Propoxyphene: pathways of metabolism in man and laboratory animals

Through the combined use of stable isotope labeling and gas chromatographic mass spectrometric analysis, the metabolic patterns for propoxyphene have been determined in laboratory animals and man. The rat and dog eliminated propoxyphene and its metabolites principally via the bile, while the rabbit more closely resembled man in excreting the metabolic products into urine. Metabolites in rat and rabbit existed as conjugates, whereas in dog and man the metabolites were excreted as a mixture of the free and unconjugated forms. The primary route of metabolism in all species studied was N-demethylation. However, the rat and rabbit extensively hydroxylated propoxyphene and its metabolites prior to elimination. Metabolites arising from ester hydrolysis were found in rat and man. N-acetylated products were identified in all four species. A metabolite formed from cyclization and dehydration of dinorpropoxyphene was isolated in urine and was further identified as a circulating metabolite in dog plasma.     

Summary of the working group on design of an FEL/storage ring for λ ≤ 1000 Å

The elements which go into the design of an FEL/storage ring are delineated.     

The use of stable sulfur isotope labelling to elucidate sulfur metabolism by Clostridium pasteurianum

Seven babies with 100 cm or less remaining small bowel have been evaluated for evidence of gastric hyperacidity and/or hypergastrinemia. Two babies were also studied after feeding. No patient demonstrated hyperacidity or hypergastrinemia. This infant data is discussed in regards to reported contradictory data in adult studies.     

Fractionation of Crotalus durissus cumanensis venom by gel filtration

Serum lipid levels were determined in 30 children with kwashiorkor and in 30 healthy children of comparable age. The serum concentrations of unesterified and esterified cholesterol, albumin and the cholesterol esterifying activity (CEA) were also measured in children with kwashiorkor before treatment and after recovery. All serum lipid fractions were significantly lower in kwashiorkor than in the normal children. After treatment and recovery, serum lipid levels were comparable to those observed in normal children. There was also a significant increase in serum cholesterol esterifying activity (CEA) following recovery from kwashiorkor.     

Oxygenation-linked subunit interactions in human hemoglobin: analysis of linkage functions for constituent energy terms

Resolution of the linkage functions between oxygenation and subunit association-dissociation equilibria in human hemoglobin into the constituent microscopic terms has been explored by numerical simulation and least-squares analysis. The correlation properties between parameters has been studied using several choices of parameter sets in order to optimize resolution. It is found that, with currently available levels of experimental precision and ranges of variables, neither linkage function can provide sufficient resolution of all the desired energy terms. The most difficult quantities to resolve always include the dimer-tetramer association constant for unliganded hemoglobin and the oxygen binding constants to alphabeta dimers. A feasible experimental strategy for overcoming these difficulties lies in independent determination of the dimer-tetramer association constants for unliganded and fully oxygenated hemoglobin. These constants, in combination with the median lignad concentration, provide an estimate of the energy for total oxygenation of tetramers which is essentially independent of the other constituent energies. It is shown that if these separately determinable parameters are fixed, the remaining terms may be estimated to good accuracy using data which represents either linkage function. In general it is desirable to combine information from both types of experimental quantities. A previous paper (Mills, F.C., Johnson, M.L., and Ackers, G.K. (1976), Biochemestry, 15, the preceding paper in this issue) describes the experimental implementation of this strategy.     

Quantitative and morphologic analysis of bacterial translocation in neonates

OBJECTIVE: To elucidate the mechanisms of bacterial translocation in animals fed a conventional formula by correlating transmucosal bacterial passage in vitro with the structural characteristics of the neonatal intestinal mucosa. DESIGN: Newborn rabbits were randomized to receive a conventional formula or breast milk. Bacterial translocation to the mesenteric lymph nodes, liver, and spleen was quantitated after 7 days, and transmucosal passage of bacteria was measured in vitro using the Ussing chamber. The mucosal membranes were examined by light, transmission electron, and confocal laser scanning microscopy. RESULTS: Bacterial passage was rarely seen in the breast milk-fed animals in contrast to the formula-fed animals. Unlike the normal-appearing membranes from breast milk-fed animals, the epithelial cells of formula-fed animals were vacuolated but healthy, with normal polarization and microvillus border by confocal laser scanning microscopy. Villi of formula-fed animals were less densely packed than those of the breast milk-fed animals. Bacterial adhesion, internalization, and transmucosal passage were seen only in membranes from formula-fed animals. Transmission electron microscopy demonstrated bacteria incorporating into the epithelial surface through an active phagocytic process, with rearrangement of the actin cytoskeleton. Once internalized, these bacteria were seen within the cytoplasmic vacuoles and subsequently in the submucosa. No bacteria passed between epithelial cells. CONCLUSION: Morphological changes in the intestinal mucosa of formula-fed newborn rabbits may increase permeability to bacteria.     

Fluorescence of native single-Trp mutants in the lactose permease from Escherichia coli: structural properties and evidence for a substrate-induced conformational change

Six single-Trp mutants were engineered by individually reintroducing each of the native Trp residues into a functional lactose permease mutant devoid of Trp (Trp-less permease; Menezes ME, Roepe PD, Kaback HR, 1990, Proc Natl Acad Sci USA 87:1638-1642), and fluorescent properties were studied with respect to solvent accessibility, as well as alterations produced by ligand binding. The emission of Trp 33, Trp 78, Trp 171, and Trp 233 is strongly quenched by both acrylamide and iodide, whereas Trp 151 and Trp 10 display a decrease in fluorescence in the presence of acrylamide only and no quenching by iodide. Of the six single-Trp mutants, only Trp 33 exhibits a significant change in fluorescence (ca. 30% enhancement) in the presence of the substrate analog beta,D-galactopyranosyl 1-thio-beta,D-galactopyranoside (TDG). This effect was further characterized by site-directed fluorescent studies with purified single-Cys W33-->C permease labeled with 2-(4'-maleimidylanilino)-naphthalene-6-sulfonic acid (MIANS). Titration of the change in the fluorescence spectrum reveals a 30% enhancement accompanied with a 5-nm blue shift in the emission maximum, and single exponential behavior with an apparent KD of 71 microM. The effect of substrate binding on the rate of MIANS labeling of single-Cys 33 permease was measured in addition to iodide and acrylamide quenching of the MIANS-labeled protein. Complete blockade of labeling is observed in the presence of TDG, as well as a 30% decrease in accessibility to iodide with no change in acrylamide quenching. Overall, the findings are consistent with the proposal (Wu J, Frillingos S, Kaback HR, 1995a, Biochemistry 34:8257-8263) that ligand binding induces a conformational change at the C-terminus of helix I such that Pro 28 and Pro 31, which are on one face, become more accessible to solvent, whereas Trp 33, which is on the opposite face, becomes less accessible to the aqueous phase. The findings regarding accessibility to collisional quenchers are also consistent with the predicted topology of the six native Trp residues in the permease.     

Prospective randomised trial of atrial versus ventricular pacing in sick-sinus syndrome

In patients with sick-sinus syndrome, single-chamber atrial pacing has been reported, in retrospective studies, to be associated with lower frequencies of atrial fibrillation, thromboembolism, heart failure, and mortality than ventricular pacing; although single-chamber ventricular pacing is most commonly used. We did a prospective randomised trial in 225 consecutive patients (142 women, 83 men; mean age 76 years) with the sick-sinus syndrome, randomised to atrial (n = 110) or ventricular (n = 115) pacing and followed for up to 5 years (mean 40 [SD 18] months). During follow-up, the frequency of atrial fibrillation was higher in the ventricular group, except at the first follow-up at 3 months. Thromboembolic events (stroke or peripheral arterial embolus) occurred in 20 patients in the ventricular group and in 6 patients in the atrial group (p = 0.0083). 25 patients died in the ventricular group compared with 21 in the atrial group (p = 0.74). Heart failure estimated by the New York Heart Association classification and by the daily doses of diuretics did not differ between the two groups. Atrioventricular block occurred in 2 patients in the atrial group. Patients with sick-sinus syndrome should be treated with atrial pacing rather than ventricular pacing because atrial pacing is associated with lower frequencies of atrial fibrillation, thromboembolic complications, and a low risk of atrioventricular block.