Ruminal escape and apparent degradation of amino acids administered intraruminally in mixtures to cows.
The apparent ruminal degradation and escape of amino acids (AA) administered in 9 different mixtures of essential AA and 8 different mixtures of nonessential AA were studied using two cows fitted with ruminal cannulas. The 600-mmol AA mixtures, which were administered intraruminally using polyethylene glycol as a liquid marker, contained equal amounts of two, four, or eight AA. The amounts of each of the AA in the mixtures were 300, 150, and 75 mmol, respectively. Ruminal degradation and escape were compared with values previously reported for AA administered individually. Across doses, the mean rate of initial degradation (degradation during the 1st h after administration) of essential AA was 26% when the AA were administered in mixtures and 45% when the AA were administered individually. For nonessential AA, the corresponding values were 34 and 54%. Across doses, mean ruminal escape during the first 8 h after essential AA administration was 22% when the AA were administered in mixtures and 16% when the AA were administered individually. For nonessential AA, the corresponding values were 13 and 11%. After intraruminal administration of AA, both individually and in mixtures, significant negative correlations were found between rates of degradation during the 1st h and ruminal escape during an 8-h period. Some AA mixtures caused a net increase in the concentration of other AA in ruminal fluid 1 h after administration. Twelve of the mixtures that did not contain Ala caused a considerable net increase in the concentration of this AA, and 3 AA mixtures containing Arg and Ala caused a marked net increase in the concentration of Trp.
Enrichment of fusobacteria from the rumen that can utilize lysine as an energy source for growth.
Ruminal lysine degradation is a wasteful process that deprives the animal of an essential amino acid. Mixed ruminal bacteria did not deaminate lysine (50 mM) at a rapid rate, but lysine degrading bacteria could be enriched if Trypticase (5 mg/mL) was also added. Lysine degrading isolates produced acetate, butyrate and ammonia, were non-motile, stained Gram-negative and could also utilize lactate, glucose, maltose or galactose as an energy source for growth. Lactate was converted to acetate and propionate, and 16S rDNA indicated that their closest relatives were Fusobacterium necrophorum. Growing cultures produced ammonia at rates as high as 2400 nmol/mg protein/mL/min. Washed cell suspensions took up (14)C lysine (3 microM) at an initial rate of 6 nmol/mg protein/min, and glucose addition did not affect the transport. Cells washed aerobically had the same transport rate as those handled anaerobically, but only if the transport buffer contained sodium. The affinity constant for sodium was 8 mM, and sodium could not be replaced by lithium. Cells treated with the sodium/proton antiporter, monensin (5 microM), did not take up lysine, but a protonophore that inhibited growth (tetrachlorosalicylanilide, 10 microM) had no effect. An artificial membrane potential created by potassium diffusion did not increase the rate of lysine transport, and an Eadie-Hofstee plot indicated the transport rate was directly proportional to the lysine concentration. Decreasing the pH from 6.7 to 5.5 caused an 85% decrease in the rate of lysine transport. The addition of F. necrophorum JB2 (130 microg protein/mL) to mixed ruminal bacteria increased lysine degradation 10-fold, but only if the pH was 6.7 and monensin was not present. Further work will be needed to see if dietary lysine enriches fusobacteria in vivo.
The National PKI of Peru: a new certification hierarchy
In order to guarantee secure transactions through the Internet and to generate strong evidence that could be used in case of future legal disputes, several countries around the world have promoted and regulated the use of digital signatures based on Public Key Infrastructure (PKI). However, despite the high expectations, its implementation has achieved neither the desired results nor its globalization. Many of the reasons were discovered years ago, but they are still open problems for the scientific community nowadays. In order to consider the case of the national PKI of the Peruvian state as empirical evidence for studies that address the open problems, this article describes the details about a new certification hierarchy which is expected to overcome some of its predecessors’ limitations. It is also expected that the information disclosed in this article could be useful to other countries for making a preliminary assessment for possible cross-border recognition of Peruvian digital signatures.