Population toxicokinetics of tetrachloroethylene

In assessing the distribution and metabolism of toxic compounds in the body, measurements are not always feasible for ethical or technical reasons. Computer modeling offers a reasonable alternative, but the variability and complexity of biological systems pose unique challenges in model building and adjustment. Recent tools from population pharmacokinetics, Bayesian statistical inference, and physiological modeling can be brought together to solve these problems. As an example, we modeled the distribution and metabolism of tetrachloroethylene (PERC) in humans. We derive statistical distributions for the parameters of a physiological model of PERC, on the basis of data from Monster et al. (1979). The model adequately fits both prior physiological information and experimental data. An estimate of the relationship between PERC exposure and fraction metabolized is obtained. Our median population estimate for the fraction of inhaled tetrachloroethylene that is metabolized, at exposure levels exceeding current occupational standards, is 1.5% [95% confidence interval (0.52%, 4.1%)]. At levels approaching ambient inhalation exposure (0.001 ppm), the median estimate of the fraction metabolized is much higher, at 36% [95% confidence interval (15%, 58%)]. This disproportionality should be taken into account when deriving safe exposure limits for tetrachloroethylene and deserves to be verified by further experiments.     

Activation of locations in working memory in cats

Cats saw an object appear and disappear at two successive locations; the movement of the object from one location to the other was not perceived but was indicated by indirect cues and the two disappearances were separated by a 0-sec or a 20-sec interval. Performance was poorer with the 0-sec than with the 20-sec interval. With the 0-sec interval, the percentages of search attempts made at the object's initial and final hiding locations did not differ whereas with the 20-sec interval, more search attempts were made at the final than at the initial location. These results provide additional support to Goulet, Doré and Rousseau's (1994) interpretation of cats' search behaviour in terms of activation of spatial locations in working memory.     

Can optimal acid suppression prevent rebleeding in peptic ulcer patients with a non-bleeding visible vessel: a preliminary report of a randomized comparative study

BACKGROUND/AIMS: The hypothesis that profound acid suppression might prevent clot lysis and thus benefit patients with a non-bleeding visible vessel has not been confirmed. Omeprazole can suppress gastric acid remarkably and may be beneficial for patients with peptic ulcer bleeding. METHODOLOGY: Fifty-two patients with a non-bleeding visible vessel at the ulcer base were enrolled and randomized into four groups (N = 13 in each group). In the cimetidine group, the patients received cimetidine 300 mg i.v. bolus followed by 300 mg i.v. every 6 hr during hospitalization. In the heater probe thermocoagulation + cimetidine group, the patients received heater probe thermocoagulation and cimetidine 300 mg i.v. bolus followed by 300 mg i.v. every 6 h during hospitalization. In the omeprazole q.d. group, the patients received omeprazole 40 mg i.v. bolus followed by 40 mg i.v. daily for two days. In the omeprazole q 12 h group, the patients received omeprazole 40 mg i.v. bolus followed by 40 mg i.v. every 12 h for two days. A 24 hr intragastric pH was recorded for every case. RESULTS: The mean 24 hr intragastric pH were higher in the omeprazole q.d. (mean 5.8) and the omeprazole q 12 h groups (mean 6.4) than in the cimetidine (mean 4.3) and the heater probe thermocoagulation + cimetidine groups (mean 4.9) (p < 0.05). Rebleeding occurred in 5, 2, 2 and 2 patients in the cimetidine, heater probe thermocoagulation + cimetidine, omeprazole q.d., and omeprazole q 12 h groups, respectively (p > 0.05). Volume of blood transfusion and number of days in hospital were not statistically different among the four groups. CONCLUSIONS: Omeprazole can remarkably suppress gastric acid when it is compared to that of the H2 receptor blocker. Patients with a non-bleeding visible vessel using omeprazole do not exhibit a decrease in the rebleeding rate as compared with those patients using cimetidine.     

Cloning and chromosomal localization of a mouse cDNA with homology to the Saccharomyces cerevisiae gene zuotin

The eukaryotic DnaJ homologs form a family of proteins with diverse functions. One member of the family, the Saccharomyces cerevisiae gene zuotin, was isolated for its ability to bind Z-DNA. Here, we have isolated a mouse cDNA called ZRF1 (for zuotin-related factor1) with significant homology to zuotin. The DnaJ domain and candidate phosphorylation sites of zuotin and ZRF1 are highly conserved. ZRF1 gene is localized on chromosome 5. The structural similarity of zuotin and ZRF1 suggests conservation of function of this DnaJ subfamily.     

The role of ganglioside GM3 in the modulation of conformation and activity of sarcoplasmic reticulum Ca(2+)-ATPase

Rabbit sarcoplasmic reticulum does contain trace amounts of gangliosides, and the main species is GM3. Incorporation of GM3 into the SR vesicles or addition of it to the soybean phospholipid used for reconstitution of proteoliposomes obviously increased ATP hydrolysis, as well as, Ca2+ uptake activity of sarcoplasmic reticulum Ca(2+)-ATPase. Conformation changes of Ca(2+)-ATPase induced by GM3 were also observed by circular dichroism, intrinsic fluorescence and fluorescence quenching measurements.     

Hepatitis B vaccination in preterm infants

AIM: To investigate the immunogenicity and safety of existing recommendations for hepatitis B vaccination in preterm infants. METHODS: Recombinant hepatitis B vaccine (H-B-VAX II, 5 micrograms per dose) was given to 85 preterm infants divided into two groups, using two different schedules. Forty four group A infants with birthweights of < 2000 g received three doses at 1, 2, and 7 months of age. Forty one group B infants with birthweights of > or = 2000 g received three doses at 0, 1, and 6 months of age. RESULTS: After vaccination, 42 infants from group A (95%) and 37 infants from group B (90%) developed protective levels of antibody. The final seropositive rate and the geometric mean concentration of hepatitis B surface antibody between the two groups were not significantly different. The immune response of preterm infants to hepatitis B vaccines was similar to that of term infants in a previous study. CONCLUSIONS: Preterm infants can be given hepatitis B vaccines using one of the above two different schedules, at a cutoff birthweight of 2000 g.     

Fatty acylation of the rat and human asialoglycoprotein receptors. A conserved cytoplasmic cysteine residue is acylated in all receptor subunits

Functional rat or human asialoglycoprotein receptors (ASGP-Rs) are hetero-oligomeric integral membrane glycoproteins. Rat ASGP-R contains three subunits, designated rat hepatic lectins (RHL) 1, 2, and 3; human ASGP-R contains two subunits, HHL1 and HHL2. Both receptors are covalently modified by fatty acylation (Zeng, F.-Y., Kaphalia, B. S., Ansari, G. A. S., and Weigel, P. H. (1995) J. Biol. Chem. 270, 21382-21387; Zeng, F.-Y., Oka, J. A., and Weigel, P. H. (1996) Biochem. Biophys. Res. Commun. 218, 325-330). We report here that the single Cys residue in the cytoplasmic domain of each RHL or HHL subunit is fatty acylated. The degree of acylation is >/=90% per subunit. Deacylation of affinity-purified ASGP-Rs with hydroxylamine results in the spontaneous formation of dimers through reversible disulfide bonds, indicating that deacylation concomitantly generates free thiol groups. Reaction of hydroxylamine-treated ASGP-R with [14C]iodoacetamide resulted in the specific incorporation of radioactivity into all RHL and HHL subunits, verifying that fatty acids are attached via thioester linkages. To identify the Cys residue involved in the thioester linkages, 14C-carboxyamidomethylated RHL subunits were separated by SDS-polyacrylamide gel electrophoresis and digested in-gel with trypsin, and the resulting peptides were separated by reverse-phase high performance liquid chromatography. Amino acid sequence of radioactive peptides revealed that Cys35 in RHL1 and Cys54 in RHL2 and RHL3 were radiolabeled and, therefore, are fatty acylation sites. Fatty acylation of HHL subunits was analyzed by site-directed mutagenesis. Metabolic labeling of Cos7 cells transfected with wild type HHL1 cDNA resulted in substantial incorporation of [3H]palmitate into purified HHL1. Incorporation of [3H]palmitate into a C36S mutant of HHL1 was negligible ( approximately 1%) compared with wild type. This result also shows that Cys57 within the transmembrane domain of HHL1 is not normally palmitoylated. We conclude that Cys35 in RHL1, Cys54 in RHL2 and RHL3, and Cys36 in HHL1 are fatty acylated. Cys57 in HHL1 and probably Cys56 in RHL1 are not palmitoylated.     

Electrophysiological properties in patients undergoing atrial compartment operation for chronic atrial fibrillation with mitral valve disease

AIMS: Surgical treatment for atrial fibrillation is now feasible in selective cases. The aim of this study was to assess the electrophysiological properties of patients undergoing atrial compartment operation for chronic atrial fibrillation. METHODS AND RESULTS: Electrophysiological studies were performed in 20 mitral valve patients with atrial fibrillation who had been maintained in sinus rhythm for more than 1 year after atrial compartment operation. Intra-cardiac recording and programmed electrical stimulation were performed in various atrial compartments. The parameters studied included sinus node function, atrial conduction and refractoriness, atrioventricular conduction function and inducible arrhythmias if any. Intra-cardiac recordings showed that the rhythm was of sinus origin in all cases, with the earliest atrial activity located in the high right atrium. The mean sinus cycle length was 750 +/- 110 ms, AH time 106 +/- 29 ms, and HV time 53 +/- 7 ms. The sinus node function was normal in 18 patients (90%), and only two patients had prolonged sinus node recovery and sino-atrial conduction. The right atrial appendage compartment was driven by the sinus node in all patients. However, the conduction time from the high right atrium to the right atrial appendage compartment was markedly prolonged in 12 of 15 patients (80%) undergoing the three-compartment operation in which an incision was placed between the high right atrium and right atrial appendage compartments. On the other hand, the electrical activities in the left atrial compartment were much more varied. In 13 of 20 patients (65%), the left atrial compartment was driven by the sinus node; 11 of the 13 patients had a normal or mildly prolonged conduction time (ranged 75 to 146 ms), whereas two patients had a marked delay in conduction (200 ms and 266 ms, respectively). In the remaining seven patients, the left atrial compartments were dissociated from the rest of the heart; five of them had a quiescent left atrium, one a fluttering left atrial rhythm, and one a slow left atrial rhythm. The effective refractory period was longer in the left atrial compartment (242 +/- 47 ms) as compared to that of the high right atrium (224 +/- 26 ms, P < 0.01) and right atrial appendage compartments (219 +/- 25 ms, P < 0.01). Programmed electrical stimulation could not induce atrial fibrillation in any patient, whereas two patients had inducible atrial flutter and three repetitive atrial responses. CONCLUSIONS: (1) Atrial compartment operation does not impair sinus node function in most cases. (2) Elimination of atrial fibrillation while maintaining the electrical connection between different atrial compartments is feasible.     

Case report: successful obliteration of a bleeding duodenal varix using endoscopic ligation

BACKGROUND: To determine the concentration of cytokines having an immunomodulating effect in the first trimester in women who subsequently developed preeclampsia. METHODS: The serum concentrations of IL-10, TNFalpha, IL-6 and IL-2R were determined in ten women who later developed severe preeclampsia and in ten healthy controls. The groups were compared with the Mann-Whitney U test. RESULTS: The IL-2R concentration was significantly higher in the women who later developed preeclampsia than in normal patients (p = 0.028). No significant differences were detected between the groups with respect to the other evaluated cytokines. CONCLUSION: Elevated IL-2R concentrations in maternal serum as early as in the first trimester may be a sign of immunological maladaptation and might be associated with a disturbance of trophoblastic invasion.     

Predicting acute denervation in carpal tunnel syndrome

OBJECTIVE: Defects of the cochlear modiolus have been found to be associated with most cases of large vestibular aqueduct. The clinical significance of these modiolar defects has not been studied previously. The purpose of this article is to correlate clinical (functional) parameters, such as hearing outcomes, with the severity of the radiographic findings in these dysplastic inner ears. STUDY DESIGN: The study design was a retrospective chart review, supplemented with telephone interviews and clinic visits. SETTING: The study was conducted at an academic, tertiary care center. PATIENTS: Thirty consecutive patients with large vestibular aqueducts participated. RESULTS: Scores of modiolar deficiencies yielded inconsistent correlations with hearing loss. Vestibular aqueduct morphology and thickness correlated very strongly with the severity of hearing loss. CONCLUSIONS: These observations support the hypothesis that large vestibular aqueduct-related hearing loss may be caused by transmission of subarachnoid pressure forces into the inner ear. However, the thickness and morphology of the vestibular aqueduct may simply be markers for more subtle cochlear dysplasia manifest by modiolar deficiency.