Karyotype and leaf epidermis histology traits of Digitaria abyssinica (Hochst. Ex A. Rich.) (Poaceae).

Digitaria abyssinica (African couchgrass) has economic potential as forage. This species is taxonomically complex, with a high number of synonyms, basic chromosome number x = 9, and diploid and tetraploid cytotypes. Anatomical, histological, and cytotaxonomic studies may contribute to the taxonomic description of this species and reveal its polyploidization and hybridization events. To this end, this study aimed to characterize the karyotype and leaf epidermis histology of two D. abyssinica genotypes. Chromosome characterization was performed based on chromosome banding using chromomycin A (CMA) and 4,6-diamidino-2-phenylindole (DAPI) and identification of 35S and 5S rDNA sites by fluorescent in situ hybridization. Nuclear DNA quantification was performed by flow cytometry. Paradermal sections were obtained for the leaf epidermis study by light and electron microscopy. The results confirmed that both genotypes are tetraploid (2n = 36). The number and distribution of 35S and 5S rDNA sites suggest the occurrence of postpolyploidization structural chromosomal changes or hybridization processes. Despite intraspecific variation in the number of 5S rDNA sites and CMA+/DAPI+ bands, no changes were identified in karyotypical symmetry or genome size. Leaf epidermis histology traits and cytogenetic data can support breeding programs and germplasm banks in identifying species or cultivars

Chromosome numbers for the Italian flora: 4

In this contribution new chromosome data obtained on material collected in Italy are presented. It includes 9 chromosome counts for Polygala (Polygalaceae), Dianthus and Silene (Caryophyllaceae)

The renin-angiotensin system is modulated by swimming training depending on the age of spontaneously hypertensive rats

Aim: To investigate the effects of swimming training on the renin-angiotensin system (RAS) during the development of hypertensive disease. Main methods: Male spontaneously hypertensive rats (SHR) were randomized into: sedentary young (SY), trained young (TV), sedentary adult (SA), and trained adult (TA) groups. Swimming was performed 5 times/wk/8wks. Key findings: Trained young and adult rats showed both decreased systolic and mean blood pressure, and bradycardia after the training protocol. The left ventricular hypertrophy (LVH) was observed only in the TA group (12.7%), but there was no increase on the collagen volume fraction. Regarding the components of the RAS, TV showed lower activity and gene expression of angiotensinogen (AGT) compared to SY. The TA group showed lower activity of circulatory RAS components, such as decreased serum ACE activity and plasma renin activity compared to SA. However, depending on the age, although there were marked differences in the modulation of the RAS by training, both trained groups showed a reduction in circulating angiotensin II levels which may explain the lower blood pressure in both groups after swimming training. Significance: Swimming training regulates the RAS differently in adult and young SHR rats. Decreased local cardiac RAS may have prevented the LVH exercise-induced in the TV group. Both groups decreased serum angiotensin II content, which may, at least in part, contribute to the lowering blood pressure effect of exercise training. (C) 2011 Elsevier Inc. All rights reserved

Karyotype asymmetry in Cynodon Rich. (Poaceae) accessions.

Abstract Cynodon is a genus of plants with forage potential that has attracted the interest of breeders. These species have high morphological variability in a large number of varieties and cytotypes, hampering identification. This study aimed to determine the karyotype asymmetry index among accessions of Cynodon to discriminate between them. Karyotype symmetry was based on three estimates, which were compared. The basic number for the genus is x = 9. The results of the chromosome count and DNA quantification, respectively, were as follows: two diploid accessions (2n = 2x = 18 and 1.08 ± 0.094 to 1.17 ± 0.036 pg DNA and ± standard deviation), one triploid accession (2n = 3x = 27 and 1.63 ± 0.017 pg DNA), four tetraploid accessions (2n = 4x = 36 and 1.88 ± 0.069 to 2.10 ± 0.07 pg DNA), and one pentaploid accession (2n = 5x = 45 and 2.55 ± 0.098 pg DNA). C. incompletus var. hirsutus had the longest total length of the haploid lot (29.05 µm), with chromosomes that ranged from 1.7 to 6.2 µm in length. On the basis of the karyotype asymmetry indices, the accessions were divided into two groups: 1) C. dactylon var. dactylon, C. transvaalensis, C. dactylon var. polevansii, three accessions of Cynodon sp, and C. nlemfuensis; and 2) C. incompletus var. hirsutus. This is the first description of tetraploidy in C. transvaalensis. The karyotypic data facilitated a determination of the degree of proximity between the accessions