Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PROTOPLASM”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed1988

Gene amplification in malignant human gliomas: clinical and histopathologic aspects.

Gene amplification occurs in 45-50% of malignant human gliomas (MHG). In the present study, 64 genetically characterized gliomas were evaluated to determine if tumors with amplification of the epidermal growth factor receptor (EGFR), N-myc, c-myc, or gli genes had distinctive histopathologic features. There was no significant difference in age (p = 0.10) or gender (p = 0.78) between patients whose tumors contained amplified genes and those whose tumors did not exhibit this characteristic. Although the patients with amplified genes in their tumors survived slightly longer than patients whose tumors had no detectable gene amplification, these differences were not statistically significant (p = 0.21). The 28 tumors with amplification included 24/48 (50%) glioblastoma multiforme, 2/6 (33%) anaplastic astrocytomas and 2/5 (40%) gliosarcomas. No amplification was seen in one oligodendroglioma, three anaplastic mixed gliomas or one giant cell glioblastoma multiforme. Necrosis and endothelial proliferation were equally prevalent among tumors with and without amplification. Comparison of tumors with gene amplification and tumors without this characteristic revealed similar distributions of most morphologic cells types. Although prominent perivascular lymphocytic infiltrates were more frequent in tumors without amplification, this association was of borderline significance statistically. In situ hybridization of tumors with amplification using an EGFR mRNA probe showed intense labeling of different neoplastic cell types including fibrillary and protoplasmic astrocytes, gemistocytes, anaplastic cells, and multinucleated giant cells. Non-neoplastic cells such as hyperplastic endothelium within the tumors did not express detectable EGFR mRNA. These studies demonstrate that (a) cells with quite different morphology within the same tumor can contain the same genetic alteration; (b) tumors of identical histological appearance may have arisen and evolved by different molecular mechanisms; and (c) molecular analyses are necessary to evaluate gene amplification in MHG since this characteristic cannot be accurately predicted by the morphologic or clinical criteria used in this study.

Adult↗
PubMed1996

A monoclonal antibody that specifically recognizes a novel mitochondrial protein of human astrocytes.

We established a monoclonal antibody to human astrocytes using a human glial cell-rich fraction as the immunogen. The antibody, named PRAS-4, specifically labeled populations of astrocytes in a fine granular manner immunohistochemically. In formalin-fixed, paraffin-embedded tissue sections, PRAS-4-positive astrocytes were extensively distributed in the gray matter of the central nervous system, namely the cerebral cortex, basal ganglia, diencephalon, midbrain, various nuclei of the brain stem, cerebellar cortex and nuclei, and spinal cord. In the white matter, a few positive astrocytes were located mostly in the perivascular area. The reaction was lost after protease digestion and it resisted periodic acid, suggesting that the epitope is of a protein. The molecular weight of the antigen was estimated as 62 kDa. Ultrastructurally, the immunoreaction was localized on the outer and inner membranes of astrocytic mitochondria, and unlabeled mitochondria coexisted in the same cells. Extra-mitochondrial regions were not stained. PRAS-4 preferentially labeled astrocytes of the protoplasmic type, and may be applicable to studies on the development, specific functions and neoplasms of astrocytes.

Adult↗
PubMed1997

An immunohistochemical study of radial glial cells in the mouse brain prenatally exposed to gamma-irradiation.

The features of a glial cell population in the developing brain of mice prenatally exposed to 60Co gamma-irradiation at the most radiosensitive stage were studied with immunohistochemistry for anti-midkine (MK), anti-vimentin (Vim), and anti-GFAP antibodies. Anti-MK- and anti-Vim-positive radial glial fibers distributed in a similar radial fashion; these fibers were observed primarily in the embryonic period and disappeared after birth. Anti-MK- and anti-Vim-stained radial fibers ran perpendicular to the pial surface in controls, whereas such fibers were disorganized 6 hours (h) after irradiation. This finding provided new evidence that the migratory pathways of young neurons were interrupted beginning a few hours after irradiation. By E17 the ectopic cell masses formed so as to replace the parts of the ventricular zone where no anti-MK immunoreactive radial fibers were present, but where anti-GFAP-stained fibrillary astrocytes emerged in the ectopic cell masses from the early postnatal period. The results suggested a twofold source of the generated astrocytes: either directly from a separate precursor of the astrocytes, or due to the transformation of the classic radial glial cells. In the newborn, numerous protoplasmic transitional forms displaced by astrocytes in irradiated brains indicated that reactive gliosis was a powerful response of a brain exposed to irradiation.

Animals↗
PubMed1979

Possible evolutionary significance of spirochaetes.

Large symbiotic spirochaetes of the family Pillotaceae (e.g. pillotinas) are found in dry wood and subterranean termites (Hollande & Garagozlou 1967). These morphologically distinctive spirochaetes comprise several genera. Some of them contain microtubules within their protoplasmic cylinders. They demonstrate a variety of relations with their termite and protist hosts. Some are free-living within the lumen of the intestine, some tend to be associated with filamentous and other bacteria, some are found regularly coursing between the numerous undulipodia ( = eukaryotic flagella, cilia, and other (9 + 2) organelles of motility) of hypermastigotes and polymastigotes. Still other smaller termite spirochaetes are regularly attached to protists via specialized attachment sites. Some even form motility symbiosis with their host protists. The analogy between the behaviour of host-associated spirochaetes and the possible steps in the origin of the undulipodia and mitotic system of eukaryotes is discussed briefly.

Biological Evolution↗
PubMed1996

Helicobacter trogontum sp. nov., isolated from the rat intestine.

A new Helicobacter species that colonizes the colonic mucosa of Wistar and Holtzman rats was isolated and characterized. This bacterium was gram negative, its cells were rod shaped with pointed ends, and its protoplasmic cylinder was entwined with periplasmic fibers. It was catalase and oxidase positive, rapidly hydrolyzed urea, and was susceptible to metronidazole and resistant to cephalothin and nalidixic acid. The new organism was microaerophilic and grew at 42 degrees C, a feature that differentiates it from two other murine intestine colonizers, Helicobacter hepaticus and Helicobacter muridarum. On the basis of 16S rRNA sequence analysis data, the new organism was identified as a Helicobacter species that is most closely related to H. hepaticus. This bacterium is named Helicobacter trogontum. The type strain is strain LRB 8581 (= ATCC 700114).

Animals↗
PubMed1980

Ultrastructural changes in Escherichia coli grown in divalent cation-deficient medium.

Escherichia coli strains B and K12 could grow in very limiting conditions of divalent cation deficiency. Growth curves showed a long lag period of about 30 h, followed by an exponential phase bringing the bacterial concentration to about 10(7) ml-1, with a 24 min doubling time, while the growth curves of control cultures were characterized by short lag periods, maximum populations of about 10(9) ml-1 and an 18 min doubling time. The DNA/protein ratio in bacteria grown in deficient medium was 0.48 compared with 0.21 for control bacteria. Significant differences were found in the ultrastructure of the two types of bacteria. Freeze-etched control cells showed the typical appearance with the protoplasmic fracture face of the cytoplasmic membrane (PFC) having a random distribution of intramembranous particles. Bacteria growing in deficient medium in exponential phase presented several particle-free areas on the PFC. At the beginning of the stationary phase, the particle-free zones became larger and crystalline structures were formed. These structural modifications, which increased with culture age, were never observed in bacteria grown in control medium. Optical diffraction analysis of the crystalline structures in freeze-etched cells revealed regular periodic arrays with a rhomboid repeating unit approximately 7.6 x 5.4 nm in dimension and an angle between the axes of about 73 degrees. Negative staining of isolated membranes of bacteria grown in deficient medium showed a more complex organization of the crystalline arrays, each unit being clearly composed of subunits.

Calcium↗
PubMed1982

Ultrastructure of the cell envelope layers and surface details of Legionella pneumophila.

Ten strains representing six serogroups of Legionella pneumophila were examined by electron microscopy using freeze-etching, thin-sectioning and negative-staining techniques. In addition, selected strains were examined further as shadowed and freeze-dried preparations and by scanning electron microscopy. The cell envelope consisted of two membranes, evident in fractured specimens as four short ridges. The major fracture plane was through the inner membrane, and therefore the protoplasmic and extracellular fracture faces of this membrane were predominant. With the exception of one strain (Togus 1), the particle arrangement on these fracture faces was random. A peptidoglycan-like cell wall layer was revealed only in sections of partially plasmolysed cells. Membrane-bounded poly-beta-hydroxybutyrate-like granules were evident in the cytoplasm and these frequently showed plastic deformation due to fracturing. Although appendages were present, the surfaces of organisms and of isolated cell membranes showed no regular arrays of particles.

Cell Wall↗
PubMed1988

Colicin K decreases the density of intramembrane particles (IMP) in the cell membrane of Escherichia coli.

Toxic effects of both main colicin types, i.e. of porin and nuclease types, involve the direct contact of their molecules with the plasma membrane of sensitive cells. In the present study, it was tested whether this contact provokes a lateral or vertical movement of intramembrane protein particles (IMP) or a direct cleavage of the proteins. IMP were visualized by freeze-fracturing and electron microscopy on the protoplasmic fracture face (PF) of colicin-treated cells of Escherichia coli. Possible changes in distribution and in density of IMP due to treatment with colicins E1-E7 and K were followed. As a control, the bacteria were equilibrated at 0 degrees C before quenching, which caused a reversible formation of smooth areas and a decrease in the mean density of IMP on the PF. Colicins E1-E7 had no clear-cut effect on the disposition of IMP. Only colicin K decreased the IMP density, by 10% in E. coli strain 58-161 and by 17% in strain C6; the distribution of IMP remained homogeneous. Trypsin reactivation of colicin-K-inactivated bacteria was not reflected by restoration of the original density of IMP; on the contrary, it led to a further decrease, of 1-13%, in IMP density, presumably by proteolytic cleavage. Varying densities of IMP in different strains of the same bacterial species (under standard conditions) were confirmed.

Cell Membrane↗
PubMed1975

Ultrastructure of an extremely thermophilic acidophilic micro-organism.

A thermoacidophilic micro-organism, isolated from volcanic hot springs near Naples, was cultivated in vitro, and examined by electron microscopy in sections and after negative staining. The cells were almost spherical, with a diameter of about 0.7 to 1.0 mum. Their morphology was very primitive: the protoplasm was composed only of ground cytoplasm, ribosomes, and randomly distributed DNA strands. They were surrounded by a plasma membrane and by an extracellular coat about 20 nm thick which displayed a regular hexagonal pattern. Cell replication occurred by binary fission with median constriction during which a bipolar localization of nuclear material was observable. The morphology is compared with that of other known micro-organisms living in similar habitats.

Bacteria↗
PubMed1976

The cytotoxic action of leucocidan from Pseudomonas aeruginosa on human polymorphonuclear leucocytes.

Human polymorphonuclear leucocytes treated in vitro with leucocidin from Pseudomonas aeruginosa underwent characteristic morphological alterations as shown by phase-contrast and scanning electron microscopy. Within a few minutes of exposure to leucocidin the granulocytes became round, and protoplasmic extrusions appeared on the cell membrane, were withdrawn again and put out at another point of the cell. The final stage of the leucocidin-treated leucocyte was an enlarged, rounded vesicle with apparently intact plasma membrane. Omission of calcium ions from the diluting buffer caused certain differences in the morphologic appearance of the damaged leucocytes.

Calcium↗
PubMed1980

Ammonia production by intestinal bacteria: the effects of lactose, lactulose and glucose.

Ammonia production by eight groups of intestinal bacteria was measured, and the effect on ammonia production of lowered pH and ambient ammonia concentration was determined. Endogenous ammonia production from bacterial protoplasm was also examined. To examine the mechanisms by which fermentable substrates reduce ammonia formation in a faecal incubation system, the effect of lactose, lactulose or glucose on ammonia release by pure cultures of intestinal bacteria was studied. The largest amounts of ammonia were generated by gram-negative anaerobes, clostridia, enterobacteria, and Bacillus spp. Gram-positive non-sporing anaerobes, streptococci and micrococci formed modest amounts, and lactobacilli and yeasts formed very little ammonia. All groups of bacteria formed less ammonia at pH 5.0 than at pH 7.0 and production of ammonia was not inhibited when 30 mmol ammonia/litre was included in the medium. Small amounts of ammonia were formed due to endogenous metabolism of bacterial cells. Washed cell suspensions of four isolates of Bacteroides, one clostridial isolate and two streptococcal isolates formed less ammonia from alanine, methionine or histidine after growth in the presence of either lactose or lactulose. In contrast, the Bacteroides isolates formed more ammonia from aspartate than from either lactose or lactulose. Also, cultures of gram-negative anaerobes and enterobacteria, and to a lesser extent clostridia and streptococci, formed significantly less ammonia in nutrient broth when lactose, lactulose or glucose was included in the medium. This decrease in ammonia formation was not due to a fall in pH of the medium. Ammonia production by gram-positive non-sporing anaerobes was not affected by carbohydrate fermentation. These results suggest that gram-negative anaerobic bacteria make a major contribution to ammonia generated from peptides and amino acids in vivo, and that ammonia may be formed from bacterial cells in the colon. Fermentation of lactose and lactulose may repress the formation and inhibit the activity of enzymes responsible for ammonia release. In the human colon these substrate effects may decrease the amount of ammonia available to exert a toxic effect on the host, and thus contribute to the beneficial effects of lactulose when it is used in the treatment of portosystemic encephalopathy.

Amino Acids↗
PubMed1993

Ultrastructural Evidence That Intracellular Ice Formation and Possibly Cavitation Are the Sources of Freezing Injury in Supercooling Wood Tissue of Cornus florida L.

Although cellular injury in some woody plants has been correlated with freezing of supercooled water, there is no direct evidence that intracellular ice formation is responsible for the injury. In this study we tested the hypothesis that injury to xylem ray parenchyma cells in supercooling tissues is caused by intracellular ice formation. The ultrastructure of freezing-stress response in xylem ray parenchyma cells of flowering dogwood (Cornus florida L.) was determined in tissue prepared by freeze substitution. Wood tissue was collected in the winter, spring, and summer of 1992. Specimens were cooled from 0 to -60[deg]C at a rate of 5[deg]C h-1. Freezing stress did not affect the structural organization of wood tissue, but xylem ray parenchyma cells suffered severe injury in the form of intracellular ice crystals. The temperatures at which the ice crystals were first observed depended on the season in which the tissue was collected. Intracellular ice formation was observed at -20, -10, and -5[deg]C in winter, spring, and summer, respectively. Another type of freezing injury was manifested by fragmented protoplasm with indistinguishable plasma membranes and damaged cell ultrastructure but no evidence of intracellular ice. Intracellular cavitation may be a source of freezing injury in xylem ray parenchyma cells of flowering dogwood.

Journal Article↗
PubMed1998

Benzothiadiazole-mediated induced resistance to fusarium oxysporum f. sp. radicis-lycopersici in tomato

Benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a synthetic chemical, was applied as a foliar spray to tomato (Lycopersicon esculentum) plants and evaluated for its potential to confer increased resistance against the soil-borne pathogen Fusarium oxysporum f. sp. radicis-lycopersici (FORL). In nontreated tomato plants all root tissues were massively colonized by FORL hyphae. Pathogen ingress toward the vascular stele was accompanied by severe host cell alterations, including cell wall breakdown. In BTH-treated plants striking differences in the rate and extent of fungal colonization were observed. Pathogen growth was restricted to the epidermis and the outer cortex, and fungal ingress was apparently halted by the formation of callose-enriched wall appositions at sites of fungal penetration. In addition, aggregated deposits, which frequently established close contact with the invading hyphae, accumulated in densely colonized epidermal cells and filled most intercellular spaces. Upon incubation of sections with gold-complexed laccase for localization of phenolic-like compounds, a slight deposition of gold particles was observed over both the host cell walls and the wall appositions. Labeling was also detected over the walls of fungal cells showing signs of obvious alteration ranging from cytoplasm disorganization to protoplasm retraction. We provide evidence that foliar applications of BTH sensitize susceptible tomato plants to react more rapidly and more efficiently to FORL attack through the formation of protective layers at sites of potential fungal entry.

Journal Article↗
PubMed1966

Matric potential of several plant tissues and biocolloids.

The pressure membrane apparatus was used to study the matric potential (imbibition pressure or moisture tension) of plant tissues and of several organic colloidal preparations.The moisture release curves of aqueous 2% agar, 12% gelatin, and filter paper were smooth parabolic curves between matric potentials of -0.1 and -15 bars. When logarithms of the matric potentials were plotted against logarithms of the moisture content, the data yielded straight lines for agar and filter paper.Slices of fresh tissue lost little water after 2 days in the apparatus at maximum pressure of 15 bars. Osmotic forces in conjunction with cell membranes are able to retain moisture against pressure of this magnitude. After the cells were disrupted by freezing and thawing, up to 90% of the original moisture was removed by a 15 bar pressure, with lesser amounts removed at lower pressures. The results gave a parabolic relationship, and straight lines could be fitted to log-log plots of data from potato tuber and young asparagus stem slices. Sections from the tips of asparagus stems held less moisture at all matric potentials than more basal sections.The method permits the study of the matric potential of tissues independently of the osmotic potential. As measured, however, the matric potential is a composite of matric potentials of colloidal substances in the protoplasm and cell walls after disruption of cells by freezing and mixing of the contents. The value is therefore only an approximation of the matric potentials occurring in the living tissues.

Journal Article↗
PubMed1967

Translocation of Sugars in Cucurbita melopepo IV. Effects of Temperature Change.

A study has been made of the temperature control of translocation localized to regions of the stem, petiole and hypocotyl of Cucurbita melopepo. The basipetal and acropetal movement of translocated (14)C-labeled compounds in the phloem tissue, measured over a 45-minute period, was almost completely inhibited at 0 degrees . At 10 degrees a partial inhibition occurred while an extremely variable degree of inhibition occurred at 15 degrees . Above 15 degrees to 35 degrees temperature ceased to be a limiting factor in the movement of (14)C-labeled compounds. At 45 degrees partial inhibition was observed while at 55 degrees there was an almost complete cessation. The localized temperature treatment of the plant parts did not disturb the rate of (14)CO(2) assimilation or the export of (14)C compounds by the leaf blade. Translocated compounds unable to pass a temperature inhibited zone were diverted toward other importing regions of the plant. The similarity of the translocation response to temperature change in the various organs of the plant indicated a uniform mechanism throughout the plant controlling movement of the major proportion of the translocated compounds. The temperature characteristics of the mechanism were found to closely parallel those of protoplasmic streaming in chill-sensitive plants.

Journal Article↗
PubMed1967

Structure and function of tomato leaf chloroplasts during ammonium toxicity.

Ammonium toxicity resulted in morphological modifications of tomato leaf chloroplasts. The chloroplasts, which are normally flattened around the protoplast periphery, became ellipsoidally rounded and dispersed through the protoplasm. The first apparent effect of plastid degradation was development of many vesicles from the fretwork. Later the grana lamellae swelled, and some disappeared. Eventually, distinct grana could not be detected.Ammonium accumulation, chlorophyll loss, and photosynthetic decrease occurred simultaneously. Initial changes in these processes preceded the detection of modifications of fine structure; however, each continued with further breakdown of the chloroplasts.

Journal Article↗
PubMed1968

Effect of the Specific Toxin in Helminthosporium victoriae on Host Cell Membranes.

Helminthosporium victoriae toxin, which affects only hosts of the toxin-producing fungus, causes loss of electrolytes from roots, leaves, and coleoptiles of treated plants. Root hair cells lost the ability to plasmolyze after 20 minutes exposure to toxin in solution; comparable resistant cells retained plasmolytic ability during 3 hours exposure. Toxin stopped uptake of exogenous amino acids and Pi by susceptible but not by resistant tissue. Incorporation of (32)P into organic-P and (14)C-amino acids into protein was blocked in susceptible but not in resistant tissue. Apparent free space increased in susceptible but not in resistant roots. The increase was evident within 30 minutes, and reached 80% free space after 2 hours exposure to toxin. When cell wall-free protoplasts were exposed to 0.16 mug toxin/ml, protoplasmic streaming stopped and all plasma membranes of susceptible protoplasts broke within 1 hour. Resistant protoplasts were not affected significantly. Data support the hypothesis of a primary lesion of toxin in the plasma membrane. Effects on synthesis could result from lack of transport of exogenous solutes to sites of synthesis. It is possible that all other observed effects of toxin are secondary to membrane damage.

Journal Article↗
PubMed1969

Local metabolic autonomy in phycomyces sporangiophores.

The degree of dependence of the growing zone of the Phycomyces sporangiophore upon other parts of the stalk was tested by inhibiting glycolysis and oxidative phosphorylation in the stalk below the growing zone. Initially the growing zone is capable of nearly normal growth when the metabolism in the rest of the stalk is inhibited in this way. However, the growing zone appears to become depleted of something normally supplied from below, because after 3 to 4 hr its growth rate slows down and the growth stops much sooner than in normal sporangiophores. The rest of the sporangiophore appears to have a similar degree of local autonomy because isolated sections from below the growing zone can support protoplasmic streaming for 10 to 20 hr.

Journal Article↗