[Caloric test in low-tone sensorineural hearing loss].

Acute low-tone sensorineural hearing loss (ALHL) is generally has a relatively good prognosis. We have often found in long-term following-up, however, that ALHL relapses, recurs or develops into Meniere's disease. Diagnostic criteria of the Acute Altitude Deafness Research Group of the Ministry of Health, Labor, and Welfare of Japan, define ALHL as low-tone-disorder sensorineural hearing loss without vertigo in which cochlear symptoms -ear fullness, tinnitus, and deafness- develop suddenly. Over the last five years, we have treated 31 cases of ALHL, in about half of which neurotological examination showed potential peripheral vestibular dysfunction on testing positional nystagmus (a) with closed eyes and (b) in a dark room with open eyes, and by finding laterality in the peripheral labyrinth system on caloric test. These cases show high canal paresis -a maximum slow- phase eye velocity of caloric nystagmus exceeding 60%. These results, taken together, suggest that derangement extends to the peripheral labyrinth system in patients with ALHL.

Structure of thiocyanate hydrolase: a new nitrile hydratase family protein with a novel five-coordinate cobalt(III) center.

Thiocyanate hydrolase (SCNase) of Thiobacillus thioparus THI115 is a cobalt(III)-containing enzyme catalyzing the degradation of thiocyanate to carbonyl sulfide and ammonia. We determined the crystal structures of the apo- and native SCNases at a resolution of 2.0 A. SCNases in both forms had a conserved hetero-dodecameric structure, (alphabetagamma)(4). Four alphabetagamma hetero-trimers were structurally equivalent. One alphabetagamma hetero-trimer was composed of the core domain and the betaN domain, which was located at the center of the molecule and linked the hetero-trimers with novel quaternary interfaces. In both the apo- and native SCNases, the core domain was structurally conserved between those of iron and cobalt-types of nitrile hydratase (NHase). Native SCNase possessed the post-translationally modified cysteine ligands, gammaCys131-SO(2)H and gammaCys133-SOH like NHases. However, the low-spin cobalt(III) was found to be in the distorted square-pyramidal geometry, which had not been reported before in any protein. The size as well as the electrostatic properties of the substrate-binding pocket was totally different from NHases with respect to the charge distribution and the substrate accessibility, which rationally explains the differences in the substrate preference between SCNase and NHase.

Functional expression of thiocyanate hydrolase is promoted by its activator protein, P15K.

Thiocyanate hydrolase (SCNase) is a cobalt-containing enzyme with a post-translationally modified cysteine ligand, gammaCys131-SO(2)H. When the SCNase alpha, beta and gamma subunits were expressed in Escherichia coli, the subunits assembled to form a hetero-dodecamer, (alphabetagamma)(4), like native SCNase but exhibited no catalytic activity. Metal analysis indicated that SCNase was expressed as an apo-form irrespective of the presence of cobalt in the medium. On the contrary, SCNase co-expressed with P15K, encoded just downstream of SCNase genes, in cobalt-enriched medium under the optimized condition (SCNase((+P15K))) possessed 0.86 Co atom/alphabetagamma trimer and exhibited 78% of the activity of native SCNase. SCNase((+P15K)) showed a UV-Vis absorption peak characteristic of the SCNase cobalt center. About 70% of SCNase((+P15K)) had the gammaCys131-SO(2)H modification. These results indicate that SCNase((+P15K)) is the active holo-SCNase. P15K is likely to promote the functional expression of SCNase probably by assisting the incorporation of cobalt ion.

Mucosal immunity of nasopharynx: an experimental study in TCR-transgenic (OVA23-3) mice.

The ideal vaccine therapy has been warranted for activation of the mucosal immune response in the upper respiratory tract against various types of microbial infection. However, the precise study in regard to the mucosal route of vaccine administration and its mechanism of action remains to be further investigated. Therefore, to better understand the exact mechanism of nasopharyngeal mucosal immunology, from T-cell aspects, the antigen-specific antibody response was investigated in T cell receptor transgenic (OVA23-3) mice (Tg-mice) and wild type BALB/c mice, in comparison, which were stimulated with repeated nasal antigen challenges of ovalbumin (OVA) together with cholera toxin (CT) or OVA alone. OVA-specific IgA and IgG antibodies were not detected in nasal washings of BALB/c mice when these mice were intranasally stimulated with OVA alone. But they were detected in those of BALB/c mice stimulated with OVA and CT, as we have already reported. Interestingly, OVA-specific IgA and IgG antibodies were significantly higher in nasal washings of Tg-mice stimulated with OVA and CT or OVA alone rather than those of BALB/c mice stimulated with OVA and CT. In line with data of the antibody response, OVA-specific IgA and IgG antibody-producing cells significantly increased in number in nasal passage (NP), nasopharyngeal-associated lymphoreticular tissue (NALT), cervical lymph node (CLN), and spleen (SP) of these mice. In nasal washings of Tg-mice, interferon (IFN)-gamma and interleukin (IL)-4 was detected even with a small amount of antigen. To see the cytokine profile of NALT, NP, CLN, and SP of these mice, various cytokine concentrations were measured in supernatants of these cells cultured in vitro with OVA. As a result, IFN-gamma was detected at significantly higher levels in culture supernatants of lymphocytes sampled from NP, CLN, SP as well as NALT of mice having increased antibody titers in nasal washings. On the other hand, Th2 type cytokines such as IL-4, IL-6 and IL-13 were efficiently detected in culture supernatants of NP, CLN, and SP cells from Tg-mice mice, but not in those from NALT cells of those mice. All these data taken together indicate that helper T cells recruited into nasal mucosa and locally activated in an antigen-specific fashion, as well as NALT T cells, are essential for mounting local antigen-specific antibody responses.