S_mry Many previous qualitative studies have shown that tumours are less vascular in the centre, and that host tissues become more vascular in close proximity to tumours. However, quantitative findings presented here for human colorectal cancer reveal some significant differences. Sections from 20 colorectal carcinomas (ten moderately and ten poorly differentiated) were immunostained with the QB/end/10 monoclonal to demonstrate blood vessels. These were measured by interactive morphometry and vascular volume density, surface density (Sv) and length density were recorded. In poorly differentiated carcinomas, the tumour centre was significantly less vascular than the periphery for all three parameters (P=0.008 for Sv). However, no significant difference was seen for moderately differentiated tumours, which constitute the majority of colorectal cancers. Surrounding host tissues did not show a general increase in vascular density close to tumours. Furthermore, when total viable tissue was considered, the vascular density of carcinomas was not markedly different from normal mucosa. In the centre of moderately differentiated carcinomas for example, the mean value for Sv was only 1.4 times higher than the mean value for normal mucosa. These findings suggest that colorectal cancers may elicit a relatively weak angiogenic response, consistent with their exceptionally slow growth rate.
Paspalum commersonii is tetraploid and sexual. Urochloa mosambicensis, Paspalum plicatulum, and P. guenoarum are all tetraploid aposporous apomicts. The aposporous embryo sac is four-nucleate in U. mosambicensis and eight-nucleate in the Paspalum spp. Irregularities in chromosome pairing occurred at meiosis in all species except P. commersonii.
A collection of 47 accessions of Panicum coloratum was classified into five morphologically distinct types. One of these was uniformly hexaploid (2n = 54) and another was diploid (2n = 18). The other three were mainly tetraploid (2n = 36) but some pentaploid (2n = 45) plants and one septaploid (2n = 63) plant were found. Meiosis was regular in all euploid plants but nine univalents were usually present in the pentaploid plants. A variable number of accessory chromosomes were found in somatic and generative cells in some plants of two of the types, and hybridization studies indicated a close relationship between these. It is suggested that both tetraploids and hexaploids are allopolyploids and that the hexaploid has two genomes in common with the tetraploids.All accessions set adequate seed following open pollination, but shed seed readily at maturity. There was variation in the degree of self-incompatibility both within and between types. In some accessions up to 33% of the florets were capable of setting seed when self-pollinated. P. coloratum grew best and flowered earliest in long days (I6 hr) and a day temperature of 27-30°C.
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