On the mechanism of vesicle release from ATP-depleted human red blood cells

The release of spectrin-free vesicles from ATP-depleted human red blood cells (Lutz et al. (1977) J. Cell. Biol. 73, 548) can be considered the final step of a shape change from discocytes to echinocytes. The study of physical and chemical properties of released vesicles suggests that vesicle release is not merely a consequence of charge alterations within either monolayer of the budding membrane. Fresh membranes and released vesicles have within experimental error the same sialic acid content per surface area and the same electrophoretic mobilities. Vesicle release cannot be stimulated by doubling the charge density on the outer monolayerby means of a phospholipase D-treatment, but correlates with a breakdown of polyphosphoinositides to diacylglycerol on the inner monolayer. This breakdown does not lead to a significant change in the negative charge density on the inner monolayer, because an increased phosphatidate content compensates for this alteration. Furthermore, polyphosphoinositide breakdown and diacylglycerol production are not the rate-limiting step in vesicle release from ATP-depleting red blood cells. This is evident from the fact that 10 mM EDTA inhibits vesicle release to 75% without affecting polyphosphoinositide breakdown and diacylglycerol production. Hence, diacylglycerol formation may be sufficient for membrane budding as suggested earlier (Allan et al.(1976) Nature 261, 58), but vesicle release requires a second, as yet unidentified process.     

The murine bone marrow macrophage,a sensitive indicator cell for murine migration inhibitory factor and a new method for their harvest

Murine bone marrow macrophages grown on Teflon-coated petri dishes for a period of 8–16 days can be removed with a yield of 90–95% and a viability greater than 95% following incubation in 1 mM EDTA. Bone marrow cells cultured on Teflon-coated dishes did not differ in their replication rate, peroxidase and nonspecific esterase content, pinocytosis, secretion of lysozyme and neutral proteinases from bone marrow cells cultured on plastic dishes. Murine bone marrow macrophages were found to be sensitive indicator cells for mouse migration inhibitory factor (MIF). Large numbers of cells for the MIF assay can be obtained, since their yield is 10–15 times higher than the yield of oil-induced peritoneal exudate macrophages from the same number of mice.     

Induced recovery of a suppressed idiotype by immunization with anti-idiotype

Neonatal Balb/c mice were suppressed forthe H8/T15 idiotype by injection of homologous anti-H8 (D. S. Strayer, D. A. Rowley, and H. Köhler, et al J. Immunol.114, 722, 1975. Six to eight weeks later groups of these suppressed mice were immunized up to three times with isologous anti-H8 raised in Balb/c. After a rest of 4 weeks each group was challenged with R36a vaccine and bleedings were obtained before and after this challenge. All sera were assayed for total anti-PC and H8 idiotype amounts by solid-phase radioimmunoassay. After two-preimmunizations with isologous anti-H8 no increase of the H8 levels was observed though these mice responded to R36a immunization with an increase of total anti-PC antibodies. After the third preimmunization, however, the H8 idiotype was increased in sera taken before and after challenge with R36a. These findings demonstrate that the state of neonatal idiotype suppression can be broken by immunization with complementary anti-idiotype.     

Formation of mesodermal pattern by secondary inducing interactions

Summary A highly purified vegetalizing factor induces endoderm preferentially in amphibian gastrula ectoderm. After combination of this factor with less pure fractions, a high percentage of trunks and tails with notochord and somites are induced. The induction of these mesodermal tissues depends on secondary factors which may act on plasma membrane receptors of the target cells. The secondary factors are probably proteins as they are inactivated by trypsin or cellulose-bound proteinase K. They are not inactivated by thioglycolic acid.The implication of these findings for tissue determination and differentiation in normal development in relation to the anlageplan for endoderm and mesodermal tissues is discussed.     

Chromoplasts of Tropaeolum majus L.: Structure and development

Summary The fine structure of chromoplasts in epidermal cells of flower petals of Tropaeolum has been investigated by light, polarizing, and electron microscopy at different stages of development. The pale greenish-yellow petals still enclosed in the bud contain barely differentiated chloroplasts with few, irregular grana. The chromoplasts of unfolding petals show differently oriented bundles of tubules with variable diameters (mean: 17 nm). Thylakoid membranes become reduced more and more. The tubular bundles are intermingled with numerous isodiametric bodies of ca. 50 nm diameter; these bodies are better discernible at later stages when the chromoplasts possess a less dense matrix. The chromoplasts of open flowers are in a state of disorganization at a time when the cytoplasm still appears normal. A comparison is made between chromoplast tubules and tubular structures described from other kinds of plastids. The observations are discussed in view of chromoplast typology and with regard to possible processes underlying chromoplast differentiation in flowers.Abbreviations in Figures Chr chromoplast - CT chromoplast tubules - Cy cytoplasm - D dictyosome - IB isodiametric body - M mitochondrion - MT microtubule - oG osmiophilic globule - S S-body - St starch grain - V vacuole All micrographs from glutaraldehyde-OsO₄-fixed material, unless otherwise specified. The bar designates 1 m (multiples or fractions of it indicated).     

The role of auditory stimuli in the courtship of Drosophila melanogaster

Simulated courtship song of male Drosophila melanogaster was played to males or females of this species. Upon receiving the song males increase their locomotor activity and start courting each other, whereas females reduce their locomotor activity. In wingless males the locomotor activity difference between the silent control and the experimental sound situation is much larger than in winged males, due to the inactivity of wingless males in the control situation. Males which had been kept singly up to the time of the experiment exhibit higher locomotor and sexual activity than group housed males. A second component of the male courtship song ‘sine song’ is described, together with experiments which investigate the sensory basis of the effect male courtship song has on males.     

The function of pulse song and sine song in the courtship of Drosophila melanogaster

Drosophila melanogaster females were subjected to pulse song before being allowed to mix with males. Sine song increases female receptivity, pulse song does not. Pulse song does however increase receptivity if the females are subjected to it while being courted by males which are deaf and which cannot produce any auditory stimulation themselves. It is suggested that sine song is summated and has a priming effect on female receptivity whereas pulse song functions as a species recognition signal in a trigger-like fashion.     

Mapping of neurons in the gravity receptor system of the octopus statocyst by iontophoretic cobalt staining

Summary The presence of uni-, bi- and multipolar neurons beneath the hair cell epithelium of the Octopus gravity receptor system has been demonstrated by iontophoretic cobalt staining. Counts give an average number of 1,940 neurons per macula. Whether the hair cells are primary of secondary sensory cells is discussed.This work was supported by grant Wo 160/3 of the Deutsche Forschungsgemeinschaft (DFG) to H.G.W. Thanks are due to the Director and staff of the Zoological Station in Naples for their hospitality and help