Contamination of catheter-drawn blood cultures.

To assess the risk of contamination, we reviewed retrospectively 1,408 matched pairs of simultaneous catheter-drawn and venipuncture blood cultures. Catheter-drawn cultures were equally likely to be truly positive (14.4 versus 13.7%) but more likely to be contaminated (3.8 versus 1.8% [P = 0.001]). Direct venipuncture cultures are preferred.

Promotion of the development of enteric neurons and glia by neuropoietic cytokines: interactions with neurotrophin-3.

Neurotrophin-3 (NT-3) is known to promote enteric neuronal and glial development. Ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) were investigated to test the hypothesis that the development of subsets of enteric neurons and/or glia is also affected by a neuropoietic cytokine, by itself, or together with NT-3. Crest-derived cells, immunoselected from the fetal rat gut (E14) with antibodies to p75NTR, were found by RT-PCR and immunocytochemistry (after culture) to express both alpha (CNTER alpha) and beta components (gp130 and LIFR beta) of the tripartite CNTF receptor. In situ, myenteric ganglia below the esophagus were CNTFR alpha-immunoreactive by E16-E18. In vitro, CNTF and LIF induced in crest-derived cells nuclear translocation of STAT3 (signal transducer and activator of transcription 3), a concentration-dependent increase in expression of neuronal or glial markers, and a decrease in expression of the precursor marker, nestin. LIFR beta was expressed by more cells than CNTFR alpha; therefore, although the factors were equipotent, the maximal effect of LIF > CNTF. The cytokines and NT-3 were additive in promoting neuronal but not glial development. Specifically, the development of neurons expressing NADPH-diaphorase activity (an early marker found in inhibitory motor neurons) was promoted by CNTF and NT-3. These observations support the idea that a ligand for the tripartite CNTF receptor complex plays a role in ENS development.

Immunohistochemical localization of netrin-1 in the embryonic chick nervous system.

Netrin-1 has profound in vitro effects on the growth properties of vertebrate embryonic axons. In addition, netrin-1 mRNA is found in the floor plate of the embryonic nervous system, an intermediate target of many axons, including commissural axons that are affected by netrin-1 in vitro. Moreover, genetic studies of netrin-1 homologs in Caenorhabditis elegans and Drosophila implicate these proteins in commissure formation. We raised polyclonal antisera that recognize chick netrin-1 in fixed tissue sections. The antisera were used to immunohistochemically map netrin-1 in the embryonic spinal cord, brain, and retina. The relationship between netrin-1 localization and the growth of pioneering axons suggests roles for netrin-1 in the regulation of circumferential, commissural, and longitudinal axon growth in the spinal cord and brain. The data also suggest that the primary or sole effect of netrin-1 on pioneering spinal cord commissural axons is haptotactic. Furthermore, the pattern of netrin-1 localization raises the possibility that this protein helps mediate neuronal migration in the spinal cord, brain, and retina.

Immunohistochemical localization of ciliary neurotrophic factor receptor alpha expression in the rat nervous system.

Ciliary neurotrophic factor receptor alpha (CNTFR alpha) is essential for normal embryonic development and may be involved in postnatal and adult neuronal maintenance. In addition, a rapidly growing body of evidence suggests that CNTFR alpha serves as a site of action for future growth factor therapeutics capable of treating a wide variety of disorders resulting from neuronal loss. We raised two polyclonal, anti-CNTFR alpha antisera against synthetic peptides corresponding to independent regions of rat CNTFR alpha. Western blot and immunohistochemical analyses indicated that affinity-purified preparations of both antisera specifically recognize CNTFR alpha. In the adult brain, the highest levels of CNTFR alpha immunoreactivity were found in the perikarya, dendrites and, occasionally, the axons of several distinct classes of neurons including hippocampal formation neurons, some sensory neurons, and many neurons involved in motor control. CNTFR alpha immunoreactivity also was concentrated in the following: perikarya, dendrites, and axons of ventral horn motor neurons in adult spinal cord; perikarya and axons of adult dorsal root ganglion neurons; and axons in adult peripheral nerve. In embryonic tissue, the highest levels of CNTFR alpha immunoreactivity were observed in differentiating neurons and their processes. Therefore, the present data suggest that CNTFR alpha serves several diverse functions in adulthood and during development.

Ciliary neurotrophic factor receptor alpha mRNA in NB41A3 neuroblastoma cells: regulation by cAMP.

Ciliary neurotrophic factor (CNTF) affects the in vitro and in vivo survival and differentiation of several classes of neurons by binding to the CNTF receptor alpha. We examined the possibility that intracellular cAMP can regulate CNTF receptor alpha mRNA levels in two neuronal cell lines that display cAMP-dependent process outgrowth. Dibutyryl cAMP did not affect CNTF receptor alpha mRNA levels in PC12 cells but elicited a dose- and time-dependent increase in NB41A3 cell CNTF receptor alpha mRNA levels. Forskolin similarly increased CNTF receptor alpha mRNA levels in NB41A3 cells. The data suggest that signal transduction mechanisms involving cAMP may 'crosstalk' with CNTF-initiated signal transduction in a cell type-specific manner and that CNTF receptor alpha expression is not generally linked to neuronal process outgrowth.