Nitrogen fertigation of greenhouse-grown cucumber

Summary This greenhouse study investigated the response of trickle-irrigated cucumber (Cucumis sativa cv. ‘Petita’) to three N levels applied with every irrigation via the irrigation stream. The plants were grown in pots filled with 12 kg of soil. Water containing 5.8, 11.8, or 17.8 mmol N/l, and uniformly supplied with 2.0 and 3.9 mmol/l of P and K, respectively, was applied two to three times daily. In all treatments of 0.3 leaching fraction was allowed. The resulting total N applications were 15.7, 31., and 47.2 g N/plant. The total amount of water applied was 1851/plant. Total N and NO₃-N, in lajinae and petioles, increased with increasing N level whereas P and K in generated decreased. Although different NO₃/NH₄ ratios in the treatments may have influeced the response to N, it could be concluded that the highest yield was obtained with 11.8 mmol N/1 due to increased number of fruit. In the root volume of this treatment the NO₃-N concentration in the soil solution was aroun 7 mmol/1 for most of the growing season. The dry matter concentration of fruits was not affected by the N levels. It was concluded that 11.8 mmol N/1 applied with every irrigation via the irrigation stream is adequate to cover the needs of greenhous-grown cucumber for higher yield (9.42 kg/plant over a harvesting period of 93 days).     

Dual compartment (bicameral) culture: role of basement membrane in epithelial differentiation

A number of years ago we reported that tight junctions between adjacent Sertoli cells subdivide the seminiferous epithelium into two compartments, basal and adluminal, thus forming the morphological basis of the blood-testis barrier. It is now generally believed that the special milieu created by the Sertoli cells in the adluminal compartment is essential for germ cell differentiation. In order to duplicate the compartmentalization that occurs in vivo, Sertoli cells were cultured in bicameral chambers on Millipore filters impregnated with a reconstituted basement membrane. Confluent monolayers of these cells were tall columnar (40–60 µ in height) and highly polarized. These Sertoli cell monolayers established electrical resistance that peaked when the Sertoli-Sertoli tight junctions developed in culture. In addition, the monolayers formed a permeability barrier to ³H-inulin and lanthanum nitrate. The bicameral chambers were utilized in a number of studies on protein secretion, and it was revealed that numerous proteens are secreted in a polarized manner. In another study, hormone- stimulated aromatase activity was measured in Sertoli cells grown on plastic culture dishes, plastic dishes coated with laminin or Matrigel, and in the bicameral chambers. Cell culture on basement membrane substrate decreased the FSH-dependent estrogen production. No estrogen production was observed when the Sertoli cells were cultured in the bicameral chambers. These results are in accord with the hypothesis that differentiated Sertoli cells lose their ability to metabolize androgen to estrogen in an hormone-dependent manner, whereas undifferentiated cells in culture, or in vivo, have a very active FSH-dependent aromatase activity. This bicameral culture system could serve as an important model system to examine various functions of Sertoli cells including interactions of Sertoli cells with germ, Leydig, and myoid cells.     

IL-6-mediated MHC class II induction on RIN-5AH insulinoma cells by IFN-gamma occurs via the G-protein pathway

Major histocompatibility complex (MHC) class II antigen expression has been implicated in the pathogenesis of autoimmune type 1 diabetes. In this study we examined the role of various cytoldnes that may induce MHC class II surface antigen expression, using the rat insulinoma line RIN-5AH as a pertinent model system. As in another study, the ability of IFN-gamma to amplify MHC class II antigen expression 4-fold is demonstrated. At the same time we noted a 5-fold increase of these histocompatibility antigens by IL-6. Signal transduction analysis reveals that IL-6-induced MHC class II expression is specifically mediated by the G-protein system (activation of p21(ras) by IL-6) since mevalonic acid lactone (a Gprotein inhibitor) abolishes the action of IL-6. In contrast, IFN-gamma, which does not activate p21(ras), is not inhibited by protein kinase C (PKC) inhibitors but by those of the G-protein pathway. This finding raises the possibility that IFN-gamma induces RIN cells to secrete IL-6 (as shown previously, as well as in this paper) which, in turn, increases class II antigen expression via the G-protein pathway. This action may be unique to IL-6 or in synergy with IFN-gamma. Other cytokines such as IL-1alpha and beta, and TNF-alpha induce a smaller increase in MHC class II antigens on RIN cells, and appear to activate both the G-protein and the PKC signal transduction pathways to varying degrees. Therefore, injury of pancreatic beta-cells and possible induction of autoimmune type 1 diabetes via various cytokines may be caused by IL-6 or IFN-gamma, or by their ability to induce MHC class II antigen upregulation.     

Age-related changes in the function of the pituitary-gonadal axis in a sterile male rat mutant (hd/hd)

Testicular growth is depressed in the genetically sterile male rat (hd/hd) relative to its LE phenotype littermates (by 50% and 73% at 27 and 90 days of age, respectively). Within the hd/hd testis, both the tubular and seminiferous tubule tissues are affected by the mutation. In addition, there is significantly less germ cell production from the primary spermatocyte stage of spermatogenesis onwards and the total number of Sertoli cells observed is less. In the intertubular tissue, the total volume and the total number of Leydig cells per testis is significantly less, but the mean volume of an average Leydig cell is not modified. The serum gonadotropin levels are higher in the hd/hd rat, whereas from 40 days of age onwards the level of testosterone is lower. The FSH and LH binding affinity constants are unchanged by the mutation; however, the total number of FSH binding sites per 10(6) Sertoli cells is lower while that of LH per 10(6) Leydig cells is greater. Indeed, it is likely that the lesser concentration of serum testosterone in the hd/hd rat is a result of a smaller number of Leydig cells since their individual function is not modified. The testicular androgen binding protein (ABP) content and the ABP output towards the epididymis are lower as a consequence of both a lesser number and an altered function of the Sertoli cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of the transmethylation inhibitor S-adenosyl-homocysteine and of the methyl donor S-adenosyl-methionine on rat Leydig cell function in vitro

In purified rat Leydig cells, the methyl donor S-adenosyl-methionine (SAM), increases significantly in a dose dependent manner the [125I]hCG binding as well as the productions of cAMP and of testosterone; the competitive inhibitor of methylations S-adenosyl-homocysteine (SAH), has an opposite effect. Associated to oLH, SAM further enhances the cAMP synthesis while SAH inhibits significantly the adenylate cyclase activity. With regard to testosterone synthesis, SAM potentiates the stimulating roles of oLH and dbcAMP (27 and 38% increases, respectively) although SAH diminishes testosterone productions (48 and 35%, respectively under oLH and dbcAMP stimulations). Scatchard analysis has shown that SAM (1.4 mM) increases the number of LH/hCG binding sites on Leydig cells while SAH (1.4 mM) decreases it; LH/hCG Ka values are not modified neither by SAM nor by SAH. These data suggest that the in vitro regulation of steroidogenesis in purified rat Leydig cells may involve methylation processes (presumably phospholipids are the potential substrates of these reactions) which modulates the transmission of the hormonal signal through the membrane and affects the testosterone synthesis at a step beyond the adenylate cyclase.     

Assignment of 1H, 13C, and 15N resonances of YgiT, a putative DNA interacting protein from E. coli, containing one HTH and two CxxC motifs

The 131 residues protein encoded by the open reading frame ygiT of E. coli contains two characteristic domains: a zinc finger protein-like structure with two CxxC motives at its N-terminus and a helix-turn-helix (HTH) motif at its C-terminus. We report the backbone and side chain ¹H, ¹³C, and ¹⁵N resonances assignment of YgiT.     

Survival and development of immature stages of the Mediterranean fruit fly (Diptera: Tephritidae) in citrus fruit

We studied, under laboratory conditions, the performance of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), immature stages in intact whole fruit of three sweet orange varieties, lemon, and bitter oranges. Both citrus variety and fruit part (flavedo, albedo, and pulp) had strong effects on larval performance, smaller effects on pupae, and no effects on eggs. Fruit peel was the most critical parameter for larval development and survival, drastically affecting larval survival (inducing very high mortality rates). Among fruit regions, survival of larvae placed in flavedo was zero for all varieties tested except for bitter orange (22.5% survival), whereas survival in albedo was very low (9.8-17.4%) for all varieties except for bitter orange (76%). Survival of pupae obtained from larvae placed in the above-mentioned fruit regions was high for all varieties tested (81.1-90.7%). Fruit pulp of all citrus fruit tested was favorable for larval development. The highest survival was observed on bitter oranges, but the shortest developmental times and heaviest pupae were obtained from orange cultivars. Pulp chemical properties, such as soluble solid contents, acidity, and pH had rather small effects on larval and pupal survival and developmental time (except for juice pH on larvae developmental duration), but they had significant effects on pupal weight.     

Prolonged incubation with phorbol esters enhanced vasopressin-induced calcium mobilization and polyphosphatidylinositol hydrolysis of vascular smooth muscle cells

Arginine vasopressin (AVP)-induced formation of inositol phosphates and increased calcium efflux in smooth muscle cells (A-10) were inhibited by short term treatment with phorbol 12,13-dibutyrate (PDBu), an activator of protein kinase C (Ca2+/phospholipid-dependent protein kinase) (Aiyar, N., Nambi, P., Whitman, M., Stassen, F. L., and Crooke, S. T. (1987) Mol. Pharmacol. 31, 180-184). Here we report that prolonged treatment of A-10 cells (48 h) with PDBu markedly enhanced AVP-induced calcium mobilization but inhibited ATP- and thrombin-induced calcium mobilization. PDBu (400 nM) doubled [Ca2+]i induced with 3 nM AVP, while the basal calcium concentrations before and after AVP were not different from those of untreated cells. The EC50 for a 24-h exposure was 2.3 nM PDBu. Phorbol 12-myristate 13-acetate was also effective, while 4-alpha-phorbol 12,13-didecanoate (48 h at 400 nM) was without effect. 4-alpha-phorbol 12,13-didecanoate also did not affect inositol phosphate formation. PDBu markedly enhanced inositol phosphate formation induced by AVP but not by NaF. PDBu did not affect basal inositol phosphate and polyphosphoinositide levels, and cytosolic and membrane-associated phospholipase C activity. PDBu treatment (48 h, 400 nM) decreased membrane-associated and cytosolic protein kinase C activity by 80 and 90%, respectively. However, the dose response and time course of changes in protein kinase C activity did not correlate with the same curves for PDBu enhancement of AVP-induced calcium mobilization. We conclude that prolonged PDBu treatment selectively enhanced AVP-induced calcium mobilization and polyphosphoinositide hydrolysis. These effects were not caused by an increase in vasopressin receptor number and apparent affinity, an increase in phospholipase C activity, G-protein-phospholipase C coupling, formation of polyphosphoinositide, or inhibition of inositol phosphate metabolizing enzymes. Enhancement of the AVP responses did not correlate with desensitization or activation of protein kinase C. We suggest that prolonged PDBu treatment might sensitize a putative V1 receptor-G-protein-phospholipase C complex.     

Induction of G protein-coupled estrogen receptor (GPER) and nuclear steroid hormone receptors by gonadotropins in human granulosa cells

Estradiol and progesterone mediate their actions by binding to classical nuclear receptors, estrogen receptor α (ERα) and estrogen receptor β (ERβ) and progesterone receptor A and B (PR-A and PR-B) and the non-classical G protein-coupled estrogen receptor (GPER). Several animal knock-out models have shown the importance of the receptors for growth of the oocyte and ovulation. The aim of our study was to identify GPER in human granulosa cells (GC) for the first time. Moreover, the effect of different doses of gonadotropins on estrogen and progesterone receptors in the human ovary should be investigated as follicle stimulating hormone (FSH) and luteinizing hormone (LH) are also responsible for numerous mechanisms in the ovary like induction of the steroid biosynthesis. Human GC were cultured in vitro and stimulated with different doses of recombinant human FSH or LH. Receptor expression was analyzed by immunocytochemistry and quantitative real-time RT-PCR. GPER could be identified for the first time in human GC. It could be shown that high concentrations of LH increase GPER protein expression. Furthermore FSH and LH increased ERβ, PR-A and PR-B significantly on protein level. These findings were verified for high doses of FSH and LH on mRNA level. ERα was not affected with FSH or LH. We assume that gonadotropins induce GPER, ERβ and PR in luteinized granulosa cells.