Activin disrupts somitogenesis in cultured chick embryos

The anatomical and cell biological aspects of somite formation in the chick embryo have been rather well studied. Molecular regulation of somitogenesis in vertebrates is just beginning to be understood. We have studied the effects of human recombinant activin on somitogenesis in gastrulating chick embryos cultured in vitro with a view to assessing the possible role of activin-related molecules in this phenomenon. Activin disrupted somitogenesis in treated embryos, resulting in the formation of abnormal, split or ectopic somites. Light microscopic examination indicated that the ability of activin to interfere with somitogenesis might be partly due to initiation of somite formation at ectopic sites. We show that these cells are indeed somitogenic by their expression of one of the earliest somite-specific marker genes, Pax3. Scanning electron microscopic examination of control and treated embryos revealed direct effects of activin on cell-cell interactions. Cells from treated embryos exhibited disrupted intercellular adhesion leading to large intercellular spaces, altered cell shapes and modification of cell surface protrusions. The effects of activin on somitogenesis appear to be specific, since the neural structures, which are generally more susceptible to chemical insults during gastrulation, were relatively less affected. The results clearly point to a role of activin-related molecules in somitogenesis in the chick embryo.     

Apparent Strength Conceals Instability in a Model for the Collapse of Historical States

An explanation for the political processes leading to the sudden collapse of empires and states would be useful for understanding both historical and contemporary political events. We examine political disintegration across eras, cultures and geographical scale to form a simple hypothesis that can be expressed verbally yet formulated mathematically. Factions within a state make choices described by game-theory about whether to accept the political status quo, or to attempt to better their circumstances through costly rebellion. In lieu of precise data we verify our model using sensitivity analysis. We find that a small amount of dissatisfaction is typically harmless to the state, but can trigger sudden collapse when there is a sufficient buildup of political inequality. Contrary to intuition, a state is predicted to be least stable when its leadership is at the height of its political power and thus most able to exert its influence through external warfare, lavish expense or autocratic decree.     

Effect of heterosexual olfactory and visual stimulation on 5-en-3 beta-hydroxysteroids and progesterone in the male rat brain

Pregnenolone, dehydroepiandrosterone and progesterone were measured in specific areas of the brain and in the retina of young adult male rats exposed to the scent or to the scent and view of young cycling females and compared to the levels obtained in males similarly exposed to other males (control). All the steroid values observed were much higher than those found in plasma, varied considerably from one area to another and responded sometimes in opposite directions to stimulation of young adult males by the scent or by the scent and view of cycling females. In male rats exposed to the scent of young cycling females pregnenolone decreased significantly only in the olfactory bulb in comparison with the controls. There were no significant changes in dehydroepiandrosterone or progesterone in this case. When male rats were exposed to the scent and view of female rats, pregnenolone again decreased significantly in the olfactory bulb while dehydroepiandrosterone increased significantly in the olfactory bulb and the retina and progesterone decreased significantly in the hypothalamus, amygdala and parietal cortex. These results are discussed in relation with a possible new role for certain steroids in neuroregulatory mechanisms related to behaviour.     

Genes involved in phosphatidylcholine biosynthesis correlate with nuclear factor-κB in biliary tract cancer patients: Evidence from 1H NMR and computational analyses

Gallbladder cancer (GBC) is an aggressive malignancy of gastrointestinal tract. Due to uncontrolled growth, GBC cells rapidly synthesize biomolecules including lipids. The lipids are integral component of cell membrane with a wide range of cellular functions. In this study, we measured the clinicopathological features in 40 cases of histologically confirmed GBC and 16 cases of chronic cholecystitis (CC). The female to male ratio in the GBC and CC groups were 3.44:1 and 2.2:1, respectively. The GBC patients exhibited well to poorly differentiated tumor. In the CC group, all patients showed cholecystitis with no evidence of dysplasia or malignancy. The majority of GBC and CC patients reported pain. Using ¹H NMR spectroscopy, we observed 4-folds increase in the level of choline containing phospholipids (CCPLs) in the gallbladder of GBC patients as compared to CC patients. Other lipid metabolites such as cholesterol ester, C18-cholesterol and saturated fatty acids were insignificantly changed between GBC and CC patients. Moreover, the level of CCPLs in the GBC patients with BMI <25 kg/m² was significantly higher as compared to CC patients. Further, a significant increase in the CCPLs level was observed in GBC female patients in comparison to CC patients. From the computational analyses, we observed that the genes involved in the biosynthesis of phosphatidylcholine (PtdCho) indirectly interact with the RELA, which encodes the NF-κB p65 subunit. The genes involved in the PtdCho biosynthesis were also correlated with the overall and disease-free survival of cholangiocarcinoma patients. The study opens new window for exploring the diagnostic and therapeutic potential of CCPLs in GBC patients.     

Biology of <Emphasis Type="Italic">B. sorokiniana</Emphasis> (syn. <Emphasis Type="Italic">Cochliobolus sativus</Emphasis>) in genomics era

Bipolaris sorokiniana (Sacc.) Shoemaker is a hemi-biotrophic fungal pathogen, which is an anamorph (teleomorph Cochlibolus sativus). It causes spot blotch, root rot and leaf spot diseases in a number of cereals including wheat, barley and other small grain cereals. In the genomics era, the fungus has been subjected to a variety of studies using molecular approaches. Correct chromosome number was determined and molecular karyotypes were prepared using contour-clamped homogeneous electric field. Molecular maps were prepared using markers like RFLPs, SSRs, RAPDs and SNPs. For this purpose, segregating progenies derived from crosses between diverse isolates of the pathogen were used. Whole genome sequencing (WGS) data was collected not only for B. sorokiniana isolates, but also for several species of Cochliobolus. Genes involved in secondary metabolism and virulence were identified from genome sequences. The WGS data has also been utilized for comparative genomics giving useful information about evolutionary trends. A brief account of this information is presented in this review.     

Influence of cytokinins and phytochrome on nitrate reductase activity in etiolated leaves of maize

Of the different hormones tested, cytokinins stimulated nitrate-induced nitrate reductase (NR) activity in the dark. The optimal stimulation was obtained at 16 hr and this was sensitive to tungstate, 6-methylpurine and cycloheximide. The cytokinin stimulation of NR activity was further enhanced by brief irradiation with red light, but this effect was not noticed when leaves were exposed to far-red light. Both kinetin and red light, when given together, or given with a darkness interruption, stimulated the NR activity more than with either of them alone.