A comparison of the protective effects of systemic administration of a pro-glutathione drug and a Src-PTK inhibitor against noise-induced hearing loss.

Both the antioxidant, n-l-acetyl cysteine (L-NAC) and the Src inhibitor, KX1-004, have been used to protect the cochlea from hazardous noise. To date, KX1-004 has only been used locally on the round window. In the current study, the two drugs were administered systemically. LNAC was delivered intraperitoneally at a dose of 325 mg/kg while KX1-004 was administered subcutaneously at a dose of 50 mg/kg. The noise exposure consisted of a 4 kHz octave band of noise at 100 dB SPL for 6 hours/day for 4 days. The drugs were administered once each day, 30 minutes prior to the onset of the noise exposure. The animals' hearing was estimated using the evoked response records from surgically-implanted chronic electrodes in the inferior colliculi. Animals treated with LNAC and KX1-004 had from 10 to 20 dB less temporary threshold shift at day 1 and an average 10 dB less permanent threshold shift by day 21 when compared to control saline treated animals. There were no significant side effects (i.e.: appetite loss, weight loss, lethargy, etc.) related to either of the drug treatments. KX1-004 produced at least as much protection as L-NAC, but at a significantly lower concentration.

Quantitative analysis of damaging hair cells in cochleae of aging Fischer 344 rats / 解放军医学杂志

Objective To make a quantitative analysis of damaging hair cells,and investigate the progression pattern of cochlear pathology and the primary death pathway of hair cells in cochleae of aging Fischer 344 rats.Methods Thirty-two Fischer 344 rats were used in this experiment.The animals were assigned to two groups:rats in young group (n=13) were 3-4 months old,and in aging group (n=19) were 20-27 months old.Rats in aging group were further divided into two subgroups based on the animals' age:20-23-month subgroup (n=13) and 24-27-month subgroup (n=7).The auditory brainstem response (ABR) thresholds of both ears elicited with tone bursts at 5,10,20 and 40 kHz were measured in both young,and aging Fischer 344 rats.Upon completion of the auditory test,animals were decapitated,and both left and right bullae were exposed.Following fixation,whole specimens comprising the basilar membrane with Corti organ were separated from the modiolus.Propidium iodide (PI),a popular DNA intercalating fluorescent probe was used to trace the morphological changes in hair cell nuclei,and a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was used to detect nuclear DNA fragmentation in the aging cochleae.Filamentous actin (F-actin),an important structural protein of outer hair cells (OHCs),was stained with FITC-labeled phalloidin to illustrate the morphologic viability of cuticular plate and the stereocilia for affirming the missed OHCs.Each Corti organ was thoroughly inspected from the apical to the basal turns of the cochlea under a fluorescence microscope.The numbers of damaging OHCs including missed nuclei,condensed nuclei and swollen nuclei were documented,and a cochleogram was drawn.Results There were significant thresholds at all tested frequencies between the young and aging rats (P

The primary death pathway of outer hair cells of rat cochlea following styrene exposure / 解放军医学杂志

Objective To compare the prevalence of apoptosis and necrosis, and investigate the primary death pathway of outer hair cells of rat cochlea following styrene exposure. Methods Fourteen adult Long Evans rats were used in the present study. The animals were randomly assigned into test group (n=8) and control group (n=6). Animals in test group were exposed to styrene by gavage at 400 mg/kg (2g styrene was mixed with 1ml olive oil). Treatment was performed once a day, 5 days per week for 3 weeks. Animals in control group were fed by gavage the same volume of olive oil on an identical time schedule used for the test group. The auditory brainstem response (ABR) thresholds of both ears elicited with clicks were measured before and at the end of the 3-week styrene or olive oil treatment. After hearing was re-assessed, animals were sacrificed and cochleae were quickly removed from the skull. Following fixation, whole specimens comprising the basilar membrane with Corti's organ were separated from the modiolus. Apoptotic, necrotic and missing outer hair cells (OHCs) were distinguished by combined assays of nuclear staining with propidium iodide (PI), TUNEL assay and filamentous actin(F-actin)staining with FITC-phalloidin. Each Corti's organ was thoroughly examined by fluorescence microscopy. The numbers of damaged OHCs (apoptotic, necrotic and missing OHCs) were documented. Results Neither threshold shift of ABR nor sign of hair cell (HC) damage was found in the cochlea of control animals. The animals of test group showed both physiological and pathological changes in the cochleae following the 3-week styrene treatment. ABR testing revealed an average of 15 dB of threshold shifts. F-actin staining exhibited the maximal level of OHCs damage in the middle portion of Corti's organ. The major damage occurred in the third row of OHCs, followed by the second and first rows of OHCs. Three types of morphological changes in damaged OHC nuclei were revealed by PI labeling: nuclear condensation, nuclear swelling and nuclear missing. Strong TUNEL green fluorescence appeared in the OHCs with condensed nuclei. Quantitative analysis showed that the average number of apoptotic OHCs was approximately three times greater than the number of necrotic OHCs (P=0.01). Conclusion It is indicated that apoptosis is the primary death pathway of OHCs leading to generation of the cochlear lesion following styrene exposure.

Effects of mitochondrial energy-conversion efficiency on controlling the initiation and execution of the apoptotic process in outer hair cells of cochlea following noise exposure / 解放军医学杂志

Objective To examine the role of mitochondrial energy-conversion efficiency in regulating the initiation and execution of the apoptotic process in outer hair cells(OHCs)of cochlea following exposure to intense noise.Methods Seventeen adult chinchillas were used in present study.The animals were randomly assigned to one of the two groups,12 animals were exposed to noise and the remaining 5 animals without exposure to noise served as normal control.For all the animals,3-nitropropionic acid solution(3-NP,50mmol/L),an irreversible inhibitor of succinate dehydrogenase(SDH),was dropped onto the round window of the cochlea of the right ear using a micro-syringe to inhibit the mitochondrial energy production,to serve as the test ear.Artificial perilymph solution(AP)was dropped onto the round window of the cochlea of the left ear to serve as the control ear.16h after application of 3-NP and AP,the animals were exposed to 75 pairs of impulse noise at 155 dB pSPL.The cochleae were harvested 2h after the noise exposure.The cochlear basilar membrane was stained with propidium iodide(PI),a DNA intercalating fluorescent probe used to visualize the morphologic viability of hair cell nuclei.All the specimens were examined with a fluorescence microscope.Results In the 3-NP-treated cochlea,medium degree of nuclear condensation of OHCs appeared to be the dominant nuclear pathology,and only a few OHCs showed nuclear fragmentation in the damaged area of the cochlea.In contrast,the AP-treated control ear exhibited a large quantity of nuclear fragments,and a small quantity of medium degree of nuclear condensation.Conclusion The present study indicates that mitochondrial energy-conversion function plays an important role in regulating the apoptotic process.Disruption of the mitochondrial energy can not deter the apoptotic process from initiation,but can slow down the pace of apoptotic progression in outer hair cells of the cochlea following exposure to intense noise.

Prioridades de salud: problemas por resolver y nuevos retos / Unfinished problems and new challenges

En los últimos 25 años hemos sido testigos de cambios verdaderamente revolucionarios en el campo de la salud, en especial en los países de ingresos bajos y medios. En este artículo se discuten algunos de los problemas de salud que se deben resolver y los retos que habrán de enfrentarse. Dentro de ellos destacan el financiamiento de los servicios de salud, la atención a una población con un problema de edad cada vez mayor, la mejoría en la calidad de los servicios y la capacitación de recursos humanos para enfrentar futuras necesidades de salud dentro de un contexto de recursos cada vez mas limitados

In the last 25 years we have witnessed revolutionary changes in the field of health, particularly in the low and middle income countries. This paper discusses some of the new problems which need to be solved and some of the challenges which lie ahead Among the former we can mention the financing of health care services and the provision of health care to an aging population. Among the latter we include the need for improvement of the quality of health services and the training of appropriate health manpower.

Signal pathway associated with hair cell death in cochlea following exposure to intense impulse noise / 解放军医学杂志

Objective Apoptosis and necrosis are two forms of hair cell death in cochlea following exposure to intense impulse noise.The present study was designed to examine the activity of caspase-3,caspase-8 and caspase-9 in the basilar membrane of cochlea,and investigate the cellular signal pathway associated with noise-induced hair cell death in cochlea.Methods Twenty-seven adult chinchillas were used in present study.The animals were randomly assigned into test group(no.15) and control group(no.12).The animals in test group were exposed to noise for the detection of the activity of caspase-3,caspase-8 and caspase-9,respectively,each with 5 animals.Animals in control group were not exposed to noise.Chinchillas were exposed to impulse noise at 155 dB peak sound pressure level(pSPL) for 75 times.Two hours after noise exposure,both cochleae were perfused with approximately 30?l of freshly prepared solution containing one of the three caspases(caspase-3,-8 and-9) respectively using a micro-syringe.One hour after perfusion,the animals were sacrificed and the cochleae were harvested.The Corti organs were double stained with propidium iodide(PI),and a DNA intercalating fluorescent probe was used to visualize the morphologic viability of hair cell nuclei.All the specimens were observed with a fluorescence microscope.Results The normal cochlea did not exhibit green fluorescence for any of the three caspases in Corti organ.Strong caspase-3,-8 and-9 green fluorescence appeared in the outer hair cells with condensed or fragmented nuclei,a sign of apoptosis,whereas no fluorescence was observed for any of the three caspases in the swollen outer hair cell nuclei,a sign of necrosis,in the cochleae exposed to intense impulse noise.Conclusion It is indicated that caspase-9 is involved in the intrinsic and caspase-8 involved in the extrinsic apoptotic pathway which occur simultaneously in apoptotic outer hair cells.No caspase activation occurs in necrotic outer hair cell in the cochlea following exposure to intense impulse noise.

Death mode of outer hair cells in chinchilla cochlea after exposure to difference levels of intense noise / 解放军医学杂志

Objective To quantitatively analyze the occurrence of apoptotic and necrotic outer hair cells (OHCs) and to evaluate the changes of these parameters with time after noise exposure. Methods Chinchillas were exposed to a narrow band noise at either 104 or 108 dB SPL for 1 hour. The animals were executed and dissected at either 1, 4 and 30 days after the noise exposure and the cochleas were collected for detection of OHC death mode. The apoptotic and necrotic OHCs were distinguished by examining the OHC nuclear morphology and confirmed by staining for caspase 3 activity or TUNEL assay. ABR thresholds for click stimuli were used to monitor changes in auditory function. Results The number of apoptotic cells were significantly greater than those of necrotic cells shortly after the noise exposure at day 1 for the 104 dB group, day1 and day4 for 108 dB group ( P =0 01, P =0 03, P =0 01) and the difference between the number of apoptotic cells and necrotic cells became statistically insignificant at day 4 and day 30 for the 104 dB group and day 30 for 108 dB group ( P =0 67, P =0 29, P =0 52). By day 30, apoptotic and necrotic pathologies continued, although in small quantity in both 104 dB group and 108 dB group. Conclusions The results of the study indicated that the early expansion of cochlear lesion is contributed primarily by apoptosis, whereas the later stage of lesion expansion is likely contributed equally by apoptosis and necrosis. The death of OHCs not only takes place during a noise exposure, but also continues for at least 30 days after noise exposure