Transposition-mediated transcriptional overexpression as a mechanism of insecticide resistance

It has been proposed that amplification of genes for esterase that provide resistance to insecticides may originate from transposition events. To test this hypothesis, we have constructed a minigene coding for a soluble acetylcholinesterase under the control of a nontissue-specific promoter (hsp70). When introduced into Drosophila, the gene is expressed in all tissues and the extra acetylcholinesterase produced confers a low level of insecticide resistance (twofold). The minigene was mobilized by crossing the initial transformant with a strain providing a source of P-element transposase. After 34 generations of exposure to the organophosphate parathion, we obtained a strain with a higher resistance (fivefold). This strain had only one extra Ace gene, which overexpressed acetylcholinesterase. Thus, following transposition, resistance resulted from the overexpression of a single copy of the gene and not from gene amplification. Received: 9 August 1996 / Accepted: 27 May 1997     

Human acetylcholinesterase. Immunochemical studies with monoclonal antibodies

Monoclonal antibodies were used to investigate the immunochemistry of human erythrocyte acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7). A series of experiments on the sedimentation velocity and Stokes radius of acetylcholinesterase and its immune complexes indicated that each antibody recognized a single high-affinity binding site (epitope) on the monomeric enzyme. Further analysis suggested that the antibody-binding sites were replicated on multimeric enzyme forms but were subject to steric hindrance between nearby IgG molecules or adjacent enzyme subunits. The cellular localization of the epitopes was studied by measuring the binding of monoclonal antibodies to the cholinesterase of intact erythrocytes. The results implied that most of the epitopes are exposed to the external media. However, one antibody failed to bind to intact cells, despite a relatively high affinity for detergent-solubilized antigen, possibly because its epitope is buried in the lipid bilayer.     

Non‐pollinating cheater wasps benefit from seasonally poor performance of the mutualistic pollinating wasps at the northern limit of the range of Ficus microcarpa

1. Species interactions in tightly bound ecological mutualisms often feature highly specialised species' roles in which competitive exclusion may preclude multi‐species coexistence. Among the 800 fig (Ficus) species, it was originally considered that each was pollinated by their own wasp (Agaonidae). However, recent investigations show that this ‘one‐to‐one’ rule often breaks down, as fig species regularly host multiple agaonids but in ways suggesting that competitive processes still mediate biodiversity outcomes. 2. A phenological survey was conducted of the fig–fig wasp pair, Ficus microcarpa and its associated pollinating wasp, alongside its sister species, the cheating wasp, in Xishuangbanna, China. 3. Reproductive output underwent extreme seasonal variation. Seed and pollinator production fell markedly during cooler, drier months, although high levels of fig production continued. However, this resource was predominantly utilised by the cheater species, which offers no pollination services. Pollinators and cheaters rarely co‐occur, suggesting that temporal coexistence is constrained by competition for access to figs. 4. The overall findings indicate periodic rearrangements of mutualism dynamics, probably resulting from a strongly seasonal environment. Sympatric co‐occurrence may result from a window of opportunity for a functionally divergent agaonid, potentially due to constraints on the main pollinator in adapting to variable year‐round conditions that prevent competitive exclusion.     

Use of autonomous audio recordings for the rapid inventory of birds in the white‐sand forests of the Peruvian Amazon

White‐sand forests are patchily distributed ecosystems covering just 5% of Amazonia that host many specialist species of birds not found elsewhere, and these forests are threatened due to their small size and human exploitation of sand for construction projects. As a result, many species of birds that are white‐sand specialists are at risk of extinction, and immediate conservation action is paramount for their survival. Our objective was to evaluate current survey methods and determine the relative effect of the size of patches of these forests on the presence or absence of white‐sand specialists. Using point counts and autonomous recorders, we surveyed avian assemblages occupying patches of white‐sand forest in the Peruvian Amazon in April 2018. Overall, we detected 126 species, including 21 white‐sand forest specialists. We detected significantly more species of birds per survey point with autonomous recorders than point counts. We also found a negative relationship between avian species richness and distance from the edge of patches of white‐sand forest, but a significant, positive relationship when only counting white‐sand specialists. Although we detected more species with autonomous recorders, point counts were more effective for detecting canopy‐dwelling passerines. Therefore, we recommend that investigators conducting surveys for rare and patchily distributed species in the tropics use a mixed‐method approach that incorporates both autonomous recorders and visual observation. Finally, our results suggest that conserving large, continuous patches of white‐sand forest may increase the likelihood of survival of species of birds that are white‐sand specialists.     

Nearest Neighbor Classification Rule for Mixtures of Discrete and Continuous Random Variables

In this paper very simple nonparametric classification rule for mixtures of discrete and continuous random variables is described. It is based on the method of nearest neighbor proposed by Cover and Hart (1967). The bounds on the limit of the nearest neighbor rule risks are given. Both lower and upper bound depend on the Bayes risk and the loss function. Finally the method is compared with other existing methods on some practical data set.     

Increased Expression of Apolipoprotein D Following Experimental Traumatic Brain Injury

Increasing evidence suggests that apolipoprotein D (apoD) could play a major role in mediating neuronal degeneration and regeneration in the CNS and the PNS. To investigate further the temporal pattern of apoD expression after experimental traumatic brain injury in the rat, male Sprague-Dawley rats were subjected to unilateral cortical impact injury. The animals were killed and examined for apoD mRNA and protein expression and for immunohistological analysis at intervals from 15 min to 14 days after injury. Increased apoD mRNA and protein levels were seen in the cortex and hippocampus ipsilateral to the injury site from 48 h to 14 days after the trauma. Immunohistological investigation demonstrated a differential pattern of apoD expression in the cortex and hippocampus, respectively: Increased apoD immunoreactivity in glial cells was detected from 2 to 3 days after the injury in cortex and hippocampus. In contrast, increased expression of apoD was seen in cortical and hippocampal neurons at later time points following impact injury. Concurrent histopathological examination using hematoxylin and eosin demonstrated dark, shrunken neurons in the cortex ipsilateral to the injury site. In contrast, no evidence of cell death was observed in the hippocampus ipsilateral to the injury site up to 14 days after the trauma. No evidence of increased apoD mRNA or protein expression or neuronal pathology by hematoxylin and eosin staining was detected in the contralateral cortex and hippocampus. Our results reveal induction of apoD expression in the cortex and hippocampus following traumatic brain injury in the rat. Our data also suggest that increased apoD expression may play an important role in cortical neuronal degeneration after brain injury in vivo. However, increased expression of apoD in the hippocampus may not necessarily be indicative of neuronal death.     

Phosphorylation of lens membranes with a cyclic AMP-dependent protein kinase purified from the bovine lens

We report the phosphorylation of lens membranes with a cAMP-dependent protein kinase isolated from bovine lenses. The holoenzyme was eluted from DEAE agarose at less than 100 mM NaCl and from gel filtration columns with a relative molecular weight of 180 000. The regulatory subunit was identified with the affinity label 8-azido-[32P]cAMP. Four focusing variants with relative molecular weights of 49 000 were seen on two-dimensional gels. The catalytic subunit was purified approx. 5000-fold and migrated at 42 000 Mr on SDS gels. Based on these observations, the enzyme is classified as a Type I cAMP-dependent protein kinase. Purified lens plasma membranes were incubated with the holoenzyme or its catalytic subunit in the presence of 32P-labeled ATP. Several membrane proteins, including the major lens membrane polypeptide, MP26, were shown to be substrates for the kinase in this reaction. MP26 appears to be the major component of intercellular junctions in the lens. Studies with protease treatments on labeled membranes appeared to localize the phosphorylation sites to the cytoplasmic side of the membrane.     

Immunosuppressive activity of T cell clones generated from human T cells stimulated with autologous TPHA cells

T cell clones were generated from human T cells stimulated with autologous phytohemagglutinin (PHA)-activated T (TPHA) cells. Characterization of three T cell clones originated from donor SF and one from donor JM showed that they proliferated when stimulated with autologous TPHA cells, non-T cells, and peripheral blood mononuclear cells, but did not proliferate when stimulated with allogeneic TPHA cells, non-T cells, and mononuclear cells, with autologous and allogeneic resting T cells, and with PHA. These results in conjunction with the blocking of the proliferation by anti-histocompatibility leukocyte antigen class II monoclonal antibodies indicate that these class II antigens are involved in the proliferation of T cell clones stimulated with autologous lymphoid cells. The four T cell clones are cytotoxic neither to autologous lymphoid cells nor to a panel of cultured human cell lines. The four T cell clones display immunosuppressive activity, since they inhibit the proliferation of autologous and allogeneic cells stimulated with antigens and mitogens and the secretion of immunoglobulin by B cells stimulated with pokeweed mitogen in presence of T cells. Furthermore, the four T cell clones display differential inhibitory activity on the proliferation of cultured human cell lines. The immunosuppressive activity is species-specific, since the T cell clones do not inhibit the proliferation of murine cells. The suppression is mediated by a factor(s) with an apparent m.w. of 13,000 to 16,000. The suppressor activity is labile at alkaline pH and is lost following incubation with pronase (100 U/ml) for 30 min at 37 degrees C.     

Atrial natriuretic peptide detected by immunocytochemistry in peripheral organs of Tupaia belangeri

ANP (atrial natriuretic peptide), a peptide found in granules of mammalian atrial cardiac myocytes, has been shown to be active in regulation of blood pressure and body water homeostasis. The existence of ANP in atrium, pituitary, adrenal gland, and kidney of the rat had been immunocytochemically demonstrated with an antibody against rat ANP (102-126). We used the same antibody in immunocytochemical studies for the detection of ANP in peripheral organs of the tree shrew (Tupaia belangeri). The antibody stained granules in myocytes of cardiac atria which indicated that it reacted with tree shrew ANP. In contrast to the rat, no immunoreactive cells were found in pituitaries and adrenal glands. However, in the kidneys distal tubules in outer medulla and cortex were labeled. Ascending limbs of distal tubules were intensely stained when either the peroxidase-antiperoxidase (PAP) or the indirect immunofluorescence method were used. Collecting ducts and convoluted distal tubules in the outer cortex showed a granular type of staining when the immunofluorescence method was used. These data indicate that ANP is present in epithelial cells of distal tubules and collecting ducts, where it may be involved in the regulation of renal salt excretion.