Genetic and developmental evidence for a repressed genital primordium in Drosophila melanogaster

Agametic, a maternal-effect mutation, causes the absence of germ cells in approximately 40% of the gonads of flies derived from homozygous females. The nature of the deficiency in the eggs produced by these flies was examined. Ultrastructural abnormalities were seen in the polar granules of some eggs shortly after fertilization. Although a normal number of pole cells form, some are abnormal with degenerating polar granules and nuclear bodies and they contain myeloid bodies. The pole cells reach the gonads and at 14 hr of development all the gonads contain germ cells. However, in 40% of the gonads the germ cells become necrotic and disappear. Thus, the source of agametic gonads in the adult is embryonic death of pole cells in some gonads. To test whether this gonadal death is an autonomous deficiency of the mutant pole cells, mosaic pole cell populations were produced by reciprocal pole cell transplantation. In both types of transplants, the mutant pole cells died autonomously. In eight instances gonads containing only donor pole cells were obtained. Since mutant pole cells die when wild-type pole cells normally begin dividing, we suggest that the lesion affects the ability of these mutant pole cells to reenter the cell cycle.     

Molecular characterisation of inter and intra-specific somatic hybrids of potato using randomly amplified polymorphic DNA (RAPD) markers

Summary Protoplast fusion allows the transfer of both mono- and polygenic traits between species that are sexually incompatible. This approach has particular relevance for potato, and somatic hybridisation has been used to introduce a range of disease resistance genes from sexually incompatible wild species into the cultivated potato gene pool. In addition, protoplast fusion allows the resynthesis of tetraploid genotypes from pre-selected diploid or dihaploid donor parents. A limiting factor for the efficient exploitation of this technology in potato breeding is the difficulty of unequivocally identifying nuclear hybrids (heterokaryons). In order to facilitate the identification of hybrids at an early stage following fusion, Randomly Amplified Polymorphic DNA markers (RAPDs) have been used to characterise molecularly both inter- and intra-specific somatic hybrids of potato. RAPD markers detect naturally occurring polymorphism in the donor genotypes and utilise short oligonucleotide primers of arbitrary nucleotide sequence in combination with the polymerase chain reaction (PCR). The exploitation of RAPDs in the characterisation of both somatic and sexual hybrids is discussed.     

Residual radiation injury exhibited in long-term bone marrow cultures

Residual radiation injury was demonstrated in long-term primary cultures of mouse bone marrow. Control cultures underwent three phases of hematopoietic activity as distinguished by initial establishment, steady high (plateau) production of granulocytes, and gradual decline. Irradiation with 50, 300, or 550 rads, given at the end of the initial phase, did not prevent any culture flasks from entering the plateau phase. However, actual production levels and the time they were maintained varied inversely with the radiation dose so that the accumulated postradiation cell production corresponded to an exponential dose-response relationship at any time after treatment. The accumulated cell productions were found to be similar in all groups when expressed by the number of stem cell doublings necessary to produce them. The findings cannot be explained by reproductive cell death and are consistent with the notion of a limited division capacity in hematopoietic stem cells.     

Otto Kuntze,botanist. III. Type specimens of fern,gymnosperm and monocotyledon taxa from his Revisio Generum Plantarum

Type specimens of fern, gymnosperm and monocotyledon taxa described as new by Otto Kuntze in hisRevisio Generum Plantarum Vols. I and II (1891) and Vol. III (1898) known to be in the herbarium of the New York Botanical Garden (NY) are listed. Specimens for all of the new taxa were not found at NY.     

Annotated bibliography of Galapagos botany. Supplement I

This supplement to a bibliography published in 1973 lists 112 new references on Galápagos botany. The availability of accurate information in a new flora of the Galápagos Islands has brought about an increase in botanical research. Very little new work has been done on cryptogams. Many recent studies concentrate on ecology and conservation of the unique Galápagos plants.     

Patterns of silver staining in cells of six-day blastocyst and kidney fibroblast of the domestic rabbit

The distribution pattern of silver-NORs was studied in cells of six-day blastocysts and kidney fibroblasts of the rabbit using the Ag-AS technique. At metaphase and interphase there was a binomial distribution of the number of stained sites in both populations but blastocysts had a greater percentage of cells with larger numbers of stained sites. Up to 7 of the 8 chromosomes known to bear NORs were stained in cells from blastocysts while a maximum of 6 were stained in fibroblasts. A significant difference was found between the mean numbers of chromosomal NORs per cell in metaphases from blastocysts and fibroblasts, where they were 4.2 and 3.3 respectively. Similarly, the mean number of NORs in interphase was significantly greater in cells from blastocysts. The distribution of staining on chromosome pair 13 was related to cell type. Significantly more cells in blastocysts than fibroblasts showed staining in this chromosome pair.     

DFP-sensitive polypeptides of the guinea pig peritoneal macrophage

Guinea pig peritoneal exudate macrophages were reacted with [³H] diisopropyl fluorophosphate (10^?7 to 10^?4 M) and subjected to sodium dodecyl sulfate-polyacrylamide disc electrophoresis and fluorography. Macrophages reacted with 10^?5 M [³H]diisopropyl fluorophosphate contain eight major ³H-labelled polypeptides which have apparent molecular weights of 83,000, 75,000, 63,000, 48,000, 41,000, 30,000, 26,000, and 25,000. The sensitive polypeptides were not seen when guinea pig polymorphonuclear leukocytes, lymph node lymphocytes, erythrocytes, serum or plasma were reacted with [³H]diisopropyl fluorophosphate, demonstrating that these components are particular to the macrophage. The finding of a large number of diisopropyl fluorophosphate-sensitive proteins associated exclusively with the macrophage supports the concept that serine esterases play a unique role in macrophage physiology.