Effect of intestinal bacteria on incidence of liver tumors in gnotobiotic C3H/He male mice.

The effect of intestinal microflora on liver tumorigenesis was studied in gnotobiotic C3H/He male mice monoassociated, diassociated, or polyassociated with the following strains of intestinal bacteria: Escherichia coli, Streptococcus faecalis, Bifidobacterium adolescentis, Bifidobacterium infantis, Clostridium indolis, C. paraputrificum, C. perfringens, C. innocuum, C. nexile, C. ramosum, C. clostridiiforme, Bacteroides multiacidus, Bacteroides fragilis, Veillonella alcalescens, V. parvula, and Lactobacillus acidophilus. The incidence of liver tumors was higher in most of the gnotobiotes (67--100%) and conventionalized mice (82%) derived from the germfree mice than in the germfree mice (39%). The average incidence of tumor nodules in gnotobiotes associated with E. coli, S. faecalis, and C. paraputrificum was 2.9, which was significantly higher than that in the conventionalized animals (1.6). In contrast, the average incidence of tumor nodules in gnotobiotes associated with E. coli, S. faecalis, L. acidophilus, C. perfringens, and Bacteroides fragilis (0.9) was not significantly different from that in germfree animals (0.5). The present study demonstrated that the presence of certain intestinal bacteria is related to liver tumorigenesis in gnotobiotic C3H/He male mice.

Effects of adenosine and adenosine 5'-triphosphate on ventricular escape rhythm in the canine heart.

The effects of adenosine and adenosine 5'-triphosphate (ATP) on ventricular escape rhythms were studied in 16 closed chest dogs after electroablation of the His bundle region. All dogs exhibited complete atrioventricular (AV) block and stable ventricular escape rhythm with a mean cycle length of 1,210 +/- 80 ms and a QRS width of 91 +/- 5 ms. Physiologic AV sequential pacing was operative during experiments and was interrupted for rapid (less than or equal to 1 second) administration of either adenosine or ATP (3 mumol/kg) into the right atrium. Adenosine and ATP effectively depressed ventricular escape rhythms in a similar manner both qualitatively and quantitatively (cycle length from 1,210 +/- 80 to 1,764 +/- 132 ms and from 1,274 +/- 84 to 2,000 +/- 150 ms, respectively; each p less than 0.01). These effects were not significantly altered by either physostigmine (an acetylcholinesterase inhibitor) or atropine (a muscarinic cholinergic blocker), but were slightly attenuated by propranolol (a beta-adrenoceptor blocker). In the presence of autonomic blockade, the adenosine transport blocker dipyridamole markedly enhanced the depressant effects of adenosine and ATP. The adenosine competitive antagonist aminophylline reversed the action of dipyridamole. Thus, both adenosine and ATP depress ventricular escape rhythms in vivo, independent of the autonomic nervous system. Moreover, the effects of ATP can be accounted for in large part by its rapid breakdown to adenosine.

Interacting negative chronotropic effects of adenosine and the vagus nerve on the canine sinus node.

The vagus nerve and adenosine exert a negative chronotropic effect on the mammalian sinus node. In addition, adenosine is released from myocardial cells under both physiological and pathophysiological conditions, which are characterised by variable vagal tone. To determine the interaction between adenosine and the vagus nerve, 21 barbiturate anaesthetised mongrel dogs with bilateral cervical vagotomy and stellectomy were studied. In group 1 (n = 16) adenosine (3 mumol.kg-1) was rapidly (less than or equal to 1 s) administered before (control) and during 60 s of repetitive vagal stimulation. Each stimulus (consisting of a burst of 5 square wave pulses, 0.3 mA in amplitude and 1 ms in duration at 0.1 kHz) was given at a fixed point in time in each sinus cycle (that is, one burst per cycle). This protocol was repeated after a 50 ms incremental change in the phase at which vagal stimulation was given until the entire cycle length was scanned. Recovery time of at least 2 min separated any two consecutive adenosine administrations. In four animals the above protocol was performed twice using vagal stimulation amplitude of 0.3 mA and 0.6 mA in the first and second runs respectively. In this group (group 1), the effect of adenosine was altered by the vagus in a phase dependent manner. In each animal, however, there was at least one phase of the sinus cycle during which vagal stimulation significantly enhanced the effect of adenosine.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of left ventricular systolic pressure increase on ventricular arrhythmogenicity in old canine myocardial infarction.

OBJECTIVE: The aim was to examine the effect of an increase in left ventricular systolic pressure (LVSP) on ventricular arrhythmogenicity in old canine myocardial infarction. METHODS: Fourteen mongrel dogs of either sex weighing 11 to 15 kg were used. Studies were performed 28 d after creation of myocardial infarction by ligation of the anterior descending coronary artery. Electrical induction of ventricular arrhythmia and determinations of effective refractory period (ERP) and local intraventricular conduction delay (LIVCD) were performed using the extrastimulus technique with a cycle length of 300 ms in the normal and infarcted zones of the left ventricle. Heterogeneity of ERP (delta ERP) was determined as a difference between the longest and shortest ERP values in each site. LVSP was raised by constriction of the ascending aorta in a stepwise fashion (control, level A, level B). RESULTS: Incidence of electrically induced ventricular arrhythmia was increased from 28.6% at control level of LVSP [130.7(SEM 7.3) mm Hg] to 42.9% at level A [190.9(6.0) mm Hg] and to 64.3% (p < 0.05) at level B [243.3(4.0) mm Hg]. delta ERP and LIVCD were greater in the infarct zone than in the normal zone at each level of LVSP (p < 0.001). delta ERP in the infarct zone increased from 18.9(4.3) ms at control level of LVSP to 20.7(6.8) ms at level A, and to 27.1(8.1) ms at level B (p < 0.001). LIVCD in the infarct zone also increased from 22.9(6.2) ms at control level of LVSP to 26.8(4.9) ms at level A (p < 0.001), and to 36.1(6.0) ms at level B (p < 0.001). delta ERP and LIVCD in the normal zone were only slightly raised by increasing the LVSP. delta ERP and LIVCD in the infarct zone were closely correlated with incidence of electrically induced ventricular arrhythmia. CONCLUSIONS: Increasing the LVSP enhances ventricular arrhythmogenicity and pre-existing electrophysiologic abnormalities of the heart in the presence of old myocardial infarction. Thus a rise in LVSP from any cause in the old myocardial infarction can be a trigger of life threatening ventricular arrhythmias.

Arrhythmogenic properties of the ventricular myocardium in cardiomyopathic Syrian hamster, BIO 14.6 strain.

STUDY OBJECTIVE: Incidence of spontaneous cardiac arrhythmias and inducibility of ventricular arrhythmias in the cardiomyopathic hamster, BIO 14.6 strain, were examined. DESIGN: A 3 min electrocardiogram (ECG) was recorded weekly to 50 weeks of age. Programmed ventricular stimulation was then performed with single and double ventricular premature stimuli during both sinus rhythm and ventricular pacing, and with brief bursts of ventricular pacing to induce ventricular arrhythmias. EXPERIMENTAL MATERIAL: 19 male cardiomyopathic and 10 age matched normal hamsters from 16 to 50 weeks were used for recording the 3 min ECG; 11 cardiomyopathic and 10 normal hamsters aged 50 to 55 weeks were used for the induction of ventricular arrhythmias. MEASUREMENTS AND MAIN RESULTS: Spontaneous and sporadic ventricular premature contractions were documented in 8.3% of 218 ECGs from the cardiomyopathic hamsters between the ages of 30 and 46 weeks, whereas no ventricular arrhythmia was recorded in normal hamsters throughout the entire follow up period. Non-sustained ventricular tachycardia (NSVT) was induced in 7/11 cardiomyopathic hamsters by single ventricular premature stimulus. Either NSVT or ventricular fibrillation was induced in all cardiomyopathic hamsters with a significantly prolonged intraventricular conduction delay and refractory period. In contrast, neither NSVT nor ventricular fibrillation was induced in normal hamsters. CONCLUSION: This study provides the first evidence of the high arrhythmogenicity of the ventricles in cardiomyopathic hamsters.

Effect of dietary phenobarbital on spontaneous hepatic tumorigenesis in germfree C3H/He male mice.

Phenobarbital (PB) is known to be a promoter of liver tumorigenesis in rats and mice. The present study was designed to examine the effect of PB on liver tumorigenesis in C3H/He germfree (Gf) male mice. Gf and conventional (Cv) animals were given an irradiated (5 Mrad) basal diet containing 200 ppm PB from 6 weeks old until termination of the experiment. When they were 12 months old, the animals were killed under CO2 inhalation and autopsied for the number and size of tumor nodules. The incidence of liver tumors was significantly higher in PB-fed Gf animals (67%) than in non-treated Gf controls (30%), and higher in PB-fed Cv animals (100%) than in non-treated Cv controls (75%). The number of tumor nodules per mouse was also significantly higher in PB-fed Gf animals (2.0) than in non-treated Gf controls (0.4), and higher in PB-fed Cv animals (4.5) than in non-treated controls (1.3). The present study demonstrated that dietary PB induced increases in number of the tumor nodules and decreases in the tumor size of C3H/He mice.

Effect of Konjac mannan on 1,2-dimethylhydrazine-induced intestinal carcinogenesis in Fischer 344 rats.

The effect of Konjac mannan (KM) on 1,2-dimethylhydrazine (DMH-induced intestinal carcinogenesis was studied in male F344 rats. Rats were fed a diet containing 5% KM at 5 weeks of age. At 6 weeks of age, all animals were given a weekly intraperitoneal injection of 20 mg DMH/kg body wt for 13 weeks and autopsied 13 weeks after the last injection of DMH. The weight gain was lower in rats fed the KM diet than in rats fed the control diet throughout the experiment (P less than 0.05). The incidence of DMH-induced colon tumors was lower in animals fed the KM diet compared to animals fed the control diet (P less than 0.05). The number of colon adenocarcinoma per animal was also lower in animals fed the KM than in animals fed the control diet (P less than 0.05). However, the incidence of tumors of the small intestine did not significantly differ between the groups fed the KM and control diets. The present study demonstrated that colon tumorigenesis induced by DMH in F344 rat was inhibited by maintaining the KM diet.

Inhibitory effect of some intestinal bacteria on liver tumorigenesis in gnotobiotic C3H/He male mice.

Liver tumorigenesis in gnotobiotic C3H/He male mice was markedly promoted by association with a bacterial combination of Escherichia coli, Streptococcus faecalis, and Clostridium paraputrificum. This study demonstrated that this promoting effect was suppressed by addition of certain intestinal bacteria, such as Bifidobacterium longum, Lactobacillus acidophilus, and Eubacterium rectale.

Effect of Konjac mannan on spontaneous liver tumorigenesis and fecal flora in C3H/He male mice.

The effect of Konjac mannan (KM) on spontaneous liver tumorigenesis and fecal flora was studied in C3H/He male mice maintained on a diet containing 10% KM. The weight gain in the 10% KM diet group was lower than that in a control diet group throughout the experimental period. At 12 months of age, the number of liver tumor nodules per mouse in the KM diet group was significantly lower than that in the control diet group (P less than 0.05). Frequency of occurrence of bifidobacteria and bacterial counts of enterobacteriaceae in the KM diet group were significantly higher than those in the control diet group (P less than 0.05). Thus, the present study demonstrates that dietary KM inhibited spontaneous liver tumorigenesis and altered fecal flora in C3H/He male mice.

Spontaneous polyposis in the small intestine of germ-free and conventionalized BALB/c mice.

The spontaneous polyposis in the small intestine of germfree (Gf) and conventionalized (Cv) BALB/c mice was studied. Gf mice were bred in our laboratory and maintained Gf in vinyl isolators. The first generation offspring of the Cv mice derived from the Gf mice was used as Cv animals. When they were 12 months old, the animals were killed under CO2 inhalation and autopsied carefully for the number and size of polyps with the aid of a dissecting microscope. The incidence of polyposis was higher in the Gf mice (68% in female and 89% in male) than in the Cv mice (37% in female and 51% in male). The number of polyps/mouse was also higher in the Gf mice (2.3 in female and 5.7 in male) than in the Cv mice (0.8 in female and 1.3 in male). All of the polyps were histopathologically adenomatous and developed only in the upper part (mainly duodenum) of the small intestine. The present study demonstrated that development of polyposis in the small intestine of BALB/c mice was suppressed by the presence of intestinal microflora.

Endotoxic activity in faeces of mice from different microbiological environments.

Chromogenic Limulus amoebocyte lysate (LAL) tests were evaluated for measuring endotoxic activity in faeces of mice from different microbiological environments. Faeces of BALB/c mice from germ-free (GF), specific-pathogen-free (SPF) and conventional (CV) colonies had no inhibitory activity on the test reaction. GF and SPF faeces had heat-labile non-specific amidase activity which gave false-positive reaction, while CV did not. GF faeces had a heat-stable non-endotoxic effect on the LAL system. Average endotoxin levels in faeces of GF, SPF and CV mice were 0.2, 0.8 and 17 to 24 micrograms/g wet weight, respectively. Results suggest that the microbiological status of mice influences not only the faecal endotoxin level but also the specificity of the test reaction.

Modification of swine serum-induced bile duct lesion in BALB/c mice by cyclophosphamide.

Effects of cyclophosphamide (CY) on the antibody titer level and incidence and severity of swine serum (SS)-induced bile duct lesion (BDL) were examined. BDL induced by 0.2 ml of SS per head twice a week for 2 weeks was characterized by hyperplasia of biliary epithelial cells, proliferation of mucous glands, and periductal infiltration of eosinophils with mild fibrosis. CY showed no significant influence on the above-mentioned parameters at the dose levels of 140 and 210 mg/kg. On the other hand, CY lowered the antibody titer level and decreased the severity of BDL at the dose level of 280 mg/kg, and it suppressed the antibody response and BDL at the dose level of 280 x 2 mg/kg. Thus the antibody titer level and the severity of BDL were closely related each other.

Growth characteristics of Tyzzer's organism in cultured mouse hepatocytes.

The growth characteristics of Tyzzer's organisms in cultured mouse hepatocytes were examined by direct bacterial counting and plaque assay. The viability of propagated bacteria and time required for the maximum titers depended on incubation time and inoculum dose, respectively. Both infectious titers and bacterial counts at optimum harvests were much higher than those obtained from infected mouse livers. Immunofluorescence revealed, after a lag phase of about 2 h, a linear multiplication during a 6 h period.

Effect of standing on ventricular parasystole: shortening of the parasystolic cycle length.

OBJECTIVE: To investigate the effect of standing on the parasystolic cycle length in cases of "true" ventricular parasystole. METHODS: Parasystolic cycle length and sinus cycle length were measured during lying and standing in eight men with true ventricular parasystole. These cycle lengths were also measured after exercise in the lying position. RESULTS: In all cases, parasystolic cycle length and sinus cycle length both shortened on standing, by a mean of 6.4% and 17.8%, respectively, compared to lying. In all cases, the rate of shortening of the parasystolic cycle length was less than that of the sinus cycle length. Parasystolic cycle length was prolonged after exercise, in contrast to a shortening of the sinus cycle length. CONCLUSIONS: Influences on the parasystolic cycle length are not always in the same direction as on the sinus cycle length. This suggests that the effect of autonomic changes on parasystolic rhythm is not always parallel to that on sinus rhythm.

Antigenic heterogeneity of non-pigmented Bacteroides species isolated from the human oral cavity.

Serological studies on 27 strains of non-pigmented Bacteroides isolated from the human oral cavity revealed multiple serotypes within B. buccae. B. capillus (= B. buccae) and B. pentosaceus (= B. buccae) were found to be serogroups within B. buccae. B. denticola possessed cross-reactive antigens with B. buccae. Tested strains of B. oralis, B. veroralis, B. oris, and B. heparinolyticus were clearly differentiated from each other.

Modification of the minitek system for identification of lactobacilli.

Seventy-eight strains of 23 Lactobacillus species, including 41 reference strains and 37 fresh isolates from faeces of men and pigs or caecal contents of mice, were used in comparing the conventional tube test with the Minitek system (BBL) to evaluate the feasibility of the latter to identify lactobacilli. In addition, the following parameters were tested: (i) the effect of variation in inoculum broth and cultural methods, (ii) the reproducibility of reactions on each substrate. The Minitek system includes a new lactobacilli inoculum broth (LIB) and three substrates: ribose, melezitose, and amygdalin. The overall correlation was 84% by the anaerobic steel-wool jar method and 72.5% by overlaying sterile oil with the Minitek inoculum broth (MIB) for the identification of anaerobes; whereas with LIB, the overall agreement was 95.4% by the anaerobic jar method and 84.4% by the oil procedure. The agreement of the identification between the Minitek systems and conventional tests was best (85.9%) with LIB by the anaerobic jar method and poorest with the MIB overlaid with oil. In the reproducibility of reactions, 247 (17.2%) of a total of 1,440 sets of disks gave variable reactions with MIB when incubated under the anaerobic jar method as compared to only 29 (2.0%) with LIB. The Minitek system for the identification of lactobacilli is more accurate and reliable when inoculated with LIB and incubated under the anaerobic jar method.

Bacteroides pyogenes sp. nov., Bacteroides suis sp. nov., and Bacteroides helcogenes sp. nov., New Species from Abscesses and Feces of Pigs.

Bacteroides pyogenes, Bacteroides suis and Bacteriodes helcogenes, three new species isolated from abscesses and feces of pigs, are described. They are obligately anaerobic, Gram-negative, non-motile, non-pigment-forming, non-spore-forming rods that produce succinic and acetic acids (often with traces of propionic and isovaleric acids) in peptone-yeast-glucose medium and do not grow well in 20% bile. The newly described species are phenotypically similar to strains of B. ruminicola and B. oralis. However, the new species have a low level of DNA /DNA homology with B. ruminicola, B. oralis and related organisms and also with each other.

Effect of bifidobacteria feeding on fecal flora and production of immunoglobulins in lactating mouse.

To elucidate the effects of probiotics on the stimulation of immunoglobulin production during lactation, feeding trials of bifidobacteria in lactating mice were conducted. Bifidobacteria appeared in feces at 9.67+/-0.17 log 10 number per gram levels. All bifidobacteria found in the feces were the administered strain. Mice fed bifidobacteria for 12 days showed significantly high levels of fecal total IgA compared to that of the control group (P < 0.05). The levels of anti-beta-lactoglobulin IgA in milk as well as in fecal extracts were significantly higher in the bifidobacteria-fed group than that of the control group (P < 0.05). These results suggest that the intake of bifidobacteria can enhance local production of IgA in milk and the intestine, which may help to protect both pups and dams from exposure to food antigens.

Effect of a probiotic formula on intestinal immunoglobulin A production in healthy children.

The anti-infectious effect of probiotics has recently been reported and one mechanism may be the non-specific stimulation of immunity. This study was performed to elucidate the influence of a probiotic formula on intestinal microflora and local immunity in healthy children. A follow-up formula containing viable bifidobacteria was given to seven healthy Japanese children (15 to 31 months old) for 21 days. During intake of the formula, the administered strain was detected in feces from five subjects (71%) and total fecal bifidobacteria slightly increased. Fecal levels of total IgA and anti-poliovirus IgA during intake of the formula were significantly higher than those before intake (P < 0.05). The increase in local IgA levels resulting from ingestion of the probiotic formula may contribute to enhancement of the mucosal resistance against gastrointestinal infections.

Effect of Konjac mannan on intestinal microbial metabolism in mice bearing human flora and in conventional F344 rats.

The effects of dietary Konjac mannan (KM), a frequent ingredient of traditional Japanese foods, on intestinal microbial metabolism and microflora composition were investigated using two laboratory animal models, namely, conventional F344 rats and C3H/He male mice bearing human flora. Dietary KM led to a significant reduction in faecal beta-glucuronidase, nitroreductase and azoreductase activities, and in the production of phenol and indole in the faeces of conventional F344 rats. In the C3H/He male mice bearing human flora, faecal beta-glucuronidase and nitroreductase activities were significantly reduced by KM ingestion, as were the amounts of the putrefactive products, p-cresol and indole, in the faeces. Slight differences in intestinal microflora composition between control and KM diet groups were noted. The results indicate that, in C3H/He male mice bearing human flora, dietary KM may modify microbial metabolism without causing significant alterations in intestinal microflora composition.