Vectorial transport of toxins from the dinoflagellate Gymnodinium breve through copepods to fish

Toxins from the dinoflagellate Gymnodinium breve were tracedthrough experimental food chains from dinoflagellates, throughcopepod grazers, to juvenile fish. The generality of this foodweb transfer was demonstrated using three different combinationsof copepods and juvenile fish during different seasons. Fishwere not exposed directly to the toxic dinoflagellates but werefed toxin-laden copepods in order to examine sublethal vectorialintoxication. Toxins were shown to move from fish viscera tomuscle tissue within periods of 2–6 h to 25 h. A new toxindetection method was used in this first stepwise demonstrationof multi-trophic-level intoxication of a planktonic food chainby G.breve. Micellar electrokinetic capillary electrophoresiswith laser-induced fluorescence allowed measurements of toxinsat trace levels and nanoliter-sized volumes critical for planktonicfood web transfer studies.     

Adverse ffects of covert iridovirus infection on life history and demographic parameters of Aedes aegypti

Abstract Sublethal viral infections can cause changes in the body size and demography of insect vectors, with important consequences for population dynamics and the probability that individual mosquitoes will transmit disease. This study examined the effects of covert (sublethal) infection by Invertebrate iridescent virus 6 (IIV‐6) on the demography of female Aedes aegypti and the relationship between key life history parameters in covertly infected female insects compared with healthy (control) insects or non‐infected mosquitoes that had survived exposure to virus inoculum without becoming infected. Of the female mosquitoes that emerged following exposure to virus inoculum and were offered blood meals, 29% (43/150) proved positive for covert IIV‐6 infection. The net reproductive rate (R₀) of covertly infected females was 50% lower for infected females compared to control mosquitoes, whereas non‐infected exposed females had an R₀ approximately 15% lower than that of controls. Reproduction caused a significant decrease of about 13 days in mosquito longevity compared to females that did not reproduce (P < 0.001). Infected females lived 5–8 days less than non‐infected exposed females or controls, respectively (P = 0.028). Infected females and non‐infected exposed females both had significantly shorter wings than control insects (P < 0.001). There was a significant positive correlation between wing length and longevity in covertly infected female mosquitoes but not in control or non‐infected exposed mosquitoes. Longer lived females produced more eggs in all treatments. There were no significant correlations between body size and fecundity or the production of offspring. There was also no correlation between fecundity and fertility, suggesting that sperm inactivation was a more likely cause of decreased fertility in older mosquitoes than sperm depletion. We conclude that covert infection by iridescent virus is likely to reduce the vectorial capacity of this mosquito.     

Guaianolides and heliangolides from Hymenopappus newberryi

The aerial parts of Hymenopappus newberryi afforded two heliangolides, two thymol derivatives, as well as two new guaianolides and a trans, trans-germacranolide closely related to hiyodorilactone A. Furthermore, the ent-kaurene derivative abbeokutone was present. These results are of chemotaxonomic interest.     

Dinosterol side chain biosynthesis in a marine dinoflagellate, Crypthecodinium cohnii

The heterotrophic dinofiagellate, Crypthecodinium cohnii, cultured in a nutrient medium containing methionine-[CD₃] incorporated deuterium into the newly synthesized 4α-monomethyl compound dinosterol (4α,23,24-trimethylcholest-22-en-3β-ol). The MS fragmentation pattern indicated that the C-23 methyl group contained three deuterium atoms and was introduced intact by transmethylation from methionine. The C-24 methyl group contained only two deuterium atoms which is consistent with the production of a 24-methylenesterol intermediate which is subsequently reduced to give the 24-methyl side chain. Mechanisms are proposed to account for the production of the dinosterol side chain.     

Osmotic adjustment of chickpea (Cicer arietinum) is not associated with changes in carbohydrate composition or leaf gas exchange under drought

Genetic differences in osmotic adjustment (OA) have been reported among chickpea (Cicer arietinum) cultivars. In this study eight advanced breeding lines (ABLs) derived from a cross between CTS 60543 (high OA) and Kaniva (low OA) and Tyson (medium OA) and Kaniva, along with the parents, were evaluated for OA, leaf carbohydrate composition and leaf gas exchange under dryland field conditions in India. The water potential (WP) decreased to lower values (less than −2.5 MPa) in Tyson, M 110 and M 86 than in the other genotypes. With decrease in WP, OA increased by 0.5 MPa in Kaniva and CTS 60543 to 1.3 MPa in M 55. As the decrease in WP varied with genotype, when OA was regressed against WP M 39 and M 55 had greater increases in OA with decrease in WP than the remaining nine genotypes, including the parents. As WP decreased, leaf starch content decreased while total soluble sugars, hexoses and sucrose increased: the decrease in starch was much smaller in M 93 and M 129 than in Tyson and M 51, but genotypic differences could not be detected in the increase in total sugars, hexoses or sucrose. The rates of photosynthesis and transpiration decreased as the WP became more negative, but M 129 reached low rates of photosynthesis (2 μmol m⁻² s⁻¹) and transpiration at a WP of −1.7 MPa, whereas Tyson reached the same low rate at −2.4 MPa. While OA varied among the chickpea genotypes, the differences were not associated with the changes in carbohydrate composition or the rates of gas exchange at low values of WP. Further, the degree of OA of the 11 genotypes was not the same as when they were selected for differences in OA under rainout shelter conditions in the field in Australia, suggesting that OA may show poor stability depending upon the stress level, location or physiological stage of the plant. This suggests that OA is not a valuable drought-resistance trait to select for in chickpea breeding programmes.     

Measurement of the rate of stomach emptying using Indium-113m and a 10-crystal rectilinear scanner

Accurate reproducible measurements of the rate of gastric emptying have only been possible since the advent of external radionuclide detection techniques. Indium-113m and a 10-crystal rectilinear scanner have been employed to measure stomach emptying rates. The technique is simple, the results reproducible and it has proved ideal for assessing the results of drug therapy in patients with gastric retention. In the normal individual the T50% was 42 to 95 minutes, and the relationship between counts and time was, to first approximation, a linear function.     

Variation in Plasma Calcium with Induced Changes in Plasma Specific Gravity,Total Protein,and Albumin

The relationship of plasma calcium levels to changes in plasma specific gravity, total protein, and albumin induced by venous stasis was investigated. Factors were derived for adjusting calcium results to offset the effects of variation in protein concentration and thus to make them of increased discriminatory value to the clinician. The validity of an existing specific gravity correction has been substantiated, but a more exact adjustment of 0·23 mg/100 ml of calcium for every 0·001 change in specific gravity is proposed. We recommend for automated laboratories that the factor based on albumin be used: 0·09 mg/100 ml of calcium should be subtracted from the total calcium value for every increase of 0·1 g in albumin above 4·6 g/100 ml, and a corresponding addition should be made for values of albumin below 4·6 g/100 ml.Using a calcium specific electrode, it has been shown that the ionized calcium concentration does not alter with prolonged venous stasis.