Aspen bark photosynthesis and its significance to remote sensing and carbon budget estimates in the boreal ecosystem     

V. I. Kharouk  E. M. Middleton  S. L. Spencer  B. N. Rock  D. L. Williams 《Water, air, and soil pollution》1995,82(1-2):483-497

Aspen bark was investigated for photosynthetic function, pigment content, and spectral characteristics during the 1993–1994 Boreal Ecosystem-Atmosphere Study (BOREAS) summer field campaigns in the boreal zone of Saskatchewan, Canada. Parameters related to photosynthetic function were similar for bark and leaves: chlorophyll (Chl) concentration; fluorescence responses; and spectral reflectance. Similar increases along a vertical gradient from base to tree top were observed for incident photosynthetically active radiation (PAR), photosynthetic pigment content, photosynthetic capacity, and spectral reflectance variables. Since transmittance of aspen bark periderm was 20–30% in the blue, and 50–60% in the red Chl absorption bands, the PAR available to the photosynthetic cortical layer in the natural, canopy environment (<1000 μmol m^?2 s^?1) was sufficient to support positive net assimilation (<8–10 νmol CO₂ m^?2 s^?1) under ideal conditions (e.g., light, temperature, saturating CO₂), a rate approximately 30–50% that of leaves. However, the respiring tissues comprising the greater fraction of bark tissue bias the balance of CO₂ exchange in favour of respiration for the whole bark. Therefore, net photosynthesis under ambient conditions on the whole bark was, in general, negative. The total bark surface area was estimated to contain 17–40% of the whole tree Chl. The contribution of the bark surface area fraction of the full canopy (leaves plus bark) increased with age (<60 years), with a similar trend expected for bark in total tree (and stand) photosynthesis. A spectral reflectance variable, the red edge inflection point (REIP), was related to total bark Chl content (r²=0.74). A better predictive relationship (r²=0.82) for total bark Chl was observed using a spectral index calculated from the reflectance ratio of two narrow wavebands (R3/R2: R2 and R3 are between 0.715–0.726 μm and 0.734–0.747 μm, respectively), which may have greater utility in landscape remote sensing. The bark spectra for Chlcontaining bark should improve understanding of carbon balance in aspen forests, based on landscape-level radiative transfer simulations.  相似文献   

IMAGES IN MEDICINE     

Reid  Tyson  DVM  Crispin P.  Spencer  DVM  DACVR 《Veterinary radiology & ultrasound》2003,44(5):594-594

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Antibody response to modified-live canine adenovirus vaccine in African hunting dogs (Lycaon pictus).     

J A Spencer 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1991,38(6):477-479

Nine hunting dogs were bled pre and post vaccination with modified-live virus vaccine. Their antibody responses to canine adenovirus type 1 was measured by an indirect immunofluorescent antibody test. The vaccine proved to be both effective and safe.  相似文献   

Ethanol euthanasia and its effect on the binding of antibody generated against an immunogenic peptide construct.   总被引：1，自引：0，他引：1  

R Lord  G L Jones  L Spencer 《Research in veterinary science》1991,51(2):164-168

Mice were immunised with an immunogenic peptide construct CKNNNSTNSGI coupled to diphtheria toxoid as a carrier. This peptide sequence contains the epitope STNS which is the target of inhibitory monoclonal antibodies directed against the second merozoite surface antigen of Plasmodium falciparum. Antisera raised against the peptide construct were taken using an injection of 70 per cent ethanol or sodium pentobarbitone as methods of euthanasia and these methods compared by determining their effects on the binding specificity of the antibody to the antigen using the immunological criteria of immunofluorescence, immunoblotting criteria of immunofluorescence, immunoblotting and ELISA assays. There was no significant decrease in antibody binding with either sodium pentobarbitone, or ethanol with a final concentration of less than 30 per cent in mouse antisera. Antisera with an added ethanol concentration of 40 to 60 per cent relaxed antibody conformation and this raises the possibility of using the differential effects of ethanol as a tool in mapping antigenic fine structure of a range of antibodies directed against defined epitopes. The cross-reactive response of non-specific antibodies in polyclonal antisera was lowered at the suggested dosage for ethanol euthanasia. Ethanol has immense potential as an alternative method of euthanasia when barbiturate drugs, such as sodium pentobarbitone, are unavailable in specific experimental protocols. This may especially aid research workers in developing countries involved in vaccine development, antibody production and subsequent serological analysis.  相似文献   

A STUDY OF UROLITHIASIS IN GRAZING RUMINANTS IN SOUTH AUSTRALIA     

G. H. McIntosh  B.V.Sc.  Ph.D.  M. F. Pulsford  B.V.Sc.  H.D.A.†  W. G. Spencer  M.A.  Ph.D.‡ H. Rosser  Dip. App. Phys.§ 《Australian veterinary journal》1974,50(8):345-350

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Immunization against Marek's disease: influence of strain of chickens, maternal antibody, and type of vaccine   总被引：2，自引：0，他引：2  

J L Spencer  J S Gavora  A A Grunder  A Robertson  G W Speckmann 《Avian diseases》1974,18(1):33-44

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Antibody responses of sheep vaccinated with foot rot vaccines   总被引：1，自引：0，他引：1  

G R Ferrier  T L Spencer  S C Smith 《Research in veterinary science》1988,45(1):68-71

Enzyme-linked immunosorbent assay (ELISA) and crossed immunoelectrophoresis (IEP) were used to investigate antibody responses of sheep vaccinated with a double adjuvanted or single adjuvanted commercial foot rot vaccine. ELISA detected an antibody response of greater magnitude to the double adjuvant vaccine compared with the single adjuvant vaccine. Sera from sheep vaccinated with double adjuvant vaccine recognised at least six antigens of Bacteroides nodosus in crossed IEP while sera from the single adjuvant vaccinated sheep recognised one antigen. The use of non-denatured antigens of B nodosus in ELISA and crossed IEP enabled quantitative comparisons of antibody responses to the different foot rot vaccines to be made.  相似文献   

Manpower: a surplus in supply or demand?     

L Spencer 《Journal of the American Veterinary Medical Association》1989,194(9):1172-3, 1175

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Essex reveals new gene therapy for AIDS.     

L Spencer 《Journal of the American Veterinary Medical Association》1992,201(11):1673-1674

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A novel approach to growth promotion using auto-immunisation against somatostatin. I. Effects on growth and hormone levels in lambs     

G.S.G. Spencer  G.J. Garssen  I.C. Hart 《Livestock Production Science》1983,10(1):25-37

Nine three-week-old lambs were immunised against somatostatin linked to human serum globulin. Significant antibody titres were obtained in all these lambs. The rate of weight gain was greater in those animals immunised against somatostatin (treated) than in the control animals which were immunised against globulin alone (P < 0.001). The final height of the treated lambs was also significantly greater (P < 0.05) as a result of increased height velocity during the period of treatment (P < 0.01).Evaluation of the animals both before and after slaughter indicated that there was no effect of treatment upon body composition, but rather that there had been proportional growth. The carcass assessments revealed that the treated lambs had a longer leg-length (P < 0.01) and had a greater warm carcass weight (P < 0.05) than the control animals, but had similar scores for fat and muscle covering. There was no difference in wool weight between the two groups.No significant difference was found between the groups in the basal levels of either insulin or growth hormone. However, growth hormone release following arginine infusion was greater in the treated animals. There was also a small, but significant, difference (P < 0.05) in the levels of bioassayable somatomedin activity between the treated and control lambs, the treated lambs having higher somatomedin activity.Histological examination of the pancreas from control and treated lambs revealed an increased incidence of abnormalities (mainly acinar necrosis and loss of beta-cell staining) in the islets of Langerhans in the treated lambs, but it could not be concluded that auto-immunisation against somatostatin produced any specific morphological change in the betacells of the pancreatic islets.The results of this study suggest that somatostatin plays an important physiological role in regulating growth stimulation. Removal of the inhibitory effect of somatostatin (in this case by neutralisation of the effect with antibodies) can result in increased growth. The hormonal changes induced by this treatment have yet to be fully elucidated. Further investigations are required to assess the usefulness of this treatment as an alternative to the more conventional synthetic steroid treatments for growth promotion.  相似文献