The Mechanism of the Gram Reaction I. The Specificity of the Primary Dye

Dyes of all major types were tested for their suitability as the primary dye in the Gram stain. When a counterstain was not used, some dyes of all types were found to differentiate Gram-positive from Gram-negative organisms. When a counterstain was used, these dyes were found to vary greatly in their suitability. Those dyes found to be good substitutes for crystal violet were: Brilliant green, malachite green, basic fuchsin, ethyl violet, Hoffmann's violet, methyl violet B, and Victoria blue R. All are basic triphenylmethane dyes. Acid dyes were generally not suitable. Differences in the reaction of Gram-positive and Gram-negative cells to Gram staining without the use of iodine were observed and discussed but a practical differentiation could not be achieved in this manner. Certain broad aspects of the chemical mechanism of dyes in the gram stain are discussed.     

Relative Contribution of the Cell Wall, Cytoplasmic Membrane, and Cytoplasm to the Gram-Positive Characteristic of Bacillus megaterium.

Bartholomew, J. W. (University of Southern California, Los Angeles), and Thomas Cromwell. Relative contribution of the cell wall, cytoplasmic membrane, and cytoplasm to the gram-positive characteristic of Bacillus megaterium. J. Bacteriol. 90:643-647. 1965.-A comparison of the roles of the cell wall, cytoplasmic membrane, and cytoplasmic components revealed that the intact cell wall was the dominant contributor to the gram-positive state. Protoplasts of Bacillus megaterium were confirmed as being gram-negative, as reported by Gerhardt et al. The "gram-positive protoplast" report of Amano et al. was shown to be a laboratory-produced artifact, resulting from the comparison of smears made from saline suspensions of Escherichia coli cells with smears made from formalin-sucrose suspensions of B. megaterium protoplasts.     

The use of benzyloxycarbonyl[125I]iodotyrosylalanyldiazomethane as a probe for active cysteine proteinases in human tissues.

The ability of benzyloxycarbonyl-(125I)Tyr-Ala-CHN2 to label cysteine proteinases in a variety of human tissues was investigated. The inhibitor bound only to cathepsin B in tissues homogenized at pH 5.0. When liver was autolysed at pH 4.0 for up to 4 h, the inhibitor also bound to a protein of Mr 25,000. This was identified immunologically and chromatographically as cathepsin L. Both cathepsins B and L were found primarily in kidney, liver and spleen. In spleen, an additional protein of Mr 25,000 was also labelled. This protein could not be precipitated by antibodies to any of cathepsins B, H and L. This protein has tentatively been identified as human cathepsin S by its tissue distribution, chromatographic properties and molecular size. This work clearly shows that peptidyldiazomethanes are specific probes for cysteine proteinases, and that benzyloxycarbonyl-(125I)Tyr-Ala-CHN2 binds to three such enzymes in human tissues.     

THE THERMAL SIGNIFICANCE OF THE NEST OF THE SOCIABLE WEAVER PHILETAIRUS SOCIUS: SUMMER OBSERVATIONS

Extending a previous study of the thermal significance of the nest of the Sociable Weaver carried out during the winter, we measured temperature and humidity in the matrix and chambers of a large nest of this species in the Kalahari Gemsbok National Park, South Africa, during the austral summer of December 1973. Air temperatures outside the nest ranged from 16 to 33.5°C but temperatures in occupied chambers varied over a range of only 7 or 8°C and remained well within the zone of thermal neutrality for a passerine bird of this size. Compared to outside air temperatures, those within the nest matrix were lower during the day and higher at night. Thus, the nest ameliorates the effects of external temperatures and allows maintenance inside the chambers of a range of temperature favourable to the birds. In winter we found up to five roosting adults per chamber, with some chambers left empty. In the same nest in summer we found no more than two adults per chamber but virtually all chambers were occupied. The principal mechanism for maintaining chambers within the zone of minimal energetic cost is changes in the number of birds in the nest chambers at night. Humidity inside the occupied and unoccupied chambers was somewhat higher in the former but always less than that of outside air in both cases. Air movement through the desiccated nest materials causes uptake by these materials of most of the water vapour introduced by the birds, and this moisture is dissipated to the outside during the day so that the nest remains dry. The highly social and colonial habits of the birds and their year-round occupancy and maintenance of the nest favour a system of opportunistic breeding that may be initiated by rainfall at any season. Larger nests provide the most favourable environment for energy conservation and successful reproduction. Even the largest nests, however, do not prevent predation during the warm season by snakes such as the Cape Cobra, which may consume all the eggs and young in all the chambers of a large nest. The effects of such heavy predation may be offset by the birds' capability for breeding during times too cold for reptile activity. It seems likely that in smaller nests such as those on telephone poles, lack of predation would favour summer breeding while thermal problems would limit breeding success in winter. In larger nests, breeding success may be lower in summer because of predation and higher in winter when reptile predation is lacking and thermal problems are minimized by the nest structure. The large nest not only makes possible the success of the Sociable Weaver in desert areas, but the nest could only exist in such areas and the species' range is thereby restricted. Higher humidity and heavier rainfall would cause fermentation within the nest mass, loss of its thermoregulatory advantages, and ultimately its decomposition and destruction. Therefore, the unique nesting system of the Sociable Weaver appears to be initially self-reinforcing and ultimately self-limiting.     

Virus-Dependent Glycosylation

The oligosaccharides of the membrane glycoproteins of Sindbis virus, vesicular stomatitis virus, and Rous sarcoma virus were compared on the basis of apparent size and sugar composition. It appears that each virus acquires a different set of oligosaccharides during growth in a single type of cell.     

Allometry of post-flight cooling rates in moths: a comparison with vertebrate homeotherms.

1. The rates of post-flight cooling in 25 saturniid moths of 8 genera ranging in weight from 81 to 2650 mg were measured and compared with cooling rates in sphingids, birds and mammals. 2. The initial and terminal cooling rates of the saturniids did not differ significantly. 3. Large saturniids have relatively smaller thoraxes than small ones. 4. In saturniids the rate of post-flight cooling is inversely related both to thoracic volume and total weight. 5. Cooling rate is less dependent on thoracic volume in saturniids than in sphingids. 6. Weight-specific conductance calculated on the basis of total weight, shows that moths are not as well insulated as birds or mammals. However, when considered on the basis of thoracic weight, the weight-specific conductance of saturniids and sphingids closely approximates that predicted by the regression of weight-specific conductance on total body weight in birds and mammals. 7. Since the insulation of saturniids and sphingids is no more effective for animals of their size than is that of birds and mammals, their high body temperatures during activity appear to depend primarily on high levels of heat production.