Osmotic Stress in Coleoptiles and Primary Leaves of Wheat. II. Main Phosphorylated Fractions

Seedlings of wheat (Triticum durum, cv. Balcarceno-INTA) werewater-stressed in darkness with 20% polyethylene glycol (PEG)6000 or 0.3 M mannitol added to the root medium. At differenttimes and up to a total of 36 h of treatment the coleoptilesand primary leaves were cut and analysed for acid soluble-P,lipid-P, protein-P, alkali-stable organic-P, and nucleic acid-P.All the phosphorylated fractions were expressed on 100 mg oftotal coleoptile and primary leaves dry wt. Acid soluble-P (14.6µmol) accounted for most of the phosphorus. The lipid-Pfraction remained at an unchanged level (6.2 µmol/100mg dry wt) in control or in mildly osmotic stressed shoots ofseedlings over the period of treatment. The protein-P representedonly 2.4% (0.8 µmol) of the total phosphorus found incoleoptiles and primary leaves. The alkali-stable organic-Pand nucleic acid-P fractions represented 22.2% (7.2µ mol)and 11.1% (3.6 µmol) of the total phosphorus content ofshoots, respectively. All the phosphorylated fractions, exceptingthe lipid-P fraction, underwent a significant (P < 0.025)fall over periods of up to 36 h of wheat seedlings growth indarkness. A common characteristic found in all the phosphorylatedfractions was the fact that there were not significant differencesbetween control and 20% PEG 6000 or 0.3 M mannitol treated seedlingsduring 36 h of treatment and growth in darkness. However, whenseedlings were pulse-labelled with 32P during imbibition, someeffects of the osmotic stressants on several fractions couldbe seen. Specific radioactivity fell in acid soluble-P of controlshoots, but increased in 20% PEG 6000 and in 0.3 M mannitoltreated seedlings. Radioactive phosphorus was not found in thealkali-stable organic-P fraction. Lipid-P, nucleic acid-P, andprotein-P fractions increased their specific activities during36 h of shoot growth in control plants. Such 20% PEG 6000 and0.3 M mannitol restricted this increase during the same periodof time, the former being more active. Possible implicationsof phospholipid and phosphoprotein turnover in relation to waterstress are discussed.     

Incorporation of Tritium from Thymidine-methyl-H3 into DNA,RNA, Lipids and Protein in Logarithmic and Stationary Phase Tetrahymena pyriformis,Strain W*

SYNOPSIS. Numerous reports may be found in the literature on cytoplasmic and non-DNA utilization of tritium from H³-thymidine. Such reports underscore the need to clarify the metabolic fate of H³-thymidine. This investigation outlines the fate of thymidinemethyl-H³ (TMH³) in logarithmic phase and stationary phase Tetrahymena pyriformis, strain W. Isotope identification by liquid scintillation spectrometry in chemically derived fractions of log phase cultures grown thruout the initial 48 hours of population growth with TMH³ revealed the majority of the radioactivity (90% of intracellular recovery) to be in the DNA fraction. The remainder of the intracellular label was recovered in the acid soluble fraction, lipid fraction, and a small amount in the RNA and cell residue. On chromatographs, tritium appeared only in the thymine moiety of the nucleic acid derivatives. Hence in dividing cells, thymidine-methyl-H³ is “essentially” specific for DNA at the dosage used although some incorporation into other compounds was detected. Fractionation of the lipid extract from the above experiment on a florisil column localized most of the label to the triglyceride and phospholipid fractions with some recovery in the cholesterol-esters. Similar scintillation counting of the various fractions of early stationary phase cells incubated for the last 48 hours of culture with TMH³ revealed limited tritium distribution in all fractions.     

Effects of protein inhibitors and auxin on nucleic Acid metabolism in peanut cotyledons

The accumulation of labeled phosphorus into newly synthesized nucleic acids or peanut cotyledon slices incubated with chloramphenicol, puromycin, or 2,4-dichlorophenoxyacetic acid (2,4-D) was reduced. Promotion of nucleic acid synthesis was not noted by any of these chemicals. Chloramphenicol completely inhibited the synthesis of the DNA-RNA fraction at 1.25 × 10⁻³ m while soluble and ribosomal RNA was inhibited by 70% and 80%, respectively. At the same concentration messenger RNA was inhibited by only 40%. These effects suggest that chloramphenicol inhibit nucleic acid synthesis in peanut cotyledons in a differential manner. Similar results were noted for DNA at low concentrations of 2,4-D. However, at high concentrations of 2,4-D, DNA as well as RNA fractions were inhibited in a similar manner at a given concentration. Puromycin did not differentially inhibit nucleic acid synthesis except at 2 × 10⁻³ m where DNA was least inhibited.     

Phosphorus content and growth of fenugreek as affected by cadmium application

Changes in growth and phosphorus content in plants and seeds of fenugreek with increasing cadmium concentration was evaluated. Root length and shoot length ranged from 11.63 to 27.72 and from 9.70 to 54.78 cm, respectively. With the increasing Cd²⁺ concentration there was a significant decrease in root and shoot length, and fresh mass. Various phosphorus fractions of shoot decreased with increasing Cd²⁺ concentration except lipid P and nucleic acid P which increased at 65 and 95 d after sowing and protein P only increased at vegetative stage. In seeds (60 d after flowering) lipid P increased except at 2.5 μg(Cd²⁺) g^?1 (soil) while protein P decreased.     

Single-cell protein of Rhodotorula sp. Y-38 from ethanol, acetic acid and acetaldehyde

Summary Continuous cultivation of Rhodotorula sp. Y-38 was carried out on ethanol, acetic acid or acetaldehyde. At a feed concentration of 1.0 % (w/v) ethanol, the cell yield of 64 g/100 g ethanol and crude protein of 52 g/100 g biomass were obtained at D=0.5 h^-1. The respective value of the content of amino acids and nucleic acids was 42.6 and 9.4 g/100 g biomass. At 2.0 % (w/v) acetic acid, cell yield was found to be 50 g/100 g acetic acid at D=0.4 h^-1. The optimum dilution rate ranged between 0.3 and 0.4 h^-1. At 0.05 % (w/v) acetaldehyde, the maximum cell yield was obtained at D=0.14 h^-1.     

LM fibroblast plasma membrane subfractionation by affinity chromatography on Con A-sepharose

Affinity chromatography was used to determine the heterogeneity and orientation of plasma membrane vesicles isolated from LM fibroblasts subjected to Dounce homogenization. Two plasma membrane subfractions were obtained by Con A-Sepharose affinity chromatography of LM fibroblast plasma membranes prepared by Dounce homogenization. The desmosterol-phospholipid molar ratio, the phospholipid composition, and the phospholipid fatty acid composition were almost identical between the two fractions. However, the lipid to protein ratio was almost 2-fold greater in the nonadherent fraction A. The binding of fluorescein-concanavalin A was the same in both fractions indicating a right-side-out orientation of the vesicles. Similarly the asymmetric distribution of phosphatidylethanolamine in both membrane fractions was the same. In contrast, sialic acid content, 5′-nucleotidase activity, and (Na⁺ + K⁺)-ATPase activity were 47%, 3.7-fold, and 2.5-fold greater, respectively, in the nonadherent, lipid-rich fraction A. Structural properties of the two membrane fractions determined by fluorescence polarization and Arrhenius plots of trans-parinaric acid fluorescence were similar. These results indicate that concanavalin-A affinity chromatography separates two membrane fractions differing in sialic acid content, lipid content, and enzyme profile but having the same right-side-out orientation.     

Preparation,purification, and properties of E. coli virus T2

1. A method for the preparation of 8 to 10 liter quantities of T₂ virus lysates, titering 2 to 5 x 10¹¹ infectious units per ml. has been described. 2. Procedures have been developed for the concentration and purification of virus to a high specific infectivity. No fractionation procedure of the several used succeeded in further raising the specific infectivity of these purified preparations. 3. Some of the general properties of the better preparations have been determined. They exhibited titers of 2 x 10¹⁵ infective units per gm. of material or 1.2 x 10¹⁶ per gm. of nitrogen. 4. A study of the distribution of nitrogen among the various fractions of the virus showed that about 6 per cent of the total nitrogen is soluble in 4 per cent trichloracetic acid; that the protein nitrogen is about 40 per cent of the total and the nucleic acid nitrogen is 53 per cent. At least 96 per cent of the total phosphorus is in the nucleic acid fraction. Less than 0.5 per cent quantities of lipid and PNA were found.     

Comparitive study of the milk fat globule membrane and the mouse mammary tumour virus prepared from the milk of an infected strain of Swiss albino mice

Milk fat globule membranes and mammary tumour virus particles (d = 1.17 g/cm³) have been obtained from the milk of a Swiss albino mice strain. Comparitive biochemistry shows that these two structures differ significantly in the phospholipid, polypeptide and glycopolypeptide patterns and enzymatic activities. However, the lipid profile and the morphology of both structures suggest a filiation with the plasma membrane. Density fractions obtained from the crude virus preparation have been thoroughly investigated. The results suggest that most of these fractions represent degraded virus and/or atypical virus assembly.     

Effect of undernutrition on DNA and RNA synthesis in subcellular fractions from different regions of the developing rat brain

The effect of undernutrition on the incorporation of [methyl-³H]thymidine into DNA and of 5-[³H]uridine into RNA of cerebral hemispheres, cerebellum, and brain stem was studied in vivo and in vitro in rats. The labeling of DNA from nuclei and mitochondria and of RNA from nuclei, mitochondria, microsomes, and soluble fractions, was also measured in vitro. The results demonstrate that nucleic acid synthesis is impaired and delayed during undernutrition. Specific effects were observed for the different brain regions and subcellular fractions: at 10 days nuclear and mitochondrial DNA and RNA synthesis was impaired, whereas at 30 days only the mitochondrial nucleic acid synthesis was affected.The delay of DNA and RNA labeling, caused by undernutrition, was most evident in the cerebellum, probably due to its intense cell proliferation during postnatal development. The specific sensitivity of mitochondria as compared to other subcellular fractions, may be due to the intense biogenesis and/or turnover of nucleic acids in brain mitochondria not only during postnatal development, but also in the adult animal.     

Effect of different conditions of light on the nucleic acid fractions in cotyledons ofChenopodium rubrutn L.

The nucleic acid fractions in cotyledons of young Chenopodium rubrum plants exposed to continuous light, continuous darkness and short (8 h) day, respectively and labelled with³²P 24 h prior to harvesting were studied by means of chromatography on MAK columns. Some parameters of cotyledon growth (dry weight, cotyledon area, occurrence of mitoses) were also investigated. The changes in the nucleic acid fractions agreed with the dynamics of cotyledon growth. In continuous light the content of all fractions increased. The radioactivity of DNA and s-RNA did not undergo any great changes and only r-RNA increased. The specific activity of r-RNA increased slightly, that of soluble RNA and DNA was reduced. In continuous darkness the content of all the fractions did not undergo any great changes. The radioactivity as well as the specific activity of all fractions decreased. In short day the content of the nucleic acid fractions did not change conspicuously. Only the specific activity of s-RNA increased in a noticeable way while the radioactivity of r-RNA and the specific activity of DNA decreased and this of r-RNA did not change. The changes in nucleic acid metabolism were partially connected with changes in³²P uptake which depended upon light conditions but they were not merely a consequence of this fact. Obviously, there also exists a more direct relationship between nucleic acid synthesis and growth.     

A mathematical model of the phosphorus cycle in Lake Loosdrecht and simulation of additional measures

The phosphorus cycle in the ecosystem of the shallow, hypertrophic Loosdrecht lakes (The Netherlands) was simulated by means of the dynamic eutrophication model PCLOOS. The model comprises three algal groups, zooplankton, fish, detritus, zoobenthos, sediment detritus and some inorganic phosphorus fractions. All organic compartments are modelled in two elements, carbon and phosphorus. Within the model system, the phosphorus cycle is considered as completely closed. Carbon and phosphorus are described independently, so that the dynamics of the P/C ratios can be modelled. The model has been partly calibrated by a method based on Bayesian statistics combined with a Range Check procedure.Simulations were carried out for Lake Loosdrecht for the periods before and after the restoration measures in 1984, which reduced the external phosphorus loading to the lake from ca. 2 mgP m^–2 d^–1 to 1 mgP m^–2 d^–1. The model outcome was largely comparable withthe measured data. Total phosphorus has slowly decreased from an average 130 µgP l^–1 to ca. 80 µgP l^–1, but chlorophyll-a (ca. 150 µg 1^–1, summer-averaged) and seston concentrations (8–15 mgC 1^–1) hardly changed since the restoration measures. About two-thirds of the seston consisted of detritus, while the phytoplankton remained dominated by filamentous cyanobacteria. The P/C ratio of the seston decreased from ca. 1.0% to 0.7%, while the P/C ratios of zooplankton, zoobenthos and fish have remained constant and are much higher. The system showed a delayed response to the decreased phosphorus loading until a new equilibrium was reached in ca. five years. Major reasons for the observed resilience of the lake in responding to the load reduction are the high phosphorus assimilation efficiency of the cyanobacteria and the high internal recycling of phosphorus. A further reduction of nutrient loading, perhaps in combination with additional measures like biomanipulation, will be the most fruitful additional restoration measure.     

PHOSPHATE METABOLISM IN BLUE-GREEN ALGAE. II. CHANGES IN PHOSPHATE DISTRIBUTION DURING STARVATION AND THE “POLYPHOSPHATE OVERPLUS” PHENOMENON IN PLECTONEMA BORYANUM

Physiological aspects of phosphate utilization by the blue-green alga Plectonema boryanum were studied. It was found that the external phosphate concentration influenced the distribution of phosphorus-containing compounds in the cell. Culturing the alga in concentrations of 10, 100, and 1000 mg PO₄/l resulted in increases in the level of acid-soluble and acid-insoluble polyphosphates. The values reported for 100 and 1000 mg PO₄/l were the same, indicating that the cells were able to assimilate and utilize only fixed amounts of phosphates. The total phosphorus value for these cells was calculated to be 6.5 μg P per 10⁶ cells. Culturing the alga in 1 mg PO₄/l led to a decrease in phosphate concentration of all cell fractions. Cells grown in the absence of phosphate for 5 days had total cell phosphorus levels of 0.76 μg P per 10⁶ cells. Cells in culture for two months or longer were found to have total cell phosphorus levels of 0.73 μg P per 10⁶ cells. This was determined to be the minimum cell phosphorus level limiting growth. Transfer of cells from either culture condition to a medium containing phosphate led to an “overplus” phenomenon. This overplus phenomenon was characterized by increases in all cellular phosphorus fractions. The most dramatic increase was found in both the acid-soluble and acid-insoluble polyphosphates. These fractions often increased by more than an order of magnitude. The greatest phosphate uptake occurred within 1 hr of transfer of phosphate-starved cells into a medium containing a known amount of phosphate and is essentially complete at 4 hr. The total cell phosphorus levels for uptake never increased beyond 18.9 μg per 10⁶ cells.     

Iron content of sediment and phosphate adsorption properties

Phosphorus can occur in sediments in different forms and accordingly its availability varies. The distinction between the phosphorus fractions is made with two chemical extraction methods; an ammonium oxalate-oxalic acid extraction and an extraction according to Hieltjes & Lijklema (1980).The iron and aluminum liberated with the ammonium oxalate-oxalic acid extraction method is linearly correlated (r ² = 0.73) with the phosphorus liberated in the first two steps of the Hieltjes and Lijklema extraction by: P = 0.035 (Fe + Al) + 0.001 (P, Fe and Al in mmol g^–1).The iron and aluminum (hydr)oxides are very important fractions in the sediment adsorption capacity for phosphorus. The phosphorus sorption capacity (PSC) is 0.080 mol P (mol (Fe + Al))^–1 and the adsorption constant (k) is 11.9 µmol P l^–1. Here it is assumed that iron and aluminum (hydr)oxide have the same affinity for phosphorus.     

施磷对川西北高寒草地土壤磷形态及有效性的影响

以川西北高寒草地为研究对象,采用随机区组设计,设置0、10、20、30、40、50、60 g/m²的过磷酸钙(P₂O₅,16%)施肥试验,分析土壤不同形态磷含量和有效磷(Olsen-P)含量变化特征,探究施磷对川西北高寒草地土壤磷形态及有效磷的影响。结果表明：(1)随施磷量增加,土壤总磷(TP)含量先增加后趋于平稳而Olsen-P含量减少。高水平(50、60 g/m²)施磷下氢氧化钠有机磷(NaOH-Po)及残留磷(Residual-P)是高寒草地主要的磷素累积形态,其含量显著高于不施磷处理;(2)树脂交换态磷(Resin-Pi)、碳酸氢钠无机磷(NaHCO₃-Pi)、碳酸氢钠有机磷(NaHCO₃-Po)和氢氧化钠无机磷(NaOH-Pi)含量随施磷量增加整体呈先增加后降低趋势,表层土壤30 g/m²磷肥用量下其值均为最高,分别为21.54、22.94、65.86、64.48 mg/kg。酸溶性无机磷(HCl-Pi)随施磷量增加整体呈下...     

Differential distribution and metabolism of arachidonic acid and docosahexaenoic acid by human placental choriocarcinoma (BeWo) cells

The time course of incorporation of [¹⁴C]arachidonic acid and [³H]docosahexaenoic acid into various lipid fractions in placental choriocarcinoma (BeWo) cells was investigated. BeWo cells were found to rapidly incorporate exogenous [¹⁴C]arachidonic acid and [³H] docosahexaenoic acid into the total cellular lipid pool. The extent of docosahexaenoic acid esterification was more rapid than for arachidonic acid, although this difference abated with time to leave only a small percentage of the fatty acids in their unesterified form. Furthermore, uptake was found to be saturable. In the cellular lipids these fatty acids were mainly esterified into the phospholipid (PL) and the triacyglycerol (TAG) fractions. Smaller amounts were also detected in the diacylglycerol and cholesterol ester fractions. Almost 60% of the total amount of [3H]Docosahexaenoic acid taken up by the cells was esterified into TAG whereas 37% was in PL fractions. For arachidonic acid the reverse was true, 60% of the total uptake was incorporated into PL fractions whereas less than 35% was in TAG. Marked differences were also found in the distribution of the fatty acids into individual phospholipid classes. The higher incorporation of docosahexaenoic acid and arachidonic acid was found in PC and PE, respectively. The greater cellular uptake of docosahexaenoic acid and its preferential incorporation in TAG suggests that both uptake and transport modes of this fatty acid by the placenta to fetus is different from that of arachidonic acid.     

华西雨屏区不同林龄柳杉人工林土壤磷组分特征

磷是限制陆地生态系统生产力的关键养分因子。当前尚不了解不同土壤磷组分随柳杉林龄增长如何变化,及其与土壤微生物群落的关系。以华西雨屏区不同林龄（7年生幼龄林、13年生中龄林、24年生近熟林、33年生成熟林,53年生过熟林）柳杉（Cryptomeria japonica var. sinensis）人工林为研究对象,采用Hedley磷素分级方法、磷脂脂肪酸分析法（PLFA）来探究不同林龄柳杉人工林土壤磷组分的分布模式及影响因子。结果表明：不同林龄和土壤深度土壤磷各组分含量差异显著。随林龄增加,可溶性磷和磷灰石含量逐渐减少,残余态磷含量逐渐增加,其余磷组分含量先增加后降低。除可溶性磷、浓盐酸提取态无机磷和残余态磷组分外,其余土壤磷组分含量表现为上层（0-15 cm）高于下层（15-30 cm）。偏门特尔检验表明,微生物群落与土壤磷组分之间存在显著关联。回归分析发现,碳与有机磷比值和酸性磷酸酶活性呈正相关。冗余分析显示,pH、土壤有机碳、土壤含水量,全氮和土壤容重是影响土壤磷组分变化的主导因子。研究显示,造林初期的土壤磷组分快速积累,在中龄林阶段达到最大值,随着柳杉人工林林龄的增加,土壤中磷的限制逐渐加强,土壤磷组分含量在成熟林之后逐渐下降。这些结果可为为柳杉人工林的培育及可持续经营管理提供科学依据。     

DNA buoyant densities ofTrypanosoma (Schizotrypanum) species from bats in Ontario,Canada

Summary Two species of trypanosomes,Trypanosoma hedricki andT. myoti, isolated respectively fromEptesicus fuscus andMyotis lucifugus, were cloned.T. hedricki produced long trypomastigotesin vitro (mean length 22.1±0.3 m); the buoyant densities of its kinetoplastic and nuclear deoxyribonucleic acid (kDNA and nDNA) were respectively 1.700 and 1.710 g ml^–1 and it possessed a small amount of a satellite component (C-DNA) of density 1.716 g ml^–1. This species is in this respect closely related toT. dionisii. T. myoti produced long trypomastigotesin vitro (mean length 20.1±0.2 m); its DNA buoyant densities (g ml^–1) were: kDNA 1.700 and nDNA 1.710 (no C-DNA was detected). In this respect, therefore,T. myoti is closer toT. cruzi than the other bat trypanosomes. ac]19830129     

Evidence for the Involvement of Docosahexaenoic Acid in Cholinergic Stimulated Signal Transduction at the Synapse

[4,5-³H]Docosahexaenoic acid ([³H]DHA) or [9,10-³H]palmitic acid ([³H]PAM) was infused intravenously for 5 min to awake, adult male rats before and after treatment with arecoline (15 mg/kg, i.p.), a cholinergic agonist. Animals were killed 15 min post-infusion, the brains were rapidly removed and subcellular fractions were obtained after sucrose density centrifugation. In control animals, [³H]DHA and [³H]PAM were incorporated into the synaptosomal fractions, representing 50%–60% of total membrane label. Most remaining membrane label (30%–40%) was in the microsomal fraction. Both fractions contained the synaptic marker synaptophysin. The remaining 10% of radioactivity was in the myelin and mitochondrial fractions. Arecoline significantly increased [³H]DHA entry into the synaptosomal fractions by 100% and into the microsomal fraction by 50%. In these fractions 60%–65% of the [³H]DHA was in phospholipid, the rest corresponding to free fatty acid and diacylglycerol. In contrast, arecoline did not change [³H]PAM incorporation into any brain fraction. These results demonstrate that plasma [³H]DHA incorporation is selectively increased into synaptic membrane phospholipids of the rat brain in response to cholinergic activation. The increased incorporation of DHA but not of PAM into synaptic membranes in response to cholinergic stimulation indicates a primary role for DHA in phospholipid mediated signal transduction at the synapse involving activation of phospholipase A₂ and/or C.     

The Purification and Characterization of Gemini Particles from Abutilon Mosaic Virus Infected Malvaceae

Gemini particles were purified from Abutilon Mosaic Virus infected Abutilon sellovianum, Sida micrantha and Malva parviflora. They sediment with 82 S, possess a density of 1.30 g/cm³ in Cs₂SO₄ and a nucleic acid percentage of 18 % calculated from ultra-violett spectrometry. Their proteins are separated in SDS-PAGE into two components of 28 000 and 27 000 mol. wt. Their nucleic acid consists of single-stranded circular DNA with length distribution maxima of 2 800, 2 500 and 1 300 bases for the circular molecules and 2 050, 1 850, and 1 300 bases for the correspondmg linear molecules.     

Localization of ribosomal cistrons in metaphase chromosomes of Vicia faba (L.)

Tritiated ribosomal RNA (rRNA) was prepared from the roots of Vicia faba after incubation in ³H-uridine. Separation of the nucleic acids by MAK chromatography yielded fractions of specific activity of 4–5 × 10⁵ dpm/μg. 4 + 5S, 18S and 25S RNA fractions were used for cytological hybridization on squash preparations of Vicia faba root tip meristems. Autoradiographs of the 18S and 25S RNA preparations exhibited a clear labelling in the secondary constriction of the satellite (SAT) chromosomes after exposition times of 28 weeks.