Solution structure of the calponin homology (CH) domain from the smoothelin-like 1 protein: a unique apocalmodulin-binding mode and the possible role of the C-terminal type-2 CH-domain in smooth muscle relaxation

The SMTNL1 protein contains a single type-2 calponin homology (CH) domain at its C terminus that shares sequence identity with the smoothelin family of smooth muscle-specific proteins. In contrast to the smoothelins, SMTNL1 does not associate with F-actin in vitro, and its specific role in smooth muscle remains unclear. In addition, the biological function of the C-terminal CH-domains found in the smoothelin proteins is also poorly understood. In this work, we have therefore determined the solution structure of the CH-domain of mouse SMTNL1 (SMTNL1-CH; residues 346-459). The secondary structure and the overall fold for the C-terminal type-2 CH-domain is very similar to that of other CH-domains. However, two clusters of basic residues form a unique surface structure that is characteristic of SMTNL1-CH. Moreover, the protein has an extended C-terminal alpha-helix, which contains a calmodulin (CaM)-binding IQ-motif, that is also a distinct feature of the smoothelins. We have characterized the binding of apo-CaM to SMTNL1-CH through its IQ-motif by isothermal titration calorimetry and NMR chemical shift perturbation studies. In addition, we have used the HADDOCK protein-protein docking approach to construct a model for the complex of apo-CaM and SMTNL1-CH. The model revealed a close interaction of SMTNL1-CH with the two Ca(2+) binding loop regions of the C-terminal domain of apo-CaM; this mode of apo-CaM binding is distinct from previously reported interactions of apo-CaM with IQ-motifs. Finally, we comment on the putative role of the CH-domain in the biological function of SMTNL1.

Characterization of protein kinase pathways responsible for Ca2+ sensitization in rat ileal longitudinal smooth muscle

We investigated the protein kinases responsible for myosin regulatory light chain (LC20) phosphorylation and regulation of myosin light chain phosphatase (MLCP) activity during microcystin (phosphatase inhibitor)-induced contraction at low Ca2+ concentrations of rat ileal smooth muscle stretched in the longitudinal axis. Application of 1 microM microcystin induced LC20 diphosphorylation and contraction of beta-escin-permeabilized rat ileal smooth muscle at pCa 9. The PKC inhibitor GF-109203x, the MEK inhibitor PD-98059, and the p38 MAPK inhibitor SB-203580 significantly reduced this contraction. These inhibitory effects were abolished when the microcystin concentration was increased to 10 muM, indicating that application of these kinase inhibitors generated an increase in MLCP activity. GF-109203x and PD-98059, but not SB-203580, significantly decreased the phosphorylation level of the myosin-targeting subunit of MLCP, MYPT1, at Thr-697 (rat sequence) during microcystin-induced contraction at pCa 9. On the other hand, SB-203580, but not GF-109203x or PD-98059, significantly reduced the phosphorylation level of the PKC-potentiated phosphatase inhibitor of 17 kDa (CPI-17). A zipper-interacting protein kinase (ZIPK) inhibitor (SM1 peptide) and a Rho-associated kinase inhibitor (Y-27632) had little effect on microcystin-induced contraction at pCa 9. In conclusion, PKC, ERK1/2, and p38 MAPK pathways facilitate microcystin-induced contraction at low Ca2+ concentrations by contributing to the inhibition of MLCP activity either through phosphorylation of MYPT1 or CPI-17 [probably mediated by integrin-linked kinase (ILK)]. ILK and not ZIPK is likely to be the protein kinase responsible for LC20 diphosphorylation during microcystin-induced contraction of rat ileal smooth muscle at pCa 9, similar to its recently described role in vascular smooth muscle. The negative regulation of MLCP by PKC and MAPKs during microcystin-induced contraction at pCa 9, which is not observed in vascular smooth muscle, may be unique to phasic smooth muscle.

Patient and physician agreement on abdominal pain severity and need for opioid analgesia

Whereas controversy surrounds emergency department (ED) analgesia administration to patients with undifferentiated abdominal pain, few studies have addressed the level of patient-physician agreement on abdominal pain severity and need for opioid analgesia. This prospective study was undertaken to assess concordance between emergency physicians and patients on abdominal pain severity. Study subjects were a convenience sample of 30 adults seen in an urban university-affiliated tertiary care ED (annual census 65,000) who had undifferentiated abdominal pain meeting an initial severity threshold of 5 on a 10 cm visual analog scale (VAS) marked by the patient. Patients' and physicians' VAS scores, obtained in blinded fashion at presentation (t0) and at one (t1) and two (t2) hours into the ED stay, were compared with t test (VAS scores) and sign-rank (percent change in VAS scores) analyses. In addition, patients and physicians were asked at each assessment time, in blinded fashion, "Is the pain severe enough to warrant morphine?" The kappa statistic was used to characterize the degree of agreement between physician and patient assessments as to whether opioids were indicated. At t0, t1, and t2, patients' mean VAS scores (7.5, 6.7, and 5.1) were significantly (P < .05) higher than the corresponding physicians' VAS scores (5.3, 4.7, and 3.9). Though VAS scores for physicians started lower than those of patients, the percentage changes in scores from one assessment to the next were similar by Wilcoxon sign-rank testing (P > .50 for time intervals t0 - t1 and t1 - t2). Overall, patients and physicians agreed on the question of whether pain was sufficient to warrant opioids in 71 of 90 (78.9%) assessments; the corresponding kappa statistic of .57 indicated moderate agreement (P < .0001). These results, indicating that patients and physicians usually agree on whether opioids are warranted for abdominal pain, have important implications for further research on ED analgesia in this population.

Egg substitutes: use and preference--with and without nutritional information

Three egg substitutes, plus fresh and dried whole eggs, were evaluated by a consumer panel before and after receiving information on cost and caloric and cholesterol content of the products, and before and after sensory evaluations. Initially, most of the thirty panelists believed that the egg substitutes would cost the same or less than fresh eggs. After receiving information on cost and caloric and cholesterol content, the panelists perceived no significant differences in the nutritional value of the products. Fresh whole egg was the preferred product. After tasting, the consumers judged the nutritional value of all of the products higher, but their preferences were lower for all products except the fresh whole egg. Presentation of information on the caloric and cholesterol content of the egg substitutes without explanation of possible benefit in current health problems appears insufficient to change consumers' perception of a fat-modified product.

Egg substitutes: chemical and biologic evaluations

The total lipid, cholesterol, phospholipid, and fatty acid content of dried whole egg (DWE), a refrigerated liquid egg substitute, a powdered egg substitute, and a commercial egg yolk replacer (EYR) were compared. All substitutes contained less total lipid, cholesterol, and phospholipid than DWE. The powdered substitute contained only half the total lipid content reported by the producers and only a fifth of the cholesterol of DWE, while the percentage distribution of fatty acids was similar to that of DWE. The liquid substitute and EYR had fatty acid distributions similar to soybean oil. Rat growth and lipid response were compared for diets containing either DWE or a mixture of EYR and egg white. Both diets were fed with and without vitamin and mineral supplements. Rat growth response was greatest on the DWE diets, either with or without the supplements, was intermediate on the supplemented EYR diets, and was least on the unsupplemented EYR diets. The consumption of DWE-containing diets, when compared with the EYR-containing diets, caused greater liver weight, greater liver total lipid and total cholesterol content, and slightly higher serum cholesterol.