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Biomedical subjects

N A Evans

Publications and source records attributed to N A Evans.

At least 19 recordsLinked to original sources
PubMed2003

Comparison of the activity of selamectin, fipronil, and imidacloprid against flea larvae (Ctenocephalides felis felis) in vitro.

The activity of selamectin, fipronil and imidacloprid against larval cat fleas (Ctenocephalides felis felis) was evaluated in an in vitro potency assay system. One hundred microliters of each compound at various concentrations in acetone were added to glass vials (1.5 by 3 cm) to which had been previously added 20 mg of sand and 10 mg of flea feces. Vials were then ball milled to allow the acetone to evaporate. Selamectin and fipronil were tested at 0.001, 0.003, 0.005, 0.01, 0.03, 0.05, 0.11, 0.3, and 0.5 microg of active compound per tube. Imidacloprid was tested at 0.01, 0.03, 0.05, 0.1, 0.3, 0.5, 1.0, 3.0, and 5.0 microg of active compound per tube. Thirty first instar C. felis larvae were added to each vial. The number of larvae remaining alive in each vial was determined once daily for 72 h. With selamectin, reductions of >/=93.5% were achieved at 24 h after exposure at doses of >/=0.3 microg. In contrast, at 24 h neither fipronil nor imidacloprid reached 90% reduction, even at the highest doses tested (0.5 microg for fipronil and 5.0 microg for imidacloprid). Selamectin was significantly (P</=0.05) more potent than imidacloprid and fipronil at levels >/=0.03 microg. A similar pattern of activity was observed at both 48 and 72 h, but higher percentages of larvae were killed for each of the compounds as the incubation time increased. At 72 h selamectin was significantly (P</=0.05) more potent than imidacloprid at levels of 0.01-0.1 microg and significantly (P</=0.05) more potent than fipronil at levels of 0.003-0.01 microg. Therefore, selamectin was more potent than either fipronil or imidacloprid in killing flea larvae in this in vitro assay system.

Animals↗
PubMed2003

Efficacy of selamectin against biting lice on dogs and cats.

The efficacy of selamectin was evaluated against naturally acquired Trichodectes canis infestations on dogs and against Felicola subrostratus infestations on cats. Twenty dogs and 18 cats were randomly allocated to treatment with either a placebo or selamectin (6 mg/kg), administered topically once only on day 0. The treatment had no adverse effects in either the dogs or the cats. Efficacy was assessed by counting the live lice (adults and nymphs) on each animal by using a coat-parting technique on days -3, 7, 14, 21, 28, 35 and 42 for the dogs, and on days -1, 7, 21, 35 and 42 for the cats. On day 43, the number of live lice on each dog was also assessed by using a whole-body combing technique. Selamectin was 100 per cent effective in killing biting lice on the dogs and cats throughout the period of assessment; the louse counts on the treated dogs and cats were significantly lower than the pretreatment counts (P = 0.0001) and were also significantly lower than on the placebo-treated dogs (P < 0.05) and cats (P = 0.0001). There was a marked reduction in the prevalence of clinical signs associated with ectoparasite infestation in the treated dogs and no clinical signs were observed in any of the treated cats.

Administration, Cutaneous↗
PubMed2003

Immunization of broiler chicks by in ovo injection of Eimeria tenella sporozoites, sporocysts, or oocysts.

Immunization of chickens by in ovo injection of Eimeria tenella parasite stages was investigated. Fertile Hubbard x Petersen broiler chicken eggs were injected through the air cell on d 18 of incubation with sporozoites, sporocysts, or oocysts of E. tenella. Injected doses were in the range of 1 x 10(2) to 1 x 10(6) sporozoites, 2 x 10(5) to 2 x 10(7) sporocysts, or 1 x 10(2) to 5 x 10(6) oocysts per egg. Hatch rates were generally unaffected. Hatched chicks shed oocysts, with oocysts per gram of feces reaching a maximum at 3 d posthatch for chicks injected with sporozoites and at 7 d posthatch for chicks receiving oocysts or sporocysts in ovo. After 2 wk in wire-floored cages or 3 wk on litter, birds were challenged with 2.5 x 10(4) sporulated oocysts of E. tenella. Chicks immunized by in ovo injection of parasite stages had significantly reduced lesion scores compared to their nonimmunized counterparts. The results demonstrate the feasibility of immunizing broiler chickens against E. tenella infection by in ovo injection of sporozoites, sporocysts, or oocysts.

Animals↗
PubMed2001

Intracrystalline proteins and the hidden ultrastructure of calcium oxalate urinary crystals: implications for kidney stone formation.

The external appearance of urinary calcium oxalate (CaOx) crystals suggests that they are solid, homogeneous structures, despite their known association with proteins. Our aim was to determine whether proteins comprising the organic matrix of CaOx crystals are superficial or intracrystalline in order to clarify the role of urinary proteins in the formation of kidney stones. CaOx crystals were precipitated from centrifuged and filtered, or ultrafiltered, healthy human urine. They were then treated with dilute NaOH to remove bound proteins, partially demineralized with EDTA, or fractured and subjected to limited proteolysis before examination by low-resolution scanning electron microscopy or field emission scanning electron microscopy. Crystals precipitated from centrifuged and filtered urine had a complex interior network of protein distributed throughout the mineral phase, which appeared to comprise closely packed subcrystalline particles stacked in an orderly array among an amorphous organic matrix. This ultrastructure was not evident in crystals deposited in the absence of macromolecules, which were completely solid. This is the first direct evidence that crystals generated from cell-free systems contain significant amounts of protein distributed throughout a complex internal cribriform ultrastructure. Combined with mineral erosion in the acidic lysosomal environment, proteins inside CaOx crystals would render them susceptible to attack by urinary and intracellular renal proteases and facilitate their further dissolution or disruption into small particles and ions for removal by exocytosis. The findings also have broader ramifications for industry and the materials sciences, as well as the development and resorption of crystals in biomineralization systems throughout nature.

Adolescent↗
PubMed2001

Visualizing differences in ligand-induced beta-arrestin-GFP interactions and trafficking between three recently characterized G protein-coupled receptors.

beta-Arrestin 1-GFP or beta-arrestin 2-GFP were coexpressed transiently with G protein-coupled receptor kinase 2 within cells stably expressing the orexin-1, apelin or melanin-concentrating hormone (MCH), receptors. In response to agonist ligands both the orexin-1 and apelin receptors were able to rapidly translocate both beta-arrestin 1-GFP and beta-arrestin 2-GFP from cytoplasm to the plasma membrane. For the MCH receptor this was only observed for beta-arrestin 2-GFP. beta-Arrestin 1-GFP translocated by the apelin receptor remained at the plasma membrane during prolonged exposure to ligand even though the receptor became internalized. By contrast, for the orexin-1 receptor, internalization of beta-arrestin 1-GFP within punctate vesicles could be observed for over 60 min in the continued presence of agonist. Co-internalization of the orexin-1 receptor was observed by monitoring the binding and trafficking of TAMRA-(5- and 6-carboxytetramethylrhodamine) labelled orexin-A. Subsequent addition of an orexin-1 receptor antagonist resulted in cessation of incorporation of beta-arrestin 1-GFP into vesicles at the plasma membrane and a gradual clearance of beta-arrestin 1-GFP from intracellular vesicles. For the melanin-concentrating hormone receptor the bulk of translocated beta-arrestin 2-GFP was maintained at concentrated foci close to, or at, the plasma membrane. These results demonstrate very distinct features of beta-arrestin-GFP interactions and trafficking for three G protein-coupled receptors for which the natural ligands have only recently been identified and which were thus previously considered as orphan receptors.

Animals↗
PubMed2001

Analysis of the C-terminal tail of the rat thyrotropin-releasing hormone receptor-1 in interactions and cointernalization with beta-arrestin 1-green fluorescent protein.

Coexpression of the rat thyrotropin releasing hormone receptor-1 with beta-arrestin 1-green fluorescent protein (GFP) in human embryonic kidney 293 cells results in agonist-dependent translocation of the arrestin to the plasma membrane followed by its cointernalization with the receptor. Truncations of the receptor C-terminal tail from 93 to 50 amino acids did not alter this. Truncations to fewer than 47 amino acids prevented such interactions and inhibited but did not fully eliminate agonist-induced internalization of the receptor. Deletion and site-directed mutants of the C-terminal tail indicated that separate elimination of a potential casein kinase II phosphorylation site or clathrin/clathrin adapter motifs was insufficient to prevent either internalization of the receptor or its cointernalization with beta-arrestin 1-GFP. Alteration of sites of acylation reduced internalization and prevented interactions with beta-arrestin 1-GFP. Combinations of these mutants resulted in lack of interaction with beta-arrestin 1-GFP and a 10-fold reduction in internalization of the receptor. Despite this, the receptor construct that lacked the three protein sequence motifs was fully functional. These studies map sites that contribute the interactions of the thyrotropin releasing hormone receptor-1 C-terminal tail required for effective contacts with beta-arrestin 1-GFP and indicate key roles for these interactions in agonist-induced internalization of the receptor.

Amino Acid Motifs↗
PubMed2000

Receptor for the pain modulatory neuropeptides FF and AF is an orphan G protein-coupled receptor.

Opiate tolerance and dependence are major clinical and social problems. The anti-opiate neuropeptides FF and AF (NPFF and NPAF) have been implicated in pain modulation as well as in opioid tolerance and may play a critical role in this process, although their mechanism of action has remained unknown. Here we describe a cDNA encoding a novel neuropeptide Y-like human orphan G protein-coupled receptor (GPCR), referred to as HLWAR77 for which NPAF and NPFF have high affinity. Cells transiently or stably expressing HLWAR77 bind and respond in a concentration-dependent manner to NPAF and NPFF and are also weakly activated by FMRF-amide (Phe-Met-Arg-Phe-amide) and a variety of related peptides. The high affinity and potency of human NPFF and human NPAF for HLWAR77 strongly suggest that these are the cognate ligands for this receptor. Expression of HLWAR77 was demonstrated in brain regions associated with opiate activity, consistent with the pain-modulating activity of these peptides, whereas the expression in adipose tissue suggests other physiological and pathophysiological activities for FMRF-amide neuropeptides. The discovery that the anti-opiate neuropeptides are the endogenous ligands for HLWAR77 will aid in defining the physiological role(s) of these ligands and facilitate the identification of receptor agonists and antagonists.

Amino Acid Sequence↗
PubMed2000

Selamectin: a novel broad-spectrum endectocide for dogs and cats.

Selamectin, 25-cyclohexyl-25-de(1-methylpropyl)-5-deoxy-22, 23-dihydro-5-(hydroxyimino)-avermectin B1 monosaccharide, is a novel endectocide with a unique combination of efficacy and safety in dogs and cats following both oral and topical administration. The compound is active against fleas and ticks, intestinal hookworms and ascarids, and immature heartworms. Also it is well tolerated at higher dosages than 22,23-dihydroavermectin B1a (DHAVM) or milbemycin oxime in Collies, which is a breed known to exhibit idiosyncratic sensitivity to avermectins.

Administration, Topical↗
PubMed2000

Dose selection of selamectin for efficacy against adult fleas (Ctenocephalides felis felis) on dogs and cats.

Selamectin, a novel avermectin, was evaluated in two controlled studies (one in Beagles, one in domestic shorthaired cats) to determine an appropriate topical dose for efficacy against adult Ctenocephalides felis felis (C. felis) fleas on dogs and cats for 1 month. For each study, animals were allocated randomly to four treatments. One treatment consisted of the inert formulation ingredients (vehicle) administered as a negative control, and the other three treatments consisted of a single topical dosage of 3, 6, or 9mgkg(-1) of selamectin. In each study, selamectin was administered as a topical dose applied to the skin in a single spot at the base of the neck in front of the scapulae. Dogs and cats were infested with 100 viable unfed C. felis (50 males and 50 females) on days 4, 11, 18, and 27. Seventy-two hours (+/-2h) after each infestation, on days 7, 14, 21, and 30, a comb count to determine the number of viable fleas present on each animal was performed. Efficacy of selamectin on day 30 was used to select an appropriate dose. For dogs and cats, percentage reductions in geometric mean flea comb counts for the three selamectin treatments ranged from 94. 6 to 100% on days 7, 14, and 21, compared with the negative-control treatment. On day 30, reductions in flea comb counts were 81.5, 94.7, and 90.8% for dogs, and 79.8, 98.0, and 96.2% for cats treated with selamectin at 3, 6, or 9mgkg(-1), respectively. For day 30 flea comb counts for dogs and cats, analysis of variance showed that the three selamectin treatments resulted in significantly (P< or =0.05) lower counts than did the negative-control treatment. For dogs and cats, geometric mean flea counts for selamectin administered at a dosage of 3mgkg(-1) were significantly (P< or =0.05) higher than those for the 6 and 9mgkg(-1) treatment dosages combined. There were no significant differences in flea counts between the 6 and 9mgkg(-1) treatments. This analysis was confirmed by linear-plateau modeling. Thus, the optimal dose of selamectin for efficacy against adult fleas for both dogs and cats, as estimated by the turning point (plateau) in the dose response curve, was 6mgkg(-1).

Administration, Topical↗
PubMed2000

Avermectins and flea control: structure-activity relationships and the selection of selamectin for development as an endectocide for companion animals.

Evaluation of a wide range of avermectin derivatives for flea activity in an in vitro feeding screen using the cat flea, Ctenocephalides felis, revealed a narrow structure-activity relationship (SAR) with activity surprisingly associated with monosaccharides and especially their C-5-oximes. We discovered commercially exploitable flea activity in a single compound, selamectin 33, which also possessed the necessary antiparasitic spectrum and margin of safety for development as a broad-spectrum companion animal endectocide.

Animals↗
PubMed1998

Ultrastructural analysis of ruptured tendon from anabolic steroid users.

Tendon rupture has been linked with anabolic steroid abuse on the basis of a small number of published case reports. Although experimental data from animal models suggest steroids alter the biomechanical properties of tendon, ultrastructural evidence to support this theory is lacking. Indeed, microscopic analysis of human tendon from steroid users has not previously been reported. In this study, specimens of ruptured human tendon from four patients were biopsied during surgical repair. Two of the subjects were anabolic steroid users, and two subjects were used as nonsteroid-user controls. Ruptured tendon from both groups was examined using electron microscopy. No differences in collagen fibril ultrastructure were seen. We conclude that anabolic steroids did not induce ultrastructural collagen changes that might predispose to tendon rupture in humans.

Adult↗
PubMed1997

Gym and tonic: a profile of 100 male steroid users.

OBJECTIVE: To identify unsupervised anabolic steroid regimens used by athletes. METHODS: 100 athletes attending four gymnasia were surveyed using an anonymous self administered questionnaire. RESULTS: Anabolic steroid doses ranged from 250 to 3200 mg per week and users combined different drugs to achieve these doses. Injectable and oral preparations were used in cycles lasting four to 12 weeks. Eighty six per cent of users admitted to the regular use of drugs other than steroids for various reasons, including additional anabolic effects, the minimisation of steroid related side effects, and withdrawal symptoms. Acne, striae, and gynaecomastia were the most commonly reported subjective side effects. CONCLUSIONS: Multiple steroids are combined in megadoses and self administered in a cyclical fashion. Polypharmacy is practised by over 80% of steroid users. Skeletal muscle hypertrophy along with acne, striae, and gynaecomastia are frequent physical signs associated with steroid use.

Acne Vulgaris↗
PubMed1997

Playing with metal: fracture implants and contact sport.

OBJECTIVE: To assess the outcome of athletes returning to contact sport with indwelling fracture implants. METHOD: A retrospective analysis of professional rugby union players competing in the South Wales premier league. RESULTS: Fifteen athletes were identified who had returned to competitive rugby union with retained fracture implants during the period 1990-97. After fracture fixation, the players resumed their preinjury level of contact sport within one to 12 months. Only two athletes suffered complications in relation to the retained implant, whereas the other 13 athletes played for up to six years without symptoms. CONCLUSION: The results from this preliminary series suggest that an early return to contact sport is feasible in selected cases. Avoiding the extended delay associated with implant removal affords not only minimal disruption to competitive participation, but also prevents prolonged financial losses for the professional player.

Adolescent↗
PubMed1993

Doramectin--a potent novel endectocide.

Doramectin, 25-cyclohexyl-5-O-demethyl-25-de(l-methylpropyl)avermectin A1a, was selected as the best of a series of novel avermectins prepared by mutational biosynthesis. The primary evaluation of its in vivo antiparasitic activity was carried out using a rat Trichostrongylus colubriformis model and a rabbit Psoroptes cuniculi model. In each case the new avermectin performed favourably relative to dihydroavermectin B1a (DHAVM), the major component of ivermectin. Doramectin was extensively evaluated in cattle using an experimental micelle formulation, proving highly effective in cattle infected with Ostertagia ostertagi, Cooperia oncophora and Dictyocaulus viviparus when administered subcutaneously at 200 micrograms kg-1. The plasma pharmacokinetic characteristics of doramectin in cattle following intravenous administration revealed a plasma half-life of approximately 89 h. In the micelle formulation, doramectin administered subcutaneously at 400 micrograms kg-1 provided persistent activity against infection of cattle with C. oncophora and O. ostertagi for at least 8 and 12 days respectively.

Administration, Oral↗
PubMed1986

Nebulized salbutamol and ipratropium bromide in asthmatic children.

Varying doses of nebulized salbutamol, ipratropium bromide and a combination of both were given to 20 asthmatic children. All therapies produced effective bronchodilation. Ten mg salbutamol caused elevation of pulse rate and finger tremor whilst the duration of action of 0.6 mg salbutamol was too short. Dose-response effects were clearly seen with salbutamol but not with ipratropium bromide. A summation effect was not demonstrated when the medications were combined.

Adolescent↗