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Biomedical subjects

C M Davis

Publications and source records attributed to C M Davis.

At least 37 records · Page 2Linked to original sources
PubMed1996

Tryptophan depletion and aggressive responding in healthy males.

In order to study the effect of decreasing plasma tryptophan levels on aggressive responding in a controlled laboratory setting, we administered two doses (25 g and 100 g) of a tryptophan-free amino acid mixture to ten healthy male subjects after 24 h of a low tryptophan diet. Subjects were screened for current or past psychiatric, or non-psychiatric medical illness. Aggressive responding on a free-operant laboratory measure of aggression (the Point Subtraction Aggression Paradigm) and plasma tryptophan levels were measured before and after drinking the amino acid mixture. There was a significant increase in aggressive responding 5 h after the 100 g mixture and a significant increase in aggressive responding 6 h after the 25 g mixture compared to a baseline day when no drink was administered. There was also a significant decrease in plasma tryptophan at 5 hours after ingestion compared to baseline for both doses of amino acid mixture. This study supports the hypothesis that tryptophan depletion increases aggressive responding in healthy males in a laboratory setting, probably by decreasing brain serotonin.

Adult↗
PubMed1996

Strain-dependent susceptibility to radiation-induced mammary cancer is a result of differences in epithelial cell sensitivity to transformation.

Variations in sensitivity to radiation-induced mammary cancer among different strains of mice are well known. However, the reasons for these variations have not been determined. In the present study, the cell dissociation assay was used to determine the radiation-induced transformation frequencies in sensitive BALB/c mice and resistant C57BL mice as well as the resistant hybrid B6CF1 independent of host environment. The influence of host environment on the progression of transformed cells to the neoplastic phenotype was also examined. Results demonstrated that the variations in sensitivity among these sensitive and resistant mice are a result of inherent differences in the sensitivity of the mammary epithelial cells to radiation-induced transformation. Under the conditions used, host environment played no role in the initiation of transformed cells by radiation or in the progression of these cells to the neoplastic phenotype.

Animals↗
PubMed1996

An ounce of prevention? Evaluation of the 'Put Prevention into Practice' program.

BACKGROUND: The "Put Prevention into Practice" (PPIP) program was designed to enhance the capacity of health care providers to deliver clinical preventive services. This study was designed to evaluate the program's effectiveness when applied to family physicians in private practice settings. METHODS: Eight Midwestern practices that had purchased PPIP kits were identified and agreed to participate in the study. A comparative case study approach encompassing a variety of data collection techniques was used. These techniques included participant observation of clinic operations and patient encounters, semistructured and key informant interviews with physicians and staff members, chart reviews, and structured postpatient encounter and office environment checklists. Content analysis of the qualitative data and construction of the individual cases were done by consensus of the research team. RESULTS: PPIP materials are not being used, even by the clinics that ordered them. Physicians already providing quality preventive services prefer their existing materials to those in the PPIP kit. Sites that are underutilizing preventive services are unable or unwilling to independently implement the PPIP program. CONCLUSIONS: Development of technical support may facilitate implementation of PPIP materials into those practices most deficient in providing preventive services. Given the diversity of practice environments it is unlikely that a "one size fits all" approach will ever be able to address the needs of all providers.

Delivery of Health Care↗
PubMed1995

Latent expression of p53 mutations and radiation-induced mammary cancer.

EF42 is a clonally derived preneoplastic cell lineage from irradiated mouse mammary tissue, which becomes neoplastic with time in vitro or in vivo. We now report that multiple mutations in p53 occur before the acquisition of the neoplastic phenotype. The selective expansion of mutant cells is accompanied by loss of heterozygosity at the p53 locus and c-myc amplification. Although p53 mutations represent critical early events, our data argue these mutations were not directly induced by radiation but arose in the progeny of irradiated cells several cell generations later. The data are consistent with a multistep model of carcinogenesis that identifies genomic instability as the earliest step.

Animals↗
PubMed1995

Reconstitution of the bacterial core light-harvesting complexes of Rhodobacter sphaeroides and Rhodospirillum rubrum with isolated alpha- and beta-polypeptides, bacteriochlorophyll alpha, and carotenoid.

Methodology has been developed to reconstitute carotenoids and bacteriochlorophyll alpha with isolated light-harvesting complex I (LHI) polypeptides of both Rhodobacter sphaeroides and Rhodospirillum rubrum. Reconstitution techniques first developed in this laboratory using the LHI polypeptides of R. rubrum, R. sphaeroides, and Rhodobacter capsulatus reproduced bacteriochlorophyll alpha spectral properties characteristic of LHI complexes lacking carotenoids. In this study, carotenoids are supplied either as organic-solvent extracts of chromatophores or as thin-layer chromatography or high performance liquid chromatography-purified species. The resulting LHI complexes exhibit carotenoid and bacteriochlorophyll a spectral properties characteristic of native LHI complexes of carotenoid-containing bacteria. Absorption and circular dichroism spectra support the attainment of a native-like carotenoid environment in the reconstituted LHI complexes. For both R. sphaeroides- and R. rubrum-reconstituted systems, fluorescence excitation spectra reveal appropriate carotenoid to bacteriochlorophyll alpha energy-transfer efficiencies based on comparisons with the in vivo systems. In the case of R. rubrum reconstitutions, carotenoids afford protection from photodynamic degradation. Thus, carotenoids reconstituted into LHI exhibit spectral and functional characteristics associated with native pigments. Heterologous reconstitutions demonstrate the applicability of the developed assay in dissecting the molecular environment of carotenoids in light-harvesting complexes.

Bacteriochlorophylls↗
PubMed1995

Intra- and interethnic variability in reduced haloperidol to haloperidol ratios.

Steady-state haloperidol and reduced haloperidol concentrations were measured in 250 schizophrenic patients from 4 ethnic groups: 39 Blacks, 66 Caucasians, 82 Chinese, and 63 Mexican Americans. The distribution of the reduced haloperidol to haloperidol concentration (RH/HL) ratios was bimodal in all ethnic groups, with the antimode determined by probit plot as 0.46, 0.51, 0.36, and 0.76, respectively. With these antimodes, the proportion of patients with low RH/HL ratios were 41%, 42%, 73%, and 57% in the four ethnic groups, respectively. Compared with the other three ethnic groups, in the Chinese patients the ratio was lower. The mean RH/HL ratio in the Chinese was 0.34 compared with 0.81 to 0.87 in the non-Chinese groups. In 53 patients who were treated with two or more haloperidol dosage regimens, steady-state haloperidol and reduced haloperidol drug concentrations obtained from the different regimens were positively correlated with the haloperidol dose (R = .79 and R = .62, respectively). Our data suggest not only the existence of a bimodal distribution in the RH/HL ratio, but also that the antimode separating the low and high ratio subgroups is different among the various ethnic groups.

Adult↗
PubMed1995

Early family experiences and helping behaviors of physical therapists.

BACKGROUND AND PURPOSE: Ineffective or excessive helping behavior may encourage helpee dependence and overextension of helper resources. Early family experiences and perceptions of the helpee's situation both contribute to the expression of helping behavior in health professionals. The purpose of this study was to determine how early family experiences and variations in perceived patient responsibility influence physical therapist helping behavior. SUBJECTS AND METHODS: Five hundred physical therapists were surveyed by mail, resulting in a final sample of 221 (44%) respondents who completed the Family of Origin Scale (FOS), measuring the nature of their early family experiences, and a Helping Questionnaire, measuring their helping behavior, perceptions of replaceability, and feelings of compassion for four hypothetical patients. The four patients represented Brickman's models of helping and coping, varying in high and low responsibility for the problem and high and low responsibility for the solution to the problem. RESULTS: Subjects who scored in the dysfunctional or neutral ranges on the FOS had lower scores on their willingness to help and feelings of compassion than did subjects who scored in the functional range on the FOS. Regardless of early family experiences, subjects' scores were higher for willingness to help and feelings of compassion and lower in their perceptions of replaceability for patients who were not thought to be responsible for their medical problem (medical and compensatory models). In contrast, subjects' scores were lower for their willingness to help and feelings of compassion and higher in their perceptions of replaceability when patients were felt to be responsible for their medical problem (enlightenment and moral models). CONCLUSION AND DISCUSSION: All subjects, regardless of early family experience, showed helping responses that linked feelings of compassion with greater tendencies to help. Variations in perceived patient responsibility for the medical problem, rather than early family experience, appears to be a major determinant in motivating both compassion and helping behavior. Thus, helpers may be more likely to overextend themselves or create patient dependence when patients are perceived to be not responsible for the cause of their problem. [Curtis KA, Davis CM, Trimble TK, Papoulidis DK. Early family experiences and helping behaviors of physical therapists.

Adult↗
PubMed1994

A truncated recombinant intercellular adhesion molecule-1 inhibits adhesion of leukemic cell lines to upregulated endothelial cells.

Intercellular adhesion molecule-1, a member of the immunoglobulin supergene family, is the ligand for the integrin lymphocyte function associated antigen-1. Intercellular adhesion molecule-1 and lymphocyte function associated antigen-1 binding interactions mediate leukocyte adherence and migration. Previous work has shown that the adherence of lymphocyte function associated antigen-1 is directed to the first immunoglobulinlike domain of the endothelial cell surface protein intracellular adhesion molecule-1. We have constructed a truncated intercellular adhesion molecule-1 gene encoding the first 185 amino acids from the amino terminus and overexpressed it in Escherichia coli. The recombinant protein was purified from insoluble inclusion bodies and refolded into an active conformation by a denaturation/renaturation cycle. The identity of the protein was confirmed by microsequencing and by Western blot analysis using a polyclonal antibody to ICAM-1. We have demonstrated that this soluble region of the otherwise membrane-bound ligand is an inhibitor of Molt or HL-60 cell adhesion to cytokine-stimulated endothelial cells.

Amino Acid Sequence↗
PubMed1993

Identification of a role of the vitronectin receptor and protein kinase C in the induction of endothelial cell vascular formation.

When cultured on a basement membrane substratum, endothelial cells undergo a rapid series of morphological and functional changes which result in the formation of histotypic tube-like structures, a process which mimics in vivo angiogenesis. Since this process is probably dependent on several cell adhesion and cell signaling phenomena, we examined the roles of integrins and protein kinase C in endothelial cell cord formation. Polyclonal antisera directed against the entire vitronectin (alpha v beta 3) and fibronectin (alpha 5 beta 1) receptors inhibited cord formation. Subunit-specific monoclonal antibodies to alpha v, beta 3, and beta 1 integrin subunits inhibited cord formation, while monoclonal antibodies to alpha 5 did not, which implicated the vitronectin receptor, and not the fibronectin receptor, in vascular formation. Protein kinase C inhibitors inhibited cord formation, while phorbol 12-myristate 13-acetate (PMA) caused endothelial cells to form longer cords. Since the vitronectin receptor has been shown to be phosphorylated in an in vitro system by protein kinase C, the possible functional link between the vitronectin receptor and protein kinase C during cellular morphogenesis was examined. The vitronectin receptor was more highly phosphorylated in cord-forming endothelial cells on basement membrane than in monolayer cells on vitronectin. Furthermore, this phosphorylation was inhibited by protein kinase C inhibitors, and PMA was required to induce vitronectin receptor phosphorylation in endothelial cells cultured on vitronectin. Colocalization studies were also performed using antisera to the vitronectin receptor and antibodies to protein kinase C. Although no strict colocalization was found, protein kinase C was localized in the cytoskeleton of endothelial cells initially plated on basement membrane or on vitronectin, and it translocated to the plasma membrane of C-shaped cord-forming cells on basement membrane. Thus, both the vitronectin receptor and protein kinase C play a role in in vitro cord formation.

Antibodies, Monoclonal↗
PubMed1993

Acquired immunodeficiency syndrome-like illness associated with systemic Mycoplasma fermentans infection in a human immunodeficiency virus-negative homosexual man.

A 35-year-old homosexual man developed a composite nodal Kaposi's sarcoma and peripheral T-cell lymphoma that were associated with a peripheral blood CD4-positive lymphocyte count of only 43/mm3. The patient subsequently developed Pneumocystis carinii pneumonitis and eventually died due to disseminated Cryptococcus neoformans. Numerous premortem tests for the presence of human immunodeficiency virus (HIV) types 1 and 2 were negative by the enzyme-linked immunosorbent assay, Western blot, viral isolation, and polymerase chain reaction techniques. Postmortem evaluations for HIV-1, HIV-2, human T-cell lymphotropic virus (HTLV)-I, and HTLV-II also were negative by polymerase chain reaction, immunofluorescence assays, and viral isolation. A systemic infection by Mycoplasma fermentans, however, was documented by immunohistochemistry and polymerase chain reaction in premortem and postmortem tissues. This recently recognized human pathogen has produced systemic infections in patients with the acquired immunodeficiency syndrome (AIDS) and in previously healthy non-AIDS patients who characteristically have a fulminant flu-like illness. Additionally, M fermentans has enhanced the cytopathic effect of HIV in in vitro studies and has produced fatal wasting illnesses with terminal lymphopenia in inoculated adult silvered leaf monkeys. This report is the first description of an association between M fermentans infection and an AIDS-like illness in an HIV-negative individual. The etiology of the severe immunosuppression in this patient and the associated role of M fermentans remain to be determined by further investigations.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Characterization of laminin receptor messenger ribonucleic acid and protein expression in mouse spermatogenic cells.

A cDNA proposed to encode the mouse laminin receptor (MLR) was isolated from a mouse round spermatid expression library. The cDNA contained complete coding and 3' untranslated regions but was missing the first 42 bases from the 5' untranslated region. Northern blot analysis using a 3' EcoRI fragment of the cDNA identified a 1.2-kb transcript in mouse testes and all somatic tissues tested. Additional transcripts of 1.3 and 0.9 kb were present in round spermatids isolated from mouse testes. Northern blots using ribonuclease (RNase) H-treated poly(A)+ RNA indicated that the difference in the size of 1.3-kb round spermatid transcripts and 1.2-kb transcripts was due to differing poly(A)+ tail lengths. The 0.9-kb round spermatid transcript hybridized to all but the 5' end of the 1.2-kb MLR cDNA, suggesting that an alternate start site is used or that transcript processing occurs in these cells. Immunoblot analysis identified proteins in spermatogenic cells corresponding to the 67-70-kDa MLR and its 43-kDa precursor. In addition, ligand binding studies and affinity chromatography procedures indicated that spermatogenic cell proteins of these sizes bind laminin. However, spermatocytes and spermatids are spatially isolated from laminin in the testes, and MLR may have other functions in these cells.

Animals↗
PubMed1993

Cigarette smoking cessation and alcohol treatment.

Cigarette smoking is common among problem drinkers and recovering alcoholics but most cessation research has not addressed this special population of smokers. Confidential survey data were collected from over 700 alcoholism counselors and medical personnel in residential and outpatient chemical dependency units (CDUs) in Nebraska to identify the quit smoking method these experts recommend and to assess their personal experiences with smoking cessation. A total of 334 respondents (45% of the group) self-identified as a recovering alcoholic, 51 (7%) as a problem drinker, and 350 (48%) as having no history of alcohol problems. Over 63% of all respondents were former or current smokers. The most frequently recommended quitting methods for people still in treatment for alcohol problems were relying on a support group (69%), adhering to Alcoholics Anonymous (AA) principles (64%), and quitting "cold turkey" (45%). In an adjusted logistic regression model, quitting "cold turkey" and relying on the principles of AA significantly increased a respondent's odds of personally becoming a successful tobacco quitter. We conclude that many recovering alcoholics and problem drinkers can successfully quit smoking and should be encouraged to use abstinence coping skills learned in alcohol treatment.

Adult↗
PubMed1992

Comparison of haloperidol and reduced haloperidol plasma levels in four different ethnic populations.

1. Plasma haloperidol and reduced haloperidol concentration were measured in four ethnic populations. 2. Plasma samples were obtained under steady-state conditions and obtained 10-12 hours post bedtime dose and prior to the morning dose. 3. Haloperidol and reduced haloperidol plasma levels were assayed by radioimmunoassay and liquid chromatography. 4. A wide interpatient variability between haloperidol dose and plasma concentration was observed for each ethnic group. 5. The Chinese group differed from the other ethnic populations. 6. A nonlinear relationship was observed between haloperidol and reduced haloperidol plasma levels in each ethnic group. Further, the relationship of haloperidol to reduced haloperidol plasma levels differed for each ethnic group. These results suggest that various ethnic groups could metabolize haloperidol and reduced haloperidol differently.

Black or African American↗
PubMed1992

Microbial etiology of acute pneumonia in hospitalized patients.

The purpose of this study was to determine the microbial etiology of pneumonia by using strict criteria among a group of hospitalized patients. Patients with acute community-acquired or hospital-acquired pneumonia were studied in a systematic and comprehensive manner for bacterial, viral, chlamydial, mycobacterial, and fungal pathogens. A total of 198 patients with 204 episodes of pneumonia were evaluated. Despite 100 percent follow-up of all surviving patients, a specific etiologic agent could be found in only 103 episodes. Among 154 episodes of community-acquired pneumonia, a diagnosis was made in 79; the most common pathogen was from the genus Legionella, followed by various Gram-negative enteric bacteria, Gram-positive cocci, influenza A virus, and Mycoplasma pneumoniae. The etiologic agent was found in 24 of the 50 patients with hospital-acquired pneumonia; no pathogen predominated. We conclude that even when elaborate diagnostic studies are done, including many invasive procedures, the etiology can be determined in only about half of the patients with acute pneumonia. The pathogens of pneumonia in this study are not markedly different between community-acquired and hospital-acquired infection.

Acute Disease↗
PubMed1992

"America responds to AIDS," but did college students? Differences between March, 1987, and September, 1988.

To assess thoughts, perceptions, attitudes, and behavior related to AIDS, data were collected from 2 similar samples of college students. The sets of data were collected 18 months apart. Results indicate increased awareness and knowledge and changed attitudes and behaviors in some cases, but the absolute magnitudes of the differences are small for most between-group comparisons. Also, the evidence suggests that many students lack detailed knowledge and fail to see the implications of their knowledge for change in their own behavior. These findings imply educational efforts must go beyond merely providing knowledge and explicitly link facts to personal belief systems and decision making.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Improving smoking cessation counseling by family practice residents.

BACKGROUND: While programs to train residents in smoking cessation counseling skills have been devised, few have assessed trainee behavioral changes in practice settings where residents were blind to the evaluation of their behavior. This study assessed the effectiveness of a training program in smoking cessation counseling and chart-prompting system in increasing the frequency and quality of counseling by residents at three clinic sites. METHODS: Twenty-eight residents participated in a training program that included epidemiology, discussion of attitudes, counseling techniques, videotaped examples, and small group role play. The chart-prompting system was implemented at two clinics 1 month after training. Patient exit interviews, during which information on resident counseling on smoking cessation was obtained, were conducted before training, after training, at 3-month follow-up, and at 6-month follow-up. Questionnaires assessing knowledge, attitudes, and self-perceived counseling behaviors were completed by residents at pretraining, posttraining, and 6-month follow-up periods. RESULTS: Interviews with 517 smokers were analyzed. Results showed an increase in counseling at 3-month follow-up but a regression toward baseline at 6 months. Counseling improved at clinics where chart prompting was initiated. The number of counseling behaviors decreased when the number of patients seen increased. Whether a patient received counseling was positively associated with prior contact with the physician. There was no correlation between resident self-perception and patient report. CONCLUSIONS: A training program in smoking cessation counseling and a chart-prompting system did not result in a lasting change in resident behavior. System factors may play an important role in long-term behavior change.

Clinical Competence↗