Determination of vitamin D levels in human biological specimens has gained a high relevance over the last decades, essentially because low levels have been associated with several biological disorders. In fact, vitamin D deficiency has become a worldwide health concern covering all ages and genders. The storage of biofluids has to be considered for determination of vitamin D and metabolites in order to fully preserve matrices status. This study attempts to evaluate lyophilization of serum and plasma as a pre-processing step for sample storage prior to quantitative analysis of vitamin D-3 and its main hydroxylated metabolites-25(OH)D-3, 24,25(OH)(2)D-3 and 1,25 (OH)(2)D-3. The protocol including sample lyophilization was characterized in terms of analytical features and compared to the same method, based on SPE-LC-MS/MS, without lyophilization. Sensitivity, precision and accuracy were not affected when we operated with lyophilized serum and plasma and results provided by a set of twenty-four serum samples from DEQAS (Vitamin D External Quality Assessment Scheme) were in agreement with reported concentrations for 25(OH)D-3 and 1,25(OH)(2)D-3. A stability study programmed for 9 months allowed ensuring that the concentration of vitamin D-3 and metabolites in lyophilized serum and plasma stored at room temperature was not affected during this period. This research has demonstrated that the quantitation of target metabolites is not under the influence of lyophilization. Therefore, including lyophilization prior to analysis could reduce shipment and storage costs, avoid delays of sample processing, and increase the stability of the target analytes due to an effective quenching process.

All-female populations of mandarin fish (Siniperca chuatsi) provide economic advantages in production because of the superior growth of females relative to males. The first step to produce all-female populations was artificially induced sex reversal of female mandarin fish; beginning at 10 dph, fish (undifferentiated) were treated with dietary 17 alpha-methyltestosterone (MT) at 50 mg/kg and 100 mg/kg dosages for 2 months. The MT treatments successfully produced all-male stocks (male rate 100%), as compared with the control group (51.11%). The survival rate of MT-treated and control groups was not significantly different. MT did not alter fish growth over the course of the experiment to 240 dph. MT treatment promoted the development of testes, and it initially inhibited gonadosomatic index (GSI) and the levels of serum steroid hormone (T and E2). Nevertheless, at the 180 dph and 240 dph, the GSI and serum steroid hormone (T and E-2) levels in MT treatment groups had no significant difference with control groups. The masculinization of mandarin fish was also demonstrated by the expression patterns of sex-specific genes, dmrt1, sox9, foxl2 and cyp19a1a; the gonads of MT-treated fish exclusively expressed male-specific dmrt1 and sox9 with no expression of female-specific foxl2 and cyp19a1a.