Comparison evaluation of liquid chromatographic and bioassay methods of analysis for determination of paralytic shellfish poisons in shellfish tissues

A liquid chromatographic (LC) method was compared with the AOAC mouse bioassay method (18.086-18.092) for determination of paralytic shellfish toxins in shellfish tissues. Shellfish samples were collected from Massachusetts coastal waters as part of a state surveillance program, and extracts of shellfish meat were analyzed for toxins by using both analytical methods. Overall correlation of the LC and bioassay methods is good (r = 0.943), but for samples with toxicities less than 100 micrograms saxitoxin/100 g shellfish meat, the correlation is significantly less (r = 0.531). Limits of detection are 10 micrograms saxitoxin/100 g shellfish meat and 40 micrograms saxitoxin/100 g shellfish meat for the LC and bioassay methods, respectively. Analytical capacity of the LC method is limited to 12 samples/person-day compared with 30 samples/person-day for the bioassay. Sampling capacity of the LC method could be increased by using a fluorescence detector with a wider response range, which would eliminate the need for dilution of concentrated samples.     

A Preliminary Investigation of Ozone Concentrations on the Lizard Peninsula Cornwall,U.K. using Continuous Monitoring and Diffusion Tubes

The Lizard Peninsula is an isolated area of unique and sensitive ecology and the occurrence of damaging ozone concentrations over the peninsula in spring challenges the successful sustainable management of the area. Ozone concentrations over Goonhilly Downs on the Lizard Peninsula in Cornwall were measured in spring 2002 using continuous monitoring and spatial mapping (diffusion tubes). Data obtained using a continuous ozone monitor (1/03/02 to 31/03/02) showed that the AOT40 5-day values were in a range from 2 to 800 μg m^-3 hr (AOT40 is the sum of the differences between the measured hourly ozone concentration (μg m^-3) and 80 μg m^-3 (when the concentration exceeds 80 μg m^-3) for the hours when global radiation exceeds 50 Wm^-2). Contour mapping of ozone concentrations measured with diffusion tubes suggested that over a 2 km² sampling area significant microscale variations were occurring with ozone concentrations ranging between 48–129 μg m^-3 for one two-week period and 62–210 μg m^-3 for the other.Unusually high diurnal variations in ozone concentrations were also observed at Goonhilly. It is thought that temperature inversions caused the entrapment of ozone at the surface level.     

Gene insertion: current progress and long-term goals

The methods for artificial gene insertion in the germline of the fly Drosophila and mice are now well established. In mice, cloned genes or retroviruses can be inserted by manipulation of newly fertilized ova, and intensive research is aimed at understanding the basis for regulation of gene expression using this technique. Manipulation of early embryos in the chicken is much more difficult. Therefore, we are concentrating on the use of avian retroviruses as vectors for gene insertion in this species. Some candidate genes are those controlling resistance to specific disease agents, those regulating humoral and cell-mediated immunity, and genes for immunogens that could be regulated to be expressed only after the development of immune competence, thus becoming an inherited vaccine. Basic research in these areas should lead to methods that will complement standard genetic selection for increased disease resistance in commercial chickens.     

Studies on the incorporation of 14 C-labelled amino acids into egg proteins

The incorporation of ¹⁴C‐labelled amino acids into egg white and yolk proteins has been studied. When the labelled amino acids were given intravenously as a hydrolysate of [U‐¹⁴C]‐protein from Chlorella, 10 per cent and 7 per cent of the ¹⁴G were recovered in the whites and yolks respectively of the first nine eggs laid. Differences in the specific activities of the conalbumin, the ovalbumins, ovomucoid, “postalbumins “ and lysozyme, isolated from the first active egg, were related to differences in amino acid composition. The specific activity of each amino acid prepared from the proteins was similar between different proteins, although within each protein specific activities of different amino acids varied widely. The proportionate rate of decrease of specific activity in the plasma of amino acids essential for egg production (except glycine) was constant or almost so, but it rapidly decreased for the non‐essential ones (except serine and proline). The specific activities of the amino acids, excepting aspartic and glutamic acids, in each protein were proportional to their mean specific activities in the plasma throughout the 24‐h period in which the egg white proteins were synthesised. It is concluded that these different proteins are synthesised from a shared amino acid pool, derived from plasma, at a rate which probably remains constant throughout the egg‐laying cycle and which is proportional to their content in the albumen.     

Differing effects of forage and concentrate diets on the oleic acid and conjugated linoleic acid content of sheep tissues: the role of stearoyl-CoA desaturase

Feeding sheep concentrate-based diets increases the oleic acid content of their tissues, whereas the cis-9, trans-11 conjugated linoleic acid (CLA) content is increased by feeding forage diets. Both these metabolic transformations could be attributable to increased activity of stearoyl-CoA desaturase (SCD). Therefore, the effect of forage or concentrate feeding regimens on the fatty acid composition of sheep tissues were investigated to determine whether any changes are related to an alteration of SCD mRNA levels. Twenty-four ewe lambs were randomly allotted to one of three dietary treatment groups: 1) dehydrated grass pellets, 2) concentrate diet fed to achieve a growth rate similar to that of the dehydrated grass pellets, and 3) the same concentrate diet approaching ad libitum intake. As expected, animals fed ad libitum concentrates grew at a greater (P = 0.001) rate (280 g/d) than those fed either of the other two diets (180 g/d), which were similar. In samples of liver and the three adipose tissue depots studied, the concentration of oleic acid from sheep fed either level of the concentrate diet was greater (P < 0.001) than from animals fed forage. This was associated with an increase (P < 0.05) in the ratio of SCD to acetyl-CoA carboxylase mRNA in adipose tissue and liver. Compared with concentrate-fed, the forage-fed lambs had increased (P < 0.05) levels of the cis-9, trans-11 isomer of CLA and C18:1, trans-11 in all their tissues, although the levels of SCD mRNA were lower. It therefore seems that the increased oleic acid content of sheep tissues in response to concentrate-rich diets is associated with an increase in SCD gene expression. By contrast, the increased concentration of CLA in animals fed forage-based diets is associated with an increase in substrate (C18:1 trans-11) availability.     

Vertical transmission of reticuloendotheliosis virus in breeder turkeys

Epizootiological studies were conducted on a commercial turkey breeder flock naturally infected with nondefective reticuloendotheliosis (RE) virus. Although RE virus was isolated from 27 (46%) of the 59 hens studied, only 4 of the 45 hens tested transmitted RE virus to progeny during a 6-week observation period and the overall transmission rate was 1.8%. The transmitter hens were of two types: three hens were consistently viremic and antigenemic and lacked antibody; one hen was viremic but lacked detectable viral antigen and possessed antibody. Toms appeared to play no role in vertical transmission of the infection. Of several tests evaluated for detection of transmitter hens, the direct enzyme-linked immunosorbent assay on albumen was probably best, since it detected three of four transmitter hens, detected relatively few nontransmitter hens, and had the best consistency of any test. No significant differences in hatchability were found between eggs from viremic and non-viremic hens. These findings can be utilized in the development of programs for eradication of RE virus from turkey breeding flocks.