Differences in the sterol composition of Heliothis zea fed Zea mays versus Medicago sativa

Larvae of Heliothis zea were fed Zea mays or Medicago sativa in order to determine how these plants affected the development and sterol composition of the insect. The larvae fed corn kernels grew more rapidly than those fed alfalfa leaves. The corn kernels contained Δ⁵-24-alkylsterols whereas the leaves as well as the sprouts and flowers of alfalfa contained Δ⁷-24-alkylsterols. The corn-fed larvae dealkylated the dietary Δ⁵-sterols and utilized primarily cholesterol in their tissues. In contrast, although the larvae fed alfalfa dealkylated the Δ⁷-sterols present in the leaves, they were unable to metabolize the B-ring of these sterols and so both the prepupae and adults utilized large quantities of lathosterol in their tissues. Interestingly, H. zea, a generalized feeder, shared its inability to metabolize Δ⁷-sterols to Δ⁵-sterols with Hypera postica, a specialized feeder on alfalfa. This coleopteran also dealkylated the Δ⁷-24-alkylsterols and contained lathosterol, but not cholesterol, in its tissues. Therefore, the ability of H. zea to utilize either Δ⁵- or Δ⁷-sterols in its tissues may help to explain its ability to complete its development on a variety of different plants, although it may prefer a host, such as corn, that produces Δ⁵-sterols and supports a more-rapid rate of growth.     

Utilization of Δ5,7 - and Δ8-sterols by larvae of Heliothis zea

Larvae from two populations of Heliothis zea were reared on artificial diets containing various sterols, which supported suboptimal growth, and their tissue sterols were characterized in order to determine how these dietary sterols are utilized by this insect. The sterols studied included Δ^5,7-sterols (7-dehydrocholesterol or ergosterol), Δ⁸-sterols (lanosterol and/or 24-dihydrolanosterol), and a Δ⁵-sterol (4,4-dimethylcholesterol). Although larvae did not develop on 4,4-dimethylcholesterol, those fed primarily Δ⁸-4,4,14-trimethylsterols developed to the third instar. When the latter sterols were spared with cholesterol, the larvae reached the sixth instar and contained 4,4,14-trimethylsterols as well as cholesterol in their tissues. When larvae were fed 7-dehydrocholesterol, <1% of the larvae from one population developed to the sixth instar and these larvae contained 7-dehydrocholesterol as their principal sterol. The other larvae successfully completed their larval stage when they were transferred from the diet containing 7-dehydrocholesterol (or no sterol) to a diet containing cholesterol within at least 9 days. The sterol composition of larvae transferred from a diet containing cholesterol to a diet containing 7-dehydrocholesterol, after they had reached 60% of their final weight, was 54% cholesterol and 46% 7-dehydrocholesterol. The major sterol isolated from the tissues of the larvae fed ergosterol was also 7-dehydrocholesterol. Therefore, although the larva of H. zea can dealkylate and saturate the side chain of the Δ^5,7,22-24β-methylsterol, it carries out little metabolism of the B ring of the nucleus. These studies demonstrate that, when Δ^5,7- or Δ⁸-sterols are the principal sterols in the diet of H. zea, they are absorbed and incorporated into its tissues, although they slow the rate of growth and may prevent complete development of the larva.     

Metabolism of Δ0-, Δ5-, and Δ7-Sterols by Larvae of Heliothis zea

Heliothis zea was reared on artificial diets containing Δ⁵-sterols (cholesterol, campesterol, or sitosterol), Δ⁷-sterols (lathosterol, epifungisterol, or spinasterol), or Δ⁰-sterols (cholestanol, epicoprostanol, campestanol, or sitostanol) in order to determine how different dietary sterols affect the type of sterols present in the tissues of the late-sixth-instar larva. Although all of the dietary sterols (except epicoprostanol) supported the growth of the larvae, not all of the sterols were metabolized to the same end products. In each case, at least 80% of the sterols in the tissues of the larvae retained the same nucleus as that of the dietary sterol, indicating that H. zea carries out very little metabolism of ring B of Δ⁵-, Δ⁷-, and Δ⁰-sterols. The larvae dealkylated the Δ⁵-, Δ⁷-, and Δ⁰-alkylsterols to 24-desalkylsterols, but a greater percentage of the Δ⁵-alkylsterols were metabolized in this manner. The sterols present as free sterols in the larva were also present as esterifed sterols which accounted for 2–4% of the total sterols. Therefore, the sterol composition of the tissues of H. zea can be altered by varying the dietary sterols.     

The Influence of Exogenous Steroids on the Growth of Aspergillus niger and Torula utilis

The yield of Aspergillus niger mycelium from a synthetic medium can be increased by the addition of microgram quantities of cholesterol, ergosterol, cholestanol, 7-dehydrocholesterol, stigmasterol, sitosterol, pregnenolone, and the vitamins D. The stimulation is not due to degradation to the acetate level. It is obtained only in highly aerated cultures. The rate of growth of Torula utilis was not increased. Both organisms were inhibited by desoxycorticosterone, testosterone, androstenedione, cortisone acetate, progesterone, and diethylstilbestrol. T. utilis was also inhibited by estradiol. A small decrease in progesterone inhibition of T. utilis was obtained by adding ergosterol, cholesterol, or pregnenolone. Of the compounds which have been adequately tested the order of stimulatory activity for A. niger is: ergosterol > cholesterol > stigmasterol > 7-dehydrocholesterol > cholestanol > pregnenolone. Progesterone was inhibitory at low concentrations but stimulatory at higher ones, while 17-hydroxyprogesterone was neither inhibitory nor stimulatory. Desoxycorticosterone and testosterone were inhibitory at all concentrations. Complete inhibition of the growth of the fungus was not obtained with any of the steroids. It is concluded that A. niger has a metabolic requirement for a steroid with a hydroxy group on carbon 3, a double bond in the 5–6 position, and a side chain similar to that in ergosterol or cholesterol and that this material is growth-limiting in the early stages of the cultures described.     

The effects of cholesterol on the development of Heliothis zea

Heliothis zea was reared on an artificial diet, which lacked supplementation with plant materials, in order to determine the effects of cholesterol on the development of this insect. A number of parameters of larval development were found to be dependent upon the concentration of dietary sterol including: the number of moults which the larvae completed within a particular time interval, the ability of the larvae to pupate and the survival of the larvae. The number of moults which a larva completed prior to pupation, though, was independent of the concentration of sterol.     

Cholesterol metabolism differs after statin therapy according to the type of hyperlipemia

AimNon-cholesterol sterols reflect cholesterol metabolism. Statins reduce cholesterol synthesis usually with a rise in cholesterol absorption. Common hyperlipemias have shown different patterns of cholesterol metabolism. We evaluated whether cholesterol absorption and synthesis may differ after statin therapy in primary hyperlipemias.Main methodsWe determined lipid profile, apoprotein B and serum sterols (lathosterol, sitosterol, campesterol by gas chromatography/mass spectrometry) before and after statins in 80 untreated hyperlipemic patients, 40 with polygenic hypercholesterolemia (PH) and 40 with familial combined hyperlipemia (FCH).Key findingsAt baseline in FCH lathosterol was significantly higher while campesterol and sitosterol were significantly lower than in PH. After statins, the reduction in LDL-C did not significantly differ between the two groups; in PH there was a significant decrease of lathosterol from 96.1 to 52.6 102 μmol/mmol cholesterol (p = 0.0001) with no significant modifications in campesterol and sitosterol; on the opposite, in FCH lathosterol decreased from 117 to 43 102 μmol/mmol cholesterol (p = 0.0001) and campesterol and sitosterol significantly increased from 38 to 48 102 μmol/mmol cholesterol (p = 0.0001), and from 75 to 86 102 μmol/mmol cholesterol, (p = 0.022), respectively. After statin therapy only in FCH Δ-LDL-C showed a significant inverse correlation with Δ-sitosterol and with Δ-campesterol.SignificancePrimary hyperlipemias show different patterns of response to statins: in PH LDL reduction appears completely “synthesis inhibition” dependent, while in FCH LDL decrease appears to be synthesis dependent, partially limited by absorption increase. Studying cholesterol metabolism before and after hypolipemic therapy might be useful in identifying the best tailored treatment.     

Quantitative analysis of five sterols in amniotic fluid by GC–MS: Application to the diagnosis of cholesterol biosynthesis defects

Cholesterol and its precursors, namely 7-dehydrocholesterol, desmosterol and lathosterol are important biochemical markers of cholesterol biosynthesis, and their quantification in body fluids is useful for the diagnosis of cholesterol biosynthesis pathway disorders. A rapid and sensitive gas chromatographic–mass spectrometric method was developed and validated for quantitative analysis of five sterols (cholesterol, 7-dehydrocholesterol, desmosterol, lathosterol and sitosterol) in amniotic fluid. The method was linear for all compounds (r² > 0.99), and intra and inter-assay coefficients of variation were typically below 5%, and inaccuracy was within a ±12% interval. The method was applied to 330 amniotic fluid samples, grouped by gestational age between 13 and 22 weeks of pregnancy, in order to establish reference intervals for sterols in this specimen. The obtained concentrations (μmol/L) for each sterol was as follows: 22.1758 ± 4.2716 at 13 weeks and 78.5082 ± 12.9041 at 22 weeks for cholesterol; 0.0039 ± 0.0007 at 13 weeks and 0.1150 ± 0.0212 at 22 weeks for 7-dehydrocholesterol; 0.1562 ± 0.0406 at 13 weeks and 0.7691 ± 0.0821 at 22 weeks for desmosterol; 0.0272 ± 0.0035 at 13 weeks and 0.8551 ± 0.1791 at 22 weeks for lathosterol; and 0.0404 ± 0.0039 at 13 weeks and 0.2326 ± 0.0386 at 22 weeks for sitosterol. The method was also applied to one pathological sample that showed decreased levels of cholesterol, and higher concentration of 7-dehydrocholesterol, which is consistent with a 7-dehydrocholesterol-reductase deficiency. Our results showed that as long as pregnancy goes on, the concentrations of cholesterol and precursors increase in amniotic fluid, which is related to the increased need for cholesterol by the fetus. The reference range of each sterol in amniotic fluid was calculated at different gestational ages and will be useful for the interpretation and validation of biochemical prenatal diagnosis of inborn errors of sterol biosynthesis.     

Insulin sensitivity regulates cholesterol metabolism to a greater extent than obesity: lessons from the METSIM Study

Cholesterol synthesis is upregulated and absorption downregulated in insulin resistance and in type 2 dia-betes. We investigated whether alterations in cholesterol metabolism are observed across the glucose tolerance status, from normoglycemia through impaired glucose tolerance to type 2 diabetes, in 781 randomly selected men 45 to 70 years of age from a population-based Metabolic Syndrome in Men Study. Cholesterol metabolism was assayed using surrogate serum markers, squalene, and noncholesterol sterols. The study population was classified into subgroups according to glucose tolerance as follows: normoglycemia, impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes. LDL cholesterol did not differ between the groups. Cholesterol synthesis markers were lowest and absorption markers highest in normoglycemia. Sitosterol was lower in subjects with impaired fasting glucose compared with normoglycemic subjects (113 ± 7 vs. 136 ± 3 10² μmol/mmol of cholesterol, P < 0.05). LDL cholesterol was not associated with lathosterol/sitosterol ratio, a marker of cholesterol metabolism. Peripheral insulin sensitivity evaluated by the Matsuda index was associated with the lathosterol/sitosterol ratio in the entire population (r = −0.457, P < 0.001) and with that of lathosterol/cholestanol independently of obesity. In conclusion, cholesterol metabolism was altered already from subjects with impaired fasting glucose. Upregulated cholesterol synthesis was associated with peripheral insulin resistance independent of obesity.     

Steinernema feltiae (= Neoaplectana carpocapsae): effect of sterols and hypolipidemic agents on development

The structure and concentration of sterol in a lipid-defined artificial medium affected the development of the entomogenous nematode, Steinernema feltiae (= Neoaplectana carpocapsae). The nematode grew normally in vitro when the medium was supplemented with delta 5-desalkylsterol (cholesterol) or delta 5-desalkylsteryl ester (cholesterol oleate). The minimum amount of cholesterol in the medium that was necessary to support the development of S. feltiae to the climax population (i.e., dauer stage) was 0.0025%. The nematode also completed its life cycle normally when delta 0- or delta 7-desalkylsterols (cholestanol and lathosterol) were substituted for cholesterol. In contrast, development was inhibited when the medium contained delta 5,7-desalkylsterol (7-dehydrocholesterol); however, the nematode population reached the climax stage, in medium containing this sterol, when cholesterol was also present. S. feltiae was able to utilize delta 5- and delta 0-24 alpha-ethylsterols (sitosterol and sitostanol) as dietary sterols; however, when a delta 22-bond was introduced into the side chain (stigmasterol) the rate of development of the nematode slowed significantly. The growth of the nematode was also retarded when the medium contained delta 5,7,22-24 beta-methylsterol (ergosterol). The nematode population reached the climax stage in medium containing delta 8,24-4,14 alpha-trimethylsterol (lanosterol) only when cholesterol was also present. When S. feltiae was exposed to certain hypolipidemic agents, which are known to lower the level of lipids in human plasma (clofibrate, cholestyramine resin, niacin, and D-thyroxine), all but D-thyroxine affected the growth and development of the nematode in vivo (in Heliothis zea) and/or in vitro. Therefore further studies are warranted to determine how these drugs affect the lipid biochemistry of this nematode.     

Mechanistic and metabolic studies of sterol 24,25-double bond reduction in Manduca sexta

Larvae of Manduca sexta were used to obtain a cell-free sterol 24,25-reductase. From the midgut of fifth instar larvae fed a mixture of sitosterol and campesterol a microsome-bound 24,25-sterol reductase was prepared that transformed desmosterol (K_m, 3 μM), lanosterol (K_m, 18 μM), and cycloartenol (K_m, 33 μM), to cholesterol, 24,25-dihydrolanosterol, and cycloartanol, respectively. With desmosterol as substrate, the microsome-bound enzyme was found to incorporate tritium into cholesterol from 4S-tritium labelled NADPH. [24-²H]lanosterol was transformed by larvae to [24-²H]24,25-dihydrolanosterol (structure confirmed by mass spectroscopy (MS) and ¹H-nuclear magnetic resonance spectroscopy. A rationally designed inhibitor of 24,25-reductase activity, 24(R,S),25-epimino-lanosterol (IL), was assayed and found to be inhibitory with an I₅₀ of 2 μM. IL was supplemented in the diet of M. sexta with either sitosterol or stigmasterol and found to inhibit development (I₅₀ 60 ppm). The major sterol which accumulated in the IL-treated larvae was desmosterol, confirming the site of inhibition was reduction of the 24,25-bond. IL was converted to [2-³H]IL when fed to the larvae. [2-³H]lanosterol was recovered from fifth instar larvae and its structure confirmed by MS and radiochemical techniques. © 1996 Wiley-Liss, Inc.     

Brachymeria lasus and Pachycrepoideus vindemiae: Sterol requirements during larval growth of two hymenopterous insect parasites reared in vitro on chemically defined media

Brachymeria lasus and Pachycrepoideus vindemiae failed to develop in vitro on sterol-free artificial media, and dietary acetate and squalene failed to maintain and/or support growth. The sterols, cholesterol, cholestanol, β-sitosterol, 7-dehydrocholesterol, and cholesterol linoleate were all utilized and maintained larvae of both species. Larval survival and development rate were greatest with cholesterol followed by cholestanol, β-sitosterol and 7-dehydrocholesterol. Although cholesterol linoleate maintained larvae little growth occurred and mortality was high. Cholestanol followed by β-sitosterol and 7-dehydrocholesterol displayed partial cholesterol sparing activity. Cholesterol linoleate had little effect on larval growth when fed with suboptimal levels of cholesterol or cholestanol. Both species contained 5 to 10% of the total body lipids as free sterol with traces of sterol ester. The major free sterol appears to be cholesterol.     

25-Azasteroid inhibition of development and conversion of C28 and C29 phytosterols to cholesterol in Spodoptera litura (F.)

Larvae of Spodoptera litura (F.) grown on an artificial diet completed larval development in 19.2 days and attained a maximum weight of 873.2 mg. When fed dietary concentrations of 50 ppm of 25-azacholesterol or 10 ppm of 25-azacholestane, the larval developmental period increased to 28.4 and 23.4 days, and the larval weights were 447.5 and 542.3 mg, respectively. Both compounds induced distinct melanization effects and caused production of larval-pupal intermediates and severe mortality. Treatments with concentrations of 50 ppm or more of either azasteroid caused a decline in pupal period and earlier eclosion and emergence of abnormal adults. Egg laying and hatchability decreased with increasing concentrations of azasteroids in the larval diets. When 1 ppm or more of 25-azasteroid is added to the artificial diet, the insect larvae contain identifiable amounts of desmosterol, in addition to cholesterol, campesterol, and sitosterol, which are present in Spodoptera grown on artificial diet alone. Desmosterol accumulation in the insect body is due to an inhibition of the Δ²⁴-sterol reductase by 25-azasteroids. An increase in the concentration of these azasteroids in the diet results in an increase in sitosterol concentration and simultaneous reduction in the cholesterol levels due to inhibition of conversion of sitosterol. This inhibition appears to be more pronounced with 25-azacholestane treatment than with 25-azacholesterol.     

Role of the exoprotease InA in the pathogenicity of Bacillus thuringiensis in pupae of Hyalophora cecropia

Two geographical biotypes of Nomuraea rileyi (from Ecuador and the United States) were topically bioassayed against seven lepidopteran species, i.e., Anticarsia gemmatalis, Heliothis zea, Heliothis virescens, Heliothis subflexa, Pseudoplusia includens, Spodoptera exigua, and Trichoplusia ni. There was an average difference of 1.7-fold in mortality in how cultures of the same insect species from different sources responded to topical applications of either biotype of N. rileyi. Regression equations and LC₅₀ values were obtained for each insect species and fungal biotype combination. Larvae of S. exigua were equally susceptible to both biotypes of N. rileyi. Although larvae of A. gemmatalis were moderately susceptible to the Ecuadoran biotype, they were relatively nonsusceptible to the Mississippian biotype. Species of Heliothis (H. zea, H. virescens, and H. subflexa) were about equally susceptible to the Mississippian biotype. Larvae of H. subflexa and H. virescens, however, were significantly less susceptible than H. zea to the Ecuadoran biotype. When the integumental barrier was breached via intrahemocoelic injections, larvae of H. virescens were as susceptible as H. zea larvae to blastospores of either biotype of N. rileyi.     

Characterization of candidate intermediates in the Black Box of the ecdysone biosynthetic pathway in Drosophila melanogaster: Evaluation of molting activities on ecdysteroid-defective larvae

Early steps of the biosynthetic pathway of the insect steroid hormone ecdysone remains the “Black Box” wherein the characteristic ecdysteroid skeleton is built. 7-Dehydrocholesterol (7dC) is the precursor of uncharacterized intermediates in the Black Box. The oxidation step at C-3 has been hypothesized during conversion from 7dC to 3-oxo-2,22,25-trideoxyecdysone, yet 3-dehydroecdysone is undetectable in some insect species. Therefore, we first confirmed that the oxidation at C-3 occurs in the fruitfly, Drosophila melanogaster using deuterium-labeled cholesterol. We next investigated the molting activities of candidate intermediates, including oxidative products of 7dC, by feeding-rescue experiments for Drosophila larvae in which an expression level of a biosynthetic enzyme was knocked down by the RNAi technique. We found that the administration of cholesta-4,7-dien-3-one (3-oxo-Δ^4,7C) could overcome the molting arrest of ecdysteroid-defective larvae in which the expression level of neverland was reduced. However, feeding 3-oxo-Δ^4,7C to larvae in which the expression levels of shroud and Cyp6t3 were reduced inhibited molting at the first instar stage, suggesting that this steroid could be converted into an ecdysteroid-antagonist in loss of function studies of these biosynthetic enzymes. Administration of the highly conjugated cholesta-4,6,8(14)-trien-3-one, oxidized from 3-oxo-Δ^4,7C, did not trigger molting of ecdysteroid-defective larvae. These results suggest that an oxidative product derived from 7dC is converted into ecdysteroids without the formation of this stable conjugated compound. We further found that the 14α-hydroxyl moiety of Δ⁴-steroids is required to overcome the molting arrest of larvae in loss of function studies of Neverland, Shroud, CYP6T3 or Spookier, suggesting that oxidation at C-14 is indispensable for conversion of these Δ⁴-steroids into ecdysteroids via 5β-reduction.     

Biosynthesis of 20-hydroxyecdysone in Ajuga hairy roots: fate of 6α- and 6β-hydrogens of lathosterol

The fate of 6α- and 6β-hydrogens of lathosterol during the transformation into 20-hydroxyecdysone was chased by feeding [3α,6β-²H₂]- and [3α,6α-²H₂]-lathosterols to hairy roots of Ajuga reptans var. atropurpurea. The behavior of 6β-hydrogen, which mostly migrated to the C-5 position of 20-hydroxyecdysone, was in agreement with that of C-6 hydrogen of cholesterol. The results strongly supported the view that cholesterol and lathosterol are first metabolized into 7-dehydrocholesterol, which is then converted into 20-hydroxyecdysone via 7-dehydrocholesterol 5α,6α-epoxide in the hairy roots.     

Esterification of cholesterol and cholestanol in the whole body,tissues, and frass of Heliothis zea

The quantity of free and esterified sterols in the whole body, intestine, hemolymph, fat body, and frass of 6th-instar larvae of H. zea, fed cholesterol or cholestanol, was measured in order to determine if there was a difference in the utilization of these two molecules. The principal sterol in the tissues of the larvae was cholestanol or cholesterol, when they were fed diet containing these two molecules, respectively; there was little, if any, metabolism of dietary cholestanol to cholesterol. There was little or no difference in the amount of total sterol in the whole body, tissues, or frass of larvae fed the two different diets, indicating that the absence of a Δ⁵-bond in cholestanol does not prevent the uptake or distribution of this sterol to various tissues. However, the relative percentage of steryl ester was significantly higher in prepupae reared on a diet containing cholestanol instead of cholesterol (6–7-, 4-, 13-, 4-, and 2-fold increase, for the whole body, intestine, hemolymph, fat body, and frass, respectively). The average percentage of total sterol that was esterified in the tissues was greater in the fat body (10.8 ± 15.4 and 44.2 ± 12.3%, respectively, for larvae fed cholesterol and cholestanol) than in the hemolymph (0.5 ± 0.1 and 6.3 ± 0.8%) and intestine (1.2 ± 0.1 and 4.7 ± 1.1%). The percentage of sterol that was esterified in the frass of larvae was large (26.9 ± 3.7 and 48.2 ± 0.5%, respectively, for larvae fed cholesterol and cholestanol). Therefore, the fact that larvae of H. zea fed cholestanol, instead of cholesterol, contain this saturated molecule as their principal tissue sterol and preferentially esterify it may explain, at least in part, why their rate of growth on cholestanol is slower than on cholesterol.     

Sterol structure dependence of insulin receptor and insulin-like growth factor 1 receptor activation

The plasma membrane is a dynamic environment with a complex composition of lipids, proteins, and cholesterol. Areas enriched in cholesterol and sphingolipids are believed to form lipid rafts, domains of highly ordered lipids. The unique physical properties of these domains have been proposed to influence many cellular processes. Here, we demonstrate that the activation of insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF1R) depends critically on the structures of membrane sterols. IR and IGF1R autophosphorylation in vivo was inhibited by cholesterol depletion, and autophosphorylation was restored by the replacement with exogenous cholesterol. We next screened a variety of sterols for effects on IR activation. The ability of sterols to support IR autophosphorylation was strongly correlated to the propensity of the sterols to form ordered domains. IR autophosphorylation was fully restored by the incorporation of ergosterol, dihydrocholesterol, 7-dehydrocholesterol, lathosterol, desmosterol, and allocholesterol, partially restored by epicholesterol, and not restored by lanosterol, coprostanol, and 4-cholesten-3-one. These data support the hypothesis that the ability to form ordered domains is sufficient for a sterol to support ligand-induced activation of IR and IGF1R in intact mammalian cells.     

Composition of the sterol fraction in horse chestnut

The Δ⁷-and Δ⁵-sterol fractions were isolated from the unsaponifiable matter of ripe, air dried, chestnut seed. The Δ⁷-sterol fraction amounted to 18.4% and the Δ⁵-sterol fraction amounted to 8.2% of the unsaponifiable matter. In the Δ⁷-sterol fraction three components were identified as Δ⁷-campesterol, α-spinasterol and Δ⁷-stigmastenol. One component was probably Δ^5,7-stigmastadienol and five components remained unidentified. Δ⁷-stigmastenol and α- spinasterol were the major components and amounted to 74.8% of the fraction. In the Δ⁵-sterol fraction at least ten components were found. Five of them were identified as cholesterol, campesterol, stigmasterol, sitosterol and Δ⁴-stigmasten-3-one. Stigmasterol and sitosterol amounted to 73.6% of the fraction.     

Effects of proximate cholesterol precursors and steroid hormones on mouse myeloma growth in serum-free medium

Summary The proximate cholesterol precursors lathosterol, 7-dehydrocholesterol and desmosterol supported the growth of NS-1 and X63 mouse myeloma cells. These cells and X63.653 cells are cholesterol auxotrophs, yet each was able to convert [³H]lathosterol to [³H]cholesterol. These results are consistent with the conclusion that cholesterol auxotrophy in these myeloma cells is due to a deficiency in 3-ketosteroid reductase activity. The steroid hormones testosterone, progesserone and hydrocortisone could not replace cholesterol as a medium supplement. These results provide a greater understanding of the cholesterol auxotrophy characteristic of cell lines clonally-derived from the MOPC 21 myeloma tumor, and they provide a rational basis for the use of sterols in defined culture medium for mouse myeloma cells. This work was supported by National Institute of Health grants CA40294 and CA37589 to G. H. Sato and by a grant from RJR nabisco Inc. Editor's Statement These results help identify the defect in myeloma cells leading to cholesterol auxotrophy. The use of these cells in hybridoma derivation adds practical utility to a detailed appreciation of cholesterol metabolism in these cultures.     

Interactions between a braconid,Microplitis croceipes,and a fungus,Nomuraea rileyi,in laboratory-reared bollworm larvae

The parasite Microplitis croceipes required 1.1 days longer at 26°C to complete development in Heliothis zea larvae than was required for the fungus Nomuraea rileyi to kill the host larvae and sporulate. Host larvae parasitized by M. croceipes or infected with N. rileyi failed to complete a fifth larval molt or pupate. Of the remaining healthy larvae, one-half completed six larval stadia before popation. Larvae parasitized by M. croceipes were predisposed to infection by N. rileyi, but the fungus inhibited development of M. croceipes if host larvae were infected with N. rileyi within 1 day after parasitization.