CD71 is selectively and ubiquitously expressed at high levels in erythroid precursors of all maturation stages: a comparative immunochemical study with glycophorin A and hemoglobin A.

Histology assessment of erythroid precursors in bone marrow biopsies can be challenging under pathologic conditions and often requires ancillary studies. CD71 (transferring receptor-1) is known to be expressed in the earliest erythroid precursors, and has been useful for flow cytometry. However, CD71 is also regarded as a proliferation marker, and its lineage specificity has not been systemically investigated by immunohistochemistry in detail. In this study, we found that CD71 was strongly expressed in all erythroid precursors in normal and dyspoietic marrows. Staining of CD71 effectively highlighted pronormoblasts in all 4 cases of parvovirus infection and erythroblasts in all 6 cases of acute erythroleukemia, for which staining of glycophorin A and hemoglobin A was either absent or unreliable. CD71 was absent in the background mature red blood cells in general, nonerythroid elements in the normal marrow, myeloid precursors in myeloproliferative disorders, and blasts in nearly all acute myeloid leukemia encompassing all common French-American-British subtypes. Benign lymphoid infiltrates and low-grade lymphomas involving the marrow also lacked detectable CD71. Although weak CD71 expression was found in acute lymphoblastic leukemia, diffuse large B-cell lymphoma, and 1 of 2 cases of acute megakaryoblastic leukemia, it had little impact on interpretation due to a high signal-to-noise ratio of the staining intensities when compared with erythroid precursors in the same section. We conclude that CD71 is selectively expressed at high levels in erythroid precursors, including those at early maturation stages. It can be reliably used as an independent erythroid marker for immunohistochemical analysis of the marrow.

Neural-specific inactivation of ShcA results in increased embryonic neural progenitor apoptosis and microencephaly.

Brain size is precisely regulated during development and involves coordination of neural progenitor cell proliferation, differentiation, and survival. The adapter protein ShcA transmits signals from receptor tyrosine kinases via MAPK (mitogen-activated protein kinase)/ERK (extracellular signal-regulated kinase) and PI3K (phosphatidylinositol 3-kinase)/Akt signaling pathways. In the CNS, ShcA expression is high during embryonic development but diminishes as cells differentiate and switches to ShcB/Sck/Sli and ShcC/N-Shc/Rai. To directly test ShcA function in brain development, we used Cre/lox technology to express a dominant-negative form of ShcA (ShcFFF) in nestin-expressing neural progenitors. ShcFFF-expressing mice display microencephaly with brain weights reduced to 50% of littermate controls throughout postnatal and adult life. The cerebrum appeared most severely affected, but the gross architecture of the brain is normal. Body weight was mildly affected with a delay in reaching mature weight. At a mechanistic level, the ShcFFF microencephaly phenotype appears to be primarily attributable to elevated apoptosis levels throughout the brain from embryonic day 10.5 (E10.5) to E12, which declined by E14.5. Apoptosis remained at normal basal levels throughout postnatal development. Proliferation indices were not significantly altered in the embryonic neuroepithelium or within the postnatal subventricular zone. In another approach with the same nestin-Cre transgene, conditional deletion of ShcA in mice with a homozygous floxed shc1 locus also showed a similar microencephaly phenotype. Together, these data suggest a critical role for ShcA in neural progenitor survival signaling and in regulating brain size.

Local anesthetic effects of cocaethylene and isopropylcocaine on rat peripheral nerves.

Cocaethylene is a naturally occurring cocaine derivative that has been used as a tool in both clinical studies of cocaine reward and as a potential model compound for agonist substitution therapy in cocaine dependence. It is equipotent to cocaine at inhibiting dopamine uptake in-vitro and in-vivo. Because it has been reported that local anesthetic properties may influence the reinforcing effects of dopamine uptake inhibitors, we investigated the local anesthetic properties of cocaethylene as well as isopropylcocaine, another potential pharmacological tool in studies of cocaine reward and agonist substitution therapy. We compared the efficacy of nerve impulse blockade by lidocaine, cocaine, cocaethylene and isopropylcocaine using rat sciatic nerves and dorsal roots (DRs). Nerves were placed in a modified sucrose gap chamber and repetitively stimulated at high frequency. The amplitude of compound action potentials (CAPs) at the beginning and end of each stimulus train was measured before and after exposure to each compound. All compounds produced concentration-dependent and use-dependent decrements in CAP amplitude, but cocaethylene and isopropylcocaine at medium to high concentration (0.375-1.875 mM) showed a more prolonged block after washout relative to cocaine or lidocaine. Patch clamp studies on dorsal root ganglion (DRG) neurons indicated a use-dependent blockade of sodium channels. These studies provide a more complete understanding of the pharmaocology of potential agonist treatment candidates, and suggest a mechanism whereby cocaethylene produces a decreased euphoria in humans compared to cocaine.