Cardiostimulant effects of urotensin-II in human heart in vitro

The effects of the recently identified human peptide urotensin-II (hU-II) were investigated on human cardiac muscle contractility and coronary artery tone. In right atrial trabeculae from non-failing hearts, hU-II caused a concentration-dependent increase in contractile force (pEC(50)=9.5+/-0.1; E-max= 31.3+/-4.8% compared to 9.25 mM Ca2+; n = 9) with no change in contraction duration. In right ventricular trabeculae from explanted hearts, 20 nM hU-II caused a small increase in contractile force (7.8+/-1.4% compared to 9.25 mM Ca2+; n= 3/6 tissues from 2 out of 4 patients). The peptide caused arrhythmic contractions in 3/26 right atrial trabeculae from 3/9 patients in an experimental model of arrhythmia and therefore has less potential to cause arrhythmias than ET-1. hU-II (20 nM) increased tone (17.9% of the response to 90 mM KCI) in 7/7 tissues from 1 patient, with no response detected in 8/8 tissues from 2 patients. hU-II is a potent cardiac stimulant with low efficacy.

Development of axon pathways in the zebrafish central nervous system

The zebrafish has a number of distinct advantages as an experimental model in developmental biology. For example, large numbers of embryos can be generated in each lay, development proceeds rapidly through a very precise temporal staging which exhibits minimal batch-to-batch variability, embryos are transparent and imaging of wholemounts negates the need for tedious histological preparation while preserving three-dimensional spatial relationships. The zebrafish nervous system is proving a convenient model for studies of axon guidance because of its small size and highly stereotypical trajectory of axons. Moreover, a simple scaffold of axon tracts and nerves is established early and provides a template for subsequent development. The ease with which this template can be visualized as well as the ability to spatially resolve individual pioneer axons enables the role of specific cell-cell and molecular interactions to be clearly deciphered. We describe here the morphology and development of the earliest axon pathways in the embryonic zebrafish central nervous system and highlight the major questions that remain to be addressed with regard to axon guidance.

Targeted delivery of heparin and LMWH using a fibrin antibody prevents restenosis

This study investigates a stent-less local delivery system for anti-restenotic agents utilizing antibodies to cross-linked fibrin (XLF). Heparin and low molecular weight heparin (LMWH) were conjugated to an antibody to cross-linked fibrin D-dinner (1D2). Rabbit right carotid arteries were injured with a balloon catheter, then the animals were given a bolus injection of 40 mug/k,g 1D2-heparin (26-70 mug/kg heparin) or 1D2-LMWH (29-80 mug/kg LMWH) conjugates or controls of saline (0.5 ml/kg), heparin (150 U/kg), LMWH (2 mg), or 1D2 (40 mug/kg), with or without a heparin bolus and sacrificed after 2 weeks (8 groups, n = 6/group). The injured artery of rabbits given 1D2-heparin or 1D2-LMWH conjugates had reduced neointimal development, with decreased luminal narrowing and positive remodelling compared with animals given control drugs. Animals given 1D2-heparin conjugate (with a heparin bolus) had three to five times more endothelial cells than the rabbits given saline or unconjugated heparin, while rabbits given 1D2-LMWH conjugate had up to 59% fewer neointimal cells than those given unconjugated drugs. There was little difference in extracellular matrix organization or composition. Thus cross-linked fibrin-antibodies can site-deliver anti-restenotic agents to injured areas of the artery wall where they influence wall remodelling and endothelial and neointimal cell number, reducing neointimal formation without systemic complications. Local delivery of anti-restenotic agents should minimise systemic effects, bleeding complications and potentially the cost of treatment due to a single, lower dose. (C) 2004 Elsevier Ireland Ltd. All rights reserved.

The nature of anterior knee pain following injection of hypertonic saline into the infrapatellar fat pad

The infrapatellar fat pad has been implicated as a possible source of anterior knee pain. This study examined the nature, distribution and time-course of experimentally induced pain in the infrapatellar fat pad. Hypertonic saline (5%) was injected into the medial fat pad of 11 healthy individuals with no history of knee pain. Severity of pain was assessed at rest and during activity using an 11 point numerical rating scale (NRS) at regular intervals over 15-30 min following injection. Participants described the size of the pain region from a series of different sized circles while the area and type of pain was established from a body chart and the McGill pain questionnaire. The effect of pain on temperature-pain threshold and sensory thresholds of the anterior knee was assessed. Participants generally reported a deep aching pain that peaked in severity around 3 min and gradually declined over 15 min. Pain levels were not altered by clinical manoeuvres designed to impinge the fat pad. The size of the pain region was related to pain intensity. Pain was most commonly felt in the region of the fat pad medial to the patella, although some individuals reported proximal referred pain as far as the groin region. Thermal and sensory thresholds were not altered at a region close to the injection site during the experimental pain. These results suggest that nociceptive stimulation of the infrapatellar fat pad may cause anterior knee pain that is not necessarily confined locally particularly if pain is severe. This has implications for the investigation of pathological structures in patients presenting clinically with anterior knee pain and provides an experimental model of anterior knee pain. (C) 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.

Antioxidative function of L-FABP in L-FABP stably transfected Chang liver cells

Liver fatty acid binding protein (L-FABP) contains amino acids that are known to possess antioxidant function. In this study, we tested the hypothesis that L-FABP may serve as an effective endogenous cytoprotectant against oxidative stress. Chang liver cells were selected as the experimental model because of their undetectable L-FABP mRNA level. Full-length L-FABP cDNA was subcloned into the mammalian expression vector pcDNA3.1 (pcDNA-FABP). Chang cells were stably transfected with pc-DNA-FABP or vector (pcDNA3.1) alone. Oxidative stress was induced by incubating cells with 400 mu mol/L H2O2 or by subjecting cells to hypoxia/reoxygenation. Total cellular reactive oxygen species (ROS) was determined using the fluorescent probe DCF. Cellular damage induced by hypoxia/reoxygenation was assayed by lactate dehydrogenase (LDH) release. Expression of L-FABP was documented by regular reverse transcription polyrnerase chain reaction (RT-PCR), real-time RT-PCR, and Western blot. The pcDNA-FABP-transfected cells expressed full-length L-FABP mRNA, which was absent from vector-transfected control cells. Western blot showed expression of 14-kd L-FABP protein in pcDNA-FABP-transfected cells, but not in vector-transfected cells. Transfected cells showed decreased DCF fluorescence intensity under oxidative stress (H2O2 and hypoxia/reoxygenation) conditions versus control in inverse proportion to the level of L-FABP expression. Lower LDH release was observed in the higher L-FABP-expressed cells in hypoxia/reoxygenation experiments. In conclusion, we successfully transfected and cloned a Chang liver cell line that expressed the L-FABP gene. The L-FABP-expressing cell line had a reduced intracellular ROS level versus control. This finding implies that L-FABP has a significant role in oxidative stress.

Genetic basis of human testicular germ cell cancer: insights from the fruitfly and mouse

The prevalence of tumours of the germ line is increasing in the male population. This complex disease has a complex aetiology. We examine the contribution of genetic mutations to the development of germ line tumours in this review. In particular, we concentrate on fly and mouse experimental systems in order to demonstrate that mutations in some conserved genes cause pathologies typical of certain human germ cell tumours, whereas other mutations elicit phenotypes that are unique to the experimental model. Despite these experimental systems being imperfect, we show that they are useful models of human testicular germ cell tumourigenesis.

Resistance of porcine blood clots to lysis relates to poor activation of porcine plasminogen by tissue plasminogen activator

In-vitro experimentation was performed on porcine and human blood to determine their comparative responsiveness to a novel fibrinolytic inhibitor and thereby assess whether the pig is a suitable animal model for subsequent in-vivo testing of this inhibitor. Thromboelastography showed the clots formed from porcine whole blood to be highly resistant to tissue plasminogen activator (t-PA)-catalyzed lysis, and this communication offers the resistance of porcine plasminogen to activation by t-PA as an explanation. Porcine blood containing 100 and 1500 IU/ml added t-PA lysed very slowly, having LY30 values of 1.9 +/- 1.4 and 2.9 +/- 1.9%, respectively. In contrast, the LY30 values for the human clots containing 100 and 1500 IU/ml t-PA were 77.1 +/- 6.3 and 93.3 +/- 1.3%, respectively. Moreover, purified porcine plasminogen was activated very slowly by added t-PA in the presence of both human and porcine fibrin. Activation of plasminogen by the endogenous activators, as measured by the euglobulin clot lysis time, was greatly prolonged for the pig (22 +/- 3 h) compared with the human (3.5 +/- 1.5 h). These results suggest caution in using the pig as an experimental model when studying the effects of various agents on fibrinolysis.

Irradiation-induced oral candidiasis in an experimental murine model

The aim of this experiment was to establish a mouse model of irradiation-induced oral candidiasis and to explore the cellular populations and mechanisms by which the infection is cleared from the oral mucosa. BALB/c mice received irradiation to the head and neck equivalent to 800 Rad using a Cobalt 60 gamma source. Both irradiated and non-irradiated mice were infected orally with 1 X 10(8) Candida albicans yeasts. Compared with untreated controls, irradiated animals developed a more severe infection of longer duration, with hyphae penetrating the oral mucosa. Monoclonal antibody depletion of CD4(+) but not CD8(+) T cells from the systemic circulation prolonged the infection in irradiated mice, but not in controls. Supernatants of submandibular and superficial cervical lymph node cultures from irradiated animals demonstrated significantly higher titers of interleukin-12, but similar levels of interferon-gamma compared with controls. Screening for cytokine production by an RNase protection assay detected only macrophage migration inhibition factor in irradiated and non-irradiated oral tissues from day 8 onwards. The results of this study demonstrate a requirement for CD4(+) T cells in the recovery from oral candidiasis induced by head and neck irradiation in mice, and are consistent with a role for Th-1-type cytokines in host resistance.

Impulse-response function of splanchnic circulation with model-independent constraints: theory and experimental validation

Modeling physiological processes using tracer kinetic methods requires knowledge of the time course of the tracer concentration in blood supplying the organ. For liver studies, however, inaccessibility of the portal vein makes direct measurement of the hepatic dual-input function impossible in humans. We want to develop a method to predict the portal venous time-activity curve from measurements of an arterial time-activity curve. An impulse-response function based on a continuous distribution of washout constants is developed and validated for the gut. Experiments with simultaneous blood sampling in aorta and portal vein were made in 13 anesthetized pigs following inhalation of intravascular [O-15] CO or injections of diffusible 3-O[ C-11] methylglucose (MG). The parameters of the impulse-response function have a physiological interpretation in terms of the distribution of washout constants and are mathematically equivalent to the mean transit time ( T) and standard deviation of transit times. The results include estimates of mean transit times from the aorta to the portal vein in pigs: (T) over bar = 0.35 +/- 0.05 min for CO and 1.7 +/- 0.1 min for MG. The prediction of the portal venous time-activity curve benefits from constraining the regression fits by parameters estimated independently. This is strong evidence for the physiological relevance of the impulse-response function, which includes asymptotically, and thereby justifies kinetically, a useful and simple power law. Similarity between our parameter estimates in pigs and parameter estimates in normal humans suggests that the proposed model can be adapted for use in humans.

An experimental and finite element poroelastic creep response analysis of an intervertebral hydrogel disc model in axial compression

A hydrogel intervertebral disc (lVD) model consisting of an inner nucleus core and an outer anulus ring was manufactured from 30 and 35% by weight Poly(vinyl alcohol) hydrogel (PVA-H) concentrations and subjected to axial compression in between saturated porous endplates at 200 N for 11 h, 30 min. Repeat experiments (n = 4) on different samples (N = 2) show good reproducibility of fluid loss and axial deformation. An axisymmetric nonlinear poroelastic finite element model with variable permeability was developed using commercial finite element software to compare axial deformation and predicted fluid loss with experimental data. The FE predictions indicate differential fluid loss similar to that of biological IVDs, with the nucleus losing more water than the anulus, and there is overall good agreement between experimental and finite element predicted fluid loss. The stress distribution pattern indicates important similarities with the biological lVD that includes stress transference from the nucleus to the anulus upon sustained loading and renders it suitable as a model that can be used in future studies to better understand the role of fluid and stress in biological IVDs. (C) 2005 Springer Science + Business Media, Inc.

Development of a quasi-chemical viscosity model for fully liquid slags in the Al2O3-CaO-'FeO'-MgO-SiO2 system. Part 2. A review of the experimental data and the model predictions for the Al2O3-CaO-MgO, CaO-MgO-SiO2 and Al2O3-MgO-SiO2 systems

A structurally-based quasi-chemical viscosity model has been developed for the Al2O3 CaO-'FeO'-MgO-SiO2 system. The model links the slag viscosity to the internal structure of melts through the concentrations of various anion/cation Si0.5O, Me2/nn+O and Me1/nn+Si0.25O viscous flow structural units. The concentrations of structural units are derived from the quasi-chemical thermodynamic model. The focus of the work described in the present paper is the analysis of experimental data and the viscosity models for fully liquid slags in the Al2O3-CaO-MgO, Al2O3 MgO-SiO2 and CaO-MgO-SiO2 systems.