An Investigation of Age-Differentiated Conversations About Electronic Nicotine Delivery Systems on Reddit

Introduction

This study analyzes age-differentiated Reddit conversations about ENDS.

Methods

This study combines 2 methods to (1) predict Reddit users' age into 2 categories (13-20 years [underage] and 21-54 years [of legal age]) using a machine learning algorithm and (2) qualitatively code ENDS-related Reddit posts within the 2 groups. The 25 posts with the highest karma score (number of upvotes minus number of downvotes) for each keyword search (i.e., query) and each predicted age group were qualitatively coded.

Results

Of 9, the top 3 topics that emerged were flavor restriction policies, Tobacco 21 policies, and use. Opposition to flavor restriction policies was a prominent subcategory for both groups but was more common in the 21-54 group. The 13-20 group was more likely to discuss opposition to minimum age laws as well as access to flavored ENDS products. The 21-54 group commonly mentioned general vaping use behavior.

Conclusions

Users predicted to be in the underage group posted about different ENDS-related topics on Reddit than users predicted to be in the of-legal-age group.

Predicting Age Groups of Reddit Users Based on Posting Behavior and Metadata: Classification Model Development and Validation

BACKGROUND

Social media are important for monitoring perceptions of public health issues and for educating target audiences about health; however, limited information about the demographics of social media users makes it challenging to identify conversations among target audiences and limits how well social media can be used for public health surveillance and education outreach efforts. Certain social media platforms provide demographic information on followers of a user account, if given, but they are not always disclosed, and researchers have developed machine learning algorithms to predict social media users' demographic characteristics, mainly for Twitter. To date, there has been limited research on predicting the demographic characteristics of Reddit users.

OBJECTIVE

We aimed to develop a machine learning algorithm that predicts the age segment of Reddit users, as either adolescents or adults, based on publicly available data.

METHODS

This study was conducted between January and September 2020 using publicly available Reddit posts as input data. We manually labeled Reddit users' age by identifying and reviewing public posts in which Reddit users self-reported their age. We then collected sample posts, comments, and metadata for the labeled user accounts and created variables to capture linguistic patterns, posting behavior, and account details that would distinguish the adolescent age group (aged 13 to 20 years) from the adult age group (aged 21 to 54 years). We split the data into training (n=1660) and test sets (n=415) and performed 5-fold cross validation on the training set to select hyperparameters and perform feature selection. We ran multiple classification algorithms and tested the performance of the models (precision, recall, F1 score) in predicting the age segments of the users in the labeled data. To evaluate associations between each feature and the outcome, we calculated means and confidence intervals and compared the two age groups, with 2-sample t tests, for each transformed model feature.

RESULTS

The gradient boosted trees classifier performed the best, with an F1 score of 0.78. The test set precision and recall scores were 0.79 and 0.89, respectively, for the adolescent group (n=254) and 0.78 and 0.63, respectively, for the adult group (n=161). The most important feature in the model was the number of sentences per comment (permutation score: mean 0.100, SD 0.004). Members of the adolescent age group tended to have created accounts more recently, have higher proportions of submissions and comments in the r/teenagers subreddit, and post more in subreddits with higher subscriber counts than those in the adult group.

CONCLUSIONS

We created a Reddit age prediction algorithm with competitive accuracy using publicly available data, suggesting machine learning methods can help public health agencies identify age-related target audiences on Reddit. Our results also suggest that there are characteristics of Reddit users' posting behavior, linguistic patterns, and account features that distinguish adolescents from adults.

Estimated Ages of JUUL Twitter Followers

This social media analysis used a prediction model to estimate the ages of followers of @JUULvapor on Twitter.

Fibroblast growth factor-18 is a trophic factor for mature chondrocytes and their progenitors

OBJECTIVE

The aim of this study was to examine the effects of recombinant human Fgf18 on chondrocyte proliferation and matrix production in vivo and in vitro. In addition, the expressions of Fgf18 and Fgf receptors (Fgfr) in adult human articular cartilage were examined.

METHODS

Adenovirus-mediated transfer of Fgf18 into murine pinnae and addition of FGF18 to primary cultures of adult articular chondrocytes were used to assess the effects of FGF18 on chondrocytes. In situ hybridization was used to examine the expression of Fgf18 and Fgfr s in adult human articular cartilage.

RESULTS

Expression of Fgf18 by adenovirus-mediated gene transfer in murine pinnae resulted in a significant increase in chondrocyte number. Chondrocytes were identified by staining with toluidine blue and a monoclonal antibody directed against type II collagen. Fgf18, Fgfr 2-(IIIc), Fgfr 3-(IIIc), and Fgfr 4 mRNAs were detected within these cells by in situ hybridization. The nuclei of the chondrocytes stained with antibodies to PCNA and FGF receptor (FGFR) 2. Addition of FGF18 to the culture media of primary articular chondrocytes increased the proliferation of these cells and increased their production of extracellular matrix. To assess the receptor selectivity of FGF18, BaF3 cells stably expressing the genes for the major splice variants of Fgfr1-3 were used. Proliferation of cells expressing Fgfr 3-(IIIc) or Fgfr 2-(IIIc) was increased by incubation with FGF18. Using FGFR-Fc fusion proteins and BaF3 cells expressing Fgfr 3-(IIIc), only FGFR 3-(IIIc)-Fc, FGFR 2-(IIIc)-Fc or FGFR 4-Fc reduced FGF18-mediated cell proliferation. Expression of Fgf18, Fgfr 3-(IIIc) and Fgfr 2-(IIIc) mRNAs was localized to chondrocytes of human articular cartilage by in situ hybridization.

CONCLUSION

These data demonstrate that Fgf18 can act as a trophic factor for elastic chondrocytes and their progenitors in vivo and articular chondrocytes cultured in vitro. Expression of Fgf18 and the genes for two of its receptors in chondrocytes suggests that Fgf18 may play an autocrine role in the biology of normal articular cartilage.

Precise, highly female-biased sex ratios in a social spider

It has been recognized for some time that the risk of producing maleless clutches should select for a lower than binomial variance in the sex ratio of organisms with female-biased sex ratios, small clutches and breeding groups containing the clutch of a single female. However, to date, precise sex ratios have only been reported for organisms with haplodiploid sex determination, a system which allows direct control of the sex of individual offspring. In contrast, under heterogametic sex determination chance is expected to play a crucial role in determining the sex composition of any one family, in particular when males are the heterogametic sex. Here, we present evidence of precise or underdispersed primary sex ratios in the Neotropical social spider Anelosimus domingo Levi. We show that this diplodiploid species with male heterogamety has not only beaten the odds of meiosis by producing mostly daughters, but has also attained relative precision in the proportion of sons and daughters produced in any one clutch. The latter finding suggests the existence of mechanisms that allow sorting of the two types of sperm in this spider species.

Development of the methylotrophic yeast Pichia methanolica for the expression of the 65 kilodalton isoform of human glutamate decarboxylase

We describe a protein expression system in the methylotrophic yeast, Pichia methanolica. Methods for transformation and genetic manipulation of the organism were developed using an ade2 strain and the wild-type ADE2 gene. A vacuolar protease-deficient strain was constructed. Two genes encoding alcohol oxidases were found, yet a single isoform of alcohol oxidase was produced during methanol-fed fermentations. The promoter from this gene was used to drive expression. An integrating plasmid for the cytoplasmic expression of the 65 kDa isoform of human glutamate decarboxylase (human GAD65) was assembled. A strain harboring eight copies of this plasmid expressed enzymatically active human GAD65 at levels approaching 0.5 g/l. Identical amounts were made in Pichia pastoris. The recombinant GAD65 was purified to greater than 90% purity.

New application of the gastrostomy button for clinical and urodynamic evaluation before vesicostomy closure

PURPOSE

We report use of the Bard gastrostomy button to occlude vesicostomy and provide access for intermittent catheterization before closure in children with vesicostomy. Evaluation of bladder function in such children usually relies on radiographic and urodynamic studies, which may fail to predict bladder compliance, emptying and continence after closure.

MATERIALS AND METHODS

Buttons were placed before vesicostomy closure in 1 boy with the prune-belly syndrome and 2 girls with cloacal anomalies 2.5 to 10 years old. The patients had undergone vesicostomy using the Blocksom technique soon after birth because of urinary infection, and impairment of bladder emptying and renal function.

RESULTS

With the button in place bladder emptying, compliance, continence and possible upper tract changes could be evaluated during several weeks. Button coaptation to the vesicostomy was complete with no urine leakage around the device, allowing easy intermittent drainage through its channel. After 4 weeks the buttons did not have any encrustation or lithiasis and patients were free of urinary infection. Vesicostomy was closed in each patient and the period of temporary closure provided by the button was predictive of future bladder behavior.

CONCLUSIONS

This new and original application of the gastrostomy button as a temporary vesicostomy closure may be useful to predict the clinical and urodynamic responses of a defunctionalized bladder in patients with vesicostomy who are candidates for urinary undiversion.

Is there a best alternative to treating the obstructed upper pole?

PURPOSE

We addressed whether salvage of upper pole renal units in comparison to partial nephrectomy affects differential renal function in patients with a duplicated obstructed upper pole.

MATERIALS AND METHODS

We retrospectively reviewed the records of all children who underwent surgery for a unilateral obstructed duplicated kidney at our institution from 1988 to 1995. Patients were evaluated with respect to postoperative complications, reoperation rate and percent change in differential renal function of the obstructed duplicated kidney, as determined by nuclear renography.

RESULTS

We identified 46 patients with a unilateral obstructed upper pole of a duplicated kidney who were divided into 2 groups. Group 1 (12 patients) underwent an upper pole salvage procedure, that is ureteropyelostomy or ureteroureterostomy, and group 2 (31 patients) underwent partial nephrectomy. Three reoperations (25%) were performed in group 1 and 1 (4%) was done in group 2. Postoperative symptomatic urinary tract infections were diagnosed in 3 group 1 patients (25%) and in 2 (8%) in group 2. Average change in ipsilateral renal function in the 8 patients who underwent upper pole salvage procedures was 2.25 +/- 2.34% (range -6 to 12). In the 8 patients who underwent upper pole nephrectomy and who also had postoperative renal scans average change in function was -1.25 +/- 4.51% (range -23 to +16).

CONCLUSIONS

There was no statistically significant loss of relative renal function in patients treated with partial nephrectomy and no significant gain in relative renal function in those treated with an upper pole salvage procedure. The reoperation rate was higher in the upper pole salvage than in the partial nephrectomy group (25 versus 4%). While not statistically significant, we believe that this rate is clinically important. We think that partial nephrectomy should remain the preferred treatment for most patients with obstructed duplicated kidneys.

The use of metrizamide for stabilizing against convection in sedimentation equilibrium

In meniscus depletion sedimentation equilibrium experiments, the solute concentration gradient in much of the cell is insufficient to stabilize against thermal convection. Experiments with spectrin at 35 degrees C led to sufficient convection that, particularly at low concentrations of solute, no apparent redistribution occurred. At low angular velocity, the density gradient provided by moderate concentrations of NaCl or additional sucrose is inadequate to overcome the convective disturbances. We have found that the use of low concentrations of metrizamide can overcome these problems. The higher molecular weight and lower partial specific volume of metrizamide vis-a-vis sucrose allow a significant and stabilizing density gradient even at angular velocities below 8000 rpm.

Self-association and active enzyme forms of Naja naja naja and Crotalus atrox phospholipase A2 studied by analytical ultracentrifugation

The dimerization of phospholipase A2 (PLPA2) from Naja naja naja (Pakistani cobra) and Crotalus atrox (Western Diamondback rattlesnake) has been studied from pH 2.5 to 11 at 20 degrees C in 1 mM CaCl2, 0.21 M ionic strength. For the C. atrox enzyme, it was found necessary to use a combination of sedimentation equilibrium and fluorescence yield data to analyze the association. Sedimentation equilibrium in the analytical ultracentrifuge sufficed for the study of the N. naja PLPA2. In the region of enzymatic activity at pH 8, the dimerization association constants found were k2 = 2.8 X 10(6) L/mol and k2 = 6.9 X 10(4) L/mol for the C. atrox and N. naja enzymes, respectively. Analytical linked functions are presented which describe the data. Because the associations are linked to Ca2+ as well as the hydrogen ion, no attempt was made to interpret the ionization of residues in terms of the molecular structure. Active-enzyme sedimentation velocity experiments have been used to study the relation between enzymatic activity and association for both the C. atrox and N. naja enzymes. The substrate 1,2-dibutyryl-sn-glycero-3-phosphocholine (diC4PC) did not dissociate the C. atrox PLPA2. The substrate 1,2-dihexanoyl-sn-glycero-3-phosphocholine (diC6PC) at 7.5 mM dissociated the C. atrox PLPA2 when monitored either as the active enzyme or as the Sr2+-inhibited enzyme. At low enzyme concentrations, 40 mM diC4PC had no effect on N. naja PLPA2 dimerization. However, the sedimentation coefficients observed at enzyme concentrations above 0.2 mg/mL in active-enzyme sedimentation velocity experiments were larger than the values predicted from the thermodynamic studies. Sedimentation coefficients observed for the N. naja PLPA2 acting on diC6PC were larger than those of the monomeric protein, which was the form layered on this substrate. The dissociation of the C. atrox PLPA2 effected by diC6PC was analyzed by the thermodynamics of association and the kinetic Michaelis constant. The analysis suffices to account for the observed sedimentation coefficient. The sedimentation behavior of the N. naja PLPA2 acting on diC6PC substrate was analyzed in terms of a protein-lipid complex. With this model, 68 +/- 16 phospholipid molecules per protein monomer were determined. It is proposed that this enzyme has two micelle nucleation sites per monomer. These putative sites promote micelle formation of the substrate on the enzyme below the critical micelle concentration of the lipid alone.