Changes in element availability induced by sterilization in heavy metal contaminated substrates: A comprehensive study

Microbiome analyses of soils and microcosm experiments depend on conditions that include sterilization in order to perform experimental manipulation of microbial communities. Still, they should represent conditions close to nature. When using metal contaminated soils, sterilization methods might alter metal availability. Here, four typical metal contaminated substrates were analyzed, representing different contamination histories and soil types. They included two very poor substrates, as they are often found at metal contaminated sites. The low contents in organic carbon and nitrogen as well as two substrates with slightly higher nutrient availability were used to perform a comprehesive study for element availability changes induced by sterilization. Autoclaving, dry heat or gamma raγ sterilization were applied and compared to a non-treated control. The sterile substrates were analyzed using sequential extraction to account for different associations of the elements. Metals forming specific (hydro)oxide layers were specifically analyzed since they in turn may also impact other metals or ions. In addition, (heavy) metals and (micro)nutrients were analyzed for changes in speciation. The effects of autoclaving (wet heat) was found acceptable, while γ-ray irradiation did show unexpected changes in metal associations, especially for one substrate. Dry heat changed metal availability to the highest degree.

Siderophore production by streptomycetes-stability and alteration of ferrihydroxamates in heavy metal-contaminated soil

Heavy metal-contaminated soil derived from a former uranium mining site in Ronneburg, Germany, was used for sterile mesocosms inoculated with the extremely metal-resistant Streptomyces mirabilis P16B-1 or the sensitive control strain Streptomyces lividans TK24. The production and fate of bacterial hydroxamate siderophores in soil was analyzed, and the presence of ferrioxamines E, B, D, and G was shown. While total ferrioxamine concentrations decreased in water-treated controls after 30 days of incubation, the sustained production by the bacteria was seen. For the individual molecules, alteration between neutral and cationic forms and linearization of hydroxamates was observed for the first time. Mesocosms inoculated with biomass of either strain showed changes of siderophore contents compared with the non-treated control indicating for auto-alteration and consumption, respectively, depending on the vital bacteria present. Heat stability and structural consistency of siderophores obtained from sterile culture filtrate were shown. In addition, low recovery (32 %) from soil was shown, indicating adsorption to soil particles or soil organic matter. Fate and behavior of hydroxamate siderophores in metal-contaminated soils may affect soil properties as well as conditions for its inhabiting (micro)organisms.

Growth of streptomycetes in soil and their impact on bioremediation

The impact of the extremely heavy metal resistant actinomycete Streptomyces mirabilis P16B-1 on heavy metal mobilization/stabilization, phytoremediation and stress level of plants was analyzed in the presence and absence of Sorghum bicolor in sterile microcosms containing highly metal contaminated or control soil. For control, a metal sensitive S. lividans TK24 was used. The metal contents with respect to the mobile and specifically adsorbed fractions of the contaminated soil were considerably decreased by addition of both, living and dead biomass of the strains, with the heavy metal resistant S. mirabilis P16B-1 showing considerably higher impact. Both strains could grow in control soil, while only S. mirabilis P16B-1 formed new tip growth in the metal contaminated soil. A plant growth promoting effect was visible for S. mirabilis P16B-1 in contaminated soil enhancing the dry weight of inoculated Sorghum plants. Thus, metal resistant strains like S. mirabilis P16B-1 are able to enhance phytoremediation of heavy metal contaminated soils.

GC content-independent amino acid patterns in bacteria and archaea

Every organism can be characterized by the amino acid composition of its proteome. So far it was assumed that these compositions are determined by the GC content of the DNA or, in some cases, by extreme lifestyles, like thermophily or halophily. Here, we focussed our analysis on eight amino acids, each of which is encoded by both, GC and AT rich codons, to identify finer amino acid patterns beyond the GC dominance. We investigated the conceptually translated proteomes of 1029 bacterial and archaeal strains with sequenced genomes for amino acid composition. Using correspondence analysis, we found that phylogenetic groups within bacteria and archaea generally can be discriminated from other groups due to their amino acid composition. In some cases, single organisms, e.g. Treponema pallidum strains or Mycoplasma penetrans, are characterized by extreme amino acid compositions. We assume that our data could provide a basis for a new approach to analyze evolution of bacterial and archaeal groups. Furthermore, for single organisms, the detailed knowledge of the amino acid composition of the entire proteome encoded in the genome could lead to a better understanding, important for pharmaceutical or biotechnological applications. We recommend that information about amino acid compositions should be provided in databases, comparable to the GC content of genomes.

In silico prediction of potential metallothioneins and metallohistins in actinobacteria

Metallothioneins and metallohistins are short peptides with a high cysteine and/or histidine content able to coordinate metals intracellularly, thereby increasing the tolerance against elevated concentrations of metals. Because of their features, they can be detected by in silico prediction from proteomes annotated from sequenced genomes. Here, we analyzed 73 sequenced actinobacterial genomes for peptides (≤ 100 amino acids) with a high content of cysteine and histidine (≥ 15%) and identified 103 putative metallothioneins and metallohistins. For 45 of these peptides, we found similarities to metal binding protein domains, including zinc fingers, heavy metal transporters or eukaryotic metallothioneins, which can serve as proof-of-principle in underscoring a potential function as metal binding peptides. An evolutionary origin from metal containing domains of enzymes is discussed and metallohistins not containing cysteine are described for the first time for bacteria.

Implementation of the microdialysis method in the hamster dorsal skinfold chamber

The aim of this study was to implement the microdialysis method, a well-established technique for measuring the local concentration of neurotransmitters and metabolites in the brain, in the dorsal skinfold chamber of the awake hamster. First, the effects of implanted, nonperfused microdialysis probes on the microcirculation were examined. Skinfold chambers were prepared with and without probes. Two and 3 days later, the following parameters were assessed: diameter, red blood cell (RBC) velocity, macromolecular leakage, leukocyte rolling fraction, and adherent leukocytes in venules, diameter and macromolecular leakage in arterioles, and functional capillary density (FCD). No significant differences between the animals of the two groups were observed in any of the parameters on either day. Second, the interstitial lactate concentration was measured at two perfusion rates in groups with and without a 4-h tourniquet ischemia. The induction of ischemia resulted in a significant increase in lactate concentration over the control values in the tissue within 1 h to 8000 +/- 860 microM, where it remained until the reperfusion, at which point the concentration returned to control values within 1 h. The microdialysis method provides the opportunity to measure the concentration of metabolites in the extravascular space of the hamster dorsal skinfold chamber.

In vivo assessment of synovial microcirculation and leukocyte-endothelial cell interaction in mouse antigen-induced arthritis

OBJECTIVE

The microcirculation and leukocyte-endothelial cell interaction in synovial tissue of an inflamed joint are known to play a crucial role in the pathogenesis of rheumatoid arthritis. The aim of this study was to characterize the in vivo changes in the microvasculature and in leukocyte-endothelial cell interactions in the mouse synovial tissue using intravital fluorescence microscopy in three stages of antigen-induced arthritis. The expression of E- and P-selectin and ICAM-1 were also studied using immunohistochemistry.

METHODS

Antigen-induced arthritis (AiA) was produced in Balb/c mice. The severity of arthritis at three different phases was quantified using a clinical and histological score. For the intravital fluorescence microscopy measurements, the patella tendon was partially resected for visualization of the intraarticular synovial tissue of the knee joint. The number of rolling and adherent leukocytes, functional capillary density (FCD) and RBC velocity were quantitatively measured in synovial microvessels. Expression of ICAM-1, E- and P-selectin was assessed by immunohistochemistry.

RESULTS

There was a significant increase in the leukocyte rolling fraction in postcapillary venules in the acute phase of AiA (from 0.26 +/- 0.05 in controls to 0.45 +/- 0.04 8 d after AiA induction). The number of leukocytes adherent to the endothelium was significantly elevated in all phases of arthritis (from 121 +/- 27 in controls to 376 +/- 62 mm2 63 d after AiA-induction). Functional capillary density was significantly enhanced in the acute (332 +/- 15 cm/cm2) and intermediate phases (320 +/- 15 cm/cm2) compared to control values (227 +/- 15 cm/cm2). Arthritis resulted in a distinct increase in the expression of ICAM-1 on the synovial endothelium in all phases of AiA. E- and P-selectin expression were detected only in the acute phase.

CONCLUSION

Our model provides new insights into the microcirculatory changes which occur in the synovial tissue of an arthritic joint.

Effects of the phlebotropic drug Daflon 500 mg on postischemic reperfusion injury in striated skin muscle: a histomorphologic study in the hamster

The objective of this study was to investigate the effects of the purified, micronized, flavonoid fraction Daflon 500 mg (S 5682, 90% diosmin and 10% hesperidin) on tissue damage and leukocyte emigration in striated skin muscle after ischemia-reperfusion, as assessed by histomorphometric analysis. The experimental model used was the transparent dorsal skin fold chamber in the awake Syrian golden hamster. Sixty-four animals were randomly allotted to two treatment groups and time points of investigation. Animals were fed with 30 mg kg(-1) body weight Daflon 500 mg (n = 32) or its vehicle, 5% Arabic gum solution (n = 32), as control 8 hours before ischemia. Before induction of a tourniquet ischemia of 4 hours' duration and at 0.5, 2, and 24 hours of reperfusion, tissue sections were preserved for light and electron microscopic analysis (n = seven or eight animals per time point). The number of intravascular and extravascular leukocytes was determined by light microscopic analysis of esterase-positive leukocytes. For quantitative analysis of ischemia-induced endothelial cell damage, the endothelial thickness of capillaries was calculated by a computer-assisted imaging system, whereas the ischemic tissue damage was assessed by means of a score system (grade 0-3) by an independent investigator. The number of emigrated leukocytes was significantly reduced in Daflon 500 mg-treated animals compared with numbers found in control animals. The histomorphologic muscle fiber damage increased after reperfusion in both groups but was significantly reduced in the Daflon 500 mg-treated animals 2 and 24 hours after reperfusion. These results suggest that the emigration of leukocytes plays an important role in the development of postischemic reperfusion injury of striated skin muscle.

Effects of the phlebotropic drug Daflon 500 mg on postischemic microvascular disturbances in striated skin muscle: an intravital microscopic study in the hamster

The objective of this study was to investigate the effects of the micronized purified flavonoid fraction Daflon 500 mg (90% diosmin and 10% hesperidin) on I/R-induced microvascular leukocyte-endothelium interaction and leakage of the high molecular weight plasma tracer FITC-dextran (relative molecular mass, 150 kd) as assessed in the striated skin muscle of the dorsal skin fold chamber model in the hamster. Intravital fluorescence microscopy was used for analysis of microvascular perfusion, leukocyte-endothelium interaction, and macromolecular leakage of FITC-dextran 150 kd in the striated skin muscle of the hamster. A tourniquet ischemia of 4 hours' duration was induced followed by reperfusion. Animals were treated with an oral administration of Daflon 500 mg (n = six) or its vehicle (5% Arabic gum solution, n = six) for 8 days at a daily dose of 30 mg/kg body weight. Measurements in the microcirculation were made before the 8-day feeding protocol before induction of ischemia and at 0.5, 2, and 24 hours of reperfusion. In the absence of I/R, no differences in microvascular perfusion, leukocyte-endothelium interaction, and macromolecular leakage were found in Daflon 500 mg and vehicle-treated control animals before and after administration of the drugs. Induction of ischemia and reperfusion, however, elicited a significant increase in venular leukocyte rolling and sticking in vehicle-treated animals, which was accompanied by enhancement of leakage of FITC-dextran 150 kd into the perivascular tissue. Treatment with Daflon 500 mg had no effect on postischemic leukocyte rolling and sticking, and macromolecular leakage of FITC-dextran 150 kd from arterioles and postcapillary venules was significantly reduced. These data indicate that Daflon 500 mg preserves the endothelial barrier function of striated skin muscle arterioles and venules after I/R, which appears to be independent of an action on postischemic intravascular leukocyte rolling and sticking.

Attenuation of postischemic reperfusion injury in striated skin muscle by diaspirin-cross-linked Hb

Hemoglobin-based oxygen carriers have been suggested to enhance the formation of oxygen free radicals, especially under conditions of ischemia-reperfusion (I/R), in which activation and adhesion of leukocytes play a pivotal role for propagation of reperfusion injury. This study investigates the effects of the hemoglobin-based oxygen carrier diaspirin-cross-linked hemoglobin (DCLHb) in an I/R model of hamster striated skin muscle. The dorsal skinfold chamber model in the awake Syrian golden hamster was used for analysis of the microcirculation and local tissue PO2 in striated skin muscle utilizing the technique of intravital fluorescence microscopy and a multiwire platinum surface (Clark type) electrode. Measurements were made before 4 h of pressure-induced ischemia and at 0.5, 2, and 24 h of reperfusion. Animals were treated with 5 ml/kg body wt of either 10% DCLHb (n = 8), 6% Dextran 60 (Dx-60; 60 kDa, n = 8), or 0.9% NaCl (n = 7), which was given intravenously 15 min before reperfusion. In animals treated with DCLHb or Dx-60, a significant decrease of leukocytes rolling along and sticking in postcapillary venules, associated with a recovery of functional capillary density and red blood cell velocity, was observed compared with saline-treated controls. In the early reperfusion period (0.5 h), DCLHb and Dx-60 efficiently restored local tissue PO2, whereas tissue PO2 decreased from 18.3 +/- 1.9 to 15.3 +/- 5.3 mmHg in 0.9% NaCl-treated animals. Electron microscopic analysis of the postischemic tissue at 24 h of reperfusion revealed markedly reduced tissue damage in animals treated with DCLHb compared with Dx-60 or isotonic saline. These results indicate that DCLHb attenuates postischemic reperfusion injury of striated skin muscle, presumably through alterations of leukocyte-endothelial cell interactions.

Effects of Daflon 500mg on postischemic macromolecular leak syndrome in striated skin muscle of the hamster

We have recently shown that the purified micronized flavonoid fraction (90% diosmin and 10% hesperidin) Daflon 500 mg attenuates reperfusion injury in the striated skin muscle of the hamster. Herein, we report on the action of Daflon 500 mg on postischemic macromolecular leakage of FITC-dextran 150 kD provoked by tourniquet ischemia. Intravital fluorescence microscopy was used for analysis of macromolecular leakage in the microcirculation model of the hamster. A tourniquet ischemia of 4 h duration was induced followed by reperfusion. Animals were treated by gavage of Daflon 500 mg (n = 6) for 8 days at a daily dose of 30 mg kg(-1) body weight. Control animals received equivalent volumes of the vehicle (5% Arabic gum solution, n = 6). Measurements of the microcirculatory parameters were made before induction of ischemia and at 0.5, 2 and 24 h of reperfusion. After induction of ischemia, macromolecular leakage from postcapillary venules was significantly enhanced in vehicle-treated animals. Treatment with Daflon 500 mg significantly attenuated macromolecular leakage of FITC-dextran 150 kD. Preliminary data from a histomorphometric analysis (n = 3/experimental group) indicated that the number of emigrated (extravascular) leukocytes after ischemia reperfusion was markedly reduced in Daflon 500 mg-treated animals as compared to controls. These data indicate that Daflon 500 mg prevents leakage of the macromolecular tracer FITC-dextran 150 kD from postcapillary venules after postischemic reperfusion, presumably through an inhibitory action on the emigration of activated leukocytes.

[Effect of adenosine on intravascular accumulation of leukocytes and tissue damage in striated muscle in endotoxemia]

Under the experimental conditions of endotoxinemia, the therapeutic use of an intravenous infusion of adenosine (110 micrograms x kg-1 x min-1) has been investigated in the microcirculation model of the BALB/c mouse. Injection of S. abortus-equi endotoxin (2 mg x kg-1 body wt. i.v.) elicited a significant increase of sticking leukocytes in postcapillary venules of striated skin muscle, which was associated with a swelling of microvascular endothelium and striated skin muscle. Infusion of adenosine effectively attenuated the endotoxin induced enhancement of leukocyte sticking and preserved microvascular endothelial and striated muscle integrity. These results imply the use of adenosine as therapeutic concept during endotoxinemia.

[Effect of Daflon 500 mg on reperfusion damage following ischemia and reperfusion of striated muscle]

The results of the current study indicate that Daflon 500 mg effectively reduces permeability for macromolecules induced by ischemia-reperfusion, thus reducing postischemic edema formation in the early reperfusion period. The inhibitory effect of Daflon 500 mg on leukocyte emigration may account for the reduction of edema formation in the postischemic tissue and favor the therapeutic use Daflon 500 mg of reperfusion-injury.

Protection of mice from mortality caused by living and heat-killed bacteria by SDZ MRL 953

Protective effects of SDZ MRL 953, a monosaccharidic lipid A analog with a reduced toxicity, were investigated in models of experimental septic shock caused by injections of LPS, and inoculations of heat-killed or live bacteria. Female B6D2F1 mice were challenged with a combination of galactosamine (800 mg/kg) plus various doses of heat-killed isolates of Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, and Staphylococcus aureus or LPS from Salmonella abortus equi. In some experiments, isolates of living bacteria at sublethal inocula were also combined with galactosamine. More than 90% of the animals died within 24 hr when the challenge was performed either simultaneously with or up to 4 hr after an intraperitoneal administration of galactosamine. No death was observed when galactosamine was omitted or administered after the microbial or LPS challenge. Pretreatment of the animals with SDZ MRL 953 (1-10 mg/kg) rendered the animals resistant to the lethal effects of both bacterial and LPS challenge in a time- and dose-dependent manner. The levels of TNF-alpha in control mice rose to greater than 600 pg/ml 2 hr postbacterial or LPS challenge, but were below detection in animals pretreated with SDZ MRL 953. Protection against both the infection and the toxicity of heat-killed bacteria or LPS was also achieved when murine anti-TNF-alpha monoclonal antibody was administered prophylactically. Together, these data suggest that SDZ MRL 953 enhances the resistance of mice against the toxicity of heat-killed gram-negative bacteria and S. aureus, and attenuates host responses to living bacteria which may lead to irreversible shock and death.

Acyclic analogues of lipid A: synthesis and biological activities

The synthesis of a series of novel acyclic analogues of lipid A, the lipophilic terminal of lipopolysaccharide (LPS), is reported. In these compounds, the reducing glucose unit of lipid A has been replaced by an acyclic analogue unit (abbreviated as AAU) consisting of a spacer (of varying length), an (R)-3-hydroxytetradecanamido moiety (of varying configuration at the carbon of attachment), and a CO2H group. The AAU has been attached to the anomeric carbon of the nonreducing glucose unit of lipid A, either through glycosidic linkage or through an acyl linkage. Further, amide isosteres of these acyclic analogues have been prepared using suitably protected 2,3-diamino-2,3-dideoxyglucose instead of 2-amino-2-deoxyglucose. All the compounds were well characterized and were tested for their ability to induce TNF-alpha in mouse bone marrow-derived macrophages, to enhance nonspecific resistance to infection in mice and to induce endotoxic shock in mice. The results showed a dramatic dependence, for the first time, on the length of the spacer and on the configuration of the carbon bearing the amido group in the AAU part of the analogues.

C-glycosidic analogues of lipid A and lipid X: synthesis and biological activities

The synthesis of a series of novel analogues of lipid A, the lipophilic terminal of lipopolysaccharides (LPS), and lipid X, the reducing monosaccharide unit in lipid A, is reported. In these compounds, the native 1-O-phosphate group has been replaced by a "bioisosteric" CH2COOH substituent. The new N,O-acylated monosaccharide C-glycosides were obtained by Wittig reaction of suitably protected glucosamine derivatives. These lipid X analogues were recognized as substrates by the enzyme lipid A synthase and could be coupled with UDP-lipid X to afford the corresponding disaccharide analogues of the lipid A precursor on preparative scale. All compounds were characterized by NMR, MS, and elemental analysis, and were tested for their ability to enhance nonspecific resistance to infection in mice and also for endotoxicity. The results clearly show that the new compounds express biological activities similar to those of their O-phosphorylated natural counterparts. Furthermore, these compounds exhibit a better therapeutic index in mouse models than the standard LPS obtained from Salmonella abortus equi.

Immunostimulatory, but not antiendotoxin, activity of lipid X is due to small amounts of contaminating N,O-acylated disaccharide-1-phosphate: in vitro and in vivo reevaluation of the biological activity of synthetic lipid X

Lipid X, a precursor in the biosynthesis of lipid A, has been claimed to possess most of the immunostimulatory activity but none of the toxicity of endotoxin. However, recent work shows that synthetic lipid X can be contaminated with small amounts of N,O-acylated disaccharide-1-phosphate (H. Aschauer, A. Grob, J. Hildebrandt, E. Schuetze, and P. Steutz, J. Biol. Chem. 265:9159-9164, 1990). Because the impurities themselves exhibit immunostimulatory properties, it was necessary to establish whether chemically pure synthetic lipid X exhibits any of the endotoxinlike biological activities previously attributed to the native compound extracted from the Escherichia coli MN7 mutant. In the present study, two batches of synthetic lipid X were used: batch A contained the contaminating disaccharide, and batch B was pure lipid X. Batch A, previously believed to be pure on the basis of spectroscopic and microanalysis data, induced murine peritoneal macrophages to secrete tumor necrosis factor, interleukin-1, and prostaglandin E2 at a minimal dose of 10 micrograms/ml in vitro. Batch B, further purified by Sephadex LH 20 chromatography, was found virtually inactive in these in vitro assays. Furthermore, batch A was pyrogenic in rabbits at a dose of 0.05 mg/kg, whereas batch B was not pyrogenic at doses of up to greater than or equal to 2 mg/kg. However, both batches were equally tolerated by galactosamine-loaded mice at doses of up to 100 mg/kg. Surprisingly, while only batch A protected neutropenic mice against lethal infection with Pseudomonas aeruginosa (50% effective dose, 12.4 mg/kg), both batches were equally protective against infection with herpes simplex virus type 1 in mice and guinea pigs, even when lipid X was administered therapeutically. Interestingly, both batches of lipid X blocked endotoxin-induced expression of monocyte procoagulant activity and priming of human neutrophils for superoxide anion release. Similarly, both batches protected galactosamine-sensitized mice from otherwise lethal endotoxemia when administered prophylactically or simultaneously with the lipopolysaccharide challenge. Thus, our findings suggest that chemically pure lipid X (batch B) is devoid of the immunostimulatory properties of lipid A or endotoxin. Rather, it behaves as a competitive inhibitor of lipopolysaccharide. We conclude, therefore, that previous studies which attributed immunostimulatory activities to any batch of synthetic lipid X should be interpreted with caution.

Recombinant murine granulocyte-macrophage colony-stimulating factor augments neutrophil recovery and enhances resistance to infections in myelosuppressed mice

The ability of recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) to protect myelosuppressed mice against lethal infections was evaluated. In mice myelosuppressed by cyclophosphamide, subcutaneously administered rmGM-CSF was a potent stimulus of granulopoiesis by increasing the number of GM-CSF-responsive precursor cells in bone marrow followed by a profound neutrophilia. Neutrophil recovery was augmented by rmGM-CSF in a dose-dependent manner at daily doses of 0.6-5.0 micrograms/mouse. In addition, rmGM-CSF increased the functional activity of circulating neutrophils at similar doses. When rmGM-CSF was administered to neutropenic mice before experimentally induced Pseudomonas aeruginosa, Staphylococcus aureus, or Candida albicans infections, it protected against these lethal infections, resulting in increased numbers of survivors. These data suggest that rmGM-CSF protects neutropenic mice from lethal infections, probably by augmenting neutrophil recovery after myelosuppression and activation of mature cells.

SDZ MRL 953, a novel immunostimulatory monosaccharidic lipid A analog with an improved therapeutic window in experimental sepsis

SDZ MRL 953, a new synthetic monosaccharidic lipid A, was investigated in vitro and in vivo for immunopharmacological activities. In experimental models of microbial infections, the compound was highly protective when it was administered prophylactically either once or three times to myelosuppressed or immunocompetent mice. The 50% effective doses of SDZ MRL 953 varied with the infectious agents and the route of its administration. In all cases, the 50% effective doses were about 10(3) times higher than those obtained with endotoxin from Salmonella abortus equi. SDZ MRL 953 was, however, less toxic than lipopolysaccharide by a factor of 10(4) to greater than 7 x 10(5) times in galactosamine-sensitized mice. The compound was also an effective inducer of tolerance to endotoxin. Hence, repeated dosing with the compound induced a transient resistance (greater than or equal to 1 week) to lethal challenges with endotoxin. In vitro, the compound was devoid of intrinsic antimicrobial activity, but it moderately induced the release of cytokines from monocytes and primed human neutrophils for the enhanced production of reactive oxygen metabolites in response to a soluble stimulus. The results presented here suggest that SDZ MRL 953 may be useful in a clinical setting for enhancing resistance to infections, particularly in patients undergoing myelosuppressive chemotherapy or irradiation, and for the prophylaxis of endotoxin shock.

Effect of SDZ MRL 953 on the survival of mice with advanced sepsis that cannot be cured by antibiotics alone

Stimulation of nonspecific immunity as an additional modality for therapy of sepsis that cannot be cured by antibiotics alone was investigated. SDZ MRL 953, a novel monosaccharidic lipid A analog as a prototype immunostimulant, and cefotaxime or gentamicin were administered to normal or myelosuppressed mice in a state of advanced sepsis caused by Escherichia coli or Staphylococcus aureus. In this novel model, antibiotic therapy was initiated when the infected mice appeared moribund. At this stage, neither pretreatment with the immunostimulant nor therapy with high doses of cefotaxime or gentamicin was effective in protecting the animals from fatal sepsis. However, pretreatment with a single dose of SDZ MRL 953 1 day prior to microbial inoculation dramatically improved the curative effects of the antibiotics. Hence, long-term survival was significantly enhanced with increasing doses of the immunostimulant in the combined therapy. Peritoneal macrophages from SDZ MRL 953-pretreated animals were primed for enhanced production of microbicidal reactive oxygen metabolites in vitro. In conclusion, the results of the present study indicate that SDZ MRL 953 is a potential candidate for use in a clinical setting as an adjunct to antimicrobial therapy for infections that cannot be treated successfully with appropriate antibiotics alone.

[Clinical morphology of bond zone in bonding agent composite systems]

Three composites--Colténe DRS, P-10, Silux--and their bonding agents (enamel bond systems, Scotchbond) have been investigated. To this purpose the usual examination of "margin close" according to Lutz in 1977 was modified in "morphology of bond zone" (bm). After one year the phosphonated bonding agents has shown better results dependent on composites than enamel bond systems. A year later the "bons zoné's morphology" of various composites did not differ from another because P-10 underlied a heavy occlusal wear. In spite of that the phosphonated bond to enamel has proven better results than to dentin. Replication technique was applied in some chosen cases with clinical acceptable bond zones.

Differing complement-mediated opsonic activity of rabbit interstitial fluids from autologous serum

Lack of appropriate methods for withdrawing extravascular or interstitial fluid from an animal host has limited in vitro study on the role of complement in the local defence of the extravascular space. In the present study, we obtained fluids from membrane diffusion chambers (porosity 0.22 micron) implanted into the kidneys, peritoneal cavity and soft tissues in rabbits. The complement-mediated opsonic activity (CMOA) of these fluids for Staphylococcus aureus ATCC 502A and Escherichia coli 01 was then compared to that of autologous sera. Soft tissue and renal interstitial fluids were as opsonic for E. coli as autologous sera but were however, poor opsonins for S. aureus. The peritoneal fluid was marginally effective in opsonization of both bacterial strains. While chelation of the fluids with MgEGTA (to block the classical pathway) did not diminish CMOA for E. coli, it reduced the CMOA for S. aureus by half. Conversely, heat-inactivation of the fluids and serum eliminated the opsonic activity for E. coli but only decreased the opsonic activity for S. aureus by half. Following a 24 h in vivo growth of E. coli in the implanted chambers, the CMOA was drastically reduced. Concomitant to the reduction in functional complement in the fluids, E. coli recovered from the chambers were found coated, though not maximally, with C3b as evidenced by studies with fluorescent antibody. The differences in opsonic content of extravascular fluids observed here might explain why certain sites of the body may be more vulnerable to attack by some bacterial species which are not effectively opsonized and therefore phagocytized.

Effect of a diazaborine derivative (Sa 84.474) on the virulence of Escherichia coli

The scope of selective inhibition of lipopolysaccharide (LPS) biosynthesis in virulent organisms with a diazaborine derivative (Sa 84.474) as a means to render them avirulent was explored. A serum resistant Escherichia coli 0111:B4 became serum sensitive following its cultivation in vitro in media containing 1.5 mg/l of Sa 84.474, a concentration shown previously to inhibit over 95% of normal LPS biosynthesis in its mutant J5 strain. An encapsulated E. coli 01:K1 was also converted to serum sensitivity. In addition, Sa 84.474-pretreatment increased the efficiency with which the previously resistant organisms were opsonized in normal human serum and subsequently phagocytosed by granulocytes. In vivo, intravenously inoculated, Sa 84.474-pretreated bacteria were rapidly removed from the blood circulation and were significantly (P less than 0.05) less virulent in inducing lethal peritoneal infections in mice (LD50 4.9 +/- 1 X 10(6) cfu) when compared to untreated control bacteria (LD50 2.2 +/- 0.97 X 10(6) cfu). The results suggest that the LPS plays an important role in the virulence of the two bacterial strains and imply that agents acting in a similar manner but with acceptable selective toxicity might be novel drugs for therapy of Gram-negative bacterial infections.

Membrane-disorganizing property of polymyxin B nonapeptide

The possibility of improving the antibacterial activities of drugs normally excluded by Gram-negative bacteria with polymyxin B nonapeptide (PMBN) has been explored. In vitro, PMBN rendered clindamycin, erythromycin, novobiocin, rifampicin and vancomycin very active against a number of Gram-negative enteric bacteria. The drug also sensitized the previously resistant bacterial strains to human, mouse or guinea pig serum. However, parenterally administered PMBN failed to influence bacterial growth in chambers implanted into mice and guinea pigs. It was also ineffective in experimental septicaemia at a dose of up to 200 mg/kg or when combined with antibiotics with which it interacted synergistically in vitro.

Influence of endotoxin on the distribution of cephalosporins in rabbits

The concentration: time courses of six different cephalosporins were studied in serum and interstitial fluid from issue cages after intravenous injection in normal and endotoxaemic rabbits. Circulatory and metabolic changes induced by endotoxin were similar to the altered organ function observed in patients with septicaemia. A significant shift of drug fractions, increase in the volume of distribution and prolonged mean residence times were observed in this model with ceftazidime, ceftriaxone and CPW 86-363, and were the result of specific changes in the peripheral compartment. The opposite findings were observed with cefotaxime, while latamoxef and cefoperazone resulted in no changes.

Opsonic activity of the alternative complement pathway in infected human intra-abdominal fluid

The complement-mediated opsonic activity (CMOA) in intra-abdominal exudates collected during laparotomy from peritonitis patients was examined by an in vitro phagocytic bactericidal assay. It was found that infected intra-abdominal exudates barely promoted detectable killing of Escherichia coli 01 by polymorphonuclear leukocytes. Only the minority of bacteria recovered by differential centrifugation from the infected exudates had C3 on their surfaces. Such bacteria were not optimally opsonized in vivo, whereas they became fully coated with C3 during a brief incubation in vitro in normal human serum. The low level of CMOA in the peritoneal fluid paralleled a depletion of complement in the peripheral blood. Thus, in cases complicated by sepsis with gram-negative bacteria, the CMOA in the blood was extremely low. These data suggest that the high susceptibility of the peritoneum to infection by gut flora, despite the normal phagocytic response, may be partly explained by the low local level of functional complement which is inadequate for optimal opsonization of the bacteria.

Therapeutic relevance of penicillin-induced hypersensitivity of Staphylococcus aureus to killing by polymorphonuclear leukocytes

There is an overwhelming body of evidence that certain Staphylococcus aureus strains become more sensitive to killing by polymorphonuclear leukocytes after their growth in media containing subinhibitory concentrations of penicillin. However, it is not clear to what extent this phenomenon contributes to the curative effect of penicillin in vivo. To explore its therapeutic relevance, we evaluated the interaction of staphylococci pretreated with penicillin in vitro with leukocytes in cell-proof diffusion chambers (porosity, 0.22 micron) implanted subcutaneously in rabbits. Under this in vivo environment, staphylococci pretreated with penicillin remained hypersensitive to leukocyte killing as under in vitro conditions. Furthermore, when the staphylococci were mixed with the leukocytes in chambers implanted intraperitoneally in mice which subsequently received intravenously a suboptimal dose of penicillin, they also became hypersensitive to leukocytic killing. However, because the staphylococcal growth rate was considerably reduced in vivo, the degree of penicillin-induced sensitivity to leukocytic killing was smaller than that obtained in test tube cultures; nevertheless, the enhanced killing was significant. Additional support that the curative effect of penicillin partly depends on its synergistic action with the leukocytes was provided by the relative decrease in virulence of staphylococci pretreated with penicillin in mice in which the cellular host defenses were already recruited at the focus of inoculation. These observations indicate that penicillin-induced hypersensitivity of staphylococci to leukocytic killing is not only an in vitro phenomenon, but an effect which has therapeutic relevance.

Differing antimicrobial potency and specificity of peripheral blood and autologous exudative polymorphonuclear leucocytes

Little is known about the antimicrobial potency and specificity of polymorphonuclear leucocytes which actually appear at the sites of bacterial invasion in tissues. In the present work we have compared inflammatory leucocytes induced by intraperitoneal injection of casein in rabbits with autologous peripheral blood cells in killing Escherichia coli serotype 01 and Staphylococcus aureus 502A. The results indicate that inflammatory leucocytes differ significantly from their virgin blood ancestors. While the blood leucocytes were only able to suppress the growth of the gram-negative bacteria, autologous exudative cells killed more than 95% of the test organisms within 1 h of incubation at 37 degrees C. The enhanced microbicidal activity of the inflammatory cells however, was only specific for the gram-negative bacteria, as evidenced by the failure of leucocytes to kill Staph. aureus to the same extent as the peripheral blood cells. In association with the enhanced gram-negative microbicidal activity the inflammatory cells produced chemiluminescence and released two to three times more O2-anions than the peripheral cells. We interpret these observations to mean that chemotactic factors such as casein activate inflammatory cells to increase their oxidative metabolism. Since microbicidal action of leucocytes is thought to proceed in part through oxygen-dependent reactions, the inflammatory leucocytes would be expected to effectively kill bacteria that are highly susceptible to these lethal oxygen metabolites. It cannot therefore be assumed that assessment of the functional capacity of the virgin peripheral blood PMNs would provide information on the functional characteristics of activated leucocytes which actually migrate to and accumulate at inflammatory sites.

Composition of fluids from diffusion chambers implanted in the soft tissue and kidneys of rabbits

The fluids from diffusion chambers implanted in soft tissue and kidneys of rabbits were analysed for total protein, albumin, enzymes, ions, glucose, creatinine, urea, uric acid, bilirubin and cholesterol. These date were compared with the corresponding values in plasma. Our data for chamber fluid are in good agreement with data reported for interstitial fluids. The composition of the kidney chamber fluid is nearly constant from three to ten weeks after implantation. The low urea, uric acid and creatinine concentrations indicate that the chamber is not located in the urine collecting area of the kidney. Three days after subcutaneous implantation of chambers, the fluid contains less protein than plasma but has an equal concentration of ions, thus meeting the principal requirements for interstitial fluid. There are indications that the healing process lasts up to ten days after the surgical implantation. In order to examine the permeability of the diffusion chambers, the equilibration half-life times of antibiotics and substances of high and low molecular weights were determined in vitro.

Measurements of antimicrobial drug concentrations in renal interstitial fluid using the diffusion chamber technique

A technique is described to obtain renal interstitial fluid (RIF) from rabbits after implantation of diffusion chambers with permeable membranes of 0.45 mu porosity in both kidneys. Pharmacokinetic studies were conducted two to three weeks after implantation. No difference in gentamicin concentrations, as measured microbiologically, was seen between RIF withdrawn from the left and right kidney chambers at the same points in time. Simultaneous drug concentrations were determined in RIF and serum of rabbits after oral administration of ampicillin or nalidixic acid and after intramuscular injection of gentamicin. Ampicillin concentrations in RIF peaked at two hours with about one fourth of the peak concentration measured in serum at one hour. These curves crossed at 3.45 hours. In RIF, the maximum concentration of gentamicin found at two hours was again approximately one fourth of the serum peak level determined at half an hour. The gentamicin curves crossed at 3.15 hours. No levels of nalidixic acid could be detected microbiologically in serum and RIF. In collected urine, however, concentrations of this drug could be measured for several sampling periods. Our results show that this diffusion chamber technique can be useful in the pharmacokinetic examination of drugs, also with respect to their distribution in the kidneys.

Concentrations of various antibiotics in serum and fluids accumulated in diffusion chambers implanted in various sites in rabbits

Diffusion chambers with Millipore membranes were implanted in soft tissue, kidneys, and peritoneal and pleural cavities of rabbits. Single doses of azlocillin, cefazolin, and gentamicin were injected intramuscularly and ampicillin was administered orally 2--5 weeks after implantation. The concentrations of the respective drugs in simultaneously collected samples of fluid from each diffusion chamber were measured and compared with concentrations found at the same time in serum. All chambers were tolerated well, and the method proved to be effective for collecting data on the distribution of drugs throughout the body.

A diffusion chamber technique for measuring concentrations of antibiotics in interstitial fluid

A method for collecting soft tissue interstitial fluid in experimental animals for the measurement of antibiotic concentrations is described. Diffusion chambers with permeable membranes of 0.45 micron porosity were implanted subcutaneously for four days in order to determine simultaneous concentrations of ampicillin and clindamycin in serum and chamber fluid after perioral administration in rabbits and of oxytetracycline after intravenous injection in dogs. The results are discussed in view of findings from other investigators using different types of tissue cages.

[Analysis of volatile nitrosamines in food of animal origin]

A method is described for the fluorescence-spectrophotometric densitometric determination of nitrosamines. For this purpose, foods of animal origin are vacuum-distilled, the distilled-over nitrosamines are extracted with methylene chloride from an acid medium and, after cleavage by hydrogen bromide, the corresponding amines are reacted with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole. The purificaton of the extract and the resolution of the corresponding fluorescent amine derivatives are effected simultaneously by two-dimensional thin-layer chromatography. The determination is achieved by in situ fluorescence spectrophotometry against test substances on the same slab. This method seems useful for investigations into the formation of nitrosamines in foods of animal origin because it permits to detect nitrosamine concentrations as low as 0.1 microgram/kg of food.

In vitro activity of tiamulin (81.723 HFU), a new pleuromulin derivative, against clinically significant anaerobes

The susceptibility of more than 40 strains of Gram-negative and Gram-positive anaerobes to tiamulin (Sandoz 81.723 hfu), a new pleuromulin (pleuromutilin) derivative, was determined by broth dilution and agar dilution tests. The influences of density of the inoculum upon MICs was studied by a specially designed pour plate-technique. Bacteroides fragilis, B. vulgatus, B. splanchnicus, B. oralis, B. asaccharolyticus, B. melaninogenicus, Fusobacterium fusiforme (F. nucleatum), Sphaerophorus necrophorus, Clostridium perfringens, C. fallax, Propionibacterium acnes and several species of Peptococcaceae showed broth dilution MICs of 0.03 similar to 1 microgram/ml. Members of B. thetaiotaomicron, B. distasonis and S. freundii (F. mortiferum) were inhibited by 8 similar to 32 microgram/ml and 2 strains of S. varius had a broth dilution MIC of 256 microgram/ml. With most strains, the agar dilution MICs were 2 similar to 4 similar to 8 times the broth dilution MICs. In pour plate-tests, the MICs were not considerably influenced influenced by varying initial concentrations of viable cells. With most anaerobes, the MBCs of tiamulin were more than 100-fold higher than the MICs. The results obtained indicated that, apart from S. varius, B. thetaiotaomicron, B. distasonis and S. freundii (F. mortiferum), members of 16 other anaerobic species including B. fragilis were without exception sensitive to tiamulin.

Blood level studies in chickens, turkey poults and swine with tiamulin, a new antibiotic

Tiamulin concentrations have been determined in the serum of chickens, turkeys and swine after a single oral administration of various doses. The compound peaked between 2 and 4 hours after drug supply. In the highest dose used (50 mg/kg body weight), mean concentrations of 3.5, 2.9, 4.5 microgram/ml for chickens, turkeys and swine, respectively, could be obtained. In poultry, the levels declined between 12 and 24 hours to values not useful for calculation. In swine at 24 hours after administration measurable values could still be detected.

[In vitro and in vivo activity of tiamulin against leptospires (author's transl)]

The minimal growth inhibiting concentration of tiamulin, a derivative of the diterpen antibiotic pleuromutilin, was evaluated in vitro against 11 different serogroups of leptospira interrogans by twofold serial dilution technique, in comparison to tetracyclin, dihydrostreptomycin and tylosin. The range of the MIC values of tiamulin is between 0.07 and 2.5 microgram/ml and thus comparable to the activities of the standard antibiotics tested (see table 1). The chemotherapeutic efficacy (ED50) of the compound was examined in two experimental leptospiral infections of the Syrian hamster, in comparison to tetracyclin. Both compounds were administered orally for 3 days. In the L. canicola infection, the ED50 values were 103.8 mg/kg and 306.3 mg/kg body-weight for tiamulin and tetracyclin, respectively. In the L. grippotyphosa infection, the ED50 values amounted to 35.16 and 277.5 mg/kg bodyweight for tiamulin and tetracyclin, respectively. Based on these values, tiamulin in comparison to tetracyclin showed 3-8 fold higher efficacy in vivo after oral administration.

[Clinical and histopathological findings in mycoplasmal polyarthritis of rats. III. Course of infection during the weeks 7-30 and 54-61 (author's transl)]

Clinical, microbiological and histological findings of the late phase of experimentally induced Mycoplasma-polyarthritis in rats are described. Investigations were carried out between the 7.-30. week and between the 54-61. week p.i. M. arthritidis could be reisolated from affected joints regularly up to the 7th week p.i. Thereafter until 12th week only occasional recovery was possible. The healing process of affected joints dominated signs of arthritis which could be confirmed histologically as a purulent process. The alterations of carpal and tarsal joints were divided into purulent, chronic deforming and chronic minor lesions. The findings derived from investigation of joints and parenchymatous organs during the course of the disease are discussed.

Antimicrobial activities of 81.723 hfu, a new pleuromutilin derivative

The new pleuromutilin derivative 81.723 hfu is extremely active against gram-positive organisms such as streptococci, staphylococci, and against mycoplasmas. A number of Shigella, Klebsiella, and Escherichia coli strains were also found to be quite susceptible to this new agent, whereas other gram-negative organisms like Pseudomonas aeruginosa, Proteus species, and Alcaligenes faecalis proved to be naturally resistant to 81.723 hfu. The new compound acts bacteriostatically. Bactericidal effects have been observed only at concentrations which are 100-fold higher than the minimal inhibitory concentrations. The new antibiotic is well tolerated in all animal species tested so far and has been successfully used in the treatment of experimental infections with gram-positive organisms and with mycoplasmas in mice and rats. Resistance against this new compound arose gradually in all microorganisms investigated. It is noteworthy that the rate at which resistance against 81.723 hfu emerged in mycoplasmas (Mycoplasma gallisepticum and Mycoplasma hyorhinis) was significantly slower than the corresponding rate at which resistance against tylosin tartrate appeared. Mycoplasma strains which became insensitive to 81.723 hfu were also resistant to tylosin tartrate, whereas mycoplasmas which developed resistance against tylosin tartrate, although less sensitive to 81.723 hfu than wild-type strains, were still eliminated by this drug. In a strain of Klebsiella pneumoniae, complete cross-resistance was observed between the pleuromutilin derivative on one hand and lincomycin and erythromycin on the other. Modest degrees of cross-resistance were also observed with chloramphenicol. However, it appears unlikely that the latter phenomenon is sufficiently pronounced to affect treatment with either antibiotic.

In vivo efficacy of 81.723 hfu, a new pleuromutilin derivative against experimentally induced airsacculitis in chicks and turkey poults

The efficacy of the pleuromutilin derivative 81.723 hfu was tested in chicks and turkey poults by experimentally infecting them with Mycoplasma gallisepticum. The data were treated to obtain the mean effective doses, and these were compared to those obtained with tylosin tartrate. The compounds were administered either by ingluvial catheter or via the drinking water. Therapy was started on the day of inoculation or 7 days thereafter, respectively. The experiments showed that the compound 81.723 hfu was significantly more active in chickens than tylosin tartrate by both methods of administration of drinking water. In turkey poults the pleuromutilin derivative and tylosin tartrate had comparable activity.