<Emphasis Type="Italic">Mycobacterium bovis</Emphasis>, but also <Emphasis Type="Italic">M. africanum</Emphasis> present in raw milk of pastoral cattle in north-central Nigeria     

Simeon I. B. Cadmus  Mohammed K. Yakubu  Abdullahi A. Magaji  Akinbowale O. Jenkins  Dick van Soolingen 《Tropical animal health and production》2010,42(6):1047-1048

Using deletion typing technique, five mycobacteria isolated from unpasteurised milk samples from cows in north-central Nigeria were characterized as Mycobacterium bovis (n = 4) and M. africanum (n = 1). This report emphasizes that transmission between the animal and human reservoir is a serious threat in Nigeria.  相似文献   

Depletion of soil organic carbon and nitrogen under Pinus taeda plantations in Southern Brazilian grasslands (Campos)     

M. Wiesmeier    D. P. Dick    C. Rumpel    R. S. D. Dalmolin    A. Hilscher  & H. Knicker 《European Journal of Soil Science》2009,60(3):347-359

Establishment of pine (Pinus spp.) plantations on grasslands could increase carbon (C) sequestration to counteract increased atmospheric carbon dioxide concentrations. In the grasslands of the southern Brazilian highland (Campos), large areas have been converted to Pinus plantations over the last 30 years. In order to assess the impact of this land‐use change on the amount and composition of soil organic matter (SOM), we investigated a grassland pasture site (G), and both an 8‐year‐old (P8) and a 30‐year‐old (P30) plantation with Pinus taeda. Soil samples down to 45 cm were analysed for texture, pH, soil organic carbon (SOC) and total nitrogen (N_tot) concentrations. Chemical composition of SOM was determined by using cross‐polarization magic angle spinning (CPMAS) ¹³C NMR spectroscopy. We analysed for stable C isotope (δ¹³C) and assessed the lignin composition by CuO oxidation. Additionally, contents of pyrogenic organic material (PyOM) were determined because the Campos is regularly burnt. Both pine plantations revealed relatively small SOC concentrations in the mineral soil of 72.6 mg g^?1 (P8) and 56.8 mg g^?1 (P30) and N_tot concentrations of 4.0 mg g^?1 (P8) and 2.9 mg g^?1 (P30) for the A horizon, while grassland showed significantly (P < 0.01) larger contents of 100.2 mg g^?1 for SOC and 5.9 mg g^?1 for N_tot. Accumulation of litter layers suggests decreased input of organic material into the mineral soil under pine, which was confirmed by the δ¹³C values and lignin composition. Smaller contents of vanillyl‐ (V), syringyl‐ (S), and cinnamyl (C)‐phenols, smaller ratios of S/V and C/V, and smaller ratios of acidic to aldehydic forms of V and S phenols indicated a high degree of decomposition of residual grass‐derived SOM in the upper part of the mineral soil (0–10 cm) under pine plantations. This was confirmed by CPMAS ¹³C NMR spectroscopy, showing an increasing Alkyl C/O‐Alkyl C ratio at the same depth. No significant changes in the contents of PyOM could be detected, but all sites tended to show the greatest concentrations at deeper soil depths > 15 cm, indicating a vertical relocation of PyOM. The results suggest that decomposition of residual SOM originating from grassland species contributes to the decrease of SOC and N_tot and to an acidification in the topsoil under pine plantations. We also suggest that slow litter decomposition and incorporation and the absence of fires at the plantations are additional reasons for the reduced amount of SOM. Depletion of SOM and the acidification of the topsoil may reduce the availability and supply of nutrients and diminish the C sequestration potential of the mineral soil.  相似文献   

Application of 13C-labeled litter and root materials for in situ decomposition studies using phospholipid fatty acids     

Jennifer Moore-Kucera  Richard P. Dick 《Soil biology & biochemistry》2008,40(10):2485-2493

Microorganisms play a central role in litter decomposition and partitioning C between CO₂ evolution and sequestration of C into semi-permanent pools in soils. At the ecosystem level, forest stand age influences rates of litter accumulation and quality, and micro-climatology which could affect the microbial community structure and C sequestration processes. Although numerous laboratory experiments have studied the decomposition of model ¹³C-labeled compounds, few studies have verified these findings under field conditions. The objective of this study was to track decomposition of ¹³C-labeled Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) materials into the soil microbial community using ¹³C-phospholipids fatty acid (PLFA) analysis in three different aged forest stands. A field experiment was conducted that had three forest stand age treatments: old-growth (>500 yrs); 8-year-old clear-cut (CC8); and 25-year-old clear-cut (CC25) (landscape reps of n = 2). Each stand age had in situ microcosms that were amended with either ¹³C-labeled surface litter or root material. Microcosms were destructively sampled seven times over a 22-month period and the soil was analyzed for the relative amounts of ¹³C incorporated (¹³C%_INCORP) into PLFAs and the proportional distribution of ¹³C incorporated into PLFAs. The ¹³C%_INCORP was affected by stand age and ¹³C source with greater ¹³C%_INCORP in samples from CC8 than OG or CC25. Also, the level of ¹³C%_INCORP was greater for labeled litter than root material in five out of the seven sample dates. In general, 18:1ω9 and 18:2ω6,9 (common fungal biomarkers) had the greatest amount of ¹³C incorporation throughout the study period in both clear-cut and old-growth sites, especially in plots with ¹³C-labeled litter. Our data showed a low fungal ¹³C-PLFA: bacterial ¹³C-PLFA ratio (0.45) 1 month after incubation was initiated compared to 5, 7 and 9 months after incubation (two of these dates were >1.0). This suggests that initially bacteria played a greater role in the decomposition of the added needles with fungi playing a more important role in subsequent sample dates. Our results illustrate that the use of ¹³C-labeled materials in field studies coupled with¹³C-PLFA profiling is a powerful tool for determining microbial dynamics during decomposition – enabling statistically significant detection of land management treatment effects on C acquisition by microbial functional groups.  相似文献   

The distribution of pepsinogen within the abomasa of cattle and sheep infected with Ostertagia spp. and sheep infected with Haemonchus contortus.     

I Scott  A Dick  J Irvine  M J Stear  Q A McKellar 《Veterinary parasitology》1999,82(2):145-159

The effect of nematode infections on the production of pepsinogen by ruminants was investigated immunohistochemically and biochemically. Abomasal tissues were collected from parasite-naive cattle and sheep, from sheep infected with predominantly Ostertagia circumcincta, sheep infected experimentally with Haemonchus contortus and cattle infected with Ostertagia ostertagi. Pepsinogen was also assayed biochemically in homogenates of fundic mucosae from sheep infected with predominantly O. circumcincta. Infection with Ostertagia spp. parasites was associated mainly with nodular hyperplasia, resulting in increased numbers of cells that produce both pepsinogen and mucus. Measured biochemically, nodules contained more pepsinogen than adjacent more normal mucosa (p < 0.05), and this effect was largely attributable to the greater mass of nodules. Infection of sheep with H. contortus was associated with generalised hyperplasia, characterised by increased numbers of mucopeptic cells and in at least one animal with reductions in parietal cell numbers. At the same time, the zymogen granule content of chief cells was reduced. Similar changes were occasionally seen in sheep infected predominantly with O. circumcincta. Generalised hyperplasia is likely to be indicative of the presence of ambulatory parasitic stages as opposed to those confined to nodules. The potential for the enhanced production of pepsinogen by increased numbers of cells with a joint mucous cell and zymogenic cell phenotype may offset decreases in the numbers of chief cells or reductions in chief cell activity.  相似文献   

Physiological and genetic control of tuber formation   总被引：7，自引：0，他引：7  

Paul C. Strunik  Dick Vreugdenhil  Herman J. van Eck  Christian W. Bachem  Richard G. F. Visser 《Potato Research》1999,42(2):313-331

Summary Tuber formation is a plalstic and complex, but well-orchestrated sequences of morphological. physiological and biochemical events. The physiological control mechanisms of this sequence of events may involve many hormones, but certainly gibberellic acids play a dominant role: they affecft most steps and are influenced by inducing or non-inducing conditions in a manner consistent with effects of these conditions on tuber induction. The genetic control is also complex. Numerous cDNA fragments have been isolated which are specifically expressed during tuberization. They can be used in anti-sense orientation in transgenic plants to thest their possible role in tuberization. In addition these cDNA fragments are used as genetic marker loci in QTL mapping studies and serve as candidate genes to exlain phenotypic variation. Profiles of the importance of QTLs over time may be combined with expression profiles of candidate genes. Such novel approaches offer unique opportunities for synergism between physiology, molecular biology and genetics.  相似文献   

Saintpaulias in their natural environment with notes on their present status in Tanzania and Kenya     

Dick R. Johansson 《Biological conservation》1978,14(1):45-62

Several species of the genus Saintpaulia, popularly known as Usambara violets, have become a remarkable success as indoor plants in Europe and the USA. Their ancestors, some twenty species in total, live in mountains and near the coast in Tanzania and Kenya. The Saintpaulias require a very special environment since they are sensitive to drought and to competition from other plants. Thus, most species live on steep rock surfaces in dense shade where few other plants thrive. The Usambara violets in cultivation are mostly referred to as Saintpaulia ionantha. Previous records of this species refere to a restricted area near Tanga in Tanzania where today it is very rare because of changes in the environment. Tree-felling to create farmland or to obtain firewood has exposed the previously shaded limestone cliffs, making them unsuitable as habitat for Saintpaulia ionantha.Generally speaking, disturbance of the environment by clearance of trees and bushes is the main threat to the survival of most species, particularly those which occur in the lowlands.  相似文献   

栗树提取物可增强机体健康     

Dick Ziggers  孔祥峰  戴宁海 《国外畜牧学(猪与禽)》2007,27(4):16-17

当你漫步在农业展览会的展厅小道时,有时可能会经过一个正在展览不为大多数人所知晓的新产品的展台。今年,在荷兰乌德勒支市的VIV交易会上,Dick Ziggers就惊奇地发现,意大利Silvamicha公司正在展览他们专为牛、猪和禽开发的饲料添加剂--栗树提取物。  相似文献   

Location of the microflora in the skin of cattle   总被引：1，自引：0，他引：1  

D H Lloyd  W D Dick  D M Jenkinson 《The British veterinary journal》1979,135(6):519-526

  相似文献   

Localisation and quantification of elements in biological tissues by electron-microprobe analysis     

David A. T. Dick 《Pest management science》1979,10(4):333-340

An introduction is provided to the basic ideas and theory of electron-microprobe analysis as applied to biological tissue. The nature of characteristic and continuous X-rays is outlined. X-ray detectors, specimen preparation and the relative advantages and disadvantages of thick and thin section techniques are discussed.  相似文献   

Comparative efficacy of fenthion, dichlorvos/fenitrothion and permethrin against the flea, Ctenocephahdes felis, on the dog     

M. A. Fisher  M. J. Hutchinson  D. E. Jacobs  I. G. C. Dick 《The Journal of small animal practice》1994,35(5):244-246

In a series of three replicated and controlled trials, nine dogs artificially infected with Ctenocephalides felis were treated with a systemically active ‘spot-on’ formulation of fenthion, six with a topical spray containing dichlorvos and fenitrothion and six with a surface active ‘spot-on’ preparation containing permethrin, all at recommended dose rates. Good knockdown efficacy was apparent at eight hours with the dichlorvos/fenitrothion combination and at 24 hours with the other formulations. Efficacy values in excess of 95 per cent persisted for at least 22 days in the case of the systemic fenthion preparation and the permethrin product and eight days for the dichlorvos and fenitrothion combination. Twenty-nine days after treatment there was still substantial protection in the fenthion- and permethrin-treated animals, indicated by an 88 and a 77 per cent reduction in flea counts in the two groups, respectively.  相似文献