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Biomedical subjects

C Johns

Publications and source records attributed to C Johns.

At least 37 records · Page 2Linked to original sources
PubMed2000

Role of alpha(2)-adrenergic receptor subtypes in the acute hypertensive response to hypertonic saline infusion in anephric mice.

Experimental evidence suggests that the acute hypertensive response induced in anephric animals by infusion of a hypertonic saline solution is mediated by disinhibition of the presynaptic sympathoinhibitory alpha(2)-adrenergic receptors (alpha(2)-AR) of the central nervous system. The purpose of the present experiments was to dissect the role of the 3 distinct alpha(2)-AR subtypes (alpha(2A)-, alpha(2B), - and alpha(2C)-AR) in this response. Groups of genetically engineered mice deficient in each one of these alpha(2)-AR subtype genes were submitted to bilateral nephrectomy followed by a 0.4-mL infusion of 4% saline over a 2-hour period, with constant direct blood pressure (BP) monitoring. The alpha(2A)-AR-deficient and alpha(2C)-AR-deficient mice responded with significant BP elevations (by 11.8+/-2.5 and 16.7+/-1.7 mm Hg, respectively), and so did their wild-type counterparts (17.8+/-2.5 and 11.8+/-2.0 mm Hg, respectively) and the wild-type alpha(2B) +/+ (13.1+/-2.4 mm Hg). However, the alpha(2B)-AR-deficient mice were unable to raise their BP and had a slightly lowered BP (by -3.0+/-4. 0 mm Hg) at the end of the infusion period. All 6 groups exhibited elevated plasma norepinephrine levels ranging between 0.8 and 1.8 ng/mL at the end of the infusion. In all cases, the alpha(2)-AR-deficient groups tended to have higher norepinephrine levels than their wild-type counterparts. Surprisingly, this difference was significant only in the alpha(2B)-AR-deficient mice, which, despite the elevated norepinephrine, were unable to raise their BP. The data suggest that a full complement of the alpha(2B)-AR is needed to mediate the hypertensive response to acute saline load, even though its absence does not prevent the release of norepinephrine under these conditions.

Acute Disease↗
PubMed1999

Dynamic cyclic changes in coronary sinus caliber in patients with and without congestive heart failure.

M-mode echography of the coronary sinus in the apical 2-chamber view enabled us to measure coronary sinus caliber at specific phases of the cardiac cycle. Coronary sinus narrowing occurs consistently during atrial contraction, but is always absent in atrial fibrillation; in patients with congestive heart failure and systemic venous congestion, this narrowing is significantly attenuated.

Coronary Vessels↗
PubMed1999

Composite B-cell and T-cell lymphoma arising 24 years after nodular lymphocyte predominant Hodgkin's disease.

Twenty-four years after apparently successful treatment for nodular lymphocyte predominant Hodgkin's disease (nLPHD), a 41-year old male developed "B" symptoms and extensive adenopathy. A right axillary lymph node biopsy showed two distinct regions including (1) histiocyte-rich B-cell lymphoma and (2) diffuse small T-cell lymphoma. A clonal rearrangement of the gene for the T-cell receptor beta chain confirmed the presence of a T-cell neoplasm, and this was further confirmed by selective polymerase chain reaction (PCR) on this morphologic zone. PCR on the morphologic B-cell lymphoma confirmed the presence of an immunoglobulin gene rearrangement. These two regions were separated by a less-defined zone containing a mixture of small CD57 positive T lymphocytes, small B lymphocytes, and rare lymphocytic and histiocytic (L&H) cells, highly suggestive of recurrent LPHD. The development of composite B-cell and T-cell lymphoma in this patient raises the speculation that nLPHD may be a neoplasm of lymphoid cells, which can differentiate in both B- and T-cell directions, with the "L&H" cells constituting their B-cell progeny.

Adolescent↗
PubMed1999

Reflection as empowerment?

Reflective practice, as an ideal model, is generally espoused as a developmental process to empower practitioners to achieve and sustain effective practice. Yet when reflective practice is accommodated into the real world of everyday practice can this ideal itself be realised? Or will reflective practice be accommodated within existing norms whereby it becomes another technology of surveillance? The paper draws on dialogue taken from a guided reflection session to consider whether reflection can be empowering and to consider those factors which limit this potential.

Female↗
PubMed1999

Home within 24 hours of laparoscopic hysterectomy.

We assessed the feasibility of safe discharge home within 24 hours following laparoscopic hysterectomy in 30 patients who met the inclusion criteria and consented to be enrolled in the study group. Patients were admitted on the day of their surgery with the expectation of discharge within 24 hours. Appropriate home nursing follow-up and phone contact by the surgical team were organized preoperatively. Inclusion criteria were: age 30-65 years, absence of any major medical history that would require prolonged hospitalization, availability of home support for the first 48 hours after discharge and presence of a working telephone line and an address within the area of the Community Home Nursing service. All 30 operative procedures were completed without incident. Six patients underwent total laparoscopic hysterectomy (TLH) (all the procedures of hysterectomy being performed laparoscopically including the suturing of uterine arteries, colpotomy and closure of the vaginal vault. The uterus was removed vaginally) and 24 patients underwent laparoscopic hysterectomy (LH) (this techniques differs from TLH in that the colpotomy was performed laparoscopically but the uterosacral ligaments were divided vaginally and the vault also was closed vaginally after the uterus was removed vaginally). The average operating time was 115 minutes (range 85-150 minutes) and the average blood loss was 97 mL (20-250 mL). There were no intraoperative complications, no requirement for transfusion and no readmission to hospital for any of the patients in the study. Postoperative complications were minor (umbilical cellulitis (1), intestinal colic (1)) and both were treated with resolution of the symptoms. Ninety per cent of patients in the study were discharged within 24 hours of their surgery, the average duration of stay being 22.9 hours (20-24 hours). Three patients were not fit for discharge at 24 hours postoperatively due to general lethargy, migraine and nausea; their average discharge time was 53.5 hours. The study showed that laparoscopic hysterectomy can be associated with a reduction in length of in-patient stay compared to traditional laparotomy. Furthermore this reduction could be safely reduced to 24 hours following laparoscopic hysterectomy. There was also an associated cost saving in terms of inpatient bed days. Patient satisfaction with this protocol was high in this selected and motivated group.

Adult↗
PubMed1999

Role of the alpha2B-adrenergic receptor in the development of salt-induced hypertension.

Salt sensitivity is a common trait in patients with essential hypertension and seems to have both an inherited and an acquired component (eg, is influenced by aging and renal insufficiency). Experimental evidence suggests that salt loading induces hypertension via a neurogenic mechanism mediated by the alpha2-adrenergic receptors (alpha2-AR). To explore the alpha2-AR subtype involved in this mechanism, we studied 2 groups of mice genetically engineered to be deficient in one of the 3 alpha2-AR subtype genes (either alpha2B-AR +/- or alpha2C-AR -/- knockout mice) compared with their wild-type counterparts. The mice (n=10 to 14 in each group) were submitted to subtotal nephrectomy and given 1% saline as drinking water for up to 35 days. Blood pressure (BP) was monitored by tail-cuff readings and confirmed at the end point by direct intra-arterial BP recording. The alpha2B-AR-deficient mice had an attenuated BP response in this protocol (baseline 101.8+/-2.7 versus end point 109.9+/-2.8 mm Hg), whereas the BP of their wild-type counterparts went from a baseline 101.9+/-2.3 to an end point 141.4+/-7.1 mm Hg. The other 2 groups had BP increases of 44. 6+/-5.17 and 46.7+/-7.01 mm Hg, with no difference between the mice deficient in the alpha2C-AR gene subtype versus their wild-type counterparts. Body weight, renal remnant weight, and residual renal function were no different among groups. These data suggest that a full complement of alpha2B-AR genes is necessary to raise BP in response to dietary salt loading, whereas complete absence of the alpha2C-AR subtype does not preclude salt-induced BP elevation. It is unclear whether the mechanism(s) involved in this process are of central origin (inability to increase sympathetic outflow), vascular origin (inability to vasoconstrict), or renal origin (inability to retain excess salt and fluid).

Aging↗
PubMed1999

Sympathoinhibitory function of the alpha(2A)-adrenergic receptor subtype.

Presynaptic alpha(2)-adrenergic receptors (alpha(2)-AR) are distributed throughout the central nervous system and are highly concentrated in the brain stem, where they contribute to neural baroreflex control of blood pressure (BP). To explore the role of the alpha(2A)-AR subtype in this function, we compared BP and plasma norepinephrine and epinephrine levels in genetically engineered mice with deleted alpha(2A)-AR gene to their wild-type controls. At baseline, the alpha(2A)-AR gene knockouts (n=11) versus controls (n=10) had higher systolic BP (123+/-2.5 versus 115+/-2.5 mm Hg, P<0. 05), heart rate (730+/-15 versus 600+/-18 b/min, P<0.001), and norepinephrine (1.005+/-0.078 versus 0.587+/-0.095 ng/mL, P<0.01), respectively. When submitted to subtotal nephrectomy and given 1% saline as drinking water, both alpha(2A)-AR gene knockouts (n=14) and controls (n=14) became hypertensive, but the former required 15. 6+/-2.5 days versus 29.3+/-1.4 days for the controls (P<0.001). End-point systolic BP was similar for both at 155+/-2.1 versus 152+/-5.2 mm Hg, but norepinephrine and epinephrine levels were twice as high in the knockouts at 1.386+/-0.283 and 0.577+/-0.143 versus 0.712+/-0.110 and 0.255+/-0.032 ng/mL, respectively, P<0.05 for both. We conclude that the alpha(2A)-AR subtype exerts a sympathoinhibitory effect, and its loss leads to a hypertensive, hyperadrenergic state.

Animals↗
PubMed1999

Unravelling the dilemmas within everyday nursing practice.

Each day, nurse practitioners are faced with clinical situations and dilemmas that have no obvious right answers. This article sets out the process of ethical mapping as a reflective device to enable practitioners to reflect on dilemmas of practice in order to learn through the experience and inform future practice. Ethical mapping is illustrated around a single experience that an intensive care practitioner shared in an ongoing guided reflection relationship. Within this process the practitioner draws on ethical principles to inform the particular situation, notably autonomy, doing harm, truth telling and advocacy. Through reflection, ethical principles are transcended and assimilated into knowing in practice, enabling the practitioner to become more ethically sensitive in responding to future situations.

Adult↗
PubMed1998

Caring through a reflective lens: giving meaning to being a reflective practitioner.

Who is a reflective practitioner? It is assumed that a reflective practitioner is someone who views and responds to practice through an appropriate reflective lens. The present paper is a reflective account that gives meaning to being a reflective practitioner within everyday practice whereby the reflective lens is structured through the Burford Nursing Development Unit (NDU) Model: Caring in Practice.

Activities of Daily Living↗
PubMed1998

Expression of alpha2-adrenergic receptors in normal and atherosclerotic rabbit aorta.

Alpha2-adrenergic receptors (alpha2-ARs) in vascular smooth muscle cells are known to mediate vasoconstriction; however, it is unknown which of the 3 subtypes of alpha2-AR (alpha2A, alpha2B, or alpha2C) is expressed in vascular tissue. We have used subtype-specific probes in in situ hybridization and RNase protection assays to analyze the expression of alpha2-AR in the thoracic aorta of New Zealand White (NZW) and Watanabe heritable hyperlipidemic (WHHL) rabbits, a model for atherosclerosis. We found that the alpha2A-AR mRNA was in endothelial and smooth muscle cells in both NZW and WHHL aorta. In addition, the shoulders and subendothelial regions of the atherosclerotic lesions in WHHL aorta showed abundant expression of alpha2A-AR mRNA. Antibodies to macrophage (RAM-11) and smooth muscle cell (HHF-35) antigens were used to localize macrophage and smooth muscle cells in aortic sections from WHHL rabbits. The expression of alpha2A-AR mRNA within the lesions of WHHL rabbits correlated with the presence of infiltrating macrophages. We discuss the potential role of alpha2A-ARs in macrophage function and in promoting atherosclerosis.

Animals↗
PubMed1996

Visualizing and realizing caring in practice through guided reflection.

Guided reflection provides a challenging and supportive milieu for practitioners to learn through reflection towards achieving desirable work. This work inevitably demands confrontation with self and the conditions of practice that limit the achievement of desirable work. It also demands an understanding of what is desirable nursing. From an ideological position, desirable work is generally defined in terms of humanistic caring. The paper discusses how caring can be visualized and realized in practice through the experiences practitioners reflect on and share within guided reflection. This work is illustrated using using guided reflection dialogue.

Conflict, Psychological↗
PubMed1996

Immortalized human bladder cell line exhibits amiloride-sensitive sodium absorption.

We have produced a continuous cell line using retroviral transduction of simian virus 40 (SV40) large T antigen into epithelial cells grown from a cystoscopic bladder biopsy from a female patient with interstitial cystitis. Immortalized urothelial cells are grown in a hormonally supplemented medium in the presence of lethally irradiated NIH-3T3 fibroblast coculture. They maintain their epithelial appearance and are positive for cytokeratins. SV40 large T antigen is localized to the cell nucleus. When grown on Anocell permeable supports, the cells form a complex epithelium with scalloped luminal membranes, apical junctional complexes containing tight junctions, stratification, transepithelial resistance of 500-1,000 omega.cm2, amiloride-sensitive short-circuit current indicative of active transepithelial Na+ absorption, and functional evidence for basolateral Na-K-adenosinetriphosphatase. This immortalized bladder cell line will facilitate the study of human bladder epithelial function and the response to diverse physiological and pathophysiological stimuli.

Absorption↗
PubMed1996

Models of experimental hypertension in mice.

Experimental models of hypertension in various animals are useful in the research of vasoactive mechanisms. Recombinant DNA technology has produced genetically engineered animals, mostly mice, useful in hypertension research. However, the development of hypertensive models in mice is fraught with technical difficulties. We describe here the successful development in mice of two common types of experimental hypertension: the renovascular two-kidney, one clip and mineralocorticoid deoxycorticosterone-salt models. By adapting technology previously used in rats, we succeeded in developing hypertension (defined as systolic pressures higher than 140 mm Hg) in more than 50% of mice so treated. We also adapted the methodology for indirect tail-cuff blood pressure measurements as well as for direct intra-arterial monitoring of blood pressure in conscious, freely moving mice. Application of these techniques in transgenic or gene knockout mice with altered vasoactive hormones or receptors should allow elucidation of the role of the target gene products in various types of hypertension.

Animals↗
PubMed1995

Framing learning through reflection within Carper's fundamental ways of knowing in nursing.

Carper's fundamental ways of knowing have been utilized as a framework for the practitioner to consider what he or she has learnt through reflection on experience. The purpose of this paper is to consider, through an interpretation of Carper's writings and through analysing one practitioner's experience shared in a supervision milieu, whether this use of Carper's work can be reasonably justified on a theoretical and practical level.

Decision Making↗
PubMed1995

A multidisciplinary team approach to day hospital patient care.

A review of practice in a mental health day hospital led to a multidisciplinary quality group being established. Outlines changes implemented leading to service improvements and increases in patient and staff satisfaction.

Community Mental Health Services↗