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Researcher, University of Calabar


We investigated the possible endocrine disruptive effects of cypermethrin in fish

We investigated the endocrine disruptive effects of varying concentrations cypermethrin on Clarias gariepinus by quantifying hormonal changes in estradiol (E2) and testosterone (T) using ELISA. The gonads were also examined for histopathological alterations. We observed a dose dependent significant increases in E2 levels across exposure concentrations compared with control. While T levels decreased significantly with increasing concentrations compared with control. Overall, molecular and biochemical responses presented herein indicate that exposure of C. gariepinus to cypermethrin may have severe reproductive and population level consequences and are valuable and effective endpoint biomarkers that can be adopted for screening the endocrine disruptive effects of other synthetic compounds.


Organophosphate flame retardants in household dust before and after introduction of new furniture.

Abstract: Flame retardant compounds originating from household items collect in household dust, a reasonable proxy for human exposure. Contributions of specific items or behaviors to dust are difficult to separate. This study examined standardized college housing before and after the introduction of new, flame retardant couches in order to explore any effect that changing upholstered furniture may have on flame retardant concentrations in dust. Two contradictory hypotheses were posited: (1) that new furniture might increase flame retardant releases immediately after introduction due to initial off-gassing of new materials or (2) that older furniture would release more flame retardants due to mechanical breakdown of polyurethane foam. This study was designed to determine which of these processes dominated. Prior to the introduction of new furniture, TDCIPP was detected in 12/20 samples at a median concentration of 22 μg/g and TCEP was detected in 1/20 samples at a concentration of 16 μg/g. TDCIPP and TCEP were not detected in any samples (N = 29) after the introduction of new couches. TPHP was detected both before (in 11/20 samples) and after (in 5/29 samples) introduction of new couches; the median concentrations before and after were 63 ± 49 and 16 ± 11 μg/g (standard deviation shown). Introduced couches contained TDCIPP (and not TPHP) at ∼1.25% (w/w). These data support the second hypothesis and indicate that removal of older furniture decreases TDCIPP and TCEP concentrations in dust and may potentially reduce total flame retardant concentrations in dust, at least immediately after introduction of the new furniture.

Pub.: 04 Feb '16, Pinned: 30 Aug '17

Thrombospondin-1 (TSP-1), a new bone morphogenetic protein-2 and -4 (BMP-2/4) antagonist identified in pituitary cells

Abstract: Bone morphogenetic proteins (BMPs) regulate diverse cellular responses during embryogenesis and in adulthood including cell differentiation, proliferation and death in various tissues. In the adult pituitary, BMPs participate in the control of hormone secretion and cell proliferation suggesting a potential endocrine/paracrine role for BMPs, but some of the mechanisms are unclear. Here, using a bioactivity test based on embryonic cells (C3H10T1/2) transfected with a BMP-responsive element, we sought to determine whether pituitary cells secrete BMPs or BMP antagonists. Interestingly, we found that pituitary-conditioned medium contains a factor that inhibits action of BMP-2 and -4. Combining surface plasmon resonance (SPR) and high-resolution mass spectrometry helped pinpoint this factor as thrombospondin-1 (TSP-1). SPR and co-immunoprecipitation confirmed that recombinant human TSP-1 can bind BMP-2 and -4 and antagonize their effects on C3H10T1/2 cells. Moreover, TSP-1 inhibited the action of serum BMPs. We also report that the von Willebrand type C (VWC) domain of TSP-1 is likely responsible for this BMP-2/4 binding activity, an assertion based on sequence similarity that TSP-1 shares with the VWC domain of Crossveinless 2 (CV-2), a BMP antagonist and member of the chordin family. In summary, we identified for the first time TSP-1 as a BMP-2/-4 antagonist and presented structural basis for the physical interaction between TSP-1 and BMP-4. We propose that TSP-1 could regulate bioavailability of BMPs, either produced locally or reaching the pituitary via the blood circulation. In conclusion, our findings provide new insights into the involvement of TSP-1 in the BMP-2/-4 mechanisms of action.

Pub.: 26 Jul '17, Pinned: 30 Aug '17

A mosquito hemolymph odorant-binding protein family member specifically binds juvenile hormone.

Abstract: Juvenile hormone (JH) is a key regulator of insect development and reproduction. In adult mosquitoes, it is essential for maturation of the ovary and normal male reproductive behavior, but how JH distribution and activity is regulated after secretion is unclear. Here, we report a new type of specific JH-binding protein, given the name mosquito juvenile hormone binding protein (mJHBP), which circulates in the hemolymph of pupal and adult Aedes aegypti males and females. mJHBP, is a member of the odorant-binding protein (OBP) family, and orthologs are present in the genomes of Aedes, Culex and Anopheles mosquito species. Using isothermal titration calorimetry, we show that mJHBP specifically binds JH II and JH III, but not eicosanoids or JH derivatives. mJHBP was crystallized in the presence of JH III and found to have a double OBP domain structure reminiscent of salivary "long" D7 proteins of mosquitoes. We observed that a single JH III molecule is contained in the N-terminal domain binding pocket that is closed in an apparent conformational change by a C-terminal domain-derived α-helix. The electron density for the ligand indicated a high occupancy of the natural 10R enantiomer of JH III. Of note, mJHBP is structurally unrelated to hJHBP from lepidopteran insects. A low level of expression of mJHBP in Ae. aegypti larvae suggests that it is primarily active during the adult stage where it could potentially influence the effects of JH on egg development, mating behavior, feeding or other processes.

Pub.: 29 Jul '17, Pinned: 30 Aug '17