Functionally Cloned pdrM from Streptococcus pneumoniae Encodes a Na+ Coupled Multidrug Efflux Pump

Multidrug efflux pumps play an important role as a self-defense system in bacteria. Bacterial multidrug efflux pumps are classified into five families based on structure and coupling energy: resistance−nodulation−cell division (RND), small multidrug resistance (SMR), major facilitator (MF), ATP binding cassette (ABC), and multidrug and toxic compounds extrusion (MATE). We cloned a gene encoding a MATE-type multidrug efflux pump from Streptococcus pneumoniae R6, and designated it pdrM. PdrM showed sequence similarity with NorM from Vibrio parahaemolyticus, YdhE from Escherichia coli, and other bacterial MATE-type multidrug efflux pumps. Heterologous expression of PdrM let to elevated resistance to several antibacterial agents, norfloxacin, acriflavine, and 4′,6-diamidino-2-phenylindole (DAPI) in E. coli KAM32 cells. PdrM effluxes acriflavine and DAPI in a Na⁺- or Li⁺-dependent manner. Moreover, Na⁺ efflux via PdrM was observed when acriflavine was added to Na⁺-loaded cells expressing pdrM. Therefore, we conclude that PdrM is a Na⁺/drug antiporter in S. pneumoniae. In addition to pdrM, we found another two genes, spr1756 and spr1877,that met the criteria of MATE-type by searching the S. pneumoniae genome database. However, cloned spr1756 and spr1877 did not elevate the MIC of any of the investigated drugs. mRNA expression of spr1756, spr1877, and pdrM was detected in S. pneumoniae R6 under laboratory growth conditions. Therefore, spr1756 and spr1877 are supposed to play physiological roles in this growth condition, but they may be unrelated to drug resistance.     

Physicochemical Parameters for Structure-Activity-Studies of Substituted Phenyl N-Methylcarbamates

The electronic and hydrophobic substituent parameters of a number of o-, m- and p- substituted phenyl N-methylcarbamates were estimated by measuring the alkaline catalyzed hydrolysis rate constant and 1-octanol/water partition coefficient. Since some o-substituted derivatives are very potent insecticides, emphasis was placed on determining the ortho substituent effects in terms of the existing free-energy related parameters. The information obtained should be useful in structure-activity studies of carbamate insecticides.     

Structure of Succinoglucan: Fragmentation by Partial Acid Hydrolysis

Succinoglucan, a succinylated polysaccharide produced by Alcaligenes faecalis var. myxogenes 10C3, was partially hydrolyzed with acid. Fractionation of the neutral oligosaccharides gave cellobiose, gentiobiose, laminaribiose, laminaritriose, 6-O-β-laminaribiosylglucose, 6-O-β-laminaritriosylglucose, and 3-O-β-cellobiosylgalactose, confirming the previous results that the polysaccharide consists of β-(l→3)-linked, (1→4)-linked and (1 →6)-linked d-glucose residues, and β-(1→3)-linked d-galactose residues.

Possible structural features of succinoglucan were discussed on the basis of the above and previous results obtained by Smith degradation.     

Constitutional Studies on the Mucilage of “Yamanoimo,” Dioscorea batatas Decne,forma Tsukune

All four stereoisomers of 10,14-dimethyloctadec-1-ene, a sex pheromone component of the apple leafminer (Lyonetia prunifoliella: Lepidoptera), were synthesized starting from (R)- and (S)-propylene oxide by applying stereospecific inversion of chiral secondary tosylates as a key step. Field evaluation showed that male moths of the Japanese population were selectively attracted by the (10S,14S)-isomer and that the activity was not inhibited by the enantiomer.     

Sequential Ubiquitination of Ribosomal Protein uS3 Triggers the Degradation of Non-functional 18S rRNA

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Comparative morphological examination of vertebral bodies of teleost fish using high-resolution micro-CT scans

Vertebral bodies of teleost fish are formed by the sclerotomal bone covering the chordacentrum. The internal part of the sclerotomal bone is composed of an amphicoelous hourglass shaped autocentrum, which is common in most fish species. In contrast, the external shape of the sclerotomal bone varies extensively among species. There are multiple hypotheses regarding the composition and formation of the external structure. However, as they are based on studies of few extant or extinct species, their applicability to other species remains to be clarified. To understand the morphology, formation, and composition of vertebral bodies in teleosts, we performed a comparative analysis using micro-CT scans of 32 species from 10 orders of Teleostei and investigated the detailed morphology of the sclerotomal bone, especially its plate-like ridge and trabeculae. We discovered two structural characteristics that are shared among most of the examined species. One was the sheet-like trabeculae that extend radially from the center of the vertebral body with a constant thickness. The other was the presence of hollow spaces on the internal parts of the lateral ridge and trabeculae. The combination of different arrangements of sheet-like trabeculae and internal hollow spaces formed different shapes of the lateral structure of the vertebral body. The properties of these two characteristics suggest that the external part of the sclerotomal bone grows outward by deposition at the bone tip, and that, concurrently, bone absorption occurs in the internal part of the sclerotomal bone. The vertebral arches were also formed by the sheet-like trabeculae, indicating that both, the vertebral body and the arches, are formed by the same component. The micro-CT scanning data were uploaded to a public database so they can be used for future studies on fish vertebrae.     

Determination of triazolam in serum by deactivated metal capillary gas chromatography with electron-capture detection

A method for the determination of trace amounts of triazolam in serum by deactivated metal capillary gas chromatography with electron-capture detection was established. The column used exhibits excellent thermostability in high-temperature analysis and easy handling and a long lifetime of the column and well shaped peaks on the chromatograms are obtained. With the metal capillary column, it was found to be easier to maintain suitable analytical conditions for the routine assay of triazolam than with a fused-silica column. With this method, 0.5 ng/ml of triazolam in serum can be determined. The method is useful for pharmacokinetic and therapeutic purposes.