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PubMed1984

[The fixed charge of protoplasm in barnacle muscle fiber; effect of the length of the sarcomeres].

The thermodynamically effective charge density (phi X) of myoplasm was measured on barnacle muscle fibers. A small section of a muscle cell formed a liquid junction between two electrolyte solutions and the electrical potential between the solutions permitted to evaluate phi X. If the sarcomere length was kept constant (Ls = 12.5 micron), phi X increased from 0.068 to 0.090 equiv./L when the water content was reduced from 75 to 65 g/100 g wet weight. This increment of X resulted from an increase of X when the concentration of macromolecules is raised in the sample of cytoplasm. But it also indicates that the counterions of the fixed charges concur less to the activity of the counterions when X is increased by lowering the water content. If the water content is maintained constant, phi X increased from 0.068 to 0.084 equiv./L for sarcomere lengths equal to 9.6 and 11.5 micron but phi X remained constant for Ls greater than 12 micron. Thus, when the length of the sarcomere is greater than 12 micron the contribution of the counterions of the fixed charges to the activity of the counterion is larger than for Ls = 9.6 micron.

Animals↗
PubMed1987

The use of alizarin red S to detect and localize calcium in gametophyte cells of ferns.

An aqueous solution of alizarin red S containing chloral hydrate both clears intact chlorophyllous gemma cells of Vittaria graminifolia and stains for protoplasmic calcium. Verification that the stain was protoplasmic rather than in the cell wall was shown by a positive reaction in extruded protoplasm. Similar staining was found in extruded protoplasm of Onoclea sensibilis spores. Differentiating gemma cells show localized protoplasmic accumulations of Ca2+ at sites where asymmetric cell divisions initiate the formation of rhizoids, antheridia or vegetative cells. The staining properties of the dye depend on careful control of pH and the addition of appropriate amounts of KCl to the mixture. Treatment of Onoclea spores and Vittaria gemmae with 100 mM EGTA for 30 min nearly abolishes staining of their extruded protoplasts and also of intact cells of gemmae. The use of alizarin red S with and without chloral hydrate demonstrates different pools of protoplasmic Ca2+. When Onoclea spores are ruptured to extrude the protoplasm, both dye mixtures stain a peripheral, granular protoplasmic component. However, the chloral hydrate-containing dye also reveals Ca2+ associated with small particulate protoplasmic components. Extruded protoplasm of gemma cells stains intensely with alizarin-chloral hydrate, but does not stain with alizarin lacking chloral hydrate.

Anthraquinones↗
PubMed1980

Studies on microplasmodia of Physarum polycephalum. I. Classification and locomotion behavior.

Depending on the conditions of the axenic shuttle culture, microplasmodia of the acellular slime mold Physarum polycephalum can be subdivided into three classes regarding fine structural organization and protoplasmic streaming activity: (1) spherical and rod-shaped types, (b) ameboid types, and (c) symmetrical types. In ameboid microplasmodia, the motive force for the irregular protoplasmic streaming activity is generated by alternative contraction and relaxation of a membrane-associated layer, morphologically consisting exclusively of thin filaments (probably actin). The protoplasm flows along a hydraulic pressure gradient produced by the filament layer within limited regions of the cell periphery. In dumbbell-shaped microplasmodia the motive force for the regular protoplasmic shuttle streaming between the two spherical heads is generated both by volume changes of the peripheral cell region (caused by the contractile activity of the membrane-associated filament layer), and by volume changes of the internal cell membrane invagination system (caused by fibrils attached to the basal region of the invaginations). The development from the unordered protoplasmic streaming pattern and less complicated fine structural organization in ameboid microplasmodia to the highly organized protoplasmic shuttle streaming and the more complicated morphology in dumbbell-shaped microplasmodia can be explained by intermediate stages. Whereas the motive force for the transport of smaller amounts of protoplasm can be generated by the exclusive action of a cortical filament layer, the existence of a filament cortex, the display of cytoplasmic fibrils, and the development of plasma membrane invaginations appear to be a necessary precondition for the transport of large amounts of protoplasm.

Cytoplasm↗
PubMed1958

Ion transport in Nitellopsis obtusa.

The distribution and rates of exchange of the ions sodium, potassium, and chloride in single internodal cells of the ecorticate characean, Nitellopsis obtusa, have been studied. In tracer experiments three kinetic compartments were found, the outermost "free space" of the cell, a compartment we have called "protoplasmic non-free space", and the cell sap. The concentrations in the vacuole were 54 mM Na(+), 113 mM K(+), and 206 mM Cl(-). The steady state fluxes across the vacuolar membrane were 0.4 pmole Na(+)/cm.(2) sec., 0.25 pmole K(+)/cm.(2) sec., and 0.5 pmole Cl(-)/cm.(2) sec. The protoplasmic Na/K ratio is equal to that in the vacuole but protoplasmic chloride is relatively much lower. Osmotic considerations suggest a layer 4 to 6 micro thick with sodium and potassium concentrations close to those in the vacuole. The fluxes between protoplasm and external solution were of the order of 8 pmoles Na(+)/cm.(2) sec. and 4 pmoles K(+)/cm.(2) sec. We suggest that the protoplasm is separated from the cell wall by an outer protoplasmic membrane at which an outward sodium transport maintains the high K/Na ratio of the cell interior, and from the vacuole by the tonoplast at which an inward chloride transport maintains the high vacuolar chloride. The tonoplast appears to be the site of the principal diffusion resistance of the cell, but the outer protoplasmic membrane probably of the main part of the potential.

Biological Transport, Active↗
PubMed1957

Studies on the electrical properties of a single plant cell; internodal cell of Nitella flexilis.

Impedance changes of single plant cells of Nitella flexilis were studied under different environmental conditions. With the analysis presented changes in resistance of the protoplasmic membrane and of cell sap can be studied independently and simultaneously. Under "transcellular osmosis," the resistance of the protoplasmic membrane and of the cell sap increase at the part of the cell where water enters, while they decrease where water goes out. Ethanol of low concentration (below 8 per cent) first decreases and later increases the resistance of the protoplasmic membrane. Concentrated ethanol (over 10 per cent), however, brings about a large decrease in resistance of the protoplasmic membrane. Its time course is not simple, but undulatory changes occur. When ethanol is applied to one part of the cell, the resistance of the protoplasmic membrane shows a different type of change, which may be attributed to the local osmotic effect of ethanol; injury generally occurs with comparatively low concentration. Methanol, ethanol, and propanol have almost the same effect upon the cell, while butanol is toxic at the same concentration. When the cell dies, the resistance of the protoplasmic membrane decreases greatly, while the resistance of the cell sap increases to a level (several hundred kilo ohms or more), expected when external solution and cell sap are freely mixed with each other.

Cells↗
PubMed1991

Two distinct steps for spontaneous generation of subprotoplasts from a disintegrated bryopsis cell.

The unusual nature of protoplasm to generate subprotoplasts spontaneously from disintegrated Bryopsis cells was examined. Protoplasm extruded from algal cells aggregated rapidly in cell sap which was derived mainly from huge central vacuoles of the cells. Electron microscopic observations revealed extensive agglutination of algal cellular membranes in the protoplasmic masses, suggesting that this is of primary importance for the wound-healing ability of the alga. Seawater caused spheration of the resultant protoplasmic aggregates. Gelatinous sheaths were formed temporarily surrounding the spherical protoplasmic masses before reformation of cell membrane. Staining with phosphotungstic and chromic acids suggested that new cell membrane was formed by fusion of the disintegrated original cell membrane with cytoplasmic vesicles on the surfaces of the protoplasmic masses. Both pH and salts were found to be essentially important at the two steps of subprotoplast generation. The newly formed cell membranes were responsible for subsequent notable plasmolysis of the wounded cells in seawater. Thus, it is suggested that unicellular marine algae Bryopsis spp. naturally contain effective materials for agglutinating and fusing particular cellular membranes through the sequential aid of acidic cell sap and alkaline seawater after disintegration of the giant cells.

Journal Article↗
PubMed2003

Pre-formed xyloglucans and xylans increase in molecular weight in three distinct compartments of a maize cell-suspension culture.

Cultured cells of maize ( Zea mays L.) were pulse-labelled with l-[1-(3)H]arabinose (Ara) and then monitored for 7 days. The (3)H-hemicelluloses present in three compartments (protoplasm, cell wall and culture medium) were size-fractionated and the fractions assayed for [(3)H]xyloglucans and [(3)H]xylans. Protoplasmic [(3)H]xylans and [(3)H]xyloglucans initially (15 min after [(3)H]Ara-feeding) had weight-average relative molecular masses ( M(w)) approximately 0.5x10(6) and 0.3x10(6), respectively, both rising to 2x10(6) by 30 min. Thus, newly formed hemicellulose molecules were joined to other polymers, or to each other, presumably within Golgi vesicles. New (3)H-hemicelluloses very rapidly bound to the cell wall; however, after 1 day, some [(3)H]xyloglucan and [(3)H]xylan was sloughed from the wall into the medium. The wall-bound [(3)H]xyloglucans were present in the form of extremely large complexes, of M(w)>17x10(6), even as early as 15 min after [(3)H]Ara-feeding. This M(w) is >70-fold greater than that observed by similar methods in cultures of a dicotyledon ( Rosa sp.). Thus, during wall-binding, newly secreted xyloglucans greatly increased in size, possibly by transglucosylation. Some modest degradation (trimming) of wall-bound [(3)H]xyloglucan occurred later. The earliest wall-bound [(3)H]xylan had M(w) approximately 2x10(6), similar to the protoplasmic [(3)H]xylan; this increased to approximately 4x10(6) by 6 h. For the first 2 days after [(3)H]Ara-feeding, the soluble extracellular (3)H-hemicelluloses present in the culture medium had M(w) approximately 1x10(6)-2x10(6), comparable to the protoplasmic hemicelluloses. However, between 2 and 3 days after [(3)H]Ara-feeding, the M(w) of the soluble extracellular [(3)H]xylans increased abruptly to approximately 10x10(6); the soluble extracellular [(3)H]xyloglucans underwent a similar but more gradual increase in M(w). Maize (3)H-hemicelluloses thus underwent increases in M(w) in three episodes: (i) intra-protoplasmically, (ii) during wall-binding (especially xyloglucans), and (iii) after sloughing into the medium. Possible mechanisms and roles of these increases are discussed.

Arabinose↗
PubMed2004

Maturation of astrocyte morphology and the establishment of astrocyte domains during postnatal hippocampal development.

Mature protoplasmic astrocytes exhibit an extremely dense ramification of fine processes, yielding a 'spongiform' morphology. This complex morphology enables protoplasmic astrocytes to maintain intimate relationships with many elements of the brain parenchyma, most notably synapses. Recently, it has been demonstrated that astrocytes establish individual cellular-level domains within the neuropil, with limited overlap occurring between the extents of neighboring astrocytes. The highly ramified nature of protoplasmic astrocytes is closely associated with their ability to create such domains. This study was an attempt to characterize the development of spongiform processes and the establishment of astrocyte domains. A combination of immunolabeling for the astrocyte-specific markers glial fibrillary acidic protein and S100beta with intracellular dye labeling in fixed tissue slices allowed for the identification of immature astrocytes and the elucidation of their complete, well-preserved morphologies. We find that during the first two postnatal weeks astrocytes extend stringy, filopodial processes. Fine, spongiform processes appear during the third week. Protoplasmic astrocytes are quite heterogeneous in morphology at 1-week postnatum, but there is a remarkable consistency in morphology by 2 weeks of age. Finally, protoplasmic astrocytes initially extend long, overlapping processes during the first two postnatal weeks. The subsequent elaboration of spongiform processes results in the development of boundaries between neighboring astrocyte domains. Stray processes that encroach on neighboring domains are eventually pruned by 1 month of age. These observations suggest that domain formation is largely the consequence of competition between astrocyte processes, similar to the well-studied competitive interactions between certain neuronal dendritic fields.

Animals↗
PubMed1967

Causal basis of gravity stimulus nullification by clinostat rotation.

Using appropriate clinostat rotation methods, it has been shown that increases in root growth and geotropic curvature of oat coleoptiles are related to and explained (within the limits of auxin economy) by increased rates of plant respiration imparted by nullification of the gravitational stimulus. Increased respiration with decreased gravitational stimulus, in turn, is explained by increased uniformity in intracellular distribution of metabolically active graviprecipitable particles.Oat seedlings grown with nullification of the gravitational stimulus show a more uniform distribution of graviprecipitable protoplasmic inclusions. Respiration involves reactions between particles of sufficient mass to be precipitated in 1 x g unidirectional force field and particles of such size that they are distributed throughout the protoplasm due to thermal energy. When plants are grown without nullification of the gravitational stimulus, graviprecipitable protoplasmic inclusions tend to accumulate in the lower portions of the cells. Respiration rates are consequently limited due to a relatively low concentration of the smaller particles in the region of high concentration of the larger particles. Distribution of the larger particles throughout the protoplasm negates the reaction rate limiting effects of these intracellular concentration gradients.It has been shown using starch particles to index graviprecipitation of intracellular particles that enhancement of respiration by nullification of the gravitational stimulus may be induced, maintained, discontinued, and reinduced by treatments which concomitantly result in the more uniform distribution of graviprecipitable protoplasmic inclusions, the maintenance of this uniform distribution, the discontinuation of this uniform distribution and its reinduction.The degree of uniformity of intracellular particle distribution in response to treatments only partially nullifying the gravitational stimulus is shown wholly consonant with growth responses of roots and coleoptiles when the growth is measured as the expression of increased respiration in the absence of auxin limitation.The findings collectively indicate that gravity sensing by plants is broadly based on the physicochemical relationship between particle distribution and the expression of respiratory metabolism as growth.

Journal Article↗