This study aimed to test these hypotheses: cystathionine ␥-lyase (CSE) is expressed in a human artery, it generates hydrogen sulfide (H 2 S), and H 2 S relaxes a human artery. H 2 S is produced endogenously in rat arteries from cysteine by CSE. Endogenously produced H 2 S dilates rat resistance arteries. Although CSE is expressed in rat arteries, its presence in human blood vessels has not been described. In this study, we showed that both CSE mRNA, determined by reverse transcription-polymerase chain reaction, and CSE protein, determined by Western blotting, apparently occur in the human internal mammary artery (internal thoracic artery). Artery homogenates converted cysteine to H 2 S, and the H 2 S production was inhibited by DL-propargylglycine, an inhibitor of CSE. We also showed that H 2 S relaxes phenylephrine-precontracted human internal mammary artery at higher concentrations but produces contraction at low concentrations. The latter contractions are stronger in acetylcholine-prerelaxed arteries, suggesting inhibition of nitric oxide action. The relaxation is partially blocked by glibenclamide, an inhibitor of K ATP channels. The present results indicate that CSE protein is expressed in human arteries, that human arteries synthesize H 2 S, and that higher concentrations of H 2 S relax human arteries, in part by opening K ATP channels. Low concentrations of H 2 S contract the human internal mammary artery, possibly by reacting with nitric oxide to form an inactive nitrosothiol. The possibility that CSE, and the H 2 S it generates, together play a physiological role in regulating the diameter of arteries in humans, as has been demonstrated in rats, should be considered.

These observations provide a basis for intervention strategies that target sprains and strains associated with materials handling and slips, trips, and falls.

SUMMARYAn evoked-potential audiogram was measured for an Indo-Pacific humpback dolphin (Sousa chinensis) living in the dolphinarium of Nanning Zoo, China. Rhythmic 20ms pip trains composed of cosine-enveloped 0.25ms tone pips at a pip rate of 1kHz were presented as sound stimuli. The dolphin was trained to remain still at the water surface and to wear soft latex suction-cup EEG electrodes used to measure the animalʼs envelope-following evoked potentials to the sound stimuli. Responses to 1000 rhythmic 20ms pip trains for each amplitude/frequency combination were averaged and analysed using a fast Fourier transform to obtain an evoked auditory response. The hearing threshold was defined as the zero crossing point of the response input-output function using linear regression. Fourteen frequencies ranging from 5.6 to 152kHz were studied. The results showed that most of the thresholds were lower than 90dBre.1Pa (r.m.s.), covering a frequency range from 11.2 to 128kHz, and the lowest threshold of 47dB was measured at 45kHz. The audiogram, which is a function of hearing threshold versus stimulus carrier frequency, presented a U-shape with a region of high hearing sensitivity (within 20dB of the lowest threshold) between approximately 20 and 120kHz. At frequencies lower than this high-sensitivity region, thresholds increased at a rate of approximately 11dBoctave -1 up to 93dB at 5.6kHz. The thresholds at high frequencies above 108kHz increased steeply at a rate of 130dBoctave -1 up to 127dB at 152kHz.

No abstract

SUMMARYThe hearing and echolocation clicks of a stranded Indo-Pacific humpback dolphin (Sousa chinensis) in Zhuhai, China, were studied. This animal had been repeatedly observed in the wild before it was stranded and its age was estimated to be ~40years. The animal's hearing was measured using a non-invasive auditory evoked potential (AEP) method. Echolocation clicks produced by the dolphin were recorded when the animal was freely swimming in a 7.5m (width)×22m (length)×4.8m (structural depth) pool with a water depth of ~2.5m. The hearing and echolocation clicks of the studied dolphin were compared with those of a conspecific younger individual, ~13years of age. The results suggested that the cut-off frequency of the high-frequency hearing of the studied dolphin was ~30-40kHz lower than that of the younger individual. The peak and centre frequencies of the clicks produced by the older dolphin were ~16kHz lower than those of the clicks produced by the younger animal. Considering that the older dolphin was ~40years old, its lower high-frequency hearing range with lower click peak and centre frequencies could probably be explained by age-related hearing loss (presbycusis).