Vegetation Composition in Hugumbirda-Gratkhassu National Forest Priority Area, South Tigray

The floristic composition and structure of the vegetation of Hugumbirda-Grat-Khassu forest, South Tigray, Northern Ethiopia is described and related to environmental factors. To analyze the vegetation and environmental data seventy-four relevè ( 20m x 20m) were used. For each species the cover/abundance value was estimated. Height and diameter at breast height (DBH) of all woody individuals taller than 2 m and thicker than 2 cm were measured. Importance Value Index was calculated for 24 tree/shrub species and the result helped to identify the five dominant tree/shrub species and to show the overall forest situation. The species and relevès were classified with the two-way indicator species analysis program TWINSPAN. We recorded 102 species belonging to 83 genera and 50 families. Five community types are described: Allophylus macrobotrys-Ficus sur, Nuxia congesta-Podocarpus falcatus, Acacia abyssinica-Olea europaea, Myrica salicifolia-Erica arborea-Maesa lanceolata and Acacia etbaica- Dichrostachys cinerea-Acacia tortilis type. Of these, community type 2 has high species richness while community type 3 is poor in species richness. The general arrangement of all species was found to show high density at lower height and DBH classes. Based on the cumulative results of Importance Value Index, Juniperus procera, Olea europaea subsp. cuspidata, Nuxia congesta, Cassipourea mallosana and Olinia rochetiana were identified to be the most dominant tree species of the forest and they contributed 71.43% of the basal area. Analysis of community-environment relationships didn’t show significant differences except for altitude and slope. Key words: Community, DBH, Floristic composition, Forest structure, Releve, Vegetation classification

Chemical genomics reveals histone deacetylases are required for core regulatory transcription

Identity determining transcription factors (TFs), or core regulatory (CR) TFs, are governed by cell-type specific super enhancers (SEs). Drugs to selectively inhibit CR circuitry are of high interest for cancer treatment. In alveolar rhabdomyosarcoma, PAX3-FOXO1 activates SEs to induce the expression of other CR TFs, providing a model system for studying cancer cell addiction to CR transcription. Using chemical genetics, the systematic screening of chemical matter for a biological outcome, here we report on a screen for epigenetic chemical probes able to distinguish between SE-driven transcription and constitutive transcription. We find that chemical probes along the acetylation-axis, and not the methylation-axis, selectively disrupt CR transcription. Additionally, we find that histone deacetylases (HDACs) are essential for CR TF transcription. We further dissect the contribution of HDAC isoforms using selective inhibitors, including the newly developed selective HDAC3 inhibitor LW3. We show HDAC1/2/3 are the co-essential isoforms that when co-inhibited halt CR transcription, making CR TF sites hyper-accessible and disrupting chromatin looping

Microbiome to Brain:Unravelling the Multidirectional Axes of Communication

The gut microbiome plays a crucial role in host physiology. Disruption of its community structure and function can have wide-ranging effects making it critical to understand exactly how the interactive dialogue between the host and its microbiota is regulated to maintain homeostasis. An array of multidirectional signalling molecules is clearly involved in the host-microbiome communication. This interactive signalling not only impacts the gastrointestinal tract, where the majority of microbiota resides, but also extends to affect other host systems including the brain and liver as well as the microbiome itself. Understanding the mechanistic principles of this inter-kingdom signalling is fundamental to unravelling how our supraorganism function to maintain wellbeing, subsequently opening up new avenues for microbiome manipulation to favour desirable mental health outcome

Thermo-Mechanical Stress Analysis in Electronic Packaging with Continuous and Partial Bond Layer

Interfacial stress due to thermal mismatch in layered structure has been considered as one of the major causes of mechanical failure in electronic packaging. The mismatch due to the differences in coefficient of thermal expansion (CTE) of the materials in multi-layered structure may induce severe stress concentration to the electronic composites namely interfacial delamination and die cracking. Therefore, the studies and evaluation of interfacial stress in electronic packaging become significantly important for optimum design and failure prediction of the electronic devices. The thermal mismatch shear stress for bi-layered assembly can be analyzed by using the mathematical models based on beam theory. In this study, Finite Element Method (FEM) simulation was performed to an electronic package by using ANSYS. The shear stress growth behavior at the interface of the bonded section was studied with the considerations of continuous and partial bond layers in the interfaces. Based on the analysis, it can be observed that the partial bond layer with small center distances can be simplified as a continuous bond layer for bi-layered shearing stress model analysis

Micro-RNAs in cognition and cognitive disorders: Potential for novel biomarkers and therapeutics

Micro-RNAs (miRNAs) are small regulatory non-coding RNAs involved in the regulation of many biological functions. In the brain, they have distinct expression patterns depending on region, cell-type and developmental stage. Their expression profile is altered by neuronal activation in response to behavioral training or chemical/electrical stimulation. The dynamic changes in miRNA level regulate the expression of genes required for cognitive processes such as learning and memory. In addition, in cognitive dysfunctions such as dementias, expression levels of many miRNAs are perturbed, not only in brain areas affected by the pathology, but also in peripheral body fluids such as serum and cerebrospinal fluid. This presents an opportunity to utilize miRNAs as biomarkers for early detection and assessment of cognitive dysfunctions. Further, since miRNAs target many genes and pathways, they may represent key molecular signatures that can help understand the mechanisms of cognitive disorders and the development of potential therapeutic agents

Artificial theta stimulation impairs encoding of contextual fear memory.

Several experiments have demonstrated an intimate relationship between hippocampal theta rhythm (4-12 Hz) and memory. Lesioning the medial septum or fimbria-fornix, a fiber track connecting the hippocampus and the medial septum, abolishes the theta rhythm and results in a severe impairment in declarative memory. To assess whether there is a causal relationship between hippocampal theta and memory formation we investigated whether restoration of hippocampal theta by electrical stimulation during the encoding phase also restores fimbria-fornix lesion induced memory deficit in rats in the fear conditioning paradigm. Male Wistar rats underwent sham or fimbria-fornix lesion operation. Stimulation electrodes were implanted in the ventral hippocampal commissure and recording electrodes in the septal hippocampus. Artificial theta stimulation of 8 Hz was delivered during 3-min free exploration of the test cage in half of the rats before aversive conditioning with three foot shocks during 2 min. Memory was assessed by total freezing time in the same environment 24 h and 28 h after fear conditioning, and in an intervening test session in a different context. As expected, fimbria-fornix lesion impaired fear memory and dramatically attenuated hippocampal theta power. Artificial theta stimulation produced continuous theta oscillations that were almost similar to endogenous theta rhythm in amplitude and frequency. However, contrary to our predictions, artificial theta stimulation impaired conditioned fear response in both sham and fimbria-fornix lesioned animals. These data suggest that restoration of theta oscillation per se is not sufficient to support memory encoding after fimbria-fornix lesion and that universal theta oscillation in the hippocampus with a fixed frequency may actually impair memory