Search PubMed⌕ Search

Biomedical subjects

Q Shi

Publications and source records attributed to Q Shi.

At least 181 records · Page 10Linked to original sources
PubMed1997

Regulation of the biological activity of glucagon-like peptide 2 in vivo by dipeptidyl peptidase IV.

Species-specific differences in the enzymatic inactivation of peptides is an important consideration in the evaluation of therapeutic efficacy. We demonstrate that glucagon-like peptide 2 (GLP-2), shown to be highly intestinotrophic in mice, promotes an increase in intestinal villus height but has no trophic effect on small bowel weight in rats. The reduced intestinotrophic activity of GLP-2 in rats is attributable to inactivation by the enzyme dipeptidyl peptidase IV (DPP-IV). GLP-2(1-33) was degraded to GLP-2(3-33) following incubation with human placental DPP-IV or rat serum but not by serum from DPP-IV-deficient rats. Administration of rat GLP-2 to DPP-IV-deficient rats was associated with markedly increased bioactivity of rat GLP-2 resulting in a significant increase in small bowel weight. A synthetic GLP-2 analog, r[Gly2]GLP-2, with an alanine to glycine substitution at position 2, was resistant to cleavage by both DPP-IV and rat serum in vitro. Treatment of wild-type rats with r[Gly2]GLP-2 produced a statistically significant increase in small bowel mass. DPP-IV-mediated inactivation of GLP-2 is a critical determinant of the growth factor-like properties of GLP-2.

Animals↗
PubMed1997

[Hodgkin's disease with concurrent infection of toxoplasmosis].

Hodgkin's disease (HD) is a specific type of malignant lymphoma characteristic of local and general lymphadenectasis. Aquired toxoplasmosis (AT) is one kind of lymphoadenopathy without fever and fatigue. When the two diseases coexist, clinical and pathological misdiagnosis may be made. This is the first male case of toxoplasmosis and Hodgkin's disease in China, diagnosed by surgical removal of the major part of the cervical and supraclavicular masses, detection of blood anti-toxoplasma gondii antibody, PCR analysis of toxoplasma gondii DNA, and pathological, ultrastructural and immunohistochemical studies of the tumour tissues. The patient treated by radiation and chemotherapy was abated.

Adult↗
PubMed1997

[Cloning and expression in Escherichia coli of an alkaline and thermostable exolipase from Pseudomonas pseudoalcaligenes].

A gene coding for an alkaline and thermostable exolipase of Pseudomonas pseudoalcaligenes was cloned into Escherichia coli LE392 by inserting Sau3 AI-generated DNA fragments into the BamHI site of pIJ285. Four colonies with esterase and lipase activities on the tributyrin agar plate were isolated by screening the constructed pseudomonas pseudoalcaligenes genomic library. Only one out of the four positive colonies showed lipase activity on the agar plate contatining olive oil and Rhodamine-B. Subclones of the 45 kb insert carrying lipase gene was obtained in E. coli HB101 using pUC118 as a vector, two of which (HB101 (pHZ1402) and HB101 (pHZ1403)), retained lipase activity, but the level seems to be different. They carried 3.0 kb and 2.9 kb inserts with a 2 kb overlapping sequence. The lipase activity of HB101 (pHZ1403) is about 4 times higher than that of HB101 (pHZ1402), as 5 times as that of original strain P. pseudoalcaligenes.

English Abstract↗
PubMed1997

[Technological study on the supercritical-CO2 fluid extraction of Curcuma longa oils].

This paper first reports technological study on the extraction of Curcuma longa oils by supercritical-CO2 fluid, mainly studies the influence of pressure, temperature, flow rate of CO2 and time on the yield of the oils, determines optimum technology of extracting the oils, analyzes chemical constituents extracted, compares the oils from SFE-CO2 and SD technology, studies industrial test on the SF-CO2 extraction. The results shows pressure and temperature are more important factors of influence; the optimum technological condition is the extracted pressure 25 MPa and temperature 45 degrees C, isolated pressure I 12.5 MPa and temperature I 60 degrees C, isolated pressure II 6MPa and temperature II 38 degrees C, CO2 flow rate 9 Kg/Kg.h, and extracted time 2 h; the constituents from SFE-CO2 and SD methods are identical, but their content has some difference; SFE-CO2 technology is better than that of SD, which is high yield shorter time, etc.; the industrial production of the oils with SFE-CO2 method is available.

Carbon Dioxide↗
PubMed1997

[Supercritical-CO2 fluid extraction of natural VE and fatty oil from the oil foot of Brassica campestris and GC-MS analysis].

Natural VE and fatty oil from the oil foot of Brassica campestris are extracted by supercritical-CO2. After saponification and esterification these acidesters and natural VE in the extraction are analyzed by GC-MS. The results show that the fatty acids from SFE-CO2 contain 10 components which of oleic acid, linodeic acid and linolenic acid are main components, linodenic acid and linoleic acid of them are increased signifantly, at the same time, natural VE can be extracted from the materials and the rate of extraction gets to 95%.

Brassicaceae↗
PubMed1997

[Studies of bone marrow T lymphocytes in patients with aplastic anemia].

OBJECTIVE: To study the role of immunological factors in the pathogenesis of aplastic anemia(AA). METHODS: Phenotype of T lymphocytes in bone marrow and CFU-GM yields of bone marrow mononuclear cells with or without T cells were assayed with APAAP and semi-solid culture method, respectively. RESULTS: The percentage of lymphocytes in bone marrow of AA patients was higher than that of normal controls, and the lymphocytes were mainly CD8 and CD25 positive cells. Changes of T lymphocyte subsets in peripheral blood of AA patients did not completely reflect the changes in the bone marrow. In some AA patients, increased percentage of CD8+ cells was found in bone marrow, while it was normal in peripheral blood. The CFU-GM yields of bone marrow cells of AA patients were much lower than that of normal controls, and were markedly improved by removing T cells before culture. CONCLUSION: The abnormalities of cell-mediated immune response played important roles in the pathogenesis of AA. The changes of T lymphocytes in bone marrow were more meaningful than that in peripheral blood. It is suggested that bone marrow T lymphocyte and its subsets should be routinely examined in all of the AA patients diagnosed so as to assess the indication and predict the effectiveness of immunosuppresive therapy.

Adolescent↗
PubMed1997

[Determination of composition of electronic material by fundamental parameter method of XRF].

The fundamental parameters (FP) method of XRF in determination of the composition of electronic ceramic materials is studied. The fundamental parameters needed in calculation are developed by math calculation and the program is developed in C language. The method can also be used in determination of the composition of alloy. Some samples are analysed by this method and the relative derivation is less than 3%.

English Abstract↗
PubMed1997

Continued risky injection subsequent to syringe exchange use among injection drug users in New York City.

Although the vast majority of injection drug users (IDUs) attending syringe exchange programs in New York City have stopped risky injection (injecting with syringes used by someone else), there remains a subgroup of IDUs who continue to engage in high-risk injecting behaviors despite access to sterile syringes. Subjects were randomly recruited from five legally authorized syringe exchange programs in New York City between October 1992 and August 1994. Participants were asked about drug and sexual risk behavior 30 days prior to their first use of the syringe exchange as well as during the 30-day period prior to the interview while using the exchange. Of the 2,465 participants, 77.4% reported no risky injection during the 30 days prior to using syringes exchange. For this analysis we included only those who reported risky injection for the 30-day period prior to using syringe exchange (N = 556). We compared sociodemographics and behavioral characteristics of a group who continued risky injection while using the syringe exchange, "continuers," N = 158 (28.8%) with a group who reported risky injection prior to using the exchange and then ceased risky injection while using the exchange, "stoppers," N = 391(71.2%). Continuers were significantly more likely to report passing on dirty syringes to social network members and to inject cocaine at least daily. We present other predictors of continued risk and discuss the implications for interventions and make recommendations for syringe exchange programs.

Adult↗
PubMed1996

HIV incidence among injecting drug users in New York City syringe-exchange programmes.

BACKGROUND: There have been no studies showing that participation in programmes which provide legal access to drug-injection equipment leads to individual-level protection against incident HIV infection. We have compared HIV incidence among injecting drug users participating in syringe-exchange programmes in New York City with that among non-participants. METHODS: We used meta-analytic techniques to combine HIV incidence data from injecting drug users in three studies: the Syringe Exchange Evaluation (n = 280), in which multiple interviews and saliva samples were collected from participants at exchange sites; the Vaccine Preparedness initiative cohort (n = 133 continuing exchanges and 188 non-exchangers, in which participants were interviewed and tested for HIV every 3 months; and very-high-seroprevalence cities in the National AIDS Demonstration Research (NADR) programme (n = 1029), in which street-recruited individuals were interviewed and tested for HIV every 6 months. In practice, participants in the NADR study had not used syringe exchanges. FINDINGS: HIV incidence among continuing exchange-users in the Syringe Exchange Evaluation was 1.58 per 100 person-years at risk (95% CI 0.54, 4.65) and among continuing exchange-users in the Vaccine Preparedness Initiative it was 1.38 per 100 person-years at risk (0.23, 4.57). Incidence among non-users of the exchange in the Vaccine Preparedness Initiative was 5.26 per 100 person-years at risk (2.41, 11.49), and in the NADR cities, 6.23 per 100 person-years at risk (4.4, 8.6). In a pooled-data, multivariate proportional-hazards analysis, not using the exchanges was associated with a hazard ratio of 3.35 (95% CI 1.29, 8.65) for incident HIV infection compared with using the exchanges. INTERPRETATION: We observed an individual-level protective effect against HIV infection associated with participation in a syringe-exchange programme. Sterile injection equipment should be legally provided to reduce the risk of HIV infection in persons who inject illicit drugs.

Adult↗
PubMed1996

Stability of the human dystrophin transcript in muscle.

The human dystrophin gene has 79 exons spanning >2300 kb making it the largest known gene. In previous studies we showed that approximately 16 h are required to transcribe the gene in myogenic cultures [Tennyson, C.N., Klamut, H.J. and Worton, R.G. (1995) Nature Genet. 9, 184-190]. To estimate the half-life of the dystrophin mRNA, the decay of the transcript was monitored by quantitative RT-PCR in cultured human fetal myotubes following exposure to actinomycin D. Results from this analysis indicated that the half-life of the dystrophin mRNA is 15.6 +/- 2.8 h in these cultures. Transcript accumulation profiles were predicted using a mathematical model which incorporated the measured half-life. The modeled accumulation profiles were consistent with observed profiles supporting the half-life measured using actinomycin D. The kinetic model was then used to predict the relative amount of nascent and mature dystrophin transcript at steady state. Measurements by quantitative RT-PCR indicated that in adult skeletal muscle tissue the concentration of mature dystrophin mRNA is 5-10 molecules per nucleus, demonstrating, as expected, that it is a low abundance transcript. Furthermore the ratio of nascent to mature dystrophin transcript indicated that dystrophin synthesis may not be at steady state in the adult skeletal muscle we tested. Alternatively, the kinetics of transcript production in skeletal muscle tissue may be different from those observed in cultured fetal myogenic cells.

Adult↗
PubMed1996

Synthesis and pharmacology of potential cocaine antagonists. 2. Structure-activity relationship studies of aromatic ring-substituted methylphenidate analogs.

As part of a program to develop medications which can block the binding of cocaine to the dopamine transporter, yet spare dopamine uptake, a series of aromatic ring-substituted methylphenidate derivatives was synthesized and tested for inhibitory potency in [3H]WIN 35,428 binding and [3H]dopamine uptake assays using rat striatal tissue. Synthesis was accomplished by alkylation of 2-bromopyridine with anions derived from various substituted phenylacetonitriles. In most cases, erythro compounds were markedly less potent than the corresponding (+/-)-threo-methylphenidate (TMP; Ritalin) derivatives. The ortho-substituted compounds were much less potent than the corresponding meta- and/or para-substituted derivatives. The most potent compound against [3H]WIN 35,428 binding, m-bromo-TMP, was 20-fold more potent than the parent compound, whereas the most potent compound against [3H]dopamine uptake, m,p-dichloro-TMP, was 32-fold more potent. Threo derivatives with m- or p-halo substituents were more potent than TMP, while electron-donating substituents caused little change or small loss of potency. All of the derivatives had Hill coefficients approaching unity, except m,p-dichloro-TMP, which had an nH of 2.0. Although the potency of the (+/-)-methylphenidate derivatives in the two assays was highly correlated (R2 = 0.986), the compounds m-chloro-,m-methyl-, and p-iodo-TMP were 4-5-fold more potent at inhibiting [3H]-WIN 35,428 binding than [3H]dopamine uptake (cocaine has a ratio of 2.3). These and other compounds may be promising candidates for further testing as potential partial agonists or antagonists of cocaine.

Animals↗
PubMed1996

Specific replacement of consecutive AGG codons results in high-level expression of human cardiac troponin T in Escherichia coli.

The adult isoform of human cardiac troponin T (TnT) contains 288 amino acids, 14 of which (4.9%) are encoded by the rarely used arginine codons (12 AGG, 2 AGA) in Escherichia coli genes. To generate sufficient quantity of TnT protein for antibody production, we cloned the corresponding cDNA and expressed it in E. coli. A low-level expression of TnT that comprised only about 1% of total cell protein was initially observed with the use of the native cDNA. The existence of two pairs of consecutive AGG codons AGG(165) AGG(166) and AGG(215) AGG(216) in the cDNA was suspected to be the main cause for this low-level expression. These two pairs of consecutive AGG codons were successively replaced with the major synonymous codon CGT by site-directed mutagenesis. As suspected, a 10-fold increase in TnT expression was obtained when one pair of the rare arginine codons was replaced and a 40-fold increase was achieved when both pairs of the rare codons were replaced. Our finding demonstrates the importance of consecutive rare codons in the suppression of high-level expression of heterologous proteins in E. coli and suggests that in order to maximize protein expression, a similar approach may be taken with other genes which contain consecutive rare codons.

Adult↗
PubMed1996

Histologic observation of continuity of transmural microvessels between the perigraft vessels and flow surface microostia in a porous vascular prosthesis.

To ascertain the histologic relationship between flow surface microostia and perigraft vessels in the healing of a porous vascular prosthesis, a series of careful histologic examinations were carried out on a preclotted, knitted Dacron graft, 8 mm in diameter and 7 cm long, after implantation in the canine infrarenal abdominal aorta for 3 months. Four adjacent longitudinal tissue blocks were taken from the middle for evaluation by means of light microscopy, scanning electron microscopy, transmission electron microscopy, and immunocytochemical staining, and the remainder of the specimen was stained with silver nitrate to allow visualization of microostia and cell borders on the flow surface. Following identification of two microostia adjacent to the area where samples had been taken for general healing evaluation, a 3 x 8 mm full-thickness block containing the microostia was embedded in glycol methacrylate and stained with hematoxylin and eosin. Of 240 serial sections cut from this block, 80 were prepared and examined. Silver staining revealed 42 microostia on the flow surface. Light, scanning, and transmission electron microscopy with endothelial factor VIII/von Willebrand factor stain confirmed a single layer of endothelial cells on the flow surface, and beneath was a well-organized neointima containing fusiform cells confirmed as smooth muscle by alpha-actin stain. Light microscopy of the serial sections revealed transmural microvessels, lined with endothelium, extending continuously between the flow surface ostia and the perigraft vessels in this porous vascular prosthesis.

Animals↗
PubMed1996

Use of enzyme immunoassay for measurement of skeletal troponin-I utilizing isoform-specific monoclonal antibodies.

OBJECTIVE: To determine the serum level of fast skeletal troponin I (fsTnl) resulting from skeletal muscle damage, we have developed a sensitive two-site enzyme immunoassay to measure skeletal troponin I. DESIGN AND METHODS: Twelve monoclonal antibodies were raised against human fsTnl. Of these antibodies, 8 were fsTnl-specific and the remaining 4 reacted with both skeletal and cardiac troponin I (cTnl). Two monoclonals were utilized for a development of this fsTnl immunoassay. Standards were made with purified recombinant human fsTnl for the range of 0-25 micrograms/mL. RESULTS: Total assay variance (CV) ranged from 1.7% to 9.6%. The upper limit of the normal reference range was established as 0.2 microgram/L by determining fsTnl concentration in sera of 108 healthy donors without evidence of muscle damage. Purified human cTnl up to 500 micrograms/L and cTnl-positive clinical serum samples yielded negative results in the fsTnl assay. The serum levels of fsTnl were determined in trauma patients, patients with chronic degenerative muscle disease, and marathon runners. In the study populations, the serum levels of fsTnl were correlated with other biochemical markers that are traditionally used to monitor striated muscle damage. CONCLUSIONS: In the present preliminary studies, measuring the serum levels of fsTnl in patients with various forms of muscle damage is more accurate than using the classical non muscle-specific biochemical markers.

Animals↗
PubMed1996

Electrophysiological effects of aconitine in rat hippocampal slices.

The electrophysiological effects of aconitine were investigated in the rat hippocampal slice and compared with those of veratridine. Both alkaloids are known to bind at site 2 of sodium channels and to block its inactivation. Extracellular recordings revealed that aconitine and veratridine exert inhibitory effects on neuronal excitability. Aconitine slowly and reversibly decreased the population spike recorded in the CA1 pyramidal cell layer. The reduction of the spike amplitude was similar whether orthodromically or antidromically activated. The aconitine-induced inhibition did not differ from that of veratridine. However, following washout of aconitine, the amplitude of the antidromic spike was increased compared to the control amplitude. The veratridine-induced inhibition was only partially reversible. This inhibition was also observed during suppression of synaptic transmission by a low Ca2+/high Mg2+-medium, indicating an inhibition of axonal conductance. The results show that in the absence of synaptic transmission the antidromic (alvear) spike is more sensitive to the inhibitory action of aconitine than the presynaptic fiber spike elicited by stimulation of the Schaffer collaterals. Furthermore, it is shown that aconitine acts in an activity-dependent manner, in that the latency of onset of the inhibition is prolonged when the stimulation frequency is decreased. Field excitatory postsynaptic potentials were also suppressed by aconitine, whereas excitatory postsynaptic currents recorded by the patch clamp technique were not influenced by aconitine when cells were held at -60 mV.

Aconitine↗