三尖杉属受精作用的研究

三尖杉属的精原细胞有一类似银杏生毛体的星状体结构,它分裂产生的2个精子,在大小与形态上都基本相同,而且在精子细胞质中具有拟核仁颗粒存在。上述结构是三尖杉属的重要特点之一。本属植物的成熟卵细胞特别长,细胞质中有丰富的拟核仁结构,卵核下方具2—3团浓稠的细胞质团,这些结构很像穗花杉的卵细胞。三尖杉属的受精作用,属于有丝分裂后类型,这种类型只在松科和三尖杉科中发现。受精后,卵细胞发生强烈的极性分化,上部细胞质变成高度液泡化;相反,下部细胞质则聚集大量蛋白泡和拟核仁颗粒。     

高等植物花粉母细胞内肌动蛋白的聚丙烯酰胺凝胶电泳分析

采用聚丙烯酰胺凝胶电泳技术分析了黑麦、蚕豆和百合花粉母细胞内肌动蛋白的存在与动态,结果表明高等植物的花粉母细胞在细胞融合期内的确存在一定量的肌动蛋白,并且,这种蛋白在早偶线期时出现,到四分体时期后消失。文章讨论了肌动蛋白的存在及其与细胞融合现象的联系。     

扁苞蕗蕨和长柄蕗蕨的细胞分类学研究

本文首次报道了四川产扁苞蕗蕨和长柄蕗蕨的染色体及孢子发生情况。它们的染色体数目分别为 n=26和n=28,都是有性生殖的二倍体。染色体基数26在蕗蕨属的发现进一步证明了它和膜蕨属、厚壁蕨属的密切亲缘关系。这两种蕗蕨的孢子囊通常形成128个孢子及少数256个孢子的情况被描述,它们应该被看成是有性生殖真蕨,尤其是在膜蕨科和薄囊真蕨中的其他较原始的类群中的正常的孢子发生路线。     

Effect of paclobutrazol on accumulation of organic acids and total phenols in apple wood

Apple trees (Malus domestica Borkh Spartan grafted on MM 106 rootstock) planted in 1976 in an orchard at Beltsville, Maryland, were treated with paclobutrazol (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-pentan-3-ol) using a foliage spray in 1982 and by trunk banding in 1983. Paclobutrazol did not inhibit shoot growth in 1983; however, shoot growth was significantly retarded in 1984. Increases in organic acids, including succinic, malic, citric, and quinic, and also in total phenols, occurred in wood produced in 1983 on paclobutrazol-treated trees when growth was not inhibited and in wood produced in 1984 when growth was inhibited. The organic acid content of both paclobutrazol-treated and untreated wood tended to decrease from the winter dormant period through growth resumption in the spring. However, the content of total phenols remained nearly the same throughout this sampling period.Mention of a trademark, proprietary product or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Metabolic changes associated with bud break induced by thidiazuron

Bud break in apple (Golden Delicious,Malus domestica Borkh) was induced by thidiazuron (N-phenyl-N-1,2,3-thidiazol-5-ylurea). In control and thidiazuron-treated shoots, higher amounts of soluble carbohydrates (sorbitol, fructose, glucose, sucrose) and galacturonic acid were found in the phloem, but higher amounts of starch and cell wall polysaccharides, including cellulose and xylose, were found in the xylem. A decrease in soluble carbohydrates and starch in both phloem and xylem was associated with induction of bud break by thidiazuron. However, little change in cell wall polysaccharides was found. Total carbohydrates were higher in the upper than in the lower portion of shoots. The breaking of dormancy by thidiazuron was also associated with an increase in organic acid content and respiration in buds. KCN inhibited bud respiration during all stages of development. Organic acid content was inversely related to carbohydrate content in developing buds. Axes contained more carbohydrates and organic acids than did scales.     

Sequence dependent conformations of oligomeric DNA's in aqueous solutions and in crystals

In order to determine the sequence dependence of the conformation of deoxynucleotides, Raman spectra have been obtained for the following oligodeoxynucleotides in aqueous salt solutions and in crystals: d(CpG)(I), d(TGCGCGCA)(II), d(CACGCGTG)(III), d(CGTGCACG)(IV), d(CGCATGCG)(V), d(ACGCGCGT)(VI), d(CGCGTACGCG)(VII), d(CGCACGTGCG)(VIII) and d(CGTGCGCACG)(IX), d(GCTATAGC) (X), d(GCATATGC) (XI), d(GGTATACC) (XII) and d(GGATATCC) (XIII). The normal B type conformation is observed for all the oligomer DNA's at low salt (0.1-1.0 M NaCl) concentration in the temperature range of 0-25 degrees C. It was considered possible that all of the first nine oligomers could go into the Z form in aqueous high salt (5.0-6.0 M NaCl) solutions, and under these conditions the last four were considered candidates to go into the A form. The B-type conformation was found to exist in high salt solutions for (I), (IV), (V), (VI), (X), (XI) and (XIII); the Z or partial Z conformation appears in high salt solution for the oligomers, (II), (III), (VII), (VIII) and (IX); an A or partial A conformation appears in high salt solution for (XII). In the crystalline state, (IV), (VIII), (X), and (XI) stay in the B-form and all of the other oligomers adopt the complete Z-form except for (XII) which crystallizes in the A form. In both the crystal and in aqueous solutions, the identification of the conformation genus was made by means of Raman spectroscopy. In the crystal of (I), grown at pH7.0, guanosine is found to be in C3'-endo/syn conformation and cytidine in C2'-endo/anti, which may be taken as the ideal building block of the typical Z conformation. At pH4, (I) crystallizes in a conformation similar to the B genus. A study of the thermally induced B to Z transition has been carried out for (II) and (III). Based on the analysis of Raman spectra of the alternating pyrimidine-purine oligomers which might be expected to go into the Z form, the tendency for these oligonucleotides to adopt the Z form can be ranked as: d(CGCGCGCG) greater than (II) greater than (III) greater than (V) approximately (VI) greater than (IV) for octamers and (VII) greater than (VIII) greater than (IX) for the decamers. Similarly, those oligomers which might have a tendency to go into the A form could be ranked as (XII) greater than (XIII) approximately (X) greater than (XI). These data should provide help in formulating rules for predicting the sequence dependence of the B to A and B to Z transitions. Some possible rules are explored, but precautions should be taken.     

Plasmid DNA adsorbed to pH-sensitive liposomes efficiently transforms the target cells

We have previously reported that plasmid DNA entrapped in the pH-sensitive immunoliposomes effectively transforms the target cells (Proc. Natl. Acad. Sci. USA, in press). In the present study, we demonstrate that DNA adsorbed on the same liposome also transforms the target cells. The transformation activity is antibody dependent, as liposomes containing no targeting antibody had reduced activity. The activity could be significantly inhibited by excess non-specific DNA (salmon sperm). Since some DNA are likely adsorbed to the liposomes during the entrapment process, the activity of the entrapped DNA is partially accounted for by the adsorbed DNA. The possibility of developing a simple DNA-mediated transfection protocol using liposome adsorbed DNA is discussed.     

Phosphorylation heterogeneity of tryptic phosphopeptides of chicken riboflavin-binding protein

The tryptic phosphopeptide of hen egg white riboflavin-binding protein has been found to exist as a mixture of peptides which differ only with respect to the number of covalently bound phosphoryl groups. Anion-exchange chromatography was used to separate homologues of the tryptic phosphopeptide of egg white riboflavin-binding protein. Four peptide peaks were obtained and analyzed using plasma desorption mass spectrometry. Molecular ions obtained agree closely with calculated molecular weight values for phosphopeptides with 8, 7 and 5 phosphoryl groups. Amino acid analyses showed that the octa- and hepta-phosphorylated peptides were pure and had the same amino acid compositions.     

Infrared and Raman studies show that poly(dA).poly(dT) and d(AAAAATTTTT)2 exhibit a heteronomous conformation in films at 75% relative humidity and a B-type conformation at high humidities and in solution

The decadeoxynucleotide d(AAAAATTTTT)2 in duplex form and the double-helical polynucleotide poly(dA).poly(dT) have been studied by Raman and infrared (IR) spectroscopy under a variety of environmental conditions. The IR spectra have been taken of cast films and compared to the IR spectra of the alternating poly(dA-dT), which shows clear B-genus and A-genus vibrational spectra under conditions of high (greater than 92%) and low (75%) relative humidity (RH). From the IR data, it is shown that d-(AAAAATTTTT)2 and poly(dA).poly(dT) adopt a B-genus conformation in films with high water content. When the relative humidity of the film is decreased, the IR spectra reflect a gradual evolution of the geometry of both d(AAAAATTTTT)2 and poly(dA).poly(dT) into a form intermediate between the B genus and A genus, but the IR spectrum of a pure A genus has not been obtained. In these DNAs at 75% RH, the IR bands of adenosine have the same frequencies as those found in poly(dA-dT) at 75% RH where the local furanose conformation is C3' endo/anti, but the thymidine frequencies do not resemble those of poly(dA-dT) at 75% RH but rather those of poly(dA-dT) at high humidities. It is concluded that both poly(dA).poly(dT) and d(AAAAATTTTT)2 adopt a fully heteronomous duplex geometry in cast films at low humidity. For studies in aqueous solution the Raman effect was employed. As a model for the heteronomous conformation in solution, the duplex poly(rA).poly(dT) was used.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interactions of troponin subunits: free energy of binary and ternary complexes

We have determined the free energy of formation of the binary complexes formed between skeletal troponin C and troponin T (TnC.TnT) and between troponin T and troponin I (TnT.TnI). This was accomplished by using TnC fluorescently modified at Cys-98 with N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)ethylenediamine for the first complex and TnI labeled at Cys-133 with the same probe for the other complex. The free energy of the ternary complex formed between troponin C and the binary complex TnT.TnI [TnC.(TnT.TnI)] was also measured by monitoring the emission of 5-(iodoacetamido)eosin attached to Cys-133 of the troponin I in TnT.TnI. The free energies were -9.0 kcal.mol-1 for TnC.TnT, -9.2 kcal.mol-1 for TnT.TnI, and -8.7 kcal.mol-1 for TnC.(TnT.TnI). In the presence of Mg2+ the free energies of TnC.TnT and TnC.(TnT.TnI) were -10.3 and -10.9 kcal.mol-1, respectively; in the presence of Ca2+ the corresponding free energies were -10.6 and -13.5 kcal.mol-1. Mg2+ and Ca2+ had negligible effect on the free energy of TnT.TnI. From these results the free energies of the formation of troponin from the three subunits were found to be -16.8 kcal.mol-1, -18.9 kcal.mol-1, and -21.6 kcal.mol-1 in the presence of EGTA, Mg2+, and Ca2+, respectively. Most of the free energy decrease caused by Ca2+ binding to the Ca2+-specific sites is derived from stabilization of the TnI-TnC linkage.(ABSTRACT TRUNCATED AT 250 WORDS)