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1.
Abstract The chick embryo model was evaluated as a method to compare virulence between selected strains of Neisseria meningitidis . Inoculation of 13-day-chick embryos via the egg yolk distinguished strains having an LD50 of 103 colony forming units (CFU) or greater (low virulence) from those having an LD50 of approximately 101 or less (high virulence). A strain of serogroup B and a spontaneous nonpiliated strain of group C were found to be of relatively high virulence while a strain of N. lactamica , a serogroup A carrier strain, and certain nongroupable strains were found to be of low virulence. Strains having an LD50 of 102 were not differentiated from either of these. Alternatively, inoculation of the chorioallantoic membrane (CAM) of 9-day-old chick embryos statistically differentiated most strains of N. meningitidis although inoculation via this route was less sensitive.  相似文献   

2.
Abstract: [3H]Strychnine specifically binds to membrane fractions isolated from rat retinae. The binding is saturable, with an apparent dissociation constant, K D, of 14.3 × 10−9 M and 205 fmol bound/mg protein. Specific binding is time-dependent and proportional to protein concentration. Glycine and taurine are equally potent inhibitors of [3H]strychnine binding ( K i= 4 × 10−5 M); no other amino acids endogenously present in the retina inhibited [3H]strychnine binding.  相似文献   

3.
Abstract: The present study addresses the possibility that there are different cocaine-related and mazindol-related binding domains on the dopamine transporter (DAT) that show differential sensitivity to cations. The effects of Zn2+, Mg2+, Hg2+, Li+, K+, and Na+ were assessed on the binding of [3H]mazindol and [3H]WIN 35,428 to the human (h) DAT expressed in C6 glioma cells under identical conditions for intact cell and membrane assays. The latter were performed at both 0 and 21°C. Zn2+ (30–100 µ M ) stimulated binding of both radioligands to membranes, with a relatively smaller effect for [3H]mazindol; Mg2+ (0.1–100 µ M ) had no effect; Hg2+ at ∼3 µ M stimulated binding to membranes, with a relatively smaller effect for [3H]mazindol than [3H]WIN 35,428 at 0°C, and at 30–100 µ M inhibited both intact cell and membrane binding; Li+ and K+ substitution (30–100 m M ) inhibited binding to membranes more severely than to intact cells; and Na+ substitution was strongly stimulatory. With only a few exceptions, the patterns of ion effects were remarkably similar for both radioligands at both 0 and 21°C, suggesting the involvement of common binding domains on the hDAT impacted similarly by cations. Therefore, if there are different binding domains for WIN 35,428 and mazindol, these are not affected differentially by the cations studied in the present experiments, except for the stimulatory effect of Zn2+ at 0 and 21°C and Hg2+ at 0°C.  相似文献   

4.
The sludge from hospital waste treatment facilities is a potential source of infectious organisms. The average numbers of micro-organisms in the sludge of hospital wastewater in Taiwan were as follows: total count 8·1 × 107 cfu g−1 (dry weight of sludge), and 1·4 × 106, 3·6 × 105, 1·6 × 105, 2·2 × 105 and 5·5 × 104 cfu g−1 (dry weight of sludge) for total coliforms, faecal coliforms, faecal streptococci, Pseudomonas aeruginosa and Salmonella spp., respectively . Salmonella spp. were detected in 37% (10 of 27) of the sludges from hospital wastewaters. Therefore, the treatment of such sludge to reduce pathogenic micro-organisms should be considered.  相似文献   

5.
Rapid Brain Uptake of Manganese(II) Across the Blood-Brain Barrier   总被引:1,自引:0,他引:1  
Abstract: 54Mn2+ uptake into brain and choroid plexus from the circulation was studied using the in situ rat brain perfusion technique. Initial uptake from blood was linear with time (30 s to 6 min) and extrapolated to zero with an average transfer coefficient of ∼6 × 10-5 ml/s/g for brain and ∼7 × 10-3 ml/s/g for choroid plexus. Influx from physiologic saline was three- to fourfold more rapid and exceeded that predicted for passive diffusion by more than one order of magnitude. The lower uptake rate from blood could be explained by plasma protein binding as the free fraction of 54Mn2+ in rat plasma was ≤30%. Purified albumin, transferrin, and α2-macroglobulin were each found to bind 54Mn2+ significantly and to restrict brain 54Mn2+ influx. The results demonstrate that 54Mn2+ is readily taken up into the CNS, most likely as the free ion, and that transport is critically affected by plasma protein binding. The results support the hypothesis that Mn2+ transport across the blood-brain barrier is facilitated by either an active or a passive mechanism.  相似文献   

6.
The efficacy of high-temperature, short-time (HTST) pasteurization (72 °C/15 s) when low numbers (≤ 103 cfu ml −1 ) of Mycobacterium paratuberculosis are present in milk was investigated. Raw cows' milk spiked with Myco. paratuberculosis (103 cfu ml−1, 102 cfu ml−1, 10 cfu ml−1, and 10 cfu 50 ml−1) was subjected to HTST pasteurization using laboratory pasteurizing units. Ten bovine strains of Myco. paratuberculosis were tested in triplicate. Culture in BACTEC Middlebrook 12B radiometric medium detected acid-fast survivors in 14·8% and 10% of HTST-pasteurized milk samples at the 103 and 102 cfu ml−1 inoculum levels, respectively, whereas conventional culture on Herrold's egg yolk medium containing mycobactin J detected acid-fast survivors in only 3·7% and 6·7% of the same milk samples. IS900-based PCR confirmed that these acid-fast survivors were Myco. paratuberculosis . No viable Myco. paratuberculosis were isolated from HTST-pasteurized milk initially containing either 10 cfu ml−1 or 10 cfu 50 ml−1.  相似文献   

7.
The pathogenic activities in vitro and in vivo of live bacteria and extracellular products (ECP) of 24 motile Aeromonas strains were investigated. Most Aer. hydrophila and Aer. jandaei isolates were pathogenic for eels (LD50 105·4-107·6 cfu fish-1) but no Aer. sobria , Aer. caviae and Aer. allosaccharophila caused mortality in eels at doses of > 108·4 cfu fish-1. Of these Aeromonas strains, Aer. hydrophila and Aer. jandaei in particular produced elastases and haemolysins against fish erythrocytes. ECP from Aer. hydrophila and Aer. jandaei caused degenerative changes in fish cell lines and were strongly toxic for eels (LD50 1·0–3·2 μg (g fish)-1) reproducing the symptoms associated with natural disease. ECP from non-pathogenic species were inactive on fish cell lines as well as being poorly lethal for eels (LD50 > 9·2 μg (g fish)-1). All these biological activities of Aeromonas ECP were lost after heat treatment. These findings indicate differences between pathogenic and non-pathogenic Aeromonas species with respect to the expression of virulence factors, and show that elastases, haemolysins and exotoxins play a leading role in the pathogenicity of motile Aeromonas for eels.  相似文献   

8.
Abstract The transferrin-iron uptake system of six Neisseria meningitidis strains was characterized using 125I-transferrin in receptor assays and 55Fe-loaded transferrin in uptake assays. Receptors for transferrin varied among the strains both in number (from 700 to 4700 receptors per cell) and in their affinity constants for the protein ( K a ranged from 0.7×107 to 4.0×107 1 mol−1). Neither receptor numbers nor affinity constants were significantly different in carrier and invasive strains, although the Ka seem to be somewhat higher in the latter. Iron uptake from transferrin was also variable among the strains, but showed the same lack of correlation with their origin.  相似文献   

9.
Abstract M proteins are major virulence factors of group A streptococci which enable the bacteria to resist phagocytic attack. Their binding capacity for different plasma proteins seems to be one reason for the antiphagocytic activity of M protein. In the present study we demonstrate that M3 protein, isolated from the streptococcal culture supernatant of strain 4/55, and the recombinant form (rM3), purified from an E. coli lysate after cloning in phage γ-EMBL3, show a multiple binding to fibrinogen, albumin and fibronectin in Western blot and dot binding assays. Binding of M3 protein to the multifunctional extracellular matrix and plasma protein fibronectin may not only influence phagocytosis but may also contribute to the adherence of these bacteria to endothelial and epithelial cells.  相似文献   

10.
Fibrinogen is known to bind to group A streptococci and precipitate with extracts containing streptococcal M protein. We have previously shown that the binding of fibrinogen to M-positive streptococci prevents opsonization by complement and protects that organism from phagocytosis in nonimmune blood. In the present study, we used 3H-labeled fibrinogen, a highly purified peptide fragment of type 24 M protein (pep M24), and anti-pep M sera to show that fibrinogen binds to M-positive streptococci with high affinity (dissociation constants, 1 to 5 nM); occupation of the high-affinity binding sites suffices to protect the organism from phagocytosis; proteolytic treatments that remove M protein from streptococcal cells abolish binding; binding is competitively inhibited by anti-pep M sera; pep M24 precipitates fibrinogen; and binding to type 24 cells is inhibited by pep M24. We conclude that M protein is the cell surface structure principally responsible for binding fibrinogen on the surface of M-positive streptococci and that this binding contributes to the known antiopsonic property of M proteins.  相似文献   

11.
Burgos cheese was manufactured from pasteurized ewes milk inoculated with Staphylococcus aureus strains FRI 137 and FRI 361, at levels of ca 103 and 105 cfu/ml and stored at 4°, 10° and 15°C and at room temperature (10°-15°C). Populations of Staph. aureus and mesophilic aerobes, pH, and production of thermonuclease and enterotoxins C1 and C2 were investigated. Aerobic counts increased during cheese-making and storage. With both test strains, important growth was observed only during the storage period, the larger levels corresponding to the higher temperatures. Although Staph. aureus strains attained populations of over 108 cfu/g, no enterotoxin was detected. Strain FRI 361 reached 107 cfu/g without production of a detectable amount of thermonuclease. With strain FRI 137, the minimal population associated with enzyme activity was influenced by the inoculum size. Staphylococcus aureus counts are better indicators of staphylococcal growth in Burgos cheese than the thermonuclease test.  相似文献   

12.
Abstract: A tritiated heptapeptide, [3H]Tyr-Gly-Gly-Phe-Met-Arg-Phe ([3H]Met-enkephalin-Arg6-Phe7), with high specific radioactivity has been synthesized in order to characterize its opioid binding activity to frog brain membrane fractions. The apparent K D value of the radioligand calculated from homologous displacement experiments was 3.4 n M , and the maximal number of specific binding sites was 630 fmol/mg of protein. The K D determined from equilibrium saturation binding studies was found to be 3.6 n M . However, the Hill coefficient was far below unity ( n H = 0.43), which suggests the presence of a second, lower affinity binding site. The presence of this binding component is strengthened by the displacement experiments performed with levorphanol and some other ligands. It is assumed that the lower affinity site has no opiate character. The rank order of potency of the applied ligands in competing reversibly with [3H]Met-enkephalin-Arg6-Phe7 binding reflects a κ2- and/or δ-subtype specificity of the heptapeptide. Binding to a κ1 and/or μ site of opioid receptors is excluded, but the existence of a novel endogenous opiate receptor subtype for Met-enkephalin-Arg6-Phe7 in frogs cannot be ruled out. The [3H]Met-enkephalin-Arg6-Phe7 binding was inhibited by both sodium ions and GppNHp, which suggests the opioid agonist character of the heptapeptide.  相似文献   

13.
THE DISTRIBUTION OF GROUP D STREPTOCOCCI IN CATTLE AND SHEEP   总被引:3,自引:3,他引:0  
Numbers and types of Lancefield group D streptococci have been determined in samples from the colons of 17 cattle and 9 sheep. Mean total streptococcal counts of 8 × 104/g in cattle and 2 × 106/g in sheep were obtained. Streptococcus bovis was found in every sample and was the predominant species in 15 of the cattle and 6 of the sheep. Other group D streptococci ( Strep. faecalis, Strep. faecium and Strep. durans ) were rare in cattle, but in sheep they formed a significant proportion of the population. Of 60 Strep. faecium, Strep. durans and related strains, 51 fermented raffinose. Many of the strains of Strep. faecium were also atypical in that they fermented sorbitol and appreciably reduced tetrazolium in broth at pH 6.0.
Strep. bovis remained the predominant streptococcus in faeces samples from 4 dairy cows when they were tested again after an interval of 17 and 18 months.  相似文献   

14.
Abstract: Treatment of cultured bovine adrenal chromaffin cells with 12- O -tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C (PKC), decreased [3H]saxitoxin ([3H]STX) binding in a concentration (IC50 = 19 n M )- and time ( t 1/2 = 4.5 h)-dependent manner. TPA (100 n M for 15 h) lowered the B max of [3H]STX binding by 53% without altering the K D value. Phorbol 12,13-dibutyrate (PDBu) also reduced [3H]STX binding, whereas 4α-TPA, an inactive analogue, had no effect. The inhibitory effect of TPA was abolished when H-7 (an inhibitor of PKC), but not H-89 (an inhibitor of cyclic AMP-dependent protein kinase), was included in the culture medium for 1 h before and during TPA treatment. Simultaneous treatment with TPA in combination with either actinomycin D or cycloheximide, an inhibitor of protein synthesis, nullified the effect of TPA. TPA treatment also attenuated veratridine-induced 22Na+ influx but did not alter the affinity of veratridine for Na channels as well as an allosteric potentiation of veratridine-induced 22Na+ influx by brevetoxin. These results suggest that an activation of PKC down-regulates the density of Na channels without altering their pharmacological features; this down-regulation is mediated via the de novo synthesis of an as yet unidentified protein(s), rather than an immediate effect of Na channel phosphorylation.  相似文献   

15.
The in vitro antimicrobial activity of geraniol and citronellol towards seven strains of Erwinia amylovora , the causal agent of 'fire blight'of Rosaceous plants, was assessed in tube cultures. All of the strains tested at 1 × 105 cfu/ml were inhibited for 24 h by geraniol in the range 600–1500 mg/1, whereas its minimum bactericidal concentration was 800–1700 mg/1. Citronellol was less effective, being bactericidal for only two of seven strains. RIF-NY, isolated from apple orchards, was relatively resistant to geraniol; 1700 mg/1 of the chemical only reduced the growth of an inoculum of 1 × 107 cfu/ml. In general, such terpenoids commenced exerting a bactericidal effect 6 h after addition to the suspensions, even if geraniol added at 1700 mg/1 to 1 × 103 cfu/ml of five strains, commenced its bactericidal activity earlier than 6 h.  相似文献   

16.
The amylase-producing ability of the intestinal microflora in cultured specimens of ayu, carp, channel catfish, Japanese eel and tilapia was determined. Mean viable counts of aerobes and anaerobes ranged from 1·1×106 to 3·7×108 cfu g−1 and from 1·3×103 to 1·6×108 cfu g−1, respectively. Aeromonas spp. and Bacteroidaceae were predominant in four to five fish species. Of 206 strains examined, 65 (31·6%) produced ≥0·01 U amylase ml−1. The percentage of producers differed among families and genera of bacteria and fish species. While 56% of the anaerobes produced amylase, only 20% of the aerobes did. More than 50% of Aeromonas , Bacteroidaceae and Clostridium strains produced amylase efficiently while Acinetobacter , coryneforms, Enterobacteriaceae, Moraxella , Plesiomonas and Streptococcus strains did not. High amylase production (≥0·05 U ml−1) was found in 12 strains, 11 from Aeromonas and one Pseudomonas . The percentage of high amylase producers in Japanese eel was lower than the other four fish (2–30%). These results strongly suggest that the amylase produced by the intestinal microflora play an important role in the digestion of starch in freshwater fish to some extent.  相似文献   

17.
Abstract: The present study reports the ion dependency of 2β-carbomethoxy-3β-(4-fluorophenyl)[3H]tropane ([3H]- CFT) binding to the dopamine transporter in the rat striaturn. The results indicate that [3H]CFT binding to synaptosomal P2 membranes requires low concentrations of Na+ (peak binding between 20 and 50 m M Na+), is stimulated by phosphate anion or l-, but is unaffected or only slightly affected by F-, Cl-, Br-, NO3-, or SO42-, Concentrations of Na+ of >50 m M become inhibitory except in the presence of l-, which shifts peak binding levels toward higher Na+ concentrations and also elevates the peak binding level. K+ strongly decreased [3H]CFT binding with a shallow inhibition curve, and Na+ could not overcome this effect. Saturation analysis of [3H]CFT binding revealed a single binding site changing its affinity for CFT depending on the concentration of sodium phosphate buffer (6, 10, 30, 50, 130, or 200 m M ; 1 mM plus 49 mM NaCIversus 10 m M plus 40 m M NaCI; or 1 mM plus 129 m M Nal versus 10 m M plus 120 m M Nal). No differences were observed in the density of CFT binding sites between any of the conditions examined.  相似文献   

18.
In vitro and in planta sensitivity of an indirect enzyme-linked immunoassaytechnique, using a monoclonal antibody specific for the lipopolysaccharide (LPS) of Xanthomonas campestris pv. vesicatoria , was increased 10-foldby using a newextraction buffer (gl of : KH2PO4, 2; NaHPO4, 11·5; EDTAdisodium, 0·14; thimerosal, 0·02; and lysozyme, 0·2). The procedure improvedsensitivity without increasing background levels. In vitro , the limit of detection wasbetween 1×107 and 1×108 cells ml−1 with the conventionalextraction buffer phosphate-buffered saline (PBS) and less than 1×106 cells ml−1 when lysozyme extraction buffer was substituted for PBS. In comparing 22 X. c.vesicatoria strains, absorbance readings were increased close to three-fold with the lysozymeextraction buffer as opposed to PBS. When leaf tissue extract was spiked with the bacterium, thelimit of detection was 1×107 cfu ml−1 and 1×108 cfu ml−1 with the lysozyme solution and PBS, respectively, as the extraction buffers. Whenusing the lysozyme extraction buffer in combination with a commercial amplification system, thelimit of detection was decreased to less than 1×105 cfu ml−1 in leaftissue. The addition of the lysozyme and EDTA to the phosphate buffer resulted in release of asignificant quantity of LPS and concomitant dramatic increase in sensitivity. The new procedure,termed lysozyme ELISA (L-ELISA), should increase sensitivity of ELISA reactions where LPS isthe reacting epitope.  相似文献   

19.
Abstract The relationship between the cytotoxic effect and binding to different cell lines of Clostridium perfringens enterotoxin was investigated. The enterotoxin released 51Cr from Vero and MDCK cells labeled with Na2-51CrO4. The effect varied depending upon the dose of enterotoxin and the duration and temperature of the interaction. The enterotoxin gave no effect on FL, KB, or L-929 cells. [125I]Enterotoxin bound specifically to Vero and MDCK cells via a binding site of distinct nature, but not to FL, KB, or L-929 cells. The number of the binding sites located on one MDCK cell (1.98 × 106 sites/cell) was three times that on one Vero cell (5.64 × 105 sites/cell), although the binding affinity of MDCK cell ( K a/ 3.76 × 107 M−1) was 0.1 that of Vero cells ( K a/ 3.23 × 108 M−1). Binding of the enterotoxin to susceptible cells was temperature-independent.  相似文献   

20.
Abstract A method was developed for direct extraction, purification and amplification of DNA from forest soil. Eighty-two % of the DNA in Pseudomonas aeruginosa UG2Lr introduced into soil was recovered. The detection limit for the strain was approximately 800 cfu g−1 of dry soil based on the polymerase chain reaction (PCR). Survival of κ-carrageenan-encapsulated and unencapsulated UG2Lr was monitored by antibiotic selective and bioluminescence-based nonselective plating and PCR-amplification of a tnsA fragment. After freeze-thaw treatment of soil samples, the unencapsulated UG2Lr declined from an initial population density of 1 × 109 cfu g−1 of dry soil to below the detection threshold of both selective (14 cfu g−1 of dry soil) and nonselective (1 × 103 cfu g−1 of dry soil) plating. However, presence of nonculturable UG2Lr cells in the soil was revealed by PCR and resuscitation of the bacteria. Population density of the encapsulated UG2Lr increased from 2.7 × 106 to 2.9 × 108 cfu g−1 of dry soil after a 3-week incubation at 22°C and declined to 6.3 × 106 cfu g−1 of dry soil after the freeze-thaw treatment.  相似文献   

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