DL-endopeptidases function as both cell wall hydrolases and poly-γ-glutamic acid hydrolases.

Biopolymers on the cell surface are very important for protecting microorganisms from environmental stresses, as well as storing nutrients and minerals. Synthesis of biopolymers is well studied, while studies on the modification and degradation processes of biopolymers are limited. One of these biopolymers, poly-γ-glutamic acid (γ-PGA), is produced by Bacillus species. Bacillus subtilis PgdS, possessing three NlpC/P60 domains, hydrolyses γ-PGA. Here, we have demonstrated that several dl-endopeptidases with an NlpC/P60 domain (LytE, LytF, CwlS, CwlO, and CwlT) in B. subtilis digest not only an amide bond of d-γ-glutamyl-diaminopimelic acid in peptidoglycans but also linkages of γ-PGA produced by B. subtilis. The hydrolase activity of dl-endopeptidases towards γ-PGA was inhibited by IseA, which also inhibits their hydrolase activity towards peptidoglycans, while the hydrolysis of PgdS towards γ-PGA was not inhibited. PgdS hydrolysed only the d-/l-Glu‒d-Glu linkages of d-Glu-rich γ-PGA (d-Glu:l-Glu=7 : 3) and l-Glu-rich γ-PGA (d-Glu:l-Glu=1 : 9), indicating that PgdS can hydrolyse only restricted substrates. On the other hand, the dl-endopeptidases in B. subtilis cleaved d-/l-Glu‒d-/l-Glu linkages of d-Glu-rich γ-PGA (d-Glu:l-Glu=7 : 3), indicating that these enzymes show different substrate specificities. Thus, the dl-endopeptidases digest γ-PGA more flexibly than PgdS, even though they are annotated as "dl-endopeptidase, digesting the d-γ-glutamyl-diaminopimelic acid linkage (d‒l amino acid bond)".

Are muscle relaxants needed for nasal intubation in propofol and remifentanil anesthesia?

PURPOSE: The authors hypothesized that a muscle relaxant would have no meaningful difference in intubation conditions during nasal intubation under remifentanil and propofol anesthesia. MATERIALS AND METHODS: This parallel-group, double-blinded, randomized controlled trial included 44 patients who received saline (S group; n = 22) or rocuronium (R group; n = 22). In addition to remifentanil 0.5 µg/kg per minute and propofol 5 mg/kg per hour, propofol 0.5 mg/kg was administered until loss of consciousness. Nasal intubation was performed 10 minutes after administration of R or S 0.6 mg/kg. Significant differences in intubation conditions and salivary amylase levels before and after intubation were tested (P < .05). RESULTS: Vocal cord status (P = .003) and response to intubation or cuff filling (P = .008) were significantly different, but intubation conditions were not. Salivary amylase level was significantly lower with R administration (P = .022). No patient complained of postoperative throat pain and hoarseness. CONCLUSION: Muscle relaxants during nasal intubation performed after bolus administration of propofol 0.9 mg/kg in addition to 10 minutes of remifentanil 0.5 µg/kg per minute plus propofol 5 mg/kg per hour are unnecessary.

Lipopolysaccharide-induced microglial activation induces learning and memory deficits without neuronal cell death in rats.

We used lipopolysaccharide (LPS) to activate microglia that play an important role in the brain immune system. LPS injected into the rat hippocampus CA1 region activated microglial cells resulting in an increased production of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha in the hippocampus during the initial stage of treatment. Immunostaining for IL-1beta was increased at 6 hr after LPS injection. IL-1beta-immunopositive cells were co-localized with immunostaining for CD11b. Subacute treatment with LPS by the same route for 5 days caused long-term activation of microglia and induced learning and memory deficits in animals when examined with a step-through passive avoidance test, but histochemical analysis showed that neuronal cell death was not observed under these experimental conditions. The increased expression of the heme oxygenase-1 (HO-1) gene, an oxidative stress maker, was observed. However, the genetic expression of brain-derived neurotrophic factor (BDNF) and its receptor, TrkB, decreased during the course of LPS treatment. We found decreases in [3H]MK801 binding in the hippocampus CA1 region by LPS-treatment for 5 days. The data shows that glutamatergic transmission was attenuated in the LPS-treated rats. These results suggest that long-term activation of microglia induced by LPS results in a decrease of glutamatergic transmission that leads to learning and memory deficits without neuronal cell death. The physiologic significance of these findings is discussed.