Strial Capillaries Research Articles

Permeability for horseradish peroxidase in strial capillaries in each turn of cochlea.

The capillary permeability of the stria vascularis in each turn of cochlea was examined at intervals of 10 and 30 min and 1 and 2 h after an injection of horseradish peroxidase (HRP), using light and electron microscopic techniques. Ten minutes after HRP was administered, 18% of examined vessels showed HRP leakage. Thereafter, the level of HRP leakage increased with time. One hour after the injection, HRP had leaked from almost all vessels of the upper three turns. Two hours after the injection, the tracer in the vessel lumen became sparse with very thin staining or nonstaining, and a large amount of HRP was observed outside the vessels. It was noted that the capillary permeability to HRP at the basal turn was different from that of the upper three turns. This seems to be the result of the different pinocytic activity in the capillaries of these two regions. When the tracer disappeared from the vessels (2 h after the HRP injection), labelled vesicles in endothelial cells were frequently visible near the outside surface, whereas very few were visible near the inner surface. It is speculated, therefore, that HRP which has leaked can be reabsorbed back into the blood circulation via a similar micropinocytosis down the concentration gradient.

Alterations in Capillary Permeability of Stria Vascularis of Guinea Pigs following Decapitation

Ten minutes after an intravenous injection of HRP, guinea pigs were killed by decapitation. The bullas were removed and opened, and the cochleas were fixed by perilymphatic infusion with glutaraldehyde. Blood shudging and considerable HRP leagage were observed in the capillaries of the stria vascularis. When blood was replaced with plasma expander, blood sludging did not appear after decapitation because few blood cells remained in the capillaries. Moreover, HRP leakage was scarecely observed in the strial capillaries. Even if the strial capillaries were contracted by the decapitation, HRP leakage did not occur without blood sludging. The high pressure between capillary endothelium and blood cells produces many marginal bolds, which efficiently transport HRP out of the capillaries.

Strial Circulation Impairment due to Acoustic Trauma

Blood circulation in the cochlear lateral wall after exposure to a non-physiological level of sound (120-125 dB SPL, 3 h) was investigated immunohistologically. Kanamycin (KM), which was expected to function as a tracer of blood flow, was administered to guinea pigs 5 min to 21 h after sound termination. At 5-30 min, KM was scarce in the capillaries of the stria vascularis (CSVs), whereas abundant KM was present in the spiral ligament vessels. These findings differed markedly from those in non-sound-exposed animals. After the initial period, KM gradually did enter into the CSVs, but its pattern of existence there differed from the normal pattern. These observations suggest that acoustic trauma causes blood stagnation in the strial capillaries, leading to strial dysfunction.

Transplacental Transfer of Kanamycin to the Embryonal or Fetal Inner Ear

Transplacental distribution of kanamycin (KM) to 35-60 day embryonal or fetal inner ear of the guinea pig following maternal treatment was investigated by an immunohistological technique. KM, administered at any stage of pregnancy, migrated through the placenta and entered into the cochlea. The drug pathway to the organ of Corti seemed to consist of two routes: the spiral vessels and the capillaries of the spiral limbus. However, at an early stage of pregnancy, KM was detected only slightly in the area corresponding to the stria vascularis, probably due to immaturation of strial capillaries.

Cochlear Microcirculation in Young and Old Gerbils

Human postmortem studies as well as epidemiologic investigations have implicated the peripheral vascular system as one of the etiologic factors of presbycusis. This study uses the surface dissection microsphere method for regional cochlear blood flow analysis and morphometric techniques for quantifying capillary density in the stria vascularis. In this study 11 old and 10 young gerbils were used. Our results indicate that blood flow in the cochlea was decreased in the old gerbils. This decrease was most obvious in the lateral portion (stria vascularis). The decrease of blood flow in older animals was clearly not related to loss of strial capillaries with aging. The decreased flow to the lateral portion must arise from either decreased perfusion pressure or from increased vascular resistance. This decreased blood flow in the aged animals supports a vascular theory of presbycusis.

Velocity of red blood cell flow in capillaries of the guinea pig cochlea

Velocities of red blood cells (RBCs) in the lateral wall of the cochlea were determined in the anesthetized guinea pig from direct optical microscopic observations. Mean flow velocity of the blood was measured by timing the passage of a fluorescently-labeled subpopulation of RBCs across a measured capillary length. The optical observations were achieved using an intravital microscope equipped for epifluorescence and the measurements were derived from video images acquired with an image intensified television camera. In the third turn of the cochlea the velocity of RBCs differed significantly between two major classes of capillaries. The mean velocity in spiral ligament vessels was 0.12 mm/s while stria vascularis flow was slower (0.08 mm/s). In a typical animal, the range of velocities among different vessels of the ligament was 0.09-0.18 mm/s while it was 0.03-0.10 mm/s for stria vascularis vessels. Corresponding to this velocity difference, the apparent mean vessel diameters for the two types of vessels also differed. Spiral ligament capillaries were 9.3 micron while strial capillaries were 12.2 micron in diameter. Comparison of flow velocity in different turns of the cochlea indicated that the distribution of blood velocity throughout the cochlea lateral wall is constant.

Change in the capillary permeability of the stria vascularis by different methods of death and fixation.

The permeability of the stria vascularis to horseradish peroxidase (HRP) was examined. Ten minutes after an intravenous injection of HRP, 15 guinea pigs were killed and fixed by four different methods: cochleas fixed 3 minutes after decapitation, administration of an overdose of pentobarbital, cochleas fixed for 5 minutes before decapitation, and cochleas fixed immediately after decapitation. In the animals in group 1, HRP leakage was observed in almost all strial vessels (86%), and blood sludging and amorphous HRP reaction product in 98% of strial capillaries. In the animals in group 2, strial capillaries were observed both with noticeable HRP leakage and with no evidence of leakage. Blood sludging was associated with amorphous HRP reaction product, while no blood sludging was associated with granular HRP reaction product. In group 3 animals, only faint or no HRP reaction product was observed in the perivascular spaces. Only 3% of the capillaries had blood sludging. In the animals in group 4, blood sludging but no HRP leakage was observed in almost all capillaries (82%). It is speculated that HRP does not normally leak from the strial capillaries, although many researchers have reported to the contrary. It appears that HRP leaks from the strial capillaries only when acute anoxia or hypotension continues for a few minutes. These conditions induce blood sludging and are followed by the appearance of many marginal folds in these capillaries.

The influence of steroid hormone to the blood flow of strial capillaries

The influence of steroid hormone to the blood flow of strial capillaries

The effect of bumetanide on the stria vascularis: a stereological analysis of cell volume density.

The purpose of this research was to determine the effect of bumetanide on the volume density (Vv) of the cells, capillaries and intercellular spaces of the stria vascularis (SV). 29 chinchillas were divided into seven groups. There were 3 experimental groups, three control groups and one normal, untreated, group of animals. After either a 20 mg/kg intravenous injection of bumetanide or an injection of a control solution, the animals were killed at 10 min, 1 h and 24 h. One complete radial section of the SV was analyzed in each animal. This section was located at 70% of the length of the basilar membrane as measured from the cochlear apex. Marginal cell volume decreased by 24% and 15% at 10 min and 1 h, respectively, after bumetanide administration. Intermediate cell volume increased by 31% and 27% at 10 min and 1 h, respectively, after bumetanide administration. Intercellular space volume increased by 14% and 21% at 10 min and 1 h, respectively, after bumetanide administration. No significant alteration in the Vv was observed in the strial capillaries or basal cells. A hypothetical model of the ion transporting properties of the SV is presented.

Alteration of strial capillary transport in kanamycin-treated guinea pigs.

Ferritin transport through the strial capillary during kanamycin intoxication was examined under a transmission electron microscope. Twelve guinea pigs were treated intramuscularly with kanamycin (400 mg/kg/day) for 2-3 weeks. When full hearing loss was recognized by estimating the Preyer reflex or auditory brain-stem response (ABR), ferritin was given intravenously and animals were sacrificed 1/3, 1, and 2 h later. At 1/3 h, ferritin was present diffusely not only in the endothelial cell but also in the basal lamina and within vesicles in the strial cell. Alternatively, it was discharged into the endolymphatic space. At 2 h, ferritin was seen on the luminal surface and in the cytoplasm of the endolymphatic cells of Reissner's membrane. These results suggest that the basal lamina of the strial capillary was altered qualitatively by kanamycin administration.

Ultrastructural and electrophysiological studies of acute ototoxic effects of furosemide.

Previous studies of the effects of ethacrynic acid on the inner ear following intraperitoneal injection of the diuretic have shown a progression of reversible changes occurring in the stria vascularis. The time course of these changes approximately parallels alterations in endolymphatic potential (EP). In this report, some preliminary findings concerning the effects of furosemide after intraperitoneal injection of 80 mg/kg are described. EP declined over a longer time course than that recorded with intravenous injection. Cochlear microphonic (CM) and compound action potential (CAP) also declined but to differing degrees. In the stria vascularis a progression of changes was apparent. In general, the changes were similar to those observed following ethacrynic acid intoxication and affected marginal cells, intermediate cells and strial capillaries. The upper basal turn of the cochlea was affected first and the damage spread apically. In the organ of Corti, stereocilia on the outermost row of outer hair cells were disorganized. This was apparent in approximately the same region as initial strial effects and was only observed when strial derangement was quite marked.

Replacement of perilymph with K+-free media abolishes positive endocochlear potential (guinea pig)

Perfusion of the perilymphatic space with K+-free media leads to a gradual decline of the endocochlear potential (EP) to negative values near those observed during anoxia. The input resistance of scala media does not decrease during this time. In sharp contrast to anoxia, the ATP content of the stria vascularis (SV) remains near normal during K+-free perfusion (85%). Thus, a significant interference with strial energy generation appears unlikely. Following K+-free perfusion, the K+ content of the spiral ligament (SL) was reduced from 227 to 59 and that of the SV from 410 to 266 mmoles/kg dry wt. The pronounced reduction of the K+ content of the SL indicates that the perfusate reaches the lateral wall of the SV. These results demonstrate that a reduction of the [K+] of perilymph leads to an inhibition of the generator of the positive component of the EP. If it is true that the SV is responsible for the production of the +EP, the results suggest furthermore that K+, contained in the strial capillaries, may not have access to the generator of this potential. [Supported by NIH and NSF.]

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.

Symposium on basic ear research. II. Strial atrophy in clinical and experimental deafness

AbstractThe hair cells and the first‐order neurons of the cochlear nerve are usually considered to be the primary targets of traumatic, ototoxic, and degenerative processes affecting the inner ear. The purpose of this paper is to show that several forms of sensori‐neural deafness are associated with atrophy of the stria vascularis, and that strial atrophy often precedes and may indeed be an important cause of hair cell loss.Strial atrophy was found: 1. in presbycusis; 2. in hereditary deafness in Dalmatian dogs; 3. after noise exposure; and 4. after ototoxic drugs. The technique used was that of dissecting the cochlea, stained with Osd4, into surface preparations. Special attention was given to the spiral ligament and the‐stria vascularis.In man, sensori‐neural degeneration with aging was invariably associated with strial atrophy. There appeared to be a direct relation between severity of strial atrophy and hair cell loss. The findings in two old animals were similar to those in man. We found no cases with obvious strial atrophy and a normal hair cell population.Four litters of deaf Dalmatian dogs were studied. Two litters were from deaf parents and two were from a deaf bitch and a hearing male. Animals sacrificed at various ages displayed a series of changes involved in cochleosaccular degeneration. The following phases were observed: 1. strial atrophy; 2. a. sagging of Eeissner's membrane and onset of hair cell degeneration, b. collapse of Reissner's membrane, ductus reuniens, and the membranous wall of the saccule; 3. complete hair cell degeneration, involving first the outer hair cells, then the inner hair cells; and 4. nerve degeneration.The offspring of deaf parents showed bilateral degeneration, occurring mainly during the first two to three weeks postnatally. In the litter from a deaf female and a hearing male, several pups had complete cochleo‐saccular degeneration on one side, with partial involvement on the opposite side. Four of these pups had strial atrophy in the middle and apical turns, and recent outer hair cell degeneration in the corresponding area. This finding suggests a close relation between strial atrophy and hair cell degeneration. The capillaries in the atrophic stria were narrow and had markedly thickened walls.Cats were given high doses of neomycin and ethacrynic acid. Guinea pigs were given gentamicin, also in high doses. All three drugs caused strial atrophy, which was most severe in the basal turn but was also pronounced in the apical turn in the neomycin and ethacrynic acid‐treated animals. The neomycin‐ and gentamicin‐treated animals showed severe to total hair cell degeneration, but ethacrynic acid‐treated cats showed virtually no hair cell loss despite severe strial changes. With one exception the neomycin‐treated animals had the most severe changes, with only an epithelium and network of empty, atrophic capillaries and strands remaining in the most affected areas. The stria of the ethacrynic acid‐treated animals had a distinctive appearance, with swollen osmiophilic cells clumped around the capillaries and severe atrophy between the blood vessels.Twelve guinea pigs were exposed to a wide‐band noise at 120 db SPL for eight, 30 and 110 hours. In one 110‐hour animal and two 30‐hour animals, ultrastructural changes were observed in the stria vascularis. The marginal cells displayed marked loss of cell processes and their nuclei were pyknotic. The basement membrane of the strial capillaries was thickened.Strial atrophy appears to be a common denominator in sensory degeneration. It is suggested that the atrophy alters the composition of the endolymph, and may thus cause hair cell degeneration; however, the temporal relationship between stria atrophy and hair cell loss is still to be ascertained.

The fine structure of the stria vascularis of the cat inner ear.

AbstractThe fine structure of the cat stria vascularis was studied with the electron microscope. It consists of three layers of epithelial cells in close association with intraepithelial capillaries. The cells of the superficial row have a convex luminal surface bordering on the cochlear duct lumen. The apical cytoplasm contains numerous coated vesicles and vesicular invaginations which are interpreted as a type of micropinocytosis. Deep infoldings of the plasmalemma divide the lower two‐thirds of these cells into thin compartments containing numerous mitochondria. It is suggested that marginal cells are well adapted by their fine structure to participate in regulation of the ion composition of endolymph. The cells of the intermediate and basal rows have pale cytoplasm and numerous processes Ascending processes of the basal cells form cup‐like structures which partially isolate each apical cell from the rest of the epithelium.The endothelium of the strial capillaries is not remarkable and no discontinuities of the endothelial lining were observed. The endothelial basement lamina sends out numerous extensions into a system of interconnected extracellular passages that permeate the epithelium. These are interpreted as pathways for the rapid diffusion of materials from the capillaries.