Thermally and photochemically triggered self-assembly of peptide hydrogels.
Explore the source record for details and available documents.
Amino Acid Sequence↗
Biomedical subjects
B H Hu
Publications and source records attributed to B H Hu.
Intense noise-induced apoptosis in hair cells of guinea pig cochleae.
Cells can die by two distinct pathways: apoptosis and necrosis. To explore whether intense noise can induce hair cell (HC) death via the apoptotic pathway, we systematically examined morphological changes in guinea pig cochlear HC nuclei stained with Hoechst 33342, a fluorescent dye specifically labelling the nuclear DNA. A narrow band noise centred at 4 kHz with levels at 110 dB, 115 dB or 120 dB (SPL) was applied for 4 h and the exposed cochleae were collected at various intervals (3 h, 3 or 14 days) after the noise exposure. Auditory function was monitored by measuring thresholds of auditory brain stem responses. In the noise-damaged cochleae, there were two major types of nuclear changes, nuclear condensation appeared as karyorrhexis or karyopyknosis and nuclear swelling. Karyorrhexis and karyopyknosis predominately appeared in the severely damaged cochlear region in the animals exposed to 120 dB noise and examined 3 h after the noise exposure. In contrast, swelling of nuclei occurred in all of the noise-exposed cochleae, and was the feature change in the animals exposed to 110 and 115 dB noise. This pathological change persisted at least for 14 days after the noise exposure. The typical changes of karyorrhexis and karyopyknosis noted in the animals exposed to 120 dB noise were morphologically similar to those nuclear changes described in previous studies for apoptosis, suggesting that the apoptotic process may be involved in intense noise-induced HC death.
Animals↗
Selective loss of inner hair cells and type-I ganglion neurons in carboplatin-treated chinchillas. Mechanisms of damage and protection.
Carboplatin preferentially destroys inner hair cells (IHCs) and type-I spiral ganglion neurons while sparing outer hair cells (OHCs). Loss of IHCs and type-I ganglion cells is associated with a significant reduction of the compound action potential (CAP). However, the cochlear microphonic (CM) potential and distortion product otoacoustic emissions (DPOAEs) remain normal, indicating that the OHCs are functionally intact. In the vestibular system, carboplatin selectively destroys type-I hair cells and their afferent neurons. Damage of type-I vestibular hair cells and their afferent terminals is associated with significant depression of nystagmus induced by cold, caloric stimulation. Histochemical studies revealed a rapid decrease in succinate dehydrogenase (SDH) staining in IHCs soon after carboplatin treatment, and staining intensity remained depressed in surviving IHCs for at least 1 month after carboplatin treatment. These results suggest that carboplatin depresses the metabolic function in surviving IHCs. Several lines of evidence suggest that free radicals may contribute to carboplatin-induced sensory cell damage. Intracochlear infusion of L-buthionine-[S,R]-sulfoximine (BSO), which depletes intracellular glutathione (GSH), increases IHC and OHC loss. Previous in vitro studies have shown that neurotrophin 4/5 (NT-4/5) promotes the survival of spiral ganglion neurons from cisplatin ototoxicity. In vivo perfusion of NT-4/5 promoted the survival of spiral ganglion neurons, but did not protect the hair cells.
Action Potentials↗
Intracochlear infusion of buthionine sulfoximine potentiates carboplatin ototoxicity in the chinchilla.
The aim of this experiment was to determine if buthionine sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, enhances the ototoxicity of carboplatin. Osmotic pumps were used to infuse BSO into the right cochleas of 12 adult chinchillas for 14 days. The left cochleas served as controls. Animals were assigned to three groups: a drug control group that did not receive carboplatin, a group that received a single dose of carboplatin (25 mg/kg i.p.), and a group that received a double dose of carboplatin (25 mg/kg i.p. x 2), with 4 days between injections. Carboplatin was administered after three days of BSO pre-treatment. Ototoxicity was assessed with evoked potentials recorded from electrodes implanted in the inferior colliculi (ICPs), distortion product otoacoustic emissions (DPOAEs), and cochleograms. BSO infusion itself caused no long-term functional or morphological changes. One of four animals treated with it single dose of carboplatin showed a significant loss of inner hair cells (IHCs), with greater loss in the BSO-treated ear. All animals in the double-dose carboplatin group showed marked differences between BSO-treated and control ears. Average IHC losses were 59% in BSO-treated ears vs. 18% in control ears. Moreover, BSO-treated ears sustained significantly greater outer hair cell (OHC) losses than control ears (37% vs. 2%, respectively). ICP and DPOAE response amplitudes were reduced slightly in BSO-treated ears relative to control ears, consistent with their greater hair cell loss. The results clearly show that BSO can enhance carboplatin ototoxicity in the chinchilla, supporting a role of GSH and reactive oxygen species in platinum ototoxicity.
Animals↗
The role of the cochlear efferent system in acquired resistance to noise-induced hearing loss.
Previous work has shown that the cochlear efferent system may play a role in protecting the ear from noise-induced temporary threshold shifts (TTS) following exposures to a single tone or series of moderate-level noises ('toughening'). However, whether the olivocochlear bundle (OCB) is important in decreasing noise-induced permanent threshold shifts (PTS) remains an open question. The importance of the OCB in decreasing the ear's susceptibility to noise, as reflected by 2f1-f2 distortion product otoacoustic emissions, was assessed by sectioning both the ipsilateral and contralateral divisions of the efferent system and exposing chinchillas while awake to an octave band noise (4 kHz) at a low level (85 dB SPL) for 10 days (6 h/day) and then at a high level (95 dB SPL) for 48 h. Complete de-efferentation was verified by cochlear acetylcholinesterase staining. The ears that were de-efferent showed substantially more TTS, greater PTS and larger cochlear lesions of outer hair cells. The results suggest that the efferent system may influence the ear's ability to develop resistance to noise trauma.
Animals↗
Recovery of structure and function of inner ear afferent synapses following kainic acid excitotoxicity.
The present study was conducted to examine the re-establishment of IHC/VIII nerve synapses following kainic acid (KA) excitotoxicity and to discern if the re-organized afferent could render not only a normal auditory threshold but also a normal supra-threshold function. KA (60 mM) applied to the intact round window membrane in chinchilla destroyed postsynaptic endings of the auditory nerve, depressed the input-output (I/O) functions of auditory evoked potentials (EVP) and produced an average loss of sensitivity of over 80 dB at 4, 8, and 16 kHz, with less substantial losses (40-60 dB) at lower frequencies. However, there was no significant difference in 2f1-f2 distortion-product otoacoustic emissions (DPOAE) before and after the application of KA. The nerve endings went through a sequence of swelling, degeneration and recovery over a 3-5 day period at higher frequency. Auditory sensitivity and supra-threshold response returned accordingly. In contrast, complete recovery at lower frequencies (1 and 2 kHz) required more than 5 days. The results provide strong evidence that (1) excitotoxically damaged cochlear afferent neurons can recover and render both a normal EVP threshold and EVP I/O function and (2) afferent innervation to IHCs is not necessary for DPOAE generation.
Animals↗
The influence of the cochlear efferent system on chronic acoustic trauma.
The role of the olivocochlear bundle (OCB) in modulating noise-induced permanent injury to the auditory periphery was studied by completely sectioning the OCB fibers in chinchillas and exposing the animals while awake to a broad-band noise at 105 dB SPL for 6 h. Outer hair cell (OHC) function was assessed by measuring 2f1-f2 distortion product otoacoustic emissions (DPOAE) at frequencies from 1.2 to 9.6 kHz and cochlear microphonics (CM) at frequencies from 1 to 8 kHz. As a result of de-efferentation, the CM was decreased but the DPOAEs were unchanged in de-efferented ears as compared with efferented control and sham-operated ears. Following noise exposure, the ears that were de-efferented showed significantly more depression of DPOAE input/output functions and greater decrement of CM amplitude. The differences between de-efferented and efferent-innervated ears were evident across all the frequencies. The cochlear lesions of the OHCs reflected by traditional cytocochleograms, however, were minimal in both efferented and de-efferented ears. The results indicate that cochlear de-efferentation decreases the CM in chinchilla and increases the ear's susceptibility to noise-induced permanent hearing damage. More importantly, de-efferentation increases susceptibility at low frequencies as well as high frequencies.
Animals↗
Changes in F-actin labeling in the outer hair cell and the Deiters cell in the chinchilla cochlea following noise exposure.
It has been found that 'conditioning' noise exposures can render the inner ear more resistant to traumatic noise exposures. To explore the possible mechanisms underlying this phenomenon, filamentous actin (F-actin), labeled by rhodamine-phalloidin, was examined in the chinchilla cochlea using confocal fluorescence microscopy. The conditioning noise was 0.5 kHz octave band noise (OBN) at 90 dB SPL for 6 h/day and the high-level noise was the same noise but at 105 dB SPL for 4 h. A variety of pathological changes were found in the chinchilla cochlea after exposure to noise. Subjects exposed to conditioning noise (1 day or 10 days) and only high-level noise showed an increase in F-actin labeling than unexposed controls. By contrast, subjects who had 5 days quiet after the 10-day conditioning exposure exhibited a decrease in F-actin labeling. Interestingly, subjects exposed to high-level noise with prior 10-day conditioning exposure also showed a decrease in F-actin labeling in the cuticular plate and the stereocilia. The F-actin decreases in the stereocilia and the cuticular plates may decrease the mechanical rigidity of the organ of Corti. A more pliable organ of Corti may have reduced the possibility of fracture or ripping of cell junctions during the motion of the basilar membrane induced by acoustic overstimulation.
Acoustic Stimulation↗
R-phenylisopropyladenosine attenuates noise-induced hearing loss in the chinchilla.
Reactive oxygen species, which are cytotoxic to living tissues, are thought to be partly responsible for noise-induced hearing loss. In this study R-phenylisopropyladenosine (R-PIA), a stable non-hydrolyzable adenosine analogue which has been found effective in upregulating antioxidant enzyme activity levels, was topologically applied to the round window of the right ears of chinchillas. Physiological saline was applied to the round window of the left ears (control). The animals were then exposed to a 4 kHz octave band noise at 105 dB SPL for 4 h. Inferior colliculus evoked potential thresholds and distortion product otoacoustic emissions (DPOAE) were measured and hair cell damage was documented. The mean threshold shifts immediately after the noise exposure were 70-90 dB at frequencies between 2 and 16 kHz. There were no significant differences in threshold shifts at this point between the R-PIA-treated and control ears. By 4 days after noise exposure, however, the R-PIA-treated ears showed 20-30 dB more recovery than saline-treated ears at frequencies between 4 and 16 kHz. More importantly, threshold measurements made 20 days after noise exposure showed 10-15 dB less permanent threshold shifts in R-PIA-treated ears. The amplitudes of DPOAE also recovered to a greater extent and outer hair cell losses were less severe in the R-PIA-treated ears. The results suggest that administration of R-PIA facilitates the recovery process of the outer hair cell after noise exposure.
Adenosine↗
[Isoflavones from Glycyrrhiza eurycarpa].
A new isoflavone, named eurycarpin A and a new natural product isoflavone named eurycarpin B have been isolated from the roots of Glycyrrhiza eurycarpa P. C. Li. Their structures were determined to be 7,2',4'-trihydroxy-3'-(3,3-dimethylallyl) isoflavone(I) and 7,2'-dihydroxy-6",6"-dimethylpyrano-(2",3":4',3') isoflavone(II) on the basis of spectroscopic analysis (UV, EI-MS, 1HNMR, 13CNMR, NOE difference and HMBC). In addition, three known isoflavones, licoisoflavone A, calycosin and formononetin, were obtained for the first time from this plant.
Drugs, Chinese Herbal↗
Effect of focal cochlear vascular lesion on endocochlear potential in guinea pigs.
The alteration endocochlear potential (EP) in response to total cochlear ischemia induced by various experimental manipulations has been studied. However, the effect of restricted areal damage to the microvessels (restricted to small area in the lateral wall of a cochlear turn) on the EP value is still unknown. In the current investigation we adopted a photochemical method to produce a focal (i.e., restricted area) microvessel injury in the lateral wall of the guinea pig cochlea and examined the effect of these insults on EP recorded in the same region. The small area of the microvessel lesion (small fenestra: approximately 0.2 x 0.4 mm2) induced by photoactivation did not yield significant EP changes, suggesting that damage to such a small area of microcirculation in the lateral wall of the cochlea has no statistically significant effects on EP values. In subjects with a large area of the microvessel lesion (large fenestra: approximately 0.2 x 0.8 mm2), a decrease in the EP value (mean +/- SEM 7.9 +/- 0.8 mV) was noted. However, the control group animals with a large fenestra but without microvessel lesion also displayed a decrease (8.6 +/- 0.8 mV) in EP. In the current study we were unable to differentiate whether the EP changes in animals with the large fenestra microvessel lesions were caused by the cochlear blood flow decrease or by the surgical preparation. However, the results of this study indicated if the EP value was affected by the large area of the microvessel lesion, the level of decrease would not be large. That is, the EP decrease was less than the EP change in the control group (mean: 8.6 mV). Considering the dependence of EP on blood flow, the data of this study suggest that compensatory mechanisms in the cochlea may maintain the EP following a focal lesion in the lateral wall of the cochlea. This study also indicates that the photochemical method provides a reliable approach to produce the animal model with the focal microvessel lesion in the lateral wall of the cochlea.
Animals↗
New tetrasaccharide flavonol glycoside from Epimedium acuminatum.
A new tetrasaccharide flavonol glycoside was isolated from the aerial parts of Epimedium acuminatum, along with three known flavonoids. The structure of the new compound, named acuminatoside [1], was established to be anhydroicaritin-3-O-alpha-L-rhamnopyranosyl(1----2)-alpha-L-rhamno pyranoside-7- O-beta-D-glucopyranosyl-(1----2)-beta-D-glucopyranoside by means of spectroscopic techniques (uv, eims, fdms, fabms, 1H nmr, 1H-1H COSY, 2D-J, 13C nmr, APT, and 1H-13C HETCOR) and chemical methods (acid hydrolysis, enzymatic hydrolysis, and tlc-densitometry). The known compounds were identified as icariin, epimedoside A, and kaempferitrin.
Carbohydrate Sequence↗
[Effect of anisodamine on cochlear blood flow in living guinea pigs].
Anisodamine is commonly used in clinic as vasodilator. In the present study, the effects of anisodamine on cochlear blood flow were investigated in living guinea pigs using intravital microscopic techniques. The results showed that intravenous infusion of anisodamine (10mg/kg, 5mg/kg, 2 mg/kg) produced a dose dependent reduction in blood pressure. Large dose (10mg/kg) caused significant decrease in blood flow rate to 68.7 +/- 7.4% of the control value with no significant change in vessel diameter. On the other hand, medium and small doses (5mg/kg, 2mg/kg), which produced relatively smaller reduction in blood pressure caused no significant alternation in blood flow rate and vessel diameter. Also, when intramuscular, infusion of anisodamine (2mg/kg) was used no significant difference in blood flow rate, vessel diameter as well as blood pressure were found. The results indicated that increase in cochlear blood supply can not be induced by anisodamine in normal guinea pigs.
Animals↗
[Acuminatin from the aerial part of Epimedium acuminatum].
A new flavonol glycoside, C27H28O10, mp 151-152 degrees C (MeOH), named acuminatin (I), was isolated from the aerial part of Epimedium acuminatum Franch in addition to four known compounds. By means of UV, FAB-MS, EI-MS, 1HNMR, 13CNMR and chemical evidences, the structure of acuminatin was established as 6", 6"-dimethylpyrano (2", 3": 7, 8) 4'-methyl kaempferol-3-O-alpha-L-rhamnopyranoside. The known compounds were identified as kaempferol-3-O-alpha-L-rhamnopyranoside (II), quercitrin (III), hyperin (IV) and daucosterol (V).
Drugs, Chinese Herbal↗
Plasmodium falciparum synthesizes O-glycosylated glycoproteins containing O-linked N-acetylglucosamine.
Asexual blood forms of the human malaria parasite, Plasmodium falciparum, synthesize a major glycosylated 195 kDa protein that has been considered for the development of a vaccine. beta-Elimination-borohydride reduction of the 195 kDa glycoprotein and its 16 kDa processed product after metabolic labeling of their carbohydrates, showed the presence of derived, labeled glucosaminitol and alanine. This suggests that the 195 and 16 kDa glycoproteins contain distinct O-glycosyl linkages and that N-acetylglucosamine and serine residues are involved in the attachment of carbohydrate moieties to the protein core. Endo-O-glycanase treatment of total glycoproteins shows that O-glycosidycally-linked sugars represent a major carbohydrate moiety in P. falciparum glycoproteins.
Acetylglucosamine↗
[Structure revision of triptophenolide].
A diterpenoid-lactone, white thin crystals, C20H24O3, m/z: 312 (M+), mp 222-223 degrees C, UV lambda max (EtOH) 217 (log epsilon 4.36) nm, has been isolated from the ethyl acetate extract of the roots of Tripterygium wilfordii Hook. f., in a yield of 0.025%. Its structure was elucidated by spectral analysis (UV, IR, MS, 1HNMR and 13CNMR) and X-ray SCD. It is the known triptophenolide with revision of structure. Triptophenlolide was shown to have obvious inhibiting effects on lymphocyte and IgG (P less than 0.01) when mice and rats were given ig 1.5 mg/kg. The total complements in blood serum was increased. When BALB/C mice were given ig 1.5 mg/kg, the ear oedema induced by dimethyl benzene was significantly inhibited (P less than 0.01); The ear oedema induced by croton oil in SD rats at a dose of ig 1.0 mg/kg was also significantly inhibited (P less than 0.05). The vitamin C content of the adrenal gland was reduced in mice at a dose of 1.5 mg/kg. The ig LD50 of triptophenolide was greater than 30 mg/kg.
Animals↗
[Studies on the structure of scuteamoenin from the root of Scutellaria amoena].
In containing our studies on the flavonoids from Scutellaria amoena C.H. Wright, a new flavanone (I) and six known compounds (II-VII) were isolated from the roots of this plant. On the basis of spectroscopic analysis (UV, 1H NMR, 13C NMR, MS and CD) and chemical evidence, the structure of the new compound was elucidated as (2S) -2',5,6'-trihydroxy-7-methoxyflavanone (I) and named scuteamoenin, the other six known compounds were identified as (2R,3R) -3,5,7-trihydroxyflavanone (II), 2',3,5,6,7-pentahydroxyflavone (III), 2',5,7-trihydroxy-6-methoxyflavone (IV), skullcaflavone II (V), chrysin (VI) and beta-sitosterol (VII) respectively. Compounds II-VII were obtained from this plant for the first time.
Drugs, Chinese Herbal↗
[Studies on the structures of new flavonoids from the root of Scutellaria amoena].
From the root of Scutellaria amoena C.H. Wright, two new flavonoids (I, II) and six known flavonoids (III-VIII) were isolated. On the basis of spectroscopic analysis (UV, 1HNMR, 13CNMR, MS and CD) and chemical evidences, the structures of I and II were elucidated as (2S)-2',5,6'-trihydroxy-7-methoxyflavanone-2'-O-beta-D-glucopyrano side (I) and (2R, 3R)-2',3,5,7-tetrahydroxyflavanone (II) respectively. The other six known compounds were identified as (2S)-5,7,8-trihydroxyflavanone (III), (2S)-2',5,6',7-tetrahydroxyflavanone (IV), (2R, 3R)-2',3,5,6',7-pentahydroxyflavanone (V), 2',5,6',7-tetrahydroxyflavone (VI) norwogonin (VII) and oroxylin-A (VIII) respectively. Compounds III-VIII were obtained from this plant for the first time.
Chemical Phenomena↗