In a study of 530 individuals with non-syndromic, sensorineural hearing loss, we identified 18 mutations at connexin 26 (Cx26), four of which are novel (À23G4T, I33T, 377_383dupTCCGCAT, W172R) and the remaining 14 (ivs1 þ 1G4A, M1V, 35delG, W24X, I35S, V37I, R75W, W77X, 312del14, E120del, Q124X, Y136X, R143W, R184P) being mutations previously described. To gain insight into functional consequences of these mutations, cellular localization of the mutant proteins and their ability to permit lucifer yellow transfer between cells was studied in seven of them (W24X, I33T, I35S, R75W, E120del, W172R and R184P). I35S and R184P showed impaired trafficking of the protein to the plasma membrane. I33T, R75W, E120del and W172R showed predominantly membrane localization but did not form functional gap junction channels. Surprisingly, W24X, a protein-truncating mutation, apparently permits formation of a full-length protein, perhaps due to a stop codon read-through mechanism. These results provide further evidence that Cx26 mutations affect gap junction activity by mis-regulation at multiple levels.

Mutations in the autosomal genes TMPRSS3, TMC1, USHIC, CDH23 and TMIE are known to cause hereditary hearing loss. To study the contribution of these genes to autosomal recessive, non-syndromic hearing loss (ARNSHL) in India, we examined 374 families with the disorder to identify potential mutations. We found four mutations in TMPRSS3, eight in TMC1, ten in USHIC, eight in CDH23 and three in TMIE. Of the 33 potentially pathogenic variants identified in these genes, 23 were new and the remaining have been previously reported. Collectively, mutations in these five genes contribute to about one-tenth of ARNSHL among the families examined. New mutations detected in this study extend the allelic heterogeneity of the genes and provide several additional variants for structure-function correlation studies. These findings have implications for early DNA-based detection of deafness and genetic counseling of affected families in the Indian subcontinent.

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The composition of the major acidic extracellular polysaccharide (EPS) of 25 strains of Rhizobium japonicum was determined. Eight strains synthesized an acidic EPS containing rhamnose and 4-0methylglucuronic acid and were closely related according to DNA homology. These same strains also expressed high levels of ex planta nitrogenase activity. Sixteen strains produced an acidic EPS containing glucose, mannose, galacturonic acid, and galactose and were also related by DNA homology. These strains developed little or no nitrogenase activity under the experimental conditions employed.Previous results from this laboratory demonstrated a negative correlation between the amount of extracellular polysaccharide (EPS) produced and ex planta nitrogenase activity with many strains of Rhizobium japonicum (1). In addition, it was suggested that the differences in EPS production may not only be quantitative, but qualitative as well. Two different types of a major acidic EPS from R. japonicum have been characterized. One type has a tetrasaccharide repeating unit with a backbone of three rhamnosyl residues and a side chain containing one residue of 4-0-methylglucuronic acid (12). The second type has a pentasaccharide repeating unit with a backbone of two residues of glucose and one each of mannose and galacturonic acid and a side chain containing one residue of galactose or 4-0-methylgalactose (26). Compositional studies of the EPS from numerous strains of R. japonicum suggest that, with the exception of some strains isolated in the Far East (15, 16), most strains produce an EPS having a composition that is consistent with one of these two structures (11,12,25,26).Numerous workers have presented evidence suggesting that a reconsideration of Rhizobium classification is needed (see, e.g., references 14, 17, and 18). Recently, Hollis et al. (20) suggested that strains classified as R. japonicum could be separated into at least three DNA homology groups based on DNA-DNA hybridization studies. Two of the groups were so widely divergent that the authors suggested that separate species status may be appropriate. Using many of the same strains that Hollis et al. (20) studied, we have found that EPS composition and ex planta nitrogenase activity are related to the DNA homology group.Microorganisms. R. japonicum strains were obtained from and Rhizobium lupini ATCC 10319).Stock cultures were maintained on solid medium as previously described (1). The cells were routinely grown on * Corresponding author. t Contribution no. 824 from the Charles F. Kettering Research Laboratory.defined liquid medium containing 7.4 mM K2HPO4 (pH 6.5), 0.8 mM MgSO4, 50 FLM CaCl2, 0.1 mM FeSo4, 0.5% sodium gluconate, 0.1% glutamate, and trace metals (1).Composition of EPS. EPS was prepared by centrifuging 50 ml of log-phase cultures at 27,000 x g for 30 min. The clear supernatants were lyophylized and redissolved in 6 ml of water. Four milliliters of this concentrate was loaded onto a column (2.5 by 40 cm) containing Fractogel TSK HW-55F (Pierce Chemical Co., Roc...

There was no significant difference between the two groups in the postoperative air-bone gap and air-bone gap closure at 1, 2, 3, and 6 months.

Thirty-nine wild-type strains of Rhizobium japonicum have been studied for their ability to synthesize nitrogenase ex planta in defined liquid media under microaerobic conditions. Twenty-one produced more than trace amounts of acetylene reduction activity, but only a few of these yielded high activity. The oxygen response curves were similar for most of the nitrogenase-positive strains. The strains derepressible for activity had several phenotypic characteristics different from non-derepressible strains. These included slower growth and lower oxygen consumption under microaerobic conditions and lower extracellular polysaccharide production. Extracellular polysaccharide production during growth on gluconate in every nitrogenase-positive strain assayed was lower under both aerobic and microaerobic conditions than the non-derepressible strains. These phenotypic characteristics may be representative of a genotype of a subspecies of R. japonicum. These studies were done in part to enlarge the base number of strains available for studies on the physiology, biochemistry, and genetics of nitrogen fixation. MATERIALS AND METHODS M/icroorganisms. R. japonicum strains were obtained from Deane Weber or Harold H.

Four acute cases of volar carpometacarpal dislocations of the medial four metacarpals were treated in our hospital's emergency room. Our initial diagnosis after clinical examination was confirmed by routine x-rays of the hand. Closed reduction was followed by percutaneous fixation of the carpometacarpal joints with Kirschner wires. Satisfactory function of the hand was obtained in all cases.