Identification and characterization of aquaporin-2 water channel mutations causing nephrogenic diabetes insipidus with partial vasopressin response

Congenital nephrogenic diabetes insipidus (NDI) is a rare disease caused most often by mutations in the vasopressin V2 receptor (AVPR2). We studied a family which included a female patient with NDI with symptoms dating from infancy. The patient responded to large doses of desmopressin (dDAVP) which decreased urine volume from 10 to 4 I/day. Neither the parents nor the three sisters were polyuric. The patient was found to be a compound heterozygote for two novel recessive point mutations in the aquaporin-2 (AQP2) gene: L22V in exon 1 and C181W in exon 3. Residue Cys181 in AQP2 is the site for inhibition of water permeation by mercurial compounds and is located near to the NPA motif conserved in all aquaporins. Osmotic water permeability (Pf) in Xenopus oocytes injected with cRNA encoding C181W-AQP2 was not increased over water control, while expression of L22V cRNA increased the Pf to approximately 60% of that for wild-type AQP2. Co-injection of the mutant cRNAs with the wild-type cRNA did not affect the function of the wild-type AQP2. Immunolocalization of AQP2-transfected CHO cells showed that the C181W mutant had an endoplasmic reticulum-like intracellular distribution, whereas L22V and wild-type AQP2 showed endosome and plasma membrane staining. Water permeability assays showed a high Pf in cells expressing wild-type and L22V AQP2. This study indicates that AQP2 mutations can confer partially responsive NDI.      

Description of a hybridoma bank towards Bordetella pertussis toxin and surface antigens

This paper describes the development of a murine bank of monoclonal antibodies against Bordetella pertussis toxin, filamentous hemagglutinin (FHA), pili, lipopolysaccharide (LPS), or outer membrane proteins (OMPs). Subunits S1, S2, S3 of pertussis toxin (PT) bound immunoglobulins and glycoproteins such as fetuin and haptoglobin in an unspecific manner. The specificity of monoclonal antibodies towards subunits S1, S2, S3 or S4 of PT could be demonstrated by using purified immunoglobulins or their Fab2 fragments. A set of FHA-specific monoclonal antibodies could be differentiated on the basis of their binding to the various breakdown products present in FHA preparations. Pili-specific monoclonal antibodies reacted with either native pili or denatured pilin, and both demonstrated serotype specificity. Monoclonal antibodies to Bordetella pertussis OMPs were directed to either the virulent phase-regulated trypsin-sensitive, detergent-extractable OMPs 92 kDa, 32 kDa, and 30 kDa or the non-virulent phase-expressed, not-trypsin sensitive OMPs 38 kDa, 33kDa, and 18 kDa.     

Multiple cerebral metastases: detectability with Gd-DTPA-enhanced MR imaging

Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.     

Pulse oximetry--principle and first experiences during anesthesia

Oximetry is a photometric method for simple, non-invasive, and continuous measurement of the O2 saturation (SaO2). The addition of the word "pulse" indicates that, directed by a photo-electric plethysmogram, measurements are only performed during arterial pulsations. It appears from our first experiences with pulse oximetry during anesthesia that each decrease in SaO2 is indicated quickly and reliably. From a practical point of view it is important that the apparatus is connected quickly and easily, and that the O2 saturation is monitored continuously, also in those periods when normally no blood samples are taken. An additional advantage is that by means of the plethysmogram the circulation is also monitored.     

Recirculatory and compartmental pharmacokinetic modeling of alfentanil in pigs: the influence of cardiac output

BACKGROUND: Cardiac output (CO) is likely to influence the pharmacokinetics of anesthetic drugs and should be accounted for in pharmacokinetic models. The influence of CO on the pharmacokinetic parameters of alfentanil in pigs was evaluated using compartmental and recirculatory models. METHODS: Twenty-four premedicated pigs were evaluated during halothane (0.6-2%) anesthesia. They were assigned randomly to one of three groups. One group served as control. In the other groups, the baseline CO was decreased or increased by 40% by pharmacologic intervention (propranolol or dobutamine). Boluses of alfentanil (2 mg) and indocyanine green (25 mg) were injected into the right atrium. Blood samples were taken for 150 min from the right atrium and aortic root. Arterial concentration-time curves of indocyanine green and alfentanil were analyzed using compartmental models (two-stage and mixed-effects approach) and a recirculatory model, which can describe lung uptake and early distribution. RESULTS: The CO of individual pigs varied from 1.33 to 6.44 l/min. Three-compartmental modeling showed that CO is a determinant of the central compartment volume (V1, r2 = 0.54), fast peripheral compartment volume (V2, r2 = 0.29), steady state distribution volume (Vss, r2 = 0.29), fast distribution clearance (Cl12, r2 = 0.39), and elimination clearance (Cl10, r2 = 0.51). Recirculatory modeling showed that CO is a determinant of total distribution volume (r2 = 0.48), elimination clearance (r2 = 0.54), and some distribution clearances. The pulmonary distribution volume was independent of CO. CONCLUSIONS: Cardiac output markedly influences the pharmacokinetics of alfentanil in pigs. Therefore, accounting for CO enhances the predictive value of pharmacokinetic models of alfentanil.     

First-pass lung uptake and pulmonary clearance of propofol: assessment with a recirculatory indocyanine green pharmacokinetic model

BACKGROUND: The principal site for elimination of propofol is the liver. The clearance of propofol exceeds hepatic blood flow; therefore, extrahepatic clearance is thought to contribute to its elimination. This study examined the pulmonary kinetics of propofol using part of an indocyanine green (ICG) recirculatory model. METHODS: Ten sheep, immobilized in a hammock, received injections of propofol (4 mg/kg) and ICG (25 mg) via two semipermanent catheters in the right internal jugular vein. Arterial blood samples were obtained from the carotid artery. The ICG injection was given for measurement of intravascular recirculatory parameters and determination of differences in propofol and ICG concentration-time profiles. No other medication was given during the experiment, and the sheep were not intubated. The arterial concentration-time curves of ICG were analyzed with a recirculatory model. The pulmonary uptake and elimination of propofol was analyzed with the central part of that model extended with a pulmonary tissue compartment allowing elimination from that compartment. RESULTS: During the experiment, cardiac output was 3.90+/-0.72 l/min (mean +/- SD). The blood volume in heart and lungs, measured with ICG, was 0.66+/-0.07 l. A pulmonary tissue compartment of 0.47+/-0.16 l was found for propofol. The pulmonary first-pass elimination of propofol was 1.14+/-0.23 l/min. Thirty percent of the dose was eliminated during the first pass through the lungs. CONCLUSIONS: Recirculatory modeling of ICG allows modeling of the first-pass pulmonary kinetics of propofol concurrently. Propofol undergoes extensive uptake and first-pass elimination in the lungs.     

The influence of Helicobacter pylori on oesophageal acid exposure in GERD during acid suppressive therapy

BACKGROUND: Helicobacter pylori exaggerates the effect of acid suppressive drugs on intragastric pH. It is unknown whether this is relevant for the treatment of GERD. AIM: To compare oesophageal acid exposure and symptoms in H. pylori-negative and H. pylori-positive GERD patients during low and profound acid suppression. METHODS: Barrett's oesophagus patients with gastro- oesophageal acid reflux were studied by 24-h oesophageal pH-metry at baseline and during randomized treatment with omeprazole 40 mg b.d. or ranitidine 150 mg b.d. H. pylori status was determined by a serum IgG ELISA. Symptoms were scored on a four-graded scale. RESULTS: Of 58 patients, 26 (14 H. pylori-negative, 12 H. pylori-positive) were randomized to omeprazole, 32 (16 H. pylori-negative, 16 H. pylori-positive) to ranitidine. At baseline, oesophageal acid exposure and symptoms did not differ between H. pylori-negative and H. pylori-positive: mean time proportion pH < 4 per 24 h was 16.1% (95% CI 11.5-23.2) in H. pylori-negative, and 15.8% (11.3-21.4) in H. pylori-positive patients. Omeprazole treatment resulted in a decrease of acid reflux per 24 h from 23.4% (7.9-39.3) to 0.0% (0.0-2.9) in H. pylori-negative, and from 17.3% (8.9-38.8) to 0.1% (0.0-1.7) in H. pylori-positive patients; ranitidine resulted in a decrease from 14.4% (10.5-18.5) to 9.3% (5.6-12.8) in H. pylori-negative, and from 15.1% (9.8-21.0) to 9.0% (3.1-20.1) in H. pylori-positive patients, the difference between H. pylori-negative and H. pylori-positive patients being N.S. There was no significant difference between H. pylori-negative and H. pylori-positive patients with respect to erect and supine acid reflux, or symptom scores in both treatment groups. CONCLUSIONS: H. pylori infection does not influence oesophageal acid reflux and symptoms in patients with Barrett's oesophagus, either at baseline or during low as well as profound acid suppressive therapy. We conclude that the dose of acid suppression does not have to be titrated upon H. pylori status in GERD.