Changes in nuclear K+ electrochemical activity and total nuclear K+ content in salivary glands of Chironomus tentans were measured with ion-selective microelectrodes based on valinomycin and with flameless atomic absorption spectrometry, respectively. The K+ activity increased by a factor of 2.6 and the total K+, by a factor of 1.5 as oligopausing larvae developed into prepupae. The extent of decondensation (puffing) of K+sensitive regions in the polytene chromosomes underwent a parallel increase during this developmental event. In vitro culture of glands from oligopausing larvae resulted in similar changes with respect to nuclear K+ activity and puffing. Changes in nuclear ion concentrations have been suggested to be involved in fundamental biological processes such as egg maturation and activation, cell replication and differentiation, aging, regeneration, and hormone action (1-7). Moreover, many constituents of nuclei (including chromatin and RNA and DNA polymerases) exhibit specific ion sensitivities (for references see refs. 5 and 8). Unfortunately, data (5, 9-11) on in ivo ion changes within cell nuclei are scarce and of limited utility, because the methods used (atomic emission and absorption spectrometry and neutron or electron activated y-and x-ray emission analysis) permit the measurement of the total contents of the particular ions only-i.e., of the sums of their bound and free fractions. However, the ion sensitivities of nuclear constitutents most likely depend above all upon the free fractions of ions, more specifically on their electrochemical actimties.In order to be able to determine ion activities directly, we decided to use ion-sensitive microelectrodes. Here we report results obtained with a K+-sensitive microelectrode based on the neutral ionophore valinomycin (12,13 The total K+ content was determined by flameless atomic absorption spectrometry of nuclei isolated in the lyophilized state. The salivary glands were frozen (and subsequently lyophilized) in situ: the glands and the nuclei were manually isolated under silicone oil, which does not take up any measurable amounts of water, Na+, or K+; the nuclear dry weight was determined on an evacuated quartz fiber balance (22).Oligopause in the middle of fourth instar of C. tentans was
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The development of Chironomus plumosus within the 4th larval instar was investigated under long day (18 h light/6 h dark) and short day (6/18) conditions at a temperature of 15°C. The state of the imaginal discs was the criterion of the state of development of the larvae.In general long day treatment induced subitaneous without delay development. Occasionally an endogenic developmental check, termed long day dormancy, occurred through long day treatment. Under long day conditions in the 4th larval instar only, the males developed faster on average than the females. The 4th larval instar was the most important in larval growth since about 80-85% of the maximum larval weight was formed during this period. By subitaneous development the weight of the larvae increased parallel to their respective development in both sexes.A developmental check, an oligopause, was induced by short day conditions. Its duration varied considerably but could last several months. In the majority of the larvae it ended spontaneously and metamorphosis began. The oligopause affected the imaginal disc phases 3-4 to 6. Under short day conditions the dormant larvae grew rapidly at first, but after some time their weights remained relatively constant, fluctuating only slightly around a mean value.When larvae of short day induced dormancy were placed under long day conditions, metamorphosis began immediately. Larvae kept individually developed more quickly than did those in a mass culture. A regulatory system of dormancy for Chironomus plumosus is proposed.
Ineichen, H. 1978. "Photoperiodische Kontrolle der Entwicklung vonChironomus tentans und entwicklungsspezifische Puff-Veränderungen (in vivo und in vitro)." Revue suisse de zoologie 85, 807-809.
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