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Biomedical subjects

R Roberts

Publications and source records attributed to R Roberts.

At least 505 records · Page 28Linked to original sources
PubMed1982

Inhibition of the bronchial response to respiratory heat exchange by increasing doses of terbutaline sulphate.

Ten asthmatic patients inhaled terbutaline sulphate (250, 500, or 1000 micrograms) or placebo on separate days, double blind and in random order, 30 minutes before isocapnic hyperventilation induced by cold air inhaled in doses that increased in a precisely controlled manner. The respiratory heat exchange (RHE) was calculated for each level of ventilation and the results were expressed as the RHE causing a fall in FEV1 of 10% (PD10RHE). The PD10RHE after placebo was highly reproducible. After terbutaline inhalation there was a highly significant shift in the RHE dose-response curves to the right and a trend towards a linear increase in PD10RHE with increasing doses of terbutaline. The subjects who were most responsive to the RHE required more terbutaline to inhibit the response completely. The results indicate that RHE dose-response curves are a precise method to examine the effects of drugs on hyperventilation-induced asthma, that increasing doses of terbutaline can produce increasing protection, and that the degree of protection is dependent on the level of increased bronchial responsiveness to RHE.

Adult↗
PubMed1982

Variability of fiber type distributions within human muscles.

The variability of fiber type distributions between different regions of the same human muscle is believed to be small, based on the sampling of between two and four sites. The objective of the present investigation was to determine the variability of slow-twitch (ST) and fast-twitch (FT) fiber distributions using a more extensive sampling technique than those previously employed. The soleus, biceps, triceps, and vastus lateralis muscles were excised from each of four young men who had died suddenly. Between 13 and 17 sites were sampled from each of the muscles; 3 transverse areas were then examined within each sample. Fiber type distributions were determined from photographs of sections stained for myofibrillar adenosine triphosphatase at pH 10.3, 10.0, or 4.3. The numbers of fibers counted in the four muscles ranged between a mean of 13,660 and a mean of 21,601. The variability in fiber type distributions observed between sites and areas within a site were statistically greater (P less than 0.01) than could be expected from muscles whose fiber type distributions are equally distributed throughout the muscle. It was concluded that sampling between 3 and 5 sites in the different muscles was necessary to reduce the between-site standard deviation to 5%.

Adenosine Triphosphatases↗
PubMed1982

Characterization of nontransmural myocardial infarction by positron-emission tomography.

The present study was performed to determine whether positron emission tomography (PET) performed after i.v. 11C-palmitate permits detection and characterization of nontransmural myocardial infarction. PET was performed after the i.v. injection of 11C-palmitate in 10 normal subjects, 24 patients with initial nontransmural myocardial infarction (defined electrocardiographically), and 22 patients with transmural infarction. Depressed accumulation of 11C-palmitate was detected with sagittal, coronal and transverse reconstructions, and quantified based on 14 contiguous transaxial reconstructions. Defects with homogeneously intense depression of accumulation of tracer were detected in all 22 patients with transmural infarction (100%). Abnormalities of the distribution of 11C-palmitate in the myocardium were detected in 23 patients with nontransmural infarction (96%). Thallium scintigrams were abnormal in only 11 of 18 patients with nontransmural infarction (61%). Tomographically estimated infarct size was greater among patients with transmural infarction (50.4 +/- 7.8 PET-g-Eq/m2 [+/- SEM SEM]) compared with those with nontransmural infarction (19 +/- 4 PET-g-Eq, p less than 0.01). Residual accumulation of 11C-palmitate within regions of infarction was more intensely depressed among patients with transmural compared to nontransmural infarction (33 +/- 1 vs 39 +/- 1% maximal myocardial radioactivity, p less than 0.01). Thus, PET and metabolic imaging with 11C-palmitate is a sensitive means of detecting, quantifying and characterizing nontransmural and transmural myocardial infarction.

Adult↗
PubMed1982

Vitamin B-12 (cobalamin) deficiency: a heretofore undescribed control mechanism for plasma corticosteroid-binding globulin concentration in man.

Six of eight patients with Addisonian pernicious anemia were found to have diminished corticosteroid-binding globulin (CBG) concentrations, which returned within 2 weeks to normal after the im administration of cobalamin. T4-binding globulin was found to be completely normal before and after cobalamin replacement. Other estrogen-responsive proteins, i.e. ceruloplasmin, alpha 1-trypsin inhibitor, haptoglobin, transferrin, and alpha 2-macroglobulin, also did not follow CBG concentration in a parallel fashion. The immunoglobulins similarly did not follow a course parallel to that of CBG. The CBG concentration in two untreated patients had a normal increase in response to estrogen administration, similar to that described in CBG deficiency from other causes. No clue was found regarding the mechanism by which B12 influences the putative hepatic control of CBG concentration. It is speculated that at least two control points may be necessary for a normal CBG concentration. Patients with a genetic deficiency of CBG may also have to have cobalamin deficiency in order for them to reach a concentration approaching zero.

Anemia, Pernicious↗
PubMed1981

Serial plasma catecholamine response early in the course of clinical acute myocardial infarction: relationship to infarct extent and mortality.

Clinical and experimental evidence suggest that sympathoadrenal activation contributes to mortality in patients with ischemic heart disease. To determine the level of sympathoadrenal activation in the very early phase of acute myocardial infarction (AMI) and to determine if location of infarction (anterior versus inferior) was related to sympathoadrenal activation, we studied norepinephrine (NE) and epinephrine (E) within 4 hours after the onset of symptoms and prior to any rise in plasma creatine kinase (CK). Mean (+/- SE) initial (NE = 591 +/- 111 pg/ml and E = 73 +/- 19 pg/ml), peak (NE = 1356 +/- 178 and E +/- 1098 +/- 608) and average (NE = 815 +/- 142 and E = 252 +/- 68) plasma catecholamine concentrations were considerably above normal (NE = 228 +/- 10 and E = 34 +/- 2 pg/ml, n 60) and values were similar for inferior and anterior infarctions. During an 18-month follow-up, three patients died in whom the AMI mean NE and E and peak CK were higher than in the eight late survivors. Thus the three AMI patients with peak EP values greater than 1000 died, whereas the eight AMI patients with peak EP values less than 1000 survived (p less than 0.01). The magnitude of sympathoadrenal activation early in the course of clinical AMI appeared related to the extent of myocardial damage and late mortality.

Acute Disease↗
PubMed1981

Factors presaging early recurrent myocardial infarction ("extension").

A prospective study of 200 consecutive patients with acute myocardial infarction was undertaken to characterize the frequency and severity of early recurrent infarction (extension), manifested by secondary plasma MB creatine kinase (CK) and myoglobin peaks, and to identify patients at particularly high risk. Serial MB CK and myoglobin determinations and continuous electrocardiographic recordings were obtained in all patients for 14 days, and serial radioventriculograms were obtained in selected patients. Chest pain and S-T segment changes occurred often, in 57 and 43 percent, respectively, of the entire group of patients. However, a secondary rise in plasma MB CK levels indicative of recurrent infarction, occurring an average of 10 +/- 4 days after the initial infarct, was evident in only 17 percent of patients. Forty-three percent (25 of 58) of patients with initial subendocardial infarction exhibited recurrent infarction compared with only 8 percent of those with initial transmural infarction. The mortality rate was 7 percent in patients with subendocardial infarction without early recurrence compared with 16 percent among those with recurrent. Logistic regression analysis indicated that obese women with initial subendocardial infarction and repeated episodes of prolonged chest pain had a high probability rate (60 percent) of recurrence in contrast to the low probability (2 percent) in patients without these features. Thus, early recurrent infarction is frequent after subendocardial infarction and is associated with a marked increase in mortality. These results suggest that patients with subendocardial infarction are at particularly high risk for recurrent infarction and that patients with this type of infarction require vigorous monitoring and prolonged surveillance.

Aged↗