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Biomedical subjects

D P Jenkins

Publications and source records attributed to D P Jenkins.

At least 19 recordsLinked to original sources
PubMed2003

The SoS trial.

Explore the source record for details and available documents.

Angioplasty, Balloon, Coronary↗
PubMed2001

Delayed presentation of right ventricular bullet embolus.

Venous bullet embolism to the heart is a rare complication of penetrating gunshot trauma. There are little data regarding long-term follow-up of missiles retained in the right ventricle. We report a rare case of right ventricular bullet embolus following a left-sided thoracic gunshot wound. The patient presented with delayed onset of cardiac irritability symptoms 4 years after injury.

Adult↗
PubMed2001

Risk stratification for training in cardiac surgery.

BACKGROUND: There is a potential conflict of interest in providing the best possible outcome for patients undergoing cardiac surgery and good training for junior cardiac surgeons. METHODS: We analysed training with reference to volume of work, risk stratification and outcome for consultant and trainee procedures. The Parsonnet system was used for risk stratification. A retrospective audit was performed for a 6-year period. RESULTS: During the study period, 6037 operations were performed, of which 2166 were carried out by trainees. Direct consultant assistance in a trainee operation varied between 17% and 51% and increased towards the end of the study period. Of the operations performed by trainees, 88% were CABG. The median Parsonnet score for consultant operations was 9 compared with 4 for trainees. Actual mortality was below predicted for all surgeons. Morbidity was also lowest for trainees (10%). CONCLUSIONS: With appropriate case selection, trainees in cardiac surgery can achieve good results. As training changes in the UK, trainees should receive increased supervised exposure to a wider range of procedure to compensate for a lower volume of workload.

Adult↗
PubMed2000

Recurrent arterial embolization from a metastatic germ cell tumor invading the left atrium.

Arterial embolization of a malignant tumor is extremely rare. We report an unusual case of a young adult man who presented with acute lower limb ischemia and a mass in the right lung and left atrium. These clinical manifestations were the result of metastases and embolization from a germ cell tumor and were the first indication of malignancy in this patient. The importance of appropriate investigations in the subsequent treatment is stressed.

Adult↗
PubMed1997

Ischaemic preconditioning reduces troponin T release in patients undergoing coronary artery bypass surgery.

OBJECTIVE: To investigate whether ischaemic preconditioning could reduce myocardial injury, as manifest by troponin T release, in patients undergoing elective coronary artery bypass surgery. DESIGN: Randomised controlled trial. SETTING: Cardiothoracic unit of a tertiary care centre. PATIENTS: Patients with three vessel coronary artery disease and stable angina admitted for first time elective coronary artery bypass surgery were invited to take part in the study; 33 patients were randomised into control or preconditioning groups. INTERVENTION: Patients in the preconditioning group were exposed to two additional three minute periods of myocardial ischaemia at the beginning of the revascularisation operation, before the ischaemic period used for the first coronary artery bypass graft distal anastomosis. MAIN OUTCOME MEASURE: Serum troponin T concentration at 72 hours after cardiopulmonary bypass. RESULTS: The troponin T assays were performed by blinded observers at a different hospital. All patients had undetectable serum troponin T (< 0.1 microgram/l) before cardiopulmonary bypass, and troponin T was raised postoperatively in all patients. At 72 hours, serum troponin T was lower (P = 0.05) in the preconditioned group (median 0.3 microgram/l) than in the control group (median 1.4 micrograms/l). CONCLUSIONS: The direct application of a preconditioning stimulus in clinical practice has been shown, for the first time, to protect patients against irreversible myocyte injury.

Adenosine Triphosphate↗
PubMed1996

Ischaemic preconditioning and cardiac surgery.

OBJECTIVE: This review discusses the phenomenon of ischaemic preconditioning and its potential application to cardiac surgery. The biology of ischaemic preconditioning is explained and the more limited evidence suggesting that the human heart can be preconditioned is discussed. METHODS AND RESULTS: It is now accepted that the heart is capable of short-term rapid adaptation in response to brief ischaemia so that during a subsequent, more severe ischaemic insult myocardial necrosis is delayed-ischaemic preconditioning. The infarct-delaying properties of ischaemic preconditioning have been observed in all species studied. Five minutes of ischaemia is enough to initiate preconditioning and the protective period lasts for 1-2 h. Laboratory experiments have demonstrated that the stimulation of adenosine receptors initiates preconditioning and the intracellular signal transduction mechanisms involve protein kinase C and ATP-dependent potassium channels, although there may be some differences between species. An analysis of studies on myocardial infarction in humans has revealed that some patients reporting angina in the days before infarction have a better outcome and this may be due to the ischaemia causing preconditioning. More direct evidence has come from an investigation of patients undergoing percutaneous transluminal angioplasty in whom the ST-segment changes induced by balloon inflation were more marked during the first inflation than the second. In patients undergoing coronary artery bypass grafting the decline in ATP content during the first 10 min of ischaemia was reduced in patients subjected to a brief preconditioning protocol. CONCLUSIONS: Preconditioning is a powerful and reproducible method of protecting the myocardium from irreversible ischaemic injury. There is now evidence indicating that the human heart can be preconditioned. However, more trials are necessary in patients undergoing cardiac surgery before the role of preconditioning as a means of myocardial protection can be assessed.

Adenosine Triphosphate↗
PubMed1996

Telemedicine: caring for patients across boundaries.

Telemedicine combines computer, video and telecommunications to provide healthcare to patients at distant sites. With the improved camera and transmission technologies of the 1990s, telemedicine can be used in a variety of situations. There are two basic technological systems: live interactive video and still image ("store and forward"). Potential users include patients who live in rural or difficult to reach geographic areas, who are confined (i.e. prison inmates), Telemedicine can allow ambulatory patients to continue living at home rather than moving into costly nursing facilities. Home telemedicine also allows greater responsiveness and higher frequency of visits by home care nurses, potentially reducing future hospital visits and costs. Two home telemedicine models are the personal telemedicine unit and the enhanced personal telemedicine module with pc-based video. Telemedicine technologies developed by the military for use on the battlefield that could be adapted for civilian use include medical simulations, individual monitoring devices and biosensors, portable retinal display monitors, life support for trauma/transport, and diagnostic ultrasound imagery. Ultimately, the benefits of telemedicine will be consistency of care, easy access to specialized consultants, higher responsiveness to patient needs, and lower overall healthcare costs.

Home Care Services↗
PubMed1995

Preconditioning the human myocardium: recent advances and aspirations for the development of a new means of cardioprotection in clinical practice.

Ischemic preconditioning has been shown to be one of the most powerful means of protecting the myocardium from ischemic injury in experimental animal models, although the mechanism is incompletely understood. In this review we discuss the evidence for preconditioning occurring in ischemic syndromes in humans, whether the human myocardium can be preconditioned, and whether preconditioning would have a place as a therapeutic tool in clinical practice. Some studies evaluating patients after acute myocardial infarction have shown a better outcome in patients reporting angina before the onset of the infarction, but this is not a universal finding, and it is difficult to exclude other confounding factors, such as collateral flow, from influencing the results. More controlled prospective studies have evaluated patients undergoing percutaneous transluminal coronary angioplasty and have found less ST-segment change and less reported angina during the second balloon inflation when compared with the first. Again, it is impossible to completely exclude other causes for this effect, but the dependence on mechanisms that are known to be important for preconditioning in animal models does suggest the phenomena are the same. Further experiments using isolated human atrial muscle have shown that human myocardium can be preconditioned and that the mechanisms involved are similar to those elucidated in animal models (adenosine, protein kinase C, and ATP-dependent potassium channels). In clinical medicine preconditioning is most likely to benefit patients when it is used to protect against the ischemia induced by cardiac surgery. In this respect, a study has shown that in patients undergoing coronary artery bypass grafts, the reduction in ATP occurring during the first ischemic period is attenuated in those given an ischemic preconditioning protocol beforehand. Despite these advances, it is likely that the full potential of preconditioning in clinical practice will not be realized until the whole mechanism of protection is understood and a safe pharmacological "preconditioning" agent becomes available.

Angina Pectoris↗
PubMed1995

Ischaemic preconditioning in a model of global ischaemia: infarct size limitation, but no reduction of stunning.

It is well known that ischaemic preconditioning delays infarct size during regional ischaemic insults. However, the extent of this protective effect against different ischaemia periods has not been established, and any reduction in stunning has been difficult to demonstrate with regional models. In this study we have investigated ischaemic preconditioning in a buffer-perfused isolated rabbit heart model with a global ischaemic insult, and measured both infarct volume and functional recovery. Experiments were performed with three ischaemia time periods of 15, 20 and 30 min at 37 degrees C. Infarct volume (expressed as a percentage of left ventricular volume) was measured by tetrazolium staining after 2 hours reperfusion, and left ventricular developed pressure with an intraventricular balloon. Hearts preconditioned with 5 min ischaemia and 10 min reperfusion were compared with a control group. In this model, preconditioning resulted in a 57% reduction in infarct volume compared with control hearts (P = 0.02) subjected to 20 min of global ischaemia, but the degree of this infarct delaying effect was dependent on the ischaemia time and was only 37% (P = 0.02) and 11% (N.S.) with a 30 min and 15 min ischaemic challenge respectively. Recovery of post-ischaemic left ventricular developed pressure as a percentage of the pre-ischaemic value correlated very well with infarct volume in control r = -0.82 (P < 0.001) and preconditioned r = -0.78 (P < 0.001) groups, and the slope of the regression lines was similar for both groups. These results demonstrate that the degree of protection produced by preconditioning is not uniform but varies with the length of the ishaemic insult. By measuring both infarct volume and functional recovery we have been able to confirm that any post-ischaemic improvement in global left ventricular function produced by preconditioning is secondary to reduced infarction, and hence that preconditioning does not attenuate stunning.

Animals↗
PubMed1994

Audit of upper limb fracture management in an accident and emergency department.

The objective of this study was to audit the initial management of patients with upper limb fractures, and to determine whether the accident and emergency (A&E) management of fractures is improved by using guidelines for treatment and referral. This was achieved by comparing the standard of treatment, as determined by fracture clinic doctors, before and after the introduction of fracture treatment guidelines in the A&E department of a London teaching hospital. A total of 326 patients seen in the department and referred to the fracture clinic over two 2-month periods were included in the audit. The first audit revealed some error in 69/215 (32.1%) referrals and 51/215 (23.7%) of these were potentially liable to increased morbidity. After introducing the guidelines the total errors fell to 14/111 (12.6%) patients referred, of which only eight patients (7.2%) were at risk of increased morbidity. This represents an overall improvement of 19.5% [95% confidence interval (CI) 12.3 to 29.7%] and a 16.5% (95% CI 9.1 to 23.9%) reduction in the potentially more significant errors. Hence, the use of audit and implementation of simple guidelines for fracture management in an A&E department improves the standard of treatment.

Arm Injuries↗
PubMed1985

A plane layered model to estimate in situ ultrasound exposures.

Determination of in situ ultrasound exposures in experimental animals and patients is necessary to assess any potential hazard of ultrasound implied by reported biological effects in animals. A layered model was used to calculate total attenuation of ultrasound pulses as they passed through tissue layers to an organ site, thus enabling calculation of in situ intensities from free-field transducer emissions. The model assumes plane homogeneous layers of tissue of known thickness, attenuation and acoustic impedance. Calculations based on the model, compared with in situ measurements in a human cadaver specimen, were accurate to within approximately +/- 3 dB. We then calculated in situ clinical exposures using published obstetric B-scans. Total attenuation to the fetus averaged approximately 11 dB at 3.5 MHz.

Cadaver↗
PubMed1985

Dansylated estramustine, a fluorescent probe for studies of estramustine uptake and identification of intracellular targets.

Fluorescence-microscopic studies with dansylated estramustine (DnsEM) has permitted investigation of the mechanism of estramustine (EM) uptake in live human prostatic tumor cells (DU 145). DnsEM appeared to enter cells rapidly at the peripheral cell margins. A progressive increase in fluorescence was observed until the perinuclear material and cytoplasm were labeled brightly and the nucleoplasm was labeled faintly. Light microscopy showed that DnsEM is assimilated first in preexisting vesicles and then in numerous newly created vesicles that accumulate in the cytoplasm and around the nucleus. Colony-forming assays showed EM and DnsEM to be equally cytotoxic to cultured DU 145 cells. Cellular uptake and subsequent manifestation of cytotoxicity are presumably dependent upon these vesicles. However, after uptake of DnsEM, its diffusion into the cytoplasm was observed.

Animals↗
PubMed1978

Estrogen and tracheal secretion: the effect of estrogen on the epithelial secretory cells of the rat trachea.

Epithelial secretory cells of the tracheal mucosa obtained from ovariectomized control and ovariectomized estrogen-treated rats were studied morphologically by scanning and transmission electron microscopy and by the combined periodic acid Schiff (PAS) and alcian blue (AB) staining method. A significant decrease was observed in the number of large PAS-reactive secretory cells following estrogen treatment. Concomitantly the number of the Mixed+ cells containing both weakly acid and neutral glycoproteins was found to increase significantly. A majority of the observed secretory cells exhibited either an apical protrusion loaded with secretory granules, extending to a maximum distance of 7.9 micrometer into the tracheal lumen or an apical indentation devoid of mature secretory granules, descending to 5.6 micrometer below the luminal surface. The frequency of cells exhibiting an apical indentation was significantly greater in estrogen-treated animals than in controls. The present findings indicate that estrogen treatment of ovariectomized rats results in: 1) an increase in the synthesis of weakly acid glycoprotein within tracheal secretory cells; 2) a concomitant decrease in the frequency of secretory cells containing neutral glycoprotein; and 3) a general increase in the secretion by the tracheal cells.

Animals↗
PubMed1976

Kinetics of horseradish peroxidase migration through cerebral cortex.

This study provides a semiquantitative description of the migration of the extracellular space marker, horseradish peroxidase (HRP), through the cerebral cortex. Following a continuous subarachnoid infusion of HRP, this marker was fixed rapidly within the cortical extracellular space (ECS) by intravascular aldehyde perfusion fixation. Microscopic measurements of the maximum depth of penetration of HRP into the cortex perpendicular to the pial surface were taken from coronal whole brain sections of rabbits that had been exposed to HRP for varying periods of time. The depth of penetration plotted as a function of time of exposure to HRP produced a 'diffusion profile'. The failure of experimental points to conform to an ideal diffusion curve indicates that simple diffusion alone is an inadequate explanation of the rate of movement of large molecular solutes from the subarachnoid space through the cerebral cortical ECS. The complex pattern of migration velocity of HRP through cortex may be due to alterations of flux of this solute which result from variations in the volume of ECS in different cortical laminae and to the presence of bulk flow of extracellular fluid in the deeper cortical regions.

Animals↗