PubMed Health⌕ Search

Biomedical subjects

Jun Cao

Publications and source records attributed to Jun Cao.

At least 55 records · Page 3Linked to original sources
PubMed2004

The effect of acute stress on LTP and LTD induction in the hippocampal CA1 region of anesthetized rats at three different ages.

Not all experiences are memorized equally well. Especially, some types of stress are unavoidable in daily life and the stress experience can be memorized for life. Previous evidence has showed that synaptic plasticity, such as long-term potentiation (LTP) that may be the major cellular model of the mechanism underlying learning and memory, is influenced by behavioral stress. However, the effect of behavioral stress on age-related synaptic plasticity in vivo was primarily known. Here we found that the LTP induction in the hippocampal CA1 region of anesthetized rats obviously showed inverted-U shape related to ages (4, 10 and 74 weeks old rats), but low-frequency stimulation was unable to induce reliable long-term depression (LTD) in these animals. Furthermore, acute elevated platform (EP) stress enabled reliable LTD significantly and completely blocked LTP induction at these ages. Importantly, LTD after exposure to acute EP stress showed similar magnitude over these ages. The present results that stress enables LTD but impairs LTP induction at these three ages strengthen a view that stress experience-dependent LTD (SLTD) may underlie stress form of aberrant memories.

Age Factors↗
PubMed2004

Cell-to-cell adhesion modulates Stat3 activity in normal and breast carcinoma cells.

Stat3 (signal transducer and activator of transcription-3) activity is required for transformation by a number of oncogenes, while a constitutively active form of Stat3 alone is sufficient to induce neoplastic transformation. Although in most instances Stat3 is growth-promoting, the impact of cell density on Stat3 activation status and the biological importance of Stat3 during growth arrest have not been characterized. Previous results indicated that cell density alters tyrosine phosphorylation levels of cultured cells. Since signalling through Stat3 is determined by a key phosphorylation at tyr705, we examined the effects of cell density upon Stat3 activity in normal breast epithelial cells, breast carcinoma lines and normal mouse fibroblasts. Intriguingly, the results revealed a dramatic increase in Stat3, tyr705 phosphorylation and activity with cell density, which gradually declined at later stages. This activation was dependent upon cell-cell contact, since it was eliminated if cell adhesion was disrupted through calcium chelation, while it was reinstated through cell aggregation. Furthermore, this activation was suppressed following inhibition of JAKs (Janus kinases) but not inhibition of Fer, IGF1-R, or kinases of the c-Src family. On the other hand, constitutively active Stat3 in carcinoma lines, known to harbor activated Src, was blocked by pharmacological inhibitors of Src as well as JAKs. These results point to the existence of two distinct pathways of Stat3 activation in breast carcinomas, based on Src dependence. More importantly, our results suggest that Stat3 activity is upregulated during the confluence-mediated growth arrest by a signalling mechanism that requires JAKs.

Animals↗
PubMed2004

Multimedia fate model for hexachlorocyclohexane in Tianjin, China.

A level III fugacity model was applied to characterize the fate of gamma-HCH in Tianjin, China, before the 1990s when the contamination reached its maximum at steady state. Geometric means were used as model inputs. The concentrations of gamma-HCH in air, surface water, soil, sediment, crops, and fish as well as transfer fluxes across the interface between the compartments were derived under the assumption of steady state. The calculated concentrations were validated by independent data collected from the literature. There was generally good agreement between the estimated and the observed concentrations, and the differences were all less than 0.6 log units for air, water, soil, sediment, and fish and approximately 1 order of magnitude for crops. Around 97% of gamma-HCH accumulated in soil and sediment. Wastewater irrigation was not an important pathway for delivering gamma-HCH to soil as compared to the dominant source of agricultural application. Degradation and advective airflow carried much gamma-HCH out of the system. Sensitivities of the model estimates to input parameters were tested, and a coefficient of variation normalized sensitivity coefficient was defined for the test. The most influential parameters were degradation rates in sediment and soil, application rates, concentrations in wastewater, and adsorption coefficients. Monte Carlo simulation was conducted for model uncertainty analysis. The model was run 20 000 times using randomly generated data from predefined log-normal distribution density functions. All calculated concentrations and fluxes were log-normally distributed. The dispersions of the calculated and observed concentrations were compared in terms of coefficients of variation to distinguish between true variability and model uncertainty.

Air↗
PubMed2004

Stress enables synaptic depression in CA1 synapses by acute and chronic morphine: possible mechanisms for corticosterone on opiate addiction.

The hippocampus, being sensitive to stress and glucocorticoids, plays significant roles in certain types of learning and memory. Therefore, the hippocampus is probably involved in the increasing drug use, drug seeking, and relapse caused by stress. We have studied the effect of stress with morphine on synaptic plasticity in the CA1 region of the hippocampus in vivo and on a delayed-escape paradigm of the Morris water maze. Our results reveal that acute stress enables long-term depression (LTD) induction by low-frequency stimulation (LFS) but acute morphine causes synaptic potentiation. Remarkably, exposure to an acute stressor reverses the effect of morphine from synaptic potentiation (approximately 20%) to synaptic depression (approximately 40%), precluding further LTD induction by LFS. The synaptic depression caused by stress with morphine is blocked either by the glucocorticoid receptor antagonist RU38486 or by the NMDA-receptor antagonist D-APV. Chronic morphine attenuates the ability of acute morphine to cause synaptic potentiation, and stress to enable LTD induction, but not the ability of stress in tandem with morphine to cause synaptic depression. Furthermore, corticosterone with morphine during the initial phase of drug use promotes later delayed-escape behavior, as indicated by the morphine-reinforced longer latencies to escape, leading to persistent morphine-seeking after withdrawal. These results suggest that hippocampal synaptic plasticity may play a significant role in the effects of stress or glucocorticoids on opiate addiction.

Animals↗
PubMed2004

Stress-facilitated LTD induces output plasticity through synchronized-spikes and spontaneous unitary discharges in the CA1 region of the hippocampus.

Long-term potentiation (LTP) and long-term depression (LTD) of the excitatory synaptic inputs plasticity in the hippocampus is believed to underlie certain types of learning and memory. Especially, stressful experiences, well known to produce long-lasting strong memories of the event themselves, enable LTD by low frequency stimulation (LFS, 3 Hz) but block LTP induction by high frequency stimulation (HFS, 200 Hz). However, it is unknown whether stress-affected synaptic plasticity has an impact on the output plasticity. Thus, we have simultaneously studied the effects of stress on synaptic plasticity and neuronal output in the hippocampal CA1 region of anesthetized Wistar rats. Our results revealed that stress increased basal power spectrum of the evoked synchronized-spikes and enabled LTD induction by LFS. The induction of stress-facilitated LTD but not LFS induced persistent decreases of the power spectrum of the synchronized-spikes and the frequency of the spontaneous unitary discharges; However, HFS induced LTP in non-stressed animals and increased the power spectrum of the synchronized-spikes, without affecting the frequency of the spontaneous unitary discharges, but HFS failed to induce LTP in stressed animals without affecting the power spectrum of the synchronized-spikes and the frequency of the spontaneous unitary discharges. These observations that stress-facilitated LTD induces the output plasticity through the synchronized-spikes and spontaneous unitary discharges suggest that these types of stress-related plasticity may play significant roles in distribution, amplification and integration of encoded information to other brain structures under stressful conditions.

Action Potentials↗
PubMed2004

Estrogen influences the differentiation, maturation and function of dendritic cells in rats with experimental autoimmune encephalomyelitis.

AIM: To examine if estrogen can affect the immune response at the dendritic cells (DCs) level in rats with experimental autoimmune encephalomyelitis (EAE). METHODS: Lewis rats were immunized with inoculum containing MBP(68-86). DCs were derived from spleen monocytes of EAE rats with IL-4 and GM-CSF in presence of 17 beta-estradiol (E2). Nitric oxide (NO) was detected by Griess reagent. The surface markers and cytokines production of DCs were shown by flow cytometry. DCs were cocultured with MBP-specific T cells, [(3)H]-TdR incoportation was used to reveal the antigen presentability, the supernatant of the coculture were collected to examine the cytokines secretion by ELISA. RESULTS: E2 activated DCs by accelerating the maturation process characterized by upregulation of MHC II and costimulating molecule B7-1, B7-2, drastic high expression of CD40. IFN-kappa-producing DCs were also elevated without any alteration of IL-10. Estradiol-treated DCs (E2-DCs) secreted more NO in the culture supernatant. By contrast, E2-DCs showed decreased antigen presentation ability with reduced secretion of IFN-kappa but no alteration of IL-10 in the coculture with T cells. CONCLUSION: Estrogen can affect the differentiation, maturation and function of DCs from EAE rats, which may be attributed to its protection against EAE and the remission of multiple sclerosis patients in pregnancy.

Animals↗
PubMed2004

[Diversity of Frankia in nodules of Alnus nepalensis at Gaoligong Mountains revealed by IGS, PCR-RFLP analysis].

30 nodule samples were used to assess the diversity of Frankia strains symbiotically associated with Alnus nepalensis naturally occurring at the Gaoligong Mountains in Yunnan Province, China. DNA was extracted directly from nodules, and its two target DNA regions that encode nifD-nifK intergenic spacer (IGS) and 16S-23S rDNA IGS was studied by PCR-RFLP. The PCR fragments yielded by the nifD-nifK IGS were noticeably different in size, and when they were digested by Hae III and Afa I, 15 nif-type Frankia strains could be detected, the PCR-RFLP result of this region also could show that more than one genotype Frankia strains could form symbiosis with individual plants at the same time. The 16S-23S rDNA IGS had similar PCR fragments, but still identified 15 rrn-type strains after digested by Hae III and Afa I. 20 genotype strains could be found only when combined the PCR-RFLPs of two target regions.

Alnus↗
PubMed2004

Morphological observation of immunological alterations in the spleens from estrogen receptor deficient mice.

AIM: To evaluate some immunological parameters in the spleens from estrogen receptor(ER) deficient mice. METHODS: Immunohistochemistry and immunofluorescence analysis were used in the study. RESULTS: Multiple alterations were found in the spleens of ER deficient mice, especially in ERbeta deficient mice, such as increased expression of proinflammatory cytokines and inducible nitric oxide synthase, elevated number of proliferating splenocytes and increased IgM/IgG production. Moreover, The splenocytes lack of ERbeta were resistant towards estrogen's suppression on proliferation. The activation of nuclear factor (NF)-kappaB in ERbeta deficient spleens may account for the above hyperactivity. CONCLUSION: ER, especially ERbeta, plays a key role in mediating the modulation of immune response by estrogen. ERbeta disruption may increase the sensibility towards autoimmune diseases.

Animals↗
PubMed2004

Estrogen affects the differentiation and function of splenic monocyte-derived dendritic cells from normal rats.

AIM: To explore the mechanism resulting in the preventive effect of estrogen on experimental autoimmune encephalomyelitis (EAE), which is an animal model for multiple sclerosis (MS), and examine if estrogen can affect the immune response in EAE at dendritic cell (DC) level. METHODS: Flow cytometry was used to reveal the surface marker expression. 3H-thymidine incorporation was applied to examine the cellular proliferation. Levels of anti-myelin basic protein (MBP)(68-86) antibody and cytokines were determined by enzyme-linked immunospot and ELISA, respectively. RESULTS: 17beta-estradiol (E2) could dose-dependently accelerate the differentiation process of DCs by up-regulating CD11c, B7-2 and CD40 expressions, but exert no effect on its antigen presentation ability. MBP-specific T cells cocultured with E2-treated DCs (E2-DC) produced more IL-10 and less IFN-gamma in the supernatant than those without E2 pretreatment (ctr-DC). In contrast to ctr-DC, E2-DC, if injected i.v. into EAE rats on day 5 post immunization, could initiate antigen nonspecific hyper-responsivity in T cells in terms of enhanced proliferation and cytokine secretion of mononuclear cells in LN, but suppressed antibody secretion from splenocytes. CONCLUSION: These results suggest that estrogen can affect the differentiation and function of DCs, which leads T cells switching to Th2 secretion. This may account partly for the protective effect of estrogen on EAE.

Animals↗
PubMed2004

[PAHs in foliar dust from Beijing urban area].

A five-step sequential elution procedure with or without supersonic effect was tested for extraction of foliar dust from leaves of Euonymus japonicus collected at two locations of Beijing urban area. The samples were collected from either roadside or campus far away from any motor traffic. The foliar dust was characterized for size distribution, organic carbon content, and PAHs content. It was found that majority of the foliar dust can be eluted in 4 min by distill water under supersonic effect at room temperature without shaking. The amount of foliar dust on the sample from roadside was almost twice as much as those from campus, while the particle size of the former was relatively large. Large amount of coarse particles came from disturbance of motor vehicles. Slightly high concentrations of PAH species were detected in the sample from campus compared to those in the samples collected from roadside.

Cities↗
PubMed2004

[Protective effect of lycopene on the oxidative damage of lung in rat induced by ozone].

OBJECTIVE: To observe the effect of Lycopene (LP) on the oxidative damage of lung induced by exposing ozone. METHODS: The injury model of lung was induced by exposing ozone. The xanthines oxidize method and TBA was used to determine SOD, MDA and GSH-Px in serum and lung respectively. RESULTS: Compared with model rats, SOD and GSH-Px in the group of LP administrated were increased and MDA were decreased significantly (P < 0.05). CONCLUSION: it was showed that LP could protect oxidative damage of lung induced by ozone in rats.

Animals↗
PubMed2004

[Analysis of the sequences of the ribosomal DNA ITS2 region for differentiating anopheline mosquitoes within hyrcanus group].

OBJECTIVE: To analyze the genetic characteristics of ribosomal DNA ITS2 region for differentiating anopheline mosquitoes within Hyrcanus group. METHODS: The ribosomal DNA ITS2 region of both laboratory line and filed collected An. anthropophagus and An. sinensis as well as the field collected An. yatsushiroensis and An. lesteri were amplified and sequenced. The sequencing data were then analyzed for the restriction mapping using Omega Sequencing analysis program. RESULTS AND CONCLUSION: The length of the sequences of An. sinensis, An. anthropophagus, An. yatsushiroensis and An. lesteri are 472, 452, 456 and 456 bp respectively. The restriction mapping showed that there were different restriction digesting sites among the ribosomal DNA ITS2 region sequences from An. sinensis, An. anthropophagus, An. yatsushiroensis and An. lesteri. On the basis of the sequence differences among the anopheline species within Hyrcanus group, it is possible to develop new technique for genetic identification of anopheline mosquitoes.

Animals↗
PubMed2003

Transgenic plants expressing two Bacillus thuringiensis toxins delay insect resistance evolution.

Preventing insect pests from developing resistance to Bacillus thuringiensis (Bt) toxins produced by transgenic crops is a major challenge for agriculture. Theoretical models suggest that plants containing two dissimilar Bt toxin genes ('pyramided' plants) have the potential to delay resistance more effectively than single-toxin plants used sequentially or in mosaics. To test these predictions, we developed a unique model system consisting of Bt transgenic broccoli plants and the diamondback moth, Plutella xylostella. We conducted a greenhouse study using an artificial population of diamondback moths carrying genes for resistance to the Bt toxins Cry1Ac and Cry1C at frequencies of about 0.10 and 0.20, respectively. After 24 generations of selection, resistance to pyramided two-gene plants was significantly delayed as compared with resistance to single-gene plants deployed in mosaics, and to Cry1Ac toxin when it was the first used in a sequence. These results have important implications for the development and regulation of transgenic insecticidal plants.

Adaptation, Physiological↗
PubMed2003

Fate modeling of phenanthrene with regional variation in Tianjin, China.

A multimedia fate model with spatially resolved air and soil phases was developed and evaluated. The model was used for calculation of phenanthrene concentrations in air, water, soil, and sediment in Tianjin area and transport fluxes between the adjacent bulk phases under steady-state assumption. Both air and soil phases were divided into 3113 individual compartments of 4 km2 each to assess the spatial variation of phenanthrene concentrations and fluxes. Independently measured phenanthrene concentrations in air, water, and soil were used for model validation. The spatial variation in soil was validated using a set of measured phenanthrene concentrations of 188 surface soil samples collected from the area. Most data used either for model calculation or for model validation were collected during the last 5 years. As the results of the model validation, the calculated mean values for phenanthrene concentrations in various bulk phases are in fair agreement with those independently observed and are very close to those calculated using the model without spatial variation. The absolute difference between the calculated and the measured mean concentrations are 0.14, 0.48, and 0.13 log-units (mol/m3) for air, water, and soil, respectively. The spatial distribution patterns of phenanthrene in both air and soil were well modeled. Spatially, however, the model overestimated the soil phenanthrene level at low concentration range and underestimated it at high concentration range. The calculated distribution of phenanthrene in the air matches well with the emission from fossil fuel combustion, while the calculated distribution pattern in the soil is similar to that observed.

China↗
PubMed2003

[Test of transient expression of green fluorescent protein gene transferred to bone marrow stromal cells].

OBJECTIVE: To determine the optimized condition under which BMP expression vector will be constructed to transfect bone marrow stromal cells (MSCs), plasmid vector coding enhanced green fluorescence protein (EGFP) gene pEGFP was transferred into MSCs. The transfer efficiency and transient expression were subsequently tested. METHODS: pEGFP plasmid was amplified and tested by an enzyme cutting technique in vitro. MSCs, which were initially obtained from the bone marrow of rabbits, were cultured in vitro and transferred with pEGFP by means of lipofectamine media methods. The ratio of plasmid and lipofectamine was varied according to the experiment design. Transfer efficiency and transient expression were evaluated by fluorescent microscopy. RESULTS: Transfer efficiency was correlated with the ratio of plasmid and lipofectamine. The expression of EGFP began in 24 hours after transferring, reached maximum in 48-72 hours and decreased in 1 week, however there remained a weak expression for more than 3 weeks. CONCLUSION: The efficiency of transferring pEGFP into MSCs could achieve to 30% with proper ratio of plasmid and lipofactamine. pEGFP was an ideal transient expression vector for MSCs gene transference.

Animals↗
PubMed2003

Lead exposure through gestation-only caused long-term learning/memory deficits in young adult offspring.

Numerous observations in clinical and preclinical studies indicate that the developing brain is particular sensitive to lead (Pb)'s pernicious effects. However, the effect of gestation-only Pb exposure on cognitive functions at maturation has not been studied. We investigated the potential effects of three levels of Pb exposure (low, middle, and high Pb: 0.03%, 0.09%, and 0.27% of lead acetate-containing diets) at the gestational period on the spatial memory of young adult offspring by Morris water maze spatial learning and fixed location/visible platform tasks. Our results revealed that three levels of Pb exposure significantly impaired memory retrieval in male offspring, but only female offspring at low levels of Pb exposure showed impairment of memory retrieval. These impairments were not due to the gross disturbances in motor performance and in vision because these animals performed the fixed location/visible platform task as well as controls, indicating that the specific aspects of spatial learning/memory were impaired. These results suggest that exposure to Pb during the gestational period is sufficient to cause long-term learning/memory deficits in young adult offspring.

Animals↗