Empirical evidence for key hosts in persistence of a tick-borne disease

An important epidemiological consequence of aggregated host-parasite associations occurs when parasites are vectors of pathogens. Those hosts that attract many vectors will tend to be the focus of transmission. But to what extent, and can we identify characteristics of these key hosts? We investigated these questions with respect to the host-tick relationship of the yellow-necked mouse, Apodemus flavicollis, a critical host in the maintenance of the zoonotic disease, tick-borne encephalitis. Transmission of the virus occurs when ticks feed in a 'co-feeding' aggregation. Thus, the number and frequency of co-feeding groups provides an estimate of the potential rate of virus transmission. We recorded the spatio-temporal variations in co-feeding on a population of rodents in conjunction with recording individual host characteristics. Using Lorenz curves, we revealed conformation of tick-borne encephalitis transmission potential to the 20/80 Rule, where the 20% of hosts most infested with ticks were accountable for 80% of transmission potential. Hosts in the transmission cohort were identified as the sexually mature males of high body mass. Therefore control efforts targeted at this group would substantially reduce transmission potential compared to non-targeted control of the population, which resulted in a linear reduction in transmission potential. Focusing on the 'wrong' functional group would have little impact upon transmission potential until a considerable proportion of the population had been subject to control. However, individuals can change their functional status over time making it difficult to predict the contribution of these individuals to future transmission.     

Differential effects of iron deficiency on the expression of CD80 and CD86 co-stimulatory receptors in mitogen-treated and untreated murine spleen cells

The interaction of CD28 and its ligands (CD80, CD86) on antigen presenting cells and that of TCR/CD3-MHC are required for T lymphocyte activation. To determine whether impaired lymphocyte proliferation associated with iron deficiency is due to reduced expression of these ligands, spleen cells obtained from eight to nine C57BL/6 mice/group of iron deficient (ID), iron replete (R), control (C), pair-fed (PF), and high iron (HI) mice were labeled with anti-CD80-fluorescein isothiocyante (FITC) and anti-CD86-FITC. Diets differed only in iron concentration: 5, 50, and 125 mg/kg for the ID, C, and HI, respectively. Mean levels of hemoglobin and liver iron stores of ID and R mice were less than 50% those of C mice (P < 0.005). In non-activated and concanavalin A-treated cultures, significant differences were observed among groups in the percentage of CD80 + cells: ID>R > C = PF = HI (P < 0.05). The same trend was observed for CD86 + cells (P > 0.05). Fluorescence intensity (FI) of either marker did not significantly change by iron status. In vitro iron chelation by deferoxamine (20, 200 microg/ml) for 1, 2, and 24 h increased FI of both markers on unactivated B and T cells (P < 0.05). However, it had no effect on FI of either marker of mitogen-treated cells presumably because the maximum levels are achieved by the mitogen. Lymphocyte proliferative responses to mitogens positively and significantly correlated with CD80 and CD86 FI (r = 0.41-0.59) but negatively correlated with the percentages of CD80 + cells (r = -0.48) (P < 0.05). Data suggest that impaired lymphocyte proliferation associated with iron deficiency is not due to reduced CD80 and CD86 expression.     

Conformational study of N(epsilon)-(carboxymethyl)lysine adducts of recombinant gammaC-crystallin

N -(carboxymethyl)lysine, an advanced glycation end product, is present in the human lens. The effects of CML formation on protein conformation and stability were studied using the recombinant C-crystallin as a model. Conformational change was studied by spectroscopic measurements such as fluorescence and circular dichroism. Conformational stability was determined by unfolding with heat. The results indicated that no conformational change was observed due to CML formation, but conformational stability decreased. These observations can be explained in terms of the relatively stable structure of -crystallin, especially when compared with other crystallins. The lens nucleus is rich in -crystallin and its stable conformation can assist -crystallin sustained insults and remain soluble.     

Base-induced side reactions in Fmoc-solid phase peptide synthesis:Minimization by use of piperazine as Nα-deprotectionreagent

Base-induced aspartimide (cyclic imide) and subsequentbase adduct formation in the Fmoc-solid phasesynthesis of sensitive sequences are serious sidereactions that are difficult to both anticipate andcontrol. The effect of extended treatment ofpiperazine as N-Fmoc deprotection reagenton two sensitive peptide sequences was examined. Forcomparison, other bases were also investigated,including piperidine, 1-hydroxypiperidine,tetrabutylammonium fluoride, and1,8-diazabicyclo[5.4.0]undec-7-ene. The results showedthat all bases induced varying degrees of bothaspartimide and, in some cases, base adduct formation,although piperazine caused the least side reaction.Use of N-(2-hydroxy-4-methoxybenzyl) peptidebackbone amide protection was confirmed to confercomplete protection against side reaction. In theabsence of such protection, for all bases, the use of1-hydroxybenzotriazole as additive had some, but notcomplete, beneficial effect in further reducing sidereaction. Best results were obtained with piperazinecontaining 0.1M 1-hydroxybenzotriazole indicating thatthis reagent merits serious consideration forN-deprotection in the Fmoc-solid phasesynthesis of base-sensitive sequences. A furtheradvantage of this reagent is that it causes littleracemisation of resin-bound C-terminal cysteine, anoccasionally serious base-mediated problem in Fmoc-solidphase assembly.     

Maximum glucoamylase production by a temperature-sensitive mutant of Saccharomyces cerevisiae in batch culture

In order to maximize the glucoamylase production by recombinant Saccharomyces cerevisiae in batch culture, first a temperature-controlled expression system for a foreign gene in S. cerevisiae was constructed. A temperature-sensitive pho80 mutant of S. cerevisiae for the PHO regulatory system, YKU131, was used for this purpose. A DNA fragment bearing the promoter of the PHO84 gene, which encodes an inorganic phosphate (P_i) transporter of S. cerevisiae and is derepressed by P_i starvation, was used as promoter. The glucoamylase gene connected with the PHO84 promoter was ligated into a YEp13 vector, designated pKU122. When the temperature-sensitive pho80 ^ts mutant harboring the plasmid pKU122 is cultivated at a lower temperature, the expression of glucoamylase gene is repressed, but at a higher temperature it is expressed. Next the effect of temperature on the specific growth rate, μ, and specific production rate, ρ, was investigated. Maximum values of ρ and ρ at various temperatures were at 30°C and 34°C, respectively. The optimal cultivation temperature strategy for maximum production of glucoamylase by this recombinant strain in batch culture was then determined by the Maximum principle using the relationships of μ and ρ to the cultivation temperature. Finally, the optimal strategy was experimentally realized by changing the cultivation temperature from Tμ (30°C) to Tρ (34°C) at the switching time, t_s. Received 18 September 1997/ Accepted in revised form 07 January 1998     

足细胞病与相关循环因子的表达

肾小球足细胞的损伤不仅是遗传性肾小球病的发病基础,还在很多后天的肾小球疾病中发挥重要作用。常见的足细胞病以微小病变性肾病(Minimal Change Disease,MCD)和局灶阶段性肾小管硬化(Focal Segmental glomerulosclerosis,FSGS)为主,有实验证明,足细胞损伤同时参与了各种不同类型的肾小球疾病,比如糖尿病肾病,HIV相关肾病,膜性肾病及其他获得性肾小球病等,因此,了解足细胞病损伤的机制尤为重要。临床观察提出局灶节段行肾小球硬化患者体内可能存在一种与大量蛋白尿发生有关的循环因子,相关的动物实验和体外观察同时也证实了循环因子的存在。越来越多的研究支持T细胞功能不全,细胞因子异常释放可能是循环因子的来源之一。如果能对患者循环因子进行检测,借助它来指导治疗方案的选择(免疫抑制剂、血浆置换),可能成为局灶节段行肾小球硬化诊断和治疗中的一个突破。本文以国内外研究文献为基础,对文献资料进行分析、归纳和总结,综述了足细胞病中相关循环因子的表达,探讨足细胞病发生及复发的机理,为足细胞病的定向治疗提供帮助。     

Insights into the role of components of the tumor microenvironment in oral carcinoma call for new therapeutic approaches

The research on oral cancer has focused mainly on the cancer cells, their genetic changes and consequent phenotypic modifications. However, it is increasingly clear that the tumor microenvironment (TME) has been shown to be in a dynamic state of inter-relations with the cancer cells. The TME contains a variety of components including the non-cancerous cells (i.e., immune cells, resident fibroblasts and angiogenic vascular cells) and the ECM milieu [including fibers (mainly collagen and fibronectin) and soluble factors (i.e., enzymes, growth factors, cytokines and chemokines)]. Thus, it is currently assumed that TME is considered a part of the cancerous tissue and the functionality of its key components constitutes the setting on which the hallmarks of the cancer cells can evolve. Therefore, in terms of controlling a malignancy, one should control the growth, invasion and spread of the cancer cells through modifications in the TME components. This mini review focuses on the TME as a diagnostic approach and reports the recent insights into the role of different TME key components [such as carcinoma-associated fibroblasts (CAFs) and inflammation (CAI) cells, angiogenesis, stromal matrix molecules and proteases] in the molecular biology of oral carcinoma. Furthermore, the impact of TME components on clinical outcomes and the concomitant need for development of new therapeutic approaches will be discussed.