Search PubMed⌕ Search

Biomedical subjects

P Zhou

Publications and source records attributed to P Zhou.

At least 19 recordsLinked to original sources
PubMed2006

Studies on the preparation, crystal structure and bioactivity of ginsenoside compound K.

Microbial transformation of Panaxnotoginseng saponins (PNS) using Aspergillus niger afforded, as the main metabolite, ginsenoside compound K (20-O-beta-glucopyranosyl-20(S)-protopanaxadiol). Its structure was determined spectroscopically and by X-ray analysis, and this is the first time the crystal structure of ginsenoside has been reported. In comparison with ginsenoside Rb1, the pro-drug for this metabolite, compound K exhibits potent cytotoxic activity against tumor cell lines. The mean concentrations of compound K needed to inhibit the proliferation of cells by 50% (IC50) were 12.7, 11.4, 8.5 and 9.7 microM for mouse high-metastatic melanoma (B16-BL6), human hepatoma (HepG2), human myeloid leukemia (K562) and human high-metastatic lung carcinoma (95-D) cell lines, respectively. The data show that ginsenoside compound K is a good antitumor drug candidate.

Animals↗
PubMed2006

Role of natural killer cell subsets in cardiac allograft rejection.

To achieve donor-specific immune tolerance to allogeneic organ transplants, it is imperative to understand the cell types involved in acute allograft rejection. In wild-type mice, CD4(+) T cells are necessary and sufficient for acute rejection of cardiac allografts. However, when T-cell responses are suboptimal, such as in mice treated with costimulation-targeting agents or in CD28-deficient mice, and perhaps in transplanted patients taking immunosuppressive drugs, the participation of other lymphocytes such as CD8(+) T cells and NK1.1(+) cells becomes apparent. We found that host NK but not NKT cells were required for cardiac rejection. Ly49G2(+) NK cells suppressed rejection, whereas a subset of NK cells lacking inhibitory Ly49 receptors for donor MHC class I molecules was sufficient to promote rejection. Notably, rejection was independent of the activating receptors Ly49D and NKG2D. Finally, our experiments supported a mechanism by which NK cells promote expansion and effector function of alloreactive T cells. Thus, therapies aimed at specific subsets of NK cells may facilitate transplantation tolerance in settings of impaired T-cell function.

Animals↗
PubMed2006

TLR engagement prevents transplantation tolerance.

In many experimental models, heart, pancreas and kidney allografts are accepted long-term following costimulation-targeting therapies, whereas skin, lung and intestine resist the induction of tolerance under the same regimens. We noted that a common feature of the resistant organs is their constant exposure to commensal microbes and hypothesized that these microorganisms may stimulate Toll-like receptors (TLRs), promote alloresponses and prevent tolerance induction. This hypothesis prompts the predictions that TLR engagement at the time of transplantation should avert tolerance to heart allografts in animals treated with costimulation-targeting therapies, whereas inhibition of TLR signaling should promote tolerance to skin allografts under the same conditions. Indeed, engagement of a single TLR was sufficient to prevent anti-CD154-mediated long-term cardiac allograft acceptance and correlated with abolished intragraft recruitment of CD4+/FoxP3+ regulatory T cells and the development of linked-suppression. Conversely, a lack of donor and recipient MyD88-dependent signaling led to successful skin allograft acceptance in anti-CD154-treated animals. Thus, the status of TLR signaling contributes to the resistance versus susceptibility of organs to transplantation tolerance.

Animals↗
PubMed2005

Transplanted islets from lpr mice are resistant to autoimmune destruction in a model of streptozotocin-induced type I diabetes.

The mechanism by which beta-cells die during autoimmune diabetes has remained a subject of intense investigation. The loss of beta-cells in the disease is T cell mediated and thought to result from a number of different insults including apoptosis induction through the death receptor CD95. However, the role of CD95 in autoimmune diabetes, studied primarily in the non-obese diabetic (NOD) mouse model, has been controversial. We have used an alternative model of autoimmune diabetes triggered by repeated low doses of streptozotocin. In this model, islet grafts from C3H mice that carry the lpr mutation, and therefore lack the ability to undergo apoptosis through CD95-CD95L interaction, were completely protected when grafted in autoimmune diabetic mice despite periinsulitis (infiltration of T cells) which however did not progress to islet destruction. In contrast wild-type grafts were rapidly eliminated in autoimmune recipients. Our data provide strong support for a major role of CD95 in the destruction of islets in autoimmune mice.

Animals↗
PubMed2005

Hematopoietic stem cell mobilization with intravenous melphalan and G-CSF in patients with chemoresponsive multiple myeloma: report of a phase II trial.

Multiple myeloma (MM) is an incurable hematologic malignancy for which autologous hematopoietic stem cell transplantation (HCT) is a standard therapy. The optimal method of stem cell mobilization is not defined. We evaluated intravenous melphalan (60 mg/m2), the most effective agent for MM, and G-CSF (10 microg/kg/day) for mobilization. End points were safety, adequacy of CD34+ collections, MM response, and contamination of stem cell components (SCC). In total, 32 patients were mobilized. There were no deaths or significant bleeding episodes; 14 patients (44%) required hospitalization for neutropenic fever. Median days of grade 3 or 4 neutropenia or thrombocytopenia were 7 (2-20) and 8 (3-17). Median mobilization days, CD34+ cells/kg and total leukaphereses were 16 (12-30), 12.1 million (2.6-52.8), and 2 (1-5) respectively. Four patients (12.5 %) failed to achieve the target of 4 million CD34+ cells/kg in five leukaphereses. Reduction in myeloma was seen in 11 patients (34%) with 3 (9%) achieving complete response; 15 (47%) maintained prior responses. Estimated MM contamination per SCC (N=48) was 0.0009% (range 0-0.1) and 0.21 x 10(4) cells per kg (range 0-41.2). Increased contamination was associated with increased patient age. This strategy for mobilization is feasible, frequently requires hospitalization and transfusion, and controls disease in most patients.

Adult↗
PubMed2004

Systemic AL amyloidosis due to non-Hodgkin's lymphoma: an unusual clinicopathologic association.

Systemic AL amyloidosis (AL) is a disorder in which light chains form fibrillar deposits, leading to organ dysfunction and death. Rarely, AL has been associated with non-Hodgkin's lymphoma (NHL), although this association has not been well characterized. We report a series of six patients with AL associated with NHL, primarily lymphoplasmacytic lymphoma. Organ involvement was variable, with frequent bulky lymphadenopathy and visceral cavity deposits, but no cardiac involvement. Positron emission tomography scans were negative. Bone marrow and lymph node biopsies showed a mixed population of CD20+ lymphoid and CD138+ plasma cells. Serum free light chains were elevated, and correlated with response to therapy. Immunoglobulin light chain variable region (Ig VL) germline gene use was typical for AL, reflecting previously observed correlations between germline gene use and organ tropism. Five patients received rituximab-based therapies with two responses. Two patients underwent autologous stem cell transplantation with one complete haematological response. Four patients survive at 10-132 months from diagnosis. AL with NHL has distinctive clinical features but employs the same Ig VL gene repertoire as AL with clonal plasma cell dyscrasias. Serial serum free light chain levels are useful for tracking response to therapy. Treatments aimed at both lymphoid and plasma cell components appear warranted.

Aged↗
PubMed2003

Therapeutic penetrating keratoplasty in severe fungal keratitis using cryopreserved donor corneas.

AIMS: To investigate whether cryopreserved donor cornea could be used for therapeutic penetrating keratoplasty (PKP) to eradicate the infection, obviate complications, and preserve anatomical integrity in severe fungal keratitis. METHODS: In this retrospective, consecutive case series, 45 eyes of 45 patients with severe fungal keratitis, which exhibited anterior chamber collapse, corneal perforation, and/or large suppurative corneal infiltrate, received therapeutic PKP after removal of the infected corneal tissue, irrigation of the anterior chamber by 0.2% fluconazole solution, iris dissection of fibrinoid membrane, and iridectomy and therapeutic PKP using corneas cryopreserved at -20 degrees C. RESULTS: Among 45 eyes, 39 eyes (86.7%) were successfully eradicated the fungal infection without recurrence and maintained their anatomical integrity without any complication. Four of 45 eyes (8.9%) showed postoperative rise of intraocular pressure, of which three were controlled with subsequent antiglaucoma surgeries, whereas one eye needed additional antiglaucoma medications. Two of 45 eyes (4.4%) were enucleated because of uncontrollable fungal infection and secondary retinal detachment, respectively. 23 eyes received subsequent optical PKP and, among them, 21 maintained clear corneal grafts and two suffered from graft failure due to allograft rejections. CONCLUSION: Cryopreserved donor corneas are effective substitutes in therapeutic PKP to control severe fungal corneal infection and preserve the global integrity, and may offer additional advantages over conventional PKP in reducing allograft rejection, eradicating fungal infection during the postoperative period, and improving the success of optical PKP for visual rehabilitation.

Administration, Oral↗
PubMed2002

Degradation of aniline by newly isolated, extremely aniline-tolerant Delftia sp. AN3.

A bacterial strain, AN3, which was able to use aniline or acetanilide as sole carbon, nitrogen and energy sources was isolated from activated sludge and identified as Delftiasp. AN3. This strain was capable of growing on concentrations of aniline up to 53.8 mM (5000 mg/l). Substituted anilines such as N-methylaniline, N, N-dimethylaniline, 2-methylaniline, 4-methylaniline, 2-chloroaniline, 3-chloroaniline, o-aminoaniline, m-aminoaniline, p-aminoaniline, and sulfanilic acid did not support the growth of strain AN3. The optimal temperature and pH for growth and degradation of aniline were 30 degrees C and 7.0, respectively. The activities of aniline dioxygenase, catechol 2,3-dioxygenase and other enzymes involved in aniline degradation were determined, and results indicated that all of them were inducible. The K (m) and V (max) of aniline dioxygenase were 0.29 mM and 0.043 mmol/mg protein/min, respectively. The K (m) and V (max) of catechol 2, 3-dioxygenase for catechol were 0.016 mM and 0.015 mmol/mg protein/min, respectively. Based on the results obtained, a pathway for the degradation of aniline by Delftiasp. AN3 was proposed. The importance of the strain to the operation of municipal wastewater treatment plants is discussed.

Ammonia↗
PubMed2002

Defining the roles of perforin, Fas/FasL, and tumour necrosis factor alpha in T cell induced mucosal damage in the mouse intestine.

BACKGROUND AND AIMS: Mucosal flattening and epithelial cell apoptosis are typical features of T cell induced inflammatory diseases of the bowel, such as coeliac disease and graft versus host disease. Mice injected with a T cell activating anti-CD3 antibody develop a severe diarrhoeal illness. We describe the histological features of this enteropathy and define the effector mechanisms involved in T cell induced mucosal injury in this in vivo model. METHODS: Wild-type and genetically modified mice were injected with the anti-CD3 antibody 3C11 (50 microg). Changes in the murine intestine were characterised by light microscopy analysis and terminal uridine nick-end labelling (TUNEL) assay. The role of perforin, Fas/Fas ligand (FasL), tumour necrosis factor alpha (TNF-alpha), and interferon gamma (IFN-gamma) in T cell induced mucosal damage was assessed using selected immunodeficient mouse strains. RESULTS: T cell activation caused severe damage, including small intestinal mucosal flattening and apoptosis of crypt epithelial cells. Mucosal damage was unaltered in anti-CD3 treated mice lacking IFN-gamma, Fas, or TNF-alpha receptors. In mice lacking TNF-alpha receptors and Fas (TNF-R1xR2 lpr/lpr strain), enterocyte apoptosis was diminished but there was no significant reduction in tissue damage. Apoptosis and mucosal injury were significantly reduced in perforin knockout mice. Abrogation of both FasL and perforin (perforin KOxgld mice) further significantly reduced tissue damage and apoptotic bodies. CONCLUSIONS: T cell induced mucosal injury is mediated by the combined effect of multiple pathways but predominantly by perforin. The redundancy of the mechanisms of tissue damage will have significant impact on therapeutic strategies aimed at specific and targeted inhibition of inflammatory processes.

Animals↗
PubMed2001

The non-receptor tyrosine kinase Syk is a target of Cbl-mediated ubiquitylation upon B-cell receptor stimulation.

The negative regulator Cbl functions as a ubiquitin ligase towards activated receptor tyrosine kinases and facilitates their transport to lysosomes. Whether Cbl ubiquitin ligase activity mediates its negative regulatory effects on cytoplasmic tyrosine kinases of the Syk/ZAP-70 family has not been addressed, nor is it known whether these kinases are regulated via ubiquitylation during lymphocyte B-cell receptor engagement. Here we show that B-cell receptor stimulation in Ramos cells induces the ubiquitylation of Syk tyrosine kinase which is inhibited by a dominant-negative mutant of Cbl. Intact tyrosine kinase-binding and RING finger domains of Cbl were found to be essential for Syk ubiquitylation in 293T cells and for in vitro Syk ubiquitylation. These same domains were also essential for Cbl-mediated negative regulation of Syk as measured using an NFAT-luciferase reporter in a lymphoid cell. Association with Cbl did not alter the kinase activity of Syk. Altogether, our results support an essential role for Cbl ubiquitin ligase activity in the negative regulation of Syk, and establish that ubiquitylation provides a mechanism of Cbl-mediated negative regulation of cytoplasmic targets.

Cell Line↗
PubMed2001

Cutting edge: membrane lymphotoxin regulates CD8(+) T cell-mediated intestinal allograft rejection.

Blocking the CD28/B7 and/or CD154/CD40 costimulatory pathways promotes long-term allograft survival in many transplant models where CD4(+) T cells are necessary for rejection. When CD8(+) T cells are sufficient to mediate rejection, these approaches fail, resulting in costimulation blockade-resistant rejection. To address this problem we examined the role of lymphotoxin-related molecules in CD8(+) T cell-mediated rejection of murine intestinal allografts. Targeting membrane lymphotoxin by means of a fusion protein, mAb, or genetic mutation inhibited rejection of intestinal allografts by CD8(+) T cells. This effect was associated with decreased monokine induced by IFN-gamma (Mig) and secondary lymphoid chemokine (SLC) gene expression within allografts and spleens respectively. Blocking membrane lymphotoxin did not inhibit rejection mediated by CD4(+) T cells. Combining disruption of membrane lymphotoxin and treatment with CTLA4-Ig inhibited rejection in wild-type mice. These data demonstrate that membrane lymphotoxin is an important regulatory molecule for CD8(+) T cells mediating rejection and suggest a strategy to avoid costimulation blockade-resistant rejection.

Abatacept↗
PubMed2001

UV-damaged DNA-binding proteins are targets of CUL-4A-mediated ubiquitination and degradation.

Cul-4A, which encodes a member of the cullin family subunit of ubiquitin-protein ligases, is expressed at abnormally high levels in many tumor cells. CUL-4A can physically associate with the damaged DNA-binding protein (DDB), which is composed of two subunits, p125 and p48. DDB binds specifically to UV-damaged DNA and is believed to play a role in DNA repair. We report here that CUL-4A stimulates degradation of p48 through the ubiquitin-proteasome pathway, resulting in an overall decrease in UV-damaged DNA binding activity. The R273H mutant of p48 identified from a xeroderma pigmentosium (group E) patient is not subjected to CUL-4A-mediated proteolysis, consistent with its inability to bind CUL-4A. p125 is also an unstable protein, and its ubiquitination is stimulated by CUL-4A. However, the abundance of p125 is not dramatically altered by Cul-4A overexpression. UV irradiation inhibits p125 degradation, which is temporally coupled to the UV-induced translocation of p125 from the cytoplasm into the nucleus. CUL-4A is localized primarily in the cytoplasm. These findings identify DDB subunits as the first substrates of the CUL-4A ubiquitination machinery and suggest that abnormal expression of Cul-4A results in reduced p48 levels, thus impairing the ability of DDB in lesion recognition and DNA repair in tumor cells.

Animals↗
PubMed2001

High-efficiency gene transfer into rhesus macaque primary T lymphocytes by combining 32 degrees C centrifugation and CH-296-coated plates: effect of gene transfer protocol on T cell homing receptor expression.

Although steady progress has been made in transducing human T lymphocytes by Moloney murine leukemia virus (Mo-MuLV)-based vectors, few studies have been done to define ex vivo gene transfer protocols to transduce rhesus macaque primary T lymphocytes. Given the fact that simian immunodeficiency virus (SIV) infection in rhesus macaque is a well-characterized model for human immunodeficiency virus (HIV), it is of great interest to develop an efficient protocol to transduce rhesus macaque primary T cells. In this study, we have used MuLV-10A1-pseudotyped retrovirus expressing enhanced green fluorescent protein (EGFP) to evaluate a number of ex vivo gene transfer protocols in rhesus macaque primary T lymphocytes. Our objectives in designing these protocols were (1) to test whether higher efficiency gene transfer could be obtained by combining two previously defined protocols, centrifugation at 32 degrees C and the CH-296-coated plate; and (2) to study the effect of an ex vivo gene transfer protocol on the expression of lymphocyte homing receptors L-selectin and alpha 4 beta 7 and alpha 4 beta 1 integrins. From seven independent experiments we demonstrate by flow cytometry analyses of EGFP expression that whereas centrifugation at 32 degrees C or the fibronectin fragment CH-296-coated plate protocol alone yielded 10-14% transduction efficiency, combining these two protocols resulted in 28.1-51.2% transduction efficiency. EGFP in transduced cells was expressed highly throughout the 14 days of posttransduction expansion. Our results also demonstrate that whereas the transduction procedure per se did not significantly alter the expression of lymphocyte homing receptors, anti-CD3 and anti-CD28 antibody stimulation profoundly reduced the expression of L-selectin. The selective reduction of L-selectin may result in significant in vivo consequences if transduced cells are infused.

Animals↗
PubMed2001

Specific actions of cyanide on membrane potential and voltage-gated ion currents in rostral ventrolateral medulla neurons in rat brainstem slices.

The present study examined specific effects of sodium cyanide (CN) on the membrane potential (MP), spontaneous discharge (SD) and voltage-gated ion current of the identified bulbospinal rostral ventrolateral medulla (RVLM) neuron in the rat pup brainstem slice. 125 microM CN rapidly depolarized MP in the RVLM neuron by 11.6 mV as well as enhanced the SD rate by 300%. In contrast, the same dose of CN immediately hyperpolarized unlabeled, non-RVLM neurons by 4.8 mV. 50 microM CN did not significantly affect voltage-gated Ca(++) or A-type K(+) currents. The same concentration of CN, however, rapidly and reversibly suppressed voltage-gated Na(+) currents and sustained outward K(+) currents in the RVLM neuron by 22.5% and 23%, respectively. Tetraethylammonium could mimic the effect of CN on MP, SD and sustained K(+) current in the RVLM neuron. It is concluded that: (1) like that from the adult rat, the rat pup bulbospinal RVLM neuron can be selectively and rapidly excited by CN; (2) the hypoxia-sensitive, sustained outward K(+) channel may play an important role in the acute hypoxia-induced excitation of the RVLM neurons.

Animals↗
PubMed2001

Cloning of DGAT2, a second mammalian diacylglycerol acyltransferase, and related family members.

Studies involving the cloning and disruption of the gene for acyl-CoA:diacylglycerol acyltransferase (DGAT) have shown that alternative mechanisms exist for triglyceride synthesis. In this study, we cloned and characterized a second mammalian DGAT, DGAT2, which was identified by its homology to a DGAT in the fungus Mortierella rammaniana. DGAT2 is a member of a gene family that has no homology with DGAT1 and includes several mouse and human homologues that are candidates for additional DGAT genes. The expression of DGAT2 in insect cells stimulated triglyceride synthesis 6-fold in assays with cellular membranes, and DGAT2 activity was dependent on the presence of fatty acyl-CoA and diacylglycerol, indicating that this protein is a DGAT. Activity was not observed for acyl acceptors other than diacylglycerol. DGAT2 activity was inhibited by a high concentration (100 mm) of MgCl(2) in an in vitro assay, a characteristic that distinguishes DGAT2 from DGAT1. DGAT2 is expressed in many tissues with high expression levels in the liver and white adipose tissue, suggesting that it may play a significant role in mammalian triglyceride metabolism.

3T3 Cells↗
PubMed2001

MCL1 transgenic mice exhibit a high incidence of B-cell lymphoma manifested as a spectrum of histologic subtypes.

Viability-promoting genes such as BCL2 play an important role in human cancer but do not directly cause aggressive tumors. BCL2 transgenic mice develop lymphoma at low frequency, hindering studies of tumorigenesis and its inhibition in the presence of such gene products. MCL1 is a member of the BCL2 family that is highly regulated endogenously and that promotes cell viability and immortalization when introduced exogenously. Mice expressing an MCL1 transgene in hematolymphoid tissues have now been monitored for an extended period and were found to develop lymphoma with long latency and at high probability (more than 85% over 2 years). In most cases, the disease was widely disseminated and of clonal B-cell origin. A variety of histologic subtypes were seen, prominently follicular lymphoma and diffuse large-cell lymphoma. MCL1 thus sets the stage for the development of lymphoma as does BCL2, disease occurring with high probability and recapitulating a spectrum of subtypes as seen in human patients. These findings with the transgene underscore the importance of the normal, highly regulated pattern of MCL1 expression, in addition to providing a model for studying tumorigenesis and its inhibition in the presence of a viability promoting BCL2 family member. (Blood. 2001;97:3902-3909)

Animals↗
PubMed2001

Solution structure of DFF40 and DFF45 N-terminal domain complex and mutual chaperone activity of DFF40 and DFF45.

Apoptotic DNA fragmentation is mediated by a caspase-activated DNA fragmentation factor (DFF)40. Expression and folding of DFF40 require the presence of DFF45, which also acts as a nuclease inhibitor before DFF40 activation by execution caspases. The N-terminal domains (NTDs) of both proteins are homologous, and their interaction plays a key role in the proper functioning of this two-component system. Here we report that the NTD of DFF45 alone is unstructured in solution, and its folding is induced upon binding to DFF40 NTD. Therefore, folding of both proteins regulates the formation of the DFF40/DFF45 complex. The solution structure of the heterodimeric complex between NTDs of DFF40 and DFF45 reported here shows that the mutual chaperoning includes the formation of an extensive network of intermolecular interactions that bury a hydrophobic cluster inside the interface, surrounded by intermolecular salt bridges.

Amino Acid Sequence↗