Granular Matrices Research Articles

New model for the genesis and maturation of viroplasms induced by fijiviruses in insect vector cells.

Plant reoviruses are thought to replicate and assemble within cytoplasmic, nonmembranous structures called viroplasms. Here, we established continuous cell cultures of the white-backed planthopper (Sogatella furcifera Horváth) to investigate the mechanisms for the genesis and maturation of the viroplasm induced by Southern rice black-streaked dwarf virus (SRBSDV), a fijivirus in the family Reoviridae, during infection of its insect vector. Electron and confocal microscopy revealed that the viroplasm consisted of a granular region, where viral RNAs and nonstructural proteins P6 and P9-1 accumulated, and a filamentous region, where viral RNAs, progeny cores, viral particles, as well as nonstructural proteins P5 and P6 accumulated. Our results suggested that the filamentous viroplasm matrix was the site for the assembly of progeny virions. Because viral RNAs were produced by assembled core particles within the filamentous viroplasm matrix, we propose that these viral RNAs might be transported to the granular viroplasm matrix. P5 formed filamentous inclusions and P9-1 formed granular inclusions in the absence of viral infection, suggesting that the filamentous and granular viroplasm matrices were formed primarily by P5 and P9-1, respectively. P6 was apparently recruited in the whole viroplasm matrix by direct interaction with P9-1 and P5. Thus, the present results suggested that P5, P6, and P9-1 are collectively required for the genesis and maturation of the filamentous and granular viroplasm matrix induced by SRBSDV infection. Based on these results, we propose a new model to explain the genesis and maturation of the viroplasms induced by fijiviruses in insect vector cells.

Mobility of Functionalized Quantum Dots and a Model Polystyrene Nanoparticle in Saturated Quartz Sand and Loamy Sand

Quantum dots (QDs) are one example of engineered nanoparticles (ENPs) with demonstrated toxic effects. Yet, little is known about the behavior of QDs in the natural environment. This study assessed the transport of two commercial carboxylated QDs (CdTe and CdSe) and carboxylated polystyrene latex (nPL) as a model nanoparticle using saturated laboratory-scale columns. The influence of solution ionic strength (IS) and cation type (K(+) or Ca(2+)) on the transport potential of these ENPs was examined in two granular matrices - quartz sand and loamy sand. The retention of all three particles was generally low in the quartz sand columns within the range of studied IS (0.1-100 mM) for the monovalent salt (KCl). In contrast, the retention of the three ENPs in the quartz sand was significant in the presence of 10 mM Ca(2+). Moreover, ENP attachment efficiencies (α) were enhanced by at least 1 order of magnitude in columns packed with loamy sand (for IS between 0.1-10 mM KCl). Although all three ENPs used here are carboxylated, they differ in the type of surface coating (e.g., choice of polymers or polyelectrolytes). Regardless of the surface coatings, the three ENPs exhibit comparable mobility in the quartz sand. However, the ENPs demonstrate variable transport potential in loamy sand suggesting that differences in the binding affinities of surface-modified ENPs for specific soil constituents can play a key role in the fate of ENPs in soils.

Analytic Hierarchy Process (AHP) in Group Decision Making and its Optimization With an Allocation of Information Granularity

In group decision making, one strives to reconcile differences of opinions (judgments) expressed by individual members of the group. Fuzzy-decision-making mechanisms bring a great deal of flexibility. By admitting membership degrees, we are offered flexibility to exploit different aggregation mechanisms and navigate a process of interaction among decision makers to achieve an increasing level of consistency within the group. While the studies reported so far exploit more or less sophisticated ways of adjusting/transforming initial judgments (preferences) of individuals, in this paper, we bring forward a concept of information granularity. Here, information granularity is viewed as an essential asset, which offers a decision maker a tangible level of flexibility using some initial preferences conveyed by each individual that can be adjusted with the intent to reach a higher level of consensus. Our study is concerned with an extension of the well-known analytic hierarchy process to the group decision-making scenario. More specifically, the admitted level of granularity gives rise to a granular matrix of pairwise comparisons. The granular entries represented, e.g., by intervals or fuzzy sets, supply a required flexibility using the fact that we select the most suitable numeric representative of the reciprocal matrix. The proposed concept of granular reciprocal matrices is used to optimize a performance index, which comes as an additive combination of two components. The first one expresses a level of consistency of the individual pairwise comparison matrices; by exploiting the admitted level of granularity, we aim at the minimization of the corresponding inconsistency index. The second part of the performance index quantifies a level of disagreement in terms of the individual preferences. The flexibility offered by the level of granularity is used to increase the level of consensus within the group. Given an implicit nature of relationships between the realizations of the granular pairwise matrices and the values of the performance index, we consider using particle swarm optimization as an optimization vehicle. Two scenarios of allocation of granularity among decision makers are considered, namely, a uniform allocation of granularity and nonuniform distribution of granularity, where the levels of allocated granularity are also subject to optimization. A number of numeric studies are provided to illustrate an essence of the method.

Mast Cells Play a Crucial Role in Staphylococcus aureus Peptidoglycan-Induced Diarrhea

Bacterium-induced diarrhea results in 2 to 2.5 million deaths in the world each year. The mechanism needs to be further understood. Staphylococcus aureus infection has a close relation with diarrhea; its cell wall component peptidoglycan (PGN) has strong biological activity on immune cells and possibly plays a role in S. aureus-induced diarrhea. The present study showed that oral PGN-induced diarrhea in mice in a dose-dependent manner. Intestinal epithelial cells absorbed PGN via the intracellular pathway. Intestinal mast cells were activated after PGN gavage. Toll-like receptor (TLR)2 expression was detected in mast cells in the intestine as well as in the murine mast cell line p815 cells. Blocking TLR2 or nucleotide-binding oligomerization domain (NOD)1 with related antibodies or RNA interference abolished PGN-induced p815 cell activation. The mast cell mediator histamine and serotonin had synergistic effects in PGN-induced diarrhea. In summary, oral PGN can induce diarrhea in mice, and TLR2 and NOD1 mediate the PGN-induced mast cell activation that plays a critical role in diarrhea induction. Blockade of TLR2 or NOD1 or treating mice with a mast cell stabilizer can efficiently inhibit PGN-induced-diarrhea, providing potential therapeutic significance.

A mutation in the cathepsin D gene ( CTSD) in American Bulldogs with neuronal ceroid lipofuscinosis

We obtained DNA, brains, and eyes from American Bulldogs with neurodegeneration due to neuronal ceroid lipofuscinosis (NCL). The diagnosis of NCL was confirmed by detection of autofluorescent cytoplasmic inclusions within neurons throughout the brains, in retinal ganglion cells, and along outer limiting membranes of the retinas. Electron microscopy revealed that the inclusions had coarsely granular matrices surrounding well-delineated spherical structures and that the inclusions near the retinal outer limiting membranes were within photoreceptor cells, mostly cones. Affected American Bulldogs were homozygous for the A allele of a G to A transition in the cathepsin D gene ( CTSD), which predicts the conversion of methionine-199 to an isoleucine. Only the G allele was detected in DNA samples from 131 randomly selected dogs representing 108 breeds other than American Bulldog; however, the A allele had a frequency of 0.28 among 123 genotyped American Bulldogs. Transmission analysis in a 99 dog pedigree of American Bulldogs indicated a probability of less than 10 −7 that alleles from any mutation unlinked to CTSD would be concordant with the pedigree and phenotypes of the dogs. Brain samples from affected dogs had 36% of the cathepsin D-specific enzymatic activity found in control dog brains; whereas, specific enzymatic activities of 15 other lysosomal enzymes were unchanged or increased. Compared to previously described NCLs in mice and sheep that completely lack cathepsin D activity, the clinical course of NCL in the American Bulldogs was less severe and more closely resembled that of many human NCLs.

Drug release from a multiparticulate pellet system.

Multiparticulate pellet systems are used as both immediate and modified release dosage forms. Previous work has classified uncoated pellet systems prepared from microcrystalline cellulose as an inert matrix. The Higuchi square root of time equation, derived to describe drug release from a single planar system, is the accepted method to evaluate drug release from both planar and spherical heterogeneous inert granular matrices. A second equation of interest, the Higuchi cubic equation, was derived to describe drug release from a spherical pellet. Both equations predict a linear relationship between drug release and the square root of time or time. The purpose of the present study was to evaluate drug release from a multiparticulate pellet system using both equations and to study any differences when both equations are used to describe the same drug release data. By evaluating dissolution data from various pellet mesh cuts representing different bead radii and surface areas, changes in the slopes of both plots would be expected. Pellets were manufactured using extrusion/spheronization technology and consisted of 90% microcrystalline cellulose and 10% acetaminophen. Statistical comparison indicates that the Higuchi cubic equation seems to be more sensitive to changes in pellet size. While the square root of time equation describes the drug release data from granular, inert, spherical pellets, it may be better to utilize the Higuchi cubic equation because it is more sensitive to changes in particle size.

Monoplastidy in spermatogenesis of Lycopodium obscurum

Unlike Lycopodium laterale, which is polyplastidic during spermatogenesis, Lycopodium obscurum exhibits monoplastidy beginning in the early proliferative stages of antheridial development. Previous cell generations are polyplastidic and plastid fusion involving connective cylinders establishes the monoplastidic condition. Plastid and nuclear divisions are coordinated in L. obscurum with the plastids positioned at opposite poles prior to spindle development. Unlike monoplastidic cell divisions with morphogenetic plastid migration and polarity in other lycophytes, mosses, and hornworts, however, the spindles in L. obscurum do not originate from the plastid envelopes but from endoplasmic reticulum positioned against the plastid. In the final divisions, spindle microtubules emanate from structurally defined microtubule organizing centers that develop between the plastids and nucleus. Preceding the appearance of centrioles in the spermatid mother cell, the centrosomes comprise electron-dense granular matrices with associated vesicles and endoplasmic reticulum. Among archegoniate microtubule organizing centers, the discrete acentriolar centrosomes of Lycopodium most closely resemble the microtubule organizing centers in moss spore development and the polar organizer of liverwort mitosis. Key words: annulate lamellae, centrosome, Lycopodium, microtubule organizing center, monoplastidy, plastid dividing ring.

Drug release mechanism from a microcrystalline cellulose pellet system.

A common form of modified release is the encapsulation of specially formulated or coated pellets. An important first step in the development of a multiparticulate coated dosage form is to characterize the uncoated pellet. In earlier work, an uncoated pellet system developed in these laboratories and prepared from microcrystalline cellulose (MCC) was investigated and found to exhibit both the physical characteristics of an inert matrix and varying degrees of in vitro modified release. The use and characterization of MCC as a spheronization matrix material forms the basis for this formulation study. The drug release mechanism has been verified by varying selected formulation factors and evaluating the resulting pellets according to the relationship developed by T. Higuchi for granular inert matrices. In all cases, this MCC pellet system adhered to the theoretical relationships and the drug release mechanism can, therefore, be classified as an inert matrix.

Three-dimensional ultrastructure of normal rat hepatocytes by quick-freezing and deep-etching method.

The three-dimensional ultrastructure of nuclei and cell organelles including rough-surfaced endoplasmic reticulum (RER), mitochondria, and cytoskeleton were studied in normal rat hepatocytes by the quick-freezing and deep-etching method. Peroxisomes and mitochondria were observed as spherical structures with granular matrices. Peroxisomes were identified by their size and matrices, which were more condensed than those of mitochondria. Ribosomes were identified as granular structures and were attached to the surface of endoplasmic reticulum. Cytoskeletal filaments were identified by their differences in diameter on the replica membranes, as well as in conventional ultrathin sections. Microfilaments were mainly localized around the bile canaliculi and adjacent to sinusoids. Intermediate filaments were observed around the bile canalicular microfilaments. Only a few filaments were observed near the lateral plasma membranes. Cross-bridges measuring 5-7 nm in diameter were localized between the lamellae of RER and the surface of mitochondria. The quick-freezing and deep-etching method could be used to clarify the three-dimensional association between the cytoskeleton and membrane-bound organelles in hepatocytes.

Heterogeneity of Leukemic Cells with Basophilic Features: Cytochemical, Ultrastructural and Immunophonotypic Analysis of 8 Cases.

We have studied leukemic cells, derived from acute nonlymphocytic leukemia with basophilic features and basophilic crisis of chronic myelogenous leukemia (CML), by cytochemical and ultrastructural examination and analysis of surface markers. Cytochemical results varied from case to case, while the ultrastructural appearances of the granules were different from normal granules. The granules had more delicate granular matrices with or without myelinoid figures, whorled or scroll matrix, multivesicular bodies structures, theta granules, and crystalloid structures. Leukemic cells in all cases had myeloid surface markers with some degree of variability. In addition, they were occasionally positive for lymphoid markers, but not for CD10 and IgE receptors. The present results show that leukemic cells with basophilic features are heterogeneous in their morphology, cytochemistry and surface markers.

Ultrastructure of granulated cells in the bile duct of reindeer

The presence and ultrastructural characteristics of mast cells and globule leucocytes in bile ducts of the reindeer have not been previosly documentated. Tissue blocks of ductus bepaticus communis from six reindeer were processed by commonly used methods for TEM and examined with a JEOL JEM 100 S electron microscope. The present material originates from reindeer without clinical signs of parasites. However, several types of granulated cells were identifiable. The granules of connective tissue and subepithelial mast cells were small and mostly diffusely electron dense but also fine granular matrices were shown. The globules of intraepithelial globule leucocytes were fewer in number and distinctly larger than the granules of the mast cell. In addition there were noted intraepithelial granulated cells appearing similar to the neuroendocrinic cells reported in bovine bile ducts.

Sustained release albumin microspheres containing antibacterial drugs: Effects of preparation conditions on kinetics of drug release

Albumin microspheres containing a variety of antibacterial drugs were prepared using bovine, egg and human albumin. The effects of such preparation conditions as denaturation time, denaturation temperature, agitation rate and concentration of cross-linking agent on the extent of drug incorporation and size of microspheres were determined. The release of chlorhexidine dihydrochloride and diacetate, metronidazole and cetylpyridinium chloride from various bovine, egg and human albumin microspheres were determined as a function of the pH of the release medium and with agitation of the release medium. The release rates from such microspheres were also studied in the presence of a proteolytic enzyme, pepsin, in the release medium. The kinetics of release from albumin microspheres containing the four drugs were compared to the theoretical models of Baker and Higuchi for diffusional release from spherical matrices. The kinetics of release of the drugs from albumin microspheres conformed to the Higuchi model. The effects of such release medium variables as agitation, pH and presence of enzymes, combined with electro micrographs of the microsphere surface and interior, suggest that release of drugs from microspheres occurs via leaching of the drug from spherical granular matrices.

Chromosomes of amphibian oocytes as a model for gene expression: significance of lampbrush loops.

Amphibian lampbrush chromosome loops exhibit morphological variability in their RNP matrix. The biological significance of such variability remains unknown. In order to approach this problem, the structural organization of each RNP matrix type was analyzed in relation to transcriptional and post-transcriptional processes. First, autoradiographic and transcription inhibition studies in conjunction with macromolecular spread analysis revealed a particular transcription pattern in the most typical loops, i.e. the globular loops. This pattern was characterized by asynchronous variations in RNA synthesis in the different transcription units present in a given loop. Second, morphological and experimental studies provided evidence that the typical morphologies of different RNP matrices were interconvertible and that the differences between the different RNP matrices resulted from various degrees of tightness in packaging of transcription products. In particular, analysis of thermic-shock-induced changes in the structure of lampbrush chromosomes enabled us to visualize the progressive disorganization of dense RNP matrices into globular, granular and normal matrices. Furthermore, these studies suggested that changes in post-transcriptional processes might play a determining role in the specific morphology of the loops. In particular, the kinetics of each of these different processes, related to one another and/or proteins specific to one or another of these processes, might determine the morphological appearance of the loops. The immunological approach revealed that specific nuclear proteins might therefore interfere with each of these processes. Third, the problem of a possible relationship between the specific morphologies of lateral loops and the expression of particular DNA sequences was approached at the molecular level.

Structure of landmark loop ribonucleoprotein matrices in Pleurodeles waltlii lampbrush chromosomes visualized by scanning electron microscopy.

Landmark loop ribonucleoprotein (RNP) matrices of Pleurodeles waltlii lampbrush chromosomes were systematically examined by scanning electron microscopy (SEM). The results, which corroborated similar studies by electron microscopy (EM), showed that RNP transcripts in normal loops, and RNP matrices in granular, globular and dense loops, are composed of one basic structure: an RNP particle with a diameter of 30 nm. SEM observations also clarified the spatial arrangement of this particle in the RNP matrices of all the loop types examined. The specific morphology of normal, granular, globular and dense loop RNP matrices depended on the degree of compaction of the transcription products; this compaction resulted both from the packaging of RNP transcripts and the progressive coiling of the loop axis.

Microbody-like organelles as taxonomic markers among oomycetes

Zoospores of Oomycetes contain a variety of microbody-like organelles with highly structured matrices. Although in general their function is unknown, the appearance of similar organelles in related taxa suggests the ultrastructural differences could be used as taxonomic characters. This study surveys microbody-like organelles of oomycetous zoospores to determine if this is an additional criterion by which the phylogeny of these fungi can be evaluated. In zoospores of the order Saprolegniales, kinetosome-associated organelles (K-bodies) are found which typically consist of tubular and/or granular matrices. K-bodies are not found associated with kinetosomes in zoospores of the Peronosporales, but microbodies containing tubules, and in some genera marginal plates, are located near the kinetosomes, along the groove, and in other peripheral areas. K-bodies have been reported in only one member of the order Lagenidiales. These K-bodies lack a granular matrix, but contain a single curved plate from which tubules arise, forming a cone. In the one genus of the Leptomitales examined, a similar K-body contains a plate and scattered tubules. Organisms with similar microbody-like organelles are probably more closely related than those with different types of microbody-like organelles. The presence of an organelle resembling K-bodies in zoospores of an alga in the Tribophyceae supports the phylogenetic association between algae and Oomycetes. A complete survey of Oomycete genera may well reveal intermediates between the structurally different types of microbody-like organelles, allowing the reconstruction of the phylogenetic history of an organelle.

Disseminated intravascular coagulation in Korean hemorrhagic fever.

To investigate the nature and role of coagulation and complement alterations in the pathogenesis of Korean hemorrhagic fever (KHF), the profiles from the early stages in 27 male patients were serially evaluated. Evidence of disseminated intravascular coagulation (DIC) was observed in 14 of the 27 patients (51.8%) sometime during the course of the disease. The earlier the coagulation tests were performed, the more frequently the evidence of DIC was found. The mean serum C3 concentration was significantly decreased during the early stages, while serum C4 concentrations revealed no significant variation. A significant decrease of the serum C3 concentration, however, was found only in the group with DIC. Korean hemorrhagic fever (KHF) is an acute, systemic disease characterized by fever, hemorrhagic manifestations, and renal failure. This disease has been known to occur from the Pacific Ocean to the Baltic Sea under various synonyms and toponyms including epidemic hemorrhagic fever, hemorrhagic nephrosonephritis and hemorrhagic fever with renal syndrome. Recent investigations demonstrated the identity of these conditions described from Korea, the Soviet Union, Japan, and China. Nephropathia epidemica of Scandinavia was also revealed to have a close serological relation to this disease, but with antigenic differences. The etiologic agent was identified in 1978 by Lee et al., who isolated a viral antigen from a field mouse, Apodemus agrarius coreae, which is the natural reservoir of this disease in Korea. The KHF or Hantaan virus has been propagated in cell cultures and observed electronmicroscopically. In thin sections, the virus was detected within the cytoplasmic granular matrices (viroplasms) of the infected cells. Virus particles were spherical and had an extremely electron-dense core. Negative-contrast staining showed that the virus had an icosahedral structure and annular surface capsomeres. The morphology and morphogenesis of the virus were similar to those of the orbiviruses. The characteristic pathologic findings observed in fatal cases of KHF are congestion and hemorrhage of the renal medulla, hemorrhage in the right atrial wall of the heart, and hemorrhage and necrosis in the anterior lobe of the pituitary gland. The microscopic characteristics of these lesions consist of hemorrhage, coagulation necrosis, and mononuclear cell infiltration. The clinical course of typical KHF may be divided into five phases, each designated for a characteristic physiologic aberration; febrile, hypotensive, oliguric, diuretic, and convalescent.(ABSTRACT TRUNCATED AT 400 WORDS)

ELECTRON MICROSCOPE APPEARANCE OF HANTAAN VIRUS, THE CAUSATIVE AGENT OF KOREAN HAEMORRHAGIC FEVER

The morphology and morphogenesis of three strains of Hantaan virus, which causes Korean haemorrhagic fever (KHF), were examined by thinsection and negative-contrast electron microscopy of infected A549 cell-culture specimens. In thin sections, virus was detected within cytoplasmic granular matrices (viroplasms) of the infected cells. Virus particles were spherical (diameter 73±5 nm), and had an extremely electron-dense core (diameter 47±6.5 nm). Replication and maturation of the virus seemed to occur in the viroplasm. As infection progressed, viral particles increased in number and were packed into the granular matrices as cytoplasmic crystalline arrays. Viruses seemed to be released from infected cells by cell dissolution. Negative-contrast staining showed that the virus had an icosahedral structure (diameter 80±2 nm) and annular surface capsomeres. Viruses clumped when exposed to anti-Hantaan virus serum from a convalescent patient. The morphology and morphogenesis of the virus were compatible with those of orbiviruses.

Formation of chlamydospores in Gilbertella persicaria

The cytological events involved in the transformation of vegetative hyphae of the zygomycete Gilbertella persicaria (Eddy) Hesseltine into chlamydospores were studied with light and electron microscopy. Thirty hours after sporangiospores were inoculated into YPG broth, swellings appeared along the aseptate hyphae. Later, septa, traversed by plasmodesmata, delimited each end of the hyphal swellings and compartmentalized these hyphal regions as they differentiated into chlamydospores. Nonswollen regions adjacent to chlamydospores remained as isthmuses. Two additional wall layers appeared within the vegetative wall of the developing chlamydospores. An alveolate, electron-dense wall formed first, and then an electron-transparent layer containing concentrically oriented fibers formed between this layer and the plasma membrane. Rather than a mere condensation of cytoplasm, development and maturation of the multinucleate chlamydospores involved extensive cytoplasmic changes such as an increase in reserve products, lipid and glycogen, an increase and then disappearance of vacuoles, and the breakdown of many mitochondria. Underlying the plasma membrane during chlamydospore wall formation were endoplasmic reticulum, multivesicular bodies, vesicles with fibrillar contents, vesicles with electron-transparent contents, and cisternal rings containing the Golgi apparatus marker enzyme, thiamine pyrophosphatase. Acid phosphatase activity was localized cytochemically in a cisterna which enclosed mitochondria and in vacuoles which contained membrane fragments. Tightly packed membrane whorls and single membrane bounded sacs with finely granular matrices surrounding vacuoles were unique during chlamydospore development. Microbodies were rare in the mature chlamydospore, but endoplasmic reticulum was closely associated with lipid globules. As chlamydospores developed, the cytoplasm in the isthmus became highly vacuolated, lipid globules were closely associated with vacuoles, mitochondria were broken down in vacuoles, unusual membrane configurations appeared, and eventually the membranes degenerated. Unlike chlamydospores, walls of the isthmus did not thicken, but irregularly shaped appositions containing numerous channels formed at intervals on the inside of these walls. The pattern of cytoplasmic transformations during chlamydospore development is similar to events leading to the formation of zygospores and sporangiospores.

Ultrastructure of freeze-substituted hyphae of the basidiomyceteLaetisaria arvalis

The ultrastructure of freeze-substituted (FS) hyphae ofLaetisaria arvalis is described and compared to that of similar hyphae preserved by conventional chemical fixation (CF). The outline of membrane-bound organelles as well as the plasma membrane was smooth in FS cells. In contrast, hyphae preserved by CF exhibited membrane profiles that were extremely irregular. Centers of presumed Golgi activity were best preserved by FS. Microvesicles, 27–45 nm diameter and hexagonal in transverse section, were observed most readily in FS cells. Filasomes (= microvesicles within a filamentous matrix) were only observed in FS cells. Apical vesicles, 70–120 nm diameter, associated with the centers of Golgi activity and within the Spitzenkorper region exhibited finely granular matrices in FS hyphae, whereas in CF hyphae the contents were coarsely fibrous and less electron-dense. Microvesicles were present at hyphal apices and regions of septa formation. Filasomes were also found at regions of septa formation as well as along lateral hyphal tip cell walls. Microvesicles, but not filasomes, were observed in membrane-bound vesicles (= multivesicular bodies) and in larger vacuoles. Filaments, 5.2–5.4 nm wide, were juxtaposed with centripetally developing septa. Cytoplasmic inclusions, 20–40 μm in length, composed of bundles of 6.7–8.0 nm wide filaments were observed in both FS and CF hyphae.

Acute effects of cadmium on the spot Leiostomus xanthurus (Teleostei): tissue distribution and renal ultrastructure.

Spot (Leiostomus xanthurus) were exposed to 1, 5, 10, 15, and 25 ppm cadmium chloride for 48 h. Analysis by atomic absorption spectrophotometry showed that cadmium accumulated mainly in the liver, followed by heart, gut, kidney, and gill. Brain and body muscle did not concentrate the metal. Electron microscopy showed that the proximal tubule cells were severely affected by cadmium levels of 10, 15, and 25 ppm. The proximal tubule cells exhibited responses that ranged from an increase in heterogeneous bodies to epithelial desquamation. Mitochondria of degenerating proximal tubule cells showed changes similar to metal-poisoned mammalian kidney cells. Some mitochondria were contracted and dense while others were swollen with granular matrices and focal electron densities. In exposures of 25 ppm, Bowman's space of the renal corpuscle was swollen and often contained cellular debris. This study showed that after acute exposure to cadmium the metal accumulated mainly in visceral organs of the spot and at levels of 10 ppm and greater resulted in severe damage to proximal tubule cells of the kidney.