A simple design for a small fixed four-electrode brain stimulation array.

Anatomical studies of intracranial self-stimulation (ICSS) reward in rats often use the lesion method and, therefore, require repeated behavioral testing before and after the lesion. Other anatomical studies on unlesioned rats use a moveable electrode to permit testing at a number of ICSS sites. Combining these methods would yield still more information, but repeated testing is not possible due to the damage created by lowering the electrode. To meet this need, an array of 4 fixed vertically-spaced electrodes was devised. Electrodes are constructed from strands of 0.14-mm (0.0045'') Teflon-insulated stainless-steel wire, 4 of which are glued into an implantable bundle. A 4-channel IC rotary switch is implanted on the rat's head to permit the use of an inexpensive 2-channel electrode lead and commutator. In our laboratory, electrodes were vertically spaced at 0.3 mm, spanning the dorsoventral extent of the lateral hypothalamus and yielded stable rate-frequency curves over the usual 3-4 month period of behavioral testing.

Multiplex sequencing of 1.5 Mb of the Mycobacterium leprae genome.

The nucleotide sequence of 1.5 Mb of genomic DNA from Mycobacterium leprae was determined using computer-assisted multiplex sequencing technology. This brings the 2.8-Mb M. leprae genome sequence to approximately 66% completion. The sequences, derived from 43 recombinant cosmids, contain 1046 putative protein-coding genes, 44 repetitive regions, 3 tRNAs, and 15 tRNAs. The gene density of one per 1.4 kb is slightly lower than that of Mycoplasma (1.2 kb). Of the protein coding genes, 44% have significant matches to genes with well-defined functions. Comparison of 1157 M. leprae and 1564 Mycobacterium tuberculosis proteins shows a complex mosaic of homologous genomic blocks with up to 22 adjacent proteins in conserved map order. Matches to known enzymatic, antigenic, membrane, cell wall, cell division, multidrug resistance, and virulence proteins suggest therapeutic and vaccine targets. Unusual features of the M. leprae genome include large polyketide synthase (pks) operons, inteins, and highly fragmented pseudogenes.