Cross-sectional area of flexible tubes

Kresch (1977) presented the results of calculations which determined the cross-sectional shapes assumed by flexible, elastic tubes for varying transmural pressures. Extensions of these results are presented here in the form of graphs of the cross-sectional area as a function of the transmural pressure. Since the circumferential arc length, theX-axis intercept and theY-axis intercept were necessarily computed, and are of interest, graphs of these are also presented. Each graph is a composite of several curves. Each curve in the graph shows the behavior of the parameter as a function of the relative pressure (P) for a specific value ofR, a parameter related to the wall thickness. The curves are shown for both positive and negative values ofP. The most negative value ofP shown is the point where the walls touch and the most positive value shown is the point where the equations fail to converge. The cross sections were assumed to be elliptical when the transmural pressure was zero. Graphs for three of these initial shapes are shown: nearly circular, major-to-minor axis ratio equal to 2, and an intermediate case. For the nearly circular case, the curves divide into two regimes: one where stretching clearly predominates and another where bending clearly predominates. For the more eccentric initial cross-sections, the distinction between the two regimes cannot be made in this simple manner.     

In vitro adhesion of tufted oral streptococci toBacterionema matruchotii

The adhesive interaction between the ectosymbionts of the corn cob configuration (CCC), a naturally occurring bacterial consortium in human dental plaque, was studied. In vitro association was produced in mixed cultures consisting ofBacterionema matruchotii and streptococci resemblingStreptococcus sanguis previously isolated from human CCC. Phase-contrast, selective immunofluorescence, and scanning electron microscopy showed that in this aggregative system, a tuftlike polar structure typical of the coccal epibiont mediated binding to the core filament. This aggregative model provides evidence that a specialized structure on the cell surface of epiphytic organisms may participate in interbacterial adherence.     

High voltage electron microscopical analysis of chromosomal number in the slime mold Echinostelium minutum de bary

Utilizing serial thick sectioning techniques in combination with high voltage electron microscopy and stereopair analysis a count of 124 chromosomes was determined for a metaphasic plasmodial nucleus of the slime mold E. minutum.     

Hormonal control of urine-marking in wild and domestic Norway rats

Wild and domestic Norway rats will actively urine-mark a small rod suspended across their home cage. Administration of testosterone to castrated male rats indicated that the urine-marking response is hormone dependent.     

Biosynthesis of azetidine-2-carboxylic acid from methionine in Nicotiana tabacum

The administration of dl-methionine-[1¹⁴C] to Nicotia tabacum resulted in the formation of radioactive azetidine-2-carboxylic acid (isolated by dilution) which was specifically labelled on its carboxyl group. This result and other evidence strongly indicates that this imino acid is a normal component of tobacco.