Strain variation in Dermatophilus congolensis demonstrated by cross-protection studies

Cross-protection studies were conducted with vaccines prepared from two isolates of Dermatophilus congolensis (designated strain 1 and strain 2). The vaccines were prepared as either heat-inactivated, washed, formalized filamentous phase bacterium, mixed with alum as an adjuvant, and inoculated intramuscularly (type A vaccine) or sedimented live filaments inoculated intradermally (type B vaccine). The vaccinated sheep were challenged with D. congolensis zoospores of one or other strain. Challenge sites were observed for the presence and severity of lesions. Serum antibody levels to D. congolensis were monitored after vaccination and challenge. Type A and B vaccines from both strains produced some reduction in the severity of lesions when sheep were challenged with strain 1 but not with strain 2. Unvaccinated control sheep developed more severe and persistent lesions when challenged with strain 2 than controls challenged with strain 1. Serum antibody levels to the type B vaccine prepared from strain 1 were significantly higher (P less than 0.05) than antibody levels to type B vaccine from strain 2. These findings showed there was significant variation in virulence and antigenicity between these two isolates of D. congolensis.     

Musculoskeletal Growth Gradients: A Contribution to Quadrupedal Mechanics

Postnatally, the axial skeleton of the pig shows peaks of high relative growth at the sites of attachment of the fore and hindlimbs, corresponding to the regions of highest relative growth in the limbs. This supports the concept that musculoskeletal growth gradients are a propulsive adaptation.     

Use of limestone wastes from metal mining as agricultural lime: potential heavy metal limitations

Abstract. Finely ground limestone waste from lead mining is discarded as useless but could be a valuable alternative to agricultural limestone. A glasshouse pot experiment established that it is an effective liming material. Two kinds were used: one from north Wales (HMT) represented metal-rich waste produced by the older water-gravity separation of ores; the other (NLB) was a modern flotation tailings. A commercial lime (CLS) was used for comparison. The materials were applied to an acid soil in quantities sufficient to raise the pH to 7 (single liming) and at much greater rates equivalent to annual limings for 369 years. All treatments were replicated five times and the soil/lime mixtures were analysed for EDTA-extractable lead, zinc and cadmium. Radish was grown as the test plant and hypocotyl and leaf tissue were analysed for the same metals. The larger additions of HMT and NLB caused chlorosis and decreased yields. The cadmium and lead concentrations of leaves and hypocotyls suggested that the HMT material could be safely applied to soil annually for 79 years and NLB for 277 years. It is concluded that NLB can be used as agricultural limestone.     

Infection of specific-pathogen-free lambs with parainfluenza virus type 3, Pasteurella haemolytica and Mycoplasma ovipneumoniae

Groups of specific-pathogen-free lambs were inoculated with combinations of parainfluenza virus type 3 (PI₃), Pasteurella haemolytica (P.h.) and Mycoplasma ovipneumoniae ( (M.o.). Acute, necrotising bronchopneumonia developed in 8/9 lambs inoculated with PI₃ followed by P.h. whereas only 1/5 lambs inoculated with PI₃ followed by a combination of M.o. and P.h. developed a pneumonic lesion. When M.o. was inoculated 29 days before PI₃ and P.h., pneumonia developed in 3/4 lambs but M.o. was not reisolated from any of the lungs. Pneumonia was observed in 1/5 lambs inoculated with P.h. alone and in 1/5 inoculated with M.o. plus P.h. In addition, one lamb in the latter group died of acute septicaemic pasteurellosis. None of the lambs inoculated with M.o. alone, PI₃ alone or PI₃ followed by M.o. had any gross or microscopic evidence of pneumonia although the virus alone, or in combination, did produce minor pulmonary lesions.These data suggest that M.o. is not an important primary or secondary lung pathogen.     

Amylase activity in potato tubers

Summary Amylase activity in extracts of sprouted tubers was optimised at final concentrations of soluble starch in the incubation medium of 0.6–2.0 mg cm⁻³. Optimum pH was 6. The exclusion of calcium ions from extraction and incubation media did not result in reduced enzyme activity. This, together with a shift in the absorption maximum of the starch-iodine complex almost identical to that observed with pure β-amylase, indicates the predominance of β-amylase in the extracts. Over a 15-min incubation period the linearity of the response was dependent upon the volume of tuber extract included in the assay medium. Gel filtration of extracts did not influence this response.     

Advances in Functional Genomics and Genetic Modification of Potato

The challenges facing potato breeding have actually changed very little over the years with resistance to pests and pathogens remaining high on the agenda together with improvements in storability, reduction in blemishes, and novelty and consistency in cooking/processing qualities. The need to expand the range of targets for potato improvement is being driven by requirements for reduced agrochemical usage and by predictions of the effects of changing climates. Thus fertiliser and water use efficiency are moving up the political agenda. Genetic variation present in germplasm collections needs to be harnessed to provide the genes and alleles required. This paper provides examples of the functional genomics tools and approaches being developed and deployed to provide new options for advancing the breeding of next generation crops. Whilst genetic modification (GM) approaches remain contentious in Europe, this paper will also provide some recent examples of the range of potential impacts that GM approaches could make. It will also consider the value of so-called intragenic or cisgenic approaches to potato genetic engineering.     

Conservation and management of the rivers of the Kruger National Park: Suggested methods for calculating instream flow needs

1. Six major river systems flow west to east across the Kruger National Park (South Africa). All arise outside the western boundary of the KNP, and are outside the jurisdiction of the Park authorities. 2. Growing human populations to the west of the Park are placing increasing demands on the water resources of these rivers, and a variety of artificial changes threaten the ecological integrity of the rivers. 3. As a result, the Luvuvhu and Letaba Rivers to the north no longer have a perennial flow, while the flow of the Crocodile River on the southern boundary of the Park has been regulated to a more constant regime due to irrigation demands. The Letaba, Olifants, and Crocodile Rivers all receive diverse pollutants. The Sabie River, at present the least disturbed system, and biologically the most diverse in South Africa, is threatened with multiple regulation within the next five years. 4. The paper describes the development of initial protocols for the assessment of instream flow needs for the Luvuvhu and Sabie Rivers. These methods require an extension of existing methods developed in the USA to ensure the maintenance of ecological processes, rather than the maintenance of single target species. 5. Two methods are described: one that identifies the consumptive and non-consumptive water requirements of the rivers, adding all consumptive to the limiting non-consumptive quantity to give a base-flow requirement. 6. A second method uses a conservation status model to assess the ecological consequences of flow reductions generated through a hydrological model, in response to different impoundment conditions. 7. Both methods are successful in appropriate circumstances, but we conclude that the proposed impoundment and agricultural development of the Sabie River, in particular, is an inappropriate use of this unique resource, and that the catchment would be more advantageously developed for tourism, recreation, and nature conservation.     

Investigations on sprout growth in cv. Maris Piper: tuber wounding effects and growth from tuber cores of different dimensions

Summary Sprout dry weight accumulation was stimulated by an increase in the amount of tuber substrate available. Wounding had an additional promotory effect on both dry weight accumulation and extension growth. Sprout dry weight accumulation from tuber cores of the same fresh weight was enhanced by an increase in the diameter of the core when samples were planted either in perlite or UC compost. In compost, elongation rates of both main and branch sprouts were inversely related to core fresh weight but positively related to core diameter when fresh weight was kept constant. The number of branch sprouts per eye was positively related to core fresh weight.

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Zusammenfassung Der Verlauf des Keimwachstums wurde mit Knollen, die in verschiedenen Abst?nden vom keimenden Auge verletzt waren. untersucht. Die Inkubation erfolgte bei 12°C im Dunkeln in feuchtem ‘University of California’ Kompost. Obwohl die Steigerung des Keimtrockengewichtes mit der Zunahme an verfügbarem Knollensubstrat erh?ht wurde, hatte die Verletzung noch einen zus?tzlichen steigernden Einfluss, sowohl auf das Keimtrockengewicht als auch auf das L?ngenwachstum, das noch st?rker gef?rdert wurde (Abb. 1). Wahrscheinlich sind sowohl das Ausmass der Verletzung als auch der Abstand der Verletzung vom Keim wichtig in bezug auf den Wachstumseinfluss. Der Einfluss der Gr?sse der Knollenstücke auf das Keimwachstum wurde ebenfalls untersucht. Zus?tzlich zu der positiven Wirkung des steigenden Knollenstückgewichtes auf die Erh?hung des Keimtrockengewichtes zeigte sich noch ein weiterer Einfluss durch eine Vergr?sserung des Knollenstückdurchmessers (Abb. 2). Wurden die Knollenstücke in Kompost gepflanzt, zeigte sich in bezug auf das L?ngenwachstum sowohl der Haupt-als auch der Seitentriebe ein umgekehrtes Verh?ltnis zum Frischgewicht der Knollenstücke, aber ein positives zum Durchmesser der Knollenstücke bei konstantem Frischgewicht (Abb. 3). Die Zahl der Seitentriebe pro Auge war mit dem Frischgewicht der Knollenstücke positiv korreliert.

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Résumé La cinétique de la croissance du germe a été étudiée à l'aide de tubercules blessés à différentes distances des yeux, en maintenant des explantats à 12°C et à l'obscurité, dans un compost humide mis au point à l'Université de Californie. Bien que l'accumulation de matière sèche dans le germe ait été stimulée par l'augmentation du substrat assimilable provenant des gros explantats, la blessure a provoqué un effet cumulatif sur la teneur en matière sèche du germe et, de fa?on plus conséquente, sur son élongation (fig. 1). Il semble que l'importance de la blessure ainsi que sa distance par rapport à l'oeil jouent un r?le déterminant sur le dégré de réponse du germe. Des expériences ont également été réalisées sur des fragments de tubercules pour déterminer l'effet de la dimension de l'explantat sur la croissance du germe. En plus de l'effet positif sur la teneur en matière sèche, d? à l'augmentation du poids de l'explantat, on a observé un effet favorable lorsque le diamètre de ce dernier était plus élevé (fig. 2). Après plantation dans le compost, le taux d'élongation du germe principal et des germes ramifiés tendait à être inversé par rapport au poids frais de l'expplantat mais restait positif par rapport à son diamètre, à poids frais égal (fig. 3). Le nombre de ramifications par oeil était en relation directe avec le poinds frais de l'explantat.