Evolution of alpha 2-macroglobulin. The purification and characterization of a protein homologous with human alpha 2-macroglobulin from plaice (Pleuronectes platessa L.) plasma.

A papain-binding protein (PB-protein) was purified to homogeneity from the plasma of plaice (Pleuronectes platessa L.). PB-protein inhibited the activity of trypsin and pancreatic elastase (serine proteinases), thermolysin (a metalloproteinase) and papain (a cysteine proteinase). Presaturation of PB-protein with trypsin prevented the subsequent inhibition of thermolysin, and vice versa. Only catalytically active endopeptidases were bound by PB-protein. The catalytic activity of trypsin bound by PB-protein was inhibited by 95% against an insoluble protein substrate, but only by 38% against a low-molecular-weight synthetic substrate. The remaining activity of the bound trypsin was partially protected against further inhibition by soya-bean trypsin inhibitor. Trypsin bound by PB-protein showed a decrease of 67% in its reactivity with antibodies. The inhibitory activity of PB-protein was inactivated at pH 8.0 by methylamine (0.2M) or dithiothreitol (1 mM). The inhibition of proteinases by plaice PB-protein shows the distinctive characteristics of inhibition by human alpha 2-macroglobulin, and it is concluded that the plaice protein is a homologue of the human macroglobulin.     

温度对干旱、盐胁迫下两种黄芪属种子萌发和幼苗生长的影响

为探讨温度对干旱、盐胁迫下黄芪属种子萌发和幼苗生长特性的影响,以黄芪属蒙古黄芪和扁茎黄芪2种种子为研究对象,纯净水处理为对照组,NaCl、PEG处理为实验组,设置4个渗透势水平(0、-0.1、-0.3、-0.5 MPa),置于5种不同的温度(10、15、20、25、30 ℃)下,每日观察并记录两种种子萌发和幼苗生长情况。结果表明：旱盐胁迫下蒙古黄芪和扁茎黄芪种子萌发最适宜的温度分别为25和20 ℃左右;蒙古黄芪耐高温不耐低温,而扁茎黄芪恰恰相反;但25和20 ℃均适宜两种幼苗生长,包括胚根、胚轴和子叶的生长。蒙古黄芪各处理组(除未发芽的种子)的平均发芽时间都比扁茎黄芪长;NaCl胁迫程度的增加使得两种种子的最终发芽率降低,但蒙古黄芪的耐盐性高于扁茎黄芪;随着PEG胁迫程度的增加,二者的发芽均受到抑制,甚至会出现完全不萌发,但扁茎黄芪的耐旱性高于蒙古黄芪;在相同的渗透势时,尤其是-0.5 MPa,PEG比NaCl对两种种子的影响大;交互胁迫作用下,随着渗透势的增加两种幼苗的鲜重、干重以及胚根、胚轴、子叶的长和宽变化较大;利用Design Expert软件预测发现：温度25 ℃、NaCl渗透势为-0.1 MPa,温度24 ℃、PEG渗透势为-0.04 MPa的处理是蒙古黄芪种子萌发和幼苗生长达到最优化的组合;而扁茎黄芪最优化的组合则为23 ℃下NaCl渗透势为-0.07 MPa的处理,20 ℃下PEG渗透势为-0.13 MPa的处理。     

Influence of Protein Synthesis on NO(3) Reduction, NH(4) Accumulation, and Amide Synthesis in Suspension Cultures of Paul's Scarlet Rose

Changes in the concentrations of NH₄⁺ and amides during the growth of suspension cultures of rose (Rosa cv. Paul's Scarlet) cells were examined. When cells were grown in medium possessing only NO₃⁻ as a nitrogen source, the concentrations of NH₄⁺ and amides increased to 4.0 × 10⁻¹ and 5.9 micromoles per gram fresh weight, respectively. The amounts of both constituents declined during the later stages of growth. When a trace amount of NH₄⁺ was added to the NO₃⁻ base starting medium, the concentration of NH₄⁺ in the cells was increased to 7.0 × 10⁻¹ micromoles per gram fresh weight.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Schistosoma mansoni: Electrophoretic characterization of strains selected for different levels of infectivity to snails

Individual adult Schistosoma mansoni from strains selected for high or low infectivity to specific strains of the snail intermediate host, Biomphalaria glabrata, were subjected to enzyme electrophoresis on starch gels. Fourteen enzyme systems were analyzed in an attempt to find electrophoretic markers associated with genes for infectivity to snails. The S. mansoni strains were selected from different isolates from Puerto Rico in several strains of B. glabrata. Of an estimated 18 loci, 3 were polymorphic and the remainder monomorphic. For 1 of the 3 polymorphic enzyme loci, lactate dehydrogenase (Ldh, EC 1.1.1.27), phenotype frequencies were correlated with infectivity to snails. In schistosome strains of low infectivity, frequencies of the Ldh-N phenotype ranged between 0.56 and 0.69, while in strains of high infectivity, Ldh-N frequencies were typically 0.91 to 1.00. Whether the correlation is accidental or due to some form of association, such as chromosomal linkage, between the locus responsible for variation in lactate dehydrogenase and a gene for infectivity to snails remains to be determined.     

Dynamic light scattering from collagen solutions. II. Photon correlation study of the depolarized light.

The depolarized forward-scattered light from solutions of rat tail collagen has been studied by photon correlation spectroscopy. The measured autocorrelation function is seen to decay on two widely different time scales. The decay time for the fast component is consistent with the rotational diffusion of rodlike collagen monomers. The slowly decaying autocorrelation component is attributed to large nonspecific aggregates of collagen. A substantial fraction of the collagen is in this aggregated form. Extrapolation of the faster decay times to zero concentration yields a value of θ = 1082 ± 30 sec^?1 for the rotational diffusion coefficient of the collagen monomer.     

P blood group regulation of glycosphingolipid levels in human erythrocytes.

The neutral glycosphingolipid content of normal human erythrocytes was analyzed by a new method which utilizes high performance liquid chromatography. This rapid and accurate technique permits the quantitation of each of the major neutral glycolipids from individual blood samples. A correlation between the P blood group and the relative quantities of neutral glycosphingolipids is demonstrated. Erythrocytes from P1 individuals are shown to contain more globotriaosylceramide and less lactosylceramide than do erythrocytes from P2 individuals. The results of these experiments suggest the existence of a new phenotype in the P blood group system, and have further implications regarding the biosynthesis of the P blood group glycosphingolipids.     

Estimated Drainage of Carbon from the Tricarboxylic Acid Cycle for Protein Synthesis in Suspension Cultures of Paul's Scarlet Rose Cells

The amount of carbon (μmoles of carbon atoms) drained from the tricarboxylic acid cycle for protein synthesis was compared with μmoles of CO₂ released from the cycle at 2-day intervals during the growth of suspension cultures of Paul's Scarlet rose. We concluded that during the period of most rapid protein synthesis (day 0-4) one-sixth as much carbon was drained from the tricarboxylic acid cycle for protein synthesis as was released as CO₂. By day 8, one-thirtieth of the amount of carbon released as CO₂ was incorporated into protein. Net protein synthesis stopped on day 8, but the evolution of CO₂/culture continued at its maximum rate until day 10.