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At least 19 recordsLinked to original sources

PubMed1978

Effect of alternating magnetic fields (60--100 gauss, 60 Hz) on Tetrahymena pyriformis.

Tetrahymena pyriformis and neuroblastoma cells were studied following exposure to low intensity low frequency alternating magnetic fields. Tetrahymena showed cytomorphologic changes, with delayed and reduced cell division concurrent with increased oxygen uptake. The resulting dead cells appeared intact, as compared with dissolution characteristic of the control group. In contrast, magnetically exposed actively growing neuroblastoma cells showed no growth alterations in vitro, but were affected when exposed in vivo.

Animals↗

PubMed1979

A dolichyl phosphate-cleaving acid phosphatase from Tetrahymena pyriformis.

Tetrahymena pyriformis contains an enzyme which hydrolyzed dolichyl phosphate. This activity was solubilized from lyophilized samples of this organism and was relatively stable when stored frozen. The soluble enzyme preparation had an acid pH optimum and hydrolyzed both dolichyl and phytanyl phosphates at equivalent rates. The polyprenylphosphate phosphatase activity was compared with the acid phosphatases which hydrolyzed p-nitrophenyl phosphate and marked differences were found. Dolichyl phosphate hydrolysis required Mg2+ for maximum activity while the bulk of the phosphatase activity was not effected by the absence of this ion. Other differences were that the polyprenylphosphate phosphatase was relatively insensitive to inhibitors such as tartrate and vanadium oxide sulfate which had a pronounced effect on the rate of p-nitrophenyl phosphate hydrolysis. The two activities also appeared to have different subcellular distributions. The polyprenylphosphate phosphatase was markedly inhibited by ethoxy formic anhydride, a reagent which is active against enzymes containing a histidine residue at their active site, while p-nitrophenyl phosphate hydrolysis was unaffected. The polyprenylphosphate phosphatase may be important in regulating the level of dolichyl phosphate in T. pyriformis and thus the rate of glycoprotein synthesis. It is also a useful tool which is capable of liberating dolichol from dolichyl phosphate under mild conditions which will permit the further characterization of the polyprenols.

4-Nitrophenylphosphatase↗

PubMed1976

Effect of hexachlorobenzene (HCB) on growth of Tetrahymena pyriformis.

Tetrahymena pyriformis Wh 14 was incubated with HCB (0.001 - 0.5 ppm) in Erlenmeyer flasks under continuous stirring at 30degreesC for 10 days in an incubator. HCB decreased growth as deduced from measurements of dry weight, carbohydrates, and total nitrogen. Total nitrogen and carbohydrates are decreased drastically while dry matter is reduced only by a factor of two. The excretion of a compound into the nutrient solution which yields a colour with modified Ehrlich reagent like porphobilinogen is very strongly increased by HCB. All effects observed were very well correlated with the concentration of this compound applied.

Animals↗

PubMed1979

RNA synthesis in starved deciliated Tetrahymena pyriformis.

Tetrahymena pyriformis which has been starved for 20 h by incubation in buffer, and then deciliated, can regenerate its cilia in about 90 min while still in suspension in non-nutrient medium. The process of reciliation is accompanied by protein synthesis which begins a few minutes after deciliation and by synthesis of ribosomal and messenger RNAs during a period extending from about 1 h to about 3 h after deciliation. Although net synthesis of RNA remains at a very low level until 1 h after deciliation, a qualitative change in the translatable poly(A)-containing messenger RNA content of deciliated cells, and in particular, formation of beta-tubulin mRNA can be detected almost immediately after deciliation.

Animals↗

PubMed1975

Inhibition of rRNA synthesis following incorporation of 5-bromodeoxyuridine into DNA of Tetrahymena pyriformis.

Tetrahymena pyriformis was grown on chemically defined medium in the presence of 5-bromodeoxyuridine (BUdR). Under these growth conditions more than 60% of the thymidine sites in DNA were substituted with BUdR. It was found that RNA synthesis was strongly inhibited by the presence of BUdR in DNA. To assure that incorporation of BUdR into DNA was a prerequisite of the effect observed, BUdR was added to synchronously dividing cells. BUdR had no effect on the cells when present outside the period of nuclear DNA replication, whereas RNA synthesis was strongly inhibited as soon as the genes coding for ribosomal RNA had replicated in the presence of BUdR.

Animals↗

PubMed1978

Effect of hexachlorobenzene (HCB) on the activity of some enzymes from Tetrahymena pyriformis.

Tetrahymena pyriformis Wh 14 was grown in Erlenmeyer flasks under continuous stirring at 30 degrees C for three days . After the culture had produced dry matter of about 100 mg HCB was added in acetone at a dose level of 0, 0.001, 0.1 and 1.0 ppm to the culture and incubated for another 7 days. At a dose level of 0.001 ppm the activity of delta-aminolevulinate dehydratase, hexokinase, and pyruvate kinase remained unaffected but was increased for glutamic-oxaloacetic transaminase, glutamic dehydrogenase, isocitrate dehydrogenase, and malate dehydrogenase while 0.1 ppm HCB increased the activity of all enzymes studied, the only exception being glutamic-pyruvic transaminase, the activity of which was depressed by HCB exposure. A concentration of 1.0 ppm HCB depressed the activity of most of the enzymes below control values with the exception of the two mitochondrial enzymes, MDH and ICDH, studied here.

Animals↗

PubMed1975

Studies on tetrahymena membranes. Modification of surface membrane lipids by replacement of tetrahymanol by exogenous ergosterol in Tetrahymena pyriformis.

Tetrahymena pyriformis WH-14 cells were grown in the medium supplemented with ergosterol (1 mg/100 ml) and the effects of replacement of tetrahymanol by ergosterol upon the lipid composition in the surface membranes (cilia and pellicles) were examined. 1. By scanning and freeze-etch electron microscopy it was suggested that exogenous ergosterol would be inserted into the lipid regions in the surface membranes. Although freeze-etched faces of filipin-treated membranes containing the native tetrahymanol showed a random distribution of 85-a protein particles, the ergosterol-replaced membranes after the same polyene treatment revealed the marked ultrastructural alterations on the fracture faces. 2. The replacement of tetrahymanol in membranes by ergosterol induced a profound alteration in the phospholipid class composition and a marked increase in phosphatidylethanolamine with a compensatory decrease in phosphatidylcholine and 2-aminoethylphosphonolipid. 3. There are significant and quantitative but not qualitative changes in the fatty acid composition of total lipids from the ergosterol-replaced membranes. There are also increases in saturated and decreases in unsaturated fatty acids. Phosphatidylethanolamine acyl chains particularly become more saturated, as compared with two other phospholipids, in ergosterol-replaced pellicles. This increase in saturation is due to an appreciable increase in C14:0, C16:0 and iso-C17:0, and a decrease in C18:1(delta9), C18:2(delta9,12) and C18:3(delta6,9,12). 4. These results suggest that profound alterations in phospholipids as well as in their fatty acyl chains are required to modify the overall membrane lipid composition for the maintenance of proper membrane fluidity. Our data would also support the thesis that polat head groups are involved in the membrane lipid organization and that sterols interact selectively with phospholipid molecules containing the appropriate fatty acyl chain composition in biological membranes.

Acetates↗

PubMed1975

Dealkylation of 24-ethylsterols by Tetrahymena pyriformis.

When Tetrahymena pyriformis was incubated with sitosterol ([24R]-24-ethylcholest-5-en-3 beta-ol]) or its trans-delta22-derivative (stigmasterol), the C-24-dealkylated product, cholesta-5,7,trans-22-trien-3 beta-ol, was obtained in both cases. 24(S)-24-Ethylcholesta-5,7,trans-22-trien-3 beta-ol also was found to be a metabolite. When sitosterol was the substrate, 24(R)-24-ethylcholesta-5,7-dien-3 beta-ol was obtained as a third product. Identifications were made by mass spectroscopy, quantitative chromatography, labeling with 14C, and by other means. The dealkylated product (cholestratrienol) represented 30 percent of the sterols isolable after incubation. The administration of sterols to this organism did not induce sterol biosynthesis, since 2-14C-mevalonate failed to yield radioactive sterol in the presence of added stigmasterol.

Animals↗

PubMed1976

Studies on Tetrahymena membranes. In vivo manipulating of membrane lipids by 1-O-hexadecyl glycerol-feeding in Tetrahymena pyriformis.

1. Tetrahymena pyriformis NT-I cells were grown in the medium supplemented with 1-O-hexadecyl glycerol which is the precursor for alkyl ether-containing phospholipids; choline phosphoglyceride and 2-aminoethylphosphonolipid, and alterations in the plasma membrane and microsome lipid composition were examined. No incorporation of supplemented 1-O-hexadecyl glycerol was seen in ethanolamine phosphoglyceride. 2. The hexadecyl glycerol fed membranes contain more polyunsaturated fatty acids than do the native membranes. However, the level of oleic acid (C 18:1) drops strikingly in the phospholipids of plasma and microsome membranes. 3. The hexadecyl glycerol-feeding induced a remarkable alteration in the polar headgroup composition of plasma membrane, especially a large increase in 2-amino-ethylphosphonolipid with a compensatory decrease in ethanolamine phosphoglyceride of plasma membranes. 4. The fatty acyl chain composition of phospholipids, especially ethanolamine phosphoglyceride, of the hexadecyl glycerol-fed plasma membranes and microsomes was found to be significantly different from that of the native membranes. 5. These results may indicate that marked alterations in polar headgroup as well as fatty acyl chain composition of membranes induced by glyceryl ether-feeding would be required for maintaining proper membrane fluidity.

Animals↗

PubMed1975

Putrescine-insensitive S-adenosyl-L-methionine decarboxylase from Tetrahymena pyriformis.

Extracts of Tetrahymena pyriformis contain a soluble S-adenosyl-L-methionine decarboxylase which, in contrast to the enzyme from most eukaryotic organisms, is not stimulated by putrescine or spermidine. The protozoan adenosylmethionine decarboxylase, unlike the putrescine-insensitive enzyme form Escherichia coli, did not require any metal ions for catalytic activity either. Adenosylmethionine decarboxylase from Tetrahymena resembled the prokaryotic enzyme as far the inhibition by methylglyoxal bis(guanylhydrazone) was concerned, but behaved more like putrescine-activated enzyme in regard to the inhibition by 4-bromo-3-hydroxy benzyl-oxyamine. Adesylmethionine decarboxylase from rat liver, baker's yeast, E. coli and Tetrahymena were strongly inhibited by S-methyladenosylhomocysteamine (decarboxylated adenosylmethionine), the product of the reaction. The function of adenosylmethionine decarboxylase from Tetrahymena like that of the enzymes from other organisms appears to be closely connected to the synthesis of spermidine.

Adenosylmethionine Decarboxylase↗

PubMed1976

Numbers of 5S and tRNA genes in macro- and micronuclei of Tetrahymena pyriformis.

Macronuclei of Tetrahymena pyriformis contain approximately 200 copies of the genes for 25S and 17S ribosomal RNA (rRNA) per haploid genome. Micronuclei, however, contain only a few copies of the rRNA genes per haploid complement. Since macronuclei develop from products of meiosis, fertilization and division of micronuclei, we suggested that the multiple copies of the rRNA genes in macronuclei are generated by amplification of the small number of genes in micronuclei (Yao et al., 1974). This process provides a simple mechanism for maintaining the homogeneity of the repeated rRNA gnes. To test if amplification is a general mechanism operating on all repeated genes in Tetrahymena, we have examined the numbers of 5S RNA and tRNA genes in macro- and micronuclei. 5S RNA was purified by polyacrylamide gel electrophoresis and hybridized to saturation against macro- and micronuclear DNA. Approximately 0.013-0.014% of macronuclear DNA and about 0.009% of micronuclear DNA is complementary to 5S RNA. After correcting for the differences in the DNA sequence complexities between the two nuclei, we calculate that there are 300-350 5S genes per haploid macro- or micronuclear genome. From these data we conclude that there is little or no detectable amplification of the 5S genes in macronuclei relative to micronuclei. Similar studies using tRNA indicate that these genes are also highly repeated in both nuclei; about 800 genes are present per haploid genome. Thus, amplification from a small number of genes can be excluded as the mechanism for generating the repeated copies of the 5S and tRNA genes in Tetrahymena and it is likely that another, as yet unidentified, mechanism operates to maintain the homogeneity of these genes.

Animals↗

PubMed1979

The effect of temperature on unsaturated fatty acid loss in Tetrahymena pyriformis.

Cultures of Tetrahymena pyriformis W incorporate exogenous 3-[14C]-cilienic acid and gamma-[1(-14)C] linolenic acid, terminal products of unsaturated fatty acid synthesis, into glycerophosphatides without randomization of the radiolabel. There was no difference in the rate of loss of each of the two acids at 15 or 28.5 degrees C. Differential turnover of these fatty acids, therefore, does not appear to be the cause of the shift in fatty acid pattern observed with temperature reduction.

Fatty Acids, Unsaturated↗

PubMed1979

Synchronizing temperatures and rRNA metabolism in Tetrahymena pyriformis.

1. In Tetrahymena pyriformis pre-rRNA is synthesized and efficiently processed and translocated into the cytoplasm at both a supraoptimal (34 degrees C) and a suboptimal (8 degrees C) synchronizing temperature. 2. At the heat shock temperature (34 degrees C) no substantial differences in the kinetics of the main intracellular events of rRNA-metabolism compared to the optimal growth temperature (28 degrees C) were found. 3. The high temperature, however, induces a strong retardation of uptake of [3H]adenosine into the cells and a reduction of the cellular ATP pool size. 4. At the cold shock temperature (8 degrees C) the rates of transcription and nucleocytoplasmic transport of rRNA as well as of nucleotide pool equilibration are reduced to a similar extent (25-30% of the optimal rates at 28 degrees C). 5. The results are discussed and compared with the effects of sub- and supraoptimal temperatures on rRNA synthesis and processing in mammalian cells.

Adenosine Triphosphate↗

PubMed1975

Cytochemical localization of peroxisomes in Tetrahymena pyriformis.

Pronounced staining of Tetrahymena pyriformis peroxisomes was demonstrated when glutaraldehyde-fixed cells were incubated in an alkaline medium containing 3,3'-diaminobenzidine and hydrogen peroxide. A variable amount of electron-opague deposit was observed when cells were incubated in diaminobenzidine and H2O2 for 1 hr while an intense deposit followed incubation for 4 hr in the same medium. The staining was abolished completely when 3-amino-1,2,4-triazole, KCN or NaN3 was added to the incubation medium. Based on these cytochemical observations and the morphologic identification by size, shape and other ultrastructural details, it is suggested that this study presents evidence for a conclusive morphologic identification of Tetrahymena peroxisomes.

Amitrole↗

PubMed1977

Effect of puromycin on synthesis, processing, and nucleocytoplasmic translocation of rRNA in Tetrahymena pyriformis.

1. Treatment of Tetrahymena pyriformis with various concentrations of puromycin results in a more pronounced inhibition of [3H]uridine accumulation in stable RNA than of protein synthesis. 2. At a concentration of 500 micrograms/ml, which is almost completely inhibitory to [3H]uridine incorporation in vivo, puromycin has no influence on the incorporation of [3H]UTP into RNA in isolated macronuclei. Pretreatment of the cells with the antibiotic, however, reduces the activity of RNA polymerases in isolated nuclei to less than 30%. 3. In puromycin-treated cells a small amount of pre-rRNA is synthesized but not processed into cytoplasmic rRNAs. 4. Puromycin reduces the nucleocytoplasmic translocation of pre-existing RNA to about 25% of the control rate within 5 min, resulting in an accumulation of relatively stable rRNA precursor molecules in the macronucleus.

Animals↗

PubMed1978

Introduction of hidden breaks during rRNA maturation and ageing in Tetrahymena pyriformis.

The stability of Tetrahymena pyriformis cytoplasmic rRNAs and nuclear rRNA precursors has been studied by polyacrylamide gel electrophoresis under partly and completely denaturing conditions. Cytoplasmic 17-S rRNA (Mr = 0.66 X 10(6) consists of a continuous polynucleotide chain throughout its lifetime, whereas the bulk of 26-S rRNA (Mr = 1.2m X 10(6) dissociates upon denaturation. Two large fragments (F1, F2) of somewhat different molecular weights (Mr 0.63 X 10(6) and 0.58 X 10(6) and the small 5.8-S rRNA fragment (Mr about 50 000) are regularly observed. Some additional distinct minor fragments (F3-F6) are noted under certain preparative conditions, suggestive of artifactual origin. The following conclusions were made from the data obtained . (a) Newly synthesized 26-S rRNA molecules do not contain the 'central' hidden break (separating F1 and F2) until about 15 min after their appearance in the cytoplasm; however, they release during denaturation the 5.8-S and/or a short-lived 7-S fragment (Mr about 75 000) which might represent a direct precursor to the 5.8-S rRNA. (b) The immediate nuclear precursor to the 26-S rRNA (Mr 1.39 X 10(6) releases a small fragment of similar size (7 S). (c) The largest stable transcription product of the rDNA (pre-rRNA) does not contain any hidden break.

Animals↗

PubMed1975

The effects of isovalerate supplementation on growth and fatty acid composition of Tetrahymena pyriformis W.

Cultures of Tetrahymena pyriformis W respond to isovalerate supplementation by an increase in odd-numbered saturated, unsaturated and alpha-hydroxy iso-fatty acids and by a decrease in even-numbered normal fatty acids in the glycerolipids and sphingolipids. Supplementation, however, did not alter the relative amount of unsaturated fatty acids found in the polar lipids. The unsaturated acids 17 : 1(i) and 19 : 1(i) were isolated from cells grown with [1-14C]isovalerate and found to have a higher specific activity than the monoenes of the normal series. Isotopic and gas-chromatographic analyses also indicated the presence of dienoic and trienoic acids of the iso-acid series. The iso-fatty acid content was elevated with isovalerate levels up to 5.0 mM and an inhibition of growth was noted. At higher concentrations of the short chain precursor, no further increase in total cellular iso-acids was detected although growth inhibition was more pronounced. The alpha-hydroxy iso-fatty acids of the sphingolipids, however, were elevated in a fashion that paralleled the external concentration of isovalerate; thus, the amount of alpha-hydroxy iso-acids and the degree of growth inhibition show a direct relationship. The increase in alpha-hydroxy iso-acid content of the sphingolipids was at the expense of the saturated normal and iso-acid components. The impact on the physiology of the cells can be envisaged as the result of changes in membrane fluidity due to the presence of high levels of iso-fatty acids without an accompanying reduction in unsaturated acids.

Fatty Acids↗

PubMed1977

Isocitrate dehydrogenase of Tetrahymena pyriformis.

We have studied the isocitrate dehydrogenase of Tetrahymena pyriformis. This enzyme is able to utilize both NAD and NADP, but kinetic studies suggest that the enzymatic activity with NAD is not of physiological signifance. Some of the factors that might regualte the NADP-dependent isocitrate dehydrogenase were also studied. This enzyme has an absolute requirement for divalent cations; Mg,+ and Mn2+ will serve as cofactors but the latter is more effective than the former. It is known that this enzyme is subject to a concerted inhibition by oxaloacetate and glyoxylate. Either glyoxylate or oxaloacetate alone also are capable of inhibiting the enzyme although higher concentrations are required. We have found concerted inhibition also for the NAD-dependent isocitrate dehydrogenase from rat liver and yeast. The activity of the Tetrahymena pyriformis enzyme is inhibited by NADPH. This inhibition is competitive with NADP. The Ki and Km values are, respectively, 20 micrometers and 18 micrometers.

Animals↗