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Biomedical subjects

J R Dykes

Publications and source records attributed to J R Dykes.

At least 19 recordsLinked to original sources
PubMed1998

Embolization therapy as an alternative to thoracotomy in vascular injuries of the chest wall.

Hemothorax and persistent thoracic bleeding is frequently an indication for thoracotomy after trauma. Unfortunately, the source of the hemorrhage is often not identified. Presently, selective arteriography and transcatheter embolization (SATE) offers a good and safe alternative to localize and control hemorrhage from arterial injuries in selected patients. The records of eight patients who underwent SATE were reviewed. There were six blunt and two penetrating chest injuries. Four patients had significant preexisting medical comorbidities. Three patients with blunt injuries had undergone exploratory thoracotomy, but continued to bleed postoperatively. In three patients, angiography was indicated for associated thoracic and pelvic injuries, and five patients had SATE specifically due to thoracic hemorrhage. In all patients, SATE was effective to diagnose and control the hemorrhage. There were no complications related to the SATE procedure. Two patients died secondary to severe cerebral injuries. Given hemodynamic stability, SATE can be considered in patients who have already had a thoracotomy, have significant associated medical conditions, or those in need of other angiographic studies. Careful technique and a readiness to abandon SATE in unstable patients or when a suitable catheter position cannot be achieved are important technical points.

Adult↗
PubMed1997

Cardiac herniation producing tamponade: the critical role of early diagnosis.

BACKGROUND: Rupture of the pleuropericardium (PP) occurs rarely, with most patients dying of associated injuries before arriving at the hospital. Among patients who initially survive, the diagnosis is often delayed until cardiogenic shock secondary to cardiac herniation is evident. METHODS: The records of 10 patients with PP lacerations and cardiac herniations were reviewed. RESULTS: All but one patient had a normal chest x-ray (CXR) film on admission. After the patients became symptomatic, seven of nine had abnormal findings on CXR film demonstrating herniation of the heart into the left hemithorax. The other two patients underwent surgery without a repeat CXR film. Except for one who was taken directly to the operating room, all patients had been previously stabilized before developing cardiogenic shock, on average 9 hours after admission. Operative therapy was closure of the pericardium for five patients and completion pericardiotomy for the others. All survivors developed significant complications, and four of them died. CONCLUSIONS: The diagnosis of PP rupture should be considered for patients with multiple trauma who develop sudden and unexpected cardiogenic shock after their initial condition has been stabilized. A repeat CXR film is diagnostic in most cases and should be used as the most efficient and expeditious route to making the diagnosis.

Accidents, Traffic↗
PubMed1997

Intraoperative duplex scanning reduces both residual stenosis and postoperative morbidity of carotid endarterectomy.

To evaluate the effect of intraoperative duplex scanning (IDS) on the incidence of perioperative and postoperative strokes as well as residual and recurrent stenosis, we reviewed 141 patients who underwent 152 consecutive carotid endarterectomies (CEAs) between July, 1990 and June, 1995. Follow-up of 129 cases, with a mean follow-up of two years, revealed no perioperative deaths and three strokes for a combined perioperative stroke-death rate of 2.3 per cent. In 50% (64 of 129) of the CEAs, intraoperative duplex scans were obtained based on the attending surgeon's preference. We noted that the incidence of residual stenosis (>50% stenosis on the first duplex after CEA) was significantly lower in those undergoing IDS (3/64) versus those without IDS (13/65) (P < 0.05; risk ratio 0.31; 95% confidence interval 0.11, 0.91). IDS resulted in a modification of the internal carotid reconstruction in 9 per cent (6 of 64) of the cases with no resulting postoperative strokes or residual/recurrent stenosis. There was no significant difference in the frequency of recurrent stenosis (>50% stenosis after a normal duplex) in the two groups (3 of 64 with vs 2 of 65 without). Of patients not undergoing intraoperative scanning, four underwent redo CEA for symptomatic residual stenosis due to a retained intimal flap in the internal carotid artery. There were three strokes observed within 30 days of the initial CEA, all of which occurred in patients who did not undergo IDS at their initial operation. We conclude that IDS can identify technical defects following internal carotid reconstruction, thereby reducing the incidence of both residual stenosis and postoperative morbidity in patients undergoing CEA.

Carotid Stenosis↗
PubMed1990

A neutrophil GTP-binding protein that regulates cell free NADPH oxidase activation is located in the cytosolic fraction.

The dormant O2(-)-generating oxidase in plasma membranes from unstimulated neutrophils becomes activated in the presence of arachidonate and a multicomponent cytosolic fraction. This process is stimulated by nonhydrolyzable GTP analogues and may involve a pertussis toxin insensitive GTP-binding protein. Our studies were designed to characterize the putative GTP-binding protein, localizing it to either membrane or cytosolic fraction in this system. Exposure of the isolated membrane fraction to guanosine-5'-(3-O-thio)triphosphate (GTP gamma S), with or without arachidonate, had no effect on subsequent NADPH oxidase activation by the cytosolic fraction. Preexposure of the cytosolic fraction to GTP gamma S alone did not enhance activation of the membrane oxidase. However, preexposure of the cytosol to GTP gamma S then arachidonate caused a four-fold enhancement of its ability to activate the membrane oxidase. This enhancement was evident after removal of unbound GTP gamma S and arachidonate, and was not augmented by additional GTP gamma S during membrane activation. A reconstitution assay was developed for cytosolic component(s) responsible for the GTP gamma S effect. Cytosol preincubated with GTP gamma 35S then arachidonate was fractionated by anion exchange chromatography. A single peak of protein-bound GTP gamma 35S was recovered that had reconstitutive activity. Cytosol preincubated with GTP gamma 35S alone was similarly fractionated and the same peak of protein-bound GTP gamma 35S was observed. However, this peak had no reconstitutive activity. We conclude that the GTP-binding protein regulating this cellfree system is located in the cytosolic fraction. The GTP gamma S-liganded form of this protein may be activated or stabilized by arachidonate.

Arachidonic Acid↗
PubMed1981

Perceptual encoding and decision strategies for integral dimensions.

These three experiments employed rectangles in stimulus identification tasks. Consistent with the stimulus set used by Weintraub, the rectangles were generated by modifying a square. Across experiments, the number of stimulus/response alternatives was varied (two-, three-, and four-choice tasks). In the two-choice task, redundancy gain for the positively correlated set was just as large as for the negatively correlated set. In contrast, reaction time ws faster for the negatively correlated set than for the positively correlated set in the three-choice task (after extended practice) and in the four-choice task. Considered in the context of previous research, the data support two conclusions. First, the initial perceptual processing of rectangles is accomplished by separate dimensional analyzers operating in parallel. Second, observers adopt a different decision strategy for the negatively correlated set than for the positively correlated and the single dimension sets when the number of stimulus/response alternatives is increased.

Decision Making↗
PubMed1979

A demonstration of selection of analyzers for integral dimensions.

Three experiments investigated the integrality of height and width of rectangles and the ability of observers to selectively attend to only one dimension. In Experiment 1, redundancy gain and orthogonal interference were demonstrated in a same/different task. Orthogonal interference was due to the output of the "irrelevant" analyzer interfering with the output of the "relevant" analyzer. These results indicated that height and width are integral, but they can be most parsimoniously explained by assuming that rectangles are initially processed by separate dimensional analyzers. Experiment I demonstrated that with sufficient practice (160 trials), observers are able to selectively attend to the more frequently relevant dimension. Performance for the stressed dimension increased, whereas performance for the unstressed dimension declined. Experiment 3 also demonstrated that with sufficient practice (192 trials), observers are able to selectively attend to the relevant dimension and ignore the irrelevant dimension. Orthogonal interference disappeared. The results are discussed in terms of the ability of observers to modify the perceptual process.

Attention↗
PubMed1975

Effects of truncal, selective, and highly selective vagotomy on glucose tolerance and insulin secretion in patients with duodenal ulcer. Part I-Effect of vagotomy on response to oral glucose.

An oral glucose tolerance test was performed in patients who had undergone truncal vagotomy and pyloroplasty, bilateral selective vagotomy and pyloroplasty, or highly selective vagotomy without a drainage procedure at least six months earlier. The results were compared with those from patients with chronic duodenal ulcer before operation. In all three groups of patients after vagotomy more rapid rates of rise of blood glucose and higher peak concentrations were observed than in patients who were tested before operation. These differences were statistically significant only in patients who had undergone truncal or selective vagotomy with pyloroplasty and were probably due to more rapid rates of gastric emptying after these operations. Plasma insulin concentrations were lower after truncal vagotomy than after selective or highly selective vagotomy, the difference between truncal vagotomy and highly selective vagotomy being statistically significant. Truncal vagotomy resulted in a diminished insulin response to oral glucose, which could have been due to vagal denervation of the pancreas or, more probably, impaired release of small-bowel hormones which normally augment the pancreatic insulin response.

Adult↗
PubMed1975

Effects of truncal, selective, and highly selective vagotomy on glucose tolerance and insulin secretion in patients with duodenal ulcer. Part II-Comparison of response to oral and intravenous glucose.

Paired oral and intravenous glucose tolerance tests were carried out in patients who had undergone truncal vagotomy and pyloroplasty, selective vagotomy and pyloroplasty, or highly selective vagotomy at least six months earlier. Intravenous glucose tolerance was similar in all three groups. Oral glucose elicited significantly higher concentrations of plasma insulin in patients who had undergone selective and highly selective vagotomy than in those treated by truncal vagotomy. When the same amount of glucose was given intravenously, however, plasma insulin concentrations were similar in all three groups of patients. The insulin secreted in response to intravenous glucose expressed as a percentage of that secreted in response to oral glucose was 112% for truncal vagotomy, 51% for selective vagotomy, and 52% for highly selective vagotomy. Truncal vagotomy thus led to a diminished insulin response to oral glucose, which was probably due to impaired release of small-bowel hormones.

Administration, Oral↗
PubMed1972

Glucose tolerance and insulin secretion in patients with chronic duodenal ulcer.

An oral glucose tolerance test has been used to compare carbohydrate metabolism in patients suffering from chronic duodenal ulceration with that in a matched group of normal subjects. A significantly greater rise in blood glucose concentration was observed in the duodenal ulcer group, and this was associated with a significantly greater output of insulin. The reason for these findings may be an abnormal secretion of one or more of the small-bowel hormones.

Adult↗
PubMed1970

Autonomic control of insulin secretion and the treatment of heart failure.

To investigate the role of the autonomic nervous system in controlling insulin secretion 13 normal subjects and 5 patients with heart failure underwent insulin secretion tests. Alpha-adrenergic stimulation and beta-receptor blockade significantly depressed the secretion of insulin in response to intravenous tolbutamide in normal subjects, while both alpha-blockade and beta-stimulation significantly increased the insulin secretion response in both normal subjects and patients in heart failure. Parasympathetic stimulation and blockade had no significant effect on the insulin secretion response. These findings suggest that drugs that block the alpha-adrenergic receptors or stimulate the beta-adrenergic receptors by their ability to counteract the insulin suppression resulting from increased sympathetic nervous activity may play a vital metabolic part in the deranged metabolism of the failing heart in addition to their direct haemodynamic benefits.

Adrenergic alpha-Agonists↗