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Biomedical subjects

J D Buchanan

Publications and source records attributed to J D Buchanan.

At least 19 recordsLinked to original sources
PubMed1990

Evaluation of N-acetylcysteine and methylprednisolone as therapies for oxygen and acrolein-induced lung damage.

Reactive oxidizing species are implicated in the etiology of a range of inhalational pulmonary injuries. Consequently, various free radical scavengers have been tested as potential prophylactic agents. The sulfydryl compound, N-acetylcysteine (NAC) is the only such compound clinically available for use in realistic dosages, and it is well established as an effective antidote for the hepatic and renal toxicity of paracetamol. Another approach in pulmonary injury prophylaxis is methylprednisolone therapy. We evaluated NAC and methylprednisolone in two rat models of inhalational injury: 40-hr exposure to greater than 97% oxygen at 1.1 bar and 15-min exposure to acrolein vapor (210 ppm). For oxygen toxicity, NAC (80 mg) or methylprednisolone (10 mg) were given IP every 2 or 6 hr, respectively. For acrolein, single doses of NAC (1 g/kg) and methylprednisolone (30 mg/kg) were given intravenously 15 min before exposure. In sham-exposed control animals, neither treatment favorably effected mortality, lung wet/dry weight ratios, or pulmonary histology. The increases in lung wet/dry weight ratios, seen with both oxygen and acrolein toxicity were reduced with both treatments. However, with oxygen, NAC therapy was associated with considerably increased mortality and histological changes. Furthermore, IP NAC administration resulted in large volumes of ascitic fluid. With acrolein, IV, NAC had no significant effect on mortality or pulmonary histological damage. Methylprednisolone had no beneficial effects on either the mortality or histological damage observed in either toxicity model. We caution against the ad hoc use of NAC in the management of inhalational pulmonary injury.

Acrolein↗
PubMed1989

Spinal cord degeneration associated with type II decompression sickness: case report.

The medical history, clinical and neuropathological findings at necropsy are described in a 50-year-old male amateur diver who suffered from Type II decompression sickness, a spinal 'bend'. He survived as a paraplegic for 4 years. In the spinal cord upward Wallerian degeneration in the posterior columns and downward degeneration in the corticospinal tracts was explained by multiple small and medium sized infarcts affecting the centripetal blood supply to the cord. There was preservation of a rim of subpial fibres on the surface of the posterior and lateral columns. The grey matter and nearby white matter (supplied by the centrifugal arterial supply) was unaffected.

Decompression Sickness↗
PubMed1989

Fine needle aspiration cytology as part of a three stage diagnostic approach to breast lumps in a District general hospital.

Recent studies from specialist breast centres have suggested that fine needle aspiration cytology in conjunction with mammography and clinical examination can provide a prompt and accurate diagnosis of breast lumps. These three methods of diagnosis have been assessed in the context of a district general hospital by analysing 104 consecutive breast lesions with known histology, of which 75 were benign and 29 malignant. The results are presented in terms of the sensitivity and specificity for each method. Fine needle aspiration cytology had a sensitivity for malignancy of 88% (n = 26) and a specificity of 97% (n = 58). Similarly, sensitivity for mammography was 95% (n = 20) and clinical examination 90% (n = 29). Respective specificities were 96% (n = 45) and 83% (n = 75). In none of the 29 patients with breast cancer were all three modalities negative. It is concluded that without specialist breast clinicians and cytologists, a combination of fine needle aspiration cytology, clinical examination and mammography can still provide a degree of preoperative diagnostic accuracy comparable with specialist centres, allowing prompt counselling with all the subsequent benefits.

Adult↗
PubMed1986

The thermodynamics of calcium binding to thermolysin.

Calcium binding isotherms were determined for thermolysin in the range pH 5.6-10.5, and from 5 to 45 degrees C. An extensive statistical analysis of the binding data suggests that at least two of the four binding sites bind Ca2+ with complete positive cooperativity and independently of the other two. Nonlinear regression analysis of the binding data was used to calculate cooperative (K1) and independent (K2) binding constants for the four calcium sites. Thermodynamic parameters obtained from a van't Hoff analysis indicate that calcium binding to both cooperative and independent sites is an entropy-driven process. At pH 7.0, delta H1 = 90.4 kJ/mol; delta H2 = 97.5 kJ/mol; delta S1 = 456 J K-1 mol-1; delta S2 = 262 J K-1 mol-1. These results are compared to those obtained for other calcium-binding proteins. An analysis of the pH dependence of the calcium binding constants indicates that the binding of four protons at the cooperative site and one to two protons at the independent sites, modulates the calcium affinity. This confirms an earlier structural assignment of the double-site as the locus of the two cooperatively binding Ca2+. Calcium binding to thermolysin is enhanced in the presence of an active site directed inhibitor, suggesting that there may be positive cooperativity between substrate and calcium binding.

Calcium↗
PubMed1986

Left atrial rupture in osteogenesis imperfecta.

A 60 year old man with features of osteogenesis imperfecta presented in biventricular failure with evidence of mitral regurgitation. He responded to conventional treatment but later collapsed and died at home. Necropsy showed a haemopericardium caused by a tear in the left atrium. There was also rupture of the mitral chordae tendineae.

Echocardiography↗
PubMed1983

Thermodynamic parameters associated with the binding of adrenalin and norephedrine to heparin.

Pulse radiolysis has been used to determine the thermodynamic parameters (delta G', delta H' and delta S') governing the binding of adrenalin and norephedrine to heparin. These complexes were completely dissociated by increasing concentrations of inorganic salts. Lower concentrations of divalent cations (e.g. Ca2+) than of monovalent cations (e.g. Na+) were necessary to effect dissociation of the complex. For each interaction an increase in drug binding occurred as the temperature was increased from ambient. However, a transition temperature was observed (48 degrees C) above which the drug was progressively released as the temperature was increased. These observations are discussed in terms of conformational changes induced in the polymer below and above its melting temperature.

Epinephrine↗
PubMed1983

A pulse radiolysis study of the interaction of ephedrine with carrageenans.

Pulse radiolysis has been used to determine the thermodynamic parameters (delta G', delta H' and delta S') governing the binding of ephedrine to three carrageenans. For each interaction an increase in drug binding occurred as the temperature was increased from ambient. However, a transition temperature was observed (49 degrees C) above which the drug was progressively released as the temperature was increased. These observations are discussed in terms of conformational changes induced in the polymers below and above their melting temperatures.

Carrageenan↗
PubMed1982

Angiodysplasia of the colon. Experience of 26 cases.

26 patients referred for colonoscopy with unexplained anaemia or blood loss per rectum were found to have angiodysplasia located in the caecum and/or ascending colon. All patients had undergone previous extensive investigation. After endoscopic photography of the lesions coagulation and biopsy were carried out in 23 patients. In 3 patients the extent of the lesion demanded surgical management, and right hemicolectomy was carried out without prior coagulation biopsy, 3 other patients underwent surgery at a later date-2 for further bleeding and 1 for complications of coagulation biopsy. Colonoscopy with photography and coagulation biopsy proved a safe and effective approach to the management of angiodysplasia in the majority of patients. It provided successful treatment and confirmation of the diagnosis without resort to major surgery, which in elderly patients is associated with high morbidity and mortality.

Aged↗
PubMed1982

Effect of ovulation on the ionic and water content of rabbit oviduct.

The water content, extracellular space, intracellular water, potassium, sodium and chloride content of oviduct and uterus removed from rabbits in estrus and 24 and 72 h following hCG injection have been determined. Following ovulation, there was an increase in water content of the region of the oviduct corresponding to the ampullary -isthmic junction which, at 24 h, is probably due to increased intracellular water. In the ampullary-isthmic junction, ovulation decreases the potassium content and, at 24 h in the isthmic region of the oviduct, chloride is reduced. The water and ionic content of mucosa and smooth muscle cells has been calculated and mucosa cells have greater intracellular water and chloride and sodium content and less potassium and extracellular space than the smooth muscle cells of the oviduct. The significance of the changes in ionic and water content is discussed.

Animals↗
PubMed1982

Primary hyperaldosteronism in pregnancy.

We report a case of primary hyperaldosteronism in a 37-year-old woman presenting early in pregnancy with hypertension and hypokalaemia. Plasma renin concentration was suppressed and unaffected by sodium restriction or upright posture at 16 and 35 weeks gestation, or seven days post-partum. Recumbent plasma aldosterone was elevated, and normal postural response lost both at 35 weeks gestation and seven days post-partum. Vaginal delivery, following induction at 38 weeks, was uncomplicated. Two months postpartum C.T. scan and adrenal venous catheterisation studies indicated a left sided adenoma and left adrenalectomy was performed. Within seven days the patient was normotensive with normal serum potassium and urinary aldosterone on no treatment.

Adenoma↗