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Biomedical subjects

H Susskind

Publications and source records attributed to H Susskind.

32 records · Page 2Linked to original sources
PubMed1984

Acute response to elastase in sheep lungs measured with Ga-67.

The early inflammatory changes in sheep's lungs were studied with Ga-67 citrate, injected i.v. immediately following intrabronchial instillation of different doses of elastase into the right diaphragmatic lobes of 15 sheep. The elastase-induced lesions in the first five sheep (two received 4,000 units; three got 6,000) were imaged up to seven times in an 8-day period to measure the temporal changes in the lesion and to select the appropriate imaging time; the other ten sheep (800-8,000 units) were imaged once at 52 hr. Localization of Ga-67, as seen on the posterior and right lateral projections, was confined to a well-circumscribed region in the right lung field. The lesion could be detected as early as 4 hr after elastase instillation. It decreased to 60% of its initial area at 4 hr, while the total Ga-67 activity in the sheep remained constant after 52-75 hr. Gallium-67 uptake in the lesion correlated positively with the dose of elastase (r = 0.88, p less than 0.001) and with the reduction in perfusion, as determined 4 wk after the elastase instillation (r = 0.66, p less than 0.05). Early Ga-67 uptake in inflammatory lung lesions could therefore be used as a reliable predictor of the size of the acute elastase-induced inflammatory reaction, as well as of the sequelae involving the regional vascular supply 4 wk later.

Animals↗
PubMed1983

Evaluation of the urinary desmosine radioimmunoassay as a monitor of lung injury after endobronchial elastase instillation in sheep.

Thirty male sheep were treated with varying doses of endobronchial elastase. Urinary excretion of elastin peptides was then measured by desmosine radioimmunoassay and compared with pre-enzyme values. Mean linear intercepts were measured in treated and untreated lobes 4 wk later, and in addition, lung perfusion, ventilation, and volume were measured before enzyme treatment and 4 wk later using radionuclide-imaging techniques. Most of the elevation in urinary desmosine excretion occurred in the first 48 h after elastase administration. The increase in desmosine excretion was positively correlated with: enzyme dose (r = 0.74, p less than 0.01), increase in mean linear intercept (r = 0.61, p less than 0.05), decrease in lung perfusion (r = 0.77, p less than 0.01), and decrease in ventilation (r = 0.58, p less than 0.05). These results demonstrate that the urinary desmosine radioimmunoassay is a reliable index of pulmonary elastin breakdown and of several resultant anatomic and physiologic stigmata of pulmonary emphysema.

Amino Acids↗
PubMed1981

Comparison of airway closure measured in vivo and from single-breath washout curve.

The volume of air trapped (Vat) in alveoli subtended by airways closed at residual volume (RV) was correlated with the volume of air left in the lungs at the start of airway closure (CC) in a clinical study of 13 patients with a variety of pulmonary disorders and 5 normal subjects. Vat was quantitated at RV from the in vivo distribution differences between 127Xe inspired as a bolus and again after equilibrium; CC was measured from the inflection point on the single-breath washout curve at the onset of phase IV. 127Xe activity was measured with a scintillation camera, and activity profiles were obtained for 28-45 consecutive 6.5-mm horizontal lung slices between base and apex. Three well-defined regions were found: A, in the upper lung, all of whose airways remained completely open; B, located above the base and containing both open and closed airways; and C, above the base, all of whose airways were closed. Of the Vat of 0.43 liter for the normals, 41% was located in region C. For the patients, the values were 59% of 0.59 liter. The relationship between the onset of phase IV and regional airway closure was confirmed for normals as well as patients. A statistically significant increase in closure was found for the patients over the normals. Excellent agreement was obtained between Vat/TLC (total lung capacity) and CC/TLC (r = 0.79, P less than 0.001) for normals as well as patients, and CC appears to reflect regional airway closure in both health and disease. Similar excellent agreement was obtained for the normals between lung height with closed airways and CC/TLC (r = 0.88, P less than 0.001). Vat appears to be the most important physiological determinant of phase IV, the value at RV representing the limiting case.

Adult↗
PubMed1981

Sensitivity of Kr-81m and Xe-127 in evaluating nonembolic pulmonary disease.

The relative sensitivities of Kr-81m and Xe-127 in detecting lung ventilation defects was evaluated in 80 patients with nonembolic pulmonary diseases. Krypton-81m ventilation images (500,000 count) were interdigitated with Tc-99m MAA perfusion images; both were compared with Xe-127 images. The distributions of the two gases were also compared on the basis of point-by-point computer analyses. Xenon-127 was found to be more sensitive than Kr-81m in clinical evaluations of scintiphotos--although they were equivalent by computer analyses--in indicating regions of impaired ventilation in patients with obstructive airways disease.

Computers↗
PubMed1978

Reproducibility of ventilation studies.

Differences in ventilation patterns were observed in several instances in two consecutive ventilation studies with 127 Xe and 133Xe gas involving a group of 20 patients with COPD and other pulmonary disorders. Included were differences in the distribution of a tracer gas bolus during the initial inspiration, the distribution of gas tracer after equilibration and during gas washout, artifacts external to the lung, and variations in the half-time for gas washout. The observed discrepancies are clinically significant and could lead to erroneous or ambiguous diagnoses.

Aged↗
PubMed1978

Studies of whole-body retention and clearance of inhaled noble gases.

The in vivo measurements of 127Xe and 79Kr clearance from the whole body indicate five components, with biologic half-times ranging from 13 sec to 17.04 h. The slowest component correlated highly with percent total-body fat, the half-time varying between 7.59 and 17.04 for xenon and between 4.20 and 9.62 h for krypton. The long-term retention was localized to regions of high fat content as determined by the coincidence mode of the whole-body counter and images obtained with the scintillation camera. The estimated dose based on the retention data of this study would indicate increased doses to body fat and gonads as compared with those previously calculated. These increased doses are due to the longer retention of noble gases in fat. After 10-min inhalations of a mixture of 127Xe and air and 79Kr and air, approximately one third of the total 127Xe and one fifth of the total 79Kr were transferred to the body tissues, extrapolated back to the start of gas washout. Of this amount, approximately 13% of the 127Xe and approximately 9% of the 79Kr were associated with the slowest component.

Adipose Tissue↗
PubMed1977

Whole-body retention of radioxenon.

The total-body retention of 127Xe, and its variation with time following short, nonequilibrium periods of inhalation, were measured in vivo so as to refine dosimetry calculations. Radioactivity in the chest region and in the recirculating xenon-air mixture was measured continuously during re-breathing of the gas mixture and in the first 5 min of the immediate gas-washout period using a scintillation camera and shielded NaI detector, respectively. Subjects were then counted in a whole-body counter at varying time intervals until background levels were reached, usually in 72 hr. Five components of Xe clearance from the entire body were measured; they had biologic half-times of 21.7+/-12.4 sec, 3.05+/-1.72 min, 0.04+/-0.11 hr, and 2.71+/-0.87 hr, and a long-term component varied between 7.59 and 17.04 hr. The half-time of the last component correlated highly with the percent of total-body fat. After 10-min inhalations of the xenon-air mixture, approximately one-third of the total xenon was transferred to the body tissues, extrapolated back to the start of gas washout. Of this amount, 13% was associated with the slowest component of clearance.

Adipose Tissue↗
PubMed1977

A clinical comparison of Xe-127 and Xe-133 for ventilation studies.

Xenon-133 and xenon-127 were compared by performing ventilation studies with both radionuclides in 19 patients with a variety of lung diseases. Assessment of the counting rate over the chest, relative to the radioactivity in the lungs, permitted the evaluation of each isotope in terms of usable photons detected by a scintillation camera with a large field of view and appropriate collimation. A greater photon yield was obtained with Xe-127. Markedly improved resolution was shown by measurement of a line phantom, but was not apparent on subjective appraisal of scintiphotos except in the washout phase. Xenon-127 appears to be preferable to Xe-133 because of the higher counting rates, lower patient radiation dose, and longer shelf life. In addition, a prior perfusion study using a Tc-99m radiopharmaceutical does not affect the quality of a Xe-127 ventilation study. The use of Xe-127 therefore permits the selection for ventilation studies of only those patients with suspected pulmonary embolism, and eliminates unnecessary radiation exposure. A further improvement in image quality obtained with Xe-127 should be possible with certain modifications of the scintillation camera that would permit use of the 375-keV photopeak along with the 172- and 203-keV gamma energies. Charcoal traps designed for Xe-133 will require additional shielding and longer storage time when used for Xe-127. Xenon-127, however, might be used again after appropriate processing.

Adult↗
PubMed1973

Closing volume.

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Adolescent↗
PubMedDate not supplied

Assessment of elastase-induced structural and functional changes in sheep lungs.

A large-animal model of elastase-induced emphysema is being developed, which permits the evaluation of corresponding changes in lung structure and function under controlled conditions. Varying doses of elastase were instilled intrabronchially into the lower right lobes of 12 sheep. Changes in regional distribution of lung perfusion (Q) and ventilation (V), corrected for lung volume, were determined from in vivo measurements with radioactive Tc-99m MAA, Kr-81m and Xe-127, respectively, before and four weeks after elastase treatment. Lung injury was assessed by histological examinations of tissue removed post mortem. A positive correlation (r = 0.74; p less than 0.01) was observed between the dose of instilled elastase (range: 800-8,000 units) and a reduction in Q. A decrease in Q also correlated significantly (r = 0.63; p less than 0.05) with an increase in alveolar mean linear intercept (Lm). V also decreased with increasing dose of elastase and with increasing Lm, but the results did not attain statistical significance. These results suggest that computer analysis of regional Q and V by radionuclide imaging techniques represents a reliable, sensitive and non-invasive means of assessing elastase-induced pulmonary injury in the sheep.

Animals↗