bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic Interactions Between Glucose, Glycerol, Alanine and Acetate in Leishmania braziliensis panamensis Promastigotes
Authors: DARLING T. N. , DAVIS D. G. , LONDON R. E. , BLUM J. J.
Published: May 2007

13C‐nuciear magnetic resonance (NMR) spectroscopy was used to investigate the products of glycerol and acetate metabolism released by Leishmania braziliensis panamensis promastigotes and also to examine the interaction of each of these substrates with glucose or alanine. The NMR data were supplemented by measurements of the rates of oxygen consumption and substrate utilization, and of 14CO2 production from 14C‐labeIed substrate. Cells incubated with [2‐13C]glycerol released acetate, succinate and D‐lactate in addition to CO2. Cells incubated with acetate released only CO2. More succinate C‐2/C‐3 than C‐l/C‐4 was released from both [2‐13C]glycerol and [2‐13C]glucose, indicating that succinate was formed predominantly by CO2 fixation followed by reverse flux through part of the Krebs cycle. Some redistribution of the position of labeling was also seen in alanine and pyruvate, suggesting cycling through pyruvate/oxaloacetate/phosphoenolpyruvate. Cells incubated with combinations of 2 substrates consumed oxygen at the same rate as cells incubated with 1 or no substrate, even though the total substrate utilization had increased. When promastigotes were incubated with both glycerol and glucose, the rate of glucose consumption was unchanged but glycerol consumption decreased about 50%, and the rate of 14CO2 production from [l,(3)‐14C]glycerol decreased about 60%. Alanine did not affect the rates of consumption of glucose or glycerol, but decreased 14CO2 production from these substrates by increasing flow of label into alanine. Although glucose decreased alanine consumption by 70%, it increased the rate of 14CO2 production from [U‐14C]‐ and [l‐14C]alanine by about 20%. This is consistent with rapid equilibration of alanine with pyruvate derived from glucose and yet little decrease in the specific activity of the large alanine pool.
Plasmodium falciparum Gametocyte Formation In Vitro: Its Stimulation by Phorbol Diesters and by 8‐Bromo Cyclic Adenosine Monophosphateau WILLIAM TRAGER
Authors: GILL GOKAL S.
Published: May 2007

. Phorbol 12‐myristate 13‐acetate increased the number of gametocytes by 50 to 100% in well or petri dish cultures of the HB‐3 clone of Plasmodium falciparum. Phorbol dibutyrate had a similar effect. The optimal concentration for each of these agents was 20 ng/ml or approximately 30 nM. No effect of forskolin was found, other than a general inhibition of growth at concentrations over 10 μM. An inhibitor of phosphodiesterase, 8‐bromo cyclic adenosine monophosphate (at concentrations of 0.1 and 1.0 μM) also significantly increased the number of gametocytes formed by this clone.
Circular DNA of Entamoeba histolytica Encodes Ribosomal RNA
Authors: BHATTACHARYA SUDHA , BHATTACHARYA ALOK , DIAMOND LOUIS S. , SOLDO ANTHONY T.
Published: May 2007

. The presence of repeated DNA sequences encoding RNA in Entamoeba histolytica has been reported. In the present study we demonstrate by agarose gel electrophoresis, DNase digestion and electron microscopic analysis that these genes are located on extrachromosomal circular DNA molecules with an approximate size of 26 kb. Detection of replication intermediates suggests the episomal nature of these molecules.

Amplified, extrachromosomal rRNA genes appear to be a common feature among the lower eukaryotes, occurring more commonly as linear molecules and less commonly as circles. Entamoeba histolytica is 1 of the few organisms studied in which rRNA genes are located predominantly on extrachromosomal circles.
Cellular Behaviour Modulated by Ions: Electrophysiological Implications
Authors: MACHEMER HANS
Published: May 2007

. This essay considers the responses of Paramecium and other ciliates to the inorganic ion environment from an elec‐trophysiological point of view. In reviewing data from published and unpublished sources it is shown that ions affect the cellular behaviour in multiple ways because the transmembrane potential can change due to the alteration of equilibrium potentials, ion conductances and surface charges of the membrane. Sensory input including effects from the ionic environment converge upon the membrane potential which has a temporal and spatial summing function. Hyperpolarizing and depolarizing potential shifts from the set point are near‐simultaneously and omnidirectionally transmitted along the membrane including the ciliary boundaries. The membrane potential regulates ciliary motility via an intraciliary messenger, Ca2+, which can enter, and presumably leave, the cytosol directly adjacent to the ciliary motor. Integration of the responses of thousands of cilia occurs in accordance with the electrical and structural provisions of the cell. Potential‐regulated motor and behavioural responses attenuate with time. This phenomenon, which has been loosely termed adaptation, has an electrophysiological basis in analogy to membrane accommodation following sustained stimulus input. The mechanisms of adaptation serve to restore, in principle, the membrane resting state and, thereby, the sensitivity to depolarizing and hyperpolarizing shifts of the membrane potential and the cell's responsiveness to environmental stimuli, respectively. For the inorganic ions involved in chemosensation the terms attractant and repellent are not applicable. They should be reserved to signalling substances which per se can define the behaviour of the cell.
Ultrastructure of Sporozoites and Zoites of Hammondia heydorni
Authors: SPEER C. A. , DUBEY J. P.
Published: May 2007

The ultrastructure of sporozoites and zoites of Hammondia heydorni was studied in cultured bovine cells. In addition to ultrastructural features typical of coccidian parasites, H. heydorni sporozoites and zoites contain rhoptries that are located posteriorly as well as anteriorly. Also, sporozoites contain a posteriorly located crystalloid body (1.2 μm in diameter); a small crystalloid body (0.5 μm in diameter) was occasionally seen in the anterior end. Zoites resulting from the 1st division of endodyogeny contain a posteriorly located crystalloid body, which is absent in zoites formed by subsequent divisions. Zoites contain posteriorly located amylopectin granules and a relatively large anterior vacuole which is not present in sporozoites. During penetration, the host cell plasmalemma ballooned laterally around the sporozoite creating a large cavity, which later disappeared. Sporozoites and zoites undergoing cell penetration usually exhibit partially empty anterior rhoptries; no changes occur in posterior rhoptries. Lysosomes fuse with the par‐asitophorous vacuole surrounding killed sporozoites but not live sporozoites.
In Vitro Killing of Babesia bovis by the Ornithine Analog α‐monofluoromethyldehydroornithine Methyl Ester
Authors: JASMER DOUGLAS P. , GOFF WILL L.
Published: May 2007

The effects of the 2 ornithine decarboxylase inhibitors α‐difluoromethylomithine (DFMO) and α‐monofluoromethyl‐dehydroormithine methyl ester (ΔMFMO‐ME) on growth ofBabesia bovis blood stages in vitro were tested. The DFMO had no apparent effects on in vitro growth of B. bovis nor on the morphology of the parasite at concentrations up to 20 mM. In contrast, ΔMFMO‐ME had cytotoxic effects on B. bovis at 0.5 mM which were more pronounced at 5 mM. ΔMFMO‐ME caused both a decrease in percentage parasitized erythrocytes and a degeneration of parasites after 12 h exposure, and the magnitude of both effects was dose‐dependent. The effects of ΔMFMO‐ME were not reversible for B. bovis precultured for 12 h (5 mM) or 24 h (0.5 mM) in drug before culturing the parasite in drug‐free medium. Unexpectedly, 300 μM putrescine did not reverse the effects of ΔMFMO‐ME on B. bovis blood stage, raising the possibility that inhibition of omithine decarboxylase is not responsible for these effects.
Substrates Determine Spatial Distribution of Oxytricha bifaria (Ciliata Hypotrichida)
Authors: RICCI NICOLA , ERRA FABRIZIO , RUSSO ANTONINO , BANCHETTI ROSALBA
Published: May 2007

The extent to which a particular substrate (scratched glass) affects the distribution of a population (Oxytricha bifaria) that settled on it was measured, yielding the following results: (1) the species distinguishes among substrates slightly differing in the quality of their superficial scratches (average dimensions of 2, 2.8, 3.5, 6.5, 17 and 25 μm, respectively); (2) it “chooses” the preferred substrate by adopting specific differential behaviors; and (3) population cell density conditions its overall distribution.
Oral Assembly in Left‐Handed Tetrahymena thermophila
Authors: NELSEN E. MARLO , FRANKEL JOSEPH , WILLIAMS NORMAN E.
Published: May 2007

We have investigated oral development in a non‐genically derived left‐handed (LH) form of Tetrahymena thermophila, in which the large‐scale asymmetry of arrangement of cortical structures is reversed whereas the local asymmetry of ciliary architecture remains normal. Approximately 1/2 of the oral apparatuses (OAs) of LH cells develop in the form of superficial mirror‐images of OAs of RH cells. In most of these OAs, membranelles are assembled from the cells’anterior to posterior. Nonetheless, the posterior ends of these membranelles undergo the basal body displacements that lead to a “sculptured” appearance, so that the membranelles of LH OAs become organized as rotational permutations of membranelles of normal RH OAs. Many of these membranelles re‐orient to a normal orientation near the end of oral development. Membranelles and undulating membranes (UMs) may develop independently of each other, and formation of postciliary microtubules of UMs is separate from that of ribbed wall microtubules. In some cases, the entire OA develops and remains as a 180° rotational permutation of the normal, resembling the inverted OAs of mirror‐image doublets and LH cells of Glaucoma scintillans described by Suhama [36, 37]. We present a model (Fig. 37) for these complex developmental outcomes. These developmental patterns resemble those described previously and less completely for “secondary” OAs of cells with mirror‐image global patterns, including janus cells. The present study demonstrates that such alterations in oral development are not a direct outcome of genotypic changes.
Studies on the Attachment of Leishmania Flagella to Sand Fly Midgut Epithelium
Authors: WARBURG ALON , TESH ROBERT B. , McMAHON‐PRATT DIANE
Published: May 2007

An in vitro assay was developed to study the recognition mechanism for attachment of Leishmania flagella to sand fly midgut epithelium. Frozen sections of sand fly guts were incubated with Hagella preparations, and probed with a flagella‐specific monoclonal antibody. Tissue‐specific adhesion of flagella to midgut epithelium was demonstrated by indirect immunofluorescence. None of the 13 sugars, screened to test for possible lectin‐mediation, appeared to significantly inhibit the adhesion of flagella to gut sections. Similarly no inhibition was achieved by incubating flagella with pep 63 which inhibits the promastigote‐macrophage recognition mechanism. Significant inhibition was attained by incubating flagella preparations with a monoclonal antibody which binds to a flagellar membrane‐component. The possible relevance of the described mechanism for the biology of Leishmania in their sand fly hosts, is discussed.
A New Species of Blood Trypanosome from Little Penguins (Eudyptula minor) in Tasmania
Authors: JONES HUGH I. , WOEHLER ERIC J.
Published: May 2007

ABSTRACT. Trypanosoma eudyptulae n. sp. was present in 9 blood smears from 57 Little Penguins (Eudyptula minor Forster) from Tasmania. Trypanosoma eudyptulae is long and slender (with the kinetoplast situated close to the nucleus) with a long and attenuated posterior end. This is the first report of a trypanosome from a penguin.
Structure of Major Surface Determinants and DNA Diagnosis of Pneumocystis carinii
Authors: NAKAMURA YOSHIKAZU , TANABE KIYOKATSU , EGAWA KOHJI
Published: May 2007

Pneumocystis carinii is a pathogen which causes fatal pneumonia in patients with the acquired immune deficiency syndrome (AIDS). To facilitate the basic study of P. carinii, wc have analyzed its major surface proteins by both immunochemical and biochemical methods. The major protein components of both cysts and trophozoites are a group of proteins called “PI 15” with apparent masses of 105–120 kd. It includes 6 isoelectric variants. A monoclonal antibody raised against cysts recognizes all 6 variants and reacts with epitopes located in the cell wall indicating that PI 15 is an immunoreactive surface component. The isoelectric variants contain identical or closely related protein components and they are mannose‐rich glycoproteins. The isoelectric variation may be due primarily to differences in glycosylation. The majority of sera from humans with diagnosed pneumocystosis that were tested reacted strongly with the PI 15 proteins. To develop probes for DNA diagnosis and to facilitate molecular studies, a genomic DNA library of P. carinii has been constructed. Some of these clones were used for DNA hybridization analysis of rat and human lungs.
Methods for Inducing Selfing, Selfing and Its Role in the Life Cycle of Euplotes woodruffi syngen 3 (Ciliophora)
Authors: KOSAKA TOSHIKAZU
Published: May 2007

Methods for inducing selfing, and the relation between selfing and the life cycle of Euplotes woodruffi syngen 3 are reported. Three intercrossing stocks were used in this experiment. Selfing was induced with several treatments as follows: cell‐free fluid from the cultures of complementary mating types; intact cells of GI or S phase in the cell cycle; heat‐killed cells, and lysed cells of GI‐, S‐, and D‐phase cells which were prepared by freeze‐thawing. Stock SJ‐27 was used as a parental stock from which Fl clones were originated through selfing. The other two stocks, SJ‐8 and SJ‐19, were used as testers. The period of immaturity varied from clone to clone. The heterotypic conjugation of clones with cells of stock SJ‐8 seems to occur earlier in the life cycle than with cells of stock SJ‐19. This result shows that this syngen has an adolescent period in the life cycle. The length of selfing immaturity seems to be different from that of crossing immaturity, and selfing appeared slightly later than crossing with testers. But the clones in which selfing 1st occurred are considered to be in adolescence or maturity, not in senility. Once selfing appeared in any clone, the clone continued to produce selfing pairs till just before clonal death. The viability of selfing and of outcrossing were compared and found not significantly different. Inbreeding depression took place in some of the F2 clones by successive selfing. The viability of F2 clones from young parents was significantly higher than that from old parents (220 to 230 fissions) both in selfing and outcrossing. The total life spans which were studied in three F1 clones were 168 to 264 fissions.
Ortholinea alata n. sp. (Myxosporea: Ortholineidae) in the Northern Butterfly Fish Chaetodon rainfordi
Authors: KENT MICHAEL L. , MOSER MIKE
Published: May 2007

Ortholinea alata n. sp. is described from the northern butterfly fish, Chaetodon rainfordi collected at Heron Island, Great Barrier Reef, Australia. Spherical, disporous trophozoites (10–15 μ) and spores were observed in the lumina of kidney tubules and collecting ducts. Spores are broadly triangular with two short, broad processes that extend dorsoventrad from the posterior end of each of the two spore valves. Valves are bisected by a suture in the plane of the polar capsules. Spores are 12.6 μ (length) × 9.6 μ (width) × 9.9 μ (length), and at the anterior end contain two spherical, divergent polar capsules measuring 4.6 (4.1–5.1) μ. Sporogenesis is similar to that of renal Sphaerospora spp.: the intraluminal trophozoites of O. alata n. sp. correspond to pseudoplasmodia described for Sphaerospora spp. and no large, multinucleate plasmodia are formed. No significant histopathological changes were observed in the kidneys of infected fish.
Antimalarial Properties of Imipramine and Amitriptyline12
Authors: DUTTA PURABI , PINTO JOHN , RIVLIN RICHARD
Published: May 2007

Dietary riboflavin deficiency is known to diminish malarial parasitemia. In this study, we determined whether imipramine and amitriptyline, drugs which inhibit riboflavin metabolism, have antimalarial efficacy. In addition, we evaluated whether these drugs, like other antimalarial agents, increase the hemolytic response to ferriprotoporphyrin IX (FP). The growth of Plasmodium falciparum (FCR3) in the absence and presence of these drugs (10 to 75 μM) was measured by determining (3H)hypoxanthine uptake by intraerythrocytic parasites for 48 h in RPMI 1640 medium. The uptake of (3H)hypoxanthine was significantly reduced in a dose‐dependent manner by both imipramine and amitriptyline. The IC50 values of imipramine and amitriptyline at 48 h were 56 and 45 μM, respectively. Both drugs enhanced hemolysis induced by FP (10 or 20 μM). No hemolysis by these drugs was detected in the absence of FP. It is concluded that the tricyclic antidepressants, imipramine and amitriptyline, possess substantial antimalarial properties.
Influence of Host Diet on the Fatty Acid Composition and Content of Rumen Protozoa in Cattle
Authors: O'KELLY JOHN C. , SPIERS WILLIAM G.
Published: May 2007

The fatty acid profiles and contents of protozoa from the rumen fluid of cattle varied according to the type of diet consumed by their host. Changing from a high‐quality hay diet to a low‐quality hay diet (DA) decreased the proportions of saturated acids and increased the proportions of the unsaturated acids 18:1 cis‐9, 18:2 and 18:3 in neutral lipids (NL) and phospholipids (PL). Adding sucrose, urea and sulphur (SUS) to DA increased the proportions of branched chain acids in PL while addition of safflower oil increased polyunsaturated acids in PL and 18:1 trans‐11 in NL. Diet did not alter the PL fatty acid content of protozoa but oil supplement of DA resulted in a 10‐fold increase in the content of free fatty acids. The defaunating effect of oil supplement was partly reversed by SUS suggesting that factors other than the fatty acid content of cells are important in determining the toxicity of oil to rumen protozoa. The results indicate that the amounts of individual long‐chain fatty acids taken up by rumen ciliates are largely determined by their concentrations in rumen digesta.
The Effect of Ultraviolet Radiation on the Germination of Nosema algerae Vávra and Undeen (Microsporida: Nosematidae) Spores1
Authors: UNDEEN ALBERT H. , MEER ROBERT K. VANDER
Published: May 2007

Spores of Nosema algerae Vávra and Undeen were subjected to various dosages of 254 nm ultraviolet radiation (UV). Very high dosages of UV were required to block germination. Germination was normal immediately after UV dosages of 0.2 to 1.0 J/cm2, followed by a delayed effect in which both percentage germination and the intrasporal concentration of trehalose decreased with time after UV exposure. Although a few spores were germinated, most of them were inactivated (rendered temporarily unable to germinate) by exposure to UV of 1.1 J/cm2. Ultraviolet radiation between 1.1 and 3.4 J/cm2 stimulated spores to germinate. However, spores were completely unable to germinate immediately after exposure to dosages above 3.8 J/cm2. Ammonia had little effect on stimulation by UV but was inhibitory to germination after stimulation had occurred. These results demonstrate that UV behaves like a germination stimulus and are discussed in terms of the hypothesis that germination is initiated by the breakdown of barriers between trehalose and trehalase.
The Plasma Membrane of Myxosporidian Valve Cells: Freeze Fracture Data
Authors: DESPORTES‐LIVAGE ISABELLE , NICOLAS GISELE
Published: May 2007

Freeze fracturing of Myxosporidian spores reveals the occurrence of a continuous layer of transmembrane particles all over the surface area of the valve cells which form the spore envelope. These particles are densely packed all over the P face membrane. Due to their polygonal outline, their diameter (6‐7 nm) and their central core, they resemble the particles forming the connections of gap junctions which metabolically couple the neighboring cells in animal tissues. In the present report, the role of the transmembrane particles is still hypothetical. However, they might represent a membrane structural specialization of the spores which are submitted to osmotic variations of the fluid external medium. Furthermore similar transmembrane particles are observed at the level of the septate junction which seals the valve cells. In this occurrence, they are arranged in a series of 40 double rows parallel to the suture of the spore envelope. These findings support the view that Myxosporidia are Metazoa and raise the problem of their origin.
Amoeboid Locomotion of Naegleria gruberi: the Effects of Cytochalasin B on Cell‐Substratum Interactions and Motile Behaviour
Authors: PRESTON T. M. , COOPER L. G. , KING C. A.
Published: May 2007

The major manifestations of amoeboid locomotion in Naegleria—cytoplasmic streaming, pseudopod production, cell polarity and focal contact production—require that the actin‐based cytoskeleton be extremely dynamic. Whether these features are causally linked is unclear. In an attempt to answer this question we have used the fungal product cytochalasin B (cyt B) to dissect the motility process. This drug can perturb the organisation of actin filaments both in vivo and in vitro. Essentially cyt B acts as a molecule which can cap the barbed ends of actin filaments. Not surprisingly therefore cyt B has an effect on rates of actin polymerization and the dynamic state of actin in the cytoplasm.

We have found that cyt B has a profound effect on focal contact production and breakdown. Within minutes of addition of cyt B focal contact production ceases, existing focal contacts are stabilised but cytoplasmic streaming and pseudopod production are not blocked. In conclusion it is now clear that the state of actin required for focal contact production is different from that required for pseudopod extension and cytoplasmic streaming.
The Ultrastructure of Chaenea teres and an Analysis of the Phylogeny of the Haptorid Ciliates
Authors: LIPSCOMB DIANA. L. , RIORDAN GAVIN P.
Published: May 2007

Chaenea teres has typical haptorid ultrastructure. The somatic monokinetid has two transverse microtubular ribbons, an overlapping postciliary microtubular ribbon, and a laterally directed kinetodesmal fiber. The evered cytopharynx forms a dome at the apical end of the cell. The base of the dome is surrounded by oral dikinetids. The left, anterior kinetosome of the oral pair is not ciliated and has a transverse microtubular ribbon, a nematodesmata and a single postciliary microtubule. The right, posterior kinetosome is ciliated and has only postciliary microtubules. The kinetosomes at the anterior ends of the somatic kinetics are close together and their transverse microtubules and nematodesmata contribute to the support of the cytopharynx. The transverse microtubules of these oralized somatic kinetosomes, together with those from the oral dikinetids, line the cytopharynx. Accessory or bulge microtubules arise perpendicular to the transverse microtubules. A dorsal brush of three kineties of clavate cilia is found on the cell surface just posterior to the oral region. Mucocysts and a single type of toxicyst are present. The toxicysts are confined to the oral region. There are multiple ovoid macronuclei that stain weakly. Micronuclei were not observed. Cladistic analysis indicates the Chaenea may be most closely related to Fuscheria and Acropisthium. The cladistic analysis also suggests that existing taxonomies of the subclass Haptoria need to be revised. We propose some modifications to Foissner & Foissner's classification that include transferring Helicoprorodon, Actinobolina, the buetschiliids, and the balantidiids to the order Haptorida and recognizing the close relationship between pleurostomes and spathidiids.
Strombidium inclinatum n. sp. and a Reassessment of Strombidium sulcatum Claparède and Lachmann (Ciliophora)
Authors: MONTAGNES DAVID J. S. , TAYLOR F. J. R. , LYNN D. H.
Published: May 2007

Strombidium sulcatum is the type species for the genus Strombidium and has been repeatedly referred to over the last 130 yr. However, there are several taxonomic problems associated with it. We discuss why the original description of S. sulcatum lacks resolution to describe a single species. We conclude that: (1) the description of S. sulcatum sensu Fauré‐Fremiet, 1912 be used to diagnose the species; (2) there are ambiguities in several redescriptions of S. sulcatum; and (3) S. sulcatum sensu Lynn et al., 1988 is Strombidium emergens (Leegaard, 1915) Kahl, 1932. From this analysis we present a description for Strombidium inclinatum n. sp. (previously S. sulcatum sensu Fenchel and Jonsson, 1988).
Morphology of Diplomonad Flagellates: Spironucleus torosa N. Sp. from Atlantic Cod Gadus morhua L., and Haddock Melanogrammus aeglefinus (L.) and Hexamita salmonis Moore from Brook Trout Salvelinus fontinalis (Mitchill)
Authors: POYNTON SARAH L. , MORRISON CAROL M.
Published: May 2007

ABSTRACT. A diplomonad flagellate, Spironucleus torosa n. sp. is described from Atlantic Cod Gadus morhua and haddock Melanogrammus aeglefinus. This is believed to be the 1st confirmed report of Spironucleus from a marine fish. Organisms swimming in the rectal lumen were broadly pyriform to elongate, and measured 10.5–18.6 μm long and 3.2–13.3 μm wide; other elongate organisms were attached to the rectal epithelium, via apical extensions appearing continuous with the microvilli. The posterior end of the body was extended into a caudal projection, on either side of which was a posteriolateral ring‐shaped protrusion or torus, with a recurrent flagellum emerging from its centre. A symmetrical system of microtubules and lamellae, forming a “V” in protargol impregnated specimens, supported the flanges of the body surrounding the tori, the tori themselves and the caudal projection. Supranuclear microtubules were an inverted V to U shape in transverse section, and an electron dense band accompanied the cytostomes. Lightly staining homogenous cytoplasm was usually present in the anterior part of the body, the remainder being highly vacuolated with numerous dark granules. In swimming organisms, rough endoplasmic reticulum (RER) was present around the nuclei and cytostomes, and bacteria were occasionally seen in the cytoplasm. In “attached” organisms, RER was reduced, and bacteria were absent. Hexamita salmonis Moore from Salvelinus fontinalis was studied by light and scanning electron microscopy for comparison; its cytoplasm was not highly vacuolated. The two recurrent flagella emerged close together from the blunt posterior end of the body.
A Cytochemical Ultrastructural Study of the Lysosomal System of Different Species of Malaria Parasites
Authors: SLOMIANNY C. , PRENSIER G.
Published: May 2007

ABSTRACT. We have used ultrastructural techniques in different malarial species to demonstrate a lysosomal system. First, we have tried to localize acid phosphatase, a typical lysosomal label. Its activity was localized in the endoplasmic reticulum and in endocytic vesicles, and in dense‐cored vesicles near the digestive vacuoles, especially in Plasmodium falciparum (FCR3 strain). Then, we have studied the different cellular compartments of the malarial parasite by the zinc iodide‐osmium tetroxide technique that heavily contrasted the cellular compartments of the parasite. This experiment led to the observation of a profound rearrangement of the endoplasmic reticulum, especially in P. berghei. A very atypical but functional Golgi apparatus was demonstrated in all the growing stages of the parasite and lysosome‐like vesicles were observed, showing a structure very similar to those of the coated vesicles of a true Golgi complex. The presence of these organelles are in favor of the existence of a lysosomal system and of the endogenicity of some enzymes involved hemoglobin degradation.
Rapid Shape Change and Release of Ninhydrin‐Positive Substances by Leishmania major Promastigotes in Response to Hypo‐Osnjotic Stress
Authors: DARLING THOMAS N. , BURROWS CHRISTINE M. , BLUM J. JOSEPH
Published: May 2007

ABSTRACT. Leishmania major promastigotes were grown to late‐log phase and washed and resuspended in an isosmotic buffer. When osmolality was suddenly decreased by 50%, the cells rapidly became shorter and increased in width. Cell volume, calculated assuming a prolate‐ellipsoidal shape, increased 1.4 times after 1 min. Over the next several minutes, the average length and width returned to control values while the volume returned to baseline, indicating the ability to regulate volume. Concomitantly with the swelling, large amounts of alanine and other ninhydrin‐positive substances were released. All of the alanine pool was released within 1 min after reduction of the osmolality by 66%. Cells pre‐loaded with [14C]‐aminoisobutyric acid also released it very rapidly upon hypo‐osmotic stress. Release of ninhydrin‐positive substances resulted from decreased osmolality rather than changes in ionic composition. The same results were obtained if osmolality was decreased by reducing only the NaCl content of the buffer instead of diluting it with water, and mannitol could substitute for the NaCl. Promastigotes were able to grow well over several days in media as low as 154 mOsm/kg. The nature of the signalling mechanism(s) that initiates the rapid shape change and efflux of ninhydrin‐positive substances in response to hypo‐osmotic stress is at present unknown.
On the Correlation of the Volume of a Prolate‐Spheroidal Cell, Tetrahymena as Determined by Electronic Particle Counters and by Morphometry
Authors: NILSSON JYTTE R.
Published: May 2007

ABSTRACT. The cell volume provided by electronic particle counters may be incorrect. As a particle, or cell, passes the counting device, its volume is calculated as a sphere. The electronically derived, mean cell volume (electronic MCV) of a population of Tetrahymena (prolate spheroid) is smaller than the volume (morphometric MCV) calculated from measured cell length and width. This discrepancy was studied using a Coulter Multisizer particle counter and cell morphometry. The electronic MCV averaged 0.70 of the morphometric MCV (1.00) but changed from 0.72 (fast growth) to 0.63 and 0.76 (slow or no growth) for cells having a mean length/width of 2.05, 2.33, and 1.61, respectively. The measured diameter of latex particles (used for calibration) was identical to that stated, but the diameter of the electronic MCV was larger than the width of the cells which related to wehther the length/width of the cells was above, or below, 2.00. Hence, electron particle counters register primarily the width of a prolate‐spheroidal cell, oriented with its long axis in the direction of flow, and uses this value as diameter for the calculated sphere, whereas for more spherical cells, tumbling without any orientation, a mean of the axes is used. Factors for correction of the electronic MCV of Tetrahymena are provided.
Eimeria tenella: Incomplete Excystation in the Presence of EDTA in a Taurodeoxycholate‐Based Medium
Authors: DULSKI PAULA M.
Published: May 2007

ABSTRACT. Normally, sporozoites of Eimeria tenella are efficiently excysted in vitro with trypsin and bile salts. However, a one hour treatment at °40C with a chelator‐supplemented excystation medium (purified trypsin and chymotrypsin, taurodeoxycholate and ethylenediaminetetraacetic acid in buffered saline) produced incomplete excystation. The treatment removed the sporocyst plug and left an opened sporocyst containing motile sporozoites, but the release of sporozoites was greatly reduced (<12% release). Some of the sporozoites extended a portion of their anterior end through the sporocyst opening then retracted it into the sporocyst. Sporozoites were released when magnesium was added to the chelator‐supplemented medium. Manganese was less effective and calcium was ineffective in producing release. Also, sporozoites were released when the incompletely excysted sporocysts were transferred to buffered saline with albumin and this became the basis for a new assay. The assay demonstrated that ethylenediaminetetraacetic acid reduced release in the presence of taurodeoxycholate but not in its absence. Hydrophobic and hydrophilic chelators were tested in the assay. Ethylene‐dioxy diethylene‐dinitrilotetraacetic acid and 8‐hydroxyquinoline were inactive. The chelator 1,10‐phenanthroline did not require bile salt to reduce release. The inhibitory effects by phenanthroline were eliminated in the presence of magnesium or manganese, while calcium had no effect. Thus, although certain chelators can inhibit release, a consistent correlation between chelation and inhibition of release has not been established. The application of ethylenediaminetetraacetic acid with taurodeoxycholate as a reversible inhibitor of release is discussed.
Identification of an Apically‐Located Antigen That Is Conserved in Sporozoan Parasites
Authors: TAYLOR DIANE W. , EVANS CHARLES B. , ALEY STEPHEN B. , BARTA JOHN R. , DANFORTH HARRY D.
Published: May 2007

ABSTRACT. Sporozoan parasites of the phylum Apicomplexa all possess common apical structures. The current study used a monoclonal antibody (mAb‐E12) to identify a conserved antigen in the apical region of merozoites of seven species of Plasmodium (including rodent, primate and human pathogens), tachyzoites of Toxoplasma gondii, bradyzoites of Sarcocystis bovis, and sporozoites and merozoites of Eimeria tenella and E. acervulina. The antigen was also present in sporozoites of haemosporinid parasites. Immunofluorescence studies showed that the antigen was restricted to the apical 3rd of these invasive stages. Using immunoelectron microscopy, labeling was demonstrated in the region of the polar ring, below the paired inner membranes of the parasite pellicle, and near the subpellicular microtubules radiating from the polar ring of merozoites and sporozoites of E. tenella. The majority of the antigen could be extracted with 1% Triton‐X 100, but a portion remained associated with the cytoskeletal elements. The molecule has a relative rate of migration (Mr) of 47,000 in Plasmodium spp. and 43–46,000 in coccidian species. Since the epitope recognized by mAb‐El 2 is highly conserved, restricted to motile stages, and appears to be associated with microtubules, this antigen could be involved in cellular motility and cellular invasion.
Further Studies on Substrates Inducing Metacyclogenesis in Trypanosoma cruzi
Authors: KRASSNER STUART M. , GRANGER BARBARA , PHERMSANGNGNAM PAT , LE TUAN , LINDEN VIC
Published: May 2007

Epimastigotes of Trypanosoma cruzi, Peru strain, incubated in Contreras' artificial triatomine urine transformed into metacyclic trypomastigotes when 10 mM L‐glutamine, L‐asparagine or D‐fructose was added to the medium. Metacyclogenesis with these substrates was comparable to the percent metacyclic morphotype formation induced by L‐proline and significantly greater than that stimulated by 10 mM D‐glucose. Sodium acetate (10 mM) increased transformation induced by L‐proline, and L‐hydroxyproline (10 mM) increased transformation induced by D‐fructose. Phosphoenolpyruvate (10 mM) inhibited L‐proline‐induced metacyclic trypomastigote stage formation. Three antimetabolites, azetidine 2‐carboxylate (5 mM), malonic acid (1 mM), and desthiobiotin (5 mM), completely inhibited D‐fructose‐induced but not L‐proline‐induced transformation. The Costa Rica, Y, and CL strains of T. cruzi showed different patterns of percent metacyclogenesis with substrates that induce transformation in the Peru strain.
Further Observations on Cryptobia dahli (Mastigophorea: Kinetoplastida) Parasitizing Marine Fish
Authors: KHAN RASUL A.
Published: May 2007

Studies were conducted primarily to ascertain the mode of transmission of Cryptobia dahli parasitizing the digestive tract of lumpfish (Cyclopterus lumpus). Another flagellate, morphologically similar to C. dahli, was also observed in the gut of a deepsea fish (Macrourus berglax). Several invertebrates, which are food for lumpfish, were examined for flagellates, but were neither infected nor showed evidence of cystic stages. Parasites were more abundant in the stomach, especially at about pH 5, than in other areas of the digestive tract. Transmission was achieved by pipetting the parasites into the stomach of uninfected fish, by feeding food contaminated with flagellates, and also by holding infected and uninfected fish in the same aquarium. In nature, lumpfish probably acquire parasites during winter when they aggregate and regurgitate into seawater because parasites can survive for short periods outside their host.
Localization of Thermoreceptor Systems that Induce Step‐Up and Step‐Down Thermophobic Responses and Switching in the Dominance of These Systems in Blepharisma
Authors: MATSUOKA TATSUOMI , IMANAKA TAKANOBU , ARITA TOMIKAZU , TANEDA KOJI
Published: May 2007

The distribution of thermoreceptor systems that initiate step‐up and step‐down thermophobic responses in bisected cells of Blepharisma was examined. Anterior cell fragments responded by ciliary reversal to a step‐down in temperature and by repression of spontaneous ciliary reversal to a step‐up. Posterior fragments responded by ciliary reversal to a step‐up in thermal stimulation and by repression of spontaneous ciliary reversal in response to step‐down stimulation. Results indicate that two kinds of thermoreceptor systems exist in the anterior half of each cell; one is responsible for ciliary reversal induced by step‐down stimulation, and the other is responsible for repression of the ciliary reversal caused by step‐up thermal stimulation. Likewise, there are also two kinds of thermoreceptor systems in the posterior half of the cell; one is responsible for ciliary reversal in response to a step‐up in temperature, and the other is responsible for the repression of ciliary reversal on a step‐down in thermal stimulation. Below about 27°C, intact cells showed ciliary reversal only when a step‐down in thermal stimulation occurred, while above about 27°C cells only responded to a step‐up in thermal stimulation. At about 27°C there was a switch in the dominant response from the anterior to the posterior half of an individual cell.
Malaria Sporozoites Release Circumsporozoite Protein from Their Apical End and Translocate It along Their Surface
Authors: STEWART MICHAEL J. , VANDERBERG JEROME P.
Published: May 2007

Plasmodium sporozoites, the causative agents of malaria, release circumsporozoite (CS) protein into medium when under conditions simulating those that the parasites encounter in the bloodstream of the vertebrate host. CS protein of the rodent parasite, Plasmodium berghei, is released as the lower molecular weight form, Pb44. This release is substratum‐ and antibody‐independent. Previous studies show that CS protein is released at the trailing, posterior end of motile sporozoites. Video and electron microscopic studies now demonstrate that CS protein is released at the apical end of cytochalasin b‐immobilized sporozoites. We propose that CS protein released from the apical end, the leading end of gliding sporozoites, adheres to the sporozoite surface and is translocated posteriorly by a cytochalasin‐sensitive and apparently actin‐mediated surface motor, which drives gliding motility. This model explains the mechanism of both the circumsporozoite precipitation (CSP) reaction and formation of the CS protein trail by gliding sporozoites.
Sequence of a Euplotes crassus Macronuclear DNA Molecule Encoding a Protein with Homology to a Rat Form‐I Phosphoinositide‐specific Phospholipase C
Authors: KLOBUTCHER LAWRENCE A. , TURNER LEAH R. , PERALTA M. EVANGELINE
Published: May 2007

A 604‐base pair macronuclear DNA molecule from the hypotrichous ciliate Euplotes crassus was cloned and its DNA sequence determined. The DNA sequence contains an open reading frame capable of encoding a protein 141 amino acids in length. The putative protein contains significant sequence similarity to other eukaryotic proteins, including the rat form‐I phosphoinositide‐specific phospholipase C.
Glucan Synthesis in Pneumocystis carinii
Authors: WILLIAMS DEBRA J. , RADDING JEFFREY A. , DELL ANNE , KHOO KAY‐HOOI , ROGERS MARK E. , RICHARDS FRANK F. , ARMSTRONG MARTINE Y. K.
Published: May 2007

Rat‐derived Pneumocystis carinii lysed with sodium deoxycholate catalysed the incorporation of uridine diphospho‐glucose into an insoluble polymer. This enzyme activity was present in both the pellet and the supernatant when the P. carinii preparations were centrifuged. The polymer whose production was catalysed by the supernatant was examined by mass spectrometry and found to be an α 1→4 glucan, which is either unbranched or has relatively few branches. Polymer formation was completely inhibited by the addition of α amyloglucohydrolase to the supernatant. Polymer formation in the pellet of deoxycholate P. carinii preparations, unlike that in the supernatant, was partially resistant to α amyloglucohydrolase. The soluble glucan synthase activity in the supernatant was stable for more than 30 h at room temperature and was approximately 50 times more active on a cell‐to‐cell basis than the supernatant from deoxycholate preparations of the yeast Saccharomyces cerevisae.
Commitment to the First Cortical Reorganization During Conjugation in Stylonychia mytilus: An Argument for Homology with Cortical Development During Binary Fission
Authors: ZOU SHI FA , NG STEPHEN F.
Published: May 2007

The asexual nature of the first cortical reorganization of conjugation in Stylonychia was analyzed by comparing the effect of amputation performed at different stages of early conjugation to that performed on vegetative cells at different stages of the cell cycle. Amputation of vegetative cells delineated a point of commitment to binary fission at 0.51–0.57 of the cell cycle. Cells amputated before this point were induced to undergo the regenerative mode of asexual development, but those amputated after this point continued with binary fission. In parallel, during conjugation a similar commitment was made around the time of formation of tight mating‐pairs: early conjugants amputated around this time might undergo regeneration, and those operated on after this stage continued with the first cortical reorganization as in typical conjugants. The two mates of a pair might differ in their response to amputation, suggesting that the timing of commitment to the first cortical reorganization is not related to the events of conjugation, but rather is individually determined in the vegetative cycle of the cells before they pair up in mating. These observations provide support for the notion that the first cortical reorganization of conjugants is homologous to the asexual mode of cortical development in dividers, according to the theory of developmental heterochrony in the sexual reproduction of hypotrichs. The timing of commitment to the first cortical reorganization was found to temporally correlate with the entrance of the micronuclei into meiosis. Since the first cortical reorganization can proceed without the micronucleus, this raises the possibility that initiation of micronuclear meiosis is closely coupled with, and may be determined by, the commitment to the first cortical reorganization.
Ultrastructural Study of the Development of Pleistophora schubergi Zwölfer, 1927 (Protozoa, Microsporida) in Larvae of the Spruce Budworm, Choristoneura fumiferana and Its Subsequent Taxonomic Change to the Genus Endoreticulatus
Authors: CALI ANN , GARHY MANAL EL
Published: May 2007

This study demonstrates that Pleistophora schubergi Zwölfer, 1927, a microsporidium originally isolated from the midgut epithelium of Nygmia phaeorrhoea Don (Euproctis chrysorrhoea L.) and Porthetria dispar L., and subsequently reported in several other insects including the spruce budworm, Choristoneura fumiferana (the host used in this investigation), does not belong in the genus Pleistophora Gurley, 1893. Pleistophora schubergi lacks the major features that are characteristic of Pleistophora typicalis, the type species of this genus. A comparison of ultrastructural observations reported for the type species of the genus Pleistophora, P. typicalis, and our observations of P. schubergi revealed significant differences. A thick (0.5 μm) amorphous coat, derived from parasite secretions and deposited external to the parasite plasmalemma, surrounds all developmental stages in P. typicalis. Double membranes, derived from host rough endoplasmic reticulum cisternae encircle the parasite plasmalemma of all developmental stages in P. schubergi. The sporophorous vesicle encases the spores in P. typicalis, and originates from the parasite‐secreted coat that is present around meronts. In P. schubergi, the host endoplasmic reticulum cisternae form the envelope that surrounds the meronts. Moreover, the sporophorous vesicle envelope in P. typicalis persists around groups of spores, while in P. schubergi this envelope breaks easily to release the spores in the host cytoplasm. By comparing the characteristics of the microsporidium found in the spruce budworm with those of the recently created polysporous genera that sporulate within a vesicle, we found that P. schubergi does belong in the new genus Endoreticulatus Brooks et al. 1988, and consequently rename it Endoreticulatus schubergi (Zwölfer, 1927) n. comb.
Effect of Hyper‐Osmotic Stress On Alanine Content of Leishmania Major Promastigotes
Authors: BURROWS CHRISTINE , BLUM J. JOSEPH
Published: May 2007

ABSTRACT Earlier studies showed that Leishmania major promastigotes are sensitive to osmotic conditions. A reduction in osmolality caused the cells to shorten and to rapidly release most of their large internal pool of alanine. In this study some effects of hyper‐osmotic stress were examined. an increase in osmolality of the culture medium from 308 to 625 mOsm/kg caused only a small decrease in growth rate. When cells grown in the usual culture medium (308 mOsm/kg) were washed, resuspended in iso‐osmotic buffer, and subjected to acute hyper‐osmotic stress by addition of mannitol, the alanine content increased even in the absence of exogenous substrate. Promastigotes, depleted of alanine by a 5‐min exposure to hypo‐osmotic conditions, also synthesized alanine when resuspended in iso‐osmotic buffer. Washed cells resuspended in iso‐osmotic buffer consume their internal pool of alanine under aerobic conditions, Rates of consumption decreased on addition of mannitol, becoming zero at about 440 mOsm/kg. At higher osmolalities, alanine synthesis occurred. to estimate whether proteolysis could account for alanine synthesis in the absence of exogenous substrate, cells that had been grown with [1‐14C]leucine were washed and resuspended under hypo‐, iso‐, and hyper‐osmotic conditions and the amounts of 14CO2 and 14C‐labelled peptides released in 1 h were measured. Little proteolysis occurred under these conditions, but the possibility that proteolysis was the source of the alanine increase, observed in response to hyper‐osmotic stress, cannot be ruled out.
The Protozoan‐Metazoan Trophic Link In Pelagic Ecosystems
Authors: GIFFORD DIAN J.
Published: May 2007

ABSTRACT The evidence for a qualitatively and quantitatively important trophic link between planktonic Protozoa and higher order metazoan consumers is reviewed. the available data are obtained primarily, but not exclusively, from laboratory studies of calanoid copepod consumers and tintinnid ciliate prey from marine estuarine and nearshore environments. the data indicates that the protozoan‐metazoan link is of similar magnitude and importance in the pelagic ecosystems of freshwaters. It is proposed that planktonic Protozoa constitute a high quality, nitrogen‐rich food in the diets of their metazoan consumers. Implications of die trophic link to the consumers, prey, and ecosystem are discussed.