Colonisation and transmission of Clostridium difficile in healthy individuals examined by PCR ribotyping and pulsed-field gel electrophoresis

Healthy adults who had not been exposed to antimicrobial agents for the preceding 4 weeks were examined for intestinal carriage of Clostridium difficile. The 1234 individuals examined were composed of seven groups: three classes of university students, hospital workers at two hospitals, employees of a company and self-defence force personnel at a local station. Overall, 94 (7.6%) individuals were positive for C. difficile by faecal culture but carriage rates among the study groups ranged from 4.2% to 15.3%. Typing by PCR ribotyping and pulsed-field gel electrophoresis demonstrated clusters of carriers colonised by a single type in each of three groups, indicating that cross-transmission of C. difficile can occur in community settings. Follow-up culture was performed on 38 C. difficile-positive individuals and C. difficile was isolated again from 12 (32%) of them 5-7 months after the initial culture; six (50%) of these 12 individuals had a new strain on repeat culture. Two or more family members were C. difficile-positive in five of 22 families examined. C. difficile with an identical type was isolated from persons within a family in only one family. These results suggest that intestinal carriage by healthy adults may play a role as a reservoir for community-acquired C. difficile-associated diarrhoea, but that cross-transmission of C. difficile does not occur frequently among family members at home.

Specific immunoglobulin E responses in ZAP-70-deficient patients are mediated by Syk-dependent T-cell receptor signalling

ZAP-70 deficiency is a rare primary immunodeficiency characterized by the absence of peripheral CD8+ T cells and defects in T-cell receptor (TCR) signalling. T cells in ZAP-70-deficient patients are assumed to have no helper functions for B-cell immunoglobulin synthesis, whereas the patients rarely have antigen-specific antibodies. We experienced a ZAP-70-deficient patient, who had immunoglobulin E (IgE) antibodies specific to food allergens, and we investigated the mechanisms of switching to IgE in the patient. Peripheral blood mononuclear cells from the patient did not proliferate upon stimulation with the antigens but produced distinct levels of interleukin-4 (IL-4). Cell sorting analysis indicated that the cells that produced IL-4 in response to the antigens were enriched in CD4+ T cells. Purified CD4+ T cells from the patient produced IL-4 and expressed CD40L upon stimulation with anti-CD3. Moreover, CD4+ T cells pretreated with anti-CD3 induced mature epsilon transcript on naive B cells. Since the results indicated that there remained sufficient T-cell receptor (TCR)-signalling in the patient's T cells to exert antigen-specific IgE switching on B cells, we next investigated the expression of the ZAP-70-homologous kinase Syk. Syk was present in high levels in patient's CD4+ T cells and was tyrosine-phosphorylated after TCR stimulation. Inhibition of Syk by piceatannol resulted in decreased production of IL-4 and expression of CD40L on patient's CD4+ T cells. Moreover, Syk was expressed on all human T-cell leukaemia virus (HTLV-1)-transformed T-cell lines derived from peripheral blood of the patient, whereas it was low or undetectable in control lines. It was therefore concluded that specific IgE responses in the patient were most likely to be mediated by Syk-dependent TCR-signalling.

Inhibitory effects of TA-993 and its metabolite MB3 on platelet activation induced by collagen and U-46619 in human platelets

In the present study, we investigated the effects of TA-993 and its metabolite MB3 on platelet activation in vitro. TA-993 and MB3 concentration-dependently inhibited platelet aggregation and ATP release induced by collagen in human platelets. Thromboxane (Tx) A2 formation, as determined by the production of TxB2, and the increase in intracellular Ca2+ concentration ([Ca2+]i) were also suppressed by TA-993 and MB3. TA-993 and MB3 did not inhibit TxA2 formation caused by arachidonic acid. These results suggest that the inhibition of platelet activation by TA-993 and MB3 is partly mediated by an inhibition of TxA2 formation at a step prior to cyclooxygenase. Furthermore, TA-993 and MB3 inhibited U-46619-induced platelet aggregation without blockade of the increase in [Ca2+]i, suggesting that they are likely to exert some additional effects on the intracellular events induced by Ca2+.

Incidence of beta-lactamase production and antimicrobial susceptibility of anaerobic gram-negative rods isolated from pus specimens of orofacial odontogenic infections

The incidence of beta-lactamase production in anaerobic gram-negative rods isolated from 93 pus specimens of orofacial odontogenic infections and the antimicrobial susceptibility of these isolates against 11 antibiotics were determined. A total of 191 anaerobic gram-negative rods were isolated from the specimens. Beta-lactamase was detected in 35.6% of the black-pigmented Prevotella and 31.9% of the nonpigmented Prevotella. However, no strains among the other species isolated produced beta-lactamase. Ampicillin, cefazolin and cefotaxime showed decreased activity as regards beta-lactamase-positive Prevotella strains, whereas the activity of ampicillin/sulbactam, cefmetazole, and imipenem continued to be effective against such strains. All tested beta-lactam antibiotics were effective against Porphyromonas and Fusobacterium. Erythromycin showed decreased activity against nonpigmented Prevotella and Fusobacterium. Clindamycin, minocycline and metronidazole were powerful antibiotics against which anaerobic gram-negative rods could be tested. The present study showed that beta-lactamase-positive strains were found more frequently in the Prevotella strains than in any of the other species of anaerobic gram-negative rods. The effectiveness of adding sulbactam to ampicillin was demonstrated, as well as the difference in cephalosporin activity against beta-lactamase-positive strains.

Genetic analysis of type E botulinum toxin-producing Clostridium butyricum strains

Type E botulinum toxin (BoNT/E)-producing Clostridium butyricum strains isolated from botulism cases or soil specimens in Italy and China were analyzed by using nucleotide sequencing of the bont/E gene, random amplified polymorphic DNA (RAPD) assay, pulsed-field gel electrophoresis (PFGE), and Southern blot hybridization for the bont/E gene. Nucleotide sequences of the bont/E genes of 11 Chinese isolates and of the Italian strain BL 6340 were determined. The nucleotide sequences of the bont/E genes of 11 C. butyricum isolates from China were identical. The deduced amino acid sequence of BoNT/E from the Chinese isolates showed 95.0 and 96.9% identity with those of BoNT/E from C. butyricum BL 6340 and Clostridium botulinum type E, respectively. The BoNT/E-producing C. butyricum strains were divided into the following three clusters based on the results of RAPD assay, PFGE profiles of genomic DNA digested with SmaI or XhoI, and Southern blot hybridization: strains associated with infant botulism in Italy, strains associated with food-borne botulism in China, and isolates from soil specimens of the Weishan lake area in China. A DNA probe for the bont/E gene hybridized with the nondigested chromosomal DNA of all toxigenic strains tested, indicating chromosomal localization of the bont/E gene in C. butyricum. The present results suggest that BoNT/E-producing C. butyricum is clonally distributed over a vast area.

Bacteriologic features and antimicrobial susceptibility in isolates from orofacial odontogenic infections

OBJECTIVE

The aim of this study was to obtain information for an effective antimicrobial therapy against orofacial odontogenic infections; such information was obtained from recent bacteriologic features and antimicrobial susceptibility data.

STUDY DESIGN

The bacteriology and antimicrobial susceptibility of major pathogens in 163 patients with orofacial odontogenic infections to 7 antibiotics was examined.

RESULTS

Mixed infection of strict anaerobes with facultative anaerobes (especially viridans streptococci) was observed most often in dentoalveolar infections, periodontitis, and pericoronitis. Penicillin (penicillin G) was effective against almost all pathogens, although it did not work well against beta-lactamase-positive Prevotella. Cefmetazole was effective against all test pathogens. Erythromycin was ineffective against viridans streptococci and most Fusobacterium. Clindamycin exerted a strong antimicrobial activity on anaerobes. Minocycline was effective against almost all the test pathogens. The antimicrobial activity of levofloxacin against viridans streptococci was not strong.

CONCLUSIONS

An antibiotic that carries out antimicrobial activity against both viridans streptococci and oral anaerobes should be suitable for treatment of dentoalveolar infection, periodontitis, and pericoronitis. Penicillin remains effective as an antimicrobial against most major pathogens in orofacial odontogenic infections. Cefmetazole, clindamycin, and minocycline may be effective against most pathogens, including penicillin-unsusceptible bacteria.

The virulence of mixed infection with Streptococcus constellatus and Fusobacterium nucleatum in a murine orofacial infection model

Orofacial infections are usually polymicrobial, and it is the microbial interactions of pathogenic species that cause tissue destruction. In this study, the microbial interaction between Streptococcus constellatus and Fusobacterium nucleatum was characterized using a murine orofacial infection model. A mixture of viable S. constellatus and F. nucleatum cells (both 2 x 10(8) CFU/mouse) was injected into the submandible; as a result, all of the test mice died. In contrast, none of the experimental animals monoinjected with either S. constellatus or F. nucleatum died (P<0.001), indicating that the synergism between the two resulted in the virulence. When a mixture of viable S. constellatus cells and a culture filtrate of F. nucleatum was tested, lethality and the bacterial cell count per lesion were significantly enhanced as compared with monoinjections (P<0.02). However, the virulence of F. nucleatum was not enhanced by infection of a culture filtrate of S. constellatus. The enhancement of virulence was observed even when viable S. constellatus cells and the culture filtrate of F. nucleatum were injected at separate sites. Heat treatment of the culture filtrate of F. nucleatum did not affect the enhancement. These results indicate that a heat-stable substance(s) produced by F. nucleatum contributes to the microbial synergy of S. constellatus and F. nucleatum in orofacial infections.

Spontaneous regression of hepatocellular carcinoma and review of literature

A 68-year-old man presented with multiple hepatocellular carcinoma, which was considered to be unresectable at the first admission in January 1994. Pathological diagnosis was made by biopsy of the one lesion among them. From January 1994 to December 1997, 10 transarterial chemoembolizations and six percutaneous ethanol injection therapies were performed on the tumours in the cirrhotic liver. In February 1998 the tumour situated in the right lobe began to increase in size. The maximum tumour diameter was 6.3 cm measured by computed tomography (CT). In the beginning of May 1998 moderate ascites was present and mild hepatic encephalopathy was noticed. The patient was in the terminal stage of hepatocellular carcinoma and no further treatment was possible at that time. However, serum alpha-fetoprotein and protein induced by vitamin K absence or antagonist II dramatically decreased in June 1998. The CT scan also showed that the tumour had completely regressed without specific treatment. In February 1999 a new biopsy-proven hepatocellular carcinoma, 2 cm in diameter, developed in the lateral segment of the liver. It was well treated by percutaneous ethanol injection therapy. The patient was alive in good condition without any symptoms or tumour recurrence in June 1999. It was concluded that a rare case of spontaneous regression of hepatocellular carcinoma had occurred.

Characterization of bacterial orofacial infections using a new murine model

We devised a new murine orofacial infection model using bacteria from odontogenic infection origins and characterized the experimental infections. In this model, bacteria were injected into the submandible of mice. Streptococcus constellatus and Peptostreptococcus micros produced a single abscess at the injection site and their abscess-forming and lethal abilities were low: the median abscess-forming dose (AF(50)) of S. constellatus and P. micros were 10(8.5-10.7)and 10(10.2-10.6)cfu/mouse, and their median lethal dose (LD(50)) were >11 and 10(10.6-11)cfu/mouse, respectively. Prevotella oralis and Fusobacterium nucleatum produced multiple abscesses and their abscess-forming and lethal abilities were strong: AF(50)of P. oralis and F. nucleatum were 10(6.0-6.4)and 10(7. 0-8.7)cfu/mouse, and their LD(50)were 10(7.0-7.7)and 10(8.3-9. 9)cfu/mouse, respectively. LD(50)of P. intermedia and P. gingivalis were 10(9.4->11)and 10(8.9-9.1)cfu/mouse, respectively. Prevotella intermedia and Porphyromonas gingivalis generated a necrotizing lesion, which progressed rapidly. We conclude that this murine model could reflect human orofacial odontogenic infections and is useful to investigate the pathogenicity of causative bacteria of such infections.

Antiplatelet mechanisms of TA-993 and its metabolite MB3 in ADP-induced platelet aggregation

We investigated the antiplatelet mechanisms of TA-993 [(-)-cis-3-acetoxy-5-(2-(dimethylamino)ethyl)-2, 3-dihydro-8-methyl-2-(4-methylphenyl)-1,5-benzothiazepin-4(5H)-one maleate] and its metabolite MB3 (deacetyl and N-monomethyl TA-993) in human platelets stimulated by ADP in vitro. TA-993 and MB3 concentration-dependently inhibited fibrinogen binding to the ADP-stimulated platelets as well as inhibiting platelet aggregation. The antiplatelet effect of MB3 was about 300 times more potent than those of TA-993 and a glycoprotein IIb/IIIa receptor antagonist, Arg-Gly-Asp-Ser (RGDS). Aggregation of ADP-treated fixed platelets caused by the addition of fibrinogen was inhibited by RGDS but not by TA-993 and MB3. TA-993 and MB3 inhibited ADP-induced polymerization of actin filaments. Neither TA-993 nor MB3 affected cyclic AMP and cyclic GMP levels in resting platelets, and nor suppressed the increase in intracellular Ca(2+) concentration induced by ADP. These results suggest that the antiplatelet mechanisms of TA-993 and MB3 may involve inactivation of glycoprotein IIb/IIIa receptors via inhibition of the polymerization of actin.

Past administration of beta-lactam antibiotics and increase in the emergence of beta-lactamase-producing bacteria in patients with orofacial odontogenic infections

OBJECTIVE

The purpose of this study was to determine the current status of beta-lactamase-producing bacteria in orofacial odontogenic infections.

STUDY DESIGN

Microbiologic data regarding purulent exudate from 111 cases with orofacial odontogenic infections were analyzed in relation to the past administration of beta-lactams.

RESULTS

beta-lactamase-producing bacteria were isolated more frequently from the beta-lactam-administered group (38.5%) than from the beta-lactam-nonadministered group (10.9%; P <.005), and they were isolated more frequently as the duration of administration increased. The predominant bacteria isolated included Prevotella (the most frequent isolate), viridans streptococci, Peptostreptococcus, and Fusobacterium, and 7.1% of total isolates produced beta-lactamase. Penicillin and cefazolin worked well with beta-lactamase-nonproducing Prevotella but were remarkably affected by beta-lactamase-producing Prevotella. Cefmetazole, sulbactam/cefoperazone, and imipenem worked well against both types of Prevotella.

CONCLUSIONS

beta-lactams are still suitable for the first antimicrobial therapy in the treatment of these infections. However, because past beta-lactam administration increases the emergence of beta-lactamase-producing bacteria, beta-lactamase-stable antibiotics should be prescribed to patients with unresolved infections who have received beta-lactams.

[Transition of branched-chain amino acids and tyrosine ratio (BTR) in the blood of acute hepatitis patients]

The molar ratio of branched-chain amino acids to tyrosine (BTR) correlates well with the Fischer ratio, and can be measured in a short period of time. It is regarded as the method of analysis that will eventually replace the Fischer ratio. But clinical significance of BTR in terms of acute liver disorders has not been examined thoroughly as of yet. In this study, we measured BTR of 34 patients with acute hepatitis, and examined the transition of the acute period of acute hepatitis and its recovery process. Thirty-four patients diagnosed with acute viral hepatitis became subjects of examination (16 patients of A type, 15 patients of B type, 1 patient of C type, 2 patients of non-A, non-B, non-C type). Out of the 34 patients, 11 were in serious stages (HPT under 40%), including 3 in fulminant condition. By using preserved serum obtained during the acute period (within 1 week of the highest transaminase value), recovery period (within 4 weeks), and treatment period (3 months and later), measurements were conducted with Diacolor:BTR (enzymatic analysis, ONO Pharmaceutical Co., Ltd.), and the results were compared with those of 50 healthy subjects (25 men, 25 women). BTR correlated well with the Fischer ratio for chronic hepatic patients, and with albumin (Alb), PT, and ICGR15 as well, proving that it is useful as an indicator of hepatic reserve ability. But BTR has not been thoroughly examined as it relates to acute liver disorders. In this study, BTR fell in the acute period, correlating with the serious period, proving that it is a useful indicator. For acute liver damage, BTR supports conventional indicators (Alb, Ch-E, HGF, etc.) for assessing serious damage. Also, it has been suggested that measuring the passage of BTR could be the indicator of true recovery, including amino acid metabolism for liver disorders.

Ultraviolet-cured polymer microlens arrays

A method for fabricating microlens arrays that uses the contraction effect of UV-curable photopolymers is presented. Lenses with diameters ranging from 0.2 to 2 mm that were made under different conditions are optically evaluated. The optimum conditions for producing low f-number lenses are discussed.

Isolation and characterisation of neurotoxigenic Clostridium butyricum from soil in China

Soil specimens collected from a site around the home of patients with food-borne type E. botulism probably caused by neurotoxigenic Clostridium butyricum in Guanyun, Jiangsu province, China, were examined for the presence of neurotoxigenic C. butyricum. Five lakeside sites of Weishan lake, in an area near to the sites where the type E. botulism outbreaks caused by neurotoxigenic C. butyricum occurred were also surveyed. Type E toxin-producing C. butyricum was isolated from soil from four sites including the site in Guanyun. Polymerase chain reaction assay demonstrated the presence of the type E toxin gene in all the toxigenic isolates. The biochemical properties of the isolates from the Guanyun soil and the lakeside soil were identical except for inulin fermentation and starch hydrolysis properties. These results indicate that neurotoxigenic C. butyricum has its principal habitat in soil.

Laboratory diagnosis of toxigenic Clostridium difficile by polymerase chain reaction: presence of toxin genes and their stable expression in toxigenic isolates from Japanese individuals

Clostridium difficile causes pseudomembranous colitis and antibiotic-associated diarrhea. The definitive diagnosis of C. difficile infection is finally accomplished by the isolation of toxigenic C. difficile. However, only a small number of Japanese clinical laboratories are able to reach a definitive diagnosis of C. difficile infection, probably because simple reliable assays for toxins in the isolates are not available. In this study, we examined the compatibility of a polymerase chain reaction (PCR) assay and tissue culture assay to identify toxigenic C. difficile, in toxigenic and nontoxigenic C. difficile isolates from Japanese patients and healthy carriers. The specificity of PCR primers was demonstrated by restriction endonuclease digestion and seminested PCR in C. difficile VPI 10463 strain. No PCR product was amplified in the eight other clostridial species used to check the specificity of the PCR assay. The detection limit was 10(3) cells. Both toxin A and toxin B genes (the genes encoding the major virulence factors of C. difficile) were detected in 58 toxigenic C. difficile isolates, which showed a wide range of cytotoxic activity in tissue culture assays. Neither of the toxin genes was carried by 40 nontoxigenic strains of C. difficile. The results of this study strongly suggest that a definitive diagnosis of C. difficile infection can be accomplished by PCR detection of the toxin genes rather than by tissue culture assay of isolates.

Second site suppressor mutations of a GTPase-deficient G-protein alpha-subunit. Selective inhibition of Gbeta gamma-mediated signaling

G proteins transmit signals from cell surface receptors to intracellular effectors. The intensity of the signal is governed by the rates of GTP binding (leading to subunit dissociation) and hydrolysis. Mutants that cannot hydrolyze GTP (e.g. GsalphaQ227L, Gi2alphaQ205L) are constitutively activated and can lead to cell transformation and cancer. Here we have used a genetic screen to identify intragenic suppressors of a GTPase-deficient form of the Galpha in yeast, Gpa1(Q323L). Sequencing revealed second-site mutations in three conserved residues, K54E, R327S, and L353Delta (codon deletion). Each mutation alone results in a complete loss of the beta gamma-mediated mating response in yeast, indicating a dominant-negative mode of inhibition. Likewise, the corresponding mutations in a mammalian Gi2alpha (K46E, R209S, L235Delta) lead to inhibition of Gbeta gamma-mediated mitogen-activated protein (MAP) kinase phosphorylation in cultured cells. The most potent of these beta gamma inhibitors (R209S) has no effect on Gi2alpha-mediated regulation of adenylyl cyclase. Despite its impaired ability to release beta gamma, purified recombinant Gpa1(R327S) is fully competent to bind and hydrolyze GTP. These mutants will be useful for uncoupling Gbeta gamma- and Galpha-mediated signaling events in whole cells and animals. In addition, they serve as a model for drugs that could directly inhibit G protein activity and cell transformation.

Characterization of Clostridium botulinum type B neurotoxin associated with infant botulism in japan

The neurotoxin of strain 111 (111/NT) associated with type B infant botulism showed antigenic and biological properties different from that (Okra/NT) produced by a food-borne botulism-related strain, Okra. The specific toxicity of 111/NT was found to be about 10 times lower than that of Okra/NT. The monoclonal antibodies recognizing the light chain cross-reacted with both neurotoxins, whereas most of the antibodies recognizing the carboxyl-terminal half of the heavy chain of Okra/NT did not react to 111/NT. Binding experiments with rat brain synaptosomes revealed that 125I-labeled 111/NT bound to a single binding site with a dissociation constant (Kd) of 2.5 nM; the value was rather lower than that (0.42 nM) of 125I-Okra/NT for the high-affinity binding site. In the lipid vesicles reconstituted with ganglioside GT1b, 125I-Okra/NT interacted with the amino-terminal domain of synaptotagmin 1 (Stg1N) or synaptotagmin 2 (Stg2N), fused with the maltose-binding protein, in the same manner as the respective full-length synaptotagmins, and the Kd values accorded with those of the low- and high-affinity binding sites in synaptosomes. However, 125I-111/NT only exhibited a low capacity for binding to the lipid vesicles containing Stg2N, but not Stg1N, in the presence of ganglioside GT1b. Moreover, synaptobrevin-2, an intracellular target protein, was digested to the same extent by the light chains of both neurotoxins in a concentration-dependent manner. These findings indicate that the 111/NT molecule possesses the receptor-recognition site structurally different from Okra/NT, probably causing a decreased specific toxicity.

Inhibition of enhanced toxin production by Clostridium difficile in biotin-limited conditions

Production of toxins A and B by Clostridium difficile is enhanced in a defined medium with biotin-limited conditions. In the present study compounds inhibitory to enhanced toxin production by a C. difficile strain were examined. Increases in biotin concentration from 0.05 nM to 50 nM accelerated growth and inhibited enhanced toxin production. Asparagine, glutamic acid and glutamine (10 mM) showed an effect on growth and toxin production similar to that of biotin. Lysine (10 mM) suppressed growth and inhibited toxin production. Addition of these toxin-inhibitory compounds within an incubation period of 2 days inhibited the enhanced toxin production, but later addition showed only slight inhibition of toxin production. Amino acids contained in the defined medium under the biotin-limited conditions were actively utilised in the presence of the three toxin-inhibitory amino acids, but in the presence of lysine, amino-acid utilisation was suppressed. Different mechanisms of action of these toxin-inhibitory molecules, which may be divided into excess biotin, asparagine-glutamic acid-glutamine group, and lysine, are discussed.

Effect of isoleucine on toxin production by Clostridium difficile in a defined medium

Supplementation of a carbohydrate-free minimal medium with a high level (100 mM) of histidine, methionine, valine, isoleucine, proline and leucine, in particular isoleucine, markedly increased toxin production by Clostridium difficile VPI 10463. The effect of isoleucine was further examined. Increasing the concentration of isoleucine from 20 to 100 mM remarkably increased toxin production, while bacterial growth decreased gradually. Amino acid analysis of the culture revealed that, at 100 mM isoleucine, consumption of isoleucine was remarkably increased. During the incubation period when toxin titers increased markedly but bacterial growth was declining, isoleucine, leucine and cysteine were taken up preferentially and alanine and cystathionine, which were not found at 1 mM isoleucine, were produced in large quantities. These findings suggest that isoleucine may play an important role in toxin production by C. difficile and that alanine and cystathionine production may be co-regulated with the toxin production in the absence of fermentable carbohydrates.

Cardiovascular effect of a new 1,5-benzothiazepine derivative TA-993 in anesthetized dogs

TA-993 is a new 1,5-benzothiazepine derivative having l-cis configuration and shows a potent antiplatelet aggregating action. We studied its cardiovascular effect in anesthetized dogs by using diltiazem as a reference compound. TA-993 (> or = 10 microg/kg, i.v.) significantly increased blood flows of common carotid, brachial, and femoral arteries. The peak of its effect was observed approximately 60 min after the administration, and the peak level was maintained until > or = 300 min after the administration. TA-993 (100 microg/kg, i.v.) slightly increased cardiac output in the same manner. However, TA-993 did not cause any persistent effects on arterial pressure, LVdP/dtmax, or vertebral, coronary, superior mesenteric, and renal blood flows. TA-993 caused concentration-dependent vasorelaxation in the isolated canine femoral artery contracted with 40 mM K+, but its potency was approximately 1/20 that of diltiazem. The increasing action of TA-993 on femoral blood flow was completely inhibited by pretreatment with hexamethonium in anesthetized dogs. These results indicate that TA-993 has a selective increasing action on common carotid, brachial, and femoral blood flows and suggest that the action is mediated by the autonomic nervous system.

Effect of arginine on toxin production by Clostridium difficile in defined medium

Twenty strains of Clostridium difficile were examined for the effect of arginine on toxin production in a defined medium. In three strains, the production of toxins A and B was greatly enhanced in the absence of arginine. These strains showed distinctively poorer growth in the absence of arginine in comparison with the remaining 17 strains, indicating that the presence of arginine is required for good growth among the three strains. From the present results, test strains were divided into two groups: a group in which arginine insufficiency caused distinctly poor growth and enhanced toxin production, and another group in which there was neither distinctly poor growth nor enhanced toxin production. The phenomenon is discussed in relation to the biosynthesis and catabolism of arginine.