Life Sciences Commons^™

The Light Microscopy Of Triglyceride Digestion, John S. Patton, Russel D. Vetter, Margit Hamosh, Bengt Borgstrom, Mats Lindstrom, Martin C. Carey

Food Structure

During fat digestion (lipolysis) a number of physiochemical events can be seen directly by light microscopy. Hydrolysis of emulsified fat droplets bylipases at pHs above about 6.5 proceeds with the formation of visible product phases that may include both crystalline as well as liquid crystalline phases. The crystalline phase is primarily calcium-fatty acid soap and its formation is favored by high calcium concentrations, alkaline pHs, and inhibited by low pH and monoglycerides. The formation of liquid crystalline product phases are favored by low calcium-concentrations. monoglycerides and lipid saturated bile salt solutions. Both phases are solubilized by bile salts but the …

Early Research On The Fibrous Microstructure Of Meat, H. J. Swatland

Food Structure

The older scientific literature on the histology of skeletal muscle describes the trans verse fragmentation of myofibrils to form sarcomere disks and the attachment of Z lines to the sarcolemma in contracted muscle. These phenomena may now be explained by recent research on the cytoskeletal framework of muscle fibers, particularly desmin and vinculin. The formation of sa rcomere disks might be developed as a simple method to study cytoskeletal integrity in meat. In early research, contraction bands and the disappearance of transverse striations during contraction caused considerable confusion with ordinary light microscopy. These problems were largely resolved by the use …

Application Of Electron Spin Resonance Techniques To Model Starch Systems, L. E. Pearce, E. A. Davis, J. Gordon, W. G. Miller

Food Structure

Starch model systems were examined by electron spin resonance (ESR) techniques with either 16-DOXYL-stearic acid or TEMPO spin probes in water or hexane. Room temperature starchwater- 16-DOXYL-stearic acid spectra showed strong adsorption occurred between the starch and probe. Starch-water-TEMPO spectra at room temperature did not show strong adsorption between starch and probe, but did show some slowed motion of the probe as a result of different local environments experienced by the probe within the starch granule. Starch-water-probe spectra from systems heated from 45-95° C showed no major differences from unheated samples. Also, no major spectral differences existed for each starch …

Development Of Microstructure In A Cream Cheese Based On Queso Blanco Cheese, Miloslav Kalab, H. Wayne Modler

Food Structure

A Cream cheese was made by mixing cultured high fat cream (5~% fat) with Queso Blanco curd and by homogenizing the mix at 70°C. The final product contained 30. 01. to 33.)% fat and 54.1 to 54.5% moisture. The Queso Blanco curd was obtained by precipitating the casein and denatured whey protein from heated whole milk (b2.~ to SI8.0°C) by bringing the pH to 5.3-5.5 with citric acid, using a continuous process. The extent of denaturation of the whey protein portion varied from 5 to 100%, depending on the heat treatment of the milk. Scanning and transmission electron microscopy revealed …

Small Angle X-Ray Scattering Of Hydrated Wheat Starch Granules, M. Yang, J. Grider, J. Gordon, E. A. Davis

Food Structure

Wheat starch:water (1:2) dispersions were studied by small angle x-ray scatter diffractometry (SAXS), and by light, polarizing microscopy, and scanning electron microscopy (SEM). X-ray scatter data were collected in the 64-661 A range. Radii of gyration (Rg) of spherically shaped regions and d-spacings were calculated for samples that were treated as follows: 25° C and run at 25° C; heated to 88° C and run at 82° C; heated to 88° C, stored at 25° C for 2 h or 3 days and run at 25° C; heated to 88° C, stored at 2° C for 3 days and run …

Seed Microstructure: Review Of Water Imbibition In Legumes, Barry G. Swanson, Joe S. Hughes, H. Paul Rasmussen

Food Structure

Scanning electron microscopy (SEM) is an invaluable tool for studying foods and food products. SEM has been particularly va luable in the study of seed microstructure and the ro le of microstructure in water imbibition by legumes. Controversy continues to surround the causes of hard ness in legumes as addi tional research revea ls differences between legumes that imbibe water and legumes that fail to imbibe water. SEM observation of the microstructural changes occurring in legumes during water imbibition ofkrs a better undcrstandi ng of d i ffc rcnces that ex ist betwee n hard and normal beans. Structural changes …

Microstructural Changes In Maturing Seeds Of The Common Bean (Phaseolus Vulgaris L.), Joe S. Hughes, Barry G. Swanson

Food Structure

Seeds of Phaseolus vulgaris L. beans were collected at weekly intervals throughout maturation and examined by scanning electron microscopy (SEM). No major structural changes were observed on the surface of the seed coat during the seven week study period. A cross-sectional examination of the seed coat revealed a substantial increase in thickness of the parenchyma cell layer in young seeds followed by a dramatic decrease in thickness as the seed approached maturity. In the cotyledons, the diameter of the storage cells and starch granules increased over time, with distinct protein bodies becoming visible only in the later stages of maturity. …

Changes In Typical Organelles In Developing Cotyledons Of Soybean, K. Saio, K. Kondo, T. Sugimoto

Food Structure

Soybean cotyledonary cells harvested every 5-10 days at 15 to 60 days after flowering (OAF), were investigated by means of light and transmission electron microscopy. In the early developing stages (15-20 OAF) most of the cells were occupied by large, centrally located vacuoles while the cytoplasm was restricted to a thin layer against the cell wall and contained numerous ribosomes, mitochondria, plastids, small amounts of endoplasmic reticulum (ER) and minute lipid bodies. At about 25 OAF, spherical organelles which contained protein, lipid and sugar (PLS bodies), appeared and then increased in number and in size. Vacuoles had protein deposits lining …

Structure Of Coarse And Fine Fractions Of Corn Samples Ground On The Stenvert Hardness Tester, Y. Pomeranz, Z. Czuchajowska

Food Structure

Kernels from a pair of isogenic lines (with regard to hardness) and two commercial hybrids of dent corn (that varied in hardness) were ground on the Stenvert Hardness Tester and separated by sieving into coarse (>0.710 mm) and fine (<0.500 mm) fractions. The corn samples differed little in oil contents. The coarse particles from the hard corn samples were angular and sharp-edged; those from the soft corn samples were rounded. The yield of coarse particles was higher and they contained less oil in hard than in soft corn. Fine particles from all four corn samples had higher oil content than the coarse particles. Visual examination, observation at low magnification under a light microscope, and use of a scanning electron microscope revealed consistent differences in the extent and mode of corn kernel breakdown during grinding. Particles in the coarse fraction from hard kernels were to a large extent intact with little exposure of their contents. In the soft kernels, particles in the coarse fraction were broken extensively and their contents exposed. It is postulated that differences in the extent of mechanical breakdown and oil content are related to differences in shelf life of corn grits.

Combining Microscopy And Physical Techniques In The Study Of Cocoa Butter Polymorphs And Vegetable Fat Blends, J. D. Hicklin, G. G. Jewell, J. F. Heathcock

Food Structure

Transmission electron microscopy, differential scanning calorimetry and X-ray diffraction have been used to study the cocoa butter polymorphs and blends of cocoa butter with a hydrogenated vegetable fat. The results indicate the presence of six polymorphs and confirm observations made by other workers. Vegetable fat addition affects both the molecular structure and the morphology of the crystals observed. After temperature cycling, a blend containing 50% vegetable fat developed two crystal types and differences in the X-ray pattern were apparent. Correlations could be made between the known molecular structure and the morphology observed in most of the polymorphs. In selected cases, …

Rheological And Scanning Electron Microscopic Examination Of Skim Milk Gels Obtained By Fermenting With Ropy And Non-Ropy Strains Of Lactic Acid Bacteria, S. M. Schellhaass, H. A. Morris

Food Structure

Physical and rheological parameters of skim milk gels fermented with slime producing (ropy) cultures and non-ropy cultures were compared. The skim milk gels were made from steamed reconstituted nonfat dry milk inoculated with 2% of a single strain starter culture and incubated at 32, 37, and 45°C until pH 4. 5 + 0.05 was attained.

Skim milk gels fermented by slime-producing strains of Streptococcus thermophilus, Streptococcus cremoris, and Lactobacillus bulgaricus exhibited similar rheological and physical characteristics. Electron micrographs of the ropy skim milk cultures showed that slime produced by the organisms was associated with the cell surface as well as …

Particle Structure In Spray-Dried Whole Milk And In Instant Skim Milk Powder As Related To Lactose Crystallization, Zenichi Saito

Food Structure

The structure of instant skim milk and whole milk powders was studied by scanning electron microscopy with special respect to lactose crystallization during storage. X-ray diffraction analysis was used to confirm the crystallization. Some samples were ashed in a plasma asher and the residues were also examined by scanning electron microscopy. The structures of instant skim milk and whole milk powder particles were well-preserved after the ashing procedure.

The crystallization of ~X-Iactose hydrate occurred in instant skim milk and whole milk powders according to moisture uptake. In instant skim milk powder, ~X-Iactose hydrate crystals were observed on the particle surface. …

Microstructure Of Spray-Dried And Freeze-Dried Microalgal Powders, L. P. Lin

Food Structure

Chiarella and Spirulina algae were spray-dried and freezedried under several different conditions, and the morphological changes induced were studied by scanning electron microscopy. The internal structure of the particles (granules) was revealed by cryofracturing. The cellular composition of the two algae, method of drying, cell concentration, feed conditions, temperature, and drying times all affected the external morphology of the resulting powders. In the case of spray-drying, at a temperature of 160 °C for 6 sec, the particles shrunk or collapsed; if the drying time was over 10 sec at 160 °C, similar results were observed. The cell concentration affected the …

Effect Of Ionizing Irradiation And Storage On Mushroom Ultrastructure. I. The Gills Of Agaricus Bisporus (Lge.) Imbach And Pleurotus Ostreatus (Jacq. Ex Fr.) Kummer, A. Keresztes, J. Kovacs, E. Kovacs

Food Structure

We have investigated the gills of both the control and gamma-irradiated groups of A.bisporus and P.ostreatus (2.5 kGy or 2.5 and 5.0 kGy doses, respectively) by scanning (SEM) and transmission (TEM) electron microscopy. The primary aim of our study was to see, how gamma-irradiation used for shelflife extension inhibits spore production. We have found in both species that inhibition of spore production in irradiated specimens is caused by the destroying of basidia rather than by retarding normal spore development. In P.ostreatus the hymenium appears to be more sensitive to irradiation than in A.bisporus. In both species the subhymenium and trama …

Immuno-Cytochemistry With Backscattered Electrons, D. Soligo, E. De Harven, M. T. Nava, G. Lambertenghi-Deliliers

Scanning Electron Microscopy

Some cytochemical reaction products are visible inside the cytoplasm of cells observed with the scanning electron microscope (SEM) using the backscattered electron imaging (BEI) mode. Methods can be utilized whenever they result in the deposition of heavy metal, like silver, lead or osmium at the sites of the enzymatic reaction.

More recently the BEI mode of the SEM has been demonstrated to improve the detection of immunogold labeled cell surface antigens. Colloidal gold particles, 40 to 15 nm in diameter can be efficiently used for immuno-specific labeling. Moreover, cytochemical reactions can be applied to previously immunogold labeled cells, therefore combining …

The State Of Water In The Cell, William Negendank

Scanning Electron Microscopy

A number of scientists in the early 20th century conceived cell water and ions as existing in unique "colloidal" or "bound" states. Work in the 1930's, however, established the assumption that most of cell water and of K exist in a free state like that of a dilute aqueous solution, so that the osmotic activity of cell K serves to balance that of the high concentration of extracellular Na. This assumption underlies theoretical concepts of membrane pumps, Donnan equilibria, and cell potentials, and led to the now classical membrane-osmotic-pump-leak concept of cell ionic distributions and volume maintenance. Nevertheless, the results …

Two Opposing Theories Of The Cell: Experimental Testing By Cryomethods And Electron Microscopy, L. Edelmann

Scanning Electron Microscopy

A main controversial issue in cell biology concerns the molecular mechanism responsible for K⁺ accumulation in living cells and Na⁺ exclusion from them. The alternative theoretical descriptions of these phenomena are based on different assumptions about the physical state of cellular Na⁺, K⁺ and H₂O. In this article it is shown with striated muscles how cryomethods and microanlytical electron microscopy may be used to test the opposing theories. It is concluded that these methods may yield more realistic informations about the physical state of cellular K⁺ and Na⁺ than measurements with …

Demonstrable Fixative Interactions, Keith M. Meek, John A. Chapman

Scanning Electron Microscopy

Electron-optical examination of reconstituted collagen fibrils fixed with tannic acid and/or glutaraldehyde and positively stained with heavy metal anions and cations reveals distinct changes in the high resolution staining patterns seen in TEM. Correlation with the known sequence data demonstrates that these changes are caused by (a) interaction of the fixative with certain charged groups in the collagen and (b) localized stain-exclusion effects following fixation. We have analysed the positive and negative staining patterns from glutaraldehyde-treated collagen in detail. In positive staining, uptake of staining ions is shown to be inhibited not only at residues known to interact with glutaraldehyde …

Tandem Scanning Reflected Light Microscopy, Mojmir Petran, Milan Hadravsky, Alan Boyde, Martin Mueller

Scanning Electron Microscopy

Most attempts at optical microscopy of bulk living objects have failed because of reflections from optical components and the object surface, and overlapping of unsharp out-of-focus images with the one (weak) sharp in-focus image. The optical signal in the image plane thus consists of a strong d.c. component, a weak noise and a still weaker signal. Most of the first two components can be suppressed by scanning in concordance with both the illuminating and the image-forming rays. In the first scan the focussed-on-object plane is illuminated only in several very fine discrete spots. In the second scan only that light …

Cryofixation And Cryosubstitution For Routine Work In Transmission Electron Microscopy, H. Sitte, K. Neumann, L. Edelmann

Scanning Electron Microscopy

After a brief review of the present state of the theory of cryofixation, methods and instruments as well as criteria for the application of cryofixation and cryosubstitution in daily routine work in cell biology and medicine are described. Good results are obtainable using liquid nitrogen for impact freezing on highly polished copper surfaces or by plunging into liquefied propane. Based on these results a versatile and safe system for routine plunging and impact freezing for the majority of biomedical objects has been developed. In order to enable ultramicrotomy at ambient temperature a cryosubstitution system according to the Edelmann principle has …

Problems Associated With The Preparation Of Cell Suspensions For X-Ray Microanalysis Highlighted By The Comparison Of Results With Those Obtained From Tissue Sections, A. Warley, M. D. Kendall, I. W. Morris

Scanning Electron Microscopy

Fully quantitative X-ray microanalysis of freeze dried frozen sections allowed the concentration of monovalent ions in the nuclei of mouse thymocytes in tissue sections to be compared with those from thymocytes which had been isolated by a simple preparation procedure. Isolated cells showed increased concentrations of Na and Cl. This was further investigated in the rat where the size of the thymus a 11 owed comparison between different isolation media using cells derived from the same animal. Use of autologous serum as the final suspending medium gave reproducible results, whereas with suspension in BSS, or 20% dextran the results were …

Low Temperature Embedding, E. Carlemalm, W. Villiger, J. -D. Acetarin, E. Kellenberger

Scanning Electron Microscopy

The Lowicryl resins K4M and HM20 are methacrylate/acrylate based formulations which can re used for embedding biological material at low temperature in conjunction with either the progressive lowering of temperature (PLT) technique or with freeze-substitution. The resins are applicable over a very extended temperature range, approximately 210°K to 340°K. Even lower temperatures down to ca. 190°K can be reached with two new resins, K11M and HM23. Test embeddings of unfixed material after freeze-substitution have given promising results which could re useful for imnunocytochemical labeling. Lipid extraction is small or absent when the two new resins are used in combination with …

Cryopreparation Of Tissue For Electron Microscopy, John G. Linner, Stephen C. Bennett, Donna S. Harrison, Alton L. Steiner

Scanning Electron Microscopy

An apparatus able to remove amorphous phase tissue water without recrystallization or rehydration has been produced. Application of this technique to biological samples achieves both the preservation of ultrastructure and the retention of cellular macromolecules and solute without redistribution or modification.

Small pieces of fresh tissue were cryofixed by the method of bounce free metal-mirror freezing on polished copper bars at liquid nitrogen temperature. Tissue samples were then placed under liquid nitrogen in a copper sample holder equipped with a thermocouple and feedback controlled heating circuit. Under liquid nitrogen the sample block was placed in a stainless steel sample chamber …

Freeze Substitution And Low Temperature Embedding, B. Humbel, M. Müller

Scanning Electron Microscopy

The problems of conventional EM-preparation techniques based on chemical fixation may be overcome to a considerable extent by freeze substitution techniques. Although at present substitution cannot be performed at sufficiently low temperatures to prevent the recrystallization of vitrified aqueous specimens, thin sectioned biological samples show an improved information density. If freeze-substitution is combined with conventional embedding above 273 K (Epon/Araldite, Spurr's resin) the substituting organic solvent must contain stabilizing agents such as osmiumtetroxide, glutaraldehyde or uranylions. In combination with low temperature embedding procedures (Lowicryl) completely unfixed samples are obtained, which are suitable for immunolabelling and electron spectroscopic experiments. Water in …

Colloidal Gold Particles Detected On Highly Structured Surfaces Of Large Samples By Backscattered Electrons In The Scanning Electron Microscope, D. Studer, R. Hermann

Scanning Electron Microscopy

Colloidal gold labelled surface antigens on large, highly structured samples were unambiguously visualized at high magnification with backscattered electrons at 25 kV in a field emission scanning electron microscope (SEM). Secondary electron (SE) and backscattered electron (BSE) images of large and highly structured specimens are frequently disturbed by charging effects. By optimizing the thickness of the conducting carbon layer and the intensity of the incident electron beam, this problem can be overcome. The midgut of the lepidopteran larvae of Spodoptera litoralis was used as specimen. The activated 𝛿-endotoxin of Bacillus thuringiensis coupled to colloidal gold binds to the microvilli exposed …

Immunocytochemical Labeling Of Enzymes In Low Temperature Embedded Plant Tissue: The Precursor Of Glyoxysomal Malate Dehydrogenase Is Located In The Cytosol Of Watermelon Cotyledon Cells, C. Sautter

Scanning Electron Microscopy

The Lowicryl-technique in combination with protein A gold was used in order to localize the precursor of glyoxysomal malate dehydrogenase in watermelon cotyledons. Preservation of the antigen was evaluated by a preembedding technique in isolated organelles. The glyoxysomal malate dehydrogenase was localized in tissue sections by a postembedding technique. Antigens of glyoxysomal malate dehydrogenase were found in the glyoxysomal matrix and in the cytosol, whereas the endoplasmic reticulum was completely free of labeling. Controls are presented by preimmunserum, by a serum against various proteins of the glyoxysomal membrane and by application of cycloheximide in order to inhibit translation at cytosolic …

To Resin Or Not To Resin In Immunocytochemistry, J. J. Wolosewick

Scanning Electron Microscopy

Hydrated resinless sections produced by a variety of methods (cryoultramicrotomy or polyethylene glycol techniques) appear to be excellent specimens for post-embedding immunocytochemistry at the electron microscopic level. A perplexing problem is the lack of apparent penetration throuqhout the section thickness of particulate probes such as ferritin or colloidal gold. This report draws attention to the possible causes for this phenomenon namely the size of the probe and the possible effects of fixation or processing. Smaller probes, gentler fixation or permeabilization procedures and increased incubation times all seem to be logical approaches to increasing penetration of immunoreagents into thick hydrated sections.

Wood Resource In Aspen: Ecology And Management In The Western United States, J.R. Jones, N.V. Debyle, R.P. Winokur

Aspen Bibliography

Aspen has not been cut extensively in the West; in fact, it has been grossly underutilized. For example, as recently as 1975, the aspen harvest from National Forests in four Forest Service regions in the Rocky Mountain area was 7.64 million board feet.¹ Additional minor volumes were cut on special-use permits for products such as fuel and corral poles. The total amount cut represented only 0.1% of the net volume available in these aspen forests.

Distribution In Aspen: Ecology And Management In The Western United States, J.R. Jones

Aspen Bibliography

No abstract provided.

Morphology In Aspen: Ecology And Management In The Western United States, J.R. Jones, N.V. Debyle

Aspen Bibliography

No abstract provided.