The metabolic significance of octulose phosphates in the photosynthetic carbon reduction cycle in spinach

(14)C-Labelled octulose phosphates were formed during photosynthetic (14)CO(2) fixation and were measured in spinach leaves and chloroplasts. Because mono- and bisphosphates of d-glycero-d-ido-octulose are the active 8-carbon ketosugar intermediates of the L-type pentose pathway, it was proposed that they may also be reactants in a modified Calvin–Benson–Bassham pathway reaction scheme. This investigation therefore initially focussed only on the ido-epimer of the octulose phosphates even though (14)C-labelled d-glycero-d-altro-octulose mono- and bisphosphates were also identified in chloroplasts and leaves. (14)CO(2) predominantly labelled positions 5 and 6 of d-glycero-d-ido-octulose 1,8-P(2) consistent with labelling predictions of the modified scheme. The kinetics of (14)CO(2) incorporation into ido-octulose was similar to its incorporation into some traditional intermediates of the path of carbon, while subsequent exposure to (12)CO(2) rapidly displaced the (14)C isotope label from octulose with the same kinetics of label loss as some of the confirmed Calvin pathway intermediates. This is consistent with octulose phosphates having the role of cyclic intermediates rather than synthesized storage products. (Storage products don’t rapidly exchange isotopically labelled carbons with unlabelled CO(2).) A spinach chloroplast extract, designated stromal enzyme preparation (SEP), catalysed and was used to measure rates of CO(2) assimilation with Calvin cycle intermediates and octulose and arabinose phosphates. Only pentose (but not arabinose) phosphates and sedoheptulose 7-phosphate supported CO(2) fixation at rates in excess of 120 μmol h(−1) mg(−1) Chl. Rates for octulose, sedoheptulose and fructose bisphosphates, octulose, hexose and triose monophosphates were all notably less than the above rate and arabinose 5-phosphate was inactive. Altro-octulose phosphates were more active than phosphate esters of the ido-epimer. The modified scheme proposed a specific phosphotransferase and SEP unequivocally catalysed reversible phosphate transfer between sedoheptulose bisphosphate and d-glycero-d-ido-octulose 8-phosphate. It was also initially hypothesized that arabinose 5-phosphate, an L-Type pentose pathway reactant, may have a role in a modified Calvin pathway. Arabinose 5-phosphate is present in spinach chloroplasts and leaves. Radiochromatography showed that (14)C-arabinose 5-phosphate with SEP, but only in the presence of an excess of unlabelled ribose 5-phosphate, lightly labelled ribulose 5-phosphate and more heavily labelled hexose and sedoheptulose mono- and bisphosphates. However, failure to demonstrate any CO(2) fixation by arabinose 5-phosphate as sole substrate suggested that the above labelling may have no metabolic significance. Despite this arabinose and ribose 5-phosphates are shown to exhibit active roles as enzyme co-factors in transaldolase and aldolase exchange reactions that catalyse the epimeric interconversions of the phosphate esters of ido- and altro-octulose. Arabinose 5-phosphate is presented as playing this role in a New Reaction Scheme for the path of carbon, where it is concluded that slow reacting ido-octulose 1,8 bisphosphate has no role. The more reactive altro-octulose phosphates, which are independent of the need for phosphotransferase processing, are presented as intermediates in the new scheme. Moreover, using the estimates of phosphotransferase activity with altro-octulose monophosphate as substrate allowed calculation of the contributions of the new scheme, that ranged from 11% based on the intact chloroplast carboxylation rate to 80% using the carboxylation rate required for the support of octulose phosphate synthesis and its role in the phosphotransferase reaction

Protein metabolism in the pectoralis muscle and liver of hibernating bats, Eptesicus fuscus

Seasonal variations in protein metabolism of the pectoralis muscle and liver of the big brown bat, Eptesicus fuscus , are examined in relation to seasonal changes in physiological status. A technique is described for the determination of protein synthetic rates in vivo in animals too small for conventional methods. The results indicate no detectable rates of protein synthesis in hibernating bats during torpor bouts (Table 2). Rates of synthesis in hibernating bats during periods of arousal are comparable to those of active summer bats (Table 2), despite the fact that the hibernating bats had not eaten in over 2 months. Rates of protein degradation were calculated from the rate of urea formation in torpid bats (Figs. 4, 5), the overall loss of pectoralis muscle and liver protein mass during hibernation (Table 3), the proportion of the total time of hibernation spent in torpor and arousal (Table 1), and the observed rates of protein synthesis (Table 2). These estimates (Table 4) indicate negligible rates of protein degradation in torpid bats. However, protein degradation during periodic arousals is comparable to that of summer bats after an overnight fast. These findings are consistent with earlier observations suggesting that significant gluconeogenesis from tissue protein occurs during spontaneous arousals from hibernation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47129/1/360_2004_Article_BF00689738.pd

Evolução da prevalência de parasitoses intestinais em escolares em Caxias do Sul, RS Evolution of the prevalence of intestinal parasitosis among schoolchildren in Caxias do Sul, RS

Relatos da prevalência das parasitoses intestinais no Brasil são pontuais e têm sido descritos em diferentes populações, tornando difícil um diagnóstico abrangente. Visando estudar a variação em 35 anos da prevalência de enteroparasitoses em escolares de Caxias do Sul, RS, foram avaliados 9.787 exames parasitológicos de fezes realizados por centrífugo-sedimentação. Resultaram positivas 5.655 (58%) amostras sendo mais prevalente a infestação por Ascaris lumbricoides (47%), Trichuris trichiura (36%), Enterobius vermicularis (8%) e os protozoários: Giardia lamblia (24%) e Entamoeba coli (20%). A prevalência geral diminuiu de 89% para 37%, com um decréscimo médio de 1,4% ao ano. Houve redução na prevalência de Ascaris lumbricoides de 61 para 26% e de Trichuris trichiura de 38 a 18%. Para Giardia lamblia não houve alteração significativa. A prevalência de Entamoeba coli cresceu de 29 a 46%. Os decréscimos obtidos na prevalência dos helmintos são provavelmente devidos às melhorias da infra-estrutura e às ações formativas desenvolvidas nas escolas.<br>Reports on the prevalence of intestinal parasitosis in Brazil have been local in nature, with descriptions of different populations, which makes comprehensive diagnosis difficult. With the aim of studying the variation in the prevalence of intestinal parasitosis among schoolchildren in Caxias do Sul, Rio Grande do Sul, over a 35-year period, 9,787 parasitological stool tests that had been performed using centrifugal sedimentation were evaluated. There were positive results from 5,655 samples (58%), and the most prevalent infestations were of Ascaris lumbricoides (47%), Trichuris trichiura (36%), Enterobius vermicularis (8%) and the protozoa Giardia lamblia (24%) and Entamoeba coli (20%). The overall prevalence diminished from 89% to 37%, indicating an average decrease of 1.4% per year. Reductions in prevalence were observed for Ascaris lumbricoides (61 to 26%) and Trichuris trichiura (38 to 18%). No significant change was observed for Giardia lamblia. The prevalence of Entamoeba coli increased from 29 to 46%. The decreases in helminth prevalence were probably due to infrastructure improvements and educational actions undertaken in schools