Altered expression of the carboxylesterases ES-4 and ES-10 by peroxisome proliferator chemicals.

The nonspecific carboxylesterases (EC.3.1.1.1) are a large group of enzymes that play important roles in the metabolism of foreign xenobiotics and endogenous lipids, including activators of the peroxisome proliferator-activated receptor alpha, a nuclear receptor that is the central mediator of peroxisome proliferator (PP) effects in the rodent liver. A number of reports have demonstrated that PP exposure leads to alterations in levels of carboxylesterases in the liver. In this study, we determined by Western blot analysis whether exposure to diverse PP results in alteration of expression of two highly expressed microsomal carboxylesterases. Chronic exposure to the PP WY-14,643 (WY) and gemfibrozil (GEM), but not di-n-butyl phthalate (DBP), led to decreases in ES-4 in male rat livers. ES-4 was increased in female rat livers treated with GEM. WY exposure led to decreases in ES-10 in male and female rat livers. ES-10 was increased in female rats treated with DBP. Compared with other end points that are altered within days after PP exposure, the downregulation of ES-4 and ES-10 by WY was considerably slower, occurring between 1 and 5 weeks of exposure. Decreased expression of ES-4 was observed at doses of WY or GEM as low as 10 or 8000 ppm, respectively, whereas decreased expression of ES-10 was more resistant to changes by any PP occurring only with WY at doses as low as 50 ppm. After chronic exposure to WY or diethylhexyl phthalate in wild-type mice, kidney, but not liver, expression of ES-4 and ES-10 was downregulated. These decreases in kidney ES expression were not observed in PPARalpha-null mice lacking a functional PPARalpha gene, demonstrating the importance of this transcription factor in these changes. These studies demonstrate that ES protein expression is under complex control by PP that is sex- and compound-dependent. These results lend support to the hypothesis that PP exposure leads to a reprogramming of expression of enzymes important in the metabolism of PPARalpha activators.

Germination, growth rates, and electron microscope analysis of tomato seeds flown on the LDEF.

The purpose of the experiment was to determine cosmic rays long-term effects on living tissue. A batch of tomato seeds were flown in orbit aboard the Long Duration Exposure Facility (LDEF) for almost 6 y. During this time, the seeds received an abundant exposure to cosmic radiation. Upon the return of the LDEF to Earth, the seeds were distributed throughout the United States and 30 foreign countries for analysis. Our university analysis included germination and growth rates as well as scanning electron microscopy (SEM) and X-ray analysis of the control as well as space exposed tomato seeds. In analyzing the seeds under the electron microscope, usual observations were performed on the nutritional and epidermis layer of the seed. These layers appeared to be more porous in the space exposed seeds than on Earth-based control seeds. This unusual characteristic may explain the increases in the space seeds growth pattern. (Several test results showed that the space-exposed seeds germinated sooner than Earth-based seeds. Also, the space-exposed seeds grew at a faster rate.) The porous nutritional region may allow the seeds to receive necessary nutrients and liquids more readily, thus enabling the plant to grow at a faster rate. Roots, leaves and stems were cut into small sections and mounted. After sputter coating the specimens with argon/gold palladium plasma, they were viewed under the electron microscope. Many micrographs were taken. The X-ray analysis displayed possible identifications of calcium, potassium, chlorine, copper, aluminum, silicon, phosphate, carbon, and sometimes sulfur and iron. The highest concentrations were shown in potassium and calcium. As a result of the electron interaction and X-ray production within the open seeds, the traditional layers of the space-exposed seed gave peaks of Mg, P and S, while the Earth seed gave an iron peak, which was not detected in the space-exposed seed because of electron beam positioning difference. The space-exposed seed and the Earth-control seed specimens displayed high concentrations of copper.