Bull selection and use in northern Australia. Part 2. Semen traits

Detailed semen evaluations were carried out on approximately 363 Santa Gertrudis, 5/8 Brahman and Brahman bulls on 12 different properties across northern Australia, as part of systematic breeding soundness examinations. A subset of bulls (n=245) were subsequently mated in groups, to cows and heifers at bull:female ratios of 2.5-6.0%, with the paternity of resulting calves being determined by microsatellite DNA testing. Motility traits of semen and spermatozoa were moderately repeatable and correlated with each other, but were unrelated to calf output. The percentage of morphologically normal spermatozoa in ejaculates was moderately to highly repeatable (e.g. r=0.10-0.64). The most common morphological abnormalities seen were mid-piece abnormalities, in particular, distal mid-piece reflex associated with a cytoplasmic droplet. Semen quality, particularly percent normal spermatozoa, was consistently related to calf output. In general, bulls with <50% normal spermatozoa sired few calves while bulls with the highest calf outputs had >70% normal spermatozoa. The presence or absence of heparin binding proteins in semen did not influence calf output. Semen from 93% of tested bulls was positive for heparin binding proteins. These results confirm that examination of semen, in particular, evaluation of percent morphologically normal spermatozoa, should be included in the breeding soundness examination of bulls.     

A prospective cluster-randomized trial to implement the Canadian CT Head Rule in emergency departments

Background

The Canadian CT Head Rule was developed to allow physicians to be more selective when ordering computed tomography (CT) imaging for patients with minor head injury. We sought to evaluate the effectiveness of implementing this validated decision rule at multiple emergency departments.

Methods

We conducted a matched-pair cluster-randomized trial that compared the outcomes of 4531 patients with minor head injury during two 12-month periods (before and after) at hospital emergency departments in Canada, six of which were randomly allocated as intervention sites and six as control sites. At the intervention sites, active strategies, including education, changes to policy and real-time reminders on radiologic requisitions were used to implement the Canadian CT Head Rule. The main outcome measure was referral for CT scan of the head.

Results

Baseline characteristics of patients were similar when comparing control to intervention sites. At the intervention sites, the proportion of patients referred for CT imaging increased from the “before” period (62.8%) to the “after” period (76.2%) (difference +13.3%, 95% CI 9.7%–17.0%). At the control sites, the proportion of CT imaging usage also increased, from 67.5% to 74.1% (difference +6.7%, 95% CI 2.6%–10.8%). The change in mean imaging rates from the “before” period to the “after” period for intervention versus control hospitals was not significant (p = 0.16). There were no missed brain injuries or adverse outcomes.

Interpretation

Our knowledge–translation-based trial of the Canadian CT Head Rule did not reduce rates of CT imaging in Canadian emergency departments. Future studies should identify strategies to deal with barriers to implementation of this decision rule and explore more effective approaches to knowledge translation. (ClinicalTrials.gov trial register no. NCT00993252)More than six million instances of head and neck trauma are seen annually in emergency departments in Canada and the United States.¹ Most are classified as minimal or minor head injury, but in a very small proportion, deterioration occurs and neurosurgical intervention is needed for intracranial hematoma.^2,3 In recent years, North American use of computed tomography (CT) for many conditions in the emergency department, including minor head injury, has increased five-fold.^1,4 Our own Canadian data showed marked variation in the use of CT for similar patients.⁵ Over 90% of CT scans are negative for clinically important brain injury.^6–8 Owing to its high volume of usage, such imaging adds to health care costs. There have also been increasing concerns about radiation-related risk from unnecessary CT scans.^9,10 Additionally, unnecessary use of CT scanning compounds the Canadian problems of overcrowding of emergency departments and inadequate access to advanced imaging for nonemergency outpatients.Clinical decision rules are derived from original research and may be defined as tools for clinical decision-making that incorporate three or more variables from a patient’s history, physical examination or simple tests.^11–13 The Canadian CT Head Rule comprises five high-risk and two medium-risk criteria and was derived by prospectively evaluating 3121 adults with minor head injury (Figure 1) (Appendix 1, available at www.cmaj.ca/cgi/content/full/cmaj.091974/DC1).⁶ The resultant decision rule was then prospectively validated in a group of 2707 patients and showed high sensitivity (100%; 95% confidence interval [CI ] 91–100) and reliability.¹⁴ The results of its validation suggested that, in patients presenting to emergency departments with minor head trauma, a rate of usage of CT imaging as low as 62.4% was possible and safe.Open in a separate windowFigure 1The Canadian CT Head Rule, as used in the study. Note: CSF = cerebrospinal fluid, CT = computed tomography, GCS = Glasgow Coma Scale.Unfortunately, most decision rules are never used after derivation because they are not adequately tested in validation or implementation studies.^15–19 We recently successfully implemented a similar rule, the Canadian C-Spine Rule, at multiple Canadian sites.²⁰ Hence, the goal of the current study was to evaluate the effectiveness and safety of an active strategy to implement the Canadian CT Head Rule at multiple emergency departments. We wanted to test both the impact of the rule on rates of CT imaging and the effectiveness of an inexpensive and easily adopted implementation strategy. In addition, we wanted to further evaluate the accuracy of the rule.     

Seeing 'cool' and 'hot'--infrared thermography as a tool for non-invasive, high-throughput screening of Arabidopsis guard cell signalling mutants

The use of Arabidopsis mutants defective in abscisic acid (ABA) perception has been instrumental in the understanding of stomatal function, in particular, ABA signalling in guard cells. The considerable attention devoted to ABA signalling in guard cells is due in part to (1) the fundamental role of ABA in drought stress and (2) the use of a screening protocol based on the sensitivity of seed germination to ABA. Such a screen has facilitated the isolation of ABA signalling mutants with genetic lesions that exert pleiotropic effects at the whole plant level. As such, there is a requirement for new approaches to complement the seed germination screen. The recent advances made in the use of infrared thermography as a non-invasive, high-throughput tool are reviewed here and the versatility of this technique for screening Arabidopsis defective in stomatal regulation is highlighted.     

Alterations in dihydropyridine receptors in dystrophin-deficient cardiac muscle

The deficiency of dystrophin, a critical membrane stabilizing protein, in the mdx mouse causes an elevation in intracellular calcium in myocytes. One mechanism that could elicit increases in intracellular calcium is enhanced influx via the L-type calcium channels. This study investigated the effects of the dihydropyridines BAY K 8644 and nifedipine and alterations in dihydropyridine receptors in dystrophin-deficient mdx hearts. A lower force of contraction and a reduced potency of extracellular calcium (P < 0.05) were evident in mdx left atria. The dihydropyridine agonist BAY K 8644 and antagonist nifedipine had 2.7- and 1.9-fold lower potencies in contracting left atria (P < 0.05). This corresponded with a 2.0-fold reduction in dihydropyridine receptor affinity evident from radioligand binding studies of mdx ventricular homogenates (P < 0.05). Increased ventricular dihydropyridine receptor protein was evident from both radioligand binding studies and Western blot analysis and was accompanied by increased mRNA levels (P < 0.05). Patch-clamp studies in isolated ventricular myocytes showed no change in L-type calcium current density but revealed delayed channel inactivation (P < 0.05). This study indicates that a deficiency of dystrophin leads to changes in dihydropyridine receptors and L-type calcium channel properties that may contribute to enhanced calcium influx. Increased influx is a potential mechanism for the calcium overload observed in dystrophin-deficient cardiac muscle.     

Fluctuating asymmetry in bank vole populations (Rodentia, Arvicolinae) reflects stress caused by landscape fragmentation in the Mont-Saint-Michel Bay

In intensively farmed, reclaimed areas (polders) of Mont-St-Michel Bay, France, bank voles ( Clethrionomys glareolus ) live in fragmented hedgerows, where populations are small and dispersal rates and genetic diversity are low. These small populations are likely to have been exposed to potential environmental and/or genetic stress. The sensitivity of development to stress can be measured by fluctuating asymmetry (FA). FA was calculated for three samples from a disturbed area and one sample from an adjacent, more connected and undisturbed landscape. Size FA was estimated from 16 measurements of the skull and teeth whilst shape asymmetry was estimated from the skull alone. Bank voles in fragmented hedgerows of the disturbed area had a higher degree of FA than bank voles from the more extensive and more connected hedges of the undisturbed area. These results were confirmed by the study of shape asymmetry, body mass and centroid size of the skull. There were no differences in FA between the three disturbed area samples. We conclude that FA does not reveal differences in the development of bank voles living in isolation under different local conditions in the various parts of the disturbed area. However, FA may allow differentiation between populations from greatly contrasting landscapes.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 37–44.     

Giant lizards occupied herbivorous mammalian ecospace during the Paleogene greenhouse in Southeast Asia

Mammals dominate modern terrestrial herbivore ecosystems, whereas extant herbivorous reptiles are limited in diversity and body size. The evolution of reptile herbivory and its relationship to mammalian diversification is poorly understood with respect to climate and the roles of predation pressure and competition for food resources. Here, we describe a giant fossil acrodontan lizard recovered with a diverse mammal assemblage from the late middle Eocene Pondaung Formation of Myanmar, which provides a historical test of factors controlling body size in herbivorous squamates. We infer a predominately herbivorous feeding ecology for the new acrodontan based on dental anatomy, phylogenetic relationships and body size. Ranking body masses for Pondaung Formation vertebrates indicates that the lizard occupied a size niche among the larger herbivores and was larger than most carnivorous mammals. Paleotemperature estimates of Pondaung Formation environments based on the body size of the new lizard are approximately 2–5°C higher than modern. These results indicate that competitive exclusion and predation by mammals did not restrict body size evolution in these herbivorous squamates, and elevated temperatures relative to modern climates during the Paleogene greenhouse may have resulted in the evolution of gigantism through elevated poikilothermic metabolic rates and in response to increases in floral productivity.     

Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)

1. The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status.
2. In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g^–1 day^–1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g^–1 day^–1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g^–1 day^–1.
3. In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability.
4. These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory.