Bioconversion of leukotriene C4 by rat glomeruli and papilla

Since leukotriene C₄ (LTC₄) may be locally synthesized by bone marrow-derived cells infiltrating the kidney in inflammatory renal diseases we examined the in vitro metabolism of exogenously added |³H| LTC₄ by rat glomeruli and papilla using radiometric HPLC. Homogenized as well as intact glomeruli converted |³H| LTC₄ mainly into |³h| LTE₄ (83%) and, at a smaller extent, into |³H| LTD₄ (4%). Intact |³H| LTC₄ represented 13% of the sum of radioactive leukotrienes. Addition of L-cysteine resulted in accumulation of LTD₄. In contrast, there was nearly no conversion of |³H| LTC₄ (87% ntact) in the presence of homogenized papilla. The metabolism of |³H| LTC₄ by the glomeruli was time- and temperature- dependent. The 10,000 g supernatant and pellet of homogenized glomeruli both retained the ability to metabolize |³H| LTC₄. The papillary 10,000 g supernatant was inactive, as found for the total homogenate, whereas the papillary 10,000 g pellet separated from its supernatant could transform |³H| LTC₄ into its metabolites, LTD₄ and LTE₄. Addition of increasing amounts of papillary 10,000 g supernatant to homogenized glomeruli progressively protected |³H| LTC₄ from its bioconversion. These results demonstrate that both glomeruli and papilla possess the γ-glutamyl transpeptidase and dipeptidase necessary to process LTC₄. However, the enzyme activity of the papilla is unmasked only when the inhibitor present in the 10,000 g supernatant is separated from the enzyme present in the pellet.     

The structure of Sipunculus nudus erythrocyte chromatin

The structure of the Sipunculus erythrocyte chromatin has been characterized by electron microscopy and nuclease digestion (staphylococcal nuclease and pancreatic nuclease). Contrary to previous results [1], we were able to isolate and characterize a histone H_2B in sipunculid nuclei. Though the histones H_2A and H_2B were markedly different from their vertebrate homologues, the subunit structure of the chromatin is the same. But the length of the repeat unit of DNA in the chromatin, is 177 ± 5 bp for the sipunculid erythrocyte nuclei, close to that reported for the chromatin of some lower eukaryotes.     

Distinguishing rice (Oryza sativa Poaceae) from wild Oryza species through Phytolith analysis: Results of preliminary research

Asian rice is an important grain, not only in its homeland but in many areas of the world. Identifying rice in the archaeological record is a challenge, especially in the moist tropics, where organic materials preserve only when charred. Phytolith analysis, the identification of opaline silica bodies, provides an alternative method for identifying this important crop. Results of our research suggest thatOryza contributes phytoliths that are genus-specific, that bulliform characteristics alone do not permit separation of wild and domesticatedOryza in regions where species overlap, and that a number of phytolith types, especially silicified glumes, show promise for separating wild from domesticated forms. With further research it should be possible to identify rice through its phytolith assemblage in archaeological soils in the heartland of its domestication and use.