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Biomedical subjects

I Karl

Publications and source records attributed to I Karl.

16 recordsLinked to original sources
PubMed1998

Cell contraction caused by microtubule disruption is accompanied by shape changes and an increased elasticity measured by scanning acoustic microscopy.

The state of crosslinking of microfilaments and the state of myosin-driven contraction are the main determinants of the mechanical properties of the cell cortex underneath the membrane, which is significant for the mechanism of shaping cells. Therefore, any change in the contractile state of the actomyosin network would alter the mechanical properties and finally result in shape changes. The relationship of microtubules to the mechanical properties of cells is still obscure. The main problem arises because disruption of microtubules enhances acto-myosin-driven contraction. This reaction and its impact on cell shape and elasticity have been investigated in single XTH-2 cells. Microtubule disruption was induced by colcemid, a polymerization inhibitor. The reaction was biphasic: a change in cell shape from a fried egg shape to a convex surface topography was accompanied by an increase in elastic stiffness of the cytoplasm, measured as longitudinal sound velocity revealed by scanning acoustic microscope. Elasticity increases in the cell periphery and reaches its peak after 30 min. Subsequently while the cytoplasm retracts from the periphery, longitudinal sound velocity (elasticity) decreases. Simultaneously, a two- to threefold increase of F-actin and alignment of stress fibers from the cell center to cell-cell junctions in dense cultures are induced, supposedly a consequence of the increased tension.

Actins↗
PubMed1997

Heat shock induces IkappaB-alpha and prevents stress-induced endothelial cell apoptosis.

OBJECTIVE: To determine whether prior heat shock would attenuate endothelial cell apoptosis and whether any effect of preemptive heat shock is mediated through a nuclear factor kappa B and inhibitor kappa B alpha mechanism. DESIGN: A randomized, controlled in vitro study. SETTING: A laboratory in a large, academic medical center. INTERVENTIONS: Cultured primary porcine endothelial cells were treated with increasing doses of sodium arsenite (40-160 micromol/L), after which the interval until subsequent apoptotic (lipopolysaccharide-arsenite) challenge was varied (4-16 hours). The degree of cell death and apoptosis were determined using neutral red uptake and staining with annexin V and propidium iodide, respectively. Inducible heat shock protein 70 and inhibitor kappa B alpha levels in treated cells were determined by Western blot analysis. Lipopolysaccharide-induced nuclear factor kappa B activity was assessed using an electrophoretic mobility shift assay. RESULTS: Prior arsenite treatment decreased cell death by apoptosis in a time- and dose-dependent manner. Specifically, a higher sodium arsenite concentration and shorter intervals afforded better protection (P=.01, 160 micromol/L at 4 hours). Protection against apoptosis correlated with increased heat shock protein 70 and inhibitor kappa B alpha levels and decreased nuclear factor kappa B binding activity. CONCLUSIONS: Arsenite, an inducer of the heat shock response, decreased stress-induced endothelial cell apoptosis. The mechanism of this protection may include decreased nuclear factor kappa B activity or increased inducible heat shock protein 70 levels. Heat shock protein 70 may serve as a molecular marker to determine not only the phenotypic state of the cell but also the durability of protection afforded by heat shock. These data support the hypothesis that stress-induced changes in transcription factor activity and protein expression can regulate the induction of apoptosis.

Animals↗
PubMed1995

Abnormal calcium homeostasis and mitochondrial polarization in a human encephalomyopathy.

Patients with several inherited human encephalomyopathies exhibit systemic and neurological symptoms in association with specific mitochondrial mutations. The mechanisms by which these mitochondrial mutations result in cellular injury have not been elucidated. One potential cause of neuronal vulnerability is an inability to effectively buffer intracellular calcium. We report that fibroblasts from patients with one specific inherited encephalomyopathy, MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) syndrome, have elevated levels of ionized calcium and cannot normally sequester calcium influxes. Quantitative fluorescence imaging demonstrated that this abnormality was associated with a relative decrease in mitochondrial membrane potential compared to control fibroblasts. This documentation of pathological calcium homeostasis in a genetic neurological disease extends the calcium hypothesis of toxic cell injury to human mitochondrial encephalomyopathies.

Adenosine Triphosphate↗
PubMed1994

Spinal cord ischemia and reperfusion metabolism: the effect of hypothermia.

PURPOSE: The metabolic and neurologic functional effects of regional hypothermia induced by cold (4 degrees C) heparinized saline perfusion on spinal cord ischemia were evaluated in 35 rabbits. METHODS: Spinal cord ischemia was induced for 20 minutes by infrarenal aortic occlusion in anesthetized animals. Regional spinal cord hypothermia was obtained by perfusing the lumbar arteries supplying the spinal cord through an infrarenal aortic catheter. The lumbar spinal cord was "snap frozen" in situ with liquid nitrogen and harvested immediately at the conclusion of the ischemic period or after 24 hours of normothermic reperfusion and neurologic observation. Spinal cord metabolic studies included determination of the energy charge and the intracellular concentrations of adenosine triphosphate, glucose, lactate, glutamate, and aspartate. RESULTS: Postoperative neurologic function was normal in all but one animal treated with hypothermia, while normothermic ischemia resulted in paralysis in all animals (p = 0.002). Spinal cord temperature during 20 minutes of ischemia and hypothermic perfusion decreased from 37.5 degrees +/- 0.43 degrees C to 22.8 degrees +/- 0.00 degrees C (p = 0.0001) compared to a fall in systemic temperature from 38.8 to 36.1 (p = 0.0001). Hypothermia reduced the decline in energy charge, adenosine triphosphate concentration and glucose concentration during ischemia but had no effect on markedly elevated levels of lactate acid. High-energy phosphates were restored after reperfusion in both normothermic and hypothermic animals and were not predictive of postoperative paraplegia. Intracellular glutamate and aspartate concentrations were unchanged during normothermic ischemia but decreased after reperfusion in all paralyzed animals. Intracellular glutamate and aspartate concentrations increased during hypothermic perfusion and remained elevated after reperfusion in animals with a normal or mildly abnormal neurologic examination result. CONCLUSIONS: We conclude that spinal cord hypothermia induced by cold heparinized saline perfusion is a simple technique that prevents paraplegia after 20 minutes of ischemia and preserves intracellular concentrations of important metabolites.

Adenosine Triphosphate↗
PubMed1994

Hyperthermia induces IL-1 alpha but does not decrease release of IL-1 alpha or TNF-alpha after endotoxin.

Heat treatments administered prior to the onset of sepsis or endotoxemia markedly increase survival. A potential mechanism for the beneficial effect of heat could be effects on IL-1 alpha and TNF-alpha, important mediators of sepsis and endotoxemia. Administration of IL-1 or TNF prior to development of sepsis and endotoxemia increases survival; thus, prophylactic heat treatments may protect by releasing IL-1 or TNF. Paradoxically, an alternative mechanism of protection of prophylactic heat treatments could be to decrease the amount of IL-1 and TNF released during sepsis or endotoxemia. Cells pretreated with heat do not produce as much IL-1 or TNF in response to endotoxin as cells that have not been pretreated with heat. The purpose of this investigation was to determine if hyperthermia caused release of cytokines and/or blunted the rise in cytokines occurring after endotoxin. Mice were anesthetized with ketamine/xylazine and immersed in a water bath at 37.0 or 42.0 degrees C for sham or heat treatments. At 6-7 h after recovery from anesthesia and immersion, sham and heat-treated mice were injected with Escherichia coli endotoxin. Both heat-treated and sham mice had elevated plasma IL-1 alpha 2 h after anesthesia and immersion but IL-1 alpha was approximately 3-fold greater in the heated mice, 732 +/- 50 vs. 256 +/- 76 pg/ml (p < 0.01). Blood samples obtained after endotoxin revealed no difference in levels of TNF-alpha (5477 +/- 742 vs. 6514 +/- 652 pg/ml) or IL-1 alpha (546 +/- 72 vs. 603 +/- 121 pg/ml) in the sham vs. heated mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Hyperthermia protects mice against the lethal effects of endotoxin.

Recently, investigators have reported that heat shock proteins (HSPs) can protect isolated cells from cytotoxicity induced by two important mediators of sepsis: interleukin-1 and tumor necrosis factor. The present study was undertaken to examine the hypothesis that transient whole body hyperthermia could decrease mortality from subsequent challenge with gram-negative endotoxin. We demonstrate that heat pretreatments improved long-term survival fivefold in a mouse endotoxin model and this was correlated with the production of HSPs. There was a marked difference in individual organ expression of the inducible 72-kDa heat shock protein (HSP72). Heat treatments caused significant HSP72 formation in lung, liver, kidney, and small intestine, but much lesser formation in heart, brain, and abdominal wall muscle. Additional experiments demonstrated that the protective effect of hyperthermic treatments against an endotoxin challenge occurred early, i.e., 1 and 2 h after heating, was maximal at 12 h, and had significantly diminished by 48 h. The formation and decay of HSP72 demonstrated a time course that paralleled the survival curve from endotoxin challenge, thus suggesting a possible role for HSP72 in the protective effect. Surprisingly, and in contrast to studies reported in incubated cells, endotoxin alone did not cause significant formation of HSP72 in vivo.

Anesthesia↗
PubMed1992

Dietary supplementation with L-arginine ameliorates the progression of renal disease in rats with subtotal nephrectomy.

We studied the effect of dietary supplementation with L-arginine for 6 weeks on the progression of renal disease in female Sprague-Dawley rats subjected to sham-operation (groups 1 and 2) or surgical ablation of 85% to 90% of the total renal mass (groups 3 and 4). All rats were fed a standard rat chow containing 22.8% protein. Rats in groups 1 (n = 5) and 3 (n = 9) served as controls and drank tap water ad libitum. Rats in groups 2 (n = 6) and 4 (n = 6) drank tap water supplemented with 1% L-arginine. Rats in groups 1 and 2 had similar values for glomerular and tubular function and serum chemistries 6 weeks after sham-operation. Sham-operated rats given L-arginine had significantly greater urine urea excretion than similar rats drinking tap water. Rats with subtotal nephrectomy (groups 3 and 4) had a significantly higher blood pressure, greater proteinuria, and a significantly lower plasma albumin than sham-operated rats (groups 1 and 2). Rats with remnant kidneys given 1% L-arginine (group 4) had significantly greater values for glomerular filtration rate (GFR) and P-amino hippurate (PAH) clearance than similar rats given tap water (group 3), despite comparable levels of systemic blood pressure, hematocrit, body weight, plasma chemistries, including L-arginine, and urine chemistries, except urea excretion. The remnant kidney of rats given L-arginine (group 4) had a greater number of normal or minimally abnormal glomeruli and fewer interstitial changes than that of rats given tap water (group 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Effects of food restriction and insulin treatment on (Ca2+ + Mg2+)-ATPase response to insulin in kidney basolateral membranes of noninsulin-dependent diabetic rats.

Insulin increases (Ca2+ + Mg2+)-ATPase activity in cell membranes of normal rats but fails to do so in membranes of non-insulin-dependent diabetic (NIDD) rats. The loss of regulatory effect of the hormone on the enzyme might contribute to the insulin resistance observed in the NIDD animals. To further test this hypothesis, the effects of insulin treatment and acute food restriction on the ability of insulin to regulate the ATPase activity in kidney basolateral membranes (BLM) of NIDD rats were studied. Although insulin levels in NIDD and control rats were similar, plasma glucose was higher in the NIDD rats (18.3 +/- 1.5 v 19.3 +/- 1.7 microU/mL and 236 +/- 32 v 145 +/- 3 mg/dL, respectively). Insulin treatment (2 U/100 g), which increased plasma insulin in the NIDD rats (47.8 +/- 11.5 microU/mL; P less than .05), did not decrease their glucose (221 +/- 25 mg/dL). Higher insulin dose (4 U/100 g) decreased glucose level in the NIDD rats (73 +/- 3 mg/dL; P less than .001) but increased their plasma insulin 10-fold (202.5 +/- 52.5 microU/mL). Acute food restriction decreased glucose levels in the NIDD rats to levels seen in controls (135 +/- 3 mg/dL), while their insulin decreased by half (8.5 +/- 1.0 microU/mL; P less than .05). Basal (Ca2+ + Mg2+)-ATPase activity in BLM of all diabetic rats was higher than in controls (P less than .05). None of the treatments reversed this defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

An in vivo analysis of pancreatic protein and insulin biosynthesis in a rat model for non-insulin-dependent diabetes.

The purpose of these experiments was to estimate insulin biosynthesis in vivo in a rat model for non-insulin-dependent diabetes. Insulin biosynthesis rates were determined in 4-wk-old animals that had been injected with 90 mg/kg of streptozotocin 2 d postpartum. Control and diabetic animals did not differ in body weight or fasting plasma glucose. Fed plasma glucose was significantly elevated (186 +/- 13 micrograms/dl vs. 139 +/- 7 mg/dl, P less than 0.05) and pancreatic insulin content was reduced (41 +/- 2 micrograms/g vs. 63 +/- 8 micrograms/g, P less than 0.05) in the diabetic rats. Insulin biosynthesis was estimated in vivo by measuring and comparing [3H]leucine incorporation into proinsulin with that into total pancreatic protein 45 min after injection. Insulin biosynthesis was 0.391 +/- 0.07% of pancreas protein synthesized in control rats and 0.188 +/- 0.015% (P less than 0.05) in diabetic rats. In animals of the same age, the fractional and absolute rate of pancreatic protein synthesis were determined. Total pancreatic protein synthesis was not reduced in streptozotocin treated animals (185.5 +/- 14.1%/d vs. 158.6 +/- 14.9%/d, NS) but was markedly reduced in control rats after a 48-h fast (to 70.8 +/- 5.5%/d, P less than 0.01). Because total pancreatic protein synthesis was not decreased in the diabetic rats, the decrease in the fraction of radiolabel incorporated into insulin seems to represent an absolute decrease in the rate of insulin biosynthesis in this animal model for diabetes. Through RNA blot hybridization with 32P-labeled cloned rat insulin complementary DNA, proinsulin messenger RNA (mRNA) was estimated as the rate of insulin biosynthesis in control and diabetic animals. There was a 61% reduction in proinsulin mRNA at 4 wk and an 85% reduction at 7 wk (P less than 0.001) in the diabetic animals. After streptozotocin injection in neonatal rats, there is marked beta-cell damage and hyperglycemia. Beta-cell regeneration occurs with return to normoglycemia, but with age hyperglycemia develops. The reduction in insulin synthesis and proinsulin mRNA seemed disproportionate with the more modest reduction in beta-cell number. The importance of these observations is that, in this animal model, diabetes is associated with a limited ability to regenerate beta-cell mass and to synthesize insulin. The relationship between the defect in glucose-stimulated insulin release and impaired insulin biosynthesis has yet to be determined.

Animals↗
PubMed1982

Biochemical characterization of the layers of subcutaneous adipose tissue in the pig body.

During the formation of two layers of adipose tissue in the pig's body, starting from the 80th day after birth, samples were obtained by biopsy and analyzed for gross constituents and enzymes concerned with fatty-acid biosynthesis. These two layers differ in total lipid and water content and demonstrate more subtle differences amongst DNA, protein, collagen and sodium concentrations when comparisons are made in regard to age, sex, and breeding selection for low-fat animals. Acetyl-CoA carboxylase, malic enzyme and glucose-6-phosphate dehydrogenase are more active in the inner layer, while 6-phosphogluconate and isocitrate dehydrogenases are distinguishable in the two layers of adipose tissue as well if age, sex, and breeding line are taken into consideration. The data form the basis for a more detailed study of lipogenic potentials in adipose tissue (next paper).

Acetyl-CoA Carboxylase↗
PubMed1979

Phenobarbital-induced alterations in the metabolism of [3H]vitamin D3 by the perfused rachitic rat liver in vitro.

Anticonvulsant therapy of seizure disorders in man is associated with the development of complications involving bone and mineral metabolism including hypocalcemia, elevated serum immunoreactive parathyroid hormone levels, and increased amounts of unmineralized bone or osteoid. The latter has been attributed to a reduction in serum-25-hydroxycholecalciferol levels resulting from increased hepatic metabolism of vitamin D. Using an in vitro recycling hepatic perfusion system, we have demonstrated that 5 d of phenobarbital treatment increases the hepatic production of [(3)H]25-hydroxyvitamin D(3) (4.3+/-0.3 vs. 3.3+/-0.2%/h, P <0.025) without affecting the biliary excretion of radioactivity. Furthermore, rachitic livers perfused with blood obtained from animals treated with phenobarbital for 5 d also manifested an increase in [(3)H]25-hydroxyvitamin D(3) production (4.6+/-0.5 vs. 3.3+/-0.2%/h, P < 0.02). Addition of phenobarbital or its major metabolite, p-hydroxyphenobarbital, directly to the perfusion apparatus had no effect on [(3)H]25-hydroxyvitamin D(3) production. Phenobarbital treatment was also attended by a decrease in the intrahepatic content of [(3)H]vitamin D(3) (11.7+/-0.4 vs. 17.5+/-0.7 dpm/mg liver protein, P < 0.001) without alterations in the content of [(3)H]25-hydroxyvitamin D(3). The data collectively suggest that the increased hepatic conversion of [(3)H]vitamin D(3) to [(3)H]25-hydroxyvitamin D(3) attending phenobarbital treatment is secondary to stimulation of the hepatic 25-hydroxylation system(s) by a metabolite of phenobarbital other than p-hydroxyphenobarbital and/or by metabolic alterations resulting from phenobarbital therapy.

Animals↗
PubMed1976

The role of growth hormone and cortisone on glucose and gluconeogenic substrate regulation in fasted hypopituitary children.

Panhypopituitarism may be associated with spontaneous hypoglycemia and marked insulin sensitivity. Five children with both growth hormone (GH) and adrenocorticotrophin (ACTH) insufficiency were studied in three periods: a) on no therapy; b) during cortisone acetate; and c) during GH and cortisone acetate replacement. With total caloric restriction prior to therapy, all patients became hypoglycemic (109 +/- 18 leads to 37 +/- 3.5 mg/dl, mean +/- SEM) and ketonemic (beta-hydroxybutyrate 0.10 +/- 0.02 leads to 3.04 +/- 0.63 mM and acetoacetate 0.05 +/- .01 leads to 0.80 +/- 0.15 mM) within 30 hours. Glutamine and alanine concentrations fell with fasting (511 +/- 13 leads to 293 +/- 26 muM and 394 +/- 58 leads to 137 +/- 12 muM, respectively) but to levels lower than in normal children. However, only alanine was significantly lower (P less than 0.05). With cortisone plus GH therapy, fasting glycemia was improved (73 +/- 6 mg/dl) at 30 hours fasting and was associated with increased alanine and glutamine concentrations (206 +/- 28 muM and 448 +/- 40 muM, respectively) and less ketonemia (beta-hydroxybutyrate 1.13 +/- 0.39 mM). Cortisone therapy alone resulted in intermediate improvement of these values. Only combined therapy resulted in increased lactate and pyruvate concentrations, which fell to normal with fasting. Fasting urinary ammonia excretion was unchanged whereas urea nitrogen excretion decreased significantly with therapy. The responses to alanine infusions following each study period in one patient were normal. The glycemic response to iv glucose was similar during each study period; however, post-prandial and glucose-stimulated insulin responses were increased with cortisone and cortisone plus GH therapy. We suggest that the hypoglycemia observed in hypopituitary patients is a substrate-mediated phenomenon, and that cortisone and growth hormone replacement therapy improve fasting glucose homeostasis, increase circulating alanine and glutamine concentrations, and decrease hepatic gluconeogenesis. These effects may be mediated through an increase in fat catabolism.

Adolescent↗
PubMed1975

Physiologic mechanisms in the development of starvation ketosis in man.

The present study was undertaken to determine whether alterations in ketone body utilization and hepatic production, independent of the FFA load, were also involved in the development of fasting ketosis. Plasma Beta-OH butyric acid (Beta-OHB) increased to 2.5-4.5 mM and plasma FFA to 1,000-1,400 muEq/L. in normal weight individuals after five to seven days' starvation and in obese subjects after ten to fourteen days' fasting. Acute elevations fo the plasma FFA greater than 1,500 muEq/L. for sixty minutes in fed normal weight and obese subjects with a fat meal-heparin regimen resulted in peak elevations of plasma Beta-OHB (0.25-0.45mM), only 10 percent of that seen during fasting. When plasma FFA were lowered acutely during fasting with the antilipolytic agent Pyrazole to control levels (400-600 muEq/L.), plasma Beta-OHB decreased 35 plus or minus 5 per cent. Comparable lowering of plasma FFA in normal weight or obese starved subjects given dexamethasone to maintain elevated fasting plasma insulin levels resulted in an 87 plus or minus 3 per cent decrease in plasma Beta-OHB. Similar studies in obese fasted subjects pretreated with an intravenous infusion of insulin (1.0 U/hr. for eight hours) before receiving Pyrazole resulted in a 65 plus or minus 5 per cent decrease in plasma Beta-OHB. Plasma Beta-OHB half-life, determined after injections of 12 gm. Beta-OHB, increased significantly during fasting (110 plus or minus 15 minutes) and was decreased when the fasting subjects were maintained on dexamethasone (65 plus or minus 7 minutes). These studies indicate that accelerated hepatic ketogenesis during starvation is a result of both enhanced activity of the enzymatic system(s) involved in ketone body production as well as an increased FFA load. The increase in plasma Beta-OHB during fasting reflects not only an accelerated rate of hepatic ketogenesis but also an impairment of peripheral utilization, both processes apparently being sensitive to insulin. Diabetes 24:10-16, January, 1975.

Acidosis↗
PubMedDate not supplied

Mechanical basis of cell shape: investigations with the scanning acoustic microscope.

The shape of cells during interphase in sparse cultures often resembles that of fried eggs. XTH-2 cells, which have been derived from tadpole heart endothelia, provide a typical example of this type of shape. To understand the physical basis of this shape, the cytoskeleton of these cells has been investigated in detail. Subcellular elasticity data have been achieved by scanning acoustic microscopy (SAM). Their changes were observed during treatment of the cells with microtubule-disrupting agents (colcemid and low temperature), and shape generation in giant cells produced by electro-fusion was observed with SAM, revealing the role of the nucleus as a force centering organelle. From these observations combined with well-documented observations on cellular dynamics described in the literature, a model is developed explaining the fried-egg shape of cells by means of interacting forces and fluxes (cortical flow, bulk flow of cytoplasm, microtubule-mediated transport of cytoplasm) of cytoplasm. The model also allows the comprehension of the increase of tension in cells treated with colcemid.

Acoustics↗