The Role of Iron-Deficiency Stress Responses in Stimulating Heavy-Metal Transport in Plants1

Plant accumulation of Fe and other metals can be enhanced under Fe deficiency. We investigated the influence of Fe status on heavy-metal and divalent-cation uptake in roots of pea (Pisum sativum L. cv Sparkle) seedlings using Cd2+ uptake as a model system. Radiotracer techniques were used to quantify unidirectional 109Cd influx into roots of Fe-deficient and Fe-sufficient pea seedlings. The concentration-dependent kinetics for 109Cd influx were graphically complex and nonsaturating but could be resolved into a linear component and a saturable component exhibiting Michaelis-Menten kinetics. We demonstrated that the linear component was apoplastically bound Cd2+ remaining in the root cell wall after desorption, whereas the saturable component was transporter-mediated Cd2+ influx across the root-cell plasma membrane. The Cd2+ transport system in roots of both Fe-deficient and Fe-sufficient seedlings exhibited similar Michaelis constant values, 1.5 and 0.6 μm, respectively, for saturable Cd2+ influx, whereas the maximum initial velocity for Cd2+ uptake in Fe-deficient seedlings was nearly 7-fold higher than that in Fe-grown seedlings. Investigations into the mechanistic basis for this response demonstrated that Fe-deficiency-induced stimulation of the plasma membrane H+-ATPase did not play a role in the enhanced Cd2+ uptake. Expression studies with the Fe2+ transporter cloned from Arabidopsis, IRT1, indicated that Fe deficiency induced the expression of this transporter, which might facilitate the transport of heavy-metal divalent cations such as Cd2+ and Zn2+, in addition to Fe2+.

The Impact of Prefrontal Cortex "Warm Up" on Immediate Cognitive Reappraisal Ability in Older Adolescents with Elevated Symptoms of Depression

Cognitive Reappraisal (CR) is a central component of Cognitive Behavioral Therapy for adolescent depression. Yet, previous research indicates that a brain region highly associated with successful CR in adults, the Prefrontal Cortex (PFC), is not fully developed until early adulthood. Thus, there is growing concern that CBT interventions directed at building CR abilities in depressed teens might be constrained by PFC immaturity. However, CR is an effective strategy for regulating affect. The current study evaluated an intervention aimed at enhancing CR performance through PFC “warm up” with a working memory task. Additionally, the study examined moderators of intervention response, as well as cognitive correlates of self-reported CR use. Participants included 48 older adolescents (mean age=19.1, 89% female) with elevated symptoms of depression who were randomly assigned to a lab-based WM or control activity followed by a CR task. Overall, results failed to support the effectiveness of “warm up” to augment CR performance. However, current level of depression predicted negative bias and sadness ratings after CR instructions, and this effect was qualified by an interaction with condition. The moderator analysis showed that depressive symptoms interacted with condition such that in the control condition, participants with higher depressive symptoms had significantly lower negative bias scores than individuals with lower depressive symptoms, but this pattern was not found in the experimental condition. Contrary to hypotheses, history of depression did not moderate treatment response. Additional analyses explored alternative explanations for the lack of intervention effects. There was some evidence to suggest that the WM task was frustrating and cognitively taxing. However, irritation scores and overall WM task accuracy did not predict subsequent CR performance. Lastly, multiple cognitive variables emerged as correlates of self-reported CR use, with cognitive flexibility contributing unique variance to self-reported CR use. Results pointed to new directions for improving CR performance among youth with elevated symptoms of depression.

Influence of nitrogen deficiency on senescence and the amounts of RNA and proteins in wheat leaves

Senescence-associated coordination in amounts of enzymes localized in different cellular compartments were determined in attached leaves of young wheat (Triticum aestivum L. cv. Arina) plants. Senescence was initiated at the time of full leaf elongation based on declines in total RNA and soluble protein. Removal of N from the growth medium just at the time of full leaf elongation enhanced the rate of senescence. Sustained declines in the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39), and a marked decrease in the rbcS transcripts, just after full leaf elongation indicated that Rubisco synthesis/degradation was very sensitive to the onset of senescence. Rubisco activase amount also declined during senescence but the proportion of rca transcript relative to the total poly A RNA pool increased 3-fold during senescence. Thus, continued synthesis of activase may be required to maintain functional Rubisco throughout senescence. N stress led to declines in the amount of proteins located in the chloroplast, the peroxisome and the cytosol. Transcripts of the Clp protease subunits also declined in response to N stress, indicating that Clp is not a senescence-specific protease. In contrast to the other proteins, mitochondrial NADH-glutamate dehydrogenase (EC 1.4.1.2) was relatively stable during senescence and was not affected by N stress. During natural senescence with adequate plant nitrate supply the amount of nitrite reductase (EC 1.7.7.1) increased, and those of glutamine synthetase (EC 1.4.7.1) and glutamate synthase (EC 6.3.1.2) were stable. These results indicated that N assimilatory capacity can continue or even increase during senescence if the substrate supply is maintained. Differential stabilities of proteins, even within the same cellular compartment, indicate that proteolytic activity during senescence must be highly regulated.

Summary of boron isotope and Mg/Ca data

Biological productivity and carbon export in the equatorial Atlantic are thought to have been dramatically higher during the last glacial period than during the Holocene. Here we reconstruct the pH and CO2 content of surface waters from the eastern equatorial Atlantic Ocean over the past ~30 k.y. using the boron isotope composition of Globigerinoides ruber (a mixed-layer-dwelling planktic foraminifera). Our new record, combined with previously published data, indicates that during the last glacial, in contrast to today, a strong west to east gradient existed in the extent of air:sea equilibrium with respect to pCO2 (DeltapCO2), with the eastern equatorial Atlantic acting as a significant source of CO2 (+100 µatm) while the western Atlantic remained close to equilibrium (+25 µatm). This pattern suggests that a fivefold increase in the upwelling rate of deeper waters drove increased Atlantic productivity and large-scale regional cooling during the last glacial, but the higher than modern DeltapCO2 in the east indicates that export production did not keep up with enhanced upwelling of nutrients. However, the downstream decline of DeltapCO2 provides evidence that the unused nutrients from the east were eventually used for biologic carbon export, thereby effectively negating the impact of changes in upwelling on atmospheric CO2 levels. Our findings indicate that the equatorial Atlantic exerted a minimal role in contributing to lower glacial-age atmospheric CO2.

Chemistry of boron and boron compounds : a literature search /

"January 1959."

Observations on the distinguishing symptoms of three different species of pulmonary consumption, the catarrhal, the apostematous, and the tuberculous, with some remarks on the remedies ... /

Mode of access: Internet.

The London practice of physic : wherein the definition and symptoms of diseases, with the present method of cure ...

Mode of access: Internet.

American journal of mental deficiency.

Includes the association's conference proceedings and addresses.

The domestic physician or Guardian of health : Pointing out, in the most familiar manner, the symptoms of every disorder incident to mankind; together with their gradual progress and method of cure ... : To which is added, an appendix, forming a complete dispensatory /

Mode of access: Internet.

Observations on the distinguishing symptoms of three different species of pulmonary consumption, the catarrhal, the apostematous, and the tuberculous : with some remarks on the remedies and regimen best fitted for the prevention, removal, or alleviation of each species /

Mode of access: Internet.

The new London practice of physic, pointing out the characters, causes, and symptoms, of the various diseases to which the human body is liable; and the most approved method of treatment, with prescriptions according to the nomenclature of the New Pharmacopoeia.

Earlier ed. issued under title: The modern practice of physic.

Report of the committee, appointed to inquire into and report the amount of the deficiency in the account of the late treasurer Skinner ... June 11, 1812.

Mode of access: Internet.

Intelligence and social valuation, a practical method for the diagnosis of mental deficiency and other forms of social inefficiency,

Mode of access: Internet.