Bioelectric aspects of the hemipteran telotrophic ovariole (Dysdercus intermedius)

Summary Two systems of steady extra-cellular currents were found along the surface of the telotrophicDysdercus ovarioles by means of a vibrating probe. The first covers the subgerminal tropharium and all the previtellogenic follicles. The current leaves the 3 or 4 small follicles of early euplasmic growth stages laterally and enters the syncytial tropharium. We presume that a similar intracellular current flows between the trophoplasm and the ooplasm which are interconnected by narrow nurse strands. Preliminary intracellular measurements indicate a potential gradient within this continuous cytoplasm, the ooplasm being electropositive to that of the tropharium. This current system fits into a model of polarized intracytoplasmic transport by electrophoresis. It is possible to explain the well known directed and selective flow of RNA from the tropharium via the nurse strands into the oocytes by means of such a model. The second current system occurs around every one of the 2 to 8 vitellogenic follicles. The pattern is completely different from that described for the first system. In the vitellogenic stages the current enters the follicle laterally all along the now much extended surface. It is balanced by a strong peak current which leaves the interfollicular region. As data on intracellular currents are not yet avialable, it is only a matter of speculation whether the circuit is closed through the ooplasm or only by a tangential loop through the follicle epithelium. The possible significance of this second current system for vitellogenin accumulation and uptake by the vitellogenic oocytes is also uncertain as yet.Supported by the Deutsche Forschungsgemeinschaft (Schwerpunkt Differenzierung)     

On the evolution and population genetics of hybrid-dysgenesis-causing transposable elements in Drosophila

Much has been learned about transposable genetic elements in Drosophila, but questions still remain, especially concerning their evolutionary significance. Three such questions are considered here. Has the behaviour of transposable elements been most influenced by natural selection at the level of the organism, the population, or the elements themselves? How did the elements originate in the genome of the species? Why are laboratory stocks different from natural populations with respect to their transposable element composition? No final answers to these questions are yet available, but by focusing on the two families of hybrid dysgenesis-causing elements, the P and I factors, we can draw some tentative conclusions.     

The synaptinemal complex in yeast

The occurrence of a synaptinemal complex in yeast was demonstrated by an electron-microscopical examination of meiotic prophase I. The complex is formed during the interval between the maximum of meiotic DNA synthesis and the first division.     

The postnatal growth of the skull in the house mouse Mus musculus Linné, 1758, and in 2 different large subspecies of the field mouse Microtus arvalis Pallas, 1779. I. Introduction, materials and methods]

In order to describe postnatal skull growth in Mus musculus, Microtus arvalis arvalis and M. a. asturianus, a total of 408 animals were raised and measured. The growth rate of single bones was followed by means of a maximum-likelihood estimator for the parameters A, B and C of the growth function Y(t) = A-B exp(-Ct). Supplementary techniques used to estimate the morphological divergence of the different taxa included methods of allometry research and multivariate statistical methods such as discriminate analysis and MANOVA. Drawings of selected stages of skull-bone ossification are provided to assist researchers in determining the age of undated specimens.     

Backbone modified oligodeoxynucleotides: stereoselective synthesis of methylphosphonates and HIV inhibitory capacity of phosphorothioates.

Oligonucleotides bearing phosphorothioate linkages of the HIV tatIII splice acceptor site were synthesized by automated solid phase synthesis. Especially 5'- and 3'-end capped thioates of the sequence 5'-ACACCCAATTCTGAAAATGG-3' show microM inhibition of HIV replication. ODN-methylphosphonates of defined stereochemistry were obtained with suitably modified proline phosphonamidite derivatives as monomeric building blocks. Asymmetric induction for nucleosidephosphonamidates up to 5:1 (Rp:Sp rsp. Sp:Rp depending on configuration of proline-moiety) could be reached. The intermediate phosphonamidite can be further reacted to dinucleoside methylphosphonates of enriched diastereomeric excess.