Interactions of Cd with Zn, Cu, Mn and Fe for lettuce (Lactuca sativa L.) in hydroponic culture

Abstract. The effect and accumulation of cadmium (Cd) in lettuce grown by means of the hydroponic technique was investigated by multivariate analysis, and was found to be affected by the concentration of other trace elements. Particularly iron acted in a strongly antagonistic way against Cd. Consequently, no absolute toxicity limits for Cd can be drawn without considering other trace elements.     

Genotype and allele frequencies of the polymorphic methylenetetrahydrofolate reductase gene in Turkey

The polymorphic methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms C677T and A1298C cause mild hyperhomocysteinemia, not only in homozygotes for C677T, but also in compound heterozygotes for C677T/A1298C. The aim of this study was to determine allelic frequencies of the polymorphic MTHFR gene C677T, A1298C. In this regard, we have investigated the allelic frequencies of C677T and A1298C polymorphisms of the MTHFR gene in 1684 randomized individuals around Turkey. DNA samples isolated from peripheral blood samples of randomized individuals were analysed. The study population consisted of 1004 females and 680 males. The frequency in Turkey of the C677T was 42.9 %; of C677C, 47.4 %; and of T677T, 9.6 %. The frequency in Turkey of A1298C was 43.7 %; of A1298A, 46.3 %; and of C1298C, 10.0 %. The allelic frequencies of the T allele of MTHFR 677 and the C allele of MTHFR 1298 were 33.34 and 33.16 %, respectively. The frequency of C677T/A1298C compound heterozygosity is highest in Turkey (21.6 %), as compared to Canada (15 %), the United States (17 %) and The Netherlands (20 %).     

The role of peripheral chemoreceptor activity on the respiratory responses to hypoxia and hypercapnia in anaesthetised rabbits with induced hypothyroidism

The purpose of this study was to investigate the role of peripheral chemoreceptor activity on the hypoxic and hypercapnic ventilatory drives in rabbits with induced hypothyroidism. Experiments were carried out in control and hypothyroid rabbits. Hypothyroidism was induced by an administration of an iodide-blocker, methimazole in food (75 mg/100 g food) for ten weeks. At the end of the tenth week, triiodothyronine (T3) and thyroxine (T4) levels significantly decreased (P<0.001) while thyroid stimulating hormone (TSH) increased (P<0.001). Tidal volume (VT), respiratory frequency (f/min), ventilation minute volume (VE) and systemic arterial blood pressure (BP) were recorded during the breathing of the normoxic, hypoxic (8% O2-92% N2) and hypercapnic (6% CO2-Air) gas mixtures, in the anaesthetised rabbits of both groups. At the end of each experimental phase, PaO2, PaCO2, and pHa were measured. The same experimental procedure was repeated after peripheral chemoreceptor denervation in both groups. VT significantly decreased in some of the rabbits with hypothyroidism during the breathing of the hypoxic gas mixture (nonresponsive subgroup) (P<0.05). After chemodenervation, a decrease in VT was observed in this nonresponsive subgroup during normoxia (P<0.05). The percent decrease in VT in nonresponsive subgroup of hypothyroid rabbits after chemodenervation was lower than that of the chemodenervated control animals (P<0.01). When these rabbits with hypothyroidism were allowed to breath the hypercapnic gas mixtures, increases in VT and VE were not significant. In conclusion, although there is a decrease in peripheral chemoreceptor activity in hypothyroidism, it does not seem to be the only cause of decrease in ventilatory drive during hypoxia and hypercapnia.     

Achene anatomy and stomatal characteristics of eighteen Crepis L. (Asteraceae) taxa from Turkey with notes on their systematic significance

Achene anatomy and stomatal characteristics of eighteen Crepis taxa from Turkey are here described for the first time. In all taxa examined the pericarp is composed of several layers of sclerenchymatous and parenchymatous cells. As for the achene, differences among taxa mainly concern the pericarp structure and its thickness and width. Stomata are present on both surface of the leaf in all studied taxa and all taxa have anomocytic type stomata. However, the dimensions (length and width) and density of the stomata differ significantly among the studied taxa. In addition, the dimensions of stomata are negatively correlated with stomata density. It is concluded that achene anatomy and stomatal characteristics are useful for delimitation of Crepis taxa and a key to taxa based on these characters is provided. However, based on achene anatomy and stomatal characteristics, we found no argument for an exclusion of the Lagoseris group from Crepis as has previously been proposed.     

Top-down Proteomics Reveals Concerted Reductions in Myofilament and Z-disc Protein Phosphorylation after Acute Myocardial Infarction

Heart failure (HF) is a leading cause of morbidity and mortality worldwide and is most often precipitated by myocardial infarction. However, the molecular changes driving cardiac dysfunction immediately after myocardial infarction remain poorly understood. Myofilament proteins, responsible for cardiac contraction and relaxation, play critical roles in signal reception and transduction in HF. Post-translational modifications of myofilament proteins afford a mechanism for the beat-to-beat regulation of cardiac function. Thus it is of paramount importance to gain a comprehensive understanding of post-translational modifications of myofilament proteins involved in regulating early molecular events in the post-infarcted myocardium. We have developed a novel liquid chromatography–mass spectrometry-based top-down proteomics strategy to comprehensively assess the modifications of key cardiac proteins in the myofilament subproteome extracted from a minimal amount of myocardial tissue with high reproducibility and throughput. The entire procedure, including tissue homogenization, myofilament extraction, and on-line LC/MS, takes less than three hours. Notably, enabled by this novel top-down proteomics technology, we discovered a concerted significant reduction in the phosphorylation of three crucial cardiac proteins in acutely infarcted swine myocardium: cardiac troponin I and myosin regulatory light chain of the myofilaments and, unexpectedly, enigma homolog isoform 2 (ENH2) of the Z-disc. Furthermore, top-down MS allowed us to comprehensively sequence these proteins and pinpoint their phosphorylation sites. For the first time, we have characterized the sequence of ENH2 and identified it as a phosphoprotein. ENH2 is localized at the Z-disc, which has been increasingly recognized for its role as a nodal point in cardiac signaling. Thus our proteomics discovery opens up new avenues for the investigation of concerted signaling between myofilament and Z-disc in the early molecular events that contribute to cardiac dysfunction and progression to HF.Despite recent advances in the treatment of heart failure (HF),¹ this devastating syndrome remains a leading cause of morbidity and mortality worldwide and imposes a significant economic burden, especially on developed countries (1–3). The most common cause of HF, myocardial infarction (MI), induces left ventricular (LV) remodeling characterized by chamber dilation and hypertrophy of the non-infarcted (remote) myocardium, which is ultimately maladaptive, leading to depressed global contractility and predisposing the heart to failure (4). Current treatments for HF have primarily focused on symptom management after the occurrence of irreversible remodeling and functional impairment, which only delays the syndrome (1). Understanding the molecular mechanisms driving cardiac dysfunction at the early stages could enable the development of therapeutic interventions to prevent the onset of HF. However, the molecular changes that occur immediately after MI but prior to the maladaptive remodeling remain poorly understood (5).Myofilaments are responsible for cardiac contraction and relaxation and play a central role in myocardial pathophysiology (6, 7). Moreover, recent evidence suggests that cardiac myofilaments have a critical role in signal reception and transduction in HF (8, 9). Myofilaments consist of thin filament proteins, which include actin, tropomyosin (Tm), and the troponin (Tn) complex (TnI, TnT, and TnC), and thick filament proteins including myosin (S-1 head domain, S-2 rod domain, essential light chain, and regulatory light chain (MLC2)), as well as a number of accessory proteins such as myosin binding protein C (6, 10–12). In addition to these major myofilament proteins, a significant number of proteins have been identified in the cardiac myofilament subproteome (13). Cardiac contraction requires the integrated activity of highly coordinated protein–protein interactions among myofilament proteins in the sarcomere (6, 8, 9). Post-translational modifications (PTMs) and mutations of myofilament proteins can change these protein–protein interactions, thereby altering cardiac contractility. Thus, it is of paramount importance to gain a comprehensive understanding of the PTM changes of myofilament proteins in the regulation of early molecular events in contractile dysfunction immediately after acute myocardial infarction (AMI).Top-down mass spectrometry (MS) (12, 14–22) has unique advantages for the comprehensive assessment of protein modifications through the detection and quantification of all proteoforms (a unified term used to define all of the different molecular forms arising from PTMs, mutations or polymorphisms, and alternative splicing events (23)). Subsequently, the modification sites can be precisely localized via MS/MS including but not limited to collisionally activated dissociation (CAD) and electron capture dissociation (ECD) (12, 14–22, 24, 25). We have successfully developed a novel liquid chromatography–mass spectrometry (LC/MS)-based top-down quantitative proteomics strategy to assess the concerted changes in myofilaments and their associated proteins in the myofilament subproteome. Specifically, we have rapidly separated and quantified intact proteins extracted from a minimal amount of myocardial tissue (∼500 μg of tissue per experiment) by means of LC/MS with high reproducibility and throughput. Notably, we discovered a concerted significant reduction in the phosphorylation of three crucial cardiac proteins in acutely infarcted myocardium using a clinically relevant swine AMI model (26): a thin filament regulatory protein, cardiac TnI (cTnI); a thick filament regulatory protein, MLC2; and, unexpectedly, a critical Z-disc protein, enigma homolog isoform 2 (ENH2). Subsequently, we unambiguously localized the phosphorylation sites of these three important proteins using ECD. Particularly, for the first time, we comprehensively sequenced swine ENH2 by means of top-down MS and identified it as a phosphoprotein with its phosphorylation site precisely pinpointed. ENH2 belongs to the PDZ-LIM protein family that co-localizes with α-actinin at the Z-disc (27, 28). Although traditionally viewed as a structural component in the sarcomere, the Z-disc is increasingly recognized for its prominent role as a nodal point for cardiac signaling (27, 29, 30). Thus, our proteomic discovery opens up new avenues for investigations of the concerted signaling between myofilament and Z-disc proteins in the early molecular events that may contribute to cardiac dysfunction and subsequent HF.     

Widespread distribution and high prevalence of an alpha-proteobacterial symbiont in the tick Ixodes ricinus

The tick Ixodes ricinus is responsible for the transmission of a number of bacterial, protozoan and viral diseases to humans and animals in Europe and Northern Africa. Female I. ricinus from England, Switzerland and Italy have been found to harbour an intracellular alpha-proteobacterium, designated IricES1, within the cells of the ovary. IricES1 is the only prokaryote known to exist within the mitochondria of any animal or multicellular organism. To further examine the distribution, prevalence and mode of transmission of IricES1, we performed polymerase chain reaction screening of I. ricinus adults from 12 countries across its geographic distribution, including tick colonies that have been maintained in the laboratory for varying periods of time. IricES1 was detected in 100% of field-collected female ticks from all countries examined (n = 128), while 44% of males were found to be infected (n = 108). Those males that are infected appear to harbour fewer bacteria than females. Sequencing of fragments of the 16S rRNA and gyrB genes revealed very low nucleotide diversity among various populations of IricES1. Transmission of IricES1 from engorged adult females to eggs was found to be 100% (n = 31). In tick colonies that had been maintained in the laboratory for several years, a relatively low prevalence was found in females (32%; n = 25). To our knowledge, IricES1 is the most widespread and highly prevalent of any tick-associated symbiont.