An Abnormality in the Life Cycle of Tokophrya infusionum

SYNOPSIS. Tokophrya infusionum reproduces by endogenous budding, forming a ciliated embryo within a brood pouch. The embryo is released to the outside medium, where it swims for some time, then undergoes metamorphosis by the formation of a disk, stalk, and tentacles. In one of the clones (E22), 1–2% of the adults display abnormalities during reproduction. In some of the abnormal adults, the embryo is retained inside a greatly enlarged brood pouch and undergoes metamorphosis within the parent; in others, the embryo is not formed, and only a large empty brood pouch appears. Attempts to establish a separate clone composed only of abnormal organisms were unsuccessful, and led to the conclusion that all members of clone E22 are potentially abnormal. Experiments were performed to increase the percentage of abnormal organisms; it was found that overfeeding is one of the factors favoring abnormal reproduction. Physiological and genetic explanations of the abnormality are proposed and discussed.     

A Cytological Study and Reclassification of Trichophrya collini (Saedeleer & Tellier)1

ABSTRACT. Trichophrya collini has a polygonal, dorsoventrally flattened body (up to 75 μm diam.), with capitate tentacles arranged in 1–3 rows within peripheral fascicles. There is a central polymorphic macronucleus, an associated micronucleus, and numerous peripheral contractile vacuoles with ventral discharge pores. The cell has a multilayered cortex and the cytoplasm contains suctorian organelles such as crescentic bodies, elongate dense bodies, and haptocysts. The highly contractile tentacles have an axoneme with an outer ring of 24 microtubules separated into six groups and an inner ring of six curved lamellae, each with five microtubules. The lamellae at the distal and proximal ends of the axoneme are arranged in a helix, and the outer ring microtubules are joined in a distal connective sheath. In the apical knob of the tentacle, the haptocysts are borne on a central capsule, Reproduction is by endogenous budding to produce a single oval-shaped swarmer, with equatorial ciliature, which metamorphoses within 3 h. These observations suggest that this organism, previously known as Heliophrya collini Saedeleer & Tellier, is synonymous with Platophrya rotunda Gönnert, Craspedophrya rotunda Rieder, and Heliophrya rotunda Matthes. Its endogenous mode of budding assigns it to the genus Trichophrya. but it is distinct from Trichophrya rotunda Hentschel, and should be reclassified to Trichophrya collini (Saedeleer & Tellier).     

Cytoskeleton Structure and Composition in Choanoflagellates

The structure and composition of the cytoskeleton has been studied in Monosiga ovata (Protozoa: Order Choanofiagellida Kent 1880) using a combination of methods in association with light and electron microscopy. Supplementary observations are included for Desmarella moniliformis. The basal body of the single anterior flagellum is subtended proximally and at right angles by a second, non-flagellar basal body. The edges of the two basal bodies are connected by a fibrillar bridge. A long, narrow, striated, fibrillar rootlet extends posteriorly from the lower edge of the non-flagellar basal body towards the Golgi apparatus. It is associated throughout most of its length with the surface of a flattened sac. Rootlet microtubules pass radially from a ring of electron dense material which encircles the distal end of the flagellar basal body. These microtubules extend outwards for about one-third of the length of the cell. Within each collar tentacle is a longitudinal bundle of microfilaments composed of actin as illustrated by rhodamine-phalloidin staining for fluorescence microscopy. The base of each microfilament bundle is associated with one or more rootlet microtubules by fine fibrillar bridges. The attachment between microtubules and tentacle microfilaments is further demonstrated by their coordinated displacement when the cytoskeleton becomes dislodged. The role of the cytoskeleton in maintaining the position of the collar tentacles during interphase and cell division is discussed.     

The oral apparatus of Tetrahymena pyriformis, strain WH-6. IV. Observations on the organization of microtubules and filaments in the isolated oral apparatus and the differential effect of potassium chloride on the stability of oral apparatus microtubules.

This report is an ultrastructural analysis of the organization of the isolated oral apparatus of Tetrahymena pyriformis, strain WH-6, syngen 1. Attention has been focused on the organization of microtubules and filaments in oral apparatus membranelles. Oral apparatus membranellar basal bodies were characterized with respect to structural differentiations at the distal and proximal ends. The distal region of membranellar basal bodies contains the basal plate, accessory microtubules and filaments. The proximal end contains a dense material from which emanate accessory microtubules and filaments. There are at least two possibly three different arrangements of accessory structures at the proximal end of membranellar basal bodies. All membranellar basal bodies appear to have a dense material at the proximal end from which filaments emanate. Some of these basal bodies have accessory microtubules and filaments emanating from this dense material. A possible third arrangement is represented by basal bodies which have lateral projections, from the proximal end, of accessory microtubules and filaments which constitute cross or peripheral connectives. There are at least three examples of direct associations between oral apparatus microtubules and filaments: (1) filaments which form links between basal body triplet microtubules, (2) filaments which link the material of the basal plate to internal basal body microtubules, (3) filaments which link together microtubule bundles from membranellar connectives. KCl extraction of the isolated oral apparatus resulted in the selective solubilization of oral apparatus basal bodies, remnants of ciliary axonemes and fused basal plates. Based on their response to KCl extraction two distinct sets of morphologically similar micro tubules can be identified: (a) microtubules which constitute the internal structure of basal bodies and ciliary axonemes, (b) microtubules which constitute the fiber connectives between basal bodies.     

The Stalk of the Suctorian Tokophrya infusionum: Histochemistry, Biochemistry, and Physiology

Tokophrya infusionum, a sessile suctorian with an external stalk and adhesive disc, has in its life cycle a ciliated, swimming embryo which metamorphoses into the adult form. The addition of NiCl₂ to the medium induced metamorphosis immediately; however, other salts had no effect. Incomplete metamorphosis, without stalk formation, occurred if the organism began metamorphosis before its anterior (stalk-forming) end touched a substrate. The stalk was studied by histochemical and biochemical technics to determine its composition. The stalk stained with mercury-bromphenol blue, and Alcian blue under a variety of conditions, but not with PAS. These results suggest that the stalk contains protein and sulfate groups, possibly in the form of a sulfated protein-polysaccharide. The stalk was insoluble in several common laboratory reagents, but did dissolve in hot 6 N HCl, 2 N NaOH, and papain. It was evident from amino acid analysis of the stalk and of the whole organism that 15% of the total protein is located in the stalk.     

水螅异常极性体轴的形成及矫正进程的观察

目的:如何建立和维持体轴是一个基本的发育生物学问题,而淡水水螅是适合进行形态发生和个体发育调控机制研究的重要模式生物。本文观察了大乳头水螅异常极性体轴的形成及矫正进程,初步探讨水螅极性体轴的维持和调控机制。方法:先切取水螅的整个头部,再获得带二根触手的口区组织。通过ABTS细胞化学染色法检测水螅基盘分子标志物过氧化物酶的表达,判别水螅基盘组织(水螅足区的末端)是否形成。结果:从40块口区组织再生得到的水螅个体中有1例极性体轴发育异常的个体,其身体两端均发育成头区,且两端的头区均具有捕食能力。随后水螅其中一端头区的触手逐渐萎缩、退化,最终该端头区转化成具有吸附能力的基盘组织。结论:水螅组织的再生涉及极性体轴的重建,而一些特殊因素可能造成临时性的水螅极性体轴调控紊乱。本研究表明水螅具备自我矫正异常极性体轴的能力。另外,本研究结果显示水螅触手可以萎缩直至退化,该现象涉及的细胞学过程可能是非常复杂的,有可能涉及到触手细胞的凋亡转化过程,也可能是触手的高度分化细胞仍然具备去分化能力、去分化后再转移到身体其他地方,其具体机制值得进一步探究。     

草鱼鳃上寄生毛管虫一新种——变异毛管虫的研究

吸管亚纲(Subclass suctoria)中,多数种类具有或长或短的炳,附着它物上营固着生活。寄生在鱼类体表、鳃丝内的毛管虫(Trichophrya)和簇管虫(Erastophrya)的种类中,至今未见报道有固着柄的代表。       

Ultrastructural studies of the commensal suctorian,Choanophrya infundibulifera hartog

Summary The feeding tentacles of Choanophrya contain a central canal lined by microtubules. Only one tentacle develops during metamorphosis of the embryo into the adult, but others develop at intervals throughout adult life. Each tentacle forms adjacent to a solitary, subcortical kinetosome which lies parallel to the body surface, lacks accessory elements and never develops a cilium. Small condensations of electron-dense material and short bundles of microtubules form adjacent to the cartwheel region of the kinetosome. Initially these bundles are orientated randomly but later they become radially arranged and curved into prolamellae around a disc-shaped condensation centre, to form a paddlewheel-like tentacle primordium 0.8–1.1 m in diameter. The condensation centre consists of alternating concentric electron-dense and electron-transparent zones, and lies with its axis perpendicular to both the kinetosome and the cortex. The microtubules in each prolamella increase in number and pairs of short tip microtubules develop between adjacent prolamellae. Subsequently the developing lamellae become enclosed by a cylinder of ring microtubules. Once all the microtubule components of the tentacle primordium are established it increases in length by addition of material to the basal ends of the microtubules to form a short microtubule canal. As the canal elongates the epiplasm above it disappears and the pellicle membranes become uplifted around the protruding tentacle. An epiplasmic collar differentiates around the growing tentacle whilst spheroid vesicles and solenocysts begin to accumulate in the surrounding cytoplasm.This investigation was supported by the J.S. Dunkerley Fellowship in Protozoology, awarded by the University of Manchester.     

The development and fine structure of ultimobranchial glands in larval anurans

A comparative optical microscopic and ultrastructural study on the ultimobranchial (UB) glands of three common species of Israeli anurans: Bufo viridis, Hyla arborea, and Rana ridibunda during metamorphosis is presented. The UB glands typically consist of a single follicle with a central lumen, though occasionally secondary follicles are present in Hyla and Rana. A single UB cell type is found which appears either in a very electron-dense "dark" form or as a less dense "light" form, though the ratio of dark: light cells from gland to gland at any one stage of metamorphic development is quite variable. By the end of metamorphosis in Bufo and Hyla all the UB cells are usually of the light variety, whereas in Rana the dark cells persist. The organelles of these secretory cells including secretory granules, granular endoplasmic reticulum, free ribosomes, tonofilaments, microtubules, Golgi bodies, and lipid droplets, their distribution, abundance, and possible functions in relation to metamorphosis are described. Apocrine secretion into the central lumen of the gland is also described and discussed.     

Fertilization inNicotiana tabacum: Cytoskeletal modifications in the embryo sac during synergid degeneration

The cytoskeletal organization of the embryo sac of tobacco (Nicotiana tabacum L.) was examined at maturity and during synergid degeneration, pollen-tube delivery and gamete transfer using rapid-frozen, freeze-substituted and chemically fixed material in combination with immunofluorescence and immunogold electron microscopy. Before fertilization, the synergid is a highly polarized cell with dense longitudinally aligned arrays of microtubules adjacent to the filiform apparatus at the micropylar end of the cell associated with major organelles. The cytoskeleton of the central cell is less polarized, with dense cortical microtubules in the micropylar and chalazal regions and looser, longitudinally oriented cortical microtubules in the lateral region. In the synergid and central cell, F-actin is frequently found at the surface of the organelles and co-localizes with either single microtubules or microtubule bundles. Egg cell microtubules are frequently cortical, randomly oriented and more abundant at the chalazal end of the cell; actin filaments are associated with microtubules and the cortex of the egg cell. At 48 h after pollination and before the pollen tube arrives, the onset of degeneration is evident in one of the two synergids: the electron density of cytoplasmic organelles and the ground cytoplasm increases and the nucleus becomes distorted. Although synergids otherwise remain intact, the vacuole collapses and organelles degenerate rapidly after pollen-tube entry. Abundant electron-dense material extends from the degenerated synergid into intercellular spaces at the chalazal end of the synergid and between the synergids, egg and central cell. Rhodamine-phalloidin and anti-actin immunogold labeling reveal that electron-dense aggregates in this region contain abundant actin forming two distinct bands termed coronas. This actin is part of a mechanism in the egg apparatus which appears to precisely position and facilitate the access of male gametes to the egg and central cell for fusion.Abbreviations ES embryo sac - FA filiform apparatus - Mf microfilament - Mt microtubule - PT pollen tube - RF-FS rapid-freeze freeze-substitution - TEM transmission electron microscopy We thank Gregory W. Strout for technical assistance in the use of the RF-FS technique and Dr. Hongshi Yu for providing Fig. 1. This research was supported by U.S. Department of Agriculture grants 88-37261-3761 and 91-37304-6471. We gratefully acknowledge use of the Samuel Robert Noble Electron Microscopy Laboratory of the University of Oklahoma.     

Fine Structure of Sporozoites of Eimeria nieschulzi*

SYNOPSIS. An electron microscope study of sporozoites of Eimeria nieschulzi Dieben, 1924 revealed that they have a pellicle which is thickened at the anterior end to form 2 polar rings. Radiating posteriorly from the rings, directly beneath the pellicle, are approximately 25 microtubules which may aid in support and locomotion of the sporozoite. Within the polar ring is a dense conoid. Numerous toxonemes extend posteriorly from the area of the conoid. Two paranuclear bodies are present and some toxonemes are closely associated with the anterior body. Numerous ribosomes, bodies containing granular material, and osmiophilic vesicle bounded bodies are also present. Each sporozoite has a single nucleus with a diffuse karyosome and distinct nuclear double membrane.     

Serotonin immunoreactivity in the nervous system of the free‐swimming larvae and sessile adult females of Stephanoceros fimbriatus (Rotifera: Gnesiotrocha)

Unlike most rotifers (Rotifera), which are planktonic and direct developers, many gnesiotrochan rotifers (Monogononta: Gnesiotrocha) are sessile and have indirect development. Few details exist on larval metamorphosis in most gnesiotrochans, and considering the drastic transformation that takes place at metamorphosis—the replacement of the ciliated corona with a new head that bears ciliated tentacles (the infundibulum)—it is perhaps surprising that there are limited data on the process. Here, we document part of this metamorphosis by examining the presence and distribution of neurons with serotonin immunoreactivity in the nervous system of both planktonic larvae and sessile adult females. Using antibodies against serotonin combined with confocal laser‐scanning microscopy (CLSM) and 3D reconstruction software, we mapped the immunoreactive cell bodies and neurites in both life stages and found that relatively few changes occurred during metamorphosis. The larvae possessed a total of eight perikarya with serotonergic immunoreactivity (5HT‐IR) in the brain, with at least two pairs of perikarya outside the brain in the region of the corona. Cells with 5HT‐IR in the brain innervated the larval corona and also sent neurites to the trunk via the nerve cords. During metamorphosis, the corona was replaced by the infundibulum, which emerged from the larval mouth to become the new functional head. This change led to a posterior displacement of the brain and also involved the loss of 5HT‐IR in the lateral brain perikarya and the gain of two perikarya with 5HT‐IR in the anterior brain region. The innervation of the anterior end was retained in the adult; neurites that extended anteriorly to the mouth of the larva formed a distinct neural ring that encircled the infundibulum after metamorphosis. Significantly, there was no innervation of the infundibular tentacles by neurites with 5HT‐IR, which suggests that ciliary control is unlikely to be modulated by serotonin within the tentacles themselves.     

Scanning Electron Microscopy of Budding and Metamorphosis in Discophrya collini (Root)*

SYNOPSIS. Budding and metamorphosis in the suctorian ciliate, Discophrya collini, have been investigated by scanning electron microscopy. The adult body form, tentacles, stalk, and attachment disk are described. A field of depressions or small pits was observed in the pellicle of adult suctorians in the early stages of bud formation. These pits deepen and coalesce until one large pore, the birth pore, remains. Cilia protrude through the pore, and as eversion of the bud proceeds the meridional arrangement of the larval ciliation is evident. After eversion is completed, a pronounced division furrow is found between the adult and soon-to-be-released swarmer. The stalk-forming region is seen on swarmers. Metamorphosing swarmers produce tentacles upon settling before any indication of ciliary resorption. Resorption of cilia and change in body form occur progressively with the production of the attachment disk and stalk.     

Scanning electron microscopy of budding and metamorphosis in Discophrya collini (Root).

Budding and metamorphosis in the suctorian ciliate, Discophrya collini, have been investigated by scanning electron microscopy. The adult body form, tentacles, stalk, and attachment disk are described. A field of depressions or small pits was observed in the pellicle of adult suctorians in the early stages of bud formation. These pits deepen and coalesce until one large pore, the birth pore, remains. Cilia protrude through the pore, and as eversion of the bud proceeds the meridional arrangement of the larval ciliation is evident. After eversion is completed, a pronounced division furrow is found between the adult and soon-to-be-released swarmer. The stalk-forming region is seen on swarmers. Metamorphosing swarmers produce tentacles upon settling before any indication of ciliary resorption. Resorption of cilia and change in body form occur progressively with the production of the attachment disk and stalk.     

The fine structure of the brain of Gastrocotyle trachuri (Monogenea: Platyhebninthes)

Summary The fine structure of the brain of the monogenean Gastrocotyle trachuri (Platyhelminthes) is described. The brain consists of a central neuropile surrounded by a layer of cell bodies. The neuropile is composed of a fine meshwork of naked neurites which contain various types of vesicles and other organelles although microtubules have not been found. Five kinds of vesicles; three clear types and two dense types, were found within the neuropile.Two types of neuronal cell body were identified on the basis of their vesicle contents although it is possible that these two types represent the extremes of a single cell type. A characteristic feature of the neuronal perikarya of Gastrocotyle is the presence of deep infoldings into the cell of the outer membrane. These infoldings often contain fibrous interstitial material and in a number of cases hemidesmosome-like structures have been found in the distended, distal end of the infoldings.     

七星瓢虫精子鞭毛的超微结构(英文)

应用细胞整装制备和超薄切片技术,在透射电子显微镜下检查了七星瓢虫成熟精子鞭毛的超微结构。精子鞭毛是由一个典型的9＋9＋2轴丝,两个同形结晶的线粒体衍生物,两个附体（每个附体具有两部分,一个嗜锇致密月牙体和一个海绵月牙体）和一个非结晶体组成,在鞭毛终端部,仅存的轴丝失去了两个中央微管保留了9个具有动力蛋白臂的双微管和9个附微管。     

Budding and Metamorphosis in Acineta tuberosa. An Electron Microscopic Study on Morphogenesis in Suctoria

SYNOPSIS. All stages (except conjugation) of the life cycle in Acineta tuberosa (Suctoria) were studied in the electron microscope. Budding starts with the invagination of a small pellicular area near the opening of the vacuole and bearing rows of barren basal bodies. Some of these basal bodies are incorporated into the swarmer-anlage and give rise to 8 rows of cilia, while the other basal bodies remain barren on the mother cell's side of the brood pouch. They will provide their own genetic continuity and later give rise to the swarmer of the next generation. Kineties are not spaced on the growing swarmer-anlage until their cilia are fully grown. Further details on the stalk-forming crganelle and general features of the development of the larvae are given.
Metamorphosis starts with the formation of basal disc and stalk. The stalk-forming material is released thru scopular pores into a tube-like mold formed by the scopula after having been pulled inward. Later, scopula pores spread from the scopular area proper and move upward. On their way to the apical part of the animal the cuticle is secreted. The differentiation of tentacles is described and new observations regarding a possible mode of haptocyst formation are given.
The results are discussed with respect to the morphogenetic potentialities of cortical structures in general.     

Comparison of the ultrastructure of stimulated and unstimulated mechanoreceptors in the taste hairs of the blowfly Phaenicia serricata

The structure of mechanoreceptors at the base of labeilar taste hairs of the blowfly Phaenicia serricata were examined in stimulated and unstimulated conditions (i.e. with the hair bent or unbent). Physiological recordings from the mechanoreceptor showed that the receptors responded when the hair is bent dorsally or ventrally and when the hair is bent at extreme angles. These conditions are the same as those placed on hairs in the anatomical studies. Bending the hair toward the ventral labellar surface caused the hair base to compress and indent the tubular body and its surrounding membrane and sheath at the distal end of the mechanoreceptor dendrite. In compressed tubular bodies, microtubules oriented longitudinally were bent and separated a greater distance from each other. Separation as much as 70 nm was observed in compressed tubular bodies as compared with a maximum of 26 nm between microtubules in tubular bodies of unbent hairs. The dense amorphous material between microtubules of compressed tubular bodies formed prominent bridges 18 nm thick connecting the microtubules at intervals of 48–74 nm. Thin 10 nm filaments were also evident in the spaces between microtubules. When the hair was bent toward the proximal end of the proboscis, the tip of the tubular body was bent about 15 °. The tubular body appears to function as a firm but resilient structure over which the dendritic membrane can be stretched during mechanostimulation. Comparison of morphology of bent and unbent hairs suggests a means by which mechanical force from the movement of the hair is transferred to the receptors by structures in the hair socket region. No differences were found in ciliary structures of stimulated and unstimulated receptors.     

The effect of chloroquine on the intralysosomal degradation of cell-coat glycoproteins in the absorptive cells of cultured human small-intestinal tissue as shown by silver proteinate staining

Summary The effect of chloroquine on the intralysosomal degradation of cell-coat glycoproteins in cultured intestinal absorptive cells was investigated by silver proteinate staining. The results of this staining method, which is specific for carbohydrate containing macromolecules such as glycoproteins and mucopolysaccharides, showed that in the presence of the drug considerable amounts of silver proteinate-positive material accumulated in one type of lysosome-like body: the dense bodies. The staining pattern of other cell organelles was not affected by chloroquine. The presence of the drug in the culture medium also resulted in the occurrence of numerous small vesicular structures in the matrix of the dense bodies. These showed a similar size and structure to those present in the other type of lysosome-like body: the multivesicular bodies. This observation, together with earlier autoradiographical data, suggests that cell-coat material is transferred from multivesicular to dense bodies by fusion between these organelles. This study thus provides further evidence for a regulatory mechanism of cell-coat glycoprotein transport by the lysosome-like bodies in human intestinal absorptive cells.