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PubMed1963

ULTRASTRUCTURAL STUDIES ON THE BLUE-GREEN ALGAL SYMBIONT IN CYANOPHORA PARADOXA KORSCHIKOFF.

Studies conducted on the ultrastructure of Cyanophora paradoxa Korschikoff (a cryptomonad) have shown that its intracellular symbiont is closely related to unicellular blue-green algae. Due to its peculiar habitat, the intracellular symbiont lacks the characteristic cyanophycean double-layered cell wall, but is surrounded by a thin protoplasmic membrane. The protoplasm itself is differentiated into a lamellated chromatoplasm containing photosynthetic pigments, polyphosphate granules, and possible oil droplets, and a non-lamellar centroplasm with a large centrally located electron-opaque body surrounded by a fibril-containing halo. This halo-central body complex may be nuclear in nature. Binary fission of the organism is described. Since this cyanelle has not yet been classified, we name it Cyanocyta korschikoffiana nov. gen. nov. sp.; and because of its structural peculiarities, we find it necessary to create a new family for it, Cyanocytaceae, in the order Chroococcales.

Animals↗
PubMed1956

Electron microscopy of growing oocytes of Rana pipiens.

1. In the cytoplasm of oocytes of stage Y(0), prior to the appearance of yolk, one observes a few scattered profiles of endoplasmic reticulum and numerous filamentous mitochondria, usually distributed at random but sometimes clustered. As the nuclear membrane begins to bulge outward, small granules and short rods appear in the perinuclear cytoplasm and endoplasmic reticulum becomes more prominent throughout the cytoplasm. 2. Coincident with the appearance of the first yolk platelets, which are deposited in a narrow peripheral ring within the endoplasm at stage Y(1), protoplasmic processes, the microvilli, push out all over the surface of the oocyte. At the same time follicle cells pull away but remain attached to the oocyte at some points through finger-like processes which interdigitate with neighboring microvilli. It is estimated that the microvilli increase the absorptive area of the surface to about thirty-five times that of a simple sphere. Just beneath the microvillous layer is the basal protoplasm of the cortex, now containing tiny granules probably synthesized from newly absorbed raw materials. Cortical granules appear and become aligned below the basal layer on the external border of the endoplasm. Both the cortical granules and the yolk platelets measure up to 1 micro in diameter at this stage. 3. By stage Y(3) (yolk filling peripheral three-fourths of cytoplasm), the basal layer of the cortex is folded so that it appears in section as alternating ridges and valleys. The microvilli now extend from the summits of the cortical ridges. Small, ring-shaped granules are abundant in the cortex. Cortical granules have increased to 2 micro in diameter. 4. Yolk platelets continue to be synthesized around the cortical granules and in the subjacent endoplasm. The largest platelets measured in the interior cytoplasm at stage Y(4) (cytoplasm filled with yolk) were 3.7 micro wide by 5.8 micro long. Pigment granules increase in size from 0.15 micro in diameter at stage Y(3) to 0.30 micro in diameter at stage Y(4).

Animals↗
PubMed1956

Morphogenesis of the retinal rods; an electron microscope study.

The morphogenesis of the retinal rods has been studied with the electron microscope in white mice from birth up to the 16th day of age. Observations have been mainly concentrated on specimens of the 8th and 12th days and on the differentiation of the inner and outer segments of the retinal rods. In the morphogenesis of the outer segment three main stages have been considered. The first stage consists in the development of a primitive cilium projecting from a bulge of protoplasm which constitutes the primordium of the inner segment. A basal body, nine pairs of peripheral filaments, a surface membrane, and a matrix filled with a fine vesicular material have been recognized as components of the primitive cilium. The vesicles are called "morphogenetic material" because it is believed that they represent the macromolecular primordium of the rod sacs of the future outer segment. The second stage corresponds to the great enlargment of the apical region of the primitive cilium due to the rapid building up of the lamellar material of the rod sacs. The primitive rod sacs appear to be connected with the ciliary filaments. The basal portion of the primitive cilium remains undifferentiated and constitutes the connecting cilium of the adult rod (1). The third stage consists in the remodelling and reorientation of the rod sacs into their permanent transverse disposition. This process starts in the middle portion of the outer segments and proceeds towards both extremities which can be considered as zones of growth of the outer segment. The inner segment is at the beginning a bulge of protoplasm containing unoriented mitochondria, a basal body, a small Golgi zone, and numerous dense particles. Then this region becomes elongated and the different components assume the stratified disposition found in the adult (1). The demonstration that the entire outer segment of the rod cell is the result of the differentiation of a primitive cilium is discussed in view of the conflicting interpretations found in the literature. The possible macromolecular mechanisms that may be involved in the submicroscopic morphogenesis of the rod sacs are discussed and the possible role of the morphogenetic material is considered. The results described in this paper confirm and extend the interpretation of the submicroscopic morphology of the adult rod cell as presented in a previous paper (1).

Electrons↗
PubMed1964

FINE STRUCTURE OF THE GRAM-NEGATIVE BACTERIUM ACETOBACTER SUBOXYDANS.

The morphological features of the cell wall, plasma membrane, protoplasmic constituents, and flagella of Acetobacter suboxydans (ATCC 621) were studied by thin sectioning and negative staining. Thin sections of the cell wall demonstrate an outer membrane and an inner, more homogeneous layer. These observations are consistent with those of isolated, gram-negative cell-wall ghosts and the chemical analyses of gram-negative cell walls. Certain functional attributes of the cell-wall inner layer and the structural comparisons of gram-negative and gram-positive cell walls are considered. The plasma membrane is similar in appearance to the membrane of the cell wall and is occasionally found to be folded into the cytoplasm. Certain features of the protoplasm are described and discussed, including the diffuse states of the chromatinic material that appear to be correlated with the length of the cell and a polar differentiation in the area of expected flagellar attachment. Although the flagella appear hollow in thin sections, negative staining of isolated flagella does not substantiate this finding. Severe physical treatment occasionally produces a localized penetration into the central region of the flagellum, the diameter of which is much smaller then that expected from sections. A possible explanation of this apparent discrepancy is discussed.

Acetobacter↗
PubMed1976

Similarity of junctions between plasma membranes and endoplasmic reticulum in muscle and neurons.

The structure of membranes at junctions between the plasma membrane and underlying cisterns of endoplasmic reticulum in amphioxus muscle and mouse cerebellar neurons was studied using the freeze-fracture technique. In amphioxus muscle, subsurface cisterns of sarcoplasmic reticulum form junctions with the surface membrane at the level of the sarcomere I bands. On the protoplasmic leaflet of the sarcolemma overlying these junctions were aggregates of large particles. On the protoplasmic leaflet of the membranes of cerebellar basket, stellate and Purkinie cells there were similar aggregates of large particles. In both tissues, the corresponding external membrane halves had arrays of pits apparently complementary to the aggregates of large particles. Cross fractures through junctions showed that the particle aggregates in neuronal and muscle membranes were consistently located over intracellular cisterns closely applied to the plasma membrane. Thus, a similar plasma membrane specialization is found at subsurface cisterns in mammalian neurons and amphioxus muscle. This similarity supports the hypothesis that subsurface cisterns in neurons, like those in muscle, couple some intracellular activity to the electrical activity of the plasma membrane.

Animals↗
PubMed1961

Silver impregnation of ultrathin sections for electron microscopy.

A new procedure is described for silver impregnation of thin sections for electron microscopy. Sections of various tissues, fixed in OsO(4) and embedded in methacrylate, were treated with an ammoniacal silver solution, directly or after oxidation with periodic acid or hydrogen peroxide. After OsO(4) fixation all cellular membranous systems exhibit a primary argentaffinity probably due to the reduction of ammoniacal silver solution by the reduced osmium bound to unsaturated lipids. Bleaching the sections with hydrogen peroxide removes the argentaffinity of protoplasmic structures. Treatment of the sections with periodic acid results in decreased argentaffinity of protoplasmic components while the argentaffinity of metaplasmic structures is greatly enhanced. The latter procedure appears particularly useful for enhancing the contrast of basement membranes.

Cell Membrane↗
PubMed1984

High density of transmembrane glycoproteins on the flagellar surface of boar sperm cells.

Membrane halves of boar sperm flagella were produced by freeze-fracture and labeled in situ with concanavalin A and wheat germ agglutinin; the lectins were visualized with protein-gold complexes. Concanavalin A and wheat germ agglutinin binding sites partition with both protoplasmic and exoplasmic halves of the membrane. A high density of lectin marking was found on protoplasmic membrane halves; we conclude that the label corresponds to transmembrane glycoproteins that, on freeze-fracture, are dragged across the outer (exoplasmic) half of the phospholipid bilayer. Our demonstration of numerous transmembrane proteins in sperm flagella offers the structural setting for previous models on flagellar surface motility that postulate accessibility of motile membrane components to the submembranous cytoskeleton.

Animals↗
PubMed1965

ON THE ACTION OF COLCHICINE, THE MELANOCYTE MODEL.

The effect of colchicine was studied on the rapid, reversible darkening of frog skin under the influence of melanocyte-stimulating hormone (MSH). Darkening is due to dispersion of melanin granules in melanocytes and is thought to be accompanied by a gel-to-sol cytoplasmic transformation. After subsequent washing, the skin lightens, with aggregation of melanin granules and cytoplasmic gelation. Preincubation of skin with colchicine had the following effects: 1. Darkening induced by MSH was increased in comparison to control skins, and on removal of MSH, lightening was inhibited. Inhibition was a function of both concentration (1 x 10(-5) to 9 x 10(-5)M) and exposure time (2 to 30 minutes). Once established, inhibition was maintained throughout the remainder of the experiment. 2. The same effects were noted (a) when darkening was effected by agents other than MSH (ATP) 0.9 x 10(-3)M; caffeine, 5.2 x 10(-3)M; ethyl acetate, 0.8 x 10(-2)M), and (b) when lightening was effected by addition of chemical agents (melatonin, 4.3 x 10(-10)M; hydrocortisone, 1 x 10(-3)M; norepinephrine, 1 x 10(-3)M), instead of by washing. 3. Colchicine alone produced a gradual, irreversible, dosage-dependent darkening over several hours. This darkening was inhibited by melatonin, 4.3 x 10(-10)M. The melanocyte model is used to construct a general theory of colchicine action on living cells, an action resulting in decreased protoplasmic viscosity. In this formulation colchicine lowers the potential limit of protoplasmic gelation, and does it rapidly, reversibly, in low concentration, in a dosage-dependent manner, and without killing the cell. The theory allows interpretation of "synergism" and "antagonism" to colchicine by other substances. It suggests a tentative approach to the understanding of colchicine action in acute gouty arthritis, where interference with ameboid activities of polymorphonuclear leukocytes is one possible aspect of the anti-inflammatory effect of colchicine. Finally, the colchicine-treated melanocyte is viewed as a good, live physical model that can be used to elucidate some fundamental biological properties.

Acetates↗
PubMed1950

Higher permeability for water than for ethyl alcohol in Nitella.

If we apply water at one end of a Nitella cell, A, and place at the other end, B, a solution of a substance which does not penetrate, such as sucrose, water enters the cell at A, passes along inside the cell, and escapes at B. But if in place of sucrose we use a substance which penetrates such as ethyl alcohol the flow of water is lessened and this fact makes it possible to measure the amount of alcohol which enters. (An increase in the size of cells placed in solutions of alcohol does not necessarily indicate that the number of mols of alcohol entering is greater than the number of mols of water leaving the cell.) The permeability for water is more than 18 times as great as for ethyl alcohol. The behavior of the 2 substances was compared in the same individual cell with a driving force which at the start was the same for both substances. The number of mols entering per second per cm.(2) of surface with a driving force of 1 atmosphere at 25 degrees C. is 0.772 (10(-6)) for water and 0.042 (10(-6)) for ethyl alcohol. The experiments indicate that the non-aqueous substance at the surface of the protoplasm has a higher partition coefficient for water than for ethyl alcohol, although the protoplasmic surface is composed of materials not miscible with water.

Cytoplasm↗
PubMed1950

Distant effects of toxic agents.

Toxic solutions applied at one end of a Nitella cell 6 cm. long may produce little or no visible change in the structure of the protoplasm at the place of application but if the opposite end is covered with water its protoplasm soon disintegrates. If the middle of the cell is covered with mineral oil this region remains normal in appearance for half an hour or more. The result is due to the movement of substances in the cell. The loss of substances at the end where the toxic agent is applied results in loss at the opposite end if it is covered with water since water enters and travels along inside the cell carrying substances with it. This causes injury at the spot where the water enters. The conception developed here differs fundamentally from the usual view that the effects of injury spread gradually from the region where the toxic agent is applied to the immediately adjoining regions and thence to more remote places. The change produced by loss of substances produces an interesting pattern which deserves study.

Cells↗
PubMed1987

A reappraisal of the caloric requirements of men.

The resting metabolic rates (RMR) of 60 lean and obese men, aged 18-82 y and weighing 60-171 kg, were measured and body compositions were determined. Body compositional variables reflecting active protoplasmic tissue were all highly interrelated. Body weight alone gave prediction values for RMR that were comparable to those of other variables of active protoplasmic tissue mass. Regional distribution of fat had no influence on the RMR and the influence of age on RMR was trivial. The classic prediction equations and tables overestimate RMR of men. The 95%-confidence limits for both lean and obese men were broad. This conclusively demonstrates that metabolic efficiency is not necessarily or exclusively related to obesity. New regression equations for predicting the RMR based on weight and fat-free mass were developed: RMR = 879 + 10.2 WT kg and RMR = 290 + 22.3 FFMD kg, where FFMD is fat-free mass from densitometry measurements.

Adult↗
PubMedDate not supplied

Structural and immunoreactive characteristics of hepatitis B core antigen.

The ultrastructural study of liver tissues from 38 patients with type B viral hepatitis consistently showed the presence of hepatitis B core antigen of 21-25 nm size in the liver cell nuclei and to a lesser extent in the cytoplasm. This finding and the demonstration of the tubular form of hepatitis B surface antigen in the proliferative degranulated endoplasmic reticulum constituted the etiologic criterion for the diagnosis of the disease. The double-shelled Dane-like particles were frequently found in association with the tubular form of the surface antigen. The core particles were found in the protoplasmic processes of hepatocytes and this correlated with the immunofluorescent microscopic findings that the antigen may be shed into circulation with the protoplasm. The core antigen was found to resist digestion by various enzymes such as protease, DNase, RNase, phospholipase C, lipase, lysozyme, diastase, neuraminidase and hyaluronidase, all of which did not destroy the immunoreactivity as demonstrated by immunoelectron and immunofluorescent microscopy. Similarly, sodium dodecyl sulfate, Tween 80 and mercaptoethanol also had no effect. The formalin-fixed paraffin-embedded liver tissue sections could be treated with protease to facilitate the immunofluorescent staining for the core antigen in tissue.

Antibodies, Viral↗
PubMed1968

Rotational streaming in fiber cells and its role in translocation.

All visible protoplasmic streaming in sections of various plant stems was reversibly stopped by 2,4-dinitrophenol (DNP). Sections contained epidermal, cortical, and fiber cell types. Cells treated with DNP retained their semipermeability as evidenced by their plasmolysis in sucrose solutions. Washing out the DNP resulted in the rapid resumption of protoplasmic streaming in all 3 cell types. Both the rate of movement of sodium fluorescein and the shape of the advancing dye front were greatly altered by DNP treatment. Dye transport was decreased in the fibers and little affected in cortical cells. The results suggest that rotational streaming accelerates the translocation of soluble substances in fiber cells.

Journal Article↗
PubMed1988

Hierarchical Response of Light Harvesting Chlorophyll-Proteins in a Light-Sensitive Chlorophyll b-Deficient Mutant of Maize.

The light-sensitive chlorophyll b (Chl b)-deficient oil yellow-yellow green (OY-YG) mutant of maize (Zea mays) grown under conditions of high light exhibits differential reductions in the accumulation of the three major Chl b-containing antenna complexes and characteristic changes in thylakoid architecture. When observed by freeze-fracture electron microscopy, the most notable changes in the OY-YG thylakoid structure are: (a) a major reduction in the number of 8 nanometer particles of the protoplasmic fracture face of stacked membrane regions (PFs) paralleled by a 60% reduction in the chlorophyll-proteins (CP) associated with the peripheral light harvesting complex (LHCII) for photosystem II (PSII) and which give rise to the LHCII oligomer/monomer (CPII(*)/CPII) bands on mildly dissociated green gels; (b) a sizable decrease in the proportion of 11 to 13 nanometer particles of the protoplasmic fracture face of unstacked membrane regions (PFu) that parallels the loss of light harvesting complex I (LHCI) antennae from photosystem I (PSI) centers and a 40% reduction of the band containing CP1 and LHCI (CPI(*)) on mildly dissociating green gels; (c) an unchanged or slightly increased average size of particles of the exoplasmic fracture face of stacked (or appressed) membrane regions (EFs) along with a relative increase in CP29, the postulated bound LHC of PSII, and of CP47 and CP43, PSII core antenna complexes. This latter result sets the OY-YG mutant apart from all other Chl b-deficient mutants studied to date, all of which possess EFs particles that are substantially reduced in size. Based on these findings, we postulate that the bound LHCII associated with EFs particles consists mostly of CP29 chlorophyll proteins and very little, if any, CPII(*)/CPII chlorophyll proteins. Indeed, the CPII(*)/CPII chlorophyll proteins may be exclusively associated with the ;peripheral' LHCII units that give rise to 8 nanometer PF particles. The differential effect of the Chl b deficiency on the accumulation of the three main antenna complexes (CPII(*)/CPII>CPI(*)>CP29) suggests, furthermore, that there is a hierarchy among Chl b-binding proteins, and that this hierarchy might be an integral part of long-term photoregulation mediating Chl b partitioning in the chloroplast.

Journal Article↗
PubMed1986

Particles and pits matched in native membranes.

We have obtained high resolution electron microscopic images of complementary membrane surface replicas of purified microsomal vesicles from pig kidney outer medulla containing Na+,K+-ATPase. Ultra-rapid freezing of a membrane suspension was followed by fracturing and replicating of the liquid helium cooled specimen under ultra-high vacuum conditions free of hydrocarbon contaminants. The protoplasmic fracture faces are populated with intramembrane particles while the external fracture faces reveal complementary pits. This is the first demonstration of extended precise matching of individual intramembrane particles and their corresponding pits in biological membranes containing transmembrane proteins. The data are also consistent with the theory that the majority of Na+,K+-ATPase mass is located at the protoplasmic half of the membrane.

Animals↗
PubMed1991

Perception and response to gravity in higher fungi--a critical appraisal.

Considering that research on gravitropism in higher fungi has a history of over 100 years, the harvest of established fact is disappointingly meagre. We can be reasonably certain of the following. Hymenomycete 'mushroom' fruit bodies (polypore and agaric) exhibit a number of tropisms of which anemotropism, gravitropism, phototropism and thigmotropism have been clearly demonstrated. At any one time one tropism usually predominates but the inferior tropisms can be demonstrated if the predominating ones can be removed by manipulation of the growth conditions. In ascending order, the hierarchy appears to be: thigmotropism, gravitropism, anemotropism, phototropism. During the course of development of a fruit body different tropisms predominate at different times. The youngest fruit body initials grow perpendicularly away from their substratum. The nature of this tropism is completely unknown but perpendicular growth of fruit body initials has been remarked upon in experiments at a variety of light intensities and in gravitational fields from +/- 0 to 4.5 g. The fruit-body primordium then becomes first positively phototropic but later negative gravitropism predominates. The switch between predominance of the two tropisms has been associated with the onset of sporulation in a number of different studies. The major adjustment of the direction of growth in response to a tropic stimulus is made by the mushroom stem. It is the apex of the stem which makes the most immediate gravitropic response. Gravitropic growth curvatures are limited to the normal growth zones of the stem and seem to depend on re-allocation of available growth resources. If the fruit body is reoriented late in the growth of the stem, it may not be able to respond fully. In these cases gravitropic movements of the cap may still be able to bring the hymenophore back to the vertical. Mechanical forces may influence and contribute to the 'gravitropic' response but this has not been experimentally examined. The hymenophore (gill, tube or tooth) is positively gravitropic and responds independently of the stem. Bracket polypores do not show tropisms but exhibit gravimorphogenetic responses such that gross disturbance leads to renewal of growth to produce and entirely new fruiting structure suitably reoriented to the new spatial position. One experiment performed on an orbiting space station suggests that, in the absence of a light stimulus, gravity may be required for initiation of fruiting in Polyporus brumalis. Otherwise, the indications from both clinostat and space-borne experiments are that the basic form of the mushroom (overall tissue arrangement of stem, cap, gills, hymenium, veil) in agaric and polypore alike is established independently of the gravity vector. Abnormal stem growth has been observed in clinostat cultures of Panus (= Lentinus) tigrinus and Polyporus brumalis, but the morphogenetic event which seems most dependent on gravity is sporulation (in the broadest sense). Cultures of P. brumalis on orbiting space craft fail to produce the poroid hymenophore and in clinostat experiments on the ground even karyogamy was rare in similar cultures. Coprinus cinereus grown on the clinostat was able to produce apparently normal fruit body primordia which failed to produce spores and then aborted, forming a new flush of primordia on the old. Taken together with the clear association between observation of gravitropism and the onset of sporulation, the implication is that commitment to the meiosis-sporulation pathway both requires the gravity vector and couples it in some way to fruit-body growth. There is no convincing evidence for a graviperception mechanism in fungi. There is no evidence for any organised means of communicating the gravitropic stimulus once it has been perceived. Reports of three different experimental studies reveal the authors' conviction that the apparently coordinated expression of gravitropic response is in truth a common, but independent, response by the individual component hyphae of the structure concerned. There is some evidence that in the negatively gravitropic Phycomyces sporangiophore the vacuole floats in the protoplasm. If this is generally true it could affect protoplasmic volumes above and below the vacuole such that a greater proportion of the cell's potential for wall growth was adjacent to the lower wall. This is not only an attractive way of accounting for asymmetric wall growth, but since the relative density of the vacuole can presumably be controlled by regulation of water influx and efflux, it is also an attractive means of accounting for the control of gravitropic responses. Phycomyces also exhibits a response to the mechanical consequences of reorientation which is additional to (and different from) the longer term gravitropic response. [TRUNCATED]

Basidiomycota↗
PubMed1989

Spontaneous glutamate release by a "fibrous"-like cerebellar astroglial cell clone.

To investigate the role of astrocytes in the metabolism of glutamate, the neurotransmitter of the granule cells of the cerebellar cortex, we have analyzed various parameters related to the synthesis of glutamate in astroglial cell clones that may be the in vitro counterparts of the cerebellar astrocytes. The "fibrous"-like clone spontaneously released large quantities of glutamate, even in the absence of glutamine in the culture medium, but did not release alanine. In contrast, the "Golgi-Bergmann"-like cells released alanine but not glutamate, whereas the "velate-protoplasmic"-like astrocytes released little glutamate and alanine. However, the glutamate oxaloacetate transaminase and glutamate pyruvate transaminase activities of the three astroglial cell lines, measured in the direction of glutamate synthesis, were comparable. In addition, the "velate protoplasmic" and "Golgi-Bergmann" clones did not consume glutamine present at 2 mM in the culture medium. These data suggest that the different types of in vivo cerebellar astrocytes may have distinct roles regarding glutamate-glutamine metabolism.

Alanine↗
PubMed1984

Multiple fission in Allogromia sp., strain NF (Foraminiferida): release, dispersal, and ultrastructure of offspring.

The release, dispersal, and ultrastructure of juveniles arising through multiple fission in the benthic foraminiferan Allogromia sp., strain NF (Lee & Pierce, 1963) has been examined by light and electron microscopy. An extensive reticulopodial network participates in the dispersal of fully differentiated young as they emerge from the fragmented parental test. During the earliest stages of release, offspring are of two classes--aroused and unaroused. Unaroused juveniles, which have not extended pseudopods, attach externally to the network and are transported bidirectionally along its surface. Aroused juveniles, which have extended pseudopods and are in protoplasmic continuity with the network, move quickly to the periphery of the network. Within 24 h, juveniles establish a communal "feeding reticulum" in which dispersed individuals are in protoplasmic continuity with neighbors via a common reticulopodial network. At the ultrastructural level, the cell body cytoplasm of unaroused juveniles contains numerous patches of a paracrystalline material, which disappears as their pseudopodia are extended to join the communal feeding reticulum. This paracrystalline material therefore appears to be a temporary reservoir of precursors required for pseudopod construction.

Animals↗