bluuebunny/crossref_metadata_2025 huggingface dataset:
Sichere Druckwasserstoff‐Logistik — Speicherung und Transport
Authors: Baumgärtner K. , Kesten M.
Published: May 2005

Safe handling of pressurized hydrogen – storage and transport.For the necessary future transition to non‐fossile energy sources hydrogen is considered to be the ideal energy vector and will therefore assume ever‐increasing importance. However, safe handling of the gas will be a basic requirement. A particular difficulty with pressurized hydrogen is its relative incompatibility with many materials which are commonly used for pressure vessels, either for transportation or for storage. The paper summarizes the major factors instrumental in hydrogen embrittlement. In particular, it stresses the role played by service conditions and by the quality of the internal surface of the vessels when exposed to the gas. On the basis of these findings a number of recommendations are given with respect to vessel design and operating measures in order to secure safe working with high pressure hydrogen gas.
Die verbrennungstechnische Entsorgung eines Chemiebetriebes
Authors: Hüning Werner , Nentwig Hermann , Gockel Claus
Published: May 2005

Incineration of waste from a chemical facility. Waste from chemical plants includes solids, liquids, gases – all of which require disposal. Solid and liquid wastes can be readily incinerated or deposited in a central plant. Gas purification is the final step of the process, performed at a limited distance from the production plant. If several substances having different properties are involved then thermal waste air purification is appropriate. This paper considers the design concepts of such a thermal waste air purification unit.
Kenntnisstand und Entwicklungslinien der Schüttgutmechanik
Authors: Molerus Otto
Published: May 2005

Mechanics of particulate solids – state of the art and current trends. Beginning with the pioneering work of Jenike during the fifties, the mechanics of particulate solids has been developed further to such a state of the art that the behaviour of cohesive powders is understood from the standpoint of particle interactions. Particle interactions can be quantified by evaluation of shear tests, and the behaviour of certain types of systems is now predictable. Three major tendencies can be identified in current developments in the mechanics of particulate solids: the attempt to apply results derived in subregimes to describe more general properties of the particulate solids; the quantitative description of the flow – particle interactions in the presence of adhesion forces; and the investigation of rapidly moving particle layers.
Fouling von Wärmeübertragungsflächen
Authors: Bohnet Matthias
Published: May 2005

Fouling of heat transfer surfaces. Fouling of heat transfer surfaces in industry causes considerable costs. Overcoming fouling is therefore essential for technical and economic reasons. Solution of the problems requires a better understanding of the physical, chemical and biological processes causing fouling. It is shown, that the prediction of the fouling behaviour of heat transfer equipment based on existing mathematical models is not jet satisfactory. This article presents a new physical model describing particulate and precipitation fouling based on the assumption of a deposition and a removal process. Experiments to prove the results of the theoretical considerations were carried out using an aqueous CaSO4 solution. The test unit which is also suitable for in‐situ measurements is described in detail. Measured and predicted asymptotic fouling factors agree with acceptable accuracy.
Grenzflächenphysik in der Verfahrenstechnik – Beispiele aus der Praxis
Authors: Menold Richard
Published: May 2005

Interface physics in chemical engineering – practical examples. A series of practical examples is used to demonstrate the possible ways in which interface physics can help the chemical engineer in his work. The article first presents some fundamental principles of interface physics and appropriate methods and model concepts. It is then shown how this armamentarium can be profitably applied in specific cases: questions of coating, formulation, adhesion, granulation of powders, production of trickling films, and flotation are considered. It becomes very clear that interfacial effects have a very wide and far‐reaching influence on industrial processes. The problems encountered can be solved only by close cooperation between chemical engineers and interface physicists.
Rückgewinnung von Metallen aus niedrigkonzentrierten Lösungen
Authors: Marr Rolf , Draxler Josef
Published: May 2005

Recycling of metals from low concentrated solutions. A review is given of processes used for the separation of metals from aqueous solutions, especially low concentration waste waters. Purification processes for waste water used only to reach values set by law are compared with processes that allow recovery of metals. Precipitation with and without additives, adsorption, processes with ion exchange resins, solvent extraction and membrane processes, especially liquid membrane permeation, are described. As a result of these considerations, a qualitative comparison of all the described processes becomes possible. For the separation of zinc from a waste water stream, a special economic comparison is also shown between precipitation processes and the liquid membrane permeation process. Finally, the latest developments in the fields of solvent extraction and liquid membrane permeation are discussed.
Desaktivierung von technischen Silber‐Trägerkatalysatoren für die Herstellung von Ethylenoxid
Authors: Schwarzmann Matthias , Mroß Wolf‐Dieter , Böhning Karl‐Heinz
Published: May 2005

Deactivation of industrial supported silver catalysts for ethylene oxide production. In view of the model character of the reaction and the unique nature of the catalyst system, it is of interest to study the deactivation behaviour of technical supported silver catalysts for the production of ethylene oxide. In the present study the influence of the catalyst components support, silver, promoter and inhibitor upon the deactivation behaviour is described. The results of chemical, physical and technical investigations of various catalysts and catalyst components are presented. The investigations show that a decrease in the surface area of the exposed silver and increased deposition of chloride are responsible for catalyst deactivation. The possible influence of alkali promoters is discussed and modifications to the catalyst which have been described in the literature as influencing the deactivation are also evaluated.
Radioaktive Indikatormethode in der chemischen Verfahrenstechnik
Authors: Seher Albrecht , Dorn Ingo Helmut , Engelhardt Hubert , Gruber Wolfgang , Maichel Karl Walter
Published: May 2005

The radioactive tracer method in the chemical industry. In the chemical industry the radioactive tracer method has become a method of analysis with a variety of applications, which range from determining traces of biologically active substances to process analysis in production plants. Process analysis, for instance the determination of residence‐time distributions or of intermingling of streams of different substances, can be carried out under widely varying operating conditions. If the streams of material are labelled with gamma‐ray emitters the distribution of the tracers can be determined by means of detectors outside the plant. To demonstrate the possible applications of the method to process analysis, measurements in three different plants are described. Exhaust gases were labelled with Ar‐41 to determine the residence‐time distribution in plant for the combustion of waste residues consisting of a rotary tube furnace, an afterburn chamber, and a waste‐heat boiler. The waste water entering the activation tank of sewage‐treatment plant was labelled with Na‐24 to determine its residence‐time distribution. Individual particles labelled with Mn‐56 were used to investigate mixing of the powder in the stirred‐bed reactor of a polypropylene plant. The knowledge gained from these measurements has contributed to optimization of existing and planned plant.
Geschichte der Regelung und Automatisierung in der Verfahrenstechnik
Authors: Canavas Constantin
Published: May 2005

History of Control and Automation in Chemical Engineering. Control and automatization have been associated with chemistry and chemical engineering since long before the present information era. Since the early history of mankind precedents of what were to be called unit operations have been closely associated with control and automation concepts. The history of these concepts illustrates the development of theory and practice from the classic Greek times through Islamic and European Middle Ages up to today's chemical engineering. It also demonstrates the close interdependence of such development with leading social and scientific concepts, education systems and economic conditions.
Untersuchungen zur Trennung von Gasen an mikroporösen Membranen
Authors: Neumann Bernhard , Futterer Eberhard
Published: May 2005

Studies of Gas Separation on Microporous Membranes. The composition of Gas Mixtures can be influenced with the aid of microporous membranes by exploitation of the Knudsen effect. The components of lower molecular mass are enriched in the permeated gases while the components of higher molecular mass are concentrated in the retained gases. The best separation is achieved at higher Knudsen numbers. The maximum achievable separation factor is limited by the molecular mass ratio. Hence the gas components in the permeate can be enriched or depleted but never completely separated. In the present experiments, separation factors up to 1.39 and enrichment factors up to 1.10 were attained. However, these values should be substantially improved on use of surface modified porous membranes. Use of ceramic membrane materials permits use of this separation mechanism at very high temperatures.
Organische Reaktionen ohne Lösungsmittel
Authors: Epple Matthias
Published: May 2005

Organic Reactions without Solvent Reactions involving organic solids are of both fundamental and applied importance. First, they provide a basis for understanding structure‐property relationships in crystalline materials, and secondly, they offer opportunities (as yet largely under‐exploited) for environmentally‐friendly synthetic procedures requiring no solvent. The current state of the art is reviewed with special emphasis on possible practical applications.
Einsatz von magnetischen Mikropartikeln in der chemischen Technik
Authors: Böhm Dirk , Voß Harald
Published: May 2005

Application of Magnetic Microparticles in Chemical Engineering Technology In chemical engineering technology microparticles are used in a diversity of fields. Particles with essential chemical characteristics and additional magnetic properties open new opportunities for developing novel processes in many areas. Separation processes such as adsorption and chromatography as well as reactions with catalysts are especially interesting applications. A high specific surface is advantageous for most of these unit operations. Because of the small size of the particles used their handling is not trivial. The magnetically stabilized fluidized bed (MSFB) is a promising example of a magnetically assisted process. This technology permits design of new processes whose favorable operations conditions lie outside the range of conventional operation. Common to all applications is that the magnetic properties of the particles provide a new free and adjustable parameter for managing the process.
Dämpferückgewinnungsanlagen für Ottokraftstoffe in Deutschland – Verfahrenstechnik aus der Sicht des Explosionsschutzes
Authors: Frobese D.‐H. Dirk‐Hans
Published: May 2005

Vapour Recovery Units for Petrol in Germany – Process Technology from the Point of View of Explosion Protection.

It is a requirement of environmental protection that the vapour/air mixtures formed during the storage, transport and refilling of petrol be collected and that the vapour contained in these mixtures be recovered. By vapour balancing within the distribution chain, the vapour/air mixtures are returned to the distribution depots where they are intermediately stored in vapour tanks, if need be, and processed in vapour recovery and exhaust air cleaning units. The more comprehensive the technical measures of discharging, conveying or processing the vapour/air mixtures of flammable liquids, the greater the problems of explosion protection. In this contribution, petrol will serve as an example to present and elucidate the explosion protection measures to be taken in exhaust air cleaning or vapour recovery units.
GVC‐Fachausschuß „Trocknungstechnik”︁
Authors: Zank J. , Stein J. , Wagner G. R.
Published: May 2005

Am 31. März und 1. April 1998 stellten in Magdeburg in der Arbeitssitzung des GVC‐Fachausschusses „Trocknungstechnik”︁ Fachleute aus Industrie und Universität ihre neuesten Forschungsergebnisse auf diesem Gebiet vor. Parallel tagte der GVC‐Fachausschuß „Agglomerations‐ und Schüttguttechnik”︁, über dessen Sitzung schon in der CIT 8/98, Seite 920 bis 922, berichtet wurde. Durch die Überschneidung mit diesem GVC‐Fachausschuß war zudem die Möglichkeit gegeben, im größeren Rahmen Probleme an der Schnittstelle der beiden Fachgebiete zu diskutieren.

Der Fachausschuß „Trocknungstechnik”︁ ging in insgesamt 12 Fachvorträgen sowie 6 Postern vor allem auf die Wirbelschichttrocknung und ‐granulation, die Kontakttrocknung, Sprühtrocknung und Konvektionstrocknung ein.
Projections from orbitofrontal cortex to anterior piriform cortex in the rat suggest a role in olfactory information processing
Authors: Illig Kurt R.
Published: May 2005

The orbitofrontal cortex (OFC) has been characterized as a higher‐order, multimodal sensory cortex. Evidence from electrophysiological and behavioral studies in the rat has suggested that OFC plays a role in modulating olfactory guided behavior, and a significant projection to OFC arises from piriform cortex, the traditional primary olfactory cortex. To discern how OFC interacts with primary olfactory structures, the anterograde tracer Phaseolus vulgaris leucoagglutinin was injected into orbitofrontal cortical areas in adult male rats. Labeled fibers were found in the piriform cortex and olfactory bulb on the side ipsilateral to the injection. Notably, the projection to piriform cortex was predominantly from ventrolateral orbital cortex, and was not uniform; rostrally, the projection to the ventral portion of the anterior piriform cortex (APC) was substantial, while the dorsal APC was virtually free of labeled fibers. Labeled fibers were found in both the dorsal and ventral portions in more caudal regions of APC. Most labeled fibers were found in layer III, although a substantial number of fibers were observed in layers Ib and II. Labeled fibers in posterior piriform cortex also were seen after injection into orbitofrontal areas. Taken together with previous reports, these findings suggest that piriform cortex includes multiple subdivisions, which may perform separate, parallel functions in olfactory information processing. Further, these results suggest that the OFC, in addition to its putative role in encoding information about the significance of olfactory stimuli, may play a role in modulating odor response properties of neurons in piriform cortex. J. Comp. Neurol. 488:224–231, 2005. © 2005 Wiley‐Liss, Inc.
Propriospinal fiber connections of the cervical motor nuclei in the cat: A light and electron microscope study
Authors: Matsushita Matsuo , Ikeda Michiko
Published: May 2005

Propriospinal fiber connections of the cervical motor nuclei were studied in the cat with the Nauta and the Golgi methods. Synaptic boutons belonging to this fiber system were observed and identified under the electron microscope.

Lamina IX of the cervical cord receives a large number of fibers from the short ascending and descending propriospinal tracts but only a very restricted number from the long ascending propriospinal tract. Observations with the Golgi method show that these fibers are collaterals derived from axons ascending or descending in the ventrolateral cord. They are of three types of terminal patterns: Fibers terminating in a confined area of lamina IX with repeated branchings, fibers terminating in a wide area of both laminae IX and VIII with short terminal fibers, and simple, unbranched fibers giving off short terminal fibers to cells of laminae IX and VII.

In the cervical motor nuclei, it was found that synaptic boutons containing round vesicles usually form asymmetrical synapses with wide synaptic clefts while those containing flattened vesicles form symmetrical synapses with narrow clefts. There are some boutons which contain round synaptic vesicles and make symmetrical synapses. However, they are invariably associated with wide synaptic clefts. In lamina IX of the cervical cord many axodendritic and axosomatic boutons were found to be degenerate after section of the proprispinal fibers. They were filled with either round or flattened vesicles. A few large boutons, filled with round synaptic vesicles and associated with subsynaptic cisternae, were also seen to be degenerate.
Ventral motor nucleus of the cervical enlargement in some mammals; its specific afferents from the lower cord levels and cytoarchitecture
Authors: Matsushita Matsuo , Ueyama Teizo
Published: May 2005

Specific projections from the lower spinal cord to the ventral motor nucleus of the cervical enlargement were studied in four mammalian species (cat, rabbit, dog and rat) with the Nauta and the Fink‐Heimer methods.

Following hemisection of the lower spinal cord a medium amount of degeneration in laminae VII and VIII and scanty degeneration in the dorsolateral part of lamina IX were observed ipsilaterally at the levels from C6 to T2. In contrast, in all of these animals very dense and circumscribed degeneration was seen in a special ventral or ventrolateral cell group of lamina IX, designated here as ventral motor nucleus (VMN). Cytoarchitectonic study shows that this nucleus exists in the ventral or ventrolateral part of lamina IX from the caudal C7 to the rostral T1 segments, attaining the highest development in the C8 segment.

Projections of short descending propriospinal fibers and dorsal root fibers to this nucleus were also studied in cats and rabbits. There was a small projection from a neighboring rostral segment, but no termination was found of dorsal root fibers. These results indicate that VMN in the C7 to the T1 segments is a special cell group which receives predominantly a strong projection from the lower cord levels of the same side.
Autoradiographic investigations of glial proliferation in the brain of adult mice. The DNA synthesis phase of neuroglia and endothelial cells
Authors: Korr Hubert , Schultze Brigitte , Maurer Werner
Published: May 2005

The proliferation of glial cells outside the subependymal layer of the lateral ventricle as well as of endothelial cells was studied autoradiographically in the brain of the adult and untreated mouse. The double labeling method with 3H‐ and 14C‐thymidine was applied in order to show experimentally the existence of a DNA synthesis phase (S phase) and to measure its duration. Adult mice received a first injection of 14C‐thymidine, two or four hours later a second injection of 3H‐thymidine and were sacrificed one hour after the last injection by perfusion fixation. Double layer autoradiographs were made from serial sections of the region from the corpus callosum/commissura anterior up to the corpus callosum/commissura fornicis ventralis in order to register purely 3H‐, doubly 3H‐ and 14C‐, and purely 14C‐labeled nuclei. From the ratio of all 3H‐labeled cells with and without 14C to the purely 3H‐labeled cells a DNA synthesis phase of 9.4 ± 0.5 hours for glial cells and one of 11.0 ± 2.2 hours for endothelial cells was obtained. Based on the first appearance of labeled mitoses and labeled pairs of glial cells after injections of labeled thymidine the G2 phase was estimated to be < three hours and G2 + M about five hours. The duration of the measured S phase as well as the appearance of labeled mitoses about three hours after application of labeled thymidine are very similar to these cycle parameters in many other somatic cells in different kinds of animals. This has led to the conclusion that a well‐defined DNA synthesis phase with doubling of the DNA content and a successive mitosis also exists in glial and endothelial cells of the adult mouse brain.
Ascending central gustatory pathways
Authors: Norgren Ralph , Leonard Christiana M.
Published: May 2005

The central gustatory pathways of the albino rat have been traced using a combined electrophysiological‐neuroanatomical technique.

Gustatory responses in the medulla were recorded in the region of the solitary nucleus which receives the seventh nerve primary afferents. Fibers traced from lesions of these recording sites did not cross as expected into the medial lemniscus, but instead travelled rostrally to terminate ipsilaterally in a small celled area dorsal and ventral to the brachium conjunctivum as it enters the pons.

Since gustatory responses could be recorded in this region it represents a previously undescribed secondary “pontine taste area.” Lesions of PTA result in degeneration of a bilateral ascending pathway travelling in the dorsomedial tegmentum to terminate in the classical gustatory nuclei of the thalamus. Other fibers in this pathway continue rostrally and distribute in the subthalamus, dorsolateral hypothalamus and subpallidal gray in the ventral forebrain.

These findings in a mammal resemble those established nearly three quarters of a century ago by Herrick ('05) in the carp, and confirm his prediction that “broad lines of similarity [would be found] between both the peripheral and central gustatory paths in all vertebrates”.
The structure of the optic nerve of the teleost: Eugerres plumieri
Authors: Tapp R. L.
Published: May 2005

The morphology and ultrastructure of the intra‐orbital portion of the optic nerve of Eugerres plumieri is described. Attention is drawn to the ribbon‐like form of the nerve and to the presence of non‐myelinated axons, the majority of which are grouped into a tract at one edge of the ribbon. Fibrous astrocytes and oligodendrocytes are both present and clearly distinguishable. A third type of glial cell which shows evidence of phagocytic activity is also present. It is almost identical in ultrastructure with the multipotential glial cell described by Vaughn and Peters ('68).
Structurally specialized contacts between the photoreceptors of the retina of the axolotl
Authors: Custer Nancy V.
Published: May 2005

Electron microscopic examination of the retina of the axolotl, Ambystoma mexicanum, revealed several types of morphological junctions between individual photoreceptors. Distal to the outer limiting membrane of the retina, gap junctions were found between neighboring rods and between neighboring rods and cones. In the external plexiform layer, the synaptic terminals of cones and double cones are often in positions opposite the synaptic ribbons of rod terminals that have been traditionally defined as postsynaptic. A few tight junctions between photoreceptor telodendria were observed. Relationships between the members of double cones are also described.
The central connections of the posterior lateral line nerve of Gnathonemus petersii
Authors: Maler L. , Karten H. J. , Bennett M. V. L.
Published: May 2005

The central distribution of the posterior lateral line nerve (NLLp) was studied in the weakly electric African fish, Gnathonemus petersii. Lesions were made in the ganglion of NLLp and the degeneration traced by means of the Fink‐Heimer technique. NLLp distributes to the ipsilateral posterior lateral line lobe, anterior lateral line lobe, and lobus caudalis cerebelli. The posterior lateral line lobe is laminated and NLLp terminates in an organized manner within three of its six laminae. In addition the projection of NLLp to the posterior lateral line lobe is topographic. The projection of NLLp to the anterior lateral line lobe is more diffusely organized.
Neuromuscular junctions in the leech
Authors: Yaksta‐Sauerland Barbara A. , Coggeshall Richard E.
Published: May 2005

Neuromuscular junctions on leech body wall muscle have been described. Based on vesicle morphology, there are two types of junctions, (I) clear vesicle terminals, and (II) dense core vesicle terminals. Further, the dense core terminals are‐of two types, (1) small terminals which appear to directly innervate body wall muscle cells, and (2) large terminals which appear to synapse on clear vesicle terminals which in turn innervate body wall muscle cells. The clear vesicle ending resembles known cholinergic junctions in other systems. The cores in the dense core vesicle terminals are regarded as containing 5‐HT because (1) they are structurally identical with the 5‐HT containing cores in granules of the Retzius cells, (2) they contain a chromaffin substance, and (3) they become radioactive when tritiated 5‐HT is present but not when 5‐HTP or noradrenaline is present.
Atlas of estradiol‐concentrating cells in the central nervous system of the female rat
Authors: Pfaff Donald , Keiner Melvyn
Published: May 2005

Two hours following intraperitoneal injection, estradiol‐H3 is concentrated by cells in a system of limbic and hypothalamic structures. Preoptic‐hypothalamic nuclei containing estrogen‐concentrating cells include the medial preoptic area, medial anterior hypothalamus, ventromedial nucleus, arcuate nucleus and ventral premammillary nucleus. Limbic structures include the medial and cortical nuclei of the amygdala, lateral septum, bed nucleus of the stria terminalis, diagonal band of Broca, olfactory tubercle, ventral hippocampus, and prepiriform and entorhinal cortex. Labelled cells were also found in the lateral and ventrolateral portions of the mesencephalic central grey. Compared to these regions, most other regions of the nervous system, including the spinal cord, have very small numbers of labelled cells, which are relatively weakly labelled, and are not found in regular, specific locations. The distribution of estrogen‐concentrating cells determined with the present autoradiographic method agrees with previous autoradiographic conclusions and with biochemical results from cell fractionation experiments.

The locations of estrogen‐concentrating cells coincide in several brain regions with locations of estrogen‐dependent neuroendocrine control mechanisms, as determined by brain implants, lesions, electrical stimulation, and electrophysiological recording. Moreover, experimental neuroanatomical studies have provided evidence for several pathways connecting regions which concentrate radioactive estradiol. Taken together, the evidence suggests a limbic‐hypothalamic system of estrogen‐concentrating neurons which participate in the control of mating behavior and of gonadotrophin release from the pituitary.
Neuroglial response to sciatic neurectomy. II. Electron microscopy,
Authors: Kerns James M. , Hinsman Edward J.
Published: May 2005

The response of oligodendrocytes, astrocytes, multipotential glia (MPG), and pericytes to sciatic neurectomy in young adult rats was studied by electron microscopy. Animals were perfused with aldehyde fixative at 2, 4, 7, and 14 days postoperative (dpo).

Neuronal changes were slight and there was no apparent response in either oligodendrocytes or pericytes. Typical reactive changes observed in the astrocytes included an increase in glial filament bundles and microtubles. At 2 dpo mitotic cells were observed and by 4 dpo many MPG were located around affected neuron cell bodies apparently isolating them. The MPG processes formed overlapping sheets of processes between neurons and the elements of the neuropil. Hence synaptic boutons were displaced from the surfaces of the ensheathed neurons, but phagocytosis of synaptic boutons was rarely observed. The role and origin of the MPG and their similarity to microglia are discussed.
Mitral cell development in the mouse olfactory bulb: Reorientation of the perikaryon and maturation of the axon initial segment
Authors: Hinds James W. , Ruffett Trudy L.
Published: May 2005

The proximal portion of mitral cell axons was examined in electron microscopic serial sections and Golgi impregnations of mouse embryos on the fifteenth day of gestation (E15), E16, postnatal day one (P1), and P4. During this time the cell body of developing mitral cells appears to transform from tangential to radial orientation and then migrate peripherally while the tangential axon remains relatively fixed. In E15, E16 and P1 animals, electron microscopy of most radial mitral cells reveals that the microtubules of the axon proper are continued as a bundle of approximately the same diameter through the voluminous subnuclear cytoplasm to one side of the nucleus. The rest of the subnuclear cytoplasm is nearly devoid of microtubules and contains only free ribosomes and an occasional mitochondrion. It is suggested that the position of the axon is determined within the perikaryon by a bundle of microtubules; the nucleus and rest of the subnuclear cytoplasm then migrates peripherally leaving only a relatively thin axon. If some of the perikaryal cytoplasm failed to migrate peripherally, a bleb or process might be left, as in fact has been observed in Golgi impregnations and electron microscopy. We have also examined the ultrastructure of the developing axon initial segment, in cross‐sections of the axons from E15 to P4, as well as in longitudinal serial sections. Fascicles of closely apposed microtubules have been noted in some advanced mitral cells at E15 and E16, and by P1 such fascicles are common and well developed in most mitral cells. In P1 animals some mitral cell initial segments show a faint and patchy dense undercoating of the axolemma, but many axons at this time appear to completely lack this feature. By P4 nearly all initial segments show a fairly well developed dense undercoating. In general, therefore, the development of fascicles of closely apposed microtubules precedes the elaboration of the dense undercoating of the axolemma.
Transport of proteins across normal cerebral arterioles
Authors: Westergaard E. , Brightman M. W.
Published: May 2005

Portions of certain arterioles on the surface of the brain and within it can transfer protein from blood to perivascular basement membrane. One to 50 mg of horseradish peroxidase (MW: 40,000) were injected intravenously into normal, adult mice. Three to 30 minutes later, their brains were fixed by vascular perfusion of aldehydes, incubated, and processed for electron microscopy.

Segments of some cerebral arterioles, with an average diameter of 15‐30 μ, transported peroxidase. The pial arterioles were mainly situated within sulci, the parenchymal ones in the ventral part of the diencephalon and adjacent brain stem. The arteriolar segments were, commonly, bifurcations and short, straight portions. Similar vessels transferred protein in normal rats and hamsters. Neither increasing the dose of peroxidase above 10 mg nor the circulation time from 3 to 30 minutes altered the number of transferring vessels in mice.

The endothelial cells were, as in cerebral capillaries, linked by tight junctions that prevented the extracellular passage of peroxidase. When peroxidase was injected 45 minutes after fixation, it did not reach the basement membrane. Moreover, ferritin, too large a molecule (MW: 900.000) to pass through these endothelial junctions, was also transported across the same segments 3 minutes after 100‐500 mg had been injected intravenously. These observations indicate that vesicular transport rather than passive, extracellular movement was the means of transferring proteins from blood to perivascular basement membrane. It is probable that serum albumin and globulins are likewise transferred in normal rodents.
Organization of cerebellar cortex secondary to deficit of granule cells in weaver mutant mice
Authors: Rakic Pasko , Sidman Richard L.
Published: May 2005

This study deals with some consequences of the early postnatal abnormalities of cerebellar Bergmann glial fibers and granule cell neurons. (1) Cerebellar size is mildly reduced in heterozygous weaver (+/wv) mice and markedly reduced in homozygotes (wv/wv), but the pattern of fissures is essentially normal. Comparison with other mutants displaying small cerebella suggests that cell proliferation rate in the external granular layer is a key deteminant of cerebellar cortical folding. (2) Mossy fiber terminals differentiate on schedule despite the reduced number and abnormal positions of granule cells. However, many of them enter the modified molecular layer, and as noted especially in noninbred wv/wv mice one to two years old, form synapses with dendrites of aberrant granule cells. Where granule cells are absent, mossy fibers form more than the normal number of synapses with dendrites of Golgi type II neurons. (3) Purkinje cells are only mildly affected by the disorder of neighbouring cells. Their dendrites grow abnormally into the territory occupied by external granule cells, reach the external surface, and may turn inward. They form few tertiary branches. Dendritic spines are present in profusion and show membrane thickenings akin to normal postsynaptic elements. Although they receive no axonal contacts, the spines persist, enveloped by glial processes, for at least two years. Apart from the absence of parallel fiber contacts, afferent and intrinsic axons form the normal classes of synaptic connections with Purkinje cells. (4) Interneurons of the molecular layer are generated on schedule. At the time of their earliest recognition, they reside in the external granular layer, where they receive synaptic contacts from climbing fibers and other interneurons. In the absence of parallel fibers, interneurons differentiate in situ but their dendrites are abortive and randomly oriented. Growth of their dendrites, in contrast to that of Purkinje cell dendrites, appears to be markedly influenced by the organization of the local cellular milieu.
Osmotic opening of tight junctions in cerebral endothelium
Authors: Brightman Milton W. , Hori Masaharu , Rapoport Stanley I. , Reese Thomas S. , Westergaard Erik
Published: May 2005

Hyperosmotic solutions of 3 M urea, either infused into one internal carotid artery or applied topically to the pia mater of rabbits, results in the opening of endothelial tight junctions through which horseradish peroxidase passes from blood to extracellular fluid of the brain. The evidence for this opening of the blood‐brain barrier to protein is the entry of peroxidase into the extracellular pools between successive tight junctions. In animals not receiving 3 M urea, the interjunctional pools are inaccessible to proteins. Having passed through the endothelial junctions, the peroxidase spreads along the extracellular channels of the perivascular neuropil for approximately 100 μ in 90 seconds. Most of the affected vessels are capillaries, though larger vessels are rendered leaky as well. Calyciform cisterns, that lie beneath shallow notches in the endothelium of untreated rabbits, appear to be enlarged after the administration of 3 m urea. It is undetermined whether these few endothelial cisterns and vesicles are involved in carrying protein from blood to the cerebral extracellular fluid.
Unmyelinated axons in the ventral roots of the cat lumbosacral enlargement
Authors: Coggeshall Richard E. , Coulter Joe Dan , Willis William D.
Published: May 2005

The ventral roots L7 and S1 of the cat spinal cord were examined with the light and electron microscopes. Differences in the morphology of Schwann cells associated with large myelinated fibers and with small myelinated or unmyelinated fibers were observed. The blood vessels were largely encircled by pericytes. The most noteworthy finding was that 29% of the axons in these roots were unmyelinated. These unmyelinated axons were greatly reduced in number proximal but not distal to a ventral rhizotomy. Furthermore, they were reduced in number following dorsal root ganglionectomy, but not after dorsal rhizotomy, sympathectomy or peripheral nerve section. It is concluded that the ventral roots of the lumbosacral enlargement contain a large population of unmyelinated fibers originating from dorsal root ganglion cells.
The anatomical organization of hindlimb motoneurons in the lumbar spinal cord of the frog, Rana catesbiana
Authors: Cruce William L. R.
Published: May 2005

The precise location of lumbar spinal motoneurons was studied in the bullfrog by observing the retrograde reaction following injury to nerves which innervate different hindlimb muscles. The results were confirmed and their usefulness for physiological studies was demonstrated by iontophoretically injecting dye through an intracellular recording micropipette into motoneurons which were identified by antidromic spike invasion. The effects of plexus variation upon the location of motoneuron pools was considered in order to standardize the results and make possible comparisons between different frogs.

New determinations were made of frog hindlimb muscle function with reference to jumping in order to assess the possible functional significance of motoneuron organization. In general, motoneurons acting upon proximal joints are located rostrally to motoneurons acting upon distal joints and flexor motoneurons are located rostrally to extensors.

The somatotopic significance of motoneuron organization was also assessed and it was found that within the lateral motoneuron column there are three groups of cells, each of which innervates different, but somatotopically related groups of muscles. This organization is quite similar to that found in cats. The developmental and functional implications of this similarity are considered.
Observations on the synaptic organization of the retina of the albino rat: A light and electron microscopic study
Authors: Leure‐Dupree Alphonse E.
Published: May 2005

An electron microscopic study of the retina of the albino rat, with particular emphasis on the synaptic organization of the inner and outer plexiform layers, has been correlated with specimens impregnated with a modified Golgi technique.

The central element of the photoreceptor “triad” in the outer plexiform layer is a bipolar cell dendrite.

Two types of synaptic contacts were observed in the inner plexiform layer, the “dyad” ribbon synapse and the conventional synapse. The postsynaptic elements of the “dyad” consisted of an amacrine process and a ganglion cell dendrite. Conventional synapses were made by amacrine processes which were usually presynaptic to bipolar terminals. Reciprocal synapses between processes making ribbon synapses and those making conventional synapses were seen.

Golgi technique revealed the presence of two types of bipolar cells, three types of amacrine cells, and one type each of horizontal and ganglion cell.

These findings are discussed in relation to reported receptive field organization.
Ascending connections of a thalamic auditory area in a crocodile, Caiman crocodilus
Authors: Pritz Michael B.
Published: May 2005

Nucleus reuniens pars centralis is the major recipient of the ascending auditory lemniscus from the midbrain in the crocodile, Caiman crocodilus. Its ascending connections were studied by means of the Fink‐Heimer procedure with the light microscope after anodal, stereotaxic lesions. Following unilateral destruction of nucleus reuniens pars centralis, degenerating axons assemble on the lateral aspect of the pars centralis, pass through the pars diffusa, and enter the dorsal peduncle of the lateral forebrain bundle. These fascicles travel rostrally in the lateral forebrain bundle where they remain restricted to the medial aspect of this tract. At more rostral levels, these degenerating axons turn dorsad, pass through and perhaps synapse on interposed neurons of the medial portion of the ventrolateral area, and end on cells located in the overlying dorsolateral area. This terminal field is composed of small, round, tightly packed neurons located in a medial caudal part of the dorsolateral area.

This experiment together with a previous report demonstrates the existence of a specific and sharply localized auditory pathway leading from the central nucleus of the torus semicircularis by way of nucleus reuniens pars centralis to the telencephalon. The findings of this study are compared with similar research on thalamotelencephalic projections of diencephalic auditory areas in other amniotes.
A cytoarchitectonic study of the diencephalon of the tegu lizard, Tupinambis nigropunctatus
Authors: Cruce J. A. F.
Published: May 2005

Nuclei in the hypothalamus, ventral thalamus, dorsal thalamus, epithalamus, and pretectum are described and named in the Tegu lizard, Tupinambis nigropunctatus. Many of the nineteen cell groups in the hypothalamus contain small, round cells located near the ventricle; two groups of magnocellular elements, nucleus supraopticus and nucleus paraventricularis, are also present. Of the eight cell groups in the ventral thalamus, nucleus geniculatus lateralis pars ventralis, located medial to the optic tract, is the most conspicuous. Six nuclei are described in the dorsal thalamus; nucleus rotundus and nucleus dorsolateralis anterior are very prominent. The epithalamus consists of medial and lateral habenular nuclei. In the pretectum, seven nuclear groups are recognized.
Axon numbers and distribution, myelin thickness, and the reconstruction of the compound action potential in the optic nerve of the teleost: Eugerres plumieri
Authors: Tapp R. L.
Published: May 2005

The optic nerve of Eugerres plumieri contains about 200,000 fibers. Only 2.5% are non‐myelinated and the majority of these are grouped into a single tract. The axon diameters of the myelinated fibres range between 0.2 μ and 7.6 μ (mode, 0.7 μ) and the external fibre diameters range between 0.26 μ and 9.2 μ (mode, 1.0 μ). The relationship between myelin thickness, t, and axon diameter, d, shows a mode at about 0.25 (d/D = 0.67) but the distribution is wide and skewed positively. The compound action potential can be reconstructed arithmetically from morphological data and correlates well with electrophysiological recordings.
Synaptogenesis in the outgrowth of rat cerebellum in organized culture
Authors: Privat A. , Drian M. J. , Mandon P.
Published: May 2005

Synaptogenesis was studied in the outgrowth of newborn rat cerebellum, cultivated in vitro.

As soon as the second day after explatation, membrane specializations were found between axons and dendrites. Synaptic vesicles were, at this age, absent from the vicinity of these contacts.

Four days after explantation, axodendritic as well as axosomatic synapses were present, with usually a paucity of synaptic vesicles. Contacts without vesicles were again numerous at this age.

Six to eight days after explanation, some of these synapses showed already a mature appearance, and characters reminiscent of those of their in vivo counterpart. For instance, typical “en passant” synapses of parallel fibers were found. Contacts without vesicles were rare at this age. A sequence of events leading to the onset of mature synapses is suggested.

Finally, an attempt was made to correlate the ultrastructure of synapses as seen with transmission electron microscopy with scanning electron microscopic pictures.
Fluorescence histochemistry of monoamine‐containing cell bodies in the brain stem of the squirrel monkey (Saimiri sciureus). II. Catecholamine‐containing groups
Authors: Hubbard Jack E. , Carlo Vincenzo Di
Published: May 2005

In this second paper of the series on the monoamine‐containing cell bodies found in the brain stem of the squirrel monkey (Saimiri sciureus) by the fluorescence histochemical technique, a description is presented of the catecholaminergic neurons. The first paper was a report on the locus caeruleus (a norepinephrine containing group), which, in consideration of its physiological importance, was the object of a particularly detailed study. The other groups of catecholaminergic cell bodies were found to have a topographic distribution and general morphological characteristics quite similar to those described for the rat. In particular, in the squirrel monkey brain stem homologous groups of neurons were observed for each group described in the rat, with the exception of the weakly fluorescing group A3. In comparing the findings on the squirrel monkey with the description of the catecholaminergic cell groups in the cat some significant differences were noticed.
Corticorubral projections in the rat
Authors: Brown Leroy T.
Published: May 2005

In a series of young adult albino rats the terminal projections of corticorubral fibers were studied by light and electron microscopic methods following unilateral sensorimotor cortex suction ablation. Degenerating axons could be traced from the ipsilateral cerebral peduncle to the periphery of the red nucleus. Within the red nucleus the degeneration was sparse. No degeneration was seen contralaterally. With the electron microscope degenerating axons showed electron dense axoplasm and seemed devoid of their normal complement of organelles. Electron‐dense degenerating synaptic terminals, one to two per grid square, were found in the more rostral portions of the red nucleus. These terminals were of the asymmetrical type with increased density of the post‐synaptic membrane and made contact with small to medium sized dendrites. No degenerating axosomatic or axoaxonal knobs were seen. No degenerating terminals were seen in the caudal regions of the red nucleus. This study finds that following ablation of the sensorimotor cortex in the rat there is a projection to the ipsilateral red nucleus and that the contacts are primarily of the axodendritic type as revealed by the electron microscope.
Anatomical organization of pretectal nuclei and tectal laminae in the cat
Authors: Kanaseki T. , Sprague J. M.
Published: May 2005

Seven nuclei of the pretectum in the cat have been identified and described using material stained for cytoarchitecture and myeloarchitecture, and these have been related to comparable nuclei in other species. These nuclei are termed (1) N. pretectalis anterior, pars compacta and (2) pars reticularis, (3) N. p. medialis, (4) N. p. posterior, (5) N. tractus opticus, (6) N. p. subopticus and (7) N. p. olivaris. Fink‐Heimer stains of terminal degeneration following enucleation indicate that retinopretectal fibers terminate primarily contralaterally in nuclei 4, 5 and 7, and in nuclei 5 and 7 ipsilaterally. At least seven laminae in the superior colliculus have been identified by cytoarchitecture: I. Stratum zonale (two sublayers), II. S. griseum superficiale (three sublayers), III. S. opticum, IV. S. griseum profundum, VII. S. album profundum. The lateral nucleus of the periaqueductal gray might be included as the eighth tectal lamina. Ninety percent or more of the terminal degeneration following enucleation is found on the contralateral side, primarily in the first sublayer of lamina II, with small amounts in the second sublayer; the sparse ipsilateral degeneration is limited to the second sublayer.