Enhancement of long-chain acyl-CoA hydrolase activity in peroxisomes and mitochondria of rat liver by peroxisomal proliferators

The present study has confirmed previous findings of long-chain acyl-CoA hydrolase activities in the mitochondrial and microsomal fractions of the normal rat liver. In addition, experimental evidence is presented in support of a peroxisomal localization of long-chain acyl-CoA hydrolase activity. (a) Analytical differential centrifugation of homogenates from normal rat liver revealed that this activity (using palmitoyl-CoA as the substrate) was also present in a population of particles with an average sedimentation coefficient of 6740 S, characteristic of peroxisomal marker enzymes. (b) The subcellular distribution of the hydrolase activity was greatly affected by administration of the peroxisomal proliferators clofibrate and tiadenol. The specific activity was enhanced in the mitochondrial fraction and in a population of particles with an average sedimentation coefficient of 4400 S, characteristic of peroxisomal marker enzymes. Three populations of particles containing lysosomal marker enzymes were found by analytical differential centrifugation, both in normal and clofibrate-treated rats. Our data do not support the proposal that palmitoyl-CoA hydrolase and acid phosphatase belong to the same subcellular particles. In livers from rats treated with peroxisomal proliferators, the specific activity of palmitoyl-CoA hydrolase was also enhanced in the particle-free supernatant. Evidence is presented that this activity at least in part, is related to the peroxisomal proliferation.     

Influence of dietary status on liver palmitoyl-CoA hydrolase, peroxisomal enzymes, CoASH and long-chain acyl-CoA in rats

In the livers of fasted rats, the activity of mitochondrial palmitoyl-CoA hydrolase was increased whereas the microsomal palmitoyl-CoA hydrolase activity decreased. Refeeding with a high-carbohydrate diet (glucose), the corresponding enzyme activities were decreased while refeeding with a high-fat diet (sheep tallow) increased the enzyme activities over the control values. The increased content of long-chain acyl-CoA and free CoASH under fasting and fat-refeeding was mainly attributed to the mitochondrial fraction with the remainder in the light mitochondrial fraction which contains peroxisomes. The results suggest a correlation of the compartmentation of the palmitoyl-CoA hydrolase and the content and compartmentation of the CoA derivatives in the liver under different nutritional states. The peroxisomal palmitoyl-CoA oxidase activity was increased by fasting. Fat-refeeding increased the activity even more; 1.8-fold as compared to the fasting animals. On the other hand, the activities of other peroxisomal enzymes which are not directly involved in the fatty acid metabolism such as urate oxidase were decreased to approximately the same extent by fasting. Re-feeding with glucose and fat further decreased the corresponding enzyme activity, particularly seen in the glucose-refed group.     

Neurotoxic Effects of Prenatal Trichlorfon Administration in Pigs

Pregnant sows were administered trichlorfon (Neguvon®) during gestation. Examination of the offspring revealed clinical symptoms which included ataxia and tremor. The weights of the cerebrum and the celebellum were significantly reduced (67% and 41% of the control values). There was a clear correlation between the decrease in total brain weight and decrease in cerebellar weight (r = 0.94). Histological examination showed a well preserved lamination of the cerebral and cerebellar cortex. Periodical loss of Purkinje cells was the most notable finding in the cerebellum. The molecular layer in such regions was markedly thinned. Neurochemical investigations of the cerebellum showed a significant decrease in specific activity of the transmitter synthesizing enzymes choline acetyltransferase, glutamate decarboxylase and aromatic amino acid decarboxylase (61.6%, 30.3% and 47.1% of the control values, respectively). No effect in high affinity D-aspartate uptake was observed.     

Heritabilities and quantitative trait loci for blood gases and blood pH in swine

Maintaining pH and blood gases in a narrow range is essential to sustain normal biochemical reactions. Decreased oxygenation, poor tissue perfusion, disturbance to CO₂ expiration, and shortage of HCO₃⁻ can lead to metabolic acidosis. This is a common situation in swine, and originates from a broad range of medical conditions. pH and blood gases appear to be under genetic control, and populations with physiological traits closer to the pathological thresholds may be more susceptible to developing pathological conditions. However, little is known about the genetic basis of such traits. We have therefore estimated phenotypic and genetic variability and identified quantitative trait loci (QTL) for pH and blood gases in blood samples from 139 F₂ pigs from the Meishan/Pietrain family. Samples were taken before and after challenge with Sarcocystis miescheriana , a protozoan parasite of muscle. Twenty-seven QTL influencing pH and blood gases were identified on nine chromosomes. Five of the QTL were significant on a genome-wide level; 22 QTL were significant on a chromosome-wide level. QTL for pH-associated traits have been mapped to SSC3, 18 and X. QTL associated with CO₂ have been detected on SSC6, 7, 8 and 9, and QTL associated with O₂ on SSC2 and SSC8. QTL showed specific health/disease patterns that were related to the physiological state of the pigs from day 0, to acute disease (day 14), convalescence (day 28) and chronic disease (day 42). The results demonstrate that pH and blood gases are influenced by multiple chromosomal areas, each with relatively small effects.     

Acetylcholinesterases of the nematode Steinernema carpocapsae. Characterization of two types of amphiphilic forms differing in their mode of membrane association.

We analyzed the molecular forms of acetylcholinesterase (AChE) in the nematode Steinernema carpocapsae. Two major AChEs are involved in acetylcholine hydrolysis. The first class of AChE is highly sensitive to eserine (IC50 = 0.05 microM). The corresponding molecular forms are: an amphiphilic 14S form converted into a hydrophilic 14.5S form by mild proteolysis and two hydrophilic 12S and 7S forms. Reduction of the amphiphilic 14S form with 10 mM dithiothreitol produces hydrophilic 7S and 4S forms, indicating that it is an oligomer of hydrophilic catalytic subunits linked by disulfide bond(s) to a hydrophobic structural element that confers the amphiphilicity to the complex. Sedimentation coefficients suggest that 4S, 7S, 12S forms correspond to hydrophilic monomer, dimer, tetramer and that the 14S form is also a tetramer linked to one structural element. The second class of AChE is less sensitive to eserine (IC50 = 0.1 mM). Corresponding molecular forms are hydrophilic and amphiphilic 4S forms (monomers) and a major amphiphilic 7S form converted into a hydrophilic dimer by Bacillus thuringiensis phosphatidylinositol-specific phospholipase C. This amphiphilic 7S form thus possesses a glycolipid anchor. It appears that Steinernema (a very primitive invertebrate) presents AChEs with two types of membrane association that closely resemble those described for amphiphilic G2 and G4 forms of AChE in more evolved animals.