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Biomedical subjects

Y Mullen

Publications and source records attributed to Y Mullen.

At least 109 records · Page 6Linked to original sources
PubMed1986

Transfer of autoimmune diabetes mellitus with splenocytes from nonobese diabetic (NOD) mice.

The nonobese diabetic (NOD) mouse, a model of human type I diabetes, develops insulitis beginning at 4-6 wk of age. By 30 wk of age, 72% of females and 39% of males develop spontaneous diabetes, apparently because of an overwhelming autoimmune response to the insulin-producing beta-cells within the islets. To identify the immune mechanism responsible for destruction of beta-cells in the NOD mouse, we developed an adoptive transfer protocol that induces diabetes in NOD mice at an age when spontaneous diabetes is rarely observed. Splenocytes from overtly diabetic NOD mice were unable to transfer diabetes to very young (less than or equal to 6 wk) irradiated NOD mice but effectively transferred diabetes to irradiated NOD mice greater than 6 wk of age. In such transfers, overt diabetes was induced within 12-22 days in greater than 95% (79/82) of the recipients. Thus, transfer of splenocytes to young mice induces them to become diabetic at a higher frequency and at a younger age than their untreated littermates. Equally successful transfers with as few as 5 X 10(6) spleen cells have been performed in male and female NOD mice, even though males display a lower spontaneous incidence of diabetes than females. Splenocytes obtained from diabetic mice maintained on insulin for up to 2 mo also transferred diabetes. Because NOD mice display increasing levels of insulitis with age, spleen cells obtained from nondiabetic NOD mice of different ages were tested for their ability to transfer diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1984

Fetal pancreas transplantation in miniature swine. I. Developmental characteristics of fetal pig pancreases.

The genetically defined miniature pig developed by Sachs et al. was selected as a large animal model to test the feasibility of fetal pancreas transplants for reversal of insulin-dependent diabetes. In order to test our approach, the first key was to characterize the development of the pig pancreas tissues throughout fetal life. Pancreas samples were obtained from 102 farm pig fetuses ranging in age from 35-110 days and from 39 minipig fetuses removed by Caesarean section from 5 timed-pregnant sows between 33 and 73 days after conception. The development of the endocrine and exocrine pancreases were examined by immunobiochemical assays of insulin, chymotrypsinogen, and trypsinogen. Light and electron microscopic examination of pancreases from the critical fetal ages (35-55 days) were used to confirm the above results. Insulin was already present at day 33 and increased rapidly till birth (day 114: 2.2 U/pancreas). Chymotrypsinogen activity was first detected at day 43 and trypsinogen activity at days 49-50. Enzyme content increased rapidly till days 65-70 and then more gradually until birth. Morphological development of exocrine cell granules conformed to the above results. The results clearly demonstrated in the pancreas of a larger mammal, the pig, that the endocrine elements mature prior to the exocrine system. Thus, as we found in rats, pig fetal pancreas also has this advantage as a donor tissue for transplantation. An appropriate fetal age for pig donors is estimated to be between 45 and 50 days.

Animals↗
PubMed1983

Normalization of six key hepatic enzymes after fetal pancreas transplantation in diabetic rats.

In diabetic rats transplanted with fetal pancreata we measured the activities of six important enzymes to assess the return of liver metabolism to normal. Comparison was made among the responses of transplanted rats with and without renal-portal vein shunts and of those not transplanted and injected with insulin in varying doses. Insulin supply was not limited since three or four fetal pancreata were first grown in normal rats before transfer into the diabetic animals. Transplantation normalized blood and urine glucose and the rate of disappearance of intravenous glucose. Glucokinase and pyruvate kinase activities in liver rose toward normal at 7 days after transplantation and reached normal levels at 30 and 90 days. The response of the other four enzymes, glucose-6-phosphate dehydrogenase, citric lyase, fructose-1,6-bisphosphatase, and glucose-6-phosphatase, was more rapidly restored to normal at 7 days and remained normal at 30 and 90 days. No difference was observed in the enzyme activities of transplanted-shunted rats to nonshunted animals. Glucokinase activity was restored to normal after 1 wk of daily injections of 1 U of PZI; pyruvate kinase restoration required 3 U/day. Glucose-6-phosphate dehydrogenase and citric lyase required 2 U/day to be restored to normal; 3 U daily resulted in temporary supernormal activities. The gluconeogenic enzymes, fructose-1,6-bisphosphatase and glucose-6-phosphatase, were only partially suppressed toward normal by insulin even with 3 U daily for 3 wk. These findings indicate that pancreas transplantation is a more effective regulator of liver metabolism in diabetes than insulin injections.

ATP Citrate (pro-S)-Lyase↗
PubMed1982

Normal response to pregnancy in rats cured of streptozotocin diabetes by transplantation of one fetal pancreas.

We have investigated glucose homeostasis and insulin response to glucose in seven rats before, during and after pregnancy, who were previously successfully transplanted with a single fetal pancreas. Increased need for insulin during pregnancy provides an opportunity to test the reserve capacity of the transplanted organ. Plasma glucose in seven rats was normal before pregnancy (7.3 +/- 0.7 mmol/l), during pregnancy (6.6 +/- 1 mmol/l) and after parturition (6.7 +/- 0.3 mmol/l). Fasting plasma glucose was lower after parturition (5.1 +/- 1 mmol/l) than before pregnancy (6.1 +/- 0.7 mmol/l). The disappearance rate of injected glucose was the same before (2.3 +/- 0.2%/min) as after pregnancy (2.6 +/- 0.2%/min). Basal plasma insulin before pregnancy was elevated and there was no rise from glucose; after parturition the basal and pattern of response was normal. The total insulin content of the transplants (859 +/- 154 mU) was only 21% of that of normal rats; we conclude that this provides a reserve adequate for the needs of pregnancy.

Animals↗
PubMed1982

Fetal pancreas allografts for reversal of diabetes in rats. II. Induction of life-term-specific unresponsiveness to pancreas allografts across nonmajor histocompatibility complex barriers.

Specific unresponsiveness to LEW whole fetal pancreases was induced in F344 rats across non-RT1 incompatibilities. Our treatment regimen was a modification of that developed by Brent and Opara and used an i.v. injection of donor liver extracts (equivalent to 250 to 500 mg wet tissues) between days -18 and -24 followed by a single i.p. injection each of procarbazine hydrochloride (one-third of the LD50 dose) and 0.5 ml of antilymphocyte serum (ALS) within a few days of transplantation. Complete and life-term (greater than 1 year) reversal of streptozotocin (SZ)-induced diabetes was observed in 13 of 16 treated recipients, while the reversal of diabetes was only transient in 2 recipients as a result of graft rejection which occurred between days 30 and 50. The remaining one recipient did not respond to the treatment. Allograft viability was confirmed by the visual observations and histological examination of tissues, by the recurrence of diabetes after the graft removal, and by the reversal of diabetes in the secondary recipients in which long-term surviving allografts were retransplanted. Specificity of the induced unresponsiveness was demonstrated by the prolonged survival times of donor-type skin but the normal rejection of third-party skin which was grafted onto the diabetes-reversed F344 recipients carrying viable LEW pancreases. Prolonged but limited survival times of donor-type skin grafts suggested that the induced unresponsiveness is specific to donor alloantigens as well as organ-specific antigens. This immunosuppressed state was transferable into ALS-treated syngeneic F344 rats by nylon-wool-nonadherent spleen cells. Thus, LEW skin grafts survived for 30 days in ALS-treated F344 rats receiving test spleen cells, while those in controls survived for 19 days. LEW pancreases surviving for more than 300 days were fully capable of eliciting rejection reaction when the grafts were retransplanted into a nonimmunosuppressed secondary F344 recipient along with the primary host kidney.

Animals↗
PubMed1980

Fetal pancreas allografts for reversal of diabetes in rats. I. Allograft survival in nonimmunosuppressed recipients.

Survival times of allogeneic fetal pancreases were determined across various immunogenetic barriers using several inbred rat strains. Pancreases from 17-day-old embryos transplanted beneath the kidney capsule of normal, nonimmunosuppressed recipients were richly vascularized within a short period regardless of histoincompatibilities. The transplants grew progressively, increased beta cell number, and synthesized insulin at a rate similar to that in isografts until rejection intervened. Survival end points were scored by (1) complete disappearance of intrinsic vascularization and necrotic change of tissue by gross observation of grafts, (2) a sharp decrease in insulin content in a graft as compared to that in a control isograft, and (3) destruction and disappearance of beta cells in histological examination. Although fetal pancreases were rejected within 10 days in all strain combinations, there were clear differences in host immune-reactions in terms of immunogenetic barriers between donor and recipient.

Animals↗
PubMed1980

Characteristics of the second-set kidney allograft reactions in rats.

Unlike skin allografts in rats, accelerated rejection of second-set kidney allografts was a rare occurrence. Host reactivity was generally suppressed as a consequence of first-set kidney rejection, resulting in prolonged survival of a second-set kidney bearing the same alloantigens. Three variables with potentially important clinical implications were critical for induction of extended survival of the second kidneys: (1) Longer first-set kidney retention or sensitization periods promoted prolonged second-set allograft survival; the longer the period (tested up to 50 days), the greater was the observed immunosuppression. (2) Shorter intervals between first set removal and second-set grafting greatly prolonged second-set survival times; the shorter the interval, the greater the immunosuppressive effect. The optimal timing for facilitation of second kidney survival may be assumed as the time of first kidney removal. (3) Lesser or weaker histoincompatibility of the second kidney clearly promoted prolonged or indefinite survival. Thus, the second kidney from semiallogeneic F1 hybrids survived far longer than fully allogeneic parental kidneys. Prolongation of second-set F1 kidney survival could be achieved under less strict conditions. Spleen lymphocytes from second kidney recipients showed suppressed alloreactivity in the popliteal lymph node graft-versus-host (GVH) assay. Prolonged survival of repeated renal allografts is attributable to intervention of an active immunoblocking process rather than acquired tolerance.

Animals↗
PubMed1979

Importance of hepatic portal circulation for insulin action in streptozotocin-diabetic rats transplanted with fetal pancreases.

The importance of the hepatic portal circulation in the response to insulin was assessed in streptozotocin-diabetic rats transplanted with syngeneic fetal pancreases. Partial reversal of diabetes was accomplished by transplantation of two or three fetal pancreases beneath the capsule of the kidney; complete reversal followed shunting of the venous drainage from the transplants to the liver. Plasma glucose after streptozotocin of 509+/-31 mg/dl (mean+/-SEM) fell after transplantation to 395+/-23 and after the shunt to 143+/-5 mg/dl. Urine volume fell from 84+/-4 to 50+/-5 ml/d and then to normal (17+/-1 ml/d) after the shunt. Glucose excretion which was 8.1+/-0.3 g/d after streptozotocin fell after transplantation to 4.8+/-0.3 g/d and after the shunt completely disappeared from the urine. The disappearance rate of glucose injected into the circulation, which was 0.50+/-0.07%/min in untreated diabetes, increased to 1.39+/-0.38%/min after transplantation and to 2.52+/-0.31%/min after the shunt, not different from normal controls (2.79+/-0.25). Plasma immunoreactive insulin (IRI) was below normal (25-35 muU/ml) and unresponsive to glucose in untreated diabetic rats. After transplantation IRI levels ranged from 73-223 muU/ml and there was no rise after glucose injection. After the shunt both the basal IRI (36+/-5 muU/ml) and the peak response to glucose at 10 min (58+/-7 muU/ml) were the same as in normal controls (42+/-4 and 62+/-7 muU/ml, respectively). The fall in IRI after the shunt is explained by increased extraction of insulin passing into the liver and also diminished secretion. After removal of the transplants plasma glucose and urine values returned almost to pretransplant levels. Secretion of insulin by transplanted pancreases into the liver enhances the effectiveness probably by increased extraction and action and reveals the importance of the normal route for insulin delivery.

Animals↗
PubMed1978

Reversal of diabetes in rats using fetal pancreases stored at -196 C.

Fetal rat pancreases frozen to and stored at -196 C were used for transplantation into streptozotocin-induced diabetic syngeneic adult recipients. Transplantation was carried out either directly after thawing from -196 C, or after a 21-day growth period in a syngeneic, normoglycemic adult carrier. All transplants were placed under the kidney capsule. A single, frozen fetal rudiment was sufficient to restore blood glucose, urine volume, and urine glucose to normal, provided it had first been grown for 21 days in a normal carrier. It vitro perfusion studies showed that fetal pancreases stored at -196 C were equivalent to fresh rudiments in their responses to a glucose stimulus.

Animals↗
PubMed1977

Immunity to MCA-induced rat sarcomas: analysis of in vivo and in vitro results.

Three in vivo techniques were used to establish the specificity of tumor immunity induced after sensitization of F344 rats to syngeneic MCA-induced sarcomas: (1) post-excision resistance to tumor challenge, (2) passive tumor neutralization (the Winn test), and (3) concomitant immunity. In general, these assays revealed unique non-cross-reactive antigens associated with each of three sarcomas, FMF1, FMM2, and FMM3. However, spleen cells from tumor-sensitized rats did not demonstrate cell-mediated cytotoxicity in vitro corresponding to the specificity of tumor resistance in vivo. In the (3H)-proline cytotoxicity assay, spleen cells from FMM3 tumor-bearing rats or from FMM3 tumor-immune rats were not selectively cytotoxic for cultured FMM3 target cells. Parallel analysis of spleen cells from normal or FMM3-sensitized rats using the Winn assay and the (3H)-proline assay revealed that (1) spleen cell cytotoxicity in vitro did not correlate with effective tumor protection in vivo; and (2) normal spleen cells were cytotoxic against cultured sarcoma target cells in vitro and inhibited tumor growth in vivo. Thus, passive tumor protection by normal spleen cells in vivo corresponded with the demonstration of natural cytotoxicity in vitro, but induced specific anti-tumor reactivity was observed only in vivo.

Animals↗
PubMed1977

Micro mixed hemadsorption assay--a sensitive method for detecting antibodies against tumor-associated antigens.

Antibodies against methylcholanthrene (MCA)-induced sarcomas in Fischer (F344) rats were detected by a modified micro mixed hemadsorption (MHA)-assay. The assays detected anti-tumor antibodies as titers up to 1 : 320 in sera from hyperimmunized rats and at titers up to 1 : 160 in sera from rats bearing a 5-8 cm3 progressively growing tumor. MHA-titers decreased when sera were absorbed with sarcoma cells prior to MHA-assays. IgG antibodies in sera from tumor bearing rats showed titers of 1:20 and 1:5. These anti-tumor sera formed rosettes on the corresponding sarcoma cells as well as other sarcomes induced by MCA in F344 and Lewis strain rats tested. The assay was modified for a micro technique using a microtest plate (No. 3034, Falcon, CA). This modification yielded as assay requiring only 10 microliter of test sera. The test is quantitative and highly sensitive and results are reproducible. Several critical factors which influence test results in this assay were examined.

Animals↗
PubMed1977

Cytotoxic versus immunoblocking effects of specific alloantibodies: effects of IgM, IgG, and IgG2 on rat kidney allograft survival.

Passively introduced IgM alloantibodies of antidonor specificity regularly led to decreased kidney allograft survival times, whereas IgG alloantibodies from the same hyperimmune sera had a specific immunoblocking effect that promoted prolonged allograft survival. These strikingly opposite effects as a function of antibody isotype occurred across both strong H-1 (Ag-B) and moderate non-H-1 histocompatibility barriers. However, IgM and IgG directed against non-H-1 specificities were far more effective, respectively, in either curtailing or prolonging renal allograft survival. In the Fischer to Lewis strain combination, this was reflected in a 4-fold diminution in median survival time of IgM-treated recipients from 115 to 31 days, in contrast to indefinitely prolonged survival of IgG-treated recipients (greater than 350 days). Purified IgG2 alloantibodies proved as effective as the whole IgG fraction in passively promoting long-term renal allograft survival across a strong H-1 barrier. Conflicting data from other sources is evaluated. Possible mechanisms of specific immunoregulation are briefly discussed in relation to antibody properties of specificity, idiotype, class-subclass, and avidity-affinity.

Animals↗