ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05991.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SYNOPSISCells of the order Kinetoplastida possess a single mitochondrion which contains a large amount of a uniquely organized DNA. This kinetoplastic DNA (K‐DNA), representing 10–20% of the total cell DNA in different species, has as its major molecular component a small closed circular molecule present in large numbers. The size and thereby the amount of genetic information carried by the minicircles varies from species to species:Leishmania tarentolaeand the Salivarian trypanosomes have the smallest, the Stercorarian trypanosomesTrypanosoma lewisiandTrypanosoma cruziintermediate, andCrithidiaand alsoTrypanosoma megathe largest minicircles. InL. tarentolae, purified minicircles, which are the size of 1 gene, have been shown by renaturation kinetics to consist of only 1 or 2 classes.L. tarentolaeK‐DNA also contains another molecular species—a long molecule which may represent up to 30% of the total K‐DNA. The minicircles, nevertheless, represent a gene amplification of the order of 104. In all species that have been examined so far, the K‐DNA consists of a single sheet of interlocked closed circular molecules which can be isolated in an intact form because of its resistance to shear forces and its high molecular weight. In addition, at least inL. tarentolae, 6–9% of the K‐DNA is either free in the mitochondrion or loosely bound. The main K‐DNA structure has been termed a “network” and can be seen in the light microscope after staining in solution with acridine orange or after fixing and staining with Giemsa's, or in the electron microscope. The quaternary structure of such networks in terms of the organization of minicircles and long molecules is not understood. Controlled breakdown of networks fromL. tarentolaewas achieved by sonication, and the release of open and closed monomeric minicircles, catenated dimers, trimers and higher oligomers, and short linear fragments was measured. A maximum of 43% of the total network DNA was released in the form of closed monomers, dimers, and trimers, thus providing a minimal estimate for the percentage of minicircles in K‐DNA from this species. K‐DNA replicates fairly synchronously with nuclear DNA in all species that have been examined. Replication of DNA molecules in the kinetoplast networks is limited to the periphery, as seen in autoradiographs of networks isolated from cells (L. tarentolae, Crithidia fasciculata) pulsed with3H‐thymidine. The molecular implications of this unusual replication pattern remain an open question, as does the genetic f

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05993.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SYNOPSISIt is commonly observed in hypotrichs that new ciliary rudiments arise directly from or in close juxtaposition to certain pre‐existing ciliary elements. Oral primordia often are initiated near specific cirri, cirral rudiments frequently arise as a result of the disaggregation of certain old cirri, and new dorsal ciliature is formed within pre‐existing ciliary rows. In the first 2 situations it has been demonstrated experimentally that neither the old ciliature in question nor the specific cortical site marked by that ciliature is essential for the appearance of the new cirral rudiment. The experimental analysis done thus far suggests that the positions of oral and cirral primordia are determined by interacting gradients established in relation to certain reference points. The nature of the reference points is not fully elucidated; in some cases at least these points appear to be more closely related to topographic features of the cell than to specific pre‐existing cortical structures.In the dorsal ciliary rows ofEuplotesnew ciliary units are formed usually and perhaps invariably in close proximity to old ones, and are generally oriented along the axis of the pre‐existing row. The result is a tendency to perpetuate the preexisting row number across cell generations. Changes in row number, however, can occur as a result of occasional formation of new units at right angles to the row, a process that is much enhanced in certain homozygous segregants (basal body deficient). The optimal row number (stability range) as well as the number of ciliary units are under genic control. In addition, the spatial pattern of distribution of ciliary units among rows is invariant in all of the material examined. This pattern is presumed to result from an underlying field whose geometry is independent of both the number of units and the number

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05994.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SYNOPSISThe macro‐ and micronucleus ofTetrahymena pyriformisare formed from a common diploid synkaryon during conjugation. Shortly after the 2nd postzygotic division, distinct morphologic and physiologic differences develop between the 2 nuclei. Micronuclei remain small, presumably diploid, and electronmicroscopic observations indicate that micronuclear DNA is contained in a dense, fibrous, chromosome‐like coil. Macronuclei contain considerably more DNA than micronuclei, and the DNA of the macronucleus is found largely in the chromatin bodies typical of ciliate nuclei. The functional differences between macro‐ and micronuclei in vegetative cells also are striking. The template activity of DNA in the micronucleus is highly restricted compared to that in the macronucleus. Micronuclei synthesize and contain little RNA, and do not contain either nucleoli or ribonucleoprotein granules. Macronuclei, on the other hand, synthesize and contain large amounts of RNA and have many nucleoli and ribonucleoprotein granules. Macro‐ and micronuclei also have distinct differences in the timing of DNA synthesis during the cell cycle and in the timing and mechanism of nuclear division. Finally, during conjugation the macronucleus becomes pycnotic and disappears while the micronucleus undergoes meiosis and fertilization, ultimately giving rise to new macro‐ and new micronuclei. In short, the macro‐ and micronuclei ofTetrahymenaprovide an excellent system for studying the molecular mechanisms by which the same (or related) genetic information is maintained in different structural and functional states.Methods have been devised to isolate and purify macro‐ and micronuclei ofTetrahymenain the hope of correlating differences in the nucleoprotein composition of these nuclei with differences in their structure and function. The DNAs of macro‐ and micronuclei have been found to differ markedly in their content of a methylated base, N6‐methyl adenine, and major differences in the histones of the 2 nuclei have been observed. Macronuclei contain histones similar to those found in vertebrate nuclei, while 2 major histone fractions seem to be missing in micronuclei. In addition, histone fraction F2A1 which is found in multiple, acetylated forms in macronuclei, is present only as a single, unacetylated fo

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05995.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SYNOPSISA review of the recent literature on the structure and physico‐chemical properties of the myoneme and its specialization, the spasmoneme, of peritrich ciliates was made. Myonemes are composed of tightly packed bundles of 3–5 nm microfibrils which parallel, more or less, the long axis of the bundle and are of indefinite length. The presence of contractility in these ciliates is correlated with the presence of myonemes. Associated with the microfibrils is a system of membrane‐bound tubules and saccules continuous with the endoplasmic reticulum (ER). This system is known to accumulate calcium. Myonemes differ from muscles in their structure, solubility properties, birefringence pattern, and in the time during the contraction‐relaxation cycle at which they require energy. They may be related more closely to the cytochalasin B‐sensitive microfibrils of higher organisms than to muscles. Contraction of extracted stalks can be induced solely by raising the calcium ion concentration above a certain threshold. Thus the calcium‐accumulating myoneme‐associated ER would appear to play an important role in the control of myoneme contractility. A specialization at the interface between the myoneme and the ER membranes is described as it appears inVorticellaandOpercularia.This structure, called a linkage complex, is found both in the body myonemes and the spasmoneme and links the membranes of the ER to the microfibrils. It also has microfilaments that pass from the ER‐myoneme interface to the surface membranes. The uniqueness of this structure and its location suggests that it may play a role in controlling the movements of calcium between the ER and myoneme and also in transmission of messages from the pellicular membranes, possibly the alveolar

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05996.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05997.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SYNOPSISOne species ofTyzzeriaand 4 new species ofEimeriaare described from the Ceylon jungle fowlGallus lafayettei.The sporulated oocysts ofTyzzeria gallisp. n. are 13.8 (12–15)μm; ofEimeria lafayetteisp. n., 19.5 (19–21) X 14.2 (13.5–15)μm; ofEimeria indentatasp. n., 30.3 (29.5–32) X 21.4 (20–22)μm; ofEimeria symmetricasp. n., 35 × 28.5μm, and ofEimeria dissanaikeisp. n., 21 (19–23) X 14 (12–16)μm.E. indentata, E. symmetrica, andE. dissanaikeiproduced patent infections in domestic fowl butT. galliandE. lafayetteidid not. This is the 1st record of the genusTyzzeriafrom th

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05998.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SYNOPSISSpecimens ofAskenasia volvoxfrom southwestern Indiana have a variable body shape and a size range of 29 × 22μm to 42 × 27μm. The pectinelles, membranelles, and cirri each number 47–48, and respectively have a length of 8–10, 20, and 30μm. The pectinelles arise from ciliary rows consisting of ∼10 kinetosomes, and every membranelle originates from 2 adjacent rows of ∼14–17 kinetosomes. Different algae as well asBodoand certain other protozoa are ingested. The macronucleus, micronucleus, the cytoplasm and its inclusions, trichites, the function of the contractile vacuole, and movements and behavior

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb05999.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

RESUMEL'ampoule rectale de quelques Batraciens Anoures d'Afrique et d'Asie héberge 4 espèces de Nyctothères caractèrisèes par la prèsence d'une ventouse sur toute la face infèrieure et une topographie ciliaire presque identique. L'observation des formations squelettiques polysaccharidiques montre que ces èlèments constituent un critère taxonomique complèmentaire ayant une signification phylogènètique, ChezSicuophora macropharyngea(Bezzenberger 1904) comb. n. etS. xenopide Puytorac&Grain, 1968, les plaques de la ventouse forment un pavage. Les plaques marginales sont acuminèes.Metasicuophora petterigen. n., sp. n. est une espèce de grande taille, très aplatie. Les plaques marginales de la ventouse sont èlargies à leur extrèmitè et l'armature squelettique de la face supèrieure est très dèveloppèe. ChezParasicuophora xavieraesp. n., les èlèments squelettiques de la ventouse sont constituès par des filaments identiques à ceux observès chezP. mantellaeAlbaret, 1968.SYNOPSISThe rectum of several African and Asian anuran amphibians harbors 4 species of nyctotherid ciliates characterized by the presence of a sucker on the entire lower surface, and a nearly identical ciliary distribution. Observations of the skeletal structures made up of polysaccharides indicate that these elements constitute a complementary taxonomic criterion with a phylogenetic significance. InSicuophora macropharyngea(Bezzenberger 1904) comb. n. andS. xenopide Puytorac&Grain, 1968, the plaques of the sucker have a pavement‐like arrangement and the marginal plaques are pointed.Metasicuophora petterigen. n., sp. n. is a large, very flattened species. The marginal plaques of the sucker have terminal enlargements and the skeleton of the upper surface is well developed. InParasicuophora xavieraesp. n., the skeletal elements of the sucker consist of filaments identical to those observ

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb06000.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SYNOPSISAnacystis nidulansdisappeared rapidly from culture in the presence of an unidentified species ofOchromonas.Disappearance was light‐independent and could be induced neither by bacteria associated with, nor by soluble products released from the flagellate. Electronmicrographs of mixed cultures revealed numerousA. nidulanscells in various stages of digestion within vacuoles ofOchromonas.Evidently the disappearance of the alga from culture resulted from phagotrophy by the chrysomonad. A 2‐stage digestive process is suggested wherebyA. nidulanscells are initially sequestered in the posterior “leucosin” vacuole and then undergo the terminal stages of digestion and elimination in smaller, peripheral v

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1973.tb06001.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY