A model for water transport in the stele of plant roots

Summary The mechanism of water movement across roots is, as yet, not well understood. Some workable black box theories have already been proposed. They, however, assumed unrealistic cell membranes with low values of , or were based on a poor anatomical knowledge of roots. The role of root stele in solute and water transport seems to be especially uncertain. An attempted explanation of the nature of root exudation and root pressure by applying the apoplast canal theory (Katou andFurumoto 1986 a, b) to transport in the root stele is given. The canal equations are solved for boundary conditions based on anatomical and physiological knowledge of the root stele. It is found that the symplast cell membrane, cell wall and net solute transport into the wall apoplast are the essential constituents of the canal system. Numerical analysis shows that the canal system enables the coupled transport of solutes and water into a xylem vessel, and the development of root pressure beyond the level predicted by the osmotic potential difference between the ambient medium and the exudate. Observations on root exudation and root pressure previously reported seem to be explained quite well. It is concluded that the movement of water in the root stele although apparently active is essentially osmotic.Abbreviations J _v ^ex volume exudation per root surface - J₀ non-osmotic exudation - L^r overall radial hydraulic conductivity of an excised root - reflection coefficient - C_s difference in the osmotic concentration between the bathing medium and the exudate - R gas constant - T absolute temperature - C_K molar concentration of K⁺ - C_Cl molar concentration of Cl^– - C_j molar concentration of ion species j - P_j membrane permeability of ion j - z_j valence of ion j - F Faraday constant - V_ix intracellular electric potential with reference to the canal     

脑室注射P物质对大鼠血压、心率及交感传出活动的影响

给乌拉坦麻醉六鼠侧脑室注射P物质(SP)10μg,引起动脉血压、心率和内脏交感神经放电增加。同样剂量的SP静脉注射后却引起血压降低。阿托品预处理不影响SP的开心率作用。预先脑室注射0.25,4,64μg阿片受体拮抗剂纳洛酮,对SP的升压效应有剂量依赖式对抗作用。以上说明脑室注射SP 引起的血压升高是交感神经活动增强,导致心率加快及外周血管紧张性增加的结果,并提示SP的中枢升压效应可能与脑内释放内源性阿片样物质有关。     

Radioactive labeling techniques for the identification of G antigen in the human Rh blood group system

The G antigen is one of the erythrocyte membrane Rh antigens. The amount of Rh antigen present on the red blood cell is about 10(-15) g and radioactive labeling of membrane proteins is a useful method for its identification and characterization. In this paper, we compare 4 labeling techniques. Using a human monoclonal anti-Rh(G) antibody and an immunofixation technique, we located the G antigen on a polypeptide of an average molecular weight of 28,000 Da.     

大鼠脑室注射P物质引起的血压升高与脑啡肽和β-内啡肽有关

给乌拉坦麻醉大鼠侧脑室注射P物质(SP)10μg 引起的升压效应,可被脑室注射纳洺酮15μg 部分阻断。将抗β-内啡肽抗血清、抗甲啡肽抗血清及抗亮啡肽抗血清各10μl 分别注入侧脑室预处理60min 后,再注入 SP,其升压效应明显减弱;而抗强啡肽抗血清则对其无影响。上述结果提示:大鼠脑室注射 SP 引起的升压效应,可能是通过释放β-内啡肽和脑啡肽实现的。     

Water storage and osmotic pressure influences on the water relations of a dicotyledonous desert succulent

Abstract Water storage and nocturnal increases in osmotic pressure affect the water relations of the desert succulent Ferocactus acanthodes, which was studied using an electrical circuit analog based on the anatomy and morphology of a representative individual. Transpiration rates and osmotic pressures over a 24-h period were used as input variables. The model predicted water potential, turgor pressure and water flow for various tissues. Plant capacitances, storage resistances and nocturnal increases in osmotic pressure were varied to determine their role in the water relations of this dicotyledonous succulent. Water coming from storage tissues contributed about one-third of the water transpired at night: the majority of this water came from the nonphotosynthetic, water storage parenchyma of the stem. Time lags of 4 h were predicted between maximum transpiration and maximum water uptake from the soil. Varying the capacitance of the plant caused proportional changes in osmotically driven water movement but changes in storage resistance had only minor effects. Turgor pressure in the chlorenchyma depended on osmotic pressure, but was fairly insensitive to doubling or halving of the capacitance or storage resistance of the plant. Water uptake from the soil was only slightly affected by osmotic pressure changes in the chlorenchyma. For this stem succulent, the movement of water from the chlorenchyma to the xylem and the internal redistribution of water among stem tissues were dominated by nocturnal changes in chlorenchyma osmotic pressure, not by transpiration.     

Effects of tin and lead on organ levels of essential minerals in rabbits

The effect of tin and lead on levels of essential metals (Zn, Cu, Ca, Fe) in rabbit tissues was compared in relation to the route of administration. Animals received intraperitoneally, or per os, SnCl2 (2 mg Sn/kg) or Pb(CH3COO)2 (3.5 mg Pb/kg) every day for 5 d or for 1 mo. Copper, zinc, iron, and calcium were determined by AAS in the liver, kidneys, spleen, brain, bone marrow, and blood; lead and tin concentration were measured in the blood of animals. Tin and lead administered per os caused either no changes or the decreased concentration of endogenous metals in several tissues. The other route of administration (ip) of both metals generally contributed to the increased storage of essential elements. Blood tin levels of tin treated animals were only about less than or equal to 1/10 of blood lead concentrations of rabbits exposed to lead.     

Identification of thetrans-stilbene oxide-active glutathione transferase in human mononuclear leukocytes and in liver as GST1

A glutathione transferase from human mononuclear leukocytes with a high activity towardtrans-stilbene oxide (GT-tSBO) has been studied in liver and blood from fetus and adults and in blood from neonates. Using starch gel electrophoresis, different phenotypes of GST1 have been determined, GST1 0, GST1 1, and GST1 2. As judged from activity measurements and the fact that only those individuals who express the null allele of GST1, the GST1 0, which has a low activity towardtrans-stilbene oxide, it is concluded that the hepatic transferase GST1 is identical to GT-tSBO, as well as to hepatic transferase μ. In addition, it has been shown that the different genotypes of GST1 1 (GST1 1-1, GST1 1-0) and GST1 2 (GST1 2-2, GST1 2-0) can be separated by measuring the GT-tSBO activity in whole blood from the same individual. It is also demonstrated that GT-tSBO activity is much lower in fetal liver, approximately 10 times, compared with adult liver, while this activity seems to be unchanged in the blood from fetus and adults, as well as in neonates.     

Biological activities caused by far-infrared radiation

Contrary to previous presumption, accumulated evidence indicates that far-infrared rays are biologically active. A small ceramic disk that emist far-infrared rays (4–16 m) has commonly been applied to a local spot or a whole part of the body for exposure. Pioneering attempts to experimentally analyze an effect of acute and chronic radiation of far-infrared rays on living organisms have detected a growth-promoting effect in growing rats, a sleep-modulatory effect in freely behaving rats and an insomiac patient, and a blood circulation-enhancing effect in human skin. Question-paires to 542 users of far-infrared radiator disks embedded in bedelothes revealed that the majority of the users subjectively evaluated an improvement of their health. These effects on living organisms appear to be non-specifically triggered by an exposure to far-infrared rays, which eventually induce an increase in temperature of the body tissues or, more basically, an elevated motility of body fluids due to decrease in size of water clusters.     

Associations between blood groups, blood protein polymorphisms and breeding values for production traits in Swedish Red and White Dairy bulls

The relationships of nine blood group systems and two blood protein polymorphisms with breeding values for several production traits were examined in dairy cattle of the Swedish Red and White (SRB) breed. The material consisted of 2212 bulls; the bulls were performance tested for growth rate and their breeding values for milk yield, fat and protein content in milk were estimated from progeny tests. The direct effect of marker alleles or marker phenotypes was analysed in a multiple regression model. Several significant associations were found; many supported earlier findings. However, the contribution of the markers to the total variation of the breeding values was very small. Linkage between marker loci and production loci was studied in offspring from heterozygous sires by estimating the interactions between sire and marker alle using a model eliminating the direct effects of sire and marker alle. There were strong indications of linkage between some marker loci (e.g. B, J and Am-1 loci) and loci with large effects on production traits.     

Genetic variation and distances of five Italian native sheep breeds

Genetic distances among five of the most important Italian native sheep breeds were estimated by using gene frequencies of four blood group and seven blood protein loci and by three different computing methods. The values of the three distance matrices were highly correlated. Genetic distances were found within the range values reported in the literature for local breeds. Shorter distances fitted the historical evidence of migrations.