Pre-exposure of murine macrophages to lipopolysaccharide inhibits the induction of nitric oxide synthase and reduces leishmanicidal activity

Murine macrophages produce nitric oxide (NO) from L-arginine on stimulation with lipopolysaccharide (LPS), alone or with interferon-γ (IFN-γ). The effect of incubation of macrophages with low concentrations of LPS on NO synthesis on subsequent stimulation was investigated, using a murine macrophage cell line, J774, and peritoneal macrophages from CBA mice. Cells which had been incubated with LPS produced significantly lower amounts of NO, and expressed lower levels of NO synthase activity, following stimulation with IFN-γ and LPS, or with a high concentration of LPS. This effect was not reversed by tumor necrosis factor-α. The ability of CBA macrophages to kill the intracellular parasite Leishmania major was markedly reduced by pre-incubation with LPS. Reduced NO production by macrophages previously exposed to LPS is a manifestation of endotoxin tolerance, and may represent an important means of regulation of NO synthesis and thus a survival mechanism for intracellular parasites.     

Regulation of delayed-type hypersensitivity. II. Specific suppressor factor for delayed-type hypersensitivity to sheep erythrocytes in mice.

An antigen-specific suppressor factor for delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) in mice is described. Lymph node cells and spleen cells from mice injected intravenously with 1 x 10(9) SRBC 4 days previously were incubated in vitro for 48 h in culture medium. Supernatant obtained from the culture inhibited the induction of DTH to SRBC in normal mice. It also suppressed the expression of DTH in presensitized mice. The suppression is specific as the suppressor factor had no effect on the DTH to noncross-reacting antigen, chicken red blood cells. Treatment of the spleen cells with anti-theta serum and complement prevented the production of the suppressor factor, whereas treatment with anti-Ig serum and complement had no effect. Suppressor factor produced by H-2k mice suppressed the DTH in H-2b mice. The factor thus seems to act across the H-2 barrier. The suppressor factor was not removed by adsorption with goat anti-mouse immunoglobulin immunoadsorbent, but could be adsorbed by SRBC. It was stable at 56 degrees C for 1 h, but was partially inactivated by freezing and thawing. The factor has a molecular weight of less than 35 000 daltons.     

Regulation of ST2L expression on T helper (Th) type 2 cells

T1/ST2L, an IL-1 receptor homologue, is selectively expressed on murine Th2 cells and specific anti-ST2L antibodies can profoundly modulate the Th1/Th2 balance in vivo. Naive CD4+ T cells do not express ST2L but do so on activation with specific antigen in the presence of IL-4 or when stimulated with low doses of antigen in the absence of exogenously added IL-4. Similarly enhanced ST2L expression occurred after stimulation of Th2 cells with antigen or the mitogen ConA in the presence of APC. Restimulation of Th2 cells in the presence of IFN-gamma led to a decreased expression of ST2L to below basal levels. Conversely, Th2 cells cultured with IL-4 led to increased ST2L expression. The reduced expression of ST2L in response to high doses of antigen is also reversed by the neutralization of IFN-gamma. Using an ST2L promoter/luciferase reporter gene construct, we show that the distal but not proximal ST2L promoter is responsible for specific gene expression in Th2 cells. IL-4 enhances, whereas IFN-gamma suppresses ST2L expression via direct modulation of the distal promoter of the ST2L gene. These data provide a mechanistic explanation for the selective expression of ST2L on Th2 cells.     

LES modelling of flow in a simple airway model

Detailed information about the flow field pattern is highly important in accurately predicting particle deposition sites in the human airway. Flow in the upper airway during heavy breathing can have a Reynolds number as high as 9300, and therefore presents turbulent features. Although turbulence is believed to have an important effect on the airflow and other transport processes in the bronchial tree, to date both theoretical and numerical studies have predominantly assumed the flow to be laminar. In this paper, transitional/turbulent flow during inspiration is studied using a large eddy simulation (LES) in a single asymmetric bifurcation model of human upper airway. The influence of the non-laminar flow on the patterns and the particle paths is investigated in both 2D and 3D models. Throughout the investigation, comparisons with the laminar and conventional k- models for the same configuration and flow conditions are made. The LES model is also carefully validated against published experimental data in a stenotic tube model. The results demonstrate that the LES model is capable of capturing instantaneous eddy formation and flow separation in (almost) laminar, transitional and turbulent flow regimes, and hence may be used as a powerful and practical tool to provide much of the detailed flow information required for tracing the particle trajectories and particle deposition in human airways.     

恶性肿瘤患者血清与尿液中一氧化氮含量测定

0 引言一氧化氮（Nitric oxide,NO）是一种具有活跃生物化学性质的无机小分子. NO对许多肿瘤细胞和微生物有细胞毒性［1］,为探讨NO与肿瘤的关系,我们检测了119例恶性肿瘤患者血清及尿液中的NO.     

Diffusion-dependence of pulmonary gas mixing at 5.5 and 9.5 ATA

Gas-phase diffusivity is inversely proportional to pressure, so mixing of inspired gas in the lung can be expected to be poor in hyperbaric environments. Subjects performed multiple-breath wash-in of a mixture (4% each of SF6, Ar, Ne, and He; 21% O2, 63% N2) at 1.5, 5.5, and 9.5 ATA. At the higher pressures there were marked differences of concentrations between the indicator gases, measured by mass spectrometer at the mouth during a single expiration. Compared to heavier gases, light gases fell from dead space concentration to the "alveolar" level sooner, had a flatter plateau, and had a lower average expired concentration, indicating that more of the light gases were retained in the Functional Residual Capacity (FRC) after the breath. However, wash-in rates for the indicators were about the same; a rapid initial rate for He diminished so that it was about the same as the SF6 rate, because in later breaths a back pressure developed for He. The findings illustrate the basic principle that the amount of gas that diffuses from one location to another in a container depends not only on diffusivity, but also in an interdependent manner on concentration gradient, time for diffusion, and configuration of the container.     

Effects of Iron Supplementation on Testicular Function and Spermatogenesis of Iron-Deficient Rats

Iron deficiency is the most common micronutrient deficiency in the world. Previous studies have shown that iron deficiency increases oxidative stress and decreases antioxidant enzymes, and studies of male infertility indicated that oxidative stress may affect male reproductive functions. The aim of this study was to investigate the effects of iron supplementation on spermatogenesis and testicular functions in iron-deficient rats. Three-week-old male Sprague Dawley (SD) rats were randomly divided into two groups: an iron-adequate control (AI group, 35 ppm FeSO₄) and an iron-deficient group (ID group, <5 ppm FeSO₄). After three weeks, the iron-deficient group was divided into an original iron-deficient group and five iron-supplemented groups, the latter fed diets containing different doses of FeSO₄ (6, 12, 18, 24, and 35 ppm). After five weeks, blood and testis tissue were analyzed. We presented as median (interquartile range, IQR) for continuous measurements and compared their differences using the Kruskal–Wallis test followed by the Mann–Whitney U test among groups. The results showed that as compared with the AI group, the ID group had significantly lower serum testosterone and poorer spermatogenesis (The medians (QR) were 187.4 (185.6–190.8) of AI group vs. 87.5 (85.7–90.4) of ID group in serum testosterone, p < 0.05; 9.3 (8.8–10.6) of AI group vs. 4.9 (3.4–5.4) of ID group in mean testicular biopsy score (MTBS], p < 0.05); iron supplementation reversed the impairment of testis tissue. In the testosterone biosynthesis pathway, iron supplementation improved the lowered protein expressions of hydroxysteroid dehydrogenases caused by iron deficiency. Additionally, decreased activities of glutathione peroxidase and catalase, and increased cleaved-caspase 8 and caspase 3 expression, were found in the iron-deficient rats. The iron-supplemented rats that received > 12 ppm FeSO₄ exhibited improvements in antioxidant levels. In conclusion, iron supplementation can abrogate testis dysfunction due to iron deficiency through regulation of the testicular antioxidant capacity.     

Finite Element Analysis of Steel Plates with Rectangular Openings Subjected to Axial Stress

Steel plates with openings are among the important ship structural components used in the ship’s hull to withstand the hydrostatic forces of the ocean, which cause sagging and hogging moments at the ship’s bottom. The existence of openings on plates can cause structural rupture, stress concentration and a decrease in ultimate strength. This research is aimed at investigating the influence of selected parameters on the ultimate capacity of steel plates with rectangular holes subjected to axial stress, using ANSYS finite element analysis (FEA) under its non-linear static structural programme. The main parameters investigated in this paper are the plate thickness, opening aspect ratio, number of openings, position of openings, and the boundary condition of the plate. The influence of these parameters on the stress of plates and their deformation was evaluated. The comparison of the numerical simulation with the well-established analytical method using the Navier solution and Roark’s Formulas showed a good agreement.