Neurophilic Descending Migration of Dorsal Midbrain Neurons Into the Hindbrain

Stereotypic cell migrations in the developing brain are fundamental for the proper patterning of brain regions and formation of neural networks. In this work, we uncovered in the developing rat, a population of neurons expressing tyrosine hydroxylase (TH) that migrates posteriorly from the alar plate of the midbrain, in neurophilic interaction with axons of the mesencephalic nucleus of the trigeminal nerve. A fraction of this population was also shown to traverse the mid-hindbrain boundary, reaching the vicinity of the locus coeruleus (LC) in rhombomere 1 (r1). This migratory population, however, does not have a noradrenergic (NA) phenotype and, in keeping with its midbrain origin, expresses Otx2 which is down regulated upon migration into the hindbrain. The interaction with the trigeminal mesencephalic axons is necessary for the arrangement and distribution of migratory cells as these aspects are dramatically altered in whole embryo cultures upon disruption of trigeminal axon projection by interfering with DCC function. Moreover, in mouse embryos in an equivalent developmental stage, we detected a cell population that also migrates caudally within the midbrain apposed to mesencephalic trigeminal axons but that does not express TH; a fraction of this population expresses calbindin instead. Overall, our work identified TH-expressing neurons from the rat midbrain alar plate that migrate tangentially over long distances within the midbrain and into the hindbrain by means of a close interaction with trigeminal mesencephalic axons. A different migratory population in this region and also in mouse embryos revealed diversity among the cells that follow this descending migratory pathway

Origin and Migration of Olfactory Cajal-Retzius Cells

Early telencephalic development involves the migration of diverse cell types that can be identified by specific molecular markers. Most prominent among them are Cajal-Retzius (CR) cells that emanate mainly from the cortical hem and to a lesser extent from rostrolateral, septal and caudo-medial regions. One additional territory proposed to give rise to CR cells that migrate dorsally into the neocortex lies at the ventral pallium, although contradictory results question this notion. With the use of a cell-permeable fluorescent tracer in cultured embryos, we identified novel migratory paths of putative CR cells and other populations that originate from the rostrolateral telencephalon at its olfactory region. Moreover, extensive labeling on the lateral telencephalon along its rostro-caudal extent failed to reveal a dorsally-migrating CR cell population from the ventral pallium at the stages analyzed. Hence, this work reveals a novel olfactory CR cell migration and supports the idea that the ventral pallium, where diverse types of neurons converge, does not actually generate CR cells

Diferenciación in vitro de preadipocitos de tejido adiposo bovino

To study differentiation of bovine adipose tissue preadipocytes into adipocytes in bovines, two culture media were tested. Samples were obtained of subcutaneous and omentum fat from 3-4 yr old Holstein adults, and perirenal and omentum fat from fetuses in their last third of gestation. Although no differentiation was observed in cells obtained from adult animals' adipose tissue, fetal perirenal fibroblasts differentiated into adipocytes in the following medium: DMEM/F-12 1:1, 10 μ,,g/ml insulin, 0.25 μ,,M dexamethasone, 10 μ,,g/ml very low-density lipoproteins, 100 μ,,g/ml streptomycin, and 100 IU/ml penicillin. These results could be used to develop a model to study the molecular mechanisms of preadipocyte differentiation in bovine adipose tissue.Con objeto de obtener subcultivos seriales de preadipocitos del tejido adiposo bovino y luego tratar de diferenciarlos a adipocitos, se compararon dos medios de cultivo. Se obtuvieron muestras de tejido adiposo subcutáneo y de omento de animales adultos de 3 a 4 años de edad, y de grasa perirrenal y de omento de fetos en el íºltimo tercio de la gestación. En el caso de células adultas, se establecieron subcultivos, sin embargo no pudieron ser diferenciadas. Para el tejido adiposo fetal, se establecieron subcultivos y los fibroblastos perirrenales fueron capaces de diferenciarse con el medio apropiado (DMEM/ F-12 1:1, 10 μ,,g/ml insulina, 0.25 μ,,M dexametasona, 10 μ,,g/ml lipoproteí­nas de muy baja densidad, 100 μ,,g/ml estreptomicina, 100 UI/ml penicilina). Estos resultados podrí­an servir de base para obtener un modelo que permita estudiar los mecanismos moleculares de diferenciación de preadipocitos en tejido adiposo bovino

LIM-homeobox gene Lhx5 is required for normal development of Cajal-Retzius cells

Cajal-Retzius (C-R) cells play important roles in the lamination of the mammalian cortex via reelin secretion. The genetic mechanisms underlying the development of these neurons have just begun to be unraveled. Here, we show that two closely related LIM-homeobox genes Lhx1 and Lhx5 are expressed in reelin+ cells in various regions in the mouse telencephalon at or adjacent to sites where the C-R cells are generated, including the cortical hem, the mantle region of the septal/retrobulbar area, and the ventral pallium. Whereas Lhx5 is expressed in all of these reelin-expressing domains, Lhx1 is preferentially expressed in the septal area and in a continuous domain spanning from lateral olfactory region to caudomedial territories. Genetic ablation of Lhx5 results in decreased reelin+ and p73+ cells in the neocortical anlage, in the cortical hem, and in the septal, olfactory, and caudomedial telencephalic regions. The overall reduction in number of C-R cells in Lhx5 mutants is accompanied by formation of ectopic reelin+ cell clusters at the caudal telencephalon. Based on differential expression of molecular markers and by fluorescent cell tracing in cultured embryos, we located the origin of reelin+ ectopic cell clusters at the caudomedial telencephalic region. We also confirmed the existence of a normal migration stream of reelin+ cells from the caudomedial area to telencephalic olfactory territories in wild-type embryos. These results reveal a complex role for Lhx5 in regulating the development and normal distribution of C-R cells in the developing forebrain. Copyright © 2010 the authors.Peer Reviewe

Slit-Robo signals regulate pioneer axon pathfinding of the tract of the postoptic commissure in the mammalian forebrain

11 p., 5 figures and references.During early vertebrate forebrain development, pioneer axons establish a symmetrical scaffold descending longitudinally through the rostral forebrain, thus forming the tract of the postoptic commissure (TPOC). In mouse embryos, this tract begins to appear at embryonic day 9.5 (E9.5) as a bundle of axons tightly constrained at a specific dorsoventral level. We have characterized the participation of the Slit chemorepellants and their Robo receptors in the control of TPOC axon projection. In E9.5-E11.5 mouse embryos, Robo1 and Robo2 are expressed in the nucleus origin of the TPOC (nTPOC), and Slit expression domains flank the TPOC trajectory. These findings suggested that these proteins are important factors in the dorsoventral positioning of the TPOC axons. Consistently with this role, Slit2 inhibited TPOC axon growth in collagen gel cultures, and interfering with Robo function in cultured embryos induced projection errors in TPOC axons. Moreover, absence of both Slit1 and Slit2 or Robo1 and Robo2 in mutant mouse embryos revealed aberrant TPOC trajectories, resulting in abnormal spreading of the tract and misprojections into both ventral and dorsal tissues. These results reveal that Slit-Robo signaling regulates the dorsoventral position of this pioneer tract in the developing forebrain.Contract grant sponsor: The Wellcome Trust; Contract grant number: GR071174; Contract grant sponsor: CONACYT; Contract grant number: 101433 (to A.V.-E.); Contract grant sponsor: CONACYT (to I.R.-C. and C.M.G.-P.); Contract grant sponsor: Program Ramón y Cajal-2004, Spanish Ministry of Health, Instituto de Salud Carlos III-CIBERSAM; Contract grant sponsor: MEC; Contract grant number: SAF2008-01004; Contract grant sponsor: NIH; Contract grant number: P20 RR-016464; Contract grant sponsor: INBRE Program of the National Center for Research Resources; Contract grant number: HD38069; Contract grant number: NS054740; Contract grant sponsor: March of Dimes; Contract grant number: 1-FY06-387 (to G.S.M.); Contract grant sponsor: DGAPA-UNAM (to A.M.).Peer reviewe

Single-Chamber Electrofermentation of Rumen Fluid Increases Microbial Biomass and Volatile Fatty Acid Production without Major Changes in Diversity

Rumen fermentation (RF) is a complex system of oxidation–reduction reactions governed by the rumen microbiota, and its end-products are the volatile fatty acids (VFAs) which constitute the main energy source for the host animal. We speculated that the process could be manipulated through electrofermentation (EF) by utilizing solid-state electrodes as electron sources. This study aimed to evaluate the effects of single-chamber EF applied (0.4 vs. 0.9 V) for 6, 12, or 24 h to rumen fluid on the resulting microbial biomass, dry matter digestibility (DMD), VFA production, NADH/NAD ratio, and composition of the rumen fluid’s bacterial communities. The application of a 0.9 V electric potential for 24 h produced the most significant changes in RF compared to the control treatment (0V), increasing microbial biomass (12%), DMD (58%), and VFA concentrations (~84%), and reducing NAD/NADH ratio (~50%) without a significant impact on bacterial diversity. These results suggest that the application of a 0.9 V electric potential allows the microbiota to better hydrolyze and digest the feed’s components and could offer an electron sink for the production of VFAs. Hence, EF can provide innovative solutions to a range of challenges that limit the RF process. Nonetheless, more studies are needed to understand how the solid electrodes and external electric energy function