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" 3094-B ANATOMY ANATOMY SOMITE FORMATION IN VITRO UNDER THE INFLUENCE OF TRYPAN BLUE - - Order No. 7818179 BAREITHER, Daniel Joseph, Ph.D. University of Illinois at the Medical Center, 1978. 195pp. The teratogenic effects of trypan blue on chick somite for- mation were studied using an in vitro technique. Embryos at stages 7-8 were explanted intocontrol and trypan blue contain- ing culture media. Embryos were harvested at 2,4,6, 12 and 24 hours after the initiation of culture and subsequently pre- pared for light and electron microscopy. In the gross obser- vation of intact embryos, structural changes in treated embryos were seen primarily after 12 and 24 hours of culture. Light microscopic analysis confirmed these structural changes in later embryos as being primarily thinning of the ectoderm and reduction in the number of cells within the somitic mass. These differences in the structure of treated embryos were also noted at the ultrastructural level as well as ones at earlier stages. While the cytoplasmic organelles of cells involved in somite formation were found to be similar in control and trypan blue-treated embryos, basement membrane and junctional for- mation were found to be altered in treated embryos. Basement membrane material in association with the neural plate, noto- chord and endoderm of treated embryos was slower in forma- tion than seen in the control. Adherens type junctions between somitic cells were neither as well-developed nor as numerous as observed in the control. These changes could affect the normal morphogenetic movement and association between cells during early somite formation and result in the altered struc- ture seen in the formed somite. VERTICAL BANDING AND ASSOCIATED BEHAVIORAL RE- SPONSES EVOKED BY ELECTRICAL STIMULATION OF THE BRAIN IN ANESTHETIZED AND FREE-SWIMMING SUN- FISHES, LEPOMIS CYANELLUS AND L. MACROCIDRUS Order No. 7900934 BAUER, Diana Hoenke, Ph,D. The University of New Mexico, 1978. 96pp. A pattern of dark vertical bands is a characteristic display by Lepomis cyanellus and L. macrochirus. The rapidity with which this display can appear and disappear indicates that it is neurally controlled. This study was carried out in order to identify regions in the brain involved in the control of this color pattern and to determine other behavior patterns associated with electrical stimulation of these regions, Initially, anesthetized fish which were held in a stereotaxic device were stimulated electrically at various sites in the brain to locate regions where vertical banding could be evoked. In subsequent tests, immovable electrodes were implanted in the areas found to be involved in banding. The fish were then stimulated chronic\\11y while swimming free in a 50-gal aquar- ium and banding an,li other evoked behavior patterns were re- corded. Stimulation was applied through monopolar electrodes as biphasic square wave pulse-pairs of 2 msec duration, at fre- quencies of 5 and 50 Hz. Although higher currents were applied at some sites, only strong responses at 50 IlA or less with latencies not exceeding 10 see were considered significant in defining the banding control areas. Banding was evoked by stimulation of sites near the midline in the following regions: the preoptic area, the dorsal hypo- thalamic-ventral thalamic transition zone and the midbrain tegmentum just dorsal to the nucleus prerotundus pars medialis. Additional positive sites were located in and near the torus semicircularis, the basal midbrain (region of the supposed tectobulbar tracts), and in the rostral basomedial medulla. Areas found to be negative for evoked banding included the telencephalic lobe, the inferior lobe, the optic tectum, the optic tract, and the body and valvula of the cerebellum. Blanching was evoked at several sites in the medulla. Blanch- ing also occurred following the display of distinct banding during continuous stimulation of some points in free-swimming fish. A variety of fin and body positions and movements related to defensive behavior accompanied the evoked color changes. It is postulated that the vertical banding pattern is made up of a separate, selectively controlled system of dermal melano- phores. A hypothetical model of the neural mechanism control- ling banding is proposed. DEVELOPMENT OF THE MEDULLARY RAPHE NUCLEI OF THE RABBIT: A MIDLINE DENDRITE BUNDLE Order No. 7900385 CUMMINGS, John Patrick, Ph.D. Indiana University, 1978. 249pp. A developmental study of the medullary and pontine raphe nuclei in the rabbit has revealed a large, vertically oriented dendrite bundle in the midline of the medulla at levels of nuclei raphe obscurus and raphe pallidus. This bundle extended from the floor of the fourth ventricle to the ventral boundary of the nucleus raphe pallidus. The width of the dendrite bundle aver- ages 50-75 mu in the neonate and 150-200 mu in the adult. In the transverse sections stained with a modified Golgi-Cox technique, fibers were visible for several hundred to 1000 or more mu. Thus bundle received fiber contributions from four major sources: (1) Dendrites of midline and paramedian neu- rons of nucleus raphe obscurus; (2) Dendrites of midline and paramedian neurons of nucleus raphe pallidus; (3) Shafts from tanycytes located on the floor of the fourth ventricle; and (4) Dendrites from neurons of the medullary reticular forma- tion. Golgi-Cox, histofluorescence, and routine neuroanatomical fiber and cresyl studies showed that the vertically oriented parallel dendrites of raphe obscurus and raphe pallidus cells originated from serotonergic cells in the midline among fibers of the bundle, and from serotonergic cells adjacent to the mid- line bundle in the paramedian reticular formation. These peri- karya and their dendrites frequently directly abutted blood ves- sels in the midline bundle without visible interposition of glial processes. The tanycyte shafts extend from the floor of the fourth ventricle and ran the entire length of the bundle, inter- twining themselves among perikarya and dendrites of the medul- lary raphe nuclei. The reticular dendrites contributing to the bundle arose mainly from large cells of the reticular formation, entered the bundle at right angles to the midline, and turned dorsally or ventrally to run parallel with the other dendrites and shafts in the bundle. Additional dendrites crossed through the bundle at right angles, transversely, without contributing to it. Electron microscopic examination of the bundle confirmed the identification of parallel dendrites and revealed close mem- brane apposition without the presence of synaptic vesicles. This dendrite bundle was present at day 22 of gestation, and increased steadily in size through adulthood. All bundle components, in- cluding the tanycyte shafts, were clearly visible in adults.