The impact of insulin administration during the mixed meal tolerance test

Diabet. Med. 29, 1279-1284 (2012) ABSTRACT: Aims The mixed meal tolerance test is the gold standard measure of endogenous insulin secretion. Practical issues limit the routine clinical use of this test, including omitting insulin prior to the ingestion of a high-carbohydrate liquid mixed meal, which can result in marked hyperglycaemia. We aimed to assess whether insulin omission is necessary during the mixed meal tolerance test and whether fasting C-peptide was a practical alternative to the test. Methods Ninety-one adults with insulin-treated diabetes (Type?1 n?=?56, Type?2 n?=?35) underwent two mixed meal tolerance tests; one standard without insulin and one with the patient's usual morning insulin. Results The 90-min serum C-peptide was highly correlated in the standard mixed meal tolerance test and the test with insulin (r?=?0.98, P?相似文献   

Protein kinase-mediated regulation of calcineurin through the phosphorylation of modulatory calcineurin-interacting protein 1

Calcineurin is a serine/threonine protein phosphatase that plays a critical role in many physiologic processes such as T-cell activation, skeletal myocyte differentiation, and cardiac hypertrophy. We previously showed that active MEKK3 is capable of stimulating calcineurin/nuclear factor of activated T-cells (NFAT) signaling in cardiac myocytes through phosphorylation of modulatory calcineurin-interacting protein 1 (MCIP1). However, the protein kinases that function downstream of MEKK3 to mediate MCIP1 phosphorylation and the mechanism of MCIP1-mediated calcineurin regulation have not been defined. Here, we show that MEK5 and big MAP kinase 1 (BMK1) function downstream of MEKK3 in a signaling cascade that induces calcineurin activity through phosphorylation of MCIP1. Genetic studies showed that BMK1-deficient mouse lung fibroblasts failed to mediate MCIP1 phosphorylation and activate calcineurin/NFAT in response to angiotensin II, a potent NFAT activator. Conversely, restoring BMK1 to the deficient cells restored angiotensin II-mediated calcineurin/NFAT activation. Thus, using BMK1-deficient mouse lung fibroblast cells, we provided the genetic evidence that BMK1 is required for angiotensin II-mediated calcineurin/NFAT activation through MICP1 phosphorylation. Finally, we discovered that phosphorylated MCIP1 dissociates from calcineurin and binds with 14-3-3, thereby relieving its inhibitory effect on calcineurin activity. In summary, our findings reveal a previously unrecognized essential regulatory role of mitogen-activated protein kinase signaling in calcineurin activation through the reversible phosphorylation of a calcineurin-interacting protein, MCIP1.     

Synthesis and antifungal activity of 1H-indole-4,7-diones

1H-Indole-4,7-diones were synthesized and tested for in vitro antifungal activity against fungi. The synthesized 1H-indole-4,7-diones generally showed good antifungal activity against Candida krusei, Cryptococcus neoformans, and Aspergillus niger. The results suggest that 1H-indole-4,7-diones would be potent antifungal agents.     

Spectroscopic and biochemical analysis of regions of the cell wall of the unicellular 'mannan weed', Acetabularia acetabulum

Although the Dasycladalean alga Acetabularia acetabulum has long been known to contain mannan-rich walls, it is not known to what extent wall composition varies as a function of the elaborate cellular differentiation of this cell, nor has it been determined what other polysaccharides accompany the mannans. Cell walls were prepared from rhizoids, stalks, hairs, hair scars, apical septa, gametophores and gametangia, subjected to nuclear magnetic resonance and Fourier transform infrared spectroscopy, and analyzed for monosaccharide composition and linkage, although material limitations prevented some cell regions from being analyzed by some of the methods. In diplophase, walls contain a para-crystalline mannan, with other polysaccharides accounting for 10-20% of the wall mass; in haplophase, gametangia have a cellulosic wall, with mannans and other polymers representing about a quarter of the mass. In the walls of the diplophase, the mannan appears less crystalline than typical of cellulose. The walls of both diploid and haploid phases contain little if any xyloglucan or pectic polysaccharides, but appear to contain small amounts of a homorhamnan, galactomannans and glucogalactomannans, and branched xylans. These ancillary polysaccharides are approximately as abundant in the cellulose-rich gametangia as in the mannan-rich diplophase. In the diplophase, different regions of the cell differ modestly but reproducibly in the composition of the cell wall. These results suggest unique cell wall architecture for the mannan-rich cell walls of the Dasycladales.     

Constitutive polymorphic cyanogenesis in the Australian rainforest tree, Ryparosa kurrangii (Achariaceae)

Cyanogenesis, the liberation of volatile hydrogen cyanide from endogenous cyanide-containing compounds, is a proven plant defence mechanism and the particular cyanogens involved have taxonomic utility. The cyclopentenoncyanhydrin glycoside gynocardin was the only cyanogen isolated from foliar tissue of the rare Australian rainforest tree, Ryparosa kurrangii (Achariaceae). Mechanical damage simulating foliar herbivory did not induce a significant increase in the expression of cyanogenesis over a 24h period, indicating cyanogenic herbivore defence in R. kurrangii is constitutive. The cyanogenic potential of mature leaves was quantitatively polymorphic between trees in a natural population, ranging from 0.54 to 4.77 mg CN g(-1) dry wt leaf tissue.     

Cyclodextrin production and genetic characterization of cyclodextrin glucanotranferase of <Emphasis Type="Italic">Paenibacillus graminis</Emphasis>

Paenibacillus graminis strains were described recently as cyclodextrin (CD) producers. Cyclodextrins are produced by cyclodextrin glucanotransferase (CGTase) which has not been characterized in P. graminis. Similar amounts of α- and β-CDs were produced by P. graminis (MC22.13) and P. macerans (LMD24.10^T). Primers were designed to sequence the gene encoding CGTase from P. graminis. A phylogenetic tree was constructed and P. graminis CGTase protein showed to be closer (79.4% protein identity) to P. macerans |P31835|. Hybridization studies suggested that the gene encoding CGTase is located in different positions in the genomes of P. macerans and P. graminis.     

Evaluation of the influence of anisotropic indirect nuclear spin-spin coupling tensors on effective residual dipolar couplings for model peptides

Residual dipolar couplings (RDCs) observed between nuclear spins in molecules in partially oriented media have become a valuable source of information for NMR spectroscopists seeking to structurally characterize biological macromolecules. Examination of the form of the direct (D) and indirect (J) nuclear spin-spin coupling Hamiltonians indicates that all observed RDCs contain an unknown contribution from the anisotropic part of J (J) in addition to the direct dipolar contribution, D _PQ. Here, we evaluate the influence of J on RDCs through a series of DFT calculations on model peptides. Very small corrections to one-bond RDCs measured between heavy atoms in peptides and proteins are recommended: +0.51% for N-C spin pairs, and +0.45% for C-C spin pairs. The corrections to RDCs involving at least one proton are negligible. This latter point is likely to be equally applicable to nucleic acids and oligosaccharides in addition to peptides and proteins. Finally, the orientations of the J(N, C) and J(C, C) tensors in the molecular framework are reported for glycylglycine.     

Predicted molecular structure of the mammalian cell entry protein Mce1A of Mycobacterium tuberculosis

The proposed role of the mammalian cell entry protein 1A (Mce1A) of Mycobacterium tuberculosis is to facilitate invasion of host cells. The structure of Mce1A was modelled on the basis of the crystal structure of Colicin N of Escherichia coli by fold prediction and threading. Mce1A, as the model predicts, is an alpha/beta protein consisting of two major (alpha and beta) domains, connected by a long alpha helix. The model further revealed that the protein contains 12 helices, 9 strands, and 1 turn. The final model of Mce1A was verified through the program VERIFY 3D and more than 90% of the residues were in the favourable region. A mouse monoclonal antibody, TB1-5 76C, is directed to an epitope within a 60-mer peptide that has been shown to promote uptake of bacteria in mammalian cells. We show here that the epitope could be narrowed down to a core of 4 amino acids, TPKD. Upstream flanking residues, KRR also contributed to binding. Mce2A does not promote uptake in mammalian cells and sequence comparison of Mce1A and Mce2A indicates that the epitope mediates uptake. The epitope was located at the surface of the Mce1A model at the distal beta strand-loop region in the beta domain. The localization of this epitope in the model confirms its potential role in promoting uptake of M. tuberculosis in host cells.     

Computational study of the putative active form of protein Z (PZa): sequence design and structural modeling

Although protein Z (PZ) has a domain arrangement similar to the essential coagulation proteins FVII, FIX, FX, and protein C, its serine protease (SP)-like domain is incomplete and does not exhibit proteolytic activity. We have generated a trial sequence of putative activated protein Z (PZa) by identifying amino acid mutations in the SP-like domain that might reasonably resurrect the serine protease catalytic activity of PZ. The structure of the activated form was then modeled based on the proposed sequence using homology modeling and solvent-equilibrated molecular dynamics simulations. In silico docking of inhibitors of FVIIa and FXa to the putative active site of equilibrated PZa, along with structural comparison with its homologous proteins, suggest that the designed PZa can possibly act as a serine protease.