We sequenced the 5'-coding region of the human c-src gene, exons 2 through 5, corresponding to one-third of the human c-src protein consisting of 536 amino acids. Sequence analysis of the src type of protein kinases revealed that the amino-terminal region encoded by exon 2 contains sequences specific for the src proteins and raised the possibility that this region is involved in the recognition of a src-specific substrate(s) or receptor(s).

The unique sequence DNA's of several wild and cultivated fungi including Agaricus brunnescens (=Agaricus bisporus), Agaricus bitorquis, Amanita muscaria, Amanita phalloides, Pleurotus ostreatus, Lentinus edodes, and Schizophyllum commune were compared by DNA–DNA hybridization. In addition, the characterization of a number of fungal DNA's are reported for the first time. Unique sequence DNA from Agaricus brunnescens and P. ostreatus was labeled by nick translation and each was hybridized with an excess of unlabeled driver DNA. Unique sequence DNA from two different isolates of Agaricus brunnescens showed nearly complete homology with one another, while only 56% of the unique sequence DNA from Agaricus bitorquis hybridized with the same Agaricus brunnescens DNA. Furthermore, very little sequence homology existed between Agaricus brunnescens DNA and the DNA's of the other mushrooms studied. Similarly, very little hybridization occurred between P. ostreatus labeled DNA and the DNA's of the other species. The stability of the DNA duplexes was examined by thermal elution. The Tm of Agaricus brunnescens:Agaricus bitorquis duplexes was 7.7 °C lower than Agaricus brunnescens:Agaricus brunnescens duplexes. This indicated a 7.7–11.6% mismatch between the unique DNA's of these two species.

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interactions that promote and maintain tissue-specific differentiation. Phenotypic diversity can be maintained by growing cells under conditions which provide the necessary environmental cues for organ-like assembly, for example by growing cell aggregates in suspension culture. However, the level of tissue-specific differentiation in these aggregates is limited, in part, because of the detrimental effects of the high fluid shear stress encountered in conventional stirred fermentors. Some of these problems have recently been overcome by the introduction of the Rotating Wall Vessel (RWV) Bioreactor cell culture biotechnology, which achieves spatial co-location of cells cultured in suspension, through "simulated microgravity (µG)", i.e., randomized gravitational vectors (10 -2 g) and very low shear stress, viz. < 0.5 dynes/cm 2 ([1]. Cell culture in the RWV Bioreactors has significantly advanced our capabilities to create macroscopic three-dimensional tissue assemblies. Several groups have shown that the cell culture conditions in the RWV Bioreactors facilitate the assembly of tissue-like 3-D constructs and induce tissue-specific differentiation in a variety of normal and transformed cell types [2,3.Functionally, 3-D constructs obtained from both homotypic and heterotypic cell cultures maintained in the RWV Bioreactors, express tissue-specific markers and synthesize "products", such as soluble differentiation markers, in an organ-specific fashion [4]. Tissue-specific differentiation of the 3-D constructs is enhanced in the presence of diverse cell types in heterotypic co-cultures [2]. Thus, the culture conditions in the RWV provide an excellent in vitro system for studying the effects of environmental cues on tissuespecific cell assembly and differentiation. PC12 cells as model for neuroendocrine differentiation:PC12 pheochromocytoma cells, which are derived from a tumor of rat adrenal chromaffin cells, are an established model system for the bipotential differentiation of neural crest-derived cells of the sympathoadrenal lineage [5]. Depending on microenvironmental cues, cells of this lineage can differentiate in the presence of neurotrophins (such as NGF) into either sympathetic neurons or, in the presence of glucocorticoids (such as dexamethasone) or other differentiative agents into the neuroendocrine, chromaffin cell phenotype. Being bipotential as well as easily available, PC12 cells have become one of the best studied model systems for elucidating signaling pathways associated with neuronal and neuroendocrine differentiation [6]. Report Documentation Page