ストレス環境下における細菌の増殖と形態変化

食品の製造過程では,食品の品質低下防止および品質保持のために食品への様々な処理が行なわれる。これらの処理が不十分な場合,食品中の細菌は生残し,生残した菌体は,より厳しい処理条件に対しても適応できるようになる。本研究では加熱,塩分および三杯酢について,細菌の生存に不利であるが生残する程度のストレスを非芽胞形成細菌に負荷し,その生育状況や形態変化を検討した。走査型電子顕微鏡による観察結果から,大腸菌MC4100株では,50℃および三杯酢処理により細菌細胞が桿状から球状化する傾向が認められた。黄色ブドウ球菌NCTC8325株では,10%NaCl存在下ではコントロールと比較してやや細胞が大きくなり,また5%NaCl存在下では細胞間隙が分泌物のようなもので満たされている顕微鏡像が得られた。三杯酢で処理をすると,細胞が単独化する傾向が認められた。2種類の供試菌は,三杯酢中では1時間後にLB寒天培地上でのコロニー形成能を失うが,回復培地で培養すると再び寒天培地上でコロニーを形成した。三杯酢処理下では「生きているが通常の培地では培養できない」状態,すなわちVBNCの状態で存在していることが示唆された。In food processing environment, several treatments are given to the food to preserve its quality as well as shelf-life. If these treatments are not severe enough, the bacteria survive and are able to adapt to even harsher treatments. The purpose of this investigation was to examine the bacterial growth and morphological changes with respect to non spore-forming bacteria under adverse conditions, namely mild heat treatment, salinity or acid treatment with sanbaisu (mixture of vinegar, sugar and soy sauce). From the results of observation with scanning electron microscopy, Escherichia coli MC4100 showed that the cells tended to convert from a bacillary to a coccobacillary shape under each condition of heat treatment at 50°C for 24h, treatment with 10% NaCl for 24h or with sanbaisu for 10 min. The cells of Staphylococcus aureus NCTC 8325 grown in the presence of NaCl were appeared to be somewhat larger than control cells. Furthermore, the gaps between NaCl-grown cells were filled in something like secretion. The cells treated with sanbaisu tended to be individual cells. E. coli MC4100 and S.aureus NCTC8325 treated with sanbaisu for 1h were lost capability of the colony formation on Luria-Bertani (LB) agar plate. However, sanbaisu-treated cells cultured with recovery medium (LB broth) for 24h were restored to colony formation again. These results raised the possibility that the both organisms became transiently viable but nonculturable (VBNC) state by acid stress (sanbaisu treatment)

Adverse effects of advanced glycation end products on embryonal development

We studied the effects of advanced glycation end products (AGEs), which are known to accumulate in patients with diabetes, autoimmune diseases, or those who smoke, on embryonal development. Pronuclear (PN) embryos were obtained by flushing the fallopian tubes of rats after superovulation and mating. The cleavage rate and blastocyst yield were evaluated at 24, 72, 96, and 120 h of culture. Glyoxal, an AGE-forming aldehyde, suppressed embryonal development at every stage from PN to blastocyst in a concentration-dependent manner. The cleavage rate of the embryo was also signifi cantly decreased by treatment with glyoxal at concentrations of 1 mM or higher. The blastocyst yield was significantly decreased by treatment with glyoxal at concentrations of 0.5 mM or higher. N-acetyl-L-cysteine (L-NAC) at 1 mM significantly suppressed the glyoxal-induced embryonal toxicity. BSA-AGEs at 5 microg/ml or higher concentration signifi cantly reduced the cleavage rate and blastocyst yield compared to those for BSA-treated embryos. L-NAC at 1 mM significantly suppressed BSAAGE-induced embryonal toxicity. Because AGEs are embryo-toxic, AGE contamination may influence the pregnancy rate of in vitro fertilization and embryo transfer. AGEs, which are increased in women under pathological conditions, may also be involved in their infertility.</p

Rapid Amygdala Gamma Oscillations in Response to Eye Gaze

Background: The eye gaze of other individuals conveys important social information and can trigger multiple psychological activities; some of which, such as emotional reactions and attention orienting, occur very rapidly. Although some neuroscientific evidence has suggested that the amygdala may be involved in such rapid gaze processing, no evidence has been reported concerning the speed at which the amygdala responds to eye gaze. Methodology/Principal Findings: To investigate this issue, we recorded electrical activity within the amygdala of six subjects using intracranial electrodes. Subjects observed images of eyes and mosaics pointing in averted and straight directions. The amygdala showed higher gamma-band oscillations for eye gaze than for mosaics, which peaked at 200 ms regardless of the direction of the gaze. Conclusion: These results indicate that the human amygdala rapidly processes eye gaze

Presynaptically Released Cbln1 Induces Dynamic Axonal Structural Changes by Interacting with GluD2 during Cerebellar Synapse Formation

SummaryDifferentiation of pre- and postsynaptic sites is coordinated by reciprocal interaction across synaptic clefts. At parallel fiber (PF)-Purkinje cell (PC) synapses, dendritic spines are autonomously formed without PF influence. However, little is known about how presynaptic structural changes are induced and how they lead to differentiation of mature synapses. Here, we show that Cbln1 released from PFs induces dynamic structural changes in PFs by a mechanism that depends on postsynaptic glutamate receptor delta2 (GluD2) and presynaptic neurexin (Nrx). Time-lapse imaging in organotypic culture and ultrastructural analyses in vivo revealed that Nrx-Cbln1-GluD2 signaling induces PF protrusions that often formed circular structures and encapsulated PC spines. Such structural changes in PFs were associated with the accumulation of synaptic vesicles and GluD2, leading to formation of mature synapses. Thus, PF protrusions triggered by Nrx-Cbln1-GluD2 signaling may promote bidirectional maturation of PF-PC synapses by a positive feedback mechanism

Novel CUL4B mutation in Cabezas syndrome

Cabezas syndrome is a syndromic form of X-linked intellectual disability primarily characterized by a short stature, hypogonadism and abnormal gait, with other variable features resulting from mutations in the CUL4B gene. Here, we report a clinically undiagnosed 5-year-old male with severe intellectual disability. A genome-first approach using targeted exome sequencing identified a novel nonsense mutation [NM_003588.3:c.2698G>T, p.(Glu900*)] in the last coding exon of CUL4B, thus diagnosing this patient with Cabezas syndrome

Influence of gravitational settling on turbulent droplet clustering and radar reflectivity factor

This study investigates the influence of gravitational settling of droplets on turbulent clustering and the radar reflectivity factor. A three-dimensional direct numerical simulation (DNS) of particle-laden isotropic turbulence is performed to obtain turbulent droplet clustering data. The turbulent clustering data are then used to calculate the power spectrum of droplet number density fluctuations. The results show that the gravitational settling modulates the power spectrum more significantly as the settling becomes larger. The gravitational settling weakens the intensity of clustering at large wavenumbers for St ≦ 1, whereas it significantly enlarges the intensity for St > 1. The dependence on the Taylor-microscale-based Reynolds number is also investigated to discuss the contribution of large-scale eddies to the settling influence. The results show that large-scale eddies modulate the small scale clustering structure of large St droplets. The increment of radar reflectivity factor due to turbulent clustering is estimated from the power spectrum for the case of St = 1.0. The result shows that the influence of gravitational settling on the radar reflectivity factor can be significant for the case of large settling velocity droplets