Development of drought‐tolerant breeding lines derived from Helianthus annuus × H. argophyllus interspecific crosses

Helianthus argophyllus is a wild species known as “silver sunflower”, which possesses several traits, including morphological traits that increase drought tolerance. Therefore, introgressions between chosen cultivated lines and two H. argophyllus accessions were made, and segregating generations were established. Important agronomic traits including single heading, high pollen fertility, silver canopy (indicating more cuticular wax), and content of cuticular waxes and oil were selected over six segregating generations. The resulting F₆ lines showed introgression of water saving traits, as they had lower excise leaf water loss, with comparable yield to standard checks. However, these F₆ lines were late maturing and showed poor flowering synchronization between the cultivated and introgressed lines. Introgressed line “D‐22” was particularly promising as a breeding line, with superior agronomic and drought resistance traits. This line had the potential to be used as an inbred parental line for introgression of drought resistance traits into elite sunflower germplasm. Combining ability analysis of the introgressed lines further showed their potential for heterosis breeding or to be used as parental lines in breeding programme.     

Ecosystem collapse in Pleistocene Australia and a human role in megafaunal extinction

Most of Australia's largest mammals became extinct 50,000 to 45,000 years ago, shortly after humans colonized the continent. Without exceptional climate change at that time, a human cause is inferred, but a mechanism remains elusive. A 140,000-year record of dietary delta(13)C documents a permanent reduction in food sources available to the Australian emu, beginning about the time of human colonization; a change replicated at three widely separated sites and in the marsupial wombat. We speculate that human firing of landscapes rapidly converted a drought-adapted mosaic of trees, shrubs, and nutritious grasslands to the modern fire-adapted desert scrub. Animals that could adapt survived; those that could not, became extinct.     

A comparison of four methods for measuring respiration in organic material

Four methods for measurement of respiration (CO₂ evolution) were compared on uniformly prepared, birch forest-floor organic matter; the methods included infrared gas analysis (i.r.g.a.), gas chromatography (g.c.), KOH absorption of CO₂ (b.a.) and the Gilson respirometer. Respiration estimates were made at a single temperature and also at variable temperatures at constant moisture contents. The i.r.g.a. and b.a. methods gave maximum estimates for respiration; the g.c. gave lowest, with the Gilson intermediate. Lower estimates for the g.c. are attributed to the closed system employed, which included no means of increasing gas diffusion (such as a KOH-CO₂ sink or continuous gas flow) out of the sample into the unoccupied space of the respiration chamber.At 25°C, the minimum sensitivity of the g.c. and Gilson were 3.8 and 3.6 μg CO₂, respectively. The minimum sensitivity of the b.a. method (44 μg CO₂) could have been improved with use of a micro-liter burette for titrations. The least minimum sensitivity, 0.31 μg CO₂, was attained with the i.r.g.a.Conditions under which any of the techniques may be used to estimate respiration should be carefully worked out. The relationship between sample size, gas flow rate (open system), chamber atmosphere composition (closed system), and chamber design should be established with sufficient confidence so that stimulation of respiration by excessive gas flow rate, or exhaustion of O₂ or CO₂ inhibition through extended chamber closure does not adversely affect respiration estimates.     

Self-fertility and the distribution of seed yield in Vicia faba L.

Summary Five lines of field beans (Vicia faba L.) bred and selected for a high level of self-fertility have demonstrated heritable differences in distribution of seed yield on the reproductive nodes when grown under conditions of selfpollination. Fully self-fertile genotypes produce a large proportion of the seed yield on the lower nodes. The breeding and selection for both self-fertility and the distribution of seed yield is discussed.     

Monitoring unfractionated heparin therapy in dogs by measuring thrombin generation

Background: The calibrated automated thrombogram (CAT), an assay that permits measurement of thrombin generation in plasma, may be useful in studying hemostatic disorders and anticoagulant therapy in animals. Objectives: The aims of the study were to measure thrombin generation in healthy Beagle dogs and to evaluate the potential use of the CAT assay for monitoring therapy with unfractionated heparin (UFH). Methods: Individual platelet‐poor plasma samples and a plasma pool from 20 healthy adult Beagles were prepared. Serial UFH plasma dilutions were used to establish an in vitro heparin‐sensitivity curve. The pharmacodynamic effects of heparin in vivo were evaluated in Beagles using the CAT assay to measure thrombin generation with tissue factor at a concentration of 5 pM for initiation. Results: In healthy Beagles, the range of endogenous thrombin potential (ETP) was 238.7–414.0 nM/min (mean ± SD, 340.4 ± 63.1 nM/min). ETP intra‐assay and interassay variations were 7.1% and 12.9%, respectively. In vitro, a UFH concentration ≥0.4 U/mL resulted in total inhibition of thrombin generation. In vivo, the maximal effect of UFH on ETP was observed at 170 ± 36 minutes (range, 120–210 minutes) and resulted in a decrease in ETP of 38.5 ± 7.8% (range, 26.5–50.3%). In 210–420 minutes, ETP returned to baseline in 5 dogs. Conclusion: Our study demonstrates that thrombin generation can be measured in canine plasma and may be useful in assessing the degree of anticoagulation provided by UFH.     

Thrombectomy and thrombolysis: the interventional radiology approach

Objective – To present interventional therapeutic options for patients with thrombosis. Etiology – Thrombosis in small animals results from an unbalance in the normal hemostatic mechanisms leading to vessel occlusion. In veterinary medicine, thrombosis is recognized as a common complication of many acquired diseases, including cardiac, endocrine, immunological, inflammatory, and neoplastic disorders. Diagnosis – Clinical signs are variable depending on the location of the thrombus and various laboratory and imaging modalities can aid in its identification and localization. Therapy – Once identified, a decision must be made to whether or not intervene and which method is most appropriate. A number of minimally invasive approaches for dealing with thrombosis are available and offer veterinarians a choice of therapeutic options when dealing with a thrombotic patient. In the presence of thrombosis, a combined approach of vessel balloon dilatation, catheter‐directed thrombolysis and stenting may be most appropriate. Percutaneous mechanical thrombectomy, if available, may also be appropriate. Embolic trapping devices can be used with vena cava thrombosis to help prevent pulmonary embolism. Anticoagulant therapy may be indicated in the postoperative period to prevent further thrombus formation while the patient's fibrinolytic system breaks the clot down. Prognosis – Outcome is variable depending on the site of the thrombus formation. Arterial thrombosis can be life‐threatening while venous thrombosis tends to be less life‐threatening but may lead to pulmonary embolism.