Locating “fitness” and L. J. Henderson

Mendelsohn, Everett

doi:10.1017/cbo9780511536557.003

Cited by 10 publications

(12 citation statements)

References 15 publications

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“…Mendelsohn has discussed the implications for radiotherapy of nonproliferating tumour cells. [6][7] But of equal importance is the notion that certain malignant cells (Go stem cells) may not synthesize DNA for prolonged periods of time because they respond to environmental signals. This observation suggests that tumour cells may not be as "autonomous" and unresponsive to growthcontrolling stimuli as we have believed.…”

Section: Discussionmentioning

confidence: 99%

Degree of Differentiation in Nonproliferating Cells of Mammary Carcinoma

1973

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Section: Discussionmentioning

confidence: 99%

Degree of Differentiation in Nonproliferating Cells of Mammary Carcinoma

1973

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“…It should be mentioned that the methods used do not exclude the presence of 5~-cholestane-3a,7a,l2a,27-tetrol, since the gaschromatographic properties and mass spectrum of this compound probably are the same as those of 5~-cholestane-3a,7a,l2a,26-tetrol. However, it is likely that 5~-cholestane-3a,7a,i2a,26-tetrol predominates [2,23]. Other cholestanetetrols identified were the two C-24 epimers of 5,!j-cholestane-3a,7aI,-12a,24-tetrol, formed in about equal amounts, and 5~-cholestane-3a,7o,l2a,23~-tetrol.…”

Section: Discussionmentioning

confidence: 99%

Oxidation of 5β‐Cholestane‐3α, 7α, 12α‐triol by Rat Liver Microsomes

Cronholm

Johansson

1970

European Journal of Biochemistry

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The oxidation of 5~-cholestane-3a,7a,l2a-triol by different subcellular fractions of rat liver homogenate was studied. The most efficient oxidation was observed with the microsomal fraction fortified with the 100000 x g supernatant fluid. Efficient oxidation occurred also with the microsoma1 fraction fortified with NADPH. The main products were identified as a number of cholestanetetrols. 5~-Cholestane-3a,7a,l2a,25-tetrol and 5p-cholestane-3a,7a, 12a,26-tetrol accounted for about 60 of the cholestanetetrols. The oxidation of 5~-cholestane-3a,7a,l2a-triol by the microsomal fraction fortified with NADPH was stimulated about five-fold by administration of phenobarbital. Phenobarbital treatment stimulated hydroxylations a t C-23, C-24 and C-25 to a much greater extent than that a t (2-26. Carbon monoxide inhibited all the side-chain hydroxylations and the most marked inhibition was observed for the 26-hydroxylation.5,4-Cholestane-3a,7a,l2a,26-tetrol was found to be a much more efficient precursor of cholic acid than either 5~-cholestane-3a,7a,l2a,25-tetrol or the two C-24 epimers of 5p-cholestane3a,7a,lZa,24-tetrol.5~-Cholestane-3a,7a,l2~-triol has been shown to be an intermediate in the formation of cholic acid from cholesterol in liver [l]. The initial reaction in the conversion of 5~-cholestane-3a,7a,12n-triol into cholic acid involves predominantly hydroxylation in the 26-position [l]. Early investigations showed that the mitochondria1 fraction of rat liver homogenate was able to carry out 26-hydroxylation of 5~-cholestane-3a,7a,l2a-triol [2,3]. The possibility that the microsomal fraction might be able to carry out the same reaction was not examined in detail in these investigations. A series of investigations during recent years has shown that the microsomal fraction of liver homogenate fortified with NADPH and in the presence of molecular oxygen catalyzes hydroxylations of many different compounds including o-hydroxylation of fatty acids and aliphatic hydrocarbons [4]. I n view of these findings and those reported recently from this laboratory concerning hydroxylations in the biosynthesis and metabolism of bile acids [5,6], it appeared of interest to reexamine the metabolism of 5~-cholestane-3~w,7a,l2a-triol in different subcellular fractions of liver homogenate with special emphasis on the metabolism in the presence of the microsomal fraction. The present communication describes the results of such a study. While this work was in progress, Okuda and Hoshita EXPERIMENTAL PROCEDURE Materials 5~-[7~-~H]Cho1estane-3a7+7a,12a-trio1 (specific radioactivity, 20 pC/mg) was prepared by reduction with tritium-labeled sodium borohydride (Radiochemical Centre, Amersham, England) of 3a,12a-dihydroxy-5~-cholestan-7-one, prepared from 58-cholestane-3a,7a,l2a-triol by oxidation with N-bromosuccinimide [S]. 5,!?-[7p-3H]Cholestane-3a,7a,12a-trio1 was purified by repeated thin-layer chromatography with ethyl acetate as solvent and by reversedphase partition chromatography with phase system F2 [9]. The purified material had m....

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“…To discover the spectral response rule of MPRA to pH, both UVvis and fluorescent spectral titration experiments accompanying with their corresponding visual and fluorescent color changes were recorded first under the optimized conditions above and the results were given in Figure 4. For fluorescent [50] log[(F max -F)/F-F min ] = pH-pK a , where F is the observed fluorescence intensity, F max and F min are the corresponding maximum and minimum respectively.…”

Section: Fluorescent and Colorimetric Response Parameters For Mpra Tomentioning

confidence: 99%

A Dual‐Mode Colorimetric/Fluorescent Sensor Comprising Rhodamine B and Piperazine: Response to Acidic pH Values and Investigation of Recognition Mechanism

Luo

Yang

et al. 2020

ChemistrySelect

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A dual‐mode “turn‐on” fluorescent‐colorimetric sensor, 1‐methyl piperazine rhodamine amide (MPRA), has been identified and developed for acidic pH detection in practice. After its structure and photophysical property were characterized and investigated in detail, it was noted to find that nonfluorescent and colorless MPRA would present rose Bengal color and emit strong saffron yellow fluorescence simultaneously with pH decreasing from 7.2 to 1.8 in PBS/acetonitrile (1 : 1, v/v). Under the optimized conditions, MPRA expressed an excellent partitioned and dual‐mode response to pH, i. e., ranging from 1.8 to 3.6 and 3.6 to 7.2 for fluorescent analysis, and 1.8 to 4.0 and 4.0 to 7.2 for colorimetric one with the acidity constant (Ka) of 1.75 obtained from Henderson‐Hasselbach equation. Importantly, the sensing was real‐time and reversible, which was successfully applied for pH detection in real fruit aqueous samples with R.S.D. less than 5.0%. The selective recognition mechanism for MPRA to H+ was confirmed to be the ring‐opened amide form mechanism by 1H NMR and theoretical calculation. MPRA will be a potential dual‐mode sensor for on‐site monitoring pH in acidic environments.

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Locating “fitness” and L. J. Henderson

Cited by 10 publications

References 15 publications

Degree of Differentiation in Nonproliferating Cells of Mammary Carcinoma

Degree of Differentiation in Nonproliferating Cells of Mammary Carcinoma

Oxidation of 5β‐Cholestane‐3α, 7α, 12α‐triol by Rat Liver Microsomes

A Dual‐Mode Colorimetric/Fluorescent Sensor Comprising Rhodamine B and Piperazine: Response to Acidic pH Values and Investigation of Recognition Mechanism

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