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N Waldeck

Publications and source records attributed to N Waldeck.

At least 19 recordsLinked to original sources
PubMed1998

Ethnobotanical-directed discovery of the antihyperglycemic properties of cryptolepine: its isolation from Cryptolepis sanguinolenta, synthesis, and in vitro and in vivo activities.

Using an ethnobotanical approach in combination with in vivo-guided fractionation as a means for lead discovery, cryptolepine was isolated as an antihyperglycemic component of Cryptolepis sanguinolenta. Two syntheses of cryptolepine, including an unambiguous synthesis, are reported. The hydroiodide, hydrochloride, and hydrotrifluoromethanesulfonate (hydrotriflate) salts of cryptolepine were synthesized, and a comparison of their spectral properties and their in vitro activities in a 3T3-L1 glucose transport assay is made. Cryptolepine and its salt forms lower blood glucose in rodent models of type II diabetes. While a number of bioactivities have been reported for cryptolepine, this is the first report that cryptolepine possesses antihyperglycemic properties.

3T3 Cells↗
PubMed1998

Cryptolepis sanguinolenta: an ethnobotanical approach to drug discovery and the isolation of a potentially useful new antihyperglycaemic agent.

Evidence has been published that a wide array of plant-derived active principles, representing numerous classes of chemical compounds, demonstrate activity consistent with their possible use in the treatment of patients with Type 2 diabetes mellitus (DM). Despite these interesting observations, to date, metformin is the only ethical drug approved for treatment of Type 2 DM derived from a medicinal plant. Why is this so, given the fact that higher plants are such a potential source of new drugs? The answer to this rhetorical question may lie in the reliance of most pharmaceutical companies on random, in vitro, mechanism-based, high throughput screening in the initial phases of plant drug research. In this article we describe an alternative pathway to discovery of drugs for the treatment of Type 2 DM: on based on an ethnomedical approach, involving ethnobotany and traditional medicine. In particular, we present evidence that cryptolepine, an indoloquinolone alkaloid isolated from Cryptolepis sanguinolenta, significantly lowers glucose when given orally to a mouse model of diabetes. The antihyperglycaemic effect of cryptolepine leads to a significant decline in plasma insulin concentration, associated with evidence of an enhancement in insulin-mediated glucose disposal. Finally, cryptolepine increases glucose uptake by 3T3-L1 cells. These data permit us to conclude that an ethnobotanical approach to drug discovery can identify a potentially useful drug for the treatment of Type 2 DM.

Adipose Tissue↗
PubMed1988

Interferon responsiveness of natural killer cells in type I human diabetes.

Abnormally low circulating numbers and function of NK cells are associated with new onset type I diabetes. Since alpha interferon is a stimulator of NK function, enriched T and non-T lymphocytes were incubated with 0, 100 and 1,000 units/ml of recombinant alpha interferon (rIFN alpha) and natural killing against K562 and pancreatic islet cell targets was measured. The killing of K562 (1:20 target:effector ratio) cells by non-T cells incubated with 0, 100 and 1,000 units/ml of rIFN alpha in patients was decreased to 27% (p less than 0.014 vs control), 34% (p less than 0.001) and 39% (p less than 0.003) when compared to killing by normal control non-T cells (48%, 74% and 58% respectively). T cell mediated killing of K562 cells in patients was decreased to 3.9% (p less than 0.03), 5.3% and 6.6% (p less than 0.003) when compared to that of controls (8.7%, 10-8% and 22.6% respectively). Non-T cell mediated killing of islet cells (1:20 target:effector ratio) following treatment of effector cells with 0, 100 and 1,000 units/ml of rIFN alpha in patients was 19%, 27%, and 26% which was comparable to control subjects killing of 31%, 18% and 37% respectively. Similar data were obtained using T-cells as effectors. These data indicate that in new onset type I diabetes; (a) NK cell functional activity is diminished in both T and non-T lymphocyte subpopulations and (b) NK activity is suboptimally enhanced with rIFN alpha.

Adolescent↗
PubMed1987

Natural killer cell and islet killer cell activities in human type 1 diabetes.

Peripheral blood mononuclear cells from 14 type 1 diabetic patients were examined for natural killer cell activity using the K562 cell line as 51Cr labeled targets. Mean cytotoxicity of K562 cells by unseparated mononuclear cells derived from new onset type 1 patients (12 +/- 1.6%) was lower (P less than .01) than that observed in non diabetic controls, (25 +/- 4.2%). Mean natural killer cell cytotoxicity mediated by enriched non-T cells from patients (41 +/- 5.8%) was also lower (P less than 0.03) than in the control group (56 +/- 3.7%). Specificity of these findings was evaluated by also examining other diabetic patient subgroups. Mean non T cell mediated natural killer cell activity in type 2 diabetic patients and type 1 patients with long term disease was 65 +/- 5.4% and 62 +/- 4.8% respectively (p less than 0.001 vs new onset type 1 patients). Longitudinal studies of new onset type 1 patients during the remission (honeymoon) phase revealed no improvement of impaired natural killer cell activity. In 30 new onset and 11 remission diabetic patients, mean non-T cell-mediated cytotoxicity was also measured using dispersed 51Cr labeled pancreatic islet target cells. Mean islet cytotoxicity mediated by cells from new onset patients was 34 +/- 2.4%, whereas in nondiabetic control subjects mean cytotoxicity was 25 +/- 1.8% (p less than 0.005). During remission, islet cytotoxicity returned to normal values in over half of the patients. There was no correlation between K562 and islet cell cytotoxicity in either of the latter two patient groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Natural killer cell and islet killer cell activities in type 1 (insulin-dependent) diabetes.

Peripheral blood mononuclear cells from 20 Type 1 (insulin-dependent) diabetic patients were examined for natural killer cell activity using the K562 cell line as 51Cr labeled targets. Mean natural killer cell cytotoxicity mediated by enriched non-T cells from patients (37 +/- 4.0%) was lower (p less than 0.03) than in controls (56 +/- 3.7%). Specificity was evaluated by examining other patient subgroups. Mean non-T cell mediated natural killer cell activity in Type 2 (non-insulin-dependent) diabetic patients and Type 1 patients with long term disease was 65 +/- 5.4% and 62 +/- 4.8% respectively (p less than 0.003 vs new onset Type 1 patients). Longitudinal studies of new onset Type 1 patients during the remission (honeymoon) phase revealed persistently impaired natural killer cell activity in 3 of 4 patients. In 30 new onset and 11 remission Type 1 diabetic patients, mean non-T cell-mediated cytotoxicity was also measured using dispersed 51Cr labeled islet target cells. Mean islet cytotoxicity mediated by cells from new onset patients was 34 +/- 2.4%, whereas in non-diabetic control subjects mean cytotoxicity was 25 +/- 1.8% (p less than 0.005). During remission, islet cytotoxicity remained at similar or elevated levels in most patients. In patients evaluated simultaneously for K562 and islet cell cytotoxicity, natural killer cell activity was decreased, whereas islet killing was increased. These results suggest a dichotomy in natural killer cell and islet killer cell activities in new onset Type 1 diabetes that could have an important role in the pathogenesis of Type diabetes.

Adolescent↗
PubMed1986

The interrelationships of radioimmunoassayable urinary albumin, renal function and diabetes.

Urinary albumin, measured by radioimmunoassay, was evaluated as a method to assess early renal impairment in 76 insulin (IDD) and 36 noninsulin (NIDD)-dependent diabetic patients. Mean albumin excretion in IDD and NIDD patients was significantly higher at 23 and 12 micrograms/100 ml glomerular filtrate (GF) respectively, compared to 4 micrograms/100 ml GF in normal subjects (P less than 0.001 and P less than 0.05). Abnormal albumin excretion from 20 to 200 micrograms/100 ml GF was observed in 30% of IDD patients (P less than 0.001) and 15% of NIDD patients (P less than 0.03). Albumin excretion was significantly increased in hypertensive IDD and NIDD patients. Significant correlations between albumin excretion and age, duration of diabetes and creatinine clearance were observed, but albumin excretion did not correlate with hemoglobin A1C. These data indicate that (1) 30% of IDD patients not clinically recognized as having renal impairment have abnormal albumin excretion, (2) albumin excretion may reflect renal impairment, since albumin excretion levels independently correlate with duration of diabetes and hypertension in both diabetic subgroups and to glomerular function in NIDD patients, and (3) measurement of urinary albumin by radioimmunoassay may be the most sensitive test to evaluate early renal disease in diabetes.

Adolescent↗
PubMed1986

Multiparameter immunologic studies in patients with newly diagnosed type 1 insulin-dependent diabetes mellitus.

Peripheral blood mononuclear cells from patients with Type 1 diabetes mellitus were examined for the proportion of monoclonal antibody-defined T-cell subsets, natural killer (NK) cells, and macrophages and the proliferative response to phytohemagglutinin (PHA), Concanavalin A (Con A), pokeweed mitogen (PWM) and in the autologous mixed lymphocyte reaction (AMLR) and allogeneic mixed lymphocyte reaction (MLR). The in vitro response of purified IL-2 on PHA- and PWM-induced proliferative response was also examined. Total T cells (Leu 1+), helper/inducer phenotype (Leu 3+) T cells, suppressor/cytotoxic phenotype (Leu 2+) T cells, surface Ig+ B lymphocytes and monoclonal antibody-defined monocytes (Mac +) in patient group were comparable to the control group. The Leu 7+ NK cells were, however significantly (p less than 0.05) decreased in the diabetic group. The NK function was also deficient in the diabetic group when compared to healthy non-diabetic controls. The proliferative responses to all 3 concentrations of PHA, PWM, and Con A, and in the MLR were similar in 2 groups. However, the proliferative response in the AMLR was significantly reduced (p less than 0.05) in the diabetic group. Exogenous purified IL-2 failed to induce any enhancement in the PHA- and PWM-induced proliferative response; this was in contrast to control group in which IL-2 enhanced proliferative response to both mitogens. This study demonstrates deficiency of the AMLR, Leu 7+ and of natural killer cell function and unresponsiveness of mitogen-activated T cells to purified IL-2. The significance of these findings is discussed.

Adolescent↗
PubMed1985

Complement activation in type 1 human diabetes.

Complement activation was quantitated in serum and plasma of diabetic and normal subjects by sensitive competitive equilibrium radioimmunoassays (RIA) for C3a, C4a, C5a, Factor B, and a newly described C5 neoantigen (termed C5 activation antigen, and abbreviated C5-AA) in a stable 54-kDa fragment of C5. Plasma C3a levels were significantly elevated in 8 of 16 patients with newly diagnosed Type 1 diabetes (P less than 0.0005) with the mean C3a concentration for these patients being more than 10-times greater than the mean value of normal controls. C4a levels were also elevated in 2 of these patients (P less than 0.02), but C5a levels, although higher than normal, were not significantly increased. In contrast, the levels of C5-AA in the serum of all patients (11/11) with chronic Type 1 diabetes were significantly higher than in control Type 2 patients (noninsulin-dependent diabetes) (P less than 0.0005) and 4 of 7 patients with new onset insulin-dependent diabetes mellitus also had significantly higher levels of C5-AA than the Type 2 patients (P less than 0.01). The levels of Factor B in the serum of 5 of 9 patients with new onset diabetes were significantly higher than normal (P less than 0.0025). Five recent onset Type 1 diabetes patients were evaluated longitudinally for C3a, C4a, and C5a: in 3 the levels of C3a were elevated during new onset disease decreasing into the normal range during remission; in 2 of these patients C4a was also significantly elevated and the levels decreased during remission; and in 3 patients the levels of C5a were not significantly elevated but they decreased during remission. Purified human complement proteins and complement hemolytic assays were used to measure complement activation in serum during incubation with rat pancreatic islet cells. With diluted normal human serum, less than 20% of C3 or Factor B were consumed during 30 min at 37 degrees C, while with new onset Type 1 diabetic patient sera up to 90% of C3 and Factor B were consumed in 5/6 sera and 4/6 sera, respectively. These findings suggest (a) that complement activation fragments C3a, C4a, and C5a are generated in vivo in new onset Type 1 diabetes; (b) that both the classical and the alternative complement pathways may be activated; and (c) that this may result in a measurable activation of C5 generating biologically and immunologically active C5a and other C5 activation fragments.(ABSTRACT TRUNCATED AT 400 WORDS)

Complement Activation↗
PubMed1984

Autologous mixed lymphocyte reaction in man: XV. Cellular and molecular basis of deficient autologous mixed lymphocyte response in insulin-dependent diabetes mellitus.

The autologous mixed lymphocyte response (AMLR) and the allogeneic mixed lymphocyte response were deficient in a subset of patients with newly diagnosed insulin-dependent diabetes mellitus (IDDM). Using a single set of HLA-identical twins, the cellular and molecular basis of deficient AMLR was investigated and appears to be due to a defect in both responder T cells and stimulator non-T cells. Interleukin-2 production was diminished in the patient but not in the healthy twin. The in vitro addition of purified interleukin-2 enhanced the depressed AMLR in the diseased twin. This suggests that the deficient AMLR in IDDM may be in part due to a deficiency in the production of interleukin-2.

Adolescent↗
PubMed1984

Comparison of porcine and semisynthetic human insulins using euglycemic clamp-derived glucose-insulin dose-response curves in insulin-dependent diabetes.

In order to compare the biologic effectiveness of porcine and semisynthetic human insulins, a euglycemic clamp method was used in eight insulin-dependent diabetic subjects. Each subject was tested for each insulin on separate days. In order to derive glucose-insulin dose-response curves for both insulins, sequential but constant infusion rates of 0.2, 0.5, 1.0, and 2.0 mU/kg/min were performed. Plasma glucose levels attained during the euglycemic clamp were 96 +/- 3 mg/dL. At each insulin infusion rate, the steady-state glucose infusion rate required to maintain euglycemia was measured. At each increment of insulin infused, steady-state glucose infusion rates for porcine insulin were 1.12 +/- 0.22, 1.90 +/- 0.59, 4.28 +/- 0.61, and 9.37 +/- 0.66 mg/kg/min compared with 1.27 +/- 0.42, 2.38 +/- 0.20, 4.25 +/- 0.43, and 8.87 +/- 0.67 mg/kg/min for semisynthetic human insulin. By ANOVA, no significant difference was noted between the two insulins. Because insulin infusion rates may not result in predictable circulating free insulin levels in subjects who have circulating insulin antibodies, free insulin levels were determined. When steady-state glucose infusion rates were compared with free insulin levels achieved at the four insulin infusion rates, dose-response curves for both porcine and semisynthetic human insulins were virtually identical. These data suggest that semisynthetic human insulin has equivalent biologic effects on overall glucose metabolism compared with porcine insulin in insulin-dependent diabetes.

Adult↗
PubMed1984

Deficiency of monoclonal antibody (Leu 7) defined NK cells in newly diagnosed insulin-dependent diabetes mellitus.

Peripheral blood from 11 newly diagnosed patients with insulin-dependent diabetes mellitus (IDDM) was studied for the proportion of monoclonal antibody (HNK 1, Leu 7) defined natural killer (NK) cells using a fluorescence-activated cell sorter analyzer. The proportion of Leu 7+ cells in patients with IDDM (7.0 +/- 4.0) was significantly (P less than 0.001) lower than in simultaneously studied healthy controls (16.8 +/- 7.0). A 2-yr-old boy with recent onset IDDM had a deficiency of Leu 7+ NK cells (6.1%), while his healthy identical twin had normal proportions of Leu 7+ cells (22.2%), when compared to a simultaneously studied healthy control. Two patients reexamined in remission and one other studied in remission alone, showed deficiency of Leu 7+ NK cells. This study demonstrates a quantitative deficiency of monoclonal antibody (Leu 7+) defined NK cells in newly diagnosed patients with IDDM that persists during remission of the disease and therefore appears to be independent of metabolic abnormality. The deficiency of NK cells may predispose genetically susceptible individuals to viral-induced islet cell injury, contributing to the pathogenesis of IDDM.

Adolescent↗
PubMed1984

Mechanisms of rat pancreatic islet allograft rejection.

Since the mechanisms of rat islet allograft rejection are unknown, metabolic, histologic, and immunologic parameters were characterized during rejection. Syngeneic intraportal islet transplants in diabetic Lewis rats normalize glucose values without islet cellular infiltrates; after Wistar-Furth allografts, glucose values rapidly return to diabetic levels and infiltration of islets by mononuclear cells occurs. Using lymphocyte proliferative assays, allogeneic islets induce a 3-fold stimulation of lymphocytes derived from nondiabetic allograft recipients. Using cytotoxicity assays, cell-mediated cytotoxicity of allogeneic islet target cells although inefficient is 2-fold greater in diabetic allograft recipients than in syngeneic recipients. Antibody-dependent cellular cytotoxicity is not observed, whereas 14 days after allotransplantation, complement-dependent antibody-mediated cytotoxicity is elevated. These data suggest that islet allograft rejection using metabolic, histopathologic and immunologic methods is associated primarily with cell-mediated cytotoxicity related to histocompatibility antigens.

Animals↗
PubMed1984

Immunological events in new onset diabetes.

Data from our laboratory are reviewed showing that both cell-mediated cytotoxicity, complement-dependent antibody-mediated cytotoxicity, antibody-dependent cellular cytotoxicity, and complement-augmented antibody-dependent cellular cytotoxicity may provide mechanisms which kill pancreatic islets during pathogenesis of insulin-dependent (type I) diabetes. Xenogenic test systems employing dispersed rat islet target cells were employed. Most of the findings were reversible during clinical remission of diabetes.

Animals↗
PubMed1984

Multiple reactivities of cytotoxic monoclonal antibodies against pancreatic islet cells.

Since multiple mechanisms of antibody induced cellular killing have been described and since the mechanisms of complement augmented antibody-dependent cellular killing are poorly understood, we investigated the specificities of several monoclonal antibodies. Four murine monoclonal anti-rat pancreatic islet antibodies were evaluated for complement-dependent antibody-mediated cytotoxicity, antibody-dependent cellular cytotoxicity and complement-augmented antibody-dependent cellular cytotoxicity. Although all monoclonal antibodies were selected for islet binding properties, only 1 antibody mediated all 3 mechanisms of killing. Another monoclonal antibody which did not induce complement-dependent antibody-mediated cytotoxicity was effective in the complement-augmented antibody-dependent cellular cytotoxicity assay. These studies indicate functional multiple activities of monoclonal antibodies to islet target cells.

Antibodies, Monoclonal↗
PubMed1983

Immune islet killing mechanisms associated with insulin-dependent diabetes: three rabbit antibody-mediated islet cell cytotoxicity models.

Antibody-mediated islet cell killing mechanisms have been associated with human insulin-dependent diabetes. Several types of antibody-mediated cytotoxic mechanisms exist, but only complement-dependent antibody-mediated cytotoxicity is reported for islet killing. To evaluate further islet cytotoxic antibody mechanisms, we have studied antibody-dependent cellular cytotoxicity and complement augmented antibody-dependent cellular cytotoxicity using polyclonal rabbit anti-rat islet cell immune serum and 51Cr-labelled dispersed normal rat islet target cells. Maximal immune serum-mediated islet cell specific cytotoxicity was 80% for complement-dependent antibody-mediated cytotoxicity, 40% for antibody-dependent cellular cytotoxicity and 20% for complement-augmented antibody-dependent cellular cytotoxicity. The minimum serum dilution for maximal islet cell cytotoxicity was 1:100 for complement-dependent antibody-mediated cytotoxicity, 1:10 for complement-augmented antibody-dependent cellular cytotoxicity. These data indicate a unique optimal serum dilution for each of the three antibody killing mechanisms. Immune serum-mediated cytotoxicity was more specific for rat islet target cells than macrophage target cells. That antibody mediated these cytotoxic events was documented using immune serum-derived, DEAE purified immunoglobulin G which induced killing in all three antibody assays. Both antibody-dependent cellular cytotoxicity assays appear useful for studies of human diabetes, since human non-T mononuclear cells are cytotoxic to islet cells. These results suggest that for studies of potential islet cell killing mechanisms in insulin-dependent diabetes, specific xenogeneic assays exist not only for complement-dependent antibody-mediated islet cytotoxicity, but also for antibody-dependent cellular cytotoxicity and complement augmented antibody-dependent cellular cytotoxicity.

Adolescent↗
PubMed1983

Immune islet killing mechanisms associated with insulin-dependent diabetes: in vitro expression of cellular and antibody-mediated islet cell cytotoxicity in humans.

Because immune mechanisms are associated with insulin-dependent diabetes, multiple organ specific and xenogeneic cytotoxicity assays were developed. Human cellular and antibody effector systems were incubated with 51Cr-labeled dispersed normal rat islet target cells. In eight of 11 diabetic patients, nonenriched mononuclear cells incubated with islet target cells were more cytotoxic than cells from age- and sex-matched controls (p less than 0.01). When non-T cell-enriched mononuclear cells were used at diabetes onset, seven of 11 patients' cells showed excessive islet cytotoxicity (p less than 0.05). In four patients showing elevated cytotoxicity at diabetes onset, cytotoxicity decreased to control levels during diabetes remission. Islet specificity was suggested in that mononuclear cells derived from diabetic subjects did not mediate cytotoxicity against rat spleen or macrophage target cells. Three cytotoxic antibody mechanisms were also evaluated. C-dependent antibody-mediated cytotoxicity with the use of patient serum-coated islet target cells was elevated above control levels in four of 14 patients. Antibody-dependent cellular cytotoxicity exceeded control values in only two of 16 patients, although four assay systems were evaluated. C-augmented antibody-dependent cellular cytotoxicity was elevated in three of 14 patients. No differences were observed for antibody-mediated mechanisms in four patients evaluated at both diabetes onset and remission. Cytotoxic antibody was present in only about one-half of the patients showing increased cellular cytotoxicity, whereas most patients expressing increased cytotoxic antibody had cellular cytotoxicity. Islet cell cytotoxicity assays with the use of effector systems from patients with recent onset insulin-dependent diabetes suggest that direct cellular cytotoxicity is more active than antibody-mediated cytotoxic mechanisms, and that cellular cytotoxicity can correlate with disease activity.

Adolescent↗