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Biomedical subjects

J Bender

Publications and source records attributed to J Bender.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Clinically silent cerebral embolisms after cerebral catheter angiography].

PURPOSE: To assess for the incidence of clinically silent cerebral lesions after cerebral catheter angiography. METHODS: MRI including PD-, T2-, and diffusion-weighted images was performed shortly before and after 27 cerebral catheter angiographies. RESULTS: After 5/27 angiographies (18.5%) we found 6 new, presumably embolic cerebral lesions with a typical diameter of 2-3 mm on diffusion-weighted images. No correlation was found between the occurrence of these lesions and a preexisting arteriosclerotic cerebrovascular disease, fluoroscopy time, or number of angiographic series. CONCLUSION: Cerebral angiography appears to be associated with a relatively high risk (about 20%) of clinically silent cerebral embolism. This risk is higher than has been estimated based on the incidence of neurological deficits (0.1-0.3%) after cerebral angiography. The safety of cerebral angiography needs to be improved. Diffusion-weighted MR imaging is suitable to monitor the safety of angiographic procedures and material.

Adolescent↗
PubMed2001

Unilateral diaphragmatic palsy in association with a subclavian vein thrombus in a very-low- birth-weight infant.

Phrenic nerve paralysis due to iatrogenic injury is not uncommon in neonates. We report an unusual case of acquired unilateral paralysis of the diaphragm in a very-low-birth-weight infant, associated with a thrombus secondary to percutaneous subclavian vein catheterization. Conservative management resulted in complete resolution of the paralyzed diaphragm.

Catheterization, Central Venous↗
PubMed2000

Metabolism and pharmacokinetics of N1,N11-diethylnorspermine in a Cebus apella primate model.

The tissue distribution, metabolic profile, and pharmacokinetic parameters of i.v.-administered N1,N11-diethylnorspermine (DENSPM) are evaluated in Cebus apella primates, and the results are compared with data gathered from canine and human studies. Although the metabolic processing of DENSPM (i.e., deethylation and deaminopropylation) in dogs and primates is very similar, there are some significant differences in tissue distribution of the parent drug. In dogs, the organ concentration of DENSPM follows the order kidney >> liver approximately = lung > spleen. In the primate, the order is liver >> kidney approximately = spleen > lung. The difference in pharmacokinetic parameters between the species is profound with (area under the time-concentration curve)primate << (area under the time-concentration curve)dog; (terminal elimination half-life)primate << (terminal elimination half-life)dog; and (mean residence time)primate << (mean residence time)dog. The most notable difference between dogs and primates is seen in the fraction of parent drug excreted unchanged in the urine, 50% in the dog and < 1% in the primate. However, the pharmacokinetic parameters and urinary drug clearance in C. apella primates are remarkably similar to those in humans. Thus, C. apella is established as an excellent model for assessing the metabolism, tissue distribution, and pharmacokinetic properties of polyamine analogues.

Animals↗
PubMed2000

Activation-induced inhibition of interleukin 6-mediated T cell survival and signal transducer and activator of transcription 1 signaling.

The cytokines interleukin (IL)-2, IL-4, IL-6, IL-7, and IL-15 have all previously been shown to inhibit resting T cell death in vitro. We have found a difference in the response of T cells to IL-6, depending on the activation status of the cells. IL-6 inhibited the death of naive T cells, but had no effect on the death of either superantigen-activated T cells, or T cells bearing memory markers. This was true even when the resting and activated T cells were isolated from the same animal; thus, the determining factor for IL-6 insensitivity was the activation status or activation history of the cell, and not the milieu in the animal from which the cells were isolated. Activated T cells expressed lower levels of IL-6 receptors on their surfaces, yet there were sufficient levels of receptors for signaling, as we observed similar levels of signal transducer and activator of transcription (Stat)3 phosphorylation in resting and activated T cells treated with IL-6. However, there was profound inhibition of IL-6-induced Stat1 phosphorylation in activated T cells compared with resting T cells. These data suggest that there is activation-induced inhibition of IL-6 receptor signaling in T cells. This inhibition appears to be specific for some but not all of the IL-6-mediated signaling cascades in these cells.

Animals↗
PubMed2000

Genomic-scale analysis of gene expression in resting and activated T cells.

Recent advances in gene array technology and isolation of lymphocytes now allow comprehensive analysis of gene expression in many different types of T cells. So far only a few sets of results have been published. However it is already clear that these analyses provide accurate measurements of gene expression in T cells. This technology offers the first opportunity to examine global and subtle changes in gene expression in response to specific stimuli.

Animals↗
PubMed2000

Homeostasis of alpha beta TCR+ T cells.

Cytokines contribute to T cell homeostasis at all stages of T cell existence. However, the particular cytokine involved varies as T cells progress from a naïve through an activated to a memory state. In many cases the important cytokines are members of the interleukin 2 subfamily of the short-chain type I cytokines. A case is made for the idea that the evolutionary divergence of the short-chain family allowed for concurrent divergence in leukocytes.

Animals↗
PubMed1999

Activation changes the spectrum but not the diversity of genes expressed by T cells.

During activation T cells are thought to change their patterns of gene expression dramatically. To find out whether this is true for T cells activated in animals, the patterns of genes expressed in resting T cells and T cells 8 and 48 hr after activation were examined by using Affymetrix gene arrays. Gene arrays gave accurate comparisons of gene expression in the different cell types because the expression of genes known to vary during activation changed as expected. Of the approximately 6,300 genes assessed by the arrays, about one-third were expressed to appreciable extents in any of the T cells tested. Thus, resting T cells express a surprisingly large diversity of genes. The patterns of gene expression changed considerably within 8 hr of T cell activation but returned to a disposition more like that of resting T cells within 48 hr of exposure to antigen. Not unexpectedly, the activated T cells expressed genes associated with cell division at higher levels than resting T cells. The resting T cells expressed a number of cytokine receptor genes and some genes thought to suppress cell division, suggesting that the state of resting T cells is not a passive failure to respond to extant external stimuli.

Animals↗
PubMed1999

An inverse relationship between T cell receptor affinity and antigen dose during CD4(+) T cell responses in vivo and in vitro.

Multimeric peptide/class II MHC staining reagents were synthesized and shown to bind with appropriate specificity to T cell hybridomas. A small, expanded population of T cells detected with one of these reagents in peptide-immunized C57BL/10 mice persisted for several months. This population expanded further on secondary immunization. Equating the extent of binding of this reagent to T cell receptor affinity, we saw little correlation of immunizing peptide dose to T cell receptor affinity at the peak of the primary response. However, there was an inverse relation between peptide dose and the apparent receptor affinity of the T cells that were present several months after a primary response or after a secondary stimulation either in vivo or in vitro.

Animals↗
PubMed1999

CD4+ T cell division in irradiated mice requires peptides distinct from those responsible for thymic selection.

We investigated the mechanism by which alpha/beta T cells expand upon transfer to T cell-deficient host mice by injecting carboxyfluorescein diacetate succinimidyl ester-labeled T cells into mice depleted of T cells by sublethal irradiation. We found that CD4+ T cells divided when transferred to irradiated hosts and that the division of more than half of these cells required class II expression. However, division of transferred CD4+ T cells did not occur in irradiated hosts that expressed class II molecules occupied solely by the peptide responsible for thymic selection, indicating that peptides distinct from those involved in thymic selection cause the division of CD4+ T cells in irradiated mice. These data establish that class II-bound peptides control the expansion of CD4+ T cells transferred to T cell-deficient hosts and suggest that the same peptides contribute to the maintenance of T cell numbers in normal mice.

Animals↗
PubMed1999

Faithful expression of a heterologous gene carried on an artificial macronuclear chromosome in Euplotes crassus.

Macronuclear chromosomes of hypotrichous ciliates are gene-sized molecules carrying the coding sequence flanked by short non-translated regions and bounded by telomeres. We have constructed artificial chromosomes for investigation of transcription in the macronucleus of Euplotes crassus. The neo gene was put under the control of the 5"-non-translated region of the TBP gene of E.crassus. These molecules were introduced into the cell with the help of liposomes. The cells were transformed and survived high concentrations of geneticin. The artificial chromosomes were kept in the macro-nucleus for at least 50 days at a copy number of about 200 per macronucleus. Expression of the gene was shown by reverse transcription of the neo messenger. The transcription start was mapped and found to coincide with that found on the natural macronuclear chromosome encoding TBP in E.crassus.

5' Untranslated Regions↗
PubMed1999

Human single-chain Fv immunoconjugates targeted to a melanoma-associated chondroitin sulfate proteoglycan mediate specific lysis of human melanoma cells by natural killer cells and complement.

Two antimelanoma immunoconjugates containing a human single-chain Fv (scFv) targeting domain conjugated to the Fc effector domain of human IgG1 were synthesized as secreted two-chain molecules in Chinese hamster ovary and Drosophila S2 cells, and purified by affinity chromatography on protein A. The scFv targeting domains originally were isolated as melanoma-specific clones from a scFv fusion-phage library, derived from the antibody repertoire of a vaccinated melanoma patient. The purified immunoconjugates showed similar binding specificity as did the fusion-phage clones. Binding occurred to human melanoma cells but not to human melanocytes or to several other types of normal cells and tumor cells. A 250-kDa melanoma protein was immunoprecipitated by the immunoconjugates and analyzed by mass spectrometry, using two independent procedures. A screen of protein sequence databases showed an exact match of several peptide masses between the immunoprecipitated protein and the core protein of a chondroitin sulfate proteoglycan, which is expressed on the surface of most human melanoma cells. The Fc effector domain of the immunoconjugates binds natural killer (NK) cells and also the C1q protein that initiates the complement cascade; both NK cells and complement can activate powerful cytolytic responses against the targeted tumor cells. An in vitro cytolysis assay was used to test for an immunoconjugate-dependent specific cytolytic response against cultured human melanoma cells by NK cells and complement. The melanoma cells, but not the human fibroblast cells used as the control, were efficiently lysed by both NK cells and complement in the presence of the immunoconjugates. The in vitro results suggest that the immunoconjugates also could activate a specific cytolytic immune response against melanoma tumors in vivo.

Animals↗
PubMed1999

Determination of remifentanil in human heparinised whole blood by tandem mass spectrometry with short-column separation.

For the use in pharmacokinetic studies, a fast and sensitive assay method was developed for the determination of remifentanil in human heparinised whole blood samples of 0.5 ml. The assay method is based on tandem mass spectrometry detection (LC-MS/MS). The limit of quantification is 0.1 ng/ml and linear up to 50 ng/ml. The precision, accuracy, recovery and applicability were found to be adequate for pharmacokinetic studies.

Anesthetics, Intravenous↗
PubMed1999

An inverted repeat triggers cytosine methylation of identical sequences in Arabidopsis.

The Wassilewskija (WS) strain of Arabidopsis has four PAI genes at three sites: an inverted repeat at one locus plus singlet genes at two unlinked loci. These four genes are methylated over their regions of DNA identity. In contrast, the Columbia (Col) strain has three singlet PAI genes with no methylation. To test the hypothesis that the WS inverted repeat locus triggers methylation of unlinked identical sequences, we introduced this locus into the Col background by genetic crosses. The inverted repeat induced de novo methylation of all three unmethylated Col PAI genes, with methylation efficiency varying with the position of the target locus. These results, plus results with inverted repeat transgenes, show that methylation is communicated by a DNA/DNA pairing mechanism.

Arabidopsis↗
PubMed1999

Refractory spinal cord injury induced gastroparesis: resolution with erythromycin lactobionate, a case report.

Erythromycin lactobionate (ERY), a macrolide antibiotic, has been the focus of investigation as a new gastrointestinal prokinetic agent. In individuals who are able-bodied (AB), ERY has shown promise in various forms of gastroparesis (GP). Recent evidence suggests that medications used to stimulate intestinal motility in individuals who are AB have had similar results in those individuals with spinal cord injury (SCI). Medications that have been used in the past for GP in SCI include metaclopramide, neostigmine, and bethanechol. In this observation, a patient with T-6 paraplegia, who developed GP secondary to acute SCI, is presented. During his hospital stay, the patient was treated with gastric decompression, bowel rest, H2 blockers, intravenous metaclopramide, and eventually required parenteral nutritional support. ERY was started and symptoms abated. At this point, the nasogastric tube was removed and oral feeding was successfully started. This case report is the first to describe a patient with refractory SCI-induced GP who responded to intravenous ERY. Further study in this area is warranted.

Critical Care↗
PubMed1999

Arabidopsis PAI gene arrangements, cytosine methylation and expression.

Previous analysis of the PAI tryptophan biosynthetic gene family in Arabidopsis thaliana revealed that the Wassilewskija (WS) ecotype has four PAI genes at three unlinked sites: a tail-to-tail inverted repeat at one locus (PAI1-PAI4) plus singlet genes at two other loci (PAI2 and PAI3). The four WS PAI genes are densely cytosine methylated over their regions of DNA identity. In contrast, the Columbia (Col) ecotype has three singlet PAI genes at the analogous loci (PAI1, PAI2, and PAI3) and no cytosine methylation. To understand the mechanism of PAI gene duplication at the polymorphic PAI1 locus, and to investigate the relationship between PAI gene arrangement and PAI gene methylation, we analyzed 39 additional ecotypes of Arabidopsis. Six ecotypes had PAI arrangements similar to WS, with an inverted repeat and dense PAI methylation. All other ecotypes had PAI arrangements similar to Col, with no PAI methylation. The novel PAI-methylated ecotypes provide insights into the mechanisms underlying PAI gene duplication and methylation, as well as the relationship between methylation and gene expression.

Aldose-Ketose Isomerases↗