Repeated intravitreal injections of antivascular endothelial growth factors and risk of intraocular pressure medication use

Graefe's Archive for Clinical and Experimental Ophthalmology - To determine the risk of initiating ocular hypertension and glaucoma treatment with repeated injections of antivascular...     

Reversible left ventricular dysfunction induced by recurrent ventricular tachycardia.

Two cases of transient LV dysfunction associated with VT are described. Both patients had a history of palpitations of several years' duration without symptoms of congestive heart failure. The reason for presentation was an increase in frequency and duration of palpitation. Decreased LV wall motion, observed by 2DE, normalized shortly after treatment of the VT. Diffusely decreased LV wall motion is associated with frequent episodes of VT and may mimic DCM except that signs and symptoms of heart failure are absent.     

Rates of Systemic Degradation and Reticuloendothelial System (RES) Uptake of Thermosensitive Liposome Encapsulating Cisplatin in Rats

The systemic degradation and reticuloendothelial system (RES) uptake of cisplatin (CDDP)-encapsulated thermosensitive liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and di-stearoylphosphatidylcholine (DSPC) (DPPC/DSPC = 9/1, 7/3, and 5/5, w/w) after intravenous administration to rats were examined by measuring the platinum (Pt) levels in the blood and RES (liver and spleen). The blood liposome level profile showed first-order rate elimination for each liposome administration. The elimination rate (K _e1) was faster when the content of DSPC was lower (K _e1: 1.3/hr for 9/1-liposomes, 0.7/hr for 7/3-liposomes, 0.5/hrfor5/5-liposomes). On the other hand, the RES liposome level profile showed distribution of liposomes followed by elimination therefrom. The RES level of the liposomes was lower when the content of DSPC was smaller (maximal level: 25% for 9/1-liposomes at 1 hr, 32% for 7/3-liposomes at 1 hr, 37% for 5/5-liposomes at 2 hr). The kinetic analysis demonstrated that the RES uptake rate (K _res) was almost the same among the liposomes (0.4/hr), while the systemic degradation rate (K _deg; K _e1 – K _res) became larger as the content of DSPC decreased (0.9/hr for 9/1-liposomes, 0.3/hr for 7/3-liposomes, and 0.1/hr for 5/5-liposomes) and that the RES liposome distribution amount was dependent not only on the K _res but also on the K _deg and the rate of RES liposome degradation. The K _deg for each type of liposome corresponded with the systemic CDDP release rate.     

CD98 immunoreactivity in multinucleated giant cells of glioblastomas: An immunohistochemical double labeling study

CD98, which is identical to fusion regulatory protein‐1 (FRP‐1), has been reported to induce and regulate cell fusion and multinucleated giant cell formation. To investigate the association between CD98 and multinucleated giant cells (MNGCs) in glioblastomas, we investigate the CD98 immunoreactivity of MNGCs and the proliferative potential in CD98 immunoreactive MNGCs in paraffin‐embedded sections obtained from patients with glioblastomas. Double immunohistochemical staining for CD98 and Ki67 as a mitotic marker were performed in formalin‐fixed and paraffin‐embedded specimens obtained from 16 patients with primary glioblastomas including MNGCs. Most CD98 immunoreactive (CD98+) tumor cells were negative for Ki67. CD98+ MNGCs were identified in 15 cases. CD98+ Ki67– MNGCs were identified in 14 cases and ranged in number from one to 48 (6.7 ± 11.5). CD98– Ki67+ MNGCs were identified in 15 cases and ranged in number from one to 32 (11.1 ± 9.6). Mitotic index (MI) of CD98+ MNGCs (4.8 ± 2.7%) was significantly lower than that of CD98– MNGCs (91.1 ± 24.6%) (P < 0001). These results suggest that multinucleated giant cell formation may be developed by fusion among CD98– producing cells in glioblastomas.     

Assessment of the contribution of alpha 1-acid glycoprotein to the serum binding of basic drugs using serum treated with sulphosalicylic acid and DEAE-cellulose

Treatment of human serum with DEAE-cellulose in acid conditions almost completely removed alpha 1-acid glycoprotein (alpha 1-AG) with little change in the concentration of albumin and beta-lipoprotein, while treatment with sulphosalicylic acid removed almost all the proteins except alpha 1-AG. The binding of various drugs to serum treated as above was measured by equilibrium dialysis and the contribution of alpha 1-AG to drug binding by human serum was assessed. Sulphosalicylic acid-treated serum exhibited a saturable binding for propranolol, which was considered to be due to the binding to alpha 1-AG while DEAE-cellulose-treated serum mostly exhibited non-saturable binding, for which albumin and beta-lipoprotein may be responsible. With this treated serum, alpha 1-AG was estimated to contribute approximately 40% to the binding of therapeutic concentrations of propranolol, 15% to that of imipramine and 15-20% to that of desipramine, respectively, in serum samples pooled from healthy adults. However, no contribution of alpha 1-AG was observed in the binding of salicylic acid to the serum. Dissociation constants of the propranolol binding to the high affinity site in control serum, sulphosalicylic acid-treated serum and purified alpha 1-AG showed similar values (3.7-6.7 microM). These results suggest that treatment of serum with sulphosalicylic acid and DEAE cellulose is useful in assessing the contribution of alpha 1-AG to the serum binding of basic drugs.     

Physiologically based pharmacokinetics of drug-drug interaction: A study of tolbutamide-sulfonamide interaction in rats

A blood flow rate-limited pharmacokinetic model was developed to study the effect of sulfonamide on the plasma elimination and tissue distribution of¹⁴C -tolbutamide (TB) in rats. The sulfonamides (SA) used were sulfaphenazole (SP), sulfadimethoxine (SDM), and sulfamethoxazole (SMZ). The tissue-to-plasma partition coefficients (Kp) of all tissues studied, i.e., lung, liver, heart, kidney, spleen, G.I. tract, pancreas, brain, muscle, adipose tissue, and skin, increased in the presence of SA, but except for brain, liver, and spleen, the tissue-to-plasma unbound concentration ratio (Kp, f) of other tissues did not show a significant alteration. This suggested that the tissue binding of TB is not affected by SA and that the increase of Kp is due mainly to the displacement of plasma protein-bound TB by SA. The concentrations of TB in several tissues and plasma were predicted by a physiologically based pharmacokinetic model using in vitro plasma binding and metabolic parameters, the plasma-to-blood concentration ratio and the tissue-to-plasma unbound concentration ratios having been determined from both the tissue and plasma concentrations of TB at the β-phase after intravenous administration of TB and the plasma free fraction. The predicted concentration curves of TB in each tissue and in plasma showed good agreement with the observed values except for the brain, for which the predicted concentrations were lower than the observed values in the early time period. In the SP- and SDM-treated rats, the predicted free concentration of TB in the target organ, the pancreas, at 6 h was six times higher than that of the control rats. From these findings, it is suggested that physiologically based pharmacokinetic analysis could be generally useful to predict approximate plasma and tissue concentrations of a drug in the presence of drug-drug interaction.     

Effect of phenobarbitone on the distribution and elimination of imipramine in rats

The effect of phenobarbitone on the steady state volume of distribution (Vdss) and the total body blood clearance (CLtot, b) of imipramine and the serum concentration of its metabolite, desipramine was examined. The serum disappearance of imipramine after an 8 mg kg-1 i.v. dose followed a biexponential decline in both control and phenobarbitone-treated rats while the concentration of its metabolite increased in the phenobarbitone-treated rats then rapidly declined compared with that in control rats. Since CLtot,b was nearly equal to the hepatic blood flow (QH), QH may be the rate-determining step of imipramine elimination. In the control rats the Vdss of imipramine was large at 19.9 litre kg-1. In the phenobarbitone-treated rats the pharmacokinetic parameters, biological half-life (t1/2) and Vdss significantly decreased to approximately 23-40% while CLtot,b increased to 126% of those in the control rats, although the latter difference was not statistically significant. The blood-to-plasma concentration ratios (RB) of imipramine and desipramine decreased in the phenobarbitone-treated rats. The urinary excretion ratios of imipramine and desipramine, to the dose of imipramine over 8 h, were less than 1.5% in both groups. These ratios were not significantly changed in the phenobarbitone-treated rats. It was concluded that the significant decrease in t1/2 of the phenobarbitone-treated rats may not be attributed to the changes in CLtot,b and/or in the urinary excretion, but mainly to the decrease in Vdss.     

Amelioration of experimental amnesia (passive avoidance failure) in rodents by the selective M1 agonist AF102B

Effect of AF102B (cis-2-methylspiro-(1,3-oxathiolane-5,3')-quinuclidine) on experimental amnesia was examined using a passive avoidance task in rodents. The amnesia was produced by anti-cholinergic agents, AF64A (intracerebroventricularly) and scopolamine (subcutaneously). AF102B ameliorated the memory deficits in AF64A-treated rats at 0.1-1 mg/kg, i.p. and at 1-5 mg/kg p.o. and in scopolamine-treated mice at 1-10 mg/kg, i.p. These results suggest that AF102B may compensate for central cholinergic defects and could be developed as a possible therapeutic drug for senile dementia of the Alzheimer type.     

Pharmacokinetic study on the mechanism of tissue distribution of doxorubicin: interorgan and interspecies variation of tissue-to-plasma partition coefficients in rats, rabbits, and guinea pigs

The mechanism of interorgan and interspecies variations in the tissue distribution of doxorubicin was studied in rats, rabbits, and guinea pigs. The permeation properties of doxorubicin were investigated by using isolated rat erythrocytes as a model membrane. A significant dependency of the uptake rate constant on medium pH was observed, suggesting that only un-ionized doxorubicin is diffusible through the plasma membrane. The values of plasma unbound fraction (fp) of doxorubicin were 0.344 for rats, 0.415 for rabbits, and 0.529 for guinea pigs. The tissue DNA concentrations of rats were larger than those of rabbits and smaller than those of guinea pigs in corresponding organs or tissues. An in vitro organ model that described the distribution behavior of doxorubicin in the whole body was constructed, and an equation was derived to estimate the tissue-to-plasma partition coefficients, (Kp) from in vitro experiments. The in vitro Kp values showed comparatively good agreement with the in vivo Kp values for the various organs or tissues in all three species. Doxorubicin is exclusively bound to the nuclei in the cells. The variation of the Kp values in different organs depended on the amount of nuclei per gram of tissue. The primary determinant of the interspecies variation in the Kp values was the difference in tissue DNA concentrations among rats, rabbits, and guinea pigs, and a secondary determinant was the difference in fp values.