“Eumeiosi” e “Meiosi Apoomeotipica” Seguita da “Mitosi a Diplounivalenti” Nel Tessuto Somatico di Sambucus

Summary

The Authors describe in Sambucus nigra L the occurrence of the » apohomeotypic teiosis « followed by a »mitosis with diplounivalents « (Battaglia 1945, 1947) in ae somatic tissue of the style. The AA. observed also the occasional formation f four haploid nuclei and then the occurence of the »eumeiosis« (Battaglia 1945).     

Histological Study of Adventttious bud Formation on Lactuca Sativa Cotyledons Cultured In Vitro

Abstract

Cyto-histological changes accompanying the formation of adventitious buds in excised cotyledons of Lactuca sativa were studied during the first 12 days after planting in vitro. Prospective proliferating cells can first be recognized, already on the first day after planting, by a marked increase in nuclear and nucleolar volumes, followed on the second day by a burst of cell divisions involving particularly mesophyll cells. Then lignified elements develop together with meristematic center, forming a callus-like tissue in the inner part of the cotyledons. At the third day of culture, the epidermal cells start to divide with a periclinal wall followed by an anticlinal division. In the following days of culture the epidermal cells, which divide mainly with periclinal walls, form layers of cells below the surface, gradually filling up the intercellular spaces. From the 8^th day on, the buds protude above the surface and develops into shoots. These results are discussed in relation to DNA content of nuclei of Lactuca sativa cotyledons and to the time course of cell division and tracheary element formation. The very regular sequence of changes associated with the initiation and development of the bud makes the in vitro culture of Lactuca cotyledons an appropriate System for histochemical and biochemical studies.     

Comparative Histopathology of Plodia Interpunctella (Lepidoptera: Pyralidae) and Tribolium Castaneum (Coleoptera: Tenebrionidae) As Affected by Bacillus Thuringiensis Varieties Indiana or Morrisoni

The present study was initiated to compare the histopathology of two isolates of Bacillus thuringiensis (subsp. indiana and subsp. morrisoni), in the larval tissues of Plodia interpunctella (Hübner) and Tribolium castaneum (Herbst). Most changes were localized in the midgut. Other effects were observed in muscles and tracheoles. In P. interpunctella, larvae were treated with a lethal dose of 500 μg of B.t. subsp. indiana/g of grains. Changes appeared in midgut cells 8h after treatment. At 24h after treatment, cytoplasmic vacuolization was observed in the basal part of cells. Swollen epithelial cells were accompanied by swelling of the nuclei of columnar and goblet cells. The nuclei of the columnar cells were pycnotic and the membraneous sheaths were completely ruptured. The mitochondria had vacuoles 2h after treatment followed by complete lysis 24h after treatment. The circular and longitudinal muscles showed relaxation and disintegration of their fibrils and mitochondria. In T. castaneum, larvae were treated with a lethal dose of 5000 μg of B.t. subsp. morrisoni/g of grains. Changes appear in the regenerative cells, where cytoplasmic vacuolization and pycnotic nuclei were observed. The tracheal cells showed relaxation of the taenideal cuticular lining and disintegration of mitochondria and chromatin clumping granules around the nuclear membrane 48h after treatment. Seventy-two hours after treatment, the tracheal and circular muscle fibers showed complete relaxation. The two varieties of B.t. that were collected from grain dust in Egypt, have potential as control agents for stored-product moths and beetles. The toxic action differs in the two tested insect species.     

Laticiferous canal formation in fruits of <Emphasis Type="Italic">Decaisnea fargesii</Emphasis>: a programmed cell death process?

Programmed cell death (PCD), a topic of abiding interest, remodels plants at the cell, tissue, and organ levels involving various developmental processes of plants. The aim of this study is to provide a morphological characterization of evidence of PCD involvement in the laticiferous canal formation in fruit of Decaisnea fargesii. Several ultrastructural features of PCD have been observed including disintegration of vacuole and plasma membranes, cell wall degeneration, degenerated cytoplasm, abundant membrane structures and flocculent material, mitochondria and misshapen nuclei coupled with degraded plastids in vacuoles, and nuclei enveloped by rubber granule. In D. fargesii, the nuclei of the secretory epidermal cells become TUNEL-positive from the sunken stage to the late expanding stage, then DAPI-negative during the mature stage, indicating an early event of deoxyribonucleic acid (DNA) cleavage and a late event of complete DNA degeneration. Gel electrophoresis indicates that DNA cleavage is random and does not result in the laddering pattern indicating multiples of internucleosomal units. During the PCD of secretory epidermal cells, the rubber granules continue to be synthesized and accumulated in the secretory epidermal cells despite nuclear degradation. The PCD’s role in laticiferous canal formation suggests that PCD may play important roles in gland development of plants.     

Reduction of the number of nuclei per cell ofHelminthosporium euphorbiae by protoplast isolation

Helminthosporium euphorbiae is a pathogen of the weedEuphorbia heterophylla, which causes severe losses in soybean (Glycine max) crops. The fungus causes leaf loss and affects germination, making it a promising biocontrol agent for this weed. In order to start a breeding program for this species, four isolates were examined for number of nuclei in the conidia and hyphae and nuclear behavior at different cultivation stages. The conidia were multinucleated with about 20 nuclei per conidium, and 5 to 7 nuclei were observed in the hyphae compartments. The high number of nuclei makes the genetic manipulation of this species diffucult, so the protoplast formation is an alternative for obtaining cells with a reduced number of nuclei. Thus the experimental conditions for the production and regeneration of protoplasts inH. euphorbiae were determined by assessing three enzymatic complexes and seven osmotic stabilizers. The efficiency of formation and regeneration frequency of the protoplasts varied depending on isolates, stabilizers and enzyme mixture used. The number of nuclei estimated per protoplast was reduced to 1 to 6, depending on the stage of mycelial growth during the protoplast formation process.     

Distribution of ubiquitin protein in meristematic mesophyll ceils of barley leaves

The distribution of ubiquitin protein in meristematic mesophyll cells of barley (Hordeum vulgare L.) leaves was investigated by using immunofluorescence microscopy. Simultaneous observation of nuclei was achieved byDAPI (4 6-diamidino-2-phenylindol-dihydrochloride) staining. A strong correlation between the chromatin organisation and the ubiquitin distribution could be observed. Interphase nuclei revealed an intense content of ubiquitin and accumulation of ubiquitin at the nuclear envelope, whereas condensed chromosomes of dividing cells excluded any ubiquitin appearance. During cell division, the aggregation of ubiquitin protein was detected in the area of the mitotic spindle in anaphase as well as the area of the cell plate in the late telophase.     

THE EVOLUTION OF PARASITISM IN RED ALGAE: CELLULAR INTERACTIONS OF ADELPHOPARASITES AND THEIR HOSTS1

In the initial stages of cell–cell interactions (spore germination and host penetration), the adelphoparasites Gardneriella tuberifera Kyl. and Gracilariophila oryzoides Setch. & Wilson form infection rhizoids that fuse directly with underlying host epidermal or cortical cells. In so doing, parasite nuclei and other organelles enter the cytoplasm of the host. The resulting heterokaryon may fuse with adjacent host cells either directly, via secondary pit connections, or by the dissolution or dislodgment of pit plugs from existing pit connections. The cell fusion events result in a heterokaryotic syncytium in which parasite nuclei replicate. In Gardneriella, formation of the syncytium induces surrounding host tissues to divide to form a photosynthetic callus. The internalized syncytium forms conjunctor and rhizoidal cells that fuse with host callus, eventually transforming the host callus into cells containing parasite nuclei. Gracilariophila does not induce surrounding host tissue to divide. Rather, division of the initial heterokaryotic tissue gives rise to the colorless mantle that protrudes from the host and forms reproductive structures. The heterokaryotic tissue also fuses with underlying host cells, thereby spreading parasite nuclei throughout adjacent host cells. In both these adelphoparasites, transformation of host cells by parasite nuclear invasion results in plastid dedifferentiation, an increase in mitochondria, autolysis of organelles, and accumulation of large amounts of floridean starch. The development and physiology of these parasites is similar to normal post-fertilization processes in the hosts that give rise to carposporophytes and suggests that these adelphoparasites may have originated from perturbations of developmental pathways involved in their host's post-fertilization development.     

Luteinising hormone,follicle stimulating hormone and gonadotropin releasing hormone immunoreactivity in two insects: Locusta migratoria migratoroides R&F and Sarcophaga bullata (Parker)

Summary

Materials immunologically related to luteinising hormone (LH), follicle stimulating hormone (FSH) and the gonadotropin releasing hormone (GnRH) were localised in cerebral tissue of Locusta migratoria and Sarcophaga bullata by means of the peroxidase-antiperoxidase method. Several polyclonal and a monoclonal antisera were used. From the third larval instar a positive reaction was observed in cells located in several parts of the brain. Each antiserum reacted with a constant number of well defined cells and nerve fibers. No differences between sexes were observed.     

Comparative analysis of DNA nuclear content by flow cytometry on strawberry plants propagated via runners and regenerated from meristem and callus cultures

ABSTRACT

DNA variation may occur in plant species grown either in vivo or in vitro. In this study flow cytometric analyses were undertaken on Fragaria x ananassa Duch. runner plants, and on plants regenerated from callus cultures of leaf explants and from meristem cultures. Our aims were to investigate DNA variation in runner plants of different cultivars, and to compare DNA content in plants of the same cultivar obtained by different propagation procedures (i.e. from meristems or callus cultures). Plants growing in vitro and in the greenhouse were also compared. A good regeneration ability was observed in all the cultivars, with different percentages of shoot formation. No significant differences were detected in multiplication rate and rooting percentage within cultivars. This work documents the occurrence of DNA variations in strawberry plants in vivo and in vitro. Flow cytometric measurements of DNA content showed the presence of 4C nuclei, besides 2C nuclei, in runner plants of cultivar Pajaro. DNA content variations (2C/4C nuclei) were observed in plants regenerated from callus cultures. These variations were lost after transfer of the plants to the greenhouse, except for cultivar Don. The extent of such DNA variations was influenced by genotype. Our study confirms earlier reports indicating that DNA variation induced by in vitro culture could be lost or retained after transfer of the plants to the greenhouse.     

Ricerche Embriologiche su Senecio Vulgaris L. var. Thyrrenus Fiori

Abstract

Embryological researches on SENECIO VULGARIS L. var. THYRRENUS Fiori. — Male gametophyte, development of tapetal cells and female gametophyte have been studied in Senecio vulgaris L. var thyrrenus Fiori.

1) The development of male gametophyte is normal. Divisions of the microspore mother cells are of the simultaneous type. The division of the generative nucleus has never been observed till the pollen grain was in the anther.

2) The tapetal cells follow a very simple development. The nucleus of each cell divides only twice starting at the same time with the meiotic divisions of pollen mother cells but ending much earlier; subsequently, as usually happens with the Asteraceae, the ameboid involution of the tapetum begins. Endomitosis or any other process which leads to a polyploidy not due to nuclear fusion, has never been observed.

3) The female gametophyte is eight nucleate of the normal type (Polygonum). At maturity it shows only three antipodal cells whose nucleus undergoes at first, two or three divisions. Only later these new nuclei, always within the antipodal cell, may fuse in a polyvalent one.     

Osservazioni Sull'ultrastruttura Delle Cellule Tumorali di un Ibrido Interspecifico del Genere Nicotiana

Abstract

Ultrastructural study of tumor cells of an interspecific hybrid of the genus <Nicotiana>. — The ultrastructure of tumor cells of interspecific hybrids of Nicotiana paniculata × N. langsdorffii, has been investigated. A comparative analysis between meristematic and parenchymatic cells obtained from the tumors plants of the hybrid and the controll tissues indicates that the tumor cells have an altered structure of the nuclei and of the chloroplasts and a very poor cytoplasmic content. These modifications resemble those observed in cells from plants soffering of various metabolic disturbances. A study of structural modification occurring in the necrotic areas shows that the cells undergo aspecific alterations of organelles double mambranes followed by disruption of their structure and eventually condensation of the cytoplasmic matrix.     

The rad3-1 mutant is defective in axial core assembly and homologous chromosome pairing during meiosis in the basidiomycete Coprinus cinereus

We have utilized spreading methods as well as serial sectioning three-dimensional reconstruction to examine meiotic chromosome behavior in cells homozygous for the rad3-1 mutation in Coprinus cinereus. Comparison of 42 wild-type nuclei that had been spread, stained with silver, and viewed by electron microscopy with 30 mutant nuclei treated in the same manner revealed several defects in the mutant. Axial core formation was defective in the mutant, although limited side-by-side association of axial cores was observed. To detect any differences in three-dimensional architecture between the wild-type and mutant nuclei, we reconstructed three of the former and six of the latter after serial sectioning. It was not possible to trace the expected number of axial cores from section to section in the mutant, although some tripartite synaptonemal complex was observed. Many axial core ends failed to terminate in the nuclear envelope in the mutant. This spectrum of defects (incomplete axial core assembly with some tripartite synaptonemal complex formation) had not been observed previously in either C. cinereus or other systems. We conclude that this combination of spreading and sectioning methods is very useful for analysis of meiotic mutants. © 1993 Wiley-Liss, Inc.     

Formation of a micronuclei-like structure induced by colchicine treatment in Saccharomyces cerevisiae

Minute nuclei named “smaller nuclei” were generated when the cells of Saccharomyces cerevisiae were treated with colchicine. The formation of “smaller nuclei” seemed to be related to nuclear division because those nuclei were only produced under conditions suitable for nuclear division. The fact that the average DNA content of “smaller nuclei” was almost one tenth of that of the isolated normal diploid nuclei showed that the “smaller nuclei” are not condensed nuclei but aneuploid nuclei like micronuclei in animal cells. It appeared therefore likely that a micronuclei-like structure could be produced by colchicine treatment in S. cerevisiae.     

耻垢分枝杆菌感染人脐带间充质干细胞模型的建立及其特征

【背景】结核分枝杆菌(Mycobacterium tuberculosis, Mtb)休眠菌形成被认为是潜伏结核感染(latent tuberculosis infection, LTBI)的主要原因,但目前缺乏体内和体外模型进行机制研究。新近研究表明Mtb可感染间充质干细胞(mesenchymal stem cells, MSC)并以休眠状态在细胞中长期存活。然而Mtb感染细胞模型存在周期长和生物安全要求高等问题,需要探索可用的MSC感染细胞模型用于Mtb休眠机制的研究。【目的】建立快速生长型耻垢分枝杆菌(Mycobacteriumsmegmatis,Ms)感染人脐带间充质干细胞(human umbilical cord MSC, hUCMSC)的细胞模型并研究其特征。【方法】取分离好的hUCMSC,流式细胞术鉴定其表面标志性抗原;以Ms菌株感染hUCMSC,DiI标记细胞膜,荧光显微镜下观察细胞吞噬作用;平板法计数Ms胞内存活率;油红O染色观察细胞脂滴形成;鬼笔环肽荧光染色观察细胞骨架变化;实时荧光定量PCR(realtimequantitativePCR,RT-qPCR)检测Ms...     

Nuclear changes accompanying cell differentiation in stems of Pisum sativum L.

Summary Nuclear DNA, nuclear protein and nuclear size have been measured in cells of the cortex, pith and vascular tissue from three successive internodes in the stem of Pisum sativum. New techniques of computer-linked cytophotometry were used to measure these parameters simultaneously in both section and squash preparations. In cortical cells no endoreduplicated nuclei were seen in the internodes measured. In cortical cells from the oldest internode measured, a population of large nuclei with the 2C DNA amount was observed which was not present in the younger internodes. In the oldest pith nuclei measured a few 8C nuclei were present, but maturing pith was most characterized by increasing nuclear size and the population of nuclei accumulating with the 4C DNA amount. Polyploid nuclei were present in all of the vascular tissue measured, including the youngest internode. Maturing vascular tissue was also characterized by increasing nuclear size. Nuclear protein measurements demonstrated a close link between nuclear protein and nuclear size and suggest that increased nuclear size, with constant DNA content, may be due to increased nuclear protein. This raises the question of the nature and function of this nuclear protein, perhaps more characteristic of differentiating cells than dividing cells.To whom offprint requests should be sent     

Ploidy determination in Sphagnum samples from Svalbard,Arctic Norway,by DNA image cytometry

Abstract

We measured DNA content of cell nuclei, stained with the Feulgen method, using branch tips of 11 species of Sphagnum from Svalbard, Arctic Norway, as an alternative to chromosome counting. Nine species were haploid and two were diploid, with no intraspecific variation in ploidy level. The results conformed to known chromosome numbers and/or to expectations from isozyme studies. Ploidy levels were determined for the first time in S. tundrae and S. fimbriatum ssp. concinnum (haploid) and S. arcticum and S. olafii (diploid). No mitotic divisions were observed, but unreplicated interphase nuclei still allowed precise ploidy determinations. Basic DNA contents of all Sphagnum species were very similar, and measurement of a few nuclei proved sufficient to ascertain ploidy level despite very low nuclear DNA content. Advantages of the DNA image cytometry method are: mitotic or meiotic cells are not required to be found, and only a small amount of material is required.     

Some aspects of microsporogenesis of Welwitschia mirabilis Hook

Abstract

Microsporogenesis in Welwitschia mirabilis was studied by light and electron microscopy. The meiotic process is rapid, asynchronous and a regular aggregation of organelles was observed. In early prophase I the plastids and the mitochondria are positioned around the nucleus. At telophase I they are disposed in the equatorial plane of the meiocyte between the two nuclei of the dyad. At the end of telophase II they are arranged among the four nuclei of the tetrad. Microsporogenesis ends with simultaneous cytokinesis. Degeneration of meiocytes was often observed inside pollen sacs and appeared to be induced by environmental factors.     

Taenia crassiceps: Infections of male mice lead to severe disruption of seminiferous tubule cells and increased apoptosis

This research was carried out to study the effects of infection with Taenia crassiceps cysticerci on the seminiferous epithelium histoarchitecture in the testes of male mice. Our results showed a severe disruption of the histoarchitecture of the testis epithelium in infected mice. In these animals, a significant infiltration of macrophages within seminiferous tubules was observed (P < 0.001). Generalized apoptosis of germ cells within the seminiferous tubules was observed, as assessed by TUNEL assay and apoptotic nuclei were quantified. The total number of fluorescent objects (DNA) (including clusters, singles, and objects in clusters) was significantly higher in the infected cells than in the control group (P = 0.0286). Observation of the interstitial tissue showed disorder and deterioration of many Leydig cells of infected mice, as well as intense vacuolization and destruction of their inter-cellular junctions. Several ultrastructural abnormalities were observed through electron microscopy as well. The observed pathology could lead to a state of infertility.     

Accumulation of cells containing factor XIII subunit a around the foci of intense fibrosis in human epulides

Summary On the basis of clinical and biochemical findings, Factor XIII subunita (FXIII A) has been conjectured to play an important role in fibrotic processes. Epulis samples at different stages of fibrotic tissue formation were used as a model system for studying the localization and tissue distribution of FXIII A during the course of connective tissue generation. Marker characteristics of cells containing FXIII A (FXIII A⁺ cells) were determined as well. In double immunofluorescent labelling systems, FXIII A was localized in monocyte-derived (CD-14⁺), activated (HLA-DR⁺), and phagocytosing (Ki-M7⁺) tissue macrophages, which are widely distributed homogeneously in granulation tissues, but start to accumulate around foci of fibrosis as soon as the foci appear. During the relatively long process of fibrosis, FXIII A⁺ macrophages continuously decrease in number, and their morphological appearance changes from stellate to spindle-shaped. The nuclei of these cells were not labelled by Ki-67 monoclonal antibody; this indicating that they represent a non-proliferating cell population in the connective tissue stroma. The present findings may help to link theories concerning the role of FXIII A and those of macrophages in the connective tissue formation so far found separately in the literature.     

Number of nucleoli in various cell types of the mouse

The nucleoli of cells of the adult mouse were examined by staining with toluidine blue after removal of deoxyribonucleic acid from tissue sections by deoxyribonuclease treatment. The nuclei of each cell type examined contained one or more nucleoli. This was observed even in lymphocytes and neuroglia, although these cells have occasionally been described as anucleolated. In mature spermatids and spermatozoa, however, it was not possible to detect a nucleolus. The distribution of the number of nucleoli in many diploid cells exhibited a mode of two or three nucleoli per nucleus, and a range from 1 to 6 nucleoli. In presumedly diploid hepatic nuclei, the maximum number of nucleoli was six; but in presumedly tetraploid hepatic nuclei, it was 11. Thus, nearly twice as many nucleoli are present when the chromosome number is doubled. In view of this observation, it is suggested that six nucleolar organizers are present in the diploid chromosomal complement of the mouse. However, through failure of some nucleolar organizers or more probably through fusion of nucleoli, the number of these organelles in most nuclei is less than six.