bluuebunny/crossref_metadata_2025_split huggingface dataset:
Element Effect Revisited. Variable and Inverse Element Effect in the SNAr Reaction of Picryl Halide and 2,4-Dimethoxyaniline
Authors: Sugiyama Naoki , Hayami Jun-ichi 
Published: August 2003

Abstract
Kinetic studies were made of the SNAr reaction of picryl halides (PicX, X = F, Cl) with 2,4-dimethoxyaniline in organic solvents. The element effect, kΨPicF/kΨPicCl, was found to be well-known large value at high [DMA], however, diminished continuously as the decrease of [DMA], and an inverse element effect was observed in CH3CN. Variable/inverse element effect has not been suggested for SNAr reaction and clearly shows that care must be exercised in using as the probe of reaction mechanism.
Highly Active, Thermally Robust V-based New Olefin Polymerization Catalyst System
Authors: Nakayama Yasushi , Bando Hideki , Sonobe Yoshiho , Suzuki Yasuhiko , Fujita Terunori 
Published: August 2003

Abstract
A new ethylene polymerization catalyst system containing a phenoxy-imine ligated V complex and a MgCl2-based compound has been discovered. Unlike ordinary V-based catalysts, the system exhibits higher activities at elevated temperatures, and the activity reached a very high value of 65100 kg-PE/mol-cat/h at 75 °C, representing the first example of a highly active, thermally robust V-based ethylene polymerization catalyst system.
Hydrothermal Synthesis of Fine MoS2 Crystals from Na2MoO4 and KSCN
Authors: Tian Ye , He Yu , Zhu Yongfa 
Published: August 2003

Abstract
A fine crystal MoS2 has been synthesized by hydrothermal method in a clean and efficient system consisting of Na2MoO4 and KSCN in a short time (24 h). The product is characterized by XRD and TEM, and the ED pattern reveals a hexagonal crystal. The mechanism of this reaction is also put forward. Thus this method provides us a new routine to synthesize other transition metal sulfides.
Red Luminescent Squarylium Dyes for Noncovalent HSA Labeling
Authors: Nakazumi Hiroyuki , Colyer Chista L , Kaihara Koji , Yagi Shigeyuki , Hyodo Yutaka 
Published: August 2003

Abstract
Asymmetric squarylium fluorophores with 618–680 nm emissions exhibit significantly enhanced fluorescence and increased quantum yield (maximum 97%) by the formation of 1:1 dye–protein complexes when bound as non-covalent labeling probes to human serum albumin (HSA).
Reversible Change in Optical Rotation by Phtochromism of Diarylethenes in the Stretched DNA–Quaternary Ammonium Ion Complex Films
Authors: Saito Masako , Yokoyama Yayoi , Yokoyama Yasushi 
Published: August 2003

Abstract
Transparent stretched films of DNA–dimethyldioctadecylammonium ion complex incorporating a photochromic diarylethene exhibited large change in optical rotation by its photochromic reactions. As the stretched films at the photostationary state of UV-irradiation showed the dichroism, it was suggested that the diarylethene molecules are partly intercalated between the DNA base pairs.
Structures and Magnetic Properties of Di- and Trinuclear Nickel(II) Complexes with Phenoxo and Acetato Bridges
Authors: Koizumi Satoshi , Nihei Masayuki , Oshio Hiroki 
Published: August 2003

Abstract
Reactions of NiCl2·6H2O and Ni(CH3COO)2·4H2O with tridentate ligand yielded di- and trinuclear nickel(II) complexes of [Ni2(HL1)2Cl2(MeOH)2] (1) and [Ni3(HL2)2(CH3COO)4(MeOH)2] (2) (H2L1 = N-(2-hydroxybenzyl)ethanolamine), H2L2 = N-(2-hydroxybenzyl)propanolamine), respectively; the magnetic susceptibility measurements revealed that 1 and 2 have singlet and septet spin ground states, respectively.
Friedel–Crafts Benzylation and Phenethylation Reactions Using Benzyl and Phenethyl Benzothiazol-2-yl Carbonate Derivatives
Authors: Mukaiyama Teruaki , Kamiyama Hiroaki , Yamanaka Hiroyuki 
Published: August 2003

Abstract
Friedel–Crafts benzylation and phenethylation reactions of several aromatic compounds with benzyl and phenethyl benzothiazol-2-yl carbonate derivatives were carried out in the presence of scandium triflate (Sc(OTf)3) as a catalyst. Suitable combinations of the leaving group of carbonates and acid promoters that generate cationic alkyl species were examined.
Direct Production of Hydrogen Peroxide from H2 and O2 over Highly Dispersed Au catalysts
Authors: Okumura Mitsutaka , Kitagawa Yasutaka , Yamagcuhi Kizashi , Akita Tomoki , Tsubota Susumu , Haruta Masatake 
Published: August 2003

Abstract
Highly dispersed Au catalysts were active for the direct formation of H2O2 form H2 and O2. Especially, the rate of H2O2 production greatly increased when Au nanoparticles were deposited onto SiO2, MCM-41 and active carbon supports.
Condensation of α-Amino Acid with Amine in the Absence of a Coupling Agent
Authors: Yamaguchi Jun-ichi , Nagai Shinya , Fukuoka Emi , Suyama Takayuki 
Published: August 2003

Abstract
Treatment of N-(4-nitrophenoxycarbonyl)amino acid with an equimolar amount of amine in the absence of a coupling agent gave the corresponding α-amino acid amide in high yield.
Well-aligned ZnO Whiskers Prepared by Catalyst-assisted Flux Method
Authors: Kong Xianghua , Li Yadong 
Published: August 2003

Abstract
Well-aligned ZnO whiskers were prepared by a catalyst-assisted flux method using ZnS powders as starting materials at a temperature of 860 °C. Au coating on the Si substrate plays a key role on the nucleation. The growth of ZnO whiskers was controlled by a high temperature SLS mechanism.
Photochromism of Aza-aromatics with Hydroxy Group. Intermolecular Proton Transfer in Glassy Solution
Authors: Ogawa Keiichiro , Miura Masatoshi , Nakayama Toshio , Harada Jun 
Published: August 2003

Abstract
When solutions of 2-hydroxyphenazine (1), 3-hydroxyacridine (2), and 7-hydroxyquinoline (3) were irradiated with UV light at 77 K, they became deeply colored. The color of the solutions reverted to the original one, when they were left in the dark at 77 K or at a higher temperature. We ascribe the photochromism to proton tautomerization, which is most likely induced by an intermolecular proton transfer in the excited state.
57Fe Mössbauer Study on Photoinduced Spin Transition of Ferrocene in Polymer Matrices
Authors: Einaga Yasuaki , Kotake Masahiro , Yamada Yasuhiro , Sato Osamu 
Published: August 2003

Abstract
A polymer matrix isolation technique was examined as a potentially novel strategy for realizing optically switchable materials. Not only was a ferricinium ion ([Cp2FeIII]+) produced, but also was produced an isomer of ferrocene (Cp2Fe) with high spin FeII in a poly(methyl methacrylate) (PMMA) matrix film containing CCl4 by the photoillumination of ferrocene at low temperature. The high spin state could be maintained for an extended period when the sample was kept below ≈130 K. This is the first observation of a photoinduced spin transition for ferrocene. The strategy that we used to achieve the spin transition using optical stimuli may open up many possibilities for the development of new magneto-optical devices.
Morphology of the Pancreas in Normal and Diabetic States
Authors: Clark A. 
Published: August 2003

AbstractThe islets of Langerhans form 5% of the pancreatic mass and are distributed throughout the pancreatic exocrine tissue. Islets are composed of cells containing insulin (β‐cells), glucagon (α‐cells), somatostatin (δ‐cells), and pancreatic polypeptide (PP‐cells) and have secretory granules with different characteristic morphologies. In type 1 diabetes, autoimmune destruction of β‐cells is associated with insulitis in the acute phase of the disease; other islet cells remain unaffected in islets of reduced size. Islets in type 2 diabetic subjects are not reduced in size and there is no evidence for a reduction in islet numbers or changes in the proportion of endocrine cells in most affected patients. Islet amyloid deposits formed from islet amyloid polypeptide are found in a proportion of islets (0.1–90% of islets) in more than 90% of patients at postmortem but these deposits are not a causal factor for type 2 diabetes in humans. Severe islet amyloid deposition is related to a reduction of islet cell mass and requirement for insulin therapy. Reduced islet cell mass is associated with genetically determined diabetes involving genes regulating metabolism and transcription factors (e.g. MODY, mitchondrial diabetes, Wolfram syndrome). Exocrine diseases such as pancreatitis, cystic fibrosis, and calcific pancreatitis lead to diabetes, indicating the functional association of the exocrine and endocrine pancreas.
Insulin Gene Expression and Biosynthesis
Authors: Poitout Vincent , Stein Roland , Rhodes Christopher J. 
Published: August 2003

AbstractThe insulin gene is expressed specifically and at very high levels in pancreatic β‐cells. Most of its tissue‐specific expression and metabolic regulation are conferred by approximately 340 bp upstream of the transcription initiation site. Several glucose‐responsive elements have been identified within this region, and physiological regulation of insulin gene expression relies on the cooperative and synergistic interactions between DNA‐binding factors and coactivators. Glucose is the major regulator of insulin gene expression. It activates transcription and stabilizes insulin mRNA. In addition, insulin gene expression is stimulated by glucagon‐like peptide 1, growth hormone, and lactogenic hormones, and inhibited by epinephrine, somatostatin, glucagon, and leptin. In type 2 diabetes, chronic elevations of blood glucose and fatty acid levels impair insulin gene expression. Under most circumstances, the production of insulin is also highly regulated at the translational level. Indeed, this is the predominant control mechanism in the β‐cell whereby intracellular insulin stores are efficiently maintained in the short term. Essentially, translation of the preproinsulin mRNA template to preproinsulin protein occurs in a fashion typical of most eukaryotic mRNAs. In general, nutrients that stimulate insulin secretion, of which glucose is the most physiologically relevant, also stimulate proinsulin biosynthesis at the translational level. Recently, it has been shown that specific control of glucose‐induced proinsulin biosynthesis in the β‐cell resides incis‐elements in the 5′‐ and 3′‐untranslated regions of preproinsulin mRNA itself. After proinsulin is translocated into the lumen of the rough endoplasmic reticulum, correctly folded proinsulin can then be delivered in transport vesicles to thecis‐Golgi apparatus in an ATP‐dependent process. The major site for processing of the proinsulin to biologically active insulin is the immature granule compartment of the β‐cell. Production of insulin occurs via limited proteolysis of the proinsulin precursor molecule, which is catalyzed by two endopeptidases, proprotein convertase 2 (PC2) and proprotein convertase 3 (PC3) (also known as PC‐1), and an exopeptidase, carboxypeptidase‐H (CP‐H). Similar to their deleterious effects on insulin gene expression, chronic hyperglycemia and hyperlipidiemia impair proinsulin biosynthesis.
β‐Cell Biology of Insulin Secretion
Authors: Wollheim Claes B. , Maechler Pierre 
Published: August 2003

AbstractBlood glucose homeostasis critically depends on the precise regulation of insulin secretion from the pancreatic β‐cells. The chapter describes how glucose enters the β‐cell, is phosphorylated, and yields metabolic coupling factors mainly in the mitochondria. These factors modify K+and Ca2+fluxes across the plasma membrane. It is discussed how cytosolic Ca2+triggers exocytosis of the insulin stored in the secretory granules. This process is under tight control of proteins implicated in granule movement, docking, and ultimate fusion with the plasma membrane, resulting in insulin release. Certain β‐cell defects are also illustrated, in particular those linked to mitochondrial dysfunction or mutations in key proteins involved in metabolism–secretion coupling.
Normal Insulin Secretion in Humans
Authors: Utzschneider Kristina M. , Porte Daniel , Kahn Steven E. 
Published: August 2003

AbstractNormal insulin secretion in humans is mainly regulated by glucose, but additional factors including other nutrients, hormones, and neural input play an important role. In the basal state, insulin is released in a rapid pulsatile manner, with pulses occurring every 6–10 min. These pulses are superimposed on an oscillatory pattern of 11–15 oscillations per 24 h. Dynamic insulin release also occurs in response to stimuli. The insulin response to intravenous glucose has been shown to have two distinct phases: an early first phase response lasting for 10 min, and a slower longer second phase response lasting as long as the glucose level is elevated. Preexistent elevations in the plasma glucose level are able to increase the insulin response to a subsequent glucose stimulus, an effect called priming. Glucose is also capable of potentiating the insulin response to non‐glucose secretagogues such as amino acids, peptides, and sulfonylureas. Non‐glucose factors that affect insulin secretion include amino acids, free fatty acids, medications, and the response to stress. Neural inputs regulate islet secretory function through both the sympathetic and parasympathetic nervous systems. The gastrointestinal peptides glucagon‐like peptide 1 (GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP), released from the intestine during oral intake, have been found to play a significant role in augmenting insulin release, an effect known as the incretin effect. When assessing the effect of all these different secretagogues on β‐cell function, it is important to take into account the prevailing insulin sensitivity, as variations in insulin sensitivity lead to compensatory changes in insulin release. Understanding the dynamics and complex regulation of normal insulin secretion in humans provides the basis for understanding the consequences of β‐cell dysfunction observed in diabetes.
Neuropeptides and Insulin Secretion
Authors: Ahrén Bo 
Published: August 2003

AbstractThe pancreatic islets are richly innervated by parasympathetic, sympathetic, and, sensory nerves and these nerves have been shown to be of importance for the regulation of islet function. The terminals of the islet autonomic nerves harbor, however, not only the classical neurotransmitters, acetylcholine and noradrenaline, but also several neuropeptides. These neuropeptides are vasoactive intestinal polypeptide (VIP), pituitary adenlyate cyclase activating polypeptide (PACAP), and gastrin releasing peptide (GRP) in the parasympathetic nerve terminals; galanin and neuropeptide Y (NPY) in the sympathetic nerve terminals; and calcitonin gene‐related peptide (CGRP) and substance P (SP) in the sensory nerves. These neuropeptides may mediate activation of the autonomic nerves on islet hormone secretion. Thus, insulin secretion stimulated by parasympathetic nerves may be mediated by VIP, PACAP, and GRP, which all stimulate insulin secretion, whereas inhibition of insulin secretion by sympathetic nerve activation may be mediated by galanin and NPY, which both inhibit insulin secretion. The neuropeptides in the sensory nerve terminals—CGRP and SP—inhibit insulin secretion.The actions of the neurotransmitters on insulin secretion are elicited by different receptors affecting different signaling pathways in the β‐cells. For example, VIP and PACAP activate adenylate cyclase and GRP activates phospholipase C, whereas galanin and NPY inhibit adenylate cyclase. In addition, the neurotransmitters affect ionic channel activity and exert direct influences on the exocytosis machinery.The islet autonomic nerves seem to be of physiological importance for insulin secretion in various conditions. Thus, parasympathetic nerves mediate the cephalic phase of insulin secretion after a meal intake and synchronize the islets to function as a unit, allowing oscillations of islet hormone secretion. The sympathetic nerves optimize islet hormone secretion during metabolic stress or physical activity. The autonomic nerves might also be involved in the islet adaptation to insulin resistance with possible implication for the development of glucose intolerance and type 2 diabetes.The islet innervation is thus of importance both for the physiology and pathophysiology of the islets through contribution by all branches of the autonomic nerves and several different neurotransmitters.
Biological Effects of C‐peptide and Proinsulin
Authors: Wahren John , Ekberg Karin , Shafqat Jawed , Johansson Jan , Johansson Bo‐Lennart , Jörnvall Hans 
Published: August 2003

AbstractC‐peptide: In contrast to the earlier view, new data now indicate that proinsulin C‐peptide does exert important physiological effects and shows the characteristics of an endogenous peptide hormone. C‐peptide in nanomolar concentrations binds specifically to cell membranes, probably to a G‐protein coupled receptor, resulting in subsequent activation of Ca2+‐ and MAP‐kinase‐dependent signaling pathways. C‐peptide's binding to cell membranes is stereospecific and the C‐terminal pentapeptide segment participates in the process. Some studies indicate that C‐peptide and insulin may exert a synergistic effect on the insulin signaling pathway. C‐peptide stimulates Na+,K+‐ATPase and endothelial nitric oxide synthase activities. C‐peptide administration in replacement doses in animal models of diabetes or in type 1 diabetic patients results in increased blood flow in skeletal muscle, myocardium, kidney, nerve, and skin. C‐peptide replacement decreases glomerular hyperfiltration, reduces urinary albumin excretion, and corrects glomerular expansion. It also increases nerve conduction velocity, improves sensory nerve function, and reduces or reverses the characteristic diabetes‐induced nodal and paranodal nerve structural changes. The evidence suggests that replacement of C‐peptide together with insulin may be beneficial in patients with type 1 diabetes and serve to retard or prevent the development of long‐term complications.Proinsulin: Only a very small proportion of proinsulin is released in its intact form to the circulation in healthy subjects. In contrast, in type 2 diabetes, plasma proinsulin and its conversion intermediates may be higher than in healthy individuals. Proinsulin binds to the insulin receptor with approximately 10% of insulin's affinity. The suggestion of a specific effect of proinsulin in lowering hepatic glucose output has not been verified in direct studies. Clinical trials designed to evaluate the usefulness of proinsulin as an insulin analogue in type 2 diabetic patients were discontinued because of increased incidence of myocardial infarction. Recent reports of specific high affinity proinsulin receptors in several tissues are intriguing and warrant further investigation.
Biosynthesis, Secretion, and Action of Glucagon
Authors: Lefèbvre Pierre J. 
Published: August 2003

AbstractGlucagon is a very ancient and tightly conserved molecule and is an important hormone exerting numerous metabolic effects, including stimulation of hepatic glycogenolysis, gluconeogenesis, and ketogenesis; inhibition of liver glycogen synthesis; and, at least in some species, stimulation of adipose tissue lipolysis. All these effects of glucagon are strongly antagonized by insulin. Glucagon originates in the A‐cells of the islets of Langerhans of the pancreas, where it is synthesized in the form of a large precursor, preproglucagon. Several peptides derived from the preproglucagon molecule are also expressed in the gut and the brain; they include glicentin, oxyntomodulin, glucagon, and glucagon‐like peptides 1 and 2, while a smaller molecule, mini‐glucagon, is generated at the hormone target cells. Glucagon release is increased in various physiological situations including hypoglycemia, low circulating levels of free fatty acids, high levels of numerous amino acids, and stimulation of both vagal and adrenergic nervous systems. Prolonged starvation, long‐lasting exercise, stress, and adaptation to the extrauterine life are also associated with high circulating levels of glucagon. All these effects of glucagon make it above all a “hormone of energy need.” Diabetes is characterized by excessive circulating levels of glucagon, which are now considered to stem largely from the absolute or relative insulin deficiency that is observed in this syndrome. Studies are in progress to identify inhibitors or glucagon secretion or action as new tools in the pharmacological treatment of diabetes.
Islet Amyloid Polypeptide/GLP‐1/Exendin
Authors: Baggio Laurie L. , Drucker Daniel J. 
Published: August 2003

AbstractGastrointestinal peptides exert important physiological roles in the control of feeding behavior, gut motility, nutrient absorption, and energy assimilation. Islet amyloid polypeptide is secreted from islet β‐cells, and exerts inhibitory actions on appetite, gastric motility, and glucagon secretion. Glucagon‐like peptide 1 (GLP‐1) is released from enteroendocrine cells and regulates food intake, gastric emptying, insulin and glucagon secretion, and β‐cell proliferation and apoptosis. Exendin‐4, a lizard‐derived peptide, is a potent and stable GLP‐1R agonist that exerts GLP‐1‐like actionsin vivo. The overlapping glucose‐lowering properties of these peptides have fostered considerable interest in their development as new therapeutic agents for the treatment of diabetes mellitus.
The Genetics of Human Obesity
Authors: Bouchard Claude , Pérusse Louis 
Published: August 2003

AbstractThis chapter summarizes the research on the role of genetic variation in human obesity. It provides a brief review of our current understanding of the level of heritability and of the familial risk for increasing levels of excess body weight. Single‐gene defects known to cause obesity are discussed. The results of a large number of association studies performed with candidate genes are described. The candidate genes with at least five positive studies are highlighted. All published genomic scan studies relevant to obesity are reviewed, with an emphasis on the linkage results characterized by apparent convergence in at least two cohorts. Finally, the role of gene–environment interactions in the response to chronic positive or negative energy balance is examined.