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Biomedical subjects

J Tai

Publications and source records attributed to J Tai.

At least 37 records · Page 2Linked to original sources
PubMed1994

Effect of FK506 on rat Leydig cell function--in vivo and in vitro study.

FK506, a macrolide antibiotic, is a potent immunosuppressant and has a biological effect similar to that of cyclosporin A (CsA). In this study, the in vivo and in vitro effects of FK506 on rat Leydig cell function were investigated. In vivo, basal testosterone levels and secretion in response to human chorionic gonadotropin (hCG) stimulation in ACl rats treated with intramuscular (IM) injections of FK506 at a dosage of 1 or 2 mg/kg/d for 14 days were not different from those of age-matched normal controls. Testicular weights (g) from rats treated with 14 injections of 1 mg/kg/d FK506 (1.08 +/- 0.08, n = 14) were similar to weights from age-matched controls (1.04 +/- 0.08, n = 14). Similarly, Wistar (Wi) rats treated with FK506 at a dosage of 1 mg/kg/d for 2 weeks showed basal testosterone and luteinizing hormone (LH) levels and secretion in response to hCG stimulation similar to those of normal controls. Histologically, the Leydig cells and germ cells in FK506-treated animals appeared normal. In vitro, basal testosterone production and response to hCG stimulation by both ACI and Wi rat Leydig cells exposed to overnight treatment of FK506 (10 to 1,000 ng/mL) were not significantly different from those of control Leydig cells. Furthermore, the viability of the Leydig cells cultured for 3 days in FK506 was not significantly different from that of controls, and they continued to secrete testosterone at a rate similar to that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Successful islet allotransplantation in diabetic rats immunosuppressed with FK506: a functional and immunological study.

The effect of a novel immunosuppressive agent, FK506, on fresh islet allografts was evaluated in diabetic rats across major histocompatibility complex (MHC) barriers with respect to the transplantation (TR) site, islet source, treatment regimen, and antidonor antibody (Ab) titers of the recipients after TR. The functional periods of Wistar (Wi) islets transplanted under kidney capsule (KC) or intraportally (IPo) and of a mixture of Wi and Lewis (Le) islets under KC or IPo in nonimmunosuppressed ACI rat recipients were 6.9 +/- 0.4 (n = 7), 6.4 +/- 0.5 (n = 7), 5.6 +/- 0.4 (n = 7), and 6.2 +/- 0.4 (n = 5) days, respectively. FK506 treatment at 1 mg/kg/d intramuscularly (IM) for 2 weeks (protocol I) following islet TR under KC and IPo significantly prolonged the allograft function to more than 71.8 +/- 11.3 (n = 10) and 161.7 +/- 18.6 (n = 11) days, respectively. Additional treatment with FK506 at 1 mg/kg/wk (protocol II) further increased the islet survival under KC to more than 212.6 +/- 22.3 (n = 8) days. With this FK506 treatment protocol, the Wi + Le mixed-islet allograft function was extended to more than 106.1 +/- 10.5 (n = 7) and 167.9 +/- 28.6 (n = 7) days under KC and IPo, respectively. Nephrectomy in 8/8 ACI rats with long-term-functioning Wi (n = 6) and Wi + Le (n = 2) islet allografts resulted in their return to hyperglycemia. Immunohistochemical staining showed abundant insulin-positive cells at the graft site, with small numbers of CD4- and CD8-positive cells present in the vicinity of the normal-appearing islets. Macrophages were not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Cryopreservation of rat Leydig cells for in vitro and in vivo studies.

Leydig cells lose their ability to secrete testosterone following short-term in vitro culture. A procedure for effective storage of these cells would be useful. In this study, rat Leydig cells were cryopreserved in the presence of 10, 15 or 20% dimethylsulfoxide (DMSO) at approximately 1 degree C/min to -70 degrees C and then stored in LN2. After thawing, the cells cryopreserved in the presence of 15% DMSO showed the highest viability of over 75%. These cells secreted basal levels of testosterone in vitro as well as responded to hCG stimulation by secreting over 9-fold increase in testosterone. The viability of these cells was further confirmed by the demonstration of 3 beta-HSD positive cells under the kidney capsule of rats isografted with cryopreserved Leydig cells. This study demonstrated that purified rat Leydig cells can be cryopreserved and the cryopreserved cells retained normal function and were responsive to hCG stimulation. Cryopreservation is a simple procedure for long-term storage of functional Leydig cells.

3-Hydroxysteroid Dehydrogenases↗
PubMed1993

A diabetic rabbit model for pig islet xenotransplantation.

An alloxan-diabetic rabbit model was established for the testing of the function of discordant xenogeneic pig islets isolated and purified from adult pig pancreata. The functional state of the pig islet transplants and immunological state of the rabbit recipients were assessed. Intraportal transplantation of 0.47 +/- 0.01 ml of pig islets with estimated 57418 +/- 5020 in number containing an estimated insulin content of 33.93 +/- 2.97 units (n = 7; mean +/- SEM) resulted in the normalization of blood glucose with a corresponding rise in insulin levels in the diabetic rabbit recipients for 2 days. An intravenous glucose tolerance test performed in 4 recipients during the normoglycemic period resulted in an improved K rate (2.5 +/- 0.4) over the diabetic controls, but this was significantly lower than the normal control animals (K rate = 4.5 +/- 0.4; n = 8). In vitro studies demonstrated that the preformed antibodies detected in the rabbit recipients were cytotoxic to the pig islet cells and lymphocytes. Heat treatment at 56 degrees C and mercaptoethanol treatment markedly reduced the cytotoxic activities of the sera. These findings implicated involvement of complement and IgM class antibodies in the killing of the pig islet cells. Furthermore, pig islet transplants at the kidney capsule site were coated with IgM class antibodies. This study has demonstrated that pig islets can be successfully isolated and purified in sufficient numbers for xenotransplantation studies in alloxan-diabetic rabbit. The porcine islet-to-alloxan diabetic rabbit combination can serve as a highly stringent and useful discordant model for assessing the effectiveness of various immunomodulation and immunosuppressive regimens. The finding of an optimal approach to immunorejection would potentially be applicable to actual clinical islet xenotransplantation in diabetic patients.

Animals↗
PubMed1992

A vaccine carrier derived from Neisseria meningitidis with mitogenic activity for lymphocytes.

Protein carriers vary in their ability to increase the immunogenicity of poorly immunogenic or T-lymphocyte-independent antigens. We examined one such carrier, the outer membrane protein complex derived from Neisseria meningitidis serogroup B strain B11, in an attempt to determine why this outer membrane protein complex was more immunogenic in young infants and in relevant animal models than two other carriers used in conjugates made with Haemophilus influenzae type b polysaccharide, a T-cell-independent antigen. A single protein of the outer membrane protein complex, the class 2 porin protein, was purified and shown to function as a T-helper lymphocyte carrier protein. Unexpectedly, it was also found to have mitogenic activity for lymphocytes that was not due to lipopolysaccharide. This mitogenic activity appears to date to be unique to this carrier protein of the carrier proteins tested and may contribute to the ability of the H. influenzae type b conjugate vaccine made with the outer membrane protein complex to generate IgG anti-polysaccharide antibody responses in mice and infant monkeys and protective immune responses in infants less than 6 months of age.

Animals↗
PubMed1992

Transplantation of discordant pig islet xenografts in diabetic rats.

Xenotransplantation of pig islets under the kidney capsule (KC) of diabetic rats was performed. Natural preformed ACI rat anti-pig leukocytotoxicity, leukoagglutination and hemagglutination antibody titers ranged from Neat-1: 16, 1:8-1:32 and 1:128-1:256, respectively (n = 14). Normal ACI sera were non-toxic to pig islets during short term incubation. Pig islet xenograft survival times in the nonimmunosuppressed ACI rats, ACI rats immunosuppressed with antithymocyte serum (ATS) or cyclosporin A were 3.8 +/- 0.4 (mean +/- SE; n = 5), 10.4 +/- 0.7 (n = 13) and 6.0 +/- 1.0 (n = 5) days, respectively. Pig islets implanted in the abdominal testis of ACI recipients immunosuppressed with 5 doses ATS survived for a mean of 6.4 +/- 1.0 days (n = 7). The mean K rate following an intravenous glucose tolerance test (IVGTT) in ACI rats 1 week after transplantation with pig islet under the KC was 2.2 +/- 0.4 (n = 10) compared to that of 2.91 +/- 0.30 found in normal control rats (n = 8). Peak insulin at 1 min was 60.1 +/- 3.9 microU/ml (n = 4). Histological and immunohistochemical examination showed that the xenograft from recipients treated with 5 doses of ATS still contained well-preserved islet tissue with many insulin- and glucagon-containing cells on the day of graft removal when blood glucose had returned to hyperglycemic level. Both CD4 and CD8 positive cells were in the vicinity of the graft tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination↗