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At least 217 records · Page 12Linked to original sources
PubMed1994

Coexistence of substance P, neuropeptide Y, VIP, and CGRP in the nerve fibers of the carotid labyrinth of the bullfrog, Rana catesbeiana: a double-labelling immunofluorescence study in combination with alternate consecutive sections.

Double immunohistochemical staining with rhodamine- and fluorescein isothiocyanate (FITC)-conjugated antisera revealed the coexistence of substance P (SP) and neuropeptide Y (NPY), and SP and calcitonin gene-related peptide (CGRP) in most nerve fibers in the intervascular stroma of the carotid labyrinth of the bullfrog, Rana catesbeiana, although there were a few fibers which showed only SP- or NPY-immunoreactivity. Approximately one third of SP-immunoreactive fibers also showed coexistence with vasoactive intestinal polypeptide (VIP)-immunoreactivity, and a few fibers contained VIP without SP. The combination of the double immunofluorescence technique and alternate consecutive sections further demonstrated the possible coexistence of SP, VIP, NPY, and CGRP. This coexistence of four different peptides in the same nerve fibers was proved by the following two evident facts: 1) some SP fibers which demonstrated coexistence with NPY-immunoreactivity were assumed to be continuous with those showing VIP-immunoreactivity, and 2) almost all of the SP fibers showed coexistence with CGRP-immunoreactivity. By this reasoning, nearly one third of SP fibers may demonstrate coexistence with NPY-, VIP-, and CGRP-immunoreactivities. These multiple peptides might be involved in vascular regulatory function, which is a possible function of the amphibian carotid labyrinth.

Animals↗
PubMed1992

Ontogeny of substance P-, CGRP-, and VIP-containing nerve fibers in the amphibian carotid labyrinth of the bullfrog, Rana catesbeiana. An immunohistochemical study.

The ontogeny of substance P, CGRP (calcitonin gene-related peptide), and VIP (vasoactive intestinal polypeptide) containing nerve fibers in the carotid labyrinth of the bullfrog, Rana catesbeiana, was examined by the peroxidase-antiperoxidase method. The time of appearance of these three peptides was different for each. First, CGRP fibers appeared in the wall of the carotid arch and external carotid arteries, and in a thin septum between these two arteries at an early stage of larval development (stage III). At stage V, substance P immunoreactive fibers appeared, and VIP fibers were detected at the early metamorphic stage (stage XXII). Up to the completion of metamorphosis, the number of these fibers remained low. From 1 to 5 weeks after metamorphosis, substance P, CGRP, and VIP fibers increased in number to varying degrees. By 8 weeks after metamorphosis, the distribution and abundance of these fibers closely resembled those of the adults. Some CGRP and VIP immunoreactive glomus cells were found at the stages immediately before and after the completion of metamorphosis. These findings suggest that substance P, CGRP, and VIP fibers during larval development and metamorphosis may be nonfunctional, and start to participate in vascular regulation only after metamorphosis. The transient CGRP and VIP in some glomus cells may be important for the development of the labyrinth, or may take part in vascular regulation through the close apposition of the glomus and smooth muscle cells (g-s connection).

Animals↗
PubMed1976

Microcirculation in the labyrinth.

The inner ear is unique in the number and variety of specialized microvascular networks that furnish blood to its parts. Four distinct capillary networks arranged in parallel supply the structures of the outer wall, and four others those of the spiral lamina. Most of the capillaries are surrounded by pericapillary spaces favoring filtration and reabsorption of fluid. In the guinea pig those of the spiral prominence and outer sulcus show a special pericapillary tissue. The strial capillaries are larger in diameter and are closely invested by strial cells. The blood within them has a higher hematocrit and flows more slowly than elsewhere in the labyrinth. The arcades of the tympanic lip and basilar membrane receive occasional innervation by fine unmyelinated nerve fibers. A possible role of prostaglandins in controlling the tone of the cochlear microvasculature is suggested. Although it appears unlikely that vascular lesions within the labyrinth could be responsible for the hydrops of Menière's syndrome, devascularization and atrophy of the endolymphatic sac might be contributory factors.

Animals↗
PubMed1985

Responses of Renshaw cells coupled with hindlimb extensor motoneurons to sinusoidal stimulation of labyrinth receptors in the decerebrate cat.

Contraction of ipsilateral limb extensors during side-down roll tilt of the head, leading to selective stimulation of labyrinth receptors, is attributed to an increased discharge of excitatory vestibulospinal (VS) neurons (alpha-responses) and a decreased discharge of medullary inhibitory reticulospinal (RS) neurons (beta-responses), both of which act on ipsilateral extensor motoneurons. Experiments were performed in decerebrate cats, with the de-efferented gastrocnemius-soleus (GS) muscle fixed at a constant length, to find out whether Renshaw (R) cells linked with GS motoneurons responded to labyrinth stimulation elicited by head rotation, while the neck had been bilaterally deafferented. We hoped in this way to clarify the role and the mechanism by which these inhibitory interneurons act on limb extensor motoneurons during the vestibular reflexes. 72.7% of the R-cells, disynaptically excited by group I volleys elicited by single shock stimulation of the GS nerve, weakly responded to head rotation at frequencies of 0.026-0.15 Hz and at a peak amplitude of 10 degrees. For the frequency of head rotation of 0.026 Hz, +/- 10 degrees C, most of the GS R-cells increased their firing rate during side-down head displacement (alpha-responses); some responses were related to head position, but others showed some phase lead or lag with respect to head position. The gain of the first harmonic of these unit responses was very low and corresponded on the average to 0.084 +/- 0.062, S.D. imp./s/deg, while the sensitivity corresponded to 2.14 +/- 2.35, S.D.%/deg (base frequency, 6.85 +/- 5.97, S.D. imp./s). These responses were attributed to the activity of VS neurons, the increased discharge of which during side-down head rotation exerts a weak excitatory influence on a limited number of GS motoneurons and, through their recurrent collaterals, on the related R-cells. The modulation of the firing rate of R-cells coupled with the GS motoneurons increased linearly by increasing the peak amplitude of displacement from 5 degrees to 20 degrees at the frequency of 0.026 Hz, so that the response gain remained almost unchanged. An increase in frequency of head rotation from 0.026 to 0.32 Hz at a fixed amplitude of 10 degrees, thus changing the maximal angular acceleration from 0.26 degrees/s2 to 41.7 degrees/s2, reversed the response pattern of R-cells reported above. The resulting beta-responses, which also showed some phase lead or lag with respect to head position, were attributed to vestibular activation of RS neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Interaction of tonic labyrinth and neck reflexes in man.

Interaction of tonic labyrinth and neck reflexes was studied in 3 healthy volunteers by analyzing changes in Soleus H-Reflex (SHR) area in relation to both lateral tiltings and neck rotations. By using a Kermath chair each subject was tilted laterally from the vertical to the left and to the right up 15 degrees in steps of 5 degrees and at the same time the longitudinal body axis, keeping the head fixed, was rotated to the right and to the left up to 15 degrees in steps of 5 degrees. All combinations of lateral tiltings and neck rotations were tested. Each test position was followed by a return to 0 degree for both rotation and tilting (control position). Twelve H-reflexes of right soleus muscle were recorded in each test and control position and the changes in RSHR area were expressed as percentage variations from the mean value absorbed in the pretest and post-test control position. Our data indicate that in man, as in animals, labyrinth and neck reflexes act in the opposite direction, and that in the static condition their contribution to postural stabilization is equal.

Adult↗
PubMed1976

Fine structure of the placental labyrinth in the rat at term and during prolonged gestation.

The fine structure of the placental labyrinth in the rat was described at term (Day 22) and during prolonged gestation (Day 23, 24 and 25). Gestation was prolonged by dialy subcutaneous injection of progesterone to the mothers from Day 20 through Day 24 of pregnancy. The placental labyrinth at term consisted of maternal and foetal blood spaces separated by three layers of trophoblast and an endothelium. During prolonged gestation (Day 24 and 25 only) the layers of trophoblast exhibited discontinuity, loss of cytoplasmic elements and the presence of fibronoid material. In addition ot the morphological observations, it was found that foetal blood glucose levels on Day 24 and 25 were significantly lower than values at term. The results were discussed in reference to placental insufficiency and its effect on the foetus.

Animals↗
PubMed1981

Origin of centrifugal fibers to the labyrinth in the frog (Rana esculenta). A study with the fluorescent retrograde neuronal tracer 'Fast blue'.

After injecting a solution of a fluorescent retrograde neuronal tracer (Fast blue, Diamidino compound 253/50) into the perilymphatic space of the frog labyrinth (Rana esculenta), labeled cells were found in the ventral and dorsal nuclei of the VIIIth nerve and in the nucleus reticularis medius. We consider these labeled cells to be the origin of the efferent innervation of the frog labyrinth. No evidence was found for the existence of a direct cerebello-labyrinthine connection.

Afferent Pathways↗
PubMed1985

Presynaptic actions of cholinergic agents upon the hair cell-afferent fiber synapse in the vestibular labyrinth of the frog.

Spontaneous activity of semicircular canal afferents in the isolated labyrinth of the frog is altered by bath application of cholinergic agonists. Muscarinic agonists can produce an increase in action potential frequency of individual afferents. This increase develops slowly and is prolonged in the time course of its action. Nicotinic agonists can either increase (most cases) or decrease afferent activity. These effects occur rapidly and decay during the period of activation, suggesting desensitization. Muscarinic effects are blocked by prior administration of atropine and nicotinic effects (both increases and decreases in action potential frequency) by curare. Intracellular recordings reveal that the nicotinic effects on afferent action potential frequency are the result of alterations in the frequency of spontaneous synaptic potentials, indicating a presynaptic site of action on the hair cells for these compounds. This conclusion is supported by the fact that in the presence of high Mg2+/low Ca2+, which blocks hair cell release of transmitter, cholinergic agonists do not affect the resting membrane potential of the vestibular afferent. Electrical stimulation of the VIIIth cranial nerve can result in either an increase or a decrease in spontaneous synaptic potential and action potential frequency of an afferent. These effects are blocked by prior administration of curare or of nicotinic agonists. Repetitive or continuous stimulation of the VIIIth nerve results in a reversible reduction of the evoked response, suggesting desensitization. Transection of the VIIIth cranial nerve two weeks prior to recording eliminates these actions of electrical stimulation, but not the responses to cholinergic agonists, indicating that the effects of electrical stimulation are mediated by centrally arising efferents. These findings confirm that acetylcholine is probably the transmitter released from centrally arising vestibular efferents, and, in addition, demonstrate that efferent-mediated effects are predominantly expressed through nicotinic receptors. Studies comparing the effects of isolation of the semicircular canal alone versus the intact labyrinth suggest that the method of isolation may be an important factor in determining whether efferent activity results in a predominant increase or decrease in afferent activity.

Acetylcholine↗
PubMed1993

Coexistence of substance P and calcitonin gene-related peptide in the nerve fibers of the carotid labyrinth of the bullfrog, Rana catesbeiana.

Double immunohistochemical staining with fluorescein isothiocyanate (FITC)- and rhodamine-conjugated antisera revealed the coexistence of substance P (SP) and calcitonin gene-related peptide (CGRP) in most nerve fibers in the intervascular stroma of the carotid labyrinth of the bullfrog, Rana catesbeiana. A few fibers contained SP without CGRP. The results suggest that the vascular regulatory function, which is one of the possible functions of the carotid labyrinth, may be controlled in part by the interaction of SP and CGRP.

Animals↗
PubMed1988

Effect of denervation of carotid labyrinths on breathing in unrestrained Xenopus laevis.

The effect of denervation of the carotid labyrinths on breathing responses to simultaneously applied aerial and aquatic normoxia, hypoxia, or hypercapnia has been studied in unrestrained Xenopus laevis. Denervation significantly reduced VI of normoxic toads compared with VI in intact and sham-operated toads, due to a significant reduction in the volume of each buccal pumping movement (VB) in denervates. Breathing increased significantly in response to environmental hypoxia or hypercapnia in intact and sham-operated toads as well as in denervates. Breathing frequency (fRESP) was the major determinant of the increase in VI for VB was unchanged and even fell slightly in denervates in hypercapnia. Dive time (DT) was significantly reduced in both hypoxia and hypercapnia, from that in normoxia. DT fell significantly more in hypoxia than in hypercapnia in both denervates and intact and sham-operated toads. It is concluded that the carotid labyrinth does not play a major role in regulating breathing in hypoxia or hypercapnia in unrestrained Xenopus.

Animals↗
PubMed1989

Efferents to the labyrinth of the river lamprey (Lampetra fluviatilis) as revealed with retrograde tracing techniques.

The cells of origin of centrifugal fibres to the labyrinth were examined in a jawless vertebrate, the lamprey, with several retrograde tracers (horseradish peroxidase (HRP), fluorescein isothiocyanate (FITC) and rhodamine coupled dextran-amines (FDA and RDA), and cobalt-lysine) that had been applied to the eighth nerve. With all 3 techniques, up to 20 cells were consistently labelled ipsilaterally, adjacent to the Mauthner cell; none were labelled on the contralateral side. The axons of the efferent cells emanate either from lateral dendrites or the perikaryon and course laterally towards the ipsilateral eighth nerve root. The dendrites ramify widely in the basal plate and may thus receive diverse inputs. The same tracers were applied to the lateral-line nerve and afferent fibres were labelled but no efferent cells, thus confirming previous reports. These data suggest that lampreys have an efferent innervation to the labyrinth but not to the lateral line.

Animals↗
PubMed2005

The membranous labyrinth during larval development in lamprey (Lampetra planeri, Bloch, 1784).

SEM and CLSM studies were performed on the membranous labyrinth of Lampetra planeri, a threatened species of brook lamprey, spanning from the 1st to the 4th year of ammocoetes larval stages and on the adults. In all the examined stages, the entire membranous labyrinth does not show any morphologic differences, but only a progressive increase in size. SEM and CLSM observations show that the ciliated chamber is lined with numerous unsensorial multiciliated cells. In the early stages, the ciliary bundles were approximately 15 microm long, while in the late stages they reached 30 microm. In the crista sensory area, we observed two populations of hair cells. "Type II" cells are peculiar for this species and show both long stereocilia decreasing in length and a long kinocilium (10-12 microm). Two other types of ciliary bundles have been found on the sensory hair cells of the Macula communis: the first one has both kinocilium and stereocilia about 4-5 microm long; the second shows a long kinocilium (7-10 microm in length) and short stereocilia bundles with a gradual increase in length. In the early stages of development, the three macular areas show few and sparsely distributed hair cells. In the late developmental stages, hair cells become more numerous and densely populated.

Analysis of Variance↗
PubMedDate not supplied

Development of the haemophagous region and labyrinth of the placenta of the tenrec, Echinops telfairi.

Our purpose was to determine how the central haemophagous region and cellular haemomonochorial labyrinth of the tenrec placenta are formed. The haemophagous region is preceded by a region of invasion of the endometrium by trophoblast comprising a cytotrophoblast layer covered by syncytial trophoblast and contiguous with numerous masses of multinucleate trophoblast. The trophoblast intrudes into the endometrium, eliminating the stroma, although small vessels and clumps of glandular epithelium persist. This extensive central region is connected to the forming disk by a ring of chorioallantois covered by a single layer of columnar trophoblast. Later the multinucleate masses and syncytial trophoblast degenerate. The unilaminar cytotrophoblast remains, is elaborated into folds, and phagocytoses glandular secretion, cell debris and erythrocytes. As the central area is transforming, fetal capillaries move into the cytotrophoblast pads surrounding the central zone. Prior to this, the cytotrophoblast has formed a multilayered structure and interrupted maternal vessels to create an anastomotic network of blood spaces lined by cytotrophoblast. The invasion of fetal capillaries transforms this preplacental pad into a cellular haemomonochorial labyrinth with the uninvaded portion forming an underlying spongy zone. Thus interaction of the trophoblast with the endometrium is substantially different in the central zone compared to the area of the preplacental pad.

Animals↗
PubMed1986

Neuropeptides in macula utriculi and macula sacculi of guinea pig labyrinth. An immunohistochemical study.

The neuropeptides Substance P, beta-Endorphin, Prolactin, Cholecystokinin, and Glucagon were investigated by means of Sternbergers PAP technique in the neuroepithelium of the Maculae utriculi and sacculi of the labyrinth of newborn guinea pigs. This brief report will show the localization of some neuropeptides in the neuroepithelium of the Maculae utriculi and sacculi. We could not find information about similar studies on this topic in the literature. In connection with investigations of the sensory apparatus of the inner ear we have recently presented neuropeptides evidence for the presence of certain peptides in the Ggl. spirale and the hair cells of the organ of Corti. With this paper we continue to report on neuropeptides in the labyrinth of the juvenile guinea pig as revealed by immunohistochemistry (Nowak et al., in press).

Acoustic Maculae↗
PubMed1991

Responses of locus coeruleus neurons to labyrinth and neck stimulation.

The electrical activity of a large population of locus coeruleus (LC)-complex neurons, some of which were antidromically activated by stimulation of the spinal cord at T12-L1, was recorded in precollicular decerebrate cats during labyrinth and neck stimulation. Some of these neurons showed physiological characteristics attributed to norepinephrine (NE)-containing LC neurons, i.e., (i) a slow and regular resting discharge; (ii) a typical biphasic response to compression of the paws consisting of short impulse bursts followed by a silent period, which was attributed to recurrent and/or lateral inhibition of the corresponding neurons; and (iii) a suppression of the resting discharge during episodes of postural atonia, associated with rapid eye movements (REM), induced by systemic injection of an anticholinesterase, a finding which closely resembled that occurring in intact animals during desynchronized sleep. Among the neurons tested, 80 of 141 (i.e., 56.7%) responded to the labyrinth input elicited by sinusoidal tilt about the longitudinal axis of the whole animal at the standard parameters of 0.15 Hz, +/- 10 degrees, and 73 of 99 (i.e., 73.7%) responded to the neck input elicited by rotation of the body about the longitudinal axis at the same parameters, while maintaining the head stationary. A periodic modulation of firing rate of the units was observed during the sinusoidal stimuli. In particular, most of the LC-complex units were maximally excited during side-up tilt of the animal and side-down neck rotation, the response peak occurring with an average phase lead of about +17.9 degrees and +34.2 degrees with respect to the extreme animal and neck displacements, respectively. Similar results were also obtained from the antidromically identified coeruleospinal (CS) neurons. The degree of convergence and the modalities of interaction of vestibular and neck inputs on LC-complex neurons were also investigated. In addition to the results described above, the LC-complex neurons were also tested to changing parameters of stimulation. In particular, both static and dynamic components of single unit responses were elicited by increasing frequencies of animal tilt and neck rotation. Moreover, the relative stability of the phase angle of the responses evaluated with respect to the animal position in most of the units tested at increasing frequencies of tilt allowed the conclusion to attribute these responses to the properties of macular ultricular receptors. This conclusion is supported by the results of experiments showing that LC-complex neurons displayed steady changes in their discharge rate during static tilt of the animal.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1998

Effect of RGH-2716 on learning and memory deficits of young and aged rats in water-labyrinth.

RGH-2716 is a novel 1-oxa-3,8-diazaspiro[4.5] decan 2-one, which was published to have potent inhibitory effect on neuronal Na and Ca movement and stimulatory action on nerve growth factor (NGF)-production, as well as to show significant antiamnesic activity in experimental amnesia models. The aim of the present experiments was to study the effect of the compound on the learning process and on the different stages of memory using water-labyrinth in normal and memory impaired young animals, as well as to study cognitive effect of RGH-2716 on aged animals. At the doses of 0.5 mg/kg i.p. or 3 mg/kg p.o. given before daily swimming, this compound improved the learning process of young animals impaired by either diazepam (DIA) or scopolamine (SCOP). In retrograde amnesia model RGH-2716 (3 mg/kg p.o.) significantly ameliorated consolidation process and retrieval of information impaired by SCOP or DIA. Nimodipine and vinpocetine (10 mg/kg p.o.) showed moderate effect compared to RGH-2716. Aged rats pretreated with daily i.p. RGH-2716 performed the tasks with significantly fewer errors and shorter swimming time than untreated aged rats. When aged animals had to solve a new labyrinth problem, treated aged rats showed significantly better learning ability than aged controls. One month of oral treatment of aged rats with 3 mg/kg dose of RGH-2716 two times daily resulted in a "tendency-like" improvement in learning of aged Fischer 344 and spontaneously hypertensive (SH) rats. The present results make RGH-2716 an interesting compound for the treatment of cognitive disorders.

Aging↗
PubMed1998

Development of the blood-labyrinth barrier in the rat.

Systemically administered cationic polyethyleneimine (PEI) passes through the capillary endothelial cell and attaches to anionic sites on the capillary basal lamina (BL). Thus, the distribution of PEI on the BL reflects the changes in the endothelial cell transport system. A 0.1% PEI solution was administered by intravenous injection (7.5 ml/kg) to developing (4, 7, 11, 14, 21 days after birth) and adult rats to evaluate the development of endothelial cell transport in the cochlear capillary as related to age. One hour later, the bony labyrinth was removed and embedded in Epoxy resin. Ultrathin sections of the cochlear lateral wall were then viewed with a transmission electron microscope. The distribution of PEI in the capillary BL in the stria vascularis of the 4-, 7- and 11-day-old rats was significantly greater compared to the adult rats. The distribution of PEI in the capillary BL in the spiral ligament of the 4- and 7-day-old rats was also significantly greater compared to the adult rats. These findings suggest that the endothelial cell transport is more robust in the developing rat cochlea and that the blood-labyrinth barrier becomes mature by 14 days after birth in rats.

Animals↗
PubMed2000

Walk counts, labyrinthicity, and complexity of acyclic and cyclic graphs and molecules

It is demonstrated how the complexity of a (molecular) graph can be quantified in terms of the walk counts, extremely easily obtained graph invariants that depend on size, branching, cyclicity, and edge and vertex weights (unsaturation, heteroatoms). The influence of symmetry is easily accounted for. The term labyrinthicity is proposed for what is measured by walk counts alone, neglecting symmetry. The total walk count and recently advanced measures of labyrinthicity or complexity are compared with respect to the ordering of structures and to the computational effort required to obtain numerical values.

Journal Article↗