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PubMed1987

Applications of laser microprobe mass analysis in medicine.

An instrument for laser microprobe mass analysis (LAMMA) has been available for applied research for several years. The value of this sensitive microanalytical technique has been demonstrated in various fields of science, including medicine and biology. The LAMMA instrument comprises two laser systems. The first is a weak continuous pilot laser that can be aimed at a region of interest of the sample, e.g., a histological microtome section, using a light microscope. The second is a powerful pulsed laser that can evaporate the selected area. The generated ions are then analyzed in a time-of-flight mass spectrometer. The advantages of LAMMA present new perspectives in biomedical research. Elements can be located and analyzed down to the parts per million-level with a 1 micron spatial resolution. Speciation and/or fingerprinting of (in)organic molecules may be obtained. However, the technique is destructive, the quality of the light-microscopic view is poor, and quantification is still under investigation. In this review, the analytical characteristics of LAMMA are evaluated, including instrumental features, detection sensitivity, ionization parameters, molecular speciation, and quantification. Applications of LAMMA in medicine are reviewed, covering the microanalysis of a wide range of physiological and toxic constituents (alkali metals, calcium, aluminum, titanium, fluorine and iodine, heavy metals, transition elements, and molecular compounds).

Humans↗

PubMed2001

The mammalian guanine nucleotide exchange factor mSec12 is essential for activation of the Sar1 GTPase directing endoplasmic reticulum export.

The Sar1 GTPase is an essential component of COPII vesicle coats involved in export of cargo from the endoplasmic reticulum of mammalian cells. To begin to elucidate its mechanism of action, we now report the identity of the mammalian homolog to the yeast Sec12 guanine nucleotide exchange factor (18% identity) that promotes Sar1 activation. Mammalian Sec12 (mSec12) is a type II transmembrane protein with a large cytosolic domain, a fragment of which has previously been reported as the transcription factor prolactin regulatory element binding protein (PREB). mSec12 promotes efficient guanine nucleotide exchange on Sar1, but not Arf1 or Rab GTPases. mSec12 is localized to the endoplasmic reticulum and an antibody to the cytosolic domain of mSec12 potently inhibits Sar1 recruitment and the formation of COPII vesicles in vitro. The dominant negative GDP-restricted mutant Sar1[T39N] is shown to be a potent inhibitor of mSec12 activity, consistent with its role in preventing COPII vesicle formation in vitro and during transient expression in vivo. We propose that mSec12 is an evolutionarily distant guanine nucleotide exchange factor directing Sar1 GTPase activation in mammalian cells. Its divergence from yeast Sec12p may reflect the specialized needs of the mammalian endoplasmic reticulum involving the formation of Sar1-dependent transitional elements (Aridor M, et al. J Cell Biol 2001;152:213-229) and selection of cargo into prebudding complexes.

ADP-Ribosylation Factor 1↗

PubMed1984

Logical elements in living cells.

Recognition processes with enhanced accuracy (as performed by structures like enzymes or ribosomes) are investigated using elementary ideas of statistical mechanics and related concepts of thermodynamics. The analysis starts from a formal definition of recognition and provides a correspondence with appropriate physical properties of the macromolecular logical elements. Transitions of the recognizing system between different modifications are a necessary feature of a more exacting recognition process. Rearrangement steps provide the process with higher accuracy by performing two physical operations: (1) rearranging the phase space of the system so that the "correct" states be better separated from the "wrong" states and the probability of occupation of the "correct" states be enhanced, (2) directing the process toward the more favourable modifications thus formed. Both operations are related to changes in the physical properties of the recognizing system. These changes can be expressed as differences of macromolecular Gibbs energy levels; if ligand binding or release participate in a step, directivity of the step depends also on the actual chemical potentials of the ligands in solution. The two operations just mentioned resemble two basic operations known to be necessary in electronic digital networks: directivity of control and signal standardization. An analysis of the entire reaction catalysed by a macromolecular logical element takes into account the requirements imposed by the logical functions as well as the need that the chemical potential of the product be not restricted to very low values. To satisfy these conditions, the reaction must be supported by a so-called non-specific reaction, usually implemented by the cleavage reaction of a nucleoside triphosphate.

Catalysis↗

PubMed2001

Application of prominent spectral lines in the 125-180 nm range for inductively coupled plasma optical emission spectrometry.

A new axially viewed ICP optical emission spectrometer featuring an argon-filled optic and CCD detectors was evaluated for the application of prominent spectral lines in the 125-180 nm range. This wavelength range was investigated for several analytical applications of inductively coupled plasma optical emission spectrometry (ICP-OES). There are different advantages for the application of spectral lines below 180 nm. A number of elements, such as Al, Br, Cl, Ga, Ge, I, In, N, P, Pb, Pt, S and Te, were found to have the most intense spectral lines in the wavelength range from 125-180 nm. Compared with lines above 180 nm higher signal-to-background ratios were found. Low limits of detection using pneumatic nebulization of aqueous solutions for sample introduction were calculated for Al II 167.080 nm (0.04 microg L(-1)), Br I 154.065 nm (9 microg L(-1)), Cl I 134.724 nm (19 microg L(-1)), Ga II 141.444 nm (0.8 microg L(-1)), Ge II 164.919 nm (1.3 microg L(-1)), II 142.549 nm (13 microg L(-1)), In II 158.583 nm (0.2 microg L(-1)), P I 177.500 nm (0.9 microg L(-1)), Pb II 168.215 nm (1.5 microg L(-1)), Pt II 177.709 nm (2.6 microg L(-1)), S I 180.731 nm (1.9 microg L(-1)) and Te I 170.00 nm (4.6 microg L(-1)). Numerous application examples for the use of those lines and other important spectral lines below 180 nm are given. Because of fewer emission lines from transition elements, such as Fe, Co, Cr, lines below 180 nm often offer freedom from spectral interferences. Additional lines of lower intensity for the determination of higher elemental concentrations are also available in the vacuum ultraviolet spectral range. This is specially useful when the concentrations are not in the linear range of calibration curves obtained with commonly used lines.

Journal Article↗

PubMed1994

Isolation and characterization of the principal ATPase associated with transitional endoplasmic reticulum of rat liver.

The transfer of membranes from the endoplasmic reticulum to the Golgi apparatus occurs via 50-70 nm transition vesicles which derive from part-rough, part-smooth transitional elements of the endoplasmic reticulum (TER). Vesicle budding from the TER is an ATP-dependent process both in vivo and in vitro. An ATPase with a monomer molecular weight of 100 kD by SDS-PAGE has been isolated from TER and designated as TER ATPase. The native TER ATPase has been characterized as a hexamer of six 100-kD subunits by gel filtration. The protein catalyzes the hydrolysis of [gamma 32-P]ATP and is phosphorylated in the presence of Mg2+. It is distinct from the classical transport ATPases based on pH optima, ion effects, and inhibitor specificity. Electron microscopy of negatively stained preparations revealed the TER ATPase to be a ring-shaped structure with six-fold rotational symmetry. A 19-amino acid sequence of TER ATPase having 84% identity with valosin-containing protein and 64% identity with a yeast cell-cycle control protein CDC48p was obtained. Anti-synthetic peptide antisera to a 15-amino acid portion of the sequence of TER ATPase recognized a 100-kD protein from TER. These antisera reduced the ATP-dependent cell-free formation of transition vesicles from isolated TER of rat liver. In a reconstituted membrane transfer system, TER ATPase antisera inhibited transfer of radiolabeled material from endoplasmic reticulum to Golgi apparatus, while preimmune sera did not. The results suggest that the TER ATPase is obligatorily involved in the ATP requirements for budding of transition vesicles from the TER. cDNA clones encoding TER ATPase were isolated by immunoscreening a rat liver cDNA library with the affinity-purified TER ATPase antibody. A computer search of deduced amino acid sequences revealed the cloned TER ATPase to be the rat equivalent of porcine valosin-containing protein, a member of a novel family of ATP binding, homo-oligomeric proteins including the N-ethylmaleimide-sensitive fusion protein.

Adenosine Triphosphatases↗

PubMed1985

Action of polyvalent cations on sodium transport across skin of larval and adult Rana catesbeiana.

The actions of alkaline earth (AE) and transition element (TE) cations on Na+ transport across skin of larval and adult Rana catesbeiana were compared. Bathed on the outside by Ca+2-free Ringer's, both larval and adult skins maintained a stable short-circuit current (3-4 mu Amps cm-2 for larval skin and 20-30 mu Amps cm-2 for adult skin). Addition of Ca+2 to the external bath reduced the SCC; maximal inhibition was about 36% for larval skin and 22% for adult skin. Other AE divalent cations were also inhibitory. The order of effectiveness was: Ba+2 = Ca+2 greater than Sr+2 greater than Mg+2 for larval skin and Ba+2 greater than Ca+2 = Mg+2 for adult skin. Sodium influx was markedly elevated when Ca+2 was removed from the external medium. Current-voltage analysis indicated that Ca+2 increases the resistance of the active pathway without affecting the shunt resistance or the electromotive force of Na+ transport (ENa) in larval and adult skins. The SCC across adult skin was stimulated by TE cations (Co+2, Cd+2, La+3). These ions were inhibitory on larval skin. The transition in the response occurred at stage XXI. The inhibitory effect of TE on larvel skin resembles that seen in response to AE cations and we postulate a common mechanism. Since larval skin lacks the selective Na+ channels found in apical membranes of adult skin, we infer that the mechanism of inhibition by AE cations is not on these channels. A more general phenomenon such as change in surface charge at the apical membrane seems more reasonable.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

Factors influencing the reductive cleavage of C-x multiple bonds in their reactions with meal-meal multiple bonds (X = C, N, O, S).

Though metal-metal multiple bonds of the transition elements are redox active, their reactivity towards C-X multiple bonds (X = C, N, O, S) vary greatly depending principally on: 1. The coordination geometry of the metal. 2. The oxidation state of the metal and the electronic configuration of the M-M bond. 3. The nature of the attendant ligands. Specific examples of C-X multiple bond activation at dimolybdenum and ditungsten centers are presented that illustrate the importance of these factors. Evidence is presented to support the view that reductive cleavage of a C-X multiple bond can be considered to be equivalent to an intramolecular redox reaction within a [M2CX] "cluster complex," for which the frontier orbital energies of the C-X and M-M multiple bonds are of paramount importance. Some applications of these C-X reductive cleavage reactions toward organic synthesis are described.

Journal Article↗

PubMed2004

Ti and Fe speciation by X-ray photoelectron spectroscopy(XPS) and Mössbauer spectroscopy for a full crystal chemical characterisation of Ti-garnets from Colli Albani (Italy).

Different analytical and structural methods (Electron Probe Micro-Analysis, Single Crystal X-ray diffraction, X-ray Photoelectron Spectroscopy, Mössbauer spectroscopy) were combined to fully characterise the crystal chemistry of natural Ti-bearing garnets from Colli Albani (Lazio, Italy). The study of the relevant complex crystal chemistry ( large number of cation substitutions affecting the three independent X(8-fold), Y(6-fold) and Z(4-fold) crystallographic sites and Fe and Ti transition elements exhibiting several oxidation states and coordination environments) benefited from the multi-technique approach. Electron probe microanalysis provided elemental composition of the analysed samples, which have low Ti-content (TiO2 in the range 1.99 - 3.48 wt %) and slightly different Fe/Al ratios. For all samples, two doublets were fitted to room temperature Mössbauer spectra and assigned to Fe3+(Y) (approximately 95%) and Fe2+(X) (approximately 5%). Up to three doublets (Ti3+(Y), Ti4+(Y), Ti4+(Z)) were fitted to XPS spectra and yielded direct evaluation of Ti site population. XPS technique confirmed its potential for the study of speciation of Ti in minerals.

Crystallization↗

PubMedDate not supplied

Metal content in river suspended particulate matter: data on Po River.

The present study summarizes the last ten years of literature on heavy metal distribution in Suspended Particulate Matter (SPM) and dissolved phase in the Po River (Italy). The work compares different methodologies employed to collect, concentrate and fractionate the samples. The importance of metal speciation as a function of particle size is underlined and two approaches to metal speciation in the colloidal fraction of Po River SPM are presented: Sedimentation Field-Flow Fractionation (SdFFF) and pH-dependent extractions. Finally, emphasis is placed on the need for comparison with a reference "natural background level" of the metal load in Po River particulate matter in order to determine the real human contribution to river pollution. The high values of some trace transition elements, such as Cr and Ni, have been compared with clay sediments around Ferrara and with bricks in historic buildings. The highly comparable natural concentration of these metals in Po fine sedimentary rocks and in historic brick buildings of Ferrara (XII-XVI centuries) can provide information on natural geochemical anomalies.

Environmental Monitoring↗

PubMedDate not supplied

Simultaneous determination of arsenic, selenium and mercury in foodstuffs by chemical vapour generation inductively coupled plasma optical emission spectroscopy.

A procedure for the simultaneous determination of arsenic, selenium and mercury in foodstuffs has been developed. After a two-step microwave-assisted wet digestion in closed vessels, using concentrated nitric acid and hydrogen peroxide, the solution was analysed by inductively coupled plasma multichannel-based emission spectrometry using chemical vapour generation as the sample introduction system. All steps of the procedure, such as solid sample dissolution, pre-reduction to the suitable oxidation state, vapor generation, transport and atomization have been designed and optimised taking into account the concomitant presence of all the analytes considered. Temporal variation of analytical signals as well as interfering effects due to transition elements were also studied. Under the optimised operating conditions, the achieved detection limits for the simultaneous determination of arsenic, selenium and mercury in foodstuffs were 0.006, 0.023 and 0.018 microg g(-1), respectively, allowing their determination in real samples. Precision of the analytical procedure was 6.8% for arsenic, 5.2% for selenium and 7.7% for mercury (n=7). The accuracy and reliability of the method was verified by the analysis of both standard reference materials (rice flour and spinach leaves) and real samples (natural and Se-enriched rice).

Arsenic↗

PubMedDate not supplied

A review of the study of protein secretion applying the protein A-gold immunocytochemical approach.

Exocrine and endocrine types of secretion were investigated in various cells by applying the protein A-gold immunocytochemical approach. Several proteins secreted by rat pancreatic and parotid acinar cells, mouse ameloblasts, rat pancreatic B cells and lymph-node plasma cells, and frog hepatocytes were studied using specific antibodies. While light microscope immunohistochemistry has allowed for good topographical identification of positive cells in tissues, the protein A-gold approach used at the electron microscope level has demonstrated the presence of specific antigenic sites in particular cellular compartments. All secretory proteins studied were detected in the rough endoplasmic reticulum, the Golgi apparatus, and the secretory granules of the corresponding secreting cells. In addition, some of the proteins were also found in lysosome-like structures. When good ultrastructural preservation of the cellular organelles was achieved, the labeling was revealed with very high resolution and precise localization. In such cases, we found labeling over transitional elements of the endoplasmic reticulum and in smooth vesicles in the Golgi area. The Golgi apparatus was subdivided into three compartments according to differences in labeling: the cisternae on the cisside, those of the trans-side and the trans-most rigid one. Quantitative evaluations of the intensities of labeling have allowed for 1) demonstration of the high specificity of the different labelings; 2) revelation of the existence of a gradient of increasing intensity that follows precisely the progress of the proteins along their secretory pathway; and 3) identification of intracellular sites where increments of protein antigenicity occur. Furthermore, they have revealed the existence of alterations in protein processing that occurred under experimental and pathological conditions. Double-labeling approaches were performed to demonstrate two different antigenic sites on the same tissue section by applying protein A-gold complexes formed by gold particles of different sizes. Protein A-gold immunocytochemistry has also been combined with cytochemical and radioautographic techniques. This review thus demonstrates that high-resolution quantitative immunocytochemistry can contribute significantly to the investigation of the intracellular processing of secretory proteins. It also illustrates the potential and versatility of the protein A-gold technique, which in combination with other procedures constitutes a powerful method in cell biology.

Ameloblasts↗

PubMedDate not supplied

Ultrastructural localization of insulin and C-peptide antigenic sites in rat pancreatic B cell obtained by applying the quantitative high-resolution protein A-gold approach.

Insulin and C-peptide antigenic sites have been revealed in rat pancreatic B cells by applying immunohistochemical and cytochemical techniques. Fluorescein and rhodamine stains at the light-microscope level have detected both antigens in the same B cells. With the protein A-gold technique, labeling for both antigens was found in the cisternae of the rough endoplasmic reticulum, in those of the transitional elements, in all the cisternae of the Golgi apparatus except in the trans-most one, in the smooth but not in the coated vesicles, in the immature and mature secretory granules, and in some lysosomal (multigranular) structures. The fixation procedure used yielded excellent ultrastructural preservation which allowed for high resolution. The various control experiments demonstrated the high specificity of the results. Quantitative evaluations confirmed the qualitative observations in that they documented the specificity of the label and revealed the presence of an increasing gradient for both antigenic sites along the endoplasmic reticulum-Golgi-granule secretory pathway. The quantification also demonstrated various sites in which an increased labeling occurs: the rough endoplasmic reticulum, the smooth vesicles, the trans-cisternae of the Golgi apparatus, and the immature and the mature secretory granules. The Golgi apparatus was composed of three different subcompartments distinguished by their concentration of label. These include the cisternae on the cis-side, those on the trans-side, and the trans-most rigid cisternae. Since insulin and C-peptide form the proinsulin chain, their antigenic sites were found in the same locations along the secretory pathway; differences in location appeared only in the secretory granules, where insulin was concentrated in the core, while C-peptide was found in both the core and the halo of the granules. Furthermore, in the mature secretory granules displaying a crystalline core, insulin was restricted to the core, while C-peptide was confined to the halo. These results are in accord with the biochemical data, which indicate that simultaneous localization of both antigenic sites in compartments upstream to the immature secretory granules reflects their presence in the form of proinsulin. However, upon dissociation of proinsulin into insulin and C-peptide, both antigenic sites are segregated in different locations. The peptides appear to share parallel pathways and a fate which includes secretion through exocytosis or degradation by the lysosomal system.

Animals↗

PubMed1993

Gallium nitrate increases type I collagen and fibronectin mRNA and collagen protein levels in bone and fibroblast cells.

Gallium is a Group IIIa transitional element with therapeutic efficacy in the treatment of metabolic bone disorders. Previously described antiresorptive effects of gallium on osteoclasts are not sufficient to account for the full range of effects of gallium on bone structure and metabolism. We have recently shown that gallium nitrate inhibits osteocalcin gene expression and the synthesis of osteocalcin protein, an osteoblast-specific bone matrix protein that is thought to serve as a signal to trigger osteoclastic resorption. Here we present evidence for an additional mechanism by which gallium may function to augment bone mass by altering matrix protein synthesis by osteoblastic and fibroblastic cells. Rat calvarial explants exposed to gallium nitrate for 48 h showed increased incorporation of 3H-proline into hydroxyproline and collagenase digestible protein. In addition, gallium treatment increased steady-state mRNA levels for fibronectin and type I procollagen chains in primary rat calvarial osteoblast-enriched cultures, the ROS 17/2.8 osteoblastic osteosarcoma line, and nontransformed human dermal fibroblasts. These findings suggest that the exposure of mesenchymally-derived cells to gallium results in an altered pattern of matrix protein synthesis that would favor increased bone formation.

Adult↗

PubMed1985

Distribution and characterization of mineral-binding phosphoprotein particles in Bivalvia.

Representative species of four bivalve subclasses were examined for the presence of mineral-binding phosphoprotein particles in the physiological fluids. The particles were identified in Heterodont bivalves only, and particles from nine different Heterodont species were isolated and characterized. All phosphoprotein particles are internally cross-linked via histidinoalanine residues. In all species over 80% of the amino acid residues in the particles are aspartic acid, phosphoserine (and/or phosphothreonine), and histidine. These amino acids are probably the only residues directly related to mineral ion binding, since all phosphoprotein particles bind mineral irrespective of the minor amino acid content, which is species dependent. In their native state the phosphoprotein particles contain large amounts of calcium, magnesium, and inorganic phosphate ions (up to 45 metal ions and 8 phosphate ions per 100 amino acid residues) and trace amounts of transition elements. Evidence for the presence of calcium phosphate complexes in the native phosphoprotein particles was obtained by observing a concomitant increase in the inorganic phosphate and calcium ion content of the particles with pH in vivo.

Minerals↗

PubMed1994

Giardia lamblia: ultrastructural basis of protein transport during growth and encystation.

Giardia, an early diverging eukaryote, is reported to have no Golgi apparatus. Moreover, the structural basis for its ability to sort key proteins and transport them to the trophozoite plasma membrane or to the extracellular wall during encystation is not well-understood. Therefore, we have used ultrastructural techniques that enhance the endomembrane system to evaluate the presence and relationships of cytoplasmic organelles and structures that correspond to those present in higher cells. In addition to the perinuclear cisternae, we found rough endoplasmic reticulum (ER), transitional elements, putative tubular-vesicular elements, Golgi-like smooth perinuclear membrane stacks, and lysosome-like peripheral vesicles. Moreover, we observed many small (50-80 nm) vesicles, many of which were coated, that resemble the small transport vesicles that carry proteins between successive ER and Golgi compartments. Importantly, many of these membrane elements appeared to be captured in the process of budding (or fusing). These elements of the endomembrane system are present during both vegetative growth and encystation of Giardia lamblia. In contrast, the encystation-specific vesicles (ESV) are novel large regulated secretory vesicles that transport cyst antigens to the nascent wall. The present studies suggest that ESV may have unusual pathways of formation and traffic. Our findings support the idea that Giardia, a primitive parasite, has complex structures for protein transport. The elements that show similarities to higher cells may have evolved early, while those that differ may represent biologic fossils or specializations for the parasitic life cycle.

Animals↗

PubMed2001

Carcinosarcoma of the uterus: immunohistochemical and genetic analysis of clonality of one case.

BACKGROUND: Carcinosarcomas of the uterus are characterized by admixtures of malignant epithelial and stromal cells, and their histogenesis remains controversial. CASE: An operated case of carcinosarcoma of the uterus in a 49-year-old woman is reported with clonal analysis. The tumor was composed of carcinomatous, sarcomatous, and transitional elements in the frontal wall of the uterine body and therefore was diagnosed as a carcinosarcoma. On immunohistochemical analysis, the sarcomatous component proved negative for epithelial membrane antigen and keratin while both components were positive for vimentin. Analysis of X-chromosome inactivation showed the same pattern throughout and additionally, the same K-ras and p53 mutations were homogeneously detected. Microsatellite instability analysis showed loss of heterozygosity at D5S346 in the sarcomatous but not the carcinomatous component. CONCLUSIONS: This tumor appears monoclonal in line with the combination tumor theory, with late divergence in genetic alteration in the sarcomatous elements.

Carcinosarcoma↗

PubMed1994

Environmental biochemistry of chromium.

Chromium is a d-block transitional element with many industrial uses. It occurs naturally in various crustal materials and is discharged to the environment as industrial waste. Although it can occur in a number of oxidation states, only 3+ and 6+ are found in environmental systems. The environmental behavior of Cr is largely a function of its oxidation state. Hexavalent Cr compounds (mainly chromates and dichromates) are considered toxic to a variety of terrestrial and aquatic organisms and are mobile in soil/water systems, much more so than trivalent Cr compounds. This is largely because of differing chemical properties: Hexavalent Cr compounds are strong oxidizers and highly soluble, while trivalent Cr compounds tend to form relatively inert precipitates at near-neutral pH. The trivalent state is generally considered to be the stable form in equilibrium with most soil/water systems. A diagram of the Cr cycle in soils and water is given in Fig. 6 (Bartlett 1991). This illustration provides a summary of environmentally relevant reactions. Beginning with hexavalent Cr that is released into the environment as industrial waste, there are a number of possible fates, including pollution of soil and surface water and leaching into groundwater, where it may remain stable and, in turn, can be taken up by plants or animals, and adsorption/precipitation, involving soil colloids and/or organic matter. Herein lies much of the environmental concern associated with the hexavalent form. A portion of the Cr(VI) will be reduced to the trivalent form by inorganic electron donors, such as Fe2+ and S2-, or by bioprocesses involving organic matter. Following this conversion, Cr3+ can be expected to precipitate as oxides and hydroxides or to form complexes with numerous ligands. This fraction includes a vast majority of global Cr reserves. Soluble Cr3+ complexes, such as those formed with citrate, can undergo oxidation when they come in contact with manganese dioxide, thus reforming hexavalent Cr. In trace amounts, Cr is an essential component of animal nutrition, functioning mainly in glucose metabolism, and possibly in fat metabolism. While shown to be nonessential for plants, it is required by some microbes, possibly as a cofactor for specific enzyme systems. Bacteria with plasmid-conferred resistance to Cr(VI) have been isolated from water, soil, and sediments, and the resistance mechanisms have been somewhat characterized. One of the chief mechanisms is bioreduction of toxic Cr(VI) to the relatively nontoxic Cr(III). This has been shown to occur directly, by enzymatic processes at the cell membrane, and indirectly, with microbially produced H2S acting as the reductant.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

Distribution and characteristics of the different astroglial cell types in the adult lizard (Lacerta lepida) spinal cord.

The astroglial cells have been studied in the lizard spinal cord by means of metallic impregnations, immunohistochemical (glial fibrillary acidic protein) and ultrastructural methods. Three astroglial cell types have been immunohistochemically identified: ependymocytes, radial astrocytes and astrocytes. Transitional forms have also been observed. Scarce immunopositive ependymocytes were located in the dorsal and ventral regions of the ependyma. The radial astrocytic somata were located around the ependymal layer and their processes reached the subpial glia limitans. Typical astrocytes were the most abundant astroglial cell type; astrocytes located in the ventral horn showed a greater development than those of the dorsal horn. In the white matter, the astrocytes were large and their processes formed part of the subpial glia limitans; on some occasions, astrocytic cell bodies also formed part of this subpial limitans. Transitional elements between astrocytes and radial astrocytes were observed in both grey and white matter. The perivascular and subpial glia limitans were continuous and showed a strong immunoreactivity. The comparative analysis of our results in the lizard spinal cord with those in other vertebrate groups leads us to conclude that reptiles could represent the key group in the phylogenetic evolution of the astroglial cells in vertebrates.

Animals↗