The Role of Organ Cultures in the Study of Vitamins and Hormones

The Last Half Century of Fish Explant and Organ Culture

Explants are three-dimensional tissue fragments maintained outside the organism. The goals of this article are to review the history of fish explant culture and discuss applications of this technique that may assist the modern zebrafish laboratory. Because most zebrafish workers do not have a background in tissue culture, the key variables of this method are deliberately explained in a general way. This is followed by a review of fish-specific explantation approaches, including presurgical husbandry, aseptic dissection technique, choice of media and additives, incubation conditions, viability assays, and imaging studies. Relevant articles since 1970 are organized in a table grouped by organ system. From these, I highlight several recent studies using explant culture to study physiological and embryological processes in teleosts, including circadian rhythms, hormonal regulation, and cardiac development.

Programmed cell death 50 (and beyond)

In the 50 years since we described cell death as 'programmed,' we have come far, thanks to the efforts of many brilliant researchers, and we now understand the mechanics, the biochemistry, and the genetics of many of the ways in which cells can die. This knowledge gives us the resources to alter the fates of many cells. However, not all cells respond similarly to the same stimulus, in either sensitivity to the stimulus or timing of the response. Cells prevented from dying through one pathway may survive, survive in a crippled state, or die following a different pathway. To fully capitalize on our knowledge of cell death, we need to understand much more about how cells are targeted to die and what aspects of the history, metabolism, or resources available to individual cells determine how each cell reaches and crosses the threshold at which it commits to death.

Inhibition of plasminogen activator production in organ cultures by cycloheximide

The production of tissue plasminogen activator (TPA) in rat tongue organ cultures is strongly inhibitied by low concentrations of the protein synthesis inhibitor cycloheximide. TPA production is fully resumed after the removal of cycloheximide from the culture medium.

[Squamous metaplasia of human mammary epithelium in long-term organ culture]

Squamous metaplasia of the mammary epithelium was observed in human breast tissue maintained in long-term organ culture. The phenomenon occurred only in the synthetic medium 199 with Earle's salts. Insulin and/or glucose enrichment enhanced its occurrence.

Effects of retinoic acid on embryonic chick skin

The influence of vitamin A on differentiating epithelia was examined in explants of skin from 14-day chick embryos exposed to retinoic acid (RA) in low, moderate, and high doses. The changes observed in RA-treated cultures are both dose- and time-dependent and are reversible when explants are transferred to control medium. The periderm sloughs prematurely and horizontal stratification is lost. Keratinization is inhibited and fewer desmosomes and tonofilaments are seen. Surface epidermal cells develop microvilli, bulge upwards, and detach. Golgi elements, rough endoplasmic reticulum, and polyribosomes are unusually prominent. Mucin granules form and gland-like structures develop with intercellular canaliculi characterized by tight junctions, brush borders, and dense secretory contents. On the basis of present evidence there are several possible mechanisms by which RA could alter epidermal differentiation. RA-induced gaps in the basal lamina allow direct contact between epidermal basal cells and fibroblasts and collagen fibers which could result in inappropriate dermal signals reaching the epidermis. In younger embryos the entire epidermis, including the mitotically inactive surface cells, appears to respond to RA, and this could imply an epigenetic modulation of cell phenotype. Finally, after the formation of a stratum corneum in older embryos only the relatively undifferentiated basal layer shows a metaplastic response, indicating that RA could be acting directly on the genome.

Role of biological membranes in some skeletal reactions

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