Alterations of GABA-A and dopamine D-2 brain receptors in dogs with portal-systemic encephalopathy.

The binding characteristics of gamma-aminobutyric acid-A (GABA-A) receptors and the kinetic characteristics of the target enzyme of GABA synthesis in nerve terminals, glutamic acid decarboxylase (GAD), were studied in a dog model of portal-systemic encephalopathy obtained by porta-caval shunt performed in dimethylnitrosamine pretreated animals. Furthermore the properties of dopamine receptors and the levels of catecholamines of encephalopathic dogs were investigated. The mild stage of encephalopathy was characterized by an up-regulation of the inhibitory GABA-A receptors probably related to a decrese of GABA in nerve terminals since GAD was decreased and by a slight decrease of catecholamines and by an increased synthesis of octopamine associated with a decreased affinity of dopamine receptors. In the severe stage there was a selection of high affinity GABA-A receptors with an increased number of benzodiazepine recognition sites which were supersensitive to GABA stimulation, a decreased number of Dopamine D-2 receptors and a marked reduction of catecholamines. These data seem to suggest that the neurological disturbances of experimental portal-systemic encephalopathy might be the result of an imbalance between inhibitory and excitatory systems leading to a prevalence of the first one.     

Effect of freezing and freeze-drying on the viability and storage of Lilium longiflorum L. and Zea mays L. pollen

The freeze-preservation of pollen is dependent on the interaction of several factors such as freezing rate, thawing rate, freeze-drying temperature and duration, storage temperature and environment and rehydration rates. Changes in any of these variables affects the others directly or indirectly.Rapid freezing of pollen at rates of approximately 200 °C/min maintains the highest degree of viable pollen in combination with rapid thawing rates of 218 °C/min. Rapid cooling and slow rewarming resulted in a substantial loss of pollen viability. This might indicate that intracellular ice crystals formed during rapid cooling perhaps grow into larger ice masses during slow rewarming or storage at temperatures above ?50 °C.The germinability of pollen freeze-dried at temperatures below ?50 °C was also prolonged over that of the controls. Germination values for unfrozen pollen stored for 30 days at 0–5 °C averaged 50% for lily and 20% for corn. Freeze-dried pollen stored for 30 days at the same temperature yielded considerably higher viability percentages for both lily and corn pollen. Drying time is an important factor, perhaps indicating that residual moisture is critical. Freeze-dried pollen can be stored at higher temperatures than frozen and control pollen. Freeze-dried material stored for five months at 0–5 °C, upon slow rehydration yielded intact grains which has average germination percentages of 25 for lily and 15 for corn. The same pollen upon rapid rehydration showed rupturing of 20–40% of the cells and practically no germination.     

Additive effect of TAp63 deficiency on the adrenocortical dysplasia (acd) phenotype

Adrenocortical dysplasia (acd) is a spontaneous autosomal recessive mouse mutation exhibiting caudal truncation, vertebral segmentation defects, hydronephrosis, limb hypoplasia, and perinatal lethality. Acd encodes TPP1, a component of the shelterin complex that maintains telomere integrity, and consequently acd mutant mice have telomere dysfunction and genomic instability. We previously showed that apoptosis is the primary mechanism causing the acd skeletal phenotype, and that p53 deficiency rescues the skeletal defects of the acd phenotype but has no effect on the perinatal lethality. The Trp63 gene encodes multiple isoforms, which play a role in proliferation, apoptosis, and stem/progenitor cell maintenance. Different p63 isoforms exhibit both proapoptotic (TAp63) and antiapoptotic (ΔNp63) functions. We hypothesized that deficiency of proapoptotic TAp63 isoforms might rescue the acd skeletal phenotype, similar to our previous observations with deficiency of p53. Mice heterozygous for a null allele of TAp63 were crossed to heterozygous acd mice to determine the effect of TAp63 deficiency on the acd mutant phenotype. In contrast to our results with the acd?×?p53 cross, skeletal anomalies were not rescued by deficiency of TAp63. In fact, the limb and vertebral anomalies observed in double-mutant embryos were more severe than those of embryos with the acd mutation alone, demonstrating a dose-dependent effect. These studies suggest that TAp63 isoforms do not facilitate p53-like apoptosis during development in response to acd-mediated telomere dysfunction and are consistent with the proposed roles of TAp63 in maintaining genomic stability.     

CaMK activation during exercise is required for histone hyperacetylation and MEF2A binding at the MEF2 site on the Glut4 gene

The role of CaMK II in regulating GLUT4 expression in response to intermittent exercise was investigated. Wistar rats completed 5 x 17-min bouts of swimming after receiving 5 mg/kg KN93 (a CaMK II inhibitor), KN92 (an analog of KN93 that does not inhibit CaMK II), or an equivalent volume of vehicle. Triceps muscles that were harvested at 0, 6, or 18 h postexercise were assayed for 1) CaMK II phosphorylation by Western blot, 2) acetylation of histone H3 at the Glut4 MEF2 site by chromatin immunoprecipitation (ChIP) assay, 3) bound MEF2A at the Glut4 MEF2 cis-element by ChIP, and 4) GLUT4 expression by RT-PCR and Western blot. Compared with controls, exercise caused a twofold increase in CaMK II phosphorylation. Immunohistochemical stains indicated increased CaMK II phosphorylation in nuclear and perinuclear regions of the muscle fiber. Acetylation of histone H3 in the region surrounding the MEF2 binding site on the Glut4 gene and the amount of MEF2A that bind to the site increased approximately twofold postexercise. GLUT4 mRNA and protein increased approximately 2.2- and 1.8-fold, respectively, after exercise. The exercise-induced increases in CaMK II phosphorylation, histone H3 acetylation, MEF2A binding, and GLUT4 expression were attenuated or abolished when KN93 was administered to rats prior to exercise. KN92 did not affect the increases in pCaMK II and GLUT4. These data support the hypothesis that CaMK II activation by exercise increases GLUT4 expression via increased accessibility of MEF2A to its cis-element on the gene.     

Simulation of the conditions of wave excitation for the optimization of the lower hybrid current drive in the Globus-M spherical tokamak

At present, the method of current drive by means of lower hybrid waves is not applied to low-aspect-ratio tokamaks, because, in the traditional approach, it would be necessary to use waves with a very high slowing-down factor. However, studies of new transparency regions for waves in a nonuniform magnetized plasma, performed earlier at the Ioffe Physical Technical Institute, Russian Academy of Sciences, made it possible to develop an approach in which slow waves are excited in the poloidal (rather than toroidal) direction. In this approach, moderately slowed-down waves first propagate in the poloidal direction, but then turn in the toroidalal direction and get into the dense plasma. In this work, this approach is further developed using numerical methods. In particular, the influence of the density profile in the edge plasma on the efficiency of wave excitation for given antenna parameters is studied in detail.     

Visual event related potentials. The origin of wave P300. A computer model

This five-layered model consisting of 180 neurons is aimed at simulating some elementary functions of primary visual cortex of mammals in form detection. Its main achievements are: 1. Detection of points, lines, simple geometric figures in the V1. 2. Abstraction of 19 different qualities of geometric figures. 3. Simulation and rational explanation of processing of peripheral stimuli in the V1, explanation of mechanism of origin of visual ERPs, including P300 wave. 4. Simulation and explanation of the nature and build up of the cognitive function within V1 and its possible relation to long-term memory. 5. The model is based partly on Hebb-type synapses, illustrates the role of neuronal assemblies, sheds light on the functional relationship of excitatory and inhibitory neurons, in their conformity with special tasks of different cortical layers.     

On the parallelisation of bioinformatics applications

This paper surveys the computational strategies followed to parallelise the most used software in the bioinformatics arena. The studied algorithms are computationally expensive and their computational patterns range from regular, such as database-searching applications, to very irregularly structured patterns (phylogenetic trees). Fine- and coarse-grained parallel strategies are discussed for these very diverse sets of applications. This overview outlines computational issues related to parallelism, physical machine models, parallel programming approaches and scheduling strategies for a broad range of computer architectures. In particular, it deals with shared, distributed and shared/distributed memory architectures.     

Cardiac glycosides and oviposition by Danaus plexippus on Asclepias fruticosa in south-east Queensland (Australia), with notes on the effect of plant nitrogen content

Abstract. 1. Previous studies which attempt to relate oviposition by female monarchs, Danaus plexippus (L.), to the cardiac glycosides of their milkweed host plants are reviewed and found to be defective.
2. Here we followed ovipositing females in the field and recorded their oviposition behaviour on individual Asclepias fruticosa (L.) plants. The cardenolide glycoside and per cent nitrogen of each of these plants and also of a control set of plants was recorded.
3. Milkweeds accepted by females, on which egg laying took place, had significantly lower mean cardenolide levels compared with rejected plants and a control sets of plants.
4. Most oviposition ( c. 70%) took place on plants with intermediate cardenolide (CG) levels (=200–300 μg/0.1 g DW).
5. The mean CG level in A.fruticosa was 345 μg/0.1 g DW (SD = 138, n =122, range 119–719).
6. There was no relationship between monarch oviposition behaviour and plant per cent nitrogen.