QUANTITATIVE PRECIPITATION OF VARIOUS 3β-HYDROXYSTEROLS WITH DIGITONIN

1966 ◽  
Vol 44 (1) ◽  
pp. 119-128 ◽  
Author(s):  
H. L. Haust ◽  
A. Kuksis ◽  
J. M. R. Beveridge
Keyword(s):  
Thin Layer ◽  
Excess Reagent ◽  
Pyridine Solution ◽  
Free Sterols

Conditions are described for the quantitative precipitation of nine 3β-hydroxysterols with digitonin. After removal of excess reagent, the sterol and digitonin moieties are dissolved in a known volume of dry pyridine. An aliquot of the pyridine solution is processed to give a measure of total 3β-hydroxysterol by estimating the digitonin moiety with the use of anthrone. From another aliquot, the free sterols may be regenerated for differential-photometric and gas–liquid or thin-layer chromatographic analysis.Recoveries for each sterol at three levels of concentration were as follows: β-sitosterol, 98.6 ± 1.8% (mean and S.D.); campesterol, 99.1 ± 1.9%; stigmasterol, 98.9 ± 1.7%; stigmastanol, 99.1 ± 1.9%; cholesterol, 100.1 ± 1.5%; cholestanol, 100.8 ± 1.3%; coprostanol, 93.6 ± 1.6%; Δ7-cholestenol, 98.5 ± 1.8%; and 7-dehydrocholesterol, 91.9 ± 1.8%.

Skin penetration by cercariae of the bird schistosome Austrobilharzia terrigalensis: the stimulatory effect of cholesterol

Parasitology ◽  
1969 ◽  
Vol 59 (4) ◽  
pp. 973-989 ◽  
Author(s):  
J. A. Clegg
Keyword(s):  
Mass Spectrometry ◽  
Thin Layer ◽  
Skin Surface ◽  
Sterol Fraction ◽  
Surface Lipid ◽  
Skin Lipid ◽  
Free Sterols ◽  
Bird Schistosome ◽  
Chicken Skin ◽  
Skin Surface Lipid

An artificial skin of hardened gelatine was used to examine the factors affecting penetration of skin by cercariae of the bird schistosome, Austrobilharzia terrigalensis.The percentage of cercariae able to penetrate through a gelatine membrane was increased by a factor of 3–4 by coating the membrane with a thin layer of lipid collected from the surface of chicken skin.The free sterol fraction, isolated from chicken skin surface lipid by thin-layer chromatography, stimulated penetration to the same extent as whole skin lipid.Cholesterol was detected in the sterol fraction by mass spectrometry and pure cholesterol had the full stimulating effect on cercarial penetration.Skin lipid, from which free sterols had been removed, lost the stimulatory effect on cercariae, but full activity was recovered by adding cholesterol to the sterol-free lipid. Fractions of skin lipid containing free fatty acids or triglycerides, wax esters and sterol esters similarly failed to stimulate penetration.These results establish that penetration of A. terrigalensis cercariae is greatly stimulated by the free sterols present in the surface lipid of chicken skin but cholesterol may not be the only active sterol. Cholestanol and the plant sterols campesterol and β-sitosterol were also detected in chicken skin surface lipid. These sterols were not tested for activity on cercariae because samples free from cholesterol could not be obtained.Some cercariae were able to penetrate plain gelatine membranes not coated with cholesterol but small amounts of free sterol were detected in the gelatine itself. This sterol could not be completely removed by prolonged solvent extraction and consequently it is not known whether any cercariae are able to penetrate in the complete absence of sterols.Temperature had a marked effect on penetration of cercariae; lowering the temperature from 40 to 25 °C reduced the number of successful penetrants by a factor of 4.I am grateful to Miss V. Bowen for excellent technical assistance and to Dr J. McLeod of the Research School of Chemistry, Australian National University, who performed and interpreted the mass spectrometry. This investigation was partly supported by a research grant from the World Health Organization.

Pairing and aggregation of Amblosoma suwaense (Trematoda: Brachylaimidae) metacercariae in vitro and partial characterization of lipids involved in chemo-attraction

Parasitology ◽  
1981 ◽  
Vol 82 (2) ◽  
pp. 225-229 ◽  
Author(s):  
B. Fried ◽  
G. A. Robinson
Keyword(s):  
Thin Layer ◽  
Neutral Lipid ◽  
Sterol Ester ◽  
Neutral Lipids ◽  
Sterol Esters ◽  
Free Sterols ◽  
Lipid Fractions ◽  
Oil Red O

SUMMARYHistochemical and thin-layer chromatographic (t.l.c.) analyses were made on neutral lipids in the free (unencysted) metacercariae of Amblosoma suwaense (Brachylaimidae). As determined by t.l.c. the major neutral lipid fractions in metacercariae removed directly from Campeloma decisum snails were free sterols and sterol esters. Metacercariae incubated for 1 h at 37±1° C in sterile Locke's solution released mainly sterol esters and a lesser amount of free sterols into the medium. As determined by Oil Red O (ORO) staining, metacercariae accumulated neutral lipid in the intestinal caeca during incubation and the excretory system was ORO negative. Behavioural studies showed that metacereariae paired and aggregated in vitro and were attracted to lipophilic but not to hydrophilic worm products. Following t.l.c. preparative analysis it was demonstrated that metacercariae were attracted to sterol ester worm products but not to free sterol products.

Thin-layer chromatography and identification of free sterols

1965 ◽  
Vol 20 ◽  
pp. 354-357 ◽  
Author(s):  
N.W. Ditullio ◽  
C.S. Jacobs ◽  
W.L. Holmes
Keyword(s):  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Free Sterols ◽  
Layer Chromatography

Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

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