bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical studies of taste sensation. VII. Enhancement of taste stimulus binding to a catfish taste receptor preparation by prior exposure to the stimulus
Authors: Cagan Robert H.
Published: January 2005

The technical assistance of Ardithanne Boyle, Linda Graham and Pamela Burke is appreciated. I thank Dr. H. Ronald Kaback and Dr. Leonard D. Kohn for their suggestions of experiments relevant to transport questions. This research was supported in part by NIH research grant No. NS‐08775 from NINCDS.

The taste receptor membrane fraction (Fraction P2) was prepared from a homogenate of the taste tissue of the channel catfish Ictalurus punctatus. This included the rostral, dorsal, and dorsolateral surfaces of the catfish in addition to those of the barbels. The yield of Fraction P2 is 4–7 mg protein from an individual fish, with a purification averaging 8‐ to 15‐fold over that of the crude whole homogenate and essentially quantitative recovery of binding activity in Fraction P2.

Treatment of Fraction P2 in vitro with a high concentration of the taste stimulus molecule L‐alanine led to a several‐fold enhancement of binding activity. Enhancement of the binding of 3H L‐alanine was observed after treatment with unlabeled 10mM L‐alanine and removal of the L‐alanine by washing. Enhancement occurred whether the preparation was stored frozen (−65°C) for an extended period in the presence of the L‐alanine, or merely exposed to it in the cold without freezing. D‐Alanine enhanced the binding activity of 3H L‐alanine to about 60% of the level induced by L‐alanine. Nonspecific binding of 3H L‐alanine was unaffected by the treatment. Scatchard analyses of saturation curves for binding of 3H L‐alanine to freshly prepared Fraction P2 and to L‐alanine‐treated Fraction P2 revealed no change in the KD value, but a several‐fold increase occurred in the amount bound.

Binding activity is operationally defined. Because the enhancement observed here is reminiscent of an increase in transport due to a countertransport effect, further studies were carried out to examine whether the phenomenon reflects transport or true binding. The measured binding was not increased in the presence of Na+, indicating that it is not due to an Na+‐ coupled transport of L‐alanine. When Fraction P2 was preloaded with L‐alanine (10−6 – 10 −2M) prior to assay, no stimulation of binding was observed; instead, binding decreased. This result is consistent with a true binding phenomenon but not with a carrier‐mediated transport process to expiain the enhancement phenomenon. Binding assays carried out over a range of osmolarities revealed decreased binding at high osmotic strengths, suggesting that a significant portion of the ligand might be contained in vesicles.

It is postulated that “hidden” or “buried” receptor sites exist in the Fraction P2 as isolated, and that these are exposed upon perturbation of the membrane structure by ahigh ligand concenration.
Ultrastructure of Aplysia neurons having different degrees of light sensitivity
Authors: Krauhs J. M. , Andresen M. C. , Baur P. S. , Brown A. M.
Published: January 2005

The relationship between ultrastructure and photosensitivity of pigmented neurons of the abdominal ganglion of Aplysia californica was investigated using electron microscopy and electrophysiological methods. Four identified neurons of similar light microscopic appearance were examined; two are photoresponsive and two are not. Illumination hyperpolarizes both responsive neurons. One of them, R2, requires roughly 100 times greater light intensities than does the other, the ventral photoresponsive neuron (VPN), for similar responses. Two neurons lying adjacent to VPN and similar in appearance to VPN do not have measurable electrophysiological responses to even the highest light intensities. All four neurons contained lipochondria, pigmented organelles associated with the light response. Therefore the presence of these organelles is not the only requirement for light sensitivity in these neurons. Illumination appeared to increase the number of membranous lipochondria in both R2 and the ventral neurons, but only in R2 was this increase significant. Factors such as the concentration of lipochondria near the plasma membrane may affect quantitative aspects of the light response, but in the insensitive cells the lipochondria are apparently uncoupled from other factors required for the light response.
Correlated effects of acetylcholine and cyclic guanosine monophosphate on membrane properties of mammalian neocortical neurons
Authors: Swartz B. E. , Woody C. D.
Published: January 2005

The effects of successive extracellular iontophoresis of acetylcholine (ACh) and atropine, and intracellular hyperpolarizing iontophoresis of cyclic GMP (cGMP) were studied in single neurons of the coronal‐pericruciate cortex of awake cats. (a) Fifty‐seven percent of the neurons that were tested responded to ACh with an increase in neuronal input resistance (Rm) and 50% responded to ACh with an increase in firing rate; 65% responded to cGMP with an increase in Rm and 60% responded to cGMP with an increase in firing rate. (b) After application of atropine, increases in Rm and firing rate associated with iontophoresis of ACh failed to recur. (c) Persistent increases in Rm following application of ACh accompanied by current‐induced neuronal discharge were not diminished by subsequent application of atropine. (d) Atropine did not prevent increases in Rm and firing rate associated with intracellular iontophoresis of cGMP. (e) All cells tested with both ACh and cGMP that were shown initially to respond to extracellular ACh with increases in Rm were later shown to have comparable responses to cGMP.
Interganglionic axonal transport of neural peptides within the nervous system of Aplysia
Authors: Berry Robert W. , Geinisman Yuri
Published: January 2005

Neurons of the circumesophageal ganglia of Aplysia synthesize 1‐2000 dalton peptides and subject them to axonal transport in large quantities in the pleuro‐visceral connective and pedal nerves. Most of the protein transported in the connective nerves accumulates in the abdominal ganglion, although some passes out its peripheral nerves. Autoradiography revealed no evidence for terminations of the transporting axons in possible neurohemal areas of this ganglion. It is suggested that these data reflect the existence of a pathway mediating the “directed delivery” of neural peptides in this nervous system.
Secretion of axonally transported neural peptides from the nervous system of Aplysia
Authors: Berry Robert W.
Published: January 2005

The possibility that proteins reaching the abdominal ganglion of Aplysia by axonal transport from the circumesophageal ganglia might be subject to secretion in that structure was examined. Transported labeled protein was found to be released from the abdominal ganglion; such release was enhanced by exposure to a high K+ medium and by electrical stimulation of the transporting axons. Stimulation of release was inhibited by lowering the Ca2+/Mg2+ ratio of the medium. The released material is predominantly of 1–2000 daltons in molecular weight and appears to have been derived from a group of transported peptides of about the same size. The possibility is raised that these data may reflect the existence of a peptidergic second‐order neurosecretory pathway in this nervous system.
Batrachotoxin inhibits axonal transport without affecting membrane potential in single neurons of Aplysia californica
Authors: Kumara‐Siri M. H.
Published: January 2005

Intrasomatic injection of 0.25 ng of batrachotoxin (BTX) caused no depolarization of giant cerebral neurons (GCN) of Aplysia californica within 4 hr at 23° C. The amplitude of action potential and the input resistance were slightly and reversibly decreased. The same dose of BTX caused a 68% inhibition of fast axonal transport.
Mg++‐sensitivity of neuromuscular transmission in two crustaceans: Correlation with blood Mg++ levels
Authors: Lang Fred , Cleveland Mark B. , Atwood Harold L.
Published: January 2005

Neuromuscular transmission was measured in muscles of spider crabs (Hyasareneus) and lobsters (Homarus americanus). Solutions containing 40 and 10 mM/1 Mg++, which were approximately the same as those measured in the blood of Hyas and Homarus, respectively, were used to soak the preparations prior to testing. In Homarus, neuromuscular transmission was severely depressed by 40 mM Mg++. In spider crabs, neuromuscular transmission was not severely depressed. Although the amount of transmitter released by nerve impulses was reduced, total membrane depolarization during trains of impulses was not reduced because a compensating increase in muscle fiber membrane resistance occurred in Hyas preparations exposed to 40 mM Mg++. Hyas, but not Homarus, is physiologically adapted to function at relatively high blood Mg++ concentrations.
Properties of a calcium‐activated protease in squid axoplasm which selectively degrades neurofilament proteins
Authors: Pant Harish C. , Gainer Harold
Published: January 2005

Axoplasm extruded from the giant axon of the squid contains Ca2+‐activated proteases. The protease in the 100,000X g of supernatant of axoplasm is very specific and degrades only the 200,000 MW, neurofilament protein (NF200), whereas the protease(s) in the pellet has a much wider range of substrate specificity. The activation of the supernatant protease is restricted to the Ca2+ ion, and no other divalent cation will substitute. The protease requires Ca2+ at a higher concentration than 0.5 mM for activation, and has a pH optimum of about 7.5. Degradation of the NF200 appears to proceed through a 100,000 MW and possibly a 47,000–50,000‐MW intermediate form before degradation to TCA‐soluble peptides. Activity of the protease is inhibited by divalent cation chelators, Cu2+ and Fe2+, sulphydryl inhibitors, and leupeptin. This specific Ca2+‐activated protease in squid axoplasm has identical properties to Ca2+‐activated proteases found in various non‐neural tissues. Despite its narrow protein substrate specificity, Ca2+‐activated protease purified from human platelets effectively degrades squid NF200, suggesting a possible structural relationship between platelet and muscle actin‐binding proteins and neurofilament proteins.
Innervation, synaptic physiology, and ultrastructure of three muscles of the second maxilla in crayfish
Authors: Moody‐Corbett F. , Pasztor V. M.
Published: January 2005

Innervation patterns, synaptic properties, and fiber ultrastructure were studied in three muscles of the second maxilla of Procambarus clarkii and Orconectes virilus. All three muscles, ASDM (anterior scaphognathite depressor muscle), CFM (coxopodite flexor muscle), and SFM (scaphognathite flexor muscle), were polyneuronally innervated, receiving two, three, and four excitors, respectively. Two of the four excitors innervating SFM were branches of the two excitors supplying ASDM. No muscle received inhibitor axons. Synapses tended to be low output and show a high degree of facilitation as measured by the facilitation index of Atwood and Bittner. Ranges of EPSP amplitudes and facilitation indices were common to all excitors. Muscle fibers uniformly showed short sarcomere lengths and low thin‐to‐thick filament ratios. These physiological and ultrastructural peripheral features are consistent with the nature of the motor score from the central rhythm generator.
Fine structural analysis of membrane changes during reaggregation culture of chick optic tectum
Authors: Wood John G. , McLaughlin Barbara J. , Byrd Frances I.
Published: January 2005

Thin section and freeze‐fracture electron microscopy have been used to characterize the changes in membrane morphology of reaggregating cultures of chick optic tectum. The cells are rounded and freely dispersed at 0 hr after dissociation. Between 2 and 6 hr the cells become closely apposed on all sides by other cells and form small aggregates. At this time punta adhaerentia junctions and focal densities are seen along the membranes of neighboring cells. Between 1 and 5 days in vitro (DIV) neurites containing growth cone regions are present. At 5 DIV the first synaptic contacts are observed. Between 7 and 14 DIV, the number of synaptic contacts increase and fewer growth cone regions are observed. As early as 7 DIV profiles are observed which strongly resemble both astrocytic and oligodendroglial cell somata and processes. Freeze‐fracture analysis of aggregates at 0–4 hr reveals a sparse particle distribution on the P and E faces of apposed cells. By 1 DIV small clusters of loosely packed, large sized particles are seen on the P face of apposed cell membranes which may represent junctional contacts. Apparent coated vesicle fusion sites are common on the P face at 1–2 DIV. By 7 DIV, E face particle arrays are seen on cell bodies and neurites which correspond to specializations characteristic of excitatory synaptic junctions. By 8–10 DIV particle arrays are seen on the P face of post‐synaptic membrane which may represent inhibitory synaptic contacts. Other types of particle specializations seen in freeze‐fracture replicas include: specializations characteristic of gap junctions between cells and orthogonal assemblies of particles thought to be characteristic of astrocytes.
A method for controlling body wall turgor during electrophysiological recording from central neurons in ecdysing insects
Authors: Carlson Joseph R.
Published: January 2005

A method for obtaining intracellular recordings from central neurons of insects during the performance of ecdysial behaviors is described. Body wall turgor must be restored to high levels in order to provide the CNS with appropriate sensory feedback required for the generation of motor output. This is accomplished by installing the insect in a decompression chamber so that an opening in the animal's ventral surface communicates with the atmosphere. Reduction of chamber pressure causes expansion of the insect's body, and access to thoracic ganglia is provided by the ventral opening in the animal's body wall. It is suggested that adaptations of this technique to invertebrates with hydrostatic skeletons is possible and would permit electrophysiological studies of behaviors which normally require high blood pressures for their performance.
Synthesis of the myelin proteolipid protein in the developing mouse brain
Authors: Campagnoni Anthony T. , Hunkeler Markus J.
Published: January 2005

Mice ranging in age from 16 to 44 days were injected intracerebrally with 3H‐leucine, and incorporation into total brain proteolipids and the myelin proteolipid protein was measured. All proteolipids were isolated from whole brain by ether precipitation and separated into their individual components by SDS polyacrylamide gel electrophoresis. Two major proteolipids with apparent molecular weights of 20,700 and 25,400 were observed in these preparations, and their proportion increased over the developmental period examined. A Ferguson plot analysis comparing these proteins with those of isolated myelin showed that the 25,400‐dalton proteolipid component from whole brain was the myelin proteolipid protein. Rates of incorporation of 3H‐leucine into total brain proteolipids peaked at 22 days of age. Synthesis of the myelin proteolipid protein increased rapidly to a maximum value at 22 days and decreased rather slowly until at 44 days it was about 83% of its maximum rate of synthesis. The data indicate that the developmental pattern of synthesis of the myelin proteolipid protein is unlike that of the myelin basic proteins. Synthesis of the major myelin proteins is developmentally asynchronous in that peak synthesis of the myelin proteolipid appears to occur several days later than the basic proteins. In addition, it maintains its maximum rate of synthesis over a longer period of time than do the basic proteins.
Pineal cells enhance choline acetyltransferase activity in sympathetic neurons
Authors: Rowe Vernon , Parr James
Published: January 2005

Cells derived from the neonatal rat pineal gland were cocultured with cells derived from neonatal rat superior cervical ganglia (SCG) in an attempt to determine whether a sympathetic target organ with only adrenergic properties could enhance the development of adrenergic transmitter properties in sympathetic neurons in tissue culture. Choline acetyltransferase was measured as an index of cholinergic differentiation, and tyrosine hydroxylase was measured as an index of adrenergic differentiation. As indices of total cell number and cellular volume, DNA and protein, respectively, were also measured. We found that the pineal‐SCG cocultures contained ten times greater choline acetyltransferase activity than sister neuronal cultures cultured without pineal cells, thus indicating that the pineal cells enhanced cholinergic properties in the sympathetic neurons. This cholinergic enhancement was dependent upon the presence of nerve growth factor and could not be obtained with pineal‐conditioned medium. Tyrosine hydroxylase activity, measured on cultures sister to those mentioned above, was low in all cultures and decreased somewhat in SCGs cultured alone. TH activity in the pineal‐SCG cocultures, however, increased slightly. Some tyrosine hydroxylating activity developed in pineals cultured alone, however, and may have been responsible for the small increase in tyrosine hydroxylase activity noted in the pineal‐SCG cocultures. The implications of these results for a determination of the role that target organ plays in the development of the transmitter properties of sympathetic neurons are discussed.
Biochemistry and ultrastructure of serotonergic nerve endings in the lobster: Serotonin and octopamine are contained in different nerve endings
Authors: Livingstone Margaret S. , Schaeffer Susan F. , Kravitz Edward A.
Published: January 2005

In this article we report that the distribution of serotonin in the lobster nervous system parallels the distribution of octopamine and that the same tissues that contain endogenous serotonin can synthesize it from tryptophan. Octopamine and serotonin are highly concentrated in a neurosecretory region of the second thoracic roots in association with a group of neurosecretory cells. The roots possess separate high‐affinity uptake systems for both serotonin and tryptophan. Radioactive serotonin, accumulated in tissues during incubations with either tritiated serotonin or tritiated tryptophan, can be released, in a calcium‐dependent manner, by depolarization with potassium. A detailed morphological examination of the second thoracic roots shows four distinct categories of nerve endings in the vicinity of the neurosecretory cells. Octopamine is synthesized in one of these types of endings and serotonin in another. The high‐affinity uptake systems for serotonin and tryptophan are found only in association with the endings that make serotonin. These endings and all the biochemical parameters of serotonin metabolism in the roots are selectively destroyed by previous injection of animals with the neurotoxin 5,7‐dihydroxytryptamine.
Unique, identifiable local nonspiking interneurons in the locust mesothoracic ganglion
Authors: Wilson John A.
Published: January 2005

The hypothesis that local nonspiking interneurons are unique and identifiable has been tested rigorously for a neuron in the mesothoracic ganglion of the locust. Neurons were physiologically characterized and subsequently stained with cobalt ions. The resulting preparations were examined in whole mounts and serial sections. It is concluded that at least three neurons are unique, based upon a combination of their function, gross morphology, and the location and size of their main processes relative to other neurons. It is strongly suggested that there are other local nonspiking interneurons that are unique and identifiable. A classification system for local nonspiking interneurons is proposed. The implications of this finding for future neuroethological studies are discussed.
Studies on the localization of newly added membrane in growing neurites
Authors: Feldman E. L. , Axelrod D. , Schwartz M. , Heacock A. M. , Agranoff B. W.
Published: January 2005

Explant culture of the adult goldfish retina results in vigorous neuritic growth, provided that the optic nerve has been previously crushed in vivo. The site of new membrane addition in these growing neurites was studied with a membrane‐binding lectin Concanavalin A (Con A) in conjunction with a fluorescent indirect antibody method. Explant cultures were labeled with Con A, followed by rabbit antibodies to Con A. This treatment was shown to immobilize Con A receptors while permitting growth. Twenty‐four hours later, the washed preparation was treated with fluorescent goat antirabbit antibodies. The bound fluorescent antibodies appeared as a pattern of contiguous fluorescent speckles confined to the area of old growth while regions near the distal end of the neurite were not fluorescent. These results are compatible with the hypothesis that new membrane is added in the region of the growing tip of the neurite.
Extent of multiple innervation of purkinje cells by climbing fibers in the olivocerebellar system of weaver, reeler, and staggerer mutant mice
Authors: Mariani Jean
Published: January 2005

Multiple innervation of cerebellar Purkinje cells (PCs) by climbing fibers (CFs) has been described recently in adult weaver, reeler, and staggerer mutant mice, instead of the monoinnervation found in normal adults. In the present study, the extent of this multiple innervation was estimated by two methods, using both evoked and spontaneous activity of the olivocerebellar system. Concordant values were obtained: the mean number of CF collaterals per PC was between 3.5 and 4 in weaver and staggerer and close to 3.2 for the multiply innervated PCs of reeler mice. These values are of the same order of magnitude as those for the transient multiple innervation in developing rats (Mariani and Changeux, 1981a, b).
Evidence for peptide‐mediated neurotransmission in a molluskan brain
Authors: Snow Robert W.
Published: January 2005

The previous report (Snow, 1982) characterized the monosynaptic actions of an identified cerebral interneuron (C2) in the marine mollusk Tritonia. The C2 neurons produce four types of postsynaptic potentials in an identified pedal neuron (Pd5). A high‐molecular‐weight (≈︁1400 daltons by Sephadex G‐15 gel filtration) compound, which could mimic the four postsynaptic responses in Pd5, was isolated from C2 somata. The C2 somata had the ultrastructural characteristics of peptide‐secreting cells, including profuse rough endoplasmic reticulum and large (170 nm average diameter) dense secretory vesicles. These data are consistent with the hypothesis that the synaptic transmitter of C2 neurons is a peptide(s).
Attenuation of catecholamine‐coupled adenylate cyclase following surgical isolation of rat caudate
Authors: Pajer Kathleen A. , Palmer Gene C. , Chronister Robert B. , Marco Luis A.
Published: January 2005

Six weeks following complete unilateral surgical isolation of the rat caudate nucleus, activation of adenylate cyclase was reduced in response to dopamine (DA), norepinephrine (NE), 5′‐guanylyl‐imidodiphosphate [Gpp(NH)p], DA + Gpp(NH)p, and NaF. The low Km form of cyclic AMP phosphodiesterase was elevated in the isolated side when compared to the intact caudate. No changes in activities of guanylate cyclase or in high Km cyclic AMP phosphodiesterase (with or without the calcium‐dependent regulator protein, calmodulin or CDR) were observed between the control and isolated caudate. Histologically, the neural damage to the isolated caudate was principally confined to reduced numbers of dendritic spines of the remaining intrinsic caudate neurons.
All‐or‐none control of the bursting properties of the pacemaker neurons of the labster pyloric pattern generator
Authors: Moulins Maurice , Cournil Isabelle
Published: January 2005

In Crustacea the central pattern generator for the pyloric motor rhythm (filtration to the midgut) is known to be located within the stomatogastric ganglion (STG); its cycling activity is known to be organized by three endogenous burster neurons acting as pacemakers and driving 11 follower neurons. In Homarus, recordings from the isolated stomatogastric nervous system (Fig. 1) indicate that (1) the pyloric output can be generated only when the STG is afferented (i.e., connected to the more rostral oesophageal and commissural ganglia) (Fig. 2) and (2) the deafferntation of the STG results in a complete loss of the bursting properties of the pacemaker neurons (Fig. 4). Manipulation of the STG inputs responsible for unmasking the properties of the pacemakers strongly suggests that (1) they are not phasic inputs (Fig. 5) and (2) they are long‐term acting inputs (Fig. 6). These results provide evidence for a neural all‐or‐none control of the bursting properties of the pacemaker neurons of a motor pattern generator.
Ultrastructure of the water‐movement‐sensitive sensilla in the medicinal leech
Authors: Phillips Christine E. , Friesen W. Otto
Published: January 2005

Behavioral and physiological experiments have shown that medicinal leeches are able to detect low amplitude surface waves, and further, that the transduction of this stimulus modality occurs primarily, if not exclusively, at the annular sensilla (Young, Dedwylder, and Friesen, 1981; Friesen, 1981). Here we examine the morphology of these specialized sensory structures using light, scanning electron, and transmission electron microscopes. We found that three types of ciliated sensory cells occur at the sensilla: (1) a uniciliate cell, with an axial cilium that projects at least 12 μm beyond the cuticle; (2) a multiciliate cell with from two to four grouped cilia that extend 1–3 μm beyond the cuticle; and (3) a second multiciliate cell, whose cilia project parallel to the body surface but remain within the cuticle. The cilia of all three cell types arise from the cuplike depressions which form the apices of slender, elongated cells (approximately 2 μm diameter × 50 μm length). A complexly interconnected ring of microvilli surrounds the cilium of the uniciliate cells. The morphology of the uniciliate cells closely resembles the structure of vibration‐sensitive sensory neurons found in other species. We propose, based on previous results and our new findings, that the uniciliate receptor cells are the sensillar movement receptors which mediate leech sensitivity to water movements.
Malice's wonderland: Research funding and peer review
Authors: Osmond D. H.
Published: January 2005

The players all played at once, without waiting for turns, quarreling all the while and fighting for the hedgehogs; and in a very short time the queen was in a furious passion and went stamping about, and shouting “off with his head” or “off with her head,” about once a minute.

Alice began to feel very uneasy: to be sure she had not as yet had any dispute with the queen, but she knew that it might happen any minute, “and then” thought she, “what would become of me? They're dreadfully fond of beheading people here: the great wonder is, that there's any one left alive”.
Electroretinographic and ultrastructural study of the regenerated eye of the snail cryptomphallus aspersa
Authors: Flores D. Vladimir , Salas Pedro J. I. , Vedra Jorge Pecci Saa
Published: January 2005

The electroretinographic responses of regenerated eyes of snails (C. aspersa) were studied by means of suction electrodes and single or repetitive flash stimulation. The eyes were fixed and observed under light and electron microscopy. The results indicate that the electroretinographic response of regenerated eyes does not differ from control eyes after dark adaptation. However, the repetitive stimulation of the regenerated eyes induced an earlier fatigue of the response, evident after the fifth stimulus. This fatigue is a function of light intensity. Ultrastructural features of the regenerated eyes are similar to those of the control eyes but regenerated eyes show smaller rhabdomeres, fewer photic vesicles, and fewer paracrystalline bodies. It is suggested that the regenerated eye lability to the repetitive stimulation might be due to the decrease in the amount of photic vesicles and paracrystalline bodies, to the decrease in membrane surface of the rhabdomeres, or to some other metabolic failure not distinguished at electron microscopic level, like the membrane ionic regulation. The appearance of photic vesicles in the axon cones of regenerated and stimulated cells also suggests a possible failure in the mechanism of transport of vesicles.
Effects of c‐amp, caffeine, theophylline, and vinblastine on spontaneous transmitter release at locust nerve‐muscle junctions
Authors: Fahim M. A. , Usherwood P. N. R.
Published: January 2005

The effects of c‐AMP, phosphodiesterase inhibitors (caffeine and theophylline) and vinblastine on spontaneous transmitter release was investigated at locust neuromuscular junctions. c‐AMP, theophylline, caffeine, and vinblastine caused facilitation of transmitter release. None of these drugs had any effect on the amplitude of miniature excitatory postsynaptic potentials (min. E.P.S.P.'s), or on the resting membrane potential, but vinblastine increased the proportion of [large] min. E.P.S.P.'s The effect of theophylline (but not c‐AMP and caffeine) on min. E.P.S.P. frequency was found to be calcium dependent. The effects of these drugs on the locust glutamatergic synapse are compared with their actions at other synapses.
Axonal transport blockade and denervation have qualitatively different effects upon skeletal muscle metabolism
Authors: Ramírez Beatriz U.
Published: January 2005

The activity and isoenzyme pattern of muscle lactic dehydrogenase (LDH) was measured at different times after axonal transport blockade by colchicine or after denervation. After denervation, total LDH activity decreased and the isoenzyme pattern was altered, LDH‐1 being the most affected form. In contrast, after axonal transport blockade there was a decrease in LDH activity but the isoenzyme pattern was not modified. Denervation abolishes both nerve‐evoked muscle activity and the release of neuro trophic substances from the nerve whereas colchicine blocks axonal transport without affecting the nerve capacity to conduct action potentials or neuromuscular transmission. It is then concluded that nerve‐evoked muscle activity is the most important factor in the regulation of muscle LDH isoenzyme distribution. On the other hand, muscle metabolism can also be regulated by axonally transported molecules.

The results presented here show that there is a qualitative difference between the effects of denervation and those of axonal transport blockade upon the muscle, since only denervation altered the isoenzyme pattern of muscle LDH.
Quantitative effects of a neurotoxin upon serotonin levels within tissue compartments of the medicinal leech
Authors: Lent Charles M.
Published: January 2005

The serotonin (5‐hydroxytryptamine, 5‐HT) content of tissue compartments in the medicinal leech, Hirudo medicinalis, was measured by means of highpressure liquid chromatography coupled with electrochemical detection (HPLC–EC). Each segmental ganglion contains 21.3 ± 2.9 (9) pmol 5‐HT [X ± SEM (N)]. The pharynx contains 7.1 ± 1.1 (9) pmol 5‐HT/mg wet weight; the salivary glands 3.2 ± 0.9 (10), ventral body wall 2.0 ± 0.2 (11), and vasofibrous tissue 1.2 ± 0.2 (11). The blood of hungry leeches contains 8.7 ± 1.9 (7) nM 5‐HT while that of well‐fed leeches is 2.2 ± 0.4 (6) nM.

Leeches were injected with the cytotoxic analog of serotonin, 5,7‐dihydroxytryptamine (5,7‐DHT) producing selective lesions of the peripherally projecting serotonin‐containing neurons, and which in turn abolished their feeding behavior. The serotonin content of the pharynx and ganglia of these toxin‐treated leeches were lowered significantly. The serotonin levels within the body wall and salivary glands were not altered significantly by the toxin treatment, but the levels within the vasofibrous tissue and blood were elevated substantially.
Ring neuron control of columellar motor neurons during egg‐laying behavior in the pond snail
Authors: Jansen Rene F. , Ter Maat Andries
Published: January 2005

Egg‐laying in Lymnaea is characterized by the stereotyped egg‐laying behavior (ELB), composed of foot contractions and shell movements. Egg‐laying can be induced by a clean water stimulus, that triggers a discharge of the neuroendocrine caudo‐dorsal cells (CDCs), which release the ovulation hormone into the blood. A part of the behavior is lost when egg‐laying is triggered by hormone injection, indicating that during natural stimulus‐induced or spontaneous egg‐laying this part (the first phase) may be controlled by neuronal events in the CNS triggered by (a) factor(s) not released to the blood. The authors have identified an unpaired neuron, the ring neuron, that is excited during an in vitro afterdischarge of the CDCs, and which, by its numerous axonal branches in the pedal ganglia, modulates motorneurons of the columellar muscle, which controls shell movements. These motorneurons, identified as such in reduced preparations by 1 for 1 muscle potentials and elements in the connecting nerve, all receive either excitatory or inhibitory input from the ring neuron, as well as from an unknown neuron which has common input of the ring neuron and the motorneurons. The action of the CDCs on the ring neuron cannot be mimicked by the ovulation hormone, and we therefore conclude that the first part of the ELB is probably caused by a nonhormonal local action of the CDCs on the ring neuron and possibly the common input neuron.
Triple innervation of the crayfish opener muscle: The astacuran common inhibitor
Authors: Wiens Theodore J.
Published: January 2005

Part of the much‐studied crayfish opener muscle receives a second inhibitory input in addition to its well known specific excitatory and inhibitory innervation. This second inhibitor, formerly thought to innervate only four of the seven peripheral leg muscles, is in fact a common inhibitor of all seven. This has significance both for previous findings in this muscle and for the role of the common inhibitor in decapods.
The central morphology of mechanoreceptor afferents in the metathoracic leg of the cockroach, Periplaneta americana (insecta)
Authors: Collin Shaun P.
Published: January 2005

The sensory arborizations of the femoral chordotonal organ (FECO), trochanteral campaniform sensilla (CS) and the trochanteral hairplate (THP) are restricted to the ipsilateral hemiganglion and possess large dendritic fields in the dorsal and ventral neuropiles. The efferent projections of the fast (Df) and the slow (Ds) depressor motoneurons project into the same areas.

Three groups of trichoid sensilla located on the coxal and trochanteral cuticular walls have central contralateral projections and in one case intersegmental projections. All sensory projections terminate either just lateral of or in the Ventral Association Centre (VAC).

Comparisons with the mechanoreceptors of other insects reveal similar projection patterns for some proprioceptors and non‐homologous central configurations for others.
Serotonin immunoreactivity in the nervous system of the dragonfly nymph
Authors: Longley Alison J. , Longley Roger D.
Published: January 2005

Serotonin‐like immunoreactivity was mapped using an antiserotonin antibody in wholemounts of the ventral nerve cord from dragonfly nymphs (Epitheca sp. and Pachydiplax logipennis). In both species, an immunoreactive cell ventral to each connective tract and an immunoreactive median cell cluster on the ganglion ventral surface were found in the unfused abdominal ganglia. Axon(s) from the median cell cluster branch in the anterior unpaired median nerve. Posterolaterally, in all of the ganglia examined, two or more intensely immunoreactive, bilaterally symmetric pairs of neurons were seen. Comparison of these posterolateral neurons, which appear to be serially homologous, with similar antiserotonin immunoreactive neurons described in other insects suggests that these neruron pairs may have cross‐species homology as well.
Early differences between alternate n blast cells in leech embryo
Authors: Bissen Shirley T. , Weisblat David A.
Published: January 2005

Segmentally interated tissues of the mature leech comprise five distinct sets of definitive progeny that arise from chains of blast cells (m, n, o, p, and q bandlets) produced by five bilateral pairs of stem cells (M, N, O/P, O/P, and Q teloblasts). In each n and q bandlet, two blast cells are needed to generate one set of hemisegmental progeny, and two alternating classes of blast cells (nf and ns, qf and qs) can be distinguished after their first divisions. Furthermore, two distinct subsets of definitive N and Q progeny exist within each hemisegment. Here we first show that there is a fixed correspondence between the class of blast cell and the subset of final progeny: ns cells contribute mainly anteior ganglionic neurons and epidermal cells; nf cells contribute mainly posterior ganglionic neurons, peripheral neurons and neuropil glia; qs cells contribute both ventral and dorsal progeny; and qf cells contribute only dorsal progeny. Second, ablation studies indicate that the two classes of n blast cells do not behave as an equivalence group in the germinal band. Finally, we show that the cycles giving rise to nf and ns blast cells differ. These data suggest that cellular interactions within the germinal band may not be critical in establishing the distinct nf and ns cell fates and that, conversely, differences between the two classes of n blast cells may be established at birth.
Isolation of the heparan sulfate proteoglycans from the extracellular matrix of rat skeletal muscle
Authors: Brandan Enrique , Inestrosa Nibaldo C.
Published: January 2005

We have previously shown that asymmetric collagen‐tailed acetylcholinesterase (AChE) is anchored to the extracellular matrix (ECM) by heparan sulfate proteoglycans (HSPGs). Here we present our studies on the characterization of such PGs from the ECM of rat skeletal muscles. After radiolabling with 35SO4 for 24 h, PGs were extracted from the muscle ECM with 4.0 M guanidine‐HCl containing protease inhibitors. PGs were subsequently isolated using sequential DEAE‐Sephacel chromatography, digestion with chondroitinase ABC, and Sepharose CL‐4B. Two different hydrodynamic size species of HSPGs were found. One type had a Mr of 4–6 × 105 (Kav = 0.25) as estimated by gel chromatography in the presence of 1% SDS and accounted for 75% of the total HSPGs. The other HSPG had a Mr 1.5–2.5 × 105 (Kav = 0.41). The glycosaminoglycan (GAG) side chains (Mr 20,000 and 12,000) were found composed only of heparan sulfate as determined by nitrous acid oxidation and heparitinase treatment. The large‐sized HSPG, which is concentrated in synaptic regions, contains only GAG chains of Mr 20,000, suggesting that each HSPG contains only one kind of heparan sulfate chain in its structure. Our results definitively establish by biochemical criteria that the basement membrane of mammalian skeletal muscle contains HSPGs, the likely matrix receptor for the immobilization of the asymmetric collagen‐tailed AChE at the neuromuscular junction.
Regulation of synaptic frequency: Comparison of the effects of hypoinnervation with those of hyperinnervation in the fly's compound eye
Authors: Fröhlich A. , Meinertzhagen I. A.
Published: January 2005

At the anterior rim of the first optic neuropile, or lamina, of the housefly's (Musca domestica) compound eye, the terminals of photoreceptors (R) innervate postsynaptic neurons in variable numbers to provide a continuous range of natural hypo‐and hyperinnervations. Frequencies of photoreceptor synapses have been measured from quantitative electron microscopy on single sections of the lamina's unit synaptic modules, called cartridges. These are normally innervated by six photoreceptor terminals (6R cartridges). At the lamina's edge hypoinnervated cartridges (2R–5R) are found, whereas hyperinnervated cartridges (7R, 8R) are located at the equator between dorsal and ventral eye halves. In 2R cartridges each presynaptic terminal forms up to 1.5 times the normal, 6R cartridge number of synapses, thereby offsetting the reduced number of terminals and partially conserving the input upon the postsynaptic neurons. Thus the terminals have a reserve synaptogenic capacity never normally revealed. By comparison, terminals in 8R cartridges form about the same numbers of synapses as in “normal” eye regions, so that their postsynaptic neurons have a synaptic input increased by the extra number of terminals. The number of synapses formed between input terminals and target neurons is therefore not fixed but changes as a function of the total receptor terminal complement. The size of a photoreceptor terminal covaries to a certain extent with the number of its presynaptic sites; the spacing density of presynaptic sites over the terminals' surface in a 2R cartridge compared with an 8R cartridge increases far less (only 17%) than the increase in the number of sites (43%). The pair of postsynaptic cell interneurons in each 2R cartridge also shows a decrease in axonal diameter compared with those in 8R cartridges. Thus both the pre‐ and postsynaptic cells show size changes correlated with changes in their synaptic engagement.
Possible interactions of a steroid hormone and neural inputs in controlling the death of an identified neuron in the moth Manduca sexta
Authors: Fahrbach S. E. , Truman J. W.
Published: January 2005

The emergence of the adult Manduca sexta moth is followed by the loss of almost half of this insect's abdominal motoneurons and interneurons (Truman, 1983). This programmed cell death completes the transformation of the nervous system of the caterpillar into that of the moth. The death of these neurons has been previously shown to be a response to an endocrine signal: the decline in ecdysteroids that occurs at the end of metamorphosis (Truman and Schwartz, 1984). Our current research is focussed on the regulation of the fate of a pair of identified motoneurons, the MN‐12 cells, in the third abdominal ganglion. Isolation of this ganglion from anterior parts of the nervous system can prevent the death of these cells at the time when they would normally die in response to the decline in ecdysteroids. Transection of the ventral nerve cord at various levels revealed that the source of this regulatory „death signal”︁ is the fused pterothoracic ganglion and that it is transmitted via the interganglionic connectives. We hypothesize that the factors mediating this effect may act in concert with the ecdysteroid decline to specify the exact time of death for individual neurons.
Compression and expansion without impulse activity in the retinotectal projection of goldfish
Authors: Meyer Ronald L. , Wolcott Leslie L.
Published: January 2005

The capacity of regenerating optic fibers to undergo retinotopic compression and expansion in the absence of impulse activity was tested by eliminating activity with periodic intraocular injections of tetrodotoxin (TTX) during regeneration. To test for compression, the posterior half of tectum was removed and the optic nerve crushed. For expansion, the temporal half of retina was ablated and the nerve also crushed. The projection was then subsequently examined with electrophysiological mapping and autoradiographic tracing.

Like electrically active fibers, silent fibers formed a retinotopically ordered projection that was compressed onto the anterior half tectum. Similarly, TTX‐treated fibers from a nasal half retina formed a retinotopic projection that was expanded across the entire tectum. Except for some enlargement of receptive fields produced by the TTX, the topography was equivalent to that formed by active fibers.

Thus, fibers can apparently maintain relative positions irrespective of absolute tectal position without the benefit of activity‐dependent ordering. This implies the existence of an activity‐independent mechanism for relative positioning that may operate across larger distances than the activity‐dependent ordering responsible for fine topography and ocular dominance columns.
An identified cell is required for the formation of a major nerve during embryogenesis in the leech
Authors: Jellies John , Kristan William B.
Published: January 2005

Investigations of the cues by which axonal growth cones navigate long distances to their targets have revealed the use of a rich and complex diversity of cellular and extracellular information. In the present study we describe one of the most conceptually simple pathfinding cues: a single identified cell in the leech, Hirudo medicinalis, that may guide axons several hundred micrometers to innervate a particular target. One of the stereotyped nerves of H. medicinalis is a “sex nerve” thatprojects from the anterior root of ganglion 6 [SNA (6)] tothe male reproductive structures in the adjacent anterior segment. The pathway for SNA (6) is completely underlainbya single peripheral cell, here called the axonal runway cell (ARC), before axons enter the pathway. The ARC is apparently a nonneuronal cell that stains with a monoclonalantibody that recognizes leech muscle cells. The importance ofthe ARC for establishing SNA (6) was tested by ablating itbefore axons entered the pathway. When the ARC was killed either by physical disruption with a microelectrode, or byphotoablation after filling it with the fluorescent dye Lucifer yellow, SNA(6) always failed to form, whereas all other nerves formed normally. Killing other peripheral cellsin proximity to the ARC did not interfere with SNA(6) formation. Ablation of possible “pioneer neurons” for SNA(6) also did not prevent its formation. These results show that formation of a particular nerve requires onlya single cell to serve as a guide for outgrowingprocesses.
Overlaping taste and tactile maps of the oropharynx in the vagal lobe of the channel catfish, Ictalurus punctatus
Authors: Kanwal Jagmeet S. , Caprio John
Published: January 2005

Microelectrode mapping experiments indicate an ipsilateral representation of the oropharynx and a well‐defined, bilateral input from the proximal portion of the maxillary barbels and snout region within the vagal lobe of channel catfish. The map of the oropharyngeal epithelium is distorted so that the gill arches are rotated through an angle of 90° along the transverse plane, and the dorsally mapped region of the gill rakers is tilted posteriorly in the sagittal plane of the vagal lobe. Multiunit recording studies fail to provide definitive boundaries of adjacently mapped domains of oropharyngeal structures. Gustatory receptive fields of neurons in the vagal lobe correspond to their location on the topological map obtained by tactile stimulation of the oropharyngeal epithelium. A few single unit recordings indicate restricted receptive fields and different response patterns of taste, tactile, and proprioceptive neurons in the vagal lobe of catfish.