Differential susceptibility epidemic models

We formulate compartmental differential susceptibility (DS) susceptible-infective-removed (SIR) models by dividing the susceptible population into multiple subgroups according to the susceptibility of individuals in each group. We analyze the impact of disease-induced mortality in the situations where the number of contacts per individual is either constant or proportional to the total population. We derive an explicit formula for the reproductive number of infection for each model by investigating the local stability of the infection-free equilibrium. We further prove that the infection-free equilibrium of each model is globally asymptotically stable by qualitative analysis of the dynamics of the model system and by utilizing an appropriately chosen Liapunov function. We show that if the reproductive number is greater than one, then there exists a unique endemic equilibrium for all of the DS models studied in this paper. We prove that the endemic equilibrium is locally asymptotically stable for the models with no disease-induced mortality and the models with contact numbers proportional to the total population. We also provide sufficient conditions for the stability of the endemic equilibrium for other situations. We briefly discuss applications of the DS models to optimal vaccine strategies and the connections between the DS models and predator-prey models with multiple prey populations or host-parasitic interaction models with multiple hosts are also given.This research was partially supported by the Department of Energy under contracts W-7405-ENG-36 and the Applied Mathematical Sciences Program KC-07-01-01.     

Intratumoral expression of IL-17 and its prognostic role in gastric adenocarcinoma patients

In this study, we characterized the intratumoral expression of IL-17 and CD8(+) TILs in gastric adenocarcinoma patients after resection and determined the correlation between the survival probability of gastric adenocarcinoma patients and the expression of IL-17 in tumor. Expression of IL-17 and CD8 was assessed by immunohistochemistry, and the prognostic effects of intratumoral IL-17 expression and CD8(+) TILs were evaluated by Cox regression and Kaplan-Meier analysis. Immunohistochemical detection revealed the presence of IL-17 and CD8(+) cells in gastric adenocarcinoma tissue samples (90.6%, 174 out of 192 patients and 96.9%, 186 out of 192 patients, respectively). We have also found that intratumoral IL-17 expression was significantly correlated with age (p=0.004) and that the number of CD8(+)TILs was significantly correlated with UICC staging (p=0.012) and the depth of tumor invasion (p=0.022). The five-year overall survival probability among patients intratumorally expressing higher levels of IL-17 was significantly better than those expressing lower levels of IL-17 (p=0.036). Multivariate Cox proportional hazard analyses revealed that intratumoral IL-17 expression (HR: 0.521; 95% CI: 0.329-0.823; p=0.005) was an independent factor affecting the five-year overall survival probability. We conclude that low levels of intratumoral IL-17 expression may indicate poor prognosis in gastric adenocarcinoma patients.     

An NO Donor Approach to Neuroprotective and Procognitive Estrogen Therapy Overcomes Loss of NO Synthase Function and Potentially Thrombotic Risk

Selective estrogen receptor modulators (SERMs) are effective therapeutics that preserve favorable actions of estrogens on bone and act as antiestrogens in breast tissue, decreasing the risk of vertebral fractures and breast cancer, but their potential in neuroprotective and procognitive therapy is limited by: 1) an increased lifetime risk of thrombotic events; and 2) an attenuated response to estrogens with age, sometimes linked to endothelial nitric oxide synthase (eNOS) dysfunction. Herein, three 3^rd generation SERMs with similar high affinity for estrogen receptors (ERα, ERβ) were studied: desmethylarzoxifene (DMA), FDMA, and a novel NO-donating SERM (NO-DMA). Neuroprotection was studied in primary rat neurons exposed to oxygen glucose deprivation; reversal of cholinergic cognitive deficit was studied in mice in a behavioral model of memory; long term potentiation (LTP), underlying cognition, was measured in hippocampal slices from older 3×Tg Alzheimer''s transgenic mice; vasodilation was measured in rat aortic strips; and anticoagulant activity was compared. Pharmacologic blockade of GPR30 and NOS; denudation of endothelium; measurement of NO; and genetic knockout of eNOS were used to probe mechanism. Comparison of the three chemical probes indicates key roles for GPR30 and eNOS in mediating therapeutic activity. Procognitive, vasodilator and anticoagulant activities of DMA were found to be eNOS dependent, while neuroprotection and restoration of LTP were both shown to be dependent upon GPR30, a G-protein coupled receptor mediating estrogenic function. Finally, the observation that an NO-SERM shows enhanced vasodilation and anticoagulant activity, while retaining the positive attributes of SERMs even in the presence of NOS dysfunction, indicates a potential therapeutic approach without the increased risk of thrombotic events.     

The Effects of Root-knot Nematode Infection and Mi-mediated Nematode Resistance in Tomato on Plant Fitness

The Mi-1.2 resistance gene in tomato (Solanum lycopersicum) confers resistance against several species of root-knot nematodes (Meloidogyne spp.). This study examined the impact of M. javanica on the reproductive fitness of near-isogenic tomato cultivars with and without Mi-1.2 under field and greenhouse conditions. Surprisingly, neither nematode inoculation or host plant resistance impacted the yield of mature fruits in field microplots (inoculum=8,000 eggs/plant), or fruit or seed production in a follow-up greenhouse bioassay conducted with a higher inoculum level (20,000 eggs/plant). However, under heavy nematode pressure (200,000 eggs/plant), greenhouse-grown plants carrying Mi-1.2 had more than ten-fold greater fruit production than susceptible plants and nearly forty-fold greater estimated lifetime seed production, confirming prior reports of the benefits of Mi-1.2. In all cases Mi-mediated resistance significantly reduced nematode reproduction. These results indicated that tomato can utilize tolerance mechanisms to compensate for moderate levels of nematode infection, but that the Mi-1.2 resistance gene confers a dramatic fitness benefit under heavy nematode pressure. No significant cost of resistance was detected in the absence of nematode infection.     

沙冬青愈伤组织对培养基的特殊要求和球形胚状分化结构的诱导

通过对沙冬青未成熟子叶进行离体培养,获得了愈伤组织。基本培养基采用Ｂ５,再配合ＭＳ培养基的铁盐成分,对沙冬青未成熟子叶愈伤组织的诱导和生长效果最佳。愈伤组织的诱导和生长对培养基的附加成分要求十分严格,２,４－Ｄ浓度为０．５ｍｇ／Ｌ,６－ＢＡ浓度为０．５ｍｇ／Ｌ,蔗粮不宜超过２％。愈伤组织最初为乳白色透明松散状态,生长比较缓慢,极易褐化死亡。如果培养基中的蔗糖浓度低于２％,两周后未成熟子叶愈伤组织逐     

Microsatellite mapping of a Triticum urartu Tum. derived powdery mildew resistance gene transferred to common wheat (Triticum aestivum L.)

A powdery mildew resistance gene from Triticum urartu Tum. accession UR206 was successfully transferred into hexaploid wheat (Triticum aestivum L.) through crossing and backcrossing. The F₁ plants, which had 28 chromosomes and an average of 5.32 bivalents and 17.36 univalents in meiotic pollen mother cells (PMC), were obtained through embryos rescued owing to shriveling of endosperm in hybrid seed of cross Chinese Spring (CS) × UR206. Hybrid seeds were produced through backcrossing F₁ with common wheat parents. The derivative lines had normal chromosome numbers and powdery mildew resistance similar to the donor UR206, indicating that the powdery mildew resistance gene originating from T. urartu accession UR206 was successfully transferred and expressed in a hexaploid wheat background. Genetic analysis indicated that a single dominant gene controlled the powdery mildew resistance at the seedling stage. To map and tag the powdery mildew resistance gene, 143 F₂ individuals derived from a cross UR206 × UR203 were used to construct a linkage map. The resistant gene was mapped on the chromosome 7AL based on the mapped microsatellite makers. The map spanned 52.1 cM and the order of these microsatellite loci agreed well with the established microsatellite map of chromosome arm 7AL. The resistance gene was flanked by the microsatellite loci Xwmc273 and Xpsp3003, with the genetic distances of 2.2 cM and 3.8 cM, respectively. On the basis of the origin and chromosomal location of the gene, it was temporarily designated PmU.