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Biomedical subjects

B Johnson

Publications and source records attributed to B Johnson.

At least 55 records · Page 3Linked to original sources
PubMed2000

Using video vignettes to evaluate children's personal safety knowledge: methodological and ethical issues.

OBJECTIVE: The study aimed to assess children's personal safety knowledge by seeking their responses to video-delivered simulations of child maltreatment. METHOD: In seeking to do this, methodological and ethical difficulties were encountered. These arose during several phases of consultation, the refinement of an interview protocol to be used with the vignettes, and during discussions over the ethical integrity of the research. RESULTS: Using visually graphic vignettes to probe children's personal safety knowledge proved to be methodologically difficult and ethically problematic and controversial. The main objections to the approach were that it could harm participants, and that parents needed extensive information about the study to exercise "informed consent." CONCLUSIONS: The study demonstrated the nature and extent of negotiations that were needed to "push the boundaries" of evaluation research to develop more valid, authentic and complex ways of accessing children's thinking about personal safety concepts and strategies.

Acting Out↗
PubMed2000

The experience of being an adolescent child of a parent who has a mood disorder.

The purpose of this phenomenological study was to describe the experiences of adolescent children living with a parent who has a mood disorder. Three female adolescents each participated in two unstructured, tape-recorded interviews. Interviews were analysed using the Giorgi (1985) method. Three themes emerged. First, participants experienced a serious disruption in family life due to the unavailability of the ill parent, which evoked feelings of an intense sense of responsibility, fear and loss. This disruption led to the adolescent taking on parental roles and tasks. Second, participants perceived themselves to lack knowledge and understanding, leading to frustration and fears that their parents may not get better, and that they themselves may become ill like their parents. They sought information in order to better adjust to and understand the illness. Third, participants struggled to come to terms with the burden of having a psychiatrically ill parent. The effort of trying to cope and make sense of the experience involved a variety of cognitive and affective responses. Implications for nursing practice and research are discussed.

Adaptation, Psychological↗
PubMed2000

Steady-state pharmacokinetics of indinavir in cerebrospinal fluid and plasma among adults with human immunodeficiency virus type 1 infection.

To characterize steady-state indinavir pharmacokinetics in cerebrospinal fluid and plasma, 8 adults infected with human immunodeficiency virus underwent intensive cerebrospinal fluid sampling while receiving indinavir (800 mg every 8 hours) plus nucleoside reverse transcriptase inhibitors. Nine and 11 serial cerebrospinal fluid and plasma samples, respectively, were obtained from each subject. Free indinavir accounted for 94.3% of the drug in cerebrospinal fluid and 41.7% in plasma. Mean values of cerebrospinal fluid peak concentration, concentration at 8 hours, and area under the concentration-time profile calculated over the interval 0 to 8 hours [AUC(0-8)] for free indinavir were 294 nmol/L, 122 nmol/L, and 1616 nmol/L x h, respectively. The cerebrospinal fluid-to-plasma AUC(0-8) ratio for free indinavir was 14.7% +/- 2.6% and did not correlate with indexes of blood-brain barrier integrity or intrathecal immune activation. Indinavir achieves levels in cerebrospinal fluid that should contribute to control of human immunodeficiency virus type 1 replication in this compartment. The cerebrospinal fluid-to-plasma AUC(0-8) ratio suggests clearance mechanisms in addition to passive diffusion across the blood-cerebrospinal fluid barrier, perhaps by P-glycoprotein-mediated efflux.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Nosocomial methicillin-resistant Staphylococcus aureus bacteremia: is it any worse than nosocomial methicillin-sensitive Staphylococcus aureus bacteremia?

OBJECTIVE: To determine the comparative virulence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) by consideration of predisposing factors and outcomes in patients infected with these organisms in the healthcare setting. DESIGN: Analysis of an historical cohort of 504 bacteremic patients (316 MSSA and 188 MRSA), examining factors associated with mortality. SETTING: A 916-bed, university-affiliated, tertiary referral hospital. RESULTS: Risk factors for the development of MRSA include male gender, admission due to trauma, immunosuppression, presence of a central vascular line or an indwelling urinary catheter, and a past history of MRSA infection. Overall mortality was 22%. Death due to bacteremia was significantly greater in the MRSA group (risk ratio, 1.68; P<.05), although these patients were not found to be more likely to die due to underlying disease during treatment of bacteremia. In those patients who recovered from bacteremia, no significant differences for the outcome of death could be determined between the MRSA and MSSA groups. CONCLUSIONS: There is a general consensus in the published literature that MRSA bacteremia is more likely to be associated with death, and we confirm this conclusion. However, in contrast to other studies, our MRSA cohort does not appear to be more at risk of death due to underlying disease during treatment for bacteremia. Similarly, the general consensus that MRSA patients have an increased overall mortality was not confirmed in our study. Differences in comorbidities of patients may provide some explanation of these conflicting results, while an alternate explanation is that MRSA strains are more virulent than MSSA in some centers. Perhaps the most plausible explanation is that treatment is provided earlier and in a more aggressive fashion in some centers, leading to an overall lower mortality rate in all staphylococcal bacteremias in these institutions.

Australia↗
PubMed2000

Mutations in the WRN gene in mice accelerate mortality in a p53-null background.

Werner's syndrome (WS) is a human disease with manifestations resembling premature aging. The gene defective in WS, WRN, encodes a DNA helicase. Here, we describe the generation of mice bearing a mutation that eliminates expression of the C terminus of the helicase domain of the WRN protein. Mutant mice are born at the expected Mendelian frequency and do not show any overt histological signs of accelerated senescence. These mice are capable of living beyond 2 years of age. Cells from these animals do not show elevated susceptibility to the genotoxins camptothecin or 4-NQO. However, mutant fibroblasts senesce approximately one passage earlier than controls. Importantly, WRN(-/-);p53(-/-) mice show an increased mortality rate relative to WRN(+/-);p53(-/-) animals. We consider possible models for the synergy between p53 and WRN mutations for the determination of life span.

4-Nitroquinoline-1-oxide↗
PubMed2000

Prenyltransferase inhibitors block superoxide production by pulmonary vascular smooth muscle.

We recently showed that the farnesyltransferase inhibitor FTI-277 blocks interleukin 1beta (IL-1beta)-induced nitric oxide production in pulmonary vascular smooth muscle cells (SMC), whereas the geranylgeranyltransferase inhibitor GGTI-298 enhances this effect. Here we show that IL-1beta and platelet-derived growth factor (PDGF) stimulate superoxide production by pulmonary vascular SMC and that this effect is blocked by both FTI-277 and GGTI-298, suggesting that farnesylated and geranylgeranylated proteins are required for superoxide production. We also show that FTI-277 and GGTI-298 block superoxide production stimulated by constitutively active mutant H-Ras. Furthermore, superoxide production by IL-1beta, PDGF factor, and constitutively activated Ras is blocked by diphenyleneiodonium, implicating NAD(P)H oxidase as the generating enzyme. Given the role of oxidant radicals in vascular reactivity and injury, the action of both FTI-277 and GGTI-298 in suppressing superoxide generation by an inflammatory cytokine as well as by a potent smooth muscle mitogen may be therapeutically useful.

Animals↗
PubMed2000

Does prosthetic covering of nitinol stents alter healing characteristics or hemodynamics?

PURPOSE: To evaluate placement of polyester (Dacron) coverings on nitinol stents implanted in the canine aorta to determine the effect on cross-sectional lumen area, development of intimal hyperplasia, device endothelialization, and flow hemodynamics. METHODS: Ten polyester-covered and 10 uncovered nitinol stents (60-mm length, 10- or 12-mm diameter) were deployed percutaneously in the normal infrarenal aorta of 20 adult mongrel dogs using random assignment. Angiography, intravascular ultrasound (IVUS), and duplex ultrasound performed at device deployment and before explantation at 6 weeks were used to measure aorta/device diameter and cross-sectional area. Pressure-perfusion-fixed aortic segments were compared for surface endothelialization (CD31 staining) and for thickness of neointimal formation. RESULTS: All 20 endoluminal devices were accurately positioned in the infrarenal aorta without early or delayed evidence of device thrombosis, significant lumen narrowing, or device deformity. IVUS and duplex scanning identified no anatomical stenosis in either the covered or the bare devices by duplex ultrasound; peak systolic velocity measurements were similar (106+/-25 cm/s in the covered stent versus 96+/-25 cm/s for bare stents, p > 0.05). Mean neointimal thickness was significantly greater (p < 0.005) in the covered (326+/-145 microm) compared with the bare (219+/-62 microm) stents. Intima-to-media height ratios were greater in the covered stents (3.0+/-1.1 compared with 1.1+/-0.2, p < 0.003). Mean surface area endothelialization in the proximal, middle, and distal sections of each device was similar (p > 0.05) in covered (59%, 56%, and 69%) and bare (59%, 65%, and 53%) stents. CONCLUSIONS: Deployment and balloon dilation of a covered nitinol stent in a nondiseased canine aorta increased neointimal development compared with an uncovered stent, but overall lumen cross-sectional area was preserved. No differences in device patency, intradevice thrombus formation, flow hemodynamics, or luminal endothelialization were demonstrated, despite a thicker intradevice neointima induced by the polyester covering.

Alloys↗
PubMed2000

Biochemical and molecular approaches to understanding protein import into peroxisomes.

Peroxisomes are eukaryotic organelles that perform diverse and variable functions. Although genetic studies in yeasts and mammals have identified approximately 20 genes (PEX genes) required for the biogenesis of this important organelle, biochemical studies of protein targeting and import have lagged behind and in many cases we have no idea of the function of the PEX gene products (peroxins). Using an import assay in vitro derived from sunflower cotyledon cells and recombinant proteins, we have obtained translocation intermediates on the peroxisome import pathway and are using cross-linking to identify interacting partners. We have also used antibodies raised against human PEX14 to inhibit the import of matrix proteins in this system. To obtain homologous antibodies for inhibition experiments, to immunoprecipitate cross-linked products and to enable us to study the import pathways of peroxins we have cloned and characterized plant orthologues of three PEX genes, PEX6, PEX10 and PEX14.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2000

Men's perspectives on the impact of prostate cancer: implications for oncology nurses.

PURPOSE/OBJECTIVES: To describe the perspectives of men with recurrent prostate cancer regarding their experiences with the disease, its impact, and the help they received and to compare these individuals to men without recurrent prostate cancer. DESIGN: Cross-sectional survey. SETTING: Physicians' offices and prostate cancer self-help groups in Canada. SAMPLE: A convenience sample of 120 men with recurrent prostate cancer and 845 men without recurrent disease. METHODS: A survey instrument was developed following in-depth interviews with men living with prostate cancer. The men received survey packages from their physicians or through a self-help group, completed the instrument at home, and returned it in a prestamped addressed envelope. MAIN RESEARCH VARIABLES: Impact on lifestyle, satisfaction with communication, importance of information, satisfaction with information received, problems experienced, and assistance received for problems. FINDINGS: Significant differences related to a number of factors were found between the men with recurrent prostate cancer and those without recurrent disease. A large number of those with recurrent disease experienced problems with side effects, anger, and pain and received help for their pain; experienced a negative impact on leisure time and on mental health; experienced difficulty talking with healthcare professionals; and felt the need to talk with someone about their cancer. Many of the men with recurrent disease were dissatisfied with the information they received about their medical condition and possible side effects. CONCLUSIONS: Men with prostate cancer experience both physical and psychosocial difficulties. Many perceive that they are not receiving adequate help for these difficulties. Future research is needed to increase understanding of how men are managing the impact of prostate cancer and what types of interventions would be most useful. IMPLICATIONS FOR NURSING PRACTICE: Findings emphasize the need for nurses to be certain that they are conducting broad-based assessments of patients with prostate cancer throughout the illness experience. Nurses need to inform patients about services available to assist them, help patients understand the emotional responses to illness, and provide opportunities for patients to talk about the illness and its impact.

Aged↗
PubMed1999

Regulation of cell movement is mediated by stretch-activated calcium channels.

Intracellular calcium regulates many of the molecular processes that are essential for cell movement. It is required for the production of actomyosin-based contractile forces, the regulation of the structure and dynamics of the actin cytoskeletons, and the formation and disassembly of cell-substratum adhesions. Calcium also serves as a second messenger in many biochemical signal-transduction pathways. However, despite the pivotal role of calcium in motile processes, it is not clear how calcium regulates overall cell movement. Here we show that transient increases in intracellular calcium, [Ca2+]i, during the locomotion of fish epithelial keratocytes, occur more frequently in cells that become temporarily 'stuck' to the substratum or when subjected to mechanical stretching. We find that calcium transients arise from the activation of stretch-activated calcium channels, which triggers an influx of extracellular calcium. In addition, the subsequent increase in [Ca2+]i is involved in detachment of the rear cell margin. Thus, we have defined a mechanism by which cells can detect and transduce mechanical forces into biochemical signals that can modulate locomotion.

Animals↗
PubMed1999

Clinical and economic impact of newer versus older antipsychotic medications in a community mental health center.

This pilot study was conducted to compare both the clinical effectiveness and the treatment costs of newer (atypical) antipsychotic medications (clozapine and risperidone) with those of older (classic) neuroleptic medications (chlorpromazine and haloperidol) for psychosis in a community mental health care setting. The study used a retrospective, uncontrolled, open, nonrandomized, within-subjects design and relied on medical records as a data source for 37 clients. All clients received older antipsychotics for at least 1 year, newer antipsychotics for a transition period of 3 months, and the newer agents for at least an additional year. The newer antipsychotic medications were more effective and less costly (total cost of care, $3000 less per client per year [1997 dollars]) than the older medications. Effect-size estimates for the measured variables provide a guide for future research into the cost-effectiveness of these newer medications within the community mental health care setting. These findings can provide policy makers with guidance on treating people with major mental disorders in the most effective and efficient manner. Because of limited budgets, community mental health centers making the investment in newer, more expensive medications to improve client outcomes have to maintain the same or lower total cost of care. Results of the current study suggest that short-term investment in the newer medications by community mental health centers offers superior clinical effectiveness and lower long-term overall cost of care.

Adult↗
PubMed1999

Emergency department hemodialysis in a case of severe ethylene glycol poisoning.

A 36-year-old man with a history of depression presented to the emergency department after ingesting approximately 3,000 mL of ethylene glycol antifreeze in a suicide attempt. The patient's ethylene glycol concentration, 1,889 mg/dL, was higher than any level previously documented in the medical literature. Although his course was complicated by nausea, emesis, lethargy, metabolic acidosis, and kidney failure, the patient survived without persistent kidney failure or other chronic problems. Sustained hemodialysis and ethanol infusion were instituted in the ED, on the basis of the patient's history, before laboratory confirmation of the ingestion was obtained.

Adult↗
PubMed1999

Vascular surgical society of great britain and ireland: limb outcome following failed femoropopliteal polytetrafluoroethylene bypass for intermittent claudication

BACKGROUND: Femoropopliteal (FP) bypass using polytetrafluoroethylene (PTFE) is still considered by many surgeons to be a reasonable procedure for severe intermittent claudication (IC) without limb-threatening ischaemia. The consequences of FP graft failure were examined. METHODS: Over 8 years, 54 patients had 55 FP grafts (that subsequently occluded) inserted for severe IC (42 PTFE and 13 vein grafts) above (30) or below (25) the knee. There were no operative deaths. During the same interval a total of 191 FP grafts were placed, 100 of which were vein grafts. Patient demography and risk factor analysis was similar for both groups. RESULTS: Nineteen patients required amputation subsequent to a failed graft, all of these following PTFE grafts. Mean time to occlusion was 12.2 (range 0-79) months. For PTFE grafts, the mean(s. d.) ankle index rose from 0.51(0.14) to 0.95(0.15) after operation but fell to 0.25(0.15) after occlusion, confirming a highly significant deterioration from preoperative levels, which was not seen in vein graft occlusions. CONCLUSION: Long-term FP bypass patency rates with vein are superior to those obtained with PTFE. Failed PTFE grafts show a significant deterioration in pressure indices compared with preoperative values. FP grafts for IC carry an intrinsic risk of limb loss which is much greater when vein is not used (P < 0.001).

Journal Article↗
PubMed1999

Chronic mentally ill individuals reentering the community after hospitalization. Phase II: The urban experience.

The purpose of this qualitative study was to explore the experiences of persons reentering an urban community after hospitalization for mental illness. The sample consisted of five men and three women, aged early 30's to mid-50's, mostly diagnozed with schizophrenia, and who had had several hospitalizations within the previous year. Most returned to places where they had lived before, frequently to boarding homes for former psychiatric patients. Most lived alone. Each participant was interviewed shortly before discharge and one to two times in the community. The tape-recorded interviews were analyzed according to the Giorgi method. Three themes emerged from the data, related, respectively, to the hospital and its environs remaining a focus of the participants' lives, the added burden of social and financial conditions, and the presence of goals which nevertheless had barriers to their achievement. Contrasts are drawn with the findings of Phase I (Montgomery & Johnson 1998), in which there was found a much stronger sense of discharge marking a new beginning. The findings add to our knowledge about what it is like for chronic mentally ill individuals to live outside hospital, but also raise questions about the influence of particular diagnoses, community characteristics and changes in adjustment over time.

Adaptation, Psychological↗