Non-alcoholic fatty liver disease (NAFLD)--a novel common aspect of the metabolic syndrome

Non-alcoholic fatty liver disease (NAFLD) is emerging as one of the most common liver disorders claiming the urgent attention of both medical professionals and the public sphere because of the imminent epidemic of advanced liver injury that appendages epidemic of obesity. Recent research reveals simple triglyceride accumulation in hepatocytes (i.e., liver steatosis) frequently becoming complicated by inflammation (i.e., non-alcoholic steatohepatitis, or NASH) that may progress into more advanced stages of the disease including cirrhosis or, eventually, hepatocellular carcinoma. The exact mechanisms of the progression of NAFLD into overt NASH and advanced disease stages are largely unknown. There is urgent need in terms of both intensive research pursuits and effective practical measures to deal with this common threat.     

Synthesis of the vasoactive intestinal peptide (VIP) : IV. The sequence 14–28

A protected pentadecapeptide with the C-terminal sequence of the vasoactive intestinal peptide (VIP) was prepared by coupling the tetrapeptide derivative t-butyloxycarbonyl- -arginyl-N-benzyloxycarbonyl- -lysyl- -glutaminyl- -methionine azide to the partially deprotected hendecapeptide -alanyl- -valyl-N-benzyloxycarbonyl- -lysyl-N-benzyloxycarbonyl- -lysyl- -tyrosyl- -leucyl- - asparaginyl- -seryl- -isoleucyl- -leucyl- -asparaginamide. The preparation of the protected tetradecapeptide t-butyloxycarbonyl-N-benzyloxycarbonyl- -lysyl- -glutaminyl- -methionyl- -alanyl- -valyl-N- benzyloxycarbonyl- -lysyl-N-benzyloxycarbonyl- -lysyl- -tyrosyl- -leucyl- -asparaginyl- -seryl- -isoleucyl- -leucyl- -asparaginamide is also reported. The protecting groups were removed from samples of the tetradeca- and pentadecapeptides. The resulting free peptides showed, although at high dose levels, increase of visceral blood flow and reduction of blood pressure in the dog, and also relaxation of different smooth muscle preparations, which are the characteristic biological activities of VIP.     

Human mesotrypsin is a unique digestive protease specialized for the degradation of trypsin inhibitors

Mesotrypsin is an enigmatic minor human trypsin isoform, which has been recognized for its peculiar resistance to natural trypsin inhibitors such as soybean trypsin inhibitor (SBTI) or human pancreatic secretory trypsin inhibitor (SPINK1). In search of a biological function, two conflicting theories proposed that due to its inhibitor-resistant activity mesotrypsin could prematurely activate or degrade pancreatic zymogens and thus play a pathogenic or protective role in human pancreatitis. In the present study we ruled out both theories by demonstrating that mesotrypsin was grossly defective not only in inhibitor binding, but also in the activation or degradation of pancreatic zymogens. We found that the restricted ability of mesotrypsin to bind inhibitors or to hydrolyze protein substrates was solely due to a single evolutionary mutation, which changed the serine-protease signature glycine 198 residue to arginine. Remarkably, the same mutation endowed mesotrypsin with a novel and unique function: mesotrypsin rapidly hydrolyzed the reactive-site peptide bond of the Kunitz-type trypsin inhibitor SBTI, and irreversibly degraded the Kazal-type temporary inhibitor SPINK1. The observations suggest that the biological function of human mesotrypsin is digestive degradation of trypsin inhibitors. This mechanism can facilitate the digestion of foods rich in natural trypsin inhibitors. Furthermore, the findings raise the possibility that inappropriate activation of mesotrypsinogen in the pancreas might lower protective SPINK1 levels and contribute to the development of human pancreatitis. In this regard, it is noteworthy that the well known pathological trypsinogen activator cathepsin B exhibited a preference for the activation of mesotrypsinogen of all three human trypsinogen isoforms, suggesting a biochemical mechanism for mesotrypsinogen activation in pancreatic acinar cells.     

Importation of nuclease colicins into E coli cells: endoproteolytic cleavage and its prevention by the immunity protein

A major group of colicins comprises molecules that possess nuclease activity and kill sensitive cells by cleaving RNA or DNA. Recent data open the possibility that the tRNase colicin D, the rRNase colicin E3 and the DNase colicin E7 undergo proteolytic processing, such that only the C-terminal domain of the molecule, carrying the nuclease activity, enters the cytoplasm. The proteases responsible for the proteolytic processing remain unidentified. In the case of colicin D, the characterization of a colicin D-resistant mutant shows that the inner membrane protease LepB is involved in colicin D toxicity, but is not solely responsible for the cleavage of colicin D. The lepB mutant resistant to colicin D remains sensitive to other colicins tested (B, E1, E3 and E2), and the mutant protease retains activity towards its normal substrates. The cleavage of colicin D observed in vitro releases a C-terminal fragment retaining tRNase activity, and occurs in a region of the amino acid sequence that is conserved in other nuclease colicins, suggesting that they may also require a processing step for their cytotoxicity. The immunity proteins of both colicins D and E3 appear to have a dual role, protecting the colicin molecule against proteolytic cleavage and inhibiting the nuclease activity of the colicin. The possibility that processing is an essential step common to cell killing by all nuclease colicins, and that the immunity protein must be removed from the colicin prior to processing, is discussed.     

Murine peripherin gene sequences direct Cre recombinase expression to peripheral neurons in transgenic mice

Group B streptococcus (GBS) induced macrophage apoptosis by which it could avoid host defence mechanisms. Macrophages, which constitutively express phosphatidylserine (PtdSer) on the outer leaflet of plasma membrane, increased PtdSer exposure during GBS-induced apoptosis. Induction of apoptosis decreased PtdSer radioactivity of macrophages incubated with [³H]serine. The effect appeared not due to increasing conversion of PtdSer to phosphatidylethanolamine or phosphatidylcholine nor to the release of radioactive membrane vesicles. The radioactivity in lysoPtdSer was also reduced. These results confirm that induction of apoptosis involves a modification of PtdSer metabolism and point out the typical features of the GBS-induced apoptosis with respect to other models of apoptosis.     

Three decades of research in bacterial photosynthesis and the road leading to it: A personal account

In this minireview I present a very personal account of my life and research in bacterial photosynthesis. It is divided into two parts. The first part is autobiographical and narrates the events that led me to change fields from electrical engineering to physics and ultimately to biophysics. The second part describes the work on the primary processes in bacterial photosynthesis carried out with numerous collaborators in our laboratory over the past 30 years.     

The solution structure of a gallium-substituted putidaredoxin mutant: GaPdx C85S

The Fe₂S₂ cluster of the ferredoxin putidaredoxin (Pdx) can be replaced by a single gallium ion, giving rise to a colorless, diamagnetic protein in which, apart from the metal binding site, the major structural features of the native ferredoxin are conserved. The solution structure of the C85S variant of gallium putidaredoxin (C85S GaPdx), in which a non-ligand cysteine is replaced by a serine, has been determined via multidimensional NMR methods using uniformly ¹⁵N,¹³C labeled samples of C85S GaPdx. Stereospecific assignments of leucine and valine methyl resonances were made using ¹³C,¹H HSQC spectra obtained with fractionally ¹³C-labeled samples, and backbone dihedral angle restraints were obtained using a combination of two-dimensional J-modulated ¹⁵N,¹H HSQC and three-dimensional (HN)CO(CO)NH experiments. A total of 1117 NOE-derived distance restraints were used in the calculations, including 454 short range ($i - j 3$), 456 long range (i - j 4) interresidue restraints and 207 non-trivial intraresidue restraints. 97 and 55 ₁ angular restraints were also included in the calculation of a family of 20 structures using a combined distance geometry-simulated annealing protocol. Most regions of the protein are well defined in the calculations, with an RMSD of 0.525 Å for backbone atoms excluding the metal binding loop (residues 34–48) and the last three C-terminal residues (residues 103–106). Where comparison is possible, these regions show an increase in dynamic behavior over the native protein, as does the loop containing residues 74–76. Structural and dynamic differences between native Pdx and GaPdx are discussed in relation to charge and packing of the metal binding site.     

Molecules and cognition: The latterday lessons of levels,language, and iac. Evolutionary overview of brain structure and function in some vertebrates and invertebrates

The characteristics of the nervous systems of a number of organisms in different phyla are examined at the recombinant DNA, protein, neuroanatomic, neurophysiological, and cognitive levels. Among the invertebrates, special attention is paid to the advantages as well as the shortcomings of the fly Drosophila melanogaster, the worm Caenorhabditis elegans, the honey bee Apis mellifera, the sea hare Aplysia californica, the octopus Octopus vulgaris, and the squid Loligo pealei. Among vertebrates, the focus is on Homo sapiens, the mouse Mus musculus, the rat Rattus norvegicus, the cat Felis catus, the macaque monkey Macaca fascicularis, the barn owl Tyto alba, and the zebrafish Brachydanio rerio. Vertebrate nervous systems have also been compared in fossil vs. extant organism. I conclude that complex nervous systems arose in the Early Cambrian via a big bang that was underpinned by a modular method of construction involving massive pleiotropy of gene circuits. This rapidity of construction had enormous implications for the degrees of freedom that were subsequently available to evolving nervous systems. I also conclude that at the level of neuronal populations and interactions of neuropiles there is no model system between phyla except at the basic macromolecular level. Further, I argue that to achieve a significant understanding of the functions of extant nervous systems we need to concentrate on fewer organisms in greater depth and manipulate genomes via transgenic technologies to understand the behavioral outputs that are possible from an organism. Finally, I analyze the concepts of “perceptual categorization” and “information processing” and the difficulties involved in the extrapolation of computer analogies to sophisticated nervous systems. © 1993 John Wiley & Sons, Inc.