Comparison of electron microscopy and polyacrylamide gel electrophoresis in the diagnosis of avian reovirus and rotavirus infections.

Electron microscopy (EM) and genome electropherotyping by polyacrylamide gel electrophoresis (PAGE) for the detection of avian rotaviruses and reoviruses in intestinal specimens and cell cultures were compared. Fifty-eight field samples of intestine with intestinal contents, referred to as direct specimens, from turkey and chicken flocks located in different regions of California and submitted during 1989 for virus isolation were randomly selected as test samples. Also, 38 field intestinal specimens with suspected viral infection that had been passaged three times in primary chicken embryo kidney (CEK) cell cultures were used in their third passage. The percentage of agreement and the Kappa statistic of positive and negative results between these two tests were calculated. In the comparison, EM was considered the standard test. By statistical analysis, an agreement of 87% was observed in cell-culture samples analyzed by the two virus-detection methods, as contrasted with an agreement of 72% for direct specimens. The analysis of the number of segments and band migration profiles of reference and field virus strains indicated that only reoviruses replicated in CEK cell cultures and mainly rotaviruses were detected by both tests in direct specimens. The Kappa statistic analysis indicated substantial agreement (0.69) between the two tests for CEK samples, with moderate agreement (0.45) for the direct specimens examined.     

Differences in ovary size among olive (Olea europaea L.) cultivars are mainly related to cell number,not to cell size

Differences in mature fruit size among olive cultivars are related to differences in ovary size at bloom, but it is not known whether cell number or size determines the variation in ovary size. In this study we measured cell size and number in equatorial cross-sectional areas of the principal ovary tissues (mesocarp and endocarp) in eight cultivars with very different fruit and ovary size. The results showed that cell number explained most of the differences in ovary size, while cell size was not related to ovary size, except for a weak (R² = 0.33) correlation in the endocarp. Since sink strength is thought to be related to cell number, this finding supports the hypothesis that larger ovaries represent stronger sinks. The implications of greater sink strength with bigger ovaries are discussed. Within cultivars, while the cross-sectional areas of mesocarp and endocarp were similar, cell number was higher in the mesocarp but cell size was smaller compared to the endocarp.     

Generalized biomass equations for the main aboveground biomass components of maritime pine across contrasting environments

• Introduction   

In order to predict the biomass of aerial components of maritime pine stands (Pinus pinaster Ait.), generalized allometric equations were developed using data collected from the southern and northern margins of its geographical area.     

Isolation and identification of locally isolated bacterial strains effective against whitefly Bemisia tabaci

Potent bacterial strains effective against the whitefly, Bemisia tabaci, nymphs (second instar), were isolated from tomato cultivated fields at Fayoum governorate, Giza, Egypt. Of 72 isolates, 12 with the most morphologically distinct-looking bacterial colonies were selected and named A1, A2, A3, A6, A7, A9, A12, A13, A107, B37, B45 and B100. All isolates were preliminarily identified as members of the genus Bacillus based on morphological, physiological and biochemical characteristics. When tested for their pathogenicity against Bemisia tabaci, the 12 isolates revealed varying efficiencies with isolates A1 and A9 being superior, exhibiting maximum mortality of 92.2 and 90.8% on day 10, respectively. Isolate A7 recorded the lowest percentage at 18.3%. Further genetic characterization of the 12 isolates was performed using inter simple sequence repeat (ISSR), randomly amplified polymorphic DNA (RAPD) and 16S rDNA gene sequencing analysis. RAPD and ISSR results confirmed each other. The combined ISSR and RAPD phylogenetic tree showed two major clusters. With 16S rRNA gene analysis, isolate A1 and A12 sequences recorded 100% identity with Bacillus thuringiensis, while isolates A7 and B100 showed 95.7% and 95.6% identity with Bacillus cereus and Bacillus sphaericus, respectively.     

Effects of Zn2+ on Ca2+ uptake by mitochondria and endoplasmic reticulum in permeabilized tilapia gill cells

An intracellular ATP-dependent Ca²⁺ pumping mechanism, distinct from mitochondrial Ca²⁺ accumulation, was identified within tilapia gill cells. Cell suspensions treated with 0.003% saponin, which selectively permeabilizes the plasma membrane, were used to characterize the Ca²⁺ sequentering mechanisms as endoplasmic reticulum and mitochondria and to determine the effect of Zn²⁺ on their Ca²⁺ storing activity. Of the Ca²⁺ taken up by the endoplasmic reticulum, 80% was released by IP₃ (10 mol l^–1). The Ca²⁺ pump of the endoplasmic reticulum was 2.5 times less sensitive to Zn²⁺ (IC₅₀=0.05 nmol l^–1) than was the mitochondrial uptake mechanism (IC₅₀=0.20 nmol l^–1). The results indicate that Ca²⁺ is stored predominantly within the endoplasmic reticulum at 0.1 mol l^–1 and that this storing capacity is seriously attenuated by namomolar concentrations Zn²⁺.     

Exploring the impacts of different fasting and refeeding regimes on Nile tilapia (Oreochromis niloticus L.): growth performance,histopathological study,and expression levels of some muscle growth-related genes

Fish Physiology and Biochemistry - The current study investigated how different fasting and refeeding regimes would impact Nile tilapia growth performance, histopathological examination, and gene...     

Effect of Garlic,Echinacea, Organic Green and Vet-Yeast on Survival,Weight Gain,and Bacterial Challenge of Overwintered Nile Tilapia Fry (Orechromis niloticus)

The purpose of this study was to examine the effect of some immunostimulants and probiotics on the survival rate, final weight, and disease resistance of overwintered tilapia fry. There were five treatments: T1 (control) fed a balanced diet (35% protein) without additives. Treatments 2 to 5 were fed diets supplemented with 4% garlic, 4 g/kg Echinacea, 4 g/kg Organic Green or 4 g/kg Vet-Yeast, respectively. Growth and resistance to disease challenge with Aeromonas hydrophila and Pseudomonas flourescens were not different among treatments, but survival of overwintered fry increased in treatments fed probiotics or immunostimulents. The use of garlic in overwintering feeds could allow hatchery operators to increase their prices for fry and fish farmers to stock production ponds earlier, increasing hatchery revenues by 74% and improving land use efficiency and productivity for the Egyptian aquaculture industry.     

Growth performance,oxidative stress indices and hepatic carbohydrate metabolic enzymes activities of juvenile Nile tilapia,Oreochromis niloticus L., in response to dietary starch to protein ratios

The effect of various dietary starch to proteins ratios (STA/P) on growth performance, oxidative status and liver enzyme activities involved in intermediary metabolism in juvenile Nile tilapia was evaluated. Four isocaloric‐practical diets (12.73 MJ kg^?1 digestible energy) with increasing STA/CP ratios were formulated. These were designated D₀ (344 g crude protein (CP) and 163.5 g starch (STA) kg^?1), D₁ (310 g CP and 243 g STA kg^?1), D₂ (258 g CP and 322 g STA kg^?1) and D₃ (214 g CP and 401 g STA kg^?1). Each diet was fed to triplicate groups of 60 fish (2.7 g) for 45 days. Compared with the control diet (D₀), significantly (P < 0.05) depressed growth and feed efficiency were observed only in the groups fed on diet D₃. The activities of hepatic enzymes involved in glycolysis and lipogenesis pathways were significantly enhanced in groups fed on diet D₃ compared with other diets. A significant (P < 0.05) increase in catalase activity was detected only in groups fed on diet D₃. Similarly, a significant (P < 0.05) enhancement in superoxyde dismutase, glutathione S‐transferases and glutathione peroxidise was observed in groups fed on diets D₂ and D₃ compared with other diets. Results demonstrate the ability of juvenile Nile tilapia to spare protein by dietary carbohydrate.