bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genes of Acanthamoeba: DNA, RNA and Protein Sequences (A Review)1
Authors: BYERS THOMAS J. , HUGO ERIC R. , STEWART VALERIE J. 
Published: May 2007

ABSTRACTThis review summarizes knowledge about the structure of nuclear genes and mitochondrial DNA in Acanthamoeba. The information about nuclear genes is derived from studies of DNA, RNA and protein sequences. The genes considered are those for 5S, 5.8S and 18S rRNA, actin I, profilins Ia/b and II, myosins IB, IC and II, and calmodulin. All of the sequences show strong similarities to comparable sequences from other organisms. Introns have been found in the actin and myosin genes. The location of the actin intron is unique, but many of the myosin introns occur at the same sites as introns in myosins of other organisms. Sequence comparisons, especially of 5S and 5.8S rRNA and actin, support previous evidence, based primarily on 18S rRNA, that Acanthamoeba genes are at least as closely related to those of higher plants and animals as they are to various other protistan genera. The functional organization of the promoter region for the nuclear rDNA transcription unit has been studied extensively, but there is a need for information about the functional organization of regulatory sequences for other genes. Restriction fragment length profile (RFLP) studies of mitochondrial DNA reveal relatively high levels of overall sequence diversity, but information on the structure and function of individual genes is needed. The RFLP appear to have potential as tools for taxonomic studies of this genus.
Regulation of Ornithine decarboxylase activity in the Growth cycle of Tetrahymena thermophila
Authors: EICHLER WOLFGANG 
Published: May 2007

ABSTRACTCells of the Ciliated Protozoan Tetrahymena Theermophila, grown in proteose peptone medium to late logarithmic phase, harvested by centrifugation, and resuspended in fresh medium to almost the same cell density, underwent one more divison cycle within 5 h after inoculation, thereafter being definitely in full stationary phase. This growth cycle proved to be a useful tool to investigate the activation and deactivation of ornithine decarboxylase ODC1 in Tetrahymena: In late logarithmic phase the cells contained a very low specific activity of ODC of 3 nmol Co2.h‐1. mg‐1 in the soluble protein fraction. After growth stimulation the cells the activity was increased up to 100‐fold within 1 h. This high activity was maintained for about 5 h‐ about as long as divison activity—then rapidly declined with a half life time(t1/2 of about 15 min to the original low level.Inhibition assays with cycloheximide and actionomycin D revealed that: i. the rapid increase of ODC activity was biphasic with one component of translation ofpreexisting mRNA and one component of translation of newly transcribed mRNA; ii. the1/2 of the mRNA of ODC was estimated to be about 2 h; iii. inhibition of protein biosynthesis before ODC inactivation at 5 h caused a decrease of ODC with t1/2 of 55 min instead of 15 min.These findings suggest that ODC activity in Tetrahymena is regulated on both leavels: transcriptition and translation and translation and by an inactivating protein factor which is regulated at the level of biosynthesis.
Temperature‐Sensitive Responses in Blepharisma
Authors: MATSUOKA TATSUOMI , MAMIYA RYUSUKE , TANEDA KOJI 
Published: May 2007

ABSTRACTTemperature sensitivity of Blepharisma cultured at 23°C was investigated in a temperature range between 18.5°C and 33.5°C. The cells accumulated in an optimal temperature (ca. 27°C) region when they were placed in a chamber with a temperature gradient, although a certain population of the cells accumulated at much higher temperatures. The quantitative analysis of behavioral responses exhibited by the cells revealed that three types of thermal response were responsible for thermoaccumulation of the cells in an optimal temperature: (1) an increase in the frequency of thermophobic response in the cells swimming away from the optimal temperature region; (2) acceleration of forward swimming velocity of the cells swimming toward the optimal temperature region; and (3) higher frequency of spontaneous ciliary reversal of the cells in higher temperature regions.
Development of Amblyospora campbelli (Microsporida: Amblyosporidae) in the Mosquito Culiseta incidens (Thomson)
Authors: DICKSON DAVID L. , BARR A. RALPH 
Published: May 2007

ABSTRACTThe complete life cycle of Amblyospora campbelli (Kellen and Wills, 1962) (Microsporida: Amblyosporidae) requires a two‐host system involving the mosquito host, Culiseta incidens (Thomson), and an obligatory intermediate copepod host. The parasite has dimorphic spore development producing meiospores (haploid condition) and binucleated spores (diploid condition), either as an exclusive infection or simultaneously (within females only). This is the 1st known report of concurrent spore development within an adult mosquito host, and, therefore, shows the Amblyospora campbelli system to be uniquely different from other Amblyospora spp. cycles previously described. The significance of dimorphic spore development is discussed. In females, diplokaryotic meronts may invade oenocytes, causing a benign‐type of infection. A blood‐meal is required to initiate sporulation of the binucleate spore. The binucleate spore contains the sporoplasm involved in transovarial transmission. A 2nd sporulation sequence, primarily in adipose tissue, may involve both males and females. In this sequence, repeated merogonic division greatly increased the density of diplokaryotic meronts and generally involved most of the body of the host. Production of meiospores, unlike that for the binucleate spore, appeared to be spontaneous (i.e. no obligatory blood meal). Survivorship of male and female larval mosquitoes was nearly equal. Adult females spread the parasite in three ways: transovarial, transovum, and by meiospore deposition.
Analysis of Chlamydomonas reinhardtii Histones and Chromatin
Authors: MORRIS RODNEY L. , KELLER LAURA R. , ZWEIDLER ALFRED , RIZZO PETER J. 
Published: May 2007

ABSTRACTChromatin spreads made from isolated nuclei of the unicellular green alga Chlamydomonas reinhardtii show the beaded fibers typical of eukaryotic polynucleosomes. Micrococcal nuclease digestions confirmed the presence of nucleosomes with a repeat length of 189 base pairs, essentially the same as typical mammalian cells. Basic nuclear proteins extracted from isolated nuclei or chromatin with 1 M calcium chloride and 0.3 M hydrochloric acid are resolved into seven major components by electrophoresis in the presence of sodium dodecyl sulfate (SDS). These seven components were subjected to qualitative peptide mapping with V8 protease on SDS gels for comparison with the major histone components of calf thymus. Finally, the C. reinhardtii basic nuclear proteins were fractionated by reversed phase high performance liquid chromatography and their amino acid composition determined. From these studies, we conclude that C. reinhardtii has a full complement of the five histones with properties very similar to those of both higher animals and higher plants.
Cytopathic Action of Naegleria fowleri Amoebae on Rat Neuroblastoma Target Cells
Authors: MARCIANO‐CABRAL FRANCINE , ZOGHBY KATHY L. , BRADLEY S. GAYLEN 
Published: May 2007

ABSTRACTThe axenically cultured, weakly pathogenic Naegleria fowleri LEE and the highly pathogenic, mouse passaged N. fowleri LEEmp are cytopathic for B103 rat nerve cells in culture. Cytopathogenicity was measured by release of radiolabeled rubidium or radiolabeled chromium from B103 target cells. Cytopathogenicity was time‐dependent for up to 18 h and dependent upon amoebae effector to nerve cell target ratios of less than 1:1. Release of51 Cr from B103 cells by either LEE or LEEmp amoebae was enhanced by addition of calcium or magnesium to medium free of these divalent cations but the ion‐channel inhibitor, verapamil, or the ionophore A23187 and phorbol myristate acetate did not alter release of 51 Cr from B103 cells cocultured with the amoebae. Cycloheximide or actinomycin D impaired release of 51 Cr from B103 target cells injured by either LEE or LEEmp amoebae. Both strains of amoebae were fractionated by glass bead disruption and high speed centrifugation into membrane and soluble fractions. Each fraction was incubated with either 86Rb or 51 Cr labeled nerve cells. The membrane fraction from LEEmp was more active than the soluble fraction in facilitating rubidium and chromium release. In contrast, the soluble fraction from LEE was more active than the membrane fraction in facilitating rubidium release from radiolabeled target cells. The sequential release of 86Rb and 51 Cr from target cells rather than the simultaneous release of the two isotopes indicates that target cell death is due to the release of ions followed later by the release of large macromolecules. The results indicate that N. fowleri amoebae injure nerve cells by two alternate mechanisms, trogocytosis or contact‐dependent lysis.
Relationship Between Spatial Pattern of Basal Bodies and Membrane Skeleton (Epiplasm) During the Cell Cycle of Tetrahymena: cdaA Mutant and Anti‐Membrane Skeleton Immunostaining
Authors: KACZANOWSKA JANINA , BUZANSKA LEONORA , OSTROWSKI MAREK 
Published: May 2007

ABSTRACTMicrotubular basal bodies and epiplasm (membrane skeleton) are the main components of the cortical skeleton of Tetrahymena. The aim of this report was to study functional interactions of basal bodies and epiplasm during the cell cycle. The cortex of Tetrahymena cells was stained with anti‐epiplasm antibody. This staining produced a bright epiplasmic layer with a dark pattern of unstained microtubular structures. The fluorescence of the anti‐epiplasm antibody disappeared at sites of newly formed microtubular structures, so the new basal body domains and epiplasmic layer could be followed throughout the cell cycle.Different patterns of deployment of new basal bodies were observed in early and advanced dividers. In advanced dividers the fluorescence of the epiplasmic layer diminished locally within the forming fission line where the polymerization of new basal bodies largely extincted. In wild type Tetrahymena, the completion of the micronuclear metaphase/anaphase transition was associated with a transition from the pattern of new basal body deployment and epiplasm staining of the early divider to the pattern of the advanced dividers. The signal for the fission line formation in Tetrahymena (absent in cdaA1 Tetrahymena mutationally arrested in cytokinesis) brings about 1) transition of patterns of deployment of basal bodies and epiplasmic layer on both sides of the fission line; and 2) coordination of cortical divisional morphogenesis with the micronuclear mitotic cycle.
Directed Positioning of Micronuclei in Paramecium tetraurelia with Laser Tweezers: Absence of Detectible Damage After Manipulation
Authors: AUFDERHEIDE KARL J. , DU QING , FRY EDWARD S. 
Published: May 2007

ABSTRACTPossible covert damage from the use of the laser optical force trap (laser tweezers) to reposition micronuclei in Paramecium tetraurelia was assessed by measuring proliferation rates and postautogamous survival and mutation rates of cells after laser manipulations. No differences in subsequent daily proliferation rates among laser manipulated and various control classes of cells were seen. Similarly, the rates of postautogamous lethality and of “slow growth mutations” after repositioning of both micronuclei were not different from such rates in unmanipulated controls. In spite of extensive manipulations of micronuclei by the laser tweezers, there is no evidence of any damage induced by these manipulations. The laser tweezers therefore appears to be a tool of benign effect upon living cells, with tremendous potential use in many cell and developmental biological investigations.
Aminotransferase and the Production of Alanine During Hyperosmotic Stress in Paramecium calkinsi
Authors: CRONKITE DONALD L. , DIEKMAN ALAN B. , LEWALLEN BETH , PHILLIPS LISA 
Published: May 2007

ABSTRACTWhen Paramecium calkinsi encounter hyperosmotic stress, intracellular free alanine increases. In vivo assays indicate that the reaction catalyzed by alanine aminotransferase contributes to the build up of alanine in response to hyperosmotic shock. 14C‐pyruvate is converted to 14C‐alanine in cells grown axenically at 200 mosm. When shifted to 600 mosm, the rate of conversion of pyruvate to alanine increases, and conversion at either 200 or 600 mosm is blocked by 1 mM aminooxyacetic acid (AOA), an inhibitor of aminotransferase. Intracellular free alanine increase is partially inhibited by AOA, and AOA prevents cells living in fresh water from acclimating to higher salinities, an indication that the increase in intracellular alanine is physiologically significant.
Characterization of Pneumocystis carinii Preparations Developed for Lipid Analysis
Authors: KANESHIRO EDNA S. , WYDER MICHAEL A. , ZHOU LINDA HUA , ELLIS JAYNE E. , VOELKER DENNIS R. , LANGRETH SUSAN G. 
Published: May 2007

ABSTRACT Pneumocystis carinii organisms were isolated from viral antibody‐negative rats that had been infected by intratracheal intubation of organism preparations tested negative for common bacteria and fungi. Infection scores of lungs from infected animals at the time of parasite isolation was > 5 (100‐1,000 organisms/oil immersion field). Electron microscopy of heavily infected lungs revealed that the pathogens adhered to Type I pneumocytes and to each other, resulting in obstructions up to several cell layers thick, which extended into the alveolar lumen. Protocols for purifying the organisms were developed to optimize separation from each other and from host cells, and to optimize preparation purity, recovery efficiency, and organism viability. The study tested mucolytic agents, sieving, various centrifugation speeds, lysis of host cells by osmotic shock and filtration through membranes of different pore diameter. Final preparations contained no intact host cells as determined by light microscopy. Only minor amounts (< 5%) of host debris were detected by electron microscopy. Most organisms and their pellicles were ultrastructurally intact but no longer adhered to one another. The final preparation was characterized biochemically by quantitation of the specific lung surfactant marker surfactant protein A, which indicated > 99.5% purity. The total non‐P. carinii protein in the final preparation (< 6%, depending on the level of infection) was estimated by the protein content of pelletable material resulting from processing uninfected lungs in an identical manner. Elimination of free cholesterol and phospholipids from host lung tissue was monitored during the purification process. Exogenous stigmasterol, added as an extracellular marker, decreased during the purification process and was undetectable in the final organism preparation. Yields of 108‐109 organisms/rat were routinely obtained. Viability, assessed by the calcein acetoxymethyl ester‐propidium iodide assay, was 80–95%.
Genes Encoding Antigenic Surface Glycoproteins in Pneumocystis from Humans
Authors: STRINGER SAUNDRA L. , GARBE THOMAS , SUNKIN SUSAN M. , STRINGER JAMES R. 
Published: May 2007

ABSTRACT Pneumocystis is a eukaryotic microbe that causes pneumocystosis, an AIDS‐associated pneumonia. Pneumocystosis also occurs in many other mammalian species, and animal‐derived organisms have been extensively utilized in Pneumocystis research. Pneumocystis from diverse hosts contain a large glycoprotein (gpA/MSG) on the surface. Antibodies elicited against gpA/MSG of Pneumocystis from humans sometimes cross‐react with epitopes on proteins of similar size from Pneumocystis from other host species. Here we report the isolation and partial sequence of two presumptive gpA/MSG genes from human‐derived Pneumocystis. The cloned human‐derived Pneumocystis gpA/MSG genes and predicted peptides were different from those previously isolated from Pneumocystis from rats and ferrets. The genome of human‐derived Pneumocystis contained multiple copies of sequences related to the two cloned gpA/MSG genes.
Cilia‐Mediated Oriented Chemokinesis in Tetrahymena thermophila
Authors: LEICK VAGN , KOPPELHUS UFFE , ROSENBERG JENS 
Published: May 2007

ABSTRACTThe role of the cilia in the locomotion (“gliding”) of Tetrahymena thermophila in a semi‐solid medium has been studied when cells were migrating in gradients of attractant. Video recordings and computer‐aided motion analysis of migrating cells and their ciliary activity show that Tetrahymena thermophila migrate by swimming forward in semi‐solid methyl cellulose, using their cilia. Ciliary reversals occur at certain intervals and cause a termination (“stop”) of cellular migration. Cells with reversed cilia resume forward migration when normal ciliary beating resumes. In gradients of attractants, cells migrating towards the attractant suppress ciliary reversals, which leads to longer runs between stops than in control cells. Cells migrating away from the attractant have a higher frequency of ciliary reversals than the control cells resulting in shorter runs. Stimulated cells adapt to a particular ambient concentration of attractant several times during migration in the gradient. Adaptation is followed by de‐adaptation, which occurs during the “stop”. In the presence of cycloheximide, a strong inhibitor of chemoattraction, the attractant‐induced suppression of ciliary reversal is abolished (cells become desensitized to the attractant). It is concluded that Tetrahymena has a short‐term memory during adaptation. This is important for the efficiency of migration towards an attractant.
The Role of Trichocyst Discharge and Backward Swimming in Escaping Behavior of Paramecium from Dileptus margaritifer1
Authors: HARUMOTO TERUE 
Published: May 2007

ABSTRACTTrichocyst discharge is an effective defense of Paramecium against Dileptus margaritifer. The possible defensive function of backward swimming, which often follows trichocyst discharge upon Paramecium‐Dileptus encounters was studied. Mutants incapable of backward swimming (pawnA in P. tetraurelia, cnrA in P. caudatum) escaped from dilepti nearly as frequently as wild‐type cells. Double mutants (pawnA‐nd7, cnrA‐tnd2) were eaten nearly as frequently as mutants incapable of trichocyst discharge. Thus, in the defense of Paramecium against D. margaritifer, the role of backward swimming is minor, if any, compared to trichocyst discharge. Among escaped cells, about a half of wild‐type and essentially none of pawnA (cnrA) cells showed backward swimming. Paramecium behavior during the encounter can be mimicked by the local, not global, application of lysozyme which is a strong secretagogue of trichocyst.
Characterization of the Eyespot Regions of “Blind”Chlamydomonas Mutants after Restoration of Photophobic Responses
Authors: LAWSON MOIRA A. , SATIR PETER 
Published: May 2007

ABSTRACT Chlamydomonas reinhardtii exhibits photophobic and positive and negative phototactic responses that can be defined for cell populations using computerized cell tracking and motion analysis. Mutants CC‐2359 and FN68 are pigment deficient mutants that are blocked in carotenoid synthesis and lack these photo responses. In particular, neither mutant exhibits flash‐induced photophobic responses to visible light stimuli to which wild‐type gametic cells exhibit a strong response, with several behavioral stages. Upon addition of all‐trans retinal to these mutants, the photophobic responses are restored with minor quantitative differences from wild‐type populations. Using both light and electron microscopy, we have compared the ultrastructural characteristics of wild‐type C. reinhardtii to those of both mutants. As previously described, wild‐type cells contain an eyespot consisting of 2–4 layers of pigmented granules encased within thylakoid membranes, located between the distal extremities of the flagellar root. This structure is also visible as an orange‐red spot in light microscopy. The photoreceptor is thought to be concentrated in the plasma membrane above the eyespot. The mutant, CC‐2359, lacks this eyespot as seen by both light and electron microscopy, even when the photophobic response has been restored. FN68‐like mutants studied earlier by Morel‐Laurens and Feinlieb and others contain an eyespot which can be seen only by electron microscopy. In FN‐68, the eyespot generally has the same dimensions as in wt cells, differing mainly in pigment granule appearance. Consistent with these findings, several laboratories have shown that the full range of phototactic responses can be reconstituted in FN68 and CC‐2359, but that negative phototaxis requires a significantly stronger light stimulus in the latter strain. We confirm the suggestion that the eyespot is not necessary for the photophobic response, and is not critical for the appropriate assembly and function of the photophobic response receptor in the membrane. Furthermore, the locus of reconstitution of the functional receptor is not the eyespot. Because of the definitive demonstration of the absence of the eyespot in CC‐2359, however, the eyespot may play a role in negative phototaxis.
A New rDNA Repeat Unit in Human Giardia
Authors: UPCROFT JACQUELINE A. , HEALEY ANDREW , UPCROFT PETER 
Published: May 2007

ABSTRACTThe rDNA repeat unit from a new human Giardia duodenalis strain shows significant differences from the previously reported G. duodenalis rDNA repeat. Twelve base‐pair changes occurred in 490 bp of the SSrRNA gene and new restriction enzyme sites occurred in the LSrRNA gene. The overall length of the rRNA genes is the same but the spacer is 76 bp longer than previously reported. A boundary within the spacers of the two different rDNA units divides a region of 50% homology near the LSrRNA gene from a region of 80% homology toward the SSrRNA gene. This boundary region includes two copies of a 78 bp repeat.
Isolation of the Flagellar Swelling and Identification of Retinal in the Phototactic Flagellate, Ochromonas danica (Chrysophyceae)
Authors: WALNE PATRICIA L. , PASSARELLI VINCENZO , LENZI PAOLA , BARSANTI LAURA , GUALTIERI PAOLO 
Published: May 2007

ABSTRACT Ochromonas danica, a freshwater, planktonic chrysophyte, is capable of sensing the light conditions of its environment. This biflagellate alga has a swelling near the base of the short flagellum and a chloroplastidic stigma in close association with it. A procedure is described for the isolation of this three dimensional flagellar swelling, the presumed photoreceptor. In contrast to an earlier method developed for the isolation of the paraflagellar swelling from Euglena gracilis, the protocol reported here for Ochromonas results in higher yields that should facilitate future biochemical investigations and could open avenues of investigation for the isolation and purification of the presumptive receptor protein. To verify the hypothesis that a rhodopsin‐like protein might be present in this alga, we applied a standard extraction procedure successfully used in the identification of retinal. We here report the purification and identification of all‐trans retinal in Ochromonas cells by column chromatography, HPLC and GC‐MS. Since retinal is the chromophore of rhodopsin‐like proteins, this finding may suggest that in these unicellular algae, too, a rhodopsin‐like protein could be the photoreceptor pigment.
Transcription Factor Genes from Rat Pneumocystis carinii
Authors: SUNKIN SUSAN M. , STRINGER JAMES R. 
Published: May 2007

ABSTRACTGenes encoding the TFIID TATA‐box binding protein (TBP) from two probable species of rat Pneumocystis carinii (prototype and variant) were sequenced. The two P. carinii TBP gene sequences were 91% identical to each other, and 65‐77% identical to TBP genes from other species. A cDNA from one of the two P. carinii TBP genes was sequenced, which showed that four small introns resided in identical positions within the TBP genes from the prototype and variant rat P. carinii. Conservation of the 180 amino acids that constitute the conserved core of TBP was 97% between the P. carinii TBP, which were 95% and 97% identical to conserved core sequences of TBP from Saccharomyces cerevisiae and Schizosaccharomyces pombe respectively.