A Simple Evaluation Method for the Quality of Dietary Protein in Rats Using an Indicator Amino Acid Oxidation Technique.

We demonstrated that the indicator amino acid oxidation (IAAO) method could be employed for the evaluation of quality of dietary protein by comparing the protein intakes required to meet metabolic demand in rats fed different proteins. The objective of this study was to validate a simple evaluation method for determining the quality of dietary protein using the IAAO technique. Male Sprague-Dawley rats (5-6 wk old) were fed meals composed of graded protein, using either casein, wheat gluten (WG), soy protein isolate (SPI), or egg white protein (EW), every 3 h from 09:00 to 18:00. Administration of L-[1-(13)C]phenylalanine was performed hourly from 15:00 to 18:00. The (13)CO2 level in breath CO2 was measured at 18:30. The protein intake values required to meet the metabolic demand based on the breath (13)CO2 data for the dietary casein, WG, SPI, and EW intake were 18.0, 22.2, 17.5, and 10.1 g/kg BW/d, respectively. The breath (13)CO2 concentrations corresponding to the protein intake of 7.5 g/kg BW/d for casein, WG, SPI, and EW were 9.8, 10.9, 10.3, and 8.9 (‰)/100 g BW, respectively. A significant correlation was demonstrated between the protein intake required to meet the metabolic demands and the (13)CO2 concentration in the breath for a protein intake of 7.5 g/kg BW/d (r=0.967; p<0.05). These results demonstrated that the protein intake required to meet metabolic demand could be estimated and that the quality of the dietary protein could be evaluated using the (13)CO2 concentration in the breath with a protein intake of 7.5 g/kg BW/d.

The proton pumping pathway of bovine heart cytochrome c oxidase.

X-ray structures of bovine heart cytochrome c oxidase have suggested that the enzyme, which reduces O(2) in a process coupled with a proton pumping process, contains a proton pumping pathway (H-pathway) composed of a hydrogen bond network and a water channel located in tandem across the enzyme. The hydrogen bond network includes the peptide bond between Tyr-440 and Ser-441, which could facilitate unidirectional proton transfer. Replacement of a possible proton-ejecting aspartate (Asp-51) at one end of the H-pathway with asparagine, using a stable bovine gene expression system, abolishes the proton pumping activity without influencing the O(2) reduction function. Blockage of either the water channel by a double mutation (Val386Leu and Met390Trp) or proton transfer through the peptide by a Ser441Pro mutation was found to abolish the proton pumping activity without impairment of the O(2) reduction activity. These results significantly strengthen the proposal that H-pathway is involved in proton pumping.

Retrospective seroepidemiological survey for human babesiosis in an area in Japan where a tick-borne disease is endemic.

A total of 1,335 archived human sera collected in 1985 from an area in Japan where a tick-borne disease is endemic were examined by indirect immunofluorescence antibody test (IFAT) to estimate seroprevalence against three serologically distinct types of Babesia microti-like parasites; namely, Hobetsu, Kobe, and U.S. types. Eighteen sera (1.3%) were found to be IFAT-positive (titer 1:100-1:6,400), of which 14 and three were ascertained by Western blot analysis to be positive against the Hobetsu and Kobe types, respectively. In addition, four sera showed an IFAT titer of 1:100 against the U.S. type, but they appeared to be false-positive because they were cross-reactive against the Hobetsu and Kobe types, and also because a U.S.-type parasite has not been found in Japan. Our results suggest that human babesiosis in Japan occurred prior to the discovery of the index case in 1999 and that the infections were caused mainly by Hobetsu-type parasites.