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Biomedical subjects

K Furuno

Publications and source records attributed to K Furuno.

At least 91 records · Page 5Linked to original sources
PubMed1992

Isolation and characterization of a novel membrane glycoprotein of 85,000 molecular weight from rat liver lysosomes.

We have purified and characterized a novel glycoprotein (r-lamp-3) with an apparent molecular weight (Mr) of 85,000 from membranes of triton-filled lysosomes (tritosomes) by the use of immunoaffinity chromatography on a column of monoclonal antibody-Sepharose 4B. r-lamp-3 accounted for approximately 4% of the total proteins in tritosomal membranes. The isoelectric point (pI) of r-lamp-3 was 4.5 and it was shifted to 6.5 after neuraminidase treatment with its molecular weight decreased by about 7000. Pulse-chase experiments in cultured rat hepatocytes using [35S]methionine showed that r-lamp-3 was initially synthesized as a 77,000 polypeptide and processed to a mature protein with an Mr of 85,000. Upon treatment with endo-beta-N-acetylglucosaminidase H (Endo H), the precursor and mature forms were converted to 55,000 and 73,000 polypeptides, respectively. From the Mr reduction of the precursor form, we estimated the presence of 10--12 N-linked oligosaccharides/r-lamp-3 polypeptide. The data on enzymatic deglycosylation suggested that the mature form of r-lamp-3 contained the same numbers of high mannose-type and complex-type N-linked oligosaccharide chains.

Animals↗
PubMed1992

Plasma alpha 1-acid glycoprotein concentration in rats with chemical liver injury.

The influence of liver injury on the plasma concentrations of alpha 1-acid glycoprotein (AGP) and albumin was examined in several different models of chemically-induced liver injury. The plasma AGP concentration in carbon tetrachloride (CCl4), allyl alcohol, bromobenzene, acetaminophen or N-nitrosodimethylamine-induced liver injury was increased to 2-3.5 times the normal level at 24 h after the intoxication. The plasma AGP concentration was unchanged in ethionine-induced liver injury and was markedly decreased in galactosamine-induced injury. The plasma albumin concentration was significantly decreased by the damage due to galactosamine, allyl alcohol or N-nitrosodimethylamine-induced liver injury, while no influence was observed by other hepatotoxin-induced liver injury. The plasma protein binding of propranolol was also determined in relation to the plasma concentrations of AGP and albumin in all the experimental models. Propranolol binding, expressed as bound to free ratio, showed a good correlation with the AGP concentration (r = 0.940; p < 0.001), but not with the albumin concentration.

Animals↗
PubMed1992

Effects of standard cigarette smoke and nicotine-reduced cigarette smoke on plasma concentrations of indomethacin administered orally to rats.

The influence of acute exposures to standard (ST) and nicotine-reduced (NR) cigarette smokes on the plasma concentration of orally administered indomethacin (IM, 5 mg/kg) was investigated in rats. IM plasma concentrations in the ST- and NR-groups were lower than those in the non-smoking control group, while the lowered effect in the NR-group was slightly weaker than in the ST-group. These results suggest that the plasma concentrations of IM administered orally are lowered by the acute exposure of cigarette smoke, and this influence may be attributed largely to constituents other than nicotine in the cigarette smoke as well as slightly attributable to nicotine.

Administration, Oral↗
PubMed1992

Influences of long-term cigarette smoke exposure on pharmacokinetics of theophylline, and on liver microsomal enzymes in rats.

The influences of long-term cigarette smoke exposure on pharmacokinetics of oral theophylline (20 mg/kg), and on liver microsomal enzymes which metabolize drugs were studied in rats. Animals were exposed to cigarette smoke for 20 min each in the morning and evening every day for 26 days in the pharmacokinetic study, and 27 days for the enzyme assays. Theophylline was administered 13 h after the last exposure to smoke, and plasma concentrations were measured using HPLC. Plasma concentrations of theophylline during the absorption phase and 6 h after oral administration were lower in the long-term cigarette smoke-exposed group than in the control group. In the smoke-exposed group, the AUC and Ka were lower, and the Ke was slightly higher than in the control group. Liver weight and the ratio of liver weight to body weight were lower in the smoke-exposed group, and cytochrome b5 content and NADPH-cytochrome P-450 reductase activity were higher, but cytochrome P-450 content did not differ from the control group. These results indicate that long-term exposure to cigarette smoke suppresses theophylline absorption from the gastrointestinal tract, accelerates its elimination, and affects liver microsomal enzymes which metabolize drugs.

Animals↗
PubMed1992

In vivo and in vitro release of indomethacin from water-soluble and fatty base suppositories.

The plasma concentration of indomethacin was measured after the rectal administration of water-soluble and fatty base suppositories in rats. The results were compared with the in vitro indomethacin release from suppositories determined by Paddle method using three different types of membranes: cellulose membrane, artificial sausage membrane and natural sausage membrane. The plasma concentrations of indomethacin during the first 4h after the rectal administration were higher in rats that received water-soluble base suppositories than in those that received fatty base types. When either a cellulose membrane or an artificial sausage membrane of cow protein was used in the Paddle method, the amount of indomethacin released from fatty base suppositories was significantly higher than that from water-soluble base ones. However, the results were reversed when a natural sausage membrane of pig colon was used. The discrepancy in the in vitro experiments using water-soluble base suppositories seemed to be due to the difference of pore size of membrane used. Careful consideration should be given to the membrane used in the Paddle method especially when this method is employed to examine the release of poorly soluble drugs like indomethacin in both water-soluble and fatty base suppositories.

Animals↗
PubMed1992

Immunohistochemical studies of Merkel cell carcinoma of the eyelid.

Merkel cell carcinoma of the eyelid is a rare malignant tumor. Immunohistochemical studies can be helpful in establishing the diagnosis of this tumor. We encountered a case of Merkel cell carcinoma of the eyelid and conducted an immunohistochemical analysis for clarification of its cell properties. The patient in this study was a 78-year-old man who noted a small mass on his right upper eyelid, which was subsequently removed. However, the lesion recurred and progressively enlarged. The results of a biopsy indicated the possibility of a highly malignant tumor. The lesion was removed by orbital exenteration. Merkel cell carcinoma was finally diagnosed by using light and electron microscopy. In immunohistochemical studies, the tumor cells showed both neuron-specific enolase and cytokeratin. Most of the cells were also labeled with antibodies against the protein gene product 9.5, endocrine granule constituent and chromogranin A. However, no neuropeptides were labeled. The properties of the tumor cells appeared virtually the same as those of normal human Merkel cells.

Aged↗
PubMed1991

Tail-tremor induced by exposure to cigarette smoke in rats.

Tremors appearing only in the tail (tail-tremor) induced by cigarette smoke and subcutaneous nicotine were investigated using a smoking machine and Wistar rats. Daily exposure (twice a day) to smokes of two commercial cigarettes (Mild-Seven Select for the first 7 days and Long-Peace for the next 6 days) caused the tail-tremor to appear even if it was slight. A single subcutaneous nicotine (0.5 mg/kg) administration to rats exposed to the cigarette smokes for 13 days markedly caused the tail-tremor. On the other hand, daily subcutaneous injection of nicotine (0.5 mg/kg/day) also caused the tail-tremor to appear beginning on the 4th day and the incidence of tremor increased to 100% by the 12th day. These results indicate that tail-tremor can be caused not only by daily subcutaneous administration of nicotine but also by daily exposure to cigarette smoke.

Animals↗
PubMed1991

Purification, some properties, and tissue distribution of a major lysosome-associated membrane glycoprotein (r-lamp-2) of rat liver.

We previously purified and characterized a major lysosomal membrane glycoprotein (r-lamp-1) from rat liver [Akasaki et al. (1990) Chem. Pharm. Bull. 38, 2766-2770]. The present study describes the purification of another major lysosomal membrane glycoprotein (r-lamp-2) from rat liver and compares the tissue distribution of r-lamp-1 and r-lamp-2 in rats. R-lamp-2 was purified to apparent electrophoretic homogeneity from rat liver by a simple method with a protein yield of approximately 4.0 micrograms/g wet weight of liver. The purification procedure includes: preparation of tritosomal membranes, extraction of tritosomal membranes with Lubrol PX, wheat germ agglutinin (WGA)-Sepharose affinity chromatography, and monoclonal antibody-Sepharose affinity chromatography. R-lamp-2 exhibited an Mr of 96,000 on SDS-PAGE and had an acidic pI of less than 3.5. R-lamp-2 contained 52.3% carbohydrates. Its carbohydrate moieties were composed of numerous sialyl complex type N-linked oligosaccharides and small amounts of O-linked oligosaccharides. Both r-lamp-1 and r-lamp-2 were detected in all rat tissues examined by immunoblot analyses, while their apparent molecular weights differed among the tissues. Immunological quantitative analysis showed that the protein concentrations of r-lamp-2 were consistently lower than those of r-lamp-1 in all the tissues tested. There was a significant correlation with a regression coefficient of 0.86 in the tissue distribution between r-lamp-1 and r-lamp-2. A good correlation was also observed in the tissue distribution between acid phosphatase and r-lamp-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Influence of standard and nicotine-reduced cigarette smoke on plasma concentrations of isosorbide dinitrate and its metabolites in rats.

Rats dosed orally with isosorbide dinitrate (1 mg kg-1) were exposed to smoke from standard and nicotine-reduced cigarettes for 8 min using a smoking machine. Plasma concentrations of isosorbide dinitrate and 5-isosorbide mononitrate, one of its major metabolites were approximately equal in the exposed groups, but were lower than in the non-smoking control group. The 2-isosorbide mononitrate concentration was also lower in the group exposed to smoke from standard cigarettes. Since the pharmacokinetics were influenced by smoke from both types of cigarette smoke, the effect may be attributed in large part to non-nicotine components of the smoke.

Animals↗
PubMed1991

Effect of cigarette smoking on theophylline pharmacokinetics in rats.

The effect of acute cigarette smoke inhalation on the plasma levels of theophylline administered orally and parenterally to rats has been studied. The animals were exposed to smoke containing low- or high-nicotine/tar concentration for 10 min immediately after oral, intraperitoneal (i.p.) or intravenous (i.v.) administration of theophylline. The plasma levels of theophylline when administered orally (20 mg kg-1) were lower in the two cigarette smoke-inhaling groups than in the non-smoking restrained control group, with the lowest values in the high-nicotine/tar group. The plasma levels (8 and 12 h after administration) in the high-nicotine/tar group when theophylline was administered i.p. (10 mg kg-1), were also slightly lower than in the non-smoking restrained control group but this was not significant. When theophylline was administered i.v. (5 mg kg-1), there was no difference between the high-nicotine/tar group and the non-smoking restrained control group. These data indicate that cigarette smoke inhalation causes suppression or delay of theophylline absorption from the gastrointestinal tract.

Administration, Oral↗
PubMed1991

Increase in the plasma protein binding of weakly basic drugs in carbon tetrachloride-intoxicated rats.

Plasma protein binding of weakly basic drugs such as propranolol and quinidine was determined in rats with carbon tetrachloride (CCl4)-induced hepatic disease. Free fractions of propranolol and quinidine in the plasma of rats at 24 h after CCl4-intoxication were decreased by 41 and 30%, respectively, compared to those of control rats. An addition of Tris (butoxyethyl) phosphate (TBEP), a specific displacer for basic drugs from alpha 1-acid glycoprotein (AGP), to the plasma increased the free fractions of the basic drugs, resulting in no difference in the extent of the plasma free fraction of each drug between control and CCl4-intoxicated rats. Plasma concentration of AGP in CCl4-intoxicated rats was elevated 2.7-fold of that in control rats at 24 h after the CCl4 intoxication and reached a peak of 4.8-fold elevation at 48 h. A regression analysis revealed a high degree of positive correlation between ratios of bound to free fraction of propranolol and plasma concentrations of AGP. These results suggest that the plasma protein binding of the basic drugs was increased mainly due to the rise in the plasma AGP concentration in CCl4-intoxicated rats.

Animals↗
PubMed1991

Influences of cigarette smoke inhalation on pharmacokinetics of cimetidine in rats.

The influences of cigarette smoke inhalation on the pharmacokinetics of cimetidine administered orally and parenterally were investigated in rats using a smoking machine. The animals were exposed to two kinds of cigarette smoke, low- or high-nicotine.tar, inhaled for 10 min immediately after oral (50 mg/kg), intraperitoneal (25 mg/kg) or intravenous (10 mg/kg) administration of cimetidine. The plasma level after cimetidine was administered orally was lower in the absorption phase in the two cigarette smoke inhaling groups than in the non-smoking control group, and was particularly marked in the high-nicotine.tar cigarette smoke inhaling group. In contrast, no significant difference was found in cimetidine plasma level between the cigarette smoke inhaling groups and the non-smoking control group when administered intraperitoneally or intravenously. These results suggest that cigarette smoke inhalation may cause a suppression or a delay in cimetidine absorption from the gastrointestinal tract, and that the degree of influence is dependent upon the content of nicotine.tar in the cigarette smoke.

Administration, Oral↗
PubMed1991

Clonazepam serum levels in epileptic patients determined simply and rapidly by high-performance liquid chromatography using a solid-phase extraction column.

We studied the use of high-performance liquid chromatography (HPLC), using a solid phase extraction column (Bond Elut cartridge column), for the simple, rapid and sensitive determination of serum clonazepam levels in epileptic patients. Extracted aliquots were analyzed by HPLC, using a reverse phase ODS column (mu-Bondapak C18). The analytical mean recovery of clonazepam added to the blank serum averaged 99.9%. The detection limit was as high as approximately 2 ng/ml in the serum. The reproducibilities were 2.3-8.6 CV % in the within-day assay and 6.5 CV % in the between-day assay, indicating that the analysis method was effective in the determination of clonazepam serum levels. Accordingly, we suggest that the present method, using a solid phase extraction column, may be useful for the routine monitoring of clonazepam serum levels in epileptic patients.

Chromatography, High Pressure Liquid↗
PubMed1990

Transport of acid phosphatase to lysosomes does not involve passage through the cell surface.

In foregoing studies, we reported that LGP107, a major lysosomal membrane glycoprotein in the rat liver, distributes in and circulates continuously throughout the endocytic membrane system (endosomes, lysosomes and plasma membrane), in hepatocytes (1,2). In the present study we examined whether acid phosphatase (APase), an enzyme that is transported to lysosomes as a transmembrane protein, passes through the cell surface during intracellular transport, because transport of newly synthesized APase to lysosomes involves the passage of endosomes containing a ligand which is internalized via receptors on the cell surface and is finally dispatched to lysosomes for degradation (3). When localization of APase in rat hepatocytes was investigated by immunoelectron microscopy, APase was found to be localized in lysosomes and endosomes, but not in coated pits on the cell surface, which are positive for LGP107, and from which antibodies for LGP107 are internalized. Further, unlike LGP107, newly synthesized APase was not detected in plasma membranes isolated from livers of rats given [35S]methionine, and when cultured hepatocytes were exposed to 125I-labeled anti APase IgG at 37 degrees C, there was no transfer of the antibody to lysosomes even after 24 h incubation. Therefore, these results indicate that intracellular movement of APase does not involve cell surface passage in rat hepatocytes, and clearly differs from the recent report that human APase is transported to lysosomes via the cell surface in BHK cells transfected with its cDNA (4).

Acid Phosphatase↗
PubMed1990

Role of different proteolytic systems in the degradation of muscle proteins during denervation atrophy.

In order to clarify the cellular mechanisms of denervation atrophy of skeletal muscle, we have studied protein turnover in denervated and control rat soleus muscles in vitro under different conditions. By 24 h after cutting the sciatic nerve, overall protein breakdown was greater in the denervated soleus than in the contralateral control muscle, and by 3 days, net proteolysis had increased about 3-fold. Since protein synthesis increased slightly following denervation, the rise in proteolysis must be responsible for the muscle atrophy and the differential loss of contractile proteins. Like overall proteolysis, the breakdown of actin (as shown by 3-methyl-histidine production by the muscles) increased each day after denervation and by 3 days was 2.5 times faster than in controls. Treatments that block the lysosomal and Ca2(+)-dependent proteolytic systems did not reduce the increase in overall protein degradation and actin breakdown in the denervated muscles (maintained in complete medium at resting length). However, the content of the lysosomal protease, cathepsin B, increased about 2-fold by 3 days after denervation. Furthermore, conditions that activate intralysosomal proteolysis (incubation without insulin or amino acids) stimulated proteolysis 2-3-fold more in the denervated muscles than in controls. Also, incubation conditions that activate the Ca2(+)-dependent pathway (incubation with Ca2+ ionophores or allowing muscles to shorten) were 2-3 times more effective in enhancing overall proteolysis in the denervated muscle. None of these treatments affected 3-methylhistidine production. Thus, multiple proteolytic systems increase in parallel in the denervated muscle, but a nonlysosomal process (independent of Ca2+) appears mainly responsible for the rapid loss of cell proteins, especially of myofibrillar components.

Actins↗