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At least 739 records · Page 41Linked to original sources
PubMed1990

Ultrastructural localization of acid phosphatase in spermatic cells of Ceratitis capitata (Diptera).

The cytochemical study of acid phosphatase in spermatic cells of Ceratitis capitata defines the enzimatically active sites, relating this enzyme with morphological modifications of the cell components during spermiogenesis. In the axoneme, acid phosphatase is associated with the metabolism of phosphates which promote flagellar motility. The enzymatic activity verified on the cytoplasmic membranes demonstrates the importance of this enzyme in the process of cellular differentiation.

Acid Phosphatase↗
PubMed1975

Achiasmate meiosis and centromere shift in Eusimulium aureum (Diptera-Simuliidae).

Light and electronmicroscope studies indicate that Eusimulium aureum (n equals 2 metacentrics) is male-achiasmate. Supporting evidence for achiasmate meiosis includes lack of recombination between, I) widely separated differential segments of X and Y chromosomes and 2) linked autosomal inversions. In sibling C, chromosome II exists in an alternate "neoacrocentric" form interpreted as originating through the three-break shift of a small segment including centromere and nucleolar organizer. Male-achiasmate meiosis appears to be a prerequisite for the establishment of rearrangements that include large displacements of the centromere. This suggestion is supported by a correlation between achiasmate male meiosis and the fixation of gross pericentric changes in a number of other black fly species.

Animals↗
PubMed1975

[Identification of the genetic sex chromosomes in the monogenic blowfly Chrysomya rufifacies (Calliphoridae, Diptera)].

Previous investigations have shown the sex determination in the monogenic blowfly Chrysomya rufifacies to be controlled by a cytologically not discernible homogametry-heterogamety mechanism in the female. Female-producing (thelygenic) females are assumed to be heterozygous for a dominant female sex realizer (F') with sex-predetermining properties, while male-producing (arrhenogenic) females as well as males are supposed to be homozygous for the recessive allele (f). In order to identify the genetic sex chromosomes of C. rufifacies among its five pairs of long euchromatic chromosomes (nos. 1-5) plus one pair of small heterochromatic ones (no. 6), all chromosomes were marked by reciprocal translocations induced by X-ray treatment of adult males. The inheritance of thirteen different heteroxygous translocations has been analyzed. All of the translocations (eleven) between two of the four longer chromosomes did not show sex-linked inheritance, thus demonstrating the autosomal character of the chromosomes nos 1, 2, 3 and 4. The same is true for the translocation T6 (2/6). Therefore the small heterochromatic chromosome no. 6, corresponding to the morphlogically differentiated six chromosomes within the amphogenic calliphorid species, remains without sex determining function in the monogenic fly. This could be confirmed by the analysis of monosomic (monosomy-6) and trisomic (trisomy-6) individuals, which resulted from meiotic non-disfunction in T6/+ translocation heterozygotes. Contrary to these translocations, the heteroxygous 5/2 translocation (T14) exhibited sex-linked inheritance: There was but a very low frequency (0,76 per cent) of recombinants resulting from crossing-over between F'/f and the translocation breakage point in theylgenic F1 T14/+females. The sex-linked inheritance of T14 was confirmed by the progeny of a thelygenic F1 T14/+ female crossed to a homozygous T14/T14 translocation male.Among the offspring of that F1 T14/+ female, which had received the translocation from its father, all of the F2 T14/+ females were thelygenic compared to their arrhenogenic T14/T14 sisters. These results prove that the chromosomes of pair no. 5 genetically act as X'X-XX sex chromosomes in C. rufifacies.

Animals↗
PubMed1975

X-ray induced visible alterations in the giant chromosomes of Phryne cincta (Nematocera, Diptera): relation of radiation sensitivity to pronuclear chromosome structure.

In order to induce chromosomal rearrangements, males were exposed to x-rays and then mated to non-irradiated females. The number of each type of structural alteration was determined by examination of the polytene chromosomes of the F1 progeny. -- A comparison of the results with similar studies made on Drosophila revealed a significantly greater sensitivity in Phryne. Parallel to that an extremely high frequency of small inversions was ascertained in Phryne, and the observed ratio of inversions to translocations was the inverse of that which would be expected from purely mathematical considerations based on the lengths of the different chromosomes. These facts allow the conclusion that the paternal pronuclear chromosomes in Phryne are highly spiralized. Besides, the kinetochore-to-translocation-breakpoint distance was measured in both of the chromosomes involved in each reciprocal translocation and the differences (kinetochore-break distance differences) were registered and from them the arrangement of the chromosomes in the pronucleus of Phryne deduced. The data obtained support the assumption of an ordered, polar-field type of orientation. In Drosophila, in contrast, the comparable data showed that the pronuclear chromosomes are not spiralized and are randomly arranged (Bauer, 1939). -- These results seem to indicate that a close correlation exists between the different radiation sensitivities of Drosophila and Phryne and the different states of spiralisation and arrangements of their chromosomes in the pronucleus stage. It is hypothesized that the influence of the maternal genome on the degree of spiralization of the paternal chromosomes could account for differences in the pronuclear chromosome structure of both species.

Animals↗
PubMed1988

GATA tandem repeats detect minisatellite regions in blowfly DNA (Diptera: Calliphoridae).

A DNA probe containing GATA tandem repeats detected numerous dispersed minisatellite regions in the genomes of the blowflies Chrysomya rufifacies and Calliphora erythrocephala. These regions seemed to be actively transcribed into poly(A)+ RNA in a tissue-specific manner. When genomic DNA of blastoderm embryos was compared with adult genomic DNA some loci hybridizing to GATA displayed a marked stage-specific variation in length. In Calliphora, a small sex-linked dimorphism of GATA mini-satellite-associated restriction fragments was observed.

Animals↗
PubMed1976

Polytene chromosomes in pupal and adult blackflies (Diptera: Simuliidae).

A number of pupal and adult tissues of eight Australian blackfly species representing three genera, Austrosimulium, Cnephia and Simulium, were examined for the presence of polytene chromosomes. Banded polytene chromosomes were found in malpighian tubules, hind gut, fat body, and ovary, but only those from the malpighian tubules of female adults and pupae were of good quality. A detailed comparison of polytene chromosomes from larval salivary glands and adult malpighian tubules was made in S. ornatipes and, to a limited extent, in S. melatum. The banding patterns of chromosomes from both tissues were found to be identical with minor differences in puffing patterns in S. ornatipes and chromocenter characteristics in S. melatum. A survey of the remaining six species shows five of them to have malpighian chromosomes suitable for detailed cytological analysis. Simultaneous studies of larval, pupal and adult polytene chromosome systems offer a novel approach to the analysis of population problems in blackflies. The ability to recognise sibling species in adults also has potential practical significance in efforts to control vectors of onchocerciasis.

Animals↗
PubMed1975

Q-, C-, and G-banding patterns in the germ-line and somatic chromosomes of Miastor sp. (Diptera: Cecidomyidae).

Q-, C-, and G-banding patterns are described for the germ-line and somatic chromosomes of Miastor sp. The chromosome number in the germ line is 36, which is 3 less than that previously reported for the same cultured line 18 years ago. There are 8 chromosome groups: 8 large acrocentrics, 11 large and medium submetacentrics, 4 medium metacentrics, 4 medium subtelocentrics, 6 medium telocentrics, one medium acrocentric, one small submetacentric, and one small telocentric. All 8 large acrocentrics have a Q-band and an interstitial C-band in the short arm, suggesting that these chromosomes are at least partially homologous (or homeologous) and that the germ line originally was polyploid. Only one other germ-line chromosome, the small submetacentric, has a Q-band and an interstitial C-band. In somatic cells there are 8 chromosomes, 28 chromosomes having been eliminated during early cleavage. Three of the four pairs of somatic chromosomes are heteromorphic, despite the indications of a polyploid origin of the germ-line chromosomes and despite the presence of somatic pairing. Furthermore, there is a great deal of restriction on which chromosomes are retained in somatic cells, and it may be that the same 8 chromosomes are retained by all embryos. The G-banding pattern is not as clear as the other two banding patterns. The findings are discussed in relation to observations in other cecidomyids, and a model for the evolution of the chromosome system of Miastor is presented.

Animals↗