Brain Iron: Persistent Deficiency following Short-term Iron Deprivation in the Young Rat

This study was designed to determine the content of non-haem iron in the brain as iron deficiency develops in the rapidly growing rat. Rats were provided with either an iron-deficient diet or an identical control diet with added ferrous sulphate starting at 10 d of age and continuing after weaning at 21 d. At 28 d or 48 d of age the deficient animals received 5 mg of iron (iron dextran) i.m. and were placed on the control diet regimen. The deficient animals had a concentration of non-haem iron in the brain that was 27% below the control value at 28 d and 22% below at 48 d. After 14-45 d of iron treatment, the non-haem iron remained depressed, 19-29% below the control means (P less tha 0.05 to 0.001). Ferritin iron in brain also remained depressed, 33-42% below the control means (P less than 0.01). In contrast, haematocrit, liver non-haem iron, and liver ferritin iron, although they were more profoundly depressed in the iron-deficient animals, promptly returned to control values after treatment with iron. Thus, a brief period of severe iron deficiency in the young rat resulted in a deficit of brain iron that persisted in the adult animal despite an adequate intake of iron.     

Programmed Cell Death in Rat Intestine: Effect of Feeding and Fasting

Background: The regulation of intestinal cell death by luminal factors is poorly understood. The objectives of this study were to determine whether a diurnal rhythm of intestinal apoptosis exists, and to determine the role that feeding and fasting play in this process. Methods: Mucosal apoptotic death was measured in fed and 24-h fasted rats and at various times after feeding by DNA fragmentation and in situ immunohistochemical staining (TUNEL). Results: In 24-h fasted rats, 32% of total mucosal DNA was fragmented as compared to 9% in fed animals. In both jejunal and ileal segments, the fragmented DNA exhibited characteristic apoptotic DNA ladders on agarose gels. Immunohistochemical staining revealed significant location of apoptotic cells at the upper third of the intestinal villus. In the duodenum, DNA fragmentation at 6-12 h post feeding was 20% and decreased to 4% at 24 h. In comparison, DNA fragmentation in the jejunum and ileum was low from 0 to 6 h post feeding (2%-9%) and significantly increased at 12 h (18% versus 12%) and 24 h (30% versus 32%), respectively. These results are consistent with a temporal relationship between percent fragmented DNA and time after feeding with greater cell death at longer fasting period. A postprandial rhythm of DNA fragmentation was evident in the jejunum and ileum, in which fragmentation was at a peak between 0900 h and 1200 h. Conclusion: Collectively, the data show that initiation of apoptosis in apical enterocytes is coincident with cessation of feeding and commencement of fasting, and is consistent with a rhythm of programmed cell death in these cells that parallels the cyclical pattern of feeding and fasting.     

Ethanol Oxidation by Rat Brain in Vivo

Can brain metabolize ethanol? We present data demonstrating that brain catalase in conjunction with endogenous H₂O₂ will oxidize ethanol in vivo. The method is based on an H₂O₂-dependent inhibition of brain catalase in vivo by 3-amino-1,2.4-triazole and its prevention by ethanol. The irreversible inhibition of catalase by aminotriazole is known to proceed via the reaction of (catalase-H₂O₂) compound I with aminotriazole. Inhibition can be prevented by compounds that are oxidized by compound I. Ethanol is one such compound. Prevention of the inhibition of brain catalase in vivo by prior administration of ethanol constitutes indirect evidence for the oxidation of ethanol to acetalde-hyde in rat brain. The catalase content of the tissues represented catalase in the brain parenchyma, from which erythrocytes and capillaries had been excluded. Ethanol did not alter the levels of aminotriazole in brain. These results constitute the first demonstration of ethanol oxidation by living brain.     

Azelnidipine Inhibits H2O2-Induced Cell Death in Neonatal Rat Cardiomyocytes

Purpose Oxidative stress plays an important role in the pathogenesis of cardiovascular diseases. Azelnidipine is a novel dihydropyridine calcium channel blocker. Several studies have demonstrated that some dihydropyridine calcium channel blockers have antioxidant effects. We evaluated the antioxidant effects of azelnidipine compared to another dihyropyridine calcium channel blocker, nifedipine, in neonatal rat cardiomyocytes. Materials and methods We examined effects of azelnidipine and nifedipine on the H₂O₂-induced mitogen-activated protein kinase (MAPK) activity and cell death in neonatal rat cardiomyocytes. Results Extracellular signal-regulated protein kinases (ERK), p38 MAPK and c-Jun NH₂-terminal kinases (JNK) were activated by H₂O₂ stimulation. Azelnidipine and nifedipine did not affect the H₂O₂-induced activation of ERK and p38 MAPK. In contrast, azelnidipine, but not nifedipine, inhibited the H₂O₂-induced JNK activation. The numbers of viable cell were significantly decreased by H₂O₂ treatments (65.8 ± 4.11% of control, P < 0.0001). Azelnidipine, but not nifedipine, inhibited the H₂O₂-induced cell death (azelnidipine: 76.0 ± 4.66% of control, P < 0.05; nifedipine: 70.7 ± 4.01% of control, P = 0.32). Conclusion Azelnidipine inhibited the H₂O₂-induced JNK activation and cardiac cell death. Azelnidipine may have cardioprotective effects against oxidative stress. This study was supported in part by a grant-in-aid for Scientific Research (No. 17590702) from the Ministry of Education, Science, Sports and Culture, Japan, a grant-in-aid from the twenty-first century center of excellence (COE) program of the Japan Society for the Promotion of Science, and grants from Takeda Science Foundation and Fukuda Foundation for Medical Technology.     

脑死亡诊断的研究进展

脑死亡的诊断标准包括临床标准和确认标准 ,诊断方法包括意识状态检查、脑干反射、呼吸暂停试验、阿托品试验、经颅多普勒超声、脑电图、体感诱发电位、磁共振、血管造影等多种。     

脑死亡研究进展

脑死亡的概念当前脑死亡概念主要有三种 :全脑死亡 (wholebraindeath)　 196 8年哈佛大学医学院首次提出脑死亡诊断标准时提出 :“脑死亡是包括脑干在内的全脑功能丧失的不可逆状态”。近来不少学者对“全脑功能丧失”的含义有异议 ,如 :1.Truog等指出 ,脑死亡患者的全脑功能并非完全丧失 ,部分患者仍保留一些脑的内分泌功能。举例来说 ,垂体后叶分泌抗利尿激素 ,如果垂体后叶功能消失 ,会出现中枢性尿崩症 ,然而脑死亡时中枢性尿崩症的发生率仅为 38%～ 87% ,可见相当一部分患者并无中枢性尿崩症表现 ,说明垂体后叶功能仍存在。2 .从病理…     

吸烟大鼠脑血管内皮细胞基质金属蛋白酶9的表达

目的 观察不同吸烟量的大鼠脑血管内皮细胞基质金属蛋白酶9的表达，初步探讨吸烟导致脑缺血的发病机制。方法 选择健康Wistar大鼠60只，分为正常对照组、短期大量吸烟组、长期大量吸烟组、长期小量吸烟组、戒烟组和非吸烟组。通过免疫组织化学染色观察大鼠脑血管内皮细胞基质金属蛋白酶9的表达。结果 基质金属蛋白酶9阳性反应物呈棕黄色，正常对照组及非吸烟组细胞基质金属蛋白酶9表达极少，余各组有不同程度表达，且与对照组比较有显著性差异（P〈0．05）。结论 吸烟可致脑血管内皮细胞基质金属蛋白酶9表达增加，且随着吸烟量和吸烟时间的增加表达增多，戒烟后表达下降。细胞基质金属蛋白酶9在吸烟时脑血管内皮细胞的表达增加可能是吸烟致脑梗死的主要途径之一。     

Iron Mobilization in the Pregnant Rat

S ummary . Iron exchange in the pregnant rat was quantitated by repeated determinations of plasma iron turnover (PIT), transferrin iron distribution and measurements of storage iron and food iron utilization employing selective radio-iron probes. Despite a sixfold increase in PIT, intestinal absorption of iron accounted for 40% of the PIT throughout pregnancy, with variations not exceeding ±5%. Increased fetal requirements were efficiently compensated for by the mobilization of iron from maternal tissue stores and by increased absorption, and there was no subsequent reduction in iron supply to maternal tissues. Enhancement of iron absorption occurred in the absence of a reduction in serum iron levels or the size of iron stores. In view of the close correlation between PIT and rates of absorption it is postulated that iron absorption in the pregnant rat is regulated by PIT which in turn is determined by the rate of plasma iron clearance by the placenta and the maternal erythroid marrow.     

Maternofoetal Iron Transfer in the Rat

S ummary . The distribution of ⁵⁹Fe in maternal, placental and foetal tissues of the rat was determined at intervals of 8, 12, 15, 17, 19, 20 and 21 days of gestation. Large amounts of ⁵⁹Fe are transferred from maternal plasma to the foetuses in late gestation when foetal development is proceeding at a rapid rate. The deposition of ⁵⁹Fe in the developing foetus appears governed by erythropoiesis; liver and carcass are the principal sites. ⁵⁹Fe is rapidly transported across the placenta; there is no indication of a large iron pool within it. Both the allantoic and yolk sac placentae contribute significantly to placental iron uptake during the period of maximum iron transfer. Very little iron is deposited in the uterus during gestation; hence secretions from uterine glands entering the yolk sac cavity are a minor source of foetal iron. There is diminished uptake of ⁵⁹Fe by the maternal liver and spleen during the period of rapid iron accumulation by the foetuses.     

Maternofoetal Iron Transfer in the Rat

S ummary . The distribution of ⁵⁹Fe in maternal, placental and foetal tissues of the rat was determined at intervals of 8, 12, 15, 17, 19, 20 and 21 days of gestation. Large amounts of ⁵⁹Fe are transferred from maternal plasma to the foetuses in late gestation when foetal development is proceeding at a rapid rate. The deposition of ⁵⁹Fe in the developing foetus appears governed by erythropoiesis; liver and carcass are the principal sites. ⁵⁹Fe is rapidly transported across the placenta; there is no indication of a large iron pool within it. Both the allantoic and yolk sac placentae contribute significantly to placental iron uptake during the period of maximum iron transfer. Very little iron is deposited in the uterus during gestation; hence secretions from uterine glands entering the yolk sac cavity are a minor source of foetal iron. There is diminished uptake of ⁵⁹Fe by the maternal liver and spleen during the period of rapid iron accumulation by the foetuses.     

Iron Transport by Rat Small Intestine in Vitro: Effect of Body Iron Status

S ummary . Both mucosal uptake and serosal transfer of iron by everted sacs of rat small intestine were maximal in the duodenum and decreased progressively towards the ileum. Transport of iron against a concentration gradient did not occur in any part of the intestine. When the iron concentration in the bathing medium was varied over the range 10–500 μM a saturable transport process was revealed in the proximal small intestine. In iron-deficient rats mucosal uptake of iron was increased but in iron-loaded rats it remained normal. The results suggest that iron transport across the proximal small intestine of the rat in vitro involves a carrier mechanism which responds adaptively to iron deficiency but not to overload.     

Uptake of Transferrin-Bound Iron by Rat Cells in Tissue Culture

The in vitro uptake of transferrin-bound iron by rat liver cells and rat embryo cells in culture, and by rat reticulocytes, was studied using labelled rat serum. The uptake of iron by rat liver cells was linear with time and showed a curvilinear relationship with the serum iron concentration. Over 40% of the cell radioactivity was found to be ferritin associated. Incubation of rat transferrin doubly labelled with ⁵⁹Fe and ¹²⁵l showed a difference between the uptakes of the two isotopes suggesting reflux of transferrin from the cell after iron uptake. In order to compare iron uptake from half saturated (Tf-Fe 1) and fully saturated (Tf-Fe2) transferrin, the three cell systems were each incubated in sera labelled with ⁵⁵Fe at 10% saturation and with ⁵⁹Fe at varying iron saturations ranging from 10% to 90%. Similar experiments were performed with sera having been randomly labelled with ⁵⁵Fe and labelled with ⁵⁹Fe but preincubated with reticulocytes in order to produce iron bound to non-reticulocyte orientated transferrin binding sites. The data obtained confirms the presence of a functional heterogeneity with respect to the half and fully saturated transferrin. Thus iron uptake from fully saturated transferrin was almost twice that for the half saturated molecule with rat liver cells or reticulocytes, and over three times that of the half saturated molecule with rat embryo cells. In contrast no such differences could be detected when iron uptake from serum randomly labelled with iron and serum with labelled non-reticulocyte orientated binding sites were compared. Finally, the effect of pre-incubating each of the three cell systems in unlabelled sera of varying percentage iron saturations on subsequent radio-iron uptake was studied. An inverse relationship between percentage saturation of the preincubation serum and subsequent uptake was demonstrated indicating that cellular mechanisms also influence cell iron uptake.     

Mobilisation of Iron from Peritoneal Rat Macrophages by Desferrioxamine

The amount of radioiron released from rat peritoneal macrophages after phagocytosis of ⁵⁹Fe labelled erythrocytes can be enhanced by addition of desferrioxamine. The effect is dose dependent and the iron chelated by desferrioxamine appears to be at the expense of ferritin. However, desferrioxamine does not appear to chelate iron already incorporated into ferritin. It seems likely that the iron comes from a labile chelatable pool through which the iron from haemoglobin catabolism passes before being incorporated into ferritin. The desferrioxamine appears to enter the macrophage and chelate iron to form ferrioxamine which subsequently leaves the macrophage. In vivo it was not possible to show substantial iron chelaton by desferrioxamine in rats when ⁵⁹Fe labelled non-viable red cells were injected intravenously. This suggests that in vivo mobilization of reticuloendothelial iron by desferrioxamine may be of limited significance.     

Induction of Transferrin Receptor by Ethanol in Rat Primary Hepatocyte Culture

Background: It is not uncommon for alcoholics to have iron accumulation in the liver, a condition that may contribute to the development of alcoholic liver disease. Recently, we reported that the expression of transferrin receptor, which mediates cellular iron uptake, was increased in hepatocytes in patients with alcoholic liver disease. To elucidate the mechanism of the iron accumulation in hepatocytes in such disease, we examined whether ethanol exposure induced the transferrin receptor expression and increased the cellular iron uptake.
Methods: Rat primary hepatocytes were isolated and cultured in the presence of 20 μmol/liter of iron and 25 mmol/liter of ethanol.
Results: Ethanol exposure to the hepatocytes demonstrated an ˜2-fold increase in transferrin receptor expression for 24 hr, shown by Western blot analysis and ³⁵S-methionine metabolic labeling, 19% increase in ⁵⁹Fe-transferrin uptake by hepatocytes, and 20% increase in activity of iron regulatory protein examined by band shift assay.
Conclusion: Ethanol exposure induced the transferrin receptor expression, partially through the activation of iron regulatory protein, and increased the transferrin-bound iron uptake in rat hepatocyte cultures. The induction of transferrin receptor by ethanol might be one of the mechanisms of iron accumulation in the hepatocytes in alcoholic liver disease.     

Pancreatic Duct Stricture Caused by Islet Cell Tumors

We report three cases of pancreatic islet cell tumors causing stricture of the main pancreatic duct. The clinical presentation was consistent with episodes of acute pancreatitis or biliary colic. One patient in whom the diagnosis was delayed died of metastatic disease. Islet cell tumors are an important clinical entity that must be considered in the differential diagnosis of pancreatic duct strictures.     

Muscarinic Cholinergic Binding in Rat Brain

Binding sites with high affinity and specificity for [(3)H]quinuclidinyl benzilate (QNB) are present in homogenates of rat brain. The characteristics of the binding sites resemble those of muscarinic cholinergic receptors. Specific binding is saturable with respect to [(3)H]QNB and tissue concentration and is time-, temperature-, and pH-dependent. The bimolecular rate of association (2.0 x 10(8) M(-1) min(-1)) and dissociation (1.2 x 10(-2) min(-1)) at 35 degrees indicate a dissociation constant of 60 pM and a density of 65 pmol/g of brain. Muscarinic antagonists and agonists displace specific [(3)H]QNB binding, while nicotinic and non-cholinergic drugs possess little affinity for [(3)H]QNB-binding sites.     

A Study of Storage Iron in the Pregnant Rat

S ummary . It has been established that maternal storage iron is depleted during pregnancy in order to supply part of the iron required by the developing foetus and by the increasing red cell mass of the mother. It is also accepted that ferritin and haemosiderin are equally available as sources of storage iron.
We measured the quantity of ferritin and haemosiderin in the liver and spleen of the rat at intervals during the latter half of pregnancy and have shown that ferritin iron is reduced whereas haemosiderin iron remains unchanged. The 2 and 24 hr uptake of ⁵⁹Fe by these compounds was also measured. ⁵⁹Fe is incorporated into both compounds; the uptake of ⁵⁹Fe by ferritin falls in late pregnancy. Newlydeposited ⁵⁹Fe is withdrawn from ferritin but not from haemosiderin.
These results indicate that ferritin is the major source of storage iron in the pregnant rat. Ferritin iron is reduced in the liver and spleen because of a decreased uptake of iron as well as an increased mobilization.     

Properties of Opiate-Receptor Binding in Rat Brain

[(3)H]Naloxone, a potent opiate antagonist, binds stereospecifically to opiate-receptor sites in rat-brain tissue. The binding is time, temperature, and pH dependent and saturable with respect to [(3)H]naloxone and tissue concentration. The [(3)H]naloxone-receptor complex formation is bimolecular with a dissociation constant of 20 nM. 15 Opiate agonists and antagonists compete for the same receptors, whose density is 30 pmol/g. Potencies of opiates and their antagonists in displacing [(3)H]naloxone binding parallel their pharmacological potencies.     

Alanine Prevents the in Vitro Inhibition of Glycolysis Caused by Phenylalanine in Brain Cortex of Rats

Glycolysis is the main route that provides energy to brain functioning. In this study we investigated the in vitro effects of phenylalanine, the main metabolite known to accumulate in phenylketonuria, and/or alanine, on pyruvate kinase activity, glucose utilization, lactate release, and ADP concentration in brain cortex homogenates from 30-day-old Wistar rats. We found that phenylalanine decreased PK activity, glucose utilization, and lactate release, and increased ADP brain levels. We also verified that alanine per se did not modify these parameters, but prevented the effects of phenylalanine. Our data suggest that the inhibition of pyruvate kinase by phenylalanine decreases glycolysis and energy production, and that alanine, a known competitor of phenylalanine on the enzyme activity, prevents the reduction of glycolysis and energy production caused by phenylalanine, probably by preventing the enzyme inhibition provoked by the amino acid. These results suggest that inhibition of brain PK activity by phenylalanine may be related to the diminution of glucose metabolism observed in the brain of phenylketonuric patients and may be one of the mechanisms responsible for the neurological dysfunction found in these patients.