Evidence for extracellular deamination of adenosine in the rat heart

• 1.1. In rat heart perfused with adenosine (10⁻⁶M), dilazep (10⁻⁴M) inhibited incorporation of adenosine into nucleotides (an index of nucleoside transport and phosphorylation) to a greater extent (70%) than metabolism to inosine and uric acid (40%) and actually increased the recovery of inosine to 30% of the adenosine infused.
• 2.2. Extrapolating for complete inhibition of transport suggested that 60% of adenosine metabolism was intracellular and 40% extracellular.
• 3.3. Static incubations of atria also gave an estimate for extracellular metabolism of 40%.
• 4.4. Adenosine deaminase was localised by immunocytochemistry to the extracellular surface of endothelial cells of small coronary arteries.
• 5.5. Extracellular deamination may explain the lack of effect of nucleoside transport inhibitors on responses to adenosine in rat heart.

     

Metabolism of testosterone in human,rat and rabbit fetal lungs and in rabbit neonatal lung in vitro

• 1.1. Metabolism of 4-¹⁴C-testosterone was investigated in human, rat and rabbit fetal lung subcellular fractions and also in rabbit neonatal lungs. Androst-4-ene-3,17-dione, 17β-hydroxy-5α-androstan-3-one and both 5α- and 5β-androstane-3α,17β-diols were identified as metabolites of testosterone.
• 2.2. The microsomal fraction produced mainly 5α-reduced epimers while the cytosol incubations resulted in 5β-reduced metabolites.
• 3.3. No conjugation was found.
• 4.4. The amounts of polar metabolites in the microsomal incubations and the amounts of dihydroxy-lated metabolites in the soluble fraction incubations were statistically significantly greater in the neonatal rabbit lung incubations compared with those of fetal lungs.

     

Interference of benzo[a]pyrene with cytochrome P-450-mediated steroid metabolism in pyloric caeca microsomes of the sea star Asterias rubens L.

• 1.1. The effects of benzo[a]pyrene (BaP) on the metabolism of progesterone and pregnenolone, and the effects of steroids on BaP metabolism were examined in pyloric caeca microsomes of female Asterias rubens.
• 2.2. The patterns of metabolism of progesterone and pregnenolone in microsomes were similar to those found in previous studies for homogenates and tissue incubations of pyloric caeca.
• 3.3. BaP reduced the rate of hydroxylation of progesterone and pregnenolone, but had no effect on metabolite formation by non-cytochrome P-450-catalysed reactions.
• 4.4. Microsomal BaP hydroxylase activity was reduced by the presence of progesterone, but pregnenolone and testosterone had no such effect.
• 5.5. The reductions in steroid or BaP metabolism were progressive with increasing ratios of the concentration of the interfering compound to that of the assay substrate and were maximally 50% or less at ratios of × 100.
• 6.6. It is concluded that isoenzymic forms of cytochrome P-450 are present, with preferences towards either steroid or BaP metabolism. The implications of the results for the in vivo situation are discussed.

     

Role of antiproteolytic heparin-binding serum protein(s) in modulating the levels of sialyl- and galactosyltransferase activity released during the incubation of rat jejunal slices

• 1.1. Sialyltransferase released into the medium during the incubation of rat jejunal slices in serum-free buffer, was susceptible to proteolytic degradation. Heat inactivated horse serum or its antiproteolytic heparin-binding fraction was found to be necessary in determining the activity of sialyltransferase released (Nadkarni et al., 1991).
• 2.2. In the present study, we have shown that heat inactivated rat serum (HRS) or its antiproteolytic heparin-binding fraction (HBF) had a role in determining the sialyltransferase activity released during jejunal slice incubations.
• 3.3. Galactosyltransferase was also released during incubations, but was not proteolytically degraded and the presence of HRS or HBF in incubations did not alter the levels of galactosyltransferase activity released.
• 4.4. Trypsin activity in serum-free incubation medium was higher compared to medium containing HRS.
• 5.5. Addition of serum-free medium obtained from 4 hr incubations of the jejunal slices, to medium obtained from parallel incubations done in the presence of HRS, caused inhibition of sialyl- but not galactosyltransferase activity.
• 6.6. In jejunal homogenates stored at −20°C, sialyltransferase activity was decreased during 0–45 days of storage, whereas galactosyltransferase activity remained fairly stable for upto 56 days.
• 7.7. Inclusion of HRS or HBF in homogenates resulted in higher sialyl- but not galactosyltransferase activity compared to serum-free homogenate samples.
• 8.8. The results suggest that HRS or its antiproteolytic heparin-binding proteins have a role in determining the sialyltransferase activity released from the jejunal slices. In contrast galactosyltransferase released was not susceptible to proteolysis, and HRS or HBF was not required to express its activity.

     

Phospholipid metabolism in Trypanosoma cruzi—I. Phosphate moiety turnover

• 1.1. The percentage distribution of T. cruzi phospholipids remained constant during the latent, logarithmic and stationary phases of growth.
• 2.2. Short term incubations with ³²Pi revealed a higher turnover of phosphatidylinostitol when cells were in lag phase, whereas in exponential or stationary phases its specific radioactivity was equal to phosphatidylethanolamine.
• 3.3. When ³²Pi was present in the culture medium all throughout the three phases, phosphatidylethanolamine and phosphatidylinositol displayed equally high phosphate moiety turnover.

     

Changes in high-energy phosphate metabolism in the water scorpion,Ranatra chinensis,under cold water-warm water stress

• 1.1. To evaluate changes in high-energy phosphate metabolism in the water scorpion (Ranatra chinensis) under restraint and cold water-warm water stresses, in vivo [³¹P]NMR spectra were obtained.
• 2.2. Under restraint stress, arginine phosphate (Arg-P) decreased by 10% after 1 hr and remained at that level thereafter, while β-ATP showed negligible changes over 6 hr.
• 3.3. As the water temperature gradually increased or decreased, the relative concentration of Arg-P decreased due to enzyme regulation.
• 4.4. Repeated cold water-warm water stress, which consisted of repeated 15 min exposures to cold water (5°C) followed by 15 min exposures to warm water (30°C) caused distinct decreases in Arg-P and β-ATP concentration. These decreases were dependent on the frequency of exposure.
• 5.5. Phosphomonoesters (PME) increased not only with restraint stress but also with cold water-warm water stress.
• 6.6. The effect of cold water-warm water stress on high-energy phosphate metabolism was greater than that of restraint stress.

     

Metabolism of benzo[a]pyrene and persistence of DNA adducts in the brown bullhead (Ictalurus nebulosus)

• 1.1. The in vitro metabolism of [³H]benzo[a]pyrene (BP) and [¹⁴C]benzo[a]pyrene-7,8-dihydrodiol (BP-7,8-diol) by liver of brown bullhead (Ictalurus nebulosus) was characterized, as was the formation and persistence of BP-DNA adducts in vivo.
• 2.2. Compared to rat liver microsomes, bullhead liver microsomes produced relatively larger amounts of BP-7,8-diol (predominantly the [−] enantiomer) and smaller amounts of BP-4,5-diol.
• 3.3. BP phase I metabolites were efficiently converted by freshly isolated bullhead hepatocytes to conjugates, predominantly glucuronides.
• 4.4. BP-7,8-diol was metabolized by hepatocytes 4-fold more rapidly than was BP and was converted to approximately equal amounts of glucuronides, glutathione conjugates and sulfates.
• 5.5. BP-DNA adducts formed in bullhead liver with a lag time of several days and maximum adduct formation at 25–30 days. The major adduct was anti-BPDE-deoxyguanosine.

     

Phosphonomonoesterase activity in Metridium senile L.

• 1.1. An esterase which hydrolyzes 4-nitrophenyl(phenyl)phosphonic acid (4-NPPP) was purified from M. senile (sea anemone).
• 2.2. The enzyme showed no 5′-nucleotide phosphodiesterase activity with 5′-(4-nitrophenyl) TMP or phosphomonoesterase activity with 4-nitrophenylphosphate.
• 3.3. Addition of excess Zn²⁺ restored activity after inactivation by EDTA.
• 4.4. Thiol reagents and phenylmenthanesulfonylfluoride did not inactivate, whereas, dithiothreitol inactivated.
• 5.5. Aminoethylphosphonic acid (AEP) was a competitive inhibitor of 4-NPPP indicating possible activity with phosphonomonoesters of AEP.

     

Phosphorylation in crayfish (Procambarus clarkii) eggs during hatching

• 1.1.|The high-energy phosphorylation metabolism in crayfish, Procambarus clarkii eggs during brooding and juvenile crayfish after hatching was studied by in vivo³¹P nuclear magnetic resonance (³¹P NMR) spectroscopy.
• 2.2.|Inorganic phosphoric acid (Pi) and adenosine-5′-triphosphate ATP(γ-,α-,β-) were detected in the dark brownish red eggs after oviposition.
• 3.3.|In orange unhatched eggs, only sugar phosphate (SP), Pi and resolved phosphometabolite from ATP were observed.
• 4.4.|Peaks of SP, Pi, arginine phosphate (Arg-P), and ATP (γ,α,β) appeared in larvae of crayfish after hatching (nauplius, zoea and juvenile crayfish).
• 5.5.|The high-energy phosphorylation metabolism changed to an anaerobic condition along with a decrease in the concentration of dissolved oxygen in fresh water.

     

Changes in the EEL intestine during seawater adaptation

• 1.1. Rate of fluid absorption by eel (Anguilla rostrata) intestinal sacs in vitro reached seawater adapted values 3 days after transfer from freshwater to seawater.
• 2.2. After 3 days in seawater oxygen consumption and Na-K-ATPase activity of intestinal mucosa had not increased over freshwater values.
• 3.3. The weight of intestinal mucosa increased 32% during seawater adaptation as a result of an increase in the number of mucosal cells (hyperplasia).
• 4.4. The rate of intestinal fluid absorption was reduced by 10⁻⁴ M ouabain and was not affected by 10⁻⁴ M acetazolamide.

     

In vitro oxidation of [3-14C]acetoacetate in brain cortex from hibernating hamsters and ground squirrels

• 1.1. A comparison was made of the utilization of acetoacetate in brain tissue from hibernating and nonhibernating hamsters, Mesocricetus auratus, and ground squirrels, Citellus tridecemlineatus.
• 2.2. In vitro oxidation of [3-¹⁴C] acetoacetate was used as an index of ketone utilization.
• 3.3. Oxidative metabolism of acetoacetate in cerebral tissue from both hibernating and nonhibernating hamsters and ground squirrels was evident, and at 27°C (compared with 37°C) levels were much reduced.
• 4.4. Incorporation of acetoacetate in cerebral tissue from hamster was much greater than in ground squirrel in both hibernating and nonhibernating animals.

     

Purine metabolism in cotyledons and embryonic axes of black gram (Phaseolus mungo L.) Seedlings

• 1.1. The metabolism of purine bases and nucleosides in cotyledons and embryonic axes of black gram (Phaseolus mungo L.) was studied.
• 2.2. A large portion of absorbed [8-¹⁴C]adenine, [8-¹⁴C]guanine and [8-¹⁴C]adenosine was salvaged in nucleotide and nucleic acid synthesis.
• 3.3. Most of the radioactivity of [8-¹⁴C]hypoxanthine and [8-¹⁴C]inosine was incorporated into allantoin and allantoic acid.
• 4.4. Activity of adenine phosphoribosyltransferase in enzyme extracts was much higher than that of hypoxanthme and guanine phosphoribosyltransferase(s).
• 5.5. Apparent activity of adenosine kinase was higher than that of inosine kinase. 6. NAD⁺-dependent xan thine dehydrogenase was detected in both cotyledons and embryonic axes of the seedlings.
• 6.7. The capacity of purine salvage was higher m 24 hr old cotyledons than 24 and 48 hr old embryonic axes. The reverse was observed concerning that of purine degradation.

     

Active transport of d-glucose in intestinal segments,in vitro,of the scup,Stenotomus versicolor and the puffer,Spheroides maculatus

• 1.1. Active transport of d-glucose was shown using intestinal sac preparations, in vitro, made from two marine fish, the scup, Stenotomus versicolor and the puffer, Spheroides maculatus.
• 2.2. Differences in absorption characteristics were evident in populations from year to year.
• 3.3. Anaerobiotic conditions, i.e. 100 per cent nitrogen gassing of the incubation medium, inhibit the active transport of d-glucose in scup and puffer intestine.
• 4.4. Phlorizin, 5 × 10⁻⁴ M, inhibits the active transport of d-glucose in scup intestine.
• 5.5. Intestinal transmural glucose transport mechanisms operate well at incubation temperatures, 20°–27°C, i.e. temperatures close to habitat and holding tank temperatures, whereas movement of the sugar against a concentration gradient is interrupted at higher incubation temperatures, 29° and 30°C.
• 6.6. Detailed comparison of procedures and results with those used by other workers in the field of in vitro intestinal absorption of poikilotherms suggests that aerobic metabolism may not be a uniformly significant energy source in intestinal active transport.

     

Effects of membrane-perturbing drugs and noradrenalin on cAMP accumulation and red cell water content in carp (Cyprinus carpio) red cells

• 1.1. Carp red cells were treated with drugs that affect the cell membranes. The water content of the cells and the accumulation of cAMP in the cells were measured in normoxia and in hypoxia using non-stimulated and adrenergically stimulated cells.
• 2.2. WGA, DIDS + CCCP and A23187 increased the water content of nonstimulated normoxic cells.
• 3.3. In hypoxia ouabain and DIDS + CCCP increased the water content but cytochalasin B, NPM, DIDS, CCCP and A23187 + CA²⁺ abolished the hypoxia-induced swelling.
• 4.4. Any membrane perturbation induced some cAMP formation, Sophora and Anquilla lectins being most potent.
• 5.5. Also in adrenergically stimulated cells, membrane perturbation generally increased cAMP formation.
• 6.6. However, cAMP accumulation diminished in cells treated with cytochalasin B, CCCP and DIDS + CCCP.
• 7.7. The adrenergic swelling of carp red cells was reduced in normoxia by DIDS. NPM and CCCP increased the adrenergic swelling in normoxia to hypoxic level.
• 8.8. In hypoxia WGA and Anquilla lectin decreased the swelling.

     

In vitro substrate utilization for lipid synthesis in liver explants from hyperthyroid chickens

• 1.1. Indian River male broiler chickens growing from 7 to 28 days of age were fed diets containing 12, 18, 24 and 30% protein + 0 or 1 mg triiodothyronine (T₃)/kg of diet to study energetic costs of lipogenesis and the use of various substrates for in vitro lipogenesis.
• 2.2. De novo lipid and CO₂ production were determined in the presence of [1-¹⁴C]pyruvate, [2-¹⁴q]pyruvate, [3-¹⁴C]pyruvate, [2-¹⁴C]acetate and [U-¹⁴C]alanine.
• 3.3. Oxygen consumption was determined in mitochondrial preparations to estimate the energetic costs in expiants synthesizing lipid.
• 4.4. Radiolabeled CO₂ derived from [1-¹⁴C]pyruvate was used as an estimate of coenzyme A availability in liver expiants. Lipids derived from [2-¹⁴C]pyruvate, [2-¹⁴C]acetate and [U-¹⁴C]alanine estimate relative substrate efficiency.
• 5.5. Labeled CO₂ production from [1-¹⁴C]pyruvate was greatest in that group fed a 12% protein diet and least in the group fed a 30% protein diet.
• 6.6. In addition, T₃ increased CO₂ production from [1-¹⁴C]pyruvate.
• 7.7. The production of ¹⁴CO₂ from the second carbon of pyruvate or acetate was increased by T₃.
• 8.8. The low-protein diet (12% protein) increased (P <0.05) lipogenesis.
• 9.9. Adding T₃ to the diets decreased carbon flux into lipid from all substrates, but increased CO₂ production from all substrates without changing stage 3 and 4 respiration rates in mitochondrial preparations.
• 10.10. These observations imply that coenzyme A availability may have regulated de novo lipogenesis in the present study.
• 11.11. It was also concluded that previously noted effects of T₃ on intermediary metabolism may involve metabolic pathways that do not involve changes in mitochondrial function.

     

31P-NMR study on effects of electric shock on swimming leeches,Hirudo medicinalis

• 1.1. We evaluated the effect of electric shock on swimming leeches by measuring changes in high-energy phosphate metabolism using in vivo³¹P-NMR.
• 2.2. Leeches electrically stimulated during swimming showed anodal galvanotaxis, and stopped swimming with stimulation at strong current.
• 3.3. Comparison of the concentrations of high-energy phosphate metabolites before and after electric shock using ³¹P-NMR revealed a marked decrease in β-ATP and an increase in that of Pi.
• 4.4. Electric shock apparently induces excessive muscle fatigue in leeches, resulting in transient paralysis.

     

Organ specific changes in energy metabolism due to anaerobiosis in the sea mussel Mytilus edulis (L.)

• 1.1. Anaerobic energy metabolism was investigated in different organs of Mytilus edulis and the whole animal.
• 2.2. Succinate accumulates to high levels in most organs but remains low in the hemolymph.
• 3.3. After 16 hours propionate accumulation is observed in all organs. Experimental evidence is not sufficient yet to point out organs that produce more propionate than others.
• 4.4. Acetate is a minor end product.
• 5.5. Acetate and propionate are found in the hemolymph in amounts equal to those in the organs.
• 6.6. Animals incubated in oxygen-free seawater accumulate more end products than animals exposed to air, in the form of volatile fatty acids that are excreted into the incubation water.
• 7.7. Alanine and glutamine increase in the posterior adductor muscle. Aspartate decreases in the total animal, posterior adductor muscle and gills, while in the hemolymph decrease in alanine, asparagine, serine, threonine and proline are observed.

     

Protein,fatty acids,calcium and phosphate absorption along the gastrointestinal tract of the young turkey

• 1.1. The net absorption of protein, fatty acids, calcium and phosphate along the small intestine of the turkey (Meleagris gallopovo) was evaluated with the aid of ⁹¹Y as a reference substance.
• 2.2. About 85% of the ingested protein was absorbed, with most of the absorption occurring in the duodenum and upper jejunum.
• 3.3. The overall lipid absorption coefficient was around 90%, and was inversely related to the fatty acid chain length and saturation.
• 4.4. Most of the lipid absorption occurred in the duodenum and jejunum.
• 5.5. Calcium absorption also occurred in the duodenum and jejunum: its fractional rate decreased with calcium intake.
• 6.6. Phosphate absorption occurred mostly in the duodenum and jejunum and its efficacy was only slightly affected by dietary phosphate intake.
• 7.7. The high nutrient absorption in the turkey duodenum, relative to that of the chick (Gallus domesticus), was discussed.

     

Effects of water stress on hemolymph volume,osmotic potential and chemical composition in Megetra cancellata

• 1.1. Rates of water loss in Megetra cancellata were very high compared to those reported for other xeric arthropods.
• 2.2. Hemolymph weight in hydrated animals was 43.0% of the total body weight while it was 24.7% in desiccated animals that had lost 16.1% of their body weight as water.
• 3.3. Hemolymph osmotic potential increased from 417 to 447 mOsm/kg in desiccated beetles, but osmotic regulation was evident.
• 4.4. Total hemolymph protein mass and concentration decreased in desiccated beetles while amino acid concentrations remained constant (at about 70 mM).
• 5.5. Na⁺ and −PO₄ concentrations increased in desiccated beetles.
• 6.6. Cl⁻ and K⁺ concentrations in desiccated beetles were equal to those in undesiccated beetles.

     

Isotopic labeling of taurine; implications for its synthesis in selected tissues of Homarus americanus

• 1.1. The abdominal muscle and ventral nerve chord of Homarus americanus were incubated with radioactive precursors.
• 2.2. ³⁵SO₄ and ¹⁴C-CO₂ were not incorporated into amino acids in the abdominal muscle.
• 3.3. ¹⁴C-glucose was incorporated into serine, cysteine, cysteine-sulfinic acid and taurine in the abdominal muscle.
• 4.4. ¹⁴C-CO₂ appeared to be slightly incorporated into taurine in the ventral nerve chord.
• 5.5. ¹⁴C-glucose incubation with the ventral nerve chord resulted in labeling of the same amino acids as in the abdominal muscle.
• 6.6. The results are discussed in view of the catabolism of carbohydrates and the synthesis of taurine.