Inhibitory effect of the flavonoid silymarin on the erythrocyte hemolysis induced by phenylhydrazine

The flavonoid silymarin, which is used as a therapeutical agent in the treatment of liver diseases, can inhibit the hemolysis and lipid peroxidation induced by phenylhydrazine on erythrocytes obtained from rats treated with the flavonoid. This effect is ascribed to the antioxidant properties as a free radical scavenger exhibited by the flavonoid. Silymarin failed to inhibit the glutathione depletion induced by phenylhydrazine on erythrocytes. It is proposed that the flavonoid acts at the membrane level of the cell avoiding the lipid peroxidative and fluidizing effect of phenylhydrazine.     

Isolation and characterization of an ipt gene from the Ti plasmid Bo542

Summary A 1.9 kb clone of the T-DNA region of the Agrobacterium tumefaciens Ti plasmid Bo542 which exhibited homology to the isopentenyl transferase (ipt) locus of pTiA6 was identified by low stringency DNA hybridization. Introduction of this segment of pTiBo542 DNA into cells of Nicotiana tabacum or N. glauca caused tumor formation in vivo, and allowed hormone independent growth in vitro. Furthermore, this DNA segment complemented ipt mutant strains of A. tumefaciens, restoring their ability to cause tumors on Kalanchöe leaves and tomato stems. The complete DNA sequence of this segment has been determined, revealing an open reading frame homologous to other known Agrobacterium ipt genes.     

Selective interactions among Rh,ABO, and sex ratio of newborns

Summary The hypothesis that the Rh and ABO blood systems behave like the HLA system in relation to mother-conception tolerance-rejection mechanisms was tested in 25,501 mother-infant pairs. According to this hypothesis, heterozygotes carrying a paternal gene that is not present in their mother should be better tolerated than homozygotes. Significantly more BO infants born to AO mothers. AO infants born to BO mothers, Rh(+) heterozygotes born to Rh(-) mothers, and less significantly AO infants born to OO mothers confirm the hypothesis. Fewer homozygotes occurred in Rh(-) infants born to Rh(+) mothers and in O infants born to non-O mothers. Deviations from the Hardy-Weinberg equilibrium found in the ABO system were modified by the Rh and sex of the infant. These data strongly support the hypothesis that at least two feto-maternal systems influence the denstiny of pregnancies: the classical known incompatibility system which operates late in pregnancy and a new one which is based on the induction of maternal tolerance early in pregnancy: maternal tolerance seems to be better elicited by heterozygous eggs or embryos carrying a gene not present in the mother. The data also support the hypothesis that the sex ratio is influenced by feto-maternal tolerance-rejection mechanisms associated with the ABO and Rh systems.     

Increased Resistance Against Oxidative Stress Is Observed During A Short Period of Renal Reperfusion After A Temporal Ischaemia

Reperfusion of rat kidney submitted to temporal ischaemia induces a decrease in glutathione content. Lipid peroxidation is not detected in kidney homogenates but microsomes obtained after periods of reperfusion longer than 60 minutes show increased malondialdehyde values correlated with high oxygen consumption and superoxide free radical generation. Microsomes obtained from kidneys submitted to 15 or 60 minutes of reperfusion are resistant to NADPH-induced lipid peroxidation but after 120 minutes of reperfusion an increased lipid peroxidative response is observed. Although the mechanism of the protection found in microsomes against the induction of oxidative stress in the first 60 minutes of reperfusion is unknown, it is postulated that this subcellular fraction plays an important role in the oxidative stress observed after longer periods of reperfusion.     

Stimulation of the adenylyl cyclase activity in human endometrial membranes by VIP and related peptides

Vasoactive intestinal peptide (VIP) has been shown to stimulate adenylyl cyclase activity in human endometrial membranes. The effect was dependent on the time and temperature of incubation as well as on the concentration of endometrial membrane proteins in the medium. In the presence of 1 M GTP, half-maximal stimulation of adenylyl cyclase activity was observed at 25.0±7.0 nM VIP, whereas the maximal activity (at 1 M VIP)corresponded to an increase of about 140% with respect to basal values (7.5±0.6 pmol cyclic AMP/min/mg of protein). However, the maximal stimulation of adenylyl cyclase activity was obtained with helodermin (1 M) that increased the activity by 170% over the basal. The relative potency of VIP-related peptides upon the adenylyl cyclase activity was: helodermin (ED₅₀=1.8±1.4 nM)>VIP(ED₅₀=25.0±7.0 nM)>PHI (ED₅₀=725.0±127.2 nM). Secretin had a faint effect upon the adenylyl cyclase activity and glucagon was completely inefficient at this level. The presence of _s and _i subunits of G proteins in human endometrium was detected by immunoblot. Preliminary results showed the presence of two classes of¹²⁵I-VIP receptors in human endometrial membranes with the following stoichoimetric parameters: high affinity receptor (Kd=2.0 nM, binding capacity 0.1 pmol VIP/mg protein) and low affinity receptor (Kd=0.43 M, binding capacity 13.1 pmol VIP/mg protein). The present results together with the known presence of VIP in human uterus and the actions of this neuropeptide in the adjacent myometrial tissue support the idea that VIP and related peptides may have a role in human endometrium.     

Is there hybridization between diploid and tetraploid Euphrasia in a secondary contact zone?

Premise

Strong postzygotic reproductive isolating barriers are usually expected to limit the extent of natural hybridization between species with contrasting ploidy. However, genomic sequencing has revealed previously overlooked examples of natural cross-ploidy hybridization in some flowering plant genera, suggesting that the phenomenon may be more common than once thought. We investigated potential cross-ploidy hybridization in British eyebrights (Euphrasia, Orobanchaceae), a group from which 13 putative cross-ploidy hybrid combinations have been reported based on morphology.

Methods

We analyzed a contact zone between diploid Euphrasia rostkoviana and tetraploid E. arctica in Wales. We sequenced part of the internal transcribed spacer (ITS) of nuclear ribosomal DNA and used genotyping by sequencing (GBS) to look for evidence of cross-ploidy hybridization and introgression.

Results

Common variant sites in the ITS region were fixed between diploids and tetraploids, indicating a strong barrier to hybridization. Clustering analyses of 356 single-nucleotide polymorphisms (SNPs) generated using GBS clearly separated samples by ploidy and revealed strong genetic structure (F_ST = 0.44). However, the F_ST distribution across all SNPs was bimodal, indicating potential differential selection on loci between diploids and tetraploids. Demographic inference suggested potential gene flow, limited to around one or fewer migrants per generation.

Conclusions

Our results suggest that recent cross-ploidy hybridization is rare or absent in a site of secondary contact in Euphrasia. While a strong ploidy barrier prevents hybridization over ecological timescales, such hybrids may form in stable populations over evolutionary timescales, potentially allowing cross-ploidy introgression to take place.