Biology subjects

Doan, J.

Publications and source records attributed to Doan, J..

4 recordsLinked to original sources

bioRxiv2026

Parkinson Disease vs Aging Features Impairments in Formation and Release of a Power Grip in Real and Pantomimed String-Pulling

Parkinson disease (PD) impairs skilled reaching tasks but less is known about its effects on rhythmic bimanual actions. We used a bimanual hand-over-hand string-pulling task that requires repeated reach, grasp, pull, push and release movements. We predicted that participants with PD would show impairment in making the rotary skilled hand movement of retrieving the string, analogous to impairments observed in single handed target reaching. Nine participants with PD (mean UPDRS-III: 24.6), 16 older adults, and 10 young adults successfully performed a real string-pulling task and then pantomimed the action. Video analyses combined optical-flow estimation of whole-body movement speed, markerless 2D pose estimation of upper-limb kinematics, and expert frame-by-frame scoring of hand and finger shaping. Machine-learning classification then identified the discriminative information carried by these multilevel movement components. Participants with PD showed lower movement speed, a smaller hand workspace, and reduced hand and finger shaping, with older adults showing intermediate values. All participants grasped the real string with a power grip, but participants with PD showed reduced rotary movements of the arm and the wrists and absent of arpeggio-like sequential finger movement during grasp and release. During pantomime, participants with PD moved faster and made larger hand movements, while grasp-related hand opening and finger sequencing was reduced or absent. The findings suggest that PD is expressed across this multicomponent movement manifold, and that the movement organization changes with task demands: real string pulling requires formation and release of a power grip, whereas pantomime does not place demands on grasping ability.

neuroscience↗

bioRxiv2020

Quantifying Color Vision Changes Associated with Cataracts Using Cone Contrast Thresholds

PurposeThe cone contrast threshold (CCT) test quantified color vision changes in subjects of all ages and those undergoing cataract surgery. MethodsTwenty-four healthy volunteers from two cohort studies performed CCT using best corrected visual acuity, filters, mydriasis, and pinhole correction. Retrospective cross-sectional study of patients seen in eye clinics evaluated the relationship between age and color vision, and age and lens status in 355 eyes. Lastly, 25 subjects performed CCT before and after cataract surgery. ResultsCCT scores were most reliable in the non-mydriatic condition without pinhole correction. Progressively dense brown filters produced small but significant reductions in S-cone sensitivity. Linear regression analysis of phakic subjects showed a decline for all cone classes with age. Rate of decline was greater for S-cones (slope (95% CI) = -1.09 (-1.23, 0.94)) than M-cones (slope (95% CI) = -0.80 (-0.95, -0.66)) and L-cones (slope (95% CI) = -0.66 (-0.81, - 0.52)). CCT scores increased for S-cones but reduced for L- and M-cones in pseudophakic subjects compared to phakic patients. CCT scores after cataract surgery increased for S-cones, M-cones, and L-cones by 33.0 (p<0.001), 24.9 (p=0.001), and 22.0 (p=0.008). ConclusionsCCT assessment allows for clinically practical quantitation of color and contrast vision improvement after cataract surgery and aging patients who note poor vision despite good visual acuity. Translational RelevanceCCT testing, historically used in research, is now a clinically practical tool to evaluate age and cataract related changes in color and contrast vision and routinely quantify vision beyond black and white visual acuity testing.

pathology↗

bioRxiv2020

Isolation and characterization of Streptomyces bacteriophages and Streptomyces strains encoding biosynthetic arsenals

The threat to public health posed by drug-resistant bacteria is rapidly increasing, as some of healthcares most potent antibiotics are becoming obsolete. Approximately two-thirds of the worlds antibiotics are derived from natural products produced by Streptomyces encoded biosynthetic gene clusters. Thus, in order to identify novel gene clusters, we sequenced the genomes of four bioactive Streptomyces strains isolated from the soil in San Diego County and used Bacterial Cytological Profiling adapted for agar plate culturing in order to examine the mechanisms of bacterial inhibition exhibited by these strains. In the four strains, we identified 101 biosynthetic gene clusters. Some of these clusters were predicted to produce previously studied antibiotics; however, the known mechanisms of these molecules could not fully account for the antibacterial activity exhibited by the strains, suggesting that novel clusters might encode antibiotics. When assessed for their ability to inhibit the growth of clinically isolated pathogens, three Streptomyces strains demonstrated activity against methicillin-resistant Staphylococcus aureus. Additionally, due to the utility of bacteriophages for genetically manipulating bacterial strains via transduction, we also isolated four new phages (BartholomewSD, IceWarrior, Shawty, and TrvxScott) against S. platensis. A genomic analysis of our phages revealed nearly 200 uncharacterized proteins, including a new site-specific serine integrase that could prove to be a useful genetic tool. Sequence analysis of the Streptomyces strains identified CRISPR-Cas systems and specific spacer sequences that allowed us to predict phage host ranges. Ultimately, this study identified Streptomyces strains with the potential to produce novel chemical matter as well as integrase-encoding phages that could potentially be used to manipulate these strains.

microbiology↗

bioRxiv2018

Visual field advantage: Redefined by training?

In 1990, Fred Previc postulated that most peri-personal space interactions occurred in the lower visual field (LVF), leading to an advantage when compared to the upper visual field (UVF). It is not clear if extensive practice can affect the difference between interactions in the LVF/UVF. We tested male and female basketball varsity athletes and non-athletes on a DynaVision D2 visuomotor reaction task. We recruited basketball players because in their training they spend significant amount of time processing upper visual field information. We found a lower visual field advantage in all participants, but this advantage was significantly reduced in the athletes. The results suggest that training can be a powerful modulator of visuomotor function.

neuroscience↗