Search PubMed⌕ Search

Biomedical subjects

R Keller

Publications and source records attributed to R Keller.

At least 217 records · Page 12Linked to original sources
PubMed1989

Yeast cyclophilin: isolation and characterization of the protein, cDNA and gene.

Cyclophilin (CPH) has been isolated from the yeast Saccharomyces cerevisiae, purified to homogeneity and partially sequenced. Oligodeoxyribonucleotides deduced from this sequence were used to isolate the corresponding cDNA and gene. An open reading frame coding for a 162-amino acid (aa) protein with a calculated Mr of 17,392, was deduced from the nucleotide sequence. Comparison between yeast and human CPH shows a very high overall sequence conservation (65% aa homology). The binding of yeast CPH to cyclosporin A is identical to that of human and bovine CPH. Unlike in Neurospora crassa, a mitochondrial form of CPH could not be detected in yeast. Southern-blot analysis of yeast DNA shows that only one CPH-related sequence is present per haploid genome, whereas at least 20 genes or pseudogenes were detected in the human and rat genome. Purified yeast CPH exhibits peptidyl-prolyl cis-trans isomerase activity, albeit to a far lesser extent than the mammalian protein.

Amino Acid Sequence↗
PubMed1989

Cloning and sequence analysis of cDNA for precursor of a crustacean hyperglycemic hormone.

Crustacean hyperglycemic hormone (CHH) from Carcinus maenas, a 72 amino acid neuropeptide, originates in neurosecretory perikarya in the eyestalk ganglia. Poly (A)RNA was isolated from these perikarya and a cDNA library was prepared. Screening of 20,000 clones with a 26-mer oligonucleotide, corresponding to a partial sequence of CHH, yielded one positive clone with an insert of approximately 2,000 bp, which contained the complete coding sequence for a pre-pro CHH. This precursor consists of a putative 26 amino acid signal sequence, a 38 amino acid peptide of unknown function (Peptide C), and the CHH sequence at the carboxyl end. The CHH-sequence is flanked N-terminally by a Lys-Arg cleavage site and C-terminally by the tetrapeptide Gly-Arg-Lys-Lys which is followed by the stop codon.

Amino Acid Sequence↗
PubMed1989

Discrepancy in the abilities of lymphokines and bacteria to mediate tumor protection in vivo and/or tumoricidal activity by macrophages in vitro.

In the present study, the ability of lymphokines (MAF and IFN gamma) and microbial agents (CP and LM) to induce and maintain tumoricidal activity in BMMP in vitro and to enhance local resistance to the DA rat D-12 ascites tumor in vivo was assessed comparatively. Under standard conditions in vitro, i.e., when present during the 24-hr induction and the 36-hr effector phase, both lymphokines and microbes were similarly potent for eliciting tumoricidal activity in BMMP. When the activating agents were present only during the induction phase, and effector cells were interacted with tumor targets after a 24-hr interval, clear differences were observed: BMMP which had been incubated with lymphokines had largely if not completely lost their tumoricidal activity; in contrast, BMMP which had been incubated with microbes still manifested considerable tumoricidal activity. Experiments performed to assess the in vivo significance of the discrepancy established in vitro have shown that resistance to the D-12 ascites tumor was markedly enhanced after local inoculation of microbes but was affected very little or not at all by soluble lymphokines. The causes responsible for the discrepancy in the antitumor potential of lymphokines vs. microbes are probably manifold. Extensive attempts to improve the efficacy of lymphokines by repeated administration or by incorporation into liposomes were not successful.

Animals↗
PubMed1989

Amino acid sequence of the crustacean hyperglycemic hormone (CHH) from the shore crab, Carcinus maenas.

Crustacean hyperglycemic hormone (CHH) was isolated from sinus glands of Carcinus maenas, and its primary structure was determined by manual microsequencing, using the DABITC-PITC double-coupling method. The neurohormone consists of 72 amino acid residues (8524 Da). Three disulfide bridges are present and both the N- and C-terminus are blocked. CHH does not show significant sequence homology to any known peptide hormone or protein.

Amino Acid Sequence↗
PubMed1989

Surface phenotype of rat bone marrow-derived mononuclear phagocytes.

Utilizing a panel of currently available monoclonal antibodies, the surface phenotype of a pure population of resting rat bone marrow-derived mononuclear phagocytes (BMM phi) was analyzed by means of flow cytometry. The present work provides an extensive list of surface markers expressed by BMM phi and also outlines advantages and limitations of flow cytometric analysis of this cell type. The results show that the majority of surface markers considered to be expressed selectively by T lymphocytes, such as Thy-1, CD2 and CD5 antigens, leukosialin (W3/13), or an alloantigen of peripheral T cells, are not expressed by BMM phi. On the other hand, the CD8 antigen and the leukocyte common antigen recognized by MRC OX-33, considered to represent specific markers of cytotoxic T cells and/or peripheral B cells, are expressed on a variable, often considerable proportion of BMM phi. Monoclonal antibodies W3/25, MRC OX-35, and MRC OX-38, directed against epitopes on the CD4 molecule, labeled a variable proportion of BMM phi. Among the 39 monoclonal antibodies examined, none appeared to recognize an epitope which is expressed selectively by mononuclear phagocytes.

Animals↗
PubMed1989

[Pulmonary rehabilitation in pulmonary emphysema].

Respiratory rehabilitation in patients with pulmonary emphysema should be focussed first on the prevention and elimination of harmful inhalative factors, e.g. smoking habits and environmental or occupational pollution. In addition, distinct therapeutical procedures are mostly effective in preventing a progressive course of the disease and interrupting the vicious circle of dyspnea, physical inactivity and overall disability as well. In patients with advanced disease, mostly complicated by features of chronic respiratory insufficiency and cor pulmonale, long-term administration of oxygen often relieves symptoms, increases physical performance and may even reduce hospital admissions for a longer period. As a consequence, most patients with severe disability also suffer from severe psychological and social problems which should be considered more attentively within the concept of the overall rehabilitation program.

Adaptation, Psychological↗
PubMed1989

Cell intercalation during notochord development in Xenopus laevis.

Morphometric data from scanning electron micrographs (SEM) of cells in intact embryos and high-resolution time-lapse recordings of cell behavior in cultured explants were used to analyze the cellular events underlying the morphogenesis of the notochord during gastrulation and neurulation of Xenopus laevis. The notochord becomes longer, narrower, and thicker as it changes its shape and arrangement and as more cells are added at the posterior end. The events of notochord development fall into three phases. In the first phase, occurring in the late gastrula, the cells of the notochord become distinct from those of the somitic mesoderm on either side. Boundaries form between the two tissues, as motile activity at the boundary is replaced by stabilizing lamelliform protrusions in the plane of the boundary. In the second phase, spanning the late gastrula and early neurula, cell intercalation causes the notochord to narrow, thicken, and lengthen. Its cells elongate and align mediolaterally as they rearrange. Both protrusive activity and its effectiveness are biased: the anterioposterior (AP) margins of the cells advance and retract but produce much less translocation than the more active left and right ends. The cell surfaces composing the lateral boundaries of the notochord remain inactive. In the last phase, lasting from the mid- to late neurula stage, the increasingly flattened cells spread at all their interior margins, transforming the notochord into a cylindrical structure resembling a stack of pizza slices. The notochord is also lengthened by the addition of cells to its posterior end from the circumblastoporal ring of mesoderm. Our results show that directional cell movements underlie cell intercalation and raise specific questions about the cell polarity, contact behavior, and mechanics underlying these movements. They also demonstrate that the notochord is built by several distinct but carefully coordinated processes, each working within a well-defined geometric and mechanical environment.

Animals↗
PubMed1989

Mediolateral cell intercalation in the dorsal, axial mesoderm of Xenopus laevis.

The pattern of mediolateral cell intercalation in mesodermal tissues during gastrulation and neurulation of Xenopus laevis was determined by tracing cells labeled with fluorescein dextran amine (FDA). Patches of the involuting marginal zone (IMZ) of early gastrula stage embryos, labeled by injection of FDA at the one-cell stage, were grafted to the corresponding regions of unlabeled host embryos. The host embryos were fixed at several stages, serially sectioned, and examined with fluorescence microscopy and three-dimensional reconstruction. Patterns of mixing of labeled and unlabeled cells show that mediolateral cell intercalation occurs in the posterior, dorsal mesoderm as this region undergoes convergent extension and differentiates into somites and notochord. In contrast, it does not occur in any dorsoventral sector of the anterior, leading edge of the mesodermal mantle. These results, taken with other evidence, suggest that the mesoderm of Xenopus consists of two subpopulations, each with a characteristic morphogenetic movement, cell behavior, and tissue fate. The migrating mesoderm (1) does not show convergent extension; (2) migrates and spreads on the blastocoel roof; (3) is dependent on this substratum for its morphogenesis; (4) shows little mediolateral intercalation; (5) consists of the anterior, early-involuting region of the mesodermal mantle; and (6) differentiates into head, heart, blood island, and lateral body wall mesoderm. The extending mesoderm (1) shows convergent extension; (2) is independent of the blastocoel roof in its morphogenesis; (3) shows extensive mediolateral intercalation; (4) consists of the posterior, late-involuting parts of the mesodermal mantle; and (5) differentiates into somite and notochord.

Animals↗
PubMed1989

Cell rearrangement and segmentation in Xenopus: direct observation of cultured explants.

We make use of a novel system of explant culture and high resolution video-film recording to analyse for the first time the cell behaviour underlying convergent extension and segmentation in the somitic mesoderm of Xenopus. We find that a sequence of activities sweeps through the somitic mesoderm from anterior to posterior during gastrulation and neurulation, beginning with radial cell intercalation or thinning, continuing with mediolateral intercalation and cell elongation, and culminating in segmentation and somite rotation. Radial intercalation at the posterior tip lengthens the tissue, while mediolateral intercalation farther anterior converges it toward the midline. This extension of the somitic mesoderm helps to elongate the dorsal side of intact neurulae. By separating tissues, we demonstrate that cell rearrangement is independent of the notochord, but radial intercalation - and thus the bulk of extension - requires the presence of an epithelium, either endodermal or ectodermal. Segmentation, on the other hand, can proceed in somitic mesoderm isolated at the end of gastrulation. Finally, we discuss the relationship between cell rearrangement and segmentation.

Animals↗
PubMed1989

A new AT III-heparin-complex preparation: in vitro and in vivo characterisation.

The in vitro experiments show that the anticoagulant affect of a new AT III-Heparin-complex preparation in plasma is similar to heparin. The in vivo experiments indicate that the thrombin inhibition is even improved by using the complex preparation, because the aPTT values after complex treatment remained stable for more than one hour in the desired range. Bleeding complications are less likely after complex treatment, because much smaller maximum aPTT values are reached. The prolonged half life of the complex preparation possibly allows a reduced and more accurate dosage.

Animals↗
PubMed1989

[Check-ups in pneumonology].

Check-up examinations in chest medicine are useful tests for early detection of numerous diseases of the respiratory system. They should focus in particular on the most frequent and chronically progressive airway-diseases (asthma, chronic bronchitis) in order to avoid severe illness and early disability including bronchial carcinoma and tuberculosis to offer a more favourable outcome to the patient. By the correct planning of an individual check-up the patient's conditions have to be carefully considered by estimating epidemiological facts, personal risk factors, the presence of prodromal symptoms and the availability of cost-effective diagnostic procedures as well. The efficacy of the individual screening in respiratory diseases implies systematic and periodical check-up examinations which unfortunately are not everywhere established.

Adolescent↗
PubMed1988

Laminar flow induces cell polarity and leads to rearrangement of proteoglycan metabolism in endothelial cells.

Bovine aortic endothelial cells in tissue culture were incubated with [35S]-sulfate to examine the pattern of proteoglycan production at various shear rates. It was observed that culturing bovine aortic endothelial cells under laminar flow changes the secretion pattern of proteoglycans to that observed in perfused organ cultures, induces polarity of secretion, down-regulates proteoglycan biosynthesis and decreases uptake of sulfate. These results indicate that surface shear is a major force influencing the endothelial cellular phenotype. The changed pattern of proteoglycan release under static conditions may contribute to the anticoagulant effect of endothelial cells which is much needed when activated coagulation factors are not dispersed by flow.

Animals↗
PubMed1988

[Periodic nocturnal ventilation using an Emerson chest respirator as an alternative to permanent tracheostomy with positive pressure ventilation in patients with idiopathic scoliosis and severe global respiratory insufficiency].

Sustained success was achieved in treating a 40-year-old patient who had had severe progressive thoracic kyphoscoliosis since childhood and developed cardiorespiratory failure with terminal alveolar hypoventilation and hypoxemia due to acute pulmonary infection. On emergency admission to this hospital mechanically controlled ventilation by tracheostomy tube produced a remarkable improvement in cardiorespiratory function. Weakness of the respiratory muscles made complete disconnection from ventilatory support impossible. Instead of positive pressure ventilation by tracheostomy tube with resultant patient invalidity, nighttime external negative pressure ventilation with an Emerson chest respirator was started leaving the patient free for daytime activity. This type of ventilation is a simple, effective and well tolerated long-term treatment at low cost. The patient has been using it nightly at home for over 6 months and no problems have arisen. These findings show that intensive care is indicated in patients with severe thoracic kyphoscoliosis and cardiorespiratory failure since long-term treatment of terminal hypoventilation and cardiorespiratory failure is possible with a cheap and simple nocturnal ventilation system.

Adult↗
PubMed1988

[Cost-benefit analysis of thoracic computerized tomography as exemplified in the N-staging of bronchial carcinoma].

In 60 selected patients affected by a limited stage of bronchial carcinoma according to clinical examinations, routine computed tomography and mediastinoscopy were performed to detect metastatic lymph-node involvement. Patients with histologically proven mediastinal lymph-node metastasis (stage N 2-3) subsequently were excluded from surgical therapy. As alternative diagnostic procedures four different strategies are discussed to estimate the greatest efficacy regarding costs and benefits in preoperative staging of malignant lung tumors: (1) primary thoracotomy, (2) routine mediastinoscopy, (3) thoracic CT-scanning and (4) CT-scanning combined with selective mediastinoscopy. Efficacy was then evaluated by the criteria of financial expenditure for each curative resection. As a result there are but small differences between the four diagnostic approaches and thoracic CT-scanning definitely does not reduce the overall costs of curative surgery or markedly improve the diagnostic yield. However, the combination of selected mediastinoscopy with CT-scanning at least increased comfort and safety in preoperative staging of patients without loss of sensitivity or specificity in detecting resectable tumors. This method should therefore be favoured for evaluating the resectability of bronchial carcinoma.

Carcinoma, Bronchogenic↗
PubMed1988

[Pulmonary gas exchange and hemodynamics].

The purpose of investigating pulmonary gas exchange and pulmonary circulation is detection of functional abnormalities of the cardiorespiratory system. Other than clinical features, a number of specialized methods used today are of high accuracy and therefore serve to recognize early disorders and to quantify functional impairment. In clinical practice arterial blood gas analysis and the measurement of diffusing capacity are sensitive screening tests for patients with acute and chronic respiratory failure and thus have important diagnostic and therapeutic implications (e.g. indication for oxygen therapy, mechanical ventilation, chest physiotherapy, specific drug regimen etc.). Spiroergometry and right heart catheterization, as the more invasive methods, are useful tests in evaluating overall cardiopulmonary function to detect limiting factors in physical performance (e.g. thoracic surgery, occupational diseases, sport medicine).

Blood Gas Analysis↗