Reduced affinity of iodinated forms of Tyr0 C-type natriuretic peptide for rat natriuretic peptide receptor B

Tyr(O)CNP is an analogue of C-type natriuretic peptide (CNP) with a tyrosine residue added to the NH2 terminus to allow its iodination. In the present study, the suitability of iodinated Tyr(O)CNP as a ligand was tested, and its potency was compared with that of other natural rat natriuretic peptides or structural analogues by radioligand binding experiments. Binding studies were performed on membranes of COS-1 cells transfected with expression plasmids for either rat natriuretic peptide receptor (NPR)-A, rat NPR-B, or bovine NPR-C. 125I-ANP(99-126) was used as a ligand to assess the binding characteristics of NPR-A and -C, and 125I-Tyr(O)CNP was used to study NPR-B. Binding associated to membranes of nontransfected COS cells was always < 3% of the total binding observed in membranes from cells transfected with receptor expression plasmids. Receptor densities in transfected cells ranged from 500 to 2500 fmol/mg of protein. High performance liquid chromatography and ionspray mass spectrometry analyses revealed that the reagents used in the course of iodination (lactoperoxidase, chloramine T, or N-chloromorpholine altered the structure of Tyr(O)CNP, most likely by changing the thiol of the Met17 residue into a sulfoxide. To further evaluate the usefulness of forms of iodinated Tyr(O)CNP on the cGMP responses in cells transfected with NPR-B. In conclusion, the suitability iodinated forms of Tyr(O)CNP as radioligands, we performed iodination of the peptide with cold iodine (Na-127I-). After purification by high performance liquid chromatography, three different modified peptides (i.e. Tyr(O)Met(O)17CNP, 127I-Tyr(O)Met(O)17CNP, and 127I2-Tyr(O)Met(O)17CNP) were recovered, and they were compared with CNP-22, Tyr(O)CNP, ANP(99-126), BNP-32, and des[Gin18, Ser19, Gly20, Leu21, Gly22]ANP(4-23) NH2 (c-ANP) for their ability to bind to transfected receptors. The binding affinity of Tyr(O)CNP for NPR-A and -B receptors is similar to that of CNP. However, oxidation of the Met17 residue into methionine sulfoxide reduces the affinity of the compound for NPR-B by > 10-fold, whereas the addition of one or two iodines did not further reduce its affinity. Similar results were obtained on evaluation of the ability of the oxidized form of monoiodinated Tyr(O)CNP on the cGMP responses in cells transfected with NPR-B. In conclusion, the suitability of iodinated forms of Tyr(O)CNP as radioligands for binding studies on rat NPR-B is not optimal, and the results of studies using such compounds for the detection, identification, and quantification of this receptor should be interpreted with caution.     

Urokinase and the intestinal mucosa: evidence for a role in epithelial cell turnover

The enzyme nitric oxide synthase catalyzes the oxidation of the amino acid L-arginine to L-citrulline and nitric oxide in an NADPH-dependent reaction. Nitric oxide plays a critical role in signal transduction pathways in the cardiovascular and nervous systems and is a key component of the cytostatic/cytotoxic function of the immune system. Characterization of nitric oxide synthase substrates and cofactors has outlined the broad details of the overall reaction and suggested possibilities for chemical steps in the reaction; however, the molecular details of the reaction mechanism are still poorly understood. Recent evidence suggests a role for the reduced bound pterin in the first step of the reaction--the hydroxylation of L-arginine.     

Structural characteristics of chemical vapor polymerized polypyrrole/polycaprolactam fiber composites

Structural characteristics of polypyrrole (PPy)‐coated polycaprolactam (PA6) fiber composites prepared by chemical vapor deposition, in the presence of ferric chloride as the oxidizing agent, were investigated. A multi‐layered coating structure was observed by transmission electron microscopy (TEM), where a compact and denser layer existed between the PPy and PA6 fibers with two diffused layers on each side of the denser layer. The compact layer had a thickness of 200–300 nm. The experimental results show that there was no chemical interaction between PPy and PA6 in the PPy‐coated PA6 fibers. However, there was a stronger interaction between PPy and PA6 molecules in the interphase of PPy‐coated PA6 fiber after heat treatment at elevated temperature. The surface morphology of PPy‐coated PA6 fibers changed with the application of different processing treatments, e.g. swelling and heat treatment. Copyright © 2005 Society of Chemical Industry     

Potentiation of 5-fluorouracil-leucovorin activity by alpha2a-interferon in colon adenocarcinoma xenografts

The present study examined the effect of received support on adjustment by foreign students, with data from 33 Chinese students who completed questionnaires at three occasions: three months (the first period), nine months (the second period), and one year and nine months (the third period) after they arrived in Japan. The Social Support Scale for Chinese Students in Japan (Jou, 1993a) and items for measurement of adjustment were used in the questionnaires. Analysis of Variance results revealed no differences among the amounts of support received during the three periods, but compared with the first or second, adjustment was better during the third period. Results from path analysis indicated that support in the first period was positively related to adjustment in the first period, the first period adjustment and second period support positively to the second period adjustment, and only the second period adjustment positively to the third period adjustment. Thus, the present study suggests that it is especially necessary to provide more support to foreign students during the critical early period in order to facilitate their adjustment.     

Management considerations for treating vesicoureteral reflux in children with solitary kidneys

OBJECTIVES: To evaluate the management approach for vesicoureteral reflux (reflux) into a solitary kidney. METHODS: Outcomes of all children with solitary kidneys and reflux managed between 1981 and 1996 were reviewed. Solitary kidneys were documented by nuclear renography and ultrasonography; reflux was graded after cystography. Management consisted of observation and antimicrobial prophylaxis or surgery by ureteroneocystostomy or subureteric injection of polytetrafluoroethylene (STING). Follow-up ranged from 3 months to 14 years and included serial cystography, sonography, and serum creatinine measurement. RESULTS: Twenty-one patients with a median follow-up of 26 months were identified. Etiologies included contralateral renal agenesis (14 children), multicystic dysplastic kidney (5 children), or nonfunctioning ureteropelvic junction obstruction (2 children). Low-grade (I to II) reflux was identified in 6 children, and high grade (III to V) was identified in 15. Reflux resolved in 20 patients. Five children with low-grade reflux were managed without surgery and demonstrated reflux resolution after a mean of 20.5 months. Renal function deteriorated in only 1 child. Ureteroneocystostomy was performed in 13 children with grades III to V reflux, and STING was performed in 1 child with grade II reflux. Every surgical patient maintained stable renal function and was infection-free during a mean follow-up of 56 months. Management by observation in 2 children with grades IV to V reflux resulted in spontaneous resolution in one and stable grade IV in the other. CONCLUSIONS: Reflux into the solitary functioning kidney may be managed by the same strategies used to manage unilateral reflux in children with two normally functioning kidneys: low-grade reflux by observation/ chemoprophylaxis until spontaneous resolution occurs, and higher grades by surgery to protect renal function; however, chemoprophylaxis and serial imaging may be used until well-defined indications for surgery are satisfied. Renal function should be monitored diligently.     

Contrasting patterns of nucleotide sequence variation at the glucose dehydrogenase (Gld) locus in different populations of Drosophila melanogaster

We have analyzed nucleotide sequence variation at the Glucose dehydrogenase (Gld) locus from four populations of Drosophila melanogaster from four continents. All four population samples show a significant reduction in silent variation compared to the neutral expectation. The levels of silent variation across all four populations are consistent with the predictions of the background selection model; however, Zimbabwe has a remarkably low level of variation. In the face of dramatically reduced silent polymorphism, an amino acid variant, leading to the common allozyme polymorphism at Gld, remains in low to intermediate frequency in all non-African samples. In the Chinese population sample, the ratio of replacement to silent variation is significantly elevated compared to the neutral expectation. The difference in patterns of variation across these population samples suggests that selection on Gld (or the Gld region) has been different in the Chinese population than in the other three.