Behaviour of photosynthetic products associated with growth and grain production in the rice plant

Summary A study of the behaviour of the photosynthetic products assimilated at different growth stages was conducted in the field and in the greenhouse using C¹⁴ tracer.In general, the assimilated carbon is translocated to and accumulates in the growing organs. The carbon assimilated at the maximum tiller number stage is distributed mostly to the lower leaves. The carbon assimilated at the booting stage is distributed mostly to the spikelet, certain leaf sheaths and culms. The carbon accumulated in the form of carbohydrates in the leaf sheaths and the culm before flowering is retranslocated to the panicle after flowering. However, because of the consumption by respiration, the efficiency of this type of carbohydrate in grain production is not very high. The carbon assimilated after flowering accumulated mostly and efficiently in the brown rice.The release of the assimilated carbon as CO₂ is most intense immediately after assimilation. Thirty-five to 60 per cent of the assimilated carbon is consumed through respiration under the conditions of this experiment. As the carbon, which is in the form of sugars, rapidly changes to other forms, and also is consumed by respiration, the consumption declines rapidly. The retention percentage of assimilated carbon decreases as mutual shading increases.The large proportion of carbon released through respiration indicates the importance of studies on the significance of respiration in relation to growth.A portion of the thesis for the Master of Science degree submitted by Mr. Shen Lian to the Graduate School, University of the Philippines, College of Agriculture.     

Circular dichroism measurements of benzyl L-aspartate–nitrobenzyl L-aspartate copolymers and their use in detecting and characterizing preferred polymer conformations

We have examined the nature of the circular dichroism band at 330 mμ for a series of copolymers of β-p-nitrobenzyl L -aspartate with β-benzyl L -aspartate. The circular dichroism band arises from an electronic transition in the nitroaromatic group. In order to interpret the effect quantitatively, we employed a simplified statistical treatment and curve fitting for six copolymers. Both approaches gave consistent results, which indicates that the dichroism comes from pairwise interactions between two nitrobenzyl groups. We constructed a molecular model that meets the constraints and requirements of the analyses developed in this paper. In this model, it is proposed that the main chain forms a right-handed α-helix and that nitrobenzyl groups separated by four residues interact with each other.     

THE ACROSOME REACTION IN MYTILUS EDULIS : I. Fine Structure of the Intact Acrosome

The intact acrosome of the Mytilus edulis spermatozoon consists of a conical vesicle, the basal side of which is deeply invaginated so that the whole vesicle forms a sheath around a very slender axial rod, about 2.7 µ long, inserted in a tube passing through the nucleus. The annular base of the acrosomal vesical is filled with a homogeneous substance; the outer wall of the vesicle is lined with a somewhat irregular layer of a particulate substance interspersed with very fine tubular elements, and its lumen is nearly filled by a strand of material which extends from the inner tip of the invagination to the apex of the acrosome. The lumen of the invagination appears empty except for the rod and a delicate sleeve-like structure which surrounds it. The plasma membrane of the sperm cell lies in immediate contact with the acrosomal membrane over its whole outer surface. In its general organization, this molluscan acrosome shows a rather close homology with that of the annelid Hydroides.     

Production of the Milk Agent in Cultures of Mouse Mammary Carcinoma

Thin sections of tissue cultures grown from tumors of the RIII high-breast-cancer strain mice were studied in the electron microscope. These tissues contain an abundance of particles whose morphology is consistent with biophysical measurement of the milk agent. These particles, found only extracellularly in our cultures, are formed at the cell membrane. The process of formation, as reconstructed from sections, appears to include a thickening and protrusion of the cell membrane which then evolves gradually into a dense sphere and separates from the cell in much the same manner as does influenza virus. The contents of the newly formed body are later rearranged to form a nucleoid within a membranous sac.     

生物素标记寡核苷酸探针探测扩增的病理性突变珠蛋白基因

用末端转移酶催化生物素核苷酸底物(Biotin-ll-dUTP)共价连接在合成的寡核苷酸3’羟基末端,从而合成了两种寡核苷酸探针(β~T_(41-42)及β~A_(41-42))。用它们分别与克隆化扩增的正常和突变的β—珠蛋白基因片段杂变。结果表明该探针都具有与~(32)P探针相似的特异性,其杂交的灵敏度为2—3pg(特异序列)。进而将探测HbS基因的正常和异常两种寡核苷酸19聚体(β~A_6和β~S_6)用~(32)P和生物素分别标记;将HbS杂合子病人的白细胞DNA经聚合酶链反应(PCR)法扩增,并以含正常β—珠蛋白基因的DNA片段作对照,与两种探针分别进行斑点杂交。所得结果完全一致;Hbs杂合子DNA对正常和异常探针都显出杂交信号,而正常DNA只与β~A探针显杂交信号。     

三乙醇胺基强碱性聚苯乙烯树脂共价固定胰酶的研究

用多孔强碱型三乙醇胺基聚苯乙烯阴离子交换树脂做为载体,用CNBr与载体上的多羟基作用共价偶联了胰酶。红外光谱表明:其共价偶联反应机理与用CNBr活化多糖类载体并接酶的机理相类似。最适偶联条件研究表明:CNBr用量增多,酶蛋白载量增加。但比活下降。偶联pH为10时,固定化酶有适宜的载量和较高的比活。由于胰酶水解蛋白反应释放出H~+质子,这些质子在载体内积累,使微环境内H~+质子浓度增加,进而使得固定化胰酶的pH—活性曲线在pH9～11范围内未出现下降。在变温和60℃恒温下对固定化酶的热稳定性测试表明:固相酶的热稳定性比天然酶的热稳定性有所提高。     

Stereoselective high-performance liquid chromatographic assay for propranolol enantiomers in serum

A simple and sensitive stereoselective high-performance liquid chromatographic assay for the quantitation of propranolol enantiomers in serum is described. The method involves conversion of the propranolol enantiomers to diastereomeric urea derivatives by reaction with the chiral reagent (+)-phenylethylisocyanate, followed by chromatographic separation of the diastereomeric products. Conditions of the derivatization reaction were optimized to achieve rapid and quantitative yield with either of the enantiomers. Baseline resolution of the diastereomers was achieved on a reversed phase C₈ column with an isocratic mobile phase. Fluorescence detection afforded an absolute on-column detection limit of 100 pg. The assay has been applied to pharmacokinetic studies in humans and small laboratory animals.     

PUC衍生质粒的一个低拷贝数突变型

本文报道大肠杆菌的ColE1类似质粒的一个低拷贝数突变型。从载体质粒pUC4衍生的重组质粒pPGVT3在大肠杆菌宿主DF2145中是不稳定的,以pPGVT3转化DF2145时在4o℃培养得不到转化子。用诱发点突变的羟胺体外处理pPGVF3质粒DNA,得到一个稳定性提高了的突变质粒pPGVT3HA,突变的位置被确定在质粒的pUC部分,突变降低了pUC及其衍生质粒的拷贝数。文中对质粒的稳定性与拷贝数的关系作了讨论。     

X射线对根尖细胞分裂和分化的作用

用30—70GyX射线照射小麦幼苗(浸种后5天)后发现根毛区到根尖的距离缩短,根毛变密,根毛长度为对照的2—3倍。照射后2—3天就可看到该现象。根毛着生处到根尖的距离随剂量增加而减少,甚至根尖全为根毛所复盖,另外还看到有分叉的根毛。根尖纵切片表明根尖分生区随剂量增加而缩小,分生区后接着就出现输导组织。玉米和黄瓜也有类似现象。这现象说明根细胞的分裂过程对射线很敏感,而分化过程则相当耐辐射,细胞分裂停止后立即转向细胞分化过程。