Multiexponential T2 relaxation in Fricke agarose gels: implications for NMR dosimetry

NMR relaxation times T1 and T2 of agarose and Fricke agarose gels have been measured in the range 17-51 MHz. The analysis of the spin echo curves indicates a multiexponential behaviour, characterized by three components, at all the examined frequencies. The relative T2 values, ranging from a few to a hundred milliseconds, can be attributed to different species of water molecules present in the gel. Two of these components are characterized by relaxation rates R2a and R2b, more sensitive than R1 to gamma irradiation, the sensitivity S being S(R1) = 0.066 s-1 Gy-1, S(R2a) = 0.088 s-1 Gy-1, S(R2b) = 0.17 s-1 Gy-1. The three T2 values decrease as a function of frequency, but no gain in dose sensitivity is obtained by changing the working frequency in the examined range. The relaxivity of agarose gels containing ferrous or ferric ions has also been measured and found to be different from those of the corresponding solutions in the absence of agarose. Thus it was possible to estimate the irradiation yield from three independent parameters, R1, R2a and R2b. No effect of the dose rate or of the source energy has been observed for any of these parameters.     

Tomsk complex for neutron-transmutation doping of silicon

All-Union Scientific-Research Institute of Nuclear Physics at the S. M. Kirov Tomsk Polytechnical University. Translated from Atomnaya énergiya, Vol. 79, No. 1, pp. 38–40, July, 1995.     

Electron-beam CT scanning for detection of coronary calcification and prediction of coronary heart disease

Electron-beam or ultrafast computerized tomographic (CT) scanning provides a convenient and sensitive means of detecting coronary calcification, which is an early index of atherosclerosis. The procedure has strong negative predictive power for the presence of coronary artery disease, but a limited ability to predict disease severity. However, preliminary indications are that it is as good or better than conventional risk factors in this respect. Although further validation is needed before electron-beam CT can be regarded as an established method of detecting presymptomatic coronary atherosclerosis, the procedure has potential in this context.     

Fluconazole versus itraconazole for candida esophagitis in acquired immunodeficiency syndrome. Candida Esophagitis

BACKGROUNDS & AIMS: Contrasting opinions exist about the pharmacological treatment of esophageal candidiasis in patients with acquired immunodeficiency syndrome (AIDS). The aim of this study was to assess the long-term efficacy of fluconazole and itraconazole treatment. METHODS: This study evaluated 2213 human immunodeficiency virus-positive patients at first episode of esophageal candidiasis diagnosed by endoscopy; 1105 received fluconazole and 1108 received itraconazole. The endoscopic and clinical response to treatment was assessed periodically until the end of the follow-up period (1 year). RESULTS: At week 2, endoscopic cure occurred in 81.2% of patients treated with fluconazole and in 65.6% of patients treated with itraconazole (P < 0.001). Clinical cure was observed in 81.5% of patients treated with fluconazole and in 75.2% of patients treated with itraconazole (P < 0.001). At the end of the follow-up period, endoscopic and clinical cure were observed in 96% of patients treated with fluconazole and in 95.6% of patients treated with itraconazole (P = 0.788), with similar differences by intention-to-treat analysis (93.6% vs. 93.3%; P = 0.853). Treatment failure was observed in 22.3% of fluconazole-treated patients and in 26.6% of itraconazole-treated patients (P = 0.022). CONCLUSIONS: Fluconazole and itraconazole are provided with good long-term therapeutic efficacy in the treatment of Candida esophagitis in patients with AIDS. Fluconazole is associated with a higher rate of cure than itraconazole in short-term treatment.     

Expression studies of delta-globin gene alleles associated with reduced hemoglobin A2 levels in Greek Cypriots

We previously identified five delta-globin gene alleles associated with reduced hemoglobin (Hb) A2 (Trifillis, P., Ioannou, P., Schwartz, E., and Surrey, S. (1991) Blood 78, 3298-3305). We have now evaluated functional consequences of the changes after expression in COS-1 cells to monitor effects on RNA splicing. In addition, variant Hb A2 tetramers were expressed in yeast to assess effects of amino acid changes on oxygen binding and stability to heat and mechanical agitation. The G --> T change at codon 27 and the A --> G change in IVS-2 both affect RNA splicing, whereas the C --> T change at codon 97 and the AT deletion in IVS-2 have no effect. Oxygen equilibrium curves of the Hb A2 variants expressed in yeast were similar to that of wild type Hb A2. None of the three variant Hb A2 tetramers (Thr --> Ile at codon 4 (Hb deltaT4I), Ala --> Ser at codon 27 (Hb deltaA27S), and Arg --> Cys at codon 116 (Hb deltaR116C)) showed decreased heat stability compared with Hb A2, whereas the Hb deltaT4I variant showed highest instability to mechanical agitation. Co-expression in yeast of alpha-globin chain and the delta-chain variant containing a Leu --> Pro change at codon 141 yielded no identifiable tetramers, suggesting lack of assembly or severe tetramer instability. These studies show the probable cause for decreased Hb A2 for two alleles is due to defective splicing, whereas decreased protein stability, increased tetramer association with red cell membranes, increased interdisulfide bond formation of delta-chains, which inhibits assembly with alpha-chains, and/or reduced assembly is suggested for the other three alleles.     

Prostaglandin E receptor subtypes in mouse osteoblastic cell line

PGE2 is one of the key molecules in the osteoblast. It is the major prostanoid in the bone, and its production is under the control of both systemic and local factors. PGE2 has been reported to have multiple actions in the osteoblast, such as growth promotion and cell differentiation. To better understand the action of PGE2 in the osteoblast, we determined the PGE receptor subtypes in MC3T3-E1, an osteoblastic cell line derived from the normal mouse calvaria. Northern blot analysis revealed that EP1 and EP4 subtypes are expressed in MC3T3-E1. In contrast, EP3 subtype was not detected by either Northern blot analysis or RT-PCR. The contribution of each subtype was evaluated by studying the effects of subtype-specific analogs on osteoblastic function at confluency and 5 days after confluency. An EP1 agonist, 17-phenyl-omega-trinor PGE2, increased DNA synthesis and decreased alkaline phosphatase activity. 11-Deoxy-PGE1, and EP2 and EP4 agonist, decreased DNA synthesis and increased alkaline phosphatase activity at both stages. Butaprost, an EP2-selective agonist, showed effects similar to those of 11-deoxy-PGE1 only at confluency. Another and more differentiated osteoblastic marker, osteocalcin production, was detectable and was stimulated by 11-deoxy-PGE1 only 5 days after confluency. The exposure of these cells to EP1 agonist changed the cell shape to a more fibroblastic appearance. These results indicate that EP1, EP4, and probably EP2 are present in MC3T3-E1 cells; EP1 promotes cell growth, and EP2 and EP4 mediate differentiation of the osteoblast. Furthermore, the decreased response to EP2-specific agonist 5 days after confluency suggests that the expression of PGE receptor subtype is dependent on the stage of osteoblastic differentiation. This is the first report to determine PGE receptor subtypes in the bone.