Measurement of J/ psi and psi ' production in 300-GeV/c proton, antiproton, and pi +/- interactions with nuclei.
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Journal Article↗
Biomedical subjects
C Shen
Publications and source records attributed to C Shen.
T1 and T2 of ferritin at different field strengths: effect on MRI.
Nuclear magnetic relaxation times T1 and T2 were measured in ferritin solutions at field strengths from 0.04 to 1.5 T. T1 was relatively constant, but 1/T2 increased linearly with field strength, in agreement with earlier MRI observations in the monkey brain. This finding supports the theory that ferritin is responsible for T2 shortening in brain nuclei containing iron. The linear dependence of 1/T2 on magnetic field is unique and not explained by present theories of the magnetic properties of ferritin.
Animals↗
Induction of alpha v beta 3 integrin-mediated attachment to extracellular matrix in beta 1 integrin (CD29)-negative B cell lines.
beta 1 integrin containing complexes have been implicated as the primary adhesion structures in many lymphocyte extracellular matrix (ECM) interactions. However, many B lymphocytes lack surface expression of the beta 1 subunit, implying that this subpopulation of lymphoid cells must employ alternate adhesion structures if they are to maintain an interactive capacity with ECM. An examination of the adherence properties of the beta 1 integrin-negative B cell line JY indicated that these cells exhibit little or no basal adherence to any of the ECM components examined. However, these cells could be induced to adhere to the ECM components fibronectin, laminin, and vitronectin following treatment with PMA. Blocking studies with monoclonal antibodies indicated the alpha v beta 3 integrin complex was involved in the attachment to each of these ligands. However, the adherence to fibronectin displayed a complex pattern of inhibition suggesting the involvement of other ECM receptors. The utilization of the alpha v beta 3 complex was not unique to the JY cell line. Other B cell lines were observed to employ alpha v beta 3, and these lines similarly lacked expression of beta 1 integrin. These results indicate that alpha v beta 3 can act as a lymphoid ECM-adhesion structure which may provide an alternative means for lymphocytes to interact with ECM. Furthermore, these studies provide evidence for the presence of lymphoid-associated alpha v beta 3 integrins with regulatable activity, which contrasts with the constitutive adhesive potential of these complexes when present on other cell types.
Antibodies, Monoclonal↗
Strengthening of porcelain by ion exchange subsequent to thermal tempering.
The purpose of this study was to test the hypothesis that high-leucite content feldspathic porcelain can be strengthened best by thermal tempering followed by ion exchange, compared with either thermal tempering or ion exchange alone. The results of biaxial flexure testing indicate that thermal tempering was the most effective way of strengthening the porcelain among the three methods tested. The combined procedure did not yield the greatest strengthening effect as hypothesized, but one that is only slightly stronger than that produced by ion exchange alone. Weibull analysis indicated that the ion-exchange treatment resulted in a narrower distribution of biaxial flexural strength compared with that of untreated or thermally tempered porcelain. The narrower distribution of biaxial flexural strength is considered desirable for enhancing the longevity of ceramic-based dental restorations.
Dental Porcelain↗
Effect of different sealers on thermoplasticized Gutta-percha root canal obturations.
The objective of this study was to test the hypothesis that the apical seal provided by thermoplasticized root canal obturations depends on the film thickness of the sealer used. The root canals of 120 maxillary cuspid teeth were instrumented and divided into six equal groups of 20 teeth. A thermoplasticized gutta-percha root canal obturator was used to make an impression of the lubricated canal and coated with a sealer cement before reseating. Five different sealer cements of known film thickness were studied. They were, in the decreasing order of film thickness, Roth's Type I Cement, Seal-apex, Lee Endofil, AH26, and Ketac-Cem. The control group that received no sealer was prepared as recommended by the manufacturer. The degree of microleakage was based on the depth of dye penetration from the apical end measured by two independent examiners. The data collected were analyzed by analysis of variance and Weibull distribution. Analysis of variance shows that the control group exhibited significantly higher dye penetration depth (p < 0.05) while there were no significant differences among the other five groups. Analysis by Weibull distribution function shows that Lee Endofil and AH26 exhibited a higher percentage of lower linear dye penetration values compared with other groups.
Analysis of Variance↗
Reactivity of gamma delta T cells induced by the tumour cell line RPMI 8226: functional heterogeneity of clonal populations and role of GroEL heat shock proteins.
The human tumour cell lines RPMI 8226 and Daudi are potent inducers of V gamma 9-expressing T cells. The inducing element of RPMI 8226 has not been defined but evidence suggests that a member of the GroEL heat shock protein (HSP) family (HSP 58) may have a role in the induction by Daudi cells. The present study examined the reactivity patterns of gamma delta T-cell clones generated in response to RPMI 8226 and addressed the possible role of HSP 58 in this process. RPMI 8226 induced a population of V gamma 9 TCR+ cells which were heterogeneous in terms of their cell surface markers, patterns of proliferation and cytotoxic responses. All clones expressed CD3, CD2, CD18 and CD29. They demonstrated variability in expression of CD56, CD8 and HLA-DR. RPMI 8226 stimulated proliferation in purified bulk gamma delta cultures and clones. Daudi was also capable of inducing these cells to proliferate while mycobacterial products were not effective. The clones demonstrated a limited non-MHC-restricted cytotoxicity pattern with some evidence of clonal heterogeneity. Although both Daudi and RPMI 8226 were sensitive to lysis by the clones, cold inhibition experiments indicated differential activity towards these targets. Anti-HSP 58 was inhibitory to gamma delta T-cell induction by RPMI 8226, Daudi and mycobacterial products. However, the anti-HSP 58 antibody appears to bind to the surface of at least six different tumour cell lines with no correlation to their ability to induce gamma delta T cells and the anti-HSP 58 inhibited non-gamma delta responses.
Bacterial Proteins↗
Baseline fibrinolytic state and the risk of future venous thrombosis. A prospective study of endogenous tissue-type plasminogen activator and plasminogen activator inhibitor.
BACKGROUND: Although isolated abnormalities of plasminogen activation and inhibition have been reported among selected patients with venous thrombosis, it is unclear whether these deficiencies of fibrinolysis are important risk factors for thromboembolic disease. METHODS AND RESULTS: To evaluate whether baseline levels of endogenous tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) predict the future occurrence of venous thrombosis, levels of these proteins were measured in prospectively collected plasma samples from 55 participants in the Physicians' Health Study who later developed deep venous thrombosis or pulmonary embolism and from an equal number of age- and smoking-matched control subjects who remained free of vascular disease during a mean follow-up period of 60.2 months. Overall, there were no statistically significant differences between case patients and control subjects in baseline levels of PAI-1 (50.5 versus 59.5 ng/ml, p = 0.26), t-PA (13.4 versus 13.3 ng/ml, p = 0.94), or PAI-1:t-PA ratio (6.84 versus 6.58, p = 0.82). No evidence of a threshold effect or trend was seen when these data were analyzed by increasing quartiles of PAI-1 (p = 0.73), t-PA (p = 0.62), or PAI-1:t-PA ratio (p = 0.93). These results were unchanged after multivariate analysis that simultaneously controlled for other baseline cardiovascular risk factors. CONCLUSIONS: In contrast to previous uncontrolled case series and smaller retrospective studies, these prospective data provide strong evidence that baseline fibrinolytic state, as measured by t-PA and PAI-1, does not predict the occurrence of future venous thrombosis.
Adult↗
Strengthening of feldspathic porcelain by ion exchange and tempering.
This study investigated the effectiveness of tempering and ion-exchange treatments on crack growth and bi-axial flexural strength of seven feldspathic porcelains. The results showed that tempering treatment was more effective in strengthening porcelain than was the ion-exchange process as measured by the bi-axial flexural strength. However, the results of initial crack size induced by a microhardness tester showed that ion-exchange yielded a surface that was more resistant to crack initiation than was that yielded by the tempering treatment. EDX and microprobe analyses showed that there was evidence of exchange between Na+ within the porcelain surface and K+ from the ion-exchange agent applied on the surface.
Aluminum Silicates↗
Effects of ammonium and lactate on hybridoma cell growth and metabolism.
The effects of ammonium and lactate at different concentrations on the growth of 2F7 hybridoma cells, involving glucose consumption, lactate accumulation and cell viability, are investigated. The results suggest that growth inhibition occurs at 2.5 mM ammonium and 2.5 mg/ml lactate, and that severe inhibition occurs at 5 mM ammonium and 5.0 mg/ml lactate.
Ammonia↗
Tumors of the heart. An analysis of 79 cases.
There were 79 cases of cardiac tumors seen from 1957 to July 1988. 49 (62.0%) of them were benign and 30 (38.0%) malignant. All the 49 benign tumors except 2 were surgically excised and found to be myxoma. Of them, 18 patients were male and 31 female. 85.7% of the tumors were located in the left atrium, 12.2% in the right atrium and 2.0% in the left ventricle. Palpitation, dyspnea, chest oppression, fever, episodes of syncope and hemiplegia, cough, diastolic and systolic murmurs at the apical or tricuspid area were the common symptoms and signs. Atrial fibrillation was found only in 2 cases. Echocardiographic findings were diagnostic while ECG and X-ray findings were nonspecific. Four patients died after operation. Of the 30 cases of malignant tumors, 15 were secondary tumors metastasized mainly from the lung or mediastinal malignancies. Of 11 primary tumor cases (7 males and 4 females), 3 were malignant lymphoma, 2 mesothelioma of pericardium, 2 malignant myxoma, 1 angiosarcoma, 1 leiomyosarcoma, 1 fibrosarcoma and 1 rhabdomyosarcoma. Another 4 cases were not studied histopathologically. The clinical manifestations, ECG and X-ray findings of the 11 primary tumors were nonspecific but echocardiography was helpful to the diagnosis. Six patients were operated on and 1 died during hospitalization.
Adolescent↗
New inhibitors of aldose reductase: anti-oximes of aromatic aldehydes.
Aldose reductase is an NADPH-dependent enzyme which catalyzes the reduction of glucose to sorbitol. Specific potent inhibitors of aldose reductase are of potential pharmacological use because elevated levels of sorbitol produced by this enzyme in lens, peripheral nerve, retina, and renal glomeruli may be responsible for the pathogenesis associated with chronic diabetes. These inhibitors could also serve as probes of the mechanism of action of aldose reductase. anti-Oximes of aromatic aldehydes (e.g., benzaldoxime and 4-fluorobenzaldoxime) have proved to be effective inhibitors of aldose reductase rivaling pharmacological agents currently used to inhibit this enzyme in vivo. The kinetic patterns of inhibition in which benzyl alcohol is used as the oxidizable substrate suggest that the inhibition is due to the formation of a stable ternary complex composed of aldose reductase, NADP+, and the anti-oxime. Analogus ternary complexes are formed at the active site of horse liver alcohol dehydrogenase which is also inhibited by anti-oximes of efficient substrates.
Alcohol Dehydrogenase↗
Influence of initial flaw size on crack growth in air-tempered porcelain.
Tempering of dental porcelain by forced convective cooling in air has been shown previously to inhibit the sizes of cracks induced in porcelain surfaces. However, the depth of compressive stress that is produced by tempering of feldspathic porcelain has not been determined. It can be assumed that the potential of tempered specimens to inhibit crack formation is reduced as the flaw size exceeds some critical value, since the compressive stress decreases with distance from the surface. The objective of this study was to test the hypothesis that the effectiveness of tempering stress in porcelain decreases with the increasing size of initial surface flaws. Body porcelain discs, 16 mm in diameter and 2 mm in thickness, were tempered (T) by forced convective cooling in air from an initial temperature of 982 degrees C at a pressure of 0.34 MPa for 90 s. Nontempered control discs (NT) were slowly cooled by termination of power to the furnace. The half crack-lengths (c) of surface cracks induced by a Vickers microhardness indenter at loads ranging from 2.0 to 39.2 N were determined initially and over a period of 24 h. The initial half crack-lengths, co, for the tempered specimens were significantly smaller (p less than 0.05) than the corresponding values for the slow-cooled specimens. The mean value of the stress corrosion susceptibility coefficient (n), which is inversely related to the slope of log crack size vs. log time, was only slightly smaller for the NT specimen groups (15.3), compared with the mean value for the T groups (17.1).(ABSTRACT TRUNCATED AT 250 WORDS)
Air↗
Analysis of ras gene mutations in gastrointestinal cancers.
Point mutations of c-Ki-ras genes were analyzed in 33 samples of human gastrointestinal malignancy. DNA extracted from the frozen tissue was amplified by polymerase chain reaction (PCR) and analyzed by direct sequencing and slot-blot hybridization at codons 12, 13 and 61 of c-Ki-ras. In 7 cases out of 19 colorectal cancers, point mutations were found: 3 cases at codon 12, 1 at codon 13, 2 at codon 61 of c-Ki-ras and one case had double mutations at codon 12 and codon 13. In 11 cases of gastric cancer, 4 showed point mutations: 1 at codon 12 and 3 at codon 13 of c-Ki-ras. In 3 pancreatic carcinomas, 2 had point mutations: one at codon 12 and the other at codon 13 of c-Ki-ras. The results indicate that c-Ki-ras gene point mutations are involved in the tumorigenesis of the human gastrointestinal system.
Adult↗
[A study of histamine receptors in peripheral lymphocytes in asthmatic subjects].
The identification and quantitative analysis of specific histamine H1 and H2 receptors on lymphocytes were acquired and histamine-induced suppressor cell activity was examined by using 3H-histamine radioligand-binding assay and co-culture technique. The quantitative analysis of H2 receptors decreased on the lymphocytes of extrinsic asthmatic subjects. Peripheral-lymphocytes from asthmatic subjects generated less histamine-induced suppressor activity than did those from normal individuals. In the asthmatics, the functional suppressor-cell abnormality positively correlated with the decreased quantity of H2 receptors on the lymphocytes.
Adult↗
The enhancement activities of histidyl-histidine in some prebiotic reactions.
The prebiotic synthesis of His and its dimer has led us to study the possible catalytic properties of His-His. The enhancing effect of His-His has been tested in the dephosphorylation of dAMP, the hydrolysis of oligo(A)12, and the oligomerization of 2'3'-cAMP.
Adenine Nucleotides↗
Prebiotic synthesis of histidine.
The prebiotic formation of histidine (His) has been accomplished experimentally by the reaction of erythrose with formamidine followed by a Strecker synthesis. In the first step of this reaction sequence, the formation of imidazole-4-acetaldehyde took place by the condensation of erythrose and formamidine, two compounds that are known to be formed under prebiotic conditions. In a second step, the imidazole-4-acetaldehyde was converted to His, without isolation of the reaction products by adding HCN and ammonia to the reaction mixture. LC, HPLC, thermospray liquid chromatography-mass spectrometry, and tandem mass spectrometry were used to identify the product, which was obtained in a yield of 3.5% based on the ratio of His/erythrose. This is a new chemical synthesis of one of the basic amino acids which had not been synthesized prebiotically until now.
Aldehydes↗
Prebiotic synthesis of histidyl-histidine.
Histidyl-histidine (His-His) has been synthesized in a yield of up to 14.4% under plausible prebiotic conditions using histidine (His), cyanamide, and 4-amino-5-imidazole carboxamide. A trace amount of His trimer was also detected. Because the imidazole group of His is involved in a number of important enzymatic reactions, and His-His has been shown to catalyze the prebiotic synthesis of glycyl-glycine, we expect this work will stimulate further studies on the catalytic activities of simple His-containing peptides in prebiotic reactions.
Aminoimidazole Carboxamide↗
[Communication skills of psychiatric nurses].
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Communication↗