Biomedical subjects

K Oguri

Publications and source records attributed to K Oguri.

At least 73 records · Page 4Linked to original sources

PubMed1993

Difference in laminin expression between high and low metastatic cell clones derived from murine Lewis lung carcinoma.

We investigated the expression of laminin in two cell lines with different metastatic potentials established from murine Lewis lung carcinoma. Immunostaining of the cells with anti-laminin antibody and Northern blot analysis of laminin mRNA demonstrated that the high metastatic clone expressed less laminin than the low metastatic one. In contrast, expressions of 67 kDa-laminin receptor were at similar levels between these two lines. These findings show the possibility that endogenous laminin may contribute to the difference in metastatic properties in the murine Lewis lung carcinoma cell lines examined.

Animals↗

PubMed1993

Purification and characterization of a morphine UDP-glucuronyltransferase isoform from untreated rat liver.

A morphine UDP-glucuronyltransferase was purified from liver microsomes of untreated Sprague-Dawley rats. A new gel, omega(beta-carboxypropionylamino)octyl Sepharose 4B, was prepared by coupling monomethylsuccinate with omega-aminooctyl Sepharose 4B and this was used as an efficient tool for the separation of microsomal enzymes. Emulgen 911 solubilized microsomes were applied to a column packed with the gel and eluted at pH 7.4 while increasing KCl concentration in a stepwise manner. An isoform was further purified with UDP-hexanolamine Sepharose 4B gel. The purified UDP-glucuronyltransferase (morphine UGT of untreated rat, morphine UGTUT) exhibited a molecular weight of 52000 on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and was capable of glucuronidating the 3-hydroxyl group of morphine. The isoform catalyzed to a small extent the glucuronidation of 4-hydroxybiphenyl; however, no glucuronidation activity towards androsterone, testosterone, bilirubin, 4-nitrophenol and the 6-hydroxyl group of morphine was observed. The difference in properties, compared with morphine UGT (molecular weight 56000) which was purified previously from phenobarbital-treated rats, is discussed.

Animals↗

PubMed1993

Metabolic formation of dimethylamine and methylamine from basic drugs containing N-methyl group: a newly established chromatographic assay and its application to the determination of deaminase activity.

A new method of assaying deaminase activity was established in which methylamine and/or dimethylamine formed from drugs containing N,N-dimethyl or N-methyl group were derivatized with phenylisothiocyanate to phenylthiourea derivatives. After purification with Sep-PAK C18 cartridge, the derivatives were separated by a reversed phase high-performance liquid chromatography monitored by ultraviolet absorption. The recoveries and determination limits of methylamine and dimethylamine were over 55% and about 0.4 nmol/ml of incubation mixture, respectively. The method was used to measure the deaminase activities of liver microsomes of rats, rabbits and guinea pigs for 11 drugs. Of the compounds tested, diphenhydramine and diltiazem are deaminated with microsomes from all the above animal species; rat and rabbit liver microsomes also well deaminated promethazine. Most other drugs such as chlorpromazine, promazine, imipramine, amitriptyline and tetracaine were found to be poor substrates. In general, dimethylamine but not methylamine was the predominant metabolite formed from drugs containing N,N-dimethylamino group. The results also suggested that the deamination of these compounds takes place mainly via a one step mechanism, thus implying that the sequential reaction consisting of N-demethylation and elimination of ammonia is of minor importance. The relation between in vitro deaminase activity and the extent of the in vivo deamination for drugs is discussed.

Aminohydrolases↗

PubMed1993

Identification of in vitro metabolites of 2,4,6,2',4',6'-hexachlorobiphenyl from phenobarbital-treated dog liver microsomes.

We studied in vitro metabolites of 2,4,6,2',4',6'-hexachlorobiphenyl (HCB, IUPAC PCB No. 155) produced by liver microsomes of a phenobarbital (PB)-treated beagle dog. The major metabolites were 3-hydroxy-2,4,6,2',4',6'-HCB (M-1), 4-hydroxy-2,6,2',4',6'-pentachlorobiphenyl (PenCB, M-2) and 3,4-dihydroxy-2,6,2',4',6'-PenCB (M-3). Furthermore, 4-hydroxy-2,3,6,2',4',6'-HCB (M-4), which could be formed via the 3,4-epoxidation and the subsequent NIH-shift of the chlorine from the 4 to the 3 position, was also detected. We found that M-3 is a common secondary metabolite of the two major monohydroxy metabolites, M-1 and M-2. These results indicate that the dog seems to metabolize and eliminate this congener not only by a mechanism involving direct insertion of a hydroxyl group but also via an arene oxide intermediate.

Animals↗

PubMed1993

Deficient differentiation of mast cells in the skin of mi/mi mice. Usefulness of in situ hybridization for evaluation of mast cell phenotype.

The staining property of skin mast cells changed from Alcian blue+/berberine sulfate- to Alcian blue+/berberine sulfate+ in the skin of normal (+/+) and Wv/Wv mice. In contrast, this change did not occur in the skin of mi/mi mice. Heparin content and histamine content per a mi/mi skin mast cell were estimated to be 34% and 18% those of a +/+ skin mast cell, respectively. The low heparin content of mi/mi skin mast cells seemed to be consistent with the Alcian blue+/berberine sulfate- staining property. Expression of genes encoding mast cell-specific proteolytic enzymes was examined by Northern blotting and in situ hybridization. Messenger RNA of mast cell carboxypeptidase A was expressed most of all by +/+, Wv/Wv, and mi/mi skin mast cells, but mRNA of mouse mast cell protease (MMCP)-6 was expressed by approximately a half of +/+ and Wv/Wv skin mast cells and by only 3% of mi/mi skin mast cells. A significant amount of MMCP-2 mRNA was not expressed in the skin of all +/+, Wv/Wv and mi/mi mice. This shows the presence of at least three phenotypes in skin mast cells of mice: berberine sulfate+/MMCP-6+, berberine sulfate+/MMCP-6-, and berberine sulfate-/MMCP-6-. The in situ hybridization of mRNA of mast cell-specific proteolytic enzymes seemed to be useful to describe abnormalities of mast cell differentiation in the skin of mi/mi mice.

Animals↗

PubMed1993

[Inducing ability of co-planar PCBs toward bilirubin UDP-glucuronyltransferase of liver microsomes: the remarkable difference between guinea pigs and rats].

The induction of liver microsomal UDP-glucuronyltransferase (UGT) activity toward bilirubin by pretreatment with 3, 4, 3', 4'-tetrachlorobiphenyl (TCB), 3, 4, 5, 3', 4'-pentachlorobiphenyl (PenCB) and 3-methylcholanthrene (MC) was studied in guinea pigs and rats. In addition, microsomal benzo(a)pyrene 3-hydroxylase and cytosolic DT-diaphorase activities were also measured for the comparison. All of the PenCB, TCB and MC significantly induced the bilirubin UGT activity of guinea pig liver microsomes. The highest induction (6-fold over the control) was seen in the PenCB-treated animal, and MC (3.2-fold) and TCB (2.4-fold) were less effective. On the other hand, the induction of benzo(a)pyrene 3-hydroxylase and DT-diaphorase activities of guinea pigs was not so remarkable as that of bilirubin UGT activity. In the guinea pig, the inducibility of bilirubin UGT activity seemed to be correlated with the toxicity induced with PenCB, TCB and MC. In contrast to the guinea pig, UGT activity toward bilirubin in the rat was significantly decreased by the treatment with the inducers described above. These results suggest that bilirubin UGT activity in the guinea pig can be an index for the toxicity of polychlorinated biphenyls as like as benzo(a)pyrene 3-hydroxylase and DT-diaphorase activities in the rat.

Animals↗

PubMed1993

[Metabolism in vivo of 2, 4, 6, 2', 4', 6'-hexachlorobiphenyl in dog and partial characterization of cytochrome P-450 isozyme responsible for biotransformation of the congener].

We reported previously that the dog is a unique species which can metabolize 2, 4, 5, 2', 4', 5'-hexachlorobiphenyl (HCB) by unusual mechanism via 2,3-arene oxide intermediate formation. 2, 4, 5, 2', 4', 5'-HCB is known as one of the PCB congeners showing the highest concentration in the blood of Yusho patients at present. Therefore, further investigation on the mechanism of biotransformation of PCB in the dog is very useful to obtain informations about metabolic fates of persistent congeners in the bodies of Yusho patients. In the present study, we examined in vivo metabolic pathways of 2, 4, 6, 2', 4', 6'-HCB in a dog, and also a role of cytochrome P-450 isozymes in its metabolism. In these experiments, three major metabolites were found in feces of the dog. These were identified to be 3-hydroxy-2, 4, 6, 2', 4', 6'-HCB (M-1), 4-hydroxy-2, 6, 2', 4', 6'-pentachlorobiphenyl (M-2) and 3, 4-dihydroxy-2, 6, 2', 4', 6'-PenCB (M-3), which were previously identified as the major metabolites in vitro. 4-Hydroxy-2, 3, 6, 2', 4', 6'-HCB has also been isolated as a metabolite in vitro, but not detected in this in vivo study. In conclusion, the present in vivo study supported the previous in vitro results that the dog metabolizes this congener at least two mechanisms including direct hydroxylation and arene oxide formation. It was also indicated that cytochrome P-450 isozymes responsible for metabolism of this congener may be in part different from those catalyzing the 2, 4, 5, 2', 4', 5'-HCB metabolism.

Animals↗

PubMed1992

Structural differences between heparan sulphates of proteoglycan involved in the formation of basement membranes in vivo by Lewis-lung-carcinoma-derived cloned cells with different metastatic potentials.

This study addresses the characterization of heparan sulphates of the basement-membrane proteoglycans in tumour formed after the subcutaneous implantation of Lewis-lung-carcinoma-derived different metastatic clones (P29, LM12-3 and LM60-D6 clones with low, medium and high metastatic potentials respectively). Heparan sulphate proteoglycans (125-158 micrograms of hexuronate/g dry weight of tissue) were isolated from chondroitin ABC lyase digests of a proteoglycan fraction obtained after DEAE-Sephacel chromatography of tissue extracts. The proteoglycans were separated into three molecular species by Sepharose CL-4B chromatography followed by CsCl-density-gradient centrifugation: large proteoglycans with an estimated M(r) of 820,000-130,000, which consisted of two components with low (< 1.34 g/ml; PGII-M) and high (> 1.37 g/ml; PGII-B) density, and a small proteoglycan with an M(r) of less than 80,000 (PGIII). Of these, only the PGII-M proteoglycan (34-37 micrograms of hexuronate/g dry weight) reacted with the antiserum against proteoglycan of Engelbreth-Holm-Swarm-tumour basement membrane, and represented, therefore, a basement-membrane proteoglycan. Digestion with heparan sulphate lyases I and II of the heparan sulphates (M(r) 36,000) from the PGII-M proteoglycan of the three tumours resulted in almost complete depolymerization to give six unsaturated disaccharides identified as 2-acetamido-2-deoxy-4-O-(4-deoxy-alpha-L-threo-hex-4-enopyranosyluron ic acid)-D-glucose, 2-acetamido-2-deoxy-4-O-(4-deoxy-alpha-L-threo-hex-4-enopyranosyluron ic acid)-6-O-sulpho-D-glucose, 2-deoxy-2-sulphamino-4-O-(4-deoxy-alpha-L-threo-hex-4-enopyrano syluronic acid)-D-glucose, 2-deoxy-2-sulphamino-4-O-(4-deoxy-alpha-L-threo-hex-4-enopyrano syluronic acid)-6-O-sulpho-D-glucose, 2-deoxy-2-sulphamino-4-O-(4-deoxy-2-O-sulpho-alpha-L-threo-hex-4- enopyranosyluronic acid)-D-glucose and 2-deoxy-2-sulphamino-4-O-(4-deoxy-2-O-sulpho-alpha-L-threo-hex-4- enopyranosyluronic acid)-6-O-sulpho-D-glucose. Comparison of the relative amounts of these disaccharides produced from the three tumour-derived heparan sulphates demonstrated that the degree of sulphation of the heparan sulphates correlated with the degree of morphological organization of the tumour basement membranes; the heparan sulphate from the more highly metastatic tumour with more highly organized basement membrane exhibited a higher degree of overall sulphation along the glycosaminoglycan chains, which was due to an increased content of the three repeating disaccharides having 6-O-sulphated glucosamine residues.

Animals↗

PubMed1992

Morphological characteristics of tumours formed by Lewis lung carcinoma-derived cloned cell lines with different metastatic potentials: structural differences in their basement membranes formed in vivo.

Tumour basement membrane (BM) is an extracellular matrix produced by tumour cells of epithelial origin. We examined the structure and function of the tumour BM of tumour tissues formed by Lewis lung carcinoma-derived cloned cell lines (P29, LM12-3 and LM60-D6 cells) with low, medium and high metastatic potentials, respectively. Immunohistochemical staining of major BM constituents laminin and type IV collagen demonstrated that all the cell lines produced and deposited these materials extracellularly in vivo. However, the continuity of the tumour BM composed of these materials was much greater in the higher metastatic LM12-3 and LM60-D6 tumours than in those with the low metastatic P29 tumour. Electron microscopic examination revealed that in the higher metastatic tumours, especially the LM60-D6 tumour, the tumour BM had a highly organized structure consisting of lamina densa and lamina rara. Parallel bilayers of BM and their fusion were often observed and tumour cells were in direct contact with the BM. In the vicinity of tumour blood vessels, similar interactions between the tumour BM and the vascular BM were observed, and the tumour cells rested on their own BM, the fused BM or the vascular BM. In contrast, in the low metastatic tumour in which the tumour BM was not clearly defined, this close contact between tumour cells and the vascular BM was not observed. In vitro studies showed that the higher metastatic cells adhered more firmly than the LMP cells to a subendothelial matrix. These results suggest that the adhesiveness of tumour cells to the vascular BM in vivo is correlated with their ability to form an integrated BM in vivo, and that this adhesiveness of the tumour cells may be mediated in part by the tumour BM via BM fusion.

Animals↗

PubMed1992

Tissue-specific expression, induction, and inhibition through metabolic intermediate-complex formation of guinea pig cytochrome P450 belonging to the CYP2B subfamily.

The tissue-specific expression and induction of P450GP-1, a constitutive form of cytochrome P450 of the guinea pig classified into the CYP2B subfamily, were studied. Prior to these studies, a P450 form (P450GP-1 PB) was purified from phenobarbital-treated guinea pigs and the properties were compared with those of the P450GP-1. This form was judged to be the same as P450GP-1 existing in untreated animals by comparisons of their N-terminal amino acid sequences, peptide maps, and affinities toward anti-P450GP-1 antibody. Immunostaining of P450GP-1 revealed that the lung and small intestine as well as the liver of untreated guinea pigs contain P450GP-1, while none or only small amounts of this P450 form were observed in the kidney, heart, spleen, urinary bladder, and testis. The amount of liver P450GP-1 protein expressed in untreated guinea pigs was estimated to be 19.4% of the total cytochrome P450 and this form was increased 1.7-fold by phenobarbital treatment. Similarly, intestinal P450GP-1 was increased by phenobarbital treatment. However, lung P450GP-1 was not increased by the treatment. It was also observed that the liver P450GP-1 is induced with SKF-525A to the same extent as with phenobarbital. On the other hand, dexamethsone, p,p'-dichlorodiphenyltrichloroethane, and isosafrole showed no or only a weak ability to increase the liver P450GP-1 content. The drug-metabolizing activities in the liver microsomes of SKF-525A-pretreated guinea pigs were lower than those in phenobarbital-treated animals, although the P450GP-1 protein was induced equally by these treatments. The low activities of SKF-525A-treated animals in the drug metabolisms were attributed to the formation of the metabolic-intermediate complex between P450GP-1 and SKF-525A metabolite. These results permitted us to conclude that the tissue specificity in the expression of guinea pig P450 belonging to the CYP2B subfamily and the inducibility with chemicals are similar to those of rat CYP2B1, although the constitutive expression of guinea pig liver P450GP-1 is much higher than that of CYP2B1.

Amino Acid Sequence↗

PubMed1992

Enhanced elimination of theophylline, phenobarbital and strychnine from the bodies of rats and mice by squalane treatment.

Our previous study suggested that squalane would be a good candidate for an antidote to reduce the toxicity of drug ingested accidentally at a high dose by enhancing the drug elimination from the body. In the present study, we investigated whether squalane given orally could enhance the elimination of theophylline, phenobarbital and strychnine which were administered parenterally to rats or mice. Squalane increased the fecal excretion of theophylline and reduced the serum level of the drug in rats. Squalane accelerated the fecal excretion of strychnine in mice. These results suggest that squalane may stimulate more the elimination of neutral (theophylline) or basic (strychnine) drugs which should be present in unionized form in intestinal lumen, than that of acidic drugs.

Algorithms↗

PubMed1992

Metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl with liver microsomes of phenobarbital-treated dog; the possible formation of PCB 2,3-arene oxide intermediate.

1. Metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl (HCB) was investigated in vitro using liver microsomes of one male beagle dog after phenobarbital treatment. 2. Three major metabolites were isolated and identified as 3-hydroxy-2,4,5,2',4',5'-HCB, 2-hydroxy-4,5,2',4',5'-pentachlorobiphenyl (PenCB), and 2-hydroxy-3,4,5,2',4',5'-HCB, by comparison of g.l.c.-mass spectrometry and 1H-n.m.r. data with those of authentic samples. 3. 2-Hydroxy-3,4,5,2',4',5'-HCB was found as a metabolite of 2,4,5,2',4',5'-HCB for the first time using dog liver microsomes. Present result indicate that this metabolite and the dechlorinated PenCB are derived from a metabolic intermediate, namely, 2,3-epoxy-2,4,5,2',4',5'-HCB. 2,3-Epoxide formation is a new metabolic pathway of PCB.

Animals↗

PubMed1992

Regiochemical differences in cytochrome P450 isozymes responsible for the oxidation of methylenedioxyphenyl groups by rabbit liver.

The cytochrome P450 isozymes catalyzing the oxidation of the methylenedioxyphenyl compounds methylenedioxybenzene (MDB) and methylenedioxyamphetamine (MDA) have been investigated in rabbit liver preparations. The aromatic ring in MDB undergoes both demethylenation to catechol and aromatic hydroxylation to sesamol, whereas that in MDA undergoes only demethylenation to dihydroxyamphetamine. Formation of catechol and sesamol from MDB in microsomal incubation mixtures was enhanced about 5- and 3-fold, respectively, by pretreatment of the rabbits with phenobarbital, which induced CYP2B4 and CYP4B1. The cytochrome P450 isozyme responsible for aromatic hydroxylation of MDB was induced by beta-naphthoflavone and was inhibited by alpha-naphthoflavone. Microsomal demethylenation of MDA was minimally sensitive to pretreatment of the rabbits with phenobarbital, beta-naphthoflavone, pyrazole, or rifampicin. However, MDA competitively inhibited the N-demethylation of erythromycin. Antibodies against CYP2B4, but not those against CYP4B1, caused a marked inhibition of the demethylenation and aromatic hydroxylation of MDB. Antibodies against CYP2C3 did not inhibit the demethylenation of MDA, nor did substrates or inhibitors of the CYP2D family except for bufuralol. MDB and MDA were both capable of forming metabolic intermediate complexes, and the rate of complex formation was accelerated by phenobarbital induction. Reconstitution experiments with CYP2B4 suggested that phenobarbital-inducible complex formation from MDA was not due to the carbene pathway involving the methylenedioxy group but was due to oxidation of the amino group. These results indicate that CYP2B4 oxidizes different regions of methylenedioxyphenyl compounds depending on their structure. MDB undergoes oxidation at the methylenedioxy group (major) and the benzene ring (minor). MDA is oxidized at the alkylamino side chain at the nitrogen and alpha-carbon. The results suggested that one or more constitutive isoforms (probably unknown) of cytochrome P450 present in rabbit liver microsomes are primarily responsible for MDA demethylenation but that CYP3A6 contributes slightly.

3,4-Methylenedioxyamphetamine↗

PubMed1991

A constitutive form of guinea pig liver cytochrome P450 closely related to phenobarbital inducible P450b(e).

In order to provide evidence that a cytochrome P450 belonging to the IIB subfamily is expressed as a constitutive form in the guinea pig, we tried to purify an isozyme from liver microsomes of untreated guinea pigs by assessing its reactivity with anti-P450b antibody in the present study. One form of cytochrome P450, named P450GP-1, was obtained. The minimum molecular weight of this isozyme was estimated to be 52,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino terminal sequence up to the 33rd amino acid of P450GP-1 was determined. As expected, comparison of the amino acid sequence with those of cytochrome P450 isozymes from other species reported so far indicated that P450GP-1 was highly homologous to P450s categorized in the IIB subfamily; that is, 67% similarity to rat P450b, 82% to rabbit LM2, 76% to dog PBD-2, 70% to mouse pf 3/46, and 73% to human IIB1. On the other hand, P450GP-1 showed only low similarity, less than 41%, to other cytochrome P450s of the II subfamily and those of the I, III, and IV families. Affinity of P450GP-1 to anti-P450b immunoglobulin G was confirmed to be comparable with that of a principal antigen, P450b. Immunoblot analysis revealed that P450GP-1 in the guinea pig liver microsomes was induced by phenobarbital treatment, but the increase was not as large as in the rat. P450GP-1 efficiently catalyzed benzphetamine N-demethylation, strychnine 2-hydroxylation, and testosterone 16 beta-hydroxylation, all of which are also catalyzed by P450b. Based on these results, it was strongly suggested that the IIB-type of cytochrome P450 in guinea pigs, at least one of them, is a constitutive form which is moderately induced by phenobarbital.

Amino Acid Sequence↗

PubMed1991

Purification and characterization of novel heparan sulfate proteoglycans produced by murine erythroleukemia cells in the growing phase.

Murine erythroleukemia cells (Friend erythroleukemia cells of a C-10-6 line) synthesized sulfated glycosaminoglycans consisting mainly of heparan sulfate (more than 95%) with a small amount of chondroitin 4-sulfate. The heparan sulfate occurred as proteoglycans, of which the cell-associated component was separated into urea-insoluble (UI) and urea-soluble (US) fractions. The UI proteoglycan consisted of a single homogeneous molecular species with an estimated Mr of 360,000 (C(UI)PG), whereas the US component was composed of two subfractions: a homogeneous species with an Mr of 280,000 (C(US)PGI) and a mixture of compounds with Mr values of less than 80,000 (C(US)PGII), which were isolated in yields of about 110, 340, and 80 micrograms of hexuronate (HexUA), respectively, from 1.37 g of an acetone powder prepared from 5.7 x 10(9) cells in the logarithmic phase of growth. The proteoglycan released into the medium (12 liters) was a single homogeneous species with an Mr of 320,000 (MPG) which was purified in a yield of 500 micrograms of hexuronate. The major, cell-associated proteoglycan, C(US)PGI, had very high contents of serine and glycine, accounting for approximately 80% of the total amino acids. This proteoglycan as well as the other two large proteoglycans, C(UI)PG and MPG, were highly resistant to degradation by various proteinases. These three proteoglycans, C(UI)PG, C(US)PGI, and MPG, had heparan sulfates with estimated Mr values of 32,000, 27,000, and 30,000. On the other hand, the Mr of the smaller proteoglycan, C(UI)PGII, was not significantly different before and after beta-elimination, indicating that it contains only a small peptide, if any. The heparan sulfate of this proteoglycan consisted of smaller and heterogeneous molecular species with Mr values of 26,000, 20,000, and 4,000. Digestion of these heparan sulfates with heparitinase I plus II resulted in almost complete depolymerization and gave six unsaturated disaccharides, delta HexUA-GlcNAc, delta HexUA-Glc-NAc(6-SO4), delta HexUA-GlcNSO3, delta HexUA-GlcNSO3 (6-SO4), delta HexUA(2-SO4)-GlcNSO3, and delta HexUA(2-SO4)-GlcNSO3(6-SO4). The relative amounts of these disaccharides generated from the individual heparan sulfates showed that an average ratio of sulfate residues to repeating disaccharide units of the C(US)PGII-derived heparan sulfate (0.97) was significantly higher than those of the other three large proteoglycan-derived glycosaminoglycans (0.54-0.70).

Amino Acids↗

PubMed1991

Close association between tumour cells and vascular basement membrane in gastric cancers with liver metastasis. An immunohistochemical and electron microscopic study with special attention to extracellular matrices.

To investigate morphological features valuable in estimating the propensity of gastric cancer to metastasize to the liver, we examined the primary tumours from 49 surgically resected advanced gastric cancers (24 with liver metastasis) and 45 autopsy cases, 19 with liver metastasis. We paid special attention to extracellular matrices--connective tissue stroma and basement membrane (BM)--using immunohistochemistry and electron microscopy. Type IV collagen staining showed that in differentiated carcinomas neoplastic glands were occasionally located in close proximity to the BM of thin-walled tumour blood vessels in back-to-back fashion. In poorly differentiated lesions, tumour cells were also oriented toward the vascular BM in pseudorosette-like pattern. Type III collagen staining and electron microscopy showed that in such regions tumour cells, with continuous or discontinuous BM, were immediately adjacent to vascular BM with no connective tissue stroma in between. On occasion tumour cells were in direct contact with vascular BM. These close associations were often found in carcinomas with a medullary growth pattern, irrespective of the degree of histological differentiation. However, they were virtually never seen in their benign counterpart. Of the resected cases, all 24 with liver metastasis showed this association, whereas only 10 of 25 (40%) without liver metastasis did so (P less than 0.001). In the autopsied cases, a similar positive correlation was observed between liver metastasis and this association. Furthermore, the tumor cells showing this juxtaposition showed evidence of vascular invasion. These results suggest that the close association between tumour cells and vascular BM is specific to the malignant neoplasm, and may be related to liver metastasis. Immunohistochemistry can be a great help in estimating the probability of liver metastasis.

Basement Membrane↗

PubMed1991

Site-selective oxidation of strychnine by phenobarbital inducible cytochrome P-450.

The metabolism of strychnine was studied using liver microsomes of rats treated with phenobarbital or 3-methylcholanthrene (MC). The phenobarbital-treatment resulted in 7.9-fold and 4.8-fold increases in 2-hydroxylation and N-oxidation of strychnine, respectively. The formation of 16-hydroxystrychnine, strychnine 21,22-epoxide and 22-hydroxystrychnine was induced about 2-fold. MC-treatment resulted in only 1.4-fold induction of each oxidation activity. In addition, strychnine 2-hydroxylation activity was markedly induced in liver microsomes of phenobarbital-treated mice, guinea pigs, rabbits and dogs (2.5-10.5-fold). Induction of N-oxidation activity was also higher than that of the three other oxidation activities. A reconstituted system of strychnine metabolism using cytochrome P-450 isozymes, P-450I (P450IIB1) and P-450II (P450IIB2), purified from liver microsomes of phenobarbital-treated rats showed significantly high and selective activities towards 2-hydroxylation and N-oxidation of strychnine. This characteristic metabolism of strychnine appears to occur in common with interspecies P450IIB gene subfamily. The pH Optima of 2-hydroxylation and N-oxidation of strychnine were between 8.4 and 8.6 in the microsomes of phenobarbital-treated rats, while that of N-demethylation of benzphetamine, a typical substrate of phenobarbital-inducible cytochrome P-450, was between 7.4 and 7.6. In a reconstituted system with P-450I, strychnine oxidation was little affected by pH change, while benzphetamine N-demethylation activity was decreased in the alkaline side. Among several oxidations tested, only ethylmorphine N-demethylation underwent the same pH effect as did strychnine oxidation with the microsomes and reconstituted system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Species difference of site-selective glucuronidation of morphine.

Species difference in glucuronidation of morphine was studied using mice, rats, guinea pigs and rabbits in vivo and in vitro. Morphine-3-glucuronide (M-3-G) and morphine-6-glucuronide (M-6-G) were determined by high-performance liquid chromatography. M-3-G was the major urinary metabolite of morphine in all these animal species. However, a remarkable species difference was observed in the urinary excretion of the M-6-G. Excretion ratios of the M-3-G to M-6-G were approximately 4:1 and 50:1 in guinea pigs and rabbits, respectively. The urinary excretion of M-6-G in mice and rats was too small to be determined. On the other hand, the ratios of uridine diphosphate-glucuronyltransferase (UDPGT) activities toward 3- and 6-hydroxyl groups of morphine in liver microsomes of mice, rats, guinea pigs and rabbits were approximately 300:1, 90:1, 4:1 and 40:1, respectively. Ratios of two morphine UDPGT activities in the liver microsomes of guinea pigs and rabbits, thus, reflected those of urinary excretion of morphine glucuronides.

Animals↗