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Biomedical subjects

J C Davis

Publications and source records attributed to J C Davis.

At least 73 records · Page 4Linked to original sources
PubMed1988

Postoperative glucose metabolism in patients with gastrointestinal malignancy.

Patients with gastrointestinal malignancy demonstrate impaired postoperative glucose disposal (17.5 +/- 1.4 mumol/kg min vs 28.9 +/- 2.5 mumol/kg min; P less than 0.001) and a reduced insulin response, during steady state hyperglycaemia, when compared with control. Analysis of glucose disposal when compared with insulin concentration suggested insulin resistance as a factor in the causation of impaired glucose disposal. In the control group both glucose disposal and insulin response demonstrated a negative correlation with malnutrition score (as assessed by a 13 factor, three grade scoring system), whereas in the cancer group only the insulin response was related to malnutrition score. However, the insulin response in the cancer group was quantitatively different from control subjects. The possible clinical implications of these findings are discussed.

Adult↗
PubMed1987

Insulin resistance in patients with colorectal cancer.

The euglycaemic glucose clamp technique has been used to assess insulin resistance in patients with colorectal adenocarcinoma. Ten cancer patients were studied and compared with control subjects matched for age, sex and nutritional status. Forty-one euglycaemic clamps were performed at one of five different insulin infusion rates (20, 30, 40, 100 or 200 milliunits min-1 m-2). Glucose disposal was significantly decreased in the cancer group at all insulin infusion rates, whilst attained insulin levels and metabolic clearance rates of insulin were comparable in the control and cancer groups. Analysis of dose-response data allowed assessment of sensitivity (insulin concentration of half maximal glucose disposal) and responsiveness (maximal glucose disposal). Responsiveness was significantly reduced in the cancer group (40.3 versus 71.5 mumol kg-1 min-1; P less than 0.001), whilst sensitivity was similar (93.7 milliunits l-1 in controls versus 90.8 milliunits l-1 in cancer patients), suggesting a postreceptor defect in insulin action in the cancer group.

Adenocarcinoma↗
PubMed1987

Plasma progesterone concentration in women with and without adenocarcinoma of the endometrium.

In the search for the postulated but elusive "estrogenic bias" in patients developing endometrial cancer, several authors have suggested lack of progesterone as the common denominator. In this study 21 patients at the time of diagnosis of Stage I disease are compared to stringently matched healthy control subjects. No significant difference was found in plasma progesterone concentrations between the two groups. These results, in conjunction with other calculated estrogenic indices based on these patients, provide no evidence of lack of progesterone at the onset of clinical disease. However, the effects of long-term progesterone lack related to chronic anovulation are not excluded by these findings.

Adenocarcinoma↗
PubMed1987

Coexistent Mahaim and Kent accessory connections: diagnostic and therapeutic implications.

Six patients with coexistent Mahaim and Kent accessory connections are described. Two had left nodoventricular Mahaim connections, the first reported cases demonstrating these findings. In neither were the left-sided Mahaim connections components of a tachycardia and their presence was incidental. In two of four with nodoventricular connections, associated atrioventricular (AV) node conduction and coexistent posteroseptal accessory pathways were found. One of these had the unusual finding of a right-sided Mahaim connection arising from a "fast" AV node pathway. In only one patient did the tachycardia incorporate the Mahaim connection. In this patient, anterograde conduction during tachycardia occurred over a right nodoventricular connection whereas retrograde conduction occurred through a concealed right free wall Kent connection. Two patients had fasciculoventricular connections that were associated with either septal (one patient) or left free wall (one patient) Kent connections. The latter also had evidence of enhanced AV node conduction. This report is unique in that it describes in detail two patients with left nodoventricular connections (Mahaim) inserting in or near the left posterior fascicle. Combined Kent and Mahaim connections, present in the six patients, appear to occur in approximately 5% of patients with the Wolff-Parkinson-White syndrome. Precise identification of bypass connections critical for reentrant circuits is essential for intelligent application of treatment options.

Adult↗
PubMed1987

Effects of catheter-delivered electrical discharges near the tricuspid anulus in dogs.

The possibility of using electrical discharges to ablate right free wall accessory pathways by delivering a series of catheter shocks near the tricuspid anulus was assessed in a canine model. Before the shock, the amplitudes of the atrial and ventricular electrograms recorded from the distal electrodes were compared (A/V ratio), and the atrial pacing threshold was determined. To assess effects on function and arrhythmogenicity, right heart pressures were measured and programmed ventricular stimulation was performed before the shock and prior to sacrifice 7 to 10 days after the shock. Nine dogs received a total of 24 discharges at varying energies (50 to 400 J). Nonsustained ventricular tachycardia occurred with 13 shocks (62%) and transient atrioventricular block with 9 shocks (43%). There was no worsening in cardiac or valvular function as determined by right heart pressure measurements or right ventriculography. Programmed ventricular stimulation performed before the shocks and repeated before sacrifice failed to induce ventricular arrhythmias. The endocardial lesion produced by the shock was roughly circular and its area correlated with both the magnitude of the shock as well as the atrial pacing threshold. Transmural necrosis always occurred at the anulus when the A/V ratio was between 1.00 and 1.50 and preshock atrial pacing threshold suggested adequate wall contact (less than 1.5 mA). There was mild inflammation of the adventitia of the right coronary artery near two discharge sites (both 200 J) and inflammation of the media near one discharge site (400 J); no intimal involvement was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Successful management of Cushing's disease during pregnancy by transsphenoidal adenectomy.

Pregnancy in patients with Cushing's syndrome is rare. It is associated with a high fetal loss, increased frequency of preterm labour and excessive maternal morbidity. We describe a patient who became pregnant while investigations for hypertension were being done. Cushing's disease was diagnosed and the patient had transsphenoidal pituitary surgery at 22 weeks gestation. To our knowledge this is the first time this operation has been done during pregnancy for this condition. Cushing's disease was controlled, but because of worsening hypertension, she had a caesarean section at 30 weeks gestation. Subsequently her blood pressure fell and her hydrocortisone replacement therapy is being withdrawn. Her daughter is now thriving after initial problems with pneumothoraces.

Adenoma↗
PubMed1987

Catheter ablation of ventricular tachycardia with intracardiac shocks: results in 33 patients.

Catheter electrical ablation of ventricular tachycardia (VT) was attempted in 33 patients who had recurrent unimorphic VT refractory to 3.7 +/- 1.2 (mean +/- SD) antiarrhythmic drugs. Their mean age was 56 +/- 14 years. Twenty-two patients had coronary artery disease, six had other types of heart disease, and five had no structural heart disease. The mean left ventricular ejection fraction was 0.34 +/- 0.17. Thirty patients had only one documented morphologic type of spontaneous VT, whereas three patients had more than one. One to four shocks of 100 to 300 J each were delivered to the endocardial exit site of VT, as identified by endocardial activation mapping and pace-mapping. In each patient endocardial activation at the exit site of VT preceded the onset of the QRS complex (mean activation time -50 +/- 30 msec). Pace-mapping was possible in 26 patients, and in all but two patients the QRS complexes during VT and during pacing at the exit site of VT were very similar in at least 10 of 12 electrocardiographic leads. In 29 patients, shocks were delivered between an endocardial electrode (cathode) and a patch electrode on the chest wall (anode). Seven patients (including three who first received shocks using an external anode) whose VT originated in the septum received transseptal shocks between two electrodes positioned on either side of the septum. The procedure was successful in 15 patients (45%), who had no recurrence of VT either on no antiarrhythmic therapy or on the same regimen that was ineffective before ablation, over a follow-up period of 15.5 +/- 10 months (range 5 to 35). The ablation attempt was unsuccessful in 18 patients (55%). There were no significant differences in clinical and electrophysiologic variables between patients with and without a successful outcome. Seven nonfatal complications occurred in six patients: sustained nonclinical VT immediately after the shock, ventricular fibrillation on days 5 and 6 after ablation, neurologic deficits (n = 2), atrioventricular block (n = 2), and brachial artery thrombosis. In conclusion, catheter electrical ablation of VT has modest efficacy and is relatively safe in a selected group of patients who have predominantly one configuration of unimorphic VT.

Cardiac Catheterization↗
PubMed1987

The use of adjuvant hyperbaric oxygen in treatment of the diabetic foot.

Hypoxia in the relatively ischemic diabetic foot impairs leukocyte bacterial killing and fibroblast-collagen support for capillary angiogenesis. Infection in even the relatively young, "warm-foot" diabetic with microangiopathy, neuropathy, and infection leads to hypoxia due to local high oxygen consumption. The 1100 to 1300 mm Hg arterial PO2 achievable with hyperbaric oxygen results in elevation of wound PO2. Periodic correction of wound hypoxia improves leukocyte bacterial killing and support for capillary angiogenesis. Hyperbaric oxygen is usually futile in the elderly diabetic with significant and generalized large-vessel occlusion.

Aged↗
PubMed1987

Pyoderma gangrenosum: skin grafting after preparation with hyperbaric oxygen.

Four patients with pyoderma gangrenosum were treated with hyperbaric oxygen to prepare the wounds for skin grafting. Each wound responded to a course of daily hyperbaric oxygen with reduction of infection and increased capillary angiogenesis. During follow-up periods of 12 to 30 months, all wounds remained healed. Although the exact etiology of pyoderma gangrenosum is unknown, vasculitis with wound ischemia and infection are prominent components. Inspired oxygen partial pressures of 1100 to 1300 mmHg elevate wound oxygen tension despite relative ischemia. The impaired intracellular bacterial killing of hypoxic leukocytes is corrected during each day's 2-hour bolus of hyperbaric oxygen. Daily wound oxygenation increases collagen production by fibroblasts to support capillary angiogenesis.

Adolescent↗
PubMed1987

Glucose metabolism in patients with gastrointestinal malignancy but without excessive weight loss.

Patients with gastrointestinal malignancy demonstrate impaired glucose disposal during steady state hyperglycaemia, 20.5 +/- 1.4 mumol/kg min when compared with controls 28.2 +/- 2.2 mumol/kg min. This appears to be unrelated to antecedent weight loss, but is related to the presence of metastatic spread (P less than 0.05). Insulin response to hyperglycaemia is normal, but analysis of glucose disposal with time suggests insulin resistance as a factor in the causation of impaired glucose disposal. Free fatty acid levels fail to suppress in cancer patients but their role in the causation of insulin resistance remains unclear.

Adenocarcinoma↗
PubMed1986

The interaction of phosphate with the purple acid phosphatase from beef spleen: evidence that phosphate binding is accompanied by oxidation of the iron chromophore.

Reaction of the reduced (pink) form of the purple acid phosphatase from beef spleen with excess phosphate at pH 5.0, monitored by optical and low temperature EPR spectroscopy and by measurement of enzymatic activity, results in parallel loss of activity and oxidation of the iron chromophore. Colorimetric and radiochemical (32P) experiments indicate the presence of one mole of tightly bound phosphate in the oxidized (purple) form of the enzyme; this phosphate is released upon reduction. Acid hydrolysis of 32P-phosphate-containing enzyme, followed by high voltage paper electrophoresis, gave no evidence for significant amounts of acid-stable phosphoamino acids.

Acid Phosphatase↗
PubMed1986

The relationship between plasma prolactin and testosterone levels in male hypogonadism.

Fifty seven male patients either complaining of poor sexual development, gynecomastia or dwarfism and signs of sexual infantilism were studied. Plasma prolactin (PRL) and testosterone (T) were estimated in all patients while 33 of them were also subjected to full pituitary function tests. Twelve of the latter had an elevated basal plasma cortisol or growth hormone which suggested the patient may have been "stressed"; the results were analyzed both excluding and including these patients. The remaining patients were divided into those with a plasma T less than 8.0 nmol/l (Group A, 25 patients) and those with a plasma T greater than 8.0 nmol/l (Group B, 20 patients). The results were compared with those from 18 normal men (Group C). The mean plasma PRL in group A (108.1 mU/l) was significantly lower than that in group B (181.5 mU/l, p less than 0.005) or group C (255.7 mU/l, p less than 0.001). The difference between groups A and B became much less (p less than 0.01) when results from the "stressed" patients were included but this did not affect the difference with group C. The mean plasma PRL in group B was also significantly lower (p less than 0.05) than that in group C but the significance of the difference disappeared when all the patients were included (p less than 0.2). In the patients there was a significant correlation between plasma and PRL plasma T (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Failure of prophylactic surgery to avert massive pituitary expansion in pregnancy.

Macroprolactinomas have a well-recognized potential for marked expansion during pregnancy. Measures advocated to minimize this risk include prior treatment with dopamine agonists, radiotherapy and pituitary surgery. We describe a patient who underwent transsphenoidal surgery with the removal of an histologically proven prolactin-secreting adenoma with the intention of rendering subsequent pregnancy safe. The patient remained hyperprolactinaemic and received prolonged therapy with metergoline and bromocriptine which suppressed prolactin to normal and she conceived after induction of ovulation with human menopausal gonadotrophin and human chorionic gonadotrophin. At 3 months gestation she developed headaches, vomiting, reduced visual acuity and bitemporal hemianopia caused by massive pituitary expansion. Reintroduction of bromocriptine rapidly abolished features of tumour expansion and after delivery of a full-term normal female infant, repeat CT scan documented tumour shrinkage.

Bromocriptine↗