Chromatin organization during spermiogenesis in Octopus vulgaris. II: DNA-interacting proteins

In this article we study the proteins responsible for chromatin condensation during spermiogenesis in the cephalopod Octopus vulgaris. The DNA of ripe sperm nuclei in this species is condensed by a set of five different proteins. Four of these proteins are protamines. The main protamine (Po2), a protein of 44 amino acid residues, is extraordinarily simple (composed of only three different amino acid types: arginine (R), serine (S), and glycine (G). It is a basic molecule consisting of 79.5 mol% arginine residues. The rest of the protamines (Po3, Po4, Po5) are smaller molecules (33, 28, and 30 amino acid residues, respectively) that are homologous among themselves and probably with the main Po2 protamine. The ripe sperm nucleus of O. vulgaris also contains a small quantity of a molecule (Po1) that is similar to Po2 protamine. This protein could represent a Po2 protamine-precursor in a very advanced step of its processing. We discuss the characteristics of these proteins, as well as the relation between the complexity of chromatin condensation and the transitions of nuclear proteins during spermiogenesis in O. vulgaris.     

17β-estradiol downregulates angiotensin-II-induced endothelin-1 gene expression in rat aortic smooth muscle cells

It is well documented that 17-estradiol (E₂) exerts a cardiovascular protective effect. A possible role of E₂ in the regulation of endothelin-1 (ET-1) production has been reported. However, the complex mechanisms by which E₂ inhibits ET-1 expression are not completely understood. The aims of this study were to examine whether E₂ may alter angiotensin II (Ang II)-induced cell proliferation and ET-1 gene expression and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with E₂, then stimulated with Ang II, and [³H]thymidine incorporation and ET-1 gene expression were examined. The effect of E₂ on Ang-II-induced extracellular signal-regulated kinase (ERK) phosphorylation was tested to elucidate the intracellular mechanism of E₂ in proliferation and ET-1 gene expression. Ang II increased DNA synthesis which was inhibited with E₂ (1–100 nM). E₂, but not 17-estradiol, inhibited the Ang-II-induced ET-1 gene expression as revealed by Northern blotting and promoter activity assay. This effect was prevented by coincubation with the estrogen receptor antagonist ICl 182,780 (1 µM). E₂ also inhibited Ang-II-increased intracellular reactive oxygen species (ROS) as measured by a redox-sensitive fluorescent dye, 2,7-dichlorofluorescin diacetate, and ERK phosphorylation. Furthermore, E₂ and antioxidants, such as N-acetyl cysteine and diphenylene iodonium, decreased Ang-II-induced cell proliferation, ET-1 promoter activity, ET-1 mRNA, ERK phosphorylation, and activator protein-1-mediated reporter activity. In summary, our results suggest that E₂ inhibits Ang-II-induced cell proliferation and ET-1 gene expression, partially by interfering with the ERK pathway via attenuation of ROS generation. Thus, this study provides important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of estrogen on the cardiovascular system.     

Circulating TNF-alpha and its soluble receptors during experimental acute pancreatitis

Clinical and experimental studies have shown increased concentrations of TNF-alpha and its soluble receptors in serum of patients with acute pancreatitis. In this work, we have investigated the time-course of TNF-alpha and its soluble receptors during taurocholate-induced acute pancreatitis. In addition, since TNF-alpha itself could mediate the shedding of its receptors, we have assessed the effect of inhibiting TNF-alpha production on the release of soluble TNF-alpha receptors in experimental acute pancreatitis. Our results indicate that soluble receptors are released in the early stages of the disease and this increase is concomitant with the release of TNF-alpha, which is mainly bound to specific proteins. The increased concentrations of its receptors strongly suggest that they could be these binding proteins. Inhibition of TNF-alpha generation with pentoxifylline abrogated the shedding of sTNF-alphaR1, but had no effect on sTNF-alphaR2. This finding suggests that the shedding of sTNF-alphaR1 is induced by TNF-alpha itself, but in the case of sTNF-alphaR2, the shedding appears to be induced by another mechanism.     

Cell wall analysis

The cell wall is a rigid structure essential for survival of the fungal cell. Because of its absence in mammalian cells, the cell wall is an attractive target for antifungal agents. Thus, for different reasons, it is important to know how the cell wall is synthesized and how different molecules regulate that synthesis. The Schizosaccharomyces pombe cell wall is mainly formed by glucose polysaccharides and some galactomannoproteins. Here, we describe a fast and reliable method to analyze changes in S. pombe cell wall composition by using specific enzymatic degradation and chemical treatment of purified cell walls. This approach provides a powerful means to analyze changes in (1,3)beta-glucan and (1,3)alpha-glucan, two main polysaccharides present in fungal cell walls. Analysis of cell wall polymers will be useful to search for new antifungal drugs that may inhibit cell wall biosynthesis and/or alter cell wall structure.     

In vitro effects of LPS, IL-2, PDGF and CRF on haemocytes of Mytilus galloprovincialis Lmk

The cells in charge of the innate immune response in the marine mussel Mytilus galloprovincialis Lmk. are the haemocytes. These cells respond in different ways to agents such as lipopolysaccharide (LPS), interleukin-2 (IL-2), platelet-derived growth factor (PDGF) and corticotropin releasing factor (CRF). After stimulation of the haemocytes, the expression of molecules reactive with monoclonal antibodies raised to the alpha chain of the IL-2 receptor, present in their membrane, differed depending on the agent used. The same happened with regard to the levels of dopamine, adrenaline and noradrenaline released to the medium by the haemocytes. It should also be noted that no catecholamine release was detected and the level of expression of IL-2Ralpha showed no significant variation in cultured cells that had not been treated with inducers. These facts would indicate that most haemocytes were in the same starting condition at the moment that the stimulation was performed. Therefore, cultured haemocytes can be a highly reliable model in the study of the innate immune system.     

Pex30p, Pex31p, and Pex32p form a family of peroxisomal integral membrane proteins regulating peroxisome size and number in Saccharomyces cerevisiae

The peroxin Pex23p of the yeast Yarrowia lipolytica exhibits high sequence similarity to the hypothetical proteins Ylr324p, Ygr004p, and Ybr168p encoded by the Saccharomyces cerevisiae genome. Ylr324p, Ygr004p, and Ybr168p are integral to the peroxisomal membrane and act to control peroxisome number and size. Synthesis of Ylr324p and Ybr168p, but not of Ygr004p, is induced during incubation of cells in oleic acid-containing medium, the metabolism of which requires intact peroxisomes. Cells deleted for YLR324w exhibit increased numbers of peroxisomes, whereas cells deleted for YGR004w or YBR168w exhibit enlarged peroxisomes. Ylr324p and Ybr168p cannot functionally substitute for one another or for Ygr004p, whereas Ygr004p shows partial functional redundancy with Ylr324p and Ybr168p. Ylr324p, Ygr004p, and Ybr168p interact within themselves and with Pex28p and Pex29p, which have been shown also to regulate peroxisome size and number. Systematic deletion of genes demonstrated that PEX28 and PEX29 function upstream of YLR324w, YGR004w, and YBR168w in the regulation of peroxisome proliferation. Our data suggest a role for Ylr324p, Ygr004p, and Ybr168p--now designated Pex30p, Pex31p, and Pex32p, respectively--together with Pex28p and Pex29p in controlling peroxisome size and proliferation in Saccharomyces cerevisiae.     

Photosynthetic responses of the tropical spiny shrub Lycium nodosum (Solanaceae) to drought, soil salinity and saline spray

Water relations and photosynthetic characteristics of plants of Lycium nodosum grown under increasing water deficit (WD), saline spray (SS) or saline irrigation (SI) were studied. Plants of this perennial, deciduous shrub growing in the coastal thorn scrubs of Venezuela show succulent leaves which persist for approx. 1 month after the beginning of the dry season; leaf succulence is higher in populations closer to the sea. These observations suggested that L. nodosum is tolerant both to WD and salinity. In the glasshouse, WD caused a marked decrease in the xylem water potential (psi), leaf osmotic potential (psi(s)) and relative water content (RWC) after 21 d; additionally, photosynthetic rate (A), carboxylation efficiency (CE) and stomatal conductance (gs) decreased by more than 90 %. In contrast, in plants treated for 21 d with a foliar spray with 35 per thousand NaCl or irrigation with a 10 % NaCl solution, psi and RWC remained nearly constant, while psi(s) decreased by 30 %, and A, CE and gs decreased by more than 80 %. An osmotic adjustment of 0.60 (SS) and 0.94 MPa (SI) was measured. Relative stomatal and mesophyll limitations to A increased with both WD and SS, but were not determined for SI-treated plants. No evidence of chronic photoinhibition due to any treatment was observed, since maximum quantum yield of PSII, Fv/Fm, did not change with either drought in the field or water or salinity stress in the glasshouse. Nevertheless, WD and SI treatments caused a decrease in the photochemical (qP) and an increase in the non-photochemical (qN) quenching coefficients relative to controls; qN was unaffected by the SS treatment. The occurrence of co-limitation of A by stomatal and non-stomatal factors in plants of L. nodosum may be associated with the extended leaf duration under water or saline stress. Additionally, osmotic adjustment may partly explain the relative maintenance of A and gs in the SS and SI treatments and the tolerance to salinity of plants of this species in coastal habitats.     

Effects of cortisol and prolactin on Na+ and Cl- transport in cultured branchial epithelia from FW rainbow trout

The electrophysiological and ion-transporting properties of cultured gill epithelia from freshwater (FW) rainbow trout were examined in the presence of cortisol and prolactin as media supplements. Epithelia were of the double-seeded insert (DSI) type containing both pavement cells (PVCs) and mitochondria-rich cells (MRCs) and were grown in Leibovitz's L15 media on filters allowing exposure to different apical media conditions. Experiments were carried out in two series after 7-9 days symmetrical (L15 apical-L15 basolateral) culture. In both series, 100% L15 was maintained as the basolateral medium throughout and supplemented with physiologically relevant doses of either prolactin (50 ng/ml), cortisol (500 ng/ml), or cortisol + prolactin (500 + 50 ng/ml, respectively). In series 1, epithelia were exposed to progressively diluted apical media (100, 75, 50, 25, 12.5% L15, and FW) at 24-h intervals. The preparations retained integrity [high transepithelial resistance (TER); low ion efflux rates] during this prolonged dilution protocol. Cortisol, or cortisol + prolactin, resulted in a greater TER and reduced ion efflux rates during dilution, likely an effect on junctional permeability of PVCs, but did not promote active Na+ and Cl- uptake from apical FW. In series 2, epithelia were directly exposed to apical FW and ion fluxes measured over the first 6 h. Under these conditions, cortisol or cortisol + prolactin promoted active uptake of both Na+ and Cl- simultaneously from apical FW, probably attributable to actions on the MRCs. However, Na+-K+-ATPase activities were not significantly altered by any of the treatments in either series. Overall, prolactin alone did not appear to promote FW adaptation but exhibited synergism with cortisol. These results provide further support for the cultured DSI epithelium as an in vitro model for ion transport in FW fish.     

镉负荷大鼠一氧化氮和肿瘤坏死因子-α释放在介导多器官机能活动障碍中的作用

选择健康SD雄性成年大鼠36只,随机分成对照组(C组)、镉负荷中剂量组(M组)、镉负荷高剂量组(H组).将分析纯CdCl2·2.5H2O用生理盐水稀释成含镉0.4 mg/ml浓度的注射溶液,高压灭菌.M组和H组大鼠每天分别按含镉0.5和1.0 mg/kg体重腹腔注射染毒,C组用同样方法注射与H组同等剂量的生理盐水,进行急性镉负荷实验,连续观察7 d.研究急性镉负荷对大鼠血液及几种组织中一氧化氮(NO)自由基、肿瘤坏死因子-α(TNF-a)变化的影响及作用.结果显示在整个实验期内,镉负荷大鼠体重与对照组比较明显下降;睾丸、心脏和肝脏组织中的镉含量极显著上升,并随镉负荷剂量和时间而增加;血浆NO水平M组虽高于对照组,但差异不显著,而H组极显著高于对照组,M和H组血浆TNF-α明显高于对照组;在整个实验期内,镉负荷大鼠睾丸、心脏和肝脏组织匀浆中NO较对照组高或明显高于对照组,睾丸和心脏组织匀浆中TNF-a也均高于或明显高于对照组,但肝脏中的TNF-a三组间没有差异.结果提示,镉负荷诱发NO、TNF-α大量释放在导致大鼠多种器官机能活动障碍发生过程中可能起重要作用.     

Ontogeny has a phylogeny: background to adjunctive behaviors in pigeons and budgerigars

Animals coping with operant conditioning tasks often show behaviors that are not recorded by keys, levers and similar response transducers. Nevertheless, these adjunctive behaviors should not be disposed of by classifying them as incidental. Often they are found to be at least partially influenced by the experimentally programmed contingencies, and under certain conditions they can in turn influence conditioned behaviors. Here we describe the occurrence and characteristics of two such behaviors, stimulus grasping in operantly key-pecking pigeons and intra-delay stereotypies in a delayed matching-to-sample task with budgerigars. It is argued that for a proper account of these behaviors it is necessary to refer to a behavioral systems approach that appeals to longer ranging ontogenetic and phylogenetic histories than is usually considered in the psychological literature. The gaping towards on-key stimuli by pigeons is attributed to the hypothesis that operantly conditioned key-pecks probably relate to a grasp-pecking response that is normally executed towards non-edible items covering food. The intra-delay behaviors shown by the budgerigars are assumed to have originated from stress-induced displacement responses that adventitiously came under the influence of differential reinforcement contingencies. Finally, we discuss what kinds of evidence are needed to put these hypothetical explanations on a more certain footing.