LN-6: a monoclonal antibody to vimentin expressed in non-hematopoietic mesenchymal cells and derived tumors and reactive in B5-fixed, paraffin-embedded tissues

A novel mouse model of glucagon-like peptide-1 receptor expression: A look at the brain

Glucagon-like peptide-1 (GLP-1) is an incretin hormone with a number of functions to maintain energy homeostasis and contribute to motivated behavior, both peripherally and within the central nervous system (CNS). These functions, which include insulin secretion, gastric emptying, satiety, and the hedonic aspects of food and drug intake, are primarily mediated through stimulation of the GLP-1 receptor. While this receptor plays an important role in a variety of physiological outcomes, data regarding its CNS expression has been primarily limited to regional receptor binding and single-label transcript expression studies. We thus developed a bacterial artificial chromosome transgenic mouse, in which expression of a red fluorescent protein (mApple) is driven by the GLP-1R promoter. Using this reporter mouse, we characterized the regional and cellular expression patterns of GLP-1R expressing cells in the CNS, using double-label immunohistochemistry and in situ hybridization. GLP-1R-expressing cells were enriched in several key brain regions and circuits, including the lateral septum, hypothalamus, amygdala, bed nucleus of the stria terminalis, hippocampus, ventral midbrain, periaqueductal gray, and cerebral cortex. In most regions, GLP-1R primarily colocalized with GABAergic neurons, except within some regions such as the hippocampus, where it was co-expressed in glutamatergic neurons. GLP-1R-mApple cells were highly co-expressed with 5-HT3 receptor-containing neurons within the cortex and striatum, as well as with dopamine receptor- and calbindin-expressing cells within the lateral septum, the brain region in which GLP-1R is most highly expressed. In this manuscript, we provide detailed images of GLP-1R-mApple expression and distribution within the brain and characterization of these neurons.

Postnatal growth of the human pons: a morphometric and immunohistochemical analysis

Despite its critical importance to global brain function, the postnatal development of the human pons remains poorly understood. In the present study, we first performed magnetic resonance imaging (MRI)-based morphometric analyses of the postnatal human pons (0-18 years; n = 6-14/timepoint). Pons volume increased 6-fold from birth to 5 years, followed by continued slower growth throughout childhood. The observed growth was primarily due to expansion of the basis pontis. T2-based MRI analysis suggests that this growth is linked to increased myelination, and histological analysis of myelin basic protein in human postmortem specimens confirmed a dramatic increase in myelination during infancy. Analysis of cellular proliferation revealed many Ki67(+) cells during the first 7 months of life, particularly during the first month, where proliferation was increased in the basis relative to tegmentum. The majority of proliferative cells in the postnatal pons expressed the transcription factor Olig2, suggesting an oligodendrocyte lineage. The proportion of proliferating cells that were Olig2(+) was similar through the first 7 months of life and between basis and tegmentum. The number of Ki67(+) cells declined dramatically from birth to 7 months and further decreased by 3 years, with a small number of Ki67(+) cells observed throughout childhood. In addition, two populations of vimentin/nestin-expressing cells were identified: a dorsal group near the ventricular surface, which persists throughout childhood, and a parenchymal population that diminishes by 7 months and was not evident later in childhood. Together, our data reveal remarkable postnatal growth in the ventral pons, particularly during infancy when cells are most proliferative and myelination increases.

TrkA immunoreactive astrocytes in dendritic fields of the hippocampal formation across estrous

Neurotrophins are important modulators of structural synaptic plasticity. (Through trophic action (Jordan. J Neurobiol 40:434-445, 1999), astrocytes serve as permissive substrates to support axonal regrowth (Ridet et al. Trends Neurosci 20:570-571, 1997), and are involved in estrogen-induced synaptic structural plasticity (Garcia-Segura et al. Cell Mol Neurobiol 16:225-237, 1996). Previously, we reported that tyrosine kinase A receptor (TrkA) immunoreactivity was present both in presynaptic neuronal processes (axons and terminals) and in select astrocytes of the male rat hippocampal formation (Barker-Gibb et al. J Comp Neurol 430:182-199, 2001). We show that the number of TrkA-immunoreactive astrocytes in female rats fluctuates 16-fold across the estrous cycle in dendritic fields of the hippocampal formation, with the greatest number at estrus after the peak plasma estradiol concentration of proestrus. Few TrkA-labeled astrocytes were found in ovariectomized animals; after estrogen replacement, this number increased by 12-fold in the hippocampal formation, indicating estrogen-mediated induction. Dual-labeling studies showed that TrkA-labeled astrocytes were also immunoreactive for vimentin, a protein expressed by reactive astrocytes. Ultrastructural analysis of the dentate gyrus molecular layer demonstrated that TrkA immunoreactive astrocytes are positioned primarily next to dendrites and unmyelinated axons. Because nerve growth factor (NGF) has been reported to stimulate astrocytes to function as substrates for axon growth (Kawaja and Gage. Neuron 7:1019-1030, 1991), these findings are consistent with the theory that TrkA immunoreactive astrocytes serve a role in structural plasticity, axon guidance, and synaptic regeneration across the estrous cycle in the hippocampal formation.

Tanycytes present in the adult rat mediobasal hypothalamus support the regeneration of monoaminergic axons

We have recently shown that tanycytes present in the median eminence (ME) constitute a preferential support for the regeneration of lesioned neurohypophysial oxytocinergic and vasopressinergic axons. However, although tanycytes are particularly abundant in the ME, they are also present along the third ventricle wall. This study was thus undertaken to determine whether tanycytes present in the mediobasal hypothalamus overlying the ME were also able to support the regeneration of the numerous monoaminergic axons innervating this region. Using confocal laser scanning microscopy combined with double or triple fluorescence immunostaining, we have compared the relationships occurring between glial cells and lesioned catecholaminergic and serotonergic axons at the levels of surgical cuts placed in the dorsomedial hypothalamus devoid of tanycytes or in the ventromedial hypothalamus containing numerous tanycyte processes. In dorsal lesions, catecholaminergic and serotonergic transected fibers were found to abut onto the scar formed along the surgical cut and composed of closely inderdigitating astrocyte processes strongly immunoreactive for both glial fibrillary acidic protein (GFAP) and vimentin (VIM). In ventral lesions, the lesional scar was composed of GFAP-immunoreactive (IR) and VIM-IR astrocyte processes and of VIM-IR but GFAP-negative processes that were identified as tanycytic processes. In all the ventral lesions examined, numerous catecholaminergic and serotonergic fibers were found to regenerate into the surgical cut in association with the VIM-IR, GFAP-negative tanycyte processes. On the other hand, such regenerating fibers were never found in scar portions containing only GFAP-IR astrocytic structures. These data indicate that, like in the ME, tanycytes present in the mediobasal hypothalamus of adult rat provide a substrate that favors the regeneration of lesioned axons.

Fas and Fas ligand in embryos and adult mice: ligand expression in several immune-privileged tissues and coexpression in adult tissues characterized by apoptotic cell turnover

The cell surface receptor Fas (FasR, Apo-1, CD95) and its ligand (FasL) are mediators of apoptosis that have been shown to be implicated in the peripheral deletion of autoimmune cells, activation-induced T cell death, and one of the two major cytolytic pathways mediated by CD8+ cytolytic T cells. To gain further understanding of the Fas system., we have analyzed Fas and FasL expression during mouse development and in adult tissues. In developing mouse embryos, from 16.5 d onwards, Fas mRNA is detectable in distinct cell types of the developing sinus, thymus, lung, and liver, whereas FasL expression is restricted to submaxillary gland epithelial cells and the developing nervous system. Significant Fas and FasL expression were observed in several nonlymphoid cell types during embryogenesis, and generally Fas and FasL expression were not localized to characteristic sites of programmed cell death. In the adult mouse, RNase protection analysis revealed very wide expression of both Fas and FasL. Several tissues, including the thymus, lung, spleen, small intestine, large intestine, seminal vesicle, prostate, and uterus, clearly coexpress the two genes. Most tissues constitutively coexpressing Fas and FasL in the adult mouse are characterized by apoptotic cell turnover, and many of those expressing FasL are known to be immune privileged. It may be, therefore, that the Fas system is implicated in both the regulation of physiological cell turnover and the protection of particular tissues against potential lymphocyte-mediated damage.