[D-Pen2,4'-125I-Phe4,D-Pen5]enkephalin: a selective high affinity radioligand for delta opioid receptors with exceptional specific activity

[D-Pen2,4'-125I-Phe4,D-Pen5]enkephalin ([125I]DPDPE) is a highly selective radioligand for the delta opioid receptor with a specific activity (2200 Ci/mmol) that is over 50-fold greater than that of tritium-labeled DPDPE analogs. [125I]DPDPE binds to a single site in rat brain membranes with an equilibrium dissociation constant (Kd) value of 421 +/- 67 pM and a receptor density (Bmax) value of 36.4 +/- 2.7 fmol/mg protein. The high affinity of this site for delta opioid receptor ligands and its low affinity for mu or kappa receptor-selective ligands are consistent with its being a delta opioid receptor. The distribution of these sites in rat brain, observed by receptor autoradiography, is also consistent with that of delta opioid receptors. Association and dissociation binding kinetics of 1.0 nM [125I] DPDPE are monophasic at 25 degrees C. The association rate (k + 1 = 5.80 +/- 0.88 X 10(7) M-1 min-1) is about 20- and 7-fold greater than that measured for 1.0 nM [3H DPDPE and 0.8 nM [3H] [D-Pen2,4'-Cl-Phe4, D-Pen5]enkephalin, respectively. The dissociation rate of [125I]DPDPE (0.917 +/- 0.117 X 10(-2) min-1) measured at 1.0 nM is about 3-fold faster than is observed for either of the other DPDPE analogs. The rapid binding kinetics of [125I]DPDPE is advantageous because binding equilibrium is achieved with much shorter incubation times than are required for other cyclic enkephalin analogs. This, in addition to its much higher specific activity, makes [125I]DPDPE a valuable new radioligand for studies of delta opioid receptors.

Delta opioid receptor-selective ligands: [D-Pen2,D-Pen5]enkephalin-dermenkephalin chimeric peptides

A number of DPDPE-dermenkephalin chimeric peptides have been synthesized in which the putative C-terminal delta-address of dermenkephalin has been linked to the highly delta opioid selective cyclic peptide [D-Pen2,D-Pen5]enkephalin (DPDPE). Asp, Met-Asp and Leu-Met-Asp have been added to the C-terminus of DPDPE and both the carboxyl terminal and the carboxamide terminal series have been prepared. The bioassays using the mouse vas deferens and guinea pig ileum preparations have revealed a steady decrease in potency (compared to DPDPE) at delta and mu receptors as the dermenkephalin sequences were added. Some of the analogues, however, retained high delta selectivity. Similar results were obtained using radioligand binding assays. These findings suggest that the C-terminal amino acid sequence of dermenkephalin plays a role of delta-address which is specific to dermenkephalin itself, and is not additive with another delta selective ligand such as DPDPE.

Virus-specific delayed-type hypersensitivity (DTH). Cells mediating lymphocytic choriomeningitis virus-specific DTH reaction in mice

We had previously shown that the local lymphocytic choriomeningitis virus-induced delayed-type hypersensitivity (DTH) reaction in mice consists of two well delineated phases that are mediated by CD8+ and CD4+ T lymphocytes, respectively. These findings have been confirmed and extended by showing that the first CD8+ cell-dependent part of the response was enhanced by either the presence of CD4+ cells or systemic treatment with IL-2 and that it developed in the absence of detectable numbers of mononuclear phagocytes, whereas the later CD4+ cell part required monocytes or related elements. Furthermore, in the DTH reaction that was elicited with noninfectious viral Ag in mice previously immunized by infection, only the CD4+ cells participated. Thus, the two phases of the lymphocytic choriomeningitis-viral DTH reaction are principally different, which has to be taken into account when trying to assess the relevance of DTH during this virus infection.

Virus-specific delayed-type hypersensitivity (DTH). Cells mediating lymphocytic choriomeningitis virus-specific DTH reaction in mice

We had previously shown that the local lymphocytic choriomeningitis virus-induced delayed-type hypersensitivity (DTH) reaction in mice consists of two well delineated phases that are mediated by CD8+ and CD4+ T lymphocytes, respectively. These findings have been confirmed and extended by showing that the first CD8+ cell-dependent part of the response was enhanced by either the presence of CD4+ cells or systemic treatment with IL-2 and that it developed in the absence of detectable numbers of mononuclear phagocytes, whereas the later CD4+ cell part required monocytes or related elements. Furthermore, in the DTH reaction that was elicited with noninfectious viral Ag in mice previously immunized by infection, only the CD4+ cells participated. Thus, the two phases of the lymphocytic choriomeningitis-viral DTH reaction are principally different, which has to be taken into account when trying to assess the relevance of DTH during this virus infection.

Mechanism of recovery from acute virus infection. IX. Clearance of lymphocytic choriomeningitis (LCM) virus from the feet of mice undergoing LCM virus-specific delayed-type hypersensitivity reaction

As shown previously, after inoculation into the footpad of a mouse the lymphocytic choriomeningitis (LMC) virus multiplies locally. Beginning on day 6 or 7 after infection, the foot undergoes a delayed-type hypersensitivity (DTH) reaction which consists of two distinct phases that are mediated by CD8+ cells and CD4+ cells, respectively, and at about the same time the virus is eliminated. In general, for terminating infection of the mouse with LCM virus the CD8+ cytotoxic/suppressive T lymphocyte (CTL) is essential; we have now determined the cells that mediate control of the virus in a tissue undergoing a specific DTH reaction. Depletion, in infected mice, of all T lymphocytes by treatment with anti-Thy-1 monoclonal antibody prevented virus elimination from the foot, and the same was true when the CD8+ CTLs were removed. Depletion of the CD4+ helper/suppressor subset only marginally impaired the ability of the mice to rid themselves of the virus. The conclusion that here too the principal antiviral element is the CD8+ CTL was confirmed by experiments in which footpad-infected mice were adoptively immunized with virus-immune splenocytes from syngeneic mice selected for subclasses of T lymphocytes, or from mice differing in defined regions of the major histocompatibility complex (MHC), and also by experiments in which monocytes were virtually absent. However, CD8+ CTL alone or cells from MHC recombinant mice with identity in class I loci were never as antivirally active as unseparated splenocytes from syngeneic donor mice. Since the CD8+ cells' performance could be optimized by interleukin-2, we assume that the CD4+ T lymphocytes function as accessory cells; the same probably applies to monocytes.

Combined kidney and pancreas transplantation in diabetics

Kidney and pancreaticoduodenal transplantation were simultaneously performed in 12 insulin-dependent diabetic patients. These patients had advanced secondary complications, including blindness, vascular disease, and disabling neuropathy. Average posttransplant hospitalization and charges were 17.7 days and $42,780 compared with 11.2 days and $29,000 for patients who received renal allografts alone. Following transplantation, blood glucose and glycosylated hemoglobin A levels promptly returned to normal in all patients. Two patients subsequently died, one after five months of a cytomegalovirus infection and one after seven months of a ruptured bladder. After a mean of 11.6 months of follow-up, ten patients (83%) remained independent of insulin and dialysis. The success of pancreas transplantation in diabetics with advanced complications now approaches that of other organ allografts. It therefore appears reasonable to recommend transplantation for diabetics with less severe secondary complications, since these candidates are most likely to realize the potential benefits of long-term normoglycemia.

Rapid automated synthesis via diisopropyl phosphoramidite in situ activation. Chemical synthesis and cloning of a calmodulin gene

A gene coding for a calmodulin was synthesized and cloned. The chemical synthesis of the gene, coding for 149 amino acids, was achieved by the enzymatic ligation of 61 chemically synthesized DNA fragments. The DNA fragments were synthesized using a solid support with a diisopropyl phosphoramidite intermediate and in situ activation. The automated standard cycle time was 10 min/addition. The synthesizer was designed and constructed from inexpensive, readily available parts and controlled by a Commodore 64 computer. The gene possesses 27 unique, regularly spaced, restriction endonuclease cleavage sites to facilitate gene mutagenesis.

Evolving use of OKT3 monoclonal antibody for treatment of renal allograft rejection

OKT3, a monoclonal antibody reactive with a surface glycoprotein present on all postthymic T cells, was used to treat the initial acute episode of rejection in 30 recipients of cadaveric donor renal allografts. The first 16 patients received 1-5 mg daily for a period of 10-21 days during which the azathioprine and prednisone dosages were sharply reduced. Circulating T cells were eliminated within minutes after the first OKT3 infusion. T cells reactive with OKT3 remained depressed throughout the period of treatment, although a significant number of cells reactive with other T cells subset reagents became detectable after several days of OKT3 treatment. In all instances, the established rejection episode was reversed in 2-8 days without the addition of other immunosuppressive measures. Recurrent rejection occurred in 12 of 16 patients, but with further conventional immunosuppression, 50% of the renal allografts remain functional 20-44 months after transplantation. Fever, chills, and, in some instances, dyspnea following the first dose of OKT3 were the only side-effects observed. Most patients developed antiidiotypic or antimouse immunoglobulin antibodies without apparent clinical sequelae. In the subsequent 14 patients, modifications in the protocol included a steroid bolus prior to the first OKT3 infusion, limitation of therapy to 10 days, resumption of maintenance levels of azathioprine and prednisone prior to discontinuing OKT3, and addition of 3 i.v. doses of cyclophosphamide at the termination of treatment. Respiratory symptoms after the first infusion of the reagent have been eliminated. Antibody responses to OKT3 have been reduced, occurring in 38% as compared with 73% of patients treated previously. Recurrent rejection episodes observed in 8 of 14 patients have been reversible in all but one case. Allograft survival is 86% at 6-17 months posttransplantation. In the entire series of 30 OKT3-treated patients, only 4 grafts (13%) have been lost because of recurrent episodes of rejection.