Measuring the in vivo binding parameters of [18F]-fallypride in monkeys using a PET multiple-injection protocol.

The goal of this work was to quantify the in vivo transport and binding parameters of [F-18]fallypride and the D2/D3 receptor density (B'max) in both the striatal (putamen, caudate, ventral striatum) and extrastriatal regions (thalamus, amygdala, cerebellum, temporal and frontal cortices) of the rhesus monkey brain. Multiple-injection PET experimental protocols with injections of radiolabeled and unlabeled doses of fallypride were used to estimate the K1, k2, kon/VR, koff and B'max kinetic parameters. The experimental design was chosen using the D-optimal criterion to maximize the precision of the estimated binding parameters for the various brain regions. There was a significant range in B'max for the putamen (27 pmol/mL), caudate (23 pmol/mL), ventral striatum (14 pmol/mL), thalamus (1.8 pmol/mL) and amygdala (0.9 pmol/mL). Significant receptor binding was also found in the cortical regions. Knowledge of these in vivo rate constants serves as a necessary step in using [F-18]fallypride PET to measure D2/D3 receptor density and drug occupancy in clinical research applications. We believe the precise parameter estimates derived from these complicated experimental protocols are necessary for proper application of drug occupancy and clinical research studies with [F-18]fallypride, which often rely on the validity of assumptions regarding the model parameters.     

Synthesis and evaluation of ether containing 99mTc-nitrido dithiocarbamate complexes as brain perfusion imaging agent.

In the present study, a series of (99m)Tc-nitrido dithiocarbamate complexes containing ether linkages have been prepared and their brain perfusion characteristics studied. Two primary dithiocarbamates and two secondary dithiocarbamates were synthesized in >80% yield and were characterized by elemental analyses. The ligands were then labeled using a (99m)Tc-nitrido intermediate, prepared from sodium pertechnetate using commercially available nitrido kit-vials, at a low ligand concentration of 0.1 mg. The prepared complexes were obtained in more than 95% yield and were characterized by paper electrophoresis and HPLC. All the complexes were found to be neutral and eluted out as a single species in HPLC. Biodistribution studies were carried out in normal Swiss mice. All the complexes showed uptake in the brain. (99m)TcN complexes of secondary dithiocarbamates showed higher initial brain uptake (5 min p.i.) than their primary amine counterparts. However, all the complexes exhibited rapid washout from the brain.     

The contrary position to the nonresective treatment for abdominal aortic aneurysm

The operative mortality rate for abdominal aortic aneurysm resection remains high (20% to 66%) for high-risk patients. The high-risk factors are severe cardiac, respiratory, and renal insufficiency and morbid obesity. Those advocating the alternative nonresective treatment of aneurysm thrombosis and axillofemoral bypass grafts have reduced the operative mortality rate to between 0% and 7%. However, in a collective series of 87 patients, there was a mortality rate of 10.3% in the patients with aortic aneurysms treated by the nonresective method and an incidence of reoperation for complications of axillofemoral graft of 31.0%. Many of these patients had subsequent operations and/or radiologic procedures to complete the process of aneurysm thrombosis (23.0%). Because there is an increasing trend toward this method of treatment, we reviewed our experience with the conventional aneurysm resection in a similar group of patients. Of 105 consecutive patients, 19 qualified as high risk. One patient died, resulting in an operative mortality rate of 5.2%. Cerebral, cardiac, and renal morbidity was transient and subsequent operations were not required. Eighteen patients were discharged as well. In the remaining 86 patients, one died, resulting in an operative mortality rate of 1.2%. The mortality rate for the entire series was 1.9%. Indications for the nonresective treatment appear to be increasing by the addition of other risk factors. This trend is of concern. We believe that there are limited indications for the treatment of aortic aneurysms without resection. However, the procedure should not be offered lightly as an alternative form of treatment.     

The effects of valvular regurgitation on thermodilution ejection fraction measurements.

Through the use of thermodilution principles and rapid response thermistors, it is now possible to measure right ventricular ejection fractions serially in patients. However, to our knowledge, the extent to which tricuspid regurgitation affects the accuracy of thermodilution ejection fraction measurements has not been quantified. The purpose of this study was to compare actual and thermodilution ejection fraction measurements in an in vitro model of tricuspid regurgitation over a wide range of ejection fractions. Stepwise perforation of the inlet valve resulted in regurgitant fractions ranging from 4 to 40 percent. At each increment of inlet valve regurgitation, triplicate sets of thermodilution (EFthermo) ejection fraction measurements were obtained and compared with actual ejection fractions (EFactual). The mean difference between EFactual and EFthermo significantly increased with 8 percent regurgitation and significantly increased with greater increments of inlet valve regurgitation. EFthermo consistently underestimated EFactual over the entire range of regurgitant values. Linear regression analysis revealed a significant correlation between EFactual and EFthermo for all degrees of regurgitation; however, the correlation coefficient significantly declined from control valves with 13 percent regurgitation and declined further with 33 percent regurgitation. Qualitative classification of the inlet valve regurgitation into mild, moderate, and severe regurgitation was performed using pulsed Doppler echocardiography. Mild inlet valve regurgitation resulted in a significantly increased difference between EFactual and EFthermo from control values. A significant increase in the difference between EFactual and EFthermo was observed with both moderate and severe regurgitation. In summary, thermodilution underestimated actual ejection fraction in a direct linear relationship to the degree of inlet valve regurgitation. Thus, in the presence of tricuspid regurgitation, this method may still be useful in serially measuring changes in right ventricular ejection fraction.     

Culture media variation as related to in vitro aging of human fibroblasts: II. Effects on nucleolar number/cell, volume/nucleolus and total nucleolar volume/cell

The relative effect of five commonly used culture media (MEM, BME, McCoy's 5A, M199 and HMEM) on the average nucleolar number/cell, the average volume/nucleolus and the total nucleolar volume/cell was examined during in vitro senescence of WI-38 human fetal fibroblasts. Statistical analyses show that cells aging in MEM show a higher number of nucleoli/cell than that of cells aging in any other medium. For cells aging in the other four media, there are no significant differences in the average number of nucleoli/cell. Linear regression analysis shows that in all cases there is a linear decrease in the average number of nucleoli/cell as a function of PDL. Statistical analyses show that the average volume/nucleolus is significantly greater for cells aging in M199 than in any other medium. Cells aging in HMEM show smaller average nucleolar volume than cells aging in M199, but display larger volumes than that of cells aged in BME, McCoy's 5A, or MEM. Cells aging in BME and McCoy's 5A media show no significant difference among each other in terms of average nucleolar volume, but a difference in this parameter is noted in cells aging in BME and MEM. A linear regression analysis shows that the average volume/nucleolus increases linearly as a function of age for cells grown in all five media. Analysis of the total nucleolar volume/cell in the five media shows that cells aging in M199 and HMEM are not significantly different from each other in terms of this variable, but show significantly larger volumes than those of cells aging in BME, McCoy's 5A and MEM. Cells aging in BME, McCoy's 5A and MEM display no significant difference with regard to this parameter. Linear regression analysis shows a positive linear relationship between the PDL and the total nucleolar volume/cell. The relative effects of all five media are not the same on the three cellular variables studied during in vitro aging of WI-38 cells. We, therefore, suggest that one should note this medium differential in order to allow meaningful comparison of results on possible changes in various morphological parameters during in vitro senescence of diploid human fibroblasts.     

Development of in vitro screening system for assessment of antifilarial activity of compounds

Evaluation of antifilarial activity of new potential agents in vivo is extremely time consuming and uneconomic. In the present study effort has been made to develop an in vitro screening method using Acanthocheilonema viteae, a subcutaneously dwelling rodent filariid with anaerobic metabolic characteristics like human filariids, W. Bancrofti/Brugia malayi as test parasite. Motility test and tetrazolium (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT) based colorimetric assay were used as parameters in in vitro assay. Results showed that 92.3% of compounds (in vivo active) could be picked up in the in vitro assay when both adults and microfilarae (mf) were used simultaneously. Mf and adult stages separately detected, respectively, 84.6 and 69.2% of in vivo active compounds. The adults and mf separately and both the life stages together exhibited, respectively, 80.0, 50.0 and 80.0% false positive results in the in vitro test with in vivo inactive compounds. It is felt that mf stage when used in in vitro test using motility and MTT assays as parameters would be useful in primary screening of new potential filaricides.