Prevalence and predictors of mental health outcomes in UK doctors and final year medical students during the COVID-19 pandemic

BACKGROUND

The mental health of doctors is an ongoing concern, both prior to and during the COVID-19 pandemic. This study aimed to: i) assess the prevalence of symptoms of depression, anxiety, PTSD, and burnout in UK doctors and final year medical students during the pandemic, and ii) analyse the hypothesised relationships between psychological flexibility, intolerance of uncertainty and resilience with these mental health outcomes.

METHODS

A cross-sectional online study of UK-based doctors and final year medical students was conducted between 27/09/2020 and 31/01/2021. Outcomes were measured using the PHQ9, GAD7, PCL-5, and aMBI. Independent variables included the CompACT-SF, IUS-12, and CD-RISC-10. Descriptive statistics, between-group analyses, and multiple regression were performed.

RESULTS

Prevalence of anxiety symptoms was 26.3%, depression 21.9%, PTSD 11.8%, and burnout 10.8%. Psychological flexibility negatively predicted all outcomes, apart from low personal achievement. Intolerance of uncertainty positively predicted anxiety and PTSD scores. Resilience negatively predicted scores on burnout subscales.

LIMITATIONS

Cross-sectional design and non-probability sampling method means that assumptions about causality cannot be made and may have implications for bias and generalisability of results.

CONCLUSION

Doctors and medical students in the UK reported high levels of mental health symptoms during the pandemic, between September 2020 and January 2021. All three independent variables explained significant variance in mental health outcomes. Psychological flexibility was the most consistent predictor, over and above sociodemographic variables and other psychological predictors. These findings have implications for interventions to improve retention of our essential medical workforce, and for providing support at future times of national crisis.

The thermodynamics of Pr55Gag-RNA interaction regulate the assembly of HIV

The interactions that occur during HIV Pr55^Gag oligomerization and genomic RNA packaging are essential elements that facilitate HIV assembly. However, mechanistic details of these interactions are not clearly defined. Here, we overcome previous limitations in producing large quantities of full-length recombinant Pr55^Gag that is required for isothermal titration calorimetry (ITC) studies, and we have revealed the thermodynamic properties of HIV assembly for the first time. Thermodynamic analysis showed that the binding between RNA and HIV Pr55^Gag is an energetically favourable reaction (ΔG<0) that is further enhanced by the oligomerization of Pr55^Gag. The change in enthalpy (ΔH) widens sequentially from: (1) Pr55^Gag-Psi RNA binding during HIV genome selection; to (2) Pr55^Gag-Guanosine Uridine (GU)-containing RNA binding in cytoplasm/plasma membrane; and then to (3) Pr55^Gag-Adenosine(A)-containing RNA binding in immature HIV. These data imply the stepwise increments of heat being released during HIV biogenesis may help to facilitate the process of viral assembly. By mimicking the interactions between A-containing RNA and oligomeric Pr55^Gag in immature HIV, it was noted that a p6 domain truncated Pr50^{Gag Δp6} is less efficient than full-length Pr55^Gag in this thermodynamic process. These data suggest a potential unknown role of p6 in Pr55^Gag-Pr55^Gag oligomerization and/or Pr55^Gag-RNA interaction during HIV assembly. Our data provide direct evidence on how nucleic acid sequences and the oligomeric state of Pr55^Gag regulate HIV assembly.

Formation of any virus particle will require energy, yet the precise biophysical properties that drive the formation of HIV particles remain undefined. Isothermal titration calorimetry (ITC) is a biophysical technique that is the gold standard to reveal parameters governing biochemical and biophysical reaction. However, ITC requires large amount of proteins for analysis. As large quantities of full-length recombinant HIV Pr55^Gag proteins have not been available in the past 30 years due to technical limitation, a comprehensive thermodynamic analysis of full-length HIV Pr55^Gag has not been possible. Here, we have generated sufficient amount of full-length recombinant HIV Pr55^Gag protein for isothermal titration calorimetry analysis. Our analyses have shown that the major interactions amongst HIV proteins and RNA sequences during viral assembly are energetically favourable reactions. In other words, HIV Pr55^Gag proteins and viral RNA have evolved to overcome the energy barrier for virus formation by utilising energy obtained from protein-RNA interactions in order to facilitate the viral assembly process. Furthermore, HIV also use the oligomeric states of HIV Pr55^Gag proteins and the RNA sequences as means to regulate the viral assembly process.

Plasmonic Ge-doped ZnO nanocrystals

We present the first colloidal synthesis of Ge-doped ZnO nanocrystals, which are produced by a scalable method that uses only air and moisture stable precursors. The incorporation of tetravalent Ge ions within ZnO nanocrystals generates a surface plasmon resonance in the near-mid infrared, and induces a change in morphology, from isotropic spheroidal nanocrystals to rod-like, elongated structures with a distinctive c-axis orientation.

Novel steric stabilizers for lyotropic liquid crystalline nanoparticles: PEGylated-phytanyl copolymers

Lyotropic liquid crystalline nanostructured particles (e.g., cubosomes and hexosomes) are being investigated as delivery systems for therapeutics in biomedical and pharmaceutical applications. Long term stability of these particulate dispersions is generally provided by steric stabilizers, typically commercially available amphiphilic copolymers such as Pluronic F127. Few examples exist of tailored molecular materials designed for lyotropic liquid crystalline nanostructured particle stabilization. A library of PEGylated-phytanyl copolymers (PEG-PHYT) with varying PEG molecular weights (200-14K Da) was synthesized to assess their performance as steric stabilizers for cubosomes and to establish structure-property relationships. The PEGylated-lipid copolymers were first found to self-assemble in excess water in the absence of cubosomes and also displayed thermotropic liquid crystal phase behavior under cross-polarized light microscopy. An accelerated stability assay was used to assess the performance of the copolymers, compared to Pluronic F127, for stabilizing phytantriol-based cubosomes. Several of the PEGylated-lipid copolymers showed steric stabilizer effectiveness comparable to Pluronic F127. Using synchrotron small-angle X-ray scattering and cryo-transmission electron microscopy, the copolymers were shown to retain the native internal lyotropic liquid crystalline structure, double diamond cubic phase (Q2(D)), of phytantriol dispersions; an important attribute for controlling downstream performance.

Higher and lower supramolecular orders for the design of self-assembled heterochiral tripeptide hydrogel biomaterials

The use ofd- orl-amino acids allows for a high or low supramolecular order and stability to design self-assembled peptide hydrogels.

Rational design of a hexapeptide hydrogelator for controlled-release drug delivery

The amphiphilic peptide sequence H-Phe-Glu-Phe-Gln-Phe-Lys-OH (MBG-1) is developed as a novel hydrogelator for use in controlled-drug release administration, which is the smallest tunable ionic self-complementary hydrogelating peptide reported to date making it attractive for larger scale preparation. Hydrogelation is demonstrated to result from self-assembly of the peptide into beta-sheet nanofibers that are physically cross-linked by intertwining as well as larger bundle formation. Finally, the release of two small molecule cargos, fluorescein sodium and ciprofloxacin hydrochloride, is demonstrated revealing a two-stage zero-order sustained release profile up to 80% cumulative release over eight days.

Thermostability and reversibility of silver nanoparticle-protein binding

The interactions between nanoparticles (NPs) and proteins in living systems are a precursor to the formation of a NP-protein "corona" that underlies cellular and organism responses to nanomaterials. However, the thermodynamic properties and reversibility of NP-protein interactions have rarely been examined. Using an automated, high-throughput and temperature-controlled dynamic light scattering (DLS) technique we observed a distinct hysteresis in the hydrodynamic radius of branched polyethyleneimine (BPEI) coated-silver nanoparticles (bAgNPs) exposed to like-charged lysozyme during the processes of heating and cooling, in contrast to the irreversible interactions between bAgNPs and oppositely charged alpha lactalbumin (ALact). Our discrete molecular dynamics (DMD) simulations offered a new molecular insight into the differential structure, dynamics and thermodynamics of bAgNPs binding with the two protein homologs and further revealed the different roles of the capping agents of citrate and BPEI in NP-protein interactions. This study facilitates our understanding of the transformation of nanomaterials in living systems, whose implications range from the field study of nanotoxicology to nanomaterials synthesis, nanobiotechnology and nanomedicine.

Remobilisation of silver and silver sulphide nanoparticles in soils

Manufactured nanoparticles (NPs) present in consumer products could enter soils through re-use of biosolids. Among these NPs are those based on silver (Ag), which are found sulphidised (e.g. silver sulphide, Ag2S) in biosolids. Herein, our aim was to examine the release of retained Ag(0) and Ag2S NPs in soils and biosolids as facilitated by environmentally and agriculturally relevant ligands. Under natural soil conditions, exemplified by potassium nitrate and humic acid experiments, release of Ag retained in soil was limited. The highest total Ag release was facilitated by ligands that simulated root exudates (citrate) or fertilisers (thiosulphate). Released Ag was predominantly present in the colloidal phase (>3 kDa-< 0.45 μm); intact NPs only identified in Ag2S-NP extracts. For biosolids containing nanoparticulate-Ag-S, release was also enhanced by thiosulphate, though mostly as colloidal-Ag - not intact NPs. These results suggest that exposure to NPs as a result of its release from soils or biosolids will be low.

Synthesis and Self-Assembly of a Peptide - Amphiphile as a Drug Delivery Vehicle

The formation of functional liposomes by the self assembly of a peptide–amphiphile that comprises the neuroprotective tripeptide motif glycyl-prolyl-glutamic acid linked to a hydrophobic moiety is reported. The self-assembled peptide–lipid conjugate displays long range order and can be dispersed as nanometre sized particles.

Temperature-Responsive Self-Assemblies of ‘Kinked' Amphiphiles

The synthesis of novel norbornane-based amphiphiles and the thermal response of their corresponding colloids is presented. It was found that the hydrodynamic diameter (DH) expansion or contraction of 1–4 in response to increasing temperature was governed by the length of the hydrophobic region possessed by the amphiphile (a 12 or 16 carbon chain). These data were used as a starting point to extend into an active tumour targeting system whereby two amphiphiles were modified to incorporate the oestrogen receptor antagonist Tamoxifen at the polar head group. This was achieved by a triazole moiety while both the C12 (18) or C16 (19) hydrophobic chains were incorporated as the hydrophobic region in an attempt to retain the response to thermal stimuli observed in our preliminary findings. These functionalised novel amphiphiles possessed critical aggregation concentration values of 510 and 19 µM, while aqueous self-assemblies of 56 and 106 nm for 18 and 19 were observed. Imaging by cryogenic transmission electron microscopy showed 18 to possess liposomal morphology, while 19, bearing a C16 hydrophobic portion, formed non-defined amorphous aggregates. Finally, the response to temperature of these assemblies was investigated with only the C12 variant 18 displaying a temperature response in the 5–55°C thermal window investigated.

Unzipping the role of chirality in nanoscale self-assembly of tripeptide hydrogels

Change of chirality is a useful tool to manipulate the aqueous self-assembly behaviour of uncapped, hydrophobic tripeptides. In contrast with other short peptides, these tripeptides form hydrogels at a physiological pH without the aid of organic solvents or end-capping groups (e.g. Fmoc). The novel hydrogel forming peptide (D)Leu-Phe-Phe ((D)LFF) and its epimer Leu-Phe-Phe (LFF) exemplify dramatic supramolecular effects induced by subtle changes to stereochemistry. Only the d-amino acid-containing peptide instantly forms a hydrogel in aqueous solution following a pH switch, generating long fibres (>100 μm) that entangle into a 3D network. However, unexpected nanostructures are observed for both peptides and they are particularly heterogeneous for LFF. Structural analyses using CD, FT-IR and fluorescent amyloid staining reveal anti-parallel beta-sheets for both peptides. XRD analysis also identifies key distances consistent with beta-sheet formation in both peptides, but suggests additional high molecular order and extended molecular length for (D)LFF only. Molecular modelling of the two peptides highlights the key interactions responsible for self-assembly; in particular, rapid self-assembly of (D)LFF is promoted by a phenylalanine zipper, which is not possible because of steric factors for LFF. In conclusion, this study elucidates for the first time the molecular basis for how chirality can dramatically influence supramolecular organisation in very short peptide sequences.

Modulation of amyloid-β 1-42 structure and toxicity by proline-rich whey peptides

A proline-rich peptide product prepared from bovine whey protein that was enriched in several hydrophobic amino acids including proline (whey proline-rich peptide, wPRP) was shown to modulate the folding pathway of human amyloid beta peptide 1-42 (Aβ42) into oligomers. Concentration-dependent changes in ThT-binding to Ab42 by wPRP indicated suppression of oligomerisation, that was supported by Transmission Electron Microscopy. Suppression of β-sheet and specifically, anti-parallel β-sheet structures by wPRP was demonstrated by ATR-FTIR spectroscopy, where evidence for capacity of wPRP to dissociate pre-existing β-sheet structures in Aβ42 was also apparent. Suppression of anti-parallel β-sheets of oligomeric Aβ42 was associated with rescue of yeast and SH-SY5Y neuronal cells providing important evidence for the association between anti-parallel β-sheet structure and oligomer toxicity. It was proposed that the interaction of wPRP with Aβ42 interfered with the anti-parallel folding pathway of oligomeric Aβ42 and ultimately produced 'off-pathway' structures of lowered total β-sheet content, with attenuated cellular toxicity.

Structure of the dengue virus glycoprotein non-structural protein 1 by electron microscopy and single-particle analysis

The flavivirus non-structural protein 1 (NS1) is a glycoprotein that is secreted as a soluble hexameric complex during the course of natural infection. Growing evidence indicates that this secreted form of NS1 (sNS1) plays a significant role in immune evasion and modulation during infection. Attempts to determine the crystal structure of NS1 have been unsuccessful to date and relatively little is known about the macromolecular organization of the sNS1 hexamer. Here, we have applied single-particle analysis to images of baculovirus-derived recombinant dengue 2 virus NS1 obtained by electron microscopy to determine its 3D structure to a resolution of 23 Å. This structure reveals a barrel-like organization of the three dimeric units that comprise the hexamer and provides further insights into the overall organization of oligomeric sNS1.

Revisiting β-casein as a stabilizer for lipid liquid crystalline nanostructured particles

Lipid liquid crystalline nanoparticles such as cubosomes and hexosomes have unique internal nanostructures that have shown great potential in drug and nutrient delivery applications. The triblock copolymer, Pluronic F127, is usually employed as a steric stabilizer in dispersions of lipid nanostructured particles. In this study, we investigated the formation, colloidal stability and internal nanostructure and morphology of glyceryl monooleate (GMO) and phytantriol (PHYT) cubosome dispersions on substituting β-casein with F127 in increasing proportion as the stabilizer. Internal structure and particle morphology were evaluated using small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM), while protein secondary structure was studied using synchrotron radiation circular dichroism (SRCD). The GMO cubosome dispersion stabilized by β-casein alone displayed a V(2) (Pn3m) phase structure and a V(2) to H(2) phase transition at 60 °C. In comparison, F127-stabilized GMO dispersion had a V(2) (Im3m) phase structure and the H(2) phase only appeared at higher temperature, that is, 70 °C. In the case of PHYT dispersions, only the V(2) (Pn3m) phase structure was observed irrespective of the type and concentration of stabilizers. However, β-casein-stabilized PHYT dispersion displayed a V(2) to H(2) to L(2) transition behavior upon heating, whereas F127-stabilized PHYT dispersion displayed only a direct V(2) to L(2) transition. The protein secondary structure was not disturbed by interaction with GMO or PHYT cubosomes. The results demonstrate that β-casein provides steric stabilization to dispersions of lipid nanostructured particles and avoids the transition to Im3m structure in GMO cubosomes, but also favors the formation of the H(2) phase, which has implications in drug formulation and delivery applications.

Durability and inflammogenic impact of carbon nanotubes compared with asbestos fibres

Background

It has been suggested that carbon nanotubes might conform to the fibre pathogenicity paradigm that explains the toxicities of asbestos and other fibres on a continuum based on length, aspect ratio and biopersistence. Some types of carbon nanotubes satisfy the first two aspects of the fibre paradigm but only recently has their biopersistence begun to be investigated. Biopersistence is complex and requires in vivo testing and analysis. However durability, the chemical mimicking of the process of fibre dissolution using in vitro treatment, is closely related to biopersistence and more readily determined. Here, we describe an experimental process to determine the durability of four types of carbon nanotubes in simulated biological fluid (Gambles solution), and their subsequent pathogenicity in vivo using a mouse model sensitive to inflammogenic effects of fibres. The in vitro and in vivo results were compared with well-characterised glass wool and asbestos fibre controls.

Results

After incubation for up to 24 weeks in Gambles solution, our control fibres were recovered at percentages consistent with their known in vitro durabilities and/or in vivo persistence, and three out of the four types of carbon nanotubes tested (single-walled (CNT_SW) and multi-walled (CNT_TANG2, CNT_SPIN)) showed no, or minimal, loss of mass or change in fibre length or morphology when examined by electron microscopy. However, the fourth type [multi-walled (CNT_LONG1)] lost 30% of its original mass within the first three weeks of incubation, after which there was no further loss. Electron microscopy of CNT_LONG1 samples incubated for 10 weeks confirmed that the proportion of long fibres had decreased compared to samples briefly exposed to the Gambles solution. This loss of mass and fibre shortening was accompanied by a loss of pathogenicity when injected into the peritoneal cavities of C57Bl/6 mice compared to fibres incubated briefly. CNT_SW did not elicit an inflammogenic effect in the peritoneal cavity assay used here.

Conclusions

These results support the view that carbon nanotubes are generally durable but may be subject to bio-modification in a sample-specific manner. They also suggest that pristine carbon nanotubes, either individually or in rope-like aggregates of sufficient length and aspect ratio, can induce asbestos-like responses in mice, but that the effect may be mitigated for certain types that are less durable in biological systems. Results indicate that durable carbon nanotubes that are either short or form tightly bundled aggregates with no isolated long fibres are less inflammogenic in fibre-specific assays.

Structural and functional basis of resistance to neuraminidase inhibitors of influenza B viruses

We have identified a virus, B/Perth/211/2001, with a spontaneous mutation, D197E in the neuraminidase (NA), which confers cross-resistance to all NA inhibitors. We analyzed enzyme properties of the D197 and E197 NAs and compared these to a D197N NA, known to arise after oseltamivir treatment. Zanamivir and peramivir bound slowly to the wild type NA, but binding of oseltamivir was more rapid. The D197E/N mutations resulted in faster binding of all three inhibitors. Analysis of the crystal structures of D197 and E197 NAs with and without inhibitors showed that the D197E mutation compromised the interaction of neighboring R150 with the N-acetyl group, common to the substrate sialic acid and all NA inhibitors. Although rotation of the E275 in the NA active site occurs upon binding peramivir in both the D197 and E197 NAs, this does not occur upon binding oseltamivir in the E197 NA. Lack of the E275 rotation would also account for the loss of slow binding and the partial resistance of influenza B wild type NAs to oseltamivir.

Engineered antibody intervention strategies for Alzheimer's disease and related dementias by targeting amyloid and toxic oligomers

Most neurodegenerative disorders, such as Alzheimer's (AD), Parkinson's, Huntington's and Creutzfeldt-Jakob disease, are characterised by the accumulation of insoluble filamentous aggregates known as amyloid. These pathologies share common pathways involving protein aggregation which can lead to fibril formation and amyloid plaques. The 4 kDa Abeta peptide (39-43 amino acids) derived from the proteolysis of the amyloid precursor protein is currently a validated target for therapy in AD. Both active and passive immunisation studies against Abeta are being trialled as potential AD therapeutic approaches. In this study, we have characterised engineered antibody fragments derived from the monoclonal antibody, WO-2 which recognises an epitope in the N-terminal region of Abeta (amino acids 2-8 of Abeta). A chimeric recombinant Fab (rFab) and single chain fragments (scFvs) of WO-2 were constructed and expressed in Escherichia coli. Rationally designed mutants to improve the stability of antibody fragments were also constructed. All antibody formats retained high affinity (K(D) approximately 8 x 10(-9) M) for the Abeta peptide, comparable with the intact parental IgG as measured by surface plasmon resonance. Likewise, all engineered fragments were able to: (i) prevent amyloid fibrillisation, (ii) disaggregate preformed Abeta(1-42) fibrils and (iii) inhibit Abeta(1-42) oligomer-mediated neurotoxicity in vitro as efficiently as the whole IgG molecule. These data indicate that the WO-2 antibody and its fragments have immunotherapeutic potential. The perceived advantages of using small Fab and scFv engineered antibody formats which lack the effector function include more efficient passage across the blood-brain barrier and minimising the risk of triggering inflammatory side reactions. Hence, these recombinant antibody fragments represent attractive candidates and safer formulations of passive immunotherapy for AD.

Alzheimer's Abeta fused to green fluorescent protein induces growth stress and a heat shock response

The 42 amino acid Alzheimer's Abeta peptide is involved in the progression of Alzheimer's disease. Here we describe the effects of intracellular Abeta, produced through its attachment to either end of a green fluorescent protein, in yeast. Cells producing Abeta exhibited a lower growth yield and a heat shock response, showing that Abeta fusions promote stress in cells and supporting the notion that intracellular Abeta is a toxic molecule. These studies have relevance in understanding the role of Abeta in the death of neuronal cells, and indicate that yeast may be a new tractable model system for the screening for inhibitors of the stress caused by Abeta.

Availability bias in clinical formulation: the first idea that comes to mind

This study tested whether initial client formulations are based simply on the ideas that come most readily to mind, irrespective of the validity of these ideas. This phenomenon is known in decision theory literature as availability bias. The study tested the influence of two possible sources of availability bias in formulation: (a) theoretical orientation; and (b) a suggestion in a referral letter. Forty-four qualified and 20 trainee clinical psychologists participated in a procedure designed to reflect clinical practice. Clinical materials consisted of a fictional referral letter describing a client with adult attachment difficulties and post-traumatic stress disorder. Participants recalled information from the referral letter, described their areas of further interest and initial hypotheses. Results showed no evidence of an availability bias in clinical formulation as a result of theoretical orientation. Theoretical orientation towards attachment did appear to influence the availability of attachment ideas and predicted clinicians taking a stronger attachment focus when discussing the client. In particular, a self-report measure of theoretical orientation demonstrated high predictive validity. However, orientation towards attachment did not predict bias in the sense of selective recall of attachment information or neglect of alternative psychological frameworks. The study provided an inadequate test of availability bias as a result of a suggestion in the referral letter, possibly due to a ceiling effect, and no conclusions can be drawn as to clinical materials as a potential source of availability bias. The discussion addresses implications for further research and for a scientist-practitioner approach to individual case formulation.