Response of respiratory exchange ratio (R) to sinusoidal work load in humans

An examination was made of the response of respiratory exchange ratio (R), carbon dioxide output (VCO2) and oxygen uptake (VO2) to sinusoidal work load with periods (T) of 1-16 min in six healthy men to determine whether R response is sinusoidal. The influence of the ratio of the amplitude of VCO2 to that of VO2 and the phase lag between them on R response was also studied by computer simulation. The results and conclusions obtained are as follows: 1) With decrease in the period, the amplitudes of VO2 and VCO2 dropped exponentially, becoming least at T of 1 min (T = 1 min). In contrast, the amplitude of R was largest at T = 4 min and subsequently decreased progressively. 2) The peak amplitude of R at T = 4 min can be explained by the larger phase lag and relatively low of amplitude of VCO2 to VO2. 3) The smallest amplitude of R at T = 1 min was due not to the ratio of amplitude or phase lag, but to remarkably smaller amplitudes of VO2 and VCO2. 4) The phase lag of VO2 to sinusoidal work load was smaller than that of VCO2. Phase lag of R was considerably larger than that of VO2 or VCO2. 5) The response curve of VO2 and VCO2 is a sinusoidal curve with the same period as exercise. However, the response of R is not a real sinusoidal but a deformed biphasic curve with a high crest and low trough. The deformity is determined by the phase lag between VO2 and VCO2 response and also the ratio of amplitude of VCO2 to that of VO2.     

Gas chromatographic—mass spectrometric determination of plasma 5-fluorouracil after administration of 1-hexylcarbamoyl-5-fluorouracil to dogs and humans

A simple, sensitive and specific method for determining 5-fluorouracil (5-FU) in plasma after the administration of 1-hexylcarbamoyl-5-fluorouracil (HCFU) was developed using gas chromatography—mass spectrometry. Thymine was used as the internal standard. After removal of interfering substances with chloroform, diethyl ether and Amberlite XAD-2 resin, 5-FU and thymine were extracted with 16% n-propanol in diethyl ether and methylated with trimethylanilinium hydroxide. Fragment ions at m/e 158 and 154, the molecular ion of the dimethyl derivatives of 5-FU and thymine, respectively, were used to monitor 5-FU and thymine. The sensitivity of the method is 10 ng/ml, which is sufficient to determine the 5-FU levels in plasma after the administration of therapeutic doses of HCFU to patients.     

The MerE protein encoded by transposon Tn21 is a broad mercury transporter in Escherichia coli

In order to clarify the physiological role of the merE gene of transposon Tn21, a pE4 plasmid that contained the merR gene of plasmid pMR26 from Pseudomonas strain K-62, and the merE gene of Tn21 from the Shigella flexneri plasmid NR1 (R100) was constructed. Bacteria with plasmid pE4 (merR-o/p-merE) were more hypersensitive to CH₃Hg(I) and Hg(II), and took up significantly more CH₃Hg(I) and Hg(II), than the isogenic strain. The MerE protein encoded by pE4 was localized in the membrane cell fraction, but not in the soluble fraction. Based on these experimental results, we suggest for the first time that the merE gene is a broad mercury transporter mediating the transport of both CH₃Hg(I) and Hg(II) across the bacterial membrane.     

Pulsed cytochrome c oxidase from the thermophilic bacterium PS3.

A caa3-type terminal cytochrome c oxidase (EC 1.9.3.1) from the thermophilic bacterium PS3 containing three subunits showed conversion from resting into pulsed form. Upon pulsing (reduction and re-oxidation), the cytochrome c oxidase activity increased over 10-fold. This enhanced activity of the pulsed enzyme gradually decayed. Addition of phospholipids, necessary for the enzyme activity, did not affect this decay process. Small changes in the absorption spectrum were observed for the resting-into-pulsed transition and for H2O2 ligation to the pulsed enzyme. The e.p.r. spectrum of the resting enzyme was very similar to that of mitochondrial enzyme, but the transient g = 5, 1.78 and 1.69 set of e.p.r. signals, associated with the pulsed bovine heart oxidase, were not observed in the case of pulsed bacterium-PS3 enzyme.     

Purification and characterization of subtilisin inhibitors 'Marinostatin' produced by marine Alteromonas sp.

The four novel peptide subtilisin inhibitors, which have been named Marinostatin B-1, B-2, C-1 and C-2, were purified from the culture supernatant fluid of a marine bacterium, Alteromonas sp. A combination of Diaion HP-20 and CM-cellulofine ion exchange column chromatographies, Sephadex G-25 gel filtration and preparative high performance liquid chromatography (HPLC) were employed. Final preparations gave a single peak on HPLC. The molecular weights by gel filtration of Marinostatin B-1 and C-1 were estimated to be 1500, and those of B-2 and C-2 were 1700. All the inhibitors were stable in acidic (pH range 4–6) but less stable in alkaline solutions (pH 10). The metal ions Co²⁺ and Fe²⁺ repressed the inhibitory activity by 30 and 20%, respectively. The four inhibitors had inhibitory effects on serine proteases like α-chymotrypsin.     

Evidence for three alpha subunits in one molecule of F1-ATPase from thermophilic bacterium PS3.

The numbers of sulfhydryl residues in F₁-ATPase of thermophilic bacterium PS3 and its isolated subunits were analyzed with Ellman's reagent. This F₁-ATPase contained three sulfhydryl residues and no disulfide bridge. Of the five kinds of subunits of the F₁-ATPase, only the α subunit contained one sulfhydryl residue. So there are three α subunits in one molecule of the F₁-ATPase.     

Isolation of two new gibberellins from immature seeds of Canavalia

Summary Two new gibberellins, Canavalia gibberellin-I (CG-I) and Canavalia gebberellin-II (CG-II), were isolated from immature seeds of sword bean, Canavalia gladiata DC. The molecular formulas C₁₉H₂₂O₇ and C₁₉H₂₂O₆, were assigned to CG-I and CG-II, respectively, on the basis of high resolution mass, infrared and NMR spectra. The growth-promoting effects of CG-I and CG-II on dwarf maize mutants d ₁ and d ₅, rice seedlings and dwarf peas, Progress No. 5, are reported.