Iron plaque enhances phosphorus uptake by rice (Oryza sativa) growing under varying phosphorus and iron concentrations

Both solution culture and pot experiments were performed to investigate (a) the effects of external Fe (II) concentrations and forms on the formation of iron plaque on the roots of rice (Oryza sativa) and subsequent P adsorption on iron plaque and shoot P concentrations and (b) the effects of soil moisture regimes on the formation of iron plaque and P adsorption on root surfaces and P accumulation in shoots. The results showed that iron plaque was significantly increased with increasing Fe²⁺ concentrations in the solution culture. The amounts of P adsorbed on the iron plaque were increased significantly with external Fe²⁺ concentrations. Although shoot P concentration was not significantly affected by Fe²⁺ treatment after incubation for 2 days, it was significantly increased in the Fe‐treated plants compared with Fe‐deprived ones after incubation for 4 days. Soil culture experiment showed that the formation of iron plaque on root surfaces was promoted by exogenous iron, with greater amount of iron plaque being formed by addition of ferric hydroxide than of ferric oxide. Phosphorus adsorption on iron plaque also increased with the addition of iron oxides, and increasing soil P increased the amounts of P associated with the iron plaque and shoot P concentration. The amounts of iron plaque were almost sixfold higher under flooding condition than under field capacity condition. Plants pretreated under flooding condition generally had higher shoot P concentrations when they were transplanted to solutions with varying P levels, and this was most pronounced in the treatment with highest solution P concentration. The results suggest that iron plaque acts as a nutrient reservoir for phosphorus in the rhizosphere and helps enhance P acquisition by rice.     

Effects of oxygen on the growth and metabolism of Actinomyces viscosus

Abstract Actinomyces viscosus is a predominant microorganism in dental plaque. It is, just as the oral Streptococcus spp., a saccharolytic and aero-tolerant organism. We have investigated the effects of oxygen on the growth and metabolism of A. viscosus . To this end A. viscosus Ut 2 was grown in a glucose limited chemostat culture on a chemically defined medium ( D = 0.2 h⁻¹) with exposure to variable amounts of oxygen. The Y_glucose increased from 62.5 g · mol⁻¹ under anaerobic conditions to 149 g · mol⁻¹ under aerobic conditions, while, concomitantly, the carbon recovery from acidic fermentation products decreased from 75% to 7%. Addition of [¹⁴C]glucose to the chemostat showed that the glucose, which was not converted to acidic fermentation products, was instead converted to carbon dioxide or used for the production of biomass. Under aerobic and anaerobic conditions identical cytochrome spectra, containing only two cytochrome b -type absorption bands, were found. It was concluded that electron transport phosphorylation probably occurs both under aerobic and anaerobic conditions. Anaerobically, fumarate served as the electron acceptor, while the high growth yields observed under aerobic conditions are likely to be explained by citric acid cycle activity coupled to electron transport phosphorylation.     

紫外激光消融主动脉斑块和感生荧光光谱观测

利用XeCI准分子激光辐照主动脉血管正常组织和斑块组织,观察到组织被激光消融。消融所产生的凹坑与辐射时间呈对数直线关系。308nm激光感生的血管壁荧光光谱在可见波段出现二个荧光极大值,用二极值的相对强度之比可以判断正常或斑块组织。     

Temporal Profiles of Proteins Responsive to Transient Ischemia

The responses of long and short half-lived proteins to ischemia were measured in rat brain during 6 days of recovery from 30 min of transient forebrain ischemia produced by four-vessel occlusion. At the end of the ischemic interval, the neocortical activities of four vulnerable enzymes [ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylases, and RNA polymerases I and II] were unchanged, but within 30 min of reperfusion, their activities dropped by 25-50%. The loss of substance P in the striatum and substantia nigra was slower, reaching about 50% by 12 h. On the other hand, the activities of 5 long half-lived enzymes did not change in the neocortex at 5 and 15 h of reperfusion and regional protein concentrations were essentially unaffected over 6 days survival. The rate and extent of normalization of the amounts or activities of the vulnerable proteins varied. RNA polymerase II and ODC activities were restored within 4 h, and ODC showed a biphasic increase in activity, with peaks at 10 h and 2-3 days. RNA polymerase I and SAMDC activities were restored by 18 h and 5 days, respectively, whereas substance P concentrations did not completely recover, even at 6-15 days. The greater the regional reduction of blood flow during ischemia, the larger the net change (gain or loss) of SAMDC or ODC activity and the longer the time required to normalize the activities of these enzymes. The average rate of proteolysis, assessed by measuring the rate of clearance of 14C from protein prelabeled with [14C]bicarbonate, was abnormal during the first 2 days of reperfusion. Postischemic changes in both protein synthesis and degradation could affect the amounts of some of the proteins responsive to transient ischemia.     

流行性乙型脑炎病毒血清抗体半微量空斑抑制法的改进

本文报道一种检测流行性乙型脑炎(简称乙脑)中和抗体的简化空斑抑制试验方法,用BHK21传代细胞在24孔塑料板上进行试验,在细胞未形成单层时,将病毒直接接种在刚消化的细胞悬液内,孵育后加甲基纤维素复盖物,再培养,细胞层经染色后即可计算空斑数。 用该法检查47名儿童乙脑疫苗免疫前后的中和抗体,与常规的鸡胚细胞全量法或BHK21传代细胞微量中和试验法作了比较,结果表明本法与其它常规法的敏感性一致,且具有简便快速、节省人力和原材料、空斑形成率高的优点,便于大量血清学检测。     

Immunohistochemical characteristics of the constituents of senile plaques and amyloid angiopathy in aged cynomolgus monkeys

Abstract: In this study, we immunohistochemically examined the several constituents of senile plaques (SPs) and cerebral amyloid angiopathy (CAA) in aged cynomolgus monkeys. Apolipoprotein E (apoE) deposited in all mature plaques and CAA, and in half of the diffuse plaques. Alpha-1-antichymotripsin (αACT) deposited in half of the mature plaques and in one third of the CAA. Amyloid precursor protein (APP), ubiquitin (Ub), and microtubule-associated protein-2 (MAP-2) accumulated in the swollen neurites of mature plaques. Glial fibrillary acidic protein (GFAP) was detected in the astrocytes and their processes surrounding the mature plaques. Tau was detected in neither the SPs nor CAA. Therefore, mature plaques involved extracellular Aβ, apoE, and αACT, and also astrocytes and swollen neurites. However, diffuse plaques involved only extracellular Aβ and apoE. Since these features, except for tau, were consistent with those in humans, this animal model will be useful for studying the pathogenesis of cerebral amyloid deposition.     

Diverse programs of ascus development in pseudohomothallic species of Neurospora,Gelasinospora, and Podospora

Meiosis and ascospore development in the four-spored pseudohomothallic ascomycetes Neurospora tetrasperma, Gelasinospora tetrasperma, Podospora anserina, and P. fefraspora have been reexamined, highlighting differences that reflect independent origins of the four-spored condition in the different genera. In these species, as in the heterothallic eight-spored N. crassa, fusion of haploid nuclei is followed directly by meiosis and a postmeiotic mitosis. These divisions take place within a single unpartitioned giant cell, the ascus, which attains a length of >0.1 mm before nuclei are enclosed by ascospore walls. Two basically different modes underlie the delivery of opposite mating type nuclei into each of the four ascospores in the different genera. In N. tefrasperma on the one hand, the mating type locus is closely centromere-linked. Mating types therefore segregate at the first meiotic division. The second division spindles of N. tefrasperma overlap and are usually parallel to one another, in contrast to the their tandem arrangement in N. crassa. As a result, nonsister nuclei of opposite mating type are placed close together in each half-ascus and a pair is enclosed in each ascospore. In the Podospora and Gelasinospora species on the other hand, the second-division spindles are in tandem, with sister nuclei of opposite mating type associated as a pair in each half-ascus. It is established for P. anserina and inferred for P. fetraspora and G. fefrasperma that a single reciprocal crossing over almost always occurs in the mating type-centromere interval, ensuring that mating types segregate at the second meiotic division and that nuclei of opposite mating type are enclosed in each ascospore. Other differences are also seen that are less fundamental. Neurospora tetrasperma differs from the other species in the orientation of chromosomes and spindle pole body plaques at interphase (I.) Third-division spindles are oriented parallel to the ascus wall in Gelasinospora but across the ascus in Podospora and Neurospora. The two Podospora species differ from one another in nuclear behavior following mitosis in the young ascospores. In P. tefraspora, two of the four nuclei migrate into the tail cell, which degenerates, leaving one functional nucleus of each mating type. In P. anserina, by contrast, only one of the four nuclei moves into the tail cell, leaving the germinating ascospore with two functional nuclei of one mating type and one of the other. The pseudohomothallic condition with its heterokaryotic vegetative phase has significant consequences for both the individual organism and the breeding system. Genetic controls of development and recombination are complex. Inbreeding is not obligatory. © 1994 WiIey-Liss, Inc.     

益生菌辅助治疗牙周病的研究进展

牙周病是累及牙周支持组织的慢性感染性疾病。牙菌斑生物膜中的微生物及其代谢产物是其必不可少的始动因素,可导致口腔微生态失衡和宿主免疫反应,最终引起牙周病的发生发展。目前,牙周病的基础治疗主要是机械清除牙菌斑生物膜和牙石,但治疗效果具有局限性。益生菌通过产生抑菌物质、刺激局部免疫反应、与致病菌争夺黏膜受体和营养物质,从而改善口腔微生态平衡,促进牙周病的治疗。本文就近年来益生菌在牙周病治疗上的实验和临床研究、作用机制、安全性等进行综述,为将来益生菌辅助治疗牙周病的应用提供参考。     

Glutamine synthetase (GS) expression is reduced in senile dementia of the Alzheimer type

Glutamine synthetase (GS), a metabolic marker of the mature astrocyte, was investigated in the temporal neocortex of postmortem brain samples of 8 cases, either not demented or affected by senile dementia of the Alzheimer type. A negative correlation between the GS protein level and the density of both classical A4 deposits and senile plaques was evidenced. Such a correlation for GS underlies a dysfunction of the astroglial metabolism and particularly of the glutamate and ammonia neutralization. Since GS is sensitive to oxidative lesioning, the changes in GS level that were observed, occurring at the posttranslational stage, might reflect oxidative damage and have severe consequences on the pathological cascade of events.     

Chemical interactions with herpes simplex type 2 virus: Enhancement of transformation by hydrazine and 1,2-dimethylhydrazine

Quantitative assays for the morphological transformation of 3T3 Swiss mouse cells by herpes simplex type 2 virus (HSV-2) were employed to examine the effect on cell transformation of chemical carcinogens and suspected carcinogens. Exposure of the cells to the chemical compound, followed by virus infection, resulted in enhancement of transformation when compared to that observed with chemical or virus alone. Enhancement occurred in tests utilizing either UV light-inactivated HSV-2 (strain 333) or a temperature-sensitive (ts) mutant of HSV-2 [A₈(293)]. A series of seven ts-mutants were tested and exhibited varying degrees of transformation. Enhancement of transformation occurred in cells treated with hydrazine (HZ) and 1,2-dimethylhydrazine (SDMH). No enhancement occurred when cells were treated with monomethylhydrazine, 1,1-dimethylhydrazine and the jet fuels JP-5, JP-10, RJ-4 and RJ-5. A strong time dependence after treatment was demonstrated with some enhancement seen at 6 h after chemical treatment but the greatest enhancement appeared when virus infection began after 24 h of chemical exposure.