Induction of DT-diaphorase by benzo(a)pyrene in rat liver. Relation to the cell cycle.
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Aging↗
Biomedical subjects
F A Hommes
Publications and source records attributed to F A Hommes.
Some biochemical observations on biotin deficiency in the rat as a model for human pyruvate carboxylase deficiency.
Biotin deficiency was induced in newborn rats by feeding pregnant rats a biotin-deficient, avidin-rich diet. Signs typical of biotin deficiency are seen as soon as the young rat develops its fur. Deficiency of pyruvate carboxylase (PC) activity in the brains of the young animals (70%) is higher than has been reported before. The highest PC activity is found in the brain stem of control and biotin-deficient rats. Normally fed rats show, shortly after birth, a maximum in liver PC activity, which is absent in biotin-deficient animals. The biochemical changes observed in these rats seem to indicate that a specific deficiency of PC activity was induced as exemplified by hyperlactatemia and hypoglycemia and the absence of increased plasma concentrations of propionic acid and beta-methylcrotonic acid. This offers the possibility to use biotin deficiency in the rat as an animal model for patients with lactic acidosis in whom PC deficiency has been postulated.
Amino Acids↗
Quantitative analysis of morphological changes in skeletal muscle of the rat after hormone administration.
Thyroxine and cortisone acetate administration of rats of 4--7 days of age is not only accompanied by the induction of the muscle-specific enzyme, creatine kinase, but the hormones also induce morphological changes in the gastrocnemius during this period. Administration of thyroxine to these rats causes a splitting of myofibrils as shown by stereological measurements on electron micrographs. This splitting of myofibrils was not observed upon cortisone acetate administration and when both hormones were given simultaneously. It is suggested that cortisone acetate counteracts the effect of thyroxine. Both thyroxine and cortisone acetate increase the volume percentage taken by the mitochondria at 7 days of age. The effect of the simultaneous injection of both hormones is equal to the sum of the separate effects of these hormones. These changes in volume percentage of the mitochondria were compared with changes in a mitochondrial marker enzyme, i.e. citrate synthase. The difference between the morphological measurements and citrate synthase activity is due to a change in the specific activity of citrate synthase in the mitochondria.
Animals↗
Effect of hormones on the development of creatine kinase activity in rat skeletal muscle.
Various approaches have been used in order to determine whether or not a certain hormone is a stimulus for the development of the muscle-specific enzyme, creatine kinase. Both thyroxine and glucocorticoids can be considered as naturally occurring stimuli for the synthesis of creatine kinase. The maximum increase of creatine kinase activity after stimulation by glucocorticoids (about 25%) occurs between 5 and 7 days after birth. A single injection of thyroxine has virtually no effect during this period. However, when a pretreatment with thyroxine is given, cortisone acetate administration increases creatine kinase activity to about 155%. The effect of cortisone acetate is due to de novo synthesis of creatine kinase. The augmentation of the effect of cortisone acetate by thyroxine is dependent on DNA synthesis. Thyroxine administration apparently causes the formation of more competent muscle cells. The effects of both hormones are age-dependent. Thyroxine and cortisone acetate administration to fetuses can prematurely evoke to MM isoenzyme of creatine kinase. Both hormones probably play a role in the activation of the M gene during embryonic development. Sex hormones are able to influence neither creatine kinase activity nor muscle growth. However, castration of male rats immediately after birth causes an impairment of growth at older ages. The androgen production by the testes immediately after birth seems to be of main importance for body growth development. It can be concluded from these results that creatine kinase in muscle is under multiple hormonal control, just as is observed for a number of enzymes in other tissues.
Adrenalectomy↗
Effect of cyclic nucleotides on weight of gastrocnemius and creatine kinase activity after denervation of muscle in young rats.
Denervation of the gastrocnemius muscle at various stages of development reduces muscle weight and creatine kinase activity. An inverse relationship between the muscle-specific enzyme, creatine kinase, and the lysosomal enzyme, acid phosphatase, was shown. An increased percentage of the BB isoenzyme of creatine kinase is observed after long-term denervation. Apparently the muscle tissue has the ability to regenerate and presumptive myoblasts are formed from satellite cells. When the denervated muscle is treated with dibutyryl-cyclic-GMP administration new muscle tissue has been formed. Similar effects could not be demonstrated with either cyclic AMP or succinylcholine. The higher percentage of the BB isoenzyme after dibutyryl-cyclic-GMP administration supports the theory that presumptive myoblasts are derived from satellite cells. Succinylcholine also causes an increase of the B-type of creatine kinase. It can be concluded that cyclic GMP, generated via the nerve, has an important role in maintaining muscle weight.
Acid Phosphatase↗
2,3-Dihydroxybutane: an unusual compound found in the gaschromatographic analysis of volatile compounds of urine.
2,3-Dihydroxybutane, a compound not observed in normal urines, was identified in the urine of two patients by combined gas chromatography-mass spectrometry. It is suggested, that this 2,3-dihydroxybutane is derived from pyruvate by bacterial metabolism.
Butylene Glycols↗
Adenine nucleotides in foetal rat liver cells. Compartmentation and variation with age.
The digitonin method for the separation of cytosolic and mitochondrial fractions was applied to liver cells isolated from foetal rats. The cytosolic [ATP]/[ADP] ratio approximately doubles during the last 4 days of gestation, whereas the mitochondrial ratio remains constant. In the presence of oligomycin and added glucose, the cytosolic [ATP]/[ADP] ratio does not increase with age, but is still considerably higher than the mitochondrial ratio. Without added glucose, and when the glycogen content of foetal liver is still very low (more than 3 days before birth), the cytosolic [ATP]/[ADP] ratio in the presence of oligomycin becomes very low and equal to the mitochondrial ratio. It is concluded that the increasein the cytosolic [ATP]/[ADP] ratio during the last 4 days of gestation is solely due to enhanced mitochondrial activity in this period. Atractyloside and bongkrekic acid do not influence the O2 consumption, nor the [ATP]/[ADP] ratios in either compartment of foetal liver cells. Respiration of isolated foetal mitochondria, however, is strongly inhibited by both compounds. The implications of these findings are discussed.
Adenosine Diphosphate↗
Studies on ATP: thiamine diphosphate phosphotransferase activity in rat brain.
The experiments described in this paper serve as a contribution to the solution of the discrepancies which exist in the assay of ATP:thiamine diphosphate phosphotransferase activity (EC 2.7.4.15), presently in use as a tool for the diagnosis of Leigh's disease (SNE, subacute necrotizing encephalomyelopathy). The results obtained with this phosphotransferase assay can, in part, be explained by the presence of thiamine triphosphate (ThTP) in the preparation of thiamine diphosphate (ThDP) used as a substrate, by the inhibition by ATP of the ThTP phosphohydrolase activity, present in fractions of rat brain homogenates, and by the stimulation by ThDP of the ATPase activity. When [2(-14)C-thiazole]thiamine was used for the synthesis of [14C]ThTP in fractions of rat brain, it was found that after chromatographic separation of thiamine and its phosphates, 14C radioactivity could be demonstrated in the ThTP fractions, even in the absence of an enzyme source. Probably a complex is formed between [14C]thiamine and a phosphate ester which behaves chromatographically as ThTP. It is concluded that the assay system for the measurement of ThTP synthesis in its present form is, in our hands, not suitable for diagnostic purposes.
Adenosine Triphosphate↗
Non-ketotic hyperglycinemia (NKH): an inborn error of metabolism affecting brain function exclusively.
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Amino Acid Metabolism, Inborn Errors↗
Particulate and free hexokinase in fetal rat liver.
The association of hexokinase with particulate fractions of liver has been studied during the development of the rat. In the fetal rat liver about 50% of the total hexokinase is bound to the mitochondria. This proportion decreases gradually after birth. No association of hexokinase with mitochondria could be demonstrated in the adult rat liver. It is suggested that the binding of hexokinase to the mitochondria is a consequence of a property which is lost during development of the mitochondrial membranes. At least part of the hexokinase is rather tightly bound to the mitochondria. Glucose-6-phosphate or ATP do not solubilize the enzyme. The proportion of hexokinase bound to the mitochondria is independent of the metabolic state of the hepatocyte as exemplified by studies with inhibitors of oxidative phosphorylation, using the digitonin technique for the separation of particulate and cytosol fractions of isolated fetal rat hepatocytes.
Adenosine Triphosphate↗
The development of DT-diaphorase in rat liver and its induction by benzo(a)pyrene.
The development of cytosolic DT-diaphorase--NAD(P)H dehydrogenase, quinone, EC 1.6.99.2--and its induction by benzo(a)pyrene has been studied in rat liver. DT-diaphorase belongs to the late suckling cluster, because the largest increase in activity can be observed 18 days after birth. A considerable activity is present, however, in the neonatal period. The activity of the enzyme can be prematurely induced by benzo(a)pyrene. A lag phase of 10 h can be observed before the activity of DT-diaphorase starts to increase. This increase in activity proved to be sensitive to inhibitors of mixed-function oxydase and RNA and DNA synthesis.
Age Factors↗
A rapid screening test for lactic aciduria.
A rapid test for the determination of lactate in urine is described, which differentiates adequately between normal and elevated urine lactate levels. The method depends on the enzymatic decolourization of the blue dye dichlorophenolindophenol by lactate in the presence of the enzyme L-lactate cytochrome c oxidoreductase (EC 1.1.2.3). Interference by vitamin C is prevented by pre-treatment with charcoal. The test is simple and inexpensive, and a compact testing unit, which is stable and convenient for most laboratories, can be assembled in a glass capillary.
2,6-Dichloroindophenol↗
(2-Ethoxyethoxy)acetic acid: an unusual compound found in the gas chromatographic analysis of urinary organic acids.
An unknown acidic compound was detected in a number of urine samples from patients with a suspected metabolic disorder and some patients treated with chemotherapy. The structure of this compound has been characterized as (2-ethoxyethoxy)acetic acid, using a gas chromatography/mass spectrometry/computer system. The authentic compound was synthesized and compared with the unknown. Urinary (2-ethoxyethoxy)acetic acid is assumed to be formed endogenously from an exogenous precursor, probably 2-(2-ethoxyethoxy)ethanol.
Acetates↗
Studies on the regulation of glycolysis in isolated fetal rat hepatocytes.
The contribution to the glycolytic flux by glycogen breakdown versus glucose phosphorylation has been determined in isolated fetal rat hepatocytes, prepared in different media and subsequently incubated with different glucose concentrations. A high glucose concentration in cells prepared in a medium containing a high concentration of inorganic phosphate decreases the contribution to the glycolytic flux by glycogenolysis to less than 15%. It is suggested that one of the factors which initiate glycogenolysis in the living animal after birth is a lowered blood glucose concentration, independent of hormonal changes. Under conditions where glycogenolysis does not contribute the larger part to the glycolytic flux, the control of glycolysis is shifted from glycogen breakdown to the glucose phosphorylation step and phosphofructokinase.
Animals↗
Early findings of a case of non-ketotic hyperglycinaemia.
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Age Factors↗
Letter: Nonketotic hyperglycinemia with increased propionic acid excretion and hyperammonemia.
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Amino Acid Metabolism, Inborn Errors↗
A case of methylmalonic and propionic acidemia due to methulmalonyl-CoA carbonylmutase apoenzyme deficiency.
A patient presenting with a deep metabolic acidosis after birth is described. Gas chromatographic analysis of short chain fatty acid and non volatile organic acids revealed the presence of both propionic and methylmalonic acid. In plasma obtained immediately after death the propionic- and methylmalonic acid concentrations were measured after separation of both acids by thin layer chromatography. The propionic acid concentration was about 5 mM while the methylmalonic acid concentration was 2.6 mM. The methylmalonic acid concentration in urine was 6.8 mM. Propionyl-CoA carboxylase activity measured in leucocytes and liver-mitochondria revealed normal values (53 pmoles/min/mg protein and 6.5 nmoles/min/mg protein respectively). 2-14C-Methyl-malonate oxydation in intact fibroblasts was totally blocked in the patient's cells. The methylmalonyl-CoA carbonyl mutase activity was found to be absent in the patient's fibroblasts. Addition of vit. B12 coenzyme to the incubation mixture stimulated 14C-succinate formation in the control cells but not in the patient's cells.
Acidosis↗
Two cases of phosphoenolpyruvate carboxykinase deficiency.
Two children are described who suffered from hypoglycemia and liver impairment. Assays of gluconeogenic enzymes in liver samples taken immediately after death demonstrated a deficiency of phosphoenolpyruvate carboxykinase, a key enzyme of gluconeogenesis. Post mortem examination demonstrated massive fat deposition in liver and kidney and to a lesser extent in other tissues. The fatty changes in liver and kidney could be explained by the absence of phosphoenolpyruvate carboxykinase, which would cause an alteration in the mitochondrial-cytosolic processes related to gluconeogenesis.
Fatty Acids↗