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Biomedical subjects

S Q Li

Publications and source records attributed to S Q Li.

At least 73 records · Page 4Linked to original sources
PubMed1991

Fetal pig pancreas--a preliminary assessment of tissue for transplantation.

Porcine fetal pancreases (PFP) obtained from 4 pregnant sows were pooled, minced into 1 mm3 fragments and studied in organ culture for up to 30 days to determine tissue viability and insulin production in vitro. After 7-9 days in culture, some of these explants were transplanted into euglycemic, N:NIH-nu(s) nude recipient mice, and studied histologically over 69 days following grafting. Using RPMI 1640 supplemented with 5% fetal calf serum as the culture medium in 90% air/10% CO2, it was found that explants were viable with insulin production detected in vitro, which was maximal at day 7 (197 +/- 18.9 mU/L, n = 11), and gradually declined thereafter. By 22 days, insulin levels were less than 60.1 +/- 28.5 mU/L (n = 6). Histology of the explants showed viable tissue with evidence of mitoses present in insulin-positive cells at day 16 in vitro. Beyond this time, tissue viability diminished. Explants transplanted into euglycemic nude mice did not undergo rejection during the observation period of 69 days. Grafts remained viable with evidence of an increase in mitotic activity in the endocrine tissue on immunoperoxidase staining. These preliminary investigations confirm that pancreatic explants from porcine fetuses can be maintained in culture for up to 16 days. Such explants, when transplanted under the kidney capsule of euglycemic, nude mice, did not undergo necrosis, but remained viable, with evidence of mitoses in the islet tissue.

Animals↗
PubMed1991

Accessory heart graft as a surgical model in studies of transplantation immunology.

The heterotopic heart graft was examined as a surgical model for in vivo studies of transplantation immunology. Two innovations previously described distinguish it from an orthotopic heart transplant; its heterotopic, superficial position in the neck, and the use of portex cuffs to facilitate anastomoses of donor aorta and pulmonary artery to recipient common carotid artery and external jugular vein respectively. In this study, few modifications to the original technique were required. However, to ensure a high technical success rate exceeding 95%, it was found that the use of small donors (less than 200 g) and large recipient rats (greater than 230 g) was required. The former minimised the risk of kinking of the venous anastomoses, and the latter ensured an adequate luminal diameter of the carotid artery to facilitate the cuff anastomosis. With the vena cava and pulmonary veins ligated, the transplant served purely as an indicator graft with rhythmic contractions discernible by inspection or palpation. This simplified monitoring of the graft, with no requirement for ECG or biochemical studies. The direction of blood flow was established by angiography as via the aorta to the coronary vessels, returned to the right atrium and ventricle and out through the pulmonary artery to the recipient circulation. As the accessory heart did not provide any life-sustaining function, it could be removed for histological studies once rejection had occurred without compromising the survival of the recipient animal. This allowed the use of the recipient for further studies on its immunological status, including the performance of second grafts.

Animals↗
PubMed1991

Induction of tolerance to vascularised skin allografts using cyclosporin A--an experimental study on rats.

This study investigates the induction of tolerance to vascularised skin allografts in a low responder rodent strain combination. Pedicle skin grafts based on the epigastric vessels were grafted between Dark Agouti (DA) and Piebald Virol Glaxo (PVG) rats (n = 24). An extended treatment protocol of high dose cyclosporin A (CyA) (25 mg/kg) spanning nine weeks was used. The mean survival time of epigastric skin grafts in the no treatment control group was 7.6 days (n = 10). With high dose CyA (25 mg/kg), 5/14 animals died during CyA treatment with intact skin grafts. The remaining nine animals enjoyed prolonged graft survival throughout the treatment period. Between one and four weeks following cessation of CyA, rejection occurred in six of nine animals which could not be reversed by pulse CyA treatment. Long term graft survival greater than 200 days was achieved in three animals, but two animals went on to reject their grafts at 231 and 238 days post transplant. Only one animal became tolerant, as confirmed by the retention of a fresh donor-specific free skin graft, without the need for further CyA. This study confirms the difficulty of tolerance induction to vascularised skin grafts, despite using a dose schedule of CyA far in excess of that required to achieve tolerance to other solid organ grafts such as hearts.

Animals↗
PubMed1991

A study of the xenogeneic response in an isolated liver perfusion circuit--preliminary observations.

An isolated liver perfusion circuit was developed to study the xenogeneic reaction of human blood to porcine liver, and investigate the feasibility of using such a system for liver dialysis in fulminant hepatic failure. Three experimental groups were studied: a control group where pooled porcine blood was perfused through pig liver (n = 12), a xenogeneic group where banked human blood was perfused through porcine liver (n = 23), and a modified xenogeneic group where decomplemented human blood was perfused through porcine liver (n = 4). The following parameters of liver function were assessed: liver function tests, serum electrolytes, bile and ascites production. In addition, liver histology was assessed at the start and completion of each perfusion experiment. Control experiments established that the use of low perfusion pressures (mean inlet pressure of 29.5 +/- 7.4 mmHg), and low haematocrit of 20.5 +/- 8.9% (n = 14), enabled five hour perfusions to be consistently achieved with maintenance of normal acid base and electrolyte balance. Bile production over 5 hours was 18.8 +/- 8.0 ml in controls (n = 5) and 17.0 +/- 6.7 ml in the xenogeneic (human-pig) circuit (n = 11) (NS). Ascites production was 235.8 +/- 157.3 ml/hr in controls (n = 5) and 205 +/- 142.0 ml/hr in the xenogeneic circuit (n = 7) (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Investigation of Lyme disease in Xinjiang.

From April through July 1988, an epidemiological investigation on Lyme disease was carried out in Nalati Xanyuan, Xinjiang Uygur Autonomous Region, China. Of 150 Ixodes persulcatus ticks examined by darkfield microscopy, 42 (28%) were found to have spirochetes. Two strains of spirochetes were isolated from I. persulcatus with BSK medium. Rabbits inoculated with the spirochetes showed erythema chronicum migrans at the sites of inoculation and the spirochetes were found in the cerebrospinal fluid by darkfield microscopy. Serum samples from 63 patients were examined for antibodies to B. burgdorferi by IFA test and 11 of them were positive with a titer of 1:64. Upon these results, it may be concluded that natural focus of Lyme disease exists in Xinjiang, China.

Animals↗
PubMed1990

Generation of seal influenza virus variants pathogenic for chickens, because of hemagglutinin cleavage site changes.

Influenza virus A/seal/Mass/1/80 (H7N7) was adapted to grow in MDCK cells and chicken embryo cells (CEC) in the absence of exogenous protease. The biological properties of the virus variants obtained coincided with intracellular activation of the hemagglutinin (HA) by posttranslational proteolytic cleavage and depended on the cell type used for adaptation. MDCK cell-adapted variants contained point mutations in regions of the HA more distant from the cleavage site. It is proposed that these mutations are probably responsible, through an unknown mechanism, for enhanced cleavability of HA in MDCK cells. Such virus variants were apathogenic in chickens. CEC-adapted variants, on the other hand, contained an insertion of basic amino acids at the HA cleavage site, in addition to scattered point mutations. The insertions converted the cleavage sites in the variant virus HAs so that they came to resemble the cleavage site found in highly pathogenic avian influenza viruses. CEC variants with such cleavage site modifications were highly pathogenic for chickens. The lethal outcome of the infection in chickens demonstrated for the first time that an influenza virus derived from a mammalian species can be modified during adaptation to a new cell type to such an extent that the resulting virus variant becomes pathogenic for an avian species.

Amino Acid Sequence↗
PubMed1990

Recombinant bivalent live vaccines against neonatal colibacillosis in piglets.

The genes of colonization factor K88 and avirulent heat-labile enterotoxin LT A-B+ of enterotoxigenic E. coli (ETEC) have been ligated, and a vaccine strain containing recombinant plasmid that efficiently expresses two antigens has been obtained. Using the activity of beta-galactosidase as a selection marker instead of drug resistance, another bivalent vaccine strain with the same expression level has also been constructed. The vaccine strains have no toxicity and do not cause any adverse reactions. In challenge study and field trials, a high degree of protection from colibacillosis was afforded to piglets when their dams were immunized orally or parenterally. Practice of bivalent live vaccines including colonization factor and enterotoxin antigens and without antibiotic resistance gene shows effective.

Adhesins, Escherichia coli↗
PubMed1989

The parascapular flap for treatment of lower extremity disorders.

The parascapular flap was used as a free microvascular transfer for soft-tissue resurfacing of 11 lower extremities. The diagnoses included four cases of osteomyelitis, three cases of vascular ulceration, one case of combined osteomyelitis and vascular ulceration, two cases of posttraumatic heel defects, and one case of extensive soft-tissue contracture overlying a posttraumatic defect of the femur. All cases were successful clinically. Anatomically, the parascapular flap is supplied by the cutaneous parascapular artery, a branch of the circumflex scapular artery, which itself derives from the subscapular artery. Flap territory may reach 15 x 30 cm, and the vascular pedicle can extend 14 cm if the subscapular artery is taken. Advantages of this flap include the constancy, length, and caliber of the vascular pedicle; the length and width attributes, which allow both coverage of large wounds and primary closure of the donor defect; and an absence of disruption of musculoskeletal function.

Adolescent↗
PubMed1989

Epidemiologic study of cancer mortality among chloroprene workers.

Both case-control and cohort studies were undertaken from July 1, 1969 to June 30, 1983 to ascertain whether exposure to chloroprene increases the risk of cancer. Fifty-five cases of cancer deaths were verified, 16 of which had histories of exposure to chloroprene ranging from 3 to 23 years (median 11 years) with a latent period of 8-27 years, except for one case of 3 years (median 12.5 years). Fifty-four pairs were obtained by matching the cancer deaths to noncancer deaths in accordance with strict requirements. The odds ratio for the paired data was 13, X2 = 8.64, P less than 0.005. The average age at death from cancer of workers exposed to chloroprene was 12.7 years younger than that of unexposed workers, t' = 2.98, P less than 0.001. The total cohort consisted of 1213 persons, among whom 149 (11.6%) had histories of exposure for over 25 years, 381 (31.5%) for over 20 years, and 852 (70.2%) for over 15 years. The SMR for the total cohort was 2.38 (P less than 0.01), and all SMRs for the high-exposure occupations were of significance (P less than 0.05 or P less than 0.01), in contrast to those of the low-exposure grups whose SMRs were low or zero. Thus, a dose-response relationship existed. Among the high-exposure occupations, maintenance mechanics seem to have the highest risk of cancers, and SMRs for liver, lung, and lymphatic cancers were significant in this group. These results suggested that chloroprene exposure increases the risk of developing cancer.

Butadienes↗
PubMed1989

Short-term test for the induction of lung tumor in mouse by chloroprene.

In a previous study by the authors, positive results from both a case-control study and a cohort study were reported. In the present study a short-term test for the induction of mouse lung tumor by chloroprene was conducted to confirm whether chloroprene monomer itself can induce tumors. Kunming albino mice weaned at 2 weeks were subjected to inhaling 0, 2.9 +/- 0.3, 19.2 +/- 1.9, and 189.0 +/- 13.3 mg/m3 chloroprene (GC purity, 99.8%) 4 h daily (except Sunday) for 7 months. All survivors were killed at the end of the 8th month or when moribund. No lung tumors were found before the 6th month. Thus, survivors at the 6th month were counted as effective animals. Most lung tumors observed were papilloadenomas (50/57), and a few were adenomas (7/57). The tumor incidence in the 2.9 mg/m3 group was 8.1% in comparison to 1.3% in the control group, with the significance level at P less than 0.05. The higher the concentration, the higher the incidence. Examination of the multiplicity of tumor induction also demonstrated a dose-response relationship, and the number of tumors per mouse in the 189 mg/m3 group was significant at P less than 0.01.

Animals↗
PubMed1989

[Lung tumors induction short-term test of chloroprene in mice].

In a previous report by the authors, positive results in both case-control study mouse lung tumor induction short-term test of chloroprene for carcinogenicity was conducted to determine whether chloroprene monomer itself could induce tumor. Kuangming albino mice weaned 2 wk were subjected to inhale 0.0, 2.9 +/- 0.34, 19.18 +/- 1.89, 189.00 +/- 13.26 mg/m3, chloroprene (GC purity 99.69%) 4 h daily (except Sunday) for 7 month. All survivors were killed at the end of the 8th month or when moribund. No lung tumor was found before the 6th month. Thus survivors at the 6th month were counted as effective animals. Most lung tumors observed were papillo-adenoma (50/57), and a few were adenoma (7/57). Tumor incidence of the 2.9 mg/m3 group increased to 8.1% in comparison with that of the control group (1.3%) at a significant level of P less than 0.05; and the higher the concentration the higher the incidence. Examination of the multiplicity of tumors also demonstrated the dose-response relationship, and the number of tumors per mouse in the 189 mg/m3 group was significant at P less than 0.01.

Animals↗
PubMed1989

[Low-dose cytosine arabinoside in treatment of 17 patients with acute nonlymphocytic leukemia].

Low dose Ara-C (LDAra-C, Ara-C 10-15 mg/12 h, i.m. x 14-21 days) was used in the treatment of 17 patients with ANLL, and from 14 patients blast cells were isolated before chemotherapy and cultured in the presence of Ara-C (10(-8) and 10(-7) mol/L), no definite induction of differentiation of leukemic cells was found. Of the 17 cases, 5 obtained CR, only one of them with M4 entered CR without pancytopenia or bone marrow aplasia during the LDAra-C treatment. For the rest, 4 with M2 obtained PR, and 8 did not respond. Toxic effects, including pancytopenia and bone marrow aplasia, were observed in most of the patients. Laboratory results showed that differentiation was not induced by Ara-C in low concentration in in vitro culture. LDAra-C is thought to be effective in the treatment of ANLL, and the mechanism may involve both the cytotoxicity and the induction of differentiation of leukemic cells, but the former is far more important.

Adolescent↗
PubMed1988

The use of isolated rat hepatocyte in prescreening of hepatotoxicants: observation on toxic effects of 14 compounds.

Fourteen compounds, differing in structure, mechanism of action, and primary target organs, were tested for cytotoxic responses in isolated hepatocyte suspensions prepared by a nonperfusion method from male Sprague-Dawley rats. The trypan blue exclusion test, measurement of enzyme activities in supernatants, and enzyme histochemistry were taken as indexes of cytotoxicity. All 14 compounds inhibited enzyme activities in hepatocytes. However, the activities of GOT and LDH in supernatants increased after exposure to the three haloalkanes, but decreased after exposure to the other chemicals (Na2CrO4, etc.). The number of dyed cells increased after exposure to six haloalkanes and the order of their relative toxicities in vitro was roughly in concordance with that of their in vivo hepatoxicities. These results indicate that isolated hepatocytes are useful for prescreening of potential hepatotoxicants; the so-called "enzyme leakage" should be replaced by "enzyme in supernatant" to reflect toxicities of different kinds of compounds; enzyme histochemistry is also a sensitive index in toxicological tests with isolated rat hepatocytes.

Animals↗