Live imaging of neuronal connections by magnetic resonance: Robust transport in the hippocampal-septal memory circuit in a mouse model of Down syndrome

Connections from hippocampus to septal nuclei have been implicated in memory loss and the cognitive impairment in Down syndrome (DS). We trace these connections in living mice by Mn(2+) enhanced 3D MRI and compare normal with a trisomic mouse model of DS, Ts65Dn. After injection of 4 nl of 200 mM Mn(2+) into the right hippocampus, Mn(2+) enhanced circuitry was imaged at 0.5, 6, and 24 h in each of 13 different mice by high resolution MRI to detect dynamic changes in signal over time. The pattern of Mn(2+) enhanced signal in vivo correlated with the histologic pattern in fixed brains of co-injected 3kD rhodamine-dextran-amine, a classic tracer. Statistical parametric mapping comparing intensity changes between different time points revealed that the dynamics of Mn(2+) transport in this pathway were surprisingly more robust in DS mice than in littermate controls, with statistically significant intensity changes in DS appearing at earlier time points along expected pathways. This supports reciprocal alterations of transport in the hippocampal-forebrain circuit as being implicated in DS and argues against a general failure of transport. This is the first examination of in vivo transport dynamics in this pathway and the first report of elevated transport in DS.     

Evidence for myosin motors on organelles in squid axoplasm.

Squid axoplasm has proved a rich source for the identification of motors involved in organelle transport. Recently, squid axoplasmic organelles have been shown to move on invisible tracks that are sensitive to cytochalasin, suggesting that these tracks are actin filaments. Here, an assay is described that permits observation of organelles moving on unipolar actin bundles. This assay is used to demonstrate that axoplasmic organelles move on actin filaments in the barbed-end direction, suggesting the presence of a myosin motor on axoplasmic organelles. Indeed, axoplasm contains actin-dependent ATPase activity, and a pan-myosin antibody recognized at least four bands in Western blots of axoplasm. An approximately 235-kDa band copurified in sucrose gradients with KI-extracted axoplasmic organelles, and the myosin antibody stained the organelle surfaces by immunogold electron microscopy. The myosin is present on the surface of at least some axoplasmic organelles and thus may be involved in their transport through the axoplasm, their movement through the cortical actin in the synapse, or some other aspect of axonal function.     

Biological and immunological characterization of ATG and ALG

Antithymocyte globulin (ATG) and antilymphocyte globulin (ALG) are effective therapies in aplastic anemia; their mechanism of action is undefined. We assayed multiple properties of ATG and ALG to address the biological and immunological bases for differences between ATG and ALG and lot variation. In addition, we studied a lot reported to be inactive in an American clinical trial; however in retrospect, this lot appeared to be active in patients treated in Europe. Immunoprecipitation of thymocyte and lymphocyte membrane proteins with ATG and ALG showed between 14 and 18 major bands on SDS-PAGE, but the patterns for ATG and ALG were not identical. The ability of ATG and ALG to block binding of labeled monoclonal antibodies was assessed using flow cytometry and a radioimmunoassay. In general, there was more lot variation among ALGs than ATGs; however, all ALG lots were more potent blockers of binding of anti-HLA-DR and anti-Leu 1 antibodies than was ATG. Both ALG and ATG effectively blocked binding of anti-Leu 2a, anti- Leu 3a, anti-Leu 4, anti-Leu 5b, and anti-IL 2 receptor abs; neither blocked binding of anti-Leu 7. All preparations were capable of inducing T-cell blastogenesis, although there was considerable lot variation. All lots lysed 60% to 75% T cells in a rabbit complement- mediated cytotoxicity assay, with most having a plateau of activity at 5 to 10 ug/mL. Two lots of ALG, including the lot reported to be clinically inactive, showed less toxicity at suboptimal concentrations and did not plateau even at 80 ug/mL. In total, these results indicate important differences between ATG and ALG in general, more lot variation among ALGs than ATGs and only differences in cytotoxicity between an "inactive" lot of ALG and most, but not all, other active ATG and ALG preparations.     

An endogenous glycosylphosphatidylinositol-specific phospholipase D releases basic fibroblast growth factor-heparan sulfate proteoglycan complexes from human bone marrow cultures

Basic fibroblast growth factor (bFGF) is a hematopoietic cytokine that stimulates stromal and stem cell growth. It binds to a glycosylphosphatidylinositol (GPI)-anchored heparan sulfate proteoglycan on human bone marrow (BM) stromal cells. The bFGF- proteoglycan complex is biologically active and is released by addition of exogenous phosphatidylinositol-specific phospholipase C. In this study, we show the presence of an endogenous GPI-specific phospholipase D (GPI-PLD) that releases the bFGF-binding heparan sulfate proteoglycan and the variant surface glycoprotein (a model GPI-anchored protein) from BM cultures. An involvement of proteases in this process is unlikely, because released proteoglycan contained the GPI anchor component, ethanol-amine, and protease inhibitors did not diminish the release. The mechanism of release is likely to involve a GPI-PLD and not a GPI-specific phospholipase C, because the release of variant surface glycoprotein did not reveal an epitope called the cross- reacting determinant that is exposed by phospholipase C-catalyzed GPI anchor cleavage. In addition, phosphatidic acid (which is specifically a product of GPI-PLD-catalyzed anchor cleavage) was generated during the spontaneous release of the GPI-anchored variant surface glycoprotein. We also detected GPI-PLD-specific enzyme activity and mRNA in BM cells. Therefore, we conclude that an endogenous GPI-PLD releases bFGF-heparan sulfate proteoglycan complexes from human BM cultures. This mechanism of GPI anchor cleavage could be relevant for mobilizing biologically active bFGF in BM. An endogenous GPI-PLD could also release other GPI-anchored proteins important for hematopoiesis and other physiologic processes.     

Nodular mixed lymphoma: results of a randomized trial failing to confirm prolonged disease-free survival with COPP chemotherapy

Fifty-two patients with stage III or IV nodular mixed lymphocytic- histiocytic lymphoma (NM) were entered on a prospective randomized trial comparing cyclophosphamide-prednisone (CP) to either COPP (cyclophosphamide, vincristine, procarbazine, prednisone) or BCVP (BCNU, cyclophosphamide, vincristine, prednisone). The COPP regimen utilized in this Eastern Cooperative Oncology Group (ECOG) trial was similar to the four-drug regimen C-MOPP reported by the National Cancer Institute to achieve prolonged relapse-free survival in this histology. No significant differences in complete response rates, response duration, or overall survival were noted among the three regimens. A pattern of continuous late relapse was observed for all three chemotherapy programs. Although 11 of the 18 (61%) COPP patients achieved a complete response, only 3/11 (27%) remain disease-free with a median follow-up of over 3 yr. However, two of these three long-term complete responders have died with no clinical evidence of recurrent disease. The COPP patients received 84% of the calculated ideal doses of cyclophosphamide and 78% of the ideal dosage of procarbazine. Grade 3-4 hematologic toxicity was noted in 22% of the COPP group, 36% with BCVP, and 0% for the CP patients. We were unable to confirm the ability of COPP to achieve durable complete remissions in NM lymphoma. The cyclophosphamide-prednisone combination was equally effective when compared with COPP and BCVP, but produced minimal toxicity.     

Asymmetric polyarthritis as an initial presentation of Rosai‐Dorfman disease

Rosai‐Dorfman disease (RDD) is a rare benign reactive lymphoproliferative disorder characterised by a histopathological pattern with sinus histiocytosis and hemophagocytosis. It usually presents with fever, elevated erythrocyte sedimentation rate, cervical lymphadenopathy, other lymph node and extra‐nodal site involvement. We present the case of a 25‐year‐old female patient with polyarthritis mimicking rheumatoid arthritis (RA). When the para‐aortic lymph node was biopsied, it showed extensive histiocytic proliferation; some clusters of plasma cells, lymphocytes and rare multinucleated cells were seen, suggesting a diagnosis of RDD. There is nothing in the literature regarding the polyarthritic presentation of the disease. To the best of our knowledge, our patient is the first case of RDD presenting with a clinical picture mimicking atypical seronegative RA.