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Biomedical subjects

H Sezaki

Publications and source records attributed to H Sezaki.

At least 73 records · Page 4Linked to original sources
PubMed1989

Characterization of mitomycin C-induced gastrointestinal damage. I. In situ recirculation experiment.

The effects of mitomycin C (MMC), an anti-tumor agent, on the intestinal absorption of various drugs in rats were investigated. Based on microscopic observations, preadministration of a single intravenous dose of MMC (3 mg/kg) caused serious degeneration of epithelial cells, villous atrophy, and mitotic arrest in crypts at 48 hr after pretreatment. At this time point, absorption of sulfanilamide, salicylic acid, cephalexin, and L-tryptophan was shown to be significantly decreased by means of an in situ recirculation technique. The histological changes and the decrease in absorption of sulfanilamide, a model for passively absorbed drugs, were shown to depend on the timing of MMC pretreatment. Maximal effects were observed 48 hr after dosing. The MMC-induced reduction in the absorption of drugs was not a result of differences between treated and control animals with respect to pH of the drug solution, binding of drugs with intraluminal macromolecules, or intestinal mucosal blood flow. The absorption of sulfanilamide from the small intestine in the in situ system correlated well with the wet weight of the small intestine regardless of pretreatment dose or route. This suggests that the change in absorptive surface area of the intestinal mucosa may play a major role in the MMC-induced decrease in absorption capacity of the intestine.

Animals↗
PubMed1989

Characterization of mitomycin C-induced gastrointestinal damage. II. In vitro everted sac experiment.

The everted gut sac technique was employed to clarify the effects of preadministration of mitomycin C (MMC) on intestinal transport of various drugs. Loss of intestinal tissue weight and increase in mucosal-to-serosal fluxes of passively absorbed drugs were noted in the case of MMC pretreatment, although the extent of the latter effect varied according to the inherent absorbability of each drug. The maximal effect of MMC on intestinal tissue weight and transport of sulfanilamide, a model of a passively absorbed drug, was observed 48 hr after pretreatment. The increase in the transfer of sulfanilamide correlated well with the MMC-induced decrease in intestinal tissue weight. These phenomena may result from the shortened transfer distance from mucosal to serosal fluid and impaired barrier function of the intestinal mucosa. On the other hand, transport of actively absorbed 3-O-methyl-D-glucose was not influenced by MMC pretreatment, which could be explained by an increment in the passive permeation counterbalancing the decrement in the active permeation. The present study also suggested that the measurement of transport of drugs through everted gut sacs might be useful as a simple and qualitative index of gastrointestinal mucosal damage.

3-O-Methylglucose↗
PubMed1989

Disposition of a polymeric prodrug of mitomycin C, mitomycin C-dextran conjugate, in the perfused rat liver.

The disposition of a polymeric prodrug of mitomycin C (MMC), mitomycin C-dextran conjugate (MMC-D), was studied in the single-pass perfused rat liver in order to clarify the effect of physico-chemical properties, such as molecular weight and electric charge, on the hepatic uptake of MMC-D. Six types of MMC-D were used: both cationic MMC-D (MMC-Dcat) and anionic MMC-D (MMC-Dan) conjugated with dextran with molecular weights of 10,000, 70,000, and 500,000. Outflow curves were analyzed using statistical moment theory. Remarkable hepatic uptake of MMC-Dcat was observed and the uptake amount increased with an increase in molecular weight (i.e., approximately 80% of the dose was taken up by the liver during a single passage of the conjugate with a molecular weight of 500,000). Intrinsic clearance (CLint,i) and apparent distribution volume (Vi) also increased as the molecular weight increased. On the other hand, almost 100% of applied MMC-Dan was recovered in the outflow regardless of molecular weight, with almost the same moment parameters as those of the vascular reference substance (VRS), 131I-labeled human serum albumin (HSA). In a repeated application, the uptake of MMC-Dcat decreased in a stepwise manner, suggesting a saturation in the hepatic uptake of MMC-Dcat, while the uptake of MMC-Dan was unchanged. The MMC-Dcat pretreatment also affected the uptake of Evans blue (EB) bound to bovine serum albumin (BSA). These results demonstrate that molecular weight and electric charge determine the hepatic disposition of macromolecular prodrugs.

Animals↗
PubMed1989

Control of pharmaceutical properties of soybean trypsin inhibitor by conjugation with dextran. I: Synthesis and characterization.

The Kunitz-type soybean trypsin inhibitor (STI), a model protein, was conjugated with dextran (Mw, approximately 9900; STI-D), and its physicochemical and biochemical properties were studied to develop a novel delivery system for a protein drug. Conjugation was carried out using periodate oxidation, and cyanogen bromide, carbodiimide, cyanuric chloride, epichlorhydrin, and N-succiniimidyl-3-(2-pyridyldithio)propionate (SPDP) reagent methods. Dextran was conjugated to STI at a molar ratio of 1.5 to 4.6, but the degree of modification, as well as yield and contamination extent of unreacted STI and dextran, varied with the method of synthesis. Gel filtration and electrophoresis confirmed the covalent attachment of dextran to STI but also demonstrated the broad molecular weight distribution of the conjugates. The STI-D conjugate retained satisfactory activity, although the attachment partially reduced its inhibitory activity against trypsin. The periodate oxidation method seemed to be the best for the preparation of STI-D since it gave the conjugate with a high modification ratio (4.6 molecules per STI), high yield (95%), and satisfactory activity recovery (63%). Chemical modification of STI was also carried out with activated polyethylene glycol (PEG) for comparison. The STI-PEG conjugate was obtained in a satisfactory yield (96%) and modification degree (5.8 molecules per STI), but the remaining activity was considerably lower (34%). Thus, conjugation of protein with dextran by the periodate oxidation method is suggested to be preferable for preparing a protein-carrier system without significant diminution of its biological activity.

Carbodiimides↗
PubMed1989

Control of pharmaceutical properties of soybean trypsin inhibitor by conjugation with dextran. II: Biopharmaceutical and pharmacological properties.

Biopharmaceutical and pharmacological properties of the Kunitz-type soybean trypsin inhibitor (STI)-dextran conjugate (STI-D) were studied. Dextran having a molecular weight of approximately 10,000 was covalently attached to the STI molecule by periodate oxidation. The STI-polyethylene glycol (PEG) conjugate (STI-PEG) was also tested for comparison. After iv injection to mice, native STI showed rapid elimination of activity from plasma (t 1/2 = 2 min), and approximately 60% of the dose was excreted in urine within 1 h after injection. On the other hand, STI-D was slowly cleared from plasma and its urinary excretion was restricted. The STI-PEG conjugate showed a pharmacokinetic behavior similar to that of STI-D. Pharmacological activities of native and modified STI were evaluated by two animal experimental models; that is, trypsin-induced shock in mice and acute pancreatitis in rats. In mice, shock induced by iv injection of trypsin was inhibited by the iv pretreatment with native STI, but the effect was observed for only 1 h. The STI-D conjugate showed a superior inhibitory effect on trypsin-induced shock to that of STI alone at the same dose, and this effect continued for 5 h. A similar effect was also observed in mice given an iv injection of STI-PEG. In rats with acute pancreatitis, no significant therapeutic effect was shown by the iv treatment with native STI, as well as saline treatment. On the other hand, the iv treatment with STI-D at the same dose as STI lowered the mortality of the rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The effect of immunization with protein-hapten conjugate on the intestinal uptake of p-aminobenzoic acid as a hapten.

Intestinal uptake of p-aminobenzoic acid was examined by means of an in vitro everted sac technique in rats immunized with ovalbumin-p-aminobenzoic acid conjugate. A dose-dependent and antigen-specific decrease in the serosal transfer of p-aminobenzoic acid was observed in rats immunized 6 times with protein-hapten conjugate compared with the control. There was a significant increase in the recovery of p-acetamidobenzoic acid, a metabolite of p-aminobenzoic acid, in mucosal fluid, tissue, and serosal fluid in the jejunum. In the case of ileum, increase of p-acetamidobenzoic acid was observed in mucosal fluid. However, there was no significant effect in the ileal p-acetamidobenzoic acid in tissue and serosal fluid between immunized and non-immunized rats. To examine the increased metabolism of immunized rats, N-acetyltransferase activity of the small intestinal mucosa was examined. There was a significant increase in mucosal N-acetyltransferase activity in immunized rats compared with the control animals. These observations suggested that the mucosal immune system may play an important role in regulating the intestinal uptake of the low molecular weight compounds.

4-Aminobenzoic Acid↗
PubMed1989

Statistical moment analysis of hepatobiliary transport of phenol red in the perfused rat liver.

A new experimental system was applied to study hepatobiliary transport of drugs. Rat livers were perfused using a single-pass technique, and phenol red was momentarily introduced to this system from the portal side. Outflow dilution patterns of phenol red were analyzed using statistical moment theory, and kinetic parameters of hepatic distribution and elimination of phenol red were calculated from moments, namely, the hepatic extraction ratio (Ei) and elimination rate constant (kel,i). A larger distribution volume (Vi) was obtained for phenol red than for 131I-human serum albumin (HSA) and 51Cr-red blood cells (RBC), indicating its extravascular diffusivity. The biliary excretion of conjugated phenol red was delayed relative to that of the free agent. The larger biliary mean transit time (tbile,conj.) represents the processes of biliary transport and intrahepatic metabolism. Further, the effects of dose and perfusion temperature on the hepatobiliary transport of phenol red were determined. With high doses or low perfusion temperatures (20 and 27 degrees C), Ei, kel,i, and intrinsic clearance (CLint,i) of phenol red and biliary recovery of free and conjugated phenol red (Fbile,free, Fbile,conj) significantly decreased. The temperature-dependent and saturable processes in hepatic uptake, metabolism, and biliary excretion of phenol red were assessable to moment analysis.

Animals↗
PubMed1989

[Biopharmaceutical aspects of a chemical approach to drug delivery: macromolecule-drug conjugates].

Some recent advances pertaining to the biopharmaceutical aspects of drug delivery are briefly given, followed by a review of the current status of the application of soluble macromolecular carriers for drug delivery. The dextran conjugates were selected as model compounds to demonstrate the implications of the biopharmaceutical approach in the design, evaluation, and delivery of macromolecular conjugates.

Animals↗
PubMed1988

Structure-activity relationship of 1-alkyl- or 1-alkenylazacycloalkanone derivatives as percutaneous penetration enhancers.

Nine azacycloalkanone (5-, 6-, or 7-member ring) derivatives with an alkyl or alkenyl (terpene) chain (10, 15, or 20 carbons) were compared with 1-dodecylazacycloheptan-2-one (azone, 1) for their effects on the percutaneous penetration of 6-mercaptopurine (6-MP) through excised guinea pig skin. Pretreatment of skin with an enhancer markedly increased penetration and skin accumulation of 6-MP. Superior enhancing effects were observed for enhancers having a terpene chain of 10 carbons and an azacyclo ring with one carbonyl group. Enhancers with a C20 tail chain were less effective. Enhancer ring size had little effect on enhancing activity, whereas the increase in the number of carbonyl groups in the ring caused a decrease. Computer fitting of a penetration profile to Fick's diffusion equation gave two parameters corresponding to diffusion and partitioning of 6-MP. The diffusion parameter was little affected by pretreatment with an enhancer, whereas the partition parameter was markedly increased. This suggests that enhancement is determined by the ability to increase the drug partitioning into the skin and to enlarge the drug concentration gradient in the skin barrier. The primary skin irritation was examined with rabbit dorsal skin in vivo. The enhancers with an alkyl chain induced severer primary irritation (erythema and edema) than those with an alkenyl chain. From the balance between enhancing and irritating activities, it is concluded that 1-geranylazacycloheptan-2-one, 1-farnesylazacycloheptan-2-one and 1-farnesylazacyclopentan-2-one are favorable enhancers.

Animals↗
PubMed1988

Enhanced membrane permeability to phenol red by medium-chain glycerides: studies on the membrane permeability and microviscosity.

To clarify the mechanism of the drug absorption enhancement by medium-chain glycerides (MCG), the changes in membrane permeability provoked by MCG were investigated with liposomal uptake experiments. Uptake of phenol red (PR) into liposomes increased with an increase in MCG content in the liposomal membrane, suggesting that PR absorption was enhanced in the "transcellular route." However, the apparent membranous microviscosity obtained in fluorescence depolarization studies tended to increase with the addition of MCG in both the hydrophobic core and the polar head regions of the liposomal membrane. Thus, an enhancement in membrane permeability caused by MCG was not accompanied by a decrease in the apparent membranous microviscosity.

Absorption↗
PubMed1988

The accumulation mechanism of cationic mitomycin C-dextran conjugates in the liver: in-vivo cellular localization and in-vitro interaction with hepatocytes.

To elucidate the mechanism of the accumulation of mitomycin C-dextran conjugate (MMC-D) in the liver, in-vivo cellular uptake and in-vitro cellular interaction of MMC-D have been studied. Localization of cationic and anionic MMC-D (MMC-Dcat. and MMC-Dan.) in different liver cell types following i.v. administration was examined in rats and the significant contribution of parenchymal cells demonstrated. In-vitro cellular interaction was determined by measuring the drug concentration in the medium after incubation with rat isolated hepatocytes. MMC-Dcat. was highly adsorbed on the surface of hepatocytes at pH 7.2, while the interaction between MMC-Dan. and hepatocytes was negligible. The percentage association of MMC-Dcat. with hepatocytes remained almost constant during the course of incubation and no significant difference was observed between the incubation at 4 and 37 degrees C. The adsorption phenomenon was shown to conform to Langmuir's adsorption isotherm. The amount of MMC-Dcat. associated with hepatocytes increased as the molecular weight of the dextran chain increased. These results showed that MMC-Dcat. was adsorbed on the surface of hepatocytes by an electrostatic force and this binding was responsible for its remarkable accumulation in the liver in-vivo. Thus some physicochemical properties of the MMC-D conjugates are thought to play an important role in the disposition characteristics of the conjugates.

Animals↗
PubMed1988

Analysis of drug penetration through skin considering donor concentration decrease.

A diffusion model for in vitro drug penetration through the skin was constructed which considered drug concentration decrease in the donor solution. The Laplace transforms of the equations corresponding to the time courses of the drug amount in the receptor solution, in the skin and in the donor solution were derived. Computer fitting of the penetration profiles of in vitro experiments to the obtained Laplace transformed equation by a non-linear least squares program based on first inverse Laplace transform algorithm (MULTI(FILT)) gave two parameters corresponding to drug diffusion and partitioning. These parameters well estimated the drug amount remaining in the donor solution and in the skin. The mean transit time (MTT) was defined for drug penetration through the skin and was calculated using these parameters. MTT was shown to be a good index of drug penetrability.

Animals↗
PubMed1987

Disposition characteristics of mitomycin C-dextran conjugate in normal and tumor-bearing muscles of rabbits.

Disposition characteristics of the macromolecular prodrug of mitomycin C (MMC), mitomycin C-dextran conjugate (MMC-D), in normal and tumor (VX2 carcinoma)-bearing rabbit thigh muscles were studied using the in situ vascular perfusion technique. Three types of cationic MMC-D (MMC-Dcat) and two types of anionic MMC-D (MMC-Dan) with different carrier molecular weights were used. After bolus arterial injection in normal muscles, 83-96% of injected MMC-D was recovered in the venous outflow regardless of the carrier size or charge, whereas less than 60% of MMC was recovered in the same system. By applying statistical moment analysis to the outflow pattern of these drugs, pharmacokinetic parameters representing their disposition characteristics were obtained. Smaller intrinsic clearance (CLint) and distribution volume (V) were noted for MMC-D than for MMC, indicating low extravascular diffusion of MMC-D. In the tumor-bearing muscle, blood contamination from other parts of the body increased and a shortage of flow recovery due to the neovascularization of the tumors occurred. The disposition parameters of MMC-Dcat with a molecular weight of 500,000 (T-500) indicated some tissue distribution and sequestration in the tumor preparation. After constant infusion of [14C]MMC-D (T-500) for 4 h, tissue radioactivity concentrations were determined in various tissues. A higher radioactivity was observed in the viable region of the tumor and the lymph node compared with the normal muscle tissue and the necrotic region of the tumors. 131I-Labeled human serum albumin also gave similar results. In conclusion, higher tumor localization of antitumor agents may be made possible by the application of macromolecular prodrugs.

Animals↗
PubMed1987

Treatment of cystic hygroma and lymphangioma with the use of bleomycin fat emulsion.

Of the several types of treatment for cystic hygromas and lymphangiomas, surgical excision has been the preferred treatment. However, there is a high recurrence rate because lymphangiomas tend to infiltrate the surrounding tissues. Bleomycin in a microsphere-in-oil (S/O) emulsion was used in this study as a sclerosing agent for lymphangiomas. Experimental studies using domestic rabbits showed that the bleomycin emulsion caused more marked fibrotic changes at the injection site than other formulations, such as a blank emulsion and bleomycin solution. In clinical trials, 27 of 33 patients received bleomycin S/O emulsion injected directly into the tumors with satisfactory results. Histologic pictures of the clinically resected specimens confirmed the findings of the experimental studies. Comparative studies of treatments between bleomycin S/O emulsion and surgery indicated that injection therapy of bleomycin S/O emulsion would be more beneficial than surgical excisions.

Animals↗
PubMed1987

Decreased transport of D-glucose and L-alanine across brush-border membrane vesicles from small intestine of rats treated with mitomycin C.

To elucidate the mechanisms underlying the dysfunctions of intestinal absorption induced by antitumor drugs, the effect of pretreatment with mitomycin C on sodium gradient-dependent D-glucose and L-alanine transports was studied in rat brush-border membrane vesicles. 24, 48, 96, or 120 h following a single intravenous injection of mitomycin C, brush-border membrane vesicles were prepared from rat small-intestines. The uptake of D-glucose and L-alanine was shown to be Na+ gradient-dependent even in the case of vesicles obtained from mitomycin C-treated rats, but uptake rates measured at 15 s and magnitude of overshooting effect in uptake of both solutes were decreased in vesicles maximally from 48 h mitomycin C-treated rats. The rate of D-glucose uptake calculated at 15 s recovered to the control level in vesicles prepared at 96 h and 120 h after mitomycin C-treatment, indicating that the effect of mitomycin C on Na+ gradient-dependent D-glucose transport would be fully reversible. Tracer exchange experiments under Na+ and D-glucose equilibrated conditions indicated that the Na+/D-glucose transporters were similarly operative in the vesicles from control and 48 h mitomycin C-treated rats. Rates of 22Na+ uptake measured at 15 s in vesicles from 48 h mitomycin C-treated rats, however, were increased. The increased permeability to Na+ might bring about a more rapid dissipation of the Na+ gradient in these vesicles and this would secondarily cause the decrease in Na+-dependent D-glucose uptake in vesicles from mitomycin C-treated rats.

Alanine↗