Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PROTOZOA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed1981

Isoenzyme studies on Theileria (Protozoa, Sporozoa). Enzyme activity associated with the erythrocytic stage.

Bovine blood containing piroplasms of Theileria parva, as well as non-infected blood, was lysed and subjected to iso-electric focussing. Staining for 13 different enzymes revealed parasite-associated bands of glucose phosphate isomerase (GPI) activity, not of any of the other enzymes. There were no variations between individual donor animals in the host cell GPI bands and these bands did not interfere with the recognition of the parasite-associated bands, so that purification of the piroplasms was unnecessary. Blood from cattle infected with T. mutans also gave parasite-associated bands of GPI, but no such bands were seen in zymograms of blood from cattle infected with a Theileria sp. from Japan. Dependent on the level of parasitaemia, up to four parasite-associated bands were found in one strain of T. parva and up to three in two other strains. Among the disadvantages of using piroplasm material for the study of isoenzymes of T. parva is the fact that animals often die before their parasitaemia is sufficiently high, and that some strains never give rise to a high parasitaemia.

Animals↗
PubMed1986

Different structural states of a microtubule cross-linking molecule, captured by quick-freezing motile axostyles in protozoa.

Freeze-etch preparation of the laminated bundles of microtubules in motile axostyles demonstrates that the cross-bridges populating individual layers or laminae are structurally similar to the dynein arms of cilia and flagellae. Also, like dynein, they are extracted by high salt and undergo a change in tilt upon removal of endogenous ATP (while the axostyle as a whole straightens and becomes stiff). On the other hand, the bridges running between adjacent microtubule laminae in the axostyle turn out to be much more delicate and wispy in appearance, and display no similarity to dynein arms. Thus we propose that the internal or "intra-laminar" cross-bridges are the active force-generating ATPases in this system, and that they generate overall bends or changes in the helical pitch of the axostyle by altering the longitudinal and lateral register of microtubules in each lamina individually; e.g., by "warping" each lamina and creating longitudinal shear forces within it. The cross-links between adjacent laminae, on the other hand, would then simply be force-transmitting elements that serve to translate the shearing forces generated within individual laminae into overall helical shape changes. (This hypothesis differs from the views of earlier workers who considered a more active role for the later cross-links, postulating that they cause an active sliding between adjacent layers that somehow leads to axostyle movement.) Also described here are physical connections between adjacent intra-laminar cross-bridges, structurally analogous to the overlapping components of the outer dynein arms of cilia and flagella. As with dynein, these may represent a mechanism for propagating local changes from cross-bridge to cross-bridge down the axostyle, as occurs during the passage of bends down the length of the organelle.

Adenosine Triphosphatases↗
PubMed1967

Fine structure of division in ciliate protozoa. I. Micronuclear mitosis in Blepharisma.

The mitotic, micronuclear division of the heterotrichous genus Blepharisma has been studied by electron microscopy. Dividing ciliates were selected from clone-derived mass cultures and fixed for electron microscopy by exposure to the vapor of 2% osmium tetroxide; individual Blepharisma were encapsulated and sectioned. Distinctive features of the mitosis are the presence of an intact nuclear envelope during the entire process and the absence of centrioles at the polar ends of the micronuclear figures. Spindle microtubules (SMT) first appear in advance of chromosome alignment, become more numerous and precisely aligned by metaphase, lengthen greatly in anaphase, and persist through telophase. Distinct chromosomal and continuous SMT are present. At telophase, daughter nuclei are separated by a spindle elongation of more than 40 micro, and a new nuclear envelope is formed in close apposition to the chromatin mass of each daughter nucleus and excludes the great amount of spindle material formed during division. The original nuclear envelope which has remained structurally intact then becomes discontinuous and releases the newly formed nucleus into the cytoplasm. The micronuclear envelope seems to lack the conspicuous pores that are typical of nuclear envelopes. The morphology, size, formation, and function of SMT and the nature of micronuclear division are discussed.

Animals↗
PubMed1998

First report on the systematic sequencing of the small genome of Encephalitozoon cuniculi (Protozoa, Microspora): gene organization of a 4.3 kbp region on chromosome I.

Belonging to a large group of parasitic amitochondrial protozoans (Microspora), Encephalitozoon cuniculi infects humans and other mammals. Because of its medical importance and small genome size (2.9 Mbp), we are systematically sequencing its smallest (217 kbp) chromosome. The shotgun cloning strategy now has produced the sequence of randomly dispersed contigs representing more than 180 kbp of this chromosome. The present report describes analysis of the 4.3 kbp contig, which includes the complete coding regions of dihydrofolate reductase (DHFR), thymidylate synthase (TS), and serine hydroxymethyl transferase (SHMT) genes and the partial coding region of an aminopeptidase (AP) gene. In contrast to the other reported protozoan genes, DHFR and TS are encoded by two different open reading frames (ORFs). The SHMT gene is the first one identified in a protozoan and corresponds to the cytosolic form of the enzyme. No introns were detected, and the intergenic noncoding regions do not exceed 50 bp. The mean GC content is close to 60%, and there is a G or C third-base codon bias. Transcription and translation initiation signals also are analyzed, and a model for the mRNA-ssu rRNA interactions is proposed.

Amino Acid Sequence↗
PubMed1991

MCS/SEL/BAS program--an overlapping clustering method with examples from mating type interactions of ciliated protozoa.

The MCS/SEL/BAS program provides a method for group recognition, based on a criterion of homogeneity within the groups. The basic aim of this clustering method is not to 'force' data into a number of separate groups, as it allows the possibility that a given element in the data set can be assigned to more than one group. Moreover, a parsimonious path through the groups is sought by selecting groups on the basis of two suitably chosen, peak-ordered criteria. This selection continues until a covering of the data set is obtained (i.e., until each element in the data set is assigned to at least one group). Then relationships occurring among the set of selected groups are investigated by means of two coefficients, called overlapping and cohesion coefficient, respectively. The utility of this program has been demonstrated here in elaborating large sets of data derived from mating type interactions of ciliates, but it can be used also for analyzing data derived from a wide spectrum of compatibility phenomena exhibited by other living organisms. Algorithms of this program are written in BASIC and formulated in a conversational mode for processing on a Macintosh. A computer program (MCS/SEL/BAS) is available from G. Mancini upon request.

Algorithms↗
PubMed2001

Glycoconjugate structures of parasitic protozoa.

Glycoconjugates are abundant and ubiquitious on the surface of many protozoan parasites. Their tremendous diversity has implicated their critical importance in the life cycle of these organisms. This review highlights our current knowledge of the major glycoconjugates, with particular emphasis on their structures, of representative protozoan parasites, including Leishmania, Trypanosoma, Giardia, Plasmodia, and others.

Animals↗