U-102408 has been isolated from S. arginensis cultures and fully characterized by NMR and MS. These studies indicate that U-102408 is identical with sulfomycin, and this data confirm the structure of sulfomycin which was assigned by chemical degradation and limited NMR studies. The biosynthetic origins of all U-102408 structural features have been elucidated through isotopic labeling experiments with primarily 13C but also using 14C, deuterium or tritium. Of particular interest, the 4-hydroxy-2-amino-2-pentenoic acid moiety was determined to originate from threonine and a one carbon unit derived from the two position of glycine or the S-methyl of methionine. The biosynthetic pathway for U-102408 differs from that for nosiheptide, thiostrepton, and berninamycin in that cysteine and serine do not cross label sites in U-102408, while this has been observed for the other thiopeptides. In U-102408 cysteine and serine are each incorporated into unique sites within the molecule. This indicates that the interconversion of cysteine and serine is not an active pathway for S. arginensis. In fact for fermentations in defined medium the addition of cysteine was found to be necessary to achieve higher antibiotic titer. Unlike the other thiopeptides that have been studied, threonine was incorporated into sites labeled by serine though serine did not incorporate into sites labeled by threonine within U-102408. No cross labeling of threonine and serine has been observed in studies of nosiheptide, thiostrepton, or berninamycin. In the current study glycine is investigated as a precursor for U-102408. The interconversion of glycine to serine is a very facile pathway in S. arginensis; glycine labels all sites labeled by serine. This data suggests glycine as a possible precursor for nosiheptide, thiostrepton, and berninamycin which has not been investigated for these other thiopeptides. Incorporation of label from 3-2H-serine is facile for thiostrepton and nosiheptide and was used to probe the mechanism of formation of the pyridine ring. However, no incorporation from 3-2H-serine or 3-3H-serine was observable for U-102408. While the lack of incorporation may be due to washout of the label from the precursor, it also may be due to the interconversion of serine and glycine causing loss of the label from the serine pool.

Background: Pharmacokinetic and pharmacodynamic assessment of ester-containing drugs can be impacted by hydrolysis of the drugs in plasma samples post blood collection. The impact is different in the plasma of different species. Objective: This study was to evaluate stability of a prodrug, ketoprofen methylester (KME) in commercially purchased and freshly collected plasma of mouse, rat, dog, cat, pig, sheep, cattle and horse. Methods: KME hydrolysis was determined following its incubation in commercially purchased and freshly collected plasma of those species. Different esterase inhibitors were evaluated for prevention of the hydrolysis in rat, dog and pig plasma. Results: KME was rapidly hydrolyzed in both commercially purchased and freshly collected plasma of mouse, rat, and horse. The hydrolysis was initially quick and then limited in cat plasma. KME hydrolysis was minimum in commercially purchased plasma of dog, pig, sheep and cattle but substantial in freshly collected plasma of those species. Different esterase inhibitors showed different effects on stability of KME in rat, dog and pig plasma. Conclusion: These results indicate that plasma of different species has different hydrolytic activities to ester-containing drugs. The activities in commercially purchased and freshly collected plasma may be different and species dependent. Esterase inhibitors have different effects on prevention of hydrolysis of the ester-containing drugs in the plasma of different species.

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OBJECTIVE The lactulose-to-mannitol ratio test is a test to assess the disorders associated with gut permeability. The test requires an oral administration of the mixture of lactulose and mannitol and urine collection. The urinary ratio of lactulose to mannitol is an indicator of intestinal permeability. Due to the complexity of urine collection in animal studies, plasma exposure ratios of lactulose to mannitol compared to their urinary concentration ratios were evaluated following an oral administration of the sugar mixture in pigs. ANIMALS 10 pigs were orally dosed with a solution of lactulose and mannitol mixture. PROCEDURES Plasma samples were collected at predose, 10 and 30 minutes and 2, 4, and 6 hours postdosing, and cumulated urinary samples were collected at 6 hours for liquid chromatography–mass spectrometry analysis. The ratios of pharmacokinetic parameters of lactulose to mannitol and the plasma sugar ratios at a single time point or the mean values of several time points were compared to their urinary sugar ratios. RESULTS The results revealed that the lactulose-to-mannitol ratios of AUC0–6h, AUCextrap, and Cmax were correlated to the urinary sugar ratios, and the plasma sugar ratios of a single time point at 2, 4, or 6 hours and the mean values of those time points were also appropriate to replace their urinary ratios in pigs. CLINICAL RELEVANCE Following an oral administration of lactulose and mannitol mixture, blood collection, and assay can be an option for assessing intestinal permeability, especially in animal studies.

II E aaxi = /(yi. • • •. y a) i-i i-i have been given. We generalize the equation by solving the equation 2»» 2n_1 (1) II £*r*i-zoo. i=l J-l in which we suppose that f(y) =f(yi, • • • , ya) is a homogeneous polynomial, with integral coefficients, of degree m, where m is of the form 2p(2a+l), q being a non-negative integer, p is one of the integers 0, 1, • • • , n-l, and thus m^O (mod 2"). We suppose further that the rank of the matrix of the forms ^-i1 auXj (i=l, • • • , 2n) is 2n-1 and thus we may choose the notation such that A, the determinant of the first 2n-1 forms, does not vanish. Let An be the cofactor of a,y in A.