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11.
Papadakis EN Dokianakis DN Spandidos DA 《The International journal of biological markers》2003,18(3):195-199
H-ras is a member of the ras superfamily of genes. This gene encodes for a 21 kDa protein (p21) which is located on the inner surface of the plasma membrane. Ras genes are involved in a wide variety of human tumors, and there is a known correlation between H-ras activation and breast carcinogenesis. H-ras contains a polymorphic region, a repeated hexanucleotide -GGGCCT - located in intron 1 close to the 5' of the gene (HRM region). Three alleles of this region, P1, P2 and P3, have been identified that contain two, three and four repeats of the hexanucleotide, respectively. H-ras possesses a minisatellite DNA of the variable tandem repeat (VTR) which is located 1000 bp downstream of the gene displaying linkage disequilibrium with HRM. The purpose of this study was to estimate the frequency of P1, P2 and P3 in the normal population and in patients with breast cancer. We studied 56 biopsy specimens from patients with breast cancer, 61 normal blood samples, and 30 pairs of normal and tumoral breast tissues for VTR analysis. There was a difference in the distribution of P1, P2 and P3 alleles between normal and breast cancer samples. The frequency of P1 homozygosity was shown to be almost twice as high in women with breast cancer compared to healthy women (72% versus 39%). These results suggest that P1 homozygosity may be considered as a potential risk factor in breast carcinogenesis. In VTR analysis one sample presented a shift in mobility, but no polymorphism in the BstN I pattern of the 28 bp repetition core was observed. 相似文献
12.
Carbohydrate recognition by proteins is a key event in many biological
processes. Concanavalin A is known to specifically recognize the
pentasaccharide core (beta-GlcNAc-(1-->2)-alpha- Man-(1-->3)-[beta-
GlcNAc-(1-->2)-alpha-Man-(1-->6)]-Man) of N-linked oligosaccharides
with a Ka of 1.41 x 10(6 )M-1. We have determined the structure of
concanavalin A bound to beta-GlcNAc-(1-->2)-alpha-Man-(1-->3)-[beta-
GlcNAc-(1-->2)-alpha-Man- (1-->6)]-Man to 2.7A. In six of eight
subunits there is clear density for all five sugar residues and a well
ordered binding site. The pentasaccharide adopts the same conformation in
all eight subunits. The binding site is a continuous extended cleft on the
surface of the protein. Van der Waals interactions and hydrogen bonds
anchor the carbohydrate to the protein. Both GlcNAc residues contact the
protein. The GlcNAc on the 1-->6 arm of the pentasaccharide makes
particularly extensive contacts and including two hydrogen bonds. The
binding site of the 1-->3 arm GlcNAc is much less extensive.
Oligosaccharide recognition by Con A occurs through specific protein
carbohydrate interactions and does not require recruitment of adventitious
water molecules. The beta-GlcNAc-(1-->2)-Man glycosidic linkage PSI
torsion angle on the 1-->6 arm is rotated by over 50 degrees from that
observed in solution. This rotation is coupled to disruption of
interactions at the monosaccharide site. We suggest destabilization of the
monosaccharide site and the conformational strain reduces the free energy
liberated by additional interactions at the 1-->6 arm GlcNAc site.
相似文献
13.
Background
The rapid and accurate identification of species is a critical component of large-scale biodiversity monitoring programs. DNA arrays (micro and macro) and DNA barcodes are two molecular approaches that have recently garnered much attention. Here, we compare these two platforms for identification of an important group, the mammals. 相似文献14.
15.
DN Akongyuure S Amisah TK Agyemang RE Edziyie 《African Journal of Aquatic Science》2017,42(2):143-154
Fishery characteristics and livelihood status of fishers at Tono Reservoir, Ghana, were investigated between January 2015 and June 2016. Data on fisher demography, fishing gears, fishing methods, perceptions of the state of fish stocks, management practices, income and consumption of fishers were obtained through structured interviews. Censuses of fishers and fishing gears were conducted through direct observation and counts. The population of fishers was 950 and the majority (74%) of the sampled respondents fell within the ages of 24–41 years. Gillnet, cast net, trap and hook and line were the four main gears utilised. Illegal methods of fishing observed included the use of mosquito nets (nets with mesh <1.0 cm) and the use of brewer’s waste (pito mash) as bait. Brycinus nurse, Synodontis spp., Parailia spiniserrata and Chrysichthys spp. were perceived to have disappeared from the reservoir. The fishers were unaware of the existence of any fisheries regulations, hence there was no adherence to management practices. Their daily income was derived mainly from fishing. The incidence of poverty among fishers was low (8%). The Tono Reservoir has a great potential for supporting livelihood if it is properly managed. 相似文献
16.
Despite concerted surveys, the Maloti minnow Pseudobarbus quathlambae (Barnard 1938) had not been recorded in South African waters for almost eighty years since the original collections were made at the type locality in the upper uMkhomazana River in 1938. The species was therefore declared extinct in South Africa, whereas extant populations were considered confined to various rivers in the Lesotho highlands. In April 2017, however, this species was rediscovered in the Mzimkhulu River system in KwaZulu-Natal. The rediscovery of a species that was considered locally extinct supports the need for extensive surveys to determine its distribution range, estimate population sizes, assess conservation status and implement effective strategies to ensure its continued existence in KwaZulu-Natal. 相似文献
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