Efficacy of moxidectin against internal parasites of sheep.

The efficacy of injectable and oral formulations of moxidectin, at a dosage of 0.2 mg kg -1 live mass was evaluated by the non-parametric method (NPM) against the most common internal parasites of sheep in 9 trials involving a total of 201 sheep. Both formulations obtained an A classification (more than 80% effective in more than 80% of the treated animals) against the third (L3) and fourth (L4) larval and adult stages of Haemonchus contortus, Teladorsagia circumcineta, Trichostrongylus colubriformis, Gaigeria pachyscelis, Chabertia ovina, Oesophagostomum columbianum and Dictyocaulus filaria, and L3 Nematodirus spathiger. The injectable formulation was similarly effective against L4 Strongyloides papillosus and the oral formulation against L4 N. spathiger and adult S. papillosus and N. spathiger. In contrast, a B classification (more than 60% effective in more than 60% of the treated animals) was obtained by the oral formulation against L4 of S. papillosus and by the injectable formulation against L4 and adult N. spathigher. Both formulations were ineffective against L3 S. papillosus, and the oral formulation also against the adults of this species.

Efficacy of moxidectin against a strain of Haemonchus contortus resistant to ivermectin, a benzimidazole and a salicylanilide.

The efficacy of moxidectin at 0.2 mg kg-1 live body mass against the multiple anthelmintic resistant White River Krtz strain of H. contortus was determined and compared to that of ivermectin, a benzimidazole, a salicylanilide and levamisole. Moxidectin and levamisole were effective against this strain of H. contortus and reduced the arithmetic mean burdens of this parasite in the sheep by 99.98% and 99.59%, respectively, while the efficacy of ivermectin, albendazole and closantel was only 29.1%, 33.75% and 78.3%, respectively.

Defining the valid hemizona assay: accounting for binding variability within zonae pellucidae and within semen samples from fertile males.

OBJECTIVE: To achieve a better understanding of the variability in sperm and oocyte binding capacities will optimize use of the hemizona assay (HZA) as a predictor of sperm function. DESIGN: Limitations of the HZA were more clearly delineated by current studies: (1) variability of sperm binding capacity of men over a 90-day interval; (2) variability of sperm binding using different oocytes; and (3) lower limits of the number of sperm bound from the fertile control in two laboratories. PATIENTS: Semen was obtained from proven fertile men and one subfertile individual. MAIN OUTCOME MEASURE: The number of sperm tightly bound to the hemizona were measured and compared. RESULTS: In the initial study, 6 fertile control men exhibited a similar degree of variability in zona binding when studied over a 90-day interval. Average sperm binding for individuals ranged from 68 to 127. Second, 3 of the 15 simultaneous assays showed very low numbers of sperm bound, indicating that 20% of the zonae had poor binding. Third, from 18 men who had 0% fertilization in an in vitro fertilization system using mature oocytes, evaluation of their sperm by HZA was performed. The sperm bound poorly and the 95% confidence interval was 20 sperm bound. Thus, the fertile controls should bind greater than 20 sperm to distinguish them from the infertile group in the HZA system resulting in a valid assay. CONCLUSIONS: With these guidelines, applications of the HZA may be made with greater reassurance of a valid bioassay of sperm fertilizing potential.

Electron microscopic evidence on the acrosomal status of bound sperm and their penetration into human hemizonae pellucida after storage in a buffered salt solution.

The hemizona assay (HZA) was developed to evaluate sperm binding potential using microbisected human zona pellucida. In this study, eight human oocytes stored in a buffered salt solution for 60 days were bisected into two identical hemispheres (hemizonae) and coincubated with the spermatozoa from a fertile man. All evaluated spermatozoa were tightly bound to the outer surface or had begun penetration into the zona pellucida. The hemizonae with bound spermatozoa were prepared and fixed for transmission electron microscopy (TEM) using standard techniques. Among the 108 sperm bound to the zone we were able to evaluate 25 by TEM. Twenty (80%) of the zona bound spermatozoa were partially or completely acrosome reacted, while six (20%) of the zona bound sperm had intact acrosomes. Acrosome intact, partially acrosome reacted and completely reacted spermatozoa were observed within the zona. Penetration pathways or tunnels were seen within the zona matrix. The results illustrate, that typically spermatozoa tightly bound the human zona pellucida show induction of the acrosome reaction. Importantly, following storage of human eggs in salt solution (buffered to 7.4), the zona pellucida retain their biological and functional characteristics for at least 90 days.

Functional aspects of human sperm binding to the zona pellucida using the hemizona assay.

The hemizona assay (HZA) has facilitated investigations of sperm function in relation to zona pellucida binding. In this study, the authors examined: 1) the association between hyperactivated sperm motility and HZA binding; 2) the binding kinetics and efficiency of sperm from subfertile men; and 3) the influence of sperm freezing and thawing on binding capacity. For each HZA, a nonviable human oocyte was cut into equal zona hemispheres. The mean number of bound sperm and the incidence of hyperactivation were significantly greater for samples of sperm from fertile men compared with sperm from subfertile men (P less than 0.05). Subfertile sperm had a binding curve that paralleled the curve for fertile sperm, although the magnitude of binding was markedly reduced. Freezing and thawing of sperm from fertile samples impaired their capacity to bind to the zona pellucida. The HZA binding efficiency was reduced by 30%, although the binding curves for fresh versus frozen samples remained parallel.