Calcium activity versus "calcium threshold" as the key factor in the induction of yeast flocculation in simulated industrial fermentations

1991 ◽  
Vol 37 (4) ◽  
pp. 295-303 ◽  
Author(s):  
Charlotte L. Masy ◽  
Myriam Kockerols ◽  
Michèle M. Mestdagh
Keyword(s):  
Calcium Concentration ◽  
Chelating Agents ◽  
Laboratory Culture ◽  
Culture Conditions ◽  
Free Calcium ◽  
Yeast Saccharomyces Cerevisiae ◽  
Calcium Activity ◽  
Yeast Flocculation ◽  
Key Factor ◽  
Two Parameters

Yeast flocculation is regulated by two parameters: the free-calcium activity and the "calcium threshold" or the quantity of calcium at which cells flocculate in a turbidimetric test. The study of the influence of different factors such as calcium concentration, pH, and chelating agents on flocculation has led us to put forward the following hypothesis. Flocculation occurs when the calcium threshold becomes equal to free-calcium activity, i.e., when the medium contains the exact quantity of calcium necessary for flocculation to occur. This hypothesis has been confirmed under standard laboratory culture conditions and in simulated industrial fermentations. Key words: flocculation, yeast, Saccharomyces cerevisiae, calcium induction.

scholarly journals Signaling and sites of interaction for RX-871024 and sulfonylurea in the stimulation of insulin release

1998 ◽  
Vol 274 (4) ◽  
pp. E751-E757 ◽  
Author(s):  
Alexandre M. Efanov ◽  
Sergei V. Zaitsev ◽  
Ioulia B. Efanova ◽  
Shunsheng Zhu ◽  
Claes-Göran Östenson ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Calcium Concentration ◽  
Signal Transduction Pathway ◽  
Free Calcium ◽  
Direct Stimulation ◽  
Perfused Rat Pancreas ◽  
Free Calcium Concentration ◽  
Two Parameters ◽  
Insulinotropic Effect ◽  
Stimulation Of

The objective of this study was to compare effects of RX-871024, a compound with imidazoline structure, and the sulfonylurea glibenclamide, representatives of two groups of ATP-dependent potassium channel (KATP) blockers, on insulin secretion and cytoplasmic free calcium concentration ([Ca2+]i). Furthermore, we studied the interaction of the compounds on these two parameters. The experiments were performed in the perfused rat pancreas, isolated rat pancreatic islets, and dispersed β-cells. At maximal effective concentrations of the compounds, RX-871024 had a more pronounced insulinotropic effect than glibenclamide, but the increase in [Ca2+]iwas similar. Glibenclamide enhanced the insulinotropic effect of suboptimal concentrations of RX-871024 at 3.3 and 16.7 mM glucose. Notably, glibenclamide and RX-871024 also stimulated insulin secretion under Ca2+-clamped conditions, i.e., during plasma membrane depolarization with KCl and glucose or in permeabilized islets. The magnitudes of insulin stimulation under the latter types of conditions were similar for both compounds. It is concluded that RX-871024 and the sulfonylurea glibenclamide promote insulin secretion by two mechanisms, namely closure of KATP channels and a direct stimulation of exocytosis. At a similar increase in [Ca2+]i, the maximal stimulatory effect of RX-871024 on insulin secretion was stronger than that of glibenclamide, implying that RX-871024 also affects insulin secretion by a signal transduction pathway that is not activated by glibenclamide.

Hypothalamic Hypophyseal Inhibitory Factor (HHIF) Increases Intrasynaptosomal Free Calcium Concentration

Hypertension ◽  
1997 ◽  
Vol 29 (6) ◽  
pp. 1337-1343 ◽  
Author(s):  
Mercedes Ricote ◽  
Elena Garcia-Martin ◽  
Jose Sancho ◽  
Carlos Gutierrez-Merino
Keyword(s):  
Calcium Concentration ◽  
Inhibitory Factor ◽  
Free Calcium ◽  
Free Calcium Concentration

Identification of ecto-PKC on surface of human platelets: role in maintenance of latent fibrinogen receptors

2000 ◽  
Vol 278 (6) ◽  
pp. H2008-H2019 ◽  
Author(s):  
Anna Babinska ◽  
Michael V. Hogan ◽  
Tomasz Sobocki ◽  
Malgorzata B. Sobocka ◽  
Yigal H. Ehrlich ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Calcium Concentration ◽  
Surface Protein ◽  
Human Platelets ◽  
Surface Proteins ◽  
Free Calcium ◽  
Platelet Surface ◽  
Inhibitory Peptides ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration

Human platelets express a protein phosphorylation system on their surface. A specific protein kinase C (PKC) antibody, monoclonal antibody (MAb) 1.9, which binds to the catalytic domain of PKC and inhibits its activity, causes the aggregation of intact platelets while inhibiting the phosphorylation of platelet surface proteins. Photoaffinity labeling with 100 nM 8-azido-[α32P]ATP identified this ecto-PKC as a single surface protein of 43 kDa sensitive to proteolysis by extracellular 0.0005% trypsin. Inhibition of the binding of 8-azido-[α32P]ATP to the 43-kDa surface protein by MAb 1.9 identified this site as the active domain of ecto-PKC. Covalent binding of the azido-ATP molecule to the 43-kDa surface protein inhibited the phosphorylative activity of the platelet ecto-PKC. Furthermore, PKC pseudosubstrate inhibitory peptides directly induced the aggregation of platelets and inhibited azido-ATP binding to the 43-kDa protein. Platelet aggregation induced by MAb 1.9 and by PKC inhibitory peptides required the presence of fibrinogen and resulted in an increase in the level of intracellular free calcium concentration. This increase in intracellular free calcium concentration induced by MAb 1.9 was found to be dependent on the binding of fibrinogen to activated GPIIb/IIIa integrins, suggesting that MAb 1.9 causes Ca2+flux through the fibrinogen receptor complex. We conclude that a decrease in the state of phosphorylation of platelet surface proteins caused by inhibition of ecto-PKC results in membrane rearrangements that can induce the activation of latent fibrinogen receptors, leading to platelet aggregation. Accordingly, the maintenance of a physiological steady state of phosphorylation of proteins on the platelet surface by ecto-PKC activity appears to be one of the homeostatic mechanisms that maintain fibrinogen receptors of circulating platelets in a latent state that cannot bind fibrinogen.

Extracellular ATP increases [Ca 2+]i in distal tubule cells. I. Evidence for a P2Y2 purinoceptor

2000 ◽  
Vol 279 (1) ◽  
pp. F92-F101 ◽  
Author(s):  
Michel Bidet ◽  
Guy De Renzis ◽  
Sonia Martial ◽  
Isabelle Rubera ◽  
Michel Tauc ◽  
...  
Keyword(s):  
Calcium Concentration ◽  
Distal Tubule ◽  
Calcium Flux ◽  
Free Calcium ◽  
Receptor Subtype ◽  
Cytoplasmic Calcium ◽  
P2y2 Receptor ◽  
Nucleotide Analogs ◽  
Flux Measurements ◽  
Free Calcium Concentration

Experiments were performed to characterize the P2 purinoceptor subtype responsible for cytoplasmic calcium mobilization in cells from the initial part of rabbit distal convoluted tubule (DCT). Free calcium concentration was measured in a DCT cell line (DC1) with the probe fura 2. Both ATP and UTP increased cytosolic Ca2+ concentration ([Ca2+]i; EC50 3 and 6 μM, respectively). The order of potency for nucleotide analogs was ATP = UTP > adenosine 5′- O-[thiotriphosphate] ≫ ADP > UDP, which is consistent with the pharmacology of the P2Y2 receptor subtype. The increased [Ca2+]iresponses to ATP and UTP were strongly inhibited by suramin. Pretreatment of cells with pertussis toxin (PTX) attenuated the action of both nucleotides. Inhibition of phospholipase C with U-73122 totally blocked the [Ca2+]i response to ATP. Thus ATP- and UTP-stimulated [Ca2+]i mobilization in DC1 cells appears to be mediated via the activation of P2Y2 purinoceptors coupled to a G protein mechanism that is partially sensitive to PTX. Calcium flux measurements showed that lanthanum- and nifedipine-sensitive calcium channels are involved in the [Ca2+]i response to ATP.

Platelet Cytosolic Free Calcium in Essential Hypertension: Responses to Vasopressin

1989 ◽  
Vol 77 (2) ◽  
pp. 183-188 ◽  
Author(s):  
A. F. Dominiczak ◽  
J. J. Morton ◽  
G. Murray ◽  
P. F. Semple
Keyword(s):  
Essential Hypertension ◽  
Arginine Vasopressin ◽  
Calcium Concentration ◽  
Systolic Pressure ◽  
Extracellular Calcium ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Hypertensive Patients ◽  
Free Calcium Concentration ◽  
The Difference

1. Resting and stimulated free calcium concentrations have been measured in platelets loaded with the fluorescent probe quin2 from 30 patients with essential hypertension and from 30 age-matched controls. 2. Cytosolic free calcium concentrations were 94.6 ± 2.7 (mean ± sem) in the hypertensive group and 91.7 ± 2.8 nmol/l in the normotensive group, the difference was not significant. 3. Arginine vasopressin caused a transient increase in platelet free calcium concentration in all subjects. In the presence of extracellular calcium the increase was significantly higher in the control subjects than in the hypertensive patients (P = 0.005). In the absence of extracellular calcium, arginine vasopressin caused much smaller increases, and there was then no difference between the responses of the two groups. 4. Platelet free calcium concentrations were measured again in 13 patients after 8 weeks treatment with either verapamil (n = 6) or atenolol (n = 7). The reductions in systolic pressure after drug treatment were correlated with the changes in cytosolic free calcium concentrations (r = 0.75, P < 0.01).

scholarly journals pH Variability and its Relationship with Sarcomere Length and Free Calcium in Beef from Commercial Cattle in Puerto Rico

2019 ◽  
Vol 3 (2) ◽  
Author(s):  
Y. I. Torres-Burgos ◽  
H. Sánchez-Rodríguez ◽  
M. Pagán-Morales ◽  
A. Casas-Guernica ◽  
C. Calkins ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Beef Cattle ◽  
Dairy Cattle ◽  
Calcium Concentration ◽  
Sarcomere Length ◽  
Free Calcium ◽  
Ph Values ◽  
And Gender ◽  
The University ◽  
The Relationship

ObjectivesResearch conducted at the University of Puerto Rico noted that beef with elevated pH values (> 5.86) resulted in more tender meat (P ≤ 0.05). It has been established that proteolytic degradation mechanisms can be influenced by pH and calcium concentration in muscle. Beef with pH values ≥ 5.86 is classified as Dark Firm and Dry (DFD) but there are negative implications associated with greater pH values. However, observations indicating increased tenderness with increased pH raise the question: can variations in pH be associated with differences in sarcomere length (SL) and free calcium concentration (FCC)? Therefore, the objectives of this project were to: (1) document pH distribution; (2) determine the incidence of DFD; and (3) evaluate the relationship between pH, SL, and FCC in commercial cattle harvested in Puerto Rico.Materials and MethodsLongissimus lumborum samples (n = 51) were obtained and background information was noted including number of permanent incisors (PI), type (Dairy or Beef), and gender. The pH values were used to categorize beef into the following groups: Low (≤ 5.40), Normal (5.41 to 5.59), High (5.60 to 5.85) and DFD (≥ 5.86). Meat was flash frozen, powdered, and placed on a microscope slide and a Helium-Neon laser was used to determine SL. A subset of samples was sent off and prepared at the University of Nebraska-Lincoln for FCC quantification (Ward Laboratories; Kearney, NE) with an inductively coupled plasma emission spectrometer (iCAP 6500 Radial; Thermo Electron, Cambridge, UK). All statistical analyses were conducted in SAS (9.4). The Proc FREQ was used to determine pH category distributions and incidence of DFD. The Proc GLIMMIX and Tukey adjustment (α = 0.05) were used to determine the effects of number of PI, type, and gender on pH category, SL and FCC. The Proc CORR was used to evaluate the relationship between pH category, SL and FCC.ResultsThe pH category distribution for the current samples was as follows: 3.92% Low, 41.18% Normal, 35.29% High and 19.61% DFD. The SL ranged from 1.69 to 1.46 mm with an average of 1.53 mm. The FCC ranged from 132.19 to 31.39 mM with an average of 64.23 mM. Longer sarcomeres were detected in cattle with eight and zero PI (1.57 and 1.56 mm, respectively); cattle with two and four PI had intermediate SL (1.53 and 1.52 mm, respectively), and cattle with six PI had the shortest sarcomeres (1.51 mm; P = 0.03). Dairy cattle had longer sarcomeres relative to beef cattle (1.56 vs. 1.52 mm; P = 0.02). Dairy cattle tended to have increased FCC relative to beef cattle (70.72 vs. 58.38 mM; P = 0.08). Also, FCC tended to be greater within the Normal and Low pH categories relative to the High and DFD categories (72.36 vs. 57.31 mM; P = 0.06). The SL and FCC had no relationship (P > 0.05) within the Low, Normal and High pH categories. However, DFD beef had longer SL (0.78; P = 0.01), while having decreased FCC (–0.66; P = 0.04).ConclusionOver half (54.90%) of the beef samples analyzed fell into the High and DFD pH categories, with nearly 20% being classified as DFD. Although, a clear relationship was not established between SL and FCC within the Low, Normal or High pH categories, the results indicate that the increased pH in samples surpassing the DFD threshold correspond to longer sarcomeres and decreased free calcium.

scholarly journals Research Advance: Extending chemical perturbations of the Ubiquitin fitness landscape in a classroom setting

2017 ◽  
Author(s):  
David Mavor ◽  
Kyle A. Barlow ◽  
Daniel Asarnow ◽  
Yuliya Birman ◽  
Derek Britain ◽  
...  
Keyword(s):  
Fitness Landscape ◽  
Nickel Chloride ◽  
Cobalt Acetate ◽  
Laboratory Culture ◽  
Culture Conditions ◽  
Sequence Conservation ◽  
Classroom Setting ◽  
Evolutionary Time ◽  
The Difference ◽  
Chemical Conditions

AbstractAlthough the primary protein sequence of ubiquitin (Ub) is extremely stable over evolutionary time, it is highly tolerant to mutation during selection experiments performed in the laboratory. We have proposed that this discrepancy results from the difference between fitness under laboratory culture conditions and the selective pressures in changing environments over evolutionary time scales. Building on our previous work (Mavor et al 2016), we used deep mutational scanning to determine how twelve new chemicals (3-Amino-1,2,4-triazole, 5-fluorocytosine, Amphotericin B, CaCl2, Cerulenin, Cobalt Acetate, Menadione, Nickel Chloride, p-fluorophenylalanine, Rapamycin, Tamoxifen, and Tunicamycin) reveal novel mutational sensitivities of ubiquitin residues. We found sensitization of Lys63 in eight new conditions. In total, our experiments have uncovered a sensitizing condition for every position in Ub except Ser57 and Gln62. By determining the Ubiquitin fitness landscape under different chemical constraints, our work helps to resolve the inconsistencies between deep mutational scanning experiments and sequence conservation over evolutionary timescales.Builds onMavor D, Barlow KA, Thompson S, Barad BA, Bonny AR, Cario CL, Gaskins G, Liu Z, Deming L, Axen SD, Caceres E, Chen W, Cuesta A, Gate R, Green EM, Hulce KR, Ji W, Kenner LR, Mensa B, Morinishi LS, Moss SM, Mravic M, Muir RK, Niekamp S, Nnadi CI, Palovcak E, Poss EM, Ross TD, Salcedo E, See S, Subramaniam M, Wong AW, Li J, Thorn KS, Conchúir SÓ, Roscoe BP, Chow ED, DeRisi JL, Kortemme T, Bolon DN, Fraser JS. Determination of Ubiquitin Fitness Landscapes Under Different Chemical Stresses in a Classroom Setting. eLife. 2016.Impact StatementWe organized a project-based course that used deep mutational scanning in multiple chemical conditions to resolve the inconsistencies between tolerance to mutations in laboratory conditions and sequence conservation over evolutionary timescales.

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