Studies on lipogenesis in vivo: Comparison of cholesterol and fatty acid synthesis in rats and mice

1. The importance of fatty acid synthesis as a pathway for the disposal of ingested glucose has been evaluated in rats and mice given a purified diet high in glucose and low in fat. [U-¹⁴C]Glucose was either added to the diet and fed for 24hr. or given by stomach tube as a 250mg. (mice) or 1000mg. (rats) meal. The two methods of isotope administration gave similar results. 2. Under the conditions employed fatty acid synthesis appeared to be a more important pathway for glucose disposal in mice than in rats. In mice 15·3% of ingested [U-¹⁴C]glucose was converted into fatty acid and in rats the corresponding value was 8·6%. In contrast, the conversion of [U-¹⁴C]glucose into cholesterol, as a percentage of dose, was twice as high in rats as in mice. 3. The effect of 20% of corn oil in the diet on the conversion of dietary [U-¹⁴C]glucose into fat was also investigated. Mice given diets containing 1% or 20% of corn oil converted 14·6% or 7·0% respectively of dietary [U-¹⁴C]glucose into fatty acid over a 24hr. period. There was no effect of fat on the incorporation of the isotope into cholesterol. 4. In mice given diets containing 1% or 20% of corn oil approx. 10% and 2% respectively of newly synthesized fatty acids were found in the liver. Hepatic fatty acid synthesis appears to be more sensitive to dietary fat than is extrahepatic synthesis.     

Studies on lipogenesis in vivo: Fatty acid and cholesterol synthesis in hyperglycaemic-obese mice

1. Lipogenesis has been studied in intact genetically obese mice by measuring the incorporation of a single oral dose of 250mg. of [U-¹⁴C]glucose into fatty acid and cholesterol in the liver and extrahepatic tissues. Studies were also carried out with [U-¹⁴C]glucose added to the diet and fed for 24hr. With either method of isotope administration, the conversion of [U-¹⁴C]glucose into fatty acid was greatly elevated in the livers of the obese mice. In contrast, conversion of the single dose of [¹⁴C]glucose into fatty acid in extrahepatic tissues of obese mice was only half that occurring in the non-obese litter mates. When [¹⁴C]glucose was given in the diet for 24hr. the total accumulation of labelled fatty acid in extrahepatic tissues of obese mice was slightly less than in the non-obese. Uptake of labelled glucose and conversion into fatty acid in adipose tissue of the obese mice decreased with age. 2. Conversion of the single dose of [¹⁴C]glucose into liver cholesterol was comparable in obese and non-obese mice fed on a purified low-fat diet. However, obese mice given this diet for 12 weeks accumulated 1·54% of cholesterol in the liver compared with 0·29% in the non-obese litter mates. This accumulation apparently resulted from a decrease in removal of cholesterol from the liver, rather than an increased synthesis. 3. Conversion of the single dose of [¹⁴C]glucose into extrahepatic fatty acid was decreased by 18hr. starvation proportionally as much in obese as in non-obese mice. The decrease in liver fatty acid synthesis caused by starvation also was considerable in obese mice, although somewhat less marked than in the non-obese. 4. The metabolic derangements in the liver could be more fundamental to the development of the obesity than the changes seen in extrahepatic tissues.     

Calcium activation of mougeotia potassium channels

Phytochrome mediates chloroplast movement in the alga Mougeotia, possibly via changes in cytosolic calcium. It is known to regulate a calcium-activated potassium channel in the algal plasma membrane. As part of a characterization of the potassium channel, we examined the properties of calcium activation. The calcium ionophore A23187 activates the channel at external [Ca(2+)] as low as 20 micromolar. However, external [Ca(2+)] is not required for activation of the channel by photoactivated phytochrome. Furthermore, when an inhibitor of calcium release from internal stores, 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate, hydrochloride (TMB-8), is present, red light no longer stimulates channel activity. We conclude that phytochrome activates the plasma membrane potassium channel by releasing calcium from intracellular calcium vesicles; the elevated cytosolic calcium then stimulates channel activity by an unknown mechanism. In the presence of TMB-8, red light does induce chloroplast rotation; thus, potassium channel activation may not be coupled to chloroplast rotation.     

Brassica S-Proteins Accumulate in the Intercellular Matrix along the Path of Pollen Tubes in Transgenic Tobacco Pistils

A tobacco plant transformed with a Brassica oleracea SLG-22 gene was analyzed by immunocytochemical methods to determine the localization of the transgene-encoded protein product. Immunolabeling was observed in the pistil along the path followed by pollen tubes after pollination. S-antigen accumulated in the intercellular matrix of the transmitting tissue of the style and its continuation in the basal portion of the stigma and outside a few special cells of the placental epidermis of the ovary. This pattern of S-antigen distribution closely resembles that described for the S-associated glycoproteins of self-incompatible Nicotiana alata and differs from its distribution in B. oleracea.     

Development of persistent ovarian follicles during synchronization of estrus influences the superovulatory response to FSH treatment in cattle

The synchronization of estrus with synthetic progestins or progesterone (P(4)) results in the development of a large, persistent ovarian follicle. The objectives of the present study were to determine if development of a persistent ovarian follicle during synchronization of estrus suppresses recruitment of additional follicles during FSH treatment. On Day 5 of the estrous cycle (estrus = Day 0), beef cows were treated with 0.5 or 2.0 P(4) releasing intravaginal devices (PRIDs) for 8 d (Experiment 1, n = 20), 5 or 2 d (Experiment 2, n = 44) before initiation of FSH treatment. Prostaglandin F(2alpha) (25 mg) was administered on Days 5 and 6. Superovulation was induced with 24 mg of recombinant bovine FSH (rbFSH, Experiment 1) or 28 mg of FSH-P (Experiment 2) over a 3- or 4-d period, respectively. The PRIDs were removed concurrently with the 5th injection of rbFSH or FSH-P. There was a treatment-by-day interaction (P < 0.001) for the concentration of 17beta-estradiol in cows treated for 8, 5 or 2 d before FSH treatment. In Experiment 1, FSH treatment initiated 8 d after insertion of a 0.5 PRID did not affect the number of CL (6.9 +/- 1.4 vs 6.7 +/- 1.6), ova/embryos (3.7 +/-1.3 vs 3.0 +/- 1.3) and transferable embryos (2.4 +/- 0.9 vs 3.0 +/- 0.9) compared with that of the 2.0 PRIDs. In Experiment 2, FSH treatment initiated 5 d after insertion of a 0.5 PRID decreased the number of CL (4.0 +/- 0.5 vs 8.3 +/- 0.8; P < 0.001), ova/embryos (3.0 +/- 0.6 vs 5.9 +/- 1.2; P < 0.03) and transferable embryos (2.3 +/- 0.6 vs 5.1 +/- 1.0; P < 0.03) compared with that of a 2.0 PRID, respectively. Initiation of FSH treatment 2 d after insertion of a 0.5 PRID compared with a 2.0 PRID had no affect on the number of CL (8.0 +/- 2.1 vs 8.7 +/- 1.2), total ova (4.8 +/- 1.4 vs 6.9 +/- 1.4) and transferable embryos (2.9 +/- 1.2 vs 6.1 +/- 1.7). In conclusion, treatment with low doses of P(4) (0.5 PRID) for 5 d but not for 2 or 8 d before initiation of FSH treatment results in the development of a dominant ovarian follicle, which reduces recruitment of ovarian follicles, and the number of CL, total ova and transferable embryos.     

Characterization of compost biofiltration system degrading dichloromethane

The effects of acclimatization of microbial populations, compound concentration, and media pH on the biodegradation of low concentration dichloromethane emissions in biofiltration systems was evaluated. Greater than 98% removal efficiency was achieved for dichloromethane at superficial velocities from 1 to 1.5 m(3)/m(3). min (reactor residence times of 1 and 0.7 min, respectively) and inlet concentrations of 3 and 50 ppm Although acclimatization of microbial populations to toluene occurred within 2 weeks of operation start-up, initial dichloromethane acclimatization took place over a period of 10 weeks. This period was shortened to 10 days when a laboratory grown consortium of dichloromethane degrading organism, isolated from a previously acclimatized column, was introduced into fresh biofilter media. The mixed culture consisted to 12 members, which together were able to degrade dichloromethane at concentrations up to 500 mg/L. Only one member of the consortium was able to degrade dichloromethane were sustained for more than 4 months in a biofilter column receiving an inlet gas stream with 3 ppm(v) of dichloromethane acidification of the column and resulting decline in performance occurred when a 50-ppm(v) inlet concentration was used. A biofilm model incorporating first order biodegradation kinetics provided a good fit to observed concentration profiles, and may prove to be a useful tool for designing biofiltration systems for low concentration VOC emissions. (c) 1994 John Wiley & Sons, Inc.     

Biphasic Stimulation of Translational Activity Correlates with Induction of Translation Elongation Factor 1 Subunit [alpha] upon Wounding in Potato Tubers

Potato (Solanum tuberosum) tubers exhibit an increase in translational activity in response to mechanical wounding. The response is biphasic, with an initial stimulation apparent within the first 2 h after wounding and a second increase occurring 12 to 24 h after wounding. Increased activity is apparent by measurement of protein synthesis both in vivo and in vitro using a cell-free extract. Accumulation of the translational elongation factor 1 subunit [alpha] (EF-1[alpha]) parallels translational activity. Changes in the steady-state level of EF-1[alpha] mRNA, and expression of a chimeric EF-1[alpha] promoter/[beta]-glucuronidase construct in transgenic potato tubers, indicate that the gene encoding EF-1[alpha] is transcribed during both periods of translational stimulation. These results indicate that stimulation of translational activity is coordinated with increased expression and accumulation of translation factors.     

A three-phase pattern in growth, monoclonal antibody production, and metabolite exchange in a hybridoma bioreactor culture

The use of partial cubic spline data interpolation for the calculation of volumetric metabolite exchange rates suggested the existence of three distinct metabolic phases during bioreactor culture of a hybridoma cell line. During phase 1, a rapid amino acid uptake rate and ammonia release rate were observed. The growth rate was low and glutamine synthetase activity fell. In phase 2, maximum growth rate and minimum glutamine assimilation and ammonium production rates were observed. Attempts to corroborate the apparent ammonia assimilation in this phase using (15)NH(4)Cl resulted in low incorporation rates into alanine and glutamine. Maximum glutamine synthetase activity took place during this period. Maximum antibody production rate was observed during phase 3 during which peaks in glutamine assimilation, ammonia release, and glutamine synthetase activity were observed. The apparent existence of the three phases prompted us to carry out Northern blot analysis of glutamine synthetase RNA at appropriate times during the process. This revealed a pattern of appearance and dis-appearance of mRNA consistent with the three phases indicated by the fermentation parameters. (c) 1993 John Wiley & Sons, Inc.