Biomedical subjects

Pu Zhang

Publications and source records attributed to Pu Zhang.

29 records · Page 2Linked to original sources

PubMed2004

Enhancement of hematopoietic stem cell repopulating capacity and self-renewal in the absence of the transcription factor C/EBP alpha.

The transcription factor C/EBP alpha is required for granulopoiesis and frequently disrupted in human acute myeloid leukemia (AML). Here, we show disruption of C/EBP alpha blocks the transition from the common myeloid to the granulocyte/monocyte progenitor but is not required beyond this stage for terminal granulocyte maturation. C/EBP alpha-deficient hematopoietic stem cells (HSCs) have increased expression of Bmi-1 and enhanced competitive repopulating activity. Bone marrow in adult C/EBP alpha-deficient mice was filled with myeloblasts, similar to human AML, supporting the notion that disruption of C/EBP alpha cooperates with other events in the development of leukemia. Therefore, C/EBP alpha is not only essential for granulocyte development but, in addition, is a regulator of hematopoietic stem cell activity.

Aging↗

PubMed2004

Benefits of 8-bromo-guanosine 3',5'-cyclic monophosphate (8-br-cGMP) in human ovarian cortical tissue culture.

Guanosine 3',5'-cyclic monophosphate (cGMP) is an important intracellular second messenger in many cells of the body; however, its importance in the ovary is only now being realized. The effects of the cGMP analogue 8-bromo-guanosine 3',5'-cyclic monophosphate (8-br-cGMP) were tested on human ovarian follicle development and survival using an established tissue culture method. Ovarian biopsies were collected from 27 women (mean age 32 years) undergoing Caesarean sections or gynaecological operations. Tissue was cut into small pieces and cultured in the presence or absence of 5 mmol/l 8-br-cGMP for 7 and 14 days. 8-br-cGMP enhanced the rate of follicle growth to the secondary stage after both 7 and 14 days of culture. Furthermore, it significantly improved the proportion of viable follicles when compared with control cultures. All cultured follicles reaching the secondary stage were smaller than those uncultured. This suggests that although granulosa cells were stimulated to proliferate and form a double layer, the cells themselves did not become larger as usually occurs with maturation and differentiation. Oestradiol production was greater in the 8-br-cGMP-containing cultures after 12 days compared with control cultures, presumably due to the concurrent increase in the proportion of secondary follicles. In the early stages of human ovarian tissue culture, 8-br-cGMP may be a necessary component as both a growth enhancer and survival factor.

Adult↗

PubMed2004

In vitro effect of cyclic adenosine 3', 5'-monophosphate (cAMP) on early human ovarian follicles.

PURPOSE: To test the effect of cyclic adenosine 3', 5'-monophosphate (cAMP) on early human ovarian follicles during prolonged culture period. METHODS: Donated ovarian biopsies from 16 women undergoing gynecological laparoscopy were cut into slices and cultured in parallel for 1, 2, or 3 weeks in the presence and the absence of 0.5 mM 8-bromo-cAMP. The developmental stages, sizes, and viability of the follicles were recorded from histological sections of all samples. RESULTS: On day 14, cortical slices cultured with 8-bromo-cAMP showed a significantly higher proportion of secondary follicles (50.0% vs. 20.0%) and a lower proportion of primordial follicles (9.7% vs. 26.7%) when compared with those cultured without 8-bromo-cAMP. On day 21, the proportion of viable follicles in cortical slices with 8-bromo-cAMP treatment was significantly higher than that without 8-bromo-cAMP treatment (79.6% vs. 55.2%). CONCLUSION: CyclicAMP promoted folliculogenesis and follicle survival during 14-21 days' culture of human ovarian cortical slices.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2004

Phosphorylation of C/EBPalpha inhibits granulopoiesis.

CCAAT/enhancer-binding protein alpha (C/EBPalpha) is one of the key transcription factors that mediate lineage specification and differentiation of multipotent myeloid progenitors into mature granulocytes. Although C/EBPalpha is known to induce granulopoiesis while suppressing monocyte differentiation, it is unclear how C/EBPalpha regulates this cell fate choice at the mechanistic level. Here we report that inducers of monocyte differentiation inhibit the alternate cell fate choice, that of granulopoiesis, through inhibition of C/EBPalpha. This inhibition is mediated by extracellular signal-regulated kinases 1 and/or 2 (ERK1/2), which interact with C/EBPalpha through an FXFP docking site and phosphorylate serine 21. As a consequence of C/EBPalpha phosphorylation, induction of granulocyte differentiation by C/EBPalpha or retinoic acid is inhibited. Our analysis of C/EBPalpha by fluorescent resonance energy transfer revealed that phosphorylation induces conformational changes in C/EBPalpha, increasing the distance between the amino termini of C/EBPalpha dimers. Thus, myeloid development is partly regulated by an ERK1/2-mediated change in the conformation of C/EBPalpha that favors monocyte differentiation by blocking granulopoiesis.

3T3-L1 Cells↗

PubMed2003

The amino terminal and E2F interaction domains are critical for C/EBP alpha-mediated induction of granulopoietic development of hematopoietic cells.

The transcription factor C/EBP alpha (CCAAT/enhancer binding protein alpha) is critical for granulopoiesis. Gene disruption in mice blocks early granulocyte differentiation and disruption of C/EBP alpha function has been implicated in human acute myeloid leukemia (AML), but no systematic structure-function analysis has been undertaken to identify the mechanisms involved in C/EBP alpha-mediated granulocyte differentiation. Here we demonstrate that loss of either of 2 key regions results in disruption of C/EBP alpha granulocytic development: the amino terminus and specific residues residing on the non-DNA binding face of the basic region. Mutation of either results in loss of C/EBP alpha inhibition of E2F and down-regulation of c-Myc, but only mutation of the basic region results in loss of physical interaction with E2F. In contrast, while the amino terminal mutant retains the ability to interact with E2F, this mutant fails to bind a C/EBP alpha site efficiently, fails to activate C/EBP alpha target genes, and is also defective in inhibition of E2F activity. These results further emphasize the importance of inhibition of proliferative pathways in granulopoiesis and demonstrate that several regions of the C/EBP alpha protein are involved in this mechanism.

Amino Acid Sequence↗

PubMed2003

Cryopreservation of follicles in human ovarian cortical tissue. Comparison of serum and human serum albumin in the cryoprotectant solutions.

BACKGROUND: Cryopreservation of follicles in ovarian cortical tissue has been suggested as a method for preserving fertility for young women who need to undergo cytotoxic therapy. Varying compositions of cryoprotectant solutions have been used to prevent tissue damage during cryopreservation and thawing. We compared human serum [20% (v/v)] and human serum albumin (HSA) (25 mg/ml) in cryoprotectant solutions containing propanediol and sucrose to evaluate whether serum-free medium could be used for this purpose. METHODS: Biopsies of ovarian cortical tissue were obtained from 23 subjects after informed consent. Fourteen underwent Caesarean section and nine underwent sterilization by laparoscopy. The cortical tissue was cut into pieces of 1-1.5 mm(3 )and cryopreserved in cryoprotectant solutions containing serum or HSA. After thawing, a total of 1318 follicles were analysed using light microscopy, transmission electron microscopy (TEM) or live/dead assay. RESULTS: Viability of the follicles was 99.3% in freshly dissected tissue. After thawing, 65% of the follicles and 75% of the oocytes were viable with serum, and 69 and 74%, respectively, with HSA. No significant differences were observed between results in solutions containing serum versus HSA. TEM showed similar results; however, poor survival of stromal tissue was evident in this analysis. The live/dead assay showed 82% viability after thawing for both groups. No benefits were seen from post-thawing culture for 4 h before histological preparation. CONCLUSIONS: A cryoprotectant solution containing HSA was equally effective as one containing serum. Good viability of follicles was confirmed when using propanediol and sucrose as cryoprotectants, with a large number of follicles.

Adult↗

PubMed2003

[An experimental study of 3-dimension zygomatic suture extension for suture osteogenesis].

OBJECTIVE: To explore a methods of 3-Dimension expansion of zygomatic suture in a goat model. METHODS: Seven goats were used in this study. The 3-D extensive applicator was designed and used to extend the zygomatic suture of the goats by placing it in the zygomatic bone through an infraorbital incision. Ten days after the first operation, it was gradually extended on a speed of 0.09 cm/d for 7 days. The zygomatic movement and the osteogenesis of the suture was evaluated in two weeks. RESULTS: The zygomatic bone was extended for 0.6 cm long in average, and the osteogenesis was also shown significantly in the suture. CONCLUSION: The above mentioned technique could be a safe and effect method to be applied for the zygomatic extension.

Animals↗

PubMed2002

Patterns in spherical Rayleigh-Bénard convection: a giant spiral roll and its dislocations.

Thermal convection in a moderately thin spherical fluid layer in the presence of spherically symmetric gravity, spherical Rayleigh-Bénard convection, is investigated through fully three-dimensional numerical simulations. A steady spherical pattern in the form of a single giant spiral roll covering the whole spherical surface without defects is discovered near the onset of convection. Successive dislocations of the giant spiral roll are also found at larger Rayleigh numbers.

Journal Article↗

PubMed2002

Induction of granulocytic differentiation by 2 pathways.

The CCAAT enhancer binding protein alpha (C/EBP alpha) transcription factor plays a critical role in granulocytopoiesis. Mice with a disruption of the C/EBP alpha gene demonstrate an early block in granulocytic differentiation, and disruption of C/EBP alpha function is a common theme in many types of human acute myelogenous leukemia, which is characterized by a block in myeloid development. To characterize further the nature of this block, we derived cell lines from the fetal liver of C/EBP alpha-deficient animals. These lines resembled morphologically the immature myeloid blasts observed in C/EBP alpha(-/-) fetal livers and did not express messenger RNA encoding early myeloid genes such as myeloperoxidase. Similarly, granulocytic markers such as Mac-1 and Gr-1 were not expressed; nor were erythroid and lymphoid surface antigens. Introduction of an inducible C/EBP alpha gene into the line revealed that conditional expression of C/EBP alpha induced the C/EBP family members C/EBP beta and C/EBP epsilon and subsequent granulocyte differentiation. Similar results were obtained when C/EBP alpha(-/-) cells were stimulated with the cytokines interleukin-3 and granulocyte-macrophage colony-stimulating factor, but not with all-trans retinoic acid, supporting a model of at least 2 pathways leading to the differentiation of myeloid progenitors to granulocytes and implicating induction of other C/EBP family members in granulopoiesis.

Animals↗

PubMed2002

Few instead of many: human follicle collection from follicular aspirates at oocyte retrieval.

BACKGROUND: The aim of this study was to determine if follicular aspirates obtained during oocyte retrieval for IVF were a good source of ovarian follicles for research purposes. METHODS: Follicular aspirates from 86 patients were collected and examined for the presence of follicles, and histological examination of tissue sample found was undertaken. RESULTS: Follicles were only obtained from aspirates of seven out of a total of 86 patients. From these samples a total of 14 follicles was found. The follicles were primordial, primary or secondary, 40-80 microm in diameter. Three of these recovered follicles were cultured and all degenerated within 2 days. In all aspirates some groups of granulosa cells that did not contain follicles or oocytes were found, as was vaginal epithelium that was also identified and verified by histology. CONCLUSIONS: Follicular aspirates are not a useful source of human follicles. Some structures found in the aspirates may be erroneously identified as follicles.

Adult↗

PubMed2002

Downregulation of c-Jun expression by transcription factor C/EBPalpha is critical for granulocytic lineage commitment.

The transcription factor C/EBPalpha is crucial for the differentiation of granulocytes. Conditional expression of C/EBPalpha triggers neutrophilic differentiation, and C/EBPalpha can block 12-O-tetradecanoylphorbol-13-acetate-induced monocytic differentiation of bipotential myeloid cells. In C/EBPalpha knockout mice, no mature granulocytes are present. A dramatic increase of c-Jun mRNA in C/EBPalpha knockout mouse fetal liver was observed. c-Jun, a component of the AP-1 transcription factor complex and a coactivator of the transcription factor PU.1, is important for monocytic differentiation. Here we report that C/EBPalpha downregulates c-Jun expression to drive granulocytic differentiation. An ectopic increase of C/EBPalpha expression decreases the c-Jun mRNA level, and the human c-Jun promoter activity is downregulated eightfold in the presence of C/EBPalpha. C/EBPalpha and c-Jun interact through their leucine zipper domains, and this interaction prevents c-Jun from binding to DNA. This results in downregulation of c-Jun's capacity to autoregulate its own promoter through the proximal AP-1 site. Overexpression of c-Jun prevents C/EBPalpha-induced granulocytic differentiation. Thus, we propose a model in which C/EBPalpha needs to downregulate c-Jun expression and transactivation capacity for promoting granulocytic differentiation.

Animals↗