Cytoplasmic organization and quantitation of microtubules in bovine mammary epithelial cells during lactation and involution

Summary Ultrastructural examination of milk secretory cells from lactating bovine mammary gland revealed presence of numerous microtubules in the apical and paranuclear cytoplasm, particularly in the vicinity of Golgi components. Most microtubules were oriented perpendicular to the apical plasma membrane and appeared to form a framework around Golgi dictyosomal elements and secretory vesicles. In comparison, non-secretory cells obtained from involuting glands displayed few microtubules and these were randomly located throughout the cytoplasm with no particular orientation.     

Airborne Stability of Tailless Bacterial Viruses S-13 and MS-2

The effect of relative humidity (RH) on the airborne stability of two small bacterial viruses, S-13 and MS-2, was studied. Poorest recovery of S-13 was obtained at 50% RH. Humidification prior to aerosol sampling significantly increased the recovery of S-13 at RH deleterious to the airborne virus. A commercial preparation of MS-2 suspended in a buffered saline solution showed a rapid loss of viability at RH above 30%, whereas a laboratory preparation containing 1.3% tryptone showed high recoveries at all RH studied. Dilution of the commercial MS-2 into tryptone broth conferred stability on the airborne virus. Humidification prior to sampling significantly reduced the viable recovery from aerosols of commercial MS-2, whereas the laboratory preparation was unaffected.     

X-Ray Diffraction of Myelin Membrane: II. Determination of the Phase Angles of the Frog Sciatic Nerve by Heavy Atom Labeling and Calculation of the Electron Density Distribution of the Membrane

The phase signs of the five main X-ray reflections from normal frog sciatic nerve have been determined as all positive using a technique of labeling with very small amounts of heavy metal. The changes in intensity of the individual reflections were studied as a function of uptake of metal label by the membrane. The possible localization of the metal label was decided from computer-analogue studies and from Patterson calculations. These phases are different from those determined by previous workers using techniques of trial of the best set of phases, or a step model, to give the best fit of the combined intensity data of normal and swollen myelin membranes. The electron density map has been calculated using eight reflections and their experimentally determined phases. The map shows an inner low electron density region which is different from that shown by earlier calculations. The center of the low electron density region shows a small region of increased electron density. However, without fixing absolute electron density levels in the map, it is not yet possible to allocate regions of low electron density to pure lipid or lipoprotein. The map shows the two sides of the membranes to be different in molecular structure without significant water spaces between the membranes.     

Uneven distribution of aerobic mesophilic bacteria on human skin.

Viable aerobic mesophilic bacteria are not evenly distributed on the skin of the volar forearm. An increase in the size of the area sampled did not result in a proportional increase in the number of the viable aerobic mesophilic bacteria recovered.     

The reduction of hydroxamic acids with titanium(III) chloride: a tool for the characterization of siderophores

Hydroxamic acid siderophores were observed to be inactivated by exposure to titanium(III) chloride. To study the reaction, a series of eight model hydroxamic acids were prepared and reacted with titanium(III) chloride. The products were shown by ir and NMR comparisons with authentic compounds to be the corresponding amides. The reduction was found to require 2 mol of titanium(III) per mol of hydroxamic acid.