PubMed Health⌕ Search

Biomedical subjects

N Johnston

Publications and source records attributed to N Johnston.

At least 19 recordsLinked to original sources
PubMed2000

The stanley foundation brain collection and neuropathology consortium.

The Stanley Foundation brain collection is an attempt to supplement existing brain collections for the purpose of promoting research on schizophrenia and bipolar disorder. Specimens are collected with the permission of the families in a standardized manner, with half of each specimen being frozen and half fixed in formalin. The Neuropathology Consortium is a subset of 60 specimens from the collection, well-matched groups of 15 each with diagnoses of schizophrenia, bipolar disorder, major depressive disorder without psychotic features, and normal controls. More than 75000 sections and blocks from the Consortium have been sent to over 50 research groups worldwide to carry out a wide variety of assessments. These data will be integrated to provide a more complete picture of the neuropathology of these disorders.

Adult↗
PubMed1999

The emergency use of recombinant hirudin in cardiopulmonary bypass.

The most common anticoagulant used for cardiopulmonary bypass is heparin. An alternate form of anticoagulant therapy is needed for patients who have immune-mediated heparin-associated thrombocytopenia (HIT). Thrombocytopenia causes bleeding and may lead to serious arterial and venous thrombosis. HIT or heparin-induced thrombocytopenia with thrombosis type II (HITT) are both described as adverse reactions to heparin. They are diagnosed with a platelet count less than a 100,000/mcl for 2 consecutive days. HITT, the severe form, is characterized with the thrombocytopenia in combination with thromboembolic complications, such as strokes, myocardial infarctions, and limb ischemia. Two cases are presented in which r-hirudin was used for anticoagulation for aortocoronary bypass surgery and mitral valve replacement. The activated partial prothrombin time (aPTT) was used to monitor coagulation. In the first case, the aPTT was maintained greater than 100 seconds, and at the termination of cardiopulmonary bypass, some clot was noted in the cardiopulmonary bypass circuit. In the second case, a longer cardiopulmonary bypass run was anticipated, the hirudin bolus and infusion rate were increased, and the aPTT was maintained at greater than 200 sec. Adequate coagulation resulted, and, at the end of bypass, no clot was noted. These case studies seem to suggest a higher dosage of r-hirudin may be required for the use of cardiopulmonary bypass and a need to maintain aPTT values greater than 200 sec to help monitor anticoagulation.

Anticoagulants↗
PubMed1997

Children of the mentally ill: a qualitative focus group approach.

Children of the mentally ill constitute a group neglected by mental health care providers. Increased rates of psychopathology, impaired attention processes, disturbances in interpersonal relationships, and reduced overall adaptive functioning are reported as significant outcomes for offspring of parents with a mood disorder. While epidemiological studies underscoring the risks from a hereditary standpoint are many, there are few studies examining the subjective experience of living with a depressed parent. Findings from this pilot study elucidate the subjective experience of preadolescents/adolescents living with an affectively ill parent, applying a qualitative focus group design. Videotaped sessions were analysed using methods consistent with qualitative research. 'Struggle to understand the illness', 'managing the illness', 'recognizing the signs', and 'impact of parent's hospitalization' emerged as central themes, capturing the essence of participants' experiences. The first two themes were further divided into subthemes. Findings illuminate the need to broaden nursing interventions and research, to include family perspectives, particularly when parental mental illness is a factor.

Adaptation, Psychological↗
PubMed1996

Psychological testing and pilot licensing.

This article reviews contemporary trends in the psychological testing of pilots. It is written in the particular context of draft European Joint Aviation Authorities licensing proposals which, in certain circumstances, envisage psychological testing for pilot licensing purposes. The article aims to clarify issues relating to the validity, reliability, and value of pilot psychological testing in this particular context. It is first suggested that the entire domain is characterized by terminological and methodological confusion. The economic and other benefits of psychological testing are contrasted with the potential risks, including abuse and the use of tests in circumstances for which they were never designed. Reference also is made to cultural differences that potentially may impact on the practical realities of psychological testing--especially within the European context, where the debate is presently at its most intense.

Aerospace Medicine↗
PubMed1993

Urinary dopamine response to angiotensin II is not abnormal in type 1 (insulin-dependent) diabetes mellitus.

To examine the interaction between angiotensin II (ANGII) and dopamine in type 1 diabetes mellitus, urinary dopamine excretion was examined during ANGII infusion in 15 diabetic patients and 10 control subjects after pretreatment with lithium 750 mg and placebo. The antinatriuretic response and the urinary dopamine response to ANGII did not differ within or between the two groups on each study day. No correlation was observed between the decrements in urinary sodium excretion and urinary dopamine output during ANGII infusion in either group. The effect of insulin on urinary dopamine excretion was studied separately in seven non-diabetic subjects; sodium and potassium retention occurred during a hyperinsulinaemic euglycaemic clamp, but urinary dopamine did not change. The data suggest that the relationship between urinary sodium excretion and tubular dopamine synthesis remains normal in early type 1 diabetes mellitus both at baseline and during the antinatriuresis induced by angiotensin II. The cause of the reduction in urinary dopamine during ANGII infusion is unclear, but is probably not mediated directly by changes in proximal tubular sodium transport.

Adult↗
PubMed1992

A process-oriented approach. Selecting a nursing model for psychiatric nursing.

The nursing literature is replete with articles and books that describe nursing conceptual frameworks and models and encourage their use in clinical, education, and research activities. Although much information exists on the content of nursing models, less has been written about how a model is to be chosen and the process that may facilitate the choice of a model. This article reviews potential benefits and limitations of nursing models and conceptual frameworks and describes a three-phase process for selecting a model for psychiatric nursing practice.

Choice Behavior↗
PubMed1990

Purification and characterization of the reconstitutively active tricarboxylate transporter from rat liver mitochondria.

The tricarboxylate transporter has been purified in reconstitutively active form from rat liver mitochondria. The transporter was extracted from mitoplasts with Triton X-114 in the presence of cardiolipin and citrate and was then purified by sequential chromatography on hydroxylapatite, Matrex Gel Orange A, Matrex Gel Blue B, and Affi-Gel 501. Analysis of the purified material via sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated the presence of one main protein band with an apparent molecular mass of 32.5 kDa. Upon incorporation into phospholipid vesicles, the purified transporter catalyzed a 1,2,3-benzenetricarboxylate-sensitive citrate/citrate exchange with a specific transport activity of 3240 nmol/4 min/mg of protein. This value was enhanced 831-fold with respect to the starting material. Substrate competition studies indicated that the reconstituted transport could be substantially inhibited by isocitrate, malate, and phosphoenolpyruvate, but not by alpha-ketoglutarate, succinate, malonate, pyruvate, or inorganic phosphate. Moreover, in addition to 1,2,3-benzenetricarboxylate, the reconstituted exchange was sensitive to the anion transport inhibitor n-butylmalonate but was insensitive to phenylsuccinate, alpha-cyano-4-hydroxycinnamate, and carboxyatractyloside. Finally, studies with covalent modifying agents indicated the purified transporter was inhibited by sulfhydryl reagents and by diethyl pyrocarbonate, 2,3-butanedione, phenylglyoxal, and pyridoxal 5-phosphate. In conclusion, these studies describe the first procedure to yield a highly purified tricarboxylate transport protein that both displays a high specific transport activity and can be obtained in quantities that readily enable further structural as well as functional studies. Based on its substrate specificity and inhibitor sensitivity, the purified 32.5-kDa protein appears to represent the complete tricarboxylate transport system found in rat liver mitochondria. Finally, new information is presented concerning the effect of covalent modifying reagents on the function of this transporter.

Animals↗
PubMed1990

Humoral immune responses in mice using gamma inulin preparations as adjuvants for hepatitis B vaccines.

There is an urgent need for new, powerful adjuvants suitable for use with sub-unit and peptide vaccines in humans. We have measured the humoral immune response in BALB/c mice to vaccine formulations using recombinant HBsAg antigens, and gamma inulin and alum adjuvants. Using Merck, Sharpe & Dohme (MSD) HBsAg at 10 micrograms/mL, high levels of anti-HBs were generated and geometric mean S/N ratios of 88, 133 and 107 were obtained for alum absorbed vaccine, gamma inulin, and a mixture of the two adjuvants, respectively. A dilution series produced ED50 values of 0.08, 0.15 and 0.22 micrograms/mL respectively. In a second series of experiments comparing alum and algamulin (a complex of gamma inulin and alum), MSD HBsAg induced anti-HBs levels of 81 and 52, and ED50 values of 0.3 and 0.4 when used in conjunction with alum and algamulin, respectively. SKF HBsAg induced anti-HBs levels of 126 and 111 with alum and algamulin, and ED50 values of 0.11 and 0.075. The class, subclass and level of antibody produced in mice boosted with a second dose of vaccine at 21 days was also examined. Both alum and gamma inulin induced higher levels of total antibody, IgG1 and minor IgG subclasses than algamulin, or HBsAg alone. Overall, gamma inulin appears to be an equivalent adjuvant to alum, although their mechanisms of action are different. Mixtures or complexes of the two adjuvants appear to be less effective in inducing humoral immune responses in mice than either alone.

Adjuvants, Immunologic↗
PubMed1988

A study of the cells in the explanted viable cryopreserved allograft valve.

From June 1975 to December 1987, 231 patients underwent aortic valve replacement with a viable cryopreserved allograft aortic valve. Throughout this era, a uniform procurement and preservation was used to maintain leaflet fibroblast viability. The allograft valve was obtained from coroner's autopsies within 24 hours of death, and more recently from organ donors, incubated for 24 hours in low dose antibiotic solution followed immediately by cryopreservation (mean time interval 39 hours after donor death). Viability was ensured by monitoring glucose utilization of the aortic and pulmonary valves and by demonstrating fibroblast growth in tissue cultured from the pulmonary valve. A uniform protocol for valve preparation was used during the entire experience. Nine allograft aortic valves have been obtained by eight reoperations (two were for leaflet degeneration) and one autopsy. The time intervals from implantation to explantation were 2 months, 10 months, 20 months, 22 months, 2.2 years, 5 years, 8.3 years, 9.2 years, and 10.8 years. Histologic examination of the leaflet tissue disclosed a variable degree of cellularity, ranging from a highly cellular matrix (9.2 years) to minimal cellularity (20 months). Within the same valve (10 months), one leaflet was completely acellular with a moderate degree of cellularity in the other two leaflets. The competent valve recovered at autopsy (8.2 years) was essentially acellular. Fibroblasts could consistently be cultured from leaflets in which viable cells were seen histologically. Chromosomal analysis of cultured cells from a valve leaflet (9.2 years) that was implanted with a donor and recipient sex mismatch demonstrated persistence of donor cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1987

The viable cryopreserved allograft aortic valve.

One hundred and twenty-four patients underwent aortic valve replacement with a nonviable 4 degrees C refrigerated aortic allograft valve. One hundred and eighty-four patients underwent aortic valve replacement with a viable cryopreserved aortic allograft valve in a later era. The longest follow-up was 16 years for the group with the nonviable valve and 11 years for the group with the viable valves. Within this time frame, reoperation was required in 23 patients with nonviable valves for leaflet perforation or rupture whereas no patients in the group with viable valves developed this complication (p less than 0.0001). The prevalence of endocarditis and thromboembolism was very low in both groups. Viability of leaflet tissue is associated with an important improvement in durability over nonviable allograft valves. Consequently, long-term follow-up results of allograft valves might be best expressed in terms of viability. The current evidence suggests that the viable cells are donor in origin. The viable cryopreserved aortic allograft valve offers significant advantages over current nonviable allograft valves, mechanical valves, and bioprostheses.

Actuarial Analysis↗
PubMed1987

Evaluation of public health preschool child developmental screening: the process and outcomes of a community program.

We conducted a randomized controlled trial of a public health and education screening program aimed at all 4,797 four to five year old children registering for kindergarten in three school districts of southern Ontario, Canada. Children received either the Denver Developmental Screening Test (DDST) with a community health intervention program for positive screeness; the DDST with no intervention for positive screenees; or no screening test. The intervention program consisted of referral to the child's physician for assessment; a review conference between the child's teacher and the school health nurse; parent counseling; and monitoring of the child in school by the school health nurse. At the end of the third school year, no differences were found between positive screenees in the community health intervention group and the "no intervention" groups using individual academic achievement, cognitive, and developmental tests. Parents' reports revealed no differences between groups in children's mental, social, and behavioral well-being. However, parents of intervention program children had more worry about their child's school progress suggesting a potentially harmful labeling effect. In comparison to a random sample of children with normal DDST results, or a random sample of children who had randomly not been screened, the children with positive preschool DDSTs had substantially more school problems three years after screening.

Child Development↗
PubMed1986

Biomedical surveillance: rights conflict with rights.

Medical screening and biomedical monitoring violate individual rights. Such conflicts of right with right are acted upon synergistically by uncertainty which, in some important respects, increases rather than decreases as a result of research. Issues of rightness and wrongness, ethical issues, arise because the human beings who are subjects of medical screening and biological monitoring often have little or no option whether to be subjected to them. We identify issues of rightness and wrongness of biomedical surveillance for various purposes of occupational health and safety. We distinguish between social validity and scientific validity. We observe that principles are well established for scientific validity, but not for social validity. We support guidelines as a way forward.

Aviation↗
PubMed1985

Occupational stress and the professional pilot: the role of the Pilot Advisory Group (PAG).

This paper discusses the role of pilot peer group involvement, using the Pilot Advisory Group (PAG), in assisting pilots who manifest personal problems which derive from occupational and other stressors. Some general aspects of "background" occupational stress are discussed. Attitudes and opinions of professional aviators are identified and their role in denial of symptomatology is developed. The concept of the Pilot Advisory Group (PAG) is then discussed in detail before its role in relation to occupational stress is introduced. While some of the better known problems associated with occupational stress in pilots are mentioned, the emphasis in the paper is on developing new perspectives regarding the identification of stress-induced dysfunction, and also in exploring the suitability of PAG involvement. The formal obligations of management and regulatory authorities are contrasted with what the author sees as the countervailing imperatives of pilot attitudes and beliefs.

Aerospace Medicine↗