ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05272.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.The interaction of contiguous proteins is explored in microtubules, rosettes, and membranes based on the well established molecular phenomena of cooperativity and allosterism. It is proposed that conformational gradients in protein arrays cause the formation of gradions by nearest‐neighbor interactions. Gradions are repeating functional molecular sequences that contain several conformational forms of one or more proteins, with the result that different reactive sites can exist in the same molecular architecture at any one time. Gradionators are small controlling molecules that may be microscopically visible as layers or linkages, but could also be smaller. Some of the presently available supporting evidence and its functional implications are discussed, including the possibility that theraison d'etrefor membrane‐particle arrays is to enhance the regulation and amplification capabilities of cell syst

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05273.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.Comparative studies of axopodial microtubule pattern in 10 different centrohelidan Heliozoa belonging to the generaAcanthocystis, RaphidiophrysandHeterophryssuggest that 2 basic principles govern pattern formation in centrohelidan Heliozoa. While the larger “open” arrays with unspecified number of microtubules, e.g. inA. aculeataandR. ambigua, may result from self‐linkage of additional microtubules around centroplast‐nucleated “starter microtubules,” the smaller “closed” arrays with specified microtubule number, e.g. inA. pectinataandH. marina, favor a template‐driven linkage mechanism. The centroplast is a highly complex microtubule organizing center involved in the control of orientation, number, and diameter of the axonemes. Its shell may serve as a surface upon which the microtubule nucleating sites assemble, but how the precise positioning of these sites occurs is still open to debate. Some of the unsolved problems of microtubule pattern formation may be explained by the “linker nucleation hypothesis” which is an extension of the “gradion hypothesis” by Roth et al. It is shown how both the formation of closed arrays and the balanced lateral growth of open arrays may result from linker‐ind

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05274.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.The expression of intracellular patterning is perhaps nowhere more impressive than in the arrangements of structural elements associated with the cell surface in protozoa. The view is proposed that biochemical studies of protozoan plasma membranes and associated surface structures represent important contributions of potential significance for the understanding of the perpetuation, and expression of positional information at the intracellular level. Some recent work dealing with the isolation, identification, and metabolism of pellicular proteins inTetrahymenais presented and discussed. Some integral membrane proteins have been identified by iodination and polyacrylamide gel electrophoresis. Labeling studies suggest heterogeneous turnover rates within the group of presently identified membrane proteins. High molecular weight proteins with some similarity to spectrin have been isolated fromTetrahymenaepiplasm. It is suggested that the ciliate epiplasm is one example of membrane‐associated, actomyosin‐like systems found in a variety of cell types. The epiplasm may play a role in the positioning of surface‐associated structures and in the control of cell

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05275.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.The modes of pattern regulation found in the ciliatesDileptusandParaurostylaare compared. These forms are systematically distant but both possess very extensive regenerative capacities. They are characterized by 2 types of ciliary patterns: the ciliature ofDileptushas largely a simple pattern composed of single kinetosomes while that ofParaurostylahas a complex pattern composed of aggregates of kinetosomes interconnected by amorphic matter. In both ciliates a change in cell size evokes pattern regulation which differs substantially in the extent of pattern replacement, timing, and localization of morphogenetic activities. It is concluded that these differences result from the pattern constituents.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05276.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.Three apparently conflicting generalizations concerning the relationships between molecules and cell structure may be derived from studies on cellular patterning in the ciliates. (A) Cells with identical genes and molecular composition may have different hereditary patterns. (B) Genes, through their prescribed molecular derivatives, constrain the modes of pattern permutation and define the states of greatest stability. (C) Cells with identical hereditary patterns may have entirely different genes and molecular compositions. These principles may be reconciled through the recognition that they are characteristically applicable over different time intervals. Hereditary differences within a clone and without related molecular differences (principle A) may persist for hundreds of cell generations, but they are resolved eventually within a constant environment (principle B) as the configuration of minimal free energy is approached. On an even longer time scale, molecular substitutions have occurred for many or most components of the cell, but these have been constrained by selective pressures on an ancient design (principle C) that disallow substitutions affecting certain form‐function relations which have been elevated to an adaptive pea

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05277.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.After reviewing reports of the hosts, structure and life cycle ofToxoplasma, the genus is placed in the apicomplexan family Eimeriidae and the following 7 species are recognized:Toxoplasma gondii(Nicolle&Manceaux) (type species) from about 200 species of mammals and birds, with oocysts in felids;Toxoplasma alencari(Da Costa&Pereira) from the frogLeptodactylus ocellatus; Toxoplasma brumptiCoutelen from the iguanaIguana tuberculata; Toxoplasma colubriTibaldi from the snakesColuber melanoleucusandColuber viridiflavus; Toxoplasma hammondi(Frenkel&Dubey) (a new combination forHammondia hammondi) from the house mouse with oocysts in the domestic cat;Toxoplasma ranaeLevine&Nye from the leopard frogRana pipiens; andToxoplasma serpaiScorza, Dagert&Iturriza Arocha from the toadBufo marinus.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05278.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.A checklist is given of the 89 named species of the gregarine family Lecudininae, exclusive of the 42 named species of the genusLecudina(phylum Apicomplexa. class Sporozoea, subclass Gregarinia, order Eugregarinida, suborder Aseptatina). The list includes also the synonyms, host names, locations in hosts, known geographic distributions of the species, as well as key references. Another list is given of synonyms,lapsi calami, nomina nuda, etc., associated with the genera. A new genus, Paraophioidina g. n., with type species,Paraophioidina haeckeli(Mingazzini, 1891) and a new species, Lankesteria ormieresi sp. n., are described. There are also new combinations in the generaBhatiella, Ancora, Monocystella, Ascocystis, andParaophioidina.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05279.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.Nosema parkeri sp. n. is described from nymphs and adults of the argasid tick,Ornithodoros parkeriCooley, from a laboratory colony. Schizogonic and sporogonic stages are described from various tick tissues. Spores are binucleate, measuring 3.2 (3–4) × 1.9 (1.8–2.5) μm. Transmission is transovarial and transstadial. The parasite does not appear to affect adversely the development or reproduction of the tick.Dermacentor andersoniStiles was experimentally infected. Attempts to infect Swiss mice by tick feeding or by injection of infected tick suspensions were unsuccessful. The microsporidan differs in structure fromEncephalitozoon ixodisWeiser) andNosema slovacaWeiser&Reháček, the only other microsporidans known fro

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05280.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SYNOPSIS.The endogenous stages ofIsospora seriniAragão andIsospora canariaBox are described from experimentally infected canaries,Serinus canariusLinnaeus. Unlike other Coccidia, the first part of theI. serinilife cycle takes place in mono‐nuclear phagocytes. Five asexual generations are described from this cell type; 2 additional asexual generations and the sexual stages take place in the intestinal epithelium.Isospora canaria, on the other hand, has a conventional coccidian life cycle in that all of the endogenous stages are in the epithelium of the small intestine, with 3 asexual generations and the sexual generation described in the duodenal epithelium. The 2 species differ in their position relative to the nucleus of the intestinal epithelial cell.Isospora seriniis usually on the lumenal side of the nucleus whileI. canariais below the nucleus, toward the basement membrane. The prepatent period is 4–5 days forI. canariaand 9–10 days forI. serini.Patency lasts for 11–13 days inI. canariainfections, but duration of oocyst output is more chronic inI. seriniinfections, persisting for as long as 231 days. Both species have a diurnal periodicity of oocyst discharge which occurs in late afternoon and

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1977.tb05281.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY