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Biomedical subjects

C Purcell

Publications and source records attributed to C Purcell.

At least 19 recordsLinked to original sources
PubMed1998

Vascular tissue adaptations in end-to-end autologous arterial grafts in rats: a morphometric analysis.

Autologous vein grafts are employed extensively to bypass stenoses in the arterial circulation. More recently arterial segments have been used for such bypass surgery. In this study the adaptation of regenerating vascular tissues in experimental autologous artery grafts (4 mm long and 1 mm in diameter) in 20 adult male Wistar rats was analysed. At 1, 2, 4, 8 and 16 wk after insertion, 4 grafts per time interval were removed, processed for high resolution light microscopy and the thicknesses of the media and neointima, as well as the area fractions of smooth muscle cells, were analysed morphometrically. All grafts were reendothelialised by 2 wk. Neointimal hyperplasia (a subendothelial layer of smooth muscle cells) developed in all grafts and reached its maximal thickness (40.4 +/- 4.7 microns) at 2 wk. The area fraction of smooth muscle cells in the neointima of the artery grafts did not change significantly at any time from 2 to 16 wk. The media underlying the neointima of the artery grafts remained relatively constant throughout the 16 wk duration of the experiment. Whilst the total wall thickness of the grafts reduced significantly between 2 and 4 wk after insertion, at all times the grafts were thicker than the host artery.

Analysis of Variance↗
PubMed1997

Withdrawing treatment from a critically-ill child.

In this paper the ethical and legal implications of withdrawing treatment from a critically-ill child are examined. Paediatric nurses in intensive care units often rely on intuition for resolving emotive issues such as the withdrawal of treatment from a child. To enhance their contribution in the decision-making process nurses need knowledge of ethical theories and principles, and the law. Advances in technology, together with political and economic factors, could well result in more attention being placed on ethical and legal issues in paediatric intensive care units. For the purpose of this paper pseudonyms have been used.

Beneficence↗
PubMed1997

Neo-intimal hyperplasia in vascular grafts and its implications for autologous arterial grafting.

With the advent of modern microsurgical procedures and an improved understanding of the cellular dynamics of vascular graft adaptation, arterial grafts are being used more frequently in surgical practice. In this article the structure and development of neointimal hyperplasia in vascular grafts, both venous and arterial, are reviewed briefly. The underlying biology of venous graft adaptation is now well understood. However, in addition to venous grafts, many different arterial conduits are now being used; these include the radial artery, internal mammary (thoracic) and gastroepiploic arteries. The different clinical outcomes of these arterial grafts and the underlying cell biology of their adaptation to the grafted environment are also reviewed.

Arteries↗
PubMed1996

Preparation of school-age children and their parents for intensive care following cardiac surgery.

The preparation of school-age children and their parents for intensive care following cardiac surgery for congenital heart disease merits discussion. The prospect of cardiac surgery and the ensuing admission to an intensive care unit can pose many real and imagined threats and can be extremely stressful for both children and their parents. The focus in this paper is on methods of preparation, aspects of hospitalisation and intensive care that children and their parents find stressful and how preparation can help to alleviate this stress.

Adult↗
PubMed1995

Acceleration of experimental lapine osteoarthritis by calcium pyrophosphate microcrystalline synovitis.

OBJECTIVE: To investigate the effects of chronic calcium pyrophosphate dihydrate (CPPD) synovitis on the development of osteoarthritic (OA) lesions in an animal model. METHODS: OA was induced in the right knees of 30 male New Zealand white rabbits by partial lateral meniscectomy and section of the fibular collateral and sesamoid ligaments (PLM/LS), followed by 8 weekly intraarticular (IA) injections of 1 mg (low-dose) or 10 mg (high-dose) of CPPD crystals in 3 sets of experiments (10 rabbits each). The contralateral left knees served as controls: experiment 1 PLM/LS alone, experiment 2 8 weekly IA injections of CPPD crystals alone, and experiment 3 sham surgery plus 8 weekly IA injections of CPPD crystals. RESULTS: At 8 weeks, repeated IA injections of low-dose and high-dose CPPD crystals into meniscectomized right knees resulted in more severe OA than in meniscectomized but noninjected left knees (experiment 1) (P = 0.003 and P = 0.001, respectively). One-fourth of the meniscectomized knees (11 of 40), both CPPD-injected and noninjected, showed embedded synovial cartilage shards. CONCLUSION: The data demonstrate a worsening effect of chronic CPPD crystal-induced synovitis on experimental OA produced in the rabbit knees by PLM/LS, and support a possible role for CPPD microcrystalline inflammation in the progression of OA lesions in clinical CPPD crystal deposition disease.

Animals↗
PubMed1993

Holistic care of a critically ill child.

This paper describes two different models of nursing that have been used to care for children in hospital, emphasising how such care is planned and delivered. Although it began as an academic exercise, it is hoped that in using the ideas contained in it nurses involved in the care of critically ill children could begin to look at alternative methods of planning and delivering holistic care. In particular it is suggested that more traditional methods of care planning may not always provide enough reference to the important psychosocial and developmental needs of each child in an intensive care unit (ICU).

Child↗
PubMed1992

Sleep disordered breathing and cognitive function in a retirement village population.

Sleep disordered breathing (SDB) may be associated with cognitive dysfunction in non-demented elderly people. A random sample of 96 retirement village residents were given both neuropsychological assessment and overnight sleep monitoring with a portable microprocessor based system (Vitalog PMS-8). Respiratory disturbance index (RDI) was calculated as the number of apnoeas and hypopnoeas per hour of sleep. RDI was not associated with 'memory', 'verbal', and 'motor' factors identified from the analysis of cognitive tests, but was associated with the 'cerebral efficiency' factor (R2 = 0.21, p less than 0.0001). Seventy-three subjects had repeat neuropsychological tests, median time to follow-up being 17 months. Baseline RDI did not predict changes in scores on the two factors identified from the second analysis. We conclude that mild to moderate disturbance of breathing during sleep is not associated with cognitive dysfunction in non-demented subjects.

Activities of Daily Living↗
PubMed1991

Tests of EEG localization accuracy using implanted sources in the human brain.

The accuracy with which electrical sources in the brain can be localized by using electroencephalograms measured on the scalp is not well known. In this study, tests of localization accuracy were performed by using implanted dipolar sources in the human brain. These dipoles are created by passing a weak (subthreshold) current through intracerebral electrodes implanted in the brains of epileptic patients for seizure monitoring. The locations of these dipoles are accurately known from roentgenographs. First, 16 electroencephalograms produced by these dipoles were recorded, then inverse solutions were calculated for the apparent sources of these electroencephalograms. Finally, the locations of the apparent sources were compared with the known locations of the implanted dipoles to determine localization error. The average localization error for a total of 28 dipoles in 3 subjects was 1.1 cm. These results indicate that good localization accuracy for focal sources in the brain can be provided by scalp electroencephalograms.

Brain↗
PubMed1991

Magnetocardiographic localisation and modelling.

In our magnetocardiographic (MCG) localisation studies, two modelling approaches have been applied: (a) modelling the sources with dipole and quadrupole moments in a general multipole expansion and using a homogeneous, semi-infinite volume conductor, and (b) using a single current dipole source in a homogeneous, realistically shaped torso. Both approaches have been successfully applied in localising the premature ventricular excitation site in patients suffering from the Wolff-Parkinson-White syndrome. In addition, we have participated in developing a model of propagation of electrical activation in the ventricles. Anisotropic conductivity properties and spiral arrangement of myocardial fibres are included in the model.

Heart Function Tests↗
PubMed1991

The effect of the pneumatic antishock garment (PASG) on hemodynamics, hemorrhage, and survival in penetrating thoracic aortic injury.

To determine if the increased blood pressure associated with application of a pneumatic antishock garment (PASG) affects outcome in thoracic hemorrhage, we assessed hemodynamics, blood loss, and survival in three groups of eight anaesthetized piglets with a 2.5-mm laceration of the descending thoracic aorta. Baseline measurements were made before aortic hemorrhage. During one hour of aortic hemorrhage or until death of the animal, the PASG was not inflated in Group I while the PASG in the other two groups was inflated to maintain carotid artery pressure at 15 torr below baseline (Group II) and at baseline (Group III), respectively. Survival was 100% in Group I, 50% in Group II, and 0% in Group III. Hemorrhage at 22.5 +/- 4.0 mL/min stopped after 18-24 minutes in Group I; the survivors in Group II bled at a rate of 32.5 +/- 3.0 mL/min compared with 43.6 +/- 4.0 mL/min over 26-35 minutes in the Group II nonsurvivors. Group III pigs bled at 107.5 +/- 8.0 mL/min over the 10-18 minutes of survival. The intended blood pressure could not be maintained beyond 30 minutes. Bleeding stopped in Group I when the blood pressure fell to 58.2 +/- 4.5 torr from a baseline of 119.0 +/- 10.0 torr. The blood pressure fell to 48.0 +/- 5.0 torr in the four Group-II survivors. After a transient maintenance of baseline blood pressure in Group III, a precipitous drop in blood pressure with death in 10-18 minutes occurred in all these animals. In this porcine model of thoracic aortic injury, PASG inflation increases hemorrhage and mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Describing head shape with surface harmonic expansions.

Surface harmonic expansions are used to represent boundaries between regions of different conductivity in the human head. This facilitates calculation of the electric potential and magnetic field generated by neural current sources using discretized integral equations.

Computer Simulation↗
PubMed1990

MEG versus EEG localization test using implanted sources in the human brain.

It is believed that the magnetoencephalogram (MEG) localizes an electrical source in the brain to within several millimeters and is therefore more accurate than electroencephalogram (EEG) localization, reported as 20 mm. To test this belief, the localization accuracy of the MEG and EEG were directly compared. The signal source was a dipole at a known location in the brain; this was made by passing a weak current pulse simulating a neural signal through depth electrodes already implanted in patients for seizure monitoring. First, MEGs and EEGs from this dipole were measured at 16 places on the head. Then, computations were performed on the MEG and EEG data separately to determine the apparent MEG and EEG source locations. Finally, these were compared with the actual source location to determine the MEG and EEG localization errors. Measurements were made of four dipoles in each of three patients. After MEGs with weak signals were discounted, the MEG average error of localization was found to be 8 mm, which was worse than expected. The average EEG error was 10 mm, which was better than expected. These results suggest that the MEG offers no significant advantage over the EEG in localizing a focal source. However, this does not diminish other uses of the MEG.

Adult↗
PubMed1990

Recognition of depression in the elderly: a comparison of general practitioner opinions and the Geriatric Depression Scale.

As part of a larger study, 133 subjects aged 70 years and over were screened for depression using the Geriatric Depression Scale, a 30-item questionnaire, as the screening instrument. Cognitive status was assessed using the Mini Mental State Examination. The subject's own general practitioner was asked his/her opinion as to whether the subject was depressed. Poor agreement was found between depression as measured by the Geriatric Depression Scale and the general practitioner's assessment. Possible reasons for this include the difficulty of finding a satisfactory operational definition of depression for use by general practitioners, the problems of identifying depression in the elderly, the arbitrary definition provided by the scale and the confounding of depression, as measured by the scale, with cognitive status.

Aged↗
PubMed1990

Use of medications by the elderly.

Our study confirms that multiple medications are frequently taken by relatively healthy residents of a retirement village, the more so when they are less socially active during the day, and when they are living in hostel accommodation. There were few drug combinations that caused a potential interaction, suggesting that safe use of medication by the elderly should be an achievable goal.

Aged↗
PubMed1988

Relationship between the nerve growth factor-regulated clone 73 gene product and the 58-kilodalton neuronal intermediate filament protein (peripherin).

Exposure of PC12 cells to nerve growth factor (NGF) has been shown to induce an mRNA that encodes a novel neuronal intermediate filament protein. The findings presented here concern the identity of this filament protein. The major protein in NGF-treated PC12 cell cytoskeletons derived by extraction with 1% Triton X-100 is of apparent Mr = 58,000, focuses by isoelectric focusing as several closely spaced spots of pl 5.6-5.8, and is elevated relative to non-NGF-treated cells. Partial microsequencing of this material reveals 2 internal sequences that are identical to a 14-residue sequence encoded by the NGF-regulated clone 73 mRNA, but not to sequences of other known proteins. An antiserum raised against a 19-residue synthetic peptide corresponding to the deduced C-terminus of the protein encoded by the NGF-regulated clone 73 mRNA specifically recognizes the 58,000-Mr protein. Properties of the 58-kilodalton protein strongly suggest that it corresponds to an intermediate filament protein (peripherin) previously identified in PC12 cells and in peripheral and certain CNS neurons. Identification of the intermediate filament protein encoded by an NGF-induced message should facilitate studies of its regulation and function.

Adrenal Gland Neoplasms↗
PubMed1987

The effect of torso geometry on magnetocardiographic isofield maps.

Using a computer model of a realistically shaped human torso with lungs and intraventricular blood masses, we have assessed how torso geometry and composition affect the extracorporal magnetic field produced by a current dipole in the centre of the ventricular mass. The magnetic induction vector B arising from the dipole has been calculated at points of a precordial measuring grid and the influence of boundaries has been assessed qualitatively, by comparing contour maps of the B component normal to the torso's frontal plane. We found that the maps reflected relatively faithfully the underlying dipolar source for the homogeneous torso and even for the torso with lungs. However, the intraventricular blood masses caused a noticeable rotation of the maps' extrema. Both lungs and blood masses tended to swing the distribution towards the distribution that would have been caused by a dipole oriented along the anatomical axis of the heart.

Computer Simulation↗