Early and discrete changes in permeability of Escherichia coli and certain other gram-negative bacteria during killing by granulocytes

Rapid killing of Escherichia coli by intact or disrupted rabbit granulocytes or by granulocyte fractions was found to be accompanied by an equally rapid increase in permeability of the E.coli envelope. This increase in permeability was detected by determining entry of substances that normally do not cross E.coli's permeability barrier, namely actinomycin D and o-nitrophenyl-beta-D-galactopyranoside (ONPG), a substrate for cytoplasmic beta-galactosidase. Because E.coli continue to incorporate radioactively labeled precursors into bacterial RNA and protein for at least 1 h, despite rapid killing by granulocytes, entry of actinomycin D could be measured by its inhibitory effect on macromolecular synthesis. Entry was evident within minutes after exposure to granulocytes or granulocyte fractions and is independent of pH over a range of 6.5-9.0. The effect of disrupted granulocytes or partially purified fractions on susceptibility of E.coli to actinomycin D and entry of ONPG is dose dependent. That the entry of actinomycin D and ONPG was not caused by gross destruction of the envelope is indicated by two sets of observations: (a) net influx of (42)K was maintained for at least 15 min, even though efflux of potassium was immediately accelerated upon addition of bactericidal concentrations of granulocyte fractions; (b) beta-galactosidase did not leak out of E.coli under conditions that produce maximal inhibition by actinomycin D. Different species of gram-negative bacteria exhibited different susceptibilities to the bactericidal and permeability effects of granulocyte fractions. Thus, three strains of E.coli and one strain of Salmonella typhimurium were highly susceptible to both the bactericidal and the permeability enhancing effects of granulocyte fractions, whereas two strains of Serratia marcescens and one strain of Pseudomonas aeruginosa were resistant to both effects. Another strain of P. aeruginosa was rendered susceptible to actinomycin D without being killed and two strains of S. typhimurium remained insensitive to actinomycin D while being killed by granulocytes.

Retrograde radioisotope myocardial perfusion patterns in dogs

A retrograde coronary vein injection technique for concentrating radioisotope in ischemic myocardial regions was evaluated in dogs. Potassium-43 in saline solution was injected into the coronary veins during complete closure of the coronary sinus. In the presence of coronary inflow obstruction, the venous potassium-43 was distributed mainly to the low pressure vessels in ischemic heart regions; i.e., the ratio of potassium-43 in the occluded-to-unoccluded areas ranged from 2:1 to 3:1 thirty seconds after retrograde injections. Krypton-85 in saline solution was injected under pressure into the coronary veins during partial closure of the coronary sinus. In the presence of inflow obstruction, the ratio of krypton-85 in the occluded- to-unoccluded areas ranged from 4:1 to 6:1 sixty seconds after retrograde injections; larger ratios may be expected after rapid washout of gas from the normally perfused region is nearly complete. Myocardial potassium-43 imaging techniques were applied to locate and measure the size of the ischemic heart region as a radioisotopic hot spot. Detection of hypoperfused areas of extremely small size may be accomplished by this technique.

Determination of membrane potentials in human and Amphiuma red blood cells by means of fluorescent probe

1. Changes in the fluorescent intensity of the dye, 3,3'-dihexyl-2,2'-oxacarbocyanine, added to suspensions of human and Amphiuma red blood cells were measured in parallel with changes in the membrane potentials of these cells. In these studies the membrane potential was altered in three different ways: by the addition of valinomycin to alter the ratio, P(K)/P(Cl), by a change in the pH of the medium to alter the ratio, Cl(c)/Cl(0), and by the substitution of impermeant anions for Cl(0) again to alter the ratio, Cl(c)/Cl(0). In each case hyperpolarization led to a decrease and depolarization to an increase in fluorescent intensity.2. The change in fluorescence with the addition of valinomycin was dependent on the concentration of K in both the cells and the medium. Changes in fluorescence were not observed when valinomycin was added to suspensions of frozen-thawed, haemoglobin-free ghosts with dye in KCl or NaCl solutions. Such changes were observed with reconstituted ghosts provided that there was a K concentration gradient across the membrane.3. From values of cellular K and the corresponding external K concentrations for which there were no changes in fluorescence with valinomycin, estimations of membrane potentials were made. The potential was -5 to -8 mV for the human red cell and -19 mV for Amphiuma. These values are in good agreement with the potentials estimated from the Cl ratios (-9 mV for human and -17 to -20 mV for Amphiuma) and from those obtained by direct electrical measurements (-15 mV for Amphiuma).4. Fluorescent intensity of the dye in suspensions of human red cells was shown to be a linear function of the log Cl(c)/Cl(0).5. The dye (2.9 x 10(-6)M) increased the inward rate constants for (24)Na (3-4-fold) and (42)K (0.5-2-fold) for human red cells. In addition, the dye was found to be haemolytic (5-6% in 1 hr) at 22 degrees C.6. In contrast, the dye did not alter the rate of (35)SO(4) efflux at 37 degrees C from human red cells previously equilibrated with a Cl-free SO(4) medium.7. The dye was also seen to interact with certain impermeant anions and other compounds, e.g. inhibitors of anion permeability, of interest. These interactions and other limitations of the use of this dye are discussed.

Energy provision, tissue utilization, and weight loss in prolonged starvation

Daily weight loss measurements in 76 fasting, obese patients (58 females, 18 males) have shown a characteristic pattern of rapid loss initially (up to day 14) followed by a slower but uniform reduction in weight. There were significant sex differences. Measurements of tissue breakdown showed that the initial rapid weight loss was due to the continuing utilization by the nervous system of glucose derived from lean tissue. This requirement fell noticeably from the second week of starvation. Irreversible fluid elimination also contributed to the initial phase of rapid weight loss. Fat remained the primary source of energy throughout starvation and in established fasting (more than 14 days) contributed 96% of that requirement.

Sodium and potassium transport rates in normal human leucocytes in hypo-osmolal extracellular fluid

1. Sodium and potassium transport rates were studied in normal human leucocytes exposed to iso-osmolal and hypo-osmolal extracellular fluid.

2. Hypo-osmolality of the extracellular fluid led to an increase in sodium influx and a decrease in potassium influx expressed as mmol h−1 kg−1 cell dry weight. The fall in potassium influx was smaller than the rise in sodium influx and was confined to the ouabain-insensitive portion of the flux.

3. The rate constants for sodium and potassium efflux did not differ significantly between the iso-osmolal and hypo-osmolal media.

Rest and exercise potassium-43 myocardial perfusion imaging for the noninvasive evaluation of aortocoronary bypass surgery

Sixteen patients undergoing aortocoronary bypass surgery were evaluated with rest and exercise potassium-43 ( 43 K) myocardial imaging and contrast angiography an average of 5.5 months postoperatively. The results of 43 K imaging allowed the division of these patients into two groups. Group 1 consisted of patients in whom there was either normalization or significant improvement in postoperative images when compared to abnormal preoperative studies (five patients), or patients in whom preoperative imaging was not accomplished but whose postoperative images both at rest and exercise showed a normal homogenous pattern of 43 K distribution (four patients). All patients in this group had at least one patent bypass graft, and 13 of 16 total grafts were patent. Group 2 consisted of seven patients in whom postoperative rest and exercise 43 K studies were either not significantly different from preoperative evaluation, or had worsened. Of these patients, three experienced intraoperative infarction, two demonstrated significant distal native coronary disease, and one had a single occluded graft. In both groups there was good correlation between the anatomic sites of graft patency or occlusion and the location of either increased perfusion or lack thereof on the 43 K image. Perfusion abnormalities occurring in the presence of occluded grafts, or improvement in perfusion occurring in the presence of patent grafts were best appreciated by comparison of exercise images. Abnormalities occurring in the presence of infarction were detected at rest as well. Thus, in this initial group of patients, 43 K rest and exercise myocardial imaging appeared to offer a sensitive noninvasive means of evaluating the results of aortocoronary bypass surgery.

An estimate of sodium-potassium pump activity and the number of pump sites in the smooth muscle of the guinea-pig taenia coli, using (3H)ouabain

1. Binding of tritiated ouabain to the smooth muscle of the guinea-pig taenia coli showed two components, one saturable at lower glycoside concentrations and the other linear with increasing concentrations.2. The saturable component alone was affected by extracellular potassium concentrations. This component seems to be bound to sodium pumping sites, and when completely saturated binds 1.1 x 10(11) molecules per mg fresh wt. of tissue, or 250-300 molecules per square micron of membrane, assuming a volume:surface area ratio of 1.5 mum.3. Only a fraction of (42)K uptake by the cells can be blocked by ouabain at maximal concentrations. In normal Krebs solution two thirds can be blocked. The remaining one third is presumably passive uptake. The fraction blocked is reduced as the extracellular potassium concentration, and thus passive uptake, is increased.4. The amount of potassium pumped into the cells at various concentrations of extracellular potassium has been calculated. In normal Krebs solution the amount pumped in 45 min was 20.0 m-mole/kg fresh wt., and this was increased at higher potassium concentrations.5. On the assumption of a stoichiometry of 3Na: 2K, the pump sites in normal Krebs solution have a turnover rate of 1320 min(-1).6. Indirect calculations of sodium movements suggest that the sodium permeability may be about 0.9 x 10(-8) cm sec(-1) and the pump may generate a current of 0.9 x 10(-7) A cm(-2). This crossing an Ohmic membrane resistance of 30-60 kOmega cm(2) would be equivalent to a potential difference of 3-5 mV.

Effects of myocardial strains on coronary blood flow

Systole causes a redistribution of coronary blood flow away from the subendocardium. In the present study the relative contribution of shortening of the myocardial fibers (wall strains) and of pressure development in the ventricular lumen to redistribution were determined. The distribution of coronary blood flow during systole in hearts ejecting into a severed aorta (large wall strains and near-zero afterload) was compared with that in isovolumetrically contracting hearts (reduced wall strains and significant afterload). A quantitative index of the distribution of coronary blood flow during systole was provided by the myocardial uptake of a bolus of 86 Rb or 42 K injected when constant-pressure perfusion of the left coronary artery was restricted with a solenoid-controlled pump to the period of systole. The coronary blood flow during systole in the subendocardium of the ejecting heart was 62% of that in the subepicardium. A similar gradient in the systolic flow with the endocardium receiving 37% of the blood flow to the epicardium was observed in the hearts contracting isovolumetrically. Removing the afterload by severing the aorta abolished the transmural differences in coronary blood flow. In the present experiment cardiac strains per se did not redistribute coronary blood flow through shear or traction forces on the coronary vasculature, but rather, coronary blood flow was affected only by compressive stresses in the myocardium. Contraction in the absence of afterload influenced overall coronary resistance, however; 18% of the resting coronary resistance was associated with shortening alone. An additional 11% of the resting coronary resistance appeared when pressure development accompanied shortening. Coronary blood flow patterns indicated two separate compressive stresses in the left ventricle. The first stress was associated with pressure development and increased with myocardial depth. The second stress was smaller; it was associated with shortening and uniformly distributed.

Specific electron donor-energized transport of alpha-aminoisobutyric acid and K+ into intact cells of a marine pseudomonad

The transport of alpha-aminoisobutyric acid and K(+) into K(+)-depleted cells of a marine pseudomonad (ATCC 19855) was stimulated strongly by ethanol, reduced nicotinamide adenine dinucleotide (NADH), and ascorbate-reduced N, N, N', N'-tetramethyl-p-phenylenediamine. In the presence of the quinone inhibitor 2-heptyl-4-hydroxyquinoline-N-oxide, only ascorbate-reduced N, N, N', N'-tetramethyl-p-phenylenediamine was active. Primary and secondary, but not tertiary, alcohols from ethanol to n-amyl alcohol stimulated both alpha-aminoisobutyric acid and K(+) transport and were oxidized by the cells. Malate and succinate, which were oxidized rapidly by the cells, had little or no capacity to energize the transport of alpha-aminoisobutyric acid into K(+)-depleted cells but were partially effective in promoting K(+) uptake. Ethanol stimulated the transport of alpha-aminoisobutyric acid into K(+)-preloaded cells. The transport of both alpha-aminoisobutyric acid and K(+) was inhibited 20% by iodoacetate, 85% by N-ethylmaleimide, and 90 to 100% by both NaCN and p-chloromercuribenzoate. The addition of Na(3)Fe(CN)(6) permitted the ethanol-induced transport of alpha-aminoisobutyric acid into K(+)-preloaded cells in the presence of NaCN, but little or no uptake of alpha-aminoisobutyric acid or of K(+) into K(+)-depleted cells under the same conditions. The transport of alpha-aminoisobutyric acid into K(+)-depleted cells required both K(+) and an electron donor. The oxidation of NADH and ethanol by K(+)-depleted cells was stimulated strongly by K(+). Parallels between these studies and those with membrane vesicles show that results with membrane vesicles of the marine pseudomonad have physiological significance for the intact cells. The results support the conclusion that the energy for the active transport of both alpha-aminoisobutyric acid and K(+) into cells of this organism is provided by electron flow through a region of the respiratory chain lying between cytochrome c and O(2).