This study shows that exposure of neonatal mice to inhaled sevoflurane could cause not only learning deficits but also abnormal social behaviors resembling autism spectrum disorder.

The extracellular signal-regulated kinase (ERK) 1 and 2 are important signaling components implicated in learning and memory. These isoforms display a high degree of sequence homology and share a similar substrate profile. However, recent findings suggest that these isoforms may have distinct roles: whereas ERK1 seems to be not so important for associative learning, ERK2 might be critically involved in learning and memory. Thus, the individual role of ERK2 has received considerable attention, although it is yet to be understood. Here, we have generated a series of mice in which ERK2 expression decreased in an allele dose-dependent manner. Null ERK2 knock-out mice were embryonic lethal, and the heterozygous mice were anatomically impaired. To gain a better understanding of the influence of ERK2 on learning and memory, we also generated knockdown mice in which ERK2 expression was partially (20 -40%) reduced. These mutant mice were viable and fertile with normal appearance. The mutant mice showed a deficit in long-term memory in classical fear conditioning, whereas short-term memory was normal. The mice also showed learning deficit in the water maze and the eight-arm radial maze. The ERK1 expression level of the knockdown mice was comparable with the wild-type control. Together, our results indicate a noncompensable role of ERK2-dependent signal transduction in learning and memory.

The epidermal growth factor (EGF) receptor is both an activator and a target of growth factor-stimulated kinases involved in cellular signaling. , and Raf (7). Presumably, there are other proteins that complex with these receptors and participate in the signaling process. The EGF receptor is both an activator and a target of phosphorylation by kinases that are believed to be involved in cellular signaling (8). At least two major sites of phosphorylation on the EGF receptor have been identified: (i) threonine-654 (T654), a target of protein kinase C phosphorylation, which mediates inhibition of the EGF-stimulated tyrosine kinase (9, 10); and (ii) threonine-669 (T669), the major phosphorylated residue in A-431 human epidermoid carcinoma cells and a residue that is phosphorylated in response to a variety of stimuli including EGF, phorbol esters, and the nonphorbol tumor promoter thapsigargin (11,12). Although the functional consequence of phosphorylating T669 is not known, this residue is the only major phosphorylated site on the EGF receptor following treatment with thapsigargin, which inactivates the receptor tyrosine kinase through a protein kinase C/T654-independent mechanism (13). Since the kinase that phosphorylates this residue is responsive to a variety of growth signals, it presumably represents one of the functionally activated intermediates in the signaling process.Here we report that the EGF receptor T669 peptide kinase from 3T3-L1 preadipocytes is a MAP kinase. Originally described as an insulin-stimulated serine/threonine kinase that phosphorylates microtubule-associated protein 2 (MAP-2) (14), MAP kinase has also been shown to phosphorylate myelin basic protein (MBP) (15)

The amino acid sequence of jack bean urease has been determined. The protein consists of a single kind of polypeptide chain containing 840 amino acid residues. The subunit relative molecular mass calculated from the sequence is 90770, indicating that urease is composed of six subunits. Out of 25 histidine residues in urease, 13 were crowded in the region between residues 479 and 607, suggesting that this region may contain the nickelbinding site. Limited tryptic digestion cleaved urease at two sites, Lys-128 and Lys-662. Proteolytic products were not dissociated and retained full enzymatic activity. Five tryptic peptides containing the reactive cysteine residues were isolated and characterized with the aid of sulfhydryl-specific reagents, N-iodoacetyl-N'-(5-sulfo-lnaphthy1)ethylenediamine and N-(7-dimethylamino-4-methyl-3-coumarinyl)-maleimide. The reactive cysteine residues were located at positions 59,207, 592,663, and 824. The possibility that Cys-59, Cys-207, Cys-663, and Cys-824 are involved in the urease activity of the enzyme has been eliminated. Cys-592, which is essential for enzymatic activity, is located in the above-mentioned histidine-rich region.Jack bean urease was the first enzyme isolated as a crystalline protein by Sumner in 1926 [l]. However, the subunit structure of this enzyme has been somewhat ambiguous. The relative molecular mass reported first for the native urease was 480000 [2] while recently the value of 590 000 was reported [3]. The values reported for the monomer range over 30000-97000 [3-61. On the other hand, the subunits of ureases from microorganisms appear to be smaller than jack bean urease in size and number [7-91. Recently it was suggested that one large and two small polypeptides may be generally associated with microbial ureases [lo].Jack bean urease is also the first example of a nickel metalloenzyme and contains two nickel ions per 96600-M, subunit [ l l , 121. Spectrophotometric studies showed that the nickel ion has an essential role in catalysis and that the substrate and inhibitors of urease bind to the nickel ion [13, 141. A model for the mechanism of action of urease, taking into consideration the nickel ion, has been proposed [15].The presence of sulfhydryl groups in a protein was first described for jack bean urease [16]. The sulfhydryl groups in the enzyme are classified into the exposed ones which are titrated in the native conformation and the buried ones which can be titrated only in the presence of denaturant. Urease has been reported to have 27 -35 reactive exposed cysteine residues per urease molecule [17 -191. These cysteine residues were divided into the inessential ones, which readily react with sulfhydryl reagents like 5,5'-dithiobis(2-nitrobenzoic acid) without activity loss, and the essential ones, which react more

Experimental pulmonary hypertension induced in a hypobaric hypoxic environment (HHE) is characterized by structural remodeling of the heart and pulmonary arteries. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) both have diuretic, natriuretic, and hypotensive effects, and both are involved in cardiovascular homeostasis as cardiac hormones. To study the effects of HHE on the natriuretic peptide synthesis system, 170 male Wistar rats were housed in a chamber at the equivalent of the 5500-m altitude level for 1-12 weeks. After 1 week of HHE, pulmonary arterial pressure was significantly raised, and the ratio of left ventricle plus septum over right ventricle of the heart showed a significant decrease (compared with those of ground-level control rats). In both ventricular tissues, the expression of ANP messenger (m)RNA and BNP mRNA increased after exposure to HHE. The amounts of ANP and BNP had decreased significantly in right atrial tissue at 12 weeks of HHE (compared with those of the controls), whereas in ventricular tissues at the same time point, both levels had increased significantly. In in situ hybridization and immunohistochemical studies, the staining of the mRNAs for ANP and BNP and of ANP and BNP themselves was more intense in both ventricular tissues after exposure to HHE than before (i.e., in the controls). The results suggest that, in response to HHE, the changes in ventricular synthesis are similar for ANP and BNP. These changes may play a role in modulating pulmonary hypertension in HHE. However, under our conditions, pulmonary hypertension increased progressively throughout the HHE period.