PubMed Health⌕ Search

Biomedical subjects

Jun Cai

Publications and source records attributed to Jun Cai.

44 records · Page 3Linked to original sources
PubMed2004

Characterization of melanin produced by a wild-type strain of Bacillus thuringiensis.

Bt L-7601 is a UV resistant wild-type strain, which belongs to Bacillus thuringiensis subsp. dendrolimus serotype H4a4b. It was isolated from nature, and produced a dark brown pigment during the exponential phase of growth. Bt L-7601 had the ability to produce pigment in a general nutrition-abundant medium, which had no L-tyrosine. The pigment was identified as melanin based on chemical testing, its light absorbance, and FT-IR analysis. Bt L-7601 has a strong resistance to UV light. After 30 min irradiation its survival rate was 17 times higher than that of the strain B. thuringiensis subsp. colmeri 15A3, which had no pigment. Results of the bioassays of residual insecticidal activity of Bt formulation with and without pigment produced by Bt L-7601 against larvae of Helicoverpa armigera and Spodoptera exigua after exposure to UV irradiation showed that the pigment is an excellent UV protective agent for the insecticidal proteins.

Animals↗
PubMed2003

Region-specific and stage-dependent regulation of Olig gene expression and oligodendrogenesis by Nkx6.1 homeodomain transcription factor.

During early neural development, the Nkx6.1 homeodomain neural progenitor gene is specifically expressed in the ventral neural tube, and its activity is required for motoneuron generation in the spinal cord. We report that Nkx6.1 also controls oligodendrocyte development in the developing spinal cord, possibly by regulating Olig gene expression in the ventral neuroepithelium. In Nkx6.1 mutant spinal cords, expression of Olig2 in the motoneuron progenitor domain is diminished, and the generation and differentiation of oligodendrocytes are significantly delayed and reduced. The regulation of Olig gene expression by Nkx6.1 is stage dependent, as ectopic expression of Nkx6.1 in embryonic chicken spinal cord results in an induction of Olig2 expression at early stages, but an inhibition at later stages. Moreover, the regulation of Olig gene expression and oligodendrogenesis by Nkx6.1 also appears to be region specific. In the hindbrain, unlike in the spinal cord, Olig1 and Olig2 can be expressed both inside and outside the Nkx6.1-expressing domains and oligodendrogenesis in this region is not dependent on Nkx6.1 activity.

Animals↗
PubMed2003

Oligodendrocytes can be generated from the local ventricular and subventricular zones of embryonic chicken midbrain.

It is well established that early oligodendrocyte progenitors (OLPs) are induced by Sonic hedgehog (Shh) from the ventral ventricular zone throughout the entire neural axis. Here, we report that OLP cells can also be generated from the dorsal ventricular and subventricular zone in embryonic chicken midbrain at later stages. Concomitantly, a low level of Shh expression is detected in the adjacent ventricular and subventricular zones, implying that oligodendrogenesis in the dorsal midbrain is also regulated by Shh. In addition, Nkx2.2 and Olig2 are co-expressed in the same OLPs generated from the dorsal midbrain, suggesting that the dorsal oligodendrogenesis is similarly under the dual control of these two transcription factors as in the developing spinal cord.

Animals↗
PubMed2003

Molecular mapping of the origin of postnatal spinal cord ependymal cells: evidence that adult ependymal cells are derived from Nkx6.1+ ventral neural progenitor cells.

Recent studies have suggested that the ependymal cells lining the central canal of postnatal spinal cord possess certain properties of neural stem cells. However, the embryonic origin and developmental potential of the postnatal spinal cord ependymal cells remain to be defined. In this report, we investigated the developmental origin of postnatal spinal ependymal cells by studying the dynamic expression of several neural progenitor genes that are initially expressed in distinct domains of neuroepithelium in young embryos. At later stages of development, as the ventricular zone of the embryonic spinal cord is reduced, expression of Nkx6.1 progenitor gene is constantly detected in ependymal cells throughout chick and mouse development. Expression of other neural progenitor genes that lie either dorsal or ventral to the Nkx6.1+ domain is gradually decreased and eventually disappeared. These results suggest that the remaining neuroepithelial cells at later stages of animal life are derived from the Nkx6.1+ ventral neuroepithelial cells. Expression of Nkx6.1 in the remaining neuroepithelium is closely associated with, and regulated by, Shh expression in the floor plate. In addition, we suggested that the Nkx6.1+ ependymal cells in adult mouse spinal cords may retain the proliferative property of neural stem cells.

Animals↗
PubMed2003

Activation of vascular endothelial growth factor receptor-1 sustains angiogenesis and Bcl-2 expression via the phosphatidylinositol 3-kinase pathway in endothelial cells.

Vascular insufficiency and retinal ischemia precede many proliferative retinopathies and stimulate secretion of various vasoactive growth factors, including vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF). It is unclear, however, how PlGF, which is elevated in proliferative diabetic retinopathy and is a VEGF homolog that binds only to VEGF receptor (VEGFR)-1, promotes pathological angiogenesis. When primary microvascular endothelial cells were grown on collagen gels, PlGF-containing ligands upregulated Bcl-2 expression and stimulated the formation of capillary-like tube networks that were retained for up to 14 days in culture. The inhibition of VEGFR-1 results in a dramatic decrease in the number of capillary connections, indicating that VEGFR-1 ligands promote branching angiogenesis. In contrast, VEGF-induced tube formations and Bcl-2 expression were significantly decreased at the end of this period. Flow cytometry analysis of annexin-V/propidium iodide-stained cells revealed that PlGF and PlGF/VEGF heterodimer inhibited apoptosis in serum-deprived endothelial cells. These two growth factors stimulated a survival signaling pathway phosphatidylinositol 3-kinase (PI3K), as identified by increased Akt phosphorylation and because blocking PI3K signalling by adenovirus-mediated overexpression of wild-type phosphatase and tensin homolog on chromosome 10 (PTEN) disrupted angiogenesis and decreased Bcl-2 expression by PlGF and PlGF/VEGF heterodimer, whereas a dominant-negative PTEN mutant enhanced endothelial sprout formation and Bcl-2 expression. Together, these findings indicate that PlGF-containing ligands contribute to pathological angiogenesis by prolonging cell survival signals and maintaining vascular networks.

Animals↗
PubMed2002

Dual origin of spinal oligodendrocyte progenitors and evidence for the cooperative role of Olig2 and Nkx2.2 in the control of oligodendrocyte differentiation.

In this study, we have investigated the relationship of Olig2+ and Nkx2.2+ oligodendrocyte progenitors (OLPs) by comparing the expression of Olig2 and Nkx2.2 in embryonic chicken and mouse spinal cords before and during the stages of oligodendrogenesis. At the stages of neurogenesis, Olig2 and Nkx2.2 are expressed in adjacent non-overlapping domains of ventral neuroepithelium. During oligodendrogenesis stages, these two domains generate distinct populations of OLPs. From the Olig2+ motoneuron precursor domain (pMN) arise the Olig2+/Pdgfra+ OLPs, whereas the Nkx2.2+ p3 domain give rise to Nkx2.2+ OLPs. Despite their distinct origins, both populations of OLPs eventually appear to co-express Olig2 and Nkx2.2 in the same cells. However, there is a species difference in the timing of acquiring Nkx2.2 expression by the Olig2+/Pdgfra+ OLPs. The co-expression of Nkx2.2 and Olig2 in OLPs is tightly associated with myelin gene expression in the normal and PDGFA(-/-) embryos, suggesting a cooperative role of these transcription factors in the control of oligodendrocyte differentiation. In support of this suggestion, inhibition of expression of these two transcription factors in culture by antisense oligonucleotides has an additive inhibitory effect on OLP differentiation and proteolipid protein (PLP) gene expression.

Animals↗
PubMed2002

[Treatment for chronic dacryocystitis by dacryocystorhinotomy with Ho: YAG laser under endoscope].

OBJECTIVE: To analyze the experience and curative effect in treating chronic dacrocystitis by dacryocystorhinotomy with Ho:YAG laser under endoscope. METHOD: 20 patients of chronic dacryocystitis were treated by dacryocystorhinotomy with Ho:YAG laser under endoscope, followed-up for 1 approximately 2 years to observe the curative effects. RESULT: One was unplugged 8 months after the operation, six after 6 months, four after 4 months and nine after 3 months. No recidivations was found one year after the operation and the effective rate was 100%. There was no complications in all of the cases. CONCLUSION: The technique of dacryocystorhinotomy with Ho: YAG laser under endoscope overcomes the disadvantages of traditional method of operation.

Adult↗