Antennal sensory organs in the millipede Eurypauropus ornatus: Fine structure of the flagella and globulus

On the antennal tip of Eurypauropus ornatus are 3 threadlike sensilla—the flagella, and a single spheroid sensillum—the globulus. Each of the 3 flagella is innervated by 2 groups of sensory cells. One group contains 4 cells, the other, 5. All cells of the “four group” and 3 of the “five group” are comprised of single cilia and unbranched dendrites which extend along the lumen of the flagellum. Two cells of the “five group” have double cilia and pairs of unbranched dendrites. One pair also enters the flagellum and the other pair terminates beneath the flagellar base to form a concentric array of lamellae. No pores are present in the cuticular wall. Eight sensory cells innervate the globulus. They are arranged in 3 groups, one triplet and 2 pairs, in addition to a single cell. The single cell contains a pair of cilia whose unbranched dendrites differentiate into tubular bodies that are inserted into the base of the globulus. Each of the other 7 sensory cells has a single cilium. Their unbranched dendrites penetrate into the globulus in 3 groups as described for the sensory cells. The dendrites in each group terminate in an individual pore channel at the globulus tip and completely fuse with the electron-dense material that plugs the pore channel. Based on structural similarities to sensilla having known functions, it is probable that the flagella and the globulus are chemoreceptors, the former responding to odors, the latter sensitive to substances in aqueous solution.     

Developmental Exposure to Fluoxetine Modulates the Serotonin System in Hypothalamus

The selective serotonin reuptake inhibitor (SSRI) fluoxetine (FLU, Prozac®) is commonly prescribed for depression in pregnant women. This results in SSRI exposure of the developing fetus. However, there are knowledge gaps regarding the impact of SSRI exposure during development. Given the role of serotonin in brain development and its cross-talk with sex hormone function, we investigated effects of developmental exposure to pharmacologically relevant concentrations of FLU (3 and 30 nM (measured)) on brain neurotransmitter levels, gonadal differentiation, aromatase activity in brain and gonads, and the thyroid system, using the Xenopus tropicalis model. Tadpoles were chronically exposed (8 weeks) until metamorphosis. At metamorphosis brains were cryosectioned and levels of serotonin, dopamine, norepinephrine, and their metabolites 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid, and homovanillic acid were measured in discrete regions (telencephalon, hypothalamus and the reticular formation) of the cryosections using high-performance liquid chromatography. Exposure to 30 nM FLU increased the concentration of 5-hydroxyindoleacetic acid in hypothalamus compared with controls. FLU exposure did not affect survival, time to metamorphosis, thyroid histology, gonadal sex differentiation, or aromatase activity implying that the effect on the serotonergic neurotransmitter system in the hypothalamus region was specific. The FLU concentration that impacted the serotonin system is lower than the concentration measured in umbilical cord serum, suggesting that the serotonin system of the developing brain is highly sensitive to in utero exposure to FLU. To our knowledge this is the first study showing effects of developmental FLU exposure on brain neurochemistry. Given that SSRIs are present in the aquatic environment the current results warrant further investigation into the neurobehavioral effects of SSRIs in aquatic wildlife.     

Sexual differentiation in Mucor: Trisporic acid response mutants and mutants blocked in zygospore development

Spores of a minus strain of Mucor mucedo (Bref.) were treated with 1-methyl-[3-nitro]-1-nitro-soguanidine and mutants were isolated either by testing for zygophore induction with externally supplied trisporic acids (TA) or by mating with wild type plus colonies. Mutants were found defective (Tar^?) or temperature-sensitive (Tar-Ts) in their reaction towards trisporic acids, blocked or temperature-sensitive in their mating with plus strain (Mat^? or Mat-Ts) or temperature-sensitive in zygospore development (Zyg-Ts). The inability to react against externally supplied trisporic acids was not necessarily coupled with an inability to mate with plus strain (phenotype Tar^? Mat⁺). This indicated that the diffusion and uptake of trisporic acids is not a necessary prerequisite to the sexual interaction of Mucor mating types.     

Inositol Phospholipid Hydrolysis by Rat Sciatic Nerve Phospholipase C

Rat sciatic nerve cytosol contains a phosphodiesterase of the phospholipase C type that catalyzes the hydrolysis of inositol phospholipids, with preferences of phosphatidylinositol 4'-phosphate (PIP) greater than phosphatidylinositol (PI) much greater than phosphatidylinositol 4',5'-bisphosphate (PIP2), at a pH optimum of 5.5-6.0 and at maximum rates of 55, 13, and 0.7 nmol/min/mg protein, respectively. Analysis of reaction products by TLC and formate exchange chromatography shows that inositol 1,2-cyclic phosphate (83%) and diacylglycerol are the major products of PI hydrolysis. [32P]-PIP hydrolysis yields inositol bisphosphate, inositol phosphate, and inorganic phosphate, indicating the presence of phosphodiesterase, phosphomonoesterase, and/or inositol phosphate phosphatase activities in nerve cytosol. Phosphodiesterase activity is Ca2+-dependent and completely inhibited by EGTA, but phosphomonoesterase activity is independent of divalent cations or chelating agents. Phosphatidylcholine (PC) and lysophosphatidylcholine (lysoPC) inhibit PI hydrolysis. They stimulate PIP and PIP2 hydrolysis up to equimolar concentrations, but are inhibitory at higher concentrations. Both diacylglycerols and free fatty acids stimulate PI hydrolysis and counteract its inhibition by PC and lysoPC. PIP2 is a poor substrate for the cytosolic phospholipase C and strongly inhibits hydrolysis of PI. However, it enhances PIP hydrolysis up to an equimolar concentration.     

Cloning and expression of the gene for a fibronectin-binding protein from Staphylococcus aureus.

The gene encoding the fibronectin-binding protein (FNBP) from Staphylococcus aureus strain 8325-4 was isolated from a gene bank in pBR322. The original clone, containing a 6.5-kb insert, gave a functional product present in the periplasm of Escherichia coli. Analysis of polypeptides isolated after affinity chromatography on fibronectin-Sepharose followed by ion-exchange chromatography revealed two gene products, 87 and 165 kd in mol. wt. The amino acid compositions of these two polypeptides and a native FNBP from S. aureus strain Newman were very similar. Antibodies raised against the native FNBP from strain Newman precipitated the 125I-labelled 165-kd polypeptide, and unlabeled 165- and 87-kd polypeptides as well as native FNBP inhibited the immunoprecipitation reactions. The region of the fnbp-gene encoding the fibronectin-binding activity has been identified and subcloned in an expression vector based on the staphylococcal protein A gene. The resulting product in E. coli is an extracellular fusion protein consisting of two IgG-binding domains of protein A followed by a fibronectin-binding region. The fusion protein binds to fibronectin and completely inhibits the binding of fibronectin to intact cells of S. aureus.