Biology subjects

Pujari, A. N.

Publications and source records attributed to Pujari, A. N..

6 recordsLinked to original sources

bioRxiv2026

Exploring roles for essential proteins in yeast filamentous growth identifies the WASP homolog Las17 as a regulator of the Cdc42-dependent fMAPK pathway

Cell differentiation into distinct cell types generates functional specialization in eukaryotic organisms. Many fungal species undergo filamentous growth, where cells differentiate into elongated and adhesive filaments capable of expansion and invasion into new environments. The budding yeast Saccharomyces cerevisiae also undergoes filamentous growth, and the regulatory pathways that control the response have been well characterized; however, the roles essential proteins play in this response have not been systematically explored. To address this gap in understanding, we constructed a collection of 332 temperature-sensitive (ts) alleles in 320 essential genes in a strain background that undergoes filamentous growth (called {Sigma}1278b or Sigma). The ts Sigma collection showed differences in temperature sensitivity compared to a ts laboratory strain collection, revealing unexpected phenotypic diversity in essential alleles across populations of individuals. Screening the ts Sigma collection for phenotypes related to filamentous growth uncovered new phenotypes for >35% of essential alleles. New regulators of the Mitogen-Activated Protein Kinase (MAPK) pathway that regulates filamentous growth (fMAPK) were identified, including Las17, a homolog of Wiskott-Aldrich Syndrome Protein (WASP) in humans. Las17 regulated the fMAPK pathway by promoting delivery of the sensor protein, Sho1, and Rho GTPase Cdc42 to the plasma membrane. Las17 also functioned as a hub coordinating separate parallel aspects of the filamentation response. The widespread roles for essential proteins in regulating a eukaryotic differentiation response suggest broader roles essential proteins than is currently appreciated.

genetics↗

bioRxiv2024

The Impact of Excessive Muscle Co-contraction on Sit-to-Stand Performance in High-Heeled Footwear

This study aimed to analyse the effects of co-contraction on quadriceps and hamstring muscles during sit-to-stand tasks for females wearing shoes with different heel heights. The study aimed to identify compensatory strategies during sit to stand task in response to excessive muscle co-contraction during high heeled gait. Sixteen healthy young women (age: 24.4{+/-}1.7 years, body mass index: 18.4{+/-}1kg/m2, weight: 50.2{+/-}5.2kg, height: 1.63{+/-}4.4m) participated in this study. Electromyography signals were recorded from three quadriceps (vastus medialis, vastus lateralis, and rectus femoris) and one hamstring (semitendinosus) muscles. The participants wore shoes with different heights, including 4cm, 6cm, 8cm, and 10cm. For each heel height, we computed co-contraction index to measure postural balance using quadriceps to hamstring muscle pairs. The results that were obtained and quantified with statistical measures show that for elevated shoes if co-contraction increases, both quadriceps and hamstring muscles tend to compensate. This suggests that the capacity of quadriceps and hamstring muscles to compensate is essential to retain normal walking and sit-to-stand (STS) tasks in co-contracted persons. However, the compensation mechanisms may induce imbalance, muscle stiffness, and fatigue for women who regularly use high-heeled shoes during sit-to-stand tasks.

bioengineering↗

bioRxiv2023

Modulators of MAPK pathway activity during filamentous growth in Saccharomyces cerevisiae

Mitogen-activated protein kinase (MAPK) pathways control the response to intrinsic and extrinsic stimuli. In the budding yeast Saccharomyces cerevisiae, cells undergo filamentous growth, which is regulated by the fMAPK pathway. To better understand the regulation of the fMAPK pathway, a genetic screen was performed to identify spontaneous mutants with elevated activity of an fMAPK-pathway dependent growth reporter (ste4 FUS1-HIS3). In total, 159 mutants were isolated and analyzed by secondary screens for invasive growth by the plate-washing assay, and filament formation by microscopy. Thirty-two mutants were selected for whole-genome sequencing, which identified new alleles in genes encoding known regulators of the fMAPK pathway. These included gain-of-function alleles in STE11, which encodes the MAPKKK, as well as loss-of-function alleles in KSS1, which encodes the MAP kinase, and RGA1, which encodes a GTPase activating protein (GAP) for CDC42. New alleles in previously identified pathway modulators were also uncovered in ALY1, AIM44, RCK2, IRA2, REG1 and in genes that regulate protein folding (KAR2), glycosylation (MNN4), and turnover (BLM10). C-terminal truncations in the transcription factor Ste12p were also uncovered that resulted in elevated reporter activity, presumably identifying an inhibitory domain in the C-terminus of the protein. We also show that a wide variety of filamentous growth phenotypes result from mutations in different regulators of the response. The alleles identified here expand the connections surrounding MAPK pathway regulation and reveal new features of proteins that function in the signaling cascade. ARTICLE SUMMARYSignaling pathways control the response to stimuli. In yeast, a signaling (MAPK) pathway controls a fungal behavioral response called filamentous growth. A genetic screen was performed to identify spontaneous mutants that show hyperactivity of a MAPK pathway-dependent reporter. Select mutants were analyzed by whole-genome sequencing. New alleles in known regulatory proteins were identified. A potential inhibitory domain in the C-terminus of the transcription factor Ste12p was also uncovered. Our results indicate that filamentous growth is determined by the combinatorial effects of multiple positive and negative regulatory inputs.

genetics↗

bioRxiv2020

Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but not Corticospinal Pathways

The aim of this study was to investigate whether indirect upper limb vibration (ULV) modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right flexor carpi radialis (FCR) muscle. To assess spinal pathways, Hoffmann reflexes (H-reflexes) elicited by stimulation of the median nerve were recorded from FCR with motor response (M-wave) amplitudes matched between conditions. An H-reflex conditioning paradigm was also used to assess changes in presynaptic inhibition by stimulating the superficial radial (SR) nerve (5 pulses at 300Hz) 37 ms prior to median nerve stimulation. Cutaneous reflexes in FCR elicited by stimulation of the SR nerve at the wrist were also recorded. To assess corticospinal pathways, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation of the contralateral motor cortex were recorded from the right FCR and biceps brachii (BB). ULV significantly reduced H-reflex amplitude by 15.7% for both conditioned and unconditioned reflexes (24.0{+/-}15.7 vs 18.4{+/-}11.2 % Mmax; p<0.05). Middle latency cutaneous reflexes were also significantly reduced by 20.0% from CONTROL (-1.50 {+/-} 2.1 % Mmax) to ULV (-1.73 {+/-} 2.2 % Mmax; p<0.05). There was no significant effect of ULV on MEP amplitude (p>0.05). Therefore, ULV inhibits cutaneous and H-reflex transmission without influencing corticospinal excitability of the forearm flexors suggesting increased presynaptic inhibition of afferent transmission as a likely mechanism. A general increase in inhibition of spinal pathways with ULV may have important implications for improving rehabilitation for individuals with spasticity (SCI, stroke, MS, etc).

neuroscience↗

bioRxiv2018

Fatiguing Effects of Indirect Vibration Stimulation in Upper Limb Muscles- pre, post and during Isometric Contractions Superimposed on Upper Limb Vibration

BackgroundIndirect vibration stimulation i.e. whole body vibration and upper limb vibration (ULV), are gaining popularity as exercise intervention for sports and rehabilitation applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. In addition, current vibration stimulation devices have a series of limitations. For this scope, we investigated the effects of ULV superimposed on fatiguing graded isometric contractions using a newly, purpose developed upper limb stimulation device. Twelve healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions, at 80% of the maximum voluntary contractions (V) and just isometric contractions performed on a custom designed arm curl/flexion device- Control (C). The stimulation used consisted of 30Hz frequency of 0.4mm amplitude. Surface electromyographic (EMG) activity of the Biceps Brachii (BB), Triceps Brachii (TB), and Flexor Carpi Radialis (Forearm- FCR) were measured during both V and C conditions. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels respectively.\n\nResultsAll three muscles BB, TB and FCR displayed significantly higher reduction in MEFs and corresponding significant increase in EMGrms with the V than the C, during fatiguing contractions (P < 0.05). Post vibration treatment, all muscles showed higher levels of MEFs after recovery compared to the control.\n\nConclusionsOur results show that near maximal (80% of MVC) isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show, higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment, potentially through the augmentation of stretch reflex and/or higher central motor command excitability.

bioengineering↗

bioRxiv2018

The Effects of Different Vibration Frequencies, Amplitudes and Contraction Levels on Lower Limb Muscles during Graded Isometric Contractions Superimposed on Whole Body Vibration Stimulation

BackgroundIndirect vibration stimulation i.e. whole body vibration or upper limb vibration, has been suggested increasingly as an effective exercise intervention for sports and rehabilitation applications. However, there is a lack of evidence regarding the effects of whole body vibration (WBV) stimulation superimposed to graded isometric contractions superimposed on. For this scope, we investigated the effects of WBV superimposed to graded isometric contractions in the lower limbs on muscle activation. We also assessed the agonist-antagonist co-activation during this type of exercise.\n\nTwelve healthy volunteers were exposed to WBV superimposed to graded isometric contractions, at 20, 40, 60, 80 and 100% of the maximum voluntary contractions (V) or just isometric contractions performed on a custom designed horizontal leg press Control (C). Tested stimulation consisted of 30Hzand 50Hz frequencies and 0.5mm and 1.5mm amplitudes. Surface electromyographic activity of Vastus Lateralis (VL), Vastus Medialis (VM) and Biceps Femoris (BF) were measured during V and C conditions. Co-contraction activity of agonist-antagonist muscles was also quantified. The trials were performed in random order.\n\nResultsBoth the prime mover, (VL) and the antagonist, (BF) displayed significantly higher (P < 0.05) EMG activity with the V than the C condition. For both the VL and BF, the increase in mean EMGrms values depended on the frequency, amplitude and muscle contraction level with 50Hz-0.5mm stimulation inducing the largest neuromuscular activity. 50Hz-0.5mm V condition also led to co-activation ratios significantly (P< 0.05) higher at 40, 80 and 100% of MVC than the C condition.\n\nConclusionsOur results show that the isometric contraction superimposed on vibration stimulation leads to higher neuromuscular activity compared to isometric contraction alone in the lower limbs. Compared to the control condition, the vibratory stimulation leads to higher agonist-antagonist co-activation of the muscles around the knee joint in all vibration conditions and effort levels. The combination of vibration magnitude (frequency and amplitude) and the level of muscle contraction affect neuromuscular activity rather than vibration frequency alone. Results of this study suggest that more parameters need to be taken into consideration when designing vibration exercise programs for sports and rehabilitation purposes.

bioengineering↗