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981.
S Freitag I Le Trong A Chilkoti LA Klumb PS Stayton RE Stenkamp 《Canadian Metallurgical Quarterly》1998,279(1):211-221
Previous thermodynamic and computational studies have pointed to the important energetic role of aromatic contacts in generating the exceptional binding free energy of streptavidin-biotin association. We report here the crystallographic characterization of single site tryptophan mutants in investigating structural consequences of alterations in these aromatic contacts. Four tryptophan residues, Trp79, Trp92, Trp108 and Trp120, play an important role in the hydrophobic binding contributions, which along with a hydrogen bonding network and a flexible binding loop give rise to tight ligand binding (Ka approximately 10(13) M-1). The crystal structures of ligand-free and biotin-bound mutants, W79F, W108F, W120F and W120A, in the resolution range from 1.9 to 2.3 A were determined. Nine data sets for these four different mutants were collected, and structural models were refined to R-values ranging from 0.15 to 0.20. The major question addressed here is how these mutations influence the streptavidin binding site and in particular how they affect the binding mode of biotin in the complex. The overall folding of streptavidin was not significantly altered in any of the tryptophan mutants. With one exception, only minor deviations in the unbound structures were observed. In one crystal form of unbound W79F, there is a coupled shift in the side-chains of Phe29 and Tyr43 toward the mutation site, although in a different crystal form these shifts are not observed. In the bound structures, the orientation of biotin in the binding pocket was not significantly altered in the mutant complex. Compared with the wild-type streptavidin-biotin complex, there were no additional crystallographic water molecules observed for any of the mutants in the binding pocket. These structural studies thus suggest that the thermodynamic alterations can be attributed to the local alterations in binding residue composition, rather than a rearrangement of binding site architectures. 相似文献
982.
SD Ladas H Malamou-Lada G Economou PS Tassios SA Raptis 《Canadian Metallurgical Quarterly》1998,45(21):761-764
BACKGROUND/AIMS: Octreotide is used to arrest peptic ulcer hemorrhage. Since it has anti-secretory properties, it could also be used in Helicobacter pylori eradication therapy, to cure peptic ulcer before discharging patients from hospital. The aim of this pilot study was to determine safety and efficacy of an ultra short quadruple octreotide containing H. pylori eradication therapy in patients with peptic ulcer. METHODOLOGY: Twenty-six consecutive symptomatic H. pylori-positive patients with duodenal (n = 20) or gastric ulcer (n = 6), were treated with a three-day course of octreotide 0.3 mg/day subcutaneously, amoxicillin plus metronidazole 2 g/day orally and colloid bismuth subcitrate 480 mg/day. CLO-test, culture and crush tissue smears were performed on admission to the study, at 4 and 8 weeks post treatment. The effect of octreotide on intragastric pH (n = 10) was also investigated. RESULTS: Octreotide significantly increased the mean 24-hour intragastric pH > 3 over 68.9% of the time (37.1%-99.5%). There were no treatment side effects. Ulcer pain was abolished at between 2-12 days. By intention-to-treat 24/26(92.3%, 95% CI 82%-100%) ulcers had healed at 4 weeks. H. pylori eradication rate at 8 weeks was 88.5% (23/26) (95% CI 76%-100%). CONCLUSIONS: Our ultra-short octreotide containing quadruple therapy is a safe and effective regime in eradicating H. pylori and healing peptic ulcers. It may be a suitable therapy for hospitalized patients with peptic ulcer hemorrhage. 相似文献
983.
E Kalapothakis CL Penaforte RM Le?o JS Cruz VF Prado MN Cordeiro CR Diniz MA Romano-Silva MA Prado MV Gomez PS Beir?o 《Canadian Metallurgical Quarterly》1998,36(12):1971-1980
The cDNAs (Tx3-2 and Pn3A) encoding precursor of toxin Tx3-2 and an isoform called Pn3A have been isolated from a library constructed from stimulated venom glands of the spider Phoneutria nigriventer. The cDNA of Tx3-2 reveals the presence of a signal peptide of 21 amino acids and of an intervening propeptide (with 16 amino acids) preceding the toxin sequence, which was followed by additional amino acid residues at the C-terminus (C-terminal peptide), implying post-translational modifications of the synthesised peptide. The deduced amino acid sequence for the mature toxin confirms the previous sequence published. In addition, by using the whole-cell patch clamp technique, we have determined that purified Tx3-2 decreases L-type currents present in GH3 cells. Finally, the presence of the cDNA Pn3A, with high sequence identity with Tx3-2, reveals the existence of a putative new toxin showing, at the cDNA level, 85.4% identity in its whole segment. 相似文献
984.
We presented an unusual case of cutaneous and bilateral ovarian metastases of malignant melanoma. There was no previously identifiable cutaneous or mucous lesion or teratoid element. Past history revealed that the patient had undergone removal of a blackish, elevated, irregular shaped tumor from the right arm eleven years previously. This lesion was considered to be the primary melanoma; therefore, it was thought to be very unusual as metastasis occurred in both the skin and ovaries after an eleven year disease-free interval. 相似文献
985.
OBJECTIVE: Quantifiable outcome measures for disabling diseases such as osteoarthritis (OA) of the knee are necessary in order to compare the impact of different interventions competing for financial resources. Current subjective and questionnaire data are not satisfactory for such study. In this study, we examine the potential of the direct measurement of ambulatory activity as such a measure. POPULATION: Patients with X-ray evidence of OA of the knee recruited to studies of anti-inflammatory agents (n = 29). Patients with OA of the knee awaiting knee replacement surgery (n = 28). METHODS: Comparison of various standard measures with total energy output data from an activity monitor. RESULTS: Spearman rho correlations of ambulatory energy output (number of steps x average amplitude of steps) correlated with other measures. Correlation with physician's opinion was greater than with patient's opinion (r = 0.4 and 0.2, respectively). There was no correlation with visual analogue pain scale or OA severity index. Correlation with scales of the Nottingham Health Profile questionnaire were not significant either for mobility (r = - 0.15) or for pain (r = - 0.13). There was, however, a significant correlation between poor sleep and increased activity (r = 0.34, P < 0.05). Correlation with Kellgren X-ray grade was significant (r = - 0.45, P = 0.01). Patients recruited to anti-inflammatory studies were 69% more active than those awaiting replacement surgery. CONCLUSION: The monitoring of ambulatory activity shows some construct and discriminant validity, and is worthy of further study. 相似文献
986.
The perirhinal cortex (PRC) plays a major role in memory processes. This role may be influenced by activity in the adjacent entorhinal cortex (EC) and hippocampus (HPC), particularly during the processing of spatial information. In the current experiment we sought to determine whether the cholinergically mediated (type II) theta rhythm, which is a prominent electrophysiological feature of both HPC and EC activity, influenced neuronal firing in the PRC of urethane-anesthetized rats. When the spontaneous firing activity of single units recorded in PRC was related to theta recorded from the hippocampal fissure, it was determined that the firing of 50/163 (31%) PRC neurons exhibited a statistically significant phase relationship (mean phase angle = 188 degrees) to HPC theta. Thirty-three (66%) of these neurons tended to fire near the trough, and 17 near the peak, of this activity. These data indicate that a high proportion of PRC neurons participate in hippocampal-entorhinal theta activity. This activity may support information transmission and storage within and between these structures. 相似文献
987.
PS Cook 《Canadian Metallurgical Quarterly》1996,30(3):405-409
In our laboratory we have developed a relatively simple method for cardiac surgery in rats. The operation is carried out through a small incision in the chest wall using inexpensive equipment. This method allows for the delivery of tissue fragments and cells from a donor rat to an intact or damaged area of ventricular myocardium of a host rat, with easy subsequent localisation of the transplanted/grafted tissue. The rats recover well after the surgery and survive for long periods of time. The technique could also be used for the direct injection of chemicals or molecular probes into the heart. In our experiments we have found that embryonic rat cardiomyocytes that have been transplanted into adult host rat ventricular myocardium using this method survive and develop characteristics typical of heart muscle, thus indicating that using this technique the host heart offers a favourable environment for the transplanted embryonic heart cells. 相似文献
988.
TJ Hiltermann CR de Bruijne J Stolk AH Zwinderman FT Spieksma W Roemer PA Steerenberg PH Fischer L van Bree PS Hiemstra 《Canadian Metallurgical Quarterly》1997,156(6):1765-1772
Asthma is an inflammatory disease of the airways, and exacerbations of this disease have been associated with high levels of air pollution. The objective of this study was to examine whether ambient air pollution and/or allergen exposure induces inflammatory changes in the upper airways of asthmatics. Sixty patients with intermittent to severe persistent asthma visited the Hospital's Out Patient Clinic every 2 wk for a period of 3 mo, and on each visit a nasal lavage was obtained. Associations between nasal inflammatory parameters and seasonal allergens and/or air pollution exposures were analyzed using linear regression analysis. The study ran from July 3 to October 6, 1995, during which period ozone (8-h mean: 80 micrograms/m3) and PM10 (24-h mean: 40 micrograms/m3) were the major air pollutants; the major aeroallergen was mugwort pollen (24-h mean: 27 pollen grains/m3). Effects on both cellular and soluble markers in nasal lavage were demonstrated for both ozone and mugwort pollen, but not for PM10. Ambient ozone exposure was associated with an increase in neutrophils (112% per 100 micrograms/m3 increase in 8-h average ozone concentration), eosinophils (176%), epithelial cells (55%), IL-8 (22%), and eosinophil cationic protein (ECP) (19%). Increases in environmental mugwort pollen counts were associated with an increase in nasal eosinophils (107% per 100 pollen/m3) and ECP (23%), but not with neutrophils, epithelial cells, or lL-8. This study demonstrated that both ambient ozone and allergen exposure are associated with inflammatory responses in the upper airways of subjects with asthma, although the type of inflammation is qualitatively different. 相似文献
989.
MC Sharma S Gaikwad AK Mahapatra PS Menon C Sarkar 《Canadian Metallurgical Quarterly》1998,22(12):1538-1541
A rare case of hypothalamic hamartoma with unusual radiologic and histopathological features is described, possibly the first of its type in English literature. A 1.5-year-old female child presented with precocious puberty. MR scan of the brain revealed a pedunculated hypothalamic mass, most of which was isointense with normal brain on T1- and T2-weighted images. However, a sizeable component of the lesion was hyperintense on T1-weighted images, suggestive of adipose tissue. Microscopically, the lesion was a hamartoma composed of an admixture of neuroectodermal elements, namely glial cells, neurons, and nerve bundles along with mesenchymal elements in the form of fibroadipose tissue. 相似文献
990.
Two designs of total knee replacements were analysed to determine how the geometry of their bearing surface would affect the susceptibility of their ultra high molecular weight polyethylene tibial inserts to delamination. Orientations of the femoral components on the tibial surfaces were calculated with use of rigid body analysis for discrete intervals during the stance phase of gait. For each successive orientation, finite element analysis was used to compress the components together to determine the stresses in the tibial inserts. A damage function analogous to strain energy density was defined to account for the accumulated amplitudes and frequencies of the maximum shear stress cycles and hence to predict fatigue failure. The damage function was applied to each polyethylene element in the tibial insert, and the highest value calculated for each design was its damage score. One knee had a damage score more than three times less than that of the other because of lower stresses and because the contact points moved in the medial-lateral as well as anterior-posterior directions during internal-external rotation. The femoral and tibial components of this knee had large outer frontal radii and close conformity in the frontal plane. We propose that this method, which accounts for the motions and stresses endured during walking, makes different predictions regarding the likelihood of delamination compared with the predictions made by conventional static compression tests performed when the knee is in a neutral position. 相似文献