DNA Topoisomerase II Is Not Detectable on Lampbrush Chromosomes but Enriched in the Amplified Nucleoli of Xenopus Oocytes

In somatic cells DNA topoisomerase II (topo II) is thought to be involved in the domain organization of the genome by anchoring the basis of chromatin loops to a chromosomal scaffold. Lampbrush chromosomes of amphibian oocytes directly display this radial loop organization in cytological preparations. In order to find out whether topo II may play a role in the organization of these meiotic chromosomes, we performed immunofluorescence studies using antibodies against Xenopus topo II. Our results indicate that topo II is apparently absent from lampbrush chromosomes and is hence unlikely to act as a "fastener" of the numerous lateral chromosomal loops. Topo II was, however, enriched in the amplified nucleoli of Xenopus oocytes.     

Modes of action of fraxinellone against the tobacco budworm, Heliothis virescens

Fraxinellone significantly reduced the relative growth rate, food consumption rate as well as the efficiency of conversion of ingested food into biomass of Heliothis virescens when incorporated into artificial diets at concentrations of 4.31 × 10⁻⁵ mol/L and above. After being fed with fraxinellone-treated diets for 24 h, the larval midguts of H. virescens possess significantly lower activities of α-amylase and non-specific proteases and higher activities of cytochrome P450s. In vitro , the compound did not inhibit the activities of α-amylase and non-specific proteases extracted from the larval midguts. Clear evidence of post-ingestive toxicity of fraxinellone to midgut cells was observed under an electron microscope. The modes of action of the compound against insects were discussed.     

Import of glyoxysomal malate dehydrogenase precursor into glyoxysomes: A heterologous in-vitro system

A heterologous in-vitro system is described for the import of the precursor to glyoxysomal malate dehydrogenase from watermelon (Citrullus vulgaris Schrad., cv. Kleckey's Sweet No. 6) cotyledons into glyoxysomes from castor-bean (Ricinus communis L.) endosperm. The 41-kDa precursor is posttranslationally sequestered and correctly processed to the mature 33-kDa subunit by a crude glyoxysomal fraction or by glyoxysomes purified on a sucrose gradient. The import and the cleavage of the extrasequence is not inhibited by metal chelators such as 1,10-phenanthroline and ethylenediaminetetraacetic acid. Uncouplers (carbonylcyanide m-chlorophenylhydrazone), ionophores (valinomycin), or inhibitors of oxidative phosphorylation (oligomycin) and ATP-ADP translocation (carboxyatractyloside) do not interfere, thus indicating the independence of the process of import by the organelle from the energization of the glyoxysomal membrane.Abbreviations CCCP carbonylcyanide m-chlorophenylhydrazone - EDTA ethylenediaminetetraacctic acid - gMDH glyoxysomal malate dehydrogenase - PMSF phenylmethylsulfonyl fluoride     

Neurochemical effects of the synthetic ACTH4-9-analog Hoe 427 (Ebiratide) in rat brain

The ACTH4-9-analog Hoe 427 systemically injected in a dose range from 0.01-10 micrograms/kg caused a fall in acetylcholine (ACh) content in different brain areas of the rat. This effect occurred 0.5 hour after a single administration and lasted up to 24 hours. The decrease in ACh content induced by Hoe 427 was more pronounced when the animals were pretreated with dexamethasone (over 7 days 1 mg/kg SC, daily). Coadministration of the choline uptake inhibitor hemicholinium-3 (HC-3) and Hoe 427 potentiated the decrease in ACh content induced by HC-3. In the same dose range Hoe 427 acutely evoked an increase of the activity of the enzyme choline acetyltransferase as well as an elevation of brain cyclic GMP content. These data indicate that Hoe 427 enhances ACh metabolism in rat brain after systemic administration.