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Biomedical subjects

O D Rotstein

Publications and source records attributed to O D Rotstein.

At least 145 records · Page 8Linked to original sources
PubMed1988

Cytoplasmic pH regulation in macrophages by an ATP-dependent and N,N'-dicyclohexylcarbodiimide-sensitive mechanism. Possible involvement of a plasma membrane proton pump.

Cytoplasmic pH (pHi) regulation was studied in thioglycolate-elicited murine macrophages using fluorescent probes. Acid-loaded macrophages regained normal pHi by extrusion of H+ equivalents across the plasma membrane. A fraction of this recovery was due to Na+/H+ exchange, as evidenced by its partial Na+ dependence and amiloride sensitivity. The residual, Na+-independent pHi recovery (approximately 50% of the total) persisted in the nominal absence of HCO3- and was insensitive to disulfonic stilbenes, ruling out mediation by anion exchange. In contrast, intracellular alkalinization and H+ extrusion from the cells were inhibited by N-ethylmaleimide, by N,N'-dicyclohexylcarbodiimide or by prior depletion of intracellular ATP. These observations are consistent with the existence of a H+-pumping ATPase in the plasma membrane of macrophages. The mechanism of activation of the ATP-dependent H+ extrusion process was also investigated. In other systems, Ca2+ mobilization has been suggested to signal an exocytic insertion of H+ pumps into the plasma membrane. Acid loading of macrophages was accompanied by an elevation of the cytosolic Ca2+ concentration ([Ca2+]i), measured using indo-1. These results are consistent with a role for Ca2+ mobilization in the activation of H+ extrusion.

Adenosine Triphosphate↗
PubMed1988

Fibrin sealant in high-risk colonic anastomoses.

The use of fibrin sealant has been advocated to enhance the healing of high-risk intestinal anastomoses. Colonic anastomoses were performed in 162 rats randomly assigned to four groups: control animals with or without fibrin sealant applied to the anastomosis and steroid-treated animals with or without fibrin sealant. At five days postoperatively, the use of steroids alone significantly reduced the anastomotic bursting pressure (ABP) and enhanced abscess and adhesion formation. The addition of fibrin sealant to the anastomosis in steroid-treated animals did not improve ABP and, in fact, further increased abscess formation. In control animals, the use of fibrin sealant also reduced ABP and enhanced abscess and adhesion formation. By ten days, there was no difference in ABP among the groups, and the rate of abscess formation was reduced in all groups. These findings indicated that short-term treatment with steroids delayed colonic anastomotic healing. Fibrin sealant did not enhance the integrity of these high-risk anastomoses. The present data do not support the use of fibrin sealant in high-risk colonic anastomoses.

Abscess↗
PubMed1988

The deleterious effect of reduced pH and hypoxia on neutrophil migration in vitro.

The effect of altered microenvironment on human neutrophil locomotion was investigated. Reduced pH impaired both random and chemotactic migration using both the under-agarose and Boyden chamber techniques. Using the under-agarose technique, migration was progressively inhibited below pH 6.5, achieving significance at pH 5.5 (P less than 0.01 vs pH 7.5 for chemotactic and random migration). A similar pattern was noted using the Boyden chamber technique. At pH 7.40, extreme hypoxia (less than 30 mm Hg) caused a small (15-25%) but significant reduction in chemotactic migration. An additive deleterious effect of low pH and hypoxia on PMN migration was also found. These studies suggest that altered local microenvironment may contribute to the failure of host leukocytes to resolve infection.

Atmosphere Exposure Chambers↗
PubMed1988

Na+/H+ exchange and the regulation of intracellular pH in polymorphonuclear leukocytes.

1. Regulation of the cytoplasmic pH(pHi) was studied in quiescent and activated human neutrophils. Acid-loaded unstimulated cells regulate pHi by activating an electroneutral Na+/H+ exchange. 2. When activated, neutrophils undergo a biphasic change in pHi: an acidification followed by an alkalinization. The latter is due to stimulation of the Na+/H+ antiport. 3. The acidification, which is magnified in Na+-free or amiloride-containing media, is associated with net H+ efflux from the cells. 4. A good correlation exists between cytoplasmic acidification and superoxide generation: inhibition of the latter by adenosine, deoxyglucose or pertussis toxin also inhibits the pHi changes. 5. Moreover, acidification is absent in chronic granulomatous disease patients, which cannot generate superoxide. 6. Regulation of pHi is essential for neutrophil function. The oxygen dependent bactericidal activity is inhibited upon cytoplasmic acidification. This can result from impairment of Na+/H+ exchange, or from influx of exogenous acid equivalents. 7. The latter mechanism may account for the inability of neutrophils to resolve bacterial infections in abscesses, which are generally made acidic by accumulation of organic acids that are by-products of bacterial anaerobic metabolism.

Abscess↗
PubMed1988

Prevention of intra-abdominal abscesses by fibrinolysis using recombinant tissue plasminogen activator.

We studied whether intraperitoneal fibrinolysis using recombinant tissue plasminogen activator (t-PA) could prevent abscess formation in the rat model of intra-abdominal infection caused by fibrin clots. Single-dose administration of t-PA at concentrations greater than 0.005 mg/mL at surgery or delivered by open lavage within 1 h of surgery completely obviated abscess formation induced by Bacteroides fragilis-infected clots without altering mortality (approximately 0.6%). With mixed Escherichia coli-B. fragilis clots, t-PA increased the mortality rate from the control level of 43.8% to 81.3% but prevented abscesses in survivors. This increased mortality rate was probably due to an acute E. coli bacteremia. Antibiotics plus t-PA prevented both mortality and abscess formation. Intraperitoneal fibrinolysis may be a useful adjunct to antibiotics and appropriate surgery in the management of intra-abdominal infection.

Abscess↗
PubMed1988

The spectrum of Escherichia coli--Bacteroides fragilis pathogenic synergy in an intraabdominal infection model.

Pathogenic synergy between Escherichia coli and Bacteroides fragilis was investigated in an intraabdominal infection model. Defined inocula of E. coli and B. fragilis, alone or in combination, were enmeshed within a fibrin clot and surgically implanted into the peritoneal cavity of rats. A spectrum of bacterial synergy ranging from synergistic abscess formation to synergistic lethality was demonstrated using this model. The type of synergy exhibited was dependent upon the initial E. coli inoculum. When combined with B. fragilis, high inocula of E. coli (greater than 10(8) cfu/clot) produced synergistic lethality while low inocula (2 x 10(2) to 2 x 10(7) cfu/clot) resulted in synergistic abscess formation. With respect to abscess formation, there was reciprocal synergy between E. coli and B. fragilis. Abscesses resulting from mixed inocula were larger and had significantly higher numbers of E. coli and B. fragilis than abscesses initiated by monomicrobial inocula. These studies define a clinically relevant model of bacterial interactions in the setting of intraabdominal infection and suggest that conclusions drawn from experimental models of bacterial synergy should consider the type of model examined, the strains of bacteria studied, and the number of bacteria inoculated.

Abscess↗
PubMed1988

pH-dependent impairment of the neutrophil respiratory burst by the Bacteroides byproduct succinate.

The mechanisms by which Bacteroides species contribute to the virulence of polymicrobial intraabdominal infections are poorly defined. One potential mechanism may be their ability to inhibit host defenses, thereby permitting their co-pathogens to survive and exert their intrinsic virulence. The purpose of these studies was to examine the effect of the major Bacteroides byproduct, succinate, on the generation of the respiratory burst by neutrophils. Succinate caused a dose-dependent inhibition of both superoxide and hydrogen peroxide production. This phenomenon was markedly pH-dependent, i.e. inhibition occurred following incubation of cells in succinate at pH 5.5 but not at pH 7.4. It was further hypothesized that succinate effected this inhibition by reducing cytoplasmic pH. Presumably, at low pH, succinate in its protonated form traversed the plasma membrane and dissociated within the cytoplasmic space, thereby reducing pH. The cytoplasmic pH was determined fluorimetrically. Succinate-containing medium at pH 5.5 significantly reduced cytoplasmic pH compared to both control medium pH 5.5 and succinate medium pH 7.4. In further support of the hypothesis, it was shown that uptake of 14C-succinate by neutrophils was 8-fold increased at pH 5.5 compared to pH 7.4. Reduced temperature (4 degrees C) protected cells from the inhibitory effect of succinate at pH 5.5. Measurements of cytoplasmic pH and uptake of 14C-succinate suggested that this protection was achieved by retarding the uptake of succinic acid at low temperature. These studies suggest that fatty acid production by Bacteroides species in the acid milieux of an infection may be a potential mechanism by which Bacteroides species enhance the virulence of mixed infections.

Bacteroides↗
PubMed1988

Mead Johnson Critical Care Symposium for the Practising Surgeon. 5. The diagnosis and management of common soft-tissue infections.

Soft-tissue bacterial infections range from the superficial, relatively benign form, readily treated by oral administration of antibiotics, to the highly lethal variety which requires extensive surgical débridement, administration of broad-spectrum antibiotics and patient monitoring in the intensive care unit. The key to patient survival in the latter group is early diagnosis and treatment. Those at risk of serious infections include diabetic and cirrhotic patients and trauma victims who have been treated either surgically or medically. In addition to awareness of the possibility of serious infection, x-ray films of the soft tissue to show gas, aspiration of fluid collections for Gram's staining and local incision of the tissue to inspect fascia and muscle are all useful aids in diagnosis. This review attempts to classify soft-tissue infections and to recommend an approach to diagnosis and management.

Bacterial Infections↗
PubMed1988

Prevention of intra-abdominal abscesses with fibrinolytic agents.

Fibrin deposition during secondary peritonitis predisposes to abscess formation by protecting bacteria from host-defence mechanisms. To test the hypothesis that local fibrinolytic therapy can prevent the formation of intra-abdominal abscess, daily injections of the fibrinolytic enzymes trypsin and tissue plasminogen activator (t-PA) were administered intraperitoneally to Wistar rats inoculated intraperitoneally with infected fibrin clots. After 5 days, trypsin (1 mg/ml) had significantly (p less than 0.001) reduced abscess formation in animals inoculated with monomicrobial Bacteroides fragilis clots (20% versus 87%) or mixed Escherichia coli-B. fragilis clots (11% versus 91%). Bacteroides fragilis abscesses were also completely prevented with t-PA (0.25 mg/ml). The number of B. fragilis organisms present in residual abscesses in the trypsin-treated group was significantly (p less than 0.05) lower than in the control group (8.2 +/- 0.2, n = 7 versus 5.7 +/- 1.4, n = 4, log CFU/g abscess). In-vitro studies demonstrated that trypsin had no bactericidal effect on B. fragilis, suggesting enhanced clearance of bacteria. From these studies it appears that controlled fibrinolysis at operation may be a useful adjunct to surgery and systemic antibiotics in preventing abscess formation postoperatively.

Abdomen↗
PubMed1987

Control of cytoplasmic pH by Na+/H+ exchange in rat peritoneal macrophages activated with phorbol ester.

The mechanisms underlying cytoplasmic pH (pHi) regulation in elicited rat peritoneal macrophages were investigated by electronic sizing and fluorescence determinations. Acid-loaded cells rapidly regained normal pHi by means of an amiloride-sensitive Na+/H+ exchange. When stimulated by 12-O-tetradecanoyl phorbol 13-acetate, macrophages displayed a biphasic pHi change: a marginal acidification followed by an alkalinization. The latter results from activation of Na+/H+ exchange, since it is Na+-dependent and prevented by amiloride. When the antiport is inhibited, the full magnitude of the initial acidification can be appreciated. This acidification is independent of the nature of the ionic composition of the medium and probably reflects accumulation of protons generated during the metabolic burst. Under physiological conditions, these protons are rapidly extruded by the Na+/H+ antiport.

Animals↗
PubMed1987

Succinic acid production by Bacteroides fragilis. A potential bacterial virulence factor.

We previously demonstrated that Bacteroides species elaborate a factor that impairs polymorphonuclear leukocyte (PMN) migration. This factor, active at a pH of 5.5 but not at 7.4, had similar inhibitory characteristics as the Bacteroides metabolite succinic acid. We examined the kinetics of production of this inhibitory factor and correlated its presence with succinic acid concentrations in the culture filtrate. In the four to six hours after Bacteroides fragilis 9032 reached the stationary phase of growth, there was a large increase in succinic acid production with an accompanying reduction in culture pH. This correlated well with the generation of a leukocyte-inhibitory factor. Pure succinic acid in sterile culture medium at concentrations similar to those detected in the 18-hour culture filtrate (20 mmol/L) produced comparable reduction in PMN migration. Following gel filtration chromatography of B fragilis culture filtrate, the fractions containing succinic acid labeled with carbon 14 inhibited PMN migration.

Bacteroides↗
PubMed1987

The role of Bacteroides encapsulation in the lethal synergy between Escherichia coli and Bacteroides species studied in a rat fibrin clot peritonitis model.

Encapsulation in Bacteroides species has been thoroughly studied in vivo as a virulence factor in abscess formation. Its pathogenic role in lethal infections caused by a mixture of pathogens has been less well investigated. Our previous studies using the rat fibrin clot peritonitis model have demonstrated lethal synergy between Bacteroides fragilis and Escherichia coli. In order to determine the synergistic role of the encapsulation of the Bacteroides component in this model, inoculations of E. coli plus one of seven Bacteroides strains of differing degrees of encapsulation were assessed for their effect on mortality. Both unencapsulated Bacteroides strains tested (B. distasonis 1244, B. vulgatus 4300) produced an early lethal synergistic effect with E. coli while the heavily encapsulated strain, B. thetaiotaomicron 1603 did not do so. The four other Bacteroides strains tested were encapsulated and their synergy with E. coli was demonstrated. Control Gram-positive strains, Streptococcus faecalis and Staphylococcus aureus, did not alter mortality when mixed with E. coli in this model. These studies support the concept that virulence factors other than encapsulation are important in the outcome of polymicrobial infections in which Bacteroides species play a part.

Animals↗
PubMed1987

The Bacteroides by-product succinic acid inhibits neutrophil respiratory burst by reducing intracellular pH.

Short-chain fatty acids, particularly succinic acid, are major metabolic by-products of Bacteroides species. To determine their role as potential virulence factors in infections containing Bacteroides species, short-chain fatty acids were examined for their effect on the neutrophil respiratory burst. Succinate (30 to 50 mM) irreversibly impaired superoxide and hydrogen peroxide production in response to opsonized zymosan and phorbol myristate acetate when neutrophils were treated at pH 5.5 but not pH 6.0 or greater. Several other short-chain fatty acids tested produced similar inhibition. Reversible inhibition of oxygen consumption was found when neutrophils were incubated in succinate-containing medium (pH 6.0) as well as control medium (pH 6.0 and 5.5). Neutrophil cytoplasmic pH was measured by fluorimetric techniques to determine whether the inhibition was mediated via a reduction in intracellular pH. The intracellular pH of cells in control medium (pH 6.5 or less) was significantly reduced compared with pH 7.4. The addition of succinate (30 mM) to these media caused a further significant reduction in cytoplasmic pH at each pH level. The reduction in intracellular pH was sufficient to account for both the irreversible and reversible impairment of the neutrophil respiratory burst. Thus, short-chain fatty acids appear to exert their inhibition, at least in part, by reducing intracellular pH. These data also demonstrate the potential for interactions between Bacteroides species and their microenvironment to increase the virulence of an infection.

Bacteroides↗
PubMed1986

A Bacteroides by-product inhibits human polymorphonuclear leukocyte function.

We have previously demonstrated that Bacteroides fragilis enhanced Escherichia coli-induced lethality in the rat fibrin-clot peritonitis model. As a possible mechanism for this phenomenon, it was hypothesized that B fragilis inhibited host defense mechanisms, allowing the E coli to flourish and kill the animal. Culture filtrates of three Bacteroides species were tested in vitro for their effect on human polymorphonuclear leukocyte (PMN) chemotaxis and random migration. Two of these, B fragilis and Bacteroides distasonis, impaired PMN migration. The other, Bacteroides thetaiotaomicron, caused variable inhibition of neutrophil chemotaxis. The ability of the culture filtrates to inhibit neutrophil function appeared to depend on two factors: (1) adequate growth of the Bacteroides culture, permitting production of the leukotoxic factor, and (2) reduction of the culture pH to a level at which the putative toxin could exert its effect. Further studies revealed that the factor was heat stable, had a molecular weight less than 500, and that its effect on PMNs was only partially reversed by multiple washings. This supports the concept that Bacteroides species may contribute to the pathogenicity of mixed infections by producing a factor that inhibits host neutrophil function.

Bacterial Toxins↗
PubMed1986

Intestinal bacteria translocate into experimental intra-abdominal abscesses.

Experimental intra-abdominal abscesses were initiated by surgical implantation of a fibrin clot contaminated with either Bacteroides fragilis, Bacteroides thetaiotaomicron, or B fragilis-Escherichia coli. Seven days after surgery the numbers of bacteroides (per gram) in B fragilis and B thetaiotaomicron abscesses were typically log10 8.4 +/- 0.5 (n = 6) and log10 6.4 +/- 0.6 (n = 4), respectively; B fragilis-E coli abscesses typically contained log10 8.9 +/- 0.5 B fragilis and log10 7.6 +/- 0.6 E coli (n = 5). Of 38 B fragilis abscesses, 14 B fragilis-E coli abscesses, and nine B thetaiotaomicron abscesses, additional intestinal bacteria were recovered from 21 (55%), 13 (93%), and seven (89%) abscesses, respectively. The additional organisms, in decreasing order of frequency, were enterococci, E coli, staphylococci, alpha-streptococci, lactobacilli, and Proteus species in numbers ranging from 2.5 log10 to 7.9 log10 per gram of abscess. Histologic sections of contaminated abscesses adherent to the intestine, liver, or spleen revealed normal tissue histology and no breakdown of the abscess wall. Thus, intestinal bacteria translocated into intra-abdominal abscesses by a mechanism that did not appear to be surgical soilage.

Abdomen↗
PubMed1986

Tricuspid valve Candida endocarditis. Successful treatment with valve-sparing debridement and antifungal chemotherapy in a multiorgan transplant recipient.

Tricuspid valve Candida albicans endocarditis developed in a multiple-organ transplant recipient six months after successful treatment of Candida peritonitis. She has had no recurrence or valvular incompetence two years after valve-sparing debridement of the vegetation and prolonged therapy with amphotericin B. This is the second report of long-term success following valve-sparing debridement for tricuspid valve Candida endocarditis. In selected patients without annular involvement or gross valve destruction, excision of the fungal vegetation may allow for long-term cure and a competent valve.

Adult↗
PubMed1986

Thigh abscess. An uncommon presentation of intraabdominal sepsis.

Abscesses of the thigh are rare and, although easily diagnosed, their cause is often obscure. We present two cases of thigh abscesses which resulted from the extension of intraabdominal sepsis. A review of the literature reveals only 46 previously reported cases. The underlying pathologic abnormality is usually a retroperitoneal perforation of a colorectal neoplasm or diverticular disease, whereas origin from the small bowel or appendix is distinctly less common. Routes of extension of infection into the thigh can be either direct, through the subcutaneous tissues, or through naturally occurring defects in the abdominal wall. These include: (1) along the psoas muscle deep to the inguinal ligament; (2) through the femoral canal; (3) by way of the obturator foramen; and (4) through the sacrosciatic notch. The two cases presented are unusual in that they both followed radical cystectomy with lymph node dissection, which opens up these natural avenues to the spread of intraabdominal infection. The overall mortality in the literature is high (53 percent), but recognition of an abdominal source and appropriate treatment combined with local drainage of the thigh abscess appears to improve survival.

Abscess↗