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At least 937 records · Page 52Linked to original sources
PubMed1997

Cloning and sequencing of gene coding for a periplasmic 5.4 kDa peptide of the macronucleus-specific symbiont Holospora obtusa of the ciliate Paramecium caudatum.

We purified a 5.4 kDa peptide which is present in the intermediate and infectious form, but not in the reproductive form of a symbiotic bacterium Holospora obtusa of the ciliate Paramecium caudatum. Sequencing of its gene revealed that it encodes a peptide composed of 49 amino acids, and that the peptide is preceded by a putative signal peptide of 19 amino acids. We determined the transcription start point for the gene by primer extension analysis, indicating that the transcription starts with a G nucleotide located 33 nucleotides upstream from the translational initiation codon. Northern blot hybridization showed that the gene is highly expressed in the intermediate form, a transitional stage from the reproductive to infectious form of the bacterium. Immunoelectron microscopy with anti-5.4 kDa peptide antiserum revealed that the 5.4 kDa peptide is localized in the periplasm of the infectious form.

Animals↗
PubMed2002

Variability of autogamy-maturation pattern in genetically identical populations of Paramecium tetraurelia.

Autogamy in Paramecium tetraurelia is a form of sexual reproduction in a single cell that results in homozygosity in every genetic locus. Autogamy becomes inducible by natural starvation several fissions after the previous autogamy, and percent autogamy increases gradually with clonal age to reach 100%. We here report the degree of variability of the autogamy-maturation pattern, and how it is inherited through autogamous generations. We assessed the autogamy-maturation pattern by monitoring percent autogamy at the ages of 9, 18 and 27 fissions in the wild-type stock 51. To determine how the autogamy-maturation pattern is inherited, clones that showed the lowest and the highest percent autogamy at age 18 in a given autogamous generation (Gn) were examined for their percent autogamy in the next autogamous generation (Gn+1). This procedure was repeated through successive autogamous generations. We found that percent autogamy at ages 9 and 27 was rather stable (low and high, respectively), while it was extremely variable at age 18 ranging from 3% to 100%. We also found that percent autogamy at age 18 in the progeny clones was variable irrespective of percent autogamy at age 18 in the parental clones; there was no regular rule such as producing progeny with higher (or lower) percent autogamy from parents with lower (or higher) percent autogamy.

Animals↗
PubMed2004

Control of the ciliary beat by cyclic nucleotides in intact cortical sheets from Paramecium.

The locomotor behavior of Paramecium depends on the ciliary beat direction and beat frequency. Changes in the ciliary beat are controlled by a signal transduction mechanism that follows changes in the membrane potential. These events take place in cilia covered with a ciliary membrane. To determine the effects of second messengers in the cilia, cortical sheets were used with intact ciliary membrane as a half-closed system in which each cilium is covered with a ciliary membrane with an opening to the cell body. Cyclic nucleotides and their derivatives applied from an opening to the cell body affected the ciliary beat. cAMP and 8-Br-cAMP increased the beat frequency and the efficiency of propulsion and acted antagonistically to the action of Ca(2+). cGMP and 8-Br-cGMP increased the efficiency of propulsion accompanying clear metachronal waves but decreased the beat frequency. These results indicate that the cyclic nucleotides affect target proteins in the ciliary axonemes surrounded by the ciliary membrane without a membrane potential and increase the efficiency of propulsion of the ciliary beat. In vitro phosphorylation of isolated ciliary axonemes in the presence of cyclic nucleotides and their derivatives revealed that the action of cAMP was correlated with the phosphorylation of 29-kDa and 65-kDa proteins and that the action of cGMP was correlated with the phosphorylation of a 42-kDa protein.

Animals↗
PubMed2005

Augmented ciliary reorientation response and cAMP-dependent protein phosphorylation induced by glycerol in triton-extracted Paramecium.

In the presence of 30% glycerol, the cilia of a permeabilized cell model from Paramecium exhibit dynamic orientation changes while displaying only a restricted cyclic beating with a very small amplitude. The direction of cilia under these conditions corresponds to the direction of the effective power stroke of cilia beating in the absence of glycerol, i.e., pointing posteriorly in the absence of Ca2+ and anteriorly at > 10(-6) M Ca2+. Ciliary reorientation toward the posterior in response to the removal of Ca2+ is particularly conspicuous; all the cilia become predominantly pointing to the posterior end all through their beating phases. Previous studies suggested that the effect of glycerol is caused through modification of cAMP-dependent protein phosphorylation. To determine whether glycerol in fact affects ciliary reorientation through changes in protein phosphorylation, here we examined protein phosphorylation in the axonemes. Glycerol stimulated cAMP-induced phosphorylation of 29-kDa and 65-kDa proteins. The stimulation of phosphorylation was found to be partly due to the inhibition of endogenous phosphodiesterase (PDE), and partly due to the inhibition of the dephosphorylation of the 29-kDa and 65-kDa phosphoproteins within the axoneme. Thus glycerol appears to cause predominant posterior orientation of cilia by stimulating cAMP-dependent phosphorylation on those proteins. In addition, glycerol appears to inhibit ciliary beating through inhibition of dynein ATPase.

Animals↗
PubMed1984

Characterization of cytoplasmic factors which complement Ca2+ channel mutations in Paramecium tetraurelia.

The analysis of Ca2+-channel function in the single-celled eukaryote Paramecium can be extended to a biochemical based on recent observations that transfer of cytoplasm from wild-type cells into mutants lacking Ca2+-channel function ("pawn" mutants) causes the mutant cells to regain Ca2-channel activity. Using a convenient behavioral assay for Ca2+-channel function, we have used microinjection of cytoplasmic fractions into mutant cells to enrich for and characterize those components from wild-type cytoplasm which can "cure" cells carrying mutations in the 3 different pawn genes affecting Ca2+-channel activity (pwA,pwB, and pwC). In each case, the curing factor appears to be a protein component of an intracellular membrane. They are distinguishable on the basis of thermal, pH and divalent ion sensitivities. In addition, the factor curing the pwC mutational defect has been purified more than 180-fold. Furthermore, the pwB curing activity appears to be amplified during sequential transfer between pwB cells.

Animals↗
PubMed1986

Mutations resulting in resistance to polyene antibiotics decrease voltage-sensitive calcium channel activity in Paramecium.

In this report, the isolation of Paramecium tetraurelia mutants resistant to the polyene antibiotics amphotericin B and filipin are described. These antibiotics are known to specifically interact with membrane sterols to produce a cytotoxic effect. Four mutants resistant to amphotericin B and two mutants resistant to filipin have been isolated. In each case, an individual mutant shows resistance to both amphotericin B and filipin. Genetic analysis indicates that all 6 mutations map to the same complementation group and are not allelic to any of the 3 pawn mutations or to either of the two "barium shy" mutations. The behavioral analysis suggests that these mutations cause an alteration of normal ion channel function. Direct electrophysiological analysis of one mutant indicates mutations to polyene antibiotic resistance cause a specific decrease in voltage-sensitive Ca2+ channel activity.

Amphotericin B↗
PubMed1996

Toward cloning genes by complementation in Paramecium.

Conventional methods of gene cloning by complementing mutant defects is made difficult by the 800 ploidy of the Paramecium macronucleus. However, this nucleus is some 30 microns in diameter and readily propagates exogenous DNA fragments as cells divide. These attributes allow for massive injection of engineered DNA fragments and their maintenance in the transformed descendant. If a genomic DNA fraction injected into a mutant macronucleus effects complementation, it should be possible to sort a fractional library to isolate the complementing gene. Here, we investigated four aspects of establishing this method for general use. First, using the cloned CAM gene as a test case, we further investigated transformation by macronuclear injection and showed that phenotypic reversion is directly correlated with the copy number of the transgene, even when it is of a recessive allele, cam2, which has a missense mutation but produces a partially functional protein. Second, we examined the copy number of the transgene established in cells of older clonal age and discussed the likely dilution of the transgene in younger descendants of the injected cell. Third, we showed that the degree of phenotypic reversion is correlated with the transgene product, the cam2 calmodulin protein in the cell. Fourth, we extended the investigation to very recessive mutants whose genes are to be cloned. We showed that size fractions of wild-type genomic DNA digests effect strong phenotypic reversions in several pawn mutants, setting the stage for cloning these Ca(2+)-channel related genes. The general usefulness of this method in cloning genes that complement recessive alleles and current limitations of this method in dealing with dominant alleles are assessed and discussed.

Animals↗
PubMed2005

Recent data on the occurrence of species of the Paramecium aurelia complex in Europe.

Among 15 species of the Paramecium aurelia complex known world-wide, 10 have been found in Europe, namely: P. primaurelia, P. biaurelia, P. triaurelia, P. tetraurelia, P. pentaurelia, P. sexaurelia, P. septaurelia, P. novaurelia, P. dodecaurelia, and P. tredecaurelia. Recent data on the frequency of occurrence of the species in Europe are given in the paper.

Animals↗
PubMed2006

Occurrence of Paramecium species in Western Siberia, Russia.

Paramecium strains collected in Central Russia, Western Siberia (the West Siberian Lowland and the Altai Mountains in the south) were studied. The presence of P. caudatum, P. bursaria, P. multimicronucleatum, P. polycaryum, and four species of the P. aurelia complex, i.e. P. primaurelia (in Omsk), P. biaurelia (in Krasnoyarsk and the Altai Mountains), P. triaurelia (in Krasnoyarsk), and P. pentaurelia (in Novosibirsk, Altai Foreland, and Altai Mountains) was revealed. P. triaurelia and P. pentaurelia were found for the first time in Asia.

Animals↗
PubMed2006

Posttranscriptional control is a strong factor enabling exclusive expression of surface antigens in Paramecium tetraurelia.

Variable antigens are large proteins located on the outer membrane of parasitic but also of free-living protists. Multigene families encoding surface antigens demonstrate an exclusive expression of proteins. The resulting presence of just one protein species on the cell surface is required for surface antigen function; therefore, the molecular mechanism of exclusive expression is of main interest. Regulation of gene expression and mechanisms establishing switching of antigens are hardly understood in any organism. Here we report on the reaction of Paramecium to the artificial knock down of surface antigen 51A expression by bacteria-mediated RNAi. This technique involves the feeding of dsRNA-producing bacteria. We analyzed different fragments of the target gene for dsRNA template regarding their specific knock down efficiency and found great differences. Treatment of Paramecia with RNAi against the 51A antigen demonstrated that although a massive amount of mRNA was present, the protein was not detected on the cell surface. Moreover, a minor abundance of 51D transcripts resulted in an exclusive presence of 51D proteins on the cell surface. This posttranscriptional regulation was confirmed by the transcript ratio (51A/51D) determined by real-time (RT) PCR of single cells. Because we were able to document unexclusive transcription also in wild-type cells our results indicate that this posttranscriptional regulation is a main factor of enabling exclusive gene expression. The comparison of serotype shifts, caused by efficient and inefficient knock down, indicates an involvement of full-length transcripts in regulation of gene expression. Thus, our study gives new insights into the mechanism of exclusive expression on the molecular level: (i) exclusive transcription does not occur, (ii) posttranscriptional regulation is a powerful factor enabling exclusive antigen expression, and (iii) surface antigen mRNA is shown to be involved in this mechanism in a regulating way.

Animals↗
PubMed1976

Complement consumption in fresh blood sera by double culture of Paramecium caudatum and Aerobacter cloacae compared with survival and stage of disease in some malignant tumors in man.

Using the complement consumption test by double culture of Paramecium caudatum and Aerobacter cloacae (DPA) as antigen we examined blood sera and compared survival rates and stage of disease in 124 patients with carcinoma of cervix uteri, corpus uteri, ovaries and breast. The evidence suggests that bacteria Aerobacter cloacae constitute the proper antigenically effective substances of DPA. The intensity of reaction and therapy the relative titres of antibodies detected by the test were expressed by the amount of complement consumed in the reaction and designated by the abbreviation "NMHD", i. e. number of minimum haemolytic doses of complement fixed by antigen in the reaction. Patients with NMHD above 8 (i. e. with an intensive reaction corresponding to a high level of antibodies) exhibited partly higher three-year survival rates -- starting from the time of diagnosis, partly more often the clinical stages of disease I or II as compared with patients with NMHD below 4. The best survival rates were found in patients with NMHD above 8 and clinical stage I or II. NMHD values in patients with the initial period of disease and in healthy women did not differ substantially.

Animals↗
PubMed1975

[Symbiotic bacteria of the macronucleus of Paramecium caudatum].

Particles of a newly described endosymbiont of Paramecium caudatum, clone M-115, here referred to as iota--particles, are Gram--negative bacteria. The symbionts are only present within macronuclei and not in the cytoplasm or in the micronuclei. The cells of clone M-115 iota do not display any killer-effect when mixed with "clean" cultures of Paramecia. In life cycle of the symbiont, there is an alternation of two morphological forms: a spindle-shaped form 2.0--2.5 microns long and a rod-shaped form -- about 18 microns long. The data obtained revealed a high ability to infect cell of "clean" clones of P. caudatum with iota-particles. The antagonistic relationships between two different species of endonucleosymbionts: iota- and omega-particles, are detected. The revealed biological features of iota can be used for studying the mechanisms of nuclear differentiation in ciliates.

Animals↗
PubMed2000

A comparative hybridization analysis of yeast DNA with Paramecium parafusin- and different phosphoglucomutase-specific probes.

Molecular probes designed for the parafusin (PFUS), the Paramecium exocytic-sensitive phosphoglycoprotein, gave distinct hybridization patterns in Saccharomyces cerevisiae genomic DNA when compared with different phosphoglucomutase specific probes. These include two probes identical to segments of yeast phosphoglucomutase (PGM) genes 1 and 2. Neither of the PGM probes revealed the 7.4 and 5.9 kb fragments in Bgl II-cut yeast DNA digest detected with the 1.6 kb cloned PFUS cDNA and oligonucleotide constructed to the PFUS region (insertion 3--I-3) not found in other species. PCR amplification with PFUS-specific primers generated yeast DNA-species of the predicted molecular size which hybridized to the I-3 probe. A search of the yeast genome database produced an unassigned nucleotide sequence that showed 55% identity to parafusin gene and 37% identity to PGM2 (the major isoform of yeast phosphoglucomutase) within the amplified region.

Animals↗
PubMed1975

Genetic dissection of the excitable membrane of Paramecium.

Paramecium aurelia is chosen as the material for a genetic dissection of the excitable membrane. The simple innate behavior makes the behavioral analyses easy and mutant screening possible. Autogamy, which leads to complete homozygosity, guarantees the expression of recessive mutations. The size of these giant cells allows intracellular recording in electrophysiological studies.--Some two hundred lines of behavioral mutants are isolated. Several of them are studied in detail genetically, behaviorally as well as electrophysiologically. Mutants devoid of proper active electrogenesis are now available. Some of them are shown to be temperature-dependent. They have a slightly aberrant electric pattern when grown at the permissive temperatures and lose their excitability completely when cultured at the restrictive temperatures.--Systematic modifications of the membrane excitation process is demonstrated in this interdisciplinary study. Three unlinked mutations are shown to block the generation of Na-triggered depolarizations at different positions resulting in three different altered forms of electrical activities. The bioelectric profiles of 25 types of single or double mutants are now known. The search for the relevant gene products on the surface membrane is now underway.

Animals↗
PubMed1993

Swimming velocity of Paramecium under the conditions of weightlessness.

During the 6 min-lasting "free-fall conditions" (4 x 10(-6) g) of the parabolic flight of a sounding rocket Paramecium aurelia cells showed an increase of 7.5 % in their mean swimming velocity. A detailed analysis revealed that the kinetic response was transient: after 3 min the velocity decreased to the speed of the former horizontal swimming at 1 g. Control experiments simulating the influence of vibration and hypergravity during launch of the rocket lead to the conclusion that the increase of the velocity during the parabolic flight was exclusively induced by the transition to 0 g. An increased velocity was also observed under the condition of simulated weightlessness on a fast-rotating clinostat microscope.

Acceleration↗