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Magnetization transfer of pure DNA and purified sperm nuclei (1996)

Virta, Anette ; Kormano, Martti ; Paranko, Jorma

Springer

Magnetic resonance materials in physics, biology and medicine 4 (1996), S. 135-138

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ISSN: 1352-8661

Keywords: magnetization transfer ; DNA ; chromatin ; sperm

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Physics

Notes: Abstract Magnetization transfer (MT) imaging provides a novel opportunity to characterize interactions between tissue water and macromolecules. Although severalin vitro investigations have shown that proteins and lipids are important determinants of MT, the contribution of DNA is still unknown. This study was designed to determine whether DNA and cell nuclear material exhibit MT. We measured the magnetization transfer effect of pure DNA strands and purified bovine sperm head nuclei. Although no transfer of magnetization could be detected in samples of pure DNA strands, the sperm head nuclei exhibited a strong MT effect that increased with increasing solid content of the samples. Since the purified bovine sperm head samples consist of large nuclei with only minor traces of perinuclear matrix, the measured MT effect arises from the chromatin of the nuclei. The DNA fills 90% of the nuclear volume and it is extremely tightly packed as chromatin fibers by nucleoproteins. We hypothesize that the numerous intra- and intermolecular disulfide bonds that stabilize the chromatin fibers restrict the movement of the surface water binding sites of both DNA and protamines and thus facilitate the transfer of magnetization. Therefore, the results indicate that the amount of nuclear material may positively contribute to MT in tissues.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01772520

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Actin, α-actinin, and spectrin with specific associations with the postacrosomal and acrosomal domains of bovine spermatozoa (1995)

Yagi, Ahmed ; Paranko, Jorma

New York, NY [u.a.] : Wiley-Blackwell

The @Anatomical Record 241 (1995), S. 77-87

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ISSN: 0003-276X

Keywords: Spermatozoa ; Actin ; α-actinin ; Spectrin ; Acrosomal lamina ; Bovine ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine

Notes: Background: Characteristic membrane changes in spermatozoa culminating in acrosome reaction and sperm-egg fusion, and suspected involvement of actin-containing cytoskeleton in membrane changes in general, prompted us to investigate subcellular distribution of actin and actin-binding proteins in bovine spermatozoa subjected to various extractions which sequentially denude the sperm investments.Methods: Spermatozoa were treated with either 1% SDS, 0.1% Triton X-100, 0.1% Hyamine, or 1 M MgCl2 or were sonicated. Immunostaining of actin, α-actinin, spectrin, and acrosin as well as electron microscopic analysis of extracted spermatozoa were carried out.Results: Extractions caused evagination of the acrosomal lamina which retained focal contacts with the inner acrosomal membrane. Extractions further revealed lateral prongs at the anterior border of the postacrosomal sheath. Labeling for α-actinin and spectrin was localized in the acrosinpositive acrosomal lamina, neck, and principal piece, the latter containing also relatively extraction-resistant oligomeric or polymerized actin. In the postacrosomal area, actin was accumulated in the extraction-resistant posterior ring structure and anteriorly at the sites apparently related to the lateral prongs. Notably, spectrin reactivity was enhanced by MgCl2 in head, neck, and principal piece, and sonication abolished cytoskeletal immunoreactivity in the head.Conclusions: Destabilization of membranes with selected extractions induces changes in the acrosomal lamina mimicking acrosomal vesicle formation. The lateral prongs and posterior ring structure, respectively, may serve as anterior and posterior anchors for the extraction-resistant post-acrosomal sheath. The lateral prongs may also be a merger zone for actin, α-actinin, and spectrin with important implication on sperm function. The latter two proteins may be involved in acrosomal vesicle formation. It is apparent that extractions have a significant effect on the detectability of sperm cytoskeletal elements. © 1995 Wiley-Liss, Inc.

Additional Material: 6 Ill.