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Biomedical subjects

Mark E Johnson

Publications and source records attributed to Mark E Johnson.

At least 19 recordsLinked to original sources
PubMed2007

Reliability and criterion-related validity of self-report of syphilis.

OBJECTIVE: To determine the test-retest reliability, sensitivity and specificity, and criterion-related validity of the Risk Behavior Assessment (RBA) syphilis questions. The RBA is a standardized instrument that has been used in several studies of STDs in drug users. METHODS: For the test-retest reliability study, 219 injection drug users completed the RBA twice within a 48-hour period. To determine criterion-related validity, 207 individuals, who also completed the RBA, were tested with the rapid plasma reagin test (RPR), and 206 individuals were also tested with the Serodia Treponema pallidum particle agglutination test (TP-PA). RESULTS: The test-retest reliability for the question "How many times have you been told by a doctor or a nurse that you had syphilis?" was 0.78. The test-retest reliability for the question "In what year were you last treated for syphilis?" was 0.89. For the comparison of self-report with the RPR test, the sensitivity of self-report was 46.2% and the specificity was 95.7%. For the comparison of self-report with the TP-PA test, the sensitivity of self-report was 37% and the specificity was 97.7%. CONCLUSIONS: Self-reports of syphilis infection history were found to have good reliability, excellent specificity, and moderate sensitivity. These characteristics need to be taken into account in any study using these self-report items.

Adult↗
PubMed2006

Exploring differences in caseloads of rural and urban healthcare providers in Alaska and New Mexico.

OBJECTIVES: Although it is commonly accepted that rural healthcare providers face demands that are both qualitatively and quantitatively different from those faced by urban providers, this conclusion is based largely on data from healthcare consumers and relies on qualitative work with small sample sizes, surveys with small sample sizes, theoretical reviews and anecdotal reports. To enhance our knowledge of the demands faced by rural healthcare providers and to gain the perspectives of healthcare providers themselves, this study explored the caseloads of rural providers compared with those of urban providers. METHOD: An extensive survey of over 1500 licensed clinicians across eight physical and behavioural healthcare provider groups in Alaska and New Mexico was undertaken to explore differences in caseloads based on community size (small rural, rural, small urban, urban), state (Alaska, New Mexico) and discipline (health, behavioural). RESULTS: Findings indicated numerous caseload differences between community sizes that were consistent across both states, with complex case presentations being described most commonly by small rural and rural providers. Substance abuse, alcohol use, cultural diversity, economic disadvantage and age diversity were issues faced more often by providers in rural and small rural communities than by providers in small urban and urban communities. Rural, but not small rural, providers faced challenges around work with prisoners and individuals needing involuntary hospitalization. Although some state and discipline differences were noted, the most important findings were based on community size. CONCLUSIONS: The findings of this study have important implications for provider preparation and training, future research, tailored resource allocation, public health policy, and efforts to prevent 'burnout' of rural providers.

Adolescent↗
PubMed2006

Effect of surfactant protein A on the physical properties and surface activity of KL4-surfactant.

SP-A, the major protein component of pulmonary surfactant, is absent in exogenous surfactants currently used in clinical practice. However, it is thought that therapeutic properties of natural surfactants improve after enrichment with SP-A. The objective of this study was to determine SP-A effects on physical properties and surface activity of a new synthetic lung surfactant based on a cationic and hydrophobic 21-residue peptide KLLLLKLLLLKLLLLKLLLLK, KL(4). We have analyzed the interaction of SP-A with liposomes consisting of DPPC/POPG/PA (28:9:5.6, w/w/w) with and without 0.57 mol % KL(4) peptide. We found that SP-A had a concentration-dependent effect on the surface activity of KL(4)-DPPC/POPG/PA membranes but not on that of an animal-derived LES. The surface activity of KL(4)-surfactant significantly improved after enrichment with 2.5-5 wt % SP-A. However, it worsened at SP-A concentrations > or =10 wt %. This was due to the fluidizing effect of supraphysiological SP-A concentrations on KL(4)-DPPC/POPG/PA membranes as determined by fluorescence anisotropy measurements, calorimetric studies, and confocal fluorescence microscopy of GUVs. High SP-A concentrations caused disappearance of the solid/fluid phase coexistence of KL(4)-surfactant, suggesting that phase coexistence might be important for the surface adsorption process.

Animals↗
PubMed2006

Rural-urban health care provider disparities in Alaska and New Mexico.

Compared to their urban counterparts, rural residents face numerous disparities in obtaining health care, including limited access to care providers. We assessed disparities in provider availability in rural versus urban Alaska and New Mexico, with emphasis on professionals likely to provide mental health care. Using lists of licenses, we categorized physical and mental health care providers into rural versus urban and calculated rural versus urban disparity ratios. Rural residents had significantly less access to health care providers and discrepancies grew with level of required provider education and specialization. Addressing disparities via creative strategies is crucial to improving rural care delivery.

Alaska↗
PubMed2006

Moderating effects of control on the relationship between stress and change.

Given the well-documented impact of stress on employees, it is important to understand moderating factors, especially in behavioral health treatment settings, where constant change occurs. Staff members at four mental health (n=663) and four substance abuse (n=256) treatment agencies completed questionnaires inquiring about perceptions of direct and indirect agency changes, stress experienced due to changes, and control and input into the changes. Results revealed that as direct and indirect change increased, stress increased; as level of control and input into changes increased, stress decreased. Control and input served as a moderating variable between stress and direct change, but not for indirect change.

Adult↗
PubMed2006

Barriers to healthcare as reported by rural and urban interprofessional providers.

The research literature is replete with reports of barriers to care perceived by rural patients seeking healthcare. Less often reported are barriers perceived by the rural healthcare providers themselves. The current study is an extensive survey of over 1,500 healthcare providers randomly selected from two US states with large rural populations, Alaska and New Mexico. Barriers consistently identified across rural and urban regions by all healthcare professionals were Patient Complexity, Resource Limitations, Service Access, Training Constraints, and Patient Avoidance of Care. Findings confirmed that rural areas, however, struggle more with healthcare barriers than urban and small urban areas, especially as related to Resource Limitations, Confidentiality Limitations, Overlapping Roles, Provider Travel, Service Access, and Training Constraints. Almost consistently, the smaller a provider's practice community, the greater the reports of barriers, with the most severe barriers reported in small rural communities.

Alaska↗
PubMed2006

Physical properties and surface activity of surfactant-like membranes containing the cationic and hydrophobic peptide KL4.

Surfactant-like membranes containing the 21-residue peptide KLLLLKLLLLKLLLLKLLLLK (KL4), have been clinically tested as a therapeutic agent for respiratory distress syndrome in premature infants. The aims of this study were to investigate the interactions between the KL4 peptide and lipid bilayers, and the role of both the lipid composition and KL4 structure on the surface adsorption activity of KL4-containing membranes. We used bilayers of three-component systems [1,2-dipalmitoyl-phosphatidylcholine/1-palmitoyl-2-oleoyl-phosphatidylglycerol/palmitic acid (DPPC/POPG/PA) and DPPC/1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC)/PA] and binary lipid mixtures of DPPC/POPG and DPPC/PA to examine the specific interaction of KL4 with POPG and PA. We found that, at low peptide concentrations, KL4 adopted a predominantly alpha-helical secondary structure in POPG- or POPC-containing membranes, and a beta-sheet structure in DPPC/PA vesicles. As the concentration of the peptide increased, KL4 interconverted to a beta-sheet structure in DPPC/POPG/PA or DPPC/POPC/PA vesicles. Ca2+ favored alpha<-->beta interconversion. This conformational flexibility of KL4 did not influence the surface adsorption activity of KL4-containing vesicles. KL4 showed a concentration-dependent ordering effect on POPG- and POPC-containing membranes, which could be linked to its surface activity. In addition, we found that the physical state of the membrane had a critical role in the surface adsorption process. Our results indicate that the most rapid surface adsorption takes place with vesicles showing well-defined solid/fluid phase co-existence at temperatures below their gel to fluid phase transition temperature, such as those of DPPC/POPG/PA and DPPC/POPC/PA. In contrast, more fluid (DPPC/POPG) or excessively rigid (DPPC/PA) KL4-containing membranes fail in their ability to adsorb rapidly onto and spread at the air-water interface.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2006

Depression as measured by the Beck Depression Inventory-II among injecting drug users.

This study conducts a confirmatory factor analysis of the Beck Depression Inventory-II (BDI-II) with a sample of 598 individuals who reported recent injecting drug use. Findings indicate that out of four models tested, the best model for this sample is a three-factor solution (somatic, affective, and cognitive) previously reported by Buckley, Parker, and Heggie. The findings that nearly 50% of participants provided BDI-II scores indicating significant depressive symptomatology reveals that these individuals are in need of treatment for their psychiatric symptoms as well as substance use. Somatic symptoms are endorsed more strongly than affective or cognitive symptoms of depression, suggesting a possible, but yet poorly defined, relationship between depressive symptomatology and drug use that centers on shared somatic symptomatology.

Adolescent↗
PubMed2006

Survey return rates as a function of priority versus first-class mailing.

Prior research indicates survey procedures that signal significance and individualized mailings have higher response rates. Thus, it was hypothesized that surveys delivered via Priority mail would result in higher return rates than surveys delivered via First-Class. 260 surveys were sent to individuals randomly selected from lists of licensed physical and behavioral healthcare providers in Alaska and New Mexico. Half of the selected individuals were assigned randomly to receive mailings using Priority mail, the other half received First-Class mailings. Return rate was 39% for First-Class and 35% for Priority. Z tests of proportion indicated no statistically significant differences between methods. Given increased costs with no resultant increase in response rate, sending surveys to potential participants via Priority mail does not appear warranted.

Adult↗
PubMed2005

Patient requests and provider suggestions for alternative treatments as reported by rural and urban care providers.

OBJECTIVES: Explored the relationship between different types of care providers' willingness to suggest alternative and complementary treatments (CAM), patients' requests for CAM, and provider perceptions about CAM as barriers to effective healthcare. DESIGN: Large survey. SETTING: Alaska and New Mexico. MAIN MEASURES: Survey responses from 1528 physical and behavioral healthcare providers. RESULTS: Over 97% of providers suggested CAM; over 97% reported patients asked for CAM. Providers were more likely to suggest CAM than perceived CAM as a barrier to care. Healthcare providers who were female, from small rural areas, or specializing in behavioral healthcare were more likely to suggest CAM and less likely to perceive CAM as a barrier. Patients of physical healthcare providers asked for CAM more often than patients of behavioral healthcare providers, yet physical care providers suggested CAM less frequently. CONCLUSIONS: Healthcare providers of all disciplines, regions, and gender are sensitive to patients' desire for CAM and do not perceive CAM as a barrier to care.

Alaska↗
PubMed2005

Sensitivity analysis for computer model projections of hurricane losses.

Projecting losses associated with hurricanes is a complex and difficult undertaking that is fraught with uncertainties. Hurricane Charley, which struck southwest Florida on August 13, 2004, illustrates the uncertainty of forecasting damages from these storms. Due to shifts in the track and the rapid intensification of the storm, real-time estimates grew from 2 billion dollars to 3 billion dollars in losses late on the 12th to a peak of 50 billion dollars for a brief time as the storm appeared to be headed for the Tampa Bay area. The storm struck the resort areas of Charlotte Harbor and moved across the densely populated central part of the state, with early poststorm estimates in the 28 dollars to 31 billion dollars range, and final estimates converging at 15 billion dollars as the actual intensity at landfall became apparent. The Florida Commission on Hurricane Loss Projection Methodology (FCHLPM) has a great appreciation for the role of computer models in projecting losses from hurricanes. The FCHLPM contracts with a professional team to perform onsite (confidential) audits of computer models developed by several different companies in the United States that seek to have their models approved for use in insurance rate filings in Florida. The team's members represent the fields of actuarial science, computer science, meteorology, statistics, and wind and structural engineering. An important part of the auditing process requires uncertainty and sensitivity analyses to be performed with the applicant's proprietary model. To influence future such analyses, an uncertainty and sensitivity analysis has been completed for loss projections arising from use of a sophisticated computer model based on the Holland wind field. Sensitivity analyses presented in this article utilize standardized regression coefficients to quantify the contribution of the computer input variables to the magnitude of the wind speed.

Journal Article↗
PubMed2005

Uncertainty analysis for computer model projections of hurricane losses.

Projecting losses associated with hurricanes is a complex and difficult undertaking that is wrought with uncertainties. Hurricane Charley, which struck southwest Florida on August 13, 2004, illustrates the uncertainty of forecasting damages from these storms. Due to shifts in the track and the rapid intensification of the storm, real-time estimates grew from 2 to 3 billion dollars in losses late on August 12 to a peak of 50 billion dollars for a brief time as the storm appeared to be headed for the Tampa Bay area. The storm hit the resort areas of Charlotte Harbor near Punta Gorda and then went on to Orlando in the central part of the state, with early poststorm estimates converging on a damage estimate in the 28 to 31 billion dollars range. Comparable damage to central Florida had not been seen since Hurricane Donna in 1960. The Florida Commission on Hurricane Loss Projection Methodology (FCHLPM) has recognized the role of computer models in projecting losses from hurricanes. The FCHLPM established a professional team to perform onsite (confidential) audits of computer models developed by several different companies in the United States that seek to have their models approved for use in insurance rate filings in Florida. The team's members represent the fields of actuarial science, computer science, meteorology, statistics, and wind and structural engineering. An important part of the auditing process requires uncertainty and sensitivity analyses to be performed with the applicant's proprietary model. To influence future such analyses, an uncertainty and sensitivity analysis has been completed for loss projections arising from use of a Holland B parameter hurricane wind field model. Uncertainty analysis quantifies the expected percentage reduction in the uncertainty of wind speed and loss that is attributable to each of the input variables.

Journal Article↗
PubMed2005

Ethical considerations in rural health care: a pilot study of clinicians in Alaska and New Mexico.

To investigate differences in the experiences of rural versus non-rural clinicians, we surveyed caregivers in New Mexico and Alaska regarding ethical aspects of care provision. Consistent with past literature, rural compared to non-rural clinicians perceived patients as having less access to health care resources. They reported more interaction with patients and less awkwardness in relationships with their patients outside of work. Rural clinicians also reported their patients expressed more concern about knowing them in both personal and professional roles, had more concerns over confidentiality, and experienced more embarrassment concerning stigmatizing illnesses. Ethical issues and implications of these results for providing care in rural areas are discussed.

Adult↗
PubMed2004

A single vaccination with protein-microspheres elicits a strong CD8 T-cell-mediated immune response against Mycobacterium tuberculosis antigen Mtb8.4.

Efficient protein-based vaccine delivery systems are needed to achieve a persistent memory immune response capable of detecting and eliminating intracellular pathogens such as Mycobacterium tuberculosis (TB). We have developed a novel protein-microsphere formulation using the recently discovered TB antigen Mtb8.4. Immunization of mice with a single dose of this Mtb8.4-microsphere formulation resulted in both humoral and cellular responses against Mtb8.4. The Mtb8.4-specific CD8 T-cell responses following a single administration of Mtb8.4-microspheres exceeded that elicited by protein plus adjuvant following multiple immunizations. These results demonstrate the efficacy of a single dose protein-microsphere vaccine for the induction of strong cell-mediated and humoral immune responses against M. tuberculosis antigens.

Adjuvants, Immunologic↗
PubMed2004

Frequent amplification and rearrangement of chromosomal bands 6p12-p21 and 17p11.2 in osteosarcoma.

Osteosarcoma (OS) is a highly malignant bone neoplasm of children and young adults. It is characterized by chaotic karyotypes with complex marker chromosomes. We applied a combination of molecular cytogenetic techniques including comparative genomic hybridization (CGH), spectral karyotyping (SKY), and fluorescence in situ hybridization (FISH) to decipher the chromosomal complexity in a panel of 25 tumors. Combined SKY and G-banding analysis identified several novel recurrent breakpoint clusters and 9 nonrecurrent reciprocal translocations. CGH identified several recurrent chromosomal losses including 2q, 3p, 9, 10p, 12q, 13q, 14q, 15q, 16, 17p, and 18q, gains including Xp, Xq, 5q, 6p, 8q, 17p, and 20q, and high-level chromosomal amplifications at Xp11.2, 1q21-q22, 4p11, 4q12, 5p15, 6p12.1, 8q13, 8q23, 10q11, 10q22, 11q13, 11q23, 12q13-q14, 13q21-q34, 16q22, 17p11.2, 17q21-q22, 18q22, 20p11.2, and 20q12. Frequent amplification and rearrangement involving chromosomal bands at 6p12-p21 and 17p11.2 were found in 28% and 32% of cases, respectively. In an attempt to identify the genes involved in these amplicons, we used three nonoverlapping BAC clones contained within each amplicon as probes for FISH analysis, leading to a more detailed characterization and quantification of the 6p and 17p amplicons.

Adolescent↗
PubMed2004

Childhood abuse history and substance use among men and women receiving detoxification services.

According to data collected from women and adolescents, a strong link exists between childhood abuse history and substance abuse. Using a sample of 274 women and 556 men receiving detoxification services, we explored whether the same pattern emerged across genders and types of abuse. Results revealed 20% of men and more than 50% of women reported childhood physical or sexual abuse. Sexual or physical abuse had negative sequelae, regardless of gender. Individuals with abuse history reported earlier age of onset of drinking, more problems associated with use of alcohol/drugs, more severe psychopathology, and more lifetime arrests, arrests related to substance use, and arrests related to mental health. Prevention and proactive intervention activities are crucial to prevent negative sequelae of childhood victimization.

Adult↗
PubMed2004

Overexpression of Lactobacillus casei D-hydroxyisocaproic acid dehydrogenase in cheddar cheese.

Metabolism of aromatic amino acids by lactic acid bacteria is an important source of off-flavor compounds in Cheddar cheese. Previous work has shown that alpha-keto acids produced from Trp, Tyr, and Phe by aminotransferase enzymes are chemically labile and may degrade spontaneously into a variety of off-flavor compounds. However, dairy lactobacilli can convert unstable alpha-keto acids to more-stable alpha-hydroxy acids via the action of alpha-keto acid dehydrogenases such as d-hydroxyisocaproic acid dehydrogenase. To further characterize the role of this enzyme in cheese flavor, the Lactobacillus casei d-hydroxyisocaproic acid dehydrogenase gene was cloned into the high-copy-number vector pTRKH2 and transformed into L. casei ATCC 334. Enzyme assays confirmed that alpha-keto acid dehydrogenase activity was significantly higher in pTRKH2:dhic transformants than in wild-type cells. Reduced-fat Cheddar cheeses were made with Lactococcus lactis starter only, starter plus L. casei ATCC 334, and starter plus L. casei ATCC 334 transformed with pTRKH2:dhic. After 3 months of aging, the cheese chemistry and flavor attributes were evaluated instrumentally by gas chromatography-mass spectrometry and by descriptive sensory analysis. The culture system used significantly affected the concentrations of various ketones, aldehydes, alcohols, and esters and one sulfur compound in cheese. Results further indicated that enhanced expression of d-hydroxyisocaproic acid dehydrogenase suppressed spontaneous degradation of alpha-keto acids, but sensory work indicated that this effect retarded cheese flavor development.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗