日本落叶松人工林针叶中矿质营养元素的季节吸收特点及其相互关系

本文测定了日本落叶松人工林针叶中N、P、K、Ca、Mg、Cu、Zn、Fe、Mn9种矿质营养元素含量并研究了生长期内元素含量的变化规律。结果表明,在生长期内各元素含量随季节变化可用修正指数曲钱描述;探讨了落叶松针叶中常量元素与某些土壤化学因子之间的关系。土壤有机质仅与土壤全量氮、水解氮表现了显著的线性相关,与落叶松针叶中的氮没有直接的线性相关。土壤中钙镁的含量则表现出明显的对针叶中磷、钾的含量的制约关系。在日本落叶松针叶中的氮、磷、钾3个元素之间,氮、磷的比值与钾的含量有显著的线性负相关,而磷与钾之间则表现为显著的线性正相关关系。     

Cultured cell extracts support organelle movement on microtubules in vitro

Directed movements of organelles have been observed in a variety of cultured cells. To study the regulation and molecular basis of intracellular organelle motility, we have prepared extracts from cultured chick embryo fibroblasts (CEF cells) which support the movement of membraneous organelles along microtubules. The velocity, frequency and characteristics of organelle movements in vitro were similar to those within intact cells. Organelles and extract-coated anionic beads moved predominantly (80%) toward the minus ends of microtubules that had been regrown from centrosomes, corresponding to retrograde translocation. Similar microtubule-dependent organelle movements were observed in extracts prepared from other cultured cells (African green monkey kidney and 3T3 cells). Organelle motility was ATP and microtubule dependent. The frequency of organelle movement was inhibited by acidic (pH less than 7) or alkaline (pH greater than 8) solutions, high ionic strength ([ KCl] = 0.1 M), and the chelation of free magnesium ions. Treatment of the extracts with adenylyl imidodiphosphate (AMP-PNP, 7 mM), sodium orthovanadate (vanadate; Na3VO4, 20 microM), or N-ethylmaleimide (NEM, 2 mM) blocked all organelle motility. The decoration of microtubules with organelles was observed in the presence of AMP-PNP or vanadate. Motility was not affected by cytochalasin D (2 microM) or cAMP (1 mM). Kinesin (Mr = 116,000), an anterograde microtubule-based motor, was partially purified from the CEF extract by microtubule affinity purification in the presence of AMP-PNP, and was able to drive the movement of microtubule on glass coverslips. A similar preparation made in the presence of vanadate contained a different subset of proteins and did not support motility. These results demonstrate that intracellular organelle motility can be reproduced in vitro and provide the basis for investigating the roles of individual molecular components involved in the organelle motor complex.     

Effects of intestinally absorbed thymidine on tritiated thymidine utilization.

Experimental evidence presented suggests that [3H]TdR can be rapidly and efficiently transported from the intestine to the systemic circulation. This pathway for thymidine transport may be physiologically important since administration of cold thymidine in the drinking water enhances the utilization of a parenterally injected dose of [3H]TdR in several body tissues of the mouse.     

The preservation unaltered,of mineral nitrogen in tropical soils and soil extracts

Summary Experiments have been conducted on different methods of storing soils and soil extracts to preserve the mineral-N status unaltered. Neither the addition of chemicals at the rates used nor storage at sub-zero temperatures were found to preserve the mineral-N status of the soils completely unaltered over short periods of time. Furthermore, evidence was found to show that storage at sub-zero temperatures can effect subsequent mineralization of nitrogen during incubation.The mineral-N content of soil extracts prepared with an acidified K₂SO₄ reagent was not preserved over short periods by the addition of chemicals, by storing the extracts at sub-zero temperatures or by the addition of copper ions to the extracting solution. The mineral-N content of soil extracts prepared with a neutral KCl reagent could be preserved during storage at subzero temperatures but the addition of copper ions to the extracting reagent was not effective.Changes in the mineral-N content of both soils and soil extracts during storage were not consistent and in the soils appeared to be related to biological activity and the concentration of mineral N present. In soil extracts changes appeared to be related to the concentration of mineral-N present and to some other factor(s).Part of a thesis submitted for the degree of Ph. D in the University of East Africa.     

Electrophoresis of absorbed RNA

The electrophoretic mobilities of adsorbed yeast ribonucleic acid have been measured as functions of pH, ionic strength, and biopolymer concentration and the results so obtained have been critically compared with those for adsorbed DNA. Like DNA, ribonucleic acid has also been found to reverse the positive charge of alumina owing to its adsorption on the solid-liquid interface. The mobilities of adsorbed RNA have been found to be less than those of adsorbed DNA under identical conditions. The observed mobilities of adsorbed heat- and alkali-denatured RNA are significantly less than those of adsorbed native RNA at a given pH and ionic strength of the medium. The electrophoretic mobilities as observed also show the evidence of RNA adsorption on the negatively charged surface of Dowex-50 resin, but practically no adsorption of RNA on the negatively charged glass surface has been predicted.     

Effect of mineral acids on iron bacteria.

The oxidative ability of Thiobacillus ferroxidans in the presence of different concentrations of H2SO4, HC1, HNO3, and their mixtures was investigated. Bacteriological oxidation of FeSO4 is expressed as a function of time and acid concentration. For each acid and for their mixtures lethal concentrations for T. ferroxidans were found experimentally. On the basis of the lethal concentration for each acid separately the lethal concentrations of their mixtures were computed and it was found that they are in good agreement with the experimental data.     

Lymphocyte plasma membranes. V. Specificity and mitogenicity of absorbed anti-lymphocyte sera.

Anti-lymphocyte sera against human thymus [ALS-(THY)] were absorbed serially with cultured human lymphoblasts (CHL) or thymus and residual antigen-binding activity was tested. The absorbed ALS were used to bind 125I-labeled antigens from lymphocytes labeled by the lactoperoxidase catalyzed iodination technique. Absorption of ALS(THY) with CHL led to the absorbed serum having less than 5 to 10% of its original antigen-binding activity against labeled CHL antigens while maintaining from 20 to 40% of its original activity against labeled THY. Serial absorption of ALS(THY) with THY led to an equal decrease in activity against both THY and CHI. When the immunoprecipitates from these experiments were examined on polyacrylamide gels containing SDS it was found that serial absorption of ALS(THY) with THY first removed activity against a component of m.w. similar to 48,000 leaving relatively greater activity against material of apparent high molecular wieght. In contrast, absorption of ALS-(THY) with CHL removed the antibodies against the high molecular weight material while leaving activity against the component of m.w. 48,000. When these absorbed ALS were used to induce in vitro lymphocyte proliferation, it was found that ALS(THY) absorbed with CHL, did not. The retention or loss of mitogenicity seemed to correlate with retention or loss of binding activity against the component(s) of m.w. similar to 48,000.     

The structure of water absorbed in collagen. I. The dielectric properties

The dielectric constant and the loss factor of water in collagen are measured for various water, NaCl, and HCl contents at frequencies ranging from 10² to 10⁵ Hz and at temperatures ranging from ?70° to +23°C. For all measurements, both the dielectric constant and the loss decrease monotonically as the frequency increases, or the temperature decreases; the absence of a maximum in the loss curves as a function of temperature and frequency indicates an extremely broad spectrum of relaxation times. By shifting the curves obtained for the dielectric constant and the loss factor along the log–frequency axis, all data, obtained at different temperatures, can be represented on master curves valid for 23°C. In order to explain these results, water molecules are assumed to be hydrogen bonded to each other in long chains. All water molecules in a chain can, cooperatively, be oriented in two different directions along the channel, resulting in large, reversible, dipole moments. These chains are not rigid, but are flexible liquid-like structures. Diffusion of chains as entities is assumed to be the rate-limiting step for dipole reorientation. Although the rate of diffusion decreases inversely proportional to chain length, the activation energy is independent of chain length. At lower temperatures, diffusion becomes slower, until at the glass point, approximately ?100°C, it ceases.     

Space radiation absorbed dose distribution in a human phantom.

The radiation risk to astronauts has always been based on measurements using passive thermoluminescent dosimeters (TLDs). The skin dose is converted to dose equivalent using an average radiation quality factor based on model calculations. The radiological risk estimates, however, are based on organ and tissue doses. This paper describes results from the first space flight (STS-91, 51.65 degrees inclination and approximately 380 km altitude) of a fully instrumented Alderson Rando phantom torso (with head) to relate the skin dose to organ doses. Spatial distributions of absorbed dose in 34 1-inch-thick sections measured using TLDs are described. There is about a 30% change in dose as one moves from the front to the back of the phantom body. Small active dosimeters were developed specifically to provide time-resolved measurements of absorbed dose rates and quality factors at five organ locations (brain, thyroid, heart/lung, stomach and colon) inside the phantom. Using these dosimeters, it was possible to separate the trapped-proton and the galactic cosmic radiation components of the doses. A tissue-equivalent proportional counter (TEPC) and a charged-particle directional spectrometer (CPDS) were flown next to the phantom torso to provide data on the incident internal radiation environment. Accurate models of the shielding distributions at the site of the TEPC, the CPDS and a scalable Computerized Anatomical Male (CAM) model of the phantom torso were developed. These measurements provided a comprehensive data set to map the dose distribution inside a human phantom, and to assess the accuracy and validity of radiation transport models throughout the human body. The results show that for the conditions in the International Space Station (ISS) orbit during periods near the solar minimum, the ratio of the blood-forming organ dose rate to the skin absorbed dose rate is about 80%, and the ratio of the dose equivalents is almost one. The results show that the GCR model dose-rate predictions are 20% lower than the observations. Assuming that the trapped-belt models lead to a correct orbit-averaged energy spectrum, the measurements of dose rates inside the phantom cannot be fully understood. Passive measurements using 6Li- and 7Li-based detectors on the astronauts and inside the brain and thyroid of the phantom show the presence of a significant contribution due to thermal neutrons, an area requiring additional study.     

Kissiris: A mineral support for the promotion of ethanol fermentation by Saccharomyces cerevisiae

Ethanol production using Saccharomyces cerevisiae, promoted by the mineral kissiris, is reported on. A three-fold increase of ethanol productivity in the fermentation of molasses was achieved. An ethanol yield factor 0.43 g/g and conversion of 93.3% at an initial sugar concentration (ISC) 208.5 g/l were obtained in the presence of this mineral in molasses fermentation, compared to 0.21 g/g and 44.2% in its absence. It is also shown that the fermentation of molasses takes place even at relatively higher ethanol levels, with kissiris contributing to a 35% reduction of the energy demand in grade-fuel and potable ethanol production. The proposed mineral was shown to have a smaller effect in fermentations carried out in synthetic media containing glucose or saccharose.     

Evidence in vivo that most of the intraluminally absorbed glucose is absorbed intact into the portal vein and not metabolized to lactate.

Studies in vitro and acute studies in vivo have indicated that the intestine may be a significant producer of portal-venous lactate, a major carbon source for liver glycogen synthesis. To determine if a significant portion of intraluminal glucose is converted into lactate by the intestine in vivo, we measured the ratio of intraluminal glucose which is absorbed intact into the portal vein to that which is converted into lactate by the intestine in a chronically catheterized rat, in which catheters were surgically placed into the portal vein, aorta and stomach. This ratio was 36-42 when intraluminal [U-14C]glucose concentrations of 5-200 mM were used, suggesting that the intestine may not be a significant source of portal-venous lactate in vivo. Under hypoxic conditions [PaO2 less than 40 Torr (5.3 kPa)] the ratio decreased to 2.1, indicating that the amount of intraluminal glucose converted into lactate had increased significantly.