Magnetic resonance urography by breath-hold contrast-enhanced three-dimensional FISP

The purpose of this study was to present our initial experience with contrast-enhanced MR urography with a breath-hold three-dimensional imaging technique. We performed MR urographic studies in two pigs (four studies) and five human subjects using gadopentetate dimeglumine. The FISP sequence we used was the same as the one used for contrast-enhanced three-dimensional breath-hold angiography. MR three-dimensional urograms were obtained 7-24 minutes after the contrast injection with a dose as low as .03 mmol/kg. The calyces, renal pelves, and ureters were very well visualized. Three-dimensional MR urography can be acquired within a single breath-hold after administration of gadolinium chelates. This technique could become part of a protocol that could potentially lead to a single comprehensive diagnostic workup for suspected ureteral obstruction and gross hematuria.     

Synaptic physiology and mitochondrial function in crayfish tonic and phasic motor neurons

Phasic and tonic motor neurons of crustaceans differ strikingly in their junctional synaptic physiology. Tonic neurons generally produce small excitatory postsynaptic potentials (EPSPs) that facilitate strongly as stimulation frequency is increased, and normally show no synaptic depression. In contrast, phasic neurons produce relatively large EPSPs with weak frequency facilitation and pronounced depression. We addressed the hypothesis that mitochondrial function is an important determinant of the features of synaptic transmission in these neurons. Mitochondrial fluorescence was measured with confocal microscopy in phasic and tonic axons and terminals of abdominal and leg muscles after exposure to supravital mitochondrial fluorochromes, rhodamine-123 (Rh123) and 4-diethylaminostyryl-N-methylpyridinium iodide (4-Di-2-Asp). Mitochondria of tonic axons and neuromuscular junctions had significantly higher mean Rh123 and 4-Di-2-Asp fluorescence than in phasic neurons, indicating more accumulation of the fluorochromes. Mitochondrial membrane potential, which is responsible for Rh123 uptake and is related to mitochondrial oxidative activity (the production of ATP by oxidation of metabolic substrates), is likely higher in tonic axons. Electron microscopy showed that tonic axons contain approximately fivefold more mitochondria per microm2 cross-sectional area than phasic axons. Neuromuscular junctions of tonic axons also have a much higher mitochondrial content than those of phasic axons. We tested the hypothesis that synaptic fatigue resistance is dependent on mitochondrial function in crayfish motor axons. Impairment of mitochondrial function by uncouplers of oxidative phosphorylation, dinitrophenol or carbonyl cyanide m-chlorophenylhydrazone, or by the electron transport inhibitor sodium azide, led to marked synaptic depression of a tonic axon and accelerated depression of a phasic axon during maintained stimulation. Iodoacetate, an inhibitor of glycolysis, and chloramphenicol, a mitochondrial protein synthesis inhibitor, had no significant effects on either mitochondrial fluorescence or synaptic depression in tonic or phasic axons. Collectively, the results provide evidence that mitochondrial oxidative metabolism is important for sustaining synaptic transmission during maintained stimulation of tonic and phasic motor neurons. Tonic neurons have a higher mitochondrial content and greater oxidative activity; these features are correlated with their greater resistance to synaptic depression. Conversely, phasic neurons have a lower mitochondrial content, less oxidative activity, and greater synaptic fatigability.     

Exhaled breath condensate isoprostanes are elevated in patients with acute lung injury or ARDS

BACKGROUND: Oxidant stress is a purported mechanism of tissue damage in patients with ARDS and acute lung injury (ALI). Isoprostanes, prostanoid compounds primarily formed nonenzymatically via lipid peroxidation, are precise markers of in vivo oxidant stress. Plasma levels of metabolites of 8-iso-prostaglandin-F2alpha (8-iso-PGF2alpha) correlate with outcome in patients with ARDS. OBJECTIVE: To examine exhaled breath condensate levels of 8-iso-PGF2alpha as a noninvasive quantification of pulmonary oxidant stress in patients with, or at risk for, ARDS/ALI. METHODS: Breath condensate was collected from 22 patients with, or at risk for, ARDS/ALI by placing Tygon tubing submerged in an ice bath in line with the expiratory limb of the ventilator circuit. Ten patients without lung disease, who were intubated while undergoing minor surgical procedures, served as control subjects. Between 1 and 3 mL of condensate was collected over a 30- to 60-min period, then immediately frozen and stored at -70 degrees C until analysis. The 8-iso-PGF2alpha was purified and derivatized, then quantified by stable isotope dilution in conjunction with gas chromatography/mass spectrometry. RESULTS: The mean level of exhaled 8-iso-PGF2alpha in the patients with ALI/ARDS, 87+/-28 pg/mL, was significantly higher than the mean in the normal group, 7+/-4 pg/mL (p = 0.007). The 8-iso-PGF2alpha levels were greater than two standard deviations above the mean of the normal group in 12 of 22 patients with or at risk for ARDS/ALI. CONCLUSIONS: These results provide further evidence that lipid peroxidation does occur in patients with ARDS/ALI. The measurement of exhaled isoprostanes provides a novel, noninvasive method to quantify oxidant stress in such patients.     

Role of ATP in the mechanism of serotonin absorption by lung tissue

Tests set up on the isolated perfused lungs of albino rats and on intact dogs demonstrated that the serotonin absorption by the pulmonary tissue is attended by a drop of the ATP amount in the lungs. The exogenous ATP has no essential effect on the serotonin absorption by the pulmonary tissue, its considerable quantities being metabolized in the pulmonary capillaries.     

Carbon dioxide field flooding minimizes residual intracardiac air after open heart operations

Transesophageal echocardiographic studies were used to monitor the presence of air bubbles in the heart after open heart operations. After cardiac valvular procedures all 22 patients managed with careful deairing procedures had persistence of air bubbles for at least 30 minutes and usually for 45 minutes. In 56 patients with CO2 field flooding, all foam disappeared in less than 1 minute in 48 patients and the remaining 8 had complete disappearance in 1 to 24 minutes. These observations demonstrate the ineffectiveness of the usual deairing maneuvers and the effectiveness of CO2 field flooding in displacing air.     

Scanning electron microscopic study and shear bond strength measurement with 5% and 37% phosphoric acid

Direct bonding of orthodontic attachments has become a clinical reality with the application of the acid etch technique, using 37% phosphoric acid. The objective of this study was to detect the etch pattern with scanning electron microscopy and the shear bond strength with a Hounsefield tensometer (Nene Instruments Ltd., Northampton, England) by using 37% and 5% phosphoric acid (H3PO4). It was observed that with 5% H3PO4 there was minimal enamel loss compared with 37% H3PO4. There was no significant difference in shear bond strength, when enamel surface was etched with 5% H3PO4 and 37% H3PO4.