GnRHR gene polymorphisms and their effects on reproductive performance in Chinese goats

In this study, polymorphisms in the goat GnRHR gene exon 1 were detected by PCR-SSCP and DNA sequencing methods in 786 individuals from two different goat breeds. Two haplotypes (A and B), two observed genotypes (AA and AB), and two single nucleotide polymorphisms (SNPs) were detected, which resulted in five amino acid substitutions. The frequencies of haplotypes A and B in the two goat breeds were 0.78–0.83 and 0.17–0.22, respectively. The SNP locus was in Hardy–Weinberg disequilibrium in the two goat breeds (P < 0.05). Polymorphisms of the GnRHR gene were shown to be associated with litter size in the two goat breeds. The SNPs in the goat GnRHR gene had significant effects on litter size (P < 0.05). Therefore, these results suggest that the GnRHR gene is a strong candidate gene that affects litter size in goat.     

Dietary supplementation with <Emphasis Type="Italic">Astragalus</Emphasis> polysaccharide enhances ileal digestibilities and serum concentrations of amino acids in early weaned piglets

Two experiments were conducted to evaluate the effects of dietary supplementation with Astragalus polysaccharide (APS) on growth performance, apparent ileal digestibilities (AID) of amino acids (AA), and their serum concentrations in early weaned piglets. In Exp. 1, 60 pigs were weaned at 21 days of age (BW 7.35 ± 0.23 kg) and allocated to three treatments (20 pigs/treatment), representing supplementing 0.0% (control), 0.02% colistin (antibiotic), or 0.1% APS to a corn- and soybean meal-based diet. Average daily gain (ADG), average daily feed intake (ADFI), and feed/gain ratio (F/G) were measured weekly. Blood samples were obtained from five pigs selected randomly from each treatment for the measurement of serum free AA concentrations on days 7, 14, and 28. In Exp. 2, 12 pigs were weaned at 21 day of age (BW 7.64 ± 0.71 kg), assigned to three treatment groups as in Exp. 1, and surgically fitted with a simple T-cannula at the terminal ileum. Ileal digesta samples were obtained for the measurement of AID of AA on days 7, 14 and 28. Dietary APS did not affect ADFI, but enhanced (P < 0.05) ADG by 11 and 4.4%, and improved F/G by 5.6 and 8.4%, respectively, compared with the control and antibiotic groups. Addition of APS to the diet increased AID and serum concentrations of most nutritionally essential and non-essential AA (including arginine, proline, glutamate, lysine, methionine, tryptophan, and threonine) on days 14 and 28. Circulating levels of total AA were affected by the age of pigs and treatment × time interaction. Collectively, these findings indicate that APS may ameliorate the digestive and absorptive function and regulate AA metabolism to beneficially increase the entry of dietary AA into the systemic circulation, which provide a mechanism to explain the growth-promoting effect of APS in early weaned piglets.     

The discovery of a structurally novel class of inhibitors of the type 1 glycine transporter

The type 1 glycine transporter plays an important in regulating homeostatic glycine levels in the brain that are relevant to the activation of the NMDA receptor by the excitatory neurotransmitter glutamate. We describe herein the structure–activity relationships (SAR) of a structurally novel class of GlyT1 inhibitors following on a lead derived from high throughput screening, which shows good selectivity for GlyT1 and potent activity in elevating CSF levels of glycine.     

Elucidation of the stability and functional regions of the human coronavirus OC43 nucleocapsid protein

Human coronavirus OC43 (HCoV‐OC43) is one of the causes of the “common cold” in human during seasons of cold weather. The primary function of the HCoV‐OC43 nucleocapsid protein (N protein) is to recognize viral genomic RNA, which leads to ribonucleocapsid formation. Here, we characterized the stability and identified the functional regions of the recombinant HCoV‐OC43 N protein. Circular dichroism and fluorescence measurements revealed that the HCoV‐OC43 N protein is more highly ordered and stabler than the SARS‐CoV N protein previously studied. Surface plasmon resonance (SPR) experiments showed that the affinity of HCoV‐OC43 N protein for RNA was approximately fivefold higher than that of N protein for DNA. Moreover, we found that the HCoV‐OC43 N protein contains three RNA‐binding regions in its N‐terminal region (residues 1–173) and central‐linker region (residues 174–232 and 233–300). The binding affinities of the truncated N proteins and RNA follow the order: residues 1–173–residues 233–300 > residues 174–232. SPR experiments demonstrated that the C‐terminal region (residues 301–448) of HCoV‐OC43 N protein lacks RNA‐binding activity, while crosslinking and gel filtration analyses revealed that the C‐terminal region is mainly involved in the oligomerization of the HCoV‐OC43 N protein. This study may benefit the understanding of the mechanism of HCoV‐OC43 nucleocapsid formation.     

Two doses of humanized anti-CD25 antibody in renal transplantation: A preliminary comparative study

HuCD25mAb is a humanized anti-CD25 antibody which has the same amino acid sequence as daclizumab (Zenapax, Roche). HuCD25mAb is expressed in Chinese hamster ovary (CHO) cells while daclizumab is expressed in the NSO myeloma cell line. A comparative study was performed to evaluate the pharmacokinetics and pharmacodynamics between huCD25mAb and daclizumab in a two-dose regimen incorporating triple immunosuppressant treatment regimens (MMF, CsA and steroids). Fifteen patients were enrolled and randomized to receive intravenous infusion of either huCD25mAb (n = 10) or daclizumab (n = 5) at a dosage of 1 mg·kg⁻¹ on operation day 0 and post-operation day 14. Serum concentrations of huCD25mAb and daclizumab were measured by a validated competitive ELISA. Subgroups of CD3⁺, CD25⁺, CD4⁺ and CD8⁺ lymphocytes were monitored periodically by flow cytometry. The concentration-time curves of huCD25mAb and daclizumab were found to fit well to a one-compartment model. A significant decline of proportion (%) of CD3-CD25⁺ and CD3⁺CD25⁺ lymphocytes was observed 30 min after first infusion on day 0 (3.40 ± 1.83 to 0.03 ± 0.07, 3.35 ± 2.02 to 0.37 ± 0.49), and these levels remained low for at least 70 days (0.03 ± 0.05, 0.31 ± 0.47). All pharmacokinetic parameters of huCD25mAb seemed similar to those of daclizumab. The two-dose huCD25mAb regimen was as effective as daclizumab in rapidly achieving high therapeutic concentration in the treated patients, and a significant decrease of CD3⁻CD25⁺ and CD3⁺CD25⁺ lymphocytes was demonstrated. This suggests that two-dose regimen is feasible in maintaining host immunosuppression and may provide an effective and economical strategy for reducing incidence of acute graft rejection.Key words: CD25, pharmacokinetics, kidney transplantation, enzyme immunoassay, flow cytometry, monoclonal antibody     

Influence of light on ascorbate formation and metabolism in apple fruits

To further understand the regulatory mechanism of light on the formation of ascorbic acid (AsA) in the sink organs of plants, a systematical investigation on AsA levels, activities of two key biosynthsis enzymes and their mRNA expression as well as the recycling was performed in the fruits of apple (Malus domestica Borkh), under different levels of shade. After the whole trees were shaded with the sun-light about 50–55% for 20 days, AsA levels were significantly decreased in fruit peel, flesh and leaves, while mRNA expression levels and activities of l-galactose dehydrogenase (l-GalDH, EC 1.1.1.117) and l-galactono-1,4-lactone dehydrogenase (l-GalLDH, EC 1.3.2.3) as well as activities of recycling enzymes was clearly declined in the leaf and peel but not in the flesh. By shading fruits only for 20 days, AsA levels, relative mRNA levels and activities of l-GalDH and l-GalLDH as well as activities of recycling enzymes all showed obvious decrease in the peel, but not in the flesh. However, their levels in the peel were markedly increased after the full shade was removed and re-exposed these fruits on natural light for 5 days. It is concluded that light affects AsA biosynthesis and recycling in the peel and leaf, but did not in the fresh. Results also suggest that apple fruit is potential to biosynthesize AsA via the l-galactose pathway, and AsA content in the fruits may depend partly on levels of AsA or other photochemistry controlled by light in the leaves.     

Oligomeric Structure of the Human Reduced Folate Carrier: IDENTIFICATION OF HOMO-OLIGOMERS AND DOMINANT-NEGATIVE EFFECTS ON CARRIER EXPRESSION AND FUNCTION*

The ubiquitously expressed reduced folate carrier (RFC) is the major transport system for folate cofactors in mammalian cells and tissues. Previous considerations of RFC structure and mechanism were based on the notion that RFC monomers were sufficient to mediate transport of folate and antifolate substrates. The present study examines the possibility that human RFC (hRFC) exists as higher order homo-oligomers. By chemical cross-linking, transiently expressed hRFC in hRFC-null HeLa (R5) cells with the homobifunctional cross-linker 1,3-propanediyl bis-methanethiosulfonate and Western blotting, hRFC species with molecular masses of hRFC homo-oligomers were identified. Hemagglutinin- and Myc epitope-tagged hRFC proteins expressed in R5 cells were co-immunoprecipitated from both membrane particulate and surface-enriched membrane fractions, indicating that oligomeric hRFC is expressed at the cell surface. By co-expression of wild type and inactive mutant S138C hRFCs, combined with surface biotinylation and confocal microscopy, a dominant-negative phenotype was demonstrated involving greatly decreased cell surface expression of both mutant and wild type carrier caused by impaired intracellular trafficking. For another hRFC mutant (R373A), expression of oligomeric wild type-mutant hRFC was accompanied by a significant and disproportionate loss of wild type activity unrelated to the level of surface carrier. Collectively, our results demonstrate the existence of hRFC homo-oligomers. They also establish the likely importance of these higher order hRFC structures to intracellular trafficking and carrier function.Folates are members of the B class of vitamins that are required for the synthesis of nucleotide precursors, serine, and methionine in one-carbon transfer reactions (1). Because mammals cannot synthesize folates de novo, cellular uptake of these derivatives is essential for cell growth and tissue regeneration (2, 3). Folates are hydrophilic anionic molecules that do not cross biological membranes by diffusion alone, so it is not surprising that sophisticated membrane transport systems have evolved to facilitate their accumulation by mammalian cells.The ubiquitously expressed reduced folate carrier (RFC)² is widely considered to be the major transport system for folate co-factors in mammalian cells and tissues (3, 4). RFC plays a generalized role in folate transport and provides specialized tissue functions such as transport across the basolateral membrane of renal proximal tubules (5), transplacental transport of folates (6), and folate transport across the blood-brain barrier (7), although the contribution of RFC to intestinal absorption of folates remains controversial (8, 9). Loss of RFC expression or function portends potentially profound physiologic and developmental consequences associated with folate deficiency (10). RFC is also a major transporter of antifolate drugs used for cancer chemotherapy such as methotrexate (Mtx), pemetrexed, and raltitrexed (4). Loss of RFC expression or synthesis of mutant RFC protein in tumor cells results in antifolate resistance caused by incomplete inhibition of cellular enzyme targets and low levels of antifolate substrate for polyglutamate synthesis (4, 11).Reflecting its particular physiologic and pharmacologic importance, interest in RFC structure and function has been high. Since 1994, when murine RFC was first cloned (12), application of state-of-the-art molecular biology and biochemistry methods for characterizing polytopic membrane proteins has led to a progressively detailed picture of the molecular structure of the carrier, including its membrane topology, N-glycosylation, functionally or structurally important domains and amino acids, and packing of α-helix transmembrane domains (TMDs) (4, 13). Although no crystal structure for RFC has yet been reported, a detailed homology model for human RFC (hRFC) based on the bacterial lactose/proton symporter LacY and glycerol 3-phosphate/inorganic phosphate antiporter GlpT was generated (13, 14) that permits testing of hypotheses related to hRFC structure and mechanism in a manner not previously possible.Considerations of hRFC structure and mechanism to date have all been based on the notion that a single 591-amino acid hRFC molecule is sufficient to mediate concentrative uptake of folate and antifolate substrates. However, a growing literature suggests that quaternary structure involving the formation of higher order oligomers (e.g. dimers, tetramers, etc.) is commonly an important feature of the structure and function of many membrane transporters (15-18). For major facilitator superfamily proteins, both monomeric (e.g. LacY, GlpT, UhpT, and GLUT3) (19-22) and oligomeric (e.g. LacS, AE1, GLUT1, and TetA) (23-28) structures have been reported, establishing the lack of a clear structural consensus for these related proteins.In this report, we explore the question of whether hRFC exists as a homo-oligomeric species composed of multiple hRFC monomers. Based on results with an assortment of biochemical methods with wt and a collection of mutant hRFC proteins, we not only demonstrate the existence of oligomeric hRFC but also establish the probable importance of these higher order structures to intracellular trafficking and carrier function.     

观赏桃ISSR-PCR反应体系的优化

采用改良CTAB法从观赏桃满天红叶片中提取基因组DNA,通过单因素实验探讨了模板DNA、Mg~(2+)、dNTPs和Taq DNA酶等条件对观赏桃ISSR-PCR扩增结果的影响,建立了ISSR-PCR扩增的最佳体系:2.5μl反应体系中包含10×Buffer 2.5μl,模板DNA 40ng,Mg~(2+)浓度2.5mmol/L,引物浓度04 μmol/L,dNTPs浓度0.4mmol/L,Taq DNA酶0.5U.利用所建立的体系对红叶桃、菊花桃和春艳等13份材料进行检验,其结果表明优化后的体系适合观赏桃的ISSR-PCR反应.