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Biomedical subjects

F J Hird

Publications and source records attributed to F J Hird.

At least 19 recordsLinked to original sources
PubMed1986

The importance of arginine in evolution.

The special chemistry and metabolism of arginine has been considered in relation to the evolution of metabolic and structural features of animals. Arginine and compounds derived from it act in muscle as a major reserve of ATP and as a regulatory sink for phosphate. The metabolism of arginine in less complex animals has been extended to produce urea, firstly as an osmotic regulator and subsequently as a means for terrestrial animals to excrete surplus nitrogen. The ornithine component of arginine is metabolised to form important polyamines and also proline. It is also argued that the change from phosphoarginine to phosphocreatine was a permissive step in the development of the vertebrates which are rich in connective tissue.

Adenosine Triphosphate↗
PubMed1986

The oxidation of proline by mitochondrial preparations.

The oxidation by mitochondria of various rat tissues of proline, pyrroline-5-carboxylate (P5C) and a number of aldehydes has been studied and ADP/O ratios determined for liver mitochondria. High oxidative activity for proline and P5C was found only in the liver and kidney. During the oxidation by liver and kidney mitochondria of proline and P5C; glutamate, ammonia, aspartate and some ornithine accumulated, thus suggesting that proline may normally be converted to ornithine by mitochondria. The oxidation of P5C (glutamic acid semialdehyde) by a mitochondrial dehydrogenase may be the same enzyme that oxidizes succinic acid semi-aldehyde but different from that oxidizing acetaldehyde.

Aldehyde Dehydrogenase↗
PubMed1986

The collagen content of selected animals.

The collagen contents of a selected group of animals have been determined and considered in relation to a hypothesis that animals which changed from phosphoarginine to other phosphagens had a selective advantage in converting arginine to proline for the synthesis of connective tissue.

Animals↗
PubMed1986

Investigations on the origin and metabolism of the carbon skeleton of ornithine, arginine and proline in selected animals.

The origin and metabolism of the carbon skeletons of the amino acids ornithine and arginine have been investigated in selected animals--an earthworm, an edible mollusc, a starfish, a sea-squirt, a freshwater crustacean and a rat. Only in the rat and microorganisms of sea water was any evidence obtained for the conversion of glutamate (or N-acetylglutamate) to ornithine. Apart from the crustacean, the other animals were able to synthesise the amidine moiety of arginine. All animals were able to hydrolyse (arginase) the amidine moiety from arginine and had the enzymic capacity to convert ornithine to proline. All the animals had some enzymic ability to oxidise proline to pyrroline-5-carboxylic acid. The crustacean (Cherax destructor) was able to conserve the high concentrations of arginine in its tail muscles during fasting. The hypothesis is put forward that, as arginine appears to be an essential amino acid in the diet of this animal, its demonstrated cannibalism is, among other things, a way of supplementing dietary arginine. The results are discussed in relation to the evolution of different phosphagens derived from arginine.

Animals↗
PubMed1985

Studies on phosphagen synthesis by mitochondrial preparations.

Mitochondrial preparations from muscles of a crab (Cancer pagurus), two fish (Trachurus trachurus and Scyliorhinus canicula) and a bird (Columba livia) are able to synthesise, through ATP, the phosphagen related to that species. This indicates the presence of a bound phosphagen kinase. Addition of creatine kinase and creatine to crab mitochondria results in the synthesis of phosphocreatine. Similarly, the addition of arginine kinase and arginine to mitochondrial preparations from the fish and bird results in the synthesis of phosphoarginine. In the crab, the mitochondrial form of arginine kinase released by sonication had the same kinetic affinity constants and electrophoretic mobility and could not be distinguished immunologically from the cytosolic form. The close similarity of bound and cytosolic forms of arginine kinase in this crustacean suggests that the two forms have not evolved separately as has creatine kinase in the mammal.

Adenosine Triphosphate↗
PubMed1983

Synthesis of phosphocreatine and phosphoarginine by mitochondria from various sources.

Mitochondria from heart, skeletal muscle and the liver of the rat have been shown to synthesise phosphoarginine through ATP if supplied with arginine and lobster arginine kinase. Liver mitochondria have been shown to synthesise phosphocreatine through ATP with the aid of the cytosolic isomer of creatine kinase. Mitochondria prepared from muscles of a crustacean, a fish and a bird have been shown oxidatively to synthesise phosphocreatine (crustacean) and phosphoarginine (fish and bird) provided they are supplied with the appropriate kinase and catalytic amounts of ATP. Within one second of the addition of either cytosolic kinases, mitochondria from skeletal muscle and liver begin a steady state synthesis of phosphoarginine or phosphocreatine. The results suggest that, with respect to phosphagen synthesis, the addition of the cytosolic enzymes can substitute for the mitochondrial enzyme. It is difficult therefore to accept a special vectorial function for the bound mitochondrial enzyme at the biological concentrations of ATP and the cytosolic enzymes normally associated with phosphagen synthesis.

Animals↗
PubMed1983

On the possible significance of the transamidination reaction in evolution.

The origin of the various muscle phosphagens during evolution is considered in the context of the need to conserve ornithine for the synthesis of proline for connective tissue necessary for structural strength and flexibility and/or a complicated musculature. In each phosphagen, arginine is known to have contributed its amidine moiety thus maintaining the function of the phosphagen and setting free the proline precursor ornithine. Tissues from an earthworm, a starfish and a sea-squirt have been found to contain the enzymes arginase, ornithine aminotransferase and pyrroline-5-carboxylate reductase which are necessary to convert arginine to proline. For each of the animals studied analysis for the relevant free amino acids and for the characteristic amino acids (Pro, Oh-Pro, Oh-Lys, Gly) of collagen are presented. The amino acid composition of the diet of the sea-squirt Pyura stolonifera and of the starfish Coscinasterias calamaria is presented along with the level of the phosphagen kinases of the animals studied. The significance of the experimental results is discussed in connection with the importance of the transamidination reaction.

Amino Acids↗
PubMed1978

Comparative aspects of aminotransferases in the rat, pigeon and rainbow trout.

1. The activities of aminotransferases catalysing the transfer of amino groups from aspartate, alanine and leucine to 2-oxoglutarate in different tissues of the rat, pigeon and trout have been determined. 2. Alanine-2-oxoglutarate aminotransferase was high in the liver of the rat and trout and low in that of the pigeon. 3. Aspartate-2-oxoglutarate aminotransferase was usually the dominant aminotransferase in all tissues and was highest in oxidative tissues where the TCA cycle is active. Its activity in the various livers is not correlated with the function of aspartate in nitrogen excretion. 4. The activity of aspartate-2-oxoglutarate aminotransferase in oxidative tissues argues that aspartate in conjunction with this enzyme serves as a buffer of oxaloacetate to keep the TCA cycle running and/or to mediate the transfer of reducing equivalents across mitochondrial membranes.

Animals↗
PubMed1978

Comparative aspects of adenylic acid deaminase and aspartate-2-oxoglutarate aminotransferase.

1. The content of adenylic acid deaminase and of aspartate-2-oxoglutarate aminotransferase of skeletal muscle tissue from a variety of animals has been determined. 2. White (fast) muscle contained large amounts of adenylic acid deaminase and red (slow) muscle contained large amounts of aspartate aminotransferase. There was a general inverse relationship between the adenylic acid deaminase and the aspartate aminotransferase content of muscles from various vertebrates. Thus, there is no simple correlation between the capacity to produce inosinic acid and ammonia from adenylic acid and the capacity to catalyse the formation of aspartate for conversion of inosinic acid back to adenylic acid. 3. The absence of adenylic acid deaminase from the tail muscles of the yabbie and other invertebrates indicates a marked difference in the Animal Kingdom.

AMP Deaminase↗
PubMed1977

Gluconeogenesis in vertebrate livers.

1. The hypothesis is advanced that it would be logical for a tissue (liver) to evolve as a gluconeogenic organ in order to recover the lactate produced as a result of rapid and sustained contraction of skeletal muscle. 2. Lactate was present in skeletal muscle of all animals examined and increased following electrical stimulation. It was also present in the blood. 3. Gluconeogenesis from lactate occurred in liver slices of all animals excepting amphibia. However, livers of these animals also contained much glycogen and are probably gluconeogenic. 4. Phosphoenolpyruvate carboxykinase was present in all animals investigated; pyruvate carboxylase was present in all animals excepting the toad.

Ambystoma↗
PubMed1977

Ketogenesis in vertebrate livers.

1. The hypothesis is advanced that a gluconeogenic organ such as the liver would evolve to oxidise fatty acids as its source of ATP for gluconeogenesis. It is also argued that such an organ might, in the light of current knowledge, be expected to be ketogenic. The animals investigated were lamprey, rainbow trout, eel, toad, axolotl, lizard and rat. 2. The respiratory quotients of liver slices from all animals was close to 0.74. Ketone bodies were produced from butyrate by all livers excepting the lamprey and ketone bodies were present in all blood samples examined. 3. There was no convincing evidence that direct deacylation of acetoacetyl CoA was important in any liver. HMGCoA synthase activity could not be found in the livers of the lamprey and eel. This enzyme was present in livers of the other animals. There was a large amount of acetoacetyl CoA-succinate transferase in the livers of the rainbow trout and eel, but only small amounts in the higher animals. 4. It is suggested that, initially the transferase was the important ketogenic pathway and the HMGCoA pathway evolved later.

Acyl Coenzyme A↗
PubMed1977

Lactic acid formation in crustaceans and the liver function of the midgut gland questioned.

1. The possibility of the midgut gland of the crustacean (Cherax destructor) functioning as a liver has been investigated. 2. Seven species of crustaceans accumulate lactic acid in the haemolymph when exercised. The rate of disappearance of lactate in Homarus gammarus and in C. destructor is very slow when compared with man. 3. In the midgut gland of C. destructor no firm evidence was obtained for gluconeogenesis from lactate and for ketogenesis from fatty acids. 4. It is concluded that there is at present no justification for the common practice of calling the midgut gland an hepatopancreas.

Animals↗
PubMed1972

Ketogenesis from butyrate and acetate by the caecum and the colon of rabbits.

1. When studied in vitro, tissue from the caecum and the proximal colon of rabbits converted butyrate into ketone bodies. The conversion was similar to that observed with liver slices. The ketogenic activity was associated with the mucosa rather than the muscle of the gut wall and, in the colon, diminished as the distance from the caecal-colonic junction increased. 2. Tissue from the wall of the ileum, caecum, proximal colon and distal colon was also shown to metabolize [1-(14)C]butyrate to carbon dioxide. 3. Enzyme assays showed that in both liver tissue and caecal mucosa the activity of hydroxymethylglutaryl-CoA synthase was more than ten times that of acetoacetyl-CoA deacylase. Labelling experiments in vitro gave confirmation of the hydroxymethylglutaryl-CoA pathway. 4. The significance of the conversion of butyrate into ketone bodies is discussed.

Acetates↗