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P Vella

Publications and source records attributed to P Vella.

5 recordsLinked to original sources
PubMed1998

Culture and transfer of human blastocysts increases implantation rates and reduces the need for multiple embryo transfers.

OBJECTIVE: To determine whether the transfer of blastocysts on day 5, developed in sequential culture media, resulted in an increase in implantation rate compared with embryos transferred on day 3. DESIGN: Comparative study of embryo culture regimes. SETTING: Private practice assisted reproductive technology center. PATIENT(S): Twenty-three patients undergoing routine IVF cycles. INTERVENTION(S): Culture of embryos to day 3 in either standard culture conditions or a serum-free chemically defined medium. One hundred one embryos were subsequently cultured from day 3 to day 5 in a second serum-free medium specifically designed to support development of the blastocyst. MAIN OUTCOME MEASURE(S): Embryo cell number and quality on day 3. Blastocyst development on day 5. Implantation rate (determined by fetal heart) and ongoing pregnancy rate (PR). RESULT(S): Implantation rates for embryos transferred at the blastocyst stage of development were twice that observed for embryos transferred on day 3, around the eight-cell stage. Significantly more embryos were required for transfer on day 3, compared with day 5, to establish similar PRs. CONCLUSION(S): Viable human blastocysts can be obtained in sequential culture media in the absence of coculture and serum. Transfer of blastocysts in IVF will facilitate high PRs while limiting the number of embryos transferred and therefore minimizes the risk of multiple gestation.

Adult↗
PubMed1988

Variable quantitation of Haemophilus influenzae type b anticapsular antibody by radioantigen binding assay.

The measurement of antibody to Haemophilus influenzae type b capsular polysaccharide is important in the study of natural immunity and in the immunogenicity evaluation of H. influenzae type b vaccines. Several radioantigen binding assays (RABA) have been developed to measure H. influenzae type b anticapsular antibody, but recent immunogenicity data obtained with structurally similar vaccines suggest major differences in antibody quantitation in different laboratories. To evaluate interlaboratory variability in the measurement of anticapsular antibody levels, we blindly evaluated a sample of 40 pre- and postimmunization sera by eight RABAs in different laboratories. Evaluation of RABA methods revealed differences in polysaccharide antigens, radiolabeling methods, concentration and volume of antigen and antibody, and other assay methods. The reported results of assays varied significantly between laboratories (up to sixfold differences in geometric means), in part because of differences in assay sensitivity and different proportions of samples having undetectable levels of antibody (0 to 65% of specimens with undetectable levels). After standardizing the limit of sensitivity for all assays (0.125 microgram/ml), the results of all combinations of paired analyses of RABA assays correlated well (r = 0.88 to 0.99) but the geometric mean levels still varied as much as twofold. For individual sera, the differences between paired assays often were substantial (P less than or equal to 0.0001, paired t test), with some results varying as much as 64-fold. Differences were greatest for lower levels of antibody. There was good comparability and interlaboratory reproducibility of some assays but not of others. Intrinsic or extrinsic labeling of the antigen was not a major determinant of comparability. In most instances, the current variation in the quantitation of antibody levels by these assays precludes interassay comparisons. A standardized measurement of antibody needs to be developed to adequately compare results between different H. influenzae type b immunogenicity studies.

Antibodies, Bacterial↗