The effect of ethanol extract of a macroalgae Laurencia snyderia on growth parameters and vibriosis resistance in shrimp Litopenaeus vannamei

Bacterial diseases have been reported to be the major limiting factor in shrimp production. The use of natural products such as antimicrobials has been reported as a solution to the problem. The crude extract of a red seaweed Laurencia snyderiae obtained from the Persian Gulf was evaluated for shrimp growth performance and to determine in vivo efficacy of this seaweed in the prevention of shrimp Vibriosis. The ethanol extract from L. snyderiae (EELS) that was fed to the Artemia instar I for their enrichment was found to be non toxic to them. Shrimp Litopenaeus vannamei juveniles were fed with these enriched Artemia at 0 mg mL^-1 (Control group), 200 mg mL^-1, 400 mg mL^-1 and 600 mg mL^-1 for 30 days. The results obtained showed a significant increase (p<0.05) in survival rate in treatment groups compared with that in the control group. Shrimps fed with enriched Artemia showed a significant improvement in growth parameters when compared to those in the control group. When these juvenile shrimps were exposed to Vibrio harveyi (after 30 days) they showed notably lower mortality than the control. These results indicate that EELS has a good potential in promoting growth and antibacterial activities against V. harveyi that is useful in shrimp aquaculture

Transcriptional interference by RNA polymerase III affects expression of the Polr3e gene.

Overlapping gene arrangements can potentially contribute to gene expression regulation. A mammalian interspersed repeat (MIR) nested in antisense orientation within the first intron of the Polr3e gene, encoding an RNA polymerase III (Pol III) subunit, is conserved in mammals and highly occupied by Pol III. Using a fluorescence assay, CRISPR/Cas9-mediated deletion of the MIR in mouse embryonic stem cells, and chromatin immunoprecipitation assays, we show that the MIR affects Polr3e expression through transcriptional interference. Our study reveals a mechanism by which a Pol II gene can be regulated at the transcription elongation level by transcription of an embedded antisense Pol III gene

A case of white eye syndrome in cultured whiteleg shrimp (Litopenaeus vannamei) in concrete ponds

A month after movement of 1800 pieces of L. vannamei (average weight of 16g) from culture ponds in Heleh region to concrete ponds of Bandargah hatchery (Bushehr province) some shrimps showed symptoms such as decrease in growth rate, loss of appetite, dark pigmentation of cuticle and presence of black foci on it, redness of uropods and white, irregular and circular spots on the eye with 2-5mm diameters. For detection of etiological agent samples were taken for PCR, bacteriological and histo-pathological tests. Nested PCR test using IQ2000 kits for detection of major shrimp viral pathogens (IHHNV, WSSV, YHV and TSV) were conducted and all results were negative. In histo-pathological tests, lesions in eyes were liquefactive necrosis of cone cells and cone crystals with infiltration of hemocyte and formation of micro abscess in the diapteric region of eye. In bacteriological tests, a gram negative pleomorphic bacterium of the genus Aeromonas was isolated. However, it seems that this bacterium is the secondary agent and for detection of the primary agent more research is needed

Effects of Laminaria digitata and Aschophylum nodossum in controlling white spot disease (WSD) in white leg shrimp (Litopenaeus vannamei)

Complementary feedstuff extract from Laminaria digitata and Ascophylum nodossum containing 1% alginic acids as stimulator of immune system in Litopenaeus vannamei for controlling WSSV was used in this study. The test shrimps, Litopenaeus vannamei, in larvae stage (Z1-131,1), post larvae stage (PL1-PLO and juvenile (from day 30 to 40) were fed by complimentary feed stuff as the other test conditions in the test and control group were the same. Both groups were exposed to WSSV after 40 days by oral inoculation. The clinical signs and mortality were recorded for 10 days. The results showed the survival rate of the test group was higher than the control group and it was significant (P<0.05). The results also showed that the mortality in the test group occurred 48 hours later than the control group. This study can lead us to new methods for controlling White Spot Disease

An investigation on Vibrionaceae family of bacteria as probiotic factors in shrimp culture

We investigated the effects of Vibrionaceae family of bacteria as probiotics in the process of growth and survival rate of shrimp during propagation stages. Bacterial flora were extracted from seawater, culture farms, shrimp culture farms and sludge of private propagation farms. Different bacteria such as Vibrio alginolyticus (serotype 1-4), Vibrio splendidus I, Vibrio fluvialis II, Vibrio anguillarum I, Vibrio costicul, Vibrio vulnificaus, Vibrio nereis, Vibrio camplbelli, Vibrio natriegens, Vibrio proteolyticus, Vibrio plegius II ,Vibrio fischeri, Aeromonas hydrophila, Aeromonas schuberti, Aeromonas salmonisida, Aeromonas veronii were isolated, identified and lyophilized. These bacteria were used in different experiments on shrimp life cycle stages while the shrimps were being fed on live food such as Chaetoceros, Skeletonema and Tetraselmis algae. Vibrio alginolyticus (serotype 1) with 107 cells/ml increased proliferation of Tetraselmis sp to 71 % in 6 days compared to the control experiment. Also Vibrio alginolyticus (serotype 4) with 105 cells/in' increased Tetraselmis sp. production to 389% in 6 days compared to control. Vibrio splendidus I was also found to be able to increase shrimp fork length in postlarvae stage 3 up to 23% as compared to control. Vibrio alginolyticus and Vibrio fischeri increased survival, fork lenght and body weight of green tiger shrimp in postlarvae stage significantly (P<0.05)

Effect of hot-water extract of brown seaweed Sargassum glaucescens via immersion route on immune responses of Fenneropenaeus indicus

The development of shrimp aquaculture, in spite of its global necessity, is largely at stake as significant ecological and pathological problems are increasing in the vast majority of the shrimp producing countries. Shrimp immunology is a key element in establishing strategies for controlling diseases in shrimp aquaculture. The total haemocyte count (THC), differential haemocyte count (DHC), total plasma protein (TPP), Phagocytic activity (PA), bacterial clearance efficiency (BCE) and bactericidal activity (BE) were examined when the F. indicus shrimps (11.32±1.20 g) were immersed in seawater (39 ppt and 25 ± 1 ºC) containing hot-water extracts of brown alga Sargassum glaucescens at 100, 300 and 500 mg/l. These parameters increased significantly (p < 0.05) when the shrimp were immersed in seawater containing hot-water extracts at 100 mg/l after 3h and 300 and 500 mg/l after 2 h. F. indicus shrimps that were immersed in hot-water extracts at 300 and 500 mg/l had increased phagocytic activity and clearance efficiency to Vibrio spp. after 2 hours. But bactericidal activity increased significantly after 1 hour in the same concentrations

The improvement of Mo/4H-SiC Schottky diodes via a P2O5 surface passivation treatment

Molybdenum (Mo)/4H-silicon carbide (SiC) Schottky barrier diodes have been fabricated with a phosphorus pentoxide (P2O5) surface passivation treatment performed on the SiC surface prior to metallization. Compared to the untreated diodes, the P2O5-treated diodes were found to have a lower Schottky barrier height by 0.11 eV and a lower leakage current by two to three orders of magnitude. Physical characterization of the P2O5-treated Mo/SiC interfaces revealed that there are two primary causes for the improvement in electrical performance. First, transmission electron microscopy imaging showed that nanopits filled with silicon dioxide had formed at the surface after the P2O5 treatment that terminates potential leakage paths. Second, secondary ion mass spectroscopy revealed a high concentration of phosphorus atoms near the interface. While only a fraction of these are active, a small increase in doping at the interface is responsible for the reduction in barrier height. Comparisons were made between the P2O5 pretreatment and oxygen (O2) and nitrous oxide (N2O) pretreatments that do not form the same nanopits and do not reduce leakage current. X-ray photoelectron spectroscopy shows that SiC beneath the deposited P2O5 oxide retains a Si-rich interface unlike the N2O and O2 treatments that consume SiC and trap carbon at the interface. Finally, after annealing, the Mo/SiC interface forms almost no silicide, leaving the enhancement to the subsurface in place, explaining why the P2O5 treatment has had no effect on nickel- or titanium-SiC contacts

Strong polarization-induced reduction of addition energies in single-molecule nanojunctions

We address polarization-induced renormalization of molecular levels in solid-state based single-molecule transistors and focus on an organic conjugate molecule where a surprisingly large reduction of the addition energy has been observed. We have developed a scheme that combines a self-consistent solution of a quantum chemical calculation with a realistic description of the screening environment. Our results indeed show a large reduction, and we explain this to be a consequence of both (a) a reduction of the electrostatic molecular charging energy and (b) polarization induced level shifts of the HOMO and LUMO levels. Finally, we calculate the charge stability diagram and explain at a qualitative level general features observed experimentally.Comment: 9 pages, 5 figure

Assessment of different methods of water treatment on decreasing pathogenic bacteria in shrimp hatcheries

The project of "Assessment of different methods of water treatment on decreasing pathogenic bacteria in shrimp hatcheries" achieved by mean of reviewing the effectiveness of various methods on the water treatment to reduce bacterial load of sea water. The project performed in Bandargah region of Bushehr province in order to checking the effect of different methods on the sea water and bacterial population. This project has been done over a year. In this study a total of 138 samples was collected during seven times and was evaluated as well as 7 treatments. In this study, the comparison of the effect of each factors (sand filter, chlorine, ultra violet ray, chlorine combined with ultra violet ray) was analyzed on the sea water by means of disinfection. During this study, other environmental factors such as water temperature, dissolved oxygen, pH and salinity was measured till we can ensure that they don’t have any negative impact on the treatments. Results showed that the density of total bacteria in sea water (Control) was averagely 5187 CFU/ml, this was done while the total density of bacteria in the sea water, reservation pool sample, sand filter water, water that irradiated with ultraviolet rays, chlorinated water and the water that was influenced by both chlorine and ultra violet ray was respectively 5187 2137, 4449 2042, 2782 1335, 1164 692, 143 104, 87 76 CFU/ml. Therefore, reservation pool, sand filter, ultra violet ray, chlorine, chlorine-ultra violet ray each of them was reduce respectively 14, 46, 77, 97, 98 percent of the density of total bacteria or in other words they reduced 0.06, 0.27, 0.65, 1.56, 1.77 log of the total population of bacteria in water. Moreover, the results from the total count of vibrios showed that reservation pool, sand filter, ultra violet ray, chlorine, chlorine-ultra violet ray each of them was reduce respectively 17, 47, 74, 98, 99 percent of the density of total vibrios or in other words they reduced respectively 0.08, 0.27, 0.59, 1.66, and 1.95 log of the total population of vibrios in sea water. Also the bacteria that isolated from each treatment were identified with the use of biochemical methods that totally were includes a wide range of bacteria, the identified vibrios were: Vibrio alginolyticus, V. costicola, V. fischeri, V. fluvialis I, V. fluvialis II, V. harveyi, V. natriegens, V. nigripulchritudo, V. parahaemolyticus, V. plagius I, V. vulnificus, V. anguilarum I, V. campbellii, V. nereis, V. proteolyticus, V. splendidus, and Unknown V. spp. Other identified bacteria belonging to the following genus: Acinetobacter, Aeromonas, Alcaligenes, Bacillus, Borkholderia, Eschricia, Enteroacter, Flavobacterium, Micococcus, Proteus, Pseudomonas, Serratia, Staphaphylococcus, Streptococcus, and Unknown Bacteria spp. By comparing the results, we concluded that the best result was related to treatment that the sea water had been disinfected after the combined effects of chlorine and ultraviolet ray. It was determined that this process in compared with other treatments, had been reduced the total number of bacteria, the total number of Vibrios, the number of sucrose fermentative vibrios, and the number of non-sucrose fermentative vibrios respectively 98, 99, 98, 99 percent. In other words, the number of bacteria was reduced respectively 1.77, 1.94, 1.82, 2.23 log. So in this study, the applied method was introduced as the most effective way of disinfecting sea water. Meanwhile, none of pathogenic bacteria for shrimp including Vibrio harveyi was isolated by using this treatment. Comparing the results showed that the combined effects of chlorine and ultraviolet radiation is the most effective applied method for disinfecting sea water

Early career retention of Malawian medical graduates: a retrospective cohort study.

OBJECTIVE: There have been longstanding concerns over Malawian doctors migrating to high-income countries. Early career is a particularly vulnerable period. After significant policy changes, we examined the retention of recent medical graduates within Malawi and the public sector. METHODS: We obtained data on graduates between 2006 and 2012 from the University of Malawi College of Medicine and Malawi Ministry of Health. We utilised the alumni network to triangulate official data and contacted graduates directly for missing or uncertain data. Odds ratios and chi-squared tests were employed to investigate relationships by graduation year and gender. RESULTS: We traced 256 graduates, with complete information for more than 90%. Nearly 80% of registered doctors were in Malawi (141/178, 79.2%), although the odds of emigration doubled with each year after graduation (odds ratio = 1.98, 95% CI = 1.54-2.56, P < 0.0001). Of the 37 graduates outside Malawi (14.5%), 23 (62.2%) were training in South Africa under a College of Medicine sandwich programme. More than 80% of graduates were working in the public sector (185/218, 82.6%), with the odds declining by 27% for each year after graduation (odds ratio = 0.73, 95% CI = 0.61-0.86, P < 0.0001). CONCLUSIONS: While most doctors remain in Malawi and the public sector during their early careers, the odds of leaving both increase with time. The majority of graduates outside Malawi are training in South Africa under visa restrictions, reflecting the positive impact of postgraduate training in Malawi. Concerns over attrition from the public sector are valid and require further exploratory work