Hemophilus vaginalis bacteremia.

During 1975--77 Hemophilus vaginalis bacteremia occurred post partum in eight previously healthy women. Seven had been admitted for delivery at term and one because of threatened abortion. Six underwent cesarean section. Post-partum pyrexia and neutrophilia were the main features. All the patients recovered uneventfully while receiving antibiotics. H. vaginalis is an infrequent agent of bacteremia; it affects predominantly women after obstetric trauma.     

Nucleotide sequence and hormonal regulation of mouse glycerophosphate dehydrogenase mRNA during adipocyte and muscle cell differentiation

We have studied the structure and regulation of glycerophosphate dehydrogenase (GPD) mRNA during mouse adipocyte and muscle cell differentiation. This message has a size of 2.8 kilobases that includes a coding segment of 1050 bases and a large untranslated 3' end of about 1700 bases. There is a high degree of amino acid homology (91%) between the mouse adipocyte and rabbit muscle GPD proteins. GPD mRNA is not detected in myoblasts, but, as in adipogenesis, it is expressed upon differentiation into myotubes. The modulation of GPD mRNA by cyclic AMP analogues and tumor necrosis factor has been examined in both adipocytes and myotubes. Dibutyryl cAMP or 8-bromo-cAMP causes a large reduction of GPD mRNA levels in both cell types, with less than 20% remaining after 18 h of treatment. Tumor necrosis factor effects a dramatic and rapid reduction in GPD mRNA in fat cells and a slower but significant decrease in the level of this mRNA in muscle cells. These results indicate that GPD gene expression is linked to cell differentiation in both fat and muscle cells, and suggest certain similarities in hormonal modulation in both cell types.     

A miniaturised parallel-plate shearing apparatus for the measurement of cell adhesion

The design and construction of a miniaturised shearing apparatus is described. Cultures (24 h) of an established epithelial cell line (BEB) were exposed to flow conditions in the shearing chamber at 37 degrees C, and subsequently glass coverslip cultures were prepared for photography. The critical shear radius (CSR) was determined by densitometry from a negative film and the minimum distraction force (MDF) at the CSR calculated using predetermined viscosity values of the flow medium. The mean calculated MDF of BEB cells ranged from 1.04-1.36 Nm-2, and was independent of the culture inoculation density (9 to 37 X 10(4) cells cm-2) and the time (5-20 min) of exposure to shearing conditions. The MDF was increased to 3.3 Nm-2 by a 30 min exposure of cultures to concanavalin A (50 micrograms ml-1), and this effect was abolished by treating with mannose (0.05 M). The results demonstrated that the radial flow chamber principle is applicable to the measurement of cell to substratum adhesion of cultured mammalian cells.     

Quantitative studies of increased cell-to-substratum adhesion at low temperature

The cell-to-substratum adhesion of an established epithelial cell line cultured for 24 h on glass coverslips was determined at 4 degrees C, 8 degrees C and 37 degrees C using a miniaturised parallel-plate shearing apparatus. The measurements of the minimum shear necessary to dislodge the cells (minimum distraction force, MDF) demonstrated a three- to fourfold increase in the adhesion of the cells at 4 degrees C (6.17 Pa) compared to that at 37 degrees C (1.36 Pa). At 8 degrees C the MDF was 2.31 pascals. Part of the adhesion was resistant to mild trypsinisation. Trypsin-resistant adhesion (TRA) was stabilised by low temperature, and by treatment with concanavalin A (50 micrograms ml-1) or colchicine (200-400 microM). The effects of con A (140 micrograms ml-1) and low temperature (4 degrees C) were additive, giving a combined MDF of greater than 9.27 pascals. On the basis of their different temperature and protease susceptibility it is suggested that trypsin-sensitive adhesion (TSA) and TRA represent separate functional classes of cell-to-substratum attachment corresponding to 'frictional' and 'tractional' adhesion, respectively.     

Effect of temperature on the circular dichroism spectra of beta 2-microglobulins

When the temperature was lowered from 25 to 5 degrees C dramatic changes were observed in the near-ultraviolet circular dichroism spectra of bovine and caprine but not human beta 2-microglobulin. Comparison of the protein sequences suggests that the conformational change occurs in the amino-terminal 24 residues and that a tyrosine residue located on a potential beta-turn acts as a reporter group. Because delta H degrees is small (-22 kcal X mol-1), such conformational changes, possibly not readily observed, may occur at low temperatures in other proteins having potential beta-turns in otherwise aperiodic regions of sequence.     

Two-dimensional impedance studies of BSA buoyant density separated human erythrocytes

Combined DC (Coulter Volume) and radio frequency impedance studies were performed on human erythrocytes which had been separated by buoyant density in linear, neutral, isotonic bovine serum albumin gradients. The individual buoyant density fractions showed no reproducible shift in volume with buoyant density but did show a shift with opacity, radio frequency impedance divided by dc impedance. This new electronic parameter of opacity can be related to cell age, since both it and cell age are directly related to buoyant density. This increase in opacity with buoyant density is correlated with a change in shape.