Cell culture of mammalian thymic epithelial cells: growth, structural, and antigenic properties

The thymus plays an important role in the maturation and differentiation of T lymphocytes. Many of its functions have been attributed to its epithelial component. Past in vitro studies of putative thymic epithelial cells have been hampered by the inability to produce well-characterized cultures of these cells. Using lethally irradiated 3T3 cells as a feeder layer, we have succeeded in growing virtually pure cultures of thymic epithelial (TE) cells from rabbits, mice, and humans. Antikeratin staining provides an unambiguous criterion for positive identification of the epithelial cells. These cells were found to lack Ia-like or theta-like antigens. The ability to culture large quantities of mammalian TE cells should allow for their detailed functional characterization.     

Physico-chemical and antigenic properties of adenovirus filaments

Hydrophobic interactions are shown to be predominant in stabilization of the quaternary structure of the adenovirus fiber and in preservation of its antigenic activity. The computer analysis has revealed at least five peptides with maximal hydrophilicity in the fiber protein composition. They may participate in the formation of antigenic determinants. The presence of type-specific, subgenus-specific, intersubgenus-specific and new genus-specific (common for both human and monkey Ad) antigenic determinants are determined in the composition of the Ad h1 fiber by the enzyme-immunoassay.     

The antigenic properties of bacterial spores

Summary 1°. Bacterial spores are antigenic.2°. Spore-antigen is distinct and separate from the antigens of the bacillary forms to which the spores give rise on germination.3°. Antigens of the spores of various kinds of spore-bearing bacilli are also mutually distinct.I am greatly indebted to Miss A.de Groot for her technical assistence.     

Specificity and distribution of mammalian carnosinase.

Hog kidney carnosinase (EC 3.4.13.3) was found to have a narrow specificity; it hydrolyzed carnosine, anserine and glycyl-L-histidine, but did not split L-alanyl-L-histidine or homocarnosine. The isoelectric point of this enzyme was 5.8 and its molecular weight was about 84 000. Carnosinase was found to be widely distributed in various tissues of the rat. Uterus, kidney, liver and lung contained high levels of carnosinase, whereas moderate concentrations were found in spleen, heart and brain, with low levels in small intestine, skeletal muscle and stomach, and none in blood.     

哺乳动物味觉的细胞生物学

味觉对于生命具有重要作用,在一定程度上决定了动物对食物的选择。哺乳动物味觉识别主要依赖于舌味蕾中的味细胞,味蕾由50～100个极化的神经上皮细胞聚集而成。通过对味蕾细胞的分析显示,味蕾是一种精巧的单元结构。这篇文章综述了味蕾细胞的形态、结构功能、细胞生物学活性以及味觉信息的传导。     

Mitochondrial morphology and distribution in mammalian cells

It is now appreciated that mitochondria form tubular networks that adapt to the requirements of the cell by undergoing changes in their shape through fission and fusion. Proper mitochondrial distribution also appears to be required for ATP delivery and calcium regulation, and, in some cases, for cell development. While we now realise the great importance of mitochondria for the cell, we are only beginning to work out how these organelles undergo the drastic morphological changes that are essential for cellular function. Of the few known components involved in shaping mitochondria, some have been found to be essential to life and their gene mutations are linked to neurological disorders, while others appear to be recruited in the activation of cell death pathways. Here we review our current understanding of the functions of the main players involved in mitochondrial fission, fusion and distribution in mammalian cells.     

Tissue distribution of radioiodinated neoglycoproteins and mammalian lectins

Quantitation of tissue distribution of radioiodinated neoglycoproteins 1 h after intravenous injection into mice allowed to evaluate their suitability to uncover potential selectivity in tracer retention. Variations within the panel of neoglycoproteins were introduced to the carbohydrate determinant, its density and linkage to the carrier. Five arrays of neoglycoproteins, encompassing up to twelve different carbohydrate moieties were used. The individual response on the level of organ content showed differences, accounted for by carbohydrate structure and density. However, increase in sugar density eventually caused general decrease in tissue retention, emphasizing the importance of synthetic parameters. Attachment of sugar residues to the spacer via primarily the C-6 group of monosaccharides led to rather prolonged survival in circulation of the resulting neoglycoprotein compared to the application of neoglycoproteins with p-aminophenyl glycosides as derivatives for coupling. Besides applying neoglycoproteins tissue uptake was also measured for several organs, when four mammalian lectins were employed as radiotracers. These lectins bind to cellular carbohydrate ligands, namely beta-galactosides, alpha-fucosides or heparin. Differences were measured for retention in liver, kidneys, spleen, stomach, thymus and bone marrow. The distinct properties of different tissues with respect to binding of neoglycoproteins as well as to endogenous lectins, exhibiting a certain degree of selectivity, are a step within the framework to attempt to therapeutically exploit the carrier potential of probes by recognitive protein-carbohydrate interactions.     

Cell and fiber-type distribution of dystrophin

Duchenne muscular dystrophy is the result of dystrophin deficiency. We have determined the cell types likely to express the pathogenic effects of this neuromuscular disease by determining the pattern of dystrophin expression in normal cells. We find that all physiological types of muscle cells express dystrophin at similar levels, and that the dystrophin content of various tissues correlates with the myogenic cell population of each tissue. The dystrophin content of brain and spinal cord, however, is found not to correlate with any type of muscle cell, and it is suggested that neurons express dystrophin. The potential involvement of striated muscle fibers, the vasculature, and the nervous system in the etiology of Duchenne muscular dystrophy makes it likely that the disease is a complex disorder of combined pathogenesis. We also find that the dystrophic chicken does not represent an animal model for dystrophin deficiency.     

Cell lineage in mammalian craniofacial mesenchyme

We have analysed the contributions of neural crest and mesoderm to mammalian craniofacial mesenchyme and its derivatives by cell lineage tracing experiments in mouse embryos, using the permanent genetic markers Wnt1-cre for neural crest and Mesp1-cre for mesoderm, combined with the Rosa26 reporter. At the end of neural crest cell migration (E9.5) the two patterns are reciprocal, with a mutual boundary just posterior to the eye. Mesodermal cells expressing endothelial markers (angioblasts) are found not to respect this boundary; they are associated with the migrating neural crest from the 5-somite stage, and by E9.5 they form a pre-endothelial meshwork throughout the cranial mesenchyme. Mesodermal cells of the myogenic lineage also migrate with neural crest cells, as the branchial arches form. By E17.5 the neural crest-mesoderm boundary in the subectodermal mesenchyme becomes out of register with that of the underlying skeletogenic layer, which is between the frontal and parietal bones. At E13.5 the primordia of these bones lie basolateral to the brain, extending towards the vertex of the skull during the following 4-5 days. We used DiI labelling of the bone primordia in ex-utero E13.5 embryos to distinguish between two possibilities for the origin of the frontal and parietal bones: (1) recruitment from adjacent connective tissue or (2) proliferation of the original primordia. The results clearly demonstrated that the bone primordia extend vertically by intrinsic growth, without detectable recruitment of adjacent mesenchymal cells.