Amacrine cells, displaced amacrine cells and interplexiform cells in the retina of the rat

The amacrine cells in the retina of the rat are described in Golgi-stained whole-mounted retinae. Nine morphologically distinct types of cell were found: one type of diffuse cell, five types of unistratified cell, two types of bistratified cell, and one type of stratified diffuse cell. Measurements show that the largest unistratified cells have a dendritic field 2 mm across. One type of interplexiform cell is also described. Wide-field diffuse amacrine cells and unistratified amacrine cells were found with their somata located in either the inner nuclear layer or the ganglion cell layer. It is clear that there may be an amacrine cell system in the ganglion cell layer of the rat retina.     

Stem cells in the root and the problem of stem cells in plants

Plant cells are capable of reversible transition from the proliferating to the stem state. This transition is determined by a system of cell-cell interactions and interrelationships between plant parts. Stem cells defined as the cells preserving the capacity to divisions and differentiation for a long time arise repeatedly during development of the root and shoot primordial, rather than are clones of a population of stem cells laid down at a certain stage of embryogenesis. The quiescent center cells, rather than the surrounding actively dividing cells, best correspond to the characteristics of stem cells according to Loeffler and Potten. The factors that determine the quiescent center formation and maintenance in the root have been analyzed. The available data suggest that among these factors, indoleacetic acid transport and cap influence are of paramount significance. The cap formation precedes the quiescent center formation both during the root development and in the course of meristem regeneration after the root decapitation. The capacity of tem cell formation by the meristem suggests that not only meristem arises from the stem cells, but also that stem cells are formed from actively dividing cells. Repeated formation of stem cells allows long-term preservation of the capacity of plants for open morphogenesis and vegetative propagation.     

Stem cells in the root and the problem of stem cells in plants

Plant cells are capable of reversible transition from the proliferating to the stem state. This transition is determined by a system of cell-cell interactions and interelationships between plant parts. Stem cells defined as the cells preserving the capacity to divisions and differentiation for a long time arise repeatedly during development of the root and shoot primordial, rather than are clones of a population of stem cells laid down at a certain stage of embryogenesis. The quiescent center cells, rather than the surrounding actively dividing cells, best correspond to the characteristics of stem cells according to Loeffler and Potten. The factors that determine the quiescent center formation and maintenance in the root have been analyzed. The available data suggest that among these factors, indoleacetic acid transport and cap influence are of paramount significance. The cap formation precedes the quiescent center formation both during the root development and in the course of meristem regeneration after the root decapitation. The capacity of stem cell formation by the meristem suggests that not only meristem arises from the stem cells, but also that stem cells are formed from actively dividing cells. Repeated formation of stem cells allows long-term preservation of the capacity of plants for open morphogenesis and vegetative propagation.     

Role of dendritic cells in the induction of regulatory T cells

Dendritic cells (DCs) play a key role in initiating immune responses and maintaining immune tolerance. In addition to playing a role in thymic selection, DCs play an active role in tolerance under steady state conditions through several mechanisms which are dependent on IL-10, TGF-β, retinoic acid, indoleamine-2,3,-dioxygenase along with vitamin D. Several of these mechanisms are employed by DCs in induction of regulatory T cells which are comprised of Tr1 regulatory T cells, natural and inducible foxp3+ regulatory T cells, Th3 regulatory T cells and double negative regulatory T cells. It appears that certain DC subsets are highly specialized in inducing regulatory T cell differentiation and in some tissues the local microenvironment plays a role in driving DCs towards a tolerogenic response. In this review we discuss the recent advances in our understanding of the mechanisms underlying DC driven regulatory T cell induction.     

Comparative anatomy of oil cells and mucilage cells in the leaves of the Lauraceae in China

The distribution density of oil cells, the morphology and structure of both oil and mucilage cells, and their localization in the mesophyll of 112 species, 5 varieties and 2 forms in 21 genera of the Lauraceae are comparatively studied with the methods of tissue clearing and paraffin sectioning. The results show that there exist obvious differences of the distribution density of oil cells among the species in the Lauraceae. The presence of oil cells and mucilage cells is found to be a marked anatomical feature of the leaves in most of the plants in the Lauraceae. Their distribution in the mesophyll can be divided into 4 types: type Ⅰ , in which only oil cells are present; type Ⅱ, in which both the oil and mucilage cells are present; type Ⅲ, in which only mucilage cells are present; type Ⅳ, in which neither oil cells nor mucilage cells are present. The distribution density of oil cells, the distribution types of oil cells and mucilage cells and their localization in the mesophyll are of some taxonomic value at the specific level in the Lauraceae. In the whole Lauraceae or in some large genera, the evolutionary trend of the distribution types of oil cells and mucilage cells might be as follows: type Ⅰ → type Ⅱ →type Ⅲ →type Ⅳ. The characteristics of the 4 distribution types of oilcells and mucilage cells support the division of two subfamilies in the Lauraceae.     

中国樟科植物叶中油细胞和粘液细胞的比较解剖研究

利用组织透明法和石蜡制片法对樟科21属、112种、5变种和2变型植物叶中油细胞的分布密 度、油细胞与粘液细胞(腔)的形态结构及其在叶肉中的具体分布进行了比较研究。油细胞和粘液细胞 (腔)是樟科植物叶片解剖的显著特征,其在叶肉中的分布可以划分为4种类型：只有油细胞分布;只有 粘液细胞(腔)分布;油细胞和粘液细胞(腔)共存;油细胞和粘液细胞(腔)皆无。油细胞的分布密度、油 细胞与粘液细胞(腔)是否共存、是否单独存在或无,以及其具体分布部位等方面在种间存在一定的差 异,这对于属以下等级的区分具有一定意义。在本科内甚至在某些属内,油细胞和粘液细胞(腔)分布的 4种类型的演化趋势为：只有油细胞分布—油细胞与粘液细胞(腔)共存—只有粘液细胞(腔)分布—油细胞与粘液细胞(腔)皆无。油细胞和粘液细胞(腔)4种分布类型的划分支持樟科两个亚科的划分。     

Granulosa cells promote differentiation of cortical stromal cells into theca cells in the bovine ovary

Formation of a theca cell (TC) layer is an important physiologic event that occurs during early follicular development. Nevertheless, little is known concerning the nature and regulation of the formation of the TC layer during follicular growth. Using an established coculture system in this study, we examined the hypothesis that stromal cells differentiate into TCs during early follicular development and that this process involves interaction with granulosa cells (GCs). Ovarian stromal cells from the bovine ovarian cortex (S(C)) and medulla (S(M)) were cultured with or without GCs from small antral follicles. The presence of GCs increased the number of lipid droplets and mitochondria, and it stimulated androstenedione production in S(C) and S(M). However, luteinizing hormone/choriogonadotropin receptor (LHCGR) mRNA abundance and hCG-induced cAMP and androstenedione production were increased in S(C) but not in S(M) by the presence of GCs. The present results indicate that GCs are involved in the functional differentiation and the acquisition of LH responsiveness in stromal cells of the ovarian cortex. We suggest that GC-S(C) interaction is important in the formation of the TC layer during early follicular development, although the nature of this interaction remains to be determined.     

Mast cells and cells producing alpha-endorphin in the mucosa of the antral section of the stomach

The distribution of mast cells, alpha-endorphine-producing cells (AER-cells) and argyrophilic cells in lamina propria of the antral mucosa was determined quantitatively in 13 normal men. The cells were detected by histochemical and immunohistochemical (PAP) methods. The form and site of AER-cells resembled those of mast cells and mucosal argyrophilic cells (in lamina propria). The authors assume that part of human gastric mucosal cells have argyrophilic properties and contain alpha-endorphine.     

Biogenesis of lysosomes in marshall cells and in cells of the male reproductive system

The mechanism of plasma membrane trafficking and degradation is still poorly understood. This investigation deals with the biogenesis of lysosomes during endocytic flow in Marshall cells and in various cell types of the male reproductive system. Marshall cells were exposed to ammonium chloride (NH4Cl) and leupeptin after labeling with cationic ferritin. In some experiments, the treated cells were immunogold labeled with anti-prosaposin antibody. NH4Cl and leupeptin are lysosomotropic agents that affect the endosomal-lysosomal progression. Testes, efferent ducts and epididymis from mouse mutants with defects affecting plasma membrane degradation were also used to analyze this process. NH4Cl produced a retention of cationic ferritin in endosomes and hindered the endosomal/lysosomal progression. Leupeptin did not affect this process. NH4Cl decreased the labeling of prosaposin in endosomes and lysosomes, while leupeptin increased the labeling of prosaposin in lysosomes. The number of lysosomes per cytoplasmic area was higher in treated cells than in controls. These findings suggest that leupeptin affected lysosomes whereas NH4Cl affected both endosomes and lysosomes. The endosomal and lysosomal accumulation of prosaposin induced by the treatment with NH4Cl and leupeptin indicated that the site of entry of prosaposinwas both the lysosome and endosome. Electron microscopy (EM) of tissues from mouse mutants with defects affecting plasma membrane degradation substantiated these observations. The EM analysis revealed a selective accumulation of multivesicular bodies (MVBs) and the disappearance of lysosomes, in testicular fibroblasts, nonciliated cells of the efferent ducts and principal cells of the epididymis, suggesting that MVBs are precursors of lysosomes. In conclusion: (1) endosomes and MVBs are a required steps for degradation of membranes; (2) endosomes and MVBs are precursors of lysosomes; and (3) endosomes, MVBs, and lysosomes appear to be transient organelles.     

Immune cells associated with M cells in the follicle-associated epithelium of Peyer's patches in the rat

Summary Follicle-associated epithelium of Peyer's patches can be differentiated from nearby villous epithelium by the presence of M cells which are antigen-sampling epithelial cells, and by an increase in intraepithelial lymphocytes that are in close contact with M cells. The phenotype of the immune cells close to the M cells of the follicle-associated epithelium of rat Peyer's patches was determined by immunohistochemistry and compared with that of the intra-epithelial lymphocytes of the villous epithelium. Lymphoid T cells, predominantly of the cytotoxic/suppressor phenotype, were observed both in follicle-associated epithelium and in villous epithelium. Lymphoid B cells, mainly immunoblasts and plasma cells containing intracytoplasmic IgM, were present only in the follicle-associated epithelium, near M cells. Macrophages were also present, in contact with M cells, in follicle-associated epithelium, but not in villous epithelium. In addition, M cells bore Ia molecules on their apical membranes. These findings reinforce the concept of immune specialization of the follicle-associated epithelium, by demonstrating that this epithelium contains all the effector cells of immune responses.     

Peripolar cells form the majority of granulated cells in the kidneys of antelopes and goats

Investigation of renal cortical tissue in 5 adult hartebeests (Alcelaphus buselaphus cokii), 3 impalas (Aepyceros melampus), 1 defassa waterbuck (Kobus defassa) and 5 goats (Capra hircus) revealed large granulated peripolar cells at the junction between the parietal and the visceral epithelial layers of the renal corpuscles. All four animal species under study contained 1 or more peripolar cells for the majority of renal corpuscles sectioned through the vascular pole. In the hartebeests, up to 3 parietal cells and the first podocyte were granulated. Peripolar cells contained intracytoplasmic electron-dense membrane-bounded granules-200-2,800 nm in diameter in the hartebeests, 200-1,740 nm in the impalas, 150-950 nm in the waterbuck and 200-2,140 nm in the goats. Epithelioid granulated juxtaglomerular cells around afferent and efferent arterioles were rarely seen. When observed, they contained smaller granules than those of the peripolar cells. This distribution suggests that peripolar cells play a role in the regulation of body electrolytes and water, probably acting in concert with the renin-angiotensin-aldosterone system.     

Study of the interaction between germ cells and Sertoli cells in vitro

The nature of membrane components involved in the binding between Sertoli cells and pachytene spermatocytes in culture and the metabolic requirements for the binding to occur have been studied. Mild proteolytic digestion of germ cells by trypsin completely inhibited adhesion of germ cells to somatic monolayer. Protein synthesis and glycosylation were required to restore the adhesive properties of trypsin-treated germ cells, showing that surface molecules involved in the binding are glycoproteins. Trypsinization of germ cells after labelling causes a great reduction of several bands which become detectable again after 12 h of recovery from trypsin digestion. Among these, two bands with apparent molecular weight (MW) of 78 000 and 51 000 could be candidate components in cell adhesion.     

Stem cells in the eye

In the adult organism, all tissue renewal and regeneration depends ultimately on somatic stem cells, and the eye is no exception. The importance of limbal stem cells in the maintenance of the corneal epithelium has long been recognised, and such cells are now used clinically for repair of a severely damaged cornea. The slow cycling nature of lens epithelial cells and their ability to terminally differentiate into fiber cells are suggestive of a stem cell lineage. Furthermore, recent studies have identified progenitor cells in the retina and ocular vasculature which may have important implications in health and disease. Although the recent literature has become flooded with articles discussing aspects of stem cells in a variety of tissues our understanding of stem cell biology, especially in the eye, remains limited. For instance, there is no definitive marker for ocular stem cells despite a number of claims in the literature, the patterns of stem cell growth and amplification are poorly understood and the microenvironments important for stem cell regulation and differentiation pathways are only now being elucidated. A greater understanding of ocular stem cell biology is essential if the clinical potential for stem cells is to be realised. For instance; How do we treat stem cell deficiencies? How do we use stem cells to regenerate damaged retinal tissue? How do we prevent stem cell lineages contributing to retinal vascular disease? This review will briefly consider the principal stem cells in the mature eye but will focus in depth on limbal stem cells and corneal epithelium. It will further discuss their role in pathology and their potential for therapeutic intervention.