Michael K. Elson

The effects of stress on central nervous system concentrations of the opioid peptide, dynorphin

Dynorphin is an opioid peptide distributed throughout the central nervous system. Using a highly specific and sensitive radioimmunoassay for dynorphin we have examined the effect of stress on ir-dynorphin levels in the cortex and hypothalamus of the rat. Stresses related to food ingestion, i.e. starvation (72 hr), mild tail-pinch and insulin (10 U/kg) induced hypoglycemia all produced alterations in ir-dynorphin levels in the cortex. In contrast, restraint stress and 10-minute swim stress produced no changes in ir-dynorphin levels in either the hypothalamus or the cortex. Two hour exposure at 4 degrees C resulted in a fall in ir-dynorphin levels in the hypothalamus. Taken together with previously reported pharmacological effects of dynorphin-(1-13), these results suggest a possible physiological role for dynorphin in appetite and temperature regulation.

Amphetamine-Induced Hyperthyroxinemia

Four patients had high serum thyroxine (T4) concentrations during periods of heavy amphetamine abuse. After amphetamine was withdrawn, serum T4 returned to normal. Administration of amphetamine to monkeys induced a rise in serum T4; in this model the high T4 level appeared to be caused by increased serum thyrotropin. The mechanism of this effect is unclear but is presumably mediated via the hypothalamus. Awareness of transient hyperthyroxinemia due to amphetamine may allow the physician to avoid confusion with true thyrotoxicosis.

Hyperprolactinaemia in male diabetics.

We recently investigated two patients with diabetes and elevated serum prolactin levels in whom no cause of hyperprolactinaemia could be found. For this reason we measured fasting serum prolactin levels in 72 diabetic males and compared the results with those of 63 healthy males and 90 nondiabetic males attending an Impotence Clinic. The diabetic group had significantly higher serum prolactin levels (13.1 +/- 0.9 ng/ml) than the two control groups (9.9 +/- 0.6 ng/ml for normal males and 7.7 +/- 0.3 ng/ml for the non-diabetic impotent group). Eighteen percent of the diabetics studied had serum prolactin levels above the normal range for males (greater than 20 ng/ml). There was no correlation between serum prolactin levels and duration of diabetes, glycosylated haemoglobin level or presence of clinically apparent retinopathy. The correlation between serum prolactin level and fasting plasma glucose was weak though statistically significant (r = 0.26, P less than 0.05).

Radiotherapy of CD19 Expressing Daudi Tumors in Nude Mice with Yttrium-90-Labeled Anti-CD19 Antibody

Studies were performed to determine the suitability of using two different anti-CD19 monoclonal antibodies to deliver the high energy beta-particle emitting isotope 90Y to B-cell lymphoma grown as flank tumors in athymic nude mice. The antibodies BU12 and HD37, both of the IgG1 subclass, recognize CD19, an internalizing B-lineage-specific membrane glycoprotein and member of the Ig supergene family. The antibodies were readily labeled with 90Y using the highly stable chelate, 1B4M-MX-DTPA. The radioimmunoconjugates selectively bound to the CD19 expressing B cell line Daudi, but not to CD19 negative control cells. Significantly more 90Y anti-CD19 bound to Daudi tumors growing in nude mice than did a control non-binding antibody (p = 0.001). The biodistribution data correlated with an anti-tumor effect. Anti-tumor activity was dose dependent and the best results were observed in mice receiving a single dose of approximately 300 uCi. The anti-CD19 antibody had significantly better anti-tumor activity as compared to a control 90Y-labeled antibody and most mice survived over 119 days with no evidence of tumor (p < 0.003). Histology studies showed no significant injury to the kidney, liver, or small intestine. Because radiolabeled anti-CD19 antibody can be used to deliver radiation selectively to lymphohematopoietic tissue, these data support the use of 90Y anti-CD19 antibodies in treating B-cell malignancies.

Levels of immunoreactive dynorphin in brain and pituitary of hyperthyroid and hypothyroid rats

Dynorphin is a potent opioid peptide. Using a highly sensitive radioimmunoassay we have measured the levels of immunoreactive (ir) dynorphin in the cortex, hypothalamus, anterior and posterior pituitary in hyperthyroid and hypothyroid rats. Ir dynorphin levels were increased in the cortex of hypothyroid animals and decreased in the hypothalamus of hyperthyroid rats.

Preclinical Studies Targeting Normal and Leukemic Hematopoietic Cells with Yttrium-90-Labeled anti-CD45 Antibody in Vitro and in Vivo in Nude Mice

A study was undertaken to investigate the suitability of using a high affinity (Kd = 1.1 nM) anti-CD45 monoclonal antibody for delivering the high energy beta-particle emitting isotope (90)Y to lymphohematopoietic target cells in vivo. The antibody, AHN-12, recognized the tyrosine phosphatase CD45 expressed on the surface of normal and malignant hematopoietic cells and studies showed that it reacted with both CD45-expressing normal peripheral blood cells and leukemia cells from patients. The antibody was readily labeled with (90)Y using the highly stable chelate 1B4M-DTPA and the radioimmunoconjugate was designated (90)Y-anti-CD45. The agent selectively bound to CD45(+) B cell line Daudi, but not CD45(-) control cells and significantly (p = 0.007) more bound to Daudi tumors growing in athymic nude mice than did a control non-reactive antibody. Moreover, biodistribution data correlated well to an anti-Daudi effect observed against established tumors in nude mice. The effect was dose dependent and irreversible with the best results in mice receiving a single dose of 137 microCi (90)Y-anti-CD45. These mice displayed a significantly (p < 0.0095) better anti-tumor effect than a control (90)Y-labeled antibody and survived over 135 days with no evidence of tumor. Histology studies showed no significant injury to kidney, liver, or small intestine even at 254 microCi, the highest dose tested. Because radiolabeled anti-CD45 antibody can be used to deliver radiation selectively to lymphohematopoietic tissue, these data indicate that this agent may be used to improve treatment of hematopoietic malignancies, particularly leukemia and lymphoma, when combined with hematopoietic stem cell transplantation in a future clinical trial.

Dosimetry and pharmacokinetics of monoclonal antibody A6H with human renal cell carcinoma xenografts: single dose study.

Implantable miniature thermoluminescent dosimeters and conventional biodistribution analysis were used to determine the locally absorbed radiation dose delivered to three morphologically distinct human renal cell carcinoma xenografts (TK-39, TK-82 and TK-177C; N = 87) following a 50 microCi infusion of 131iodine-labeled monoclonal antibody A6H. Xenografts were clearly detected by radioimmuno-scintigraphy. Pronounced differences were noted among the three xenografts in MAb pharmacokinetics and in the locally absorbed irradiation doses which ranged from 2 to 5 cGy per injected microCi of 131iodine-labelled A6H.

Comparison of Fresh Tissue Incubation Assay and the in Vivo Localization of Monoclonal Antibodies to Renal Cell Carcinoma

Few in vitro tests currently available are able to accurately predict the in vivo localization of monoclonal antibodies (Mabs) to cancer. We report on a fresh tissue incubation assay (FTIA) and compare the results of this assay to the in vivo localization of renal cell carcinoma (RCC)-reactive Mab A6H and control Mab AFP-22 to RCC and non-RCC xenografts implanted in nude mice. Both the FTIA and in vivo localization study demonstrated highly selective uptake of A6H in RCC but not in non-RCC xenografts. Radioimmunoscintigraphy using A6H clearly visualized RCC xenografts in every attempt, while AFP-22 did not highlight any of the tumor xenografts. The results demonstrate that FTIA may be a useful in vitro assay for selecting Mabs for in vivo application, and that radioimmunoscintigraphy is a potentially useful tool in detecting cancer sites.