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Biomedical subjects

D Swartz

Publications and source records attributed to D Swartz.

At least 19 recordsLinked to original sources
PubMed2001

Soluble L-selectin at levels present in septic patients diminishes leukocyte-endothelial cell interactions in mice in vivo: a mechanism for decreased leukocyte delivery to remote sites in sepsis.

OBJECTIVE: Recent in vivo studies of both septic humans and animals demonstrate that leukocyte delivery is attenuated to sites remote from the primary infection. The mechanisms for this are not entirely clear. L-selectin is integral to rolling, the first step in leukocyte recruitment to an inflammatory site. L-selectin is shed from leukocytes in sepsis, resulting in increased levels of soluble L-selectin in plasma (2.33 microg/mL). This study investigates the effects of soluble L-selectin at levels found in sepsis on leukocyte trafficking in vivo. DESIGN: Prospective, controlled trial. SETTING: Surgical research laboratory in a university hospital. SUBJECTS: Swiss white male mice of 25-35 g. INTERVENTIONS: Mice were randomized to one of three study groups: soluble L-selectin 2.33, soluble L-selectin 8.0, or albumin. Intravital microscopy was performed on postcapillary venules of 20-40 microm in diameter in the cremaster muscle of mice. Leukocyte-endothelial cell interactions (rolling, adherence, and rolling velocity) were measured pre- and post- (1, 15, 30, and 45 mins) intravenous infusion of human recombinant soluble L-selectin (2.33 and 8.0 microg/mL) or human albumin (8.0 microg/mL). MEASUREMENTS AND MAIN RESULTS: The intravenous administration of soluble L-selectin to a systemic concentration of 2.33 microg/mL diminished rolling significantly. Soluble L-selectin at 8.0 microg/mL decreased rolling and increased rolling velocity to a greater degree. Injection of albumin did not alter leukocyte-endothelial cell interactions at any time point. No difference between groups in blood pressure, shear rate, or leukocyte counts was detected. CONCLUSIONS: Soluble L-selectin diminishes leukocyte rolling at levels present in sepsis (2.33 microg/mL). This effect is dose dependent, and could not be explained by differences in blood pressure, shear rate, or leukocyte counts. These findings identify increased soluble L-selectin levels as one of the mechanisms for decreased leukocyte delivery and exudation to remote sites in septic patients.

Analysis of Variance↗
PubMed2000

Ductus venosus flow velocity in newborn lambs during increased pulmonary artery pressure.

The aim of the present study was to assess with ultrasound the ductus venosus flow velocity in newborn lambs with increasing pulmonary artery pressures and to evaluate whether this is a useful method to detect elevated pulmonary artery pressure. The ductus venosus flow velocity was studied with pulsed-wave Doppler echocardiography in nine newborn lambs < or = 30 h old. The lambs were anesthetized, mechanically ventilated, and instrumented to measure mean airway pressure and pulmonary artery and arterial blood pressures. A vascular occluder was placed around the main pulmonary artery. With mean pressures ranging from 20 to 50 mm Hg in the pulmonary artery, the ductus venosus flow velocity was examined. In seven lambs, the mean portal pressure and central venous pressure were also measured. With a stepwise increase in the pulmonary artery pressure, the minimum ductus venosus flow velocity during atrial systole decreased to a reversed flow, and the duration of this reversed flow component increased. The systolic forward peak flow velocity signal also gradually decreased. No changes were detected in the mean central venous or in the portal pressure with increasing pulmonary artery pressure or changes in ductus venosus flow. The flow velocity in the ductus venosus, which is higher than in other precordial veins, shows a reduction and even reversal of the nadir and an increase of the duration of reversed flow during atrial systole as a response to increased pulmonary artery pressure. Thus, Doppler ultrasound of the ductus venosus flow velocity may be a useful noninvasive diagnostic supplement to detect pulmonary hypertension of the newborn.

Animals↗
PubMed1999

Production and characterization of an anti-serotonin 1A receptor antibody which detects functional 5-HT1A binding sites.

We describe the production and characterization of a specific anti-5-HT1A receptor antibody made against a fusion protein consisting of glutathione-S-transferase (GST) coupled to a 75-amino acid sequence from the middle portion of the third intracellular loop (5-HT1A-m3i, serine253-arginine327) of the rat 5-HT1A receptor protein. This region was chosen to avoid putative phosphorylation and glycosylation sites and regions of known homology with other 5-HT receptors. Western blot analysis indicated that the polyclonal anti-5-HT1A-m3i antibody accurately recognized the fusion protein expressed in bacteria and labeled a prominent 67 kDa protein band in the hippocampus, cortex, brainstem, cerebellum and kidney with a density profile corresponding to the relative abundance of the 5-HT1A receptor in these tissues. No protein was detected in liver or muscle tissue preparations, and no protein bands were labeled in any of the above tissues following preabsorption of the antibody with the 5-HT1A-m3i fusion protein. Immunohistochemistry revealed prominent labeling in limbic structures including the hippocampus, amygdala, entorhinal cortex, and septum as well as in raphe nuclei. In the hippocampus, 5-HT1A-m3i labeling revealed a characteristic laminar pattern that coincided with that seen by autoradiographic binding of the 5-HT1A agonist [3H]-8-OH-DPAT in all strata of the hippocampal formation. In the dorsal and medial raphe nuclei, anti-5-HT1A-m3i antibodies labeled the somatodendritic membranes of 5-HT neurons, consistent with its role as an autoreceptor. The detailed matching of the anti-5-HT1A-m3i antibody with [3H]-8-OH-DPAT binding suggests that the antibody recognizes a functionally active form of the 5-HT1A receptor protein capable of binding 5-HT1A agonist ligands. These anti-5-HT1A antibodies may therefore be useful tools in localizing functional 5-HT1A receptors in specific regions of the brain as well as in studying the plasticity and ontogeny of the 5-HT1A receptor at the cellular and subcellular level.

Amino Acid Sequence↗
PubMed1998

Parathyroid hormone regulates the expression of the nuclear mitotic apparatus protein in the osteoblast-like cells, ROS 17/2.8.

The parathyroid hormone (PTH) signaling pathways that effect changes in osteoblast gene expression also alter the organization of the cytoskeletal proteins. PTH regulates the expression of nucleoskeletal proteins, such as nuclear mitotic apparatus protein (NuMA) and topoisomerase II-alpha. NuMA is a structural component of the interphase nucleus and organizes the microtubules of the mitotic spindle during mitogenesis. We propose that PTH-induced alterations in osteoblast cytoarchitecture are accompanied by changes in osteoblast nuclear structure that contribute to changes in gene expression. We used immunofluorescence and confocal microscopy to determine the effect of PTH on the expression and nuclear distribution of NuMA in the rat osteosarcoma cell line, ROS 17/2.8. Cells were treated with PTH or vehicle, then fixed and stained with NuMA antibody. Optical sections of interphase naive cells revealed a diffuse distribution of NuMA, interspersed with speckles, in the central nuclear planes but not in nucleoli. During the metaphase and anaphase, NuMA localized at the mitotic spindle apparatus. The percentage of NuMA-immunopositive ROS 17/2.8 cells decreased with increasing confluence, but serum starvation did not attenuate NuMA expression. Cell density-dependent changes in cytoskeletal organization were observed in these cells. PTH treatment induced changes in cytoskeletal organization and increased the percentage of NuMA-immunopositive ROS 17/2.8 cells. These data suggest that PTH effects changes in osteoblast nuclear architecture by regulating NuMA, and that these alterations may be coupled to cytoskeletal organization.

Animals↗
PubMed1997

Topoisomerase II expression in osseous tissue.

The molecular mechanisms that mediate the transition from an osteoprogenitor cell to a differentiated osteoblast are unknown. We propose that topoisomerase II (topo II) enzymes, nuclear proteins that mediate DNA topology, contribute to coordinating the loss of osteoprogenitor proliferative capacity with the onset of differentiation. The isoforms topo II-alpha and -beta, are differentially expressed in nonosseous tissues. Topo II-alpha expression is cell cycle-dependent and upregulated during mitogenesis. Topo II-beta is expressed throughout the cell cycle and upregulated when cells have plateaued in growth. To determine whether topo II-alpha and -beta are expressed in normal bone, we analyzed rat lumbar vertebrae using immunohistochemical staining. In the tissue sections, topo II-alpha was expressed in the marrow cavity of the primary spongiosa. Mature osteoblasts along the trabecular surfaces did not express topo II-alpha, but were immunopositive for topo II-beta, as were cells of the marrow cavity. Confocal laser scanning microscopy was used to determine the nuclear distribution of topo II in rat osteoblasts isolated from the metaphyseal distal femur and the rat osteosarcoma cells, ROS 17/2.8. Topo II-alpha exhibited a punctate nuclear distribution in the bone cells. Topo II-beta was dispersed throughout the interior of the nucleus but concentrated at the nuclear envelope. Serum starvation of the cells attenuated topo II-alpha expression but did not modulate expression of the beta-isoform. These results indicate that the loss of osteogenic proliferation correlates with the downregulation of topo II-alpha expression.

Animals↗