NOD mouse peritoneal cellular response to poly-L-lysine-alginate microencapsulated rat islets.
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Alginates↗
Biomedical subjects
A Becker
Publications and source records attributed to A Becker.
Stable expression of human endothelin receptors ETA and ETB by transfected baby hamster kidney cells.
The cDNAs for human endothelin receptors ETA and ETB were subcloned into the eukaryotic expression vector pMPSV/CMV and transfected, in parallel with plasmids carrying resistances for hygromycin B and puromycin, into baby hamster kidney (BHK) cells. Cell clones constitutively expressing high levels of either receptor were obtained through the combined selective pressure of both antibiotics. This was further confirmed by Northern blot analysis using ETA- or ETB-specific oligonucleotide probes. The calculated KD for endothelin (ET)-1 binding to ETA and ETB were 2.2 x 10(-10) M and 5.3 x 10(-10) M, respectively. Competitive binding experiments using the different ET forms showed the expected isopeptide-selective and non-isopeptide-selective profiles for ETA and ETB, respectively. BQ 123, a specific ETA antagonist, competed with ET-1 for binding to ETA but not to ETB.
Animals↗
Paramagnetic Meissner effect in high-temperature superconductors.
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Journal Article↗
Characterisation of the ATP-dependent taurocholate-carrier protein (gp110) of the hepatocyte canalicular membrane.
The canalicular domain-specific glycoprotein gp110, which recently has been shown to function as an ATP-dependent taurocholate transporter, has been purified 1800-fold from rat liver plasma membranes. gp110 has been characterised as an integral plasma membrane protein with M(r) of 100,000-115,000 and pI of 2.5-3.5 and possesses a highly glycosylated and negatively charged extra-cellular domain. The broad range of M(r) and pI values results from the existence of numerous glycoforms composed of sialylated N-glycans. After deglycosylation, the polypeptide has M(r) 48,000 and pI 5.0. In primary cultures of rat hepatocytes, gp110 is synthesised with M(r) 110,000, while in the presence of tunicamycin the non-glycosylated form has M(r) 48,000. In the presence of 1-deoxymannojirimycin, two forms of M(r) 83,000 and M(r) 91,000 were found, which were converted by endo-beta-N-acetylglucosaminidase H into a single 52,000-M(r) band, indicating the existence of two basic glycoforms at the oligomannosyl stage of biosynthesis. gp110 was phosphorylated at serine residues in primary cultures of hepatocytes. The sequences of ten internal peptides of gp110 were identical to the sequence of the high-M(r) form of ecto-ATPase, but ecto-ATPase activity from plasma-membrane extracts was not depleted by anti-(gp110) serum. In contrast, Fab fragments of these antibodies inhibit the aggregation of freshly isolated hepatocytes.
ATP-Binding Cassette Transporters↗
Expression of human endothelin receptor ETB by Escherichia coli transformants.
Membrane fractions from Escherichia coli transformed with an expression vector for the human endothelin receptor ETB were found to exhibit specific and saturable binding sites for labeled ET-1. Binding properties were similar to those observed in eukaryotic cells: KD was 110 pM and the three endothelin isoforms were equipotent in competition experiments. The importance of the cysteines located in each of the three extracellular loops was assessed by replacing them individually with alanine residues. Impaired binding was observed in each case but the effect was far more pronounced for the cysteine mutants of the first and second loop pointing to their critical importance for active ETB expression.
Base Sequence↗
[Diagnosis of cerebellopontile angle tumors--only a problem for specialists?].
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Cerebellar Neoplasms↗
Bibrotoxin, a novel member of the endothelin/sarafotoxin peptide family, from the venom of the burrowing asp Atractaspis bibroni.
A new member of the endothelin/sarafotoxin family of vasoconstrictor peptides, bibrotoxin (BTX), was isolated from the venom of the burrowing asp Atractaspis bibroni by reversed-phase FPLC. The amino acid sequence of BTX differs from SRTX-b in the substitution Ala4 instead of Lys4, which suggests that it represents the peptide isoform of Atractaspis bibroni corresponding to SRTX-b. BTX competed for [125I]ET-1 binding to human ETB-type receptor with a Ki of 3.2 x 10(-9) M compared to 4.2 x 10(-9) M for SRTX-b. In rat thorax aorta BTX induced vasoconstrictions with a threshold concentration of 3 x 10(-8) M compared to 1 x 10(-9) for ET-1.
Amino Acid Sequence↗
Analysis of the Rhizobium meliloti exoH/exoK/exoL fragment: ExoK shows homology to excreted endo-beta-1,3-1,4-glucanases and ExoH resembles membrane proteins.
Nucleotide sequencing of a 4.15 kb DNA fragment from megaplasmid 2 of Rhizobium meliloti 2011 revealed the location of the genes exoH, exoK and exoL. The putative proteins encoded by these genes have molecular weights of 41, 30, and 44 kDa, respectively. The hydrophobicity profile of the ExoH amino acid sequence resembles that of transmembrane proteins. The predicted exoL gene product does not contain hydrophobic regions, indicating a cytoplasmic localization. The exoK gene product is characterized by a putative signal peptide and exhibits significant homology to endo-beta-1,3-1,4-glucanases of bacilli and Clostridium thermocellum. R. meliloti exoK mutants induced pink nodules and synthesized a reduced amount of exopolysaccharide (EPS). Colonies of this mutant showed a delay in the appearance of the Calcofluor white fluorescence. In addition, the formation of the characteristic halo was strongly delayed. R. meliloti exoL and exoH mutants induced pseudonodules. The exoH, but not the exoL mutant, synthesized an EPS that could be precipitated by cetyl pyridinium chloride (CPC) and also by ethanol. Plasmid integration mutagenesis revealed promoter regions preceding exoH, exoK and exoL.
Amino Acid Sequence↗
Identification and analysis of the Rhizobium meliloti exoAMONP genes involved in exopolysaccharide biosynthesis and mapping of promoters located on the exoHKLAMONP fragment.
Sequence analysis of a 7.494 kb DNA fragment from megaplasmid 2 of Rhizobium meliloti 2011 involved in exopolysaccharide I (EPS I) biosynthesis revealed the presence of five exo genes designated exoA, exoM, exoN, exoO, and exoP. ExoN was found to show strong homology to a UDP-glucose pyrophosphorylase from Acetobacter xylinum, whereas ExoO displayed weak homologies to the NodC proteins from R. meliloti and R. loti. Surprisingly, different mutations in exoP resulted in divergent phenotypes. One exoP mutant was able to establish an effective symbiosis with alfalfa, although no EPS I polymer could be detected. In contrast, other exoP mutations prevented the formation of an effective symbiosis. The transcriptional organization of the exoA-exoP gene region has been analysed in conjunction with the exoH, exoK and exoL genes. Using exo-lacZ transcription fusions in association with plasmid integration mutagenesis a strong promoter was identified upstream of exoH, which is able to direct transcription of the whole exoHKLAMONP gene cluster. A much weaker promoter upstream of exoL was found to be involved in the transcription of the exoLAMONP genes. In addition, weak promoters were identified upstream of exoK, exoA, exoN and exoP.
Amino Acid Sequence↗
Effect of antihypertensive drugs on glomerular hyperfiltration and renal haemodynamics. Comparison of captopril with nifedipine, metoprolol and celiprolol.
Glomerular hyperfiltration and hypertension may contribute to the progression of chronic renal insufficiency regardless of the underlying disease. Protein restriction and antihypertensive treatment are used to slow the decline in renal function. However, little is known about the interaction of protein loading and antihypertensive treatment on glomerular haemodynamics in humans. This paper compares the renal haemodynamic effects of beta-adrenoceptor blockers with those of the calcium channel antagonist nifedipine and the ACE inhibitor captopril on resting glomerular filtration and during glomerular hyperfiltration. In two separate studies the effects of nifedipine, captopril, metoprolol, and celiprolol on renal haemodynamics have been investigated. In two groups of healthy volunteers (n = 13) inulin and PAH clearances were measured, first under fasting conditions and afterwards during aminoacid infusion. In fasting subjects nifedipine and metoprolol induced glomerular hyperfiltration, while celiprolol and captopril did not significantly affect GFR. Without premedication, and also after nifedipine, metoprolol and celiprolol, the aminoacid infusion significantly increased the GFR. After premedication with captopril, however, aminoacid-induced hyperfiltration was prevented. In fasting subjects captopril, celiprolol and metoprolol elevated PAH clearance. With our without premedication aminoacid infusion increased renal plasma flow compared to baseline on the control day. We conclude that in healthy subjects, acute administration of antihypertensive drugs results in different renal haemodynamic responses. In contrast to captopril and celiprolol, nifedipine and metoprolol induce glomerular hyperfiltration like protein loading. Thus, they may counteract the renal haemodynamic effects of protein restriction. Celiprolol behaves similarly to captopril, since it increases renal perfusion without inducing glomerular hyperfiltration, a pattern which might reflect lower glomerular pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
Antihypertensive Agents↗
Resorbed lateral incisors adjacent to impacted canines have normal crown size.
The importance of detecting maxillary canine impaction is that it may compromise dental health, particularly since a small but significant proportion of impacted canines is associated with the resorption of the roots of neighboring teeth. It has been shown that the existence of small and peg-shaped lateral incisors is highly correlated with maxillary canine palatal impaction. To date, however, it has not been established whether the root resorption that occurs has a similar correlation or a predilection for one or other types of lateral incisor crown structure. Accordingly, a group of patients with buccally or palatally impacted canines, in which root resorption of the lateral incisor could be diagnosed roentgenographically, was examined and compared with a group of cases with palatally impacted canines, none of which showed root resorption, which served as controls. The mesiodistal crown dimension of the lateral incisor in the experimental group was found to be normal in all patients except three (13%), which was significantly different from the distribution of lateral incisor size in the control group (p < 0.001). In the majority of the cases, aggressive root resorption of the lateral incisor root had occurred. We would speculate that in these cases, the normal-sized and early developing lateral incisor root obstructs the deviated eruption path of the canine and consequently stands a considerably greater chance of being damaged by resorption.
Adolescent↗
Ectopic eruption of maxillary canines.
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Child↗
Extracellular cysteine residues 174 and 255 are essential for active expression of human endothelin receptor ETB in Escherichia coli.
The coding sequences for the non-isopeptide-selective human endothelin receptor ETB were introduced into the prokaryotic expression vector pKK233-2, and the resulting construct was used for transformation of competent E. coli JM105 cells. Specific binding was observed for bacterial membrane fractions, using labeled ET-1 as a ligand. Site-directed mutagenesis was employed to individually modify the triplets for the cysteines of the first and second extracellular loops of ETB to alanine codons. E. coli JM105 transformed with the mutated plasmids no longer displayed specific ET-1 binding to membranes, which suggests a crucial role for these extracellular cysteines in agonist binding or receptor stability.
Cell Membrane↗
Binding characteristics of recombinant human endothelin receptors ETA and ETB expressed in baby hamster kidney cells.
Expression constructs for human endothelin (ET) receptors ETA and ETB were made by subcloning the corresponding coding sequences into the pMPSV/CMV vector. They were used together with plasmids bearing resistances to puromycin and hygromycin for transfection of baby hamster kidney cells. Culture in the presence of both antibiotics allowed the selection of cell lines stably expressing one receptor or the other. Competitive binding experiments using ET-1 and ET-3 showed the typical isopeptide-selective and non-isopeptide-selective profiles for recombinant ETA and ETB, respectively.
Animals↗
Glutamate binding to brain membranes is increased in pentylenetetrazole-kindled rats.
The specific binding of L-[3H]glutamate to its receptors was investigated on crude membrane preparations from different brain regions of pentylenetetrazole-kindled rats using a binding assay technique. Pentylenetetrazole kindling induced by 10 intraperitoneal applications of 45 mg/kg over a period of 20 days resulted in a significant increase of both the convulsive susceptibility of animals to the convulsant and the specific L-[3H]glutamate binding in hippocampus and in motor, frontal, and inferotemporal (acoustic) cortex tested with a L-[3H]glutamate concentration of 50 nM. No differences were observed in the other brain structures studied. Kinetic studies indicated that the enhanced L-[3H]glutamate binding to hippocampal membranes from kindled rats reflects changes in the density of the glutamate binding sites rather than an increase in receptor affinity. To study the effect of acute generalized convulsions on L-[3H]glutamate binding to synaptosomal membranes of hippocampus and visual cortex, rats were treated 24 h before the experiment with 60 mg/kg of pentylenetetrazole, i.p. Under these conditions, no differences between treated and control rats were observed. From these findings, it is concluded that the increase in glutamate receptor density demonstrated in hippocampus and several neocortical brain structures of pentylenetetrazole-kindled rats may be the expression of a specific enhancement of susceptibility of glutamatergic systems to this excitatory amino acid developing in the course of formation of pentylenetetrazole-induced kindling.
Animals↗
Leukotriene generation and metabolism in dogs: inhibition of biosynthesis by MK-0591.
Peptidoleukotriene metabolism in dogs was investigated to determine the suitability of this species for the development of in vivo biochemical models of asthma and inflammation. Circulatory metabolism of [3H]leukotriene (LT)C4 (0.5 microCi/kg, i.v.) to [3H]LTE4 and subsequent clearance was rapid (T1/2 = 100 sec). After 3 h, the major urinary metabolite was [3H]16-carboxydihydrotetranor LTE4 (identified by radiochromatography), with [3H]LTE4 accruing to a significant 1.7 +/- 0.9% (n = 3) of the original [3H]LTC4 dose. Immunoreactive LTE4 was excreted into canine urine at 1.85 +/- 0.35 to 2.35 +/- 0.57 ng/h (n = 4) over a 6-h period, suggesting that this metabolite may be an index of acute in vivo 5-lipoxygenase activity. MK-0591, a high-affinity ligand for the canine homolog of the human 5-lipoxygenase activating protein, dose-dependently inhibited the systemic generation of peptidoleukotrienes as measured by urinary LTE4 excretion (ED50 1 microgram/kg/min), the time course of disappearance of LTE4 from the urine being similar to that of the clearance of [3H]LTE4. Because the therapeutic improvements in human allergic asthmatics treated with LT synthesis inhibitors and challenged with antigen appear to be related to the degree of in vivo inhibition of LT biosynthesis (measured by urinary LTE4), the dog may be an appropriate species for preclinical assessment of LT inhibitors.
5-Lipoxygenase-Activating Proteins↗
Growth of Hodgkin cell lines in severely combined immunodeficient mice.
No animal model exists for the in vivo growth of Hodgkin's-lymphoma-derived cells. Neither unmanipulated Hodgkin's-disease(HD)-derived cell lines nor primary biopsy tissue could be grown in nude mice. Since the severe combined immunodeficient (SCID) mouse has been reported to be a better recipient for transplanted human lymphatic tissue than the nude mouse, we tested whether SCID mice provide suitable conditions for the in vivo growth of HD cell lines. Tumorigenicity of HD cells was tested in untreated and pre-treated SCID mice and in another combined immunodeficient mouse strain, beige/nude/X-linked immunodeficient (BNX) mouse. SCID mice supported in vivo growth of the 6 HD cell lines tested (L428, L540, L591, DEV, HD-LM2, KM-H2). Only one of the 6 lines (DEV) was tumorigenic in BNX mice. No HD cell line proliferated in T-cell-deficient nude mice. Thus, in vivo growth of HD cell lines appeared to be related to the degree of host immunodeficiency. Additional growth supportive treatments such as fibrosarcoma co-transplantation, intraperitoneal mineral oil injection or immunosuppressive pre-treatment (anti-asialo-GMI-antibody injection) permitted growth of 3 additional HD cell lines in BNX mice. The immunophenotype and karyotype of explanted graft cells were identical to the original cell lines. Our experiments describe an effective and reproducible xenograft model for growth of Hodgkin's-disease-derived cell lines. This may be of value for elucidating the growth characteristics of Hodgkin's-lymphoma-derived cells as well as for testing new therapeutic regimens.
Animals↗
A yeast cyclophilin gene essential for lactate metabolism at high temperature.
The cyclophilins are a family of ubiquitous eukaryotic proteins first identified by high affinity for cyclosporin A (CsA). The immunosuppressant and cytotoxic effects of CsA are thought to result from formation of a toxic complex between cyclophilin and CsA rather than from inhibition of cyclophilin function. The physiological role(s) of the cyclophilins is unknown. Cyclophilins have in vitro peptidylprolyl cistrans isomerase (PPIase) activity, and thus may be involved in protein folding in vivo. We have isolated a yeast cyclophilin gene, CPR3, which encodes a presumptive mitochondrial isoform. While CPR3 disruption mutants lack any phenotype at 30 degrees C, they are unable to grow on L-lactate at 37 degrees C. Disruptions of two other cyclophilin genes (CPR1, CPR2) and of FPR1, the gene encoding an FK506 binding protein with PPIase activity, do not affect growth on L-lactate at 37 degrees C. L-Lactate metabolism requires transcriptional induction of CYB2, the gene encoding flavocytochrome b2; cpr3 mutants induce transcription of this gene normally. This result demonstrates a conditional lethal phenotype for a cyclophilin mutation and presents a system for genetic and biochemical analysis of cyclophilin function.
Amino Acid Isomerases↗