Biomedical subjects

J Shao

Publications and source records attributed to J Shao.

At least 91 records · Page 5Linked to original sources

PubMed1998

Restricted lesions to ventral prefrontal subareas block reversal learning but not visual discrimination learning in rats.

Previous studies have shown that extensive damage to the medial prefrontal cortex (mPFC) of rats causes reversal learning deficits. The mPFC of rats, however, consists of several subareas that are different from each other in both cytoarchitecture and neural connectivity, suggesting a functional dissociation among the mPFC subareas. In the present study, selective lesions of the mPFC of rats were made with a specially designed microknife whose intracranial placement could be controlled stereotaxically. Restricted lesions were made to each of the 3 parts of the mPFC: the anterior cingulate area (AC) (including the medial precentral area, PrCm), the prelimbic area (PL), and the infralimbic area (IL). One week after surgery, rats were trained in an aversively motivated visual discrimination task in a novel rotating T-maze. After reaching the acquisition criterion, rats were trained in a reversal task in the same maze. No difference was found in acquisition between control and mPFC lesioned rats. However, lesions of either the PL or the IL produced a marked deficit in the reversal task. This behavioral deficit was not found in rats with lesions of the AC. The results indicate that the mPFC of rats is not essential for discrimination learning, but that each of the 2 ventral subareas of the mPFC, PL, and IL, plays a critical role in reversal learning.

Animals↗

PubMed1998

Induction of cyclooxygenase-2 by activated Ha-ras oncogene in Rat-1 fibroblasts and the role of mitogen-activated protein kinase pathway.

Elevated cyclooxygenase-2 (COX-2) expression and activity have been observed in several different transformed cell types that express mutated ras genes. To investigate the mechanism of increased COX-2 expression following Ras-mediated transformation, Rat-1:iRas cell line was transfected with an Ha-RasVal-12 cDNA expression vector that is under the transcriptional control of the lac operon and is inducible with isopropyl-1-thio-beta-D-galactopyranoside (IPTG). IPTG treatment caused parallel increases in the levels of Ha-Ras and COX-2 proteins in Rat-1:iRas cells. The increased expression of COX-2 was accompanied by increased prostaglandin E2 production. Selective inhibition of COX-2 activity suppressed the production of prostaglandin E2 by >90% but did not alter the progress of the morphological transformation. The level of COX-2 mRNA was up-regulated by activated Ha-Ras. Induction of Ras increased the transcription of COX-2 by 44.3 +/- 10.1% and increased the half-life of COX-2 mRNA by approximately 3.5-fold. A specific mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) inhibitor (PD 98059) caused a delay in both the activation of ERK1/2 and the induction of COX-2 in IPTG-induced Rat-1:iRas cells. Inhibition of ERK activity by PD 98059 also suppressed the induction of COX-2 by epidermal growth factor in intestinal epithelial cells and significantly reduced the expression of COX-2 in Ha-Ras-transformed rat intestinal epithelial cells. ERK activity appears to be required for induction of COX-2 by Ras.

Animals↗

PubMed1998

TGF-beta1 effects on proliferation of rat intestinal epithelial cells are due to inhibition of cyclin D1 expression.

Transforming growth factor-beta 1 (TGF-beta1) arrests intestinal epithelial cells (RIE-1 and IEC-6) in the G1 phase of the cell cycle and inhibits cyclin D1 expression. This report describes experiments designed to elucidate the mechanism of cyclin D1 inhibition and to determine whether inhibition of cyclin D1 expression is the cause, rather than the result, of TGF-beta1-mediated cell cycle arrest. TGF-beta1 inhibition of IEC-6 cell proliferation was associated with a decrease in the abundance of cyclin D1/Cdk4 complexes and a corresponding decrease in Cdk4-dependent phosphorylation of the retinoblastoma protein. Metabolic labeling studies indicated that TGF-beta1 inhibited cyclin D1 synthesis without altering the rate of cyclin D1 protein degradation. Cyclin D1 antisense oligonucleotides blocked serum-stimulated induction of cyclin D1 and DNA synthesis, whereas cyclin D1 sense oligonucleotides had no effect. RIE-1 cells were engineered to overexpress human cyclin D1 under the control of a tetracycline-repressible promoter. These cells entered S phase in the presence of TGF-beta1 only when human cyclin D1 was derepressed by the withdrawal of tetracycline. These data indicate that TGF-beta1 inhibits the synthesis of cyclin D1 in gut epithelial cells and that this inhibition is the cause, rather than the result, of TGF-beta1-mediated arrest of intestinal epithelial cell proliferation.

Animals↗

PubMed1998

Down-regulation of the novel gene melastatin correlates with potential for melanoma metastasis.

We have used differential cDNA display to search for genes whose expression correlates with an aggressive phenotype in variants of the B16 murine melanoma line, B16-F1 and B16-F10. This analysis identified a novel gene, termed melastatin, that is expressed at high levels in poorly metastatic variants of B16 melanoma and at much reduced levels in highly metastatic B16 variants. Melastatin was also found to be differentially expressed in tissue sections of human melanocytic neoplasms. Benign nevi express high levels of melastatin, whereas primary melanomas showed variable melastatin expression. Melastatin transcripts were not detected in melanoma metastases. Within the set of human primary cutaneous melanomas examined, melastatin expression appeared to correlate inversely with tumor thickness. The expression pattern observed suggests that loss of melastatin expression is an indicator of melanoma aggressiveness.

Amino Acid Sequence↗

PubMed1998

Modulation of apoptosis and Bcl-2 expression by prostaglandin E2 in human colon cancer cells.

Previously, we have shown that forced expression of prostaglandin endoperoxide synthase-2 [also called cyclooxygenase (COX) 2] leads to inhibition of programmed cell death in intestinal epithelial cells. More recently, we have demonstrated that growth of human colonic cancer xenografts is inhibited by treatment with a highly selective COX-2 inhibitor in tumors that express COX-2 (HCA-7) but not in those that lack COX-2 expression (HCT-116). To explore the biochemical mechanisms involved in these effects, we have evaluated the role of COX-2-derived eicosanoid products on programmed cell death in human colon cancer cells. Here we report that PGE2 treatment of human colon cancer cells leads to increased clonogenicity of HCA-7, but not HCT-116 cells. Treatment with a highly selective COX-2 inhibitor (SC-58125) decreases colony formation in monolayer culture and this growth inhibition was reversed by treatment with PGE2. Additionally, PGE2 inhibits programmed cell death caused by SC-58125 and induces Bcl-2 expression, but did not affect Bcl-x or Bax expression in human colon cancer (HCA-7) cells. Therefore, decreased cell death caused by PGE2 would enhance the tumorigenic potential of intestinal epithelial cells. Thus, these results may help to explain a component of the mechanism by which COX inhibitors prevent colorectal cancer in humans.

Animals↗

PubMed1998

Studies on the genotoxicity of molybdenum salts in human cells in vitro and in mice in vivo.

Molybdenum is an essential element in plants and animals as a cofactor for enzymes. Molybdenum trioxide is used in metallurgical processes, in cosmetics as a pigment, and in contact lens solution, yet limited information is available on molybdenum genotoxicity. In the present study the micronucleus (MN) assay in human lymphocytes and mouse bone marrow and the dominant lethal assay in mice were used to assess the genotoxic effects of molybdenum salts in vitro and in vivo. Two salts of molybdenum were tested in whole blood cultures. Ammonium molybdate was more potent than sodium molybdate in causing a dose-dependent decrease in viability and replicative index and an increase in MN formation in binucleated lymphocytes (P < 0.001). A dose-response in both kinetochore-positive MN (caused by chromosome lagging) and kinetochore-negative MN (associated with chromosome breakage) was observed. Based on the results of a toxicity study of sodium molybdate, two doses, 200 and 400 mg/kg, were assessed in the bone marrow MN assay in mice (two i.p. injections 24 and 48 hr prior to euthanasia). A modest but statistically significant increase in MN frequency in polychromatic erythrocytes was observed (P < 0.05). The same treatment protocol was used to analyze dominant lethality. A dose-dependent increase in postimplantation loss represented mostly by early resorptions was observed the first week after treatment (P = 0.003). These preliminary data suggest that sodium molybdate induces dominant lethality at the postmeiotic stage of spermatogenesis. Overall, molybdenum salts produced moderately positive results both in vitro in human cells and in vivo in mice.

Adult↗

PubMed1998

Expression of anti-CD4 human/murine chimeric antibody and their killer tumor activity.

From the mouse hybridoma cell line secreting an anti-CD4 monoclonal antibody (McAb), total RNA was prepared. The VH and VL genes were amplified by RT-PCR with family specific primer pairs. The PCR products were cloned into pGEM-T vectors, then tranfected into JM109. The VH and VL genes were analyzed by automatic DNA sequencer. According to Kabat classification, the VH and VL genes belong to the mouse Ig heavy subgroup II (A) and kappa chain subgroup III, respectively. The VH and VL genes were subcloned into p gamma 1-Expr and p kappa-Expr respectively, then transfected into XL2-Blue. The VH- p gamma 1 and VL- p kappa were transfected by electroporation into mouse myeloma cell X63Ag8. 653. The transfectoma cells were selected by G418 screening, and then supernatant of cultured transfectoma were analyzed by ELISA and immunofluorescence techniques. We have acquired transfectoma cells secreting anti-CD4 chimeric antibodies. These chimeric antibodies are able to kill tumor cells specifically in vitro.

Animals↗

PubMed1998

cDNA sequence analysis of monoclonal antibodies against the human placental acidic isoferritin.

By using human placental acidic isoferritin (PAF) as antigen to immunize BALB/c mice and conventional cell fusion, we have established three mouse hybridoma cell lines that secrete IgG monoclonal antibodies (MAbs) to PAF, termed as Z-2-3, Z-2-5, and Z-3-6, respectively. In ELISA, the MAbs were shown to react specifically with human PAF. We then applied the polymerase chain reaction (PCR) technique to clone variable region genes of the heavy (V(H)) and light (V(L)) chains of these MAbs, and appropriate full-length cDNA clones were obtained and characterized by nucleotide sequence analysis. V(H) and V(L) segments of anti-human PAF MAbs belong to the J558 and Vkappa19 family, respectively. The nucleotide sequence of Z-3-6 in the V(H) segment is highly homologous to that of MAb 18.1.16 except for their diversity minigenes. The light chain sequences of these MAbs show high homology with that of MAb cc92. It is implied that the D segment and the nucleotides inserted at the V(H)-D and D-J splice junctions are mostly responsible for the specificity of Z-3-6, and that the differences between the V(H) and V(L) sequences of these MAbs may determine their different affinity or recognition of different antigenic determinants.

Animals↗

PubMed1998

Nuclear translocation of beta-catenin in hereditary and carcinogen-induced intestinal adenomas.

The physical interaction between beta-catenin and the adenomatous polyposis coli (APC) gene, and the ability of APC to regulate cytoplasmic levels of beta-catenin suggest a role for beta-catenin in colorectal carcinogenesis. In this study, we found that beta-catenin immunoreactivity was detected exclusively in the cell membrane and cytoplasm of morphologically normal intestinal epithelial cells with predominant distribution in the differentiated nonproliferative cell population. In contrast, beta-catenin was localized predominantly in the nucleus of adenomas from Min/+ mice and transgenic mice expressing a mutant truncated form of the APC gene (Apc(delta716) mice). Beta-catenin was expressed predominantly at the cell membrane and cytoplasm of the nontransformed rat intestinal epithelial (RIE-1) cells in culture, whereas predominantly nuclear localization of beta-catenin was observed in the human colon cancer cell line SW480. In the azoxymethane (AOM) treated rats, overexpression and nuclear localization of beta-catenin was observed in all adenomas. Previous studies have indicated the incidence of APC mutations amongst AOM-induced tumors to be 15% or less. These results demonstrate that nuclear localization of beta-catenin is a common event in colorectal tumorigenesis.

Adenoma↗

PubMed1998

[Free fatty acids promoting PTP1B expression in rat skeletal muscle and hepatic cells].

OBJECTIVE: To determine whether that free fatty acids (FFAs) impair glucose metabolism is associated with altered insulin signaling system. METHODS: After skeletal muscle and hepatic cells were incubated with palmitate (0.25 mmol/L) or oleate (0.125 mmol/L) for 6, 12 or 24 hours, the protein abundance of SH-PTP2 and PTP1B was assessed by western blot. RESULTS: SH-PTP2 protein levels showed no significant change in both fatty acids treated muscle and hepatic cells at all time points. The PTP1B was significantly elevated in both liver and muscle cells incubated with FFAs at 6, 12 and 24 hours. CONCLUSIONS: FFAs promote the expression of PTP1B in rat skeletal muscle and liver cells, and the elevated PTP1B may mediate the insulin resistance induced by FFAs.

Animals↗

PubMed1998

[Detection of interleukin-8 level in peripheral blood of patients with aplastic anemia].

OBJECTIVE: To investigate the role of interleukin-8 in the pathogenesis of aplastic anemia (AA) and its correlation with clinical status. METHODS: Serum level of IL-8 in 24 AA patients and 20 normal controls was measured by sandwich enzyme linked immunosorbent assay(ELISA). RESULTS: The levels of IL-8 were increased significantly(P < 0.05) in AA patients than in normal controls, and the IL-8 levels in severe AA group were much higher than those in chronic AA group (P < 0.05). Serum IL-8 in AA patients with infection were elevated significantly(P < 0.005). CONCLUSION: IL-8 may have a potential role in the pathogenesis of AA and determination of serum IL-8 may be helpful for evaluation of severity and infectious complication of AA.

Adolescent↗

PubMed1998

[Establishment of Hymenolepis diminuta-animal model and morphology of cysticercoid].

AIM: To observe the morphological changes in the process of the development of Hymenolepis diminuta. METHODS: The life cycle of Hymenolepis diminuta was established between Rattus domesticus albus and Triboliun castaneum. The morphology of cysticercoid were observed microscopically, and the ultrastructure of the body surface of cysticercoid were observed by scanning electron microscopy. RESULTS: Three phases including the mature stage, the blister stage and the protective outer membrane-forming stage during the growing course of cysticercoid were observed microscopically. Under scanning electron microscope, lots of sieve-like micropores on the surface of mature cysticercoid were seen in the second week after infection. The blister phase was found in the third week and the outer membrane measuring about 45 microns in thickness were found surrounding the cysticercoid and vesicular surface, forming a smooth cyst wall in the fourth week. CONCLUSION: The life cycle of Hymenolepis diminuta has been established in the animal-model. The finding of the three phases during the growing course of cysticercoid is reported for the first time.

Animals↗

PubMed1997

Molecular cloning and sequencing of the cDNA encoding mouse glutamate-cysteine ligase regulatory subunit.

Reverse transcription-polymerase chain reaction (RT-PCR) was used to amplify and clone the regulatory subunit of mouse glutamate-cysteine ligase (Glclr) using primers adapted from the published rat Glclr cDNA sequence, and from mouse genomic DNA. Amplified cDNA was cloned into a plasmid vector, and additional RT-PCR reactions coupled with 3' RACE were used to amplify and sequence 3' regions covered by the rat primer. Comparison of the mouse Glclr cDNA sequence and predicted protein sequence with that of rat Glclr and human GLCLR revealed extensive homology in cDNA and amino acid sequences among these species.

Amino Acid Sequence↗

PubMed1997

Prediction bounds for random shelf-lives.

Every drug product requires indication of a shelf-life on the immediate container label. The labelled shelf-life is usually determined by a stability analysis with several batches of the drug product. Because of the existence of batch-to-batch variation, the true shelf-lives of different batches differ and can be treated as random variables. To obtain a single labelled shelf-life applicable to all future batches of the drug product, we propose to use a prediction bound of the random shelf-life of a future batch. Under some assumptions, the proposed labelled shelf-life (prediction bound) is lower than the true random shelf-life with a probability approximately equal to a pre-assigned level. For illustration, we provide an example concerning a new drug application stability analysis conducted in a pharmaceutical company. We also discuss an application of our technique to the problem of clean-up of contaminated soils.

Decontamination↗

PubMed1997

Statistical methods for two-sequence three-period cross-over designs with incomplete data.

In clinical trials, and in bioavailability and bioequivalence studies, one often encounters replicate cross-over designs such as a two-sequence three-period cross-over design to assess treatment and carry-over effects of two formulations of a drug product. Because of the potential dropout (or for some administrative reason), however, the observed data set from a replicate cross-over design is incomplete or unbalanced so that standard statistical methods for a cross-over design may not apply directly. For inference on the treatment and carry-over effects, we propose a method based on differences of the observations that eliminates the random subject effects and thus does not require any distributional condition on the random subject effects. When no datum is missing, this method provides the same results as the ordinary least squares method. When there are missing data, the proposed method still provides exact confidence intervals for the treatment and carry-over effects, as long as the dropout is independent of the measurement errors. We provide an example for illustration.

Clinical Trials as Topic↗

PubMed1997

Inhibition of human colon cancer cell growth by selective inhibition of cyclooxygenase-2.

A considerable amount of evidence collected from several different experimental systems indicates that cyclooxygenase-2 (COX-2) may play a role in colorectal tumorigenesis. Large epidemiologic studies have shown a 40-50% reduction in mortality from colorectal cancer in persons taking aspirin or other nonsteroidal antiinflammatory drugs on a regular basis. One property shared by all of these drugs is their ability to inhibit COX, a key enzyme in the conversion of arachidonic acid to prostaglandins. Two isoforms of COX have been characterized, COX-1 and COX-2. COX-2 is expressed at high levels in intestinal tumors in humans and rodents. In this study, we selected two transformed human colon cancer cell lines for studies on the role of COX-2 in intestinal tumorigenesis. We evaluated HCA-7 cells which express high levels of COX-2 protein constitutively and HCT-116 cells which lack COX-2 protein. Treatment of nude mice implanted with HCA-7 cells with a selective COX-2 inhibitor (SC-58125), reduced tumor formation by 85-90%. SC-58125 also inhibited colony formation of cultured HCA-7 cells. Conversely, SC-58125 had no effect on HCT-116 implants in nude mice or colony formation in culture. Here we provide evidence that there may be a direct link between inhibition of intestinal cancer growth and selective inhibition of the COX-2 pathway.

Animals↗

PubMed1997

Study on immunoregulation by interleukin-1 receptor antagonist in NZB/W F mice.

The immunoregulating effect of Interleukin-1-receptor antagonist (IL-1ra) in lupus-like NZB/W F1 mice was investigated to find possible approach to prevent lupus nephritis. 12 female NZB/W F1 mice of 13 weeks were randomly divided into 2 groups. Each mouse in the treated group was intraperitoneally injected with IL-1ra once every 2 weeks for 3 times at the dosage of 100 micrograms each time, while the control group was given injection of 0.1 ml normal saline. All the mice were killed at the age of 9 months and the immunologic function was examined. Results showed that this dosage could not completely prevent the development of lupus nephritis, but the renal damage was alleviated and the urine protein was decreased. Moreover, it could improve the immunofunction by significantly reducing the levels of serum IL-1 and obviously increase the activities of NK cells and IL-2 induced by ConA in mononuclear cells of spleen. There was no significant difference in the levels of serum IL-6 and TNF-alpha between the treated group and control group. It is concluded that IL-1ra has certain regulatory effect on the immunologic function of lupus-like NZB/W F1 mice.

Animals↗

PubMed1997

Five complete genomes of JC virus type 3 from Africans and African Americans.

The central demyelinating disease progressive multifocal leukoencephalopathy (PML) is caused by the human polyomavirus JC virus (JCV). JCV evolved as geographically based genotypes of which Type 3 is an African variant first characterized in HIV-1 positive patients from Tanzania. This study reports the complete sequence of five JCV Type 3 strains. The entire JCV genome was PCR amplified from urine specimens of three African and two African-American individuals. The African consensus sequence was compared to the Type 1 and Type 2 prototype strains, JCV (Mad-1) and JCV(GS/B), respectively. Type 3 differed in 2.2% of its coding region genome from JCV (Mad-1) and in 1.3% from JCV(GS/B). Within the coding region the sequence variation among the three types was higher in the capsid protein VP1 and in the regulatory protein large T antigen than in the agnoprotein or in VP2/3. Notable Type 3-specific changes were located at sites adjacent to the zinc finger motif and near the major donor and acceptor splice junctions of large T antigen. Four of the five urinary Type 3 strains had an unrearranged, archetypal regulatory region. African strain #309 showed a 10-bp deletion at a location similar to that previously described for #307 from Tanzania. The African-American Type 3 strain #312 was closely related to the African consensus sequence. The complete genome of a urinary JCV strain from another African-American male, previously reported as a possible Type 5, showed a sequence difference of only 0.52% from the Tanzanian consensus and has been reclassified as a subtype of Type 3.

Amino Acid Sequence↗