Oxidation of Tris to One-Carbon Compounds in a Radical-Producing Model System,in Microsomes,in Hepatocytes and in Rats

The buffer substance tris(hydroxymethyl)aminomethane (Tris) is converted to formaldehyde in an hydroxyl radical producing model system and in rat liver microsomes, and to CO₂ in rat hepatocytes and in the intact rat. In microsomes, formaldehyde formation from Tris is inhibited by catalase, by the antioxidant propylgallate and by the iron chelator deferoxamine, formaldehyde formation is stimulated by the addition of Fe (II) EDTA. In hepatocytes, the formation of [¹⁴C] CO₂ from [¹⁴C] Tris is inhibited by propylgallate and by the iron chelator o-phenanthroline and is stimulated by the presence of a xanthine oxidase system plus Fe (II) EDTA in the medium. In the intact rat, the administration of [¹⁴C] Tris results in the exhalation of [¹⁴C] CO². The results indicate that an oxidant formed via a Fenton-type reaction, possibly the hydroxyl radical, may be involved in the formation of one-carbon compounds from Tris.     

Strong Patterns in Homooligomer Tracts Occurrences in Non-Coding and in Potential Regulatory Sites in Eukaryotic Genomes

Abstract

Previous studies of the dinucleotides flanking both the 5′ and 3′ ends of homooligomer tracts have shown that some flanks are consistently preferred over others (1,2). In the first preferred group, the homooligomer tracts are flanked by the same nucleotide and/or the complementary nucleotides, e.g., ATA_n, TTA_n, CCG_n, where n=2–5. Runs flanked by nucleotides with which they cannot base pair are distinctly disfavored. (In this group A/T_n are flanked by C and/or G; G_n/C_n are flanked by A/T, e.g., CGA_n, T_nGG, G., AT). The frequencies of runs flanked by AorT, and G or C (“mixed” group) are as expected. Here we seek the origin of this effect and its relevance to protein-DNA interactions. Surprisingly, within the first group, runs flanked by their complements with a pyrimidine-purine junction (e.g., TTA_n, C_nGG) are greatly preferred. The frequencies of their purine-pyrimidine junction mirror-images is just as expected. This effect, as well as additional ones enumerated below, is seen universally in eukaryotes and in prokaryotes, although it is stronger in the former. Detailed analysis of regulatory regions shows these strong trends, particularly in GC sequences. The potential relationship to DNA conformation and DNA-protein interaction is discussed.     

Collagenolytic activities in methylcholanthrene-induced fibrosarcomas in mice

Summary Methylcholanthrene-induced fibrosarcomas in mice were found to possess two kinds of collagenolytic activities towards [³H]collagen, one having a pH- optimum of 4.2 and the other of pH 7.4. These two activities could be separated on a column of Celite 545 by a reverse ammonium sulfate gradient. Activity at pH 4.2 was enhanced by cysteine and EDTA and inhibited by the chloromethylketones of tosyllysine and tosyl-phenylalanine, iodoacetate, and p-hydroxymercuribenzoate. Activity at pH 7.4 was inhibited by cysteine and EDTA and enhanced by Ca²⁺. Both enzymes were inhibited by ₂-macroglobulin but neither one by ₁-antitrypsin. An electrophoretic examination of the products produced from collagen by the pH 4.2 and pH 7.4-active enzymes revealed that the former caused extensive degradation of collagen, whereas the latter yielded products of limited cleavage (^A, ^A and ^B) characteristic of mammalian collagenases. When tumor cells were cultured in vitro, the pH 7.4 activity appeared in the medium, whereas the pH 4.2 activity remained bound to the tumor cells. An enzyme capable of hydrolyzing 4-phenylazobenzoyloxycarbonyl-L-Pro-L-leu-Gly-L-Pro-D-Arg (designated as Pz-peptide) was also present but could be seperated from the other two activities. Since all three of these activities were highest in the periphery or invasion zone of the tumor, they could play a role in the invasive property of the tumor.     

Nuclear changes in allium cepa in response to infection by fusarium moniliforme

Fusarium moniliforme was isolated [into culture] from white onion and inoculated into holes bored in onion bulbs. After 48 hrs, the nuclear dry mass of onion cells 0–5 mm ahead of the mycelium had decreased by 19% as determined by quantitative interference microscopy as compared to nuclear dry mass decreases of 11 % caused by avirulent Aspergillus niger, 26 % by an unidentified onion pathogen, 41 % by virulent Botrytis allii, and 42 % by virulent Aspergillus niger. In the present study, the nucleolar dry mass declined by 34 % in response to F. moniliforme under the same conditions. Degradation or exit of nuclear and nucleolar macromolecules in response to fungal products secreted in advance of mycelium may be responsible for lower nuclear and nucleolar dry mass.     

Increase in nitrate reductase activity in the presence of sucrose in bean leaf segments

The supply of sucrose to leaf segments from light-grown bean seedlings caused a substantial increase in substrate inducibility of in vivo and in vitro nitrate reductase activity but only a small increase in total protein. Cycloheximide and chloramphenicol inhibited the increase in enzyme activity by nitrate and sucrose. The in vivo decline in enzyme activity in nitrate-induced leaf segments in light and dark was protected by sucrose and nitrate. The supply of NADH also protected the decline in enzyme activity, but only in the light. In vitro stability of the extracted enzyme was, however, unaffected by sucrose. The size of the metabolic nitrate pool was also enhanced by sucrose. The experiments demonstrate that sucrose has a stimulatory effect on activity or in vivo stability ' of nitrate reductase in bean leaf segments, which is perhaps mediated through increased NADH level and/or mobilization of nitrate to the metabolic pool.     

Flooding and groundwater dynamics in fens in eastern Poland

Abstract. Dynamics in hydrology and water chemistry in the Biebrza mires (Poland) were examined by means of a sampling survey that was repeated four times between 1987 and 1992. The dynamics in the vertical stratigraphy of water types in the peat profile are considerable from close to the mire surface to a depth of 50 cm. Water composition in the root zone correlated best with vegetation types during extremely dry or wet conditions. In the root zone of groundwater-fed rich fens with Caricetum limoso-diandrae and Calamagrostietum strictae vegetation, specific groundwater types evolve from the interaction of discharging groundwater from below the root zone and the temporal influence of precipitation and evapotranspiration. The Caricetum limoso-diandrae is fed by the continuous discharge of nutrient-poor, relatively mineral-rich water. The site conditions in the Calamagrostietum strictae are determined by occasional flooding and the presence of discharging mineral-poor groundwater in the lower part of the root zone. In the Caricetum limoso-diandrae and the Calamagrostietum strictae the maximum variations in water level were 56 and 86 cm, respectively. The composition of shallow groundwater of the Betuletum humilis/Caricetum rostratodiandrae fen is diluted most compared to other vegetation types by rainwater in wet periods. In periods of prolonged drought it has a water type that is affected by evapotranspiration and peat mineralisation. The water level varies by only 33 cm. In the Magnocaricion and Glycerietum maximae in the floodplain the water composition is determined by spring flooding of the river and the natural draw-down that occurs in the following summer. Here, maximum variations in water level were 108 and 117 cm, respectively.     

Occurrence of Fumonisin in Forage Grass in New Zealand

Fumonisin B₁ (FB₁) was isolated from samples of forage grass originating in paddocks associated with an idiopathic disease of Canadian wapiti and wapiti-red deer hybrids characterized by “ill thrift” and liver dysfunction. Four of 40 samples contained 1, 3, 6, and 9 ppm (micrograms per gram) of FB₁ and 4, 0.5, 2, and 0.5 ppm, respectively, of the methyl ester of FB₁. Analyses were done by ion spray mass spectrometry and confirmed by both fast atom bombardment (solids probe) and mass spectral analysis by electron impact ionization of the trifluoroacetate derivative of the base hydrolyzed product (pentolamine) of FB₁. This article contains the first report of the presence of fumonisin B₁ in grass.     

Changes in free-calcium levels and pH in synaptosomes during transmitter release

The free cytoplasmic Ca²⁺ concentration ([Ca²⁺]_i) in rat brain synaptosomes estimated by the indicator quin 2 is 104±8 nM (S.D.) in artificial cerebrospinal fluid (1.2 mM Ca²⁺), but decreases at lower Ca²⁺ concentrations in the medium. The presence of quin 2 in the synaptosomes does not affect either the spontaneous release of transmitter (γ-aminobutyric acid) or the release induced by K⁺ depolarisation. In quin 2-loaded synaptosomes, depolarisation by K⁺ causes an abrupt increase in [Ca]_i (less than 2-fold) that is approximately proportional to the extent of depolarisation, whereas depolarisation by veratrine alkaloids produces a slow rise in [Ca]_i. The increase in [Ca]_i produced by K⁺ depolarisation does not occur in the absence of Ca²⁺ in the medium. The data are consistent with a direct correlation between [Ca_i] and transmitter release in functional synaptosomes. The pH in synaptosomes estimated by the indicator quene 1 is 7.04±0.07 and is stable in media containing 5 mM bicarbonate. The pH in synaptosomes was decreased by protoveratrine but not by K⁺ depolarisation.     

Nitrogen accumulation in kaolin mining wastes in cornwall

Summary Nitrogen accumulation was studied in mica and sand mining wastes of Cornwall after twelve forage legume varieties were established with the use of lime and fertilizers containing phosphorus and potassium. In the finetextured mica waste legume productivity and nitrogen accumulation were similar to those for upland pastures in Cornwall; but legume growth was limited by summer drought on the coarse-textured sand waste. Native perennial legumes well adapted to the British climate were the most productive and showed the highest potential for nitrogen fixation. More than 500 kg N/ha accumulated during the 2-year period whenTrifolium pratense andLotus corniculatus were established on mica waste, and more than 250 kg N/ha was accumulated by these legumes on sand waste.Trifolium pratense andLotus corniculatus were persistent on both the mica and sand waste, andMedicago lupulina showed an unusually high tolerance for competition from invading and sown grass on the sand waste.Trifolium repens andT. hybridum are recommended for waste sites where grazing is a part of management.Nitrogen accumulation on mica waste was consistent with N fixation rates expected from climatic conditions. Nitrogen fixation by free-living bacteria is limited by the low organic matter content of the wastes. The nitrogen fixation potential by legumes on sand wastes has been underestimated because leaching losses were not adequately evaluated. Since nitrogen accumulation rates by earlyTrifolium pratense andT. repens were 70 percent higher than the maximum rate estimated for natural legumesi.e. (Ulex europaeus) on sand waste, the use of forage legumes should reduce reclamation time considerably. re]19760512Department of Botany Liverpool University     

Ontogenetic changes in pacemaker activity in chick heart

Pacemaker activity of the isolated chick heart changed considerably during development. The spontaneous impulse frequency increased up to the 11th–15th incubation day. This period of acceleration was followed by a marked deceleration around the time of hatching. Both acceleration and deceleration appeared to be caused by changes intrinsic to the pacemaker. Deceleration was related to a decrease in rate of slow diastolic depolarization. The results were compared with well-known ontogenetic changes in heart rate $\text{in vivo}$. This comparison indicates that the deceleration of pacemaker firing around hatching is counteracted by the development of sympathetic cardiac reflexes $\text{in vivo}$.     

Role of calcium in nitric oxide-induced programmed cell death in tobacco protoplasts

We tried to determine the mechanisms by which Ca²⁺ mediated NO-induced programmed cell death (PCD) in tobacco protoplasts. Treatment of tobacco protoplasts with the NO donor sodium nitroprusside (SNP) resulted in a rapid [Ca²⁺]_cyt accumulation and decrease in mitochondrial membrane potential (ΔΨ_m) before the appearance of PCD. NO-induced PCD could be largely prevented not only by NO scavenger c-PTIO, but also by EGTA (Ca²⁺ chelator), LaCl₃ (Ca²⁺-channel blocker) or CsA (a specific mitochondrial permeability transition pore inhibitor, which also inhibit Ca²⁺ cycling by mitochondria). All results suggested that NO-induced PCD is mediated through mitochondrial pathway and regulated by Ca²⁺.     

Modelling changes in VOC emission in response to climate change in the continental United States

The alteration of climate is driven not only by anthropogenic activities, but also by biosphere processes that change in conjunction with climate. Emission of volatile organic compounds (VOCs) from vegetation may be particularly sensitive to changes in climate and may play an important role in climate forcing through their influence on the atmospheric oxidative balance, greenhouse gas concentration, and the formation of aerosols. Using the VEMAP vegetation database and associated vegetation responses to climate change, this study examined the independent and combined effects of simulated changes in temperature, CO₂ concentration, and vegetation distribution on annual emissions of isoprene, monoterpenes, and other reactive VOCs (ORVOCs) from potential vegetation of the continental United States. Temperature effects were modelled according to the direct influence of temperature on enzymatic isoprene production and the vapour pressure of monoterpenes and ORVOCs. The effect of elevated CO₂ concentration was modelled according to increases in foliar biomass per unit of emitting surface area. The effects of vegetation distribution reflects simulated changes in species spatial distribution and areal coverage by 21 different vegetation classes. Simulated climate warming associated with a doubled atmospheric CO₂ concentration enhanced total modelled VOC emission by 81.8% (isoprene + 82.1%, monoterpenes + 81.6%, ORVOC + 81.1%), whereas a simulated doubled CO₂ alone enhanced total modelled VOC emission by only + 11.8% (isoprene + 13.7%, monoterpenes + 4.1%, ORVOC + 11.7%). A simulated redistribution of vegetation in response to altered temperatures and precipitation patterns caused total modelled VOC emission to decline by 10.4% (isoprene – 11.7%, monoterpenes – 18.6%, ORVOC 0.0%) driven by a decline in area covered by vegetation classes emitting VOCs at high rates. Thus, the positive effect of leaf-level adjustments to elevated CO₂ (i.e. increases in foliar biomass) is balanced by the negative effect of ecosystem-level adjustments to climate (i.e. decreases in areal coverage of species emitting VOC at high rates).     

Fibroblast-myocyte interactions in in vitro cardiomyogenesis

When in dissociated cell culture, heart muscle cells and fibroblasts taken from 8-day chick embryos do not remain unaffected by one another. Instead they interact from early incubation on. The interaction of dissociated heart cells appears to form the basis of cardiomyogenesis in vitro as obtained by various laboratories. Our cinematographs of monolayer cultures show six different phenomena: 1. When a fibroblast, wandering in a heart cell monolayer culture, enters the sphere of influence of a myocyte, contact between the two cell types occurs. To this effect the fibroblast changes its direction or its leading lamella ramifies. 2. The area of the muscle cell contacted by the fibroblast tends to dart out. The resulting myocyte process advances along the fibroblast. 3. Similar processes can be pulled out by the retracting fibroblast, and be guided passively to neighboring myocytes. 4. Thin threads produced in like manner and often repeatedly contacted by the handling lamella of the fibroblast subsequently broaden and develop into intercellular bridges. 5. A conspicuous reaction of myocytes after contact with fibroblasts is the accelerated initiation of the spreading phenomenon in which the muscle cell polarizes and starts to beat. 6. After contact, a myocyte can be transported to a neighboring muscle cell by a fibroblast. These six interactions result in the development of synchronously pulsating muscle cell units.     

Experimental hyperthyroidism in rats suppresses in vitro prostaglandin metabolism in lung and kidney

Metabolism of prostaglandin (PG) F2α and PGE2 was depressed 40–62% in 100,000 g cytoplasmic supernatants of lungs and kidneys prepared from rats made hyperthyroid by 18 daily L(-) thyroxine injections (200μg,s-c). These hyperthyroid rats had elevated serum thyroxine levels, cardiac hypertrophy and thyroid atrophy. There were no differences in soluble protein concentrations, NAD⁺ utilisation by endogenous enzymes and substrates, or in the NAD⁺ dependence of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) between the supernatants prepared from hyperthyroid rats and saline-injected controls. Thyroxine did not inhibit PG metabolism in vitro up to 260 μM. These results suggest that thyroxine specifically decreases intracellular levels of PG-metabolising enzymes, especially of the rate-limiting 15-PGDH. Metabolism of PGF2α and PGE2 by 15-PGDH was faster in smaller rats and declined with increasing animal weight. These studies imply that some of the clinical features of hyperthyroidism in man might be caused by deficiencies in PG metabolism.     

Methylmalonate-semialdehyde dehydrogenase is induced in auxin-stimulated and zinc-stimulated root formation in rice

Proteins induced in rice by auxin and zinc were determined by proteome analysis. Cultured suspension cells of rice were treated with 2,4-dichlorophenoxyacetic acid and ZnSO₄ and then proteins were separated by two-dimensional polyacrylamide gel electrophoresis; seven proteins were found to be induced by auxin and zinc. Of these seven, methylmalonate-semialdehyde dehydrogenase (MMSDH) was elevated by treatment with auxin alone. MMSDH was detected in cultured suspension cells, root and leaf sheath, but not in leaf blades. MMSDH responded to auxin and gibberellin, but did not respond to brassinolide and cytokinin. Furthermore, the amount of MMSDH in slr1, a constitutive gibberellin response mutant, was 2-fold that of wild type. MMSDH mRNA and protein were stimulated in root formation induced by auxin and/or zinc over a 4-week period. These results suggest that MMSDH may be necessary for root formation in rice induced by auxin and/or zinc.Abbreviations BA 6-Benzylaminopurine - BL Brassinolide - CBB Coomassie Brilliant Blue - 2,4-D 2,4-Dichlorophenoxyacetic acid - GA Gibberellic acid - IAA Indole-3-acetic acid - MALDI-TOF MS Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry - MMSDH Methylmalonate-semialdehyde dehydrogenase - 2D-PAGE Two-dimensional polyacrylamide gel electrophoresis - PVDF Polyvinylidene difluoride     

Rapid Ethylene Production in Soybean in Response to the Cupric Ion

Very rapid accumulation of free 1-aminocyclopropane-1-carboxylicacid (ACC), followed by stimulation of ethylene production wereinduced by a Cu²⁺ in soybean cuttings. The accumulation mustbe attributed to an increase in ACC synthesis, because: (1)it was completely inhibited by aminoethoxyvinylglycine (AVG);and (2) the ethylene stimulation was inhibited by AVG, indicatingthat free ACC cannot be released from its conjugated form. Theactivity of the ethylene-forming enzyme slightly decreased followingthe Cu²⁺ pulse, and this event was accompanied by a slight increasein electrolyte leakage from the treated soybean tissues. Glycine max L., soybean, ethylene, cupric ion     

Secular trends in childhood obesity in Denmark during 50 years in relation to economic growth

Objective: Our aim was to examine whether secular trends in childhood overweight and obesity during five decades could be explained by economic growth. Research Methods and Procedures: Annual measurements of height and weight were available for all children born between 1930 and 1983 attending primary school in the Copenhagen Municipality: 165,389 boys and 163,609 girls from the age of 7 through 13 years. After computerization, we calculated BMI (kg/m²) and estimated the prevalence of overweight and obesity, according to international age‐ and gender‐specific criteria, by year of birth and of measurement, and separately by each age group and gender. Economic growth was indicated by the Gross National Product and the overall consumption per capita, adjusted for inflation. Results: The prevalence of overweight occurred in phases: an increase from 1930 until the 1950s, followed by a plateau period between the 1950s and the 1960s and a steep increase thereafter. This pattern was apparent across all age groups and in both genders. Obesity trends showed a similar phase pattern; the prevalence remained relatively stable from 1930 until the 1940s, increased until the mid‐1950s, followed by a plateau until 1965, and thereafter a second steep increase. Obesity trends were similar among boys across all age groups, although only among girls from 11 to 13 years of age. In both genders, increments were most pronounced in the upper BMI percentiles. After stagnation until 1947, the economic growth indicators showed a steady increase; i.e., after the first increase started in overweight and obesity, whether analyzed by year of birth or year of measurement, there were no indications of phases in the rise thereafter. Discussion: Prevalence of overweight and obesity among Danish children rose in phases, which were not paralleled by trends in economic growth. The macroeconomic growth indicators seem inappropriate as proxies for the environmental exposures that have elicited the obesity epidemic.     

Role of heterotrophic bacteria in promoting N2 fixation byAnabaena in aquatic habitats

Anabaena species are commonly colonized by bacteria, especially during N₂-fixing blooms. Generally these associations do not represent bacterial attack on algal hosts. Instead, the algal N₂-fixing capabilities are increased in the presence of the bacteria. Possible mechanisms promoting the mutual growth of algae and attached bacteria were investigated by observing specific sites of bacterial attachment, by noting reduced microzones created by the bacteria, and by locating sites of bacterial uptake of organics representative of algal excretion products.Attached bacteria show preference for typical algal excretion products and their growth is enhanced by such products. In return, enhancement of algal nitrogenase activity occurs when bacteria create O₂-consuming microzones around the nitrogenase-bearing heterocysts.     

Localization of endothelin receptors in bleomycin-induced pulmonary fibrosis in the rat

Pulmonary fibrosis is characterized by excessive extracellular matrix deposition with concomitant loss of gas exchange units, and endothelin-1 (ET-1) has been implicated in its pathogenesis. Increased levels of ET-1 from tissues and bronchoalveolar lavage have been reported in patients with pulmonary fibrosis and in animal models after intratracheal bleomycin. We characterized the cellular distribution of alveolar ET receptors by immunohistochemistry in bleomycin-induced pulmonary fibrosis in the rat and determined the regulation by bleomycin of ET receptor mRNA expression in isolated alveolar macrophages and rat lung fibroblasts. We found significant increases in the numbers of fibroblasts and macrophages at day 7 compared to day 28 and control animals. ET_B receptor immunoreactivity was observed on fibroblasts and invading monocytes. Isolated fibroblasts expressed both ET_A and ET_B receptor mRNA, and ET_A receptor mRNA was upregulated by bleomycin. Isolated resident alveolar macrophages expressed neither ET_A nor ET_B receptor mRNA which were also not induced by bleomycin. We conclude that, while ET_B receptor stimulation of fibroblasts and monocytes recruited during bleomycin-induced lung injury exerts antagonistic effects on fibroblast collagen synthesis, the observed increase in the number of fibroblasts in vivo and upregulation of fibroblast ET_A receptor mRNA by bleomycin in vitro point to a predominance of the profibrotic effects of ET receptor engagement.