In vitro synthesis of vitamin D-3 by cultured human keratinocytes and fibroblasts: action spectrum and effect of AY-9944

With delineation of the photochemical events occurring in the skin after ultraviolet exposure, there has been increased interest in the skin's role in the vitamin D-3-endocrine system. We provide here in vitro conditions for the generation of both labelled (from [3H]acetate) and unlabelled vitamin D-3 in cultures of human keratinocytes and fibroblasts. Sterol precursors and photoproducts in irradiated and non-irradiated cultures are identified by co-chromatography, ultraviolet absorbance spectra, thermal conversion characteristics of previtamin D-3 and mass spectrometry. Because the conversion of 7-dehydrocholesterol to cholesterol is more efficient in vitro than in vivo, the specific delta 7 inhibitor, AY-9944, was added in non-toxic doses to modulate 7-dehydrocholesterol content. Both cell types were equally capable of generating photoproducts, depending on the amount of 7-dehydrocholesterol present. The 290 +/- 5 and 295 nm filters were much more efficient than the 305 nm filter for generating previtamin D-3 and vitamin D-3 in fibroblasts. In contrast, the 305 nm filter was as efficient as the 290 +/- 5 and 295 nm filters in keratinocytes, where it yielded previtamin D-3, with much less lumisterol and tachysterol than appeared with the shorter-wavelength filters. The amount of lumisterol and tachysterol versus previtamin D-3 formed in both cell types was dependent on the total energy applied, with lower energies (less then 1 J/cm2) favoring previtamin D-3 over the other photoproducts. The use of cultured cells provides a system whereby the regulation of vitamin D-3 synthesis by extracutaneous factors can be studied in a homogeneous setting.     

A preliminary note on the use of milk substitutes in the early weaning of dromedary camels

The experiment was performed using two young male camels which weighed 24 and 36 kg respectively at birth. Each young camel was weighed and abruptly separated from its mother after 30 days of nursing (or at 1 month of age). The weaned calves were fed milk substitutes prepared commercially for lambs by Mabarot Chemical and Veterinary Products (Israel). The weanling camels averaged daily weight gains of 0.400 and 1.0 kg per day respectively during the 30 day initial period when the milk substitutes were used. Following the period when milk substitutes were used, the camels achieved normal growth to arrive at 135 and 145 kg respectively at 6 months of age.     

Minireview: Metabolic control of the reproductive physiology: Insights from genetic mouse models

This article is part of a Special Issue Energy Balance.     

Stoichiometric differences in DNA molecules containing the atpA gene suggest mechanisms for the generation of mitochondrial genome diversity in maize

Four genomic arrangements of the maize mitochondrial atpA gene (encoding the α subunit of the F₁ ATPase), have been characterized. Most N (fertile) and S (male-sterile) cytoplasms contain two atpA arrangements of equal abundance. Prolonged exposure of blots of maize mitochondrial DNA probed with atpA-specific sequences show that cytoplasms previously reported to lack one of the atpA arrangements do contain the second arrangement but at low levels. Similarly, restriction fragments containing the atpA gene previously thought unique to male-sterile S and T cytoplasms are present in low abundance in fertile cytoplasms. These observations suggest that fertile and male-sterile cytoplasms of maize may be more closely related than previously thought, and suggest possible mechanisms to explain the observed mitochondrial genome diversity.