Synthesis and evaluation of PET probes for the imaging of I2 imidazoline receptors in peripheral tissues

IntroductionTo explore the possible use of positron emission tomography (PET) probes for imaging of I₂-imidazoline receptors (I₂Rs) in peripheral tissues, we labeled two new I₂R ligands, 2-[2-(o-tolyl)vinyl]-4,5-dihydro-1H-imidazole (K_i for I₂Rs, 3.7 nM) and 2-[2-(o-tolyl)ethyl]-4,5-dihydro-1H-imidazole (K_i for I₂Rs, 1.7 nM) with ¹¹C ([¹¹C]metrazoline and [¹¹C]TEIMD), respectively, and evaluated these ligands and the recently developed I₂R ligand 2-[3-fluoro-[4-¹¹C]tolyl]-4,5-dihydro-1H-imidazole ([¹¹C]FTIMD) by in vivo studies.Methods[¹¹C]Metrazoline and [¹¹C]TEIMD were prepared by a palladium-promoted cross-coupling reaction of the tributylstannyl precursor and [¹¹C]methyl iodide. Their biodistribution in mice was investigated by tissue dissection. In addition, PET scans and metabolite analysis were performed.Results[¹¹C]Metrazoline and [¹¹C]TEIMD were successfully synthesized with a suitable radioactivity for injection. In the liver and pancreas expressing I₂Rs, coinjection with the high-affinity I₂R ligand, BU224, induced a reduction in the radioactivity level at 30 min after injection of [¹¹C]metrazoline and [¹¹C]FTIMD. However, the radioactivity level after injection of [¹¹C]TEIMD was unchanged. In the PET study, coinjection with BU224 induced a decrease in the radioactivity level in the liver and pancreas after more than 15 min of injection of [¹¹C]metrazoline and [¹¹C]FTIMD as compared with the results obtained for controls. In metabolite analysis, coinjection with BU224 induced a significant reduction in the percentage of unchanged [¹¹C]metrazoline at 30 min after injection as compared with that in the control, although no significant difference was observed in the percentage of unchanged [¹¹C]FTIMD.Conclusion[¹¹C]Metrazoline may be a more useful PET probe than [¹¹C]FTIMD for imaging of I₂Rs in peripheral tissues.     

PET study using [11C]FTIMD with ultra-high specific activity to evaluate I2-imidazoline receptors binding in rat brains

IntroductionWe recently developed a selective ¹¹C-labeled I₂-imidazoline receptor (I₂R) ligand, 2-(3-fluoro-4-[¹¹C]tolyl)-4,5-dihydro-1H-imidazole ([¹¹C]FTIMD). [¹¹C]FTIMD showed specific binding to I₂Rs in rat brains having a high density of I₂R, as well as to I₂Rs those in monkey brains, as illustrated by positron emission tomography (PET) and autoradiography. However, [¹¹C]FTIMD also showed moderate non-specific binding in rat brains. In order to increase the specificity for I₂R in rat brains, we synthesized [¹¹C]FTIMD with ultra-high specific activity and evaluated its binding.Methods[¹¹C]FTIMD with ultra-high specific activity was prepared by a palladium-promoted cross-coupling reaction of the tributylstannyl precursor and [¹¹C]methyl iodide, which was produced by iodination of [¹¹C]methane using the single-pass method. Dynamic PET scans were conducted in rats, and the kinetic parameters were estimated.Results[¹¹C]FTIMD with ultra-high specific activity was successfully synthesized with an appropriate level of radioactivity and ultra-high specific activity (4470±1660 GBq/μmol at end of synthesis, n=11) for injection. In the PET study, distribution volume (V_T) values in all the brain regions investigated whether I₂R expression was greatly reduced in BU224-pretreatead rats compared with control rats (29–45% decrease). Differences in V_T values between control and BU224-pretreated rats using [¹¹C]FTIMD with ultra-high specific activity were greater than those using [¹¹C]FTIMD with normal specific activity (17–34% decrease) in all brain regions investigated.ConclusionQuantitative PET using [¹¹C]FTIMD with ultra-high specific activity can contribute to the detection of small changes in I₂R expression in the brain.     

Age-related effects of fasting on ketone body production during lipolysis in rats

Objective

The age-related effects of fasting on lipolysis, the production of ketone bodies, and plasma insulin levels were studied in male 3-, 8-, and 32-week-old Sprague–Dawley rats.

Methods

The rats were divided into fasting and control groups. The 3-, 8- and 32-week-old rats tolerated fasting for 2, 5, and 12 days, respectively.

Results

Fasting markedly reduced the weights of perirenal and periepididymal white adipose tissues in rats in the three age groups. The mean rates of reduction in both these adipose tissue weights during fasting periods were higher in the order of 3 > 8 > 32-week-old rats. Fasting transiently increased plasma free fatty acid (FFA), total ketone body, β-hydroxybutyrate, and acetoacetate concentrations in the rats in the three age groups. However, plasma FFA, total ketone body, β-hydroxybutyrate, and acetoacetate concentrations in the 3-week-old rats reached maximal peak within 2 days after the onset of fasting, although these concentrations in the 8- and 32-week-old rats took more than 2 days to reach the maximal peak. By contrast, the augmentation of plasma FFA, total ketone body, β-hydroxybutyrate, and acetoacetate concentrations in the rats in the three age groups had declined at the end of each experimental period. Thus, the capacity for fat mobilization was associated with tolerance to fasting. Plasma insulin concentrations in the rats in the three age groups were dramatically reduced during fasting periods, although basal levels of insulin were higher in the order of 32 > 8 > 3 week-old rats.

Conclusion

These results suggest that differences in fat metabolism patterns among rats in the three age groups during prolonged fasting were partly reflected the metabolic turnover rates, plasma insulin levels, and amounts of fat storage.     

Study of the cases with multidrug-resistant Pseudomonas aeruginosa by sputum culture]

We evaluated the clinical features of multidrug-resistant Pseudomonas aeruginosa cases determined by sputum culture between April, 2005 and December, 2006. The clinical features of most cases were: (1) pneumonia in the elderly with cerebrovascular diseases, (2) previous administration of carbapenems and antipseudomonal cephems, (3) PIPC, CAZ and ISP sensitve MDRP, (4) MRSA was isolated concurrently, (5) not necessary of therapy against MDRP, (6) good outcome.     

Major histocompatibility complex class I-specific cytolytic T cells, derived from gld mice, lacking Thy-1, CD4, and CD8

Thy-1 is a major cell surface molecule expressed on murine thymocytes and peripheral T cells. Its physiological function is unknown, but in vitro studies suggest that Thy-1 may transmit activation signals to T cells and may play a role in the growth and/or differentiation of thymocytes [Kroczek, R. A., Gunter, K. C., Seligmann, B. & Shevach, E. M. (1986) J. Immunol. 136, 4379-4384; Kroczek, R. A., Gunter, K. C., Germain, R. N. & Shevach, E. M. (1986) Nature (London) 322, 181-184]. However, not all mouse thymocytes are Thy-1+ [Scollay, R., Wilson, A., D'Amico, A., Kelly, K., Egerton, M., Pearse, M., Wu, L. & Shortman, K. (1988) Immunol. Rev. 104, 81-120]. In addition, C3H-gld/gld mice accumulate large numbers of Thy-1- (and Thy-1+) T-cell antigen receptor-positive CD8- CD4- (double negative) T cells in peripheral lymphoid organs. Our previous studies of these Thy-1- and Thy-1+ double negatives suggested that lack of Thy-1 expression correlated with diminished capacity to respond to T-cell stimuli. In this report, we describe a Thy-1- alpha/beta T-cell receptor-positive major histocompatibility complex-specific cytotoxic T-cell clone derived from C3H-gld/gld lymph node-residing cells. The data show that, at least in this system, Thy-1 (and CD8/CD4) expression is not required for growth, cytolytic activity, or expression of functional T-cell receptor complexes in vitro and raise the possibility that Thy-1 expression may not be obligatory in vivo for development of cytotoxic T-lymphocyte precursors in gld mice.     

Serum PGI2-regulating factors in acute myocardial infarction

Human serum or plasma contains two factors which regulate PGI2 metabolism. The one is "PGI2-synthesis stimulating factor" which stimulates PGI2 synthesis in the vessel wall. The other is "PGI2-stabilizing factor" which stabilizes PGI2 in the blood. In the very early phase of acute myocardial infarction, the serum levels of these two factors were significantly reduced, which may be related to the thrombus formation in the coronary artery in acute myocardial infarction.     

Effect of celecoxib on experimental liver fibrosis in rat.

BACKGROUND/AIM: Cyclooxygenase-2 (COX-2), an inducible enzyme that catalyzes prostaglandin synthesis, has been implicated in a number of hepatic stellate cell (HSC) functions. In the current study, we assessed the in vivo effect of celecoxib, a COX-2-selective inhibitor, in experimental liver fibrosis in rats. METHODS: Male Sprague-Dawley rats received experimental treatments for 5 weeks. Serum alanine transminase at the time of sacrifice was measured. Quantitative assessment of liver fibrosis was performed by computerized morphometry. Expression of COX-2, alpha smooth muscle actin and connective tissue growth factor (CTGF) was evaluated by immunohistochemistry. Real-time quantitative PCR was used to determine the expression of genes associated with fibrogenesis and extracellular matrix degradation. RESULTS: Liver fibrosis was significantly worse in rats that received both carbon tetrachloride (CCl4) and celecoxib, compared with rats that received CCl4 and gavage of water (P = 0.037). There was also more HSC activation, and upregulation of collagen alpha1(I), heat-shock protein 47, alphaB crystallin, matrix metalloproteinase (MMP)-2, MMP-9 and tissue inhibitor of MMP (TIMP)-2. The expression of TIMP-1 and CTGF was not significantly different between the two groups. The pro-fibrogenic effect of celecoxib in toxin-induced liver fibrosis in rats was further confirmed in thioacetamide model of liver injury. CONCLUSIONS: Celecoxib potentiates experimental liver fibrosis; further studies are warranted to investigate the potential pro-fibrogenic effect of celecoxib in other animal models of liver fibrosis and in patients with chronic hepatitis.