Consumer Versus Resource Control in Freshwater Pelagic Food Webs     

MT Brett  CR Goldman 《Science (New York, N.Y.)》1997,275(5298):384-386

Models predict that food-web structure is regulated by both consumers and resources, and the strength of this control is dependent on trophic position and food-web length. To test these hypotheses, a meta-analysis was conducted of 11 fish (consumer)-by-nutrient (resource) factorial plankton community experiments. As predicted, zooplankton biomass was under strong consumer control but was weakly stimulated by nutrient additions; phytoplankton biomass was under strong resource control with moderate control by fish. However, the phytoplankton and zooplankton responses to nutrient additions did not follow theoretical predictions based on the number of trophic levels in the food web.  相似文献   

Evaluation of a regimen using a progesterone releasing intravaginal device (CIDR) and PMSG as a treatment for post partum anoestrus in dairy cattle     

TF. JUBB  P. BRIGHTLING  J. MALMO†  MT. LARCOMBE  GA. ANDERSON  SJ. HIDES‡ 《Australian veterinary journal》1989,66(10):334-336

Anoestrous dairy cows in seasonally calving herds in the Macalister Irrigation District of Gippsland, Victoria were treated at the start of the mating period with a progesterone releasing intravaginal device (CIDR). The CIDR was inserted for 7 days and 400 IU of PMSG was injected intramuscularly at removal. There was no clinically useful difference among cows receiving the CIDR, a placebo and untreated cows in the interval from treatment to either first oestrus or conception, the conception rate to first service or percent pregnant by the end of mating. Analyses of data from 2-year-old cows, older cattle, cows calved at least 45 days or cows calved at least 55 days and cows treated 3 weeks after the start of mating did not show improved reproductive performance following treatment with the CIDR.  相似文献   

Intrauterine Idiopathic Amputation of the Head of a Porcine Foetus     

JS Agerholm  MT Garoussi 《Reproduction in domestic animals》2013,48(3):e38-e40

An anencephalic full‐term porcine foetus accompanied by a mummified head was submitted for examination. The neck almost entirely lacked skin and was covered by granulation tissue as were the exposed parts of the spine and spinal cord. The case represents a rare case of intrauterine amputation. A definitive cause could not be established because the placenta was not available. The most likely cause is strangulation of the neck. Such strangulation could be due to a defect of the allantoamnion with herniation of the foetal head or entanglement by amniotic constriction bands.  相似文献   

Arthropathy caused by a lead bullet in a dog     

Barry SL  Lafuente MP  Martinez SA 《Journal of the American Veterinary Medical Association》2008,232(6):886-888

CASE DESCRIPTION: A 3-year-old spayed female Labrador Retriever was evaluated for progressive lameness of the left forelimb 21 months after being shot in the elbow with a lead bullet. CLINICAL FINDINGS: Physical examination findings were consistent with moderate osteoarthritis of the left elbow joint. Orthogonal radiographic views of the elbow revealed multiple metallic fragments in and around the joint space as well as signs of osteoarthritis. TREATMENT AND OUTCOME: The elbow joint was evaluated arthroscopically. A lead-based bullet fragment was seen in the lateral synovial compartment and removed in multiple pieces. Excess fibrin and synovium were removed, and microfractures were created in exposed subchondral bone to stimulate neovascularization and fibrocartilage formation. In a follow-up telephone conversation 4 months after surgery, the owner reported a marked improvement in the lameness. CLINICAL RELEVANCE: Removal of lead intra-articular foreign bodies may be indicated even if the material is not believed to mechanically interfere with joint motion.  相似文献   

Carbohydrate content and metabolism as related to maturity and chilling sensitivity of cv. Fortune mandarins.     

N Holland  J M Sala  H C Menezes  M T Lafuente 《Journal of agricultural and food chemistry》1999,47(7):2513-2518

Fruits of cv. Fortune mandarin were periodically harvested throughout the ripening period to evaluate changes in carbohydrate content and metabolism in flavedo tissue and to determine the potential role of carbohydrates in the tolerance of citrus fruit to chilling injury (CI). Sucrose showed little change in the flavedo during the season, but fructose and glucose increased, in nearly equal amounts, throughout the fall and winter, reaching a maximum in January. Starch levels were less abundant than soluble carbohydrates and rose continuously until March. Sucrose phosphate synthase (SPS; EC 4.1.14) activity decreased from December throughout ripening. Changes in sucrose synthase (SS; EC 2.4.1.13) and acid and alkaline invertase (Inv; EC 3.2.1.26) activities correlated with changes in the reducing sugars, but acid invertase was less active than the other sucrose-metabolizing enzymes. Carbohydrate changes in the flavedo of Fortune mandarins with fruit maturity appear not to be related to the chilling tolerance of fruits during cold storage.  相似文献   

Ultrastructure of the hydrophobic gastric surfactant barrier in the dog   总被引：1，自引：0，他引：1  

MT ETHELL  DR HODGSON  BA HILLS 《Australian veterinary journal》1999,77(4):240-244

OBJECTIVES: To confirm the hydrophobicity of the luminal surface of the canine stomach and to elucidate the ultrastructure of the lining imparting that property. DESIGN AND PROCEDURES: Gastric and duodenal mucosal samples from eight dogs were collected immediately after euthanasia and subjected to contact angle measurement using a goniometer. Other samples were examined by electron microscopy following a fixation procedure known to preserve phospholipids and oligolamellar structures. RESULTS: Contact angles for the canine gastric mucosal surface (85.1 +/- 5.5) were significantly greater (P < 0.0001) than for the duodenum (24.0 +/- 1.7). Electron microscopy revealed the existence of surfactant as abundant osmiophilic phospholipid material within the gastric and duodenal mucosae. CONCLUSION: We have confirmed the hydrophobic nature of the canine gastric mucosa whereas the luminal surface of the duodenum is hydrophilic. We propose that the water-repellent nature of the canine gastric lining contributes to the 'gastric mucosal barrier' and is imparted by an oligolamellar layer of surface-active phospholipid ('gastric surfactant') adsorbed to the surface. Both gastric and duodenal mucosae may also utilise phospholipids as an intercellular defense mechanism in the event that tight junctions are breached by acid. It is tempting to speculate that a deficiency of gastric phospholipids may predispose dogs to ulcers. Further, exogenous administration of phospholipids may be useful in preventing gastric ulceration.  相似文献   

Parasitic weed management by using strigolactone‐degrading fungi          下载免费PDF全文

Angela Boari  Biancamaria Ciasca  Rocío Pineda‐Martos  Veronica MT Lattanzio  Koichi Yoneyama  Maurizio Vurro 《Pest management science》2016,72(11):2043-2047

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Validation of the BioPRYN enzyme‐linked immunosorbent assay for detection of pregnancy‐specific protein‐B (PSPB) and diagnosis of pregnancy in American bison (Bison bison)          下载免费PDF全文

DM Love  MT Mefford  JC Ramer 《Reproduction in domestic animals》2017,52(5):791-797

This study assessed the accuracy of the commercial BioPRYN^® ELISA for the detection of pregnancy‐specific protein‐B (PSPB) using a single blood sample to determine pregnancy status in American bison (Bison bison). A total of 49 bison cows were used in the study, and sampled at two time‐points during the gestation period, fall and spring, correlating with early‐ to mid‐term gestation (average 62.9 days post‐mating) and mid‐ to late‐term gestation (average 229.2 days post‐mating), respectively. Sensitivity of the test during early‐ to mid‐term gestation sampling period (fall) was 87.1%, while specificity was 100%; sensitivity of the test during late‐term gestation sampling period (spring) was 96.3%, while specificity remained at 100%. In total, the test showed a total sensitivity of 91.4%, specificity of 100% and total accuracy of 93.8%, similar to domestic cattle. Use of the single‐sample BioPRYN^® ELISA in American Bison for pregnancy diagnosis is economical and practical, minimizing animal handling time, frequency and subsequent stress while providing accurate results for pregnancy diagnosis at 62 days post‐mating. This method should be considered over more traditional pregnancy diagnosis methods for use in managed bison herds.  相似文献   

Simultaneous Removal of H2S, NH3, and Ethyl Mercaptan in Biotrickling Filters Packed with Poplar Wood and Polyurethane Foam: Impact of pH During Startup and Crossed Effects Evaluation     

J. Hernández  J. Lafuente  ó. J. Prado  D. Gabriel 《Water, air, and soil pollution》2012,223(6):3485-3497

The present work discusses the startup and operation of different biotrickling filters during the simultaneous removal of NH₃, H₂S, and ethyl mercaptan (EM) for odor control, focusing on (a) the impact of pH control in the stability of the nitrification processes during reactor startup and (b) the crossed effects among selected pollutants and their by-products. Two biotrickling filters were packed with poplar wood chips (R1 and R2A), while a third reactor was packed with polyurethane foam (R2B). R2A and R2B presented a pH control system, whereas R1 did not. Loads of 2?C10?g N?CNH₃ m^?3?h^?1, 5?C16?g S?CH₂S m^?3?h^?1, and 1?C6?g EM m^?3?h^?1 were supplied to the bioreactors. The presence of a pH control loop in R2A and R2B proved to be crucial to avoid long startup periods and bioreactors malfunctioning due to biological activity inhibition. In addition, the impact of the presence of different concentrations of a series of N species (NH ₄ ⁺ , NO ₂ ^? , and NO ₃ ^? ) and S species (SO ₄ ^2? and S^2?) on the performance of the two biotrickling filters was studied by increasing their load to the reactors. Sulfide oxidation proved to be the most resilient process, since it was not affected in any of the experiments, while nitrification and EM removal were severely affected. In particular, the latter was affected by SO ₄ ^2? and NO ₂ ^? , while nitrification was significantly affected by NH ₄ ⁺ . The biotrickling filter packed with polyurethane foam was more sensitive to crossed effects than the biotrickling filter packed with poplar wood chips.  相似文献   

Toxic effects of methoxychlor on the episodic prolactin secretory pattern: Possible mediated effects of nitric oxide production     

Anunciación Lafuente  Teresa Cabaleiro  Pilar Cano  Ana I Esquifino 《Journal of circadian rhythms》2006,4(1):3-9

Background  

This work addresses the issue of whether methoxychlor (MTX) exposure may modify the ultradian secretion of prolactin through changes in the synthesis of nitric oxide (NO) induced by N^ω-nitro-L-arginine methyl ester (L-NAME) in the hypothalamic-pituitary axis. Associated changes in dopamine (DA) content in the anterior (AH), mediobasal (MBH) and posterior hypothalamus (PH) and median eminence (ME) were evaluated.  相似文献