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At least 865 records · Page 48Linked to original sources
PubMed1993

Post-translational modifications of the Dictyostelium discoideum glycoprotein PsA. Glycosylphosphatidylinositol membrane anchor and composition of O-linked oligosaccharides.

Prespore-specific antigen (PsA) is a cell-surface glycoprotein isolated from Dictyostelium discoideum, which is post-translationally modified by addition of carbohydrate to threonine residues of the carboxy-terminal peptide domain, and a glycosylphosphatidylinositol (GPI) anchor which attaches the glycoprotein to the cell membrane. The GPI anchor was isolated by proteolytic cleavage of the protein, and the structure of the lipid and glycan portions of the anchor were determined. The lipid moiety of the anchor is an inositolphosphoceramide which contains C18:0 phytosphingosine as a long chain base, and a mixture of fatty acids with a C18:1 mono-unsaturated fatty acid as the major component. The purified GPI anchor was susceptible to digestion by a bacterial phosphatidylinositol-specific phospholipase-C enzyme. The glycan of the GPI anchor consisted of two molecular species present in the ratio 55:45, the structures of which were determined by exoglycosidase sequencing and found to be Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcNH2 and Man alpha 1-2Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcNH2. The glucosamine in both structures is glycosidically linked to the inositol ring of the inositolphosphoceramide. The GPI glycan structures are consistent with the conserved core structure of all characterised GPI anchors, and the structure of the D. discoideum GPI moiety has features in common with structures from yeast, protozoa and higher eukaryotes. Compositional analysis of the carbohydrate attached to threonine residues in the carboxy-terminal peptide domain is also presented. The oligosaccharides bind to wheat germ agglutinin, and contain glucosamine and fucose as the major constituents.

Amino Acid Sequence↗
PubMed1989

Identification of four nuclear transport signal-binding proteins that interact with diverse transport signals.

The transport of proteins into the nucleus requires not only the presence of a nuclear transport signal on the targeted protein but also the signal recognition proteins and the nuclear pore translocation apparatus. Complicating the search for the signal recognition proteins is the fact that the nuclear transport signals identified share little obvious homology. In this study, synthetic peptides homologous to the nuclear transport signals from the simian virus 40 large T antigen, Xenopus oocyte nucleoplasmin, adenovirus E1A, and Saccharomyces cerevisiae MAT alpha 2 proteins were coupled to a UV-photoactivable cross-linker and iodinated for use in an in vitro cross-linking reaction with cellular lysates. Four proteins, p140, p100, p70, and p55, which specifically interacted with the nuclear transport signal peptides were identified. Unique patterns of reactivity were observed with closely related pairs of nuclear transport signal peptides. Competition experiments with labeled and unlabeled peptides demonstrated that heterologous signals were able to bind the same protein and suggested that diverse signals use a common transport pathway. The subcellular distribution of the four nuclear transport signal-binding proteins suggested that nuclear transport involves both cytoplasmic and nuclear receptors. The four proteins were not bound by wheat germ agglutinin and were not associated tightly with the nuclear pore complex.

Adenovirus Early Proteins↗
PubMed1980

Interaction of lectins with Neisseria gonorrhoeae.

Fifty-four strains of Neisseria gonorrhoeae were examined for their ability to be agglutinated by various lectins. Wheat germ agglutinin, ricin, soybean lectin, and peanut agglutinin agglutinated all strains tested. Dolichos biflorus, Sophora japonica, Maclura pomifera, Ulex Europaeus, Lens culinaris, Canavalia ensiformis, Phaseolus lunatus, and Bandeiraea simplicifolia BS I and BS II lectins either failed to agglutinate or agglutinated some strains but not others. Agglutination of gonococci by wheat germ agglutinin, ricin, and soybean lectin is sugar specific and most effectively inhibited by ligands known to interact with lectin combining sites. Lectin reactive groupings appear to be independent of antigenic determinants conferring Gc serogroup specificity. Interactions with wheat germ agglutinin and ricin suggest the occurrence of multiple beta-linked N-acetyl-D-glucosamine (D-GlcNAc) and beta-D-galactosyl (beta-D-Gal) units as common structural features of gonococcal cell envelope polysaccharide. Interactions with soybean agglutinin, peanut agglutinin, and Dolichos biflorus lectins suggest that alpha-N-acetyl-D-galactosamine (alpha-D-GalNAc) units and beta-D-Gal linked to GalNAc and (or) GlcNAc may also occur as structural features of the polysaccharide components of the cell envelope of some gonococci.

Agglutination↗
PubMed1995

Afferent projections to the ventromedial hypothalamic nucleus in a lizard, Gekko gecko.

Afferent projections to the ventromedial hypothalamic nucleus (VMH) of a lizard, Gekko gecko, were studied with wheat germ agglutinin conjugated to horseradish peroxidase. Results indicated that the shell and core areas of the VMH are largely innervated by different telencephalic nuclei but similar brain-stem nuclei. The common brainstem projections include the superior raphe, two isthmal populations (the ventral isthmal nucleus and parvocellular isthmal nucleus), and a dorsal thalamic projection from the posteroventral nucleus. Brainstem projections to the shell but not to the core of the VMH arise from the laterodorsal tegmental nucleus. Telencephalic projections to the VMH core originate from the ventrolateral septum, centromedial DVR, lateral amygdala, medial amygdala, interstitial amygdala, and ventral anterior amygdala. Telencephalic projections to the VMH shell come from the ventral pallidum, the anterior septal nucleus, the dorsal septal nucleus, the striatoamygdalar area, and the ventral posterior amygdala. These results, combined with connectional and topological information from other studies in amphibians, reptiles, and mammals, will be used to suggest homologies between a number of limbic areas, including several amygdalar nuclei.

Afferent Pathways↗
PubMed1984

Characterization and Complexity of Wheat Developing Endosperm mRNAs.

Free and membrane-bound (MB) polysomes and the corresponding polyadenylated RNAs (polyA(+) RNAs) have been isolated from developing wheat endosperm (Triticum aestivum L.) Free and MB poly(A)(+) RNAs, analyzed on isokinetic sucrose gradient with [(3)H]polyuridylic acid [poly(U)] hybridization detection, appear to be 11S to 12S in size with a 7% poly(A) tail for MB RNAs. cDNAs synthesized using both of these mRNA populations in presence of a potent RNase inhibitor (RNasin), have been used for hybridization kinetics experiments. The mean square fitting analysis of the hybridization kinetics between MB cDNA and its template reveals the presence of two abundance classes representing roughly (2/3) and (1/3) of the MB poly(A)(+) RNAs and containing the information for approximately 75 superabundant species (21,000 copies per cell) and 750 intermediate species (530 copies per cell), respectively. The mRNA population extracted from free polysomes is divided into three abundance classes. The first one is composed of superabundant sequences which would correspond to the MB superabundant mRNAs. The free mRNAs consist of about 11,000 diverse sequences, most of them being rare sequences. Heterologous hybridizations of MB cDNAs to free mRNAs have shown that some mRNAs are common to both populations. This could be explained either by a partial contamination or by free polysomes en route to their membrane destination. Contrary to the low number of diverse mRNAs corresponding to the legume seed storage proteins, the wheat endosperm superabundant mRNAs consist of about 75 different sequences which would encode most of the seed storage proteins, especially gliadins.

Journal Article↗
PubMed1988

Thalamic branched and unbranched axons to feline polysensory cortex.

Thalamic afferents to polysensory neocortex of the suprasylvian, anterior lateral, and pericruciate gyri were demonstrated by retrograde axonal transport of wheat germ agglutinin lectin-bound horseradish peroxidase (HRP) and nuclear yellow (NY). Marker injections were placed in areas identified as responsive to auditory stimuli through the use of click-evoked potentials. Both HRP and NY labeled neurons were found in close proximity or in overlapping regions of the rostral intralaminar nuclei and the adjacent ventral lateral nucleus of the thalamus. While thalamic neurons projecting to different polysensory neocortical areas were often in overlapping fields, double labeling was rare. These results indicate that similar auditory responses seen in different cortical polysensory areas are mediated by mainly separate but topographically related populations of thalamocortical neurons. Similarities in auditory response patterns seen across widely separated areas of polysensory neocortex may be due to common inputs relayed through overlapping or adjacent areas of the thalamus.

Animals↗
PubMedDate not supplied

Determination of niacin in infant formula and wheat flour by anion-exchange liquid chromatography with solid-phase extraction cleanup.

Niacin content must be included on food labels of infant formula products and bakery products containing enriched flour. Liquid chromatographic (LC) determination of niacin in complex food matrixes is complicated by the presence of endogenous compounds that absorb at the commonly used wave-length of 260 nm. Also, the presence of particulate matter in the standard sulfuric acid extraction procedure results in reduced life of LC columns and precolumns. A simple, rapid, solid-phase extraction (SPE) procedure for separation and cleanup of niacin from a complex food matrix digest has been developed. By using a vacuum manifold with the SPE column system, multiple samples can be processed quickly and efficiently for LC analysis, compared with gravimetric column cleanup. Sulfuric acid sample digest is passed over an aromatic sulfonic acid cation-exchange (ArSCX-SPE) or a sulfonated Florisil SPE column. Niacin is eluted with 0.25M sodium acetate-acetic acid, pH 5.6 buffer in vacuo. LC chromatograms of the resulting eluate are free of interference from other components absorbing at 260 nm at the retention time of niacin. Validation of the method was obtained from agreement of analytical results on available reference materials. For both SPE methods, values for niacin in SRM 1846 Infant Formula (milk-based powder) were within uncertainty ranges of the certified value. Use of several calibration procedures (the LC computer program, a peak area response graphic standard curve, or the method of standard additions) with both SPE procedures resulted in niacin values for 3 RM-Wheat Flours (not certified for niacin) in agreement (90-105%) with their respective values reported in the literature. Several commercial wheat flours showed a broad 260 nm interference, resulting in high niacin values. Niacin recoveries from spiked soy-based liquid infant formulas ranged from 95-107% with the ArSCX-SPE column. Calibration curves of niacin were linear up to 400 micrograms/mL, with a detection limit of 0.2 microgram/mL.

Chromatography, Ion Exchange↗
PubMed2002

Cortical synaptic arrangements of the third visual pathway in three primate species: Macaca mulatta, Saimiri sciureus, and Aotus trivirgatus.

The koniocellular (K) pathway is one of three pathways from the lateral geniculate nucleus (LGN) to primate visual cortex (V1). K pathway projections to the cytochrome oxidase (CO) blobs of V1 suggest involvement in chromatic processing given reports that the CO blobs in diurnal primates contain cells selective for color. K LGN layers and CO blobs, however, are also well developed in nocturnal primates such as owl monkeys, which are likely to be color blind. Thus, the K pathway plays either different roles in different species or some as yet unidentified common role(s). Because synaptic arrangements underlie functional mechanisms, the purpose of this investigation was to compare the synaptic circuitry related to the K pathway within the CO blobs of two diurnal primates (macaque monkeys and squirrel monkeys) and one nocturnal primate (owl monkey). Presynaptic K axons were labeled with wheat germ agglutinin-HRP, and presynaptic and postsynaptic profiles in CO blobs were identified with post-embedding immunocytochemistry for GABA and glutamate. In all three species, K axon terminals are glutamatergic and larger than local axon terminals, suggesting that they have a greater impact on postsynaptic CO blob targets than signals arriving via layer IV from the P or M pathways. A greater proportion of K axons, however, synapse with larger glutamatergic shafts in the diurnal monkeys than in the nocturnal owl monkey, perhaps reflecting the importance of color within the K pathway of these diurnal species. Alternatively, the loss of color vision in the owl monkey could impact K pathway circuitry earlier in the pathway. The basic similarities between K axon circuitry within the CO blobs of the three primate species examined also could indicate that this pathway plays some common role or roles across species.

Animals↗
PubMed1989

Sequence variability in three wheat germ agglutinin isolectins: products of multiple genes in polyploid wheat.

Three highly homologous wheat germ isolectins (95-97%) are distinct gene products in hexaploid wheat. The amino acid sequences of two of these [wheat germ agglutinin 1 (WGA1) and 2 (WGA2)] are compared with sequence data derived from a complementary DNA (cDNA) clone for the third isolectin (WGA3). This comparison includes three corrections to earlier amino acid sequence data of both WGA1 and WGA2 at positions 109 (from Ser to Phe), 134 (from Gly to Lys), and 150 (from Gly to Trp). These reassignments are based on new results from crystal structure refinement and amino acid sequence data of WGA1, as well as the recently determined nucleotide sequence of WGA3. In addition, the C-terminal residue of WGA1 has been revised to Gly171 and now differs from WGA2 (Ala171). Four other positions, Asn9, Ala53, Gly119, and Ser123, at which WGA1 and WGA2 are identical but differ from the DNA sequence of WGA3, were also reinvestigated by amino acid sequencing techniques and confirmed. Variability among the three isolectins is observed at a total of 10 sequence positions: 9, 53, 56, 59, 66, 93, 109, 119, 123, and 171. Pairwise comparisons indicate that WGA3 deviates to a much larger extent from WGA1 (at eight positions) and from WGA2 (at seven positions) than the latter from one another (at five positions). Eight of the 10 mutations are equally distributed between domains B and C, the two interior and more highly conserved of the four WGA domains (A, B, C, D). Correlation of the variable residues with the three-dimensional structure indicates that all except the two previously described B-domain residues, 56 and 59 (Wright and Olafsdottir 1986), are easily accommodated at the dimer surface. WGA3 displays a higher degree of inter-domain similarity than found in WGA1 and WGA2. Of the seven variable positions that are located in the domain core (residues 3-31), five are in perfect agreement with our earlier predicted domain ancestor sequence. This suggests that of the three isolectins WGA3 is most closely related to the common ancestral molecule.

Amino Acid Sequence↗
PubMed1997

Plasmon analyses of Triticum (wheat) and Aegilops: PCR-single-strand conformational polymorphism (PCR-SSCP) analyses of organellar DNAs.

To investigate phylogenetic relationships among plasmons in Triticum and Aegilops, PCR-single-strand conformational polymorphism (PCR-SSCP) analyses were made of 14.0-kb chloroplast (ct) and 13. 7-kb mitochondrial (mt)DNA regions that were isolated from 46 alloplasmic wheat lines and one euplasmic line. These plasmons represent 31 species of the two genera. The ct and mtDNA regions included 10 and 9 structural genes, respectively. A total of 177 bands were detected, of which 40.6% were variable. The proportion of variable bands in ctDNA (51.1%) was higher than that of mtDNA (28. 9%). The phylogenetic trees of plasmons, derived by two different models, indicate a common picture of plasmon divergence in the two genera and suggest three major groups of plasmons (Einkorn, Triticum, and Aegilops). Because of uniparental plasmon transmission, the maternal parents of all but one polyploid species were identified. Only one Aegilops species, Ae. speltoides, was included in the Triticum group, suggesting that this species is the plasmon and B and G genome donor of all polyploid wheats. ctDNA variations were more intimately correlated with vegetative characters, whereas mtDNA variations were more closely correlated with reproductive characters. Plasmon divergence among the diploids of the two genera largely paralleled genome divergence. The relative times of origin of the polyploid species were inferred from genetic distances from their putative maternal parents.

Journal Article↗
PubMedDate not supplied

Numerous small rearrangements of gene content, order and orientation differentiate grass genomes.

Comparative genetic mapping has indicated that the grass family (Poaceae) exhibits extensive chromosomal collinearity. In order to investigate microcollinearity in these genomes, several laboratories have begun to undertake comparative DNA sequence analyses of orthologous chromosome segments from various grass species. Five different regions have now been investigated in detail, with four regions sequenced for maize, rice and sorghum, plus two for wheat and one for barley. In all five of these segments, gene rearrangements were observed in at least one of the comparisons. Most of the detected rearrangements are small, involving the inversion, duplication, translocation or deletion of DNA segments that contain only 1-3 genes. Even closely related species, like barley and wheat or maize and sorghum, exhibit approximately 20% alterations in gene content or orientation. These results indicate that thousands of small genetic rearrangements have occurred in several grass lineages since their divergence from common ancestors. These rearrangements have largely been missed by genetic mapping and will both complicate and enrich the use of comparative genetics in the grasses.

Alcohol Dehydrogenase↗
PubMed1978

Messenger RNA is conserved during drying of the drought-tolerant moss Tortula ruralis.

On rehydration after complete drying, the drought-tolerant moss Tortula ruralis (Hedw.) Gaertn., Meyer, and Scherb reforms its polyribosomes and can resume protein synthesis without new RNA synthesis. Results obtained with the double-label ratio technique coupled with polyacrylamide disc gel electrophoresis show that (i) the proteins synthesized on rehydration are largely similar to those synthesized at the time of dehydration and (ii) inhibition of RNA synthesis does not alter the rate or the pattern of protein synthesis during rehydration of slowly dried moss. Poly(A)-rich RNA has been isolated from fresh and dried moss by chromatography on oligo(dT)-cellulose and has been translated in vitro in the cell-free wheat germ system. It is concluded that mRNA is conserved during complete drying of T. ruralis and supports protein synthesis on subsequent rehydration. This ability to conserve mRNA is a characteristic held in common by vegetative drought-tolerant tissue of T. ruralis and air-dried seeds of higher plants.

Journal Article↗
PubMed1989

The effect of complexing phosphoproteins to decalcified collagen on in vitro calcification.

Decalcified samples of chicken bone containing phosphoproteins of varying concentrations were used to assess the effect of phosphoproteins and of protein-bound Ser(P) and Thr(P) in the in vitro nucleation of a Ca-P solid phase from metastable solutions of Ca and P. Phosphoproteins of bone as well as the phosphoproteins from egg yolk (phosvitin) were used. Increasing concentrations of phosphoprotein [as measured by the amount of protein bound Ser(P) and Thr(P)] in the decalcified bone particles significantly reduced the time required for nucleation to occur after exposure to metastable solutions of Ca and P (decreased operational lag times). Treatment with wheat germ acid phosphatase markedly reduced the concentration of Ser(P) and Thr(P) in the decalcified bone samples and in the decalcified bone collagen samples complexed with phosphoproteins (almost to zero). The loss of the organic phosphate groups significantly increased the operational lag time, but did not abolish nucleation of apatite crystals by the bone collagen fibrils essentially devoid of Ser(P) and Thr(P). Bone phosphoproteins were not specific; substitution of phosvitin for bone phosphoproteins as complexes with bone collagen also proved to be effective facilitators of nucleation, which was interesting since both types of phosphoproteins have certain common chemical and structural characteristics. Noncollagenous components other than phosphoproteins were present in the decalcified bone samples. However, the marked dependence of the lag time on the Ser(P) and Thr(P) concentrations and the very marked diminution in the efficacy of the nucleation phenomenon as a result of treatment with wheat germ acid phosphatase, clearly suggests that the organic phosphate residues of the phosphoproteins play a direct and significant role in the process of in vitro nucleation of a solid phase of Ca and P (apatite) by bone collagen, and by implication, possibly in in vivo mineralization as well.

Acid Phosphatase↗
PubMed1994

The pontocerebellar projection: longitudinal zonal distribution of fibers from discrete regions of the pontine nuclei to vermal and parafloccular cortices in the rat.

A longitudinal parasagittal organization (alternating labeled and unlabeled stripes) of mossy fiber terminals in the paraflocculus and in the vermal lobule VII of the cerebellum was found after small injections (less than 50 nl) of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into discrete regions of the basilar pontine nuclei (BPN) of rats. Up to three stripes were found within the paraflocculus of both sides, following injections (of about 500 microns in diameter) in either the medial or lateral region of the caudal half of the BPN. Up to five stripes were found in the vermal lobule VII after similar size injections into the rostro-ventral region of the BPN. These results emphasize the possibility that the parasagittal zonal arrangement could be a common pattern of organization shared by climbing and mossy fiber afferents.

Animals↗
PubMed2003

Identification of dorsal root ganglion neurons that innervate the common bile duct of rats.

Pain originating in the bile duct is common and many patients who have suffered from it report that it is one of the most intense forms of pain that they have experienced. Many uncertainties remain about the mechanisms underlying pain originating in the bile duct. For example, the dorsal root ganglion (DRG) neurons that give rise to the sensory innervation of the common bile duct (CBD) have not been identified and examined in any species. The goal of the present study was to determine the number, distribution, and size of DRG neurons that innervate the CBD in rats. Injections of WGA-HRP or CTB-HRP were restricted to the lumen of the bile duct. Injections of WGA-HRP labeled a mean number of about 500 DRG neurons bilaterally throughout all thoracic and upper lumbar levels. Injections of CTB-HRP labeled smaller numbers of DRG neurons. Application of colchicine onto the surface of the CBD reduced the number of cells labeled following injections of WGA-HRP into the lumen of the CBD by roughly 86%, suggesting that tracer had not spread in large amounts out of the CBD and labeled afferent fibers in other tissues. Approximately 85% of the neurons labeled with WGA-HRP had cell bodies that were classified as small; the remainder were medium in size. Injections of CTB-HRP labeled cell bodies of varying sizes, including a few large diameter cell bodies. These results indicate that a large number of primarily small DRG cells, located bilaterally at many segmental levels, provide a rich innervation of the common bile duct.

Animals↗
PubMed1983

Iron fortification: an update.

Iron fortification is the optimal approach to reducing the high prevalence of iron deficiency in developing countries. Selection of the iron source entails a compromise between the use of inert compounds which are poorly absorbed and chemically reactive forms with high bioavailability. Although the vehicle and fortification compound must be chosen in tandem because most iron compounds cause discoloration or rancidity, the emphasis in this review is on the food vehicle. Technology for fortifying wheat flour and bread is well established and the use of these vehicles has probably had a significant impact on iron status in Western countries. Recent studies in India indicate that the fortification of common salt is technically feasible and field trials have shown a good hematological response. Similar success has been achieved by fortifying refined sugar with NaFeEDTA in Guatemala. Rice has advantages as a vehicle in those areas where it is the staple food but the technology requires further development. Fish-based condiments have been successfully fortified with NaFeEDTA and show promise as a vehicle in East Asian countries. The fortification of infant foods poses no technical problems and should be encouraged. Additional work is needed to identify other fortification options and to develop targeted fortification programs that will direct iron to those segments of a population in greatest need.

Anemia, Hypochromic↗
PubMed1988

Degree of starch gelatinization, digestion rate of starch in vitro, and metabolic response in rats.

Glycemic response after ingestion of starchy foods varies. Starch in many common ready-to-eat foods is only partly gelatinized. In view of this, the relationships among degree of starch gelatinization, in vitro digestion rate, and in vivo metabolic response in rats were studied. Wheat starch with different degrees of gelatinization was used in the experiments. Plasma glucose and insulin responses as well as the rate of in vitro hydrolysis with alpha-amylase were strongly correlated to the degree of starch gelatinization (r = 0.88, r = 0.90, and r = 0.96, respectively). Plasma glucose and insulin responses were also positively correlated to the rate of hydrolysis with alpha-amylase in vitro (r = 0.98 and r = 0.76, respectively). These results suggest that the degree of starch gelatinization is an important determinant both for the rate of starch hydrolysis in vitro and for the metabolic response in vivo.

Animals↗
PubMed1979

The specific, diverse effects of purine and pyrimidine nucleoside-5'-di(tri)-3'-diphosphates on the eucaryote translation system in vitro.

All the eight 5'-di(tri)-3'-diphosphates of four common ribonucleosides were prepared by the enzymic pyrophosphoryl transfer catalysed by Streptomyces adephospholyticus ATP:nucleotide pyrophosphokinase (E.C.2.7.6.4) form dATP to the respective 5'-phosphates, and their effects on the translation of mRNAs by a wheat germ system in vitro were studied. (p) ppPupp decreased the total 14C-leucine incorporation directed by a rat liver mRNA whereas (p) ppPypp did not. With a silkworm pupa ovary mRNA, distinctly reverase results were obtained. Gel electrophoretic profiles of the translation products disclosed the mRNA species-specific stimulatory or inhibitory effects for each of the polyphosphates tested.

Adenine Nucleotides↗