Divergent glial fibrillary acidic protein and its mRNA in the activated supraoptic nucleus

Previous studies have shown decreased immunoreactive glial fibrillary acidic protein (GFAP) in the supraoptic nucleus (SON) when magnocellular neuroendocrine cells (MNCs) are activated by lactation or dehydration. This is thought to underlie structural plasticity of glial processes that occurs during these times. Here, we investigated how this apparent reduction in protein relates to GFAP mRNA expression in the dehydrated rat as visualized by in situ hybridization. Densitometry of silver grains in the SON revealed low levels of mRNA expression in control, 2-day dehydrated and 21-day rehydrated (R21) animals. Conversely, the SON from 7-day dehydrated (D7) subjects displayed significantly more silver grains. Thus, the pattern of GFAP mRNA expression is the inverse of what we previously observed for GFAP immunoreactivity in tissue sections of the SON. No differences in mRNA levels due to hydration state were seen in the lateral hypothalamic area, suggesting that increases in GFAP mRNA at D7 were specifically related to MNC activation. These data indicate a divergence in GFAP mRNA and protein expression in the SON.     

Adventitious knot formation complicating catheterization of the infant bladder

Bladder catheterization is a common technique employed in obtaining urine for culture, monitoring urine output and for diagnostic radiological procedures. We present two cases of knot formation in male infants catheterized with a 5 gauge feeding tube. We discuss avoidance, recognition and management of this complication.     

Perinatal hypoxia/ischemia damages and depletes progenitors from the mouse subventricular zone

Hypoxia-ischemia (H/I) as a result of asphyxia at term remains a major cause of neurologic disability. Our previous studies in the P7 rat model of perinatal H/I have shown that progenitors within the subventricular zone (SVZ) are vulnerable to this insult. Since many investigators are using transgenic and knockout mice to determine the importance of specific molecules in the evolution of damage after a stroke, there is a need to perform comparative studies on the relative vulnerability of the mouse SVZ. Here we assess damage to the SVZ of 5-, 7- and 10-day-old C57BL/6 mice after unilateral common carotid artery cauterization followed by 70 min of H/I (10% O2). Whereas 5- and 7-day-old mice sustained little SVZ damage as assessed by hematoxylin and eosin staining, there was a 16% reduction of cellularity in 10-day-old animals by 18 h of recovery. Additionally, swollen cells were observed in the medial region of the SVZ of 10-day-old mice. However, few caspase-3+ and TUNEL+ cells were observed in this region, which contains the putative neural stem cells. Rather, the majority of the dying cells were situated in the mediolateral and lateral tail of the SVZ. At 18 h of recovery, there was a 2-fold increase in the frequency of TUNEL+ cells in the ipsilateral SVZ as well as a 3-fold increase in the frequency of active-caspase-3+ cells. We conclude that progenitors within the neonatal mouse SVZ are vulnerable to hypoxic/ischemic insult. The demise of these early progenitors likely leads to depletion of neuronal and late oligodendrocyte progenitors, contributing to cerebral dysgenesis.     

Astrocytic ceruloplasmin expression,which is induced by IL-1beta and by traumatic brain injury,increases in the absence of the IL-1 type 1 receptor

IL-1alpha and IL-1beta are induced immediately after insults to the brain, and signaling through the type 1 IL-1 receptor is essential for a normal microglial and astroglial response to injury. To better understand which genes are induced in astrocytes by IL-1beta, we used the unbiased technique of differential display to analyze mouse astroglial gene expression after IL-1beta treatment. Two novel genes were induced, as well as the gene for ceruloplasmin, a ferroxidase with antioxidant properties. Ceruloplasmin was analyzed further by Northern and Western blot. RNA and protein levels of ceruloplasmin were increased when astrocytes were treated with IL-1beta. To determine whether the IL-1 type 1 receptor (IL-1R1) is essential for the injury-induced expression of ceruloplasmin, a Western blot analysis was performed after a traumatic brain injury on mice that were IL-1R1-deficient. Ceruloplasmin increased significantly above controls after injury; however, injury-induced levels of ceruloplasmin were lower in IL-1R1-deficient (2.7-fold increase) than in the wild-type animals (3.5-fold increase). These data indicate that while IL-1R1 deletion has a slight effect on ceruloplasmin expression, it is not essential for either the basal or the induced expression of ceruloplasmin in vivo. Since ceruloplasmin buffers free copper, oxidizes ferrous iron, and catalyzes the dismutation of free radicals, increased levels of ceruloplasmin likely protect neurons and glia from sustaining damage after injury. Furthermore, as the IL-1R1 has been proposed to be a target for achieving neuroprotection after injury, these data suggest that the protection afforded by ceruloplasmin will be retained even when the IL-1R1 is antagonized.     

Astrocytes produce CNTF during the remyelination phase of viral-induced spinal cord demyelination to stimulate FGF-2 production

Multiple sclerosis is characterized by multiple lesions with selective loss of myelin and oligodendrocytes, leading to deficits of sensation and movement, as well as cognitive disabilities. Consequently, a major research endeavor is to identify strategies to enhance oligodendrocyte regeneration and remyelination. FGF-2 is a potent mitogen for OPCs, and it is induced in astrocytes in animal models of demyelinating diseases in conjunction with successful remyelination. However, the factors responsible for inducing FGF-2 after demyelination in astrocytes are unknown. Here we show that CNTF mRNA and protein increase coincident with spinal cord remyelination in mice recovering from MHV-induced demyelination. We identify CNTF within astrocytes surrounding and within remyelinating lesions, and show that CNTF increases FGF-2 ligand and receptor mRNAs in spinal cord after direct application. Furthermore, we show that CNTF increases FGF-2 mRNA approximately 2.5-fold in cultured mouse spinal cord astrocytes. Altogether, these results strongly implicate CNTF as an important cytokine in demyelinating disease and as an upstream regulator of FGF-2 production in astrocytes during early remyelination.     

Neural stem cells in the subventricular zone are a source of astrocytes and oligodendrocytes,but not microglia

The developmental origin of microglia remains a controversial subject. While it is generally accepted that primitive fetal macrophages that migrate from the yolk sac to the brain become microglia, it also has been argued that there is a second source of microglia that are of neuroectodermal lineage. To determine whether progenitors in the dorsolateral subventricular zone (SVZDL) are capable of producing microglia as well as macroglia, we infected perinatal rat SVZDL cells with a mixture of two replication-deficient retroviruses, placed these progenitors in vitro and then varied the media formulations to promote microglial differentiation. Mixed macroglial clones were obtained, but no heterogeneous clones containing microglia were observed, regardless of the media components. Among the macroglial clones, we observed every possible combination of type 1 astrocyte and O-2A lineage cells. Some clones were homogeneous and contained cells belonging to a single macroglial lineage. Other clonal clusters were heterogeneous and were comprised of type 1 astrocytes and oligodendrocytes, type 1 and type 2 astrocytes, or type 2 astrocytes and oligodendrocytes. Of 130 clones examined, where we used triple immunofluorescence with antibodies that recognize microglia, 2 clonal clusters contained OX-42+ microglia that were retrovirally labeled, but all of the cells in those clones expressed the microglial marker and none expressed either GFAP or O4. In addition, we isolated neural stem cells from the perinatal SVZDL and assessed their capacity to generate macroglia and microglia. Confirming and extending our previous analyses, neural stem cells generated homogeneous and heterogeneous macroglial clones, but they did not generate microglia. We conclude that brain macroglia and microglia do not share a common precursor, even though the neural stem cells in the SVZDL cells can produce neurons, astrocytes and oligodendrocytes. Therefore, the microglia that reside in the SVZDL are immigrants from nonneural precursors.     

Methacholine Inhalational Challenge in the Evaluation of Chronic Cough in Children

The medical records of 58 children (age range, 7 to 16 years) who presented with chronic cough were retrospectively analyzed to determine the value of methacholine (MCH) bronchial challenge in reaching a specific diagnosis. Baseline lung function tests were normal in all subjects, apart from an elevated residual volume/total lung capacity ratio (RV/ TLC) in 11 patients, and a reduced midexpiratory flow rate (FEF_25-75) in five of these patients. Thirty-one patients had a positive response to MCH, but these patients could not be identified on the basis of clinical criteria or spirometric parameters. MCH-positive patients did have a significantly higher RV/ TLC than did MCH-negative patients. Twenty-seven of the 31 MCH-positive patients responded to a trial of bronchodilator therapy (albuterol/the-ophylline), confirming the diagnosis of cough variant asthma in these patients. We conclude that children with chronic cough should be considered for methacholine challenge in order to identify patients who are likely to benefit from specific bronchodilator therapy.