Asexual development

Abrahamsen MS, Templeton TJ, Enomoto S, Abrahante JE, Zhu G, Lancto CA, Deng M, Liu C, Widmer G, Tzipori S, Buck GA, Xu P, Bankier AT, Dear PH, Konfortov BA, Spriggs HF, Iyer L, Anantharaman V, Aravind L, Kapur V (2004) Complete genome sequence of the apicomplexan Cryptosporidium parvum. Science 304 441-445 Aji T, Flanigan T, Marshall R, Kaetzel C, Aikawa M (1991) Ultrastructural study of asexual development of Cryptosporidium parvum in a human intestinal cell line. J Protozool 38 82S... 

In the cyclophyllidean Mesocestoides corti, uniquely, an asexual development pattern occurs in the definitive host intestine. Both the recently ingested larva (a tetrathyridium) and the adult worm are capable of undergoing asexual multiplication. This is illustrated dramatically by an experiment in which 2000 tetrathyridia were fed to a dog and 45 days later some 15 000 worms were recovered on autopsy (739). This unusual development was first shown by Eckert et al. (192) and has since been studied by a number of workers (383, 607, 739, 871, 907). 

Bruce, M. C., Alano, P., Duthie, S., and Carter, R. (1990). Commitment of the malaria parasite Plasmodium falciparum to sexual and asexual development. Parasitology 100(Pt 2), 191-200. 

Tsitsigiannis DI, Kowieski TM, Zarnowski R, Keller NP. (2005) Three putative oxyhpin biosynthetic genes integrate sexual and asexual development in Aspergillus nidulans. Microbiology 151 1809-1821. 

Cleary, M. D., Singh, U., Blader, 1. J., Brewer, J. L., and Boothroyd, J. C., 2002, Toxoplasma gondii asexual development identification of developmentaUy regulated genes and distinct patterns of gene expression. Eukaryot Cell 1 329-340. 

Malaria. Malaria infection occurs in over 30% of the world s population and almost exclusively in developing countries. Approximately 150 X 10 cases occur each year, with one million deaths occurring in African children (87). The majority of the disease in humans is caused by four different species of the malarial parasite. Vaccine development is problematic for several reasons. First, the parasites have a complex life cycle. They are spread by insect vectors and go through different stages and forms (intercellular and extracellular sexual and asexual) as they grow in the blood and tissues (primarily fiver) of their human hosts. In addition, malaria is difficult to grow in large quantities outside the natural host (88). Despite these difficulties, vaccine development has been pursued for many years. An overview of the state of the art is available (89). 

Interest in vaccine development has centered around the asexual erothrocytic stage of the life cycle, especially the mero2oite. Several proteins associated with these stages have been identified and produced by recombinant techniques (92,93). The most prominent is the MSA-1 protein of the mero2oite. A clinical trial with this protein is being planned (93). 

Patients who have blood transfusion malaria are infected with the asexual erythrocytic parasites only exoerythrocytic tissue forms apparently do not develop. Plasmodium malariae has been known to produce an infection after transfusion, even when the blood was obtained from a person whose only contact with malaria was 40 years previous to the donation of blood. 

Endospore An asexual spore developed within the cell. 

Cloning. Asexual propagation (cloning) of plants ordinarily occurs by virture of the ability of embryonic meristematic tissue to differentiate into roots and shoots. If isolated phloem cells or other more differentiated cells are cultured, the result is often the formation of a callus, a dedifferentiated mass of cells somewhat reminiscent of embryonic cells. Under proper conditions, e.g., in a coconut milk culture and in the presence of the correct auxin-to-cytokinin ratio, some carrot root phloem cells revert to embyronic cells and develop into intact plants.99 This experiment provided proof that the differentiated carrot phloem cells... 

Variations of the life cycle occur. For example, a process called apomixis leads to asexual formation of seed.469 In many plants, including maize, separate flowers form the ovule and the pollen. This is one mechanism for avoiding inbreeding.470 In many plants systems of self-incompatibility have evolved.471 In some, e.g., Arabidopsis and other crucifers, pollen germination is disrupted unless it falls on a stigma possessing a different allele-specific receptor. In other cases development of the pollen tube is disrupted at a later stage. In maize and in more than 150 other... 

PATENTABILITY. The qualifications for obtaining a patent on an invention of chemical process. These arc (1) the invention must not nave been published in any country or in public use in the U.S., in either case for more than 1 year before the date of filing the application (2) it must not have been known in the IJ.S. before date of invention by the applicant (3) it must not be obvious to an expert in the art (4) it must be useful for a purpose not immoral and not injurious to the public welfare (5) it must fall within the five statutory classes on which patents may be granted, i.e., (a) composition of matter, (b) process of manufacture or treatment, (c) machine, (d) design (ornamental appearance), or (e) a plant produced asexually. Special regulations relate to atomic eneigy developments and subjects directly affecting national security (Robert Calvert). Note In 1980, the Supreme Court m al landmark decision upheld the patentability of synthetic bacteria created by recombinant DNA techniques. 

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