Spatial and temporal variation of microstimulation thresholds for inhibiting the tail-flick reflex from the rat's rostral medial medulla.

Suppression of the tail-flick reflex by microstimulation of the rostral medial medulla in rats lightly anesthetized with barbiturates was studied with regard to spatial and temporal variations in electrical threshold. Trains of constant-current pulses with linearly descending amplitudes (called 'ramps') were passed through the extracellular brain microelectrode during noxious heating of the tail. The pulse amplitude at the time of the reflex, after allowance for conduction and reaction latencies, was taken as the threshold reading. This new method revealed a range of vertical electrode positions corresponding roughly to the nucleus raphe magnus, where the thresholds tended to be lowest (a mean of 4.1 microA for 0.4-ms pulses delivered at 50 Hz). In confirmation of the technique's validity neither the duration of the ramp nor its starting amplitude, within their useful range, significantly affected the measured threshold. Pronounced temporal fluctuation was seen in thresholds measured every 2 min. Spatial variability within the low-threshold region and differences between preparations were statistically much smaller sources of variation. The temporal fluctuation appeared to have a stationary mean for at least 20 min under constant conditions of anesthesia. In some experiments, action potentials from single neurons were recorded through the stimulating electrode, and classified into those inhibited during the tail-flick (off-cells), those excited (on-cells), and those unaffected (neutral cells). The thresholds where off-cells exhibited their maximum action potential were on average significantly lower than corresponding thresholds for on-cells. Short-range (less than 0.2 mm) spatial variations in the threshold appeared however to be uncorrelated with the distance to an individual recorded off-cell or on-cell.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in body temperature and urinary cortisol after routine immunization in babies with intrauterine growth retardation

Aim : To investigate whether infants with intrauterine growth retardation (IUGR) experience different changes in temperature and cortisol excretion after routine immunization compared with normal healthy infants. Methods : Overnight deep body temperature and urinary cortisol to creatinine ratios were measured on the night after immunization and a control night in normal and IUGR infants. Results : In 60 normal infants, first vaccination at about 10 wk of age led to a significant increase in minumum overnight temperature compared to the control night, mean rise 0.25°C (95% CI, 0.12 to 0.38). In 35 IUGR infants the mean rise in temperature between immunization night and control night was 0.35°C (95% CI, 0.15 to 0.55). The increases in minimum temperature did not differ significantly between the normal and IUGR infants ( p = 0.11). Cortisol to creatinine ratios measured from overnight urine samples showed that 23 IUGR infants had consistently higher levels than 39 normal infants; control night medians 34 and 15 ( p = 0.01) and immunization night medians 56 and 26 ( p= 0.02), respectively. However, the percentage increase did not differ significantly between the IUGR infants and the normal infants. A smaller number of second immunizations were studied, but no significant differences were found.

Conclusion : These results suggest that although the impact of immunization is the same for IUGR and normal infants, because IUGR infants are less mature and at greater stress before immunization, the absolute levels that they experience after immunization are higher than those for normal infants.     

Pulmonary embolism after hip or knee replacement: postoperative changes on pulmonary scintigrams in asymptomatic patients

Serial pulmonary imaging has proved to be effective in the evaluation of patients undergoing total joint arthroplasty. A clinical dilemma arises in asymptomatic patients whose postoperative pulmonary images differ from the preoperative images. The authors prospectively evaluated 403 patients with serial imaging to determine the significance of changed postoperative images in asymptomatic patients undergoing total hip or knee arthroplasty. Twenty-two (5.5%) patients had significant changes on postoperative images. Seventeen were asymptomatic; all but one underwent pulmonary angiography. Documented pulmonary emboli were demonstrated in 100% of patients whose postoperative images changed to indicate a high probability of pulmonary embolism, 71% whose images changed to a moderate probability, and 0% whose images changed to indeterminate probability. Overall, pulmonary emboli occurred in 76% of all asymptomatic patients with significantly change postoperative images. Asymptomatic pulmonary embolism is a significant occurrence after total hip or knee repair, and a changed lung scan with appropriate clinical evaluation is an accurate indicator of pulmonary emboli in asymptomatic postarthroplasty patients.     

Quantitative assessment of portal vein flow in subjects with active chronic hepatitis: comparison of magnetic resonance angiography with bolus tracking with color Doppler ultrasonography]

PURPOSE: To assess the accuracy of time-of-flight MR Angiography (MRA) with bolus tracking in evaluating mean blood velocity and flowrate in the portal vein in patients with chronic hepatitis versus healthy volunteers. MATERIAL AND METHODS: Fifteen patients with clinically-defined post-viral chronic hepatitis (viruses B and C) were examined with bolus tracking MRA and color Doppler US to evaluate portal blood flow. Both examinations were performed before and after a 1500 kcal meal. We evaluated mean blood flow velocity and flowrate in the portal vein. MRA results were compared with color Doppler findings; the results in chronic hepatitis patients were compared with those of healthy volunteers. RESULTS: The correlation between mean portal blood velocity, as measured with MRA and color Doppler US, was r = .82 before and r = .79 after the meal. There was no significant difference in mean velocity between the chronic hepatitis patients and the healthy volunteers. The correlation between portal flowrate, as measured with MRA and color Doppler US, was r = .87 before and r = .91 after the meal. There was no significant difference in mean flowrate between the chronic hepatitis patients and the healthy volunteers. In contrast, there were significant differences in mean velocity and portal flowrate, as measured with MRA before the meal, between the chronic hepatitis patients and the healthy volunteers. DISCUSSION AND CONCLUSIONS: Bolus tracking MRA is superior to color Doppler US in quantitating blood flow in the portal vein and evaluating changes after a meal. Decreased mean velocity and flowrate may indicate impaired function, as it happens in early chronic hepatitis.     

Complete Metabolic Response with Recanalization of Portal Vein Tumor Thrombosis after Sunitinib in a Patient with Advanced Hepatocellular Carcinoma

The prognosis of patients with advanced hepatocellular carcinoma (HCC) is very poor. The outcome of these patients is particularly bleak when the disease is complicated by portal vein tumor thrombosis (PVTT), since the increased portal pressure often causes serious gastrointestinal bleedings. Before the introduction of sorafenib (SOR), a tyrosine kinase inhibitor, no effective treatment was available for patients with advanced disease. SOR is now considered the standard treatment even for patients with tumor thrombosis, although the well-known interference between tyrosine kinase inhibitors and the coagulation pathway calls for caution against their use in this setting. Here, we report the case of a 74-year-old male patient with advanced HCC and PVTT treated with sunitinib (SUN), another multikinase inhibitor. During the third cycle, our patient experienced a life-threatening hematemesis with hemorrhagic shock that required intensive care treatment and SUN discontinuation. However, he completely recovered, and the PET/CT scan performed 1 year after the adverse effect demonstrated no evidence of the tumor together with portal vein recanalization. The short course of SUN causing both tumor response and gastrointestinal bleeding warrants further studies on the effectiveness of SUN in this setting as well as on the duration of treatment with multikinase inhibitors in patients with tumor thrombosis.     

The influence of physicochemical parameters on the biliary excretion of a series of nitroimidazoles

The relationship between physicochemical parameters and biliary excretion of nitroimidazoles was investigated. The unmetabolized form of each drug was detected in the bile by means of a UV procedure. A highly significant reversed parabolic relationship was shown between the Rm values and the biliary excretion of the test compounds. In other words, the compounds closer to the optimal Rm value are excreted less than those characterized by higher or lower Rm values. Since the Rm values seem to account for both the lipophilic and polar character of nitroimidazoles, the reversed parabola could be due to plasma protein binding and/or some protein binding within the hepatocyte. In fact, both the lipophilic and polar character seem to play an important role in protein binding of chemicals.