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PubMedDate not supplied

Virtual labyrinthoscopy: visualization of the inner ear with interactive direct volume rendering.

Computed tomography (CT) is the modality of choice for detailed imaging of the bony labyrinth. Usually, information about the complex three-dimensional anatomic structures of the inner ear is presented as two-dimensional section images. Interactive direct volume rendering is a powerful method for visualization of the labyrinth. Unlike other visualization methods, direct volume rendering enables direct visualization of the bony labyrinth without explicit segmentation prior to the visualization process. Direct volume rendering was applied to visualization of the structures of the temporal bone in five patients without pathologic conditions and four patients with pathologic conditions. In all cases, clear representations of the bony labyrinth and the facial canal were provided. Because standard CT examinations combined with interactive visualization based on direct volume rendering are used, the method is fast and flexible. Therefore, this approach is applicable in routine clinical work. Problems occur in patients with effusion in the temporal bone because adjustment of imaging parameters for proper delineation of the target structures is difficult in this situation. However, direct volume rendering can produce meaningful images of high quality even in these problematic cases. The term virtual labyrinthoscopy is suggested for visualization of the labyrinth by using direct volume rendering.

Cochlea↗
PubMed1992

Vestibular inputs to brain stem neurons that participate in motor learning in the primate vestibuloocular reflex.

1. Previous studies have described a subpopulation of interneurons in the vestibuloocular reflex (VOR) pathways that express large changes in their responses to head turns in conjunction with motor learning in the VOR. These neurons are called flocculus target neurons (FTNs) because they are inhibited at monosynaptic latencies by stimulation of the flocculus and ventral paraflocculus. 2. Electrical stimulation of the vestibular labyrinth revealed that FTNs receive excitatory monosynaptic inputs from the ipsilateral vestibular labyrinth and longer-latency, excitatory inputs from the contralateral labyrinth. 3. Our data show that commissural inhibition, which has been thought to be an important feature of vestibular processing, does not provide the dominant inputs from the contralateral labyrinth to FTNs. Instead, the inputs from both labyrinths are excitatory and may be functionally antagonistic. Changes in the balance of excitatory inputs from the two horizontal canals to FTNs could contribute to motor learning in the VOR.

Animals↗
PubMed1976

[Position and bony structures of the vestibular apparatus in the guinea pig].

The study of the inner ear of the guinea pig intended to give an explanation to what extent there are differences discernible in relation to the human labyrinth. Additional histological research should clarify the question, if structural differences exist in the osseous labyrinth capsule of the same animal. It has turned out that in normal headbearing the position of the semicircular canals deviates from the human vestibular apparatus. The semicircular canals are nearly vertical to each other, but in comparison to the human labyrinth they are shifted around the longitudinal axis of the utriculus caudal by ca. 30 degrees. In general the position of the vestibulo-cochlear organ is fixed to a great extent by the inclined course of the petrosal pyramid. This different position of the semicircular canals in man and animal is supposed to be due to the phylogenetic evolution and the adjustment to upright walk. Size and extension of the single semicircular canals are very different within the same animal. These differences in size indicate causalities of form and function. The relations in the build of the osseous labyrinth are extremely complicated. Compared to the other corporal regions the static parts of the petrosal pyramid are exceptional massive and of remarkable hard consistency. In the inner capsule of the ear there are three different bone strata to be seen. The characteristic lamel structure is most solid nearest to the semicircular canals. The fetal characteristics in the maturing process of the petrosal bone were traced a long while in the postnatal life. The typical building of the labyrinthal bone structures contributes to the mechanical stability of the capsule.

Animals↗
PubMed1986

Anatomic basis for labyrinthine preservation during posterior fossa acoustic tumor surgery.

Earlier diagnosis of acoustic tumors promises to increase our opportunity to identify patients with serviceable hearing. Critical to a posterior fossa transmeatal approach for acoustic tumor resection is preservation of the underlying labyrinth. Although the labyrinth has been recognized as a limiting factor in exposure of tumor in the internal auditory canal, few reports have detailed the microscopic surgical anatomy posterior to the internal auditory canal. An anatomic study was undertaken to determine consistent relationships between critical structures within the temporal bone relevant to hearing preservation surgery. The results of this study indicate that, whereas topographic landmarks are helpful for orientation, the more consistent relationship of the labyrinth to the vestibular aqueduct and singular canal allows a more accurate localization of the underlying labyrinth. Although the vestibule frequently prevents direct visualization of the transverse crest, a dissection based upon the microsurgical anatomy will maximize visualization of the lateral fundus while preserving the integrity of the labyrinth.

Cochlea↗
PubMed1997

[Controversial aspects of magnetic resonance imaging in sudden onset cochleovestibular diseases].

Sudden deafness and vertigo are a challenge for the otolaryngologist. With its high fluid content, the membranous labyrinth is best evaluated through Magnetic Resonance Imaging (MRI). Recently gadolinium-enhanced MRI has opened new perspectives in the imaging of the pathological labyrinth, able to directly detect labyrinthine lesions. To date the main role of MRI has been to rule out the presence of retrocochlear involvement in patients with sudden deafness and/or vertigo. However, in the past few years, several authors, reporting on gadolinium-enhanced MRI, have described better labyrinthine imaging, revealing direct labyrinth or nerve bundle involvement in all such patients. On the contrary, other studies have not revealed any enhancement of post-contrast labyrinthine images upon MRI but have shown an increase in signal intensity upon T2-weighted images. In this light, the purpose of the present study has been a) to evaluate the prevalence of labyrinthine abnormalities found upon MRI in consecutive patients with sudden deafness and vertigo and b) to assess the correlation between the severity of clinical and audiological findings and the MRI abnormalities encountered. Twelve consecutive patients with sudden hearing loss and/or vertigo were included in the study (age range 9-59 years; 6 males and 6 females). All subjects underwent complete otoneurological examination. MRI was performed with a 0.5 T superconducting magnet system allowing 2 mm-thick sections through the temporal bone. Within 29 days of onset of the complaints all patients were studied both before and after administration of the contrast medium (gadolinium-DTPA, 0.01 mmol/l, i.v.). Two of the 12 subjects had sudden deafness, 5 sudden deafness and vertigo while 5 had vertigo alone. Gadolinium enhancement and/or a high signal intensity upon T2-weighted images of the pathological labyrinth and nerve bundle was observed in 4 patients. The patients were divided into groups by etiology. MRI abnormalities were only found in the group where the etiology was viral. There was no correlation between the severity of clinical findings and the presence of MRI abnormalities nor between MRI and ABR findings. Analysis of such controversial data is discussed, stressing the importance of gadolinium-enhanced MRI of the labyrinth as a new diagnostic tool in sudden deafness and vertigo.

Acute Disease↗
PubMedDate not supplied

Vascular interrelationships of near-term mink placenta: light microscopy combined with scanning electron microscopy of corrosion casts.

The microvasculature of the near-term zonary placenta of the mink has been studied using light microscopy and scanning electron microscopy of corrosion casts, prepared from maternal and fetal vessel systems, respectively. The zonary area, most important for placental exchange, includes a characteristic labyrinth. The labyrinth is composed of lobules oriented in a maternal-fetal direction. One maternal stem artery serves as the central axis of a lobule, and about six pairs of fetal stem arteries and stem veins of the chorionic primary villi mark the periphery of the lobule. Viewed from the fetal side of the labyrinth, this lobular structure presents a roughly hexagonal pattern, with the central maternal stem artery and radially oriented arteriolar branches giving the lobule the shape of a star. These arterioles frequently form bridges to neighboring lobular systems; however, the majority continue into the feto-maternally oriented three-dimensional network of maternal capillary sinusoids, which converge on the outlets of the maternal stem veins on the maternal side of the labyrinth. Maternal main crypts are delimited by the rays of the star-shaped lobules containing chorionic primary villi. The latter penetrate into maternal crypts from the fetal side, and are characterized by their axial arterial and venous stem vessels. Fetal secondary villi are arranged at different levels from these stem vessels. The secondary villi are characterized by arterioles and venules branching in pairs from the stem vessels and supply the tributary capillary complexes of terminal villi. The lobular structure of the placental labyrinth provides a three-dimensional framework of vessels where maternal capillary sinusoids and fetal capillaries meet in a one-way cross-current arrangement. The blood flow conditions and the peculiarities of the mink placenta interhemal membrane are compared to those of other carnivores and discussed with respect to the efficiency of the endotheliochorial placenta.

Animals↗
PubMed1998

Unilateral testing of utricular function.

A modified rotatory chair test is reported in which radial acceleration, generated by eccentric displacement of the subject during constant angular velocity, is exploited as a unilateral stimulation to the otolith organs. During constant angular rate rotation, the test subject is displaced laterally on the rotating turntable by 3.5 cm, so that one labyrinth becomes aligned with the rotatory axis while the second - eccentric - labyrinth is solely exposed to the altered gravito-inertial acceleration (GIA). Previously reported results showed that the direction of the response is independent of the direction of turntable rotation, ruling out any canal influence, and indicated that in a normal population the response, measured in one eye, was symmetrical for displacement of the left and right labyrinths. This mode of stimulus thus appears to elicit a unilateral otolith-ocular response (OOR). Examination of this unilateral OOR was extended in the present study; comparative testing with head-tilt to gravity, i.e. involving bilateral stimulation to the otolith organs, was carried out. Movements of both eyes were recorded (by three-dimensional video-oculography), in order to examine response conjugacy. To verify the specificity of the unilateral stimulus, tests were performed with patients who had previously undergone unilateral section of the vestibular nerve as treatment for acoustic neuroma. The eccentric displacement profile (EDP) and head-tilt stimulus each included ten cycles of left-right oscillation in order to permit signal averaging. In the normal subjects (n=12) the torsional component of the OOR proved to be both labyrinth-symmetrical and conjugate, during both bilateral and unilateral otolith stimulation. OOR gain (ocular torsion/GIA tilt) was higher for bilateral than unilateral stimulation. Bilateral OORs, obtained from three of the five unilaterally deafferented patients, proved less symmetrical and conjugate than in the normals. Unilateral OORs in all five patients were characteristically asymmetrical, with little or no response during stimulation of the diseased labyrinth.

Acceleration↗
PubMedDate not supplied

Placental and fetal growth retardation following partial progesterone withdrawal in rat pregnancy.

This study investigated placental expression of the two main isoforms of the progesterone receptor and the regulation of placental and fetal growth by progesterone over the final third of rat pregnancy, the period of maximal fetal growth. Expression patterns of mRNAs encoding the two major progesterone receptor isoforms (PR-A and PR-B) were measured by real-time RT-PCR in the two morphologically- and functionally-distinct regions of the placenta, the basal and labyrinth zones, at days 16 and 22 of pregnancy (term=day 23). PR-A and PR-B mRNA expression was extremely low in labyrinth zone on days 16 and 22, close to the limits of detection. In contrast, the basal zone exhibited much higher levels of mRNA expression for both PR-A (>10-fold higher than in labyrinth zone) and PR-B (3-fold higher at day 16). To assess the role of progesterone in placental growth, maternal progesterone was reduced from day 16 by ovariectomy with full estradiol replacement and partial progesterone replacement until day 22. Progesterone reduction lowered fetal (10%), whole placental (24%), basal zone (37%) and labyrinth zone (14%) weights at day 22 compared with sham-controls, whereas fetal and placental weights (both zones) were maintained in ovariectomised rats given full estradiol/progesterone replacement. The effects of progesterone withdrawal were not associated with changes in placental expression of either IGF-II or IGFBP-2, both important players in growth factor regulation of placental growth. Importantly, however, IGF-II expression remained elevated in the labyrinth zone but fell markedly in basal zone ( approximately 7-fold) between days 16 and 22 of normal pregnancy, consistent with the growth patterns of these two placental regions over this period.

Animals↗
PubMed1999

Neuronal response sensitivity to bidirectional off-vertical axis rotations: a dimension of imbalance in the bilateral vestibular nuclei of cats after unilateral labyrinthectomy.

In decerebrate cats after acute hemilabyrinthectomy, the response sensitivity of extracellularly recorded vestibular nuclear neurons on the lesioned and labyrinth-intact sides were examined quantitatively during constant velocity off-vertical axis rotations with an aim to elucidate the functional contribution of otolithic inputs to the ipsilateral and contralateral vestibular nuclei. The bidirectional response sensitivity, delta, was determined as the ratio of the gain during clockwise to that during counterclockwise rotations. A continuum of response sensitivity was identified: one-dimensional neurons showed symmetrically bidirectional response patterns, while two-dimensional neurons showed asymmetrically bidirectional patterns that in some cases approached unidirectional patterns with change in velocity. The proportion of two-dimensional neurons was significantly increased after acute hemilabyrinthectomy. Two-dimensional neurons that responded only to one direction of rotation in at least one of the velocities tested were described as unidirectional neurons. This unidirectional response pattern was observed in one-third of the entire neuronal population studied, but not in cats with both labyrinths intact, thus suggesting that such prominent broadly tuned responses are normally masked by converging otolithic inputs from the contralateral side. These neurons were found in higher proportion on the lesioned side than on the labyrinth-intact side. Among the 70% of unidirectional neurons that exhibited bidirectional response at some velocities and unidirectional response at others, prominent shifts in delta values (i.e. between 0/infinity and finite values) with velocity can be computed for each neuron. The shifts in delta values correlated with large shifts in the response dynamics and spatial orientation as the response pattern changed with velocity. The response orientations of the unidirectional neurons pointed in all directions on the horizontal plane. When all the two-dimensional neurons (i.e. both the unidirectionally and bidirectionally responsive ones) were pooled, imbalances in the distribution of the response orientations and in response gain were found between the ipsilateral-side-down/head-down half-circle and the contralateral-side-down/head-up half-circle on the labyrinth-intact side, but not on the lesioned side. These results, derived from spatiotemporal processing of gravitational signals, reveal a novel dimension of imbalance between neuronal populations in the two vestibular nuclear complexes after acute lesion of one labyrinth. This feature would provide, on the one hand, deranged cues of spatial orientation and direction during slow head excursions and, on the other, a framework for the dynamic behavioral deficits associated with hemilabyrinthectomy.

Animals↗
PubMed2000

Fatty acid transport regulatory proteins in the developing rat placenta and in trophoblast cell culture models.

The placenta forms a selective barrier that is able to transport nutrients that are of critical use to the fetus. Delivery of essential fatty acids to the fetus is dependent upon transplacental transport and provides the backbone for the biosynthesis of biological membranes, myelin and various signalling molecules. The primary objective of this research was to elucidate the expression patterns of genes that regulate fatty acid transport across the placenta. Several fatty acid transport regulatory genes have been identified in the rat including; cytoplasmic heart fatty acid binding protein (hFABP), plasma membrane fatty acid binding protein (FABPpm), fatty acid translocase (FAT) and fatty acid transport protein (FATP). In this study, we have elucidated temporal and spatial expression patterns for these genes in the rat placenta and in cell culture models of the rat placenta by Northern blot, RT-PCR, Western blot and/or by in situ hybridization analyses. Expression of hFABP was specific to the labyrinth zone, the main barrier and site of transplacental transport in the rat placenta. In addition, the levels of hFABP expression increased with gestational age, suggesting a growing requirement for fatty acid transport with advancing stages of pregnancy. FABPpm, FAT and FATP are expressed in both the junctional and labyrinth zones of the rat placenta. FAT was predominantly localized to the labyrinth zone by in situ hybridization analysis. The placental cell expression patterns of the genes involved in fatty acid transport were supported by our observations of HRP-1 (labyrinth zone) and Rcho-1 (junctional zone) trophoblast cell culture models. Given their cell surface location, we predict that FABPpm, FAT and FATP potentially participate in placental fatty acid uptake. The predominant expression of hFABP and FAT in the labyrinth zone of the chorioallantoic placenta implicates hFABP and FAT in the transplacental movement of fatty acids from maternal to fetal compartments.

Animals↗
PubMed2005

Placental expression of peroxisome proliferator-activated receptors in rat pregnancy and the effect of increased glucocorticoid exposure.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Recent gene deletion studies indicate that PPARG and PPARD play critical roles in rodent development, including effects on placental vascularization. In this study we investigated the expression of the PPAR isoforms and their heterodimeric partner, RXRA, in the two functionally and morphologically distinct zones of the rat placenta during normal gestation and after glucocorticoid-induced fetal and placental growth restriction. Real-time reverse transcription-polymerase chain reaction and immunohistochemical analysis demonstrated markedly higher expression of Ppara, Pparg, and Rxra mRNA in labyrinth zone trophoblast as compared with basal zone near term. There was also a marked increase in Pparg (65%, P < 0.05) and Ppara (91%, P < 0.05) mRNA specifically in the labyrinth zone over the final third of pregnancy. In contrast, expression of Ppard mRNA fell (P < 0.001) in both placental zones over the same period. Maternal dexamethasone treatment (1 mug/ml in drinking water; Days 13-22, term = 23 days) reduced placental (44%) and fetal (31%) weights and resulted in a fall in Pparg (37%, P < 0.05) mRNA expression specifically in the labyrinth zone at Day 22. Placental expression of Ppara, Ppard, and Rxra was unaffected by dexamethasone treatment. These data suggest that PPARG:RXRA heterodimers play important roles in labyrinth zone growth late in pregnancy, possibly supporting vascular development. Moreover, glucocorticoid inhibition of placental growth appears to be mediated, in part, via a labyrinth-zone-specific suppression of PPARG.

Animals↗
PubMed1996

Zonal distribution of 11 beta-hydroxysteroid dehydrogenase types 1 and 2 messenger ribonucleic acid expression in the rat placenta and decidua during late pregnancy.

Glucocorticoid action in several target tissues is dependent on expression of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), and in the placenta 11 beta-HSD is thought to regulate transfer of active glucocorticoid to the fetus. This study compared expression of the two recognized 11 beta-HSD enzymes, types 1 and 2, in the rat placenta and decidua on Days 16 and 22 of gestation (term = Day 23). According to S1 nuclease protection analysis, although mRNA for 11 beta-HSD-1 was only just detectable in the labyrinth zone on Day 16, by Day 22 this expression had increased almost 20-fold. There was also an increase (approximately 2-fold) in 11 beta-HSD-1 mRNA in the basal zone between Days 16 and 22. In Day 16 decidua, 11 beta-HSD-1 mRNA was also highly expressed, but insufficient tissue was available for analysis on Day 22. Western blot analysis showed that immunoreactive 11 beta-HSD-1 (molecular mass 34 kDa) was present in those tissues with the highest 11 beta-HSD-1 mRNA expression (Day 16 decidua and Day 22 labyrinth zone). With respect to mRNA for 11 beta-HSD-2, high expression was observed in the decidua and labyrinth zone at Day 16, but in the latter this expression then declined 90% by Day 22. In contrast, expression of mRNA for 11 beta-HSD-2 increased more than 3-fold in the basal zone over the same period. Consistent with coexpression of the two 11 beta-HSD enzymes, both 11-oxoreductase and 11 beta-dehydrogenase bioactivity were clearly evident in all tissues, and each varied with stage of gestation. Specifically, 11 beta-dehydrogenase activity in the basal zone increased from 38 +/- 2% (mean +/- SEM) on Day 16 to 56 +/- 2% on Day 22, while 11-oxoreductase activity fell from 55 +/- 3% to 43 +/- 2% over the same period. In contrast, 11 beta-dehydrogenase activity in the labyrinth zone fell with advancing pregnancy (Day 16: 63 +/- 2%; Day 22: 48 +/- 2%). Both 11-oxoreductase (58 +/- 3%) and 11 beta-dehydrogenase (38 +/- 4%) activities were also evident in decidua at Day 16. In conclusion, this study shows that expression of 11 beta-HSD-1 and -2 is zone-specific in the placenta and maternal decidua. Moreover, opposite changes in the expression of the two enzymes occur in the basal and labyrinth zones of the placenta over the last days of pregnancy, indicative of distinct regulatory mechanisms and functional significance for the enzymes in the two placental zones.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1996

Surgical approach to the internal auditory meatus in acoustic neuroma surgery: significance of preoperative high-resolution computed tomography.

OBJECTIVE AND METHOD: To establish a surgical approach that provides better access to the internal auditory meatus (IAM) in acoustic tumor removal via a suboccipital transmeatal route, the anatomic location of the labyrinth with regard to the sigmoid-fundus line and the extent of bone removal from the IAM were evaluated by pre- and postoperative high-resolution computed tomography for 47 patients. RESULTS: The labyrinth was located lateral to the sigmoid-fundus line in 22 cases (lateral type, 46.8%), on the line in 9 (on-the-line type, 19.1%), and medial to the line in 16 (medial type, 34.0%). Postoperative high-resolution computed tomography showed that the mean length of the posterior wall from the fundus was shortened to 5.1 +/- 1.1 mm (n = 27) in the partially resected group and to 2.0 +/- 0.6 mm (n = 20) in the widely opened IAM group. The labyrinth was damaged in four cases from the widely opened IAM group; the preoperative status of the labyrinth was medial to the sigmoid-fundus line in three and on the line in one. The cochlear nerve was preserved in seven (31%) partially resected and in eight (50%) widely opened IAM cases. The overall success rate of hearing preservation was 4 of 22 (18.2%) partially resected and 5 of 16 (31.2%) widely opened cases. CONCLUSION: Preoperative evaluation of the anatomic relation between the IAM and the labyrinth by high-resolution computed tomography provides an efficient surgical approach to the IAM and contributes to anatomic and functional preservation of the cochlear nerve.

Female↗
PubMed2005

Ultrastructural studies and Na+,K+-ATPase immunolocalization in the antennal urinary glands of the lobster Homarus gammarus (Crustacea, Decapoda).

Unlike in crustacean freshwater species, the structure and ultrastructure of the excretory antennal gland is poorly documented in marine species. The general organization and ultrastructure of the cells and the localization of Na(+),K(+)-ATPase were examined in the antennal gland of the adult lobster Homarus gammarus. Each gland is composed of a centrally located coelomosac surrounded ventrally by a labyrinth divided into two parts (I and II) and dorsally by a voluminous bladder. There is no differentiated nephridal tubule between them. The labyrinth and bladder cells have in common a number of ultrastructural cytological features, including basal membrane infoldings associated with mitochondria, apical microvilli, and cytoplasmic extrusions, and a cytoplasm packed with numerous vacuoles, vesicles, lysosome-like bodies, and swollen mitochondria. Each type of cell also presents distinctive characters. Na(+),K(+)-ATPase was detected through immunofluorescence in the basal part of the cells of the labyrinth and in the bladder cells with an increasing immunostaining from labyrinth I to the bladder. No immunoreactivity was detected in the coelomosac. The cells of the labyrinth and of the bladder present morphological and enzymatic features of ionocytes. The antennal glands of the lobster thus possess active ion exchanges capabilities.

Animals↗
PubMedDate not supplied

[The electrovestibular reactions].

The article reviews results of studies of electric stimulation of the labyrinth in humans and animals. Electrostimulation of this organ either amplifies or inhibits vestibular reactions till complete suppression of both labyrinths revealed by muteness of labyrinth reflexes and loss of the ability to swim. Uniateral labyrinth destruction can be remedied by cathodal stimulation. Results of the author's investigations implicate current effectivness in controlling the vestibular input including cases of severe vestibular disfunction, e.g. death of labyrinth receptor formations, bilateral tumors, mechanic damage of nerve 8 and others.

Adaptation, Physiological↗
PubMed2004

[CT of the temporal bone in the study of the inner ear structures in detection of the causes of neurosensory hypoacusis].

Computed tomograms of the inner ear structures (n=175) of 150 patients (age 0-75 years) with unaffected temporal bones were studied in detail. It is shown that polyposition CT of the temporal bone is a non-invasive method of visualization of the osseous labyrinth structures: cochlea, vestibule, semicircular canals, aqueducts of the labyrinth and internal acoustic meatus which are reflected on tomograms in 100% cases irrespective of the patient age. Their age-related features are analysed. CT imaging was made in 65 patients with neurosensory hypoacusis of inherited and acquired genesis. The following causes of neurosensory hypoacusis and deafness were revealed: congenital malformation of the labyrinth of Mondini type, common cavity of the labyrinth, cochlear hypoplasia, dysplasia of the vestibule and semicircular canals, a wide aqueduct of the vestibule, stenosis of the internal acoustic meatus, bulboform enlargement of the inner acoustic meatus, neurinoma (schwannoma) of the hearing nerve, Langerhans-cell histiocytosis with affection of the labyrinth capsule, atypical cholesteatoma. The detected changes in the inner ear structures determine further treatment policy.

Adolescent↗
PubMed1986

Differential induction of ethoxyresorufin-O-deethylase in tissues of the rat placenta.

The placenta of the rat during late gestation is comprised of the yolk sac membranes, labyrinth and basal zone, which are of fetal origin, and the decidua basalis, which is derived maternally. Studies investigated whether the placental monooxygenase activity induced by administration of beta-naphthoflavone (beta-NF) and 3-methylcholanthrene (3-MC) to pregnant rats was localized differentially in these separate portions of the organ. Ethoxyresorufin-O-deethylation (EROD) was measured by fluorometric assay in homogenates of the respective placental tissues and of intact fetuses. EROD was very low or undetectable in feto-placental homogenates from untreated control animals. The administration of beta-NF and 3-MC increased EROD activity 50-fold over control in labyrinth and fetal homogenates, 10- to 15-fold in decidua, 8- to 20-fold in fetal membranes and 8-fold in basal zone preparations. The apparent Km value for ethoxyresorufin was significantly lower than control for EROD in labyrinth preparations from both beta-NF- and 3-MC-treated animals. Enzyme activity in labyrinth homogenates was maximally induced by 3-MC treatment for 1 to 3 days. In contrast, EROD activity was maximal after 1 to 2 days beta-NF administration, but declined markedly with longer duration of treatments. Subsequent studies compared the in vitro effects of alpha-naphthoflavone (alpha-NF) and beta-NF on induced EROD in feto-placental homogenates. The two benzoflavones were found to be equipotent as inhibitors with IC50 values less than 1 microM for labyrinth, maternal liver and fetal preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Angioneurosis in Menière's disease.

The main aim of this paper was to analyse whether labyrinthic angioneurosis, Menière's disease, can be provoked by immunity reaction at labyrinth level. The Menière's disease immunologic thesis dates back to the 1920's when Duke supposed an allergic origin for Menière's disease. Actually, this allergy could show local autonomic nervous system disturbances. This would be cholinergic and as a consequence, it would involve vascular elements of the inner ear. In any case, one should not forget that it has been found out that some patients suffering from Menière's disease have showed hypersensitivity to inhalants and food. A new theory has recently drawn scientists' attention. It states that atopic hypersensitivity cannot be mediated just from an immunologic point of view. Therefore, labyrinthic angioneurosis is not to be considered as immunomediated allergy but as a sort of altered reactivity of autonomic activities, to chemical mediators. These mediators can be released thanks to various stimulations: mental, physical, chemical and infective. We think that in some cases labyrinthic angioneurosis is not to be ascribed to labyrinth immune reaction which is immunomediated but this disease must be analysed from a chemical neuromediation point of view.

Antibody Formation↗