Role of N-acetylneuraminic acid in rat renal brush-border membrane vesicle aggregation by aminoglycosides

Interaction between aminoglycosides (AGs) and rat renal brush-border membrane (BBM) vesicles was investigated by the aggregation technique. The order of aggregation was gentamicin greater than dibekacin not equal to netilmicin greater than amikacin, and this order corresponds to the strength of the nephrotoxicity of the aminoglycosides in vivo rather than the number of amino groups in the aminoglycosides. BBM vesicles were aggregated through ionic interaction, as evident from the finding that aggregation ceased to occur at alkaline pH. By addition of N-acetylneuraminic acid (NANA) to the incubation medium, the vesicle aggregation induced by gentamicin was significantly inhibited. To affect the liberation of the NANA residue from BBM vesicles, the vesicles were treated with neuraminidase, resulting in an about 60% release with a significant decrease in the uptake of gentamicin into the vesicles. The decrease in the degree of vesicle aggregation was in proportion to the amount of NANA liberated. It follows from the findings that the NANA residue may in some way be responsible for the accumulation of aminoglycosides in renal proximal tubular cells.

Interactions between aminoglycosides and phospholipids using liposomes: a possible mechanism of nephrotoxicity

Interactions of aminoglycosides with phospholipids were estimated by the increase in turbidity of liposomes consisting of various phospholipids. The turbidity of liposomes containing negatively charged phospholipids was increased by gentamicin, the highest increase in turbidity being observed for phosphatidylinositol-4,5-diphosphate-containing liposomes. The extent of turbidity was dependent on the concentration of acidic phospholipid in the liposomal membrane as well as the number of amino groups of the aminoglycosides. The release of glucose from glucose-entrapped liposomes depended on the concentration of gentamicin. The turbidity of liposomes containing lipids extracted from rat renal cortex was also increased by aminoglycosides depending on the number of amino groups. From electron microscopic observations, the increase in turbidity of liposome suspensions was caused by liposome fusion.

Preparation of EGF labeled liposomes and their uptake by hepatocytes

The preparation of epidermal growth factor (EGF) bearing liposomes (EGF-liposomes) and their uptake by rat hepatocytes were described. EGF was bound to the liposomal surface by the disulfide bridge linkage using a heterobifunctional cross-linking reagent, N-hydroxysuccinimidyl-3-(2-pyridyl-dithio) propionate. EGF-liposomes were taken up in a significant amount by rat hepatocytes in an EGF receptor mediated manner, and their uptake was dependent on the amount of labeled EGF coupled to the liposomal surface. These results raise the possibility that the EGF-liposomes may be an effective drug carrier to the cells having EGF-receptors like some cancer cells.

Newly synthesized analogues of the spider toxin block the crustacean glutamate receptor

Effects of synthetic compounds similar to the structure of a spider toxin were studied on the glutamate receptors in crustacean neuromuscular synapses. Two kinds of analogues, 2,4-dihydroxyphenylacetyl-asparaginyl cadaverine (C-1) and 2,4-dihydroxyphenylacetyl-asparaginyl spermine (C-2), suppressed the excitatory postsynaptic potentials in a manner similar to natural spider toxin (JSTX). The dose-response relationship showed that the relative potency of the compounds is C-1 less than C-2 less than JSTX. While the effect of JSTX was irreversible, those of C-1 and C-2 were reversible. These synthetic compounds may serve as important tools in studying the structure and function of glutamate receptors.

Inhibition of alkaline phosphatase activity and D-glucose uptake in rat renal brush-border membrane vesicles by aminoglycosides

The binding of aminoglycoside antibiotics to, and their effects on, the plasma membrane were studied using isolated rat renal brush-border membrane vesicles. Dibekacin was noted to bind with brush-border membrane vesicles having a single class of many binding sites. 3H-labeled dibekacin binding was inhibited competitively by unlabeled dibekacin, gentamicin or amikacin. The inhibition constants obtained from the Dixon plots followed the order of gentamicin approximately equal to dibekacin greater than amikacin. The alkaline phosphatase activity of brush-border membrane vesicles was inhibited by gentamicin significantly, as was also observed by a histochemical study. Sodium-dependent D-glucose uptake by brush-border membrane vesicles was significantly inhibited by the addition of gentamicin.

Correlation of the size of isolated right ventricular infarction with the changes of ST segment in dogs

Vectorcardiographic, electrocardiographic, and hemodynamic changes in isolated infarction (infarct confined to the right ventricular free wall) were studied in 19 mongrel dogs. An isolated right ventricular infarction was produced by embolizing the right coronary artery with Spongel under closed chest conditions. The size of the infarct, identified by TTC staining, accounted for 6-65% (35.9 +/- 22.0%, mean +/- SD) of the right ventricular free wall. The STx, STy, STz, and the spatial magnitude of the ST segment (STM) were continuously recorded with an automated, real-time vectorcardiographic ST-segment analyzer (ST-monitor) using the Frank lead system. The cardiac index (CI) ratio (CI after embolization/CI before embolization) of all dogs with larger infarcts (infarct greater than 35% of the right ventricle) was below 1.0. In dogs with smaller infarcts (% RVI less than or equal to 35%), there were no differences in the hemodynamic data before and 4 h after embolization. In dogs with larger infarcts, however, pulmonary arterial pressure and heart rate 4 h after embolization were significantly decreased compared with those before embolization. In addition, right atrial pressure 4 h after embolization in the larger infarct group was significantly elevated compared with that in the smaller infarct group. In dogs with larger infarcts, STx, STy, and STM were significantly larger than in those with smaller infarcts both 15 min and 4 h after embolization. There were no significant correlations between infarct size and change in vectorcardiographic ST segments in the smaller infarct group.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific incorporation of asialofetuin-labeled liposomes into hepatocytes through the action of galactose-binding protein

Asialofetuin-labelled liposomes (AF-liposomes) having mean diameters of 0.13 micron ([S]) and 0.35 micron ([L]) were obtained by the subsequent extrusion method in combination with dialysis. Intravenously administered AF-liposomes [S] were rapidly cleared from the systemic circulation. By pre- and post-treatment of the rats with free asialofetuin (AF), the rate of elimination decreased to that of non-labelled liposomes (N-liposomes) [S]. The liver uptake of AF-liposomes [S] (60 per cent of dose in 30 min) was about twice that of N-liposomes [S]. Forty-seven per cent of the AF-liposomes [S] incorporated into the liver were found in the parenchymal cell fraction as against 20 per cent in the non-parenchymal cell fraction. In contrast, N-liposomes [S] were taken up primarily by non-parenchymal cells as was also the case for AF- or N-liposomes [L]. Both the lipid and aqueous markers of AF-liposomes [S] were detected in subcellular fractions of the liver, but their distribution was noted to change differently with the lapse of time. Intravenously administered AF-liposomes [S] were specifically recognized by galactose-binding protein and underwent disruption in the cell after being taken up by hepatocytes. AF-liposomes [S] may possibly be utilized to deliver drugs into hepatocytes.

Uptake of aminoglycoside antibiotics into brush-border membrane vesicles and inhibition of (Na+ + K+)-ATPase activity of basolateral membrane

The effects of aminoglycoside antibiotics on plasma membranes were studied using rat renal basolateral and brush-border membrane vesicles. 3',4'-Dideoxykanamycin was bound to the basolateral membrane and brush-border membrane vesicles. They had a single class of binding sites with nearly the same constant, and the basolateral membrane vesicles had more binding sites than those of the brush-border membrane. Dideoxykanamycin B was transported into the intravesicular space of brush-border membrane vesicles, but not into that of basolateral membrane vesicles. The (Na+ + K+)-ATPase activity of the plasma membrane fraction prepared from the kidney of rat administered with dideoxykanamycin B intravenously decreased significantly. Aminoglycoside antibiotics entrapped in the basolateral membrane vesicles inhibited (Na+ + K+)-ATPase activity, but those added to the basolateral membrane vesicles externally failed to do so. The activity of (Na+ + K+)-ATPase was non-competitively inhibited by gentamicin. It is thus concluded that aminoglycoside antibiotics are taken up into the renal proximal tubular cells across the brush-border membrane and inhibit the (Na+ + K+)-ATPase activity of basolateral membrane. This inhibition may possibly disrupt the balance of cellular electrolytes, leading to a cellular dysfunction, and consequently to the development of aminoglycoside antibiotics' nephrotoxicity.

Preparation and disposition of asialofetuin-labelled liposome

A liposome labelled with asialofetuin(AF-liposome) was prepared by the detergent dialysis method. Asialofetuin in the amount of 34-68 micrograms were imposed among the 1 microM of phospholipids constituting the outer surface of liposome. The AF-liposome containing [14C]-cholesterol in the lipid layer and [3H]-sucrose in the aqueous layer was intravenously administered to rats. Both radioactivities were biphasically cleared from systemic circulation at rates faster than that of the fetuin-labelled liposome. These radioactivities were recovered in the liver by about 90 per cent within 60 min, and per gram of tissue, were highest in this organ. In an in vitro experiment using isolated rat hepatocytes, the high affinity of the AF-liposome toward hepatocytes was observed from scanning electron micrographs. Based on these findings, the AF-liposome may possibly be stable in circulation and function as a carrier of encapsulated drugs to hepatocytes.

Binding of 3',4'-dideoxykanamycin B to ATP and its related compounds

The interactions of aminoglycoside, 3',4'-dideoxykanamycin B(DKB) with ATP and its related compounds were investigated. ATP, ADP, cyclic AMP and FAD bound to the DKB-conjugated Sepharose 4B column. The binding of DKB to ATP was also confirmed by equilibrium gel filtration. In the acidic pH region, the fluorescence of nucleotides was quenched by DKB. The Stern-Volmer plots showed that the molar ratios of the complexes were 1:1. The apparent stability constant was dependent on the number of the phosphate groups of nucleotides and was in the order of ATP greater than ADP greater than AMP.

Hydrolysis of leucine enkephalin in the nasal cavity of the rat--a possible factor in the low bioavailability of nasally administered peptides

In order to investigate the utility of intranasal administration of peptides for systemic medication, the nasal absorption of the model peptide, leucine enkephalin (Tyr-Gly-Gly-Phe-Leu), was studied in the rat. At a concentration of 60 micrograms/ml in Ringer's buffer the pentapeptide was found to undergo, extensive hydrolysis in the nasal cavity. The hydrolysis rather than the polarity of the pentapeptide appears responsible for limiting the nasal absorption of this model compound. In the presence of dipeptides, the hydrolysis of leucine enkephalin was significantly inhibited. These results suggest that the nasal administration of peptides may become an important route for drug administration provided that the peptidases in the nasal mucosa can be transiently inhibited via coadministration of pharmacologically inactive peptidase substrates.

Selective incorporation of asialofetuin into hepatocyte of rat

The disposition of asialofetuin was studied in the rat. The radioactivity of 3H-asialofetuin administered intravenously disappeared rapidly from the blood. Asialofetuin was specifically and rapidly incorporated into the liver, and had no affinity toward other tissues such as the lung, spleen, heart, and kidney. Asialofetuin accumulated in the lysosomal and microsomal fractions of the rat liver cells immediately after administration, shifted to the low dense fraction (cytosol fraction) with the elapsing of time, and was possibly digested by lysosomes. The elimination of 3H-asialofetuin from the liver was fast and the degradates excreted into the bile and urine represented 90 per cent of the dose administered by 180 min following administration. It was suggested that asialofetuin functions as a carrier of drugs to the liver, especially to hepatocytes.

Effect of the purified unsaponifiable fraction of soybean on primary type II hyperlipoproteinemia

We evaluated the large dose effect of the purified unsaponifiable fraction of soybean (PUFS) given over 24 weeks to 19 patients with primary types IIa and IIb hyperlipoproteinemia. The percent reduction of plasma cholesterol in types IIa and IIb were 13.2% and 11.5%, respectively. PUFS significantly reduced LDL cholesterol levels, but had little affect on VLDL or HDL cholesterol. The triglyceride/cholesterol ratio in HDL fraction was also significantly reduced, suggesting that PUFS plays a role in the catabolism of HDL. PUFS contained tocopherol and unsaturated fatty acid. The relative impact of the individual components could not be assessed directly, however, it seemed reasonable to conclude that the hypo-cholesterolemic effect of PUFS results from a summation effect of plant sterols, tocopherols and unsaturated fatty acids.

Effect of different growth media on the synthesis of carbohydrate-Binding protein from Dictyostelium discoideum NC-4

The carbohydrate-binding protein, discoidin, was synthesized from Dictyostelium discoideum NC-4 grown on a Bacto peptone (Difco) containing medium together with bacteria. When the cells were transferred by serial passage to a Proteose peptone (Daigo)-containing medium, the productivity of discoidin was reduced to a negligible amount, but the cells formed aggregates, and another protein which binds with Sepharose 4B was detected by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. We conclude that discoidin synthesis is already regulated during growth, and even when the amount of this protein is nil or negligible, the cells still retain aggregate-forming ability.

Correlation between circadian rhythms of polyamine synthesis and cell proliferation in rat liver

In rats fed ad libitum, a marked circadian rhythm with a peak at night was observed in the hepatic level of ornithine decarboxylase (ODC) [EC 4.1.1.17], the enzyme for the first step of polyamine synthesis. A similar rhythm was found in the hepatic content of putrescine, but not of spermidine or spermine. The mitotic activity of the liver also exhibited a clear rhythm with a peak in the daytime. The rhythms of both ODC and mitosis were generated by cyclic ingestion of proteinous food, since the peaks shifted when rats were meal-fed and both activities disappeared on starvation or protein deprivation. The close parallel between the rhythms suggested that synthesis of polyamine, especially that of putrescine, was a prerequisite for the rhythmic growth of liver. The dietary induction of hepatic ODC depended on the nutritive value of dietary protein; zein or gelatin was effective only when supplemented with limiting amino acids and there was a good correlation between the hepatic ODC level and the relative growth rate.

Mitogenic andadjuvant activities of polysaccharides from the cellular slime mold, Dictyostelium discoideum NC-4

Cell surface and extracellular polysaccharide fractions obtained from Dictyostelium discoideum NC-4 cultured in bacteria-free medium showed strong B-cell mitogenic activities. Upon periodate treatment of the extra-cellular polysaccharide fraction this activity completely disappeared. The extracellular polysaccharide fraction could also enhance the antibody response in vitro against sheep red blood cells.

Extracellular agglutination factor of myxamoebae produced by Dictyostelium discoideum NC-4

A non-dyalyzable specific agglutination factor of myxamoebae obtained from culture broth during the growth phase of Dictyostelium discoideum NC-4 was thermostable but the agglutination activity disappeared below pH 5.0. In the case of formalinized myxamoebae, digestion of the factor with Pronase decreased the activity, but periodate treatment of the factor did not affect the activity. Myxamoebal agglutination by this factor was inhibited by the addition of uronic acid, polyuronide (protuberic acid), and cell-surface polysaccharide prepared from the myxamoebae, but the agglutination was not affected by citric acid or glycine. The factor was purified by ethanol precipitation, column chromatography using DEAE-cellulose and Sepharose-2B, and zone electrophoresis. Chemical analysis of the purified factor gave 61.0% carbohydrate and 26.1% protein, and glucose, mannose, xylose and rhamnose (molar ratios of 9,3 : 3.2 : 2.1 : 1.0) were detected as the component sugars. The content of uronic acid was 12.9%. When the myxamoebae of the growth phase were starved in Millipore-supporting medium, the agglutination activity was detected in the supernatant of the medium.