Impact of the intersection of anaesthesia and gender on burnout and mental health, illustrated by the COVID-19 pandemic

Physician burnout and poor mental health are prevalent and often stigmatised. Anaesthetists may be at particular risk and this is further increased for women anaesthetists due to biases and inequities within the specialty. However, gender-related risk factors for and experiences of burnout and poor mental health remain under-researched and under-reported. This negatively impacts individual practitioners, the anaesthesia workforce and patients and carries significant financial implications. We discuss the impact of anaesthesia and gender on burnout and mental health using the COVID-19 pandemic as an example illustrating how women and men differentially experience stressors and burnout. COVID-19 has further accentuated the gendered effects of burnout and poor mental health on anaesthetists and brought further urgency to the need to address these issues. While both personal and organisational factors contribute to burnout and poor mental health, organisational changes that recognise and acknowledge inequities are pivotal to bolster physician mental health.

New insights into the obligatory nature of cyclooxygenase-2 and PGE2 during early chick embryogenesis

Temporal expression patterns and activity of two cyclooxygenase (COX-1 and COX-2) isoforms were analysed during early chick embryogenesis to evaluate their roles in development. COX-2 inhibition with etoricoxib resulted in significant structural anomalies such as anophthalmia (born without one or both eyes), phocomelia (underdeveloped or truncated limbs), and gastroschisis (an opening in the abdominal wall), indicating its significance in embryogenesis. Furthermore, the levels of PGE₂, PGD₂, PGF_2α, and TXB₂ were assessed using quantitative LC-MS/MS to identify which effector prostanoid (s) had their synthesis initiated by COX-2. COX-2 inhibition was only shown to reduce the level of PGE₂ significantly_, and hence it could be inferred that the later could be largely under the regulation of activated COX-2 in chick embryos. The compensatory increase in the activity of COX-1 observed in the etoricoxib-treated group helped to maintain the levels of PGD₂, PGF_2α, and TXB₂. Though the roles of these three prostanoids in embryogenesis need to be further clarified, it appears that their contribution to the observed developmental anomalies is minimal. This study has shown that COX-2 is functionally active during chick embryogenesis, and it plays a central role in the structural configuration of several organs and tissues through its downstream effector molecule PGE₂.

The Effectiveness of Accelerated Skill Acquisition Program for Upper Extremity Motor Training in Bilateral Stroke

The bilateral stroke is an added challenge for functional recovery. The evidence of effective therapy intervention for bilateral stroke is rare. A protocol of 30 hours (5 hours/week for 6 weeks) of accelerated skill acquisition program (ASAP) has been administered to a patient with bilateral ischemic middle cerebral artery syndrome at sub-acute stage. Two sessions per day (separately for right and left) were administered. Nepali Wolf Motor Function Test (WMFT) was used to evaluate performance time before and after the treatment. The performance time on Wolf Motor Function Test got largely and consistently reduced on all items of both extremities. There was improvement in grip strength and weight lifting items. Bilateral hand items and turn key in lock were successfully completed after the treatment. Thus, the accelerated skill acquisition program yielded large reduction in performance time, improved hand skills and demonstrated functional improvement of both upper extremities in individual with bilateral stroke.

Identification of Azoxystrobin Glutathione Conjugate Metabolites in Maize Roots by LC-MS

Xenobiotic detoxification in plant as well as in animals has mostly been studied in relationship to the deactivation of the toxic residues of the compound that, surely for azoxystrobin, is represented by its β-methoxyacrylate portion. In maize roots treated for 96 h with azoxystrobin, the fungicide accumulated over time and detoxification compounds or conjugates appeared timewise. The main detoxified compound was the methyl ester hydrolysis product (azoxystrobin free acid, 390.14 m/z) thought to be inactive followed by the glutathione conjugated compounds identified as glutathione conjugate (711.21 m/z) and its derivative lacking the glycine residue from the GSH (654.19 m/z). The glycosylated form of azoxystrobin was also found (552.19 m/z) in a minor amount. The identification of these analytes was done by differential untargeted metabolomics analysis using Progenesis QI for label free spectral counting quantification and MS/MS confirmation of the compounds was carried out by either Data Independent Acquisition (DIA) and Data Dependent Acquisition (DDA) using high resolution LC-MS methods. Neutral loss scanning and comparison with MS/MS spectra of azoxystrobin by DDA and MSe confirmed the structures of these new azoxystrobin GSH conjugates.

CFM-ID 3.0: Significantly Improved ESI-MS/MS Prediction and Compound Identification

Metabolite identification for untargeted metabolomics is often hampered by the lack of experimentally collected reference spectra from tandem mass spectrometry (MS/MS). To circumvent this problem, Competitive Fragmentation Modeling-ID (CFM-ID) was developed to accurately predict electrospray ionization-MS/MS (ESI-MS/MS) spectra from chemical structures and to aid in compound identification via MS/MS spectral matching. While earlier versions of CFM-ID performed very well, CFM-ID's performance for predicting the MS/MS spectra of certain classes of compounds, including many lipids, was quite poor. Furthermore, CFM-ID's compound identification capabilities were limited because it did not use experimentally available MS/MS spectra nor did it exploit metadata in its spectral matching algorithm. Here, we describe significant improvements to CFM-ID's performance and speed. These include (1) the implementation of a rule-based fragmentation approach for lipid MS/MS spectral prediction, which greatly improves the speed and accuracy of CFM-ID; (2) the inclusion of experimental MS/MS spectra and other metadata to enhance CFM-ID's compound identification abilities; (3) the development of new scoring functions that improves CFM-ID's accuracy by 21.1%; and (4) the implementation of a chemical classification algorithm that correctly classifies unknown chemicals (based on their MS/MS spectra) in >80% of the cases. This improved version called CFM-ID 3.0 is freely available as a web server. Its source code is also accessible online.

Non-response to first-line anti-tuberculosis treatment in Sikkim, India: a risk-factor analysis study

Setting: Sikkim, India, has the highest proportion of tuberculosis (TB) patients on first-line anti-tuberculosis regimens with the outcome 'failure' or 'shifted to regimen for multidrug-resistant TB (MDR-TB)'. Objective: To assess the factors associated with non-response to treatment, i.e., 'failure' or 'shifted to MDR-TB regimen'. Methods: We conducted a retrospective cohort study using Revised National Tuberculosis Control Programme data of all TB patients registered in 2015 for first-line TB treatment. In addition, we interviewed 42 patients who had not responded to treatment to ascertain their current status. Results: Of 1508 patients enrolled for treatment, about 9% were classified as non-response to treatment. Patient factors associated with non-response were urban setting (adjusted odds ratio [aOR] 2.39, 95%CI 1.22-4.67), ethnicity (being an Indian tribal, aOR 1.73, 95%CI 1.17-2.57, Indian [other] aOR 1.83, 95%CI 1.29-2.60 compared to patients of Nepali origin) and those on retreatment (aOR 2.40, 95%CI 1.99-2.91). Of the patients interviewed, 28 (67%) had received treatment for drug-resistant TB. Conclusion: In Sikkim, one in 11 patients had not responded to first-line anti-tuberculosis treatment. Host-pathogen genetics and socio-behavioural studies may be required to understand the reasons for the differences in non-response, particularly among ethnic groups.

Maize root culture as a model system for studying azoxystrobin biotransformation in plants

Hairy roots induced by Agrobacterium rhizogenes are well established models to study the metabolism of xenobiotics in plants for phytoremediation purposes. However, the model requires special skills and resources for growing and is a time-consuming process. The roots induction process alters the genetic construct of a plant and is known to express genes that are normally absent from the non-transgenic plants. In this study, we propose and establish a non-transgenic maize root model to study xenobiotic metabolism in plants for phytoremediation purpose using azoxystrobin as a xenobiotic compound. Maize roots were grown aseptically in Murashige and Skoog medium for two weeks and were incubated in 100 μM azoxystrobin solution. Azoxystrobin was taken up by the roots to the highest concentration within 15 min of treatment and its phase I metabolites were also detected at the same time. Conjugated metabolites of azoxystrobin were detected and their identities were confirmed by enzymatic and mass spectrometric methods. Further, azoxystrobin metabolites identified in maize root culture were compared against azoxystrobin metabolites in azoxystrobin sprayed lettuce grown in green house. A very close similarity between metabolites identified in maize root culture and lettuce plant was obtained. The results from this study establish that non-transgenic maize roots can be used for xenobiotic metabolism studies instead of genetically transformed hairy roots due to the ease of growing and handling.

Liquid chromatography-tandem mass spectrometry method for simultaneous quantification of azoxystrobin and its metabolites, azoxystrobin free acid and 2-hydroxybenzonitrile, in greenhouse-grown lettuce

Lettuce is an important part of the diet in Europe. The permitted levels of pesticides in lettuce are strictly regulated and there is growing urge among food safety authorities to analyse pesticide metabolites as well. Azoxystrobin is one of pesticides that is frequently detected in lettuce. Although there are several analytical methods for the determination of azoxystrobin in lettuce, a sensitive method for the determination of its metabolites in lettuce is lacking. This study aimed at developing an extraction and LC-MS/MS method for the simultaneous determination of azoxystrobin, and its metabolites azoxystrobin free acid and 2-hydroxybenzonitrile in lettuce. Accelerated solvent extraction, QuEChERS extraction, and shaking extraction were compared using various solvents. The final method consisted of shaking freeze-dried sample in 0.1% formic acid in 80% aqueous acetonitrile. The selected method was validated by spiking each analyte at 125 ng/g and 500 ng/g. The method resulted in acceptable recovery for 2-hydroxybenzonitrile, azoxystrobin free acid, and azoxystrobin, with a RSD of <10%. The matrix-matched calibration curve for each analyte was linear over the range of quantification, with a correlation coefficient ≥0.98. The method was sensitive for the determination of 2-hydroxybenzonitrile, azoxystrobin free acid, and azoxystrobin, with limits of quantification of 0.36, 0.48, and 0.68 ng/g dry weight, respectively. The method was successfully applied to quantify 2-hydroxybenzonitrile, azoxystrobin free acid, and azoxystrobin in greenhouse-grown lettuce.

Hormone responsiveness of cultured Sertoli cells obtained from adult rats after their rapid isolation under less harsh conditions

During adulthood, testicular Sertoli cells (Sc) coordinate all stages of germ cell (Gc) development involved in sperm production. However, our understanding about the functions of adult Sc is limited because of the difficulties involved in the process of isolating these cells from the adult testis, mainly because of the presence of large number of advanced Gc which interfere with Sc isolation at this age. Most of our knowledge about Sc function are derived from studies which used pre-pubertal rat Sc (18 ± 2-day old) as it is easy to isolate and culture Sc at this age. To this end, we established a less time consuming and less harsh procedure of isolating Sc from adult (60 days of age) rat testis for facilitating research on Sc-mediated regulation of spermatogenesis during adulthood. The cells were isolated using collagenase digestion at higher temperature, reducing the exposure time of cells to the enzyme. Step-wise digestion with intermittent removal of small clusters of tissue helped in increasing the yield of Sc. Isolated Sc were cultured and treated with FSH and testosterone (T) to evaluate their hormone responsiveness in terms of lactate, E2 , cAMP production. Adult Sc were found to be active and produced high amounts of lactate in a FSH-independent manner. FSH-mediated augmentation of cAMP and E2 production by adult Sc was less as compared with that by pre-pubertal Sc obtained from 18-day-old rats. Androgen-binding ability of adult Sc was significantly higher than pre-pubertal Sc. Although T treatment remarkably augmented expression of Claudin 11, it failed to augment lactate production by adult Sc. This efficient and rapid procedure for isolation and culture of functionally viable adult rat Sertoli cells may pave the way for determining their role in regulation and maintenance of spermatogenesis.

Study on the Soil Corrosivity towards the Buried-Structures in Soil Environment of Tanglaphant-Tribhuvan University Campus-Balkhu Areas of Kirtipur

Soil parameters such as moisture, pH, resistivity, oxidation-reduction potential, chloride and sulfate ions were investigated, because these parameters affect the corrosive nature of soils toward the buried-galvanized steels and cast-iron pipelines used to supply drinking water in Tanglaphant-Tribhuvan University Campus-Balkhu areas of Kirtipur. The soil parameters examined in the study areas are found as: moisture (7-48%), pH (7.0-7.9), resistivity (6,300-37,000 ohm.cm), oxidation-reduction potential (307-490 mV vs SHE), chloride (13-92 ppm) and sulfate (62-309 ppm) contents. The results gave an indication of mildly corrosive to non-corrosive nature of soils on the buried galvanized steels and cast-iron pipes used to supply drinking water in the study areas of Kirtipur.  DOI: http://dx.doi.org/10.3126/njst.v14i2.10417   Nepal Journal of Science and Technology Vol. 14, No. 2 (2013) 65-72

Role of vaccine manufacturers in developing countries towards global healthcare by providing quality vaccines at affordable prices

Vaccines represent one of the greatest achievements of science and medicine in the fight against infectious diseases. Vaccination is one of the most cost-effective public health tools to prevent infectious diseases. Significant progress has been made in expanding the coverage of vaccines globally, resulting in the prevention of more than two million deaths annually. In 2010, nearly 200 countries endorsed a shared vision to extend the benefits of vaccines to every person by 2020, known as the Decade of Vaccine Initiative (DoV). Vaccine manufacturers in developing countries, as represented by the Developing Countries Vaccine Manufacturers Network (DCVMN), make a significant contribution to DoV by supplying quality vaccines at affordable prices to the people who need them most. About 70% of the global Expanded Program on Immunization (EPI) vaccine supplies are met by DCVMN. Besides EPI vaccine supplies, DCVMN is also targeting vaccines against rotavirus, Japanese encephalitis, pneumonia, human papillomavirus, meningitis and neglected tropical diseases. This article reviews the roles and contributions of DCVMN in making the vaccines accessible and affordable to all.

Tired heart and mute brain: handle with care

Managing a case of stroke is complex. Presence of variable sized brain infarct and heart failure is even more complex to manage. On top of this, presence of clot in the heart adds to confusion in medical management of stroke patients because of limited scientific evidences. With increasing number of stroke patients and improving diagnostic facility, it is interesting to find thrombus in ventricles of few of these patient, which otherwise were uncommon previously in our set up. We present a 64-year-old man, a case of ischemic stroke caused by left ventricular thrombus secondary to dilated cardiomyopathy and highlight the present recommendation to manage the condition. DOI: http://dx.doi.org/10.3126/jcmsn.v7i3.6714 Journal of College of Medical Sciences-Nepal, 2011, Vol-7, No-3, 68-70  

Microalbuminuria and macroalbuminuria in type 2 diabetes

BACKGROUND

Type 2 diabetes is the leading cause of end stage renal disease worldwide. Prevalence of diabetic nephropathy (DN) varies in the different ethnic groups. Nepal is country with great ethnic diversity. This study has been done to find the prevalence of microalbuminuria and macroalbuminuria in the two ethnic groups Jyapu and Brahmin.

METHODS

In our study we have included two ethnic groups Jyapu and Brahmin type 2 diabetic patients.

INCLUSION CRITERIA

Age ≥ 30 years, clinically diagnosed type 2 diabetic patients.

EXCLUSION CRITERIA

Patients with a history of urinary tract infection, hematuria, renal failure, intercaste marriage and women with menstruation at the time of sample collection.

RESULTS

The overall prevalence of albuminuria was 49.05%. The prevalence of microalbuminuria was 35.89% in Jyapu and 37.73% in Brahmin which was comparable. There was significantly higher prevalence of macroalbuminuria in Jyapu 20.75% and Brahmin 3.77%. Association of dietary habit was seen with microalbuminuria and macroalbuminuria in both ethnic groups.

CONCLUSIONS

The overall prevalence of albuminuria in type 2 diabetes of our study was high and there was significantly higher macroalbuminuria in Jyapu compared with Brahmin. It, therefore, predicts a higher risk of having kidney disease in Jyapu population.

Increased response of muscle sensory neurons to decreases in pH after muscle inflammation

Acid sensing ion channels (ASIC) are found in sensory neurons, including those that innervate muscle tissue. After peripheral inflammation there is an increase in proton concentration in the inflamed tissue, which likely activates ASICs. Previous studies from our laboratory in an animal model of muscle inflammation show that hyperalgesia does not occur in ASIC3 and ASIC1 knockout mice. Therefore, in the present study we investigated if pH activated currents in sensory neurons innervating muscle are altered after induction of muscle inflammation. Sensory neurons innervating mouse (C57/Bl6) muscle were retrogradely labeled with 1,1-dioctadecyl-3,3,3,3 tetramethylindocarbocyanine perchlorate (DiI). Two weeks after injection of DiI, mice were injected with 3% carrageenan to induce inflammation (n=8; 74 neurons) or pH 7.2 saline (n=5; 40 neurons, control) into the gastrocnemius muscle. 24 h later sensory neurons from L4-L6 dorsal root ganglia (DRG) were isolated and cultured. The following day the DRG neuron cultures were tested for responses to pH by whole-cell patch-clamp technique. Approximately 40% of neurons responded to pH 5 with an inward rapidly desensitizing current consistent with ASIC channels in both groups. The mean pH-evoked current amplitudes were significantly increased in muscle sensory neurons from inflamed mice (pH 5.0, 3602 ± 470 pA) in comparison to the controls (pH 7.4, 1964 ± 370 pA). In addition, the biophysical properties of ASIC-like currents were altered after inflammation. Changes in ASIC channels result in enhanced responsiveness to decreases in pH, and likely contribute to the increased hyperalgesia observed after muscle inflammation.

Variation of total serum cholesterol among the patient with thyroid dysfunction

BACKGROUND

Thyroid hormone has its effect in the lipid metabolism. Thus, thyroid disorder is usually associated with the dyslipidaemia. Hypercholesterolemia is an established risk factor for the cardiovascular disease (CVD) and therefore in case of overt hypothyroidism which is associated with hypercholesterolemia, CVD is most likely to occur.

OBJECTIVES

controversies still persist about the hypercholesterolemia and sub clinical hypothyroidism. Hence, we conducted our study to elucidate the relation of thyroid hormone with cholesterol in different thyroid disorder.

MATERIAL AND METHOD

All patients suspected of thyroid disorder within a period of one year were included in the study and free thyroxine-3 (fT3), free thyroxine-4 fT4, Thyroid Stimulating Hormone (TSH) and total cholesterol (TC) in the serum were estimated. Statistical analysis was carried out by using SPSS. 13.

RESULTS

Among the 169 cases, 32.5% of the patients were having thyroid disorder. In which 8.3% were of hypothyroid, 7.1% were of sub clinical hypothyroid, 8.3% were of hyperthyroid, 7.7% were of sub clinical hyperthyroid and 1.2% cases were of pan hypothyroid. We observed significant negative correlation between TC & fT3(r = -0.226, p = 0.003), significant negative correlation between total cholesterol & fT4(r = -0.197, p = 0.010) and significant positive correlation between TC & TSH(r = 0.365, p = 0.000). Total cholesterol was significantly raised in hypothyroidism (Mean ±SD 283 ± 53, p = 0.000) in comparison to euthyroid population (mean ±SD, 195 ± 58). But cholesterol was not significantly increased in sub clinical hypothyroidism (mean ±SD, 240 ± 46)

CONCLUSION

Our results show that total cholesterol level in serum is affected by the blood thyroid hormone level. Therefore, screening for hypercholesterolemia could be useful in patients with hypothyroidism to reduce associated disease.

The impact of past alcohol use on treatment response rates in patients with chronic hepatitis C

BACKGROUND

Studies have shown that past alcohol consumption reduces response rates in patients with chronic hepatitis C treated with interferon monotherapy.

AIM

To clarify the importance of alcohol consumption on response rates in patients undergoing treatment with pegylated interferon and ribavirin.

METHODS

In a single centre, prospective study, median daily alcohol consumption (determined by previously validated method) and quartiles of alcohol consumption were calculated. Univariate and binary logistic regression analyses were performed using treatment response status as the dependent variable.

RESULTS

Overall, in an intention-to-treat analysis, 34 of 115 patients (30%) responded to treatment. In univariate analysis, black patients, especially those with hepatitis C virus genotype 1, high viral load and low alanine aminotransferase were significantly less likely to respond. Predictors of response by regression analysis included alcohol <30 g/day (OR=3.02, 95% CI: 1.02-8.93; P=0.04), non-genotype 1 status (OR=1.98, 95% CI: 1.03-3.80; P=0.04) and non-black race (OR=2.79, 95% CI: 1.33-5.85; P=0.006).

CONCLUSIONS

Median daily alcohol use >30 g/day is associated with failure to respond to pegylated interferon and ribavirin for treatment of hepatitis C. Past alcohol use should be evaluated when considering treatment for hepatitis C.

Deletion of N-terminal rapsyn domains disrupts clustering and has dominant negative effects on clustering of full-length rapsyn

The peripheral muscle membrane protein rapsyn is essential for the formation and maintenance of high density acetylcholine receptor aggregates at the neuromuscular synapse. Rapsyn is concentrated at synaptic sites and is colocalized with acetylcholine receptors from the earliest stages of synaptogenesis. Previous studies have shown that recombinant rapsyn expressed in heterologous cells forms clusters, and acetylcholine receptors coexpressed with rapsyn are colocalized with rapsyn clusters. However, the molecular interactions involved in clustering of rapsyn are not well defined. To analyze the process of cluster formation by rapsyn we examined the formation of rapsyn clusters and complexes using mutant constructs specifically deleted for individual domains of rapsyn in the presence and absence of tagged, full-length rapsyn. Specific deletions of the tetratricopeptide repeat (TPR) domains 1 and 3 of rapsyn abrogated not only clustering of mutant rapsyns, but also, in a dominant negative fashion, the clustering of tagged, full-length rapsyn. We also analyzed rapsyn protein complexes isolated from cells transfected with tagged and untagged rapsyn. Our results show that both tagged and untagged rapsyn are present in immunoprecipitates of rapsyn from cotransfected cells, demonstrating that rapsyn molecules interact directly or indirectly to form oligomers. Mutants that were dominant negatives were also present in complexes containing tagged, full-length rapsyn. Together these results indicate that rapsyn forms clusters at the synapse by oligomerization, and suggest models for the mechanistic bases of this oligomerization via interactions mediated by TPRs 1 and 3.

Immune response modulation to DPT vaccine by aqueous extract of Withania somnifera in experimental system

Immunopotentiation on oral feeding of standardized aqueous extract of Withania somnifera (Linn. Dunal, Family Solanaceae) was evaluated in laboratory animals immunized with DPT (Diphtheria, Pertussis, Tetanus) vaccine. The immunostimulation was evaluated using serological and hematological parameters. Treatment of immunized animals with test material (100 mg/kg/day) for 15 days resulted in significant increase of antibody titers to B. pertussis (P=0.000007). Immunized animals (treated and untreated) were challenged with B. pertussis 18,323 strain and the animals were observed for 14 days. Results indicate that the treated animals did show significant increase in antibody titers as compared to untreated animals after challenge (P=0.000003). Immunoprotection against intracerebral challenge of live B. pertussis cells was evaluated based on degree of sickness, paralysis and subsequent death. Reduced mortality accompanied with overall improved health status was observed in treated animals after intracerebral challenge of B. pertussis indicating development of protective immune response. Present study indicates application of the test material as potential immunopotentiating agent possible applications in immunochemical industry. The test material also offers direct therapeutic benefits resulting in reduced morbidity and mortality of experimental animals.

Maintenance intravenous iron therapy in pediatric hemodialysis patients

Iron supplementation is required for optimal response to erythropoietin (EPO) in hemodialysis patients. This is due to blood lost in the dialysis tubing after dialysis and the increased demand for iron by EPO therapy. Maintenance intravenous (IV) iron was administered according to a standardized protocol to pediatric patients on hemodialysis in our institution. The effect of this protocol on EPO dose, iron indices, anemia, and medication costs was evaluated. Data on two groups of patients were retrieved from the health records. Group 1 (n=14) consisted of patients treated in the 18 months prior to the protocol. These patients received oral iron supplements and occasional IV iron. Group 2 (n=5) consisted of all patients treated with the IV iron protocol. There was no difference in clinical characteristics and mean values for monthly hemoglobin, serum iron, ferritin, and transferrin saturation between groups. The dose of EPO was significantly reduced in group 2 compared with group 1 (193.9 +/- 121.4 vs. 73.9 +/- 39.0 units/kg per week, P<0.05). Medication costs were reduced by 26% in group 2. No significant adverse events were seen. Maintenance IV iron reduced the dose of EPO required to maintain blood hemoglobin levels. Our results also suggest that maintenance IV iron is a more-economic method of iron supplementation for pediatric hemodialysis patients.

Exhaust emissions from engines of the Detroit Diesel Corporation in transit buses: a decade of trends

In the U.S.A., exhaust emissions from city buses fueled by diesel are not characterized well because current emission standards require engine tests rather than tests of whole vehicles. Two transportable chassis dynamometer laboratories developed and operated by West Virginia University (WVU) have been used extensively to gather realistic emission data from heavy-duty vehicles, including buses, tested in simulated driving conditions. A subset of these data has been utilized for a comprehensive introspection into the trends of regulated emissions from transit buses over the last 7 years, which has been prompted by continuously tightening restrictions on one hand, along with remarkable technological progress, on the other hand. Two widely used models of diesel engines manufactured by the Detroit Diesel Corporation (DDC) have been selected as a case-study for such an overview, based on full-scale, on-site testing of actual city buses, driven in accordance with the SAE J1376 standard of a Commercial Business District (CBD) cycle. The results provide solid, quantitative evidence that most regulated emissions from engines produced by DDC have declined over the years, especially with the transition from the 6V-92TA to the Series 50 models. This improvement is remarkable mainly for the emissions of particulate matter (PM), that are lower by over 70%, on average, for the Series 50 engines, though the emissions of nitrogen oxides (NOx) exhibit a reversed trend, showing a degradation of about 6%, on average, with the transition from 6V-92TA to the Series 50 engines. The expected trend of decreasing emission levels with the model year of the engine is clear and consistent for particulate matter (PM), hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), starting with the 1990 models, although it is not conclusive for carbon dioxide (CO2) emissions.

Frequency- and time-dependent effects of fendiline on action potentials of guinea pig papillary muscle

The action of fendiline on cardiac electrical activity was investigated in guinea pig papillary muscle by monitoring frequency- and time-dependent changes in membrane potential, action potential (AP) configuration and conduction velocity. Isolated guinea pig papillary muscles driven at 0.1 to 3 Hz showed a concentration-dependent reduction of +Vmax, overshoot, and AP duration at -20mV (APD20) in the presence of fendiline (1-320 microM), reflecting inhibition of Na+ and L-type Ca2+ channels, respectively. No significant change in resting potential and AP duration at 90% repolarization (APD90) were observed. Inhibition of +Vmax and APD20 was more prominent at higher frequency of stimulation (2 Hz) than at lower ones (0.2 Hz), demonstrating frequency-dependent block of Na+ and Ca2+ channels including an open channel block. A good relationship between changes in +Vmax and APD20 suggested some commonality in the mechanism of inhibition of Na+ and Ca2+ channels by fendiline. Time-dependence of effects of fendiline, observed in presence of bolus dose (200 microM), showed an earlier onset of inhibition of +Vmax and APD20, particularly at higher frequencies. Missed beats and conduction block also appeared earlier in preparations driven at higher frequency. These findings suggest a frequency-dependent (and open channel) block of Na+ and Ca2+ channels by fendiline, leading to inhibition of fast and slow conduction in addition to its reported inactivated Ca2+ channel block.

Roles of rapsyn and agrin in interaction of postsynaptic proteins with acetylcholine receptors

At the neuromuscular junction, aggregates of acetylcholine receptors (AChRs) are anchored in the muscle membrane by association with rapsyn and other postsynaptic proteins. We have investigated the interactions between the AChR and these proteins in cultured C2 myotubes before and after treatment with agrin, a nerve-derived protein that induces AChRs to cluster. When AChRs were isolated from detergent extracts of untreated C2 myotubes, they were associated with rapsyn and, to a lesser degree, with utrophin, beta-dystroglycan, MuSK, and src-related kinases, but not with syntrophin. Treatment with agrin increased the association of AChRs with MuSK, a receptor tyrosine kinase that forms part of the agrin receptor complex, without affecting other interactions. Analysis of rapsyn-deficient myotubes, which do not form protein clusters in response to agrin, revealed that rapsyn is required for association of the AChR with utrophin and beta-dystroglycan, and for the agrin-induced increase in association with MuSK, but not for constitutive interactions with MuSK and src-related kinases. In rapsyn -/- myotubes, agrin caused normal tyrosine phosphorylation of AChR-associated and total MuSK, whereas phosphorylation of the AChR beta subunit, both constitutive and agrin-induced, was strongly reduced. These results show first that aneural myotubes contain preassembled AChR protein complexes that may function in the assembly of the postsynaptic apparatus, and second that rapsyn, in addition to its role in AChR phosphorylation, mediates selected protein interactions with the AChR and serves as a link between the AChR and the dystrophin/utrophin glycoprotein complex.

Distinct phenotypes of mutant mice lacking agrin, MuSK, or rapsyn

Differentiation of the postsynaptic membrane at the neuromuscular junction requires agrin, a nerve-derived signal; MuSK, a critical component of the agrin receptor in muscle; and rapsyn, a protein that interacts with acetylcholine receptors (AChRs). We showed previously that nerve-induced AChR aggregation is dramatically impaired in knockout mice lacking agrin, MuSK, or rapsyn. However, the phenotypes of these mutants differed in several respects, suggesting that the pathway from agrin to MuSK to rapsyn is complex. Here, we compared the effects of these mutations on two aspects of synaptic differentiation: AChR clustering and transcriptional specialization of synapse-associated myonuclei. First, we show that a plant lectin, VVA-B4, previously shown to act downstream of agrin, can induce AChR clusters on MuSK-deficient but not rapsyn-deficient myotubes in culture. Thus, although both MuSK and rapsyn are required for AChR clustering in vivo, only rapsyn is essential for cluster formation per se. Second, we show that neuregulin, a nerve-derived inducer of AChR gene expression, activates AChR gene expression in cultured agrin- and MuSK-deficient myotubes, even though synapse-specific transcriptional specialization is disrupted in agrin and MuSK mutants in vivo. We propose that agrin works through MuSK to determine a synaptogenic region within which synaptic differentiation occurs.

Alopecia due to psychotropic medications

OBJECTIVE

To review the literature and describe the incidence and nature of psychotropic drug-related alopecia to assist clinicians in their therapeutic decisions when this adverse event occurs.

DATA SOURCES

A MEDLINE search (December 1966-March 1998), using each drug name and the keywords alopecia or hair loss, was conducted. A database from the Clarke Institute of Psychiatry in Toronto was also searched. Additional English-language articles were identified through the bibliography of the reviewed literature. Certain pharmaceutical companies were also consulted.

STUDY SELECTION

All published case reports and review articles were considered for study evaluation.

DATA EXTRACTION

When possible, details regarding psychotropic drug therapy, development of alopecia, and clinical outcomes were collected for each case.

DATA SYNTHESIS

Hair loss from the scalp, eyebrows, and pubic area was identified as a possible, yet uncommon, adverse effect of most psychotropic medications. There are few effective management options for alopecia; however, resolution was achieved on discontinuation of the offending drug in almost all of the cases reported. Alopecia was perceived to be an undesirable effect by most patients, often resulting in poor compliance and hence therapeutic failures.

CONCLUSIONS

Due to the self-limiting nature of mild to moderate hair loss with psychotropic medications, clinicians should consider continuing therapy if there is a good clinical response and the patient agrees with this decision. If severe alopecia occurs, it is recommended to discontinue the medication and pursue therapy with another agent. This is to ensure positive therapeutic outcomes and improved patient compliance.

Metabolic stabilization of muscle nicotinic acetylcholine receptor by rapsyn

Although the metabolic half-life of muscle endplate acetylcholine receptor (AChR) changes during development and after denervation in the adult, little is known about the molecular mechanisms that influence receptor stability. We have investigated the effect on AChR turnover of its interaction with rapsyn, a 43 kDa peripheral membrane protein that is closely associated with the AChR in muscle cells and is required for its clustering at endplates. Both in transfected COS cells and in cultured myotubes from rapsyn-negative and rapsyn-positive mice, we have found that the presence of rapsyn slows the turnover of AChRs by as much as twofold. The effect was similar for both embryonic (alpha2betadeltagamma) and adult (alpha2betadeltaepsilon) AChRs and for AChRs whose beta subunit lacked a putative tyrosine phosphorylation site. Neither colchicine nor cytochalasin D altered AChR turnover or prevented the rapsyn effect. Mutant rapsyn proteins whose N-terminal myristoylation signal was eliminated, or whose C terminus or zinc-finger domains were deleted, failed to change the rate of receptor turnover. Each of these mutations affects the association of the AChR with rapsyn, suggesting that AChR stability is altered by interaction between the two proteins. Our results suggest that, in addition to its role in AChR clustering, rapsyn also functions to metabolically stabilize the AChR.