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Digitale Medien

Contribution of collagen and mineral to the elastic anisotropy of bone (1994)

Hasegawa, K. ; Turner, C. H. ; Burr, D. B.

Springer

Calcified tissue international 55 (1994), S. 381-386

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ISSN: 1432-0827

Schlagwort(e): Acoustic microscopy ; Bone ; Collagen fiber ; Elastic anisotropy ; Mineral crystal

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin , Physik

Notizen: Abstract It has long been thought that collagen fibers within the bone matrix are deposited in an aligned pattern that channels mineral growth. If this model of bone structure is correct, both organic and inorganic phases of bone should have similar elastic anisotropy. Using an acoustic microscope, we measured longitudinal and transverse acoustic velocities of cortical specimens taken from 10 dog femurs before and after removal of either the mineral (using 10% EDTA) or collagen phases (using 7% sodium hypochlorite) and calculated longitudinal (CL) and transverse (CT) elastic coefficients. The anisotropy ratio (CL/CT) decreased significantly after demineralization (1.61 before versus 1.06 after, P〈0.0001, paired t-test). However, there was no significant change after decollagenization (1.51 before versus 1.48 after, P=0.617, paired t-test). We conclude that the orientation of mineral crystals is the primary determinant of bone anisotropy, and the collagen matrix within osteonal bone has little directional orientation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00299319

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Digitale Medien

Cloning and characterization of a maize cDNA encoding phytoene desaturase, an enzyme of the carotenoid biosynthetic pathway (1996)

Li, Zhou-Hui ; Matthews, Paul D. ; Burr, Benjamin ; [weitere]

Springer

Plant molecular biology 30 (1996), S. 269-279

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ISSN: 1573-5028

Schlagwort(e): carotenoid biosynthesis ; endosperm ; gene ; maize ; phytoene desaturase ; regulation

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract To study regulation of the plastid-localized maize carotenoid biosynthetic pathway, a cDNA encoding phytoene desaturase (PDS) was isolated and characterized. The DNA sequence of the maize Pds cDNA was determined and compared with available dicot Pds genes. The deduced PDS protein, estimated at 64.1 kDa (unprocessed), had a dinucleotide binding domain and conserved regions characteristic of other carotene desaturases. Alignment of available PDS sequences from distantly related organisms suggests that Pds has potential as a phylogenetic tool. By use of heterologous complementation in Escherichia coli, maize PDS was shown to catalyze two desaturation steps converting phytoene to ζ-carotene. RFLP (restriction fragment length polymorphism) mapping was used to place Pds on chromosome 1S near viviparous5 (vp5), and RT-PCR (reverse-transcriptase polymerase chain reaction) analysis indicated reduced Pds transcript in vp5 mutant relative to normal endosperm. Other phytoene-accumulating mutant endosperms, vp2 and white3 (w3), showed no difference in Pds transcript accumulation as compared with normal endosperm counterparts. RT-PCR analysis of Pds transcript accumulation in developing endosperm showed Pds was constitutively expressed. Therefore, endosperm carotenogenesis is not regulated by increasing the level of Pds transcripts.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00020113

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Digitale Medien

Sequence, identification and characterization of cDNAs encoding two different members of the 18 kDa heat shock family of Zea mays L. (1991)

Goping, Ing Swie ; Frappier, J. Roger H. ; Walden, David B. ; [weitere]

Springer

Plant molecular biology 16 (1991), S. 699-711

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ISSN: 1573-5028

Schlagwort(e): heat shock ; heat shock cDNAs ; maize ; small heat shock proteins

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Heat-shocked maize seedlings (cv. Oh43) synthesize a characteristic set of heat-shock proteins (hsps) which include an 18 kDa family containing at least six major isoelectric variants. A cDNA library was constructed from poly(A)+ RNAs isolated from the radicles of heat-shocked maize seedlings and screened with a DNA fragment from the theoretical open reading frame of a putative Black Mexican Sweet maize hsp 18 genomic clone. Two clones, cMHSP18-3 and cMHSP18-9, were isolated, and the RNA transcripts generated from them were translated into proteins which immunoreact with antibodies directed against the maize 18 kDa hsps and exhibit the same electrophoretic characteristics as two different members of the 18 kDa hsp family. Nucleotide sequence analyses of the cDNAs in these clones reveal that their 5′ and 3′ untranslated regions exhibit 33–34% identity and that their protein encoding regions share 93% identity. The deduced amino acid sequences of these clones show 90% identity, and the apparent molecular masses and isoelectric points of these proteins agree with those established for two different 18 kDa hsps, numbered 3 and 6. This report substantiates that at least two of the 18 kDa hsps in maize are products of different but related genes. Moreover, it establishes that transcripts for these proteins accumulate during heat shock and that both their nucleotide and deduced amino acid sequences share extensive similarities with the class VI small hsps in soybean and with transcripts expressed during meiosis in Lilium.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00023434

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