bluuebunny/crossref_metadata_2025 huggingface dataset:
Series mechanism of enzyme deactivation. Characterization of intermediate forms
Authors: Gianfreda Liliana , Marrucci Giuseppe , Grizzuti Nino , Greco Guido
Published: December 2004

Acid phosphatase (E.C. 3.1.3.2) undergoes complex thermal deactivation phenomena, as revealed by the two‐slope pattern of the enzyme logarithmic‐specific‐activity versus time curves. The native enzyme first decays toward an equilibrium distribution of less, but still active, intermediate structures and these, in turn, undergo a final degradation to a completely inactive form. The effect of the experimental conditions at which the enzyme is kept during the deactivation process on the characteristics of these intermediate enzymatic structures has been investigated. The kinetic parameters of p‐nitro‐phenyl phosphate hydrolysis, as catalyzed by some of these intermediate forms, have been determined and the results compared to those obtained with the native enzyme.
Enzyme adsorption in porous supports: Local thermodynamic equilibrium model
Authors: Pedersen Henrik , Furler Larry , Venkatasubramanian K. , Prenosil Jiri , Stuker Ernst
Published: December 2004

Enzyme adsorption from a finite bath (batch adsorption) onto porous spherical supports is investigated both experimentally and theoretically using β‐galactosidase and Duolite ion‐exchange resin as a model system. Efficient numerical techniques are presented that have been used in conjunction with a parameter estimation routine to evaluate adsorption isotherm constants. Results show that even for adsorption processes lasting almost 10 h, the majority of the enzyme is confined to the outer half of the support and, for high initial enzyme concentrations in the bath, this loading takes place as a slowly moving front. Information on the enzyme distribution has practical importance in the design of immobilized enzyme reactors that in previous works have almost always been analyzed assuming a uniform catalyst distribution.
Steady‐state and transient behavior in microbial methanification: I. Experimental results
Authors: Bhatia D. , Vieth W. R. , Venkatasubramanian K.
Published: December 2004

The process of methanification of volatile fatty acids (VFA) was studied to elucidate its kinetics. An upflow anaerobic sludge bed (UASB) system was used to perform the experiments. At residence times of less than 2.5 h the UASB system was found to exhibit hysteresis with respect to acetic and propionic acid consumption but not with respect to butyric acid consumption. These hysteretic effects could be attributed to the manner in which the various VFA‐consuming cultures were structured inside the flocculated biomass in light of the cross‐inhibitory effects of the acetic‐ and propionic‐acid‐consuming fractions of the total culture. (Butyric acid proved to be non‐interactive.) Production of methane was found to respond almost instantaneously to changes in the inlet conditions of the UASB system. This indicated that methane is not primarily growth associated, as has often been assumed, but is related to changes in the culture's maintenance energy requirements. Reactor operation was found to be stable even when the concentration of each VFA in the feed was simultaneously changed by 50%. Even at very high organic throughput rates (35 kg COD/day m3‐reactor) conversions of 82% were observed.
Role of cometabolism in biological oxidation of synthetic compounds
Authors: Venkataramani E. S. , Ahlert R. C.
Published: December 2004

A significant portion of the total biodegradative activity toward synthetic compounds may involve cometabolism; thus, the latter represents an important type of microbial process. A mixed microbial population acclimated to highstrength industrial wastewater degraded about 90% of the organic carbon present in the wastewater. A reasonable agreement in the carbon balance provided clear evidence for the biodegradability of residual organic species. Based on the growth expression of Haldane to account for substrate inhibition, a substrate utilization model to quantify the role of cometabolism coupled with cellular maintenance is proposed. The kinetic parameters of the model have been estimated from experimental data. If the maintenance values are assumed negligible, as has been observed for wastewater systems, it is possible to quantify the magnitude of co‐metabolism encountered in the biological oxidation of synthetic organic compounds.
Recycle of enzymes and substrate following enzymatic hydrolysis of steam‐pretreated aspenwood
Authors: Mes‐Hartree M. , Hogan C. M. , Saddler J. N.
Published: December 2004

The commercial production of chemicals and fuels from lignocellulosic residues by enzymatic means still requires considerable research on both the technical and economic aspects. Two technical problems that have been identified as requiring further research are the recycle of the enzymes used in hydrolysis and the reuse of the re calcitrant cellulose remaining after incomplete hydrolysis. Enzyme recycle is required to lower the cost of the enzymes, while the reuse of the spent cellulose will lower the feedstock cost. The conversion process studied was a combined enzymatic hydrolysis and fermentation (CHF) procedure that utilized the cellulolytic enzymes derived from the fungus Trichoderma harzianum E58 and the yeast Saccharomyces cerevisiae. The rate and extent of hydrolysis and ethanol production was monitored as was the activity and hydrolytic potential of the enzymes remaining in the filtrate after the hydrolysis period. When a commercial cellulose was used as the substrate for a routine 2‐day CHF process, 60% of the original treated, water‐extracted aspenwood was used as the substrate, only 13% of the original filter paper activity was detected after a similar procedure. The combination of 60% spent enzymes with 40% fresh enzymes resulted in the production of 30% less reducing sugars than the original enzyme mixture. Since 100% hydrolysis of the cellulose portion is seldom accomplished in an enzymatic hydrolysis pro cess, the residual cellulose was used as a substrate for the growth of T. harzianum E58 and production of celulolytic enzymes. The residue remaining after the CHF process was used as a substrate for the production of the cellulolytic enzymes. The production of enzymes from the residue of the Solka Floc hydrolysis was greater than the production of enzymes from the original Solka Floc.
Kinetic models for enzymic cellulose degradation in aqueous two‐phase systems
Authors: Mandenius Carl Fredrik , Nilsson Bernt , Persson Ingrid , Tjerneld Folke
Published: December 2004

Cellulose materials can readily be degraded into cellobiose and glucose by hydrolysis of the enzymes cellulase and β‐glucosidase in aqueous media. Product inhibition does, however, retard the reaction rate and reduce productivity. This may be avoided by carrying out the degradation of cellulose in an aqueous two‐phase system, which permits the enzymes and the substrate to be partitioned to one phase and the products to be extracted into a second phase. In addition, two‐phase systems also allow recycling of the enzymes. Here, three models previously developed for “one‐phase” enzymic degradation are compared to data from enzymic degradation in an aqueous two‐phase system. The models tested agreed relatively well with batch experiments during a period of 200 h. For one of the models tested, continuous degradation also gave accurate agreement.
Shear breakage of nylon membrane microcapsules in a turbine reactor
Authors: Poncelet Denis , Neufeld Ronald J.
Published: December 2004

The breakage of nylon membrane microcapsules is proposed as a new method to study and quantify shear effects in biological systems. A critique of this method shows that a narrower particle size distribution may be an important improvement in the breakage study as well as breakage control in many bioreactor and biotechnological applications. In a turbine reactor, it was shown that the primary process which determines the microcapsule breakage is the shear effect. The breakage kinetics are first order with regard to the microcapsule concentration. The breakage kinetic constant was ob served to be dependent on the temperature and the particle size, and proportional to the average shear rate and the third power of the turbine angular velocity. Decrease of the breakage kinetic constant with temperature can be explained by a decrease of fluid viscosity and a change in nylon membrane properties. An increase in the breakage kinetic constant with the microcapsule diameter can be due to a lowering of internal pressure and a reduction of the membrane resistance with size. Proportionality between the breakage kinetic constant and the shear rate shows that shear is the main process which leads to microcapsule breakage. The additional intervention in the shear rate expression of the turbine angular speed in the form of the turbine and particle velocities, results in the dependence of the breakage kinetic constant on the third power of the angular velocity.
A dispersion model for predicting the extent of starch liquefaction by Bacillus licheniformis α‐amylase during reactive extrusion
Authors: Komolprasert Vanee , Ofoli Robert Y.
Published: December 2004

A Baker–Perkins corotating twin screw extruder was used as a bioreactor to hydrolyze pregelantinized corn starch by themophilic Bacillus licheniformis α‐amylase. The extruder was modeled as a tube, and characterized as a closed system. This characterization is not in the thermodynamic sense; rather, it relates to the profile of a tracer fluid upon entry to and exit from the reaction zone. The reaction kinetics were modeled by a modified first‐order equation, which allowed the dispersion equation to be solved analytically with the Danckwerts boundary condition. Data from several extrusion runs were super‐imposed to obtain a profile to evaluate the model. The dispersion number, determined from the first and second moments of the RTD curve, was primarily a function of the length of the reaction zone. There was good agreement between predictions and experimental data, especially at low dispersion numbers. In general, the axial dispersion model appears to be suitable for analysis of enzymatic reactions of up to 30% conversion. At a fixed flow rate and constant temperature, the extent of starch conversion depends significantly on moisture content, residence time and enzyme dosage, but not on screw speed.
Lipase‐catalyzed hydrolysis of 2‐naphtyl esters in biphasic system
Authors: Miyake Yoshikazu , Ohkubo Misahiro , Teramoto Masaaki
Published: December 2004

The authors measured the rate of hydrolysis of the homologs of 2‐naphtyl ester by using a Lewis cell with constant interfacial area to elucidate the kinetic mechanism of the lipase‐catalyzed hydrolysis in biphasic system. On the basis of the two‐film model, it was found from the analysis of experimental results that the hydrolysis of these substrates proceeds at the interface between the aqueous and organic phases. The interfacial reaction rate could be correlated by Michaelis–Menten mechanism. The values of the rate constant and the Michaelis constant were almost independent of the kinds of 2‐naphtyl ester. The values of the interfacial kinetic parameters for 2‐naphtyl ester were much greater than those for the hydrolysis in the aqueous phase.
Activity studies of eight purified cellulases: Specificity, synergism, and binding domain effects
Authors: Irwin Diana C. , Spezio Michael , Walker Larry P. , Wilson David B.
Published: December 2004

The activities of six purified Thermomonospora fusca cellulases and Trichoderma reesei CBHI and CBHII were determined on filter paper, swollen cellulose, and CMC. A simple method to measure the soluble and insoluble reducing sugar products from the hydrolysis of filter paper was found to effectively distinguish between exocellulases and endocellulases. Endocellulases produced 34% to 50% insoluble reducing sugar and exocellulases produced less than 8% insoluble reducing sugar. The ability of a wide variety of mixtures of these cellulases to digest 5.2% of a filter paper disc in 16 h was measured quantitatively. The specific activities of the mixtures varied from 0.41 to 16.31 μmol cellobiose per minute per micromole enzyme. The degree of synergism ranged from 0.4 to 7.8. T. reesei CBHII and T. fusca E3 were found to be functionally equivalent in mixtures. The catalytic domains (cd) of T. fusca endocellulases E2 and E5 were purified and found to retain 93% and 100% of their CMC activity, respectively, but neither cd protein could digest filter paper to 5.2%. When E2cd and E5cd were substituted in synergistic mixtures for the native proteins, the mixtures containing E2cd retained 60%, and those containing E5cd retained 94% of the original activity. Addition of a β‐glucosidase was found to double the activity of the best synergistic mixture. Addition of CBHI to T. fusca crude cellulase increased its activity on filter paper 1.7‐fold. © 1993 John Wiley & Sons, Inc.
Modulation of secretion of vasoactive materials from human and bovine endothelial cells by cyclic strain
Authors: Carosi Joseph A. , McIntire Larry V. , Eskin Suzanne G.
Published: December 2004

The effects of cyclical expansion and elaxation of the vessel wall on endothelial cell metabolism have been modeled using a uniaxial strain device and cultured endothelial cell monolayers. Also, the effects of stopping and then restarting cyclic strain on metabolite secreation rates were determined. Secretion rates of prostacyclin (PGI2), endothelin, tissue plasminogen activator (t‐PA), and plasminogen activator inhibitor‐type 1 (PaI‐1) by endothelial cells were constant over24‐h periods The secreation of both PGI2 and endothelin was enhanced in cells exposed to high physiological levels of cyclical strain (10% at 1Hz) compared with controls, while tPA production was unaltered. These results were true for both human and bovine endothelial cells. Characterization of the response of human endothelial cells to cyclical strain made evaluation of stretch effects on PAl‐1 secretion possible. A nearly twofold increase in PAl‐1 secretion by cells exposed to arterial levels of strain was observed. Endothelin secretion remained elevated even after strain was stopped for 12 h, while PGl2 secretion returned to control values upon cessation of cyclic stretch. These results indicate that physiological levels of cyclic mechanical strain ca significantly modulate secretion of vasoactive metabolited form endothelial cells. The changes sen secretion are, in some cases, quite different from those caused by arterial levels of fluid shear stress exposure. © 1994 John Wiley & Sons, Inc.
Operational patterns affecting lactic acid production in ultrafiltration cell recycle bioreactor
Authors: Xavier A. M. R. B. , Gonçalves L. M. D. , Moreira J. L. , Carrondo M. J. T.
Published: December 2004

Lactic acid production with cell recycling on an ultrafiltration tubular membrane reactor was studied; higher lactic acid concentrations as well as productivities were obtained under long‐term fermentations compared with other high cell density systems. Different operational conditions, namely dilution rates and start‐up modes, were assessed. Performances were very different at the three different dilution rates tested (D = 0.20 h−1, D = 0.40 h−1, or D = 0.58 h−1). The different behaviours are discussed and factors responsible for them are presented. The best way to operate for lactic acid production is chosen, the dilution rate of D = 0.40 h−1 being the one providing the best overall performance. On the other hand, results show that of the two start‐up modes tested, continuous start (membrane open) permits higher permeabilities throughout the operational runs than batch start (membrane closed). Operational stability was found to be directly associated with membranes that work at “steady state,” the membrane permeability being kept around 15 L/m2 h. Optimized cell bleed can improve time of operation if such membrane permeability can be maintained for a longer time. A comparison of results with those obtained in other lactic acid production systems is presented; such comparison shows that this tubular ultrafiltration membrane cell recycle reactor presents three important advantages: (1) concomitant lactic acid concentrations and productivities; (2) long periods of operation at reasonable permeabilities; and (3) good mechanical stability permitting the use of steam sterilization. © 1995 John Wiley & Sons, Inc.
Ion exchange of amino acids at a natural organic ion exchanger: Thermodynamics and energetics
Authors: Bowen W. Richard , Moran Enda B.
Published: December 2004

The thermodynamics and energetics of the ion exchange of four amino acids at a cellulosic ion exchanger have been studied. Experimental work included determination of ion exchange isotherms and the use of high‐sensitivity titration microcalorimetry. A rigorous thermodynamic analysis of the data was developed allowing calculation of the standard free energy, the standard enthalpy, and standard entropy of exchange, and also the differential free energy, incremental enthalpy, and incremental entropy of exchange. The results show that the relative contributions of the enthalpy and entropy to the overall free energy differ markedly for the chosen amino acids. The reasons for these differences are analyzed and discussed. A knowledge of these fundamental thermodynamic properties indicates the solution conditions likely to give enhanced affinity of the ion exchanger for selected amino acids. The experimental techniques and analysis procedures developed are generally applicable to ion exchange separations of biomolecules. © 1995 John Wiley & Sons, Inc.
Studies on the nervus terminalis: Mammals
Authors: Larsell Olof
Published: January 2005

The nervus terminalis of mammals is made up in part, at least, of sympathetic fibers, and its ganglionic clusters contain sympathetic cells. The wide distribution and large number of fibers of the peripheral plexus (as noted by Brookover), in comparison with the small size of the central connections, resemble the relation of preganglionic fibers to the postganglionic fibers of the sympathetic system. This resemblance is strengthened by the occurrence of pericellular baskets on inany of the ganglion cells of the intracranial clusters.
The sympathetic vasodilator outflow — A cortico‐spinal autonomic pathway
Authors: Lindgren Percy , Rosén Anders , Strandberg Per , Uvnäs Börje
Published: January 2005

Sympathetic vasodilator nerves to the skeletal muscles in the dog and cat were activated by topical electric stimulation in the brain.
The anterior ventral cochlear nucleus
Authors: Harrison J. M. , Irving R.
Published: January 2005

The anterior cochlear nucleus was examined with a view to describing its subdivisions. The brains of 29 adult rats were paraffin embedded, sliced at 16 μ and impregnated according to the protargol method of Bodian. From examination of this material the nucleus was divided into three major regions.

Region III contained round cells with short dendrites which received as synaptic endings two or three bulbs of Held and many terminal rings. The cells of the region gave rise to small diameter (less than 1 μ) nerve fibers which entered the trapezoid body. This region appeared to be identical with region III of Lorente de No.

Region II occupied the ventral one third of the nucleus and contained cells of various types, Synaptic endings in this region consisted principally of terminal rings of various sizes and complexities. Nerve fibers which originated in this region were between 1.0 μ and 2.2 μ in diameter and entered the trapezoid body. The region did not conform to region II of Lorente de No.

Region I occupied the dorsal two thirds of the nucleus and contained medium and small cells. Synaptic endings consisted of pale, small bulbs of Held. This region differed from region I of Lorente de No.
Selectivity in fasciculation of nerve fibers in Vitro
Authors: Nakajima Shinshu
Published: January 2005

Interactions between nerve fibers were observed in the dissociated cultures of spinal ganglion cells from chick embryos. After a nerve fiber made filopodial contacts with another fiber, three types of interactions were found: the two fibers formed a bundle, one crossed over the other, or one or both fibers retracted. It is suggested that selectivity among nerve fibers with regard to fasciculation is exerted through the filopodial contacts.
Redefinition of the macula neglecta in mammals
Authors: Igarashi Makoto
Published: January 2005

The rudimentary sensory end organ in the vestibule at the junctions of the utricle and semicircular canals was investigated in 70 mammalian inner ears, cut serially in horizontal plane. The epithelial mound at the horizontal semicircular canal‐utricular junction, which has been called macula neglecta, was observed in almost all of the human and dog specimens and in 25% of the squirrel monkeys. The designation “epithelial moud of latero‐posterior utricular fold” is recommended. In the cat and dog, but in none of the other mammalian ears examined, a rudimentary sensory end organ was observed on the anterior medial wall of the inferior utricular sinus. The designation “sensura neglecta” is suggested.
Perinatal changes in epidermal innervation in rat and mouse
Authors: Fitzgerald M. J. T.
Published: January 2005

The development of cutaneous innervation in the rat and the rat and the mouse has been studied by silver techniques. In particular, the innervation patterns of adult and of perinatal skin have been compared. From the second parental day until the sixth postnatal day, the relatively thick epidermis is freely penetrated by nerve fibers; thereafter, the nerve endings appear to be confined to the dermis. The intra‐epidermal axons are directed obliquely, with a rough (and not exact) correspondence to the plane of future emergence of the hair shafts. The appearance of a transitory development of intra‐epidermal nerves elsewhere.
A peculiar mode of muscular innervation in amphioxus. Light and electron microscopic studies of the so‐called ventral roots
Authors: Flood Per R.
Published: January 2005

The present study demonstrates a neuromuscular junction between the so‐called ventral root fibers and the surface of the spinal cord of amphioxus.

The ventral root fibers, interconnected by numerous zonulae occludentes, appear to be projections from muscle fibers of the myotome and end in conical expansions at the surface of the spinal cord, separated from an extensive layer of axon endings or boutons by an extracellular cleft containing a basement membrane.

Within each ventral root two kinds of ventral root fibers can be identified. Each corresponds to a compartment of the bouton layer. The so‐called thick ventral root fibers are opposed to a long ventral compartment of small boutons tightly packed with vesicles about 1,000 Ä in diameter, but without a dense core. The so‐called thin ventral root fibers are opposed to a short dorsal compartment of large boutons filled with synaptic vesicles about 600 Ä in diameter.
The interstitial cell and its place in the concept of the autonomic ground plexus
Authors: Rogers Donald C. , Burnstock Geoffrey
Published: January 2005

1. The autonomic interstitial cells have been studied in the toad small and large intestine and guinea‐pig taenia coli by means of both the light and electron microscopes. The guinea‐pig superior cervical ganglion has also been examined.

2. Apart from muscle cells, neurons and Schwann cells, at least one other cell type has been observed. These cells have been designated connective tissue cells on the basis of their gross form, fine structure and relation to other cells. In many respects they resemble fibroblasts and macrophages.

3. These cells are in close relation to nerve fiber bundles and smooth muscle cells. They often form a complete sheath around bundles of axons and Schwann cells. Many of the processes of the connective tissue cells lie in grooves on the surface of the muscle cells; the distance between apposing cell membranes is about 200 Ä.

4. The processes of the connective tissue cells often interdigitate with each other in a most complex manner, the opposing cell membranes being about 200 Ä apart. Such a close relationship would appear with the light microscope to be a fusion forming a syncytium.

5. Observation with the light microscope on the terminal ramifications of the autonomic nervous system where small bundles of fine axons are enclosed by connective tissue cells could give rise to the impression that they contained “neurofibrils.”

6. It is suggested that the term autonomic interstitial cell covers a number of cell types which have been confused. The cells designated connective tissue cells along with Schwann cells have between them the characteristics of the autonomic interstitial cells as described by previous workers. Cajal's original description of sympathetic interstitial cells was actually a description of connective tissue cells.
Autoradiographic and histological studies of postnatal neurogenesis. I. A longitudinal investigation of the kinetics, migration and transformation of cells incoorporating tritiated thymidine in neonate rats, with special reference to postnatal neurogenesis in some brain regions
Authors: Altman Joseph , Das Gopal D.
Published: January 2005

Neonate rats were injected systemically with thymidine‐H3 and killed after different periods of survival. Cell proliferation, migration and transformation in the brain were studied autoradiographically. It was established that cells multiplying in the ependymal and subependymal walls of the olfactory ventricle migrate outward into the olfactory bulb, where they become differentiated into granule cells. These postnatally formed granule cells contribute to the formation of the granular and several other layers of the olfactory bulb. Cells multiplying at a high rate in the wall of the lateral ventricle migrate to the hippocampus and contribute to the formation of the granule cells in the granular layer of the dentate gyrus. Cells multiplying at a high rate in the external and internal granular layers of the cerebellum become differentiated into granule cells, and, to a lesser extent, other types of nerve cells of the cerebellar cortex. Evidence was also obtained of the postnatal origin of many of the granule cells of the cochlear nucleus. Postnatal neurogenesis is restricted to these short‐axoned granule cells or microneurons; the long‐axoned nerve cells or macroneurons of the brain are formed prenatally.
Nervous system of the snail Helix aspersa. I. Structure and histochemistry of ganglionic sheath and neuroglia
Authors: Fernandez Juan
Published: January 2005

The ganglionic sheath is structured upon a complex fibrocellular framework. A tridimentional network of anastomosed connective tissue lamellae constitutes the extracellular space. In the deep ganglionic region these lamellae display alkaline phosphatase activity. Sheath cells appear embedded in network fenestrae. The most peculiar of these are the superficial voluminous globular cells. Its cytoplasm appears built of a lipoprotein network containing glycogen and “lipofuscin pigments.” These two latter substances appear to undergo seasonal changes. The gland cells seem to be unicellular endocrine glands, containing many droplets giving positive reaction for carbohydrates, lipids and proteins. Muscle cells are placed throughout the sheath. The cytoplasm gives an intense reaction for proteins but does riot exhibit myofibrilles. These cells could play an important role in ganglonic movements and in addition could modify the amplitude of the extracellular sheath space. Pigment cells, containing melanin granules, are distributed among the other sheath cells. Cellular groups of the sheath show many large spheroidal mitochondria and sudanophilic droplets. These cells could be involved in the synthesis of some unknown substance or/and in metabolic transport across the sheath. Glial cells are located under the sheath and surrounding the entire neuronal surface. The cytoplasm appears connected with alkaline phosphatase and with an acidic substance. The histochemical and topographical characteristics of these cells point to their role in metabolic transportation, mechanical support and nervous homeostasis.
Increases in cortical depth and glia numbers in rats subjected to enriched environment
Authors: Diamond Marian C. , Law Fay , Rhodes Helen , Lindner Bernice , Rosenzweig Mark R. , Krech David , Bennett Edward L.
Published: January 2005

We have previously reported anatomical and chemical changes in the cerebral cortex of rats living in an enriched, stimulating environment. The present study includes additional histological measures such as more extensive depth measures, differential cell counts, and cell size measurements.

Celloidin‐embedded, thionin‐stained sections of the visual cortex from environmentally enriched rats and their impoverished littermates were measured. Two methods for calculating cortical depths were used: one, with an ocular micrometer taking eight measures lateral to the elevation in the corpus callosum on each hemisphere; two, on enlarged photographs taking 51 measurements 2 mm apart on each hemisphere. With the ocular micrometer method the cortical depth of the enriched brains was 6.4% greater than the depth of the impoverished cortex. On the enlarged photographs the more medial depths in the enriched rats showed greater increases than the lateral depths.

Overlapping photomicrographs were made of a medial cortical area 1.00 mm by 0.75 mm on each transverse section and were combined into one composite picture for each animal. Differential cell counts from the composite pictures were determined independently by two technicians. Results indicate a 14% (p<0.01) increase in glia among the enriched rats. No significant differences between enriched and impoverished groups were found in the perikarya and nuclear circumferences as measured with a planimeter from camera lucida drawings.
Cortical projections to brain stem and spinal cord in the goat by way of the pyramidal tract and the bundle of Bagley
Authors: Haartsen Adrianus Bartholomeus , Verhaart Willem Jozef Cornelis
Published: January 2005

In this paper the cortical fibers in the brain stem of the goat are studied. The preparations were stained according to the method of Nauta‐Gygax. It was proved that the fibers descend both through the pyramidal tract and Bagley's corticotegmental tract. The latter terminates in the ipsilateral trigmidal spinal tract nucleus and the lateral part of the reticular formation of the medulla, but pyramidal fibers do not terminate in the first nucleus. At the transition of the medulla and the cord three pyramidal tracts, all consisting of both direct and crossed cortical fibers enter the cord, whereas in all probability the fibers of Bagley's tract do not reach the cord. A ventral intercommissural tract carries the majority of the fibers, it reaches the seventh cervical segment. A small lateral tract in the lateral funiculus and a dorsal in the dorsal funiculus reach the third and the second cervical segments. The site of origin of Bagley's tract appeared to be identical to that of the medullary pyramid.
The development of hippocampal and dorsolateral pallial regions of the cerebral hemisphere in fetal rabbits. III. Twenty‐nine millimeter stage, marginal lamina
Authors: Stensaas L. J.
Published: January 2005

The structure of the cerebral hemisphere of 29 mm rabbit embryos was stuided with aniline and Golgi stains. Particular attention was devoted to the structure of the marginal lamina. In aniline stained sections it is a light, relatively acellular layer at the surface of the embryonic cerebral hemisphere and corresponds to layer I, the molecular layer, of the adult cerebral cortex. Even in early embryonic stages the marginal lamina consists mainly of terminal remifications of pyramidal cell apical dendrites and ascending axons. This layer of neuropile is of particular interest since it greatly precedes the development of other cortical zones rich in axons and dendrites. The reasons for the precocious development of dendritic branches at this level are unknown but may be related to the presence of ascending axons of nerve cells in the cortical plate or to horizontal cells.

Large and small horizontal neurons are the only intrinsic cells at this level. Axons are present on the small elements, but were seen only infrequently on large cells. Some of the latter are similar to Cajal‐Retzius cells of perinatal stages, but have relatively few ascending branches.
Differential projections of habenular nuclei
Authors: Akagi Katsuhito , Powell Ervin W.
Published: January 2005

Lesions were made in the lateral and medial habenular nuclei of the cat. Subsequent degeneration of nerve fibers and terminalis was studied using Nauta‐Gygax silver technique. The medial and lateral habenular nuclei project differentially to the septum, olfactory, tubercle, thalamus, midbrain tegmentum and tectum. The diffuse part of the habenulopeduncular tract rises from the lateral habenular nucleus and the compact part rises from both nuclei. Degenerating terminals were seen caudally in the following nuclei: interpeduncular, central superior, dorsal raphae, ventral tegmental (from the medial habenular nucleus), dosral tegmental (from the lateral habenular nucleus), pretectal area, superior colliculus and inferior colliculus (from the lateral habenular nucleus). Rostral projections course in the medial part of the stria medullaris from the medial habenular nucleus and in the lateral part of the stria medullaris from the lateral habenular nucleus: Degenerating terminals were seen rostrally in the following nuclei: dorsomedial, anteroventral, anterodorsal, paraventricular, posterior medial septal (from the medial habenular nucleus) and preoptic area (from the lateral habenular nucleus). Projections occur from the medial habenular nucleus to the amygdala via the stria terminalis.

The habenular nuclei are considered to be structures of the limbic system which are differentially related to midbrain, thalamic, amygdaloid, septal and preoptic structures via feedback circuits.
Neuronal organization in long term cultures of the spinal cord of the fetal mouse
Authors: Sobkowicz Hanna M. , Guillery R. W. , Bornstein Murray B.
Published: January 2005

Explants of spinal cord from 14–16 day old fetal mice were cultured for 18–54 days in vitro. They were fixed and stained with cresyl violet or the Holmes method. In most explants a basic pattern of cell and fiber architectonics was recognizable. In many aspects the pattern seen in the explants resembles the structure of the spinal cord at the time of explantation, and some of the same cell groups are present in both. Most explants resmble a transverse section of spinal cord. A ventral commissure and dorsal and ventral roots are readily identified. In addition, two characteristic circular bands of fibers form around the periphery of the explants.

Many axons in the ventral roots arise from large ventral horn cells and form terminal arborizations at some distance from the explants. These axons are comparable to in vivo ventral root fibers. The fibers in the dorsal roots, however, are generally fibers that deviate from the circular bands and return again, thus forming extensive loops. The circular bands may represent regenerated axons of long association pathways.

The structure of these explants demonstrates that pieces of nervous tissue grown in complete isolation can maintain much of their internal organization. Their axons appear to follow relatively constant growth patterns which are characteristic for particular cell types and, to a certain extent, appropriate to the pattern that would be formed in vivo.
Microanatomy of crayfish thoracic cord and roots
Authors: Sutherland Rodrigue M. , Nunnemacher Rudolph F.
Published: January 2005

For a thorough understanding of the functions of the crustacean nervous system a knowledge of all its components is necessary. The use of the electron microscope provides accurate data of the number, size, and distribution of fibers in nerve tissue. Nerve fiber counts determined by electron microscope mapping show increases of 20 to 60% in the number of fibers over those determined by light optics. In Orconectes, the number of fibers reach close to 9,500 in the thoracic cord, 20,000 in the main walking leg roots, and 83,000 in the main claw leg roots. Fiber size distributions indicate general motor and sensory patterns of function in the thorax. High percentages (97–99) of fine and small fibers in the roots to the legs suggest the presence of multitudinous sensory‐associated organelles.
A quantitative electron microscopic study of myelination in the pyramidal tract of rat
Authors: Samorajski T. , Friede R. L.
Published: January 2005

The ultrastructure of fibers during myelin formation in the pyramidal tract of rats is described. The distribution of fiber classes based on counts of myelin lamellae was determined for newborn, young and mature rats. In newborn rats (2–12 days), growth of the axon was extremely rapid in fibers undergoing early myelination, resulting in greater variation in the relation between axon circumference and sheath thickness and, also, in the presence of myelin sheaths that were unusually thin in relation to the size of the axons. In young rats (12 days to 8 weeks), the numbers of myelin lamellae present in the sheaths increased in proportion to the increase in axon circumference. In adult rats, the numbers of myelin lamellae present in the sheaths was in linear relation to axon circumference for all sizes of myelinated fibers. Approximately 20% of the fibers were nonmyelinated. The number of glia cells per axon at the onset of myelination was approximately 20% of the adult ratio. During growth, myelination gliosis resulted in a steady increase in the number of glia cells per axon until adult levels were ultimately achieved. Our observations suggest that formation of myelin lamellae by oligodendroglia cells may be controlled by the caliber of the axon.
Discontinuities in the dorsal lateral geniculate nucleus corresponding to the optic disc: A comparative study
Authors: Kaas J. H. , Guillery R. W. , Allman J. M.
Published: January 2005

A cylindrical cellular discontinuity commonly occurs in lateral geniculate layers that are innervated by the contralateral eye. Such a discontinuity has been found in a variety of mammalian species, including carnivores, primates, a rodent and a marsupial. Electrophysiological evidence obtained from some of these species shows that the discontinuity corresponds to the blind spot. It is concluded that the representation of the retina within the lateral geniculate nucleus is extremely accurate, since the retinal receptor layer and the geniculate layers have corresponding holes.

Two possible mechanisms that would demand such a discontinuity are considered. One is an intralaminar mechanism in which the cells in each lamina accurately reflect the distribution of retinal receptors; the other is an interlaminar mechanism in which the representations of the homonymous hemiretinae are so accurately aligned that the optic disc must be represented by a cellular discontinuity.
Proliferation in the neural tube of the splotch (Sp) mutant mouse
Authors: Wilson Doris Burda
Published: January 2005

The length of each period in the cell cycle was determined radioautographically for mesencephilic ventricular cells in splotch normal (Sp/+;+/+) and abnormal (Sp/Sp) mouse embryos. At ten and 11 days' gestation, the length of the generation time in the abnormal brain was approximately 3.5 hours longer than that in the normal littermates. This overall prolongation was the result of an increase in the DNA‐synthetic (S), mitotic (M), and postmitotic (G1) periods. The increase in the length of mitotis appeared to be responsible for the increased numbers of mitotic figures which characterize this condition. The abnormal brains, however, showed a typical chronological lengthening of the cell cycle of approximately the same magnitude as is the case during normal development of the neural tube.
Evidence of a pallidohabenular pathway in the cat
Authors: Nauta Haring J. W.
Published: January 2005

The efferent projections of the entopeduncular nucleus (internal segment of the globus pallidus) in the cat have been studied by the autoradiographic tracing method. The findings reported in this article strongly suggest the existence of a substantial pathway originating in the internal segment of the globus pallidus and terminating in a large, circumscript region of the lateral habenular nucleus. Axons of this pathway follow a wide variety of routes to reach the lateral habenular nucleus. The implications of these findings are discussed in relation to the problem of connections between the limbic system and the corpus striatum.
Fibers in the ventral spinal nerves of the frog
Authors: Sutherland Rodrigue M. , Nunnemacher Rudolph F.
Published: January 2005

The use of the electron microscope provides accurate data of the number, size, and distribution of fibers in nerve tissue. Nerve fiber counts determined by electron microscope mapping show increases of two to seven times in the number of fibers over those determined by light optics. The combined counts of fibers, on one side in Rana pipiens, from the ventral spinal nerves (1, 2, and 3) supply the forelimb with 14,000 fibers; from spinal nerves (4, 5, and 6) to the trunk, 4,050 fibers; and over 20,000 fibers from the ventral spinal nerves (7, 8, 9, and 10) pass into the sciatic and crural nerves which innervate the hind limb. The greatest total number of fibers, and especially of small and fine fibes, are in the second and ninth spinal nerves. Of all the nerves studied, the sciatic contains the greatest number of fibers (16,500). The high numbers and percentages of fine and small fibers in the spinal, sciatic, and crural nerves emphasize the importance of determining the function of these fibers.
Patterning in synaptic knobs which connect with Mauthner's cell (Ambystoma mexicanum)
Authors: Kimmel Charles B. , Schabtach Eric
Published: January 2005

The Mauthner's cells (M‐cells) of the young axolotl larva receive a rich afferent supply of synaptic knobs (club and bulb synapses). The knobs may be classified into at least five types according to their ultrastructure after direct fixation in OsO4. The different types are non‐randomly arranged on the M‐cell surface such that groups of knobs of the same type are frequently observed to form a cluster or patch. The M‐cell surface pattern is thus a mosaic of such clusters. Different types of knobs may be restricted to different locations on the M‐cell; one type is found almost exclusively with the M‐cell lateral dendrites, and another two types with the axon hillock and axonal initial segment. The dorsal perikaryon is nearly devoid of knobs. This pattern is at least in part related to the pattern of fasciculation in the adjacent neural tissue, and it is likely that all or some of the distinctive types of knobs originate from different kinds of neurons.

The pattern of distribution of the synaptic knobs appears to increase in complexity during development, and this can be related to the asymmetrical growth of the M‐cell during its maturation. These observations are discussed with reference to theories of neuronal specificity.
Olfactory bulb projections in the bichir, Polypterus
Authors: Braford Mark R. , Northcutt R. Glenn
Published: January 2005

The central projections of the olfactory bulb were studied in Polypterus using the Nauta and Fink‐Heimer techniques. Two major target areas were identified in the subpallium: the lateral subpallial nucleus and the dorsal and ventral entopeduncular nuclei. The connections are predominantly, if not exclusively, ipsilateral. In the pallium a massive ipsilateral projection to the superficial third of the medial pallium was demonstrated while the remainder of the pallium was found to be free of degeneration. Thus it appears that the pallium of Polypterus is not uniform throughout, as has been suggested in the literature. This contention is also supported by an analysis of the pallial cytoarchitecture. Because the pallium of Polypterus is everted, rather than inverted and evaginated, the topographically medial pallium is in topological correspondence with the lateral pallium of tetrapods. On the basis of this topological correspondence and the similarity of afference from the olfactory bulb, it is argued that the “medial” pallium of Polypterus is homologous to the pyriform pallium of tetrapods. The findings of this study are compared to those of similar studies in teleosts, which also have an everted pallium. An apparent conflict appears and suggestions for resolving it are offered.
The cell masses in the brain stem of the turtle Testudo hermanni; α a topographical and topological analysis
Authors: Cruce William L. R. , Nieuwenhuys Rudolf
Published: January 2005

The ventricular sulcal pattern and the cytoarchitectonic organization of the brain stem of the turtle Testudo hermanni have been studied in transversely cut, Nissl stained serial sections. Four longitudinal sulci, the sulcus medianus inferior, the sulcus intermedius ventralis, the sulcus limitans and the sulcus medianus superior could be distinguished. With the aid of the usual cytoarchitectonic criteria 54 cell groups have been delimited; 12 of these are primary efferent or motor nuclei, 13 are primary afferent or sensory centers; 10 of the nuclei distinguished are considered as belonging to the reticular formation. The remaining 19 cell masses can be indicated as “relay” nuclei. In order to provide a basis for experimental hodological work the topographical position of the nuclei is illustrated in photomicrographs of representative levels and in graphical reconstructions.

In order to elucidate the morphological pattern of the cell masses and their relationship to the ventricular sulci the brain stem was subjected to a topological analysis. Essentially this method requires that (1) the cell masses are projected upon the ventricular surface and that (2) this surface, with its sulci marked on it and with the outlines of the subjacent cell masses projected upon it, is flattened out. This analysis yielded the following results: The sulcus limitans extends throughout the rhombencephalon, dividing this brain part into a basal plate and an alar plate. In the basal plate the sulcus intermedius ventralis marks the boundary between an area ventralis and an area intermedioventralis containing, respectively, the somatic motor nuclei of primary and higher order, and the visceral motor centers. Yet the terms somatic motor zone and visceral motor zone are not applicable to these two areas as a whole since both contain a number of non‐motor centers. Thus the intermedioventral zone harbours two general somatic sensory centers, i.e., the spinal‐ and princeps nuclei of V. The medial parts of the tegmentum isthmi and of the tegmentum mesencephali contain somatic motor centers of primary and higher order, and thus may be considered rostral continuations of the rhombencephalic ventral zone. The rhombencephalic alar plate contains visceral sensory, general somatic sensory and special somatic sensory centers, but these do not show a simple ventrodorsal arrangement. A prominent feature is that the special somatic sensory nuclei of termination of VIII, the cerebellar nuclei, and a number of special somatic sensory centers of higher order together constitute a continuous zone which extends from the rhombencephalic alar plate, via the isthmus into the lateral part of the tegmentum mesencephali. In the isthmus region the sulcus limitans does not mark the ventral boundary of this zone, but rather passes over its middle.