Gavin G. Gregory

Assessment of Intestinal Permeability and Absorption in Cirrhotic Patients with Ascites Using Combined Sugar Probes

Gastrointestinal dysfunction in patients with cirrhosis may contribute to complications such as malnutrition and spontaneous bacterial peritonitis. To determine whether cirrhotic patients with ascites have altered intestinal function, we compared intestinal permeability and absorption in patients with liver disease and normal subjects. Intestinal permeability and absorption were investigated in 66 cirrhotic patients (48 with ascites, 18 without ascites) and 74 healthy control subjects. Timed recovery of 3-O-methyl-D-glucose, D-xylose, L-rhamnose, and lactulose in urine following oral administration was measured in order to assess active and passive carrier-mediated, and nonmediated, absorptive capacity, as well as intestinal large-pore/small-pore (lactulose/rhamnose) permeability. Test sugars were measured by quantitative thin-layer chromatography and results are expressed as a percentage of test dose recovered in a 5-h urine collection. Sugar excretion ratios relating to small intestinal permeability (lactulose/rhamnose) and absorption (rhamnose/3-O-methyl-D-glucose) were calculated to avoid the effects of nonmucosal factors such as renal clearance, portal hypertension, and ascites on the recovery of sugar probes in urine. Compared with normal subjects, the mean lactulose/rhamnose permeability ratio in cirrhotic patients with ascites was significantly higher (0.058 vs. 0.037, P < 0.001) but not in cirrhotic patients without ascites (0.041 vs. 0.037). Cirrhotic patients with ascites had significantly lower mean recoveries of 3-O-methyl-D-glucose (23.0 vs. 49.1%; P < 0.001), D-xylose (18.8 vs. 34.5%; P < 0.001), L-rhamnose (4.0 vs. 9.1%; P < 0.001), and lactulose (0.202 vs. 0.337%; P < 0.001) than normal subjects. However, the mean rhamnose/3-O-methyl-D-glucose ratio was the same in cirrhotic patients with ascites as normal subjects (0.189 vs. 0.189), indicating that the reduction in probe recovery was due to nonmucosal factors. Compared with normal subjects, cirrhotic patients with ascites have abnormal intestinal permeability, measured by urinary lactulose/rhamnose excretion, and normal small intestinal absorption, assessed by the urinary rhamnose/3-O-methyl-D-glucose ratio. Low urine recovery of sugar probes found in cirrhotic patients appears to be the result of nonintestinal factors affecting clearance rather than reduced intestinal absorption.

On the Nonconsistency of Maximum Likelihood Nonparametric Density Estimators

One criterion proposed in the literature for selecting the smoothing parameter(s) in RosenblattParzen nonparametric constant kernel estimators of a probability density function is a leave-out-one-at-a-time nonparametric maximum likelihood method. Empirical work with this estimator in the univariate case showed that it worked quite well for short tailed distributions. However, it drastically oversmoothed for long tailed distributions. In this paper it is shown that this nonparametric maximum likelihood method will not select consistent estimates of the density for long tailed distributions such as the double exponential and Cauchy distributions. A remedy which was found for estimating long tailed distributions was to apply the nonparametric maximum likelihood procedure to a variable kernel class of estimators. This paper considers one data set, which is a pseudo-random sample of size 100 from a Cauchy distribution, to illustrate the problem with the leave-out-one-at-a-time nonparametric maximum likelihood method and to illustrate a remedy to this problem via a variable kernel class of estimators.

The relationship between sexual maturity rating, age, and increased blood pressure in adolescents

Blood pressure values are known to vary with age and body size. The effect of sexual maturity was explored in 746 patients in an adolescent clinic. Systolic blood pressure for boys and girls showed an increase with a change from Tanner stage 2 to 3. Diastolic blood pressure did not increase. Both systolic and diastolic blood pressures showed a weight effect that was generally maintained within the Tanner stages. The gradual increase in blood pressure for large groups of adolescents would appear to be the result of the aggregate increase in size (weight) resulting from the asynchronous growth spurts of individuals studied. Consequently, those individuals with a strikingly early or late onset of maturation may have erroneous interpretations of their blood pressure. As biologic outliers, the borderline hypertensive who matures early may be overidentified, while the late maturer might go unrecognized.

On Bivariate Cumulative Damage Models With Application

Bivariate cumulative damage models are proposed where the responses given the damages are independent random variables. The bivariate damage process can be either bivariate Poisson or bivariate gamma. A bivariate continuous cumulative damage model is investigated in which the responses given the damages have gamma distributions. In this case evaluation of the joint density function and bivariate tail probability function is facilitated by expanding the gamma distributions of the conditional responses by Laguerre polynomials. This approach also leads to evaluation of associated survival models. Moments and estimating equations are discussed. In addition, a bivariate discrete cumulative damage model is investigated in which the responses given the damages have a distribution chosen from a class that includes the negative binomial, the Neyman Type-A, the Polya-Aeppli, and the Lagrangian Poisson. Probabilities are obtained from recursive formulas which do not involve cancellation error as all quantities are non-negative. Moments and estimating equations are presented for these models also. The continuous and the discrete models are applied to describe the rise of systolic and diastolic blood pressure with age.

ECG in sickle cell trait at rest and during exercise and hypoxia

The electrocardiograms of 28 volunteers with sickle cell trait were compared to those of 28 control subjects. Tracings were recorded at rest, at peak exercise, at simulated sea level, and at a simulated altitude of 4,000 m. No differences between the subjects with sickle cell trait and control subjects were observed for the majority of electrocardiographic measurements. Several measurements had statistically significant differences that persisted after correcting for body surface area and physical fitness. The magnitude of the differences does not appear to have physiologic or clinical significance. The observation that the differences were greatest for resting and sea level recordings indicates that sickling is probably not responsible. Further investigation will be needed to substantiate these differences and determine whether these electrical observations have any physiologic implication.

Generalized Hodges-Lehmann estimators for the analysis of variance

For Xi, ..., Xn a random sample and K(·, ·) a symmetric kernel this paper considers large sample properties of location estimator satisfying , . Asymptotic normality of is obtained and two forms of interval estimators for parameter [theta] satisfying EK(X1 - [theta], X2 - [theta]) = 0, are discussed. Consistent estimation of the variance parameters is obtained which permits the construction of asymptotically distribution free procedures. The p-variate and multigroup extension is accomplished to provide generalized one-way MANOVA. Monte Carlo results are included.

Prevalence of irritable bowel syndrome according to the Rome criteria in a Vietnamese population

Prevalence of irritable bowel syndrome according to the Rome criteria in a Vietnamese population