抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Chem. Pharm. Bull.(オピニオン)

Chemical Ecology of Endophytic Fungi: Origins of Secondary Metabolites

Throughout history, natural products have played a dominant role in the treatment of human ailments. For example, the legendary discovery of penicillin transformed global existence. Presently, natural products comprise a large portion of current-day pharmaceutical agents, most notably in the area of cancer therapy. Examples include Taxol, vinblastine, and camptothecin. These structurally unique agents function by novel mechanisms of action; isolation from natural sources is the only plausible method that could have led to their discovery. In addition to terrestrial plants as sources for starting materials, the marine environment (e.g., ecteinascidin 743, halichondrin B, and dolastatins), microbes (e.g., bleomycin, doxorubicin, and staurosporin), and slime molds (e.g., epothilone B) have yielded remarkable cancer chemotherapeutic agents. Irrespective of these advances, cancer remains a leading cause of death worldwide. Undoubtedly, the prevention of human cancer is highly preferable to treatment. Cancer chemoprevention, the use of vaccines or pharmaceutical agents to inhibit, retard, or reverse the process of carcinogenesis, is another important approach for easing this formidable public health burden. Similar to cancer chemotherapeutic agents, natural products play an important role in this field. There are many examples, including dietary phytochemicals such as sulforaphane and phenethyl isothiocyanate (cruciferous vegetables) and resveratrol (grapes and grape products). Overall, natural product research is a powerful approach for discovering biologically active compounds with unique structures and mechanisms of action. Given the unfathomable diversity of nature, it is reasonable to suggest that chemical leads can be generated that are capable of interacting with most or possibly all therapeutic targets.

/pdf/natural-products-as-a-vital-source-for-the-discovery-of-4ar7gdxs4n.pdf

Natural Products as a Vital Source for the Discovery of Cancer Chemotherapeutic and Chemopreventive Agents.

Endophytic fungi are ubiquitous organisms found in the plants, residing intercellular or intracellular, at least for a portion of their lives without causing apparent symptoms of infection. Almost all plants are known to harbor endophytes. The choice of the plant to be used for exploring endophytes for bioactives is important. Therefore, medicinal plants which are known to be used since centuries as an alternative source of medicine, are a valuable source for bioprospecting endophytes. Nevertheless, due to many reasons there is a dire need for novel resources for novel drugs which can be an answer to many deadly diseases. It is in this context that the present review was envisaged. The review reveals the importance of endophytic fungi from medicinal plants as a source of bioactive and chemically novel compounds. The bioactive metabolites produced by endophytic fungi originate from different biosynthetic pathways and belong to diverse structural groups such as terpenoids, steroids, quinones, phenols, coumarins etc. Endophytes therefore, represent a chemical reservoir for new compounds such as, anticancer, immunomodulatory, antioxidant, antiparasitic, antiviral, antitubercular, insecticidal etc. for use in the pharmaceutical and agrochemical industries. Although, efforts have been made to accommodate as many examples as possible but the depth of the subject is so vast that it cannot be covered in one single review. This in itself speaks of the fact that endophytic fungi from medicinal plants is indeed a treasure worth searching. In the present review only some selected examples have been covered.

Endophytic fungi from medicinal plants: a treasure hunt for bioactive metabolites

Anticancer compounds derived from fungal endophytes: their importance and future challenges.

A theoretical study of cylindrical dielectric waveguide having plasma in the cladding region is investigated. The eigen-value equations for the proposed waveguide and its power calculation have been evaluated using the usual boundary conditions. By using these equations modal dispersion, normalized group velocity, power confinement factor, and fractional modal power curves are drawn for some lower-order TE and TM modes. The nature and shape of the dispersion curve is usual but the group velocity of TM01 mode is largely affected in the presence of plasma. It may also be noted that for a fixed value of plasma density, the fractional modal power sustained by a particular fiber mode can be tuned at the optimum level by adjusting the operating frequency properly. Also, the maximum power is concentrated at the interface instead, at the waveguide axis.

Modal study of plasma cladded cylindrical optical fiber

Simplified study of guided modes in plasma cladded step-index optical fiber

The general characteristic equation is derived for the helically cladded step-index optical fiber. The dispersion curves are drawn for the different pitch angles Ψ and mode order ν = 1. The effect of helix pitch angle on the dispersion characteristics and also on the modal cut-off condition is examined. Except for the lowest order mode, all the modes appear in pairs. The lowest order mode displays the negative dispersion for the some value of normalized frequency V and depends on the helix pitch angle Ψ.

/pdf/effect-of-helix-pitch-angle-on-the-modal-dispersion-3is3fxzh4r.pdf

Effect of Helix Pitch Angle on the Modal Dispersion Characteristic of Step-Index Optical Fiber

This is a review of anticancer agents isolated from endophytic fungi from 1990–2010. Endophytic fungi are defined as fungi that live asymptomatically within the tissues of higher plants. The designation ‘anticancer’ is based on the assessment of the authors of the paper of the cytotoxicity of each compound against specific cancer cell lines. Many of the compounds reported here were isolated exclusively from endophytes in culture, while other compounds had been previously reported as chemical constituents of higher plants. The uniqueness of the endophytic community of fungi is stressed as a promising source of novel compounds with anticancer activity, or as an alternative source of compounds originally isolated from higher plants. Endophytes represent a dependable source of specific secondary metabolites, and can be manipulated both physicochemically and genetically to increase yields of desired metabolites and to produce novel analogues of active metabolites.

A.K. Mishra

Papers

Anticancer compounds derived from fungal endophytes: their importance and future challenges.

Modal study of plasma cladded cylindrical optical fiber

Simplified study of guided modes in plasma cladded step-index optical fiber

Effect of Helix Pitch Angle on the Modal Dispersion Characteristic of Step-Index Optical Fiber

Anticancer Compounds Derived from Fungal Endophytes: Their Importance and Future Challenges