Pharmacokinetic and Pharmacological Profiles of Free and Liposomal Recombinant Human Erythropoietin After Intravenous and Subcutaneous Administrations in Rats

Purpose. Recombinant human erythropoietin (Epo) is used frequently through intravenous (i.v.) and subcutaneous (s.c.) administration for the clinical treatment of the last stage of renal anemia. We encapsulated Epo in liposomes to develop an alternative administration route. The purpose of our study was to evaluate the pharmacokinetics and the pharmacological effects of liposomal Epo in comparison with the Epo after i.v. and s.c. administration to rats. Methods. Epo was encapsulated in liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and soybean-derived sterol mixture (SS) prepared by the reversed-phase evaporation vesicle method. After filtration through a 0.1 m polycarbonate membrane, liposomes were gel filtered (Epo/liposomes). Results. Epo/liposomes showed higher pharmacological activity than Epo/liposomes before gel filtration after i.v. administration to rats. Non-encapsulated Epo lost its activity, whereas encapsulated Epo in liposomes retained it. The pharmacological effects of Epo/liposomes were greater than those of Epo after i.v. administration. Epo/liposomes afforded 3–9 times higher AUC, lower clearance and lower steady-state volume of distribution than Epo after both i.v. and s.c. administrations. Epo/liposomes had an improved pharmacokinetic profile compared with Epo. S.c. administration of Epo/liposomes at 7 h may penetrate primarily (40% of dose) through the blood as a liposome and partly (7% of dose) in lymph. Conclusions. Epo/liposomes may reduce the frequency of injections required for a certain reticulocyte effect in comparison to Epo. The lower clearance of Epo/liposomes may increase the plasma concentrations of Epo, which increases the efficacy.     

1H-NMR and NOE studies of 2-cephems and 3-cephems

The¹H-NMR signals of 2-cephems and 3-cephems have been assigned and the Nuclear Overhauser Effect (NOE) study of these compounds was undertaken.     

Pharmacodynamics of Phenobarbital Anesthesia and Pentylenetetrazol-Induced Maximal Seizures in a Rat Model of Neoplastic Spinal Cord Compression

The purpose of this investigation was to determine whether paraplegia induced by neoplastic cord compression affects the pharmacodynamics of phenobarbital general anesthesia or of pentylenetet-razol (PTZ)-induced convulsions. Paraplegic rats harboring a thora-columbar epidural tumor, or an identical hindlimb tumor mass, received an i.v. infusion of phenobarbital until the onset of anesthesia. At that point, the phenobarbital concentrations in the CSF and serum were measured. Similarly, PTZ was infused until the onset of maximal seizures. It was found that changes related to systemic tumor growth and newly developed paraplegia due to neoplastic spinal cord compression did not attenuate the pharmacodynamics of phenobarbital. However, sustained paraplegia of 4 days duration reduced CNS sensitivity to the hypnotic action of the barbiturate as evidenced by the higher cerebrospinal fluid phenobarbital concentration required to induce anesthesia (170 ± 31 vs 125 ± 20 mg/L; P < 0.05). On the other hand, sustained paraplegia did not affect brain threshold concentration for PTZ-induced seizures.     

Effect of 5-(p-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) enantiomers,major metabolites of phenytoin,on the occurrence of chronic-gingival hyperplasia: in vivo and in vitro study

The purpose of this study was to assess the possible role of the (R)- and (S)- enantiomers of the phenytoin metabolite p-HPPH in the pathogenesis of gingival hyperplasia (GH). About 98% of circulating p-HPPH is in the (S)-form. There were significant differences between patients with and without GH in (R)-p-HPPH level (0.055 vs 0.042 g·ml^–1), both enantiomer/racemate level ratios, and R/S enantiomeric ratio (0.0313 vs 0.0232); an increase in serum (R)-p-HPPH level was observed in patients with GH. In separate experiments, the effect of p-HPPH enantiomers on the proliferation of the normal human dermal fibroblast was studied. The in vitro study showed that (R)-p-HPPH selectively stimulated fibroblast growth. The results suggest that the least abundant metabolite, (R)-p-HPPH, is the most toxic with respect to gingival hyperplasia.     

氢化麦角碱治疗血管性痴呆30例观察

应用氢化麦角碱治疗反复发作性脑梗塞(病程>1年)最终导致不同程度痴呆病人30例,并与常规应用维脑路通治疗同期同类病人做对照。结果治疗组与对照组显效率进行比较存在显著差异,同时观察到此药的一些少见的副作用,经减量可消失,不影响正规疗程,故此药疗效肯定安全,不失为临床推广应用。     

A new approach to the study of ocular chromatic aberrations

We measured the ocular wavefront aberration at six different visible wavelengths (between 450 and 650 nm) in three subjects, using a spatially resolved refractometer. In this technique, the angular deviation of light rays entering the pupil at different locations is measured with respect to a target viewed through a centered pupil. Fits of the data at each wavelength to Zernike polynomials were used to estimate the change of defocus with wavelength (longitudinal chromatic aberration, LCA) and the wavelength-dependence of the ocular aberrations. Measured LCA was in good agreement with the literature. In most cases the wavefront aberration increased slightly with wavelength. The angular deviations from the reference stimulus measured using a magenta filter allowed us to estimate the achromatic axis and both optical and perceived transverse chromatic aberration (TCA), (including the effect of aberrations and Stiles-Crawford effect). The amount of TCA varied markedly across subjects, and between eyes of the same subject. Finally, we used the results from these experiments to compute the image quality of the eye in polychromatic light.     

A multiscale spatial filtering account of the White effect, simultaneous brightness contrast and grating induction

Blakeslee and McCourt ((1997) Vision Research, 37, 2849-2869) demonstrated that a multiscale array of two-dimensional difference-of-Gaussian (DOG) filters provided a simple but powerful model for explaining a number of seemingly complex features of grating induction (GI), while simultaneously encompassing salient features of brightness induction in simultaneous brightness contrast (SBC), brightness assimilation and Hermann Grid stimuli. The DOG model (and isotropic contrast models in general) cannot, however, account for another important group of brightness effects which includes the White effect (White (1979) Perception, 8, 413-416) and the demonstrations of Todorovic ((1997) Perception, 26, 379-395). This paper introduces an oriented DOG (ODOG) model which differs from the DOG model in that the filters are anisotropic and their outputs are pooled nonlinearly. The ODOG model qualitatively predicts the appearance of the test patches in the White effect, the Todorovic demonstration, GI and SBC, while quantitatively predicting the relative magnitudes of these brightness effects as measured psychophysically using brightness matching. The model also accounts for both the smooth transition in test patch brightness seen in the White effect (White & White (1985) Vision Research, 25, 1331-1335) when the relative phase of the test patch is varied relative to the inducing grating, and for the spatial variation of brightness across the test patch as measured using point-by-point brightness matching. Finally, the model predicts intensive aspects of brightness induction measured in a series of Todorovic stimuli as the arms of the test crosses are lengthened (Pessoa, Baratoff, Neumann & Todorokov (1998) Investigative Ophthalmology and Visual Science, Supplement, 39, S159), but fails in one condition. Although it is concluded that higher-level perceptual grouping factors may play a role in determining brightness in this instance, in general the psychophysical results and ODOG modeling argue strongly that the induced brightness phenomena of SBC, GI, the White effect and the Todorovic demonstration, primarily reflect early-stage cortical filtering operations in the visual system.     

Different pH Dependency of Mitomycin C Activity in Monolayer and Three-Dimensional Cultures

Purpose. Previous studies by other investigators have shown an enhancement of mitomycin C (MMC) activity at acidic extracellular pH (pH_e) in monolayer cultures of human cells. The goal of the present study was to determine if the efficacy of intravesical MMC therapy in patients treated for superficial bladder cancer can be enhanced by using acidified dosing solutions. We evaluated (a) the effect of pH_e on MMC activity in patient bladder tumors in vitro, and (b) the pH dependency of MMC activity in 2-dimensional monolayer and 3-dimensional multilayer cultures of human bladder RT4 tumor cells. Methods. Patient bladder tumors were maintained as 3-dimensional histocultures. RT4 cells were harvested and maintained as monolayer cultures or as 3-dimensional cell pellets on a collagen gel matrix. The cell pellets were 300–450 cell layers and 4,000–5,000 µm in diameter. Tumors or cells were incubated for 2 hr with MMC-containing media at pH_eof 5, 6, and 7.4. The drug effect was measured by the inhibition of DNA precursor (thymidine) incorporation. The stability of MMC as a function of pH_e was determined. About 24% of MMC was degraded following 2 hr exposure at pH_e 5 and 2% at pH_e 6 and 7.4. Results. The drug concentrations required to inhibit thymidine incorporation by 50% (IC₅₀) were corrected for the degraded MMC at acidic pH_e. The results showed no pH-dependent MMC activity in human patient bladder tumors nor in RT4 multilayer cultures; the IC₅₀ values were about 10 µg/ml at all three pH_e. In contrast, the monolayer RT4 cultures showed a pH-dependent MMC cytotoxicity; the IC₅₀ were 0.1, 0.8 and 1.2 µg/ ml at pH_e 5,6 and 7.4, respectively (p < 0.05). Pre-incubation of multi-layered RT4 cultures in acidic pH medium for 8 hr enhanced the MMC activity; the IC₅₀ was reduced by about 5 fold at pH_e 5 and about 3 fold at pH_e 6. Similar pH-dependent MMC activity was found when multilayers were pre-treated for 1 hr with 0.5 µml nigericin, a proton ionophore known to cause the intracellular pH (pH_i) to equilibrate with pH_e. Conclusions. These data suggest that the difference in the pH dependency of MMC activity in the monolayer and multilayer systems was due to the different experimental conditions. The time lag for pH_i to equilibrate with pH_e in the multilayer systems and the instability of MMC at low pH_e imply that the efficacy of intravesical MMC therapy is unlikely to be enhanced by using acidic dosing solution.     

Cerebral energy metabolism in patients with brain lesions at normo- and hyperbaric oxygen pressures

Summary The object of this study was to ascertain the oxygen tolerance limit and the oxygenation state of the injured brain in man. While breathing air, oxygen and hyperbaric oxygen at pressures of 1.5 and 2.0 atmospheres absolute (ATA), the cerebral arteriovenous differences (AVD) for O₂, glucose, lactate, pyruvate and blood gas pressures and pH values were measured. The balance of the cerebral glucose metabolism was calculated. The results showed that the injured brain did not tolerate the exposure to an oxygen pressure of 2.0 ATA for 10 to 15 min, but exposure to 1.5 ATA for 35–40 min was tolerated and had a favorable effect on the glucose or energy metabolism of the brain as well as on the clinical course. There was a distinctly increased cerebral glycolysis while breathing air indicating insufficient oxygen delivery to the brain. The change from breathing air to oxygen resulted in a distinct inhibition of cerebral glycolysis, which indicated improved cerebral oxygenation and energy production and gave evidence for a Pasteur effect regulating the glucose metabolism of the injured brain in man. At an inspiratory oxygen pressure of 1.5 ATA we had a nearly balanced cerebral glucose metabolism indicating an adequate cerebral oxygenation and energy formation. Further increase in inspiratory oxygen pressure to 2.0 ATA (performed only in group A) increased cerebral glycolysis considerably. This was assumed to be due to cerebral oxygen poisoning resulting in disturbed oxidative energy formation. Following this alteration an extreme reduction of the cerebral glucose uptake appeared, probably due to a disturbance of the specific glucose transport system. These metabolic alterations were not accompanied by seizures or any other clinical neurological manifestation. In group B, exposed to 1.5 ATA, such alterations of the cerebral glucose metabolism did not appear. A nearly balanced cerebral glucose metabolism was found at inspiratory oxygen pressures of 1.0 and particularly of 1.5 ATA, indicating an improved oxygenation and energy production of the affected brain. Finally, a renewed increase of the cerebral glycolysis occurred following the change from breathing oxygen to air. This again indicated an insufficient oxygen delivery to the affected brain.

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Zusammenfassung Ziel dieser Arbeit war es, die Wirkung verschiedener inspiratorischer O₂-Drucke auf den zerebralen Glukose- bzw. Energiestoffwechsel zu untersuchen. Dabei sollte insbesondere die Sauerstoff-Toleranzgrenze und der Zustand der Oxygenierung des geschädigten Hirns bestimmt werden. Unter Luft-, Sauerstoff und hyperbarer Sauerstoffatmung, d. h. bei Drucken von 1,5 und 2,0 Atmosphären, wurden die arterio-hirnvenösen Differenzen (AVD) für O₂, Glukose, Laktat, Pyruvat sowie die Blutgasdrucke und die pH-Werte gemessen. Die Bilanz des zerebralen Glukosestoffwechsels wurde bestimmt. Die Ergebnisse zeigten vor allem, daß das geschädigte Hirn eine Sauerstoffbelastung von 2,0 Atmosphären mit einer Expositionszeit von 10 bis 15 min nicht toleriert. Dagegen wurde eine Sauerstoffbelastung von 1,5 Atmosphären mit einer Expositionszeit von 35–40 min vertragen und hatte einen günstigen Einfluß auf den zerebralen Glukose- bzw. Energiestoffwechsel sowie auf den Krankheitsverlauf von traumatischen oder ischämischen Hirngewebsveränderungen. Während der Luftatmung fand sich eine erhebliche Steigerung der zerebralen Glykolyse, was auf eine mangelhafte O₂-Versorgung des Hirngewebes hinwies. Der Wechsel von Luft- auf Sauerstoffatmung führte zu einer deutlichen Hemmung der zerebralen Glykolyse. Dies zeigte eine Besserung der zerebralen Sauerstoffversorgung und Energieproduktion an und wies auf einen Pasteur Effekt bei der Regulation des Glukosestoffwechsels des geschädigten Hirns hin. Bei einem inspiratorischen Sauerstoffdruck von 1,5 Atmosphären war eine praktisch ausgeglichene Bilanz des zerebralen Glukosestoffwechsels nachweisbar, was für eine ausreichende Sauerstoffversorgung und Energiebildung des Hirns sprach. Der weitere Anstieg des inspiratorischen Sauerstoffdruckes auf 2,0 Atmosphären, der nur in Gruppe A durchgeführt wurde, bewirkte jedoch eine erhebliche Steigerung der zerebralen Glykolyse. Es ist anzunehmen, daß diese Stoffwechseländerung durch eine zerebrale Sauerstoffvergiftung hervorgerufen wurde, die vor allem zu einer Störung der oxydativen Energiegewinnung führte. Anschließend trat eine extreme Reduzierung der zerebralen Glukoseaufnahme auf, die am ehesten durch eine Störung des spezifischen Glukosetransportsystems des Hirns bedingt war. Diese Stoffwechselstörungen gingen nicht mit epileptischen Anfällen oder sonstigen klinisch-neurologischen Veränderungen einher. Bei den Patienten der Gruppe B, die nur mit einem Sauerstoffdruck von 1,5 Atmosphären belastet wurden, traten derartige Veränderungen des zerebralen Glukosestoffwechsels nicht auf. Eine praktisch ausgeglichene Bilanz des zerebralen Glukosestoffwechsels wurde bei inspiratorischen Sauerstoffdrucken von 1,0 und vor allem von 1,5 Atmosphären nachgewiesen und zeigte eine Besserung der Sauerstoffversorgung und Energiebildung des geschädigten Hirns an. Schließlich beobachteten wir nach dem Wechsel von Sauerstoff- auf Luftatmung einen erneuten Anstieg der zerebralen Glykose, was wiederum auf eine insuffiziente Sauerstoffversorgung des Hirns hinwies.

     

Cation exchange contribution to the retention of specific quaternary ammonium compounds in reversed-phase high-performance liquid chromatography

The influence of electrolytes on the retention of organic cationic solutes in reversed-phase high-performance liquid chromatography (RP-HPLC) has been investigated. The effects of the nature and concentration of electrolytes and mobile phase pH on the retention of two model quaternary ammonium compounds were studied on mu-Bondapak C18 stationary phase with aqueous methanolic eluents. The nature and concentration of inorganic cations added to the mobile phase modified the retention of the solutes. The counter anion of the added electrolyte did not perceptibly influence solute retention at constant mobile phase pH, although it did significantly influence solute retention when the electrolytes were added to unbuffered mobile phases. The retention data are consistent with the inclusion of an ion exchange contribution to the retention of cationic solutes in the systems investigated.