Spatial pattern formation in an insect host-parasitoid system

Spatial models in ecology predict that populations may form patchy distributions within continuous habitats, through strong predator-prey or host-parasitoid interactions combined with limited dispersal. Empirical support of these models is provided. Parasitoids emanating from a population outbreak of tussock moths (Orgyia vetusta) suppressed the growth of nearby experimental populations of the moth, while experimental populations farther away were able to grow. This result explains the observed localized nature of tussock moth outbreaks and illustrates how population distributions can be regulated by dynamic spatial processes.     

Childhood leukemia and fallout from the Nevada nuclear tests

Cancer mortality data from the National Center for Health Statistics, covering the period 1950 through 1978, were used to test a reported association between childhood leukemia and exposure to radioactive fallout from nuclear weapons tests in Nevada between 1951 and 1958. No pattern of temporal and geographic variation in risk supportive of the reported association was found. Comparison of these results with those presented in support of an association of risk with fallout suggests that the purported association merely reflects an anomalously low leukemia rate in southern Utah during the period 1944 to 1949.     

Humoral immune response of water buffalo monitored with three different antigens of Toxocara vitulorum

Humoral immune response of water buffalo naturally infected with Toxocara vitulorum was monitored using three different antigens of this parasite in serum and colostrum of buffalo cows and calves. Soluble extract (Ex) and excretory/secretory (ES) larval antigens and perienteric fluid antigen (Pe) of adult T. vitulorum were used to measure the antibody levels by an indirect ELISA. Serum of 7-12 buffalo cows for the first 365 days and colostrum of the same number of buffalo cows for the first 60 days of parturition, and serum of 8-10 buffalo calves for the first 365 days after birth were assayed. The ELISA detected antibodies against all three T. vitulorum antigens in the colostrum and serum of 100% of buffalo cows and calves examined. The highest antibody levels against Ex, ES and Pe antigens were detected in the buffalo cow sera during the perinatal period and were maintained at high levels through 300 days after parturition. On the other hand, colostrum antibody concentrations of all three antigens were highest on the first day post-parturition, but decreased sharply during the first 15 days. Concomitantly to the monitoring of immune response, the parasitic status of the calves was also evaluated. In calves, antibodies passively acquired were at the highest concentrations 24 h after birth and remained at high levels until 45 days coincidentally with the peak of T. vitulorum infection. The rejection of the worms by the calves occurred simultaneously with the decline of antibody levels, which reached their lowest levels between 76 and 150 days. Thereafter, probably because of the presence of adults/larvae stimulation, the calves acquired active immunity and the antibodies started to increase slightly in the serum and plateaued between the days 211 and 365. All three antigens were detected by the serum antibodies of buffalo calves; however, the concentration of anti-Pe antibody was higher than anti-EX and anti-ES, particularly after 90 days of age. By conclusion, the buffalo cows develop immunity and keep high levels of antibodies against T. vitulorum-Ex, ES and Pe antigens and these antibodies are transferred to their calves through the colostrum. This passively acquired immunity does not protect the calves against the acquisition of the infection, but these antibodies, passively or actively acquired, may have an important role during worm rejection by the calves and prevention of intestinal reinfection.     

Protein requirement of jundia fingerlings, Rhamdia quelen, at two dietary energy concentrations

A feeding trial was carried out where five protein concentrations [26%, 29%, 33%, 37%, and 41% crude protein (CP)] were fed to jundia fingerlings at two dietary energy concentrations [3200 and 3650 kcal metabolizable energy (ME)/kg diet] to establish the protein requirement for this species. Triplicate groups of 23 fish (average weight 1.52±0.34 g) were each stocked in 120-l aquaria and fed semipurified diets twice a day to apparent satiation. After 90 days, fish weight gain (WG), specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER), energy retention (ER), apparent net protein utilization (ANPU), feed consumption (% body weight) and body composition (crude protein, fat, and ash) were affected by diet composition. Weight gain, SGR, FE, ANPU and ER increased (P<0.05) as the dietary protein concentration increased up to 33% and 37%, for fish fed diets containing 3650 and 3200 kcal, respectively. A significant interaction between dietary protein and energy was observed for WG, SGR, and PER. Feed consumption was not affected by dietary energy concentration, but decreased with increasing dietary protein concentration (P<0.05). Body fat decreased as dietary protein increased at both energy concentrations, but was higher in fish fed the 3650 kcal diet. The opposite was observed for body protein, ER, and ANPU (P<0.05). Our findings demonstrate that jundia presents dietary protein sparing effect when the energy concentration increases from 3200 to 3650 kcal/kg. Jundia protein requirement, determined by the broken line method, is between 32.6% and 37.3% CP, depending on dietary energy concentration.     

Can Growth of Nannochloropsis oculata under Modulated Stress Enhance Its Lipid-Associated Biological Properties?

Nannochloropsis oculata is well-recognized as a potential microalgal source of valuable compounds such as polyunsaturated fatty acids, particularly, eicosapentaenoic acid (EPA). The content and profile of these lipids is highly dependent on the growth conditions and can, therefore, be tailored through modulation of the growth parameters, specifically, temperature. Moreover, biological activities are composition dependent. In the present work, lipid extracts obtained from N. oculata, grown under constant temperature and under modulated temperature stress (to increase EPA content; Str) were characterized by GC-FID and several bioactivities were evaluated, namely, antioxidant (L-ORAC_FL), cytotoxic (MTT), adipolytic, anti-hepatic lipid accumulation (steatosis), and anti-inflammatory properties. Both extracts exhibited antioxidant activity (c.a. 49 µmol Trolox_equivalent/mg_extract) and the absence of toxicity (up to 800 µg/mL) toward colon and hepatic cells, adipocytes, and macrophages. They also induced adipolysis and the inhibition of triglycerides hepatic accumulation, with a higher impact from Str. In addition, anti-inflammatory activity was observed in the lipopolysaccharide-induced inflammation of macrophages in the presence of either extract, since lower levels of pro-inflammatory interleukin-6 and interferon-β were obtained, specifically by Str. The results presented herein revealed that modulated temperature stress may enhance the health effects of N. oculata lipid extracts, which may be safely utilized to formulate novel food products.