Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1573-6881
    Keywords: P-glycoprotein ; multidrug resistance ; MDR ; ATPase ; drug transport ; ATP-binding cassette (ABC) transporters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Chemotherapy, though it remains one of the front-line weapons used to treat human cancer, is often ineffective due to drug resistance mechanisms manifest in tumor cells. One common pattern of drug resistance, characterized by simultaneous resistance to multiple amphipathic, but otherwise structurally dissimilar anticancer drugs, is termed multidrug resistance. Multidrug resistance in various model systems, covering the phylogenetic range from bacteria to man, can be conferred by mammalian P-glycoproteins (PGPs), often termed multidrug transporters. PGPs are 170-kD polytopic membrane proteins, predicted to consist of two homologous halves, each with six membrane spanning regions and one ATP binding site. They are members of the ATP-binding cassette (ABC) superfamily of transporters, and are known to function biochemically as energy-dependent drug efflux pumps. However, much remains to be learned about PGP structure-function relationships, membrane topology, posttranslational regulation, and bioenergetics of drug transport. Much of the recent progress in the study of the human and mouse PGPs has come from heterologous expression systems which offer the benefits of ease of genetic selection and manipulation, and/or short generation times of the organism in which PGPs are expressed, and/or high-level expression of recombinant PGP. Here we review recent studies of PGP inE. coli, baculovirus, and yeast systems and evaluate their utility for the study of PGPs, as well as other higher eukaryotic membrane proteins.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The relationship was studied between the number of transferrin-receptor positive cells and in vitro uptake of67Ga and125I-labeled transferrin in human cell lines, including two normal cell lines (WI-38 and foreskin fibroblasts), two transformed cell lines (AV-3 amnionic cells and Chang liver cells), and two neoplastic cell lines (HEp-2, larynx cancer and HeLa, cervical cancer). Transferrin receptors were determined by an indirect immunofluorescence technique based on their ability to bind purified human transferrin. Gallium-67 uptake was determined after a 24-h incubation of cells with Ga-67 in the presence and absence of transferrin (0–2.5 mg/ml).125I-labeled transferrin uptake was also obtained after a 24-h incubation. The fraction of cells with transferrin receptors was low in normal cell lines (3% and 9%), intermediate with transformed cell lines (33% and 49%), and high in neoplastic cell lines (59% and 61%). Transferrin stimulated67Ga uptake by all six cell lines. However, there was poor correlation between the number of transferrin-receptor positive cells and67Ga uptake either in the presence (r=0.21) or absence (r=0.46) of human transferrin. Likewise, there was poor correlation between the number of transferrin-receptor positive cells and125I-labeled transferrin uptake (r=0.35). In contrast, the correlation between67Ga uptake (in the presence of transferrin) and125I-labeled transferrin uptake was highly significant (r=0.96). These results suggest that human cell lines in culture are capable of both transferrin-dependent and transferrin-independent uptake of67Ga.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-7640
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Intelligent question-answering programs do more than retrieve “raw” data; they make deductive inferences in order to return all valid responses. They report logical inconsistencies, possibly at the data input phase. Similarly, more information is requested from the user if a question asked proves to be ambiguous. A question-answering system of the above type has been designed and implemented. Besides retrieving explicit and implicit temporal relations, the system discovers potentially causal relationships which also satisfy different time restrictions. Questions concerning a generalized concept of coexistence can also be answered. It is hoped that programs of a similar nature will become of much pragmatic use to researchers in physics, chemistry, biology, and so on, in evaluating complex, interrelated experimental data. Several additional applications for this type of program are mentioned, ranging from problems in criminology to air traffic control. The Associative Memory, Parallel Processing Language, AMPPL-II, was found rather satisfactory for the project. It is finally suggested that the system being described could serve as a component in a complex cognitive mechanism.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-5001
    Keywords: UBC9 ; heteronuclear NMR ; resonance assignments ; ubiquitination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A temperature-sensitive mammalian cell cycle mutant with blocks in G 1 and G2 phases of the cell cycle has been isolated in culture. When shifted from the permissive temperature of 33
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1573-1839
    Keywords: Science education for all ; general system theory ; system thinking ; learning technology ; complexity ; simulation ; real world
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract In this paper we suggest using general system theory (GST) as a unifying theoretical framework for “science and technology education for all.” Five reasons are articulated: the multidisciplinary nature of systems theory, the ability to engage complexity, the capacity to describe system dynamics and change, the ability to represent the relationship between the micro-level and macro-level of analysis, and the ability to bring together the natural and human worlds. The historical origins of system ideas are described, and the major concepts of system theory are mapped; including the mathematical, technological, and philosophical constructs. The various efforts to implement system thinking in educational contexts are reviewed, and three kinds of learning environments are defined: expert presentation, simulation, and real-world. A broad research agenda for exploring and drawing-out the educational implications of system thinking and learning is outlined. The study of both real-world and simulated learning environments is advocated.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1619-7089
    Keywords: Bone scintigraphy ; Sickle cell anemia ; Bone marrow expansion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We reviewed the nuclear medicine files of all patients enrolled in the sickle cell disease clinic who had had scans performed within the previous 5 years. We specifically looked for patterns of tracer uptake in these scans that would correlate with the severe anemia and consequent bone marrow hyperactivity of sickle cell patients. Thirtythree patients were included (21 men and 12 women) with a mean age of 26.8 years (range 17–48 years). The appearance of each of these patients' most recent scans was examined in the areas of the distal femurs, the proximal tibias and the distal tibias; a distinct triangular shaped pattern of increased activity was identified in these areas in a majority of patients. Thirty-three patients without sickle cell disease served as age-matched controls. This pattern was seen in 65.1% (95 out of 146 images) of the sickle cell patients' delayed images and 80.4% (82 out of 102 images) of their blood pool images. In contrast, the control patients demonstrated the triangular pattern in none of their blood pool studies (0%) and only 10.9% of their delayed bone images (P〈0.001). The mean age of sickle cell patients with this pattern is 25.6 years which was significantly lower than that of those without this pattern (mean=37.5 years, P〈0.05). Given the high prevalence of this unique scintigraphic pattern in a group of patients with known accelerated bone marrow function, these findings may be scintigraphic evidence of bone marrow expansion. The patient's age appears to be an important factor in visualization of this pattern.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Osteotesticular phosphatase (OST-PTPase) is a class III receptor-type tyrosine phosphatase (RPTPase). It has 10 tandem fibronectin III-like (FN-III) repeats in the extracellular region and two phosphatase domains in the intracellular region. The expression of the rat OST-PTPase gene, Esp, is restricted to osteoblasts and Sertoli cells, and the transcript level in osteoblasts is highly up-regulated by parathyroid hormone and cAMP treatment. We report here the cloning and characterization of the rat Esp gene, including a 2.9-kb 5′ flanking region sequence. Two potential binding sites for Osf2/Cbfa1, an osteoblast-specific transcription factor, are present in the promoter. Esp is composed of 35 exons, but spans merely 20 kb, making it the most compact RPTPase gene identified. Each FN-III repeat is encoded by a single exon flanked with phase 1 introns. Two phosphatase domains are encoded by 16 exons in a genomic organization similar to those in RPRPα, RPTPγ, and Ptprc genes. Esp was mapped by fluorescence in situ hybridization to rat chromosome 13q1. These results represent the first genomic structure of a mammalian class III RPTPase gene.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1619-7089
    Keywords: Lymphoma ; Breast ; 67Ga-citrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lymphomatous involvement of the breast is an uncommon cause of breast masses. A case is presented of a patient with bilateral breast involvement revealed by intense 67Ga uptake. Other foci of involvement were also detected scintigraphically, and confirmed by other imaging modalities. Multiagent chemotherapy resulted in significant clinical and scintigraphic regression of tumor, demonstrating the potential utility of 67Ga imaging in the followup of these patients.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0173-0835
    Keywords: Nonaqueous capillary electrophoresis ; Dynamic complexation ; Porphyrin ; Additives ; Separation theory ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The effect of an additive (Brij 35) on the mobilities of a group of porphyrin acids is quantitatively characterized based on a 1:1 dynamic complexation model. Varying additive concentration shifts the equilibrium and changes the viscosity of the background electrolyte. The equilibrium constant, the electrophoretic mobility of the free analyte, and the electrophoretic mobility of the complex are identified as the parameters necessary to describe the analytes' migration behavior. Several statistical methods for obtaining these parameters are discussed. The equilibrium constants and complex mobilities are calculated using three different linear regression methods. The weighted y-reciprocal method was preferred because it gives smaller error, and the data points are evenly distributed along the concentration axis. These values are confirmed using a nonlinear regression to ensure that the proper weighting was used in the linear regression plots. The parameters are then used to predict the apparent mobilities of the analytes over the entire additive concentration range, allowing the optimum separation conditions to be identified. For disclike molecules, such as porphyrins, the mobility is determined by the orientation of the molecule in an electric field, in addition to their size and charge. The strength of binding between the porphyrins and Brij 35 depends on the number of binding sites and the solvation shell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...