Laser doppler measurements of cochlear blood flow during loud sound exposure in the guinea pig

This investigation examined the effects of loud sound of different frequencies and intensities on cochlear blood flow as measured by the laser Doppler flowmeter. Cochlear blood flow was measured in anesthetized guinea pigs during a l h exposure to either a 2, 4, or 12 kHz pure tone or high-pass noise (10-40 kHz) at 90, 103, or 110 dB SPL. Cochlear function was assessed using the compound action potential audiogram before and after exposure. There was no change in blood flow in the second turn with a 2, 4, or 12 kHz tone but there was a significant (P < 0.05) decline in flow in the first cochlear turn at the end of either the 12 kHz tone or high-pass noise exposure at 103 and 110 dB SPL. There were elevations in the thresholds of the cochlear compound action potential after all but the 90 dB exposures to 12 kHz or high-pass noise. No such changes were observed in blood flow or electrophysiology in control animals. These findings demonstrate that there is a small but significant decline in cochlear blood flow with high intensity sound exposure. However, the relationship between this change in blood flow and the development of cochlear damage is unclear.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26841/1/0000401.pd

Love is heterosexual‐by‐default: Cultural heterosexism in default prototypes of romantic love

Cultural heterosexist ideologies assume heterosexuality to be the default norm. Four studies investigated when concepts of romantic love are heterosexual‐by‐default (N = 685). In Studies 1–2, participants generated features of romantic love, in general (i.e., the default prototype) or among one of three sexual orientation‐specific couples (lesbian, gay, or heterosexual). Heterosexual‐identified participants’ default prototypes were more similar to heterosexual than same‐gender prototypes (Study 1). Lesbian‐ and gay‐identified participants’ default prototypes were more similar to both heterosexual and gay male than lesbian prototypes, whereas bisexual‐identified participants’ sexual orientation‐specific prototypes were equivalently similar to the default (Study 2). However, heterosexual‐identified participants rated presented features of love similarly across sexual orientation‐specific conditions (Study 3). In a timed feature‐verification task (Study 4), participants categorized fewer peripheral features of romantic love as relevant to same‐gender than mixed‐gender couples. Activating sexual orientation‐specific representations affected subsequent default concepts of romantic love. We discuss implications for heterosexism theories and intervention

Effects of carbon monoxide on cochlear electrophysiology and blood flow

The belief that the cochlea is particularly vulnerable to a reduction in oxygen availability comes predominantly from studies reporting the disruption of electrophysiological measures, such as the compound action potential, endocochlear potential, inner hair cell intracellular potentials or afferent nerve fiber responses by asphyxiation. Because hypoxia has frequently been suggested as an underlying mechanism by which many ototoxic agents produce injury, and because such agents are not likely to completely disrupt oxygen delivery, we investigated the effects of graded hypoxia (using doses of carbon monoxide) on cochlear blood flow, the compound action potential (CAP) and the cochlear microphonic (CM). High doses of carbon monoxide injected intra-peritoneally yielded reversible loss of the CAP sensitivity for high frequency tone bursts, the extent of which was dose dependent. The loss was observed first at the highest frequency tested (50 kHz) and as carboxyhemoglobin levels increased, contiguous lower frequencies were influenced. Recovery progressed from low to high frequencies as carboxyhemoglobin levels declined. Carbon monoxide administration also produced a dose dependent elevation in the cochlear blood flow measured by a laser Doppler flow monitor. The data suggest that carbon monoxide administration disrupts cochlear function only under extremely severe exposure conditions. An elevation in cochlear blood flow may well serve as a protective mechanism which maintains cochlear function in the face of declining blood oxygen carrying capacity and delivery. While the site of action of carbon monoxide in the cochlea is uncertain, the data clearly indicate that elements involved in the generation of the CAP for high frequency tones are particularly vulnerable. This suggests that such elements may have different metabolic requirements from other lower frequency regions of the cochlea and/or that oxygen delivery (blood circulation) differs in the basal portion of the cochlea.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26857/1/0000422.pd

Differences in the distribution of F-actin in outer hair cells along the organ of Corti

There is evidence of differences in the structure, innervation and physiological responses between outer hair cells (OHCs) of the basal and apical turns of the mammalian cochlea. In this study we have used rhodamine-labelled phalloidin to investigate the differential distribution of F-actin in OHCs along the organ of Corti of the guinea pig. Isolated OHCs and surface preparations and cryosections of the organ of Corti were studied. F-actin was observed in stereocilia and the cuticular plate of all OHCs. In addition, some OHCs had a network of F-actin extending from the cuticular plate towards the nucleus. This infracuticular network was observed in most OHCs of the apical cochlear turns but was not seen in any OHCs of the basal turn. These microstructural differences between OHCs of the base and apex could be related to differences in OHC function between the apical and basal portions of the cochlea.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26926/1/0000492.pd

The collision of boosted black holes

We study the radiation from a collision of black holes with equal and opposite linear momenta. Results are presented from a full numerical relativity treatment and are compared with the results from a ``close-slow'' approximation. The agreement is remarkable, and suggests several insights about the generation of gravitational radiation in black hole collisions.Comment: 8 pages, RevTeX, 3 figures included with eps