Continuous wave, 30 W laser-diode bar with 10 GHz linewidth for Rb laser pumping.

A laser-diode bar incorporated into an external cavity with a volume Bragg mirror produced 30 W of cw output power within a 20 pm (10 GHz) spectral linewidth (FWHM) centered at 780 nm. The device output power exceeded 90% of that for the free-running laser-diode bar. The emission wavelength was tuned over a 400 pm range without broadening laser spectrum width. Absorption of 90% of the laser radiation by a 25 mm vapor cell containing Rb that has been pressure broadened with 300 torr of ethane was demonstrated.

Efficient pumping of Rb vapor by high-power volume Bragg diode laser.

A 2W cw laser diode (LD) with an external cavity produced by a reflecting volume Bragg grating (VBG) demonstrated a spectral width of 7GHz (full width at half-maximum) at 780nm. The device output power exceeded 90% of the output power of the free-running LD. The emission wavelength was tuned over a 300pm range by thermal control of the VBG. Rb vapor was shown to absorb more than 95% of the laser radiation.

Motor estimation of short time intervals under the effect of some psychotropic drugs.

A study is made of the human ability to estimate short time intervals (up to 1 s) by a simple motor response under the effect of stimulants (Amphetamine, Caffeine) and depressants (Chlorazin, Diazepam, Phenobarbital). Of all psychotropic drugs used only Chlorazin causes a statistically significant increase in the mean values of the reaction time of all subjects compared with the controls. The psychotropic drugs in the doses used have no influence on the ability of the subjects to produce a light interval of a given duration. In the task requiring reproduction of a 900 ms interval, Amphetamine schortens significantly the response times, which is explained by earlier organization of their motor responce and lack of feedback.

Semisynthetic coumermycins: structure-activity relationships.

The relative antimicrobial activity of a large series of semisynthetic coumermycins has been determined. Most of the derivatives, which were 3-substituted-4-hydroxy-8-methyl-7-[3-O-(5-methyl-2-pyrrolylcarbonyl) noviosyloxy] coumarins, had an in vitro antibacterial spectrum similar to that of the parent compound, coumermycin A(1), but were generally less potent in minimal inhibitory concentration (MIC) tests. Derivatives with an alkylcarboxamido, arylcarboxamido, or arylsulfonamido group in the 3 position had considerably greater in vitro activity than those possessing an amino-, aryl-, or alkyureido substituent. Efficacy in Staphylcoccous aureus Smith infections of mice was greater for those compounds with branched-chain alkylcarboxamido, unsubstituted, mono- or disubstituted aryl- and heteroaryl-carboxamido groups than for derivatives having an n-alkylcarboxamido, aralkyl-carboxamido, arylsulfonamido, or trisubstituted arylcarboxamido substituent. Significant in vitro activity against Klebsiella pneumoniae and other gram-negative species was restricted to those compounds having a 3-(3-n-alkyl-4-hydroxy-phenyl-carboxamido) group. Only the n-hexyl homologue demonstrated in vivo activity in a K. pneumoniae infection. Many derivatives were two- to threefold more active than coumermycin A(1) in orally treated mouse infections, despite the fact that their MIC values were considerably higher. This result was undoubtedly a reflection of the markedly greater oral absorbability possessed by many of the derivatives. Although peak oral mouse blood levels of some compounds were > 25 times higher than those of coumermycin A(1), their toxicity for the host was no greater. In addition, the semisynthetic coumermycins caused much less local irritation than coumermycin A(1) when administered parenterally.

Antipseudomonal activity of alpha-sulfoaminopenicillins.

A series of penicillins characterized by the presence of a sulfoamino or a modified sulfoamino group in the side chain was subjected to in vitro antimicrobial screening tests. Although the most potent members of the series were less active than benzylpenicillin against gram-positive bacteria and comparably active against most gram-negative bacteria, they were, on the average, 8 to 16 times more effective against strains of Pseudomonas aeruginosa. In other comparative laboratory tests against P. aeruginosa, these compounds were about as active as carbenicillin and four to eight times more active than ampicillin. An examination of structure-activity relationships indicated that maximal potency was obtained with penicillins having an alpha-(aromatic or heteroaromatic)-alpha-sulfoaminoacetamido side chain. The compound with an alpha-phenyl group was comparable in activity to those having an alpha-(2- or 3-thienyl) group, whereas any modification in position or structure of the alpha-sulfoamino group reduced activity. Results of studies with a cell-free P. aeruginosa beta-lactamase suggest that the marked inhibitory effects of alpha-sulfoamino penicillins for P. aeruginosa can be attributed, at least in part, to their high degree of resistance to this enzyme. Some derivatives, however, had weak antipseudomonal activity, despite possessing a high degree of beta-lactamase resistance.

Influence of cobalt on fermentative methylation.

Streptomyces rishiriensis produces at least five closely related antibiotics. Strain selection yielded a culture producing only the most active component, coumermycin A. Hydrolysis of this antibiotic by barium hydroxide yielded both 5-methyl-pyrrole-2-carboxylic acid and pyrrole-2-carboxylic acid, which could be separated by paper chromatography. Coumermycin A was thus shown to be two fractions, designated A(1) and A(2) depending upon the nature of the pyrrole carboxylic acid portion. The addition of cobalt to the fermentation medium at a level as low as 0.01 mug/ml shifted the fermentation exclusively to the production of coumermycin A(1). Other ions were ineffective, except nickel, whose activity could be explained by the presence of contaminating cobalt.