No abstract

The proportion of living sperm in semen from six representative mammals was assessed by means of a dual staining technique using the stains SYBR-14 and propidium iodide (PI). SYBR-14, a newly developed fluorescent nucleic acid stain, maximally absorbs at 488 nm and emits at 518 nm when bound to DNA. Microscopic examination revealed that SYBR-14 stained the nuclei of living sperm bright green as determined by simultaneous examination of fluorescence and motility. Conversely, PI stained only nonmotile sperm that had lost their membrane integrity. Sperm from bulls, boars, rams, rabbits, mice, and men were stained and examined through use of fluorescence microscopy. The proportions of living and dead sperm were determined by first staining with SYBR-14 and PI and then assessing stain uptake by flow cytometry. Similar staining patterns were observed in all six mammalian species tested. Three populations of sperm were identified: living--SYBR-14 stained, dead--PI stained, and moribund--doubly stained. The SYBR-14 staining was replaced by PI staining as sperm progressed from living to moribund. The transition from green (SYBR-14) to red (PI) fluorescence started at the posterior region of the sperm head and proceeded anteriorly. The proportions of living and dead sperm in mammalian semen were readily identified through use of dual staining with SYBR-14 and PI and quantified through use of flow cytometry.

Intact, viable X and Y chromosome-bearing sperm populations of the rabbit were separated according to DNA content with a flow cytometer/cell sorter. Reanalysis for DNA of an aliquot from each sorted population showed purities of 86% for X-bearing sperm and 81% for Y-bearing sperm populations. Sorted sperm were surgically inseminated into the uterus of rabbits. From does inseminated with sorted X-bearing sperm, 94% of the offspring born were females. From does inseminated with sorted Y-bearing sperm from the same ejaculates, 81% of the offspring were males. The probability of the phenotypic sex ratios differing from 50:50 were p less than 0.0003 for X-sorted sperm and p less than 0.004 for Y-sorted sperm. Thus, the phenotypic sex ratio at birth was accurately predicted from the flow-cytometrically measured proportion of X- and Y-bearing sperm used for insemination.

A B S T R A C TA comprehensive review of the literature about use of solvents for extraction of oilseeds is presented. Mention has been found of over 70 solvents. Currently, hexane is the major solvent in use, but recent price increases and safety, environmental and health concerns, have generated interest in alternatives. Solvents vary considerably in chemical and physical properties which affect their performance in oil extraction. The choice of solvent depends upon the primary end product desired (oil or meal). Recent research on alternative solvents has focused on ethanol, isopropanol, methylene chloride, aqueous acetone, and hexane/acetone/water mixtures. I N T R O D U C T I O NSolvent extraction has been defined as a process for transporting materials from one phase to another for the purpose of separating one or more compounds from mixtures. In the case of oilseed extraction, crude vegetable oil is separated by solvent from meal comprising proteins and carbohydrates. Various solvents have been used commercially, and others have been proposed, based on encouraging laboratory results; but currently, hexane is the solvent of choice by oilseed processors. Operating losses of solvent range between 0.2 and 2.0 gallons per ton of seed processed, and a 6-to 8-fold increase in price during the last decade, has made hexane costs a major factor in oilseed milling. Occasional scarcities of hexane, toxicological and environmental concerns, and several catastrophic explosions and fires have motivated searches for alternative solvents. Listings of references for various solvents and their usage were published on two occasions in this journal (1,2); and Hron et al.(3) recently discussed biorenewable solvents. However, a comprehensive review of alternative solvents for oilseeds extraction has not been published. D I S S O L U T I O N T H E O R YSolvent extraction dissolution theory, based on the laws of thermodynamics, has been explained by Sedine and Hasegawa (4). During dissolution, two separate substances, the solute and the solvent, form a molecular mixture. Dissolution is always accompanied by a negative free energy change. Free energy (AG) is related by the Gibbs equation to enthalpy (or heat content (AH)), absolute temperature (T), and entropy (or amount of disorder (AS)) as: z~G=~H-TASBecause dissolution involves mixing of two substances and an increase in their disorder, a positive entropy change, oecu IS.Dissolution involves two endothermic processes and one exothermic. First, solute molecules (whether solid or liquid) separate into isolated molecules. This is an endothermic process. Its energy is called "lattice energy," "heat of sublimation," or "heat of vaporization," and is small when the solute molecules are nonpolar. The separated solute molecules are next dispersed into the solvent. Energy is required to dissociate the solvent molecules, in preparation to accommodate the solute molecules. The energy required increases with increasing intermolecular interactions in the pure solvent in the following order: n...