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Papers by Tanny Tsao
Journal of the American Society of Nephrology, 1999
It has been suggested that insulin-like growth factor-1 (IGF-1) may play a role in early compensa... more It has been suggested that insulin-like growth factor-1 (IGF-1) may play a role in early compensatory renal growth. Since IGF-1 action is influenced by IGF binding proteins (IGFBP), this study was conducted to characterize the changes in gene expression not only of IGF-1 and its receptor, but also of IGFBP in the hypertrophying kidney of adult and weanling rats 1 wk after removal of the other kidney. At this time, there were distinct age-dependent changes in the renal IGF-1 axis. In the mature kidney, IGF-1 mRNA levels fell without a change in kidney IGF-1 peptide content. Likewise, although IGFBP-2,-3, and-5 mRNA levels fell, membrane
American Journal of Physiology-Renal Physiology, 1997
Following acute tubular necrosis (ATN), kidney plasma membrane insulin-like growth factor-I (IGF-... more Following acute tubular necrosis (ATN), kidney plasma membrane insulin-like growth factor-I (IGF-I) receptor number increases markedly, although IGF-I receptor mRNA levels do not change. To determine whether this increase could represent a redistribution of intracellular receptors and whether receptor function is intact in acute uremia, rats with ATN of 2 days duration and pair-fed controls were studied. Skeletal muscle receptor binding was unchanged. In contrast, binding to receptors in solubilized cortex and isolated cortical plasma membranes increased significantly due to an increase in receptor number. However, the increase in membrane binding was threefold greater than the increase in solubilized cortex binding. This indicates that the increase in total cellular IGF-I receptors can only account for a minor portion of the increase in abundance of plasma membrane receptors number and is consistent with a redistribution of receptors from an intracellular to a membrane location as ...
American Journal of Physiology-Cell Physiology, 1993
Endothelial cells isolated from a variety of vascular beds bind and transport insulin but exhibit... more Endothelial cells isolated from a variety of vascular beds bind and transport insulin but exhibit relatively low insulin degrading activity. Because endothelial cells exhibit heterogeneity and since kidney is a major site of insulin degradation, we studied the processing of insulin by glomerular endothelial cells (GEC). When exposed to 2 x 10(-10) M 125I-labeled insulin, GEC associated with the hormone in a specific manner. This interaction was inhibited by insulin but not by a number of unrelated peptide hormones. Over a 90-min period, GEC degraded 42 +/- 3% of the 125I-insulin, as measured by solubility in trichloroacetic acid (TCA). Degradation was inhibited 90% by an excess of insulin or adrenocorticotropic hormone (10(-6) M) and 57% by glucagon, whereas growth hormone and calcitonin were without effect. Separation of plasma membrane bound from internalized insulin was achieved by decreasing extracellular pH. In the steady state, 43% of cell-associated insulin was membrane bound...
American Journal of Physiology-Cell Physiology, 1989
It has been generally accepted that in renal tubular epithelium endocytosed proteohormones are tr... more It has been generally accepted that in renal tubular epithelium endocytosed proteohormones are transported to lysosomes where they undergo complete hydrolysis. En route, as endosomal pH falls, the proteohormone uncouples from the endocytosed membrane binding site, which recycles to the cell surface. However, studies in other tissues have uncovered alternate intracellular pathways for proteins. One such pathway is retroendocytosis (endocytosis then exocytosis). To determine whether a retroendocytotic pathway exists for insulin in renal epithelium, a study was carried out with confluent monolayers of a proximal-like opossum kidney cell line that exhibits receptor-mediated endocytosis of insulin. Cells were preloaded with 125I-labeled insulin (4 X 10(-10) M) for 30 min, surface-bound insulin was then removed by acid washing, and over the next 60 min the release of intracellular radioactivity into the medium was monitored. At 37 degrees C, control cells released on average 7-15% of the ...
The Journal of laboratory and clinical medicine, 1991
Amino acids inhibit breakdown of long-lived intracellular proteins in some but not all tissues st... more Amino acids inhibit breakdown of long-lived intracellular proteins in some but not all tissues studied. Because no information is available relating to the effect of amino acids on kidney cell proteolysis, this study was conducted with cultured proximal-like opossum kidney (OK) cells and primary cultured rabbit proximal tubular cells in which long-lived cell proteins were labeled with carbon 14-labeled valine. These cultured cells were acutely deprived of amino acids; this was followed by a 57% to 66% increase in the proteolytic rate in OK cells and a 22% rate increase in the rabbit kidney cells. In cultured OK cells incubated in serum-free minimal essential medium containing 13 amino acids, proteolysis averaged 4.62% +/- 0.28%/2 hr and increased to 7.66% +/- 0.38%/2 hr when amino acids were deleted. Each amino acid was then added alone. Leucine, phenylalanine, and lysine had significant effects in inhibiting the deprivation response by 40%, 26%, and 22%, respectively. Leucine appea...
The Journal of Trauma: Injury, Infection, and Critical Care, 1983
Journal of Molecular and Cellular Cardiology, 1986
The molecular signals regulating myocardial hypertrophy are unknown. We used a new model system t... more The molecular signals regulating myocardial hypertrophy are unknown. We used a new model system to study this problem. Muscle cells from the neonatal rat ventricle were cultured in serum-free medium. Control cells did not change in size over time and did not show spontaneous contractile activity. Incubation with norepinephrine or epinephrine had two major trophic effects that developed over 1-2 days. The first was stimulation of muscle cell hypertrophy or increase in size. The second was induction of spontaneous contractile activity. The hypertrophic response was mediated through an alphal-adrenoceptor. The beating response required both alpha 1-and betal-adrenergic receptor stimulation. Alpha I stimulation alone produced enlarged cells that did not beat. Alpha I plus beta I stimulation induced contractile activity even when protein synthesis and hypertrophy were inhibited. Thus, the two alpha I responses could be dissociated, providing evidence for two independently-regulated cellular pathways for the dual alpha I trophic effects, one pathway leads to hypertrophy. The other, which requires concomitant beta 1 stimulation, controls the development of beating. Preliminary work raises the possibility that different products of inositol phospholipid hydrolysis might initiate the two alpha I trophic pathways. Other preliminary work suggests that the growth pathway is associated with the expression of specific genes and might reflect an action of the alpha 1-adrenoceptor on the cell nucleus. These studies define previously unsuspected trophic roles for the alphal-adrenergic receptor. KEY WORDS alphal-adrenergic receptor, betal-adrenergic receptor, myocardial cell culture, myocarr hypertrophy, growth regulation, gene expression, oncogenes, phorbol esters, phosphoinositide turnover, serum-free cultures I NTRODUCTI ON Myocardial hypertrophy has been studied intensively for many years, because of its prominent role in development and in many cardiac diseases. Most prior experiments have used in vivo model systems (e.g. 7); a few have employed the isolated perfused heart (e.g. 17). This work has shown that myocardial hypertrophy can usually be related to alterations in hemodynamic loading conditions {52), with certain exceptions such as the idiopathic hypertrophic diseases. However, because of the multiple unknown or uncontrollable hemodynamic, humoral and neural variables in the models used, it has been very difficult to investigate a central problem: the existence and identity of molecular signals that might transduce the hemodynamic load to growth. A few years ago we developed a new heart cell culture preparation
Diabetes, 1990
In an earlier study, we described the presence of a retroendocytotic pathway for insulin in a cul... more In an earlier study, we described the presence of a retroendocytotic pathway for insulin in a cultured kidney epithelial cell line. Derived from the opossum kidney (OK), these cells possess many features of proximal tubule epithelium, which is the major site of kidney insulin metabolism. We studied the interaction between the retroendocytotic and the degradative pathways with bacitracin as a pharmacological probe. Monolayers of OK cells were loaded with 125 l-labeled insulin over 30 min, acid washed to remove membrane-bound insulin, then incubated in fresh medium for 60 min while the release of intracellular radioactivity was monitored. In experiments carried out in the presence of bacitracin (2 mM), there was a twothirds increase in intracellular radioactivity at the end of the loading phase. Measurements made during the subsequent release phase showed that bacitracin reduced the release of degradation products. Thus, although controls released 72.1 ± 8.1% of the internalized radioactivity as trichloroacetic acid (TCA)soluble products, bacitracin-treated cells released 59.2 ± 9.4% (P < 0.02). In contrast, release of TCAprecipitable insulin increased from 15.2 ± 4.6% in controls to 25.8 ± 3.7% in bacitracin-treated cells (P < 0.01). In separate experiments analyzed by gelexclusion chromatography, 6.4 ± 0.6% of radioactivity released from preloaded control cells into medium over 60 min was insulin sized compared to 29.7 ± 1.4% in bacitracin-treated cells. High-performance liquid chromotography revealed that 61.5 ± 3.5% of this insulin-sized material released from control cells preloaded with A14-insulin eluted as intact insulin and the remainder as unidentified intermediate degradation
Archives of Surgery, 1984
Previous studies from this laboratory described myocardial depression in an arterially perfused r... more Previous studies from this laboratory described myocardial depression in an arterially perfused rabbit interventricular septum following perfusion with acute septic plasma. Calcium is critical for maintenance of cardiac contractility on a beat-to-beat basis. We have investigated calcium flux in the septal tissue to determine whether altered calcium flux explains the impaired cardiac function during sepsis. Twenty-two rabbit septa were perfused with control and septic perfusate (cryo-precipitated plasma + RBCs) and calcium flux determined in seven experiments. Perfusate cations (Ca++, Na+, K+, and H+) were measured, tissue function and arterial pressure were monitored. Developed tension decreased 46%, acceleration of tension change fell 42%, and arterial pressure decreased 26%, all highly significant. All septa recovered after return to control perfusate. The septic perfusate Ca++ was significantly lower than control perfusate, while K+ and H+ were significantly elevated. Ion flux studies, however, could not demonstrate altered calcium flux associated with the depressed contractility.
Archives of Surgery, 1984
Prostacyclin, or prostaglandin I2 (PGI2), and thromboxane A2 (TXA2) are potent, endogenously prod... more Prostacyclin, or prostaglandin I2 (PGI2), and thromboxane A2 (TXA2) are potent, endogenously produced, vasoactive substances that have been implicated as mediators in the pathophysiologic nature of septic shock. We investigated the contribution and production of PGI2 and TXA2 in sepsis and septic shock, using an intact rabbit model and an in vitro rabbit isolated cardiac perfusion model. Continuous hemodynamic monitoring of both experimental models, along with serial radioimmunoassays of the metabolites of PGI2 and TXA2, indicated that myocardial depression is a common finding in subjects with septic shock and that septic shock causes a suppression of PGI2 production while augmenting TXA2 production. In addition, PGI2 and TXA2 were mediators of some cardiovascular changes in septic shock but were themselves not the toxic factor(s) responsible for the associated myocardial depression.
Archives of Surgery, 1985
Myocardial depression is a major but poorly understood component of septic shock. This study inve... more Myocardial depression is a major but poorly understood component of septic shock. This study investigates the morphologic and biochemical abnormalities associated with septic shock. Myocardial cells are incubated in normal and septic plasma in a nutrient-, oxygen-, pH-, electrolyte-, and temperature-controlled environment. Cells and media are tested for basal- and epinephrine-stimulated cyclic adenosine monophosphate (cAMP), lactic dehydrogenase (LDH), and creatine kinase. Electron microscopic studies are done at the end of incubation. Septic LDH and creatine kinase levels in the media are increased substantially, and septic cAMP levels are reduced significantly. Septic cells beat irregularly and arrest along with exhibiting abnormal electron microscopic structure. Septic myocardial dysfunction occurs independently of previously postulated causes that are controlled for in this experiment and therefore may be due to endogenously produced or accumulated toxic factor(s).
Contributions to Nephrology
Journal of Surgical Research, 1984
Untreated septic shock results in depletion of extracellular fluid, cellular swelling, increased ... more Untreated septic shock results in depletion of extracellular fluid, cellular swelling, increased intracellular sodium, and decreased intracellular potassium concentrations in primate skeletal muscle. The Langer rabbit heart interventricular septal preparation was used to determine whether similar changes occur in cardiac muscle during sepsis. Rabbit septa (n = 17) were perfused with control and septic rabbit plasma plus red blood cells. Tissue contractility (developed tension [DT] and rate of tension change [dP/dr]) was followed, plasma cations were measured (Na*, K+, Ca*+, H+), perfusion pressure (PP) was monitored, and 42K efflux was determined. The effect on 42K efflux caused by the addition of potassium chloride to control plasma was determined. During perfusion with septic plasma there was significant decline of septal function (P < 0.00 1). In 12/ 17 experiments DT fell 77.8 f 2 1.4% and dP/dt fell 75.8 + 24.8% from control values (means + 1 SD). All septa recovered when perfusion with control plasma was resumed. If [K+] was increased in control plasma during 42K washout, the percentage increase of effluent counts per minute per minute correlated with the percentage rise of control plasma [K+] (r = 0.95, P < 0.001). During perfusion with septic plasma there was no similar correlation (r = 0.277). 42K efflux increased during septic plasma perfusion independent of the differences between control and septic plasma [K+], demonstrating abnormal myocardial K+ efflux. An abnormal efflux of K+ is seen during septic plasma perfusion similar to that described in primate skeletal muscle. It is associated with and may be a mechanism of action for the observed fall of contractility. 295
Journal of Trauma-injury Infection and Critical Care, 1983
Critical Care Medicine, 1988
Renal Failure, 2001
In the growing animal, K deficiency (KD) retards body growth, but paradoxically stimulates renal ... more In the growing animal, K deficiency (KD) retards body growth, but paradoxically stimulates renal growth. If KD persists, interstitial infiltrates appear and eventually tubulointerstitial fibrosis develops. In patients with chronic KD, renal cysts may form and with time tubulointerstitial disease with renal failure develops. Since early in KD, kidney IGF-I levels increase and may be a cause of the renal hypertrophy, and as TGF-beta promotes hypertrophy and fibrosis, we examined the expression of these growth factors in chronic KD. Rats were given a KD diet or pair or ad-lib fed a normal K diet. After 21 days, KD rats weighed less than pair fed controls, while the kidneys were 49% larger Serum IGF-I and kidney IGF-I protein levels were depressed, as were IGF-I mRNA levels, and is largely attributable to decreased food intake. Kidney IGFBP-1 and TGF-beta mRNA levels were increased (p < 0.05). There was marked hypertrophy and adenomatous hyperplasia of outer medullary collecting ducts, hypertrophy of thick ascending limbs of Henle (TALH) and interstitial infiltrates. Both nephron segments stained strongly for IGF-I and IGFBP-1. Only the non-hyperplastic TALH was strongly TGF-beta positive. Interstitial infiltrates containing monocytes/macrophages were prominent. These findings are consistent with a sustained role for IGF-I in promoting the renal hypertrophy of KD and appear to be caused by local trapping of IGF-I by the over-expressed IGFBP-1. Localization of TGF-beta to the hypertrophied non-hypoplastic tubules containing IGF-I, suggests that TGF-beta may be acting to convert the proliferative action of IGF-I into a hypertrophic response. TGF-beta may also contribute to the genesis of the tubulointerstitial infiltrate. Finally, the reduced levels of serum IGF-1 levels may be a cause of the blunted body growth.
Experimental Nephrology, 2002
Recently, based on a study in rats with chronic renal failure (CRF), it has been suggested that I... more Recently, based on a study in rats with chronic renal failure (CRF), it has been suggested that IGF-I resistance in uremia may be caused in part by defective IGF-I receptor autophosphorylation and tyrosine kinase activity. Thus if such a defect were to develop in prolonged acute renal failure (ARF), this may explain why IGF-I therapy, effective in rats, has failed to promote recovery from ARF in patients. Accordingly, we examined IGF-I receptor function in rats with uremia of increasing duration and in pair-fed sham-operated controls. After 6 days of prolonged ARF, kidney IGF-I receptor binding increased twofold, while IGF-I stimulated receptor phosphorylation and tyrosine kinase activity were unchanged. Muscle receptor binding, autophosphorylation and tyrosin kinase activity were similar to control values after 6 or even 21 days of uremia. Taking all these findings together it appears that IGF-I resistance in uremia cannot be attributed to a receptor defect. This in turn argues against altered receptor function as a cause of the failure of IGF-I to modify clinical ARF.
Kidney International, 1996
Journal of the American Society of Nephrology, 1999
It has been suggested that insulin-like growth factor-1 (IGF-1) may play a role in early compensa... more It has been suggested that insulin-like growth factor-1 (IGF-1) may play a role in early compensatory renal growth. Since IGF-1 action is influenced by IGF binding proteins (IGFBP), this study was conducted to characterize the changes in gene expression not only of IGF-1 and its receptor, but also of IGFBP in the hypertrophying kidney of adult and weanling rats 1 wk after removal of the other kidney. At this time, there were distinct age-dependent changes in the renal IGF-1 axis. In the mature kidney, IGF-1 mRNA levels fell without a change in kidney IGF-1 peptide content. Likewise, although IGFBP-2,-3, and-5 mRNA levels fell, membrane
American Journal of Physiology-Renal Physiology, 1997
Following acute tubular necrosis (ATN), kidney plasma membrane insulin-like growth factor-I (IGF-... more Following acute tubular necrosis (ATN), kidney plasma membrane insulin-like growth factor-I (IGF-I) receptor number increases markedly, although IGF-I receptor mRNA levels do not change. To determine whether this increase could represent a redistribution of intracellular receptors and whether receptor function is intact in acute uremia, rats with ATN of 2 days duration and pair-fed controls were studied. Skeletal muscle receptor binding was unchanged. In contrast, binding to receptors in solubilized cortex and isolated cortical plasma membranes increased significantly due to an increase in receptor number. However, the increase in membrane binding was threefold greater than the increase in solubilized cortex binding. This indicates that the increase in total cellular IGF-I receptors can only account for a minor portion of the increase in abundance of plasma membrane receptors number and is consistent with a redistribution of receptors from an intracellular to a membrane location as ...
American Journal of Physiology-Cell Physiology, 1993
Endothelial cells isolated from a variety of vascular beds bind and transport insulin but exhibit... more Endothelial cells isolated from a variety of vascular beds bind and transport insulin but exhibit relatively low insulin degrading activity. Because endothelial cells exhibit heterogeneity and since kidney is a major site of insulin degradation, we studied the processing of insulin by glomerular endothelial cells (GEC). When exposed to 2 x 10(-10) M 125I-labeled insulin, GEC associated with the hormone in a specific manner. This interaction was inhibited by insulin but not by a number of unrelated peptide hormones. Over a 90-min period, GEC degraded 42 +/- 3% of the 125I-insulin, as measured by solubility in trichloroacetic acid (TCA). Degradation was inhibited 90% by an excess of insulin or adrenocorticotropic hormone (10(-6) M) and 57% by glucagon, whereas growth hormone and calcitonin were without effect. Separation of plasma membrane bound from internalized insulin was achieved by decreasing extracellular pH. In the steady state, 43% of cell-associated insulin was membrane bound...
American Journal of Physiology-Cell Physiology, 1989
It has been generally accepted that in renal tubular epithelium endocytosed proteohormones are tr... more It has been generally accepted that in renal tubular epithelium endocytosed proteohormones are transported to lysosomes where they undergo complete hydrolysis. En route, as endosomal pH falls, the proteohormone uncouples from the endocytosed membrane binding site, which recycles to the cell surface. However, studies in other tissues have uncovered alternate intracellular pathways for proteins. One such pathway is retroendocytosis (endocytosis then exocytosis). To determine whether a retroendocytotic pathway exists for insulin in renal epithelium, a study was carried out with confluent monolayers of a proximal-like opossum kidney cell line that exhibits receptor-mediated endocytosis of insulin. Cells were preloaded with 125I-labeled insulin (4 X 10(-10) M) for 30 min, surface-bound insulin was then removed by acid washing, and over the next 60 min the release of intracellular radioactivity into the medium was monitored. At 37 degrees C, control cells released on average 7-15% of the ...
The Journal of laboratory and clinical medicine, 1991
Amino acids inhibit breakdown of long-lived intracellular proteins in some but not all tissues st... more Amino acids inhibit breakdown of long-lived intracellular proteins in some but not all tissues studied. Because no information is available relating to the effect of amino acids on kidney cell proteolysis, this study was conducted with cultured proximal-like opossum kidney (OK) cells and primary cultured rabbit proximal tubular cells in which long-lived cell proteins were labeled with carbon 14-labeled valine. These cultured cells were acutely deprived of amino acids; this was followed by a 57% to 66% increase in the proteolytic rate in OK cells and a 22% rate increase in the rabbit kidney cells. In cultured OK cells incubated in serum-free minimal essential medium containing 13 amino acids, proteolysis averaged 4.62% +/- 0.28%/2 hr and increased to 7.66% +/- 0.38%/2 hr when amino acids were deleted. Each amino acid was then added alone. Leucine, phenylalanine, and lysine had significant effects in inhibiting the deprivation response by 40%, 26%, and 22%, respectively. Leucine appea...
The Journal of Trauma: Injury, Infection, and Critical Care, 1983
Journal of Molecular and Cellular Cardiology, 1986
The molecular signals regulating myocardial hypertrophy are unknown. We used a new model system t... more The molecular signals regulating myocardial hypertrophy are unknown. We used a new model system to study this problem. Muscle cells from the neonatal rat ventricle were cultured in serum-free medium. Control cells did not change in size over time and did not show spontaneous contractile activity. Incubation with norepinephrine or epinephrine had two major trophic effects that developed over 1-2 days. The first was stimulation of muscle cell hypertrophy or increase in size. The second was induction of spontaneous contractile activity. The hypertrophic response was mediated through an alphal-adrenoceptor. The beating response required both alpha 1-and betal-adrenergic receptor stimulation. Alpha I stimulation alone produced enlarged cells that did not beat. Alpha I plus beta I stimulation induced contractile activity even when protein synthesis and hypertrophy were inhibited. Thus, the two alpha I responses could be dissociated, providing evidence for two independently-regulated cellular pathways for the dual alpha I trophic effects, one pathway leads to hypertrophy. The other, which requires concomitant beta 1 stimulation, controls the development of beating. Preliminary work raises the possibility that different products of inositol phospholipid hydrolysis might initiate the two alpha I trophic pathways. Other preliminary work suggests that the growth pathway is associated with the expression of specific genes and might reflect an action of the alpha 1-adrenoceptor on the cell nucleus. These studies define previously unsuspected trophic roles for the alphal-adrenergic receptor. KEY WORDS alphal-adrenergic receptor, betal-adrenergic receptor, myocardial cell culture, myocarr hypertrophy, growth regulation, gene expression, oncogenes, phorbol esters, phosphoinositide turnover, serum-free cultures I NTRODUCTI ON Myocardial hypertrophy has been studied intensively for many years, because of its prominent role in development and in many cardiac diseases. Most prior experiments have used in vivo model systems (e.g. 7); a few have employed the isolated perfused heart (e.g. 17). This work has shown that myocardial hypertrophy can usually be related to alterations in hemodynamic loading conditions {52), with certain exceptions such as the idiopathic hypertrophic diseases. However, because of the multiple unknown or uncontrollable hemodynamic, humoral and neural variables in the models used, it has been very difficult to investigate a central problem: the existence and identity of molecular signals that might transduce the hemodynamic load to growth. A few years ago we developed a new heart cell culture preparation
Diabetes, 1990
In an earlier study, we described the presence of a retroendocytotic pathway for insulin in a cul... more In an earlier study, we described the presence of a retroendocytotic pathway for insulin in a cultured kidney epithelial cell line. Derived from the opossum kidney (OK), these cells possess many features of proximal tubule epithelium, which is the major site of kidney insulin metabolism. We studied the interaction between the retroendocytotic and the degradative pathways with bacitracin as a pharmacological probe. Monolayers of OK cells were loaded with 125 l-labeled insulin over 30 min, acid washed to remove membrane-bound insulin, then incubated in fresh medium for 60 min while the release of intracellular radioactivity was monitored. In experiments carried out in the presence of bacitracin (2 mM), there was a twothirds increase in intracellular radioactivity at the end of the loading phase. Measurements made during the subsequent release phase showed that bacitracin reduced the release of degradation products. Thus, although controls released 72.1 ± 8.1% of the internalized radioactivity as trichloroacetic acid (TCA)soluble products, bacitracin-treated cells released 59.2 ± 9.4% (P < 0.02). In contrast, release of TCAprecipitable insulin increased from 15.2 ± 4.6% in controls to 25.8 ± 3.7% in bacitracin-treated cells (P < 0.01). In separate experiments analyzed by gelexclusion chromatography, 6.4 ± 0.6% of radioactivity released from preloaded control cells into medium over 60 min was insulin sized compared to 29.7 ± 1.4% in bacitracin-treated cells. High-performance liquid chromotography revealed that 61.5 ± 3.5% of this insulin-sized material released from control cells preloaded with A14-insulin eluted as intact insulin and the remainder as unidentified intermediate degradation
Archives of Surgery, 1984
Previous studies from this laboratory described myocardial depression in an arterially perfused r... more Previous studies from this laboratory described myocardial depression in an arterially perfused rabbit interventricular septum following perfusion with acute septic plasma. Calcium is critical for maintenance of cardiac contractility on a beat-to-beat basis. We have investigated calcium flux in the septal tissue to determine whether altered calcium flux explains the impaired cardiac function during sepsis. Twenty-two rabbit septa were perfused with control and septic perfusate (cryo-precipitated plasma + RBCs) and calcium flux determined in seven experiments. Perfusate cations (Ca++, Na+, K+, and H+) were measured, tissue function and arterial pressure were monitored. Developed tension decreased 46%, acceleration of tension change fell 42%, and arterial pressure decreased 26%, all highly significant. All septa recovered after return to control perfusate. The septic perfusate Ca++ was significantly lower than control perfusate, while K+ and H+ were significantly elevated. Ion flux studies, however, could not demonstrate altered calcium flux associated with the depressed contractility.
Archives of Surgery, 1984
Prostacyclin, or prostaglandin I2 (PGI2), and thromboxane A2 (TXA2) are potent, endogenously prod... more Prostacyclin, or prostaglandin I2 (PGI2), and thromboxane A2 (TXA2) are potent, endogenously produced, vasoactive substances that have been implicated as mediators in the pathophysiologic nature of septic shock. We investigated the contribution and production of PGI2 and TXA2 in sepsis and septic shock, using an intact rabbit model and an in vitro rabbit isolated cardiac perfusion model. Continuous hemodynamic monitoring of both experimental models, along with serial radioimmunoassays of the metabolites of PGI2 and TXA2, indicated that myocardial depression is a common finding in subjects with septic shock and that septic shock causes a suppression of PGI2 production while augmenting TXA2 production. In addition, PGI2 and TXA2 were mediators of some cardiovascular changes in septic shock but were themselves not the toxic factor(s) responsible for the associated myocardial depression.
Archives of Surgery, 1985
Myocardial depression is a major but poorly understood component of septic shock. This study inve... more Myocardial depression is a major but poorly understood component of septic shock. This study investigates the morphologic and biochemical abnormalities associated with septic shock. Myocardial cells are incubated in normal and septic plasma in a nutrient-, oxygen-, pH-, electrolyte-, and temperature-controlled environment. Cells and media are tested for basal- and epinephrine-stimulated cyclic adenosine monophosphate (cAMP), lactic dehydrogenase (LDH), and creatine kinase. Electron microscopic studies are done at the end of incubation. Septic LDH and creatine kinase levels in the media are increased substantially, and septic cAMP levels are reduced significantly. Septic cells beat irregularly and arrest along with exhibiting abnormal electron microscopic structure. Septic myocardial dysfunction occurs independently of previously postulated causes that are controlled for in this experiment and therefore may be due to endogenously produced or accumulated toxic factor(s).
Contributions to Nephrology
Journal of Surgical Research, 1984
Untreated septic shock results in depletion of extracellular fluid, cellular swelling, increased ... more Untreated septic shock results in depletion of extracellular fluid, cellular swelling, increased intracellular sodium, and decreased intracellular potassium concentrations in primate skeletal muscle. The Langer rabbit heart interventricular septal preparation was used to determine whether similar changes occur in cardiac muscle during sepsis. Rabbit septa (n = 17) were perfused with control and septic rabbit plasma plus red blood cells. Tissue contractility (developed tension [DT] and rate of tension change [dP/dr]) was followed, plasma cations were measured (Na*, K+, Ca*+, H+), perfusion pressure (PP) was monitored, and 42K efflux was determined. The effect on 42K efflux caused by the addition of potassium chloride to control plasma was determined. During perfusion with septic plasma there was significant decline of septal function (P < 0.00 1). In 12/ 17 experiments DT fell 77.8 f 2 1.4% and dP/dt fell 75.8 + 24.8% from control values (means + 1 SD). All septa recovered when perfusion with control plasma was resumed. If [K+] was increased in control plasma during 42K washout, the percentage increase of effluent counts per minute per minute correlated with the percentage rise of control plasma [K+] (r = 0.95, P < 0.001). During perfusion with septic plasma there was no similar correlation (r = 0.277). 42K efflux increased during septic plasma perfusion independent of the differences between control and septic plasma [K+], demonstrating abnormal myocardial K+ efflux. An abnormal efflux of K+ is seen during septic plasma perfusion similar to that described in primate skeletal muscle. It is associated with and may be a mechanism of action for the observed fall of contractility. 295
Journal of Trauma-injury Infection and Critical Care, 1983
Critical Care Medicine, 1988
Renal Failure, 2001
In the growing animal, K deficiency (KD) retards body growth, but paradoxically stimulates renal ... more In the growing animal, K deficiency (KD) retards body growth, but paradoxically stimulates renal growth. If KD persists, interstitial infiltrates appear and eventually tubulointerstitial fibrosis develops. In patients with chronic KD, renal cysts may form and with time tubulointerstitial disease with renal failure develops. Since early in KD, kidney IGF-I levels increase and may be a cause of the renal hypertrophy, and as TGF-beta promotes hypertrophy and fibrosis, we examined the expression of these growth factors in chronic KD. Rats were given a KD diet or pair or ad-lib fed a normal K diet. After 21 days, KD rats weighed less than pair fed controls, while the kidneys were 49% larger Serum IGF-I and kidney IGF-I protein levels were depressed, as were IGF-I mRNA levels, and is largely attributable to decreased food intake. Kidney IGFBP-1 and TGF-beta mRNA levels were increased (p < 0.05). There was marked hypertrophy and adenomatous hyperplasia of outer medullary collecting ducts, hypertrophy of thick ascending limbs of Henle (TALH) and interstitial infiltrates. Both nephron segments stained strongly for IGF-I and IGFBP-1. Only the non-hyperplastic TALH was strongly TGF-beta positive. Interstitial infiltrates containing monocytes/macrophages were prominent. These findings are consistent with a sustained role for IGF-I in promoting the renal hypertrophy of KD and appear to be caused by local trapping of IGF-I by the over-expressed IGFBP-1. Localization of TGF-beta to the hypertrophied non-hypoplastic tubules containing IGF-I, suggests that TGF-beta may be acting to convert the proliferative action of IGF-I into a hypertrophic response. TGF-beta may also contribute to the genesis of the tubulointerstitial infiltrate. Finally, the reduced levels of serum IGF-1 levels may be a cause of the blunted body growth.
Experimental Nephrology, 2002
Recently, based on a study in rats with chronic renal failure (CRF), it has been suggested that I... more Recently, based on a study in rats with chronic renal failure (CRF), it has been suggested that IGF-I resistance in uremia may be caused in part by defective IGF-I receptor autophosphorylation and tyrosine kinase activity. Thus if such a defect were to develop in prolonged acute renal failure (ARF), this may explain why IGF-I therapy, effective in rats, has failed to promote recovery from ARF in patients. Accordingly, we examined IGF-I receptor function in rats with uremia of increasing duration and in pair-fed sham-operated controls. After 6 days of prolonged ARF, kidney IGF-I receptor binding increased twofold, while IGF-I stimulated receptor phosphorylation and tyrosine kinase activity were unchanged. Muscle receptor binding, autophosphorylation and tyrosin kinase activity were similar to control values after 6 or even 21 days of uremia. Taking all these findings together it appears that IGF-I resistance in uremia cannot be attributed to a receptor defect. This in turn argues against altered receptor function as a cause of the failure of IGF-I to modify clinical ARF.
Kidney International, 1996