The production of ethanol by Saccharomyces cerevisiae immobilized in polycation-stabilized calcium alginate gels

Summary Polycation treatment of preformed calcium alginate beads produced a matrix with higher resistance to phosphate ions. The treatment of immobilized Saccharomyces cerevisiae in the calcium alginate beads inhibited respiration of the entrapped cells but did not reduce ethanol production.     

Analysis of structural similarities between brain Thy-1 antigen and immunoglobulin domains. Evidence for an evolutionary relationship and a hypothesis for its functional significance.

The Thy-1 membrane glycoprotein from rat brain is shown to have structural and sequence homologies with immunoglobulin (Ig) domains on the basis of the following evidence. 1. The two disulphide bonds of Thy-1 are both consistent with the Ig-fold. 2. The molecule contains extensive beta-structure as shown by the c.d. spectrum. 3. Secondary structure prediction locates beta-strands along the sequence in a manner consistent with the Ig-fold. 4. On the basis of rules derived from known beta-sheet structures, a three-dimensional structure with the Ig-fold is predicted as favourable for Thy-1. 5. Sequences in the proposed beta-strands of Thy-1 and known beta-strands of Ig domains show significant sequence homology. This homology is statistically more significant than for the comparison of proposed beta-strand sequences of beta 2-microglobulin with Ig domains. An hypothesis is presented for the possible functional significance of an evolutionary relationship between Thy-1 and Ig. It is suggested that both Thy-1 and Ig evolved from primitive molecules, with an Ig fold, which mediated cell--cell interactions. The present-day role of Thy-1 may be similar to that of the primitive domain.     

A Simplified Method for Staining Mast Cells with Astra Blue

The copper phthalocyanin dye astra blue has been used to stain differentially mast cells of the intestine; however, the procedure has not been used widely because of the difficulty in preparing and using the dye solution. Described here is a simple, reliable, and consistent method for selectively staining mast cells using a dye solution that may be prepared in any laboratory without the aid of sophisticated pH metering equipment. Astra blue is mixed with an alcoholic solution containing MgCl₂ · 6H₂O and the pH indicator pararosaniline hydrochloride. Concentrated hydrochloric acid is added dropwise, changing the dye mixture from purple to violet and then to blue. In this low range the weakly ionizing ethanol provides a more stable hydrogen ion concentration than the corresponding aqueous solutions used previously. Alcoholic acid fuchsin is a convenient counterstain, and this simple procedure then provides good contrast between the blue staining mast cell granules and the red tissue background.     

Age-dependent changes in the hypothalamo-pituitary-ovarian axis of the laying hen.

The functional integrity of the components of the hypothalamo-pituitary-ovarian axis was examined in young and old laying hens. Ovarian function was tested by measuring the amount of progesterone released in response to an injection of LH, and pituitary function was investigated by measuring the increase in the plasma LH level after an injection of LH-RH. There were no differences between young and old birds in the response of the pituitary gland or the ovary to these stimuli. Hypothalamic function was investigated by studying the positive feedback action of a standard dose of progesterone on LH release; the positive feedback response was smaller (P less than 0.05) in old hens. It is suggested that the fall in the rate of lay in hens towards the end of their laying year is caused partly by a decrease in the response of the LH-positive feedback mechanism to progesterone.