Physiological responses to salt stress in young umbu plants

Soil salinity affects plant growth and development due to harmful ion effects and water stress caused by reduced osmotic potential in the soil solution. In order to evaluate the effects of salt stress in young umbu plants, research was performed in green house conditions at the Laboratory of Plant Physiology at Federal Rural University of Pernambuco, Brazil. Growth, stomatal behaviour, water relations, and both inorganic and organic solutes were studied aiming for a better understanding of the responses of umbu plants to increasing salinity. Plants were grown in washed sand with Hoagland and Arnon nutrient solution with 0, 25, 50, 75, and 100 mM NaCl. Growth, leaf water potential, transpiration, and diffusive resistance were evaluated. Na⁺, K⁺, Cl⁻, soluble carbohydrates, and free amino acid contents were measured in several plant organs. Most variables were affected with salinity above 50 mM NaCl showing decreases in: number of leaves, plant height, stems diameter, and dry masses, and increases in root-to-shoot ratio. Reductions in ψ_pd were observed in plants grown under 75 and 100 mM NaCl. All salt levels above zero increased Na⁺ and Cl⁻ contents in leaves. However, K⁺ content was not affected. Na⁺ and Cl⁻ in stems and roots reached saturation in treatments above 50 mM NaCl. Organic solute accumulation in response to salt stress was not observed in umbu plants. These results suggest that umbu plants tolerate salt levels up to 50 mM NaCl without showing significant physio-morphological alterations.     

Genotoxicity and mutagenicity of iron and copper in mice

The toxicity of trace metals is still incompletely understood. We have previously shown that a single oral dose of iron or copper induces genotoxic effects in mice in vivo, as detected by single cell gel electrophoresis (comet assay). Here, we report the effect of these metals on subchronic exposure. Mice were gavaged for six consecutive days with either water, 33.2 mg/kg iron, or 8.5 mg/kg copper. On the 7th day, the neutral and alkaline comet assays in whole blood and the bone marrow micronucleus (MN) test were used as genotoxicity and mutagenicity endpoints, respectively. Particle induced X-ray emission was used to determine liver levels of the metals. Females showed a slightly lower DNA damage background, but there was no significant difference between genders for any endpoint. Iron and copper were genotoxic and mutagenic. While copper was more genotoxic in the neutral version, iron was more genotoxic in the alkaline version of the comet assay. Copper induced the highest mutagenicity as evaluated by the MN test. Iron was not mutagenic to male mice. Iron is thought to induce more oxidative lesions than copper, which are primarily detected in the alkaline comet assay. Treatment with iron, but not with copper, induced a significant increase in the hepatic level of the respective metal, reflecting different excretion strategies.     

Sheeppox virus kelch-like gene SPPV-019 affects virus virulence

Sheeppox virus (SPPV), a member of the Capripoxvirus genus of the Poxviridae, is the etiologic agent of a significant disease of sheep in the developing world. Genomic analysis of pathogenic and vaccine capripoxviruses identified genes with potential roles in virulence and host range, including three genes with similarity to kelch-like genes of other poxviruses and eukaryotes. Here, a mutant SPPV with a deletion in the SPPV-019 kelch-like gene, DeltaKLP, was derived from the pathogenic strain SPPV-SA. DeltaKLP exhibited in vitro growth characteristics similar to those of SPPV-SA and revertant virus (RvKLP). DeltaKLP-infected cells exhibited a reduction in Ca(2+)-independent cell adhesion, suggesting that SPPV-019 may modulate cellular adhesion. When inoculated in sheep by the intranasal or intradermal routes, DeltaKLP was markedly attenuated, since all DeltaKLP-infected lambs survived infection. In contrast, SPPV-SA and RvKLP induced mortality approaching 100%. Lambs inoculated with DeltaKLP exhibited marked reduction or delay in fever response, gross lesions, viremia, and virus shedding compared to parental and revertant viruses. Together, these findings indicate that SPPV-019 is a significant SPPV virulence determinant in sheep.     

Human blood-brain barrier disruption by retroviral-infected lymphocytes: role of myosin light chain kinase in endothelial tight-junction disorganization

The blood-brain barrier (BBB), which constitutes the interface between blood and cerebral parenchyma, has been shown to be disrupted during retroviral associated neuromyelopathies. Human T cell leukemia virus (HTLV-1)-associated myelopathy/tropical spastic paraparesis is a slowly progressive neurodegenerative disease, in which evidence of BBB breakdown has been demonstrated by the presence of lymphocytic infiltrates in the CNS and plasma protein leakage through cerebral endothelium. Using an in vitro human BBB model, we investigated the cellular and molecular mechanisms involved in endothelial changes induced by HTLV-1-infected lymphocytes. We demonstrate that coculture with infected lymphocytes induces an increase in paracellular endothelial permeability and transcellular migration, via IL-1alpha and TNF-alpha secretion. This disruption is associated with tight junction disorganization between endothelial cells, and alterations in the expression pattern of tight junction proteins such as zonula occludens 1. These changes could be prevented by inhibition of the NF-kappaB pathway or of myosin light chain kinase activity. Such disorganization was confirmed in histological sections of spinal cord from an HTLV-1-associated myelopathy/tropical spastic paraparesis patient. Based on this BBB model, the present data indicate that HTLV-1-infected lymphocytes can induce BBB breakdown and may be responsible for the CNS infiltration that occurs in the early steps of retroviral-associated neuromyelopathies.     

Bacterial Productivity Distribution During a Rainy Year in an Estuarine System

Bacterial density and productivity were investigated along four salinity gradients within the estuary Ria de Aveiro. Bacterial variables and environmental parameters were measured at three to four stations spanning the entire salinity gradient of the four channels. The rather high variation in bacterial productivity (0.16–7.6 μg C L⁻¹ h⁻¹) along the profiles of salinity indicates that bacterial activity shows a reactive behavior to environmental changing. Bacterial density (0.5–11.2 × 10⁹ cells L⁻¹) with a comparative smaller variation showed a more conservative behavior, mainly reflecting the phytoplankton distribution. Contrary to expectation, minimal values of bacterial productivity were not observed in November–December but in June. In fact, in November–December, the deep zone near the mouth showed the highest values of bacterial activity. At the upper stations, the highest values were observed in October. The relatively high values of bacterial production during the cold rainy season suggest that allochthonous substrates leached out from the surroundings by rain controlled the distribution of bacterial activity in the estuarine system. The substantial decrease in salinity during the rainy season negatively affected bacterial productivity, namely in the marine zone, where water column was highly stratified. Salinity seems to play an indirect role in the regulation of estuarine bacteria because there are different bacterial communities adapted to a wide salinity range.     

Lifelong Expression of Apolipoprotein D in the Human Brainstem: Correlation with Reduced Age-Related Neurodegeneration

The lipocalin apolipoprotein D (Apo D) is upregulated in peripheral nerves following injury and in regions of the central nervous system, such as the cerebral cortex, hippocampus, and cerebellum, during aging and progression of certain neurological diseases. In contrast, few studies have examined Apo D expression in the brainstem, a region necessary for survival and generally less prone to age-related degeneration. We measured Apo D expression in whole human brainstem lysates by slot-blot and at higher spatial resolution by quantitative immunohistochemistry in eleven brainstem nuclei (the 4 nuclei of the vestibular nuclear complex, inferior olive, hypoglossal nucleus, oculomotor nucleus, facial motor nucleus, nucleus of the solitary tract, dorsal motor nucleus of the vagus nerve, and Roller`s nucleus). In contrast to cortex, hippocampus, and cerebellum, apolipoprotein D was highly expressed in brainstem tissue from subjects (N = 26, 32−96 years of age) with no history of neurological disease, and expression showed little variation with age. Expression was significantly stronger in somatomotor nuclei (hypoglossal, oculomotor, facial) than visceromotor or sensory nuclei. Both neurons and glia expressed Apo D, particularly neurons with larger somata and glia in the periphery of these brainstem centers. Immunostaining was strongest in the neuronal perinuclear region and absent in the nucleus. We propose that strong brainstem expression of Apo D throughout adult life contributes to resistance against neurodegenerative disease and age-related degeneration, possibly by preventing oxidative stress and ensuing lipid peroxidation.     

From START to FINISH: The Influence of Osmotic Stress on the Cell Cycle

The cell cycle is a sequence of biochemical events that are controlled by complex but robust molecular machinery. This enables cells to achieve accurate self-reproduction under a broad range of different conditions. Environmental changes are transmitted by molecular signalling networks, which coordinate their action with the cell cycle. The cell cycle process and its responses to environmental stresses arise from intertwined nonlinear interactions among large numbers of simpler components. Yet, understanding of how these pieces fit together into a coherent whole requires a systems biology approach. Here, we present a novel mathematical model that describes the influence of osmotic stress on the entire cell cycle of S. cerevisiae for the first time. Our model incorporates all recently known and several proposed interactions between the osmotic stress response pathway and the cell cycle. This model unveils the mechanisms that emerge as a consequence of the interaction between the cell cycle and stress response networks. Furthermore, it characterises the role of individual components. Moreover, it predicts different phenotypical responses for cells depending on the phase of cells at the onset of the stress. The key predictions of the model are: (i) exposure of cells to osmotic stress during the late S and the early G2/M phase can induce DNA re-replication before cell division occurs, (ii) cells stressed at the late G2/M phase display accelerated exit from mitosis and arrest in the next cell cycle, (iii) osmotic stress delays the G1-to-S and G2-to-M transitions in a dose dependent manner, whereas it accelerates the M-to-G1 transition independently of the stress dose and (iv) the Hog MAPK network compensates the role of the MEN network during cell division of MEN mutant cells. These model predictions are supported by independent experiments in S. cerevisiae and, moreover, have recently been observed in other eukaryotes.     

Hormonal and experiential control of female-male mounting in the female rat

Mounting behavior in the female rat has been studied extensively in same-sex interactions, but not in the heterosexual dyad. The present study examined the display of female mounting of castrated noncopulating male rats (FMM). Ovariectomized (OVX) sexually naive female rats (N = 80) were given either estrogen (E) + progesterone (P), E + oil (O), P + O, or O + O treatment for five tests with castrated male rats. FMMs were observed in both the E + P and E + O females. The influence of the ovarian cycle on FMM was also investigated. Vaginal smears from sexually naive females (N = 16) were taken daily for 12 days immediately after testing with castrated males. FMM frequency was greatest during Proestrus. Finally, OVX females (N = 30) treated with E + P were given either 0, 1, 10 multi-ejaculatory heterosexual experiences with intact, sexually experienced males, prior to tests with intact, copulating or castrated, noncopulating males for five tests. Sexually naive females displayed a greater number of mounts relative to the sexually experienced females when tested with castrated, noncopulating males. In contrast, very few FMMs were observed in females of any group tested with intact, copulating males. These data suggest that FMM occurs naturally in rats as a "super-solicitational" behavior that is modified by hormone treatment and prior heterosexual experience.     

Neonatal handling induces alteration in progesterone secretion after sexual behavior but not in angiotensin II receptor density in the medial amygdala: implications for reproductive success

Neonatal handling affects the hypothalamus-pituitary-gonadal axis in female rats. Indeed, postnatal handling induces anovulatory estrous cycles and decreases sexual receptiveness. On the other hand, Angiotensin II (Ang II) infused into the medial amygdala (MeA) reduces sexual behavior in male and female rats. Considering this, and that gonadal steroid secretion after copulatory behavior is important for reproductive success, the purpose of the present study was to investigate whether the reduction in sexual receptiveness in neonatally handled female rats is mediated by changes in Ang II receptor density in MeA. Moreover, gonadal steroid secretion after sexual behavior was analyzed. Two groups of female Wistar rats were studied: nonhandled (pups were left undisturbed) and handled (pups were handled for 1 min once a day during the first 10 days of life). Once they were 80-85 days old in the evening of the proestrus day, sexual receptiveness was recorded and after that the animals were killed by decapitation. Trunk blood samples were collected, and plasma estradiol and progesterone were measured by radioimmunoassay. The brains were removed for Ang II receptor autoradiography in MeA. The decreased lordosis quotient in the neonatally handled group was confirmed in the present study. Neonatal handling also reduced the progesterone concentration in the plasma, but did not change the estradiol and the density of Ang II receptors in MeA. The reduced progesterone could be due to the decreased lordosis frequency of handled females. However, this decreased sexual receptiveness is not mediated by changes in Ang II receptors in MeA.