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At least 649 records · Page 36Linked to original sources
PubMed1992

Combination of microdialysis and glucosensor permits continuous (on line) SC glucose monitoring in a patient operated device. II. Evaluation in animals.

The microdialysis technique was used for following the glucose content of the extracellular subcutaneous (SC) fluid under varying blood glucose levels in rats. The glucose content in the microdialysis perfusion fluid was continuously analyzed by means of the measuring flow chamber of an ex vivo glucose monitor. In six ChBB rats blood glucose levels were varied between 40 mg/dl and 575 mg/dl by intravenous (IV) infusion of glucose and by SC injections of insulin, respectively. After a running-in period of about half an hour, the glucose content in the perfusion fluid was closely related to the blood glucose concentration (r > 0.92) up to a time period of 6 hrs. The "relative recovery" rate of glucose by the microdialysis probe in the SC tissue varied within the 6 experimental sessions. The relative recovery rate could be shown to be not dependent on the absolute blood glucose levels in the individual rat within the glucose concentration range tested.

Animals↗
PubMed1991

Combination of microdialysis and Glucosensor permits continuous (on line) s.c. glucose monitoring in a patient operated device: I. In vitro evaluation.

A device for continuous glucose monitoring in fluids was obtained by combining the microdialysis technique with a measuring flow chamber of the "Glucosensor Unitec Ulm" using the GOD method for determining amperometrically blood glucose profiles. The in vitro experiments demonstrate that the relative recovery of glucose by this device is inversely related to the flow rate of the microdialysis perfusion fluid, which, in turn, is inversely related to the response time of the device. The glucose signal increases linearly with the area of the microdialysis working membrane (r = 0.98), and with the glucose concentrations of the standard solutions (r greater than 0.95). The variation coefficient for repeated measurements is below 8%. The accuracy of the device as demonstrated by mean measuring deviation ranges between 1 and 3.8%.

Biosensing Techniques↗
PubMed1995

[Do steroid-eluting pacemaker electrodes permit programming at lower pacemaker pulse amplitudes?].

A study was undertaken on 107 patients (68 men, 39 women; mean age 68 [29-100] years) with steroid-eluting ventricular electrodes to determine whether in general these electrodes make it possible routinely to set pacemaker impulses at 2.5 V instead of 5.0 V with an impulse duration of 0.5 ms. 3-12 months after implantation, impulse duration thresholds were 0.27 +/- 0.20 ms at 0.8 V, 0.13 +/- 0.09 ms at 1.6 V and 0.08 +/- 0.05 ms at 2.5 V impulse amplitude. Thus, employing a 100% margin of safety, it was possible to set the pacemakers of 103 among the 107 patients at 2.5 V and 0.5 ms. In four patients it was not possible to achieve the 2.5 V and 0.5 ms setting. With one exception (stimulation threshold rose immediately after a current accident) no circumstances arose under which thresholds increased. These results demonstrate that, using steroid-eluting electrodes, ventricles can be reliably stimulated with 2.5 V and 0.5 ms in 96% of patients. However, since it is not possible in all patients, optimal stimulation parameters must be determined in each patient even when steroid-eluting electrodes have been implanted.

Adult↗
PubMed2002

Transduction of dendritic cells by antigen-encoding lentiviral vectors permits antigen processing and MHC class I-dependent presentation.

BACKGROUND: Because antigen-presenting dendritic cells (DCs) play a major role in the polarization of T cells, including T(H)2 cells involved in allergy, strategies to modify DCs genetically are required. OBJECTIVE: The purpose of this investigation was to transduce murine bone marrow-derived DCs with lentiviral vectors encoding antigen to demonstrate antigen processing and MHC class I-dependent presentation. METHODS: Bone marrow leukocytes were incubated with antigen-encoding lentiviral constructs and cultured with GM-CSF, IL-4, and Flt-3 ligand. The capacity of the resulting DCs to express, process, and present antigen was tested in vitro. RESULTS: An average of 40% of DCs expressed antigen after 1 week of culture when antigen encoded by the lentiviral vector construct was green fluorescent protein. To demonstrate that transduced antigen can be presented by DCs on MHC class I, we chose the lymphocytic choriomeningitis virus glycoprotein (gp) as a model antigen, inasmuch as it is recognized by CD8 T cells from transgenic mice expressing an MHC class I-restricted T-cell receptor specific for the epitope of positions 33 through 41 of gp. DCs transduced with lentiviral construct encoding gp and matured with LPS activated transgenic T cells in an antigen-specific fashion. Using transporter associated with antigen presentation (TAP)-deficient mice, we show that presentation of the gp33-41 epitope is TAP-dependent, confirming processing of gp by the endogenous pathway. CONCLUSIONS: These results demonstrate that CD8 T cells can recognize MHC class I epitopes processed from antigen in DCs transduced with lentiviral vectors. Lentiviral transduction of DCs and antigen presentation to CD8 T cells could be exploited for immunotherapy, because allergen-specific CD8 T cells have been shown to be suppressive in IgE-dependent allergy models.

Animals↗
PubMed2006

Light chain inclusion permits terminal B cell differentiation and does not necessarily result in autoreactivity.

Mice in which the Jkappa cluster was replaced with a VkappaJkappa rearranged gene were studied. More than 90% of B cells from homozygous mutant mice expressed the transgenic kappa chain but showed a slightly reduced level of kappa transcripts compared with WT B lymphocytes. Light chain inclusion was apparent in 10% of B cells from these mice and raised 25% in hemizygous mice with a still lower expression of the knockin kappa chain. Beyond the rules of clonal selection, peripheral B cells developed in such animals, with included cells being activated and differentiating into class-switched or antibody-secreting cells. The high amount of included mature B cells was associated with an increase of hybrid kappa/lambda immunoglobulins but not with the increased prevalence of autoantibodies. Altogether, these data suggest that light chain exclusion prevalent in normal B cells mostly results from ordered rearrangements and stochastic mechanisms but is neither tightly ensured by a stringent cell selection process nor absolutely required for normal B cell function.

Animals↗
PubMed2006

Notch activity permits retinal cells to progress through multiple progenitor states and acquire a stem cell property.

Signaling through the Notch pathway regulates multiple aspects of development. The vertebrate retina allows an investigation of the basis for these various effects, because the major cell types of the retina arise from a common progenitor that expresses Notch1. The Notch pathway was constitutively activated in distinct populations of retinal cells during development. Prolonged Notch activity in progenitor cells maintained cells in the progenitor state without perturbing temporal identity, promoting early progenitor characteristics early in development and late progenitor characteristics later in development. Eventually, constitutive Notch activation led these cells to acquire characteristics of glial and stem cells. In contrast, reactivating the Notch pathway in newly postmitotic retinal cells promoted mature glial cell formation in a subset of cells. These data suggest that prolonged Notch activity does not disrupt the normal progression of progenitor temporal states, and that down-regulating or overcoming Notch activity is required for proper formation of both neuronal and glial cell fates.

Animals↗
PubMed2002

Enhancer action in trans is permitted throughout the Drosophila genome.

Interactions between paired homologous genes can lead to changes in gene expression. Such trans-regulatory effects exemplify transvection and are displayed by many genes in Drosophila, in which homologous chromosomes are paired somatically. Transvection involving the yellow cuticle pigmentation gene can occur by at least two mechanisms, one involving the trans-action of enhancers on a paired promoter and a second involving pairing-mediated bypass of a chromatin insulator. A system was developed to evaluate whether the action of the yellow enhancers in trans could be reconstituted outside of the natural near telomeric location of the yellow gene. To this end, transgenic flies were generated that carried a yellow gene modified by the inclusion of strategically placed recognition sites for the Cre and FLP recombinases. Independent action of the recombinases produced a pair of derivative alleles, one enhancerless and the other promoterless, at each transgene location. Transvection between the derivatives was assessed by the degree of interallelic complementation. Complementation was observed at all eight sites tested. These studies demonstrate that yellow transvection can occur at multiple genomic locations and indicate that the Drosophila genome generally is permissive to enhancer action in trans.

Alleles↗
PubMed2001

Ectopic expression of retinoic acid early inducible-1 gene (RAE-1) permits natural killer cell-mediated rejection of a MHC class I-bearing tumor in vivo.

In 1986, Kärre and colleagues reported that natural killer (NK) cells rejected an MHC class I-deficient tumor cell line (RMA-S) but they did not reject the same cell line if it expressed MHC class I (RMA). Based on this observation, they proposed the concept that NK cells provide immune surveillance for "missing self," e.g., they eliminate cells that have lost class I MHC antigens. This seminal observation predicted the existence of inhibitory NK cell receptors for MHC class I. Here, we present evidence that NK cells are able to reject tumors expressing MHC class I if the tumor expresses a ligand for NKG2D. Mock-transfected RMA cells resulted in tumor formation. In contrast, when RMA cells were transfected with the retinoic acid early inducible gene-1 gamma or delta (RAE-1), ligands for the activating receptor NKG2D, the tumors were rejected. The tumor rejection was mediated by NK cells, and not by CD1-restricted NK1.1(+) T cells. No T cell-mediated immunological memory against the parental tumor was generated in the animals that had rejected the RAE-1 transfected tumors, which succumbed to rechallenge with the parental RMA tumor. Therefore, NK cells are able to reject a tumor expressing RAE-1 molecules, despite expression of self MHC class I on the tumor, demonstrating the potential for NK cells to participate in immunity against class I-bearing malignancies.

Animals↗
PubMed2002

Mutations that permit efficient replication of hepatitis C virus RNA in Huh-7 cells prevent productive replication in chimpanzees.

The development of a subgenomic replicon derived from the hepatitis C virus (HCV) strain Con1 enabled the study of viral RNA replication in Huh-7 cells. The level of replication of replicons, as well as full-length Con1 genomes, increased significantly by a combination of two adaptive mutations in NS3 (E1202G and T1280I) and a single mutation in NS5A (S2197P). However, these cell culture-adaptive mutations influenced in vivo infectivity. After intrahepatic transfection of chimpanzees, the wild-type Con1 genome was infectious and produced viral titers similar to those produced by other infectious HCV clones. Repeated independent transfections with RNA transcripts of a Con1 genome containing the three adaptive mutations failed to achieve active HCV infection. Furthermore, although a chimpanzee transfected with RNA transcripts of a Con1 genome with only the NS5A mutation became infected, this mutation was detected only in virus genomes recovered from serum at day 4; viruses recovered at day 7 had a reversion back to the original Con1 sequence. Our study demonstrates that mutations that are adaptive for replication of HCV in cell culture may be highly attenuating in vivo.

Adaptation, Physiological↗