Involvement of histidine and tryptophan residues of glutamine binding protein in the interaction with membrane-bound components of the glutamine transport system of Escherichia coli

We treated the glutamine binding protein with diethyl pyrocarbonate (DEPC) and N-bromosuccinimide (NBS) to modify respectively the sole histidine and tryptophan residues and examined the effect of these modifications on the ability of the binding protein to bind glutamine as well as the ability to restore glutamine transport in membrane vesicles of Escherichia coli. Under the conditions used, both DEPC and NBS markedly inhibited the ability to restore glutamine transport in vesicles without any significant effect on glutamine binding. Moreover, saturating quantities of glutamine had no protective effect on the inactivation of the binding protein by DEPC or NBS. Fluorometric measurement and amino acid analysis indicate that the inactivation of the binding protein in restoring vesicle transport by NBS can be attributed to the oxidation of a single tryptophan residue. Similar analysis and the inability of hydroxylamine to reverse the effect of DEPC indicate that the effects of DEPC can probably be attributed to alterations of the sole histidine and/or one or more lysine residues of the binding protein. We conclude that the glutamine binding protein possesses at least two largely nonoverlapping functional domains, one responsible for glutamine binding and the other for the interaction with the other components of the glutamine transport system.     

MHC-like molecules in some nonmammalian vertebrates can be detected by some cross-reactive xenoantisera

Rabbit antisera raised to human and chicken MHC molecules were used to immunoprecipitate cross-reactive molecules from biosynthetically and cell surface-labeled spleen and/or blood cells of representative vertebrate species. Five major points emerged: 1) There were many nonspecific cross-reactions using these techniques, so various criteria were developed to distinguish these from true MHC-like molecules. 2) Only very small subpopulations of immunogen-specific antibodies cross-reacted with MHC-like molecules in other nonmammalian species. These subpopulations were different for each species and even within a species, sometimes being so limited as to behave like alloantisera. This led to a very scattered pattern of true cross-reactions that sometimes failed to reflect the properties of the bulk antibody population. 3) Antisera containing antibodies to class II beta- and class I alpha-chains cross-reacted better and more widely than those to B-G, class II alpha and, in general, beta 2-microglobulin. 4) Some cross-reactive antibodies were clearly directed to epitopes on the surface of the mature heterodimers, but many seemed to recognize nonlinear cryptic determinants, presumably in the contact regions between the chains. These latter antibodies recognized biosynthetic intermediates and also a variety of unusual cell surface MHC-like molecules present in reptile and amphibian, but absent in the mammal and chicken cells tested. These included E homodimers whose relationship to chicken B-G molecules is unknown. 5) MHC-like molecules were identified in a bird, three reptiles, and two amphibians, but no molecules with the expected properties were found with these reagents in any of the fish tested.     

The fate of spargana inoculated into the cat brain and sequential changes of anti-sparganum IgG antibody levels in the cerebrospinal fluid

To establish an animal model of intracranial sparganosis, the fate and behavior of the experimentally inoculated spargana were observed. A total of 102 scolices of spargana were injected into 22 cat brains, and the cats were sacrificed at 2 weeks, 1 month, 3 months and 6 months after the inoculation. Neurosparganosis was established in 77% of the cats. Of 43 recovered worms, 19 (44%) were located in the subdural or subarachnoid space, 16 (37%) in the brain parenchyme, and 2 (5%) in the lateral ventricle. One was detected at the diploic space of the skull and 5 were outside the cranial cavity. All but one were alive, and had grown tails. They were distributed in the brain parenchyme randomly. There was no place which they could not invade. No adult was found in the intestine. Cerebrospinal fluid (CSF) was collected before inoculation, 1 week, 2 weeks, 1 month, 3 months and 6 months after inoculation. The level of anti-sparganum IgG antibody in CSF measured by ELISA began to increase above the criteria of positivity 1 month after inoculation. Three months after inoculation, the values markedly increased. The present findings reveal that intracranial inoculation of spargana into the brains of cats would be a good animal model of experimental neurosparganosis.     

The changes of histopathology and serum anti-sparganum IgG in experimental sparganosis of mice

The present study is intended to observe the chronologic changes of experimental sparganosis by histopathological observation and detection of circulating anti-sparganum IgG antibody using ELISA. Each of 25 mice was infected with five spargana, and they were examined after 1, 2, 4, 10 weeks or 6 months from infection. The followings are summarized results. 1. The plerocercoids were detected in the subcutaneous tissue of the trunk, neck or axilla, but a few often extended into the skeletal muscle. The recovery rates were 72% at the first week, 80% at the second week, 95% at the fourth week, 92% at the tenth week and 100% at the sixth month. The larvae grew slowly in both length and weight until 6 months. 2. Histopathologically, most of the larvae were observed alive in the soft tissue or skeletal muscle. Numerous eosinophils, neutrophils, lymphocytes and plasma cells were infiltrated focally around the worms by the second week, but they surrounded the worms to form a layer of inflammatory reaction after 4 weeks of infection. Also histiocytes and fibroblasts began to appear around the inflammatory cells at 4 weeks. After 10 weeks, the worms encircled by a thin fibrous layer were found. After 6 months, the worms were surrounded by either fibrous tissue or active inflammatory cells. The inflammation looked more severe in the tracks left by the worms, rather than around the worms. 3. The level of anti-sparganum IgG antibody in the serum showed an increase by the fourth week, and a rapid and continuous increase was observed thereafter by the tenth week after infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of prolonged high salt intake on atrial natriuretic factor's kinetics in rats

Plasma atrial natriuretic factor (ANF) paradoxically decreases after 5 weeks (but not after 3 weeks) of 8% NaCl intake in normotensive rats. As this phenomenon remains unaccounted for by changes in ANF production, we studied the disappearance of [125I]ANF(99-126) from the circulation as an alternative explanation of plasma ANF decline. Following 5 weeks (but not 3 weeks) of an 8% NaCl diet, plasma concentrations of [125I]ANF were significantly decreased and metabolic clearance rate and volume of distribution were increased compared to control rats fed a 0.8% NaCl diet. By studying [125I]ANF tissue uptake we noted significantly greater peptide uptake after 5 weeks (but not after 3 weeks) of high salt consumption in several tissues. We hypothesize that prolonged (at least 5 weeks) 8% NaCl ingestion increases the density and/or affinity of ANF binding sites. These changes may be responsible for the previously observed decline in plasma ANF concentrations after a prolonged high salt intake.     

旱地作物生态工程的设计

旱地作物生态工程是运用生态学和系统科学的原理和方法而设计和组建的旱地作物生产工艺体系。它把作物及其环境作为一个系统,统筹兼顾,相互协调,全面安排,综合利用。其最终目标是建立高效的,相对平衡的旱地作物生态系统。工程的最大特点在于它的整体性和综合性。它是作物先进生产技术的科学组装     

中华猕猴桃胚乳植株后代的观察

对438株定植的中华猕猴桃胚乳培.养的试管苗,经四年的田间观察,并进行连续二年结果分析。与对照的母株相比,胚乳植株在株形、叶片大小、果实形态及果实的主要营养成分含量上都有较大的变化。同时还发现,由同一块愈伤组织诱导的胚乳试管苗后代中也有雌、雄性别的分化。胚乳植株后代的多样性,可为中华猕猴桃的选种及品种繁育提供丰富的材料。     

一种“无血清”培养基对肿瘤细胞生长的支持

本文报告一种为适于杂交瘤细胞生长“无血清”培养基－适量的成牛血清低分子成分超滤液、１０ｍｇ／Ｌ转铁蛋白（Ｔ）、１０ｍｇ／Ｌ胰岛素（Ｉ）、２０μｍｏｌ／Ｌ乙醇胺（Ｅ）、４０ｎｍｏｌ／Ｌ硒酸钠（Ｓ）等诸补充成分替代胎牛血清加到基础液中－也完全适用于培养肿瘤细胞,且观察到与之相似的规律性结果,癌细胞在本“无血清”培养若的生长水平达到在含胎牛血清培养基中生长的水平。对于癌细胞的生长,ＬＭＷ－ＣＳ与Ｔ、Ｉ、