Microbial adaptation to iron: a possible role of phosphatidylethanolamine in iron mineral deposition

Pseudomonas fluorescens multiplied in a minimal mineral medium supplemented with iron(III) (5 mm) complexed to citrate, the sole source of carbon, with no apparent diminution in cellular mass. Atomic absorption studies of different cellular fractions and supernatant at various growth intervals revealed that the trivalent metal was initially internalized. At approximately 41 h of incubation, the soluble cellular extract contained 9.5% of the iron originally found in the growth medium. However, as bacterial multiplication progressed, most of the metal was deposited as an extracellular insoluble gelatinous residue. Phosphatidylethanolamine appeared to be an important organic constituent of this precipitate. X-ray fluorescence and diffraction studies revealed that iron(III) was deposited as amorphous hydrated oxide. Scanning electron microscopy and energy dispersive X-ray microanalysis of the pellet aided in the identification of irregular shaped bodies rich in iron and oxygen that were associated with carbon-containing elongated structures. Examination of the bacterial cells by a transmission electron microscope equipped with an electron energy loss spectrometer indicated the deposition of iron within the cells.     

Mechanisms of voltage transients during current clamp inNecturus gallbladder

Summary Microelectrode techniques were employed to study the mechanisms of the transepithelial voltage transients (V _ms ) observed during transmural current clamps in the isolatedNecturus gallbladder. The results indicate that: a) part of V _ms is due to a transepithelial resistance change (R _t ), and part to a tissue emf change. b) R _t is entirely caused by changes of the resistance of the paracellular pathway. At all current densities employed, the measured changes are probably due to changes in both fluid conductivity and width of the lateral intercellular spaces. At high currents, in addition to the effects on the lateral spaces, the resistance of other elements of the pathway (probably the limiting junction) drops, regardless of the direction of the current. c) The magnitude and polarity of the R _t -independent transepithelial and cell membrane potential transients indicate that the largest emf change takes place at the basolateral membrane (E _b ), with smaller changes at the luminal membrane (E _a ) and the paracellular (shunt) pathway (E _s ). It is shown that two-thirds of the transient are caused by E _s , and one-third by (E _b –E _a ). E _s can be explained by a diffusion potential generated by a current-dependent NaCl concentration gradient across the tissue. E _a and E _b are caused by [K] changes, mainly at the unstirred layer in contact with the basolateral membrane.     

The effect of exogenous nucleosides on postimplantation development of mouse embryos

Exogenous nucleosides, either singly or in combination, do not enhance postimplantation development of mouse embryos in vitro, and adenosine, guanosine and thymidine are toxic to the embryos at high concentrations.     

Polyol accumulation by two filamentous fungi grown at different concentrations of NaCl

The accumulation of polyols by Aspergillus niger (van Tiegh) strain S 1 and Penicillium chrysogenum (Thom) strain S 30 was followed during growth in media of different concentrations of NaCl. The major polyols found were glycerol, erythritol and mannitol. The total polyol pool increased in both organisms in response to raised salinity, and the proportion of glycerol and erythritol was markedly enhanced at high salinity.     

Potassium binding to the (Na+ + K+)-ATPase

The number of K+ bound to the (Na+ + K+)-ATPase has been measured under equilibrium conditions by a differential-titration technique (Hastings, D.F. (1977) Anal. Biochem. 83, 416-432). 5.1 K+ were bound per 32P-labelling site. The K'D for K+ was dependent on the concentration of choline, which was included to give ionic strength. K'D was 59 +/- 2.5 microM with 97 mM choline, 26 +/-1.9 microM with 30 mM choline. The K+ : choline selectivity was 2564 : 1 and the calculated K'D for K+ with zero choline was 11 microM and for choline with zero K+ was 28 mM. 20 microM ATP in the presence of 97 mM choline incresed the K'D for potassium 3-fold to 177 +/- 14 microM. The K'D for K+ with 3 mM Na+ in the presence of 27 mM choline was 81 +/- 10 microM and with 30 mM Na+ without choline 700 +/- 250 microM. The calculated K'D for Na+ at zero K+ and zero choline was 0.6 +/- 0.2 mM. The K+ : Na+ selectivity was 54 : 1.     

Hybridoma monoclonal antibodies in the analysis fo human cell surface antigens

Summary In the present paper, we will summarize studies we have performed on two distinct human lymphocyte cell surface antigens defined by monoclonal antibodies: Leu-1 and HLA-DR. Presented in the symposium on The Biology of Hybridomas at the 32nd Annual Meeting of the Tissue Culture Association, Washington, D.C., June 7–11, 1981. This work was supported by USPHS-NIH Grants CA-21223, AI-11313, and CA-09302. This symposium was supported in part by the following organizations: Bethesda Research Laboratories, Cetus Corporation, Hybritech Incorporated, MAB-Monoclonal Antibodies, Inc., National Capital Area Branch of the Tissue Culture Association, New England Nuclear Corporation, and Ortho Pharmaceutical Corporation.     

The paracellular pathway in toad urinary bladder: Permselectivity and kinetics of opening

Summary Determination of serosa-to-mucosa fluxes of Na, K, and Cl yields information about the properties of the shunt pathway in toad urinary bladder. We show that measurement of these fluxes at 30-sec intervals following an abrupt increase in mucosal osmolality yields evidence on the rate of opening of the path and of its permselectivity. The relationship between the fluxes of any pair of these ions indicates that the shunt is paracellular both before and after the increase in conductance effected by hyperosmolality and that the transepithelial PD affects the permselectivity properties (at 0 mV,P _K/P _Na/P _Cl= 10.710.57; at +25 mV,P _K/P _Na/P _Cl=10.710.99). The relationship between any of the fluxes and the total transepithelial conductance is linear and yields an estimate of cellular conductance (the intercept of this regression on the conductance axis) which is in accord with that measured electrically. These studies provide information on tight junction permeability to nonelectrolytes, as well. Finally, they provide new information about the role of the shunt path as a controlling influence on transepithelial sodium transport and raise the possibility that, in both leaky and tight epithelia, differences in transepithelial conductance from tissue to tissue, organ to organ, and species to species may be due, in the absence of edge damage, to changes in conductance of the paracellular pathway.     

Comparative Grouping of Mastitis Streptococci by Means of Co-Agglutination and Precipitation

Two hundred bovine mastitis streptococcal strains belonging to groups B, C, E, G and L were tested comparatively by means of the co-agglutination and precipitation technique. Identical results were obtained with the two tests in 191, or 95.5 %, of the strains. Six strains, which could not be grouped by co-agglutination, proved to belong to group B when grouped by precipitation. On the other hand, one strain which proved to belong to group G and two strains to group L when grouped by co-agglutination, could not be grouped by precipitation. Some cross-reactivity was observed between groups A and C, B and G, B and L. Only a few L strains showed marked cross-reactivity which was not easily distinguished from specific reactions. However, the cross-reactivity ought to be eliminated by dilution or adsorption. Using the precipitation test as a supplementary method, the easy and rapid co-agglutination test was found to be a suitable procedure for routine grouping of mastitis streptococci.     

Estimation of levels of IgG to multiple sclerosis specific brain antigens in the cerebrospinal fluid of MS patients

The binding of partially purified multiple sclerosis (MS) specific brain antigens (MSG2) and of the corresponding antigens of non-MS brains (KG2) to cerebrospinal fluid IgG of patients with MS and other neurological diseases was assayed employing sandwich enzyme linked immunosorbent assay (ELISA). Assay of the antigen-antibody binding revealed that the concentration of MSG2 required for the optimum binding to IgG in the undiluted MS CSFs was lower than that of KG2 in all cases. The index for IgG binding capacity of an antigen (IgBC) was expressed as a ratio of the optical density of the enzymic products in ELISA at the optimal antigen-antibody binding to the lowest concentration of the antigen required for the optimal binding. The IgBC of MSG2 was found to be linearly correlated with the IgG concentration in the CSF of MS patients. These results indicate that IgG with specificity to MSG2 may be present in the CSF of MS patients.