Co-solvent effects on reaction rate and reaction equilibrium of an enzymatic peptide hydrolysis

This work presents an approach that expresses the Michaelis constant KaM and the equilibrium constant K_th of an enzymatic peptide hydrolysis based on thermodynamic activities instead of concentrations.

Acquisition of drug resistance in multidrug-resistant Mycobacterium tuberculosis during directly observed empiric retreatment with standardized regimens

The risk of acquiring additional drug resistance in strains of multidrug-resistant tuberculosis (MDR-TB) during failure of empiric standardized retreatment regimens is poorly defined. We sought to estimate this risk by comparing drug susceptibility profiles and RFLP patterns of paired MDR-TB isolates collected from 27 patients before and after retreatment failure. Among 23 patients with paired isolates with concordant RFLP patterns, 19 (83%) had become resistant to at least one additional drug after failed retreatment. In this limited group of MDR-TB patients, acquisition of resistance was common during failure of empiric drug regimens. Further study is needed to confirm these findings.

The dynamics of tuberculosis in response to 10 years of intensive control effort in Peru

Improved tuberculosis (TB) case detection and cure rates are expected to accelerate the decline in incidence of TB and to reduce TB-associated deaths. Time series analyses of case reports in Peru showed that the per capita TB incidence rate was probably steady before 1991. Case reports increased between 1990 and 1992 as a result of improved case detection. Although diagnostic efforts have continued to increase since 1993, the incidence of new pulmonary TB cases has declined in every department of the country, with a national rate of decline > or =5.8% per year (range, 1.9%-9.7%). This elevated rate of decline suggests that 27% (19%-34%) of cases (158,000) and 70% (63%-77%) of deaths (91,000) among smear-positive patients were averted between 1991 and 2000. This is the first demonstration that a significant number of TB cases can be prevented through intensive short-course chemotherapy in a high-burden country.

Effect of several germination conditions on total P, phytate P, phytase, and acid phosphatase activities and inositol phosphate esters in rye and barley

Two assays were conducted to study the evolution of rye and barley phosphatases (phytase and acid phosphatase) and the degradation of its substrates (inositol phosphate esters) during seed germination. In this manner we could obtain a low-phytate, endogenous phosphatase rich ingredient to be used in animal nutrition. In the first assay, the seeds were soaked for 1 and 14 h and germinated for 3 and 5 days with and without the addition of gibberellic acid (GA3). In the second assay, the seeds were soaked for 1 h and germinated for 1, 3, and 5 days with GA3. Phytase (up to 5739 and 3151 U x kg(-1)) and acid phosphatase (up to 18288 and 3151 U x g(-1)) activities, and IP6 (6.09 and 6.01 mg x g(-1)), IP5 (0.48 and 0.48 mg x g(-1)), and IP4 (0.13 and 0.06 mg x g(-1)) were detected in ungerminated rye and barley, respectively. The germination process caused a significant increase of Phy and AcPh activities in rye (up to 112 and 213%) and barley (up to 212 and 634%) and a reduction in the phytate phosphorus content (up to 84 and 58%, respectively). Phytate phosphorus content was affected only by soaking time in the case of rye. Finally, during the course of germination, IP6 and IP5 were rapidly degraded in rye (88 and 79%) and barley (67 and 52%), and IP4 was only a short-living intermediate, which was increased during hydrolysis and degraded to IP3. In conclusion, a marked increase of Phy and AcPh activities in rye and barley with a concomitant decrease in phytate phosphorus content and an increase in the content of lower inositol phosphates were observed during the rye and barley germination.

Nutritional value of raw and autoclaved kabuli and desi chickpeas (Cicer arietinum L.) for growing chickens

1. Two experiments were carried out to determine the effect of inclusion of raw (kabuli and desi) and autoclaved (desi) chickpea seeds in wheat-based starter diets in chickens grown to 28 d of age on the performance, digestive organ sizes, nitrogen-corrected apparent metabolisable energy (AMEn), ileal apparent protein and starch digestibilities (APD and ASD) and intestinal alpha-amylase and trypsin activities. 2. In the first experiment, diets were formulated to contain 0, 150, 300 and 450 g/kg of raw kabuli chickpea seeds. Increasing the proportion of seed in the diet negatively influenced body weight gain, food intake and food efficiency. The relative weights of the pancreas, liver and gizzard and the relative lengths of duodenum, jejunum, ileum and caeca were increased significantly when the chickpea seeds were included in the diets. Correspondingly, APD, ASD, alpha-amylase and trypsin activities and AMEn were reduced significantly when the chickpea seed was incorporated in the diets. 3. In the 2nd experiment, diets were formulated to contain 75 and 150 g/kg of raw and autoclaved desi chickpea seeds. Weight gain and food intake of the chicks given desi chickpea diets were significantly reduced compared with those fed on the control diet. Increasing the proportion of seed in the diet negatively influenced body weight gain, food intake and food efficiency. Moreover, a significant increment in the relative weights of liver and pancreas, and in the relative lengths of duodenum, ileum and caeca was observed when the concentration of chickpea seeds in the diets was increased. Feeding autoclaved seeds significantly increased the weight gains and the food intakes. However, food efficiency was not modified by the autoclaving. Relative weights of gizzard and liver and relative lengths of ileum were decreased significantly by the inclusion of autoclaved desi chickpea in the diet. 4. We concluded that the inclusion of kabuli (up to 450 g/kg) and desi (up to 150 g/kg) chickpea seeds produced a negative effect on the performance of the birds, and an increment in the relative weights and lengths of the digestive organs. In addition, the incorporation of kabuli chickpea produced a reduction of protein and starch digestibilities, alpha-amylase and trypsin activities, and AMEn of food compared with the birds given the control diet. Autoclaved treatment of desi chickpea improved the performance of the birds.

Histological alterations in the intestinal epithelium caused by the inclusion of full-fat sunflower kernels in broiler chicken diets

Changes in small intestinal morphology (jejunum) were examined at 28 d of age in chicks fed with full-fat sunflower kernels (FFSK)-based diets. Jejunal mucosa of chicks (six chicks per treatment) were embedded in Epon-812 for examination by a conventional electron microscope procedure. A portion of the tissues was also sectioned and embedded in paraffin for examination by light microscopy. Brush border, goblet cells, and intraepithelial lymphocytes, on the one hand, and fibroblast and mononuclear cells (lymphocytes, plasma cells, macrophages) were observed in the enterocytes and lamina propria, respectively. The results showed that the birds fed 150 g kg(-1) of FFSK showed a shortening and thickening of the villi, hyperplasia and vacuolar degeneration of enterocytes, and hypertrophy and hyperplasia of goblet cells. Likewise, an increment of intraepithelial lymphoid cells and hypercellularity of the lamina propria was observed. In addition, electron microscopy showed large vacuoles in the enterocytes, which could be dilations of agranular and granular endoplasmic reticulum or Golgi. There were many dark granules within the vacuoles that could be triglyceride-rich lipoproteins (portomicrons). These lesions could have been due to the presence of chlorogenic acid or to the greater concentration of oil in the FFSK diet. Our observations demonstrated that addition of 150 g kg(-1) FFSK to broiler chicken diets caused alterations in jejunal mucosa that could explain the decrease in fat digestibility observed in a previous experiment in which we incorporated FFSK into broiler diets.

Phytase and acid phosphatase activities in plant feedstuffs

A total of 183 samples representing 24 feedstuffs were analyzed for total phosphorus, phytate phosphorus content, phytase (Phy), and acid phosphatase (AcPh) activities with the objective to predict the capacity to hydrolyze phytic acid and to contribute to formulating environmentally adequate diets for monogastric animals. Of the cereals and cereal byproducts analyzed, only rye (5147 U kg(-)(1); 21 955 U g(-)(1)), wheat (1637 U kg(-)(1); 10 252 U g(-)(1)), rye bran (7339 U kg(-)(1); 56 722 U g(-)(1)), and wheat bran (4624 U kg(-)(1); 14 106 U g(-)(1)) were rich in Phy and AcPh activities. Legume seeds and oilseeds contained negligible Phy activity and a moderate amount of AcPh activity, except for kidney bean (33 433 U g(-)(1)) and full-fat linseed meal (13 263 U g(-)(1)). On the other hand, a significant linear regression between phytate phosphorus (y) and total phosphorus (x) was observed in cereal byproducts (R(2) = 0. 95; y = 0.8458x - 0.0367; P < 0.001) and oil seeds (R(2) = 0.95; y = 0.945x - 0.20; P < 0.001). Phy and AcPh were positively correlated with respect to phytate phosphorus in cereals, cereal byproducts, and other byproducts and negatively correlated in legume seeds and oilseeds. Except for cereals, the highest correlation between enzyme activities and phytate phosphorus was found for phytase. It is not possible to predict Phy and AcPh activities from phytate phosphorus content by linear and quadratic regressions. Finally, only highly significant and positive correlation was found between Phy and AcPh activities for cereals, cereal byproducts, and oilseeds.