Distinct modulation of the endothelin-1 pathway in iNOS-/- and eNOS-/- mice

We hypothesized that constitutive endothelial NO synthase (eNOS) and inducible NO synthase (iNOS) have opposite effects on the regulation of endothelin and its receptors. We therefore sought to determine whether deletions of iNOS or eNOS genes in mice modulate pressor responses to endothelin and the expression of ETA and ETB receptors in a similar fashion. Despite unchanged baseline hemodynamic parameters, anesthetized iNOS-/- mice displayed reduced pressor responses to endothelin-1, but not to that of IRL-1620, a selective ETB agonist. Protein content of cardiac ETA receptors was reduced in iNOS-/- mice compared with wild-type mice, but that of ETB receptors was unchanged. Anesthetized eNOS-/- mice presented a hypertensive state, accompanied by an enhanced pressor response to intravenous endothelin-1, whereas the pressor response to IRL-1620 was reduced. Protein levels were also found to be increased for ETA receptors, but reduced for ETB receptors, in cardiac tissues of eNOS-/- mice. In conscious animals, both strains responded equally to the hypotensive effect of an ETA antagonist, ABT-627, whereas orally administered A-192621, an ETB antagonist, increased MAP to a greater extent in eNOS-/- than in wild-type mice. Furthermore, significant levels of immunoreactive endothelin were found in mesenteric arteries in eNOS-/- but not in iNOS-/- or wild-type congeners. Our study shows that repression of iNOS or eNOS has differential effects on endothelin-1 and its receptors. We have also shown that the heart is the main organ in which iNOS or eNOS repression induces important alterations in protein content of endothelin receptors in adult mice.     

Characterization of oxidized low-density lipoprotein-induced hormesis-like effects in osteoblastic cells

Epidemiological studies indicate that patients suffering from atherosclerosis are predisposed to develop osteoporosis. Atherogenic determinants such as oxidized low-density lipoprotein (oxLDL) particles have been shown both to stimulate the proliferation and promote apoptosis of bone-forming osteoblasts. Given such opposite responses, we characterized the oxLDL-induced hormesis-like effects in osteoblasts. Biphasic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reductive activity responses were induced by oxLDL where low concentrations (10–50 µg/ml) increased and high concentrations (from 150 µg/ml) reduced the MTT activity. Cell proliferation stimulation by oxLDL partially accounted for the increased MTT activity. No alteration of mitochondria mass was noticed, whereas low concentrations of oxLDL induced mitochondria hyperpolarization and increased the cellular levels of reactive oxygen species (ROS). The oxLDL-induced MTT activity was not related to intracellular ROS levels. OxLDL increased NAD(P)H-associated cellular fluorescence and flavoenzyme inhibitor diphenyleneiodonium reduced basal and oxLDL-induced MTT activity, suggesting an enhancement of NAD(P)H-dependent cellular reduction potential. Low concentrations of oxLDL reduced cellular thiol content and increased metallothionein expression, suggesting the induction of compensatory mechanisms for the maintenance of cell redox state. These concentrations of oxLDL reduced osteoblast alkaline phosphatase activity and cell migration. Our results indicate that oxLDL particles cause hormesis-like response with the stimulation of both proliferation and cellular NAD(P)H-dependent reduction potential by low concentrations, whereas high concentrations lead to reduction of MTT activity associated with the cell death. Given the effects of low concentrations of oxLDL on osteoblast functions, oxLDL may contribute to the impairment of bone remodeling equilibrium. osteoblasts; atherosclerosis; oxysterol     

Genetic and epigenetic processes in seed development.

Seed development has emerged as an important area of research in plant development. Recent research has highlighted the divergent reproductive strategies of the male and female genomes and interaction between genetic and epigenetic control mechanisms. Isolation of genes involved in embryo and endosperm development is leading to an understanding of the regulation of these processes at the molecular level. A thorough grasp of these processes will not only illuminate an important area of plant development but will also have an impact on agronomy by helping to facilitate food production. An understanding of seed development is also likely to clarify the molecular mechanisms of apomixis, a fascinating process of asexual seed production present in many plants.     

CD4/GP120mac251 interaction induces phospholipase A2 (PLA2) activation in cynomolgus monkey lymphocytes

Cynomolgus monkey are susceptible to infection with select simian immunodeficiency virus (SIV). We investigated the early interactions between SIV envelope glycoproteins (gp120_mac251) and macaque lymphocytes. Our results demonstrate that the soluble viral glycoprotein induce a specific phospholipase A₂ (PLA₂) activation in lymphocytes through CD4. This PLA₂ activation, induced after envelope glycoprotein-CD4 interaction, because of its locally destabilizing membrane effect, may have important implications for preparing the lymphocyte membrane for fusion with the viral particle. However, this effect is not sufficient to accomplish fusion. These data indicate that the specific step of fusion may be downstream from PLA₂ activation.     

Low-conductance chloride channel activated by cAMP in the epithelial cell line T84

We have studied the modulation and pharmacological properties of two anion channels in T₈₄ cells by recording single channel and transepithelial currents. One channel had an outwardly rectifying current-voltage I/V curve, was rarely active in cell-attached patches, and was unaffected by cAMP. The other channel had lower conductance (8.7 pS at 37°C) and a more ohmic I/V relationship. Exposure to cAMP increased the probability of observing low-conductance channel activity in cell-attached patches> 6-fold. Extracellular DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) or IAA-94 (an indanyloxyacetic acid) inhibited the outward rectifier but did not affect the low-conductance channel or cAMP-stimulated transepithelial current. These results suggest the low-conductance Cl channel may contribute to apical membrane conductance during cAMP-stimulated secretion.     

Apparent T cell function of bone marrow cells from mice experiencing a graft-versus-host reaction.

The graft-versus-host (GVH) reaction, induced in adult F₁ mice by the injection of parental strain lymphoid cells (GVH mice), suppressed the in vitro plaque-forming cell (PFC) response to sheep erythrocytes (SRBC) of spleen cells obtained from the GVH mice (GVH-SC). In vitro restoration of the PFC response of GVH-SC was carried out employing a modified Marbrook culture chamber consisting of an inner culture compartment (IC) separated from an outer culture compartment (OC) by a cell-impermeable membrane. Thymus cells (TC) and lymph node cells (LNC) but not bone marrow cells (BMC) from normal mice placed in the IC restored the PFC response of GVH-SC cultured with SRBC in the OC. The restoring ability of TC and LNC was markedly reduced following treatment with anti-theta serum plus complement. BMC taken from GVH mice 3 or more days post-GVH induction (GVHBMC) and placed in the IC restored the PFC response of GVH-SC as well as TC and LNC. Treatment of GVH-BMC with anti-theta serum plus complement did not affect their restoring ability; furthermore, the number of theta-bearing cells in the bone marrow did not increase as a consequence of the GVH reaction. Two possible explanations are proposed for the T-like function of GVH-BMC.     

Micronutrient availability to cereals from calcareous soils

Summary The mechanism of higher grain production of wheat (Triticum aestivum L.) by four tillage methods was explored on a sandy calcareous soil of Sahl-Al Jafara, Libya, during the year 1976–77. Tillage methods increased grain yield and dry matter weight at the boot stage in the order of no-tillage<rotovator=disc plough < subsoiler. Rotovation to 15 cm and disc ploughing to 25 cm depth enhanced grain production mainly by eliminating weed competition. In both the cases, roots penetrated < 25 cm where plough-pan existed.Further yield increases by 50 cm deep subsoiling seems to be mainly explained by N and Cu rise in plants from their marginal to optimum levels and by reduction of Mn deficiency in plant shoots. Penetration of roots beyond the 25 cm plough-pan apparently resulted in higher absorption of these nutrients from leached or native soil supplies. Subsoiling also resulted in greater Zn concentration in plant shoots which, under marginal to deficient conditions, will also increase grain production.