BackgroundWaardenburg syndrome (WS) is the consequence of an inherited autosomal dominant mutation which causes the early degeneration of intermediate cells of cochlear stria vascularis (SV) and profound hearing loss. Patients with WS may also experience primary vestibular symptoms. Most of the current WS studies did not discuss the relationship between WS and abnormal vestibular function. Our study found that a spontaneous mutant pig showed profound hearing loss and depigmentation. MITF-M, a common gene mutation causes type WS which affect the development of the intermediate cell of SV, was then identified for animal modeling.ResultsIn this study, the degeneration of vestibular hair cells was found in pigs with MITF-M. The morphology of hair cells in vestibular organs of pigs was examined using electron microscopy from embryonic day E70 to postnatal two weeks. Significant hair cell loss in the mutant saccule was found in this study through E95 to P14. Conversely, there was no hair cell loss in either utricle or semi-circular canals.ConclusionsOur study suggested that MITF-M gene mutation only affects hair cells of the saccule, but has no effect on other vestibular organs. The study also indicated that the survival of cochlear and saccular hair cells was dependent on the potassium release from the cochlear SV, but hair cells of the utricle and semi-circular canals were independent on SV.
β-galactosidase is a critical exoglycosidase involved in the hydrolysis of lactose, the modification and degradation of glycoprotein in vivo. In this study, the β-galactosidase gene of silkworm (BmGal), whose cDNA comprises 11 exons and contains an intact ORF of 1821bp, was cloned. The protein sequence of BmGal showed high similarity with other known insect β-galactosidases. No activity of the BmGal expressed in Escherichia coli or Pichia pastoris was detected while it was successfully expressed with high enzyme activity in baculovirus–silkworm expression system, and the electrophoresis result revealed that the BmGal showed activity in oligomer mode. Enzyme activity assay showed that its optimum pH was 8.4 and its optimum temperature was 40℃. What’s more, we found that iron ions can stimulate the activity of the enzyme while cobalt, nickel or lead ions can inhibit its activity significantly. Besides, the temporal-spatial expression pattern of the BmGal mRNA level was analyzed, which showed that BmGal was expressed at the highest level in the fifth larval instar but relatively low level in the pupal and adult stage, and the highest expression level of BmGal was found in testis among all the tissues concerned.
Hexamethylol melamine resins (HMM) with low crystallization water content and low viscosity were prepared by inhibiting the condensation polymerization of low hexamethylol melamine. The effects of catalyst, pH, formalde-hyde/melamine ratio, reaction temperature and time on the synthesis parameters of HMM were investigated. The results showed that the sample (HMM8) synthesized with Na2CO3-NaHCO3 as catalyst had the crystallization water content lower than 10%, being with a viscosity of about 0.26 Pa·s. The melting temperature of HMM8/polyvinyl alcohol (PVA) curing system was about 164.3 °C. It was found that the higher the amount of formaldehyde, the greater the hydroxyl methyl bounded to each triazine ring. Compared with the traditional melamine formaldehyde resin which had the crystallization water content of about 20–30%, the production of this resin was expected to reduce the energy consumption of industrial reaction, while the resin with 10% crystallization water content was more conducive to the development of alloying HMM/PVA composite membrane.
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