Is the genotoxic effect of arsenic mediated by oxygen free radicals?

Previous investigations have shown that trivalent arsenic is inducing chromosomal aberrations and sister chromatid exchanges (SCEs). In a search for the genotoxic mechanism we have studied the effects of the oxygen-radical-scavenging enzymes superoxide dismutase (SOD) and catalase (CAT) on arsenic-induced SCEs in cultured human lymphocytes. The results indicate that SOD and possibly also CAT have a protective effect against arsenic-induced DNA damage. Arsenic, which is emitted in environmental pollutions e.g. from smelters and coal-fired power plants, appears to be underestimated as environmental mutagen and potential synergist to ionizing radiation.     

Is antigen presentation the primary function of HLA-G?

Human histocompatibility leukocyte antigen (HLA)-G is an antigen-presenting molecule. This review discusses the possibility that this might not be its primary function. HLA-G indeed modulates innate immunity by interacting with immunoglobulin-like receptors and by regulating HLA-E expression and its subsequent interaction with CD94/NKG2 receptors. HLA-G also down-modulates both CD8(+) and CD4(+) T-cell responsiveness.     

Is morphine dependence mediated exclusively by the Mu receptor?

Regional cerebral glucose utilization (RCGU) and behavior during naloxone precipitated withdrawal were studied in rats made dependent on either sufentanil, a highly selective mu opiate agonist, or morphine. Changes in RCGU during withdrawal in 23 of 24 anatomically related limbic and brainstem structures were indistinguishable between rats dependent on morphine or sufentanil. Linear regression analysis indicated that RCGU changes during withdrawal in these two groups were highly correlated (r=0.95). Withdrawal behaviors (autonomic signs of withdrawal, jumps, weight loss, and incidence of diarrhea) were likewise indistinguishable between the two groups. The correlations of both these measurements of dependence suggest that chronic occupation of mu opiate receptors alone is sufficient to produce dependence that is indistinguishable from morphine dependence.     

Does the behavioural activation detected after a single dose of a benzodiazepine reflect a withdrawal response?

The effects, in mice, of a single dose of lorazepam or oxazepam were determined, in the holeboard, 24, 48 and 72 hours after treatment. Lorazepam produced significant increases in both spontaneous locomotor activity and in rearing 48 hours after treatment and oxazepam produced a significant overall increase in rearing over the three time points. There was no detectable in vivo receptor occupancy for either drug at the 48 hour time point, so that these effects were not due to residual concentrations of drug in the brain. We therefore suggest that we were detecting a spontaneous withdrawal response to a single dose of benzodiazepine. The increases in both locomotor activity and rearing, detected 48 hours after lorazepam, could be reversed by treating simultaneously with Ro 15-1788 (a benzodiazepine antagonist). When Ro 15-1788 was injected 20 minutes prior to testing, the mice that had been treated 48 hours previously with lorazepam still showed increased locomotor activity and rearing. We conclude that the hyperactivity was not caused by any change in the levels of endogenous substances acting at the benzodiazepine receptor.     

Is the mechanical activity of epithelial cells controlled by deformations or forces?

The traction forces developed by cells depend strongly on the substrate rigidity. In this letter, we characterize quantitatively this effect on MDCK epithelial cells by using a microfabricated force sensor consisting in a high-density array of soft pillars whose stiffness can be tailored by changing their height and radius to obtain a rigidity range from 2 nN/microm up to 130 nN/microm. We find that the forces exerted by the cells are proportional to the spring constant of the pillars meaning that, on average, the cells deform the pillars by the same amount whatever their rigidity. The relevant parameter may thus be a deformation rather than a force. These dynamic observations are correlated with the reinforcement of focal adhesions that increases with the substrate rigidity.     

Induction of regulatory T cells by a murine β-defensin

β-Defensins are antimicrobial peptides of the innate immune system produced in the skin by various stimuli, including proinflammatory cytokines, bacterial infection, and exposure to UV radiation (UVR). In this study we demonstrate that the UVR-inducible antimicrobial peptide murine β-defensin-14 (mBD-14) switches CD4(+)CD25(-) T cells into a regulatory phenotype by inducing the expression of specific markers like Foxp3 and CTLA-4. This is functionally relevant because mBD-14-treated T cells inhibit sensitization upon adoptive transfer into naive C57BL/6 mice. Accordingly, injection of mBD-14, comparable to UVR, suppresses the induction of contact hypersensitivity and induces Ag-specific regulatory T cells (Tregs). Further evidence for the ability of mBD-14 to induce Foxp3(+) T cells is provided using DEREG (depletion of Tregs) mice in which Foxp3-expressing cells can be depleted by injecting diphtheria toxin. mBD-14 does not suppress sensitization in IL-10 knockout mice, suggesting involvement of IL-10 in mBD-14-mediated immunosuppression. However, unlike UVR, mBD-14 does not appear to mediate its immunosuppressive effects by affecting dendritic cells. Accordingly, UVR-induced immunosuppression is not abrogated in mBD-14 knockout mice. Together, these data suggest that mBD-14, like UVR, has the capacity to induce Tregs but does not appear to play a major role in UVR-induced immunosuppression. Through this capacity, mBD-14 may protect the host from microbial attacks on the one hand, but tame T cell-driven reactions on the other hand, thereby enabling an antimicrobial defense without collateral damage by the adaptive immune system.     

Kappa-opioid agonist induced diuresis. Is it mediated by a blood-borne factor of adrenomedullary origin?

Intravenous administration of the kappa-opioid agonists U50488H, tifluadom, and ethylketocyclazocine induced a characteristic diuresis in conscious, intact, saline-loaded rats. Naloxone pretreatment antagonized U50488H-induced diuresis. The diuretic response to the kappa-opioid agonists was significantly attenuated in adrenal demedullated rats. However, basal urine output, the diuretic response to furosemide, and the antidiuretic response to the mu-opioid agonist buprenorphine were unaffected. Transfusion studies established that 1 mL of blood, from intact donor rats treated with U50488H, induced a diuretic response when administered to intact or demedullated recipient rats, whether or not the recipients had been pretreated with naloxone. However, blood from demedullated rats treated with U50488H was unable to induce diuresis in intact or demedullated recipients. The results indicate that kappa-opioid agonist induced diuresis appears to be mediated by a nonopioid blood-borne "diuretic factor" of adrenomedullary origin and that this factor might be responsible for the dependence of the diuretic response upon an intact and functional adrenal medulla in conscious rats.     

Is the orcadian clock of gonyaulax held stationary after a strong pulse of anisomycin?

• 1.1. Gonyaulax polyedra cells were treated with two sequential pulses of a protein synthesis inhibitor (anisomycin) in order to analyse a possible stopping of the circadian clock by the first pulse.
• 2.2. Inhibition of protein synthesis during these pulses and after centrifugation and resuspension of the cells was determined by measuring the incorporation of labelled amino acids.
• 3.3. The effects of the second pulses on the clock were measured as phase shifts of the glow rhythm with respect to a control rhythm that had been subjected to the initial pulse only.
• 4.4. From the observed phase shifts of the second pulses we conclude that the clock is not stopped by the first pulse but is immediately shifted to a different phase.

     

Inhibition of Notch signaling pathway using γ-secretase inhibitor delivered by a low dose of Triton-X100 in cultured oral cancer cells

How to effectively delivering therapeutic agents, including γ-secretase inhibitors (GSIs), into live cells, remains a significant challenge. This study assessed the effect of Notch signaling inhibition by examining levels of the Notch1 intracellular domain (N1ICD) in cultured oral cancer cells analyzed with random stitched images (2D) and 3D visualizations using confocal microscopy and quantitative gene analysis. Substantially, we have developed a novel method to assist the delivery of γ-secretase inhibitor, DAPT, into live cells in the presence of an effective minimum concentration of Triton-X100 (0.001%) without damaging cell activity and membrane integrity assessed with cell proliferation assays. The images obtained in this study showed that DAPT alone could not block the γ-secretase inhibitor despite inhibiting cell growth. Further analysis of quantitative gene expressions of Notch signaling canonical pathway to verify the effectiveness of the novel method for delivering inhibitor into live cells, displayed deregulation of Notch1, Delta-like ligand 1 (DLL1) and hairy and enhancer of split 1 (Hes1). Our data suggest that Notch1/Hes1 signaling pathway is deactivated using DAPT with a low dose of Triton-X100 in this cancer cells. And the finding also suggests that Notch1 could be engaged by DLL1 to promote differentiation in oral cancer cells. Using this approach, we demonstrate that Triton-X100 is a promising and effective permeabilization agent to deliver γ-secretase inhibitor DAPT into live oral epithelial cells. This strategy has the potential to implicate in the treatment of cancer diseases.     

Counteraction of early circulatory derangement by administration of low dose steroid treatment at the onset of established endotoxemic shock is not directly mediated by TNF-α and IL-6

BackgroundOnce a septic condition is progressing, administration of steroids in the pro-inflammatory phase of septic shock ought to yield maximal effect on the subsequent, devastating inflammatory response. Recently, a retrospective study showed that early initiation of corticosteroid therapy improved survival in septic shock. We aimed to prospectively evaluate effects of early administrated hydrocortisone therapy on physiologic variables in a porcine model of septic shock.ExperimentEight anesthetized pigs were given a continuous infusion of endotoxin during this 6 h prospective, randomized, parallel-grouped placebo-controlled experimental study. At the onset of endotoxemic shock, defined as the moment when the mean pulmonary arterial pressure reached the double baseline value, the pigs were either given a single intravenous dose of hydrocortisone (5 mg kg^?1) or the corresponding volume of saline.ResultsMean arterial pressure and systemic vascular resistance index were significantly higher (both p < 0.05), and heart rate was significantly lower (p < 0.05), in the endotoxin + hydrocortisone group as compared to the endotoxin + saline group. Body temperature and blood hemoglobin levels increased significantly in the endotoxin + saline group (both p < 0.05). Urinary hydrocortisone increased significantly in both groups (p < 0.05). There were no significant differences in the plasma levels of TNF-alpha, IL-6 or nitrite/nitrate between the groups.ConclusionEarly treatment with hydrocortisone ameliorates some endotoxin mediated circulatory derangements, fever response and microvascular outflow. Our results suggest that these effects are not directly mediated by the pro-inflammatory cytokines TNF-alpha or IL-6, nor by NO.     

Is feeding behaviour in crucian carp mediated by the lateral olfactory tract?

Experiments were performed to investigate which bundle of the olfactory tract was essential for mediating feeding behaviour in crucian carp. Fish were divided in three groups: control fish, fish with only the lateral olfactory tracts (LOTs) intact and fish with the LOTs cut. The fish were maintained in physiological saline after surgery to preserve the remaining tracts and postoperative inspections revealed the functional status of the remaining tracts. With the injection of food odour into the aquaria the scores for various feeding behaviours--biting, snapping, mouth openings and vertical posture--were not significantly different between those of the control fish and the fish with the LOT intact. Those fish that had the LOT cut but the medial and lateral parts of the medial olfactory tract (mMOT, lMOT) intact had significantly lower feeding-related scores than the other two groups of fish. The results of the present study indicate that the LOT is necessary to maintain the full qualitative and quantitative extent of feeding behaviour in crucian carp.     

Is the Performance of a Specialist Herbivore Affected by Female Choices and the Adaptability of the Offspring?

The performance of herbivorous insects is related to the locations of defenses and nutrients found in the different plant organs on which they feed. In this context, the females of herbivorous insect species select certain parts of the plant where their offspring can develop well. In addition, their offspring can adapt to plant defenses. A system where these ecological relationships can be studied occurs in the specialist herbivore, Tuta absoluta, on tomato plants. In our experiments we evaluated: (i) the performance of the herbivore T. absoluta in relation to the tomato plant parts on which their offspring had fed, (ii) the spatial distribution of the insect stages on the plant canopy and (iii) the larval resistance to starvation and their walking speed at different instar stages. We found that the T. absoluta females preferred to lay their eggs in the tomato plant parts where their offspring had greater chances of success. We verified that the T. absoluta females laid their eggs on both sides of the leaves to better exploit resources. We also observed that the older larvae (3^rd and 4^th instars) moved to the most nutritious parts of the plant, thus increasing their performance. The T. absoluta females and offspring (larvae) were capable of identifying plant sites where their chances of better performance were higher. Additionally, their offspring (larvae) spread across the plant to better exploit the available plant nutrients. These behavioral strategies of T. absoluta facilitate improvement in their performance after acquiring better resources, which help reduce their mortality by preventing the stimulation of plant defense compounds and the action of natural enemies.     

Virus stimulation of human mast cells results in the recruitment of CD56? T cells by a mechanism dependent on CCR5 ligands

The trafficking of effector cells to sites of infection is crucial for antiviral responses. However, the mechanisms of recruitment of the interferon-γ-producing and cytotoxic CD56(+) T cells are poorly understood. Human mast cells are sentinel cells found in the skin and airway and produce selected proinflammatory mediators in response to multiple pathogen-associated signals. The role of human mast cell-derived chemokines in T-cell recruitment to virus infection was examined. Supernatants from primary human cord blood-derived mast cells (CBMCs) infected with mammalian reovirus were examined for chemokine production and utilized in chemotaxis assays. Virus-infected CBMCs produced several chemokines, including CCL3, CCL4, and CCL5. Supernatants from reovirus-infected CBMCs selectively induced the chemotaxis of CD8(+) T cells (10±1%) and CD3(+)CD56(+) T cells (19±5%). CD56(+) T-cell migration was inhibited by pertussis toxin (65±9%) and met-RANTES (56±7%), a CCR1/CCR5 antagonist. CD56(+) T cells expressed CCR5, but little CCR1. The depletion of CCL3, CCL4, and CCL5 from reovirus-infected CBMC supernatants significantly (41±10%) inhibited CD56(+) T-cell chemotaxis. This study demonstrates a novel role for mast cells and CCR5 in CD56(+) T-cell trafficking and suggests that human mast cells enhance immunity to viruses through the selective recruitment of cytotoxic effector cells to virus infection sites. These findings could be exploited to enhance local T-cell responses in chronic viral infection and malignancies at mast cell-rich sites.     

Is nectar reabsorption restricted by the stalk cells of floral and extrafloral nectary trichomes?

Reabsorption is a phase of nectar dynamics that occurs concurrently with secretion; it has been described in floral nectaries that exude nectar through stomata or unicellular trichomes, but has not yet been recorded in extrafloral glands. Apparently, nectar reabsorption does not occur in multicellular secretory trichomes (MST) due to the presence of lipophilic impregnations – which resemble Casparian strips – in the anticlinal walls of the stalk cells. It has been assumed that these impregnations restrict solute movement within MST to occur unidirectionally and exclusively by the symplast, thereby preventing nectar reflux toward the underlying nectary tissues. We hypothesised that reabsorption is absent in nectaries possessing MST. The fluorochrome lucifer yellow (LYCH) was applied to standing nectar of two floral and extrafloral glands of distantly related species, and then emission spectra from nectary sections were systematically analysed using confocal microscopy. Passive uptake of LYCH via the stalk cells to the nectary tissues occurred in all MST examined. Moreover, we present evidence of nectar reabsorption in extrafloral nectaries, demonstrating that LYCH passed the stalk cells of MST, although it did not reach the deepest nectary tissues. Identical (control) experiments performed with neutral red (NR) demonstrated no uptake of this stain by actively secreting MST, whereas diffusion of NR did occur in plasmolysed MST of floral nectaries at the post‐secretory phase, indicating that nectar reabsorption by MST is governed by stalk cell physiology. Interestingly, non‐secretory trichomes failed to reabsorb nectar. The role of various nectary components is discussed in relation to the control of nectar reabsorption by secretory trichomes.     

Is the originality of a species measurable?

In this paper, we introduce the concept of 'originality of a species within a set' in order to indicate the average rarity of all the features belonging to this species. Using a phylogenetic tree of 70 species of New World terrestrial Carnivora, we suggest measuring the originality by a probability distribution. This maximizes the expected number of features shared by two species randomly drawn from the set. By using this new index, we take account of branch lengths whereas current indices of originality focus on tree topology. As a supplement to Nee and May's optimizing algorithm, we find that originality must be one of the criteria used in conservation planning.     

Is the onset of senescence in leaf cells of intact plants due to low or high sugar levels?

This review examines the hypotheses that developmental programmed cell death in leaves is mediated (i) by sugar starvation in the leaf cells or (ii) by sugar accumulation in these cells. Experimental evidence for both hypotheses is critically discussed and found to be lacking. For example, some papers show that sugars prevent senescence of cut leaves placed in darkness, and prevent low sugar levels in the leaves. In these tests, the sugars seem to replace photosynthesis, hence the results have little relevance to leaf senescence in intact plants in the light. Low nitrogen nutrition and high light results in earlier senescence than the low nitrogen treatment alone. This is accompanied by high sugar levels in the leaves. The results have led to the idea that accumulation of sugars is the cause of the additional effect, or more generally, that sugar accumulation is always the direct cause of leaf senescence. Results from over-expressing, or knocking out, hexokinase genes tend to support the high sugar hypothesis, but pleiotropic effects confound this conclusion. In addition, several experiments show the effects of treatments on senescence without the increase in leaf sugar levels. Nonetheless, sugar levels are usually measured in whole leaves. Such an overall level does not reflect the differences in the onset of senescence between tissues and cells, and can therefore not be used as an argument for or against either of the two hypotheses. It is argued that future work should determine the time line of the concentrations of various sugars in various cells and cellular compartments, in relation to senescence processes in the same cells. Taken together, the data are not decisive. It is possible that neither of the two hypotheses is correct.     

Is competition between mesocarp cells of peach fruits affected by the percentage of wild species genome?

The number of cells and the mean cell volume in the mesocarps of fruits from peach genotypes with different percentages of the genome of Prunus davidiana, a wild, related, species, were evaluated. The mesocarp mass varied greatly between the four groups of genotypes. The mean cell volume and the number of cells were negatively correlated within each group. This correlation can be interpreted as a relationship of competition between cells. In order to describe the type of competition in the different groups, we tried to adjust a model of competition for resources proposed by Lescourret and Génard (Ecoscience 10:334–341, 2003). To estimate the values of the three parameters of the model for the different groups, we applied model selection. Within nested models, we identified a single best model with six parameter values. This model was roughly accurate, but it allowed us to describe the general relationship for each group. The parameter values revealed a strong and under-compensating density-dependence effect for all groups. The percentage of P. davidiana genome appeared to influence the maximal number of cells and the strength of the competition, but no effect was found on the maximal mean volume of cells.     

Is coordination of leaf and root growth mediated by abscisic acid? Opinion

Leaf growth is more inhibited than root growth when the soil is nitrogen-deficient, dry, saline, compacted, or of restricted volume. Similar differential responses in leaf and root growth occur when ABA is applied to plants in well-watered and well-fertilised conditions, and opposite responses are often found in ABA-deficient mutants. ABA levels increase in plants in dry or saline soils, suggesting a regulating role in leaf and root growth in soils of low water potential. In nitrogen-deficient or compacted soils, or soils of restricted volume, ABA only sometimes increases, and in these situations its accumulation may be of secondary importance. Use of ABA-deficient mutants has so far indicated that ABA influences leaf and root growth in unstressed plants, and plants in dry soils, but not in soils that are compacted, of restricted volume, or are nitrogen-deficient.For ABA to determine the relationship between the rate of leaf growth and the rate of root growth, there must be long-distance transport of either ABA itself or a compound that controls ABA synthesis in the growing cells of leaves and roots. ABA invariably increases in xylem sap as the soil becomes dry or saline, and sometimes when it becomes nitrogen-deficient or compacted, however the ABA is of too low a concentration to affect leaf growth. There may be a compound in xylem sap that controls the synthesis of ABA in the leaf, but no such compound has been identified. ABA accumulates in phloem sap of plants in dry or saline soil, but its function in controlling root or leaf growth is unknown.We conclude that ABA affects the ratio of root growth to leaf growth via its independent effects on root and leaf growth, and may regulate the ratio of root to leaf growth via feedforward signals in xylem or phloem, but there is no satisfactory explanation of its mechanism of control.     

Is the “soluble” phase of cells structured?

Evidence suggesting that small molecular-weight precursors as well as polymers such as proteins and RNA, are not homogeneously distributed in the "soluble" phase of the cell, and that there may be, on one hand, hitherto unidentified barriers to normal diffusion within the cell and, on the other, channels through which certain molecular species may move in the cell sap much faster than their diffusion coefficients will permit, is discussed. Some implications of such barriers and channels, if they exist, are stated.