Pelomyxa Carolinensis Research Articles

Structural responses of amoebae to the injection of heterologous cytoplasm.

Responses to the introduction of heterologous cytoplasm and the fate of foreign organelles were investigated in amoebae. Heterologous cytoplasm was transferred by microinjection from Pelomyxa carolinensis to Amoeba discoides. In control experiments, homologous cytoplasm was transferred from one A. discoides to another. Recipient cells were observed by light microscopy, and samples were prepared for ultrastructural study at intervals between 15 min nad 3 days after operation. Recipients of heterologous cytoplasm showed two main responses. First, about 40% recipients expelled small amounts of cytoplasm by a blebbing process within 30 min after injection. Second, organelles were segregated and broken down in membrane-bounded cytoplasmic vacuoles between 6 h and 2 days after operation. Acid phosphatase reaction product was observed in these vacuoles along with altered organelles. Use of electron-dense thoria particles to mark donor cells demonstrated the presence of injected cytoplasm in the vacuoles. In contrast, when amoebae were injected with homologous cytoplasm, none was expelled and vacuoles containing degenerating organelles were uncommon. The survival rate and general appearance of recipients of heterologous cytoplasm were much poorer than those of homologous recipients, and most of the former died by I week after operation. It is postulated that amoeba are capable of recognizing heterologous organelles introduced into the cytoplasm and that they respond by expulsion and/or destruction of the foreign cellular components. The previously described lethal effect of heterologous cytoplasm was confirmed.

Capacity of enucleated amoebae to recognize and respond to heterologous cytoplasm.

When amoebae are injected with heterologous cytoplasm from another type of amoeba, cellular organelles are segregated and degenerate within membrane-bounded spaces in the host's cytoplasm. In the present study, the role of the nucleus in this response was tested by injecting heterologous cytoplasm from Pelomyxa carolinensis into enucleate and enucleate Amoeba discoides. Samples were prepared for ultrastructural study at intervals between 15 min and 2d after the operation. In enucleate recipients of heterologous cytoplasm, organelles and cellular debris were observed in vacuole-like spaces indistinguishable in morphology and frequency from those of nucleated recipients. When donor cytoplasm included thoria particles, the electron-dense tracer was found along with degenerating organelles in the vacuole-like structures, confirming the presence there of injected cytoplasm. changes of comparable magnitude were not observed when either nucleated or enucleated cells were injected with homologous cytoplasm. The results indicate that nuclear activity is not necessary for the ultrastructurally observable responses of amoebae to heterologous cytoplasm. It is suggested therefore that the cytoplasm possesses a mechanism for recognition of at least some types of heterologous organelles.

Cation concentrations of the free-living amoebae: Amoeba proteus, Amoeba dubia and Pelomyxa carolinensis

1.1. The cation concentration of the free-living amoebae, Amoebaproteus, A. dubia and Pelomyxa carolinensis were determined.2.2. The concentration of Fe3+ differed in each species, the concentration of Zn2+ in only A. proteus, the concentration of Ca2+ in only A. dubia and the concentration of K+ in only P. carolinensis.3.3. The concentrations of Mg2+, Na+, Cu2+ and Mn2+ did not differ in the above species.4.4. The possibility of using (Zn2+) × 10(Fe3+) and (Fe3+) × 10(K+) ratios for characterizing single samples of A. dubia and P. carolinensis respectively is discussed.

A Method for Analysis of Protein in Individual Amoebae

SYNOPSIS The microelectrophoresis technic of Hydén and Lange has been adapted for analysis of the proteins of individual Amoeba proteus, A. dubia, and Pelomyxa carolinensis. The method has the sensitivity required for analyzing electrophoretic mobilities of the proteins of these 3 species and is reproducible. The possibility of using this technic to differentiate amoeba species according to their protein composition is discussed.

The protein amino acid compositions of Amoeba proteus, A. discoides, A. dubia and Pelomyxa carolinensis.

SYNOPSIS. A comparison has been made of the protein amino acid compositions of Amoeba proteus, A. discoides, A. dubia and Pelomyxa carolinensis. The protein amino acid compositions of each of these species differed in 1–3 of the following amino acids: arginine, aspartic acid‐asparagine, threonine and glycine. The possibility of using these characteristics as acceptable genetic markers is discussed.

Giant amoebae from Colorado identified by transplantation tolerance.

SYNOPSIS. Giant multinucleated amoebae, discovered in Colorado near Ft. Collins and tentatively identified as Pelomyxa carolinensis, were successfully cultured in a manner identical with that used for P. carolinensis. The ultrastructure of the Colorado amoebae, in comparison with that of other large amoebae, was like that of P. carolinensis, but different from those of Amoeba proteus, P. illinoisensis, and P. palustris. Protoplasmic grafts between the Colorado amoebae and P. carolinensis were then exchanged by microsurgery. These grafts were well tolerated, and the recipient amoebae reproduced at a rate comparable to that of non‐grafted controls. Other Colorado amoebae received grafts from P. illinoisensis, but all recipients died without cell division a few days after microsurgery. These nutritional, cytologic and transplantation‐tolerance data reveal that the amoebae from Colorado are P. carolinensis.

Nucleopores of the giant amoeba, Pelomyxa carolinensis.

As shown in tangential sections of Pelomyxa carolinensis nuclei, there are many pores, each with a surrounding annulus. Each annulus is composed of 8 subannuli or satellites, plus one to three central granules. Each satellite is an electron opaque mass (of much smaller opaque particulates) about 25 nm in diameter. The outer diameter of each annulus is about 115 nm while the inner, or pore diameter, is about 65 nm. The pores occur at distances averaging 185 nm from center to center. Frequently, delicate filaments connect adjacent satellites, and the central granule with the satellites. As seen in cross sections of the nucleus, nucleopores are formed by the fusion of the inner and outer nuclear envelope membranes. The pore appears as a gap, spanned by a delicate diaphragm anchored to the nuclear envelope where its two membranes are fused. Possible functions of the pore-annulus complexes are discussed.

The Effects of Weightlessness on the Amoeba, Pelomyxa carolinensis. I. Methods and Materials

The Effects of Weightlessness on the Amoeba, Pelomyxa carolinensis: I. Methods and Materials Get access BioScience, Volume 18, Issue 6, June 1968, Pages 615–617, https://doi.org/10.2307/1294310 Published: 01 June 1968

The free amino acid levels of Pelomyxa carolinensis, Amoeba dubia and Proteus.

SYNOPSIS. The free amino acid extracts of 3 species of the free‐living amoebae, Pelomyxa carolinensis, Amoeba dubia and A. proteus, were studied. Both the free amino acid patterns and levels in each species were different. Altho it appears that the free amino acid patterns were not altered by culture routines or starvation, the free amino acid levels were altered by these factors. The possibility of using free amino acid levels as a criterion for recognizing genetic differences is discussed.

Starvation effects on the ultrastructure of amoeba mitochondria.

Mitochondria in non-starved giant amoebae, Pelomyxa carolinensis, contain tubules lying at random in the matrix. Many mitochondria in starved amoebae have enlarged tubules aligned in a zigzag pattern. Tubules within the zigzag region are separated by very little matrix material. Some of these altered mitochondria are found in 70% of amoebae starved for only 24 hours, and in nearly all P. carolinensis starved for 8 days or longer. The percentage of such altered mitochondria increases from zero in most well-fed amoebae, to about 60% after two weeks of continuous starvation. Most P. carolinensis starved at 25° C survive less than three weeks. Microfilament bundles are observed in the matrix of some mitochondria in amoebae starved for more than two days.

ELECTRON MICROSCOPY OF MITOSIS IN A RADIOSENSITIVE GIANT AMOEBA.

Various aspects of the ultrastructure of the dividing nuclei in the large radiosensitive amoeba Pelomyxa illinoisensis are demonstrated. Evidence of nuclear envelope breakdown is presented, and membrane fragments are traced throughout metaphase to envelope reconstruction in anaphase and telophase. Annuli in the nuclear envelope and its fragments are shown throughout mitosis. During metaphase and anaphase some 15 to 20 mitochondria are aligned at each end of the spindle, and are called polar mitochondria. The radioresistant amoebae Pelomyxa carolinensis and Amoeba proteus do not have polar mitochondria, and Pelomyxa illinoisensis is unique in this regard. The shape of the P. illinoisensis interphase nucleoli differs from that in the two radioresistant species, and certain aspects of nucleolar dissolution in the prophase vary. Helical coils in the interphase nucleoplasm are similar to those in the radioresistant amoebae. A "blister" phase in the flatly shaped telophase nuclei of P. illinoisensis is described which is interpreted to be the result of a rapid nuclear expansion leading to the formation of the normal spherical interphase nuclei.

AN ELECTRON MICROSCOPIC STUDY OF PINOCYTOSIS IN AMEBA

This report is devoted principally to a consideration of the fate of the pinocytotic vacuole and its content in the ameba Pelomyxa carolinensis (Chaos chaos). High resolution micrographs of the plasmalemma have shown it to consist of three layers, i.e., an outermost filamentiferous zone, a middle homogeneous zone, and an inner zone which appears to be a unit membrane. The three zones can be identified in the membranes lining the pinoyctotic tunnels and vacuoles of amebas fixed shortly after pinocytosis occurred. The first apparent change in the pinocytotic vacuole is an increase in the surface-to-volume ratio which occurs during the 1st hour of its existence. Within 24 hours the marker substance commonly collects in defecation vacuoles which can be identified by the profiles of bacteria usually found in the lumen. Occasionally, however, thorotrast can be seen in the lumen of the contractile vacuole. The thorotrast appears to enter the two excretory organelles by the coalescence of vesicular fragments of the pinocytotic vacuoles with the limiting membranes of the excretory organelles.

Two methods for determining the water content of the giant amoeba Pelomyxa carolinensis

Two methods for determining the water content of the giant amoeba Pelomyxa carolinensis

Limits of transplantation tolerance in large amoebae. I. Microfusion studies using Amoeba proteus, Pelomyxa illinoisensis, and three strains of Pelomyxa carolinensis.

SYNOPSIS. Protoplasm transferred to a multinucleated amoeba is well tolerated if the donor and recipient portions are from the same amoeba, from different amoebae of a single clone, from different amoebae of the same species found in a given location, or from different amoebae of the same species found in widely separated geographic areas. On the other hand, protoplasm is not tolerated and death invariably follows interspecific or intergeneric microtransfers between any two of the three species of amoebae used in this study.Attempts to overcome the tolerance block in heterologous transfers by the use of x‐radiation failed although a significant extension of the mean survival time was obtained. The latter can also be interpreted as a limited therapeutic effect of nonirradiated, heterologous donor protoplasm on supralethally irradiated recipients.

Studies on the membrane potential of Pelomyxa carolinensis

1. 1. An average potential difference of 86.5 + 12 mV has been demonstrated across the membrane of Pelomyxa carolinensis, the cytoplasm being negative with respect to the external Pringsheim medium. 2. 2. Addition of KCl to the medium caused a sudden drop in potential, which was proportional to the logarithm of [K] out. 3. 3. The slope of the graph of membrane potential versus [K] out was 40 mV/tenfold change of concentration, although the concentration of external K necessary to abolish the potential was approximately equal to the total cell-potassium concentration. 4. 4. Addition of 10 m M NaCl to the medium produced no change in the potential during the experimental period of 15 min. 5. 5. External application of cyanide, urethane, and ouabain failed to affect the potential.

Electron microscopic studies of mitosis in amebae. II. The giant ameba Pelomyxa carolinensis.

Dividing nuclei from the giant ameba Pelomyxa carolinensis were fixed in osmium tetroxide solutions buffered with veronal acetate to pH 8.0. If divalent cations (0.002 M calcium, magnesium, or strontium as chlorides) were added to the fixation solution, fibrils that are 14 mmicro in diameter and have a dense cortex are observed in the spindle. If the divalent ions were omitted, oriented particles of smaller size are present and fibrils are not obvious. The stages of mitosis were observed and spindle components compared. Fibrils fixed in the presence of calcium ions are not so well defined in early metaphase as later, but otherwise have the same diameter in the late metaphase, anaphase, and early telophase. Fibrils are surrounded by clouds of fine material except in early telophase, when they are formed into tight bundles lying in the cytoplasm unattached to nuclei. Metaphase and anaphase fibrils fixed without calcium ions are less well defined and are not observably different from each other. The observations are consistent with the concept that spindle fibrils are composed of polymerized, oriented protein molecules that are in equilibrium with and bathed in non-oriented molecules of the same protein. Partially formed spindle fibrils and ribosome-like particles were observed in the mixoplasm when the nuclear envelope had only small discontinuities. Remnants of the envelope are visible throughout division and are probably incorporated into the new envelope in the telophase. Ribosome-like particles are numerous in the metaphase and anaphase spindle but are not seen in the telophase nucleus, once the envelope is reestablished, or in the interphase nucleus.

AN ELECTRON MICROSCOPIC STUDY OF PINOCYTOSIS IN AMEBA

The attachment to the surface of the ameba (Chaos chaos L. (Pelomyxa carolinensis, Wilson)) of two proteins, ribonuclease and ferritin, and two colloidal suspensions, thorium dioxide and gold, was studied in the electron microscope. The initial step in the pinocytosis of ferritin and thorium dioxide particles by amebas is shown to be the attachment of these substances to the "hairlike" extensions of the plasmalemma. Ribonuclease caused alterations in the structure of the plasmalemma, but on account of its relative lack of density, it could not be definitely localized. Colloidal gold did not appear to be active with respect to pinocytosis in amebas. Since molecules in solution and particles in suspension are taken up by the same mechanism, the first step of which is their attachment to the cell surface, it is suggested that a single mechanism underlies phagocytosis, pinocytosis, ropheocytosis, cytopempsis, and potocytosis.

Electron Microscopy of Pinocytosis and Food Vacuoles in Pelomyxa*

SYNOPSIS.Food vacuoles have been studied in various stages of the digestive process in cultures of Pelomyxa carolinensis and P. illinoisensis after feeding Tetrahymena and Paramecium. The vacuole wall formed immediately after capture of the food organism may be only 100 m/i thick. The changes observed in the food organisms indicate that first the membranes of the pellicle are ruptured, then mitochondria, cytoplasmic matrix, and nucleus are attacked; cilia and trichocysts are more resistant. The food vacuole membrane is involved first in the removal of water from the vacuole, then in transfer of cytoplasmic fluid into the vacuole, and finally in removal of digestion products from ihe vacuole by pinocyt. Vesicles which have been derived from the plasnulf—a b pinocytosis have been observed. They characteristically have a non‐turgid, non‐spherical appearance when located deep m the cytoplasm and are stainable with phosphotungstic acid. Pinocytosis and the function of food vacuole membranes are discussed. It is concluded that at leait two factors contribute to the benefits derived by amoebae from pinocytosis: (1) modification of the plasmalemma membrane near the time when it becomes the pinocytic vesicle membrane, and (2) increased surface area for diffusion.

Mitochondria. I. Fine structure of the complex patterns in the mitochondria of Pelomyxa carolinensis Wilson (Chaos chaos L.).

Some of the mitochondria in the free-living giant ameba Pelomyxa carolinensis (Chaos chaos) exhibit unusual and strikingly complex morphological patterns. A study of serial sections of these mitochondria reveals that the patterns are formed by the organization and packing of minute villi (cristae mitochondriales). The form of the individual villus is a regular soft zigzag (or wave) with a bulbous enlargement at each point of inflection ("elbow") on the wave. The pattern of the mitochondria may become increasingly complex as a result of branching and fusing of the wavy villi. Densely packed fibrillar material is sometimes present in the stroma of the mitochondria.

Mitochondria

This study has demonstrated that in the ameba, Pelomyxa carolinensis Wilson (Chaos chaos L.) the limiting membranes of mitochondria and postdivision nuclei are often continuous. The morphological relationship may be functional in that it permits an exchange of material resulting directly or indirectly in an increased enzyme content of the mitochondria. It is suggested that through a series of progressive foldings of its envelope, the nucleus may be a site of formation of mitochondria.