Differential transmission of human immunodeficiency virus type 1 by distinct subsets of effector dendritic cells

Dendritic cells (DC) support human immunodeficiency virus type 1 (HIV-1) transmission by capture of the virus particle in the mucosa and subsequent transport to the draining lymph node, where HIV-1 is presented to CD4(+) Th cells. Virus transmission involves a high-affinity interaction between the DC-specific surface molecule DC-SIGN and the viral envelope glycoprotein gp120 and subsequent internalization of the virus, which remains infectious. The mechanism of viral transmission from DC to T cells is currently unknown. Sentinel immature DC (iDC) develop into Th1-promoting effector DC1 or Th2-promoting DC2, depending on the activation signals. We studied the ability of these effector DC subsets to support HIV-1 transmission in vitro. Compared with iDC, virus transmission is greatly upregulated for the DC1 subset, whereas DC2 cells are inactive. Increased transmission by DC1 correlates with increased expression of ICAM-1, and blocking studies confirm that ICAM-1 expression on DC is important for HIV transmission. The ICAM-1-LFA-1 interaction is known to be important for immunological cross talk between DC and T cells, and our results indicate that this cell-cell contact is exploited by HIV-1 for efficient transmission.     

Phylogenetic analysis of 277 human G-protein-coupled receptors as a tool for the prediction of orphan receptor ligands

Background

G-protein-coupled receptors (GPCRs) are the largest and most diverse family of transmembrane receptors. They respond to a wide range of stimuli, including small peptides, lipid analogs, amino-acid derivatives, and sensory stimuli such as light, taste and odor, and transmit signals to the interior of the cell through interaction with heterotrimeric G proteins. A large number of putative GPCRs have no identified natural ligand. We hypothesized that a more complete knowledge of the phylogenetic relationship of these orphan receptors to receptors with known ligands could facilitate ligand identification, as related receptors often have ligands with similar structural features.

Results

A database search excluding olfactory and gustatory receptors was used to compile a list of accession numbers and synonyms of 81 orphan and 196 human GPCRs with known ligands. Of these, 241 sequences belonging to the rhodopsin receptor-like family A were aligned and a tentative phylogenetic tree constructed by neighbor joining. This tree and local alignment tools were used to define 19 subgroups of family A small enough for more accurate maximum-likelihood analyses. The secretin receptor-like family B and metabotropic glutamate receptor-like family C were directly subjected to these methods.

Conclusions

Our trees show the overall relationship of 277 GPCRs with emphasis on orphan receptors. Support values are given for each branch. This approach may prove valuable for identification of the natural ligands of orphan receptors as their relation to receptors with known ligands becomes more evident.     

Cardiac diastolic dysfunction in high-fat diet fed mice is associated with lipotoxicity without impairment of cardiac energetics in vivo

Obesity is often associated with abnormalities in cardiac morphology and function. This study tested the hypothesis that obesity-related cardiomyopathy is caused by impaired cardiac energetics. In a mouse model of high-fat diet (HFD)-induced obesity, we applied in vivo cardiac ³¹P magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) to investigate cardiac energy status and function, respectively. The measurements were complemented by ex vivo determination of oxygen consumption in isolated cardiac mitochondria, the expression of proteins involved in energy metabolism, and markers of oxidative stress and calcium homeostasis. We also assessed whether HFD induced myocardial lipid accumulation using in vivo ¹H MRS, and if this was associated with apoptosis and fibrosis. Twenty weeks of HFD feeding resulted in early stage cardiomyopathy, as indicated by diastolic dysfunction and increased left ventricular mass, without any effects on systolic function. In vivo cardiac phosphocreatine-to-ATP ratio and ex vivo oxygen consumption in isolated cardiac mitochondria were not reduced after HFD feeding, suggesting that the diastolic dysfunction was not caused by impaired cardiac energetics. HFD feeding promoted mitochondrial adaptations for increased utilization of fatty acids, which was however not sufficient to prevent the accumulation of myocardial lipids and lipid intermediates. Myocardial lipid accumulation was associated with oxidative stress and fibrosis, but not apoptosis. Furthermore, HFD feeding strongly reduced the phosphorylation of phospholamban, a prominent regulator of cardiac calcium homeostasis and contractility. In conclusion, HFD-induced early stage cardiomyopathy in mice is associated with lipotoxicity-associated oxidative stress, fibrosis, and disturbed calcium homeostasis, rather than impaired cardiac energetics.     

The knee adduction moment measured with an instrumented force shoe in patients with knee osteoarthritis

The external knee adduction moment (KAdM) during gait is an important parameter in patients with knee osteoarthritis (OA). KAdM measurement is currently restricted to instruments only available in gait laboratories. However, ambulatory movement analysis technology, including instrumented force shoes (IFS) and inertial and magnetic measurement systems (IMMS), can measure kinetics and kinematics of human gait free of laboratory restrictions. The objective of this study was a quantitative validation of the accuracy of the KAdM in patients with knee OA, when estimated with an ambulatory-based method (AmbBM) versus a laboratory-based method (LabBM). AmbBM is employing the IFS and a linked-segment model, while LabBM is based on a force plate and optoelectronic marker system. Effects of ground reaction force (GRF), centre of pressure (CoP), and knee joint position measurement are evaluated separately. Twenty patients with knee OA were measured. The GRFs showed differences up to 0.22 N/kg, the CoPs showed differences up to 4 mm, and the medio-lateral and vertical knee position showed differences to 9 mm, between AmbBM and LabBM. The GRF caused an under-estimation in KAdM in early stance. However, this effect was counteracted by differences in CoP and joint position, resulting in a net 5% over-estimation. In midstance and late stance the accuracy of the KAdM was mainly limited by use of the linked-segment model for joint position estimation, resulting in an under-estimation (midstance 6% and late stance 22%). Further improvements are needed in the estimation of joint position from segment orientation.     

Microtubular configurations during meiosis and megasporogenesis in Gasteria verrucosa and Chamaenerion angustifolium

Summary In Gasteria and Chamaenerion, microtubular configurations were visualized immunocytochemically during meiosis and megasporogenesis in order to study their relationship to cell development, meiotic divisions and selection of the functional megaspore. In Chamaenerion, the intensity of the fluorescence found in megaspores was weaker than that found in Gasteria. Both plants exhibited concentrations of microtubules around the meiocyte nuclei during pachytene-diplotene. Preprophase bands were not observed. In Chamaenerion, cytoplasmic microtubules radiating from meiocyte nuclei were found at late prophase, the dyad stage and in the functional megaspore; in Gasteria, they were observed only at the dyad stage and in the functional megaspore. During the second meiotic division of Gasteria, dividing cells and their nuclei exhibited differences in volumes. Also, the two microtubular spindles of the dyad cells had different widths. Fluorescence indicating the presence of the cytoskeleton diminished during maturation of the large functional megaspores in both plants, whereas in the three degenerating smaller megaspores, fluorescence intensity persisted. Our conclusion is that only an indirect relationship exists between the organization of the microtubular cytoskeleton and selection of the functional megaspore.     

Qualitative and quantitative comparison of glucose transport activity and glucose transporter concentration in plasma membranes from basal and insulin-stimulated rat adipose cells.

Conditions are described which allow the isolation of rat adipose-cell plasma membranes retaining a large part of the stimulatory effect of insulin in intact cells. In these membranes, the magnitude of glucose-transport stimulation in response to insulin was compared with the concentration of transporters as measured with the cytochalasin-B-binding assay or by immunoblotting with an antiserum against the human erythrocyte glucose transporter. Further, the substrate- and temperature-dependencies of the basal and insulin-stimulated states were compared. Under carefully controlled homogenization conditions, insulin-treated adipose cells yielded plasma membranes with a glucose transport activity 10-15-fold higher than that in membranes from basal cells. Insulin increased the transport Vmax. (from 1,400 +/- 300 to 15,300 +/- 3,400 pmol/s per mg of protein; means +/- S.E.M.; assayed at 22 degrees C) without any significant change in Km (from 17.8 +/- 4.4 to 18.9 +/- 1.4 nM). Arrhenius plots of plasma-membrane transport exhibited a break at 21 degrees C, with a higher activation energy over the lower temperature range. The activation energy over the higher temperature range was significantly lower in membranes from basal than from insulin-stimulated cells [27.7 +/- 5.0 kJ/mol (6.6 +/- 1.2 kcal/mol) and 45.3 +/- 2.1 kJ/mol (10.8 +/- 0.5 kcal/mol) respectively], giving rise to a larger relative response to insulin when transport was assayed at 37 degrees C as compared with 22 degrees C. The stimulation of transport activity at 22 degrees C was fully accounted for by an increase in the concentration of transporters measured by cytochalasin B binding, if a 5% contamination of plasma membranes with low-density microsomes was assumed. However, this 10-fold stimulation of transport activity contrasted with an only 2-fold increase in transporter immunoreactivity in membranes from insulin-stimulated cells. These data suggest that, in addition to stimulating the translocation of glucose transporters to the plasma membrane, insulin appears to induce a structural or conformational change in the transporter, manifested in an altered activation energy for plasma-membrane transport and possibly in an altered immunoreactivity as assessed by Western blotting.     

Muscle palmitate uptake and binding are saturable and inhibited by antibodies to FABPPM

Studies show that uptake of long-chain fatty acids (LCFA) across the plasma membranes (PM) may occur partly via a carrier-mediated process and that the plasma membrane fatty acid-binding protein (FABP_PM) may be a component of this system. To test the hypothesis that FABP_PM is involved in transsarcolemmal transport of LCFA in muscle, we measured palmitate uptake in giant sarcolemmal vesicles and palmitate binding to PM proteins in rat muscles, (1) in the presence of increasing amounts of unbound palmitate and (2) in the absence or presence of antibody to FABP_PM. Both palmitate uptake and binding were found to be saturable functions of the unbound palmitate concentration with calculated V_max values of 10.5 ± 1.2 pmol/mg protein/15 sec and 45.6 ± 2.9 nmol/mg protein/15 min and K_m values of 12.8 ± 3.8 and 18.4 ± 1.8 nmol/L, respectively. The V_max values for both palmitate uptake and binding were significantly decreased by 75-79% in the presence of a polyclonal antibody to the rat hepatic FABP_PM. Antibody inhibition was found to be dose-dependent and specific to LCFA. Glucose uptake was not affected by the presence of the antibody to FABP_PM. Palmitate uptake and binding were also inhibited in the presence of trypsin and phloretin. These results support the hypothesis that transsarcolemmal LCFA transport occurs in part by a carrier-mediated process and that FABP_PM is a component of this process in muscle.     

Dynamics of callose deposition and beta-1,3-glucanase expression during reproductive events in sexual and apomictic Hieracium

Callose accumulates in the walls of cells undergoing megasporogenesis during embryo sac formation in angiosperm ovules. Deficiencies in callose deposition have been observed in apomictic plants and causal linkages between altered callose deposition and apomictic initiation proposed. In apomictic Hieracium, embryo sacs initiate by sexual and apomictic processes within an ovule, but sexual development terminates in successful apomicts. Callose deposition and the events that lead to sexual termination were examined in different Hieracium apomicts that form initials pre- and post-meiosis. In apomictic plants, callose was not detected in initial cell walls and deficiencies in callose deposition were not observed in cells undergoing megasporogenesis. Multiple initial formation pre-meiosis resulted in physical distortion of cells undergoing megasporogenesis, persistence of callose and termination of the sexual pathway. In apomictic plants, callose persistence did not correlate with altered spatial or temporal expression of a β-1,3-glucanase gene (HpGluc) encoding a putative callose-degrading enzyme. Expression analysis indicated HpGluc might function during ovule growth and embryo sac expansion in addition to callose dissolution in sexual and apomictic plants. Initial formation pre-meiosis might therefore limit the access of HpGluc protein to callose substrate while the expansion of aposporous embryo sacs is promoted. Callose deposition and dissolution during megasporogenesis were unaffected when initials formed post-meiosis, indicating other events cause sexual termination. Apomixis in Hieracium is not caused by changes in callose distribution but by events that lead to initial cell formation. The timing of initial formation can in turn influence callose dissolution. Received: 18 April 2000 / Accepted: 10 July 2000     

Pentoxifylline reduces fibrin deposition and prolongs survival in neonatal hyperoxic lung injury.

Bronchopulmonary dysplasia is a leading cause of mortality and morbidity in preterm infants despite improved treatment modalities. Pentoxifylline, a phosphodiesterase inhibitor, inhibits multiple processes that lead to neonatal hyperoxic lung injury, including inflammation, coagulation, and edema. Using a preterm rat model, we investigated the effects of pentoxifylline on hyperoxia-induced lung injury and survival. Preterm rat pups were exposed to 100% oxygen and injected subcutaneously with 0.9% saline or 75 mg/kg pentoxifylline twice a day. On day 10, lung tissue was harvested for histology, fibrin deposition, and mRNA expression, and bronchoalveolar lavage fluid was collected for total protein concentration. Pentoxifylline treatment increased mean survival by 3 days (P = 0.0018) and reduced fibrin deposition by 66% (P < 0.001) in lung homogenates compared with untreated hyperoxia-exposed controls. Monocyte chemoattractant protein-1 expression in lung homogenates was decreased, but the expressions of TNF-alpha, IL-6, matrix metalloproteinase-12, tissue factor, and plasminogen activator inhibitor-1 were similar in both groups. Total protein concentration in bronchoalveolar lavage fluid was decreased by 33% (P = 0.029) in the pentoxifylline group. Pentoxifylline treatment attenuates alveolar fibrin deposition and prolongs survival in preterm rat pups with neonatal hyperoxic lung injury, probably by reducing capillary-alveolar protein leakage.