Measuring the distribution of trace elements amongst dissolved colloidal species as a fingerprint for the contribution of tributaries to large boreal rivers.

Organic and inorganic colloids play important roles governing the speciation, transport, and bioaccessibility of trace elements in aquatic systems. These carriers are especially important in the boreal zone, where rivers that contain high concentrations of iron and organic matter are prevalent. The distribution of trace elements amongst different colloidal species (or "speciation profile") can therefore be useful as a fingerprint to detect different trace element sources and for tracking colloid transformations, with implications for bioaccessibility. Asymmetrical flow field-flow fractionation coupled to an inductively coupled plasma mass spectrometer was applied to detect the source of trace elements based on their speciation profile along a 125-km stretch of a large river in the Canadian boreal forest. Both the concentration and proportion of bound trace elements were increased by tributary inputs: bound As, Co, Fe, Mn, Pb, U, and Zn increased monotonically from upstream to downstream, increasingly resembling the speciation profile of tributaries. Principal component (PC) analysis also revealed tributary contributions of bound Cu, Ni, Th, V, and Y reflecting their higher concentrations in tributaries, and PC scores also increased monotonically from upstream-downstream. Monotonically decreasing concentrations of mainly ionic and small (i.e.

Emptying the gallbladder prior to intravenous cholangiography: effect on gallbladder visualization.

Experiments were done to test the hypothesis that emptying the gallbladder prior to intravenous cholangiography (IVC) would result in earler and better opacification of the gallbladder. Five dogs were studied on two separate days in a crossover experiment. Each dog had a standard IVC (15-minute infusion of meglumine iodipamide) 2.5 cc/kg of following a 14-16-hour fasting period. On one of the days, 0.3 mcg/kg of Ceruletide was intramuscularly administered to each dog 30 to 45 minutes prior to the iodipamide infusion. Films obtained at the end of infusion and at 20, 40, 60, and 90 minutes were evaluated independently by three radiologists. The results indicate that pretreatment with Ceruletide produces a significant (p less than 0.05) improvement in the quality of gallbladder opacification during the first 90 minutes following iodipamide infusion. We conclude that earlier and better opacification of the gallbladder during IVC can be obtained by prior emptying of the gallbladder with a cholecystokinetic agent.

Normal and abnormal motility of the stomach.

The analysis of gastric motility makes possible the distinction between purely anatomic changes and those of a functional nature with or without associated morphologic alterations. Hence, through evaluation of gastric and duodenal motor function contributes significantly to the radiographic examination of the upper gastrointestinal tract.

Radionuclide and angiographic studies of placental circulation in man and rhesus monkey.

Imaging maternal and fetal circulation during perfusion of isolated human placental lobules was performed. Radionuclide and contrast angiograms, specimen scans, and histologic preparations obtained on human material during in vitro investigations were compared to the results obtained in vivo on pregnant rhesus monkeys. The distribution of maternal blood flow within the placenta appeared similar in both human and rhesus studies. The 'spurts' of radiopaque medium shown on the contrast angiograms correlated with the appearance of areas of increased radioactivity. These 'hot spots' are located where the uteroplacental spiral arteries open into the intervillous space or where the perfusion cannulae irrigate the maternal side of the placenta. Time-radioactivity curves reached an early peak and remained the same as did their distribution on delayed scans. The 15 to 30 micron microspheres injected into the intervillous spaces are not removed onto the venous side by maternal flow through arteriovenous communications (or 'shunts') but are retained in localized areas of the intervillous space adjacent to the spiral arteries. Many of these microspheres adhere to the 'brush border' of the chorionic villi syncytiotrophoblast. These comparative studies confirm that rhesus monkeys and perfused human placental lobules are relevant models to investigate uteroplacental hemodynamics.

Radiologic evaluation of swallowing.

Diagnostic imaging procedures are useful to analyze the complex mechanism of swallowing. They may be employed beneficially to answer specific questions of swallow coordination, and to distinguish between various forms of airway penetration. The pathophysiology of upper and lower airway involvement may be determined and visualized.

Examination of the patient with dysphagia.

Difficulty in swallowing is not an uncommon symptom. Approximately 10,000 persons choke to death every year in the United States, and at least 50% of patients in nursing homes have some difficulty eating or drinking. Dysphagia will become an increasing problem as the population continues to age, as more intensive resuscitative measures are applied, and as more aggressive head and neck surgery is performed. The practicing radiologist should be familiar with the examination technique and interpretation of swallowing studies.

How I do it: examination of the patient with dysphagia.

Difficulty in swallowing is not an uncommon symptom. Approximately 10,000 persons choke to death every year in the United States, and at least 50% of patients in nursing homes have some difficulty eating or drinking. Dysphagia will become an increasing problem as the population continues to age, as more intensive resuscitative measures are applied, and as more aggressive head and neck surgery is performed. The practicing radiologist should be familiar with the examination technique and interpretation of swallowing studies.

Anatomy and physiology of the pharynx.

Radiographic evaluation of the passage of a bolus from the mouth through the pharynx into the esophagus is based upon identification of specific anatomical landmarks and the integrated motion accomplished by the oral and pharyngeal muscles during swallowing. Twenty-six muscles and 6 cranial nerves must be coordinated to enable the safe performance of the complex physiological task of transporting liquids and firm food from the mouth into the esophagus. The following discussion and illustrations of pharyngeal anatomy and physiology are pertinent to an understanding of normal swallowing function.

Dynamic imaging of the pharynx.

The technique of dynamic imaging of the pharynx and some supplementary maneuvers which can be tailored to the individual patient's needs are discussed in detail. An approach to the analysis of normal and abnormal swallowing studies is presented.

Adaptation, compensation, and decompensation of the pharyngeal swallow.

Under normal circumstances, the act of swallowing adjusts to varying demands of different bolus characteristics and different head and neck postures. When the swallowing mechanism is impaired by disease, adjustment is essential to compensate for the impairment and allow swallowing. Evidence of adjustment can be demonstrated by cineradiography which provides important clues to the presence of underlying disease. When adjustment to disease is inadequate, swallowing decompensates. In this case, gross changes in swallowing performance are evident from clinical evaluation and cineradiography.