Ahmed M. Atallah

Sensitivity to amphotericin B and the cholesterol: Phospholipid molar ratios of 3T3, L, BHK and HeLa cells

Abstract The effects of amphotericin B (AmB) on four established animal cell lines were compared. measuring cell viability, inhibition of uridine incorporation into RNA, leakage of the enzyme lactate dehydrogenase, and leakage of RNA. In all assays, cell susceptibilities, in decreasing order, were: 3T3, L, BHK and HeLa. The cells, which were more sensitive, had significantly lower cholesterol:phospholipid ratios (c:p) than the less sensitive cells. Furthermore, 3T3 and L cell lines adapted to growth on higher levels of AmB had higher c:p molar ratios than did nonresistant cells. AmB binding to the cell was similar for all of the cell lines tested. These observations suggest a possible relationship between c:p ratios and sensitivity of cells to polyenes.

Translocation of sitosterol and related compounds in Pelargonium hortorum and helianthus annuus

Abstract The translocation of several plant sterols and a triterpene was studied in geranium and sunflower plants. Upward translocation of sitosterol-[ 14 C] and β-amyrin-[ 14 C] was shown within 48 hr to the upper parts of a geranium plant sectioned previously above the roots. Downward translocation of sitosterol-[ 14 C] from the leaf of application was evident in intact plants after 48 hr. In addition to free sitosterol-[ 14 C] considerable amounts of sitosteryl-[ 14 C] glycoside and traces of sitosteryl-[ 14C ] ester were found in most parts examined. Very slow downward translocation of cholesterol-[ 14 C] but not of desmosterol-[ 14 C], sitosteryl-[ 14 C] palmitate or β-amyrin-[ 14 C] was shown in geranium. In sunflower no downward translocation of cholesterol-[ 3 H], sitosteryl-[ 3 H] acetate or palmitate could be detected. In geranium, sitosteryl-[ 14 C] glycoside translocated downward from the leaf of application to all other plant parts, except other leaves, and was found in these parts after 10 days as the unchanged glycoside, free sterol and steryl ester. The effect of drying the plant parts on the recovery of radioactive steroidal material is discussed. Traces of a water soluble, dialyzable form of sterol-[ 14 C] were also detected in dried geranium roots after treatment with strong acid or alkali.

31-Nordihydrolanosterol, a Minor 4α-Methyl Sterol in Pollen of Taraxacum dens leonis

4α,14α-dimethyl-Δ8-cholesten-3β-01 (31-nordihydrolanosterol) has been identified by TLC, GLC and GLC-MS in the ester fraction of pollen from Taraxacum dens leonis.Its probable role in phytosterol biosynthesis is discussed.

Triterpenoid and steroid constituents of florida spanish moss

Abstract Both free and esterified sterols and triterpenes of Spanish Moss (Tillandsia usneoides L.; Bromeliaceae0 from Florida were examined. Besides the eight sterols and triterpenes previously reported by others as present in Spanish Moss from Mexico, cycloeucalenol, 24-methylenecycloartanol and two unidentified triterpenes of the cycloartane group were detected by GLC and GLC-Mass Spectroscopy. Campesterol and stigmasterol were detected by these techniques and cholesterol was detected by GLC. Attempts to determine the specific nature of the esters of both triterpenes and desmethyl sterols were thwarted by the extreme complexity of the ester mixture. However, saturated fatty acids from C12 to C30 were detected in the sterol and triterpene ester fraction by GLC, with palmitic acid (25%) stearic acids (20%) predominating as the fatty acid moieties.

Biosynthesis of sterols and triterpenes in Pelargonium hortorum

Abstract Although all parts of the geranium plant ( Pelargonium hortorum ) are capable of synthesizing sterols and triterpenes and their esters in vitro from mevalonic acid-[2- 14 C], the aerial portions are more active than other tissues. All plant parts were shown to incorporate mevalonic acid-[2- 14 C] into isoprenoids for at least 3 days. The leaves and petioles had the greatest incorporation on a wet weight basis. Chopped preparations showed comparable incorporations of mevalonate whereby rootlets incorporated about one half as much as most parts; the flower petals incorporated five times the average amount. In leaves the principal sterol synthesized was sitosterol. Metabolic studies with isolated leaves indicated a fairly rapid conversion of free tetracyclic triterpenes to 4-desmethyl-sterols, while β-amyrin was synthesized at a different rate than α-amyrin. Esterified tetracyclic triterpenes exhibited only a slight amount of conversion to 4-desmethylsterols.

Influence of the Position of Ring Unsaturation in Steroids and Triterpenes on the Type and Formation of Mesophases II: Influence of the Δ7-Double Bond

Abstract Several sterols and triterpenes possessing a Δ7-double bond were investigated for mesomorphic behavior. The acetates and palmitates of cholesta-5, 7-dien-3β-ol and cholest-7-en-3β-ol, exhibited distinct smectic mesophases only. The acetates of 4,4,14α-trimethylcholest-7-en-3β-ol and 4,4-dimethylcholest-7-en-3β-ol showed no mesomorphism while the palmitate of the latter gave a smectic mesophase. The Δ7-double bond seems in general to favor the formation of smectic rather than cholesteric mesophases.

The effect of non-ionic detergents and phospholipase A on enzymes involved in adult rat brain sterol biosynthesis from (2-14C)-mevalonic acid in vitro

Incubation of (2-14C)-mevalonic acid with 3000 × g adult rat brain supernate in the presence of Tween 80 or Triton X-100 produced a marked shift in the distribution of radioactivity among squalene, steryl ester and free sterol when compared to controls. Although the conversion of labeled mevalonate to cholesterol was only slightly influenced, the detergents markedly affected the turnover of squalene and methyl sterol precursors. The major neutral isoprenoid material formed had the general properties of geranylgeraniol on TLC and radioactivity-monitored-GLC. Phospholipase A from Vipera russelli, at an optimal tissue to phospholipase ratio, resulted in a 25% increase in mevalonate incorporation into total neutral isoprenoids. An increase in radioactivity of almost 25% was also seen in the free sterol fraction. Phospholipase A from bee venom did not show this type of increase. No labeled geranylgeraniol-type material was found on incubation with either of the phospholipases.

Liquid Crystalline Properties of Some Pollinastanol Fatty Acid Esters

Abstract Pollinastanol, the only known naturally occurring 3-desmethyl sterol possessing a 9,19-cyclopropane ring, is capable of exhibiting liquid crystalline properties, cholesteric and smectic, when esterzed with certain even-chain acids. The decanoate and the palmitate exhibited a markedly colored cholesteric mesophase, while the laurate and myristate showed no colors except in the presence of traces of solvent. These specific mesophase formations are believed to be due to the distinctive structure of pollinastanol, which is intermediate between that of the tetracyclic triterpene 31-norcycloartanol(2) and cycloartanol(3,4) both known to form distinct liquid crystalline mesophases. Pollinastanol was isolated from the pollen of Taraxacum dens leonis where it is present in minute quantities mainly in esterified form. Its possible presence as a naturally occurring liquid crystal is discussed.

Liquid Crystalline Properties of Fatty Acid Esters of Lophenol, a Cholesterol Biosynthetic Intermediate

Abstract Lophenol (4α-methyl-cholest-7-en-3β-ol) an established biosynthetic precursor of cholestrol, forms a smectic mesophase only, when esterified with short (C2-C4) and long (C10-C16) even chain fatty acids. This is in contrast to cholesterol, which forms both cholesteric and smectic mesophases. This difference in behavior is attributed to the C7 double bond in lophenol, as opposed to the C5 doule bond in cholesterol.

Calorimetric Study of Liquid Crystalline Behavior for some 9,19–Cyclopropane Tetracyclic Triterpene Palmitatest

A calorimetric investigation has been made of the mesomorphic behavior for the palmitate esters for four tetracyclic triterpenes-pollinastanol, 31-norcycloartanol, cyclaoartanol, and cyclorartenol....