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Biomedical subjects

J B Baird

Publications and source records attributed to J B Baird.

5 recordsLinked to original sources
PubMed1999

Prognostic value of dipyridamole thallium imaging after acute myocardial infarction in older patients.

OBJECTIVE: To assess the utility of intravenous dipyridamole thallium testing for predicting major cardiac events following acute myocardial infarction in older patients. DESIGN: Prospective cohort study with a median follow-up of 18 months. SETTING: A university teaching hospital. PARTICIPANTS: 73 patients aged 65 years and older with enzymatically confirmed acute myocardial infarction (mean age 75 years, 56% male, 71% white). MEASUREMENTS: All patients underwent a detailed clinical assessment, an echocardiogram, and an intravenous dipyridamole thallium stress test before hospital discharge. The study endpoint was death or nonfatal reinfarction during the follow-up period. RESULTS: Overall, 24 patients (33%) died or developed recurrent myocardial infarction during follow-up. Among 44 patients with a reversible thallium defect, 19 (43%) reached the study endpoint, compared with only five of 29 patients (17%) without reversible ischemia (P = .04). On multivariate analysis, independent prognostic variables included non-use of aspirin at hospital discharge (P = .002), decreased left ventricular systolic function (P = .009), non-use of a beta-blocker at hospital discharge (P = .013), and reversible ischemia on thallium scintigraphy (P = .025). The relative risks for death or reinfarction associated with non-use of aspirin, non-use of a beta-blocker, left ventricular dysfunction, and reversible ischemia were 2.65, 2.39, 2.01, and 2.51, respectively. Patients with three or four of these risk factors had an 83% probability of death or reinfarction, compared with 41% in patients with two risk factors and 6% in patients with one or no risk factor (P < .001). CONCLUSION: Intravenous dipyridamole thallium imaging provides independent prognostic information in older patients with acute myocardial infarction. Moreover, the combination of clinical, echocardiographic, and dipyridamole thallium variables effectively stratifies older postinfarction patients into high-, intermediate-, and low-risk categories for death or recurrent myocardial infarction.

Aged↗
PubMed1979

Effects of phencyclidine, d-amphetamine and pentobarbital on spaced responding in mice.

The effects of acute IP administration of phencyclidine (PCP), d-amphetamine (AMPH) and pentobarbital (PB) were determined in 10 mice trained to lever press on a differential reinforcement of low rate 10 sec schedule of sweetened milk presentation. The effects of PCP were highly consistent, with large response rate increases (and a corresponding shift toward shorter interresponse times) at doses of 1 and 3 mg/kg. Higher doses generally decreased response rates and resulted in a bimodal interresponse time distribution. The effects of AMPH were similar to PCP but less consistent. Although some of the subjects showed substantial response rate increases at doses between 0.3 and 10 mg/kg, half of the subjects did not show increased response rates at any dose. The effects of AMPH on the interresponse time distribution were similar to PCP. The effects of PB were least like those of PCP. The effect in most subjects was to produce a dose-related decrease in response rate and a flattening of the interresponse time distribution. Occasional small response rate increases were observed with PB.

Animals↗
PubMed1965

Kinetics and mechanism of catalysis by proteolytic enzymes. The kinetics of hydrolysis of esters of gamma-guanidino-L-alpha-toluene-p-sulphonamidobutyric acid by bovine trypsin and thrombin.

1. Esters of gamma-guanidino-l-alpha-toluene-p-sulphonamidobutyric acid (alpha-N-toluene-p-sulphonyl-l-norarginine) have been synthesized and shown to be hydrolysed by bovine trypsin and thrombin. As substrates for these enzymes, they were better than esters of alpha-N-toluene-p-sulphonyl-l-homoarginine or of alpha-N-toluene-p-sulphonyl-l-ornithine but not as good as esters of alpha-N-toluene-p-sulphonyl-l-arginine. 2. With trypsin as catalyst, the methyl and propyl esters are hydrolysed at the same rate at high substrate concentrations and hence deacylation of the acyl-enzyme appears to be rate-determining. In the presence of thrombin, however, the methyl ester is hydrolysed much faster than the n-propyl ester. 3. The variation of k(0) with pH indicates that groups with pK((app.)) values of 7.05+/-0.02 and 6.53+/-0.02 must be dissociated in trypsin and thrombin respectively for hydrolysis to proceed. 4. Activation constants have been determined for the trypsin-catalysed hydrolysis of methyl gamma-guanidino-l-alpha-toluene-p-sulphonamidobutyrate and have been compared with the corresponding constants for the hydrolysis of homologous substrates. 5. Cholate increases k(0) and decreases K(m); the effects are more pronounced with thrombin than with trypsin.

Amino Acids↗