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PubMed2004

Zooidogamy in the Late Permian genus Glossopteris.

We describe details of anatomically preserved fossil glossopterid ovules from the Late Permian of Queensland, Australia, that contain several pollen tubes at various stages of releasing flagellated sperm. Each sperm is approximately 12.7 microm long and 13.9 microm wide, with a conspicuous spiral structure comprised of a series of dots that resemble the position of basal bodies of flagella aligned along the multilayered structure (MLS). This configuration is similar to the helically arranged flagella in the sperm of cycads, Ginkgo, and many pteridophytes. However, the motile gametes of Glossopteris are considerably smaller than those of Ginkgo and cycads, and more similar in size, number of basal bodies, and number of gyres in their helix to pteridophyte forms. Glossopteris thus shares the intermediate stage of motile male gamete formation and apparently that of haustorial pollen tubes with cycads and Ginkgo.

Cycadopsida↗
PubMed2005

Size distribution in ultraphytoplankton: a comparative analysis of counting methods.

Water samples taken at three depth layers from the offshore oligotrophic Cretan Sea were analyzed for ultraphytoplankton size fractionation using different methods: (a) sequential filtration on filters of pore size 5, 1 and 0.2 microm, (b) separate filtration using filters 5 and 0.2 microm as well as 1 and 0.2 microm and (c) direct filtration on 0.2 microm filters after staining of the samples with DAPI. Total abundance of photosynthetic organisms as well as the abundance of different groups such as flagellates and cyanobacteria measured by means of sizing after DAPI staining were significantly higher than those obtained by the other methods. This indicates that although there were no significant differences between the estimates provided by the separate and sequential filtration, both these methods underestimated total abundance by at least 25-50%. The estimates for the size fractions were also found to range from relatively imprecise to completely unreliable depending on the group and the size range. Although size fractionation through direct observation after staining largely depends on the expertise of the observer, this study suggests that it may provide more informative estimates than the other two methods. Although it is difficult to generalize the results of this study in a global context, the paper provides strong indications on the limitations of the sequential and separate methods for size fractionation of photosynthetic organisms and implies that their results are likely to be less accurate than is presently believed.

Analysis of Variance↗
PubMed1989

Binding of lectin-gold conjugates by two Trypanosoma cruzi strains in ampullae and rectum of Triatoma infestans.

The ampullae and recta of Triatoma infestans infected with Trypanosoma cruzi were incubated with lectin-gold conjugates of wheat germ agglutinin (WGA) and soy bean agglutinin (SBA) and investigated by electron microscopy. T. cruzi colonized the whole lumen of the ampullae. The rectal pads with their intensive intracellular membrane system and thin cuticle were often covered by a compact layer of flagellates, whereas the remaining rectal sac- recognizable by a thick layered cuticle - was colonized less densely. All freely accessible stages of T. cruzi strain 'Chile 5' (Zymodeme 1) showed a reaction with SBA-gold complexes but not with WGA, revealing that N-acetyl-galactosamine and/or galactose but no N-acetyl-glucosamine residues were present on the surface. T. cruzi strain 'Chile 7' (Zymodeme 2) also reacted with SBA. WGA-bovine serum albumin-gold conjugates bound strongly to the surface of epimastigotes of this strain, in variable amounts to stages in transition to trypomastigotes, but not to metacyclic trypomastigotes.

Animals↗
PubMed1979

Detection and characterization of DNA polymerase from Trypanosoma brucei.

The predominant DNA polymerase activity has been isolated from the parasitic flagellated protozoan, Trypanosoma brucei. Like mammalian DNA polymerase-alpha the trypanosome DNA polymerase is of large molecular weight (S, 6--8), is resistant to thermal denaturation, is sensitive to N-ethylmaleimide, and is inhibited by high ionic strength. However, specific antisera that cross-react with mammalian DNA polymerase-alpha from different species fail to cross-react with the trypanosome polymerase.

Animals↗
PubMed1980

In vitro polymerization of polyhook protein from Salmonella SJW880.

Polyhooks were isolated from Salmonella SJW880, a non-flagellated mutant, and purified by cesium chloride density gradient centrifugation. The polyhooks were disintegrated into protein subunits (monomer) by heat in the absence of salt. The monomer was repolymerized in the presence of moderately high concentrations of sodium citrate at neutral pH. Three types of polymer were produced. One type of polymer, produced at room temperature and at citrate concentrations less than 0.3 M, had no regular shape and no definite thickness. Another type of polymer, produced at room temperature and at citrate concentrations greater than 0.4 M, had a straight shape and a similar thickness to that of polyhook but was easily dissociated into monomer in the absence of salt. A third type of polymer was produced at low temperature, independently of the concentration of citrate, and seemed to be a tubular polymer with a thickness similar to that of polyhook but had no helical curvature. However, this type of polymer was shown to have a structure locally the same as that of polyhook by electron microscopic observation, optical diffraction and circular dichroism measurements.

Bacterial Proteins↗
PubMed1991

Photoisomerization of retinal at 13-ene is important for phototaxis of Chlamydomonas reinhardtii: simultaneous measurements of phototactic and photophobic responses.

A real-time automated method was developed for simultaneous measurements of phototactic orientation (phototaxis) and step-up photophobic response of flagellated microorganisms. Addition of all-trans retinal restored both photoresponses in a carotenoid-deficient mutant strain of Chlamydomonas reinhardtii in a dose-dependent manner. The phototactic orientation was biphasic with respect to both the light intensity and the concentration of retinal. All-trans retinal was more effective than 11-cis retinal to regenerate both photobehavioral responses. Analogs having locked 11-cis configurations and a phenyl ring in the side chain also induced photoresponses, although at concentrations more than two orders of magnitude higher than all-trans retinal. According to the present assay method, the responses were hardly detectable in cells incubated with retinal analogs in which the 13-ene was locked in either its trans or cis configuration. The results strongly suggest that the isomerization of the 13-14 double bond is important for photobehavioral signal transduction and that a single retinal-dependent photoreceptor controls both phototactic and photophobic responses.

Cell Movement↗
PubMed1984

Differential effects of inhibitors of purine metabolism on two trichomonad species.

Tritrichomonas foetus and Trichomonas vaginalis are both incapable of de novo purine nucleotide synthesis. Previous studies indicated that T. foetus relies mainly on the salvage of hypoxanthine and subsequent conversion of IMP to AMP and GMP, whereas T. vaginalis depends on direct conversions of exogenous adenosine to AMP and guanosine to GMP without much interconversion between the two nucleotides. These two different types of purine salvage suggest the possibility of differential sensitivities between the two species of trichomonad flagellates toward different purine antimetabolites. Mycophenolic acid, hadacidin, 8-azaguanine, and formycin B inhibited the growth of T. foetus but had no effect on T. vaginalis. Mycophenolic acid acted by blocking conversion of IMP to GMP, hadacidin inhibited conversion of IMP to AMP, and 8-azaguanine was incorporated into the T. foetus nucleotide pool, likely via hypoxanthine phosphoribosyl transferase. Formycin B was converted to 5'-monophosphate in T. foetus and inhibited the conversion of IMP to AMP. Its precise mechanism of action on T. foetus remains, however, to be elucidated. Alanosine, whose ribonucleotide derivative is a potent inhibitor of adenylosuccinate synthetase, had no effect on the growth or hypoxanthine incorporation in T. foetus, which may be due to the lack of conversion of alanosine to the ribonucleotide because of the absence of de novo purine nucleotide synthesis in parasites. Four adenosine analogs, adenine arabinoside, tubercidin, sangivamycin, and toyocamycin, were found inhibitory to the growth of T. vaginalis but showed little effect on T. foetus growth. Further investigations suggested that these four compounds acted on T. vaginalis by blocking incorporation of adenosine into the adenine nucleotide pool.

Alanine↗
PubMed1993

Role of cyclic GMP in the mediation of circadian rhythmicity of the adenylate cyclase-cyclic AMP-phosphodiesterase system in Euglena.

Cyclic AMP (cAMP) and cyclic GMP (cGMP) are two second messengers that have been proposed to act as a dualistic system in biological regulation. To determine if cGMP plays a role in the mediation of circadian rhythmicity of the adenylate cyclase (AC)-cAMP-phosphodiesterase (PDE) system in the achlorophyllous ZC mutant of the unicellular flagellate Euglena, the levels of cAMP and cGMP were monitored in synchronized cell populations, and the effects of the cGMP analog 8-bromo-cGMP (8-Br-cGMP) and the cGMP inhibitor 6-anilinoquinoline-5,8-quinone (LY 83583) on the activity of AC and PDE, as well as on the level of cAMP, were measured in vivo. A bimodal, 24-hr rhythm of cGMP content was found in both dividing and nondividing cultures in either a 12-hr:12-hr light-dark cycle or constant darkness. The peaks and troughs of the cGMP rhythm occurred 2 hr in advance of those of the cAMP rhythm that has been reported previously. The addition of 8-Br-cGMP at different circadian times increased the cAMP level in vivo by two to five times, whereas LY 83583 reduced the amplitude of the cAMP rhythm so that it disappeared. The effects of 8-Br-cGMP on the activity of AC and PDE were circadian phase-dependent and consistent with the changes in cAMP content. These findings suggest that cGMP may serve as an upstream effector that mediates the cAMP oscillation by regulation of the AC-cAMP-PDE system.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Biosynthetic preparation of radioactively labelled ethanolamine plasmalogen (1-O-[1'-14C]octadec-1'-enyl-2-acyl-sn-glycero-3-phosphoethanola mine) using a protozoan cell culture.

Ethanolamine plasmalogen radiolabelled mainly in the O-alkenyl moiety was prepared from cell suspension cultures of the flagellate Leishmania donovani previously incubated with [1-14C]octadecanol over one growth period. The optimal concentration of [1-14C]octadecanol for labelling was shown to be 1 microM, when 60% of total lipid radioactivity appeared in the 1,2-diradyl-sn-glycero-3-phosphoethanolamine fraction, with an overall yield of approx. 35%. Analysis of this fraction revealed that 93% of the label was present in O-octa-dec-1-enyl, 3% in O-alkyl and 4% in acyl moieties. A specific radioactivity of approx. 14 mCi/mmol was determined. Raising the culture medium concentration of [1-14C]octadecanol to 2 microM yielded a product with a specific radioactivity of 25 mCi/mmol.

Animals↗
PubMed1991

Reproductive cell specification during Volvox obversus development.

Asexual spheroids of the genus Volvox contain only two cell types: flagellated somatic cells and immotile asexual reproductive cells known as gonidia. During each round of embryogenesis in Volvox obversus, eight large gonidial precursors are produced at the anterior extremity of the embryo. These cells arise as a consequence of polarized, asymmetric divisions of the anteriormost blastomeres at the fourth through nine cleavage cycles, while all other blastomeres cleave symmetrically to yield somatic cell precursors. Blastomeres isolated from embryos at any point between the 2-cell and the 32-cell stage cleaved in the normal pattern and produced the same complement and spatial distribution of cell types as they would have in an intact embryo. This result indicates that intrinsic features control the cleavage patterns and developmental potentials of blastomeres, and rules out any significant role for cell-cell interactions in gonidial specification. When substantial quantities of anterolateral cytoplasm were deleted from uncleaved gonidia or 4-cell stage blastomeres, the cell fragments frequently regulated and embryos were produced with the expected number of asymmetrically cleaving cells and gonidial precursors at their anterior ends. However, when anterior cytoplasm was deleted from 8-cell stage blastomeres, the depleted cells frequently failed to cleave asymmetrically and produced no gonidial precursors. Furthermore, when compression was used to reorient cleavage planes at the fourth division cycle, so that anterior cytoplasm was transmitted to more than the normal number of cells, those cells receiving a significant amount of such cytoplasm cleaved asymmetrically to produce supernumerary gonidial precursors. Together, these last two experiments indicate that blastomeres in the V. obversus embryo acquire (at least by the end of the third cleavage cycle) a polarized organization in which anterior cytoplasm plays a causal role in the process of reproductive-cell specification.

Animals↗
PubMed1985

Cell cycle oscillators. Temperature compensation of the circadian rhythm of cell division in Euglena.

The effects of different constant temperatures ranging from 16 degrees to 32 degrees C on the free-running, circadian rhythm of cell division were examined in axenic, photoautotrophic batch cultures of the unicellular algal flagellate Euglena gracilis Klebs. A comparative study was undertaken on the wild-type (Z strain) and a diuron-(DCMU)-resistant (ZR) strain. Although the overall growth rate (g) of both strains was rather dependent on temperature, lengthening increasingly at temperatures both higher and lower than the optimum range (about 23 degrees-29 degrees C), the free-running period (tau) of the oscillator hypothesized to underlie the overt rhythmicity in the cell division cycle (CDC) was found to be temperature-compensated over at least a 10 degrees C range. The degree of temperature compensation was most striking in the Z strain (Q10 = 1.05) over the permissive temperature interval of 22 degrees-32 degrees C, where periodic growth could occur. This Z strain had a slightly faster growth rate and displayed a higher degree of synchrony than that observed in the ZR strain, whose circadian clock was not as well compensated (Q10 = 1.23) over the permissive temperature interval of 18 degrees-28 degrees C. These results imply that the CDC is regulated by a circadian oscillator sharing the same features as those generating the many other overt biochemical and physiological circadian periodicities that have been documented for Euglena.

Cell Division↗
PubMed1986

Giardia lamblia: electrophysiology and ultrastructure of cytopathology in cultured epithelial cells.

The pathogenicity of Giardia lamblia is a subject of debate. Some studies of human biopsy material have mentioned the presence of trophozoites inside the intestinal mucosa, while in others, flagellates have only been found attached to the epithelium. To study the possible cytopathic effects of G. lamblia cultured under axenic conditions, trophozoites of the human 1/Portland and WB strains were placed in contact with monolayers of Madin Derby Canine Kidney cells, a well characterized cell strain with morphological and functional properties similar to those of a transporting epithelium. After 24 and 48 hr of interaction, the effect of the parasite on epithelial cells was assessed by transmission, scanning, and freeze fracture electron microscopy. In addition, the possible action of living trophozoites and sonicates of G. lamblia on the transepithelial resistance of MDCK monolayers mounted in Ussing chambers was analyzed for periods varying up to 48 hr. The results demonstrate that G. lamblia trophozoites do not invade epithelial monolayers. Furthermore, the parasites fail to produce cytoplasmic changes on target cells and have no effect on transepithelial resistance as judged both electrophysiologically and by the failure to open the occluding junctions that bind together epithelial cells. Damage induced by the parasites to cultured cells was limited to focal distortion or depletion of microvilli at the site of adhesion, which may progress to leave circular areas devoid of microvilli, different from the adhesion marks reported by others for G. muris. Therefore, under the in vitro conditions described here, giardias showed no toxic or invasive effect.

Adhesiveness↗
PubMed1989

Trypanosoma cruzi: quantitative studies of development of two strains in small intestine and rectum of the vector Triatoma infestans.

This paper describes the development stages and numbers of flagellates of two strains of Trypanosoma cruzi living in the small intestine and rectum of the insect, Triatoma infestans, during the first 12 weeks postinfection (pi). Mainly epimastigotes and occasionally amastigotes and final trypomastigotes developed in the small intestine but after starvation periods of 3 or 4 weeks higher percentages of spheromastigotes including their transitional forms to/from epimastigotes were found. In the rectum, the percentage of final trypomastigotes increased in two steps; the second, but not the first, correlated with the development of intermediates originating from epimastigotes. For both strains the total number in the small intestine increased during the first 8 or 9 weeks, although there were reduced numbers when the bugs had starved for 3 or 4 weeks. In the rectum the numbers increased up to 10 weeks pi; only about 25% of these lived in the lumen, the others were located at the rectal wall. In small intestine and rectum the "Chile 5" strain of T. cruzi (zymodeme 1) nearly always reached higher population densities than the "Chile 7" strain (zymodeme 2).

Animals↗
PubMed1992

Leishmania major: differential regulation of the surface metalloprotease in amastigote and promastigote stages.

During its life cycle, the protozoan parasite Leishmania major alternates from an intracellular amastigote form in the mammalian host to a flagellated promastigote form in the insect vector. The expression of the surface metalloprotease (PSP) during differentiation in vitro was investigated by Western and Northern blots, by immunoprecipitation of cells metabolically labeled with [35S]methionine or labeled at the surface with radioactive iodine, and by quantification of the proteolytic activity in substrate-containing polyacrylamide gels. We report that the surface metalloprotease is down-regulated at both the mRNA and the protein level in amastigotes, where it represents less than 1% of the equivalent proteolytic activity detected in promastigotes. A significant amount of mRNA is detected 4 hr after the onset of differentiation. The expression of the protease begins at that time and reaches steady state 8 hr later. The synthesis of PSP precedes the complete morphological differentiation to the promastigote stage and the appearance of the lipophosphoglycan, another major promastigote surface component. In contrast to PSP, a family of mercaptoethanol-activated proteases present in the amastigote exists only at a reduced level in the promastigote. The confinement of the surface metalloprotease to the insect stage of the parasite suggests that it has no physiological function in the parasitism maintenance of mammalian host macrophages.

Animals↗
PubMed1986

The occurrence and distribution of alpha-hydroxy-acid dehydrogenase in some members of the order Kinetoplastida.

LDH-X is the isoenzyme of lactate dehydrogenase found in mammalian spermatozoa, occurring in cytosolic and mitochondrial locations. Gossypol strongly inhibits it, and the spermicidal action of this compound is attributed to the disruption of a reducing shuttle. The flagellated protozoan, Trypanosoma cruzi, contains an enzyme activity similar to LDH-X, called alpha-hydroxy-acid dehydrogenase, which is here shown to possess cytosolic and glycosomal components. The glycosome is a microbody-like organelle containing the early glycolytic enzymes. We postulate that the inhibition of replication of T. cruzi by gossypol derives from interference with glycosomal reducing shuttles. T. lewisi resembles T. cruzi in this respect.

Alcohol Oxidoreductases↗
PubMed1992

Diversion of the sign of phototaxis in a Chlamydomonas reinhardtii mutant incorporated with retinal and its analogs.

The blind mutant FN68 of the unicellular flagellate green alga Chlamydomonas reinhardtii is negatively phototactic in the presence of the native chromophore all-trans retinal. In contrast, analog chromophores such as a ring-acyclic retinal and those in which trans/cis isomerization about the C11 = C12 double bond was blocked induced predominantly positive phototaxis in the same strain under the same experimental conditions. These observations can be interpreted by assuming that the negative and the positive phototaxis is mediated distinctively by two rhodopsin species which differ in their affinities with the exogenous chromophores. However, a more reasonable explanation, which requires fewer assumptions, is that the sign of phototaxis depends on a delay in intracellular photosignal transduction. This novel view was deduced directly from the widely accepted hypothesis [1980, Microbiol. Rev. 44, 572-630] on phototaxis mechanisms.

Animals↗
PubMed1988

Polysaccharide and glycolipid composition in Tritrichomonas foetus.

1. The polysaccharide and glycolipid composition in Tritrichomonas foetus was studied by paper, thin-layer and gas-liquid chromatographic analysis. 2. The carbohydrate components of the polysaccharide were glucose (47%), galactose (34%) and mannose (19%). N-acetylneuraminic acid was the sialic acid derivative characterized in the flagellate whole cells. 3. The sialic acid density was estimated as 2.7 x 10(7) residues/cell. 4. The long-chain base dihydrosphingosine, the carbohydrates galactose (67%), glucose (21%) and mannose (12%) as well as the fatty acids myristic (48%) and palmitic (52%) acids were characterized as components of the total glycolipids of T. foetus. 5. Total glycolipids were fractionated: a galactocerebroside and a ganglioside were identified.

Animals↗
PubMed1993

Oxygen affinities of metronidazole-resistant and -sensitive stocks of Giardia intestinalis.

The common protozoon, Giardia intestinalis, parasitizes the upper small intestine of man, and is often refractory to treatment by metronidazole. Defective oxygen-scavenging mechanisms have been implicated as a cause of metronidazole resistance of another flagellate Trichomonas vaginalis, where metronidazole is also the most common drug treatment. Oxygen consumption of six clinical isolates of G. intestinalis and one line selected for resistance to metronidazole was measured over 0-50 microM-O2 using an oxygen electrode open for gas exchange. At > 30 microM-O2, inhibition of respiration was demonstrated in all seven stocks. Apparent oxygen affinities (KmO2) were found to range from 0.5 to 5.2 microM-O2; however, isolates from patients who failed to respond to treatment with metronidazole did not have measurably defective O2-scavenging capabilities compared with metronidazole-sensitive isolates. These strains did, however, show elevated NADPH-oxidase activities compared with metronidazole-sensitive strains. Results indicate that biochemical mechanisms of drug resistance in G. intestinalis may be quite different from those operating in T. vaginalis.

Animals↗