Atmospheric oxidation capacity sustained by a tropical forest.

Terrestrial vegetation, especially tropical rain forest, releases vast quantities of volatile organic compounds (VOCs) to the atmosphere, which are removed by oxidation reactions and deposition of reaction products. The oxidation is mainly initiated by hydroxyl radicals (OH), primarily formed through the photodissociation of ozone. Previously it was thought that, in unpolluted air, biogenic VOCs deplete OH and reduce the atmospheric oxidation capacity. Conversely, in polluted air VOC oxidation leads to noxious oxidant build-up by the catalytic action of nitrogen oxides (NO(x) = NO + NO2). Here we report aircraft measurements of atmospheric trace gases performed over the pristine Amazon forest. Our data reveal unexpectedly high OH concentrations. We propose that natural VOC oxidation, notably of isoprene, recycles OH efficiently in low-NO(x) air through reactions of organic peroxy radicals. Computations with an atmospheric chemistry model and the results of laboratory experiments suggest that an OH recycling efficiency of 40-80 per cent in isoprene oxidation may be able to explain the high OH levels we observed in the field. Although further laboratory studies are necessary to explore the chemical mechanism responsible for OH recycling in more detail, our results demonstrate that the biosphere maintains a remarkable balance with the atmospheric environment.

Myosin light chain phosphorylation does not modulate cross-bridge cycling rate in mouse skeletal muscle.

An attempt was made to determine whether phosphorylation of the myosin light chain represents a thick filament-associated mechanism for modulating the rate of cross-bridge cycling in mouse skeletal muscle. When the degree of light chain phosphorylation was varied independently of tetanus duration, there was no correlation of phosphorylation with cross-bridge turnover rate, as measured by the shortening velocity of the muscle. It is concluded that in intact skeletal muscle phosphorylation of the myosin light chain does not in itself modulate cross-bridge cycling rate and that previously reported changes in cycling rate were due to other factors that may vary with tetanus duration.

Crossbridge attachment, resistance to stretch, and viscoelasticity in resting mammalian smooth muscle.

There exist a calcium-dependent resistance to stretch in resting mammalian smooth muscle that is not caused by depolarization of the cell membrane or release of calcium from intracellulr sites. The similarity of the resistance to stretch in the resting state to that in rigor suggests that most, if not all, crossbridges are attached and thus able to resist stretch in noncontracting smooth muscles. When the muscle is stretched the breaking and subsequent reformation of links in nonstrained positions accounts for most of the so-called viscoelasticity, except at extreme lengths.

Megakaryocytic differentiation of K562 cells is associated with changes in the cytoskeletal organization and the pattern of chromatographically distinct forms of phosphotyrosyl-specific protein phosphatases.

We have analyzed morphological and biochemical changes occurring during megakaryocytic differentiation of the human chronic myelogenous leukemia cell line K562 induced by phorbol 12-myristate 13-acetate (PMA). PMA-treated cells became growth arrested, were slightly larger and irregular in shape, adhered better to the culture flask surface, and expressed the glycoprotein IIIa on their surfaces. The morphological changes induced by PMA treatment were associated with the disappearance of actin from the cytosol and presumably reflect PMA-induced actin polymerization. Megakaryocytic differentiation was accompanied by about a 3-fold decrease in the specific phosphotyrosine protein phosphatase (PTPase) activity in the particulate membrane fraction, whereas the activity in the soluble cytosol fraction increased about 3-fold. The decrease of PTPase activity in the particulate membrane fraction could be attributed to the disappearance of at least 1 distinct PTPase form displaying an apparent native Mr of 200,000 and a reduction in activity of a Mr 43,000 PTPase found associated with membranes of all cells examined to date. The increase of PTPase activity in the cytosol fraction manifested itself by the appearance of a new Mr 40,000 PTPase and a reduction of a Mr 60,000 PTPase. These results suggest the existence of several growth- and/or differentiation-related PTPase activities in K562 cells.

Chemical energetics of force development, force maintenance, and relaxation in mammalian smooth muscle.

High-energy phosphate utilization (delta approximately P) associated with force development, force maintenance, and relaxation has been determined during single isometric tetani in the rabbit taenia coli. ATP resynthesis from glycolysis and respiration was stopped without deleterious effects on the muscle. At 18 degrees C and a muscle length of 95% l0, the resting rate of energy utilization is 1.8 +/- 0.2 nmol/g . s-1, or 0.85 +/- 0.2 mmol approximately P/mol of total creatine (Ct) . s-1, where Ct = 2.7 mumol/g wet wt. During the initial 25 s of stimulation when force is developed, the average rate of delta approximately P was -8.2 +/- 0.8 mmol/mol Ct . s-1, some four times greater than during the subsequent 35 s of force maintenance, when the rate was -2.0 +/- 0.6 mmol approximately P/mol Ct . s-1. The energy cost of force redevelopment (0 to 95% P0) after a quick release from the peak of a tetanus is very low compared with the initial force development. Therefore, the high rate of energy utilization during force development is not due only to internal work done against the series elasticity nor to any high rate of cross-bridge cycling inherently associated with force development. The high economy of force maintenance compared with other muscle types is undoubtedly due to a slower cross-bridge cycle time. The energy utilization during 45 s of relaxation was not statistically significant, and integral of Pdt/delta approximately P was higher during relaxation than during force maintenance in the stimulated muscle.

Cytoplasmic free calcium, myosin light chain phosphorylation, and force in phasic and tonic smooth muscle.

The time course of [Ca2+]i, tension, and myosin light chain phosphorylation were determined during prolonged depolarization with high K+ in intact tonic (rabbit pulmonary artery) and phasic (longitudinal layer of guinea pig ileum) smooth muscles. [Ca2+]i was monitored with the 340 nm/380 nm signal ratio of the fluorescent indicator fura-2. The fluorescence ratio had a similar time course in both muscle types during depolarization with 109 mM [K+]o; after a transient peak, there was a decline to 70% of its peak value in tonic smooth muscle, and to 60% in phasic smooth muscle. Tension, however, continued to increase in the pulmonary artery, while in the ileum it declined in parallel with the [Ca2+]i. On changing [K+]o from 109 to 20 mM, tension and [Ca2+]i either remained unchanged or declined in parallel in the pulmonary artery. Phosphorylation of the 20-kD myosin light chain, measured during stimulation of muscle strips with 109 mM [K+]o in another set of experiments, increased from 3% to a peak of 50% in the intact pulmonary artery, and then declined to a steady state value of 23%. In the intact ileum, a very rapid, early transient phosphorylation (up to 50%) at 2-3 s was seen. This transient declined by 30 s to a value that was close to the resting level (7%), while tension remained at 55% of its peak force. A quick release during maintained stimulation induced no detectable change in the [Ca2+]i in either type of smooth muscle. We discuss the possibility that the slowly rising tonic tension in pulmonary artery could be due to cooperativity between phosphorylated and nonphosphorylated crossbridges.

Promoter analysis of a growth hormone transgene in Atlantic salmon.

The ocean pout (Macrozoarces americanus) op5a antifreeze protein gene promoter has been used to generate a line of growth hormone (GH) transgenic Atlantic salmon with greatly enhanced growth rates. A study of the genomically integrated GH transgene (EO-1 alpha) in this line of salmon revealed that the first 1579 bp of the 2115-bp promoter was deleted and relocated downstream of the GH coding region, raising questions regarding the ability of the truncated promoter to drive expression of the GH transgene and the potential influence of the relocated 5' promoter region. In this study, 11 promoter constructs were fused to a luciferase reporter gene, and their transcriptional ability was examined after transfection into salmon and human cell lines cultured at 21 and 37 degrees C, respectively. Construct expression was similar in all cell lines, apart from those of less than 266 bp, where expression in the salmon cells greatly exceeded that of the human cells. The results demonstrated the presence of positive and negative regulatory regions within the promoter that would allow the regulation of gene expression at multiple sites. Removal of the first 1579 bp from the promoter resulted in a 70% loss of the luciferase expression exhibited by the full-length promoter, whereas ligating the deleted 5' promoter sequence downstream of the luciferase reporter gene only restored approximately 10% of this loss. These results suggested that in vivo expression of the EO-1 alpha transgene is driven by elements within the weak truncated promoter in conjunction with the relocated 5' promoter region.

Phenomenological evidence for two types of paranoia.

OBJECTIVE: Two types of paranoia have been identified, namely persecution (or 'Poor Me') paranoia, and punishment (or 'Bad Me') paranoia. This research tests predicted differences in phenomenology--specifically, in person evaluative beliefs, self-esteem, depression, anxiety, and anger. METHOD: Fifty-three people with current paranoid beliefs were classified as Poor Me, Bad Me, or neither (classification was reliable). Key dependent variables were measured. RESULTS: All predictions were supported, except the one relating to anger, where the two groups did not differ. The Bad Me group had lower self-esteem, more negative self-evaluative thinking, lower negative evaluations about others, higher depression and anxiety. Importantly, the differences in self-esteem and self-evaluations were not fully accounted for by differences in depression. CONCLUSION: Data support the presence of two distinct topographies of paranoia. Future research is needed to explore the theory further and examine clinical implications.

Chemical energy usage and myosin light chain phosphorylation in mammalian smooth muscle.

Experiments have been done to determine the relationships among active force output, average rate of high-energy phosphate utilization, and the degree of phosphorylation of the 20,000-dalton myosin light chain in the rabbit tenia coli at 18 C. During an isometric tetanus at l0 the degree of light chain phosphorylation increases to a maximum of 30-40% before maximum force is developed, and then phosphorylation slowly decreases while active force is maintained. During the period when there is a small decrease in degree of phosphorylation, the average rate of chemical energy usage falls by fourfold. In contrast, when the calcium concentration of the bathing medium is lowered from 1.9 to 1.0 mM a very large decrease in degree of phosphorylation is associated with only a small decrease in both energy usage and active force. At lower calcium levels both force and chemical energy usage decrease proportionately with little further decrease in degree of phosphorylation. We conclude that under isometric conditions there is no consistent relationship between degree of myosin light chain phosphorylation and the rate of cross-bridge cycling as measured by the rate of high-energy phosphate usage in this mammalian smooth muscle.

Control of cross-bridge cycling by myosin light chain phosphorylation in mammalian smooth muscle.

This review focuses on experiments in which the single turnover of myosin-bound ADP is used to characterize the regulation of the cross-bridge cycle by myosin light chain phosphorylation in mammalian smooth muscle. Under isometric conditions, at rest, when the myosin light chain is not phosphorylated, myosin cycles very slowly (about 0.004 s-1), while phosphorylation of the light chain results in a 50-fold increase in cycling rate of 0.2 s-1. Experiments consistently show that some myosin does not increase its cycling rate although its light chain is phosphorylated. Studies at low levels of myosin light chain phosphorylation show that phosphorylation also induces an increase in the cycling rate of unphosphorylated myosin. The fast cycling phosphorylated myosin is the main determinant of suprabasal myosin ATPase activity, while the cycling rate of cooperatively activated unphosphorylated myosin is slow and appears to depend on the extent of phosphorylation of the entire thick filament. Single turnover experiments measuring the rate of phosphorylation and dephosphorylation of myosin light chain show that the turnover of light chain phosphate can be very rapid (0.3-0.4 s-1) at suprabasal calcium concentrations. The expected effect of such a rapid turnover of light chain phosphorylation on the turnover of myosin-bound ADP is not observed. The effects of low levels of myosin light chain phosphorylation on the single turnover of myosin suggest that the same small pool of myosin remains phosphorylated for relatively long periods of time rather than the entire pool of myosin spending a small fraction of its cycle time in the phosphorylated state.

Chemical energy usage and myosin light chain phosphorylation in mammalian skeletal muscle.

The purpose of this study was to ascertain whether phosphorylation of the regulatory light chain of myosin plays a role in modulating the rate of chemical energy usage in mammalian skeletal muscle. There was no change in the average rate of chemical energy usage with duration of isometric stimulation in the rat extensor digitorum longus (EDL), even though the degree of light chain phosphorylation increased from 5% at rest to above 60% after 7 s of stimulation. When the initial degree of phosphorylation was increased to 73% by prestimulation of the muscle, there was still no change in the chemical energy usage under isometric conditions. In contrast, under the conditions used, the mouse EDL showed changes in the average rate of energy usage that depended upon both tetanus duration and stimulation history. However, there was no consistent relationship between phosphorylation of the light chain and average rate of chemical energy usage. These results suggest that while there are factors which can change crossbridge cycling rate in mammalian skeletal muscle, phosphorylation of the regulatory light chain of myosin is neither necessary nor sufficient to cause such changes.

Chemical Energetics of contraction in mammalian smooth muscle.

Measurements of high-energy phosphate utilization during isometric tetanic contractions were made on a rabbit taenia coli preparation that had been treated so that respiration and glycolysis were blocked without altering the mechanical response to the muscle. At 18 C the first sign of high-energy phosphate usage after electrical stimulation was a net breakdown of ATP with a subsequent net resynthesis when the rate of phosphocreatine breakdown was high. The average rate of chemical energy usage was more than four times as high during the period of initial force development compared to that during maximum force maintenance. This initial high rate of energy usage was not due only to the internal work done against the series elasticity during force development. Comparison of energetics and mechanics data for the rabbit taenia coli and frog sartorius showed that smooth muscle was 100-fold more economical in maintaining isometric force and probably had a cross-bridge cycle time that was about 150-fold slower. The rate of energy usage during relaxation from an isometric tetanus in smooth muscle was very low, and force was exerted with a lower expenditure of energy during relaxation than during maximum force maintenance. Phosphorylation of the 20,000-dalton light chain of myosin occurred to the extent of 32% during a maximally activated isometric tetanus and was not proportional to the rate of energy usage during different stages of the tetanus. During isometric relaxation, the degree of phosphorylation, rate of energy usage, and active state all decreased more quickly than did active force output.

An epizootic of histoplasmosis duboisii (African histoplasmosis) in an American baboon colony.

Histoplasmosis duboisii, a chronic granulomatous disease caused by Histoplasma capsulatum var. duboisii, was diagnosed in 21 baboons at a large primate colony in San Antonio, Texas. Diagnosis was based on finding 8 to 15 microns-diameter yeast cells in histologic sections. Therapy with drugs was unsuccessful. Surgical removal of lesions was the primary treatment. Epidemiologic data suggest the incubation period to be at least 9 months. The most likely route of infection was oral and happened during grooming by the baboons.

Metabolic characteristics of alpha-toxin-permeabilized smooth muscle.

Rabbit portal veins were permeabilized using Staphylococcus aureus alpha-toxin, and adenosinetriphosphatase (ATPase) was measured as the formation of [3H]ADP, [3H]AMP, and [3H]adenosine from [3H]ATP in the solution bathing the muscle. The resting ATPase (1.96 +/- 0.15 mM/min, n = 13) is approximately 5-10 times higher than that measured in Triton X-100-permeabilized muscles (0.28 +/- 0.01 mM/min, n = 4), with nucleotide accumulating as ADP, AMP, and adenosine. The ATPase activity is also seen when the intact muscle is incubated in a Krebs solution containing 1 mM MgATP (2.76 +/- 0.10 mM/min, n = 73). This suggests that it is due primarily to an ecto-ATPase. The ectoenzyme is capable of hydrolyzing both ATP and ADP, and in both cases there is a higher rate at 3 than at 1 mM nucleotide. The high resting ATPase compromises the control of nucleotide concentrations within the permeabilized tissue even in the presence of an ATP-regenerating system consisting of phosphocreatine (PCr, 35mM) and creatine kinase (1 mg/ml). Treatment of the intact muscle with the ectonucleotidase inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) followed by alpha-toxin permeabilization and inclusion of sodium azide in subsequent solutions reduces the ecto-ATPase by approximately 70%. Addition of PCr and creatine kinase then results in the maintenance of high [ATP] and low [ADP] in the muscle, and importantly, there are no significant changes in [ATP], [ADP], [adenosine/AMP], or the ADP-to-ATP ratio upon activation of the muscle in pCa 4.5. In general, the force output in high Ca2+ increased as the metabolic profile of the muscle improved. When ATPase was measured as the appearance of [32P]Pi from [32P]PCr and [gamma-32P]ATP, the alpha-toxin-permeabilized muscle subjected to the above treatment showed only approximately 30% higher total ATPase under activated conditions compared with the freeze-glycerinated Triton-treated portal vein. The suprabasal ATPase is similar in both preparations. We conclude that the reduction of the basal ATPase by the DIDS-azide treatment permits both rigorous control of nucleotide contents and accurate measurement of ATPase activity in alpha-toxin-permeabilized smooth muscle.