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Biomedical subjects

H Schulz

Publications and source records attributed to H Schulz.

At least 343 records · Page 19Linked to original sources
PubMed1986

Gamma-L-glutamyl-taurine (Litoralon) affects conditioned taste aversion in rats.

The dipeptide gamma-L-glutamyl-taurine (Litoralon) reduced neophobia of rats at a dose of 5.0 mg/kg (i.p.) in a "one-bottle forced choice paradigm" for conditioned taste aversion (CTA), but did not significantly affect the rats' "memory" of intoxication following chronic treatment at doses of 0.05, 0.50 and 5.00 mg/kg (i.p.). Acute treatment with Litoralon (10-1000 micrograms/kg, i.p.) did not affect CTA checked in a "two-bottle test", when administered immediately following the unconditioned stimulus (LiCl injection). In contrast, when given 90 min prior to the retention test, the injection of Litoralon (50.0 micrograms/kg) and gamma-aminobutyryl ethanolamine phosphate (100 and 500 micrograms/kg) resulted in a significantly higher intake of saccharin solution by the rats. This effect is comparable to the action of diazepam tested in the same experimental procedure. The results support our hypothesis about the anti-conflict potencies of these dipeptides, exerted by reducing aversion of phobia and/or the anxiety level of the animals in the experimental situation.

Animals↗
PubMed1985

Inhibition of carnitine acetyltransferase by metabolites of 4-pentenoic acid.

The inhibition of carnitine acetyltransferase (EC 2.3.1.7) by metabolites of 4-pentenoic acid was studied. 3-Keto-4-pentenoyl-CoA, a beta-oxidation metabolite of 4-pentenoic acid, was found to be an effective inhibitor of the enzyme in the presence, but not in the absence of L-carnitine. Since acetyl-CoA protects the enzyme against this inhibition, 3-keto-4-pentenoyl-CoA seems to be an active site-directed inhibitor. 3-Keto-4-pentenoyl-CoA, which is a substrate of carnitine acetyltransferase, causes the irreversible inactivation of the enzyme. All observations together lead to the suggestion that 3-keto-4-pentenoyl-CoA is a mechanism-based inhibitor of carnitine acetyltransferase.

Acetyltransferases↗
PubMed1985

Mitochondrial metabolism of 3-mercaptopropionic acid. Chemical synthesis of 3-mercaptopropionyl coenzyme A and some of its S-acyl derivatives.

The metabolism of 3-mercaptopropionic acid in mitochondria was studied by use of purified mitochondrial enzymes and rat heart mitochondria. Metabolites of 3-mercaptopropionic acid were separated by high performance liquid chromatography and identified by comparing them with chemically synthesized derivatives of 3-mercaptopropionic acid. The initial step in the metabolism of 3-mercaptopropionic acid is its conversion to a CoA thioester, most likely catalyzed by medium-chain acyl-CoA synthetase. The resulting 3-mercaptopropionyl-CoA is a poor substrate of acyl-CoA dehydrogenase but substitutes effectively for CoASH in reactions catalyzed by 3-ketoacyl-CoA thiolase and acetoacetyl-CoA thiolase. S-Acyl-3-mercaptopropionyl-CoA thioesters formed in the thiolase-catalyzed reactions are not at all or only poorly acted upon by acyl-CoA dehydrogenases. However, they are hydrolyzed by thioesterase(s) to CoASH and S-acyl-3-mercaptopropionic acid. The hydrolysis of S-acyl-3-mercaptopropionyl-CoA thioesters proceeds more rapidly than the hydrolysis of fatty acyl-CoA thioesters of comparable chain lengths. Free CoASH is also regenerated from S-acetyl-3-mercaptopropionyl-CoA and more rapidly from 3-mercaptopropionyl-CoA as a result of their reactions with carnitine catalyzed by carnitine acetyltransferase. These findings lead to the suggestion that the major mitochondrial CoA-containing metabolites of 3-mercaptopropionic acid are S-acyl-3-mercaptopropionyl-CoA thioesters.

3-Mercaptopropionic Acid↗
PubMed1985

3-Mercaptopropionic acid, a potent inhibitor of fatty acid oxidation in rat heart mitochondria.

The effects of several short-chain mercapto acids on the rate of respiration supported by either palmitoylcarnitine, octanoate, or pyruvate was studied with coupled rat heart mitochondria. 3-Mercaptopropionic acid was found to be a potent inhibitor of respiration sustained by palmitoylcarnitine or octanoate, whereas under identical conditions respiration with pyruvate as a substrate was unaffected. 2-Mercaptoacetic acid also inhibits palmitoylcarnitine-supported respiration, but only at much higher concentrations of the inhibitor. 2-Mercaptopropionic acid has virtually no effect. Incubation of mitochondria with 3-mercaptopropionic acid did not cause the irreversible inactivation of any beta-oxidation enzyme. Since 3-mercaptopropionic acid did not inhibit beta-oxidation in uncoupled mitochondria, it appears that this compound must first be metabolized in an energy-dependent reaction before it becomes inhibitory. 3-Mercaptopropionyl-CoA and three of its S-acyl derivatives, all of which are likely mitochondrial metabolites of 3-mercaptopropionic acid, were tested for their capacity to inhibit the individual enzymes of beta-oxidation. 3-Mercaptopropionyl-CoA inhibits only acyl-CoA dehydrogenase, whereas S-myristoyl-3-mercaptopropionyl-CoA inhibits reversibly several beta-oxidation enzymes. All observations together lead us to suggest that the inhibition of beta-oxidation by 3-mercaptopropionic acid in coupled rat heart mitochondria is most likely a consequence of the reversible inhibition of acyl-CoA dehydrogenase by long-chain S-acyl-3-mercaptopropionyl-CoA thioesters and possibly by 3-mercaptopropionyl-CoA.

3-Mercaptopropionic Acid↗
PubMed1985

3-Hydroxyacyl-CoA epimerase is a peroxisomal enzyme and therefore not involved in mitochondrial fatty acid oxidation.

The subcellular location of 3-hydroxyacyl-CoA epimerase (EC 5.1.2.3) was studied by differential centrifugation and Percoll density gradient centrifugation of a rat liver homogenate. The enzyme was found to be associated with peroxisomes but not with mitochondria. This observation proves that 3-hydroxy-acyl-CoA epimerase does not function in mitochondrial beta-oxidation of polyunsaturated fatty acids which are degraded by a modified pathway.

Animals↗
PubMed1985

Channeling of a beta-oxidation intermediate on the large subunit of the fatty acid oxidation complex from Escherichia coli.

The kinetic properties of the fatty acid oxidation complex from Escherichia coli were studied with the aim of elucidating the functional consequence of having enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase associated with a multifunctional polypeptide. The kinetic parameters of individual enzymes were determined and used in model calculations based on a published theory (Storer, A. C., and Cornish-Bowden, A. (1974) Biochem. J. 141, 205-209) to predict the kinetic behavior of a system of functionally unlinked enzymes. The validity of the theory for making these calculations was proven by demonstrating a good agreement between the calculated and observed rates of intermediate and product formation for the conversion of 2-decenoyl-CoA to 3-ketodecanoyl-CoA catalyzed by a mixture of bovine liver enoyl-CoA hydratase and pig heart L-3-hydroxyacyl-CoA dehydrogenase. The conversion of 2-decenoyl-CoA to 3-ketodecanoyl-CoA catalyzed by the sequential action of the hydratase and dehydrogenase of the complex from E. coli was determined by measuring the rate of NADH formation. Stopped-flow measurements showed the rate of NADH formation to be linear without any lag period. When the initial velocity of the hydratase was 10.2 microM min-1, that of the overall reaction was 8.41 microM min-1. In contrast, the results calculated by use of the Storer and Cornish-Bowden equation for a system of unlinked enzymes predicted the overall reaction to exhibit a lag time of 30 s and to result in the accumulation of 2.1 microM 3-hydroxydecanoyl-CoA before reaching a velocity corresponding to 82.5% of that of the hydratase reaction. The high initial rate and the unusual kinetic properties of the overall reaction observed in the present study are best explained by a channeling mechanism on the large subunit of the E. coli fatty acid oxidation complex. When the apparent degree of channeling is corrected for the percentage of the dehydrogenase active sites saturated with NAD+, more than 90% of the intermediate appears to be transferred directly from the active site of enoyl-CoA hydratase to that of 3-hydroxyacyl-CoA dehydrogenase.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1985

Spontaneous awakening from sleep in infants.

Spontaneous awakenings from sleep were studied in a group of 20 infants whose sleep-waking patterns were recorded polygraphically for 24 h. While 10 infants were orally fed the other 10 underwent continuous feeding for various gastrointestinal diseases. Spontaneous awakening from sleep was analysed with regard to the prior sleep state, age and feeding condition. Infants awoke preferentially out of REM sleep and less often out of non-REM sleep. The feeding condition had no significant influence on the distribution of awakenings. The propensity for REM awakenings was significantly greater than would have been expected according to the REM sleep amount. This tendency was more pronounced for younger (less than or equal to 3 months) than for older (greater than or equal to 4 months) infants. REM sleep episodes which were interrupted by awakenings were significantly shorter than uninterrupted ones, since awakenings occurred predominantly shortly after REM sleep onset. It is proposed that the specific pattern of brain activity during REM sleep facilitates the transition from sleep into the waking state, particularly in the youngest infants.

Brain↗
PubMed1985

On the origin of early REM episodes in the sleep of depressed patients: a comparison of three hypotheses.

Shortened latency of rapid eye movement (REM) sleep is a feature frequently observed in depressed patients. Three hypotheses on the origin of early REM sleep episodes propose that short REM latency is due to (1) a phase-shift of one subset of the circadian rhythms relative to other circadian rhythms, (2) a loss of inhibition of REM sleep due to a slow wave sleep deficit, or (3) a reduction in amplitude of a putative circadian arousal cycle. From an analysis of experimental data, it is concluded that the hypothesis of a reduced circadian amplitude best explains the early occurrence of REM sleep.

Arousal↗
PubMed1985

Effects of Litoralon (gamma-L-glutamyl-taurine) and its analogues on fear-motivated behaviour of rats.

The effects of a single post-trial intraperitoneal administration of the dipeptide Litoralon (gamma-L-glutamyl-taurine) and some of its analogues were tested on the passive avoidance latency of male and female Wistar rats. The avoidance latency was significantly decreased by Litoralon and gamma-aminobutyryl-ethanolamine phosphate but lengthened by DL-beta-aminoisobutyryl-ethanolamine phosphate. No differences were observed between the responses of immature male and female rats following Litoralon treatment. The observed inter-group differences in passive avoidance behaviour following dipeptide administration were also demonstrable in tests of the open-field activity of the animals examined immediately after the 24-hour retention test. The results are discussed on the basis of a central Litoralon effect on emotional arousal and the anti-conflict potencies of the dipeptide.

Animals↗
PubMed1984

Fatty acid binding protein from rat heart. The fatty acid binding proteins from rat heart and liver are different proteins.

The binding of [3H]oleic acid and [3H]palmitic acid to the low molecular weight fatty acid binding proteins present in the cytosols of rat liver and heart was studied. Both fatty acids were bound by Z protein of liver, whereas only oleic acid was bound by the fraction of heart that contains the fatty acid binding protein. However, after delipidation of heart cytosolic proteins with butanol, the binding of palmitic acid to the fatty acid binding protein was detected. In contrast to a published report (Gloster, J., and Harris, P. (1977) Biochem. Biophys. Res. Commun. 74, 506-513), oleic acid was not bound by rat heart or bovine heart myoglobin. Both rat heart fatty acid binding protein and rat liver Z protein were purified to homogeneity or near homogeneity. On polyacrylamide gel electrophoresis under nondenaturing conditions, liver Z protein gave rise to three bands, none of which was identical with the single band due to heart fatty acid binding protein. Rabbit antibodies to rat liver Z protein were used to demonstrate that the purified fatty acid binding protein from rat liver (Z protein) and rat heart are immunologically unrelated and that no Z protein is present in rat heart cytosol. Taken together, these observations lead to the conclusion that the low molecular weight fatty acid binding proteins from rat liver and heart are different proteins.

Animals↗
PubMed1984

The activity of 3-hydroxyacyl-CoA epimerase is insufficient to account for the rate of linoleate oxidation in rat heart mitochondria. Evidence for a modified pathway of linoleate degradation.

The activities of cis-delta 3-trans-delta 2-enoyl-CoA isomerase (EC 5.3.3.8), 3-hydroxyacyl-CoA epimerase (EC 5.1.2.3), and 2,4-dienoyl-CoA reductase, all of which have been proposed to function as auxiliary enzymes in the beta-oxidation of polyunsaturated fatty acids, have been determined in mitochondria from rat heart and rat liver. In heart mitochondria the activity of 3-hydroxyacyl-CoA epimerase was lower, whereas that of 2,4-dineoyl-CoA reductase was higher than the observed rate of linoleate degration. This observation suggests that 2,4-dienoyl-CoA reductase and not 3-hydroxyacyl-CoA epimerase functions as an auxiliary enzyme in the metabolism of polyunsaturated fatty acids in heart. A modified pathway of linoleate degradation is presented.

Acyl Coenzyme A↗
PubMed1984

[Determination of the tocopherol content of the nonsaponifiable fraction of lupine oil (L. mutabilis)].

The content of individual tocopherols was determined in 11 samples of lupine oil (L. mutabilis) from Peru by GC- and HPLC-procedures. The main component is gamma-tocopherol (42-69 mg/100 g oil); alpha- and delta-tocopherol were found in traces (0.1-0.7 mg/100 g oil). The pretreatment of samples, necessary for the GC-methods leads to tocopherol losses of 30% on average, this loss is mainly caused by the saponification of the samples. The tocopherols are predominantly present in an unesterified state.

Chromatography, Gas↗
PubMed1984

The structure of wakefulness and its relationship to daytime sleep in narcoleptic patients.

Seven patients with narcolepsy-cataplexy were continuously monitored during the day using polygraphy and videotape recording. The patients were free to do whatever they wanted while confined to a sitting-at-a-table situation. Daytime activity was evaluated by distinguishing between two polygraphically defined states, namely active wakefulness and quiet wakefulness. The data from the patients were compared with those from 7 normal subjects who were studied under the same experimental conditions. While all patients had recurrent daytime sleep episodes, none of the controls napped during the recording period. The narcoleptic patients showed an altered structure of wakefulness: they spent more of their time awake in the state of active wakefulness and less in quiet wakefulness than the control subjects. Moreover, the patients remained in the quiet state for shorter periods. Daytime sleep selectively diminished the state of quiet wakefulness, whereas it did not affect the amount of time spent in active wakefulness. In addition, in 3 patients there was a clear-cut alternation of periods of sustained wakefulness and transitional phases with a mixture of sleep and wakefulness which occurred rather regularly, suggesting an ultradian cycle of sleepiness.

Adult↗
PubMed1983

The large subunit of the fatty acid oxidation complex from Escherichia coli is a multifunctional polypeptide. Evidence for the existence of a fatty acid oxidation operon (fad AB) in Escherichia coli.

The subunit locations of the five enzymes associated with the fatty acid oxidation complex from Escherichia coli were studied by immunotitration and chemical modification. Antibodies raised against the purified complex caused the parallel inhibitions of enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase, while slightly stimulating 3-ketoacyl-CoA thiolase. All five component enzymes of the complex were inactivated by treatment with iodoacetamide. The inactivation of 3-ketoacyl-CoA thiolase was rapid, whereas the four other enzymes were inactivated at much slower, but almost equal rates. All enzymes except for 3-ketoacyl-CoA thiolase were protected against this inactivation by either NADH or crotonyl-CoA. The reaction of iodo[1-14C]acetamide with the complex in the presence and absence of NADH resulted in the differential labeling of the large subunit only. These observations together with published results (Pawar, S., and Schulz, H. (1981) J. Biol. Chem. 256, 3894-3899) lead to the suggestion that enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, cis-delta 3-trans-delta 2-enoyl-CoA isomerase, and 3-hydroxyacyl-CoA epimerase are located on the 78,000-Da subunit, whereas 3-ketoacyl-CoA thiolase is associated with the 42,000-Da subunit. Additionally, this study provides further evidence for the existence of a fatty acid oxidation (fad AB) operon that codes for the multienzyme complex of fatty acid oxidation and that is located at 85 min on the E. coli chromosome.

3-Hydroxyacyl CoA Dehydrogenases↗