Assembly and architecture of the type III secretion sorting platform.

Type III secretion systems are bacterial nanomachines specialized in protein delivery into target eukaryotic cells. The structural and functional complexity of these machines demands highly coordinated mechanisms for their assembly and operation. The sorting platform is a critical component of type III secretion machines that ensures the timely engagement and secretion of proteins destined to travel this export pathway. However, the mechanisms that lead to the assembly of this multicomponent structure have not been elucidated. Herein, employing an extensive in vivo cross-linking strategy aided by structure modeling, we provide a detailed intersubunit contact survey of the entire sorting platform complex. Using the identified cross-links as signatures for pairwise intersubunit interactions in combination with systematic genetic deletions, we mapped the assembly process of this unique bacterial structure. Insights generated by this study could serve as the bases for the rational development of antivirulence strategies to combat several medically important bacterial pathogens.

Improving a regional project on diagnostic reference levels for interventional procedures (OPRIPALC) with the support of a dose management system for the protection of patients and staff.

Interventional radiology is a clinical practice with important benefits for patients, but which involves high radiation doses. The optimisation of radiation protection (RP) for paediatric interventional cardiology is a priority for both patients and staff. The use of diagnostic reference levels (DRLs) has been proposed by the International Commission on Radiological Protection to improve RP in imaging procedures. Dose management systems (DMSs) allow the automatic collection of dosimetric, geometric and technical data to assist the optimisation process, with a continuous audit of the procedures, generating alerts to implement corrective actions when necessary. Patient dose indicators may be analysed individually and for different radiation events (fluoroscopy and cine runs). Occupational doses per procedure may be analysed (if electronic dosimeters are available) and linked with patient doses for an integrated approach to RP. Regional optimisation programmes require data collection and processing from several countries to set and periodically update the DRLs. Patient data is anonymised, and each participating hospital has access to their data in a central computer server. Using DMSs may be one of the best ways to support these programs in the collection and analysis of data, raising alerts about high patient and occupational doses and suggesting optimisation actions.

White blood cell count: a valuable tool for suspecting Cushing's syndrome.

PURPOSE: Simple screening tests to determine whether Cushing's syndrome (CS) should be ruled out are lacking. Tools that enable early diagnosis could reduce morbidity and associated sequelae. The potential of glucocorticoid-induced changes in the white blood cell (WBC) count for raising suspicion of CS is assessed. METHODS: This was a retrospective case‒control study. The WBC counts of 73 cases with CS and 146 matched controls were compared. The number of leukocytes (Leu), the number and percentage of neutrophils (N, Np), the number and percentage of lymphocytes (L, Lp), neutrophil-to-lymphocyte differences in the number and percentage (N-L, Np-Lp), neutrophil-to-lymphocyte ratio in the number and percentage (NLR, NLRp), and leukocyte-to-lymphocyte differences (Leu-L) were evaluated. The area under the ROC curve (AUC) was calculated for each of these parameters. Reference values were estimated that could help disclose occult CS. RESULTS: All ten parameters showed significant differences between cases and controls. The AUC was greater than 0.7 for all ten parameters, and was the best for the NLRp and Lp (AUC: 0.89). An Lp of 23.9% showed a diagnostic accuracy of 84.9% for the diagnosis of CS. The concordance of an Lp below 24% and more than 8000 leucocytes had a PPV of 78.2% for CS, while the pairing of an Lp over 24% and a Leu below 8000 cells had an NPV of 97.3% for CS. CONCLUSION: WBC count assessment can be an effective tool to raise suspicion of CS, prompting diagnostic testing. This simple and universally available test may allow earlier diagnosis of CS before highly evolved phenotypes develop.

Higher baseline resting metabolic rate is associated with 1-year frailty decline among older adults residing in an urban area.

BACKGROUND: Dysregulated energy metabolism is one hypothesized mechanism underlying frailty. Resting energy expenditure, as reflected by resting metabolic rate (RMR), makes up the largest component of total energy expenditure. Prior work relating RMR to frailty has largely been done in cross section with mixed results. We investigated whether and how RMR related to 1-year frailty change while adjusting for body composition. METHODS: N = 116 urban, predominantly African-American older adults were recruited between 2011 and 2019. One-year frailty phenotype (0-5) was regressed on baseline RMR, frailty phenotype, demographics and body composition (DEXA) in an ordinal logistic regression model. Multimorbidity (Charlson comorbidity scale, polypharmacy) and cognitive function (Montreal Cognitive Assessment) were separately added to the model to assess for change to the RMR-frailty relationship. The model was then stratified by baseline frailty status (non-frail, pre-frail) to explore differential RMR effects across frailty. RESULTS: Higher baseline RMR was associated with worse 1-year frailty (odds ratio = 1.006 for each kcal/day, p = 0.001) independent of baseline frailty, demographics, and body composition. Lower fat-free mass (odds ratio = 0.88 per kg mass, p = 0.008) was independently associated with worse 1-year frailty scores. Neither multimorbidity nor cognitive function altered these relationships. The associations between worse 1-year frailty and higher baseline RMR (odds ratio = 1.009, p < 0.001) and lower baseline fat-free mass (odds ratio = 0.81, p = 0.006) were strongest among those who were pre-frail at baseline. DISCUSSION: We are among the first to relate RMR to 1-year change in frailty scores. Those with higher baseline RMR and lower fat-free mass had worse 1-year frailty scores, but these relationships were strongest among adults who were pre-frail at baseline. These relationships were not explained by chronic disease or impaired cognition. These results provide new evidence suggesting higher resting energy expenditure is associated with accelerate frailty decline.

Willingness toward post-mortem body donation to science at a Mexican university: an exploratory survey.

BACKGROUND: Voluntary post-mortem donation to science (PDS) is the most appropriate source for body dissection in medical education and training, and highly useful for biomedical research. In Mexico, unclaimed bodies are no longer a legal source, but PDS is legally possible, although scarcely facilitated, and mostly ignored by the general population. Therefore, we aimed to evaluate the attitude and willingness for PDS and to identify a sociodemographic profile of people with willingness toward PDS. METHODS: A validated on-line survey was distributed by the convenience method via the social networks of a Catholicism-inspired, private university in northern Mexico. Frequency analyses of all variables and coded free comments were complemented with association studies. RESULTS: Although the responder cohort (n = 143) was too small and biased to be representative of the university community (n = 13,500), willingness to post-mortem organ donation was 90.7% and to PDS 70.7%. In this cohort, PDS willingness had the strongest association with mature age (> 40 years old; P, 0.0008). Among young adults, willingness to PDS was the lowest among volunteers from technical and business schools and the highest among those from the social sciences (P, 0.009). Respondents from the social sciences were also the most consistent between attitude and behavior with respect to organ donation. A free comment option revealed respondents were interested in the unusual taboo topic. CONCLUSIONS: A small, but sufficiently large proportion expressed willingness toward PDS. In our university cohort, which was biased in higher education and altruism, mature age and social interest were associated with PDS willingness.

Constitutional risk factors for focal neuropathies in patients referred for electromyography.

BACKGROUND AND PURPOSE: It is well established that patient-related constitutional features predispose to focal peripheral neuropathies. Some of these risk factors were investigated in common focal neuropathies encountered in patients referred for electromyography. METHODS: Gender, age, height and body mass index (BMI) were analysed retrospectively as risk factors for 11 focal neuropathies. In all, 9686 patients (age range 18-96 years; 58% women) were included from three different centres, with identical methods and equipment. RESULTS: High BMI was related to carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), combined CTS and UNE, meralgia paraesthetica and lumbar radiculopathy. In women, CTS and Morton's metatarsalgia were more common, whilst long thoracic neuropathies, suprascapular neuropathies and UNE were more common in men. Older age increased the risk for CTS, UNE, Morton's metatarsalgia and radiculopathies. CONCLUSIONS: Age, gender and BMI are important risk factors for many common focal neuropathies.

HIV epidemic and cascade of care in 12 east African rural fishing communities: results from a population-based survey in Uganda.

BACKGROUND: In East Africa, fishing communities are considered most-at-risk populations for the acquisition of HIV. We estimated HIV prevalence and assessed progress towards the UNAIDS 90-90-90 targets along the HIV treatment cascade in 12 fishing communities surrounding Lakes Edward and George, Uganda. METHODS: We conducted a cross-sectional household-based survey between September and November 2016. All adults between 15 and 69 years old were eligible to participate. Children below 15 years old were eligible for HIV testing if either parent was HIV-positive. Viral load testing was done for all HIV-infected individuals. Logistic regression models adjusted for sociodemographic-behavioral variables were used to assess the association between occupation and HIV positivity. RESULTS: Overall, 1738 adults (959 women, 779 men) and 148 children were included. Adult inclusion rate was 96.0%. Of the men, 58% reported to be fishermen. The HIV-prevalence among adults was 17.5% (95%CI: 15.8-19.4) and 6.1% (95%CI: 3.1-11.4) among HIV-exposed children. HIV prevalence was higher among women than among men (20.9% vs. 13.5%, p < 0.001). Among men, fishermen had a higher HIV prevalence (18.7%; 95%CI: 15.1-22.3) and a higher risk of being HIV-positive (aOR: 4.2; 95%CI: 2.0-9.1) than men of other occupations (p < 0.001). Progress towards the UNAIDS 90-90-90 targets was as follows: 86.5% (95%CI: 82.3-90.1%) of the HIV-positive participants were diagnosed, 98.7% (95%CI: 96.1-99.6%) of those aware were on antiretroviral therapy (ART), and 87.3% (95%CI: 82.3-91.0%) of those on ART were virally suppressed. Overall, 73% of all HIV-positive individuals were virally suppressed. Viral suppression was lower among individuals 15-24 years (45.5%) than among those 25-44 years (74.0%) and 45-69 years (85.0%), p < 0.001. Fishermen did not to have significant differences in the HIV cascade of care compared to men with other occupations. CONCLUSIONS: HIV prevalence was high in these fishing communities, particularly among women and fishermen. Important progress has been made along the HIV treatment cascade, and the UNAIDS goal for viral suppression in population was achieved. However, gaps remain and HIV care strategies focusing on young people are urgently needed. HIV preventive interventions should target particularly women, young people and fishermen though HIV preventive and care services should remain available to the whole fishing communities.

Current Practice in Vitamin D Management in Allogeneic Hematopoietic Stem Cell Transplantation: A Survey by the Transplant Complications Working Party of the European Society for Blood and Marrow Transplantation.

Beyond its impact on bone health, numerous studies have investigated the immune-regulatory properties of vitamin D and shown how its deficiency can affect outcomes in allogeneic hematopoietic stem cell transplantation (HSCT), particularly in acute or chronic graft-versus-host disease. This survey, carried out by the Transplant Complications Working Party of the European Society for Blood and Marrow Transplantation (EBMT), describes the current clinical practice discrepancies across the EBMT HSCT programs. We therefore recommend the development of evidence-based guidelines to standardize evaluation criteria and to harmonize the management of vitamin D deficiency in patients undergoing allogeneic HSCT.

The Growth arrest specific 1 (Gas1) gene is transcriptionally regulated by NeuroD1 via two distal E-boxes.

Growth arrest specific 1 (GAS1) is a signaling mediator for the development of the central nervous system that works as a co-receptor for sonic hedgehog (SHH) to induce the amplification of neural progenitors during the patterning of the mammalian neural tube and establishing granular cells in the cerebellum. Recently, we confirmed that Gas1 is also expressed by neural progenitors of the developing cortex and the dentate gyrus of the hippocampus. The presence of GAS1 in progenitor stages indicates that one of its principal roles is the maintenance of these cells during neurogenic events. However, the signals responsible for the expression of Gas1 in progenitor cells are unknown, an aspect that is relevant to understand its functions during neurogenesis. Here, we focused on elucidating the mechanisms of the transcriptional regulation of Gas1 and using comparative genomics methods found two highly conserved E-boxes in the Gas1 promoter which mediate its up-regulation by NeuroD1. Additionally, we found that GAS1 and NeuroD1 co-localize in the neocortex, the dentate gyrus of the hippocampus and the external granular layer of the cerebellum, suggesting a previously unsuspected regulatory relationship. Our data indicate that Gas1 is a direct target of NeuroD1 during the induction of the neurogenic program.

Halogen-like properties of the Al13 cluster mimicking astatine.

Astatine-211 is considered to be one of the most promising alpha-emitters in targeted alpha therapy (TAT). However, its development has been hindered by its not so well understood chemistry. Hence, any attempt to understanding it better is imperative. Here, we show through DFT calculations that the neutral endohedral Al13 cluster follows a reactivity pattern very similar to At, more than any other halogen. The halogen and alkali bonding with Al13 and At presented a strong similarity in their charge transfer processes. Moreover, upon the interchange of At with Al13, we found a stable configuration of the compound corresponding to the astatination of aryliodonium salts, which have been considered as possible precursors for the synthesis of 211At-labeled tracers. Our results provide promising proof of concept that the Al13 cluster mimics the behaviour of At and might help in better understanding its chemistry and in streamlining the chemical processes of radiolabeling biomolecules.

[Research of the cadmium intoxication effect on the model of vitamin-mineral deficiency in rats].

The article presents the results of the study aimed at confirmation of the effectiveness of the rats' adaptive potential reduction under conditions of cadmium salt toxic effects. The 65-days experiment was conducted in male and female Wistar rats. Animals were divided into 6 groups of 3 control and 3 experimental, 30 males and females in each. In total 360 rats were used in the experiment (180 females and 180 males). Rats of the 1st control group received a diet with optimal (75% of the standard semisyntethic diet content) dosage of vitamins B1, B2, B3, B6 and mineral substances, Fe3+ and Mg2+, the rats of the 2nd and the 3rd control group - diets with marginal (30% for males and 28% for females) and submarginal (19% for males and 18% for females) doses of essential micronutrients. Animals of the 1-3th experimental groups received Cd2+ on the background of optimal, marginal and submarginal providing of essential micronutrients. The hematological, biochemical and morphological parameters and the antioxidant status of rats have been studied. The obtained results allowed to identify patterns of cadmium toxic effect strengthen on the background of essential nutrients reducing (in the row from optimal to submarginal). These changes showed erythrocyte and platelet blood profiles, and a set of indicators of the antioxidant defense system and lipid peroxidation of blood and liver. Thus, the activity of erythrocyte antioxidant enzymes - glutathione reductase, glutathione peroxidase, catalase and superoxide dismutase in rats of the 1st experimental group were on average by 23% higher than in animals of the 1st control group, the rats of the 2nd and the 3rd experimental groups by 62 and 67% higher, respectively. The content of lipid peroxidation products in blood and liver of male and female rats showed a similar trend: an increase by 5% in the 1st experimental group by 9 and 25% in the 2nd and 3rd experimental groups respectively. Thus, the modification of the diets' vitamin-mineral composition may be used as a model of adaptive potential reduction in rats in the toxicological research of objects with unknown toxicity, in particular novel food products.

[Effect of B-vitamin deficiency on biochemical, immunologic markers and trace element status of rats and mice of various lines].

Biochemical, vitamin, trace element and immunological changes were searched for the combined nutritional deficiency of vitamins B1, B2, B6 on in vivo models in rats and mice. Female rats of Wistar (W) strain and hybrids of the 1st generation of Dark Aguti and Wistar (DA x W) strains, female mice of BALB/c strain and DBCB tetrahybrids were used in experiment. Animals received for 35 days a balanced diet (control) according to AIN-93 or a similar diet with the exception of vitamins B1, B2, B6 (experimental groups). The content of vitamins B1, B2 in liver, riboflavin blood plasma level and urinary excretion of thiamine, riboflavin and 4-pyridoxic acid were determined, as well as in rats: blood and liver content of α-tocopherol and retinol, blood biochemical indices of lipid and nitrogen metabolism, activity of cytochrome P isoforms-450 (CYP) in liver; in mice: the circulating levels of pro- and anti-inflammatory cytokines of blood plasma, in animals of both species - the content of essential and toxic elements in the kidneys. DAxW rats compared to W and DBCB mice compared to BALB/c were more sensitive to the development of B-vitamin deficiency judging by the B-vitamin status indicators. In the rats of the experimental groups, there were signs of a deterioration in blood and liver levels of vitamin E, multidirectional shifts in vitamin A sufficiency, increased activity of the CYP3A isoform (6ß-TG), a decrease in triglycerides, total protein and albumin fraction levels with an increase in urea level. Manifestation degree of these effects depended on the choice of the animal's line. In mice, the B-vitamin deficiency was characterized by an increase in the levels of proinflammatory cytokines TNF-α, IL-10, IL-Ιß, IL-6 and a decrease in IFN-γ and IL-17A. The content of magnesium, copper, zinc, chromium and silver was lowered, of cesium - was increased in the kidneys of the rats of the experimental groups. In mice, B-vitamin deficiency resulted in diminishment of magnesium, copper, zinc, chromium, selenium, cadmium and lead content, excess accumulation of cobalt and cesium. Some of these biomarkers are supposed to be used in pre-clinical evaluation of the effectiveness of new vitamin complexes, specialized foods and dietary supplements, as well as studies of interactions of various vitamins.

Comment on "Elucidation of charge-transfer SERS selection rules by considering the excited state properties and the role of electrode potential" by M. Mohammadpour, M. H. Khodabandeh, L. Visscher and Z. Jamshidi, Phys. Chem. Chem. Phys., 2017, 19, 7833.

The differences between alternative approaches for quantifying the complex effect of the electronic structure of charged metal-molecule hybrids in SERS (the so-called chemical enhancement mechanism) are highlighted. The discussion is focussed on the predictions obtained by using different methodological tools for modelling the role of the electrode potential in the SERS relative intensities. Finite electric fields are used in the commented paper for this purpose, but we have found some inconsistences in the results and the method for calculating the Raman intensities is not made sufficiently clear, which prevents the assessment of the results.

Environmental impact of geometric earthwork construction in pre-Columbian Amazonia.

There is considerable controversy over whether pre-Columbian (pre-A.D. 1492) Amazonia was largely "pristine" and sparsely populated by slash-and-burn agriculturists, or instead a densely populated, domesticated landscape, heavily altered by extensive deforestation and anthropogenic burning. The discovery of hundreds of large geometric earthworks beneath intact rainforest across southern Amazonia challenges its status as a pristine landscape, and has been assumed to indicate extensive pre-Columbian deforestation by large populations. We tested these assumptions using coupled local- and regional-scale paleoecological records to reconstruct land use on an earthwork site in northeast Bolivia within the context of regional, climate-driven biome changes. This approach revealed evidence for an alternative scenario of Amazonian land use, which did not necessitate labor-intensive rainforest clearance for earthwork construction. Instead, we show that the inhabitants exploited a naturally open savanna landscape that they maintained around their settlement despite the climatically driven rainforest expansion that began ∼2,000 y ago across the region. Earthwork construction and agriculture on terra firme landscapes currently occupied by the seasonal rainforests of southern Amazonia may therefore not have necessitated large-scale deforestation using stone tools. This finding implies far less labor--and potentially lower population density--than previously supposed. Our findings demonstrate that current debates over the magnitude and nature of pre-Columbian Amazonian land use, and its impact on global biogeochemical cycling, are potentially flawed because they do not consider this land use in the context of climate-driven forest-savanna biome shifts through the mid-to-late Holocene.

Dermatophagoides pteronyssinus: Changes in sensitisation in the past 11 years and comparison with other centres in Mexico.

BACKGROUND: House dust mites are a ubiquitous air allergen in the human habitat. It has been shown that exposure to them is a fundamental factor in sensitisation and development of atopic disease. The objective of the study was to analyse changes in sensitisation to Dermatophagoides pteronyssinus (Der p.) in children treated in a tertiary level care hospital in Mexico City for a period of 11 years and compare with other studies carried out in Mexico. METHODS: A retrospective study was performed at the Hospital Infantil de México Federico Gómez (HIMFG). Information was gathered from skin tests for Der p. performed in the Allergy Laboratory from January 2004 to April 2015. Patients 2-18 years old who presented for examination of some type of allergic condition and who had immediate hypersensitivity tests to Der p. were included in the study. Results were compared with prior reports from other institutions. Descriptive analysis and χ2 statistics were used. RESULTS: A total of 8794 patients were included in the study; 49.3% of the tests (95% CI 48-50) were positive for Der p. The percentage of monosensitised to mites was 2.7% for Der p. (95% CI 2-3). A significant difference was found between the results of older patients and those <6 years old. The frequency of sensitisation had a tendency to decrease during the 11 years analysed in all age groups. CONCLUSIONS AND CLINICAL RELEVANCE: The frequency of sensitisation to Der p. increased with age until reaching adolescence. In the last 11 years a decrease in sensitisation to this air allergen was observed.

Diagnostic reference levels and complexity indices in interventional radiology: a national programme.

OBJECTIVES: To propose national diagnostic reference levels (DRLs) for interventional radiology and to evaluate the impact of the procedural complexity on patient doses. METHODS: Eight interventional radiology units from Spanish hospitals were involved in this project. The participants agreed to undergo common quality control procedures for X-ray systems. Kerma area product (KAP) was collected from a sample of 1,649 procedures. A consensus document established the criteria to evaluate the complexity of seven types of procedures. DRLs were set as the 3rd quartile of KAP values. RESULTS: The KAP (3rd quartile) in Gy cm2 for the procedures included in the survey were: lower extremity arteriography (n = 784) 78; renal arteriography (n = 37) 107; transjugular hepatic biopsies (THB) (n = 30) 45; biliary drainage (BD) (n = 314) 30; uterine fibroid embolization (UFE) (n = 56) 214; colon endoprostheses (CE) (n = 31) 169; hepatic chemoembolization (HC) (n = 269) 303; femoropopliteal revascularization (FR) (n = 62) 119; and iliac stent (n = 66) 170. The complexity involved the increases in the following KAP factors from simple to complex procedures: THB x4; BD x13; UFE x3; CE x3; HC x5; FR x5 and IS x4. CONCLUSIONS: The evaluation of the procedure complexity in patient doses will allow the proper use of DRLs for the optimization of interventional radiology. KEY POINTS: • National DRLs for interventional procedures have been proposed given level of complexity • For clinical audits, the level of complexity should be taken into account. • An evaluation of the complexity levels of the procedure should be made.

Clinical management departments for the neurosciences.

INTRODUCTION: Neuroscience-related clinical management departments (UGC in Spanish) represent a means of organising hospitals to deliver patient-centred care as well as specific clinical and administrative management models. DEVELOPMENT: The authors review the different UGC models in Spain and their implementation processes as well as any functional problems. We pay special attention to departments treating neurological patients. CONCLUSIONS: Neuroscience-related specialties may offer a good framework for the units that they contain. This may be due to the inherent variability and costs associated with neurological patients, the vital level of coordination that must be present between units providing care, and probably to the dynamic nature of the neurosciences as well. Difficulties associated with implementing and gaining acceptance for the new model have limited such UGCs until now.

Seroprevalence of Leishmania infection among asymptomatic renal transplant recipients from southern Spain.

BACKGROUND: The aim of this article is to assess the seroprevalence of Leishmania infection among asymptomatic renal transplant recipients in a population in the south of Spain. METHODS: Serum samples were screened for immunoglobulin-G antibodies against Leishmania with an indirect fluorescent antibody test. RESULTS: Of 625 examined serum samples, 30 (4.8%) samples were positive for Leishmania antibodies. Thirteen samples showed titers of 1:80, 15 samples showed titers of 1:160, and 2 samples showed titers of 1:320. None of the patients with positive serology to Leishmania showed signs or symptoms compatible with leishmaniasis. CONCLUSION: The prevalence of Leishmania infection found among asymptomatic renal transplant patients reinforces the need for attention in evaluation of these patients in endemic areas.

Reexamination of the origin of the pseudo Jahn-Teller puckering instability in silicene.

Silicene, the graphene-like crystal formed by the Si hexagonal lattice, presents a periodic buckled structure whose origin is due to the pseudo Jahn-Teller instability on each of its planar six membered rings. This has been attributed to the coupling of the planar D6h ground state with the first b2g excited state through a b2g vibrational mode. Here we show, by explicitly calculating the vibronic coupling constants through a complete study of the PJT effect, that the vibronic coupling of the ground state with only one excited state to explain the planar instability is inconsistent with the linear multilevel PJT effect theory. It is also shown that in order to have consistency, the PJT model should include the next excited state, which is symmetry compatible coupled to the puckering mode. This is done by the analysis, based on DFT and TDDFT calculations, of the vibronic instability of the ground state of hexasilabenzene, the basic silicon hydrogenated hexagonal ring unit defining silicene.

The electronic structure of metal-molecule hybrids in charged interfaces: surface-enhanced Raman selection rules derived from plasmon-like resonances.

DFT calculations predict that plasmon-like excitations in small metal clusters are able to selectively modify the relative intensities of specific SERS bands of adsorbed molecules. These electronic resonances provide new kinds of SERS selection rules which can explain the huge enhancement of mode 9a of pyridine in the spectra recorded at negative electrode potentials.