Evaluation of kidney repair capacity using Tc-DMSA in ischemia/reperfusion injury models

Quantitative ^99mTc-DMSA renal uptake was studied in different renal ischemia/reperfusion (I/R) mice models for the assessment of renal repair capacity. Mice models of nephrectomy, uni- and bi-lateral I/R together with sham-operated mice were established. At 1 h, 1 d, 4 d, 1, 2 and 3 wk after I/R, ^99mTc-DMSA (27.7 ± 1.3 MBq) was injected via tail vein and after 3 h post-injection, the mice were scanned for 30 min with pinhole equipped gamma camera. Higher uptake of ^99mTc-DMSA was measured in normal kidneys of uni-lateral I/R model and nephrectomized kidney I/R model at 3 wk post-surgery. Comparing the restoration capacities of the affected kidneys of nephrectomy, uni- and bi-lateral I/R models, higher repair capacity was observed in the nephrectomized model followed by bi-lateral then uni-lateral models. The normal kidney may retard the restoration of damaged kidney in uni-lateral I/R model. Moreover, 3 wk after Uni-I/R, the size of injured kidney was significantly smaller than non-ischemic contralateral and sham operated kidneys, while nephrectomy I/R kidneys were significantly enlarged compared to all others at 3 wk post-surgery. Very strong correlation between ^99mTc-DMSA uptake and weight of dissected kidneys in I/R models was observed. Consistent with ^99mTc-DMSA uptake results, all histological results indicate that kidney recovery after injury is correlated with the amount of intact tubules and kidney sizes. In summary, our study showed good potentials of ^99mTc-DMSA scan as a promising non-invasive method for evaluation of kidney restoration after I/R injuries. Interestingly, mice with Bi-I/R injury showed faster repair capacity than those with uni-I/R.     

Hepato-renal transport of phenolsulfonphthalein in analbuminemic rats: albumin is essential for hepatic compensatory elimination of a nephrophilic ligand in animals with renal dysfunction

To investigate a possible function of plasma albumin in partitioning organic anions into bile and urine, phenolsulfonphthalein (PSP) was administered intravenously and its in vivo fate was studied in normal and analbuminemic mutant rats (NAR). No significant change in the rate of PSP disappearance was observed in bilaterally nephrectomized normal rats. However, biliary excretion of the injected dye increased remarkably in nephrectomized normal rats. Intravenously injected PSP disappeared very rapidly from the circulation of NAR. Thus, the plasma clearance and distribution volume of PSP were significantly larger in NAR than in normal rats. Bilateral nephrectomy also failed to decrease the plasma clearance and distribution volume of the dye in NAR. In striking contrast to the experiments in normal rats, bilateral nephrectomy did not increase the biliary secretion of PSP in NAR. When PSP bound to equimolar albumin was injected into bilaterally nephrectomized NAR, the biliary excretion of PSP increased significantly with concomitant decrease in both plasma clearance and distribution volume of the dye. These results indicate that, in cases of renal transport dysfunction, albumin plays a critical role in hepatic compensatory excretion of PSP, a nephrophilic organic anion, whose molecular weight (MW 354) is close to the threshold value for partitioning a ligand to the eliminatory routes in liver and kidney of a rodent.     

Dichotomal role of TNF in experimental pulmonary edema reabsorption

Distinct from its receptor binding sites, TNF carries a lectin-like domain, situated at the tip of the molecule, which specifically binds oligosaccharides, such as N,N'-diacetylchitobiose. In view of the apparently conflicting data concerning TNF actions in pulmonary edema, we investigated the contribution of, on the one hand, the receptor binding sites and, in contrast, the lectin-like domain of the cytokine on pulmonary fluid reabsorption in in situ and in vivo flooded rat lungs. Receptor binding sites were blocked with the human soluble TNFR type 1 construct (sTNFR1), whereas the lectin-like domain was blunted with the oligosaccharide N,N'-diacetylchitobiose. We observed that in situ, TNF failed to stimulate alveolar liquid clearance, but did so together with the sTNFR1, and this activity was neutralized by N,N'-diacetylchitobiose. In vivo TNF inhibited liquid clearance, but activated it when complexed with the sTNFR1. A TNF-derived peptide mimic of the lectin-like domain activated fluid reabsorption in flooded lungs, and this activity was blunted by co-treatment with TNF. Our results thus indicate that in these models the receptor binding sites of TNF inhibit, whereas its lectin-like domain activates, edema reabsorption.     

Chymase,tonin and elastase in rat tissue under oxidative stress caused by administering cobalt chloride

Character of chymase, tonin and elastase activities changes in rats heart, lungs, liver, kidney under the oxidative stress, induced by cobalt chloride, was investigated. The elastase activity increase in the researched organs and all proteinase indicated in liver were revealed. The specific effect of tonin involvement in injuring effect of cobalt chloride in rat heart is shown, this effect is revealed by local absence of chymase level change, that is determined by its species unsimilarity compare with human. The conclusion about more essential significance of elastase and chymase in injuring effect in lungs and kidneys tissues is made.     

Lymphocyte migration in internally irradiated animals. Effect of internal gamma radiation on the migration properties of spleen lymphocytes labeled with 51Cr

In experiments on CBA mice it was shown that migration of 51Cr-labeled spleen lymphocytes, injected intravenously, to lymph nodes of intact recipients was suppressed 6-24 months after the administration of a radiopharmaceutic preparation of selenium-75-selenomethionine in a quantity forming the doses of 1 Gy and 1.5 Gy absorbed within the whole body and lymphoid organs, respectively. Migration of labeled lymphocytes to the liver, kidneys and lungs, as well as their retention in the circulating blood, were increased. As the result of the migration disorders the specific affinity of lymphocytes for peripheral lymphoid tissue decreased.     

Effect of unilateral nephrectomy in mice on the level of the humoral immune response to T-independent antigen

The influence of unilateral nephrectomy on the degree of humoral immune response to T-independent (polyvinylpyrrolidone, PVP) and T-dependent (sheep red blood cells, SRBC) antigens was studied. The increase in the number in antibody-forming cells (AFC) and nonspecific immunoglobulin-forming cells (nIFC) was investigated by means of the adaptive transfer model. The lethally irradiated recipients were injected with the antigen and also the spleen cells of operated and intact donors. PVP did not induce significant alterations of antibody genesis in mice receiving spleen cells of unilaterally nephrectomized animals comparing with recipients of intact spleen cells. At the same time, the kidney operation induced the increase in the number of AFC and nIFC when the SRBC were used. Hence the activation of humoral immune response induced by kidney operation was related not to the direct activation of B-lymphocytes but to T-cells. The possible causes of this activation were analyzed. Spleen cells of operated animals enhance both specific and antigen-dependent nonspecific immune response.     

Biochemical and Molecular Responses to Loss of Renal Mass: Atpase and Cyclic Nucleotides: Changes in Renal Cyclic Nucleotides as a Trigger to the Onset of Compensatory Renal Hypertrophy

In adult male Wistar rats contralateral nephrectomy was followed, within 10 minutes, by a nearly twofold rise of the content of cGMP in renal tissue. 20 and 40 minutes after contralateral nephrectomy cGMP fell to one half its control level to rise again to its normal level within 90 minutes. The initial rise of the concentration of cGMP was accompanied by a simultaneous fall of the concentration of cAMP by about 30 percent: the cAMP concentration remained 10-20 percent below control level for approximately two hours and rose again to its initial level after three hours. Cross-circulation of a nephrectomized rat with an intact animal led to a sharp increase of cGMP in the kidneys of the latter with a peak at 10 minutes after initiating cross-circulation and also to a fall of the cAMP concentration. When the same nephrectomized donor rat was subsequently cross-circulated with one, or even two, intact receiver animals, similar short-lasting changes of cyclic nucleotide concentrations were recorded in the kidneys of all the receivers. When a normal kidney was transplanted to the neck of a rat, subsequent removal of one of its own kidneys did not result in any change in cyclic nucleotide content in either the remaining or the transplanted kidney. The data are interpreted to indicate that renal tissue produces a factor inhibiting renal growth which counteracts a circulating humoral kidney growth stimulating factor of unknown origin. An initial rise of cGMP and a fall of cAMP may trigger the subsequent stimulation of protein synthesis responsible for hypertrophy.     

TNFR-Fc fusion protein expressed by in vivo electroporation improves survival rates and myocardial injury in coxsackievirus induced murine myocarditis

Tumor necrosis factor-alpha (TNF-alpha) is one of the major cytokines that modulate the immune response in viral myocarditis, but its role has not yet been thoroughly evaluated. We antagonized TNF-alpha using the expressed soluble p75 TNF receptor linked to the Fc portion of the human IgG1 gene (sTNFR:Fc) by in vivo electroporation, and evaluated its effects on experimental coxsackieviral B3 (CVB3) myocarditis. A plasmid DNA encoding sTNFR:Fc (15microg/mouse) was injected into the gastrocnemius muscles of Balb/C male mice followed by electroporation (day -1). Control mice were injected with an empty vector. One day after electroporation, mice were infected with CVB3 (day 0). Serum levels of sTNFR:Fc increased from day 2 and peaked at day 5 following electroporation. The heart virus titers of sTNFR:Fc mice were higher than those of controls at day 3. However, subsequent to day 12, the survival rates of the sTNFR:Fc mice were significantly higher than those of the controls (36% versus 0% at day 27, P<0.01). Histopathological examination indicated that inflammation and myocardial fibrosis were significantly decreased in sTNFR:Fc mice at day 12. The expressed sTNFR:Fc could modulate the inflammatory process during the post-viremic phase of viral myocarditis.     

Effect of time post mortem on the concentration of endotoxin in rat organs: implications for sudden infant death syndrome (SIDS)

The aim of the study was to test the following hypotheses: (i) that endotoxin injected 40 min prior to death can be detected in rat organs post mortem and (ii) that endotoxin levels do not change with increasing time post mortem. Rats were injected with or without endotoxin in buffered saline, 40 min prior to being killed. Endotoxin levels in rat organs were assessed using a Limulus amoebocyte assay. The effect of storage time post mortem was assessed by following various storage regimes at 25 degrees C and 8 degrees C. Significant differences (P = < 0.001) in endotoxin levels of all samples tested were found between rats injected with and without endotoxin. A significant increase in detectable endotoxin was observed between 0 h and 6 h post mortem in rats injected with or without endotoxin. No difference in detectable endotoxin levels in the kidney, liver and spleen was observed from 30 h to 102 h post mortem in rats injected with or without endotoxin. In rats injected with endotoxin, detectable endotoxin levels in the heart were raised between 0 h and 6 h, 6 h and 54 h, and 30 h and 78 h. Endotoxin injected into rats 40 min prior to death can be detected post mortem. For rats injected with saline or endotoxin prior to death levels in the kidney, liver and spleen were not affected by storage at 8 degrees C for 30-102 h, after initial storage at room temperature for 6 h. Levels of endotoxin detected in the hearts of rats injected with saline were not affected by storage up to 102 h. In rats injected with endotoxin prior to death, detectable levels in the heart were significantly affected by increasing time in storage.     

Long-Term Responses to Loss of Renal Mass: Tubular Changes: Potassium Adaptation After Reduction of Nephron Population

Two weeks after 75 percent nephrectomy in rats fed a normal diet glomerular filtration rate was found to be reduced by 2/3 and there was no hyperkalemia. Normal K balance was maintained by a threefold increase of fractional urinary potassium excretion. When infused with 0.5 M KCl solution, both normal and 75 percent nephrectomized rats increased their fractional excretion, while normal rats kept on a very high K-diet did not further increase their fractional potassium excretion. Adaptation of fractional excretion to infused KCl was blunted in 75 percent nephrectomized rats given a low K diet.Addition of 0.1 M KCl to the drinking water resulted in a three- to fourfold increase of potassium intake in normal rats: within 7 days, the Na-K-ATPase in the outer medulla of the kidney rose by 30 percent but no change occurred in the cortex. Further increases in dietary K load induced an increase of Na-K-ATPase activity, both in outer medulla and cortex, but not in other tissues. After 75 percent nephrectomy, specific Na-K-ATPase activity increased by 20-25 percent in the outer medulla and in the cortex.Dietary K loading, in normal rats, also resulted in a large increase of net potassium secretion into the perfused colon and of specific Na-K-ATPase activity of the colonic mucosa. These effects of potassium loading were not abolished by adrenalectomy and were accompanied by an increase of transmural PD. It was concluded that chronic potassium loading may enhance secretion of potassium into lower nephron tubular fluid and into colonic contents by primarily stimulating the synthesis of Na-K-ATPase and the resulting increase of the number of pumping sites. 75 percent nephrectomy may induce similar changes in the remaining nephrons.     

Effect of bacterial lipopolysaccharide on the content of lipid peroxidation products in lungs and other organs of mice

The influence of lipopolysaccharide fromEscherichia coli (LPS, 17 mg/kg body weight) on the lipid peroxidation process in organs of mice was studied. The content of conjugated dienes (CD), lipid peroxides (LP), malondialdehyde (MDA) (all three lipid peroxidation by-products), peroxidase (PO) activity and wet-to-dry weight ratio in lungs, heart, spleen, kidneys and liver were determined 1.5 h after intravenous injection of LPS. Animals observed at this time-point had reduced activity and decreased body temperature by about 2°C, however, all analysed organs did not reveal any changes of wet-to-dry weight ratio comparing to organs from mice injected with sterile, pyrogen free 0,9% NaCl. Only extracts from heart and lungs showed significant increase in the tissue level of at least two lipid peroxidation products. The heart content of CD, MDA, and LP was about 1.5-, 1.3-, and 2.4-fold higher than in control group. In lungs CD and MDA increased 3.3- and 1.3-times but in spleen only content of LP was elevated. In these organs the suppression of PO activity was also observed. Liver and kidneys did not reveal any convincing enhancement of lipid peroxidation process and alterations of PO activity. Since free radical reactions are involved in lipid peroxidation process and inactivation of PO these results suggest that heart, lungs and spleen are the organs mostly exposed to oxidative stress during the first 1.5 h after single injection of LPS in mice.Abbreviations CD conjugated dienes - LP lipid peroxides - LPS lipopolysaccharide - MDA malondialdehyde - PMNL polymorphonuclear leukocytes - PO peroxidase - TBA thiobarbituric acid     

Unilateral nephrectomy leads to up-regulation of syndecan-2- and TGF-beta-mediated glomerulosclerosis in syndecan-4 deficient male mice.

Syndecan-4 is an ubiquitous, plasma membrane-spanning heparan sulfate proteoglycan involved in proliferation, differentiation, adhesion and migration of cells in vitro. Syndecan-4 knockout (KO) mice show no obvious defects but respond abnormally to experimental stress conditions. In the adult, syndecan-4 is the most abundant syndecan of renal tissue. We therefore investigated the consequences of syndecan-4 deficiency during progression of kidney disease using unilaterally nephrectomized mice, a model of glomerular hyperfiltration and renal hypertrophy. 60 days after unilateral nephrectomy (UNX), mesangial expansion, enhanced matrix production (collagens I and IV, fibronectin) and focal segmental glomerulosclerosis, resembling early stages of diabetic nephropathy, was apparent in male but not female syndecan-4 KO mice. No defect was detected in wild type UNX males. Syndecan-2 mRNA and protein were not detectable in renal glomeruli of wild type mice, but were induced specifically in the glomeruli of the syndecan-4 deficient kidneys after unilateral nephrectomy. Due to the structural similarities of syndecans-2 and -4 we hypothesize that de novo-production of syndecan-2 in kidneys after unilateral nephrectomy reflects a compensatory response. However, this response is counterproductive since syndecan-2 supports the pro-sclerotic activity of TGF-beta1 which is increased in parallel with syndecan-2 synthesis. By contrast, signaling through syndecan-4 negatively controls the production of pro-sclerotic TGF-beta1.     

急性髓性白血病HB-1细胞系细胞具有侵入CBA/N小鼠脑部的能力

急性髓性白血病HB-1细胞系是由辐射处理的CBA／N小鼠脾脏细胞克隆并建立起来的。静脉注射HB-1细胞到正常CBA／N小鼠体内会诱发急性髓性白血病综合症,并使小鼠2周左右死亡。一般情况下,白血病细胞被接种到小鼠后会侵入造血器官、肺、肾和肝脏。我们在研究中发现了一令人感兴趣的现象,不仅在小鼠的肺、肾和肝脏中,而且在大脑和小脑中也观察到了HB-1细胞。白血病细胞能穿过血脑屏障在正常情况下是难以理解的,因为血脑屏障可阻止血细胞进入脑内,并且严格有选择地让小分子通过。因此,HB-1细胞将是阐明形成血脑屏障的内皮细胞上的附贴分子和选择性地让特殊细胞侵入脑的一个很好的模型。     

Pathogenicity of the Trudeau Strain of Mycobacterium sp. 607 for Mice

A study was made of the pathogenic properties of the Trudeau Culture Collection strain (T-67) of Mycobacterium sp. 607 for mice. The organism was highly pathogenic for CF1 mice upon intravenous injection. The animals succumbed soon after intravenous injection of a 14 x 10(6) viable cellular units. The T-67 strain proliferated in the kidneys of the animals but was unable to reproduce in the lungs, liver, and spleen. Destruction of the organisms in the latter organs commenced 24 hr after injection. Tissue bacterial counts showed that the mycobacteria were similarly destroyed in the kidneys after an interval of from 7 to 9 days after injection of the organisms. Histopathological examination of the tissues indicated that the lethal effects of the organism were due primarily to kidney damage. The liver, lungs, and spleen were similarly involved but to a lesser degree. The unique characteristics of the T-67 strain of Mycobacterium sp. 607 are discussed.     

Effectiveness of Green Tea Tannin on Rats with Chronic Renal Failure

The effects of green tea tannin on nephrectomized rats were examined. There were increases in blood urea nitrogen, serum creatinine, and urinary protein, and a decrease in creatinine clearance in the nephrectomized control rats, whereas better results for these parameters were obtained in rats given green tea tannin after nephrectomy, demonstrating a suppressed progression of the renal failure. When the renal parenchyma was partially resected, the remnant kidney showed a decrease in the activity of radical scavenger enzymes. Green tea tannin, however, was found to lighten the kidney under such oxidative stress. Mesangial proliferation and glomerular sclerotic lesions, which were conspicuous in the rats that were not given green tea tannin after nephrectomy, were also relieved.     

Tumor necrosis factor (TNF) protects resistant C57BL/6 mice against herpes simplex virus-induced encephalitis independently of signaling via TNF receptor 1 or 2

Tumor necrosis factor (TNF) is a multifunctional cytokine that has a role in induction and regulation of host innate and adaptive immune responses. The importance of TNF antiviral mechanisms is reflected by the diverse strategies adopted by different viruses, particularly members of the herpesvirus family, to block TNF responses. TNF binds and signals through two receptors, Tnfrsf1a (TNF receptor 1 [TNFR1], or p55) and Tnfrsf1b (TNFR2, or p75). We report here that herpes simplex virus 1 (HSV-1) infection of TNF-/- mice on the resistant C57BL/6 genetic background results in significantly increased susceptibility (P < 0.0001, log rank test) to fatal HSV encephalitis (HSE) and prolonged persistence of elevated levels of virus in neural tissues. In contrast, although virus titers in neural tissues of p55-/- N13 mice were elevated to levels comparable to what was found for the TNF-/- mice, the p55-/- N13 mice were as resistant as control C57BL/6 mice (P > 0.05). The incidence of fatal HSE was significantly increased by in vivo neutralization of TNF using soluble TNFR1 (sTNFR1) or depletion of macrophages in C57BL/6 mice (P = 0.0038 and P = 0.0071, respectively). Strikingly, in vivo neutralization of TNF in HSV-1-infected p55-/- p75-/- mice by use of three independent approaches (treatment with soluble p55 receptor, anti-TNF monoclonal antibody, or in vivo small interfering RNA against TNF) resulted in significantly increased mortality rates (P = 0.005), comparable in magnitude to those for C57BL/6 mice treated with sTNFR1 (P = 0.0018). Overall, these results indicate that while TNF is required for resistance to fatal HSE, both p55 and p75 receptors are dispensable. Precisely how TNF mediates protection against HSV-1 mortality in p55-/- p75-/- mice remains to be determined.     

Lung fluid balance during acute renal failure in sheep

To determine whether uremia changes lung vascular permeability, we measured the flow of lymph and proteins from the lungs of acutely uremic sheep. Acute renal failure was induced by either bilateral nephrectomy or by reinfusing urine. Both models of renal failure increased the plasma creatinine from 0.8 +/- 0.3 to 11 +/- 1 mg/dl in 3 days but caused no significant change in the flow of lymph from the lungs. To determine whether uremia increased the protein clearance response to elevated pulmonary microvascular pressures, we inflated a balloon in the left atrium for 2 h before and 3 days after inducing acute renal failure. In seven sheep, before removing the kidneys, the 20 cmH2O elevation of left atrial pressure increased the protein clearance 3.9 +/- 3.0 ml/h (from 9.5 +/- 4.9 to 13.4 +/- 5.4 ml/h). Three days after the bilateral nephrectomy the same increase in left atrial pressure increased the protein clearance 6.4 +/- 3.6 ml/h (from 6.1 +/- 2.1 to 12.5 +/- 5.2 ml/h), which was a significantly larger increase than that measured before the nephrectomy (P less than 0.05). Sham nephrectomy in seven sheep caused the protein clearance response to the elevated left atrial pressure to fall from 4.7 +/- 1.9 ml/h before the sham nephrectomy to 2.6 +/- 1.4 ml/h 3 days later (P less than 0.05). Uremia due to reinfusion of urine in five sheep did not affect the protein clearance response to elevations in left atrial pressure. Neither model of acute uremia increased the postmortem extravascular lung water volume.(ABSTRACT TRUNCATED AT 250 WORDS)     

An Experimental Study of the Pharmacokinetics of the Antitumor Drug Aurumacryl

The distribution of the antitumor drug aurumacryl (intraperitoneally injected at a dose of 100 mg/kg) in the bodies of animals with Lewis lung carcinoma was studied. The determination of aurumacryl in the tumors and organs (blood, liver, kidneys, lungs, spleen, and brain) of mice was carried out for 48 h by measuring the gold content in the test tissues using inductively coupled plasma mass spectrometry. We found the preferential accumulation of the drug in the kidneys with an extremely low gold content in the brain and a relatively uniform distribution of aurumacryl between the tumor, liver, lung, and spleen tissues.

     

Evidence that free radical generation occurs during scorpion envenomation

Although it is well established that symptomatology, morbidity and death following scorpion envenomation are due to increases in neurotransmitter release secondary to toxins binding to voltage-sensitive sodium channels, the mechanism by which venom action is involved in damaging heart, liver, lungs and kidneys remains unclear. We hypothesized that scorpion toxins could induce the generation of high levels of free radicals responsible for membrane damage in organs targeted by venom action. We have investigated lipid peroxidation in different organs, through the evaluation of thiobarbituric acid reactive substances (TBARS), after experimental envenomation of rats by toxic fractions of Androctonus australis Hector venom. We have shown that scorpion toxins cause considerable lipid peroxidation in most vital organs. We also evaluated the protective effects of antioxidants in mice injected with lethal doses of toxins. Among the drugs tested, N-acetylcysteine (NAC) was effective in protecting the mice when injected prior to toxin application. However, the free radical scavenging properties of NAC seem less implicated in these protective effects than its ability to increase the fluidity of bronchial secretions. We therefore conclude that free radical generation only plays a minor role in the toxicity of scorpion venom.     

High Levels of sTNFR p75 and TNFα in Dengue-Infected Patients

Soluble forms of the two molecular species of the cell surface TNF receptors (sTNFR p55 and sTNFR p75) can reduce the activity of TNFα but they may also enhance its function by stabilizing the active TNFα oligomer. Considering the pathophysiological importance of sTNFR p75 for the regulation of the bioavailability of TNFα in the body, we determined the serum levels of sTNFR p75 and TNFα in 45 children and 28 adults with laboratory-confirmed dengue infection by using immunoassays. The serum samples were obtained from day 1 to day 15 after the onset of the disease during the 1989–1990 outbreak of dengue-3 in Tahiti, French Polynesia. The patients were clinically classified as having dengue hemorrhagic fever (DHF) and graded according to the criteria of the World Health Organization (WHO) into four grades from less severe (grade I) to severe (grade IV). The sera of both children and adult patients of all severity grades contained higher levels of sTNFR p75 than the sera of control subjects. Although high levels of TNFα were also detected in children and adults among grade I, II, III and IV patients, we found no correlation between sTNFR p75 and TNFα. We observed in adults a moderate elevation of sTNFR p75 and TNFα in sera compared with that observed in children. The raised levels of immunoreactive sTNFR p75 and TNFα in all clinical groups of dengue-infected patients strongly indicate activation of the TNFα system during dengue infection. The balance between sTNFR p75 and TNFα may be altered in dengue infection. Further investigations are needed to understand the role of sTNFR p75 and TNFα in the pathogenesis of DHF and to improve the management of dengue infection.