MT Function Research Articles

Melatonin as an Antioxidant Supplement in Athletes: A Literature Review of Current Evidence

PURPOSE: Melatonin (MT; N-acetyl-5-methoxytryptamine) is synthesized and released during the night in specialized pineal gland cells. Among its variety of physiological properties, recent research indicates that MT has both antioxidant and anti-inflammatory actions. The aim of this literature review was to summarize recent evidence that describes the effects of MT on the muscle function and preventive role of MT on exercise-induced muscle damage.METHODS: This review included previous research using the PubMed, Science Direct, and Google Scholar databases.RESULTS: We discussed the molecular structure and biological function of MT and the potential role of this hormone in antioxidant and anti-inflammatory processes. These activities have been studied in relation to the protection of muscle function against oxidative damage. In addition, MT is reported to have positive effects on muscle damage, lipid metabolism, and inflammatory responses in well-trained athletes following exercise training. Moreover, the potential beneficial effects of melatonin and mechanisms related to performance were revealed through improved sleep quality, muscle damage, and antioxidant levels in trained athletes.CONCLUSIONS: Finally, this review suggested that possibilities of MT as a supplementation for athletes; however, further research is required to investigate the specific mechanisms involved, the dose and duration of use, and the beneficial and detrimental effects of MT on athletic performance.

Requirement of Snakeskin for normal functions of midgut and Malpighian tubules in Henosepilachna vigintioctopunctata.

Septate junctions (SJs) are located between epithelial cells and play crucial roles in epithelial barrier formation and epithelia cell homeostasis. Nevertheless, the molecular constituents, especially those related to smooth SJs (sSJs), have not been well explored in non-Drosophilid insects. A putative integral membrane protein Snakeskin (Ssk) was identified in a Coleoptera foliar pest Henosepilachna vigintioctopunctata. RNA interference-aided knockdown of Hvssk at the third-instar larval stage arrested larval development. Most resultant larvae failed to shed larval exuviae until their death. Silence of Hvssk at the fourth-instar larvae inhibited the growth and reduced foliage consumption. Dissection and microscopic observation revealed that compromised expression of Hvssk caused obvious phenotypic defects in the midgut. A great number of morphologically abnormal columnar epithelial cells accumulated throughout the midgut lumen. Moreover, numerous vesicles were observed in the malformed cells of the Malpighian tubules (Mt). All the Hvssk depleted larvae remained as prepupae; they gradually darkened and eventually died. Furthermore, depletion of Hvssk at the pupal stage suppressed adult feeding and shortened adult lifespan. These findings demonstrated that Ssk plays a vital role in the integrity and function of both midguts and Mt, and established the conservative roles of Ssk in the formation of epithelial barrier and the homeostasis of epithelial cells in H. vigintioctopunctata.

Application of Computer Multimedia Technology in College English Teaching

The 21st century is the era of multimedia, which has been applied to all walks of life, especially the education industry. With the rapid development of economy, the process of global economic integration is faster and faster, which requires higher quality of English Teaching (hereinafter referred to as ET). Therefore, multimedia technology (hereinafter referred to as MT) has become an important tool in College ET, which can not only promote the cultivation of language expression ability and thinking logic ability, but also enhance students’ interest in learning. Through MT, colleges can change the traditional teaching methods and means, which will improve students’ interest and enthusiasm. Through the introduction of computer MT, colleges effectively improve the students’ learning quality. First, this paper analyzes the important role of computer MT in ET. Then, this paper constructs the important teaching platform function of MT in Colleges. Finally, some suggestions are put forward.

Clock-controlled arylalkylamine N-acetyltransferase (aaNAT) regulates circadian rhythms of locomotor activity in the American cockroach, Periplaneta americana, via melatonin/MT2-like receptor.

Melatonin (MEL) orchestrates daily and seasonal rhythms (eg, locomotion, sleep/wake cycles, and migration among other rhythms) in diverse organisms. We investigated the effects of pharmacological doses (0.03-1mM) of exogenous MEL intake in the cockroach, Periplaneta americana, on locomotor activity. As per os MEL concentration increased, cockroach locomotor rhythm in light-dark (LD) cycles became more synchronized. The ratio of night activity to 24-h activity increased and the acrophase (peak) slightly advanced. MEL application also influenced total activity bouts in the free-running rhythm. Since MEL slightly influenced τ in the free-running rhythms, it is not a central element of the circadian pacemaker but must influence mutual coupling of multi-oscillatory system components. Arylalkylamine N-acetyltransferase (aaNAT) regulates enzymatic production of MEL. aaNAT activities vary in circadian rhythms, and the immunoreactive aaNAT (aaNAT-ir) is colocalized with the key clock proteins cycle (CYC)-ir and pigment-dispersing factor (PDF)-ir These are elements of the central pacemaker and its output pathway as well as other circadian landmarks such as the anterior and posterior optic commissures (AOC and POC, respectively). It also partially shares immunohistochemical reactivity with PER-ir and DBT-ir neurons. We analyzed the role of Pamericana aaNAT1 (PaaaNAT1) (AB106562.1) by injecting dsRNAaaNAT1 . qPCR showed a decrease in accumulations of mRNAs encoding PaaaNAT1. The injections led to arrhythmicity in LD cycles and the arrhythmicity persisted in constant dark (DD). Continuous administration of MEL resynchronized the rhythm after arrhythmicity was induced by dsRNAaaNAT1 injection, suggesting that PaaaNAT is the key regulator of the circadian system in the cockroach via MEL production. PaaaNAT1 contains putative E-box regions which may explain its tight circadian control. The receptor that mediates MEL function is most likely similar to the mammalian MT2, because injecting the competitive MT2 antagonist luzindole blocked MEL function, and MEL injection after luzindole treatment restored MT function. Human MT2-ir was localized in the circadian neurons in the cockroach brain and subesophageal ganglion. We infer that MEL and its synthesizing enzyme, aaNAT, constitute at least one circadian output pathway of locomotor activity either as a distinct route or in association with PDF system.

Search for a common baryon source in high-multiplicity pp collisions at the LHC

We report on the measurement of the size of the particle-emitting source from two-baryon correlations with ALICE in high-multiplicity pp collisions at s=13 TeV. The source radius is studied with low relative momentum p–p, p‾–p‾, p–Λ , and p‾–Λ‾ pairs as a function of the pair transverse mass mT considering for the first time in a quantitative way the effect of strong resonance decays. After correcting for this effect, the radii extracted for pairs of different particle species agree. This indicates that protons, antiprotons, Λ s, and Λ‾ s originate from the same source. Within the measured mT range (1.1–2.2) GeV/c2the invariant radius of this common source varies between 1.3 and 0.85 fm. These results provide a precise reference for studies of the strong hadron–hadron interactions and for the investigation of collective properties in small colliding systems.

Investigating Sociocognitive Functions of Mother Tongue in a Postgraduate EFL Classroom in Pakistan

Recent studies, however, have shown that MT serves a symbolic tool and can be way more effective in L2 learning than the exclusive use of TL. While many studies have examined the extent and functions of MT, only a few have explored the sociocognitive functions using Vygotsky's sociocultural (SCT) framework. The present study, therefore, adopted SCT to examine the amount and sociocognitive functions of MT. Classroom observations and stimulated recalls interviews were used to collect data from MBA students (n=6). Results showed that, learners MT use made up only 14% of the total amount of speech in L2 classroom. Most importantly, MT performed important functions, such as scaffolding, intersubjectivity and cognitive regulation. MT facilitated vocabulary learning in L2 through scaffolded help; created intersubjectivity by increasing motivation, reducing anxiety, and helped internalize L2 through cognitive self-regulation. A number of implications for classroom pedagogy and language policy have also been discussed.

Significance of the pineal gland hormone melatonin in maintaining the health of women of reproductive age (a review)

Introduction. Maintaining women's reproductive health is an important task that requires safe approaches based on the pathogenesis. More and more studies address the role of the pineal gland (epiphysis) hormone melatonin (МТ) in the functioning of the reproductive system, as well as the impact of МТ deficiency on the women’s health.Aim: to analyze and summarize the available literature about the role of the pineal gland hormone МТ in the pathogenesis of gynecological diseases in women of reproductive age (infertility, endometriosis, polycystic ovary syndrome, premenstrual syndrome), and also about the impact of МТ deficiency on the health of women working night shifts.Materials and methods. The relevant publications were searched in domestic (eLibrary, CyberLeninka.ru) and international (Pubmed, Cochrane Library) databases; we looked up the materials published in the recent 7 years. In our search, we prioritized the free access to full text articles. The selection of sources was limited to the period from 2012 to 2019.Results. МТ is involved in the development of follicles by causing the oocytes maturation, promoting the development of embryos, inhibiting the synthesis of steroids in the ovaries and, therefore, reducing the level of steroids in the blood. MT delays ovarian aging through a variety of mechanisms, including the antioxidant action, the maintenance of the due length of the telomere, the upregulated expression of the aging-related SIRT genes, and also the regulation of the ribosome functioning. As MT protects germ cells from oxidative stress, it is essential for normal ovulation, fertilization and further development of the embryo; this hormone has an impact on the duration of the woman's fertility and the onset of menopause. MT has a potential therapeutic effect on endometriosis. The oncostatic role of MT in hormone-dependent breast tumors has been described. Disruption of normal MT production during night shifts is associated with the risk of developing breast cancer in shift workers. MT deficiency leads to circadian desynchronosis and may cause both somatic disorders (metabolic syndrome, obesity, oncopathology) and neuroendocrine dysregulation of the female reproductive system.Conclusion. The variety of physiological functions of the pineal gland hormone MT emphasizes the pathogenetic role of its deficiency in many gynecological and somatic diseases. Of particular relevance is the increased risk of cardiovascular disorders, the development of metabolic syndrome and breast cancer in women who work night shifts. Therefore, it is important both to maintain normal endogenous level of MT and also use its therapeutic potential to maintain the health of women of reproductive age.

DDIS-29. BRAIN-PENETRANT MICROTUBULE-TARGETING AGENT, ST-401, KILLS GLIOBLASTOMA THROUGH A NOVEL MECHANISM

Abstract Glioblastomas are particularly sensitive to mitotic disruption when compared with nonmalignant cells and thus microtubule-targeting agents (MTA) represent promising therapeutics to treat patients with glioblastomas; but few such compounds pass the blood brain barrier. We developed a series of modified carbazoles, evaluated their anti-cancer activity in glioblastoma cells in culture and identified ST-401 as the most potent compound (IC50, 10 – 102 nM, depending on the cell line). Testing of ST-401 on the NCI 60 cancer cell panel indicated that its anti-tumor activity does not correlate with any of the compounds tested thus far through this platform but showed weak correlations for taxol (p=0.46) and vinblastine (p=0.34). Thus, ST-401 may kill cancer cells through a novel mechanism related to disruption of MT function. Biochemical analysis indicates that ST-401 binds to the colchicine site of tubulin and inhibits tubulin assembly. Real-time imaging of MT dynamics in cells in culture shows that ST-401 reduces MT assembly rates but in a reversible fashion. ST-401 potently blocks mitotic progression and triggers cell death in multiple glioblastoma lines in culture, including patient-derived glioblastomas of the proneural, mesenchymal and classical subtypes. We established the maximum tolerated dose (MTD) of ST-401 in mice (20 mg/kg/bdip) and found that its acute i.p. injection results in micromolar amounts of ST-401 in mouse brain. Using this treatment regimen, we found that ST-401 reduces tumor growth and doubles overall survival in a human tumor xenograft mouse model system. ST-401 also increases by 2-fold overall survival in the genetic RCAS-PDGF glioblastomas mouse model treated with standard care (radiation and Temodar® treatments). Histological analysis of RCAS-PDGF glioblastoma tissue shows that ST-401 triggers mitotic arrest of glioblastoma cells. ST-401 represents a promising lead compound for the treatments for patients diagnosed with glioblastomas.

Melatonin prevents sepsis-induced renal injury via the PINK1/Parkin1 signaling pathway

Melatonin (N-acetyl-5-methoxytryptamine; MT) has been shown to have a protective effect against sepsis-induced renal injury, however, the mechanisms underlying the function of MT remain to be elucidated. Therefore, in the present study, the potential mechanisms underlying the preventive role of MT in sepsis-induced renal injury were investigated. Hematoxylin and eosin staining was used to detect the effect of MT on the reduction of renal tissue damage, and immunohistochemistry (IHC), ELISA and western blot analysis were performed to determine the influence of MT on the protein expression of PTEN-induced putative kinase 1 (PINK1), nucleotide-oligomerization binding domain and leucine-rich repeat pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC1), interleukin (IL)-18, IL-1β, IL-6 and cleaved caspase-1. Finally, a TUNEL assay was used to compare the rate of apoptosis of renal tissues among the sham, cecal ligation and puncture (CLP), and CLP + MT groups. The extent of tissue damage in the CLP group was the highest and the extent of tissue damage in the sham group was the lowest. The IHC and western blot analysis showed that the sham group had the highest protein level of PINK1, whereas the CLP group had the lowest protein level of PINK1. By contrast, the sham group had the lowest protein level of NLRP, whereas the CLP group had the highest level of NLRP3. Furthermore, CLP treatment enhanced the protein expression of ASC1 and cleaved caspase-1, whereas the administration of MT reduced the protein expression of ASC1 and cleaved caspase-1 to a certain degree. Finally, the apoptotic rate was found to be the highest in the CLP group and the lowest in the sham group. Taken together, in evaluating the therapeutic effect of MT on sepsis-induced renal injury, the results of the present study showed that MT alleviated sepsis-induced renal injury by regulating the expression of PINK1, Parkin1, NLRP3, ASC and cleaved caspase-1 in rats.

Exogenous melatonin confers salt stress tolerance to Chlamydomonas reinhardtii (Volvocales, Chlorophyceae) by improving redox homeostasis

:Melatonin (MT; N-acetyl-5-methoxy-tryptamine), a natural derivative of tryptophan, is a central biomolecule synthesised by almost all organisms, including animals and plants. As an antioxidant, MT is involved in many cell responses associated with the protection of plants against abiotic stress. However, there are few studies on the function of MT in microalgae. Our work focused on the relationship between exogenous MT and salt stress in the single-celled eukaryote Chlamydomonas reinhardtii, evaluating for growth, cell morphology, malondialdehyde (MDA) content (the peroxidation product of the cell membrane), activity of antioxidant enzymes and MT concentration under 100 mM NaCl treatment. Growth of Chlamydomonas was promoted at MT concentrations of 0.1 and 1.0 μM, but at 10 and 100 μM, MT was associated with negative effects on growth. MT at 1 μM maintained intact cell morphology and cellular aggregation in an unfavourable salt environment. MT concentrations of 0.1, 1 and 10 μM MT led to increased activity of the antioxidants superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) but reduced MDA. In conclusion, by increasing relative enzyme activity and maintaining a balanced redox state, exogenous MT may improve salt tolerance of C. reinhardtii to allow normal growth. A suitable concentration of exogenous MT improved the growth of C. reinhardtii in a salt environment and increased the activity of antioxidant system–related enzymes to protect cells. These results provide insight into the function of MT in a model green alga.

Early-life inflammation, immune response and ageing.

Age-related diseases are often attributed to immunopathology, which results in self-damage caused by an inappropriate inflammatory response. Immunopathology associated with early-life inflammation also appears to cause faster ageing, although we lack direct experimental evidence for this association. To understand the interactions between ageing, inflammation and immunopathology, we used the mealworm beetle Tenebrio molitor as a study organism. We hypothesized that phenoloxidase, an important immune effector in insect defence, may impose substantial immunopathological costs by causing tissue damage to Malpighian tubules (MTs; functionally equivalent to the human kidney), in turn accelerating ageing. In support of this hypothesis, we found that RNAi knockdown of phenoloxidase (PO) transcripts in young adults possibly reduced inflammation-induced autoreactive tissue damage to MTs, and increased adult lifespan. Our work thus suggests a causative link between immunopathological costs of early-life inflammation and faster ageing. We also reasoned that if natural selection weakens with age, older individuals should display increased immunopathological costs associated with an immune response. Indeed, we found that while old infected individuals cleared infection faster than young individuals, possibly they also displayed exacerbated immunopathological costs (larger decline in MT function) and higher post-infection mortality. RNAi-mediated knockdown of PO response partially rescued MTs function in older beetles and resulted in increased lifespan after infection. Taken together, our data are consistent with a direct role of immunopathological consequences of immune response during ageing in insects. Our work is also the first report that highlights the pervasive role of tissue damage under diverse contexts of ageing and immune response.

Computational neuroscience and localized neural function

In this paper I criticize a view of functional localization in neuroscience, which I call “computational absolutism” (CA). “Absolutism” in general is the view that each part of the brain should be given a single, univocal function ascription. Traditional varieties of absolutism posit that each part of the brain processes a particular type of information and/or performs a specific task. These function attributions are currently beset by physiological evidence which seems to suggest that brain areas are multifunctional—that they process distinct information and perform different tasks depending on context. Many theorists take this contextual variation as inimical to successful localization, and claim that we can avoid it by changing our functional descriptions to computational descriptions. The idea is that we can have highly generalizable and predictive functional theories if we can discover a single computation performed by each area regardless of the specific context in which it operates. I argue, drawing on computational models of perceptual area MT, that this computational version of absolutism fails to come through on its promises. In MT, the modeling field has not produced a univocal computational description, but instead a plurality of models analyzing different aspects of MT function. Moreover, CA cannot appeal to theoretical unification to solve this problem, since highly general models, on their own, neither explain nor predict what MT does in any particular context. I close by offering a perspective on neural modeling inspired by Nancy Cartwright’s and Margaret Morrison’s views of modeling in the physical sciences.

Melatonin regulates somatotrope and lactotrope function through common and distinct signaling pathways in cultured primary pituitary cells from female primates.

Melatonin (MT) is secreted by the pineal gland and exhibits a striking circadian rhythm in its release. Depending on the species studied, some pituitary hormones also display marked circadian/seasonal patterns and rhythms of secretion. However, the precise relationship between MT and pituitary function remains controversial, and studies focusing on the direct role of MT in normal pituitary cells are limited to nonprimate species. Here, adult normal primate (baboons) primary pituitary cell cultures were used to determine the direct impact of MT on the functioning of all pituitary cell types from the pars distalis. MT increased GH and prolactin (PRL) expression/release in a dose- and time-dependent fashion, a response that was blocked by somatostatin. However, MT did not significantly affect ACTH, FSH, LH, or TSH expression/release. MT did not alter GHRH- or ghrelin-induced GH and/or PRL secretions, suggesting that MT may activate similar signaling pathways as ghrelin/GHRH. The effects of MT on GH/PRL release, which are likely mediated through MT1 receptor, involve both common (adenylyl cyclase/protein kinase A/extracellular calcium-channels) and distinct (phospholipase C/intracellular calcium-channels) signaling pathways. Actions of MT on pituitary cells also included regulation of the expression of other key components for the control of somatotrope/lactotrope function (GHRH, ghrelin, and somatostatin receptors). These results show, for the first time in a primate model, that MT directly regulates somatotrope/lactotrope function, thereby lending support to the notion that the actions of MT on these cells might substantially contribute to the define daily patterns of GH and PRL observed in primates and perhaps in humans.

Area MT encodes three-dimensional motion.

We use visual information to determine our dynamic relationship with other objects in a three-dimensional (3D) world. Despite decades of work on visual motion processing, it remains unclear how 3D directions-trajectories that include motion toward or away from the observer-are represented and processed in visual cortex. Area MT is heavily implicated in processing visual motion and depth, yet previous work has found little evidence for 3D direction sensitivity per se. Here we use a rich ensemble of binocular motion stimuli to reveal that most neurons in area MT of the anesthetized macaque encode 3D motion information. This tuning for 3D motion arises from multiple mechanisms, including different motion preferences in the two eyes and a nonlinear interaction of these signals when both eyes are stimulated. Using a novel method for functional binocular alignment, we were able to rule out contributions of static disparity tuning to the 3D motion tuning we observed. We propose that a primary function of MT is to encode 3D motion, critical for judging the movement of objects in dynamic real-world environments.

Measuring response saturation in human MT and MST as a function of motion density.

The human brain areas MT and MST have been studied in great detail using fMRI with regards to their motion processing properties; however, to what extent this corresponds with single cell recordings remains to be fully described. Average response over human MT+ has been shown to increase linearly with motion coherence, similar to single cell responses. In response to motion density some single cell data however suggest a rapid saturation. We ask how the combination of these responses is reflected in the population response. We measured the blood oxygen level dependent (BOLD) response function of MT and MST using a motion density signal, comparing with area V1. We used spatially fixed apertures containing motion stimuli to manipulate the area covered by motion. We found that MT and MST responded above baseline to a very minimal amount of motion and showed a rather flat response to motion density, indicative of saturation. We discuss how this may be related to the size of the receptive fields and inhibitory interactions, although necessarily residual attention effects also need to be considered. We then compared different types of motion and found no difference between coherent and random motion at any motion density, suggesting that when combining response over several motion stimuli covering the visual field, a linear relationship of MT and MST population response as a function of motion coherence might not hold.

Predicting the Supremum: Optimality of ‘Stop at Once or Not at All’

Let (X t )0 ≤ t ≤ T be a one-dimensional stochastic process with independent and stationary increments, either in discrete or continuous time. In this paper we consider the problem of stopping the process (X t ) ‘as close as possible’ to its eventual supremum M T := sup0 ≤ t ≤ T X t , when the reward for stopping at time τ ≤ T is a nonincreasing convex function of M T - X τ. Under fairly general conditions on the process (X t ), it is shown that the optimal stopping time τ takes a trivial form: it is either optimal to stop at time 0 or at time T. For the case of a random walk, the rule τ ≡ T is optimal if the steps of the walk stochastically dominate their opposites, and the rule τ ≡ 0 is optimal if the reverse relationship holds. An analogous result is proved for Lévy processes with finite Lévy measure. The result is then extended to some processes with nonfinite Lévy measure, including stable processes, CGMY processes, and processes whose jump component is of finite variation.

Predicting the Supremum: Optimality of ‘Stop at Once or Not at All’

Let (Xt)0 ≤ t ≤ T be a one-dimensional stochastic process with independent and stationary increments, either in discrete or continuous time. In this paper we consider the problem of stopping the process (Xt) ‘as close as possible’ to its eventual supremum MT := sup0 ≤ t ≤ TXt, when the reward for stopping at time τ ≤ T is a nonincreasing convex function of MT - Xτ. Under fairly general conditions on the process (Xt), it is shown that the optimal stopping time τ takes a trivial form: it is either optimal to stop at time 0 or at time T. For the case of a random walk, the rule τ ≡ T is optimal if the steps of the walk stochastically dominate their opposites, and the rule τ ≡ 0 is optimal if the reverse relationship holds. An analogous result is proved for Lévy processes with finite Lévy measure. The result is then extended to some processes with nonfinite Lévy measure, including stable processes, CGMY processes, and processes whose jump component is of finite variation.

Abnormal cortical processing of pattern motion in amblyopia: Evidence from fMRI

Converging evidence from human psychophysics and animal neurophysiology indicates that amblyopia is associated with abnormal function of area MT, a motion sensitive region of the extrastriate visual cortex. In this context, the recent finding that amblyopic eyes mediate normal perception of dynamic plaid stimuli was surprising, as neural processing and perception of plaids has been closely linked to MT function. One intriguing potential explanation for this discrepancy is that the amblyopic eye recruits alternative visual brain areas to support plaid perception. This is the hypothesis that we tested. We used functional magnetic resonance imaging (fMRI) to measure the response of the amblyopic visual cortex and thalamus to incoherent and coherent motion of plaid stimuli that were perceived normally by the amblyopic eye. We found a different pattern of responses within the visual cortex when plaids were viewed by amblyopic as opposed to non-amblyopic eyes. The non-amblyopic eyes of amblyopes and control eyes differentially activated the hMT+ complex when viewing incoherent vs. coherent plaid motion, consistent with the notion that this region is centrally involved in plaid perception. However, for amblyopic eye viewing, hMT+ activation did not vary reliably with motion type. In a sub-set of our participants with amblyopia we were able to localize MT and MST within the larger hMT+ complex and found a lack of plaid motion selectivity in both sub-regions. The response of the pulvinar and ventral V3 to plaid stimuli also differed under amblyopic vs. non-amblyopic eye viewing conditions, however the response of these areas did vary according to motion type. These results indicate that while the perception of the plaid stimuli was constant for both amblyopic and non-amblyopic viewing, the network of neural areas that supported this perception was different.

The RF-chain limited mimo system- part I: optimum diversity-multiplexing tradeoff

The large gain promised by the multi-input multioutput (MIMO) technology comes with a cost. In particular, multiple analog radio frequency (RF) chains, which are expensive and power consuming, are required at both the transmitter and receiver sides. On the other hand, the antennas connecting to the RF chains are less expensive. Hence, one engineering compromise is to implement more antennas than RF chains and to use only a subset of them based on some antenna selection (AS) algorithm. An interesting question therefore arises: given a RF chain limited MIMO system, what is the fundamental performance gain by adding more antennas? In this two-part paper, we answer this question by using the diversity-multiplexing (D-M) gain tradeoff metric. Consider a Rayleigh fading channel with M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) antennas and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ⩽ M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) RF chains at the transmitter while M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> antennas and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ⩽ M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) RF chains at the receiver. We obtain the fundamental D-M tradeoff as a function of M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> , M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> , and min(L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> , L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ). Referring to the special case where L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> = M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> as the RF unlimited system (or full system) and RF limited system (or pruned system) otherwise, we prove that the pruned system with optimal channel-dependent AS has the same D-M tradeoff as the full system if the multiplexing gain is less than some integer threshold P, while it suffers from some diversity gain loss for multiplexing gains larger than P. In particular, if min(L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> , L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) = K = min(M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> , M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ), then P = K, i.e. the D-M tradeoffs of the pruned system and the full system are the same. Moreover, this result can be extended to more general fading channels such as Nakagami channel. A fast and D-M tradeoff-optimal AS algorithm is proposed as a byproduct of our analysis. Index Terms?Antenna selection, diversity gain, fast algorithm, MIMO, Nakagami fading, outage probability, Rayleigh fading, spatial multiplexing gain, tradeoff.

An intact SAM‐dependent methyltransferase fold is encoded by the human endothelin‐converting enzyme‐2 gene

A recent survey of protein expression patterns in patients with Alzheimer's disease (AD) has identified ece2 (chromosome: 3; Locations: 3q27.1) as the most significantly downregulated gene within the tested group. ece2 encodes endothelin-converting enzyme ECE2, a metalloprotease with a role in neuropeptide processing. Deficiency in the highly homologous ECE1 has earlier been linked to increased levels of AD-related {beta}-amyloid peptide in mice, consistent with a role for ECE in the degradation of that peptide. Initially, ECE2 was presumed to resemble ECE1, in that it comprises a single transmembrane region of {approx}20 residues flanked by a small amino-terminal cytosolic segment and a carboxy-terminal lumenar peptidase domain. The carboxy-terminal domain has significant sequence similarity to both neutral endopeptidase, for which an X-ray structure has been determined, and Kell blood group protein. After their initial discovery, multiple isoforms of ECE1 and ECE2 were discovered, generated by alternative splicing of multiple exons. The originally described ece2 transcript, RefSeq NM{_}174046, contains the amino-terminal cytosolic portion followed by the transmembrane region and peptidase domain (Fig. 1, isoform B). Another ece2 transcript, available from the Mammalian Gene Collection under MGC2408 (Fig. 1, isoform C), RefSeq accession NM{_}032331, is predicted to be translated into a 255 residue peptidemore » with low but detectable sequence similarity to known S-adenosyl-L-methionine (SAM)-dependent methyltransferases (SAM-MTs), such as the hypothetical protein TT1324 from Thermus thermophilis, PDB code 2GS9, which shares 30% amino acid sequence identity with ECE2 over 138 residues of the sequence. Intriguingly, another 'elongated' ece2 transcript (Fig. 1, isoform A) (RefSeq NM{_}014693) contains an amino-terminal portion of the putative SAM-MT domain, the transmembrane domain, and the protease domain. This suggests the possibility for coexistence of the putative SAM-MT and protease domains in a single polypeptide and their transmembrane interplay. Although sequence conservation across the SAM-MT family is weak, the structural fold is highly conserved. The most conserved part of this fold is the SAM-binding subdomain, which is shared between MGC2408 and hypothetical protein TT1324. Typically, the SAM-binding subdomain is flanked by a variable Nterminal extension and, at the C-terminus, by a substrate- binding subdomain, which varies enormously in size but preserves a conserved topology with three antiparallel b-strands. The 'elongated' transcript of ece2 lacks this substrate-binding subdomain. To test the hypothesis that the 255 residue ece2 gene product MGC2408 represents a complete SAM-MT fold, we have determined a crystal structure of this protein in the presence of SAH.« less