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PubMed1990

Thalamic retrograde degeneration following cortical injury: an excitotoxic process?

Traumatic or stroke-like injuries of the cerebral cortex result in the rapid retrograde degeneration of thalamic relay neurons that project to the damaged area. Although this phenomenon has been well documented, neither the basis for the relay neuron's extreme sensitivity to axotomy nor the mechanisms involved in the degenerative process have been clearly identified. Physiological and biochemical studies of the thalamic response to cortical ablation indicate that pathological overexcitation might contribute to the degenerative process. The responses of thalamic projection neurons, protoplasmic astrocytes, and inhibitory thalamic reticular neurons in adult mice were examined from one to 120 days following ablation of the somatosensory cortex as part of an investigation of the role of excitotoxicity in thalamic retrograde degeneration. The responses of thalamic neurons to cortical ablation were compared with those produced by intracortical injection of the convulsant excitotoxin kainic acid, since the degeneration of neurons in connected brain structures distant to the site of kainic acid injection is also thought to occur via an excitotoxic mechanism. Within two days after either type of cortical injury, protoplasmic astrocytes in affected regions of the thalamic ventrobasal complex and the medial division of the posterior thalamic nuclei became reactive and expressed increased levels of immunohistochemically detectable glial fibrillary acidic protein. Within the affected regions of the ventrobasal complex an increased intensity of puncta positive for glutamate decarboxylase immunoreactivity, presumably due to an increase in its content within the terminals of the reciprocally interconnected thalamic reticular neurons, was also evident. These immunohistochemically detectable alterations in the milieu of the damaged thalamic neurons preceded the disappearance of the affected relay neurons by at least two days following cortical ablation and by seven to 10 days following intracortical kainic acid injection. Regions of the thalamus containing reactive astrocytes corresponded very closely to the regions undergoing retrograde degeneration. Protoplasmic astrocytes in these areas remained intensely reactive up to 60 days after cortical injury. Levels of glutamate decarboxylase were only transiently elevated in the degenerating regions of the ventrobasal complex following cortical ablation and returned to normal by 14 days. Increased glutamate decarboxylase immunoreactivity was transiently seen through the entire ventrobasal complex following intracortical kainic acid injection but was markedly more intense in degenerating regions. These patterns of labeling did not return to normal until 50 days after intracortical kainic acid injection, well after the death of the relay neurons. Cortical ablation and intracortical kainic acid injection produce similar alterations in thalamic neuronal and glial populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1981

Ionic currents traverse the slime mould physarum.

Self generated electric currents were studied in protoplasmic drops and small plasmodia of Physarum polycephalum with the aid of an extracellularly measuring vibrating electrode. Ionic currents up to 15 microamperemetercm-2 density were found to traverse the objects. In protoplasmic drops current always enters the numerous protrusions and leaves areas with a smooth surface. In monopodial plasmodia current enters the strand and leaves both the advancing front and the retracting end. This result points toward large changes in membrane arrangement or properties occurring during development of plasmodia from protoplasmic drops.

Cytoplasm↗
PubMed1989

Strategy and tactics in electron microscopy of cell surfaces.

Over the past decade new methods have been developed to visualize both the external and the protoplasmic surfaces of cultured cells in the electron microscope. In this review the emphasis is on cell monolayers, though some of the techniques are also applicable to cells in suspension. There is no universal method which would satisfy all our requirements i.e. the preservation of native structure and antigenicity and the visualization of the whole cell surface at high resolution. While surface replicas of freeze-dried or critical point-dried cells are eminently suited for high resolution studies including gold immunolabelling, scanning electron microscopy provides a view of the whole cell and a large sample for 'statistical' evaluation. Whole mount preparations of cleaved cells prove useful in studies of plasma membrane associated structures such as the cytoskeleton. A series of new procedures have been developed for studies of cytoskeleton/membrane interactions, identification of intramembrane particles and their contacts with the glycocalyx, to mention some of the biological problems. Although the lysis-squirting technique appears most suitable for the visualization and immunolabelling of protoplasmic surfaces of ventral membranes, dry- or wet-cleaving represent a useful alternative for studies of the protoplasmic surfaces of dorsal membranes and of the ventral membrane associated cytoplasmic domains. An assessment of the methods is given though this should only serve as guidance and it is up to the experimentor to choose the most useful technique for the project under study. Briefly the aim of the project determines the choice of the method. A multi-methodical approach is recommended when one method does not provide satisfactory results.

Animals↗
PubMed2005

3-D physical models of amitosis (cytokinesis).

Based on Newton's laws, extended Coulomb's law and published biological data, we develop our 3-D physical models of natural and normal amitosis (cytokinesis), for prokaryotes (bacterial cells) in M phase. We propose following hypotheses: Chromosome rings exclusion: No normally and naturally replicated chromosome rings (RCR) can occupy the same prokaryote, a bacterial cell. The RCR produce spontaneous and strong electromagnetic fields (EMF), that can be alternated environmentally, in protoplasm and cortex. The EMF is approximately a repulsive quasi-static electric (slowly variant and mostly electric) field (EF). The EF forces between the RCR are strong enough, and orderly accumulate contractile proteins that divide the procaryotes in the cell cortex of division plane or directly split the cell compartment envelope longitudinally. The radial component of the EF forces could also make furrows or cleavages of procaryotes. The EF distribution controls the protoplasm partition and completes the amitosis (cytokinesis). After the cytokinesis, the spontaneous and strong EF disappear because the net charge accumulation becomes weak, in the protoplasm. The exclusion is because the two sets of informative objects (RCR) have identical DNA codes information and they are electro magnetically identical, therefore they repulse from each other. We also compare divisions among eukaryotes, prokaryotes, mitochondria and chloroplasts and propose our hypothesis: The principles of our models are applied to divisions of mitochondria and chloroplasts of eucaryotes too because these division mechanisms are closer than others in a view of physics. Though we develop our model using 1 division plane (i.e., 1 cell is divided into 2 cells) as an example, the principle of our model is applied to the cases with multiple division planes (i.e., 1 cell is divided into multiple cells) too.

Bacteria↗
PubMed1988

Resting metabolic requirements of men and women.

The resting metabolic rates (RMRs) of 44 lean and obese women, 8 of whom were trained athletes, and of 60 lean and obese men were measured by indirect calorimetry. These healthy humans, ranging from 18 to 82 years old and from 43 to 171 kg in weight, were mentally and physically active. Body composition was determined by densitometry and skinfold thickness. Stepwise multiple regression analysis was used to determine whether one or several variables best predicted RMR. Body compositional variables reflecting active protoplasmic tissue were all highly interrelated. Body weight alone yielded prediction values for RMR comparable to those of other variables of active protoplasmic tissue mass. Among these mentally and physically active women and men, the influence of age on RMR was trivial, and regional distribution of fat had no influence on the RMR. The 95% confidence limits for RMR in both lean and obese subjects were broad. Thus, metabolic efficiency is not necessarily or exclusively related to obesity. In fact, the caloric requirements of humans, based on body weight or active protoplasmic tissue mass, may vary twofold. With the exception of the elderly men, the classic prediction equations and tables developed during the first half of this century greatly overestimated the RMR of healthy lean and obese humans. Therefore, new regression equations for predicting the RMR based on weight and fat-free mass were developed.

Adolescent↗
PubMed1976

The longest symbiotic bacterium as found in a membracid insect.

An insect tumour cell, carrying germs, contains nuclei and also cellular debris as protoplasmic and nuclear degradation bodies. In histological sections the nucleus may be seen surrounded by such bodies, cut across, which then appear round in form. They have therefore been mistaken for yeast-like germs, called "Cicadomyces". But in smears the protoplasmic debris is stained blue and reveals bizarre shapes. T. assamensis is an exception and offers the key to properly interpret the bodies named Cicadomyces. Its symbiote is a long filamentous bacterium and persists in protoplasmic debris, the so-called Cicadomyces. Since Cicadomyces themselves cannot be infected by germs as long as themselves, the former can only represent cellular degradation bodies.

Adipose Tissue↗
PubMed2003

Ultrastructure of astrocytes in the cortex of the hippocampal gyrus and in the neocortex of the temporal lobe in experimental valproate encephalopathy and after valproate withdrawal.

The aim of the study was to analyse the astrocyte ultrastructure within the hippocampal gyre cortex and neocortex of the temporal lobe in valproate encephalopathy induced by chronic administration of an anti-epileptic drug - sodium valproate (VPA) to rats for 1, 3, 6, 9 and 12 months, once daily intragastrically, in a dose of 200 mg/kg b.w. and after its withdrawal for 1 and 3 months. Prolonged application of VPA caused damage to protoplasmic astrocytes of the cortex regions examined, mainly in the pyramidal layer, which intensified in the later stages of the experiment, especially after 9 and 12 months. Ultrastructural alterations in astroglia during this experiment did not differ significantly between the hippocampal cortex and neocortex. The most pronounced astroglial abnormalities, concerning about 2/3 of protoplasmic astrocytes after 9 and 12 months, were characterized by considerable swelling of cells, with the presence of empty vacuolar structures in the cytoplasm, a substantial decrease in the number of gliofilaments or even their complete loss, which indicated fibrillopoietic failure of the cell, and the appearance of astrocytes showing phagocytic activity. The astrocytic changes coexisted with distinct damage to neurones and structural elements of the blood-brain barrier. One month after termination of chronic exposure to the drug, the abnormalities did not subside, whereas after 3 months features of distinct normalization could be observed in a considerable number, more than a half, of astrocytes. In valproate encephalopathy, apart from any direct effect of VPA and/or its metabolites on astrocytes, the main cause of the protoplasmic astroglial damage in the cortex of the CNS structures examined could be associated with changes in microcirculation in the cortex (vasogenic factor), leading to its ischaemia.

Animals↗
PubMed1982

T-lymphocyte heterogeneity: wheat germ agglutinin labeling of transmembrane glycoproteins.

We have recently described "fracture-label" techniques that permit direct cytochemical labeling of freeze-fractured cells. We report here the use of fracture-labeling to investigate the distribution and partition of wheat germ agglutinin (WGA) receptor sites over the protoplasmic and exoplasmic plasma membrane faces of freeze-fractured human thymus-derived (T) lymphocytes. All exoplasmic faces are strongly labeled by WGA. In contrast, the protoplasmic faces exhibit remarkable variation, ranging from virtual absence of label in some faces to very high densities in other faces. We interpret the presence of WGA receptor sites over the protoplasmic faces to reflect the presence of transmembrane WGA-binding sialoglycoproteins that, during freeze-fracture, partition with the inner half of the plasma membrane. Our results, therefore, indicate heterogeneous expression of integral membrane proteins within populations of human T cells. Fracture-label techniques thus represent an additional tool in the definition of lymphocyte subpopulations.

B-Lymphocytes↗
PubMed1993

Composite, large spirochetes from microbial mats: spirochete structure review.

Phenomena previously unknown in free-living spirochetes are reported: large-sized cells with variable diameter (length to 100 microns, width between 0.4 and 3.0 microns), composite structure (smaller spirochetes inside larger ones), and positive phototropic behavior. These bacteria, Spirosymplokos, are compared with all other spirochete genera. The large spirochete, grown in mixed culture, was studied live and by transmission EM. The protoplasmic cylinder was replete with spherical granules 20-32 nm in diameter, and three to six periplasmic 26-nm flagella were inserted subterminally. Comparably granulated and flagellated small spirochetes were located inside the protoplasmic cylinder and in the periplasm of the large ones. When exposed to air, movement became erratic, protoplasmic cylinders retracted to lie folded inside the outer membrane, and refractile membranous structures formed. From one to four structures per still-moving spirochete were seen. Spirosymplokos was enriched from laboratory samples exposed to oxygen-rich and desiccating, but not dry, conditions for at least 4 mo after removal of microbial mat from the field.

Microscopy, Electron↗
PubMed1982

Effects of amphotericin B and its methyl ester on plasma membranes of Candida albicans and erythrocytes as examined by freeze-fracture electron microscopy.

Freeze-fracture electron microscopy of the plasma membranes of Candida albicans yeast cells and red blood cells treated with amphotericin methyl ester and amphotericin B showed that amphotericin B (50 micrograms ml-1) caused extreme aggregation of intramembranous particles on the protoplasmic fracture face of the C. albicans membrane, and a marked reduction of the density of intramembranous particles. On the other hand, the rearrangement of intramembranous particles induced by amphotericin methyl ester (50 micrograms ml-1) produced elevations of the particle-free membrane domains toward the outside of the cells, so that the particles were aggregated in linear furrows surrounding these elevations on the protoplasmic fracture face, and the corresponding ridges on the exoplasmic fracture face. The density of intramembranous particles was greatly reduced on the protoplasmic fracture face. Both polyenes produced only small changes in the erythrocyte membranes at the same concentration. These results suggest that amphotericin methyl ester affects the ergosterol-containing membranes more than amphotericin B, and that ergosterol has a higher sensitivity for these two polyene antibiotics than cholesterol.

Amphotericin B↗
PubMed1955

Electron microscope studies on the cells of the malpighian tubules of the grasshopper (Orthoptera, Acrididae).

For purposes of description, the cells of the Malpighian tubules of the grasshopper may be divided into basal, intermediate, and apical zones. The basal zone of the cell contains what appears to be an elaborate infolding of the cell membrane at the base. This condition results in the basal cell cytoplasm being divided into many compartments. The compartments contain mitochondria that are often arranged in rows. Other small bodies which possess relatively dense outer borders and less dense cores were observed within the compartments. These bodies are unidentified. The brush border of the apical zone contains a multitude of vertically arranged protoplasmic processes. Stages were found which suggest that the filamentous mitochondria migrate from the cell body to the base of the protoplasmic processes, where they enter them and move apically. Some of the mitochondria were observed at the very tips of the processes where they enlarge producing an accompanying bulging of the tips. This condition is interpreted as a stage in the pinching off of the mitochondria-laden tips of the protoplasmic processes.

Animals↗
PubMed1957

The parasporal body of Bacillus laterosporus Laubach.

On sporulation the slender vegetative rods swell and form larger spindle-shaped cells in which the spores are formed. When the spores mature they lie in a lateral position cradled in canoe-shaped parasporal bodies which are highly basophilic and can be differentiated from the surrounding vegetative cell cytoplasm with dilute basic dyes. On completion of sporulation the vegetative cell protoplasm and the cell wall lyse, leaving the spore cradled in its parasporal body. This attachment continues indefinitely on the usual culture medium and even persists after the spores have germinated. In thin sections of sporing cells the bodies are differentiated from the cell protoplasm by differences in structure. Whereas the protoplasm has a granular appearance, in both longitudinal and cross-sections the parasporal body comprises electron-dense lamellae running parallel with the membranes of the spore coat and less electron-dense material in the interstices of the lamellae. The inner surface of the body is contiguous with that of the spore coat as if it were part of the spore, rather than a separate body attached to the spore. The staining reactions of the parasporal body are not consistent with those of any substance described in bacteria. With Giemsa the bodies stain like chromatin, but the Feulgen reaction indicates that they do not contain the requisite nucleic acid. With an aqueous solution of toluidine blue they stain metachromatically, but with an acidified solution the results are variable. Neisser's stain for polyphosphate is negative. The basophilic substance is removed from the body with some organic solvents. This basophilic substance has not been specifically identified with any material seen in ultrathin sections, but it is suggested that it might be the less electron-dense material in the interstices of the lamellar structure. In contrast to the spore coat of B. laterosporus, those of its two relatives B. brevis and B. circulans take up basic stain like the parasporal body. Thin spore sections of these species have shown that the walls are thicker than those surrounding the spores of B. laterosporus, and it is suggested that the outer stainable layer of brevis and circulans spores is an accessory coat which in laterosporus may have been deformed to give a parasporal body.

Bacillus↗
PubMed1959

A light and electron microscope study of the epithelial cells of the gut of Fasciola hepatica L.

The structure of the epithelial cells of the alimentary tract of Fasciola hepatica was investigated by means of light and electron microscopy. Tissue prepared for electron microscopy was fixed in 1 per cent osmium tetroxide, buffered with veronal to a pH of 7.4, and embedded in butyl methacrylate with 1 per cent benzoyl peroxide as a catalyst. Polymerisation was carried out at 60 degrees C. The majority, if not all, the epithelial cells pass through both absorptive and secretory cycles. The free ends of absorptive cells possess fine protoplasmic processes that project into the lumen of the gut. These are apparently concerned with the absorption of nutriment. In electron micrographs, the protoplasmic (absorptive) processes are frequently seen to be in the form of tubular loops both ends of which arise from the same cell. The free end of a process is often expanded into a ribbon-like structure. Each process possesses an external limiting membrane and an internal membranous ultrastructure. When a cell becomes glandular in function, the protoplasmic processes seem to become less numerous. The plasma membrane is invaginated into the basal part of an absorptive cell. In the neighbourhood of the lumen of the gut where two tall cells are in contact, bands of amorphous cytoplasmic material are in contact with each cell membrane.

Animals↗
PubMed1977

Rearrangements of integral membrane components during in vitro aging of sheep erythrocyte membranes.

In vitro aged sheep erythrocytes and sheep erythrocyte ghosts spontaneously release vesicles that consist of long protrusions affixed to flattened headlike structures. The intramembranous particles seen on the protoplasmic face of freeze fracture electron micrographs of vesicle protrusions are arranged in paired particle rows. On the equivalent fracture face of headlike structures, the particle density is low; if particles are present, they are clustered along the rim of the flattened headlike structure and at the junction with the protrusion. The released vesicles are depleted of the intramembranous particles seen on the exoplasmic face of ghost but retain almost exclusively particles of the protoplasmic face. Correspondingly, the exoplasmic face of ghosts that have released vesicles reveals a 28 percent higher density of intramembranous particles than that of fresh ghosts. Purified vesicles are depleted of spectrin but retain integral membrane proteins, with one of an apparent mol wt of 160,000 accounting for nearly 50 percent of the total protein (Lutz, H.U.,R. Barber, and R.F. McGuire. 1976. J. Biol. Chem. 251:3500-3510). When vesicles are modified with the cleavable cross-linking reagent [(35)S]dithiobis (succinimidyl propionate)at 0 degrees C, the 160,000 mol wt protein is rapidly converted to disulfide-linked dimers and higher oligomers. Exposure of intact ghosts to the reagent in the same way fails to yield equivalent polymers. A comparison of the morphological and biochemical aspects of ghosts and vesicles suggest that a marked rearrangement of membrane proteins accompanies the supramolecular redistribution of intramembranous particles during spontaneous vesiculation. The results also suggest that the paired particles of the protoplasmic face of vesicle protrusions are arranged in paired helices and contain the 160,000 mol wt protein as dimers.

Animals↗
PubMed1982

Freeze-fracture cytochemistry: partition of glycophorin in freeze-fractured human erythrocyte membranes.

Thin-section and critical-point-dried fracture-labeled preparations are used to determine the distribution and partition of glycophorin-associated wheat germ agglutinin (WGA) binding sites over protoplasmic and exoplasmic faces of freeze-fractured human erythrocyte membranes. Most wheat germ agglutinin binding sites are found over exoplasmic faces. Label is sparse over the protoplasmic faces. These results contrast with previous observations of the partition of band 3 component where biochemical analysis and fracture-label of concanavalin A (Con A) binding sites show preferential partition of this transmembrane protein with the protoplasmic face. Presence of characteristic proportions of WGA and Con A binding sites over each fracture face is interpreted to indicate the operation of a stochastic process during freeze-fracture. This process appears modulated by the relative expression of each transmembrane protein at either surface as well as by their association to components of the erythrocyte membrane skeleton.

Erythrocyte Membrane↗
PubMed1983

Regionalization of transmembrane glycoproteins in the plasma membrane of boar sperm head is revealed by fracture-label.

We used fracture-label and surface labeling techniques to characterize the distribution and topology of wheat germ agglutinin (WGA) receptors in the plasma membrane of boar sperm heads. We show that freeze-fracture results in preferential, but not exclusive, partition of WGA-binding sites with the outer (exoplasmic) half of the plasma membrane. Labeling of the inner (protoplasmic) half of the membrane is significant, and is denser over the areas that overlie the acrosome. Exoplasmic membrane halves are uniformly labeled. Analysis of freeze-fracture replicas revealed that the distribution of intramembrane particles over protoplasmic faces parallels that of WGA-binding sites as observed by fracture-label. Coating of intact spermatozoa with cationized ferritin results in drastic reduction of the labeling of both protoplasmic and exoplasmic membrane halves. Labeling of sperm cells lysed by short hypotonic shock fails to reveal the presence of WGA-binding sites at the inner surface of the plasma membrane. We conclude that: (a) all WGA-binding glycoconjugates are exposed at the outer surface of the membrane; (b) some of these glycoconjugates correspond to transmembrane glycoproteins that, on fracture, partition with the inner half of the membrane; (c) these transmembrane proteins are accumulated in the region of the plasma membrane that overlies the acrosome; and (d) parallel distribution of intramembrane particles and WGA-binding glycoproteins provides renewed support for the view of particles as the morphological counterpart of integral membrane proteins.

Animals↗
PubMed1956

Observations on an ATP-sensitive protein system from the plasmodia of a myxomycete.

1. Extracts of the plasmodia of the myxomycete, Physarum polycephalum, exhibit reversible decreases in viscosity in response to the addition of ATP under appropriate conditions. The protoplasm material prepared by extraction with KCl solution can apparently exist in either a high or a low viscosity state. As prepared, it is in the low viscosity condition. Rapid and extensive increases in viscosity of the extract are brought about by addition of AMP, inorganic phosphate, or, under certain conditions, of ATP. Only after the high viscosity state has been attained does addition of appropriate quantities of ATP cause a reversible decrease in viscosity. 2. The active principle of crude plasmodial extracts may be concentrated by fractional precipitation with ammonium sulfate and is found in the fraction precipitated between 30 and 40 per cent saturation. This material possesses a higher viscosity than does the original crude extract and is apparently in the high viscosity state since the addition of ATP causes an immediate reversible decrease in viscosity. 3. The ATP-sensitive fraction of myxomycete plasmodia possesses a viscosity which is dependent upon its previous thermal treatment. Extracts incubated at 0 degrees for a period of a few hours increase greatly in viscosity when they are returned to 24.5 degrees . This increased viscosity is structural in nature, is destroyed by mechanical agitation of the solution, and may be reversibly destroyed by addition of ATP. 4. It is suggested that the ATP-responsive protein of myxomycete plasmodia may be related to sol-gel transformations which have been observed in intact plasmodia and may participate in the protoplasmic streaming of the intact organism. This suggestion is based upon the following facts: (a) the protoplasmic streaming of myxomycete plasmodia is increased by microinjection of ATP; (b) the gel portion of the cytoplasm at the site of the microinjection of ATP is extensively converted to the sol state. The changes in structure of the intact cytoplasm are thus similar in nature to the changes exhibited in response to ATP by the purified ATP-sensitive protein. 5. The ATP-sensitive protein of myxomycete plasmodia appears to undergo reversible aggregation to form a high viscosity state. The function of ATP is to break down the aggregates thus formed. Since a specific ATPase activity is associated with the purified material, added ATP is gradually destroyed and recovery of viscosity attends the spontaneous reconstitution of aggregates.

Adenosine Triphosphate↗
PubMed1957

Studies on Streptococcus pyogenes. III. The effect of trypsin and a cationic detergent on the structure, permeability, and metabolism of the cell.

Electron microscopic observations of Streptococcus pyogenes (strain S43, type 6) treated with trypsin and cetyltrimethylammonium bromide (Cetab) are presented. The concentration of trypsin necessary to remove the M protein antigen was shown to bring about a partial digestion of the cells. The cell protoplasm and protoplasmic membrane were affected. No microscopic changes appeared in the cell wall. Cetab did not alter the appearance of the cells. Both trypsin and detergent altered the permeability of the cell so that citrulline and carbamylphosphate were metabolized. Cells exhibiting enzyme activity on these substrates after Cetab treatment were characterized by the release of lysine, glutamic acid, nucleic acid, and other cellular material. Enzymes responsible for the metabolism of arginine, citrulline, and carbamylphosphate were shown to reside in the cell protoplasm. Cells which had lost their viability after Cetab treatment still possessed the ability to utilize the latter substrates. Under similar conditions the metabolism of glucose did not occur. Normal cells were shown to possess the ability to fluoresce in the presence of a dye. The intensity of the fluorescence was reduced by trypsin treatment.

Ammonium Compounds↗