Purinergic signalling in rat GFSHR-17 granulosa cells: an <Emphasis Type="Italic">in vitro</Emphasis> model of granulosa cells in maturing follicles

Purinergic signalling in rat GFSHR-17 granulosa cells was characterised by Ca²⁺-imaging and perforated patch-clamp. We observed a resting intracellular Ca²⁺-concentration ([Ca²⁺]_i) of 100 nM and a membrane potential of −40 mV. This was consistent with high K⁺− and Cl⁻ permeability and a high intracellular Cl⁻ concentration of 40 mM. Application of ATP for 5–15 s every 3 min induced repeated [Ca²⁺]_i increases and a 30 mV hyperpolarization. The phospholipase C inhibitor U73122 or the IP₃-receptor antagonist 2-aminoethoethyl diphenyl borate suppressed ATP responses. Further biochemical and pharmacological experiments revealed that ATP responses were related to stimulation of P2Y₂ and P2Y₄ receptors and that the [Ca²⁺]_i increase was a prerequisite for hyperpolarization. Inhibitors of Ca²⁺-activated channels or K⁺ channels did not affect the ATP-evoked responses. Conversely, inhibitors of Cl⁻ channels hyperpolarized cells to −70 mV and suppressed further ATP-evoked hyperpolarization. We propose that P2Y₂ and P2Y₄ receptors in granulosa cells modulate Cl⁻ permeability by regulating Ca²⁺-release.     

(3,3-Difluoro-pyrrolidin-1-yl)-[(2S,4S)-(4-(4-pyrimidin-2-yl-piperazin-1-yl)-pyrrolidin-2-yl]-methanone: A potent,selective, orally active dipeptidyl peptidase IV inhibitor

A series of 4-substituted proline amides was synthesized and evaluated as inhibitors of dipeptidyl pepdidase IV for the treatment of type 2 diabetes. (3,3-Difluoro-pyrrolidin-1-yl)-[(2S,4S)-(4-(4-pyrimidin-2-yl-piperazin-1-yl)-pyrrolidin-2-yl]-methanone (5) emerged as a potent (IC₅₀ = 13 nM) and selective compound, with high oral bioavailability in preclinical species and low plasma protein binding. Compound 5, PF-00734200, was selected for development as a potential new treatment for type 2 diabetes.     

Modified Bacillus thuringiensis Toxins and a Hybrid B. thuringiensis Strain Counter Greenhouse-Selected Resistance in Trichoplusia ni

Resistance of greenhouse-selected strains of the cabbage looper, Trichoplusia ni, to Bacillus thuringiensis subsp. kurstaki was countered by a hybrid strain of B. thuringiensis and genetically modified toxins Cry1AbMod and Cry1AcMod, which lack helix α-1. Resistance to Cry1AbMod and Cry1AcMod was >100-fold less than resistance to native toxins Cry1Ab and Cry1Ac.Insecticidal proteins from Bacillus thuringiensis are used widely for pest control, but evolution of resistance by pests can reduce their efficacy (3, 4, 6, 14). Resistance to B. thuringiensis toxins has been reported in field populations of four species of Lepidoptera, one species in response to sprays (3, 14) and three species in response to transgenic crops (10, 15, 16). Here, we focus on understanding and countering resistance to sprays of Bacillus thuringiensis subsp. kurstaki that evolved in commercial greenhouse populations of the cabbage looper, Trichoplusia ni (7, 17).We compared responses to single toxins and formulations of B. thuringiensis by two resistant strains (GipBtR and GlenBtR) and two related susceptible strains (GipS and GlenS) of T. ni. All four strains were started by the collection of larvae in 2001 from commercial greenhouses near Vancouver in British Columbia, Canada (7). Resistance evolved in the greenhouses in response to repeated sprays of DiPel (7), a formulation of B. thuringiensis subsp. kurstaki strain HD1 containing Cry1Aa, Cry1Ab, Cry1Ac, and Cry2Aa (9). Previously reported concentrations required to kill 50% of larvae (LC₅₀s) indicated that, relative to a susceptible laboratory strain, initial resistance to DiPel was 113-fold in the Gip population (labeled T2c in reference 7) and 24-fold in the Glen population (labeled P5 in reference 7).We reared larvae on a wheat germ diet (5) at 26°C on a light-to-dark schedule of 16 h:8 h. GipS and GlenS were reared on diet without B. thuringiensis toxins, which allowed resistance to decline (7). To maintain resistance, GipBtR and GlenBtR were reared each generation on a diet treated with 5 or 10 mg of DiPel WP (Abbott Laboratories, Ontario, Canada) per milliliter of diet (7). In bioassays, groups of five third-instar larvae were put in 60-ml plastic cups containing diet, and mortality was assessed after 3 days by gently probing larvae for movement.We used diet overlay bioassays to evaluate the toxicity to GipBtR and GipS of the protoxin forms of Cry1Ab, Cry1Ac, Cry1AbMod, and Cry1AcMod produced in B. thuringiensis strains (12). Cry1AbMod and Cry1AcMod are genetically engineered variants of Cry1Ab and Cry1Ac, respectively, each lacking 56 amino acids from the amino-terminal region, including helix α-1 (12). An 80-μl aliquot containing distilled water and toxin was dispensed evenly over the surfaces of 2 ml of diet (a mean surface area of 7.1 cm²) and allowed to dry. Fifty to 200 larvae from each strain were tested at five to eight concentrations of each toxin.We used diet incorporation bioassays (7) to evaluate the toxicities of DiPel and Agree WG (Certis, Columbia, MD) to GipS, GipBtR, GlenS, and GlenBtR. Agree is a formulation of hybrid strain GC91, which was created from the conjugation-like transfer of a plasmid from B. thuringiensis subsp. kurstaki strain HD191 into B. thuringiensis subsp. aizawai strain HD135, and it contains Cry1Ac, Cry1C, and Cry1D (1, 8). DiPel and Agree were diluted in distilled water and mixed into diet (7). Twenty-five to 50 larvae from each strain were tested at six to seven concentrations of DiPel and Agree.We used probit analysis (13) to estimate the LC₅₀s and their 95% fiducial limits (FL), as well as the slopes of concentration-mortality lines and their standard errors. The mortality of larvae fed treated diet was not adjusted for the mortality of control larvae on untreated diet, because the control mortality was low (mean, 3.6%; range, 0 to 16%). LC₅₀s with nonoverlapping 95% FL are significantly different. Resistance ratios were calculated as the LC₅₀ of a resistant strain (GipBtR or GlenBtR) divided by the LC₅₀ of its susceptible counterpart (GipS or GlenS).The genetically modified toxins Cry1AbMod and Cry1AcMod were much more effective than the native toxins Cry1Ab and Cry1Ac against larvae of T. ni from the resistant GipBtR strain (Table ​(Table1).1). Resistance ratios of GipBtR were 580 for Cry1Ab and 1,400 for Cry1Ac but only 5.5 for Cry1AbMod and 9.3 for Cry1AcMod (Table ​(Table1).1). Against GipBtR, the LC₅₀ was 53-fold higher for Cry1Ab than for Cry1AbMod and 11-fold higher for Cry1Ac than for Cry1AcMod (Table ​(Table1).1). Against GipS, however, the LC₅₀ was 2-fold higher for Cry1AbMod than for Cry1Ab and 14-fold higher for Cry1AcMod than for Cry1Ac (Table ​(Table11).

TABLE 1.

Responses of resistant (GipBtR and GlenBtR) and susceptible (GipS and GlenS) strains of T. ni to native toxins (Cry1Ab and Cry1Ac), modified toxins (Cry1AbMod and Cry1AcMod), and formulations (DiPel and Agree)

Edwardsiella ictaluri Encodes an Acid-Activated Urease That Is Required for Intracellular Replication in Channel Catfish (Ictalurus punctatus) Macrophages

Genomic analysis indicated that Edwardsiella ictaluri encodes a putative urease pathogenicity island containing the products of nine open reading frames, including urea and ammonium transporters. In vitro studies with wild-type E. ictaluri and a ureG::kan urease mutant strain indicated that E. ictaluri is significantly tolerant of acid conditions (pH 3.0) but that urease activity is not required for acid tolerance. Growth studies demonstrated that E. ictaluri is unable to grow at pH 5 in the absence of urea but is able to elevate the environmental pH from pH 5 to pH 7 and grow when exogenous urea is available. Substantial production of ammonia was observed for wild-type E. ictaluri in vitro in the presence of urea at low pH, and optimal activity occurred at pH 2 to 3. No ammonia production was detected for the urease mutant. Proteomic analysis with two-dimensional gel electrophoresis indicated that urease proteins are expressed at both pH 5 and pH 7, although urease activity is detectable only at pH 5. Urease was not required for initial invasion of catfish but was required for subsequent proliferation and virulence. Urease was not required for initial uptake or survival in head kidney-derived macrophages but was required for intracellular replication. Intracellular replication of wild-type E. ictaluri was significantly enhanced when urea was present, indicating that urease plays an important role in intracellular survival and replication, possibly through neutralization of the acidic environment of the phagosome.Identification of virulence factors is vitally important to an understanding of the pathogenesis of Edwardsiella ictaluri and to the development of methods for controlling the spread of disease. Although the pathogenesis of E. ictaluri was reviewed in 1993 (28, 31), recent reports demonstrated that E. ictaluri is a facultative intracellular pathogen (3) and that a type III secretion system is required for intracellular survival and replication within channel catfish head kidney-derived macrophages (HKDM) (30). Using signature-tagged mutagenesis (STM) in an immersion challenge model for E. ictaluri, Thune et al. (30) identified 50 transconjugants carrying transposon insertions in genes required for survival and replication in the channel catfish host. Two of those mutants had insertions in genes encoding homologs of UreG and UreF, proteins that are essential for the production of an active urease enzyme in other bacteria (6, 10, 14, 26). UreG is a GTP-binding accessory protein that functions in energy-dependent assembly of the urease holoenzyme (19), while UreF is a urease accessory protein that functions in the generation or delivery of carbon dioxide to the urease metallocenter assembly site (19). Both the ureG and ureF mutant strains were further characterized in a competitive challenge with the wild-type (WT) parental strain and were confirmed to be significantly attenuated (30). The identification of two mutants with insertions in urease-associated genes suggests an important role for urease activity in E. ictaluri pathogenesis, despite the fact that E. ictaluri is urease negative in standard biochemical tests. Consequently, the objectives of this study are to characterize the E. ictaluri urease pathogenicity island (PAI), to evaluate conditions for E. ictaluri urease activity, and to establish a possible role for urease in E. ictaluri pathogenesis.     

Two Decades of Research on Euthanasia from the Netherlands. What Have We Learnt and What Questions Remain?

Two decades of research on euthanasia in the Netherlands have resulted into clear insights in the frequency and characteristics of euthanasia and other medical end-of-life decisions in the Netherlands. These empirical studies have contributed to the quality of the public debate, and to the regulating and public control of euthanasia and physician-assisted suicide. No slippery slope seems to have occurred. Physicians seem to adhere to the criteria for due care in the large majority of cases. Further, it has been shown that the majority of physicians think that the euthanasia Act has improved their legal certainty and contributes to the carefulness of life-terminating acts. In 2005, eighty percent of the euthanasia cases were reported to the review committees. Thus, the transparency envisaged by the Act still does not extend to all cases. Unreported cases almost all involve the use of opioids, and are not considered to be euthanasia by physicians. More education and debate is needed to disentangle in these situations which acts should be regarded as euthanasia and which should not. Medical end-of-life decision-making is a crucial part of end-of-life care. It should therefore be given continuous attention in health care policy and medical training. Systematic periodic research is crucial for enhancing our understanding of end-of-life care in modern medicine, in which the pursuit of a good quality of dying is nowadays widely recognized as an important goal, in addition to the traditional goals such as curing diseases and prolonging life.     

Vector competence of Australian Culex gelidus Theobald (Diptera: Culicidae) for endemic and exotic arboviruses

The recent recognition of established populations of the mosquito, Culex gelidus Theobald, in Australia has raised concerns about local transmission of arboviruses. The vector competence of a mainland population of Cx. gelidus was investigated for two local alphaviruses, Ross River (RRV) and Barmah Forest (BFV) viruses, and three flaviviruses, Japanese encephalitis (JEV), Kunjin (KUNV) and Murray Valley encephalitis (MVEV) viruses. Colonised mosquitoes were exposed to virus via blood-soaked pledgets and transmission was tested using a capillary-tube method. The important Australian vectors, Aedes vigilax (Skuse) and Culex annulirostris Skuse, were used as internal controls for the alphaviruses and flaviviruses, respectively. Overall, Cx. gelidus was a more efficient vector of flaviviruses than alphaviruses. Culex gelidus was refractory to infection with BFV, and nearly 25% transmitted RRV, which was comparable to Ae. vigilax . Culex gelidus was susceptible to all three flaviviruses, with transmission rates of 96%, 95% and 41% for JEV, KUNV and MVEV, respectively. JEV transmission rates in Cx. annulirostris were unexpectedly low and this was possibly due to differences in susceptibility to JEV genotypes I and II. Considering the high susceptibility to the flaviviruses demonstrated here, and the natural infections with RRV and JEV that have been detected from northern Australian populations, the establishment of the exotic mosquito, Cx. gelidus , in Australia is potentially a significant public health concern.