Protein kinase B/Akt mediates cAMP- and cell swelling-stimulated Na+/taurocholate cotransport and Ntcp translocation

Cyclic AMP and cell swelling stimulate hepatic Na+/TC cotransport and Ntcp translocation via the phosphoinositide 3-kinase signaling pathway. To determine the downstream target of the phosphoinositide 3-kinase action, we examined the role of protein kinase B (PKB)/Akt using SB203580 in hepatocytes as well as by transfection with a dominant negative (DN-PKB) or a constitutively active (CA-PKB) form of PKB in HuH-Ntcp cells. Both cAMP and cell swelling stimulated p38 mitogen-activated protein (MAP) kinase as well as PKB activity. Although 100 microm SB203580 inhibited cell swelling- and 8-chlorophenylthio-cAMP-induced activation of both p38 MAP kinase and PKB, 1 microm SB203580 inhibited activation of p38 MAP kinase, but not of PKB, in hepatocytes. 100 microm, but not 1 microm SB203580, inhibited cell swelling- and cAMP-induced increases in taurocholate (TC) uptake and Ntcp translocation in hepatocytes. TC uptake in HuH-Ntcp cells was more than 90% dependent on extracellular Na+. Cyclic AMP and cell swelling increased TC uptake by 50-100% and PKB activity 2-4-fold in HuH-Ntcp cells transfected with the empty vector and failed to increase PKB activity, TC uptake, and Ntcp translocation in DN-PKB-transfected HuH-Ntcp cells. Transfection with CA-PKB increased PKB activity, TC uptake, and Ntcp translocation in HuH-Ntcp cells compared with cells transfected with the empty vector. In contrast, transfection with DN-PKB did not affect basal PKB activity, TC uptake, or Ntcp translocation. Taken together, these results strongly suggest that cell swelling and cAMP-mediated stimulation of hepatic Na+/TC cotransport and Ntcp translocation requires activation of PKB and is mediated at least in part via a phosphoinositide 3-kinase/PKB-signaling pathway.     

Root responses and nitrogen acquisition by<Emphasis Type="Italic"> Artemisia tridentata</Emphasis> and<Emphasis Type="Italic"> Agropyron desertorum</Emphasis> following small summer rainfall events

Resources in the Great Basin of western North America often occur in pulses, and plant species must rapidly respond to temporary increases in water and nutrients during the growing season. A field study was conducted to evaluate below ground responses of Artemisia tridentata and Agropyron desertorum, common Great Basin shrub and grass species, respectively, to simulated 5-mm (typical summer rain) and 15-mm (large summer rain) summer rainfall events. The simulated rainfall was labeled with K(15)NO(3) so that timing of plant nitrogen uptake could be monitored. In addition, soil NH(4)(+) and NO(3)(-) concentrations and physiological uptake capacities for NO(3)(-) and NH(4)(+) were determined before and after the rainfall events. Root growth in the top 15 cm of soil was monitored using a minirhizotron system. Surprisingly, there was no difference in the amount of labeled N acquired in response to the two rainfall amounts by either species during the 7-day sample period. However, there were differences between species in the timing of labeled N uptake. The N label was detected in above ground tissue of Agropyron within 1 h of the simulated rainfall events, but not until 24 h after the rainfall in Artemisia. For both Agropyron and Artemisia, root uptake capacity was similarly affected by the 5-mm and 15-mm rainfall. There was, however, a greater increase in uptake capacity for NH(4)(+) than for NO(3)(-), and the 15-mm event resulted in a longer response. No root growth occurred in either species in response to either rainfall event during this 8-day period. The results of this study indicate that these species are capable of utilizing nitrogen pulses following even small summer rainfall events during the most stressful period of the summer and further emphasize the importance of small precipitation events in arid systems.     

Structure-wise discrimination of adenine and guanine by proteins on the basis of their nonbonded interactions

We have analyzed the nonbonded interactions of the structurally similar moieties, adenine and guanine forming complexes with proteins. The results comprise (a) the amino acid–ligand atom preferences, (b) solvent accessibility of ligand atoms before and after complex formation with proteins, and (c) preferred amino acid residue atoms involved in the interactions. We have observed that the amino acid preferences involved in the hydrogen bonding interactions vary for adenine and guanine. The structural variation between the purine atoms is clearly reflected by their burial tendency in the solvent environment. Correlation of the mean amino acid preference values show the variation that exists between adenine and guanine preferences of all the amino acid residues. All our observations provide evidence for the discriminating nature of the proteins in recognizing adenine and guanine.     

Genotyping of alpha-thalassemia in microcytic hypochromic anemia patients from North India

Microcytic hypochromic anemia is a common condition in clinical practice and alpha-thalassemia has to be considered as a differential diagnosis. Molecular diagnosis of alpha-thalassemia is possible by polymerase chain reaction. The aim of this study was to evaluate the frequency of alpha-gene numbers in subjects with microcytosis. In total, 276 subjects with microcytic hypochromic anemia [MCV<80fl; MCH<27pg] were studied. These include 125 with thalassemia trait, 48 with thalassemia major, 26 with sickle-cell thalassemia, 15 with E beta-thalassemia, 40 with iron-deficiency anemia, 8 with another hemolytic anemia, and 14 patients with no definite diagnosis. Genotyping for -alpha3.7 deletion, -alpha4.2 deletion, Hb Constant Spring, and a-triplications was done with polymerase chain reaction. The overall frequency of -alpha3.7 deletion in 276 individuals is 12.7%. The calculated allele frequency for a-thalassemia is 0.09. The subgroup analysis showed that co-inheritance of a-deletion is more frequent with the sickle-cell mutation than in other groups. We were able to diagnose 1/3 of unexplained cases of microcytosis as a-thalassemia carriers. The a-gene mutation is quite common in the Indian subcontinent. Molecular genotyping of a-thalassemia helps to diagnose unexplained microcytosis, and thus prevents unnecessary iron supplementation.     

Neovascular age-related macular degeneration risk based on CFH, LOC387715/HTRA1, and smoking

Background

Age-related macular degeneration (AMD) is the major cause of blindness in the elderly. Those with the neovascular end-stage of disease have irreversible loss of central vision. AMD is a complex disorder in which genetic and environmental factors play a role. Polymorphisms in the complement factor H (CFH) gene, LOC387715, and the HTRA1 promoter are strongly associated with AMD. Smoking also contributes to the etiology. We aimed to provide a model of disease risk based on these factors.

Methods and Findings

We genotyped polymorphisms in CFH and LOC387715/HTRA1 in a case–control study of 401 patients with neovascular AMD and 266 controls without signs of disease, and used the data to produce genetic risk scores for the European-descent population based on haplotypes at these loci and smoking history. CFH and LOC387715/HTRA1 haplotypes and smoking status exerted large effects on AMD susceptibility, enabling risk scores to be generated with appropriate weighting of these three factors. Five common haplotypes of CFH conferred a range of odds ratios (ORs) per copy from 1 to 4.17. Most of the effect of LOC387715/HTRA1 was mediated through one detrimental haplotype (carriage of one copy: OR 2.83; 95% confidence interval [CI] 1.91–4.20), with homozygotes being at particularly high risk (OR 32.83; 95% CI 12.53–86.07). Patients with neovascular macular degeneration had considerably higher scores than those without disease, and risk of blinding AMD rose to 15.5% in the tenth of the population with highest predicted risk.

Conclusions

An individual''s risk of developing AMD in old age can be predicted by combining haplotype data with smoking status. Until there is effective treatment for AMD, encouragement to avoid smoking in those at high genetic risk may be the best option. We estimate that total absence of smoking would have reduced the prevalence of severe AMD by 33%. Unless smoking habits change or preventative treatment becomes available, the prevalence of AMD will rise as a consequence of the increasing longevity of the population.     

Response of no-till and conventionally planted grain sorghum to weed control method and row spacing

Grain sorghum can substitute for corn as a full season crop and replace soybeans in double cropping systems with wheat in the southeastern United States. Relatively few studies have been conducted to measure the response of grain sorghum to tillage, weed control method, and row spacing. These experiments were designed to determine the effects of weed control method and row spacing on no-till planted grain sorghum (Sorghum bicolor L. Moench G1516-BR) after wheat (Triticum aestivum L. Coker 68–15) and crimson clover (Trifolium incarnatum L. Bigbee) grown for winter forage in comparison to sorghum planted on a conventionally prepared seedbed. The experiment included 45, 60, and 90 cm row spacings and three weed control regimes: none, mechanical, and chemical. Grain sorghum planted no-till in crimson clover or wheat sod yielded considerably more grain than conventionally planted sorghum. Grain sorghum produced significantly higher yields in 45-cm rows than in 60-and 90-cm row spacings with all three planting methods. Effects of chemical weed control on weed population with all tillage methods and on grain yield with conventional tillage were significant. There were no significant differences in grain protein content due to row spacing or weed control method.     

High regenerative nature ofMentha arvensis internodes

Media and incubation conditions have been defined for highly efficient regeneration of shoots from internode explants of slow and fast growing cultivars ofMentha arvensis. Internodal segments excised from thein vitro raised shoots were inoculated on the MS medium supplemented with combinations of 5 concentrations of l-napthalene acetic acid (NAA) and 3 concentrations of 6-benzyl amino purine (BAP). The media containing 2 μg ml⁻¹ NAA, 10 Μg ml⁻¹ BAP and 1 μg ml⁻¹ NAA, 5 μg ml⁻¹ BAP proved best for shoot regeneration and growth responses on cv Himalaya and cv Kalka explants, respectively. In 12 weeks time, on average one explant of cv Himalaya produced about 200 shoots and that of cv Kalka produced about 180 shoots. The Himalaya explants required higher concentrations of NAA and BAP for high efficiency proliferation as compared to the Kalka explants. The experiments demonstrated that internodal tissue inMentha arvensis can be induced to obtain direct shoot regenerants with high efficiency. The analysis of the RAPD profiles of 100 regenerated plantlets each of cv Himalaya and Kalka showed more than 99.9% homogeneity in bands with respect to the parents.