7 research outputs found
Effect of Fetal Striatal and Astrocyte Transplants into Unilateral Excitotoxin-Lesioned Striatum
Studies have suggested that neurotrophic
mechanisms may underlie transplant-induced
functional recovery. Astrocytes have been
reported to be a source of neurotrophic factors.
The present study examined the possible role of
cultured astrocytes in promoting recovery of
apomorphine-induced rotation behavior in rats
with unilateral kainic acid (KA) lesions of the
striatum. Five weeks after the lesions, one group
of rats received fetal striatal tissue (E17)
transplants, another group received transplants
of cultured astrocyte suspension, and the
remaining rats received sham transplants and
served as controls. Apomorphine-induced
rotation behavior was tested 4 weeks after the
KA lesions, and 5 and 10 weeks following the
transplantation. The KA-induced rotation
behavior was reduced by the striatal transplants
but not by the cultured astrocyte transplants 5
and 10 weeks following the transplantation.
Histochemicai analysis indicated that the striatal
transplants had survived and grown and
contained neurons and glia with similar
morphology to those in the host brain.
Immunocytochemical analysis of the astrocyte
transplant sites revealed heavy glial fibrillary
acidic protein and OX-42 staining in the
transplant areas, suggesting that the
transplanted astrocytes may have survived in the host brain. Although fetal striatal
transplants can ameliorate apomorphine-induced
rotation behavior, transplants of
astrocytes alone may not be sufficient to reverse
the functional deficits produced by KA lesions
Altered Forebrain and Hindbrain Development in Mice Mutant for theGsh-2Homeobox Gene
AbstractThe patterning of the mammalian brain is orchestrated by a large battery of regulatory genes. Here we examine the developmental function of theGsh-2nonclustered homeobox gene. Whole-mount and serial sectionin situhybridizations have been used to better defineGsh-2expression domains within the developing forebrain, midbrain, and hindbrain.Gsh-2transcripts are shown to be particularly abundant in the hindbrain and within the developing ganglionic eminences of the forebrain. In addition, mice carrying a targeted mutation ofGsh-2have been generated and characterized. Homozygous mutants uniformly failed to survive more than 1 day following birth. At the physiologic level the mutants experienced apnea and reduced levels of hemoglobin oxygenation. Histologically, the mutant brains had striking alterations of discrete components. In the forebrain the lateral ganglionic eminence was reduced in size. In the hindbrain, the area postrema, an important cardiorespiratory chemosensory center, was absent. The contiguous nucleus tractus solitarius, involved in integrating sensory input to maintain homeostasis, was also severely malformed in mutants. Immunohistochemistry was used to examine the mutant brains for alterations in the distribution of markers specific for serotonergic and cholinergic neurons. In addition,in situhybridizations were used to define expression patterns of the Dlx 2 and Nkx 2.1 homeobox genes in Gsh-2 mutant mice. The mutant lateral ganglionic eminences showed an abnormal absence of Dlx 2 expression. These results better define the genetic program of development of the mammalian brain, support neuromeric models of brain development, and further suggest similar patterning function for homeobox genes in phylogenetically diverse organisms
Spatiotemporal distribution of the insulin-like growth factor receptor in the rat olfactory bulb.
Insulin-like growth factor I (IGF-I) and its receptor (IGF-IR) are involved in growth of neurons. In the rat olfactory epithelium, we previously showed IGF-IR immunostaining in subsets of olfactory receptor neurons. We now report that IGF-IR staining was heaviest in the olfactory nerve layer of the rat olfactory bulb at embryonic days 18, and 19 and postnatal day 1, with labeling of protoglomeruli. In the adult, only a few glomeruli were IGF-IR-positive, some of which were unusually small and strongly labeled. Some IGF-IR-positive fibers penetrated deeper into the external plexiform layer, even in adults. In developing tissues, IGF-IR staining co-localized with that for olfactory marker protein and growth associated protein GAP-43, but to a lesser extent with synaptophysin. In the adult, IGF-IR-positive fibers were compartmentalized within glomeruli. IGF-I may play a role in glomerular synaptogenesis and/or plasticity, possibly contributing to development of coding patterns for odor detection or identification.Fil: Ferrari, Carina Cintia. University Of Cincinnati; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Johnson, Brett A.. University of California at Irvine; Estados UnidosFil: Leon, Michael. University of California at Irvine; Estados UnidosFil: Pixley, Sarah K.. University of Cincinnati; Estados Unido
Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies
Flare frequency distributions represent a key approach to addressing one of
the largest problems in solar and stellar physics: determining the mechanism
that counter-intuitively heats coronae to temperatures that are orders of
magnitude hotter than the corresponding photospheres. It is widely accepted
that the magnetic field is responsible for the heating, but there are two
competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To
date, neither can be directly observed. Nanoflares are, by definition,
extremely small, but their aggregate energy release could represent a
substantial heating mechanism, presuming they are sufficiently abundant. One
way to test this presumption is via the flare frequency distribution, which
describes how often flares of various energies occur. If the slope of the power
law fitting the flare frequency distribution is above a critical threshold,
as established in prior literature, then there should be a
sufficient abundance of nanoflares to explain coronal heating. We performed
600 case studies of solar flares, made possible by an unprecedented number
of data analysts via three semesters of an undergraduate physics laboratory
course. This allowed us to include two crucial, but nontrivial, analysis
methods: pre-flare baseline subtraction and computation of the flare energy,
which requires determining flare start and stop times. We aggregated the
results of these analyses into a statistical study to determine that . This is below the critical threshold, suggesting that Alfv\'en
waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The
Astrophysical Journal on 2023-05-09, volume 948, page 7