烟草愈伤组织器官发生过程中外源激素的作用

近年来,利用愈伤组织系统在与器官发生有关的形态学、生理学和生物化学研究方面已经取得了一些进展(Thorpe 1980,刘涤 1983)。对烟草愈伤组织系统的研究明确了外源激素对器官发生类型的调节作用(Skoog 1971,Engelke等1973,刘涤等1980)。但是,这些研究仅考虑到外源激素的作用,而对器官发生过程中的其它变化并不了解。最近,Kamada和Harada(1981)比较了胡萝卜体细胞胚发育过程中内源IAA和ABA含量的变化,Noma等(1982)证实形成胚的和不形成胚的细胞间GA_3含     

Physiological profile of world-class high-altitude climbers

The functional characteristics of six world-class high-altitude mountaineers were assessed 2-12 mo after the last high-altitude climb. Each climber on one or several occasions had reached altitudes of 8,500 m or above without supplementary O2. Static and dynamic lung volumes and right and left echocardiographic measurements were found to be within normal limits of sedentary controls (SC). Muscle fiber distribution was 70% type I, 22% type IIa, and 7% type IIb. Mean muscle fiber cross-sectional area was significantly smaller than that of SC (-15%) and of long-distance runners (LDR, -51%). The number of capillaries per unit cross-sectional area was significantly greater than that of SC (+ 40%). Total mitochondrial volume was not significantly different from that of SC, but its subsarcolemmal component was equal to that of LDR. Average maximal O2 consumption was 60 +/- 6 ml X kg-1 X min-1, which is between the values of SC and LDR. Average maximal anaerobic power was 28 +/- 2.5 W X kg-1, which is equal to that of SC and 40% lower that that of competitive high jumpers. All subjects were characterized by resting hyperventilation both in normoxia and in moderate (inspired O2 partial pressure = 77 Torr) hypoxia resulting in higher oxyhemoglobin saturation levels in hypoxia. The ventilatory response to four tidal volumes of pure O2 was similar to that of SC. It is concluded that elite high-altitude climbers do not have physiological adaptations to high altitude that justify their unique performance.     

Encapsulation of hemoglobin in phospholipid liposomes: characterization and stability

Hemoglobin is encapsulated in liposomes of different lipid composition. The resulting dispersion consists primarily of multilamellar liposomes (hemosomes) of a wide particle size distribution (diameter ranging mainly between 0.1 and 1 micron). The encapsulation efficiency is significantly larger with liposomes containing negatively charged lipids as compared to liposomes made of phosphatidylcholine. The integrity of the phospholipid bilayer is maintained in the presence of hemoglobin. The reaction rate of CO binding to encapsulated hemoglobin is reduced compared to that of free hemoglobin, but it is still greater than that observed in red blood cells. Hemoglobin encapsulated in liposomes made from negatively charged phospholipids is less stable than hemoglobin entrapped in isoelectric phosphatidylcholine. The instability of hemoglobin is due to the protein interacting with the negatively charged lipid bilayer. This interaction leads in turn to hemoglobin denaturation, possibly involving the dissociation of the heme group from the heme-globin complex. The nature of the negatively charged phospholipid is important in promoting the interaction with hemoglobin, the effect being in the order phosphatidic acid greater than phosphatidylinositol congruent to phosphatidylglycerol greater than phosphatidylserine. The presence of equimolar amounts of cholesterol in the phospholipid bilayer has a stabilizing effect on hemoglobin. This effect is pronounced with saturated phospholipids, but it is also observed, though to a lesser extent, with unsaturated ones, indicating that the bilayer fluidity has a modulating effect. The presence of cholesterol possibly interferes with secondary interactions following the binding of hemoglobin to the negatively charged lipid bilayer.     

Kinetics of oxygen and carbon monoxide binding to liver fluke (Dicrocoelium dendriticum) hemoglobin. An extreme case?

The kinetics of oxygen and carbon monoxide binding to the monomeric liver fluke (Dicrocoelium dendriticum) hemoglobin have been studied. The ligand association rates are approximately 1 X 10(8) and approximately 3 X 10(8) M-1 s-1, respectively, for CO and O2 and show no pH dependence. On the contrary the ligand dissociation rates decrease by lowering the pH below 7, the pK of the transition being around 5.5. These findings, together with spectroscopic properties of the protein, are discussed in relation to the fact that, in this hemoglobin, the distal histidine is replaced by a glycine.     

Further evidence for the presence of specific binding sites for prolactin in the rabbit brain. Preferential distribution in the hypothalamus and substantia nigra

In the present research we have extended our work on the presence of binding sites for prolactin in the rabbit brain focusing our attention on the brain areas with high dopamine cell bodies density. Among these areas the hypothalamus showed the highest specific binding of labeled ovine prolactin (oPRL). Clearly detectible specific binding was observed also in substantia nigra, whereas in other brain regions the specific binding was very small, except for the striatum where a low but not negligible binding was found in female rabbits. The binding of 125I-oPRL showed a hormonal specificity and Scatchard analysis of the binding showed no clear difference in dissociation constant (Kd) between hypothalamus, nigra and striatum.     

Dual action of respiratory inhibitors: inhibition of germination and prevention of dormancy induction in lettuce seeds

`Grand Rapids' lettuce Lactuca sativa L. seeds germinate readily at 15°C but poorly at 25°C in darkness. When held in dark at 25°C for an extended period, the ungerminated seeds become dormant as shown by their inability to germinate or transfer to 15°C in darkness. Induction of dormancy at 25°C was prevented by exposure to CN<sup>−</sup>, azide, salicylhydroxamic acid (SHAM), dinitrophenol, and pure N<sub>2</sub> as determined by subsequent germination at 15°C on removal of inhibitors. The effectiveness of inhibitors to break dormancy declined as dormancy intensified. At relatively low levels, CN<sup>−</sup>, SHAM, and azide promoted dark germination at 25°C while at high levels they were inhibitory. Uptake of O<sub>2</sub> by seeds held at 25°C for 4 days in 1.0 millimolar KCN was inhibited by 67% but was promoted 61% when KCN was removed. Correspondingly greater inhibition (79%) and promotion (148%) occurred when 1.0 millimolar SHAM was added to KCN solution. When applied alone, SHAM had little effect on O<sub>2</sub> uptake. These data indicate that Cyt pathway of respiration plays a dominant role in the control of both dormancy induction and germination of lettuce seeds, and `alternative pathway' is effectively engaged in presence of CN⁻. The channeling of respiratory energy use for processes governing germination or dormancy is subject to control by physical and chemical factors.

A scheme is proposed that illustrates compensatory use of energy for processes controlling dormancy induction and germination. A block of germination, e.g. by low water potential polyethylene glycol solution or a supraoptimal temperature spares energy to be utilized for dormancy induction while a block of dormancy induction by low levels of CN⁻ (similar to GA and light effects) drives germination. Blocking both processes by inhibitors (e.g. CN⁻, CN⁻ + SHAM) presumably leads to accumulation of `reducing power' with consequent improvement in O₂ uptake and oxidation rates of processes controlling germination or dormancy induction upon removal of the inhibitors.

     

Structural differences in the cell binding region of human fibronectin molecules isolated from cultured normal and tumor-derived human cells

Fibronectins isolated from human plasma (pFN) and from the conditioned media of normal (N-cFN) and tumor (T-cFN) human cells were compared by cathepsin D digestion followed by immunostaining of released fragments with the monoclonal antibody 3E3, specific for the cell binding site. Two different staining patterns were obtained, one specific for pFN and N-cFN, the second common to fibronectins from the 3 different kinds of tumors studied. This indicates structural differences between N-cFN and T-cFN in the cell binding region of the fibronectin molecule.     

辣椒四个品种的核型研究

本文对我国栽培辣椒Capsicum annuum L.的四个品种即汉川椒、华椒一号、牛角椒和二金条进行了核型分析,其染色体数目均为2n=2x=24,核型公式均为2n=24=20m+2sm+2st,但汉川椒和华椒一号具一对随体,牛角椒和二金条具两对随体。本文还对它们的进化关系进行了讨论。     

番茄五个品种的核型研究（摘要）

本文研究了番茄五个不同品种(武昌大红、加拿大、佛特、荷兰五号、青北早)的核型。1.番茄的核型公式如下: (1) 武昌大红。2n=24=2M+8m+12sm+2st (2) 加拿大。2n=24=4M+8m+12sm (3) 佛特。2n=24=2M+8m+10sm+4st (4) 荷兰五号2n=24=2M+14m+8sm (5) 青北早2n=24=4M+8m+12sm 2、五个品种中都具有一对随体染色体,但位于那一对染色体上也有相同和相异。“武昌大红”与“佛特”的随体在第9对上。“加拿大”在第7对上。“荷兰五号”及“青北早”位于第4对染色体上,并发现“武昌大红”、“加拿大”品种的随体,在同一品种也出现随体大小的差异。3、在各个品种中,染色体的全长、相对长度、臂比都存在着一些差异。4、对于番茄染色体的随体的大小及其在染色体对数的位置,染色体的形态结构,核形与番茄起源的关系进行了初步讨论。