一株携带质粒的人两歧双歧杆菌的分离与鉴定

目的:分离携带天然质粒的人双歧杆菌.方法:用自制的改良型Blb双歧杆菌选择培养基,从人新鲜粪便分离双歧杆菌,对初步质粒检测阳性的单菌落通过糖发酵试验、(G C)mol%测定和16S rDNA序列分析,进行菌株鉴定.结果:筛选到一株携带天然质粒的人双歧杆菌,编号B200304,在1.0%琼脂糖凝胶上,测得质粒的相对分子质量约为22 kb.通过对该菌株的形态学观察和糖发酵试验等生理生化特征研究,证明该菌株为两歧双歧杆菌(Bifidobacterium bifidum);HPLC法测得其(G C)mol%为55.6,16SrDNA序列分析进一步证实该菌株为两歧双歧杆菌.结论:分离得到一株携带天然质粒的人两歧双歧杆菌新菌株.     

Genetic monogamy in blue-headed vireos and a comparison with a sympatric vireo with extrapair paternity

Based on the breeding synchrony hypothesis, we predicted, intwo congeners that nest in simiilar habitat but differ in nestingsynchrony, that blue-headed vireos (Vireo solitarius) wouldhave fewer extrapair fertilizations (EPFs) thaii red-eyed vireos(V. olivaceus EPFs were rare in blue-headed vireos (1/37 nestlings),but common in red-eyed vireos (11/19 nestlings). We studiedthe behavior of blue-headed vireos to determine what factorscould promote genetic monogamy. We found no evidence that malesmate guarded to prevent extrapair copulations from occurring.Males did not follow fertile mates closely when mates left thenest (14–25% of female departures) and, during the egg-layingperiod, males were often alone on the nest (22.3 mm/h). Femaleblue-headed vireos, but not red-eyed vireos, obtain direct benefitsfrom social mates such as nest building and incubation (49.1%of the total), and they assess male quality long before becomingfertile. Female blue-headed vireos spent more time incubatingwhen their mates had low incubation effort. Furthermore, maleincubation effort was positively correlated with nest survivalduring incubation. We discuss the evolution of genetic monogamyand sex role convergence in blue-headed vireos in relation toasynchronous breeding.     

Reversible and specific interaction of dehydrogenases with a coenzyme-coated surface continuously monitored with a reflectometer

Reversible affinity binding of NAD-dependent dehydrogenase to an NAD-coated silicon surface ("NAD biochip") has been accomplished. The silicon surface, which is favorable for use with optical techniques because of its excellent reflection properties, was precoated with a polymer to prevent nonspecific and irreversible adsorption. Using a new reflectometry technique based on measurement of the polarization change of light reflected upon the biochip, continuous monitoring of the affinity binding and subsequent desorption of alcohol dehydrogenase and lactate dehydrogenase from the NAD surface were possible; allowing repeated use of the same NAD chip--an advantage when the assay was carried out in a continuous reflectometer. With a flow rate of 0.5 ml/min, response times on the order of 30 s were obtained.     

Men Who Have Sex with Men (MSM) and Factors Associated with Not Using a Condom at Last Sexual Intercourse with a Man and with a Woman in Senegal

Background

Men who have sex with other men (MSM) are a vulnerable population in Africa that has been insufficiently explored. Given the high rate of bisexuality among MSM (73% in the past year), it is important to understand their risk-taking behaviors regarding both men and women.

Methodology/Principal Findings

A socio-behavioral survey was carried out in 2007 among 501 MSM recruited using the snowball sampling method. We explore in this article why a condom was not used during last sexual intercourse with a man and with a woman, taking into account the respondent''s characteristics, type of relationship and the context of the sexual act. In the survey, 489 men reported that they had had sexual intercourse at least once with another man during the previous year, and 358 with a man and with a woman. The main risk factors for not using a condom at last sexual intercourse with another man were having sex in a public place (aOR = 6.26 [95%CI: 2.71–14.46]), non-participation in an MSM prevention program (aOR = 3.47 [95%CI: 2.12–5.69]), a 19 years old or younger partner (aOR = 2.6 [95%CI: 1.23–4.53]), being 24 years or younger (aOR = 2.07 [95%CI: 1.20–3.58]) or being 35 years or over (aOR = 3.08 [95%CI:1.11–8.53]) and being unemployed (aOR = 0.36 [95%CI: 0.10–1.25]). The last sexual intercourse with the respondent''s wife was hardly ever protected (2%). With women, the other factors were a 15 years or younger partner (aOR = 6.45 [95%CI: 2.56–16.28]), being educated (primary: aOR = 0.45 [95%CI: 0.21–0.95], secondary or higher: aOR = 0.26 [95%CI: 0.11–0.62]), being a student (aOR = 2.20 [95%CI: 1.07–4.54]) or unemployed (aOR = 3.72 [95%CI: 1.31–10.61]) and having participated in a MSM prevention program (aOR = 0.57 [95%CI: 0.34–0.93]).

Conclusion

Having participated in a prevention program specifically targeting MSM constitutes a major prevention factor. However, these programs targeting MSM must address their heterosexual practices and the specific risks involved.     

Lactate dehydrogenase associated with the mitochondrial fraction and with a mitochondrial inhibitor--II. Enzyme interaction with a mitochondrial inhibitor

A LDH inhibitor has been isolated from the LDH-free crude mitochondrial fraction of rabbit skeletal muscle. The inhibitor is only released after solubilization of the particle bound enzyme. It only interacts with soluble LDH, since the enzyme bound to the mitochondrial fraction was not inhibited. The inhibitor molecular weight is above 10,000 dalton, it is precipitated by 7.5% trichloroacetic acid or 80% (NH4)2SO4 saturation. It is highly stable to heat and pH variations. The inhibitor only interacts with the enzyme at ionic strengths below 20 mM and at pH 6.0 or less. The kinetic behavior of the inhibited enzyme is non-hyperbolic and is similar to the mitochondrial fraction bound enzyme.     

Monitoring bird migration with a fixed-beam radar and a thermal-imaging camera

ABSTRACT.   Previous studies using thermal imaging cameras (TI) have used target size as an indicator of target altitude when radar was not available, but this approach may lead to errors if birds that differ greatly in size are actually flying at the same altitude. To overcome this potential difficulty and obtain more accurate measures of the flight altitudes and numbers of individual migrants, we have developed a technique that combines a vertically pointed stationary radar beam and a vertically pointed thermal imaging camera (VERTRAD/TI). The TI provides accurate counts of the birds passing through a fixed, circular sampling area in the TI display, and the radar provides accurate data on their flight altitudes. We analyzed samples of VERTRAD/TI video data collected during nocturnal fall migration in 2000 and 2003 and during the arrival of spring trans-Gulf migration during the daytime in 2003. We used a video peak store (VPS) to make time exposures of target tracks in the video record of the TI and developed criteria to distinguish birds, foraging bats, and insects based on characteristics of the tracks in the VPS images and the altitude of the targets. The TI worked equally well during daytime and nighttime observations and best when skies were clear, because thermal radiance from cloud heat often obscured targets. The VERTRAD/TI system, though costly, is a valuable tool for measuring accurate bird migration traffic rates (the number of birds crossing 1609.34 m [1 statute mile] of front per hour) for different altitudinal strata above 25 m. The technique can be used to estimate the potential risk of migrating birds colliding with man-made obstacles of various heights (e.g., communication and broadcast towers and wind turbines)—a subject of increasing importance to conservation biologists.     

An epidemiological model with a delay and a nonlinear incidence rate

An epidemiological model with both a time delay in the removed class and a nonlinear incidence rate is analysed to determine the equilibria and their stability. This model is for diseases where individuals are first susceptible, then infected, then removed with temporary immunity and then susceptible again when they lose their immunity. There are multiple equilibria for some parameter values, and, for certain of these, periodic solutions arise by Hopf bifurcation from the large nontrivial equilibrium state.Research supported in parts by Centers for Disease Control Contract 200-87-0515Research supported in part by NSERC A-8965     

Isolation and identification of a calicivirus from a dog with diarrhoea

The isolation and the characterisation of a calicivirus strain (213/95) from a dog with diarrhoea are reported. The virus grows only in cell cultures of feline origin (Crandell Feline Kidney Cells), and in neutralisation test the isolate demonstrated a slight antigenic correlation with the reference feline calicivirus strain (FCV-F9).     

Apolipoprotein(a) and plasminogen interactions with fibrin: a study with recombinant apolipoprotein(a) and isolated plasminogen fragments.

Lipoprotein(a) [Lp(a)], but not low-density lipoprotein (LDL), was previously shown to impair the generation of fibrin-bound plasmin [Rouy et al. (1991) Arterioscler. Thromb. 11, 629-638] by a mechanism involving binding of Lp(a) to fibrin. It was therefore suggested that the binding was mediated by apolipoprotein(a) [apo(a)], a glycoprotein absent from LDL which has a high degree of homology with plasminogen, the precursor of the fibrinolytic enzyme plasmin. Here we have evaluated this hypothesis by performing comparative fibrin binding studies using a recombinant form of apo(a) containing 17 copies of the apo(a) domain resembling kringle 4 of plasminogen, native Lp(a), and Glu-plasminogen (Glu1-Asn791). Attempts were also made to identify the kringle domains involved in such interactions using isolated elastase-derived plasminogen fragments. The binding experiments were performed using a well-characterized model of an intact and of a plasmin-digested fibrin surface as described by Fleury and Anglés-Cano [(1991) Biochemistry 30, 7630-7638]. Binding of r-apo(a) to the fibrin surfaces was of high affinity (Kd = 26 +/- 8.4 nM for intact fibrin and 7.7 +/- 4.6 nM for plasmin-degraded fibrin) and obeyed the Langmuir equation for adsorption at interfaces. The binding to both surfaces was inhibited by the lysine analogue AMCHA and was completely abolished upon treatment of the degraded surface with carboxypeptidase B, indicating that r-apo(a) binds to both the intrachain lysines of intact fibrin and the carboxy-terminal lysines of degraded fibrin. As expected from these results, both r-apo(a) and native Lp(a) inhibited the binding of Glu-plasminogen to the fibrin surfaces.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction of a high-current electron beam with hybrid waveguide and plasma modes in a dielectric Cherenkov maser with a plasma layer

The characteristics of a high-current electron beam-driven microwave amplifier—a dielectric Cherenkov maser—are investigated in the framework of linear theory for the case of a plasma layer present at the surface of the maser slow-wave structure. The dispersion relation for axisymmetric perturbations is obtained for the conventional configuration (a circular dielectric-lined waveguide and a thin annular beam propagating within the vacuum region inside the annular plasma) in the model of a fully magnetized plasma and beam. The results of numerically solving the dispersion relation for different beam and plasma parameters are presented, and an analysis based on these results is given with regard to the features of the beam interaction with the hybrid waves of the system (both hybrid waveguide and hybrid plasma modes). For the hybrid waveguide mode, the dependences of the spatial growth rate on the frequency demonstrate an improvement in the gain at moderate plasma densities, along with narrowing the amplification band and shifting it toward higher frequencies. For the hybrid plasma mode, the interaction with a mildly relativistic (200–250 keV) beam, when the wave phase velocity is close to the speed of light in the dielectric medium, is most interesting and, therefore, has been studied in detail. It is shown that, depending on the beam and plasma parameters, different regimes of the hybrid plasma mode coupling to the hybrid waveguide mode or a usual, higher order plasma mode take place; in particular, a flat gain vs. frequency dependence is possible over a very broad band. The parameters at which the ?3-dB bandwidth calculated for the 30-dB peak gain exceeds an octave are found.     

Angiotensin and thirst: studies with a converting enzyme inhibitor and a receptor antagonist

Although exogenous angiotensin is recognized as a potent dipsogen, the participation of endogenous angiotensin in thirst has not been well established. To investigate this question, we produced thirst in rats by relative cellular dehydration (hypertonic NaCl injection), or hypovolemia (hyperoncotic polyethylene glycol injection). An angiotensin receptor antagonists (sar(1)-ala(8)- angiotensin II, P-113), or a converting enzyme inhibitor (SQ, 20, 881, SQ) given to thirsty rats by intracerebroventricular (IVT) or peripheral routes. P-113 infused i.v. (10 μg/kg/min) or injected IVT (10 μg) did not alter the drinking response to either thirst stimulus. The latter treatment reduced the drinking response to 50 ng of IVT angiotensin II (p < 0.005). SQ given i.m. (2 mg/kg), IVT (2 × 50 μg), or both routes did not alter relative cellular dehydration thirst. Injection of SQ IVT did not alter hypovolemic thirst, whereas a significantly (p < 0.005) enhanced response occured after i.m. SQ. The enhanced response was not observed when animals were given both IVT and i.m. SQ. The IVT treatment with SQ markedly reduced (P < 0.005) drinking after 50 ng IVT angiotensin I. The data demonstrate that inhibition of angiotensin receptors or converting enzyme does not prevent appropriate drinking responses to primary thirst stimuli. Thus, if angiotensin participates in these endogenous thirst drives, its role is not an absolute requirement.     

Aph2, a protein with a zf-DHHC motif,interacts with c-Abl and has pro-apoptotic activity

c-Abl is a non-receptor tyrosine kinase implicated in DNA damage-induced cell death and in growth factor receptor signaling. To further understand the function and regulation of c-Abl, a yeast two-hybrid screen was performed to identify c-Abl-interacting proteins. Here we report the identification of Abl-philin 2 (Aph2), encoding a novel protein with a unique cysteine-rich motif (zf-DHHC) and a 53-amino acid stretch sharing homology with the creatine kinase family. The zf-DHHC domain is highly conserved from yeast to human. Two proteins containing this motif, Akr1p and Erf2p, have been characterized in Saccharomyces cerevisiae, both implicated in signaling pathways. Deletion analysis by two-hybrid assays revealed that the N-terminal portion of Aph2 interacts with the C terminus of c-Abl. Aph2 was demonstrated to interact with c-Abl by co-immunoprecipitation assays. Aph2 is expressed in most tissues tested and is localized in the cytoplasm, mainly in the endoplasmic reticulum (ER). The sequences required for ER location reside in the N terminus and the zf-DHHC motif of Aph2. It has been reported that a portion of c-Abl is localized in the ER. We demonstrate here that Aph2 and c-Abl are co-localized in the ER region. Overexpression of Aph2 leads to apoptosis as justified by TUNEL assays, and the induction of apoptosis requires the N terminus. Co-expression of c-Abl and Aph2 had a synergistic effect on apoptosis induction and led to a decreased expression of both proteins, suggesting either that these two proteins are mutually down-regulated or that cells expressing both c-Abl and Aph2 rapidly disappeared from the culture. These results suggest that Aph2 may be involved in ER stress-induced apoptosis in which c-Abl plays an important role.     

Plasmids associated with a phagelike particle and with a satellite inclusion in Bacillus thuringiensis ssp. israelensis

Variants of Bacillus thuringiensis ssp. israelensis were isolated using a 42 degrees C plasmid curing method. Those that were missing the large toxic crystalline inclusion still possessed in their sporulated cells a small inclusion similar to the satellite inclusion of the wild type. These crystal-minus but satellite-positive variants, like the wild type, produced sporulation-dependent phagelike particles; variants lacking both the crystal and the satellite did not. These latter strains lacked both a 75 and a 68 megadalton plasmid present in the wild type. However, a crystal-positive, satellite-minus strain possessing the 75 but lacking the 68 megadalton plasmid produced the phagelike particles. Examination of recipient strains that were initially devoid of crystal, satellite, and plasmids revealed the satellite and phagelike producing characteristics could have been cotransformed with the 68 megadalton plasmid. Likewise the toxic crystal and phagelike particle producing characters could have been cotransformed into a recipient which had acquired the 75 megadalton plasmids already known to be associated with the synthesis of the crystal inclusion. Thus the gene coding for the satellite inclusion appears to reside in the 68 megadalton plasmid, while that coding for the phagelike particle can reside in either the 68 or 75 megadalton plasmid.