Inactivation of the geranylgeranyl reductase (ChlP) gene in the cyanobacterium Synechocystis sp. PCC 6803

AbstractGeranylgeranyl reductase catalyses the reduction of geranylgeranyl pyrophosphate to phytyl pyrophosphate required for synthesis of chlorophylls, phylloquinone and tocopherols. The gene chlP (ORF sll1091) encoding the enzyme has been inactivated in the cyanobacterium Synechocystis sp. PCC 6803. The resulting ΔchlP mutant accumulates exclusively geranylgeranylated chlorophyll a instead of its phytylated analogue as well as low amounts of α-tocotrienol instead of α-tocopherol. Whereas the contents of chlorophyll and total carotenoids are decreased, abundance of phycobilisomes is increased in ΔchlP cells. The mutant assembles functional photosystems I and II as judged from 77 K fluorescence and electron transport measurements. However, the mutant is unable to grow photoautotrophically due to instability and rapid degradation of the photosystems in the absence of added glucose. We suggest that instability of the photosystems in ΔchlP is directly related to accumulation of geranylgeranylated chlorophyll a. Increased rigidity of the chlorophyll isoprenoid tail moiety due to three additional CC bonds is the likely cause of photooxidative stress and reduced stability of photosynthetic pigment–protein complexes assembled with geranylgeranylated chlorophyll a in the ΔchlP mutant

Фракционная анизотропия белого и серого вещества головного мозга в остром периоде ишемического инсульта как маркер неврологического, когнитивного и функционального статуса

Aim. To study the fractional anisotropy of white and gray brain matter and its associations with clinical and instrumental data in acute ischemic stroke. Materials and methods. The parameters of fractional anisotropy of 10 areas of white and gray brain matter were analyzed in 30 acute ischemic stroke patients by diffusion-tensor imaging. The neurological (NIHSS), cognitive (MMSE), functional (Rivermead Mobility Index and Modified Rankin Scale) and some laboratory and instrumental data were assessed. Results. The fraction anisotropy was analyzed on the side of lesion and symmetrically. The decline of anisotropy was revealed in posterior limb of internal capsule on the side of stroke independently of the lesion location. Also the interactions between fraction anisotropy and stroke severity, global cognitive status and duration of hospital treatment were found. Conclusion. The obtained data may suggest that in acute period of stroke the neurodegeneration and neuroreparational ready start. It appears the changes of white and gray matter integrity. According to the concept “heart-vessels-brain” we received the data indicating the significance of vascular risk factors which lead to hypoperfusion and hypoxia in the development of microstructural changes. Some parameters of fractional anisotropy may predict clinical and functional outcome on discharge.Цель исследования: оценить фракционную анизотропию белого и серого вещества головного мозга и ее связь с клинико-инструментальными характеристиками в остром периоде ишемического инсульта. Материал и методы. Измерены показатели фракционной анизотропии 10 зон белого и серого вещества головного мозга у 30 пациентов в остром периоде ишемического инсульта методом диффузионно-тензорного изображения. Оценены показатели неврологического (NIHSS), когнитивного (MMSE), функционального статусов (индекс мобильности Ривермид и модифицированная шкала Ренкина), а также лабораторно-инструментальные данные. Результаты. Проанализированы различия фракционной анизотропии на стороне очага поражения и симметричных участках головного мозга. Выявлено снижение показателя в зоне задней ножки внутренней капсулы на стороне очага по сравнению с симметричными зонами интактного полушария вне зависимости от расположения зоны инфаркта. Продемонстрирована взаимосвязь между значениями фракционной анизотропии в исследованных зонах со степенью неврологического дефицита и когнитивным статусом при выписке, а также длительностью лечения. Заключение. Проведенное исследование может свидетельствовать о том, что уже в остром периоде ишемического инсульта параллельно инициируются процессы нейродегенерации и нейрорепарации, проявляющиеся изменением интегральности белого и серого вещества головного мозга. В подтверждение концепции “сердце-сосуды-мозг” получены данные о значимости сосудистых факторов риска, обусловливающих гипоперфузию и гипоксию, в развитии микроструктурных изменений изученных зон мозга. Ряд показателей фракционной анизотропии, рассмотренных в работе, могут служить предикторами неврологического и функционального исхода при выписке пациентов из стационара

Limit Distributions for the Estimates of the Digamma Distribution Parameters Constructed from a Random Size Sample

In this paper, we study a new type of distribution that generalizes distributions from the gamma and beta classes that are widely used in applications. The estimators for the parameters of the digamma distribution obtained by the method of logarithmic cumulants are considered. Based on the previously proved asymptotic normality of the estimators for the characteristic index and the shape and scale parameters of the digamma distribution constructed from a fixed-size sample, we obtain a statement about the convergence of these estimators to the scale mixtures of the normal law in the case of a random sample size. Using this result, asymptotic confidence intervals for the estimated parameters are constructed. A number of examples of the limit laws for sample sizes with special forms of negative binomial distributions are given. The results of this paper can be widely used in the study of probabilistic models based on continuous distributions with an unbounded non-negative support

Asymptotically Normal Estimators for the Parameters of the Gamma-Exponential Distribution

Currently, much research attention has focused on generalizations of known mathematical objects in order to obtain adequate models describing real phenomena. An important role in the applied theory of probability and mathematical statistics is the gamma class of distributions, which has proven to be a convenient and effective tool for modeling many real processes. The gamma class is quite wide and includes distributions that have useful properties such as, for example, infinite divisibility and stability, which makes it possible to use distributions from this class as asymptotic approximations in various limit theorems. One of the most important tasks of applied statistics is to obtain estimates of the parameters of the model distribution from the available real data. In this paper, we consider the gamma-exponential distribution, which is a generalization of the distributions from the gamma class. Estimators for some parameters of this distribution are given, and the asymptotic normality of these estimators is proven. When obtaining the estimates, a modified method of moments was used, based on logarithmic moments calculated on the basis of the Mellin transform for the generalized gamma distribution. On the basis of the results obtained, asymptotic confidence intervals for the estimated parameters are constructed. The results of this work can be used in the study of probabilistic models based on continuous distributions with an unbounded non-negative support

The Estimators of the Bent, Shape and Scale Parameters of the Gamma-Exponential Distribution and Their Asymptotic Normality

When modeling real phenomena, special cases of the generalized gamma distribution and the generalized beta distribution of the second kind play an important role. The paper discusses the gamma-exponential distribution, which is closely related to the listed ones. The asymptotic normality of the previously obtained strongly consistent estimators for the bent, shape, and scale parameters of the gamma-exponential distribution at fixed concentration parameters is proved. Based on these results, asymptotic confidence intervals for the estimated parameters are constructed. The statements are based on the method of logarithmic cumulants obtained using the Mellin transform of the considered distribution. An algorithm for filtering out unnecessary solutions of the system of equations for logarithmic cumulants and a number of examples illustrating the results obtained using simulated samples are presented. The difficulties arising from the theoretical study of the estimates of concentration parameters associated with the inversion of polygamma functions are also discussed. The results of the paper can be used in the study of probabilistic models based on continuous distributions with unbounded non-negative support

Post-operative insulin resistance

Post-operative insulin resistance (IR) is a recognised marker of surgical stress. However, the reasons underlying post-operative IR and its clinical value are still unclear. IR has been described as a pathological condition, in which organs and tissues fail to respond to the hormone insulin, resulting in acute hyperglycaemia. Post-operative IR in patients without type 2 diabetes has been identified as an independent, negative predictor of post-operative outcome. Studies have shown a direct relationship between post-operative morbidity (including complications from infection) and total mortality in patients with acute hyperglycaemia compared with diabetic patients. IR and stress-induced hyperglycaemia in the early post-operative period may be corrected by insulin infusion; however, this has often been associated with hypoglycaemia. Detection and modification of risk factors in the pre- and intra-operative periods may decrease the frequency of IR and hyperglycaemia and eliminate the use of insulin. In this literature review, the mechanisms underlying the development and prevention of post-operative IR, and its clinical value are discussed. This study demonstrates the relationship between IR and post-operative morbidity, highlighting the benefits of a complex approach to prevent the adverse events of post-operative IR and stress-induced hyperglycaemia

Formation of solitons in a waveguide at second harmonic generation

Second harmonic generation in a quadratic nonlinear waveguide is analyzed analytically and numerically. Formation of spatio-temporal solitons is demonstrated. They can form both positive and negative coefficients of group velocity dispersion due to the waveguide geometry. Analytical results are confirmed by computer simulations

Formation of solitons in a waveguide at second harmonic generation

Second harmonic generation in a quadratic nonlinear waveguide is analyzed analytically and numerically. Formation of spatio-temporal solitons is demonstrated. They can form both positive and negative coefficients of group velocity dispersion due to the waveguide geometry. Analytical results are confirmed by computer simulations