G protein-coupled receptor signalling in astrocytes in health and disease: A focus on metabotropic glutamate receptors

Work published over the past 10–15 years has caused the neuroscience community to engage in a process of constant re-evaluation of the roles of glial cells in the mammalian central nervous system. Recent emerging evidence suggests that, in addition to carrying out various homeostatic functions within the CNS, astrocytes can also engage in a two-way dialogue with neurons. Astrocytes possess many of the receptors, and some of the ion channels, present in neurons endowing them with an ability to sense and respond to an array of neuronal signals. In addition, an expanding number of small molecules and proteins have been shown to be released by astrocytes in both health and disease. In this commentary we will highlight advances in our understanding of G protein-coupled receptor signalling in astrocytes, with a particular emphasis on metabotropic glutamate (mGlu) receptors. Discussion will focus on the major mGlu receptors expressed in astrocytes, mGlu3 and mGlu5, how these receptors can influence different aspects of astrocyte physiology, and how signalling by these G protein-coupled receptors might change under pathophysiological circumstances

Evaluation of some ceramic properties of Gadabiu clay deposit (Kwali Area Council, Abuja, Nigeria)

Purpose. To evaluate some ceramic properties of Gadabiu clay deposit, Kwali Area Council, Abuja Nigeria. Methods. Soil samples from the study area were subjected to various physical and mechanical tests such as; X-ray diffraction (XRD), porosity, grain size distribution, cold crush strength, modulus of rupture, linear shrinkage, bulk density, water absorption, loss on ignition, moisture content, plasticity index and refractoriness. Findings. Results of XRD of the samples indicate that the deposit is of three crystalline components of quartz – 64.73%, feldspar – 6.05% and kaolinite – 29.22%. XRD also identified the dominant oxide compositions of the clay to be silicon oxide and aluminum oxide; while titanium oxide and manganese oxide were found in traces. Laboratory analysis on physical properties of the clay like porosity, grain size distribution, cold crushing strength, modulus of rupture, linear shrinkage, bulk density, water absorption, loss on ignition, moisture content, plasticity index and refractoriness were carried out, and well presented in the paper. Originality. The results can be compared to standard requirements in clay soil for ceramic productions. Practical implications. The results from this investigation can guide intending investors in their decision making. It can also be used as supporting document when applying for mine license and bank loan.Мета. Оцінка керамічних властивостей глини родовища Гадабіу, територіальна рада Квалі (Абуджа, Нігерія) на основі фізико-механічних випробувань для можливості її використання у промислових цілях. Методика. Були відібрані 12 проб глини родовища з глибин 3, 7 і 10 м та піддані фізичним і механічних випробуванням, а також рентгеноструктурному аналізу (РСА) для визначення пористості, розподілу зерна за величиною, межі міцності на розрив і стиск, лінійного стиску, об’ємної щільності, гігроскопічності, втрати ваги при прокалюванні, вмісту вологи, коефіцієнта пластичності й вогнетривкості. Результати. Встановлено, що зразки глини родовища містять три кристалічних компоненти: кварц – 64.73%, польовий шпат – 6.05% і каолініт – 29.22%. РСА дозволив визначити, що в глинах родовища переважають оксиди кремнію та алюмінію, тоді як оксиди марганцю й титану представлені дуже незначно. Досліджені такі фізичні властивості глини як пористість, розподіл зерна по величині, межа міцності на розрив і стиск, лінійний стиск, об’ємна щільність, гігроскопічність, втрата ваги при прокалюванні, вміст вологи, коефіцієнт пластичності та вогнетривкість, що знаходяться в межах прийнятних стандартів для виробництва кераміки. Встановлено середній пластичний індекс глини, який є вище мінімальних вимог, необхідних для виробництва кераміки. Наукова новизна. Виявлено зональне покращення фізико-механічних властивостей та сортності глини з глибиною (від 3 до 10 м) в умовах родовища Гадабіу. Практична значимість. Встановлена промислова придатність глини родовища Гадабіу для виробництва кераміки.Цель. Оценка керамических свойств глины месторождения Гадабиу, территориальный совет Квали (Абуджа, Нигерия) на основании физико-механических испытаний для возможности ее применения в промышленных целях. Методика. Были отобраны 12 проб глины месторождения с глубины 3, 7 и 10 м и подвергнуты физическим и механическим испытаниям, а также рентгеноструктурному анализу (РСА) для определения пористости, распределения зерна по величине, предела прочности на разрыв и сжатие, линейного сжатия, объемной плотности, гигроскопичности, потери веса при прокаливании, содержания влаги, коэффициента пластичности и огнеупорности. Результаты. Установлено, что образцы глины месторождения содержат три кристаллических компонента: кварц – 64.73%, полевой шпат – 6.05%, и каолинит – 29.22%. РСА также позволил определить, что в глинах месторождения преобладают оксиды кремния и алюминия, тогда как оксиды марганца и титана представлены очень незначительно. Исследованы такие физические свойства глины как пористость, распределение зерна по величине, предел прочности на разрыв и сжатие, линейное сжатие, объемная плотность, гигроскопичность, потеря веса при прокаливании, содержание влаги, коэффициент пластичности и огнеупорность, находящиеся в пределах приемлемых стандартов для производства керамики. Установлен средний пластический индекс глины, который является выше минимальных требований, необходимого для производства керамики. Научная новизна. Выявлено зональное улучшение физико-механических свойств и сортности глины с глубиной (от 3 до 10 м) в условиях месторождения Гадабиу. Практическая значимость. Установлена промышленная пригодность глины месторождения Гадабиу для производства керамики.The authors are grateful for the support of management of West African Ceramics Ltd, Ajaokuta, Kogi State, Nigeria

Bayesian model-independent evaluation of expansion rates of the universe

Marginal likelihoods for the cosmic expansion rates are evaluated using the `Constitution' data of 397 supernovas, thereby updating the results in some previous works. Even when beginning with a very strong prior probability that favors an accelerated expansion, we obtain a marginal likelihood for the deceleration parameter $q_0$ peaked around zero in the spatially flat case. It is also found that the new data significantly constrains the cosmographic expansion rates, when compared to the previous analyses. These results may strongly depend on the Gaussian prior probability distribution chosen for the Hubble parameter represented by $h$, with $h=0.68\pm 0.06$. This and similar priors for other expansion rates were deduced from previous data. Here again we perform the Bayesian model-independent analysis in which the scale factor is expanded into a Taylor series in time about the present epoch. Unlike such Taylor expansions in terms of redshift, this approach has no convergence problem.Comment: To appear in Astrophysics and Space Scienc

Phylogenetic analyses reveal unexpected patterns in the evolution of reproductive modes in frogs

Understanding phenotypic diversity requires not only identification of selective factors that favor origins of derived states, but also factors that favor retention of primitive states. Anurans (frogs and toads) exhibit a remarkable diversity of reproductive modes that is unique among terrestrial vertebrates. Here, we analyze the evolution of these modes, using comparative methods on a phylogeny and matched life-history database of 720 species, including most families and modes. As expected, modes with terrestrial eggs and aquatic larvae often precede direct development (terrestrial egg, no tadpole stage), but surprisingly, direct development evolves directly from aquatic breeding nearly as often. Modes with primitive exotrophic larvae (feeding outside the egg) frequently give rise to direct developers, whereas those with nonfeeding larvae (endotrophic) do not. Similarly, modes with eggs and larvae placed in locations protected from aquatic predators evolve frequently but rarely give rise to direct developers. Thus, frogs frequently bypass many seemingly intermediate stages in the evolution of direct development. We also find significant associations between terrestrial reproduction and reduced clutch size, larger egg size, reduced adult size, parental care, and occurrence in wetter and warmer regions. These associations may help explain the widespread retention of aquatic eggs and larvae, and the overall diversity of anuran reproductive modes. © 2012 The Society for the Study of Evolution.Peer Reviewe

Finite bounded expanding white hole universe without dark matter

The solution of Einstein's field equations in Cosmological General Relativity (CGR), where the Galaxy is at the center of a finite yet bounded spherically symmetrical isotropic gravitational field, is identical with the unbounded solution. This leads to the conclusion that the Universe may be viewed as a finite expanding white hole. The fact that CGR has been successful in describing the distance modulus verses redshift data of the high-redshift type Ia supernovae means that the data cannot distinguish between unbounded models and those with finite bounded radii of at least $c \tau$. Also it is shown that the Universe is spatially flat at the current epoch and has been at all past epochs where it was matter dominated.Comment: 11 pages, revised versio

The natural history of renal disease in Australian Aborigines. Part 1. Changes in albuminuria and glomerular filtration rate over time

The natural history of renal disease in Australian Aborigines. Part 1. Changes in albuminuria and glomerular filtration rate over time.BackgroundThe purpose of this study was to describe changes over time in albuminuria and glomerular filtration rate (GFR) in a cohort of Australian Aborigines from a community with high rates of renal disease and renal failure.MethodsParticipants were 486 adult community members (20+ years at first exam) who were screened for renal disease and related factors on at least two occasions (mean 2.7 occasions), at least a year apart, between 1990 and 1997. Renal function was assessed by the albumin:creatinine ratio (ACR; g/mol) on a random urine specimen and by the GFR estimated from the Cockcroft-Gault formula. Evolution over time was expressed as the average annual changes in these parameters.ResultsOn baseline examination, 70% of participants had albuminuria (ACR 1.1+ g/mol) There was a significant net increase in ACR and a fall in GFR in the cohort over time. Among individuals, however, changes were strongly correlated with ACR levels at baseline. There was no loss of GFR in persons with normal renal parameters at baseline and a rapid loss of GFR in those with substantial levels of albuminuria at baseline. Other factors significantly correlated with progression of ACR included age, baseline body mass index and systolic blood pressure, the presence of diabetes (or levels of fasting glucose), and elevated levels of serum gamma glutamyl transferase. Factors significantly associated with loss of GFR included body mass index, diabetes, systolic and diastolic blood pressures, microscopic hematuria, and marginally high cholesterol levels.ConclusionAlbuminuria progresses and GFR is lost over time in individuals in this community, at rates that are strongly dependent on levels of pre-existing albuminuria. Much loss of GFR and all renal failure should be avoided by preventing the development of albuminuria and minimizing its progression. This depends on improving the weight, blood pressure, and metabolic profile of the entire community and reducing infections. Modification of the course in people with established disease depends on vigorous control of blood pressure and the metabolic profile and the specific use of angiotensin-converting enzyme inhibitors

Rod Electroretinograms Elicited by Silent Substitution Stimuli from the Light-Adapted Human Eye

YesPurpose: To demonstrate that silent substitution stimuli can be used to generate electroretinograms (ERGs) that effectively isolate rod photoreceptor function in humans without the need for dark adaptation, and that this approach constitutes a viable alternative to current clinical standard testing protocols. Methods: Rod-isolating and non-isolating sinusoidal flicker stimuli were generated on a 4 primary light-emitting diode (LED) Ganzfeld stimulator to elicit ERGs from participants with normal and compromised rod function who had not undergone dark-adaptation. Responses were subjected to Fourier analysis, and the amplitude and phase of the fundamental were used to examine temporal frequency and retinal illuminance response characteristics. Results: Electroretinograms elicited by rod-isolating silent substitution stimuli exhibit low-pass temporal frequency response characteristics with an upper response limit of 30 Hz. Responses are optimal between 5 and 8 Hz and between 10 and 100 photopic trolands (Td). There is a significant correlation between the response amplitudes obtained with the silent substitution method and current standard clinical protocols. Analysis of signal-to-noise ratios reveals significant differences between subjects with normal and compromised rod function. Conclusions: Silent substitution provides an effective method for the isolation of human rod photoreceptor function in subjects with normal as well as compromised rod function when stimuli are used within appropriate parameter ranges. Translational Relevance: This method of generating rod-mediated ERGs can be achieved without time-consuming periods of dark adaptation, provides improved isolation of rod- from cone-based activity, and will lead to the development of faster clinical electrophysiologic testing protocols with improved selectivity

Antiprotons at Solar Maximum

New measurements with good statistics will make it possible to observe the time variation of cosmic antiprotons at 1 AU through the approaching peak of solar activity. We report a new computation of the interstellar antiproton spectrum expected from collisions between cosmic protons and the interstellar gas. This spectrum is then used as input to a steady-state drift model of solar modulation, in order to provide predictions for the antiproton spectrum as well as the antiproton/proton ratio at 1 AU. Our model predicts a surprisingly large, rapid increase in the antiproton/proton ratio through the next solar maximum, followed by a large excursion in the ratio during the following decade.New measurements with good statistics will make it possible to observe the time variation of cosmic antiprotons at 1 AU through the approaching peak of solar activity. We report a new computation of the interstellar antiproton spectrum expected from collisions between cosmic protons and the interstellar gas. This spectrum is then used as input to a steady-state drift model of solar modulation, in order to provide predictions for the antiproton spectrum as well as the antiproton/proton ratio at 1 AU. Our model predicts a surprisingly large, rapid increase in the antiproton/proton ratio through the next solar maximum, followed by a large excursion in the ratio during the following decade

Model- and calibration-independent test of cosmic acceleration

We present a calibration-independent test of the accelerated expansion of the universe using supernova type Ia data. The test is also model-independent in the sense that no assumptions about the content of the universe or about the parameterization of the deceleration parameter are made and that it does not assume any dynamical equations of motion. Yet, the test assumes the universe and the distribution of supernovae to be statistically homogeneous and isotropic. A significant reduction of systematic effects, as compared to our previous, calibration-dependent test, is achieved. Accelerated expansion is detected at significant level (4.3 sigma in the 2007 Gold sample, 7.2 sigma in the 2008 Union sample) if the universe is spatially flat. This result depends, however, crucially on supernovae with a redshift smaller than 0.1, for which the assumption of statistical isotropy and homogeneity is less well established.Comment: 13 pages, 2 figures, major change