Purpose: To compare the effect of noninvasive ventilation (NIV) and standard oxygen therapy on tr... more Purpose: To compare the effect of noninvasive ventilation (NIV) and standard oxygen therapy on treating acute lung injury (ALI). Methods: A search on PubMed, Embase, Springer, Cochrane Central Register of Controlled Trials and Clinical Trials was carried out up to Nov 2015 for randomized controlled trials (RCTs) with NIV as cases and standard oxygen therapy as controls. Risk ratios and weight mean difference were used for estimation. Results: This meta-analysis included seventeen RCTs. Results showed NIV significantly reduced the intubation rate, length of ICU stay and hospital mortality. The length of hospital stay and ICU mortality were not different. High heterogeneity was found across the studies of intubation rate. The types of acute respiratory failure might be a source of heterogeneity. Conclusion: Our results suggest that NIV is effective for ALI in reducing the intubation rate, hospital mortality and length of ICU stay than the standard oxygen therapy.
Medical Engineering, Division of Engineering and Applied Sciences, California Institute of Techno... more Medical Engineering, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 301-46, Pasadena, CA 91125, USA Applied and Computational Mathematics, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 9-94, Pasadena, CA 91125, USA Graduate Aerospace Laboratories, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 205-45, Pasadena, CA 91125, USA Medical Engineering, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 217-50, Pasadena, CA 91125, USA Keck School of Medicine, University of Southern California, 1510 San Pablo Street, Suite 322, Los Angeles, CA 90033, USA
INTRODUCTION: Increased aortic stiffness is correlated with many clinically adverse cardiovascula... more INTRODUCTION: Increased aortic stiffness is correlated with many clinically adverse cardiovascular outcomes. The “gold standard” quantitative index for arterial stiffness is the pulse wave velocity (PWV). We have developed a new method called the Intrinsic Frequency ( IF ), which views the arterial pressure waveform as a piecewise combination of two coupled systems, the heart and arterial system which are decoupled upon closure of the aortic valve. Each of these dynamical systems has an inherent frequency of operation (ω1 and ω2) which gives information about LV function (ω1) as well as arterial dynamics (ω2). METHODS: IF methodology is based on Sparse Time-Frequency Representation method. It uses an effective L2-minimization to extract the second intrinsic frequency (ω2) from an aortic pressure waveform. To examine the clinical relevance of this method, IF was applied to aortic pressure waveforms taken from published works. These aortic waveforms were selected from a healthy popula...
In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in t... more In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in the concentration of the organist molecule. The mammalian parathyroid gland is a representative case. Small (5%) changes in serum calcium result in tenfold (1000%) changes in glandular parathyroid hormone (PTH) release. In vitro, single isolated cells are observed to secrete fewer hormones than cells residing within a connected group, suggesting that a network has emergent regulatory properties. In PTH secreting tumors however, the ability to quickly respond to changes in calcium is strongly damped. A unifying hypothesis that accounts for these phenomena is realized by extra-cellular modulation of calcium diffusivity. A theoretical model and computational experiments demonstrate qualitative agreement with published experimental results. Our results suggest that in addition to the cellular mechanisms, endocrine glandular networks may have regulatory prowess at the level of interstitial tra...
Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance... more Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance plays a central role in metabolic syndrome, which astonishingly affects 1 out of 3 adults in North America. The insulin resistance state can precede the manifestation of diabetes and hypertension by years. Insulin resistance is correlated with a low-grade inflammatory condition, thought to be induced by obesity as well as other conditions. Currently, the methods to measure and monitor insulin resistance, such as the homeostatic model assessment and the euglycemic insulin clamp, can be impractical, expensive, and invasive. Abundant evidence exists that relates increased pulse pressure, pulse wave velocity (PWV), and vascular dysfunction with insulin resistance. We introduce a potential method of assessing insulin resistance that relies on a novel signal-processing algorithm, the intrinsic frequency method (IFM). The method requires a single pulse pressure wave, thus the term " wave biopsy."
In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in t... more In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in the concentration of the organist molecule. The mammalian parathyroid gland is a representative case. Small (5%) changes in serum calcium result in tenfold (1000%) changes in glandular parathyroid hormone (PTH) release. In vitro, single isolated cells are observed to secrete fewer hormones than cells residing within a connected group, suggesting that a network has emergent regulatory properties. In PTH secreting tumors however, the ability to quickly respond to changes in calcium is strongly damped. A unifying hypothesis that accounts for these phenomena is realized by extra-cellular modulation of calcium diffusivity. A theoretical model and computational experiments demonstrate qualitative agreement with published experimental results. Our results suggest that in addition to the cellular mechanisms, endocrine glandular networks may have regulatory prowess at the level of interstitial tra...
The clinical features of 47 frail nursing home diabetic patients with a mean age of 81 +/- 1.6 ye... more The clinical features of 47 frail nursing home diabetic patients with a mean age of 81 +/- 1.6 years were compared to those of 61 nondiabetic nursing home residents with a mean age of 80.2 +/- 1.2 years. Diabetic patients had a higher prevalence of renal failure, proteinuria, retinopathy, neuropathy, and infections than did other nursing home residents. Macroangiopathic disease tended to be equally common in both age groups. Diabetic nursing home residents had higher body weights compared to nondiabetic nursing home residents. Surprisingly, however, 21% of nursing home diabetics were greater than 20% below average body weight (compared to 24.5% of other nursing home residents), suggesting that undernutrition is a major problem in diabetic patients in a nursing home setting. Overall, the diabetic nursing home patients had better blood glucose control than younger ambulatory diabetic patients (mean age 66.2 +/- 4.7 years). The glycosylated hemoglobin (HbA1) level in those on oral agen...
The electrogenic Na(+)-HCO(3)(-) cotransporters play an essential role in regulating intracellula... more The electrogenic Na(+)-HCO(3)(-) cotransporters play an essential role in regulating intracellular pH and extracellular acid-base homeostasis. Of the known members of the bicarbonate transporter superfamily (BTS), NBC1 and NBC4 proteins have been shown to be electrogenic. The electrogenic nature of these transporters results from the unequal coupling of anionic and cationic fluxes during each transport cycle. This unique property distinguishes NBC1 and NBC4 proteins from other sodium bicarbonate cotransporters and members of the bicarbonate transporter superfamily that are known to be electroneutral. Structure-function studies have played an essential role in revealing the basis for the modulation of the coupling ratio of NBC1 proteins. In addition, the recent transmembrane topographic analysis of pNBC1 has shed light on the potential structural determinants that are responsible for ion permeation through the cotransporter. The experimentally difficult problem of determining the nature of anionic species being transported by these proteins (HCO(3)(-) versus CO(3)(2-)) is analyzed using a theoretical equilibrium thermodynamics approach. Finally, our current understanding of the molecular mechanisms responsible for the regulation of ion coupling and flux through electrogenic sodium bicarbonate cotransporters is reviewed in detail.
ABSTRACT An announcement to halt the intensive glucose lowering arm of the Action to Control Card... more ABSTRACT An announcement to halt the intensive glucose lowering arm of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial has received tremendous press recently. The basis for stopping the trial was that more deaths from cardiovascular events were noted in the treatment group. 1 No specific cause has been identified as yet. Past studies that aimed for "tight" control such as the Diabetes Control and Complications Trial (DCCT) 2 have concluded that lower hemoglobin A1c levels were associated with improved cardiovascular health. The new findings appear to contradict this conclusion. One important difference in the ACCORD trial is the study population. In the DCCT trial, exclusion criteria eliminated concurrent hypertension and hyperlipidemia, whereas in the ACCORD study, one of the objectives was to examine the effect of intensive glycemic lowering in subjects who had concurrent hyperlipidemia and hypertension. A known mathematically described principle in control engineering (conservation of uncertainty) states that every connected system has a conserved or constant amount of uncertainty and that attempts to rein in more certainty in one area automatically create uncertainty in another area. When applying this principle to physiology, and in particular the ACCORD study, it is conceivable that attempts to constrain or increase certainty in glycemic control, blood pressure, and hyperlipidemia all at the same time, may be inducing uncertainty or vulnerability in other physiological functions, potentially resulting in a catastrophic event. For a review of this principle, refer to the Journal of Diabetes Science and Technology commentary article. 3 In light of recent ACCORD findings, it will be important to consider a range of potential mechanisms and explanations that may be at play. The conservation of the uncertainty principle, in fact, predicts the consequences resulting from restricting the system's range of physiological responses. These consequences might include increased fragility in the microvasculature, leading to myocardial infarction, stroke, or unwanted adverse effects, such as increased risk of hypoglycemia or other neuroendocrine problems. A precise event cannot be specified without a detailed model of the system's complete physiology. Moving forward, when dealing with the complexity of several interconnected physiological functions, careful consideration should be given to studying the system biology along with the specific molecular and cellular mechanisms.
We studied the effects of cyclosporin A on the renin-aldosterone axis in Sprague-Dawley rats. Two... more We studied the effects of cyclosporin A on the renin-aldosterone axis in Sprague-Dawley rats. Two weeks of intragastric administration of cyclosporin A (5 mg/kg/day or or 20 mg/kg/day) resulted in large increases in plasma renin concentration (23 +/- 5, 70 +/- 12, and 79 +/- 11 ng/ml/hr in control rats and rats receiving 5 mg and 20 mg of cyclosporin A, respectively), with no parallel increments in plasma aldosterone. In vitro angiotensin II (ANG II)-stimulated aldosterone secretion by zona glomerulosa cells obtained from cyclosporin A-treated rats was also reduced (4.8 +/- 0.5, 1.5 +/- 0.2, and 0.2 +/- 0.2 ng/10(5) cells in control rats and rats receiving 5 mg and 20 mg of cyclosporin A, respectively). In contrast, in vitro aldosterone response to graded increments of potassium (3.7-10.7 mmol/L) or adrenocorticotropic hormone (ACTH) (10(-11)-10(-8) M) was preserved in cyclosporin A-treated rats. When added in vitro to zona glomerulosa cells from untreated rats, cyclosporin A also attenuated ANG II-stimulated aldosterone secretion, but did not affect potassium or ACTH-mediated aldosterone production. Thus, cyclosporin A-induced hyperreninemic hypoaldosteronism in the rat depends on opposing renal and adrenal effects, with a direct or feedback stimulation of renin secretion and a specific blockade of ANG II-mediated aldosterone production.
Proceedings of the National Academy of Sciences of the United States of America, Jan 22, 2004
In embryogenesis, immature mesenchymal cells aggregate and organize into patterned tissues. Later... more In embryogenesis, immature mesenchymal cells aggregate and organize into patterned tissues. Later in life, a pathological recapitulation of this process takes place in atherosclerotic lesions, when vascular mesenchymal cells organize into trabecular bone tissue within the artery wall. Here we show that multipotential adult vascular mesenchymal cells self-organize in vitro into patterns that are predicted by a mathematical model based on molecular morphogens interacting in a reaction-diffusion process. We identify activator and inhibitor morphogens for stripe, spot, and labyrinthine patterns and confirm the model predictions in vitro. Thus, reaction-diffusion principles may play a significant role in morphogenetic processes in adult mesenchymal cells.
American journal of physiology. Endocrinology and metabolism, 2002
In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in t... more In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in the concentration of the agonist molecule. The mammalian parathyroid gland is a representative case. Small (5%) changes in serum calcium result in 10-fold (1,000%) changes in glandular parathyroid hormone (PTH) release. In vitro, single isolated cells are observed to secrete fewer hormones than cells residing within a connected group, suggesting that a network has emergent regulatory properties. In PTH-secreting tumors, however, the ability to respond quickly to changes in calcium is strongly damped. A unifying hypothesis that accounts for these phenomena is realized by extracellular modulation of calcium diffusivity. A theoretical model and computational experiments demonstrate qualitative agreement with published experimental results. Our results suggest that, in addition to the cellular mechanisms, endocrine glandular networks may have regulatory prowess at the level of interstitial tr...
Proceedings of the 2010 international conference on Compilers, architectures and synthesis for embedded systems - CASES '10, 2010
ABSTRACT The current practice of medicine, while utilizing the advances in biological and physica... more ABSTRACT The current practice of medicine, while utilizing the advances in biological and physical science, still takes place in the physician office or hospital. Unfortunately, traditional practice as integrated into the current Healthcare system is unsustainable. Accommodating the increase demand for medical services with the attendant rising costs has caused a crisis in healthcare. Telemedicine, the practice of medicine by means of mobile/internet is a transformative process that will impact healthcare globally. Already, teleradiology (diagnostic radiology remotely by means of digital images that are electronically exported) and electronic medical records are gaining wide acceptance. The ability to distribute medical services by means of mobile and internet technology is a natural and almost irresistible direction for the field of Medicine. The healthcare crisis has created an opportunity for new solutions and mobile/Internet technology has laid the infrastructure upon which one can build a powerful, innovative and badly needed platform for health services: The Global Virtual Hospital (GVH). The GVH will be a group of connected centers around the world that overlap (in time zones) throughout the working day. Patients will have access through the Internet or mobile phones. Medical records will be electronically stored, shared among authorized personal and updated with each medical interaction. The GVH, will serve as a platform and laboratory for the creation of innovative devices and technology that will improve the remote interaction.The Global Virtual Hospital System will exemplify the convergence of technology and medicine and will be integrated into standard practice in the next 5-10 year.
Purpose: To compare the effect of noninvasive ventilation (NIV) and standard oxygen therapy on tr... more Purpose: To compare the effect of noninvasive ventilation (NIV) and standard oxygen therapy on treating acute lung injury (ALI). Methods: A search on PubMed, Embase, Springer, Cochrane Central Register of Controlled Trials and Clinical Trials was carried out up to Nov 2015 for randomized controlled trials (RCTs) with NIV as cases and standard oxygen therapy as controls. Risk ratios and weight mean difference were used for estimation. Results: This meta-analysis included seventeen RCTs. Results showed NIV significantly reduced the intubation rate, length of ICU stay and hospital mortality. The length of hospital stay and ICU mortality were not different. High heterogeneity was found across the studies of intubation rate. The types of acute respiratory failure might be a source of heterogeneity. Conclusion: Our results suggest that NIV is effective for ALI in reducing the intubation rate, hospital mortality and length of ICU stay than the standard oxygen therapy.
Medical Engineering, Division of Engineering and Applied Sciences, California Institute of Techno... more Medical Engineering, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 301-46, Pasadena, CA 91125, USA Applied and Computational Mathematics, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 9-94, Pasadena, CA 91125, USA Graduate Aerospace Laboratories, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 205-45, Pasadena, CA 91125, USA Medical Engineering, Division of Engineering and Applied Sciences, California Institute of Technology, 1200 East California Boulevard, MC 217-50, Pasadena, CA 91125, USA Keck School of Medicine, University of Southern California, 1510 San Pablo Street, Suite 322, Los Angeles, CA 90033, USA
INTRODUCTION: Increased aortic stiffness is correlated with many clinically adverse cardiovascula... more INTRODUCTION: Increased aortic stiffness is correlated with many clinically adverse cardiovascular outcomes. The “gold standard” quantitative index for arterial stiffness is the pulse wave velocity (PWV). We have developed a new method called the Intrinsic Frequency ( IF ), which views the arterial pressure waveform as a piecewise combination of two coupled systems, the heart and arterial system which are decoupled upon closure of the aortic valve. Each of these dynamical systems has an inherent frequency of operation (ω1 and ω2) which gives information about LV function (ω1) as well as arterial dynamics (ω2). METHODS: IF methodology is based on Sparse Time-Frequency Representation method. It uses an effective L2-minimization to extract the second intrinsic frequency (ω2) from an aortic pressure waveform. To examine the clinical relevance of this method, IF was applied to aortic pressure waveforms taken from published works. These aortic waveforms were selected from a healthy popula...
In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in t... more In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in the concentration of the organist molecule. The mammalian parathyroid gland is a representative case. Small (5%) changes in serum calcium result in tenfold (1000%) changes in glandular parathyroid hormone (PTH) release. In vitro, single isolated cells are observed to secrete fewer hormones than cells residing within a connected group, suggesting that a network has emergent regulatory properties. In PTH secreting tumors however, the ability to quickly respond to changes in calcium is strongly damped. A unifying hypothesis that accounts for these phenomena is realized by extra-cellular modulation of calcium diffusivity. A theoretical model and computational experiments demonstrate qualitative agreement with published experimental results. Our results suggest that in addition to the cellular mechanisms, endocrine glandular networks may have regulatory prowess at the level of interstitial tra...
Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance... more Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance plays a central role in metabolic syndrome, which astonishingly affects 1 out of 3 adults in North America. The insulin resistance state can precede the manifestation of diabetes and hypertension by years. Insulin resistance is correlated with a low-grade inflammatory condition, thought to be induced by obesity as well as other conditions. Currently, the methods to measure and monitor insulin resistance, such as the homeostatic model assessment and the euglycemic insulin clamp, can be impractical, expensive, and invasive. Abundant evidence exists that relates increased pulse pressure, pulse wave velocity (PWV), and vascular dysfunction with insulin resistance. We introduce a potential method of assessing insulin resistance that relies on a novel signal-processing algorithm, the intrinsic frequency method (IFM). The method requires a single pulse pressure wave, thus the term " wave biopsy."
In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in t... more In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in the concentration of the organist molecule. The mammalian parathyroid gland is a representative case. Small (5%) changes in serum calcium result in tenfold (1000%) changes in glandular parathyroid hormone (PTH) release. In vitro, single isolated cells are observed to secrete fewer hormones than cells residing within a connected group, suggesting that a network has emergent regulatory properties. In PTH secreting tumors however, the ability to quickly respond to changes in calcium is strongly damped. A unifying hypothesis that accounts for these phenomena is realized by extra-cellular modulation of calcium diffusivity. A theoretical model and computational experiments demonstrate qualitative agreement with published experimental results. Our results suggest that in addition to the cellular mechanisms, endocrine glandular networks may have regulatory prowess at the level of interstitial tra...
The clinical features of 47 frail nursing home diabetic patients with a mean age of 81 +/- 1.6 ye... more The clinical features of 47 frail nursing home diabetic patients with a mean age of 81 +/- 1.6 years were compared to those of 61 nondiabetic nursing home residents with a mean age of 80.2 +/- 1.2 years. Diabetic patients had a higher prevalence of renal failure, proteinuria, retinopathy, neuropathy, and infections than did other nursing home residents. Macroangiopathic disease tended to be equally common in both age groups. Diabetic nursing home residents had higher body weights compared to nondiabetic nursing home residents. Surprisingly, however, 21% of nursing home diabetics were greater than 20% below average body weight (compared to 24.5% of other nursing home residents), suggesting that undernutrition is a major problem in diabetic patients in a nursing home setting. Overall, the diabetic nursing home patients had better blood glucose control than younger ambulatory diabetic patients (mean age 66.2 +/- 4.7 years). The glycosylated hemoglobin (HbA1) level in those on oral agen...
The electrogenic Na(+)-HCO(3)(-) cotransporters play an essential role in regulating intracellula... more The electrogenic Na(+)-HCO(3)(-) cotransporters play an essential role in regulating intracellular pH and extracellular acid-base homeostasis. Of the known members of the bicarbonate transporter superfamily (BTS), NBC1 and NBC4 proteins have been shown to be electrogenic. The electrogenic nature of these transporters results from the unequal coupling of anionic and cationic fluxes during each transport cycle. This unique property distinguishes NBC1 and NBC4 proteins from other sodium bicarbonate cotransporters and members of the bicarbonate transporter superfamily that are known to be electroneutral. Structure-function studies have played an essential role in revealing the basis for the modulation of the coupling ratio of NBC1 proteins. In addition, the recent transmembrane topographic analysis of pNBC1 has shed light on the potential structural determinants that are responsible for ion permeation through the cotransporter. The experimentally difficult problem of determining the nature of anionic species being transported by these proteins (HCO(3)(-) versus CO(3)(2-)) is analyzed using a theoretical equilibrium thermodynamics approach. Finally, our current understanding of the molecular mechanisms responsible for the regulation of ion coupling and flux through electrogenic sodium bicarbonate cotransporters is reviewed in detail.
ABSTRACT An announcement to halt the intensive glucose lowering arm of the Action to Control Card... more ABSTRACT An announcement to halt the intensive glucose lowering arm of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial has received tremendous press recently. The basis for stopping the trial was that more deaths from cardiovascular events were noted in the treatment group. 1 No specific cause has been identified as yet. Past studies that aimed for "tight" control such as the Diabetes Control and Complications Trial (DCCT) 2 have concluded that lower hemoglobin A1c levels were associated with improved cardiovascular health. The new findings appear to contradict this conclusion. One important difference in the ACCORD trial is the study population. In the DCCT trial, exclusion criteria eliminated concurrent hypertension and hyperlipidemia, whereas in the ACCORD study, one of the objectives was to examine the effect of intensive glycemic lowering in subjects who had concurrent hyperlipidemia and hypertension. A known mathematically described principle in control engineering (conservation of uncertainty) states that every connected system has a conserved or constant amount of uncertainty and that attempts to rein in more certainty in one area automatically create uncertainty in another area. When applying this principle to physiology, and in particular the ACCORD study, it is conceivable that attempts to constrain or increase certainty in glycemic control, blood pressure, and hyperlipidemia all at the same time, may be inducing uncertainty or vulnerability in other physiological functions, potentially resulting in a catastrophic event. For a review of this principle, refer to the Journal of Diabetes Science and Technology commentary article. 3 In light of recent ACCORD findings, it will be important to consider a range of potential mechanisms and explanations that may be at play. The conservation of the uncertainty principle, in fact, predicts the consequences resulting from restricting the system's range of physiological responses. These consequences might include increased fragility in the microvasculature, leading to myocardial infarction, stroke, or unwanted adverse effects, such as increased risk of hypoglycemia or other neuroendocrine problems. A precise event cannot be specified without a detailed model of the system's complete physiology. Moving forward, when dealing with the complexity of several interconnected physiological functions, careful consideration should be given to studying the system biology along with the specific molecular and cellular mechanisms.
We studied the effects of cyclosporin A on the renin-aldosterone axis in Sprague-Dawley rats. Two... more We studied the effects of cyclosporin A on the renin-aldosterone axis in Sprague-Dawley rats. Two weeks of intragastric administration of cyclosporin A (5 mg/kg/day or or 20 mg/kg/day) resulted in large increases in plasma renin concentration (23 +/- 5, 70 +/- 12, and 79 +/- 11 ng/ml/hr in control rats and rats receiving 5 mg and 20 mg of cyclosporin A, respectively), with no parallel increments in plasma aldosterone. In vitro angiotensin II (ANG II)-stimulated aldosterone secretion by zona glomerulosa cells obtained from cyclosporin A-treated rats was also reduced (4.8 +/- 0.5, 1.5 +/- 0.2, and 0.2 +/- 0.2 ng/10(5) cells in control rats and rats receiving 5 mg and 20 mg of cyclosporin A, respectively). In contrast, in vitro aldosterone response to graded increments of potassium (3.7-10.7 mmol/L) or adrenocorticotropic hormone (ACTH) (10(-11)-10(-8) M) was preserved in cyclosporin A-treated rats. When added in vitro to zona glomerulosa cells from untreated rats, cyclosporin A also attenuated ANG II-stimulated aldosterone secretion, but did not affect potassium or ACTH-mediated aldosterone production. Thus, cyclosporin A-induced hyperreninemic hypoaldosteronism in the rat depends on opposing renal and adrenal effects, with a direct or feedback stimulation of renin secretion and a specific blockade of ANG II-mediated aldosterone production.
Proceedings of the National Academy of Sciences of the United States of America, Jan 22, 2004
In embryogenesis, immature mesenchymal cells aggregate and organize into patterned tissues. Later... more In embryogenesis, immature mesenchymal cells aggregate and organize into patterned tissues. Later in life, a pathological recapitulation of this process takes place in atherosclerotic lesions, when vascular mesenchymal cells organize into trabecular bone tissue within the artery wall. Here we show that multipotential adult vascular mesenchymal cells self-organize in vitro into patterns that are predicted by a mathematical model based on molecular morphogens interacting in a reaction-diffusion process. We identify activator and inhibitor morphogens for stripe, spot, and labyrinthine patterns and confirm the model predictions in vitro. Thus, reaction-diffusion principles may play a significant role in morphogenetic processes in adult mesenchymal cells.
American journal of physiology. Endocrinology and metabolism, 2002
In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in t... more In endocrine glands, vigorous and coordinated responses are often elicited by modest changes in the concentration of the agonist molecule. The mammalian parathyroid gland is a representative case. Small (5%) changes in serum calcium result in 10-fold (1,000%) changes in glandular parathyroid hormone (PTH) release. In vitro, single isolated cells are observed to secrete fewer hormones than cells residing within a connected group, suggesting that a network has emergent regulatory properties. In PTH-secreting tumors, however, the ability to respond quickly to changes in calcium is strongly damped. A unifying hypothesis that accounts for these phenomena is realized by extracellular modulation of calcium diffusivity. A theoretical model and computational experiments demonstrate qualitative agreement with published experimental results. Our results suggest that, in addition to the cellular mechanisms, endocrine glandular networks may have regulatory prowess at the level of interstitial tr...
Proceedings of the 2010 international conference on Compilers, architectures and synthesis for embedded systems - CASES '10, 2010
ABSTRACT The current practice of medicine, while utilizing the advances in biological and physica... more ABSTRACT The current practice of medicine, while utilizing the advances in biological and physical science, still takes place in the physician office or hospital. Unfortunately, traditional practice as integrated into the current Healthcare system is unsustainable. Accommodating the increase demand for medical services with the attendant rising costs has caused a crisis in healthcare. Telemedicine, the practice of medicine by means of mobile/internet is a transformative process that will impact healthcare globally. Already, teleradiology (diagnostic radiology remotely by means of digital images that are electronically exported) and electronic medical records are gaining wide acceptance. The ability to distribute medical services by means of mobile and internet technology is a natural and almost irresistible direction for the field of Medicine. The healthcare crisis has created an opportunity for new solutions and mobile/Internet technology has laid the infrastructure upon which one can build a powerful, innovative and badly needed platform for health services: The Global Virtual Hospital (GVH). The GVH will be a group of connected centers around the world that overlap (in time zones) throughout the working day. Patients will have access through the Internet or mobile phones. Medical records will be electronically stored, shared among authorized personal and updated with each medical interaction. The GVH, will serve as a platform and laboratory for the creation of innovative devices and technology that will improve the remote interaction.The Global Virtual Hospital System will exemplify the convergence of technology and medicine and will be integrated into standard practice in the next 5-10 year.
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Papers by danny petrasek