Regulation of cholangiocyte bile secretion.
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Animals↗
Biomedical subjects
S Glaser
Publications and source records attributed to S Glaser.
A radiation hybrid map of the zebrafish genome.
Recent large-scale mutagenesis screens have made the zebrafish the first vertebrate organism to allow a forward genetic approach to the discovery of developmental control genes. Mutations can be cloned positionally, or placed on a simple sequence length polymorphism (SSLP) map to match them with mapped candidate genes and expressed sequence tags (ESTs). To facilitate the mapping of candidate genes and to increase the density of markers available for positional cloning, we have created a radiation hybrid (RH) map of the zebrafish genome. This technique is based on somatic cell hybrid lines produced by fusion of lethally irradiated cells of the species of interest with a rodent cell line. Random fragments of the donor chromosomes are integrated into recipient chromosomes or retained as separate minichromosomes. The radiation-induced breakpoints can be used for mapping in a manner analogous to genetic mapping, but at higher resolution and without a need for polymorphism. Genome-wide maps exist for the human, based on three RH panels of different resolutions, as well as for the dog, rat and mouse. For our map of the zebrafish genome, we used an existing RH panel and 1,451 sequence tagged site (STS) markers, including SSLPs, cloned candidate genes and ESTs. Of these, 1,275 (87.9%) have significant linkage to at least one other marker. The fraction of ESTs with significant linkage, which can be used as an estimate of map coverage, is 81.9%. We found the average marker retention frequency to be 18.4%. One cR3000 is equivalent to 61 kb, resulting in a potential resolution of approximately 350 kb.
Animals↗
Analysis of BR96 binding sites for antigen and anti-idiotype by codon-based scanning mutagenesis.
We performed a scanning mutagenesis study of heavy chain complementarity-determining region (CDR) residues to identify how mutations affected binding of the anti-carcinoma mAb BR96 to Ag, Lewis Y, and to an anti-Id Ab (anti-Id). By ELISA, we demonstrated that the anti-Id bound close to the Ag binding site of BR96, but the anti-Id and Ag sites were not identical. Immunoblot analysis and screening of light and heavy chain CDR libraries with multiple mutations in each CDR suggested that the heavy chain had greater involvement in anti-Id binding. We then analyzed contributions of individual residues in the heavy chain CDRs to binding of Ag and anti-Id. In a filamentous phage vector containing BR96 V region sequences, mutations were introduced by codon-based mutagenesis at single positions within the three heavy chain CDRs. The resulting libraries of Fab fragments had all amino acids represented at a CDR position. We evaluated the expressed Fabs for binding to Ag and anti-Id by plaque lift assay. We identified the positions with mutations that had the greatest negative effect on binding to the anti-Id and to Ag and analyzed them on the basis of the BR96 x-ray structure. The residues most important for binding to the anti-Id were located in heavy chain CDR1 and CDR2 and were peripheral to the residues within the Lewis Y binding pocket.
Animals↗
Structural studies of histidine-containing phosphocarrier protein from Enterococcus faecalis.
Based on the complete sequential assignment of the 1H-NMR spectrum by multidimensional NMR techniques the secondary structure and the local geometry of the active site of histidine-containing phosphocarrier protein (HPr) from Enterococcus faecalis were elucidated. We present a comparative analysis of the active site in the seven known structures of HPr from different organisms determined by NMR or X-ray crystallography. In catalysis, HPr is phosphorylated at the ring N61 of His15. No general agreement exists in literature regarding the structure of the active-centre loop. In the crystal structure of HPr from E. faecalis, a torsion strain of the backbone at position 16 was observed, which was assumed to be important to the catalytic mechanism. Coupling constants were determined in order to calculate phi angles to establish whether there are strained torsion angles in HPr from E. faecalis in the solution state. The evaluation of data obtained indicate a stable and well-defined structure of HPr from E. faecalis, with an overall fold similar to that found in HPr from other bacteria. We find that in the active-site region there are relatively large variations in local geometry between the evaluated structures. In HPr from E. faecalis, a particularly detailed view of the phosphate-binding His15 and residues in close spatial proximity was obtained by determination of coupling constants obtained from the double-quantum-filtered COSY spectrum. Our data indicate that in aqueous solution, in the dominant conformational state there is no torsion strain of the backbone at position 16, as observed in the crystal state. The maximum population of a strained conformation in solution can be estimated to be smaller than 23%. The analysis of the data suggests that the active-centre loop is able to adopt different conformations in solution. A similar observation was made for HPr from E. faecalis phosphorylated at its regulatory site (Ser46). 31P-NMR shows that phosphorylated HPr exists in two conformational substates with nearly equal populations.
Bacterial Proteins↗
Endothelin-1 inhibits secretin-stimulated ductal secretion by interacting with ETA receptors on large cholangiocytes.
We studied the expression of endothelin-1 (ET-1) receptors (ETA and ETB) and the effects of ET-1 on cholangiocyte secretion. The effects of ET-1 on cholangiocyte secretion were assessed in normal and bile duct-ligated (BDL) rats by measuring 1) basal and secretin-induced choleresis in vivo, 2) secretin receptor gene expression and cAMP levels in small and large cholangiocytes, and 3) luminal expansion in response to secretin in intrahepatic bile duct units (IBDU). ETA and ETB receptors were expressed by small and large cholangiocytes. ET-1 had no effect on basal bile flow or bicarbonate secretion in normal or BDL rats but decreased secretin-induced bicarbonate-rich choleresis in BDL rats. ET-1 decreased secretin receptor gene expression and secretin-stimulated cAMP synthesis in large cholangiocytes and secretin-induced luminal expansion in IBDU from normal or BDL rats. The inhibitory effects of ET-1 on secretin-induced cAMP synthesis and luminal duct expansion were blocked by specific inhibitors of the ETA (BQ-610) receptor. ET-1 inhibits secretin-induced ductal secretion by decreasing secretin receptor and cAMP synthesis, two important determinants of ductal secretion.
Animals↗
Coating of titanium alloy with soluble laminin-5 promotes cell attachment and hemidesmosome assembly in gingival epithelial cells: potential application to dental implants.
The formation of a biological seal around the transmucosal portion of dental implants may be crucial for the long-term success of these therapies. Data to date suggest that the gingival epithelium attaches to dental implants through the formation of hemidesmosomes. Biochemical and genetic data indicate that the laminin isoform, laminin-5, a component of basement membranes, plays a crucial role in the assembly and maintenance of hemidesmosomes. We report the use of soluble laminin-5 as a biological coating of titanium-alloy to promote cell attachment of the gingival epithelial cell line, IHGK. Monoclonal antibodies reactive with laminin-5 depleted the coating solution of all cell attachment activity and blocked cell attachment to laminin-5-coated disks. Immunodepletion with antibodies to fibronectin had no effect. Finally, we demonstrate that IHGK cells assembled hemidesmosomes within 24 h of attachment to laminin-5-coated titanium alloy but not to the titanium alloy alone. These results suggest that soluble laminin-5 may have clinical applications as a dental implant coating to promote the formation of a biological seal.
Alloys↗
Large but not small intrahepatic bile ducts are involved in secretin-regulated ductal bile secretion.
We have shown that agonist-regulated ductal secretion is limited to large cholangiocytes. To directly study cholangiocyte heterogeneity along the length of the normal biliary tree, we defined the genetic and functional expression of agonist-induced ductal secretion in intrahepatic bile duct units (IBDU) of different sizes. Small IBDU (< 15-microns diam) were separated from large IBDU (> or = 15-microns diam), and then ducts of different sizes were characterized by morphometric analysis, gene expression, secretin-induced adenosine 3',5'-cyclic monophosphate (cAMP) synthesis, and secretion by change in luminal size in response to agonists. IBDU diameters ranged from 11 to 65 microns. Secretin increased ductal secretion solely in large IBDU. Forskolin induced a modest increase in ductal secretion in small IBDU but markedly increased ductal secretion in large IBDU. Secretion increased Cl-/HCO3- exchanger activity and cAMP levels in large but not small IBDU. Secretin receptor and Cl-/HCO3 exchanger mRNAs were detected only in large IBDU. We propose that agonist-induced ductal secretion occurs in large (> or = 15-microns diam) but not small (< 15-microns diam) intrahepatic ducts.
Animals↗
Bile acids stimulate proliferative and secretory events in large but not small cholangiocytes.
Accumulation of bile acids (BA) and cholangiocyte proliferation occur in cholestasis, but BA effects on the proliferative and secretory capacity of cholangiocytes are undefined. Cholangiocyte proliferation coupled with increased expression of H3 histone and secretin receptor (SR) genes and secretin-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) levels is limited to large cholangiocytes. We isolated pooled small and large cholangiocytes and studied the effect of taurocholic (TC) and taurolithocholic (TLC) acids on proliferation, by measurement of H3 histone gene expression, and secretion, by measurement of SR gene expression, cAMP levels, and Cl-/HCO3- exchanger activity. In pooled cholangiocytes, TC and TLC increased H3 histone (12-fold) and SR (3-fold) gene expression and both spontaneous (1.4-fold) and secretin-induced (4-fold) cAMP response. TC and TLC increased H3 histone (10-fold) and SR (2-fold) gene expression and secretin-induced cAMP response and Cl-/HCO3- exchanger activity (3-fold) only in large cholangiocytes. In large cholangiocytes, BA may have a signaling function in the modulation of ductal secretion.
Animals↗
Changes in expression of monoclonal antibody epitopes on laminin-5r induced by cell contact.
Laminin-5r is a basement membrane component that promotes rapid adhesion and hemidesmosome formation in epithelial cells. We raised monoclonal antibodies and identified their corresponding epitopes on the constituent chains of laminin-5r by western blotting. Using a combination of immunoprecipitation and ELISA assays, we determined that these epitopes are differentially exposed on two forms of the laminin-5r heterotrimer: soluble (passively adsorbed onto plastic) and cell-associated. Antibody 5C5 epitope is exposed on the cell-associated form, but not the soluble/passively adsorbed form of laminin-5r. Epitopes reactive with antibodies CM6, FM3, and TR1 are also preferentially exposed on cell-associated laminin-5r, such that reactivity of these antibodies with the cell-associated form is fourfold higher than with the soluble/passively adsorbed form in ELISA assays. Incubation of passively adsorbed laminin-5r with the human epithelial cell line SCC12 induced exposure of 5C5 and CM6, FM3, or TR1 epitopes. These data suggest that cells actively modify laminin-5r, perhaps during matrix assembly, and that the 5C5 epitope may serve as a marker for assembled laminin-5r matrix.
Animals↗
[nCPAP/nBIPAP therapy in sleep-related obstructive respiratory disorders in childhood].
nCPAP/nBIPAP-therapy is a possibility of treatment of sleep related disturbances also in childhood. We will demonstrate the therapeutic effect of therapy in 13 patients in the age range 3 to 14 years on behaviour, school performance, number of infections in the upper airways as well as on polygraphic parameters, i.e., sleep structure, number of apneas, oxygen saturation and mean heart rate.
Child↗
The use and costs of physician services for ophthalmic surgical procedures in 1988 and 1991.
BACKGROUND AND OBJECTIVE: To examine the change in volume and costs of physician services for ophthalmic surgical procedures associated with physician fee cuts. MATERIALS AND METHODS: The authors analyzed the physician claims (Part B) data for a 5% random sample of the Medicare population. Number, rate, average allowed charge, and total cost of physician services for ophthalmic surgical procedures were compared for 1988 and 1991. RESULTS: An estimated 3.1 million (98 per 1000) ophthalmic surgical procedures were performed on Medicare beneficiaries in 1991, compared with 2.3 million (76 per 1000) in 1988. There was a 35% increase in number and a 28% increase in rate. The average allowed charge for these services decreased by 26% ($1155 vs $852 per procedure), with an overall cost of $2.6 billion in both years. CONCLUSION: A reduction in fee for physician services for ophthalmic surgical procedures from 1988 to 1991 was associated with an increase in the volume of the services. The overall costs of physician services for ophthalmic surgical procedures remained consistent between the two years.
Direct Service Costs↗
[Ondine syndrome: presentation of pediatric aspects based on a case report].
The congenital central alveolar hypoventilation syndrome (Undine's syndrome, or Ondine's curse) is a rare disorder of central ventilation. In recent years a successful therapy has been found consisting of pacing of the diaphragm. Early diagnosis is therefore significant for preoperative management. In our paper, we present the clinical course of a female newborn with Ondine's curse. Conclusions for the further management by the paediatric staff are demonstrated.
Carbon Dioxide↗
Plasma levels of DSIP in infants in the first year of life and SIDS risk.
In searching for abnormalities related to the sudden infant death syndrome (SIDS), delta sleep-inducing peptide (DSIP), a regulatory peptide with sleep promoting actions, was investigated in the first year of life in four groups of children: (1) preterm infants (n = 28), (2) infants with a high mean apnea duration evaluated polysomnographically (n = 26), (3) healthy full-term infants (n = 37) and (4) siblings of SIDS-victims (n = 26). DSIP was radioimmunoassayed in plasma. Half of the infants were also investigated polygraphically during sleep. The ratio between quiet sleep and active sleep was determined. There was no age dependence of the plasma level of DSIP in the first year of life but there was an increase in the ratio of quiet/active sleep depending of maturity. The level of DSIP in healthy full-term infants was significantly higher (P less than 0.05) (median: 1885 pmol/l, interquartile range: 757 pmol/l) than in preterms (1595; 385) and in infants with a high mean apnea duration (1542; 373). There was no significant difference in DSIP concentrations between healthy full-term infants and SIDS-siblings (1605; 271).
Age Factors↗
Plasma levels of beta-endorphin and substance P in the first year of life in full-term and preterm infants.
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Age Factors↗
Substance P, mean apnoea duration and the sudden infant death syndrome (SIDS).
In order to evaluate disturbances of the respiratory control in the first year of life in children with a statistically enhanced risk of SIDS, substance P-like immunoreactivity (SPLI) in plasma and mean apnoea duration (MA) were examined. 4 groups of infants were investigated: Controls, full-term infants with anamnestic SIDS-risk factors, preterm infants with additional risk factors and preterm infants without such factors. Infants aged from -4(corrected age) to 63 weeks. SPLI in plasma was determined by a specific, homologous radioimmunoassay. The SPLI-level was significantly higher in controls (n = 41; means +/- SE = 36.37 +/- 4.86 pg/ml) than in preterm infants without (n = 21; 25.41 +/- 5.54 pg/ml) or with additional anamnestic risk factors (n = 111; 25.89 +/- 3.09 pg/ml). SPLI was higher in full-term SIDS-risk infants (n = 150; 30.73 +/- 2.35 pg/ml) than in the preterm groups. There is a significant age dependence in the groups full-term SIDS-risk infants and preterm infants with additional risk factors. During maturation the SPLI-level in plasma rises in these groups from lower values. The MA-values were determined by means of a daytime polygraphy. There is an age dependence of the MA-values during active sleep in full-term SIDS-risk infants and in preterm infants with additional anamnestic risk factors. In the age group 4-17 weeks (peak of SIDS frequency) in active sleep the MA-values were significantly higher in all 3 risk groups than in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)
Humans↗
Heart rate fluctuations in rabbits during different behavioural states.
Heart rate fluctuations (HRF) were investigated in 18 adult female rabbits (Weisses Grosssilber) in chronical experiments at rest, during motor activity, passive and active avoidance. Pharmacological blockades of the neurovegetative transmission were used to determine the characteristics of neurovegetative mediation during the behavioural states examined. Mean heart rate was always increased during vagal blockade and decreased during beta-adrenergic blockade. At rest the HRF in rabbits are mainly vagally mediated. Vagal blockade reduced the overall heart rate variability by more than 50%. Vagal blockade did not abolish respiratory heart rate fluctuations. If the mean respiratory frequency is greater than half of the mean heart rate frequently occurring in rabbits, the respiratory HRF are generated not synchronously with respiration but in a slower frequency range according to the physiologic effect of "cardiac aliasing". The movement related heart rate increase was absent if the movements were performed during combined beta adrenergic and vagal blockade. The heart rate reaction during passive avoidance was characterized by a heart rate deceleration abolished by vagal blockade. Respiratory HR were increased. Furthermore, the heart rate was returned to the previous mean level and the slow HRF not induced by respiration increased, mediated by beta adrenergic activation. Vagal blockade and beta adrenergic blockade diminished the heart rate acceleration and reduced the overall heart rate variability by more than 50% during active avoidance. Combined vagal and beta-adrenergic blockade fully abolished the heart rate acceleration effect during active avoidance. The ratio of the vagal to sympathetic reaction components differed in behavioural types.
Adrenergic alpha-Antagonists↗
Structure and function of proteins involved in sugar transport by the PTS of gram-positive bacteria.
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Amino Acid Sequence↗
[Sudden and unexpected infant death].
SIDS is a topical problem in pediatrics. The cause of SIDS is still unknown. The paper considers different possible pathomechanisms and on the basis of different observations a variety of hypotheses: There is the apnoe hypothesis, the sleep hypothesis, the QT-hypothesis, the arousal hypothesis and the functional deficit primarily concerning the reticular formation of the brainstem. Therefore there is an urgent need for screening programms to find out children at risk of SIDS. Finally, aspects of prophylaxis and treatment in case of recognized risk are discussed.
Humans↗