Search

During the CalNex (California Research at the Nexus of Air Quality and Climate Change) field study in May-June 2010, measurements of volatile organic compounds (VOCs) were performed in the Los Angeles (LA) basin onboard a NOAA research aircraft and at a ground site located in Pasadena. A weekday-weekend effect in ozone, caused by lower NOx emissions due to reduced diesel truck traffic in the weekends, has been previously observed in Los Angeles and other cities. Measurements in the Caldecott tunnel show that emission ratios of VOCs do not vary with the day of the week, but measurements during CalNex2010 show a VOC weekday-weekend effect through faster photochemical processing at lower ambient NOx mixing ratios. Ambient VOC enhancement ratios of long-lived species such as benzene are the same between weekdays and weekends, whereas enhancement ratios of short-lived species, such as trimethyl benzene, are up to a factor of three lower on weekends. Based upon the observed differences in VOC enhancement ratios to CO, we determine that photochemical processing was on average 65%-75% faster on weekends during CalNex2010, which indicates that ambient OH radical concentrations were larger by this factor causing the observed change in VOC composition. A box model calculation based on the Master Chemical Mechanism was used to verify the increase in photochemical processing in the weekends. Key PointsSpatial and temporal photochemical processing in Los AngelesVOC weekday-weekend effectFaster photochemistry in weekends ©2013. American Geophysical Union. All Rights Reserved.

In April-July 2008, intensive measurements were made of atmospheric composition and chemistry in Sabah, Malaysia, as part of the "Oxidant and particle photochemical processes above a South-East Asian tropical rainforest" (OP3) project. Fluxes and concentrations of trace gases and particles were made from and above the rainforest canopy at the Bukit Atur Global Atmosphere Watch station and at the nearby Sabahmas oil palm plantation, using both ground-based and airborne measurements. Here, the measurement and modelling strategies used, the characteristics of the sites and an overview of data obtained are described. Composition measurements show that the rainforest site was not significantly impacted by anthropogenic pollution, and this is confirmed by satellite retrievals of NO2 and HCHO. The dominant modulators of atmospheric chemistry at the rainforest site were therefore emissions of BVOCs and soil emissions of reactive nitrogen oxides. At the observed BVOC:NOx volume mixing ratio (∼100 pptv/pptv), current chemical models suggest that daytime maximum OH concentrations should be ca. 105 radicals cm-3, but observed OH concentrations were an order of magnitude greater than this. We confirm, therefore, previous measurements that suggest that an unexplained source of OH must exist above tropical rainforest and we continue to interrogate the data to find explanations for this.

The atmospheric oxidation of organics occurs primarily via reaction cycles involving gas phase radical species, catalysed by nitric oxide (NO), which result in the production of secondary pollutants such as ozone. For these oxidation cycles to occur, they must be initialized by a primary radical, i.e., a radical formed from non-radical precursors. Once formed, these primary radicals can result in the oxidation of organic compounds to produce peroxy radicals that, providing sufficient NO is present, can re-generate "secondary" radicals which can go on to oxidize further organics. Thus, one primary radical can result in the catalytic oxidation of multiple organics. Although the photolysis of ozone in the presence of water vapor to form two hydroxyl (OH) radicals is accepted as the dominant tropospheric primary radical source, multiple other primary radical sources exist and can dominate in certain environments. The chemical reactivity of different radicals to organic and inorganic compounds can be very different, however, and how these differences in radical chemistry impact atmospheric organic oxidation under different atmospheric conditions has not been previously demonstrated. In this work, we use a series of model simulations to investigate the impact of the chemical reactivity of the primary radical on the effectiveness in initializing organic oxidation and thus the production of the secondary pollutant ozone. We compare the chemistries of the OH and atomic chlorine (Cl) radicals and their effectiveness at initializing organic oxidation under different nitrogen oxide and organic concentrations. The OH radical is the dominant tropospheric radical, with both primary and secondary sources. In contrast, Cl has primary sources that show significant spatial heterogeneity throughout the troposphere but is not typically regenerated in catalytic cycles. Both primary OH and Cl can initiate organic oxidation, but this work shows that the relative effectiveness with which they oxidize organics and produce ozone depends on their balance of propagation vs termination reactions which is in turn determined by the chemical environment in which they are produced. In particular, our work shows that in high NOx radical-limited environments, like those found in many urban areas, Cl will be more efficient at oxidizing organics than OH., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Delhi, India, suffers from periods of very poor air quality, but little is known about the chemical production of secondary pollutants in this highly polluted environment. During the postmonsoon period in 2018, extremely high nighttime concentrations of NO x (NO and NO 2 ) and volatile organic compounds (VOCs) were observed, with median NO x mixing ratios of ∼200 ppbV (maximum of ∼700 ppbV). A detailed chemical box model constrained to a comprehensive suite of speciated VOC and NO x measurements revealed very low nighttime concentrations of oxidants, NO 3 , O 3 , and OH, driven by high nighttime NO concentrations. This results in an atypical NO 3 diel profile, not previously reported in other highly polluted urban environments, significantly perturbing nighttime radical oxidation chemistry. Low concentrations of oxidants and high nocturnal primary emissions coupled with a shallow boundary layer led to enhanced early morning photo-oxidation chemistry. This results in a temporal shift in peak O 3 concentrations when compared to the premonsoon period (12:00 and 15:00 local time, respectively). This shift will likely have important implications on local air quality, and effective urban air quality management should consider the impacts of nighttime emission sources during the postmonsoon period., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Particulate nitrate ([Formula: see text]) has long been considered a permanent sink for NO x (NO and NO 2 ), removing a gaseous pollutant that is central to air quality and that influences the global self-cleansing capacity of the atmosphere. Evidence is emerging that photolysis of [Formula: see text] can recycle HONO and NO x back to the gas phase with potentially important implications for tropospheric ozone and OH budgets; however, there are substantial discrepancies in "renoxification" photolysis rate constants. Using aircraft and ground-based HONO observations in the remote Atlantic troposphere, we show evidence for renoxification occurring on mixed marine aerosols with an efficiency that increases with relative humidity and decreases with the concentration of [Formula: see text], thus largely reconciling the very large discrepancies in renoxification photolysis rate constants found across multiple laboratory and field studies. Active release of HONO from aerosol has important implications for atmospheric oxidants such as OH and O 3 in both polluted and clean environments.

A summary of the catalytic synthesis and reactivity of N -silylated amines is presented. Dehydrocoupling of amines with silanes, hydrosilylation of imines and dealkenylative coupling of amines with vinylsilanes are three ways to achieve their catalytic syntheses. The resultant N -silylamines serve as substrates in a variety of reactions, including C-N and C-C bond forming reactions, and are preferred in transformations because of the facile Si-N hydrolytic cleavage to reveal free amine products upon reaction completion. This review highlights the distinct electronic properties of N -silyl amines, N -silyl imines and N -silyl enamines that result in complementary reactivity to that of parent non-silyl variants.

Oxidation of isoprene by nitrate radicals (NO 3 ) or by hydroxyl radicals (OH) under high NO x conditions forms a substantial amount of organonitrates (ONs). ONs impact NO x concentrations and consequently ozone formation while also contributing to secondary organic aerosol. Here we show that the ONs with the chemical formula C 4 H 7 NO 5 are a significant fraction of isoprene-derived ONs, based on chamber experiments and ambient measurements from different sites around the globe. From chamber experiments we found that C 4 H 7 NO 5 isomers contribute 5%-17% of all measured ONs formed during nighttime and constitute more than 40% of the measured ONs after further daytime oxidation. In ambient measurements C 4 H 7 NO 5 isomers usually dominate both nighttime and daytime, implying a long residence time compared to C 5 ONs which are removed more rapidly. We propose potential nighttime sources and secondary formation pathways, and test them using a box model with an updated isoprene oxidation scheme., Competing Interests: The authors declare no conflicts of interest relevant to this study., (© 2022. The Authors.)

The formation of isoprene nitrates (IsN) can lead to significant secondary organic aerosol (SOA) production and they can act as reservoirs of atmospheric nitrogen oxides. In this work, we estimate the rate of production of IsN from the reactions of isoprene with OH and NO 3 radicals during the summertime in Beijing. While OH dominates the loss of isoprene during the day, NO 3 plays an increasingly important role in the production of IsN from the early afternoon onwards. Unusually low NO concentrations during the afternoon resulted in NO 3 mixing ratios of ca. 2 pptv at approximately 15:00, which we estimate to account for around a third of the total IsN production in the gas phase. Heterogeneous uptake of IsN produces nitrooxyorganosulfates (NOS). Two mono-nitrated NOS were correlated with particulate sulfate concentrations and appear to be formed from sequential NO 3 and OH oxidation. Di- and tri-nitrated isoprene-related NOS, formed from multiple NO 3 oxidation steps, peaked during the night. This work highlights that NO 3 chemistry can play a key role in driving biogenic-anthropogenic interactive chemistry in Beijing with respect to the formation of IsN during both the day and night.

Technology is pervasive in society and reaches across all age-groups. The use of technology in youth has risen steadily in the past two decades through access to television, internet, computers, social media, and gaming in various formats. Due to this increased exposure and access, concerns have developed among mental health and healthcare providers regarding gaming addiction in youth. The American Psychiatric Association mentioned internet gaming disorder in the 2013 publication of the Diagnostic and Statistical Manual of Mental Disorders (5th ed.). While not recognized as a specific diagnosis at the time of publication, there was a call for further research and evaluation of this phenomenon. Research indicates there are negative impacts on academic performance, social development, and self-concept in game-addicted youth. The purpose of this article is to provide the school nurse with information needed to recognize and care for youth at risk for and those experiencing gaming addiction. The school nurse is poised to provide nursing care in the school setting to educate, prevent, and help manage youth with gaming addiction risks and experiences, as part of an interdisciplinary team.

Hydroaminoalkylation is a 100% atom economic method for forming Csp3-Csp3 bonds through C-H activation α to an amine and subsequent reaction with an alkene. When catalyzed by early transition metals, this reaction allows for alternative disconnections for the synthesis of structurally complex amines. This method avoids the installation of protecting groups or directing groups and does not require added oxidants, or photoredox catalysts. In this feature article, we discuss the various selectively substituted amines that can be accessed by hydroaminoalkylation, with a special focus on the development of early transition metal catalysts for their rapid, step and atom efficient assembly.

The design of an easy to use catalyst system for the regio- and diastereoselective intermolecular hydroaminoalkylation of alkenes with secondary amines is reported. The method utilizes commercially available ligands and tantalum starting materials, and does not require the isolation of air and water sensitive organometallic complexes. The in situ prepared catalyst is active toward a variety of secondary amine substrates, including those with ethyl substituents which yield α- and β-alkylated amines as a single diastereomer. This catalytic transformation can be used to prepare amines containing functionality that promotes ring closure to achieve the diastereoselective synthesis of di- and trialkylated N-heterocycles.

Low cost air pollution sensors have substantial potential for atmospheric research and for the applied control of pollution in the urban environment, including more localized warnings to the public. The current generation of single-chemical gas sensors experience degrees of interference from other co-pollutants and have sensitivity to environmental factors such as temperature, wind speed and supply voltage. There are uncertainties introduced also because of sensor-to-sensor response variability, although this is less well reported. The sensitivity of Metal Oxide Sensors (MOS) to volatile organic compounds (VOCs) changed with relative humidity (RH) by up to a factor of five over the range of 19-90% RH and with an uncertainty in the correction of a factor of two at any given RH. The short-term (second to minute) stabilities of MOS and electrochemical CO sensor responses were reasonable. During more extended use, inter-sensor quantitative comparability was degraded due to unpredictable variability in individual sensor responses (to either measurand or interference or both) drifting over timescales of several hours to days. For timescales longer than a week identical sensors showed slow, often downwards, drifts in their responses which diverged across six CO sensors by up to 30% after two weeks. The measurement derived from the median sensor within clusters of 6, 8 and up to 21 sensors was evaluated against individual sensor performance and external reference values. The clustered approach maintained the cost competitiveness of a sensor device, but the median concentration from the ensemble of sensor signals largely eliminated the randomised hour-to-day response drift seen in individual sensors and excluded the effects of small numbers of poorly performing sensors that drifted significantly over longer time periods. The results demonstrate that for individual sensors to be optimally comparable to one another, and to reference instruments, they would likely require frequent calibration. The use of a cluster median value eliminates unpredictable medium term response changes, and other longer term outlier behaviours, extending the likely period needed between calibration and making a linear interpolation between calibrations more appropriate. Through the use of sensor clusters rather than individual sensors, existing low cost technologies could deliver significantly improved quality of observations.

Low cost pollution sensors have been widely publicized, in principle offering increased information on the distribution of air pollution and a democratization of air quality measurements to amateur users. We report a laboratory study of commonly-used electrochemical sensors and quantify a number of cross-interferences with other atmospheric chemicals, some of which become significant at typical suburban air pollution concentrations. We highlight that artefact signals from co-sampled pollutants such as CO2 can be greater than the electrochemical sensor signal generated by the measurand. We subsequently tested in ambient air, over a period of three weeks, twenty identical commercial sensor packages alongside standard measurements and report on the degree of agreement between references and sensors. We then explore potential experimental approaches to improve sensor performance, enhancing outputs from qualitative to quantitative, focusing on low cost VOC photoionization sensors. Careful signal handling, for example, was seen to improve limits of detection by one order of magnitude. The quantity, magnitude and complexity of analytical interferences that must be characterised to convert a signal into a quantitative observation, with known uncertainties, make standard individual parameter regression inappropriate. We show that one potential solution to this problem is the application of supervised machine learning approaches such as boosted regression trees and Gaussian processes emulation.

The purpose of this investigation was to systematically examine the variability associated with temporally-oriented invertebrate data collected by citizen scientists and consider the value of such data for use in stream management. Variability in invertebrate data was estimated for three sources of variation: sampling, within-reach spatial and long-term temporal. Long-term temporal data were also evaluated using ordinations and an Index of Biotic Integrity (IBI). Through two separate investigations over an 11-year study period, participants collected more than 400 within-reach samples during 44 sampling events at three streams in the western United States. Within-reach invertebrate abundance coefficient of variation (CV) ranged from 0.44-0.50 with approximately 62% of the observed variation strictly due to sampling. Long-term temporal CV ranged from 0.31-0.36 with 27-30% of the observed variation in invertebrate abundance related to climate conditions (El Niño strength) and sampling year. Ordinations showed that citizen-generated assemblage data could reliably detect differences between study streams and seasons. IBI scores were significantly different between streams but not seasons. The findings of this study suggest that citizen data would likely detect a change in mean invertebrate density greater than 50% and would also be useful for monitoring changes in assemblage. The information presented here will help stream managers interpret and evaluate changes to the stream invertebrate community detected by citizen-based programs., Competing Interests: The author has declared that no competing interests exist.

The secondary organic aerosol (SOA) mass yields from NO3 oxidation of a series of biogenic volatile organic compounds (BVOCs), consisting of five monoterpenes and one sesquiterpene (α-pinene, β-pinene, Δ-3-carene, limonene, sabinene, and β-caryophyllene), were investigated in a series of continuous flow experiments in a 10 m(3) indoor Teflon chamber. By making in situ measurements of the nitrate radical and employing a kinetics box model, we generate time-dependent yield curves as a function of reacted BVOC. SOA yields varied dramatically among the different BVOCs, from zero for α-pinene to 38-65% for Δ-3-carene and 86% for β-caryophyllene at mass loading of 10 μg m(-3), suggesting that model mechanisms that treat all NO3 + monoterpene reactions equally will lead to errors in predicted SOA depending on each location's mix of BVOC emissions. In most cases, organonitrate is a dominant component of the aerosol produced, but in the case of α-pinene, little organonitrate and no aerosol is formed.

The United States is now experiencing the most rapid expansion in oil and gas production in four decades, owing in large part to implementation of new extraction technologies such as horizontal drilling combined with hydraulic fracturing. The environmental impacts of this development, from its effect on water quality to the influence of increased methane leakage on climate, have been a matter of intense debate. Air quality impacts are associated with emissions of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs), whose photochemistry leads to production of ozone, a secondary pollutant with negative health effects. Recent observations in oil- and gas-producing basins in the western United States have identified ozone mixing ratios well in excess of present air quality standards, but only during winter. Understanding winter ozone production in these regions is scientifically challenging. It occurs during cold periods of snow cover when meteorological inversions concentrate air pollutants from oil and gas activities, but when solar irradiance and absolute humidity, which are both required to initiate conventional photochemistry essential for ozone production, are at a minimum. Here, using data from a remote location in the oil and gas basin of northeastern Utah and a box model, we provide a quantitative assessment of the photochemistry that leads to these extreme winter ozone pollution events, and identify key factors that control ozone production in this unique environment. We find that ozone production occurs at lower NOx and much larger VOC concentrations than does its summertime urban counterpart, leading to carbonyl (oxygenated VOCs with a C = O moiety) photolysis as a dominant oxidant source. Extreme VOC concentrations optimize the ozone production efficiency of NOx. There is considerable potential for global growth in oil and gas extraction from shale. This analysis could help inform strategies to monitor and mitigate air quality impacts and provide broader insight into the response of winter ozone to primary pollutants.

The purpose of this study was to determine if mobile phones interfere with adolescent sleep. We conducted a pilot test in a pediatric primary care practice of 454 patients, half female (51.2%), 12 to 20 years old (mean = 15) attending a well-child visit. Adolescents completed paper-and-pencil surveys in the waiting room. More than half took their mobile phone to bed (62.9%) and kept it turned on while sleeping (56.8%). Almost half used their phone as their alarm (45.7%). More than one-third texted after going to bed (36.7%). Two or more times per week, 7.9% were awakened by a text after going to sleep.

We present a sensitive, compact detector that measures total reactive nitrogen (NOy), as well as NO2, NO, and O3. In all channels, NO2 is directly detected by laser diode based cavity ring-down spectroscopy (CRDS) at 405 nm. Ambient O3 is converted to NO2 in excess NO for the O3 measurement channel. Likewise, ambient NO is converted to NO2 in excess O3. Ambient NOy is thermally dissociated at ∼700 °C to form NO2 or NO in a heated quartz inlet. Any NO present in ambient air or formed from thermal dissociation of other reactive nitrogen compounds is converted to NO2 in excess O3 after the thermal converter. We measured thermal dissociation profiles for six of the major NOy components and compared ambient measurements with other instruments during field campaigns in Utah and Alabama. Alabama measurements were made in a rural location with high biogenic emissions, and Utah measurements were made in the wintertime in unusual conditions that form high ozone levels from emissions related to oil and gas production. The NOy comparison in Alabama, to an accepted standard measurement method (a molybdenum catalytic converter/chemiluminescence instrument), agreed to within 12%, which we define as an upper limit to the accuracy of the NOy channel. The 1σ precision is <30 pptv at 1 s and <4 pptv at 1 min time resolution for all measurement channels. The accuracy is 3% for the NO2 and O3 channels and 5% for the NO channel. The precision and accuracy of this instrument make it a versatile alternative to standard chemiluminescence-based NOy instruments.

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.

A new bacterium, Saccharopolyspora pogona (NRRL30141) was discovered which produced a series of very potent insecticidal compounds structurally related to the 'classical' (i.e., C-21-ethyl) spinosyns. A series of fermentations gave sufficient extract to allow the isolation and characterization of a total of 31 new metabolites. The majority of these compounds contained a but-1-enyl group at C-21 of the macrolide in place of the ethyl group in the 'classical' spinosyn series, corresponding to an additional acetate group incorporated during their biosynthesis. Additionally a variety of other new functionality was seen including hydroxylations, several novel forosamine sugar replacements, and a novel 14-membered macrolide ring analog.

Some bovine enteric caliciviruses form a new genus in the family Caliciviridae. In this study, Bayesian phylogenetic analysis of 31 full length capsid sequences from Europe, North America and Asia revealed that this new genus had four currently circulating lineages that showed both temporal and geographical distribution. These groupings were supported by the distribution of the frequency of pair-wise distances. However, the nucleotide and amino acid heterogeneity was low, with a maximum nucleotide and amino acid divergence of 16.7% and 8.4%, respectively. Most variability was found between amino acid residues 288 and 420 of the capsid protein and the sequence motifs observed in this region supported the division of the four lineages. Homology modelling using the structure of the San Miguel sea lion capsid indicated that most variation occurred in the predicted P2 domain and thus, may affect antigenic sites on the surface of the capsid of this newly described genus.

Many compounds, including some pesticides, contain structural centres of asymmetry, which convey the property of a type of stereoisomerism known as chirality. Such compounds can exist in two or more forms, depending on the number of chiral atoms and are termed stereoisomers or enantiomers. Stereoisomers of a particular compound can have different biological properties; one such of particular importance for toxicological evaluation, is the potential for differences in metabolic disposal of and binding of stereoisomers to molecular targets in the cell. The combination of differential metabolism of chiral organophosphorus (OP) pesticides and opposing stereoselectivity of inhibition of neuropathy target esterase (NTE) and acetylcholinesterase (AChE) can affect the value of the hen test, performed to OECD guidelines, in predicting the potential to cause organophosphate-induced delayed polyneuropathy (OPIDP) in humans. This is a mixed central and sensory and motor neuropathy. The experimental data on structural analogues of the pesticide methamidophos and the evidence for stereoselective OPIDP are reviewed and a model is given demonstrating how the properties of a chiral OP can result in the neuropathic potential not being detected by the standard hen test. A strategy for the assessment of a racemic mixture comprised of two OP enantiomers for the potential to induce OPIDP is outlined. The strategy uses information from structure activity relationships (SAR), in vitro tests and in vivo tests to allow risk assessment decisions to be made. It is suggested that the potential for stereoselective toxicity of pesticides should be routinely considered in regulatory assessments.

The possible involvement of alpha-MSH-like peptides in the regenerative response of peripheral nerves was investigated with a competitive antagonist of alpha-MSH, the synthetic hexapeptide [D-Trp7,Ala8,D-Phe10)alpha-MSH(6-11)-amide. Subcutaneous administration of the alpha-MSH antagonist during the first 10 days following sciatic nerve crush significantly decreased functional recovery as measured by the foot flick withdrawal test and the walking pattern analysis. Hypophysectomy delayed both the initial sprouting response and the outgrowth rate after major caudal nerve crush. When hypophysectomized rats were treated with the alpha-MSH antagonist, a further delay in initial sprouting was observed, whereas the outgrowth rate of nerve fibers was not affected. These results suggest that 1) endogenous alpha-MSH-like peptides stimulate nerve outgrowth following peripheral nerve injury and 2) alpha-MSH-like peptides derived from a source other than the pituitary may contribute to the physiological stimulus leading to sprouting.

The neurotrophic peptide Org 2766 accelerates the regeneration of peripheral nerves. Although the mechanism of action of this neuropeptide is not yet understood, functional, pharmacological, and morphological evidence has demonstrated that Org 2766 exerts its beneficial effect during the early stages of nerve regeneration. The induction of some members of the Immediate Early Gene (IEG) family such as c-jun and c-fos is one of the first molecular events following peripheral nerve damage. The Fos and Jun proteins act as a transcription factor and may stimulate the expression of a number of genes implicated in nerve regeneration. We examined whether Org 2766 stimulates nerve regeneration by enhancing or prolonging the expression of c-fos mRNA. Following a crush lesion of the sciatic nerve, the expression of c-fos mRNA was induced in the spinal cord and in the damaged nerve at 30 min following injury in untreated animals as demonstrated with Northern blot. No effect of the crush lesion was observed in dorsal root ganglia (DRG). The induction of c-fos mRNA in the damaged nerve was more robust as compared to the relatively small induction observed in the spinal cord. With in situ hybridization an increase in c-fos mRNA expression both in the dorsal and in the ventral horn of the spinal cord was demonstrated at 30 min post-lesion. In the distal sciatic nerve portion the expression of c-fos mRNA was predominantly localized around Schwann cell nuclei at 30 min after nerve crush. The effect of Org 2766 treatment on the expression of c-fos mRNA was investigated using semiquantitative dot blots.(ABSTRACT TRUNCATED AT 250 WORDS)

Six pediatric orthopaedic specialists and six senior orthopaedic residents independently classified 60 radiographs of infantile tibia vara according to the six-stage Langenskiöld classification. Correlation coefficients and percentage agreement were similar in both groups. Interobserver agreement was good for early and late stages, but was poor for intermediate stages. We caution clinicians that small but frequent discrepancies in radiographic staging impart a dubious prognostic value to the Langenskiöld classification.

We have detected mRNA for B-50 (GAP-43, pp46, F1, neuromodulin), which was originally believed to be a neuron-specific protein, in non-neuronal cells in the rat sciatic nerve. In control rats, the level of B-50 mRNA in sciatic nerve tissue was much lower than in dorsal root ganglia. Following nerve crush or transection, the expression of B-50 mRNA in the distal nerve stump increased dramatically between 1 and 2 days post-injury. The B-50 mRNA levels in the distal stump of crushed nerves remained elevated for up to 4 weeks and subsequently returned to control levels after 7 weeks. In contrast, after nerve transection B-50 mRNA levels in the distal nerve portion continued to increase up to 7 weeks post-lesion. No changes in the levels of the B-50 transcript were observed in the proximal portion of either crush-lesioned or transected sciatic nerves. In situ hybridization demonstrated B-50 mRNA associated with Schwann cells in the distal nerve stump. The observation that Schwann cells are capable of producing B-50 mRNA was confirmed by Northern blot analysis of total RNA isolated from primary Schwann cell cultures. Taken together, these data show the expression of B-50 mRNA by Schwann cells and the up-regulation of B-50 mRNA in reactive Schwann cells upon loss of axonal contact.

Neuropeptides related to alpha-melanocyte-stimulating hormone (alpha-MSH) stimulate nerve outgrowth following peripheral nerve injury and may play an important physiological role in peripheral nerve regeneration. The mechanism of action underlying the neurotrophic effect of pharmacologically administered alpha-MSH is unknown. Here we investigate the hypothesis that reexpression of the proopiomelanocortin (POMC) gene, the prohormone of alpha-MSH/adrenocorticotropic hormone (ACTH)-like peptides, is part of the endogenous repertoire of peripheral nerve responses following injury. The effect of sciatic nerve crush on the expression of POMC mRNA between 0.5 h and 14 days after crush was investigated using polymerase chain reaction (PCR) and Northern blot analysis. The presence of a POMC transcript in dorsal root ganglia (DRG), spinal cord and in the sciatic nerve at the crush site could be demonstrated in both control and lesioned animals by PCR using primers located in exon 1 and 3 of the POMC gene. Minute quantities of two POMC transcripts (1200 nt and 800 nt) could be detected by Northern blot analysis of total RNA prepared from DRG, spinal cord and the sciatic nerve of control animals and of animals subjected to nerve crush. POMC mRNA expression was, however, not increased following nerve crush. Probes specific for exons 1 and 2 or specific for exon 3 of the POMC gene were employed to demonstrate that the 800 nt transcript represents the truncated POMC mRNA previously shown to be present in extra-pituitary tissue. The larger 1200 nt transcript comigrates with the full length POMC mRNA expressed in the pituitary gland. The present results demonstrate the expression of small amounts of POMC mRNA in all compartments of the sciatic nerve. The absence of an induction of POMC expression in response to nerve crush suggests that the stimulating effect of exogenously applied alpha-MSH does not mimic a POMC derived neurotrophic peptide induced in the nerve following nerve injury.

Acrylamide causes degeneration of sensory nerve axons in a range of experimental animals and in humans. Evidence of selective vulnerability of large diameter fibers has been derived largely from histological and electrophysiological measurements. We have examined the effect of repeated doses of acrylamide on the function of small diameter peripheral pain fibers in rats by measuring the intensity of neurogenic edema initiated by chemosensitive nerve endings and assessing the sensitivity of the hind paws to a noxious stimulus. These effects have been compared to the impaired sensorimotor performance (landing foot spread) resulting from acrylamide treatment and the change in functional integrity of the pain fibers following surgical lesioning of the sciatic nerves. Our results show that the selective vulnerability of large over small diameter sensory fibers previously reported in the literature is reflected in the differential impairment of proprioceptive and pain-related functions in the rat.

Experimental acrylamide neuropathy has been studied as a model of degenerative neurological disorders of the 'dying-back' type for over 30 years. Functional, histological, ultrastructural, electrophysiological and biochemical aspects of acrylamide neuropathy have been described and several hypotheses concerning the mode of action proposed. However, the mechanism whereby acrylamide causes axonal degeneration and inhibits nerve sprouting remains unknown. By analogy with agonist/antagonist comparisons used by the pharmacologist, we have reconsidered the acrylamide problem in the light of the opposite effects summarized in Table 1, of neurotrophic peptides related to ACTH/MSH (collectively termed melanocortins). The contrasting effects on sprouting and the eventual quality of repair of mechanically lesioned nerves have suggested a mechanism whereby sprouting may regulate perikaryal adjustments to injury. We have also posed the question as to whether a common biochemical mechanism, namely selective proteolysis of neurofilament protein may underlie the opposing effects of acrylamide and melanocortins on nerve sprouting. This possibility implies a hitherto unknown role for neurofilament protein turnover in neuronal maintenance and repair, a suggestion that may provoke further research and discussion.

Experiments using peripheral nerve lesions (crush or transection) in rats to study repair processes are hampered by the tendency for the animals to attack the limb in which the peripheral nerves are damaged (autotomy). In this paper we describe a simple method which significantly reduces the incidence of autotomy after peripheral nerve lesions. The method consists of painting the hind paws of operated rats with a commercially available non-toxic lotion, which is used to discourage nail-biting and thumb-sucking in humans. Although the method is not absolute, it was extremely beneficial in our experiments, since the number of animals that had to be taken out of the experiment due to severe autotomy was greatly reduced. We believe that this method may prove to be as beneficial to other investigators who are using experimental peripheral nerve lesions to study the regenerative aspects of the nervous system.

Org 2766 is one of a series of melanocortins (ACTH and related peptides) that exert trophic influences on the central and peripheral nervous system of the rat. We used acrylamide neuropathy in rats as an experimental model of peripheral neuropathies of the dying-back type in order to assess the potential therapeutic efficacy of Org 2766 in this type of nerve damage. The peptide reversed the delayed persistent deficit in sensory conduction velocity without preventing the initial loss of motor coordination. The recovery of apparently normal coordination was unaffected by the peptide, but resistance to a second toxic challenge suggested that recovery was more complete in the peptide-treated rats. The finding that Org 2766 improved the quality of the repair following acrylamide neuropathy, together with previous studies showing beneficial effects in neuropathies caused by cisplatin or diabetes and after mechanical trauma, strongly suggests that Org 2766 may be beneficial in the treatment of various conditions in which the nervous system has sustained damage.

The protein core of high mol. wt polymorphic epithelial mucin (PEM--approximately 400 kDa glycoprotein) which is associated with breast carcinomas, consists of a repeating 20 amino acid peptide motif [Gendler et al. (1988) J. biol. Chem. 263, 12,820-12,823]. Monoclonal antibodies C595 (anti-urinary mucin) and NCRC-11 (anti-breast carcinoma cells), and other antibodies against human milk fat globule membranes, were found to recognize determinants present within this 20 amino acid peptide. A model of the peptide was developed based on hydropathicity and structure prediction calculations and these indicated that the repeated structure is dominated by a hydrophilic domain of seven amino acids, extending into two flanking beta turns. NMR analysis of the 20 amino acid peptide was undertaken to probe the secondary structure. Epitope mapping experiments involving solid phase synthesis of overlapping heptapeptides in the repeat unit identified the minimum structures for antibody binding as Arg-Pro-Ala-Pro and Arg-Pro-Ala for the C595 and NCRC-11 antibodies, respectively. These determinants were found within the predicted hydrophilic turn region domain of the peptide. The epitopes for six other PEM-reactive monoclonal antibodies were also determined to reside within the predicted hydrophilic turn domain. This evidence is in accord with the disposition of this region of the PEM peptide core being at the exterior of the glycoprotein where it would be accessible to antibody recognition and binding events.

Antibodies binding to the 150 kDa neurofilament protein NF150 have been purified from a serum raised by immunizing a rabbit with alpha-MSH. The NF150-binding antibodies were purified by affinity chromatography on a column of cytoskeletal proteins coupled to CNBr-activated Sepharose-4B. Immunocytochemical application of these antibodies, followed by a FITC-coupled second antibody, labels axons in intact and regenerating nerves and provides a means of identifying and counting small regenerating sprouts from 48 h after nerve crush. We have been able to demonstrate that treatment with the neurotrophic melanocortin analog, Org.2766, increases the number of regenerating axons present in the nerve as early as 72 h after nerve crush.

As reported previously the prominent protein kinase C substrate protein B-50 is present in growth cones isolated from fetal rat brain and in outgrowing hippocampal neurites. These findings suggest that B-50 plays a role in axonal growth during development of the nervous system. In the present paper the fate of B-50 is investigated in regenerating rat sciatic nerve. Using affinity-purified anti-B-50 antibodies B-50 levels have been compared in crushed and contralateral intact nerves by means of immunoblotting and radioimmunoassay. B-50 levels in the crushed nerve increased 5.3-fold as compared to non-crushed controls. Furthermore, the cellular localization of B-50 has been assessed by immunohistochemistry. Virtually no B-50 immunoreactivity was seen in control nerves, but bright immunofluorescence appeared in regenerating sprouts. Our data are in line with current evidence from several laboratories that B-50 is a member of a small family of growth-associated proteins and support the hypothesis that B-50 is involved in axonal growth.

2-Allyl-2-isopropylacetamide (AIA) causes a depletion of liver glutathione in rats only if the animals have been pretreated with phenobarbitone. Phenobarbitone stimulates the excretion in bile of a component derived from AIA and glutathione which is apparently not the same as the conjugate formed by reaction of the two components in simple solutions. The significance of these findings are considered in relation to the suggestion that AIA is metabolised to an epoxide by the microsomal enzyme system; in addition several differences between AIA and the non-porphyrogenic compound, acrylamide, are discussed.

Immunoblot techniques and immunohistochemistry have been used to investigate epitopes shared by alpha-melanocyte-stimulating hormone (alpha-MSH) and the 150-kD neurofilament protein (NF150). Three anti-alpha-MSH antisera (namely 31H2T, 4394, and M5) from a total of 12 sera were found to react with NF150. The three crossreacting sera are different in their binding properties to peptide fragments related to alpha-MSH, suggesting that at least two distinct epitopes are shared by NF150 and alpha-MSH. The only known sequence common to NF150 and alpha-MSH, the N-terminal Ac-S-Y residues, appears to be essential for binding of sera 31H2T and 4394. However, the binding of antiserum M5 involves other, currently unknown, similarities between NF150 and alpha-MSH. This is shown by the binding of M5 to peptides such as ACTH(4-10), which do not contain the N-terminal Ac-S-Y sequence. Binding of M5 to tobacco mosaic virus coat protein (TMV-coat protein), which is homologous with alpha-MSH and NF150 in its Ac-S-Y residues, was negligible. The peptide structures that are recognized by M5 have previously been shown to exert neurotrophic activity. The data are discussed in the light of the hypothesis that similarity between NF150 and alpha-MSH, as illustrated by binding to M5, may be significant in the neurotrophic activity of MSH-related peptides.