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排序方式: 共有573条查询结果,搜索用时 15 毫秒
1.
M.L. Fravolini P.G. Fabietti 《Computer methods in biomechanics and biomedical engineering》2014,17(13):1464-1482
This paper proposes a scheme for the control of the blood glucose in subjects with type-1 diabetes mellitus based on the subcutaneous (s.c.) glucose measurement and s.c. insulin administration. The tuning of the controller is based on an iterative learning strategy that exploits the repetitiveness of the daily feeding habit of a patient. The control consists of a mixed feedback and feedforward contribution whose parameters are tuned through an iterative learning process that is based on the day-by-day automated analysis of the glucose response to the infusion of exogenous insulin. The scheme does not require any a priori information on the patient insulin/glucose response, on the meal times and on the amount of ingested carbohydrates (CHOs). Thanks to the learning mechanism the scheme is able to improve its performance over time. A specific logic is also introduced for the detection and prevention of possible hypoglycaemia events. The effectiveness of the methodology has been validated using long-term simulation studies applied to a set of nine in silico patients considering realistic uncertainties on the meal times and on the quantities of ingested CHOs. 相似文献
2.
Studies with substrate analogues and the pH optimum indicated the involvement of carboxyl group in the active site of goat
carboxypeptidase A. Chemical modification of the enzyme with 1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide methoI -p-toluene sulphonate, a carboxyl specific reagent, led to loss of both esterase and peptidase activities. Protection studies
showed that this carboxyl group was in the active site and was protected by Βp-phenylpropionic acid and glycyl-L-tyrosine. Kinetic studies also confirmed the involvement of carboxylic group because the
enzyme modification with water soluble carbodiimide was a two step reaction which excluded the possibility of tyrosine or
lysine which are known to give a one step reaction with this reagent 相似文献
3.
Hans-Jürgen Hahn Erik Gylfe Bo Hellman 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,630(3):425-432
The effect of cyclic AMP on calcium movements in the pancreatic β-cell was evaluated using an experimental approach based on in situ labelling of intracellular organelles of ob/ob-mouse islets with 45Ca. Whereas the glucose-stimulated 45Ca incorporation by mitochondria and secretory granules was increased under a condition known to reduce cyclic AMP (starvation), raised levels of this nucleotide (addition of 3-isobutyl-1-methylxanthine or N6,O2′-dibutyryl adenosine 3′,5′-cyclic monophosphate) reduced the mitochondrial accumulation of 45Ca. Conditions with increased cyclic AMP were associated with a stimulated efflux of 45Ca from the secretory granules but not from the mitochondria. The microsomal fraction differed from both the mitochondrial and secretory granule fractions by accumulating more 45Ca after the addition of 3-isobutyl-1-methylxanthine. The results suggest that cyclic AMP potentiates glucose-stimulated insulin release by increasing cytoplasmic Ca2+ at the expense of the calcium taken up by the organelles of the pancreatic β-cells. 相似文献
4.
Iain L. Campbell Keith W. Taylor 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,676(3):357-364
The process of cyclic AMP efflux from rat islets of Langerhans has been studied. The dynamics of glucose-induced cyclic AMP efflux closely resembled the pattern of glucose-induced insulin release. Thus, both processes were dose-dependent for glucose having the same threshold concentrations (4–8 mmol/l glucose), with the time course of cyclic AMP efflux and insulin release from 0–60 min being very similar. Galactose did not affect insulin release, cyclic AMP efflux and intra-islet cyclic AMP accumulation. On the other hand, inosine, N-acetylglucosamine, α-ketoisocaproic acid, L-leucine and xylitol all promoted insulin release and cyclic AMP efflux. Except for L-leucine, all these substances enhanced the intracellular accumulation of cyclic AMP. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, greatly augmented all these parameters in the presence of glucose whereas in the absence of glucose, insulin release was not enhanced, while both cyclic AMP efflux and cyclic AMP accumulation were elevated. The drug, probenecid, did not alter either insulin release or intra-islet cyclic AMP levels, while cyclic AMP efflux was markedly reduced (though not abolished). Papaverine inhibited both insulin release and cyclic AMP efflux, but was found to augment the intra-islet cyclic AMP levels. The efflux of cyclic AMP correlates more closely with insulin release than with the cyclic AMP accumulation in most instances. The efflux is independent of either insulin secretory granule extrusion or intracellular fluctuations of the nucleotide, though it is not yet known whether cyclic AMP efflux may have some regulatory significance in insulin release. 相似文献
5.
Ontogeny of lipase expression in winter flounder 总被引:3,自引:0,他引:3
H. M. Murray J. W. Gallant J. C. Perez-Casanova S. C. Johnson S. E. Douglas 《Journal of fish biology》2003,62(4):816-833
The partial sequencing of two lipases from winter flounder Pseudopleuronectes americanus , one most closely related to gastric, lingual and lysosomal acid lipase from other vertebrates and one most closely related to bile salt-activated lipase, is reported. Biochemical analyses of enzymatic activity demonstrated the greater contribution made by bile salt-activated lipase relative to neutral bile salt-independent lipase. Using molecular techniques, the tissue-specific expression of bile salt-activated lipase in pancreatic tissue and acid triacylglycerol lipase in a wide variety of organs was demonstrated. Furthermore, the developmental expression of these types of lipase in larval fish was established. 相似文献
6.
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8.
Michel Roberge Adrien R. Beaudoin 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,716(3):331-336
The pancreatic secretion of anesthetized pigs was collected by cannulation after pulse labeling with [3H]leucine. Collection at 5 min intervals started immediately post-pulse labeling up to 85 min. The volume, the protein content and the trichloroacetic acid-precipitable radioactivity of the juice were measued. The specific radioactivity of the secertory proteins was compared to that of a zymogen granule fraction isolated from the same animal. The latter was very much higher. Caerulein stimulation for 5 min at 80 min post-pulse caused a sharp drop in the specific activity of secretory proteins in the juice, to a level lower than that of the zymogen granule content. These data support the concept of more than one pool of secretory proteins in the pancreas and are incompatible with the concept that secretory proteins derive from an homogeneous granule compartment in a functionally homogeneous population of cells. To explain our results the hypothesis of a second intracellular route for the secretory proteins is proposed. 相似文献
9.
10.
Diane C. Saunders Marcela Brissova Neil Phillips Shristi Shrestha John T. Walker Radhika Aramandla Greg Poffenberger David K. Flaherty Kevin P. Weller Julie Pelletier Tracy Cooper Matt T. Goff John Virostko Alena Shostak E. Danielle Dean Dale L. Greiner Leonard D. Shultz Nripesh Prasad Alvin C. Powers 《Cell metabolism》2019,29(3):745-754.e4