Escherichia coli B/r cells were plasmolyzed in sucrose solutions and observed under phase contrast. The prevalence of plasmolysis under various conditions was noted, and the degree of plasmolysis was categorized as slight, extensive, or severe. The presence of ions reduced the prevalence of plasmolysis. Survival curves showed that extensive plasmolysis was not lethal to colony-forming ability. Plasmolysis represents a dramatic morpho

The influence of plasma proteins on erythrocytes was studied by interference microscopy, scanning electron microscopy (SEM), and by Westergren erythrocyte sedimentation rate (ESR). Albumin kept erythrocytes dispersed as discoid spheres. Fibrinogen seemed responsible for the rouleaux phenomenon, but needed the co‐influence of an immunoglobulin to induce rouleaux type of aggregates and high ESR. IgG, IgA and IgM caused immunologic type of aggregates. Albumin acted synergistically with fibrinogen and immunoglobulins. Normal blood contained a network of rouleaux, which probably explained the low normal ESR. High ESR was either due to rouleaux type aggregates where fibrinogen was dominant, or immunologic type aggregates where IgG, IgA or IgM were dominant proteins. Cold agglutinin disease showed normal blood morphology and normal ESR at 37°C and immunologic type aggregates and high ESR at 25°C.

SUMMARY Single, intact, frog skeletal muscle fibres and whole frog hearts were quick‐frozen on a polished, liquid‐He‐cooled copper block and examined in the electron microscope after freeze‐substitution and freeze‐fracture. In both kinds of striated muscle, collapse of the peripheral and intracristal membrane spaces in mitochondria was found to increase with increasing distance from the point of first impact (PFI) of the muscle cells on the cold copper block. The changes correlated with a previously described gradient of Z line and A band cryodamage occurring with distance from the PFI. The findings in thin sections from freeze‐substituted preparations were confirmed by freeze‐fracture preparations. It is concluded that, since the mitochondrial membrane changes are concurrent with, and follow the same spatial distribution of, other manifest cryoarte‐facts, the cryoartefactual nature of the mitochondrial changes must be excluded before functional significance is attributed to them. The collapse of mitochondrial membrane spaces as a sensitive indicator of quality of cryopreservation may apply to non‐muscle cells as well.

The distribution of two non-collagenous glycoproteins of high molecular weight, fibronectin (FN) and laminin (LMN), was investigated in myocardial cells from the ventricle of rats, and from biopsies collected from the auricle of patients undergoing a coronary bypass operation. In order to elucidate the expression of FN and LMN across cells, non-invasive serial sectioning has been carried out by laser scanning confocal microscopy of frozen, immunostained tissue sections. In addition, immunoelectron microscopy was used to study the distribution of these antigens at higher magnifications. These studies show that FN is part of the basement membrane of the surface sarcolemma of both ventricular and atrial cells, in addition to being an abundant protein of the extracellular matrix (ECM). Along transverse tubular(TT)-membranes, FN was only detected in tubules exceeding 200 nm in diameter. Even here, the intensity of labelling varied greatly and was generally low. By contrast, a heavy investment of LMN was organized in the basal lamina along the surface sarcolemma and along ramifications of the entire TT-system in ventricular heart muscle cells. In this way, the network of TT-membrane systems of working heart muscle cells provides a supply of LMN to all depths of the myocardial fibre. In human atrial muscle cells, a regular TT-system appears to be absent. Instead occasional, deep sarcolemmal invaginations occur with diameters of 300-500 nm, the surfaces of which are also invested with LMN. The significance of the present findings has been discussed, with special reference to LMN as a possible component of a series of proteins involved in transmembrane communication between the ECM and the sarcoplasm.

Large surface blebs were observed with phase-contrast optics on Escherichia coli B/r and B s-1 heated to temperatures at which colony-forming ability was lost. Characterization of such blebs was consistent with the view that they were formed by a physical process and were bounded by the outer membrane of the cell. A hypothesis for thermal inactivation of E. coli is presented that places membrane damage near the primary lethal event.