Biomedical subjects

R E Baughn

Publications and source records attributed to R E Baughn.

At least 73 records · Page 4Linked to original sources

PubMed1983

Isolation and preliminary characterization of circulating immune complexes from rabbits with experimental syphilis.

Immune complexes isolated from sera of rabbits with experimental, disseminated syphilis were found to have sedimentation coefficients greater than 19s. By radioimmunoblot assays, materials precipitated with 2.5% polyethylene glycol or chromatographed on DEAE-Affi-Gel Blue were found to contain albumin, C3, immunoglobulin M (IgM), IgG, and treponemal antigen(s), whereas control materials contained only albumin and IgG. When polyethylene glycol precipitation of immune complexes from syphilitic rabbits was followed by immobilization on protein A and acid elution, radioimmunoblots detected only IgG and treponemal antigen(s).

Animals↗

PubMed1983

Circulating immune complexes in experimental syphilis: identification of treponemal antigens and specific antibodies to treponemal antigens in isolated complexes.

As a prelude to characterization of the host and treponemal antigens present in purified immune complexes from the sera of rabbits with disseminated syphilis, autoradiographic and immunoenzymatic analyses of solubilized extracts of Treponema pallidum, Treponema phagedenis biotype Reiter, and Treponema refringens were performed on electroblots of polypeptides first separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electroblots of purified immune complexes were developed with the same panel of antisera so that protein profiles could be compared. Eight treponemal antigens were consistently present in isolated complexes; four of these cross-reacted with antisera prepared against avirulent treponemes. The average molecular weights of these antigens were 87,000, 76,000, 66,000, and 45,000. Antibodies dissociated from isolated immune complexes, when used for the development of T. pallidum electroblots, reacted with four antigens of comparable molecular weight. Antibodies to those polypeptides were also present in the sera of animals immunized with immune complexes. The demonstration of treponemal antigens in purified immune complexes convincingly argues that their occurrence in experimental syphilis is not merely due to tissue destruction and responses to endogenous host antigens.

Animals↗

PubMed1983

Pneumonia and acute febrile tracheobronchitis due to haemophilus influenzae.

Of 30 patients with pneumonia due to Haemophilus influenzae, 26 had infection due to nontypable and 4 due to typable organisms. Biotype I isolates were implicated with surprising frequency. Blood cultures were positive in six patients. An additional 14 patients, all with nontypable H. influenzae infection, had febrile purulent tracheobronchitis that was clinically indistinguishable from pneumonia except for the absence of a radiographic infiltrate; none were bacteremic. Penicillin susceptibility was shown for 95% of isolates, and response to ampicillin was prompt. Patients had high serum levels of bactericidal antibody on admission but had lower levels of serum opsonizing activity against their own organism than did uninfected carriers with chronic bronchitis; 2 to 3 weeks later, levels of opsonizing antibody had risen to equal those of carriers. Deficient opsonizing activity may have contributed to susceptibility to infection. These findings identify both host and bacterial factors that may cause susceptibility to pulmonary infection from H. influenzae.

Antibodies, Bacterial↗

PubMed1982

Studies on the pathogenesis of the Jarisch-Herxheimer reaction: development of an animal model and evidence against a role for classical endotoxin.

The etiology of the Jarisch-Herxheimer reaction is unknown, but the reaction may result from toxic products of dead or dying treponemes reacting with sensitized syphilitic tissues. Because of similarities of spirochetes with gram-negative bacteria, endotoxin has been proposed as the responsible toxin. In 19 patients with syphilis, a reaction occurred in 15 (79%) during treatment with penicillin. Endotoxemia was not found by the limulus amoebocyte lysate test. All animal model of the Jarisch-Herxheimer reaction was developed in rabbits infected with Treponema pallidum. When treated with penicillin, 18 (78%) of 23 rabbits infected 18-29 days previously developed a reaction that resembled that in humans. Endotoxemia was not detected by the lysate test. After the reaction, rabbits were not refractory to the pyrogenic effects of endotoxin, and syphilitic rabbits rendered tolerant to endotoxin still developed fever when treated with penicillin. These data suggest that classical endotoxin is not the cause of the Jarisch-Herxheimer reaction.

Adult↗

PubMed1982

Reappraisal of lymphocyte responsiveness to concanavalin A during experimental syphilis: evidence that glycosaminoglycans in the sera and tissues interfere ith active binding sites on the lectin and not with the lymphocytes.

No significant differences were noted between the responses of lymphocytes from normal and Treponema pallidum-infected rabbits to concanavalin A. When added to cultures of normal peripheral blood lymphocytes, however, sera and tissue supernatant fluids from infected rabbits were capable of suppressing the response to concanavalin A. Although immune complexes were regularly present in suppressive sera and tissue extracts, additional experiments in which both direct and indirect approaches were used indicated that immune complexes were not responsible for the observed depression. Sequential stimulation studies, done with purified glycosaminoglycan materials obtained from suppressive sera and testicular fluids, and specific absorption studies suggested that this material blocks active sites on the lectin and merely prevents recognition of the mitogen by otherwise functionally active cells.

Animals↗

PubMed1981

Evaluation of rosaramicin phosphate in treatment of experimental syphilis in rabbits.

The in vivo activity of rosaramicin phosphate in disseminated and localized Treponema pallidum infections in rabbits was compared with that of penicillin G benzathine. Rabbits were injected either intradermally or intravenously to establish infection. Groups of four animals each then received either two weekly injections of 200,000 U of penicillin G benzathine, injections of 12.5 or 25 mg of rosaramicin per kg of body weight twice a day for 10 days, or no antibiotic therapy. Treatment of the intradermal and intravenous infections was initiated on days 7 and 14 postinfection, respectively. With both infection models, striking differences were noted between the untreated control rabbits and the three groups receiving treatment; no discernible differences, however, were detected among any of the treated groups. Rabbits that had been infected intravenously did not develop disseminated lesions or orchitis after treatment, and chancres produced by intradermal infection regressed and healed rapidly after the initiation of therapy. Continued increases in treponemal and nontreponemal antibody titers posttreatment did not occur in any of the treated rabbits. Infectivity studies also suggested that the lymph nodes and testes of treated animals were free from infectious organisms. Overall, at the dosage regimens employed, both rosaramicin and penicillin G benzathine appeared to effect complete control of the experimental disease.

Animals↗

PubMed1980

Hypoglycemia as a manifestation of sepsis.

Hypoglycemia has rarely been described as a clinical sign of severe bacterial sepsis. We recently encountered nine patients in whom hypoglycemia (mean serum glucose of 22 mg/dl) was associated with overwhelming sepsis. Clinical disease in these patients included pneumonia and cellulitis; in three patients, no focus of infection was apparent. Altered mental status, metabolic acidosis, leukopenia, abnormal clotting studies and bacteremia were common features in these cases. In four patients, no cause for hypoglycemia other than sepsis was present. In five patients, another possible metabolic cause for hypoglycemia was present (alcoholism in four and chronic renal insufficiency in one) although none had been observed to be hypoglycemic on previous hospitalizations. Streptococcus pneumoniae (three cases) and Hemophilus influenzae, type b, (two cases) were the most common pathogens, and the over-all mortality was 67 per cent. The mechanism(s) for hypoglycemia with sepsis is not well defined. Depleted glycogen stores, impaired gluconeogenesis and increased peripheral glucose utilization may all be contributing factors. Incubation of bacteria in fresh blood at room temperature does not increase the normal rate of breakdown of glucose suggesting that the hypoglycemia occurs in vivo. Hypoglycemia is an important sign of overwhelming sepsis that may be more common than has previously been recognized.

Acidosis↗

PubMed1980

Detection of circulating immune complexes in the sera of rabbits with experimental syphilis: possible role in immunoregulation.

The in vivo and in vitro immunoglobulin G plaque-forming cell responses to sheep erythrocytes (SRBC) are nearly obliterated during disseminated syphilitic infection (3 to 8 weeks post-intravenous injection) in rabbits. Splenic and lymph node cells obtained from infected rabbits during this time period were capable of suppressing the normal in vitro responses of uninfected, SRBC-primed cells. Cell-free washings of cells from infected animals were also suppressive. This finding coupled with the fact that treatment of infected cells with proteolytic enzymes abrogated the suppressive effect constitute arguments against involvement of a specific suppressor cell population. The incidence of elevated levels of circulating immune complexes in the sera of rabbits with disseminated disease was also significantly different from that of uninfected controls or infected rabbits before the onset or after the regression of lesions. When added to cultures of lymphocytes from uninfected, SRBC-sensitized rabbits, sera containing complexes caused dose-related suppression of the in vitro immunoglobulin responses. Unlike immune complexes, no correlation was found between the presence of mucopolysaccharide materials and the stage of infection or the ability of serum to suppress the immunoglobulin responses to SRBC.

Animals↗

PubMed1979

Selection of small-colony variants of Enterobacteriaceae by in vitro exposure to aminoglycosides: pathogenicity for experimental animals.

Small-colony variants of gram-negative genera of Enterobacteriaceae were selected by in vitro exposure to gentamicin. These variants were shown to have decreased susceptibility in vitro to aminoglycosides. They were lethal for mice following intraperitoneal injection, with the LD50 (50% lethal dose) being the same as, or slightly less than, that for the parent organism. Variants of strain no. 2401 of Proteus mirabilis caused urinary tract infection in mice after implantation into their bladders. Although the variants grew somewhat less rapidly than did parent organisms, both parent and variant colonies alkalinized urine at the same rate. Electron microscopic study showed no differences between colonies of parents and variants. These studies indicated that small-colony variants of Enterobacteriaceae are pathogenic for experimental animals. Further, they may cause disease in humans and should not necessarily be regarded as only laboratory curiosities.

Aminoglycosides↗

PubMed1979

Effects of BCG infection on the susceptibility of mouse macrophages to endotoxin.

Mice infected intravenously with Mycobacterium bovis (BCG) are 100 to 1,000 times more sensitive to the lethal effects of bacterial lipopolysaccharides (LPS). Since BCG infection results in macrophage activation and LPS may cause pathophysiological effects through interaction with this cell type, it was of interest to determine whether macrophages from BCG-infected animals were more susceptible to the toxic effects of LPS in vitro. When LPS-susceptible, C57BL/6 mice were infected with BCG, a significant reduction in the 50% lethal dose of LPS was first observed after 7 days and persisted for several weeks. Macrophages from these animals had greatly increased susceptibility to LPS in vitro, which correlated with the development of acquired cellular resistance as determined by their ability to inhibit the growth of Listeria monocytogenes. In contrast, BCG infection of C3H/HeJ mice, a strain resistant to LPS, did not alter the 50% lethal dose of LPS for these animals or increase the sensitivity of their peritoneal macrophages to LPS in vitro. These results indicate that susceptibility of BCG-infected mice to the lethal effects of LPS parallels the susceptibility of their macrophages in vitro; release of vasoactive substances from LPS-susceptible activated macrophages in vivo may be, in part, responsible for lethality.

Animals↗

PubMed1979

Aberrant secondary antibody responses to sheep erythrocytes in rabbits with experimental syphilis.

Rabbits infected with Treponema pallidum have strikingly depressed in vivo immunoglobulin G responses to sheep erythrocytes. To gain further insight into the nature of this suppression, the immune responses of splenic and peripheral blood lymphocytes from infected rabbits to sheep erythrocytes were studied in vitro. Spleen cells from rabbits that had been sensitized with sheep erythrocytes during active syphilis had greatly decreased immunoglobulin M and G responses after in vitro incubation with sheep erythrocytes, when compared to the results obtained with cells from sensitized uninfected animals. Suppressor cells could be demonstrated in peripheral blood lymphocytes of control rabbits 6 months after sensitization with sheep erythrocytes; these cells could be removed by nylon wool filtration. When primary sensitization with sheep erythrocytes was carried out during active syphilis, these suppressor cells were not detectable in peripheral blood lymphocytes 6 to 9 months later. These findings provide further evidence that induction of immune responses may be abnormal early in treponemal infection and may help to explain the failure of the host to produce antibodies which eradicate the organism during the first 2 to 3 months of infection.

Animals↗

PubMed1979

Two forms of Staphylococcus aureus in blood of patients with staphylococcal sepsis.

Two distinctly different and stable forms of Staphylococcus aureus were isolated from the blood of each of two patients with staphylococcal sepsis. In each case, one form was hemolytic and the other nonhemolytic, although both had the same biochemical reactions, phage types, and antibiotic susceptibilities, and both were virulent for mice. Variant forms of S. aureus may be selected in vivo by host factors and may be responsible for causing and/or perpetuating infection.

Adult↗

PubMed1979

Ultrastructural study of satellite lymph nodes in syphilitic rabbits.

In an electron microscopy study of lymph nodes from syphilitic rabbits plasmablasts and plasma cells were unequivocally identified in germinal centres. Up to 20% of the plasma cells possessed unusual cytological features. Paracortical hypoplasia was shown to be associated with actively phagocytic histiocytes. These findings may reflect morphological correlates of the aberrant immune regulation which has been observed in infection with Treponema pallidum.

Animals↗

PubMed1978

Mitogenic activity of bacterial lipopolysaccharides in vivo: morphological and functinal characterization of responding cells.

The in vivo effect of bacterial lipopolysaccharides (LPS) on mouse spleen cell subpopulations was investigated. Intravenous administration of LPS resulted in marked enlargement of the spleen, accompanied by increased cellular proliferation and enhanced nucleated cell recoveries. At least two morphologically distinct cell types appeared to be targets for LPS. Polymorphonuclear leukocytes accumulated rapidly with a relatively minor degree of cell division. In contrast, a substantial proportion of splenic lymphocytes transformed into large lymphocytes and blast cells which actively incorporated [3H]thymidine. Proliferating cells were identified as bone marrow-derived (B) lymphocytes by their ability to form C3-dependent rosettes and to synthesize immunoglobulin. These cellular responses were not antigenically induced, since LPS derived from mutants lacking the polysaccharide moiety gave similar results. Thus, splenic B lymphocytes appear to interact and respond to LPS in vivo in the same manner as observed in vitro. These data suggest that the capacity of LPS to directly activate B lymphocytes, initiate cellular proliferation, and induce immunoglobulin production by bone marrow-derived cells in vivo may contribute to its adjuvant activity.

Animals↗

PubMed1978

Strain-dependent cytotoxic effects of endotoxin for mouse peritoneal macrophages.

The cytotoxic effects of bacterial lipopolysaccharides (LPS) on mouse leukocytes have been examined in vivo and in vitro. Intraperitoneal injection of LPS into C57BL/6 mice greatly reduced the recovery of mononuclear cells; LPS was cytotoxic for macrophages, but had a mitogenic effect on lymphocytes. Similar effects of LPS on peritoneal leukocytes were observed in vitro. When monolayers of adherent peritoneal cells were studied in vitro, cytotoxicity was also observed, suggesting that the effect of LPS on macrophages is direct and does not require participation by lymphocytes. Entirely different results were obtained when peritoneal macrophages from LPS-resistant C3H/HeJ mice were studied. LPS failed to activate lymphocytes and was not cytotoxic for macrophages in vitro or in vivo. The effect of LPS on polymorphonuclear leukocytes appeared to be the same in all mouse stains studied. Lipid A was shown to be the most biologically active portion of the LPS molecule. Whereas polysaccharide-deficient endotoxins extracted from rough mutants of Salmonella typhimurium were cytotoxic for macrophages in vitro, polysaccharides that lacked esterified fatty acids did not exhibit this activity. Since LPS may mediate its effects through affinity for mammalian cell membranes, the cellular unresponsiveness of C3H/H3J mice to LPS may reflect an inability of cells from LPS-resistant strains to interact with LPS at the membrane level.

Animals↗

PubMed1978

Altered immune responsiveness associated with experimental syphilis in the rabbit: elevated IgM and depressed IgG responses to sheep erythrocytes.

Generalized suppression of immunoglobulin G (IgG) synthesis detectable by depressed responses to heterologous antigens may be a mechanism by which certain parasites evade host defenses and establish chronic infections. To determine if such a mechanism occurs in syphilis, rabbits were infected with Treponema pallidum, and at weekly intervals thereafter these rabbits and uninfected controls were sensitized with SRBC. Seven days later the number of antibody-forming cells present in the spleen was determined by the Jerne plaque technique. After a transient suppression in the 1st week, IgM-PFC were elevated from up to 7 weeks after infection. The IgG response to SRBC was depressed early in infection and continued to decline to less than one-tenth of control levels over the next few weeks persisting throughout overt infection and returning to normal by the end of 2 months. IgG-PFC, and 2-ME-resistant hemagglutinins and hemolysins were also significantly depressed in infected rabbits after two immunizing doses of SRBC. These results suggest that the depressed IgG response caused by syphilitic infection may enable treponemes to evade host immunity by interfering with immunoregulatory mechanisms.

Animals↗

PubMed1977

Emergence of variant forms of Staphylococcus aureus after exposure to gentamicin and infectivity of the variants in experimental animals.

Exposure of a large inoculum of Staphylococcus aureus in vitro to concentrations of gentamicin that exceeded the minimal bactericidal concentration regularly resulted in the emergence of aminoglycoside-resistant bacterial variants. Variants lacked typical properties that are associated with S. aureus: they produced small, nonhemolytic colonies that were mostly coagulase-, deoxyribonuclease-, and mannitol-negative. In some instances phage type also differed from that of the parent forms. Animal models of subcutaneous and intravenous infection were studied with use of parent and variant forms of S. aureus. Subcutaneous injection of variants into rats readily produced abscesses, and intravenous inoculation into mice caused pyelonephritis, although in each experimental model in which equivalent bacterial inocula were used, parents produced more extensive disease. These data show that variants of S. aureus cause infection in experimental animals, although these variants appear to be somewhat less virulent than the parents from which they are derived. Preliminary studies in our laboratory have also shown that gentamicin-resistant variants of gram-negative bacilli can be induced by a single in vitro exposure to gentamicin. The virulence of these organisms and their role in antibiotic-susceptibility patterns of hospital flora warrant further investigation.

Animals↗

PubMed1977

Inability of spleen cells from chancre-immune rabbits to confer immunity to challenge with Treponema pallidum.

Although several lines of evidence suggest that cellular immune mechanisms play a role in controlling infection due to Treponema pallidum, recent studies have shown that induction of acquired cellular resistance by antigenically unrelated organisms fails to protect rabbits against syphilitic infection, thereby casting doubt on this hypothesis. In the present paper we describe attempts to transfer immunity to syphilis by using spleen cells from chancre-immune rabbits. Intravenous infusion of 2 X 10(8) spleen lymphocytes was capable of transferring acquired cellular resistance to Listeria and delayed hypersensitivity to tuberculin. However, in eight separate experiments using outbred or inbred rabbits, 2 X 10(8) spleen cells from syphilis-immune animals failed to confer resistance to T. pallidum whether by intravenous or intradermal challenge. Mixing immune lymphocytes with treponemes immediately before intradermal inoculation also failed to confer resistance. Despite the fact that syphilitic infection stimulates cellular immune mechanisms and induces acquired cellular resistance to antigenically unrelated organisms, cellular immunity may not play an important role in immunity to syphilis.

Animals↗