Biomedical subjects

A Becker

Publications and source records attributed to A Becker.

At least 19 recordsLinked to original sources

PubMed1992

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↗

PubMed1992

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↗

PubMed1992

Biosynthesis and metabolism of dipeptidylpeptidase IV in primary cultured rat hepatocytes and Morris hepatoma 7777 cells.

N-Glycosylation, biosynthesis and degradation of dipeptidylpeptidase IV (EC 3.4.14.5) (DPP IV) were comparatively studied in primary cultured rat hepatocytes and Morris hepatoma 7777 cells (MH 7777 cells). DPP IV had a molecular mass of 105 kDa in rat hepatocytes and of 103 kDa in MH 7777 cells as assessed by SDS/PAGE under reducing conditions. This difference in molecular mass was caused by differences in covalently attached N-glycans. DPP IV from hepatoma cells contained a higher proportion of N-glycans of the oligomannosidic or hybrid type and therefore migrated at a slightly lower molecular mass. In both cell types DPP IV was initially synthesized as a 97-kDa precursor which was completely susceptible to digestion with endo-beta-N-acetylglucosaminidase H converting the molecular mass to 84 kDa. The precursor was processed to the mature forms of DPP IV, glycosylated with N-glycans mainly of the complex type with a half-life of 20-25 min. The transit of newly synthesized DPP IV to the cell surface displayed identical or very similar kinetics in both cell types with the major portion of DPP IV appearing at the cell surface after 60 min. DPP IV molecules were very slowly degraded in hepatocytes as well as in hepatoma cells with half-lives of approximately 45 h. Inhibition of oligosaccharide processing with 1-deoxymannojirimycin led to the formation of DPP IV molecules containing N-glycans of the oligomannosidic type. This glycosylation variant was degraded with the same half-life as complex-type glycosylated DPP IV. By contrast, inhibition of N-glycosylation with tunicamycin resulted into rapid degradation of non-N-glycosylated DPP IV molecules in both cell types. Non-N-glycosylated DPP IV could not be detected at the cell surface indicating an intracellular proteolytic process soon after biosynthesis.

Animals↗

PubMed1992

Mediation of inorganic anion transport by the hydrophobic domain of mouse erythroid band 3 protein expressed in oocytes of Xenopus laevis.

A cDNA clone of the mouse erythroid band 3 protein encoding the 556 amino acid residues of the hydrophobic domain from Thr-374 to the C-terminal Val-929 is shown by immunoprecipitation to be expressed in Xenopus oocytes. Measurements of 36Cl- efflux indicate that the translation product mediates Cl- transport, which is inhibitable reversibly by DNDS or H2DIDS, specific inhibitors of band 3-mediated transport. The apparent KI values are 3.6 microM and 0.094 microM, respectively, and hence similar to those found in the wild type band 3-mediated anion transport. The rapid reversible inhibition by H2DIDS slowly changes to irreversible inhibition. The rate of change increases with increasing pH, again similar as to the wild-type band 3. It is concluded that the hydrophobic domain of band 3 is capable of executing anion transport essentially similar to the full-length band 3, although minor differences with respect to transport and inhibition kinetics cannot be ruled out.

Amino Acid Sequence↗

PubMed1992

Expression of a functional chimeric Ig-MHC class II protein.

We have generated a chimeric protein molecule composed of the alpha- and beta-chains of the MHC class II I-E molecule fused to antibody V regions derived from anti-human CD4 mAb MT310. Expression vectors were constructed containing the functional, rearranged gene segments coding for the V region domains of the antibody H and L chains in place of the first domains of the complete structural genes of the I-E alpha- and beta-chains, respectively. Cells transfected with both hybrid genes expressed a stable protein product on the cell surface. The chimeric molecule exhibited the idiotype of the antibody MT310 as shown by binding to the anti-idiotypic mAb 20-46. A protein of the anticipated molecular mass was immunoprecipitated with anti-mouse IgG antiserum. Furthermore, human soluble CD4 did bind to the transfected cell line, demonstrating that the chimeric protein possessed the binding capacity of the original mAb. Thus, the hybrid molecule retained: 1) the properties of a MHC class II protein with regard to correct chain assembly and transport to the cell surface; as well as 2) the Ag binding capacity of the antibody genes used. The generation of hybrid MHC class II molecules with highly specific, non-MHC-restricted binding capacities will be useful for studying MHC class II-mediated effector functions such as selection of the T cell repertoire in thymus of transgenic mice.

Animals↗

PubMed1992

Kindling and its consequences on learning in rats.

To study the learning performance of pentylenetetrazol- and amygdala-kindled Wistar rats we used the following learning tests: short-term memory was tested in the response-to-change model, brightness discrimination was tested in a Y-chamber, and two-way active avoidance learning was tested in a shuttle-box. Short-term memory was not impaired by both kindling procedures. Considering two-way active avoidance learning the performance of pentylenetetrazol (PTZ)-kindled rats was significantly diminished. This effect persists over a period of 4 weeks. However, amygdala (AMY)-kindled rats acquired this task like the controls. In brightness discrimination reaction (BDR) the learning performance of PTZ-kindled animals was not influenced. Although the acquisition of BDR was nearly identical, the 24-h retention was remarkably diminished in AMY-kindled rats. It was hypothesized that the different kindling procedures interfere in different ways and extent with neuronal circuits resulting in different functional impairments.

Amygdala↗

PubMed1992

The effects of infraocclusion: Part 2. The type of movement of the adjacent teeth and their vertical development.

This second article discusses how the inclusion of a vertical component (the infraocclusion of the deciduous molar) into the otherwise horizontal band of transseptal fibers affects the vertical development of the two adjacent teeth. From the hypothesis proposed in the first article of this series, it seemed logical to assume that the occlusal heights of the teeth adjacent to the affected tooth would themselves be lowered, when measured to the inferior border of the mandible and compared with the height of the occlusal table of the control side. Secondly, since the vertical component affects only one side of each adjacent tooth, these teeth would be tilted about a center of rotation which is much higher (coronal) than is seen in a tooth that merely tips forward as the result of available space in the immediate vicinity in the arch. In this study, both these assumptions were confirmed, with a very high degree of statistical significance.

Bicuspid↗

PubMed1992

The effects of infraocclusion: Part 1. Tilting of the adjacent teeth and local space loss.

The normal arrangement of the transseptal fibers in the dentition is one of a completely horizontal system that links the mesial and the distal aspects of each tooth within the dental arch, from the most distal tooth of one side to the most distal tooth of the other, across the midline. This continuous fiber band is parallel to the occlusal plane, being attached to each tooth coronal to the level of the interradicular alveolar bone crest and apical to the cementoenamel junction. Alteration of the occlusal plane will be mirrored by a similar change in the plane of the transseptal fiber system. From the clinical observation of young people with infraoccluded deciduous teeth, over many years, the regular and concomittant occurrence of certain other, well-defined phenomena appears to be the rule. It was thought that these phenomena could be explained in terms of the inclusion of a vertical component (infraocclusion) into this horizontal system. Two of these phenomena are discussed here. The first and most obvious of these relates to the exaggerated tipping that affects the adjacent tooth mesially and distally. The second parameter measures the amount of actual horizontal (mesiodistal) space change that occurs locally, within the dental arch, between the two teeth adjacent to the infraoccluded tooth, measured at both the occlusal level and at the level of their root apices. With a high degree of statistical validity, it was found that infraocclusion is related to severe tilting of the two adjacent teeth toward the affected tooth, with minimal space loss in the dental arch at the occlusal level, but a wide separation of root apices.

Ankylosis↗

PubMed1992

The effects of infraocclusion: Part 3. Dental arch length and the midline.

The third and final article in this series examines the effect of infraocclusion on the midline of the mandibular dental arch. From clinical observation, a shift in the dental midline to the side affected by infraocclusion seemed very common, and this could be explained within the terms of the hypothesis proposed in the first article. A method was devised on a panoramic radiograph to define and to distinguish the anatomic (skeletal) midline and the dental midline. This confirmed the existence of a dental shift to the affected side. The hemiarch length of each side was measured on the film, from the distal of the second deciduous molar/second premolar to both constructed midlines, and was found to be longer on the affected side, confirming an abnormally distal position of the first molar on that side.

Ankylosis↗

PubMed1992

Bioassay of a tracheal smooth muscle-constricting factor released by respiratory epithelial cells.

Epithelium-derived factors of unknown identity have been proposed to modulate airway smooth muscle tone. We developed a novel sensitive bioassay system that allows serial perfusion of cultured respiratory epithelial cells and guinea pig trachea (GPT). GPT responses were assessed as diameter changes by computerized video microscopy (resolution, 15 microns). A permanent hamster lung epithelial cell line was grown on microcarrier beads and perfused in a cell column. When the outflow tubing from the epithelial cell column was connected to the inflow cannula, the detector GPT contracted, reaching 28 +/- 6% of the maximum methacholine (100 microM)-induced contraction (n = 12, P less than 0.001). Perfusion of the cell column with diclofenac (10 microM) or lysin-mono-acetylsalicylic acid (100 microM) abolished the GPT contraction, whereas selective perfusion of the detector GPT with either agent did not block the contraction. Analysis of the effluent of the epithelial cell column demonstrated a significant basal release of prostaglandins F2 alpha and E2 (PGF2 alpha and PGE2) and 6-ketoprostaglandin F1 alpha, whereas only marginal amounts of thromboxane B2 were detected. When given exogenously, PGF2 alpha, PGE2, PGI2, and U-46619 all contracted the GPT. It is concluded that lung epithelial cells can contract GPT by releasing a transferable factor. This factor is likely to be a constrictor cyclooxygenase product that is not produced in epithelium-denuded GPT.

Animals↗

PubMed1992

Mechanisms of loss of heterozygosity in retinoblastoma.

Retinoblastoma (RB) tumors arise when both alleles of the RB1 gene are inactivated by two mutational events (M1 and M2). M1 can be an initial germline or somatic mutation; M2 is frequently loss of heterozygosity (LOH), which makes the cell homozygous or hemizygous for the original mutation. LOH is the major mechanism by which many cancers are initiated. To further delineate the mechanism of LOH, we screened a total of 37 RB tumors for LOH by Southern blot analysis. The tumors were from 17 bilaterally and 17 unilaterally affected patients. Nineteen of 30 informative tumors (63%) from 27 patients showed LOH. Proximal and distal flanking markers on chromosome 13 were informative in 13 tumors, allowing evaluation of the mechanisms by which LOH occurred. Mitotic recombination was implicated in 6 (46%) of the 13 tumors.

Blotting, Southern↗

PubMed1992

2-alpha-(N-dansyl-4-aminophenylthio)-N-acetyl-9-O-acetylneuraminic acid. A new specific and highly sensitive substrate in sialate-O-acetylesterase assay.

2-alpha-(N-Dansyl-4-aminophenylthio)-N-acetyl-9-O-acetylneuraminic acid (10) was prepared as a new specific and highly sensitively detectable sialate-9-O-acetyl-esterase substrate. It is built up from a sialidase-stable aminophenyl-alpha-thioketoside of N-acetylneuraminic acid. By labeling this thioketoside with dansyl chloride a fluorescent neuraminic acid derivative was prepared which allows determinations down to the picomol range. Regioselective acetylation with trimethylorthoacetate results in the corresponding 9-O-acetyl derivative. After incubation with esterase from bovine brain the hydrolysis products were separated on a HPLC column and fluorimetrically detected at 334 nm excitation and 564 nm emission. The Km value of 2.5 mM was in the range between the values of the completely unspecific methylumbelliferyl acetate and the less sensitively detectable N-acetyl-9-O-acetylneuraminic acid which have been used up to now as standard substrates.

Acetylesterase↗

PubMed1992

Indication for the identity of palmoplantar keratoderma type Unna-Thost with type Vörner. Thost's family revisited 110 years later.

Palmoplantar keratoderma (PPK) type Unna-Thost is known to be the most common form of a hereditary disorder of keratinization of palms and soles. The disease is clinically identical with PPK type Vörner which is histologically characterized by epidermolytic hyperkeratosis. By reinvestigation of the family originally seen by Thost in 1880, the features of epidermolytic hyperkeratosis were found histologically confirming the diagnosis PPK of Vörner. This proves the identity of PPK type Thost with PPK of Vörner. Because of the histological variability of epidermolytic hyperkeratosis, detailed light and electron microscopic studies are necessary in cases of diffuse types of PPK.

Adult↗

PubMed1992

[The potentiality of antero-posterior orthodontic extraoral traction: clinical and cephalometric results].

Heavy posterior orthopedic forces used for massive retropositioning of maxillary bone are among the orthopedic treatments preconised during mixed dentition. The clinical and cephalometric results of twelve cases treated by these means indicate that only dental movements can be obtained without the possibility of any orthopedic remodeling. These results corroborate those of other studies and it is possible to conclude that heavy orthopedic forces represent a very imprecise therapy which lead to side effects that are greater than the desired objectives.

Cephalometry↗

PubMed1992

[The use of growth prediction and V.T.O.: special concepts].

Growth induces very important modifications of the skeletal positions of the maxilla and the mandible and the precise position of the teeth is not foreseeable before an attempt to evaluate the situation the bones will be in by the end of the treatment has been made. Predictability factors are examined and a specific construction of V.T.O. is suggested. Then a new superposition is proposed which allows to determine the direction and range of teeth displacements.

Cephalometry↗

PubMed1992

[Pharmacokinetic aspects of a combination of metoclopramide and paracetamol. Results of a human kinetic study and consequences for migraine patients].

An open trial was carried out in eight healthy male and female volunteers to examine the bioavailability as well as the main kinetic parameters of Migränerton (metoclopramide and paracetamol; CAS 364-64-5 and CAS 103-90-2, resp). in comparison with reliable literature data. The results reported here clearly show that the absorption of both active ingredients from the fixed combination is complete and that therapeutically relevant plasma concentrations are achieved within 30 min. Bioavailability as well as tmax, t1/2, and time-lag are comparable with data resulting from reliable and internationally acknowledged kinetic studies. The fixed combination was shown to be kinetically compatible with regard to all parameters determined for metoclopramide and paracetamol.

Acetaminophen↗

PubMed1991

Isolation of Drosophila genes encoding G protein-coupled receptor kinases.

G protein-coupled receptors are regulated via phosphorylation by a variety of protein kinases. Recently, termination of the active state of two such receptors, the beta-adrenergic receptor and rhodopsin, has been shown to be mediated by agonist- or light-dependent phosphorylation of the receptor by members of a family of protein-serine/threonine kinases (here referred to as G protein-coupled receptor kinases). We now report the isolation of a family of genes encoding a set of Drosophila protein kinases that appear to code for G protein-coupled receptor kinases. These proteins share a high degree of sequence homology with the bovine beta-adrenergic receptor kinase. The presence of a conserved family of G protein-coupled receptor kinases in vertebrates and invertebrates points to the central role of these kinases in signal transduction cascades.

Amino Acid Sequence↗

PubMed1991

Gangliosides improve a memory deficit in pentylenetetrazol-kindled rats.

Epileptic patients often show impairments in a number of cognitive functions. Kindling is considered to be a useful experimental model for human epilepsy. Recently we have demonstrated a learning impairment in a shuttle box experiment in pentylenetetrazol (PTZ)-kindled rats. This model offers the possibility to investigate the relation between repeated convulsions and their consequences on learning and on the other side to test the effectiveness of substances on both processes. Although systemic application of gangliosides has neither an effect on the development of seizures induced by repeated injections of PTZ, nor on seizures induced by PTZ in kindled animals, the treatment protects against the memory-impairing effect of convulsions. These findings suggest a new useful strategy in the therapy of epileptic patients with the aim of diminishing the psychosocial problems in persons with seizure disorders: a combination of the anticonvulsive basic therapy and gangliosides.

Animals↗