Selection of cellular genetic markers for the detection of infectious poliovirus.

AIMS: Cellular responses of an established cell line from human intestinal epithelial cells (INT-407 cells) against poliovirus (PV) infections were investigated in order to find cellular genetic markers for infectious PV detection. METHODS AND RESULTS: Gene expression profile of INT-407 cells was analysed by DNA microarray technique when cells were infected with poliovirus 1 (PV1) (sabin) at multiplicity of infection of 10-3 and incubated for 12 h. Poliovirus infection significantly altered the gene expressions of two ion channels, KCNJ4 and SCN7A. The expression profile of KCNJ4 gene was further investigated by real-time RT-qPCR, and it was found that KCNJ4 gene was significantly regulated at 24 h postinfection of PV1. CONCLUSIONS: KCNJ4 gene, coding a potassium channel protein, is proposed as a cellular genetic marker for infectious PV detection. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to show the availability of cellular responses to detect infectious PV. The selection of cellular genetic markers for infectious viruses using DNA microarray and RT-qPCR can be applicable for the other enteric viruses.

Structure and function of neonatal social communication in a genetic mouse model of autism.

A critical step toward understanding autism spectrum disorder (ASD) is to identify both genetic and environmental risk factors. A number of rare copy number variants (CNVs) have emerged as robust genetic risk factors for ASD, but not all CNV carriers exhibit ASD and the severity of ASD symptoms varies among CNV carriers. Although evidence exists that various environmental factors modulate symptomatic severity, the precise mechanisms by which these factors determine the ultimate severity of ASD are still poorly understood. Here, using a mouse heterozygous for Tbx1 (a gene encoded in 22q11.2 CNV), we demonstrate that a genetically triggered neonatal phenotype in vocalization generates a negative environmental loop in pup-mother social communication. Wild-type pups used individually diverse sequences of simple and complicated call types, but heterozygous pups used individually invariable call sequences with less complicated call types. When played back, representative wild-type call sequences elicited maternal approach, but heterozygous call sequences were ineffective. When the representative wild-type call sequences were randomized, they were ineffective in eliciting vigorous maternal approach behavior. These data demonstrate that an ASD risk gene alters the neonatal call sequence of its carriers and this pup phenotype in turn diminishes maternal care through atypical social communication. Thus, an ASD risk gene induces, through atypical neonatal call sequences, less than optimal maternal care as a negative neonatal environmental factor.

Bayesian modeling of virus removal efficiency in wastewater treatment processes.

Left-censored datasets of virus density in wastewater samples make it difficult to evaluate the virus removal efficiency in wastewater treatment processes. In the present study, we modeled the probabilistic distribution of virus removal efficiency in a wastewater treatment process with a Bayesian approach, and investigated how many detect samples in influent and effluent are necessary for accurate estimation. One hundred left-censored data of virus density in wastewater (influent and effluent) were artificially generated based on assumed log-normal distributions and the posterior predictive distribution of virus density, and the log-ratio distribution were estimated. The estimation accuracy of distributions was quantified by Bhattacharyya coefficient. When it is assumed that the accurate estimation of posterior predictive distributions is possible when a 100% positive rate is obtained for 12 pairs of influent and effluent, 11 out of 144, 60 out of 324, and 201 out of 576 combinations of detect samples gave an accurate estimation at the significant level of 0.01 in a Kruskal-Wallis test when the total sample number was 12, 18, and 24, respectively. The combinations with the minimum number of detect samples were (12, 9), (16, 10), and (21, 8) when the total sample number was 12, 18, and 24, respectively.

Human herpesvirus 6 reactivation on the 30th day after allogeneic hematopoietic stem cell transplantation can predict grade 2-4 acute graft-versus-host disease.

BACKGROUND: Viral infections and their occult reactivation occasionally cause not only organ damage, but also exacerbation of acute graft-versus-host disease (aGVHD), which may increase transplantation-related mortality synergistically. To determine correlations between viral reactivation and transplantation-related complications, we performed various viral screening tests on the 30th day after allogeneic hematopoietic stem cell transplantation (HSCT), and assessed the clinical implications. PATIENTS AND METHODS: Between August 2007 and January 2013, 49 patients (37 men, 12 women) underwent HSCT in our hospital. The stem cell sources were bone marrow (n = 21), peripheral blood (n = 13), and cord blood (n = 15). The presence of cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpesvirus (HHV) 6, and HHV7 in plasma samples prospectively collected from HSCT recipients on day 30 after HSCT was assayed by quantitative polymerase chain reaction, and the correlations with transplantation-related complications were evaluated. RESULTS: The positivities of CMV, EBV, HHV6, and HHV7 were 44.9%, 22.4%, 53.1%, and 18.3%, respectively. We analyzed transplantation-related complications, and a significant correlation was found only between HHV6 and grade 2-4 aGVHD from day 30 to day 100 (P < 0.001). Using a receiver operating characteristic curve, the area under the curve was calculated as 0.86 (95% confidence interval [CI], 0.74-0.98) between the viral load (VL) of HHV6 and grade 2-4 aGVHD. The sensitivity and specificity were 79% and 93%, respectively, when a cutoff value of 87 copies/mL was used. In multivariate analysis using the Fine and Gray proportional hazards model, the clinically determined high-risk patients (P = 0.004; hazard ratio [HR], 3.69; 95% CI, 1.52-9.00) and the positivity of HHV6 (P < 0.001; HR, 9.957; 95% CI, 2.68-37.06) were extracted as independent risk factors for the cumulative incidence of grade 2-4 aGVHD on or after post-HSCT day 30. The only risk factor extracted for the elevation of HHV6 VL >87 copies/mL was cord blood transplantation (P = 0.0032; odds ratio, 7.10; 95% CI, 1.98-30.00). CONCLUSION: All of the risk factors previously reported to predict severe aGVHD were obtained only during, but not after, HSCT. Our study suggests that the reactivation of HHV6 (≥ 87 copies/mL) at 30 days after HSCT is a possible predictive marker for grade 2-4 aGVHD on or after post-HSCT day 30.

Nitrate-dependent ferrous iron oxidation by anaerobic ammonium oxidation (anammox) bacteria.

We examined nitrate-dependent Fe(2+) oxidation mediated by anaerobic ammonium oxidation (anammox) bacteria. Enrichment cultures of "Candidatus Brocadia sinica" anaerobically oxidized Fe(2+) and reduced NO3(-) to nitrogen gas at rates of 3.7 ± 0.2 and 1.3 ± 0.1 (mean ± standard deviation [SD]) nmol mg protein(-1) min(-1), respectively (37°C and pH 7.3). This nitrate reduction rate is an order of magnitude lower than the anammox activity of "Ca. Brocadia sinica" (10 to 75 nmol NH4(+) mg protein(-1) min(-1)). A (15)N tracer experiment demonstrated that coupling of nitrate-dependent Fe(2+) oxidation and the anammox reaction was responsible for producing nitrogen gas from NO3(-) by "Ca. Brocadia sinica." The activities of nitrate-dependent Fe(2+) oxidation were dependent on temperature and pH, and the highest activities were seen at temperatures of 30 to 45°C and pHs ranging from 5.9 to 9.8. The mean half-saturation constant for NO3(-) ± SD of "Ca. Brocadia sinica" was determined to be 51 ± 21 µM. Nitrate-dependent Fe(2+) oxidation was further demonstrated by another anammox bacterium, "Candidatus Scalindua sp.," whose rates of Fe(2+) oxidation and NO3(-) reduction were 4.7 ± 0.59 and 1.45 ± 0.05 nmol mg protein(-1) min(-1), respectively (20°C and pH 7.3). Co-occurrence of nitrate-dependent Fe(2+) oxidation and the anammox reaction decreased the molar ratios of consumed NO2(-) to consumed NH4(+) (ΔNO2(-)/ΔNH4(+)) and produced NO3(-) to consumed NH4(+) (ΔNO3(-)/ΔNH4(+)). These reactions are preferable to the application of anammox processes for wastewater treatment.

Introduction of a degassing membrane technology into anaerobic wastewater treatment.

The effectiveness of degasification using a degassing membrane to improve chemical oxygen demand (COD) removal efficiency was investigated using a bench-scale upflow anaerobic sludge blanket (UASB) reactor. Vacuum degasification was able to transfer dissolved gas in the bulk liquid of the UASB reactor inside the membrane. Such a process might provide thermodynamically favorable conditions for the degradation of organic compounds. The COD-removal efficiency improved from 83% during normal operation to 90% during the degassing operation.

Characterization of microbial community structures and their activities in single anaerobic granules by beta imaging, microsensors and fluorescence in situ hybridization.

The spatial distribution of microorganisms and their in situ activities in anaerobic granules were investigated by fluorescence in situ hybridization (FISH), beta imaging and microsensors. FISH results revealed a layered structure of microorganisms in the granule, where Chloroflexi was present in the outermost layer, Smithella spp. and Syntrophobacter spp. were found in a depth of ca. 100 µm, and Archaea was restricted to the inner layer (below ca. 300 µm from the surface). Substrate uptake patterns elucidated by beta imaging demonstrated that glucose uptake was highest at 50 µm depth, whereas propionate uptake had a peak at 200 µm depth. In addition, microsensor measurements revealed that acid was produced mainly at 100 µm depth and H(2) production was detected at a depth from 100 to 200 µm. H(2) consumption and corresponding CH(4) production were found below 200 µm from the surface. Direct comparison of these results implied sequential degradation of complex organic compounds in anaerobic granules; Chloroflexi contributed to fermentation of organic compounds and acid production in the outermost layer, volatile fatty acids were oxidized and H(2) was produced mainly by Smithella spp. and Syntrophobacter spp. at a depth from 100 to 200 µm, and Archaea produced CH(4) below ca. 300 µm from the surface.

Triad stimulation frequency for cortical facilitation in cortical myoclonus.

BACKGROUND: Abnormally enhanced cortical rhythmic activities have been reported in patients with cortical myoclonus. We recently reported a new triad-conditioning transcranial magnetic stimulation (TMS) method to detect the intrinsic rhythms of the primary motor cortex (M1). Triad-conditioning TMS revealed a 40-Hz intrinsic rhythm of M1 in normal subjects. In this investigation, we study the motor cortical facilitation induced by rhythmic triple TMS pulses (triad-conditioning TMS) in patients with cortical myoclonus. METHODS: Subjects were 7 patients with cortical myoclonus (28-74 years old) and 13 healthy volunteers (30-71 years old). Three conditioning stimuli over M1 at the intensity of 110% active motor threshold preceded the test TMS at various interstimulus intervals corresponding to 10-200 Hz. The resulting amplitudes of conditioned motor evoked potentials recorded from the contralateral hand muscle were compared with those evoked by the test stimulus alone. RESULTS: The facilitation at 25 ms (40 Hz) observed in normal subjects was absent in patients with cortical myoclonus. Instead, triad-conditioning TMS induced facilitation at a 40 ms interval (25 Hz) in cortical myoclonus. DISCUSSIONS: This change in the timing of facilitation may be explained by a shift of the most preferential intrinsic rhythm of M1, or by some dysfunction in the interneuronal network in cortical myoclonus.

Short-interval intracortical inhibition in Parkinson's disease using anterior-posterior directed currents.

Reduced short-interval intracortical inhibition (SICI) is reported in Parkinson's disease (PD) and is considered to reflect abnormal GABAergic inhibitory system of the primary motor cortex in PD. We have recently shown, however, that SICI using anterior-posterior directed currents in the brain was normal in focal dystonia even though that using posterior-anterior currents was abnormal, indicating that the GABAergic system of the primary motor cortex is largely normal in dystonia. Here, we studied SICI in PD to clarify whether the GABAergic system is completely impaired in PD. We used paired-pulse transcranial magnetic stimulation to study SICI at interstimulus intervals of 3 and 4 ms with anterior-posterior or posterior-anterior directed currents in eight PD patients and ten healthy volunteers. The amount of SICI with posterior-anterior directed currents was reduced in PD patients compared with healthy volunteers; in contrast, SICI studied with anterior-posterior directed currents was normal in PD patients. These observations may be due to the difference in I-wave composition generated by the two directed currents and/or the difference in responsible inhibitory interneurons for the inhibition between the two current directions. We suggest that some or a part of inhibitory interneurons are not involved in PD. This discrepancy between SICI using posterior-anterior and anterior-posterior directed currents experiments may provide additional information about the circuits of the motor cortex.

Inhibitory effect of polysulfide, an endogenous sulfur compound, on oxidative stress-induced TRPA1 activation.

Polysulfide (PS), an endogenous sulfur compound, generated by oxidation of hydrogen sulfide, has a stimulatory action on the nociceptive TRPA1 channel. TRPA1 is also activated by reactive oxygen species such as hydrogen peroxide (H2O2) produced during inflammation. Here, we examined the effect of PS on H2O2-induced responses in native and heterologously expressed TRPA1 using a cell-based calcium assay. We also carried out behavioral experiments in vivo. In mouse sensory neurons, H2O2 elicited early TRPA1-dependent and late TRPA1-independent increases of [Ca2+]i. The former was suppressed by the pretreatment with PS. In cells heterologously expressed TRPA1, PS suppressed [Ca2+]i responses to H2O2. Simultaneous measurement of [Ca2+]i and the intracellular PS level revealed that scavenging effect of PS was not related to the inhibitory effect. Removal of extracellular Ca2+, a calmodulin inhibitor and dithiothreitol attenuated the inhibitory effect of PS. Pretreatment with PS diminished nociceptive behaviors induced by H2O2. The present data suggest that PS suppresses oxidative stress-induced TRPA1 activation due to cysteine modification and Ca2+/calmodulin signaling. Thus, endogenous sulfurs may have regulatory roles in nociception via functional changes in TRPA1 under inflammatory conditions.

Disruption of the Bcl6 gene results in an impaired germinal center formation.

The Bcl6 gene has been identified from the chromosomal translocation breakpoint in B cell lymphomas, and its products are expressed highly in germinal center (GC) B cells. To investigate the function of Bcl6 in lymphocytes, we have generated RAG1-deficient mice reconstituted with bone marrow cells from Bcl6-deficient mice (Bcl6(-/-)RM). Lymphogenesis in primary lymphoid tissues of Bcl6(-/-)RM is normal, and Bcl6(-/-)RM produced control levels of primary IgG1 antibodies specific to T cell-dependent antigens. However, GCs were not found in these mice. This defect was mainly due to the abnormalities of B cells. Therefore, Bcl6 is essential for the differentiation of GC B cells.

Do photobleached fluorescent microtubules move?: re-evaluation of fluorescence laser photobleaching both in vitro and in growing Xenopus axon.

We previously documented differences in the behavior of microtubules in growing axons of two types of neurons, adult mouse sensory neurons and Xenopus embryonal spinal cord neurons. Namely, the bulk of microtubules was stationary in mouse sensory neurons both by the method of photoactivation of caged-fluorescein-labeled tubulin and photobleaching of fluorescein-labeled tubulin, but the bulk of microtubules did translocate anterogradely by the method of photoactivation. Although these results indicated that the stationary nature of photobleached microtubules in mouse neurons is not an artifact derived from the high levels of energy required for the procedure, it has not yet been settled whether the photobleaching method can detect the movement of microtubules properly. Here we report photobleaching experiments on growing axons of Xenopus embryonal neurons. Anterograde movement of photobleached microtubules was observed at a frequency and translocation rate similar to the values determined by the method of photoactivation. Our results suggest that, under appropriate conditions, the photobleaching method is able to reveal the behavior of microtubules as accurately as the photoactivation method.

Microtubule dynamics in nerve cells: analysis using microinjection of biotinylated tubulin into PC12 cells.

To study microtubule (MT) dynamics in nerve cells, we microinjected biotin-labeled tubulin into the cell body of chemically fused and differentiated PC12 cells and performed the immunofluorescence or immunogold procedure using an anti-biotin antibody followed by secondary antibodies coupled to fluorescent dye or colloidal gold. Incorporation of labeled subunits into the cytoskeleton of neurites was observed within minutes after microinjection. Serial electron microscopic reconstruction revealed that existing MTs in PC12 neurites incorporated labeled subunits mainly at their distal ends and the elongation rate of labeled segments was estimated to be less than 0.3 micron/min. Overall organization of MTs in the nerve cells was different from that in undifferentiated cells such as fibroblasts. Namely, we have not identified any MT-organizing centers from which labeled MTs are emanating in the cell bodies of the injected cells. Stereo electron microscopy revealed that some fully labeled segments seemed to start in the close vicinity of electron dense material within the neurites. This suggests new nucleation off some structures in the neurites. We have also studied the overall pattern of the incorporation of labeled subunits which extended progressively from the proximal part of the neurites toward their tips. To characterize the mechanism of tubulin incorporation, we have measured mean density of gold labeling per unit length of labeled segments at different parts of the neurites. The results indicate access of free tubulin subunits into the neurites and local incorporation into the neurite cytoskeleton. Our results lead to the conclusion that MTs are not static polymers but dynamic structures that continue to elongate even within the differentiated nerve cell processes.

Differential behavior of photoactivated microtubules in growing axons of mouse and frog neurons.

To characterize the behavior of axonal microtubules in vivo, we analyzed the movement of tubulin labeled with caged fluorescein after activation to be fluorescent by irradiation of 365-nm light. When mouse sensory neurons were microinjected with caged fluorescein-labeled tubulin and then a narrow region of the axon was illuminated with a 365-nm microbeam, photoactivated tubulin was stationary regardless of the position of photoactivation. We next introduced caged fluorescein-labeled tubulin into Xenopus embryos and nerve cells isolated from injected embryos were analyzed by photoactivation. In this case, movement of the photoactivated zone toward the axon tip was frequently observed. The photoactivated microtubule segments in the Xenopus axon moved out from their initial position without significant spreading, suggesting that fluorescent microtubules are not sliding as individual filaments, but rather translocating en bloc. Since these observations raised the possibility that the mechanism of nerve growth might differ between two types of neurons, we further characterized the movement of another component of the axon structure, the plasma membrane. Analysis of the position of polystyrene beads adhering to the neurites of Xenopus neurons revealed anterograde movement of the beads at the rate similar to the rate of microtubule movement. In contrast, no movement of the beads relative to the cell body was observed in mouse sensory neurons. These results suggest that the mode of translocation of cytoskeletal polymers and some components of the axon surface differ between two neuron types and that most microtubules are stationary within the axon of mammalian neurons where the surface-related motility of the axon is not observed.

Incorporation and turnover of biotin-labeled actin microinjected into fibroblastic cells: an immunoelectron microscopic study.

We investigated the mechanism of turnover of an actin microfilament system in fibroblastic cells on an electron microscopic level. A new derivative of actin was prepared by labeling muscle actin with biotin. Cultured fibroblastic cells were microinjected with biotinylated actin, and incorporated biotin-actin molecules were detected by immunoelectron microscopy using an anti-biotin antibody and a colloidal gold-labeled secondary antibody. We also analyzed the localization of injected biotin-actin molecules on a molecular level by freeze-drying techniques. Incorporation of biotin-actin was rapid in motile peripheral regions, such as lamellipodia and microspikes. At approximately 1 min after injection, biotin-actin molecules were mainly incorporated into the distal part of actin bundles in the microspikes. Heavily labeled actin filaments were also observed at the distal fringe of the densely packed actin networks in the lamellipodium. By 5 min after injection, most actin polymers in microspikes and lamellipodia were labeled uniformly. These findings suggest that actin subunits are added preferentially at the membrane-associated ends of preexisting actin filaments. At earlier times after injection, we often observed that the labeled segments were continuous with unlabeled segments, suggesting the incorporation of new subunits at the ends of preexisting filaments. Actin incorporation into stress fibers was a slower process. At 2-3 min after injection, microfilaments at the surface of stress fibers incorporated biotin-actin, but filaments in the core region of stress fibers did not. At 5-10 min after injection, increasing density of labeling along stress fibers toward their distal ends was observed. Stress fiber termini are generally associated with focal contacts. There was no rapid nucleation of actin filaments off the membrane of focal contacts and the pattern of actin incorporation at focal contacts was essentially identical to that into distal parts of stress fibers. By 60 min after injection, stress fibers were labeled uniformly. We also analyzed the actin incorporation into polygonal nets of actin bundles. Circular dense foci, where actin bundles radiate, were stable structures, and actin filaments around the foci incorporated biotin-actin the slowest among the actin-containing structures within the injected cells. These results indicate that the rate and pattern of actin subunit incorporation differ in different regions of the cytoplasm and suggest the possible role of rapid actin polymerization at the leading margin on the protrusive movement of fibroblastic cells.

Tau proteins: the molecular structure and mode of binding on microtubules.

Tau is a family of closely related proteins (55,000-62,000 mol wt) which are contained in the nerve cells and copolymerize with tubulin to induce the formation of microtubules in vitro. All information so far has indicated that tau is closely apposed to the microtubule lattice, and there was no indication of domains projecting from the microtubule polymer lattice. We have studied the molecular structure of the tau factor and its mode of binding on microtubules using the quick-freeze, deep-etch method (QF.DE) and low angle rotary shadowing technique. Phosphocellulose column-purified tubulin from porcine brain was polymerized with tau and the centrifuged pellets were processed by QF.DE. We observed periodic armlike elements (18.7 +/- 4.8 nm long) projecting from the microtubule surface. Most of the projections appeared to cross-link adjacent microtubules. We measured the longitudinal periodicity of tau projections on the microtubules and found it to match the 6-dimer pattern better than the 12-dimer pattern. The stoichiometry of tau versus tubulin in preparations of tau saturated microtubules was 1:approximately 5.0 (molar ratio). Tau molecules adsorbed on mica took on rodlike forms (56.1 +/- 14.1 nm long). Although both tau and MAP1 are contained in axons, competitive binding studies demonstrated that the binding sites of tau and MAP1A on the microtubule surfaces are most distinct, although they may partially overlap.

Differential dynamics of neurofilament-H protein and neurofilament-L protein in neurons.

Neurofilaments (NFs) are composed of triplet proteins, NF-H, NF-M, and NF-L. To understand the dynamics of NFs in vivo, we studied the dynamics of NF-H and compared them to those of NF-L, using the combination of microinjection technique and fluorescence recovery after photobleaching. In the case of NF-L protein, the bleached zone gradually restored its fluorescence intensity with a recovery half time of approximately 35 min. On the other hand, recovery of the bleached zone of NF-H was considerably faster, taking place in approximately 19 min. However, in both cases the bleached zone was stationary. Thus, it was suggested that NF-H is the dynamic component of the NF array and is interchangeable, but that it assembles with the other neurofilament triplet proteins in a more exchangeable way, implying that the location of NF-H is in the periphery of the core NF array mainly composed of NF-L subunits. Immunoelectron microscopy investigations of the incorporation sites of NF-H labeled with biotin compounds also revealed the lateral insertion of NF-H subunits into the preexisting NF array, taking after the pattern seen in the case of NF-L. In summary, our results demonstrate that the dynamics of the L and H subunit proteins in situ are quite different from each other, suggesting different and separated mechanisms or structural specialization underlying the behavior of the two proteins.

Dynamics of microtubules bundled by microtubule associated protein 2C (MAP2C).

MAP2C is a microtubule-associated protein abundant in immature nerve cells. We isolated a cDNA clone encoding whole mouse MAP2C of 467 amino acid residues. In fibroblasts transiently transfected with cDNA of MAP2C, interphase microtubule networks were reorganized into microtubule bundles. To reveal the dynamic properties of microtubule bundles, we analyzed the incorporation sites of exogenously introduced tubulin by microinjection of biotin-labeled tubulin and the turnover rate of microtubule bundles by photoactivation of caged fluorescein-labeled tubulin. The injected biotin-labeled tubulin was rapidly incorporated into distal ends of preexisting microtubule bundles, suggesting a concentration of the available ends of microtubules at this region. Although homogenous staining of microtubule bundles with antibiotin antibody was observed 2 h after injection, the photoactivation study indicated that turnover of microtubule bundles was extremely suppressed and < 10% of tubulin molecules would be exchanged within 1 h. Multiple photoactivation experiments provided evidence that neither catastrophic disassembly at the distal ends of bundles nor concerted disassembly due to treadmilling at the proximal ends could explain the observed rapid incorporation of exogenously introduced tubulin molecules. We conclude that microtubules bundled by MAP2C molecules are very stable while the abrupt increase of free tubulin molecules by microinjection results in rapid assembly from the distal ends within the bundles as well as free nucleation of small microtubules which are progressively associated laterally with preexisting microtubule bundles. This is the first detailed study of the function of MAPs on the dynamics of microtubules in vivo.

Dynamics of the neuronal intermediate filaments.

We have analyzed the dynamics of neuronal intermediate filaments in living neurons by using the method of photobleaching of fluorescently-labeled neurofilament L protein and immunoelectron microscopy of incorporation sites of biotinylated neurofilament L protein. Low-light-level imaging and photobleaching of growing axons of mouse sensory neurons did not affect the rate of either axonal growth or the addition of intermediate filament structures at the axon terminal, suggesting that any perturbations caused by these optical methods would be minimal. After laser photobleaching, recovery of fluorescence did occur slowly with a recovery half-time of 40 min. Furthermore, we observed a more rapid fluorescence recovery in growing axons than in quiescent ones, indicating a growth-dependent regulation of the turnover rate. Incorporation sites of biotin-labeled neurofilament L protein were localized as numerous discrete sites along the axon, and they slowly elongated to become continuous arrays 24 h after injection. Collectively, these results indicate that neuronal intermediate filaments in growing axons turn over within the small area of the axoplasm possibly by the mechanism of lateral and segmental incorporation of new subunits.

Qualitative and quantitative estimation of host-specific fecal pollution using Bacteroides-Prevotella 16S rRNA genetic markers by T-RFLP and real-time PCR analyses.

Rapid and reliable determination of the non-point sources of fecal pollution is a critical issue for the environmental microbiologists all over the world. In this work we evaluated the use of anaerobic bacterial group Bacteroides-Prevotella as an alternative fecal pollution indicator. Terminal restriction fragment length polymorphism (T-RFLP) and real-time polymerase chain reaction (RT-PCR) analyses were used to monitor and quantify human-, cow- and pig-specific fecal contamination in natural river waters. We also included DNA sequence analysis of the identified fecal markers revealed by T-RFLP in order to clarify the specificity of each marker. It was suggested that the most influent peaks for each fecal source could be used to identify the source of fecal pollution. Development of specific probes based on these markers permit to quantify source of contamination by quantitative RT-PCR. Therefore, we combined the T-RFLP results and RT-PCR assay to quantify fecal contamination by certain host. We can conclude that T-RFLP and RT-PCR analyses showed high reproducibility and sensitivity during analyzing real water samples and can be used to identify, track and quantify host-specific bacterial genetic markers in complex natural water environments.