Blackhead disease: reduced sensitivity of Histomonas meleagridis to nitarsone in vitro and in vivo.

Histomonas meleagridis, a flagellated protozoan parasite, is the causative agent of blackhead disease or histomoniasis in gallinaceous birds. Currently nitarsone (4-nitrophenylarsonic acid) is the only approved preventative drug available in the United States against blackhead disease. Initially we tested the sensitivity of three different isolates of H. meleagridis collected from outbreaks in North Carolina (strain MNC), Michigan (strain ZM), and Georgia (strain BG) to nitarsone using in vitro culture conditions. Strain ZM and strain BG at 100 and 400 ppm showed reduced growth in comparison to their respective control groups. However, there was no inhibition of growth in strain MNC treated with nitarsone at 100 ppm, while reduced growth was seen at 400 ppm. To test the resistance of strain MNC to nitarsone in vivo, turkey poults fed a nitarsone or a control diet were inoculated cloacally with H. meleagridis. The nitarsone-treated group of birds did not show any significant difference compared to that of infected control group when measuring weight gain and liver and cecal lesions scores. Histomonas meleagridis were reisolated from the nitarsone-fed turkeys and subjected to the in vitro assay. Regenerated H. meleagridis maintain their resistance to nitarsone at 100 ppm. This study demonstrates that strain MNC has acquired partial resistance to nitarsone.

Amino acid digestibility and metabolizable energy of genetically selected soybean products.

To determine the ME and amino acid digestibility of 5 soybean meal (SBM) samples, a precision-fed rooster assay and a chick assay were conducted. The 5 samples were cold-pressed (extruded) soybean meals or solvent-extracted (defatted) soybean meal. Of the cold-pressed varieties (unheated), there was an ultra-low trypsin SBM, a low-trypsin SBM, and a heated and unheated commodity SBM. The solvent-extracted SBM was a heated commodity blend. The TME and AME values were compared between each category: cold-pressed and defatted, as well as between the 2 assays. Semipurified diets containing dextrose as the main energy source were formulated to meet the bird's nutrient requirements, with each diet containing a different SBM product. The TME rooster assay was a precision-fed rooster assay in which 5 birds per diet were fasted for 24 h, crop intubated with 35 g of the test diet containing 46.58% cold-pressed or defatted SBM, and excreta was then collected for 48 h. The total aromatic amino acids rooster assay followed the same protocol, but cecectomized birds were used. For the chick assay, 480 one-day-old chicks were fed a standard corn-SBM starter diet until 17 d of age, and on d 18, the chicks were allowed ad libitum access to the SB-dextrose diets. Excreta were collected on d 22, dried, ground, and analyzed for gross energy and CP to determine ME. The SBM samples that were genetically selected to have lower trypsin inhibitor levels and higher protein had higher ME values and increased amino acid digestibility than the commodity cold-pressed SBM samples. Genetic selection of soybeans for certain traits can have positive effects on the ME value and amino acid digestibility for roosters and chicks.

No evidence of temperature-dependent sex determination or sex-biased embryo mortality in the chicken.

Skewing the sex ratio at hatch in commercial poultry would be economically beneficial to the poultry industry. The existence of temperature-dependent sex determination is uncertain in birds. This experiment investigated if incubation temperatures skew sex ratios of commercial broilers. Three incubators were each set at a hot (38.3°C), standard (37.5°C), or cool (36.7°C) single-stage incubation temperature one time over 3 trials to eliminate incubator effect as a Latin square design. Sex ratios of hatched chicks and dead embryos were monitored. In one trial, embryo weights were evaluated. The percentages of male hatched chicks did not differ based on incubation temperature (P = 0.4486; 49.5% in the hot treatment, 51.4% at standard temperature, and 49.8% in the cool treatment). The percent hatch of eggs set was lower in the hot treatment (83.6%) than the standard (93.5%) and cool (91.6%) treatments (P < 0.0001) with greater late embryonic mortality in the hot treatment (P < 0.0001); however, the sex ratio of dead embryos did not differ among treatments (P = 0.9863). Pooled data of embryo mortality found no sex-biased embryo mortality with a female/male sex ratio of 1.22:1 (χ(2) = 1.27; P = 0.2596). Embryos from the hot treatment were heavier than those from the standard treatment by d 14 of incubation and were heavier than the embryos from the cool treatment by d 9 of incubation (P < 0.0001). These data indicate that incubation temperature affects embryonic mortality and embryonic growth rate, but it does not affect the sex ratio of broiler chickens. Additionally, no evidence was found for sex-biased embryo mortality in commercial broilers even at the incubation temperatures of this study.

An outbreak of blackhead disease (Histomonas meleagridis) in farm-reared bobwhite quail (Colinus virginianus).

An outbreak of blackhead disease (Histomonas meleagridis) in farm-reared flock of 13,500 bobwhite quail (Colinus virginianus) resulted in mortality totaling approximately 1500 in 4 wk. Necropsy of 56 dead birds at midoutbreak (from a total that day of 131) revealed that 55 had severe cecal lesions typical of blackhead, and only 3 had visible lesions in the liver. Necropsy of apparently healthy birds failed to detect any signs of infection. Presence of H. meleagridis in affected ceca was proved by culture in vitro and PCR tests.

Trichomonosis in free-ranging Eurasian collared doves (Streptopelia decaocto) and African collared dove hybrids (Streptopelia risoria) in the Caribbean and description of ITS-1 region genotypes.

We report the first documented occurrence of an outbreak of trichomonosis in a free-ranging small flock of Eurasian collared doves (Streptopelia decaocto) and African collared dove hybrids (Streptopelia risoria) in the Caribbean. In total, 18 birds were examined, including six African collared dove x Eurasian collared dove hybrids and 12 Eurasian collared doves. The affected age class consisted of adults. Sex distribution was equal. With a flock population size of 200 birds, mortality rate for the outbreak was estimated at 15-20%. Living birds were weak, showing evidence of mucus-stained beaks and open-mouth breathing. Caseous ulcerative yellow lesions were restricted to the upper gastrointestinal tract, with the exception of one bird, which had lesions in the upper gastrointestinal tract and in the liver. Ninety-four percent (17/18) of the affected birds had multiple extensive lesions. Lesions located on the roof of the oral cavity extended in 33% (6/18) into the orbit and in 11% (2/18) into the braincase. Using wet-mount microscopy, we were able to confirm Trichomonas gallinae in 22% (4/18) of the sampled animals. Fifteen samples submitted for PCR analysis tested positive. Sequence analysis of the internal transcribed spacer 1 (ITS-1) region of the ribosomal RNA (rRNA) revealed two distinct genotypes of Trichomonas. One sequence had 100% identity to the prototype T. gallinae isolate, whereas the other sequences had 98-100% identity to recently described Trichomonas-like parabasalid. On the basis of gross and histologic findings, along with the sequence results from the columbids in this report, it is likely that this Trichomonas-like parabasalid is pathogenic.

Tolerance and efficacy of tribasic manganese chloride in growing broiler chickens.

These studies were designed to determine the relative bioavailability and tolerance of tribasic Mn chloride (TBMC) for growing broiler chickens. In experiment 1, birds were fed a basal diet (starter, 102 ppm; grower, 209 ppm) or the basal diet supplemented with 3,600, 4,500, or 5,400 ppm Mn from either TBMC or manganese sulfate (MnSO(4)), and BW, feed intake, and plasma Mn were measured. In experiments 2 and 3, diets included the basal diet (45 and 43 ppm Mn, respectively) and the basal diet supplemented with graded levels of either TBMC or MnSO(4) ranging from 30 to 240 ppm Mn. Body weight and feed intake were measured and tibia, bile, and liver were collected for mineral analysis; heart samples were taken for manganese superoxide dismutase activity, protein, and relative mRNA abundance. In experiment 1, BW differed among treatments, with higher Mn leading to lower BW (P < 0.05). Birds from all treatments showed higher plasma Mn than birds fed the basal diet. Birds supplemented with the highest level of MnSO(4) had the highest level of plasma Mn (P < 0.05). In experiment 2, tibia and liver Mn increased with higher dietary Mn regardless of source (P < 0.05). Liver Mn increased up to the 60 ppm diets whereas Mn in the tibia was highest with the 130 ppm diets. Bile Mn increased with increasing dietary Mn, but these differences were not significant. In experiment 3, manganese superoxide dismutase activity, protein, and relative mRNA abundance were not affected by diet. The calculated bioavailabilities of TBMC and MnSO(4) did not differ significantly (P > 0.20). Together, these results indicate that TBMC is as effective as and better tolerated than MnSO(4) and that supplementing Mn at the lowest level used in this study may be sufficient for normal development of broiler chickens.

Low-dose immunization of northern bobwhites (Colinus virginianus) with Eimeria lettyae provides protection against a high-dose challenge.

To determine whether northern bobwhite quail (Colinus virginianus) could be immunized against Eimeria lettyae by a low-dose inoculation of oocysts, we inoculated 30 birds each with either 100 or 1000 oocysts at 2 days of age (given orally by pipette). Four weeks after immunization, the immunized birds and unimmunized controls were challenged with 1 x 10(6) E. lettyae oocysts. Eight days after challenge, birds were killed and weighed, and their intestines examined for gross lesions. Effectiveness of the immunization was measured by analyzing weight gain, intestinal lesions, severity of diarrhea, feed conversion ratio, and oocyst production. After challenge, birds immunized with 100 or 1000 oocysts gained an average of 33.3 g and 28.9 g, respectively, whereas unimmunized challenged birds gained an average of 11.5 g. Immunized quail produced approximately 99.7% fewer oocysts, had minimal gross intestinal and cecal lesions, had minimal diarrhea, and had a 50% lower feed conversion ratio compared to unimmunized challenged controls. These findings indicate that vaccination is a viable option for controlling coccidiosis in quail and that further research into vaccination is warranted.

Establishment of culture conditions for survival of Histomonas meleagridis in transit.

Fresh ceca samples from turkeys in North Carolina infected with Histomonas meleagridis were collected at necropsy, inoculated into warmed Dwyers medium, and sent by overnight courier to our laboratory at The University of Georgia. Further incubation at 40 C yielded positive cultures from all four samples. PCR and DNA sequencing confirmed the presence of H. meleagridis. To further establish conditions for survival in transit, we infected turkeys with H. meleagridis, euthanatized the birds 10 days postinfection, and allowed carcasses to incubate at room temperature for either 2 or 24 hr. After incubation, samples of cecal contents (0.5 g) were placed in Dwyers medium and held at 4, 25, or 30 C for 6, 18, 24, 48, 72, 96, or 120 hr, simulating holding conditions during transit. Samples were placed in a 40 C incubator at the specified times and examined daily for histomonad growth by light microscopy. Positive histomonad growth was detected from cecal samples obtained from the 2-hr incubated carcass and from cultures held at 30 C for 6, 18, 24, 48, and 72 hr. No growth was seen from cultures held at 25 or 4 C or at any temperature from the carcass allowed to incubate for 24 hr at room temperature. These results suggest that positive isolation can be made from field samples, provided that material is collected at warm temperatures and transported rapidly to the laboratory.

Oviduct Fluke (Prosthogonimus macrorchis) Found Inside a Chicken Egg in North Carolina.

A video received by faculty at North Carolina State University's Prestage Department of Poultry Science revealed a live parasite inside a chicken egg. The parasite was identified as an oviduct fluke (Prosthogonimus macrorchis), a trematode with a three-host life cycle: the primary host, a galliform bird, then an aquatic snail, and finally a dragonfly larva or adult consumed by the infected bird. The egg was from a "backyard flock" with access to a watercourse. No other instances of this parasite were seen in eggs from the flock. The presence of this parasite inside an egg suggests that the worms had migrated above the shell gland in the oviduct to be incorporated inside the egg. Currently, the occurrence of an oviduct fluke inside an egg in the United States is rare. Such parasites are not found in eggs from caged layers because those birds do not have access to watercourses. This case reinforces the view that parasites requiring intermediate hosts may become more common in birds reared under free-range conditions.

Synaptic vesicle size and number are regulated by a clathrin adaptor protein required for endocytosis.

Clathrin-mediated endocytosis is thought to involve the activity of the clathrin adaptor protein AP180. However, the role of this protein in endocytosis in vivo remains unknown. Here, we show that a mutation that eliminates an AP180 homolog (LAP) in Drosophila severely impairs the efficiency of synaptic vesicle endocytosis and alters the normal localization of clathrin in nerve terminals. Most importantly, the size of both synaptic vesicles and quanta is significantly increased in lap mutants. These results provide novel insights into the molecular mechanism of endocytosis and reveal a role for AP180 in regulating vesicle size through a clathrin-dependent reassembly process.

Neurexin IV, caspr and paranodin--novel members of the neurexin family: encounters of axons and glia.

Axonal insulation is of key importance for the proper propagation of action potentials. In Drosophila and other invertebrates, it has recently been demonstrated that septate junctions play an essential role in axonal insulation or blood-brain-barrier formation. Neurexin IV, a molecular component of Drosophila septate junctions, has been shown to be essential for axonal insulation in the PNS in embryos and larvae. Interestingly, a vertebrate homolog of Neurexin IV, caspr--also named paranodin--has been shown to localize to septate-like junctional structures. These vertebrate junctions are localized to the paranodal region of the nodes of Ranvier, between axons and Schwann cells. Caspr/paranodin might play an important role in barrier formation, and link neuronal membrane components with the axonal cytoskeletal network.

Bonus, a Drosophila TIF1 homolog, is a chromatin-associated protein that acts as a modifier of position-effect variegation.

Bonus, a Drosophila TIF1 homolog, is a nuclear receptor cofactor required for viability, molting, and numerous morphological events. Here we establish a role for Bonus in the modulation of chromatin structure. We show that weak loss-of-function alleles of bonus have a more deleterious effect on males than on females. This male-enhanced lethality is not due to a defect in dosage compensation or somatic sex differentiation, but to the presence of the Y chromosome. Additionally, we show that bonus acts as both an enhancer and a suppressor of position-effect variegation. By immunostaining, we demonstrate that Bonus is associated with both interphase and prophase chromosomes and through chromatin immunoprecipitation show that two of these sites correspond to the histone gene cluster and the Stellate locus.

Nutritional quality of eggs from hens fed distillers dried grains with solubles.

A feeding trial was conducted with laying hens where either 10% or 20% regular-fat distiller's dried grains with solubles (R-DDGS) or low-fat DDGS (L-DDGS) were incorporated into the feed. Production parameters and the effect of DDGS on egg nutritional quality, focusing on yolk lipids, were evaluated. Neither R-DDGS nor L-DDGS at up to 20% of laying hen feeds had a statistically significant impact on hen weight gain, egg production, feed intake, feed efficiency, egg mass, or egg weight. Specific gravity was slightly lower for eggs from hens fed 10% R-DDGS or 20% L-DDGS. Eggs from layers fed DDGS had enhanced levels of tocopherols, tocotrienols, and xanthophylls in the yolk, as well as also increased yolk yellow and red color. Eggs from L-DDGS diet had higher tocopherol content, but eggs from R-DDGS diets had higher xanthophylls. Fatty acid composition in eggs was slightly altered by DDGS, but the ratio of saturated to unsaturated fatty acids was very similar. Feeding DDGS to layer hens had no effect on lecithin or cholesterol content of the eggs. Thus, inclusion of DDGS in the diet of laying hens resulted in increases of several beneficial lipophilic nutrients in egg yolks with no apparent detrimental effects.

A novel, simplified technique to amplify Eimeria (Coccidia: Apicomplexa) DNA from oocysts.

A new method to amplify coccidia DNA by polymerase chain reaction (PCR) was developed by placing freeze-thawed oocysts in Ready-to-Go PCR bead tubes and using a 5-min initial heat denaturation step. Positive PCR reactions were found in 3 of 3 samples containing 20 or 50 oocysts; when ≤5 oocysts were used, 1 of 3 samples was positive. This technique shows potential for effectively and efficiently detecting and identifying oocysts from soil, feces, and other matter.

The thalamostriatal projection in the cat.

The organization of the projections from the intralaminar and other thalamic nuclei to the caudate nucleus (CD), putamen (PU), nucleus accumbens (Acc), and olfactory tubercle (TO) were examined in the cat by autoradiography after deposits of 3H-amino acids in individual thalamic nuclei and by retrograde cell labeling after intrastriatal deposits of wheat-germ-conjugated horseradish peroxidase. All of the rostral intralaminar nuclei, here considered to include the central lateral (CL), paracentral (PC), central medial (CeM), and rhomboid nuclei (Rh), project to the striatum. Projections closely associated with those of the rostral intralaminar group arise from cells of the paraventricular nucleus (PV) and a region lateral to the stria medullaris. These nuclei, which roughly form a ring around the mediodorsal nucleus, project in a highly particular, but loosely arranged topographic pattern to all parts of the striatum. The medially located cells in Rh, PV, and those alongside the stria medullaris project mainly to medial parts of Acc and CD; the dorsolaterally located cells of CL project mainly to the dorsolateral parts of CD and PU; cells in PC and CeM project to progressively more ventral and medial parts of CD and PU, and the lateral part of Acc. Superimposed on this projection from the rostral intralaminar region is the projection from the caudal intralaminar group including the centromedian (CM), parafascicular (PF), and subparafascicular nuclei (subPF). Together these nuclei project in a loosely but specifically organized topography to the entire striatum. The lateral and dorsal parts of CD and PU receive fibers mainly from CM. Ventral and medial parts of CD and PU and Acc receive fibers mainly from PF; TO receives fibers from subPF and the ventral part of PF. Several nuclei in the lateral nuclear mass of the thalamus also project to particular parts of the striatum. Thus, cells in the rostromedial part of the ventral anterior nucleus project to the head of CD and some cells in the rostral part of the ventromedial nucleus project to the head of CD and to PU. Several cells scattered in the lateral posterior complex project to lateral parts of the head of CD, and cells in the rostral extension of the medial subdivision of the posterior nuclear complex project to lateral parts of the head and body of CD. Finally, several cells of the paratenial nucleus project selectively to Acc. These data provide a detailed map of the total thalamostriatal projection in the cat and, hence, form a basis for more specific functional questions about this poorly understood system.

Convergent thalamic and mesencephalic projections to the anterior medial cortex in the rat.

Small microelectrophoretic deposits of horseradish-peroxidase (HRP) were placed at various loci within the gray matter of the rat's anterior medial cortex. A comparison of the patterns of retrograde cell-labeling charted in 26 such cases confirmed earlier findings in fiber-degeneration studies according to which the respective thalamocortical projections of the mediodorsal (MD) and anteromedial nucleus (AM) overlap each other over a wide region of the anterior medial cortex. This region of thalamocortical convergence, extending from pregenual levels caudalward as far as the anterior border of the retrosplenial cortex, corresponds almost exactly to the cortical region from which locally deposited HRP was found to be transported so as to label cells in one or both of two mesencephalic cell groups: the ventral tegmental area (AVT) dorsal and lateral to the interpeduncular nucleus, and the medial one-quarter of the pars compacta of the substantia nigra (SNC).

Immunohistochemical demonstration of differential substance P-, met-enkephalin-, and glutamic-acid-decarboxylase-containing cell body and axon distributions in the corpus striatum of the cat.

The immunohistochemical localization of neuronal cell bodies and axons reactive for substance P (SP) and methionine-enkephalin (ME) was investigated in the corpus striatum of the adult cat brain and compared with that of glutamate decarboxylase (GAD), synthetic enzyme for gamma-aminobutyric acid. Striatal cell bodies reactive for ME could be identified only in colchicine treated cats, are medium size, ovoid striatal cells, and are found in large numbers in a more or less even distribution throughout the caudate nucleus, putamen, and nucleus accumbens. The striatal region most densely occupied by ME-immunoreactive cells is the ventral and central part of the caudate head. Modest numbers of larger ME-reactive neurons are dispersed throughout the entopeduncular nucleus and the pars reticulata of the substantia nigra. Striatal cells of medium size reactive for SP could be identified, with or without colchicine, in largest numbers in the medial half of the caudal three-fourths of the putamen and in clusters of irregular size and shape in the head of the caudate nucleus. Cells reactive for SP are also common in layer II and the islands of Calleja of the olfactory tubercle. We could not reliably visualize GAD-positive cell bodies in the striatum, even with colchicine treatment; however, they could be seen readily in all pallidal structures such as the globus pallidus, ventral pallidum, entopeduncular nucleus, and substantia nigra. Axons reactive for ME are found mainly in the globus pallidus where they form a dense and even network throughout the nucleus. The globus pallidus is almost devoid of SP reactivity except near its extreme caudal pole. Conversely, SP-immunoreactive axons form dense meshworks in the entopeduncular nucleus and substantia nigra where ME immunoreactivity is minimal. Fewer, but still ample numbers, of SP-reactive axons are present also in the ventral tegmental and retrorubral areas of the midbrain tegmentum and in the ventral pallidum of the basal forebrain, but only sparse ME-reactive axons are present in these areas. This differential distribution of SP- and ME-containing axons in the pallidal and nigral structures stands in contrast to the relatively homogeneous and dense distribution of GAD-containing axons throughout the dorsal and ventral pallidum, entopeduncular nucleus, and substantia nigra.(ABSTRACT TRUNCATED AT 400 WORDS)

The lateral suprasylvian corticotectal projection in cats.

The projection from the lateral suprasylvian visual areas to the superior colliculus was investigated in cats using both anterograde and retrograde tracing techniques. The retrograde transport of horseradish peroxidase (HRP) or wheat germ agglutinin-HRP (WGA-HRP) from their site of deposit in the superior colliculus indicates that all divisions of the lateral suprasylvian visual areas project to both the superficial and deep layers of the superior colliculus. However, following tracer deposits in the superior colliculus that are confined to the layers below the stratum opticum (deep layers), more neurons are labeled along the lateral bank than along the medial bank of the middle suprasylvian sulcus. Conversely, tracer deposits in the superior colliculus dorsal to and including the stratum opticum label more cells in the medial than the lateral bank. These retrograde experiments also confirm that the visual cortex along the lateral gyrus (areas 17 and 18) projects to the superficial, but apparently not to the deep layers. The visual area in the cortex surrounding the caudal two-thirds of the anterior ectosylvian sulcus projects to the deep, but not to the superficial layers. The laminar and areal patterns of anterograde axon labeling in the superior colliculus were examined after single deposits of 3H-amino acids (autoradiography), HRP, or WGA-HRP in the lateral suprasylvian cortical regions, or combined isotope and WGA-HRP deposits. Axon labeling in the superior colliculus is generally densest in the stratum opticum and extends either dorsally into the superficial layers or ventrally into the intermediate gray layer. Specifically, the anterior divisions of the lateral suprasylvian cortex project primarily to the lateral portion of the superior colliculus, with the projection from the medial bank biased toward the superficial layers and axons from the lateral bank aimed mainly at the intermediate gray layer with some axons even reaching the deepest gray layer of the superior colliculus. Both the posteromedial and posterolateral divisions of the lateral suprasylvian cortex project to more extensive portions of the mediolateral and rostrocaudal dimensions of the superior colliculus than the anterior divisions. However, the posterolateral division projects more heavily to the intermediate gray layer than the posteromedial division; from the latter, axons distribute more superficially in the superior colliculus. Finally, the cortex surrounding the posterior suprasylvian sulcus projects primarily to the medial part of the superficial layers of the superior colliculus.(ABSTRACT TRUNCATED AT 400 WORDS)

An autoradiographic examination of the central distribution of the trigeminal, facial, glossopharyngeal, and vagal nerves in the monkey.

The central distributions of primary afferent axons in cranial nerves V, VII, IX, and X have been re-examined autoradiographically after 3H-proline injections into their peripheral ganglia. Fiber-labeling after subtotal injections of the trigeminal ganglion, besides confirming earlier classical descriptions, suggests that trigeminal fibers of the ophthalmic and mandibular (but not maxillary) branches enter the ventrolateral part of the nucleus of the solitary tract (NST). Injection of VII's geniculate ganglion labels fibers which both ascend and descend upon reaching NST. The ascending fibers distribute in a compact and circumscribed zone immediately dorsal to the spinal V nucleus as far rostral as the caudal pole of the principal trigeminal nucleus. The descending fibers distribute to the lateral NST rostral to the level at which X joins the solitary tract. For a short distance caudal to this level, sparse label is confined to a small part of lateral NST ventral to the solitary tract, which corresponds to the zone receiving direct trigeminal afferents. Fiber-labeling after injections of the ganglia of nerves IX and X suggest the following. Although, upon reaching NST, a few fibers of either IX or X ascend as far rostrally as had those of VII, both have a much larger descending component which distributes to more caudal levels of NST. Most of IX's axons appear to end in the lateral NST; only a few travel as far as the obex. Fibers of X, on the other hand, are abundant in the medial and commissural parts of NST. Moreover, only X appears to have a crossed projection in the commissural nucleus and caudal portion of the contralateral NST. A few fibers of vagal origin also appear to enter the area postrema. Whereas fibers of X appear to constitute the solitary tract, few if any fibers of VII or IX travel within that fascicle. A significant descending components of labeled fibers appears in the spinal V tract when the superior ganglion of either IX or X is injected. These fibers distribute mainly in the pars caudalis of the spinal V nucleus and, to a lesser degree, the cuneate nucleus.