Duplications in the polytene chromosomes of Drosophila auraria

A study of the salivary gland chromosomes of two strains of Drosophila auraria has revealed a suprisingly high number of inverted tandem duplications and one triplication. The possible origin and significance of these are discussed.     

Activities of the nuclear envelope in the salivary glands of Drosophila

Morphological data are presented concerning the single-membrane-bound vesicles ("oval bodies") associated with the nuclear envelopes of larval salivary gland cells of Drosophila. Data are also presented concerning the existence of cytoplasmic annulate lamellae in these same cells. The mode of formation of these structures, as well as the relationships between them and with other cytoplasmic organelles are described. The possible functional significance of these phenomena is discussed.     

Toxicity of Bacillus thuringiensis to laboratory populations of the olive fruit fly (Dacus oleae).

A survey of Bacillus thuringiensis recovered from the environments of olive groves in Greece was carried out. Of 80 soil samples, 24 were found to contain B. thuringiensis with parasporal crystal inclusions; these were tested for toxicity against the olive fruit fly (Dacus oleae). Mortality levels of larvae caused by the different isolates varied from 7 to 87%. Higher levels of mortality were observed if a mixture of relatively pure crystals and spores was used compared with the mortality resulting from either fraction alone. We were able to show that the toxicity of the most active isolate is likely to be specific for D. oleae.     

Stimulation of the P2Y Purinergic Receptor on Type 1 Astroglia Results in Inositol Phosphate Formation and Calcium Mobilization

Cultured astroglia express purinergic receptors that initiate phosphoinositide metabolism and calcium mobilization. Experiments were conducted to characterize the purinergic receptor subtype on type 1 astroglia responsible for stimulation these second-messenger systems. Inositol phosphate (IP) accumulation and calcium mobilization were measured after stimulation with ATP or purinergic receptor subtype-selective ATP analogues. ATP (10(-5) M) increased IP accumulation severalfold. Dose-effect assays monitoring astroglial IP accumulation revealed the order of potency that defines the P2Y receptor: 2-methylthioadenosine 5'-triphosphate greater than ATP greater than alpha beta-methyleneadenosine 5'-triphosphate greater than beta gamma-methyleneadenosine 5'-triphosphate. The influence of ATP on intracellular calcium levels in individual type 1 astroglia was examined using the calcium indicator dye, fura-2. Dose-effect experiments indicated that ATP was equally potent for generating inositol phosphates and increasing cellular calcium. The most prevalent response (87% of total responses) to ATP consisted of a rapid increase in calcium to a peak level that was approximately five times greater than the prestimulation level. This peak was followed by a decline to a plateau level that was significantly above baseline. This plateau phase of the calcium increase was maintained for at least 5 min in the presence of ATP and was dependent on external calcium. Many (23%) astroglia exhibited spontaneous calcium oscillations whose frequency and magnitude increased after the addition of 10(-5) M ATP. Immunocytochemical staining indicated that the responses occurred in glial fibrillary acidic protein positive cells. We conclude that type 1 astroglia express the P2Y purinergic receptor which regulates IP production and calcium mobilization.     

Developmental studies inDrosophila

Summary Alkaline phosphatases and several dehydrogenases and oxidases separated by a microdisc electrophoresis technique have been studied during larval and early pupal development ofD. pseudoobscura salivary glands, fat body, hemolymph, body wall and whole body. Tissue-specific enzymes were observed and the qualitative differences occurring during the development are discussed.This work was supported in part by grants GM-16736-03 and FR-05426-09 from U.S. Department of Health, Education, and Welfare. The work presented is a portion of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy.     

Developmental studies in Drosophila

A study of the puffing patterns of the salivary gland chromosomes of D. pseudoobscura was carried out through several larval, prepupal, and pupal stages of development. A total of 176 puffs were found, 111 of which changed during the stages studied. As described in previous investigations with other Drosophila species there are two major peaks of puffing activity. These two peaks occur during puparium formation and pupation. Additionally, a minor activity-peak occurs during mid-prepupal life. Attempts have been made to establish correlations between the puffing data and those obtained from electrophoretic and ultrastructural studies.Supported in part by grants GM-16736-03 and FR-05426-09 from the U.S. Department of Health, Education, and Welfare. Ann Jacob Stocker was a holder of a University of Texas predoctoral fellowship.     

A comparative chromosome study in the incipient species of the Drosophila paulistorum complex

The gene arrangements in the chromosomes of the races or incipient species of the Drosophila paulistorum complex have been compared in the interracial hybrids. The results are correlated with those obtained by Dobzhansky and Pavlovsky (1962), and also with data on the intraracial polymorphisms, to be published elsewhere. A Standard strain was chosen arbitrarily, the Palmira stock of the Transitional race, and other races and strains described in terms of comparison with the Standard. The minimal number of inverted sections differentiating the Andean race from the Standard is 1, Centroamerican 5, Orinocan 3, Amazonian 6. Little chromosome pairing takes place in the hybrids between the Standard and the Guianan strains. These strains may well be regarded as belonging to a full-fledged species distinct from D. paulistorum complex. The results of the present study furnish little support to the Mayr-Carson hypothesis, according to which diverging incipient species are expected to share few or no intrapopulational polymorphisms.The work reported in this article has been carried under Contract No. AT (30-1)-3096-10, U.S. Atomic Energy Commission.     

Heterochromatic chromosomes and satellite DNAs of Drosophila nasutoides

Drosophila nasutoides is distinguished from other Drosophila species in that the metaphase karyotype shows a pair of very large V-shaped chromosomes. With Giemsa, a distinctive C-banding pattern is revealed along the arms of this large chromosome, indicating a largely heterochromatic nature. Furthermore, the banding patterns of the arms are symmetrical, indicating that it is an iso-chromosome. A comparison between the metaphase karyotype and polytene chromosomes suggests that the large V chromosome appears as the dot chromosome in polytene squash. One autosome has twice the arm length of typical Drosophila polytene chromosomes and arose either by centric fusion and a pericentric inversion, or by translocation connecting distal ends with a subsequent loss of one centromere. This chromosome appears to have a short arm which ectopically pairs with the proximal region of the long arm, representing a duplication of about ten bands. When the nuclear DNA is examined by neutral CsCl gradient, four satellites are observed. As much as sixty percent of the total DNA appears as satellites in the lysate of larval brains. No satellite was detectable in the lysate of salivary glands. These observations led us to suggest that the heterochromatic nature of the large V chromosome is due to the presence of all four satellites in this chromosome and that this large chromosome appears as the dot because of the under-reduplication of the satellites during polytenization.