bluuebunny/crossref_metadata_2025 huggingface dataset:
Interrelation and dynamic activity of visceral muscle and nerve cells from insect embryos in long‐term cultures
Authors: Aloe L. , Levi‐Montalcini R.
Published: January 2005

Multiple segments of esophagus dissected out from 16‐day cockroach embryos were cultured in vitro in a chemically defined medium in the presence of dissociated nerve cells from the same donors. A first migratory wave of cells took place from the explants between the first and fourth week of culture. The morphological characteristics of these cells suggest that they originate from tracheolar cells. Between the second and fifth month of culture, a second migratory wave of a different cell type replaces the first wave of short‐living cells. These cells migrate out only after nerve fibers from the ingluvial ganglion have branched into the medium. They form long cellular ribbons and exhibit spontaneous contractility. The characteristics of the contractile cycles were examined at the inverted microscope, with Nomarski optics, and in time‐lapse cinematography. The cells were identified as myocytes and their origin traced to the longitudinal and circular muscle layer of the explants. The contratile cell ribbons establish firm contact with nerve fibers from the ingluvial ganglion, which in turn exhibit a vibratory motion identical to that of the cells. The most plausible interpretation is that nerve fibers are pushed and pulled by contractile myocytes. The results of these in vitro experiments show a strong affinity of myocytes for nerve fibers and bring to light a new aspect of the relationship between these cells and the visceral fibers which provide for their innervation.
Axoplasmic transport: Differential inhibition by cytochalasin‐B
Authors: Fernandez Hugo L. , Samson Frederick E.
Published: January 2005

Slow (1 mm/day) and fast (10mm/day) axoplasmic transport of labelled protein, shown by the movement of sharp peaks of radioactivity along the crayfish nerve cord, are blocked by cytochalasin‐B. Labelled proteins in the slow peak maintain their sharp distribution; however, those in the fast peak disperse over a broad area after the drug‐induced blockage.
Fast axonal transport in the C‐fibers of the garfish olfactory nerve
Authors: Gross Guenter W. , Beidler Lloyd M.
Published: January 2005

The application of aqueous solutions of tritiated L‐Leucine to the olfactory epithelium of the longnosed garfish (Lepisosteus osseus) results in a rapid sorption of the labeled precursor and the subsequent establishment along the nerve of a profile of labeled macromolecular constituents. This profile consists of a sharp wavefront, a peak and a saddle region. At 23°C, the wavefront enters the nerve 1.8 hr after the isotope application and moves away from the cell bodies at an average rate of 222 ± 2.4 mm/day. As the labeled material is propelled along the nerve fiber, its distribution undergoes several characteristic profile changes. The peak broadens and decreases in height and the slope of the wavefront becomes gradually less steep, while the area of the profile increases. These systematic, time‐dependent changes suggest a redistribution of some of the labeled axonal material during transport.
Experimental inhibition of myelination in spinal cord tissue cultures: Enzyme assays
Authors: Fry June M. , Lehrer Gerard M. , Bornstein Murray B.
Published: January 2005

Seven specific enzyme activities were assayed in embryonic mouse spinal cord cultures during normal development and under conditions of myelination inhibition and disinhibition. Sulfatase A activity in the inhibited and disinhibited cultures was slightly lower than in the normal control cultures. No specific differences for glucose‐6‐phosphate dehydrogenase, β‐galactosidase, β‐glucuronidase, acid prosphatase, and NADP‐isocitrate dehydrogenase activities were found among these three experimental conditions. However 2′,3′‐cyclic nucleotide phosphohydrolase, an enzyme which has been specifically associated with myelin, showed identical patterns of inhibition and disinhibition as were previously observed for sulfatide synthesis.
Electrophysiological analysis of the actions of strychnine, bicuculline and picrotoxin on the axonal membrane
Authors: Freeman Alan R.
Published: January 2005

Strychnine, bicuculline, and picrotoxin show similar effects on the membrane of the lobster giant axon. At concentrations above 5 × 10−5 M these compounds cause depolarization of the resting potential and a broadening of the action potential contour. Also occurring is an increase in excitability as defined by a decrease in stimulus threshold. Repetitive firing of action potentials is sometimes observed during the depolarizing process. Drug levels of 5 × 10−4 M and higher may secondarily induce depolarizing inactivation of the spike generating mechanism. The loss in resting potential is accounted for by a shift in relative membrane selectivity away from potassium and towards sodium. Associated with this alteration in selectivity is a marked fall in total conductance and abolition of delayed rectification. The results indicate that strychnine, bicuculline, and picrotoxin cause potassium inactivation and further that this effect is manifest in both the resting and active electrogenic state of the membrane.
The protein subunit of calf brain neurofilament
Authors: Davison Peter F. , Winslow Boyd
Published: January 2005

A preparation of the protein subunits from calf neurofilaments has been obtained. Axon segments from an homogenate of calf brain white matter have been concentrated by a subcellular fractionation procedure. After further steps to achieve a complete elimination of unbound lipid, the neurofilament protein was dissolved in 4M guanidine hydrochloride solutions. The neurofilalment subunit was the major constituent of the guanidine hydrochloride extracts; other proteins of higher molecular weight were eliminated by agarose gel filtration in urea solutions. Dialysis to solutions of low ionic strength allowed the reformation of fibril aggregates, some of which, under electron microscopy, resembled the original neurofilaments in morphology.

The physical characteristics of the neurofilament subunit protein are reported and a preliminary amino acid analysis is given. The neurofilament protein is clearly distinguishable from actin and tubulin on physical and chemical grounds.
The properties and connections of supernumerary sensory and motor nerve cells in the central nervous system of an abnormal leech
Authors: Kuffler Damien P. , Muller Kenneth J.
Published: January 2005

The characteristic features of individual neurons in leech ganglia are highly consistent from animal to animal. Hy chance a leech was dis‐ covered that had more cells to be seen than usual in many of its ganglia.

In some segmental ganglia of the abnormal animal there were four or even five sensory cells responding independently to touch (T cells) instead of the usual complement of three on each side. Ganglia also contained three or four pressure sensitive cells (P cells) and three or four nociceptive cells (N cells) instead of two of each. The membrane properties, as well as the shapes, sizes, and positions, of all these cells were normal. Their axons reached the skin by the appropriate nerve bundles.

Two sensory neurons of one modality, often independently innervated, overlay regions of skin that normally would be supplied by one cell. On the other hand, the areas innervated by some supernumerary cells were abnormal in their shape and position.

In some ganglia instead of one motor neuron that raised the skin into bumps (the annulus erector, or AE cell) there were two, each of which could independently erect annuli. The regions innervated by the extra AE cells appeared normal and overlapped extensively.

Normal synaptic interactions were found between supernumerary sensory cells and motor cells.

The results with this animal indicate that two or more nerve cells can form effective connections with other neurons and with skin that normally would be innervated by a single cell.
Distribution of putrescine, spermidine, and spermine in rhesus monkey brain: Decrease in spermidine and spermine concentrations in motor cortex after electrical stimulation
Authors: Russell Diane H. , Gfeller Eduard , Marton Laurence J. , LeGendre Stephen M.
Published: January 2005

Polyamine levels vary markedly throughout the brain of the rhesus monkey. In general, there is an inverse relationship between spermine and spermidine concentrations; i.e., areas with high spermine levels have low spermidine levels and vice versa. The ratio of spermidine to spermine is as high as 13 in the optic nerve, and as low as 1.2 in the vermis. The variability of this ratio suggests that the functions of the polyamines in the adult brain may be different from those in other tissues. For instance, the ratio of spermidine to spermine in adult rat liver and most other organs is approximately 1, and this ratio increases in growth‐stimulated systems. The precursor of spermidine, diaminobutane, is present in very low quantities in the brain. Electrical stimulation of the precentral gyrus was found to decrease the content of both spermidine and spermine, and these data provide further evidence for a separate brain function of the polyamines. Depletion of spermidine and spermine in the motor cortex by electrical stimulation suggests that these amines may be involved in transmission phenomena.
Changes in conduction velocity within a nerve net
Authors: Pickens Peter E.
Published: January 2005

Conduction velocity within the through‐conducting nerve net of the sea anemone Calamactis praelongus is altered as a result of the passage of one or more impulses. Facilitation of conduction velocity occurs when the second evoked impulse follows the first by less than 2 sec. The facilitating effect increases with decreasing interval between shocks until impulses are less than 0.5 sec apart and then it declines. Antifacilitation occurs when the nerve net is shocked at frequencies between one per 2 sec and one per 20 sec. It is seen also after the first two or three responses when shocks are applied at higher frequencies. Facilitation and antifacilitation increase with spread of excitation. Although the relationship of velocity changes to the behavior of Calamactis has not yet been determined, facilitation of conduction velocity in the net may produce greater synchronization of muscle contraction.
Seizure susceptibility in the developing mouse and its relationship to glutamate decarboxylase and pyridoxal phosphate in brain
Authors: Tapia Ricardo , Pasantes‐Morales Herminia , Taborda Efrain , de la Mora Miguel Pérez
Published: January 2005

The relationship between the susceptibility to convulsions, the content of pyridoxal 5′‐phosphate and the activity of pyridoxal kinase (EC 2.7.1.35) and glutamate decarboxylase (EC 4.1.1.15) in brain, was studied in the developing mouse. Seizures were induced by pyridoxal phosphate‐σ‐glutamyl hydrazone (PLPGH), a drug previously reported to reduce the levels of pyridoxal 5′‐phosphate and as a consequence to inhibit the activity of glutamate decarboxylase in brain of adult mice. It was found that the seizure pattern, as well as the time of appearance of convulsions, differed between 2‐ and 5‐day old mice and 10‐day old or older mice, indicating a progressive increase in seizure susceptibility during development. In brain, pyridoxal kinase activity and pyridoxal 5′‐phosphate levels were decreased by the administration of PLPGH at all ages studied, whereas glutamate decarboxylase activity was inhibited less than 25% in 2‐ and 5‐day old mice, and about 50% thereafter. Parallelly, the activation of glutamate decarboxylase by pyridoxal 5′‐phosphate added in vitro to control homogenates was less in 2‐ and 5‐day old mice than in older animals. It is concluded that the increase in the susceptibility to seizures induced by PLPGH during development is probably related to the increase observed in the sensitivity of glutamate decarboxylase in vivo to a decrease of pyridoxal 5′‐phosphate levels. The correlation between pyridoxal 5′‐phosphate, glutamate decarboxylase, and seizure susceptibility seems to be established at about 10 days of age.
Comparison of lipids in total brain tissue from five mouse genotypes
Authors: Sampugna J. , Clements Janice , Carter T. P. , Campagnoni A. T.
Published: January 2005

Brain tissue from adult male and female mice of the C57BL/6J, C57BL/6J‐Aw—J, BALB/cJ, SJL/J, and DBA/2J genotypes was examined for brain weight, total protein, total lipid, cholesterol, phospholipid, plasmalogen, sulfatide, nonganglioside—glycolipid sphingosine, and ganglioside N‐acetyl neuraminic acid, fatty acid, and sphingosine. No significant differences were found between sexes for any of these constituents. When compared to the overall average obtained for other animals, the DBA/2J, C57BL/6J‐Aw−J, and BALB/cJ mice contained lower quantities of nonganglioside—glycolipid sphingosine. The DBA/2J and C57BL/6J‐Aw−J mice also contained lower quantities of plasmalogen and sulfatide compared to the overall averages obtained for the other genotypes. In addition, the sterol content in DBA/2J mice was significantly higher than the overall average value obtained for the other animals.
Physical and physiological properties of the crayfish antennal flagellum
Authors: Taylor Robert C.
Published: January 2005

Mechanoreceptors in the crayfish antennae are divided into four functional categories: vibration (13%), bidirectional displacement (19%), unidirectional displacement (45%), and position (23%) receptors. The distribution of receptors along the length of the flagellum follows a logarithmic progression, decreasing from about 40% at the base to less than 5% at the tip.

Vibratory stimulation of the antennae was found to induce a traveling wave. Because of an impedance gradient along the length of the flagellum, the traveling wave moves most efficiently from base to tip. The wave was observed to travel at an average velocity of 6.0 m/sec.

Large deflections of the tip are not uniformly transferred to the base, but decrease logarithmically. This is due to the existence of the impedance gradient.

Receptor output probability was found to be greatest when low frequency/high intensity stimulation was applied to the flagellar base.

Characteristics of large (2 cm) posterior‐going deflections of the flagellar tip that are effective in producing response differences are displacement: (a) amplitude, (b) velocity, and (c) acceleration.
Beating intraocular hearts: Light‐controlled rate by autonomic innervation from host iris
Authors: Olson Lars , Seiger Åke
Published: January 2005

The sympathetic adrenergic ground plexus of the rat iris is able to innervate whole embryonic hearts transplanted to the anterior eye chamber. The transplants beat continuously from the time of transplantation and for at least five months, initially at 150–200 beats/min, and later approximately 250 beats/min. From seven days postoperatively onwards increased light to the eye produced deceleration while decreased light produced acceleration of the transplants. The rate changes coincided with changes in pupil diameter. Topical atropine reduced the light dependent rate variations of the transplants, especially the dramatic decrease in rate at white light.

Waking stress caused a large rate increase. The “waking‐effect” was strongly reduced by sympathetic decentralization and completely abolished by propranolol. The high rate seen in red light was decreased to the low rate of white light by decentralization. Isoprenaline restored red light rate levels in the decentralized transplant.

The intraocular heart thus receives a dual functional autonomic input from the host iris and becomes a sensitive monitor of an autonomic nervous activity that can easily be varied at will in a physiological way by changing the light influx to the eye.
Anatomical basis for an apparent paradox concerning conduction velocities of two identified axons in Aplysia
Authors: Pinsker Harold , Feinstein Robert , Sawada Masashi , Coggeshall Richard
Published: January 2005

Larger axons usually have faster conduction velocities, lower thresholds, and larger extracellular action potentials than smaller axons. However, it has been shown that the largest fiber, R2, in the right pleurovisceral connective of the marine mollusc, Aplysia, has a higher threshold and a slower conduction velocity than does the smaller axon of cell R1, even though the amplitude of R2's spike is larger than R1's spike. One explanation of this apparent paradox is that the two axons have different “intrinsic membrane and axoplasmic constants” (Goldman, L. (1961), J. Cell Comp. Physiol. 57: 185–191). However, the deep infolding of R2's axonal membrane suggested that differences in the shape of the two axons might also account for the paradox. Accordingly, we measured the conduction velocities of the two axons and then examined the same axons in the electron microscope in order to measure their volumes and surface areas. Our morphological observations indicate that the extensive infolding of surface membrane causes R2 to have a smaller volume to surface area ratio than R1. Thus, since conduction velocity is proportional to the square root of the volume to surface area ratio (Hodgkin, A. L. (1954), J. Physiol. 125: 221–224), it is predictable that the smaller axon would have a faster conduction velocity. The results suggest that the paradoxical conduction velocities can be explained largely as resulting from differences in the shapes of the two axons. However, certain discrepancies between the measured and the predicted values suggest that other factors are contributing as well.
The abdominal ganglion of Aplysia brasiliana: A comparative morphological and electrophysiological study, with notes on A. dactylomela
Authors: Blankenship J. E. , Coggeshall R. E.
Published: January 2005

The ultrastructure and electrophysiological properties of neurons in the abdominal (visceral) ganglion of the marine opisthobranch gastropod Aplysia brasiliana have been investigated to determine whether this preparation compares favorably with the well studied A. californica for neurobiological research. In general, the topography, morphology and physiological characteristics, including synaptic connections, of neurons in this ganglion are quite similar to those of A. californica. There is close correspondence between the two animals in terms of each of the identified cells or neuronal clusters in the ganglion, including the presence of the cell L10 (interneuron I) in A. brasiliana which makes synaptic connections comparable with those in A. californica. New follower cells of this interneuron have been found in A. brasiliana. This species offers some advantages in that the connective tissue surrounding the ganglion is thinner and more transparent, making cell identification and penetration easier. A. brasiliana appears to exhibit the behaviors of A. californica that have been used in previous functional analyses of neural circuits. In addition, this species swims and exhibits a „burrowing”︁ activity less commonly seen in A. californica. The rich repertoire of behaviors and accessibility of large identifiable and functionally interconnected neurons makes this species of Aplysia an excellent model preparation for future neurobiological studies. Similar, less thorough, investigations of the abdominal ganglion of A. dactylomela indicate that this species is also very similar to A. californica in terms of the identified cells in the abdominal ganglion.
Ultrastructural differentiation during drosophila neurogenesis in vitro
Authors: Gerson Ines , Seecof Robert L. , Teplitz Raymond L.
Published: January 2005

Drosophila melanogaster neuroblasts differentiate in vitro, and each gives rise to a cluster of about 18 daughter neurons. Electron microscopic observations of single clusters show that axons from daughter neurons form a neuropile within the cluster of cell bodies. The neuropile increases in size and complexity for several hours, during which time chemical, and probably electrotonic, synapses form between neurites. Clear vesicles with diameters of about 35 nm and dense core vesicles with diameters of about 60 and 160 nm were detected. The development of the neuropile indicates that the prerequisite cell recognition phenomena were manifested during differentiation in vitro, and the complexity of the neuropile suggests it may have attained the capacity to process information.
Characterization of the postnatal development of superior laryngeal nerve fibers in the postnatal kitten
Authors: Miller Arthur J. , Dunmire Carole R.
Published: January 2005

A combined electron microscopic and electrophysiological study of the superior laryngeal nerve (SLN) was undertaken in postnatal kittens ranging in age from 1–63 days. The superior laryngeal nerve is predominantly a sensory nerve innervating the upper respiratory tract, and could play a potential role in the modulation of respiration, particularly in the infant animal. Distribution of fibers in the developing SLN indicates that within the first postnatal month, 75% of the fibers are unmyelinated, and by 42 days, the myelinated fibers increase in number to approximately 50%. Of the myelinated fibers present in the one day old kitten, 3–4% of those exceeded 4 μm in total diameter, which is the minimum diameter for normal conduction velocity of action potentials. The distribution of the diameter sizes of the myelinated fibers is bell‐shaped within the first 45 days after which the curve becomes skewed to the right (43–61 days; mean 2.6 μm, range 0.5–8.0 μm) to resemble the adult distribution of myelinated fibers (mean 4.2 μm, range 1.6–13.0 μm). Two variable plots of myelin width to axon diameter suggest a steeper slope for developing fibers as compared to that of the adult fibers. Electrical stimulation of the sectioned SLN indicates that evoked potentials could be recorded from the recurrent laryngeal nerve innervating the laryngeal intrinsic muscles and from the hypoglossal nerve to the tongue musculature in the youngest kittens tested (i.e., age 9 days). Stimulation at selected frequencies of 3 and 30/sec readily evoked apnea in the youngest kitten studied (i.e., age 5 days), while swallowing was more readily evoked at 28–30 days when using electrical stimulation.
Regional differences of respiration in the bullfrog brain based on cell density
Authors: Potter Richard L.
Published: January 2005

The comparison of analogous and homologous regions of the anuran and mammalian brains, according to their rate of oxygen uptake per unit weight of DNA, has revealed a lack of correspondence between the respective brain regions. This discrepancy between corresponding regions was observed during incubation either in low‐potassium or in high‐potassium Ringer. Per unit weight of DNA, the rate of cellular respiration in the amphibian hindbrain exceeded that of the thalamus‐midbrain, and cells in the latter region exceeded those in the telencephalon. Hindbrain values were only higher if based on unit weight of DNA, and were actually lower on a wet weight basis. This pattern contrasted with a uniform rate of oxygen consumption for the homologous regions of the mammalian brain. Such inequalities between the regional brain metabolism of two different classes of vertebrates clearly illustrate the unique evolutionary history of both forms.

The intensity of potassium‐stimulated oxygen uptake in the three brain regions of the amphibian was interpreted as probably being proportional to the number of glial cells in each area. The smallest percentage of stimulation in the hindbrain may signify fewer glia, and the highest percentage of stimulation in the mid‐ and forebrain may indicate more numerous glia. Histological descriptions of ependymal glia in consecutive regions of the anuran brain appear to confirm this distribution of non‐neuronal cells.
Primitive nervous systems: Peripheral habituation in decerebrate polyclad flatworms
Authors: Bernardo K. , Stone G. C. , Koopowitz H.
Published: January 2005

The response to a vibration stimulus recorded from the cords of the ventral submuscular plexus of the polyclad flatworm, Notoplana acticola, consists of a burst of action potentials. The response can be abolished by the application of MgCl2 to the sea water bathing the preparation. With repeated application of the stimulus, decreasing numbers of action potentials can be measured. This waning responsiveness can be dishabituated by applying a more intense vibration stimulus or with electrical shocks applied directly to the ventral nerve plexus. With electrical stimuli a number of shocks have to be applied before the response can be dishabituated. Changes in responsiveness can be measured simultaneously in a number of sites in the plexus even after the nerves between recording sites have been severed. With different interstimulus intervals the extent of habituation changes. As interstimulus intervals increase from 1 to 5 sec, there appears to be a decrease in responsiveness which recovers when interstimulus intervals become longer than 5 sec.
The presence of transfer RNA in the axoplasm of the squid giant axon
Authors: Black M. M. , Lasek R. J.
Published: January 2005

Previous work has revealed that 4S RNA is the primary species of RNA in the axoplasm from the giant axons of the squid and Myxicola. This study shows that axoplasmic 4S RNA from the squid giant axon has the functional properties of tRNA. Axoplasmic RNA was charged with amino acids by aminoacyl‐tRNA synthetases prepared from squid brain. The aminoacylation was prevented by incubating the RNA with RNase prior to running the reaction. The amino acid‐RNA complex was labile at pH 9, which is characteristic of the acyl linkage between an amino acid and its tRNA. Aminoacyl‐tRNA synthetase activity was also present in the axoplasm, primarily in the soluble fraction.
Direct comparison of the rapid axonal transport of norepinephrine and dopamine‐β‐hydroxylase activity
Authors: Brimijoin Stephen , Wiermaa Mary Jo
Published: January 2005

Stop‐flow techniques were used to examine the rapid axonal transport of norepinephrine in rabbit sciatic nerves. When the midpoint of a nerve incubated in vitro was cooled to 2°C while the remainder was kept at 37°C, norepinephrine accumulated proximal to the cooled region at a rate corresponding to an average transport velocity between 5 and 6 mm/hr in a distal direction. Since only about half of the norepinephrine appeared to be free to move, the mean velocity of the moving fraction was probably twice as great. No norepinephrine accumulated distal to a broad cooled region under conditions in which there would have been a significant accumulation of dopamine‐β‐hydroxylase activity. Therefore, unlike dopamine‐β‐hydroxylase, norepinephrine may not be subject to rapid retrograde transport. When nerves that had been locally cooled for 1.5 hr were rewarmed uniformly to 37°C, a wave of norepinephrine moved exclusively in a distal direction. The peak of this wave moved at a velocity of 12.2 ± 0.5 mm/hr or 293 ± 12 mm/day; the front of the wave moved at about 18 mm/hr. or 430 mm/day; and the tail probably moved faster than 6 mm/hr. This spectrum of velocities was virtually identical to the one displayed by the wave of dopamine‐β‐hydroxylase activity that was generated under the same conditions. Our results are consistent with the conclusion that all axonal structures containing norepinephrine also contain dopamine‐β‐hydroxylase, but they are not consistent with the converse.
Release of acetylcholinesterase by cultured spinal cord cells
Authors: Oh Tae H. , Chyu Juliana Y. , Max Stephen R.
Published: January 2005

The release of acetylcholinesterase from neurons was studied using cultured chick‐embryo spinal‐cord cells. Cells dissociated from 12‐day‐old chick‐embryo spinal cords were grown in culture for 10–12 days. Numerous well differentiated spinal neurons were found after 7–10 days in culture. Acetylcholinesterase activity per dish increased by 60‐fold from days 2–12. Acetylcholinesterase was released into the surrounding media by the cells when they were incubated either in the standard culture medium or the serum‐free medium. Acetylcholinesterase release was significantly reduced when protein synthesis and microtubules were disrupted by cycloheximide and colchicine, respectively. Histochemical localization of acetylcholinesterase indicated that the synthesis and release of acetylcholinesterase are attributable to neurons. Cultured chick‐embryo brain and neuroblastoma cells also released acetylcholinesterase into the media. These results are discussed with regard to possible physiological roles for acetylcholinesterase secretion from neurons.
Thermosensitivity of single units in the hypothalamus of the conscious pekin duck
Authors: Simon E. , Hammel H. T. , Oksche A.
Published: January 2005

Adult Pekin ducks were chronically equipped with a thermode device which allowed local thermal stimulation and simultaneous single‐unit recording in the hypothalamus of the conscious animals during a period of up to three months. In two animals the activities of 29 single units were recorded extracellularly for sufficient time to measure static firing rates as a function of local temperature ranging from 32° to 42°C. Eleven units could be classified as warm sensitive, five units as cold sensitive, five neurons were insensitive to repeated local cooling and heating, and eight were variably active but not correlated with local temperature. The results indicate that the percentage of thermosensitive neurons in the hypothalamus of the two ducks may have been higher than the percentage found in several cats, rabbits, and dogs. The warm sensitive units recorded in the two ducks and additional 6 hypothalamic warm units found in three other ducks exhibited Q10 values between 2 and 17 with a mean of 4.8 · 4.3 s.d., i.e., their sensitivities were equal to those of warm‐sensitive neurons recorded in the hypothalamus of mammals. Thermoreceptivity has been attributed to the thermosensitive neurons in the rostral brainstem of mammals, since heating this tissue increases the rate of heat loss whereas cooling the same tissue reduces the rate of heat loss and increases the rate of heat production. In ducks, and penguins as well, cooling the rostral brainstem does not induce shivering or vasoconstriction but only inhibits metabolism and vasoconstriction. Thermosensitivity of a neuron in the rostral brainstem is not a sufficient criterion for presuming a thermoreceptive role for it in the duck, and probably not in a mammal either.
Nonhomogeneous excitatory synapses of a crab stomach muscle
Authors: Atwood H. L. , Govind C. K. , Kwan I.
Published: January 2005

Neuromuscular synapses of pyloric muscle P1 in the blue crab Callinectes sapidus were examined using electrophysiological and electron microscopic methods. The muscle is innervated by a single excitatory axon of the stomatogastric ganglion. Excitatory postsynaptic potentials show striking facilitation at very low frequencies of stimulation, indicating very slow decay of the facilitation process after a single nerve impulse. Quantal content of transmitter release at a low frequency of stimulation averaged 1.5. Evidence was obtained that not all synapses on a muscle fiber are equivalent. This was particularly evident at the morphological level in serially sectioned nerve terminals. On each nerve terminal examined, a wide range of synapse sizes was found. Synaptic contact areas ranged from less than 0.5 μm2 to almost 10 μm2; the latter value is large compared with those obtained for other crustacean neuromuscular synapses. Most of the smaller synapses lacked the presynaptic dense bodies which are putative release sites for the transmitter substance. The larger synapses all had presynaptic dense bodies, and some showed evidence of splitting apart into smaller subunits. It is postulated that about half the morphologically identified synapses are relatively inactive.
Brain reaggregate cultures: Biochemical evidence for myelin membrane synthesis
Authors: Sheppard J. R. , Brus David , Wehner Jeanne M.
Published: January 2005

Myelin membrane synthesis was studied using mechanically dissociated fetal rodent CNS which formed spherical reaggregates while being maintained in rotating culture flasks. These reaggregate cultures exhibited myelinogenesis in vitro after precisely the same period of time needed for myelin synthesis to commence in vivo. The myelin membrane related enzymes, 2′,3′ cyclic nucleotide phosphohydrolase (CNP) and cerebroside sulfotransferase (CST), appear similar in their specific activities and follow the same developmental patterns that these enzymes exhibit in vivo. In addition, phosphorylation of myelin basic protein occurs by the third week in vitro which agrees with previously published in vivo studies. These experiments indicate that this nerve‐cell culture system may be an appropriate model for studying the biological regulation of myelinogenesis as well as a variety of other nervous‐system functions.
The caudal ganglion of the leech, with particular reference to homologues of segmental touch receptors
Authors: Rubin Eric
Published: January 2005

The caudal ganglion of the leech, which provides sensory and motor innervation to the posterior sucker, represents the fusion of seven embryonic segmental ganglia. Although fused, each of the seven contributing ganglia (“subganglia”) of the caudal ganglion can be distinguished morphologically and functionally. The roots from each subganglion carry the axons of mechanoreceptors homologous to “touch” cells found in the segmental ganglia and the subesophageal compound ganglion. The receptive fields supplied by the touch cells of the caudal ganglion are uniquely arranged and reveal the modified segmentation of the circular posterior sucker. Extensive overlap of sensory innervation occurs between adjacent segments of the sucker, beyond the overlap characteristic of the homologous cells of body segments. It thus appears that the touch receptors of the caudal ganglion are less restricted than receptors of the segmental ganglia with regard to their territories of innervation. The caudal ganglion has additional unique properties that establish it as a distinct integrative center of the leech CNS.
Lack of limb motor asymmetry in the neonate
Authors: Korczyn Amo S. D. , Sage J. I. , Karplus M.
Published: January 2005

Neonates were examined for evidence of lateralization of motor function. The stepping test was done and the foot that moved first was recorded. The reaction of both arms to avoid an obstacle was also tested. No evidence for lateralization was found. Previous studies in the neonate have shown asymmetry of anatomical structures subserving language, and functional asymmetry of auditory functions and head position. However, the development of limb handedness occurs only at a later age.
The brain‐specific S‐100 protein on neuronal cell membranes
Authors: Hydén Holger , Rönnbäck Lars
Published: January 2005

The S‐100 protein has been localized to the neuronal plasma membranes of isolated Deiters' neurons by fluorescence microscopy using fluorescein‐conjugated antiserum to the protein and by immunoelectron microscopy using peroxidase‐conjugated anti‐S‐100 antiserum. In the present study this is shown also by incubating neurons with Sepharose 4B or methylacrylate spherules to which were coupled anti‐S‐100 antibodies. The specificity of the antiserum is discussed in the text. The technique described can be used to study the topography of antigenic characteristics of nerve cells by using antisera insolubilized on spherules of suitable size.
Neurobiology of Polyorchis. II. Structure of effector systems
Authors: Spencer A. N.
Published: January 2005

The gross and fine morphology of the major effector systems in the anthomedusan, Polyorchis penicillatus, is described and discussed in relation to the known physiological and behavioral properties of these systems. Swimming is controlled by an anastomosing network of giant neurons within the inner nerve ring and radial nerves. Although these neurons may be coupled by gap junctions it is likely that they form a syncytium. The photosensitivity of the “giants” is attributed to reflexive membranes within the cytoplasm. Giant neurons act as both the pre‐ and postsynaptic cell when forming synapses with other neurons of the inner nerve ring. Neuromuscular synapses between “giants” and the striated swimming muscle are found around the margin and along the radii. Swimming muscle cells are connected laterally by gap junctions and end‐to‐end by desmosomes which are sometimes elaborated with extra‐thick filaments. Unstriated sphincter and radial muscles, the major muscles associated with crumpling, are both greatly folded over mesogloeal ridges and have processes that cross the mesogloea to contact the ring and radial canals, respectively. Synapses or other sites that might be responsible for exciting these muscles during crumpling have not been found. The ability of the endodermal lamella and canals to propagate action potentials can be accounted for by the numerous gap junctions that are seen in these tissues. The precise location where excitation is transferred to the nervous system to initiate crumpling is not known but epithelial bridges crossing the mesogloea are likely routes. Synapses between neurons originating in the outer nerve ring and tentacle longitudinal muscle can account for the control of tentacle length. Neurons of the outer nerve ring also synapse onto velar, radial fibers and the sphincter muscle. The inner and outer nerve rings have nervous connections. The organisation of the outer nerve ring and the arrangement of nerves within the endodermal plexus is described. A diagram showing the major connections and interactions of components of the effector systems is presented.
Retrograde axonal transport of specific macromolecules as a tool for characterizing nerve terminal membranes
Authors: Dumas M. , Schwab M. E. , Thoenen H.
Published: January 2005

The uptake of macromolecules by nerve terminals which is followed by retrograde axonal transport seems to occur by two different mechanisms, a specific and a nonspecific one. The nonspecific uptake depends on the presence of macromolecules (e.g., horseradish peroxidase) in the vicinity of the nerve terminals at very high concentrations and is enhanced by neuronal activity. In contrast, the specific uptake and subsequent retrograde axonal transport becomes apparent at much lower concentrations of the appropriate macromolecules, depends on the affinity of these ligands for specific binding sites on the surface of the neuronal membrane, and is independent of neuronal activity. The fact that lectins and some bacterial toxins bind to specific membrane glycoproteins or glycolipids allows conclusions to be drawn regarding qualitative and even quantitative aspects of the composition of the plasma membrane of the nerve terminals.

125I‐labelled nerve growth factor (NGF), tetanus toxin, cholera toxin, wheat germ agglutinin (WGA), ricin II, phytohemagglutinin (PHA), and concanavalin A (ConA) were injected into the anterior eye chamber of rats where they were taken up by adrenergic nerve terminals and transported retrogradely to the superior cervical ganglion. The saturation of the uptake‐transport found for NGF, WGA, choleragenoid and an atoxic binding‐fragment of tetanus toxin indicates that limited numbers of binding sites, which showed also different affinites, are present for each ligand on the membrane of the nerve terminals. Competition experiments showed that the binding sites for the ligands investigated are largely independent. Two different classes of binding sites (high affinity‐low capacity and intermediate affinity‐intermediate capacity) seem to be involved in the saturable retrograde axonal transport of NGF. In contrast, WGA seems to have only a single class of binding‐uptake sites with high capacity and relatively low affinity. Strong evidence for positive cooperativity was obtained for the uptake and subsequent transport of the tetanus toxin fragment.
L9 modulation of gill withdrawal reflex habituation in Aplysia
Authors: Lukowiak Ken
Published: January 2005

Repeated tactile stimulation of the siphon in Aplysia normally results in habituation of the gill withdrawal reflex and a concomitant decrease in the amplitude of the excitatory synaptic input to gill motor neurons in the abdominal ganglion. It was found, however, that induced low‐level tonic activity in motor neuron L9, which does not itself elicit a gill withdrawal movement, prevented habituation of the reflex from occurring. Further, in preparations already habituated, this tonic low‐level activity brought about a reversal of habituation. Although tonic L9 activity prevented the occurrence of habituation or brought about its reversal, it did not interfere with the synaptic decremental process which normally accompanies gill reflex habituation. Motor neurons L7 and LDG1 were found not to possess this ability of L9 to modulate gill reflex habituation. Evidence suggests that L9's modulatory effect is mediated in the periphery, in the gill and not centrally in the abdominal ganglion.
Effects of L‐proline and some of its analogs on retinal spreading depression
Authors: Van Harreveld A.
Published: January 2005

L‐Protine inhibits glumate‐based spreading depressions (SDs) at low concentrations (2–2.5mM) and promotes K+‐based SDs at higher concentrations (5 mM). The inhibition of glutamate‐based SDs was postulate receptors on somatic and dendritic plasma membranes. The binding of proline to glutamate receptors was furthermore postulated to result in a result in a release of K+ from the intracellular compartment, enhancing the extracellular K+ concentration sufficiently to promote K+ based SDs. A proline analog, L‐baikiain, containing a double bond and one more based A atom in the ring structure than proline had similar affects as the latter amino acid, but an analog, L‐azetidine‐2‐hydroxylic acid, with one less C atom in the ring had little effect on SD in the retina.
Functional characterization of the neurodepressing hormone in the crayfish
Authors: Aréchiga Hugo , Cabrera‐Peralta Casimiro , Huberman Alberto
Published: January 2005

The effect of the neurodepressing hormone (NDH) was studied on different identified motoneurons in the abdominal ganglia of the crayfish Procambarus bouvieri (Ortmann). Although differences in sensitivity were apparent, all the neurons tested responded to NDH with a reduction in spontaneous firing rate, which lasted as long as NDH was present, and, depending on the concentration and time od action of the hormone, for even longer periods. NDH activity was determined in the various parts of the central nervous system of the crayfish, being highest in the eyestalk, gradually diminishing away from the eyestalk, with a cephalo‐caudal gradient, being lowest in the abdominal ganglia. High levels of NDH activity were detected in the blood. After eyestalk ablation, NDH concentrations steadily diminishes, in the blood and central nervous systems, until virtually disappearing after 4 days; from day 5 onwards, the activity is recovered up to its original levels. NDH synthesis takes place with a time constant of approximately 3 hr in cultured segments of central nervous system, being highest in the eyestalk.
Neurotrophic control of 16S acetylcholinesterase at the vertebrate neuromuscular junction
Authors: Fernandez Hugo L. , Duell Myron J. , Festoff Barry W.
Published: January 2005

Endplate 16S acetylcholinesterase (16S‐AChE) from rat anterior gracilis muscle was assessed, 6 hr to 10 days after denervation, by velocity sedimentation analysis on linear sucrose gradients. The innervating obturator nerve was transected either close (1‐2 mm, short stump) or far (35‐40 mm, long stump) from the muscle. In both instances, the activity of 16S‐AChE gradually decreased and reached approximately the same level (10%‐20% of control) by 6 days after denervation. However, enzymatic decay started considerably earlier in short stump (12‐24 hr) as compared to long stump (4‐5 days) preparations, i.e., the time of onset of 16S‐AChE loss depended on the length of nerve that remained attached to the muscle. Whether this result extended to other AChE molecular forms (10S, 4S) in muscle endplates could not be determined because, in contrast to 16S‐AChE, these forms were also detected in red blood cells (4S) and plasma (10S). Only small amounts of 16S‐AChE were found in intact obturator nerves (1/100 of that in gracilis endplate regions). Thus a faster depletion of enzyme from shorter nerve stumps after axotomy could not entirely account for the substantial effect of nerve stump length on 16S‐AChE. Since muscle contraction ceases immediately following nerve transection, regardless of nerve stump length, the results can be ascribed to the lack of some neural influence other than nerve‐evoked muscle activity. The present findings are consistent with the view that maintenance of 16S‐AChE at neuromuscular junctions primarily depends on regulatory substances which are conveyed by axonal transport and released from nerve terminals.
Photomechanical migrations of pigment granules along the retinula cells of the crayfish
Authors: Frixione Eugenio , Aréchiga Hugo , Tsutsumi Victor
Published: January 2005

The light‐dependent migrations of proximal pigment granules along the photoreceptors of the crayfish compound‐eye were studied in isolated retinas and eyestalks. The extent and kinetics of movement in each direction were found quantitatively equivalnt to those observed in the organ in situ. These and other features make these cells to appear as intrinsically independent pigmentary effectors, directly responsive to light. During dark adaptation (DA) the pigment migrates away from the cell nucleus and accumulates along the axon in two distinct steps. Each step constitutes half of the total distance of about 180 μm and proceeds at 0.30 μm/sec. Only prolonged metabolic impairment inhibited the first phase, while the second was blocked by hypoxia, cyanide, colchicine, and D2O. The maintenance of a full DA position was also shown to be highly dependent upon metabolism. Light incidence on DA eyes is followed by an apparently monophasic expansion of the pigment from the axon towards the perikaryal region at 0.38 μm/sec. This movement was not affected by any of the foregoing agents and seems to be a passive relaxation process. Cytochalasin B had no effect on either motion. The migration in either direction has an exponential time course and is temperature dependent. Electron microscopy revealed two separate patterns of cytoplasmic organization corresponding to the cell areas where the two phases of DA occur. In the region close to the nucleus the pigment appears irregularly scattered, whereas in the axon the granules are situated around a thick longitudinal bundle of microtubules. These results suggest the existence of two different mechanisms of pigment granule translocation operating in two separate regions of the retinula cell.
Subcellular particles involved in the translocation of proteins in rat brain
Authors: White Fredric P.
Published: January 2005

Protein translocation systems which are inhibited by vinblastine, colchicine, and low calcium concentrations have been found in the cells of the brain slice. The early steps in the translocation pathways of newly synthesized protein have been studied by use of a double‐label experiment in conjunction with subcellular fractionation. Certain subcellular particles have been positioned on the pathways with reference to vinblastine‐sensitive translocation steps. There appears to be many subcellular organelles that are located downstream from a vinblastine‐sensitive translocation step and which receive significant quantities of translocated protein within an hour of its synthesis. Some of these organelles co‐enrich with the enzyme marker 5′‐AMPase. Myelinated axons, Golgi derived vesicles, and smooth and rough endoplasmic reticulum all are enriched in fractions which contain a net vinblastine‐sensitive importation of protein. The major particles, which lie upstream from a vinblastine‐sensitive translocation step and are net exporters of protein on this system, are found in a brain capillary fraction. It is suggested that the most likely exporter present in these capillaries are the end feet of astrocyte glial cells.