Ultrastructural examinations of HeLa cells exposed to cadmium ions

Destructive changes in cadmium-treated HeLa cells affecting practically all the cell structures and organelles, were observed. Side by side with it compensation and adaptation responses of cells, which in definite period reduced cell pathological effect of this microelement were revealed.     

Ultrastructural changes in Mycobacterium rubrum cells exposed to sulfochloranthine

The object of this work was to study the effect of sulfochlorantine (SCA), a new disinfecting compound containing chlorine, on Mycobacterium rubrum cells. The sensitivity of the cells to this agent was studied as well as their ultrastructure at the doses 0.01, 0.025, 0.05 and 0.1%. Even at high doses, the cells did not die off immediately when their growth and division stopped. Changes in the ultrastructural organization of the cells depended on the concentration of SCA. The structure of the nucleoid, membranes and ribosomes was damaged. Considerable changes were found in the formation of cross septa. The structure of the cells wall was modified to a lesser degree. The results are consistent with the biochemical data available.     

Ultrastructural changes in the mitochondria of Retzius' neuron exposed to hydrocortisone

The ultrastructure of the Retzius cell (gigantic neurone) mitochondria of the medical leech was investigated. After seven repeated injections of hydrocortisone into the coelomic cavity, the transformation of laminar cristae of mitochondria into tubule-vesiculated structures was discovered. A question of correlation between the structure and function independently of the systematical position of the organism is discussed.     

Ultrastructural changes in populations of the pertussis microbe exposed to antibiotics

The ultrastructural changes in the populations of the pertussis causative agent maintained for a prolonged period of time on nutrient media containing antibiotics were studied with the method of electron microscopy. Significant changes in the ultrastructure of the cells and the population composition due to the effect of tetracycline, levomycetin or erythromycin were observed. The ultrastructure of the populations affected by penicillin or streptomycin and their biological properties were most similar to those of the initial strains. The electronogrammes revealed morphological heterogeneity of the initial and experimental cultures and changes in the subpopulation composition induced by the antibiotics.     

Differential ultrastructural changes in tomato hormonal mutants exposed to cadmium

Cadmium (Cd) is a toxic heavy metal, which can cause severe damage to plant development. The aim of this work was to characterize ultrastructural changes induced by Cd in miniature tomato cultivar Micro-Tom (MT) mutants and their wild-type counterpart. Leaves of diageotropica (dgt) and Never ripe (Nr) tomato hormonal mutants and wild-type MT were analysed by light, scanning and transmission electron microscopy in order to characterize the structural changes caused by the exposure to 1 mM CdCl₂. The effect of Cd on leaf ultrastructure was observed most noticeably in the chloroplasts, which exhibited changes in organelle shape and internal organization, of the thylakoid membranes and stroma. Cd caused an increase in the intercellular spaces in Nr leaves, but a decrease in the intercellular spaces in dgt leaves, as well as a decrease in the size of mesophyll cells in the mutants. Roots of the tomato hormonal mutants, when analysed by light microscopy, exhibited alterations in root diameter and disintegration of the epidermis and the external layers of the cortex. A comparative analysis has allowed the identification of specific Cd-induced ultrastructural changes in wild-type tomato, the pattern of which was not always exhibited by the mutants.     

Antioxidant enzymes responses to cadmium in radish tissues

To investigate the antioxidant responses of radish (Raphanus sativus L.) to cadmium (Cd) treatment, seedlings of a tolerant variety were grown in increasing concentrations of CdCl(2), ranging from 0.25-1 mM, for up to 72 h in a hydroponic system. Analysis of Cd uptake indicated that most of the Cd accumulated in the roots, but some was also translocated and accumulated in the leaves, especially at the higher concentrations of Cd used in the experiments. Roots and leaves were analysed for catalase, glutathione reductase and superoxide dismutase activities. Catalase and glutathione reductase activities increased considerably in the roots and leaves after 24 h exposure to the metal, indicating a direct correlation with Cd accumulation. The analysis of native PAGE enzyme activity staining, revealed several superoxide dismutase isoenzymes in leaves, with the two predominant isoenzymes exhibiting increases in activity in response to Cd treatment. The results suggest that in radish, the activity of antioxidant enzymes responds to Cd treatment. The main response may be via the activation of the ascorbate-glutathione cycle for the removal of hydrogen peroxide, or to ensure the availability of glutathione for the synthesis of Cd-binding proteins.     

Ultrastructural changes in isolated rat hepatocytes exposed to different CCl4 concentrations

Ultrastructural data are presented on time-course changes in isolated rat hepatocyte suspensions exposed either to 1.2 or 1.8 mM CCl4 for up to 1 h. The subcellular changes at the lower concentration, but not the higher, are shown to closely parallel those reported to occur in rat hepatocytes following ingestion of CCl4.     

Ultrastructural changes in thyrocytes exposed to the antithyroid preparations betazin and diiodotyrosine

Ultrastructure changes in the thyroid gland cells of rats were studied when feeding of bethazine and diiodthyrozine to rats at doses 0.01, 0.1 and 1.0 mg/kg of body's weight for 12 months. The ultrastructure changes in thyrocytes typical both for hyper- and for hypofunction of the gland were revealed.     

Reactive oxygen species formation and cell death in catalase-deficient tobacco leaf disks exposed to cadmium

The physiological responses of tobacco (Nicotiana tabacum L.) to oxidative stress induced by cadmium were examined with respect to reactive oxygen species (ROS) formation, antioxidant enzymes activities, and cell death appearance in wild-type SR1 and catalase-deficient CAT1AS plants. Leaf disks treated with 100 or 500 µM CdCl₂ increased Evans blue staining and leakage of electrolytes in SR1 or CAT1AS plants, more pronouncedly in the transgenic cultivar, but without evidence of lipid peroxidation in any of the cultivars compared to controls. Cadmium significantly reduced the NADPH oxidase-dependent O ₂ ^? formation in a dose dependent manner in SR1 very strongly at 500 µM (to 5% of the activity in the nontreated SR1 leaf disks). In CAT1AS, the NADPH oxidase activity was constitutively reduced at 50% with respect to that of SR1, but the magnitude of the decay was less prominent in this cultivar, reaching an average of 64% of the C at 21 h, for both Cd concentrations. Hydrogen peroxide formation was only slightly increased in SR1 or CAT1AS leaf disks at 21 h of exposure compared to the respective controls. Cd increased superoxide dismutase activity more than six times at 21 h in CAT1AS, but not in SR1 and reduced catalase activity by 59% at 21 h of treatment only in SR1 plants. Despite that catalase expression was constitutively lower in CATAS1 compared to SR1 nontreated leaf disks, 500 µM CdCl₂ almost doubled it only in CAT1AS at 21 h. The mechanisms underlying Cd-induced cell death were possibly not related exclusively to ROS formation or detoxification in tobacco SR1 or CAT1AS plants.     

Ultrastructural pathologic changes of rat extraembryonic visceral endodermal cells exposed to teratogenic antibodies in vivo

It has been well established that certain heterologous tissue antibodies may induce abnormal embryonic development when injected into pregnant rodents during the organogenetic period. It has been postulated that these antibodies indirectly cause embryopathy by interfering with the normal functions of the yolk-sac placenta. The exact mechanism whereby these antibodies may induce placental pathology is not known. Specific teratogenic antibodies against a homogeneous rat kidney glycoprotein or a visceral yolk-sac glycoprotein antigen were injected intraperitoneally into 9th day pregnant rats. Electron microscopic examinations of the extraembryonic visceral endodermal cells of the egg cylinder were performed at 4, 6, 9, and 24 hours after the administration of the teratogenic antibodies. Control animals were injected with normal rabbit serum proteins. Extraembryonic visceral endodermal cells were similarly processed and examined as the experimental groups. The results seemed to indicate that the teratogenic antibodies induced increased autophagocytosis and morphologic changes associated with the phagolysosomes (secondary lysosomes) within the extraembryonic visceral endodermal cells at 9 hours following antibody administration. After 24 hours there was an apparent reduction or a complete disappearance of the supranuclear phagolysosome-like and lysosome-like structures, and the appearance of many large and small electron lucent vacuoles containing finely granular materials. Similar ultrastructural pathology was not observed in the 4 and 6 hour experimental and all of the control groups of animals. No other obvious intracellular or intercellular changes were observed in all of the experimental groups. Although the exact mechanism whereby the teratogenic antibodies may induce pathologic changes in the extraembryonic visceral endodermal cells remains to be determined, the present ultrastructural study demonstrated, for the first time, that teratogenic antibodies induced abnormal pathology in the extraembryonic visceral endodermal cells during the critical period of organogenesis.     

Ultrastructural changes in the plasma membrane of A-431 cells exposed to epidermal growth factor

The plasma membrane ultrastructural changes after the action of epidermal growth factor were studied in A-431 cells using freeze-fracture methods. The incubation with EGF (100 ng/ml, 0 degree C, 60 min) led to a decrease in density of intramembrane particles on the P surface of ventral cell membrane, while the number of coated pits increased there. The revealed effects of EGF may be related to direct consequences of EGF-receptor complex formation, because all the temperature dependent steps of its processing were blocked. The data obtained testify to an active involvement of the membrane ventral surface in the formation of cell response towards growth factors.     

Growth and protein profile changes in Lepidium sativum L. plantlets exposed to cadmium

Plant metabolic response to heavy metal stress is still to be clarified. The present investigation was undertaken to examine the influence of different concentrations of cadmium on the Lepidium sativum L. plantlets. Exposure of seedlings of L. sativum L. to increasing concentrations of cadmium results in the growth inhibition and in the accumulation of proteins in the 10–25 kDa range in cotyledons and hypocotyls of the plantlets. Most of these proteins are also found in extracts of L. sativum seeds. Analysis by ESI-MS after two-dimensional electrophoresis showed that these proteins exhibit sequences similar to those of storage proteins from various Cruciferae species. The response to metal exposure during germination and initial plantlet elongation thus involves inhibition of both storage protein catabolism and plant protein anabolism. In addition, two of the proteins present in higher amounts in plantlets exposed to cadmium heat-shock, in agreement with literature data, and jasmonate-like inducible protein are related to cellular stress and another two (LEAs or late embryogenesis abundant) are involved in embryogenesis. Changes in protein expression can be detected by two-dimensional electrophoresis after exposure to heavy metal concentrations lower than those at which morphometric changes become evident. Proteomics of germinating L. sativum thus constitutes a very sensitive tool for evaluating environmental pollution.     

Ultrastructural changes in the neural tube of 10-day-old mouse embryos exposed to colchicine and hydroxyurea

The ultrastructural changes in the neural tube of 10-day-old mouse embryos were investigated between 1.5 hr and 4 hr after application of either 1 mg/kg colchicine (Col) or 500 mg/kg hydroxyurea (HU) or simultaneous application of both substances. During the investigated period, the shape of the nuclei of the neuroepithelial cells had changed from elongated to round after Col application. The chromatin in the nuclei was condensed and arranged in clusters. A breakdown of polysomes into ribosomes and an enlargement of the rough ER was observed in the cytoplasm. At the luminal surface, bleb-like cytoplasmic processes of the neuroepithelial cells containing monoribosomes protruded into the lumen. No cell necroses were visible in the neural tube after Col application. A condensation of chromatin in the nuclei of some neuroepithelial cells was visible 1.5 hr after HU application. Shortly thereafter, cell necroses appeared in the neural tube and 4 hr after HU application the entire spinal cord was strongly damaged. After simultaneous application of Col and HU, the ultrastructural changes in the neuroepithelial cells of the neural tube did not differ from the results obtained after Col application alone. In contrast to the results obtained after HU application alone, no necroses occurred after simultaneous application of Col and HU.     

Growth parameters and photosynthetic pigments in leaf segments of Zea mays exposed to cadmium, as related to protection mechanisms

The influence of cadmium on growth parameters and photosynthetic pigment content was studied in maize leaf segments differing in tissue maturity. Experiments were carried out with maize seedlings Zea mays L. cv. Hidosil treated with 25, 50, 100, 150 and 200 microM Cd for 14 days under low light conditions. Tissue age-dependent decrease of fresh mass, dry mass and area of the leaf segments was correlated with Cd concentration in the growth medium. Cd induced changes in chlorophyll and carotenoid contents, and the specific areas and densities of the leaf segments were dependent on age and metal concentration. Results are discussed with respect to the protection mechanisms in the leaf segments.     

Ultrastructural and biochemical changes in Mycobacterium rubrum and Streptomyces bacillaris cells exposed to the herbicide semeron

The work was aimed at studying how the herbicide semerone affected the ultrastructure of two soil microorganisms, Mycobacterium rubrum and Streptomyces bacillaris. Depending on its concentration, the herbicide inhibited growth processes so that biomass yield decreased, cell division was interfered with, and giant and misshapen cells appeared. The herbicide taken at a concentration of 50-100 mg/ml increased the amount of membrane structures of the respiration type in some cells. This compound at a concentration of 400-500 mg/ml changed the nucleoid structure in certain cells. The decrease number of ribosomes and their peculiar distribution in the cell cytoplasm are most typical responses of the cells to the herbicide action. These responses were found in all cells at any of the tested herbicide concentrations. The results of cytological experiments are supported by statistically reliable data on the effect of the herbicide on RNA and protein synthesis. RNA synthesis is inhibited at a semerone concentration as low as 1 mg/ml, which is a very sensitive indicator of its presence in the medium.