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Biomedical subjects

B Buxton

Publications and source records attributed to B Buxton.

At least 37 records · Page 2Linked to original sources
PubMed1989

Atrial fibrillation after coronary artery bypass grafting. Is it a disorder of the elderly?

A total of 1666 patients undergoing isolated coronary artery bypass were studied for the occurrence of postoperative atrial fibrillation. Possible associations of this arrhythmia with various preoperative, intraoperative, and postoperative factors were studied by univariate (chi 2 and t tests) and multivariate (logistic regression) analyses. The overall incidence of postoperative atrial fibrillation was 28.4%, with the major occurrence 2 days after the operation. Both univariate and multivariate studies indicated the patient's age to be the dominant factor promoting postoperative atrial fibrillation, with an increasing prevalence in older patients (p = 0.0001). Multivariate analysis showed that postoperative beta-blocker therapy conveyed considerable protection against postoperative atrial fibrillation (p = 0.001) but was less effective in the older patients. Men were more prone to this arrhythmia (p = 0.02). Although these associations appeared significant, the logistic model proved to be a poor predictor of postoperative atrial fibrillation, which suggests that other factors not studied, or mere chance, may also be responsible.

Adrenergic beta-Antagonists↗
PubMed1987

Primary structure and differential expression of beta-amylase in normal and mutant barleys.

The primary structure of barley endosperm beta-amylase, an enzyme which catalyses the liberation of maltose from 1,4-alpha-D-glucans, has been deduced from the nucleotide sequence of a cloned full-length cDNA. The mRNA is 1754 nucleotides long [excluding the poly(A) tail] and codes for a polypeptide of 535 amino acids with a relative molecular mass of 59,663. The deduced amino acid sequence was compared with the sequences of ten peptides obtained from the purified enzyme and unambiguous identification was obtained. The N-terminal region of the deduced sequence was identical to a 12-residue cyanogen-bromide-peptide sequence, indicating that beta-amylase is synthesized as the mature protein. A graphic matrix homology plot shows four glycine-rich repeats, each of 11 residues, preceding the C-terminus. Southern blotting of genomic DNA demonstrates that beta-amylase is encoded by a small gene family, while cDNA sequence analysis indicates the presence of at least two types of mRNA in the endosperm. Dot and northern blot analysis show that Hiproly barley contains greatly increased levels of beta-amylase mRNA compared to the normal cultivar Sundance, whereas Risø mutant 1508 contains only trace amounts. These results correlate well with the deposition of beta-amylase during endosperm development in these lines. Low but similar amounts of beta-amylase mRNAs sequences were detected in leaves and shoots from normal and mutant barleys, demonstrating that the mutant lys3a (1508) and lysl (Hiproly) genes do not affect the expression of beta-amylase in these tissues.

Amino Acid Sequence↗
PubMed1987

Nucleotide sequence of barley chymotrypsin inhibitor-2 (CI-2) and its expression in normal and high-lysine barley.

cDNA clones for chymotrypsin inhibitor-2 (CI-2) have been isolated from an endosperm-specific library of barley using a synthetic oligonucleotide probe. The nucleotide sequences of several of the cDNAs predict an open reading frame (beginning with an ATG codon) which encodes a protein of 84 residues (Mr 9380). In the longest clone another ATG codon is present, a further 69 nucleotides upstream. The nucleotide sequence between these two ATG codons predicts an amino acid sequence with the characteristics of a signal peptide, as found in other cloned plant protease inhibitors. However, it contains an in-frame TAA stop codon, which is also present in all of the shorter cDNAs which extend into this region. From in vitro translation experiments, using mRNAs synthesized from cDNAs, we conclude that, in vitro, translation of all or the vast majority of CI-2 mRNAs begins at the second ATG codon, 31 nucleotides downstream from the ochre stop codon. Southern blotting of genomic DNA shows that CI-2 is encoded by a small multigene family, while sequence analysis of the cDNAs shows that at least two sub-families of mRNAs, which are more than 90% homologous, are present in the endosperm. Northern blotting analysis shows that related but different sequences are present in leaf and shoot RNA populations. Further Northern blot hybridizations using RNA from the normal line, Sundance, and the high-lysine barley mutant, Hiproly, show that endosperms of the latter contain greatly increased levels of CI-2 mRNA. This correlates with the increased amount of CI-2 protein deposited in Hiproly, and demonstrates that the differential expression of CI-2 in the two genotypes is controlled at the level of transcription and/or stability of the mRNA. In contrast, the abundance of CI-2 mRNAs in leaves and shoots is not affected.

Amino Acid Sequence↗
PubMed1987

Combined carotid and coronary surgery.

A retrospective review of 40 consecutive patients undergoing combined coronary artery bypass grafting (CABG) and unilateral carotid endarterectomy (CEA) was carried out to determine the stroke rate for the procedure. Patients presenting with severe coronary artery disease judged to be at risk of imminent myocardial infarction, who had signs of cerebral ischaemia (70%) or asymptomatic carotid bruits (30%), were investigated for extracranial carotid vascular disease. Patients with severe stenotic carotid lesions associated with high risk coronary artery disease underwent combined CEA/CABG. Three patients had a previous contralateral CEA. The average age of the patients was 62 years, and there were 31 males and nine females. CEA was completed prior to CABG under the same general anaesthetic. There were 24 CEAs on the left and 16 on the right. Six patients suffered a postoperative cerebral ischaemic event (15.4%): a reversible ischaemic neurological deficit in three (7.7%), a transient ischaemic cerebral event in two (5.1%), and a permanent stroke occurred in one (2.6%). Two deaths occurred and both were cardiac related. Combined CEA/CABG in patients with stenotic lesions of the coronary and extra-cranial carotid vascular systems who are at risk of cerebral or myocardial infarction, can be performed with a permanent stroke rate within the published range for either CEA or CABG alone and with a mortality of 5%.

Aged↗
PubMed1987

Nitrous oxide and cerebrospinal fluid markers of ischaemia following cardiopulmonary bypass.

Twenty patients with good ventricular function undergoing coronary artery bypass surgery were studied to determine whether the pre-bypass use of nitrous oxide resulted in any differences in cerebrospinal fluid markers indicative of cerebral ischaemia. All patients were anaesthetised with diazepam, fentanyl and pancuronium, after which ten patients received 50-60% nitrous oxide in oxygen until commencement of bypass, and the remaining patients 100% oxygen. Because of the known effect of nitrous oxide in expanding gaseous bubbles, any neurological dysfunction of gaseous microembolic origin may be worsened in the presence of nitrous oxide. Patients were lumbar punctured 24 hours after cardiopulmonary bypass and cerebrospinal fluid analysed for the following markers of central nervous system ischaemia: creatine kinase, lactate, total protein, noradrenaline, adrenaline and adenylate kinase. There was a statistically significant difference in cerebrospinal fluid lactate between the two groups. There were no statistically significant differences in the other cerebrospinal fluid markers of ischaemia.

Adenylate Kinase↗
PubMed1986

Cardiac surgery in a private hospital. With special reference to coronary artery surgery.

In a four-year period in a private hospital there were 1396 open heart operations of which 1275 were for isolated coronary artery disease. The various techniques that were used for coronary artery reconstruction were saphenous vein grafts and internal mammary artery grafts, both singly and sequentially, and endarterectomy. The operative mortality for isolated coronary artery surgery was 1.1% and the perioperative infarction rate was 2.1%. When combined with an endarterectomy of the right coronary artery, the mortality was 3% and the infarction rate was 4% (not significant); when combined with endarterectomy of the left anterior descending coronary artery, the mortality was 11.7% (not significant), and the infarction rate was 11.7% (not significant). The operative risk was no higher in patients with poor ventricular function.

Adult↗
PubMed1981

Protamine sulphate hypersensitivity.

Protamine hypersensitivity has been documented by intra-dermal skin testing in three patients who demonstrated sudden cardiovascular collapse and bronchospasm following the use of intravenous protamine sulphate. All patients had been given protamine previously. The effects of the anaphylactic response were terminated quickly by the administration of intravenous adrenaline associated with plasma volume expansion. Intra-dermal skin testing against all anaesthetic agents is recommended so that the specific allergen can be identified. In patients who are shown to be allergic to protamine sulphate and who require cardiac or vascular surgery careful monitoring of heparin dosage and neutralisation with hexadimethrine (Polybrene) intravenously appears to be a safe alternative.

Anaphylaxis↗
PubMed1980

The significance of vein wall thickness and diameter in relation to the patency of femoropopliteal saphenous vein bypass grafts.

Two hundred and twenty-five reversed saphenous vein femoropopliteal bypass graft procedures were performed on 186 patients with occlusive vascular disease. These grafts were followed for a mean of 19 months, with the longest period being 64 months. Numerous factors ascertained before, during, and after operation were analyzed using a life-table technique to see how these factors correlated with graft patency. The internal diameter and wall thickness of the vein grafts appeared to significantly influence graft patency. The best results were obtained using veins with a large internal diameter and a thin wall. In contrast, none of the other factors studied (which included age, sex, blood pressure, height, weight, indication for surgery, diabetic state, serum lipids, angiographic data, the site of the upper and lower anastomoses, the use of spliced vein segments, the type of vein preparation and the consumption of cigarettes before operation) were useful predictors of graft patency. It is suggested that vein diameter and vein wall thickness should be taken into consideration when analyzing the results of saphenous vein femoropopliteal bypass graft procedures, and also that the assessment of these factors may influence the choice of graft material for a femoropopliteal bypass graft.

Adult↗
PubMed1978

Transdiaphragmatic approach to the descending thoracic aorta for proximal control during surgery on the abdominal aorta.

A technic of mobilizing and clamping the lower descending thoracic aorta from the abdomen through the incision in the diaphragm is described. This technic is simple and may be useful when it is difficult to obtain proximal control of the abdominal aorta during surgery. In addition, certain surgical procedures on the upper abdominal aorta may be facilitated by the use of this technic.

Aorta, Abdominal↗
PubMed1978

The measurement of abdominal aortic aneurysms.

A study was made of the accuracy of different methods currently used in assessing the transverse diameter of abdominal aortic aneurysms. The maximum transverse diameter of the abdominal aorta was estimated by clinical palpation, plain radiology, ultrasonography and aortography, in a group of 47 patients who were subjected to either a surgical exploration or elective aneurysm resection. The results of these estimations were compared with the actual measurements obtained during the surgical procedure. Measurements of aortic wall calcification seen on the plain X-ray film correlated best with the operative findings. However, calcification was seen in only 30% of the patients. Ultrasonography was almost universally applicable as a technique of assessing aortic size and was found to be a reliable technique for measuring the aortic diameter.

Aorta, Abdominal↗
PubMed1978

Distal profunda femoris to popliteal artery bypass for patients with a short length of long saphenous vein.

A technique of distal profunda femoris to popliteal artery bypass is described in two patients in whom the length of long saphenous vein available for grafting was too short for a conventional femoropopliteal bypass. Because each patient has a large profunda system which was free from proximal disease, a bypass was constructed betweeen the distal profunda femoris and the upper popliteal arteries, utilizing the short length of long saphenous vein available. Both patients had complete relief of their symptoms and objective evidence of improvement.

Aged↗
PubMed1977

Techniques of reinforcing the ascending thoracic aorta.

Two techniques of reinforcing the ascending thoracic aorta with Dacron vascular prosthetic material are described. Circular reinforcement has been used patients with fusiform dilatation of the ascending thoracic aorta in whom it was considered that graft replacement was unsuitable, and also in patients with a thin-walled aorta, where reinforcement was thought to be beneficial in preventing dehiscence of an aortic suture line. The techniques are described in two patients who underwent aortic valve replacement and who had aneurysmal dilatation of the ascending thoracic aorta.

Aged↗
PubMed1976

Plasma and brain amino acids in fulminant hepatic failure and their relationship to hepatic encephalopathy.

Amino acid concentrations were determined in plasma, whole blood, cerebrospinal fluid and brain tissue of 45 patients with grade 3 or 4 coma due to fulminant hepatic failure. The concentration of 15 of the 19 amino acids determined were significantly increased in blood and the increases were greatest for the amino acids concerned with neurotransmitter metabolism. There was no correlation, however, between the plasma concentration of these amino acids and changes in the grade of hepatic coma. The plasma concentrations of the branched chain amino acids were normal except in those patients who subsequently recovered in whom levels were slightly decreased. Phenylalanine- tyrosine and methionine were among the 15 out of 18 amino acids which were significantly increased in cerebrospinal fluid and among the 15 out of 21 amino acids which were significantly increased in the brain. The increase in tryptophan was associated with a significant elevation in brain 5-hydroxyindoleacetic acid concentration suggesting an increase in 5-hydroxytryptamine turnover in hepatic coma. Brain to plasma ratios of most amino acids in hepatic coma patients were similar to control subjects suggesting that plasma concentration is the main factor controlling the cerebral concentration. However, for the branched chain amino acids, cerebrospinal fluid and brain concentrations were increased when plasma concentrations were normal suggesting an increase in brain uptake.

Amino Acids↗