Seroprevalence to Leptospira interrogans serovar hardjo in Merino stud rams in South Australia

Summary A serological survey of 2160 Merino stud rams on 36 farms detected positive reactions greater than or equal to 1/100 in 42% of animals using the microscopic agglutination test (MAT) to Leptospira interrogans serovar hardjo. Twenty flocks had seroprevalence values greater than 30% with 15 flocks having values 60%. The enzymelinked immunosorbent assays showed that 47% and 3% of rams on the 36 farms were positive for IgG and IgM antibodies, respectively. Forty-five percent of hardjo reactions were in rams that had not been exposed to cattle. Significant correlations were found between IgM reactors and creek/dam water pumped into troughs, and between MAT/IgG reactors and total flock size. No statistical relationships were detected between positive reactors and two different annual average rainfall gradients, the time of the year in which samples were obtained, or agricultural regions of South Australia. Infections with an organism of the Sejroe serogroup is widespread in Merino stud rams.     

巴美肉羊INHA和INHBA基因多态性与产羔数关系研究

为了研究INHA和INHBA这两个基因对巴美肉羊产羔数的影响,采用PCR-SSCP技术检测抑制素α亚基(α-inhibin,INHA)和βA亚基(βA-inhibin,INHBA)基因在巴美肉羊中的单核苷酸多态性。结果发现,引物1,4,6扩增片段有多态性,其余3对引物的扩增片段均不存在多态性。引物1,巴美肉羊有2种基因型AB型和AA型,平均产羔数AB型比AA型多0.17只(P<0.01)。引物4,巴美肉羊存在3种基因型(CC、DD和CD),巴美肉羊平均产羔数DD型比CC型多0.44只(P<0.01)。引物6,巴美肉羊有3种基因型(EE、FF和EF),EE型比EF型平均产羔数多0.21只(P<0.01),结果表明,抑制素α亚基(α-inhibin,INHA)和βA亚基(βA-inhibin,INHBA)基因是影响巴美肉羊产羔数的重要基因。     

Inhibition of seed germination and seedling growth by hound's-tongue (Cynoglossum officinale L.) seed leachate

The leaching of phenolics from decoated seeds, seed coats and pericarps of hound's-tongue ( Cynoglossum officinale L.), factors affecting leaching, and seed germination and seedling growth inhibitory activities of the leachate were investigated. Embryonic axes and cotyledons contained a large amount of methanol-soluble phenolic substances. Decoated seeds released phenolics into an aqueous incubation medium and this solution was capable of inhibiting root elongation of several grassy and broadleaf species, but not of hound's-tongue. The leachate and the phenolic fraction of the leachate inhibited germination of bluebunch wheatgrass ( Pseudoroegnaria spicata (Pursh) A. Löve [syn. Agropyron spicatum (Pursh) Scribn. and J. G. Sm.]). The non-phenolic fraction of the leachate did not inhibit seed germination or root and shoot elongation of bluebunch wheatgrass. Low oxygen and an increasing temperature significantly increased the amount of phenolic substances leached from decoated seeds. Increased leaching of phenolic substances related to an increasing temperature was associated with the loss of seed viability. Further investigation of the role of water-extractable hound's-tongue seed phenolics in the interaction of this species with its biotic environment under field conditions is needed to determine the ecological significance of these findings.     

Comparison of the Strength and Holding Power of 4 Pin Designs for Use with Half Pin (Type I) External Skeletal Fixation

The strength and holding power of four pin designs for use with half pin (type I) external skeletal fixation were evaluated. Pins that were tested were fully threaded, nonthreaded, two cortices partially threaded, and one cortex partially threaded. The study involved three parts: (1) resistance of the pins to axial extraction immediately after insertion; (2) resistance of the pins to axial extraction 8 weeks after being inserted into the tibiae of live dogs; and (3) resistance of the pins to bending load. Pins with threads engaging two cortices were more resistant to axial extraction than nonthreaded pins in both the acute (p less than 0.0001) and chronic (p less than 0.0001) studies. Nonthreaded pins were more resistant to bending than fully threaded and two cortices partially threaded pins (p less than 0.0005). One cortex partially threaded pins possessed similar bending strength to nonthreaded pins (p = 0.21) and had 5.3 times more resistance to axial extraction in the acute study (p less than 0.0001) and 6.9 times more in the chronic study (p less than 0.0001). Though one cortex partially threaded pins were not as resistant to axial extraction as pins with threads engaging two cortices (p less than 0.0001), they were more resistant to bending loads (p less than 0.0005). Loss of holding power and pin failure are two of the most serious problems associated with fracture stabilization using external skeletal fixation. The results of this study suggest that one cortex partially threaded pins are better at maintaining holding power and resisting bending and breaking than nonthreaded pins.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of barley yellow dwarf virus on susceptibility of barley cultivars to net blotch (Pyrenophora teres) and leaf blotch (Rhynchosporium secalis)

The effect of barley yellow dwarf virus (BYDV) on the development of net blotch (Pyrenophora eves) and leaf blotch (Rhynchosporium secalis) was examined on seven barley cuitivars. Seedlings were infected with BYDV at the two-leaf stage (G.S. 12). Their susceptibility to three isolates of p teres and isolates of two races (U.K. 1, U.K. 2) of R. secalis was examined at the four-leaf stsge (G.S. 14) and when plants were more mature (G.S. 33/38). At G.S. 14 numbers of lesions produced by P. teres and R. secalis were reduced, on average, by 37 and 72% respectively, and at G.S. 33/38 by 61 and 74%.     

Testing a mechanistic model. V. The points of zero salt effect for phosphate retention, for zinc retention and for acid/alkali titration of a soil

The pH of samples of a soil was altered by adding acid or lime and incubating the moistened soil at 60°C. The effect of varying the concentration of salt on pH, retention of phosphate, and retention of zinc was then measured. At low pH, increasing the concentration of salt decreased phosphate retention; at high pH, it increased it. The pH at which the effects crossed over (that is, the point of zero salt effect on phosphate retention) was higher than the point of zero salt effect on pH. This is opposite to effects observed with uniform surfaces. These results were described by a model in which it was assumed that individual sites varied in their electrostatic potential and that phosphate was retained preferentially by sites with the highest potential. Zinc retention was decreased by high concentrations of salt. This was partly because of effects of salt in decreasing the pH of solutions in contact with soil. There was no indication of a crossing-over of effects at low pH. This suggested that the electrostatic potential of zinc-retaining sites did not vary much with pH.