Ascorbic acid requirement and histopathological changes due to its deficiency in juvenile spotted rose snapper Lutjanus guttatus (Steindachner, 1869)     

María Cristina Chávez-Sánchez  Miguel Angel Olvera-Novoa  Briseida Osuna-Durán  Isabel Abdo de la Parra  Selene María Abad-Rosales  Irma Martínez-Rodríguez 《Aquaculture International》2014,22(6):1891-1909

A 13-week feeding trial was conducted to determine the optimal dietary ascorbic acid (AA) requirement of juvenile spotted rose snapper (Lutjanus guttatus). Six experimental diets containing 0, 7, 19, 29, 62 and 250 mg AA equivalent kg^?1 diet, supplied as l-ascorbyl-2-polyphosphate designated as VC0, VC7, VC19, VC29, VC62 and VC250, were fed ad libitum to triplicate groups of 20 juveniles [initial weight (IW) of 8 ± 1.85 g]. Nutrient deficiency resulting in fin erosion, dark skin, desquamation and erratic swimming was observed after 8 weeks in fish fed diets from 0 to 29 mg AA kg^?1. Fish that were fed all diets showed gill, kidney and brain alterations. The degree of tissue change values indicates that increasing vitamin C (VC) levels reduces these alterations. Fish fed diets VC29, VC62 and VC 250 showed a significantly higher growth rate in comparison with those fed the diets VC0, VC7 and VC17 (P > 0.05). The dietary requirement of VC in L. guttatus was estimated to be 29 mg kg^?1 of AA based on weight gain and specific growth rate, but more than 250 mg kg^?1 of AA is required to eliminate clinical signs and histopathological lesions.  相似文献   

Effect of formulation and repeated applications on the enantioselectivity of metalaxyl dissipation and leaching in soil          下载免费PDF全文

Rafael Celis  Beatriz Gámiz  María A Adelino  Juan Cornejo  María C Hermosín 《Pest management science》2015,71(11):1572-1581

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High population densities of Macrolophus pygmaeus on tomato plants can cause economic fruit damage: interaction with Pepino mosaic virus?          下载免费PDF全文

Rob Moerkens  Els Berckmoes  Veerle Van Damme  Nelia Ortega‐Parra  Inge Hanssen  Martine Wuytack  Lieve Wittemans  Hans Casteels  Luc Tirry  Patrick De Clercq  Raf De Vis 《Pest management science》2016,72(7):1350-1358

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Genetic characterisation and analysis of infectious bronchitis virus isolated from Brazilian flocks between 2010 and 2015     

Claudia Carranza  Claudete S. Astolfi-Ferreira  Silvana H. Santander Parra  Luis F. N. Nuñez  Zoltan Penzes  Jorge L. Chacón 《British poultry science》2017,58(6):610-623

1. Infectious bronchitis virus (IBV) variants in Brazil were isolated during 2010–2015 for epidemiological and molecular analysis to characterise the different variants and perform a bioinformatic analysis to compare with sequences of variants collected over the previous 40 years.

2. Of the 453 samples examined, 61.4% were positive for IBV and 75.9% of these were considered to have the BR-I genotype and were detected in birds of all ages distributed in all five Brazilian regions.

3. The ratio of non-synonymous substitutions per non-synonymous site (dN) to synonymous substitutions per synonymous site (dS), i.e. dN/dS, revealed a predominance of codons with non-synonymous substitutions in the first third of the S1 gene and a dN/dS ratio of 0.67. Additionally, prediction of N-glycosylation sites showed that most of the BR-I variants (from 2003 to early 2014) had an extra site at amino acid position 20, whereas the newest variants lacked this extra site.

4. These results suggest that Brazilian IBV variants probably underwent drastic mutations at various points between 1983 and 2003 and that the selection processes became silent after achieving a sufficiently effective antigenic structure for invasion and replication in their hosts. Brazilian IBV genotype BR-I is currently the predominant genotype circulating in Brazil and South America.  相似文献   

Long-term effects of N fertilization on cropping and growth of olive trees and on N accumulation in soil profile     

R. Fernndez-Escobar  L. Marin  M.A. Snchez-Zamora  J.M. García-Novelo  C. Molina-Soria  M.A. Parra 《European Journal of Agronomy》2009,31(4):223-232

Two experiments were conducted for 13 years in two olive groves of southern Spain to study the long-term effect of nitrogen (N) fertilization on trees and soil. In the first experiment, 12-year-old ‘Picual’ olive trees were arranged in a split plot design with method of N application (soil versus a 50% soil:50% foliar combination) as the whole plot factor, and amount of N applied annually (0, 0.12, 0.25, 0.5 or 1.0 kg N tree⁻¹) as the subplot factor. In the second experiment, N application to 50-year-old ‘Picual’ trees was based on the previous season's leaf N concentration. Urea was the source of N in both experiments. During the last 4 years, soil samples were taken at 0–20, 20–40, 40–60, 60–80, and 80–100 cm depth to evaluate the effect of N application on soil eutrophication. Fertilization with N had no significant effects on yield, fruit characteristics, and growth of olive trees for the 13 years of study, even when leaf N concentration increased with the amount of fertilizer N applied. Combining soil and foliar application may reduce the amount of fertilizer N necessary to correct a possible N deficiency because our experiments showed this practice to be more effective in increasing leaf N that applying N only to the soil. Our results question the established deficiency threshold of 1.4% of N in dried leaf because no reduction in yield or growth was observed for lower concentrations. However, leaf N concentration did not drop below 1.2% after 13 years with no N application, probably because of N inputs from rainfall and the mineralization of organic N. Whereas under natural conditions of the non-fertilized treatments NH₄⁺–N represented the dominant fraction of mineral N in soil, accumulation of high amounts of NO₃⁻–N in the soil profile occurred in the fertilized plots, which represents a high risk of N leaching from soil. All these results suggest that annual applications of fertilizer N are unnecessary to maintain high productivity and growth in olive. Applying N only when the previous season's leaf analysis indicates that leaf N concentration is below the deficiency threshold, is thus a recommended practice to optimize N fertilization in olive orchards and to reduce N losses by leaching.  相似文献   

Antibodies to hepatitis B surface antigen potentiate the response of human T lymphocyte clones to the same antigen   总被引：10，自引：0，他引：10  

E Celis  T W Chang 《Science (New York, N.Y.)》1984,224(4646):297-299

Human t-helper lymphocyte clones specific for hepatitis B virus surface antigen (HBsAg) proliferate on stimulation with HBsAg in vitro. Antibodies specific for HBsAg, but no other antibodies, augment this proliferative response. In the presence of antibodies to HBsAg, the maximum response could be achieved at HBsAg concentrations that were 1 percent of those required in the absence of the antibodies. These findings suggest that antigen-specific antibodies exert regulatory controls on T cells that recognize the same antigens.  相似文献   

Ehrlichia platys (Anaplasma platys) in dogs from Maracaibo,Venezuela: an ultrastructural study of experimental and natural infections     

Arraga-Alvarado C  Palmar M  Parra O  Salas P 《Veterinary pathology》2003,40(2):149-156

Since 1982 Ehrlichia platys, now emended as Anaplasma platys, has been diagnosed in dogs from Maracaibo, Venezuela, using buffy coat smears stained with Dip Quick. Three dogs were inoculated with an A. platys strain. When parasitemia reached 60-97%, blood samples obtained from the inoculated dogs and from two naturally infected dogs were centrifuged to obtain platelet-rich plasma, which was mixed with 0.1% glutaraldehyde at 37 C for 10 minutes. Platelet pellets were fixed in 3% glutaraldehyde for 72 hours and processed for conventional transmission electron microscopy. Platelets contained pleomorphic organisms with a distinct double membrane that was not observed when the bodies were in a determinate developmental stage. There were 1-15 individual bodies included in a host cell vacuole. The organisms had an electron-lucent inner area, whereas the internal surface of their inner plasma membranes exhibited an electron-dense rough substance. In naturally infected dogs, organisms with different ultrastructural features were found inside the same platelet. Some organisms contained central dense material surrounded by a pale zone, which was in turn surrounded by a moderately dense peripheral area. Other organisms contained an eccentrically electron-dense material. The intravacuolar space appeared fully electron-lucent. Each organism usually exhibited inner fine strands. Empty structures displaying junctions with the vacuolar membrane were observed. Our results indicate that distinct ultrastructural characteristics are associated with different stages of A. platys development and may differ among A. platys strains.  相似文献   

Immunohistochemical localisation of rabbit haemorrhagic disease virus VP-60 antigen in early infection of young and adult rabbits     

Prieto JM  Fernandez F  Alvarez V  Espi A  García Marín JF  Alvarez M  Martín JM  Parra F 《Research in veterinary science》2000,68(2):181-187

This study evaluated the time course distribution of rabbit haemorrhagic disease virus (RHDV) structural protein VP60 in tissues from experimentally infected rabbits from three different age groups. Viral VP60 antigen could not be detected in tissue samples from animals under four weeks, and only a few hepatocytes (0.01 to 0.2 per cent) were stained in the 6-week-old animals. A 6-week-old rabbit euthanised at 72 hpi showed VP60-labelling in hepatocytes and macrophages close to areas of inflammation. Viral VP60 antigen was detected as early as 12 hpi in a few hepatocytes (0.03 per cent) from adult animals. Within this age group, the extent of hepatocyte labelling considerably increased at 18 (3.0 per cent), 24 (25.5 per cent), 36 (50 per cent) and 48 (60 per cent) hpi. Extrahepatic viral VP60 antigen was also detected at 36 and 48 hpi in spleen macrophages and lymphocytes from adult rabbits. These findings support the hypothesis that the hepatocyte is the only cell type in the liver able to support RHDV replication almost immediately after viral infection.  相似文献   

An intensive hatchery rearing protocol for larvae of the bullseye puffer,Sphoeroides annulatus (Jenyns)     

Maria Isabel Abdo‐de la Parra  Armando García‐Ortega  Irma Martínez‐Rodríguez  Blanca González‐Rodríguez  Gabriela Velasco‐Blanco  Crisantema Hernández  Neil Duncan 《Aquaculture Research》2010,41(10):e554-e560

In this study bullseye puffer, Sphoeroides annulatus larvae were reared from hatching through to 1 or 2 months after weaning on an experimental scale in three replicate 600 L tanks and on three occasions during the spawning season (nine tanks in total). The rearing protocol used was green water (Nannochloropsis oculata and Isochrysis sp.) 100 000 cells mL^?1 from 0 to 11 days after hatch (DAH), 5–10 rotifers, Brachionus rotundiformis mL^?1 from 2 to 26 DAH, 0.1–1 Artemia mL^?1 from 21 to 34 DAH and weaning from 29 to 34 DAH. Survival to a month after weaning was 1%, a total of 3153 juveniles were produced with an average wet weight of 0.29 ± 0.07 g and a length of 27.5 ± 0.82 mm.  相似文献   

The effect of dietary phosphatidylcholine and its constituent fatty acids on microdiet ingestion and fatty acid absorption rate in gilthead sea bream, Sparus auratus, larvae   总被引：1，自引：0，他引：1  

Koven  Parra  Kolkovski  & Tandler 《Aquaculture Nutrition》1998,4(1):39-45

This study tested the effect of the level of dietary phosphatidylcholine (PC) and its constituent medium-chain fatty acids on microdiet ingestion (μg diet larva⁻¹ h⁻¹) and the absorption rate of the free fatty acid [¹⁴C]16:0 (pmole larva⁻¹ h⁻¹) in 15, 20, 21, 25, 26, 30 and 31-day-old gilthead sea bream, Sparus auratus L., larvae. Fish were fed four microdiets (A, B, C and D): microdiet A contained no phospholipid (PL), while microdiet B included 10 g kg⁻¹ Artemia nauplii PL (3.7 g kg⁻¹ PC). Microdiets C and D contained 10 g kg⁻¹ purified saturated PC dimyristoyl (C_14:0) and polyunsaturated PC dilinoleoyl (C_{18:2[cis]−9,12}), respectively.
Larvae from one or both of the PC microdiets demonstrated significantly higher ( P < 0.05) ingestion rates (μg diet larva⁻¹ h⁻¹) than the non-PL microdiet control in 15, 21, 22, 25 and 26-day-old larvae and the Artemia PL microdiet in 15, 22 and 26-day-old larvae. However, microdiet ingestion and fatty acid absorption rate appeared to be independent of the associated medium carbon chain saturated or polyunsaturated fatty acid moiety of the PC diets. Apparent absorption, as measured by the retention of radio-labelled [¹⁴C]16:0 following 8 h of non-labelled microdiet feeding, was possibly related to feeding.  相似文献