Aneuploidy, structural chromosome changes, and DNA amounts in the annual taxa of the Haplopappus spinulosus complex.

Haplopappus gracilis (n = 2), Haplopappus ravenii (n = 4), and Haplopappus wigginsii (n = 4) are isolated by F1 hybrid sterility due mainly to translocation heterozygosity. There is no evidence that this can be overcome at the diploid level so that introgression can occur among them. They are also separated geographically, but occasional populations of H. gracilis and H. ravenii may be brought together along roadways to form sterile hybrids. There were no statistically significant differences in nuclear DNA content among the same or structurally different aneuploid n = 2 and n = 3 chromosome races or ecotypes of H. gracilis. Some of the H. gracilis races were not significantly different from one race of the ancestral H. ravenii, and these samples of both species were from plants growing on poor soils in contrast to accessions from normal habitats. How much and which classes of DNA in these species are subject to changes induced by environmental effects is not known. There were no correlations between DNA amounts and altitude, latitude, and longitude. H. wigginsii had a greater amount of DNA per nucleus than either H. ravenii or H. gracilis, and its increased DNA content may reflect a more rapid accumulation of noncoding sequences due to facultative self-compatibility not found in the other two species.

Hematopoietic differentiation cell surface antigen switching in the bone marrow of different aged chickens.

Immune cytolysis and immunofluorescence were used to examine chicken fetal antigen CFA) and chicken adult antigen (CAA) expression on the differentiation/maturation series of definitive erythroid cells obtained from the bone marrow of different aged chickens. We found that erythroid cells undergo changes in CFA/CAA antigenic expression dependent on their differentiation/maturation stages as well as the developmental age of the chicken. All differentiation/maturation stages of erythroid cells in the bone marrow of 12 and 18-day-old embryos express CFA only. Erythroblasts obtained from 7-day post-hatched chickens express either CFA or CAA. All three CFA/CAA phenotypes (i.e., CFA, CAA, and CFA + CAA) are observed in subsequent maturation stages, but only the CFA + CAA phenotype is observed in mature erythroid cells in the bone marrow of 7-day post-hatched chickens. Erythroblasts from 62 day post-hatched chickens exhibit all three CFA/CAA phenotypes. Cells in the subsequent maturation stages express various CFA, CAA, or CFA + CAA phenotypes resulting in a majority of the mature erythrocytes expressing both CFA and CAA, and a small population of mature erythrocytes expressing CAA only. Erythroblasts from adult chickens express both CFA and CAA; however, CFA is lost during erythroid maturation resulting in mature erythrocytes which express CAA only. These studies indicate that both the erythroid differentiation/ maturation stage and the developmental age of the chicken influence CFA and CAA antigenic expression on erythroid cells undergoing cellular differentiation/maturation in the bone marrow.

Silver staining for nucleolar organizing regions of vertebrate chromosomes.

Refinements to a simple, one-step silver staining technique for nucleolar organizing regions are described. These include fixation of silver stained material with sodium thiosulfate and standardization of silver development conditions for different groups of vertebrates. The central advantages to the method are that it is rapid, reliable, simple, and inexpensive. Additional benefits include (i) consistent and uniform silver staining of nucleolar organizing regions, (ii) few reduced silver deposits elsewhere on the chromosomes or on the slides, (iii) generally unaltered chromosome morphology after silver treatment, and (iv) relative permanence of Permounted preparations. The method works equally well on chromosomes made from cell cultures and from solid tissues of live specimens.

Autocidal control of screwworms in North America.

The larva of the blowfly Cochliomyia hominivorax, also known as the screwworm, eats the living flesh of cattle and sheep and other warm-blooded animals. A program to eradicate the screwworm in the United States was initiated in the 1950's. The program was very effective until 1968, but severe screwworm outbreaks occurred in 1972 to 1976 and in 1978. Although the program has again been effective since 1979, the possibility of outbreaks recurring in the future has highlighted the need for a broader understanding of the pest. Studies of screwworm populations in the United Stated and Mexico indicate that much of the genetic diversity of this insect is distributed among sympatric non-interbreeding populations. A new approach may be required to retain the effectiveness of the control program and to prevent a serious outbreak from threatening the economic viability of the U.S. livestock industry.

Chicken fetal antigen (CFA) expression on the primitive erythroid maturation series.

Indirect immunofluorescence was utilized to study the expression of chicken fetal antigens (CFA), developmentally phasic membrane antigens, on the primitive erythroid series during chick embryo development. Cells of this series expressed CFA determinants at all four stages of cellular maturation. However, the relative intensity of fluorescent staining (measurement of CFA determinants) varied with development. CFA determinant loss was correlated with the age of the embryo, and the stage of cellular maturation. Indirect immunofluorescence utilizing antisera capable of detecting eight individual CFA determinants revealed that all eight CFA determinants were present on early polychromatic erythrocytes of the primitive series, but that a selective and sequential loss of CFA determinants occurred in later stages. The data suggest that certain CFA determinants are differentially expressed during primitive erythroid cellular maturation in the developing chick embryo.

Non-random position of the A-T rich DNA sequences in early embryos of Drosophila virilis.

Examination of early embryos of Drosophila virilis by light and electron microscopy has shown that the A-T rich satellite DNA sequences have a non-random distribution within the nuclei. As observed by 33258 Hoechst staining and fluorescent microscopy, these sequences are consistently found to be located on the sides of the nuclei nearest to the vitelline membrane. This arrangement of the A-T rich sequences has been observed from the syncytial balstoderm stage into the gastrula stage where, in each nucleus, the satellite DNA sequences remain at a point nearest the topological outside of the organism.

The fluorescence localization of mouse satellite DNA in interphase nuclei.

Nuclei from various mouse tissues exhibit a pattern of fluorescence characteristic of the cell type when stained with the fluorescent compound Hoechst 33258. When such preparations are hybridized in situ with 3H-RNA complementary to the A-T rich satellite of mouse, it is clearly seen that only the fluorescent regions of the nuclei contain the satellite DNA. Thus Hoechst 33258 allows the precise localization of satellite DNA at all stages of the mouse cell cycle.

The organization of interphase chromatin in drosophilidae: the self adhesion of chromatin containing the same DNA sequences.

Cytological evidence is presented which shows that for Drosophila virilis and Samoaia leonensis at least, each satellite DNA is condensed into a distinct heterochromatic mass during interphase. This is seen as just one example of a general phenomenon in which chromatin containing a particular DNA sequence binds to other chromatin containing the same sequence. It is proposed that DNA sequence specific proteins can account for this phenomenon.