Biological half-life of iodine in adults with intact thyroid function and in athyreotic persons

A joint project between the Human Monitoring Laboratory (HML) and the Ottawa Hospital has measured the retention of 131I in patients who have received the radioiodine diagnostically. Thirty-nine subjects with intact thyroid glands and nine athyreotic subjects were measured in the HML's whole-body/thyroid counter to determine the retention of 131I following its medical administration. The average biological half-life of 131I in 26 euthyroid subjects was found to be 66.1+/-6.3 days which may he statistically significantly lower than the ICRP recommended value of 80 days. Nine hyperthyroid patients had a mean biological half-life of 38.2+/-8.6 days and in three hypothyroid patients the corresponding value was 29.3+/-8.8 days. Thyroid 131I uptake was measured in a conventional clinical fashion at the Ottawa Hospital Civic campus 24 h after oral administration of the radioiodine using a collimated thick sodium iodide detector placed over the neck anteriorly. Measured values were 10.144+/-0.009, 0.314+/-0.035 and 0.045+/-0.010 of the administered dose in euthyroid, hyperthyroid and hypothyroid patients respectively. The euthyroid range at the hospital is 0.06 - 0.22. Uptake was significantly lower for the euthyroid group than the ICRP value of 0.3. The radioiodine retention in athyreotic subjects followed a two compartment model with biological half-lives of 1.0+/-1.2 days and 18.4+/-1.1 days.

Psychological and physical stress induce differential effects on human colonic motility

OBJECTIVE

Stress modulates gut function, but whether the type of stressor influences colonic motor activity is unclear. The motor patterns and regional variations are also poorly understood. Our aim was to determine the effects of psychological and physical stress on colonic motility.

METHODS

Ambulatory colonic manometry was performed by placing a six-sensor probe up to the mid-transverse colon, without sedation, in 12 healthy subjects. Five hours later, a dichotomous listening test (psychological stress) was performed, which was preceded by listening to a narrative passage (control); recovery entailed listening to relaxing music (1 h each). Subsequently, intermittent hand immersion in cold (4 degrees C) water (physical stress) was performed, preceded by hand immersion in warm (37 degrees C) water (1/2-h each). Colonic pressure activity and cardiovascular responses were measured throughout the study.

RESULTS

When compared with the control period, both stressors induced a greater number of pressure waves (p < 0.05), and the area under the curve (p < 0.01), but only physical stress increased (p < 0.05) pulse rate and blood pressure. There were no regional differences in colonic motility. During recovery, the motor activity returned to baseline after physical stress, but remained high after psychological stress. Psychological stress induced more (p < 0.05) propagated contractions, whereas physical stress induced more (p < 0.05) simultaneous contractions.

CONCLUSIONS

Both stressors enhanced colonic motor activity, but psychological stress induced a prolonged response with propagated activity and without appreciable autonomic response. Thus, colonic motor responses may vary depending on the stressor.

Psychological and physical stress induce differential effects on human colonic motility

OBJECTIVE

Stress modulates gut function, but whether the type of stressor influences colonic motor activity is unclear. The motor patterns and regional variations are also poorly understood. Our aim was to determine the effects of psychological and physical stress on colonic motility.

METHODS

Ambulatory colonic manometry was performed by placing a six-sensor probe up to the mid-transverse colon, without sedation, in 12 healthy subjects. Five hours later, a dichotomous listening test (psychological stress) was performed, which was preceded by listening to a narrative passage (control); recovery entailed listening to relaxing music (1 h each). Subsequently, intermittent hand immersion in cold (4 degrees C) water (physical stress) was performed, preceded by hand immersion in warm (37 degrees C) water (1/2-h each). Colonic pressure activity and cardiovascular responses were measured throughout the study.

RESULTS

When compared with the control period, both stressors induced a greater number of pressure waves (p < 0.05), and the area under the curve (p < 0.01), but only physical stress increased (p < 0.05) pulse rate and blood pressure. There were no regional differences in colonic motility. During recovery, the motor activity returned to baseline after physical stress, but remained high after psychological stress. Psychological stress induced more (p < 0.05) propagated contractions, whereas physical stress induced more (p < 0.05) simultaneous contractions.

CONCLUSIONS

Both stressors enhanced colonic motor activity, but psychological stress induced a prolonged response with propagated activity and without appreciable autonomic response. Thus, colonic motor responses may vary depending on the stressor.

Psychological and physical stress induce differential effects on human colonic motility

OBJECTIVE

Stress modulates gut function, but whether the type of stressor influences colonic motor activity is unclear. The motor patterns and regional variations are also poorly understood. Our aim was to determine the effects of psychological and physical stress on colonic motility.

METHODS

Ambulatory colonic manometry was performed by placing a six-sensor probe up to the mid-transverse colon, without sedation, in 12 healthy subjects. Five hours later, a dichotomous listening test (psychological stress) was performed, which was preceded by listening to a narrative passage (control); recovery entailed listening to relaxing music (1 h each). Subsequently, intermittent hand immersion in cold (4 degrees C) water (physical stress) was performed, preceded by hand immersion in warm (37 degrees C) water (1/2-h each). Colonic pressure activity and cardiovascular responses were measured throughout the study.

RESULTS

When compared with the control period, both stressors induced a greater number of pressure waves (p < 0.05), and the area under the curve (p < 0.01), but only physical stress increased (p < 0.05) pulse rate and blood pressure. There were no regional differences in colonic motility. During recovery, the motor activity returned to baseline after physical stress, but remained high after psychological stress. Psychological stress induced more (p < 0.05) propagated contractions, whereas physical stress induced more (p < 0.05) simultaneous contractions.

CONCLUSIONS

Both stressors enhanced colonic motor activity, but psychological stress induced a prolonged response with propagated activity and without appreciable autonomic response. Thus, colonic motor responses may vary depending on the stressor.

A study of thyroid radioiodine monitoring by Monte Carlo simulations: implications for equipment design

Monte Carlo simulations have been performed to evaluate the design of collimated detectors used to measure 125I or 131I in the thyroid gland. Two detector sizes were simulated for each radioisotope: (i) for 125I monitoring 2.54 cm diameter and 7.62 cm diameter and 0.2 cm thickness and (ii) for 131I monitoring 2.54 cm diameter, 3.2 cm thickness and 7.62 cm diameter, 6.4 cm thickness. The virtual thyroid gland was 20 g. Activity was placed in both the gland and the remainder of the body in varying amounts to assess the efficacy of collimation. The results show that the detector should be sufficiently large so that its solid angle of acceptance when placed 15 cm anterior to the skin surface will include the whole of a moderately enlarged thyroid gland. Heavy collimation to reduce the contribution of extrathyroidal radioiodine within the subject's body is not normally required. It may be of more value as a positioning device and spacer ensuring an appropriate and constant neck to detector distance than in cutting down counts from extrathyroidal activity. In specifying a sensitive detector system for monitoring intrathyroidal radioiodine, a wide angle of acceptance and sufficient detector crystal thickness take precedence over collimation and shielding.

Nephrotoxicity of ioxaglate and ioversol assessed by glomerular filtration rate: a pilot study

OBJECTIVE

To determine the effect of ioxaglate and ioversol on glomerular filtration rate (GFR) in a heterogeneous inpatient group to allow calculation of the necessary sample size for a randomized trial.

PATIENTS AND METHODS

The study group consisted of 36 men and 12 women, ranging in age from 25 to 79 (mean 63) years. Fourteen of the patients, those undergoing abdominal aortography with or without renal arteriography, received ioxaglate (Hexabrix 320; 40 to 240 [mean 141] mL), and the remaining 34, those receiving intravenous injections and those undergoing computed tomography with arterioportography or carotid arteriography, received ioversol (Optiray 320; 20 to 180 [mean 87] mL). GFR was measured by determining the clearance of diethyl-enetriaminepenta-acetic acid labelled with technetium-99m up to 72 hours before and 24 hours after administration of the contrast medium. Risk factors for nephrotoxicity included diabetes (7 patients) and pre-existing renal impairment (mild in 11 and severe in 6).

RESULTS

GFR decreased by 20% to 34% in six patients (13%); in only one of these was the serum level of creatinine increased at 24 hours. One of these six patients had received 120 mL of ioversol for carotid arteriography and had no risk factors for nephrotoxicity. The other five had received 40 to 187 (mean 115) mL of ioxaglate, three for abdominal aortography and two for selective renal arteriography. The risk factors in these patients included diabetes (two patients) and severe pre-existing renal impairment (two patients). Renal failure necessitating treatment did not develop in any of the patients.

CONCLUSIONS

A decrease in GFR occurred more often with ioxaglate than with ioversol and usually occurred in patients with additional risk factors. Injection of contrast medium into the abdominal aorta or the renal artery may increase the risk of nephrotoxicity. Changes in serum level of creatinine at 24 hours were not reliable in identifying patients with decreased GFR. On the basis of these data, the authors estimate that a group of 194 patients would be necessary for a randomized trial comparing the nephrotoxicity of ioxaglate and ioversol for abdominal aortography.

Differences in particle deposition between the two lungs

Certain inhalational diseases show a predilection for a particular region of one or the other lung that may be related to the site of deposition of inhaled particles. We conducted inhalation studies with monodispersed aerosol particles in 22 healthy student volunteers to determine how deposition varied between the two lungs. Ventilation lung scans were obtained with the subjects seated in front of a gamma camera while breathing radiolabelled particles. Subsequently we made paired comparisons of the radioactivity deposited in corresponding regions of the right and left lungs. Although regional differences in deposition between the left and right lung were often statistically significant, they were not always consistent between individuals. Particle deposition and the degree of penetration differed between the two lungs with there being generally more deposition in the perihilar region of the right lung. We suggest that the anatomy of the central airways may influence the pattern of deposition, thereby introducing disparities in particle deposition between the two lungs. The present findings lend support to experimental lung cast data and to the concept that anatomical differences between the two lungs influence the site of deposition.

A simple method for studying lung ventilation

A simple method of precisely administering a compact gas bolus during selectable portions of the inspiratory cycle was developed to examine certain fundamental attributes of lung physiology and ventilation. The method allows for a small, well-defined bolus to be delivered during different phases of inspiration in a precise fashion. A pneumatically driven three-way switching valve is synchronized to the breathing pattern and controls the interjection of radioxenon boli in the inspiratory stream, spiking a small portion of the inhaled breath. The 133Xe dispersion and redispersion in the lungs is mapped and the clearance followed. Regional differences are analysed to determine how ventilation might influence the development of lung diseases due to inhaled toxins. Scintillation imaging at 20 frames s-1 allows near real-time characterization of the ventilation distribution. Novelty comes from the application of fast data gathering, the flow through valve design for delivery of tightly compacted boli and from tracing different fractions of the breath. The procedure involves low radiation exposure. An apparatus and method for acquiring data on lung filling and emptying not previously available is described. Potential applications are identified which may allow the re-examination of orthodox lung physiology.

A potential imaging agent for the GABAA receptor: 4-t-butyl-1-(4-[123I]iodophenyl)-2,6,7-trioxabicyclo-[2.2.2]octane

Based upon the known high toxicity and high antagonist activity of t-butylorthobenzoates towards the GABA receptor complex, 4-t-butyl-1-(4-iodophenyl)-2,6,7-trioxabicyclo[2.2.2]octane 5 and its radioiodo analogues ([123I]-5 and [131I]-5 were prepared as potential markers for the gated chloride channel of GABAA receptors. Mice showed rapid clearance of [131I]-5 from all organs including the brain. The radioactivity was found to proceed into the urine in spite of the high lipophilicity of 5, the high binding affinity of 5 for plasma protein and the apparent chemical stability of 5 in plasma.

Radioiodinated 2-nitrobenzyl carbamates as bioreductive alkylating agents for tissue hypoxia

Three N-methylcarbamates of iodonitrobenzyl alcohols (4-iodo-2-nitrobenzyl alcohol 2, 5-iodo-2-nitrobenzyl alcohol 3 and 4-iodo-2,6-dinitrobenzyl alcohol 4) bearing [125I] have been prepared and characterized for their lipophilicity, their reduction potentials and the in vivo liability of the radioiodine in healthy mice. Based upon these results, 2 and 4 were tested in tumour-bearing mice showing limited uptake of radioactivity in tumours and a tumour-to-blood ratio of less than 1. Consequently these particular carbamates are not satisfactory as hypoxia imaging agents.

Subchondral bone infractions in acute ligamentous knee injuries demonstrated on bone scintigraphy and magnetic resonance imaging

Bone scintigraphy is used to detect radiographically silent fractures. Magnetic resonance imaging (MRI) is currently used to screen knee injuries for cartilage and ligament damage. MRI also delineates bone marrow and fractures. We investigated the bone scintigraphic findings in patients who had subchondral bone injuries demonstrated on MRI. Thirteen patients underwent MRI, three-phase bone scintigraphy with SPECT, and arthroscopic surgery after sustaining acute traumatic hemarthrosis of a knee. They all had clinically unsuspected subchondral bone injuries demonstrated on MRI with normal radiographs and normal overlying articular cartilage at arthroscopy, consistent with occult fractures. All showed focal bone repair on scintigraphy. Two of the 13 patients showed additional bone injuries only on bone scan. Two other patients scintigraphically showed focal bone repair at the medial femoral condyle due to avulsion of the medial collateral ligament. SPECT was easier to interpret than multi-view planar imaging. Bone scintigraphy confirms subchondral fractures demonstrated on MRI but also demonstrates ligament avulsion injuries and additional more subtle bone injuries.

Amino and iodotamoxifens: synthesis, estrogen receptor affinity and biodistribution

Both geometrical isomers (E and Z) of an aminotamoxifen (2) have been prepared as precursors of the corresponding E and Z iodotamoxifens (1). The ability of E and Z-1 and 2 to compete with [3H]estradiol for estrogen receptors in rat uterine cytosol was measured relative to Z-tamoxifen and estradiol. The four tamoxifen derivatives showed affinities ranging from 50% to 1600% of that of tamoxifen. Under the same conditions, tamoxifen's relative binding affinity was 0.2% of that of estradiol. Preparative routes to the radioiodo-tamoxifens, [131I]-E and Z-1, were also developed and provided approximately 100 MBq of 'no carrier added' material in 40-60% radiochemical yield. Study of the biodistribution of these radioligands in tumor-bearing mice demonstrated significant radioactivity in the tumors and in the uterus. For [131I]-E-1, target to background ratios reached 28 for uterus/blood and 10 for tumor/blood; corresponding optimum ratios for [131I]-Z-1 were 10 and 5. A washout study using estradiol indicated selective uptake in the uterus of Swiss white mice. However, tumor uptake and image contrast in humans following intravenous administration of either [131I]-E or Z-1 were insufficient to allow diagnostic use of the radioiodotamoxifens.

Systemic Hypovolemia after Subarachnoid Hemorrhage

Two patients who had suffered subrachnoid hemorrhage were subjected to intensive monitoring of parameters of circulating blood flow, cardiovascular dynamics, and fluid and electrolyte balance. Among the parameters studied were red cell volume, plasma volume, and total blood volume, cardiac output, and central venous and pulmonary capillary wedge pressures. Both patients experienced acute neurological deterioration during the study. Red cell volume fell in a premonitory fashion prior to neurological deterioration in both, and in one patient plasma volume and total blood volume decreased by almost 50% in the 5 days prior to neurological deterioration. Central venous and pulmonary capillary wedge pressures fell initially but did not predict the deterioration. Systemic vascular resistance fell prior to clinical deterioration in one patient following ventriculoperitoneal shunting, and in the other following craniotomy and subarachnoid drainage. The falls in systemic vascular resistance may have caused shunting of cardiac output away from the compromised cerebral circulation, thereby triggering neurological deterioration.

Inhaled particle deposition and body habitus

As a result of the intrapleural pressure gradient that exists in the human lung, both ventilation and particle deposition increase from apex to base. Since the intrapleural gradient varies with the height of the subject, it was decided to compare regional particle deposition in tall, short, and obese subjects to ascertain whether it was influenced by height and weight. Surprisingly, deposition in the vertical plane was not significantly influenced by the height of the subject when corrected for ventilated lung volume. In addition, it was shown that in obese subjects there was increased deposition in the middle zones relative to the apices and bases. This finding persisted after correction for ventilated lung volume and differential attenuation resulting from non-uniform thickness of the fat layer in the obese subject's chest. In the tall and short groups there was a consistent pattern in the concentric deposition of particles with there being a gradient from the central or hilar region to the periphery of the lungs, with the latter showing the most deposition.

Clearance of inhaled particles in ankylosing spondylitis

Patients with ankylosing spondylitis may uncommonly develop apical fibrobullous lung disease, the cause of which is unknown. It is postulated here that rigidity of the thoracic cage leads to reduced apical clearance of inhaled particles and may thereby predispose to chronic infection. Deposition and clearance of inhaled technetium-99m sulphur colloid particles were studied in eight male patients with ankylosing spondylitis who had chest wall rigidity (mean (SD) chest expansion 1.8 (1.07) cm) but normal chest radiographs. As a reference population eight healthy male volunteers were also studied. Particle deposition showed an increasing gradient from apex to base, with no significant difference between patients and controls. Clearance was assessed by comparing absolute counts, corrected for decay, at 24 hours with the baseline values. No delay in particle clearance in those with ankylosing spondylitis was apparent.

Cerebral perfusion imaging with technetium-99m HM-PAO in brain death and severe central nervous system injury

We performed 38 cerebral perfusion studies in 33 patients with brain death or with severe central nervous system injury using technetium-99m hexamethyl-propyleneamine oxime [( 99mTc]HM-PAO). Uptake by the cerebrum and/or cerebellium was present in all patients who were not clinically brain dead (ten studies) although the study was often abnormal. In those patients who were brain dead, 16/17 studies demonstrated no uptake in either the cerebrum or cerebellum. In patients suspected of brain death, but who had conditions interfering with the diagnosis the test demonstrated no uptake in 9/11 studies, confirming brain death. A radionuclide angiogram (RNA) of the head was also performed in 33/38 studies and showed complete agreement with the [99mTc]HM-PAO uptake, except in one case. We conclude that cerebral perfusion imaging with [99mTc]HM-PAO is a simple, noninvasive and reliable test to confirm brain death. By comparison with conventional technetium agents, [99mTc]HM-PAO is not dependent on the quality of the bolus injection, is easier to interpret and allows evaluation of posterior fossa blood flow.

The topography of particle deposition in the human lung

The effect of varying particle size on the site of deposition of inhaled particles in the human lung was measured in 11 young healthy male subjects. The simultaneous inhalation of two chemically inert, radiolabelled particles, differing in size but in no other respect, controlled for all other variables including airways geometry, breathing pattern and posture. Under conditions of quiet respiration the larger particles (3.5 microns) were preferentially deposited in the upper rather than the lower zones of the lungs as compared with the smaller particles (1.1 microns). Furthermore, the penetrance of the larger particles beyond the mucociliary escalator was greater for 3.5 microns particles in all lung zones and particularly at the apex. These findings may be of significance in the pathogenesis of those diseases induced by the inhalation of particles, vapours or fumes.

Metabolic effects of continuous subcutaneous insulin infusion: evidence that a rise and fall of portal vein insulin concentration with each major meal facilitates post-absorptive glycemic control

Eighteen lean adult volunteers with insulin-requiring diabetes mellitus attempted to achieve normoglycemia using continuous subcutaneous insulin infusion (CSII) or conventional insulin therapy (CIT) in a randomized crossover trial of 68 +/- 2.5 weeks (mean +/- SEM) duration. As reported (Diabetes Care 8: 447-55, 1985) the group with absent to low beta-cell function (C-peptide negative, n = 11) attained mean post-absorptive normoglycemia only during CSII vs CIT (p less than 0.05). Only following CSII was this without change in post-absorptive serum triglyceride concentrations (-4 +/- 5.6 vs 12 +/- 4.7 mg/dl; -0.04 +/- 0.6 vs 0.14 +/- 0.05 mM, p less than 0.05) or body weight (0.01 +/- 0.02 vs 0.05 +/- 0.01 kg/week, p less than 0.05). In the group with glucagon stimulated serum C-peptide 100-400 pmol/L (C-peptide positive) responses to CSII or CIT were equal. As total daily insulin dosage (0.05 +/- 0.04 U/kg/day) was the same under all conditions, to explain the efficacy of CSII, glucoregulatory hormone responses were examined. Pre- and post-test breakfast serum free immunoreactive insulin and plasma glucagon concentrations were essentially unaffected by C-peptide or treatment status. Erythrocyte 125I-insulin binding was decreased in the C-peptide negative group only during CSII (8.6 +/- 0.5 vs 10.1 +/- 0.7%, p less than 0.005); C-peptide positive group receptor binding was consistently low (8.2 +/- 0.8, 8.4 +/- 0.9%). During CIT using intermediate-acting insulin post-lunch peripheral venous insulin failed to rise (p less than 0.05), but in the C-peptide positive group, on the basis of C-peptide responses to breakfast an undetected rise and fall of portal venous insulin was assumed to coincide with each meal. Thus, only during CIT in the C-peptide negative group, which received on average 6.4/wk/subject fewer pre-meal regular insulin boluses (p less than 0.01), was the frequency of meal-related change in portal insulinemia decreased. Consistent meal-related fluctuations in portal insulinemia inherent in CSII hepatocytes sensitized by a post-receptor mechanism to the suppressive effects of insulin on glucose output and thus were indirectly responsible for the observed improvement in glycemic control and lipid metabolism in the C-peptide negative group.

Gastric emptying before and after transverse gastroplasty for morbid obesity

Twenty-three morbidly obese patients underwent gastric emptying studies (Tc-99m egg salad sandwich--a semisolid meal) preoperatively, and at three months and 12 months postoperatively to evaluate the effect of transverse gastroplasty on gastric emptying and to determine the predictive value of this study for weight loss. At three months pouch emptying was variable with nine of 23 patients having prolonged half-times, and 14 shortened half-times compared with preoperative values, despite both groups having identical weight loss. At 12 months pouch half-times returned to baseline. The data suggests that this type of gastroplasty causes weight loss solely by reducing the gastric volume resulting in reduced meal volume. Weight loss is not related to impaired pouch emptying, which might result in a prolonged feeling of fullness. Gastric emptying studies neither preoperatively nor postoperatively have weight loss predictive value for this particular operation.

Preparation and evaluation of radioiodinated (iodophenyl)cholines and their morpholinium and piperidinium analogues as myocardial perfusion imaging agents

A series of nine radioiodinated quaternary ammonium salts related to phenylcholine were synthesized, characterized, and radiolabeled by exchange. These compounds were evaluated as myocardial perfusion imaging agents in mice, pigs, and humans. Mice biodistribution studies showed that five of the nine compounds were taken up in the heart to the same extent as 201Tl+ at 5 min. At 60 min myocardial retention was significantly better than 201Tl+ for six of the compounds. Several of the compounds showed more favorable heart/blood and heart/liver ratios when compared to 201Tl+. Evaluation of three of the more promising compounds in pigs and humans however revealed no selective myocardial uptake.

Aminophylline and mucociliary clearance in patients with irreversible airflow limitation

Were aminophylline to improve mucociliary function, it might prove useful in the management of irreversible airflow limitation. Eight subjects with irreversible airflow limitation due to emphysema inhaled an aerosol of 99mTc sulphur-colloid particles on each of 2 days. On day 1 aminophylline was administered intravenously, while on the other nothing was given. Particle clearance was measured by recording posterior gamma-camera images sequentially over a 24 h period. No significant differences were recorded between aminophylline and control studies, but there were marked variations in clearance between study days and between individuals. These differences were compatible with the known effects of airways obstruction and breathing pattern on the sites of particle deposition within the bronchial tree. The latter factors appeared to exert a far greater influence on the observed mucociliary clearance than did aminophylline.

Regional deposition of particles in the lung during cigarette smoking in humans

Studies were carried out on 11 habitual cigarette smokers to ascertain whether there was a difference in the regional deposition of particles during cigarette smoking compared with tidal breathing and also to investigate whether the ventilatory maneuvers associated with smoking influence the deposition site. A cigarette holder was constructed that permitted cigarette smoke to mix with a radioaerosol. An added resistance simulated the airflow resistance present in a filter-tipped cigarette. Respiratory patterns for the control period of tidal breathing and during smoking were monitored with a respiratory inductance plethysmograph. Smoking resulted in greater apical and central deposition than expected from the distribution of resting ventilation. The changes in the site of deposition during smoking are probably influenced mainly by the properties of the particles concerned, namely, its size, reactivity, and hygroscopicity. Changes in respiratory patterns that occur during inhalation of cigarette smoke may also have an effect but are difficult to quantify and show marked intersubject variation. In selected subjects smoking caused apical deposition to exceed that of the lower zones.

Zinc absorption and leukocyte zinc in alcoholic and nonalcoholic cirrhosis

To determine if malabsorption of zinc contributes to the zinc deficiency found in cirrhosis, the absorption of an oral dose of ZnCl2, labeled with 65Zn and a nonabsorbed marker 51CrCl3, was determined from the ratio of these isotopes in a stool specimen. Average 65Zn absorption in 25 alcoholic cirrhotics, 37 +/- 17% (SD), was low compared to 55 +/- 16% in 31 healthy volunteer controls (P less than 0.01). In contrast, mean 65Zn absorption, 47 +/- 11%, in 11 nonalcoholic cirrhotics was not significantly different from the average result in healthy controls. Low 65Zn absorption was accompanied by low leukocyte zinc in a subgroup of alcoholic cirrhotics with ascites and/or ascites and encephalopathy, but not in the subgroup in which these clinical features were absent. Thus, low zinc absorption contributes to zinc deficiency in decompensated alcoholic cirrhosis. The failure to find similar abnormalities in nonalcoholic cirrhosis suggests that the long-standing consumption of alcoholic beverages contributes to the malabsorption of zinc.

Does the oral zinc tolerance test measure zinc absorption?

Increases in plasma zinc concentration were compared with radiozinc absorption after oral test doses. Ten healthy, fasting subjects were each given 385 mumol zinc chloride (25 mg Zn) labelled with 0.5 muCi 65ZnCl2 and a non-absorbed marker, 51CrCl3, dissolved in 100 ml of water; another 10 persons were given 354 mumol zinc chloride and 125 g of minced turkey containing 31 mumol zinc also labelled with 65Zn and 51Cr. Measurements were made of plasma zinc concentration at hourly intervals for 5 hours, radiozinc absorption by stool counting of unabsorbed radioactivity 12-36 hours later, and radiozinc retention by whole body counting at 7 days. The mean percentage of radiozinc absorbed and retained in the body from the two test meals was found to be identical (42%). In contrast the increased area under the plasma zinc curve up to 5 hours after the turkey meal, 28 +/- 9 mumol/L (mean +/- SD) was significantly less than that for zinc chloride alone, 47 +/- 15 mumol/L, p less than 0.005. Despite this difference, a good correlation was found between the area under the plasma zinc curve and 65Zn absorption in individual subjects after each meal. The discrepancy between the results of zinc absorption derived from the plasma zinc curve and 65Zn absorption for the liquid and solid test meals was most likely explained by binding of zinc to food and delayed gastric emptying of the solid meal. With a test meal of turkey meat at least this dampened the plasma appearance of zinc but did not affect its overall absorption.

Dual-isotope method for determination of human zinc absorption: the use of a test meal of turkey meat

The percentage of 65Zn taken up (absorbed) from extrinsically labeled turkey meat was calculated from the amounts of 65Zn and a nonabsorbed 51Cr marker present in the body or in a single stool specimen after 1-2 d. 51CrCl3 proved to be a suitable marker for unabsorbed 65Zn and so the early determination of 65Zn absorption was possible. With stool counting, 65Zn absorption data from first stool samples after 1-2 d were accurate as judged by correlation with the amount of 65Zn in the body 7-10 d later (retention); results from subsequent stools gave lower absorption values due to the early excretion of some absorbed 65Zn. The dual-isotope method gave reproducible results when four successive tests of zinc absorption were carried out in a group of six subjects. The average (mean +/- SD) 65Zn absorption from turkey meals containing 31 mumol (2 mg) and 46 mumol (3 mg) of zinc was 39 +/- 8% and 29 +/- 6%, respectively, measured by stool counting; 65Zn absorption and retention correlated well in both studies. A series of different beverages was given in place of water with the turkey meal. Orange juice significantly reduced 65Zn absorption and milk also showed this tendency, but tea, whiskey, wine or beer had no significant effect on the absorption of 65Zn from the turkey meal. In groups of subjects the mean ratio of 65Zn absorption from extrinsically labeled turkey meat on two occasions (1.06) was not significantly different from that of the absorption of extrinsic to intrinsic 65Zn labels (1.16). The dual-isotope technique with either stool or body counting is suitable for the rapid determination of 65Zn absorption from extrinsically labeled turkey within 2 d.

Effects of iron, tin, and copper on zinc absorption in humans

Zinc absorption as measured by body retention of [65Zn]zinc chloride or a turkey test meal extrinsically labeled with 65Zn was determined in human subjects by whole body counting after 7 days. Average 65Zn absorption from zinc chloride in persons with a high iron-absorbing capacity was similar to persons with a low capacity to absorb iron. Inorganic iron, 920 mumol (51 mg), or HB iron, 480 mumol (26 mg), inhibited 65Zn absorption from 92 mumol (6 mg) of zinc chloride. When 610 mumol of iron (34 mg) was added to a turkey test meal containing 61 mumol of zinc (4 mg), 65Zn absorption was not inhibited. Tin, 306 mumol (36 mg), given with zinc chloride or turkey test meals (61 mumol, 4 mg, of Zn) significantly reduced 65Zn absorption. Copper, 79 mumol (5 mg), had no significant effect on the 65Zn absorption from 7.9 mumol (0.5 mg) of zinc chloride. In summary, the capacity to absorb iron did not influence 65Zn absorption, but both inorganic iron and heme-iron inhibited 65Zn absorption from zinc chloride. Inorganic iron had no effect, however, on 65Zn absorption from the turkey test meal. Tin in a large dose also inhibited 65Zn absorption from both zinc chloride and the turkey test meal.

The effect of exercise on the deposition of an inhaled aerosol

We investigated the regional deposition in the lungs, of an inhaled submicron aerosol at rest and during exercise in 13 normal volunteers of whom 5 were cigarette smokers. The degree of exercise (VO2 approximately 2 L/min) was chosen to simulate moderately heavy physical labour. Tracheobronchial and alveolar components of deposition were measured by comparing images immediately after inhalation of aerosol and 24 h later when mucociliary clearance was complete. At rest almost all deposition was alveolar (97%). The increase in total deposition on exercise was of similar order to the increase in ventilation. On exercise regional alveolar deposition became more even, although basal still exceeded apical deposition. Tracheobronchial deposition on exercise was increased in all zones but particularly in the upper zones, thereby contrasting with the base to apex gradient of parenchymal deposition. These changes were exaggerated in the smokers. The increased upper zone tracheobronchial deposition may have implications in regard to the pathogenesis of diseases caused by the inhalation of dusts and fumes.

Radionuclide diagnosis of splenic rupture in infectious mononucleosis

Spontaneous splenic rupture is a rare but serious complication of infectious mononucleosis. Although radionuclide spleen imaging is a well accepted method for diagnosis of traumatic rupture, interpretation can be difficult in the setting of mononucleosis, as tears may be ill-defined and diagnosis hampered by inhomogeneous splenic uptake. Four proven cases of spontaneous rupture are presented, three of which illustrate these diagnostic problems.

Histamine bronchial challenge: effect on regional ventilation and aerosol deposition

We studied regional changes in ventilation and aerosol deposition after histamine challenge in six patients with asthma and two with rhinitis and a history of wheezing. All were known to have bronchial hyperreactivity and all showed an increased response to histamine. Ventilation and aerosol deposition studies, using xenon-133 and an aerosol of sulphur colloid tagged with technetium 99m, were performed while they were sitting. Before administration of histamine radioaerosol scintiscans were abnormal in five of six patients; after histamine challenge all were abnormal and central deposition was significantly greater in all of them. The decrease in aerosol penetration correlated with the percentage decrease in FEV1, indicating that the efficiency of aerodynamic filtration depends on the degree of airway narrowing. In six of the eight subjects the distribution of ventilation changed from predominantly basal to predominantly apical after histamine, which suggests the airways response was greater, at least initially, in the better ventilated regions. This indicates a close relationship between regional ventilation and the site of histamine deposition and has implications for the delivery of aerosolised agents in general.

Diagnosing papillary stenosis by technetium-99m HIDA scanning

The diagnosis of papillary stenosis, occasionally seen after cholecystectomy, is confirmed by endoscopic retrograde cholangiopancreatography (ERCP), which demonstrates delayed emptying of contrast material into the duodenum for more than 45 minutes. The authors assessed 2,6-dimethyl phenyl carbamoyl methyl iminodiacetic acid labelled with technetium-99m (99mTc HIDA) as a less invasive procedure in these circumstances by comparing it with the findings from ERCP. Twenty-six patients who had pain after cholecystectomy were studied by continuous 1-hour scintigraphy after injection of 99mTc HIDA. Biliary flow was estimated by measuring uptake and clearance of the entire liver and common bile duct. Volunteers who had no pain after cholecystectomy served as controls. Of the 26 study patients, all 99mTc HIDA scan findings were within the control range in 11. Of these, 10 had normal biliary drainage confirmed by ERCP. The one patient with delayed drainage did not improve after endoscopic sphincterotomy. Two patients demonstrated pooling of 99mTc HIDA in cystic dilatations of the biliary tree, while the other 13 patients had obstruction of the distal common bile duct and impaired flow demonstrated on the 99mTc HIDA scan. All 13 of these patients had papillary stenosis proven by ERCP. The authors conclude that 99mTc HIDA scanning is a valuable, minimally invasive method of diagnosing papillary stenosis.

Factors influencing the regional deposition of inhaled particles in man

1. Although ventilation in normal human lungs has been shown to decrease from apex to base, comparable observations are lacking in regard to particle deposition. 2. We compared regional ventilation and particle deposition in normal subjects by using radioactive xenon and a radioactive aerosol while sitting, lying, and while breathing at an increased rate. Both smokers and non-smokers were studied. 3. Particle deposition and ventilation were closely related, and the greater the ventilation the greater the deposition of particles, a situation which prevailed irrespective of position and breathing rate. While supine, the apex to base gradient for both ventilation and particle deposition decreased but did not entirely disappear. At higher respiratory rates, central deposition of particles, especially in smokers, increased. 4. We concluded that there are regional differences in the deposition of particles and that such differences are closely related to regional ventilation.

Technique for determination of human zinc absorption from measurement of radioactivity in a fecal sample or the body

The intestinal absorption of an oral dose of zinc chloride was determined from the ratio of 65Zn and a nonabsorbed radioactive marker, 51Cr, present in a single stool specimen or the body 24-72 h later. Chromic chloride had no effect on [65Zn]zinc chloride absorption and 51Cr and 65Zn had similar intestinal transit times. In 17 healthy control subjects given 92 mumol ZnCl2 labeled with 0.5 microCi 65Zn, 52 +/- 14% (SD) of the dose was taken up from the lumen. Intestinal absorption of 65Zn at 24 h correlated closely with 65Zn body retention of zinc measured by whole-body counting 7 days later, r = 0.995. Neither zinc absorption nor zinc retention correlated with blood leukocyte zinc levels. An average of 55% of 65Zn was retained in the body from doses of 18-90 mumol ZnCl2 but a progressively smaller proportion of zinc was absorbed from doses of 180-900 mumol. The average absorption and body retention of 65Zn were significantly reduced in 7 patients with mucosal disease of the proximal intestine but they were not affected by resection of the lower jejunum, ileum, and colon. Thus the absorption of ZnCl2 from a 92-mumol dose predominantly takes place by a rate-limited mechanism in the duodenum and upper jejunum.

The relationship between iron and lead absorption in humans

Approximately 60% of an oral dose of 100 micrograms of 203Pb was retained in 85 fasting subjects with no difference noted between males and females. Body retention was proportional to dose up to 400 micrograms of lead. It was not related to the capacity to absorb iron or to the size of body iron stores, nor was it affected by the simultaneous ingestion of a 10-fold molar excess of iron. The effect of several dietary factors was also determined. Lead retention was lowered by eating food, slightly increased by ingestion of fat, but was unaffected by the administration of lactose or a 10-fold molar excess of zinc, cobalt, or calcium. One chelating agent, ascorbic acid, slightly lowered lead retention, whereas another agent ethylenediaminetetraacetic acid, produced a marked reduction. Several of these results suggest that human gastrointestinal lead absorption behaves differently to that of rodents. In particular, human lead retention was found to be unrelated to iron absorption or to body iron stores.

Electrocardiography, cardioenzymes and myocardial imaging to detect perioperative myocardial infarction

Serial electrocardiography, technetium-99m pyrophosphate scintigraphy and measurement of myocardial creatine kinase (CK2) and lactic dehydrogenase isoenzyme activity (specifically the LD1 to LD2 ratio) were evaluated prospectively in 26 patients who underwent aortocoronary bypass grafting and 11 patients who underwent valvular or other thoracic surgery, as methods of diagnosing perioperative myocardial infarction. Of the 26 patients who had aorto coronary bypass grafting, 7 (group 1) had myocardial infarction perioperatively; of these, only 2 had positive results from all four diagnostic tests. The other 19 patients (group 2) had no perioperative myocardial infarction and the only diagnostic method yielding positive results was the LD1 to LD2 ratio, in 7 of the 19. In the 11 patients who did not undergo aortocoronary bypass grafting (group 3), only 1 patient had myocardial infarction perioperatively; results from the measurement of CK2 isoenzyme activity and LD1 to LD2 ratio were positive while electrocardiography and 99mTc pyrophosphate scintigraphy yielded negative results. The respective sensitivity (%) and specificity (%) of the four diagnostic methods were as follows: electrocardiography: 38, 100; 99mTc pyrophosphate scintigraphy: 88, 100; LD1 to LD2 ratio: 100, 68; CK2: 38, 100. When the CK2 criterion was redefined, using patients in group 2 as controls, the sensitivity and specificity of this method became 100 and 90 respectively. The authors conclude that 99MTc pyrophosphate scintigraphy and measurement of myocardial creatine kinase isoenzyme are of comparable value and are the most reliable indicators of perioperative myocardial infarction.

Platelet interaction within giant intracranial aneurysms

Turbulence within intracranial aneurysms may result in tearing of the aneurysmal wall, exposing the subendothelial matrix to circulating platelets. In this study, platelet interaction in giant intracranial aneurysms was evaluated by a dual-isotope technique employing In-labeled platelets and Tc-labeled red blood cells. The use of two isotopes allows the subtraction of the blood pool and the calculation of the ratio indium deposited:indium blood pool (In(D)/In(BP)). A ratio greater than zero indicates platelet deposition within aneurysm. Thirteen patients were evaluated in this way, with platelet deposition demonstrated in six. In these six patients, the ratio In(D)/In(BP) was found to be significantly elevated, with a mean value of 0.96 +/- 0.65. Three of these six patients has symptoms of recurrent transient neurological deficits; one of these three suffered a complete stroke following documentation of platelet deposition. In this case, the aneurysm was obtained at surgery and was found to contain intraluminal platelet aggregation when viewed by scanning electron microscopy. In the remaining seven patients, the ratio IN(D)/In(BP) was found not to be significantly elevated (mean -0.03 &/- 0.06), indicating the absence of active platelet deposition. Two of these patients had prior symptoms of cerebral ischemia; one of these was found to have an ulcer in the ipsilateral internal carotid artery which was probably responsible for thromboembolic events to the hemisphere. The authors conclude that platelet aggregation occurs more frequently than previously recognized in giant intracranial aneurysms, and their data substantiate the hypothesis that platelet metabolic products or thrombi originating from a large aneurysm may embolize to distal cerebral vessels.

Reticuloendothelial function in rheumatoid arthritis: correlation with disease activity and circulating immune complexes

Fourteen patients with active rheumatoid arthritis had their reticuloendothelial function tested with clearance of heat damaged radiolabeled autologous erythrocytes. Only 3 of these 14 patients had prolonged red blood cell (RBC) clearance. No correlation was found between RBC clearance and level of circulating immune complexes, disease activity or disease duration.

Stress myocardial imaging in mitral leaflet prolapse syndrome

Mitral leaflet prolapse syndrome has been associated with anginal chest pain, atypical chest pain, electrocardiographic abnormalities and positive stress electrocardiograms. These features overlap those of ischemic heart disease. Furthermore, coronary artery disease is frequently associated with mitral leaflet prolapse. This study evaluated the usefulness of stress myocardial scintigraphy in distinguishing these two disorders. Thirty-two patients with an angiographic diagnosis of mitral leaflet prolapse were studied. Of the 22 patients (8 men and 14 women, mean age 48 years) with a normal coronary arteriogram, 5 had "typical" angina pectoris, 6 had resting electrocardiographic abnormalities and 6 had a positive stress electrocardiogram; all 22 patients had a normal stress myocardial scintigram. Of the 10 patients (7 men and 3 women, mean age 55 years) with at least 70 percent stenosis of one coronary artery, 6 had "typical" angina pectoris, 1 had resting electrocardiographic abnormalities and 7 had a positive stress electrocardiogram. Nine of these 10 patients had one or more demonstrable perfusion defects on stress myocardial scintigrams. It is concluded that mitral leaflet prolapse syndrome is not associated with regional myocardial ischemia as demonstrated with stress scintigraphy, and that stress scintigraphy, a noninvasive technique, is useful in distinguishing the mitral prolapse syndrome from mitral prolapse associated with coronary artery disease.

Radionuclide angiocardiography, a noninvasive method for evaluating left ventricular ejection fraction and regional wall motion; comparison with contrast left ventricular angiography

The efficacy of gated synchronous acquisition (GSA) after cardiac blood pool labelling in assessing left ventricular function (ejection fraction and regional wall motion) was evaluated in 31 patients within 24 hours of contrast left ventricular angiography. With the R-wave of the electrocardiogram as a physiologic marker, radionuclide data recorded into an on-line computer allowed construction of cardiac blood pool images during sequential periods of the cardiac cycle. The images, of high count density, have good spatial resolution and can be viewed repetitively in real time in a cine mode. The ejection fractions calculated from the left ventricular time-activity curves corrected for background activity correlated well with the ejection fractions determined from dimension analysis of the contrast left ventricular angiograms (r = 0.87). The results were highly reproducible (r = 0.97). Results of analysis of left ventricular wall motion were similar with the two types of angiograms in 26 of the 31 subjects. GSA is a simple, safe means of evaluating left ventricular ejection fraction and regional wall motion noninvasively.

Diagnostic efficacy of tests for the detection of iron overload in chronic liver disease

The value of tests for the detection of body iron overload was investigated in 8 patients with clinically manifest primary hemochromatosis, 12 patients with cirrhosis and iron overload and 20 patients with liver disease and low or normal iron stores. Iron overload was defined as the presence of stainable iron in more than 50% of hepatocytes in a liver biopsy specimen. The percentages of patients with a true-positive (abnormal) or true-negative (normal) result were: serum iron concentration 65%, transferin saturation 85%, serum ferritin concentration 78%, serum ferritin:serum glutamic oxaloacetic transaminase (SGOT) index 78%, percent iron absorption 58%, percent iron absorption in relation to serum ferritin concentration 80% and percent iron absorption in relation to serum ferritin:SGOT index 93%. The calculated predictive value of a normal test result for the exclusion of iron overload in patients with liver disease, a group with an assumed prevalence of iron overload of 10%, was 98% to 99% for transferrin saturation and serum ferritin concentration used alone and 100% for these measures used together; the predictive value of an abnormal result for the diagnosis of iron overload was less than 50% for all of the above measures used alone or in combination. Hence, in patients with an increased serum ferritin concentration or transferrin saturation, or both, determination of the hepatocellular iron content of a specimen from a percutaneous liver biopsy is required for the diagnosis of iron overload.

Increased dietary cadmium absorption in mice and human subjects with iron deficiency

In mice fed a low iron diet, the addition of low levels of cadmium chloride (10 micrometer) to the drinking water impaired growth and accentuated the development of anemia. Cadmium had no effect on mice given a similar diet supplemented with iron. Iron deficiency increased the concentration of cadmium in the duodenal mucosa, the transfer of cadmium to the body from the intestinal tract, and the deposition of absorbed cadmium in the kidneys. In human subjects, the average absorption of 25 microgram of cadmium, labeled with 115mCd, from a test meal was 8.9 +/- 2.0% (mean +/- SE) in 10 people with low body iron stores (serum ferritin less than 20 ng per ml) and 2.3 +/- 0.3% in 12 subjects with normal iron stores (serum ferritin greater than 23 ng per ml). The biological half-time of the radiocadmium in 3 of the subjects ranged from 90 to 202 days. Thus, the intestinal adaptive response to iron deficiency in both experimental animals and human subjects leads to the increased absorption of cadmium, a potentially toxic element.

Noninvasive assessment of patients following aortocoronary bypass surgery

A simple, accurate, noninvasive method is required for the objective evaluation of aortocoronary bypass surgery. Stress myocardial imaging with intravenous injection of potassium-43 or thallium-201 was used an average of 4.4 months after direct myocardial revascularization in 77 patients to assess the accuracy of stress myocardial imaging in predicting completeness of revascularization. The results were correlated with maximal treadmill exercise tests, extent of revascularization and status of bypass grafts (occlusion, stenosis and distal disease). We found stress myocardial imaging to be a more sensitive method than the stress electrocardiogram for the detection of incomplete revascularization. The method appears to be a sensitive noninvasive means of evaluating the results of aortocoronary bypass surgery.

Measurement of dietary cadmium absorption in humans

Total body counting was used to determine cadmium absorption in 14 healthy subjects and in 1 patient with an ileostomy. Breakfast was extrinsically tagged with 115mCdCl2, and a poorly absorbed marker, 51CrCl3, was added to determine the point of complete elimination of unabsorbed radiocadmium from the gastrointestinal tract. The 51Cr was not an ideal marker: fecal excretion of radiocadmium continued beyond the point at which chromium was completely eliminated from the body, Nevertheless, it was helpful in six subjects in identifying the presence of unabsorbed radiocadmium still in transit in the lumen of the gastrointestinal tract 3--5 wk after the test meal. The average body retention of radiocadmium determined between 7 and 14 d after the disappearance of the chromium marker from the body was 4.6 +/- 4.0% (SD), with a range of 0.7--15.6%. The biological half-time of absorbed radiocadmium in one of the subjects was 100 d.

Predictive value of myocardial perfusion imaging for aortocoronary bypass surgery

Evaluation of patients for aotocoronary bypass (ACB) surgery is dependent on the findings at cardiac catheterization. Left ventricular angiography cannot distinguish between reversible and irreversible myocardial dysfunction. In 82 patients macroaggregates of human serum albumin, labelled with iodine-131, were injected before operation into the right coronary artery and technetium-99m labelled microspheres were injected into the left coronary artery. Two weeks after operation similar technetium-99m and iodine-131 injections were made into the native vessels and grafted vessels, respectively. Myocardial distribution of the 20 mu particles was visualized with a rectillinear scanner. Sixty-seven patients had normal myocardial perfusion scans preoperatively even though wall motion was abnormal in 34. There was substantial improvement in the left ventricular function of these 34 patients; the mean ejection fraction increased from 56 to 65%. Fifteen patients had abnormal myocardial perfusion scans; improvement in left ventricular function in this group occurred only if the bypass graft was made to an area with normal regional perfusion preoperatively. It is certain that an adequate capillary bed is present if the myocardial scan is normal, regardless of the degree of critical stenosis in either coronary artery. The patient with a completely occluded coronary artery and normal myocardial scan is a good candidate for ACB and will show improved left ventricular contraction if the ACB is patent,