Alan Steinbach - Academia.edu (original) (raw)

Papers by Alan Steinbach

A BSTRACT Xylocaine and its derivatives act specifically at the neuromuscular junction within the... more A BSTRACT Xylocaine and its derivatives act specifically at the neuromuscular junction within the concentration range 0.05 to 2.0 m. The charged form is the active form of the drugs. There is no correlation between "local anesthetic" activity and effect at the junction. Like d-tubocurarine, these drugs have little or no effect on quantum content, acetylcholinesterase activity, or the passive impedance of the muscle fiber. Yet they produce end plate potentials characterized by a brief, early component and a late, greatly prolonged component, as does procaine. Analysis of these changes in time course suggests that the drugs have little or no effect before receptors are activated by acetylcholine, but cause a decreased and often greatly prolonged response. Clear structure-activity relations indicate that the receptor to which the drugs bind to produce the prolonged response can be the receptor for acetylcholine. Comparison of the effects of the drugs on the end plate potentia...

Research publications - Association for Research in Nervous and Mental Disease, 1972

The Journal of physiology, 1968

1. J Physiol. 1968 Jul;197(1):4P-5P. Action potentials in denervated "slow" muscle fibr... more 1. J Physiol. 1968 Jul;197(1):4P-5P. Action potentials in denervated "slow" muscle fibres of the frog. Stefani E, Steinbach AB. PMID: 5675070 [PubMed - indexed for MEDLINE] MeSH Terms: Action Potentials*; Animals; Anura; ...

The Journal of Physiology, Aug 1, 1969

1. The electrical properties of frog slow muscle fibres were investigated with intracellular micr... more 1. The electrical properties of frog slow muscle fibres were investigated with intracellular micropipettes to determine their characteristic length (lambda), specific membrane resistance (R(m)) and specific membrane capacitance.2. The value of lambda was about 1 cm in fibres of 1.2 cm length. The ;short cable model' was used to calculate R(m). Its mean value was 1.12 x 10(5) ohm cm(2), about 10-20 times larger than the value for twitch fibres. The mean value for C(m) was 3.24 x 10(-6) F/cm(2).3. Resting potentials measured immediately after penetration with a single micropipette were about - 80 mV. Lower values can be attributed to the effects of damage or leakage produced by micropipette insertion.4. Changes in external K concentration produced changes in the initially recorded resting potentials which follow the constant field theory using a ratio of Na: K permeabilities P(Na)/P(K) = 0.02. Changes in external Cl concentration produced little or no change in the resting potential or membrane resistance, indicating a low Cl permeability.5. In agreement with previous work, slow fibres showed a time-dependent decrease in resistance (;delayed rectification') for membrane potentials more positive than - 60 mV. ;Anomalous rectification' observed in twitch fibres was not seen in slow fibres. In high external K concentrations the resistance of slow fibres is almost unaffected by changes in membrane potential.6. Increasing the concentration of external Ca (up to isotonic) has two distinct effects on slow fibres. It increases R(m) up to ten times, and it improves the stability of trans-membrane recordings, probably by reducing the leakage due to micropipette penetrations. Magnesium does not appear to have either of these effects.

Academic Medicine, May 1, 2001

The Journal of Physiology, Sep 1, 1971

The electrical and structural characteristics of 'slow' muscle fibres of the frog were studied in... more The electrical and structural characteristics of 'slow' muscle fibres of the frog were studied in normal and denervated muscles, and in muscles undergoing re-innervation by a mixed nerve containing large and small motor axons. 2. In agreement with previous studies, slow fibres in normally innervated muscles were incapable of producing action potentials. 3. Approximately 2 weeks after the sciatic nerve was transacted or crushed, slow muscle fibres acquired the ability to generate action potentials. These fibres were positively identified as belonging to the slow type, because their passive-electrical and ultrastructural characteristics remained essentially unchanged after the operations. 4. The action potential mechanism induced in slow fibres is sodiumdependent, and is blocked by tetrodotoxin. 5. After long-term re-innervation by a mixed nerve, slow fibres lose their acquired ability to generate action potentials, presumably because small motor axons re-establish connexion with the fibres. 6. It is concluded that the action potential mechanism of slow muscle fibres is under neural control, and is normally suppressed by small motor axons.

Nature, May 1, 1968

Fellow of the Consejo Nacional de Investigaciones Cientificas y Technicas. t NSF regular post doc... more Fellow of the Consejo Nacional de Investigaciones Cientificas y Technicas. t NSF regular post doctoral fellow.

ABSTRACTAffordable novel strategies are needed to treat COVID-19 cases complicated by respiratory... more ABSTRACTAffordable novel strategies are needed to treat COVID-19 cases complicated by respiratory compromise in resource limited settings. We report a mixed-methods pre-post assessment of 1) the useability of CPAP/O2 helmet non-invasive ventilation (NIV) to treat COVID-19, at ∼ 1% the cost of mechanical ventilation; 2) the effectiveness of a train-the-trainer practice facilitation intervention; and 3) whether use of CPAP/O2 helmet NIV was associated with increased COVID-19 infection among healthcare workers. At baseline, eight COVID-19 treatment centers in Nigeria (CircumVent network) received CPAP/O2 helmet systems, and were instructed on its use. After five months, clinicians within the CircumVent netwok participated in a 2-day train-the-trainers educational intervention. The physicians completed i) standardized forms on patient demographics, clinical course, and outcomes for patients seen in the treatment centers; ii) standardized surveys of feasibility and acceptability of use o...

Social Science & Medicine, 2009

Shortages of health care professionals have plagued rural areas of the USA for more than a centur... more Shortages of health care professionals have plagued rural areas of the USA for more than a century. Programs to alleviate them have met with limited success. These programs generally focus on factors that affect recruitment and retention, with the supposition that poor recruitment drives most shortages. The strongest known influence on rural physician recruitment is a ''rural upbringing,'' but little is known about how this childhood experience promotes a return to rural areas, or how non-rural physicians choose rural practice without such an upbringing. Less is known about how rural upbringing affects retention. Through twenty-two in-depth, semi-structured interviews with both rural-and urban-raised physicians in northeastern California and northwestern Nevada, this study investigates practice location choice over the life course, describing a progression of events and experiences important to rural practice choice and retention in both groups. Study results suggest that rural exposure via education, recreation, or upbringing facilitates future rural practice through four major pathways. Desires for familiarity, sense of place, community involvement, and self-actualization were the major motivations for initial and continuing small-town residence choice. A history of strong community or geographic ties, either urban or rural, also encouraged initial rural practice. Finally, prior resilience under adverse circumstances was predictive of continued retention in the face of adversity. Physicians' decisions to stay or leave exhibited a cost-benefit pattern once their basic needs were met. These results support a focus on recruitment of both rural-raised and communityoriented applicants to medical school, residency, and rural practice. Local mentorship and ''place-specific education'' can support the integration of new rural physicians by promoting self-actualization, community integration, sense of place, and resilience. Health policy efforts to improve the physician workforce must address these complexities in order to support the variety of physicians who choose and remain in rural practice.

The Journal of General Physiology, 1968

A kinetic scheme postulating the rapid formation of a partially active acetylcholine-receptor-dru... more A kinetic scheme postulating the rapid formation of a partially active acetylcholine-receptor-drug complex from Xylocaine (or a derivative) and the active acetylcholine-receptor complex can account for the effects of Xylocaine and its derivatives at the neuromuscular junction. Transmembrane currents generated by an analogue computer programmed according to the scheme can exactly match end plate currents produced by nerve stimulation in the presence of the drugs. The scheme also accounts for the qualitatively different effects of the drugs on the end plate potential and on responses to iontophoretically applied acetylcholine. The analysis presented is consistent with very rapid reactions between acetylcholine and receptors, characterized by rate coefficients in the range 104 to 106 sec-1. It is based on the hypothesis that the activation of receptors by acetylcholine changes the structure of the receptors and thus their affinity for Xylocaine. The analysis does not require pharmacolo...

The Journal of General Physiology, 1971

We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in... more We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in a mormyrid fish. We used an isolated preparation of skin, receptors, and sensory nerves to estimate synaptic delays, and to change solution in contact with the receptor-nerve synapse. The minimum delays between stimuli and sensory nerve responses, which must be slightly larger than synaptic delays, are about 0.7 msec in medium receptors and about 0.25 msec in large receptors. This result supports previous suggestions that transmission is chemically mediated in medium receptors and electrically mediated in large receptors. Furthermore, Mg+2 depresses synaptic transmission in medium receptors, and has little effect on transmission in large receptors. A complex dependence of response on both Mg+2 and Ca+2 masks divalent ion dependence of transmission, but a large excess of Mg+2 cannot completely block transmission in medium electroreceptors. L-glutamate, and not cholinergic drugs, produces...

The Journal of General Physiology, 1968

Xylocaine and its derivatives act specifically at the neuromuscular junction within the concentra... more Xylocaine and its derivatives act specifically at the neuromuscular junction within the concentration range 0.05 to 2.0 mM. The charged form is the active form of the drugs. There is no correlation between "local anesthetic" activity and effect at the junction. Like d-tubocurarine, these drugs have little or no effect on quantum content, acetylcholinesterase activity, or the passive impedance of the muscle fiber. Yet they produce end plate potentials characterized by a brief, early component and a late, greatly prolonged component, as does procaine. Analysis of these changes in time course suggests that the drugs have little or no effect before receptors are activated by acetylcholine, but cause a decreased and often greatly prolonged response. Clear structure-activity relations indicate that the receptor to which the drugs bind to produce the prolonged response can be the receptor for acetylcholine. Comparison of the effects of the drugs on the end plate potential and on ...

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit:

Implementation Science Communications

Background Acute respiratory failure, a major cause of death in COVID-19, is managed with high-fl... more Background Acute respiratory failure, a major cause of death in COVID-19, is managed with high-flow oxygen therapy via invasive mechanical ventilation. In resource-limited settings like Nigeria, the shortage of ventilators and oxygen supply makes this option challenging. Evidence-based non-invasive alternatives to mechanical ventilation such as the use of continuous positive airway pressure (CPAP) devices exist, but there have been concerns that non-invasive ventilation may expose healthcare workers to infection from aerosolized dispersion of SARS-CoV-2. We propose to evaluate the feasibility, adaptability and acceptability of a CPAP/O2 helmet solution for non-invasive ventilation among patients with COVID-19 and health workers in eight COVID-19 treatment and isolation centers in Nigeria. Methods The study will occur in 4 stages: (1) convene a Steering Committee of key stakeholders and recruit implementation sites; (2) use the integrated Promoting Action on Research Implementation i...

Journal of Correctional Health Care

From the Division of General Internal Medicine and Health Services Research, Department of Medici... more From the Division of General Internal Medicine and Health Services Research, Department of Medicine, University of California, Los Angeles (ND), and the UCB-UCSF Joint Medical Program, School of Public Health, University of California, Berkeley (ABS, JH). The ...

Academic Medicine, Jun 1, 2001

Urban Family Medicine, 1987

The Journal of the American Board of Family Practice / American Board of Family Practice

A venogram showed right subclavian thrombosis. Urokinase was infused intravenously, and hy the 4t... more A venogram showed right subclavian thrombosis. Urokinase was infused intravenously, and hy the 4th hospital day, a third venogram showed that most of the thrombosis had cleared. At this time, her right upper extremity was much improved clinically with dccreased swelling and less tenseness and tenderness. She was ahle to move her fingers freely. The urokinase drip was discontinued, and she was continued on heparin drip and subsequently discharged on oral warfarin for 3 months. After 3 months of oral therapy, she was reevaluated hy vascular surgeons. At that time, she underwent a first rib resection to prevent further injury. She is currently asymptomatic.

A BSTRACT Xylocaine and its derivatives act specifically at the neuromuscular junction within the... more A BSTRACT Xylocaine and its derivatives act specifically at the neuromuscular junction within the concentration range 0.05 to 2.0 m. The charged form is the active form of the drugs. There is no correlation between "local anesthetic" activity and effect at the junction. Like d-tubocurarine, these drugs have little or no effect on quantum content, acetylcholinesterase activity, or the passive impedance of the muscle fiber. Yet they produce end plate potentials characterized by a brief, early component and a late, greatly prolonged component, as does procaine. Analysis of these changes in time course suggests that the drugs have little or no effect before receptors are activated by acetylcholine, but cause a decreased and often greatly prolonged response. Clear structure-activity relations indicate that the receptor to which the drugs bind to produce the prolonged response can be the receptor for acetylcholine. Comparison of the effects of the drugs on the end plate potentia...

Research publications - Association for Research in Nervous and Mental Disease, 1972

The Journal of physiology, 1968

1. J Physiol. 1968 Jul;197(1):4P-5P. Action potentials in denervated "slow" muscle fibr... more 1. J Physiol. 1968 Jul;197(1):4P-5P. Action potentials in denervated "slow" muscle fibres of the frog. Stefani E, Steinbach AB. PMID: 5675070 [PubMed - indexed for MEDLINE] MeSH Terms: Action Potentials*; Animals; Anura; ...

The Journal of Physiology, Aug 1, 1969

1. The electrical properties of frog slow muscle fibres were investigated with intracellular micr... more 1. The electrical properties of frog slow muscle fibres were investigated with intracellular micropipettes to determine their characteristic length (lambda), specific membrane resistance (R(m)) and specific membrane capacitance.2. The value of lambda was about 1 cm in fibres of 1.2 cm length. The ;short cable model' was used to calculate R(m). Its mean value was 1.12 x 10(5) ohm cm(2), about 10-20 times larger than the value for twitch fibres. The mean value for C(m) was 3.24 x 10(-6) F/cm(2).3. Resting potentials measured immediately after penetration with a single micropipette were about - 80 mV. Lower values can be attributed to the effects of damage or leakage produced by micropipette insertion.4. Changes in external K concentration produced changes in the initially recorded resting potentials which follow the constant field theory using a ratio of Na: K permeabilities P(Na)/P(K) = 0.02. Changes in external Cl concentration produced little or no change in the resting potential or membrane resistance, indicating a low Cl permeability.5. In agreement with previous work, slow fibres showed a time-dependent decrease in resistance (;delayed rectification') for membrane potentials more positive than - 60 mV. ;Anomalous rectification' observed in twitch fibres was not seen in slow fibres. In high external K concentrations the resistance of slow fibres is almost unaffected by changes in membrane potential.6. Increasing the concentration of external Ca (up to isotonic) has two distinct effects on slow fibres. It increases R(m) up to ten times, and it improves the stability of trans-membrane recordings, probably by reducing the leakage due to micropipette penetrations. Magnesium does not appear to have either of these effects.

Academic Medicine, May 1, 2001

The Journal of Physiology, Sep 1, 1971

The electrical and structural characteristics of 'slow' muscle fibres of the frog were studied in... more The electrical and structural characteristics of 'slow' muscle fibres of the frog were studied in normal and denervated muscles, and in muscles undergoing re-innervation by a mixed nerve containing large and small motor axons. 2. In agreement with previous studies, slow fibres in normally innervated muscles were incapable of producing action potentials. 3. Approximately 2 weeks after the sciatic nerve was transacted or crushed, slow muscle fibres acquired the ability to generate action potentials. These fibres were positively identified as belonging to the slow type, because their passive-electrical and ultrastructural characteristics remained essentially unchanged after the operations. 4. The action potential mechanism induced in slow fibres is sodiumdependent, and is blocked by tetrodotoxin. 5. After long-term re-innervation by a mixed nerve, slow fibres lose their acquired ability to generate action potentials, presumably because small motor axons re-establish connexion with the fibres. 6. It is concluded that the action potential mechanism of slow muscle fibres is under neural control, and is normally suppressed by small motor axons.

Nature, May 1, 1968

Fellow of the Consejo Nacional de Investigaciones Cientificas y Technicas. t NSF regular post doc... more Fellow of the Consejo Nacional de Investigaciones Cientificas y Technicas. t NSF regular post doctoral fellow.

ABSTRACTAffordable novel strategies are needed to treat COVID-19 cases complicated by respiratory... more ABSTRACTAffordable novel strategies are needed to treat COVID-19 cases complicated by respiratory compromise in resource limited settings. We report a mixed-methods pre-post assessment of 1) the useability of CPAP/O2 helmet non-invasive ventilation (NIV) to treat COVID-19, at ∼ 1% the cost of mechanical ventilation; 2) the effectiveness of a train-the-trainer practice facilitation intervention; and 3) whether use of CPAP/O2 helmet NIV was associated with increased COVID-19 infection among healthcare workers. At baseline, eight COVID-19 treatment centers in Nigeria (CircumVent network) received CPAP/O2 helmet systems, and were instructed on its use. After five months, clinicians within the CircumVent netwok participated in a 2-day train-the-trainers educational intervention. The physicians completed i) standardized forms on patient demographics, clinical course, and outcomes for patients seen in the treatment centers; ii) standardized surveys of feasibility and acceptability of use o...

Social Science & Medicine, 2009

Shortages of health care professionals have plagued rural areas of the USA for more than a centur... more Shortages of health care professionals have plagued rural areas of the USA for more than a century. Programs to alleviate them have met with limited success. These programs generally focus on factors that affect recruitment and retention, with the supposition that poor recruitment drives most shortages. The strongest known influence on rural physician recruitment is a ''rural upbringing,'' but little is known about how this childhood experience promotes a return to rural areas, or how non-rural physicians choose rural practice without such an upbringing. Less is known about how rural upbringing affects retention. Through twenty-two in-depth, semi-structured interviews with both rural-and urban-raised physicians in northeastern California and northwestern Nevada, this study investigates practice location choice over the life course, describing a progression of events and experiences important to rural practice choice and retention in both groups. Study results suggest that rural exposure via education, recreation, or upbringing facilitates future rural practice through four major pathways. Desires for familiarity, sense of place, community involvement, and self-actualization were the major motivations for initial and continuing small-town residence choice. A history of strong community or geographic ties, either urban or rural, also encouraged initial rural practice. Finally, prior resilience under adverse circumstances was predictive of continued retention in the face of adversity. Physicians' decisions to stay or leave exhibited a cost-benefit pattern once their basic needs were met. These results support a focus on recruitment of both rural-raised and communityoriented applicants to medical school, residency, and rural practice. Local mentorship and ''place-specific education'' can support the integration of new rural physicians by promoting self-actualization, community integration, sense of place, and resilience. Health policy efforts to improve the physician workforce must address these complexities in order to support the variety of physicians who choose and remain in rural practice.

The Journal of General Physiology, 1968

A kinetic scheme postulating the rapid formation of a partially active acetylcholine-receptor-dru... more A kinetic scheme postulating the rapid formation of a partially active acetylcholine-receptor-drug complex from Xylocaine (or a derivative) and the active acetylcholine-receptor complex can account for the effects of Xylocaine and its derivatives at the neuromuscular junction. Transmembrane currents generated by an analogue computer programmed according to the scheme can exactly match end plate currents produced by nerve stimulation in the presence of the drugs. The scheme also accounts for the qualitatively different effects of the drugs on the end plate potential and on responses to iontophoretically applied acetylcholine. The analysis presented is consistent with very rapid reactions between acetylcholine and receptors, characterized by rate coefficients in the range 104 to 106 sec-1. It is based on the hypothesis that the activation of receptors by acetylcholine changes the structure of the receptors and thus their affinity for Xylocaine. The analysis does not require pharmacolo...

The Journal of General Physiology, 1971

We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in... more We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in a mormyrid fish. We used an isolated preparation of skin, receptors, and sensory nerves to estimate synaptic delays, and to change solution in contact with the receptor-nerve synapse. The minimum delays between stimuli and sensory nerve responses, which must be slightly larger than synaptic delays, are about 0.7 msec in medium receptors and about 0.25 msec in large receptors. This result supports previous suggestions that transmission is chemically mediated in medium receptors and electrically mediated in large receptors. Furthermore, Mg+2 depresses synaptic transmission in medium receptors, and has little effect on transmission in large receptors. A complex dependence of response on both Mg+2 and Ca+2 masks divalent ion dependence of transmission, but a large excess of Mg+2 cannot completely block transmission in medium electroreceptors. L-glutamate, and not cholinergic drugs, produces...

The Journal of General Physiology, 1968

Xylocaine and its derivatives act specifically at the neuromuscular junction within the concentra... more Xylocaine and its derivatives act specifically at the neuromuscular junction within the concentration range 0.05 to 2.0 mM. The charged form is the active form of the drugs. There is no correlation between "local anesthetic" activity and effect at the junction. Like d-tubocurarine, these drugs have little or no effect on quantum content, acetylcholinesterase activity, or the passive impedance of the muscle fiber. Yet they produce end plate potentials characterized by a brief, early component and a late, greatly prolonged component, as does procaine. Analysis of these changes in time course suggests that the drugs have little or no effect before receptors are activated by acetylcholine, but cause a decreased and often greatly prolonged response. Clear structure-activity relations indicate that the receptor to which the drugs bind to produce the prolonged response can be the receptor for acetylcholine. Comparison of the effects of the drugs on the end plate potential and on ...

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit:

Implementation Science Communications

Background Acute respiratory failure, a major cause of death in COVID-19, is managed with high-fl... more Background Acute respiratory failure, a major cause of death in COVID-19, is managed with high-flow oxygen therapy via invasive mechanical ventilation. In resource-limited settings like Nigeria, the shortage of ventilators and oxygen supply makes this option challenging. Evidence-based non-invasive alternatives to mechanical ventilation such as the use of continuous positive airway pressure (CPAP) devices exist, but there have been concerns that non-invasive ventilation may expose healthcare workers to infection from aerosolized dispersion of SARS-CoV-2. We propose to evaluate the feasibility, adaptability and acceptability of a CPAP/O2 helmet solution for non-invasive ventilation among patients with COVID-19 and health workers in eight COVID-19 treatment and isolation centers in Nigeria. Methods The study will occur in 4 stages: (1) convene a Steering Committee of key stakeholders and recruit implementation sites; (2) use the integrated Promoting Action on Research Implementation i...

Journal of Correctional Health Care

From the Division of General Internal Medicine and Health Services Research, Department of Medici... more From the Division of General Internal Medicine and Health Services Research, Department of Medicine, University of California, Los Angeles (ND), and the UCB-UCSF Joint Medical Program, School of Public Health, University of California, Berkeley (ABS, JH). The ...

Academic Medicine, Jun 1, 2001

Urban Family Medicine, 1987

The Journal of the American Board of Family Practice / American Board of Family Practice

A venogram showed right subclavian thrombosis. Urokinase was infused intravenously, and hy the 4t... more A venogram showed right subclavian thrombosis. Urokinase was infused intravenously, and hy the 4th hospital day, a third venogram showed that most of the thrombosis had cleared. At this time, her right upper extremity was much improved clinically with dccreased swelling and less tenseness and tenderness. She was ahle to move her fingers freely. The urokinase drip was discontinued, and she was continued on heparin drip and subsequently discharged on oral warfarin for 3 months. After 3 months of oral therapy, she was reevaluated hy vascular surgeons. At that time, she underwent a first rib resection to prevent further injury. She is currently asymptomatic.