Dynamic activity of the filopodia of sea urchin embryonic cells and their role in directed migration of the primary mesenchyme in vitro

Primary mesenchyme cells used in this study were isolated from Lytechinus pictus mesenchyme blastulae by their ability to preferentially adhere to the surface of a tissue culture dish in the presence of serum. Once isolated, primary mesenchyme cells were found to form thin, elongated, active filopodia which closely resemble the filopodia seen in vivo. The filopodia formed in vitro can move as stiffened bristles, bend gradually or very sharply, or be slowly withdrawn. The integrity of the filopodia is not affected by nocodazole but is totally disrupted by cytochalasin D. Filopodia exhibit several apparent functions in vitro: as organelles involved in contacting the external environment, as anchoring appendages that hold the cell bodies in place, and as intercellular connectives that can join cell bodies. The filopodia of primary mesenchyme cells appear to have similar roles within the embryo. The function of the filopodia has been explored by watching the behavior of isolated primary mesenchyme cells in close proximity to deposits of extracellular material (ECM) prepared from mesenchyme blastulae. When the filopodium from a mesenchyme cell makes contact with the nearby ECM, a response is initiated which causes the cell body to move in a directed manner toward the ECM deposit. The use of this type of response as a model system for the study of the migration of primary mesenchyme cells within the embryo is considered.     

Biomass Measurements in Hydrocarbon Fermentations

A rapid and accurate method to determine biomass concentration of cultures growing on hydrocarbons is presented. The technique is based on turbidity. The method eliminates the common problem of inaccurate biomass measurements due to the presence of hydrocarbons affecting the readings or because of the adherence of the cells to the hydrocarbons phase. The method uses small samples (<5ml), is non-destructive and the results do not depend on the age of the culture under study.     

Integrated pathway-genome databases and their role in drug discovery.

Integrated pathway-genome databases describe the genes and genome of an organism, as well as its predicted pathways, reactions, enzymes and metabolites. In conjunction with visualization and analysis software, these databases provide a framework for improved understanding of microbial physiology and for antimicrobial drug discovery. We describe pathway-based analyses of the genomes of a number of medically relevant microorganisms and a novel software tool that visualizes gene-expression data on a diagram showing the whole metabolic network of the microorganism.     

Cytological and molecular evidence of deletion of ribosomal RNA genes in chromosome 6 of barley (Hordeum vulgare).

The barley chromosomal mutant T-35, in which only one pair of satellite chromosomes is apparent, was analyzed using a range of cytological and molecular techniques. Using conventional Feulgen staining, Giemsa and silver banding, in situ hybridization, and Southern blot analysis, unequivocal cytological and molecular evidence was obtained that T-35 is a homozygous deletion of rRNA genes residing in the nucleolus organizer region (NOR) of chromosome 6. According to the criteria of arm ratio and Giemsa-banding pattern of this chromosome, the deletion involved the whole NOR, one of the breakpoints being localized in the short arm proximally to the NOR-associated heterochromatic band, the other probably in the satellite of the chromosome. As a result of this deletion, an increased activity of the rRNA genes (as indicated by the size of the silver bands) on the other NOR-bearing chromosome (chromosome 7) was observed. The possible reasons for this phenomenon are discussed.     

Preimplantational Ectogenesis: Science and Speculation Concerning In Vitro Fertilization and Related Procedures

In recent years, technical advances have made preimplantational ectogenesis (in vitro maturation, fertilization and early embryonic development) more than a theoretical concept. Such procedures hold great promise in medical research. However, despite our newly-acquired skills in tissue culture and microsurgical manipulation, and contrary to many sensational articles in the lay press, it is not likely that preimplantational ectogenesis will soon attain wide clinical use in humans. Adverse societal attitudes, based largely upon moral and ethical dilemmas, will probably combine with still-unresolved technical difficulties to restrict the clinical applications.