Interdisciplinary perspectives in TRPV5 & TRPV6 physiology.

Contains fulltext : 30072.pdf (publisher's version ) (Open Access)RU Radboud Universiteit Nijmegen, 05 maart 2007Promotor : Bindels, R.J.M. Co-promotor : Hoenderop, J.G.J.155 p

Clustering analyses in peptidomics revealed that peptide profiles of infant formulae are descriptive

Contains fulltext : 154788.pdf (publisher's version ) (Open Access)Prompted by the accumulating evidence on bioactive moieties of milk-derived peptides, novel methods were applied to compare the peptide composition among commercially available hydrolysate formulations and to determine batch-to-batch variations of protein hydrolysate products. Despite the availability of general methods to measure, for example, the degree of hydrolysis and peptide mass distribution at a high level, the objective of this study was to more qualitatively compare peptide sequences and composition. By a comprehensive approach combining peptidomics technologies and multivariate clustering analyses, the peptide profiles of different hydrolyzed milk protein formulations were compared. Moreover, peptide profiles of various hydrolysate batches that had been produced over a period of 5 years were included. Coupling of identified peptide sequences to the position in their corresponding milk proteins produced numerical datasets that subsequently were utilized for multivariate data analyses. These analyses revealed that batch-to-batch variation in the peptide profiles of a specific extensively hydrolyzed casein preparation was low. Moreover, extensive multivariate evaluations revealed that the peptide profiles of different commercially available hydrolyzed milk protein formulations provided a descriptive and distinct signature. Overall, the described methodology may contribute to the field of peptide research as observed dissimilarities in peptide profiles of similar products may be related to differences in their overall functionality

Coordinated control of renal Ca2+ handling.

Contains fulltext : 49260.pdf (publisher's version ) (Closed access)Ca2+ homeostasis is an important factor, which is underlined by the numerous clinical symptoms that involve Ca2+ deficiencies. The overall Ca2+ balance is maintained by the concerted action of Ca2+ absorption in the intestine, reabsorption in the kidney, and exchange from bone, which are all under the control of the calciotropic hormones that are released upon a demand for Ca2+. In the kidney, these calciotropic hormones affect active Ca2+ reabsorption, which consists of TRPV5 as the apical entry gate for Ca2+ influx, calbindin-D28K as an intracellular ferry for Ca2+ and, NCX1 and PMCA1b for extrusion of Ca2+ across the basolateral membrane. This review highlights the action of hormones on renal Ca2+ handling and focuses on the coordinated control of the renal Ca2+ transport proteins. Parathyroid hormone stimulates renal Ca2+ handling by regulating active Ca2+ reabsorption on both the genomic and non-genomic level. Estrogens harbor calciotropic hormone characteristics positively regulating the expression of TRPV5, independently of vitamin D. Besides having a strong regulatory effect on the expression of the intestinal Ca2+ transport proteins, vitamin D contributes to the overall Ca2+ balance by enhancing the expression of the Ca2+ transport machinery in the kidney. Dietary Ca2+ is involved in regulating its own handling by controlling the expression of the renal Ca2+ transport proteins. Thus, the magnitude of Ca2+ entry via TRPV5 controls the expression of the other Ca2+ transport proteins underlining the gatekeeper function of this Ca2+ channel in the renal Ca2+ handling

Physiological and morphological responces of Brachiaria spp. to flooding Respostas morfológicas e fisiológicas de Brachiaria spp. ao alagamento do solo

The physiological and morphological responses of the forage grasses Brachiaria brizantha cv. Marandu, B. decumbens and B. humidicola were compared for plants grown in pots under flooding and well-drained conditions for 14 days. Flooding reduced specific leaf area and biomass allocation to roots in all species and enhanced leaf senescence in B. brizantha and B. decumbens. Relative growth rate was reduced by flooding in B. brizantha and B. decumbens, but not in B. humidicola.Leaf elongation rate was unaffected by flooding in B. decumbens and B. humidicola, but declined in B. brizantha since the first day of flooding. Net photosynthesis and leaf chlorophyll content were reduced by flooding in B. brizantha; however, no flooding effect could be detected in the other two species. For all species, there was a close relationship between net photosynthesis and stomatal conductance under flooding. These results show that the studied species have distinct degrees of tolerance to flood, B. brizantha is intolerant, B. decumbens is moderately tolerant and B. humidicola is tolerant. Because leaf elongation rate was immediately depressed by flooding only in B. brizantha, this measurement could be appropriate as an early detection mechanism for relative flood tolerance in Brachiaria spp.<br>As respostas morfológicas e fisiológicas de Brachiaria brizantha cv. Marandu, B. decumbens e B. humidicola foram comparadas em plantas cultivadas em vasos, sob solo alagado e bem drenado durante 14 dias. O alagamento reduziu a área foliar específica e a alocação de biomassa para as raízes em todas as três espécies e aumentou a senescência foliar em B. brizantha e B. decumbens. O alagamento reduziu a taxa de crescimento relativo em B. brizantha e B. decumbens, mas não em B. humidicola. A taxa de elongação foliar não foi afetada pelo alagamento em B. decumbens e B. humidicola, mas diminuiu em B. brizantha desde o primeiro dia de alagamento. A fotossíntese líquida e o conteúdo de clorofila foliar foram reduzidos pelo alagamento em B. brizantha; no entanto, nenhum efeito do alagamento pôde ser detectado nas outras espécies. Em todas as espécies, existiu uma estreita relação entre as taxas de fotossíntese líquida e a condutância estomatal. Esses resultados mostram que as espécies estudadas diferem quanto à tolerância ao alagamento. B. brizantha é intolerante, B. decumbens é moderadamente tolerante e B. humidicola é tolerante. Em virtude de a taxa de elongação foliar ter sido imediatamente afetada somente em B. brizantha, este parâmetro pode ser empregado como um mecanismo de detecção prematura da tolerância ao alagamento em Brachiaria spp