Naltrexone partially inhibits the estrogen-induced increase in prolactin secretion and anterior pituitary weight

The effects of naltrexone, a specific opiate antagonist, on stimulation by estradiol benzoate (EB) of prolactin (PRL) release and anterior pituitary (AP) weight, were studied in gonadectomized female and male Sprague-Dawley rats. One week after castration, rats were injected for 10 days once daily with 2 μg EB alone, or together with twice daily injections of 2 mg naltrexone/kg body weight (BW). Blood was collected for radioimmunoassay of PRL by orbital sinus puncture on days 0 and 6, and by decapitation on day 11, at which time the AP was quickly removed, weighed and assayed for PRL.Serum PRL concentrations and AP weights were significantly increased by EB administration. These effects of EB were partially but significantly inhibited by naltrexone. These results suggest that endegenous opiates may be involved in the estrogen-induced rise in serum PRL and increase in pituatary weight.     

T-lymphocyte function and sensitivity to interferon in trisomy 21

Previous studies have shown that cells from subjects with trisomy 21 have enhanced sensitivity to the antiviral effects of interferon, presumably because of the location of the gene, IfRec, coding for the species-specific response to interferon on chromosome 21. Interferon is also known to have many other effects including the ability to inhibit the proliferation of many types of cells. To determine whether proliferating trisomic lymphocytes are more sensitive to the antiproliferative effect of interferon we have investigated, using healthy noninstitutionalized subjects with trisomy 21, the ability of interferon to inhibit the proliferation of lymphocytes stimulated with phytohemagglutinin P(PHA), concanavalin A (Con A), and tetanus toxoid. The trisomic subjects had normal numbers of peripheral blood leukocytes, and normal numbers and proportions of T and B lymphocytes. The production of interferon by PHA-stimulated trisomic T lymphocytes was normal. Trisomic lymphocytes also had normal proliferative responses to PHA and Con A. There were no differences between the inhibitory effects of interferon on the proliferation of PHA-stimulated trisomic and normal lymphocytes. However, trisomic lymphocytes stimulated with low doses of Con A did display significantly enhanced sensitivity to the antiproliferative effects of interferon. In contrast to normal lymphocytes, trisomic lymphocytes were not stimulated to proliferate by tetanus toxoid, and exposure to interferon resulted in enhancement, rather than inhibition, of DNA synthesis.     

Suppression of lymphokine production: I. Macrophage-mediated inhibition of MIF production

Macrophages have been found to suppress the in vitro production by stimulated T lymphocytes of a lymphokine, migration inhibitory factor. When macrophages isolated from primary MSV-induced tumors were added to antigen-stimulated MSV-immune spleen cells, a complete suppression of MIF production was observed. This suppression was nonspecific, since MIF production by antigen-stimulated alloimmune spleen cells and by PHA-stimulated normal spleen cells was also inhibited. Suppressor macrophages could also be induced by inoculation with Corynebacterium parvum, whereas light mineral oil-induced peritoneal macrophages had no detectable effect on MIF production. The failure to detect MIF in the supernatants of stimulated cultures containing activated macrophages appeared to be due to inhibition of lymphokine production rather than to absorption or inactivation of MIF or to interference with the assay for detection of MIF. Macrophages were able to suppress MIF production only when added during the first 4–5 hr of culture and they had no effect when added later. These data show that activated macrophages can nonspecifically suppress lymphokine production and that this appears to be due to inhibition of an early step in lymphocyte stimulation.     

Immunologic significance of nonspecific suppressor cells in spleens of tumor-bearing mice.

Spleen cells from mice bearing a progressively growing syngeneic tumor failed to respond to stimulation with mitogens in vitro. This lack of reactivity was due to the presence of nylon wool-adherent cells in the population that could inhibit the mitogen response of normal lymphocytes. Paradoxically, at times when strong suppressor cell activity could be detected in tumor-bearing mice, the animals responded normally to in vivo immunization with sheep erythrocytes and allogeneic tumors, and to in vitro sensitization with allogeneic tumor cells. Regression of a highly antigenic syngeneic tumor also was unaffected by the presence of these suppressor cells. Thus, the occurrence of nonspecific suppressor cells in the spleens of tumor-bearing mice did not influence the overall immunologic competence of these animals.     

Colorimetric determination of acetaldehyde in the presence of formaldehyde

A procedure is described that enables use of the p-phenylphenol color reaction to determine acetaldehyde in the presence of formaldehyde. The sample is first treated with an acidic 2,4-pentanedione reagent, which selectively removes formaldehyde. The method is applicable to blochemical reactions using tissue preparations.     

The influence upon mitogenic and cellular immunologic reactive systems in vitro by poly(I:C) and BCG murine interferons induced in vivo.

We have previously reported that lymphocytes from W/Fu rats immunized with syngeneic (C58NT)D tumor cells were cytotoxic against these cells in a 4-hr ⁵¹Cr release assay. We have investigated the feasibility of cryopreserving lymphocytes and target cells and have selected freezing conditions which provide good yields of viable cells and functional activity. Lymphocytes from different animals had a recovery of 60–80% viability which resulted in a corresponding 55–75% recovery of cytotoxic activity. Repeated testing of lymphocyte cytotoxicity from a pool of frozen spleen cells against either fresh or frozen (C58NT)D cells gave reproducible cytotoxicity. In addition, recovery of high levels of lymphocyte function was also demonstrated when cryopreserved cells were employed in long-term cytotoxic assays, i.e., ³H-proline and ¹²⁵IUdR release assays, in the lymphoproliferative response to mitogens (PHA and Con A)³ or tumor cells (MLTI) as measured by ³H-thymidine incorporation, and in the in vitro generation of secondary cytotoxicity.By employing these cryoprotective techniques it is possible to have: 1) a population of lymphoid cells with known functional activity and 2) a pool of target cells with known susceptibility to lysis and antigenic content. Furthermore, the use of frozen cells as internal standards in each test also permits the analysis of assay variation as well as the study of variation in various cell types.     

Structure of the fluorescent nucleoside of yeast phenylalanine transfer ribonucleic acid

The structure of enzymatically isolated Y nucleoside of yeast phenylalanine tRNA was established by comparing its absorption, fluorescence, and mass spectra to that of the free base. The site of ribosylation was tentatively deduced by comparing the behavior under acid conditions of the natural nucleoside to that of synthetic Y nucleoside analogs. Our results indicate that the aglycone of the enzymatically isolated nucleoside has the same structure as the free base excised by acid treatment of phenylalanine tRNA, and that the ribose is probably attached to the N-3 position of the tricyclic nucleus.     

N-ω-chloroacetyl-l-ornithine,a new competitive inhibitor of ornithine decarboxylase,induces selective growth inhibition and cytotoxicity on human cancer cells versus normal cells

Abstract

Many cancer cells have high expression of ornithine decarboxylase (ODC) and there is a concerted effort to seek new inhibitors of this enzyme. The aim of the study was to initially characterize the inhibition properties, then to evaluate the cytotoxicity/antiproliferative cell based activity of N-ω-chloroacetyl-l-ornithine (NCAO) on three human cancer cell lines. Results showed NCAO to be a reversible competitive ODC inhibitor (K_i?=?59?µM) with cytotoxic and antiproliferative effects, which were concentration- and time-dependent. The EC_50,72h of NCAO was 15.8, 17.5 and 10.1?µM for HeLa, MCF-7 and HepG2 cells, respectively. NCAO at 500?µM completely inhibited growth of all cancer cells at 48?h treatment, with almost no effect on normal cells. Putrescine reversed NCAO effects on MCF-7 and HeLa cells, indicating that this antiproliferative activity is due to ODC inhibition.     

Cytotoxic activities of Coriolus versicolor (Yunzhi) extract on human leukemia and lymphoma cells by induction of apoptosis

Coriolus versicolor (CV), also known as Yunzhi, is one of the commonly used Chinese medicinal herbs. Although recent studies have demonstrated its antitumour activities on cancer cells in vitro and in vivo, the exact mechanism is not fully elucidated. Hence, the objective of this study was to examine the in vitro cytotoxic activities of a standardized aqueous ethanol extract prepared from Coriolus versicolor on a B-cell lymphoma (Raji) and two human promyelocytic leukemia (HL-60, NB-4) cell lines using a MTT cytotoxicity assay, and to test whether the mechanism involves induction of apoptosis. Cell death ELISA was employed to quantify the nucleosome production resulting from nuclear DNA fragmentation during apoptosis. The present results demonstrated that CV extract at 50 to 800 microg/ml dose-dependently suppressed the proliferation of Raji, NB-4, and HL-60 cells by more than 90% (p < 0.01), with ascending order of IC50 values: HL-60 (147.3 +/- 15.2 microg/ml), Raji (253.8 +/- 60.7 microg/ml) and NB-4 (269.3 +/- 12.4 microg/ml). The extract however did not exert any significant cytotoxic effect on normal liver cell line WRL (IC50 > 800 microg/ml) when compared with a chemotherapeutic anticancer drug, mitomycin C (MMC), confirming the tumour-selective cytotoxicity. Nucleosome productions in HL-60, NB-4 and Raji cells were significantly increased by 3.6-, 3.6- and 5.6-fold respectively upon the treatment of CV extract, while no significant nucleosome production was detected in extract-treated WRL cells. The CV extract was found to selectively and dose-dependently inhibit the proliferation of lymphoma and leukemic cells possibly via an apoptosis-dependent pathway.