scholarly journals The metabolic sequence by which some 4,4-dimethyl sterols are converted into cholesterol

1974 ◽  
Vol 144 (1) ◽  
pp. 59-68 ◽  
Author(s):  
Geoffrey F. Gibbons
Keyword(s):  
Microsomal Fraction ◽  
Soluble Fraction ◽  
Sterol Fraction ◽  
Methyl Groups ◽  
Methyl Group ◽  
Metabolic Sequence ◽  
Cholesterol Precursor ◽  
Fold Stimulation ◽  
Better Than ◽  
Stimulation Of

Cholest-8(14)-enol is the major radioactive component of the 4-di-demethyl sterol fraction biosynthesized from 4,4-dimethyl[2-3H2]cholest-8(14)-enol by rat liver microsomal fractions, and therefore the first steps in the biosynthesis of cholesterol from the latter compound probably involve removal of the 4-methyl groups. 4,4-Dimethylcholesta-8,14-dienol therefore is not an intermediate in this process, although its presence in the incubation medium at a concentration of 0.146mm almost completely inhibits the demethylation of 4,4-dimethyl[2-3H2]cholest-8(14)-enol. Nor is cholesta-8,14-dienol an intermediate in the conversion of cholest-8(14)-enol into cholest-7-enol and cholesterol. With 4,4-dimethyl[2-3H2]cholesta-8,14-dienol as the cholesterol precursor, 4,4-dimethylcholest-8(9)-enol becomes heavily labelled and there is very little radioactivity associated with cholesta-8,14-dienol.In this case, the most heavily labelled 4-di-demethyl sterols are cholest-7-enol and cholesterol with the former predominating. There is little or no radio-activity associated with cholest-8(14)-enol. A similar labelling pattern amongst the 4-di-demethyl sterols was observed with dihydro[14C]lanosterol as the precursor. The first step therefore in the synthesis of cholesterol from the 4,4-dimethyl[2-3H2]dienol is reduction of the Δ14(15) bond and not removal of the 4α-methyl group. Depending on the nature of the precursor, addition of the soluble fraction of the cell to the microsomal fraction resulted in a two- to four-fold stimulation of 4-di-demethyl sterol biosynthesis from the 4,4-dimethyl sterols studied. Under these conditions, 4,4-dimethylcholesta-8,14-dienol is the most efficient precursor of cholesterol and cholest-7-enol, and dihydrolanosterol is better than 4,4-dimethylcholest-8(14)-enol.

scholarly journals Phosphoric acid triester–glutathione alkyltransferase. A mechanism for the detoxification of dimethyl phosphate triesters

1972 ◽  
Vol 127 (1) ◽  
pp. 285-293 ◽  
Author(s):  
D. H. Hutson ◽  
B. A. Pickering ◽  
C. Donninger
Keyword(s):  
Phosphoric Acid ◽  
Soluble Fraction ◽  
Methyl Groups ◽  
Pig Liver ◽  
Methyl Group ◽  
Similar Activity ◽  
Dimethyl Phosphate ◽  
Mammalian Liver

1. 2-Chloro-1-(2,4,5-trichlorophenyl)vinyl dimethyl phosphate (tetrachlorvinphos) is demethylated by mammalian liver supernatant (100000g) protein in the presence of GSH. 2. GSH acts as an acceptor of the transferred methyl group to form S-methyl glutathione. 3. The enzyme that catalyses this reaction is present in the soluble fraction of liver from mouse, rat, rabbit and pig at similar activity. The enzyme was purified 45-fold from pig liver, dimethyl 1-naphthyl phosphate being used as assay substrate. 4. Methyl groups are readily removed from most of the substrates studied; ethyl groups are removed at one-fiftieth to one-hundredth of the rate for methyl groups. It is likely that the enzyme plays an important role in the detoxification of the phosphate triester pesticides containing CH3–O–P groups.

Secretagogue-induced changes in subcellular Ca2+ distribution in isolated pancreatic acini

1981 ◽  
Vol 240 (2) ◽  
pp. G130-G140
Author(s):  
R. L. Dormer ◽  
J. A. Williams
Keyword(s):  
Atomic Absorption Spectrometry ◽  
High Speed ◽  
Microsomal Fraction ◽  
Absorption Spectrometry ◽  
Subcellular Fractionation ◽  
Differential Centrifugation ◽  
Zymogen Granules ◽  
Pancreatic Acini ◽  
Induced Changes ◽  
Stimulation Of

In a prior study, we demonstrated that pancreatic secretagogues increased both the uptake into and washout of 45Ca2+ from isolated mouse pancreatic acini. The net result of these processes was an initial fall in total acinar cell Ca2+ content. In the present study, we have employed subcellular fractionation of acini under conditions that minimized posthomogenization redistribution of Ca2+ in order to localize those organelles involved in intracellular Ca2+ fluxes. Homogenization and differential centrifugation of acini, preloaded with 45Ca2+ and subjected to a period of washout, showed that carbachol induced an increased loss of 45Ca2+ from all fractions isolated. The high-speed microsomal fraction lost 45Ca2+ to a greater extent than did whole acini; measurement of total Ca2+ by atomic absorption spectrometry showed a net loss of Ca2+ from this fraction. Purification of the lower-speed fractions indicated that carbachol increased 45Ca2+ exchange with both zymogen granules and mitochondria, but net Ca2+ levels in these organelles were unchanged. It was concluded that stimulation of pancreatic acini by carbachol results in the release of calcium from a microsomal compartment leading to a rise in cytoplasmic Ca2+, increased exchange with granule and mitochondrial Ca2+, and increased efflux of Ca2+ from the cell.

Kinetin-Mediated Stimulation of Accumulation of Buckwheat Flavonoids in the Dark

1983 ◽  
Vol 38 (9-10) ◽  
pp. 711-718 ◽  
Author(s):  
U. Margna ◽  
T. Vainjärv
Keyword(s):  
Anthocyanin Biosynthesis ◽  
Flavonoid Biosynthesis ◽  
Accumulation Rates ◽  
Sharp Rise ◽  
Short Treatment ◽  
Exogenous Substrate ◽  
Percent Increase ◽  
High Level ◽  
Fold Stimulation ◽  
Stimulation Of

A short treatment of excised buckwheat cotyledons with a solution of kinetin lead to an up to 9-fold stimulation of anthocyanin biosynthesis, to an about 50 percent increase in the accumula­tion of rutin, and to an about 30 percent increase, on the average, in the accumulation of C-glycosylflavones in the treated material during its posttreatment incubation in the dark. When the treated cotyledons were incubated in a solution of ʟ--phenylalanine anthocyanin accumulation in the dark practically attained the same high level as it was observed in the illuminated cotyledons fed with exogenous ʟ--phenylalanine. In experiments with l4C-labelled L-phenylalanine kinetin induced a sharp rise in the labelling (resp. in the utilization of exogenous substrate for biosynthesis) of anthocyanins and rutin in the dark and a slight increase in the radioactivity of C-glycosylflavones. Similar labelling changes occurred in the illuminated cotyledons. However, both kinetin and light still more effectively promoted biosynthetic use of the endogenous sub­strate. As a result the relative portion of flavonoids formed from exogenous L-phenylalanine under these conditions showed a decrease as compared with the ratio of precursor use in the un­treated cotyledons. The results show that low accumulation rates of anthocyanins and other flavo­noids in the dark are conditioned by the limited access of substrate (ʟ--phenylalanine) molecules to the flavonoid enzymes lending further support to the idea that flavonoid biosynthesis is normally controlled at the substrate rather than at the enzymic level.

Net charges and valence AO's in the methylamines; the hydrogen basis set and the properties of nitrogen

1985 ◽  
Vol 63 (7) ◽  
pp. 1487-1491 ◽  
Author(s):  
Giuseppe Del Re ◽  
Sándor Fliszár ◽  
Michel Comeau ◽  
Claude Mijoule
Keyword(s):  
Basis Set ◽  
Basis Sets ◽  
Methyl Groups ◽  
Extended Form ◽  
Amine Nitrogen ◽  
Methyl Group ◽  
Net Charges ◽  
Extended Basis

Net charges and valence AO's for ammonia, methylamine, dimethylamine, and trimethylamine were calculated using extended basis sets. Superposition effects, evaluated by replacing Pople's standard 6-31G* basis by an extended form in which the basis of the ammonia H atoms and of the methyl groups of trimethylamine are retained in the treatment of each molecule, indicate that the quality of the treatment of amine nitrogen atoms is strongly dependent on the number of methyl groups. A new, augmented basis is proposed for the hydrogens, which appears to be reasonably well balanced: comparison with familiar (e.g., 6-31G*) calculations illustrates in what manner the treatment of nitrogen is worsened when even just one methyl group is replaced by hydrogen unless the impoverishment of the basis is suitably taken care of.

Swelling-activated transport of taurine in cultured gill cells of sea bass: physiological adaptation and pavement cell plasticity

2009 ◽  
Vol 296 (4) ◽  
pp. R1149-R1160 ◽  
Author(s):  
Martine Avella ◽  
Olivier Ducoudret ◽  
Didier F. Pisani ◽  
Philippe Poujeol
Keyword(s):  
Sea Bass ◽  
Physiological Adaptation ◽  
Dimensional Structure ◽  
Taurine Transport ◽  
Hypotonic Shock ◽  
Cells In Culture ◽  
Membrane Stretch ◽  
Gill Cells ◽  
Fold Stimulation ◽  
Stimulation Of

We have investigated volume-activated taurine transport and ultrastructural swelling response of sea bass gill cells in culture, assuming that euryhaline fish may have developed particularly efficient mechanisms of salinity adaptation. In vivo, when sea basses were progressively transferred from seawater to freshwater, we noticed a decrease in blood osmotic pressure. When gill cells in culture were subjected to 30% hypotonic shock, we observed a five-fold stimulation of [3H]taurine efflux. This transport was reduced by various anion channel inhibitors with the following efficiency: 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) > niflumic acid > DIDS = diphenylamine-2-carboxylic acid. With polarized gill cells in culture, the hypotonic shock produced a five-fold stimulation of apical taurine transport, whereas basolateral exit was 25 times higher. Experiments using ionomycin, thapsigargin, BAPTA-AM, or removal of extracellular calcium suggested that taurine transport was regulated by external calcium. The inhibitory effects of lanthanum and streptomycin support Ca2+ entry through mechanosensitive Ca2+ channels. Branchial cells also showed hypotonically activated anionic currents sensitive to DIDS and NPPB. Similar pharmacology and time course suggested the potential existence of a common pathway for osmosensitive taurine and Cl− efflux through volume-sensitive organic osmolyte and anion channels. A three-dimensional structure study revealed that respiratory gill cells began to swell only 15 s after hypoosmotic shock. Apical microridges showed membrane outfoldings: the cell surface became smoother with a progressive disappearance of ridges. Therefore, osmotic swelling may not actually induce membrane stretch per se, inasmuch as the microridges may provide a reserve of surface area. This work demonstrates mechanisms of functional and morphological plasticity of branchial cells during osmotic stress.

scholarly journals Pengaruh Model Pendampingan Deteksi Dini Terhadap Kemampuan Guru PAUD Dalam Melaksanakan Deteksi Dini Pertumbuhan Dan Perkembangan Anak PAUD di Wilayah Puskesmas Beji Depok

2020 ◽  
Vol 11 (2) ◽  
pp. 94-100
Author(s):  
Suryati B ◽  
Bara Miradwiyana
Keyword(s):  
Early Childhood ◽  
Early Detection ◽  
Growth And Development ◽  
Intervention Group ◽  
Control Group ◽  
Childhood Growth ◽  
Childhood Education ◽  
Better Than ◽  
Stimulation Of ◽  
Mentoring Model

Impaired growth and development of children can be identified by early detection as prevention, prevention, stimulation and development. This study aims to determine the effect of early detection assistance models on the ability of early childhood education (PAUD) teachers in implementing early detection of early childhood growth and development. The research method uses pretest and posttest design with control group. Providing training and mentoring for PAUD teachers using the Stimulation of Detection and Early Intervention Growing Swell (SDIDTK)/ Child Development Pre-screening Questionnaire (KPSP) for the intervention group while for the control group for PAUD teachers by being given a KPSP booklet after the posttest. The results of the analysis showed that there were differences in scores of PAUD teachers' knowledge and skills in stimulating early childhood growth and development (p=0.001) between the intervention group and the control group after the mentoring model intervention. The knowledge of PAUD teachers who are given a mentoring model is better than the control group, there are significant differences in improving the ability of PAUD teachers to do early detection in children compared to the control group. PAUD teachers who are given the intervention of the mentoring model.

The Rates and Products of Addition of 4-Chlorobenzenesulfenyl Chloride to a Series of Side Chain Methyl Substituted Styrenes

1974 ◽  
Vol 52 (9) ◽  
pp. 1807-1812 ◽  
Author(s):  
George H. Schmid ◽  
Dennis G. Garratt
Keyword(s):  
Steric Hindrance ◽  
Side Chain ◽  
Methyl Groups ◽  
Methyl Group

The rates of addition and the product compositions have been determined for the addition of 4-chlorobenzenesulfenyl chloride to a series of seven side chain methyl substituted styrenes in 1,1,2,2-tetrachloroethane at 25°. Unlike the addition to the corresponding series of methylated ethylenes, the effect of the methyl groups is not cumulative. The effect of the methyl groups depends upon whether or not the β-methyl group is cis to the phenyl. When it is cis, the rate of addition is decreased compared to styrene and substitution of additional methyl groups has only a small effect on the rate of addition. In compounds lacking a cis-β-methyl group the rate of addition more closely resembles that for addition to the methylated ethylenes. Steric hindrance between the cis-methyl and phenyl groups is believed to be the cause of this difference in behavior between the ethylene and styrene series.

scholarly journals Stimulation of the alternative oxidase of Neurospora crassa by Nucleoside phosphates

1980 ◽  
Vol 188 (1) ◽  
pp. 141-144 ◽  
Author(s):  
J Vanderleyden ◽  
C Peeters ◽  
H Verachtert ◽  
H Bertrand
Keyword(s):  
Neurospora Crassa ◽  
Oxidase Activity ◽  
Alternative Oxidase ◽  
Purine Nucleoside ◽  
Submitochondrial Particles ◽  
Fold Stimulation ◽  
Succinate Oxidase ◽  
Stimulation Of

The alternative-oxidase-mediated succinate oxidase activity of Neurospora crassa decreases drastically when mitochondria are fractionated into submitochondrial particles or treated with deoxycholate. The activity, however, can be completely restored in the presence of nucleoside 5′-monophosphates. The purine nucleoside 5′-monophosphates are more effective than the pyrimidine homologues. 5′-GMP gives a 10-fold stimulation of the alternative-oxidase-mediated succinate oxidase activity in submitochondrial particles. A comparison is made with the results obtained earlier with Moniliella tomentosa [Hanssens & Verachtert (1976) J. Bacteriol. 125, 825–835; Vanderleyden, Van Den Eynde & Verachtert (1980) Biochem. J. 186, 309–316].

scholarly journals Glucose stimulates somatostatin secretion in pancreatic δ-cells by cAMP-dependent intracellular Ca2+ release

2019 ◽  
Vol 151 (9) ◽  
Author(s):  
Geoffrey Denwood ◽  
Andrei Tarasov ◽  
Albert Salehi ◽  
Elisa Vergari ◽  
Reshma Ramracheya ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Secretory Vesicles ◽  
Glucose Levels ◽  
Somatostatin Secretion ◽  
Elevated Glucose ◽  
Mouse Islets ◽  
Underlying Mechanisms ◽  
Fold Stimulation ◽  
Cyclase Activator ◽  
Stimulation Of

Somatostatin secretion from pancreatic islet δ-cells is stimulated by elevated glucose levels, but the underlying mechanisms have only partially been elucidated. Here we show that glucose-induced somatostatin secretion (GISS) involves both membrane potential-dependent and -independent pathways. Although glucose-induced electrical activity triggers somatostatin release, the sugar also stimulates GISS via a cAMP-dependent stimulation of CICR and exocytosis of somatostatin. The latter effect is more quantitatively important and in mouse islets depolarized by 70 mM extracellular K+, increasing glucose from 1 mM to 20 mM produced an ∼3.5-fold stimulation of somatostatin secretion, an effect that was mimicked by the application of the adenylyl cyclase activator forskolin. Inhibiting cAMP-dependent pathways with PKI or ESI-05, which inhibit PKA and exchange protein directly activated by cAMP 2 (Epac2), respectively, reduced glucose/forskolin-induced somatostatin secretion. Ryanodine produced a similar effect that was not additive to that of the PKA or Epac2 inhibitors. Intracellular application of cAMP produced a concentration-dependent stimulation of somatostatin exocytosis and elevation of cytoplasmic Ca2+ ([Ca2+]i). Both effects were inhibited by ESI-05 and thapsigargin (an inhibitor of SERCA). By contrast, inhibition of PKA suppressed δ-cell exocytosis without affecting [Ca2+]i. Simultaneous recordings of electrical activity and [Ca2+]i in δ-cells expressing the genetically encoded Ca2+ indicator GCaMP3 revealed that the majority of glucose-induced [Ca2+]i spikes did not correlate with δ-cell electrical activity but instead reflected Ca2+ release from the ER. These spontaneous [Ca2+]i spikes are resistant to PKI but sensitive to ESI-05 or thapsigargin. We propose that cAMP links an increase in plasma glucose to stimulation of somatostatin secretion by promoting CICR, thus evoking exocytosis of somatostatin-containing secretory vesicles in the δ-cell.

Transition metal-free C(sp3)–H bond coupling among three methyl groups

2017 ◽  
Vol 53 (38) ◽  
pp. 5346-5349 ◽  
Author(s):  
Yufeng Liu ◽  
Xi Zhan ◽  
Pengyi Ji ◽  
Jingwen Xu ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Methyl Groups ◽  
Methyl Ketones ◽  
Reaction Conditions ◽  
Methyl Group ◽  
Metal Free

A coupling of multiple C(sp3)–H bonds of the methyl group in methyl ketones with dimethyl sulfoxides was developed under transition metal-free reaction conditions.

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