Biomedical subjects

E M Keithley

Publications and source records attributed to E M Keithley.

At least 37 records · Page 2Linked to original sources

PubMed1995

Evidence linking the 68 kilodalton antigen identified in progressive sensorineural hearing loss patient sera with heat shock protein 70.

Immunoblotting against bovine inner ear extracts has previously identified a 68 kd antigen reactive with 22% to 58% of sera of patients with rapidly progressive sensorineural hearing loss (PSNHL) of suspected autoimmune causation. Efforts to purify and characterize this diagnostic antigen suggest that it is ubiquitous rather than inner ear-specific, and may represent the highly inducible heat shock protein (hsp) 70. The antigens identified by PSNHL sera and anti-hsp 70 monoclonal antibodies copurify on ion exchange and adenosine triphosphate affinity chromatography, and comigrate on one- and two-dimensional gel electrophoresis. Additionally, immunoblotting with positive patient sera shows dramatically increased expression of the 68 kd antigen by bovine kidney cells following heat shock in culture. Reactivity with stress proteins of various classes has been reported in a number of autoimmune diseases; however, anti-hsp 70 appears uniquely associated with ulcerative colitis and PSNHL.

Animals↗

PubMed1995

Na,K-ATPase in the cochlear lateral wall of human temporal bones with endolymphatic hydrops.

Meniere's disease has traditionally been thought to arise from a disruption in longitudinal endolymphatic flow. This view has been brought into question by recent experimental studies that have focused attention on derangements of cochlear fluid and electrolyte homeostatic mechanisms in Meniere's disease, including abnormalities in Na,K-ATPase enzymes found in the cochlear lateral wall. The current study examined the immunohistochemical labeling pattern of the major ion-transporting enzyme of the stria vascularis, Na,K-ATPase, in archival sections of hydropic and nonhydropic human temporal bones for increased density of label that could indicate overproduction of fluid. The results showed good labeling of the stria vascularis in the celloidin sections. The hydropic ears tended to have darker label, but the difference was not statistically significant. The findings are consistent with normal functioning of the stria vascularis in cases of Meniere's disease.

Animals↗

PubMed1995

Antigen diffusion from the perilymphatic space of the cochlea.

The diffusion pattern of horseradish peroxidase (HRP) injected into the scala tympani of the cochlear basal turn of guinea pigs was studied to test whether antigen presented in this manner can gain access to the endolymphatic sac. By two hours, HRP reaction product was found throughout the cochlea, with the greatest amounts in the spiral ligament, spiral limbus, basilar membrane, and organ of Corti. In several cochleas, very weak labeling was seen in the stria vascularis. HRP reaction product was maximal in the basal turn. By two hours, HRP reaction product was also observed in the endolymphatic sac lumen, epithelial cells, subepithelial tissue, and perisaccular connective tissue. It was more common in the proximal portion. At this time, macrophages within the lumen already appeared to have phagocytosed the HRP. By 72 hours after injection, the inner ear was cleared of HRP. The results of this study support the hypothesis that antigen in the scala tympani gains access to the endolymphatic sac lumen, where it may be presented by macrophages to the systemic immune system. Antigen most likely does not gain access to the endolymphatic space in the cochlea, but it gets to the endolymphatic sac through the perilymph and the perisaccular tissue.

Animals↗

PubMed1995

Assessment of serum antibodies in patients with rapidly progressive sensorineural hearing loss and Menière's disease.

The immunoreactivity of sera from patients with rapidly progressive sensorineural hearing loss (SNHL) or Menière's disease with bovine inner ear material was determined using the Western blot technique. Patients with other otologic conditions, autoimmune disorders, or arthritic disorders and age-matched randomly chosen patients with no hearing complaints served as controls. Twenty-two percent of the patients with bilateral rapidly progressive SNHL and 30% of the patients with Menière's disease had antibodies that reacted with a 68 kd antigen in the inner ear material. In the control groups, the incidence of reactivity was 5.0% (P < .001). When the results of this study were compiled with data collected previously, it was found that of 279 patients with bilateral rapidly progressive SNHL, 90 (32%) were positive with the 68 kd protein. Thus, the anti-68 kd antibody may provide a good marker for an immune etiology of these patients' hearing loss.

Adolescent↗

PubMed1994

2-Deoxyglucose uptake patterns in response to pure tone stimuli in the aged rat inferior colliculus.

The tonotopic map of the inferior colliculus (IC) of aged rats (25 months old) was examined to determine whether age-related changes known to occur in the cochlea are reflected in the 2-deoxyglucose (2-DG) uptake pattern of the IC. Because aged animals have hearing losses, auditory brainstem response thresholds were measured. Animals with threshold shifts of no greater than 30 dB relative to young animals were used. Animals were injected with radiolabeled 2-DG and stimulated with continuous pure tones presented at 70 dB above the behavioral thresholds for young animals at either 1, 4 or 32 kHz for one hour in a sound attenuated booth. The stimulus sound pressure levels were chosen to achieve comparable sensation levels between the young and aged animals. The tonotopic map of the IC in aged rats was different from that reported previously for young animals (Ryan et al., 1988), in that, the regions stimulated by 1 and 4 kHz were shifted towards the higher frequencies and the uptake areas were twice as broad for the aged animals as for the young animals. The observed 2-DG uptake patterns are consistent with an activation pattern of a high intensity stimulus and a loss of responsive elements in the cochlear apex. Similar broad and shifted bands of activated tissue may contribute to difficulties in auditory perception in aged humans with increased thresholds and sound amplification.

Acoustic Stimulation↗

PubMed1994

Fibronectin-like immunoreactivity of the basilar membrane of celloidin-embedded human temporal bone sections.

Dysfunction of the mechanical properties of the basilar membrane is a potential cause of presbycusis. In cases of minimal sensorineural or strial degeneration it is believed to play a major role. The membrane has been shown to be partly composed of fibronectin. Fibronectin immunoreactivity is diminished in aged rats. Mesothelial cell line the perilymphatic surface of the membrane and are reduced in number in the aged rat cochlea. Fibronectin immunoreactivity was examined in human temporal bone sections (6 months to 92 years old). Hematoxylin and eosin stained section (17 to 97 years) were immunoreactivity was demonstrable in the human cochlea, but was not reduced, even in the eldest cases examined The number of mesothelial cells was reduced, however, and was related to the age of the individual, but not to the clinical diagnosis or audiogram shape. These two factors do not, therefore, appear to give rise to hearing losses associated with presbycusis.

Adolescent↗

PubMed1993

Fibronectin-like immunoreactivity of the basilar membrane of young and aged rats.

Dysfunction of cochlear mechanics has been hypothesized to be a source of age-related hearing loss and the basilar membrane mass and stiffness contribute to normal cochlear mechanics. Fibronectin, a large, extracellular matrix protein and a major component of the basilar membrane, may contribute to both the mass and stiffness of the membrane. Mesothelial cells underlying the basilar membrane may produce the fibronectin and also contribute to the mass of the membrane. Changes in either the fibronectin or the mesothelial cells might, therefore, have an effect on cochlear mechanics. In order to assess basilar membrane changes in aged animals, young adult (2-4 months) and aged (24-26 months) Sprague-Dawley rats were evaluated for the presence of fibronectin-like protein and mesothelial cells. The basilar membrane in the young animals had strong fibronectin-like immunoreactivity throughout its length. The old animals, on the other hand, showed normal fibronectin immunoreactivity in the basilar membrane of the basal turn, but little or no reactivity in the apical cochlear turn. The number of mesothelial cells was reduced throughout the length of the membrane in aged animals, with the greatest loss in the basal turn (60% fewer cells). These two degenerative changes, which appear to be independent of each other, may contribute to the observed threshold shifts in aged cochleas.

Aging↗

PubMed1993

Development of high endothelial venule-like characteristics in the spiral modiolar vein induced by viral labyrinthitis.

The postcapillary venule is known to be the preferred site of lymphocyte migration into the extravascular compartment. In this study, induction of these high endothelial venule (HEV)-like vessels has been investigated by inoculation of live cytomegalovirus or inactivated virus into scala tympani of guinea pig cochleas. Endothelial cells of the spiral modiolar vein (SMV) were evaluated histologically 2 to 6 days following inoculation. The experimental group endothelial cells had larger nuclei and increased amounts of cytoplasm. In addition, many lymphocytes were adherent to and present within the vascular wall. Control SMV endothelia showed normal structure and morphology throughout the study. These findings reiterate that nonlymphoid tissues may develop HEV-like characteristics and suggest that HEV-like morphology may be acquired during an acute inflammatory condition in the cochlea.

Animals↗

PubMed1993

Evidence of direct communication of bone marrow cells with the endolymphatic sac in experimental autoimmune labyrinthitis.

In experimental autoimmune labyrinthitis, we found that the guinea pigs sensitized with bovine inner ear antigen (IEAg) developed cellular infiltration within the endolymphatic sac (E. sac). In this study, we investigated the distribution of immune mediated cells within bony vascular channels. The channels, which are normally found around the E. sac, are tiny and contain few immune-mediated cells. In contrast, in guinea pigs sensitized with IEAg bony vascular channels were large and contained immune-mediated cells. We hypothesize that immune-mediated cells in these channels are the result of the immune response directed against inner ear antigen, and that some immune-mediated cells seen in the E. sac during inner ear inflammatory events have migrated from the adjacent bone marrow.

Animals↗

PubMed1993

Inner ear inflammation and round window otosclerosis.

Recently, it has been suggested that otosclerosis represents the host's ongoing immunologic response to measles or other viral antigens. Documentation of past inflammation within the inner ear would serve as further evidence that this mechanism may be at play in the pathogenesis of the disease. Among the characteristic signs of prior inflammation in the inner ear is the presence of lamellar bone at the site of inflammation. This has been described in the temporal bone of a patient with immune-mediated deafness and with the temporal bones of experimental models of immune-mediated inner ear disease. Review of temporal bones with round window otosclerosis from the Eastern Temporal Bone Bank at the Massachusetts Eye and Ear Infirmary show that in four of ten cases there are characteristic signs of a prior severe inflammatory event centered in the scala tympani adjacent to the otosclerotic lesion. Otosclerosis, therefore, may have an inflammatory stage that is the consequence of a host response to an inciting event.

Autoimmunity↗

PubMed1992

Selective retrograde transport of nipecotic acid, a GABA analog, labels a subpopulation of gerbil olivocochlear neurons.

Perfusion of the gerbil cochlea with micromolar quantities of 3H-gamma-aminobutyric acid (GABA) results in rapid, selective labeling of 50-60% of the olivocochlear (OC) efferent terminals on afferent dendrites beneath the inner hair cells, and all of the efferent terminals beneath the outer hair cells. In order to identify the neurons from which these GABA-accumulating terminals originate, the cell bodies were localized by using retrograde transport of 3H-nipecotic acid, a metabolically inert GABA analog. With survival times of 6-30 hours after cochlear injection, myelinated OC efferent fibers and cell bodies were well labeled, with the greatest number being labeled at 12-18 hours. All of the labeled neurons belonged to the medial OC system, and no lateral OC neurons were labeled. It is concluded that the GABA-accumulating endings in the gerbil cochlea arise from medial OC neurons, and therefore that medial OC efferent neurons in this species project to both inner and outer hair cell regions.

Animals↗

PubMed1992

Cochlear degeneration in aged rats of four strains.

Animals with various degrees of inbreeding, some of which are albino, are frequently used in biological research. Albinos do not produce melanin and it is therefore absent from the cochlea. While the function of melanin is unknown, it has been hypothesized that it is involved in cochlear homeostasis. It is possible then, that age-related degeneration may be affected by the presence or absence of melanin. We therefore evaluated young (2-6 months old) and aged (24-36 months old) cochleas in 4 different rat strains: albino Fischer 344 and Lewis rats and pigmented Lewis-Brown Norway F1 rats and Brown Norway rats. Cochlear morphology was the same across all strains of young adult animals with the exception that the pigmented animals had small, darkly stained granules in the stria vascularis. The aged pigmented animals all had large granules as well as small ones. Degeneration of spiral ganglion cells in the apical region of the ganglion had occurred in the old animals of all strains. Strial degeneration at the apex was also present in aged animals. There was no correlation between the presence or absence of melanin and the magnitude of cochlear degenerative changes in the aged animals. The presence or absence of melanin therefore, appears to have no effect on cochlear degeneration in the aged rat cochlea.

Aging↗

PubMed1992

Spiral modiolar vein: its importance in viral load of the inner ear.

Guinea pig-specific cytomegalovirus and Sendai virus were inoculated into the cochleas of seronegative guinea pigs to study the route of entry of cells participating in inner ear inflammation. Inflammatory cells accumulated around the spiral modiolar vein and appeared to be streaming from this vein into the scala tympani via a collecting venule. Inactivated virus inoculated into the cochlea and normal control cochlea failed to show inflammatory cell infiltrates. The spiral modiolar vein appears to play an important role in the movement of cells from the systemic circulation into the inner ear as part of the host's normal defense against invading pathogens such as viruses.

Animals↗

PubMed1992

Effects of bacterial endotoxin applied to the guinea pig cochlea.

The ototoxic potential of bacterial endotoxin present in middle ear effusions was evaluated by inoculating endotoxin solutions of 10 micrograms/mL or 1000 micrograms/mL directly into the scala tympani of the guinea pig cochlea. Median auditory brainstem response threshold shifts of 12.5 and 20 dB were observed in the experimental ears exposed to the higher dose at days 2 and 4, respectively, with gradual improvement to near baseline by day 28. Histologic examination revealed inflammatory infiltrates in the scala tympani and scala vestibuli of several of these cochleas. The lower concentration, closer to that found in human effusions, elicited no significant loss of hearing and a milder inflammatory response. It is concluded that brief exposure of the cochlea to endotoxin from middle ear effusions is insufficient to cause hearing loss. Under chronic conditions, however, persistent inflammation within the cochlea may result in a sensorineural deficit.

Animals↗

PubMed1991

Type B Haemophilus influenzae-induced otitis media in the mouse.

To characterize the middle and inner ear cellular inflammatory responses to otitis media using immunohistochemical methods, we inoculated type B Haemophilus influenzae into the middle ears of healthy adult BALB/c mice. Mac-1+ neutrophils and macrophages appeared in the middle ear at 3 days. Lyt-1+ T cells and Lyt-2+ T suppressor/cytotoxic cells entered the middle ear mucosa on days 7 and 14. IgG+ and IgM+ T cells were present at all time points, with IgA+ lymphocytes forming the majority of mucosal immunoglobulin-bearing cells at 2 weeks. The cochlear scala tympani contained Lyt-1+ and Mac-1+ cells and two endolymphatic sacs stained diffusely with anti-IgA and -IgG antibodies. Lyt-1/L3T4+ T lymphocytes greatly outnumbered B lymphocytes, suggesting that helper/inducer T cells play a more important role in acute otitis media than has been recognized. Inner ear changes occurred after a single episode of otitis media.

Animals↗

PubMed1990

Collaterals from lateral and medial olivocochlear efferent neurons innervate different regions of the cochlear nucleus and adjacent brainstem.

Two populations of superior olivary neurons which project to different sensory cell regions in the cochlea also give off collateral projections to the ventral cochlear nucleus (VCN) and adjacent brainstem. To determine whether these VCN projections also have different targets they were characterized by selective retrograde amino acid transport. Retrograde transport of 3H-d-aspartate (D-ASP) selectively labeled the unmyelinated fibers and neurons of the lateral olivocochlear (OC) system including a dense collateral projection to the central VCN. Retrograde transport of 3H-nipecotic acid (NIP) labeled the myelinated fibers and neurons of the medial OC system, including collateral projections to the peripheral VCN, subpeduncular granule cells, and nucleus Y. Medial and lateral OC efferent collaterals thus innervate different regions of the CN. Lateral system collaterals overlap extensively with Type I spiral ganglion cell afferent input. They are well positioned to play a role in modulating afferent input to the central auditory system, as is the primary projection of these efferents to the cochlea. The medial system collaterals project near the recently described afferent projections of Type II spiral ganglion cells. The medial system collaterals may therefore be related to the function of outer hair cells, as the medial system primary axons appear to be in the cochlea.

Animals↗

PubMed1990

Comparison of immune-mediated models of acute and chronic otitis media.

The distribution of immunoglobulin-bearing cells and the pattern of histopathological changes in the middle ear (ME) mucosa, round window membrane (RWM), and inner ear were compared during acute and chronic immune-mediated otitis media with effusion (OME) in the guinea pig as an animal model. In both acute and chronic immune responses (IRs), mucosal hyperplasia, edema, neovascularization, and cellular infiltration were observed. IgG+ cells were predominant in both the acute and chronic IRs. The number of IgA+ cells, however, increased in the mucosa and RWM during chronic IRs. Only the chronic IR resulted in gland formation within the ME and inflammation within the cochlea. These results indicate that the chronic IR was more similar to reports of clinical OME than the acute IR. The cochlear inflammation associated with chronic OME can lead to sensorineural hearing loss, as reported in clinical studies.

Acute Disease↗

PubMed1990

Spiral ganglion cell endings in the cochlear nucleus of young and old rats.

The spiral ganglion cells (SGCs) forming the auditory nerve have been shown to degenerate with age in both human and animal models, presumably resulting in post-synaptic sites in the cochlear nucleus (CN) that have lost their inputs. The present study examined the morphological changes in the surviving SGC endings in the CN of aged animals. The auditory nerves of 2-3 MO and 25-26 MO male, Fisher 344 rats were anterogradely labeled with horseradish peroxidase and the CN prepared histochemically. This resulted in Golgi-like labeling of afferent fibers and their terminals. All endings within each section were drawn and the area and number of components per ending were measured. Young and old animals both had about the same proportion of "simple", "string" and "complex" endings within the ventral CN, with complex endings being predominant in both age groups. The area of many complex endings was greater in the old animals with some endings being twice as large as any seen in young animals. There was no evidence of smaller endings in the old animals, suggesting that endings are not shrinking with age. A comparison of the number of components per complex ending revealed significantly more complexity in the endings of aged animals. Following the degeneration of SGCs it seems likely that the remaining cells, by increasing the area and altering the shape of their central terminals, may cover some of the post-synaptic sites made available by degenerated endings in aged animals.

Aging↗