The biosynthesis of the free sterols and sterol esters of Neurospora crassa

1979 ◽  
Vol 57 (2) ◽  
pp. 112-116 ◽  
Author(s):  
A. M. Pierce ◽  
H. D. Pierce Jr. ◽  
A. M. Unrau ◽  
A. C. Oehlschlager ◽  
R. E. Subden ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Total Sterol ◽  
Mevalonic Acid ◽  
Ergosterol Biosynthesis ◽  
Sterol Esters ◽  
Free Sterols ◽  
Phase Culture ◽  
Esterified Sterols ◽  
Relationship Of ◽  
The Relationship

The composition of the free and esterified sterols in Neurospora crassa was examined as a function of incubation time in starvation medium containing [2-14C]mevalonic acid. The 14C incorporation was monitored in nuclear methylated and 4, 14-desmethyl sterol fractions. After 7 h incubation, sterol esterification had increased from an initial 5% in the log phase culture to 48% of the total sterol pool, with a concomitant decrease in free sterols. The relationship of the free and esterified sterol components in ergosterol biosynthesis is discussed.

Lipid composition and polyene antibiotic resistance of Candida albicans mutants

1978 ◽  
Vol 56 (2) ◽  
pp. 135-142 ◽  
Author(s):  
A. M. Pierce ◽  
H. D. Pierce Jr. ◽  
A. M. Unrau ◽  
A. C. Oehlschlager
Keyword(s):  
Fatty Acids ◽  
Candida Albicans ◽  
Parent Strain ◽  
Total Sterol ◽  
Phospholipid Fatty Acids ◽  
Sterol Esters ◽  
Free Sterols ◽  
Major Sterol ◽  
Resistant Mutants ◽  
The Individual

Four polyene-resistant mutants (C7, E4, C4, D10) of Candida albicans were derived by mutagenesis with N-methyl-N′-nitro-N-nitrosoguanidine followed by isolation on nystatin-containing medium. The mutants were cross resistant to amphotericin B, lucensomycin, and candicidin and showed the same order of increasing resistance to the four polyenes tested, i.e., C7 < E4 < C4 < D10. Free sterols, sterol esters, and phospholipid fatty acids were analyzed in the mutants and sensitive parent strain. The lipids of C7 were the same as those of the sensitive parent strain. Mutant E4 contained lichesterol and other Δ8-sterols indicating a block at the Δ8→ Δ7 isomerase, and most of the sterol ester fraction consisted of 4,14-desmethyl sterols. The most resistant mutants C4 and D10 had reduced growth rates, alterations in phospholipid fatty acids, and the absence of 4,14-desmethyl sterols. Mutants C4 and D10 had similar lipid compositions with 24-methylenelanosterol as the major sterol and lesser amounts of obtusifoliol and lanosterol. The proportion of the total sterol that was esterified was low and similar (19–34%) in cultures of the mutants and of the sensitive strain harvested in the same stage of stationary growth. Total sterol content, however, increased with resistance. Polyene resistance was better correlated with the type of sterols in the total sterol pools rather than with the degree of esterification of the individual sterols, i.e., resistance increased with the presence of Δ8- and 4,14-methyl sterols. Our data indicate that factors other than or in addition to alterations in sterol and phospholipid patterns account for polyene resistance.

scholarly journals Sterole in Blättern und Chloroplasten

1966 ◽  
Vol 21 (9) ◽  
pp. 859-867 ◽  
Author(s):  
Waldemar Eichenberger ◽  
Wilhelm Menke
Keyword(s):  
Palmitic Acid ◽  
Spinacia Oleracea ◽  
Antirrhinum Majus ◽  
Allium Porrum ◽  
Sterol Esters ◽  
Binding Partner ◽  
Free Sterols ◽  
Binding Partners ◽  
Major Sterol ◽  
Esterified Sterols

The nature and quantity of sterols in leaves and chloroplasts of Spinacia oleracea, Antirrhinum majus, and Allium porrum were determined. From dried leaves 0.05 - 0.18% free and esterified sterols were isolated, and 0.04-0.09% from chloroplasts. Although approximately half the lipids of leaves is localized in chloroplasts we found no more than a quarter of leaf sterols in the chloroplasts. The mixture of sterols contains a major sterol and minor sterols in these species. In spinach a-spinasterol is the major sterol and in Antirrhinum and Allium β-sitosterol. Moreover, we established Δ7-stigmastenol and cholesterol in spinach. Besides for free sterols, leaves contain sterol esters and glycosides. Palmitic acid is the binding partner in the sterol esters of spinach, and glucose and mannose are the binding partners in sterol glycosides. Chloroplasts contain the same sterols as leaves do. Only a trace of sterol glycosides could be detected in chloroplast preparations.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Studies on Leukemogenic and Sarcomagenic Viruses

1970 ◽  
Vol 28 ◽  
pp. 156-157
Author(s):  
Leon Dmochowski
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Morphological Properties ◽  
Mode Of Development ◽  
Relationship Of ◽  
The Relationship

Electron microscopy has proved to be an invaluable discipline in studies on the relationship of viruses to the origin of leukemia, sarcoma, and other types of tumors in animals and man. The successful cell-free transmission of leukemia and sarcoma in mice, rats, hamsters, and cats, interpreted as due to a virus or viruses, was proved to be due to a virus on the basis of electron microscope studies. These studies demonstrated that all the types of neoplasia in animals of the species examined are produced by a virus of certain characteristic morphological properties similar, if not identical, in the mode of development in all types of neoplasia in animals, as shown in Fig. 1.

The relationship of IGE receptor topography to signaling activity in RBL-2H3 mast cells

1991 ◽  
Vol 49 ◽  
pp. 236-237
Author(s):  
J.R. Pfeiffer ◽  
J.C. Seagrave ◽  
C. Wofsy ◽  
J.M. Oliver
Keyword(s):  
Mast Cells ◽  
Protein A ◽  
Scattered Electron ◽  
Ige Receptor ◽  
Receptor Complexes ◽  
Ige Binding ◽  
Electron Imaging ◽  
Small Clusters ◽  
Relationship Of ◽  
The Relationship

In RBL-2H3 rat leukemic mast cells, crosslinking IgE-receptor complexes with anti-IgE antibody leads to degranulation. Receptor crosslinking also stimulates the redistribution of receptors on the cell surface, a process that can be observed by labeling the anti-IgE with 15 nm protein A-gold particles as described in Stump et al. (1989), followed by back-scattered electron imaging (BEI) in the scanning electron microscope. We report that anti-IgE binding stimulates the redistribution of IgE-receptor complexes at 37“C from a dispersed topography (singlets and doublets; S/D) to distributions dominated sequentially by short chains, small clusters and large aggregates of crosslinked receptors. These patterns can be observed (Figure 1), quantified (Figure 2) and analyzed statistically. Cells incubated with 1 μg/ml anti-IgE, a concentration that stimulates maximum net secretion, redistribute receptors as far as chains and small clusters during a 15 min incubation period. At 3 and 10 μg/ml anti-IgE, net secretion is reduced and the majority of receptors redistribute rapidly into clusters and large aggregates.

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