An investigation into the potential of a mammalian temperature sensitive leucyl-tRNA synthetase mutant for mutagenesis studies.

Reversion of the mammalian temperature sensitive leucyl-tRNA synthetase mutant CHO tsH1 [33] has been investigated to determine its potential for mutagenesis studies. The protocol for a mutation assay using the new class of temperature sensitive conditional lethal mutants of somatic cells is presented. While it requires careful control of temperature during revertent selection it promises to provide a system complementary to the existing mutation assays.

Characteristics of responses of isolated human fallopian tube to transmural stimulation and to sympathomimetic amines.

The responses of circular and longitudinal muscle of human fallopian tube to transmural stimulation and sympathomimetic amines have been investigated. It was found that tissues from the earlier part of the menstrual cycle (i.e.

Inhibition of spontaneous contractility of the human and the rabbit fallopian tube by potassium.

Spontaneous contractions of circular and longitudal muscle of the ampulla and isthmus of human and rabbit Fallopian tubes were recorded isometrically. Addition of K+ to tissue in K+-free medium always caused immediate inhibition of spontaneous contractility. K+-induced inhibition was prevented by ouabain and reversed by removal of K+.

Mineral metabolism and microstructural defects in primate teeth.

There are numerous structural defects that occur in primate teeth due to variable calcification during certain growth stages. These interruptions are usually areas of hypomineralization in enamel and dentin which are referred to as Striae of Retzius and Hunter Shreger bands in the enamel or Incremental Lines of von Ebner and Contour Lines of Owen in the case of the dentin. The frequency of occurrence of these variations in mineralization can be related to such factors as growth tempo, dietary quality, state of health, and past disease episodes.

Effect of leucine on the temperature sensitive phenotype of a mammalian leucyl-tRNA synthetase mutant.

The concentration of leucine in the growth medium has been found to influence the expression of the temperature sensitive phenotype of a mutant of Chinese hamster ovary cells with an altered leucyl-tRNA synthetase. Plating efficiency and growth studies showed that increasing the leucine concentration allows cells to survive at normally non-permissive high temperatures and conversely decreasing the leucine concentration enhances the adverse effectsof high temperature. A similar but smaller effect was noted with isoleucine.