Zahur Ahmed - Academia.edu (original) (raw)
Papers by Zahur Ahmed
Pseudomonas aeruginosa - New Perspectives and Applications [Working Title]
The excess use of chemical fertilizers diminishes soil fertility and yield from crops gradually. ... more The excess use of chemical fertilizers diminishes soil fertility and yield from crops gradually. To regain and enhance our soil nutrients to get more yields, it is mandatory to rely on soil microbes. Some beneficial microbes’ termed as bio-fertilizers especially rhizosphere bacteria have well contribution in increasing plant growth, and yield without any toxins. It is a very natural process of interaction between plant and some microbes to increase the assimilation of nutrients and it helps plants to enhance better production. In this research, we showed the use of microbes especially Pseudomonas fluorescens survival in the soil. We applied different carriers such as dextrose, talc, and peat with freeze-dried P. fluorescens and studied the shelf-life of the P. fluorescens. Among different carrier’s peat with centrifuged cell suspension survived up to 60 days with significant CFU’s 2×107/gm CFU’s, our research will be a prospective to make new formulations and to increase the shelf-l...
165 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1979.U of I OnlyRestricted to t... more 165 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1979.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD
Journal of Neurophysiology, 1991
1. Whole-cell current responses to bath application of glycine, beta-alanine, and taurine were st... more 1. Whole-cell current responses to bath application of glycine, beta-alanine, and taurine were studied in medullary neurons cultured from embryonic rats. 2. Two current components were seen in the responses to bath application of agonist, one component that desensitized and another that did not. 3. The two current components have different dose-response characteristics, with the nondesensitizing component being activated more effectively at lower concentrations than the desensitizing component and also reaching its peak at lower concentrations. The agonist concentrations producing half-maximal responses are 26 +/- 4 (SE, n = 6) and 69 +/- 17 (n = 7) microM for the nondesensitizing and desensitizing components, respectively, for glycine; 54 +/- 7 (n = 9) and 127 +/- 37 (n = 7) microM for beta-alanine; and 153 +/- 24 (n = 9) 443 +/- 99 (n = 3) microM for taurine. Thus, for each component, the order of potency is glycine greater than beta-alanine greater than taurine. 4. When total res...
American Journal of Physiology-Cell Physiology, 1991
The effects of carbamylcholine (carbachol) on intracellular Ca2+ concentration ([Ca2+]c) of T84 c... more The effects of carbamylcholine (carbachol) on intracellular Ca2+ concentration ([Ca2+]c) of T84 cells were examined using the fluorescent Ca2+ indicator fura-2 and microfluorometric techniques. In single isolated cells, carbachol (100 microM) caused a rapid increase in [Ca2+]c of 184 +/- 15 nM (SE, n = 44) from a resting value of 56 +/- 7 nM. This initial transient was followed by a series of oscillations in 68% of the cells. Atropine (10 microM) blocked this response. Removal of bath Ca2+ did not inhibit the rise in [Ca2+]c or oscillations, but the response duration was shortened in 47% of the cells. The amplitude and latency of the initial Ca2+ rise, frequency of oscillations, and number of responding cells varied with the agonist concentration. We have previously shown that carbachol induces an oscillating K+ conductance in T84 cells [D. Devor, S. Simasko, and M. Duffey. Am. J. Physiol. 258 (Cell Physiol. 27): C318-C326, 1990]. Simultaneous measurement of membrane K+ current and ...
Methods in Enzymology, 1990
Publisher Summary This chapter describes a strategy for characterizing the changes in membrane K ... more Publisher Summary This chapter describes a strategy for characterizing the changes in membrane K + conductance that result from exposure of isolated cells of the human secretory cell line T84 to a cholinergic agonist, and the role of intracellular Ca 2+ as a mediator of that process. These findings in isolated T84 cells are consistent with the proposed model for muscarinic agonist-induced Cl- secretion by an epithelium, in which an agonist-induced increase in basolateral membrane K + conductance hyperpolarizes the cells and causes secretion by increasing the driving force for C1- exit across the apical membrane. Care must be used in interpretation of results from dialyzed cells. This is illustrated in the studies by the difference seen between the duration of the carbachol-induced K + current oscillations and Ca 2+ oscillations. In every cell studied, the K + current returned to baseline in the continued presence of carbachol.
Neuroscience Letters, 1989
Characteristics of glycine-activated currents in 10-to 20-day-old neurons were studied using the ... more Characteristics of glycine-activated currents in 10-to 20-day-old neurons were studied using the gigaseal whole-cell technique. Glycine activated a CI conductance that was blocked by strychnine acting as a mixed inhibitor, effecting both lmax and Kd. Glycine receptors with at least two different sensitivities to strychnine were found, based on the apparent inhibition constants (K,). These two Ki values were associated with different Hill coefficients for the glycine responses. Cs + activated the same receptor and also activated a relatively nonselective cation conductance. Most neurotransmitters, (e.g. acetylcholine (ACh), 7-aminobutyric acid (GABA), and glutamate) activate more than one receptor population. These distinctions result from evidence of selective agonists or antagonists for a receptor subtype. One exception has been glycine, for which strychnine is the one specific antagonist; however, there have been suggestions of glycinergic inhibitions which are relatively insensitive to strychnine [4], and some studies have shown two binding sites for glycine in the medulla and spinal cord [9, 1 1]. We report here evidence for multiple types of glycine receptors, based on patch clamp recordings from cultured medullary neurons. The method for culturing neurons has been described in detail [1]. Briefly, the myelencephalon was dissected from fetuses removed from timed 18 day pregnant Sprague Dawley rats. The tissue was enzymatically digested (0.05% trypsin) for 30 min, triturated, and cells were collected by centrifugation at 80 g for 10 min. They were grown on poly-D-lysine-coated glass coverslips in a 24-well cluster culture dish in minimal essential medium (MEM) supplemented with I% fetal calf serum and 1% horse serum (Gibco). Electrophysiological recordings were obtained after 1~20 days in culture, using gigaseal whole-cell voltage clamp techniques [7]. Patch pipettes contained 148 mM
Developmental Brain Research, 1990
Giycine-activated currents in 1-to ll-day-old rat medullary neurons were studied using patch clam... more Giycine-activated currents in 1-to ll-day-old rat medullary neurons were studied using patch clamp techniques. Glycine produced neither repeatable whole-cell current responses nor single-channel activity in the cell-attached mode until cells were in culture for a week or more. However, CI-channels were present at the early stages because glycine-activated channels were seen in excised, inside-out patches. Furthermore, for cells less than a week in culture, 10 patches which did not exhibit glycine-activated CI-channels in the cell-attached mode did upon excision. Consequently, the activation properties of these CI channels undergo a developmental change in that some cellular factor(s) presumably prevents the CI channels from opening in the intact cell during the initial stages in culture.
Cell Calcium, 1988
The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were exami... more The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were examined in the soma of Archidoris monteryensis neurons. The rate of recovery from a f&transient was examlned with two experimental protocols; in one the pulse duration was kept constant and its amplitude was varied, and in the other the duration was varied while the amplitude was kept constant. These experiments revealed that the recovery from a Catransient was approximately a first order process and the apparent first order rate constant was dependent on the duration of Ca-influx. The calcium buffer capacity of the cytoplasm was determined by an indirect method which utilised measured amounts of intracellular EGTA to reduce transient changes in free calcium. An equation for the cytoplasmic buffer capacity was derived on the assumption that the capacities of exogenous and endogenous Ca buffers summate linearly. The resting cytoplasmic Ca buffer capacity was 45.2 kM/ApCa, when it was assumed that the incoming Ca diffuses a distance of 10km into the cytoplasm. For a diffusion distance of 5pm it was 34.5@l/ApCa. In both cases, the buffer capacity increased with an increase in the size of Ca transient.
Cellular and Molecular Neurobiology, 1984
The dispersion of dye molecules and small cations injected from a point source in the cytoplasm o... more The dispersion of dye molecules and small cations injected from a point source in the cytoplasm of molluscan neurons has been measured photometrically and compared with dispersion in aqueous solution. 2. The diffusion of phenol red and arsenazo III was at least a factor of five slower in the cytoplasm than in saline. Movement of both dyes was slowed by about the same factor in a given cell. The dispersion rate of arsenazo III was not significantly affected by preloading the cytoplasm to dye concentrations up to 0.5 raM. 3. Calcium and barium dispersion was measured in neurons and saline droplets preloaded with arsenazo III, while phenol red absorbance changes were used to follow the dispersion of injected protons. Ba 2+ and H + moved very slowly in the cytoplasm compared to aqueous solution. 4. Ca 2+ movement in all probability underwent a similar retardation in the neurons but high-affinity buffering of the cytoplasm severely restricted the spread of detectable amounts of this ion away from the injection site.
Brain research, Jan 16, 1988
The gigaseal whole-cell voltage clamp technique has been used to investigate the timing of expres... more The gigaseal whole-cell voltage clamp technique has been used to investigate the timing of expression and properties of voltage-dependent inward currents in cultured neocortical pyramidal-shaped neurons. The dissociated primary cultures of synchronized (same cell cycle), growth arrested (G1-phase) and birth-dated neurons from fetal rat (E18) were maintained in a serum-free medium. The earliest inward current is expressed within 24 h. This current is carried by Na+ and the channels are located in distal neurites at discrete sites. The Na+ channels near the cell body are expressed after 5 days in culture, at which time the neuritic Na+ current persists. The magnitude of the current near the soma increases with age of the neuron. The Na+ current is blocked by both tetrodotoxin (TTX) and nitrendipine. The sensitivity to nitrendipine changes with age of the culture. The results suggest that Na channels expressed early during neuronal development have some structural component common also...
Cell Calcium, 1988
The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were exami... more The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were examined in the soma of Archidoris monteryensis neurons. The rate of recovery from a f&transient was examlned with two experimental protocols; in one the pulse duration was kept constant and its amplitude was varied, and in the other the duration was varied while the amplitude was kept constant. These experiments revealed that the recovery from a Catransient was approximately a first order process and the apparent first order rate constant was dependent on the duration of Ca-influx. The calcium buffer capacity of the cytoplasm was determined by an indirect method which utilised measured amounts of intracellular EGTA to reduce transient changes in free calcium. An equation for the cytoplasmic buffer capacity was derived on the assumption that the capacities of exogenous and endogenous Ca buffers summate linearly. The resting cytoplasmic Ca buffer capacity was 45.2 kM/ApCa, when it was assumed that the incoming Ca diffuses a distance of 10km into the cytoplasm. For a diffusion distance of 5pm it was 34.5@l/ApCa. In both cases, the buffer capacity increased with an increase in the size of Ca transient.
Pseudomonas aeruginosa - New Perspectives and Applications [Working Title]
The excess use of chemical fertilizers diminishes soil fertility and yield from crops gradually. ... more The excess use of chemical fertilizers diminishes soil fertility and yield from crops gradually. To regain and enhance our soil nutrients to get more yields, it is mandatory to rely on soil microbes. Some beneficial microbes’ termed as bio-fertilizers especially rhizosphere bacteria have well contribution in increasing plant growth, and yield without any toxins. It is a very natural process of interaction between plant and some microbes to increase the assimilation of nutrients and it helps plants to enhance better production. In this research, we showed the use of microbes especially Pseudomonas fluorescens survival in the soil. We applied different carriers such as dextrose, talc, and peat with freeze-dried P. fluorescens and studied the shelf-life of the P. fluorescens. Among different carrier’s peat with centrifuged cell suspension survived up to 60 days with significant CFU’s 2×107/gm CFU’s, our research will be a prospective to make new formulations and to increase the shelf-l...
165 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1979.U of I OnlyRestricted to t... more 165 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1979.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD
Journal of Neurophysiology, 1991
1. Whole-cell current responses to bath application of glycine, beta-alanine, and taurine were st... more 1. Whole-cell current responses to bath application of glycine, beta-alanine, and taurine were studied in medullary neurons cultured from embryonic rats. 2. Two current components were seen in the responses to bath application of agonist, one component that desensitized and another that did not. 3. The two current components have different dose-response characteristics, with the nondesensitizing component being activated more effectively at lower concentrations than the desensitizing component and also reaching its peak at lower concentrations. The agonist concentrations producing half-maximal responses are 26 +/- 4 (SE, n = 6) and 69 +/- 17 (n = 7) microM for the nondesensitizing and desensitizing components, respectively, for glycine; 54 +/- 7 (n = 9) and 127 +/- 37 (n = 7) microM for beta-alanine; and 153 +/- 24 (n = 9) 443 +/- 99 (n = 3) microM for taurine. Thus, for each component, the order of potency is glycine greater than beta-alanine greater than taurine. 4. When total res...
American Journal of Physiology-Cell Physiology, 1991
The effects of carbamylcholine (carbachol) on intracellular Ca2+ concentration ([Ca2+]c) of T84 c... more The effects of carbamylcholine (carbachol) on intracellular Ca2+ concentration ([Ca2+]c) of T84 cells were examined using the fluorescent Ca2+ indicator fura-2 and microfluorometric techniques. In single isolated cells, carbachol (100 microM) caused a rapid increase in [Ca2+]c of 184 +/- 15 nM (SE, n = 44) from a resting value of 56 +/- 7 nM. This initial transient was followed by a series of oscillations in 68% of the cells. Atropine (10 microM) blocked this response. Removal of bath Ca2+ did not inhibit the rise in [Ca2+]c or oscillations, but the response duration was shortened in 47% of the cells. The amplitude and latency of the initial Ca2+ rise, frequency of oscillations, and number of responding cells varied with the agonist concentration. We have previously shown that carbachol induces an oscillating K+ conductance in T84 cells [D. Devor, S. Simasko, and M. Duffey. Am. J. Physiol. 258 (Cell Physiol. 27): C318-C326, 1990]. Simultaneous measurement of membrane K+ current and ...
Methods in Enzymology, 1990
Publisher Summary This chapter describes a strategy for characterizing the changes in membrane K ... more Publisher Summary This chapter describes a strategy for characterizing the changes in membrane K + conductance that result from exposure of isolated cells of the human secretory cell line T84 to a cholinergic agonist, and the role of intracellular Ca 2+ as a mediator of that process. These findings in isolated T84 cells are consistent with the proposed model for muscarinic agonist-induced Cl- secretion by an epithelium, in which an agonist-induced increase in basolateral membrane K + conductance hyperpolarizes the cells and causes secretion by increasing the driving force for C1- exit across the apical membrane. Care must be used in interpretation of results from dialyzed cells. This is illustrated in the studies by the difference seen between the duration of the carbachol-induced K + current oscillations and Ca 2+ oscillations. In every cell studied, the K + current returned to baseline in the continued presence of carbachol.
Neuroscience Letters, 1989
Characteristics of glycine-activated currents in 10-to 20-day-old neurons were studied using the ... more Characteristics of glycine-activated currents in 10-to 20-day-old neurons were studied using the gigaseal whole-cell technique. Glycine activated a CI conductance that was blocked by strychnine acting as a mixed inhibitor, effecting both lmax and Kd. Glycine receptors with at least two different sensitivities to strychnine were found, based on the apparent inhibition constants (K,). These two Ki values were associated with different Hill coefficients for the glycine responses. Cs + activated the same receptor and also activated a relatively nonselective cation conductance. Most neurotransmitters, (e.g. acetylcholine (ACh), 7-aminobutyric acid (GABA), and glutamate) activate more than one receptor population. These distinctions result from evidence of selective agonists or antagonists for a receptor subtype. One exception has been glycine, for which strychnine is the one specific antagonist; however, there have been suggestions of glycinergic inhibitions which are relatively insensitive to strychnine [4], and some studies have shown two binding sites for glycine in the medulla and spinal cord [9, 1 1]. We report here evidence for multiple types of glycine receptors, based on patch clamp recordings from cultured medullary neurons. The method for culturing neurons has been described in detail [1]. Briefly, the myelencephalon was dissected from fetuses removed from timed 18 day pregnant Sprague Dawley rats. The tissue was enzymatically digested (0.05% trypsin) for 30 min, triturated, and cells were collected by centrifugation at 80 g for 10 min. They were grown on poly-D-lysine-coated glass coverslips in a 24-well cluster culture dish in minimal essential medium (MEM) supplemented with I% fetal calf serum and 1% horse serum (Gibco). Electrophysiological recordings were obtained after 1~20 days in culture, using gigaseal whole-cell voltage clamp techniques [7]. Patch pipettes contained 148 mM
Developmental Brain Research, 1990
Giycine-activated currents in 1-to ll-day-old rat medullary neurons were studied using patch clam... more Giycine-activated currents in 1-to ll-day-old rat medullary neurons were studied using patch clamp techniques. Glycine produced neither repeatable whole-cell current responses nor single-channel activity in the cell-attached mode until cells were in culture for a week or more. However, CI-channels were present at the early stages because glycine-activated channels were seen in excised, inside-out patches. Furthermore, for cells less than a week in culture, 10 patches which did not exhibit glycine-activated CI-channels in the cell-attached mode did upon excision. Consequently, the activation properties of these CI channels undergo a developmental change in that some cellular factor(s) presumably prevents the CI channels from opening in the intact cell during the initial stages in culture.
Cell Calcium, 1988
The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were exami... more The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were examined in the soma of Archidoris monteryensis neurons. The rate of recovery from a f&transient was examlned with two experimental protocols; in one the pulse duration was kept constant and its amplitude was varied, and in the other the duration was varied while the amplitude was kept constant. These experiments revealed that the recovery from a Catransient was approximately a first order process and the apparent first order rate constant was dependent on the duration of Ca-influx. The calcium buffer capacity of the cytoplasm was determined by an indirect method which utilised measured amounts of intracellular EGTA to reduce transient changes in free calcium. An equation for the cytoplasmic buffer capacity was derived on the assumption that the capacities of exogenous and endogenous Ca buffers summate linearly. The resting cytoplasmic Ca buffer capacity was 45.2 kM/ApCa, when it was assumed that the incoming Ca diffuses a distance of 10km into the cytoplasm. For a diffusion distance of 5pm it was 34.5@l/ApCa. In both cases, the buffer capacity increased with an increase in the size of Ca transient.
Cellular and Molecular Neurobiology, 1984
The dispersion of dye molecules and small cations injected from a point source in the cytoplasm o... more The dispersion of dye molecules and small cations injected from a point source in the cytoplasm of molluscan neurons has been measured photometrically and compared with dispersion in aqueous solution. 2. The diffusion of phenol red and arsenazo III was at least a factor of five slower in the cytoplasm than in saline. Movement of both dyes was slowed by about the same factor in a given cell. The dispersion rate of arsenazo III was not significantly affected by preloading the cytoplasm to dye concentrations up to 0.5 raM. 3. Calcium and barium dispersion was measured in neurons and saline droplets preloaded with arsenazo III, while phenol red absorbance changes were used to follow the dispersion of injected protons. Ba 2+ and H + moved very slowly in the cytoplasm compared to aqueous solution. 4. Ca 2+ movement in all probability underwent a similar retardation in the neurons but high-affinity buffering of the cytoplasm severely restricted the spread of detectable amounts of this ion away from the injection site.
Brain research, Jan 16, 1988
The gigaseal whole-cell voltage clamp technique has been used to investigate the timing of expres... more The gigaseal whole-cell voltage clamp technique has been used to investigate the timing of expression and properties of voltage-dependent inward currents in cultured neocortical pyramidal-shaped neurons. The dissociated primary cultures of synchronized (same cell cycle), growth arrested (G1-phase) and birth-dated neurons from fetal rat (E18) were maintained in a serum-free medium. The earliest inward current is expressed within 24 h. This current is carried by Na+ and the channels are located in distal neurites at discrete sites. The Na+ channels near the cell body are expressed after 5 days in culture, at which time the neuritic Na+ current persists. The magnitude of the current near the soma increases with age of the neuron. The Na+ current is blocked by both tetrodotoxin (TTX) and nitrendipine. The sensitivity to nitrendipine changes with age of the culture. The results suggest that Na channels expressed early during neuronal development have some structural component common also...
Cell Calcium, 1988
The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were exami... more The properties of Ca-regulation and-buffering of physiological levels of Ca-translents were examined in the soma of Archidoris monteryensis neurons. The rate of recovery from a f&transient was examlned with two experimental protocols; in one the pulse duration was kept constant and its amplitude was varied, and in the other the duration was varied while the amplitude was kept constant. These experiments revealed that the recovery from a Catransient was approximately a first order process and the apparent first order rate constant was dependent on the duration of Ca-influx. The calcium buffer capacity of the cytoplasm was determined by an indirect method which utilised measured amounts of intracellular EGTA to reduce transient changes in free calcium. An equation for the cytoplasmic buffer capacity was derived on the assumption that the capacities of exogenous and endogenous Ca buffers summate linearly. The resting cytoplasmic Ca buffer capacity was 45.2 kM/ApCa, when it was assumed that the incoming Ca diffuses a distance of 10km into the cytoplasm. For a diffusion distance of 5pm it was 34.5@l/ApCa. In both cases, the buffer capacity increased with an increase in the size of Ca transient.