PubMed · 4711111
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T R Hopkins. 1973. Another density gradient fractionator.. https://doi.org/10.1016/0003-2697(73)90444-2
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The matrix (MA) proteins of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) are known to be important for the targeting and assembly of lentiviral proteins. The objective of the present study was to determine whether the MA protein of HIV-1 was sufficient for particle assembly and release. Eukaryotic expression of wild-type HIV-1 Gag-Pol, HIV-1 MA alone, or SIV MA alone was analyzed with radio-immunoprecipitation, density centrifugation, and a protease protection assay. Cells that expressed HIV-1 Gag-Pol or SIV MA alone released virus-like particles (VLPs) with sucrose gradient densities of 1.15 or 1.12 g/ml, respectively. The MA and/or capsid proteins in these particles were protected from protease degradation, indicating the presence of a protective outer membrane. Expression of HIV-1 MA protein alone resulted in release of MA which pelleted through a 20% sucrose cushion but failed to enter a 20-60% sucrose gradient and was not protected from protease degradation. The MA protein of SIV was previously reported to be sufficient for production of VLPs (S. A. Gonzalez, H, K, Affrachino, H. R. Gelderblom, and A. Burney. Virology 194, 548-556, 1993; V. Liska, D. Spehner, M. Mehtali, D. Schmitt, A. Kirn, and A. M. Aubertin. J. Gen. Virol. 75, 2955-2962, 1994). Our study confirmed that result, but indicated that the MA protein of HIV-1 was not sufficient to assemble and release VLPs.
Methods claiming to achieve sex selection by sperm sorting have existed for many years. Numerous applications for safe and effective selection procedures exist in current clinical practice, as sex-linked conditions could be theoretically eliminated by use of appropriate sperm for fertilization or insemination. Use of such techniques could also address the need to effect family balancing for some couples. Modern preconception sex-selection methods may be classified into two general types: those that attempt to segregate spermatozoa on the basis of subtle physical or kinetic features, and those that rely on distinctive nuclear characteristics unique either to X- or Y-chromosome bearing sperm. Laboratories providing sperm sexing using the former method have been available for some years, although the associated efficiency and reproducibility are controversial. Sex selection of spermatozoa by chromatin differences has been shown to achieve significant enrichment of X- or Y-chromosome bearing sperm, but clinical experience in humans is limited. The fundamental elements of the two approaches introduced here are reviewed and compared. Selected key historical concepts in sex selection by sperm sorting are outlined, followed by a summary of promising areas for future research.
OBJECTIVE: To evaluate pregnancy rates (PRs) in women undergoing artificial insemination with sperm alternately prepared by one of five techniques: sperm washing, Percoll gradient centrifugation, swim-up, swim-down, or refrigeration/heparin treatment. DESIGN: Each treatment group alternated in a different order through the five sperm preparations. Pregnancy rates were compared for each sperm preparation. SETTING: Two infertility centers, one located in an academic institution and the other a regional hospital. PATIENT(S): Three hundred sixty-three women undergoing 898 artificial inseminations with husband semen with a progressive motile sperm count of >20 million sperm per mL were randomly placed in the five treatment groups. MAIN OUTCOME MEASURE(S): Pregnancy rates. RESULT(S): The overall ongoing PR per insemination was 9.7% (87/898), including 6.12% for natural cycles (n = 196), 12.8% for clomiphene citrate-stimulated cycles (n = 101), and 10.3% for gonadotropin-stimulated cycles (n = 601). The highest ongoing PRs for sperm preparations followed the swim-up technique (13.2%, 26/197) and the Percoll gradient centrifugation technique (12.7%, 26/204). CONCLUSION(S): These data suggest that the swim-up and Percoll gradient preparations result in higher PRs than the wash, swim-down, and refrigeration/heparin techniques.