Biomedical subjects
Publications and source records attributed to Y Chu.
A rapid and small-scale method for screening vaccinia virus recombinants employing micrococcal nuclease is described. This protocol utilizes the differential sensitivity of cellular and viral DNA to the nuclease, which can be selectively activated by addition of Ca2+ and inactivated by elimination of Ca2+. Two to five micrograms of viral DNA can be obtained from one infected L cell plate (50 mm) after overnight incubation.
McAb-HI98 has been proved to bind specifically to HL60 cells. In this study, we further observed the specific binding of HI98-Daunorubicin (DNR) conjugate to HL60 cells, the transmembranal transport of HI98-DNR and the process of internalization by immunoelectron microscopy. After HL60 cells were incubated with HI98-DNR-Au, gold particles were first found on the surface membranes of HL60 cells, and then inside the cells. Internalization was found to occur through the formation of endocytic vesicles. Results indicate that the immunoconjugate selectively binds to target cells and enters the cells specifically and rapidly, thus enhancing intracellular drug concentration.
Under exhaustive digestion conditions P1 nuclease was found to cleave a subpopulation of intracellular SV40 chromatin only once. The major P1 cleavage site in SV40 DNA was mapped at the origin of DNA replication, and the two minor sites at the SV40 enhancers. The P1-sensitive SV40 chromatin subpopulation was found to have higher superhelical density than the bulk of the intracellular SV40 chromatin. Furthermore, pulse labeled SV40 DNA which had higher superhelical density than that of the steady state viral DNA (S.S. Chen and M.T.Hsu, J. Virol 51:14-19, 1984) was also found to be preferentially cleaved by P1 nuclease. These results are consistent with a supercoil-dependent alteration of chromatin conformation near the regulatory region of the viral genome that can be recognized by P1 nuclease. Since P1 nuclease cleaves the subpopulation of SV40 chromatin only once without further degradation, this nuclease can be used as a general tool to define viral or cellular chromatin fraction with altered chromatin conformation and to map nuclease hypersensitive sites. Preliminary studies indicate that P1 makes limited double stranded cleavages in cellular chromatin to generate large DNA fragments.
Monocyte functions of Storrs strain muscular dystrophic (MD) chickens and Storrs control strain were compared. After short-term in vitro culture of monocytes, cells taken from Storrs MD chickens had a significantly lower incidence of cells capable of phagocytizing sheep red blood cells than did cells cultured from the control strain. In contrast, no difference was found in the ability of MD vs. control strain blood mononuclear cells to undergo in vitro chemotaxis in response to a bacterial culture supernatant. The study also revealed a distinct peripheral blood leukocyte profile of young MD chickens: elevated percentages and absolute numbers of granulocytes. The total leukocyte count in MD chickens was not significantly different from that of normal chickens. These findings extend previous observations concerning altered reticuloendothelial system function in MD strain chickens.
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Temporal changes in the recruitment and functional activation of Cornell K strain chicken peritoneal macrophages elicited by starch and dextrans were determined. During a 72-hr period following intraperitoneal injection, Sephadex (cross-linked dextran) elicited a gradually increasing number of peritoneal exudate cells (PECs) which contained greater than or equal to 78% macrophages in the adherent cell population. In contrast, starch tended to elicit higher numbers of PECs early in the stimulation process, with heterophils comprising a major proportion of the adherent cells. Later in the time course, macrophages were the predominant adherent cell type. Comparisons of PEC recruitment using Sephadex vs. low molecular weight dextrans demonstrated that the low-molecular weight dextrans elicited fewer PECs than did Sephadex; unlike Sephadex, however, the low molecular weight dextrans generated a significant peak of heterophil infiltration that was similar, although delayed, to that produced with starch. Sephadex-stimulated peritoneal macrophages exhibited time-dependent functional acquisitions for 1) the phagocytosis of sheep erythrocytes, 2) the engulfment of opsonized sheep erythrocytes, and 3) opsonin-erythrocyte rosetting. Acquisition of phagocytic activity for uncoated vs. opsonized erythrocytes occurred under very different rates during the time course. The results suggest that both the nature of the irritant and the time point of cell harvest can be appropriately selected to provide the particular cell population and functional status desired for subsequent in vitro analyses.
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Sixty cases of insulinoma were treated surgically. The possible causes for failure to find the tumor during exploratory surgery are discussed. Simple enucleation is preferred in most cases of single or a few insulinomas. A technique of enucleation with minimal chance of injury to adjacent pancreatic ducts and larger blood vessels can be used. When no tumor is found after thorough exploratory procedures, controlled staged resection of the pancreas under blood glucose monitoring is the procedure of choice. Postoperative complications are common but the late results are gratifying provided the operation is carried out early in the course of the disease.
The delivery of neurotrophic factors to the central nervous system (CNS) has gained considerable attention as a potential treatment strategy for neurodegenerative disorders such as Huntington's disease (HD). In the present study, we directly compared the ability of two neurotrophic factors, ciliary neurotrophic factor (CNTF), and neurotrophin-4/5 (NT-4/5), to prevent the degeneration of striatal neurons following intrastriatal injections of quinolinic acid (QA). Expression vectors containing either the human CNTF or NT-4/5 gene were transfected into a baby hamster kidney fibroblast cell line (BHK). Using a polymeric device, encapsulated BHK-control cells and those secreting either CNTF (BHK-CNTF) or NT-4/5 (BHK-NT-4/5) were transplanted unilaterally into the rat lateral ventricle. Seven days later, the same animals received unilateral injections of QA (225 nmol) into the ipsilateral striatum. Nissl-stained sections demonstrated that the BHK-CNTF cells significantly reduced the volume of striatal damage produced by QA. Quantitative analysis of striatal neurons further demonstrated that both choline acetyltransferase (ChAT)- and glutamic acid decarboxylase (GAD)-immunoreactive neurons were protected by CNTF implants. In contrast, the volume of striatal damage and loss of striatal ChAT and GAD-positive neurons in animals receiving BHK-NT-4/5 implants did not differ from control-implanted animals. These results help better define the scope of neuronal protection that can be afforded following cellular delivery of various neurotrophic factors. Moreover, these data further support the concept that implants of polymer-encapsulated CNTF-releasing cells can be used to protect striatal neurons from excitotoxic damage, and that this strategy may ultimately prove relevant for the treatment of HD.