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Images of rabbit tracheal cross sections were obtained at a series of transmural pressures ranging from 22 to -95 cmH2O by use of a nuclear magnetic resonance imaging microscope. The excised, washed tracheas were immersed in a solution of phosphate-buffered saline made up in deuterium oxide (D2O, pH 7.3). The images are maps of proton density in the image slice (2.5 mm thick). All but one series of images showed a collapse process in which the trachealis muscle invaginated asymmetrically, i.e., the muscle appeared to favor one side of the cartilage ring system more than the other. The connecting tissue between the cartilage rings appeared to be more compliant than the rings themselves, thus suggesting that the tracheal lumen became corrugated at negative pressures. In the plane of a cartilage ring, the lumen appeared to remain patent at pressures as low as -95 cmH2O. However, between rings, where the tracheal wall was more compliant, the lumen appeared to be totally occluded at -53 cmH2O. Lumen areas in both the plane of the cartilage rings and in a plane between rings were measured from each series of printed images for six tracheas. These measurements, when normalized, averaged, and plotted against transmural pressure gave asymptotic logarithmic compliances (n1 in the model of Lambert et al., J. Appl. Physiol. 52: 44-56, 1982) of 1.2 +/- 0.4 and 20 +/- 7 for the interring and ring regions, respectively. These values are greater than the critical value of 0.5 (J. Appl. Physiol. 62: 2426-2435, 1987) and are thus consistent with wave speed flow limitation being possible anywhere in the trachea during forced expiration.
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PMID:In vitro tracheal mechanics by nuclear magnetic resonance imaging. 318 47

Incubation of rat liver mitochondria with benzoquinone derivatives in the presence of succinate plus rotenone has been shown to cause NAD(P)H oxidation followed by Ca2+ release. Further investigation revealed: (1)p-Benzoquinone-induced Ca2+ release was not initiated by a collapse of the mitochondrial membrane potential. However, Ca2+ release and subsequent Ca2+ cycling caused limited increased membrane permeability. (2) p-Benzoquinone-induced NAD(P)H oxidation and Ca2+ release were prevented by isocitrate, 3-hydroxybutyrate, and glutamate but not by pyruvate or 2-oxoglutarate. (3) Inhibition of pyruvate and 2-oxoglutarate dehydrogenases by p-benzoquinone was attributed to arylation of the SH groups of the cofactors, CoA and lipoic acid. Isocitrate dehydrogenase was also inhibited by p-benzoquinone, but the cofactors NAD(P)H and Mn2+ protected the enzyme. Glutamate dehydrogenase was not inhibited by p-benzoquinone. (4) Arylation of mitochondrial protein thiols by p-benzoquinone was associated with an inhibition of state 3 respiration, which was attributed to the inactivation of the phosphate translocase. In contrast, state 4 respiration, and the F1.F0-ATPase and ATP/ADP translocase activities were not inhibited. It was concluded that inhibition of mitochondrial NAD(P)H dehydrogenases by arylation of critical thiol groups will decrease the NAD(P)+-reducing capacity, and possibly lower the NAD(P)H/NAD(P)+ redox status in favor of Ca2+ release.
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PMID:Role of sulfhydryl groups in benzoquinone-induced Ca2+ release by rat liver mitochondria. 321 68

In C6 astrocytoma cells respiring with glucose, 40% of the total production of ATP was provided by glycolysis. Anaerobiosis in the presence of glucose, reduced ATP synthesis by approximately 50%, increased lactate production by 30% and caused a 3-fold decline in [creatine phosphate]/[creatine] and consequently [ATP]free[ADP]free. There was no change in [K+]i which suggests that glycolytic production of ATP provides sufficient energy to ensure normal operation of the Na+/K+ pump. In the absence of glucose, [creatine phosphate]/[creatine] declined to less than 0.1 in 15 min and there was a loss of K+ from cells. A comparison of delta GATP and delta GNa,K under aerobic conditions with and without glucose, showed the former to be larger by 1 - 2 kcal. However, under O2-limited, glucose-restricted conditions delta GATP fell below the level necessary to maintain operation of the Na+/K+ pump and led to a collapse in ionic gradients.
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PMID:Energy relationships between ATP synthesis and K+ gradients in cultured glial-derived cell line. 367 41

The intersegmental muscles in the metamorphosing silkmoth Antheraea polyphemus were examined by two electron cytochemical procedures for demonstration of calcium compartmentation during the two-day period of degeneration after emergence. Muscle fibres were treated with either oxalate-pyroantimonate, or phosphate-pyroantimonate procedures. The elemental composition of the reaction product arising from the oxalate procedure was determined with electron probe X-ray microanalysis of unstained thin sections by energy dispersive spectrometry and wavelength dispersive spectrometry. The wavelength dispersive data revealed high peaks of calcium and antimony in the electron-dense precipitates. No reaction was obtained in muscles after treatment with the phosphate-pyroantimonate method. Shortly after the emergence of the moth, very few calcium deposits were found in the mitochondria, which also contained amorphous matrix densities. During the rapid lytic phase (17 and 30 h after ecdysis), the mitochondria, autophagic vacuoles sequestering mitochondria, and lysosomal dense bodies issuing from the latter were highly reactive in each muscle fibre. These results demonstrate that the collapse of tracheae (hypoxic conditions) is correlated with the calcium overload of mitochondria when the cell calcium homeostasis is apparently lost. Such calcium overload of the mitochondria appears to cause irreversible damage to these organelles which are then sequestered in autophagic vacuoles. This mitochondrial autophagic process leads to calcium translocation into a lysosomal compartment. We suggest that the calcium lysosomal stores may have a transient function of cell detoxification and stimulation of calcium-dependent degradative processes prior to the final muscle collapse.
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PMID:Programmed cell death. Cytochemical evidence for accumulation of calcium in mitochondria and its translocation into lysosomes: X-ray microanalysis in metamorphosing insect muscles. 380 89

Soluble phospholipase A2 has been implicated in the pathogenesis of local and systemic inflammatory reactions. Elevated levels of circulating phospholipase A2 (PLA2) correlate with the severity of circulatory collapse and pulmonary dysfunction in gram-negative septic shock. Characterization of septic shock serum PLA2 revealed a calcium-dependent enzyme with absolute 2-acyl specificity with a pH optimum of 7.5. We tested a number of therapeutic agents for their ability to inhibit PLA2 from human septic shock serum. Chloroquine, chlorpromazine, dexamethasone base, dexamethasone sodium phosphate, indomethacin, lidocaine, oleic acid, palmitic acid, promethazine, trans-retinoic acid, rutin and dl-alpha-tocopherol were all studied over the range of 10(-2) to 10(-7) M. All agents, with the sole exception of dexamethasone base, inhibited PLA2 activity at concentrations greater than 10(-3) M. PLA2 inhibition by dexamethasone sodium phosphate was factitious, due to the formation of calcium-phosphate complexes. Of the 11 agents studied, chlorpromazine was the most effective, with an IC50 of 7.5 X 10(-5) M, a membrane concentration achievable within its therapeutic range. Inhibition was non-competitive with an apparent Ki of 5 nM. Since serum PLA2 levels correlate with mortality in both experimental endotoxemia and clinical gram-negative septic shock, and chlorpromazine was previously shown to improve survival in these conditions, we postulate that its therapeutic efficacy resides at least in part in its PLA2-inhibitory activity.
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PMID:Potential therapeutic efficacy of inhibitors of human phospholipase A2 in septic shock. 382 40

Glucose-insulin-potassium (GIK) improves myocardial function during endotoxin shock but the mechanism of this action is not clear. We have studied in open chest dogs the effects of GIK (n = 9) on haemodynamics, myocardial biochemistry (repeated drill biopsies; glucose-6-phosphate, G-6-P; fructose-6-phosphate, F-6-P; adenosine triphosphate, ATP; creatinine phosphate, CP; glycogen) and myocardial histomorphometry. The animals were anaesthetised (etomidate 4 mg X kg-1 X h-1) and artificially ventilated (N2O:O2 = 2:1). After endotoxin (1.5 mg X kg-1) cardiac output (CO) and mean arterial pressure (MAP) fell rapidly, with a temporary recovery followed by gradual circulatory collapse. Coronary blood flow (cbf; radioactive microspheres) decreased, but this was not significant. G-6-P tended to fall, as did ATP levels while CP levels were unaltered. Histomorphometrical analysis showed myocardial cell swelling with compression of capillaries and decreased interstitial volume. GIK infusion (50% glucose, 2 g X kg-1bw, 8 mmol KCl and 3 U insulin kg-1bw) increased CO and coronary blood flow. Glycogen and G-6-P levels did not change, while F-6-P tended to increase. ATP levels were not influenced by ATP/CP ratio decreased. Myocardial cell swelling markedly decreased; average capillary cross-sectional area, as an index of capillary compression, returned to control value. In two dogs, which died before the end of the experiment, myocardial oedema, with disturbed capillary volume and reduced interstitial volume was unaltered after GIK. The initial effects of GIK are most likely due to restoration of myocardial perfusion. Improved perfusion, and the influence of elevated serum osmolality and insulin levels on excitation-contraction coupling may help to improve myocardial function.
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PMID:Myocardial metabolic and morphometric changes during canine endotoxin shock before and after glucose-insulin-potassium. 389 58

The pathophysiology, clinical presentation, prevention, and treatment of aluminum-related osteomalacia in renal-failure patients are reviewed. Aluminum-related osteomalacia can develop in patients exposed to high concentrations of aluminum either in dialysis solutions or through gastrointestinal aluminum absorption from aluminum-containing antacids used to treat hyperphosphatemia. Although the exact etiology of aluminum-related osteomalacia is unknown, aluminum is believed to inhibit bone mineralization by forming an inhibitory complex with citric acid at physiologic concentrations. The complex is deposited along bone mineralization fronts and in bone marrow. The major symptoms of aluminum-related osteomalacia include skeletal pain, fractures, and vertebral collapse. The disease is difficult to diagnose because patients may have normal or slightly elevated serum concentrations of calcium, phosphate, alkaline phosphatase, and parathyroid hormone. Direct measurement of bone aluminum content (using biopsy) is often needed to confirm diagnosis. The aluminum-chelating agent deferoxamine mesylate can be used to measure bone aluminum content indirectly. Aluminum intoxication can be managed either by preventing exposure to aluminum or by removing deposited aluminum from bone. New standards restrict aluminum content in dialysis solutions, and prevention now focuses on the use of aluminum-free phosphate binders for treatment of hyperphosphatemia. Calcium carbonate may be as effective as aluminum-containing antacids in controlling serum phosphate concentrations, but it should be used cautiously in patients who are hypercalcemic or at risk of developing metastatic calcification. Chelation therapy with deferoxamine has improved the symptoms and bone histology in a small number of patients. Clinical improvements have been seen in patients receiving intravenous deferoxamine 2-6 g per week for 20 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Aluminum-related osteomalacia in renal-failure patients. 389 71

A new hypothesis is proposed on the involvement of nucleosomes in Giemsa banding of chromosomes. Giemsa staining as well as the concomitant swelling can be explained as an insertion of the triple charged hydrophobic dye complex between the negatively-charged super-coiled helical DNA and the denatured histone cores of the nucleosomes still present in the fixed chromosomes. New cytochemical data and recent results from biochemical literature on nucleosomes are presented in support of this hypothesis. Chromosomes are stained by the Giemsa procedure in a purple (magenta) colour. Giemsa staining of DNA and histone (isolated or in a simple mixture) in model experiments results in different colours, indicating that a higher order configuration of these chromosomal components lies at the basis of the Giemsa method. Cytophotometry of Giemsa dye absorbance of chromosomes shows that the banding in the case of saline pretreatment is due to a relative absence of the complex in the faintly coloured bands (interbands). Pretreatment with trypsin results in an increase in Giemsa dye uptake in the stained bands. Cytophotometric measurements of free phosphate groups before and after pretreatment with saline, reveal a blocking of about half of the free phosphate groups indicating that a substantial number of free amino groups is still present in the fixed chromosomes. Glutaraldehyde treatment inhibited Giemsa-banding irreversibly while the formaldehyde-induced disappearance of the bands could be restored by a washing procedure. These results correlate with those of biochemical nucleosome studies using the same aldehydes. Based on these findings and on the known properties of nucleosomes, a mechanism is proposed that explains the collapse of the chromosome structure when fixed chromosomes are transferred to aqueous buffer solutions. During homogeneous Giemsa staining reswelling of the unpretreated chromosome is explained by insertion of the hydrophobic Giemsa complex between the hydrophobic nucleosome cores and the superhelix DNA. Selective Giemsa staining of the AT-enriched bands after saline pretreatment is thought to be due to the, biochemically well-documented, higher affinity of arginine-rich proteins present in the core histones for GC-enriched DNA, which prevents the insertion of the Giemsa complex in the interbands. Production of Giemsa bands by trypsin pretreatment can be related to the action of this enzyme on the H1 histones and subsequent charge rearrangements.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The involvement of nucleosomes in Giemsa staining of chromosomes. A new hypothesis on the banding mechanism. 392 63

Condensation of DNA by spermine has been studied by electric dichroism, electric birefringence and rotational relaxation times at 1 mM ionic strength. Using Manning's theory, we found that condensation occurs for a fraction of neutralized phosphate charges (r) equal to 0.90, in good agreement with previous studies using spermidine, synthetic polyamines and trivalent cations (e.g. Co(NH3)36 +, Tb3 +). Our results are compatible with the presence in solution of torus-shaped condensed structures in a narrow range of spermine concentration; further addition of the polyamine produced precipitation due to the self-aggregation of several toroids. For spermine concentrations lower than that required for collapse, important changes of the orientation mechanism in the electric field and of DNA stiffness were observed. Whereas free DNA was mainly oriented by a fast-induced polarizability mechanism, DNA-spermine complexes displayed an important permanent dipole component, in the spermine concentration range where extension of the DNA molecules was present. The birefringence relaxation times suggested that, in the first step, the stiffness of the DNA molecules increased, and then, at higher spermine concentration, bending of the DNA molecules occurred so that condensation into toroidal particles became possible.
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PMID:An electro-optical study of the mechanisms of DNA condensation induced by spermine. 404 Mar 95

The rate of spontaneous efflux of Ca from liver mitochondria incubated in the absence of ATP and Mg increases with time and is associated with a synchronous collapse of membrane potential and with Pi efflux. In the presence of Mg and ATP the ruthenium-red-induced Ca efflux does not change with time. The activity of the Ca efflux pathway in Pi-depleted mitochondria is 15-fold greater than in mitochondria equilibrated with 3.3 mM Pi. 50% inhibition is caused by 0.3 mM Pi. The membrane potential is not affected by changes in Pi concentration, although the steady-state extra-mitochondrial free Ca concentration reflects the alterations in efflux rate. In the presence of Pi, the ruthenium-red-induced efflux rate is independent of the total matrix Ca content; however in Pi-depleted mitochondria, with acetate substituting as permeant anion, the efflux rate increases with total matrix Ca content. The lowered efflux rate in the presence of Pi is not due to a limitation in the rate of dissociation of the matrix Ca-phosphate complex. The efflux pathway is activated by a lowered membrane potential, but the relative effect of Pi is retained. Under the present conditions Na slightly inhibits the efflux rate. The lack of an effect of total matrix Ca content on the efflux rate in the presence of Pi is used as the basis of a highly accurate determination of the activity of the Ca uniporter as a function of external free Ca concentration.
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PMID:The role of phosphate in the regulation of the independent calcium-efflux pathway of liver mitochondria. 618 18


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