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.

SourceResearch connectionFrom yearThrough year

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

At least 55 records · Page 3Linked to original sources

PubMed1959

Protoplasmic streaming of an internodal cell of Nitella flexilis; its correlation with electric stimulus.

The sudden cessation or sudden decrease in velocity of the protoplasmic streaming of Nitella flexilis is observed whenever an action potential is elicited. The action potential can be generated by an electric stimulus after its refractory period, whether the flow is at a complete standstill or on the way to recovery. The membrane potential is generally decreased more or less when the rate of flow is decreased on application of salts or other agents. There is, however, no parallelism between these two. The membrane potential decreases proportionally with applied voltage of subthreshold intensity, while the rate of flow does not change appreciably. Only on application of a superthreshold voltage does the flow stop suddenly. In one case the rate of flow decreased to half without appreciable decrease in membrane potential. In another case it continued flowing at about one-half rate, although the membrane potential was almost zero. The Q(10) of the rate of flow is about 2, while it is 1.1 to 1.5 for the membrane potential. The sudden cessation of the protoplasmic streaming is supposed to be caused by the temporary formation of certain interlinkages among contractile protein networks in the endoplasm during excitation at the cathodal half of Nitella.

Action Potentials↗

PubMed2003

Evidence for astrocyte heterogeneity: a distinct subpopulation of protoplasmic-like glial cells is detected in transgenic mice expressing Lmo1-lacZ.

The adult mammalian central nervous system (CNS) contains a large number of different cell types, which arise from the ventricular (VZ) and subventricular zones during embryonic development. In this study, we used a transgenic mouse expressing Lmo1-LacZ from a randomly inserted promoter/reporter gene construct to identify a glial subpopulation. LMO1 is an LIM domain-containing protein, thought to act in protein-protein interactions. We found first that in the adult transgenic CNS, beta-galactosidase (beta-gal) was expressed in a specific subpopulation of protoplasmic-like cells, which did not express detectable levels of glial fibrilary acidic protein unless a lesion was produced. Secondly, during development, beta-gal(+) cells were found arising from discrete regions of the VZ. Taken together, these results identify a subpopulation of protoplasmic glial cells in the adult CNS and suggest that they arise from a restricted VZ region during CNS development.

Animals↗

PubMed1976

Electrical responses of isolated Nitella protoplasm--excitations or artifacts?

Isolated protoplasmic droplets of the alga Nitella were investigated with microelectrodes under current clamp conditions. The following observations were made: 1. Long pulses of either polarity yielded almost symmetric current-voltage relations. Near the rather small resting potential (inside negative) the measuring points lay on a straight line corresponding to an apparent surface membrane resistance of 1.7 +/- 0.45 komega (mean +/- S.E.M., n=5). 2. Experiments with various pulse programs revealed no mechanism comparable to Na inactivation but stressed the electrical symmetry of the droplet with respect to the resting potential. 3. Changes of the [Ca2+] in the bathing medium between 0 to 10 mM as well as of the pH between 5 and 9 did not influence the responses. Replacing K+ by Na+ (or vice versa) or exchanging NO3 for acetylglycine or Cl- was also ineffective. These observations are not consistent with a normal excitable surface membrane. Similar responses are obtained with a RC network which is described and which may have its substrate in histological peculiarities of the protoplasmic droplet.

Action Potentials↗

PubMed1990

Preferential histochemical staining of protoplasmic and fibrous astrocytes in rat CNS with GFAP antibodies using different fixatives.

Serial sections of rat brain and spinal cord were fixed in either acid-alcohol or 4% paraformaldehyde, and stained for visualization of astrocytes using GFAP antibodies. With paraformaldehyde, GFAP-positive astrocytes were visualised almost exclusively in the grey matter of all above tissues. In sharp contrast, acid-alcohol treatment gave intensely stained GFAP-containing astrocytes in the white matter. Since fibrous astrocytes are mainly located in the white matter and protoplasmic astrocytes are located in the grey matter, it is concluded that acid-alcohol is a good fixative for fibrous astrocytes while paraformaldehyde is a better fixative for protoplasmic astrocytes.

Animals↗

PubMed1994

Fibrous and protoplasmic astrocytes express GABAA receptors that differ in benzodiazepine pharmacology.

Astrocytes cultured from spinal cord contain two morphologically distinguishable types of astrocytes: fibrous and protoplasmic cells. Both astrocyte subtypes, in culture, are able to express GABAA receptors, and their activation results in inward currents at the resting potential. Using patch-clamp electrophysiology we characterized their basic receptor pharmacology and compared it to spinal cord neurons that were also present in small numbers in these cultures. As in neuronal GABAA receptors, the local anesthetic pentobarbital effectively potentiated GABA-induced currents in both astrocyte subtypes. Similarly, the benzodiazepine diazepam, on average doubled GABA-induced currents in both astrocytes subtypes. In contrast to these effects that were similar in both astrocytes types and similar to spinal cord neurons, the response to the convulsant methyl-4-ethyl-6,7-dimethoxy-beta-carboline-3-carboxylate (DMCM), which is an inverse benzodiazepine agonist differs between astrocyte subtypes. DMCM reduced GABA-induced currents by about 50% in fibrous astrocytes as we also observed with spinal cord neurons. In contrast, DMCM increased GABA currents in protoplasmic astrocytes by up to 150%, an effect never observed in neurons. DMCM potentiations of GABA currents have recently been attributed to differences in receptor subunit composition. Our results thus indicate that subtypes of astrocytes express GABAA receptors that differ pharmacologically and likely differ also in subunit composition.

Animals↗

PubMed1985

Dynamic property of membrane formation in a protoplasmic droplet of Nitella.

A theory is presented to explain the dynamic characteristics of an electric potential and the resistance of a surface membrane during the formation of a protoplasmic droplet isolated from Nitella. Basic equations are coupled ones for describing ion concentrations near the surface of the droplet, active and passive ion fluxes on the surface, and kinetics of membrane-constituting molecules diffusing from the inside of the protoplasm. The present results give a good explanation of the observed kinetics of electric properties throughout the formative process of surface membranes after the ion concentrations are replaced by lower ones. The results can also explain well the observed data on the steady state. Oscillatory changes in the membrane potential induced by ions strongly adsorbed on the surface membrane are discussed in relation to growth and regeneration phenomena in biological systems such as bean roots and Acetabularia.

Journal Article↗

PubMed1978

Oscillating contractions in protoplasmic strands of Physarum: infared reflexion as a non-invasive registration technique.

An inexpensive electronic device employing a miniaturised infrared reflection detector is described which enables the automatic registration of intrinsic radial contraction activities of protoplasmic strands of Physarum growing on their original substrate. Advantages and shortcoming of the new registration technique are discussed in relation to recent tensiometric techniques applied to protoplasmic strands for analysing the contraction physiology of cytoplasmic actomyosins, the force generating substrate of the contraction automaticity in the Physarum system.

Cytoplasm↗

PubMed2000

Expression of gamma-glutamyl transpeptidase in mouse perivascular astrocytes and in a protoplasmic-like astroglial cell clone.

Gamma-glutamyl transpeptidase (GGT) is known to be present in the central nervous system (CNS) but its cellular localization is still subject to controversy. In this report, we have investigated, with a specific antiserum, the immunolabelling pattern of GGT in the adult mouse CNS at the light and electron microscopic (EM) levels. At the optical level, GGT immunoreactivity ensheathes the majority of vessels in the grey matter. Immunoelectron microscopy shows that labelling is essentially due to the presence of GGT in the astrocytic endfeet which surround vessels. In addition, some pericytes and periendothelial cells are also clearly labelled. We then investigated GGT activity in astroglial cell clones which may represent the in vitro counterpart of the main astroglial cell types. The striking result is that a protoplasmic-like astroglial cell clone shows a noticeable GGT activity, while, in contrast, no activity was detected in the fibrous and the Golgi-Bergmann-like astroglial clones. Taken together, these data indicate that, in the mouse CNS, GGT is essentially present in protoplasmic astrocytes.

Animals↗

PubMed1986

Protoplasmic Swelling as a Symptom of Freezing Injury in Onion Bulb Cells : Its Simulation in Extracellular KCl and Prevention by Calcium.

Freezing injury, in onion bulb tissue, is known to cause enhanced K(+) efflux accompanied by a small but significant loss of Ca(2+) following incipient freezing injury and swelling of protoplasm during the postthaw secondary injury. The protoplasmic swelling of the cell is thought to be caused by the passive influx of extracellular K(+) into the cell followed by water uptake. Using outer epidermal layer of unfrozen onion bulb scales (Allium cepa L. cv Big Red), we were able to stimulate the irreversible freezing injury symptoms, by bathing epidermal cells in 50 millimolar KCl. These symptoms were prevented by adding 20 millimolar CaCl(2) to the extracellular KCl solution. Our results provide evidence that loss of cellular Ca(2+) plays an important role in the initiation and the progression of freezing injury.

Journal Article↗

PubMed1987

Voltage-Dependent K-Channel in Protoplasmic Droplets of Chara corallina: A Single Channel Patch Clamp Study.

Passive transport of potassium through the plasma membrane of a protoplasmic droplet isolated from large internodal cells of Chara corallina Klein ex Willd., em, R.D.W. has been investigated using the patchclamp technique. When the membrane is hyperpolarized the conductance of a single K(+)-channel is of the order of magnitude of 100 picoSiemens and is reduced by tetraethylammonium chloride. Its open time is voltage dependent. This voltage-dependent K(+)-channel displays rectifying properties. The channel density is about 0.1 channel per square micrometer of membrane. When the membrane is depolarized the conductance of a single channel is of the order of magnitude of 30 picoSiemens and is insensitive to tetraethylammonium chloride. These results suggest that K(+)-channels are incorporated in the plasma membrane during membranogenesis of a protoplasmic droplet. They constitute further evidence for the existence of voltage-dependent K(+)-channels in plant cells.

Journal Article↗

PubMed1984

Isolation of protoplasmic astrocytes: a procedure based on controlled trypsin digestion.

Trypsinization of rat brain tissue for shorter (10 min) and longer (60-90 min) periods is shown to yield two distinctly different types of dissociated cell populations. The over-all yield of intact dissociated cells declines when the period of trypsinization exceeds 10 min. Comparison of the types of dissociated cells obtained after different lengths of trypsinization indicates that the protoplasmic astrocytes, which represent the bulk of the neuroglial cells in brain, are highly susceptible to degradation during tissue trypsinization. Based on this observation, a new procedure involving controlled trypsin digestion for tissue disruption and Percoll gradient centrifugation has been developed for the isolation of virtually pure populations of intact protoplasmic astrocytes (97-98% particle purity). Identification of the purified cells is based on morphological, histochemical staining, and biochemical (marker enzyme) characteristics.

Animals↗

PubMed1975

Effect of isoniazid on the protoplasmic viscosity in Mycobacterium tuberculosis.

The effect of isoniazid on the protoplasmic viscosity in the H37Ra strain of Mycobacterium tuberculosis was determined by using electron spin resonance spectroscopy and a small spin label tempone (2,2,6,6-tetramethylpiperidone-N-oxyl radical). Isoniazid (0.5 mug/ml) caused the internal cellular viscosity to increase gradually over the first 15 h of exposure from a rotational correlation time value (T(c)) of 2.4 x 10(-10) to 3.4 x 10(10) s and then decrease linearly to the control level after 27 h. These results could be interpreted to mean that isoniazid allows a continued and normal synthesis of the protoplasmic components while the rate of increase in the cell volume is reduced. A degradative process may begin after the initial 15-h exposure time, which would cause the reduction in the internal viscosity.

Cytoplasm↗

PubMed1969

Antigens of Neisseria gonorrhoeae: characterization by gel filtration, complement fixation, and agar-gel diffusion of antigens of gonococcal protoplasm.

With the use of the agar-gel-diffusion and complement-fixation techniques, it was shown that protoplasm from different gonococcal isolates reacted with sera from some humans with a history of gonorrhea but did not react with "normal" human sera. The reactive antigen(s) could be partially separated from the other antigens by passing the gonococcal protoplasm through Sephadex G-200. The antigen(s) reacting in the gel-diffusion and complement-fixation tests appeared in the same fraction. On the basis of Sephadex gel filtration, the molecular weight of this antigen(s) is probably greater than 200,000.

Animals↗

PubMed1987

[Migration of protoplasmic droplets and phagocytosis of damaged sperm during their passage through the efferent ducts in boars and bulls].

Seventeen gonad pairs of boars and ten gonad pairs of bulls were examined to evaluate the migration of protoplasmic droplets and the phagocytosis of defective spermatozoa. The material for a microscopic investigation of secretions was collected from two sites in the testis and from seven sites in the epididymis. The greatest motion of protoplasmic droplets was recorded in the caput epididymidis, although the migration of droplets from the proximal section of the connective part of the flagellum towards the distal parts could also be observed as far as in the cauda epididymidis in both animals. A proximally located droplet still occurred in the cauda epididymidis in 4.5% of the spermatozoa of boars and in 1.9% of those of bulls. Absent mitochondrial spirals or swollen connective parts were observed in the imprints of testicular tissue in almost 50% of the spermatozoa whereas in the secretion of efferent ducts they were observed only in 0.3% of bull spermatozoa and about 3% of boar spermatozoa. No such defects were recorded in the epididymis head and tail in either of the two species. The marked reduction in the number of defective spermatozoa without mitochondrial spirals in the secretion of efferent ducts and after passage through the caput epididymidis testifies to the phagocytic ability of the epithelium of this part of efferent ducts.

Animals↗

PubMed1972

Division of protoplasmic astrocytes in acute experimental hepatic encephalopathy. An electron microscopic study.

The ultrastructural features of dividing protoplasmic astrocytes, induced by the production of hepatic encephalopathy, are described. True cellular hyperplasia, as manifested by cytokinesis at the site of paired nuclei, was demonstrated. The cytoplasm contained structural elements suggesting that cell division occurs by a highly organized process. Some of the observations were similar to those found in mitotic division in other types of cells, raising the possibility that cell division in protoplasmic astrocytosis might occur by mitosis rather than by amitosis, as widely held.

Acute Disease↗

PubMed1982

Immunogenicity and humoral and cell-mediated immune responses to leptospiral whole cell, outer envelope, and protoplasmic cylinder vaccines in hamsters and dogs.

The immunogenicity of 2 leptospiral cell structural components, the outer envelope (OE) and protoplasmic cylinder (PC), as well as the leptospire whole cell (WC), was compared in hamsters and dogs. The 50% protective dose for hamsters against death (PD50D) and kidney infection (PD50k) was evaluated for Leptospira interrogans serovars canicola, icterohaemorrhagiae, pomona, and grippotyphosa. All 3 immunogens had similar PD50D values. However, the PD50K values for OE and WC vaccines ranged from 0.05 to 0.80 micrograms (dry weight), whereas the PC vaccines ranged from 7.0 to 14.0 micrograms. Cellular and humoral responses of dogs to serovar canicola WC, OE, and PC vaccines were monitored for 21 weeks. Little difference was observed among the canine humoral responses to the different preparations. Protoplasmic cylinder vaccines sensitized the greater population of lymphoid cells followed by OE and WC. Cross-reactivity was greater in the blastogenic response of lymphoid cell populations than in the humoral response.

Animals↗

PubMed1985

Enrichment of fibrillar cytoplasmic actomyosin in protoplasmic strands of Physarum polycephalum for the production of cell-free models.

The treatment of isolated protoplasmic strands of Physarum polycephalum with 2.5% ethanol in a physiological salt solution under isometric conditions induces the formation of a large amount of mostly longitudinally organized actomyosin fibrils in the endoplasmic channel, a region normally free of actomyosin fibrils. The quantity of fibrillogenesis as well as the concomitant force output during the induced contractures are dependent on the Ca++-content and the temperature of the test solution. The method was developed to optimize the structure of the plasmodial strands before their subsequent transformation into cell-free models by permeabilization and extraction of the strands. Cryosections of plasmodial strands containing cytoplasmic actomyosin fibrils stained with fluorescently labeled phallotoxins offer a further assay for the study of their contraction physiology under cell-free conditions.

Actomyosin↗

PubMed1975

Electrical responses of isolated protoplasm from Nitella.

Isolated protoplasmic droplets of the alga Nitella were investigated with microelectrodes in artificial vacuolar sap. The following observations were made: 1. Two types of preparations could be distinguished differing in size and in time of adaptation to artificial pond water but only slightly in their electrical behaviour. 2. The droplets proved to be electrically excitable in the sense that short current pulses elicited electrical responses which outlasted the stimuli. 3. The responses resembled nerve action potentials in shape and duration but they were graded and could be elicited as well in positive as in negative direction. Moreover, spontaneous changes of the normal resting potential (a few millivolts inside negative) did not influence their amplitudes. 4. In most cases the amplitudes of the responses grew with time and saturated after about 90 min. Before saturation the relation between stimulus strength and amplitude of responses was almost linear but became slightly S-shaped after saturation. The saturation value of the responses caused by 100 mus pulses of 1 muA/mm2 was taken as a standard response. In 32 experiments the standard response varied considerable between 2 and 90 mV and was 13 mV on the average. The observations suggest that quite different mechanisms are responsible for the transients of the Nitella droplets and the all-or-none responses of nerve fibres.

Chlorophyta↗