A cytological and quantitative study of neoblasts in the naidOphidonais serpentina (Oligochaeta)Bilello, Alexander; Potswald, Herbert
doi: 10.1007/BF00573227pmid: 28304850
The fine structure of the neoblasts in the naidOphidonais serpentina has been examined. The neoblasts of control worms have a relatively large nucleus, containing a large nucleolus, a sparse amount of rough endoplasmic reticulum, and an abundance of free ribosomes and mitochondria. Although Golgi membranes have been demonstrated, there is no evidence that the neoblasts are secretory in nature. Neoblasts form loose cell-to-cell contacts with one another and with peritoneal cells. In worms 12 hours after posterior transection, the neoblasts found at the end of the severed ventral nerve cord have rounded up and are no longer spindle-shaped. Counts of neoblasts immediately after posterior transection indicate that they are equally distributed in the last five segments. A statistical analysis of their distribution during posterior regeneration reveals a significant increase in neoblasts in the last three segments and a migration of neoblasts toward the wound. The role of neoblasts in oligochaete posterior regeneration is discussed.
Activity of a gene in transplanted oocytes in the annelid,PlatynereisFischer, A.
doi: 10.1007/BF00573228pmid: 28304851
Pteridine eye pigment, indicative of the activity of theor
+-allele, was observed inor/or larvae ofPlatynereis, derived from transplantedor
+/or oocytes. These heterozygous oocytes had grown up inor/or hosts, themselves deficient in pteridine pigment synthesis. It is therefore concluded that theor
+ gene product, responsible for pteridine pigment synthesis in theor/or larvae, had been synthesized by the oocyte genomes.
Effect of length of aggregation time upon sorting-out behavior of cells from chick embryo tissuesLesseps, Roland; Glowacki, Gregory
doi: 10.1007/BF00573229pmid: 28304852
The timing hypothesis of Curtis proposes that cells which go through a sequence of types of behavior at different rates sort out from one another in aggregates. In order to further test this hypothesis we have given cells from one chick embryo tissue a head start in aggregating before adding cells from a second tissue. By such experimental manipulation the normal position of cells in an aggregate should be reversed, according to predictions from the timing hypothesis. When heart ventricle cells were allowed to aggregate 6,12, 20, or 22 hours before addition of neural retina cells, the aggregates all showed internal heart cells surrounded by neural retina cells. The same final positions of heart and neural retina were found in aggregates in which neural retina cells started aggregating 4, 6, or 22 hours before addition of heart cells. Control aggregates, with heart and neural retina dissociated and co-aggregated simultaneously, also showed heart internal and neural retina external. No effect of length of aggregation time could be detected with this pair of tissues. When pigmented retina cells were allowed to aggregate 6 or 20 hours before addition of heart cells, the cells were in the same final positions as in control aggregates, namely heart external and most pigmented retina cells internal. The only position reversal occurred when heart cells were given 6 or 20 hours to aggregate before addition of pigmented retina cells, which now took up all external positions. This position reversal could result from the heart cells becoming more adhesive with time in culture.
A unique cause of female sterility inDrosophila melanogasterHolzworth, K.; Gottlieb, F.; Spector, C.
doi: 10.1007/BF00573231pmid: 28304854
Histological studies do not permit the distinction between an oocyte, ovary or oviduct malformation as the primary cause of sterility in females homozygous for the Hairywing 49c allele inDrosophila melanogaster. Reciprocal transplantations of larval ovaries between homozygous mutant larvae and normal larvae demonstrate that the sterility is due to a malfunctioning of the oviduct, presumably at the junction of the common oviduct and the uterus. This failure of the oviduct to function normally appears to represent a unique cause of female sterility in this organism.
Effect of juvenile hormone on DNA synthesis during embryogenesis inAcheta domesticusRao, K.; Krishnakumaran, A.
doi: 10.1007/BF00573232pmid: 28304855
1)
The effect of juvenile hormone on embryonic development in the cricket,Acheta domesticus, was investigated. Application of 1 to 2.5 μg of methyl 12,14-dihomojuvenate (cecropia juvenile hormone) in 1 μl of acetone to 7-day-old cricket embryos inhibited their further growth. In such embryos, differentiation of some of the embryonic organs and tissues such as nerves, muscles and cuticular structures continued. However, embryonic growth was arrested, their morphology was abnormal and they failed to hatch.
2)
Lipid extracts from adult maleHyalophora cecropia which possess juvenile hormone activity also showed similar effects on embryonic development. But lipid extracts prepared from allatectomized adult maleH. cecropia lacking juvenile hormone activity, did not inhibit embryonic development.
3)
DNA synthesis in the embryonic tissues of the JH-treated and control embryos was investigated using an autoradiographic method of determination of H3 thymidine incorporation into nuclear DNA. The results showed that DNA synthesis in epidermal and mesenchymal cells of the cricket embryo decreased gradually after application of 1 μg of JH to 7-day-old embryos and ceased within 6 days after application of JH.
4)
From these observations it is suggested that JH may inhibit embryonic development by suppression of DNA synthesis and cell divisions.