An investigation of gluconeogenesis in marine teleosts,and the effect of long-term exercise on hepatic gluconeogenesis

• 1.1. Gluconeogenesis from ¹⁴C-substrates was measured in liver slices from marine teleosts.
• 2.2. 0.56 to 2.78 μmols of lactate were incorporated/g wet wt/hr with the higher rates corresponding to the active species.
• 3.3. Snapper (Chrysophrys auratus) and bream (Acanthopagrus butcheri) exercised continuously for 14 days showed a substantial increase in the incorporation of lactate; snapper confined for 4 months showed a significant decrease in the incorporation of lactate, compared to freshly caught individuals.
• 4.4. Pyruvate carboxylase and fructose 1,6-diphosphatase were found in red muscle. Some phosphoenolpyruvate carboxykinase may also be present. The three enzymes were present in liver. Possible roles for the enzymes in teleost muscle are discussed.

     

Determination of β-phenylethylamine in catfish (Parasilurus asotus) tissues by gas chromatography/mass spectrometry

• 1.1. β-Phenylethylamine (PEA) was detected and quantitated in tissues of the catfish, Parasilurus asotus, by very specific and sensitive gas chromatography/mass spectrometry.
• 2.2. The selected ion monitoring was made with a strong quasi-molecular ion of the pentafluoropropionic derivative of PEA in the positive chemical ionization mode.
• 3.3. PEA was found in all tissues tested ranging from 2.8 to 38.2 ng/g wet wt tissue. It was highest in the spinal cord, followed by the skin, brain and intestine.

     

Control of pyruvate kinase flux during gluconeogenesis in isolated liver cells

• 1.1. With pyruvate as the gluconeogenic substrate, pyruvate kinase flux, estimated isotopically, and lactate formation were inhibited by glucagon, but only slightly affected by epinephrine.
• 2.2. The glucagon effect was unchanged in the absence of calcium.
• 3.3. Ethanol increased lactate formation from pyruvate, but depressed pyruvate kinase flux.
• 4.4. These results support the role of pyruvate kinase m the cyclic mechanism which transfers mitochondrial reducing hydrogen to the cytosol.
• 5.5. Glucagon and, to a lesser degree, epinephrine inhibit lactate formation from fructose or dihydroxyacetone.
• 6.6. Ethanol also inhibits lactate formation from these substrates, suggesting the possibility that NADH may in some manner regulate pyruvate kinase flux.

     

Inhibition of tubifex pyruvate kinase by storage phosphagens and adenosine triphosphate

• 1.1. Within the first 6–12 hr of experimental anaerobiosis the concentration of Tubifex phosphagens, phospholombricine and phosphoarginine, decrease to 10–30% of the values under aerobic conditions (7.5 and 3. μM/g dry wt).
• 2.2. High concentrations of both phosphagens (5–25 mM) inhibit Tubifex pyruvate kinase (PK) activity, the inhibitory mechanisms seem to be different. The inhibition is not mediated by the corresponding phosphagen kinases. Inhibition by phosphoarginine obviously requires an additional factor, which chemical nature is still unknown.
• 3.3. Certain phosphocreatine preparations also inhibit Tubifex PK. This inhibition, however, is likely due to contaminants than to phosphocreatine.
• 4.4. Mg-ATP demonstrates the strongest inhibitory effect on PK activity with a mixed competitive inhibition vs PEP and a non competitive vs ADP.

     

Effect of nutrition on the excretion rate of soluble nitrogenous products of Luidia clathrata (say) (Echinodermata; Asteroidea)

• 1.1. Groups of Luidia clathrata were fed maintenance level diets of Donax variabilis (50% protein by dry weight) or Penaeus duorarum (80% protein) or were starved.
• 2.2. The NH₄⁺ excretion rates for all treatments increased from 6.06 ± 2.55 to 14.39 ± 4.31 μg NH₄⁺ − N/g dry wt per hr after 20 days.
• 3.3. The urea excretion rate for all treatments was 1.25 ± 3.39 μg urea-N/g dry wt per hr for 56 days.
• 4.4. The pyloric caecum index (percentage of wet body weight) decreased 16.5 and 73.4%, for Donax variabilis-fed and starved sea stars, respectively. The pyloric caecum index of Penaeus duorarum-fed sea stars increased 81.5%. The protein level of the pyloric caeca was 47.00 ± 4.14% of the dry weight for the fed animals and 37% for the starved animals.
• 5.5. Increased NH₄⁺ excretion rates with starvation or presumed maintenance diets appear to be due to tissue catabolism.

     

Apparent and real variability in the presence and metal contents of metallothioneins in the crab Carcinus maenas including the effects of isolation procedure and metal induction

• 1.1. Reducing conditions must be maintained throughout the procedure of isolating metallothioneins from crabs. Dithiothreitol is preferred to 2-mercaptoethanol for long-term protection.
• 2.2. Two metallothioneins (10,100 and 4100 mol. wt, respectively) in the hepatopancreas of the crab Carcinus maenas showed great variability between individual crabs as to their presence and to their contents of Zn, Cu and Cd.
• 3.3. The 10,100 mol. wt metallothionein was induced in the laboratory by exposure to Cu and Cd, and variably by Zn-exposure. Laboratory induction did not raise significantly the total metal content of 0.88 ± 1.13 g atoms/mol protein of this metallothionein in crabs from the Firth of Clyde, Scotland.
• 4.4. The 4100 mol. wt metallothionein was not induced in the laboratory by exposure to Cu, Cd or Zn. This metallothionein in crabs from the Firth of Clyde, Scotland, contained 0.27 ± 0.34 g atoms of total Cu, Cd and Zn per mole of protein.

     

Light-induced effects of several enzymes of carbohydrate metabolism in Phycomyces blakesleeanus

• 1.1. The photoregulation shown by glyceraldehyde 3-phosphate dehydrogenase and glucose 6-phosphate dehydrogenase appears to be independent of the mad gene product(s) and also independent of carotene biosynthesis regulation.
• 2.2. The photoregulation of malate dehydrogenase appeared to be dependent on the mutation of the mad and car S genes.
• 3.3. Pyruvate kinase and lactate dehydrogenase may be classified as light-independent.
• 4.4. The action of ATP and fructose 1,6-bisphosphate on the enzymes studied was generally independent of light/dark grown conditions.
• 5.5. However, the effect of fructose 1,6-bisphosphate on Phycomyces pyruvate kinase appears to be light-dependent.

     

Cooperative atp inhibition and fructose-1,6-biphosphate activation of rat liver pyruvate kinase

• 1.1. For the determination of relationship between FDP and ATP in the rat liver pyruvate kinase regulation, kinelic studies have been carried out at several ATP and FDP concentrations.
• 2.2. The results obtained on FDP activation show a great cooperativity for FDP saturation with a Hill coefficient of h = 2.79.
• 3.3. Kinetic studies on ATP inhibition also show a great cooperativity for ATP saturation (h = 2.84) at high FDP concentrations.
• 4.4. These results may contribute to explain the regulation of rat liver pyruvate kinase accounting for the activity of this enzyme at high FDP concentrations modulated by small changes in ATP concentrations.

     

Locality-dependent concentrations of bromophenols in Lanice conchilega (Polychaeta: Terebellidae)

• 1.1. At 37 stations in the English Channel and the southern North Sea concentrations of four brominated phenols in Lanice conchilega were determined using ECD equipped capillary gas chromatography: 2,4-dibromophenol, 2,6-dibromo-4-methylphenol, 2,4,6-tribromophenol, 3,5-dibromo-4-hydroxybenzaldehyde.
• 2.2. Concentrations in worms of the southern North Sea were generally below 1 μg/g wet wt.
• 3.3. Levels were slightly raised in worms of sheltered shores, those of 3,5-dibromo-4-hydroxybenzaldehyde were increased in subtidal populations.
• 4.4. Concentrations in L. conchilega of Brittany were considerably higher than those in worms of the Frisian Islands, North Sea; they deviated from the latter by factors of 3, 16, 4, 4, respectively.
• 5.5. The reasons for the conspicuous differences are hitherto unknown; three explanations are suggested.

     

Sex-specific gene expression in distinct tissues of the shrimp Penaeus vannamei

• 1.1. Soluble proteins extracted from male and female Penaeus vannamei tissues such as eyes, eyestalks, brain, nerve cord, hemolymph, heart, muscle, hepatopancreas, hepatopancreas membrane and cuticular epidermis were analyzed and compared by high-resolution mini-two-dimensional polyacrylamide gel electrophoresis (mini-2D-PAGE).
• 2.2. In each shrimp tissue a large number of discrete polypeptides was observed.
• 3.3. The polypeptide patterns from the same tissue of female and male shrimp were mostly similar but both qualitative and quantitative differences were noted, suggesting the presence of sex-specific gene products in various shrimp tissues.
• 4.4. Future applications of these results are discussed.

     

Aerobic glucose disposal in the oyster: An in vivo kinetic analysis

• 1.1. Aerobic glucose disposal in starved oysters exposed to 1 mM external glucose was 2.29 μg C/g wet wt/min.
• 2.2. It was hypothesized that the maximum disposal rate is limited by the maximum rate of transepithelial glucose transport.
• 3.3. The major recipients of glucose-carbon were glycogen and amino acids. 4. The rate of glucose-carbon disposal to these two pools was 0.80 and 0.42 μg C/g/min, respectively.
• 4.5. The internal energy state determines the pathways of glucose disposal.
• 5.6. Disposal of glucose-carbon in “glucose-primed” oysters is primarily into glycogen.
• 6.7. In fasted bivalves the disposal is primarily into amino acids and carboxylic acids.
• 7.8. The uptake of dissolved glucose has the potential of contributing significantly to growth under conditions where the external glucose concentration is kept artificially high.

     

Myo-inositol in the reproductive tract of the female rat

• 1.1. myo-Inositol concentrations in oviduct, ovary and uterus were many-fold those of blood serum during all four stages of the estrous cycle of the female rat.
• 2.2. Inositol concentration was higher in oviduct than in ovary or uterus and was lower in uterine fluid than in uterus.
• 3.3. Estrus uteri had higher inositol concentrations than uteri in other phases of the cycle.
• 4.4. In order to measure dynamic aspects of the distribution of inositol. the distribution of radioactivity among organs of the reproductive tract of mature female rats was measured 45 min after i.p, injection of [2-³H]myo-inositol.
• 5.5. These organs concentrated inositol from the blood, and the tissue radioactivity (expressed as dpm/mg wet wt of tissue) increased in the sequence: vagina < cervix < uterus < ovary < oviduct.
• 6.6. The uterus and ovary concentrated myo-inositol more strongly during proestrus than during metestrus. diestrus or estrus.
• 7.7. The contents of proestrus follicles were more highly radioactive than was the ovary itself, whereas proestrus uterine fluid was less radioactive than the uterine tissue.

     

Hypoxia adaptation in the crayfish procambarus clarki

• 1.1. P. elarki is an oxyconformer, with an oxygen uptake rate of 144 ± 4 μl/g wet wt/hr at oxygen tensions above 90% saturation and an uptake rate of 18 ± 3 μl g wet wt/hr at 15 torr.
• 2.2. Between 159 and 40 tort, blood pH decreases slightly from 7.77 ± 0.03 to 7.65 ± .04, and at 15 torr, blood pH drops to 7.36 ± 0.06.
• 3.3. At normoxia, blood lactate levels are low at 0.66 ± 0.01 mM/l blood. After 2 and 5 hr exposure to 15 tort, blood lactate levels increase to 3.29 ± 0.47 and 8.91 ± 0.14 mM/l blood, respectively. Upon return to normoxia, blood lactate levels decrease and are comparable to normoxic controls after 13 hr.
• 4.4. During mild hypoxia, P. elarki maintains adequate oxygen transport by utilizing a high O₂ affinity hemocyanin in conjunction with a low metabolic demand by its tissues.

     

Non-transferrin-bound-iron in serum and low-molecular-weight-iron in the liver of dietary iron-loaded rats

• 1.1. The feeding of 0.5% (3,5,5-trimethylhexanoyl)ferrocene (TMH-ferrocene) in rats resulted in a severe and progressive liver siderosis (total liver iron, 30 mg/g liver wet weight, after 30 weeks).
• 2.2. High concentrations of an iron-rich ferritin (up to 250 mg/l) were detected in serum of heavily iron-loaded rats forming a large fraction of non-transferrin-bound-iron (5000 μg/dl in maximum).
• 3.3. Ferritin and not haemosiderin was the major iron storage protein in the liver.
• 4.4. The total liver iron concentration (from 0.4 to > 30 mg Fe/g wet wt) but not the cytosolic low-molecular-weight-iron fraction (from 0.5 to 2.5 μM) was extremely increased during iron-loading.

     

A novel inhibitor of glycogen phosphorylase from crayfish hepatopancreas

• 1.1. A novel glycogen phosphorylase inhibitor was partially purified from crayfish hepatopancreas.
• 2.2. The inhibitor was found only in two species of crayfish examined, and not in lobster, fresh and salt water clams, mussels or cockroaches.
• 3.3. The inhibitor is a small protein (M_r = 23,000) which did not show proteolytic activity.
• 4.4. Preliminary kinetic analysis of the inhibitory mechanism indicated that it bound to both glycogen and the glycogen phosphorylase protein.
• 5.5. Inhibitor binding to glycogen resulted in a competitive inhibition pattern with respect to glycogen phosphorylase (inhibition constant of ca 10 μg/ml).
• 6.6. The inhibitor also bound glycogen phosphorylase directly with a binding coefficient of 100 μg/ml resulting in a partially non-competitive inhibition pattern with respect to phosphate.

     

Preparation and properties of mitochondria from tissues of the sea mussel Mytilus edulis L

• 1.1. A method is described for the preparation of coupled mitochondria from hepatopancreas, mantle and adductor muscle of the sea mussle, Mytilus edulis.
• 2.2. NADH is a non-penetrant, whereas succinate, glutamate and malate plus pyruvate have a clear stimulatory effect on respiration. Proline does not stimulate respiration of sea mussel mitochondria.
• 3.3. No P/0 ratios could be calculated as after the addition of ADP the mitochondria remain in the active state (state III), even after enough oxygen is consumed for complete phosphorylation. The reason for this observation is discussed.
• 4.4. Mitochondrial densities based on cytochrome b levels of two tissues of the mussel are compared to rat liver. Within the mussel the mantle contains twice the amount of cytochrome of adductor muscle.

     

Palmitic acid metabolism in hepatopancreas of the freshwater shrimp Macrobrachium borellii

• 1.1. The palmitic acid fate as substrate for the synthesis of either glycerides or other fatty acids was studied in vivo and in the microsomal fraction from hepatopancreas of Macrobrachium borellii.
• 2.2. Most of the palmitic acid administered in vivo circulated to the hepatopancreas, being incorporated mainly in the triacylglycerol (TG) fraction.
• 3.3. Palmitic acid transformations into palmitoleic, stearic and oleic acids were observed in the hepatopancreas.
• 4.4. The in vitro biosynthesis of TG in hepatopancreas was more active than in other tissues. In the microsomal fraction, palmitic acid was also incorporated mainly in TG, and followed the α-glycerophosphate pathway.

     

Presence of pyruvate carboxylase in the blood of the domestic fowl (Gallus domesticus) and an assay procedure

• 1.1. The presence of pyruvate carboxylase activity in chick blood cells has been demonstrated, and a simple technique for its assay is described.
• 2.2. The activity requires the presence of acetyl-CoA and is inhibited by avidin.
• 3.3. The level of activity increases with increasing dietary biotin concentration.

     

Tissue specific isoenzymes of d-lactate dehydrogenase from the foot,mantle and hepatopancreas of Patella caerulea (L). purification and properties

• 1.1. Isoenzymes of d-lactate specific dehydrogenase from foot, mantle and hepatopancreas of Patella caerulea have been purified by Chromatographic techniques. d-lactate dehydrogenase (d-Ldh) from P. caerulea tissues was found to be tetrameric with a M_r of ca 140,000 as judged by gel filtration; subunit M_r of ca 37,000 was obtained from SDS-electrophoresis.
• 2.2. Kinetic studies suggest that P. caerulea foot and mantle d-Ldh is similar to vertebrate muscle-type l-Ldh; furthermore hepatopancreas d-LDH resembles vertebrate heart-type l-LDH since it has a higher affinity for d-lactate and is inhibited by pyruvate.
• 3.3. The results imply that the P. caerulead-Ldh isoenzymes may have distinct metabolic functions.

     

The erythrocytes of the metallic skink Niveoscineus metallicus

• 1.1. We studied the haemoglobin content, erythrocyte indices, erythrocyte enzymes and haemoglobin electrophoresis patterns of the metallic skink Niveoscineus metallicus and compared them to the small amount of published data on other small lizards.
• 2.2. Haemoglobin was much lower than that recorded for the salamander.
• 3.3. Erythrocyte enzymes (glucose phosphate isomerase and glucose 6 phosphate dehydrogenase) were lower in the skink than in the salamander. Glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase and pyruvate kinase were much higher in the skink than in the salamander.
• 4.4. A single, slow, haemoglobin component was identified by electrophoresis.