Isoetin and its derivatives: Analytics,chemosystematics, and bioactivities

Isoetin, 5,7,2′,4′,5′-pentahydroxyflavone, is a rare, structurally simple natural product belonging to the flavone sub-group of flavonoids. The first reports on naturally occurring isoetin derivatives were published in the 1970s though methoxy-derivatives with the same substitution pattern had already been synthesized a decade earlier. A glucoside of isoetin was first discovered in the genus Isoetes (Lycopodiopsida). In the forty years following the discovery of the new naturally occurring flavonoid aglycone, only a limited number of reports on isoetin and its derivatives have been published. Simple, i.e. non-methyl-ether derivatives of isoetin have been found in the Isoetaceae, Asteraceae, Ranunculaceae, Rosaceae, and Rubiaceae families; while methyl ethers and their derivatives have been found in the Lycopodiaceae, Asteraceae, Cucurbitaceae, Fabaceae, and Pedaliaceae. A total of 14 non-methyl-ether-derivatives (including isoetin) and the same number of methyl ether derivatives have been described, some methyl derivatives only as synthetic compounds, others even only as virtual compounds generated for in silico studies. The published NMR data of isoetin and its derivatives as well as chemosystematic studies using isoetin derivatives as markers are compiled and critically assessed. Moreover, the papers dealing with bioactivities of isoetin and its derivatives are summarized.     

Boron,Chromium, Manganese,and Nickel in Agricultural Animal Production

This paper provides an overview of research that has been conducted with manganese (Mn), chromium (Cr), nickel (Ni), and boron (B) in poultry, swine, and ruminants. Manganese is an essential trace mineral that functions as an enzyme component and enzyme activator. A deficiency of Mn results in a variety of bone abnormalities, and Mn deficiency signs have been observed under practical conditions in poultry and cattle. Chromium can potentiate the action of insulin, but whether Cr is an essential trace mineral is controversial. Insulin sensitivity has been enhanced by Cr in cattle, swine, and broilers. Responses to Cr supplementation have been variable. Production responses to Cr supplementation have been most consistent in animals exposed to various stressors (heat, cold, weaning, etc). The legality of supplementing Cr to animal diets varies among countries, Cr sources, and animal species. A specific biochemical function for Ni and B has not been identified in mammals. Signs of Ni deficiency have been produced experimentally in a number of animal species. Nickel may affect rumen microbial fermentation in ruminants, as Ni is a component of bacterial urease and cofactor F₄₃₀ in methanogenic bacteria. There is little evidence that dietary Ni limits animal production under practical conditions. Beneficial effects of B supplementation on growth and bone strength have been seen in poultry and swine, but results have been variable.

     

Vitiligo,Psoralen, and Melanogenesis: Some Observations and Understanding

Since the etiology of vitiligo is still unknown, we searched for some abnormal biochemical parameters, if any, in subjects with vitiligo. Higher urinary excretion of indole metabolites in vitiliginous patients have been noted, in association with higher dioxygenase, superoxide dismutase, and tyrosine aminotransferase activity in their serum. Similar results have also been found in an animal model, Bufo melanostictus, during induced tyrosinase inhibition. Treatment with psoralen can reverse the parameters, except tyrosine aminotransferase, to a normal level. Although psoralens are not the magic bullet for the therapy of vitiligo, they are still being used as a chemotherapeutic agent against vitiligo on a major scale to date. Tryptophan was found to participate in the pathway of melanogenesis, as a precursor as well as a positive regulator of tyrosinase. Its behavior in this regard is much more similar to the conventional substrates tyrosine and dopa (dihydroxyphenylalanine). In consideration of combined participation of tyrosine and tryptophan in the synthesis of melanin and its breakdown, the possible influence of different enzymatic reactions, like mono-oxygenase, dioxygenase, and deamination, has been suggested.     

Synthesis,spectroscopic, and antibacterial activity of tetraazamacrocyclic complexes of trivalent chromium,manganese, and iron

A new series of macrocyclic complexes of type [M(TML)X]X₂, where M = Cr(III), Mn(III), or Fe(III), TML is tetradentate macrocyclic ligand, and X = Cl^?, NO₃^?, CH₃COO^? for Cr(III), Fe(III) and X = CH₃COO^? for Mn (III), has been synthesized by condensation of benzil and succinyldihydrazide in the presence of metal salt. The complexes have been so formulated due to the 1:2 electrolytic nature of these complexes as shown by conductivity measurements. The complexes have been characterized with the help of various physicochemical techniques such as elemental analysis, molar conductance, electronic and infrared spectral studies, and magnetic susceptibility. On the basis of these studies, a five-coordinate distorted square pyramidal geometry, in which two nitrogens and two carbonyl oxygen atoms are suitably placed for coordination toward the metal ion, has been proposed for all the complexes. The complexes have been tested for their in vitro antibacterial activity. Some of the complexes show remarkable antibacterial activities against some selected bacterial strains. The minimum inhibitory concentrations shown by these complexes have been compared with those shown by some standard antibiotics such as linezolid and cefaclor.     

Cloning, expression, purification, and characterization of Leishmania major dihydroorotate dehydrogenase

Leishmania major Friedlin (LmjF) is a protozoan parasite whose genomic sequence has been recently elucidated. Here we have cloned, overexpressed, purified, and characterized the product of the gene from LmjF chromosome 16: LmjF16.0530, which encodes a protein with putative dihydroorotate dehydrogenase activity. Dihydroorotate dehydrogenase (DHODH) is a flavoprotein that catalyses the oxidation of L-dihydroorotate to orotate, the fourth sequential step in the de novo pyrimidine nucleotide synthesis pathway. The predicted enzyme from L. major was cloned and expressed in Escherichia coli strain BL21(DE3) as a histidine-tag fusion protein and purified to homogeneity using affinity chromatography. The final product was homogeneous in SDS-PAGE gel electrophoresis. The dihydroorotate oxidase activity has been assayed and the steady-state kinetic mechanism has been determined using fumarate as the oxidizing substrate. The catalysis by LmDHODH enzyme proceeds by a Ping-Pong Bi-Bi mechanism and the kinetic parameters Km were calculated to be 90 and 418 microM for dihydroorotate and fumarate, respectively, and Vmax was calculated to be 11 micromol min-1 mg-1. Our results confirmed that the product of the gene LmjF16.0530, whose function has previously been predicted based on homology to known proteins, can therefore be positively assigned as L. major DHODH.     

Hopi Indians, "cultural" selection,and albinism

The incidence of albinism in Hopi Indians has been estimated as approximately 1 in 200 individuals. It has been suggested that "cultural" selection as the result of a mating advantage of males with albinism has been important in the maintenance of this high incidence. To examine this hypothesis quantitatively, a model that includes male-mating advantage, mutation, and viability selection is analyzed. In order to play an important role in the maintenance of the high incidence of albinism, the necessary mating advantage of males with albinism appears unrealistically high. However, if the extent of viability selection against individuals with albinism is not as large as previously assumed, the necessary amount of mating advantage is not as high. Other related aspects are also discussed here, such as the type of albinism in Hopi Indians and its impact, the conditions for a polymorphism with male-mating advantage and viability selection, and the time necessary to change the incidence of albinism either by the relaxation or institution of male-mating advantage.     

Membrane microdomains, caveolae, and caveolar endocytosis of sphingolipids

Caveolae are flask-shape membrane invaginations of the plasma membrane that have been implicated in endocytosis, transcytosis, and cell signaling. Recent years have witnessed the resurgence of studies on caveolae because they have been found to be involved in the uptake of some membrane components such as glycosphingolipids and integrins, as well as viruses, bacteria, and bacterial toxins. Accumulating evidence shows that endocytosis mediated by caveolae requires unique structural and signaling machinery (caveolin-1, src kinase), which indicates that caveolar endocytosis occurs through a mechanism which is distinct from other forms of lipid microdomain-associated, clathrin-independent endocytosis. Furthermore, a balance of glycosphingolipids, cholesterol, and caveolin-1 has been shown to be important in regulating caveolae endocytosis.     

Antifungal peptides: Origin, activity, and therapeutic potential

Antifungal peptides have been identified in a wide range of life forms which include plants, mammals, and microorganisms. Their structures are as varied as their antifungal properties. Semisynthetic and fully synthetic analogs have been developed from a few of these natural peptides that are superior to the parent compound. A few of these peptides hold promise in combating fungal infections and have entered clinical trials.     

S-RNases and sexual incompatibility: structure, functions, and evolutionary perspectives

S-RNase-based gametophytic self-incompatibility appears to be the most phylogenetically widespread form of self-incompatibility found in the angiosperms, having been reported in the Solanaceae, Scrophulariaceae, and Rosaceae. This intraspecific breeding barrier is controlled by a single genetic locus termed S. Rejection of self-pollen has been shown to be mediated in the pistil by a highly polymorphic series of ribonucleases, but as yet the pollen component of this recognition system has not been identified. Here we review our present knowledge concerning the structure, functions, and evolution of S-RNases and the S-loci in which they reside. In addition we present two new phylogenetic analyses of S-RNases which suggest that (1). sequence variability between S-alleles is spread across the whole gene and is not as clustered as is generally believed and (2). there is evidence of recombination and/or diversifying selection in two distinct regions of S-RNases. The implications of these findings are discussed.     

Iron, infection, and neoplasia

In nearly all forms of life, the number and diversity of enzymes that contain iron or that depend on the presence of this metal for activity are impressive. Not surprisingly, chemical mechanisms have been evolved by many organisms that permit them to solubilize and acquire iron while at the same time depriving their competitors or their pathogens of this element. Proteins such as transferrin and lactoferrin that are employed by vertebrate hosts for iron transport and acquisition can, to some extent, withhold the metal from the siderophores of invading bacteria and fungi. Attempts also are made by animal hosts to withhold iron from protozoa and neoplastic cells. Unfortunately, pathogenic microorganisms have developed a variety of counter measures that are especially dangerous in hosts stressed by iron overload in specific fluids, tissues, or cells. In recent years, however, a number of possible methods and agents for strengthening iron-withholding defense have become apparent. Nearly 3,000 papers on various aspects of iron withholding are contained in the 18-year Medline Database and numerous reviews have been published since 1966. The present paper will focus on developments that have been reported within the past 2 1/2 years.     

Convergence, adaptation, and constraint

Convergent evolution of similar phenotypic features in similar environmental contexts has long been taken as evidence of adaptation. Nonetheless, recent conceptual and empirical developments in many fields have led to a proliferation of ideas about the relationship between convergence and adaptation. Despite criticism from some systematically minded biologists, I reaffirm that convergence in taxa occupying similar selective environments often is the result of natural selection. However, convergent evolution of a trait in a particular environment can occur for reasons other than selection on that trait in that environment, and species can respond to similar selective pressures by evolving nonconvergent adaptations. For these reasons, studies of convergence should be coupled with other methods-such as direct measurements of selection or investigations of the functional correlates of trait evolution-to test hypotheses of adaptation. The independent acquisition of similar phenotypes by the same genetic or developmental pathway has been suggested as evidence of constraints on adaptation, a view widely repeated as genomic studies have documented phenotypic convergence resulting from change in the same genes, sometimes even by the same mutation. Contrary to some claims, convergence by changes in the same genes is not necessarily evidence of constraint, but rather suggests hypotheses that can test the relative roles of constraint and selection in directing phenotypic evolution.     

Interleukin-1, characterization of the molecule, functional activity, and clinical implications.

Hematopoiesis is regulated by a number of growth factors, of which colony-stimulating factors (CSF) have been exclusively defined according to the cell type they grow in vitro in colony assays. A number of cytokines, including interleukin-1 (IL-1), which have been characterized to exhibit multiple activities, are also involved in the control of growth and differentiation of hematopoietic cells. Some CSFs and related cytokines have already been introduced into clinical evaluation. This review summarizes the current knowledge of the IL-1 molecules, their moleculargenetic, and protein features as well as their in vitro and in vivo actions which justify their development as therapeutic agents.     

The alphaviruses: gene expression, replication, and evolution.

The alphaviruses are a genus of 26 enveloped viruses that cause disease in humans and domestic animals. Mosquitoes or other hematophagous arthropods serve as vectors for these viruses. The complete sequences of the +/- 11.7-kb plus-strand RNA genomes of eight alphaviruses have been determined, and partial sequences are known for several others; this has made possible evolutionary comparisons between different alphaviruses as well as comparisons of this group of viruses with other animal and plant viruses. Full-length cDNA clones from which infectious RNA can be recovered have been constructed for four alphaviruses; these clones have facilitated many molecular genetic studies as well as the development of these viruses as expression vectors. From these and studies involving biochemical approaches, many details of the replication cycle of the alphaviruses are known. The interactions of the viruses with host cells and host organisms have been exclusively studied, and the molecular basis of virulence and recovery from viral infection have been addressed in a large number of recent papers. The structure of the viruses has been determined to about 2.5 nm, making them the best-characterized enveloped virus to date. Because of the wealth of data that has appeared, these viruses represent a well-characterized system that tell us much about the evolution of RNA viruses, their replication, and their interactions with their hosts. This review summarizes our current knowledge of this group of viruses.     

Plastid genome sequencing,comparative genomics,and phylogenomics:Current status and prospects

More than 190 plastid genomes have been completely sequenced during the past two decades due to advances in DNA sequencing technologies.Based on this unprecedented abundance of data,extensive genomic changes have been revealed in the plastid genomes.Inversion is the most common mechanism that leads to gene order changes.Several inversion events have been recognized as informative phylogenetic markers,such as a 30-kb inversion found in all living vascular plants minus lycopsids and two short inversions putat...     

Structure, composition, and assembly of basement membrane

Basement membranes are thin layers of matrix separating parenchymal cells from connective tissue. Their ultrastructure consists of a three-dimensional network of irregular, fuzzy strands referred to as "cords"; the cord thickness averages 3-4 nm. Immunostaining reveals that the cords are composed of at least five substances: collagen IV, laminin, heparan sulfate proteoglycan, entactin, and fibronectin. Collagen IV has been identified as a filament of variable thickness persisting after the other components have been removed by plasmin digestion or salt extraction. Heparan sulfate proteoglycan appears as sets of two parallel lines, referred to as "double tracks," which run at the surface of the cords. Laminin is detected in the cords as diffuse material within which thin wavy lines may be distinguished. The entactin and fibronectin present within the cords have not been identified as visible structures. The ability of laminin, heparan sulfate proteoglycan, fibronectin, and entactin to bind to collagen IV has been demonstrated by visualization with rotary shadowing and/or biochemical studies. Incubation of three of these substances-collagen IV, laminin (with small entactin contamination), and proteoglycan-at 35 degrees C for 1 hr resulted in a precipitate that was sectioned for electron microscopic examination and processed for gold immunolabeling for each of the three incubated substances. Three structures are present in the precipitate: 1) a lacework, exclusively composed of heparan sulfate proteoglycan in the form of two parallel lines, similar to double tracks; 2) semi-solid, irregular accumulations, composed of the three initial substances distributed on a cord network; and 3) convoluted sheets, which are also composed of the three initial substances distributed on a cord network but which, in addition, have the uniform appearance and thickness of the lamina densa of basement membrane. Hence these sheets are closely similar to the main component of authentic basement membranes.     

Cytokines, growth factors, and plastic surgery.

Numerous inflammatory cytokines and growth factors have been identified and are known to be essential for normal wound healing and host defense, and many have been implicated in disease states treated by plastic surgeons. Cytokines and growth factors are members of a large functional group of polypeptide regulatory molecules secreted by different cell lines. These peptides exert their influence through autocrine and paracrine fashions within sites of injury and repair. Although cytokines and growth factors are crucial in initiating, sustaining, and regulating the postinjury response, these same molecules have been implicated in impaired wound healing, abnormal scarring, and chronic cutaneous diseases. Therapeutic manipulation of inflammatory mediators in normal and impaired wounds has been performed, with mixed clinical results, but evolving strategies such as gene therapy, as well as further characterization of the cellular-mechanism cytokines and growth-factor triggers, will further add to our therapeutic options. This article discusses the current understanding of important cytokines and growth factors involved in the normal injury response and then addresses pathological states associated with an inappropriate expression of these mediators. Finally, a summary of various cytokine and growth factor-directed strategies being used in impaired wound healing states is presented.     

Melatonin receptors: current status, facts, and hypotheses

Great progress has been made in the identification of melatonin binding sites, commonly identified as melatonin receptors by many authors, in recent years. The bulk of these studies have investigated the sites using either autoradiographic and biochemical techniques with the majority of the experiments being done on the rat, Djungarian and Syrian hamster, and sheep, although human tissue has also been employed. Many of the studies have identified melatonin binding in the central nervous system with either tritium- or iodine-labelled ligands. The latter ligand seems to provide the most reproducible and consistent data. Of the central neural tissues examined, the suprachiasmatic nuclei are most frequently mentioned as a location for melatonin binding sites although binding seems to be widespread in the brain. The other tissue that has been prominently mentioned as a site for melatonin binding is the pars tuberalis of the anterior pituitary gland. There may be time-dependent variations in melatonin binding densities in both neural and pituitary gland tissue. Very few attempts have been made to identify melatonin binding outside of the central nervous system despite the widespread actions of melatonin. Preliminary experiments have been carried out on the intracellular second messengers which mediate the actions of melatonin.     

Carotenoid metabolism: biosynthesis, regulation, and beyond

Carotenoids are Indispensable to plants and play a critical role in human nutrition and health. Significant progress has been made in our understanding of carotenoid metabolism in plants. The biosynthetic pathway has been extensively studied.Nearly all the genes encoding the biosynthetic enzymes have been isolated and characterized from various organisms. In recent years, there is an increasing body of work on the signaling pathways and plastid development, which might provide global control of carotenoid biosynthesis and accumulation. Herein, we will highlight recent progress on the biosynthesis,regulation, and metabolic engineering of carotenoids in plants, as well as the future research towards elucidating the regulatory mechanisms and metabolic network that control carotenoid metabolism.     

Isolation,assay, biosynthesis,metabolism, uptake and translocation,and function of proline in plant cells and tissues

The amino acid L-proline has been the subject of intensive research during the past ten to fifteen years. This stems from the observations that it incorporates into peptide linkage thereby serving as a precursor to peptidyl-bound L-hydroxyproline, a constituent of “extensin,” and that it accumulates when some plants are exposed to diverse biological and environmental stresses. The contents of selected papers which have been published during the last quarter of a century regarding the isolation, assay, biosynthesis, metabolism, transport and function of L-proline within various plant tissues and their cells are both interpreted and summarized in this review. Occasionally, relevant information from animal and bacterial systems concerning these topics is included. Hydroxyproline-containing proteins are not considered. L-proline was reported to be a constituent of leaves as early as the 1950’s. Since then, it and its analogues have been extracted from the organs of a variety of plants. The analogues include: methyl-hydroxylproline; 4-methylene-DL-proline; L-azetidine-2-carboxylic acid; 2,3,cis-3,4-trans-dihydroxy-L-proline; L-pipecolic acid and 4-trans-hydroxypro-line. L-proline can be both detected and quantified by colorimetric, combined fluorometric-amino acid analyzer and gas Chromatographic procedures. L-proline may be synthesized from L-glutamic acid via the following biosynthetic pathway: L-glutamic acid \(\underrightarrow {\gamma - glutamic acid kinase}\) γ-glutamyl phosphate \(\underrightarrow {\gamma - glutamyl phosphate reductase}\) γ-glutamyl semialdehyde \(\underrightarrow {spontaneous cyclization}\) Δ′-pyrroline-5-Carboxylate (P5C) \(\underrightarrow {P5C reductase}\) L-proline. Proline can also originate from L-arginine and L-ornithine. Biosynthesis from the latter compound proceeds either through the γ-glutamyl semialdehyde and pyrroline-5-carboxylate pathway or alternatively a α-keto-δ-aminovaleric and pyrroline-2-carboxylate pathway. The metabolism of L-proline most likely involves the reverse of the biosynthetic pathway with an initial prolyl dehydrogenaseor prolyl oxidasemediated conversion of L-proline to Δ′-pyrroline-5-carboxylate. The metabolism of L-proline has been demonstrated to occur in excised tissues and cell free extracts, cell suspension cultures and reproductive structures. Little is known about the mechanism by which L-proline is taken up by cultured plant cells and excised tissues. Once within the plant Lproline can be translocated through the phloem at velocities similar to those for carbon dioxide assimilates. In addition to serving as a substrate for peptidyl-bound hydroxyproline, L-proline may function as an adaptation to diverse biological and environmental stresses, a cryoprotectant, a nitrogen pool, a precursor for chlorophyll synthesis upon relief of stress, a regulator together with L-histidine of fertility and sterility and/or a substrate for respiration.     

Reactive oxygen species, cell signaling, and cell injury

Oxidative stress has traditionally been viewed as a stochastic process of cell damage resulting from aerobic metabolism, and antioxidants have been viewed simply as free radical scavengers. Only recently has it been recognized that reactive oxygen species (ROS) are widely used as second messengers to propagate proinflammatory or growth-stimulatory signals. With this knowledge has come the corollary realization that oxidative stress and chronic inflammation are related, perhaps inseparable phenomena. New pharmacological strategies aimed at supplementing antioxidant defense systems while antagonizing redox-sensitive signal transduction may allow improved clinical management of chronic inflammatory or degenerative conditions, including Alzheimer's disease. Introduction of antioxidant therapies into mainstream medicine is possible and promising, but will require significant advances in basic cell biology, pharmacology, and clinical bioanalysis.