Congenital Absence of the Gallbladder: Case Report

The virus of human poliomyelitis has been demonstrated in excretions before onset of the disease, during the disease, and in convalescence. It may be confused with different viruses likely to be found in the same sources in clinical conditions resembling poliomyelitis.Immunologic differences between strains of poliomyelitis virus have been detected so that three types are now evident. The distribution of these types and their importance as causes of epidemics are not known. This multiplicity of immunologic types is an important factor in considering immunization of humans. Commercial manufacture of vaccines faces many technical problems.Recently the Coxsackie virus has been demonstrated in humans with a disease closely resembling poliomyelitis.     

PCR-based methods for identification of species of the Anopheles minimus group: allele-specific amplification and single-strand conformation polymorphism

We report two polymerase chain reaction (PCR)-based methods for distinguishing morphologically similar species based on amplification of a variable region of the 28S gene of ribosomal DNA. The four species we investigated are mosquitoes of the Anopheles minimus group: An. aconitus, An. varuna and An. minimus species A and C. The formally named species are vectors of human malaria parasites in south-east Asia but are difficult to distinguish with certainty on the basis of morphology. Allele-specific amplification was used to differentiate An. minimus A from An. minimus C. This technique has been widely used for the diagnosis of species. Single-strand conformation polymorphisms (SSCPs) were used to separate all four species. This technique, which has seldom been used for species identification, has many advantages: it does not require sequence information beyond that needed for amplification; it is ideally suited for the detection of heterozygotes; it utilizes more of the information in the PCR product than allele-specific amplification; it distinguishes all four species considered here and could easily be extended to other species; previously unknown intraspecific variation and additional species are likely to be detected. Thus, SSCPs provide valuable population genetic information which allele-specific amplification does not.     

Neural Stem Cells as Engraftable Packaging Lines Can Mediate Gene Delivery to Microglia: Evidence from Studying Retroviral env-Related Neurodegeneration

The induction of spongiform myeloencephalopathy by murine leukemia viruses is mediated primarily by infection of central nervous system (CNS) microglia. In this regard, we have previously shown that CasBrE-induced disease requires late, rather than early, virus replication events in microglial cells (W. P. Lynch et al., J. Virol. 70:8896-8907, 1996). Furthermore, neurodegeneration requires the presence of unique sequences within the viral env gene. Thus, the neurodegeneration-inducing events could result from microglial expression of retroviral envelope protein alone or from the interaction of envelope protein with other viral structural proteins in the virus assembly and maturation process. To distinguish between these possible mechanisms of disease induction, we engineered the engraftable neural stem cell line C17-2 into packaging/producer cells in order to deliver the neurovirulent CasBrE env gene to endogenous CNS cells. This strategy resulted in significant CasBrE env expression within CNS microglia without the appearance of replication competent virus. CasBrE envelope expression within microglia was accompanied by increased expression of activation markers F4/80 and Mac-1 (CD11b) but failed to induce spongiform neurodegenerative changes. These results suggest that envelope expression alone within microglia is not sufficient to induce neurodegeneration. Rather, microglia-mediated disease appears to require neurovirulent Env protein interaction with other viral proteins during assembly or maturation. More broadly, the results presented here prove the efficacy of a novel method by which neural stem cell biology may be harnessed for genetically manipulating the CNS, not only for studying neurodegeneration but also as a paradigm for the disseminated distribution of retroviral vector-transduced genes.     

Expression of B7 molecules in recipient, not donor, mice determines the survival of cardiac allografts.

Blockade of the CD28/CTLA4/B7 costimulatory pathway using CTLA4-Ig has great therapeutic potential, and has been shown to prolong allograft survival in a variety of animal models. To gain further insight into the mechanism by which costimulatory blockade prevents allograft rejection, we studied cardiac allograft survival in the complete absence of B7 costimulation using mice lacking B7-1 and B7-2 (B7-1/B7-2-/- mice). To determine the role of B7 on donor vs recipient cells, we used B7-1/B7-2-/- mice as either donors or recipients of allografts. Wild-type (WT) recipients acutely reject fully allogeneic hearts from both WT and B7-1/B7-2-/- mice. In contrast, B7-1/B7-2-/- recipients allow long-term survival of grafts from both WT and B7-1/B7-2-/- mice, with minimal histologic evidence of either acute or chronic rejection in grafts harvested after 90 days. The B7-1/B7-2-/- mice acutely reject B7-1/B7-2-/- allografts if CD28 stimulation is restored by the administration of Ab to CD28 and can mount an alloresponse in mixed lymphocyte reactions. Therefore, B7-1/B7-2-/- mice are capable of generating alloresponses both in vivo and in vitro. Our results demonstrate that in the alloresponse to mouse heterotopic cardiac transplantation, B7 molecules on recipient cells rather than donor cells provide the critical costimulatory signals. The indefinite survival of allografts into B7-1/B7-2-/- recipients further shows that the absence of B7 costimulation alone is sufficient to prevent rejection.     

The Effects of Inhibitors Upon Pore Formation by Diphtheria Toxin and Diphtheria Toxin T Domain

The formation of pores by membrane-inserted diphtheria toxin is closely linked to the translocation of its catalytic chain across membranes. In this report a number of aromatic polyanionic molecules were identified that inhibit toxin-induced leakage of molecules from model membrane vesicles. One inhibitor, Cibacron blue, totally blocked pore formation. Aniline blue and Fast Green decreased the size of the molecule released by a given concentration of toxin. Amaranth appeared to reduce the maximal amount of leakage, without greatly affecting the size of the molecule released at a given toxin concentration. Finally, Ponceau S and Cibacron brilliant red appeared to exhibit a mixture of these various types of inhibition. The inhibitors neither prevented the conformational transition of the toxin to form a hydrophobic state at low pH, nor (with the exception of Cibacron Brilliant Red) appeared to strongly inhibit toxin binding to model membranes. Additional experiments showed release of trapped materials from model membranes by isolated T domain of the toxin was similar to that by whole toxin. The effects of inhibitors on T domain induced release was also similar to that they have on whole toxin. Therefore, it is likely that the inhibition of pore formation by whole toxin involves inhibitor interaction with the T domain. The inhibitors identified in this study may be helpful for development of agents that interfere with toxin action in vivo. Received: 10 March 1999/Revised: 22 June 1999