Experimental studies of the role of the little raven (Corvus mellori) in surveillance for West Nile virus in Australia

Objective To study the potential role of an Australian corvid, the little raven (Corvus mellori), in the surveillance for exotic West Nile virus (WNV) in Australia. Method In a series of trials, little ravens were infected with WNV (strain 4132 New York 1999) and Kunjin virus (strain K42886) by the intramuscular route. They were observed for 20 days during which blood and swab samples were taken for virus isolation. Tissue samples were taken from ravens humanely killed during the acute infection period, and at the termination of the trials, for virus isolation, histopathology and immunohistochemistry. Results Ravens infected with WNV became mildly ill, but all recovered and seroconverted. Blood virus titres peaked around 3 to 4 days after inoculation at levels between 10^3.0 to 10^7.5 plaque forming units/mL. Virus or viral antigen was detected in spleen, liver, lung, kidney, intestine, testis and ovary by virus isolation and/or immunohistochemistry. WNV was detected in oral and cloacal swabs from 2 to 7 days post inoculation. The molecular and pathogenic characteristics of the inocula were consistent with them being of high virulence, as expected for this isolate. Ravens infected with Kunjin virus developed viraemia and seroconverted, although they did not develop disease. Conclusions Little ravens do not develop severe disease in response to virulent WNV infection and for this reason may not be important sentinel hosts in the event of an outbreak of WNV, as in North America. However, as they have relatively high viraemias, they may be able to support virus cycles.     

Leukotrienes Affect Secretory Function of Ovarian Cells In Vitro*

The aim of this study was to determine which cells are the source of production and target for leukotriene (LTs) action within the bovine ovary. Luteal (CL, days 14–16 of the oestrous cycle), steroidogenic cells (LSC) and endothelial cells (LEC) of the bovine corpus luteum (CL), and granulosa cells (GC) were isolated enzymatically, cultured in a monolayer and incubated with LTC₄, LTB₄, Azelastine (an antagonist of LTC₄) or Dapsone (an antagonist of LTB₄). Then cells were collected for determination of mRNA expression for LT receptors (LTRs) and 5‐lipoxygenase (5‐LO) by real time RT‐PCR, and media were collected for determination of prostaglandin (PG)E₂, F_2α, progesterone (P4; LSC only), endothelin‐1 (ET‐1; LEC only) and 17‐β oestradiol (E2; GC only). The greatest mRNA expression for LTR‐II and 5‐LO were found in LEC, whereas LTR‐I mRNA expression did not differ among cell types. The level of PGE₂ increased after LTs treatment in each type of ovarian cell, excluding LTC₄ treatment in LEC. The secretion of PGF_2α was also increased by LTs, but decreased after LTB₄ treatment of LSC. In GC cultures, both LTs stimulated E2 secretion; in LEC cultures, LTB₄ stimulated whereas LTC₄ inhibited P4 secretion; in LEC cultures, LTC₄ stimulated but LTB₄ inhibited ET‐1 secretion. The results show that LTs are produced locally and are involved in PGs production/secretion in all examined cells (LSC, LEC and GC) of bovine ovary. Leukotriene treatment modulate secretion of E2, by GC, P4 by LSC and ET‐1 by LEC, which indicates that LTs are involved in regulation of ovarian secretory functions.     

Spatial heterogeneity in statistical power to detect changes in lake area in Alaskan National Wildlife Refuges

Over the past 50 years, the number and size of high-latitude lakes have decreased throughout many regions; however, individual lake trends have been variable in direction and magnitude. This spatial heterogeneity in lake change makes statistical detection of temporal trends challenging, particularly in small analysis areas where weak trends are difficult to separate from inter- and intra-annual variability. Factors affecting trend detection include inherent variability, trend magnitude, and sample size. In this paper, we investigated how the statistical power to detect average linear trends in lake size of 0.5, 1.0 and 2.0 %/year was affected by the size of the analysis area and the number of years of monitoring in National Wildlife Refuges in Alaska. We estimated power for large (930–4,560 sq km) study areas within refuges and for 2.6, 12.9, and 25.9 sq km cells nested within study areas over temporal extents of 4–50 years. We found that: (1) trends in study areas could be detected within 5–15 years, (2) trends smaller than 2.0 %/year would take >50 years to detect in cells within study areas, and (3) there was substantial spatial variation in the time required to detect change among cells. Power was particularly low in the smallest cells which typically had the fewest lakes. Because small but ecologically meaningful trends may take decades to detect, early establishment of long-term monitoring will enhance power to detect change. Our results have broad applicability and our method is useful for any study involving change detection among variable spatial and temporal extents.     

Effects of low temperature on sprout growth of several potato varieties

Summary Two experiments are reported which compared the effects of a period of low temperature (3 C). before placing to sprout at ambient temperature, with continuous storage at ambient temperature, on sprout growth in thirteen potato varieties. In four varieties. Désirée, Majestic, Pentland Meteor and Vanessa, the period of low temperature induced an earlier onset of sprout growth and increased total and individual sprout length per tuber. In the varieties Civa, Craig’s Alliance, Dunluce. Home Guard. Arran Comet and Ulster Sceptre, the period of cold did not hasten the onset of sprout growth but markedly increased the numbers of growing sprouts and total sprout length, although individual sprout length was reduced. In the remaining varieties the period of low temperature had no effects on onset of sprout growth or sprout lengths at the end of storage.

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Zusammenfassung Es wird über zwei Versuche berichtet, die den Einfluss einer Periode niedriger Temperatur (3 C) vor dem Beginn normaler Keimungsbedingungen mit fortw?hrender normaler Lagerung auf das Keimwachstum vergleichen. In vier Sorten, Désirée (mittelfrüh). Majestic (mittelfrüh). Pentland Meteor (früh) und Vanessa (früh), induzierte die Periode niedriger Temperatur einen früheren Beginn des Keimwachstums als fortw?hrende Lagerung unter normalen Bedingungen (Abb. 1). Bei diesen Sorten waren die Gesamtl?nge und die individuelle Keiml?nge am Ende der Keimung gesteigert (Tabellen 1 und 2). Bei Civa, Craig’s Alliance. Dunluce. Home Guard. Arran Comet und Ulster Sceptre (alles frühe Sorten) führte die K?lteperiode nicht zu einem früheren Keimungsbeginn, aber die Zahl der wachsenden Keime stieg an und dadurch die Gesamtkeiml?nge pro Knolle. In diesen Sorten wurde die L?nge des l?ngsten keims pro Knolle durch eine K?lteperiode verringert (Tabellen 1 und 2). Bei den übrigen Sorten hatte die K?lteperiode weder einen Einfluss auf den Keimungsbeginn noch auf die Keiml?ngen am Ende der Lagerung.

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Résumé Dans deux essais sont comparés les effets d’un entreposage à basse température (3 C) suivi d’une mise en germoir, d’une part, et les effets d’une conservation uniquement en germoir, d’autre part, sur la croissance des germes de 13 variétés de pomme de terre. Pour quatre variétés. Désirée, Majestic (demitardives). Pentland Meteor et Vanessa (hatives) le passage au froid induit un départ de germination plus précoce qu’un stockage continu dans les conditions ambiantes (fig. 1). Pour ces variétés, la longueur des germes, totale et individuelle, est augmentée en fin de germination (tableaux 1 et 2). Pour Civa, Craig’s Alliance, Dunluce, Home Guard, Arran Comet et Ulster Sceptre (variétés hatives) le passage au froid ne hate pas le départ de la germination mais augmente de fa?on marquée le nombre de germes et donc la longuer totale de germe par tubercule. Dans ces variétés, la longueur du plus long germe par tubercule est réduite par le passage à basse température (tableaux 1 et 2). Pour les variétés restantes, le froid n’a pas d’effet ni sur le départ de germination, ni sur la longueur des germes à la fin du stockage.

     

Morphophysiology of forage peanut submitted to different intensities of defoliation on grazing with sheep

Tropical Animal Health and Production - The aim was to monitor the growth, the dry mass accumulation curve, and the structural photosynthetic components of forage peanut pasture, in different...     

The distribution of nitrogen in some highly organic tropical volcanic soils

The qualitative and quantitative distribution of N-compounds in 10 tropical soils, and in a number of humic materials extracted from representative samples thereof, was determined after 6 N HCl hydrolysis.Eighty to 98% of the total N in the soils and humic materials was hydrolysable by 6n HCl. Slightly less than one half the hydrolysable N in the soils and humic fractions consisted of amino acids. Well-drained soils and fulvic acids extracted from them contained unusually high concentrations of the acidic amino acids, aspartic and glutamic acids. Between 80 and 95% of the amino acids in the soils was accounted for in the humic materials + NaOH-insoluble organic residues. NH⁺₄-N released by acid hydrolysis was generally higher for the soil samples than for the humic materials. Amino sugar-N constituted relatively small proportions of the total N in the soils and humic fractions.Our data suggest that large quantities of amorphous allophanic materials coupled with relatively high enzymic activity are responsible for the observed accumulation of acidic amino acids in the well-drained tropical volcanic soils.