Thermodynamic analysis of the heparin interaction with a basic cyclic peptide using isothermal titration calorimetry

Brain natriuretic peptide (BNP) was examined as part of a continuing study of the interaction of proteins and peptides with the glycosaminoglycan heparin. BNP was tentatively identified as a heparin-binding protein on the basis of its cyclic structure and the high frequency of the basic amino acid residues, lysine and arginine. Thermodynamic analysis using isothermal titration calorimetry confirmed heparin binding to BNP with a micromolar Kd. Surprisingly, despite the high frequency (22%) of basic residues in BNP, only a small portion of the free energy of this interaction resulted from ionic contributions under physiologic conditions. The contribution of polar amino acids, representing 28% of BNP, was next examined in a variety of different buffers. These experiments demonstrated the transfer of five protons from buffer to BNP on heparin binding, suggesting that hydrogen bonding between the polar residues of BNP and heparin is a major factor contributing to the free energy of BNP binding to heparin. Hydrophobic forces apparently play only a small role in binding. Heparin contains few nonpolar functional groups, and a positive change in heat capacity (DeltaCp = 1 kcal/mol) demonstrates the loss of polar residues on BNP-heparin binding.     

2-Pyridinyl-3-(4-methylsulfonyl)phenylpyridines: selective and orally active cyclooxygenase-2 inhibitors

A series of novel 2-pyridinyl-3-(4-methylsulfonyl)phenylpyridines has been synthesized and evaluated with respect to their ability to inhibit the isozymes of cyclooxygenase, COX-1, and COX-2. Optimum COX-2 activity is observed by introduction of a substituent at C5 of the central pyridine. 5- Chloro-3-(4-methylsulfonyl)phenyl-2-(2-methyl-5-pyridinyl)pyridine 33 was identified as the optimum compound in this series.     

Changing trends in melanoma incidence and mortality

OBJECTIVES: This article analyzes trends in melanoma incidence and mortality rates. Information on sun exposure supplements these statistics. DATA SOURCES: Melanoma incidence data were obtained from the National Cancer Incidence Reporting System and from the Canadian Cancer Registry. Cancer mortality data were extracted from the Canadian Vital Statistics Data Base. Information on sun exposure is from the 1996 Sun Exposure Survey. ANALYTICAL TECHNIQUES: Incidence and mortality rates were age-standardized to the 1991 Canadian population to account for changes in the age structure of the population over time. The average annual percentage changes in age-specific rates were calculated for selected time periods. MAIN RESULTS: After years of steady increases, melanoma incidence and mortality rates have levelled off as a result of declining rates in younger age groups, and for melanoma of the trunk among men and of the leg among women. Incidence rates for men are now higher than those for women; mortality rates for men are twice as high as for women.     

Metastatic dermatofibrosarcoma protuberans mimicking meningioma

Relationships between body mass index (BMI) and weight gain with perinatal outcome and birthweight were examined. BMI was calculated on 582 consecutive pregnant women who delivered at or >37 weeks gestational age. Statistical analysis was done using Chi-square tests, analysis of variance, and multiple logistic regression. Of those studied, 13% were underweight, 39% normal, 13% overweight, and 35% obese. Obesity was associated with increasing age (P < .01), multiparity (P < .01), previous cesarean delivery (P < .01), previous macrosomia (P = .01), previous fetal death (P = .03), hypertensive disorders (P < .01), gestational diabetes (P = .02), cesarean delivery (P = .03), and neonatal intensive care unit admission (NICU) (P = .01). The underweight group had the most low birthweight (LBW) infants and the lowest mean birthweight. Ideal weight gain occurred in 31%, inadequate weight gain in 34%, and excessive weight gain in 35%. Inadequate weight gain had increased asthma (P < .05), and hyperemesis (P = .03). Women with ideal weight gain had less smokers (P < .01), fetal distress (P < .05), cesarean delivery (P = .02), and preeclampsia (P < .001). The mean birthweight was highest in the excessive weight gain (P < .01). With multivariate analysis, previous LBW, BMI, and tobacco use were significant predictors of LBW. Normal BMI and ideal weight gain in pregnancy is associated with decreased perinatal complications and an optimum birthweight.     

A thermodynamic investigation of reactions catalyzed by tryptophan synthase

In this study, we demonstrated that sodium selenite with high doses (> or = 10(-3) M) were potent in inducing a contracture type effect on heart and smooth muscles. Selenite (Se), at a concentration of 10(-3) M, caused a contracture effect in heart preparations. Also, low Se concentrations did not have any significant effect. Although low concentrations of Se (> or = 10(-5) M) had a biphasic effects on acetylcholine (ACh) induced and spontaneous ileum contractions, 10(-3) M selenite enhanced once more a contracture effect similar to that of the heart preparations. Replacing Ca2+ concentration of the bathing solution by twofold Ca2+ or Ca2+-free did not change the effects of selenite (10(-5) M) on contractility of ileum preparations. In vascular smooth muscle, low concentration of selenite (< 10(-4)) had no significant effects on KCl, and phenylephrine-induced contractions and acetylcholine-induced endothelium-dependent relaxations of isolated rabbit aorta. However, the contractions induced by phenylephrine and the relaxations induced by acetylcholine in rabbit aorta were depressed significantly by high concentration of selenite (10(-3) M). The results obtained by selenite exposure from these three different types of tissue preparations first suggest that the high concentration of selenite exposure induces some alterations in the functions of muscles and endothelium in a tissue- and dose-dependent manner. Second, this observed irreversible type of dysfunction of tissues induced by 10(-3) M selenite is not directly dependent on the Ca2+ entrance into the cytosol, but might be induced by the increase of intracellular Ca2+ with the disturbance of Ca2+ regulation.     

Important immunoregulatory role of interleukin-11 in the inflammatory process in rheumatoid arthritis

OBJECTIVE: To investigate the possible immunoregulatory role of interleukin-11 (IL-11) in rheumatoid arthritis (RA). METHODS: IL-11 protein was assayed in RA tissue, and the effect of exogenous IL-11 on neutralization of endogenous IL-11 was investigated with respect to tumor necrosis factor alpha (TNFalpha), matrix metalloproteinase (MMP), and tissue inhibitor of metalloproteinases (TIMP) production. RESULTS: IL-11 was found in RA synovial membranes, synovial fluids, and blood sera. Blockade of endogenous IL-11 resulted in a 2-fold increase in TNFalpha levels, which increased to 22-fold if endogenous IL-10 was also blocked. Addition of exogenous IL-11 inhibited spontaneous TNFalpha production in RA synovium only in the presence of soluble IL-11 receptor. However, exogenous IL-11 directly inhibited spontaneous MMP-1 and MMP-3 production, and up-regulated TIMP-1 in RA synovial tissue. CONCLUSION: IL-11 has important endogenous immunoregulatory effects in RA synovium, which suggests that exogenous IL-11 may have therapeutic activity in RA.     

Mechanisms of DNA damage by chromium(V) carcinogens

Reactions of bis(2-ethyl-2-hydroxy-butanato)oxochromate(V) with pUC19 DNA, single-stranded calf thymus DNA (ss-ctDNA), a synthetic oligonucleotide, 5'-GATCTATGGACTTACTTCAAGGCCGGGTAATGCTA-3' (35mer), deoxyguanosine and guanine were carried out in Bis-Tris buffer at pH 7.0. The plasmid DNA was only nicked, whereas the single-stranded DNA suffered extensive damage due to oxidation of the ribose moiety. The primary oxidation product was characterized as 5-methylene-2-furanone. Although all four bases (A, C, G and T) were released during the oxidation process, the concentration of guanine exceeds the other three. Orthophosphate and 3'-phosphates were also detected in this reaction. Likewise, the synthetic oliogomer exhibits cleavage at all bases with a higher frequecncy at G sites. This increased cleavage at G sites was more apparent after treating the primary oxidation products with piperidine, which may indicate base oxidation as well. DNA oxidation is shown to proceed through a Cr(V)-DNA intermediate in which chromium(V) is coordinated through the phosphodiester moiety. Two alternative mechanisms for DNA oxidation by oxochromate(V) are proposed to account for formation of 5-methylene-2-furanone, based on hydrogen abstraction or hydride transfer from the C1' site of the ribose followed by hydration and two successive beta-eliminations. It appears that phosphate coordination is a prerequisite for DNA oxidation, since no reactions between chromium(V) and deoxyguanosine or guanine were observed. Two other additional pathways, hydrogen abstraction from C4' and guanine base oxidation, are also discussed.     

Investigation of a Monte Carlo model for chemical reactions

Many new technologies are being developed to improve the efficiency and productivity of nursing staff. A key to the success of these technologies is acceptance by nurses. Davis' constructs of perceived ease of use and perceived usefulness were developed to measure the acceptance of computer systems. This article presents a discussion on nursing acceptance of computer systems, reviews the development of the perceived ease of use and perceived usefulness measures, and reports findings of a study based on these constructs along with attitude of bedside-computer systems. Results of the study showed that nurses in general are accepting of bedside-computer technology.     

Microvascular endothelial cell control of peripheral vascular resistance during sepsis

OBJECTIVE: To determine the endothelial-dependent control of decreased peripheral vascular resistance in skeletal muscle microvessels during evolving sepsis. MATERIALS AND INTERVENTIONS: Acute (4 hours, n=7), established (24 hours, n=7), or chronic (72 hours, n=8) infection was induced in Sprague-Dawley rats (150-175 g) by injecting Escherichia coli and Bacteroides fragilis (1 x 10(9) colony-forming units for both) into a subcutaneous sponge. Control animals were injected with an isotonic sodium chloride solution and analyzed at the same time points: (n=6-8 per group). Dilation in response to the topically applied endothelial-dependent agonist acetylcholine (ACH) (1 x 10(-9) to 1 x 10(-5) mol/L) was measured in inflow first-order (A1) and precapillary fourth-order (A4) arterioles in cremaster muscle in vivo with videomicroscopy. Acetylcholine dose-response curves were used to determine vascular reactivity by calculating the concentration of ACH necessary to elicit 50% of the maximal dilator response. MAIN OUTCOME MEASURES: In vivo reactivity of striated muscle microvessels to the dilation agonist ACH during acute, established, and chronic infection. RESULTS: A1 vessels were unresponsive to all doses of ACH at all time points. A4 vessels showed an increased dilator response during short-term treatment, which deteriorated over time to depressed dilation during chronic infection. CONCLUSIONS: Precapillary A4 vessels have increased dilator reactivity during early sepsis, which progresses to depressed levels with chronic infection. A1 microvessels remain dilated and are not substantially influenced by endothelial dilator mechanisms initiated by ACH. Maximum dilation of the large A1 vessels appears to contribute to the decrease in peripheral vascular resistance noted during systemic infection.