silicon and Encephalitis

Bulk micromachining techniques of silicon have been used successfully in the past several years to microfabricate microelectrodes for monitoring single neurons in acute and chronic experiments. In this study we report for the first time a novel surface micromachining technique to microfabricate a very thin polysilicon microelectrode that can be used for monitoring single-unit activity in the central nervous system. The microelectrodes are 3 mm long and 50 microm x 3.75 microm in cross-section. Excellent signal to noise ratios in the order of 25-35 dB were obtained while recording neuronal action potentials. The microelectrodes successfully penetrated the brains after a microincision of the dura mater. Chronic implantation of the microprobe for up to 33 days produced only minor gliosis. Since the polysilicon shank acts as a conductor, additional processing steps involved in laying conductor lines on silicon substrates are avoided. Further, surface micromachining allows for fabricating extremely thin microelectrodes which could result in decreased inflammatory responses. We conclude that the polysilicon microelectrode reported here could be a complementary approach to bulk-micromachined silicon microelectrodes for chronic monitoring of single neurons in the central nervous system.

Topics: Action Potentials; Animals; Artifacts; Brain; Dura Mater; Electrophysiology; Encephalitis; Gliosis; Microelectrodes; Neurons; Rats; Rats, Wistar; Silicon; Stereotaxic Techniques

Glycosylation of 5-trimethylsilyl- and 5-triethylsilyluracil as well as 5-trimethylsilylcytosine with 2-deoxy-3,5-di-O-p-toluyl-alpha-D-ribofuranosylchloride and subsequent deacylation led to alpha- and beta-anomers of 5-Me3SidUrd, 5-Et3SidUrd and 5-Me3SidCyd. 1-(alpha-D-Arabinofuranosyl)-5-trimethylsilyluracil was synthesized starting from the derivatives of 2,3,5-tri-O-benzoyl-D-arabinofuranose and then converted to alpha-5-Me3SidUrd via 1-(2,2'-anhydro-alpha-D-ribofuranosyl)-5-trimethylsilyluracil and 1-(2-chloro-2-deoxy-alpha-D-arabinofuranosyl)-5-trimethylsilyluracil+ ++. Out of all synthesized compounds, only alpha-5-Me3SidUrd inhibits the replication of HSV-1 both in vitro and in vivo; it also exerts a pronounced therapeutic effect in guinea pigs with herpes genitalis induced by HSV-2. The resistance of alpha-5-Me3SidUrd to pyrimidine phosphorylases facilitates its antiviral activity in vivo.

Topics: Animals; Chemical Phenomena; Chemistry; Encephalitis; Female; Guinea Pigs; Herpes Genitalis; Herpes Simplex; Male; Pyrimidine Nucleosides; Rats; Silicon; Trimethylsilyl Compounds