A Redescription of Climacostomum virens (Ehrenberg) Stein and Proposal of a New Heterotrich Ciliate Family, Climacostomidae fam. n.

SYNOPSIS. Structure of the vegetative and asexually dividing forms of the large ciliate Climacostomum virens is redescribed with emphasis on stomatogenesis. These findings are discussed in relation to the taxonomic and possible evolutionary position of Climacostomum among heterotrichous ciliates. Comparative considerations of the buccal and somatic structures as well as of the stomatogenic patterns in this and other closely related ciliate genera indicate the need for placing Climacostomum and Fabrea in a new family, CLIMACOSTOMIDAE . The morphologic evidence suggests that Climacostomum may represent a line linking Fabrea and Stentor.     

Light and Electron Microscopic Observations on the Heterotrich Ciliate Climacostomum virens

SYNOPSIS. Alveolar membranes and an epiplasm exist under the cell membrane of the noncontractile heterotrich ciliate Climacostomum virens. Postciliary microtubular ribbons join at the right of each somatic kinety to form a Km fiber. Two transverse microtubular fibers occur per kinetosomal pair. A myonemal network interconnects the kinetosomal bases intrakinetally and interkinetally. Ultrastructural comparisons are made between the contractile and noncontractile heterotrichs.
The buccal cortex consists of an adoral zone of membranelles, a peristomal field, a buccal tube, the apical membranelles, and a haplokinety. The kineties of the peristomal field and buccal tube are rows of paired kinetosomes, with a postciliary ribbon of microtubules arising from the posterior kinetosome of each pair, and a transverse ribbon and an oblique ribbon from the anterior kinetosome. No Km fibers exist in this region. The haplokinety is a collar of paired kinetosomes surrounding the cytostome; a postciliary microtubular ribbon descends from each kinetosomal pair into the cytostomal region. Ultrastructural details of the buccal cortex of C. virens and other heterotrichs are compared. The nemadesmata which lie under the membranelles are implicated in the body bending of C. virens.
Algae endosymbiotic in the cytoplasm of C. virens are described.     

Simple Synthesis of Climacostol,a Defensive Secretion by the Ciliate Climacostomum virens

Climacostol {1,3-dihydroxy-5-[(Z)-2'-nonenyl]benzene,1}, a defensive secretion by the protozoan ciliate Climacostomum virens against predators, was synthesized in a 43% overall yield in three steps by starting from methyl 1,3-bis(tert-butyldimethylsilyloxy) phenylacetate (3).     

Précisions Temporelles sur les Processus de la Stomatogenèse de Tetrahymena paravorax analysés en Microscopie Photonique

Resume. Une analyse des séquences morphogénétiques du CiliéTetrahymena paravorax montre que: (A) La durée de la stomatogenèse de bipartition des formes microstomes en croissance exponentielle représente 45% du temps de génération (stade 1—20%; stade 2—3%; stade 3—3%; stade 4—5%; stade 5—5%; stade 6—9%). (B) La division cytoplasmique est inégale (les proters sont plus petits que les opisthes); la différence de taille initiale entre les 2 produits de fission est probablement compensée par une prolongation de la période de croissance chez le proter. (C) Le pourcentage maximum de réorganisation buccale microstome → macrostome pour les populations asynchrones atteint –? 70% au bout de 210 mn d'incubation dans la stomatine. (D) L'initiation de la stomatogenèse de remplacement oral est connectée avec la fin d'une période dont la durée minimale est approximativement celle du stade 0 du cycle normal d'interdivision des microstomes; cette initiation est retardée chez les microstomes exposés à la stomatine dès le début du cycle cellulaire. (E) Le primordium buccal de division peut se résorber en présence de stomatine et la stomatogenèse antérieure peut commencer avant que ne soit terminée cette résorption; la résorption n'est plus induite au-delà d'un point du stade 5 qui précède le début de la constriction du corps cellulaire. SYNOPSIS. An analysis of the morphogenetic sequences in the ciliate Tetrahymena paravorax has shown that: (A) The duration of predivision stomatogenesis in exponentially growing microstomes occupies 45% of the generation time (stage 1—20%; stage 2—3%; stage 3—3%; stage 4—5%; stage 5—5%; stage 6—9%). (B) Cytoplasmic division is unequal (the proters are smaller than opisthes); the initial size difference between the 2 fission products is presumably compensated by an increased growth period in the proter. (C) The maximum percentage of microstome-to-macrostome oral reorganization is –? 70% in asynchronous populations, 210 min after suspension in stomatin. (D) Initiation of oral replacement stomatogenesis is associated with the end of a period which has a minimum duration nearly equal to that of stage 0 characteristic of the normal inter-division cycle of the microstomes; this initiation is delayed if exposure of microstomes to stomatin is begun at the onset of the cell cycle. (E) The buccal primordium formed in division can be resorbed in presence of stomatin and anterior stomatogenesis can start before the resorption is completed: this resorption is not induced if the cells have progressed beyond a point which precedes the beginning of the cell furrowing (stage 5).     

Ultrastructural Damage to the Malaria Parasite in the Sickled Cell

The process by which malaria parasites are killed in sickled erythrocytes was studied by electron microscopy. In vitro cultures of Plasmodium falciparum in sickle cell hemoglobin (HbS) homozygous (SS) and heterozygous (SA) red cells were deoxygenated for up to 6 h and fixed under anaerobic conditions. Parasites in SS cells appeared to be disrupted by intrusions of needle-like deoxyHbS aggregates; disintegration of cytoplasm and membranes followed. In SA red cells, the parasites were generally not disrupted. Instead, extensive vacuolization occurred, a sign of metabolic inhibition. The resistance of HbS gene carriers to malaria results partly from these causes of intracellular parasite death.     

Description of the Infraciliature and Morphogenesis in the Ciliate Urotricha ondina N. Sp. (Prorodontida, Urotrichidae)

Recent works on prostomatid ciliates show that some genera of this group have a differentiated oral infraciliature and that their stomatogenesis during division involves the proliferation of only a few somatic kineties. These findings have significant implications regarding the iaxonomic status of these genera and also on the terminology used for the oral structures. In Urotricha ondina , the oral infraciliature consists of (1) a paroral kinety formed of paired kinetosomes that encircle the cytostome at the anterior pole of the cell and (2) 3 adoral organelles, each formed of 2 rows of kinetosomes, ventral in position and obliquely disposed, lying above 3 short somatic kineties that do not reach the anterior pole of the cell. This oral ciliature —formerly known as the corona and brosse, respectively—originate during stomatogenesis from the proliferation of 4 somatic kineties that lie posterior to the adoral organelles of the parental cell.     

Conjugation in Polytomella agilis Araga˜o (Volvocida,Polyblepharidae)*

SYNOPSIS. The occurrence of conjugation in the flagellate, Polytomella agilis Aragão, as first reported in 1910, is confirmed. The gametes made contact with each other in a variety of positions. Our observations differ in minor ways from those reported for P. agilis and are in considerable disagreement with others published on sexual reproduction in Polytomella caeca.     

Mechanical Forces Program the Orientation of Cell Division during Airway Tube Morphogenesis

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Oral Morphogenesis of the Microstome to Macrostome Transformation in Miamiensis avidus Strain Ma/21

ABSTRACT. Miamiensis avidus, a marine scuticociliate, undergoes microstome to macrostome transformation. This process is induced by prey ciliates. the morphogenesis of this process was examined using scanning electron microscopy and light microscopy of quantitative protargol-stained specimens. Several stages are identified and described.     

Alteration of the Tetrahymena Genome During Nuclear Differentiation*†

Synopsis.
The DNA of the macro- and the micronucleus of Tetrahymena thermophila has been compared by various biochemical methods. It became evident from their thermal denaturation temperatures and buoyant densities that the 2 DNAs were very similar in overall composition. Small differences were detected when the sequence complexities of these DNAs were compared by DNA renaturation studies. The studies suggested that ˜ 10% of the micronuclear genome was lost or underrepresented in the macronucleus. Comparison of individual gene levels revealed further differences. By using the technic of gene cloning a micronuclear sequence was isolated which hybridized only with micronuclear, but not with macronuclear DNA. These results indicated the occurrence of elimination or underreplication of this sequence in the macronucleus. Gene amplification was also shown to occur. In the micronucleus only a single copy of rDNA was found integrated into the chromosome. During macro-nuclear development, amplification was observed to occur, and the amount of rDNA to increase, until there were ˜ 200 copies per haploid genome in the mature macronucleus. all of them extrachromosomal and palindromic. The 3rd case of alteration involved a simple repeated sequence, (CCCCAA)n, present in the termini of rDNA and also in many other locations of the genome. Restriction endonuclease digestion studies revealed drastic differences in the organization of the repeats between macro-and micronucleus. These differences may be interpreted as the results of chromosome fragmentation which occurs at every cluster of the repeats during macronuclear development. The relationship between this event and gene amplification and elimination is discussed.     

Observations on Gametogenesis in Plasmodium falciparum from Continuous Culture*

Synopsis. Gametocytes of Plasmodium falciparum were produced in continuous cultures but eventually declined in numbers after 3–4 months in vitro. Their development progressed in a consistent pattern, from small rounded, through triangular, to ellipsoidal, and finally after 8 days to crescentic forms. Morphologic maturity occurred at 8–9 days, but the gametocytes would not exflagellate in vitro, even after 14–18 days of development. Thus, current culture methods cannot produce a continuous supply of functional gametes for further studies.     

Regulation of Macronuclear DNA Content in Tetrahymena thermophila*†

Synopsis.
Unequal macronuclear division in Tetrahymena thermophila introduces variance into G1 macronuclei; unless eliminated such variance would result in continuous variation in DNA content. Analysis of G1 and G2 macronuclear variances reveals that the added variance is eliminated by action on the extremes of macronuclear DNA content. In this model (Model II), macronuclei with small amounts of DNA have an additional complete S phase, while those with large amounts of DNA skip S. From available data, chromatin extrusion is shown not to contribute significantly, if at all, to the elimination of variance. Computer simulations utilizing haploid subunits indicate that model II predictions apply reasonably well to experimental data in terms of coefficients of variation, mean DNA content, and frequency of additional and skipped S phases. The simulations reveal also that within certain constraints, particularly the thresholds for additional and skipped S phases, macronuclear assortment is unaffected by Model II regulation. The relationships between Model II and other aspects of the cell cycle are briefly discussed.     

Formation and Fate of Extranuclear Chromatin Bodies in Tetrahymena

The fate of extranuclear chromatin bodies (ECBs) formed by exclusion of macronuclear material at the time of karyokinesis was followed quantitatively in Tetrahymena pyriformis strain GL-I. In a logarithmic growth phase culture, 51% of the dividing cells produced one (43%) or more (8%) ECBs. Most of these gradually disappear before the next cell division, but ? 13% are retained and carried into subsequent cell cycles. The random distribution of ECBs into anterior or posterior daughter cells, their staining and morphological characteristics, and their rapid loss in cells in starvation medium, all indicate that ECBs play no more of a role in cellular activity than that of an internally produced food vacuole.     

Regulation of Macronuclear DNA Content in Paramecium tetraurelia*†

Synopsis.
The amitotic division of the macronucleus of Paramecium tetraurelia produces daughter macronuclei which frequently differ in DNA content. In wild-type cells these differences are small, but can be increased substantially by the action of mutant genes. The variance in macronuclear DNA content would increase continuously if there were no mechanism to regulate it. Paramecium has a very effective regulatory mechanism—all cells synthesize similar amounts of macronuclear DNA, regardless of the number of macronuclei or their prereplication DNA content. DNA synthesis is controlled at the level of macronuclear subunits, and the postreplication macronucleus consists of a mosaic of subunits that have undergone different numbers of replication events during the previous cell cycle. It is evident from experimental results that the amount of DNA synthesized can be influenced by the total size or mass of the cell. Experimental modification of the initial DNA content leads to no change in the amount of DNA synthesized, or in the subsequent protein content of the cells, but modification of cell size causes corresponding changes in the amount of DNA synthesized and in the size of the macronucleus. The implications of these observations for cell growth and the cell cycle are discussed.     

Partial Purification and Characterization of a Bacteriolytic Enzyme Secreted by Tetrahymena*

Synopsis. Tetrahymena pyriformis strain HSM secretes large quantities of acid hydrolases into the culture medium. An enzyme secreted by the ciliate and capable of degrading walls of streptococci was identified and purified to a considerable degree. The pH optimum of this enzyme was 3–4, and it was eluted after cytochrome c from Sephadex G-75 columns. Unlike lysozyme, the enzyme was thermolabile at pH 2.9, but relatively thermostable at pH 8.1. It degraded “C-labeled cell walls of streptococci releasing reducing groups. Cell walls prepared from different strains of streptococci differed in susceptibility to this enzyme, the most sensitive strain tested being of group A, type T12. It was shown in immunologic studies that this hydrolase released the group-specific carbohydrate from the walls. Secretions of Tetrahymena from early stationary-phase cultures had more bacterio-lytic activity than those from cells from late stationary-phase cultures. Further, cells from cultures grown in glucose-supplemented medium secreted less of the enzyme than ciliates of comparable age grown in unsupplemented proteose-peptone. The newly isolated bacteriolytic enzyme, presumably of lysosomal origin, may be helpful in characterizing streptococcal cell walls.     

Planar Cell Polarity Signaling in Collective Cell Movements During Morphogenesis and Disease

Collective and directed cell movements are crucial for diverse developmental processes in the animal kingdom, but they are also involved in wound repair and disease. During these processes groups of cells are oriented within the tissue plane, which is referred to as planar cell polarity (PCP). This requires a tight regulation that is in part conducted by the PCP pathway. Although this pathway was initially characterized in flies, subsequent studies in vertebrates revealed a set of conserved core factors but also effector molecules and signal modulators, which build the fundamental PCP machinery. The PCP pathway in Drosophila regulates several developmental processes involving collective cell movements such as border cell migration during oogenesis, ommatidial rotation during eye development, and embryonic dorsal closure. During vertebrate embryogenesis, PCP signaling also controls collective and directed cell movements including convergent extension during gastrulation, neural tube closure, neural crest cell migration, or heart morphogenesis. Similarly, PCP signaling is linked to processes such as wound repair, and cancer invasion and metastasis in adults. As a consequence, disruption of PCP signaling leads to pathological conditions. In this review, we will summarize recent findings about the role of PCP signaling in collective cell movements in flies and vertebrates. In addition, we will focus on how studies in Drosophila have been relevant to our understanding of the PCP molecular machinery and will describe several developmental defects and human disorders in which PCP signaling is compromised. Therefore, new discoveries about the contribution of this pathway to collective cell movements could provide new potential diagnostic and therapeutic targets for these disorders.     

Acid and Neutral Hydrolases in Trypanosoma cruzi. Characterization and Assay*

Twelve acid hydrolases, 4 near-neutral hydrolases and alkaline phosphatase were demonstrated in 0.34 M sucrose homogenates of Trypanosoma cruzi strain Y: p-nitrophenylphosphatase and α-naphthylphosphatase, with optimum pH at ? 6.0; α-galactosidase, β-galactosidase, β-glucosidase, N-acetyl-β-glucosaminidase, cathepsin A and peptidase I and III, with optimum pH between 5.0 and 6.0: and arylsulfatase cathepsin D, α-arabinase and α-mannosidase with optimum pH at ? 4.0 α-Glucosidase, gluccse-6-phosphatase and peptidase II had optimum pH at ? 7.0. β-Glycerophcsphatase had a broad pH-activity curve from 4.0 to 7.4, with maximum activity at pH 7.0. The main kinetic characteristics of these enzymes and their quantitative assay methods were studied. No activity was detected for α-fucosidase, β-xylosidase, β-glucuronidase, elaidate esterase. acid lipase, and alkaline phospho-diesterase.     

Cryopreservation of Ochromonas in Liquid Nitrogen with Reproducibility of Thiamin Assay

The first successful cryopreservation of Ochromonas danica and Ochromonas malhamensis is reported. The freezing method was consistently reproducible for the former, but not for the latter. Ochromonas danica cultures established from frozen material still could be used as test organisms for assay of thiamin. This is the first report of a protozoon retaining its assay property after being frozen to -196 C.     

Genetic Evidence Concerning the Structure of the Tetrahymena thermophila Macronucleus*†

Synopsis.
A satisfactory model of the Tetrahymena thermophila macronucleus must explain its genetic behavior in terms of its constituent molecules. Particular genetic phenomena requiring explanation are (a) phenotypic assortment , here interpreted as resulting from allelic disjunction rather than from differential gene expression; (b) unequal allelic input for some loci , interpreted as a consequence of unequal and selective replication of some alleles during early macronuclear development; (c) delayed assortment at some loci , interpreted as an effect of inequality of allelic input combined with a generalized elevation of DNA content during early clonal history; (d) linkage disruption , probably reflecting continuous somatic recombination rather than dissolution of chromosomes into small repliconic units; (e) assortment depression , brought about by the occasional association of homologous replicons (chromosomes) or else by a differential increase in some classes of replicons; (f) ploidy-related developmental differences in macronuclear primordia are interpreted on the basis of quantitative differences in DNA rather than in terms of an early perception of genic imbalance, (g) Ploidy independent macronuclear DNA content is consistent with several models of size regulation.