Sensitivity of boreal forest carbon balance to soil thaw   总被引：6，自引：0，他引：6  

ML Goulden  SC Wofsy  JW Harden  SE Trumbore  PM Crill  ST Gower  T Fries  BC Daube  S Fan  DJ Sutton  A Bazzaz  JW Munger 《Science (New York, N.Y.)》1998,279(5348):214-217

We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site.  相似文献   

Comparison of tiletamine-zolazepam-ketamine and tiletamine-zolazepam-ketamine-xylazine anaesthesia in sheep     

HC LIN  SS WALLACE  JW TYLER†  RL ROBBINS  JC THURMON‡  DF WOLFE 《Australian veterinary journal》1994,71(8):239-242

Summary The anaesthetic effects of intravenous tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg (TK) and tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg-xylazine 0.11 mg/kg (TKX) were evaluated in six wethers. Heart rate, respiration rate, arterial blood pressure, and the electrocardiogram were monitored during anaesthesia. Analgesia was tested by electrical stimulation in the left flank. Atropine (0.03 mg/kg) was given intramuscularly before induction, but after recording of baseline heart rate and respiratory rate. The duration of analgesia was 28.7 ± 6.9 min with TK and 82.8 ± 26.6 min with TKX. Heart rate increased significantly within 5 min after TK or TKX administration. Respiratory rate remained unchanged after TK administration, but increased significantly from 5 to 45 min after TKX administration. Arterial blood pressure decreased significantly at 15 min with TK and 30 min with TKX. Sheep remained recumbent for 201 min with TK and 166 min with TKX. All recovered uneventfully. We conclude that either TK or TKX may be used for anaesthetising sheep.  相似文献   

Maturation Status, Protein Synthesis and Developmental Competence of Oocytes Derived from Lambs and Ewes   总被引：2，自引：0，他引：2  

HPS Kochhar  B Wu  LHA Morris  BC Buckrell  JW Pollard  PK Basrur  & WA King 《Reproduction in domestic animals》2002,37(1):19-25

The efficacy of oocyte selection for in vitro embryo production depends on the abundance and diameter of follicles, cumulus layers around the oocytes and subsequent fertilization. Application of `ovum pick-up' technique allows us to utilize partially matured oocytes for embryo production even from juvenile subjects. To compare their developmental competence, oocytes derived from lambs and ewes and cultured in maturation medium for up to 26 h were assessed at 2 h intervals by confocal microscopy after chromatin and microtubulin-specific fluorochrome labelling. Lamb oocytes reached second meiotic metaphase (MII) at lower numbers at 24 h (60.0%) and 26 h (28.6%) whereas 85.7% of adult-derived oocytes attained MII status by 24 h of maturation. Radiolabelling of oocyte proteins revealed higher incorporation of [³⁵S-]-methionine and [³⁵S]-cysteine in adult-derived oocytes compared to lamb oocytes. Although the cleavage rate of lamb oocytes was similar to that of ewe oocytes, the proportion reaching blastocyst stage was significantly lower (p < 0.05) in the lamb-derived oocytes. However, blastocysts from both types of oocytes displayed similar cell lineage allocations to inner cell mass and trophectoderm.  相似文献   

Blindness in South Australian Kangaroos     

PJK DURHAM  JW FINNIE  DA LAWRENCE  P. ALEXANDER 《Australian veterinary journal》1996,73(3):111-111

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The efficacy of a controlled-release albendazole capsule in suppressing nematode burdens in sheep   总被引：3，自引：0，他引：3  

NJ BARTON  B. RODDEN†  JW STEEL‡ 《Australian veterinary journal》1990,67(11):408-410

An experiment was undertaken between July and November 1985 in East Gippsland, Victoria, to determine the efficacy of an intra-ruminal controlled-release albendazole capsule against naturally acquired worm burdens and larval challenge in Merino hoggets. Two groups of 20 sheep, one group untreated, the other dosed with a capsule were grazed together; 5 sheep from each group were slaughtered for total worm counts 30 and 101 d after capsules were administered. Serum anthelmintic concentrations, faecal egg counts and body weights were monitored. Most capsules were exhausted within 91 d of administration. During the estimated 80 d for which they remained active the capsules were highly effective against the benzimidazole-susceptible worm populations. Faecal egg counts were reduced to zero and total worm populations were reduced by over 97% 30 d after administration. By 101 d egg counts were increasing and worm counts indicated that sheep were becoming reinfected. Sheep treated with the capsules grew faster than those not treated.  相似文献   

A collapse syndrome associated with Gram-negative infection in cows treated with dexamethasone to induce parturition     

JW BROWNING  KJ SLEE  J. MALMO  P. BRIGHTLING 《Australian veterinary journal》1990,67(1):28-29

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Progressive ataxia associated with degenerative thoracic myelopathy in Merino sheep     

PAW HARPER †  JW PLANT  KH WALKER  KG TIMMINS† 《Australian veterinary journal》1991,68(11):357-358

A neurological disorder in Merino sheep, characterised clinically by progressive posterior ataxia and microscopically by Wallerian degeneration in thoracic segments of the spinal cord, is described. Animals of both sexes were affected, with the earliest onset of disease being at 5 months of age. Most affected animals died before 2 years of age. The clinical, pathological and epidemiological features suggest that this degenerative thoracic myelopathy is a previously unrecognised entity differing from other reported causes of ataxia in sheep in Australia.  相似文献   

Characterization of mRNA Expression in Preimplantation Bovine Embryos     

C Wrenzycki  D Herrmann  E Lemme  K Korsawe  JW Carnwath  H Niemann 《Reproduction in domestic animals》1998,33(3-4):307-311

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Fossil communities     

Schopf TJ 《Science (New York, N.Y.)》1979,203(4384):999-1000

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Tumour angiogenesis,anti‐angiogenic therapy and chemotherapeutic resistance          下载免费PDF全文

KA Mander  JW Finnie 《Australian veterinary journal》2018,96(10):371-378

In order for a tumour to continue to grow and disseminate, it must acquire a new blood supply. Neovascularisation can be enacted by a number of different mechanisms. This dependence of tumour progression on an augmented vascular supply has been exploited by the development of anti‐angiogenic drugs, which are designed to inhibit new blood vessel formation or disrupt existing tumour‐associated vasculature, both leading to ischaemic–hypoxic tumour cell death. However, the clinical benefits of these therapeutic approaches are frequently variable and often transient, the neoplasm sometimes being able to use other neovascularisation mechanisms to maintain its blood supply and thus evade the current anti‐angiogenic therapy. Tumours may also develop a more malignant phenotype following this treatment. Clinical outcomes may be improved by simultaneously inhibiting different angiogenic pathways, abetted by more effective drug delivery regimens such as metronomic chemotherapy and the concurrent use of other antitumour modalities.  相似文献