No abstract

A light and electron microscopical study has been carried out on the morphology and microanatomy of two marine species of Heteromastix and less completely on two freshwater samples from the same genus, one only of which is named; this one is, however, important as the type species of the genus (H. angulata Korsh.). Agreement in salient features indicates that Bipedinomonas N. Carter andAnisomonas Butcher, under which the marine species were previously described, should be discarded as later synonyms of Heteromastix Korsh. Apart from the nomenclatural clarification the most important new findings concern the details of the periplast on cell body and flagella, the presence of stellate scales as well as plate-scales on both types of surface, the presence within the body of a starch shell not giving the normal colour reaction with iodine, and of a characteristic fibrous ‘root’ joining the flagellar bases to the plastid surface. A major finding of electron microscopical interest is the clarity with which the formation of scales and of flagellar hairs has been traced to the Golgi cisternae. These observations are an important addition to previous knowledge concerning genera of related green flagellates possibly referable to the class Prasinophyceae.

No abstract

A new species provisionally attributed to the genus Nephroselmis has been described with the aid of light- and electron-microscopy. Significant features include the presence of a single layer of scales over the flagellar and cell surfaces as in Micromonas squamata Manton & Parke, though the morphology of the flagellar scales is as in the outer scale layer of Pyramimonas and Halosphaera. Reasons are given for rejection of Thalassomonas on the grounds of nomen confusum and for homologizing various representatives of it with Micromonas squamata.Some additional facts about the latter include details of the imbrication of the flagellar scales and demonstration, made possible by the use of lead staining of sections, of a close association between golgi bodies and the scale-producing vesicles.

No abstract

The effects of three membrane-active agents, filipin, digitonin, and polymyxin B on the plasma membrane of ram spermatozoa have been studied by freeze-etch electron microscopy. Filipin and digitonin both reacted with cholesterol and caused visible membrane modification in cholesterol-rich regions, with filipin being a more specific agent than digitonin. Polymyxin B, which is known to interact specifically with negatively charged phospholipids of bacterial membranes, exhibited a selective binding and subsequent modification of sperm plasma membranes. This binding was shown to be inhibited in the presence of 1 mmol/1 Ca2+. We hence propose that both filipin and polymyxin B are useful cytological markers for specific biological molecules in eukaryote membranes--filipin for cholesterol, and polymyxin B for negatively charged phospholipids.

No abstract

No abstract