Analysis of interpenetrating polymer networks via quartz crystal microbalance with dissipation monitoring.

A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to assess the physical properties of interpenetrating polymer networks (IPNs) through swelling experiments in ambient humidity and in phosphate-buffered saline (PBS), pH 7.4. The IPNs, based on acrylamide (AAm) and poly(ethylene glycol) (pEG), swell from thin, rigid films when dry (16.7 +/- 5.2 nm on Si/SiO(2)) to expanded, viscoelastic films when hydrated (107 +/- 24.2 nm on Si/SiO2). The dry IPNs could be analyzed using the Sauerbrey relationship, but for the hydrated films it was necessary to interpret QCM-D data with a Kelvin-Voigt viscoelastic model. A complex modulus |G| of 116 +/- 38.1 kPa for the swollen IPN surface on Si/SiO2 was defined by the model. The QCM-D was also employed to quantify the adsorption of human fibrinogen, a protein important in thrombus formation, onto the IPNs. Fibrinogen adsorption studies demonstrated the sensitivity of the QCM-D, as well as confirmed the nonfouling nature of the IPN surface, where less than 5 ng/cm2 of fibrinogen was adsorbed.

Regional lung function in asbestos workers: observations and speculations.

The clinical findings, occupational exposure, smoking history, pulmonary function, chest radiograph and ventilation-perfusion studies have been examined in 12 men exposed to asbestos fibers in the course of their work. Minor abnormalities of regional ventilation, consistent with early small airway dysfunction, were found in the fibrotic zones of most of the nonsmokers or mild cigarette smokers. The whole-lung washout times, estimated by visual inspection of serial washout images, were strongly correlated with measurements of airflow obstruction, but not with pack-years of smoking. There was a close correspondence between radiographic extent of pulmonary fibrosis and the abnormalities in pulmonary blood flow in these regions. The severity of the abnormalities in regional pulmonary blood flow was significantly correlated with the years of asbestos exposure (r = + 0.73, p less than 0.01). It is suggested that the magnitude of the disturbance in pulmonary blood flow in the fibrotic zones could be used to estimate the proportion of pulmonary dysfunction due to asbestos exposure.

Patterns of regional ventilation in patients with cardiomegaly or left heart failure.

Patterns of regional ventilation have been examined in 42 patients, the majority of whom had clinical evidence of left-ventricular or left-atrial dysfunction. Regional ventilation was studied with xenon-133 and regional perfusion with Tc-99m human albumin microspheres. The presence of a cardiac defect, seen in 54.8% of the washin images, was related to the depth of lung between the posterior heart border and the posterior lung border, but not to cardiac size. Washout patterns were fairly uniform in those patients (43%) who cleared their lungs within 3 min, but were remarkably variable in those with longer washout times. The presence of râles or clinical signs of a pleural effusion, and radiographic evidence of vascular redistribution or pleural effusion, were significantly associated with prolonged washout times. These observations suggest that the prolonged washout is due to edema in the walls of the smaller bronchioles, leading to airflow obstruction.

Observations and speculations on perfusion patterns in apparently normal lung scans.

The patterns of pulmonary blood flow have been studied in 21 apparently normal perfusion scans. Two patterns were identified, a predominantly lower lobar distribution and a more even pattern. The predominantly lower lobar distribution is probably the more normal pattern, which suggests that in addition to the relationships between alveolar pressure, pulmonary vascular pressures and gravity, the anatomical structure of the lung also influences the regional distribution of blood flow. West's zone I was identified in 20 of the patients and occupied, on average, 16% of the vertical height of the lung. It is suggested that recognition of this zone may enable mean pulmonary arterial pressure to be measured from a combination of ventilation-perfusion imaging and the chest radiograph.

Technetium colloid bone marrow imaging in Fanconi's anemia.

Four patients with Fanconi's anemia were evaluated with 99mTc-sulfur colloid bone marrow scans. The scans revealed similar paradoxical and irregular tracer distribution in all four patients. Normal to increased activity was demonstrated in the proximal metaphyses of the humeri with varying degrees of increased activity in more primitive marrow sites in the distal diaphyses of the humeri and tibia, the distal metaphyses of the humeri and femora, and the proximal metaphyses of the ulnae, radii, and tibia. Skip areas of normal distribution were seen in the proximal diaphyses of the humeri and femora. Although the scan reflects only the reticuloendothelial portion of bone marrow, it may be of some value in the differential diagnosis of pancytopenia.

Scrotal scanning: present value and limits of interpretation.

Forty-three testicular scans have been performed on 38 patients presenting with various scrotal symptoms. Scan diagnosis correlated correctly with the clinical findings in 86 per cent of cases. The most common cause of false positive testicular scan was found to be hydrocele. The mechanism responsible for this observation has been explored in a rat model. A false negative diagnosis was made in 2 cases owing to a small retracted scrotum in 1 patient and a markedly late discovered torsion in the second.

Observations on regional ventilation and perfusion in kyphoscoliosis.

Studies of regional ventilation and perfusion have been made in 10 patients with kyphoscoliosis. In 7 of the 10 patients ventilation was more severely impaired in the region of the maximum convexity than in the opposite lung. Perfusion was not impaired to the same degree. The resulting locally diminished ventilation-perfusion ratios may account for the hypoxemia and increased PA-aO2 gradient seen in patients with kyphoscoliosis. It is suggested that the local distortion of the chest wall, with the splayed out ribs, may account for the local change in lung mechanics.

Angiographic demonstration of non-occlusive hepatic infarction with scintigraphic and microscopic correlation.

The angiographic appearances of histologically proven hepatic infarction without vascular occlusion has not, to our knowledge, been previously described. A case of non-occlusive hepatic infarction in a diabetic patient is presented and correlated with scintigraphic and microscopic findings. It would appear to be the first recorded case of hepatic infarction associated with diabetic ketoacidosis. A follow-up angiogram showed resolution. The literature is briefly reviewed.

Lymphangiography and bone scan in the study of lymphangiomatosis.

Lymphangiomatosis is a rare congenital systemic lymphatic malformation involving multiple bones and other sites. A 12-year old boy with lymphangiomatosis was studied with lymphangiography and bone scan. Lymphangiogram demonstrated irregular pooling of contrast medium in both the mediastinal tumor and bones. Bone scan also revealed increased activity in areas which were not demonstrated radiographically.

The sodium pertechnetate Tc 99m scan: an aid in the evaluation of gastrointestinal bleeding.

Twenty pediatric patients presenting primarily with unexplained gastrointestinal bleeding were evaluated with sodium pertechnetate Tc 99m imaging. Three patients had normal barium enemas and scans consistent with Meckel's diverticulum. These three patients and three additional patients with normal scans underwent surgical exploration. Meckel's diverticula containing gastric mucosa were found in all three patients with positive scans. No diverticula were found in the three patients with normal scans. Four other patients had scans that were considered abnormal but not felt to represent Meckel's diverticula. In one of these patients a radiographic gastrointestinent, a nonspecific terminal ilial ulcer without gastric mucosa was found at surgery. The two other patients had normal radiographic gastrointestinal studies and no further evaluation was carried out. The etiology of gastrointestinal bleeding in pediatric patients is frequently unexplained even after thorough evaluation including celiotomy. The sodium pertechnetate Tc 99m scan is a safe, simple, non-invasive procedure that can demonstrate Meckel's diverticula with greater certainty than the barium enema and can suggest suspicious areas that can then be evaluated by more definitive procedures.