scholarly journals Rates of degradation and synthesis of glycosidases de novo during growth and differentiation of Dictyostelium discoideum

1975 ◽  
Vol 148 (2) ◽  
pp. 169-177 ◽  
Author(s):  
D Every ◽  
J M Ashworth
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Life Cycle ◽  
Dictyostelium Discoideum ◽  
Growth Medium ◽  
Growth Phase ◽  
Enzyme Activities ◽  
De Novo ◽  
Antibody Preparation ◽  
Differentiated Cells

1. Injection of a purified preparation of β-N-acetylglucosaminidase from the spent growth medium of myxamoebae of Dictyostelium discoideum into rabbits gave rise to an antibody preparation containing both anti-α-glucosidase and anti-β-acetylglucosaminidase activities. 2. These two activities were shown to reside in different immunoglobulin molecules and it was concluded that the β-N-acetylglucosaminidase preparation contained trace amounts of highly antigenic α-glucosidase. 3. A single precipitin band having β-N-acetylglucosaminidase activity was formed in Ouchterlony plates when this antibody preparation was tested against extracts obtained from differentiated cells or from myxamoebae grown either axenically or on bacteria. 4. The antibody preparation was used to show that both β-N-acetylglucosaminidase and α-glucosidase molecules are synthesized de novo from isotopically labelled amino acids during both the growth and differentiation phases of the life cycle and to show that neither of these proteins is significantly degraded during the growth phase or during the first 9h of differentiation. 5. The rates of accumulation of these assayable enzyme activities are thus equal to their rates of synthesis during growth and early differentiation. 6. The factors regulating cellular enzyme activity during the life cycle of D. discoideum are discussed.

scholarly journals Acid phosphatase and cathepsin activity in cuttlefish (Sepia officinalis) eggs: the effects of Ag, Cd, and Cu exposure

2010 ◽  
Vol 67 (7) ◽  
pp. 1517-1523 ◽  
Author(s):  
Thomas Lacoue-Labarthe ◽  
Estelle Le Bihan ◽  
David Borg ◽  
Noussithé Koueta ◽  
Paco Bustamante
Keyword(s):  
Heavy Metals ◽  
Enzyme Activity ◽  
Acid Phosphatase ◽  
Embryonic Development ◽  
Enzyme Activities ◽  
De Novo ◽  
Sepia Officinalis ◽  
Activity Levels ◽  
Cathepsin Activity ◽  
Hatchling Weight

Abstract Lacoue-Labarthe, T., Le Bihan, E., Borg, D., Koueta, N., and Bustamante, P. 2010. Acid phosphatase and cathepsin activity in cuttlefish (Sepia officinalis) eggs: the effects of Ag, Cd, and Cu exposure. – ICES Journal of Marine Science, 67: 1517–1523. Changes in the activity levels of acid phosphatase (AcP) and cathepsin during cuttlefish embryo development are described, as are the effects of exposure to heavy metals. Enzyme activity kinetics appear to be linked to the developmental stage. The activities of both enzymes increased during the final days of development, suggesting de novo production by the maturing embryo in the digestive gland. The effects of selected heavy metals, Ag (0.06, 1.2, 60, 1200 ng l−1), Cd (31, 61, 305, 610 ng l−1), and Cu (0.23, 2.3, 23, 230 µg l−1), were assessed based on AcP and cathepsin activities at the end of embryonic development and on hatchling weight. Enzyme activities were not impacted by Ag but were significantly inhibited by Cd, at all four concentrations for AcP and at 610 ng l−1 for cathepsin. Cu (at 2.3 µg l−1) stimulated AcP activity. No cause–effect relationship was found between the effects of metals on the enzyme activities and hatchling weight, suggesting that heavy metals could affect other physiological functions during embryogenesis.

Thymidylate kinase from Acetabularia. II. Regulation during the life cycle

1983 ◽  
Vol 64 (1) ◽  
pp. 27-36
Author(s):  
E.J. de Groot ◽  
H.G. Schweiger
Keyword(s):  
Enzyme Activity ◽  
Life Cycle ◽  
Kinase Activity ◽  
De Novo ◽  
Nuclear Genome ◽  
De Novo Synthesis ◽  
Cell Extracts ◽  
Phase Regulation ◽  
Generative Phase ◽  
Low Activity

The activity of dTMP kinase (EC 2.7.4.9) was estimated during the development of Acetabularia. Enzyme activity was increased at the beginning of the generative phase. Regulation of the dTMP kinase activity was observed even in the absence of the nucleus. More than 30 days after enucleation the enzyme activity increased two- to threefold. The increase in activity was inhibited by puromycin and cycloheximide but not by rifampicin and chloramphenicol. These results indicate that the enzyme is coded by the nuclear genome and translated on 80 S ribosomes. From mixing experiments with low-activity and high-activity cell extracts it is concluded that the regulation is due to de novo synthesis of the enzyme.

scholarly journals Rates of accumulation of glycosidase activities during growth and differentiation of Dictyostelium discoideum

1975 ◽  
Vol 148 (2) ◽  
pp. 161-167 ◽  
Author(s):  
D Every ◽  
J M Ashworth
Keyword(s):  
Life Cycle ◽  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Growth Medium ◽  
Specific Activity ◽  
Growth Conditions ◽  
Cellular Protein ◽  
Total Cellular Protein ◽  
Early Differentiation ◽  
Rate Of Accumulation

1. The rates of accumulation (enzyme units/h per 10(8) cells) of a number of glycosidase activities were studied in Dictyostelium discoideum cells during the growth and differentiation phases of this organism's life cycle. 2. The rates of accumulation of the enzymes β-N-acetylglucosaminidase, α-glucosidase and β-galactosidase remain unchanged during the growth and early differentiation phases. 3. The considerable changes in specific activity of the enzymes which occur in the early differentiation phase are due to the massive loss of total cellular protein which occurs at this time. 4. Significant alterations can occur in the rates of accumulation of α-mannosidase during both the growth and differentiation phases, and since, on the onset of differentiation, β-glucosidase activity is excreted and degraded, the rate of accumulation of this enzyme differs in the growth and differentiation phases. 5. The characteristic rates of accumulation of all these glycosidases change markedly with changes in the growth conditions of the myxamoebae, and thus these rates of synthesis must be regulated independently; however, addition of cyclic AMP to the growth medium has no effect on them.

scholarly journals Developmental Commitment in Dictyostelium discoideum

2007 ◽  
Vol 6 (11) ◽  
pp. 2038-2045 ◽  
Author(s):  
Mariko Katoh ◽  
Guokai Chen ◽  
Emily Roberge ◽  
Gad Shaulsky ◽  
Adam Kuspa
Keyword(s):  
Amino Acids ◽  
Cell Proliferation ◽  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Growth Phase ◽  
Camp Signaling ◽  
Phagocytic Function ◽  
Fruiting Bodies ◽  
Mutant Strains ◽  
Multicellular Organisms

ABSTRACT Upon starvation, Dictyostelium discoideum cells halt cell proliferation, aggregate into multicellular organisms, form migrating slugs, and undergo morphogenesis into fruiting bodies while differentiating into dormant spores and dead stalk cells. At almost any developmental stage cells can be forced to dedifferentiate when they are dispersed and diluted into nutrient broth. However, migrating slugs can traverse lawns of bacteria for days without dedifferentiating, ignoring abundant nutrients and continuing development. We now show that developing Dictyostelium cells revert to the growth phase only when bacteria are supplied during the first 4 to 6 h of development but that after this time, cells continue to develop regardless of the presence of food. We postulate that the cells’ inability to revert to the growth phase after 6 h represents a commitment to development. We show that the onset of commitment correlates with the cells’ loss of phagocytic function. By examining mutant strains, we also show that commitment requires extracellular cyclic AMP (cAMP) signaling. Moreover, cAMP pulses are sufficient to induce both commitment and the loss of phagocytosis in starving cells, whereas starvation alone is insufficient. Finally, we show that the inhibition of development by food prior to commitment is independent of contact between the cells and the bacteria and that small soluble molecules, probably amino acids, inhibit development during the first few hours and subsequently the cells become unable to react to the molecules and commit to development. We propose that commitment serves as a checkpoint that ensures the completion of cooperative aggregation of developing Dictyostelium cells once it has begun, dampening the response to nutritional cues that might inappropriately block development.

The distribution of the stalk cell differentiation inducing factor and other lipids during the differentiation of Dictyostelium discoideum

1986 ◽  
Vol 64 (2) ◽  
pp. 85-90 ◽  
Author(s):  
Nancy Neave ◽  
Linda Kwong ◽  
James I. S. MacDonald ◽  
Gerald Weeks
Keyword(s):  
Life Cycle ◽  
Cell Differentiation ◽  
Dictyostelium Discoideum ◽  
Polar Lipid ◽  
Steryl Ester ◽  
De Novo ◽  
Stalk Cell ◽  
Membrane Bound

The production of the stalk cell differentiation inducing factor (DIF) is restricted to the differentiation phase of the Dictyostelium discoideum life cycle. By the migrating pseudoplasmodial stage, the majority of the accumulated DIF is localized outside the pseudoplasmodia and the remaining pseudoplasmodial DIF is distributed between the intracellular and intercellular compartments. These results indicate possible reasons for the failure to detect gradients of DIF along the migrating pseudoplasmodia. De novo synthesized sterol is also localized predominantly outside the pseudoplasmodia. In contrast the majority of the de novo synthesized polar lipid and steryl ester are within the pseudoplasmodium. Of the de novo synthesized intracellular components, the polar lipid is almost entirely membrane bound and, although most of the sterol and steryl ester are also membrane bound, significant amounts are cytosolic. Intracellular DIF is also detectable in both membrane and cytosolic fractions.

scholarly journals Resetting of 24-nt siRNA landscape is initiated in the unicellular zygote in rice

2020 ◽  
Author(s):  
Chenxin Li ◽  
Jonathan I. Gent ◽  
Hengping Xu ◽  
Hong Fu ◽  
Scott D. Russell ◽  
...  
Keyword(s):  
Stem Cell ◽  
Life Cycle ◽  
Small Rna ◽  
De Novo ◽  
Large Fraction ◽  
Egg Cell ◽  
Critical Stage ◽  
Vegetative Tissues ◽  
Differentiated Cells ◽  
Carry Over

ABSTRACTThe zygote, a totipotent stem cell, constitutes a critical stage of the life cycle for all sexually reproducing organisms. It is produced by fusion of two differentiated cells, egg and sperm, that in plants have radically different siRNA transcriptomes from each other and from multicellular embryos. Here we examined the small RNA transcriptome of unicellular rice zygotes. We find that the overall 24-nt siRNA landscape in the zygote resembles that of the unfertilized egg cell, consistent with maternal carry-over. A large fraction (∼75%) of the siRNAs in the zygote arise from a small proportion (∼2%) of siRNA loci, which corresponded to similar loci in the egg cell and ovary. However, these highly expressing loci were distinct from endosperm siren loci that were detected in later stage endosperm. miRNA abundances changed rapidly after fertilization, resulting in a miRNA profile distinct from the egg cell. Notably, the de novo 24-nt siRNAs expressed by the zygote had characteristics of canonical siRNAs, such as proximity to genes and tendency to overlap TIR DNA transposable elements, and resembled seedling siRNA loci, indicating a return to the canonical siRNA profile typical of vegetative tissues. Taken together, our results suggest that resetting of the gametic epigenome towards the canonical vegetative profile is initiated before the first embryonic division.

A freeze-fracture-etched study of the physarum polycephalum plasma membrane during early formation of the macroplasmodial stage

1993 ◽  
Vol 51 ◽  
pp. 346-347
Author(s):  
Randolph W. Taylor ◽  
Henrie Treadwell
Keyword(s):  
Plasma Membrane ◽  
Life Cycle ◽  
Growth Phase ◽  
Filter Paper ◽  
Physarum Polycephalum ◽  
Freeze Fracture ◽  
Petri Dish ◽  
Wire Screen ◽  
Wide Mouth ◽  
Sterile Filter

The plasma membrane of the Slime Mold, Physarum polycephalum, process unique morphological distinctions at different stages of the life cycle. Investigations of the plasma membrane of P. polycephalum, particularly, the arrangements of the intramembranous particles has provided useful information concerning possible changes occurring in higher organisms. In this report Freeze-fracture-etched techniques were used to investigate 3 hours post-fusion of the macroplasmodia stage of the P. polycephalum plasma membrane.Microplasmodia of Physarum polycephalum (M3C), axenically maintained, were collected in mid-expotential growth phase by centrifugation. Aliquots of microplasmodia were spread in 3 cm circles with a wide mouth pipette onto sterile filter paper which was supported on a wire screen contained in a petri dish. The cells were starved for 2 hrs at 24°C. After starvation, the cells were feed semidefined medium supplemented with hemin and incubated at 24°C. Three hours after incubation, samples were collected randomly from the petri plates, placed in plancettes and frozen with a propane-nitrogen jet freezer.

TERATOGENIC EFFECT OF HERBICIDE GLIFONOX IN RATTUS NORVEGICUS, WISTAR STRAIN

2015 ◽  
Vol 8 ◽  
Author(s):  
Ricardo Ortiz Ortega ◽  
Karla S. Martínez Elizalde ◽  
Tomás Ernesto Villamar-Duque
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Rattus Norvegicus ◽  
Biological Material ◽  
Wistar Rats ◽  
Liver Enzymes ◽  
Teratogenic Effect ◽  
Transaminase Activity ◽  
Wistar Strain ◽  
Herbicide Glyphosate

<p>Teratogenic effect of herbicide glyphosate-Roundup, sold under the name Glifotox on Wistar rats was evaluated. The biological material was treated intraperitoneally with glyphosate at concentrations of 100, 125, and 150 mg/kg from gestation day nine. Hysterectomy was performed on day 18 of gestation, and the uterine horns where the embryos were located, in addition to recording the percentage of malformed embryos by modifying the method of Wilson were observed. The liver was removed and quantified by spectrophotometry with transaminase activity showed higher concentrations malformation rate and higher enzyme activity was 125 mg/kg, below is the average of 100 mg/kg and higher concentrations such as 150 mg/kg a large number of resorptions was obtained. It is concluded that glyphosate is toxic affecting the liver and liver enzymes involved in the formation of amino acids also produce delay in embryonic development.</p>

scholarly journals An enzymatic activation of formaldehyde for nucleotide methylation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Charles Bou-Nader ◽  
Frederick W. Stull ◽  
Ludovic Pecqueur ◽  
Philippe Simon ◽  
Vincent Guérineau ◽  
...  
Keyword(s):  
Amino Acids ◽  
Thymidylate Synthase ◽  
Active Site ◽  
De Novo ◽  
Crystallographic Structure ◽  
De Novo Synthesis ◽  
Active Site Residues ◽  
Enzymatic Activation ◽  
Enzyme Cofactors ◽  
Unique Ability

AbstractFolate enzyme cofactors and their derivatives have the unique ability to provide a single carbon unit at different oxidation levels for the de novo synthesis of amino-acids, purines, or thymidylate, an essential DNA nucleotide. How these cofactors mediate methylene transfer is not fully settled yet, particularly with regard to how the methylene is transferred to the methylene acceptor. Here, we uncovered that the bacterial thymidylate synthase ThyX, which relies on both folate and flavin for activity, can also use a formaldehyde-shunt to directly synthesize thymidylate. Combining biochemical, spectroscopic and anaerobic crystallographic analyses, we showed that formaldehyde reacts with the reduced flavin coenzyme to form a carbinolamine intermediate used by ThyX for dUMP methylation. The crystallographic structure of this intermediate reveals how ThyX activates formaldehyde and uses it, with the assistance of active site residues, to methylate dUMP. Our results reveal that carbinolamine species promote methylene transfer and suggest that the use of a CH2O-shunt may be relevant in several other important folate-dependent reactions.

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