Dietary linolenic acid-mediated increase in vascular prostacyclin formation

To define vascular effects of an enhanced dietary -linolenic acid intake, 28 spontaneously hypertensive rats were fed a 3% sunflowerseed oil (44% linoleic acid) diet; in 3 groups (7 rats each), the diet was supplemented with 1, 2.5 or 5% linseed oil containing 62% -linolenic acid. -Linolenic acid was incorporated up to 12% in the aorta of the 5% linseed oil group. The eicosapentaenoic acid content was not significantly increased. The content of arachidonic acid and docosatetraenoic acid was moderately reduced in rats fed 5% linseed oil. The generation of 6-keto-PGF₁ (degradation product of prostacyclin) assessed by HPLC/electrochemical detection was, however, markedly increased (p < 0.05) in rats fed 2.5 and 5% linseed oil. The minor prostanoids TXB₂, PGE₂ and PGF₂ were not significantly altered. The high systolic and diastolic blood pressure of SHR monitored by radio telemetry was more effectively reduced (p < 0.05) in the light, i.e. sleep, cycle. An increased prostacyclin formation and lowered vascular arachidonic acid content associated with enhanced dietary -linolenic acid intake would thus be expected to prove beneficial in the prevention of vascular disorders.     

In situ absorption of aflatoxins in rat small intestine

To evaluate the rate at which the four main aflatoxins (aflatoxins B₁, B₂, G₁ and G₂) are able to cross the luminal membrane of the rat small intestine, a study about intestinal absorption kinetics of these mycotoxins has been made. In situ results obtained showed that the absorption of aflatoxins in rat small intestine is a very fast process that follows first-order kinetics, with an absorption rate constant (k _a ) of 5.84±0.05 (aflatoxin B₁), 4.06±0.09 (aflatoxin B₂), 2.09±0.03 (aflatoxin G₁) and 1.58±0.04 (aflatoxin G₂) h^–1, respectively.     

EGF responsiveness of hepatocytes after partial hepatectomy

We investigate the effect of EGF on IP₃ production, PLCγ phosphorylation, calcium transients in rat hepatocytes isolated in quiescent liver (G₀ phase of cell cycle) and at 4 h (G₁ phase of cell cycle) and 24 h (M phase of cell cycle) after partial hepatectomy. Our results show that EGF does not utilize IP₃ and calcium as its signal transduction molecules when the hepatocytes are in vivo stimulated to entry in the cell cycle. In particular the growth factor does not phosphorylate PLCγ and induces a decrease in IP₃ content. These data suggest that EGF utilizes different signal transduction to send information from receptor to nucleus during PH with respect to the quiescent liver.     

Quantitative comparison of rat hepatocyte functions in two improved culture systems with or without rat liver epithelial cell line

We quantitatively evaluated two recently-developed novel techniques for hepatocyte cultivation in a dish level; that is, spheroid culture and membrane-supported collagen (CN) gel sandwich culture, in terms of cellular maintenance, albumin secretion and 7-ethoxycoumarin (7EC) metabolism to 7-hydroxycoumarin (7HC) as a marker for cytochrome P450 IA1 activity in the presence and absence of rat liver epithelial cell line (RLEC) during one month of culture, together with conventional coculture with RLEC in CN-coated dishes as a control. RLEC prevented spheroid loss caused by its detachment from the culture dishes often occurring in pure culture. CN-gel sandwich by itself improved remarkably hepatocyte maintenance when compared with CN-gel free systems, thereby resulting in enhancement of overall functional expressions as compared with CN-gel free systems. RLEC in CN-gel sandwhich, however, reduced cellular sustainment probably due to its suppression of hepatocyte growth. Although there were no significant differences in albumin secretion per cell among the five cultures examined, CN-gel sandwich expressed markedly higher 7EC metabolizing activity per cell, where RLEC presence had a preferable influence. Consequently, membrane-supported CN-gel sandwich was the most superior technique for hepatocyte cultivation from the standpont of both cellular maintenance and its functional expressions per cell.     

2，5－己二酮对大鼠视束纤维和视上丘细胞电生理特性的影响

应用复合动作电位记录技术研究了２,５－己二酮对大鼠视束大纤维（Ｔ１）和中纤维（Ｔ２）以及视上丘（ＳＣ）Ｃ２细胞电生理特性的影响。结果表明：２,５－己二酮使视束Ｔ１和Ｔ２轴突的传导速度降低,反应波形的幅度下降、上升时间延长、宽度增加、基强度减小。从Ｔ２到Ｃ２的突触延搁增加,Ｔ２和Ｃ２的恢复功能曲线有明显的超常兴奋性,相对不应期减小。２,５－己二酮对Ｔ２和Ｃ２细胞的电生理特性有选择性影响。     

慢性低氧下普通大鼠与低氧敏感大鼠的血液气体变化

普通大鼠（ＳＤ）与低氧敏感大鼠（ＨＳ）经减压舱内模拟海拔５０００ｍ高度下３周低氧,观察到ＳＤ与ＨＳ的Ｈｂ有显著差异,前者高于后者（分别为２７．３±０．６;２４．５±０．８ｇ％Ｐ＜０．０１）。此时ＳＤ血液中的ＰＣＯ２已恢复正常,而ＨＳ血液中的ＰＣＯ２却比ＳＤ血液中的ＰＣＯ２低（分别为４．３±０．１;５．６±０．３ｋＰａＰ＜０．０１）。在慢性低氧初期,ＨＳ的ｐＨ值比ＳＤ明显降低（分别为７．１８±０．０３;７．２９±０．０２,Ｐ＜０．０５）。但随着低氧时间延长ＨＳ的ｐＨ值很快上升并超过ＳＤ（分别为７．２５±０．０２;７．１７±０．０３Ｐ＜０．０５）。两者的血液氧没有明显差异。实验结果提示普通大鼠与低氧敏感大鼠对慢性低氧反应有不同的生理机制。     

Tissue fatty acid deposition is influenced by an interaction of dietary oil source and energy intake level in rats

To investigate the net tissue fatty acid deposition in response to graded levels of energy restriction and modification of diet fatty acid composition, rats were randomly assigned into four dietary groups and fed for 10 weeks diets containing 40% as energy of either fish, safflower, or olive oil, or beef tallow, consumed ad libitum or energy restricted to 85% or 68% of ad libitum intake by reducing diet carbohydrate content. An additional eight rats were killed before the diet regimen, to provide baseline data from which fatty acid deposition rates were calculated. Body weight, and heart, liver and fat mass gains were decreased with energy restriction (P<0.001). Olive oil feeding resulted in higher body weight gain (P < 0.03) than tallow feeding, whereas fish oil feeding was associated with highest (P < 0.007) liver weight and lowest (P < 0.03) fat mass gains. Energy deficit-related differences in the deposition of stearic, linoleic, arachidonic, and docosahexaenoic acids in heart and palmitic and docosahexaenoic acids in liver were dependent on the dietary oil consumed (P < 0.03). Similarly, interactive effects of restricted food intake and dietary oil type were found in the gain of palmitic, stearic, oleic, and linoleic acids in adipose tissue (P < 0.01) when expressed in relation to the amount of each fatty acid consumed. These data suggest that energy intake level can influence the deposition pattern, as well as oxidation rate, of tissue fatty acids as a function of tissue type, fatty acid structure, and dietary fatty acid composition.     

Effects of Excitatory Amino Acids on Cerebral Oxygen Consumption and Blood Flow in Rat

This investigation tested the importance of excitatory amino acids' effects on regional cerebral O₂ consumption and the concomitant changes in cerebral blood flow (rCBF) in isoflurane anesthetized rats. In the glutamate or N-methyl-D-aspartate (NMDA) groups, 10^–2 M glutamate or NMDA was topically applied to the right cortex and the left cortex was used as a control. One mg/kg dizocilpine maleate (MK-801), a non-competitive NMDA receptor antagonist, was administered (iv) to the MK-801 group and saline was given to the control group. Cortical rCBF was determined using ¹⁴C-iodoantipyrine and regional O₂ extraction was measured microspectrophotometrically. Cerebral O₂ consumption increased 77% after glutamate (contralateral cortex: 9.0 ± 1.1 ml O₂/min/100 g, glutamate treated cortex: 15.9 ± 3.9), while a 46% increase was observed with the same concentration of NMDA (contralateral cortex: 9.8 ± 2.0, NMDA treated cortex: 14.3 ± 5.5). After MK-801, the O₂ consumption decreased to 37% of the control value (control cortex: 7.0 ± 1.3, MK-801 treated cortex: 2.6 ± 3.9). MK-801 significantly decreased cerebral O₂ extraction from 7.1 ± 1.3 ml O₂/100 ml (control cortex) to 5.3 ± 0.6 (MK-801 treated cortex). However, there was no significant difference in cerebral O₂ extraction between treated and contralateral cortex in either the glutamate or NMDA groups. The increase in O₂ consumption caused by glutamate or NMDA was coupled with increased rCBF. Glutamate increased rCBF from 95 ± 5 ml/min/100 g (contralateral cortex) to 165 ± 31 (treated cortex), while NMDA increased rCBF from 114 ± 12 (contralateral cortex) to 178 ± 60 (treated cortex). MK-801 decreased O₂ consumption with a lesser decrease of rCBF. The rCBF was 48 ± 9 in the MK-801 treated cortex and 99 ± 22 in the control cortex. Some substances produced by the activation of NMDA receptors may be related to the coupling of cerebral metabolism and blood flow, since after blockade of NMDA receptors with MK-801, this relationship is uncoupled. These findings suggest that glutamatergic processes have a major effect on cerebral O₂ consumption and that this is at least partly due to NMDA receptors.     

M1 Acetylcholine Receptor Stimulation Increases the Extracellular Concentrations of Glutamate and GABA in the Medial Prefrontal Cortex of the Rat

The present study was undertaken to examine the effects of different muscarinic receptor agonists on glutamate and GABA concentrations in the medial prefrontal cortex of the rat. In vivo perfusions were made in the conscious rat using a concentric push-pull cannulae system. Amino acid concentrations in samples were determined by HPLC with fluorometric detection. The intracortical perfusion of arecoline, a M1-M2 muscarinic receptor agonist, produced a significant increase in extracellular [GLU] and [GABA]. McN-A-343, a M1 muscarinic receptor agonist, but not the M2 muscarinic receptor agonist, oxotremorine, produced a significant increase in extracellular [GLU] and [GABA]. The effects of McN-A-343 on extracellular [GLU] and [GABA] were blocked by pirenzepine, a M1 muscarinic receptor antagonist. These results suggest that M1 muscarinic receptor stimulation increases the extracellular concentrations of GLU and GABA in the medial prefrontal cortex of the rat.     

雌性大鼠离体垂体前叶内在促黄体生成激素释放节律性现象

众所周知,下丘脑促性腺激素释放激素以脉冲形式驱使垂体前叶释放促黄体生成激素,但垂体前叶本身彼和ＬＨ的形式却遭忽略。直到Ｍａｒｃｏ Ｇａｍｂａｃｃｉａｎｉ和谢二发现人和大鼠离体垂体的ＬＨ释放呈节律性。本文目的在于进一步证实是否确定存在ＬＨ释放的内在节律。