Range of Variation in the Somatic Infraciliature and Contractile Vacuole Pores of Tetrahymena pyriformis

SYNOPSIS. Meridian ranges and contractile vacuole pore patterns were determined for 36 strains of Tetrahymena pyriformis, including most of the “classic” amicronucleate and micronucleate strains used by many investigators, plus a dozen other strains not previously characterized with respect to these two morphological features. Uniform axenic culturing and staining techniques were employed. Meridian ranges and modes are analyzed with strain-by-strain comparisons to the reports of previous investigators. The overall inclusive range of the 36 strains was 15–25 meridians. Modes for individual strains varied from 16 to 23. Broader ranges and, especially, higher modes and higher limits are recorded than those reported by Corliss (1953) for strains grown in bacterized hay cultures. Two postoral meridians are characteristic, although a single individual having only one and a few having three postorals were observed. Three postorals were found only in those strains having the higher number of total meridians. A few individuals, showing an anterior half or a posterior half of a bipolar meridian missing, indicate a possible explanation of how a single dividing individual could produce a proter and an opisthe differing in the total number of meridians. Meridian ranges of individual strains do not overlap each other in all cases, but they do constitute a progressively overlapping series which does not warrant taxonomic separation of strains at either extreme from each other. Contractile vacuole pores varied from 1 to 3, with 2 pores (1 each in meridians 5 and 6) being characteristic of 22 of the strains. The 2-pore 6-7 pattern was modal for 8 of the strains. Presence of 3 pores (in 5, 6 and 7) was typical of only 2 strains, but 3 pores were found occasionally. Another pattern of 3 pores (in 6, 7 and 8) was observed occasionally in 10 strains. Double pores (in 6 and 7 or 7 and 8) and the triple pore patterns were observed only in the strains having the highest total number of meridians. These variations are not considered adequate justification for taxonomic separation. Strains Ki and Aq are affirmed to be T. pyriformis. Strains V¹ PP and V, formerly regarded as strains of T. vorax, are considered to be T. pyriformis, supporting the view of Shaw and Williams (1963).     

Eimeria scholtysecki n. sp. from Ord's Kangaroo Rat Dipodomys ordii*

SYNOPSIS. Eimeria scholtysecki n. sp. is described from Ord's kangaroo rat Dipodomys ordii. The sporulated oocysts are broadly ovoid to ellipsoid, averaging 24.6 by 19.6 μ. A polar granule is present. A micropyle and oocyst residuum are absent. The ovoid sporocysts average 12.1 by 8.0 μ, and have small, flattened Stieda bodies. The distinctive sporocyst residuum is composed of coarse granules. The mean prepatent period was 8.2 days. Five inoculated rats apparently became reinfected and discharged oocysts for 30 days or more.     

Ultrastructural Observations on the Development of the Microsporidian Protozoon Plistophora hyphessobryconis Schaperclaus*

SYNOPSIS. A sequence of developmental stages of Plistophora hyphessobryconis Schaperclaus, a microsporidian protozoan parasite of the muscular tissue of several species of freshwater fishes, was studied with the electron microscope. The youngest stages observed, ca. 4 × 2 μ, have a single nucleus and their plasm contains only ergastoplasmic lamellae and ribosomes. They are surrounded by a halo of lysed host tissue. They increase in volume to become large sporonts with a great number of nuclei and a thick, 2-layered membrane. Thru schizogony, a corresponding number of sporoblasts is produced within this pansporoblast membrane. Sporoblasts start to develop a thick spore membrane, and a number of smooth-membraned vesicles appear in the plasm. These vesicles fuse to make the outer membrane of the filament. Later, its inner structures originate—the axial electron-dense substance, filling the hollow lumen of the filament, and a middle, electron-transparent layer. The structure of the filament is discussed in relation to its function and with regard to the findings of other authors. The polaroplast is a laminated structure, originating possibly by transformation of endoplasmic reticulum; the polar cap forms its apical part. The cap is also lamellar; its substance reaches into the lumen of the filament for a certain distance. No micropyle was discovered in the shell; the filament is fastened to the polar cap. These observations on microsporidian development and on the structure of their spores are compared with similar data on myxosporidian species. Such a comparison speaks clearly in favor of the complete taxonomic separation of the Microsporidea from the Myxosporidea, the latter being quite different also from other sporozoa sensu lato.     

Excitation-Contraction Coupling in Crayfish

High-sensitivity recording techniques demonstrate a continuousrelation between the onset and magnitude ot tension and themembrane depolarization that is induced by increasing K in thebathing medium or by intracellularly applied outward currents.This finding is not consistent with the mechanism of signallinge-c coupling by electrotonic spread of a "critical" depolarizationinward along the membrane of the transverse tubular system.It is in accord, however, with the channelled current mechanismthat is based on the known anion-permselectivity of the membranein the terminals of the TTS. The channelled-current model alsopredicts a direct role of Cl and a possible interaction betweenCa and CI in e-c coupling. The initiation and maintenance oftension as well as its magnitude, are in fact dependent uponthe concentrations of Ca and Cl in the medium. Thus, both thesignalling to, and the activation of, the contractile systemappear to be performed by a flow of current in the loop: cellmembrane – cell interior – TTS membrane –TTS channels – exterior, as is envisaged in the channelled-currentmodel of e-c coupling.     

Ultrastructural Observations on Life Cycle Stages of Pneumocystis carinii

An ultrastructural study of life cycle stages of Pneumocystis carinii in infected rat lungs in situ was undertaken utilizing 8 different modes of fixation. Three of the fixatives employed gave good fixation of cysts and intracystic bodies, but for the trophic forms fixation was only fair. Both the trophic forms and intracystic bodies have nuclear pores. The mitochondria of the organism have cristac that appear lamellar. One of the fixation modes revealed a thin, electron-dense layer on the outer surface of the cell wall, a "fuzzy coat" that had not been described previously. This material appears to mediate tight adhesion of trophic forms with other trophic forms, cysts, and with pneumocytcs of the lung alveolus.     

Ferri- and Ferrocyanide Salts Change the Current/Voltage Relations of Chara corallina: No Correlation with the Transmembrane Redox System

The current/voltage {I/V) relations of the plasma membrane ofChara corallina cells are characteristic when the bathing mediumhas elevated (5-0 mM) concentrations of potassium Addition ofeither 0-5 mM femcyanide or 0-5 mM ferrocyanide usually induceda qualitatively similar increase in the ‘leak’ current,with a concomitant increase in membrane conductance. Both redoxreactants failed for unknown reasons to affect the I/V profileof some of the cells tested In the sensitive cells, femcyanidewas unable to generate extra current over that found upon additionof ferrocyanide Because the feiTocyanide oxidation rate of thecells is only 10% of the femcyanide reduction rate, we concludethat both forms, fern- and ferrocyanide, affect the 'leak' conductanceindependent of the redox state of the reactants, i e ferrocyanidedoes not act indirectly via an oxidation to femcyanide Hence,under the experimental conditions, we were unable to detecta current that could be assigned to the operation of a transmembraneredox system Furthermore, the fern- and ferrocyanide inducedshift in the I/V profile only reversed slowly after withdrawalof the redox reactants. This suggests that the elicited currentis independent of the presence of an extracellular electronacceptor, i.e on the continuous operation of a proposed transmembraneredox system Key words: Current/voltage curves, transmembrane reductase, voltage clamp, femcyanide, ferrocyanide, Chara     

Salt Tolerance in the Triticeae: K/Na Discrimination in Aegilops Species

Inorganic ion concentrations were measured in the leaves ofAegilops species growing in 50 or 75 mol m^–3 NaCl (+2.5or 3.75 mol m–3 CaCl₂). The low leaf Na and high leafK concentrations characteristic of the enhanced K/Na discriminationcharacter, originally found in Aegilops squarrosa and in hexaploidwheat, were also found in other Aegilops species containingthe D genome, but not in Ae. ventricosa. The S genome diploidAegilops species (section Sitopsis) all lacked the enhancedK/Na discrimination trait, as did the C genome species Ae. caudataand the N genome species Ae. uniaristata. Most of the U genomespecies (section Polyeides), except Ae. biuncialis, Ae. kotschyiand Ae. variabilis, also exhibited the trait. Examination ofamphiploid hybrids suggested that the trait was dominant incrosses involving Ae. squarrosa or Ae. umbellulata with otherspecies in which the trait was absent. Key words: Salt, ion transport, D genome, Aegilops spp     

Action of Sorghum Proteinase on the Protein Bodies of Sorghum Starchy Endosperm

Protein bodies isolated from the starchy endosperm of ungerminatedsorghum exhibited some autolytic activity but seemed incapableof significant self-hydrolysis. Enzyme assay, transmission electronmicroscopy, sodium dodecyl sulphate—polyacrylamide gelelectrophoresis and amino acid analysis revealed that a proteinaseextract from germinated sorghum could degrade the protein bodiesin a manner resembling that which takes place in vivo. The proteinbodies were degraded mainly from the periphery. Glutelin (matrixprotein) was first hydrolysed, followed by the prolamin proteinbody protein. Proteinase extracts from both the germ and endospermof germinated sorghum were capable of degrading the proteinbodies. This finding is consistent with the concept that theproteinase is synthesized in the germ and then secreted intothe starchy endosperm during germination. Key words: Sorghum bicolor, protein body degradation, proteinase.     

Heterochrony and the origin of tetrapods

Long, J. A. 1990 04 15: Heterochrony and the origin of tetrapods. Lethaia , Vol. 23, pp. 157–166. Oslo. ISSN 0024–1164.
Juveniles of the osteolepifonn fish Eusthenopteron show more features in common with primitive tetrapods than any other crossopterygian group. These similarities indicate that paedomorphosis may have played an important role directing anagenesis of cranial characters in the fish-tetrapod transition. The development of the tetrapod limb, however, probably resulted from peramorphosis. The first tetrapods may have originated in the East Gondwana vertebrate Province early in the Devonian, based on the oldest known tetrapod footprints from Australia. Furthermore, the biogeographic distribution of plesiomorphic osteichthyans indicates that the monophyletic group 'rhizodontiforms. osteolepiforms and tetrapods' most likely arose in east Gondwana.