Natural hybridization inDrosophila

Summary Although at least 159 cases of interspecific hybridization between closely related species ofDrosophila have been obtained under laboratory conditions, only 7 cases of natural interspecific hybridization have been recorded. We report yet another case, concerningD. malerkotliana andD. bipectinata.Thanks are due to the University Grants Commission for supporting the research project of J.P.G. and to the Head of the Department for laboratory facilities.     

Demonstration of tissue-specific antigens shared by normal pancreas and pancreatic neoplasms

Summary Xenoantiserum raised against extracts of normal hamster pancreas, after absorption with normal tissues, reacted specifically with normal hamster and human pancreas by immunodiffusion. Absorbed antiserum also reacted with hamster and human pancreatic carcinoma but not with other neoplasms. Immunization of hamsters with normal pancreas extracts prevented growth of transplantable pancreatic carcinomas.     

Accumulation of drastic mutants in selection lines for resistance to the insecticides dichlorvos and malathion inDrosophila melanogaster

Summary Viability tests were performed on second and third chromosomes from lines ofDrosophila melanogaster selected for increased resistance to the organophosphorus insecticides dichlorvos and malathion, in order to evaluate the accumulation of drastic alleles. Our results show that malathion reduces significantly the relative viability of chromosome 3 and also increases the frequency of drastic alleles in this chromosome, while dichlorvos increases significnatly the frequency of drastic alleles in chromosome 2.Work supported in part by the Spanish Ministry of Education and Science (Grant No. 0577/84 CAICYT).—We are grateful to Productos Cruz Verde S.A. and Agrocrós S.A. for generously supplying the insecticides dichlorvos and malathion, respectively.     

Nuclear blebs in oocytes of the fishClarias batrachus

Summary Large nuclear blebs have been observed in oocytes of the fish,Clarias batrachus. The bleb, which contains nucleoplasm, is finally extruded from the nucleus. The extruded body is DNase-sensitive, and it implies that some amount of DNA is extruded from the nucleus of these oocytes.Acknowledgments. We are thankful to Dr. R.K. Sharan, Department of Zoology, Patna University, for providing laboratory facilities, and to Dr V.G. Jhingran and Dr P.V. Dehadrai of ICAR for their keen interest in the work.     

Electrophysiology of mammalian hypothalamic and interpeduncular neurons in vitro.

Electrical activities of the hypothalamic and interpeduncular neurons were studied in vitro in brain slices prepared from the guinea-pig brain stem. Neurons preserved resting membrane potentials comparable to those of neurons in vivo, responded to stimulation of the afferent fibres, and retained stable spontaneous firings for more than several hours.     

Age-related changes of the pattern of non-histone proteins in active and condensed fractions of mouse liver chromatin and hepatocarcinoma

Summary Electrophoretic analysis of histones and non-histone acid-soluble proteins in active (nuclease sensitive) and inactive chromatin from liver of young and old CBA mice and in age-related hepatocarcinomas showed a higher ratio of NHP: histones in active chromatin in old cells. Some liver- and hepatoma-specific fractions of non-histone proteins have been identified as chromatin matrix proteins.