Studies on the CPA cysteine peptidase in the Leishmania infantum genome strain JPCM5

Background  

Visceral leishmaniasis caused by members of the Leishmania donovani complex is often fatal in the absence of treatment. Research has been hampered by the lack of good laboratory models and tools for genetic manipulation. In this study, we have characterised a L. infantum line (JPCM5) that was isolated from a naturally infected dog and then cloned. We found that JPCM5 has attributes that make it an excellent laboratory model; different stages of the parasite life cycle can be studied in vitro, it is accessible to genetic manipulation and it has retained its virulence. Furthermore, the L. infantum JPCM5 genome has now been fully sequenced.     

Fluorescent somatostatin receptor probes for the intraoperative detection of tumor tissue with long-wavelength visible light

Targeted fluorescent dyes are of substantial value for the intraoperative delineation of primary tumors and metastatic lesions. For this purpose long-wavelength red light (lambda=550-650 nm) offers advantages because of good tissue penetration and direct visibility. Since somatostatin receptors (SSTR) are overexpressed in a number of tumors, a series of potentially tumor-selective peptide-dye conjugates were synthesized by solid-phase peptide synthesis (SPPS). The octapeptides octreotate, Tyr(3)-octreotate and Tyr(3)-octreotide were employed and exhibited high affinity for somatostatin receptors (SSTR). The fluorescent dyes rhodamine 101, sulforhodamine B acid chloride, sulforhodamine 101 or rhodamine B isothiocyanate were conjugated either directly or via spacers, for example the peptidase-labile pentapeptide sequence Ala-Leu-Ala-Leu-Ala. The conjugates were completely assembled on the solid support: Fmoc-SPPS, cyclization via a disulfide linkage, N-terminal attachment of a spacer, and linkage to the fluorescent dye. An in vitro competition assay revealed that the conjugates bind to SSTRs with IC(50) values between 0.7 and 89 nM. The conjugates were generally stable to hydrolysis at pH 7-8 in buffer or serum. However, the rhodamine 101 conjugates revealed a loss of absorption at alkaline pH due to conversion to a neutral spirolactam form, as characterized by NMR.     

The synthesis and biological evaluation of a series of potent dual inhibitors of farnesyl and geranyl-Geranyl protein transferases

We have prepared a series of potent, dual inhibitors of the prenyl transferases farnesyl protein transferase (FPTase) and geranyl-geranyl protein transferase I (GGPTase). The compounds were shown to possess potent activity against both enzymes in cell culture. Mechanistic analysis has shown that the compounds are CAAX competitive for FPTase inhibition but geranyl-geranyl pyrophosphate (GGPP) competitive for GGPTase inhibiton.     

Detection and removal of contaminating hydroxylamines from the spin trap DEPMPO, and re-evaluation of its use to indicate nitrone radical cation formation and S(N)1 reactions

A previous report that the spin trap 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) allows DEPMPO radical cation formation to be detected via the production of a carbon-centred radical adduct (assigned as the cis-hydroxyethyl species, formed by an intramolecular process) is shown to be incorrect. Rather, this and other paramagnetic species arise from the facile oxidation of trace hydroxylamine impurities present in commercial DEPMPO samples. As a result, techniques for the detection and elimination of such hydroxylamine impurities from DEPMPO solutions were developed and are described; these should prove to be of general use in EPR spin trapping experiments.     

Elevated serum silicon levels in women with silicone gel breast implants

The metatolic fate of silicone gel leaked from an intact or ruptured prosthesis is unknown. In this study, serum was blindly assayed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) for elemental silicon in 72 women with silicone gel breast implants and 55 control women (mean age 48 yr, both groups). Blood was drawn and processed using silicon-free materials. The mean silicon level in controls was 0.13±0.07 mg/L (range 0.06–0.35 mg/L), whereas in implant patients, the mean was significantly higher at 0.28±0.22 mg/L (range 0.06–0.87 mg/L) (P<0.01, Student'st-test with correction for unequal variances). Using the mean of the control group +2 SD as a cutoff for normal range (0.27 mg/L), 25/72 (34.7%) implant patients exceeded this value, compared with 2/55 (3.6%) controls. There was no significant correlation between past rupture of one or both implants, current rupture at the time of the blood draw, or the number of years with implants and silicon levels. The results suggest that serum silicon levels are elevated in many women with silicone gel breast implants. The chemical species involved and kinetics of this elevation remain to be determined.     

Spatial manipulation of cells and organelles using single electrode dielectrophoresis

The selection, isolation, and accurate positioning of single cells in three dimensions are increasingly desirable in many areas of cell biology and tissue engineering. We describe the application of a simple and low cost dielectrophoretic device for picking out and relocating single target cells. The device consists of a single metal electrode and an AC signal generator. It does not require microfabrication technologies or sophisticated electronics. The dielectrophoretic manipulator also discriminates between live and dead cells and is capable of redistributing intracellular organelles.     

Last of the human protists: the phylogeny and genetic diversity of Iodamoeba

Iodamoeba is the last genus of obligately parasitic human protist whose phylogenetic position is unknown. Iodamoeba small subunit ribosomal DNA sequences were obtained using samples from three host species, and phylogenetic analyses convincingly placed Iodamoeba as a sister taxon to Endolimax. This clade in turn branches among free-living amoeboflagellates of the genus Mastigamoeba. Two Iodamoeba ribosomal lineages (RL1 and RL2) were detected whose sequences differ by 31%, each of which is found in both human and nonhuman hosts.     

Co-adaptation of seed dormancy and flowering time in the arable weed Capsella bursa-pastoris (shepherd's purse)

Background and Aims

The duration of the plant life cycle is an important attribute that determines fitness and coexistence of weeds in arable fields. It depends on the timing of two key life-history traits: time from seed dispersal to germination and time from germination to flowering. These traits are components of the time to reproduction. Dormancy results in reduced and delayed germination, thus increasing time to reproduction. Genotypes in the arable seedbank predominantly have short time to flowering. Synergy between reduced seed dormancy and reduced flowering time would create stronger contrasts between genotypes, offering greater adaptation in-field. Therefore, we studied differences in seed dormancy between in-field flowering time genotypes of shepherd''s purse.

Methods

Genotypes with early, intermediate or late flowering time were grown in a glasshouse to provide seed stock for germination tests. Secondary dormancy was assessed by comparing germination before and after dark-incubation. Dormancy was characterized separately for seed myxospermy heteromorphs, observed in each genotype. Seed carbon and nitrogen content and seed mass were determined as indicators of seed filling and resource partitioning associated with dormancy.

Key Results

Although no differences were observed in primary dormancy, secondary dormancy was weaker among the seeds of early-flowering genotypes. On average, myxospermous seeds showed stronger secondary dormancy than non-myxospermous seeds in all genotypes. Seed filling was similar between the genotypes, but nitrogen partitioning was higher in early-flowering genotypes and in non-myxospermous seeds.

Conclusions

In shepherd''s purse, early flowering and reduced seed dormancy coincide and appear to be linked. The seed heteromorphism contributes to variation in dormancy. Three functional groups of seed dormancy were identified, varying in dormancy depth and nitrate response. One of these groups (FG-III) was distinct for early-flowering genotypes. The weaker secondary dormancy of early-flowering genotypes confers a selective advantage in arable fields.     

Glucose sensing by gut endocrine cells and activation of the vagal afferent pathway is impaired in a rodent model of type 2 diabetes mellitus

Glucose in the gut lumen activates gut endocrine cells to release 5-HT, glucagon-like peptide 1/2 (GLP-1/2), and glucose-dependent insulinotropic polypeptide (GIP), which act to change gastrointestinal function and regulate postprandial plasma glucose. There is evidence that both release and action of incretin hormones is reduced in type 2 diabetes (T2D). We measured cellular activation of enteroendocrine and enterochromaffin cells, enteric neurons, and vagal afferent neurons in response to intestinal glucose in a model of type 2 diabetes mellitus, the UCD-T2DM rat. Prediabetic (PD), recent-diabetic (RD, 2 wk postonset), and 3-mo diabetic (3MD) fasted UCD-T2DM rats were given an orogastric gavage of vehicle (water, 0.5 ml /100 g body wt) or glucose (330 μmol/100 g body wt); after 6 min tissue was removed and cellular activation was determined by immunohistochemistry for phosphorylated calcium calmodulin-dependent kinase II (pCaMKII). In PD rats, pCaMKII immunoreactivity was increased in duodenal 5-HT (P < 0.001), K (P < 0.01) and L (P < 0.01) cells in response to glucose; glucose-induced activation of all three cell types was significantly reduced in RD and 3MD compared with PD rats. Immunoreactivity for GLP-1, but not GIP, was significantly reduced in RD and 3MD compared with PD rats (P < 0.01). Administration of glucose significantly increased pCaMKII in enteric and vagal afferent neurons in PD rats; glucose-induced pCaMKII immunoreactivity was attenuated in enteric and vagal afferent neurons (P < 0.01, P < 0.001, respectively) in RD and 3MD. These data suggest that glucose sensing in enteroendocrine and enterochromaffin cells and activation of neural pathways is markedly impaired in UCD-T2DM rats.