Physiological and Biochemical Mechanisms Involved in the Response to Abscisic Acid in Maize Coleoptiles

The role of abscisic acid (ABA) in controlling growth and developmenthas been studied in maize (Zea mays L.) coleoptile segments.Application of ABA reduces the elongation rate by about 50%and affects ion fluxes. In particular, proton extrusion is decreasedwhile potassium efflux is greatly enhanced. Apparently, ABAdoes not: seem to influence calcium influx from the apoplastinto the cytosol, but more likely it influences its efflux.Alteration of cytosolic calcium concentration may also be obtainedby increasing its release from internal stores. This possibilitymight be sustained by the increased hydrolysis of phosphatidylinositolupon ABA application. Change in the balance of ion fluxes shouldresult from regulation of transport mechanisms at the membranelevel and should produce changes in the transmembrane electricalpotential. The H⁺- ATPase and the ATP-dependent calcium transportactivities are both influenced by the treatment with ABA, –55%and –40%, respectively. Under these conditions [Ca²⁺]_cytand pH_cyt can be modified and, as a consequence of their regulation,they may play an important role in mediating the physiologicaland biochemical effects of ABA, acting as second intracellularmessengers. ¹Research supported by National Research Council of Italy, SpecialProject RAISA, Sub-Project N. 2, Paper n. 2782.     

Early detection of pulmonary congestion and edema in dogs by using lung sounds

Five mongrel dogs (2 interstitial and 3 alveolar edema) were studied. Lung mechanics were measured by recording the flow, volume, and esophageal pressure according to the standard technique. Edema was produced by infusion of Ringer lactate solution. Lung sounds were recorded on tape from the dependent part of the chest wall. Lung sound signals were high-pass filtered at 100 Hz and subjected to fast Fourier transform. Samples of lung sounds were analyzed before (control) and at 5, 10, 20, 30, and 40 min after the infusion. The mean, median, and mode frequencies of sound power spectra at the control time were, respectively, 169.6 +/- 29.19, 129.6 +/- 29.81, and 136.0 +/- 29.87 (SD) Hz. These values increased significantly at 5 min after infusion to 194.0 +/- 26.08 (P less than 0.0037), 150.2 +/- 23.48 (P less than 0.0085), and 164.6 +/- 28.74 Hz (P less than 0.02), respectively. These values stayed significantly elevated at 10, 20, 30, and 40 min. The pulmonary wedge pressure, lung dynamic compliance, and pulmonary resistance were measured also at the same times. The mean, median, and mode frequencies correlated with pulmonary wedge pressure (P less than 0.00001, P less than 0.0001, P less than 0.0001), lung dynamic compliance (P less than 0.001, P less than 0.0001, P less than 0.0001), and pulmonary resistance (P less than 0.00001, P less than 0.00001, P less than 0.0001), respectively. There were no significant adventitious sounds up to 40 and 50 min after infusion. We concluded that pulmonary congestion and early edema alter the frequency characteristics of lung sounds early, before the occurrence of adventitious sounds. These altered lung sounds may be used as an index of pulmonary congestion and impending edema.     

Impaired Increase of Plasma Abscisic Acid in Response to Oral Glucose Load in Type 2 Diabetes and in Gestational Diabetes

The plant hormone abscisic acid (ABA) is present and active in humans, regulating glucose homeostasis. In normal glucose tolerant (NGT) human subjects, plasma ABA (ABAp) increases 5-fold after an oral glucose load. The aim of this study was to assess the effect of an oral glucose load on ABAp in type 2 diabetes (T2D) subjects. We chose two sub-groups of patients who underwent an oral glucose load for diagnostic purposes: i) 9 treatment-naive T2D subjects, and ii) 9 pregnant women with gestational diabetes (GDM), who underwent the glucose load before and 8–12 weeks after childbirth. Each group was compared with matched NGT controls. The increase of ABAp in response to glucose was found to be abrogated in T2D patients compared to NGT controls. A similar result was observed in the women with GDM compared to pregnant NGT controls; 8–12 weeks after childbirth, however, fasting ABAp and ABAp response to glucose were restored to normal in the GDM subjects, along with glucose tolerance. We also retrospectively compared fasting ABAp before and after bilio-pancreatic diversion (BPD) in obese, but not diabetic subjects, and in obese T2D patients, in which BPD resulted in the resolution of diabetes. Compared to pre-BPD values, basal ABAp significantly increased 1 month after BPD in T2D as well as in NGT subjects, in parallel with a reduction of fasting plasma glucose. These results indicate an impaired hyperglycemia-induced ABAp increase in T2D and in GDM and suggest a beneficial effect of elevated ABAp on glycemic control.     

Abscisic Acid Transport in Human Erythrocytes

Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [³H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [³H]ABA and [³⁵S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone.     

Transglutaminases expression in human supraspinatus tendon ruptures and in mouse tendons

The ethiopathogenesis of rotator cuff disease remains poorly understood. Many studies advocate the importance of extra cellular matrix for the homeostasis of connective tissue. Transglutaminase enzymes family has been studied in the context of connective tissue formation and stabilisation. Here, we investigated transglutaminases expression pattern in biopsies of normal and injured supraspinatus tendons of human shoulders and in the Achilles tendons of transglutaminase 2 knock-out and wild-type mice. Our results show that different transglutaminase family members are differentially expressed in human and mouse tendons, and that transglutaminase 2 is down-regulated at mRNA and protein levels upon human supraspinatus tendon ruptures.     

Are drought-resistance promoting bacteria cross-compatible with different plant models?

The association between plant and plant growth promoting bacteria (PGPB) contributes to the successful thriving of plants in extreme environments featured by water shortage. We have recently shown that, with respect to the non-cultivated desert soil, the rhizosphere of pepper plants cultivated under desert farming hosts PGPB communities that are endowed with a large portfolio of PGP traits. Pepper plants exposed to bacterial isolates from plants cultivated under desert farming exhibited a higher tolerance to water shortage, compared with untreated control. This promotion was mediated by a larger root system (up to 40%), stimulated by the bacteria, that enhanced plant ability to uptake water from dry soil. We provide initial evidence that the nature of the interaction can have a limited level of specificity and that PGPB isolates may determine resistance to water stress in plants others than the one of the original isolation. It is apparent that, in relation to plant resistance to water stress, a feature of primary evolutionary importance for all plants, a cross-compatibility between PGPB and different plant models exists at least on a short-term.     

The Diadenosine Homodinucleotide P18 Improves In Vitro Myelination in Experimental Charcot‐Marie‐Tooth Type 1A

Charcot‐Marie‐Tooth 1A (CMT1A) is a demyelinating hereditary neuropathy whose pathogenetic mechanisms are still poorly defined and an etiologic treatment is not yet available. An abnormally high intracellular Ca²⁺ concentration ([Ca²⁺]_i) occurs in Schwann cells from CMT1A rats (CMT1A SC) and is caused by overexpression of the purinoceptor P2X7. Normalization of the Ca²⁺ levels through down‐regulation of P2X7 appears to restore the normal phenotype of CMT1A SC in vitro. We recently demonstrated that the diadenosine 5′,5′′′‐P1, P2‐diphosphate (Ap2A) isomer P18 behaves as an antagonist of the P2X7 purinergic receptor, effectively blocking channel opening induced by ATP. In addition, P18 behaves as a P2Y11 agonist, inducing cAMP overproduction in P2Y11‐overexpressing cells. Here we investigated the in vitro effects of P18 on CMT1A SC. We observed that basal levels of intracellular cAMP ([cAMP]_i), a known regulator of SC differentiation and myelination, are significantly lower in CMT1A SC than in wild‐type (wt) cells. P18 increased [cAMP]_i in both CMT1A and wt SC, and this effects was blunted by NF157, a specific P2Y11 antagonist. Prolonged treatment of organotypic dorsal root ganglia (DRG) cultures with P18 significantly increased expression of myelin protein zero, a marker of myelin production, in both CMT1A and wt cultures. Interestingly, P18 decreased the content of non‐phosphorylated neurofilaments, a marker of axonal damage, only in CMT1A DRG cultures. These results suggest that P2X7 antagonists, in combination with [cAMP]_i‐increasing agents, could represent a therapeutic strategy aimed at correcting the molecular derangements causing the CMT1A phenotype. J. Cell. Biochem. 115: 161–167, 2014. © 2013 Wiley Periodicals, Inc.