I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

Methods in Enzymology.

Dietary cholesterol consumption and intestinal cholesterol absorption contribute to plasma cholesterol levels, a risk factor for coronary heart disease. The molecular mechanism of sterol uptake from the lumen of the small intestine is poorly defined. We show that Niemann-Pick C1Like 1(NPC1L1) protein plays a critical role in the absorption of intestinal cholesterol. NPC1L1 expression is enriched in the small intestine and is in the brush border membrane of enterocytes. Although otherwise phenotypically normal, NPC1L1-deficient mice exhibit a substantial reduction in absorbed cholesterol, which is unaffected by dietary supplementation of bile acids. Ezetimibe, a drug that inhibits cholesterol absorption, had no effect in NPC1L1 knockout mice, suggesting that NPC1L1 resides in an ezetimibe-sensitive pathway responsible for intestinal cholesterol absorption.

https://science.sciencemag.org/content/sci/303/5661/1201.full.pdf

Niemann-Pick C1 Like 1 protein is critical for intestinal cholesterol absorption.

Mammalian AMP-activated protein kinase and yeast SNF1 protein kinase are the central components of kinase cascades that are highly conserved between animals, fungi, and plants. The AMP-activated protein kinase cascade acts as a metabolic sensor or "fuel gauge" that monitors cellular AMP and ATP levels because it is activated by increases in the AMP:ATP ratio. Once activated, the enzyme switches off ATP-consuming anabolic pathways and switches on ATP-producing catabolic pathways, such as fatty acid oxidation. The SNF1 complex in yeast is activated in response to the stress of glucose deprivation. In this case the intracellular signal or signals have not been identified; however, SNF1 activation is associated with depletion of ATP and elevation of AMP. The SNF1 complex acts primarily by inducing expression of genes required for catabolic pathways that generate glucose, probably by triggering phosphorylation of transcription factors. SNF1-related protein kinases in higher plants are likely to be involved in the response of plant cells to environmental and/or nutritional stress.

The AMP-activated/SNF1 protein kinase subfamily: metabolic sensors of the eukaryotic cell?

Cholesterol and the cell membrane.

Introduction STEROID hormones are familiar clinically and physiologically as regulators of physiological processes. Five groups of steroid hormones are generally recognized according to their physiological behavior: mineralocorticoids, which instruct the renal tubules to retain sodium; glucocorticoids, which are named for their carbohydratemobilizing properties but have many other effects as well; estrogens, which induce female secondary sexual characteristics; progestins, which are essential for reproduction; and androgens, which induce male secondary sexual characteristics. These classes of steroid hormones are structurally similar and arise from a common series of pathways. They are distinguished by their actions on one or more specific steroid hormone receptors. The hormone/receptor complexes function as tissue-specific transcriptional regulators of distinct domains of genes and, consequently, exert their broad array of physiological effects. (For reviews, see Refs. 1 and 2.) The pathways by which the...

Molecular Biology of Steroid Hormone Synthesis

Purification and properties of sterol carrier protein2.

Sterol carrier protein2. Delivery of cholesterol from adrenal lipid droplets to mitochondria for pregnenolone synthesis.

The participation of sterol carrier protein2 in the conversion of cholesterol to cholesterol ester by rat liver microsomes.

Sterol carrier protein2. Identification of adrenal sterol carrier protein2 and site of action for mitochondrial cholesterol utilization.

A major methodological problem in the intracellular localization of cholesterol is the nearly complete extraction of sterols during routine dehydration and embedding procedures for electron microscopy. Cholesterol digitonide (a sterol complex with digitonin), however, is qualitatively insoluble in these solvents. Mouse liver has been prepared as follows: (a) Flickinger's aldehyde fixative, 20 hr; (b) Flickinger's fixative containing 0.2% digitonin, 24 hr; (c) cacodylate wash, 24 hr; (d) 1% OsO(4), 2 hr; (e) acetone dehydration; and (f) Epon 812 infiltration under vacuum, 28 hr. After the last step, an analysis of the tissue for sterol content under optimal analytical conditions demonstrates a retention of 99% of the unesterified cholesterol present in unfixed mouse liver. Liver prepared in an identical manner except for omission of digitonin is essentially devoid of sterols. Cholesterol isolated chromatographically from liver processed as outlined above has been identified unequivocally by mass spectrometry. Liver from step (f) also has been polymerized, thin-sectioned, and examined in the electron microscope. A remarkable quality of fine-structural preservation is obtained. The major alteration encountered is the presence of small cylindrical "spicules," often occurring as tightly packed concentric lamellae, at membrane surfaces.

/pdf/the-quantitative-retention-of-cholesterol-in-mouse-liver-3xi06n00ls.pdf

Terence J. Scallen

Papers

Purification and properties of sterol carrier protein2.

Sterol carrier protein2. Delivery of cholesterol from adrenal lipid droplets to mitochondria for pregnenolone synthesis.

The participation of sterol carrier protein2 in the conversion of cholesterol to cholesterol ester by rat liver microsomes.

Sterol carrier protein2. Identification of adrenal sterol carrier protein2 and site of action for mitochondrial cholesterol utilization.

The quantitative retention of cholesterol in mouse liver prepared for electron microscopy by fixation in a digitonin-containing aldehyde solution