.

At least 19 recordsLinked to original sources
PubMed1992

Tyrosine kinase triggering in thymocytes undergoing positive selection.

Developing T cells undergo distinct selection processes that determine the T cell receptor (TcR) repertoire. One of these processes is positive selection. Positive selection involves the differentiation to mature T cells of thymocytes bearing TcR capable of recognizing antigens in the context of self-major histocompatibility complex (MHC) molecules. To study the potential involvement of tyrosine phosphorylation in the mechanism of positive selection, we have analyzed the activities of the tyrosine kinases pp56lck and pp59fyn in thymocytes expressing a unique TcR specific for HY antigen+ H-2 Db. Thymocytes undergoing positive selection displayed higher kinase specific activities of pp56lck and pp59fyn than nonselecting thymocytes. Furthermore, these increases in kinase activities were found only in the CD4+CD8+ subpopulation of thymocytes, where the selection process is believed to occur. These data suggest that tyrosine phosphorylation is part of the intracellular signals involved in MHC class I-driven positive selection from CD4+CD8+ immature thymocytes to CD4-CD8+ mature cells.

Animals↗
PubMed1992

Production and characterization of a polyclonal antibody to the c-erbB-3 protein: examination of c-erbB-3 protein expression in adenocarcinomas.

A polyclonal rabbit antibody was raised to the c-erbB-3 protein using a synthetic peptide corresponding to amino acids 1229-1241 of the predicted protein sequence of c-erbB-3. In Western blot analysis this antibody detects a single band at approximately 165 kD in a c-erbB-3 transfected (293/HER-3) human cell line. c-erbB-3 protein expression was then examined in a variety of adenocarcinomas. Expression of c-erbB-3 protein was indicated by membrane and/or cytoplasmic tumour cell immunoreactivity in formalin-fixed, paraffin-embedded tissue sections. c-erbB-3 protein was detected in a series of 13 out of 14 primary breast carcinomas, 3 of 5 gastric adenocarcinomas, 8 of 9 colonic adenocarcinomas, 2 of 9 prostatic adenocarcinomas, 0 of 6 renal cell carcinomas, 1 of 4 primary lung adenocarcinomas, and 5 of 7 endometrial adenocarcinomas. Immunohistochemical expression of the c-erbB-3 protein appears to be a relatively common event in adenocarcinomas, and further studies are now warranted to establish the role of the c-erbB-3 protein in neoplasia.

Adenocarcinoma↗
PubMed1992

A population-based, multivariate analysis of the association between 911 access and per-capita county trauma death rates.

STUDY OBJECTIVE: Decreased response times for injury should decrease the morbidity and mortality of trauma. The 911 telephone access is designed to improve the response time for emergencies. The purpose of this study was to analyze the association between county 911 access and per-capita county trauma death rates. METHODS: Data on all trauma deaths from 1986 through 1988 were obtained from the North Carolina Medical Examiner's data base. Counties were divided into those that had 911 access during the entire study period (15), those that never had 911 access (62), and those that installed 911 during 1987 (ten). Counties obtaining 911 access in 1986 or 1988 were excluded (13). RESULTS: The per-capita trauma death rate in counties that had 911 access throughout the study was 4.3 +/- 0.8 versus 5.0 +/- 1.1 per 10,000 population in counties that never had 911 access (P less than .01). Compared with counties with 911 access, counties without 911 were more rural, were less likely to have a trauma center, and were less likely to have advanced life support certification (P less than .03 for all). Controlling for these other factors, multivariate analysis demonstrated that 911 access had no significant independent association with per-capita county trauma death rates. In the ten counties that implemented 911 access in 1987, no significant change occurred in per-capita county trauma death rates after implementation of 911. CONCLUSION: Although counties with 911 access had lower trauma death rates by t-test, multivariate analysis showed no significant independent association of 911 access with per-capita county trauma death rates. In the ten counties that implemented 911 access in 1987, no significant changes in trauma death rates occurred after implementation. Although other factors may explain these findings, this study showed no significant independent impact of 911 access on per-capita county trauma death rates.

Emergency Medical Service Communication Systems↗
PubMed1992

Method slurring: the grounded theory/phenomenology example.

Increasingly, qualitative research methods are being embraced by nurse researchers because these approaches allow exploration of human experience. Failure to explicate qualitative methodologies is resulting in a body of nursing research that is either mislabelled or is classified broadly as qualitative and subject to charges that qualitative research lacks rigour. In this paper, the authors discuss the importance of specificity in methodology and distinguish between phenomenology and grounded theory, two frequently misused terms in the description of qualitative methodology.

Data Collection↗
PubMed1992

Neutrophil-mediated damage to human gingival epithelial cells.

Polymorphonuclear leukocytes (PMNs) have been implicated in the pathogenesis of inflammatory gingivitis and periodontitis. To further study the role of PMNs in mediating gingival injury, we cocultured these cells in vitro with monolayers of human gingival epithelial cells. Scanning electron microscopy revealed that the epithelial cells were homogeneous and SDS-PAGE/immunoblot analysis identified the presence of keratins K3, K13 and the K6/16 pair which authenticated the oral origin of the cells. Injury to the gingival cells was determined by scanning electron microscopy and measurement of cell detachment and cytolysis. Unstimulated PMNs produced minimal lysis or detachment, but PMNs stimulated by phorbol myristate acetate produced marked epithelial cell detachment without lysis, which was time- and PMN-dose-dependent. Supernatants of activated PMNs were similarly effective, indicating that the mediator was a stable soluble substance. Elastase and cathepsin G, two neutral proteases of PMN origin, produced time- and concentration-dependent detachment of gingival epithelial cells, suggesting that these enzymes may mediate this form of injury. In other studies, gingival epithelial cells were exposed to PMN myeloperoxidase (MPO), chloride and glucose plus glucose oxidase (GO) as a hydrogen peroxide (H2O2) generating system. The toxic oxygen species produced by this system caused lysis of the epithelial targets which was dependent on the duration of incubation and the concentrations of MPO and GO. Azide, an inhibitor of MPO, and catalase, a scavenger of H2O2, inhibited the lytic activity of this system. Scanning electron micrographs of gingival epithelial cells cocultured with activated PMNs showed lifting of the cells from the plating surface, while target cells attacked by the MPO system revealed extensive damage of cell membranes. These studies indicate that activated PMNs cause nonlytic detachment injury to gingival epithelial cells which may be mediated by digestion of their extracellular matrix by granule neutral proteases. Furthermore, PMN MPO is capable of generating toxic oxygen species which can lyse these epithelial cells. Collectively, these actions could have profound adverse effects on the function and integrity of the gingival epithelium.

Cell Death↗
PubMed1992

Proposed interpretive criteria and quality control parameters for ofloxacin susceptibility testing of Neisseria gonorrhoeae.

A multilaboratory study designed to determine the in vitro susceptibility criteria and quality control parameters for ofloxacin against Neisseria gonorrhoeae was conducted according to the guidelines of the National Committee for Clinical Laboratory Standards. Proposed susceptibility breakpoints are MICs of less than or equal to 0.25 microgram/ml for the agar dilution test and greater than or equal to 31 mm for the disk diffusion test. A category for resistance could not be defined. Proposed acceptable quality control MICs for N. gonorrhoeae ATCC 49226 and Staphylococcus aureus ATCC 29213 range from 0.004 to 0.03 microgram/ml and 0.25 to 1.0 microgram/ml, respectively. With 5-micrograms ofloxacin disks, acceptable inhibitory zone diameters for S. aureus ATCC 25923 and the N. gonorrhoeae control strains range from 22 to 27 mm and 43 to 51 mm, respectively.

Drug Resistance, Microbial↗
PubMed1992

Interpretive criteria and quality control limits for testing susceptibility of Neisseria gonorrhoeae to enoxacin.

For testing the susceptibility of Neisseria gonorrhoeae to enoxacin, a proposed susceptibility category includes strains for which MICs are less than or equal to 0.5 micrograms/ml and zones of inhibition are greater than or equal to 32 mm in diameter. Because of the sparcity of resistant gonococci, a resistance category was not defined, but laboratory-selected resistant mutants were appropriately categorized by the proposed criteria. A review of clinical data confirmed the utility of a single 400-mg oral dose of enoxacin for treating gonorrhea caused by strains judged to be susceptible by the proposed criteria. For quality control purposes, for N. gonorrhoeae ATCC 49226 MICs should be 0.016 to 0.06 micrograms/ml and zones of inhibition should be 43 to 51 mm in diameter.

Enoxacin↗
PubMed1991

The variability in activity of the universally expressed human cytomegalovirus immediate early gene 1 enhancer/promoter in transgenic mice.

Transcriptional control regions which direct transgene expression to all tissues in transgenic animals can be useful tools for gain-of-function experiments in transgenic animals. A candidate for this purpose is the regulatory region of the human cytomegalovirus immediate early 1 gene (HCMVIE1) which is highly expressed in many lines of tissue culture cells. Here we analyzed the activity of the HCMVIE1 enhancer/promoter using a sensitive reporter gene, the bacterial chloramphenicol acetyltransferase (CAT) gene. Three lines of transgenic mice with an intact transgene were established. All 3 lines expressed the transgene in all 28 tissues analyzed; however, levels of expression between the three lines varied up to 100,000 fold. In addition, expression levels in the high expressing line varied over a 10,000 fold continuum, while expression levels between tissues was almost uniform in the lowest expressing line. The transgene was well expressed in the high expressing line; CAT activity in the highest expressing tissues was equivalent to levels previously reported for tissue specific CAT transgenes active only in a limited number of tissues. These data support the utilization of the HCMVIE1 enhancer/promoter as a means of expressing a transgene in all tissues, but indicate that lines with substantially different overall levels of expression may be generated, and that markedly different levels of tissue specific expression may be found when the overall level of transgene expression is high.

Animals↗
PubMed1991

The spectrum of abdominal injuries associated with the use of seat belts.

Several recent reports have described abdominal injuries occurring as a result of seat belt use, raising concerns about seat belts as an agent of injury in motor vehicle crashes. The purpose of this study was to characterize the distribution of abdominal injuries after motor vehicle crashes in belted and unbelted patients admitted to trauma centers. The mortality was higher in unbelted than belted patients (7% vs. 3.2%, respectively, p less than 0.0001). Unbelted patients also had significantly more frequent and more severe head injuries (50.0% vs. 32.9%, respectively, p less than 0.001). The incidence of abdominal injury was equal in both unbelted patients (13.9%), but the spectrum of organs injured was different in the two groups. Gastrointestinal tract injuries (stomach, small bowel, colon and rectum) were significantly more frequent in belted vs. unbelted patients (3.4% vs. 1.8%, respectively, p = 0.001). The frequency of liver and spleen injuries was the same in both groups. This study demonstrates that in patients admitted to trauma centers after motor vehicle crashes, belted and unbelted patients have an equal incidence of abdominal injury, but belted and unbelted patients have a different spectrum of injuries. Hollow viscus injuries are more common in belted crash victims. Seat belt use was associated with significantly fewer head injuries and deaths. Physicians evaluating trauma victims after motor vehicle crashes should be aware of the fact that the types of abdominal injuries may vary substantially depending on seat belt use.

Abdominal Injuries↗
PubMed1991

Circulating anti-glomerular basement membrane antibodies in coeliac disease and epidermolysis bullosa acquisita.

The demonstration of circulating anti-glomerular basement membrane (GBM) antibodies is almost diagnostic for anti-GBM disease and Goodpasture's syndrome. These antibodies are, however, occasionally present in SLE and diabetes, in association with IgA disease and membranous nephropathy and after transplantation in Alport's syndrome. In addition, we describe circulating anti-GBM antibodies in a research worker who handled GBM and in whom coeliec disease later developed, and in an individual with epidermolysis bullosa acquisita. Neither patient had impaired renal function nor an abnormal urinary sediment, suggesting either that these antibodies were of low affinity, or that additional factors are required for the pathogenesis of an aggressive glomerular lesion when circulating anti-GBM antibodies are present. In at least one of these individuals anti-GBM antibodies may have developed after the exposure of basement membrane collagen type IV to activated immunological mediators and cells.

Adult↗
PubMed1991

Proposed interpretive criteria and quality control parameters for testing in vitro susceptibility of Neisseria gonorrhoeae to ciprofloxacin.

Ciprofloxacin was subjected to a multilaboratory study designed to determine its in vitro susceptibility criteria for Neisseria gonorrhoeae and its quality control parameters for both agar dilution and disk diffusion susceptibility testing for this species. All clinical isolates were susceptible, i.e., MICs were less than or equal to 0.06 microgram/ml and zones of inhibition were greater than or equal to 36 mm. A resistant category could not be defined, but in vitro-selected mutants gave zones of less than or equal to 35 mm, and MICs for these strains were greater than or equal to 0.12 microgram/ml. For quality control of ciprofloxacin agar dilution tests on supplemented GC agar, MICs for Staphylococcus aureus ATCC 29213 ranged from 0.12 to 0.5 microgram/ml. For quality control of 5-micrograms ciprofloxacin disk tests, N. gonorrhoeae ATCC 49226 and S. aureus ATCC 25923 produced acceptable zone diameter ranges of 48 to 58 mm and 22 to 26 mm, respectively.

Ciprofloxacin↗
PubMed1991

[Cultural awareness in nursing].

Cultural differences play a significant role in how people react to health problems. Culture also affects the relationship between patient and caregiver. This article describes four basic characteristics of culture: it is learned, not hereditary; it is shared by all members of the same cultural group; it develops in adaptation to the environment; and it is dynamic, in constant evolution. The author shows how a patient's culture can affect his or her health. Three specific aspects are discussed--eating habits, communication and health beliefs. The need for nurses to be aware of the cultural dimension and its significance in the caregiving process is emphasized. This is particularly important in a multicultural society such as Canada. The effectiveness of the care provided depends on the nurse's awareness and sensitivity. In the same vein, the prevention of misunderstandings requires an appreciation of the other person's culture. Nurses who reach out to understand other cultures will come to respect individual differences.

Humans↗
PubMed1991

A process-driven curriculum in nursing education.

Myers et. al. show what a curriculum looks like when it's based on learning strategies and thinking processes instead of being content based. The authors identify five critical operations: clinical process, consultation, managerial process, educative/learning and the investigative processes. New NLN procedures encourage such creative designs; you'll enjoy reading about this one.

Curriculum↗
PubMed1991

Affective and behavioral responses of gay and bisexual men to HIV antibody testing.

Fifty-six gay and bisexual men were tested for antibody to the human immunodeficiency virus. Twenty-two subjects who tested positive, 22 subjects who tested negative, and 12 subjects who chose not to learn the test results were surveyed by questionnaire after one week and after about six months after testing. Subjects who tested positive and those who tested negative were also compared two weeks after learning results. Subjects who tested positive experienced an increase in anxiety, depression, and AIDS anxiety, and subjects who tested negative experienced a decrease in these feelings after learning results. Subjects who did not learn the results of their tests experienced no change in these feelings. All three groups altered their sexual behavior. Subjects were more likely to tell test results to lovers and to regular sexual partners than to casual sexual partners. Implications for social work practice are discussed.

AIDS Serodiagnosis↗
PubMed1990

Effects of oligo sequence and chemistry on the efficiency of oligodeoxyribonucleotide-mediated mRNA cleavage.

Using the endogenous histone H4 mRNA of Xenopus oocytes as a target, we have previously shown that 20mer oligos complementary to different parts of this sequence vary in their effectiveness at causing mRNA cleavage in vivo, and that some of the RNA can never be cleaved. In this paper we show that the resistant RNA is not localised within one part of the oocyte, and that the relative resistance in vivo of endogenous or synthetic H4 mRNA to the different oligos is preserved in an in vitro assay system using deproteinised RNA. If an prior annealing step is included in vitro, all resistance is abolished. Chemical modification of one oligo by end substitution with methylphosphonate or phosphorothioate residues did not improve cleavage efficiency. Oligos with complete phosphorothioate substitution cause slower cleavage in vivo but persist for longer. Consequently phosphorothioate oligos are effective at lower doses than phosphodiester ones, provided that the incubation time is long enough (24 hours). Increasing oligo length from 20nt to 30nt increases phosphorothioate oligo efficiency over long reaction times in vivo, but decreases efficiency during short in vitro assays. Similar increases in length did not affect phosphodiester oligo performance in vivo, but caused a decrease in efficiency in vitro which was overcome by an annealing step.

Animals↗