No abstract

Pegloticase is designed to convert urate into the easily excretable allantoin to treat hyperuricemia in gout. The aim of this analysis was to describe the pharmacokinetics and pharmacodynamics of pegloticase in 40 gout patients. Pegloticase was administered as intravenous infusions every 2 weeks at 4- and 8-mg doses or every 4 weeks at 8- or 12-mg doses for 12 weeks. Serum pegloticase concentrations, plasma urate, and serum antibody response were determined. Population pharmacokinetics and pharmacodynamics analyses were performed. Data were modeled simultaneously, and covariates were investigated (age, gender, race, body weight, ideal body weight, and antibody response). The dosing regimens to maintain uric acid levels below the therapeutic target of 6 mg/dL were then predicted by the model. The pharmacokinetics were best described by a 1-compartment linear model, while the pharmacodynamics model was fitted as a direct effect of pegloticase on uric acid concentrations with a suppressive maximum effect attributed to drug (E(max)) function. Pegloticase suppressed uric acid levels up to 83%. Weight only affected clearance and volume of distribution. No covariates affected pharmacodynamics. Simulation suggests pegloticase administered at 8 mg every 2 or 4 weeks as 2-hour intravenous infusions will maintain uric acid levels well under 6 mg/dL.

Sexual differentiation of the germ cells follows gonadal differentiation, which is determined by the presence or the absence of the Y-chromosome. Consequently, oogenesis and spermatogenesis take place in the germ cells with XX and XY sex chromosomal compositions respectively. It is unclear how sexual dimorphic regulation of meiosis is associated with the sex-chromosomal composition. In the present study, we examined the behavior of the sex chromosomes in the oocytes of the B6.Y TIR sex-reversed female mouse, in comparison with XO and XX females. As the sex chromosomes fail to pair in both XY and XO oocytes during meiotic prophase, we anticipated that the pairing failure may lead to excessive oocyte loss. However, the total number of germ cells, identified by immunolabeling of germ cell nuclear antigen 1 (GCNA1), did not differ between XY and XX ovaries or XO and XX ovaries up to the day of delivery. The progression of meiotic prophase, assessed by immunolabeling of synaptonemal complex components, was also similar between the two genotypes of ovaries. These observations suggest that the failure in sex-chromosome pairing is not sufficient to cause oocyte loss. On the other hand, labeling of phosphorylated histone gH2AX, known to be associated with asynapsis and transcriptional repression, was seen over the X-chromosome but not over the Y-chromosome in the majority of XY oocytes at the pachytene stage. For comparison, gH2AX labeling was seen only in the minority of XX oocytes at the same stage. We speculate that the transcriptional activity of sex chromosomes in the XY oocyte may be incompatible with ooplasmic maturation.Reproduction (2008) 135 241-252