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At least 19 recordsLinked to original sources
PubMed1978

The pattern of appearance of enzymic activity during the development of the Golgi apparatus in amoebae.

The appearance of enzymic activity during the development of the Golgi apparatus was studied by cytochemical staining of renucleated amoebae. In cells enucleated for 4 days, there was a great decline in size and number of Golgi bodies, or dictyosomes. Subsequent renucleation by nuclear transplantation resulted in a regeneration of Golgi bodies. Samples of amoebae were fixed and incubated for cytochemical staining at intervals of 1, 6, or 24 h after renucleation. Enzymes selected for study were guanosine diphosphatase (GDPase), esterase, and thiamine pyrophosphatase (TPPase). All three were found in the Golgi apparatus of normal amoebae but they differed in their overall intracellular distribution. GDPase was normally present at the convex pole of the Golgi apparatus, in rough endoplasmic reticulum, and in the nuclear envelope. In amoebae renucleated for 1 h, light reaction product for GDPase was present throughout the small stacks of cisternae that represented the forming Golgi apparatus. By 6 h following the operation GDPase reaction product was concentrated at the convex pole of the Golgi apparatus. Esterase, which was distributed throughout the stacks of normal Golgi cisternae, displayed a similar distribution in the forming Golgi bodies as soon as they were visible. TPPase was normally present in the Golgi apparatus but was not found in the endoplasmic reticulum. In contrast to the other enzymes, TPPase reaction product was absent from the forming Golgi apparatus 1 and 6 h after renucleation, and did not appear in the Golgi apparatus until 24 h after operation. Thus, enzymes held in common between the rough endoplasmic reticulum and the Golgi apparatus were present in the forming Golgi apparatus as soon as it was detectable, but an enzyme cytochemically localized to the Golgi apparatus only appeared later in development of the organelle. It is suggested that Golgi membranes might be derived from the endoplasmic reticulum and thus immediately contain endoplasmic reticulum enzymes, while Golgi-specific enzymes are added later in development.

Amoeba↗
PubMed1979

[Microspectrophotometric study of the crystalline inclusions in different strains of Amoeba proteus].

Using microspectrometric technique, integral extinction and extinction spectra of crystalline inclusions of two amoeba strains, C and Ct, have been studied. The analysis of extinction spectrum form allowed to suggest that the crystals seen in both amoeba strains have identical chemical composition, whereas the morphological differences between cells in their transparency may be due to different mode of the crystal package. The relative amount of the crystals was measured in both amoeba strains on the basis of the integral extinction value. The distinct differences between the strains were detected in the integral extinction value and in the extinction spectra, which allowed us to use these parameters as genetic markers in the experiments on the nuclear transplantation in amoeba.

Amoeba↗
PubMed1977

Relationships between membranous organelles in amoebae studied by electron microscopic cytochemical staining.

The intracellular location of a variety of enzymes was studied in Amoeba proteus with the use of electron microscopic cytochemical methods, in an attempt to assess the relationships between different membranous organelles. One group of enzymes, including nucleoside diphosphatases (IDPase, UDPase, GDPase, ADPase), carbamoyl phosphatase, alkaline phosphatase, and BAXD oxidase was localized mainly in the rough endoplasmic reticulum, nuclear envelope, and convex side of the Golgi apparatus. Esterase activity had a similar localization except that the Golgi apparatus was "stained" throughout most of its extent. A second group of enzymes was found in Golgi cisternae and vesicles, and in come vacuoles. This group included acid phosphatase, thiamine pyrophosphatase, and aryl sulfatase. Some enzymes previously detected in cytoplasmic membranes of other cells, including glucose-6-phosphatase, showed little or no activity in amoebae. The results suggest that there are chemical similarities and probable functional relationships between the rough endoplasmic reticulum, the nuclear envelope, and the convex side of the Golgi apparatus. On the other hand, the concave pole of the Golgi apparatus, aggregates of smooth tubules and vesicles, and the cell surface appear more closely related to one another than to the endoplasmic reticulum and the convex side of the Golgi apparatus. The cytochemical similarity between the Golgi apparatus and certain vacuoles such as food vacuoles may reflect the role of the Golgi apparatus in the formation of lysosomes. The locations of reaction products of the various enzymes in amoebae are compared with observations reported for other cell types.

Alkaline Phosphatase↗
PubMed1978

A capillary technique for cloning Amoeba from single cells.

Each amoeba is placed in a drop of approximately 40 microliter of a balanced 'medium + food' solution introduced into the central region of a 7 cm long capillary tube which has first been fused at one end. Such amoebae divide to form clones of 20-30 cells without changing capillaries, though additional food may be required after 7-10 days. Experiments on damage induced by chemicals, cell cycle sensitivities and nuclear/cytoplasmic inheritance, which may involve the cloning of some 2-3,000 or more cells can be carried out with comparative ease. Apart from research, the capillary cloning technique has proved useful in the teaching laboratory. It is adaptable, and can be used for Protozoa other than amoebae, even for requiring sterile conditions.

Amoeba↗
PubMed1975

Membrane potential and conductance during pinocytosis induced in Amoeba proteus with alkali metal ions.

An investigation of the relationship between the polarized state of the membrane and the onset and the intensity of pinocytosis was made in Amoeba proteus. Membrane potential and input resistance was in all instances found to decrease in approximate proportion to the number of channels when pinocytosis was induced by a variety of alkali metal ions at varying pH. Channels began to appear when the membrane was depolarized to -30 mV by the inducer of pinocytosis. With all inducers the maximum pinocytosis was encountered at membrane potentials close to zero. No positive potentials were recorded when the chloride salts of the inducing cations were used. At high concentrations of alkali ions a transient increase of the chloride permeability caused short-lasting hyperolarizations of the membrane. Inhibition of pinocytosis by Ca++ was accompanied by an increase of input resistance and membrane potential. The selectivity of the membrane to different alkali metal ions observed as changes in pinocytosis intensity, membrane potential and input resistance was found to vary with the concentration of the inducer and with the Ca++ concentration of the extracellular solution. Displacement of membrane bound Ca++ appeared to decrease the field strength of charged groups in the membrane altering its selectivity among alkali cations. The formation of pinocytotic channels is suggested to require translocation of Ca++ from the membrane into the cell and would therefore be closely related to the electrical properties of the amoeba.

Alkalies↗
PubMed1976

Effect of ultraviolet radiation on pinocytosis in Amoeba proteua.

Ultraviolet (UV) irradiation (4 000-10 000 erg X mm(-2) decreased membrane potential and input resistance of Amoeba proteus and induced formation of pinocytotic channels. Submaximal pinocytosis induced by UV light was additive to pinocytosis induced by K+ or Na+ and stimulated in the presence of EGTA. It was not inhibited by the presence of La+++ or by pretreatment with dibucaine. In these respects and with respect to optimum pH and pCa, UV induced pinocytosis. Accumulation of K+ in the amoeba membrane after a dose of radiation may explain the similarity between pinocytosis induced by UV light and potassium salts. Ca++ present during the period of irradiation inhibited the effect of UV light. Instead Ca++ applied after irradiation (1-20 mM) increased channel formation. This effect was stimulated the presence of local anesthetic drugs. It is suggested that high doses of UV light may induce channel formation by releasing Ca++ from the cell membrane into the cell (UV induced pinocytosis). Ca++ may be released at the moment of absorption of UV light in the membrane as well as during the period of depolarization which follows irradiation. Low doses of UV light may permit extracellular Ca++ to enter the cell and stimulate channel formation (calcium induced pinocytosis). Dithiotreitol (1 mM) applied after irradiation depressed both UV and calcium induced pinocytosis so these may be the result of the same structural change which involves the formation of disulphide bonds in the membrane.

Amoeba↗
PubMed1977

The self-assembly of synthetic filaments of myosin isolated from Chaos carolinensis and Amoeba proteus.

Synthetic myosin thick filaments were formed from preparations of electrophoretically homogeneous myosin isolated from Chaos carolinensis and Amoeba proteus when dialysed to physiological ionic strength and pH. Myosin dialysed directly against low ionic strength buffers formed native-like thick filaments in the presence and absence of exogenous divalent cations. The average dimensions of the synthetic filaments grown under these conditions were 455 nm long and 16 nm wide with a distinct bare central zone 174 nm long. Myosin predialysed against EGTA-EDTA solutions at high ionic strength and then dialysed to low ionic strength formed native-like filaments only in the presence of 1mM Mg2+. 1 mM Ca2+ could not be substituted for Mg2+ under these conditions to achieve native-like filaments. Filaments grown from predialysed myosin in the absence of Mg2+ resembled EGTA-dissociated myosin filaments observed in EGTA-treated cytoplasm and were highly branched, poorly formed filaments lacking a distinct bare central zone. The average dimensions of the filaments grown from predialysed myosin in the absence of Mg2+ were 328 nm long, 13 nm wide with a bare central zone 111 nm long. Under the conditions tested, myosin isolated from these amoebae did not demonstrate a divalent cation requirement for thick filament formation. The results obtained with myosin isolated from the 2 organisms were identical.

Amoeba↗
PubMed2026

An updated checklist of testate amoebae in China.

We present an updated checklist of testate amoebae (TA) in China covering TA records in the literature of the past ∼100 years. In total 363 TA species/subspecies in 53 genera have been included in the current Chinese checklist. The updated Chinese checklist includes five recently discovered TA species (Netzelia mulanensis, Pentagonia zhangduensis, Pontigulasia pentangulostoma, Cornutheca jiuhuensis, and Planhoogenraadia wuchanica) and 24 TA species/subspecies that have been added as new records for China. TA taxonomy and classification in the updated Chinese checklist are based on current knowledge derived from morphological, physiological, and molecular (ribosomal and mitochondrial DNA sequence data, genomics) studies. Corresponding changes in the updated Chinese checklist are outlined and the taxonomy and diversity of (Chinese) TA as well as their biogeography, ecology, and conservation are discussed. As all kinds of TA studies are eventually based on a reliable taxonomy and nomenclature, we are confident that our updated Chinese checklist will be of great value for TA researchers not only in China, but also worldwide.

China↗
PubMed1975

Inhibition of induced pinocytosis in Amoeba proteus by membrane stabilizing drugs.

The effect of membrane stabilizing drugs on cation induced pinocytosis was studied in Amoeba proteus. Initially the presence of local anesthetic drugs during a pinocytosis cycle had a stimulating effect on channel formation, however, the capacity to develop pinocytotic channels was reversibly inhibited after a period of treatment with these drugs. Imipramine, vinblastine and the phenothiazines had effects similar to local anaesthetics. The local anesthetics inhibited pinocytosis in the following order: dibucaine greater than tetracaine greater than bupivacaine greater than lidocaine greater than procaine, and the phenothiazines: thioridazine greater than prochlorperazine greater chlorpromazine greater than prometazine. Pinocytosis, when induced by Na+ or tris, was more affected by the drugs and by calcium binding agents than pinocytosis induced by K+. After pretreatment with inhibitory concentration of dibucaine (3 x 10(-4) M) the depolarization of the membrane and the conductance increase during pinocytosis were normal, while the increase of oxygen uptake during the pincoytosis cycle was abolished. Addition of Ca++ before, during or after dibucaine treatment decreased the effect of the drug. Conversely, in dibucaine-treated cells, cation induced pinocytosis was less inhibited by Ca++ than pinocytosis in normal cells. Addition of EGTA to the inducing solutions potentiated the inhibitory effect of the drug. It is suggested that these drugs release Ca++ from the cell surface and at higher concentration or after prolonged incubation time interfere with a Ca++ mechanism which couples the membrane and contractile systems in the cytoplasm.

Amoeba↗
PubMed1978

Use of cell cultures as an indicator of pathogenicity of free-living amoebae.

Results comparing the time needed for the development of cytopathic effects in cell cultures with that needed to cause death in mice using inocula of Naegleria and Acanthamoeba are presented. The significance of the source and concentration of the inocula is demonstrated. The use of cell cultures as an indicator of the pathogenicity of free-living amoebae is discussed.

Amoeba↗
PubMed1976

Metabolic requirements for interactions between nuclear and cytoplasmic membranes in the repair of damaged Amoeba nuclei.

Amoeba nuclear envelopes were damaged using microsurgery, and metabolic requirements for the steps in their repair were studied, and my placing the cells in a solution containing one of several metabolic inhibitors. The first step in repair, the association of pieces of endoplasmic reticulum with holes in the nuclear membranes, appears to be a passive process since it was not affected by inhibitors of energy production, RNA synthesis, or protein synthesis. In contrast, fusion of pieces of endoplasmic reticulum with the nuclear membranes at the margins of the holes was blocked by KCN and dinitrophenol, indicating that membrane fusion requires energy derived from respiration, but RNA and protein synthesis inhibitors did not prevent fusion of pieces of endoplasmic reticulum with the nuclear membranes. The subsequent completion of repair and restoration of intact nuclear membranes was almost completely blocked by inhibitors of respiration, and it was reduced in the presence of actinomycin and emetine, suggesting that in addition to a requirement for energy, some later steps in the repair of the nuclear membranes require RNA and protein synthesis.

Amoeba↗
PubMed1978

Demonstration of membrane-associated and oriented microfilaments in Amoeba proteus by means of a Schiff base/glutaraldehyde fixative.

After fixation with a reaction product of glutaraldehyde and spermidine phosphate Amoeba proteus cells show a network of cortical microfilaments and oriented bundles of thick and thin filaments. The cortical filament network appears to be membrane-attached and extends beneath the whole cytoplasmic membrane surface. In the uroid region and in retracting pseudopods the cortical layer is thicker than in advancing cell regions. The filament bundles are located predominantly in the ectoplasmic tube within the cortical network. They strictly parallel the cell surface contours.

Amoeba↗
PubMedDate not supplied

[Isolation of free-living amoebae from the nasal mucosa of man. Potential risk (author's transl)].

From march 1976 until december 1978, we have analysed 1039 nasal swabs in order to discover the healthy free-living amoebae carriers. So, we have isolated 9 strains of which one Hartmannella vermiformis. From the 8 remaining Acanthamoebae, only one, ORL 561 (Acanthamoeba hatchetti) is as pathogenic for mice as the 2 other identical known strains and A. culbertsoni.

Adolescent↗
PubMed1975

Induction of phosphodiesterase by cyclic adenosine 3':5'-monophosphate in differentiating Dictyostelium discoideum amoebae.

Cyclic adenosine 3':5'-monophosphate added to the starvation media of Dictyostelium discoideum amoebae induces both intracellular and extracellular phosphodiesterase activities of these cells. The induced enzyme activity appears several hours earlier than that in starved cells which have not been induced with cyclic nucleotide. In both cases, the appearance of enzyme is inhibited by cycloheximide, and actinomycin D, and daunomycin. The KmS for the extracellular enzyme(s) of nucleotide-induced and uninduced control cells are identical. The induction of enzyme activity seems specific for cyclic adenosine 3':5'-monophosphate since cyclic guanosine 3':5'-monophosphate, as well as other nucleotides, have no effect. No differences in the activity or excretion of either N-acetylglucosaminidase or the inhibitory of the extracellular phosphodiesterase are observed between cyclic adenosine 3':5'-monophosphate-induced and control cells. A direct activation of phosphodiesterase by cyclic adenosine 3':5'-monophosphate can be excluded, since the addition of this nucleotide to cell lysates has no effect on the enzyme activity.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

The contractile basis of amoeboid movement III. Structure and dynamics of motile extracts and membrane fragments from Dictyostelium discoideum and Amoeba proteus.

Motile extracts from D, discoideum and A. proteus have been characterized in order to compare the structural dynamics and chemical regulation of movement in 2 different types of amoeboid cells. The structural dynamics of both extracts involve the formation of a nonmotile cytoskeleton followed by the contraction of actin and myosin to generate both direct contractile force and cytoplasmic streaming. The contractions are regulated by calcium ions and a threshold of ca. 1.0 X 10(-6) M calcium induces a transformation of actin to the free F-actin state which is capable of interacting with myosin. Furthermore, 3 low molecular weight proteins are concentrated along with actin and myosin during contraction and might play a regulatory role in movement. Several common characteristics of amoeba cytoplasm have been exhibited by these two types of amoeboid cells. The major contractile and "associated" proteins are similar, actin and associated proteins are structurally dynamic, and movement is regulated by calcium. The different modes of movement observed in different types of amoeboid cells could result from the site, rate, and extent of actin transformation followed in some regions by contractions.

Actins↗
PubMedDate not supplied

Pathogenic free-living amoebae in swimming pools: survey in Belgium.

During a short term investigation, 1 outdoor and 15 indoor swimming pools were examined for the presence of amoebae. Of all isolates from 13 pools, 43.6% belonged to the genus Acanthamoeba. The genus Naegleria accounted for 7.3% of the isolates, but none belonged to the pathogenic N. fowleri. A high percentage (70%) of the Acanthamoeba strains tested showed virulence for mice.

Amoeba↗
PubMed1975

Stimulation of late interphase Dictyostelium discoideum amoebae with an external cyclic AMP signal.

The microelectrode system described in the accompanying paper was used to investigate properties of fields of Dictyostelium discoideum amoebae in late interphase. Cells in the fields were competent to respond chemotactically to, and to relay, a c-AMP signal, but not to produce an aggregative signal autonomously. The experimental results are generally consistent with c-AMP being the sole compound required for chemotaxis and signal relaying. A periodic signal from the microelectrode can initiate and control aggregation and can complete with spontaneously arising aggregates. The electrode was used to measure the refractory period for relaying which decreases from 9 min or more to between 2 and 3 min with increasing developmental age, and to measure thresholds for chemotaxis and signal relaying. The results are discussed in relation to models for the control of aggregation in D. discoideum.

Cyclic AMP↗