Inhibition of 2-nitropropane-induced rat liver DNA and RNA damage by benzyl selenocyanate

We observed that pretreatment of male F344 rats with benzyl selenocyanate, a versatile organoselenium chemopreventive agent in several animal model systems, decreases the levels of DNA and RNA modifications produced in the liver by the hepatocarcinogen 2- nitropropane. To clarify the mechanisms involved, we pretreated male F344 rats with either benzyl selenocyanate, its sulfur analog benzyl thiocyanate, phenobarbital or cobalt protoporphyrin IX; the latter is a depletor of P450. We then determined (1) the ability of liver microsomes to denitrify 2-nitropropane, (2) effects on 2-nitropropane- induced liver DNA and RNA modifications and (3) amount of nitrate excreted in rat urine following administration of the carcinogen. Pretreatment with benzyl selenocyanate or phenobarbital increased the denitrification activity of liver microsomes by 217 and 765%, respectively, increased liver P4502B1 by 31- and 435-fold, respectively, decreased the levels of 2-nitropropane-induced modifications in liver DNA (29-70% and 17-30%, respectively) and RNA (67-85% and 30-50%, respectively), and increased the 24-h urinary excretion of nitrate by 157 and 209%, respectively. Pretreatment with benzyl thiocyanate had no significant effect on any of these parameters. Pretreatment with cobalt protoporphyrin IX decreased liver P4502B 1 by 87%, decreased the denitrification activity of liver microsomes by 76%, decreased the 24 h urinary excretion of nitrate by 88.5%, but increased the extent of 2-nitropropane-induced liver nucleic acid modifications by 17-67%. These results indicate that the metabolic sequence from 2-nitropropane to the reactive species causing DNA and RNA modifications does not involve the removal of the nitro group. Moreover, they suggest that benzyl selenocyanate inhibits 2-NP-induced liver nucleic acid modifications in part by increasing its detoxication through induction of denitrification, although it is evident that other mechanisms must also be involved.      

Flow cytometry of transitional cell carcinoma of the urinary bladder: influence of prior local therapy

A review of acridine-orange DNA and RNA flow cytometry (FCM) histograms of 249 bladder irrigation specimens from 129 patients with a previous history of transitional cell carcinoma (TCC) reveals that aneuploidy and tetraploidy (greater than 10% of total cell population) are reliable markers to detect the presence of bladder tumor in patients treated by surgical resection of tumor only. Tetraploidy is unreliable when the patient received intravesical chemotherapy or radiation therapy but aneuploidy remains accurate. A comparison of the reliability of FCM compared with cytology indicates an overall lower sensitivity and specificity for FCM (respectively, 52% and 73%) as opposed to cytology (respectively, 62% and 92%). Sensitivity is improved and raised to 77% if FCM and cytology are used in conjunction and reaches 82% in patients treated by surgery only and 88% in those who received radiation therapy. The lowest sensitivity and specificity obtained with FCM are in patients treated by intravesical chemotherapy (respectively, 44% and 58%) and the highest are in those treated by surgery without additional therapy (56% and 83%). This study demonstrates that FCM criteria for diagnosis of TCC of urinary bladder on bladder irrigation specimens depends on patient's treatment history. It also indicates that sensitivity and specificity of cytology to detect bladder tumor are superior to those obtained with FCM but both methods may be considerably improved if they are used in conjunction.     

The modulation by 3,5,3'-triiodothyronine (T3) of pituitary T3 nuclear receptors in hypothyroid rats is inhibited by cycloheximide

The density of T3 nuclear receptors is known to vary with tissues and physiopathological conditions, but the factors involved in their regulation are still unknown. We have previously shown in the anterior pituitary gland that T3 modulates its own receptors; the density of T3 receptors in hypothyroid rats is half that in normal rats, and one injection of T3 is able to restore normal density of T3 receptors within 1-3 h. To determine whether T3 has a direct action on the synthesis of its nuclear receptor, the effect of cycloheximide (Cy) on T3-induced nuclear receptor was studied. In addition, the relationship between the density of pituitary T3 receptors and the secretion of TSH in different thyroid states was examined. In normal rats one injection of Cy (0.5-8 mg/100 mg BW) induced within 3 h a dose-dependent reduction in the density of pituitary T3 receptors as well as an important decrease in plasma TSH, with no changes in T4, T3, or pituitary TSH content. In hypothyroid rats the 50% decrease in the density of pituitary T3 receptors was not further reduced by 1 mg Cy. However, when the same dose of Cy was given 30 min before T3 it completely inhibited the induction by T3 of its receptors. When Cy was given 30 min or 1 h after T3 the inhibition was only partial. An inverse correlation was found between the density of T3 receptors in the pituitary gland and plasma TSH (r = -0.8128) in all experimental groups except those treated with Cy; this drug had an inhibitory effect on both TSH secretion and the density of receptors. The present data, therefore, support the view that T3 in the pituitary gland may induce the synthesis of its own nuclear receptors and that the density of T3 receptors is also involved in the control of TSH secretion.     

Regulatory role of interleukin-10 in experimental group B streptococcal arthritis

Intravenous inoculation of CD-1 mice with 10(7) CFU of type IV group B Streptococcus (GBS) results in a high incidence of diffuse septic arthritis, associated with high levels of systemic and local production of interleukin-1beta (IL-1beta) and IL-6. In this study, the role of the anti-inflammatory cytokine IL-10 in the evolution of GBS systemic infection and arthritis was evaluated. IL-10 production was evident in sera and joints of GBS-infected mice. Neutralization of endogenous IL-10 by administration of anti-IL-10 antibodies (1 mg/mouse) at the time of infection resulted in worsening of articular lesions and 60% mortality associated with early sustained production of IL-6, IL-1beta, and tumor necrosis factor alpha (TNF-alpha). The effect of IL-10 supplementation was assessed by administering IL-10 (100, 200, or 400 ng/mouse) once a day for 5 days, starting 1 h after infection. Treatment with IL-10 had a beneficial effect on GBS arthritis, and there was a clear-cut dose dependence. The decrease in pathology was associated with a significant reduction in IL-6, IL-1beta, and TNF-alpha production. Histological findings showed limited periarticular inflammation and a few-cell influx in the articular cavity of IL-10-treated mice, confirming clinical observations. In conclusion, this study provides further information concerning the role of IL-10 in regulating the immune response and inflammation and calls attention to the potential therapeutic use of IL-10 in GBS arthritis.     

Pleomorphism of human prostatic cancer cells (DU 145) in culture--the role of cytoskeleton

The role of cytoskeletal structure in the alteration of cell shape, multinucleation, and intracellular transport of human prostatic carcinoma cells DU 145 was investigated by light microscopy, scanning and transmission electron microscopy, and by immunofluorescence microscopy. It was confirmed that alterations in cell shape and surface topography, multinucleation, and intracellular transport of these cultured cells were regulated by a microfilament system composed of actin. The presence of prekeratin confirmed the epithelial nature of these cells. It was noted for the first time that these cells were highly motile and contained fewer microtubules, a moderate amount of intermediate filaments, and a large amount of microfilaments. "Displastic" cells were quite common in long-term culture. DU 145 cells are excellent in vitro models for further research on human prostatic cancer cells.     

Induction of a stable hapten-specific immunosuppression by a hapten conjugated to poly(N-vinylpyrrolidone) (PVP).

The ability of a hapten coupled to a clinically permissive synthetic polymer (NIP-PVP) to induce suppression was investigated. NIP coupled to the low molecular weight non-immunogenic form of poly(N-vinylpyrrolidone) (PVP) was found to be capable of inducing a hapten-specific longlasting suppression of both primary and secondary responses. The previous use of PVP as a plasma expander in humans makes this polymer a potentially suitable tool for the induction of specific immunosuppression to a variety of clinically important drug and tissue specific epitopes. The possible use of low molecular weight PVP for that purpose will be investigated further, specifically with larger antigenic components.     

Small CD4+8+TCRlow thymocytes contain precursors of mature T cells

To evaluate directly the developmental potential of cortical CD4⁺8⁺ thymocytes, highly purified populations of small, nondividing CD4⁺8⁺TCR^low and large, dividing CD4⁺8⁺TCR^high thymocytes from H-2^d mice expressing a transgenic T cell receptor restricted by H-2D^b (major histocompatibility complex class I) molecules were transferred into the thymus of normal, nonirradiated H-2^b recipient mice. The results show that both populations generate CD4^?8⁺ thymocytes under these conditions, thus providing conclusive evidence that small cortical thymocytes do not represent a “dead end” but an important intermediate stage in T cell development.     

Decreased virulence of a pneumolysin-deficient strain of Streptococcus pneumoniae in murine meningitis

Pneumolysin, neuraminidases A and B, and hyaluronidase are virulence factors of Streptococcus pneumoniae that appear to be involved in the pathogenesis of meningitis. In a murine model of meningitis after intracerebral infection using mutants of S. pneumoniae D39, only mice infected with a pneumolysin-deficient strain were healthier at 32 and 36 h, had lower bacterial titers in blood at 36 h, and survived longer than the D39 parent strain. Cerebellar and spleen bacterial titers, meningeal inflammation, and neuronal damage scores remained uninfluenced by the lack of any of the virulence factors.