Ethylene glycol monomethyl ether (EGME) has been found to produce testicular atrophy in experimental rodents. The studies that follow were designed to determine the testicular cell type(s) most susceptible to EGME administration. For histologic studies, F344 rats were gavaged with 150 mg/kg/day of EGME 5 days per week, and serially sacrificed. In sections from perfusion-fixed tissue, necrotic changes were observed in some meiotic and premeiotic spermatocytes 24 hours after a single dose. Also, nuclear condensation was seen in occasional early pachytene spermatocytes. These effects were magnified after two doses; there were more necrotic pachytene and meiotic spermatocytes than necrotic stage I pachytene spermatocytes. By day 4, testes from all treated animals were affected; there was a pronounced maturation-depletion effect, seen as the absence of round spermatids from tubules in stages I to III. These effects continued to develop at days 7 and 10, leaving only Sertoli cells, spermatogonia, and late stage spermatids populating the epithelium. Other animals were treated similarly, but subject to efferent duct ligation 16 hours prior to sacrifice. Fluid production, as judged by weight gain in the testes after efferent duct ligation, was unaffected by EGME treatment. Analysis of the fluid collected at the rete testis indicated that there was no treatment-related change in the relative amounts of androgen binding protein. The data indicate that the spermatocyte is the primary target cell for the histologic effects of EGME in the testis of F344 rats.

Animals↗

PubMedDate not supplied

Ultrastructural morphology and protein content of the internal organic material of rat otoconia.

Otoconia taken from the maculae of the saccule and utricle of the rat inner ear were investigated using transmission electron microscopy (TEM). Their ultrastructure was compared using various decalcification techniques. Similar preparations were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to assess their protein constituents. TEM results show loss of organic material during prolonged decalcification. This is not seen in samples decalcified overnight. The SDS-PAGE results show that rat otoconia contain a major broad band of 90-100 kDa, a major thin band of 56 kDa, and three other bands of 33, 45, and 50 kDa. The band of 56 kDa may be associated with the surface of the otoconia.

Animals↗

PubMedDate not supplied

Medicine in long duration space exploration: the role of virtual reality and broad bandwidth telecommunications networks.

Safety of astronauts during long-term space exploration is a priority for NASA. This paper describes efforts to produce Earth-based models for providing expert medical advice when unforeseen medical emergencies occur on spacecraft. These models are Virtual Collaborative Clinics that reach into remote sites using telecommunications and emerging stereo-imaging and sensor technologies.

Aerospace Medicine↗

PubMedDate not supplied

Cellular localization of Na+,K+-ATPase in the mammalian cochlear duct: significance for cochlear fluid balance.

Cytochemical and autoradiographic procedures were employed to determine the cellular distribution of Na+,K+-ATPase in the guinea pig cochlea. The highest activity was associated with the stria vascularis and was restricted almost entirely to the contraluminal extensions of the marginal cells. Elevated levels of activity were also observed in stromal cells of the spiral prominence, external sulcus, and spiral limbus. The pattern of activity in the latter tissues was unusual in being symmetrically distributed along the plasma membranes of the reactive cells. In the organ of Corti, only neural elements showed appreciable activity. Possible functions of the enzyme are discussed in relation to cochlear fluid balance.

Animals↗

PubMedDate not supplied

Possible functional roles of Na+,K+-ATPase in the inner ear and their relevance to Ménière's disease.

This article reviews the functions of the enzyme Na+,K+-ATPase in epithelial tissues and discusses early and recent biochemical, physiologic and morphologic studies of the enzyme in the inner ear. The purpose of the investigation was to learn whether a relationship between perturbations in activity of the enzyme and Ménière's disease is possible. It is concluded that the preponderance of the evidence indicates that Na+,K+-ATPase plays a role in regulating ion transport into the scala media, but that the significance of the distribution of the enzyme along only one cell type (the marginal) in the functional chains of cells of the outer cochlear wall needs further study. The possible vasoconstrictive effects of ouabain perfusions employed by some investigators must also be taken into account. Recent cytochemical and autoradiographic studies have demonstrated high levels of Na+, K+-ATPase on cochlear nerve fibers, especially near the foramina nervosa and within the organ of Corti. Thus, perturbations in Na+,K+-ATPase activity in the inner ear not only could affect certain aspects of fluid balance, but also could account for the sensory disturbances experienced by patients who have Ménière's disease.

Animals↗

PubMedDate not supplied

Simulation studies of vestibular macular afferent-discharge patterns using a new, quasi-3-D finite volume method.

A quasi-three-dimensional finite-volume numerical simulator was developed to study passive voltage spread in vestibular macular afferents. The method, borrowed from computational fluid dynamics, discretizes events transpiring in small volumes over time. The afferent simulated had three calyces with processes. The number of processes and synapses, and direction and timing of synapse activation, were varied. Simultaneous synapse activation resulted in shortest latency, while directional activation (proximal to distal and distal to proximal) yielded most regular discharges. Color-coded visualizations showed that the simulator discretized events and demonstrated that discharge produced a distal spread of voltage from the spike initiator into the ending. The simulations indicate that directional input, morphology, and timing of synapse activation can affect discharge properties, as must also distal spread of voltage from the spike initiator. The finite volume method has generality and can be applied to more complex neurons to explore discrete synaptic effects in four dimensions.

Action Potentials↗

PubMedDate not supplied

The nature and crystal growth of otoconia in the rat.

Several types of otoconia are present in the macular regions of young rats. These include multifaceted, transitional and rounded body forms, some variant otoconia and a few rhombohedrons. The adult form has typically rounded by nonsmooth body surfaces and pointed ends with three planar faces. The multifaceted and transitional otoconia fracture and etch more readily than do the adult type. The differences in properties of the otoconia are considered in the light of known facts concerning inorganic crystal nucleating and growth. This integrated approach indicates that many otoconia originate by seeding of multiple subunits on an organic substrate and develop by the mechanism of parallel growth. The basic structural unit is the rhombohedron. By analogy to inorganic crystals of calcite, it would seem that the typical otoconium grows on the end faces but growth on the side faces is suppressed by some unknown chemical factor. Some otoconia are exceptions, evidently seeding and growing in the pure rhombohedral form. Decalcification of cleaved otoconia shows that organic material is incorporated during growth. The observations are interpreted to indicate that organic substance influences growth and achievement of the adult otoconial form.

Animals↗

PubMedDate not supplied

Observations on normal and degenerating human otoconia.

Specimens of human otoconia obtained from autopsy material and representing various stages from fetal to advanced old age, were studied by microdissection, scanning electron microscopy, electron microprobe analysis, and x-ray powder diffraction. The typical adult otoconial configuration is a cylindrical, finely serrated body with pointed ends; crystallographically, it corresponds to a single crystal of calcite. Other, less numerous typed include jointed otoconia, pure rhombohedrons and multifaceted, presumably immature forms. Many otoconia achieve the adult configuration during fetal development. The multifaceted otoconia are most numerous, and the rhombohedrons proliferate, during childhon in the young adult, but saccular otoconia are the larger. In middle and advanced age the otoconia decrease in number, especially in the saccule. Saccular otoconia degenerate progressively in a posteroanterior direction across the macula; they assume a specific, fibours, hollowed-out appearance, which is not duplicated by either chemical etching or autolysis. Neogenesis and growth of otoconia appear to occur postnatally, with different characteristic growth potentials for those of the saccule and the utricle. Age-related saccular otoconial degeneration appears to involve the organic material, which disappears either before or simultaneously with the mineral substance.

Adolescent↗

PubMedDate not supplied

Otoconial formation in the fetal rat.

The development of otoconia in the fetal rat was investigated by scanning and transmission electron microscopy and by x-ray elemental analysis. The transmission electron microscopical results indicate that primitive otoconia are highly organic appearing but are trigonal in cross section, indicating that they already possess a three-fold axis of symmetry and a complement of calcite. These otoconia develop into spindle-shaped units which accrue fibrous, organic material at an angle to their surfaces. Dumbbell-shaped otoconia, with distinct central cores and peripheral zones, result. These otoconia then mature to the adult crystal configuration having a more cylindrical body and pointed ends. The existence of trigonal, spindle- and dumbbell-shaped otoconia was verified by scanning electron microscopy of fresh-frozen material. Tissues prepared for transmission electron microscopy proved (by elemental analysis) to have been decalcified inadvertently, fortuitously revealing the arrangement of the organic material. Subsequent transmission electron microscopy of dumbbell-shaped otoconia not exposed to fluids during embedment showed that calcite deposits mimicked the arrangement of the organic material. X-ray elemental analysis demonstrated that calcium was present in lower quantities in the central core than peripherally. Findings are interpreted to indicate that organic material is essential to otoconial seeding and directs otoconial growth.

Acoustic Maculae↗

PubMedDate not supplied

Horseradish peroxidase acute ototoxicity and the uptake and movement of the peroxidase in the auditory system of the guinea pig.

When guinea pig cochlea was perfused in vivo with a solution of 1% horseradish peroxidase (HRP) in artificial perilymph, the enzyme was found in the basilar membrane, spiral limbus, some outer and inner hair cells and some supporting cells and it was gradually cleared away with time. Acute signs of cell damage included swelling, vacuolization and diffuse labeling of some hair cells, but stereocilia remained normal in configuration. Albino melanocytes of the spiral ligament were also damaged, and vacuolization of Reissner's membrane occurred after 10% HRP. Both concentrations caused a gradual decline in CM, showing that HRP is acutely ototoxic but its mode of action is unknown. No retrograde transport of HRP to spiral ganglion cells or to brain stem neurons occurred, but some brain stem neurons took up HRP from the neuropil following diffusion from the cochlea.

Animals↗

PubMedDate not supplied

Glycogen accumulation in Reissner's membrane following chemical sympathectomy with 6-hydroxydopamine.

Explore the source record for details and available documents.

Age Factors↗

PubMedDate not supplied

A survey of the effects of loop diuretics on the zonulae occludentes of the perilymph-endolymph barrier by freeze fracture.

The acute (30 min) effects of the loop diuretics piretanide, ethacrynic acid, bumetanide, furosemide, and azosemide, and the chronic (8 days) effects of furosemide and bumetanide on the zonulae occludentes (tight junctions) of the perilymph-endolymph barrier in the stria vascularis and in Reissner's membrane of the basal cochlear turns were studied by freeze-fracture. Quantitative analysis of their effects indicated that the structural integrity of the barrier was modified by either as increase or a decrease in the number, depth, and density of the strands of the tight junctions of the strial marginal cells. Only azosemide appeared to modify the tight junctions between the epithelial cells of Reissner's membrane, but it had little effect on the strial junctions. The tight junctions between the basal cells of the stria appeared to be the least affected by the various loop diuretics, although piretanide appeared to increase randomly the intercellular spaces lying between the strands.

Animals↗

PubMedDate not supplied

Morphological evidence of vestibular pathology in long-term experimental diabetes mellitus. I. Microvascular changes.

The influence of long-term experimental diabetes on the microvasculature of the saccule and utricle was investigated using quantitative light and electron microscopic techniques. Basal lamina thickening or reduplication, typically seen in diabetic microangiopathy, were not observed. However, morphometric analysis did reveal a statistically significant increase in capillary diameters along with an increased vascularization of both the saccule and utricle. Both of these microvascular abnormalities may have been caused by the hemodynamic alterations known to occur in diabetes. These alterations include decreased deformability of red blood cells and increased blood viscosity. Either of these factors can lead to a greater stress on the capillary wall and possibly to a reduced oxygen delivery to the tissues.

Analysis of Variance↗