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R M Roberts

Publications and source records attributed to R M Roberts.

At least 235 records · Page 13Linked to original sources
PubMed1981

The Glycoproteins of Plant Seeds : ANALYSIS BY TWO-DIMENSIONAL POLYACRYLAMIDE GEL ELECTROPHORESIS AND BY THEIR LECTIN-BINDING PROPERTIES.

Protein from the jack bean, peanut, soybean and kidney bean seeds were extracted with a solution containing 9.3 molar urea, 5 millimolar K(2)CO(3), 0.5% dithiothreitol and 2% Nonidet P-40 and then subjected to two-dimensional gel electrophoresis. After electrophoresis, the slab gels were stained with a variety of (125)I-labeled lectins and the lectin-binding proteins were identified after autoradiography. Incubation of slab gels of jack bean with concanavalin A, peanut with peanut agglutinin, soybean with soybean agglutinin, and kidney bean with phytohemagglutinin showed that the majority of the polypeptides in each seed type were able to bind to their homologous lectins. Control slab gels in which incubations were carried out with identical amounts of proteins, (125)I-lectin and an appropriate sugar inhibitor showed little or no lectin binding to the polypeptides. Additionally, incubation of slab gels of peanut proteins with (125)I-ricin, (125)I-wheat germ agglutinin, (125)I-concanavalin A, and (125)I-soybean agglutinin each revealed a clearly distinct binding pattern compared to the one observed with the peanut agglutinin. The results demonstrate that a large number of legume seed polypeptides are glycoproteins and that the carbohydrate groups within a seed species are heterogeneous in structure, thus indicating the existence of complex glycosylating enzyme systems in legume seeds. It is suggested that the high degree of binding between seed proteins and their homologous lectins might have some functional significance in maintaining large aggregates of protein in compact, insoluble form.

Journal Article↗
PubMed1981

Progesterone-induced secretion of a retinol-binding protein in the pig uterus.

A retinol binding protein(s) of molecular weight about 17 000 has been demonstrated in uterine secretions from pigs in the luteal phase of the oestrous cycle. This protein was induced in ovariectomized sows treated with progesterone or progesterone plus oestradiol, but not in sows given oestradiol or corn oil. The vitamin A content of secretions from progesterone-treated animals also increased relative to those in controls. The apparent Kd of the binding protein for retinol was 2.6 X 10(-6) M. The protein had some affinity for retinoic acid and oleic acid, but did not bind retinyl esters of retinal. The protein probably comprises 5% or less of the total fraction of low molecular weight proteins induced by progesterone. A similar protein was found in allantoic fluid of pregnant animals, suggesting that, like uteroferrin, it serves to transport a water-insoluble nutrient from the maternal uterine endometrium to the conceptus.

Allantoin↗
PubMed1980

The novel "g' = 1.74" EPR spectrum of pink and purple uteroferrin.

Low temperature (T less than or equal to 20 K) EPR measurements have revealed the presence of a heretofore undetected signal in uteroferrin, a purple protein bearing a single iron atom per molecule. All three of its principal g values (1.923, 1.738, and 1.583) lie well below the free electron value of 2.0023. Magnetic susceptibility data from 2-77 K confirm that the novel EPR spectrum arises from a paramagnetic center with a single unpaired electron spin. Quantitative correlation of the EPR, susceptibility, and optical data point to chromophoric iron as the source of the rhombic EPR spectrum. Furthermore, close agreement between the concentration of iron and the integrated intensity of the rhombic EPR signal show that the iron in the paramagnetic center is mononuclear. Reduction of the protein to its pink form leaves the rhombic signal essentially unaltered. The previously reported g' = 4.3 EPR signal accounts for only a small fraction of the total iron in the protein and undoubtedly arises from adventitious iron. Collectively, these results strongly suggest that uteroferrin represents a new class of low spin iron proteins.

Acid Phosphatase↗
PubMed1980

Isolation of a domain of the plasma membrane in Chinese hamster ovary cells which contains iodinatable, acidic glycoproteins of high molecular weight.

A light vesicle fraction, apparently derived from the plasma membrane, was obtained following breakage of Chinese hamster ovary (CHO) cells by means of a fluid pump disrupting device. The final preparation was enriched approx. 40-fold over the homogenate in K+,Na+-stimulated ATPase and phosphodiesterase I, but only approx. 10-fold in 125I specific radioactivity after lactoperoxidase-catalyzed iodination. This preparation was compared with another plasma membrane fraction purified as large sheets via a two-phase centrifugation procedure. Two-dimensional polyacrylamide gel electrophoresis followed by Coomassie blue staining indicated that both fractions were fairly similar in polypeptide composition, although a few consistent differences were evident. However, staining of glycoproteins by the periodic acid-Schiff technique or by overlaying with 125I-labeled concanavalin A showed that the vesicle fraction was highly enriched in groups of high molecular weight, acidic glycoproteins which stain only weakly with Coomassie blue. These glycoproteins also bound 125I-labeled ricin I agglutinin and wheat germ agglutinin. They appear to be the major receptors for wheat germ agglutinin on the CHO cell surface. After surface labeling of cells by the 125I-lactoperoxidase technique, the membrane sheet fraction contained a large number of iodinated polypeptides, whereas labeling in the vesicle fraction was restricted almost entirely to the high molecular weight, acidic glycoproteins. It is proposed that the vesicle fraction constitutes a specific domain of the cell surface which is coated on its exterior by this group of glycoproteins. These components probably mask underlying proteins of the plasma membrane from external labeling.

Animals↗
PubMed1980

Intestinal and cardiopulmonary forms of parvovirus infection in a litter of pups.

Parvovirus infection caused signs of gastrointestinal illness in all pups in a litter of 12 and death in 6 of them when 12 to 19 days old. The remaining pups recovered from the gastrointestinal infection, but 5 of the 6 died before they were 9 1/2 weeks old, with signs of cardiopulmonary disease. Necropsy findings were cardiomegaly, myocarditis, pulmonary congestion, and interstitial pneumonia. The only surviving pup also had signs of cardiopulmonary disease but was apparently well at 18 months of age.

Animals↗
PubMed1980

Effect of the conceptus on quantitative and qualitative aspects of uterine secretion in pigs.

Endometrial explants were removed from uteri of animals pregnant and pseudopregnant (5 mg oestradiol valerate on Days 11--15) for 60 days, from the gravid and non-gravid horns of unilaterally pregnant pigs at Day 60 of pregnancy and fron non-pregnant animals at Day 12 of the oestrous cycle. The tissues were cultured in the presence of L-[34S]methionine for 24 h, and the tissues and medium were then analysed separately by two-dimensional polyacrylamide gel electrophoresis. Radioactive polypeptides were identified by autoradiography of dried gels. Tissues from all all except the cyclic animals released an identical group of polypeptides into the culture medium: the major radioactive products were 4 acidic polypeptides of low molecular weight and several basic proteins, which included the purple phosphatase uteroferrin, and lysozyme. In separate experiments explants from 3 unilaterally pregnant pigs were cultured with L-[3H]leucine, and, on a fresh weight basis, the tissue from the non-gravid horn released significantly less radioactive macromolecular material into the medium in 24 h than did tissue from gravid horns. It therefore appears that although the nature of the secretion produced by the pregnant uterus is a consequence of maternal hormonal regulation alone, the tissue underlying a conceptus is quantitatively more active than that from unoccupied regions of a uterus.

Acid Phosphatase↗
PubMed1979

Resonance Raman scattering from uteroferrin, the purple glycoprotein of the porcine uterus.

Uteroferrin, a purple-colored, iron-containing glycoprotein, purified from the uterine fluid of progesterone-stimulated pigs, owes its natural purple color to a broad absorption band centered at 545 nm. Laser excitation within the visible absorption band of uteroferrin results in an intense resonance Raman spectrum which bears a striking resemblance to that reported for Fe(III)-transferrin, the iron transport protein of serum. Excitation profiles for the four resonance-enhanced bands of uteroferrin were obtained from 4579 A to 6741 A, using lines from Ar+ and Kr+ lasers. Each of the profiles have maxima near 545 nm. The spectral similarities of uteroferrin and Fe(III)-transferrin lead to the belief that the Fe(III) binding sites of the two proteins must be, at least in some respects, quite similar. In particular, it is concluded that, as in Fe(III)-transferrin, the metal binding site of uteroferrin contains a tyrosine ligand and that the visible absorption spectrum of uteroferrin results from a phenolate to Fe(III) charge transfer.

Animals↗
PubMed1979

Actions of hormones on the uterus and effect on conceptus development.

The process of reproduction in the mammalian female involves interactions between gonadal and placental steroids and, possibly, protein hormones such as placental lactogen, and the uterine endometrium. These interactions are discussed relative to available data from pigs and with the understanding that the concepts presented may not be directly applicable to other species. Swine embryos enter the uterus for continued development beyond the early blastocyst stage and, within the uterus, the spherical blastocyst, of about 2 mm diameter on day 12, undergoes rapid elongation to an organism of about 1 m in length by day 15 of pregnancy. During this period of elongation, the blastocyst appears to provide the chemical signal, presumably unconjugated estrogens, that allows for corpora lutea (CL) maintenance (luteostatic effect) and, therefore, continued production of progesterone by the CL which is essential for pregnancy. Estrogens from the blastocyst may exert their luteostatic effect on the uterus by causing prostaglandin F2 alpha, the presumed porcine uterine luteolysin, to be secreted in an exocrine (toward the uterine lumen) rather than an endocrine (toward the endometrial stroma and vasculature) direction during pregnancy. Consequently, prostaglandin F2 alpha is sequestered in the uterine lumen and does not become available, via the utero-ovarian vasculature, to exert its luteolytic effect. The potential steroid precursor(s) available to the trophoblast for estrogen synthesis appear to be produced through endometrial conversion of progesterone to unconjugated androgens, e.g., androstenedione and testosterone, and conjugated estrogens, e.g., estrone-sulfate and estradiol-sulfate. The estrogens may, in concert with progesterone and possibly other hormones, placental lactogen for example, act locally, i.e., at the site of placentation to: result in a luteostatic effect; increase uterine blood flow; enhance water, electrolyte and substrate (carbohydrate and amino acid) transport to the site of placentation and across the placenta; affect synthesis and secretion of macro-molecules (histotroph) by the uterine glands that serve as enzymes and (or) carrier molecules and control or modulate physiological and (or) biochemical events essential to placental and fetal development that are not understood.

Animals↗