Uncoupling protein 2 and aldolase B impact insulin release by modulating mitochondrial function and Ca2+ release from the ER

Uncoupling protein 2 (UCP2), a mitochondrial protein, is known to be upregulated in pancreatic islets of patients with type 2 diabetes (T2DM); however, the pathological significance of this increase in UCP2 expression is unclear. In this study, we highlight the molecular link between the increase in UCP2 expression in β-cells and β-cell failure by using genetically engineered mice and human islets. β-cell-specific UCP2-overexpressing transgenic mice (βUCP2Tg) exhibited glucose intolerance and a reduction in insulin secretion. Decreased mitochondrial function and increased aldolase B (AldB) expression through oxidative-stress-mediated pathway were observed in βUCP2Tg islets. AldB, a glycolytic enzyme, was associated with reduced insulin secretion via mitochondrial dysfunction and impaired calcium release from the endoplasmic reticulum (ER). Taken together, our findings provide a new mechanism of β-cell dysfunction by UCP2 and AldB. Targeting the UCP2/AldB axis is a promising approach for the recovery of β-cell function.

Aristolochic Acid Induces Renal Fibrosis and Senescence in Mice

The kidney is one of the most susceptible organs to age-related impairments. Generally, renal aging is accompanied by renal fibrosis, which is the final common pathway of chronic kidney diseases. Aristolochic acid (AA), a nephrotoxic agent, causes AA nephropathy (AAN), which is characterized by progressive renal fibrosis and functional decline. Although renal fibrosis is associated with renal aging, whether AA induces renal aging remains unclear. The aim of the present study is to investigate the potential use of AAN as a model of renal aging. Here, we examined senescence-related factors in AAN models by chronically administering AA to C57BL/6 mice. Compared with controls, the AA group demonstrated aging kidney phenotypes, such as renal atrophy, renal functional decline, and tubulointerstitial fibrosis. Additionally, AA promoted cellular senescence specifically in the kidneys, and increased renal p16 mRNA expression and senescence-associated β-galactosidase activity. Furthermore, AA-treated mice exhibited proximal tubular mitochondrial abnormalities, as well as reactive oxygen species accumulation. Klotho, an antiaging gene, was also significantly decreased in the kidneys of AA-treated mice. Collectively, the results of the present study indicate that AA alters senescence-related factors, and that renal fibrosis is closely related to renal aging.

OGT Regulates Hematopoietic Stem Cell Maintenance via PINK1-Dependent Mitophagy

O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) is a unique enzyme introducing O-GlcNAc moiety on target proteins, and it critically regulates various cellular processes in diverse cell types. However, its roles in hematopoietic stem and progenitor cells (HSPCs) remain elusive. Here, using Ogt conditional knockout mice, we show that OGT is essential for HSPCs. Ogt is highly expressed in HSPCs, and its disruption induces rapid loss of HSPCs with increased reactive oxygen species and apoptosis. In particular, Ogt-deficient hematopoietic stem cells (HSCs) lose quiescence, cannot be maintained in vivo, and become vulnerable to regenerative and competitive stress. Interestingly, Ogt-deficient HSCs accumulate defective mitochondria due to impaired mitophagy with decreased key mitophagy regulator, Pink1, through dysregulation of H3K4me3. Furthermore, overexpression of PINK1 restores mitophagy and the number of Ogt-deficient HSCs. Collectively, our results reveal that OGT critically regulates maintenance and stress response of HSCs by ensuring mitochondrial quality through PINK1-dependent mitophagy.

Proteomic analysis of exosome-enriched fractions derived from cerebrospinal fluid of amyotrophic lateral sclerosis patients

Exosomes contain many proteins associated with neurodegenerative diseases. To identify new candidate biomarkers and proteins associated with amyotrophic lateral sclerosis (ALS), we performed liquid chromatography-tandem mass spectrometry proteomic analysis of exosome-enriched fractions isolated from cerebrospinal fluid (CSF) of sporadic ALS patients using gel filtration chromatography. Proteomic data revealed that three proteins were increased and 11 proteins were decreased in ALS patients. The protein with the greatest increase in exosome-enriched fractions of CSF derived from ALS was novel INHAT repressor (NIR), which is closely associated with nucleolar function. By immunohistochemical analysis, we found that NIR was reduced in the nucleus of motor neurons in ALS patients. Our results demonstrate the potential utility of our methodology for proteomic analysis of CSF exosomes and suggest that nucleolar stress might play a role in sporadic ALS pathogenesis through the dysfunction of NIR.

Angiotensin II Type 1 Receptor-Associated Protein Regulates Kidney Aging and Lifespan Independent of Angiotensin

Background

The kidney is easily affected by aging‐associated changes, including glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Particularly, renal tubulointerstitial fibrosis is a final common pathway in most forms of progressive renal disease. Angiotensin II type 1 receptor (AT1R)‐associated protein (ATRAP), which was originally identified as a molecule that binds to AT1R, is highly expressed in the kidney. Previously, we have shown that ATRAP suppresses hyperactivation of AT1R signaling, but does not affect physiological AT1R signaling.

Methods and Results

We hypothesized that ATRAP has a novel functional role in the physiological age‐degenerative process, independent of modulation of AT1R signaling. ATRAP‐knockout mice were used to study the functional involvement of ATRAP in the aging. ATRAP‐knockout mice exhibit a normal age‐associated appearance without any evident alterations in physiological parameters, including blood pressure and cardiovascular and metabolic phenotypes. However, in ATRAP‐knockout mice compared with wild‐type mice, the following takes place: (1) age‐associated renal function decline and tubulointerstitial fibrosis are more enhanced; (2) renal tubular mitochondrial abnormalities and subsequent increases in the production of reactive oxygen species are more advanced; and (3) life span is 18.4% shorter (median life span, 100.4 versus 123.1 weeks). As a key mechanism, age‐related pathological changes in the kidney of ATRAP‐knockout mice correlated with decreased expression of the prosurvival gene, Sirtuin1. On the other hand, chronic angiotensin II infusion did not affect renal sirtuin1 expression in wild‐type mice.

Conclusions

These results indicate that ATRAP plays an important role in inhibiting kidney aging, possibly through sirtuin1‐mediated mechanism independent of blocking AT1R signaling, and further protecting normal life span.

Compensatory projections of primary sensory fibers in lumbar spinal cord after neonatal thoracic spinal transection in rats

Complete spinal transection in adult rats results in poor recovery of hind limb function, whereas significant spontaneous recovery can occur following spinal cord transection in rat neonates. The mechanisms underlying the recovery, however, are poorly understood. Recent studies in rodents suggested that the recovery is not due to axonal regeneration, but rather due to reorganization of the neural circuits in the spinal cord below the injury site, including central pattern generators. Few studies have reported histological evidence for changes in the primary sensory fibers or terminals. Thus, in the present study, we transected spinal cords of rats at thoracic level 8 at postnatal day 5. Four weeks after the injury, biotinylated-dextran amine (BDA), an anterograde tracer, was injected into the dorsal root ganglion of the lumbar spinal cord to examine the localization of sensory fibers and their terminal buttons in the spinal cord. BDA-positive axons in the rat spinal cord following neonatal spinal transection (neo ST) were longer than those in sham-operated or normal rats. The number of terminal buttons was also higher in spinal cords of neo ST rats compared with sham-operated or normal rats. These findings suggest that sensory fibers project more strongly and make more synapses following neo ST to compensate for the lack of supraspinal projections.

Retrograde tracing technique for neonatal animals

Tract tracing is a fundamental technique in neuroanatomy for examining fiber connections in the nervous system. After the introduction of horseradish peroxidase 40 years ago, many tracing substances have been used for neuroanatomical studies on various nervous systems. Here, we described retrograde tracing techniques using multiple fluorescent tracers, which make it possible to detect axonal collaterals. This technique is useful to study the development of axonal trajectories, as well as regenerative and compensatory mechanisms of animals that undergo neural damage at early stages.

Islet-1 expression in thoracic spinal motor neurons in prenatal mouse

The LIM homeodomain protein Islet-1, an embryonic marker for motoneurons in the spinal cord, has been reported to be heterogeneously expressed among motoneuron groups in mouse. In the present study, we examined Islet-1 expression in the thoracic and rostral lumbar spinal cord in prenatal mice. In the thoracic spinal cord at embryonic day 12.5 (E12.5) and E13.5, strong Islet-1 immunoreactivity was observed in the lateral group of the ventral horn, whereas weaker immunoreactivity was observed in the ventral group. Strong Islet-1 immunoreactivity was also observed in the intermediolateral area and more medial part of the intermediate zone. In the rostral lumbar spinal cord at E12.5 and E13.5, strong Islet-1 immunoreactivity was observed in the lateral group of the ventral horn, and in the intermediolateral nucleus, whereas weaker immunoreactivity was observed in the ventral, and dorsolateral groups. At E14.5, the number of Islet-1 immunoreactive neurons was reduced in the spinal cord, but the distribution pattern was similar to that at E12.5 and E13.5. At E15.5, Islet-1 immunoreactivity was almost completely confined to the intermediolateral area. Some weakly immunoreactive neurons were observed in the ventral horn. The findings of the present study indicated that Islet-1 expression at embryonic stages differs among the motoneuron groups in the thoracic and rostral lumbar spinal cord.

The chelonian spinal nerve ganglia are a conglomerate of the spinal nerve ganglia proper and the sympathetic ganglia

A tyrosine hydroxylase-immunoreactive cell mass is found in the caudal portion of the dorsal nerve ganglion of the red-eared slider, Trachemys scripta elegans. The ganglion appears as a flat oval structure in the horizontal plane, where the major axis runs latero-medially, and the minor axis rostro-caudally in the ventral view. A communicating branch to the sympathetic chain diverges from the top of each tubercle which lies on the caudo-lateral side of the ganglion. A tyrosine hydroxylase- immunoreactive cell mass is located in this tubercle. This cell mass exists in both sexes. Tyrosine hydroxylase-immunoreactive cells, that contain Nissl bodies in cytoplasm and are enveloped by the satellite cells, are multipolar and their neural processes are distributed in a distal direction into the spinal nerve. The range of distribution of the synapsin I-immunoreactive structures is limited to the tyrosine hydroxylase-immunoreactive cell mass. The chelonian dorsal spinal nerve ganglia are a conglomerate of the spinal nerve ganglion proper and the sympathetic ganglion.

Differential Islet-1 expression among lumbosacral spinal motor neurons in prenatal mouse

Onuf's nucleus in the lumbosacral spinal cord, comprising somatic motoneurons that innervate the pelvic floor muscles via the pudendal nerve, shares some characteristics with the autonomic preganglionic neurons and functions in coordination with the autonomic nervous system. In mouse, neurons projecting to the urethral sphincter and ischiocavernosus muscles form the dorsolateral (DL) nucleus at the caudal lumbar levels, whereas neurons projecting to the limb and hip joint muscles comprise the retrodorsolateral and ventral nucleus, as well as the DL nucleus at the rostral lumbar levels. The results of the present study in mouse revealed that the expression pattern of a LIM homeodomain protein Islet-1, an embryonic marker for motoneurons in the spinal cord, was different among motoneuronal groups at the prenatal stage (embryonic days 13.5-15.5); the highest expression was observed in the DL at the caudal lumbar cord, whereas there was little expression in the lateral part of the rostral DL. Islet-1 expression was also observed in the parasympathetic preganglionic neurons at the sacral spinal cord. These findings provide evidence that the DL neurons at the caudal lumbar cord, corresponding to Onuf's nucleus, are chemically distinct among the motoneuronal groups at the prenatal stages. This differential Islet-1 expression among the motoneuronal groups suggests that Islet-1 not only leads to a motoneuronal lineage, but also to the differentiation of motoneuronal subsets in the lumbosacral spinal cord.

Blood Flow in Snake Infrared Organs: Response-Induced Changes in Individual Vessels

OBJECTIVE

In the past the microkinetics of blood flow in the infrared pit organs of pit vipers has been studied with Doppler flowmetry using various infrared stimuli such as a human hand or soldering iron at various distances, lasers of various wavelengths, etc. Quick-acting variations in blood flow were recorded, and interpreted as a cooling mechanism for avoiding afterimage in the infrared receptors. However, the Doppler measurements provided only the summation of blood flow in a number of vessels covered by the sensing probe, but did not give data on flow in individual vessels.

METHODS

In the present work the authors introduced into the bloodstream of Gloydius and Trimeresurus pit vipers fluorescent microspheres labeled with fluorescein isothiocyanate (FITC) contained in a solution of FITC-dextran in physiological saline. They observed the passage of the microspheres through individual pit organ vessels with a fluorescent microscope to which was attached a high-speed video camera and image intensifier. Output of the camera was recorded before, during, and after stimulus with a 810-nm diode laser. Recording was done at 250 frames/s on high-speed video apparatus and downloaded to a hard disk. Disk files were loaded into proprietary software and particles were tracked and average velocities calculated. The data were then tested for significance by ANOVA with post hoc tests.

RESULTS

A significant (p<.05) increase in blood velocity was found at the focal point of the stimulus laser, but not anywhere removed from this point. Proximal severing of the pit sensory nerves caused degeneration of the pit receptor terminals and abolished stimulus-induced blood flow changes, but did not affect normal blood flow.

CONCLUSIONS

The authors conclude that the receptors themselves are directly and locally controlling the smooth muscle elements of the blood vessels, in response to heating of the receptors by infrared radiation. They speculate that the heavy vascularization constitutes a cooling system for the radiation-encoding receptors, and further that the agent of control may be a volatile neuromediator such as nitric oxide.

Prenatal development of transient receptor potential vanilloid 1-expressing primary sensory projections to sacral autonomic preganglionic neurons

The visceral reflexes of the pelvic organs are mediated by connections between primary afferents innervating the pelvic organs and parasympathetic preganglionic neurons in the intermediolateral column of the sacral spinal cord. The present immunohistochemical study revealed many varicosities expressing transient receptor potential vanilloid 1 (TRPV1) that were closely apposed to the preganglionic neuronal perikarya at embryonic day 16 in mice. Many, but not all, varicosities expressing TRPV1 in the intermediolateral column were also immunopositive for calcitonin gene-related peptide. In contrast, no nerve fibers expressing TRPV1 projected to the sympathetic preganglionic cell column in the lumbar spinal cord in prenatal stages. The results of the present study raised the possibility that the primary afferents transmit signals elicited by the activation of TRPV1 receptors to the sacral parasympathetic preganglionic neurons. Thus, the functional circuit for pelvic spinal reflexes, such as micturition induced by urine influx, might develop in the prenatal stages in mice.

Differential development of TRPV1-expressing sensory nerves in peripheral organs

In mouse ontogeny, neurons immunoreactive for transient receptor potential vanilloid receptor 1 (TRPV1) were observed primarily in the dorsal root ganglia (DRG) at embryonic day 13 (E13). In the embryonic period, the number of TRPV1(+) neurons decreased, but then gradually increased postnatally. Some of TRPV1(+) neurons were also immunoreactive for calcitonin gene-related peptide (CGRP). At postnatal day 7 (P7), 66% of CGRP(+) neurons were TRPV1(+), and 55% of TRPV1(+) neurons were also CGRP(+) in the L4 DRG. In the peripheral organs, TRPV1-immunorective nerve fibers were transiently observed in the skin at E14. They were also observed in the urinary tract at E14, and in the rectum at E15. Many TRPV1(+) nerve fibers in these organs were also CGRP(+). At P1, TRPV1(+) nerve fibers were observed in the respiratory organs, and to a lesser extent in the stomach, colon, skin, and skeletal muscles. The number of TRPV1(+) nerve fibers on each organ gradually increased postnatally. At P7, TRPV1(+) nerve fibers were also observed in the small intestine and kidneys. The percentage of total TRPV1(+) nerve fibers that co-localized with CGRP was greater in most organs at P7 than at P1. The present results indicate that TRPV1 expression on peripheral processes differs among organs. The differential time course of TRPV1 expression in the cell bodies might be related to the organs to which they project. Co-localization of TRPV1 with CGRP on nerve fibers also varies among organs. This suggests that the TRPV1-mediated neuropeptide release that occurs in certain pathophysiologic conditions also varies among organs.

Medullary efferent and afferent neurons of the facial nerve of the pit viper Gloydius brevicaudus

For the purposes of comparative anatomy, we used tracer techniques and immunohistochemistry to study the facial nerve in the pit viper Gloydius brevicaudus and obtained much new data applicable to the function of this nerve in snakes and, in particular, pit vipers. We were able to identify the superior salivatory nucleus in these snakes. Preganglionic fibers from this nucleus pass along the palatine nerve and an anterior communicating branch to reach the pterygopalatine ganglion attached to the deep branch of the trigeminal maxillary nerve. The palatine nerve also contains general somatic afferents and a very few special visceral afferents from some taste buds on the palate. In the mandibular direction, preganglionic fibers from the superior salivatory nucleus join special visceral efferents from the motor nucleus in the hyomandibular nerve, from which they pass into the chorda tympani to course together for a short distance. The special visceral efferents branch off outside the cranium, and the preganglionic fibers continue on to join the trigeminal mandibular nerve to project to small ganglia within the mandible. The chorda tympani also contains general somatic afferents from the mandibular region but no special visceral afferents. This is the first time that the superior salivatory nucleus and its adjuncts have been identified in a snake. The chorda tympani of these snakes is also distinguished from the mammalian condition by lacking any special visceral afferents and by branching outside the cranium.

Prenatal development of peptidergic primary afferent projections to mouse lumbosacral autonomic preganglionic cell columns

To examine the prenatal development of spinal visceral reflexes, primary sensory nerve fibers immunoreactive for calcitonin gene-related peptide (CGRP) were examined in the spinal cord, particularly in the autonomic preganglionic nuclei of mouse embryos. On embryonic day 16 (E16), CGRP-immunoreactive fibers were first observed in the sacral intermediolateral nucleus (IML) of the parasympathetic division as well as in the lumbar central autonomic nucleus (CA) of the sympathetic division, where they appeared in proximity to preganglionic neuronal perikarya immunoreactive for choline acetyltransferase or nitric oxide synthase. Most of the CGRP-immunoreactive varicosities were negative for substance P. Substance P-immunoreactive varicosities were scattered in these nuclei, but no appositions were seen on the preganglionic neuronal perikarya. On E18, CGRP-immunoreactive fibers were more abundant in the sacral IML and the lumbar CA. Co-expression of substance P and CGRP was frequently observed in the varicosities very close to the preganglionic neuronal perikarya on E18. CGRP-immunoreactive fibers were also observed in the lumbar IML on E18, although significantly fewer were found in this nucleus compared with the sacral IML. In contrast to the upper lumbar level, no fibers immunoreactive for CGRP were observed in the IML at the thoracic level. These results suggest that peptidergic primary sensory fibers grow to project to the selective targets of autonomic preganglionic neurons during the embryonic period. The potential direct connections between the peptidergic primary sensory fibers and preganglionic neurons innervating the pelvic viscera might provide a circuit for spinal visceral reflexes active in embryos.

The microvasculature of python pit organs: morphology and blood flow microkinetics

Boid snakes have infrared sensing pits that resemble crotaline pits in electrophysiological function and ultrastructure, but differ in gross morphology, number, and location: boids have three or more simple pits in the labial scales vs a single facial pair with more complex morphology in the crotalines. We studied the morphology of the capillary bed and the microkinetics of blood flow in a boid snake, the ball python, Python regius, and compared them with the already known condition in crotalines. We used a Doppler blood flow recorder in conjunction with an electrocardiograph to measure blood flow and heartbeat, and resin casts, transmission electron microscopy, and laser confocal microscopy to study capillary morphology. Blood flow in response to infrared stimulus was virtually identical in the two taxa, but the morphology of the capillary bed differed drastically. In the ball python pits, the capillary bed consisted of a forest of vertically oriented loops with a characteristic dome at the top in contact with the receptor layer of the fundus. Immunohistochemical staining showed pericytes constricting the capillaries and domes with smooth muscle alpha-actin-labeled processes. Since latency of response was as short as 1 ms, the capillaries were apparently responding under local control to provide both nutrition and cooling to the heat-sensitive receptors. We concluded that mitochondria-filled receptors provided with a swiftly responding cooling system were nature's most efficient way of attaining infrared imaging.

Central projections of thoracic splanchnic and somatic nerves and the location of sympathetic preganglionic neurons in Xenopus laevis

The central and peripheral organization of thoracic visceral and somatic nervous elements was studied by applying dextran amines to the proximal cut ends of the thoracic splanchnic and somatic nerves in Xenopus laevis. Many labeled dorsal root ganglion cells of visceral afferents, and all somatic afferents, were located in a single ganglion of one spinal segment, and the two types of cells were distributed topographically within the ganglion. The labeled sympathetic preganglionic neurons were located predominantly in the same area of the thoracic spinal gray as in other frogs and in mammals. The labeled visceral afferents projected to Lissauer's tract and the dorsal funiculus. The visceral fibers of the tract ascended to the level of the subcerebellar area, supplying collateral branches to the lateral one-third of the dorsal horn and to the area of brainstem nuclei, including lateral cervical and descending trigeminal nucleus, and descended to the filum terminale. The visceral fibers of the dorsal funiculus were distributed to the dorsal column nucleus and the solitary tract. A similar longitudinal projection was also seen in the somatic afferents. The dual central pathway of thoracic primary afferents in the anuran spinal cord is a property held in common with mammals, but the widespread rostrocaudal projection through Lissauer's tract may be a characteristic of the anuran central nervous system. In frogs, the direct transmission of primary afferent information to an extremely wide area of the central nervous system may be important for prompt assessment of environmental factors and control of body functions.

Distribution of myelinated and unmyelinated nerve fibers and their possible role in blood flow control in crotaline snake infrared receptor organs

We used transmission electron microscopic montages to examine the composition of nerve bundles serving the infrared pit organs of two species of crotaline snakes, Agkistrodon blomhoffii and A. brevicaudus. In the three main bundles, the myelinated fibers totaled 2,200-3,700, and unmyelinated fibers 2,400. We also discovered for the first time two accessory bundles composed almost entirely of unmyelinated fibers running alongside the main bundles, containing an average total of 3,300 unmyelinated fibers vs. an average of 10 myelinated fibers. Thus, the average total of unmyelinated fibers was nearly twice that of myelinated fibers. To study the nature of the unmyelinated fibers, we did double staining immunohistochemistry with antibodies for substance P (SP) and vasoactive intestinal polypeptide (VIP) in combination with and without capsaicin pretreatment. SP and VIP immunoreactive varicose fibers ran straight toward the center of the pit membrane in parallel with arterioles and venules, and also formed a dense network around the periphery of the membrane. There were three types of fibers: fibers containing only SP, fibers containing only VIP, and fibers containing both peptides. SP-only fibers were distributed singly throughout the pit membrane and in small bundles around the periphery. SP+VIP fibers were distributed sparsely in the pit membrane and around its periphery. VIP-only fibers were distributed throughout the pit membrane and were of smaller diameter than SP and SP+VIP fibers. After treatment with capsaicin, most of the three types of varicose fibers disappeared from the central part of the pit membrane, but those around the periphery remained unaffected. The capsaicin-sensitive fibers may be unmyelinated sensory types, and the unaffected ones may be autonomic nerve fibers.

Choline acetyltransferase immunoreactive sympathetic ganglion cells in a teleost, Stephanolepis cirrhifer

The present study showed neurons immunoreactive for choline acetyltransferase (ChAT) in the cranial sympathetic ganglia lying close to the trigeminal-facial nerve complex of the filefish. In these ganglia, less than 1% of ganglion cells were positive for choline acetyltransferase. Choline acetyltransferase-positive neurons were significantly larger than the randomly sampled neurons in this ganglion. The majority of choline acetyltransferase-positive neurons were negative for tyrosine hydroxylase, but many of them were positive for galanin (GAL). Some neurons were positive for both choline acetyltransferase and tyrosine hydroxylase, but these neurons were rarely immunoreactive for dopamine beta hydroxylase, suggesting that they are not adrenergic. In the cranial sympathetic ganglia and the celiac ganglia, many nerve fibers immunoreactive for galanin were seen, and varicose terminals were in contact selectively with neurons negative for both choline acetyltransferase and tyrosine hydroxylase, but not with those positive for choline acetyltransferase or tyrosine hydroxylase. Nerve fibers immunoreactive for choline acetyltransferase were found to be present in contact with the deep layer of chromatophores, which was observed only in the labial region. These results suggest that cholinergic postganglionic neurons are present in the filefish cranial sympathetic ganglia, and that they also contain galanin. As few cholinergic sympathetic neurons express tyrosine hydroxylase and none express dopamine beta hydroxylase, they are unlikely to synthesize noradrenaline or adrenaline.

Monoaminergic and peptidergic axonal projections to the vagal motor cell column of a teleost, the filefish Stephanolepis cirrhifer

In an immunohistochemical study, the vagal motor nucleus of a teleost, the filefish Stephanolepis cirrhifer, could be divided into a rostral part and a caudal part, and the former into a dorsolateral group and a ventromedial group. The dorsolateral group consisted of neurons immunoreactive for calcitonin gene-related peptide, whereas the ventrolateral-caudal group was negative for calcitonin gene-related peptide. The latter group was retrogradely labeled after dextran amine injection to the visceral ramus of the vagus nerve, suggesting that it is a general visceral efferent column, made up of parasympathetic preganglionic neurons, whereas the dorsolateral rostral group is a special visceral efferent column. In the general visceral efferent column, a dense concentration of nerve fibers immunoreactive for serotonin, tyrosine hydroxylase, cholecystokinin-8, and substance P, and a small number of fibers immunoreactive for neuropeptide Y was observed. Perikarya in contact with varicose terminals immunoreactive for these substances were frequently seen. In contrast, in the special visceral efferent column, only a moderate concentration of neuropeptide Y-immunoreactive nerve fibers and a sparse distribution of fibers immunoreactive for tyrosine hydroxylase were observed. Perikarya in contact with varicose terminals immunoreactive for these substances were rare. These results suggest that the vagal parasympathetic preganglionic neurons might receive multiple inputs of monoaminergic and peptidergic fibers involved in the regulation of the visceral organs. On the other hand, monoaminergic and peptidergic afferent fibers might be of much less significance in the activity of the special visceral efferent component of the vagus nerve.

Catecholaminergic innervation of the sympathetic preganglionic cell column of the filefish Stephanolepis cirrhifer

Nerve fibers immunoreactive for enzymes synthesizing catecholamines were examined in the central autonomic nucleus, a column of sympathetic preganglionic neurons, in the filefish Stephanolepis cirrhifer. Varicose nerve fibers immunoreactive for tyrosine hydroxylase were densely distributed in the rostral part, sometimes in contact with perikarya but were sparse in the caudal part of this nucleus. Fluorescent double labeling distinguished noradrenergic nerve fibers immunoreactive for both tyrosine hydroxylase and dopamine beta hydroxylase, and dopaminergic fibers immunoreactive only for tyrosine hydroxylase. In the brainstem, catecholaminergic neurons were observed in the locus coeruleus, the caudal dorsomedial reticular zone of the medulla, and the area postrema. Double labeling of tyrosine hydroxylase and dopamine beta hydroxylase showed that the neurons in the locus coeruleus were all noradrenergic, and those in the caudal dorsomedial medulla were mostly noradrenergic, whereas the area postrema contained both noradrenergic and dopaminergic neurons. No catecholaminergic neurons were found in the ventral region of the brainstem. After application of DiI to the central autonomic nucleus, retrogradely labeled neurons were seen in the caudal dorsomedial medulla but not in the locus coeruleus or the area postrema. These findings suggest that the sympathetic preganglionic neurons of the filefish may receive noradrenergic axonal projections from neurons in the caudal dorsomedial medulla. In the light of previous studies, inputs of these catecholaminergic fibers to the central autonomic nucleus may be involved in regulation of sympathetic activity of peripheral organs, together with serotoninergic and peptidergic inputs to this nucleus.

Selective projections of cholecystokinin-8 immunoreactive fibers to galanin immunoreactive sympathetic preganglionic neurons in a teleost, Stephanolepis cirrhifer

In the cellular column of sympathetic preganglionic neurons (SPNs) of the filefish Stephanolepis cirrhifer, neurons containing galanin (GAL) form a distinct population projecting specifically to non-adrenergic postganglionic neurons in the celiac and cranial sympathetic ganglia. The present study showed that virtually all of the GAL-immunopositive SPNs made contact with many nerve terminals immunopositive for cholecystokinin octapeptide (CCK-8). GAL-negative preganglionic neurons made contact with only 26% of this type of nerve terminal; CCK-8-immunopositive nerve fibers appeared to project selectively to GAL-immunopositive SPNs with projections to specific targets. The CCK-8-positive nerve fibers might be of primary sensory origin, and participate in the visceral reflexes.

Differential distribution of nerve terminals immunoreactive for substance P and cholecystokinin in the sympathetic preganglionic cell column of the filefish Stephanolepis cirrhifer

Immunoreactivity for substance P and cholecystokinin-8 was examined in the nerve fibers in the central autonomic nucleus, a cell column for sympathetic preganglionic neurons, in the filefish Stephanolepis cirrhifer. Substance P-immunoreactive fibers were distributed throughout the entire rostrocaudal extent, but were more abundant in the caudal part of the column, where substance P-immunoreactive varicosities sometimes made contacts with the sympathetic preganglionic neurons. Cholecystokinin-8-immunoreactive fibers were found almost entirely in the rostral part of the column, where a dense network of varicosities was in close apposition to a considerable number of the sympathetic preganglionic neurons. Double labeling immunohistochemistry showed that substance P fibers and cholecystokin-8 fibers were entirely different, and distinct from serotonin-immunoreactive fibers. By using immunoelectron microscopy, synaptic specialization was sometimes observed between the dendrites of preganglionic neurons and varicosities immunoreactive for substance P and cholecystokinin-8. Substance P- and cholecystokinin-8 fibers were seen from the descending trigeminal tract, through the dorsolateral funiculus and the ventral portion of the dorsal horn, to the central autonomic nucleus. After colchicine treatment, substance P-immunoreactive perikarya were found in the cranial and spinal sensory ganglia. These results suggest that the sympathetic preganglionic neurons of the filefish receive innervation by substance P fibers and cholecystokinin fibers, and that the former might be of primary sensory origin. Topographical distribution of cholecystokinin-8-immunoreactive terminals in the central autonomic nucleus along the rostrocaudal extent might underlie the differential regulation of sympathetic activity via a distinct population of sympathetic preganglionic neurons.

Ultrastructure of the capillary pericytes and the expression of smooth muscle alpha-actin and desmin in the snake infrared sensory organs

The infrared sensory membranes of pit organs of pit vipers have an extremely rich capillary vasculature that forms many vascular loops, each serving a small number of infrared nerve terminals. We clarified the ultrastructure of capillary pericytes in the pit membranes by scanning and transmission electron microscopy, and examined the immunoreactivity in their cytoplasm to two contractile proteins: smooth muscle alpha-actin (SM alpha-actin) and desmin. The capillary pericytes had two major cytoplasmic processes: thickened primary processes that radiate to embrace the endothelial tube and flattened secondary processes that are distributed widely on the endothelium. Coexpression of SM alpha-actin and desmin was observed in the pericytes of entire capillary segments, and SM alpha-actin was characterized by prominent filament bundles directed mainly at right angles to the capillary long axis. This expression pattern was different from that of capillary pericytes of the scales, where SM alpha-actin was expressed diffusely in the cytoplasm. In a series of electron microscopic sections, we often observed the pericyte processes depressing the endothelial wall. We also observed a close relationship of the pericytes with inter-endothelial cell junctions, and pericyte processes connected with the endothelial cells via gap junctions. From these findings, we surmised that capillary pericytes in the pit membrane have a close functional relationship with the endothelium, and through their contractile and relaxing activity regulate capillary bloodflow to stabilize production of infrared nerve impulses.

Nervous control of blood flow microkinetics in the infrared organs of pit vipers

The pit organ of pit vipers contains a membrane which serves as an infrared retina, processing infrared information by the degree to which the temperature of trigeminal nerve receptors (terminal nerve masses) is raised. The receptors are arranged in a monolayer array within the pit membrane and irrigated by a capillary network which both supplies energy to the terminal nerve masses and serves as a heat exchange mechanism. This mechanism maintains the receptors at a stable temperature level to increase or decrease their sensitivity and to reduce to a minimum the afterimage effect of a moving stimulus. We used a Doppler laser blood flow meter to measure the local changes in blood flow in response to a point heat source (a small soldering iron) and to direct stimuli (red and infrared lasers). Resection of any one of the trigeminal A-delta fiber trunks innervating the pit membrane abolished blood flow response in the area innervated, but resection of the main trunk between the primary neurons and the medulla left the response intact. In addition to the A-delta fibers the pit membrane contains autonomic and sensory C-fiber innervation, but preganglionic resection of parasympathetic neurons, and chemical blocking of postganglionic fibers with atropine and capsaicin had no influence on the blood flow changes. Therefore, on the basis of the rapid response time and the similarity of the blood flow curves to electrophysiological recordings from the receptors, we surmised that all blood flow changes were due to a vasomotor reaction, modulated by the terminal nerve masses directly, resulting in a change in local heat capacity that cools the stimulated receptors back to a basal temperature.

Differential innervation of the goldfish tonic red muscles and twitch white muscles by neuropeptide-immunoreactive motoneurons

Neuropeptides in the motor nerves innervating the red and white muscles of the goldfish Carassius auratus were examined. In the tonic red muscles, varicose nerve endings immunoreactive for both calcitonin gene-related peptide and substance P were found spread over the surface of the muscle fibers, but in the twitch white muscles only scattered nerve endings immunoreactive for calcitonin gene-related peptide were found. At the electron microscopic observation, dense electron products immunoreactive for calcitonin gene-related peptide and for substance P (SP) were detected in the motor nerve endings making synapses on the muscle fibers of the red muscles. In the spinal cord, all of the motor neurons showed immunoreactivity to calcitonin gene-related peptide, but the motor neurons immunoreactive for substance P were restricted to the ventrolateral group that has been shown to project predominantly to the red muscles. These results suggest that the motor neurons innervating the red and white muscles of the goldfish are distinct in their neuropeptide content. The present study also raises the possibility that SP might be related to the unique physiological properties of the tonic type red muscles, probably by direct binding to the acetylcholine receptors.

Distinct localization and target specificity of galanin-immunoreactive sympathetic preganglionic neurons of a teleost, the filefish Stephanolepis cirrhifer

Immunoreactivity for galanin was examined in the sympathetic preganglionic neurons in the spinal cord, adrenal glands, sympathetic ganglia, and some sensory ganglia of the filefish Stephanolepis cirrhifer. Galanin-immunoreactive neurons were found only in the rostral part, but not in the caudal part of the central autonomic nucleus (a column of sympathetic preganglionic neurons of teleosts). Many galanin-immunoreactive nerve terminals were found in contact with neurons in the celiac ganglia and the cranial sympathetic ganglia on both sides of the body. Most neurons encircled by galanin-immunoreactive nerve fibers were negative for tyrosine hydroxylase. Galanin-immunoreactive nerve fibers were very sparse in the spinal sympathetic paravertebral ganglia. No galanin-immunoreactive nerve fibers were found in the adrenal glands. No sensory neurons of the trigeminal, vagal, or spinal dorsal root ganglia were positive for galanin-immunoreactivity. These results suggest that galanin-immunoreactive sympathetic preganglionic neurons have distinct segmental localization and might project specifically to a population of non-adrenergic sympathetic postganglionic neurons in the celiac and cranial sympathetic ganglia.

Serotonin-immunoreactive axons in the cell column of sympathetic preganglionic neurons in the spinal cord of the filefish Stephanolepis cirrhifer

Serotonin-immunoreactive axonal components were observed in the central autonomic nucleus (CAN), a cell column of sympathetic preganglionic neurons in the rostral spinal cord of the filefish Stephanolepis cirrhifer. Serotonin-positive axonal varicosities were seen around neuronal perikarya through the whole rostrocaudal extent of the CAN, although their distribution pattern in the rostral CAN was different from that in the caudal CAN. Electron microscopically, serotonin-positive axonal varicosities were found to make axodendritic and axosomatic synapses on CAN neurons. Many serotonin-positive neuronal cell bodies were seen in the raphe nuclei in the lower brainstem, whereas only a few were found in the spinal cord. Thus most of serotoninergic axons within the CAN were considered to originate from the raphe nuclei in the lower brainstem.

Nitric oxide synthase in the glossopharyngeal and vagal afferent pathway of a teleost, Takifugu niphobles. The branchial vascular innervation

To examine the presence of nitric oxide synthase (NOS) in the sensory system of the glossopharyngeal and vagus nerves of teleosts, nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) activity and immunoreactivity for NOS were examined in the puffer fish Takifugu niphobles. The nitrergic sensory neurons were located in the ganglia of both the glossopharyngeal and the vagal nerves. In the vagal ganglion, positive neurons were found in the subpopulations for the branchial rami and the coelomic visceral ramus, but not for the posterior ramus or the lateral line ramus. In the medulla, nitrergic afferent terminals were found in the glossopharyngeal lobe, the vagal lobe, and the commissural nucleus. In the gill structure, the nitrergic nerve fibers were seen in the nerve bundles running along the efferent branchial artery of all three gill arches. These fibers appeared to terminate in the proximal portion of the efferent filament arteries of three gill arches. On the other hand, autonomic neurons innervating the gill arches were unstained. These results suggest that nitrergic sensory neurons in the glossopharyngeal and vagal ganglia project their peripheral processes through the branchial rami to a specific portion of the branchial arteries, and they might play a role in baroreception of this fish. A possible role for nitric oxide (NO) in baroreception is also discussed.

Microvasculature of crotaline snake pit organs: possible function as a heat exchange mechanism

The infrared sensory membranes of the pit organs of pit vipers have an extremely rich capillary vasculature, which has been noted passim in the literature, but never illustrated or studied in detail. We rendered the pit vasculature visible in various ways, namely, by microinjection of India ink, by a combination of ink and succinate dehydrogenase staining, and by making resin casts for scanning electron microscope study. We also used transmission electron microscopy for identifying the types (arterioles, venules, capillaries) of blood vessels. Then we compared the pit vasculature with that of the retina and the dermis. Good visualization of the vasculature was obtained with both ink and resin injection. Arterioles, venules, and capillaries could be distinguished with all methods used. The monolayer vasculature was denser in the pit membrane than in the retina or skin. Each loop of the network enclosed a small number of infrared receptors so that all receptors were in contact with a capillary on at least one side. The forward-looking areas of the pit had a denser network than side-looking areas. Since infrared rays cause nerve impulses by raising the temperature of individual receptors, the capillary network functions not only as a supplier of energy but also as a cooling mechanism to reduce afterimages. Thus the denser network in the forward-looking areas causes these areas to be more sensitive and have better image resolution than the rest of the membrane.

Gastrin/CCK-ergic innervation of cutaneous mucous gland by the supramedullary cells of the puffer fish Takifugu niphobles

The supramedullary cells (SMCs) are spinal neurons lying at the dorsal surface of teleosts. In the present study, we examined whether the SMCs of the puffer fish (Takifugu niphobles) might express gastrin/cholecystokinin-immunoreactivity, as observed in some other teleosts. All the SMCs were immunoreactive for gastrin/cholecystokinin. On the other hand, many immunoreactive varicose nerve fibers were also found terminating in the mucous glands in the skin. In addition, immunoreactive fibers were sparsely distributed in the epidermal layer. No neuronal cells other than the SMCs showed gastrin/cholecystokinin-immunoreactivity centrally or peripherally. The results suggest that gastrin/cholecystokinin-immunoreactive axons in the cutaneous mucous glands and epidermal layer are axons of the SMCs. In view of the present findings, the possible nature of SMCs was discussed.

NADPH-diaphorase activity in the vagal afferent pathway of the dogfish, Triakis scyllia

Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity was examined in the cranial sensory ganglia and brainstem of the banded dogfish, Triakis scyllia. Positive neurons were found in the vagal sensory ganglion projecting to the coelomic organs, but not in those projecting to the gills or the lateral line organs. Nerve terminals in the vagal lobe were also positive. No positive neurons were found in the glossopharyngeal, facial, or trigeminal sensory ganglia. These results suggest that use of nitric oxide in the vagal sensory transmission from the coelomic organs may have been maintained in the evolutionary process from fish to mammals.

Ultrastructure of the crotaline snake infrared pit receptors: SEM confirmation of TEM findings

BACKGROUND

Crotaline snakes possess a pair of infrared-sensing pit organs that aid the eyes in the detection and apprehension of prey. The morphology of the receptors in the pit organs has been studied by light and transmission electron microscopy, and the ultrastructure of the receptors has been inferred from the results of this work. But this theoretical reconstruction has never been confirmed by any kind of three-dimensional imaging.

METHODS

We treated the receptor-containing membrane of the pit organs with potassium hydroxide to remove collagen and expose the receptors, which we then viewed by scanning electron microscopy.

RESULTS

We were able to obtain three-dimensional views of all structures previously reported to exist within the receptor-containing membrane: terminal nerve masses formed from free nerve endings, supporting Schwann cells within the nerve masses, unmyelinated and myelinated nerve fibers, a capillary bed, and vacuole cells.

CONCLUSIONS

By providing the first three-dimensional views of the infrared receptors, we have confirmed that previous theoretical reconstructions of the receptors were substantially correct and have provided new evidence of the spatial arrangement of the receptors in a monolayer array.

Gastric cancer diagnosed by biopsy of the uterine cervix

Biopsy of the uterine cervix from a 46-year-old woman who suffered from epigastric pain and weight loss showed metastatic adenocarcinoma. The primary site of the tumor was the stomach. At laparotomy, disseminated adenocarcinoma on the peritoneum and Krukenberg's tumor in the right ovary were found. A palliative partial gastrectomy, resection of the right ovary, and postoperative chemotherapy were performed. The possible mechanism of metastasis of extragenital cancer to the uterus is discussed.

Effects of glucagon on myoelectrical activity of the stomach of conscious and anesthetized dogs

Effects of glucagon on gastric electrical and mechanical activities recorded by means of a chronically implanted suction electrode and a force strain gauge transducer were examined in conscious and anesthetized dogs. Glucagon (1-10 micrograms/kg) induced inhibition of gastric electrical activity together with mechanical activity in conscious dogs. The plasma glucagon level following exogenous glucagon administration which induced the inhibitory effects on electrical and mechanical activities was over 5 ng/ml. alpha- and beta-adrenoceptor blocking agents did not significantly alter the inhibitory effect of glucagon. Changes in plasma concentrations of glucose, cAMP, insulin, gastrin and catecholamines after glucagon administration were not correlated with the inhibitory action of glucagon on the gastric electrical and mechanical activities. Glucagon at higher concentrations (10(-6) -5 x 10(-6) g/ml) did not produce appreciable changes in motility of the canine gastric strips in vitro. In an anesthetized condition, the inhibitory action of glucagon was completely abolished. Results indicate that exogenously applied glucagon possibly acts directly on the central nervous system, and thus resulted in the inhibition of the gastric electrical and mechanical activities.

Validity of long-term recordings of electrical activity of the stomach by chronically implanted monopolar suction electrodes in the conscious dog

Twenty-four-hour changes in gastric electrical activity were recorded in conscious dogs by means of chronically implanted monopolar suction electrodes. The electrical activity consisted of an initial potential followed by a second potential with various amplitude and duration depending upon the time after feeding. Amplitude of the second potential was well correlated to magnitude of each contraction. Characteristics of the electrical activity were qualitatively similar to those obtained with the intracellular microelectrode technique. 24-hour changes in cycles of electrical activity were divided into four phases; the first phase (lasting for 2--4 hours after feeding) characterized by a significant decrease in the cycle, the second phase (until 6--8 hours after feeding) in which the cycle gradually increased, the third phase (10--16 hours after feeding), and the last phase (lasting to the next meal), showing a marked variation in the cycle. These changes occurred irrespectively at the time of feeding and were consistent day after day as long as the animals were held on a constant feeding schedule. The recording method was suitable for recording gastric electrical activity which would provide more precise informations occurring in the intracellular electrical activity of the stomach in a long period of time under a physiological condition.