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Biomedical subjects

T E Mandel

Publications and source records attributed to T E Mandel.

At least 145 records · Page 8Linked to original sources
PubMed1984

Tissue localization and retention of antigen in relation to the immune response.

Antigen persists for months or even years in lymphoid tissues of immune animals and this antigen is believed to participate in the induction and maintenance of B-cell memory as well as in the maintenance of serum antibody levels. In the present report we describe the phenomenon of antigen localization and long-term retention on mouse follicular dendritic cells (FDCs). The antigens used were injected in the hind footpads of immune mice and the popliteal lymph nodes were the lymphoid organs generally studied. In addition to presenting the morphological features of mouse FDCs, we report the results of a study of the mechanism of antigen migration from the site of initial localization in the lymph node subcapsular sinus to the regions of follicular retention in the cortex. The migration was followed by light and electron microscopy. The results support the concepts that immune complexes are trapped in the subcapsular sinus and are transported by a group of nonphagocytic cells to follicular regions. The mechanism of transport may involve either migration of pre-FDCs with a concomitant maturation into FDCs, or cell-to-cell transport utilizing dendritic cell processes and membrane fluidity; or a combination of the two mechanisms may be in operation.

Animals↗
PubMed1984

Effect of ischemia and temperature on fetal mouse pancreas. Insulin production in vitro, and function after isotransplantation.

The effects of ischemia at varying temperatures on the survival of fetal islet endocrine cells was investigated by placing 17-day-old fetal mouse pancreata in organ culture after 2, 4, or 6 h at either 4 degrees C, 22 degrees C, or 37 degrees C. Insulin secretion by the cells in vitro, the content of insulin in the cultured pancreata, and the ability of the cultured islets to reverse diabetes in syngeneic streptozotocin-diabetic mice were assessed. Fetal pancreas subjected to 2-6 h of ischemia at either 4 degrees C or 22 degrees C showed neither loss of insulin secretory capacity in vitro nor loss of ability to produce large functional grafts, and behaved identically to tissue not subjected to deliberate ischemia. In contrast, after 2 h of ischemia at 37 degrees C, although some grafts functioned, their insulin content was reduced despite apparently normal prior insulin production in vitro, but 4 or 6 h at 37 degrees C resulted in total loss of functional islet tissue. However, despite retention of functional capacity and the ability to produce large grafts with high insulin content after cold or room temperature ischemia, some loss of insulin storage capacity in vitro was noted by islets subjected to ischemic periods longer than 2 h even at 4 degrees C. Thus, fetal pancreas can withstand prolonged periods of ischemia provided its temperature is reduced, and functional recovery can be demonstrated after transplantation.

Animals↗
PubMed1984

Islet cell subpopulations in cultured mouse fetal pancreas and pancreatic isografts.

Application of the immunoperoxidase technique proved very rewarding in determining the structure and function of cultured fetal pancreas and isografted tissue. Proliferation of endocrine beta-cells was highest during the first three weeks of culture but these cells rapidly declined in number thereafter as the delta-cell mass increased. Morphologically, the optimal culture time, based on beta-cell mass, was approximately ten to 14 days and this did not appear to be dependent on whether the tissue was cultured under conventional or high oxygen conditions. It is hoped that electron microscopy may reveal the fate of the diminishing population of insulin-producing cells. Immunoperoxidase staining of long-term isografts demonstrated the presence of large islets with the typical morphologic structure of normal adult pancreatic islets. It is believed that this may be of vital importance if pancreatic islet transplantation is to be fully effective in the control of blood glucose levels, which it is hoped will help prevent the longterm diabetic complications associated with insulin-dependent diabetes.

Animals↗
PubMed1984

Anamnestic responses induced by antigen persisting on follicular dendritic cells from cyclophosphamide-treated mice.

In contrast to most mouse lymph node cells, follicular dendritic cells (FDCs) resist cyclophosphamide (Cy; 300 mg/kg)-mediated destruction in vivo. In this study we sought to determine if antigen-bearing FDCs from Cy-treated animals maintained biological activity. We were especially interested in whether FDCs from Cy-treated animals could stimulate an antibody response when combined with primed spleen cells and whether the FDCs needed to be intact and viable for stimulation to occur. The effect of Cy treatment on lymph node histology, number of T cells and B cells, and the 'spontaneous antibody response' was determined. Cy treatment resulted in a massive depletion of the lymph node cortex and a loss of follicles and germinal centres. Over 90% of B cells in the lymph node were eliminated. The paracortex was more resistant although nearly 80% of T cells were eliminated. Cy treatment also eliminated the 'spontaneous antibody response' as established by in vitro culture or after adoptive transfer. The addition of primed spleen cells to antigen-bearing FDCs including sonicated non-viable FDCs from Cy-treated animals resulted in an anamnestic antibody response. Memory lymphocytes, injected into the hind foot pads of Cy-treated animals, migrated to the follicular area of popliteal lymph nodes and cells from these reconstituted nodes spontaneously responded upon subsequent adoptive transfer. It was concluded that antigen retained on Cy-treated FDCs maintains its immunogenicity and is capable of inducing a 'spontaneous antibody response' or an anamnestic response. Furthermore antigen on FDCs or on fragments of FDCs from one animal can interact with memory cells from another animal to induce a productive antibody response. Lymph nodes enriched for FDCs by Cy treatment should be a good source of FDCs for isolation and further study of the nature of this interaction.

Animals↗
PubMed1983

The in vitro production of chimeric murine thymus from nonlymphoid embryonic precursors.

A simplified technique for the production of chimeric thymus completely in vitro from the third pharyngeal pouch (TPP) of 10-day mouse embryos has been examined. The results are similar to those obtained by a more cumbersome technique published by others. This modified technique permits the production of large numbers of synchronized chimeric thymuses, so that sufficient numbers of thymocytes are available for multiple functional assays. TPP may also be maintained in culture, then grafted into normal or thymectomized, irradiated, fetal liver-reconstituted hosts where they undergo development into histologically normal lymphoid thymic tissue.

Animals↗
PubMed1983

A comparison between islet transplantation and parenteral insulin in the control of diabetes and prevention of renal complications in mice.

The control of diabetes and the prevention of renal complications were studied in mice that received different treatment regimes for six months. Transplantation of syngeneic cultured fetal pancreas completely reversed streptozotocin-induced diabetes (mean FBG 5.1 +/- 0.4 mmole/liter six months after transplantation, versus 5.8 +/- 0.2 mmole/liter in normal mice). The mean fasting blood glucose (FBG) level of insulin-treated mice was lower than the mean FBG level of untreated diabetic mice (9.0 +/- 1.2 mmole/liter versus 11.5 +/- 1.3 mmole/liter, P less than 0.05) but exceeded the FBG level of transplanted mice (P less than 0.001) or normal controls (P less than 0.001). There were no significant differences between the mean level of glycosylated hemoglobin (HbA1c) of normal (4.8 +/- 0.3%), transplanted (4.5 +/- 0.3%), or insulin-treated mice (5.3 +/- 0.4%), but the HbA1c level in the untreated diabetic group was increased (7.0 +/- 0.5%; P less than 0.001). Six months after transplantation, the thickness of the glomerular capillary basement membrane (GCBM) was not different in the transplanted group and normal controls (156.4 +/- 5.7 nm versus 157.3 +/- 12.6 nm); the GCBM was thicker in the insulin-treated mice than in the transplanted mice (179.8 +/- 4.2 nm versus 156.4 +/- 5.7 nm; P less than 0.02), but thinner than in untreated diabetic mice (179.8 +/- 4.2 nm versus 202.2 +/- 4.4 nm; P less than 0.001). It is concluded that islet transplantation, in contrast to good control as judged by normalization of HbA1c levels achieved with parenteral insulin, prevents GCBM thickening in experimental diabetes.

Animals↗
PubMed1983

Growth of organ-cultured foetal mouse pancreas grafts in syngeneic diabetic and non-diabetic recipients.

Organ-cultured foetal mouse pancreatic islets can reverse streptozotocin-induced diabetes in syngeneic mice. Tissue from one donor is enough to produce and maintain euglycaemia in each recipient, but even smaller amounts of donor tissue may be sufficient and less than one third of a foetal pancreas frequently suffices. Insulin extracted from grafts removed after some months in situ shows that their insulin content is proportional to the amount of tissue transplanted, and suggests that the grafted foetal islets have a finite capacity for growth. In organ culture some loss of potential islet tissue may occur, and larger grafts are obtained when small pieces of tissue are cultured, thereby minimizing losses of tissue in vitro. The growth of the graft in situ also depends on the diabetic state of the host, and greater and more prolonged mitotic activity is seen in grafts in diabetic than in non-diabetic recipients. A degree of hyperglycaemia in the recipient may enhance graft growth.

Animals↗
PubMed1983

Reduction of the immunogenicity of fetal mouse pancreas allografts by organ culture in 90 percent oxygen.

BALB/c female streptozotocin-diabetic mice were transplanted under the left kidney capsule with syngeneic or allogeneic CBA 17-day fetal pancreases that had been organ-cultured for 23 days. Two isografted groups received a single graft per recipient, cultured normally (90% air, 10% CO2), or in an oxygen-rich atmosphere (90% O2, 10% CO2): 13/14 and 12/13 respectively became normoglycemic. The 3rd and 4th groups were transplanted each with 1 and 3 allogeneic fetal pancreases per recipient, which had been cultured in 90% O2: 5/12 and 2/13 mice respectively had surviving allografts after 104 days, and 2/5 of the former and both of the latter had become normoglycemic. Five out of the seven surviving allografts contained foci of infiltrating lymphocytes. After removal of the kidneys containing the grafts, surviving mice were retransplanted under the right kidney capsule, each with 2 CBA fetal pancreases which had been cultured for only 4 days under normal conditions--hence they were fully immunogenic. Rejection of the secondary allografts was delayed in the long-term, primary allograft acceptors, suggesting that a degree of tolerance had developed. This study demonstrates that it is possible for a single, cultured fetal pancreas to survive indefinitely and reverse diabetes after transplantation to a fully allogeneic, nonimmunosuppressed recipient.

Animals↗
PubMed1983

Insulin secretion by fetal human pancreatic islets of Langerhans in prolonged organ culture.

Fetal human pancreata, obtained from legally-induced abortions, were placed in organ culture to study their capacity to produce insulin over periods in vitro of between 18 and 40 days. Specimens obtained by hysterotomy usually showed increasing insulin secretion as measured by the insulin content of the media at each twice-weekly medium change. In most instances, relatively little insulin was produced during the first 7-10 days, but thereafter insulin secretion rapidly increased. In contrast, most specimens from prostaglandin-induced abortions showed high levels of insulin in the medium early in the culture period but little thereafter, indicating rapid release of insulin from damaged tissue. In some instances, after early insulin release by damaged tissue, some recovery of islet function occurred and insulin secretion again increased. The presence of differentiated endocrine cells was confirmed histologically. Tissue from each fetus was placed in a number of petri dishes, and for each individual fetus a qualitatively similar pattern of secretion was noted in each dish. These data suggest that representative and nondestructive monitoring of islet function is possible and may be important before such tissue is considered for use in islet transplantation in insulin-dependent diabetes.

Abortion, Induced↗
PubMed1983

Lymphocyte depletion of murine fetal thymus and subsequent chimeric recolonization in vitro.

Thymus from 14-day murine fetuses, maintained in organ culture, was depleted of lymphocytes when incubated for 7 days at room temperature (24 degrees C) in a gas mixture of 10% CO2 in air or 10% CO2 in O2. Shorter incubation resulted in sparing of some lymphocytes and/or their precursor populations. Cultures grown in CO2 in air maintained their Ia-positive cell population, as demonstrated in single cell suspensions, while those grown in CO2 and O2 appeared to lose Ia-positive cells. When recolonized by fetal liver (FL) the thymuses became fully lymphoid again in organ culture. Depending on the degree of lymphocyte depletion, split chimerism at various levels could be produced, when the FL used was from a strain allogeneic to the thymus.

Animals↗
PubMed1982

Characteristics of plasma membrane isolated from a mouse T lymphoma line: comparison after nitrogen cavitation, shearing, detergent treatment, and microvesiculation.

Plasma membrane was isolated from the mouse T lymphoma cell line WEHI-22 using four different methods of cell disruption followed by centrifugal fractionation. Disruption by nitrogen cavitation or by shearing with a cell pump produced plasma membrane vesicles of similar buoyant density (1.10 g/ml) and morphological appearance. Few C-type virus particles were present. Cell disruption with 2% Tween-40 produced membrane vesicles of similar morphology but lower density (1.09 g/ml). All of the above preparations resulted in vesicles with aggregated intramembranous particles after freeze fracture. Microvesiculation with sublytic concentration of a lysophosphatidylcholine analog (ET-12-H) (0.0032% w/v) produced small membrane vesicles which could be isolated without differential centrifugation. However, these had a slightly higher density than vesicles prepared by cavitation or shearing and were contaminated by virus particles. Unlike the other preparations, vesicles prepared with ET-12-H had dispersed intramembranous particles. The enzyme gamma-glutamyl transferase was enriched from 20- to 45-fold in the membrane preparations and proved a suitable plasma membrane marker for these cells whose 5'-nucleotidase content is very low.

Animals↗
PubMed1982

Insulin secretion by fetal human pancreas in organ culture.

Whole fetal human pancreases of 12-22 weeks gestation, showed histological growth and differentiation in vitro over 3 weeks. At glucose concentrations of 1-4 g/l, there was no difference in insulin secretion into culture medium over 1 h. There was no stimulation of insulin release by D-glyceraldehyde, thus defective glucose-stimulated insulin release was probably not due to impairment of an early step in glycolysis. In the presence of 0.5 mmol/l dibutyryl cyclic AMP, insulin secretion was enhanced (0.188 +/- 0.030 versus 0.100 +/- 0.012 mU x mg tissue-1 x h-1, p less than 0.001) independently of glucose concentrations. It thus appears that impairment of glucose-stimulated insulin release was unlikely to be due to insufficient intracellular cyclic AMP. Insulin release increased in response to tolbutamide and theophylline. Insulin secretion was stimulated in the presence of a fivefold increase in amino acid concentration (0.118 +/- 0.018 versus 0.031 +/- 0.008 mU x mg tissue-1 x h-1, p less than 0.001). There was a fourfold increase in basal insulin secretion from islets previously grown in high concentration of amino acids compared with standard culture medium, (0.284 +/- 0.052 versus 0.067 +/- 0.011 mU x mg tissue-1 x h-1, p less than 0.001), emphasizing the important role of amino acids as substrates for B cell metabolism and development.

Amino Acids↗