A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques

After disulphide bonds are reduced with dithiothreitol, trans-3- (α-bromomethyl)-3’-[α- (trimethylammonium)methyl]azobenzene (trans-QBr) alkylates a sulfhydryl group on receptors. The membrane conductance induced by this “tethered agonist” shares many properties with that induced by reversible agonists. Equilibrium conductance increases as the membrane potential is made more negative; the voltage sensitivity resembles that seen with 50 [mu]M carbachol. Voltage- jump relaxations follow an exponential time-course; the rate constants are about twice as large as those seen with 50 μM carbachol and have the same voltage and temperature sensitivity. With reversible agonists, the rate of channel opening increases with the frequency of agonist-receptor collisions: with tethered trans-Qbr, this rate depends only on intramolecular events. In comparison to the conductance induced by reversible agonists, the QBr-induced conductance is at least 10-fold less sensitive to competitive blockade by tubocurarine and roughly as sensitive to “open-channel blockade” bu QX-222. Light-flash experiments with tethered QBr resemble those with the reversible photoisomerizable agonist, 3,3’,bis-[α-(trimethylammonium)methyl]azobenzene (Bis-Q): the conductance is increased by cis {arrow} trans photoisomerizations and decreased by trans {arrow} cis photoisomerizations. As with Bis-Q, ligh-flash relaxations have the same rate constant as voltage-jump relaxations. Receptors with tethered trans isomer. By comparing the agonist-induced conductance with the cis/tans ratio, we conclude that each channel’s activation is determined by the configuration of a single tethered QBr molecule. The QBr-induced conductance shows slow decreases (time constant, several hundred milliseconds), which can be partially reversed by flashes. The similarities suggest that the same rate-limiting step governs the opening and closing of channels for both reversible and tethered agonists. Therefore, this step is probably not the initial encounter between agonist and receptor molecules.     

Palatability and feeding preferences of Uresiphita maorialis (Lepidoptera: Crambidae) for three Sophora species

In a three-hour bioassay, we tested the palatability and feeding preferences of Uresiphita maorialis (kōwhai moth) for Sophora tetraptera, Sophora microphylla and Sophora prostrata. Palatability tests showed no differences among the Sophora species. Feeding preferences, on the other hand, showed that S. tetraptera and S. microphylla leaves are preferred over S. prostrata leaves. Our results support our field observations in Wellington city parks and gardens showing that S. tetraptera and S. microphylla plants frequently have higher densities of larvae than S. prostrata.     

Biodeterioration of Mayan buildings at uxmal and tulum,Mexico

Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation.     

Senescence evasion in melanoma progression: uncoupling of DNA‐damage signaling from p53 activation and p21 expression

The best‐established function of the melanoma‐suppressor p16 is mediation of cell senescence, a permanent arrest following cell proliferation or certain stresses. The importance of p16 in melanoma suggests indolence of the other major senescence pathway through p53. Little or no p53 is expressed in senescent normal human melanocytes, but p16‐deficient melanocytes can undergo p53‐mediated senescence. As p16 expression occurs in nevi but falls with progression toward melanoma, we here investigated whether p53‐dependent senescence occurs at some stage and, if not, what defects were detectable in this pathway, using immunohistochemistry. Phosphorylated checkpoint kinase 2 (CHEK2) can mediate DNA‐damage signaling, and under some conditions senescence, by phosphorylating and activating p53. Remarkably, we detected no prevalent p53‐mediated senescence in any of six classes of lesions. Two separate defects in p53 signaling appeared common: in nevi, lack of p53 phosphorylation by activated CHEK2, and in melanomas, defective p21 upregulation by p53 even when phosphorylated.     

The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

Immunotherapeutic potential of whole tumour cells

Despite the identification of tumour antigens and their subsequent generation in subunit form for use as cancer vaccines, whole tumour cells remain a potent vehicle for generating anti-tumour immunity. This is because tumour cells express an array of target antigens for the immune system to react against, avoiding problems associated with major histocompatibility complex (MHC)-restricted epitope identification for individual patients. Furthermore, whole cells are relatively simple to propagate and are potentially efficient at contributing to the process of T cell priming. However, whole cells can also possess properties that allow for immune evasion, and so the question remains of how to enhance the immune response against tumour cells so that they are rejected. Scenarios where whole tumour cells may be utilised in immunotherapy include autologous tumour cell vaccines generated from resected primary tumour, allogeneic (MHC-disparate) cross-reactive tumour cell line vaccines, and immunotherapy of tumours in situ. Since tumour cells are considered poorly immunogenic, mainly because they express self-antigens in a non-stimulatory context, the environment of the tumour cells may have to be modified to become stimulatory by using immunological adjuvants. Recent studies have re-evaluated the relative roles of direct and cross-priming in generating anti-tumour immunity and have highlighted the need to circumvent immune evasion.     

Immunoregulatory effects of freeze injured whole tumour cells on human dendritic cells using an in vitro cryotherapy model

Tumour cryotherapy has been described as both immunostimulatory and immunoinhibitory in previous studies. However, previous studies have not accurately reproduced the precise conditions of current clinical cryotherapy. The objective of this study is to assess the immunological effects of cryotreated whole tumour cells on dendritic cells (DC) maturation and function using an in vitro model. Prostate cancer cells were cooled using Endocare cryo-system to mimic temperatures achieved during clinical cryotherapy. Human DC were prepared from cluster of differentiation (CD) 14 monocytes and matured with lipopolysaccharide (LPS). Cryotreated cancer cells were added to DC on day 3. On day 7, DC were harvested and phenotyped. Cytokine gene expression was assessed using real time quantitative polymerase chain reaction (RT-PCR). Functional activity of DC was assessed in allogenic mixed lymphocyte reaction (MLR) and the molecular changes using gene microarray technology. There was statistically significant upregulation of costimulatory molecules and maturation markers (CD86, CD83, CD80 and CL II) in DC loaded with cryotreated whole tumour cells compared to both control DC and DC matured with LPS (P < 0.001). There was a significant increase in stimulatory cytokines gene expression (IL-2, IL-12, IL-15, IL-18 and IFN-γ). However, IL-10 and TGF-β expression reduced significantly. The effect of different freezing temperature was equal. cDNA microarray analysis showed upregulation of interleukin 1 (IL-1) and cycline dependent kinase inhibitor 1A (CDKN1A (p21) and downregulation of Caspase 8 and BCL2. Overall, our findings suggest that the effect of cryotherapy is generally stimulatory to DC which may enhance anti-tumour effects. Therefore, the combination of cryotherapy and DC vaccine may represent a novel method to increase the efficacy of cryotherapy especially at the peripheral zones of the prostate where cells are exposed to sub-lethal temperature.     

The many faces of ubiquitinated histone H2A: insights from the DUBs

Increasing knowledge on the cell cycle deregulations in cancers has promoted the introduction of phytochemicals, which can either modulate signaling pathways leading to cell cycle regulation or directly alter cell cycle regulatory molecules, in cancer therapy. Most human malignancies are driven by chromosomal translocations or other genetic alterations that directly affect the function of critical cell cycle proteins such as cyclins as well as tumor suppressors, e.g., p53. In this respect, cell cycle regulation and its modulation by curcumin are gaining widespread attention in recent years. Extensive research has addressed the chemotherapeutic potential of curcumin (diferuloylmethane), a relatively non-toxic plant derived polyphenol. The mechanisms implicated are diverse and appear to involve a combination of cell signaling pathways at multiple levels. In the present review we discuss how alterations in the cell cycle control contribute to the malignant transformation and provide an overview of how curcumin targets cell cycle regulatory molecules to assert anti-proliferative and/or apoptotic effects in cancer cells. The purpose of the current article is to present an appraisal of the current level of knowledge regarding the potential of curcumin as an agent for the chemoprevention of cancer via an understanding of its mechanism of action at the level of cell cycle regulation. Taken together, this review seeks to summarize the unique properties of curcumin that may be exploited for successful clinical cancer prevention.