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Breast milk is changing with the progression of lactation and during a 24-h period. To determine the effect of diurnality or nocturnality on total nitrogen and protein content of the breast milk. We collected human milk samples from health mothers living throughout Community of Extremadura (Spain) from January 2008 to December 2008 with less than two months of lactation. We divided the samples in three groups: calostral group (1-5 days postpartum), transitional group (6-15 days postpartum) and mature group (> 15 days postpartum). All samples were stored in a freezer at -80 ºC. We considered as day period between 08:00-20:00 h and night period 20:00-08:00 h. Analysis of the human milk samples was based on the Kjeldahl method. Protein contents were calculated from total nitrogen x 6,25. The statistical analysis of the data was descriptive (mean ± standard deviation) and inferential (T-Student test). No differences (P > 0,05) were found to exist among the contents of individual human milk samples. The mean contents of each component were as follows: Total nitrogen of calostral, transitional and mature group was 0,30 ± 0,06 g/dL (night period), 0,29 ± 0,05 g/dL (day period); 0,26 ± 0,04 g/dL (night period), 0,25 ± 0,04 g/dL (day period); 0,22 ± 0,05 g/dL (night period), 0,20 ± 0,04 g/dL (day period) respectively, in this mature group with a statistical variation (P < 0,05). Protein content of calostral, transitional and mature group was 1,88 ± 0,4 g/dL (night period), 1,81 ± 0,3 g/dL (day period); 1,62 ± 0,3 g/dL (night period), 1,59 ± 0,3 g/dL (day period); 1,35 ± 0,3 g/dL (night period), 1,26 ± 0,3 g/dL (day period) respectively, in this mature group with a statistical variation (P < 0,05). Although we observed differences in the nitrogen and protein content during the individual stages of lactation, it is just in the population of mature lactating women, where the components analyzed varied significantly between day and night.

Sixteen milk-based starting formulas were analyzed with the aim of calculating their "true protein" content and assessing "in vitro" protein digestibility, in order to estimate levels of potentially available protein. Ten of them were designed for term infants: 7 had a casein:whey protein ratio 40:60 (adapted formulas) and 3 a ratio 80:20 (non-adapted); the 6 remaining formulas (all adapted) were for preterm infants. Nitrogen was determined by the Kjeldahl method. True protein was calculated as (total N--non-protein N) x 6.25. NPN was determined in the soluble fraction, after protein precipitation with 24% trichloroacetic acid and centrifugation. Digestibility was assessed by digestion with pepsin and pancreatin, and defined as the increase in non-protein N after enzymatic digestion. Values for true protein were from 1.3 to 2.3 g/dL and for non protein N, from 4.5 to 13.7%. Digestibility values varied between 59.0 and 92.5%; an inverse trend was observed between protein digestibility and protein content. Considering both the "true protein" levels and their digested proportions, all preterm and 60% of the term formulas would present potentially available amounts below those recommended. These observations constitute an alert, even though this method of assessing "in vitro" protein digestibility represents only an approximation to physiological processes; however, it could be useful in order to evaluate the intensity of the heat treatments to which these formulas were subjected. On the other hand, since NPN allows the estimation of the true protein provided by the formulas, either its percentage or the true protein content could be included on the label.

The basal behaviour and relationship with organic carbon (Corg) content and prevailing granulometric fractions, of organic nitrogen (Norg), total phosphorus (P-total) and C/N ratio in surface sediments of Chacopata lagoon, Sucre State, Venezuela, were studied. Concentrations and spatial gradients were determined in sixteen stations following a common method for marine sediments. Norg concentrations varied between 0.102 and 0.510% (x = 0.237%), total phosphorus between 0.012 and 0.094% (x = 0.058%) and C/N ratio between 9.27 and 44.47 (x = 20.53). The higher contents of Norg and total phosphorus are from sections with an abundance of mangroves, marine phanerogams, macroalgae, benthonic biomass and migratory birds shelters. The C/N ratio shows the typical values for carbonated sediments, indicating that the nitrogenous compounds are rapidly degraded and the organic matter presents itself as humic substances. This parameter was moderately associated with silt and clay, and showed antagonism with sand, whereas Norg and phosphorus showed no correlation with them. The organic contribution is purely autochthonous: no anthropogenous contributions were found.

An analysis of 39 Mexican coastal lagoons most in tropical environments, shows no nutrient limitation for primary productivity: even minimum nutrient values are higher than those of similar systems (mostly of temperate zones). In some cases, nutrient variations are large and indicative of heterogeneity. The N:P ratio is more important than simple nutrient concentrations. Using this ratio, coastal lagoons are classified as limited in nitrogen (< 5) or phosphorus (> 10).

In 1987 to 1989 the composition was studied of the nitrogen compounds (nitrogen and free amino acids) in the fruit juice of Persian lime during its commercial harvesting period. Adult Persian lime trees grafted on Citrus macrophylla and C. volkameriana were used, planted on a groundwater-affected red ferrilytic soil in the La Habana Province. Determination of the total nitrogen and of the free proline was carried out in May to July of each experimental year. The amino acid spectrum was established from juice samples in May 1987 and in July 1988. With the nitrogen concentrations varying between 14 and 90 mg/100 ml of juice, no consistent behaviour or pattern could be detected either in the total nitrogen content or the proline content in the juice during the 3 experimental years. 14 free amino acids were found, with about 90% of the total content formed from asparagine acid, glutamic acid, alanine, proline, gamma-aminobutyric acid, and arginine, regardless of the experimental year or the grafting basis.

The study herein reported presents information on the dietary fiber content of four food groups consumed in Central America. These are: cereals, grains and products; raw and processed beans; raw and processed vegetables, and starchy foods such as potatoes, cassava and plantain. Besides data on soluble and insoluble fiber, data on in vitro protein digestibility are included. The total dietary fiber content of the wheat flour products varied from 1.62 to 2.83% on a fresh basis, with the exception of whole-wheat bread, which showed a 7.57% content. The maize tortilla presented values ranging from 3.96 to 5.21% in respect to beans, and the values for cooked and raw beans fluctuated between 6.36 and 7.00%, independent of the color; however, fried beans reported values from 15.28 to 17.58%. Vegetables contained total dietary fiber values of 1.51 to 4.34, and the tubers, from 1.31 to 2.86%.

The bile salts, chloride, sodium, potassium and nitrogen content of the gallbladder bile was studied in goat, sheep, cattle, pig, rabbit, dog, monkey (Erythrocebus patas), chicken, lizard (Lacerta ocellata), frog (Rana esculenta), trout (Salmo gardnieri) and barbel (Barbus barbus). A significant correlation was found between bile salts and sodium (positive), chloride and sodium (negative) and chloride and bile salts (negative). The gallbladder concentrating ability was very high in monkey, lizard and trout high in dog, barbel, frog and chicken, and low in cattle, rabbit, pig and sheep. The goat was half way between the second and third groups. It seems that concentrating ability is greater in animals whose gastric emptying is intermittent, and is lower in those animals with a continuous digestive activity.

The protein quality of tollo flour evaluated by various biological methods, including digestibility, is reported. The product contained 91.52% crude protein and 69.86% true protein, the difference being non-protein nitrogen, mainly urea. Due to this reason the biological evaluations were carried out with different shark flour concentrations and evaluated at different lengths of time with each method. Diets containing 0, 3, 6, 9 and 12% shark flour were prepared and evaluated by the PER, NPR, and NGI methods. Casein was used as reference protein. The protein digestibility was 91.2%, not corrected for non-protein nitrogen. On this same basis, PER and NPR--at a protein level of 9.97% in the diet--were 2.58 and 2.05, respectively. The casein control diet gave a PER of 2.93 and an NPR of 4.52. NGI was calculated by using the non-protein diet, or without it, with values of 3.32 and 2.95, respectively. As expected, all values corrected for non-protein nitrogen were higher for protein digestibility. The differences were significant at the 5% level. Apparently, urea influenced negatively the biological evaluations. It can be concluded, therefore, that the tollo shark meat is of excellent quality.

The endogenous nitrogen content in the gut of adult male rats was studied by quantification of total, proteic, noi-proteic, ureic and ammonic nitrogen. The continuous perfusion technique was used maintaining a 20 ml flux of tyrode solution for two hours. The influence of pancreatic and biliar secretions was also studied. The values obtained for these secretions were lower than those found when all the secretions appeared in the lumen, except for ammonic nitrogen. The nitrogen content in pancreas and intestine homogenates were also determined being similar in both cases. This value was higher in pancreas when the ducts were closed.

The effect of excessive alcohol intake on the protein requirements and metabolism in normal subjects has not been clearly determined. In this study we measured the nitrogen balance, the hematrocrit, the hemoglobin, the serum albumin, the cholesterol, and the plasmatic amino acids in 7 non-alcoholic subjects of 25 +/- 5 years of age. A comparison was made of a diet containing 0.8 g of protein per k of weight and 40 Kcal per k of weight administered during 11 days with a period of the same length in which the 1.400 Kcal provided during the control period by carbon hydrates was provided by ethanol (200 g). During the alcoholic period no importants changes were observed in the nitrogen balance, a tendency towards greater positivity being registered. There was a decrease in the serum albumin of 4, 69 +/- 0.31 vs 3, 90 +/- 0,32 g/100 ml and an increase in globulin 1,74 +/- 0,70 vs 2,69 +/- 0,22 g/100 ml. The results showed that in a short period of time the excessive alcohol intake in normal subjects does not increase the protein requirements in spite of a decrease in the serum albumin being observed.

Quantitative changes in the chemical composition of stored corn infested with the grain insects Prostephanus truncatus, Sitophilus zeamais or Sitotroga cerealella were studied in the laboratory under the following conditions for each species: after infestation of samples by larvae, at the emergence of the first generation and after more than one generation. Changes occurred in the composition of all samples, the effect being more marked with larvae. Although no consistent pattern was evident, the nitrogen concentration of infested samples generally increased and the ether extract decreased. The total amounts of each constituent decreased in all samples, with up to 19% loss of energy content. Some of these changes may be attributed to selective feeding by each species, on specific regions of the maize kernel; this phenomenon was more apparent in the case of samples infested with larvae.

With a view to observing if gastroenteritis to rotavirus produced greater carbohydrate malabsorption, we studied 94 male infants, between three and thirty six months of age, with acute diarrhea and dehydration. The metabolic study included the analysis of every intake and excretion during the first 24 hours of oral rehydration and realimentation. Thirty two infants had rotavirus as the single etiological agent, but in numbers it could only be compared to 35 patients in whom we were unable to establish the causal etiological agent of diarrhea in spite of the application of all the usual techniques. No differences were noted with regard to stool and urine losses, nor nutrient intakes of the groups. The present study does not confirm the observation reported in other papers that diarrhea to rotavirus causes a greater loss of carbohydrates.

Steatorrhea and azotorrhea are evaluated, by Van de Kamer and Kjendalh methods, in 24 patients affected by cystic fibrosis in the diagnosis and in their evolution. High values were obtained for steatorrhea in 87.5% of the cases and for azotorrhea in the 79.1% at the moment of diagnosis. Steatorrhea and azotorrhea have been correlated obtaining a high statistic significant for p less than 0.01 in the diagnosis and in patients who followed treatment with the same medication, not being significative for all patients during their evolution. With results obtained, determination of fecal nitrogen, is positively evaluated not only in the diagnosis but also in the evolution of these patients to obtain an optimum nutritious condition.