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Biomedical subjects

B Morton

Publications and source records attributed to B Morton.

At least 37 records · Page 2Linked to original sources
PubMed1990

Role of transesophageal echocardiography in percutaneous balloon mitral valvuloplasty.

Echocardiography is useful in the selection of patients for percutaneous balloon mitral valvuloplasty, which is an effective treatment in suitable patients with rheumatic mitral stenosis. Transesophageal echocardiography appears superior to precordial echocardiography in this role because transesophageal echocardiography is not only reliable in the assessment of mitral valvular morphology but also more sensitive in the detection of left atrial thrombi and mitral regurgitation. Transesophageal echocardiography can be used in guiding the proper positioning of the catheters during the dilatation procedure. Complications of balloon mitral valvuloplasty such as torn mitral leaflets or atrial septal defects can also be diagnosed reliably by transesophageal echocardiography. Thus, transesophageal echocardiography should be an integral part of balloon mitral valvuloplasty.

Catheterization↗
PubMed1981

Bile salt-enhanced rat jejunal absorption of a macromolecular tracer.

Bile salt deconjugation may occur in the jejunum under conditions of fecal colonic overgrowth of the small intestine. We studied the effects of conjugated and deconjugated bile salts on rat jejunal absorption of a macromolecular tracer, horseradish peroxidase, in an in vivo perfusion system. At a 0.5 mM perfusion concentration, only the deconjugated bile salts, cholate and deoxycholate, produced a significant increase in horseradish peroxidase absorption into serum. At a 0.5 mM concentration of the conjugated salt, taurocholate, horseradish peroxidase-absorption was indistinguishable from that seen in bile salt-free preparations. At a higher 5 mM concentration, both the conjugated and deconjugated salts increased jejunal HRP absorption into serum over that seen in bile salt-free preparations; this absorption wa most marked with the deconjugated salts. At a 0.5 mM level, the bile salts induced minimal sodium and glucose transport alterations but did not produce evidence of morphologic damage to villi or absorptive epithelial cell organelles. At a 5 mM level, the deconjugated salts induced glucose and sodium transport abnormalities and appeared to damage cellular organelles. Our observations suggest that an alteration in the tight junctional barrier to macromolecular absorption may play a role in some of the enhanced horseradish peroxidase absorption seen with deoxycholic acid in these experiments. The process of an increased absorption of intact macromolecules induced by products of bacterial metabolism may be of pathologic significance in the etiology of immunologically related intestinal disease or in toxigenic processes.

Animals↗
PubMed1979

Pineal hydroxyindole-O-methyltransferase: mechanism, and inhibition by scotophobin A.

We had shown that the behaviorally active peptide, scotophobin A, a synthetic analogue of native scotophobin, acted to increase dark avoidance in goldfish by inhibiting pineal hydroxyindole-O-methyltransferase (HIOMT), the enzyme which converts N-acetylserotonin (NAS) to melatonin (MEL). Here we determine the reaction sequence of bovine pineal HIOMT and the mechanism whereby scotophobin A inhibits this enzyme. Initial rate studies in which the substrates NAS and the methyl donor, S-adenosylmethionine SAM), were independently varied indicated the enzyme reacted by a sequential mechanism. With the product, S-adenosylhomocysteine (SAH), included in the reaction mixtures, data were obtained consistent with the following order of substrate addition and product discharge: (see text). The turnover number was 5.7 moles melatonin formed/mole HIOMT/min. The substrate KMs were 4.2 x 10(-4) M for NAS and 4.9 x 10(-5) M for SAM. Further studies showed that scotophobin A is an inhibitor (KI = 7 x 10(-7) M) competitive with NAS, indicating that this peptide combines with the enzyme-SAM complex. The structural similarity of the tyrosinamide end of scotophobin A to NAS and several other HIOMT inhibitors, including two antischizophrenic drugs, is consistent with these observations.

Acetylserotonin O-Methyltransferase↗
PubMed1977

Myocardial infarction following coronary artery bypass: factors influencing its occurrence.

The authors have undertaken a prospective study on postoperative myocardial infarciton (PMI) following coronary artery bypass (CAB) grafting. PMI was diagnosed from electrocardiographic findings by the criteria of the American Heart Association. From Aug. 1, 1975 to Feb. 27, 1976, 198 patients (177 men, 21 women) underwent CAB. Their ages ranged from 31 to 71 years (mean, 49 yr). Of these patients, 18 (9%) sustained a PMI. A number of factors were analyzed to determine their influence on the occurrence rate of PMI. Preoperative factors wuch as the New York Heart Association classification, measurement of left ventricular function and evaluation of the severity of coronary artery disease were not helpful in predicting a predisposition to PMI. Endarterectomy was the only operative intervention associated with a higher inicidence of PMI (18%). Other factors such as the interval of cardiac anoxia and cardiopulmonary bypass and the number of vessels grafted did not seem to be associated with PMI. Low blood flow (less than 40 ml/min) through the graft could be correlated with the area of infarction in only 5 of 18 patients. Among the operated patients, postoperative ventricular arrhythmia was much more common in patients with PMI. The hospital mortality in this group was 11% (two patients).

Adult↗
PubMed1975

The isolation of large polysomes in high yield from unfractionated tissue homogenates.

It was found that if large quantities of both exogenous RNA and Mg-2+ were present during gentle tissue homogenization, the subsequent addition of deoxycholate to the whole homogenate produced a viscous mass from which polysomes could be isolated in large yields. These polysomes were substantially less degraded than those isolated by previous methods. In the case of rat liver, 15 ribosomes per mRNA was the species present in highest concentration. The parameters of this method were investigated and optimized. About 80 percent of the rRNA in the homogenates was recovered in the polysomes. Omission of deoxycholate permitted the isolation of less-degraded free polysomes as well. In the liver of fed rats these represented one-fourth of the total polysomes, in good agreement with results obtained by an independent approach. Using the method to isolate polysomes from the liver of starving rats, it was found that only about one percent of the large amount of monomers and dimers present resulted from polysome breakdown during isolation. It was further shown that random RNAase hydrolysis of polysomes could not produce the patterns of liver polysomes seen during starvation. Polysomes isolated by this procedure were quite stable in solution and were very active in cell-free protein synthesis. Application of this method without adaptation to eight other tissues also permitted the isolation of large polysomes in high yields.

Animals↗
PubMed1974

Late results of aortocoronary bypass grafts in 100 patients with stable angina pectoris.

From March 1969 to December 1972, 314 patients underwent elective aortocoronary saphenous vein bypass graft surgery at the Toronto General Hospital for the relief of stable disabling angina refractory to medical management. Inhospital mortality was 2.5%. Of these patients 100 agreed to return for follow-up hemodynamic and angiographic assessment at a mean interval of 19.7 months after operation. Seventy-four percent of patients were asymptomatic or had angina only with strenuous exertion at the time of follow-up. Seventy-five percent of the 142 grafts were patent, though a few had significant narrowings. Clinical improvement could be correlated with successful myocardial revascularization. Myocardial infarction was diagnosed by the presence of new Q waves after operation in 15% of patients. Many of these patients had patent grafts at follow-up and all were improved. Dyslipoproteinemia was not found to be a factor affecting late graft patency. Total left ventricular function was not shown to be improved by segmental revascularization. The trend toward improved survival in the intervening period for the total operated group is encouraging.

Adult↗