Schedule-dependent interaction of doxorubicin, paclitaxel and gemcitabine in human breast cancer cell lines

We showed previously that a sequential treatment with doxorubicin (4 hr) followed by paclitaxel (24 hr) (Dox-->Pacl) induces a synergistic cytotoxic effect in the BRC-230 breast cancer cell line and in human primary breast cancer cultures. The validity of this experimental finding was confirmed in a clinical phase I/II study on advanced breast cancer patients. To improve the cytotoxic effect obtained by the Dox-->Pacl sequence, we analyzed the effect of adding gemcitabine (Gem) to the Dox-->Pacl sequence in a preclinical study. Our study was performed on BRC-230 and MCF-7 cell lines, and cytotoxic activity was evaluated by the sulforhodamine B assay and the type of drug interaction by Drewinko's test. When Gem (0.01 microg/ml for 24 hr) was given immediately or 24 hr after Dox-->Pacl, an antagonistic cytotoxic effect was observed. Conversely, a synergistic effect was found when Gem was given 48 hr after Dox-->Pacl. From results of flow cytometric analysis, the synergistic effect was attributed to cell cycle perturbation. Cells were arrested in G2-M (95% in treated vs. 21% in control samples) 24 hr after Dox-->Pacl treatment. The block progressively recovered thereafter, and after a further 24 hr, at the time of Gem treatment, the cells progressed into the G1-S phase boundary (the cell cycle phase susceptible to the cytocidal effect of the drug). Our findings suggest that the interactions of Dox, Pacl and Gem are highly schedule- and time-dependent and should be taken into consideration in the planning of clinical protocols.     

Light-dependent changes in outer segment free-Ca2+ concentration in salamander cone photoreceptors

Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the photocurrent from the inner segment, which was drawn into a suction pipette, a laser spot confocal technique was employed to evoke fluorescence from the outer segment of a cone loaded with the Ca2+ indicator fluo-3. When a dark-adapted cone was exposed to the intense illumination of the laser, the circulating current was completely suppressed and fluo-3 fluorescence rapidly declined. In the more numerous red-sensitive cones this light-induced decay in fluo-3 fluorescence was best fitted as the sum of two decaying exponentials with time constants of 43 +/- 2.4 and 640 +/- 55 ms (mean +/- SEM, n = 25) and unequal amplitudes: the faster component was 1.7-fold larger than the slower. In blue-sensitive cones, the decay in fluorescence was slower, with time constants of 140 +/- 30 and 1,400 +/- 300 ms, and nearly equal amplitudes. Calibration of fluo-3 fluorescence in situ from red-sensitive cones allowed the calculation of the free-Ca2+ concentration, yielding values of 410 +/- 37 nM in the dark-adapted outer segment and 5.5 +/- 2.4 nM after saturating illumination (mean +/- SEM, n = 8). Photopigment bleaching by the laser resulted in a considerable reduction in light sensitivity and a maintained decrease in outer segment Ca2+ concentration. When the photopigment was regenerated by applying exogenous 11-cis-retinal, both the light sensitivity and fluo-3 fluorescence recovered rapidly to near dark-adapted levels. Regeneration of the photopigment allowed repeated measurements of fluo-3 fluorescence to be made from a single red-sensitive cone during adaptation to steady light over a range of intensities. These measurements demonstrated that the outer segment Ca2+ concentration declines in a graded manner during adaptation to background light, varying linearly with the magnitude of the circulating current.     

Synthesis, biochemical evaluation, and classical and three-dimensional quantitative structure-activity relationship studies of 7-substituted-1,2,3,4-tetrahydroisoquinolines and their relative affinities toward phenylethanolamine N-methyltransferase and the alpha2-adrenoceptor

7-Substituted-1,2,3,4-tetrahydroisoquinolines (7-substituted-THIQs) are potent inhibitors of phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28), the enzyme involved in the biosynthesis of epinephrine. Unfortunately, most of these compounds also exhibit strong affinity for the alpha2-adrenoceptor. To design a selective (PNMT vs alpha2-adrenoceptor affinity) inhibitor of PNMT, the steric and electrostatic factors responsible for PNMT inhibitory activity and alpha2-adrenoceptor affinity were investigated by evaluating a number of 7-substituted-THIQs. A classical quantitative structure-activity relationship (QSAR) study resulted in a three-parameter equation for PNMT (PNMT pKi = 0.599pi - 0.0725MR + 1. 55sigmam + 5.80; n = 27, r = 0.885, s = 0.573) and a three-parameter equation for the alpha2-adrenoceptor (alpha2 pKi = 0.599pi - 0. 0542MR - 0.951sigmam + 6.45; n = 27, r = 0.917, s = 0.397). These equations indicated that steric effects and lipophilicity play a similar role at either active site but that electronic effects play opposite roles at either active site. Two binding orientations for the THIQs were postulated such that lipophilic and hydrophilic 7-substituents would not occupy the same region of space at either binding site. Using these two binding orientations, based on the lipophilicity of the 7-substituent, comparative molecular field analysis (CoMFA) models were developed that showed that the steric and electrostatic interactions at both sites were similar to those previously elaborated in the QSAR analyses. Both the QSAR and the CoMFA analyses showed that the steric interactions are similar at the PNMT active site and at the alpha2-adrenoceptor and that the electrostatic interactions were different at the two sites. This difference in electrostatic interactions might be responsible for the selectivity of THIQs bearing a nonlipophilic electron-withdrawing group at the 7-position. These QSAR and CoMFA results will be useful in the design of potent and selective (PNMT vs alpha2-adrenoceptor affinity) inhibitors of PNMT.     

The role of CD8 and CD4 T cells in intestinal allograft rejection: a comparison of monoclonal antibody-treated and knockout mice

Studies were performed to determine the effects of PTH and related compounds on phosphatidylcholine (PC) hydrolysis in UMR-106 cells and the pathway by which the PTH effects occurred. The responses were compared with those of phorbol 12,13-dibutyrate (PDBu). Both bovine PTH-(1-34) [bPTH-(1-34)] and PDBu stimulated PC hydrolysis within 10 min. Significant effects were elicited by concentrations of 0.3-1 nM bPTH-(1-34) and 5 nM PDBu. Dose-dependent increases were seen at higher concentrations of both compounds, however, the response to bPTH-(1-34) was reduced at 30 nM. Bovine or human PTH-(1-34) and human PTH-related peptide-(1-34) [hPTHrP-(1-34)] were equipotent in their effects, whereas bovine [Nle(8,18)Tyr34]PTH-(3-34) amide [bPTH-(3-34)] and hPTH-(1-31) amide [hPTH-(1-31)] were less potent than bPTH-(1-34). bPTH-(3-34) did not antagonize the effects of bPTH-(1-34). Down-regulation of protein kinase C isozymes by 24-h treatment with PDBu completely prevented the stimulatory effect of PDBu on PC hydrolysis, but did not significantly affect the stimulatory effect of bPTH-(1-34). Both bPTH-(1-34) and PDBu stimulated transphosphatidylation of PC, indicating a phospholipase D-stimulated mechanism. The results suggest that in the UMR-106 cell line PTH can stimulate activation of PLD by a mechanism other than through protein kinase C.     

Determinants of mating success in the golden hamster (Mesocricetus auratus): III. Female acceptance of multiple mating partners.

Four studies with golden hamsters investigated females' acceptance of multiple mating partners. Findings show that females that mated only with a single, recently mated male ran a high risk of pseudopregnancy or reduced litter size. Females paired with males that had mated to satiety 30 min, 8 hrs, or 24 hrs earlier showed a reduced willingness to engage in lordosis than did females paired with a sexually rested (2 wks) male. Females paired with recently mated males were also more likely to mate with additional (fresh) males than were females exposed to rested males. Females presented with 2 anesthetized stimulus males readily discriminated between sexually rested and recently mated individuals. Neither prior sexual experience nor recent copulatory activity was required for this discrimination. It is suggested that multiple-male mating (promiscuity) in female hamsters may be an adaptation against an infertile mating as a consequence of mating with a single, recently mated, sperm-depleted male. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Viability after myocardial infarction: can it be assessed within five minutes by low-dose dynamic iodine-123-iodophenylpentadecanoic acid imaging with a multicrystal gamma camera?

Although positron emission tomography (PET) assesses myocardial viability (V) accurately, a rapid, inexpensive substitute is needed. Therefore, the authors developed a low-dose (1 mCi) Iodine-123-Iodophenylpentadecanoic Acid (IPPA) myocardial viability scan requiring analysis of only the first three minutes of data acquired at rest with a standard multicrystal gamma camera. Twenty-one patients > 2 weeks after myocardial infarction (MI) (24 MIs, 10 anterior, 14 inferoposterior, 21 akinetic or dyskinetic) had cardiac catheterization and resting IPPA imaging. V was determined by either transmural myocardial biopsy during coronary bypass surgery (12 patients, 14 MIs) or reinjection tomographic thallium scan (9 patients, 10 MIs), and 50% of MIs were viable. The IPPA variables analyzed were: time to initial left ventricular (LV) uptake in the region of interest (ROI), the ratio of three-minute uptake in the ROI to three-minute LV uptake, three-minute clearing (counts/pixel) in the ROI (decrease in IPPA after initial uptake), and three-minute accumulation (increase in IPPA after initial uptake) in the ROI. Rules for detecting V were generated and applied to 10 healthy volunteers to determine normalcy. While three-minute uptake in nonviable MIs was only 67% of volunteers (P < 0.0001) and 75% of viable MIs, uptake alone identified only 50% of viable MIs and 75% of nonviable MIs. IPPA clearing, however, was > or = 13.5 counts/pixel in 10/12 (83%) of viable MIs, and IPPA accumulation > or = 6.75 counts/pixel identified one more viable MI, for a sensitivity for V of 11/12 (92%), with a specificity of 11/12 (92%), and a 100% normalcy rate. The authors conclude low-dose IPPA (five-minute acquisition with analysis of the first three minutes of data) has potential for providing rapid, inexpensive V data after MI. Since newer multicrystal cameras are mobile, IPPA scans can be done in emergency rooms or coronary care units generating information that might be useful in decisions regarding thrombolysis, angioplasty, or bypass surgery.     

Induction of proinflammatory cytokine and antioxidant enzyme gene expression following brief myocardial ischaemia

PURPOSE: In a recent study we found an increased resistive index immediately after extracorporeal shock wave lithotripsy (ESWL) in patients older than 60 years, which suggests renovascular disturbance. The present 26-month followup study was undertaken to investigate the relevance of elevated resistive index levels and the incidence of new onset hypertension. MATERIALS AND METHODS: Of the initial 76 patients 57, including 20 of the 23 at risk patients 60 or greater years, group 3), were followed for more than 26 +/- 6 months after ESWL. Followup included 2 resistive index measurements by Doppler ultrasound of the treated and the contralateral kidney, at least 2 blood pressure measurements 1 week apart and excretory urography as well as determination of plasma renin activity in 9 patients. RESULTS: With 1 exception, elevated resistive index levels and hypertension were observed exclusively in patients older than 60 years. In these patients the resistive index ranged between 0.65 and 0.86 (mean plus or minus standard deviation 0.74 +/- 0.05, normal less than 0.7). This increase in resistive index was statistically significant (p < 0.0001). Compared to the levels obtained immediately after ESWL, the resistive index continued to increase in all 9 patients older than 60 years who had hypertension (45%), whereas in the normotensive patients the resistive index was either stable or decreased. There was a strong positive correlation (0.903) between pathological resistive index levels and blood pressure. CONCLUSIONS: Patients older than 60 years are at risk for disturbances of renal perfusion as assessed by the resistive index, and 45% of these patients have new onset hypertension within 26 months of treatment.