The epithelial calcium channel, ECaC1: molecular details of a novel player in renal calcium handling.
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Amino Acid Sequence↗
Biomedical subjects
D Müller
Publications and source records attributed to D Müller.
The structure and regulation of the oxytocin receptor.
The oxytocin receptor (OTR) is part of an ancient hormone system expressed in diverse phyla in relation to acute reproductive smooth muscle responses, such as egg-laying, birth, or milk letdown. The regulation of the OTR gene, while correlating with steroid levels in vivo, remains elusive. There appear to be both inhibitory and stimulatory influences acting upon a constitutive pattern of basal expression. We have found no evidence, however, for an effect of the sex steroids either directly on gene transcription, or on the receptor itself at the protein level. In the prostatic carcinoma cell line Du145, we have shown that up-regulation of the OTR gene transcription can be effected by cAMP. In an attempt to characterize the expression of the OTR protein in vivo, we have shown, using ligand-blotting, that the OTR can be expressed at different sizes in transfected cells and in myometrium. Also, in the myometrium at term, immunohistochemistry suggests that there is both an increase in OTR protein per cell, as well as in the number of smooth muscle cells expressing OTR, emphasizing that perinatal changes are the results of both individual gene activation events and gross cellular differentiation. The OTR is a valuable model system reflecting molecular changes in the perinatal period. When we understand how this important molecule is regulated, we will also be a long way towards understanding the mechanisms controlling myometrial contractility at birth. Experimental Physiology (2001) 86.2, 289-296.
Animals↗
MR hydrometry to assess exocrine function of the pancreas: initial results of noninvasive quantification of secretion.
PURPOSE: To evaluate magnetic resonance (MR) hydrometry, a method of quantifying fluid amounts by using MR imaging, for assessing the exocrine function of the pancreas after stimulation with secretin. MATERIALS AND METHODS: Images were obtained with a single-shot turbo spin-echo sequence by using a 1.0-T magnet with a quadrature body coil. Image postprocessing and evaluation were performed at an external workstation by using a specially designed histogram algorithm that translates the MR signal intensity of duodenal filling into an actual amount of duodenal fluid. This algorithm was tested in vitro and in vivo. Finally, MR hydrometry results in five patients were correlated with those of the secretin-cerulein test. RESULTS: The phantom measurements showed a high correlation (r = 0.99) between the actual amount of fluid in the imaging volume and the calculated results. In vivo, the ability of MR hydrometry to enable exact quantification of fluid amounts was demonstrated. In correlating the signal intensity of duodenal filling with the exact amount of additional fluid in the duodenum in volunteers, a coefficient of 0.043 gray tones per pixel per milliliter was calculated. The correlation (r) between secretin-stimulated duodenal fluid output estimated by using tube aspiration and that estimated by using MR hydrometry was 0.946 (P <.05). CONCLUSION: MR hydrometry is a promising noninvasive method of assessing fluid output as a measure of exocrine pancreatic function.
Algorithms↗
Prolonged dietary calcium restriction: a diagnostic approach in idiopathic hypercalciuria.
BACKGROUND: Although frequently observed, the etiology of idiopathic hypercalciuria (IHC) remains largely unknown. A common hypothesis postulates intestinal hyperabsorption and/or a primary renal leak as the pathophysiological basis. The aim of our study was to investigate the regulation pattern of calcium homeostasis in patients with IHC by using a prolonged period of calcium restriction. METHODS: Twenty-seven patients with IHC were investigated. After a 3-week run-in period (dietary calcium content 700-1,000 mg/24 h), a standard calcium reduced diet (300 mg/24 h) was given for 4 weeks. Thereafter, the participants received again a normal calcium-containing diet. Values for urinary calcium, PTH and calcitriol levels of all participants were obtained at different phases of the study. Forty-three healthy persons served as controls. RESULTS: During calcium restriction, two distinct groups were identified. One group displayed an increase (n = 12) in urinary calcium excretion, the second (n = 15) a marked reduction, respectively. In both groups, the values during calcium restriction were significantly different from baseline (p < 0.01). In the first group, the increase of urinary calcium excretion was accompanied by an increase of PTH and calcitriol. These values were also significantly different from baseline values (p < 0.01). The control group showed decreasing calcium excretion during oral restriction (p < 0.01). CONCLUSION: Prolonged calcium restriction proved to be useful in distinguishing apparently two major forms of IHC. The fact that one group displayed the same excretion pattern as the control group raises the question if this group just represents the upper limit of a physiological range. These findings may shed new light on diagnosis, pathogenesis and treatment of patients with IHC.
Calcitriol↗
Safety considerations of DNA in food.
Recombinant DNA techniques are capable of introducing genetic changes into food organisms that are more predictable than those introduced through conventional breeding techniques. This review discusses whether the consumption of DNA in approved novel foods and novel food ingredients derived from genetically modified organisms (GMOs) can be regarded as being as safe as the consumption of DNA in existing foods. It concludes that DNA from GMOs is equivalent to DNA from existing food organisms that has always been consumed with human diets. Any risks associated with the consumption of DNA will remain, irrespective of its origin, because the body handles all DNA in the same way. The breakdown of DNA during food processing and passage through the gastrointestinal tract reduces the likelihood that intact genes capable of encoding foreign proteins will be transferred to gut microflora. The review does not specifically address food safety issues arising from the consumption of viable genetically modified microorganisms but it shows that the likelihood of transfer and functional integration of DNA from ingested food by gut microflora and/or human cells is minimal. Information reviewed does not indicate any safety concerns associated with the ingestion of DNA per se from GMOs resulting from the use of currently available recombinant DNA techniques in the food chain.
Consumer Product Safety↗
Improving recreational, residential, and vocational outcomes for patients with schizophrenia.
As Roder and colleagues propose, we have seen three eras in the development and refinement of social skills training for individuals with schizophrenia. In the 1960s, skills training relied on the use of operant conditioning, as exemplified by the token economy. Reinforcement contingencies succeeded in activating patients with negative symptoms and in improving their social behavior. Contemporary psychiatric rehabilitation can profit from the identification and use of reinforcers to motivate anergic individuals who lack insight to participate actively in community-based programs. During the second era, in the 1970s, social learning through modeling, coaching, role playing, and behavioral assignments was introduced into skills training. These techniques were used to improve nonverbal skills, such as eye contact, fluency of speech, gestures, and facial expression, as well as conversational skills, assertiveness, and emotional expressiveness. Intervention programs of the third and current era are incorporating cognitive methods into the skills training enterprise. For example, in the modules for training social and independent living skills developed and validated by Liberman and his colleagues at the University of California at Los Angeles (1), the deficits in attention, memory, and verbal learning often experienced by persons with schizophrenia are overcome by repetition, shaping of incremental behavioral improvements, video modeling, and feedback for galvanizing attention. Procedural learning techniques that do not rely on the brain capacities that mediate verbal awareness and insight are also used. In this month's Rehab Rounds column, Roder and his colleagues present another example of a skills training approach of the third era that includes elements of cognitive remediation. As autonomous offsprings of integrated psychological therapy (IPT), which was originally developed by Hans Brenner and Volker Roder and their colleagues at the University of Bern in Switzerland (2), the new programs address deficits in the residential, vocational, and recreational domains of community functioning. Overall, social skills training has been shown to be effective in the acquisition and maintenance of skills and their transfer to community life. Moreover, evidence is accumulating that structured and systematic skills training is more effective than other psychosocial treatments with which it has been compared, such as supportive group therapy and expressive modes of occupational therapy.
Activities of Daily Living↗
Holoprosencephaly and low molecular weight proteinuria: the human homologue of murine megalin deficiency.
We encountered a child with holoprosencephaly, pulmonary insufficiency, absent circulating vitamin D metabolites, mild albuminuria, and urinary excretion of vitamin D-binding protein. The child displayed a phenotype highly reminiscent of that observed in mice genetically deficient for megalin, a member of the low-density lipoprotein receptor superfamily. Only the Guthrie card was available from the child; the DNA sufficed for a limited haplotype analysis. We were not able to implicate the megalin gene locus directly; however, the possibility of a functional megalin defect in this child remains. To the best of our knowledge, this patient represents the first report that pathologic abnormalities consistent with megalin deficiency are present in humans.
Animals↗
Generation of human high-affinity antibodies specific for the fibroblast activation protein by guided selection.
Four completely human antibody derivatives [single-chain-antibody fragments (scFvs)] with specificity for the general tumor stroma marker fibroblast activation protein (FAP) were isolated by guided selection. Highly diverse IgG, IgM and IgD isotypes comprising heavy-chain variable domain libraries were generated using cDNAs derived from diverse lymphoid organs of a multitude of donors. Three of the human scFvs were converted into bivalent minibodies and expressed in eukaryotic cells for further functional characterization. Binding-competition studies and analysis by fluorescence-activated cell sorting showed high-affinity binding (10--20 nM) for two clones and recognition of the same epitope as the murine guiding antibody. The minibodies were successfully used for immunohistology of a variety of human carcinoma biopsies, revealing specific staining of stromal fibroblasts. Therefore, they should be suitable for in vivo diagnostic and tumor-targeting studies and, because of their completely human origin, be superior to murine or humanized antibody derivatives.
Amino Acid Sequence↗
[Some religious and ethical aspects of active, direct euthanasia].
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Attitude to Health↗
[Interdisciplinary cooperation in health care].
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Cooperative Behavior↗
[Automatic social behavior: how does activation of the concepts of egoism and altruism influence helping behavior?].
An experimental study investigated the influence of priming on helping behavior. A scrambled sentence test was used to prime groups with the concepts of altruism or egoism. In a third group a neutral concept was activated. The results indicated that there is no difference in helping behavior between the altruism and the neutral group. However, in the egoism priming condition participants showed higher latencies and helped less often than participants in both other conditions.
Adult↗
The effect of desmopressin on short-term memory in children with primary nocturnal enuresis.
PURPOSE: The use of desmopressin in patients with primary nocturnal enuresis is based on the hypothesis of a nocturnal lack of endogenous arginine vasopressin. However, in addition to the kidney, other targets of desmopressin are known. Therefore, we examined whether the administration of desmopressin influences central nervous function in children with primary nocturnal enuresis. MATERIALS AND METHODS: Our prospective, randomized, double-blind, placebo controlled cross-over study was performed on 40 children with nocturnal enuresis. Patients were randomly assigned to receive either 20 microg. desmopressin intranasally or 0.9% saline solution. Each group comprised 19 and 21 to children, respectively. After 2 weeks the groups were switched. The children were tested for short-term memory and reaction time to both treatments. Statistical analysis was done using the Wilcoxon matched pairs test. RESULTS: Median patient age was 8.0 years (range 6 to 13). During desmopressin treatment children in both groups had a significant decrease of wet nights (5.3 to 3.2 per week). In contrast to reaction time, short-term memory was significantly different between both groups (p <0.05). CONCLUSIONS: Our results demonstrate an increase in short-term memory after desmopressin treatment in children with nocturnal enuresis. This finding indicates the central nervous system as a target involved in the pathogenesis of nocturnal enuresis as well as the therapeutic benefit of desmopressin treatment.
Adolescent↗
Glial cell line-derived neurotrophic factor (GDNF) and its receptors GFRalpha-1 and GFRalpha-2 in the human testis.
Glial cell line-derived neurotrophic factor (GDNF) and its receptors GFRalpha-1 and GFRalpha-2 were found in the human testis during fetal development (15-34 weeks of gestation) and in adult men (51-86 years of age) by means of RT-PCR, immunohistochemistry and Western blot techniques. Gene expression of GDNF could be established in the human testis and immunoreactivity (IR) for GDNF was detectable in Leydig cells, Sertoli cells, some spermatocytes and round spermatids as well as in smooth muscle cells of the wall of arterioles and small arteries. In the adult human testis, Sertoli and Leydig cells showed GFRalpha-1-IR, whereas GFRalpha-2-IR was located exclusively in Leydig cells. Different to man, in the rat GDNF-IR in Sertoli cells was detectable only until postnatal day10, providing evidence for species related variability in the expression of GDNF. These findings suggest a critical role for GDNF during the differentiation of testicular structures and provide evidence for an additional important function in the adult human and rodent testis.
Aged↗
Some selective reactions of moenomycin A.
A number of new moenomycin A derivatives have been prepared. Their antibiotic properties highlight the very specific recognition of moenomycin A at the transglycosylase binding site which is the basis of the transglycosylase inhibiting property of moenomycin A (4a).
Anti-Bacterial Agents↗
Gene structure and chromosomal mapping of human epithelial calcium channel.
The epithelial Ca(2+) channel, ECaC, represents the rate-limiting step of vitamin D(3)-regulated Ca(2+) (re)absorption in kidney and intestine, and provides, therefore, a new candidate gene for Ca(2+)-related disorders. To supply the basis for direct mutation analysis, we report here the structure of the human ECaC gene (ECAC1(2)). It consists of 16 exons spanning 25 kb with introns ranging from 98 to 8500 bp. The 5'-flanking region of ECAC1 contains four putative vitamin D(3)-responsive elements. At positions -92 and -13 transcription initiation sites were identified, but the former lacks the canonical TATA or CAAT boxes. ECAC1 was mapped to chromosome 7q35 by fluorescent in situ hybridization, reassigning a previous radiation hybrid mapping to 7q31.1-2. The gene of a recently identified rat intestine homologue of ECaC, named Ca(2+) transporter 1, was found juxtaposed to the ECaC gene, indicating that both genes are the products of evolutionary local gene duplication.
Amino Acid Sequence↗
The Conradi-Hünermann-Happle syndrome (CDPX2) and emopamil binding protein: novel mutations, and somatic and gonadal mosaicism.
The Conradi-Hünermann-Happle (CHH) syndrome (X-chromosomal dominant chondrodysplasia punctata type II; MIM 302960) is an X-linked dominant disorder that is characterized by ichthyosis, chondrodysplasia punctata, cataracts and short stature. The disease occurs almost exclusively in females and shows increased disease expression in successive generations (anticipation). Recently, causative mutations in the emopamil binding protein (EBP) have been identified. To better appreciate the genetics of this syndrome we analyzed the EBP gene in seven independent families using PCR, conformation-sensitive gel electrophoresis, direct sequencing and restriction enzyme analysis. We found five novel mutations: three nonsense mutations in exon 2 and exon 3 and two frameshift mutations, one deletion in exon 4 and an insertion in exon 5. In two families, known mutations affecting exon 2 were identified. Surprisingly, we failed to detect the mutation in a grandmother exhibiting minor disease symptoms such as sectorial cataract and attribute this to gonadal and somatic mosaicism. Gonadal mosaicism appeared also to be involved in the case of healthy parents having two affected girls, one of whom died due to the disease. We conclude that gonadal mosaicism has to be considered when dealing with seemingly sporadic cases.
Adolescent↗
Molecular cloning, tissue distribution, and chromosomal mapping of the human epithelial Ca2+ channel (ECAC1).
Functional and morphological analyses indicated that the epithelial Ca2+ channel (ECaC), which was recently cloned from rabbit kidney, exhibits the defining properties for being the gatekeeper in transcellular Ca2+ (re)absorption. Its human homologue provides, therefore, a molecular basis for achieving a better understanding of Ca2+ mal(re)absorption. By applying the RACE technique, the full-length cDNA of human ECaC (HGMW-approved symbol ECAC1) was obtained. It consisted of 2,772 bp with an open reading frame of 2,187 bp encoding a protein of 729 amino acids with a predicted molecular mass of 83 kDa. Phylogenetic analysis indicated that this highly selective Ca2+ channel exhibits a low level of homology (<30%) to other Ca2+ channels, suggesting that it belongs to a new family. hECaC was highly expressed in kidney, small intestine, and pancreas, and less intense expression was detected in testis, prostate, placenta, brain, colon, and rectum. These ECaC-positive tissues also expressed the 1,25-dihydroxyvitamin D3-sensitive calcium-binding proteins, calbindin-D9K and/or calbindin-D28K. The human ECaC gene mapped to chromosome 7q31.1-q31.2. Taken together, the conspicuous colocalization of hECaC and calbindins in organs that are not prime regulators of plasma Ca2+ levels could illustrate new pathways in cellular Ca2+ homeostasis.
Amino Acid Sequence↗
Cyclin E-mediated elimination of p27 requires its interaction with the nuclear pore-associated protein mNPAP60.
The Cdk2 inhibitor, p27(Kip1), is degraded in a phosphorylation- and ubiquitylation-dependent manner at the G(1)-S transition of the cell cycle. Degradation of p27(Kip1) requires import into the nucleus for phosphorylation by Cdk2. Phosphorylated p27(Kip1) is thought to be subsequently re-exported and degraded in the cytosol. Using two-hybrid screens, we now show that p27(Kip1) interacts with a nuclear pore-associated protein, mNPAP60, map the interaction to the 3(10) helix of p27 and identify a point mutant in p27(Kip1) that is deficient for interaction (R90G). In vivo and in vitro, the loss-of-interaction mutant is poorly transported into the nucleus, while ubiquitylation of p27R90G occurs normally. In vivo, co-expression of cyclin E and Cdk2 rescues the import defect. However, mutant p27(Kip1) accumulates in a phosphorylated form in the nucleus and is not efficiently degraded, arguing that at least one step in the degradation of phosphorylated p27(Kip1) requires an interaction with the nuclear pore. Our results identify a novel component involved in p27(Kip1) degradation and suggest that degradation of p27(Kip1) is tightly linked to its intracellular transport.
3T3 Cells↗