D-tagatose has low small intestinal digestibility but high large intestinal fermentability in pigs.
(1/207)
The digestibility of D-tagatose, its effect on the digestibility of macronutrients and the metabolic response of the microbiota of the gastrointestinal tract to the ingestion of this carbohydrate were studied in pigs. Eight pigs were fed a low fiber diet comprising 15% sucrose (control group). Another eight pigs were fed a similar diet except that 100 g sucrose per kg diet was replaced by D-tagatose (test group). After 18 d, the pigs were killed and the gastrointestinal contents removed for analysis. The digestibility of D-tagatose was 25.8 +/- 5.6% in the distal third of the small intestine. The small intestinal digestibilities of dry matter (86.9 +/- 1.3 vs. 92.9 +/- 0.9%), gross energy (74.4 +/- 1.6 vs. 80.7 +/- 1.8%) and sucrose (90.4 +/- 2.5 vs. 98.0 +/- 0.5%) were lower (P < 0. 05) in the pigs fed D-tagatose. Digestibilities of starch, protein and fat did not differ between groups. D-Tagatose, sucrose and starch were fully digested in the large intestine. The fecal digestibilities of energy, dry matter and fat did not differ between the two groups, whereas D-tagatose reduced the fecal digestibility of protein (91.1 +/- 0.6 vs. 93.5 +/- 0.7%, P < 0.05). D-Tagatose served as a substrate for the microbiota in the cecum and proximal colon as indicated by a reduced pH, and a greater ATP concentration, adenylate energy charge (AEC) ratio and concentration of short-chain fatty acids. In particular, the increase in the concentrations of propionate, butyrate and valerate suggests possible health benefits of this monosaccharide. (+info)
Synechococcus mutants resistant to an enamine mechanism inhibitor of glutamate-1-semialdehyde aminotransferase.
(2/207)
An enamine mechanism-based inactivator of mammalian delta-aminobutyric acid aminotransferase, 4-amino 5-fluoropentanoic acid is a potent inhibitor of cell growth and pigment formation in the cyanobacterium Synechococcus PCC 6301. It was demonstrated that 4-amino 5-fluoropentanoic acid inhibits the aminolaevulinate synthesis at glutamate 1-semialdehyde aminotransferase and that in the mutant obtained by exposing cells to 40 microM 4-amino 5-fluoropentanoic acid, this enzyme was insensitive to the inhibitor. The specific activity of glutamate 1-semialdehyde aminotransferase in cell extracts was lower in the mutant, although the cell growth rate was unaffected. The decrease in sensitivity to 4-amino 5-fluoropentanoic acid in the mutant is due to a structural gene mutation, a single base change in the hemL gene resulting in a S162T substitution in the gene product. (+info)
Carnitine import to isolated hepatocytes and synthesis are accelerated in pivalate-treated rats.
(3/207)
To investigate the effect of pivalate on carnitine import and carnitine synthesis in the liver, we measured carnitine uptake in isolated rat hepatocytes with L-[(14)C] carnitine and concentrations of free carnitine, gamma-butyrobetaine and acylcarnitines using tandem mass spectrometry. Hepatocytes from rats treated with 20 mmol/L of pivalate for 4 wk had greater L-[(14)C] carnitine uptake than those of unsupplemented rats after 5, 10, 30 and 90 min. Addition of 1 mmol/L of pivalate or 1 mmol/L of pivaloylcarnitine to control cell suspensions did not affect L-[(14)C] carnitine uptake. The K(m) values for L-[(14)C] carnitine uptake for pivalate-treated rats were significantly lower than control (2.9 +/- 0.7 mmol/L for pivalate-treated rats, 6.2 +/- 1.1 mmol/L for controls). The concentration of free carnitine was not reduced in the liver of pivalate-treated rats, whereas the concentrations of acetylcarnitine and gamma-butyrobetaine were significantly lower than controls. In the heart and muscle the concentration of free carnitine was significantly lower and that of gamma-butyrobetaine was higher than controls. These results suggest that carnitine transport from plasma into the liver and synthesis in the liver are accelerated in rats with secondary carnitine deficiency induced by the administration of pivalate. (+info)
High-level production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by fed-batch culture of recombinant Escherichia coli.
(4/207)
Fermentation strategies for production of high concentrations of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] with different 3-hydroxyvalerate (3HV) fractions by recombinant Escherichia coli harboring the Alcaligenes latus polyhydroxyalkanoate biosynthesis genes were developed. Fed-batch cultures of recombinant E. coli with the pH-stat feeding strategy facilitated production of high concentrations and high contents of P(3HB-co-3HV) in a chemically defined medium. When a feeding solution was added in order to increase the glucose and propionic acid concentrations to 20 g/liter and 20 mM, respectively, after each feeding, a cell dry weight of 120.3 g/liter and a relatively low P(3HB-co-3HV) content, 42.5 wt%, were obtained. Accumulation of a high residual concentration of propionic acid in the medium was the reason for the low P(3HB-co-3HV) content. An acetic acid induction strategy was used to stimulate the uptake and utilization of propionic acid. When a fed-batch culture and this strategy were used, we obtained a cell concentration, a P(3HB-co-3HV) concentration, a P(3HB-co-3HV) content, and a 3HV fraction of 141.9 g/liter, 88.1 g/liter, 62.1 wt%, and 15.3 mol%, respectively. When an improved nutrient feeding strategy, acetic acid induction, and oleic acid supplementation were used, we obtained a cell concentration, a P(3HB-co-3HV) concentration, a P(3HB-co-3HV) content, and a 3HV fraction of 203.1 g/liter, 158.8 g/liter, 78.2 wt%, and 10.6 mol%, respectively; this resulted in a high level of productivity, 2.88 g of P(3HB-co-3HV)/liter-h. (+info)
Activated platelets and leucocytes cooperatively stimulate smooth muscle cell proliferation and proto-oncogene expression via release of soluble growth factors.
(5/207)
BACKGROUND: Previous studies indicate that platelets and leucocytes might contribute to the development of neointimal hyperplasia following arterial injury. The present study was aimed at further investigating the role of platelets and leucocytes, alone or in combination, in promoting vascular smooth muscle cell (SMC) proliferation in vitro, focusing on the relative contribution of different soluble growth factors released by these cells, and on the ability to induce proto-oncogene expression, such as c-fos. METHODS: SMCs from rabbit aortas, made quiescent by serum deprivation, were stimulated with either activated platelets, leucocytes, or both, separated from SMCs by a membrane insert. SMC proliferation was evaluated by measuring the incorporation of 3H-thymidine. The relative contribution of different platelet-derived mediators to SMC growth was evaluated by adding either ketanserin, a 5-HT2 receptor antagonist, R68070, a TxA2 receptor antagonist, BN52021, a platelet activating factor (PAF) receptor antagonist, and trapidil, a platelet derived growth factor (PDGF) receptor antagonist. The role of different leucocyte sub-populations (neutrophils and monocytes + lymphocytes) was also determined in additional experiments. RESULTS: SMC proliferation was significantly increased by activated platelets to 360 +/- 9% of control values (P < 0.05). This effect was reduced by ketanserin, R68070, BN 52021 or trapidil. Whole leucocytes, neutrophils or lymphocytes + monocytes also increased SMC proliferation with respect to control experiments. Simultaneous stimulation of SMCs by platelets and whole leucocytes was associated with a significant greater increase in SMC proliferation as compared to SMC stimulated with platelets or leucocytes alone. c-fos expression, almost undetectable in unstimulated SMCs, was markedly increased by activated platelets or leucocytes. CONCLUSIONS: Activated platelets promote SMC proliferation in vitro via release of soluble mediators, including serotonin, thromboxane A2 PAF and PDGF; activated leucocytes also induce a significant SMC proliferation and exert an additive effect when activated together with platelets; SMCs stimulated with activated platelets and leucocytes show an early expression of the proto-oncogene c-fos. (+info)
Local sequence dependence of polyhydroxyalkanoic acid degradation in Hydrogenophaga pseudoflava.
(6/207)
The first order intracellular degradation of various polyhydroxyalkanoic acid (PHA) inclusions in Hydrogenophaga pseudoflava cells was investigated by analyzing the compositional and microstructural changes of the PHA using gas chromatography, (13)C NMR spectroscopy, and differential scanning calorimetry. Two types of PHA, copolymers and blend-type polymers, were separately accumulated in cells for comparison. The constituent monomers were 3-hydroxybutyric acid (3HB), 4-hydroxybutyric acid (4HB), and 3-hydroxyvaleric acid (3HV). It was found that the 3HB-4HB copolymer was degraded only when the polymer contained a minimal level of 3HB units. With the cells containing a 3HB/4HB blend-type polymer, only poly(3HB) was degraded, whereas poly(4HB) was not degraded, indicating the totally inactive nature of the intracellular depolymerase against poly(4HB). On the basis of the magnitude of the first order degradation rate constants, the relative substrate specificity of the depolymerase toward the constituting monomer units was determined to decrease in the order 3HB > 3HV > 4HB. (13)C NMR resonances of the tetrad, triad, and dyad sequences were analyzed for the samples isolated before and after degradation experiments. The results showed that the intracellular degradation depended on the local monomer sequence of the copolymers. The relative substrate specificity of the depolymerase determined from the NMR local sequence analysis agreed well with that obtained from the kinetics analysis. It is suggested that, without isolation and purification of the intracellular PHA depolymerase and "native" PHA substrates, the relative specificity of the enzyme as well as the microstructural heterogeneity of the PHA could be determined by measuring in situ the first order degradation rate constants of the PHA in cells. (+info)
'Microsmatic' primates revisited: olfactory sensitivity in the squirrel monkey.
(7/207)
Using a conditioning paradigm, the olfactory sensitivity of three squirrel monkeys to nine odorants representing different chemical classes as well as members of a homologous series of substances was investigated. The animals significantly discriminated dilutions as low as 1:10,000 n-propionic acid, 1:30,000 n-butanoic acid and n-pentanoic acid, 1:100,000 n-hexanoic acid, 1:1Mio n-heptanoic acid, 1:30, 000 1-pentanol, 1:300,000 1,8-cineole, 1:1Mio n-heptanal and 1:30Mio amyl acetate from the near-odorless solvent, with single individuals scoring even slightly better. The results showed (i) the squirrel monkey to have an unexpectedly high olfactory sensitivity, which for some substances matches or even is better than that of species such as the rat or the dog, and (ii) a significant negative correlation between perceptibility in terms of olfactory detection thresholds and carbon chain length of carboxylic acids. These findings support the assumptions that olfaction may play a significant and hitherto underestimated role in the regulation of primate behavior, and that the concept of primates as primarily visual and 'microsmatic' animals needs to be revised. (+info)
Exon skipping in IVD RNA processing in isovaleric acidemia caused by point mutations in the coding region of the IVD gene.
(8/207)
Isovaleric acidemia (IVA) is a recessive disorder caused by a deficiency of isovaleryl-CoA dehydrogenase (IVD). We have reported elsewhere nine point mutations in the IVD gene in fibroblasts of patients with IVA, which lead to abnormalities in IVD protein processing and activity. In this report, we describe eight IVD gene mutations identified in seven IVA patients that result in abnormal splicing of IVD RNA. Four mutations in the coding region lead to aberrantly spliced mRNA species in patient fibroblasts. Three of these are amino acid altering point mutations, whereas one is a single-base insertion that leads to a shift in the reading frame of the mRNA. Two of the coding mutations strengthen pre-existing cryptic splice acceptors adjacent to the natural splice junctions and apparently interfere with exon recognition, resulting in exon skipping. This mechanism for missplicing has not been reported elsewhere. Four other mutations alter either the conserved gt or ag dinucleotide splice sites in the IVD gene. Exon skipping and cryptic splicing were confirmed by transfection of these mutations into a Cos-7 cell line model splicing system. Several of the mutations were predicted by individual information analysis to inactivate or significantly weaken adjacent donor or acceptor sites. The high frequency of splicing mutations identified in these patients is unusual, as is the finding of missplicing associated with missense mutations in exons. These results may lead to a better understanding of the phenotypic complexity of IVA, as well as provide insight into those factors important in defining intron/exon boundaries in vivo. (+info)