Clinically feasible stable isotope technique at a reasonable price: analysis of 13CO2/12CO2-abundance in breath samples with a new isotope selective-nondispersive infrared spectrometer

Up to now, stable isotope analysis of carbon dioxide in breath samples is carried out with sensitive but very expensive and complex isotope ratio mass spectrometry (IRMS). Aiming at a more widespread application of breath tests in gastroenterological diagnostic routine, we tested a newly developed isotope selective non-dispersive infrared spectrometer (NDIRS) in comparison to IRMS. 13C-urea breath tests were performed in 63 patients as the routine screening method for Helicobacter pylori infection. Breath samples at baseline and (15) 30 min after administration of the test solution containing 13C-urea were analysed both by NDIRS and conventional IRMS. The correlation between the delta values of both devices was linear and in good agreement (r = 0.96; p < 0.0001; Y = 1.01 X -0.94). Comparing the delta over baseline-values, the correlation was Y = 1.11 X -0.36 (r = 0.98; p < 0.0001). Referring to the diagnosis of Helicobacter pylori infection with IRMS we calculated a sensitivity of 95.0% and an unchanged specificity (100%) for NDIR analysis. In conclusion, NDIRS appears a promising, easy to operate, and low cost potential alternative to conventional IRMS thus encouraging further detailed investigation and more widespread application of the noninvasive stable isotope technique in breath tests for gastrointestinal function testing.     

Familial paraganglioma

Extra-adrenal pheochromocytomas and paragangliomas are rare tumors of neural crest origin, most commonly found in the retroperitoneum. Because these tumors are so uncommon, relatively little is known about their natural history. Comparisons between adrenal pheochromocytomas and extra-adrenal pheochromocytomas have appeared in the medical literature. Like pheochromocytomas, paragangliomas may occur as functional or nonfunctional tumors. Furthermore, although the hereditary occurrence of pheochromocytomas is well documented, the familial nature of paragangliomas is unclear. We present the first report of a mother and son with nonfunctional paragangliomas occurring in the same anatomic location and describe their care and treatment.     

Prevalence and implications of perinatal substance use in Missouri

A study was conducted to determine the prevalence of perinatal substance use in Missouri. The population sample studied was selected according to a multi-stage probability-proportional-to-size sampling. The weighted prevalence for perinatal exposure to alcohol, tobacco or illicit substances was 31.9%, 10.8% for illicit substances, 21.9% for tobacco use, and 7.9% for self-reported alcohol use. In 1993, an estimated 23,925 perinatal exposures to licit and illicit substances occurred.     

Evaluation of the potential carcinogenicity and genetic toxicity to humans of the herbicide acetochlor

Comprehensive toxicological studies of the herbicide acetochlor are presented and discussed. Although it gave a negative profile of responses in the many toxicity tests conducted there were some findings that prompted further investigation. First, although non-mutagenic in the Salmonella assay, acetochlor was clastogenic to mammalian cells treated in vitro. This clastogenic potential was not expressed in vivo in four rodent cytogenetic assays (bone marrow and germ cells). Second, although acetochlor gave a negative response in rat liver UDS assays when tested at the acute MTD, gavage administration of a single, supra-MTD dose (2000 mg/kg) gave a weak positive assay response. This dose-level (2000 mg/kg) was necrotic to the liver, depressed hepatic glutathione levels by up to approximately 80%, altered the metabolism of acetochlor, and was associated with up to 33% lethality. In contrast, reference liver genotoxins such as DMN, DMH and 2AAF were shown to elicit UDS in the absence of such effects, and at approximately 400 x lower dose-levels. Finally, microscopic nasal polypoid adenomas were induced in the rat when acetochlor was administered for two years at the maximum tolerated dose (MTD). The tumours were not life-threatening, they did not metastasize, and no DNA damage was induced in the nasal cells of rats maintained on a diet containing the MTD of acetochlor for either 1 or 18 weeks (comet assay). In order to probe the mechanism of action of these high dose toxicities a series of chemical and genetic toxicity studies was conducted on acetochlor and a range of structural analogues. These revealed the chloroacetyl substructure to be the clastogenic species in vitro. Although relatively inert, this substituent is preferentially reactive to sulphydryl groupings, most evidently, to glutathione (GSH). Similar chemical reactivity and clastogenicity in vitro was observed for two related chemicals bearing a chloroacetyl group, both of which have been defined as non-carcinogens in studies reported by the US.NTP. These collective observations indicate that the source of the clastogenicity of acetochlor in vitro is also the source of its rapid detoxification in the rat in vivo, via reaction with GSH. Metabolic studies of acetochlor are described which reveal the formation of a series of GSH-associated biliary metabolites in the rat that were not produced in the mouse. The metabolism of acetochlor in the rat changes with increasing dose-levels, probably because of depletion of hepatic GSH. It is most likely that a rat-specific metabolite is responsible for the rat nasal tumours observed uniquely at elevated dose-levels. The absence of genetic toxicity to the nasal epithelium of rats exposed acutely or subchronically to acetochlor favours a non-genotoxic mechanism for the induction of these adenomas. The observation of a time- and dose-related increase in S-phase cells in the nasal epithelium is consistent with this conclusion. Despite some confusion caused by the early use of perilethal gavage administrations of acetochlor to rodents, and supra-MTD dietary concentrations in some of the chronic studies, the available MTD data are consistent with acetochlor not posing a genetic or carcinogenic hazard to humans.     

Estrogen absorption and metabolism in postmenopausal women with end-stage renal disease

Women with end-stage renal disease (ESRD) have a higher rate of death from heart disease than women with normal renal function. Because estrogen replacement therapy may significantly decrease the incidence of death due to cardiovascular disease in postmenopausal women with normal renal function, their use has been considered for women with ESRD. However, the pharmacokinetics of estrogen have not been studied in postmenopausal women with ESRD to determine the optimal estrogen dose. Six postmenopausal women with ESRD receiving maintenance hemodialysis and six controls matched for body mass index were admitted to the in-patient Clinical Research Center. A 1- or 2-mg oral estradiol (E2) pill was given while subjects fasted. Blood sampling was performed over the next 24 h for measurement of E2, estrone (E1), albumin, and sex hormone-binding globulin (SHBG). Three weeks later, the subjects were given the other E2 dose under identical conditions. At baseline, total and free E2 levels were higher in the subjects with ESRD than in controls (P = 0.0005 and 0.0035, respectively). After ingestion of 1 and 2 mg E2, total and free E2 levels remained significantly higher in the ESRD subjects from 2-8 h after treatment (P < or = 0.05). After 1 mg oral E2, total serum E2 peaked at 65 pg/mL at 4 h in ESRD subjects and at 27 pg/mL in control subjects at 8 h. After 2 mg oral E2 treatment, total serum E2 peaked at 8 h in both ESRD and control subjects, with levels of 99 and 37 pg/mL, respectively. E1 was higher in the subjects with ESRD than in the control subjects at baseline (P < 0.05). After ingestion of 1 mg E2, E1 concentrations were not significantly higher in ESRD than in control subjects, peaking at 180 and 121 pg/mL, respectively (P = 0.3). E1 concentrations were higher in ESRD than in control subjects after the ingestion of 2 mg E2, with peak levels of 376 and 201 pg/mL, respectively (P = 0.03). Total and free E2 levels are higher in patients with ESRD than in control subjects at baseline and after E2 ingestion, indicating that renal failure alters the pharmacokinetics of both endogenous and exogenous E2. Therefore, conventional E2 doses used in individuals with normal renal function may be excessive for patients with ESRD.     

Specific interactions of chromatin with the nuclear envelope: positional determination within the nucleus in Drosophila melanogaster

Specific interactions of chromatin with the nuclear envelope (NE) in early embryos of Drosophila melanogaster have been mapped and analyzed. Using fluorescence in situ hybridization, the three-dimensional positions of 42 DNA probes, primarily to chromosome 2L, have been mapped in nuclei of intact Drosophila embryos, revealing five euchromatic and two heterochromatic regions associated with the NE. These results predict that there are approximately 15 NE contacts per chromosome arm, which delimit large chromatin loops of approximately 1-2 Mb. These NE association sites do not strictly correlate with scaffold-attachment regions, heterochromatin, or binding sites of known chromatin proteins. Pairs of neighboring probes surrounding one NE association site were used to delimit the NE association site more precisely, suggesting that peripheral localization of a large stretch of chromatin is likely to result from NE association at a single discrete site. These NE interactions are not established until after telophase, by which time the nuclear envelope has reassembled around the chromosomes, and they are thus unlikely to be involved in binding of NE vesicles to chromosomes following mitosis. Analysis of positions of these probes also reveals that the interphase nucleus is strongly polarized in a Rabl configuration which, together with specific targeting to the NE or to the nuclear interior, results in each locus occupying a highly determined position within the nucleus.     

Transport properties are not altered across Caco-2 cells with heightened TEER despite underlying physiological and ultrastructural changes

Selected properties of Caco-2 cells were examined after disparate transepithelial electrical resistance (TEER) measurements were observed in two populations of Caco-2 cells. Comparisons were made between the early passages of Caco-2 cells (Caco-2E, passages 35-47) and the later passages of cells (Caco-2L, passages 87-112). Transmission electron microscopy revealed that regions of Caco-2L cells were composed of multiple cell layers rather than the monolayers observed in Caco-2E cells. Epithelial cell height (or barrier thickness) was not significantly different between the two cell populations. Intercellular and intracellular lumina were observed in the Caco-2L cells, but not in the Caco-2E cells. Results of [3H]thymidine incorporation assays showed significantly higher cell proliferation rates in Caco-2L cells relative to Caco-2E cells. Despite morphological and physiological changes, there were no significant differences in the apparent permeabilities for D-mannitol (paracellular diffusion marker), hydrocortisone (transcellular diffusion marker), or dipeptide, Gly-Sar (carrier-mediated transcellular transport marker) between the two populations of cells. The higher TEER values in Caco-2L cells may be the results of a slight perturbation of tight junctions associated with both the multiple cell layers and the presence of intercellular lumina.     

Gastric bypass in morbidly obese kidney transplant recipients

Severe post-transplant obesity has previously been shown to have a negative impact on graft survival following kidney transplantation. It also contributes to late patient mortality and is associated with hypertension, diabetes and hyperlipidemia. We undertook Roux-en-Y gastric bypass (GBP) in three morbidly obese (200-260% ideal body weight) (IBW) patients 6-8 yr following kidney transplantation. Roux-en-Y gastrojejunostomy to a 30 ml stapled gastric pouch was created with the jejunojejunostomy (both loops) 80-120 cm from the ligament of Treitz. By 12 months post-GBP, weight loss plateaued at 100-150% IBW. Both patients that had developed post-transplant diabetes mellitus (PTDM) had complete resolution within 9 months following GBP. On average the patients required 3 less hypertension (HTN) medications after GBP; 2 of the 3 patients are now normotensive off medication. Improvements in hyperlipidemia were also shown. The absolute cyclosporine (CsA) requirement (mg/d) increased by approximately 33% (p = NS), and there was also a significant increase in the weight adjusted CsA requirement from 1.8 to 3.5 mg/kg/d (p = 0.02, ANOVA) following GBP in order to maintain similar TDX trough CsA levels. GBP offers significant reduction in weight, HTN, PTDM and hyperlipidemia in morbidly obese kidney transplant recipients. However, CsA dose requirements may increase after GBP as a consequence of the defunctionalized intestine.     

Effect of variations in adrenocortical function on dopamine beta-hydroxylase and norepinephrine in the brain of the rat

The effect of adrenalectomy and corticosterone treatment on dopamine beta-hydroxylase (DBH) activity, catecholamine content and norepinephrine formation and metabolism were studied in the hypothalamus and other parts of the brain of male rats. Two days after adrenalectomy, there was a decrease in DBH activity in the hypothalamus and the brain stem but no change in norepinephrine or dopamine content. Conversion of intraventricularly administered tritiated dopamine to tritiated norepinephrine was slightly increased and norepinephrine was metabolized at a more rapid rate than normal. Corticosterone in a dose of 100 mg/kg increased DBH activity but decreased hypothalamic norepinephrine and copamine content. In adrenalectomized rats, smaller, more physiological doses of corticosterone did not change DBH activity or catecholamine content. The fact that norepinephrine formation and metabolism were increased at the same time that DBH activity in vitro was decreased suggests that DBH is not rate-limiting in adrenergic neurons in the hypothalamus, or that a change in the in vitro activity of the enzyme was not accompanied by a parallel change in its activity in vivo.