Effect of conjugation on the incorporation of glycine into Tetrahymena

• 1.1. Conjugation of Tetrahymena enhanced the incorporation of glycine into the nuclear fraction by 500%.
• 2.2. Incorporation of glycine into the microsomal supernatant was augmented by almost 500% by conjugation.
• 3.3. Mitochondrial incorporation was stimulated nearly 3-fold in the conjugating strains while the incorporation of glycine into the microsomes was enhanced approximately 2.5 times.
• 4.4. In the whole cell, glycine incorporation was increased nearly 2-fold by conjugation.
• 5.5. Strong nuclear involvement was indicated by elevated metabolic activity and incorporation of glycine into RNA and DNA.
• 6.6. Stimulation of the metabolism of Tetrahymena by cell communication suggests that the contents of a cell can have a synergistic effect on another cell.
• 7.7. Augmentation of the biosynthetic capacities of cells by fusion is a demonstration of the dominant role of the cell membrane in the regulation and control of cells.
• 8.8. Enhancement of biosynthesis of nuclear proteins in conjugating strains of cells indicates that fusion gives rise to the synthesis of new protein from previously existing protein or protein procursors.
• 9.9. The specific activities of the subcellular fractions after the incorporation of glycine into 2 separated starved strains of Tetrahymena followed the usual pattern of nucleus less than whole cells, whole cells less than mitochondria, mitochondria less than microsomes, but with the microsomal supernatant being much greater than that of the microsomes.

     

Effects of protein synthesis inhibitors on A- and L-site amino acid incorporation by bullfrog tadpole liver and tail fin cells

• 1.1. Cycloheximide and puromycin inhibited leucine transport and incorporation into isolated bullfrog tadpole tail and hepatic cells.
• 2.2. However, high concentrations of these 2 inhibitors did not affect alanine incorporation appreciably in either tissue.
• 3.3. NEM and DNP inhibited leucine and alanine incorporation in both cell types, but at different concentrations.
• 4.4. NEM stimulated leucine transport only in hepatocytes; alanine transport was inhibited by NEM in tail fin cells.
• 5.5. The results suggest different mechanisms of transport and protein synthesis for the 2 types of amino acids by tadpole liver and tail fin cells.

     

The role of citrate derived from glucose in the acetylcholine synthesis in rat brain synaptosomes

• 1.1. Synaptosomes utilizing glucose or glucose plus malate produced citrate with rates of 2.4 and 7.8 nmol/hr/mg of protein, respectively.
• 2.2. (−)Hydroxycitrate increased citrate net synthesis 4 times and inhibited acetylcholine synthesis by 40%.
• 3.3. Oxygen and glucose consumption as well as lactate and CO₂ production were not changed by this inhibitor.
• 4.4. (−)Hydroxycitrate inhibited utilization of exogenous citrate in synaptosomes by 50%.

     

Complement-like protein from the phylogenetically primitive vertebrate,Eptatretus Stouti,is a Humoral Opsonin

• 1.1. Serum from the Pacific hagfish,Eptatretus stouti,contains a complement-like protein (CLP).
• 2.2. CLP from unfractionated hagfish serum and from affinity-purified preparations binds to yeast cell surfaces.
• 3.3. Incubation with CLP enhances the phagocytosis of yeast by hagfish leukocytes.
• 4.4. CLP-mediated opsonization can be inhibited by anti-CLP antibody, EDTA, d(+)mannose and l(+)rhamnose.
• 5.5. Additional opsomic factors are also in hagfish serum.

     

Comparison of metabolic effects of EGF,TGF-α, and TGF-β1 in primary culture of fetal bovine myoblasts and rat L6 myoblasts

• 1.1. Comparative studies of EGF, TGF-α, and TGF-βl action on the synthesis of DNA and cellular proteins in rat L6 myogenic cells and fetal bovine myoblasts demonstrated considerable differences between particular growth factors, dependent on dose and target cells.
• 2.2. Among examined growth factors only EGF exerted mitostimulatory action, more pronounced at lower concentrations. EGF, progressively with dose, stimulated protein synthesis much more effectively in fetal bovine myoblasts than in L6 cells.
• 3.3. The dynamics of stimulation of protein synthesis by TGF-α was greater than by EGF in both examined types of cell cultures.
• 4.4. The maximal response of fetal bovine myoblasts to TGF-α in a concentration of 100 ng/ml reached 370%, whereas EGF in a 10 times higher concentration stimulated protein synthesis only to 123% of control.
• 5.5. In contrast to EGF, TGF-α significantly inhibits DNA synthesis. Inhibition of the mitogenic response with simultaneous stimulation of protein synthesis by TGF-α may indicate changes toward cell differentiation.
• 6.6. TGF-β 1 in smallest concentration inhibits both DNA and protein synthesis. The suppressive action of TGF-β 1 was more distinct in fetal bovine myoblasts than in the L6 cell line.
• 7.7. Increasing concentrations of TGF-β l diminished its inhibitory effect, even leading to stimulation of protein synthesis at higher doses in L6 myoblasts.

     

Induction of honeybee haemolymph sucrase activity by high levels of dietary sucrose

• 1.1. Continuous feeding of adult honeybees with a 2 M sucrose syrup results in an early increase of both trehalase and sucrase activities in haemolymph, followed by a trough at day 5, then a second phase of increasing sucrase activity.
• 2.2. In the presence of chloramphenicol as an inhibitor of protein synthesis, the induction of trehalase activity is depressed but the very early increase of sucrase is not; by contrast, the second phase of increase in sucrase activity is delayed and depressed by the inhibitor.
• 3.3. These results suggest that in the earlier phases of induction, the sucrase molecules constitute a part of the trehalase complex already present whereas the second phase corresponds to the synthesis of a more specific sucrase.
• 4.4. New carbohydrates (di and trisaccharides) are produced which might be due to the transglycosylation properties of the induced enzymes.

     

Metabolic energy and cytoskeletal requirements for synthesis and secretion by acini from rat mammary gland—ii. Intracellular transport and secretion of protein and lactose

• 1.1. Iodoacetate, 2,4-dinitrophenol, cyanide and cycloheximide inhibited protein secretion as well as synthesis by acini (alveoli) from rat mammary gland. Cytochalasin B and vinblastine inhibited protein secretion and marginally reduced protein synthesis. Colchicine was without effect on protein synthesis but inhibited secretion.
• 2.2. Intracellular protein transport was altered during incubation with metabolic and cytoskeletal inhibitors. Cycloheximide, iodoacetate. 2,4-dinitrophenol and Cytochalasin B appeared to block protein synthesis on polysomes of rough endoplasmic reticulum. Vinblastine inhibited protein transport from rough endoplasmic reticulum to Golgi apparatus and colchicine appeared to cause accumulation of protein in several endomembrane fractions.
• 3.3. Iodoacetate reduced acinar lactose content but was without effect on lactose synthetase activity. Cyanide, cycloheximide and vinblastine reduced lactose synthetase activity but not tissue lactose concentration. Cytochalasin B reduced glucose incorporation but was without effect on lactose content and lactose synthetase activity. Colchicine and 2,4-dinitrophenol did not alter glucose incorporation, lactose content or lactose synthetase activity. Lactose secretion was inhibited by all metabolic and cytoskeletal inhibitors examined.
• 4.4. Results indicated that sustained protein secretion depended on continued protein synthesis and that lactose secretion was coupled to protein secretion.

     

Effects of transforming growth factor β1 and basic fibroblast growth factor on lipoprotein lipase activity in primary cultures of chicken (Gallus domesticus) adipocyte precursors

• 1.1. The effect of TGF-β and bFGF on lipoprotein lipase activity in chicken adipocyte precursors was investigated.
• 2.2. Lipoprotein lipase activity was reduced by up to 80% by incubation with TGF-β whereas bFGF had no effect.
• 3.3. Contrary to that found with the 3T3-L1 preadipocyte cell line it was not necessary for TGF-β to be present prior to the start of differentiation in order to be effective.
• 4.4. Incubation of adipocyte precursors with actinomycin D abolished the effect of TGF-β suggesting that synthesis of a protein effector is required.
• 5.5. These results indicate differences in responsiveness to TGF-β and bFGF between primary chicken adipocyte precursors and some preadipocyte cell lines.

     

Effect of inorganic phosphate on synthesis of 5-phosphoribosyl-1-pyrophosphate in cultured plant cells

• 1.1. Inorganic phosphate (Pi) was absorbed rapidly by suspension-cultured cells of Catharanthus roseus which had previously been cultured in Pi-free Murashige Skoog medium.
• 2.2. The intracellular levels of ATP, ADP and 5-phosphoribosyl-l-pyrophosphate (PRPP) increased markedly during the 24 hr which followed the addition of Pi (1.25mM).
• 3.3. Availability of PRPP in vivo, estimated by the measurement of nucleotide synthesis from [8-¹⁴C]adenine, was also increased by addition of Pi.
• 4.4. Only a 20% increase in the maximum catalytic activity of PRPP synthetase was observed in extracts of cells, prepared 24 hr after addition of Pi.
• 5.5. In contrast to results for mammalian PRPP synthetase, the activity of PRPP synthetase, partially purified from Catharanthus roseus, was inhibited by concentration of Pi greater than 5mM.
• 6.6. The mechanisms involved in the increased availability of PRPP and the synthesis of adenine nucleotides in the plant cells cultured in Pi-containing medium are discussed.

     

A comparative study of porphyrin synthesis by whole blood and haemolysates from different mammalian species

• 1.1. There is no uniform pattern of porphyrin synthesis by whole blood and haemolysates, between the different mammalian species studied.
• 2.2. Coproporphyrin, is the dominant porphyrin synthesised by intact red cells.
• 3.3. Uroporphyrin synthesis increases significantly in the majority of species when the cells are haemolysed.
• 4.4. In the mouse large amounts of protoporphyrin are synthesised by intact red cells which increases further on haemolysis.
• 5.5. The low porphyrin synthesising capacity of cow and sheep red cells is not due to any rate-limiting activity of the enzyme ALA-dehydratase.
• 6.6. The dog has a pattern of porphyrin synthesis and excretion similar to that found in the rabbit, and the possibility exists, that a similar energy-dependent carrier mechanism for movement of uroporphyrin and coproporphyrin across red cell membranes found in the rabbit may be present in this species.
• 7.7. The findings may be of significance in the interpretation of porphyrin excretion patterns in experimental porphyria.

     

The breakdown of Tetrahymena ribosomes by lysosomal enzymes: Inhibition by cytosol

• 1.1. Extracts from Tetrahymena lysosomes contained acid RNase and proteinase. At pH 7.4 there was appreciable proteinase activity which was inhibited by a heat-stable protein present in cell sap.
• 2.2. Lysosomal enzymes rapidly converted 80S ribosomes to subunits at pH 7.4. Hydrolysis of ribosomal RNA was very slow at pH 7.4 but rapid at pH 5.0.
• 3.3. These reactions were inhibited by proteinase inhibitors and by cell sap, but the latter was relatively ineffective at pH 5.0.
• 4.4. It seems unlikely that ribosome breakdown in vivo is initiated by the release of lysosomal enzymes into the cytosol.

     

The taurine content of avian erythrocytes and its role in osmoregulation

• 1.1. The taurine content of erythrocytes from 15 avian species contained levels of taurine in the range of 20–70 mmol/kg of hemoglobin, about 100-fold that of mammalian red blood cells.
• 2.2. This high taurine content did not appear to be related to the nucleation of these cells as nucleated amphibian erythrocytes and human reticulocytes contained low levels.
• 3.3. The erythrocytes lacked cysteine sulfinic acid decarboxylase, a key enzyme in the synthesis of taurine from cysteine, indicating a probable lack of synthetic capabilities.
• 4.4. The cells were able to accumulate labeled taurine against a concentration gradient. This uptake was inhibited by β-alanine and was Na⁺-dependent.
• 5.5. When incubated in hypotonic medium, the cell volume of pigeon erythrocytes rapidly increased and was followed by a much slower return to normal size. The cell volume reduction was accompanied by a slow efflux of taurine into the medium.
• 6.6. These data suggest that taurine plays a role in cell volume maintenance and osmotic regulation in avian erythrocytes.

     

Effect of methyl methacrylate on mitochondrial function and structure

• 1.1. Treatment of isolated rat liver mitochondria with methyl methacrylate (MM) produced membrane disruption as evidenced by the release of citrate synthase, and changes in the ultrastructure of mitochondria.
• 2.2. At concentration 0.1%, MM uncoupled oxidative phosphorylation as evidenced by stimulation of state 4 respiration supported either by pyruvate plus malate or succinate (+rotenone) and ATP-ase activity in intact mitochondria.
• 3.3. At concentration 1% MM stimulated ATP-ase activity in intact mitochondria and succinate (+rotenone) oxidation at state 4 and was without effect on this substrate oxidation at state 3.
• 4.4. MM inhibited pyruvate plus malate oxidation either at state 3 or in the presence of uncoupling agents.
• 5.5. MM inhibited the NADH oxidase of electron transport particles at a concentration which failed to inhibit either succinic oxidase or the NADH-ferricyanide reductase activity.
• 6.6. The data presented suggest that in the isolated mitochondria MM inhibits NADH oxidation in the vicinity of the rotenone sensitive site of complex I.
• 7.7. The general conclusion is that MM may block an electron transport and to uncouple oxidative phosphorylation in rat liver mitochondria. The overall in vitro effect would be to prevent ATP synthesis which could result in cell death under in vivo conditions.

     

The influence of ehrlich ascites tumour growth on the turnover of lactate dehydrogenase in tissues of the mouse

• 1.1. The influence of Ehrlich ascites tumour growth on the turnover of total soluble protein and lactate dehydrogenase (LDH) in mouse tissues has been studied.
• 2.2. Turnover parameters were determined by means of double-labelling technique, with the enzyme (LDH) being isolated by affinity chromatography.
• 3.3. Tumour growth was accompanied by a decreased rate of synthesis of total protein in all tissues.
• 4.4. Lactate dehydrogenase by contrast snowed an increased rate of synthesis in all tissues but kidney.
• 5.5. These directions of change, in combination with the lesser response of degradation constants, resulted in a consequent conservation of enzyme activity in all tissues except kidney.
• 6.6. A generalized shift in the LDH isozyme pattern of these tissues was also observed during tumour growth with an increased contribution of A-type subunit.
• 7.7. These results have been discussed in relation to the redirection of protein synthesis and degradation, the occurrence of foetal isozymes, and possible mechanisms involved in the redistribution of protein resources in the animal during tumour development.

     

The stimulation of yeast mitochondrial protein synthesis by low molecular weight cytoplasmic factors: Requirement for intact mitochondria and lack of effect by folate derivatives

• 1.1. Protein synthesis by GTP -supplemented yeast mitochondria is stimulated by a fraction of molecular weight less than 2,000 isolated from yeast high-speed supernatant (S-150).
• 2.2. The low molecular weight fraction works independently of the respiratory chain as the stimulation effect is not cyanide-sensitive.
• 3.3. Stimulation of mitochondrial protein synthesis by cytoplasmic factors is dependent upon the method of mitochondrial isolation.
• 4.4. The low molecular weight stimulatory factor(s) are not reduced folate derivatives which supply formyl groups required for initiation of mitochondrial protein synthesis.

     

Partial purification and characterization of cysteine proteinase from metamorphosing tadpole tails of Rana catesbeiana

• 1.1. A leupeptin-sensitive proteinase was partially purified from regressing tadpole tails by acetone factionation and column chromatography on S-Sepharose.
• 2.2. The enzyme degraded hemoglobin and myoglobin at pH 3.0. The enzyme also hydrolyzed Z-Phe-Arg-MCA and Boc-Val-Leu-Lys-MCA at pH 4.0.
• 3.3. The enzyme activity was inhibited by leupeptin, egg cystatin, E-64 and monoiodoacetic acid and was activated by l-cysteine.
• 4.4. The enzyme degraded myosin and actin in myofibrils of tadpole tails.
• 5.5. The enzyme belongs to the cysteine proteinase and is possibly involved in tail degradation during the metamorphosis of tadpoles.

     

Electrical transport characteristics of Aplysia californica intestinal epithelium

• 1.1. Replacing chloride (Cl⁻) with sulfate (SO₄²⁻) in the bathing medium drastically reduced the mucosal membrane potential difference (ψ_m).
• 2.2. The voltage divider ratio was significantly greater than one.
• 3.3. Mucosal ^d-glucose decreased the input resistance of the intestinal epithelium.
• 4.4. Addition of furosemide to the mucosal bathing medium inhibited transepithelial potential difference and short-circuit current.
• 5.5. Addition of SITS to the mucosal bathing medium partially inhibited transepithelial potential difference and short-circuit current.
• 6.6. Diffusion potentials in the intestinal epithelium were symmetrical.