具size结构种群竞争系统的最优控制

研究基于size结构的种群模型的控制问题,利用特征线法给出了系统的形式解,由Banach不动点定理和Gronwall不等式推导了系统及其共轭系统的适定性,并依靠法锥相关知识证明了最优控制问题解的存在必要条件.     

Bovine intermediate pituitary alpha-amidation enzyme: preliminary characterization

A secretory granule-associated enzymatic activity that converts mono-[125I]-D-Tyr-Val-Gly into mono-[125I]-D-Tyr-Val-NH2 has been studied. The activity is primarily soluble and shows optimal activity at pH 7 to pH 8. Amidation activity was stimulated 9-fold by addition of optimal amounts of copper (3 microM). In the presence of optimal copper, ascorbate stimulated the reaction 7-fold; none of the other reduced or oxidized cofactors tested was as effective. Taking into account the dependence of the reaction on ascorbate and molecular oxygen and the production of glyoxylate [2], it is suggested that the alpha-amidation enzyme is a monooxygenase. Lineweaver Burk plots with D-Tyr-Val-Gly as the varied substrate demonstrated Michelis-Menten type kinetics with the values of Km and Vmax increasing with the addition of ascorbate to the assay. A variety of peptides ending with a COOH-terminal Gly residue act as inhibitors of the reaction. Two synthetic peptides, gamma 2MSH and ACTH(1-14), with carboxyl termini similar to the presumed physiological substrates for the enzyme, act as competitive inhibitors with similar K1 values. It is likely that this secretory granule alpha-amidation activity is involved in the physiological biosynthetic alpha-amidation of a wide range of bioactive peptides.     

Developmental expression of peptidylglycine alpha-amidating monooxygenase (PAM) in primary cultures of neonatal rat cardiocytes: a model for studying regulation of PAM expression in the rat heart.

Primary cultures of neonatal rat atrial and ventricular cardiomyocytes were used to investigate the expression of peptidylglycine alpha-amidating monooxygenase (PAM), a bifunctional enzyme required for the production of alpha-amidated neuroendocrine peptides. The use of assays for the individual enzymes, peptidylglycine alpha-amidating monooxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL), demonstrated that the levels of expression observed in vitro approximated those observed in vivo. Both in vivo and in vitro, atrial and ventricular PAL activity greatly exceeded PHM activity. Atrial and ventricular cardiomyocytes secreted PHM and PAL activity at a constant rate throughout the culture period. Immunofluorescence studies localized PAM proteins to the perinuclear region, with intense punctate staining. Both in vivo and in vitro, PAM mRNAs encoding integral membrane proteins predominated throughout the neonatal period, with PAM-1 mRNA becoming more prevalent after the first week in culture. Although PAM-2 mRNA decreased in prevalence in vivo at the time when PAM-1 expression increased, levels of PAM-2 mRNA remained elevated throughout 2 weeks in vitro. Western blot analysis demonstrated intact PAM-1 and PAM-2 proteins in atrial cultures, with the prevalence of PAM-1 increasing in older cultures. Atrial cardiomyocytes secreted only bifunctional PAM proteins. Many of the features of PAM expression, processing, and storage that are unique to cardiomyocytes as opposed to endocrine cells are faithfully replicated by primary atrial and ventricular cultures.     

Ability of cofactors to support peptide amidation is cell-type specific

The ability of various cofactors to substitute for ascorbate in the biosynthesis of alpha-aidated peptides from pro-ACTH/endorphin (PAE) was compared in corticotrope tumor cells (AtT-20) and in primary anterior and intermediate pituitary cultures. In all three systems, ascorbate was the most potent cofactor tested. In AtT-20 cells, dopamine, norepinephrine, epinephrine, dehydroascorbate and dihydro- and tetrahydrobiopterin supported significant alpha-amidation of joining peptide [PAE(77-94)NH2]. In contrast, amidation of joining peptide by primary corticotropes was stimulated only slightly by catecholamines and not by tetrahydrobiopterin. Neither catecholamines nor tetrahydrobiopterin stimulated peptide amidation by melanotropes. The ability of cofactors to support the synthesis of alpha-amidated peptides is cell-type specific.     

Expression of a peptide processing enzyme in cultured cells: truncation mutants reveal a routing domain.

Peptidylglycine alpha-amidating monooxygenase (PAM) is a bifunctional enzyme responsible for the alpha-amidation of peptides in secretory granules of neuroendocrine cells. The single gene encoding PAM undergoes tissue-specific alternative splicing and endoproteolytic processing to generate bifunctional membrane proteins with a single transmembrane domain as well as soluble proteins that are mono- or bifunctional. In order to examine the endoproteolytic processing and subcellular localization of the various forms of PAM in cells lacking regulated secretory granules, we established stably transfected hEK-293 cell lines expressing naturally occurring and mutant forms of PAM. As expected, newly synthesized soluble PAM proteins were rapidly secreted into the medium. Integral membrane protein forms of PAM were largely localized in the perinuclear region with punctate staining visible throughout the cell and 2-5% of the enzyme activity detectable on the cell surface. Bifunctional PAM proteins were slowly released into the medium after expression of integral membrane protein forms of PAM. Deletion of 77 amino acids from the COOH-terminus of the integral membrane forms of PAM resulted in a membrane-bound protein which retained both enzymatic activities but accumulated on the cell surface. Rapid internalization of full-length PAM proteins was observed by incubating live cells with antiserum to PAM; deletion of the COOH-terminal domain eliminated the ability of cells to internalize PAM. Thus the cytoplasmic domain of integral membrane PAM contains a routing determinant recognized by cells lacking the regulated secretory pathway.     

Moving Statues and Moving Images: Religious Artefacts and the Spiritualisation of Materiality

This paper addresses the spiritualisation of materiality integral to the expression of religious experience by devotees. It focuses on the ‘objective correlatives' of emotion‐imbued faith. Although primarily concerned with the aesthetics of contemporary Catholic mysticism, the aim is to suggestively allude to the implications for comparative analysis. Beginning with devotion to the rosary, it addresses the ‘moving statues' phenomenon, which in the mid‐1980s in Ireland led to numerous visionaries experiencing apparitions of the Virgin Mary. Arguing that sensory analogues are indispensable to the expression of feelings and thoughts, it directs our attention to the tensions implicit in the process, i.e., to the way humans (in this case, religious devotees) need to find and fix upon an adequate and appropriate sensory equivalent. It stresses that such tensions are integral to the formulation and communication of meaning. Further consideration of the imaginative power of material representations leads into a discussion of the influence now exerted by the moving image. The depiction of penitential suffering in The Passion of the Christ is then used to illustrate how film can function as an objective correlative, in this case by articulating notions of penance and redemption shared by Irish visionaries and their disciples.