ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03715.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SYNOPSIS.The results of physiochemical and electron microscope studies on the structure of the kinetoplast DNA ofCrithidiaare discussed. The molecular weight of isolated kinetoplast DNA is approximately 41 × 109daltons. The basic unit of organization of this DNA is a covalently closed circular molecule 0.8 μm in contour length (molecular weight 1.54 × 106daltons). An average of 33 such circles are held together in a group by topological interlocking of each circle with a large number of other circles in the group. An average of 804 groups are held together into a structure termed an association. A group of circles is attached to several adjacent groups. This is accomplished by 1 or more circles each interlocking with many circles in 2 (but never more) of the groups. The groups of circles are arranged in such a way that the association, comprising about 27,000 circles, has a topologically 2‐dimensional form. A model is presented for thein situarrangement of the kinetoplast DNA association. Data which we have obtained is consistent with the view that all of the circular molecules of kinetoplast DNA of one organism carry the same genetic information. The transcription product is a single RNA molecule of approximately the size of a single circular DNA molecule. From studies involving density shift experiments using deuterium oxide, buoyant density ultracentrifugation and electron microscopy we have determined the following concerning replication of kinetoplast DNA: (a) doubling of the kinetoplast DNA results from the replication of each circular molecule rather than from extensive replication of a small number of circular molecules; (b) replication of kinetoplast DNA is a semi‐conservative rather than a conservative process and there is recombination at an undefined time during the cell cycle; (c) a portion of a kinetoplast DNA association is in the form of long linear molecules during the replicative phase of that assoc

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03716.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SYNOPSIS.DNA‐dependent RNA polymerases have been solubilized from homogenates ofCrithidia fasciculatausing gentle extraction procedures. RNA polymerase I and II are separated on DEAE cellulose at 0.07M (NH4)2SO4and 0.13M (NH4)2SO4respectively. RNA polymerase II is inhibited 80% by α‐amanitin (25 μg/ml). Both RNA polymerases require DNA as a template, ribonucleoside triphosphates and Mn2+. The synthesis of RNA as a product is inhibited by DNase. RNase, pronase and actinomycin D.Purified kinetoplast and nuclear DNA can serve as templates for the RNA polymerases. Denatured DNA templates are preferred. The synthesis of RNA continues for at least an hour and is inhibited by trypanocidal drugs including suramin. antrycide, acriflavine, ethidium bromide and berenil.Complementary RNA synthesizedin vitrofromC. fasciculatakinetoplast DNA hybridizes withC. fasciculatakinetoplast DNA but not withC. fasciculatanuclear DNA orBlastocrithidia culiciskinetoplast DNA,Escherichia coli, T4 or calf thymus DNAs. The complementary RNA synthesizedin vitrofromC.fasciculatakinetoplast DNA sediments at

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03717.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SYNOPSIS.The recent literature on the physical, chemical and biological characterization of antigens from the African trypanosomes is reviewed. The antigens are divided into three major groups: a) variant‐specific antigens, b) common antigens, and c) host‐like antigens. The variant‐specific antigen(s) are relatively small molecular weight proteins located on the surface of the trypanosome, and are involved in protection and agglutination. It is suggested that there is more than a single variant‐specific antigen on the cell surface. In contrast, the common antigens are internal or somatic antigens which are believed to have structural or enzymatic functions but are not involved in either protection or agglutination. In addition, evidence is also presented which suggests that there are host‐like antigens within the surface coat and/or membranes of the trypanosomes. The importance of these three groups of antigens, and the mechanis(s) of antigenic variation are discussed in relationship to the immune response of the host to the African trypanosomes. Several possible approaches for future investigations are

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03718.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03719.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SYNOPSIS.Polytomella caeca(Phytomonadida, Polyblepharidae) reproduce by binary fission and sexual reproduction. The sexual process increases in frequency as the population becomes denser. Normally 2 monoecious isogametes engage their anterior flagella prior to fusion, which occurs by merging of the cells from their anterior to their posterior ends. This is followed by a period of zygotic enlargement before cleavage of the zygote into 4 daughter cells. Encystment occurs throughout the flagellates' bloom until they represent 80% of the individuals at the end of the bloom. Cysts are a resistant, not reproductive stage. The observations were made over long periods of time by following individual flagellates in microcultures and by viewing living cells taken at various stages from larger cultures.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03720.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

RESUMEDeux types de structure kystique ont été observés au microscope éectronique. Dans le ler, qui correspond aux kystes d'infection ou gamontokystes, la cellule est relativement libre dans l'enveloppe kystique. Celle‐ci est formée de 2 couches distinctes d'inégale épaisseur (ectokyste, endokyste) sécrétées par la cellule et doublées intérieurement par un mince feuillet cytoplasmique dûà une extension des plis cuticulaires. C'est la seule modification du cortex cellulaire.Par contre, dans le 2ème type les modifications sont beaucoup plus importantes. La cellule est étroitement accolée aux parois du kyste; crêtes et flagelles ont disparu de la surface. Cependant on retrouve leurs traces dans la région corticale, sous forme d'axonèmes intracytoplasmiques plus ou moins désorganisés et d'empilements de saccules associés à des rangées de microtubules. Ce seraient des kystes de résistance. Les structures observées dans ces derniers kystes nous permettent de discuter quelques idées sur la participation des microtubules et des systèmes membranaires à la morp

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03721.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Book reviewed in this article:Olsen, O. Wilford. 1974.Animal Parasites. Their Life Cycles and Ecology.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03722.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SYNOPSIS.The blood of each of 95 turtles (8 species) collected from southeastern Louisiana was infected with some or all of the merogonic stages and gametocyte stage ofHaemogregarina pseudemydisn. sp. Five species of turtles harboredPirhemocyton chelonarumn. sp. TurtleHaemogregarinaandPirhemocytonare locality records for Louisiana.Pirhemocytonis reported for the first time in turtles and in the continental U.S.A.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03723.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SYNOPSIS.Cryptosporidium anserinumsp. n. is described in the large intestinal mucosa of a domestic goose,Anser anserL., from Iowa. Ultrastructural studies revealed schizonts containing 4 merozoites and macrogametes and schizonts with characteristic attachment zones and double membranes. The only lesion associated with infection was shortening of the intestinal microvilli.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1974.tb03724.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY