Evaluation of the pathogenesis of flatulence and abdominal cramps in patients with lactose malabsorption

Aim of this study was to assess whether the interindividual differences in the development of flatulence and cramps in patients with lactose malabsorption are due to the quantity of malabsorbed lactose or gas accumulation, or if accelerated intestinal transit or increased perception of gas might play a role. Hydrogen breath tests were performed in 43 patients with lactose malabsorption after ingestion of 50 g lactose and, on a separate day, 25 g lactulose. The unabsorbed amount of lactose, small bowel transit time and colonic hydrogen accumulation were assessed in patients who did and did not develop flatulence and cramps after ingestion of lactose. The unabsorbed amount of lactose, small bowel transit time and volume and rate of colonic hydrogen accumulation were the same in patients who did or did not have symptoms after lactose. Patients with flatulence and cramps had a significantly longer time interval between the onset of the increase and peak breath hydrogen concentration (p < 0.05) and a significant correlation between the time of occurrence of peak symptoms and the time of peak breath hydrogen concentration (r = 0.75, p < 0.001). Our data suggest that subjective symptoms of lactose intolerance are not due to the amount of malabsorbed lactose or to the volume or rate of gas accumulation per se, but are related to increased perception of gas.     

Kinetic characterization and X-ray structure of a mutant of haloalkane dehalogenase with higher catalytic activity and modified substrate range

Conversion of halogenated aliphatics by haloalkane dehalogenase proceeds via the formation of a covalent alkyl-enzyme intermediate which is subsequently hydrolyzed by water. In the wild type enzyme, the slowest step for both 1,2-dichloroethane and 1,2-dibromoethane conversion is a unimolecular enzyme isomerization preceding rapid halide dissociation. Phenylalanine 172 is located in a helix-loop-helix structure that covers the active site cavity of the enzyme, interacts with the C1 beta of 1,2-dichloroethane during catalysis, and could be involved in stabilization of this helix-loop-helix region of the cap domain of the enzyme. To obtain more information about the role of this residue in dehalogenase function, we performed a mutational analysis of position 172 and studied the kinetics and X-ray structure of the Phe172Trp enzyme. The Phe172Trp mutant had a 10-fold higher Kcat/Km for 1-chlorohexane and a 2-fold higher Kcat for 1,2-dibromoethane than the wild-type enzyme. The X-ray structure of the Phe172Trp enzyme showed a local conformational change in the helix-loop-helix region that covers the active site. This could explain the elevated activity for 1-chlorohexane of the Phe172Trp enzyme, since it allows this large substrate to bind more easily in the active site cavity. Pre-steady-state kinetic analysis showed that the increase in Kcat found for 1,2-dibromoethane conversion could be attributed to an increase in the rate of an enzyme isomerization step that preceeds halide release. The observed conformational difference between the helix-loop-helix structures of the wild-type enzyme and the faster mutant suggests that the isomerization required for halide release could be a conformational change that takes place in this region of the cap domain of the dehalogenase. It is proposed that Phe172 is involved in stabilization of the helix-loop-helix structure that covers the active site of the enzyme and creates a rigid hydrophobic cavity for small apolar halogenated alkanes.     

Two-dimensional gel electrophoresis of Escherichia coli homogenates: the Escherichia coli SWISS-2DPAGE database

We report a patient, MT, who presented a specific, though not isolated, deficit in written calculation. Despite a preserved knowledge of simple arithmetic - single-digit addition and subtraction - he failed systematically in multi-digit subtraction. The nature of errors was consistent across problems and reflected the application of a disturbed underlying algorithm. Moreover, the pattern of error observed mimies a very common finding in developmental studies on arithmetical procedure acquisition (Fuson, 1990, 1992, Young and O'Shea, 1981; VanLehn, 1986, 1990). The data suggest that, within calculation skills, syntax may exist as a system of stable, but inappropriate, rules which are independent of any underlying conceptual knowledge.     

Irinotecan (CPT-11) metabolites in human bile and urine

A female patient was treated with irinotecan (CPT-11) for liver metastatic colon carcinoma. She had a percutaneous biliary catheter because of extrahepatic biliary obstruction. The patient was treated with CPT-11 for three courses at doses of 350 mg/m2 for the first course and 300 mg/m2 for the remaining courses, given as a 30-min i. v. infusion. Metabolism studies in bile and urine were performed by coupling high-performance liquid chromatography to electrospray mass spectrometry. Conventional spectra [liquid chromatography/mass spectrometry (LC/MS)] allowed on-line molecular mass determination of CPT-11 and its main metabolites, whereas structural information was obtained by tandem mass spectrometry (LC/MS/MS). At least 16 metabolites were detected in bile, while 8 of them were also detected in urine. Three compounds were identified as the parent drug, the active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38), and SN-38 glucuronide. The major metabolic pathway consists in oxidations of the terminal piperidine ring of the CPT-11 side chain, which eventually results in the formation of a primary amine. Other metabolites result from oxidation of the camptothecin nucleus. Finally, decarboxylation of the carboxylate form of CPT-11 was also observed. Several metabolites result from combinations of these pathways. The structures of the identified metabolites indicate for the first time a major role of monooxygenases in the elimination of a camptothecin derivative in humans. This finding will allow better understanding of interindividual variability in pharmacokinetics and intestinal toxicity of CPT-11.     

Methylprednisolone-hemisuccinate and its metabolites in serum, urine and bile from two patients with acute graft rejection

A cross-sectional assessment of differences in social class and other sociodemographic variables at hospital admission for patients with psychotic disorders was carried out through a systematic survey of psychotic patients admitted to greater Baltimore psychiatric facilities between 1983 and 1989. Female patients, first-admission patients, and patients with bipolar disorder or other, nonschizophrenic psychosis were more likely to have been admitted to community, university, and private hospitals than to state hospitals. Patients in medium and higher social class categories were 1.29 to 2.57 times more likely to be admitted to community, university, and private hospitals than to state hospitals.     

Monitored outpatient management of mild gestational hypertension remote from term in teenage pregnancies

OBJECTIVE: Our purpose was to compare maternal and perinatal outcomes of teenage and adult pregnancies with mild gestational hypertension remote from term managed with an outpatient program. STUDY DESIGN: A matched cohort design was used. Maternal and perinatal outcomes of 60 teenage pregnancies with mild gestational hypertension remote from term were compared with 120 adult controls 20 to 42 years old. The groups were matched for race, gestational age, and proteinuria status at enrollment. All were monitored on an outpatient basis with four times daily automated blood pressure measurement and daily assessment of weight, proteinuria, and fetal movement. RESULTS: The mean gestational age at enrollment was 33.5 +/- 2.6 weeks for both groups (range 27 to 36 weeks). Only 60% of teenagers had a high school degree or equivalent compared with 76% of adults (p = 0.024). The teenagers were more likely than the adults to be of single marital status (75% vs 13%, p = 0.015). The mean gestational age at delivery (37.0 +/- 2.0 vs 37.0 +/- 2.2 weeks), mean pregnancy prolongation (23.5 +/- 19.0 vs 24.5 +/- 17.4 days), and mean birth weights (2915 +/- 669 vs 2879 +/- 678 gm) were not statistically different between the teenagers and adults (all p > 0.05). There were no stillbirths, neonatal deaths, or cases of eclampsia in either group. CONCLUSIONS: In spite of a study population characterized by limited education, single marital status, and young age at enrollment, monitored outpatient management of mild gestational hypertension remote from term in teenage pregnancies is associated with maternal and perinatal outcomes similar to those observed in adults.