Eosinophil major basic protein increases membrane permeability in mammalian urinary bladder epithelium

The eosinophilgranule protein major basic protein (MBP) is toxic to a wide variety ofcell types, by a poorly understood mechanism. To determine whether theaction of MBP involves an alteration in membrane permeability, wetested purified MBP on rabbit urinary bladder epithelium usingtransepithelial voltage-clamp techniques. Addition of nanomolarconcentrations of MBP to the mucosal solution caused an increase inapical membrane conductance only when the voltage across the apicalmembrane was cell interior negative. The magnitude of the MBP-inducedconductance was a function of MBP concentration, and the rate of theinitial increase in conductance was a function of the transepithelialvoltage. The MBP-induced conductance was nonselective forK⁺ andCl. MucosalCa²⁺ reversed the inducedconductance, whereas mucosal Mg²⁺partially blocked the induced conductance and slowed the rate of theincrease in conductance. The induced conductance was partially reversedby changing the voltage gradient across the apical membrane to cellinterior positive. Prolonged exposure resulted in an irreversible lossof the barrier function of the urinary bladder epithelium. Theseresults suggest that an increase in cell membrane ion permeability isan initial step in MBP-induced loss of barrier function.

     

Potassium-Stimulated Taurine Release and Nitric Oxide Synthase Activity During Quinolinic Acid Lesion of the Rat Striatum

The microdialysis technique was used to study the effect of nitric oxide synthase (NOS) activity on taurine release. Taurine release was characterized in rat striatum that was excitotoxically lesioned compared to normal conditions. The basal taurine level of the dialysate decreased during quinolinate (QUIN) lesion in parallel to the cell degeneration process. The K⁺-stimulated taurine concentration also decreased during QUIN-lesion, but to an extent that was different from that of basal values. K⁺-stimulated taurine levels were further markedly lowered by coapplication of the NOS inhibitor L-NAME in control and in lesioned animals up to 30 days after QUIN-injection. Postdegenerative tissue did not show any NOS-dependency in K⁺-induced taurine release. We conclude that a substantial part of K⁺-induced taurine release depends on NOS-activity both in normal brain tissue and in excitotoxically induced neurodegeneration. The main source of K⁺-induced taurine release in control rats are neurons but in lesioned animals are activated astroglial cells.     

On the application of polyelectrolyte “limiting laws” to the helix-coil transition of DNA. I. Excess univalent cations

A general theory of polyelectrolyte solutions is here used to calculate the differences in Gibbs free energy, enthalpy, and entropy between the coil and helix forms of DNA at any temperature and salt concentration. The salt has univalent cations and is assumed present in excess over the base concentration. The results are restricted to sufficiently dilute solutions. It is shown that the salt concentrations effect is entirely entropic in origin. When applied to the melting temperature, the calculations yield a relation between the enthalpy difference at the melting temperature and the slope of the plot of melting temperature vs. the logarithm of the salt concentration. In accord with observation, both the Gibbs free energy difference at any fixed temperature and the melting temperature are predicted to be linear functions of the log of the salt concentration. However, the theory is not in quantitative agreement with enthalpy data. Data on various colligative and transport properties of both helix and coil forms are reviewed in the text and in Appendix B, and good agreement is found with theory for both forms. No attempt is made to explain why the theory is quantitative for these properties but not for heat measurements. Finally, in Appendix A, an approximate calculation is made of the free energy contributions due to ionic effects not associated with the salt concentration.     

THE MYOFILAMENT LATTICE: STUDIES ON ISOLATED FIBERS : II. The Effects of Osmotic Strength, Ionic Concentration, and pH upon the Unit-Cell Volume

The effects of osmotic concentration, ionic strength, and pH on the myofilament lattice spacing of intact and skinned single fibers from the walking leg of crayfish (Orconectes) were determined by electron microscopy and low-angle X-ray diffraction. Sarcomere lengths were determined by light diffraction. It is demonstrated that the interfilament spacing in the intact fiber is a function of the volume of the fiber. It is also shown that the interfilament spacing of the skinned (but not of the intact) fiber is affected in a predictable manner by ionic strength and pH insofar as these parameters affect the electrostatic repulsive forces between the filaments. From these combined observations it is demonstrated that the unit-cell volume of the in vivo myofilament lattice behaves in a manner similar to that described for liquid-crystalline solutions.     

Pseudohypertension secondary to a noncompressible brachial artery

The interesting problem is considered of a comatose alcoholic diabetic with an extremely high systolic blood pressure, as determined by the usual means, who was subsequently found to have severe medial calcinosis and normal intraarterial blood pressure. The syndrome of the noncompressible brachial artery surely accounts for this patient''s falsely elevated blood pressure reading. Though infrequently reported, this condition can be one cause of “difficult to control” hypertension in the elderly and in the diabetic patient.     

Staphylococcal Enterotoxin B and Nuclease Production Under Controlled Dissolved Oxygen Conditions

Enterotoxin B, nuclease, and total exoprotein production by Staphylococcus aureus strain S-6 was studied in a 0.5-liter fermentor system. While these extracellular products were elaborated over a wide range of aeration rates, maximal production occurred within the very narrow range of 125 to 150 cm(3) of air per min. The levels attained at the optimal aeration rate were not increased by maintaining a constant pH, although yield of enterotoxin:cell mass was highest at a constant pH of 7.0. During the growth cycle of the cultures, when aeration rate alone or aeration rate and pH were held constant, the dissolved oxygen (DO) levels, initially set at 100% of saturation, decreased to 5 to 10% 4 to 5 h after inoculation. The oxygen demand of the culture then maintained this level for an additional 4 to 6 h. This interval of low DO was characterized by maximal growth and exoprotein production. When the DO was controlled at a constant value throughout growth (by increasing or decreasing the airflow rate as appropriate), the culture demonstrated different optima for maximal growth and exoprotein production. A constant DO of 100% stimulated growth to extremely high densities, but the accumulation of toxin and nuclease was not observed. On the other hand, maintaining constant DO levels at 50 or 10% raised exoprotein levels higher than those achieved in a culture grown at the optimal aeration rate. Compared to the optimal aeration rate culture, the 10% DO culture yielded 20% more nuclease, 25% more toxin, and 40 to 50% more total exoprotein. These results indicate that it is the DO and not the aeration rate, per se, that is influential in controlling growth, toxin, nuclease, and total exoprotein production.     

Inactivated Venezuelan Equine Encephalomyelitis Vaccine Prepared from Attenuated (TC-83 Strain) Virus

Formalin-inactivated Venezuelan equine encephalomyelitis vaccine was prepared from virus propagated in rolling-bottle cultures of chicken embryo cells. The attenuated, TC-83 strain of virus was propagated in these cultures with a maintenance medium consisting of serum-free medium 199 containing 0.25% human serum albumin and antibiotics. By adjustment of maintenance medium volume (100 to 300 ml) and multiplicity of inoculum (0.04 to 0.00004), high-titered yields of virus were obtained with minimal cell destruction at convenient harvest times, viz, 18 to 24 h postinoculation. Inactivation of virus at 37 C was complete between 8 to 10 h with 0.05% Formalin and within 6 to 8 h with 0.1% Formalin. Antigen extinction potency tests in mice indicated that potent vaccines could be produced at both Formalin concentrations and, furthermore, that potency was not adversely affected by inactivation periods of up to 96 h.     

Effect of Shaking Speed on the Secretion of Enterotoxin B by Staphylococcus aureus

The concentration of enterotoxin B secreted by four strains of Staphylococcus aureus was dependent upon the shaking speed. For the conditions established, each strain demonstrated an optimal shaking speed, and speeds in excess of the optimum resulted in decreased secretion of toxin. At the optimal shaking speed, maximum secretion occurred at 37 C. At 45 C, both growth and toxin secretion were absent. By using agar containing antienterotoxin B sera, studies with strain S-6 at optimal and suboptimal shaking speeds demonstrated that individual cells vary in their toxin-synthesizing ability and that the relative numbers of high and low producers change during the growth cycle. Although most of the toxin was secreted during the first 12 hr of growth, a portion was secreted during the subsequent 6 hr, even though growth as measured by colony-forming units per milliliter decreased and Klett units increased.     

Freeze-Etching of Azotobacter vinelandii: Examination of Wall, Exine, and Vesicles

The structure of the cell wall, the arrangement of the cyst exine, and the origin and distribution of intine vesicles in Azotobacter vinelandii ATCC 12837 were examined by freeze-etching and conventional electron microscopic techniques. In the vegetative organism the cell wall appears to have a woven texture which disappears during cyst formation. The exine is composed of two different types of material: the outer layer is a fibrous, amorphous layer, and the numerous inner layers form the basic hexagonal structures which unite to form the cyst coat. The presence of intine vesicles in the encysting organism was confirmed in frozen-etched cells. The appearance of frozen-etched cells and cysts and the distribution of capsular material indicate that extracellular polysaccharide is an important factor in cyst formation.