Differential sensitivity to trypsin of human bone-derived cells in culture: surface changes detected by partitioning in aqueous two-phase systems

Human bone-derived cells, grown in monolayer culture, were dissociated by incubations with trypsin/EDTA and subjected to thin-layer counter-current distribution in a 'low potential' aqueous two-phase system. Two major populations of cells were detected. The number of cells in the second (more hydrophobic) population increased with length of trypsinization and time in culture. Cells allowed to 'regain' surface molecules lost by trypsinization did not produce the second population. Cells occupying the second population after a short period of trypsinization had a lower rate of division than peak 1 cells but showed a higher rate of protein synthesis per rate of division than peak 1 cells. These results show that the cells have markedly different sensitivities to trypsin digestion which may be related to cell division rate of growth. The possible relationship between this and osteoblast development are discussed.     

Seizure threshold, adrenalectomy and sodium-potassium stimulated ATPase in rat brain

Adrenalectomy in the rat was shown to lower seizure threshold measured with the volatile convulsant hexafluorodiethyl ether. Although the expected hyponatraemia and hyperkalaemia were demonstrated in the adrenalectomized rats, there was no associated alteration in Na-K stimulated Mg-ATPase activity either in the whole rat brain or in a microsomal fraction. These results in brain tissue are contrasted with the marked decrease in this enzyme that occurs in kidney tissue of the rat following adrenalectomy. It was suggested that the activity of the enzyme system responsible for active cation transport responds directly in proportion to the work of active transport required by the individual tissue.     

PILINIA EARLEAE N. SP. (CHLOROPHYCEAE,CHROOLEPIDACEAE) FROM THE FLORIDA WEST COAST1

Pilinia earleae n. sp. family Chroolepidaceae, was found in the Tampa Bay area of the Florida west coast in October, 1976, on the tunic of an ascidian, later on dead mollusc shells, a nylon faking line, plastic strips, and as an epiphyte of Gracilaria foliifera, a red alga. It is described on the basis of abundant material from the natural environment and laboratory cultures. The type locality is the southernmost known for the genus in the western North Atlantic.     

Freshwater snails of Oman,South Eastern Arabia

A systematic account is given of the extant freshwater snail fauna of Oman, based on recent collections made in Dhofar and in the northern mountainous areas. Also included are certain species found in brackish coastal localities. A total of 8 freshwater species is regarded as belonging to the fauna of normal freshwater; 7 have been found alive (Thiara scabra, Melanoides tuberculata, Lymnaea natalensis, Gyraulus piscinarum, Biomphalaria arabica, Bulinus wrighti and Indoplanorbis exustus) and one is known only as shells (Paludestrina glaucovirens). This report of G. piscinarum is the first for Oman and may be the first reliable identification for Arabia. Three taxa from brackish water, Gangetia miliacea, Iravadia quadrasi and Melanoides sp., are new for the fauna of Oman and of the whole Arabian peninsula. The finding of G. miliacea provides the first instance of any member of the Stenothyridae living west of the Gulf of Oman and identified from whole snails rather than empty shells. I. quadrasi is the first member of its genus to be found alive west of the Gulf of Oman.     

The effects of an inhibitor of Na+-K+-active transport on the secretory activity of rat submaxillary gland cell cultures

Summary The role of electrolyte transport in the metabolism of mucosubstance has been investigated using cell cultures derived from rat submaxillary gland. When added to the culture medium at a concentration of 1 mM, ouabain, an inhibitor of active alkali metal ion transport through cell membranes, causes extensive cytoplasmic vesiculation suggestive of an accumulation of secretory materials within the cell; the rough ER and cytoplasmic polysomes are not affected. Isotopic experiments support these conclusions by demonstrating that ouabain inhibits the secretion of radioactive mucosubstances by the cells; comparative studies with ouabain and puromycin (2×10^–4M) indicate that the inhibitory effect of ouabain is not due to an inhibition of protein biosynthesis. A relationship between secretion and alkali metal ion movement is suggested which may be of significance in connection with the genetic disease, cystic fibrosis.The generous support of the Cystic Fibrosis Research Trust made this work possible; the skilful assistance of Peter Crosby, Jacqueline Gibson and Christine Johnson is gratefully acknowledged.