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Biomedical subjects

L Gao

Publications and source records attributed to L Gao.

At least 217 records · Page 12Linked to original sources
PubMed1994

Requirement of human immunodeficiency virus type 1 nef for in vivo replication and pathogenicity.

The role of human immunodeficiency virus type 1 (HIV-1) accessory genes in pathogenesis has remained unclear because of the lack of a suitable in vivo model. The most controversial of these genes is nef. We investigated the requirement for Nef for in vivo replication and pathogenicity of two isolates of HIV-1 (HIV-1JR-CSF and HIV-1NL4-3) in human fetal thymus and liver implants in severe combined immunodeficient mice. HIV-1JR-CSF and HIV-1NL4-3 differ in their in vitro phenotypes in that HIV-1JR-CSF does not induce syncytia and is relatively noncytopathic, while HIV-1NL4-3 is highly cytopathic and readily induces syncytia. The nef mutants of both isolates grew with kinetics similar to those of parental virus strains in stimulated peripheral blood lymphocytes but demonstrated attenuated growth properties in vivo. HIV-1NL4-3 induced severe depletion of human thymocytes within 6 weeks of infection, whereas its nef mutant did not. Thus, HIV-1 Nef is required for efficient in vivo viral replication and pathogenicity.

Animals↗
PubMed1994

High density cultivation of a recombinant CD-1 cell line producing prourokinase using a Biosilon microcarrier culture system.

CD-1, a genetically-engineered CHO cell line, was cultivated with a Biosilon microcarrier culture system. We successfully cultivated CD-1 cells to a very high density (over 1 x 10(7) cells/ml). Prourokinase was stably secreted at about 180 IU/10(6) cells/24 h. Experiments showed that CD-1 cells growing on Biosilon microcarriers were able to spontaneously release from the microcarriers, then reattach and proliferate on fresh microcarriers. This makes it very easy to scale up production. The microcarriers could be reused several times without affecting adhesion, proliferation and prourokinase secretion. With CM-PECC membrane radial flow chromatography and MPG chromatography, the prourokinase in conditioned medium could be purified to a specific activity of 1 x 10(5) IU/mg of protein. The purification factor was about 600 fold, and approximately 90% of the biological activity was recovered.

Animals↗
PubMed1994

Human monoclonal anti-idiotypic antibodies bearing the internal image of hemorrhagic fever with renal syndrome virus antigen.

A human hybridoma cell line C8 secreting human monoclonal anti-idiotypic antibodies (alpha Id) was established by fusing Epstein-Barr virus transfected peripheral blood lymphocytes from a hemorrhagic fever with renal syndrome (HFRS) patient with interspecific myeloma SHM-D33 cells. The alpha ID human monoclonal antibody (hMAb) could react with anti-HFRSV Ab1 from different species, and the reaction could be inhibited by HFRSV antigen, indicating that anti-idiotype hMAb bears the internal image of HFRSV antigen. Anti-HFRSV antibodies (Ab3) with neutralizing and hemagglutination inhibition activities in BALB/c mice or rabbits induced by the alpha Id h MAb were produced, suggesting that the internal image beared by anti-idiotype antibodies may be related to neutralizing and hemagglutinating epitopes on HFRSV antigen.

Animals↗
PubMed1994

High density cultivation of genetically-engineered CHO cell lines with microcarrier culture systems.

Genetically-engineered CHO cell lines, r beta-13 and CLF-8B2, were cultivated with the MC-1 microcarrier culture system. The cell density could be enhanced by increasing the concentration of microcarrier. At a microcarrier concentration of 10 mg/ml, the cell density could reach 4 to 5 x 10(6) cells/ml. It was shown that these cell lines would spontaneously release from the microcarrier to attach to and proliferate on fresh microcarriers. We were thus able to scale up cultivation using a simple method, i.e. by adding fresh microcarriers and medium directly into the culture system to about 2, 4 or 8 times the original volume. Using a perfusion culture system, we have successfully cultivated CLF-8B2 cells in a 2 L bioreactor for several weeks at medium perfusion rates of 0.5 to 3 working volumes. Prourokinase was stably secreted.

Animals↗
PubMed1993

The SCID-hu mouse as a model for HIV-1 infection.

During normal fetal ontogeny, one of the first organs to harbour CD4-positive cells is the thymus. This organ could therefore be one of the earliest targets infected by human immunodeficiency virus type 1 (HIV-1) in utero. HIV-1-infected cells and pathological abnormalities of the thymus have been seen in HIV-1-infected adults and children, and in some fetuses aborted from infected women. Studies of HIV-1 pathogenesis have been hampered by lack of a suitable animal model system. Here we use the SCID-hu mouse as a model to investigate the effect of virus infection on human tissue. The mouse is homozygous for the severe combined immunodeficiency (SCID) defect. The model is constructed by implanting human fetal liver and thymus under the mouse kidney capsule. A conjoint human organ develops, which allows normal maturation of human thymocytes. After direct inoculation of HIV-1 into these implants, we observed severe depletion of human CD4-bearing cells within a few weeks of infection. This correlated with increasing virus load in the implants. Thus the SCID-hu mouse may be a useful in vivo system for the study of HIV-1-induced pathology.

Animals↗
PubMed1993

Structure of the rat insulin-like growth factor binding protein-4 gene.

A family of six distinct insulin-like growth factor binding proteins (IGFBPs) have been isolated and their cDNA sequences characterized from rat and human species. Recently, the gene structures of the first three IGFBPs (IGFBP-1, -2 and -3) have also been determined. We now report the isolation of the rat IGFBP-4 gene and its genomic organization, as well as the DNA sequence of the promoter region. Rat IGFBP-4 gene spans at least 12 kilobases (kb) of the genomic sequence. It consists of four exons separated by three introns with approximate size of 6.4, 0.6 and 2.7 kb. A single transcriptional start site is located at 249 nucleotides upstream of the translational initiation ATG codon. The rat IGFBP-4 gene possesses a typical TATA box and a CAAT box, as well as multiple potential cis elements, including three cAMP responsive elements, three AP-1 binding sites and one progesterone receptor binding site in the 5' flanking region. The presence of these potential cis elements supports the tissue-specific expression of the IGFBP-4 gene.

Amino Acid Sequence↗
PubMed1993

Direct in vivo gene transfer to airway epithelium employing adenovirus-polylysine-DNA complexes.

Adenovirus-polylysine-DNA complexes were evaluated for their capacity to accomplish direct in vivo gene transfer to airway epithelium employing a rodent model. Binary complexes containing transferrin or adenovirus, or combination complexes containing both transferrin and adenovirus, were evaluated. The highest in vitro gene transfer efficiency in primary cultures of airway epithelial cells was accomplished by the combination complexes. This result was paralleled in vivo. Transient gene expression of up to 1 week was observed with localization of the transduced cells to the region of the small airways. These results establish the feasibility of this type of approach for gene therapy applications.

Adenoviridae↗
PubMed1993

Preliminary experience in HDR brachytherapy for 72 nasopharyngeal carcinoma patients.

From April 1989 to July 1991, 72 patients with residual or recurrent nasopharyngeal carcinoma (NPC) were treated by MSH Ir-192 brachytherapy or combined external radiation therapy. All were proven histologically. 39 patients with residual disease and 6 with recurrent lesion at the primary site were identified after one or more courses of radical external radiation. Eleven patients had received brachytherapy for boost therapy after one or more courses of external radiation. Sixteen were treated with a planned protocol of external irradiation combined with intracavitary brachytherapy. The overall local control rate was 93.3%; the local control rate for residual and recurrent disease was 100% and 50%, respectively. Soft palate perforation was observed in 3 patients. Brachytherapy is believed to be a useful treatment for residual or recurrent NPC following radical external radiation.

Adolescent↗
PubMed1993

[Pulmonary lymphangiomyomatosis: report of a case].

A case of pulmonary lymphangiomyomatosis in a 28-year-old woman with dyspnea, hemoptysis, chylothorax and irregular menstruation as presenting symptoms was reported. Chest CT scan showed the presence of pleural effusion on right side and a honeycomb pattern throughout the lung parenchyma bilaterally. The diagnosis was confirmed histologically by transbronchial lung biopsy. Medroxyprogesterone was administered; improvement in arterial blood gas analysis and reduction of the amount of pleural effusion were noted after one month. The etiology, clinical manifestations, pathological characteristics and treatment of this disease were discussed.

Adult↗
PubMed1993

[The effects of phenytoin and carbamazepine on the cognitive function of epileptic patients].

We made a comparative study of the cognitive function of 60 epileptic patients before and after the use of phenytoin (DPH) and carbamazepine (CBZ). Five types of neuropsychological tests were adopted. Although both DPH and CBZ affected cognitive function, the degrees of their effects were not the same. DPH affected cognitive function in a broad field, including concentration, remembrance, psychological motor speed and mental processing, whereas CBZ had only slight effect on perception and motor speed. It is stressed that cognitive function disorder caused by antiepileptic drugs should be early detected by synchronous examinations of the level of antiepileptic drugs and the neuropsychological functions.

Attention↗
PubMed1993

Effects of argipressin injected into medial amygdaloid body on blood pressure and heart rate in rats.

Graded injections of argipressin (Arg, 150, 300, and 600 ng/1.5 microliters CSF, 2 min) into the medial amygdaloid body in anesthetized rats produced a dose-related increase in the mean arterial pressure and heart rate (Maximal delta MAP = 2.9 +/- 1.5 kPa, Maximal delta HR = 67 +/- 38 bpm), which lasting > 40 min at 600 ng dosage. Naloxone (15 micrograms/15 microliters CSF) injected into the lateral ventricle blocked the cardiovascular responses to Arg. These results suggest that Arg exerts a central action on the cardiovascular system via the opioid in the lateral ventricle.

Amygdala↗
PubMed1992

Repression of the embryonic myosin heavy chain phenotype in regenerating chicken slow muscle is dependent on innervation.

Ventricular-like and fast myosin heavy chains (VL-MHC and FMHC) are transiently expressed during slow skeletal muscle development. The influence of innervation on repression of these MHC isoforms is investigated over an 84-day time course in: (1) normal anterior latissimus dorsi (N-ALD) muscles, (2) regenerating ALD (R-ALD) muscles, (3) denervated ALD (D-ALD) muscles, and (4) regenerating and denervated ALD (RD-ALD) muscles. Western blotting demonstrates that the VL-MHC is expressed in R-, D-, and RD-ALD muscles, but not in N-ALD muscles. Expression of the VL-MHC is transient in R-ALD muscles. In contrast, VL-MHC expression persists in RD-ALD muscles, and appears with time in D-ALD muscles. FMHC was not detected in N-ALD muscles by Western blotting. Two FMHCs are seen in R-ALD and RD-ALD muscles, and in 13-day embryonic ALD muscles. The slower migrating FMHC (FMHCA) comigrates with developmentally regulated FMHCs in fast pectoralis muscle, while the faster migrating FMHC (FMHCB) comigrates with the faster migrating FMHC in embryonic ALD muscle (13 days in ovo). FMHCB decreases in amount over the time course in R-ALD muscles, while FMHCA persists. In contrast, substantial levels of both FMHCs persist in RD-ALD muscles, and appear with time in D-ALD muscles. The cellular distribution of MHCs is followed by immunocytochemistry. Regenerating cells expressing VL-MHC and FMHC are replaced by a mature population in R-ALD muscles. Some of the mature myofibers in R-ALD muscles express FMHC, but not VL-MHC. In RD-ALD and D-ALD muscles, both regenerating and mature muscle cells are seen which express VL-MHC and FMHC. Our results indicate that innervation is required for the repression of VL-MHC and FMHCB during regeneration of slow muscle.

Animals↗
PubMed1992

Dosimetry in photodynamic therapy: oxygen and the critical importance of capillary density.

Recently published results of tumor response to various photoradiation protocols in photodynamic therapy appear to contradict accepted definitions of photodynamic dose. In this report, the failure of standard dosimetry models to predict therapeutic outcome is interpreted on the basis of PDT-induced oxygen consumption in tumors with relatively low capillary densities. Calculated estimates of oxygen consumption in photodynamic therapy are combined with the Krogh cylinder model of oxygen diffusion. It is shown that, for tissue volumes in which the intercapillary spacing is less than a specific critical distance, oxygen may be considered constant and unaffected by the therapy. Under these conditions, the 1O2 delivered to a given volume of tissue is spatially uniform and proportional to the number of photons absorbed by the sensitizer. When the intercapillary spacing exceeds the critical distance, the dose of 1O2 varies with radial distance from the capillary wall. In this situation, dose may no longer be considered simply in terms of the product of the photon fluence and the sensitizer absorption coefficient. Since fractionation will increase the 1O2 dose only to cells relatively remote from the capillary wall, the analysis further suggests that fractionating the radiation dose should result in an improved therapeutic ratio for photodynamic therapy.

Capillaries↗
PubMed1992

[Relation between emphysema and diaphragmatic fatigue].

Emphysematous rats induced by elastase were divided into 5 groups: N (control), P1 (elastase for 3 mo.), P2 (elastase for 4.5 mo.; NS intraperitoneally for 1 mo. after 3.5 mo. elastase); A and C, aminophylline and ginseng preparation were respectively given in the same fashion as P2. The results were: 1. tension and endurance of diaphragm muscle decreased under low frequency stimulation in P2, while those no change in P1. DNA, RNA and ATPase increased, cross-sectional areas and glycogen decreased in P1, while ATPase and RNA reduced with increase of cross-sectional areas in P2; 2. in A, no change in tension, with enhanced endurance; 3. in C, tension increased with no change in endurance; 4. glycogen and cross-sectional areas increased in both A and C; 5. RNA and ATPase increased in C and no change in A.

Aminophylline↗