Assessing Gaze Patterns in Common Cosmetic Procedures With Eye-Tracking Technology.

BACKGROUND: Understanding the salient features that draw focus when assessing aesthetics is important for maximizing perceived outcomes. Eye-tracking technology provides an unbiased method for determining the features that draw attention when evaluating aesthetic plastic surgery. This study aimed to characterize viewing patterns of plastic surgery patients and laypeople when assessing facial cosmetic procedure images. METHODS: Twenty women who previously underwent cosmetic procedures and twenty women without a history of cosmetic procedures were shown sixteen pairs of preprocedure and postprocedure images of patients who underwent laser resurfacing or lip augmentation. Image pairs were randomized to whether preprocedural or postprocedural images came first. Participants viewed each image until they decided upon an aesthetic rating (scored 1-10), while an eye-tracking device recorded participants' gaze. RESULTS: The patient group's average ratings were 8.2% higher for preprocedural images and 13.3% higher for postprocedural images (P < 0.05 for both). The patient group spent 20.4% less time viewing images but spent proportionally more time evaluating the relevant features of each procedure (41.7% vs 23.3%, P < 0.01), such as the vermillion border of the upper lip, labial commissure, or periorbital region (P < 0.05 for each). For both groups, the most common site of first fixation was the nose for laser resurfacing images (26.6%) and the labial commissure for lip augmentation images (37.7%). Both groups spent more time fixated on nasolabial folds, marionette lines, and the periorbital region when viewing pre-laser resurfacing images than postprocedural images. Overall, each group had similar viewing patterns for time to first fixation on and frequency of fixations for a particular feature. CONCLUSIONS: Women who previously underwent cosmetic procedures view postprocedural images more favorably and require less time to assess images, likely related to familiarity with aesthetic procedures. These women spend more time fixated on relevant features, such as the vermillion border of the upper lip, the labial commissure, and the periorbital region, than the control group. Notably, each group spent less time focused on regions associated with wrinkles, such as the marionette and periorbital areas in post-laser resurfacing images, suggesting that the procedure reduces attention-drawing features in these areas.

Mutations in HIV-1 envelope that enhance entry with the macaque CD4 receptor alter antibody recognition by disrupting quaternary interactions within the trimer.

UNLABELLED: Chimeric simian immunodeficiency virus (SIV)/human immunodeficiency virus (HIV) (SHIV) infection of macaques is commonly used to model HIV type 1 (HIV-1) transmission and pathogenesis in humans. Despite the fact that SHIVs encode SIV antagonists of the known macaque host restriction factors, these viruses require additional adaptation for replication in macaques to establish a persistent infection. Additional adaptation may be required in part because macaque CD4 (mCD4) is a suboptimal receptor for most HIV-1 envelope glycoprotein (Env) variants. This requirement raises the possibility that adaptation of HIV-1 Env to the macaque host leads to selection of variants that lack important biological and antigenic properties of the viruses responsible for the HIV-1 pandemic in humans. Here, we investigated whether this adaptation process leads to changes in the antigenicity and structure of HIV-1 Env. For this purpose, we examined how two independent mutations that enhance mCD4-mediated entry, A204E and G312V, impact antibody recognition in the context of seven different parental HIV-1 Env proteins from diverse subtypes. We also examined HIV-1 Env variants from three SHIVs that had been adapted for increased replication in macaques. Our results indicate that these different macaque-adapted variants had features in common, including resistance to antibodies directed to quaternary epitopes and sensitivity to antibodies directed to epitopes in the variable domains (V2 and V3) that are buried in the parental, unadapted Env proteins. Collectively, these findings suggest that adaptation to mCD4 results in conformational changes that expose epitopes in the variable domains and disrupt quaternary epitopes in the native Env trimer. IMPORTANCE: These findings indicate the antigenic consequences of adapting HIV-1 Env to mCD4. They also suggest that to best mimic HIV-1 infection in humans when using the SHIV/macaque model, HIV-1 Env proteins should be identified that use mCD4 as a functional receptor and preserve quaternary epitopes characteristic of HIV-1 Env.

Risk of drug resistance among persons acquiring HIV within a randomized clinical trial of single- or dual-agent preexposure prophylaxis.

BACKGROUND: Preexposure prophylaxis (PrEP) with emtricitabine plus tenofovir disoproxil fumarate (FTC/TDF) or TDF alone reduces the risk of human immunodeficiency virus (HIV) acquisition. Understanding the risk of antiretroviral resistance selected by PrEP during breakthrough infections is important because of the risk of treatment failure during subsequent antiretroviral use. METHODS: Within the largest randomized trial of FTC/TDF versus TDF as PrEP, plasma samples were tested for HIV with resistance mutations associated with FTC (K65R and M184IV) and TDF (K65R and K70E), using 454 sequencing. RESULTS: Of 121 HIV seroconverters, 25 received FTC/TDF, 38 received TDF, and 58 received placebo. Plasma drug levels in 26 individuals indicated PrEP use during or after HIV acquisition, of which 5 had virus with resistance mutations associated with their PrEP regimen. Among those with PrEP drug detected during infection, resistance was more frequent in the FTC/TDF arm (4 of 7 [57%]), compared with the TDF arm (1 of 19 [5.3%]; P = .01), owing to the FTC-associated mutation M184IV. Of these cases, 3 had unrecognized acute infection at PrEP randomization, and 2 were HIV negative at enrollment. CONCLUSIONS: These results suggest that resistance selected by PrEP is rare but can occur both with PrEP initiation during acute seronegative HIV infection and in PrEP breakthrough infections and that FTC is associated with a greater frequency of resistance mutations than TDF.

HIV-specific antibodies capable of ADCC are common in breastmilk and are associated with reduced risk of transmission in women with high viral loads.

There are limited data describing the functional characteristics of HIV-1 specific antibodies in breast milk (BM) and their role in breastfeeding transmission. The ability of BM antibodies to bind HIV-1 envelope, neutralize heterologous and autologous viruses and direct antibody-dependent cell cytotoxicity (ADCC) were analyzed in BM and plasma obtained soon after delivery from 10 non-transmitting and 9 transmitting women with high systemic viral loads and plasma neutralizing antibodies (NAbs). Because subtype A is the dominant subtype in this cohort, a subtype A envelope variant that was sensitive to plasma NAbs was used to assess the different antibody activities. We found that NAbs against the subtype A heterologous virus and/or the woman's autologous viruses were rare in IgG and IgA purified from breast milk supernatant (BMS)--only 4 of 19 women had any detectable NAb activity against either virus. Detected NAbs were of low potency (median IC50 value of 10 versus 647 for the corresponding plasma) and were not associated with infant infection (p = 0.58). The low NAb activity in BMS versus plasma was reflected in binding antibody levels: HIV-1 envelope specific IgG titers were 2.2 log(10) lower (compared to 0.59 log(10) lower for IgA) in BMS versus plasma. In contrast, antibodies capable of ADCC were common and could be detected in the BMS from all 19 women. BMS envelope-specific IgG titers were associated with both detection of IgG NAbs (p = 0.0001) and BMS ADCC activity (p = 0.014). Importantly, BMS ADCC capacity was inversely associated with infant infection risk (p = 0.039). Our findings indicate that BMS has low levels of envelope specific IgG and IgA with limited neutralizing activity. However, this small study of women with high plasma viral loads suggests that breastmilk ADCC activity is a correlate of transmission that may impact infant infection risk.

No difference in kinetics of tau or histone phosphorylation by CDK5/p25 versus CDK5/p35 in vitro.

CDK5/p35 is a cyclin-dependent kinase essential for normal neuron function. Proteolysis of the p35 subunit in vivo results in CDK5/p25 that causes neurotoxicity associated with a number of neurodegenerative diseases. Whereas the mechanism by which conversion of p35 to p25 leads to toxicity is unknown, there is common belief that CDK5/p25 is catalytically hyperactive compared to CDK5/p35. Here, we have compared the steady-state kinetic parameters of CDK5/p35 and CDK5/p25 towards both histone H1, the best known substrate for both enzymes, and the microtubule-associated protein, tau, a physiological substrate whose in vivo phosphorylation is relevant to Alzheimer's disease. We show that the kinetics of both enzymes are the same towards either substrate in vitro. Furthermore, both enzymes display virtually identical kinetics towards individual phosphorylation sites in tau monitored by NMR. We conclude that conversion of p35 to p25 does not alter the catalytic efficiency of the CDK5 catalytic subunit by using histone H1 or tau as substrates, and that neurotoxicity associated with CDK5/p25 is unlikely attributable to CDK5 hyperactivation, as measured in vitro.

A Bayesian approach to predictive uncertainty in chemotherapy patients at risk of acute care utilization.

BACKGROUND: Machine learning (ML) predictions are becoming increasingly integrated into medical practice. One commonly used method, ℓ1-penalised logistic regression (LASSO), can estimate patient risk for disease outcomes but is limited by only providing point estimates. Instead, Bayesian logistic LASSO regression (BLLR) models provide distributions for risk predictions, giving clinicians a better understanding of predictive uncertainty, but they are not commonly implemented. METHODS: This study evaluates the predictive performance of different BLLRs compared to standard logistic LASSO regression, using real-world, high-dimensional, structured electronic health record (EHR) data from cancer patients initiating chemotherapy at a comprehensive cancer centre. Multiple BLLR models were compared against a LASSO model using an 80-20 random split using 10-fold cross-validation to predict the risk of acute care utilization (ACU) after starting chemotherapy. FINDINGS: This study included 8439 patients. The LASSO model predicted ACU with an area under the receiver operating characteristic curve (AUROC) of 0.806 (95% CI: 0.775-0.834). BLLR with a Horseshoe+ prior and a posterior approximated by Metropolis-Hastings sampling showed similar performance: 0.807 (95% CI: 0.780-0.834) and offers the advantage of uncertainty estimation for each prediction. In addition, BLLR could identify predictions too uncertain to be automatically classified. BLLR uncertainties were stratified by different patient subgroups, demonstrating that predictive uncertainties significantly differ across race, cancer type, and stage. INTERPRETATION: BLLRs are a promising yet underutilised tool that increases explainability by providing risk estimates while offering a similar level of performance to standard LASSO-based models. Additionally, these models can identify patient subgroups with higher uncertainty, which can augment clinical decision-making. FUNDING: This work was supported in part by the National Library Of Medicine of the National Institutes of Health under Award Number R01LM013362. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Prosteria - National Trends and Outcomes of More Frequent Than Guideline Recommended Prostate Specific Antigen Screening.

OBJECTIVE: To characterize national trends in and associated outcomes of more often than annual prostate-specific antigen (PSA) screening, which we term "prosteria." METHODS: Men in the Optum Clinformatics Data Mart with ≥2 years from first PSA test to censoring at the end of insurance or available data (January 2003 to June 2019) or following exclusionary diagnoses or procedures, such as PCa treatment, were included. PSAs within 90 days were treated as one PSA. Prosteria was defined as having ≥3 PSA testing intervals of ≤270 days. RESULTS: A total of 9,734,077 PSAs on 2,958,923 men were included. The average inter-PSA testing interval was 1.5 years, and 4.5% of men had prosteria, which increased by 0.53% per year. Educated, wealthy, non-White patients were more likely to have prosteria. Men within the recommended screening age (ie 55-69) had lower rates of prosteria. Prosteria patients had higher average PSA values (2.5 vs 1.4 ng/mL), but lower values at PCa diagnosis. Prosteria was associated with biopsy and PCa diagnosis; however, there were comparable rates of treatment within 2 years of diagnosis. CONCLUSION: In this large cohort study, prosteria was common, increased over time, and was associated with demographic characteristics. Importantly, there were no clinically meaningful differences in PSA values at diagnosis or rates of early treatment, suggesting prosteria leads to both overdiagnosis and overtreatment. These results support current AUA and USPTF guidelines and can be used to counsel men seeking more frequent PSA screening.

Sociodemographic factors associated with Wilms tumor treatment and survival: a population-based study.

INTRODUCTION: Though Wilms tumor (WT) is one of the most common malignancies in children, there is a paucity of epidemiologic studies exploring sociodemographic disparities in treatment and survival. Here, we leveraged a national cancer registry to examine sociodemographic factors associated with receipt of adjuvant therapy, either chemotherapy or radiation, as well as overall survival among pediatric patients with WT. MATERIALS AND METHODS: Within the Surveillance Epidemiology and End Results database (2000-2016), we identified 2043 patients (≤ 20 years of age) with unilateral WT. Multivariable logistic regression and Cox proportional hazard models were constructed to examine the association of sociodemographic factors with, respectively, adjuvant chemotherapy/radiotherapy and overall survival (OS). RESULTS: Patients in the lowest SES quintile (OR 0.56, 95% CI 0.33-0.93, p = 0.03) were less likely to receive chemotherapy as compared to those in the highest SES quintile, though this association did not persist in sensitivity analyses including only patients at least 2 years of age and patients with regional/distant disease. In addition, female patients were more likely to receive chemotherapy (OR 1.46, 95% CI 1.08-1.97, p = 0.02) than male patients. Age, race, year of diagnosis, insurance status, and tumor laterality were not associated with receipt of chemotherapy. No sociodemographic variables were associated with receipt of radiotherapy. Lastly, as compared to Non-Hispanic-White patients, Hispanic patients had worse OS (HR 1.59, 95% CI 1.08-2.35, p = 0.02); no other sociodemographic variables were associated with OS. CONCLUSIONS: This study suggests multilevel sociodemographic disparities involving ethnicity and SES in WT treatment and survival.

Global, distinctive, and personal changes in molecular and microbial profiles by specific fibers in humans.

Dietary fibers act through the microbiome to improve cardiovascular health and prevent metabolic disorders and cancer. To understand the health benefits of dietary fiber supplementation, we investigated two popular purified fibers, arabinoxylan (AX) and long-chain inulin (LCI), and a mixture of five fibers. We present multiomic signatures of metabolomics, lipidomics, proteomics, metagenomics, a cytokine panel, and clinical measurements on healthy and insulin-resistant participants. Each fiber is associated with fiber-dependent biochemical and microbial responses. AX consumption associates with a significant reduction in LDL and an increase in bile acids, contributing to its observed cholesterol reduction. LCI is associated with an increase in Bifidobacterium. However, at the highest LCI dose, there is increased inflammation and elevation in the liver enzyme alanine aminotransferase. This study yields insights into the effects of fiber supplementation and the mechanisms behind fiber-induced cholesterol reduction, and it shows effects of individual, purified fibers on the microbiome.

Machine Learning Applied to Electronic Health Records: Identification of Chemotherapy Patients at High Risk for Preventable Emergency Department Visits and Hospital Admissions.

PURPOSE: Acute care use (ACU) is a major driver of oncologic costs and is penalized by a Centers for Medicare & Medicaid Services quality measure, OP-35. Targeted interventions reduce preventable ACU; however, identifying which patients might benefit remains challenging. Prior predictive models have made use of a limited subset of the data in the electronic health record (EHR). We aimed to predict risk of preventable ACU after starting chemotherapy using machine learning (ML) algorithms trained on comprehensive EHR data. METHODS: Chemotherapy patients treated at an academic institution and affiliated community care sites between January 2013 and July 2019 who met inclusion criteria for OP-35 were identified. Preventable ACU was defined using OP-35 criteria. Structured EHR data generated before chemotherapy treatment were obtained. ML models were trained to predict risk for ACU after starting chemotherapy using 80% of the cohort. The remaining 20% were used to test model performance by the area under the receiver operator curve. RESULTS: Eight thousand four hundred thirty-nine patients were included, of whom 35% had preventable ACU within 180 days of starting chemotherapy. Our primary model classified patients at risk for preventable ACU with an area under the receiver operator curve of 0.783 (95% CI, 0.761 to 0.806). Performance was better for identifying admissions than emergency department visits. Key variables included prior hospitalizations, cancer stage, race, laboratory values, and a diagnosis of depression. Analyses showed limited benefit from including patient-reported outcome data and indicated inequities in outcomes and risk modeling for Black and Medicaid patients. CONCLUSION: Dense EHR data can identify patients at risk for ACU using ML with promising accuracy. These models have potential to improve cancer care outcomes, patient experience, and costs by allowing for targeted, preventative interventions.

Partial versus total adrenalectomy for pheochromocytoma: a population-based comparison of outcomes.

PURPOSE: The literature assessing outcomes of partial adrenalectomy (PA) among patients with pheochromocytoma patients is largely limited to isolated, single-institution series. We aimed to perform a population-level comparison of outcomes between patients undergoing PA versus those undergoing total adrenalectomy (TA). METHODS: The Surveillance, Epidemiology, and End Results (SEER) database (1975-2016) was queried to identify adults with pheochromocytoma who underwent either PA or TA. Survival was assessed using multivariable Cox proportional hazards regression, Fine and Gray competing-risks regression, propensity score matching, Kaplan-Meier analysis, and cumulative incidence plots. RESULTS: 286 patients (PA: 101, TA: 185) were included in this study. As compared to those undergoing TA, patients undergoing PA had fewer tumors ≥ 8 cm in size (28.7% versus 42.7%, p = 0.048) and were more likely to have localized disease (61.4% versus 44.3%, p = 0.01). In multivariable analysis, patients undergoing PA demonstrated similar all-cause mortality (HR = 0.71, 95% CI 0.44-1.14, p = 0.16) and cancer-specific mortality (HR = 0.64, 95% CI 0.35-1.17, p = 0.15) compared to those who underwent TA. Following 1:1 propensity score matching, Kaplan-Meier analysis revealed no difference in overall survival between PA and TA groups (p = 0.26) nor was there a difference in the cumulative incidence of cancer-specific mortality (p = 0.29). CONCLUSIONS: In this first population-level comparison of outcomes among patients with pheochromocytoma undergoing PA and those undergoing TA, we found no long-term differences in any survival metric between groups. PA circumvents the need for lifelong corticoid replacement therapy and remains a promising option for patients with bilateral or recurrent pheochromocytoma.

Comparing Outcomes of Wise-Pattern, Two-Stage Breast Reduction-Reconstruction with and without Acellular Dermal Matrix.

BACKGROUND: Aesthetic results in breast reconstruction for ptotic/obese breasts may be improved when using Wise-pattern closures compared with nipple-sparing mastectomies. In two-stage reconstruction, acellular dermal matrix is commonly used to support the prosthesis. This study tests the efficacy of an alternate technique that uses deepithelialized excess breast skin in lieu of acellular dermal matrix. To better understand whether acellular dermal matrix is necessary, the authors compared postoperative outcomes from reduction-reconstructions that used matrix to those that did not. METHODS: The authors retrospectively reviewed the outcomes of patients who underwent staged breast reconstruction following Wise-pattern closures between September of 2016 and October of 2019. Two cohorts were created based on whether acellular dermal matrix was used. Charts were reviewed for incidence of postoperative complications. RESULTS: A total of 164 breasts were reconstructed in 85 female patients. The acellular dermal matrix cohort consisted of 68 breasts, whereas the non-acellular dermal matrix cohort included 96 breasts. After the first stage, the incidence of one or more complications was similar between cohorts (acellular dermal matrix, 32.4 percent; nonmatrix, 35.4 percent; p = 0.684). Minor infection rates were significantly higher in reconstructions using acellular dermal matrix (16.2 percent versus 6.3 percent; p = 0.040). After the second stage, the complication incidence was also similar between cohorts (acellular dermal matrix, 16.2 percent; nonmatrix, 13.5 percent; p = 0.638). Final follow-up time was 445.2 days. CONCLUSIONS: Overall complication rates following both stages of reconstruction were similar with and without acellular dermal matrix. When acellular dermal matrix was used, minor infection rates were higher following expander placement. In patients desiring a reduction-reconstruction, the authors find the deepithelialized dermal flap provides ample prosthesis support, without the need for acellular dermal matrix. . CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

A soluble oligomer of tau associated with fiber formation analyzed by NMR.

Alzheimer's disease (AD) is characterized by the intracellular accumulation of the neurofibrillary tangles comprised mainly of the microtubule-associated protein, tau. A critical aspect of understanding tangle formation is to understand the transition of soluble monomeric tau into mature fibrils by characterizing the structure of intermediates along the aggregation pathway. We have carried out multidimensional NMR studies on a C-terminal fragment of human tau (tau (187)) to gain structural insight into the aggregation process. To specifically monitor intermolecular interaction between tau molecules in solution, we combined (15)N- and (14)N-labeled tau, the latter of which was modified with a paramagnetic nitroxide spin label (MTSL). Paramagnetic relaxation enhancement (PRE) of (15)N-tau by interaction with MTSL- (14)N-tau allowed identification of low molecular weight oligomers of tau (187) that formed in response to heparin-induced aggregation. Two regions, VQIINK (280) and VQIVYK (311), were exclusively broadened by MTSL located at varied positions in the tau molecule. We propose that soluble oligomers of tau (187) are generated via intermolecular interactions at these motifs triggered by heparin addition. However, the associated line broadening at these motifs cannot be due to interaction between tau (187) and heparin directly. Instead, these specific interactions necessarily occur between tau molecules and are intermolecular in nature. Our data support the idea that VQIINK (280) and VQIVYK (311) are the major, if not sole, critical regions that directly mediate intermolecular contact between tau molecules during the early phases of aggregation.

Rapid detection of HIV-1 proviral DNA for early infant diagnosis using recombinase polymerase amplification.

Early diagnosis and treatment of human immunodeficiency virus type 1 (HIV-1) infection in infants can greatly reduce mortality rates. However, current infant HIV-1 diagnostics cannot reliably be performed at the point of care, often delaying treatment and compromising its efficacy. Recombinase polymerase amplification (RPA) is a novel technology that is ideal for an HIV-1 diagnostic, as it amplifies target DNA in <20 min at a constant temperature, without the need for complex thermocycling equipment. Here we tested 63 HIV-1-specific primer and probe combinations and identified two RPA assays that target distinct regions of the HIV-1 genome (long terminal repeat [LTR] and pol) and can reliably detect 3 copies of proviral DNA by the use of fluorescence detection and lateral-flow strip detection. These pol and LTR primers amplified 98.6% and 93%, respectively, of the diverse HIV-1 variants tested. This is the first example of an isothermal assay that consistently detects all of the major HIV-1 global subtypes.

Cinnamon extract inhibits tau aggregation associated with Alzheimer's disease in vitro.

An aqueous extract of Ceylon cinnamon (C. zeylanicum) is found to inhibit tau aggregation and filament formation, hallmarks of Alzheimer's disease (AD). The extract can also promote complete disassembly of recombinant tau filaments and cause substantial alteration of the morphology of paired-helical filaments isolated from AD brain. Cinnamon extract (CE) was not deleterious to the normal cellular function of tau, namely the assembly of free tubulin into microtubules. An A-linked proanthocyanidin trimer molecule was purified from the extract and shown to contain a significant proportion of the inhibitory activity. Treatment with polyvinylpyrolidone effectively depleted all proanthocyanidins from the extract solution and removed the majority, but not all, of the inhibitory activity. The remainder inhibitory activity could be attributed to cinnamaldehyde. This work shows that compounds endogenous to cinnamon may be beneficial to AD themselves or may guide the discovery of other potential therapeutics if their mechanisms of action can be discerned.

Site-specific dynamic nuclear polarization of hydration water as a generally applicable approach to monitor protein aggregation.

We present a generally applicable approach for monitoring protein aggregation by detecting changes in surface hydration water dynamics and the changes in solvent accessibility of specific protein sites, as protein aggregation proceeds in solution state. This is made possible through the Overhauser dynamic nuclear polarization (DNP) of water interacting with stable nitroxide spin labels tethered to specific proteins sites. This effect is highly localized due to the magnetic dipolar nature of the electron-proton spin interaction, with >80% of their interaction occurring within 5 A between the unpaired electron of the spin label and the proton of water. We showcase our tool on the aggregation of tau proteins, whose fibrillization is linked to neurodegenerative disease pathologies known as taupathies. We demonstrate that the DNP approach to monitor local changes in hydration dynamics with residue specificity and local contrast can distinguish specific and neat protein-protein packing leading to fibers from non-specific protein agglomeration or precipitation. The ability to monitor tau assembly with local, residue-specific, resolution, under ambient conditions and in solution state will help unravel the mechanism and structural characteristics of the gradual process of tau aggregation into amyloid fibers, which remains unclear to this day.

TMAO promotes fibrillization and microtubule assembly activity in the C-terminal repeat region of tau.

Alzheimer's disease most closely correlates with the appearance of the neurofibrillary tangles (NFTs), intracellular fibrous aggregates of the microtubule-associated protein, tau. Under native conditions, tau is an unstructured protein, and its physical characterization has revealed no clues about the three-dimensional structural determinants essential for aggregation or microtubule binding. We have found that the natural osmolyte trimethylamine N-oxide (TMAO) induces secondary structure in a C-terminal fragment of tau (tau(187)) and greatly promotes both self-aggregation and microtubule (MT) assembly activity. These processes could be distinguished, however, by a single-amino acid substitution (Tyr(310) --> Ala), which severely inhibited aggregation but had no effect on MT assembly activity. The inability of this mutant to aggregate could be completely reversed by TMAO. We propose a model in which TMAO induces partial order in tau(187), resulting in conformers that may correspond to on-pathway intermediates of either aggregation or tau-dependent MT assembly or both. These studies set the stage for future high-resolution structural characterization of these intermediates and the basis by which Tyr(310) may direct pathologic versus normal tau function.