Variability in Nocturnal Nitrogen Oxide Processing and Its Role in Regional Air Quality

Nitrogen oxides in the lower troposphere catalyze the photochemical production of ozone (O3) pollution during the day but react to form nitric acid, oxidize hydrocarbons, and remove O3 at night. A key nocturnal reaction is the heterogeneous hydrolysis of dinitrogen pentoxide, N2O5. We report aircraft measurements of NO3 and N2O5, which show that the N2O5 uptake coefficient, g(N2O5), on aerosol particles is highly variable and depends strongly on aerosol composition, particularly sulfate content. The results have implications for the quantification of regional-scale O3 production and suggest a stronger interaction between anthropogenic sulfur and nitrogen oxide emissions than previously recognized.

Immunofluorescence localization of the unconventional myosin, Myo2p, and the putative kinesin-related protein, Smy1p, to the same regions of polarized growth in Saccharomyces cerevisiae

Myo2 protein (Myo2p), an unconventional myosin in the budding yeast Saccharomyces cerevisiae, has been implicated in polarized growth and secretion by studies of the temperature-sensitive myo2-66 mutant. Overexpression of Smy1p, which by sequence is a kinesin-related protein, can partially compensate for defects in the myo2 mutant (Lillie, S. H. and S. S. Brown, 1992. Nature (Lond.). 356:358-361). We have now immunolocalized Smy1p and Myo2p. Both are concentrated in regions of active growth, as caps at incipient bud sites and on small buds, at the mother-bud neck just before cell separation, and in mating cells as caps on shmoo tips and at the fusion bridge of zygotes. Double labeling of cells with either Myo2p or Smy1p antibody plus phalloidin was used to compare the localization of Smy1p and Myo2p to actin, and by extrapolation, to each other. These studies confirmed that Myo2p and Smy1p colocalize, and are concentrated in the same general regions of the cell as actin spots. However, neither colocalizes with actin. We noted a correlation in the behavior of Myo2p, Smy1p, and actin, but not microtubules, under a number of circumstances. In cdc4 and cdc11 mutants, which produce multiple buds, Myo2p and Smy1p caps were found only in the subset of buds that had accumulations of actin. Mutations in actin or secretory genes perturb actin, Smy1p and Myo2p localization. The rearrangements of Myo2p and Smy1p correlate temporally with those of actin spots during the cell cycle, and upon temperature and osmotic shift. In contrast, microtubules are not grossly affected by these perturbations. Although wild-type Myo2p localization does not require Smy1p, Myo2p staining is brighter when SMY1 is overexpressed. The myo2 mutant, when shifted to restrictive temperature, shows a permanent loss in Myo2p localization and actin polarization, both of which can be restored by SMY1 overexpression. However, the lethality of MYO2 deletion is not overcome by SMY1 overexpression. We noted that the myo2 mutant can recover from osmotic shift (unlike actin mutants; Novick, P., and D. Botstein. 1985. Cell. 40:405-416). We have also determined that the myo2-66 allele encodes a Lys instead of a Glu at position 511, which lies at an actin-binding face in the motor domain.

Purification of profilin from Saccharomyces cerevisiae and analysis of profilin-deficient cells

We have isolated profilin from yeast (Saccharomyces cerevisiae) and have microsequenced a portion of the protein to confirm its identity; the region microsequenced agrees with the predicted amino acid sequence from a profilin gene recently isolated from S. cerevisiae (Magdolen, V., U. Oechsner, G. Müller, and W. Bandlow. 1988. Mol. Cell. Biol. 8:5108-5115). Yeast profilin resembles profilins from other organisms in molecular mass and in the ability to bind to polyproline, retard the rate of actin polymerization, and inhibit hydrolysis of ATP by monomeric actin. Using strains that carry disruptions or deletions of the profilin gene, we have found that, under appropriate conditions, cells can survive without detectable profilin. Such cells grow slowly, are temperature sensitive, lose the normal ellipsoidal shape of yeast cells, often become multinucleate, and generally grow much larger than wild-type cells. In addition, these cells exhibit delocalized deposition of cell wall chitin and have dramatically altered actin distributions.

Cytochalasin inhibits the rate of elongation of actin filament fragments

Submicromolar concentrations of cytochalasin inhibit the rate of assembly of highly purified dictyostelium discoideum actin, using a cytochalasin concentration range in which the final extent of assembly is minimally affected. Cytochalasin D is a more effective inhibitor than cytochalasin B, which is in keeping with the effects that have been reported on cell motility and with binding to a class of high-affinity binding sites from human erythrocyte membranes (Lin and Lin. 1978. J. Biol. CHem. 253:1415; Lin and Lin. 1979. Proc. Natl. Acad. Sci. U.S.A. 76:2345); 5x10(-7) M cytochalasin B lowers it to 70 percent of the control value, whereas 10(-7) M cytochalasin B lowers the rate to 25 percent. Fragments of F-actin were used to increase the rate of assembly fivefold by providing more filament ends on to which monomers could add. Under these conditions, cytochalasin has an even more dramatic effect on the assembly rate; the concentrations of cytochalasin B and cytochalasin D required for half-maximal inhibition are 2x10(-7) M and 10(-8) M, respectively. The assembly rate is most sensitive to cytochalasin when actin assembly is carried out in the absence of ATP (with 3 mM ADP present to stabilize the actin). In this case, the concentrations of cytochalasin B and cytochalasin D required for half-maximal inhibition are 4x10(-8) M and 1x10(-9) M, respectively. A scatchard plot has been obtained using [(3)H]cytochalasin B binding to F-actin in the absence of ATP. The K(d) from this plot (approximately 4x10(-8) M) agrees well with the concentration of cytochalasin B required for half-maximal inhibition of the rate of assembly under these conditions. The number of cytochalasin binding sites is roughly one per F-actin filament, suggesting that cytochalasin has a specific action on actin filament ends.

Mechanism of action of cytochalasin: evidence that it binds to actin filament ends

To test the idea that cytochalasin retards actin assembly by binding to filament ends, we have designed a new assay for cytochalasin binding in which the number of filament ends can be varied independently of the total actin concentration. Actin is reacted with polylysine-coated polystyrene beads to make filament ends (Brown and Spudich, 1979, J. Cell Biol. 80:499-504) and then reacted with [3H]cytochalasin B. We have found that cytochalasin B binds to beads in the presence of actin, and that the number of cytochalasin B binding sites can be varied as a function of the number of filament ends independent of the total actin concentration by varying the bead concentration.

Suppression of a myosin defect by a kinesin-related gene

Motor proteins in cells include myosin, which is actin-based, and kinesin, dynein and dynamin, which are microtubule-based. Several proteins have recently been identified that have amino-acid sequences with similarity to the motor domains of either myosin or kinesin, but are otherwise dissimilar. This has led to the suggestion that these may all be motor proteins, but that they are specialized for moving different cargos. Genetic analysis can address the question of the different functions of these new proteins. Studies of a temperature-sensitive mutation (myo2-66) in a gene of the myosin superfamily (MYO2) have implicated the Myo2 protein (Myo2p) in the process of polarized secretion in yeast (Saccharomyces cerevisiae). To understand more about the role of Myo2p, we have looked for 'multicopy suppressors' (heterologous genes that, when overexpressed, can correct the temperature sensitivity of the myo2-66 mutant). Here we report the identification of such a suppressor (SMY1) that (surprisingly) encodes a predicted polypeptide sharing sequence similarity with the motor portion of proteins in the kinesin superfamily.

Anxiety and depression in the workplace: effects on the individual and organisation (a focus group investigation)

BACKGROUND

While the prevalence of anxiety and depression has increased, little is known of the impact on working life. The aim of this study was to explore the effects of anxiety and depression and the treatment for these conditions on performance and safety in the workplace.

METHOD

Nine focus groups were conducted with employees who had suffered anxiety and depression. A further 3 groups comprised staff from human resources and occupational health. The sample comprised 74 individuals aged 18-60 years, from a range of occupations. Results were presented to a panel of experts to consider the clinical implications.

RESULTS

Workers reported that the symptoms and medication impaired work performance, describing accidents which they attributed to their condition/medication. Respondents were largely unprepared for the fact that the medication might make them feel worse initially. Employees were reluctant to disclose their condition to colleagues due to the stigma attached to mental illness.

LIMITATIONS

People who had experienced problems with managing their symptoms and medication at work are more likely to volunteer to participate in such a study than those who had a satisfactory experience. Also, the researchers had no background information on severity of mental health problems of participants.

CONCLUSIONS

Anxiety and depression were associated with impaired work performance and safety. The authors consider the implications for health care and the management of mental health problems at work.

A 40,000-dalton protein from Dictyostelium discoideum affects assembly properties of actin in a Ca2+-dependent manner

A 40,000-dalton protein that affects the assembly properties of actin in a Ca2+-dependent manner has been purified from Dictyostelium discoideum. Gel filtration chromatography indicates that the native form of this protein is a monomer. A major effect of this protein is to reduce the sedimentability of F-actin in a stoichiometric fashion. Nearly complete loss of sedimentability is observed at ratios of the 40,000-dalton protein to actin of greater than 1:10. At low stoichiometries, this protein can accelerate the rate of actin assembly under certain experimental conditions. These effects of the 40,000-dalton protein on the actin assembly properties described above require calcium ion. The 40,000-dalton protein does not exert its effects by proteolyzing actin. Furthermore, peptide maps demonstrate that this protein is not a proteolytic fragment of actin.

Cooperation between microtubule- and actin-based motor proteins

Organelle transport has been proposed to proceed in two steps: long-range transport along microtubules and local delivery via actin filaments. This model is supported by recent studies of pigment transport in several cell types and transport in neurons, and in several cases, class V myosin has been implicated as the actin-based motor. Mutations in mice (dilute) and yeast (myo2) have also implicated this class of myosin in organelle transport, and genetic interactions in yeast have indicated that a kinesin-related protein (Smy1p) plays a supporting role. This link between members of two different motor superfamilies has now taken a surprising turn: There is evidence for a physical interaction between class V myosins and kinesin or Smy1p in both mice and yeast.

Connectin: cell surface protein that binds both laminin and actin

A purified cell surface receptor protein for laminin (Mr = 70,000) isolated from mouse fibrosarcoma cells binds to actin with specificity and high affinity. This binding was demonstrated both by cosedimentation of the receptor with actin and binding of the receptor to actin immobilized on nitrocellulose filters. Specificity was demonstrated by displacement of 35S-labeled receptor by unlabeled receptor. Scatchard analysis of receptor binding to actin yielded a Kd of 6 X 10(-7) M. The receptor was observed to reduce the viscosity of actin filaments. It also caused the formation of bundles of parallel filaments. This observation and the stoichiometry of binding suggest that the receptor binds along the sides of actin filaments. Based on the ability of this receptor to bind both extracellular laminin and intracellular actin, we have named this protein "connectin." Connectin may be an example of a transmembrane protein that is capable of mediating the interaction of a cell with its extracellular matrix.

Identification of MYO4, a second class V myosin gene in yeast

We have isolated a fourth myosin gene (MYO4) in yeast (Saccharomyces cerevisiae). MYO4 encodes a approximately 170 kDa (1471 amino acid) class V myosin, using the classification devised by Cheney et al. (1993a; Cell Motil. Cytoskel. 24, 215–223); the motor domain is followed by a neck region containing six putative calmodulin-binding sites and a tail with a short potential ‘coiled-coil’ domain. A comparison with other myosins in GenBank reveals that Myo4 protein is most closely related to the yeast Myo2 protein, another class V myosin. Deletion of MYO4 produces no detectable phenotype, either alone or in conjunction with mutations in myo2 or other myosin genes, the actin gene, or secretory genes. However, overexpression of MYO4 or MYO2 results in several morphological abnormalities, including the formation of short strings of unseparated cells in diploid strains, or clusters of cells in haploid strains. Alterations of MYO4 or MYO2 indicate that neither the motor domains nor tails of these myosins are required to confer the overexpression phenotype, whereas the neck region may be required. Although this phenotype is similar to that seen upon MYO1 deletion, we provide evidence that the overexpression of Myo4p or Myo2p is not simply interfering with Myo1p function.

A furanocoumarin-free grapefruit juice establishes furanocoumarins as the mediators of the grapefruit juice-felodipine interaction

BACKGROUND

Grapefruit juice (GFJ) enhances the systemic exposure of numerous CYP3A4 drug substrates, including felodipine, by inhibiting intestinal (but not hepatic) first-pass metabolism. Furanocoumarins have been identified as major CYP3A4 inhibitors contained in the juice, but their contribution to the GFJ effect in vivo remains unclear.

OBJECTIVE

To ascertain whether furanocoumarins mediate the GFJ-felodipine interaction, a furanocoumarin-free GFJ was created and tested against orange juice and the original GFJ with respect to the oral pharmacokinetics of felodipine.

DESIGN

With the use of food-grade solvents and absorption resins, furanocoumarins were removed (approximately 99%) from whole GFJ, whereas other major ingredients (flavonoids) were retained. In an open, 3-way, randomized crossover design, 18 healthy volunteers ingested felodipine (10 mg) with 1 of the 3 juices (240 mL). Blood was collected over 24 h. At least 1 wk elapsed between juice treatments.

RESULTS

The median and range of the area under the curve and the maximum concentration of felodipine were significantly (P < 0.001) greater with consumption of GFJ [110 (range: 58-270) nmol . h/L and 21 (7.6-50) nmol/L, respectively] than with that of orange juice [54 (29-150) nmol . h/L and 7.6 (3.4-13.9) nmol/L, respectively] or furanocoumarin-free GFJ [48 (23-120) nmol . h/L and 8.3 (3.0-16.6) nmol/L, respectively]. GFJ, orange juice, and furanocoumarin-free GFJ did not differ significantly (P > 0.09) in median time to reach maximum plasma concentration [2.5 (1.5-6), 2.8 (1.5-4), and 2.5 (2-6) h, respectively] or terminal half-life [6.6 (4.2-13.6), 7.8 (4.4-13.2), and 6.8 (2.6-14.4) h, respectively].

CONCLUSION

Furanocoumarins are the active ingredients in GFJ responsible for enhancing the systemic exposure of felodipine and probably other CYP3A4 substrates that undergo extensive intestinal first-pass metabolism.

Reliability of information abstracted from patients' medical records

Two recent studies by the Institute of Medicine on the reliability of hospital discharge data abstracted from patients' medical records raise serious questions about the adequacy of information on diagnoses and procedures. The findings are particularly timely, since increasingly important decisions about the content of medical care and levels of reimbursement may be based on such information. A series of recommendations are offered to guide the use and improvement of abstracted medical record information.

Spatial and temporal control of nonmuscle myosin localization: identification of a domain that is necessary for myosin filament disassembly in vivo

Myosin null mutants of Dictyostelium are defective for cytokinesis, multicellular development, and capping of surface proteins. We have used these cells as transformation recipients for an altered myosin heavy chain gene that encodes a protein bearing a carboxy-terminal 34-kD truncation. This truncation eliminates threonine phosphorylation sites previously shown to control filament assembly in vitro. Despite restoration of growth in suspension, development, and ability to cap cell surface proteins, these delta C34-truncated myosin transformants display severe cytoskeletal abnormalities, including excessive localization of the truncated myosin to the cortical cytoskeleton, impaired cell shaped dynamics, and a temporal defect in myosin dissociation from beneath capped surface proteins. These data demonstrate that the carboxy-terminal domain of myosin plays a critical role in regulating the disassembly of the protein from contractile structures in vivo.

Caffeine or theophylline for neonatal apnoea?

Caffeine, in the dose usually recommended (12.5 mg/kg loading dose and 3 mg/kg daily maintenance), and a higher dose regimen (25 mg/kg loading and 6 mg/kg daily maintenance), was compared with theophylline (7.5 mg/kg loading and 3 mg/kg thrice daily maintenance). The study was a randomised controlled trial in the treatment of a group of 44 infants of less than 31 weeks' gestation (mean gestational age 28.3 weeks) who were suffering from frequent apnoeic attacks. All three regimens produced a significant reduction in apnoeic attacks within 24 hours, but only the higher dose caffeine and theophylline groups showed a significant improvement in apnoea within eight hours. The use of caffeine for the treatment of neonatal apnoea is recommended, because a once daily dose is more easily administered, and because it was found that plasma concentrations were more predictable than those of theophylline. If used in very preterm infants, however, its is suggested that a higher dose regimen than that previously recommended be used to achieve a faster response.

Myosins in yeast

It has been a banner year for the study of yeast myosins. Thanks to the completion of the Saccharomyces cerevisiae genome project, it is now known that budding yeast contains a total of five myosins. Furthermore, functions have been newly ascribed to several of them: two have been implicated in endocytosis, and another has been implicated in generating asymmetry between mother and daughter cells.

Smy1p, a kinesin-related protein that does not require microtubules

We have previously reported that a defect in Myo2p, a myosin in budding yeast (Saccharomyces cerevisiae), can be partially corrected by overexpression of Smy1p, which is by sequence a kinesin-related protein (Lillie, S.H., and S.S. Brown. 1992. Nature. 356:358- 361). Such a functional link between putative actin- and microtubule-based motors is surprising, so here we have tested the prediction that Smy1p indeed acts as a microtubule-based motor. Unexpectedly, we found that abolition of microtubules by nocodazole does not interfere with the ability of Smy1p to correct the mutant Myo2p defect, nor does it interfere with the ability of Smy1p to localize properly. In addition, other perturbations of microtubules, such as treatment with benomyl or introduction of tubulin mutations, do not exacerbate the Myo2p defect. Furthermore, a mutation in SMY1 strongly predicted to destroy motor activity does not destroy Smy1p function. We have also observed a genetic interaction between SMY1 and two of the late SEC mutations, sec2 and sec4. This indicates that Smy1p can play a role even when Myo2p is wild type, and that Smy1p acts at a specific step of the late secretory pathway. We conclude that Smy1p does not act as a microtubule-based motor to localize properly or to compensate for defective Myo2p, but that it must instead act in some novel way.

Contribution of human-related sources to indoor volatile organic compounds in a university classroom

Although significant progress has been made in understanding the sources and chemistry of indoor volatile organic compounds (VOCs) during the past decades, much is unknown about the role of humans in indoor air chemistry. In the spring of 2014, we conducted continuous measurements of VOCs using a proton transfer reaction mass spectrometer (PTR-MS) in a university classroom. Positive matrix factorization (PMF) of the measured VOCs revealed a 'human influence' component, which likely represented VOCs produced from human breath and ozonolysis of human skin lipids. The concentration of the human influence component increased with the number of occupants and decreased with ventilation rate in a similar way to CO₂ , with an average contribution of 40% to the measured daytime VOC concentration. In addition, the human skin lipid ozonolysis products were observed to correlate with CO₂ and anticorrelate with O₃ , suggesting that reactions on human surfaces may be important sources of indoor VOCs and sinks for indoor O₃ . Our study suggests that humans can substantially affect VOC composition and oxidative capacity in indoor environments.

Acidaemia and salicylate poisoning in adults

A review of the arterial acid-base status on admission to hospital of 62 adults with severe salicylate poisoning showed that arterial pH was normal or high in most patients, but low in 8. The mean plasma salicylate concentrations of the acidaemic and nonacidaemic patients were similar and the difference in arterial pH was associated with a marked fall in standard bicarbonate in the former group. No significant difference of Pco(2) between the two groups was found, and hence no simple relationship exists between hypocapnia and the development of acidaemia in salicylate poisoning. Acidaemia is shown to be associated with impaired consciousness and to carry a grave prognosis.

Quantitative analysis of the principle soy isoflavones genistein, daidzein and glycitein, and their primary conjugated metabolites in human plasma and urine using reversed-phase high-performance liquid chromatography with ultraviolet detection

Soy isoflavones are becoming of increasing interest as nutritional agents which can be used to combat osteoporosis and hyperlipidemia, and are also being considered as potential cancer chemopreventive compounds. However, prior to their formulation and distribution as therapeutic agents, thorough pharmacokinetic and toxicological assessment needs to be completed in men and women in a variety of health conditions in order to ensure their therapeutic efficacy and safety. At this time, studies of purified soy isoflavones are possible, and are being designed to fully evaluate the pharmacological utility of these preparations. In support of these studies, quantitative analysis of soy isoflavones in biological fluids can be accomplished with a wide variety of methods and analytical instrumentation. However, the relatively ubiquitous presence of high-performance liquid chromatography with ultraviolet detection (HPLC-UV) in most analytical laboratories, the relative ease of its operation, and the lesser expense of this instrumentation as compared to more sophisticated techniques such as liquid chromatography-mass spectrometry, offers some distinct advantages for its use in pharmacokinetic studies. In this manuscript, the development and validation of an HPLC-UV method for the quantitation of the principal soy isoflavones, genistein, daidzein, and glycitein, and their primary metabolites, in human plasma and urine is described. This analytical approach allows for pharmacologically relevant concentrations of the analytes and their principle metabolites to be detected, and has been validated in close agreement with the US Food and Drug Administration's guidelines for the validation of methods to be used in support of pharmacokinetic studies.