Asymmetric synthesis of 6-<Superscript>18</Superscript>F-<Emphasis Type="Italic">L</Emphasis>-FDOPA using chiral Nickel(II) complexes

A new procedure was suggested for asymmetric synthesis of of 6-[¹⁸F]fluoro-3,4-L-dihydroxyphenylalanine (6-¹⁸F-L-FDOPA), an important radiotracer for studies of the dopaminergic system by positron emission tomography (PET). The key step of the synthesis is stochiometric asymmetric alkylation of chiral Ni(II) complexes using 3,4-methylenedioxy-6-[¹⁸F]fluorobenzyl bromide as alkylating agent. A series of Ni(II) complexes containing various substituents in the benzyl group were tested. The highest enantiomeric purity of 6-¹⁸F-L-FDOPA was attained with the complex derived from (S)-N-(2-benzoylphenyl)-1-(3,4-dichlorobenzyl)-pyrrolidine-2-carboxamide, Ni-DCBPB-Gly, under mild alkylation conditions (CH₂Cl₂, 40°C, potassium tert-butylate as base). Such conditions are favorable from the viewpoint of synthesis automation. The radiochemical yield of 6-¹⁸F-L-FDOPA corrected for the radioactive decay was 10–15% at a synthesis time of 120 min, including purification by semipreparative HPLC. The radiochemical and chemical purity of the product exceeded 99%, and the enantiomeric purity was as high as 95%, meeting the requirements for using 6-¹⁸F-L-FDOPA in PET practice.     

一种用于电力变压器局部放电在线监测的光纤传感器

描述了一种光纤声波传感器系统，这种传感器用于大型电力变压器中局部放电产生声波信号的在线监测。传感器采用融硅的共振腔和在融硅的玻璃管中形成囊状的单膜光纤来形成F—B干涉仪。干涉仪采用低相干性的光采进行干涉。实验结果表明研制的这种光纤声波传感器测量变压器油中传播的声波信号具有比较高的灵敏度和较宽的带宽。     

The regulation of gonadotropin-releasing hormone-induced calcium signals in male rat gonadotrophs by testosterone is mediated by dihydrotestosterone

The biological effects of testosterone (T) may be mediated directly by T or indirectly by its metabolites, dihydrotestosterone (DHT) and estradiol. The present study examined whether the metabolism of T is involved in the regulation of GnRH-induced Ca2+ signaling at the pituitary. In gonadotrophs from castrated rats, a significantly greater percentage of gonadotrophs demonstrated oscillatory Ca2+ responses to 100 nM GnRH than cells from intact rats (72% vs. 24%; P < 0.05). This increase was prevented by the administration of T propionate (0.1 mg/kg x day), DHT benzoate (2 mg/kg x day,), estradiol benzoate (EB; 5 microg/kg x day), or the combination of the above doses of DHT benzoate and EB. In all cases the proportion of gonadotrophs from the steroid-treated rats having oscillatory Ca2+ responses to 100 nM GnRH was between 21-25% (P > 0.05, compared with intact rats). To assess the importance of T metabolism, intact male rats were treated with the aromatase inhibitor letrozole (1 mg/kg x day), the 5alpha-reductase inhibitor finasteride (50 mg/kg x day), or their respective vehicles for 7 days. Letrozole had no effect on GnRH-induced Ca2+ signals, serum LH concentrations, or ventral prostate or testes weight. Finasteride treatment, however, mimicked the effects of castration, with significantly more gonadotrophs exhibiting Ca2+ oscillations in response to 100 nM GnRH than gonadotrophs from the vehicle-treated group (71% vs. 20% respectively; P < 0.05). Finasteride also caused a significant (P < 0.05) decrease in prostatic weight and DHT concentration, but had no significant effect on either prostatic T or serum LH concentrations. These findings suggest that in the intact male rat, the effects of T on GnRH-induced Ca2+ signaling are preferentially mediated via DHT. The results of this study also show that in the absence of androgens, estradiol may regulate GnRH-induced Ca2+ signaling in the male rat pituitary.     

The surgical treatment of aneurysms of the abdominal aorta

The sputum specimens from 1363 patients at the age of 16 to 65 years with nonspecific pulmonary diseases and the pleural exudate specimens from 325 patients were tested for fungi in 1989-1994. The etiological significance of Candida was stated at a concentration of > 10(5) GFU per 1 ml of the sputum. The identification was performed by the routine methods. An increase in the rate of the fungi isolation was studied in the time course of the observation: 15.3 +/- 1.9 per cent in 1989 and 31.6 +/- 3.4 per cent in 1994. The fungi were more frequently isolated from the patients with lung abscesses (38.0 +/- 4.1 per cent of the cases). In the patients with pyothorax the fungi were isolated from the pleural exudate specimens only in 6.8 +/- 1.4 per cent of the cases. The groups of risk of the susceptibility to Candida were revealed. They included patients at the age of 21 to 30 years and above 60. Out of 484 Candida isolates 80.7 per cent belonged to C. albicans, 4.2 per cent to C. tropicalis, 2.1 per cent to C. kefyr and 1.8 per cent to C. krusei. The isolates of C. parapsilosis, C. guillermoudii, C. utilis and C. brumptii were rate. The isolates were highly susceptible to nystatin (91,8 per cent) and lowly susceptible to levorin (35.4 per cent), amphoglucamine (24.7 per cent) and ketokonazol (16.8 per cent).