Radial Columns Research Articles

Prenatal and perinatal development of radial cell columns in the human auditory cortex.

The aim of this study was to analyse cytoarchitectonic development of radial cell columns in the human auditory cortex and to correlate these 'ontogenetic' cell columns with the 'adult' pattern of radial cell arrangement. For this cytoarchitectonic analysis, brains were obtained from human fetuses and infants ranging between 9 weeks of gestation and third postnatal month. Plastic and celloidin sections containing prospective auditory areas TC, TB and TA of Economo & Koskinas were stained by Nissl method. In youngest fetuses (8-13 weeks) radially oriented cell columns (1-3 cell wide 'ontogenetic' columns) were found in the whole thickness of the developing cortical plate. During the next developmental stage (13-26 weeks of gestation), radial cell columns were present in the superficial part of the cortical plate, while the deep part of the cortical plate showed a variable cell arrangement due to the formation of the subplate layer (13-15 weeks). The appearance of the pale bands, and development of the prospective granular layer (18-26 weeks). After 28 weeks, parallel to the intensive areal cytoarchitectonic differentiation and ingrowth of callosal afferents, there was a gradual regional rearrangement in the ontogenetic pattern of vertical cell columnation. In the area supratemporalis granulosa (TC), radial columnation was observed as increased granularity and the appearance of short cords composed of drop-like cells. In the area supratemporalis simplex (TB) there was a progressive differentiation of elongated cell columns, intervening fibrillar stripes with appearance of pyramidal cell cords in layers III ('organ pipe' formations).(ABSTRACT TRUNCATED AT 250 WORDS)

Improved high-performance liquid chromatographic separation of urinary paracetamol metabolites using radially compressed columns

Methods have been adapted for the high-performance liquid chromatographic (HPLC) analysis of urinary paracetamol metabolites on radial compression columns. Enhanced resolution and decreased analysis time were two major advances. Various modifications to existing methods were made to counter the effect of the different C18 surface. Thus in ion suppression HPLC the addition of triethylamine at pH 3.0 (phosphate buffer) was necessary to block residual hydroxyl sites, while in ion-pair HPLC a higher tetrabutylammonium hydroxide concentration of 0.01 M at pH 5.0 was used to enhance selectivity. The methods were successfully applied to the study of the metabolism of paracetamol, its glutathione conjugate and 3-thiomethylparacetamol in Sprague—Dawley rats. 3-Thiomethylparacetamol sulphoxide and its glucuronide and sulphate conjugates were shown to be metabolites of both 3-thiomethylparacetamol and paracetamol. 3-Thiomethylparacetamol sulphate was unresolved from the sulphates of paracetamol and 3-methoxyparacetamol in ion-pair HPLC. This raises a previously unrecognised problem in which the peak normally attributed to paracetamol sulphate contains metabolites arising from an oxidative metabolic pathway. Elevated levels of 3-methoxyparacetamol conjugates were found in human overdose urine and to some extent in analgesic nephropathy.

Postnatal development of auditory callosal connections in the kitten

AbstractTritiatedproline or horseradish peroxidase (HRP) was injected into the middle ectosylvian auditory cortex (AI) of one hemisphere in kittens during the first few weeks postpartum. Survival time was 24–96 hours. The tetra‐methylbenzidine (TMB) (Mesulam '78) method was used to process the HRP material. By the first postnatal day (PND 1) most neurons retrogradely filled in the contralateral auditory cortex form a densely packed, continuous band that presumably represents mainly layer III. This continuous pattern is in contrast to that seen in the adult cat where callosal neurons tend to aggregate in clusters. Other retrogradely labelled cells are more sparsely distributed in deeper layers with the greatest accumulation being in layer VI. At this time callosal neurons are elongated, with their long axes parallel to radial cell columns. In autoradiographs on PND 2, silver grains are seen throughout the thickness of the cortex, indicating that callosal axons have reached the upper layers of the gray matter. Neither the alternating vertical columns nor the laminar bands of callosal afferents that characterize this projection in the adult are clearly seen in kittens of this age. By PND 8–12 the segregation of callosal afferents into vertical bands is evident in the gray matter; by PND 18 this pattern is well developed. On the other hand, the somata of callosal neurons of layer III retain their juvenile distribution well into the seventh postnatal week and show adultlike aggregations sometime around the 14th week after birth. Projections to the medial geniculate body, inferior colliculus, putamen, caudate nucleus, and pons are clearly evident early in the first postnatal week.

Liquid chromatographic assay of phenothiazine, thioxanthene and butyrophenone neuroleptics and antihistamines in blood and plasma with conventional and radial compression columns and UV and electrochemical detection

An assay strategy for determining a wide range of phenothiazine, thioxanthene and butyrophenone neuroleptics and antihistamines both alone and in combination in blood and plasma is described. The general method employs liquid chromatography with both conventional and radial compression nitrile bonded columns. Detection is by ultraviolet absorption spectrophotometry or by amperometry depending on the concentrations to be measured. Ultraviolet absorption is suitable down to 10 ng/ml. Below this level amperometry is preferable. The various compounds are used as internal standards for each other. The lower limit of detection is approximately 0.1 ng ml −1 with a 10-ml sample. The within-run coefficient of variation is a maximum of 7.3%.

High-performance liquid chromatographic analysis of porphyrins and their isomers with radial compression columns

Porphyrin methyl esters and the isomers of uroporphyrin and heptacarboxylic porphyrin were separated by high-performance liquid chromatography. Isocoproporphyrin was also separated from coproporphyrin. By slight modifications to the solvent mixture, the separation of all biological polycarboxylic porphyrins was achieved. These separations were made possible through the high efficiency of 10- or 5-μm particle-size Radial-PAK cartridges, which have been used in the separation of porphyrins in various excreta and tissues in a number of porphyrias.

High performance liquid chromatography of steroid metabolites in the pregnenolone and progesterone pathways

Rapid separation of gonadal steroids in the progesterone(Δ 4) and pregnenolone pathway (Δ 5) has been accomplished by the use of high performance liquid chromatography (HPLC). Two HPLC systems are utilized. The first requires the use of two separate radial compression columns (C-18 and C-8), with steroids being eluted with a methanol-water gradient. The second employs a stainless steel C-18 (reversed phase) column with a 12% octadecylsilane coating. The latter system separates seven of the eight steroids in the Δ 4 and Δ 5 pathways in thirty-five minutes. For the quantitation of steroids directly, integration of the peak areas, using 254 nm absorption for the Δ 4 pathway steroids (5 ng minimum limit), and 210 nm absorption for the Δ 5 pathway steroids (25 ng minimum limit) is used. For the quantitation of radiolabeled metabolites resulting from incubation of gonadal tissue with radiolabeled steroid precursors, either one of two methods is used: (1) the eluent can be recovered from the HPLC using a fraction collector, and counted in liquid scintillation counter or (2) the entire eluent (or a portion of it) can be counted immediately by directing the flow through a radioactivity detector.

High performance liquid chromatographic analysis of anti-convulsant drugs using radial compression columns

High performance liquid chromatographic analysis of anti-convulsant drugs using radial compression columns

The retinotectal projections in the pigeon. An experimental optical and electron microscope study

Optical and electron microscope studies have been made of the termination pattern of the retinotectal projection in the pigeon. The use of Golgi impregnation and orthograde transport of peroxidase concurred to show that: (i) the majority of retinotectal preterminal segments descend obliquely rather than radially through the superficial layers of the tectum opticum; (ii) terminals in Cajal's layers 2–3 and 7 arborize tangentially, terminals in layer 4 arborize diffusely in a loose way, and, in layer 5, terminal arborizations are arranged in radial columns in which terminal ramifications are tightly packed. Radioautographic labeling of the retinotectal terminals confirmed that they do not extend beyond layer 7. It demonstrated that the total thickness of the superficial tectum opticum tends to decrease from rostral to caudal, and that the density of retinotectal terminals is higher in the plexiform 3rd and 5th layers than in the 4th and 7th layers. Fink-Heimer staining of the terminal degeneration consecutive to an enucleation confirmed the results of radioautographic studies. It showed that the evolution of the silver impregnation differs from one layer to the next. This evolution is roughly parallel in the 3rd and 5th layers on the one hand, in the 4th and 7th layers on the other hand. The electron microscope study disclosed three successive stages of terminal degeneration over the whole projection area. They respectively present a dilatation of synaptic vesicles, a hyperplasia of the neurofibrillar system, and a darkening of the axoplasm. The three stages do not appear simultaneously in the 3rd and 5th layers and in the 4th and 7th layers. Comparison between the evolution of the terminal degeneration at the electron microscopic level and that of Fink-Heimer staining at the optical microscope level shows that the Fink-Heimer technique impregnates the earliest stage of degeneration (with vesicle dilatation), but not that with neurofibrillar hyperplasia. Following the resorption of retinotectal boutons, most of the postsynaptic differentiations disappear. However, some persist and become partially reoccupied by small terminals. The possible origin of these new synaptic relations is discussed.

The central nervous system of Loligo. I. The optic lobe.

The optic nerve fibres project on to the optic lobe in a regular manner, being precisely re-assorted after passing through a chiasma. In the outer plexiform zone the optic nerve fibres end in contact with the dendrites of second-order visual cells. These presumably serve to classify the visual input and four types can be recognized anatomically: (1) The smallest have minute circular dendritic fields, in contact with one or few optic nerve fibres. (2) There are also larger circular fields. (3) Many cells have very elongated narrow dendritic fields each running straight in one direction and thus perhaps sensitive to edges. (4) The largest second-order visual cells have enormous oval dendritic fields, several millimetres long, orientated in the long axis of the lobe. Each type of field occupies a different level, producing the characteristic layering of the outer plexiform zone. Numerous amacrine cell processes end in the outer plexiform layer, some are very small with restricted branches, others have wide trees with fibres passing first inwards then outwards several times. There are thus possibilities of establishing uniform conditions of excitation or inhibition over small or large areas of the visual field. The dendrites of the centrifugal cells with axons passing to the retina spread in the various layers of the plexiform zone. They could serve to project information of the areas excited, or inhibited, out to the retina. The axons of the second-order visual cells form radial columns in the outer part of the medulla of the optic lobe. Those with the smaller dendritic fields end more superficially, the largest ones about half-way through the lobe. Each column contains fibres and neuropil at its centre, surrounded by multipolar and bipolar amacrine cells, whose branches enter the neuropil among the endings of the second-order visual cells. Horizontal multipolar cells of various sizes link the columns. Third-order visual cells send dendrites into these columns and axons deeper into the lobe, some directly to the optic tract. The giant cells of the magnocellular lobe can thus be activated by a visual pathway involving only two previous synapses (as well as by a direct static pathway involving none). Central to the zone of radial columns is a zone where many of the connexions are tangential. There is an increasing number of large cells passing centrally, many being presumably fourth-order visual neurons. They send axons either elsewhere within the lobe or to the optic tract. Fibres reaching the lobe from the central brain or opposite lobe are distributed in this region and also reach out into the radial columns. In many of the tracts leaving the optic lobes for other centres the fibres maintain precise topographical relations, as also do those of the optic commissure. This regularity is especially clear in the bundles that pass to the motor centres (peduncle lobes and anterior basal lobes) but may be present in others. There is thus a regular mapping of the visual field throughout much of the system. Other pathways show complex interweaving, for instance those for colour control, where the response pattern is not topographically related to the visual input.

Connective Tissues and Body Wall Structure, of the PolychaetePolyphysia Crassa {Lipobranchius Jeffreysii)and Their Significance

The polychaetePolyphysia crassa(Oersted) is unusual in possessing a well-developed body-wall connective-tissue layer which exceeds the combined thickness of the circular and longitudinal muscles. Both collagenous and elastic fibres are present in this layer. The collagen is organized as a loose three-dimensional lattice allowing longitudinal, circumferential or radial distension of the body wall and, as in other soft-bodied invertebrates, serves the functions of providing a base on which the muscles can act and of imposing limits to the extensibility of the system. The elastic fibres are organized as an apparently randomly oriented meshwork of stout fibres around the circular muscle blocks and are attached to both the circular and longitudinal muscles. Columns of elastic fibres extend radially from the supramuscular coarse meshwork through the ‘holes’ in the collagen lattice to the epidermal basement membrane. As the elastic columns extend outwards the fibres become finer and more numerous and flute out to give a wide area attachment to the epidermal basement membrane. The radial elastic columns are cross-linked by tangential elastic fibres. Although at any point the main collagen and elasticfibre bundles are oriented at right angles to one another, collagen fibres are invariably associated with the elastic fibres and the two fibre types form a single functionally inte-grated system.Polyphysialives in flocculent, sublittoral muds and the burrowing mechanism employed involves a pronounced direct peristaltic wave of simultaneous circular and longitudinal muscle contraction which necessitates considerable radial thickening of the body wall. The functions of the elastic fibres appear to be to oppose the radial distension of the body wall which the collagen lattice permits and to control the folding of the cuticle and epidermis and the return of the collagen system after the passage of a peristaltic wave.

Impulse breakdown between co-axial electrodes at low pressure

A capacitor bank of 9-20 μF, charged to 5-7 kV was suddenly connected to a short coaxial gap, having an electrode separation of 4 cm, filled with N2 at pressures between 4 and 4 × 10-2 torr. It was observed that in spite of gap and external electric circuit symmetry, the discharge with a peak current of 10,000 A to 60,000 A always developed initially in one or more radial columns and never in a continuous luminous ring, and that the development of each radial column occurred in three distinct stages.

Feeding Organs and Feeding Habits of Autolytus Edwarsi St. Joseph. (Studies on the Syllidae, I)

Autolytus Edwarsi St. Joseph at Plymouth lives upon Obelia. It deprives the hydroid of the hydranths and eats them. The worm cuts off the tentacles from the hydranth with the toothed crown of the chitinous tube (the ‘trepan’), and sucks them up through the protruded pharynx by establishing in the front part of the alimental tract by the activity of the proventriculus a continuous water-column which is drawn back into the intestine. The pulsation or pumping action of the proventriculus is particularly strong and distinctly visible at the outset of feeding. After a short time it dies away and the action is followed by peristalsis in the intestine. The entire organization in the front part of the alimental tract, which is the feeding apparatus of the Autolytus, suggests the system of a suction pump, the pharynx representing the pipe, the proventriculus the pump itself with a valve at each entrance, and the ventriculus the regulator of the water-column. The proventricular activity is due to the strong muscular development in the radial columns, which are stretched from the centre of the organ to the periphery. In each fibre are four contractile zones, three internodes, and two insertion parts. The contractile zones only are stainable with iron haematoxylin, and these may be comparable to the anisotropic bands of the striated fibre of the Arthropods and Vertebrates. In the middle of the internode there is a thickening, the internodular-nodule: the problem whether this point can be referred to the intrafibrillar part of the inophragm (telophragm in this case) is reserved for future discussion.