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Results for “Cytoplasmic Streaming”

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PubMed1989

[Anthrax toxin dynamics in the body].

Anthrax toxin introduced subcutaneously into white rats Fisher-344 caused specific intoxication accompanied by characteristic pathomorphological changes and, when studied by the immunoperoxidase method in histological sections, could be detected in the blood stream (in plasma) and in the cytoplasm of macrophages (in the lungs and the spleen). The content of the preparation introduced into the animals in the blood stream is directly related to its toxicity, being probably indicative of the relative functional failure of the macrophagal system.

Animals↗

PubMed1988

Ultrastructural pathology in emetine-induced myopathy.

Progressive myopathy developed in two women who consumed ipecac syrup containing emetine hydrochloride to induce vomiting as part of their anorexia nervosa. Muscle biopsy specimens were characterized by severe disruption of the sarcomeres. The ultrastructural spectrum extended from "Z-band streaming" to the formation of cytoplasmic bodies and also comprised abnormalities of the sarcotubular system, thus suggesting that muscle weakness may be related to both sarcomeric and sarcotubular lesions in this self-inflicted myopathy. It is tempting to suggest that muscle weakness may be correlated with or based on the pathology in sarcomeres and the sarcotubular system. As the myopathy is clinically reversible upon discontinuation of ipecac consumption the morphological findings should also be potentially reversible. Experimentally induced emetine myopathy may, thus, serve as a useful model to study morphological dynamics of sarcomeric lesions, which may be observed separately or simultaneously in a variety of spontaneously occurring human neuromuscular disorders.

Adult↗

PubMed1991

Modulation of contraction by gelation/solation in a reconstituted motile model.

The actin-based cytoskeleton is a dynamic component of living cells with major structural and contractile properties involved in fundamental cellular processes. The action of actin-binding proteins can decrease or increase the gel structure. Changes in the actin-based cytoskeleton have long been thought to modulate the myosin II-based contractions involved in these cellular processes, but there has been some debate concerning whether maximal gelation increases or decreases contractile activity. To address this question, we have examined how contractile activity is modulated by the extent of actin gelation. The model system consists of physiologically relevant concentrations and molar ratios of actin filaments (whose lengths are controlled by gelsolin), the actin-cross-linking protein filamin, and smooth muscle myosin II. This system has been studied at the macroscopic and light microscopic levels to relate the gel structure to the rate of contraction. We present results which show that while a minimal amount of structure is necessary to transmit the contractile force, increasing the gel structure inhibits the rate of contraction, despite an increase in the actin-activated Mg(2+)-ATPase activity of myosin. Decreasing the total myosin concentration also inhibits the rate of contraction. Application of cytochalasin D to one side of the contractile network increases the rate of contraction and also induces movement comparable to flare streaming observed in isolated amoeba cytoplasm. These results are interpreted relative to current models of the relationship between the state of gelation and contraction and to the potential effects of such a relationship in the living cell.

Actin Cytoskeleton↗

PubMed1970

Cytoplasmic filaments of Amoeba proteus. I. The role of filaments in consistency changes and movement.

The role of filaments in consistency changes and movement in a motile cytoplasmic extract of Amoeba proteus was investigated by correlating light and electron microscopic observations with viscosity measurements. The extract is prepared by the method of Thompson and Wolpert (1963). At 0 degrees C, this extract is nonmotile and similar in structure to ameba cytoplasm, consisting of groundplasm, vesicles, mitochondria, and a few 160 A filaments. The extract undergoes striking ATP-stimulated streaming when warmed to 22 degrees C. Two phases of movement are distinguished. During the first phase, the apparent viscosity usually increases and numerous 50-70 A filaments appear in samples of the extract prepared for electron microscopy, suggesting that the increase in viscosity in caused, at least in part, by the formation of these thin filaments. During this initial phase of ATP-stimulated movement, these thin filaments are not detectable by phase-contrast or polarization microscopy, but later, in the second phase of movement, 70 A filaments aggregate to form birefringent microscopic fibrils. A preparation of pure groundplasm with no 160 A filaments or membranous organelles exhibits little or no ATP-stimulated movement, but 50-70 A filaments form and aggregate into birefringent fibrils. This observation and the structural relationship of the 70 A and the 160 A filaments in the motile extract suggest that both types of filaments may be required for movement. These two types of filaments, 50-70 A and 160 A, are also present in the cytoplasm of intact amebas. Fixed cells could not be used to study the distribution of these filaments during natural ameboid movement because of difficulties in preserving the normal structure of the ameba during preparation for electron microscopy.

Adenosine Triphosphate↗

PubMed1990

[Histophysiology of the zona fasciculata of the adrenal cortex of albino rats].

Three phases have been detected in the fascicular zone of the white rat adrenal cortex. During the first phase (normoemia) blood stream is rather moderate, lipids accumulate in adrenocorticocytes. This results in increase of their volume and in decrease of nuclear-cytoplasmic relations. The second phase (functional hyperemia) is characterized with an elevated blood stream and plethora, maximal parameters of nuclear volume and nuclear-cytoplasmic relations, decreasing content of lipids and volume of adrenocorticocytes. During the third phase (functional hypoemia) parameters characterising intensity of blood stream, nuclear volume and nuclear-cytoplasmic relations decrease.

Adrenal Cortex↗

PubMed1988

Dynamic organization of Physarum plasmodium.

Birefringent fibrils (BRFs) with a positive sign composed of bundles of F-actin were found throughout the Physarum plasmodium with the mode of existence differing regionally. In the zone behind the leading edge of an advancing plasmodium, where cytoplasmic sol and gel were still not well differentiated, more BRFs came to the foreground when the endoplasm flowed backward (emptying phase), and a substantial portion disappeared when the endoplasm flowed forward (filling phase), except for nodes, from which BRFs were reorganized in the early emptying phase of each cycle. BRFs found in the wall of the streaming channel in the posterior network and the branched vein section ran in parallel to or helically around the channel. They were much more stable and maintained strong birefringence irrespective of the direction of the cytoplasmic flow. When the fan-like expanse ceased moving forward, the BRFs no longer appeared and disappeared cyclically but persisted in the area which had previously been the front. We concluded that the site of the active contraction-relaxation rhythm in an advancing plasmodium with antero-posterior polarity is restricted to its frontal zone and that the rest of the plasmodium is in a state of "tonus" which continuously imparts a certain level of hydrostatic pressure to the interior. The meaning of the tonus and the mechanics of tensile force production in the plasmodium are discussed in terms of a working hypothesis arrived at from the phase relationship between isometric and isotonic contraction waves.

Birefringence↗

PubMed1968

Further electron microscope studies on fibrillar organization of the ground cytoplasm of Chaos chaos.

Further evidence for fibrillar organization of the ground cytoplasm of Chaos chaos is presented. Fixations with osmium tetroxide at pH 6 or 8 and with glutaraldehyde at pH 6 or 7 were used on two preparations: (a) single actively streaming cells; (b) prechilled cells treated with 0.05% Alcian blue in the cold and returned to room temperature for 5-10 min. In addition, a 50,000 g pellet of homogenized cells was examined after fixation with glutaraldehyde-formaldehyde alone. In sections from actively streaming cells considerable numbers of filaments were observed in the uroid regions after glutaraldehyde fixation, whereas only traces of filaments were seen after osmium tetroxide fixation at either pH 6 or 8. Microtubules were not seen. In sections from dye-treated cells, filaments (4-6 mmicro) and fibrils (12-15 mmicro) were found with all three fixatives. The 50,000 g pellet was heterogeneous but contained both clumps of fibrils and single thick fibrils like those seen in the cytoplasm of dye-treated cells. Many fibrils of the same dimensions (12-15 mmicro wide, 0.5 micro long) were also seen in the supernatant above the pellet. Negative staining showed that some fibrils separated into at least three strands of 4-6 mmicro filaments.

Cytoplasm↗

PubMed1986

Chromatin condensation and terminal differentiation process in embryonic chicken lens in vivo and in vitro.

During embryonic chick lens differentiation, the epithelial cells become transformed into elongated fibres. Concomitantly, the fibre nuclei undergo degeneration and high molecular weight (HMW) DNA breaks down due to nuclear endodeoxyribonuclease activity. An electronmicroscopic study of lens epithelial and fibre nuclei was made at different stages of chick embryonic development, both in vivo and in vitro. The in vitro conditions are conducive to the expression of endogenous endodeoxyribonuclease activity in fibres. In both conditions we observed condensation of chromatin. The organization of some nuclear material into distinct linear arrays followed by streaming of nuclear material into the cytoplasm is recorded only in vitro. Such a condition may lead to acceleration of the process of aging in lens fibres.

Animals↗

PubMed1997

Immunodeficiencies and haematological disorders--direct connections to cellular signalling pathways.

Extracellular signals, such as cytokines and foreign antigens, regulate the development and activation of haematopoietic cells through receptor-mediated transcriptional responses. Investigation of the biochemical events that transduce receptor activation to intracellular signal transduction have revealed a general mechanism for both the antigen receptor and the cytokine receptor nuclear signalling. Receptor stimulation is coupled to down-stream signalling cascades through activation of cytoplasmic tyrosine kinases but both receptor types utilize distinct signalling proteins. Antigen receptors employ protein tyrosine kinases of the Src, Syk, and Tec families which phosphorylate and activate cytoplasmic signalling proteins leading to activation of NF-AT, AP-1 and NF-kappaB transcription factors, while the principal signal transducers for cytokine receptors are the Jak tyrosine kinases and Stat transcription factors. The molecular basis for several immune and haematological disorders has been characterized during the last few years and they have been found to be caused by defects in various signalling proteins. In this review the aetiology of immune and haematological disorders is discussed in the light of the recent developments in signal transduction.

Antigens↗

PubMed2000

Formation of spindle poles by dynein/dynactin-dependent transport of NuMA.

NuMA is a large nuclear protein whose relocation to the spindle poles is required for bipolar mitotic spindle assembly. We show here that this process depends on directed NuMA transport toward microtubule minus ends powered by cytoplasmic dynein and its activator dynactin. Upon nuclear envelope breakdown, large cytoplasmic aggregates of green fluorescent protein (GFP)-tagged NuMA stream poleward along spindle fibers in association with the actin-related protein 1 (Arp1) protein of the dynactin complex and cytoplasmic dynein. Immunoprecipitations and gel filtration demonstrate the assembly of a reversible, mitosis-specific complex of NuMA with dynein and dynactin. NuMA transport is required for spindle pole assembly and maintenance, since disruption of the dynactin complex (by increasing the amount of the dynamitin subunit) or dynein function (with an antibody) strongly inhibits NuMA translocation and accumulation and disrupts spindle pole assembly.

Biological Transport↗

PubMed1982

Slowly progressive congenital myopathy with cytoplasmic bodies--report of two cases and a review of the literature.

Observations on two patients from unrelated families are reported. Both patients were 32 years old and suffered from a congenital affection of the skeletal muscles. In one (case 2) congenital paresis of the dilator muscle of pupil and cardiomyopathy were also present. In both cases muscle biopsy showed pathologic variations of muscle fiber caliber, and in case 1 atrophic fibers were grouped in some places. Inclusions consisting of dense granular and fine filamentous components were found in skeletal muscle fibers, in about a third of the fibers in case 1 and in about a tenth of the fibers in case 2. The shape and submicroscopic structure of these inclusions were consistent with so-called cytoplasmic bodies. Surrounding or apart from the inclusions, the streaming of Z disks or their disintegration were observed. In addition, pure filamentous bodies occurred in the subsarcolemmic position in both cases. Although cytoplasmic bodies are a nonspecific type of inclusion, they were the outstanding structural anomaly in both cases. A basic defect of myofilament biosynthesis is considered to be the cause of the disorder. It is presumably evoked by a neurogenic factor affecting the trophic influence of the neuron on the muscle cell. The course of the disease may (case 1) but need not (case 2) terminate in severe impairment of skeletal muscle function.

Adult↗

PubMed1982

Relation of cytoplasmic calcium to contractility in Physarum polycephalum.

In a dumbbell-shaped plasmodium of Physarum polycephalum showing active shuttle streaming Ca was precipitated with potassium pyroantimonate (K[Sb(OH)6]), and the distribution of Ca between the cytoplasm and cellular organelles, especially vacuoles, was examined by electron microscopy. The contracting half-mass, where many empty vacuoles were present, was rich in the small Ca precipitates located in the cytoplasm. The relaxing half-mass, where many Ca-containing vacuoles were present, was poor in the cytoplasmic Ca precipitates. One half-mass of a dumbbell-shaped plasmodium was treated with Ca ionophore, X-537A, and its effect on the motive force for endoplasmic streaming and the distribution of Ca was investigated. The motive force was increased by X-537A, but the period of shuttle streaming was not changed. X-537A also induced a significant increase in the number of the cytoplasmic Ca precipitates in the X-537A-treated contracting half-mass, so that the asymmetry of the distribution of cytoplasmic Ca precipitates was enhanced. A large portion of the vacuoles were empty in the contracting half-mass, and Ca-containing in the relaxing one as in the case of the untreated plasmodium.

Calcium↗

PubMed1993

Experimental emetine myopathy: enzyme histochemical, electron microscopic, and immunomorphological studies.

Ipecac, containing emetine hydrochloride, is used by patients with anorexia nervosa to induce vomiting. Its chronic usage may result in a myopathy and a cardiomyopathy, the former marked by cytoplasmic bodies. We studied myopathological changes after daily injections of female Wistar rats with emetine hydrochloride intraperitoneally for periods of 4, 5, 9, and 10 weeks. The extensor digitorum longus muscle and the soleus muscle showed core-like lesions, streaming of the z-discs, nemaline bodies, cytoplasmic bodies, and spheroid cytoplasmic bodies. Immunomorphological studies revealed increased amounts of desmin. During a period of repair, i.e., 2, 4, and 6 weeks after termination of emetine application, these myopathological alterations faded while proliferation of the T-tubular system, i.e., honeycomb structures, was more often prevalent. Pathological features completely disappeared between 6 and 12 weeks of recovery.

Animals↗

PubMed1978

Effect of ultraviolet or laser light irradiation on the growth of Micrasterias thomasiana.

The effect of ultraviolet on laser light on growth of lobes in a green alga, Micrasterias thomasiana was investigated. During plasmolysis, the cell wall and the outermost region of the cytoplasm were separately irradiated with an ultraviolet or laser microbeam. Growth of the lobes was more effectively inhibited by irradiation of the cytoplasm than of the cell wall when the dose of irradiation was weak. Growth inhibition was observed in the irradiated cytoplasm where no apparent decrease in velocity of plasma streaming was seen, which suggested that irradiation caused more damage to the mechanism of exocytosis than to the migration of secretion vesicles. Strong irradiation resulted in gelatinization of the cytoplasm. With strong doses of irradiation on both the cytoplasm and cell wall, growth was completely inhibited.

Cell Wall↗

PubMed1981

Isolation and characterization of paracrystalline arrays of the plasma membrane of baker's yeast Saccharomyces cerevisiae.

Yeast plasma membranes were isolated from homogenized cells and analyzed by SDS-PAGE. Two glycoproteins of 160 000 and 240 000 molecular weight were found, both of which exhibited invertase activity (EC 3.2.1.26). By density gradient centrifugation a heavy membrane fraction which consisted of the glycoproteins and two hydrophobic proteins was isolated. Antibody labeling of protoplasts revealed a good correlation between the distribution of binding sites of the antibodies against the heavy fraction and the distribution of the intramembranous particles. The cytoplasmic surface of the yeast plasma membrane was visualized by freeze drying and subsequent platinum/carbon shadowing of membrane vesicles adsorbed to cationized glass and squirted with a hypotonic buffer stream. In contrast to the smooth exoplasmic surface the cytoplasmic surface showed paracrystalline arrays of particles which resembled in size, number and lattice constant the intramembranous particles. Removal of the adsorbed paracrystalline arrays and subsequent SDS-PAGE revealed the same protein pattern as the heavy membrane fraction. It can therefore be concluded that the glycoproteins which show invertase activity and the two hydrophobic proteins are the major components of the paracrystalline arrays. It is proposed that the glucose level of the nutrient medium influences the appearance and disappearance of the paracrystalline arrays, which consist mainly of invertase, because synthesis of invertase is inhibited by glucose levels higher than 1%.

Antibodies↗

PubMed1988

Sublethal muscle fibre injuries after high-tension anaerobic exercise.

The vastus lateralis muscles of eleven male elite sprinters (17-28 years) were investigated in order to examine the impact of high tension anaerobic muscular work on muscle fibre fine structure. In an attempt to reproduce the training regimen six subjects ran 20 repetitions of 25 s on a treadmill with 2 min 35 s in between, at a speed corresponding to 86% of their personal best 200 m time. PAS-stained sections of biopsies taken approximately 2 h after training generally indicated glycogen depletion in type 1 and type 2B fibres. At the light microscopic level, no signs of inflammation or fibre rupture were observed. However, at the ultrastructural level, frequent abnormalities of the contractile material and the cytoplasmic organelles were detected. Z-band streaming, autophagic vacuoles and abnormal mitochondria were the most conspicuous observations. Control specimens from sprinters who did not perform the acute exercise routine also displayed structural deviations, although to a lesser degree. It is hypothesized that during sprint training the leg musculature is put under great mechanical and metabolic stress which causes the degenerative response reported here.

Adolescent↗

PubMed1993

Heat conductance, diffusion theory and intracellular metabolic regulation.

Diffusion theory played a major role in the development of biology as an exact science. The question is raised, however, as to its relevance and applicability in the molecular interactions which occur in metabolism in the living cell. This review looks at diffusion theory from its inception and subsequent introduction into biology, its shortcomings with regard not only to whole-body physiology, but more pertinently at the intracellular level, with its failure to offer a rational basis for metabolic regulation in the internum of the cell. The conclusion is reached that although diffusion inevitably occurs within cells, its role is of little importance with regard to most metabolic activity. In comparison, perfusion of the internal surfaces of the cell by streaming of the fluid compartment of the cytoplasm seems to be the modus operandi which allows molecular interactions to occur at rates far beyond those that diffusion would permit, and at the same time offers a mechanism which permits sensitive control of metabolic activity.

Animals↗

PubMed1977

Myofibre abnormalities of orbicular muscle in malposition of the eyelid.

Fifty-five cases of senile entropion and ectropion have been studied electron microscopically. In both senile entropion and ectropion significant ultrastructural abnormalities were found in the orbicular muscle fibres, such as a disruption of fibres, Z line streaming, rod formation, Z line duplication and cytoplasmic body formation. These alterations have been described only in neuromuscular disorders and systemic diseases affecting the skeletal muscles. Our observations have confirmed that these abnormalities are not specific signs of any given disease, they rather represent the ultrastructural background of impaired muscle function independently of the aetiology of the disease.

Aged↗