Research communications in chemical pathology and pharmacology最新文献

Massive hepatic cell necrosis can be induced by Corynebacterium parvum and lipopolysaccharide (LPS) in rats. In this model, serum LDH, GOT and GPT activities are significantly increased in vivo within several hours after LPS injection. An in vitro experimental acute liver injury animal model was produced by using multicellular spheroids composed of rat parenchymal and non-parenchymal liver cells. These multicellular spheroids were prepared by detaching the confluent monolayer on the collagen-conjugated thermo-responsive polymer coated culture dish at a temperature below the lower critical solution temperature and culturing it on the non-adhesive substratum. LPS caused clear elevations of GOT, GPT and LDH activities from these spheroids into the medium. However, the increase of LDH activity was only observed in the monolayer culture system. These results suggest that the multicellular spheroids of liver cells are useful models as an alternative to animal tests for hepatotoxicity.

Platelet aggregation was induced more strongly in male than in female 5, 12, and 45 week-old rats by both collagen and arachidonic acid. This is in agreement with our previous reports which suggested that the sex differences in platelet aggregation may be a primary characteristic of rat platelets. In plasma, plasmin-like activity was higher in male than in female rats. Plasmin alone induced aggregation, and low concentrations of plasmin synergistically enhanced collagen-induced aggregation in both male and female rats. Platelets potentiated plasmin generation by plasminogen activator at various Ca2+ concentrations in both male and female rats. Platelets from males displayed more efficient plasmin generation in 2 mM extracellular Ca2+ than those from females. If platelets were activated by abnormal causes in plasma, generated plasmin could make a greater contribution to the potentiated effect of platelet aggregation in male than in female rats. This study suggests that plasmin may be a partial cofactor in sex differences in platelet aggregation in the rat.

Blood plasma shows antioxidant capacity (AOC) due to a number of molecules possessing antioxidant activity. Plasma AOC of young and aged rats fed high doses of fish oil and fish oil + dl-alpha tocopherol was assayed. It was observed that only young rats fed fish oil (with or without antioxidant) show a significant increase in their plasma AOC when compared with controls and with the aged ones. It is suggested that increased AOC results from an adaptive response of animals to the potential risk of oxidative stress due to the increase of membrane polyunsaturation after fish oil ingestion.

Petroleum creosote, dissolved in dimethyl sulfoxide, was administered by gavage to pregnant ICR mice on days 5-9 of gestation at a single dose (400 mg/kg body weight per day). Animals were euthanized on day 17 of gestation, and live fetuses were weighed and examined for skeletal and visceral malformations. Maternal body weights were significantly lowered in both the group administered creosote and the group administered the solvent alone. The number of live fetuses, dead fetuses, resorptions, and the sex ratio in the live fetuses were similar in all groups. Petroleum creosote as administered in this study was not found to be teratogenic in ICR mice.

Insulin caused an 8- or a 3-fold increase in lipogenesis in control rats (C) or diabetic rats (DM), respectively. Following insulin treatment for DM, insulin resistance was clearly reversed. Phospholipase C (PLC) caused a 4-fold increase in lipogenesis in C, but not in DM. Insulin treatment partially restored PLC-induced lipogenesis. Insulin or PLC increased protein kinase C (PKC) activity in the membrane fraction in C, but not in DM. Insulin treatment partially restored insulin- or PLC-stimulated PKC activity. 5'-Guanylylimidodiphosphate (Gpp(NH)p) exerted a stimulatory effect on diacylglycerol (DAG) generation in permeabilized adipocytes from C, but not in DM. Insulin treatment partially restored the stimulatory effect of Gpp(NH)p. These findings suggest that a particular G protein(s) is involved in the regulation of DAG generation in adipocytes, and that diabetes leads to a functional or quantitative abnormality in G protein and G protein-PLC. Insulin therapy partially restored G protein-PLC dependent glucose uptake.

To determine ischemia-induced changes in phosphodiesterase (PDE), changes in the membranous binding sites of rolipram, a cAMP-selective PDE inhibitor, were examined in the gerbil brain following transient 5 min forebrain ischemia. Coinciding with the delayed neuronal death (DND) in the hippocampal CA1 region, affinities for cerebral rolipram bindings decreased on Day 4, when intrinsic cAMP, substrate for PDE, might increase. The number of rolipram binding sites was significantly reduced in the hippocampus Day 14, despite the lack of change on Day 4. This reduction in rolipram binding was in agreement with the previously reported late onset reduction of muscarinic receptors, progressing more slowly than DND. Slowly progressive mechanisms may be involved in the ischemia-induced reduction of the hippocampal rolipram binding sites which may be PDEs.

The effects of salmon calcitonin (SCT) on intrathecally-injected N-methyl-D-aspartate (NMDA)-induced aversive behavior were investigated to clarify the involvement of the NMDA receptor/ionophore complex on the analgesic effects of SCT. Intracerebroventricular (i.c.v.) injection of SCT significantly inhibited acetic acid-induced writhing. Intrathecal (i.t.) injection of NMDA (0.25-1.0 nmol/mouse) dose-dependently induced aversive behavior such as scratching and tail biting. SCT at the doses of 0.01 and 0.1 IU/mouse (i.c.v.) significantly inhibited the NMDA-induced aversive behavior. This inhibitory effects of SCT on NMDA (i.t.)-induced aversive behavior were neither potentiated nor antagonized by i.c.v. injection of MK-801 and NMDA, respectively. Further, MK-801 (i.c.v.) and NMDA (i.c.v.) themselves did not affect the NMDA (i.t.)-induced aversive behavior. These results suggest that the NMDA receptor/ionophore complex in the brain is not directly involved in the antinociceptive effects of intracerebrally-injected SCT.

The effect of dantrolene sodium on liver injury induced by CCl4 was investigated in the rat. Liver microsomal P-450 and b5 levels, serum triiodothyronine levels (T3), and alanine aminotransferase activity (ALT) were measured over 4 to 16 h after CCl4 (0.2 ml/kg, s.c.) administration. Serum ALT rose following CCl4 administration, while liver cytochrome P-450 and b5 levels and serum T3 which reflects the liver microsomal thyroxine-5'-deiodinase activity (1) fell. Intraperitoneal administration of dantrolene sodium (5 mg/kg), 1 h before CCl4 s.c., suppressed CCl4-induced elevation of the serum ALT significantly. However, levels of P-450, b5, and serum T3 were not significantly different between dantrolene-treated and untreated groups. These results suggest that dantrolene sodium has a protective effect on CCl4-induced liver injury through a mechanism unrelated to these liver microsomal functions.

In our previous studies, the evoked purine outflow from rat brain cultured astrocytes was reported to be Na+ independent and K+ and [Ca2+]e partially dependent. Thus, the eventual [Ca2+]i influence on purine astrocyte release was investigated in an attempt to better characterize the ionic requirements of this mechanism in cells which serve many complex and still partly unknown functions within the CNS. TMB-8 and Thapsigargin (drugs described as able to inhibit and increase the ion efflux from its internal stores respectively) and BAPTA/AM (able to chelate the cytoplasmic free Ca2+), were used. TMB-8 and BAPTA/AM decreased, whereas Thapsigargin enhanced glial purine outflow. These findings suggest a significant [Ca2+]i dependence of the electrically evoked purine efflux from cultured astrocytes even though further investigations using fluorescent probes are needed.

Fischer 344 rats were fed a low-fat high carbohydrate diet (HC), an isocaloric fat-containing diet (IC), a hypercaloric fat-containing diet (HF) or rat chow. Covalent binding of AFB1 to liver DNA, RNA and total proteins was investigated in a 24 hour period following administration of a single intraperitoneal dose of AFB1 (1 mg/kg body weight). AFB1 binding to nucleic acids was greatest in the HC and was generally significantly lower (p < 0.05) in the HF, IC and rats fed chow. The results suggest that fat decreases hepatic macromolecular adduct formation by inhibiting activation of AFB1 to the epoxide or by enhancing the activity of detoxification pathways.