Biomedical subjects
Publications and source records attributed to R Heintz.
We have discovered a new series of potent MMP Inhibitors that are selective for MMP-13 over MMP-1 incorporating a gamma-sulfone thiol.
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SC-52151 is a potent, selective, tight-binding human immunodeficiency virus (HIV) protease inhibitor containing the novel (R)-(hydroxyethyl) urea isostere. The mean 50% effective concentration for lymphotropic, monocytotropic strains and field isolates of HIV type 1 (HIV-1), HIV-2, and simian immunodeficiency virus is 26 ng/ml (43 nM). The combination of SC-52151 and nucleoside reverse transcriptase inhibitors synergistically inhibited HIV-1 replication without additive toxicity. An extended postantiviral effect correlates with inhibition of gag and gag-pol polyprotein processing. SC-52151 is highly protein bound ( >90%) in human plasma, and the level of partitioning into erythrocytes is low. Physiological concentrations of alpha-1-acid glycoprotein, but not albumin, substantially affect the antiviral potency of SC-52151. The oral bioavailability of [14C]SC-52151 is 17% when it is administered as an elixir to the rat, dog, or monkey. Oxidation of the t-butyl moiety is the major route of biotransformation, and elimination is mainly by biliary excretion. No toxicologically significant effects have been observed in animals. Pharmacokinetic and metabolism studies in multiple animal species predict 20 to 30% systemic bioavailability, an elimination half-life of 1 to 2 h, and a volume of distribution of greater than 3 liters/kg in humans.
The intraperitoneal injection of insulin-producing islets immunoprotected by an alginate-poly(amino acid) membrane is a potential method of reversing diabetes without the need for lifelong immunosuppression. Previous attempts to demonstrate this technology in large animals have failed, preventing application in humans. We have determined that key factors responsible for these past failures include cytokine (interleukins 1 and 6 and tumor necrosis factor) stimulation by mannuronic acid monomers from alginate capsules with weak mechanical integrity, which results in fibroblast proliferation. With this insight, we formulated mechanically stable microcapsules by using alginate high in guluronic acid content and report prolonged reversal of diabetes in the spontaneous diabetic dog model by the intraperitoneal injection of encapsulated canine islet allografts. Euglycemia, independent of any exogenous insulin requirement, was noted for up to 172 days. Graft survival, evidenced by positive C-peptide release, was noted for as long as 726 days in a recipient receiving a single injection of immunoprotected islets. Histological evidence of viable islets retrieved from the peritoneal cavity 6 months posttransplant confirmed the biocompatibility and immunoprotective nature of this capsule formulation. The finding that intraperitoneal injection of alginate-immunoprotected islets, a minimally invasive surgical procedure, is effective in prolonged (> 1 year) maintenance of glycemic control, without the need for lifelong immunosuppression, may have significant implications for the future therapy of type I diabetes in humans.
Since 1991, the Patient Self-Determination Act (PSDA) has required all health care institutions that receive Federal funds to inform patients upon admission of their rights to make decisions about medical care and to execute advance directives. Implementation of the PSDA presents a special challenge for state mental hospitals. The relevance and possible negative therapeutic impact of discussing end of life decisions at the time of an acute psychiatric admission has recently been raised in the literature. Other ethical dilemmas arising from the interplay between mental illness and informed consent for medical treatment, particularly for older patients committed to state mental hospitals, have been highlighted by the PSDA. In this article we discuss some of the issues raised by implementation of the PSDA in this setting.
Long-term euglycemia by intraperitoneal transplantation of microencapsulated islets has not been described in the diabetic large animal model. In this study, we report the successful long-term reversal of diabetes by this method in spontaneous diabetic dogs. We have identified fundamental mechanism(s) associated with alginate-based microcapsule fibrosis, and have devised methods to ameliorate this problem. These include the use of purified alginate of low mannuronic acid content and cytokine suppression. Ten insulin-dependent, spontaneous diabetic dogs (insulin requirement 1-4 units/kg/day; absence of circulating C-peptide and diabetic K-values of 0.6 +/- 0.4) were entered into the study. Islets from mongrel donor pancreata were isolated and transplanted intraperitoneally either as free islet controls (n = 3) or as microencapsulated islet allografts (n = 7). In all seven encapsulated islet recipients, euglycemia was achieved within 24 hr (serum glucose failing from 304 +/- 117 to 116 +/- 72 mg/dl). IVGTT performed 14 days after islet transplant demonstrated normalization of K-values changing from a pretransplant level of 0.6 +/- 0.4 to 2.6 +/- 0.6. All animals receiving encapsulated islets remained euglycemic, free of the need for exogenous insulin, for a period of 63-172 days, with a median insulin-independence for 105 days. In contrast, recipients receiving free islets rejected their graft within seven days of implantation. In conclusion, this is the first report of long-term successful reversal of spontaneous diabetes in the large animal model by an intraperitoneal injection of encapsulated islets. The potential exists for this form of therapy to be explored in the treatment of type I diabetes in man.
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A simple, rapid method of islet purification is important in large-scale human islet isolation. We have previously identified monoclonal antibodies specific for acinar cells, but not islets, and described an immunologic method of purification by selective lysis of the acinar cells. An attractive alternative to lysis of the acinar cell is depletion by a magnetic immunomicrosphere technique. We report in this study a rapid, reproducible method of rat islet purification utilizing magnetic microspheres coated with acinar-cell-specific monoclonal antibodies. Pancreatic digestion with collagenase followed by depletion of acinar cells with the magnetic immunomicrospheres (MIMS) yields large numbers of intact islets. We compared the islets thus obtained with hand-picked (HP) islets (control) for yield, purity, in vitro insulin secretory capacities, and in vivo functional viability. The islet yield with the MIMS method (n = 35) was 72.7% that obtained with the HP method (n = 6) (378 +/- 8 vs. 519 +/- 31 islets per pancreas). The purity of the MIMS-isolated islets was 84 +/- 1.9%, ranging from 75-95%. Static glucose stimulation showed excellent function (2-3-fold increase of insulin release over basal levels) with no statistical difference in insulin secretion between MIMS and HP islets. Under microscopic examination, both groups revealed a well-preserved structure with healthy endocrine cells. When 1321 +/- 59 MIMS islets were transplanted into streptozotocin-induced diabetic rats (n = 10), normoglycemia (less than 200 mg/dl) was restored in all recipients following transplantation, and 100% of them remained normoglycemic on day 120 postgrafting. In summary, a rapid, consistent, and simple method of isolating viable, purified rat islets is described. The broad interspecies crossreactivity of the McAb suggests that this technique may be generally useful for islet purification in large mammalia, including man.
We have developed two immunological methods of islet purification using anti-acinar cell monoclonal antibodies (McAb). Pancreatic digestion with collagenase followed by depletion of acinar cells with McAb and complement or magnetic immunomicrospheres (MIMS) yields large numbers of intact islets. We compared the islets thus obtained with either handpicked (HP) islets, or islets separated on density gradients alone, for yield, purity, in vitro in sulin secretory capacities, and in vivo functional viability. Exposure of canine acinar tissue to the cytotoxic McAb resulted in a seven-fold enrichment in islet concentration, with preparations of 65% to 87% purity. Islet yield, however, was impaired by the procedure of McAb treatment, reducing the average yield from the control digestate of 40,000 to 60,000 islets/pancreas by 40% to 45%. Using the MIMS method in the rat model, the islet yield was 73% that obtained by the HP method (378 +/- 8 vs 519 +/- 31 per pancreas). The purity of the MIMS isolated islets was 84 +/- 1.9%, ranging from 75% to 95%. Analysis of the complement and MIMS treatments by in vitro static glucose tests and the capacity to restore normoglycemia after isografting in streptozotocin-induced diabetic rats indicates that the functional integrity of the islets was not affected by the purification process.
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1. Recent evidence suggests that monoamine oxidase (MAO) plays an important role modulating the extrapyramidal syndromes produced by neuroleptic drugs in both human and nonhuman primates. 2. To evaluate the possibility of using peripheral blood platelet MAO-B levels as indices of central nervous system MAO-B effects, we measured platelet MAO-B levels in Cebus monkeys that were previously tested with neuroleptics (N = 36) or drug naive (N = 6). 3. No platelet MAO-B was consistently detectable in these blood samples. 4. Thus platelet measures of MAO-B do not reliably reflect brain MAO-B function in nonhuman primates and do not offer a useful model for studying blood-brain MAO-B relationships.
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Identification, separation and purification of human islets from acinar cells following collagenase digestion of the pancreas remains a difficult problem. We have identified and characterized two monoclonal antibodies, CBL3 and TT62, with specific binding activity to human islets but not acinar cells. The antigens these monoclonal antibodies recognize are lipid in nature and thus unaffected by collagenase digestion of the human pancreas. These properties allow isolated human islets to be identified by fluorescein isothiocyanate-labeled CBL3 and TT62, making these monoclonal antibodies potentially useful reagents in islet identification and purification.
The neuropharmacologic mechanisms underlying neuroleptic-induced extrapyramidal syndromes (EPS) were studied using a nonhuman primate model. Twenty-six Cebus albifrons monkeys were given weekly challenges of haloperidol (0.025 mg/kg IM), and half of the animals received the monoamine oxidase (MAO) inhibitor pargyline (5 mg/kg PO) daily for 17 consecutive days during the protocol. Pargyline caused no changes in baseline behaviors, but significantly reduced haloperidol-induced acute dystonia (AD) (-67%, P less than 0.002) and parkinsonism (-56%, P less than 0.005). The majority (8 of 13) of the experimental group had complete prevention of neuroleptic-induced EPS during cotreatment with pargyline. Behavioral scores returned to baseline levels after stopping pargyline, and did not show the further sensitization to haloperidol-induced AD that occurred in the control group. The possible mechanisms by which an MAO inhibitor might influence neuroleptic-induced AD were considered. The most likely explanation would appear to involve facilitation of striatal dopamine (DA) neurotransmission by inhibition of intra- and extraneuronal MAO, thus supporting the hypothesis that AD is due to decreased striatal DA function with secondary cholinergic hyperfunction.
A center carbon atom of 1,3-diketone moiety of phenylbutazone was oxidized to give three metabolites--4-hydroxyphenylbutazone (metabolite I), 4-hydroperoxyphenylbutazone (metabolite II) and 4-chlorophenylbutazone (metabolite III)--by the action of enzymes present in leukocyte extract obtained from peritoneal exudate of rats. Both metabolites II and III were produced by peroxidases, while metabolite I was produced by enzymes other than the peroxidases.
The plasma concentration-time profile of indocyanine green (1) in the rabbit was determined by spectrophotometric and high-performance liquid chromatographic (HPLC) analysis following doses of 5 or 25 mg/kg. Spectrophotometric analysis yielded plasma concentration estimates that were higher than those obtained by an HPLC method and this difference was particularly large at time points greater than or equal to 30 min postdose. Chromatograms of plasma samples from each rabbit exhibited two peaks, both of which were maximal in the first postdose sample, suggesting an impurity in the commercial preparation. HPLC analysis of five different lots of 1 suggested a variable abundance of this impurity (1.7-4.0%). When stored in a variety of aqueous solutions, 1 degraded to a compound with a retention time identical to that of the impurity. The time for 50% degradation of 1 in deionized, distilled, and sterile water was 19, 92, and 99 h, respectively, and the rate of decay in these solvents exhibited significant interday variability. Dilute acetic acid (approximately 20 mM; pH = 3.2) was found to substantially accelerate this degradation (50% degradation in less than 1 h). Interestingly, this acid-catalyzed rate of conversion of 1 to the degradation product fit about equally well assuming a zero-order or first-order process. In an effort to elucidate the structure of this degradation product (impurity), UV-visible spectra of appropriate column eluates were obtained. The spectra of these compounds differed from that of 1 in only minor details.(ABSTRACT TRUNCATED AT 250 WORDS)