High-performance liquid chromatographic determination of alpha-aminonitrile enantiomers after derivatization with o-phthalaldehyde and chiral thiols.

o-Phthalaldehyde in combination with chiral thiols is described as a chiral reagent for the resolution of the enantiomers of alpha-H-alpha-aminonitriles and alpha-alkyl-alpha-aminonitriles. Separation of the resulting diastereomers was carried out by reversed-phase chromatography and the derivatives were detected at UV 340 nm. The identity of the diastereomeric derivatives was confirmed by LC-MS. Among the chiral thiols tested, N-acetyl-D-penicillamine and beta-mercaptoisobutyric acid gave the best resolution for the alpha-aminonitriles studied. For quantitative enantiomeric excess determination, beta-mercaptoisobutyric acid was chosen as this thiol could be obtained in high enantiomeric purity from a commercial source. The rate of the reaction of various alpha-aminonitriles with o-phthalaldehyde and beta-mercaptoisobutyric acid was studied. The accuracy of the method was investigated by a comparison of theoretical and measured enantiomeric excess.

In-source decay of hyperbranched polyesteramides in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Hyperbranched polyesteramides (DA2), prepared from hexahydrophthalic anhydride (D) and diisopropanolamine (A) have been characterized, by use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), field desorption (FD)-MS, and electrospray ionization (ESI)-MS. MALDI of polyesteramides produces protonated molecules. The spectra show a complex chemical composition distribution and end-group distribution which are mainly composed of two series of homologous oligomers DnA(n)+1 - mH2O and DnA(n) - mH2O, where m = 1-2. Signals from protonated molecules DnAn+1 and DnAn are almost absent in the MALDI spectrum, whereas these ions are responsible for the base peak of DnA(n)+1 - mH2O and DnA(n) - mH2O (m = 1-2) clusters in the ESI spectrum. The absence of -OH end-groups signals in the MALDI spectrum is due to a metastable decay of protonated DnA(n)+1 and DnAn ions in the ion source of the MALDI mass spectrometer prior to ion extraction. In-source decay results in the formation of protonated lower DnA(n)+1 - mH2O and DnA(n) - mH2O oligomers and their corresponding neutrals, leading to wrong conclusions concerning the relative end-group distribution as a function of the degree of polymerization and the chemical composition.

Household budget survey nutritional data in relation to mortality from coronary heart disease, colorectal cancer and female breast cancer in European countries. DAFNE I and II projects of the European Commission. Data Food Networking.

OBJECTIVE: We have undertaken a study to examine whether Household Budget Survey (HBS)-derived nutritional patterns are related to mortality from diseases with strong nutritional components, namely coronary heart disease, colorectal cancer and cancer of the female breast. DESIGN: Ecological correlation study. In the context of the Data Food Networking projects of the European Union, raw data from the national HBS of 10 European countries were provided. For each of the 10 participating countries, daily food availability per capita around 1990 was calculated. Individual foods were aggregated into 12 major food groups that were linked with the diseases under consideration. Mortality data were available from a World Health Organisation database. We have used a composite score to summarise the postulated influence of diet. SETTING: Ten European countries circa 1990. RESULTS: The correlation coefficients between the composite score and the age-adjusted mortality from each of the studied diseases were: + 0.51 (P approximately 0.14) for colorectal cancer; +0.72 (P approximately 0.02) for female breast cancer; and +0.60 (P approximately 0.07) for coronary heart disease, after adjustment for tobacco smoking. CONCLUSIONS: We conclude that dietary information from HBS is sufficiently reliable to reveal correlations with mortality rates from chronic diseases with fairly strong nutritional roots. HBS data could be used, with little cost, for monitoring secular trends in dietary patterns with a view to their health implications.

Influence of virginiamycin on the digestive physiology in precaecal re-entrant cannulated pigs.

The present experiment was set up to study the effect of Virginiamycin, a nutritional growth promoting antibiotic, on the digestive physiology using precaecal cannulated pigs. The semipurified diet used provided 21% protein and 60% of nitrogen free extract (NFE), 2/3 as starch and 1/3 as lactose. Due the older age of the pigs, the lactose induced some degree of malabsorption as precaecal flow rate of digesta was markedly higher (3.2 kg/d) compared with published data obtained with purified diets without lactose. This was also reflected in the rather low ileal digestibility of the nutrients (%): dry matter 68.6, protein 79.6, fat 78.4 and NFE 75.0. Virginiamycin markedly lowered flow rate (2.2 kg/d) and significantly improved apparent precaecal digestibilities (%): dry matter 74.0, protein 81.4, fat 81.9 and NFE 78.7. The faecal apparent digestibility was comparable with published data. There were no treatment differences indicating that precaecal digestibilities are much more sensitive then faecal ones. In order to explain the differences obtained the mean retention time in the upper intestine was measured. Although significant differences were noted (control: 5 h, Virginiamycin: 6 h) a direct cause-effect relationship was not evident. Also the activity of selected pancreatic enzymes in ileal contents was compared. There were no consistent differences between the two treatments, except for a lower lipase activity during Virginiamycin treatment.

Stomach emptying of milk diets in pigs. A mathematical model allowing description and comparison of the emptying pattern.

The effect of doubling the nutrient intake in pigs fed a liquid cow's milk diet was investigated. This was done, either by doubling the volume given, or by doubling the dry matter content of the milk. There were two experiments in which the cumulative outflow of fresh contents, dry matter, crude protein and total carbohydrates, relative to the intake, was studied as affected by the treatments. This was done using pigs equipped with a simple duodenal cannula and an occluding balloon. The cumulative outflow curves indicated that the emptying process was biphasic both for the fresh contents and the nutrients emptied. A rapid emptying, followed by a period during which the emptying was inhibited was seen during the first emptying phase, the so called initial emptying. Thereafter the emptying was resumed again during the second phase: the final emptying. The individual emptying patterns were described very accurately by an adapted mathematical function with four parameters: y = c (1-2-(at)b)+dt3. The parameters c, b and a describe the initial emptying which is intrinsically exponential while d is descriptive for the final emptying. The appearance of the outflowing material, changing with time from unchanged milk, whey plus clot fragments, pure whey to whey with granular clot fragments indicated that the clotting of the milk was complete after about 15 min. The clotting certainly was responsible for the biphasic appearance of the emptying pattern. The emptying pattern of fresh contents was not related to the emptying pattern of dry matter and nutrients. Due to the rather high variability, there were no significant differences between the emptying patterns of dry matter and nutrients studied, although there were clear indications that crude protein was emptied at a slower rate than the other nutrients. Doubling the nutrient intake either by doubling the volume given, or by doubling the dry matter content of the milk did not change the initial emptying pattern to a great extent, except in the first experiment, where doubling the volume increased the relative amount of dry matter and nutrients emptied. A difference of gastric capacity related to a difference in age between the pigs used in the two experiments is thought to be the reason for this discrepancy. The relative amounts of dry matter and nutrients emptied during the final emptying phase on the other hand were inversily related to the amount of nutrients given.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of virginiamycin on carbohydrate and protein metabolism in the rumen in vitro.

The effect of virginiamycin in incubations of rumen fluid with carbohydrate or protein substrate was investigated. In carbohydrate incubations, methane production was partially inhibited while propionate proportions increased. Total microbial growth was slightly decreased, but net microbial growth was considerably lower. Protein degradation was slightly lowered after addition of virginiamycin. These effects were compared with results obtained with other rumen manipulating additives.

Gastric secretion in suckling pigs and early-weaned pigs given a dry cow's-mild formula ad lib.

1. Twelve gastric-cannulated litter-mate pigs were used to study secretion and proteolytic activity in the stomach of suckling and early-weaned pigs in relation to age and food intake. 2. Results demonstrate that from the first observation at day 8, piglets were able to secrete acid. pH and acid concentration did not change during the first 4 weeks of life. 3. Proteolytic activity was low during the first 2--3 weeks of life and rapidly increased thereafter. 4. Two phenomena differentiated suckling pigs from pigs given dry cow's milk: (1) a low buffering capacity the gastric contents, beginning 1 hr after feeding the dry cow's-milk formula, results in a low total acid concentration in the weaned pigs and (2) the increase in proteolytic activity in relation to the age is much more pronounced in the artificially-reared pigs. 5. These two phenomena are discussed and related to the formation of a hard casein clot in the stomach of the cow's-milk-fed pigs, which has a long retention time and stimulates gastrin release.

Effect of fatty acid derivatives on rumen methane and propionate in vitro.

The effect of several fatty acid derivatives on methane and propionate in the rumen is described. A possible explanation for the observed inverse relationship between methane and propionate is given.

Effect of chloral hydrate on methane and propionic acid in the rumen.

Methane production from pyruvate by mixed rumen bacteria in vitro was nearly totally inhibited by chloral hydrate (0.1 mumole/ml of incubation fluid). This effect was accompanied by an accumulation of gaseous hydrogen and an increase in propionic acid production. Infusion of chloral hydrate (4 g/day) into the rumen of a sheep produced the same effects. Evidence is presented for a direct toxic effect of chloral hydrate upon methane bacteria. Results are discussed in terms of fermentation balances.

Methane production from glucose in vitro by mixed rumen bacteria.

1. Methane was produced in vitro by incubating cell suspensions of rumen bacteria with glucose, under nitrogen. The amount of methane produced varied considerably and was lowered by high glucose concentrations. Carbon dioxide, acetic acid, propionic acid, butyric acid and lactic acid were also produced. An oxidation-reduction balance of near unity could be calculated, although carbon recovery was low. Under the experimental conditions, rumen bacteria used most of the metabolic hydrogen produced during the oxidation of glucose to form lactic acid. 2. Lower methane production at high glucose concentrations was balanced by higher lactic acid production. Low pH values due to a high production rate of lactic acid might explain the inhibition of methane production. 3. No lactic acid, less methane, but considerably more propionic acid were formed when nitrogen was replaced by carbon dioxide in the incubation system.