Retrograde semaphorin-plexin signalling drives homeostatic synaptic plasticity.

Homeostatic signalling systems ensure stable but flexible neural activity and animal behaviour. Presynaptic homeostatic plasticity is a conserved form of neuronal homeostatic signalling that is observed in organisms ranging from Drosophila to human. Defining the underlying molecular mechanisms of neuronal homeostatic signalling will be essential in order to establish clear connections to the causes and progression of neurological disease. During neural development, semaphorin-plexin signalling instructs axon guidance and neuronal morphogenesis. However, semaphorins and plexins are also expressed in the adult brain. Here we show that semaphorin 2b (Sema2b) is a target-derived signal that acts upon presynaptic plexin B (PlexB) receptors to mediate the retrograde, homeostatic control of presynaptic neurotransmitter release at the neuromuscular junction in Drosophila. Further, we show that Sema2b-PlexB signalling regulates presynaptic homeostatic plasticity through the cytoplasmic protein Mical and the oxoreductase-dependent control of presynaptic actin. We propose that semaphorin-plexin signalling is an essential platform for the stabilization of synaptic transmission throughout the developing and mature nervous system. These findings may be relevant to the aetiology and treatment of diverse neurological and psychiatric diseases that are characterized by altered or inappropriate neural function and behaviour

Glycosylation of Stannyl Ceramides Promoted by Modified Montmorillonite­ in Supercritical Carbon Dioxide

The direct glycosylation of ceramides in supercritical carbon dioxide (scCO₂) successfully proceeded to produce β-glycolipids in high yield and with full stereoselectivity. The reaction is promoted by montmorillonite modified with a superacid (CF₃SO₃H). The value of this protocol was demonstrated in the efficient synthesis of isoglobotrihexosylceramide (iGB3)

Modeling Planarian Regeneration: A Primer for Reverse-Engineering the Worm

A mechanistic understanding of robust self-assembly and repair capabilities of complex systems would have enormous implications for basic evolutionary developmental biology as well as for transformative applications in regenerative biomedicine and the engineering of highly fault-tolerant cybernetic systems. Molecular biologists are working to identify the pathways underlying the remarkable regenerative abilities of model species that perfectly regenerate limbs, brains, and other complex body parts. However, a profound disconnect remains between the deluge of high-resolution genetic and protein data on pathways required for regeneration, and the desired spatial, algorithmic models that show how self-monitoring and growth control arise from the synthesis of cellular activities. This barrier to progress in the understanding of morphogenetic controls may be breached by powerful techniques from the computational sciences—using non-traditional modeling approaches to reverse-engineer systems such as planaria: flatworms with a complex bodyplan and nervous system that are able to regenerate any body part after traumatic injury. Currently, the involvement of experts from outside of molecular genetics is hampered by the specialist literature of molecular developmental biology: impactful collaborations across such different fields require that review literature be available that presents the key functional capabilities of important biological model systems while abstracting away from the often irrelevant and confusing details of specific genes and proteins. To facilitate modeling efforts by computer scientists, physicists, engineers, and mathematicians, we present a different kind of review of planarian regeneration. Focusing on the main patterning properties of this system, we review what is known about the signal exchanges that occur during regenerative repair in planaria and the cellular mechanisms that are thought to underlie them. By establishing an engineering-like style for reviews of the molecular developmental biology of biomedically important model systems, significant fresh insights and quantitative computational models will be developed by new collaborations between biology and the information sciences

Efecto citoprotector del camu-camu Myrciaria dubia en tres líneas celulares de ratón expuestos in vivo a bromato de potasio

It was evaluated in vivo the cytoprotective capacity of the fruit of Myrciaria dubia H.B.K. MC VAUGH "Camucamu (Myrtacea) against mutagenic damage caused by potassium bromate (68.5 mg/k) on three mouse cell lines (liver, kidney and blood cells). Mice (n = 120) were divided into three groups which drank ad libitum: distilled water; TI (negative control) and TIII (positive control), the TII group (positive control) drank the aqueous extract (2 %) of the fruit of Camu-camu. After ten days, only the TII and TIII groups were intraperitoneally injected with a single dose of KBr03(68.5 mg/k). The camu-camu treatment lasted 35 days more, where they were euthanized to determine the frequency of DNA damage by means of the alkaline comet assay protocol. It was observed in all cell lines a cytoprotective effect of camu-camu (p<0.05) with respect with the negative control. The DNA-damaging effects of oxidative KBrO3 action is inhibited by the 2% aqueous extract of camucamu fruit, probably by the presence of antioxidants such as ascorbic acid and flavonoids.Se evaluó in vivo la capacidad citoprotectora del fruto de Myrciaria dubia (Kunth) McVaugh Camu-camu frente al daño mutagénico producido por bromato de potasio (68,5 mg/k) sobre tres líneas celulares de ratón (hígado, riñón y células sanguíneas). Se utilizó ratones (n= 120) divididos en tres grupos los cuales bebieron ad libitum: TI= control negativo (solo agua) y el grupo TIII (control positivo); El grupo TII bebió el extracto acuoso (2% p/v) del fruto de camu-camu. A los diez días se inyectó una dosis única de KBr03 (68,5 mg/kg peso corporal) vía intraperitoneal, a los grupos TII y TIII. El tratamiento con camu-camu continuo 35 días más, luego los ratones fueron eutanizados para determinar la frecuencia del daño al DNA mediante el protocolo del ensayo cometa alcalino. El grupo TII mostró en todas las líneas celulares el efecto citoprotector del camu-camu (p< 0,05). El efecto dañino al DNA por la acción oxidativa del KBrO3 es inhibido por el extracto acuoso del fruto de camu camu, probablemente por la presencia de los agentes antioxidantes como el Acido ascórbico y los flavonoides

Simulación numérica de la circulación por marea y viento del noroeste y sur en la Bahía De La Paz, B.C.S.

A hydrodynamic barotropic model was used to simulate the circulation induced by tide and wind in the Bay of La Paz, B.C.S. The tide components M2, N2, S2, K2, 01 and K1 were considered in this model as well as winds from the Northwest and South with speeds of 4, 5 and 10 m/s. Model results showed the highest velocity values along the coast induced apparently by wind stress and topographic effects. This results were validated qualitatively and quantitatively by an analytic model and field current velocities. Some effects of the circulation are discussed in relation to possible pollution discharges

Formación de compuestos heterocíclicos, bicíclicos y tricíclicos a partir de la reacción de o-diaminas y tetraminas con cetonas aromáticas

IP 1106-05-136-9