• Korean Journal of Microbiology
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• v.40 no.2
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• pp.104-110
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• 2004

To determine evolution and genotype of new chromosomal AmpC $\beta$-lactamases among clinical isolates of Enterobacter species, we performed antibiotic susceptibility testing, pI determination, sequencing, and phy-logenetic analysis using developed expression/secretion vector. Six isolates have shown to produce AmpC $\beta$-lactamases. Six genes of AmpC $\beta$-lactamases that are responsible for the resistance to cephamycins (cefoxitin and cefotetan), amoxicillin, cephalothin, and amoxicillin-clavulanic acid were cloned and characterized in pMSG12119. Insert fragment containing the ampC genes was sequenced and found to have an open reading frame coding for 381-amino-acid $\beta$-lactamase. The nucleotide sequence of four ampC genes ($bla_EcloK992004.l$, $bla_EcloK995120.1$, $bla_EcloK99230$, and $bla_EareK9911729$) shared considerable homology with that of chromosomal ampC gene ($bla_EcloMHN1$) of E. cloacae MHN1 (more than 99.6% identity). The sequences of two ampC genes ($bla_EcloK9973$ and $bla_EcloK9914325$) showed close similarity to the chromosomal ampC gene ($bla_EcloQ908R$) of E. clo-acae 908R (99.7% identity). The results from phylogenetic analysis suggested that six ampC genes could be originated from $bla_EcloMHN1$ / or $bla_EcloQ908R$ / MIC patterns and exact pI values of six transformants indicated that the developed expression/secretion vector (pMSG1219) was suitable for the characterization of foreign genes in E. coli strain.

• Journal of Life Science
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• v.13 no.5
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• pp.642-650
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• 2003

To develop a new approach to the treatment of neuroblastoma cells we evaluated the effect of cAMP on the Ewing's sarcoma cell line CHP-100. We observed that the proliferation-inhibitory effect of cAMP analogs was due to cell cycle arrest and induction of apoptosis, which was confirmed by observing the morphological changes and DNA fragmentation. DNA flow cytometric analysis revealed that cAMP arrested the cell cycle progression at the G1 phase, which effects were associated with inhibition of phosphorylation of retinoblastoma protein (pRB) and enhanced binding of pRB and the transcription factor E2F-1. cAMP also suppressed the cyclin-dependent kinase (Cdk) 2 and cyclin E-associated kinase activity without changes of their expressions. Furthermore, cAMP induced the levels of Cdk inhibitor $p21^{WAF1/CIP1$ expression and p21 proteins induced by cAMP were associated with Cdk2. Overall, our results identify a combined mechanism involving the inhibition of pRB phosphorylation and induction of p21 as targets for cAMP, and this may explain some of its anti-cancer effects.

• Journal of Life Science
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• v.16 no.7 s.80
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• pp.1225-1228
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• 2006

Cyclic AMP receptor protein (CRP) complexed with cAMP binds to DNA and induces sharp DNA bending around ${\sim}90$ degree. Previous publication (5), however, reported that mutant CRP:cGMP complex showed high migration rate relative to mutant CRP:cAMP complex on native polyacrylamide gel. To confirm DNA structural change in the presence of CRP and cyclic nucleotide, molar cyclization factor $(j_M)$ [13] was measured with 6 constructed DNA fragments. Nonlinear regression analysis of $j_M$ data indicated that mutant CRP did not induce DNA bending in the presence of cGMP but bent DNA in the presence of cAMP without any helical twist change in DNA.

• The Korean Journal of Zoology
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• v.31 no.1
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• pp.35-48
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• 1988

This study was made to investigate the effect of testosterone and cyclic-AMP (cAMP) on rat epididymis. Peritoneai injections of testosterone and cAMP to rats were earned out The activities of acid phosphatase (ACP), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were measured and ultrastructural changes of luminal epithelial cells were observed. As a result, the activity of ACP was significanily decreased on the third day, that of ALP on the fifth day and that of LDH on the seventh day respectively in castrated group. In addition, the activities of ACP and ALP were significanily increased when treated with testosterone for 5 days, that of LDH when treated with testosterone for 7 days. In case of cAMP and cAMP - theophylline injection, the activities of ACP and LDH were increased but the range of increase was of no significance. However a significant increase in the activity of ALP was seen on both cases. On electron microscopic examination, gradually deformed Golgi complex, destructed mitochondria and disrupted stereociha were observed in castrated group. In case of testosterone injection, disrupted Golgi complex, mitochondria and stereocilia showed recovery. When cAMP and cAMP-theophylline were injected as an alternative, various cytoplasmic organelles as well as Golgi com- plex were recovered but stereocilia remained unrecovered.

• International Journal of Oral Biology
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• v.36 no.2
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• pp.83-89
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• 2011

Substantia gelatinosa (SG) neurons receive synaptic inputs from primary afferent $A{\delta}$- and C-fibers, where nociceptive information is integrated and modulated by numerous neurotransmitters or neuromodulators. A number of studies were dedicated to the molecular mechanism underlying the modulation of excitability or synaptic plasticity in SG neurons and revealed that second messengers, such as cAMP and cGMP, play an important role. Recently, cAMP and cGMP were shown to downregulate each other in heart muscle cells. However, involvement of the crosstalk between cAMP and cGMP in neurons is yet to be addressed. Therefore, we investigated whether interaction between cAMP and cGMP modulates synaptic plasticity in SG neurons using slice patchclamp recording from rats. Synaptic activity was measured by excitatory post-synaptic currents (EPSCs) elicited by stimulation onto dorsal root entry zone. Application of 1 mM of 8-bromoadenosine 3,5-cyclic monophosphate (8-Br-cAMP) or 8-bromoguanosine 3,5-cyclic monophosphate (8-Br-cGMP) for 15 minutes increased EPSCs, which were maintained for 30 minutes. However, simultaneous application of 8-BrcAMP and 8-Br-cGMP failed to increase EPSCs, which suggested antagonistic cross-talk between two second messengers. Application of 3-isobutyl-1-methylxanthine (IBMX) that prevents degradation of cAMP and cGMP by blocking phosphodiesterase (PDE) increased EPSCs. Co-application of cAMP/cGMP along with IBMX induced additional increase in EPSCs. These results suggest that second messengers, cAMP and cGMP, might contribute to development of chronic pain through the mutual regulation of the signal transduction.

• The Korean Journal of Mycology
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• v.15 no.4
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• pp.238-246
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• 1987

Aspergillus niger van Tieghem was cultured by the method of synchronous and submerged culture. The sporulation occurred through the culture and its life cycle and differentiation were completed in the experiments. The effects of cAMP, theophylline and caffeine on the sporulation of A. niger were investigated. In the sporulation medium, the sporulation was stimulated by addition of cAMP and its optimum concentration was $10^{-4}M$. In the sporulation medium, the sporulation was stimulated by addition of theophylline and its optimum concentration was 10 mg/ml. In the sporulation medium, the sporulation was stimulated by addition of caffeine and its optimum concentration was 300 mg/ml. Theophylline added to the sporulation medium together with cAMP enhanced the promotion effect of cAMP on sporulation. Caffeine added to the sporulation medium together with cAMP enhanced the promotion effect of cAMP on sporulation. In the sporulation medium, the sporulation was stimulated by addition of neither AMP nor ATP. In the potassium acetate medium, cAMP, theophylline and caffeine stimulated the sporulation, respectively.

• YAKHAK HOEJI
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• v.51 no.1
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• pp.35-43
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• 2007

To investigate the immunomodulatory roles of cyclic AMP (CAMP) on macrophage- and T lymphocyte-mediated immune responses, CAMP elevating agents were employed and carefully re-examined under the activation conditions of the cells. Various inhibitors tested dose-dependently blocked tumor necrosis factor (TNF)-${\alpha}$ production with IC$_{50}$ values ranged from 0.04 to 300 ${\mu}$M. Of the inhibitors, cAMP-elevating agents showed lower cytotoxicity assessed by lactate dehydrogenase (LDH) release, suggesting less toxic and more selective. In particular co-treatment of dbcAMP with a protein kinase C inhibitor staurosporine displayed the synergistic inhibition of TNF-${\alpha}$ production. The modulatory effect of dbcAMP on TNF-${\alpha}$ and nitric oxide (NO) was significantly affected by treatment time of dbcAMP. Thus, post-treatment of dbcAMP (three hours before LPS) abrogated dbcAMP's inhibitory activity and rather enhanced TNF-${\alpha}$ level up to 60%. In contrast, additional NO production was shown at the co-treatment of dbcAMP with LPS. Unlike simultaneous treatment of phorbol 12-myristate 13-acetate (PMA) and interferon (IFN)-${\gamma}$co-treatment, the combination of dbcAMP with other NO-inducing stimuli did not show drastic overproduction of NO. cAMP elevating agents also diminished splenocyte proliferation stimulated by concanavalin (Con) A, phytohemaglutinin A (PHA) and lipopolysaccharide (LPS). In addition, dbcAMP but not rolipram strongly suppressed CD8$^+$ T cells (CTLL-2). Finally, cAMP elevating agents were differentially involved in regulating CD98-mediated cell-cell adhesion. Thus, dbcAMP and rolipram significantly enhanced the cell-cell adhesion, whereas forskolin blocked. Therefore, our results suggest that CAMP elevating agents participate in various immune responses mediated by macrophages and T cells with a different fashion depending on cellular environments and activation signals.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1392-1396
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• 2005

Proteolytic digestion and CD measurement of wild-type and mutant cyclic AMP receptor proteins (CRPs) were performed either in the presence or absence of cyclic nucleotide. Results indicated that transition of a structural change to the hinge region by the binding of cAMP to the anti site was required for the binding of cAMP to the syn site near the hinge region and, although the occupancy of cAMP in the anti site increased the protein stability, CRP adopted more a stable conformation by the binding of cAMP to the syn site.

• BMB Reports
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• v.28 no.1
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• pp.21-26
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• 1995

The Escherichia coli mixed-function serC-aroA operon encodes biosynthethic enzymes for unrelated pathways leading to the syntheses of serine and aromatic amino acids. It has been proposed that the operon is expressed in a cAMP-dependent manner. In this work experiments were performed to investigate the cAMP-dependent expression of the operon. Exogenous cAMP increased ${\beta}$-galactosidase synthesis in the $cya^+$ and cya strains harboring the serC-aroA-lac fusion plasmid. This enhancement was more dramatic in the $cya^-$ strain grown in a minimal medium. In a dot blot assay the serC-aroA mRNA content increased in a concentration-dependent pattern after the addition of exogenous cAMP. The activity of phosphoserine aminotransferase, encoded by the serC gene, apparently increased in E. coli cells after the addition of cAMP. All results obtained confirmed that the expression of the E. coli serC-aroA operon is positively regulated by cAMP at the level of transcription.

• Korean Journal of Acupuncture
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• v.18 no.1
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• pp.143-156
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• 2001

Modulatory effect of cAMP-PKA system on inhibitory- and excitatory herbs-induced ion currents were investigated by nystatin-perforated patch clamp method under voltage-clamp condition. Ion currents induced by Bupleuri radix and Coptidis rhizoma were not affected by cAMP-PKA system. Ion current induced by Ecliptae herba was partially inhibited by cAMP-PKA system. Ion currents induced by Aconiti tuber and Boshniakiae herba were inhibitory modulated and ion current induced by Zingiberis rhizoma was excitatory modulated by cAMP-PKA system. Modulation of cAMP-PKA system on ion currents induced by Ginseng radix was fluctuated. In this results, it can be seen generally that excitatory herbs-induced ion currents were modulated by cAMP-PKA system while cAMP-PKA system did not affect inhibitory herbs-induced ion currents.