A new selective medium for Bifidobacterium spp.
(17/863)
A new selective antibiotic-free medium for Bifidobacterium spp. is defined. This medium has lactulose as the main carbon source and includes methylene blue, propionic acid, and lithium chloride as inhibitors of some related bacterial species. The low pH of the medium contributes to the inhibition of the growth of Enterobacteriaceae. This new selective medium has a simple composition, and the level of recovery it yields is similar to those yielded by nonselective media for Bifidobacterium strains. It could thus be used for routine analysis in environmental or food microbiology. (+info)
Human placental indoleamine 2,3-dioxygenase: cellular localization and characterization of an enzyme preventing fetal rejection.
(18/863)
In order to test the hypothesis (Munn, Zhou, Attwood, Bondarev, Conway, Marshall, Brown, Mellor, Science 281 (1998) 1191-1193) that localized placental tryptophan catabolism prevents immune rejection of the mammalian fetus, the cellular localization and characteristics of human placental indoleamine 2,3-dioxygenase (EC 1.13.11.42) were studied. The localization of indoleamine 2, 3-dioxygenase activity was determined quantitatively using cell fractionation by differential and discontinuous sucrose gradient centrifugation. Enzyme activity was looked for in isolated brush border microvillous plasma membranes of placental syncytiotrophoblast. We found that this membrane preparation (which showed a 32.4-fold purification from the starting homogenate with reference to the activity of a membrane marker enzyme, alkaline phosphatase (EC 3.1.3.1)) was strongly negatively enriched with indoleamine 2,3-dioxygenase (which showed a one twenty-fifth decrease in its specific activity). Placental indoleamine 2, 3-dioxygenase is thus not expressed in the maternal facing brush border membrane of syncytiotrophoblast. 1-Methyl-DL-tryptophan which was used by Munn et al. as a key experimental tool for inhibiting indoleamine 2,3-dioxygenase in the murine model showed a competitive inhibition of human placental indoleamine 2,3-dioxygenase with L-tryptophan. The hypothesis, based on experiments performed in mouse, may therefore be applicable to avoidance of immune rejection of the fetus in human pregnancy. (+info)
Blockade of the action of nitric oxide in human septic shock increases systemic vascular resistance and has detrimental effects on pulmonary function after a short infusion of methylene blue.
(19/863)
To investigate the role of nitric oxide in human sepsis, ten patients with severe septic shock requiring vasoactive drug therapy and mechanical ventilation were enrolled in a prospective, open, non-randomized clinical trial to study the acute effects of methylene blue, an inhibitor of guanylate cyclase. Hemodynamic and metabolic variables were measured before and 20, 40, 60, and 120 min after the start of a 1-h intravenous infusion of 4 mg/kg of methylene blue. Methylene blue administration caused a progressive increase in mean arterial pressure (60 [55-70] to 70 [65-100] mmHg, median [25-75th percentiles]; P<0.05), systemic vascular resistance index (649 [479-1084] to 1066 [585-1356] dyne s-1 cm-5 m-2; P<0.05) and the left ventricular stroke work index (35 [27-47] to 38 [32-56] g m-1 m-2; P<0.05) from baseline to 60 min. The pulmonary vascular resistance index increased from 150 [83-207] to 186 [121-367] dyne s-1 cm-5 m-2 after 20 min (P<0.05). Mixed venous saturation decreased from 65 [56-76] to 63 [55-69]% (P<0.05) after 60 min. The PaO2/FiO2 ratio decreased from 168 [131-215] to 132 [109-156] mmHg (P<0.05) after 40 min. Arterial lactate concentration decreased from 5.1 +/- 2.9 to 4.5 +/- 2.1 mmol/l, mean +/- SD (P<0.05) after 60 min. Heart rate, cardiac filling pressures, cardiac output, oxygen delivery and consumption did not change. Methylene blue administration was safe and no adverse effect was observed. In severe human septic shock, a short infusion of methylene blue increases systemic vascular resistance and may improve myocardial function. Although there was a reduction in blood lactate concentration, this was not explained by an improvement in tissue oxygenation, since overall oxygen availability did not change. However, there was a significant increase in pulmonary vascular tone and a deterioration in gas exchange. Further studies are needed to demonstrate if nitric oxide blockade with methylene blue can be safe for patients with septic shock and, particularly, if it has an effect on pulmonary function. (+info)
Anxiolytic effect of methylene blue microinjected into the dorsal periaqueductal gray matter.
(20/863)
The dorsal periaqueductal gray (DPAG) has been implicated in the behavioral and autonomic expression of defensive reactions. Several results suggest that, along with GABA, glutamate and serotonin, nitric oxide (NO) may play a role in defense reactions mediated by this region. To further investigate this possibility we microinjected methylene blue (MB; 10, 30 or 100 nmol/0.5 microl) into the DPAG of rats submitted to the elevated plus-maze test, an animal model of anxiety. MB has been used as an inhibitor of soluble guanylate cyclase (sGC) to demonstrate cGMP-mediated processes, and there is evidence that NO may exert its biological effects by binding to the heme part of guanylate cyclase, causing an increase in cGMP levels. The results showed that MB (30 nmol) significantly increased the percent of time spent in the open arms (saline = 11.57 +/- 1.54, MB = 18.5 +/- 2.45, P<0.05) and tended to do the same with the percentage of open arm entries (saline = 25.8 +/- 1.97, MB = 33. 77 +/- 3.07, P<0.10), but did not change the number of enclosed arm entries. The dose-response curve, however, had an inverted U shape. These results indicate that MB, within a limited dose range, has anxiolytic properties when microinjected into the DPAG. (+info)
Photobactericidal activity of methylene blue derivatives against vancomycin-resistant Enterococcus spp.
(21/863)
The toxicities and phototoxicities of methylene blue and its two methylated derivatives were measured against one standard and three vancomycin-resistant pathogenic strains of Enterococcus spp. Each of the compounds was bactericidal and the derivatives exhibited photobactericidal activity on illumination at a 'light' dose of 6.3 J/cm(2) against one or more of the strains. Increased bactericidal and photobactericidal activity in the methylated derivatives is thought to be due to their higher hydrophobicities allowing greater interaction with the bacterial cell wall. In addition, the derivatives exhibited higher inherent photosensitizing efficacies. (+info)
Stress-induced gastric lesion formation is prevented in rats with daunomycin-induced nephrosis.
(22/863)
In the present study, we investigated the susceptibility to restraint plus water-immersion stress (RWIS) in rats with daunomycin-induced nephrosis in comparison to that in normal rats. The severity of RWIS-induced gastric lesions was significantly less in nephrotic rats on the 20th and 40th days after a single i.v. injection of daunomycin (12 mg/kg) than in the respective control rats. Acid secretion in pylorus-ligated rats significantly decreased under the 3-h stress. On the 20th day after treatment with daunomycin, acid secretion was significantly less in nephrotic rats than in control rats under both stress and unstressed conditions. Pretreatment of normal rats with methylene blue, a guanylate cyclase inhibitor, or phenylephrine, a vasoconstrictor, significantly prevented the stress-induced gastric lesions and decreased acid secretion. N(omega)-Nitro-L-arginine methyl ester, a nitric oxide (NO) synthase inhibitor, prevented the stress-induced gastric lesion formation only. These results indicate that nephrotic rats are more resistant to RWIS-induced gastric lesions than normal rats. In addition, these results suggest that the decrease in acid secretion related to the decrease in the release of NO from endothelial cells may contribute, at least in part, to the prevention of the stress-induced gastric lesion formation in nephrotic rats. (+info)
The past and present role of the Sabin-Feldman dye test in the serodiagnosis of toxoplasmosis.
(23/863)
The dye test for the detection of Toxoplasma-specific antibodies was first described by Sabin and Feldman 50 years ago. The test is highly specific and sensitive and considerable information is available on the development and persistence of dye test antibodies after primary Toxoplasma infection. However, the test uses live Toxoplasma gondii and is now only employed in a few laboratories. It is still the reference method for the serodiagnosis of toxoplasmosis, and a multicentre study comparing dye test results between different laboratories was much needed. We report in this article the results of a multicentre evaluation of the test involving nineteen laboratories in eight countries. The study revealed overall satisfactory standardization between the laboratories, but there were differences in the test protocols, the use of reference/standard preparations and the interpretation of results. There is still no agreement on the level of dye test values which reflect infection with the parasite, and conversion from titres to international units (IUs) did not improve standardization. However, the results indicated that a value of > 4 IU or a titre of 1:16 met the definition of positivity of most participants. We recommend that the dye test be retained as a reference method and that interlaboratory standardization be improved by the use of a common protocol and the expression of results in titres. (+info)
Mechanisms for regulation of fluid shear stress response in circulating leukocytes.
(24/863)
We have shown that leukocytes retract their pseudopods and detach from substrates after exposure to physiological fluid shear stresses ( approximately 1.5 dyn/cm(2)). In inflammation, however, pseudopod projection during spreading and firm adhesion on endothelium is observed even in microvessels with normal blood flow and fluid shear stresses. Thus, we examined mechanisms that may serve to regulate the shear stress response of circulating leukocytes. In the presence of inflammatory mediators (platelet-activating factor [PAF] f-met-leu-phe), a subgroup of cells ceases to respond to shear stress. cGMP analogs and nitric oxide (NO) donors enhance the shear stress response and reverse the inhibitory effect of inflammatory mediators on the shear stress response, whereas depletion of cGMP leads to cessation of the shear stress response even in unstimulated leukocytes. The ability of cGMP to enhance the shear stress response is not associated with CD18 expression, because cGMP has no effect on CD18 expression in response to shear stress. The shear stress response of leukocytes in endothelial nitric oxide synthase (-/-) mice, in which NO level in blood is decreased, is attenuated compared with that in wild-type mice. In rat mesentery venules stimulated by PAF under normal blood flow, a cGMP analog diminishes pseudopod projection of leukocytes, whereas inhibition of NO leads to enhanced pseudopod projection and spreading. The evidence suggests that inflammatory mediators suppress the shear stress response of leukocytes leading to spreading even under normal physiological shear stress, whereas cGMP may serve to maintain shear stress response even in inflammation. (+info)