Electron Microscopic Studies on the Silver-stained Nucleolar Cycle of Physarum polycephalum

The dynamic changes of nucleolar ultrastructure in the cell cycle of Physarum polycephalum Schw. were studied by an en bloc silver-staining method. The results showed that the nucleolus was large in size and situated in the center of the nucleus in late G2-phase, and the fibrillar centers, dense fibrillar components and granular components could be observed in the nucleolus. During prophase, the nucleolus moved towards the periphery of the nucleus and in late prophase disintegrated near the nuclear envelope. In metaphase, the disintegrated nucleolar components were dispersed in masses and located at the periphery of the chromosomal region of the nucleus. No specifically silver-stained area and argentophilic protein sheath were observed on the chromosomes, but there were some big dispersed silver particles within the chromosomes. During telophase the nucleolar components moved towards the two poles along with the chromosomes and co-existed with the decondensing chromatin in daughter nuclei. The nucleolar components then gradually converged with one another and separated from the chromatin. A big nucleolus was formed in the nucleus about 120 min after the completion of mitosis.     

The crooked neck dwarf muscular dysgenesis in fowl is due to a selective alteration of the somitic myogenic cell line

Summary Muscular dysgenesis in trunk and limb regions of the crooked neck dwarf (cn/cn) fowl is characterized by a complete disorganization of the muscles, starting at 7.5 days of incubation and resulting, at the end of the incubation period, in a profound muscular atrophy. It has previously been attributed to progressively extending defects of the myotubes. In this paper, embryonic cn/cn head and neck muscles were subjected to histological and ultrastructural analysis. The mononucleated myoblasts of the skeletal muscles are not diseased. Pathology is only expressed in the multinucleated cells, mainly by impaired sarcomerogenesis and distension of the sarcoplasmic reticulum. In the non-skeletal (cardiac or smooth) muscles, the connective tissue scaffolding and the ultrastructural features are similar to those of normal muscles at the same age. The present report confirms that the cn defect is confined to the skeletal muscle cells. All of them belong to the same lineage, which is contained in the somitic mesoderm, whether the latter becomes segmented or not during embryogenesis.     

Receptor mediated yolk protein uptake in the crab Scylla serrata: crustacean vitellogenin receptor recognizes related mammalian serum lipoproteins

The receptor-mediated uptake of major yolk protein precursor, vitellogenin (Vg) is crucial for oocyte growth in egg laying animals. In the present study plasma membrane receptor for Vg was isolated from the oocyte of the red mud crab, Scylla serrata. Vitellogenin receptor (VgR) protein was visualized by ligand blotting using labeled crab Vg ((125)I-Vg) as well as labeled low density lipoprotein ((125)I -LDL) and very low density lipoprotein ((125)I-VLDL) isolated from rat. The endocytosis of Vg was visualized in the crab oocyte by ultrastructural immunolocalization of Vg. The Vg receptor was purified by gel filtration high performance liquid chromatography (HPLC) and its molecular weight was estimated to be 230 kDa. In direct binding studies, the receptor exhibited high affinity (dissociation constant K(d) 0.8x10(minus sign6) M) for crab Vg. Vitellogenin receptor was observed to have an increased affinity to crab Vg in the presence of Ca(2+) and the binding was inhibited by suramin, suggesting similarities between crab VgR and low density lipoprotein receptor (LDLR) superfamily of receptor protein. Furthermore, the crab VgR showed significant binding ability to mammalian atherogenic lipoproteins such as LDL and VLDL. This suggests that there is a tight conservation of receptor binding sites between invertebrate (crab) Vg and vertebrate (rat) LDL and VLDL.     

Identification of toxic metals in affected algal cells in assays of wastewaters

Chlorella fusca was the test species used in assays of two wastewaters, one characterized by a high concentration of free metal ions, and the other by high concentrations of free metal ions and chlorinated organic compounds. Fine structural damage in cells exposed for six days to the effluents was examined using an electron microscope. In the presence of organic toxicity, the affected cells displayed a characteristically large build-up of starch grains. At high metal concentrations, the chloroplasts were the only organelles altered. Within the chloroplast, there were disruptions of the thylakoidal membranes and enlargement of interthylakoidal spaces. Excess metals, detected by X-ray microanalysis in the polyphosphate (poly-P) bodies of cells where chloroplast damage was observed, were regarded as harmful. X-ray scanning of particulate material in effluent samples is proposed as a useful and low cost addition to surveillance programmes.     

Water Buffalo (Bubalus bubalis) as a spontaneous animal model of Vitiligo

Vitiligo is a multifactorial acquired depigmenting disorder. Recent insights into the molecular mechanisms driving the gradual destruction of melanocytes in vitiligo will likely lead to the discovery of novel therapies, which need to be evaluated in animal models that closely recapitulate the pathogenesis of human vitiligo. In humans, vitiligo is characterized by a spontaneous loss of functional melanocytes from the epidermis, but most animal models of vitiligo are either inducible or genetically programmed. Here, we report that acquired depigmentation in water buffalo recapitulates molecular, histological, immunohistochemical, and ultrastructural changes observed in human vitiligo and hence could be used as a model to study vitiligo pathogenesis and facilitate the discovery and evaluation of therapeutic interventions for vitiligo.     

High Humidity and Heat Stress Causes Dissociation of Endoplasmic Reticulum in Tobacco Pollen

High humidity (95 % RH) and temperature (38/45 °C) stress for 4h applied to pollen grains of Nicotiana tabacum did not affect pollen viability, assessed on the basis of the fluorochromatic reaction test, but affected in vitro germination; pollen grains treated at 38 °C showed marked delay in germination, while those treated at 45 °C failed to germinate in vitro. The major ultrastructural effect of the stress was on RER. Stacks of RER, characteristically present in fresh pollen, were largely dissociated in the stressed pollen. The extent of dissociation of RER was greater in pollen samples stressed at 45 °C than at 38 °C. The generative cell did not show any obvious change in the stressed pollen. RER was restored in pollen grains which showed germination following culture; but not in those which failed to germinate. Apart from affecting other RER-related functions the dissociation of RER is likely to result in the destruction of long-lived mRNA and thus affect the ability of pollen grains to initiate protein synthesis needed for germination.     

Immunolocalization of keratin‐associated beta‐proteins in developing epidermis of lizard suggests that adhesive setae contain glycine–cysteine‐rich proteins

The localization of specific keratin‐associated beta‐proteins (formerly referred to as beta‐keratins) in the embryonic epidermis of lizards is not known. Two specific keratin‐associated beta‐proteins of the epidermis, one representing the glycine‐rich subfamily (HgG5) and the other the glycine‐cysteine medium‐rich subfamily (HgGC10), have been immunolocalized at the ultrastructural level in the lizard Anolis lineatopus. The periderm and granulated subperiderm are most immunonegative for these proteins. HgG5 is low to absent in theOberhäutchen layer while is present in the forming beta‐layer, and disappears in mesos‐ and alpha‐layers. Instead, HgGC10 is present in the Oberhäutchen, beta‐, and also in the following alpha‐layers, and specifically accumulates in the developing adhesive setae but not in the surrounding cells of the clear layer. Therefore, setae and their terminal spatulae that adhere to surfaces allowing these lizards to walk vertically contain cysteine–glycine rich proteins. The study suggests that, like in adult and regenerating epidermis, the HgGC10 protein is not only accumulated in cells of the beta‐layer but also in those forming the alpha‐layer. This small protein therefore is implicated in resistance, flexibility, and stretching of the epidermal layers. It is also hypothesized that the charges of these proteins may influence adhesion of the setae of pad lamellae. Conversely, glycine‐rich beta‐proteins like HgG5 give rise to the dense, hydrophobic, and chromophobic corneous material of the resistant beta‐layer. This result suggests that the differential accumulation of keratin‐associated beta‐proteins over the alpha‐keratin network determines differences in properties of the stratified layers of the epidermis of lizards. J. Morphol. 2013. © 2012 Wiley Periodicals, Inc.     

Ultrastructural features of chilling-injury in Episcia reptans

Abstract. Chilling the leaves of the extremely chill-sensitive plant Episcia reptans for only a few hours at 5°C causes ultrastructural changes such as swelling and disorganization of chloroplasts and mitochondria, and vesiculation of cytoplasmic membranes. Rewarming plants after 5–6 h chilling causes further deterioration in chloroplast and mitochondrial structure and the appearance of fibrous material in the cytoplasm of epidermal, mesophyll and vascular cells. The nature of the deposit is not known but it may be the cause of the rapid development of chilling-injury on return of plants to the warmth.