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Biomedical subjects

D J Cooper

Publications and source records attributed to D J Cooper.

11 recordsLinked to original sources
PubMed1992

Plasma ionized calcium and blood lactate concentrations are inversely associated in human lactic acidosis.

Plasma ionized calcium [Ca++] concentrations are decreased in patients having lactic acidosis. To further investigate this observation, we prospectively studied nine critically ill patients who had lactic acidosis and measured arterial pH, PCO2, [Ca++], lactate, and albumin concentrations. We found a strong association between decreased [Ca++] and increased plasma lactate concentrations (r2 = 0.78, p less than or equal to 0.001). This unexpected association--[Ca++] usually increases with increasing acidosis--might be clinically important and the mechanism deserves further investigation.

Acidosis, Lactic↗
PubMed1992

Histamine decreases left ventricular contractility in normal human subjects.

To determine whether histamine alters human left ventricular contractility we measured heart rate, calibrated carotid arterial pressure, and left ventricular dimensions (echocardiogram) in nine healthy volunteers. We assessed baseline contractility using the end-systolic pressure-dimension relationship and the end-systolic meridional wall stress-rate-corrected velocity of circumferential fiber shortening relationship determined over a wide range of afterloads using phenylephrine and nitroprusside infusions. We then infused histamine for 3-5 min at a dose predetermined to decrease mean arterial pressure by 20%, both before and after H1 receptor antagonist pretreatment (diphenhydramine 50 mg i.v.). Histamine decreased end-systolic pressure but, unlike an equally hypotensive infusion of nitroprusside, did not decrease end-systolic dimension or increase fractional shortening. Histamine also decreased velocity of circumferential fiber shortening at the same end-systolic meridional wall stress as controls (P < 0.05). These effects of histamine were inhibited by H1 antagonist pretreatment. We conclude that the dominant effect of histamine on the human heart is to decrease left ventricular contractility and that this decrease in contractility is dependent, at least partially, on H1-receptor activation.

Adult↗
PubMed1991

Some electrospray mass spectrometric evidence for the existence of covalent O-acyl enzyme intermediates.

Electrospray mass spectrometry has been used to measure the masses of the species present in solutions of three serine proteases (alpha-chymotrypsin, subtilisin Carlsberg and subtilisin BPN') before, during and after completion of the hydrolytic reaction with cinnamoyl imidazole and indole acryloyl imidazole. The masses measured during the reaction demonstrated that covalent O-acyl enzyme intermediates had been formed.

Chymotrypsin↗
PubMed1991

Urethral pressures: analysis of transmission pressure ratios.

Transmission pressure ratio (TPR) analysis of urethral pressure profilometry data has been advocated for the diagnosis of genuine stress incontinence (GSI). However, the clinical usefulness of the technique has not been adequately evaluated. Using videourodynamics as the gold standard, the TPR results of 150 continent women and 153 with GSI have been compared. The mean TPR for each quartile of the functional urethral length was computed, as was the maximum TPR value (TPR-max) and the position on the urethra where it occurred (TPR-mode). There was a statistically significant difference between the 2 groups for TPR values in the distal 2 quartiles of the urethra and for TPR-max and TPR-mode. With the use of the Kappa statistic it was found that the TPR-mode was the most discriminatory of the TPR parameters. Even using this measure, the overlap between normal and GSI was so great as to make accurate diagnosis impossible. It was therefore concluded that TPR analysis is useless for the diagnosis of GSI. However, such an analysis is helpful for the understanding of the pathophysiology of GSI and its treatment.

Cough↗
PubMed1991

Diastolic stiffness impairs left ventricular function during hypovolemic shock in pigs.

To determine the causes of impaired left ventricular function during hypovolemic shock we measured diastolic and end-systolic pressure-volume relationships and hemodynamics. Left ventricular pressure (Millar catheter) and volume (3 ultrasonic crystal pairs) were measured in six open-chest, chloralose-morphine anesthetized, juvenile pigs. After baseline measurements, the pigs were bled and maintained at a mean aortic pressure of 50 cmH2O for 7 +/- 1 h. After resuscitation with all shed blood, left ventricular function was markedly impaired as indicated by increased end-diastolic pressure (20.3 vs. 8.7 cmH2O at baseline, P less than 0.05), decreased aortic pressure (36% of baseline, P less than 0.01), and decreased stroke volume (50% of baseline, P less than 0.01). Systolic contractility was increased (P less than 0.05), but diastolic compliance was greatly reduced due to decreased diastolic maximum (52% of baseline, P less than 0.01) and equilibrium volumes (57% of baseline, P less than 0.01). We conclude that impaired left ventricular function during hypovolemic shock is due entirely to increased diastolic stiffness. These results can theoretically be accounted for by a 20% reduction in myocardial muscle length with no change in muscle stress-strain characteristics. This may be the physiological expression of morphologically observed myocardial "zonal lesions" of hypovolemic shock.

Animals↗
PubMed1977

The aminoglycoside antibiotics. I. Synthesis and biological evaluation of an analog of gentamicin.

The synthesis of 2-deoxy-4-O-(2,6-diamino-2,3,4,6-tetradeoxy-alpha-D-erythrohexopyranosyl)-6-O-(3-deoxy-3-methylamino-alpha-D-xylopyranosyl)-D-streptamine (1), an analog of gentamicin A, from diideoxyneamine and methyl 3-methylamino-3-deoxy-beta-D-xylopyranoside is described. The product was characterized by its 13C nmr spectrum and was found to exhibit broad spectrum antibacterial activity.

Bacteria↗
PubMed1977

Assessment and resection of carcinoma at the gastroesophageal junction.

In a five year retrospective study of 70 patients, the roentgenologic and surgical assessments of carcinoma at the gastroesophageal junction have been compared to the histologic findings of the resected specimens. Although the lesion was demonstrated roentgenologically in all patients, no reliable indication of its limits could be obtained, and spread was seriously underestimated by both preoperative barium studies and direct examination at operation. It is suggested that the lack of roentgenologic evidence may have encouraged an inadequate surgical approach and, thus, contributed to incomplete resection and the high immediate mortality. There is, at present, no satisfactory method by which spread can be defined, either before or at operation, and neither the preoperative barium studies nor his operative assessment should influence the surgeon to limit the resection.

Adenocarcinoma↗