Energetics of mice in stable and unstable social conditions: Evidence of an air-borne factor affecting metabolism

The metabolic rates of laboratory mice were compared in three conditions: isolated mice, mice paired together over six days (stable groups), and mice paired with strange partners daily (unstable groups). Stable pairs had 15% lower metabolic rates than either isolated or unstable pairs. In other experiments when two mice were placed in separate metabolic chambers and connected together via an air flow, the metabolic rate of the recipient in the series was 35% lower than the donor. The data suggest that a ‘factor’ produced by the donor mouse was passed via the air supply into the recipient's chamber.     

Calcium and magnesium in Mueller-Hinton agar and their influence on disk diffusion susceptibility results

Concentrations of calcium and magnesium were determined for 39 lots of media, including broth and agar media used for susceptibility tests and plain agar. In addition, the effect that media with and without physiological levels of these divalent cations would have on the disk diffusion susceptibility of 21 strains ofPseudomonas aeruginosa to four antimicrobics was also ascertained. Mueller-Hinton agar showed a wide variation in calcium and magnesium content. Mueller-Hinton broth contained lower concentrations of calcium and magnesium, and there was little lot-to-lot variation. Lots of Mueller-Hinton agar with higher concentrations of calcium and magnesium yielded smaller zone diamaters than those with lower concentrations. Even at equal cation concentration, zones of inhibition varied from lot to lot. Since the addition of calcium and magnesium to Mueller-Hinton agar to obtain a predetermined level did not result in equivalent zone diameters, performance testing of susceptibility media is recommended.     

Characterization of the peptide-bound flavin of a bacterial sarcosine dehydrogenase.

As in the case of the succinate and sarcosine dehydrogenases of liver mitochondria, the flavin prosthetic group of the bacterial sarcosine dehydrogenase can be released from the enzyme by proteolytic digestion with trypsin and chymotrypsin. The flavin, isolated in the dinucleotide form and covalently bound to a peptide fragment, is converted to the mononucleotide and purified by sequential chromatography on Sephadex G-25, DEAE-Sephadex A-25, followed by preparative paper chromatography and high voltage electrophoresis.The absorption maxima of the purified flavin at pH 7 are found at 268, 350, and 447 nm, with 268:447 nm and 350:447 nm ratios of 3.08 and 0.79, respectively. The fluorescence excitation and emission maxima, 450 and 530 nm, respectively, are similar to those of flavin mononucleotide. The fluorescence of the flavin-peptide is maximal at pH 3.0–3.1.Amino acid analysis of the flavin-peptide (riboflavin form) gave the following molar ratios of amino acids to flavin: Lys(1), Asp(2), Thr(1), Ser(1), Glu(1), Gly(1), and Ala(1). Aspartic acid was the N-terminal amino acid. Upon more extensive hydrolysis, histidine was obtained in 71–84% yields. Employing aminopeptidase M, the partial sequence of amino acids in the flavin-peptide was determined to be as follows: Flavin

-Asp-Lys-Ser-Glu-Gly-His-(Asp,Ala,Thr)-Evidence is presented that the isoalloxazine ring is linked covalently via its 8 α-methyl group to N-3 of histidine.     

Correlation of the critical micelle concentrations of surfactants with their effects on a bacterial demethylase.

The activity of a sarcosine dehydrogenase isolated from a strain of Pseudomonas is enhanced by the addition of Triton X-100, Brij 35, and Tween 80, and is inhibited by deoxycholate and Sarkosyl NL-97. 2,6-Dichlorophenolindophenol, which is used as the oxidant in the dehydrogenase assay, has also been employed as an indicator in the spectrophotometric determination of the critical micelle concentrations (CMC) of both the nonionic and anionic detergents under conditions optimal for the enzyme analyses. A correlation between the activation or inhibitory activities of the surfactants and their CMC values has been established.     

Sources,transport, measurement and impact of nano and microplastics in urban watersheds

Reviews in Environmental Science and Bio/Technology - The growing and pervasive presence of plastic pollution has attracted considerable interest in recent years, especially small...