Glycine N-methyltransferase deficiency: a novel inborn error causing persistent isolated hypermethioninaemia.

This paper reports clinical and metabolic studies of two Italian siblings with a novel form of persistent isolated hypermethioninaemia, i.e. abnormally elevated plasma methionine that lasted beyond the first months of life and is not due to cystathionine beta-synthase deficiency, tyrosinaemia I or liver disease. Abnormal elevations of their plasma S-adenosylmethionine (AdoMet) concentrations proved they do not have deficient activity of methionine adenosyltransferase I/III. A variety of studies provided evidence that the elevations of methionine and AdoMet are not caused by defects in the methionine transamination pathway, deficient activity of methionine adenosyltransferase II, a mutation in methylenetetrahydrofolate reductase rendering this activity resistant to inhibition by AdoMet, or deficient activity of guanidinoacetate methyltransferase. Plasma sarcosine (N-methylglycine) is elevated, together with elevated plasma AdoMet in normal subjects following oral methionine loads and in association with increased plasma levels of both methionine and AdoMet in cystathionine beta-synthase-deficient individuals. However, plasma sarcosine is not elevated in these siblings. The latter result provides evidence they are deficient in activity of glycine N-methyltransferase (GNMT). The only clinical abnormalities in these siblings are mild hepatomegaly and chronic elevation of serum transaminases not attributable to conventional causes of liver disease. A possible causative connection between GNMT deficiency and these hepatitis-like manifestations is discussed. Further studies are required to evaluate whether dietary methionine restriction will be useful in this situation

Determinação de rotina do crômio em fezes, como marcador biológico, pelo método espectrofotométrico ajustado da 1,5-difenilcarbazida The spectrophotometric method on the routine of 1,5-diphenylcarbazide was adjusted on chromium determination in feces, after its utilization as a biological marker as chromium (III) oxide

O objetivo deste estudo foi ajustar o método espectrofotométrico da 1,5-difenilcarbazida à determinação do crômio em fezes, como marcador biológico, adequando-o à rotina laboratorial. Fatores que poderiam exercer interferência na transformação do crômio (III) à crômio (VI) foram testados, como a recuperação do metal, quantidade de amostra, quantidade e ordem de emprego dos ácidos oxidantes da digestão úmida, temperatura e tempo de digestão e perda por volatilização do crômio como cloreto de cromila, porém não se determinou estatisticamente interferência destes fatores. No método ajustado, a amostra é digerida pela clássica mistura ácida nítrica/perclórica, levando a oxidação do crômio (III) a crômio (VI), e alíquota do extrato diluído é usado para reação com 1,5-difenilcarbazida; as absorbâncias são medidas a 550nm, utilizando-se de cubetas de um centímetro de caminho óptico, contra prova em branco conduzida simultaneamente. Dicromato de potássio foi empregado como substância de referência para obtenção da curva padrão na faixa de 0,25 - 2,5mg.mL-1 de Cr2O3 (1mg Cr2O3 &ordm; 1,9355mg K2Cr2O7).<br>This work aims at adjusting the spectrophotometric method of 1,5-diphenylcarbazide for the determination of chromium in feces, as a biological marker. Factors that could interfere with the transformation of chromium (III) into chromium (VI) were tested, as the metal recovery, the sample amount, the amount and the order of use of the oxidant acids of the wet digestion, digestion temperature and digestion time, loss of chromium by volatilization as chromyl chlorid. However the interference of these factors were not statistically determined. In the adjusted method, the sample is classically digested by nitric/perchloric acid mixture leading to the oxidation of chromium (III) to chromium (VI), and an aliquot of the diluted extract is used for reaction with 1,5-diphenylcarbazide; absorbance was measured at 550nm, using 1cm path length optical cuvettes. Potassium dichromate was used as a standard substance to obtain the standard curve ranging from 0.25mg.mL-1 to 2.5mg.mL-1 of Cr2O3 (1mg Cr2O3 &ordm; 1.9355mg K2Cr2O7)

Validação do Lipe® como método para determinar a digestibilidade dos nutrientes em eqüinos Validation of Lipe® as method to evaluate the apparent digestibility of nutrients in equines

Avaliou-se a eficiência da lignina purificada e enriquecida (Lipe®) como indicador externo para estimar a digestibilidade dos nutrientes de dietas em eqüinos em comparação aos métodos de coleta total de fezes e do indicador óxido crômico. Foram utilizadas seis potras Mangalarga Marchador, com média de 2 anos de idade e 345 kg de peso vivo, alimentadas com feno de alfafa e concentrado comercial na proporção de 50:50, para ingestão de matéria seca de 3,1%PV, e sal mineral. O experimento teve duração de 29 dias, de modo que os 24 dias iniciais foram destinados à adaptação dos animais à dieta e às instalações e os cinco finais para coleta total das fezes. Utilizou-se delineamento em blocos casualizados, no qual cada animal constituiu um bloco e cada método de determinação da digestibilidade, um tratamento. Os cálculos de produção fecal e digestibilidade de cada nutriente foram feitos utilizando-se os indicadores e a taxa de recuperação fecal de cada nutriente. Os coeficientes de digestibilidade dos nutrientes obtidos utilizando-se o óxido crômico foram superiores aos da coleta total e Lipe®. Os resultados obtidos com Lipe® foram similares aos determinados por coleta total. O método do óxido crômico é inadequado, enquanto o Lipe® é eficiente para estimar a digestibilidade de nutrientes da dieta em eqüinos.<br>The objective of this work was to test the efficiency of enriched and purified lignin, Lipe®, as external indicator in order to estimate the apparent digestibility of the nutrients in equine diets, compared with the total feces collection and the chromic oxide methods. Six female Mangalarga Marchador with average of two years of age and average weight of 331 kg were used. The diet was alfalfa hay, commercial grain and mineral salt. The experimental period was of 29 days, the first 24 used for the adaptation of animals to the diet and facilities and the last five days for feed estimation and total feces collection. A random blocks design was used in which each animal constituted one block and each digestibility determination method, one treatment. The digestibility of nutrients using chromic oxide were smaller than those from the total collection and Lipe®, and those estimated by the Lipe® were similar to those from the total collection. Chromic oxide revealed to be inadequate and Lipe® was considered efficient to estimate the apparent digestibility in equine

Diminuição do teor de óxido de crômio (III) usado como marcador externo Reduction in chromium (III) oxide level as an external marker

A sensibilidade do método espectrofotométrico da s-difenilcarbazida de determinação do crômio permite que esse metal possa ser determinado em teores e em massas de amostras tão pequenas que as concentrações atualmente usadas de óxido de crômio (III) como marcador externo em ensaios biológicos poderiam ser drasticamente diminuídas. Utilizando-se do piauçu (Leporinus macrocephalus) para um estudo sobre o coeficiente de digestibilidade aparente (CDA) da fração protéica, seis níveis de óxido de crômio (III) - 0,01% - 0,02% - 0,03% - 0,05% - 0,1% e 0,2% - foram incorporados em dietas isoprotéica e isoenergética, objetivando-se verificar se o cálculo do CDA seria afetado pela variação do teor do marcador. Os seis tratamentos foram dispostos em um delineamento em blocos inteiramente casualisados, sendo as fezes coletadas durante 16 dias. Verificou-se que os resultados do coeficiente de digestibilidade aparente da fração protéica não apresentaram diferenças estatísticas significativas devidas aos teores incorporados do marcador à ração e aos dias de coleta. Conseqüentemente, e em experimentos dessa natureza, nada impede que seja reduzido o teor de óxido de crômio (III) ao menos até 0,01%: além da economia relativa ao consumo do mesmo e da facilidade na manipulação de menor quantidade de amostras de fezes, o método espectrofotométrico da s-difenilcarbazida permite dosar esse nível (e até menor do que 0,01%) de modo simples e rápido, com precisão e exatidão.<br>The objective of this study was to reduce the level of the biological marker Cr2O3 in animal diets, due to the sensibility of the sdiphenylcarbazide spectrophotometric method for chromium determination in feces, recently developed. Six levels of marker, chromium (III) oxide (0.01% - 0.02% - 0.03% - 0.05% - 0.1% and 0.2%), were incorporated into isoproteic and isoenergetic diets, for the apparent digestibility assay of the "piauçu" (Leporinus macrocephalus), in a design of entirely randomized groups. Feces were collected during sixteen days. The statistical analysis did not show significant differences in the apparent digestibility of the proteinic fraction due to the concentration levels of the marker incorporated into the diets and the collection days. Consequently, there is nothing to stop us from reducing Cr2O3 rate to at least 0.01% in these digestibility assays: spectrophotometry of sdiphenilcarbazide allows us to determine this level or even smaller levels in an accurate, simple, and quick manner

Experimental approaches to study the nutritional value of food ingredients for dogs and cats

This review covers methods that have been applied to study the nutrient value or quality of specific ingredients fed to dogs, cats and comparable species (i.e. foxes, minks, rats, etc.). Typically, the nutritional value or utilization of a specific ingredient is measured by total tract digestibility and has been expanded through the measurement of total nutrient balance (i.e. nitrogen or energy). However, to better understand digestion it is necessary to obtain a more accurate measurement of nutrients entering and leaving the small intestine. Accurate measurement of small intestinal digestion is crucial in dogs and cats because nutrient digestion and absorption occurs primarily in the small intestine. Measuring small intestinal digestibility requires access to digesta leaving the small intestine and can be obtained by placing a cannula at the terminal ileum. This approach also necessitates the use of markers (e.g. chromic oxide) to monitor flow of digesta. Specifically, this approach has been used for the direct measurement of intestinal digestion of carbohydrates and amino acids. It also permits a separate measurement of large intestinal digestion which is particularly useful for the study of fiber fermentation. Passage of foods through the gastrointestinal tract is also an important component of utilization and these methods are reviewed