Malonyl isoflavone glucosides are chiefly hydrolyzed and absorbed in the colon

Malonyl isoflavone glucosides are water-soluble derivatives of soybean hypocotyls. This study compared the hydrolysis and absorption of malonyl isoflavone glucosides and nonmalonyl isoflavone glucosides in rats. Plasma concentrations of isoflavones were measured after oral administration of malonyl isoflavone glucosides or isoflavone glucosides. After fasting, the duodenum, jejunum, ileum, and colon were excised, and homogenates were prepared. The extent of hydrolysis of each glucoside by each intestinal homogenate was measured. Plasma levels of isoflavone aglycones, such as daidzein and glycitein, were higher in rats administered malonyl isoflavone glucosides than in those administered isoflavone glucosides. The area under the curve of daidzein in plasma of rats administered malonyl isoflavone glucosides was also significantly greater than that in those administered isoflavone glucosides. A transport experiment using Caco-2 cells suggested that degradation of malonyl glucosides to aglycones is necessary for intestinal absorption. Malonyl isoflavone glucosides were hydrolyzed only in the colon, whereas hydrolysis of isoflavone glucosides occurred in the jejunum, ileum, and colon. These results indicated more effective absorption of malonyl isoflavone glucosides than of nonmalonyl isoflavone glucosides. Moreover, effective absorption of malonyl isoflavone aglycones in the colon contributed to the significant increase in plasma isoflavone levels.

Radioiodinated phenylalkyl malonic acid derivatives as pH-sensitive SPECT tracers

Introduction

In vivo pH imaging has been a field of interest for molecular imaging for many years. This is especially important for determining tumor acidity, an important driving force of tumor invasion and metastasis formation, but also in the process of apoptosis.

Methods

2-(4-[¹²³I]iodophenethyl)-2-methylmalonic acid (IPMM), 2-(4-[¹²³I]iodophenethyl)-malonic acid (IPM), 2-(4-[¹²³I]iodobenzyl)-malonic acid (IBMM) and 4-[¹²³I]iodophthalic acid (IP) were radiolabeled via the Cu⁺ isotopic nucleophilic exchange method. All tracers were tested in vitro in buffer systems to assess pH driven cell uptake. In vivo biodistribution of [¹²³I]IPMM and [¹²³I]IPM was determined in healthy mice and the pH targeting efficacy in vivo of [¹²³I]IPM was evaluated in an anti-Fas monoclonal antibody (mAb) apoptosis model. In addition a mouse RIF-1 tumor model was explored in which tumor pH was decreased from 7.0 to 6.5 by means of induction of hyperglycemia in combination with administration of meta-iodobenzylguanidine.

Results

Radiosynthesis resulted in 15–20% for iodo-bromo exchange and 50–60% yield for iodo-iodo exchange while in vitro experiments showed a pH-sensitive uptake for all tracers. Shelf-life stability and in vivo stability was excellent for all tracers. [¹²³I]IPMM and [¹²³I]IPM showed a moderately fast predominantly biliary clearance while a high retention was observed in blood. The biodistribution profile of [¹²³I]IPM was found to be most favorable in view of pH-specific imaging. [¹²³I]IPM showed a clear pH-related uptake pattern in the RIF-1 tumor model.

Conclusion

Iodine-123 labeled malonic acid derivates such as [¹²³I]IPM show a clearly pH dependent uptake in tumor cells both in vitro and in vivo which allows to visualize regional acidosis. However, these compounds are not suitable for detection of apoptosis due to a poor acidosis effect.

Effect of in vivo administration of ethylmalonic acid on energy metabolism in rat tissues

High concentrations of ethylmalonic acid (EMA) occur in tissues and biological fluids of patients affected by deficiency of short-chain acyl-CoA dehydrogenase activity, as well as in other illnesses characterized by neurological and muscular symptoms. Considering that the pathophysiological mechanisms responsible for the clinical manifestations of these diseases are virtually unknown, in the present work we developed a chemical in vivo model of ethylmalonic acidemia in young Wistar rats for neurochemical and behavioral studies through subcutaneous administration of EMA to young rats. The doses of EMA administered subcutaneously varied according to the age of the animals, being injected 3, 4, and 6 micromol g(-1) of body weight in rats of 7, 14, and 21 days, respectively. The concentrations of the acid were measured in blood and brain at regular intervals after a single injection (30-120 min) and reached the highest concentrations (3.0 mM and 0.5 micromol g(-1), approximately 0.5 mM), respectively, after 30 and 60 min of EMA injection. Next, we investigated the effects of acute EMA administration on the activities of complexes I-III, II, II-III, and IV of the respiratory chain in cerebral cortex and skeletal muscle, as well as on the activity of creatine kinase in cerebral cortex, striatum, skeletal muscle, and cardiac muscle of rats of 14 days of life. Control rats were treated with saline in the same volumes. We verified EMA administration did not change these enzymatic activities in all tissues studied. Although transient high concentrations of EMA did not alter important parameters of energy metabolism, it cannot be ruled out that chronic administration of this organic acid would disrupt energy metabolism.

Development of novel 5-FU-loaded poly(methylidene malonate 2.1.2)-based microspheres for the treatment of brain cancers

In order to treat malignant brain tumors by local delivery of antineoplastic agents, the feasibility of 5-fluorouracil (5-FU)-sustained release biodegradable microspheres with a novel material, poly(methylidene malonate 2.1.2), was investigated using an emulsion/extraction method. This polymer was expected to present a slow degradation rate, thus leading to a long term local delivery system. Microparticles were successfully obtained and characterized in terms of drug loading, size, morphology and release profile. The size of the particles was between 40 and 50 microm, which was compatible with a stereotactic injection through a needle. Sufficient drug loadings were obtained (i.e. compatible with the preparation of therapeutic 5-FU doses in a minimal volume of injection), and perfectly spherical microspheres were observed. The respective influences of the polymer molecular weight, the polymer concentration, and the emulsion time on the release profiles were studied using a 2(3) factorial design. In the same objective, the solvent extraction time was extended while keeping all the previous parameters fixed at their optimal values. The in vitro study of these different parameters allowed a reduction of the initial burst release, with a percentage of 5-FU released after 24 h that was lowered from 90 to 65%, and the achievement of a long term drug delivery system, since the release was still ongoing after 43 days. Moreover, the microparticles could be gamma-sterilized (25 kGy) without modification of the release kinetics. Thus, the requested specifications to perform animal experiments were attained.

Cerebral dicarboxylate transport and metabolism studied with isotopically labelled fumarate, malate and malonate

Transport and metabolism of dicarboxylates may be important in the glial-neuronal metabolic interplay. Further, exogenous dicarboxylates have been suggested as cerebral energy substrates. After intrastriatal injection of [(14) C]fumarate or [(14) C]malate, glutamine attained a specific activity 4.1 and 2.6 times higher than that of glutamate, respectively, indicating predominantly glial uptake of these four-carbon dicarboxylates. In contrast, the three-carbon dicarboxylate [(14) C]malonate gave a specific activity in glutamate which was approximately five times higher than that of glutamine, indicating neuronal uptake of malonate. Therefore, neurones and glia take up different types of dicarboxylates, probably by different transport mechanisms. Labelling of alanine from [(14) C]fumarate and [(14) C]malate demonstrated extensive malate decarboxylation, presumably in glia. Intravenous injection of 75 micromol [U-(13) C]fumarate rapidly led to high concentrations of [U-(13) C]fumarate and [U-(13) C]malate in serum, but neither substrate labelled cerebral metabolites as determined by (13) C NMR spectroscopy. Only after conversion of [U-(13) C]fumarate into serum glucose was there (13) C-labelling of cerebral metabolites, and only at <10% of that obtained with 75 micromol [3-(13) C]lactate or [2-(13) C]acetate. These findings suggest a very low transport capacity for four-carbon dicarboxylates across the blood-brain barrier and rule out a role for exogenous fumarate as a cerebral energy substrate.

A Phase I study of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-1,3-dioxolane] platinum(II) in patients with advanced malignancies

BACKGROUND

A Phase I study of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-1,3-dioxolane] platinum(II) (SKI 2053R), a new platinum derivative, was performed to determine the maximum tolerated dose (MTD), the dose limiting toxicities (DLTs), and the pharmacokinetic profile of SKI 2053R in patients with advanced, refractory malignancies.

METHODS

Twenty-one patients were entered into the study. SKI 2053R was administered with an intravenous infusion over 1 hour every 4 weeks. The SKI 2053R dose was escalated from 40 mg/m(2) up to 480 mg/m(2) using a modified Fibonacci scheme. Pharmacokinetic analysis was done in all patients to determine the total and ultrafiltrable platinum concentrations in both the plasma and the urine.

RESULTS

All patients were evaluable for toxicity and response. There was no significant toxicity with dosages up to 360 mg/m(2). At 480 mg/m(2), two of three patients developed Grade 4 hepatotoxicity, Grade 3 leukopenia and thrombocytopenia, and Grade 2 azotemia and proteinuria. Other toxicity included nausea and emesis, but it was controlled with antiemetics. SKI 2053R did not cause significant neurotoxicity or mucositis. There were 4 patients with stable disease among the 21 patients. Plasma decay of the total and free platinum concentrations was best fitted by using a two-compartment, open model. The terminal plasma half-life of the total platinum after SKI 2053R administration ranged from 63.4 hours to 114.1 hours in dosages ranging from 40 mg/m(2) to 480 mg/m(2) without significant dose dependency. However, the terminal plasma half-life of the free platinum concentration showed a significant dose dependent, incremental pattern. The renal excretion of SKI 2053R measured as platinum ranged from 49% to 75% of the administered dose.

CONCLUSIONS

The MTD of SKI 2053R was 480 mg/m(2). The major DLTs were hepatotoxicity, nephrotoxicity, and myelosuppression. The recommended starting dose for a subsequent Phase II study is 360 mg/m(2) once every 4 weeks.

In vitro and in vivo evaluation of poly(methylidene malonate 2.1.2) microparticles behavior for oral administration

The goal of this paper was to investigate the fate of novel poly(methylidene malonate 2.1.2) microparticles with different surface properties, i.e. prepared with or without polyvinylalcohol (PVA), after oral administration, using in vitro cell culture and an in vivo mice model. Incubation of particles with Caco-2 cells induced no cytotoxicity except for the microparticles prepared without PVA at high concentrations. At subtoxic concentrations, microparticles were highly associated to cells, independently of particles concentrations, particles surface properties (with or without PVA) or incubation time. Confocal microscopy analysis revealed that adsorption was the main phenomenon leading to the association of particles to cells. However, association was greater at 37 degrees C than at 4 degrees C, suggesting that an active process, such as endocytosis, could also occur. In vivo, radiolabeled particles were mainly found in luminal content and also adsorbed onto the epithelium. After 24 hours, more than 15% of PVA-free microparticles were still present in the gastrointestinal tract, compared to 5% for particles prepared with PVA. However, histological evaluation revealed low uptake of particles by Peyer's patches. As a conclusion, this study provided a good correlation between in vitro and in vivo evaluation. These particles could be useful for oral sustained release and delivery of drugs to intestinal and colon epithelium.

Wet decontamination-induced stratum corneum hydration--effects on the skin barrier function to diethylmalonate

Decontamination of chemical agents from the skin uses both dry and wet decontamination processes. Recent studies have shown that wet decontamination frequently results in stratum corneum hydration. To evaluate the hydration effect of wet decontamination on the skin barrier function and hence on the decontamination efficiency, a series of comparative studies were carried out on human skin contaminated with the nerve agent simulant diethylmalonate, using decontamination media having different salinity and surfactants. The results showed that, compared to non-decontaminated skin, remnant diethylmalonate on decontaminated skin penetrated at an accelerated rate in the immediate 2 h following decontamination. This transient enhancement effect, ranging from 20 to 98%, was depended on the nature of the decontamination media used and was more obvious in skin samples that were decontaminated 1 h postexposure. All decontamination media exhibited this effect, with the greatest enhancement observed in the following order: anionic surfactant > cationic surfactant > non-ionic surfactant > deionized water > 0.9% saline > 9% saline.

Inhibitory effects of malotilate on invasion and metastasis of rat mammary carcinoma cells by modifying the functions of vascular endothelial cells

Malotilate (diisopropyl,1,3-dithiol-2-ylidenemalonate, MT) is clinically used as a hepatoprotective agent. Because we noticed that MT induced the differentiation of cultured vascular endothelial cells, we have examined its effects on lung metastasis of the highly metastatic rat mammary carcinoma c-SST-2. MT was orally administered to syngeneic SHR rats from 7 days before or after s.c. inoculation of c-SST-2 cells to the end of the experiments. In the MT-treated rats, pulmonary metastasis was markedly suppressed compared with the non-treated rats. In the rats treated with MT for 19 days after i.v. inoculation of c-SST-2 cells, lung metastasis was also significantly suppressed. An in vitro invasion assay using a rat lung endothelial (RLE) cell monolayer revealed that pretreatment of the RLE cells with MT, but not c-SST-2 cells, significantly reduced the invasion of the RLE monolayer by c-SST-2 cells. An in vitro vascular permeability assay demonstrated that MT prevented the increase in permeability of the RLE monolayer by serum starvation. On the other hand, in vivo and in vitro growth, gelatinase production and adhesion to the RLE cell monolayer of c-SST-2 cells were not affected by MT treatment. These findings suggest that MT suppressed tumour metastasis by intensifying the cell-to-cell contact of endothelial cells, thus preventing tumour cells from invading vascular endothelium.

Influence of exposure and infusion times on the cytotoxicity and pharmacokinetics of cis-malonato[(4R, 5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolane]platinum(II)

The effect of exposure time on the in vitro cytotoxicity of a new platinum complex, cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolan e]platinum(II) (SKI 2053R) and cisplatin (CDDP) toward two human lung-adenocarcinoma cell lines (PC-9, PC-14) and two human stomach-adenocarcinoma cell lines (KATO III, MKN-45) was investigated by variation of the exposure time (1, 4, 12, and 24 h) and drug concentration to yield a constant product of drug concentration times exposure time (C x T). Exposure of cancer cells to low concentrations of SKI 2053R for 12 or 24 h resulted in a greater killing effect than did 1- or 4-h exposure to 24- or 6-fold higher concentrations; the inhibitory effects of SKI 2053R on the colony formation of all tumor cell lines except for KATO III were significantly increased with increasing exposure time (P < 0.05). However, the inhibitory effects of CDDP against all tumor cell lines tested except for PC-14 were inversely correlated with increasing exposure time (P < 0.05). The intracellular accumulation of SKI 2053R and CDDP was measured under the same conditions used in the cell-survival assay using MKN-45 cells. The amount of platinum accumulated from SKI 2053R into MKN-45 cells was greater for the treatment involving low concentrations and long-term exposures (12 and 24 h) than for that using high concentrations and short-term exposures (1 and 4 h) at the constant C x T values; however, the increased accumulation of CDDP was more prominent as the concentration was increased, even if the exposure time became shorter. The pharmacokinetics studies of SKI 2053R following 1-, 4-, 12-, and 24-h infusions were performed in beagle dogs. A single dose of SKI 2053R (5.0 mg/kg) was successively given over various infusion periods to three beagle dogs at 3-week intervals. The peak levels of ultrafiltrable platinum observed for SKI 2053R at the 1-, 4-, 12-, and 24-h infusions were 3.10+/-0.49 (mean +/- SD), 1.24+/-0.06, 0.43+/-0.07, and 0.25+/-0.04 microg/ml, respectively. The mean binding ratios of platinum from SKI 2053R to plasma protein at the end of 1-, 4-, 12-, and 24-h infusions were approximately 91%, 73%, 53%, and 51%, respectively. The steady-state level of free platinum was maintained during long-term infusions (12 and 24 h) after short periods (1-3 h) from the start of the infusion. This study strongly suggests that the therapeutic efficacy of SKI 2053R given by continuous long-term infusion should be investigated in future clinical studies.

Mammary excretion and placental transfer of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolane] platinum(II) in rats

The mammary excretion and placental transfer of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolan e] platinum(II) (CAS 146665-77-2, SKI 2053R), a new potential anticancer agent, were investigated in the lactating or pregnant rats after a single intravenous administration of 14C-SKI 2053R (20 mg/kg, 100 microCi/kg). The radioactivity of the milk declined in a biexponential fashion with an initial half-life of 0.39 h and with a terminal half-life of 14.05 h in the lactating rats. The radioactivity of the milk was lower than that of plasma until 1 h after dosing, but was higher than that of plasma from 4 h after dosing. 14C-SKI 2053R was well distributed to most tissues including uterus and placenta in the pregnant rats, but the levels of radioactivity in the amniotic fluid and fetuses were markedly lower than that in the maternal plasma. Therefore, it is concluded that SKI 2053R scarcely passes the blood-placenta barrier, which was confirmed by the whole-body autoradiography study.

Pharmacokinetics of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1, 3-dioxolane]platinum(II) in rats

The blood concentration-time profile, distribution, and excretion of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1, 3-dioxolane]platinum(II) (CAS 146665-77-2, SKI 2053R), a new potential anticancer agent, were investigated in rats after intravenous administration of 14C-SKI 2053R. After a single intravenous administration, the radioactivity of blood declined in a biexponential fashion with the initial half-lives of 0.42 h and 0.37 h and with the terminal half-lives of 68.67 h and 64.67 h in male and female rats, respectively. Radioactivity was distributed very rapidly and extensively into all tissues except the central nervous system. The major amount of the radioactivity was found in the gastrointestinal contents, urine, and organs of elimination at all time points. The distribution pattern of 14C-SKI 2053R observed by the measurement of tissue concentrations was in accordance with that observed by whole-body autoradiography. The 0-7 days cumulative urinary and fecal recoveries of total radioactivity after a single dose were 83.0 +/- 4.5 (mean +/- S.D.) and 11.3 +/- 1.0% in male rats and 85.1 +/- 2.6 and 11.3 +/- 2.3% in female rats, respectively, resulting in total recoveries of 94.3 +/- 3.6% in male rats and 96.3 +/- 1.1% in female rats. The 0-24 h cumulative excretions of total radioactivity in the bile after a single dose were 8.7 +/- 0.4 and 15.8 +/- 3.5% in male and female rats, respectively, showing a significant sex difference.

Pharmacokinetics, tissue distribution, and excretion of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3- dioxolane]platinum(II) in dogs

The pharmacokinetics, tissue distribution, and excretion of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3- dioxolane]platinum(II) (SKI 2053R), a new potential anticancer agent, were investigated in dogs after a single intravenous administration of [14C]SKI 2053R (7 mg/kg, 100 microCi/kg). Total radioactivity in the plasma and ultrafiltrable plasma declined in a biexponential fashion with the initial half-lives of 0.63 +/- 0.05 hr (mean +/- SD) and 0.53 +/- 0.05 hr, and with the terminal half-lives of 51.08 +/- 3.26 hr and 15.19 +/- 3.75 hr, respectively. Radioactivity was well distributed into all tissues except the central nervous system. The majority of the radioactivity was found in the gastrointestinal contents, urine, and organs of elimination at all time points. The distribution pattern of [14C]SKI 2053R in the whole-body autoradiograms was consistent with that observed by the measurement of tissue concentrations. The 0-7 days cumulative urinary and fecal recoveries of total radioactivity were 87.30 +/- 2.93% and 8.68 +/- 1.30%, respectively, resulting in a total recovery of 95.98 +/- 1.61% of the administered dose. A large portion of [14C]SKI 2053R was distributed into the cellular fraction of mouse or rat blood, but was not into that of dog or human blood in vitro. The in vitro and in vivo binding of [14C]SKI 2053R to plasma protein was minimal to moderate.

Preparation and characterization of novel poly(methylidene malonate 2.1.2.)-made nanoparticles

Poly(methylidene malonate 2.1.2.) (PMM 2.1.2.) nanoparticles were prepared in phosphate buffer through emulsion polymerization of monomeric units; the kinetics of the reaction was monitored by spectrophotometry at 400 nm. Average nanoparticle sizes, molecular weights, and biodegradability of this potential drug carrier were determined under various conditions. As previously demonstrated for other similar monomers, i.e. IHCA or IBCA, pH influenced the physico-chemical characteristics of the nanoparticles obtained. Ethanol release from the ester-bearing side chains indicated that the polymers were susceptible to hydrolysis when incubated in basic pH or in rat plasma. A secondary degradation pathway, yielding formaldehyde through a reverse Knoevenagel's reaction, was minimal. Cytotoxicity studies of this new vector, in vitro, against L929 fibroblast cells demonstrated that PMM 2.1.2. nanoparticles were better tolerated than other poly(alkylcyanoacrylate) (PACA) carriers. Pharmacokinetic studies were also carried out to observe the fate of 14C-labelled PMM 2.1.2. nanoparticles after intravenous administration to rats. Forty eight hour post-injection, more than 80% of the radioactivity was recovered in urine and faeces. The body distribution of the polymer was estimated by measuring the radioactivity associated with liver, spleen, lung and kidneys. Five minutes after injection, a maximum of 24 +/- 2% of the total radioactivity was detected in the liver and less than 0.4% in the spleen. The liver-associated radioactivity decreased according to a biphasic profile and less than 8% of the total radioactivity remained after 6 days.

Selective cellular acidification and toxicity of weak organic acids in an acidic microenvironment

The mean extracellular pH (pHe) within solid tumours has been found to be lower than in normal tissues. Agents which cause intracellular acidification at low pHe might have selective toxicity towards cells in tumours. Weak acids (or their anions) with pKa values in the range of 4-6 have a higher proportion of molecules in the uncharged form at low pHe and can diffuse more rapidly into cells. The effects of organic acids including succinate, monomethyl succinate and malonate to acidify cells have been evaluated under conditions of different pHe in the acidic range. These weak acids caused intracellular acidification of murine EMT-6 and human MGH-U1 cells in a concentration and pHe dependent fashion. At concentrations of 10 mM and above, these acids also caused in vitro cytotoxicity to these cells at low pHe (< 6.5). The rate and extent of cellular acidification caused by these weak acids, and their cytotoxicity at low pHe, were enhanced by exposure to amiloride and 5-(N-ethyl-N-isopropyl)amiloride (EIPA), agents which inhibit Na+/H+ exchange, and hence the regulation of intracellular pH. Acid dependent cytotoxicity was also investigated in a murine solid tumour using the endpoints of growth delay and colony formation in vitro following treatment in vivo. Agents were tested alone or with 15 Gy X-rays to select a population of hypoxic (and presumably acidic) cells. Achievable serum concentrations of succinate were about 1 mM and no antitumour activity of succinate was detected when used in this way. It is concluded that weak acids are selectively taken up into cells, and can cause selective cellular acidification and toxicity, at low pHe in culture. Weak acids that are normal cellular metabolites are not toxic in vivo, but weak acids carrying cytotoxic groups offer the potential for selective uptake and toxicity under the conditions of low pHe that exist in many solid tumours.

Development and use of a stability-indicating high-performance liquid chromatographic assay for Meldrum's acid

A high-performance liquid chromatographic method was developed that separates Meldrum's acid from its primary decomposition products, malonic acid and acetone. The method uses a reversed-phase column under isocratic conditions, with detection by ultraviolet absorption at 210 nm. Quantitation of the parent molecule and the acid decomposition product was possible over concentration ranges of 0.1-10.0 and 0.1-2.0 mg/ml, respectively. Acetone could be determined only at much higher concentrations. Using the malonic acid concentration as a measure of decomposition, this method was used to determine the hydrolytic stability of Meldrum's acid and its skin penetration properties.

Poly(diethyl methylidenemalonate) nanoparticles as a potential drug carrier: preparation, distribution and elimination after intravenous and peroral administration to mice

Polymerization of diethyl methylidenemalonate (DEMM, 1a) in 0.1 M phosphate buffer containing 1% dextran 70 yields nanoparticles of a diameter ranging from 140 to 250 nm depending on the pH value (6.7 to 8.7). The weight-average and number-average molecular weight of the resulting polymer were 3791 and 1084, respectively. Approximately 95% of the 14C-labeled poly(DEMM) nanoparticles were found in liver and spleen 1 h after iv administration. A statistically significant (p less than 0.01) approximately 10% decrease of the radioactivity was observed in the liver over a 3-month period. The poly(DEMM) nanoparticles were not absorbed and were totally cleared from the gastrointestinal tract 24 h after oral dosage. The very slow bioelimination process observed after iv administration limits the usefulness of poly(DEMM) nanoparticles as a systemic drug carrier. Nevertheless, their oral administration as bioavailability enhancers can be envisaged. Moreover, the fact that nanoparticles are readily produced in a medium near neutrality should be emphasized.

Clearance of phenylethylmalonamide during haemodialysis of a patient with renal failure

Information is presented for the serum concentrations during haemodialysis of primidone, phenobarbitone, and phenylethylmalonamide (PEMA) in a patient with renal failure receiving chronic primidone therapy. The concentrations of drug and metabolites fell during haemodialysis, but PEMA concentrations were above normal at all times. The average renal clearance of PEMA during 6 h of dialysis was found to be 84.7 +/- 4.6 ml min-1.

Chemical cross-linking and its effect on fatty acid synthetase activity in intact chloroplasts from Euglena gracilis

Intact chloroplasts were isolated from Euglena gracilis variety bacillaris, aliquots were exposed to several different chemical cross-linking reagents. The reagents penetrated the triple membrane of Euglena chloroplasts. This was shown by gradient acrylamide gel electrophoresis under denaturing conditions. The activity of the nonaggregated fatty acid synthetase of Euglena was located within the chloroplast stroma, and the effects of dimethylsuberimidate cross-linking on the activity of the enzyme system were examined. The acyl-carrier protein concentration in the chloroplast was measured at about 0.24 mM.

Induction of lipid peroxidation in tissues of thallous malonate-treated hamster

Thallous malonate was administered orally to hamsters in a single dose of 10 mg Tl/kg or 50 mg Tl/kg body weight. After 1 day and 3 days the levels of lipid peroxidation and non-protein sulfhydryls (NPSH) and glutathione peroxidase (GSH-Px) activity in tissues were measured. At a thallium dose of 10 mg/kg, increases in lipid peroxidation were already apparent in the kidney after 1 day. On the other hand, a marked increase in lipid peroxidation with decrease in NPSH content and GSH-Px activity in the kidney and liver were found 3 days after administration of the 50 mg Tl/kg dose, and renal and liver damage also developed. These results suggested that thallous malonate-induced tissue damage may be associated with the development of peroxidative processes caused by depression of GSH and inhibition of the GSH-Px activity-linked defensive system.

Distribution and fate of diethyl malonate and diisopropyl fluorophosphate on pig skin in vitro

The in vitro distribution and fate of [14C]diethyl malonate and [14C]diisopropyl fluorophosphate were evaluated on normal and heat-treated pig skin. The extent of hydrolysis from the skin surface, skin, and receptor fluid was determined. A significant skin-mediated hydrolysis (15-35% of applied dose) was observed for diethyl malonate in normal skin, but not in heat-treated skin. These results indicated that a heat labile process (e.g., enzymatic hydrolysis) was in part responsible for the degradation of diethyl malonate after topical application to normal skin. Heat treatment tripled the skin penetration of diisopropyl fluorophosphate and reduced the amount of recovered hydrolysis product, diisopropyl phosphoric acid. Enzymatic and spontaneous hydrolysis, as well as impurity, accounted for the presence of degradation product.

Pharmacokinetics of phenylethylmalonamide (PEMA) in elderly men

The pharmacokinetics of phenylethylmalonamide (PEMA) were studied in 6 elderly men after oral administration of a single 400 mg dose. Peak PEMA serum levels were obtained within 4 h of intake, half-life values ranged from 30.7-57.9 h in these elderly men. The elimination half-life was twice as long when compared to a study previously performed in young volunteers.