共查询到20条相似文献,搜索用时 15 毫秒
1.
The effects of three monoamine antagonists, p-chlorophenylalanine, diethyldithiocarbamate and propranolol on the morphogenesis of newt embryos were studied. Antagonists were administered during late blastula through neurula stages. In a concentration of 1 mM, all three arrested gastrulation and caused disintegration of the embryos. Lower concentrations (0.1-0.5 mM) retarded morphogenetic movements in the gastrulation and caused malformations especially in the anterior parts of the embryos; pigmentation was delayed by 1 or 2 days. In addition, p-CIPhe inhibited yolk granule degradation in the notochord and DEDTC caused notochordal hypertrophy. The results show that interference with synthesis or action of catecholamines and serotonin affects morphogenesis. With the methods used it is not possible to discover exactly how monoamines regulate the morphogenetic events because of the unspecific side effects of the antagonists and the feedback interactions between the monoamines. 相似文献
2.
3.
目的:探讨动态增强磁共振成像扫描与超声弹性成像对乳腺癌良恶性肿瘤的诊断价值,为临床诊断提供影像学依据。方法:回顾性分析2009年10月至2013年5月在我院经穿刺或手术病理证实为乳腺癌的59例患者的临床资料,患者术前均行超声与动态增强MR检查。依据病理组织活检和临床随访分别评价动态增强MR和UE对乳腺癌诊断的准确性。结果:DCE-MRI检测共发现病灶59个,55个初步诊断乳腺恶性肿瘤(BI-RADS 4-5),4个诊断为良性(BI-RADS 3),诊断准确率为93.22%(55/59)。UE对59个病灶进行评分,54个评分为乳腺恶性肿瘤,5个评分为良性,诊断率为91.53%(54/59)。UE检测乳腺癌的敏感性明显低于DCE-MRI及DCE-MRI+UE,DCE-MRI检测乳腺癌的特异性明显低于UE及DCE-MRI+UE,差异具有统计学意义(P0.05)。DCE-MRI+UE诊断乳腺癌的准确率为96.61%(57/59),明显高于DCE-MRI或UE单独检测的准确率(P0.05)。结论:动态增强MR诊断乳腺癌的敏感性较高,而超声弹性成像的特异性较好,两者联合可提高诊断准确率,对乳腺癌的早期诊断具有重要的临床应用价值。 相似文献
4.
5.
《Theriogenology》1996,45(8):1457-1462
The aim of this study was to determine the influence of hand massage of mares' ovaries on breeding activity and hormonal changes in the winter anestrous period and during the luteal phase of the oestrus cycle. The experiment was conducted on 5 experimental and 5 control mares. In winter, (January) the experimental mares underwent 30-sec daily massage of both ovaries, for 30 d, and in summer (August) from the 6th day of the cycle to the occurrence of estrus. The sexual behavior of all mares was determined each day by individual teasing by a vigorous stallion, and the ovaries were checked by palpation per rectum and with an USG. Every second day blood samples were drawn from each mare to determine progesterone and estradiol in the plasma. Ovarian massage during deep winter anestrus had no significant effect on acceleration of the mares' active breeding season. Nevertheless, a higher concentration of estradiol was observed in the experimental group. These differences occurring on the 11th, 17th and 20th days were found to be significant (P ≤ 0.05). It was shown that during the summer period, in the luteal phase of the cycle, ovarian massage shortened the length of the estrous cycle, and ovulation was brought on somewhat earlier. 相似文献
6.
7.
8.
The influences of some factors at the both sides of the solid and liquid phases on the solubilities of L-glutamic acid in α and β-forms in water were examined.As differences in the conditions of the liquid phase, the effects of co-existing inorganic neutral salts and amino acids on the solubilities were investigated; and as for the inorganic neutral salts applied here, salting-in effects were recognized, the degrees of which were in the following order, i.e., NH4Cl, (NH4)2SO4>KCl>NaCl. The effect in the β-form was larger than that of in the α-form. The influence of co-existing amino acids was very little if the amount was not so much, but the tendency to increase the solubility could be recognized.As a difference in the condition of the solid phase, the purity of the crystals was picked up, and it was clarified that the crude crystal of L-glutamic acid in α-form gave a larger value of the solubility than the purified one. 相似文献
9.
Yoshiki Sakata Toshiyuki Horikawa Kuniharu Takenoughi 《Bioscience, biotechnology, and biochemistry》2013,77(12):921-931
The behaviors of impurities such as amino acids and inorganic salts at the time of crystallization of l-glutamic acid were investigated; and it was concluded that amino acids which co-existed in the solution of l-glutamic acid followed the crystals of l-glutamic acid persistently, and the contamination mechanism would not be clarified by the adherence of mother liquor or the formation of liquid foams in the crystals, or by the mixed crystal formation, but by a physical adsorption on the crystal surfaces. 相似文献
10.
11.
The effects of phentolamine on coronary resistance and heart rate, as well as the influence of beta 1-adrenoceptor blockade on phentolamine effects were studied on the isolated cat hearts. Phentolamine reduced coronary resistance in 100% of cases (-25.9 +/- 4.4%; p less than 0.001) and increased heart rate only in 31.6% of cases (+9.1 +/- 1.4%); on average the alterations of heart rate were nonsignificant (p less than 0.1). After beta 1-blockade with Cordanum the rate of coronary dilation reduced (p less than 0.001), the changes in coronary resistance being nonsignificant (p greater than 0.1). Basal coronary resistance and tone during phentolamine infusion without or after beta 1-blockade were identical (p greater than 0.1). Thus, the reduction of coronary resistance during phentolamine infusion was due to beta 1-adrenomimetic activity of the drug. 相似文献
12.
The number of prickles upon the edge of a leaf is related bycomplex laws to the size of the leaf, the number of prickleson the other edge, the number of prickles on other leaves ofthe shoot, the phyllotaxy of the shoot, and the intrinsic asymmetryof the leaf. The available evidence indicates that pricklesarise by the interaction of not less than five recognizablephysiological systems. The physical nature of these systemsis unknown but their mathematical properties have been partlyelucidated. Some of them are found to involve the transmissionof morphogenetic impulses while others may be purely local intheir action. As one of the consequences of this physiologicalsituation it is found that shoots having opposite directionsof phyllotaxy differ quantitatively as well as qualitatively. 相似文献
13.
The behaviors of impurities on the crystallizations of the free acid and the hydrochloride, monosodium, zinc, calcium and barium salts of l-glutamic acid were examined, and a tendency was recognized that coexisting impurities were apt to be taken into the crystals when the crystallization proceeded from the zwitterion, i.e., Glu.± or The adsorption of l-tyro-sine was compared when l, d and dl-glutamic acid were crystallized with coexistence of l-tyrosine, and an effect of more or less extent of steric configuration on its behavior could be recognized. 相似文献
14.
以Swaisonine(Sw)作为高尔基体付糖链加工酶系中α-甘露糖苷酶Ⅱ的特异抑制剂,研究N-糖链结构和胰岛素受体(Ins-R)功能的关系.发现Sw不影响细胞生长和3H-亮氨酸参入SMMC7721细胞,但明显促进3H-甘露糖参入细胞总糖蛋白和表面糖蛋白,并使后者的ConA强结合组分显著增加,提示Sw使Ins-R的N-糖链变成杂合型及高甘露糖型。胰岛素结合试验后作Scatchard分析:发现Sw不改变Ins-R的结合容量和每个细胞表面的结合位点数,也不改变结合动力学。再用部分纯化的Ins-R研究自身磷酸化和对外源底物的酪氨酸蛋白激酶活力,也未发现Sw处理和对照细胞间的明显区别,表示Sw也不影响Isn-R的跨膜信息传递,结合已报道的衣霉素使细胞表面Ins-R减少的结果,提示Ins-R运送至细胞膜需要N-糖链存在,但糖链的类型对INS-R的代谢和结合动力学并不重要 相似文献
15.
L Sanna V Farina M Zedda A Asole R Panu G Palmieri 《Archivio italiano di anatomia e di embriologia》1991,96(1):43-54
Previous investigations have ascertained, according to the results obtained by Bradley et al. (1980) in the sheep, that the laryngeal surface of the epiglottis of goat and bovine is always provided with numerous taste buds. These observations have verified in other ruminant species, as the moufflon and the buffalo, the validity of the above-named datum and have ascertained that it is always inconstant in the other animal species considered (wild boar, coypu). These taste buds show a typical structure (diameter of the outer taste pore varying from 2.7 to 4.2 micron, width of the chemoreceptors varying from 30 to 60 micron and length from 27.5 to 57.5 micron). Moreover, the normal structure of the above-named taste buds is also testified by the arrangement of their innervation and particularly by the integrity of the synaptic contacts. The results of the present research have permitted a critical and more severe examination of the probable functional role of those laryngeal receptors. In fact, in the ruminants they may protect the deep airways precluding to food particles the larynx in the phase of food regurgitation. 相似文献
16.
Fluorescent proteins are now widely used in fluorescence microscopy as genetic tags to any protein of interest. Recently, a new fluorescent protein, Kaede, was introduced, which exhibits an irreversible color shift from green to red fluorescence after photoactivation with lambda = 350-410 nm and, thus, allows for specific cellular tracking of proteins before and after exposure to the illumination light. In this work, the dynamics of this photoconversion reaction of Kaede are studied by fluorescence techniques based on single-molecule spectroscopy. By fluorescence correlation spectroscopy, fast flickering dynamics of the chromophore group were revealed. Although these dynamics on a submillisecond timescale were found to be dependent on pH for the green fluorescent Kaede chromophore, the flickering timescale of the photoconverted red chromophore was constant over a large pH range but varied with intensity of the 488-nm excitation light. These findings suggest a comprehensive reorganization of the chromophore and its close environment caused by the photoconversion reaction. To study the photoconversion in more detail, we introduced a novel experimental arrangement to perform continuous flow experiments on a single-molecule scale in a microfluidic channel. Here, the reaction in the flowing sample was induced by the focused light of a diode laser (lambda = 405 nm). Original and photoconverted Kaede protein were differentiated by subsequent excitation at lambda = 488 nm. By variation of flow rate and intensity of the initiating laser we found a reaction rate of 38.6 s(-1) for the complete photoconversion, which is much slower than the internal dynamics of the chromophores. No fluorescent intermediate states could be revealed. 相似文献
17.
18.
随着全球范围珊瑚礁的退化,大型海藻在珊瑚礁区的覆盖度呈增多的趋势。大型海藻的大量生长,妨碍了珊瑚的生长、繁殖、恢复等过程。概括起来,大型海藻对珊瑚生长、繁殖及恢复过程所产生的不利影响主要包括:(1)大型海藻通过与珊瑚竞争空间和光照而影响珊瑚生长;(2)大型海藻与珊瑚直接接触时,通过摩擦作用及释放化感物质而影响珊瑚生长;(3)大型海藻的大量生长打破了珊瑚与海藻的竞争平衡,珊瑚为应对大型海藻的入侵而把用于生长和繁殖的能量转移到组织修复与防御上,进而造成珊瑚繁殖能量的减少;(4)大型海藻通过影响珊瑚幼虫的附着及附着后的存活率,而阻碍珊瑚群落的发展;(5)海藻还能通过富集沉积物、释放病原体及扰乱珊瑚共生微生物的生长等而间接影响珊瑚生长。明确的竞争机制有利于研究海藻与珊瑚的相互作用过程。在总结前人对海藻与珊瑚的竞争机制研究的基础上,把两者的竞争机制划分成物理机制、化学机制、微生物机制三大类,物理机制是研究得比较透彻的竞争机制,而化学机制与微生物机制则需要更深入的研究,是当前研究的热点。目前,我国对珊瑚礁中底栖海藻与珊瑚的相互作用研究甚少;鉴于此,对底栖海藻功能群的划分类型以及三大类型底栖海藻对珊瑚的作用特点做了简要介绍,并对珊瑚礁退化的现状和退化珊瑚礁区内海藻的表现做了概述。在此基础上,再综述国外关于大型海藻对珊瑚的影响研究进展,指出我国应该加强对南海珊瑚礁区大型海藻的种类分布及丰富度等的调查,评价大型海藻对南海珊瑚礁的影响现状;并结合生理学、分子生物学技术和生态学研究手段,在细胞与分子水平上探索海藻对珊瑚的影响机制,以期为珊瑚礁生态系统的保护提供参考。 相似文献
19.
Arthur Bierman 《Bulletin of mathematical biology》1954,16(3):203-257
The effects of structural features on various properties of enzyme systems are studied. Some of the effects are: in a homogeneous
reaction, enzyme compartmentalization decreases the rate; in a heterogeneous reaction, compartmentalization increases the
rate. The steady-state concentration of intermediates is larger in a non-uniform than in uniform systems. Periodicities do
not generally occur in the common kinetic systems; they do occur in autocatalytic systems, but compartmentalization reduces
their probability of occurrence. The conditions for overshoot are different for uniform and non-uniform systems. Multiple
stable steady states are not a common occurrence among biologically typical reactions; they do occur in combined autocatalytic
and surface systems (a mechanism for the gener position effect is suggested by this property). The local pH is affected by
the enzyme aggregation as well as by the geometry of the enzyme structure. A 2-step system can give rise to the characteristic
rate vs. pH curve, where the optimum is not necessarily at isoelectric point. The expression for the osmotic pressure inside
a spherical particle is deduced. The pressure is shown to be dependent on the radius. The rate inside a cell particle is shown
to be determined by the shape of the particle. 相似文献
20.
C Giunta M T Rinaudo R Bruno 《Bollettino della Società italiana di biologia sperimentale》1968,44(19):1639-1640