Immunohistochemical studies on electron transport proteins associated with cytochromes P-450 in steroidogenic tissues. II. Microsomal NADPH-cytochrome c reductase in the rat adrenal.

NADPH-cytochrome c reductase (NADPH : ferricytochrome oxido-reductase, EC 1.6.2.4), the flavoprotein which mediates the NADPH-dependent reduction of cytochromes P-450 in adrenocortical microsomes, has been localized immunohistochemically at the light microscopic level in rat adrenal glands. Localization was achieved through the use of sheep antiserum produced against purified, trypsin-solubilized rat hepatic microsomal NADPH-cytochrome c reductase in both an unlabeled antibody peroxidase-antiperoxidase technique and an indirect fluorescent antibody method. The sheep antibody to rat hepatic microsomal NADPH-cytochrome c reductase concomitantly inhibited the NADPH-cytochrome c reductase and progesterone 21-hydroxylase activities catalyzed by isolated rat adrenal microsomes. When sections of rat adrenal glands were exposed to the reductase antiserum in both immunohistochemical procedures, positive staining for NADPH-cytochrome c reductase was observed in parenchymal cells of the three cortical zones but not in medullary chromaffin cells. The intensity of staining, however, was found to differ among the three cortical zones, with the most intense staining being found in the zona fasciculata and the least in the zona glomerulosa. The intensity of staining was also found to differ among cells within the zona fasciculata. These immunohistochemical observations demonstrate that microsomal NADPH-cytochrome c reductase is not distributed uniformly throughout the rat adrenal cortex.     

Effects of acute and chronic restraint and estrus cycle on pituitary-adrenal function in the rat

Female Long-Evans hooded rats with 5-day estrus cycles were subjected to 4 hr of continuous restraint for either 1 or 20 days. On the last day of the stress regimen, plasma and adrenal corticosterone concentrations were determined and classified according to the stage of the estrous cycle. The results indicated that acute stress produced greater plasma corticosterone concentrations than controls only during estrus, whereas in response to chronic stress significant stress-induced increments were observed during estrus and proestrus. The results suggest that the estrous cycle influences the magnitude of the stress-induced increments for both acute and chronic stress. In addition, the pituitary-adrenal system did not show habituation to repeated administration of this stress, but sensitization was observed during proestrus.     

Interferon: effects on the immune response and the mechanism of activation of the cellular response.

The discovery of interferon in 1957 by Drs. Isaacs and Lindenmann led to major revisions in the concepts of man's defenses against viral infections. There are at least two types of interferon. Along with their antiviral properties, they have recently been shown to exert a suppressive effect on the humoral and cellular immune response; they affect both B and T lymphocytes. A variety of substances, including virus, polyribonucleotides, and mitogens for T lymphocytes, are good interferon inducers. T lymphocytes seem to be necessary for these inducers to exert their immunosuppressive effects. The immunosuppressive effects of interferon inducers suggests that interferons may be mediators of suppressor T lymphocyte effects. In the virus system, interferon does not exert its antiviral effects by direct action on the virus, but rather derepresses a cell gene that results in the production of an antiviral protein. This antiviral protein is probably the mediator of inhibition of virus replication. This is a complex sequence of events that results in the interaction of interferon with the cell membrane and the resulting production of the antiviral state in the cell. This review will examine the various steps of this involved process.     

NADPH-cytochrome P450 reductase.

The rate of reduction of cytochrome P450 in hepatic microsomes in the presence of NADPH has been measured with a dual wavelength stopped-flow spectrophotometer. The results obtained, with microsomes prepared from phenobarbital-pretreated rats, indicate that the reduction process is biphasic and most probably composed of two concurrent first-order reactions. The rate constant for the reduction of cytochrome P450 in the fast phase in the presence of ethylmorphine is 1.74 s^?1. Since approximately 50% or more of the cytochrome P450 is reduced in the fast phase under these conditions, the rate of reduction of cytochrome P450 is approximately 150 nmol min^?1 (mg of protein)^?1. Under similar conditions the rate of ethylmorphine N-demethylation is 8.6 nmol min^?1 (mg of protein)^?1. Thus the rate-limiting step in ethylmorphine N-demethylation cannot be the introduction of the first electron into cytochrome P450 by NADPH-cytochrome P450 reductase.     

The nature of the suppressive effect of interferon and interferon inducers on the in vitro immune response

Viral-induced interferon inhibition of the primary in vitro plaque-formong cell (PFC) response in the mouse (C57B1/6) involves a dynamic relationship between the nature of the antigen, the concentration of interferon added to antigen-stimulated cultures, and the time of addition of interferon relative to antigen addition. The PFC response to a thymus-dependent antigen (sheep red blood cells) was more easily suppressed by viral-induced interferon than was that to a thymus-independent antigen (E. coli 0127 LPS), both in terms of inhibitory concentrations of interferon and the time at which the interferon could be added to cultures after antigen and still inhibit the PFC response. These differential effects of interferon could be related to the difference in cellular requirements (B and T lymphocytes) of the two antigens. Interferon was effective in inhibiting the in vitro PFC response of antigen-primed spleen cells, indicating that it can block the response of memory lymphocytes. By using interferon inducers as inhibitors of the in vitro PFC response, it was possible to show that at least two antigenically distinct interferons may be involved in suppressing the immune response. It is known that one type of interferon is induced by virus and synthetic double-stranded polyribonucleotides. The other type is stimulated by antigen and T cell mitogens. A model is proposed to explain the nature of these interferon inhibitory effects in terms of mediation of immune suppressor cell effects.     

Characterization of transmissible genetic elements from sucrose-fermenting Salmonella strains.

Two of seven sucrose-fermenting Salmonella strains obtained from clinical sources were found capable of conjugal transfer of the sucrose fermentation (Scr+) property to the Escherichia coli K-12 strain WR3026. The genetic elements conferring this Scr+ property, designated scr-53 and scr-94, were then conjugally transmissible from Escherichia coli WR3026 Scr+ exconjugants to other strains of Escherichia coli at frequences of 5 times 10- minus 6 to 5 times 10- minus 3 for the scr-53 element and 10- minus 6 to 10- minus 5 for the scr-94 element. In Escherichia coli hosts, both of these elements were compatible with F-lac and with each of six previously characterized transmissible lac elements. No antibiotic resistance characteristics or colicin production were discovered to be associated with either scr-53 or scr-94. Neither scr element generated a male host response to the female-specific phage phiII, but the scr-53 element rendered its Escherichia coli host sensitive to the male-specific phage R-17. Escherichia coli hosts containing scr-53 were susceptible to lysis by P1vir, and transduction of the scr-53 element was accomplished with this phage. The scr-53 element was isolated from Escherichia coli WR3026, Scr+ transductants, and Escherichia coli WR2036 Scr+ exconjugants as a covalently closed circular deoxyribonucleic acid molecule with a molecular weight (determined by electron microscopy) of approximately 52 times 10-6. Receipt of the scr-94 element rendered Escherichia coli hosts of this element unsusceptible to lysis by P1vir, although adsorption of the phage by an Escherichia coli WR3026 exconjugant containing scr-94 occurred as efficiently as it did on WR3026 itself. Repeated examination of Escherichia coli strains harboring scr-94, as well as of the Salmonella strain which initially contained it, did not reveal the presence of circular deoxyribonucleic acid. The synthesis of the sucrose cleaving enzyme was inducible in Escherichia coli exconjugants containing either scr-53 or scr-94.     

The effect of immunosuppression on secondary Echinococcus multilocularis infections in mice.

Baron R. W. and Tanner C. E. 1976. The effect of immunosuppression on secondary Echinococcus multilocularis infections in mice. International Journal for Parasitology6: 37–42. The growth of cysts of Echinococcus multilocularis in T-cell depleted A/J mice was studied. Adult thymectomy enhances the metastasis of hydatid cysts but does not significantly affect the total cyst weight. Combined thymectomy and antithymocyte serum (ATS) treatment also increases the metastatic dissemination of the parasite and also significantly increases cyst loads. It is suggested that cell-mediated immunity controls the early phase of Echinococcus infection.     

Lack of Liver X Receptors Leads to Cell Proliferation in a Model of Mouse Dorsal Prostate Epithelial Cell

Recent studies underline the implication of Liver X Receptors (LXRs) in several prostate diseases such as benign prostatic hyperplasia (BPH) and prostate cancer. In order to understand the molecular mechanisms involved, we derived epithelial cells from dorsal prostate (MPECs) of wild type (WT) or Lxrαβ−/− mice. In the WT MPECs, our results show that LXR activation reduces proliferation and correlates with the modification of the AKT-survival pathway. Moreover, LXRs regulate lipid homeostasis with the regulation of Abca1, Abcg1 and Idol, and, in a lesser extent, Srebp1, Fas and Acc. Conversely cells derived from Lxrαβ−/− mice show a higher basal phosphorylation and consequently activation of the survival/proliferation transduction pathways AKT and MAPK. Altogether, our data point out that the cell model we developed allows deciphering the molecular mechanisms inducing the cell cycle arrest. Besides, we show that activated LXRs regulate AKT and MAPK transduction pathways and demonstrate that LXRs could be good pharmacological targets in prostate disease such as cancer.