Transfer cells and lipid droplets of someValerianaceae

Development, structure and the axial distribution of transfer cells and their lignification were investigated inValerianella locusta, Valeriana officinalis, andV. tuberosa (Valerianaceae). Fundamental new results are: (1) Transfer cells often contain numerous lipid droplets. Within the stem the distribution of cells containing lipid droplets correlates to that of transfer cells. (2) InValeriana officinalis persisting protuberances are frequently found on pit membranes of xylem transfer cells. Lignified transfer cells can undergo a second modification: a layer covering the secondary wall forms wall ingrowths similar to those of transfer cells. (3) Peripheral pith cells, abuting transfer cells, are able to modify into transfer cells. Cambial derivatives are only temporarily developed as transfer cells. (4) Phloem transfer cells are found in vascular bundles of the whole axis. (5) In roots, xylem transfer cells are poorly developed or absent. (6) Oil cells with oil bodies are present in the rape ofValeriana tuberosa. They are absent however in the stem of the species investigated. (7) Tannins occur in elements of the primary cortex, phloem and secondary xylem ofValeriana officinalis.     

A comparative study of the epidermis of the common carp and the three Indian major carp

A comparative study has been made of the mucogenic epidermis of the common carp, Cyprinus carpio var. communis, and the three Indian major carps, Catla catla, Labeo rohita and Cirrhina mrigala: on the basis of epidermis structural organization, these species are easily differentiated. The epithelial cells in the superficial layer, as in most fishes, show secretory activity, evidenced by positive histochemical reactions, which is high in C. carpio var. communis, moderate in C. catla and low in L. rohita and C. mrigala. The epithelial cells in the underlying two or three layers also give positive reactions, though their intensity is relatively weak. The mucous cells in C. carpio var. communis are distributed in large numbers arranged in several superimposed layers in the outer regions of the epidermis, whereas in C. catla they are fewer in number and are widely separated in the surface layers as well as in the deeper layers of the epidermis; in both species the mucous cells appear rounded, large, and open on the surface by wide pores. In contrast, in L. rohita and C. mrigala the mucous cells are smaller, restricted mainly to the superficial layer, close together in a single row, and open on the surface by narrow pores. The overall density of mucous cells in L. rohita and C. mrigala, as in C. catla, is much lower than in C. carpio var. communis. In the epidermis of C. carpio var. communis there are a large number of mucous cells, and the few club cells are restricted to the deeper layers. In contrast, in the epidermis of the three Indian major carp the overall density of the mucous cells is much lower and the club cells are very numerous. It is suggested that the high density of club cells compensates an overall low density of mucous cells as an adaptation for an effective defence mechanism. Increased mucus production in the epidermis of C. carpio var. communis, as evidenced by a large number of mucous cells in outer regions and high secretory activity of superficial layer epithelial cells, is associated with increased precipitation of mud held in suspension, needed as an adaptation to the species’peculiar bottom-scooping habits. The varied density of the taste buds in the epidermis of the four carp is associated with their feeding habits.     

Cell lineage of the midline cells in the amphipod crustacean Orchestia cavimana (Crustacea, Malacostraca) during formation and separation of the germ band

 Cell lineages of identified midline cells were traced in the amphipod Orchestia cavimana (Crustacea, Malacostraca) by in vivo labelling. Midline cells are a common phenomenon in the germ band of crustaceans and insects. Studies in midline cells of Drosophila showed an origin from separate, paired anlagen and a differentiation into three types of cells. The in vivo labelling of midline cells of Orchestia demonstrates that they originate from the same material as the neural and epidermal ectoderm, divide in a stereotyped cell division pattern and give rise to at least two different types of cells. During the following evolutionarily derived mode of germ band elongation in Orchestia, a morphogenetic process is intercalated that separates germ band halves. On the level of single cells, it can be shown that midline cells are the only ectodermal cells that bridge the large distance between the separated parts. The cells are stretched extensively but do not proliferate. Comparing the midline cells of Orchestia with non-malacostracan crustaceans and insects, the results favour the hypothesis that midline cells are a distinct population of cells homologous in crustaceans and insects. Received: 24 July 1998 / Accepted: 13 October 1998     

Isolation of genes predominantly expressed in guard cells and epidermal cells of Nicotiana glauca

Guard cells are specialized and metabolically active cells which arise during the differentiation of the epidermis. Using Nicotiana glauca epidermal peels as a source of purified guard cells, we have constructed a cDNA library from guard cell RNA. In order to isolate genes that are predominantly expressed in guard cells, we performed a differential screen of this library, comparing the hybridization of a radiolabeled cDNA probe synthesized from guard cell RNA to that from a mesophyll cell cDNA probe. Sixteen clones were isolated based on their greater level of hybridization with the guard cell probe. Of these, eight had high homology to lipid transfer protein (LTP), two were similar to glycine-rich protein (GRP), and one displayed high homology to proline-rich proteins from Arabidopsis thaliana (AtPRP2, AtPRP4) and from potato guard cells (GPP). Northern analysis confirmed that one or more NgLTP genes, NgGRP1, and NgGPP1 are all differentially expressed, with highest levels in guard cells, and low or undetectable levels in mesophyll cells and in roots. In addition, all are induced to some degree in drought-stressed guard cells. NgLTP and NgGRP1 expression was localized by in situ hybridization to the guard cells and pavement cells in the epidermis. NgGRP1 expression was also detected in cells of the vasculature. Genomic Southern analysis indicated that LTP is encoded by a family of highly similar genes in N. glauca. This work has identified members of a subset of epidermis- and guard cell-predominant genes, whose protein products are likely to contribute to the unique properties acquired by guard cells and pavement cells during differentiation.     

Electron cytochemical study of carbogydrate components of surface membrane in cultured glial cells of the snailHelix pomatia

Using a variety of colloidal gold-labelled lectins, the structure and topography of carbohydrate determinants of the surface membrane in different types of cultured glial cells of the snailHelix pomatia have been electron cytochemically investigated. Analysis of lectin binding having different sugar specificities have shown heterogeneity of carbohydrate pools between glial and nerve cells and among different types of glial cells. It was found that satellite glial cells displaying ultrastructural traits of intensive metabolism (type II cells) selectively bindGNA, which is specific for terminal -D-mannose residues, and do not interact (Con A) or slightly interact (LCA) with other mannose-specific lectins.GNA determinants remain during the whole period of cell growth and are absent in satellite type-I glial cells, fibrous glial cells, microglia, and neurons.LTA, PVA, andLABA do not bind to any glial cells.WGA determinants, which are abundant on the neurons, are completely absent onGNA-binding glial cells and single on other types of glial cells. The density ofPNA determinants on microglial cells is the highest, as compared with other types of glial cells or neurons. It is concluded that some lectin determinants (forRCA-1, PNA, LPA) are present on all types of glial cells, while another determinant (GNA) is specific for a certain type of glial cells only and can serve as a marker of these cells. The role of specific carbohydrate determinants for neuron-glia interaction in mature brain is discussed.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 177–189, May–June, 1994.     

Strategy of Production and Utilization of Immortal Cells

The current methods of production of conditionally immortal cells in vivo and in vitro have been considered, including the method based on transgenesis of animals. Examples are given for utilization of conditionally immortal cells obtained in vivo from tissues of transgenic mice and rats carrying the gene of mutant T-antigen tsA58 SV40. The recent studies were analyzed, which concern the investigation and utilization of embryonic and regional stem cells, as well as immortal cells obtained through transfection of the recombinant construct of telomerase gene into human cells. The main problems of cell biotechnology are discussed.     

Unusual Leucophore‐Like Cells Specifically Appear in the Lineage of Melanophores in the Periodic Albino Mutant of Xenopus laevis

In the periodic albino mutant (a^p/a^p) of Xenopus laevis, peculiar leucophore‐like cells appear in the skins of tadpoles and froglets, whereas no such cells are observed in the wild‐type (+/+). These leucophore‐like cells are unusual in (1) appearing white, but not iridescent, under incident light, (2) emitting green fluorescence under blue light, (3) exhibiting pigment dispersion in the presence of α‐melanocyte stimulating hormone (αMSH), and (4) containing an abundance of bizarre‐shaped, reflecting platelet‐like organelles. In this study, the developmental and ultrastructural characteristics of these leucophore‐like cells were compared with melanophores, iridophores and xanthophores, utilizing fluorescence stereomicroscopy, and light and electron microscopy. Staining with methylene blue, exposure to αMSH, and culture of neural crest cells were also performed to clarify the pigment cell type. The results obtained clearly indicate that: (1) the leucophore‐like cells in the mutant are different from melanophores, iridophores and xanthophores, (2) the leucophore‐like cells are essentially similar to melanophores of the wild‐type with respect to their localization in the skin and manner of response to αMSH, (3) the leucophore‐like cells contain many premelanosomes that are observed in developing melanophores, and (4) mosaic pigment cells containing both melanosomes specific to mutant melanophores and peculiar reflecting platelet‐like organelles are observed in the mutant tadpoles. These findings strongly suggest that the leucophore‐like cells in the periodic albino mutant are derived from the melanophore lineage, which provides some insight into the origin of brightly colored pigment cells in lower vertebrates.     

Ultrastructure of neuroendocrine cells in the lungs of three anuran species

Neuroendocrine cells in the lungs of three species of anurans, Bombina variegata, Bufo bufo and Bu. viridis, occur both as single cells and in the form of neuroepithelial bodies. Neuroendocrine cells are covered by ciliated cells or pneumocytes, which separate them from the lumen of the lung. Neuroepithelial bodies are dispersed in the apical part of the main septa of lungs of Bo. variegata and Bu. bufo or are situated on special protrusions of septa in the lungs of Bu. viridis. Neuroepithelial bodies are innervated by intraepithelial nerve endings of afferent and efferent types.     

Ultrastructure of the taste disc in the red-bellied toad Bombina orientalis (Discoglossidae,Salientia)

The taste disc of the red-bellied toad Bombina orientalis (Discoglossidae) has been investigated by light and electron microscopy and compared with that of Rana pipiens (Ranidae). Unlike the frog, B. orientalis possesses a disc-shaped tongue that cannot be ejected for capture of prey. The taste discs are located on the top of fungiform papillae. They are smaller than those in Ranidae, and are not surrounded by a ring of ciliated cells. Ultrastructurally, five types of cells can be identified (mucus cells, wing cells, sensory cells, and both Merkel cell-like basal cells and undifferentiated basal cells). Mucus cells are the main secretory cells of the taste disc and occupy most of the surface area. Their basal processes do not synapse on nerve fibers. Wing cells have sheet-like apical processes and envelop the mucus cells. They contain lysosomes and multivesicular bodies. Two types of sensory cells reach the surface of the taste disc; apically, they are distinguished by either a brush-like arrangement of microvilli or a rod-like protrusion. They are invaginated into lateral folds of mucus cells and wing cells. In contrast to the situation in R. pipiens, sensory cells of B. orientalis do not contain dark secretory granules in the perinuclear region. Synaptic connections occur between sensory cells (presynaptic sites) and nerve fibers. Merkel cell-like basal cells do not synapse onto sensory cells, but synapse-like connections exist between Merkel cell-like basal cells (presynaptic site) and nerve fibers.     

Statistical features of impulse trains in cat's lateral geniculate neurons

The spontaneous discharges which recorded extracellularly from cells in the lateral geniculate nucleus (LGN) of a cat were classified into the following 3 main groups depending upon the shapes of their interval histograms and autocorrelation functions: the gamma type whose interval histogram is fitted by a gamma distribution function and whose autocorrelation function has some periodic property which damps down within about several 10 ms, the burst type whose interval histogram has a peak in the first bin (less than 8 ms) and whose autocorrelation function has a large positive peak within several msec, and the multimodal type whose interval histogram has a complex shape with three or more peaks and whose autocorrelation function has a periodic property. Each type of spontaneous discharge seems to be inherent at scotopic and mesopic backgrounds, and the cells whose spontaneous discharges are the gamma type, the burst type, and the multimodal type are called here a gamma cell, burst cell, and the multimodal cell, respectively. Gamma cells are subdivided into X- and Y-cells (gamma-X and gamma-Y cells), but burst cells are all Y-cells and multimodal cells observed up to now are all X-cells. It is clear that these various types of cells are distributed significantly differently in each lamina. All the cells that we found up to now in lamina A were either burst cells or multimodal cells, but every type of cell was found in lamina A1. The majority of cells in lamina C were the gamma type. In most cases, the peak values of the PST histograms of gamma-Y cells (especially, on-center cells) are larger than those of burst cells. These results suggest that Y-cells projecting to area 17 from laminae A and A1 are the burst type, and Y-cells projecting to area 18 from laminae C and A1 are the gamma-Y type.     

A comparative ultrastructural study of blood cells from nine insect orders

Summary An ultrastructual study of hemocytes from 9 different insect orders has led to the identification of 8 cell types: (1) Plasmatocytes, whose cytoplasm is filled with small dense lysosomes and large heterogeneous structures, are phagocytic cells. (2) Granulocytes, filled with uniformly electron dense granules, are involved in capsule formation. (3) Coagulocytes, which contain granules and structured globules and which possess a well developed RER, are involved in phagocytosis. (4) Spherule cells are filled with large spherical inclusions. (5) Oenocytoids are large cells with few cytoplasmic organelles. These 5 hemocyte types represent the majority of insect blood cells. (6) Prohemocytes, blastic cells which are one of the stem cells of hemocytes, are very few in number in each species investigated. (7) Thrombocytoids and (8) Prodocytes are restricted to a small number of insect species.The ultrastructural characteristics of these hemocyte types are discussed.     

Stellate cells in the Malpighian tubules of Drosophila hydei and D. melanogaster larvae (Insecta, Diptera)

 The Malpighian tubules of Drosophila hydei and D. melanogaster larvae are composed of two types of cell, principal cells and stellate cells. In the anterior larval Malpighian tubules approximately 26% (D. hydei) and 18% (D. melanogaster), respectively, of all cells are stellate cells. In the larvae of D. melanogaster, the stellate cells are fenestrated and the hemolymph space and tubule lumen are separated only by the basal lamina. Injection of dyes into the hemolymph did not indicate any facilitated transfer of substances through the fenestrated cells. The principal cells of the distal segment are carbonic anhydrase positive indicating transport activity, whereas the stellate cells lack this enzyme. In the stellate cells of the transitional segment, the sodium content is strikingly high in comparison to the neighbouring principal cells and lumen where no sodium was detected. This finding indicates that stellate cells reabsorb sodium as supposed earlier in 1969 by Berridge and Oschman (Tissue Cell 1:247–272). Accepted: 12 February 1999     

Effects of Thiamine Deprivation and Replacement on the Mitochondrion of Polytomella agilis*

SYNOPSIS. Late log-phase cells of Polytomella agilis, grown with or without thiamine, were examined by electron microscopy. The mitochondrial profiles of cells cultivated in the presence of thiamine are relatively few in number and irregular in shape. The inner membranes, randomly dispersed in a light matrix, are elongated, vesicular, or branched in appearance. In vitamin-deficient cells, numerous mitochondrial profiles are evident. They have a regular circular or ovoid appearance. The inner membranes are regularly arrayed in an electron-dense matrix and generally appear elongated. By means of partial 3-dimensional reconstruction of whole cells the appearance of mitochondrial profiles in vitamin-deficient cells can be explained by the increased branching of a single structure. Following transfer of vitamin-deficient cells to complete medium, normal mitochondrial structure is attained by ∼3 hr. Reduced-minus-oxidized difference spectra of suspensions of normal and vitamin-deficient cells, grown with gentle aeration, were recorded. The concentrations of a- and b-type cytochromes are reduced by 80-90%, and c-type cytochromes are reduced by 40% in thiamine-deficient cells.     

The ultrastructure of the vomero-nasal organ in reptilia

Summary There are three types of cells in the vomero-nasal organ of Lacerta sicula and Natrix natrix: receptor cells, supporting cells and basal cells. The receptor cells bear microvilli and no cilia. In Lacerta centrioles are lacking, indicating that the ciliary apparatus can have no essential significance in the transducer process. In Natrix centrioles occur in the deeper dendritic region. The structural constituents of the dendrites are mitochondria, microtubules and characteristic vesicles the properties of which are described. The perikarya which have uniform structure send off axons of about 0.2 diameter. The supporting cells show signs of a very moderate secretory activity, which is different among the species investigated. The microvilli of the supporting cells are not distinguishable from those of the receptor cells. The dendrites of the latter are completely isolated by the apical parts of the supporting cells. The sheet-like processes of the supporting cells contain strands of tonofilaments and do not cover the perikarya of the receptor cells completely. Thus adjacent sensory cells or dendrites and sensory cells are separated among themselves only by the normal intercellular space. The ratio of sensory cells to supporting cells is about 71. The basal cells resemble the supporting cells and replace these in the lower portion of the epithelium. The typical cellular junctions between sensory cells and supporting cells are described. There are no true tight junctions in the vomero-nasal sensory epithelium, and they are most probably absent from the nasal mucosa too. This absence would seem to indicate special conditions for cellular communication and the accessibility of the intercellular space for certain molecules. There is no sign of regeneration of sensory cells. Both immature blastema cells and degenerating receptor cells are not discernible.     

Dual origin of melanocytes defined by Sox1 expression and their region‐specific distribution in mammalian skin

Melanocytes are pigment‐producing cells generated from neural crest cells (NCCs) that delaminate from the dorsal neural tube. The widely accepted premise that NCCs migrating along the dorsolateral pathway are the main source of melanocytes in the skin was recently challenged by the finding that Schwann cell precursors are the major cellular source of melanocytes in the skin. Still, in a wide variety of vertebrate embryos, melanocytes are exclusively derived from NCCs. In this study, we show that a NCC population that is not derived from Sox1⁺ dorsal neuroepithelial cells but are derived from Sox1^? cells differentiate into a significant population of melanocytes in the skin of mice. Later, these Sox1^? cells clearly segregate from cells that originated from Sox1⁺ dorsal neuroepithelial cell‐derived NCCs. The possible derivation of Sox1^? cells from epidermal cells also strengthens their non‐neuroepithelial origin.     

Symposium 10: Differentiation Plasticity of Stem Cells. Direct differentiation of radial glial cells from embryonic stem cells

The major role of radial glial cells in neuronal development is to provide support and guidance for neuronal migration. In vitro, neurons, astrocytes and oligodendrocytes have also been generated from neural stem cells and embryonic stem cells, but the generation of radial glial cells in vitro has not yet been reported. Since radial glial cells can lead to neurons and astrocytes during brain development, neurogenesis and gliogenesis of stem cells in vitro may at least in part also utilize the same mechanisms. To test this hypothesis, we utilized five different clones of embryonic (ES) and embryonal carcinoma (EC) stem cell lines to investigate the differentiation of radial glial cells during in vitro neural differentiation. Here, we demonstrate that radial glial cells can be generated from ES/EC cell lines. These ES/EC cell‐derived radial glial cells are similar in morphology to radial glial cells in vivo. They also express several cytoskeletal markers that are characteristics of radial glial cells in vivo. The processes of these in vitro‐generated radial glial cells are organized into scaffolds that appear to support the migration of newly generated neurons in culture. Like radial glial cells in vivo, they appear to differentiate subsequently into astrocytes. Differentiation of radial glial cells may be a common pathway during in vitro neural differentiation of ES cells. This novel in vitro model system may facilitate the investigation of regulation of radial glial cell differentiation and its biological function. Acknowledgements: Supported by USPHS Grant NS11853 and a grant from the Children's Medical Research Foundation.     

The systematic significance of surface features of theBalanophora tuber (Balanophoraceae)

The surface ofBalanophora tubers consists of a nonepidermal layer made up of two distinctive types of cells, armature cells and stellate wart cells. Both cell types are provided with a heavy wall, and are dead at maturity. Stellate warts in the three species investigated,B. elongata, B. fungosa, andB. hansenii, séem to be uniform in appearance, but armature cells are extremely distinctive for each species. They are present in large, agglomerate masses in the first, singly or in very small clusters in the second, and as completely free, individual, acicular cells in the third species. Such differences are believed to be significant systematically, and the separation ofB. hansenii is thus probably justified. Notwithstanding superficial similarities, stellate warts do not seem to be comparable to the lenticels of other plants.     

Adrenocorticotrophin secreting cells in the hypophysis of the brown spiny mouseMus platythrix (Bennett)

Adrenocorticotrophin secreting cells are identified in the hypophysis of the brown spiny mouseMus platythrix by conventional methods of light microscopy. Quantitative data showed that certain smaller acidophilic cells in thepars distalis, under conditions provoking their hypersecretion such as unilateral adrenalectomy and metopirone treatment, increase in number and size from the pre-existing corticotrophs. There is no evidence for the transmigration of these cells from the chromophobes, basophils or any other cell type. Thepars intermedia revealed two types of cells of which the type II cells are histochemically identical to adrenocorticotrophin secreting cells of thepars distalis     

Ultrastructure of Volvox carteri

Summary Somatic cells of mature asexual colonies of Volvox carteri do not possess a true cell wall, but are otherwise similar in ultrastructure to Chlamydomonas. Somatic cells are embedded in multilayered fibrillar material of the colonial matrix. The reproductive cells (gonidia) of Volvox carteri lie internal to the somatic cell layer of the colony matrix in an apparently structureless portion of the colony matrix. Mature gonidia are large vacuolate cells with a central nucleus and parietal chloroplasts and mitochondria. They are non-flagellated at maturity, but each contains a pair of kinetosomes.