Evaluation of Collaterals and Clot Burden Using Time-Resolved C-Arm Conebeam CT Angiography in the Angiography Suite: A Feasibility Study

BACKGROUND AND PURPOSE

The assessment of collaterals and clot burden in patients with acute ischemic stroke provides important information about treatment options and clinical outcome. Time-resolved C-arm conebeam CT angiography has the potential to provide accurate and reliable evaluations of collaterals and clot burden in the angiographic suite. Experience with this technique is extremely limited, and feasibility studies are needed to validate this technique. Our purpose was to present such a feasibility study.

MATERIALS AND METHODS

Ten C-arm conebeam CT perfusion datasets from 10 subjects with acute ischemic stroke acquired before endovascular treatment were retrospectively processed to generate time-resolved conebeam CTA. From time-resolved conebeam CTA, 2 experienced readers evaluated the clot burden and collateral flow in consensus by using previously reported scoring systems and assessed the clinical value of this novel imaging technique independently. Interobserver agreement was analyzed by using the intraclass correlation analysis method.

RESULTS

Clot burden and collateral flow can be assessed by using the commonly accepted scoring systems for all eligible cases. Additional clinical information (eg, the quantitative dynamic information of collateral flow) can be obtained from this new imaging technique. Two readers agreed that time-revolved C-arm conebeam CTA is the preferred method for evaluating the clot burden and collateral flow compared with other conventional imaging methods.

CONCLUSIONS

Comprehensive evaluations of clot burden and collateral flow are feasible by using time-resolved C-arm conebeam CTA data acquired in the angiography suite. This technique further enriches the imaging tools in the angiography suite to enable a "one-stop- shop" imaging workflow for patients with acute ischemic stroke.

Role of dung beetle feeding mechanisms in limiting the suitability of species as hosts for the nematode Spirocerca lupi

Various species of dung beetle serve as intermediate hosts after ingesting the embryonated eggs (11-15 × 30-37 µm) of Spirocerca lupi (Spirurida: Spirocercidae) in dog faeces. The feeding mechanisms of coprophagous dung beetles restrict the size of the food particles they can ingest and hence may determine which species can be efficient vectors for S. lupi. In this study, we aimed to exclude certain dung beetle species as possible hosts of S. lupi based on whether or not they ingested latex beads of known diameters mixed into fresh cattle dung. We found that the majority (11/14) of species tested can potentially serve as intermediate hosts of S. lupi because their mouthparts allow the passage of food particles larger than the minimum size range of the eggs of this parasite.

The development and survival of three species of coprophagous insect after feeding on the faeces of sheep treated with controlled-release formulations of ivermectin or albendazole

OBJECTIVE

To assess the toxicity from residues of controlled-release formulations of ivermectin and albendazole to insects that feed on sheep faeces.

ANIMALS

In two consecutive years, groups of sheep were treated with controlled-release capsules of ivermectin or albendazole. Untreated sheep were used as controls.

PROCEDURES

Larvae of the bush fly, Musca vetustissima, and adults and larvae of the dung beetles, Onthophagus taurus and Euoniticellus fulvus were fed on faeces collected at intervals after drug treatment. In assays using beetles, treatment effects were assessed by comparing numbers of eggs laid, survival of juveniles and survival of mature and immature adults. Survival at time of pupariation was used in assays on flies.

RESULTS AND CONCLUSIONS

Faeces from sheep treated with albendazole had no detectable effects on breeding by either flies or beetles. In contrast, faeces voided by sheep treated with controlled-release capsules of ivermectin (CRI) precluded successful breeding by each of the species tested. No fly larvae and almost no beetle larvae survived in faeces collected up to 39 days after capsule administration. Newly-emerged O taurus also suffered significant mortality whereas those that survived underwent delayed sexual maturation. Ivermectin residues had no effect on the survival of sexually mature beetles, but reduced the fecundity of O taurus. A model simulating the effects of drug residues on dung beetle populations indicates that CRIs have the potential to cause substantial declines in beetle numbers, particularly if treatment coincides with spring emergence.

Discontinuous gas exchange cycles in aphodius fossor (Scarabaeidae): a test of hypotheses concerning origins and mechanisms

It has been suggested that discontinuous gas exchange cycles (DGCs) in insects evolved in response to hypoxic and/or hypercapnic environments, and that the flutter phase of the DGC is predominantly diffusive. We tested these hypotheses by examining the rate of CO(2) release at a declining series of oxygen partial pressures in adults of Aphodius fossor, an inhabitant of moist to wet dung pats that can have low oxygen and high carbon dioxide concentrations. This mesic species showed a pronounced DGC, but progressively abandoned it when exposed to declining oxygen concentrations. That is, in response to a reduction in oxygen concentration, the closed phase declined in length and eventually disappeared, the flutter phase declined in length, while the flutter phase rate of CO(2) release increased, the open phase peak rate of CO(2) release declined and DGC frequency increased. Nonetheless, overall CO(2) release rate remained virtually unchanged. Thus, it appears that the flutter phase in A. fossor has a significant convective component. In addition, in response to declining oxygen concentrations, the spiracles are opened for prolonged periods to increase gas exchange. This behaviour is unlikely to incur a significant water loss penalty in the moist habitats in which A. fossor lives. Given the switch to continuous ventilation by A. fossor under hypoxic conditions, we conclude that current adaptive explanations for the DGC are inadequate. Rather, the DGC may be the default state of a system regulated by two interacting feedback loops when demands are absent.

Effects of drug residues in the faeces of cattle treated with injectable formulations of ivermectin and moxidectin on larvae of the bush fly, Musca vetustissima and the house fly, Musca domestica

OBJECTIVE

To assess the toxicity of residues of ivermectin and moxidectin in cattle faeces collected at intervals after treatment.

DESIGN

Replicated bioassays of faeces using larvae of the bush fly, Musca vetustissima and the house fly, Musca domestica.

ANIMALS

Two groups of five Murray Grey x Aberdeen Angus steers were treated with injectable formulations of ivermectin and moxidectin respectively. A third group was used as an untreated control.

PROCEDURE

Newly emerged fly larvae were reared in the dung of treated animals.

RESULTS

Drug residues in faeces collected 3 to 35 days after treatment with an injectable formulation of moxidectin had no significant effect on the survival of larvae of M vetustissima. Similarly, faeces dropped up to seven days after treatment caused no significant reduction in larval survival in M domestica. In day 2 dung, residues of moxidectin delayed development of M vetustissima larvae, but had no effect on their survival. In contrast, ivermectin-treated steers, produced dung that inhibited larval development of both M vetustissima and M domestica for 7 to 14 days after treatment. Significant reductions in survival of M vetustissima larvae occurred in dung collected on days 21 and 28 after treatment, but by day 35 survival did not differ from that in control dung.

CONCLUSION

Excreted faecal residues of moxidectin are relatively innocuous to larvae of both M vetustissima and M domestica. Those of ivermectin inhibit survival for 7 to 14 days after treatment and are likely to have adverse effects on non-target organisms.

Attractiveness of dung from ivermectin-treated cattle to Danish and afrotropical scarabaeid dung beetles

The effect of ivermectin treatment of cattle on the attractiveness of dung to scarabaeid dung beetles was assessed by pitfall trapping in Denmark, Tanzania and Zimbabwe. Traps were baited with dung collected at intervals after heifers were treated with ivermectin by subcutaneous injection (0.2 mg kg-1 body weight). In one Danish trial, beetles preferred control dung from untreated cattle, whereas no preference was found in two other experiments. In Tanzania, the overall tendency for beetles was also to prefer control dung. In Zimbabwe, two species (Euoniticellus intermedius and Liatongus militaris) were particularly attracted to dung from treated cattle, whereas three others did not discriminate between dung types. It is concluded that at least in some cases the attractiveness of cattle dung to scarabaeid beetles is affected by avermectin therapy. Beetle discrimination between dung types is probably attributable to some unknown side effect of the treatment rather than being a direct response to the drug itself.

Effects of ivermectin on two afrotropical dung beetles, Onthophagus gazella and Diastellopalpus quinquedens (Coleoptera: Scarabaeidae)

Subcutaneous injection of 0.2 mg kg-1 ivermectin to heifers negatively affected larvae of the afrotropical dung beetles, Diastellopalpus quinquedens and Onthophagus gazella, developing in the dung. Although closely related, the two species seem to differ in susceptibility; 28% of brood masses made of dung voided 2 days after treatment contained third instar D. quinquedens, whereas O. gazella died as first instars in dung voided up to 8 days after treatment. Folding of the head capsules and lack of mandibular wear in the dead O. gazella larvae suggest that ivermectin could be absorbed through the integument and prevent normal feeding and distension of the head capsule. In addition, the surviving third instar O. gazella in dung voided 16 days after treatment had significantly reduced clypeal and mandibular widths. The dung burial activity, mainly by D. quinquedens, estimated in a field experiment was not affected by ivermectin residues in the dung.

Reduced splash dispersal of bovine parasitic nematodes from cow pats by the dung beetle Diastellopalpus quinquedens

From a thoroughly mixed portion of cattle feces with Cooperia sp. eggs, 1-kg artificial pats were placed in 6 buckets containing 6 kg of soil each. Ten dung beetles, Diastellopalpus quinquedens, were added to each of 3 buckets. The remaining 3 buckets served as controls without beetles. When infective parasite larvae (L3) had developed in the cow pats indoors, the following procedure was followed. During occasions of rainfall each bucket was placed outdoors in the center of a wider and higher container. When the rain stopped all buckets were brought indoors, and infective larvae spread by splash droplets during the rain were collected in the containers and counted. After 33 days, the remaining dung on the soil surface in buckets with dung beetles constituted only 38% of that in the controls. Moreover, the number of L3 in feces left on the soil surface in the buckets with beetles was reduced by 88%, presumably due to beetle activity. This may explain the 70-90% reduction in splash dispersal of L3 of Cooperia sp. from cow pats attacked by beetles. The dung-burying activity of the beetles did not result in increased numbers of L3 in the soil under the cow pats, suggesting that many of the parasites in buried feces were destroyed.

Effects of treatment of cattle with some anthelmintics on the subsequent degradation of their dung

Recent reports seem to indicate that the use of certain anthelmintics in cattle may cause adverse effects on non-target faunal inhabi-tants of cow pats, thus interferring with the normal degradation and recycling of dung deposited on pasture (Anderson et al. 1984, Lumaret 1986, Wall & Strong 1987). The present communication presents some data from a microcosm experiment on the pos-sible effects of some commonly used anthel-mintics on the rate of cow dung decomposition.