The hen's egg: Shell cracking at impact on a heavy,stiff body and factors that affect it

1. Eggs from hens of three strains were dropped on to a heavy, stiff, smooth, plane body with impact at the equator of the shell; the height of drop, h_c, just sufficient to produce shell failure was measured and the corresponding impact velocity, v_c, calculated.

2. A small but commercially important percentage of the well‐formed eggs of one strain cracked when h_c was as low as 3–3 mm and v_c 250 mm/s.

3. Characteristics of the egg found to affect h_c and v_c included the overall thickness of its shell, thickness of its weak inner shell layer and average shell curvature, all measured at the point of impact, and its weight; its age also had a small effect (additional to that mediated through loss of weight); so did the degree of shell ridging.

4. No effect of shell colour was found.

5. Shell damage was typically a single hair‐crack that ran either round the equator or towards a pole.     

Synergistic and antagonistic effects of atrazine on the toxicity of organophosphorodithioate and organophosphorothioate insecticides to Chironomus tentans (Diptera: Chironomidae)

The acute toxicities of two organophosphorodithioate (dimethoate and disulfoton) and two organophosphorothioate (omethoate and demeton-S-methyl) insecticides were evaluated individually and in binary combination with the herbicide atrazine using fourth-instar larvae of the aquatic midge, Chironomus tentans. Atrazine alone up to 1000 μg/L did not show significant toxicity to the midges in a 48-h bioassay. However, atrazine concentrations as low as 1 μg/L in combination with dimethoate at EC₂₅ (concentration to affect 25% of tested midges), 100 μg/L in combination with disulfoton (EC₂₅), and 10 μg/L in combination with demeton-S-methyl (EC₂₅) significantly enhanced the toxicity of each organophosphate insecticide. In contrast, atrazine concentrations of 10 μg/L and above in combination with omethoate (EC₂₅) significantly decreased the toxicity of the insecticide. Biochemical analysis indicated that increased toxicity of dimethoate, disulfoton, and demeton-S-methyl in binary combination with atrazine correlated to the increased inhibition of acetylcholinesterase. Furthermore, cytochrome P450-dependent O-deethylation activity in the midges exposed to atrazine at 1000 μg/L was 1.5-fold higher than that in the control midges. Thus, atrazine appeared to induce cytochrome P450 monooxygenases in the midges. Elevated cytochrome P450 monooxygenase activity may increase the toxicities of dimethoate, disulfoton, and demeton-S-methyl by enhancing the oxidative activation of dimethoate into omethoate, and disulfoton and demeton-S-methyl into their sulfoxide analogs with increased anticholinesterase activity. In contrast, atrazine reduced the toxicity of omethoate possibly by enhancing the oxidative metabolic detoxification since omethoate does not require oxidative activation.     

Injection of the insertion of the deep digital flexor tendon in horses using radiographic guidance

Insertional tendinopathies of the DDFT have been reported both as the sole lesion and as part of a multifocal lesion (Dyson et al. 2003). Computed tomography (CT) and magnetic resonance imaging allow specific diagnosis of deep digital flexor tendon lesions within the hoof capsule; however, direct intralesional treatment of such lesions is difficult because of the hoof's rigid structure. A technique designed to mimic intralesional injection of insertional tendinopathies of the DDFT in the standing horse using radiographic guidance was assessed. Radiographic and contrast CT imaging and sectioning of the limbs confirmed accurate injection in all cases although inadvertant administration of injectate into adjacent structures was also evident.     

Idiopathic epilepsy in dogs: owners' perspectives on management with phenobarbitone and/or potassium bromide

OBJECTIVES: To explore seizure management from the perspective of the owners of dogs with idiopathic epilepsy. METHODS: Questionnaires were mailed to owners of 29 dogs under management for suspected or diagnosed idiopathic epilepsy through the clinics of the Small Animal Hospital of the University of Glasgow Veterinary School, using either phenobarbitone or potassium bromide alone or in combination. RESULTS: The postal survey had an 86 per cent response rate. Analysis of the responses demonstrated that "the dog's quality of life", "adequate seizure frequency" and "acceptable side effects of antiepileptic drugs" were the three greatest concerns for owners; 52 per cent of owners strongly agreed that the seizure management for their dog was adequate, though the seizure frequency reported varied within this group; the majority of owners did not consider the administration of medication a nuisance. However, approximately 60 per cent of owners reported that caring for an epileptic dog had an effect on the organisation of their free time, though this was not dependent on perception of seizure control. Opinions as to the value of further diagnostic procedures, in particular intracranial imaging, were significantly affected by having pet health insurance. CLINICAL SIGNIFICANCE: From the owners' perspective, adequacy of seizure control is determined by the balance between "the dog's quality of life", "adequate seizure frequency" and "acceptable side effects of antiepileptic drugs". A frequency of less than one seizure every three months is associated with the perception by owners of adequate seizure control.     

Influence of isoprinosine on bovine herpesvirus type-1 infection in cattle

A study was conducted to determine the in vivo efficacy of isoprinosine (ISO) in calves infected with bovine herpesvirus type-1 (BHV-1). Calves were infected with BHV-1 on day 0 and received ISO daily for 14 days. Clinical signs of disease, shedding of BHV-1, lymphocyte proliferative responses to mitogens, interleukin-2 production, and alveolar macrophage bactericidal activity were monitored during the study. Rectal temperatures were increased (P less than 0.05) in BHV-1 and ISO-BHV-1 calves at days 3 to 7 postinfection (PI). Isoprinosine did not influence BHV-1 shedding in calves. Lymphocyte proliferative responses to phytohemagglutinin (PHA) were lower (P less than 0.01) in BHV-1 calves when compared to control or ISO calves at day 4 PI, but ISO did not ameliorate this effect. Interleukin-2 activity was greater (P less than 0.05) in ISO-BHV-1 calves on days 4 and 8 PI in PHA-stimulated lymphocytes and on day 8 PI in concanavalin A-stimulated lymphocytes when compared to control, ISO or BHV-1 calves. Isoprinosine treatment of BHV-1-infected calves tended to decrease alveolar macrophage bactericidal activity. These data suggest that ISO does not reverse BHV-1 suppression of lymphocyte proliferation, but may enhance IL-2 production in BHV-1 infected calves.