Acquisition of certain streptomycin-resistant (str) mutations enhances antibiotic production in bacteria

Physiological differentiation (including antibiotic production) in microorganisms usually starts when cells encounter adverse environmental conditions and is frequently accompanied by an increase in the accumulation of intracellular ppGpp. We have found that the acquisition of certain streptomycin-resistant (str) mutations enables cells to overproduce antibiotics, demonstrating an increase in productivity 5- to 50-fold greater than that of wild-type strains. The frequency of such antibiotic-overproducing strains among the str mutants was shown to range from 3 to 46%, as examined with several strains of the genera Streptomyces, Bacillus, and Pseudomonas. Analysis of str mutants from Bacillus subtilis Marburg 168 revealed that a point mutation occurred within the rpsL gene, which encodes the ribosomal protein S12, changing Lys-56 (corresponding to Lys-43 in Escherichia coli) to Asn, Arg, Thr, or Gln. Antibiotic productivity increased in a hierarchical manner depending upon which amino acid residue replaced Lys at this position. The strA1 mutation, a genetic marker frequently used for mapping, had no effect on antibiotic productivity even though it was found to result in an amino acid alteration of Lys-56 to Ile. Gene replacement experiments with the str alleles demonstrated unambiguously that the str mutation is responsible for the antibiotic overproductivity observed. These results offer a rational approach for improving the production of antibiotic (secondary metabolism) from microorganisms.     

Improvement of cycling performance of Li1.1Mn1.9O4 at 60 °C by NiO addition for Li-ion secondary batteries

We report on electrochemical properties of NiO-blended spinel Li_1.1Mn_1.9O₄ at elevated temperature (60 °C). Thus, we employed two kinds of NiO powders, those are, larger particle size (>10 μm) and submicron-sized NiO powders obtained by a ball-milling. These NiO powders were blended to the spinel Li_1.1Mn_1.9O₄ as an additive for fabrication of cathode. The resulting discharge capacity for the larger NiO particle-blended Li_1.1Mn_1.9O₄ had similar electrochemical properties to the bare Li_1.1Mn_1.9O₄. On the other hand, submicron-sized NiO-blended Li_1.1Mn_1.9O₄ brought about slightly increased capacity and excellent capacity retention, maintaining its initial capacity of 99.2% at 25 °C and 94% at 60 °C when Li metal was employed as the anode. In Li-ion cell using graphite as the anode, the capacity retention was of about 80% during cycling at 60 °C, whereas C/Li_1.1Mn_1.9O₄ cell retained around 68% of its initial capacity. Such improved properties would be ascribed to the HF scavenging into the electrolyte by presence of the submicron-sized NiO particles in Li_1.1Mn_1.9O₄ cathode.     

Four-channel arrayed polarization independent EA modulator with anIPF carrier operating at 10 Gb/s

We have developed a four-channel 10-Gb/s electroabsorption modulator array. We have introduced an innovative technique with an impedance-matched film (IPF) carrier to feed the electrical driving signal. The IPF carrier is made of an insulating polyimide film on which a coplanar waveguide is formed. We have achieved 10-Gb/s operation for all channels with clear eye opening and with negligibly small crosstalk. Polarization independence is confirmed for each arrayed channel     

Systematic evaluation and analysis for 60-GHz dielectric resonatorscoupled to a microstrip line on a GaAs substrate

This paper presents the first systematic evaluation and analysis of 60-GHz-band TE_01δ-mode cylindrical dielectric resonators coupled to a microstrip line on a GaAs substrate. The loss components of the unloaded Q are analyzed using simple numerical techniques. The distance between the resonator center and the microstrip line which gives the maximum coupling coefficient is found to be approximately 3/5 of the resonator radius, whose ratio is almost constant for all practical cases. The temperature characteristics are also demonstrated and the origins of temperature dependences of the unloaded Q and the coupling coefficient are discussed. An equivalent circuit model for the dielectric resonator coupled to the microstrip line is presented, whose element parameters can express the dependences of the resonant frequency, the unloaded Q, and the coupling coefficient on the structural parameters and the temperature     

Effect of ribavirin on subacute sclerosing panencephalitis virus infections in hamsters

The antiviral activity of ribavirin was studied in hamsters infected with subacute sclerosing panencephalitis (SSPE) virus. Ribavirn did not improve the survival of infected hamsters when administered intraperitoneally at the maximal nonlethal dose of 50 mg/kg/day for 10 days. However, when administered intracranially, ribavirin improved the survival of infected hamsters in a dose-dependent manner. The 50% effective dose was calculated to be 1.4 mg/kg/day, and the selectivity index, based on the ratio of the 50% lethally toxic dose (31 mg/kg/day) to the 50% effective dose, was 22. When begun 12 h, but not 36 h, postinfection, ribavirin at a dose of 10 mg/kg/day completely prevented mortality and inhibited the replication of SSPE virus in brains of infected hamsters. Intrathecal or intraventricular administration of ribavirin should be explored for potential use in the treatment of patients with SSPE.     

Polymeric porogens used in the preparation of novel monodispersed macroporous polymeric separation media for high-performance liquid chromatography.

A novel approach to monosized macroporous polymeric separation media with vastly enhanced pore size distributions and chromatographic properties has been developed. Key to this approach is the combined use of monodispersed polymeric particles and suitable solvents as porogens in the copolymerization of styrene and divinylbenzene. Following polymerization, the polymeric porogen is dissolved, leaving behind the monosized beads with a controlled pore structure. The exact pore size and pore size distribution of the final beads are largely controlled by the amount of soluble polymer in the polymerizing mixture: the larger the proportion of soluble polymer in the system, the larger the pores. The uniformly sized macroporous beads prepared with an optimized ratio of polymeric and low molecular weight porogens proved to be very efficient even in short columns for the separation of polystyrene standards in the SEC mode and the separation of proteins in the reversed-phase mode. The relationship between pore size and specific surface area, on one hand, and chromatographic properties of the stationary phase, on the other, have been clearly documented.     

Margin analysis of quantum flux parametron logic gates

An analytical approach is used to estimate the (quasi-static) margins of quantum flux parametron (QFP) logic gates. The operation of a single QFP is analyzed in detail, and input biases or output variations caused by parameter fluctuations are obtained. The results are used to estimate the margins and yields of the QFP logic gates. The relations between the margin and the parameter fluctuations are obtained. The yields are estimated assuming normal distributions of the fluctuations. The calculations are consistent with experiments performed to date. The static margins of the QFP logic gates discussed here are sufficient, with presently available process technology, for medium size integrated circuits     

Descending projections from the spinal and mesencephalic nuclei of the trigeminal nerve to the spinal cord in the cat. A study with the horseradish peroxidase technique

Descending projections from the spinal (Vsp) and the mesencephalic nuclei (Vme) of the trigeminal nerve to the spinal cord were studied by means of the retrograde horseradish peroxidase technique in the cat. The number of labeled neurons was largest in the case of high cervical injections and decreased as the injections were placed caudally. Small laminae III and IV neurons of the nucleus caudalis (Vc) were labeled ipsilaterally following injections placed as caudally as the middle cervical segments (C4-C5). Lamina I (marginal) neurons of the Vc were labeled ipsilaterally after injections at the middle thoracic level (T6) but those of C1 were labeled after lumbar injections (L3). Lamina V neurons of C1 and the medullary counterparts were labeled bilaterally after injections placed caudally to thoracic segments. A few small neurons were labeled in the ipsilateral nucleus interpolaris (Vi) after injections placed as caudally as the middle cervical segments (C6). Among the subdivisions of the Vsp, the labeled neurons were most numerous in the nucleus oralis (Vo). They were medium-sized and large, and appeared bilaterally, with an ipsilateral predominance at the level of the superior olive. The great majority projected to the cervical segments but a few also projected to the lower cervical to the thoracic segments (C8-T9). Neurons of the Vme projected ipsilaterally to the upper cervical segments (C1-C3). No projections were found from the principal sensory nucleus. The present study suggests that the trigeminospinal projections of the Vsp and the Vme are composed of various cells of origin and thereby subserve not only the trigeminospinal reflex but other unknown functions.