Sodium-23 and lanthanum-139 nuclear magnetic resonance studies of cation binding to aqualysin I,a thermostable serine protease

Aqualysin I has at least two Ca2+-binding sites that have different affinities for Ca2+. The binding of various metal ions to aqualysin I was studied using 23Na- and 139La-NMR spectrometry. Evidence is presented that Ca2+, La3+, and Na+ bind to the low-affinity Ca2+-binding site of aqualysin I, but Mg2+ does not. Our results confirm that binding of metals at the low-affinity Ca2+-binding site is essential for thermostabilization, since the addition of Mg2+ did not result in thermostabilization. La3+ was found to bind to both the low-affinity Ca2+-binding site and an additional metal ion-binding site that can also be involved in the thermostabilization of aqualysin I.     

Multicenter comparison of rapid lateral flow stool antigen immunoassay and stool antigen enzyme immunoassay for the diagnosis of Helicobacter pylori infection in children

BACKGROUND AND AIM: The stool antigen enzyme immunoassay (EIA) methods are widely used for diagnosing Helicobacter pylori infection. Recently, a novel, rapid stool antigen test, the lateral flow immunoassay (LFI) method, has been developed. The primary purpose of this study was to compare the EIA method with the LFI method for the diagnosis of H. pylori infection in children. MATERIALS AND METHODS: Stool specimens from children being evaluated for H. pylori infection were also examined using the LFI (ImmunoCard STAT! HpSA) and EIA methods (Premier Platinum HpSA). The sensitivity, specificity and accuracy of the test were based on the 13C-labeled urea breath test. RESULTS: One hundred and eighty-two children and adolescents, 3-17 years of age (mean 9.2 years), were studied. In addition, 29 patients who received eradication therapy were re-evaluated 2 or 3 months post-treatment. The 13C-labeled urea breath test was positive in 64 patients (35.2%). The sensitivity, specificity and accuracy of the LFI method were 90.6% (95% CI = 80.7-96.5%), 95.8% (92.1-99.4%), and 94.0% (90.5-97.4%), respectively and for the EIA method, sensitivity, specificity and accuracy were 96.8% (95% CI, 89.0-99.6%) and 99.2% (97.5-100%), and 98.3% (96.5-100%), respectively. There were no significant differences in results among the age groups 3-5, 6-10 and 11-17 years. As for the assessment of H. pylori eradication, the results of the LFI and EIA methods agreed with those of 13C-urea breath test in 27/29 and 29/29 patients, respectively. CONCLUSIONS: The LFI stool antigen method showed a good sensitivity, specificity and accuracy for diagnosing H. pylori infection in children. This novel method may be useful in clinical practice as an office-based test because it is rapid, reliable and easy to perform.     

Human spinal motoneurons express low relative abundance of GluR2 mRNA: an implication for excitotoxicity in ALS

AMPA receptor-mediated neurotoxicity is currently the most plausible hypothesis for the etiology of amyotrophic lateral sclerosis (ALS). The mechanism initiating this type of neuronal death is believed to be exaggerated Ca2+-influx through AMPA receptors, which is critically determined by the presence or absence of the glutamate receptor subunit 2 (GluR2) in the assembly. We have provided the first quantitative measurements of the expression profile of AMPA receptor subunits mRNAs in human single neurons by means of quantitative RT-PCR with a laser microdissector. Among the AMPA subunits, GluR2 shared the vast majority throughout the neuronal subsets and tissues examined. Furthermore, both the expression level and the proportion of GluR2 mRNA in motoneurons were the lowest among all neuronal subsets examined, whereas those in motoneurons of ALS did not differ from the control group, implying that selective reduction of the GluR2 subunit cannot be a mechanism of AMPA receptor-mediated neurotoxicity in ALS. However, the low relative abundance of GluR2 might provide spinal motoneurons with conditions that are easily affected by changes of AMPA receptor properties including deficient GluR2 mRNA editing in ALS.     

Down-regulation of melanin synthesis by a biphenyl derivative and its mechanism

Down-regulation of melanin synthesis is required for recovery of pigmentary disorders and it is known that direct inhibitors of tyrosinase, the key enzyme in melanin synthesis, such as hydroquinone with a phenol structure, suppress melanin synthesis. We screened several phenolic derivatives using B16 melanoma cells and found that a biphenyl derivative, 2,2'-dihydroxy-5,5'-dipropyl-biphenyl (DDB), down-regulated melanin synthesis effectively. Although DDB has a phenol structure, it did not inhibit tyrosinase in vitro, thus we examined its mechanism in detail. Western blotting revealed that the amount of tyrosinase was decreased by DDB, and pulse-chase labeling and immunoprecipitation analysis showed a decrease of mature tyrosinase and acceleration of tyrosinase degradation in its presence. These results suggest that DDB down-regulates melanin synthesis by inhibiting the maturation of tyrosinase, leading to acceleration of tyrosinase degradation.     

Extracellular acidic polysaccharide production by a two-membered bacterial coculture

A two-membered coculture of strains KYM-7 and KYM-8, identified as Cellulomonas cellulans and Agrobacterium tumefaciens, respectively, produced a large amount of an extracellular polysaccharide, designated APK-78, from starch. Each strain in pure culture produced only very little amount of polysaccharide from starch; the coexistence of the two strains from the early stage of cultivation was indispensable for a large amount of polysaccharide to be produced. The polysaccharide APK-78 was acidic and composed of glucose, galactose, succinic acid, and pyruvic acid with a molar ratio of 8.1:1.0:1.7:1.0, indicating that it is a succinoglycan type of polysaccharide.