Citations

The isolated, perfused rat liver has been used to study the metabolic pathways of I131-labeled l-thyroxine (T4), l-3,5,3'-triiodothyronine (T3), their partially deiodinated derivatives, and d-thyroxine. l-Thyroxine was metabolized less rapidly than the l-thyronines with fewer iodine atoms. l-T4 accumulated in the liver more rapidly than l-3,3',5'T3 or l-3,3'T2 but less rapidly than l-3,5,3'T3 or d-T4. Conjugation with glucuronic acid proceeded in the liver most rapidly from 3,5,3'T3 and at much lower rates from d-T4, l-T4, l-3,3',5'T3, and l-3,3'-diiodothyronine (T2). Deiodination of l-3,3',5'T3 and l-3,3'T2 proceeded most rapidly.

Radioiodinated Hippuran was injected into the inferior vena cava of three unilaterally and three bilaterally nephrectomized dogs. Radioactivity was recorded over the precordium and remaining kidney in the former group and the precordium and renal fossa in the latter. The disappearance of I131 from plasma was analyzed and interpreted by two-compartment and three-compartment systems. Theoretical curves for cardiac and renal areas (constructed from analysis of arterial plasma samples) agreed well with curves from in vivo counting. Analyzed by either model, the first compartment exceeded the plasma volume severalfold, part seeming to be in the kidney. Extravascular compartments, impossible to sample, were not identified. About 15% of whole-blood radioactivity was in erythrocytes. Biliary excretion of Hippuran I131 was insignificant unless nephrectomy was bilateral; then up to 60% was excreted in the bile in 24 hr. Protein binding could not be demonstrated. Radiorenograms converted to fairly accurate rate constants may prove more useful than descriptive methods currently employed. Understanding the distribution and excretion of Hippuran appears helpful to accurate interpretation of the radiorenogram.

This study was undertaken to determine the site of maximal absorption of Co60-labeled vitamin B12 in the small intestine of the male albino rat. Animals were sacrificed at intervals after ingestion of the labeled vitamin. The highest concentration of radioactivity was found in the wall of the upper and mid-ileum 1/2–3 hours after ingestion. Accordingly, the absorption of tagged vitamin B12 was estimated by fecal and urinary excretion methods in animals with resections of portions of the small intestine, including the portion containing the ileocecal valve, and in normal controls. Resection of the middle half of the small bowel (the upper and mid-ileum) was found to produce significant impairment of vitamin B12 absorption. It is concluded that in the male albino rat the upper and mid-ileum is specifically adapted to most efficient absorption of vitamin B12.

The concentration and distribution of sodium and potassium in small consecutive portions of kidneys of potassium-depleted and vitamin D-intoxicated hydropenic rats were estimated by a procedure based on the principle of specific activity. By this method sodium and potassium could be measured in bits of tissue weighing less than 2 mg. The results were correlated with the corresponding urinary osmolality. In both experimental groups, a marked impairment of the elaboration of osmotically concentrated urine was observed. The relative distribution of sodium and potassium in the kidney was not altered significantly. Associated with the decreased osmolality of the urine, however, was an approximately proportionate or slightly greater reduction in the content of sodium in the papilla. The findings suggest that a failure to establish maximal medullary hypertonicity, as indicated by the diminished accumulation of sodium, may be an important factor in the impairment of concentrating mechanisms.

A study was made of the disappearance of sodium diatrizoate-I131 from the plasma of ten dogs after single intravenous injections. The plasma disappearance curves suggested a two-compartment system. The renal plasma clearance of diatrizoate-I131 calculated from these curves and the conventional renal plasma clearance of creatinine were not statistically different. Clearances calculated from the urinary excretion and midperiod plasma concentration of radioactivity in four experiments yielded values averaging 10% less than the creatinine clearance. Chromatographic studies of commercially available diatrizoate-I131 revealed the presence of about 5% free iodide and of about 5% of unidentified impurities. These impurities seem to account, partly at least, for the differences found between diatrizoate clearance and creatinine clearance. Biliary excretion and erythrocytic uptake of diatrizoate were minimal and did not appear to influence the analysis.

Urinary-excretion and fecal-recovery methods were employed in the study of intestinal absorption of cobalt60-labeled vitamin B12 in the normal male albino rat. a) The logarithm of the fecal excretion, as well as of the urinary excretion augmented by an intraperitoneal flushing dose of unlabeled vitamin, increased linearly with the logarithm of the oral dose. This same relation of fecal excretion to oral dose is also apparently true in man. b) Increasing the intraperitoneal flushing dose over a wide range brought about a progressive increase in the percentage of the labeled oral dose excreted in the urine, but this increase was of small magnitude. c) The optimal time for administration of the intraperitoneal flushing dose in the rat appeared to be about 2 hours after administration of the labeled oral dose. d) The male albino rat seems to be an excellent experimental animal for use in the study of vitamin B12 absorption.

Forty-two male and female mice, 8 weeks old, were given radioiron (Fe59) in doses of 0.006–0.1 µc, containing 0.013–0.17 µg of iron, by intraperitoneal or intravenous routes. Assays of the radioactivity of the whole body revealed an initial rapid loss of Fe59 (15–20%) lasting about 6 days. Thereafter the Fe59 left the mice at a steady rate of 0.39%/day (half-life 180 days). One 34-year-old normal man was given 10.6 µc of Fe59, containing 8.2 µg of iron, intravenously. Based on counts from the entire body, the biologic rate of loss of the Fe59 was about 0.14%/day (half-life 500 days), and there was little or no initial loss such as occurred in the mouse. The Fe59 in the circulating erythrocytes was essentially unchanged for the first 3 months. It then fell to a new level of about 90% of the previous one; the mid-point of the fall was about 120 days after the administration of the radioiron. The difference in the rates of loss of radioiron from mice and man seems to be related primarily to the life span of the circulating red cells.

AbstractBackgroundPatients at low risk for acute coronary syndrome are frequently admitted for observation and cardiac testing, resulting in substantial burden and cost to the patient and the health care system.ObjectivesThe purpose of this investigation was to measure the effect of the Chest Pain Choice (CPC) decision aid on overall health care utilization as well as utilization of specific services both during the index emergency department (ED) visit and in the subsequent 45 days.MethodsThis was a planned secondary analysis of data from a pragmatic multicenter randomized trial of shared decision making in adults presenting to the ED with chest pain who were being considered for observation unit admission for cardiac stress testing or coronary computed tomography angiography. The trial compared an intervention group engaged in shared decision making facilitated by the CPC decision aid to a control group receiving usual care. Hospital‐level billing data were used to measure utilization for the index ED visit and during the following 45 days. Patients in both groups also were asked to keep a diary recording health care utilization over the same 45‐day period. Outcomes assessed included length of time in the ED and observation, ED visits, office visits, hospitalizations, testing, imaging, and procedures.ResultsOf the 898 patients included in the original trial, we were able to contact 834 (92.9%) patients for 45‐day health care diary review. There was no difference in patient‐reported health care utilization between the study arms. Hospital‐level billing data were obtained for all 898 (100%) patients. During the initial ED visit the length of stay (LOS) was similar, and there was no difference in the frequency of observation unit admission between study arms. However, the mean observation unit LOS was 95 minutes (95% confidence interval [CI] = 40.8–149.8) shorter in the CPC arm and the mean number of tests was lower in the CPC arm (decrease in 19.4 imaging studies per 100 patients, 95% CI = 15.5–23.3). When evaluating the entire encounter and follow‐up period, the intervention arm underwent fewer tests (decrease in 125.6 tests per 100 patients, 95% CI = 29.3–221.6). More specifically, there were fewer advanced cardiac imaging tests completed (25.8 fewer per 100 patients, 95% CI = 3.74–47.9) in the intervention arm.ConclusionsShared decision making in low‐risk chest pain can lead to decreased diagnostic testing without worsening outcomes measured over 45 days.