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1

Rapid transport of protons across membranes

100%
Krishnamoorthy G., Ahmed I., Singh S., Maity H. P., Srivastava A.
Biophysics of Membrane Transport
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1994
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tom 12
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nr 1
2

High-quality plant DNA extraction for PCR: an easy approach

86%
Ahmed I., Islam M., Arshad W., Mannan A., Ahmad W., Mirza B.
Journal of Applied Genetics
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2009
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tom 50
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nr 2
105-107
Polymerase chain reaction has found wide applications in modern research involving transformations and other genomic studies. For reproducible PCR results, however, the quantity and quality of template DNA is of considerable importance. A simple and efficient plant DNA extraction procedure for isolation of high-quality DNA from plant tissues is presented here. It requires maceration of plant tissue of about 1.0 cm² (e.g. of a leaf blade) in DNA extraction buffer (100 mM Tris-HCl, 100 mM EDTA, 250 mM NaCl) using 1.5-mL microfuge tubes, followed by cell lysis with 20% SDS, and DNA extraction with phenol: chloroform: iso-amyl alcohol (25:24:1 ). Hydrated ether is then used to remove polysaccharides and other contaminants from the DNA preparation. Average DNA yield is 20-30 µg cm⁻² for fresh tissues, and ratio of absorbance at 260 nm to absorbance at 280 nm is 1.5-1.8. The DNA is quite suitable for PCR using microsatellites, RAPD and specific markers for recombinant selection. Amplifications have been obtained for these markers by using template DNA extracted from fresh as well as frozen leaf tissues of various plants, including barley, oat, potato and tomato. DNA stored for more than 2 years has been successfully amplified with microsatellite markers, which shows suitability of this method after long-term storage of DNA. Besides, the ease of use and cost-effectiveness make the procedure attractive.
3

Modular microelectronic system for in vivo electrical stimulation and recording at up to 512 electrodes

59%
Szypulska M., Wiacek P., Skoczen A., Fiutowski T., Ahmed I., Jedraczka M., Dusik J., Dwuznik M., Kublik E., Dabrowski W., Hottowy P.
Acta Neurobiologiae Experimentalis
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2017
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tom 77
|
nr Suppl.1
INTRODUCTION: Multielectrode silicon probes can record neuronal signals with combination of spatial and temporal resolution that other recording techniques cannot provide. Here we propose a novel microelectronic system that combines this functionality with advanced electrical stimulation. AIM(S): We designed a modular system for multielectrode electrical stimulation and recording in the brain of a living animal. It can be combined with any silicon probe used for brain research. It can generate complex sequences of stimulation pulses and simultaneously record at up to 512 electrodes. It can use up to 4 silicon probes in parallel, providing bidirectional communication with populations of neurons simultaneously in several brain areas. METHOD(S): The system is based on a dedicated multichannel CMOS chip. The chip includes 64 channels, digital circuitry for real-time communication with the control computer and a multiplexer that sends amplified signals from 64 electrodes into a single output line. The amplifier gain can be changed from 110 to 550. The low cut‑off frequency is set between 200 mHz and 3 Hz, the anti-aliasing filter is set at 7 kHz and the sampling rate is 40 kHz. The stimulation signal is controlled independently for each channel with 12-bit resolution and refresh rate of 40 kHz. Each amplifier can be disconnected from the electrode for the duration of the stimulation pulse for the artifact reduction. Up to 8 chips can be controlled in parallel with dedicated LabView software. RESULTS: Base version of the system was produced and tested with positive results. The final system is in the integration phase. We plan the first experiments to take place in the fall 2017 at the Nencki Institute for Experimental Biology. CONCLUSIONS: The reported system can generate complex sequences of stimulation pulses and record neuronal signals with very low artifacts at 512 electrodes, making it a powerful tool for mapping of the functional connections between brain circuits. FINANCIAL SUPPORT: Grant 2013/08/W/NZ4/00691, Polish National Science Centre.
4

Microelectronic system for low-artifact electrical stimulation and recording of brain activity at up to 512 electrodes

59%
Szypulska M., Wiacek P., Skoczen A., Ahmed I., Futowski T., Jurgielewicz P., Kolodziej K., Czerwinski M. B., Wojcik D. K., Mindur B., Kublik E., Dabrowski W., Hottowy P.
Acta Neurobiologiae Experimentalis
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2019
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tom 79
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nr Suppl.1
INTRODUCTION: We present a novel microelectronic system for in vivo stimulation and recording of neuronal activity. The system is intended for use with multielectrode silicon probes and is based on a dedicated 64‑channel CMOS chip. It can generate complex sequences of microstimulation pulses and simultaneously record (with low artifacts) neuronal responses at up to 512 electrodes. The system is compatible with most silicon probes used in the brain research and can use up to four probes in parallel, providing bidirectional communication with populations of neurons simultaneously in several brain areas. Each channel of the chip includes a recording amplifier and a stimulation circuit. The amplifier has adjustable gain (110‑550x), low cut‑off frequency (1.4‑7 Hz), and anti‑aliasing filter frequency (1.2‑14 kHz). The input‑referred noise is 6.8 µV. Signals from all the channels are digitized at 40 kHz. The stimulation signal is defined independently for each channel with 40 kHz refresh rate. The stimulation artifacts are reduced by temporally disconnecting the amplifiers from electrodes and optimization of the pulse waveform. METHOD(S): The system has been tested in experiments exploring somatosensory thalamo-cortical network in rodents. 2‑3 weeks before surgery, animals received injections of AAV‑hSyn‑ChR2‑EYFP viral vector. In anesthetized animals, multichannel probes were inserted into the barrel cortex and/or sensory thalamus for recording of LFPs and multi-unit responses to microstimulation delivered to various nodes of thalamo‑cortical network. Electrically evoked activity was compared with responses to natural whisker deflection and optical stimulation. RESULTS: The reported system can generate complex patterns of stimulation pulses and record neuronal signals with very low artifacts at up to 512 electrodes, making it a powerful tool for mapping of the functional connections between brain circuits. FINANCIAL SUPPORT: Supported by Polish National Science Centre grant 2013/08/W/NZ4/00691.
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