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  • 11
    Electronic Resource
    Electronic Resource
    The formation of ribonucleoprotein droplets in Chironomus salivary gland nuclei (1979)
    Springer
    Chromosoma 74 (1979), S. 83-103 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The appearance of RNP droplets associated with specific regions of polytene chromosomes from Chironomus larvae has been studied, systematically by light microscopy using glutarladehyde fixation and lactic acid squashing of the salivary gland. During the fourth larval instar the highest frequency of nuclei which contained droplets (over 50%) was observed in late prepupae. Several treatments (heat and cold shock, cycloheximide) were found to stimulate the formation of a large number of droplets whose features under the light and electron microscopes seemed to be identical to those observed in untreated larvae. Droplets could be observed either in a free state in the nuclear sap or grouped around specific regions of the chromosome such as some Balbiani rings and puffs. Kinetic studies suggest that droplets first appear in a free state and later group themselves on specific chromosome regions. Transcriptional activity seems to be essential for the process of droplet accumulation in the chromosome, since it does not take place if RNA synthesis is inhibited. Cytochemical tests showed striking similarities between the staining reactions of droplets and those of the fibrillar component of the nucleolus. These observations indicate that droplets probably originate from, or share a common component with, nucleolar material and that this component has a preferential affinity for some active chromosomal loci, where it accumulates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00344485
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  • 12
    Electronic Resource
    Electronic Resource
    DNA-RNA hybrids and transcriptional activity in Chironomus polytene chromosomes (1984)
    Springer
    Chromosoma 90 (1984), S. 103-110 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The distribution of DNA-RNA hybrids was studied in fixed Chironomus polytene chromosomes by means of specific antibodies directed against DNA-RNA hybrids. Attention was mainly focused on the relationship between detection of hybrids and local transcriptional activity. As a model to test such a relationship Balbiani rings, whose transcriptional activity was experimentally modified, and a new set of puffs induced by heat shock (t-puffs), were chosen. With a few exceptions DNA-RNA hybrids appeared, and when air-drying of the slides was avoided, in actively transcribing loci. When the slides were air dried, the antibody detected no DNA-RNA hybrids unless the preparations were submitted to conditions promoting denaturation and subsequent reannealing, or to a mild pronase digestion. Denaturation/renaturation led to the detection of DNA-RNA hybrids in heat-shock-induced as well as in heat-shock-inactivated loci. On the other hand, a mild pronase digestion led to the detection of hybrids only in the heat-shock-induced puffs. These results strongly suggest that in air-dried preparations the hybrids are masked by protein and that they are unmasked by a mild pronase digestion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292446
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  • 13
    Electronic Resource
    Electronic Resource
    Temperature-induced Balbiani rings in Chironomus thummi (1981)
    Springer
    Chromosoma 83 (1981), S. 341-352 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The formation of a new telomeric Balbiani ring in the right arm of chromosome III (T-BR III) has been induced in Chironomus thummi larvae by applying a wide range of temperature treatments (33 °–39 ° C). In this paper we present some kinetic and functional characteristics of this structure. T-BR III incorporates tritiated uridine, and during its formation accumulation of acidic proteins takes place. However, induction and maintenance of this puff structure appear to be insensitive to Actinomycin treatment. An additional T-BR can be induced in chromosome I by employing the most drastic temperature treatments (37 °–39 ° C). We also report the existence of a group of puffs active after heat treatments in Chironomus polytene chromosomes which could be homologous with the T-puffs of Drosophila.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327357
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  • 14
    Electronic Resource
    Electronic Resource
    Galactose-induced puffing changes inChironomus thummi Balbiani rings and their dependence on protein synthesis (1990)
    Springer
    Chromosoma 99 (1990), S. 61-70 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract InChironomus thummi, puffing changes induced by galactose treatment (sugar effect) are restricted to the Br1/BR2 (Balbiani ring) system. No obvious induction of additional BRs such as BR6 inCamptochironomus pallidivittatus occurs. The response to feeding galactose (or other sugars), i.e. BR2 regression and concomitant BR1 activation, usually takes 24–48 h but can be accelerated somewhat by the application of two 6 h galactose treatments separated by an 18 h interval without sugar. In the “special cells” composing the lateral lobe of the salivary gland galactose causes regression on BR2 without concomitant BR1 activation which, however, appears delayed. The autonomous collapse of BR2 therefore could be considered as the primary effect of galactose at the puffing level. On the other hand, inhibition experiments performed with cycloheximide (CHM) emphasize the relevance of translational events in the control of the sugar effect. At highly inhibitory doses, CHM prevents the induction or causes reactivation of galactose-repressed BR2, suggesting that both induction and maintenance of the galactose effect are dependent on newly synthesized proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01737290
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  • 15
    Electronic Resource
    Electronic Resource
    Auxin deficiency at the onset on root growth in Allium cepa (1971)
    Springer
    Planta 97 (1971), S. 364-366 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 3-Indolylacetic acid (IAA) increased the length of the epidermis cells of onion roots during the initial stage of root growth, when cell length has not yet reached its maximum value, by up to 50% (10−11 M), while in the later, steady-state or dynamic equilibrium stage no promotive effects were present. It is suggested that the lesser elongation capacity of the cells at the onset of root growth is related to a deficiency in auxin while the steady-state phase is characterized by hormonal balance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390216
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  • 16
    Electronic Resource
    Electronic Resource
    Histochemical localization of reverse transcriptase in polytene chromosomes of chironomids (1999)
    Springer
    Chromosoma 108 (1999), S. 302-307 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The localization of a reverse transcriptase-related protein in salivary gland polytene chromosomes was investigated by immunohistochemistry in two species of Chironomus. The antibodies used were raised against a recombinant protein containing phylogenetically conserved motifs of reverse transcriptases and derived from an abundant non-LTR element previously identified in Chironomus. Immunoreactive protein was found in some telomeres, in a centromeric region, in a few interstitial bands and in Balbiani ring 3. The telomeric signal was probably dependent on transcription and increased dramatically when telomeric heat shock puffs were induced. A correlation with transcription was also seen in Balbiani ring 3, the immunobinding of which disappeared after inhibition of transcription with actinomycin D.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050381
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  • 17
    Electronic Resource
    Electronic Resource
    Telomeric DNA sequences differentially activated by heat shock in two Chironomus subspecies (1988)
    Springer
    Chromosoma 96 (1988), S. 139-144 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The patterns of puffing, transcription and protein synthesis under heat shock were analysed in polytene nuclei of Chironomus thummi piger, in comparison with those obtained in the closely related subspecies C. th. thummi. Most chromosomal heat shock puffs, as well as heat shock induced polypeptides, in C. th. piger paralleled those previously reported for C. th. thummi. Nevertheless, we found a striking difference in behaviour in the induction of telomeric Balbiani rings by heat shock in the two subspecies. Although homologous sequences were present at all the telomeres in both subspecies, they were not always transcriptionally activated by heat shock. The most frequently puffed telomeres were that of chromosome III R in C. th. thummi and that of chromosome IV R in piger. Transcription of the same sequences from both telomeric Balbiani rings (T-BR-III and T-BR-IV) occurred under heat shock. The enigmatic behaviour of telomeres and the functional significance of T-BRs are discussed in relation to possible equivalents in other Diptera.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331046
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  • 18
    Electronic Resource
    Electronic Resource
    Immunoelectron microscope localization of Mr 90000 heat shock protein and Mr 70000 heat shock cognate protein in the salivary glands of Chironomus thummi (1992)
    Springer
    Chromosoma 102 (1992), S. 50-59 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The Mr 90000 heat shock protein (hsp 90) and one of the Mr 70000 heat shock cognate proteins (hsc 70) were localized by immunoelectron microscopy in salavary gland cells of normal and heat-shocked larvae of Chironomus thummi using polyclonal antibodies raised against Drosophila proteins. Immunoblotting after separation of proteins by gel electrophoresis shows that these antibodies cross-react with the corresponding proteins of Chironomus. Hsp 90 was localized both in the cytoplasm and in the nucleus, where it is associated with intrachromosomal and extrachromosomal ribonucleoprotein (RNP) fibrils, as well as with the peripheral region of compact chromatin. After heat shock the concentration of hsp 90 increases in the nucleus. This increase is prevented by actinomycin D administration during the heat shock. Hsp 90 is associated with the chromatin of puffs repressed by heat shock and with the RNP fibrils of actively transcribing heat shock puffs. Hsc 70 is mainly found in RNP fibrils and in the periphery of compact chromatin. During heat shock the concentration of hsc 70 decreases in the cytoplasm while it becomes more abundant in association with chromatin and intrachromosomal and extrachromosomal RNP fibrils. These results suggest a translocation of the existing protein from the cytoplasm toward the nucleus. They are supported by observations of the effect of heat shock carried out in the presence of actinomycin D.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352290
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  • 19
    Electronic Resource
    Electronic Resource
    Effect of cordycepin (3′-desoxyadenosine) on polytene chromosomes of Chironomus pallidivittatus salivary glands (1973)
    Springer
    Chromosoma 42 (1973), S. 345-358 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Incubation of Chironomus pallidivittatus salivary glands in the presence of cordycepin induces the collapse of Balbiani rings. In spite of the great reduction of the Balbiani ring size, 3H-uridine incorporation takes place in these structures and also in puffs and nucleolus. Modifications in the nucleolar pattern of labelling have been observed. Differences were found between the effect of cordycepin and those of actinomycin and adenosine both of which induce the collapse of Balbiani rings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399404
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  • 20
    Electronic Resource
    Electronic Resource
    Effect of galactose treatment in the puffing pattern of Chironomus thummi Balbiani rings (1978)
    Springer
    Chromosoma 69 (1978), S. 93-100 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Galactose feeding of Chironomus thummi larvae induces the regression of Balbiani ring c (BRc) and the full expansion of BRb, both localized in the IV salivary gland chromosome. This effect coincides with that described on BR2 and BR1 of Ch. pallidivittatus and Ch. tentans. The puffing changes of BRb and BRc throughout development have been studied and also show identical variations as in BR1 and BR2 of Ch. pallidivittatus and Ch. tentans. The similar behaviour of BRb and BR1, and of BRc and BR2 respectively after galactose treatment and throughout development strongly suggests that these BRs play the same physiological role in the three Chironomus species, with BRb = BR1 and BRc=BR2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327383
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