Vitamin K requirement and reproduction in bromadiolone-resistant Norway rats     

Jacob J  Endepols S  Pelz HJ  Kampling E  Cooper TG  Yeung CH  Redmann K  Schlatt S 《Pest management science》2012,68(3):378-385

BACKGROUND: Nucleotide polymorphisms in the VKORC1 gene can be linked to anticoagulant rodenticide resistance in Norway rats (Rattus norvegicus Berkenhout). This provides a fitness advantage to rats exposed to anticoagulant actives, but may also cause fitness costs. The vitamin K requirement and reproductive parameters of bromadiolone‐resistant rats (Westphalian resistant strain; VKOR variant Tyr139Cys) and bromadiolone‐susceptible Norway rats were compared. RESULTS: At vitamin K deficiency, blood clotting times increased in all homozygous resistant males within 8 days and in 80% of homozygous resistant females within 15 days. There was little effect on blood clotting in heterozygous males and no effect in heterozygous females and VKOR wild‐type individuals. Litter size was about 20% higher in sensitive pairs compared with resistant pairs. Testes growth, male gonad weight, sperm motility and testis cell concentration were unaffected by the mutation. CONCLUSIONS: The VKOR variant Tyr139Cys causes considerable physiological cost in Norway rats in terms of vitamin K requirement and reproduction. This may affect the distribution and spread of resistant individuals in the wild. Decreased litter size of resistant parents seems to be due to lowered female reproductive performance, as there was no significant effect of the mutation on any aspects of male reproduction considered, but this requires further study. Copyright © 2011 Society of Chemical Industry  相似文献   

Fenvalerate residues on cattle hair coat from impregnated ear tags     

Jupita M. Yeung  Douglas D. Colwell  Joseph A. Shemanchuk 《Pest management science》1989,26(1):21-27

A simple small-scale method for the determination of fenvalerate residues on cattle hair by gas–liquid chromatography with electron capture detection was developed and applied to the determination of fenvalerate residues from Bovaid^R ear tags. Recoveries were found to be 96–104% at 10–100 μg g^?1 levels of fenvalerate. The minimum detection limit of this method was 1 pg g^?1. With one ear tag, fenvalerate was adequately distributed over the entire body and persisted for at least 80 days on the hair of cattle.  相似文献   

Human sperm binding is mediated by the sialyl-Lewis(x) oligosaccharide on the zona pellucida     

Pang PC  Chiu PC  Lee CL  Chang LY  Panico M  Morris HR  Haslam SM  Khoo KH  Clark GF  Yeung WS  Dell A 《Science (New York, N.Y.)》2011,333(6050):1761-1764

Human fertilization begins when spermatozoa bind to the extracellular matrix coating of the oocyte, known as the zona pellucida (ZP). One spermatozoan then penetrates this matrix and fuses with the egg cell, generating a zygote. Although carbohydrate sequences on the ZP have been implicated in sperm binding, the nature of the ligand was unknown. Here, ultrasensitive mass spectrometric analyses revealed that the sialyl-Lewis(x) sequence [NeuAcα2-3Galβ1-4(Fucα1-3)GlcNAc], a well-known selectin ligand, is the most abundant terminal sequence on the N- and O-glycans of human ZP. Sperm-ZP binding was largely inhibited by glycoconjugates terminated with sialyl-Lewis(x) sequences or by antibodies directed against this sequence. Thus, the sialyl-Lewis(x) sequence represents the major carbohydrate ligand for human sperm-egg binding.  相似文献   

Periodic insolation variations on Mars     

Murray BC  Ward WR  Yeung SC 《Science (New York, N.Y.)》1973,180(4086):638-640

Previously unrecognized insolation variations on Mars are a consequence of periodic variations in eccentricity, first established by the theory of Brouwer and Van Woerkom (1950). Such annual insolation variations, characterized by both 95,000-year and 2,000,000-year periodicities, may actually be recorded in newly discovered layered deposits in the polar regions of Mars. An additional north-south variation in seasonal insolation, but not average annual insolation, exists with 51,000-year and 2,000,000-year periodicities.  相似文献   

Meat and ascorbic acid can promote Fe availability from Fe-phytate but not from Fe-tannic acid complexes     

Engle-Stone R  Yeung A  Welch R  Glahn R 《Journal of agricultural and food chemistry》2005,53(26):10276-10284

This study utilized an in vitro digestion/Caco-2 cell model to determine the levels of ascorbic acid (AA) and "meat factor" needed to promote Fe absorption from Fe complexed with phytic acid (PA) or tannic acid (TA). AA reversed the inhibition of Fe absorption by PA beginning at a molar ratio of 1:20:1 (Fe:PA:AA) but essentially had no effect on the Fe complexed with TA. Fish also reversed the inhibition of Fe uptake by PA but not by TA. TA and fish decreased total Fe solubility. Iron in the presence of PA was highly soluble. AA, but not fish, increased the percentage of soluble Fe as Fe2+ in the presence of both inhibitors. The results indicate that monoferric phytate is a form of Fe that can be available for absorption in the presence of uptake promoters. In contrast, a TA-Fe complex is much less soluble and unavailable in the presence of promoters.  相似文献   

Pearling of hull-less barley: product composition and gel color of pearled barley flours as affected by the degree of pearling     

Yeung J  Vasanthan T 《Journal of agricultural and food chemistry》2001,49(1):331-335

Barley grains from two hull-less varieties, Phoenix and Candle, were pearled to various degrees (10-80%). The composition (starch, protein, beta-glucan, lipid, and ash) of pearled grain (PG) and pearling flour (PF) was determined. Effect of pearling on Hunter L, a, and b color parameters of uncooked and cooked (gel) barley flour (milled from PG) was investigated over a 3 day storage at 4 degrees C.  相似文献   

Factors affecting the natural transmission of bovine leukaemia virus infection in Queensland dairy herds     

CK DIMMOCK  YS CHUNG  AR MACKENZIE† 《Australian veterinary journal》1991,68(7):230-233

Natural transmission of bovine leukaemia virus (BLV) infection in south-eastern Queensland dairy herds was slow in 2 herds with a low to moderate (13 to 22%) prevalence of infection. Infection spread much more rapidly in a herd that had a higher prevalence (42%) when first tested. In a 13 month study of this herd, the cumulative incidence of infection was 24%. In one herd new infections were confined almost entirely to calves of uninfected dams. Following the end of feeding bulk milk to calves, a common practice in dairy herds, no more calves in this herd became infected. In laboratory experiments, neither prolonged housing of susceptible calves with infected cattle, consumption of drinking water contaminated with infected blood, nor inoculation of sheep with saliva from infected cattle resulted in transmission of BLV infection. Sheep were infected by subcutaneous inoculation of a suspension of purified lymphocytes from an infected heifer. The minimum infective dose was 10(3) lymphocytes, equivalent to the number of lymphocytes in approximately 0.1 microliter blood. Thus, procedures involving the transfer of a very small volume of blood from animal-to-animal have the potential to transmit infection.  相似文献   

Gas-phase ionic reactions: dynamics and mechanism of nucleophilic displacements     

ML Chabinyc  SL Craig  CK Regan  JI Brauman 《Science (New York, N.Y.)》1998,279(5358):1882-1886

Nucleophilic displacement reactions (the SN2 reaction) of ions in the gas phase are a prototypical reaction system that allows a study of dynamics, mechanisms, and structure-energy relations. This article reviews aspects of the kinetics (especially the applicability of statistical reaction rate theory), the relation of structure and reactivity, and the effects of small numbers of solvent molecules on the reaction and compares the behavior of the ionic reaction in the gas phase with that in solution.  相似文献   

Acquired urethral obstruction in New World camelids: 34 cases (1995–2008)     

KF Duesterdieck‐Zellmer  DC Van Metre  A Cardenas  CK Cebra 《Australian veterinary journal》2014,92(8):313-319

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Iron uptake by Caco-2 cells from NaFeEDTA and FeSO4: Effects of ascorbic acid, pH, and a Fe(II) chelating agent     

Zhu L  Glahn RP  Yeung CK  Miller DD 《Journal of agricultural and food chemistry》2006,54(20):7924-7928

Sodium iron(III) ethylenediaminetetraacetate (NaFeEDTA) has considerable promise as an iron fortificant because of its high bioavailability in foods containing iron absorption inhibitors. In this study, uptakes of iron from NaFeEDTA, FeSO4, and FeCl3 by Caco-2 cells were compared in the absence or presence of ascorbic acid (AA), an iron absorption enhancer; at selected pH levels; and in the absence or presence of an iron absorption inhibitor, bathophenanthroline disulfonic acid (BPDS). Ferritin formation in the cells was used as the indicator of iron uptake. Uptake from all three Fe sources was similar in the absence of AA. Adding AA at a 5:1 molar excess as compared to Fe increased uptake by 5.4-, 5.1-, and 2.8-fold for FeSO4, FeCl3, and NaFeEDTA, respectively. The smaller effect of AA on uptake from NaFeEDTA may be related to the higher solubility of NaFeEDTA and/or the strong binding affinity of EDTA for Fe3+, which may prevent AA and duodenal cytochrome b from effectively reducing EDTA-bound Fe. Uptake was inversely related to the pH of the media over a range of 5.8-7.2. Because uptake by DMT-1 is proton-coupled, the inverse relationship between pH and Fe uptake in all three iron sources suggests that they all follow the DMT-1 pathway into the cell. Adding BPDS to the media inhibited uptake from all three iron compounds equally. Because BPDS binds Fe2+ but not Fe3+ and because only Fe2+ is transported by DMT-1, the finding that BPDS inhibited uptake from NaFeEDTA suggests that at least some iron dissociates from EDTA and is reduced just as simple inorganic iron at the brush border membrane of the enterocyte. Taken together, these results suggest that uptake of iron from NaFeEDTA by intestinal enterocytes is regulated similarly to uptake from iron salts.  相似文献