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PubMedDate not supplied

Segmental enhancement of the cochlea on contrast-enhanced MR: correlation with the frequency of hearing loss and possible sign of perilymphatic fistula and autoimmune labyrinthitis.

PURPOSE: To relate the finding of selective enhancement of different turns of the cochlea to the frequency range of the hearing loss measured by audiogram. METHODS: Six patients aged 23 to 53 years, four men and two women, who presented with sudden hearing loss and had segmental enhancement of different turns of the cochlea on contrast-enhanced MR imaging were included in this retrospective study. The patients were imaged on a 1.5 T MR imaging system using pre- and postcontrast axial T1-weighted images and postcontrast coronal T1-weighted images through the temporal bone. RESULTS: The basal turn of the cochlea enhanced selectively in five of the six patients and the apical turn enhanced in the sixth patient. All patients had sensorineural hearing loss. Three of the patients with basal turn enhancement had predominantly high-frequency hearing loss, whereas the patient with apical turn enhancement had predominantly low-frequency hearing loss. The two other patients with basal turn enhancement had complete hearing loss. Three patients had presumed autoimmune labyrinthitis. The other three patients had strong clinical and surgical evidence of a perilymphatic fistula. CONCLUSION: Contrast-enhanced MR imaging may demonstrate selective enhancement of different turns of the cochlea. In certain patients, the areas of enhancement may correlate with specific hearing loss in the frequencies mapped by the enhancing segment. Enhancement of the cochlea may represent radiologic evidence of cochlear inflammation secondary to a perilymphatic fistula.

Adult↗
PubMed1996

Successful revision of failed cochlear implants in severe labyrinthitis ossificans.

Labyrinthitis ossificans may complicate the insertion of a multichannel cochlear implant in patients deafened after meningitis. Two children who initially underwent partial insertion of a 22-channel cochlear implant because of severe cochlear ossification required revision surgery after several months of unsuccessful device use. At the time of revision, resection of the car canal, tympanic membrane, malleus, and incus provided access to the lateral wall of the cochlea, permitting extensive drilling of the basal turn and a circumodiolar placement of the electrode. Functional integrity of the electronic components of the original device was documented intraoperatively, avoiding the expense of a new receiver-stimulator. Complete insertion of the active electrodes was accomplished in both cases, and electrophysiologic responsiveness to the implant was documented using intraoperative electrically evoked auditory brainstem response recordings. Postoperative performance has been similar to that of cochlear implant patients with nonossified ears. Experience with these two cases suggests that efforts to optimize electrode insertion at the original surgical procedure are appropriate and may help to avoid the disappointment of an unsuccessful cochlear implant.

Child↗
PubMed2000

Immunohistochemical detection of the estrogen receptor-alpha and progesterone receptor in the canine pregnant uterus and placental labyrinth.

The presence of hormone receptors is as important as the amount of hormone to predict hormone action. Therefore, the presence of estrogen receptors of the alpha subtype (ER-alpha) and progesterone receptors (PR) was evaluated in six pregnant uteri including the placenta and in three postpartum uteri of dogs. This preliminary study is part of our immunohistochemical research project on steroid hormone receptor distribution in the canine female genital tract. Specific staining for ER-alpha or PR was found only in cell nuclei. Staining for ER-alpha was rare in the various cell types of pregnant and postpartum uteri. Staining for PR was absent or weak in epithelial cells. Moderate staining for PR was observed in endometrial stromal cells and myometrial smooth muscle cells, two cell types playing an important role in the maintenance of pregnancy. Stromal cells stained more frequently positive for ER-alpha and PR than epithelial cells, indicating that both hormones may act on epithelial cells indirectly via stromal cells. In the placental labyrinth, fetal cells showed no evidence of ER-alpha or PR. In contrast, both receptors were present in maternal mesenchymal cells that were located around the basement membrane of the maternal blood vessels. These cells showed signs of decidualization. No difference in PR distribution was seen between pregnant and postpartum uterine tissue, suggesting that during parturition the decrease in serum progesterone levels and the concomitant increase in the estrogen/progesterone ratio are probably more important than the decline in receptor availability.

Animals↗
PubMed2002

The CP molecule labyrinth: a paradigm of how endeavors in total synthesis lead to discoveries and inventions in organic synthesis.

Imagine an artist carving a sculpture from a marble slab and finding gold nuggets in the process. This thought is not a far-fetched description of the work of a synthetic chemist pursuing the total synthesis of a natural product. At the end of the day, he or she will be judged by the artistry of the final work and the weight of the gold discovered in the process. However, as colorful as this description of total synthesis may be, it does not entirely capture the essence of the endeavor, for there is much more to be told, especially with regard to the contrast of frustrating failures and exhilarating moments of discovery. To fully appreciate the often Herculean nature of the task and the rewards that accompany it, one must sense the details of the enterprise behind the scenes. A more vivid description of total synthesis as a struggle against a tough opponent is perhaps appropriate to dramatize these elements of the experience. In this article we describe one such endeavor of total synthesis which, in addition to reaching the target molecule, resulted in a wealth of new synthetic strategies and technologies for chemical synthesis. The total synthesis of the CP molecules is compared to Theseus' most celebrated athlos (Greek for exploit, accomplishment): the conquest of the dreaded Minotaur, which he accomplished through brilliance, skill, and bravery having traversed the famous labyrinth with the help of Ariadne. This story from Greek mythology comes alive in modern synthetic expeditions toward natural products as exemplified by the total synthesis of the CP molecules which serve as a paradigm for modern total synthesis endeavors, where the objectives are discovery and invention in the broader sense of organic synthesis.

Biological Factors↗
PubMed1982

The fine structure of the placental labyrinth in the sloth, Bradypus tridactylus.

The placental labyrinth of the three-toed sloth (Bradypus tridactylus) was examined by electron microscopy. The material available was from two fetuses of 55 mm and 150 mm crown-rump length (CRL). The placenta of the younger specimen was a transition form between the syndesmochorial type and the endotheliochorial type. The interhemal membrane of the 55 mm CRL specimen consisted of the following components: 1) hypertrophied maternal endothelial cells surrounding the maternal vessels; 2) a small amount of extracellular material and spindle-shaped cells, both presumed to be of maternal origin; 3) a layer of syncytial trophoblast that had an unusual, reticulated or sponge-like appearance; and 4) the fetal capillary endothelium. In addition, the fetal connective tissue contained hypertrophied mesenchymal cells that were characterized by abundant granular endoplasmic reticulum. The placenta of the 150 mm CRL fetus was poorly preserved, but it was possible to determine that the placenta was of the endotheliochorial type. There was a close apposition of maternal endothelium and trophoblast. The results confirmed virtually all of lhe light microscopic observations of Wislocki (1927; 1928b). The ultrastructure of the sloth interhemal membrane is compared to that of other endotheliochorial placentas, particularly that of the shrew, with which it shows many cytological similarities.

Animals↗
PubMed1984

Effects of endotoxin on placental labyrinth formation in the golden hamster: a light and electron microscopic study.

Animal studies of endotoxemia during pregnancy have suggested that the placenta is the primary site of action. This study was designed to evaluate the effects of endotoxin at previously established resorptive and teratogenic dose levels during the development of the placenta in the hamster. At the higher dose levels, total necrosis of the placenta was observed within 24 hr after treatment. Formation of fibrin thrombi was only apparent well after the initiation of necrotic events. At the teratogenic dose, a marked decrease in the formation of the placental labyrinth was evident, but invading fetal capillaries and fetal blood cells appeared normal. However, scattered necrotic foci of trophoblastic cells were observed.

Animals↗
PubMed1992

Intimate apposition of the glomus and smooth muscle cells (g-s connection) in the carotid labyrinth of juvenile bullfrogs.

Intimate apposition of the glomus and smooth muscle cells (g-s connection) was found in almost all glomus cells of the carotid labyrinths in juvenile bullfrogs, Rana catesbeiana. There were three types of g-s connection: between thin processes (0.1-0.2 micron in width) without dense-cored vesicles of glomus cells and smooth muscle cells; between thick processes (1.0-1.5 microns in width) with dense-cored vesicles of glomus cells and smooth muscle cells; and between the tongue-like projections of smooth muscle cells and the flat surface of the glomus cell. In some cases, a single glomus cell made g-s connections with several smooth muscle cells. Exocytosis often occurs at the g-s connection. Afferent and efferent synapses were found on the glomus cells with g-s connections. Reciprocal synapses were also observed. On the basis of these findings, the second and third types of g-s connection are presumed to participate in vascular regulation.

Animals↗
PubMed1982

The glomus cell of the carotid labyrinth of Xenopus laevis.

The ultrastructure of the glomus cells of the carotid labyrinth was investigated in the anuran, Xenopus laevis. These cells show many catecholamine containing granules. About 50 cells in groups of 3-5 are located near the sinusoids. Morphologically, their organelles are similar to those previously reported in Bufo vulgaris. Striking features are (1) intimate appostion of the glomus cell to smooth muscle (g-s connection), (2) gap junctions between adjacent glomus cells, (3) exocytotic figures. Based on these findings a possible function of the glomus cell is discussed.

Animals↗
PubMed1990

Compensation of horizontal canal related activity in the medial vestibular nucleus following unilateral labyrinth ablation in the decerebrate gerbil. II. Type II neurons.

The spontaneous activity and dynamic responses to sinusoidal horizontal head angular acceleration of type II horizontal semicircular canal related neurons in the medial vestibular nucleus (MVN) were recorded bilaterally in decerebrate Mongolian gerbils (Meriones unguiculatus) under three experimental conditions: normal labyrinths intact, acutely following unilateral labyrinthine lesion, and four to seven weeks following labyrinthine lesion. The number of type II neurons detected contralateral to the lesion was greatly reduced both in the acutely hemilabyrinthectomized animals and following compensation. The gain of the responses was depressed bilaterally acutely following the lesion. A greater reduction in response gain was noted in cells contralateral to the lesion. The gain of the contralateral type II responses increased with time such that in the compensated animal bilaterally symmetric gains were recorded. While the significant changes which occur in the gain of type II neurons with recovery from peripheral vestibular lesions can largely be attributed to type I neurons on the other side of the midline, changes in type I neurons were not entirely reflected in the type II population. The spontaneous activity of type II neurons did not undergo any significant changes following the labyrinthine lesion. We present a model utilizing the dynamic responses to estimate the functional recovery of commissural connections in compensated animals. The overall gain of the contralateral type I to ipsilateral type I commissural polysynaptic pathway appears to improve, while the efficacy in the reverse direction remains depressed, suggesting that modifications in commissural connections, particularly involving the type II to type I connections within the MVN on the injured side, mediate aspects of behavioral recovery.

Animals↗
PubMed1979

Electron microscopic study of the giant cells in the olfactory bulb of labyrinth fish (Belontiidae, perciformes).

The giant cells in the olfactory bulb of labyrinth fish, most likely belonging to the nervus terminalis, show ultrastructural features of active synthesis of secretory material. Dense core vesicles (70--100 nm in diameter), found in the perikaryon as well as in the axon, are the possible storage sites of the secretory substance. Its chemical nature is unknown. In some of these vesicles acid phosphatase is demonstrable. Large membrane-bound bodies (up to 2000 nm in diameter), either containing an electron dense matrix or debris of cytoplasmic organelles, are also acid phosphatase-positive, suggesting their lysosomal nature. Some other ultrastructural characteristics of these cells are also described.

Acid Phosphatase↗
PubMed1986

Afferent activity recorded during rotation from single fibres of the posterior nerve in the isolated frog labyrinth.

EPSPs and spikes were recorded at rest and during rotation from single fibres of the posterior nerve in the isolated frog labyrinth. The spike discharge properties of 57 units were examined at rest and during repetitive acceleratory-velocity steps. Forty of these units were subjected to excitatory steps of 5-12 s duration and 45% displayed an evident discharge adaptation. In the non-adapting units, the excitatory response also deviated from that expected on the basis of the torsion-pendulum model and exhibited an exponential time-course in only 36% of the fibres examined. The time constant T2 of the response rising phase was significantly longer than that of the decay (2.5 s versus 1.7 s). When all the 57 units were considered, a linear behaviour was found in 67%. The average gain in these linear units was 1.9 +/- 1.4 spikes X s-1/deg X s-1. Adaptive fibres exhibited a lower resting firing rate and a higher gain (3.8 spikes/s and 2.3 spikes X s-1/deg X s-2, respectively) when compared with the non-adapting ones (7.1 spikes/s and 1.5 spikes X s-1/deg X s-2). An undershoot was present in 57% of the units; it increased with acceleration and was not strictly related to adaptation. Fifteen of the 40 units tested with the 5-12 s duration excitatory steps survived repeated inhibitory accelerations of the same duration. In these units a marked response asymmetry was evident since their resting activity could be abolished by accelerations not larger than 10 deg/s2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Permeability studies of the guinea pig placental labyrinth. II. Tracer permeation and freeze-fracture of fetal endothelium.

Permeability of the fetal endothelium within the guinea pig placental labyrinth is studied by means of horseradish peroxidase (HRP) and ionic lanthanum as diffusion tracers. The paracellular transport of HRP is restricted by the occluding junctions of the fetal endothelium. In contrast, ionic lanthanum readily permeates most of the intercellular junctions and rapidly infiltrates the basal lamina. Freeze-fracture replicas reveal zonulae occludentes connecting the fetal endothelial cells. The network of the zonulae occludentes is variable, exhibiting highly complex areas as well as single strand interconnections. A correlation between the permeability studies and freeze-fracture findings is discussed.

Animals↗
PubMed1979

Functions of different receptor systems in the reptilian labyrinth.

Different biopotentials, following a mechanical stimulus, were recorded from single hair cells of the reptilian labyrinth, with electronoptically circumscript localizations: 1. From the apical cell pole, the receptor potential, intracellular or from the ciliary surface, within the physiological range proportional to stimulus amplitude, frequency or phase, without delay, and with no real threshold of mechanosensitivity, as measured by ciliary displacement amplitude or velocity. 2. From the synaptic zone, in the basal region of the hair cell, or from contacting nerve endings, the synaptic potentials, local excitatory or inhibitory processes, respectively, with measurable latencies and with non-linear distortion. 3. From the (dendritic) endings of the first afferent neuron (or neurons), spike-shaped action potentials, synchronized by the (excitatory) synaptic potentials. Characteristic curves were plotted as a quantitative representation of the mechano-electric input-output relations of the different types of hair cells. For proceeding morphological and physiological system analysis, the comparison of the different submammalian inner-ear receptor systems gives us some new possibility of a closer correlation between ultrastructure and function.

Acoustic Stimulation↗
PubMed1982

Location of efferent neurons to the labyrinth of the green tree frog (Hyla cinerea). A horseradish peroxidase study.

The origin of centrifugal fibers to the labyrinth was determined by application of horseradish peroxidase to the severed octavus nerve of the green tree frog (Hyla cinerea). Labeled neurons were found exclusively in the nucleus reticularis medius of the reticular formation ipsilateral to the injection site. In particular, no retrogradely labeled neurons were found in the octavus nuclei.

Animals↗
PubMed1976

[Ultrastructural localization of acid phosphatase and thiamine pyrophosphatase activities and of phosphotungstic staining at low pH in the placental labyrinth of the cat].

The localizations of acid phosphatase (ACPase) and thiamine pyrophosphatase (TPPase) activities were studied in the placental labyrinth of the cat during the last days of gestation. ACPase activities were observed essentially in the syncytiotrophoblast and in the "interstitial inert substance" (S.I.I.) that separates maternal from foetal tissues. Reaction product was localized in lysosomes, multivesicular bodies, and in the network of smooth-membraned tubules which open on the cell surface of the syncytiotrophoblast facing the S.I.I. The S.I.I. exhibit a strong activity, probably of syncytiotrophoblastic origin. TPPase activities were found in the syncytiotrophoblast, rarely in the Golgi apparatus but always in the lumen of the network of smooth-membrande tubules. The S.I.I. shows a moderate activity. These TPPase positive tubules being frequently observed very close to the Golgi cisternae, it is proposed that they arise from the Golgi complex and convey phosphatases to the S.I.I. After phosphotungstic acid staining at low pH, luminal surface coat of maternal endothelium is always strongly and continuously visualized, while the plasma membrane of the syncytiotrophoblast facing the S.I.I. is never stained. Staining is intense in the lumen of tubules, and continuous with the stain of the S.I.I. ACPase activity of the S.I.I. could be implicated in enzymatic degradation of maternal molecules during their transfer from maternal to foetal blood. The S.I.I. may correspond to the immunological buffer zone at the interface between maternal and foetal tissues.

Acid Phosphatase↗
PubMed1980

[Alkaline phosphatase activity in the placental labyrinth of the cat and problems of specific localization of transport adenosine triphosphatase. An ultrastructural study (author's transl)].

The ultrastructural localizations of alkaline phosphatase (ALPase) and of Na+-K+-dependent adenosine triphosphatase (Na+-K+-ATPase) were studied in the placental labyrinth of the cat during the last days of gestation. ALPase activity could be detected in the syncytiotrophoblast but was absent from maternal tissues. Enzyme activity was observed only along plasma membranes of microvilli and absorption tubules on the maternal surface of the syncytium and also on the podocytes-like cytoplasmic processes of the fetal face. The localization of the Na+-K+-ATPase activity as obtained with the method of Ernst was identical with that of ALPase. This activity was not very ouabaine sensitive or K+ dependent, but was almost completely inhibited by levamisole. The strong ALPase activity of the syncytiotrophoblast does not allow a specific detection of Na+-K+-ATPase. However, the localization of these enzymes activities on syncytiotrophoblast surfaces directly related to fetal and maternal capillaries could suggest that these surfaces are associated with transport mechanisms of the trophoblast.

Alkaline Phosphatase↗
PubMed1998

Serum antibodies against membranous labyrinth in patients with "idiopathic" bilateral vestibulopathy.

To investigate the possibility of an autoimmune mechanism in idiopathic bilateral vestibulopathy (IBV), we screened patients' sera for antibodies against inner ear structures. IgG antibodies against membranous labyrinth (ampulla, semicircular canals, saccule and utricle) were detected in 8 of 12 patients by immunofluorescence on rat inner ear cryosections. All but one serum of 22 healthy controls and the sera of 6 patients with known autoimmune disorders showed only background staining. Low-titre anti-nuclear IgM antibodies were present in three control sera and one IBV serum. High-titre anti-nuclear IgM was found in a patient with lupus erythematosus and in one with scleroderma. Anti-nuclear IgM was not organ-specific. No human serum used contained detectable anti-vascular preformed antibodies. Cross-reactivity to sections of liver, kidney, cornea, brain and skeletal muscle was absent. Double-staining for IgG and F-actin, the primary constituent of hair cell cilia, did not show predominant Ig-coating of sensory hair cells. Immunosuppressive therapy in 3 IBV patients did not improve the disorder, probably owing to irreversible loss of sensory and neural structures. These data suggest that the bulk of anti-labyrinthine autoantibodies may be an epiphenomenon, yet a small subgroup of organ-specific autoantibodies may synergize with a cellular response in the development of vestibular lesions.

Autoantibodies↗
PubMed1977

The contribution of the contralateral labyrinth to second order vestibular neuronal activity in the cat.

Vestibular brain stem units of the horizontal canal in the awake C1 transected cat were examined in acute experiments before and after the contralateral vestibular nerve was cut. The latter procedure resulted in an immediate increase in mean resting rate from 19 to 45 spikes/sec and greater spontaneous fluctuations in firing rate. Mean sensitivity to constant accelerations from 2 to 16 degrees/sec2 was significantly reduced. In the 4-6 degrees/sec2 range, for example, mean sensitivity fell from 5.7 +/- 3.2 spike/sec/deg/sec2 (range 0.7-13.6, n = 107) to 2.8 +/- 1.4 (range 0.2-5.5, n = 29). Mean sensitivity to 4-6 degrees/sec2 deceleration was reduced from about 4.5 to 3.0. On the other hand, time constants and the ratio of adapting to non-adapting units was unchanged. Removal of the midline cerebellum, including the vermis and fastigial nuclei in a portion of the animals, did not materially alter the above results. It is concluded that the contralateral labyrinth, acting via the vestibular brain stem commissural pathway, not only exerts a powerful effect on the resting activity of brain stem canal vestibular neurons, but also on their response to acceleration.

Action Potentials↗