Model of bicarbonate secretion by resting frog stomach fundus mucosa I. Transepithelial measurements

In the present in vitro experiments on gastric fundus mucosa of Rana esculenta we try to define the mechanism of alkaline secretion that is observed in summer frogs in the resting stomach (blockage of HCl secretion by ranitidine, 10^–5 mol/l). The transepithelial voltage and the rate of alkalinization (ASR) of an unbuffered gastric lumen perfusate was measured as a function of serosal (and mucosal) fluid composition. ASR was high (0.88±S.E. 0.09 Eq·cm^–2·h^–1, n=11) during serosal bath perfusion with HCO₃ ^–-Ringer solution, decreased slightly to 0.50±0.07 Eq·cm^–2·h^–1 (n=6) in HCO₃ ^–-free HEPES-buffered Ringer solution of the same pH, and decreased to approximately 20% when carbonic anhydrase was inhibited by acetazolamide. While replacement of mucosal or serosal Cl^– did not — within 1 h — significantly alter ASR, replacement of serosal Na⁺ in the presence or absence of HCO₃ ^– strongly reduced ASR, and a similar reduction was observed after serosal application of the anion transport inhibitor DIDS (4,4-diisomiocyanatostilbene-2,2-disulphonate, 2·10^–4 mol/l), the metabolic poison rotenone (10^–5 mol/l), the uncoupler dinitrophenol (10^–4 mol/l), and the Na⁺ pump inhibitor ouabain (10^–4 mol/l), while serosal amiloride (10^–4 mol/l) had no effect. These data can be accounted for by a model of alkaline secretion that consists of basolateral HCO₃ ^– uptake from the serosal fluid into the cell via a DIDS-inhibitable Na⁺(HCO₃ ^–)_n-cotransporter and HCO₃ ^– secretion from the cell to the gastric lumen via an anionic conductance pathway. Microelectrode experiments on oxyntopeptic cells reported in the subsequent paper suggest that these cells may also be involved in the resting state alkaline secretion.     

Epidemiology of Cyclospora cayetanensis and other intestinal parasites in a community in Haiti

We conducted an exploratory investigation in a community in Haiti to determine the prevalence of Cyclospora cayetanensis infection and to identify potential risk factors for C. cayetanensis infection. In 2001, two cross-sectional stool surveys and a nested case-control study were conducted. In 2002, a follow-up cross-sectional stool survey was conducted among children < or =10 years of age. Stool specimens from study participants and water samples from their wells were examined for Cyclospora and other intestinal parasites. In stools, the prevalence of infection with Cyclospora in persons of all ages decreased from 12% (20 of 167 persons) in February 2001 to 1.1% (4 of 352 persons) in April 2001, a 90.8% decrease. For children < or =10 years of age, the prevalence rates were 22.5% (16 of 71 children) in February 2001, 3.0% (4 of 135 children) in April 2001, and 2.5% (2 of 81 children) in January 2002. Use of the water from the artesian well in the northern region of the community versus the one in the south was the only risk factor associated with Cyclospora infection in multivariate analyses (odds ratio, 18.5; 95% confidence interval, 2.4 to 143.1). The water sample from one of the nine wells or water sources tested (one sample per source) in January 2001, shortly before the investigation began, was positive for Cyclospora by UV fluorescence microscopy and PCR. None of the water samples from the 46 wells or water sources tested during the investigation (one sample per source per testing period, including the artesian wells) were positive for Cyclospora. Further studies are needed to assess the role of water as a possible risk factor for Cyclospora infection in Haiti and other developing countries.     

The “small” conductance chloride channel in the luminal membrane of the rectal gland of the dogfish (Squalus acanthias)

Besides the larger Cl^– channel with a single channel conductance of about 45 pS, a small channel was observed in the luminal membrane of the dogfish rectal gland [9]. In cell excised (inside out) patches with NaCl solution on both sides, the latter channel had a single channel conductance of 11±1 pS (n=21), and its current-voltage relationship was linear in the voltage range+90 to –90 mV. The open state probability increased moderately with negative clamp potentials. Ionic replacement studies revealed a high selectivity of Cl^– over gluconate, sulfate, and iodide, whereas bromide was permeable to some extent. Also the channel is impermeable for Na⁺. The Cl^– channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate did not affect this small conductance Cl^– channel. It can be concluded that the luminal membrane of stimulated rectal gland cells possesses two types of Cl^– channels, which differ markedly in their characteristics.Supported by Deutsche Forschungsgemeinschaft Gr 480/8 and by NSF and NIH grants to the MDIBL     

Characteristic genotypes discriminate between Babesia canis isolates of differing vector specificity and pathogenicity to dogs

The first and second internal transcribed spacers (ITS1, ITS2) as well as the intervening 5.8S coding region of the rRNA gene were characterized in eight Babesia canis isolates of differing geographic origin, vector specificity, and pathogenicity to dogs. The genotypes determined by sequencing segregated into three clearly separated groups close to or near the species level and correspond to the previously proposed subspecies B. canis canis, B. canis vogeli, and B. canis rossi. The three genotypes can be distinguished by Sau96I digestion of the polymerase chain reaction (PCR)-amplified rDNA target. Received: 12 December 1997 / Accepted: 5 January 1998     

Chronic social stress: effects on limbic brain structures

Different types of stressors are known to activate distinct neuronal circuits in the brain. Acute physiological stimuli that are life threatening and require immediate reactions lead to a rapid stimulation of brainstem and hypothalamus to activate efferent visceral pathways. In contrast, psychological stressors activate higher-order brain structures for further interpretations of the perceived endangerment. Common to the later multimodal stressors is that they need cortical processing and, depending on previous experience or ongoing activation, the information is assembled within limbic circuits connecting, e.g., the hippocampus, amygdala and prefrontal cortex to induce neuroendocrine and behavioral responses. In view of the fact that stressful life events often contribute to the etiology of psychopathologies such as depressive episodes, several animal models have been developed to study central nervous mechanisms that are induced by stress. The present review summarizes observations made in the tree shrew chronic psychosocial stress paradigm with particular focus on neurotransmitter systems and structural changes in limbic brain regions.     

The impact of the Women's Health Initiative Randomized Controlled Trial 2002 on perceived risk communication and use of postmenopausal hormone therapy in Germany

OBJECTIVE: The purpose of this representative, nationwide telephone survey was to collect information about postmenopausal hormone therapy (HT) use in relation to women's knowledge about the Women's Health Initiative Randomized Controlled Trial 2002 (WHI-RCT) in Germany. DESIGN: During July 2003, telephone interviews were conducted with randomly selected women aged 45 to 60 years (N = 10,030; response 59.9%; completed interviews n = 6,007). They were asked about information sources regarding the WHI-RCT, and use of HT in conjunction with it. RESULTS: Most women stated that they knew about the WHI-RCT (88.6%), and those with high educational status appeared to have more information than those with middle or low educational status. Among informed women (uninformed excluded), 46.6% continued, 25.7% stopped, and 14.2% ceased use of HT before the WHI-RCT. The prevalence of lifetime use of HT was higher in West Germany (37.4%) than in East Germany (29.2%), the highest prevalence of use was in the group aged 55 to 59 years. The most common reason to continue HT was the benefit risk assessment by physicians (58%); the most common reason to stop HT were women's perceptions that the risks of HT exceeded the benefits (56%). If information was solely given by physicians, women were more likely to continue HT (60.4%), compared with mass media (46.1%), as a source of information. CONCLUSIONS: The survey demonstrates the impact of the WHI-RCT in Germany, and shows that both the media and advice given by physicians were important. Women who continued to use HT did so largely because of their physician's advice. Women who discontinued were mainly those who had a negative subjective perception about risk of HT.     

Isolierung von Plättchencofaktor I (Antihämophiles Globulin A,Faktor VIII) aus Rinderserum

Ohne ZusammenfassungDie Arbeit wurde teilweise mit Unterstützung der Deutschen Forschungsgemeinschaft durchgeführt.     

Quantitative Bestimmung von Pregnandiol

Ohne Zusammenfassung     

Fetal development in experimental uremia

Summary Uremic women on hemodialysis with metabolic bone disease (hyperparathyroidism, osteomalacia resulting from defective vitamin D metabolism) and anemia (erythropoietin deficiency) are known to give birth to infants without bone disease or anemia. Therefore, skeletal development (enchondral and desmal bone formation) and hepatic erythropoiesis were evaluated in fetuses of uremic rats. These fetuses failed to show defective mineralisation or evidence of bone disease. Bolus injection of high doses of exogenous PTH into the maternal or fetal organism did not affect fetal bone histology. In addition, no apparent defect of bone mineralisation or bone formation was found in fetuses of ricketic rats. Normal mineralisation in the offspring of uremic rats may be explained by fetal hyperphosphatemia and/or insensitivity of fetal (woven) bone mineralisation to vitamin D.Absence of fetal anemia (normal hematocrits, normal density of hematopoietic cells in the liver) in the presence of maternal anemia is presumably due to the insensitivity of fetal erythropoiesis to erythropoietin.With the support of Deutsche Forschungsgemeinschaft