On the tertiary structure of the extracellular domains of the epidermal growth factor and insulin receptors

Alignment of the sequences, the identification of conserved residue patterns and secondary structure predictions indicate that the extra-cellular regions of the human and Drosophila epidermal growth factor (EGF), c-erb-B2 and human insulin receptors each contain two large, homologous domains (L) which are probably comprised of at least four short alpha-helices followed by turns of conserved length and beta-strands. In the human and Drosophila EGF and c-erb-B2 receptors these homologous domains are each followed by a series of smaller cystine-rich domains (S) to give a gene-duplicated structure of L1S11S12S13L2S21S22S23. In the human insulin receptor, the second series of cystine domains is replaced by a different sequence. These duplicated structures are probably organised as a pseudo-symmetrical dimer. There are two 'hyper-variable' regions, one at the end of the large domains and one in the cystine-rich sequences, which are candidates for hormone or growth-factor binding.     

Molecular defect in factor IXBm Lake Elsinore. Substitution of Ala390 by Val in the catalytic domain

Earlier studies with factor IXBm Lake Elsinore (IXBmLE), a nonfunctional variant of factor IX, suggested that the defect in this protein may reside in the catalytic domain of the molecule (Usharani, P., Warn-Cramer, B. J., Kasper, C. K., and Bajaj, S. P. (1985) J. Clin. Invest. 75, 76-83). In this report, genomic DNA fragments from normal IX and IXBmLE alleles were cloned into phage lambda EMBL3 and the recombinant phage identified using normal IX cDNA and synthetic oligonucleotides. Exons VI, VII, and VIII of normal IX and IXBmLE gene were also amplified using a newly developed primer-directed polymerase chain reaction method. All eight exons and flanking regions of the normal IX and IXBmLE gene were sequenced by the dideoxy chain termination method. Comparison of the normal IX and IXBmLE sequences revealed a single base substitution (C----T) in the exon VIII of the BmLE variant, which results in the replacement of Ala390 by Val in the variant molecule. Although this mutation is in the catalytic domain of the molecule, purified factor IXaBmLE is indistinguishable from normal IXa in its activity toward a small synthetic substrate, L-tosylarginine methyl ester. These data, coupled with the previous data, identify a region (around residue 390) in the normal factor IXa which appears to play a major role in the extended macromolecular substrate binding site.     

Functional groups and quaternary structure of chicken liver xanthine dehydrogenase

Xanthine dehydrogenase from chicken liver is a dimeric enzyme, each hemimolecule containing one FAD and two Fe/S groups. Determination of sulfhydryl groups with 5,5-dithiobis(2-nitrobenzoic acid) (DTNB) andp-hydroxymercuribenzoic acid (PMB) showed a variable number of sulfhydryl groups depending onpH, ionic strength, and nature of the reaction medium and buffer. The number of disulfide bonds was determined with DTNB and reducing conditions. Amino groups were determined with 2,4,6,-trinitrobencensulfonic acid (TNBS). At constant temperature andpH the reaction of DTNB and TNBS with native xanthine dehydrogenase showed an exponential dependence on time. From the obtained parameters the number of available sulfhydryl and amino groups at infinite concentration of enzyme and the rate constant of the equation were determined. The absorption spectrum of the enzyme changed with time when a chaotropic agent (1 M sodium nitrate) was added to the medium. This difference was detected by measuring the absorbance in the range 450–550 nm. The absorption spectrum (between 350 and 600 nm) also changed when a denaturating agent (sodium dodecyl sulfate) was added. This modification increased with time and depended on the medium.     

New and Known Species of Pratylenchus Filipjev, 1936 (Nematoda: Pratylenchidae) from Haryana,India, with Remarks on Intraspecific Variations

Two new monosexual and one bisexual species Pratylenchus Filipjev, 1936 collected from Haryana state of India are described and illustrated. The primary distinguishing features of these species are Pratylenchus microstylus n. sp.: L = 331-458 μm, spear = 11 or 12 μm; Pratylenchus cruciferus n. sp.: L = 648-793 μm, central core of lateral fields with oblique lines, hemizonid 2-8 annules anterior to excretory pore; Pratylenchus ekrami n. sp.: spear = 11-13 μm, spermatheca oblong, post vulval uterine sac with differentiated cells, tail with 26-40 annules, males abundant. Studies on intraspecific variations of P. cruciferus, P. ekrami, and P. coffeae (Zimmermann, 1898) Goodey, 1951 revealed that spear length and value of ''V'' are the least variable characters. Body length and size of post vulval uterine sac varies to varying degrees in different species. Shape of median bulb in P. ekrami, number of incisures in P. coffeae, and tail shape in P. ekrami and P. coffeae exhibit the greatest amount of intraspecific variations. P. zeae Graham, 1936 and P. thornei Sher & Allen, 1953 are the other species collected during the present studies.     

新城疫病毒单克隆抗体的特性及应用

建立了8个分泌抗新城疫病毒(NDV)特异性单克隆抗体(McAb)的杂交瘤细胞株,根据它们的免疫生物学特性可以分为三种类型:(1)具有FA和ELISA特性(FN1、FN4、FN29、FN30、FN35、FNl22);(2)具有FA、ELISA和HI特性(FN7);(3)具有ELISA、HI特性和中和能力(FN106),根据FN30和FN106的ELISA试验,可将11个NDV毒株分为二种不同的抗原群,应用FN4-FITC,FN7-FITC和FN29-HRP试剂,对人工感染NDV和野外送检病例检测结果表明,单抗试剂的DFA阳性率(92.3％)高于病毒分离阳性率(87.2％),两种方法的符合率89.7％,这些单抗试剂用于临床诊断敏感性和特异性高,且方法快速、简便。     

Coypu insulin. Primary structure, conformation and biological properties of a hystricomorph rodent insulin.

Insulin from a hystricomorph rodent, coypu (Myocaster coypus), was isolated and purified to near homogeneity. Like the other insulins that have been characterized in this Suborder of Rodentia, coypu insulin also exhibits a very low (3%) biological potency, relative to pig insulin, on lipogenesis in isolated rat fat-cells. The receptor-binding affinity is significantly higher (5-8%) in rat fat-cells, in rat liver plasma membranes and in pig liver cells, indicating that the efficacy of coypu insulin on receptors is about 2-fold lower than that of pig insulin. The primary structures of the oxidized A- and B-chains were determined, and our sequence analysis confirms a previous report [Smith (1972) Diabetes 21, Suppl. 2, 457-460] that the C-terminus of the A-chain is extended by a single residue (i.e. aspartate-A22), in contrast with most other insulin sequences, which terminate at residue A21. In spite of a large number of amino acid substitutions (relative to mammalian insulins), computer-graphics model-building studies suggest a similar spatial arrangement for coypu insulin to that for pig insulin. The substitution of the zinc-co-ordinating site (B10-His----Gln) along with various substitutions on the intermolecular surfaces involved in the formation of higher aggregates are consistent with the observation that this insulin is predominantly 'monomeric' in nature. The c.d. spectrum of coypu insulin is relatively similar to those of casiragua insulin and of bovine insulin at low concentration.     

Polyamine Accumulation and Near Loss of Morphogenesis in Long-Term Callus Cultures of Rice (Restoration of Plant Regeneration by Manipulation of Cellular Polyamine Levels)

We have shown (S. Bajaj and M.V. Rajam [1995] Plant Cell Rep 14: 717-720) that a significant reduction in morphogenetic potential occurs in callus cultures of rice (Oryza sativa L. cv TN-1) (up to 1 year old), and that plant regeneration could be improved in such cultures with spermidine treatment. We now show a near loss in plant regeneration capacity, concomitant with massive polyamine accumulation (primarily the diamine putrescine), due to the increase in arginine decarboxylase activity and an altered putrescine-to-spermidine ratio in 20- and 36-month-old rice callus cultures. The blockage of polyamine accumulation due to the reduction in arginine decarboxylase activity by a putrescine synthesis inhibitor, [alpha]-difluoromethylarginine, completely restored plant regeneration capacity in these long-term cultures. Additionally, spermidine treatment of long-term cultures caused an increase in cellular spermidine content and a reduction in putrescine content and arginine decarboxylase activity, leading to an adjustment in putrescine-to-spermidine ratio and the restoration of plant regeneration ability.     

Respiratory instability in distillery yeasts

Summary Eight distillery yeasts and one haploid strain of Saccharomyces cerevisiae were screened for the presence of respiratory deficient cells in their populations after culturing in either yeast extract-peptone-sucrose medium or in molasses medium. It was found that the distillery yeasts yield RD cells similar to the haploid with the number varying with the yeast strain and growth temperature. In cell biomass recycling, the number of RD cells also increases considerably.     

Immunocytochemical localization of DNA in synaptonemal complexes of rat and mouse spermatocytes,and of chick oocytes

The distribution of DNA in synaptonemal complexes of rat and mouse spermatocytes, and of chick oocytes was investigated by immunogold electron microscopy. Except for a few specific sites, DNA was not immunolocalized in the space between lateral elements of the complex. Some labeled fibrils connecting the lateral elements with the central element were observed associated with recombination nodules or near them. However, other labeled fibrils in the space between lateral elements did not appear to present any relationship to recombination nodules. The immunocytochemical approaches used here confirmed the presence of significant amounts of DNA in the lateral elements as previously indicated by preferential DNA staining methods. Furthermore, our findings support the view that recombination nodules are the site of chiasma formation.