Distribution of N-([1-14C]-palmitoyl)ethanolamine in rat tissues

N-([1-14C]-palmitoyl)-ethanolamine distribution was studied in the rat tissues. The following sequence of the label inclusion into tissues by the way of decreasing the radio activity: adrenal > diaphragm > spleen > kidney > testis > lung > liver > heart > brain > plasma > erythrocytes was obtained.     

Metabolism of [1-14C]glyoxylate, [1-14C]-glycollate, [1-14C]glycine and [2-14C]-glycine by homogenates of kidney and liver tissue from hyperoxaluric and control subjects

1. The metabolism of [1-(14)C]glyoxylate to carbon dioxide, glycine, oxalate, serine, formate and glycollate was investigated in hyperoxaluric and control subjects' kidney and liver tissue in vitro. 2. Only glycine and carbon dioxide became significantly labelled with (14)C, and this was less in the hyperoxaluric patients' kidney tissue than in the control tissue. 3. Liver did not show this difference. 4. The metabolism of [1-(14)C]glycollate was also studied in the liver tissue; glyoxylate formation was demonstrated and the formation of (14)CO(2) from this substrate was likewise unimpaired in the hyperoxaluric patients' liver tissue in these experiments. 5. Glycine was not metabolized by human kidney, liver or blood cells under the conditions used. 6. These observations show that glyoxylate metabolism by the kidney is impaired in primary hyperoxaluria.     

Differences in the conversion of the polyunsaturated fatty acids [1-(14)C]22:4(n-6) and [1-(14)C]22:5(n-3) to [(14)C]22:5(n-6) and [(14)C]22:6(n-3) in isolated rat hepatocytes

The reasons why most cellular lipids preferentially accumulate 22:6(n-3) rather than 22:5(n-6) are poorly understood. In the present work the metabolisms of the precursor fatty acids, [1-(14)C]20:4(n-6), [1-(14)C]22:4(n-6) versus [1-(14)C]20:5(n-3), [1-(14)C]22:5(n-3) in isolated rat hepatocytes were compared. The addition of lactate and L-decanoylcarnitine increased the formation of [(14)C]24 fatty acid intermediates and the final products, [(14)C]22:5(n-6) and [(14)C]22:6(n-3). In the absence of lactate and L-decanoylcarnitine, no [(14)C]24 fatty acids and [(14)C]22:5(n-6) were detected when [1-(14)C]22:4(n-6) was the substrate, whereas small amounts of the added [1-(14)C]22:5(n-3) was converted to [(14)C]22:6(n-3). Lactate reduced the oxidation of [1-(14)C]22:4(n-6) and [1-(14)C]22:5(n-3) while L-decanoylcarnitine did not. No significant differences between the total oxidation or esterification of the two substrates were observed. By fasting and fructose refeeding the amounts of [(14)C]24:4(n-6) and [(14)C]24:5(n-3) were increased by 2.5- and 4-fold, respectively. However, the levels of [(14)C]22:5(n-6) and [(14)C]22:6(n-3) were similar in hepatocytes from fasted and refed versus fed rats. With hepatocytes from rats fed a fat free diet the levels of [(14)C]24 fatty acid intermediates were low while the further conversion of the n-6 and n-3 substrates was high and more equal, approx. 33% of [1-(14)C]22:4(n-6) was converted to [(14)C]22:5(n-6) and 43% of [1-(14)C]22:5(n-3) was converted to [(14)C]22:6(n-3). The moderate differences found in the conversion of [1-(14)C]22:4(n-6) versus [1-(14)C]22:5(n-3) to [(14)C]22:5(n-6) and [(14)C]22:6(n-3), respectively, and the equal rates of oxidation of the two substrates could thus not explain the abundance of 22:6(n-3) versus the near absence of 22:5(n-6) in cellular membranes.     

Lactoperoxidase-catalyzed oxidation of [4-14C]estradiol

The conversion of [4-14C]estradiol to water-soluble products by lactoperoxidase (EC 1.11.1.7) in the presence of added or generated H2O2 was studied using albumin or tyrosine as acceptor. The enzyme was able to catalyze the oxidation and binding of estradiol to albumin even in the absence of 2,4-dichlorophenol at very low concentrations of hydrogen peroxide. Other systems in which H2O2 was replaced by oxygen and Mn2+, light-sensitized riboflavin or glutathione was also shown to be active in the conversion of estradiol to water-soluble products and the effect of inhibitors on these reactions was investigated. Possible mechanisms for the peroxidase-catalyzed formation of these estradio metabolites are discussed.     

Bioisosteric replacement of dihydropyrazole of 4S-(-)-3-(4-chlorophenyl)-N-methyl-N'-[(4-chlorophenyl)-sulfonyl]-4-phenyl-4,5-dihydro-1H-pyrazole-1-caboxamidine (SLV-319) a potent CB1 receptor antagonist by imidazole and oxazole

Design, synthesis and conformational analysis of few imidazole and oxazole as bioisosters of 4S-(-)-3-(4-chlorophenyl)-N-methyl-N'-[(4-chlorophenyl)-sulfonyl]-4-phenyl-4,5-dihydro-1H-pyrazole-1-caboxamidine (SLV-319) 2 is reported. Computer assisted conformational analysis gave a direct clue for the loss of CB1 antagonistic activity of the ligands without a fine docking simulation for the homology model.     

Isoprenoid biosynthesis in a marine sponge of the Amphimedon genus: incorporation studies with [1-14C] acetate, [4-14C] cholesterol and [2-14C] mevalonate

1. We present quantitative evidence from incorporation of [1-14C] acetate that the enzymes to synthesise isoprenoids are present in the marine sponge Amphimedon sp. and that efficient carotenoid synthesis takes place. 2. The de novo synthesis of b,b-carotene and (3R,3'R)-zeaxanthin may occur in a chlorophyll a-producing microalgal symbiont with subsequent aromatisation to (3R)-isoagelaxanthin by the sponge itself. 3. Amphimedon sp. contains nuclear-modified sterols derived by modification of conventional dietary sterols.     

Studies on the distribution and metabolism of N-[14C]nitrosopyrrolidine in mice.

Pretreatments with pyrazole, ethanol, nialamide or diethyldithiocarbamate were found to strongly depress the exhalation of 14CO2 and the incorporation of radioactivity in the acid-insoluble fraction of the liver in mice injected with N-[14C]nitrosopyrrolidine. Whole-body autoradiography performed with hemisections of mice at -80 degrees C (to prevent evaporation of the volatile N-nitrosopyrrolidine) and with dry tape-sections (to localize the non-volatile metabolites), using pretreated and non-pretreated mice, indicated a uniform distribution of the non-metabolized N-nitrosopyrrolidine in the tissues. At the shortest survival intervals (1 and 5 min), a high level of metabolites were found in the liver, the tracheo-bronchial and nasal mucosa and Harder's gland, indicating a local formation of metabolits in these tissues. At later survival intervals (0.5--24 h) metabolites were in addition found in tissues with a rapid cell turnover and a high rate of protein synthesis and in brown fat, which probably reflects incorporation of metabolites via normal biosynthetic pathways. Autoradiography of N-[14C]nitrosopyrrolidine in mice given the substance orally resulted in distribution pictures similar to those obtained after i.v. injections.     

Biosynthesis of [14C]zearalenone from [1-14C]acetate by Fusarium roseum 'Gibbosum'.

Addition of [1-14C]acetate or [1,2-14C]acetate to actively growing cultures of Fusarium roseum 'Gibbosum' on rice yielded zearalenone with a specific activity ranging between 1.63 and 46.5 microCi/mmol.     

14C] GABA and [14C]GABA-pantoyl metabolism in mice

It is shown that more than 90% of the labelled substance D-[1-14C] calcium homopantotenate is rapidly removed from the organism with urea; 6-8% are products of its transformation, among them GABA is identified. An insignificant transformation of D-[1-14C] calcium homopantotenate up to 14CO2 is observed. After the preparation administration only unchanged D-[1-14C] calcium homopantotenate was found in the tissues, except of the liver where, as in urea, there is a nonidentified product with small Rf. [1-14C] GABA is rapidly transformed to 14CO2 and only its insignificant part is removed with urea, chiefly as products of transformation.     

Stearoyl[1-14C]sulfogalactosylsphingosine ([14C]sulfatide) as substrate for cerebroside sulfatase assay

A convenient method for large scale preparation of stearoyl[1-¹⁴C]sulfogalactosylsphingosine has been developed. The first step consists in preparing the lysosulfatide intermediate with a good yield, which we have successfully performed. In the second step, the lysoderivative is coupled to [1-¹⁴C]stearic acid through the acyl chloride procedure. The labeled substrate thus synthetized appears to be particularly convenient for cerebroside sulfatase determination, because of the stability of the ¹⁴C isotope, compared to the other isotopes (tritium or ³⁵S) which have been previously used for the same purpose.     

Novel N-[1-(1-substituted 4-piperidinylmethyl)-4-piperidinyl]benzamides as potent colonic prokinetic agents

A series of novel N-[1-(1-substituted 4-piperidinylmethyl)-4-piperidinyl]benzamides was prepared and its compounds were evaluated for their binding to 5-HT(4) receptors and effects on gastrointestinal motility in conscious dogs. 4-Amino-N-[1-[1-(4-aminobutyl)-4-piperidinylmethyl]-4-piperidinyl]-5-chloro-2-methoxybenzamide (15) was found to have a potent binding affinity for 5-HT(4) receptors (IC(50): 6.47nM) and showed excellent colonic prokinetic activity.     

Thermophilic Anaerobic Biodegradation of [14C]Lignin, [14C]Cellulose, and [14C]Lignocellulose Preparations

Thermophilic (55°C) anaerobic enrichment cultures were incubated with [¹⁴C-lignin]lignocellulose, [¹⁴C-polysaccharide]lignocellulose, and kraft [¹⁴C]lignin prepared from slash pine, Pinus elliottii, and ¹⁴C-labeled preparations of synthetic lignin and purified cellulose. Significant but low percentages (2 to 4%) of synthetic and natural pine lignin were recovered as labeled methane and carbon dioxide during 60-day incubations, whereas much greater percentages (13 to 23%) of kraft lignin were recovered as gaseous end products. Percentages of label recovered from lignin-labeled substrates as dissolved degradation products were approximately equal to percentages recovered as gaseous end products. High-pressure liquid chromatographic analyses of CuO oxidation products of sound and degraded pine lignin indicated that no substantial chemical modifications of the remaining lignin polymer, such as demethoxylation and dearomatization, occurred during biodegradation. The polysaccharide components of pine lignocellulose and purified cellulose were relatively rapidly mineralized to methane and carbon dioxide; 31 to 37% of the pine polysaccharides and 56 to 63% of the purified cellulose were recovered as labeled gaseous end products. An additional 10 to 20% of the polysaccharide substrates was recovered as dissolved degradation products. Overall, these results indicate that elevated temperatures can greatly enhance rates of anaerobic degradation of lignin and lignified substrates to methane and low-molecular-weight aromatic compounds.     

Synthesis of [O-methyl-11C]1-(2-chlorophenyl)-5-(4-methoxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide: a potential PET ligand for CB1 receptors

Synthesis and in vitro evaluation of [O-methyl-(11)C]1-(2-chlorophenyl)-5-(4-methoxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide ([(11)C]-1), a potential imaging agent for CB(1) receptors using PET is described. 1-(2-Chlorophenyl)-5-(4-hydroxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide (5), the precursor for radiolabeling, was synthesized from 4-OTBDPS-propiophenone (2) in five steps with 30% overall yield. The reaction of alcohol 5 with [(11)C]MeOTf at 60 degrees C afforded [(11)C]-1 with an average radiochemical yield of 14.5% (EOS) and >2000 Ci/mmol specific activity. The radiotracer was found to selectively label CB(1) receptors in slide-mounted sections of postmortem human brain containing prefrontal cortex as demonstrated by in vitro autoradiography using phosphor imaging.     

In vitro oxidation of [U-14C] palmitate, [1-14C] and [6-14C] glucose in newborn and adult rats and pigs

Studies have been made on the intensity of oxidation of [U-14C]-palmitate, [1-14C]- and [6-14C]-glucose by slices of the liver and skeletal muscles of new-born, 1-day, 5-day and adult Wistar rats and domestic pigs. It was found that the level of 14CO2 production from these substrates is higher in tissues of rats than in those of pigs. At early stages of ontogenesis, in tissues of both species intensive oxidation of glucose is observed together with oxidation of fatty acids. In the course of ontogenetic development, the intensity of glucose utilization significantly decreases, whereas the level of fatty acid catabolism remains relatively unaffected.     

Respiration of 14CO2 by intact animals of various species given l-[1-14C]fucose or d-[1-14C]arabinose

The production of ¹⁴CO₂ from l-[1-¹⁴C]fucose and d-[1-¹⁴C]arabinose has been studied in five mammalian species.Cats, guinea pigs, mice, and rabbits respired about 22% of the label of l[1-¹⁴C]fucose or of d-[1-¹⁴C]arabinose within 6 h after intraperitoneal injection of the sugar. Rats respired only 1.5% of the l-fucose label and 5% of the d-arabinose label in the same time period.Liver homogenates from cat, guinea pig, and rabbit produced significantly more ¹⁴CO₂ from l-[1-¹⁴C]fucose or d-[1-¹⁴C]arabinose than mouse or rat liver homogenates. Unlike those of the other species, guinea pig liver homogenates had very low l-fucose dehydrogenase activity.The results suggest that substantial catabolism of l-fucose and d-arabinose occurs in the tissues of some animal species. Investigators wishing to employ l-fucose as a tracer of glycoprotein metabolism must, therefore, ensure that the species that they employ does not metabolize l-fucose to products interfering with their studies.