A long-term in vitro silicon-based microelectrode-neuron connection

A novel method for long-term recording and simulation applicable to cultured neurons has been developed. Silicon-based microelectrodes have been fabricated using integrated-circuit technology and micromachining. The chronic connection is made by positioning the tip of the `diving-board electrode' into contact with the top of the cell body. The electrode support structure is then glued to the bottom of the culture dish. Two-way electrical connections to Helisoma B19 neurons have been maintained for up to four days. This capability makes it possible to conduct experiments that are not practical using conventional techniques

Cytoplasmic DNA in the unfertilized sea urchin egg: Physical properties of circular mitochondrial DNA and the occurrence of catenated forms

The mitochondrial DNA in the unfertilized egg of the sea urchin Lytechinus pictus is present in an amount approximately seven times that of the haploid nuclear DNA.(1) The mitochondrial DNA has a higher buoyant density than the nuclear DNA and consists of circular duplex molecules of a uniform size of about 5µ. The circular DNA has been recovered(1) in both the intact (closed) and nicked (open) states characteristic of the circular duplex viral DNA's(2) and the mitochondrial DNA's from birds and mammals.(3, 4

Nesting biologies of oxaeine bees.

31 pages : illustrations (some color) ; 26 cm. "Appendix: Postdefecating larva of the cleptoparasitic bees Thalestria spinosa (Fabricius) and Triepeolus kathrynae Rozen (Apidae, Nomadinae, Epeolini)": pages 28-31.This study encompasses a number of field encounters by the author and others with nests of representatives of three of the four genera of the little-known New World andrenid subfamily Oxaeinae. Species treated include Protoxaea gloriosa Fox, Oxaea flavescens Klug, O. austera Gerstaecker, and Mesoxaea nigerrima (Friese), leaving the nesting biology of only the monotypic genus Notoxaea completely unknown. Nests, all subterranean, are described and diaƠgrammed, and each is reported to consist of a moderately to very deep main burrow with vertical cells occurring at the lower end attached to the main burrow by subhorizontal lateral tunnels, each of which is closed immediately after egg deposition. To the extent known, eggs, mature larvae, and pupae are described. Two known cleptoparasites of the subfamily are reported: Triepeolus kathrynae Rozen, hosted by P. gloriosa, and Thalestria spinosa (Fabricius) (= T. smaragdina Smith), which attacks nests of both O. flavescens and O. austera. The mature larvae of these cleptoparasitic Nomadinae are described and illustrated as an appendix

Centris bicornuta and Epicharis albofasciata.

20 pages : illustrations ; 26 cm.This paper presents detailed comparative descriptions of the mature larvae and eggs of Centris (Heterocentris) bicornuta Mocsáry and Epicharis (Epicharoides) albofasciata Smith as representatives of two genera that are closely related. It strongly suggests that both species, while developing, pass through five larval instars; because the first instar remains mostly pharate within the chorion, it is only as a second instar that it begins to consume provisions and increase in size. There follows an account of how each species changes in functional anatomy from one instar to the next and how each instar of one species compares with the same instar of the other. In response to a recently published paper (Martins and Melo, 2016), which suggested that the tribe Centridini may be polyphyletic because some taxa within Centris share features with corbiculate genera, it is pointed out that all corbiculate genera uniquely share an apomorphy: they bear small paired, elevated, finely setose, sclerotized, and usually pigmented apical tubercles on the thoracic segments of mature larvae. Such thoracic tubercles are unknown in the Centridini or elsewhere among bees