Life Sciences Commons^™

Surface Heterogeneity Of Tumor Cells And Changes Upon Ionizing Radiation, Z. Somosy, Orsolya Csuka, Tamara Kubasova, J. Kovács, G. J. Köteles

Scanning Microscopy

Heterogeneous distribution of surface domains is a characteristic feature of the tumor cell surface and the distribution differs from that of normal cells. During the malignant transformation the heterogeneity may change or disappear. Cell lines with various metastasizing capacities show different distributions of membrane domains or other differences in membrane or surface organization. We have demonstrated that the amount and distribution of negatively charged sites of B 16 melanoma membranes changed upon ionizing radiation (X-ray, ⁶⁰Co-gamma). In the case of the P 388 lymphoma, however, only the amount of negatively charged sites change after irradiation, the distribution remains unaltered. …

Effect Of Heating To 200 C On Casein Micelles In Milk: A Metal Shadowing And Negative Staining Electron Microscope Study, V. R. Harwalkar, Paula Allan-Wojtas, Miloslav Kalab

Food Structure

Milk was heated to 200 C for 3 min in sealed inverted-Y-shaped glass vials and reacted with a glutaraldehyde solution at that temperature. Electron microscopy of the metal-shadowed and negatively stained samples revealed that casein micelles in the milk did not disintegrate extensively at the high-temperature used but, rather, became enlarged. Some of them were found to be either clustered or distorted.

Effects Of Protein Concentration In Ultrafiltration Milk Retentates And The Type Of Protease Used For Coagulation On The Microstructure Of Resulting Gels, Dragoljub D.J. Gavaric, Marijana Caric, Miloslav Kalab

Food Structure

Milk retentates (35~ total solids, 13~ protein) obtained by ultrafiltration were diluted with the permeate to 3 . 2, 5.0, 6.5, 10.0, and 13.0% protein and coagulated using conrnerc1al proteases. Rennet or one of microbial proteases isolated from Bacillus potymlxa , Endothla parasfttca, Mucor mtehel, or Mucor pusfllus were used . Coagulation times were decreased with the Mucor proteases as the protein concentrations in the retentates were increased but the coagulation times were increased with B. potymlxa and f. parasltlca proteases under similar conditions . Firmness was higher in gels made from homogenized retentates than from nonhomogenized retentates of the …

Grittiness In A Pasteurized Cheese Spread: A Microscopic Study, H. W. Modler, S. H. Yiu, U. K. Bollinger, M. Kalab

Food Structure

Coagulation of pasteurized (63 C for 30 min) milk and blending of the resulting curd with high-fat cream followed by heat treatment (44 to 80 C for 10 min) of the blend in preparation of a hot-pack cheese spread led to the formation of a gritty product. Microscopic examination of hard particles causing the grittiness indicated that they consisted of compacted protein. Staining for calcium failed to detect any elevated concentration of this element in the particles. They were amorphous and contained no crystalline structures.

Encapsulation of the gritty curd in agar gel tubes made it possible to freeze-fracture the …

Changes In The Ultrastructure Of Beef Muscle As Influenced By Acidic Conditions Below The Ultimate Ph, M. V. Rao, N. F. S. Gault, S. Kennedy

Food Structure

Ultrastructural changes in meat incubated with different concentrations of acetic acid were investigated by transmission electron microscopy. Discs of bovine M. longissimus dorsi (48 h postmortem) were incubated at 46 C for 48 h in various acetlc acid solutions, giving discs with pH values ranging from 5.1 to 3.9 . Below pH 4. 5 , the volume of the discs increased markedly due to water absorption.

Discs incubated in 0.01M acetic acid had a pH of 5.1, lower swelling ratios and shorter sarcomeres than control samples at pH 5. 5. Structural studies of the samples at pH 5.1 revealed that …

The Structural Basis Of The Water-Holding, Appearance And Toughness Of Meat And Meat Products, Gerald Offer, Peter Knight, Robin Jeacocke, Richard Almond, Tony Cousins, John Elsey, Nick Parsons, Alan Sharp, Roger Starr, Peter Purslow

Food Structure

A structural approach greatly clarifies which components of meat are responsible for its tenderness, water-holding and appearance, and the events occurring during processing.

In living muscle, water is held in the spaces between the thick and thin filaments. Changes in the content and distribution of water within meat originate from changes in this spacing. Myofibrils shrink laterally post mortem . The fluid expelled accumulates between fibre bundles and between fibres and is drain ed by gravity forming drip. In pale, soft and exudative meat, shrinkage of the myosin heads on denaturation increases myofibrillar shrinkage. In salt solutions used in meat …

The Size Distribution Of Casein Micelles In Camel Milk, Z. Farah, M. W. Ruegg

Food Structure

The size distribution of casein micelles in camel milk has been determined by electron microscopy. Individual and pooled samples were cryo-fixed by rapid freezing and freeze-fractured. Electron micrographs of the freeze-fracture replica revealed a relatively broad size distribution, with an average micelle dimeter around 280 nm in the volume distribution curve. The distribution was significantly broader than that of the particles of cow's or human milk and showed a greater number of large particles. The submicelles were also somewhat larger than those observed in cow's and human milk (approx. 15, 10 and 7 nm, respectively). The average values for the …