An emerging field: An evaluation of biomedical graduate student and postdoctoral education and training research across seven decades.

Biomedical graduate student and postdoctoral education and training research has expanded greatly over the last seven decades, leading to increased publications and the emergence of a field. The goal of this study was to analyze this growth by performing a cross-sectional bibliometric analysis using a systematic approach to better understand the publishing trends (including historical vs. emerging themes and research priorities); depth, structure, and evidence-basis of content; and venues for publication. The analysis documented a dramatic increase in biomedical trainee-related publications over time and showed that this area of research is maturing into its own independent field. Results demonstrated that the most frequently published article types in this field are shorter editorial and opinion pieces, and that evidence-based articles are less numerous. However, if current trends continue, projections indicate that by the year 2035, evidence-based articles will be the dominating article type published in this field. Most frequently published topics included career outcomes and workforce characterization and professional development. In recent years, the most cited articles were publications focused on diversity, equity, and inclusion, career outcomes and workforce characterization, and wellness. This study also shows that although a small subset of journals publishes most of this literature, publications are distributed diffusely across a wide range of journals and that surprisingly 68% of these journals have published only a single article on the topic. Further, we noted that the assignment of author- and index-supplied keywords was variable and inconsistent and speculate that this could create challenges to conducting comprehensive literature searches. Recommendations to address this include establishing standard keyword assignment criteria and proposing new index-supplied keywords to improve accessibility of research findings. These changes will be important for bringing visibility of this literature to our community, institutional leaders, national trainee organizations, and funding agencies.

It Takes a Village: Providing International Pediatric Pathology Services in a Resource-Limited Setting

OBJECTIVES: Partnerships between low- to middle-income countries (LMICs) and high-income countries (HICs) is one strategy to mitigate observed health disparities. Cambodia's Angkor Hospital for Children (AHC), an LMIC institution, faces shortages in health care resources, including pathology services. A partnership was created with Children's Wisconsin (CW), an HIC hospital, including provision of pathology services. We describe our established pathology workflow, examine cases seen in AHC patients, and evaluate the impact of CW's interpretations. METHODS: AHC provides clinical history and impression and ships samples to CW, which processes the samples, and pathologists provide interpretations, sending reports electronically to AHC. For analysis, final diagnoses were considered "concordant," "refined," or "discordant" based on agreement with the clinical impression. Cases were also classified as "did not change management" or "changed management" based on how CW interpretation affected clinical management. RESULTS: We included 347 specimens (177 malignant, 146 benign, 24 insufficient for diagnosis). Of these cases, 31% were discordant and 44% of cases with clinical follow-up had a change in management with CW interpretation. CONCLUSIONS: Inclusion of pathology services in LMIC-HIC partnerships is crucial for resolving health disparities between the institutions involved. The described partnership and established pathology workflow can be adapted to the needs and resources of many institutions.

Prevalence of Potentially Clinically Significant Magnetic Resonance Imaging Findings in Athletes with and without Sport-Related Concussion.

Previous studies have shown that mild traumatic brain injury (mTBI) can cause abnormalities in clinically relevant magnetic resonance imaging (MRI) sequences. No large-scale study, however, has prospectively assessed this in athletes with sport-related concussion (SRC). The aim of the current study was to characterize and compare the prevalence of acute, trauma-related MRI findings and clinically significant, non-specific MRI findings in athletes with and without SRC. College and high-school athletes were prospectively enrolled and participated in scanning sessions between January 2015 through August 2017. Concussed contact sport athletes (n = 138; 14 female [F]; 19.5 ± 1.6 years) completed up to four scanning sessions after SRC. Non-concussed contact (n = 135; 15 F; 19.7 ± 1.6) and non-contact athletes (n = 96; 15 F; 20.0 ± 1.7) completed similar scanning sessions and served as controls. Board-certified neuroradiologists, blinded to SRC status, reviewed T1-weighted and T2-weighted fluid-attenuated inversion recovery and T2*-weighted and T2-weighted images for acute (i.e., injury-related) or non-acute findings that prompted recommendation for clinical follow-up. Concussed athletes were more likely to have MRI findings relative to contact (30.4% vs. 15.6%; odds ratio [OR] = 2.32; p = 0.01) and non-contact control athletes (19.8%; OR = 2.11; p = 0.04). Female athletes were more likely to have MRI findings than males (43.2% vs. 19.4%; OR = 2.62; p = 0.01). One athlete with SRC had an acute, injury-related finding; group differences were largely driven by increased rate of non-specific white matter hyperintensities in concussed athletes. This prospective, large-scale study demonstrates that <1% of SRCs are associated with acute injury findings on qualitative structural MRI, providing empirical support for clinical guidelines that do not recommend use of MRI after SRC.

Dopamine-induced conformational changes in alpha-synuclein.

BACKGROUND: Oligomerization and aggregation of alpha-synuclein molecules play a major role in neuronal dysfunction and loss in Parkinson's disease [1]. However, alpha-synuclein oligomerization and aggregation have mostly been detected indirectly in cells using detergent extraction methods [2], [3], [4]. A number of in vitro studies showed that dopamine can modulate the aggregation of alpha-synuclein by inhibiting the formation of or by disaggregating amyloid fibrils [5], [6], [7]. METHODOLOGY/PRINCIPAL FINDINGS: Here, we show that alpha-synuclein adopts a variety of conformations in primary neuronal cultures using fluorescence lifetime imaging microscopy (FLIM). Importantly, we found that dopamine, but not dopamine agonists, induced conformational changes in alpha-synuclein which could be prevented by blocking dopamine transport into the cell. Dopamine also induced conformational changes in alpha-synuclein expressed in neuronal cell lines, and these changes were also associated with alterations in oligomeric/aggregated species. CONCLUSION/SIGNIFICANCE: Our results show, for the first time, a direct effect of dopamine on the conformation of alpha-synuclein in neurons, which may help explain the increased vulnerability of dopaminergic neurons in Parkinson's disease.

CHIP targets toxic alpha-Synuclein oligomers for degradation.

alpha-Synuclein (alphaSyn) can self-associate, forming oligomers, fibrils, and Lewy bodies, the pathological hallmark of Parkinson disease. Current dogma suggests that oligomeric alphaSyn intermediates may represent the most toxic alphaSyn species. Here, we studied the effect of a potent molecular chaperone, CHIP (carboxyl terminus of Hsp70-interacting protein), on alphaSyn oligomerization using a novel bimolecular fluorescence complementation assay. CHIP is a multidomain chaperone, utilizing both a tetratricopeptide/Hsp70 binding domain and a U-box/ubiquitin ligase domain to differentially impact the fate of misfolded proteins. In the current study, we found that co-expression of CHIP selectively reduced alphaSyn oligomerization and toxicity in a tetratricopeptide domain-dependent, U-box-independent manner by specifically degrading toxic alphaSyn oligomers. We conclude that CHIP preferentially recognizes and mediates degradation of toxic, oligomeric forms of alphaSyn. Further elucidation of the mechanisms of CHIP-induced degradation of oligomeric alphaSyn may contribute to the successful development of drug therapies that target oligomeric alphaSyn by mimicking or enhancing the powerful effects of CHIP.

Formation of toxic oligomeric alpha-synuclein species in living cells.

BACKGROUND: Misfolding, oligomerization, and fibrillization of alpha-synuclein are thought to be central events in the onset and progression of Parkinson's disease (PD) and related disorders. Although fibrillar alpha-synuclein is a major component of Lewy bodies (LBs), recent data implicate prefibrillar, oligomeric intermediates as the toxic species. However, to date, oligomeric species have not been identified in living cells. METHODOLOGY/PRINCIPAL FINDINGS: Here we used bimolecular fluorescence complementation (BiFC) to directly visualize alpha-synuclein oligomerization in living cells, allowing us to study the initial events leading to alpha-synuclein oligomerization, the precursor to aggregate formation. This novel assay provides us with a tool with which to investigate how manipulations affecting alpha-synuclein aggregation affect the process over time. Stabilization of alpha-synuclein oligomers via BiFC results in increased cytotoxicity, which can be rescued by Hsp70 in a process that reduces the formation of alpha-synuclein oligomers. Introduction of PD-associated mutations in alpha-synuclein did not affect oligomer formation but the biochemical properties of the mutant alpha-synuclein oligomers differ from those of wild type alpha-synuclein. CONCLUSIONS/SIGNIFICANCE: This novel application of the BiFC assay to the study of the molecular basis of neurodegenerative disorders enabled the direct visualization of alpha-synuclein oligomeric species in living cells and its modulation by Hsp70, constituting a novel important tool in the search for therapeutics for synucleinopathies.

Cellular localization of androgen and estrogen receptors in mouse-derived motoneuron hybrid cells and mouse facial motoneurons.

The ability of gonadal steroid hormones to augment axonal regeneration after peripheral nerve injury has been well established in rat and hamster motoneuron systems, and provides a foundation for the use of these agents as neurotherapeutics. With the advent of mouse genetics and the availability of transgenic and knockout mice, the use of mice in studies of neuroprotection is growing. It has recently been demonstrated that both androgens and estrogens rescue motoneurons (MN) from injury in mouse-derived motoneuron hybrid cells in vitro and mouse facial motoneurons (FMN) in vivo (Tetzlaff et al. [2006] J Mol Neurosci 28:53-64). To elucidate the molecular mechanisms of these effects, the present study examined the cellular localization of androgen and estrogen receptors in mouse MN in vitro and in vivo. Immunoblotting and immunocytochemistry studies established the presence of androgen receptor (AR) and estrogen receptor alpha/beta in immortalized mouse motoneuron hybrid cells and AR and estrogen receptor alpha in mouse FMN.

Mechanisms of disease II: cellular protein quality control.

Protein misfolding and aggregation are common to many disorders, including neurodegenerative diseases referred to as "conformational disorders," suggesting that alterations in the normal protein homeostasis might contribute to pathogenesis. Cells evolved 2 major components of the protein quality control system to deal with misfolded and/or aggregated proteins: molecular chaperones and the ubiquitin proteasome pathway. Recent studies have implicated components of both systems in neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, or the prion diseases. A detailed understanding of how the cellular quality control systems relate to neurodegeneration might lead to the development of novel therapeutic approaches for disorders associated with protein misfolding and aggregation.

Motoneuron injury and repair: New perspectives on gonadal steroids as neurotherapeutics.

In this review, we will summarize recent work from our laboratory on the role of gonadal steroids as neuroprotective agents in motoneuron viability following cell stress. Three motoneuron models will be discussed: developing axotomized hamster facial motoneurons (FMNs); adult axotomized mouse FMNs; and immortalized, cultured mouse spinal motoneurons subjected to heat shock. New work on two relevant motoneuron proteins, the survival of motor neuron protein, and neuritin or candidate plasticity-related gene 15, indicates differential steroid regulation of these two proteins after axotomy. The concept of gonadal steroids as cellular stress correction factors and the implications of this for acute neurological injury situations will be presented as well.

Paroxetine is effective in desensitizing 5-HT1A receptor function in adult offspring exposed prenatally to cocaine.

RATIONALE: Desensitization of postsynaptic 5-HT(1A) receptors may be responsible for the therapeutic effectiveness of serotonin selective uptake inhibitors (SSRIs). As prenatal cocaine exposure produces long-term deficits in 5-HT neurons in offspring, it may alter the ability of postsynaptic 5-HT(1A) receptors to be desensitized by chronic paroxetine. OBJECTIVES: The aim of the study is to determine (1) prenatal cocaine-induced changes in 5-HT(1A) receptor function and (2) the effectiveness of chronic treatment with paroxetine to produce 5-HT(1A) receptor desensitization in adult offspring exposed to cocaine in utero. METHODS: Pregnant rats received saline or (-)cocaine (15 mg/kg, s.c.) twice daily from gestational days 13 through 20. Adult male offspring from each of prenatal groups were treated with saline or paroxetine (10 mg/kg/day; i.p.) for 14 days. Eighteen hours post-treatment, rats were challenged with saline or the 5-HT(1A) receptor agonist (+)8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.04 or 0.2 mg/kg, s.c.). Plasma oxytocin, adrenocorticotropic hormone (ACTH), corticosterone, renin and prolactin were determined. RESULTS: Prenatal cocaine exposure did not alter 5-HT(1A) receptor-mediated neuroendocrine responses. Paroxetine treatment desensitized 5-HT(1A) receptor-mediated increases in oxytocin, ACTH and corticosterone to a comparable extent in all offspring and reduced the E(max) for ACTH only in prenatal cocaine-exposed offspring. Cortical [(3)H]-8-OH-DPAT- or [(3)H]-WAY100635-labeled 5-HT(1A) receptors were unaltered by prenatal cocaine or subsequent paroxetine treatment. CONCLUSIONS: Postsynaptic 5-HT(1A) receptor function is unaltered by prenatal cocaine exposure and paroxetine can effectively desensitize 5-HT(1A) receptor function in adult cocaine-exposed offspring. These data suggest that paroxetine may be clinically effective in treating mood disorders in adults exposed in utero to cocaine.

Functional recovery after facial nerve crush is delayed in severe combined immunodeficient mice.

The goal of the current study was to determine if T and B lymphocytes play a role in functional recovery after peripheral nerve injury. The time course of behavioral recovery following facial nerve crush injury at the stylomastoid foramen was established in scid mice which lack functional T and B cells and reconstituted scid mice as compared to wild-type mice. The average time necessary for recovery of full eye blink reflex and vibrissae movements in wild-type mice was 10.3+/-0.2 and 9.9+/-0.34 days, respectively. In contrast, recovery of full eye blink reflex and vibrissae movements took 14.8+/-0.54 and 12.3+/-0.41 days, respectively, in scid mice. Reconstitution of scid mice with whole splenocytes resulted in functional recovery times similar to wild-type, with eye blink reflex recovery and vibrissae movement being 10.5+/-0.3 and 10.0+/-0.0 days, respectively. These results suggest that the delayed behavioral recovery time observed in scid mice may be due to the absence of T and B lymphocytes.

Evidence that 5-HT2A receptors in the hypothalamic paraventricular nucleus mediate neuroendocrine responses to (-)DOI.

The present study determined whether the serotonin2A (5-HT2A) receptors in the hypothalamic paraventricular nucleus mediate the neuroendocrine responses to a peripheral injection of the 5-HT2A/2C receptor agonist (-)DOI [(-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane]. The 5-HT2A receptor antagonist MDL100,907 ((+/-)-alpha(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidinemethanol), the 5-HT2C receptor antagonist SB-242084 (6-chloro-5-methyl-1-[[2-[(2-methyl-3-pyridyl)oxy]-5-pyridyl]carbamoyl]-indoline), or vehicle were microinjected bilaterally through a chronically implanted double-barreled cannula into the hypothalamic paraventricular nucleus 15 min before a peripheral injection of (-)DOI in conscious rats. (-)DOI significantly elevated plasma levels of oxytocin, prolactin, ACTH, corticosterone, and renin. Neither the 5-HT2A receptor antagonist nor the 5-HT2C receptor antagonist, injected alone, altered the basal levels of these hormones. MDL100,907 (0.748, 7.48, and 18.7 nmol) dose dependently inhibited the (-)DOI-induced increase in all of the hormones except corticosterone. In contrast, SB-242084 (10 nmol) did not inhibit (-)DOI-increased hormone levels. To confirm the presence of 5-HT2A receptors in the hypothalamic paraventricular nucleus, 5-HT2A receptors were mapped using immunohistochemistry. Densely labeled magnocellular neurons were observed throughout the anterior and posterior magnocellular subdivisions of the hypothalamic paraventricular nucleus. Moderately to densely labeled cells were also observed in parvicellular regions. Thus, it is likely that 5-HT2A receptors are present on neuroendocrine cells in the hypothalamic paraventricular nucleus. These data provide the first direct evidence that neuroendocrine responses to a peripheral injection of (-)DOI are predominantly mediated by activation of 5-HT2A receptors in the hypothalamic paraventricular nucleus.

Effects of hippocampal injections of a novel ligand selective for the alpha 5 beta 2 gamma 2 subunits of the GABA/benzodiazepine receptor on Pavlovian conditioning.

Benzodiazepine pharmacology has led to greater insight into the neural mechanisms underlying learning and anxiety. The synthesis of new compounds capable of modulating responses produced by these receptors has been made possible by the development of an isoform model of the GABA(A)/benzodiazepine receptor complex. In the current experiment, rats were pretreated with several concentrations of the novel ligand RY024 (an alpha 5 beta 2 gamma 2 -selective benzodiazepine receptor inverse agonist) in the hippocampus and were trained in a Pavlovian fear conditioning paradigm. RY024 independently produced fear-related behavior prior to training and, at the highest concentration, decreased the strength of conditioning observed 24 h after training. These data provide further evidence for the involvement of hippocampal GABA(A)/benzodiazepine receptors in learning and anxiety.