Long-term LDR exposure may induce cognitive impairments: A possible association through targeting gut microbiota-gut-brain axis.

Environmental and occupational low-dose radiation (LDR) exposure may be harmful for health but the previous reports regarding effect of LDR on cognition are contradictory. Here we investigated the effect of long-term LDR exposure on cognition. In this study, male Balb/c mice' cognitive functions were tested at 15 weeks after being exposed to 0.5 Gy LDR in 10 fractions at each dose of 0.05 Gy. The results demonstrated that long-term LDR exposure increases escape latency and the time spent in finding exits in mice compared with non LDR exposure. Meanwhile, the inflammation-related proteins including NFκB and p38 also increased. Lipopolysaccharide (LPS) increased and short-chain fatty acid (SCFA) levels decreased following long term LDR exposure. Treatment with microbiota-derived LPS and SCFAs reversed these effects in mice. Furthermore, the gut barrier integrity was damaged in a time-dependent manner with the decreased expression of intestinal epithelial-related biomarkers such as ZO-1 and occludin. Mechanistically, long after exposure to LDR, increased LPS levels may cause cognitive impairment through the regulation of Akt/mTOR signaling in the mouse hippocampus. These findings provide new insight into the clinical applications of LDR and suggest that the gut microbiota-plasma LPS and SCFAs-brain axis may underlie long-term LDR-induced cognition effects.

Radio-detoxified LPS alters bone marrow-derived extracellular vesicles and endothelial progenitor cells.

Stem cell-based therapies raise hope for cell replacement and provide opportunity for cardiac regenerative medicine and tumor therapy. Extracellular vesicles are a membrane-enclosed intercellular delivery system with the potential to improve the therapeutic efficacy of the treatment of a variety of disorders. As the incidence of breast cancer continues to rise, radiotherapy has emerged as a leading treatment modality. Radiotherapy also increases the risk of coronary heart disease and cardiac mortality. In a chest-irradiated mouse model of cardiac injury, we investigated the effects of local irradiation. We found an increased lethality after 16 Gy irradiation. Importantly, radio-detoxified LPS (RD-LPS) treatment prolonged the survival significantly. By flow cytometry, we demonstrated that upon administration of RD-LPS, the number of bone marrow-derived endothelial progenitor cells increased in the bone marrow and, in particular, in the circulation. Furthermore, mass spectrometry analysis showed that RD-LPS altered the proteomic composition of bone marrow cell-derived small extracellular vesicles (sEVs). RD-LPS treatment increased interferon-induced transmembrane protein-3 (IFITM3) expression markedly both in bone marrow cells and in bone marrow cell-derived small extracellular vesicles. This is the first study to demonstrate that radio-detoxified LPS treatment induces an increase of circulating endothelial progenitor cells (EPCs) in parallel with a reduced radiotherapy-related mortality. While the total number of bone marrow-derived extracellular vesicles was significantly increased 24 h after treatment in the RD-LPS groups, the number of endothelial progenitor cells was reduced in animals injected with GW4896 (a chemical inhibitor of exosome biogenesis) as compared with controls. In contrast to these in vivo results, in vitro experiments did not support the effect of sEVs on EPCs. Our data raise the intriguing possibility that IFITM3 may serve as a marker of the radio-detoxified LPS treatment.

Surface property alterations and osteoblast attachment to contaminated titanium surfaces after different surface treatments: An in vitro study.

BACKGROUND: Studies have reported a high prevalence of peri-implantitis. The etiology of peri-implantitis remains unclear and no available treatments result in total resolution of established peri-implantitis. PURPOSE: To investigate the factors that interfere with osteoblast adhesion to contaminated titanium surfaces after different surface treatments. MATERIALS AND METHODS: Grade 4 titanium discs were randomly divided into 5 groups and each group was divided into 2 subgroups, with one contaminated with Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), and the other contaminated with Porphyromonas gingivalis (P. gingivalis). Group 1 did not receive bacterial inoculation or surface debridement and served as a control. Group 2 received A. actinomycetemcomitans or P. gingivalis inoculation, separately. Group 3 received bacterial inoculation and titanium curette debridement, followed by normal saline irrigation. Group 4 received bacterial inoculation, curette debridement, normal saline irrigation, and ultrasonication. Group 5 received bacterial inoculation, curette debridement, normal saline irrigation, and placement in 0.12% chlorhexidine. After various surface treatments, the surface roughness and hydrophilicity of the titanium surface were measured, the number of adhered osteoblast cells was calculated, and the amount of residual lipopolysaccharide (LPS) was quantified. RESULTS: A. actinomycetemcomitans and P. gingivalis biofilms noticeably reduced surface hydrophilicity. Groups 3-5 showed decreased hydrophilicity and fewer adhered osteoblast cells compared with the control group. Although ultrasonication was more effective in removing LPS than curette debridement and chlorhexidine, cell adhesion was not as high as with clean titanium discs. CONCLUSIONS: The non-surgical treatment used in this study was not effective in removing LPS from titanium surfaces and increasing osteoblast adhesion. A more effective method to remove LPS completely is required to enhance the treatment outcome of peri-implantitis.

Space-type radiation induces multimodal responses in the mouse gut microbiome and metabolome.

BACKGROUND: Space travel is associated with continuous low dose rate exposure to high linear energy transfer (LET) radiation. Pathophysiological manifestations after low dose radiation exposure are strongly influenced by non-cytocidal radiation effects, including changes in the microbiome and host gene expression. Although the importance of the gut microbiome in the maintenance of human health is well established, little is known about the role of radiation in altering the microbiome during deep-space travel. RESULTS: Using a mouse model for exposure to high LET radiation, we observed substantial changes in the composition and functional potential of the gut microbiome. These were accompanied by changes in the abundance of multiple metabolites, which were related to the enzymatic activity of the predicted metagenome by means of metabolic network modeling. There was a complex dynamic in microbial and metabolic composition at different radiation doses, suggestive of transient, dose-dependent interactions between microbial ecology and signals from the host's cellular damage repair processes. The observed radiation-induced changes in microbiota diversity and composition were analyzed at the functional level. A constitutive change in activity was found for several pathways dominated by microbiome-specific enzymatic reactions like carbohydrate digestion and absorption and lipopolysaccharide biosynthesis, while the activity in other radiation-responsive pathways like phosphatidylinositol signaling could be linked to dose-dependent changes in the abundance of specific taxa. CONCLUSIONS: The implication of microbiome-mediated pathophysiology after low dose ionizing radiation may be an unappreciated biologic hazard of space travel and deserves experimental validation. This study provides a conceptual and analytical basis of further investigations to increase our understanding of the chronic effects of space radiation on human health, and points to potential new targets for intervention in adverse radiation effects.

Enterobacterial common antigen and O-specific polysaccharide coexist in the lipopolysaccharide of Yersinia enterocolitica serotype O:3.

Yersinia enterocolitica serotype O : 3 produces two types of lipopolysaccharide (LPS) molecules to its surface. In both types the lipid A (LA) structure is substituted by inner core (IC) octasaccharide to which either outer core (OC) hexasaccharide or homopolymeric O-polysaccharide (OPS) is linked. In addition, enterobacterial common antigen (ECA) can be covalently linked to LPS, however, via an unknown linkage. To elucidate the relationship between ECA and LPS in Y. enterocolitica O : 3 and the effect of temperature on their expression, LPS was isolated from bacteria grown at 22 °C and 37 °C by consequent hot phenol/water and phenol-chloroform-light petroleum extractions to obtain LPS preparations free of ECA linked to glycerophospholipid. In immunoblotting, monoclonal antibodies TomA6 and 898, specific for OPS and ECA, respectively, reacted both with ladder-like bands and with a slower-migrating smear suggesting that the ECA and OPS epitopes coexist on the same molecules. These results were supported by immunoblotting with a monovalent Y. enterocolitica O : 3 ECA-specific rabbit antiserum. Also, two or three 898-positive (and monovalent-positive) TomA6-negative bands migrated at the level of the LA-IC band in LPS samples from certain OC mutants, most likely representing LA-IC molecules carrying 1-3 ECA repeat units but no OPS. These bands were also present in Y. enterocolitica O : 9 OC mutants; however, coexistence of ECA and OPS in the same molecules could not be detected. Finally, the LA-IC-ECA bands were missing from LPS of bacteria grown at 37 °C and also the general reduction in wild-type bacteria of ECA-specific monovalent-reactive material at 37 °C suggested that temperature regulates the expression of ECA. Indeed, RNA-sequencing analysis showed significant downregulation of the ECA biosynthetic gene cluster at 37 °C.

Comparative in vitro study among the effects of different laser and LED irradiation protocols and conventional chlorhexidine treatment for deactivation of bacterial lipopolysaccharide adherent to titanium surface.

OBJECTIVE AND BACKGROUND: The present in vitro study was designed to evaluate and compare the efficacy of: 1) different dental laser devices used in photoablative (PA) mode, namely commercial CO(2), Er:YAG, and Nd:YAG lasers and a prototype diode laser (wavelength = 810 nm); 2) prototype low-energy laser diode or light-emitting diode (LED) (wavelength = 630 nm), used in photodynamic (PD) mode together with the photoactivated agent methylene blue; and 3) chlorhexidine, used as reference drug, to reduce the activation of macrophages by lipopolysaccharide (LPS), a major pro-inflammatory gram-negative bacterial endotoxin, adherent to titanium surface. METHODS: RAW 264-7 macrophages were cultured on titanium discs, cut from commercial dental implants and precoated with Porphyromonas gingivalis LPS. Before cell seeding, the discs were treated or not with the noted lasers and LED in PA and PD modes, or with chlorhexidine. The release of nitric oxide (NO), assumed to be a marker of macrophage inflammatory activation, in the conditioned medium was related to cell viability, evaluated by the MTS assay and ultrastructural analysis. RESULTS: PA laser irradiation of the LPS-coated discs with Er:YAG, Nd:YAG, CO(2,) and diode (810 nm) significantly reduced NO production, with a maximal inhibition achieved by Nd:YAG and diode (810 nm). Similar effects were also obtained by PD treatment with diode laser and LED (630 nm) and methylene blue. Notably, both treatments were superior to chlorhexidine in terms of efficiency/toxicity ratio. CONCLUSIONS: These findings suggest that laser and LED irradiation are capable of effectively reducing the inflammatory response to LPS adherent to titanium surface, a notion that may have clinical relevance.

In vitro evaluation of the effects of low-intensity Nd:YAG laser irradiation on the inflammatory reaction elicited by bacterial lipopolysaccharide adherent to titanium dental implants.

BACKGROUND: The bacterial endotoxin lipopolysaccharide (LPS) represents a prime pathogenic factor of peri-implantitis because of its ability to adhere tenaciously to dental titanium implants. Despite this, the current therapeutic approach to this disease remains based mainly on bacterial decontamination, paying little attention to the neutralization of bioactive bacterial products. The purpose of the present study was to evaluate whether irradiation with low-energy neodymium-doped:yttrium, aluminum, and garnet (Nd:YAG) laser, in addition to the effects on bacterial implant decontamination, was capable of attenuating the LPS-induced inflammatory response. METHODS: RAW 264.7 macrophages or human umbilical vein endothelial cells were cultured on titanium disks coated with Porphyromonas gingivalis LPS, subjected or not to irradiation with the Nd:YAG laser, and examined for the production of inflammatory cytokines and the expression of morphologic and molecular markers of cell activation. RESULTS: Laser irradiation of LPS-coated titanium disks significantly reduced LPS-induced nitric oxide production and cell activation by the macrophages and strongly attenuated intercellular adhesion molecule-1 and vascular cell adhesion molecule expression, as well as interleukin-8 production by the endothelial cells. CONCLUSION: By blunting the LPS-induced inflammatory response, Nd:YAG laser irradiation may be viewed as a promising tool for the therapeutic management of peri-implantitis.

Inhibitory effects of a super pulsed carbon dioxide laser at low energy density on periodontopathic bacteria and lipopolysaccharide in vitro.

OBJECTIVE AND BACKGROUND: Previous studies have described the effect of irradiation by a carbon dioxide (CO2) laser at high energy density on oral bacteria, and various side-effects have also been observed. However, no published studies have examined the effect of irradiation by a CO2 laser at low energy density on oral bacteria. The purpose of this study was to investigate the effects of super pulsed CO2 laser irradiation on periodontopathic bacteria and lipopolysaccharide (LPS). METHODS: Bacterial suspensions of two species of periodontopathic bacteria received laser irradiation at energy densities of 0-12.5 J/cm2. The suspensions were then spread over agar plates and incubated anaerobically. The bactericidal effects were evaluated based on colony formation. Samples of LPS were laser-irradiated at energy densities of 0-12.5 J/cm2. The biological activity was measured, and LPS was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). RESULTS: The irradiation at low energy densities of 7.5 and 12.5 J/cm2 killed more than 99.9 and 99.999% of Porphyromonas gingivalis and more than 99% of Actinobacillus actinomycetemcomitans was sterilized by the irradiation at 7.5 J/cm2. LPS biological activity was significantly decreased by laser irradiation at energy densities of more than 7.5 J/cm2 (p < 0.05), and the components of LPS analyzed by SDS-PAGE was diminished non-specifically. CONCLUSION: The results indicate that CO2 laser irradiation at low power is capable of bactericidal effect on periodontopathic bacteria and decreasing LPS activity.

The interaction of lipopolysaccharides with phenothiazine dyes.

BACKGROUND AND OBJECTIVES: The difference in the photobactericidal efficacy of methylene blue and toluidine blue against gram-negative bacteria may result from their primary reaction with lipopolysaccharides (LPS) of the outer bacterial membrane. The aim of the present study was to compare the reactivity of these dyes with LPS extracted from different gram-negative bacteria. STUDY DESIGN/MATERIALS AND METHODS: The interactions of methylene blue and toluidine blue with LPS from Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Klebsiella pneumoniae (K. pneumoniae), and Serratia marcescens (S. marcescens) were studied spectrophotometrically in 0.45% saline. The dyes were used at the concentration of 10 microM. The concentrations of LPS ranged from 5-100 microg/ml. RESULTS: Methylene blue and toluidine blue enter into a metachromatic reaction with the LPS resulting the in generation of dimers of methylene blue and higher aggregates of toluidine blue. The more significant hypochromic and hypsochromic effects in the reaction of the latter with LPS indicate a greater metachromatic efficacy of toluidine blue than methylene blue. The equilibrium constants of the metachromatic complex between toluidine blue and different LPS were calculated. The spectrophotometric titration of LPS with the dyes was used to estimate the equivalent weight of LPS. CONCLUSIONS: Toluidine blue interacts with LPS more significantly than methylene blue in vitro. This may be one of the main factors determining its greater photobactericidal efficacy against gram-negative bacteria.

Radiodetoxified lipopolysaccharide fails to activate the hypophyseal- pituitary-adrenal axis in the rat.

Lipopolysaccharide (LPS) is known to raise the concentration of the circulating stress hormones such as ACTH, corticosterone and beta-endorphin. This effect of endotoxin is mediated by different immune system-released hormone-like factors (e.g. interleukins, tumor necrosis factor etc.). Gamma-ray irradiation of LPS alters its biological properties and results in a radiodetoxified LPS preparation with numerous beneficial effects and decreased toxicity. In this study we compared the neuroendocrine effects of a commercial LPS and our native and radiodetoxified LPS preparations in rats. Plasma ACTH, corticosterone and beta-endorphin levels were measured by specific radioimmunoassays 120 min after intraperitoneal LPS administration. Control animals were injected with saline. Results show a dramatic increase in all hormones after administration of commercial and our native LPS preparation. Hormone levels in saline-injected controls and radiodetoxified LPS-treated rats did not rise significantly. These results suggest that radio-detoxification disintegrated that part of the LPS molecule complex which is responsible for toxicity including an enhanced production of cytokines, which trigger the hypothalamo-pituitary-adrenal axis.

The effect of photodynamic action on two virulence factors of gram-negative bacteria.

Photodynamic therapy could provide an alternative to antibiotics for the treatment of local infections since a wide range of microorganisms have been shown to be susceptible to killing by photodynamic action (PDA) in vitro. The purpose of this study was to determine whether PDA was also able to affect the potency of two key bacterial virulence factors--lipopolysaccharide (LPS) and proteases. Suspensions of LPS from Escherichia coli and culture supernatants containing proteases of Pseudomonas aeruginosa were exposed to red light in the presence of toluidine blue O (TBO). The activity of each virulence factor was determined before and after irradiation. The limulus amoebocyte lysate (LAL) assay and the induction of proinflammatory cytokine (interleukin-8 and -6) release from human peripheral blood mononuclear cells (PBMC) were used for assessing the biological activity of LPS. Protease activity was quantified by azocasein hydrolysis. The biological activities of the LPS (both the LAL activity and its ability to induce cytokine release from PBMC) and the proteases were reduced significantly by irradiation with red light in the presence of TBO in a dose-dependent manner with respect to both the light energy dose and the TBO concentration. The ability of TBO-mediated PDA to reduce the activities of key virulence factors may be an additional benefit of using light-activated antimicrobial agents in the treatment of infectious diseases.

Immunomodulation of macrophages by radio-detoxified lipopolysaccharide of Salmonella typhimurium.

Lipopolysaccharide (LPS) and ratio-detoxified LPS (Rd-LPS) from Salmonella typhimurium were analysed for their ability to stimulate murine peritoneal exudate cells (PEC) and macrophages. Rd-LPS induced much more inflammatory response as compared to LPS. PEC numbers/mouse obtained were significantly higher (3-fold) in response to Rd-LPS than LPS. The haemorrhage was induced in mice by LPS but not by Rd-LPS. Activation of macrophages in vivo by Rd-LPS was significantly higher as compared to LPS. This was evident from the increase levels of their lysosomal enzymes and cytokines. Rd-LPS induced 10-fold increase in acid phosphatase contents of macrophages as compared to controls while only 7-fold increase was obtained with LPS. Arylsulfatase and beta-glucuronidase increased by about 2-fold by Rd-LPS and LPS. Macrophages incubated with Rd-LPS in vitro showed 16-fold and 20-fold increase in the cell associated levels of arylsulfatase and beta-glucuronidase respectively as compared to unstimulated cells. On the other hand, only 6-fold increase was observed in response to LPS in the levels of both the enzymes. TNF-[symbol: see text] and IL-1 secreted by macrophages increased considerably in response to Rd-LPS as compared to those released by LPS. Rd-LPS, thus seems to be a better immunomodulator than untreated LPS.

Effect of gamma irradiation on chemical and biological properties of lipopolysaccharide from Salmonella typhimurium.

Lipopolysaccharide (LPS) from S. typhimurium on exposure to gamma-radiation resulted in decrease in toxicity and was less mitogenic, Silver stained profiles of irradiated LPS on polyacrylamide gels revealed complete loss of its heteropolysaccharides which was confirmed further by analysing lipid A and LPS from Salmonella minnesota Re mutants on SDS-PAGE. Glucosamine and 2-keto 3-deoxy-octonate(Kdo) contents were significantly decreased on treatment. Lipid A obtained by removal of heteropolysaccharides from LPS was less toxic on exposure to gamma radiations.

Effects of irradiation of an erbium:YAG laser on root surfaces.

The application of erbium:YAG laser (Er:YAG) irradiation has been investigated for periodontal therapy. The purpose of this study was to evaluate the effects of Er:YAG laser irradiation on root surfaces using a scanning electron microscope (SEM) and to determine the laser's ability to remove lipopolysaccharides (LPS). Infrared spectrophotometry was used to investigate the effects of the laser on LPS applied to root dentin pellets. Premolars extracted for orthodontic reasons were prepared for this study. The crowns were resected below the cemento-enamel junction, longitudinally sectioned, and the contents of the pulp chamber were removed. Then 15 root tips (5 x 5 x 1 mm) were classified into 3 groups of 5 each as follows: group 1, tips without any treatment; group 2, planed tips with the cement layers left untouched; and group 3, planed until the dentin surface was disclosed. The center of each specimen was used as the experimental irradiated area and the peripheral area served as a control. The quantity of vapor delivered by Er:YAG laser was highly increased, and the irradiated areas displayed little morphogenetic changes. The lyophilized sample LPS 0111 B4 from E. coli was then mixed with potassium bromide and pressed into a tablet, which was examined at 4,000-650 Kayser. The lyophilized LPS had a peak at 2.94 microns. LPS on the root dentin pellets was cleared away as much as possible by 150 washings in pyrogen-free water using an ultrasonic cleaner. Five microliters of 24 EU LPS solution was dropped on the root dentin pellets, which were then irradiated by the Er:YAG laser, and washed using the ultrasonic cleaner in pyrogen-free water. The amount of the extracted LPS solution was determined by spectrophotometer at 405 nm. The Er:YAG laser could remove 83.1% of the LPS. This study suggests that Er:YAG laser irradiation might be useful for root conditioning in periodontal therapy. However, clinical testing is necessary to establish what, if any, utility the Er:YAG laser has as a part of periodontal therapy.

Radiodetoxified endotoxin-induced tolerance. Effect on endotoxin lethality and macrophage arachidonic acid metabolism.

Endotoxin (LPS) tolerance produces changes in macrophage mediator production which is thought to be responsible for the acquired LPS resistance. Detoxification of LPS by gamma irradiation has been reported to diminish certain noxious properties while retaining its tolerance inducing actions. We compared the efficacy of LPS and radiodetoxified (RD)-LPS from Escherichia coli O101 on stimulating rat peritoneal macrophage arachidonic acid (AA) metabolism, measured by thromboxane (TXB2). Changes in macrophage production of these mediators were also assessed after tolerance induction. LPS tolerance was induced by i.p. injection of LPS, RD-LPS or vehicle on day 1 (100 micrograms/kg, i.p.) and day 2 (500 micrograms/kg, i.p.). On day 5 or 4 weeks after pretreatment, peritoneal macrophages were harvested for in vitro studies, or rats were tested for lethality resistance. Macrophages were incubated +/- LPS (0.1 ng to 50 micrograms/ml), lipid A (1 or 10 micrograms/ml) or Ca+2 ionophore A23187 (10 microM) for determination of TXB2 production. Minimum effective concentrations of LPS and RD-LPS for stimulation (P < 0.05) of TXB2 were 100 ng/ml and 1 microgram/ml, respectively. Maximal stimulation of TXB2 occurred at 10 micrograms/ml of LPS or RD-LPS. Macrophages from LPS or RD-LPS tolerized rats were refractory to stimulated TXB2 with LPS or RD-LPS (0.1 ng to 50 micrograms/ml). The suppressed in vitro macrophage TXB2 production was apparent 4 weeks after rats were tolerized with LPS or RD-LPS. In subsequent mortality studies, LPS challenge of control or tolerance rats at day 5 in vivo with Salmonella enteritidis LPS (15 mg/kg, i.v.) produced a 90% mortality in control rats (N = 22), versus 13% mortality in the LPS pretreated group (N = 23) and a 20% in the RD-LPS pretreated group (N = 10) (P < 0.05 vs control). However, this lethality resistance was not apparent at 4 weeks after LPS or RD-LPS pretreatment. Both LPS and RD-LPS appear to be equipotent in inducing macrophage alterations, and in lethality resistance during LPS tolerance induction. However, these observations suggest that during LPS tolerance suppression of LPS-stimulated AA in peritoneal macrophage metabolism persists longer than acquired lethality resistance.

Radiodetoxified endotoxin-induced tolerance alters monocyte but not neutrophil CD11b and CD18 expression in response to lipopolysaccharide.

OBJECTIVES: To test the hypothesis that pretreatment with radiodetoxified endotoxin (RDE) may mitigate the deleterious effects of subsequent infection, in part by modifying leukocyte adhesion receptor expression, and to investigate the cellular mechanisms of endotoxin tolerance induced by RDE. DESIGN: To assess the effect of RDE pretreatment on mortality from bacterial peritonitis, rats were implanted with an intraperitoneal, barium-fecal inoculum at intervals of 0, 1, 3, and 5 days after RDE injection. Experiments were then conducted to test the effect on leukocyte adhesion receptor expression. Two groups of mice received saline solution, and one group, RDE. After 72 hours, one group received saline solution (saline/saline group), the others, lipopolysaccharide (LPS) (saline/LPS and RDE/LPS groups). Peripheral leukocytes were obtained 1 hour after injection and were analyzed for CD11b and CD18 expression by flow cytometry. SETTING: Laboratory animal study. RESULTS: Survival rates were not improved in rats that were pretreated with RDE 0 and 24 hours before inoculum (0% and 7%, respectively). In rats that were pretreated 72 hours and 120 hours before inoculum, 47% (P < .01) and 60% (P < .01) survived, respectively. CD18 expression on polymorphonuclear leukocytes increased twofold in the RDE/LPS (mean +/- SEM, 300.3 +/- 32.9) and the saline/LPS (mean +/- SEM, 360.4 +/- 59.9) groups compared with controls (mean +/- SEM, 176.4 +/- 18.9) (P < .05). CD11b expression on polymorphonuclear leukocytes increased threefold in the RDE/LPS (mean +/- SEM, 91.3 +/- 8.1) and the saline/LPS (mean +/- SEM, 89.8 +/- 11.4) groups compared with controls (mean +/- SEM, 32.1 +/- 1.8) (P < .05). CD18 expression on monocytes decreased in the saline/LPS group (mean +/- SEM, 134.2 +/- 14.2) and was unchanged in the RDE/LPS group (mean +/- SEM, 200.2 +/- 17.2) compared with controls (mean +/- SEM, 217.6 +/- 16.5) (P < .05). CD11b expression on monocytes decreased in the saline/LPS group (mean +/- SEM, 25.8 +/- 2.2) and was unchanged in the RDE/LPS group (mean +/- SEM, 36.4 +/- 0.9) compared with controls (mean +/- SEM, 39.7 +/- 3.9) (P < .05). CONCLUSIONS: Radiodetoxified endotoxin reduces mortality rates from bacterial peritonitis when given at least 72 hours prior to a bacterial inoculum. Tolerance to subsequent LPS challenge is associated with an abrogation of the reduced peripheral monocyte CD11b and CD18 expression observed in native LPS-stimulated mice but is not associated with changes in polymorphonuclear leukocyte CD11b and CD18 expression. The mechanism of the observed RDE-induced monocyte hyporesponsiveness to LPS and its possible protective effect is uncertain and requires further investigation.

Modifying effects of the parent and radio-detoxified endotoxins on cell-mediated cytotoxicity and cytokine release.

The cytotoxic effects of the parent and radio-detoxified lipopolysaccharides (LPS and RD-LPS, respectively) were studied at various concentrations (0-50 micrograms/ml) upon cultured human lung carcinoma target cells. There was no significant difference between the effects of the two endotoxins. LPS and RD-LPS at the same concentrations, however, modified the cytolytic activity of human leukocytes (effector cells) and their mediators in different extent. The most remarkable difference was found at 10 micrograms/ml. A much higher cytotoxic activity of effector cells was observed in the case of RD-LPS as compared to the parent LPS. This concentration used for the treatment of X-irradiated and unexposed effector cells at 24 h incubation resulted in elevated release of some cytokines as measured by ELISA. For increasing the natural defence, RD-LPS as immunomodulator may be of practical value.

Effect of soft x-ray irradiation on immunological functions in mice.

Effect of soft x-ray irradiation on immunological functions in mice was investigated. Soft x-ray irradiation with 100R or more induced a significant reduction in the number of plaque-forming cells (PFC). The reduction in the number of PFC depended on the irradiation doses. Irradiation with 600R or more showed a significant reduction in the delayed reaction of footpad swelling. However, soft x-ray irradiation with doses ranging from 100R to 1000R did not exert significant influence on the K values of carbon clearance test. Irradiation with 100R or more of soft x-ray showed a remarkable reduction of response to concanavalinA (ConA) or lipopolysaccharide (LPS) in spleen cells, and the response to ConA was lower than that to LPS. These results suggest that in the soft x-ray-irradiated mice, antibody-producing ability, delayed type hypersensitivity reaction and mitogenic activity are sensitive to soft x-ray irradiation and furthermore, T cell is more sensitive than B cell, but phagocytic activity of reticulo-endothelial system (RES) is resistant to soft x-ray irradiation.

[Isolation, purification and identification of protective substances from a culture broth of germinating Bacillus cereus spores]. / Vydelenie, ochistka i identifikatsiia protektiruiushchikh veshchestv iz kul'tural'noi zhidkosti prorastaiushchikh spor Bacills cereus.

A fraction increasing the resistance of resting spores to UV-irradiation and high temperature has been isolated from the culture medium at the stage of B. cereus st. 96 spore initiation. Amino acid analysis, gas chromatography, electrophoresis, and TLC of the products of acidic and alkaline hydrolysis of the isolated fraction demonstrated that the active component of the fraction was the lipoteichoic acid.