Well-defined Nucleus Research Articles

MORPHOLOGICAL CHARACTERISTICS OF THE TRIGEMINAL NODE OF RATS WHEN CRYOPRESERVED PLACENTA IS INTRODUCED

Cryopreserved placenta preparations have a unique composition of biologically active substances, which determines their multifaceted effect. The aim of our study was to investigate the morphological features of the trigeminal node of rats when cryopreserved placenta was injected.
 The conducted experimental study showed that a single subcutaneous injection of cryopreserved placenta causes a reaction of the vessels of the microcirculatory bed of the trigeminal node of rats in the first two weeks of observation in the form of an expansion of the diameter of arterioles, capillaries and venules and an increase in blood filling, which indicates the stimulating effect of the components of the fetoplacental complex on the microcirculatory bed. The most pronounced phenomena were observed on the 7th day.
 After transplantation of the cryopreserved placenta, the neurocytes of the trigeminal node had a large, well-defined light nucleus, well-defined cytoplasm, with deep chromatophilic substance, there were dark, smaller cells with dispersed Nissl substance, satellite cells, and nerve fibers remained intact during all observation periods.
 The obtained data confirm the trophic effect of drugs of the fetoplacental complex. Our experimental study showed that a single subcutaneous injection of cryopreserved placenta causes a reaction of the vessels of the microcirculatory bed of the trigeminal node of rats in the first two weeks of observation in the form of an expansion of the diameter of arterioles, capillaries and venules and an increase in blood filling. The most pronounced phenomena were observed on the 7th day. The obtained data indicate the stimulating effect of the components of the fetoplacental complex on the microcirculatory channel.
 After transplantation of the cryopreserved placenta, neurocytes, satellite cells, and nerve fibers remained intact during all observation periods.

Circulating tumor cells as a biomarker for monitoring: Disease progression, treatment response, and minimal residual disease.

e15021 Background: To analyze the role of Circulating tumor cells (CTC) as a confirmatory personalized biomarker for monitoring the disease progression, disease burden, and minimal residual disease in epithelial origin cancers. Methods: In this retrospective study, 127 patients with colorectal, breast, and ovarian cancer at stage III and IV were analyzed. The patients were at various stages of intensive chemo and radiotherapy while the CTCs were isolated and enumerated from 1.5 ml of blood. The decision to continue chemotherapy or change to oral metronomic therapy was based on the presence of circulating tumor cells in Stage III. While in stage IV, serial measurement of CTC guided therapy. CTCs were isolated using OncoDiscover platform possessing EpCAM antibody based immunomagnetic targeting of magnetic nanoparticles after RBC lysis. CTCs were imaged and identified as CK18+ and CD45- cells showing a well-defined nucleus using a motorized fluorescence microscope operational with a monochrome camera. CTCs were enumerated using automated image analysis software and counts were expressed as number per 1.5 ml of blood. Results: In this retrospective study we analyzed blood sample from 127 patients with the advanced stage epithelial cancers (breast- 50 %, ovarian -27 %, colorectal- 23 %) for the presence of CTCs. Amongst those, 52 % showed the presence of CTCs (breast- 52 %, ovarian -46 %, colorectal- 58 %). The CTC count ranged between 1-5 / 1.5 ml of blood with mean and median value of 2 and 1. Among the CTC positive population, majority had CTC count of 1 (44.4 %), while more than 2 CTCs were observed in 11 % of population. CTC clusters were detected in 13 % of population which predominantly were stage IV patients. 67 % among the follow up patients showed decrease in CTC count from the baseline due to the prescribed treatment, while 22 % patients showed increase in CTC count from the baseline. 11 % patients did not show change in CTC count from the baseline. When CTCs count was investigated as an independent variable to monitor the therapeutic response, it correlated well with the positive or negative outcome. In few representative cases, the reduction of CTC number from the basal value was indicative of an effective treatment. Exceptionally, in a representative colorectal cancer case, PET showed no primary as well secondary tumor burden, but the presence of CTCs in blood led further investigating an abdominal MRI that indicated multiple liver lesions suggesting micro-metastasis. Subsequent to SIRT treatment, the patient showed complete tumor regression and absence of CTCs in peripheral blood. Conclusions: Our data suggest that CTC can serve as a dynamic intermittent biomarker for monitoring the disease progression in advanced stages and assess the therapeutic response, thus emphasizing the role of CTCs in personalized cancer management.

Rational Design of Protein-Specific Folding Modifiers.

Protein-folding can go wrong in vivo and in vitro, with significant consequences for the living organism and the pharmaceutical industry, respectively. Here we propose a design principle for small-peptide-based protein-specific folding modifiers. The principle is based on constructing a "xenonucleus", which is a prefolded peptide that mimics the folding nucleus of a protein. Using stopped-flow kinetics, NMR spectroscopy, Förster resonance energy transfer, single-molecule force measurements, and molecular dynamics simulations, we demonstrate that a xenonucleus can make the refolding of ubiquitin faster by 33 ± 5%, while variants of the same peptide have little or no effect. Our approach provides a novel method for constructing specific, genetically encodable folding catalysts for suitable proteins that have a well-defined contiguous folding nucleus.

Optimization of gold core-mesoporous silica shell functionalization with TPGS and PEI for cancer therapy

Photothermal therapy (PTT) has captured the attention of different researchers around the world, since the application of NIR light responsive-nanomaterials has shown promising results in cancer therapy. Gold-core mesoporous silica shell (Au-MSS) nanoparticles allow the combination of gold mediated PTT with the drug delivery in order to improve their therapeutic potential. In this study, two different methodologies, electrostatic or chemical linkage, were explored to functionalize Au-MSS nanorods with TPGS and PEI. For that purpose, the TPGS and PEI were chemically coupled to each other or modified with 3-(triethoxysilyl)propyl isocyanate. The produced Au-MSS nanorods display a uniform morphology and a well-defined gold nucleus and silica shell. Further, the particles surface charge was dependent on the synthesis methodology. The particles modified by electrostatic interactions (Au-MSS/TPGS-PEI) were slightly negative (−16.9 and −5.1 mV) whereas the formulations produced by chemical linkage (Au-MSS/TPGS/PEI) resulted in positively charged nanoparticles (30.9 and 6.8 mV). The successful incorporation of the polymers was confirmed by Fourier Transformed Infrared spectroscopy and thermogravimetric analysis. Moreover, the Au-MSS functionalization did not affect the particles PTT capacity. However, the Au-MSS/TPGS/PEI nanorods displayed a decreased drug encapsulation efficiency. In vitro assays demonstrated the cytocompatibility of Au-MSS up to concentrations of 200 μg/mL, however the positively charged formulations only remained biocompatible until 100 and 125 μg/mL. Overall, the attained data confirm the successful modification of Au-MSS nanorods with TPGS and PEI as well as their applicability as PTT and drug delivery agents. • Optimization of gold-core silica shell nanorods functionalization. • Electrostatic or chemical linkage of TPGS and PEI. • Combination of drug delivery with photothermal therapy.

A Decoy Folding Nucleus can Modulate Protein Folding Kinetics

The ability to modulate the folding kinetics of a specific protein in a milieu can be an important tool for chemical biology and pharmacology. Kinetics and thermodynamics of folding are routinely modulated by changing solvent conditions, but such changes are not protein specific. Here we demonstrate a general principle by which specific kinetic modulation can be achieved for any protein whose folding route is known. Our strategy is to design a pre-stabilized folding nucleus of a protein. We show that the β1- β2 part (residues 1 to 17) of ubiquitin, which is the segment known to fold first (into a β-hairpin shape)[1], can make folding faster when introduced as a separate conformationally constrained peptide at excess concentrations. A weaker but still significant effect is observed when this ‘decoy nucleus’ peptide is not conformationally constrained, or is in an unfolding buffer to start with. Interestingly, the thermodynamic stability of the protein remains unchanged, as the unfolding rate also becomes faster. We simulate the system for both a weakly constrained and a strongly constrained decoy nucleus, and observe that the decoy interacts strongly with the protein only when it is conformationally constrained. Together, our results suggest that the folding of almost any protein which possesses a well-defined folding nucleus can be modulated, by introducing a nucleus-mimicking molecule with a stabilized structure. It also implies that in vivo, fragments of proteins which are naturally present as degradation by-products can in principle affect the folding of the full length proteins. [1] Atomic-level description of ubiquitin folding. Piana et al., PNAS, 2013, 110 (15), 5915-5920

Cadherins mediate sequential roles through a hierarchy of mechanisms in the developing mammillary body.

Expression of intricate combinations of cadherins (a family of adhesive membrane proteins) is common in the developing central nervous system. On this basis, a combinatorial cadherin code has long been proposed to underlie neuronal sorting and to be ultimately responsible for the layers, columns and nuclei of the brain. However, experimental proof of this particular function of cadherins has proven difficult to obtain and the question is still not clear. Alternatively, non-specific, non-combinatorial, purely quantitative adhesive differentials have been proposed to explain neuronal sorting in the brain. Do cadherin combinations underlie brain cytoarchitecture? We approached this question using as model a well-defined forebrain nucleus, the mammillary body (MBO), which shows strong, homogeneous expression of one single cadherin (Cdh11) and patterned, combinatorial expression of Cdh6, −8 and −10. We found that, besides the known combinatorial Cdh pattern, MBO cells are organized into a second, non-overlapping pattern grouping neurons with the same date of neurogenesis. We report that, in the Foxb1 mouse mutant, Cdh11 expression fails to be maintained during MBO development. This disrupted the combination-based as well as the birthdate-based sorting in the mutant MBO. In utero RNA interference (RNAi) experiments knocking down Cdh11 in MBO-fated migrating neurons at one specific age showed that Cdh11 expression is required for chronological entrance in the MBO. Our results suggest that neuronal sorting in the developing MBO is caused by adhesion-based, non-combinatorial mechanisms that keep neurons sorted according to birthdate information (possibly matching them to target neurons chronologically sorted in the same manner). Non-specific adhesion mechanisms would also prevent cadherin combinations from altering the birthdate-based sorting. Cadherin combinations would presumably act later to support specific synaptogenesis through specific axonal fasciculation and final target recognition.

Elucidating the life cycle of Marteilia sydneyi, the aetiological agent of QX disease in the Sydney rock oyster (Saccostrea glomerata)

Marteilia sydneyi (Phylum Paramyxea, Class Marteiliidea, Order Marteiliida) (the causative agent of QX disease) is recognised as the most severe parasite to infect Saccostrea glomerata, the Sydney rock oyster, on the east coast of Australia. Despite its potential impact on industry (>95% mortality), research towards lessening these effects has been hindered by the lack of an experimental laboratory model of infection as a consequence of our incomplete understanding of the life cycle of this parasite. Here, we explored the presence of this parasite in hosts other than a bivalve mollusc from two study sites on the Hawkesbury River, New South Wales, Australia. We employed PCR-based in situ hybridisation and sequence analysis of a portion of the first internal transcribed spacer of rDNA in an attempt to detect M. sydneyi DNA in 21 species of polychaete worm. Marteilia DNA was detected in 6% of 1247 samples examined by PCR; the analysis of all amplicons defined one distinct sequence type for first internal transcribed spacer, representing M. sydneyi. Of the polychaete operational taxonomic units test-positive in PCR, we examined 116 samples via in situ hybridisation DNA probe staining and identified M. sydneyi DNA in the epithelium of the intestine of two specimens of Nephtys australiensis. Two differing morphological forms were identified: a ‘primordial’ cell that contained a well-defined nucleus but had little differentiation in the cytoplasm, and a ‘plasmodial’ cell that showed an apparent syncytial structure. This finding represents the first known record of the identification of M. sydneyi being parasitic in an organism other than an oyster, and only the third record of any species of Marteilia identified from non-molluscan hosts. Future work aims at determining if N. australiensis and S. glomerata are the only hosts in the life cycle of this paramyxean, and the development of experimental models to aid the production of QX disease-resistant oysters.

Ultrastructure and oil secretion in Hiptage sericea Hook

The oil secreting glands of <i>Hiptage sericea</i> Hook. consist of three regions: epithelial, sub-epithelial and sub-glandular. In early stages, the oil secreting cells are characterized by the presence of plastids with starch grains and electron translucent vesicles, mitochondria, rER, polysomes, small vacuoles, numerous lipid bodies and well-defined nucleus with nucleolus. Later, the accumulation of plastoglobuli and inclusion bodies occur in the matrix of the plastid. Tubular, smooth endoplasmic reticulum begins to appear in the cytoplasm. With the onset of secretion, the osmiophilic contents of plastids which appear as electron dense, round droplets move-into cytoplasm and often occur in the region of the plasmalemma invaginations. However, in matured glands the lipid bodies disappear from the cytoplasm. The size of the vacuoles increases and are filled with electron opaque substance. Similar substances are also found in the sub-cuticular spaces as well as outside the cuticle.

Girvanella-coated grains from Cambrian oolitic limestone

Oolites from the Cambrian carbonate sequences of China were analyzed using standard petrographic methods. Thin-section examination reveals that Girvanella, probably representing calcified sheath of a filamentous cyanobacterium, is well preserved in carbonate grains with little diagenetic alterations. The carbonate grains preserved with Girvanella may constitute an independent category here, since Girvanella was previously rarely known in carbonate grains, especially in ooids. According to the microstructures, these carbonate grains can be divided into two types: Girvanella oncoids are ooid-sized grains composed entirely of a meshwork of Girvanella coating a poorly defined nucleus; Girvanella ooids in samples can be further subdivided into two types, Girvanella-core ooids and Girvanella-cortex ooids, according to the microstructures and the distribution of Girvanella in the ooids. Girvanella-core ooids are characterized by a well-defined Girvanella nucleus, which was probably a rounded fragment of the former cyanobacterial buildup. Girvanella-cortex ooids, in contrast, are characterized by the alternations of Girvanella laminae and the micrite laminae. Observations of this study provide direct evidence that microbes, most likely cyanobacteria, were involved in the formation of coated carbonate grains and influenced their microstructures.

Big black hole found in tiny galaxy

Conventional wisdom tells us that supermassive black holes are found exclusively in massive galaxies undergoing little star formation. But one such object has now been discovered in a star-forming dwarf galaxy. See Letter p.66 The starburst in Henize 2-10, a relatively nearby blue compact dwarf galaxy, has attracted the attention of astronomers for decades, in part because of its prodigious rate of star formation — ten times that of the Large Magellanic Cloud. Now a study of Henize 2-10 at centimetre radio wavelengths and in the near-infrared reveals a compact radio source at its centre that is spatially coincident with a hard X-ray source. This points to the presence of an actively accreting massive black hole, but one not associated with a bulge, a nuclear star cluster or any other well-defined nucleus. This means that Henize 2-10 may reflect an early phase of black hole and galaxy evolution that has not been observed previously.

Anoxia over the western continental shelf of India: Bacterial indications of intrinsic nitrification feeding denitrification

Studies on the Arabian Sea coastal anoxia have been of immense interest, but despite its ecological significance there is sparse understanding of the microbes involved. Hence, observations were carried out off Goa (15 degrees 30'N, 72 degrees 40'E to 15 degrees 30'N, 72 degrees 59'E) to understand the processes that mediate the changes in various inorganic nitrogen species in the water column during anoxia. Water column chemistry showed a clear distinct oxic environment in the month of April and anoxic condition in October. Our study based on microbial signatures indicated that oxygen deficit appeared as a well-defined nucleus almost 40 km away from the coast during the oxic period (April) and spreads there after to the entire water column synchronizing with the water chemistry. Striking results of net changes in inorganic nitrogen species in nitrification blocked and unblocked experimental systems show that denitrification is the predominant process in the water column consuming available nitrate ( approximately 0.5 microM) to near zero levels within approximately 72 h of incubation. These observations have been supported by concomitant increase in nitrite concentration ( approximately 4 microM). Similar studies on denitrification-blocked incubations, demonstrate the potential of nitrification to feed denitrification. Nitrification could contribute almost 4.5 microM to the total nitrate pool. It was found that the relation between ammonium and total dissolved inorganic nitrogen (DIN) pool (r=0.98, p<0.001, n=122) was significant compared to the latter with nitrite and nitrate. The occurrence of high ammonium under low phosphate conditions corroborates our observations that ammonium does not appear to be locked under low oxygen regimes. It is suggested that ammonium actively produced by detrital breakdown (ammonification) is efficiently consumed through nitrification process. The three processes in concert viz. ammonification, nitrification and denitrification appear to operate in more temporal and spatial proximity than hitherto appreciated in these systems and this gives additional cues on the absence of measurable nitrate at surface waters, which was earlier attributed only to efficient algal uptake. Hence we hypothesize that the alarming nitrous oxide input into the atmosphere could be due to high productivity driven tighter nitrification-denitrification coupling, rather than denitrification driven by extraneous nitrate.

Compound-nuclear reaction cross sections via surrogate reactions

The surrogate reaction method is an indirect technique for determining cross sections for nuclear reactions that proceed through a well-defined compound nucleus. In this method, the same compound nucleus is produced by an alternate (“surrogate”) reaction and its decay products measured. The assumptions underlying the method are examined for the special case of 235 U( n , f ).

Nucleation and stability of hydrogen-bond surrogate-based α-helices

We have reported a new class of artificial alpha-helices in which a pre-organized alpha-turn nucleates the helical conformation [R. N. Chapman, G. Dimartino, and P. S. Arora, J Am. Chem. Soc., 2004, 126, 12252 and D. Wang, K. Chen, J. L. Kulp, III, and P. S. Arora, J. Am. Chem. Soc., 2006, 128, 9248]. This manuscript describes the effect of the core nucleation template on the overall helicity of the peptides and demonstrates that the macrocycle which most closely mimics the 13-membered hydrogen-bonded alpha-turn in canonical alpha-helices also affords the most stable artificial alpha-helix. We also investigate the stability of these synthetic helices through classical helix-coil parameters and find that the denaturation behavior of HBS alpha-helices agrees with the theoretical properties of a peptide with a well-defined and stable helix nucleus.

The disappearing chief cell phenomenon (DCP): a preliminary report.

The appearance of chief cells was studied in normal dogs and in dogs after anterior and bilateral highly selective vagotomy. The normal chief cell is columnar in shape, with a well-defined cell membrane, basal nucleus and basophilic cytoplasm. Many cells show what has been called the 'disappearing chief cell phenomenon'--DCP. The features of the DCP are striking. There is fragmentation of the cell membrane, loss of cytoplasm, changes in the appearance of the nucleus and actual disappearance of some cells. The parietal cells remain normal. The DCP is seen in normal mucosa and should not be regarded as evidence of chronic gastritis. From this preliminary study it is suggested that the procedure of highly selective vagotomy may have a specific effect on pepsin secreting cells, increasing the amount of the DCP.

Cell detection in phase-contrast images used for alpha-particle track-etch dosimetry: a semi-automated approach

A novel alpha-particle irradiator has recently been developed that provides the ability to characterize cell response. The irradiator is comprised of a collimated, planar alpha-particle source which, from below, irradiates cells cultured on a track-etch material. Cells are imaged using phase-contrast microscopy before and following irradiation to obtain geometric information and survival rates; these can be used with data from alpha-particle track images to assess cell response. A key step in this process is determining cell location within the pre-irradiation images. Although this can be done completely by a human observer, the number of images requiring analysis makes the process time-consuming and tedious. To reduce the potential human error and decrease user interaction time, a semi-automated, computer-aided method of cell detection has been developed. The method employs a two-level adaptive thresholding technique to obtain size and position information about potential cell cytoplasms and nuclei. Proximity and geometry-based thresholds are then used to mark structures as cells. False-positive detections from the automated algorithm are due mostly to imperfections in the track-etch background, camera effects and cellular residue. To correct for these, a human observer reviews all detected structures, discarding false positives. When analysing two randomly selected cell dish image databases, the semi-automated method detected 92–94% of all cells and 94–97% of cells with a well-defined cytoplasm and nucleus while reducing human workload by 32–83%.

A three-dimensional reconstruction of the human hypothalamus

A previous three-dimensional reconstruction of the rat hypothalamus revealed an organization of nuclei into three major clusters. This clustering may relate to the presence of three hypothalamic anlagen in the embryo and to a restriction of marker proteins and transcription factors to specific regions of the hypothalamus during development. To see if a similar clustering was apparent in the human hypothalamus, a reconstruction of the hypothalamus from a male cadaver was prepared. The reconstruction showed a clustering of nuclei into three anterior-posterior groups. With reference to the well-defined human supraoptic nucleus, the suprachiasmatic and lateral mammillary nuclei were proportionately smaller in this single human specimen than would be expected from data in the rat. A high degree of homology between hypothalamic structures in the rat and human were generally observed.

Morphological study of cerebellar transplant cocultivated with cerebral cortical graft in the anterior eye chamber. I. Granular layer.

Fetal cerebral cortex and cerebellar anlage from rat fetuses of 15-16 gestational day were grafted simultaneously to the anterior eye chamber of adult female albino rat recipients. Two months after transplantation the cerebellar portion of the double graft consisted of foliated cerebellar cortex surrounding a well-defined cerebellar nucleus. In the absence of pia mater or glial scar the cerebral and cerebellar grafts were observed to establish direct contact with each other. Although much thinner than in the normal cerebellum, the overall morphological organization of the granular layer in the transplant was similar to that described for "in situ" normal cerebellum, with some remarkable differences, though. In normal cerebellum all mossy terminals contain spheroid synaptic vesicles, a characteristic morphological feature of excitatory endings. In the transplant, however, although the majority of mossy terminals contained (small or large) spheroid synaptic vesicles, numerous mossy terminals were filled with ovoid, or pleomorphic synaptic vesicles, a morphological marker of inhibitory terminals. GABA-immunogold reaction, revealed, indeed, the presence of this inhibitory transmitter in mossy terminals containing ovoid synaptic vesicles. Both GABA (-) and GABA (+) mossy terminals formed asymmetric (Gray I-type) synaptic junctions with the surrounding dendritic digits of granule cells. It is suggested that GABA-ergic fibers as well as most non-GABA-ergic axons (originating either from the cerebral cortical graft, or from the cerebellar nucleus) may develop to mossy terminal-like structures as a consequence of the hugh deficit in "natural" mossy fibers in this model.

Emission-line galaxies in the Bootes void

view Abstract Citations (64) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Emission-Line Galaxies in the Bootes Void Moody, J. Ward ; Kirshner, Robert P. ; MacAlpine, Gordon M. ; Gregory, Stephen A. Abstract The observation of three new Boo void emission-line galaxies (ELGs) in a 460-550-nm 4.5-deg prism survey, medium-dispersion spectra, and direct CCD R imagery is reported. The data are presented in tables, spectra, and isophotal maps along with data on five previously discovered Boo void ELGs. Six of the eight galaxies are shown to be similar to H II regions, with irregular morphologies, narrow lines, weak stellar continua, and diameters of about 10/h kpc; the other two are I Zw 81 (with a well-defined nucleus) and the Seyfert 1 spiral Mrk 845. The galaxy density of the void is estimated as no less than 10 percent of the cosmic mean galaxy density, and it is suggested that the fraction of ELGs in this region may be elevated. Publication: The Astrophysical Journal Pub Date: March 1987 DOI: 10.1086/184846 Bibcode: 1987ApJ...314L..33M Keywords: Emission Spectra; Galactic Clusters; Red Shift; Astronomical Spectroscopy; Galactic Structure; H Ii Regions; Astrophysics; GALAXIES: CLUSTERING; GALAXIES: REDSHIFTS full text sources ADS | data products SIMBAD (9) NED (8)

The cochlear nuclei of snakes.

The cochlear nuclei of three burrowing snakes (Xenopeltis unicolor, Cylindrophis rufus, and Eryx johni) and three non-burrowing snakes (Epicrates cenchris, Natrix sipedon, and Pituophis catenifer) were studied. The posterior branch of the statoacoustic nerve and its posterior ganglion were destroyed and the degenerated nerve fibers and terminals traced to primary cochlear nuclei in 13 specimens of Pituophis catenifer. All these snake species possess three primary and one secondary cochlear nuclei. The primary cochlear nuclei consist of a small nucleus angularis located at the cerebello-medullary junction and a fairly large nucleus magnocellularis forming a dorsal cap over the cephalic end of the alar eminence. Nucleus magnocellularis may be subdivided into a medially placed group of rounder cells, nucleus magnocellularis medialis, and a laterally placed group of more ovate and paler-staining cells, nucleus magnocellularis lateralis. A small but well-defined secondary nucleus which showed no degenerated nerve terminals after nerve root section, nucleus laminaris, underlies the cephalic part of both nucleus magnocellularis medialis and nucleus magnocellularis lateralis. Larger and better-developed cochlear nuclei were found in burrowing species than in non-burrowing species of snakes. Of the three burrowing species studied, Xenopeltis showed the greatest development of cochlear nuclei; Eryx cochlear nuclei were not quite as large but were better differentiated than in Xenopeltis; and Cylindrophis cochlear nuclei were fairly large but not as well developed nor as well differentiated as in either Xenopeltis or Eryx. The cochlear nuclei of the three non-burrowing snakes, Epicrates, Natrix, and Pituophis, were not as large nor as well developed as those of the burrowing snakes. There is some, but not complete, correlation between cochlear development and papilla basilaris length and number of hair cells. Thus, Xenopeltis and Eryx, with well-developed cochlear nuclei, have relatively long papillae basilares; but the boid, Epicrates, with less well-developed cochlear nuclei, has a fairly well-developed papilla basilaris. Cylindrophis, a burrowing species, shows only a moderate degree of cochear nuclei and papilla basilaris development. The non-burrowers, Natrix and Pituophis, have both small cochlear nuclei and relatively short papillae basilares.

The paratrigeminal nucleus. I. Neurons and synaptic organization.

The paratrigeminal nucleus, a diffuse collection of neurons on the lateral medullary surface, lies embedded in the fibres of the restiform body, ascending spinocerebellar tract and the spinal tract of the trigeminal nerve. Its rostrocaudal extent is approximately 1500--2000 micrometer in the rat, 2800--3500 micrometer in the rhesus monkey, and 5000--6000 micrometer in the human, where it is a well-defined nucleus. In Golgi preparations the neuronal somata are generally fusiform, ranging from 8--15 micrometer in width and 15--25 micrometer in length. Electron microscope studies show that their polar dendritic processes are thick and long and they intertwine in bundles among islands of cells or myelinated fibres. The perikarya have a high nucleus to cytoplasm ratio and the scanty cytoplasm is conspicuous for its paucity of organelles and its plethora of polysomal arrays. The neuropil is complex and contains a heterogeneous population of axonal varicosities displaying markedly different axoplasmic structures. Many different types of large granular vesicle-containing axons prevail. These axons engage in axo--somatic, axo--dendritic, axo--spinous and axo--axonic synapses with the processes of the cells within the nucleus.