Detection of Minchinia occulta in samples of pearl oysters Pinctada maxima infected by Haplosporidium hinei

Objective   To determine if juvenile pearl oysters ( Pinctada maxima ) infected with Haplosporidium hinei are also infected with another haplosporidian parasite, Minchinia occulta .
Design   Archived samples of pearl oysters infected with H. hinei were examined using polymerase chain reaction (PCR) assays and in situ hybridisation (ISH) to analyse and identify haplosporidians. A 144-bp and 220-bp region of Minchinia DNA were targeted by PCR and amplified DNA from formalin-fixed H. hinei -infected pearl oyster samples was sequenced. A 25-bp oligonucleotide probe targeting a variable section of the parasite's small subunit rRNA gene was used in ISH.
Results   The results of DNA-based diagnostic assays supported each other. The sequences obtained by PCR were found to be almost identical to M. occulta from rock oysters and the ISH assay demonstrated infection with M. occulta in affected pearl oysters. ISH indicated a prevalence of infection of 26.7% in one of the previous outbreaks.
Conclusion   Pearl oyster spat are susceptible to infection by a Minchinia parasite, most likely M. occulta , which was recently identified in rock oysters within the pearl-producing zones of Western Australia and is associated with mortalities of up to 80% in this species. The occurrence of haplosporidian co-infections in pearl oysters suggests the immunocompetence of juvenile oysters may be an important factor in preventing infection and therefore preventing mortalities such as those occurring in the recent outbreaks of pearl oyster oedema disease.     

The cellular and molecular origins of beak morphology

Cellular and molecular mechanisms underlying differences in beak morphology likely involve interactions among multiple embryonic populations. We exchanged neural crest cells destined to participate in beak morphogenesis between two anatomically distinct species. Quail neural crest cells produced quail beaks in duck hosts and duck neural crest produced duck bills in quail hosts. These transformations involved morphological changes to non-neural crest host beak tissues. To achieve these changes, donor neural crest cells executed autonomous molecular programs and regulated gene expression in adjacent host tissues. Thus, neural crest cells are a source of molecular information that generates interspecific variation in beak morphology.     

The effect of antibody to caseous lymphadenitis in ewes on the efficacy of vaccination in lambs

The effect of maternal antibody to the toxin of Corynebacterium pseudotuberculosis, produced by caseous lymphadenitis (CLA) in ewes or by vaccinating ewes before lambing, on the efficacy of vaccination against CLA in their lambs was examined. Lambs were allocated to treatments according to either the vaccination history of their dam or level of CLA toxin antibody of their dam. They were vaccinated twice using 2 different inoculation regimes and then artificially infected with CLA organisms. The number of lambs with CLA lesions was assessed at slaughter. In one experiment high levels of CLA toxin antibody activity in ewes were associated with decreased efficacy of CLA vaccination in their lambs, when lambs were vaccinated at 2 and 8 weeks or 8 and 14 weeks of age. In a second experiment the efficacy of lamb vaccination at 8 and 12 weeks, but not at 14 and 18 weeks of age, was decreased. In sheep flocks with a high prevalence of CLA, vaccinating lambs against CLA at less than 10 weeks of age may not produce optimum protection against CLA in lambs. There was no difference in infection rate between lambs from vaccinated and unvaccinated ewes. However, vaccination of lambs at 2 and 8 wks was less effective that vaccination at 8 and 14 weeks, probably due to reduced immunocompetence in young lambs. In sheep flocks where significant numbers of lambs receive their primary vaccination at less than 3 weeks of age vaccination programmes to control CLA in lambs may be less effective.     

Powdery mildew resistance in Czech and Slovak barley cultivars

Fifteen powdery mildew resistance genes and the gene MlaN81 derived from ‘Nepal 81’were found in 76 Czech and Slovak spring and winter barley cultivars when tested for reaction to a set of powdery mildew isolates. Nine cultivars (‘Donum’, ‘Expres’, ‘Jubilant’, ‘Orbit’, ‘Primus’, ‘Progres’, ‘Stabil’, ‘Vladan’ and ‘Zlatan’) are composed of lines with different resistance genes. The Mlat gene is present in nine cultivars and was transferred from the Anatolian landrace ‘A‐516′. The resistances derived from ‘KM‐1192’and ‘CI 7672’were identical and designated Ml(Kr). Five winter barley cultivars possess the Ml(Bw) resistance. The winter barley line ‘KM‐2099’carries the mlo gene. The parental cultivar ‘Palestine 10’was also tested in which the genes Mlk1, MlLa were identified. The German cultivar ‘Salome’, a parent of seven cultivars tested, probably carries the gene MlLa in addition to mlo and Mla7. The gene mlo6 may be present in the cultivar ‘Heris’. Most of the results were confirmed by the pedigrees of the cultivars.     

Regulatory options under the U.S. Clean Air Act: The federal view

This paper documents the evolution of Environmental Protection Agency (EPA) policy concerning the relative roles that volatile organic compounds (VOCs) and oxides of nitrogen (NO_x) emissions play in ozone nonattainment planning for State implementation plans (SIPs). It further discusses possible new control requirements, including NO_x measures, that may be required as a result of pending Clean Air Act Amendments. In the early 1970's EPA guidance emphasized the use of VOC control measures to attain the ozone (formerly oxidant) ambient air quality standard. Little if any, control requirements applied to NO_x emissions. EPA continued to focus guidance requirements upon the control of VOCs during the planning efforts associated with the 1977 Clean Air Act amendments... 1979 SIPs, 1982 plans for long-term problem areas (extension areas), and other revisions to SIPs. Preliminary air quality modeling work to support these later planning efforts revealed that, in certain cases, there were potential benefits of NO_x control in addition to VOC. With this new insight, EPA's post-1987 policy proposal required states to look at the potential benefits of NO_x controls in areas with a nonmethane organic compound to NO_x ratio of 10∶1 or greater. In Clean Air Act Amendments currently being debated in the House and Senate, there is an uncertainty with regard to the role of NO_x controls. Possibilities under consideration range from the application of reasonably available control technology for 100 ton sources of NO_x to a clean fuel motor vehicle program within 42 months of enactment.     

The tilapia prolactin cell: A model for stimulus-secretion coupling

The tilapia prolactin (PRL) cell responds rapidly (10–20 min) to small physiological changes in medium osmotic pressure (OP), releasing increasing quantities of hormone as medium OP is reduced. This release is rapidly (≤ 10 min) inhibited by somatostatin (SRIF). There is now extensive evidence that tilapia PRL cell function is regulated through the second messengers Ca⁺⁺ and cAMP. Our studies have shown that PRL release is augmented by treatments that lead to increased levels of intracellular Ca⁺⁺ or cAMP. On the other hand, PRL release is blocked when tissues are incubated in Ca⁺⁺-depleted medium or upon the addition of Co⁺⁺, an inhibitor of Ca⁺⁺-mediated processes. The use of⁴⁵Ca⁺⁺ to characterize the movement of Ca⁺⁺ into PRL cells has provided evidence that an increase in the influx of extracellular Ca⁺⁺ may participate in PRL release upon exposure to hyposmotic medium. Our studies have also shown that SRIF suppresses the increase in⁴⁵Ca⁺⁺ accumulation that is brought about when OP is reduced. We have also examined the effects of OP and SRIF on cAMP levels. The reduction of medium OP did not alter cAMP metabolism during 20 min of incubation. By contrast, cAMP accumulation in the presence of IBMX was enhanced at 1 hr of incubation in reduced OP. Thus, an increase in cAMP turnover may play a role in maintaining PRL release under sustained stimulation. SRIF reduced the accumulation of cAMP during 10 min of incubation with IBMX and also reduced the forskolin-stimulated increase in cAMP. Thus, SRIF may suppress adenylate cyclase activity. Finally, our studies have revealed that the forskolin-stimulated increase in cAMP levels is not dependent upon medium Ca⁺⁺. The presence of Ca⁺⁺ in the medium is required, however, for PRL release even when the cAMP messenger system has been activated. Moreover, cAMP accumulation was augmented when intracellular Ca⁺⁺ was increased. This raises the possibility that reduced OP may stimulate an increase in cAMP turnover indirectly through its action(s) on cytosolic Ca⁺⁺.     

Seroprevalence of psittacine beak and feather disease in wild psittacine birds in New South Wales

SUMMARY A haemagglutination inhibition assay was used to detect antibody to psittacine beak and feather disease virus in sera from wild sulphur crested cockatoos (Cacatua galerita), galahs (Eolophus roseicapillus), short-billed corellas (Cacatua sanguinea), eastern long-billed corellas (Cacatua tenuirostris) and other psittacine birds in New South Wales. The seroprevalence of psittacine beak and feather disease ranged from 41% to 94% in different flocks, indicating infection with the virus is widespread in wild populations.