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 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study was designed to establish the characteristics of the Ca2+ fluxes in isolated mitochondria of the protist Euglena gracilis. Uptake of Ca2+ and Sr2+ was supported by succinate and lactate oxidation. Ca2+ influx was slightly inhibited by 5 microM Ruthenium red and completely blocked by La3+ with a half-maximal inhibition attained at 50 microM. The addition of inorganic phosphate induced a 3-fold stimulation of Ca2+ uptake. Ca2+ uptake was inhibited by Mg2+ only in the absence of phosphate. Ca2+ efflux was induced by Na+, Li+ and K+ through a diltiazem-insensitive reaction. Ca2+ release, collapse of membrane potential and swelling were induced by Hg2+ and Cd2+ but not by carboxyatractyloside; cyclosporin A did not prevent the Ca2+ release induced by the heavy metal ions. Ca2+ uptake was achieved in the presence of 3 microM antimycin or 0.1 mM cyanide; this finding indicates that the alternative respiratory chain present in Euglena mitochondria can support this energy-dependent reaction. The data obtained suggest similar pathways, but different regulatory mechanisms, for Ca2+ transport between protist and mammalian mitochondria.
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PMID:Characterization of Ca2+ transport in Euglena gracilis mitochondria. 751 10

Seventy-eight rabbit lumbar discs were evaluated by radiographs and histology after the injection of chondroitinase ABC (40 U/ml for each disc) and compared with injection with phosphate buffer, and also with a control group who were not injected. There was considerable narrowing of the disc space after chondroitinase ABC injection. Safranin-0 depletion was present in the anterior part of the annulus fibrosus near to the nucleus pulposus in all the treated discs, indicating loss of proteoglycan. Electron microscopy showed collapse of the chondrocytes and notochordal cells. These findings suggest that chondroitinase ABC may be another chemonucleolytic agent which decreases disc volume and consequently decompresses the spinal cord or nerve roots; its effects were confined to the tissues within the intervertebral disc.
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PMID:The effect of chondroitinase ABC on rabbit intervertebral disc. Radiological, histological and electron microscopic findings. 764 79

In the presence of KCl and only at low phosphate concentrations, ATP stimulated state 4 of the respiration of isolated yeast mitochondria. This effect could be related to a partial collapse of the transmembrane potential which was created by the respiratory chain or the F0F1-ATPase. Sodium and lithium could not replace potassium ion. Atractyloside prevented the opening of this K+ pathway, suggesting that only matricial ATP operated. All these effects were inhibited by increasing phosphate concentration, or by adding propranolol, quinine, Zn2+ or Mg2+.
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PMID:ATP opens an electrophoretic potassium transport pathway in respiring yeast mitochondria. 775 May 62

A mixture of demineralized freeze-dried human cortical bone and resorbable tricalcium phosphate was used in conjunction with an expanded polytetrafluoroethylene membrane to promote deposition of bone for ridge augmentation. A titanium screw was used to prevent collapse of the regenerative materials. A clinical report is presented in which an atrophic ridge was reconstructed buccolingually, permitting the placement of a root form implant in a previously untenable site.
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PMID:Ridge augmentation utilizing guided tissue regeneration, titanium screws, freeze-dried bone, and tricalcium phosphate: clinical report. 792 Mar 87

The relationship between physical stability of freeze-dried cakes and protein stability during storage was studied using beta-galactosidase as a model protein and inositol as an excipient. Amorphous samples freeze-dried from solutions containing the enzyme and various concentrations of inositol in sodium phosphate buffer (50 mM, pH 7.4) were stored for 7 days over P2O5 at 40 to 70 degrees C. Structural collapse and inositol crystallization were observed in some of the samples, depending on the formulation and storage temperature. The physical stability of freeze-dried samples was also studied by differential scanning calorimeter (DSC). Inositol showed a protein-stabilizing effect when its amorphous form was retained during storage, regardless of structural collapse. However, crystallization of inositol during storage removed its stabilizing effect. Addition of water-soluble polymers such as dextran, Ficoll and carboxymethyl cellulose sodium salt (CMC-Na) preserved activity of the enzyme by preventing inositol crystallization.
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PMID:Physical stability and protein stability of freeze-dried cakes during storage at elevated temperatures. 793 61

Treatment of isolated mitochondria with calcium and inorganic phosphate induces inner membrane permeability that is thought to be mediated through a non-selective, calcium-dependent pore. The inner membrane permeability results in the rapid efflux of small matrix solutes such as glutathione and calcium, loss of coupled functions, and large amplitude swelling. We have identified conditions of permeability transition without large amplitude swelling, a parameter often used to assess inner membrane permeability. The addition of either oligomycin, antimycin, or sulfide to incubation buffer containing calcium and inorganic phosphate abolished large-amplitude swelling of mitochondria but did not prevent inner membrane permeability as demonstrated by the release of mitochondrial glutathione and calcium. The release of both glutathione and calcium was inhibited by the addition of cyclosporin A, a potent inhibitor of permeability transition. Transmission electron microscopy analysis, combined with the glutathione and calcium release data, indicate that permeability transition can be observed in the absence of large-amplitude swelling. Permeability transition occurring both with and without large-amplitude swelling was accompanied by a collapse of the membrane potential. We conclude that cyclosporin A-sensitive permeability transition can occur without obvious morphological changes such as large-amplitude swelling. Monitoring the cyclosporin A-sensitive release of concentrated endogenous matrix solutes, such as GSH, may be a sensitive and useful indicator of permeability transition.
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PMID:Release of mitochondrial glutathione and calcium by a cyclosporin A-sensitive mechanism occurs without large amplitude swelling. 797 91

To assess the role of hemofiltration (HF) among different treatment modalities, we reviewed our clinical material from 37 patients that consecutively underwent the treatment from 1981 on. A number of 12 patients on HF for at least 1 year deliberately switched to hemodialysis (HD) or hemodiafiltration (HDF) were studied retrospectively. Biochemical and nutritional parameters, cardiovascular aspects and morbidity data were collected during one year before and after the treatment change. A sodium balance study was performed in 9 patients during HF as well. No significant differences in plasma urea, creatinine, phosphate, body weight, serum albumin, transferrin, hemoglobin and PCR were found. BUN tended to be lower during HD-HDF because of the more efficient removal of urea with these treatments. Indeed, the Kt/V index was 0.91 during HF and it was 1.15 with HD-HDF. There were no differences in hypotensive episodes and morbidity. Sodium loss was strictly related to body fluid removal during HF session with a net sodium loss (NSL) of 128 mEq per liter of fluid removal (FR) (NSL = 6.44 + 122 FR; r:0.83; p < 0.01). Adapting sodium concentration of substitution fluid to patients weight gain, cardiovascular stability improved in those subjects more prone to collapse. With equivalence in PCR during the 2 periods, although Kt/V was 20% lower during HF, it seems reasonable to assume that the lower urea clearance might be compensated by the more efficient removal of higher molecular weight substances and/or by the improved biocompatibility of HF.
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PMID:The contribution of hemofiltration among the treatment modalities of chronic uremia. 817 95

By using a method especially adapted to intact (pea leaf) mitochondria, we studied the regulation of the F0F1 ATPase by the electrochemical proton gradient (delta mu H+) and by the matricial pH. The kinetics of decay of the ATP hydrolase activity was studied immediately after the collapse of the electrochemical proton gradient by an uncoupler. At pH 7.5, three inhibitors of the ATPase (venturicidin, tri-n-butyl tin and aurovertin), used at non-saturating concentrations, inhibited ATP hydrolysis to the same extent throughout the decay. This showed that the activity was totally controlled by the ATPase during all the decay and rules out any involvement of the phosphate or nucleotide carriers. This interpretation was confirmed by the fact that carboxyatractyloside, an inhibitor of the ATP/ADP antiporter, had a strong effect only on the initial rate of ATP hydrolysis, but not on the rate measured after some tens of seconds of decay. Oligomycin, at variance with the other ATPase inhibitors, interfered with the deactivation process, suggesting that its effect depends on the conformational state of the enzyme. Between pH 6.5 and 7.5, the hydrolase activity rose continuously and was still kinetically controlled by the ATPase. At higher pH value, the activity slightly decreased and appeared limited by at least one of the carriers. The activity of the ATPase itself, free of any transport process, seemed to increase monotonously with pH from 6.5 to 8. The electrochemical proton gradient is required to maintain the ATPase active, whereas no effect can be observed on transport processes. Matricial pH, while modulating the apparent catalytic turnover, has no marked effect on the rate of deactivation. These results, obtained with intact mitochondria, extend previous observations on the isolated enzyme and question the binding of IF1 as a rate-limiting step for ATPase deactivation.
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PMID:Deactivation of F0F1 ATPase in intact plant mitochondria. Effect of pH and inhibitors. 818 64

We have examined the effects of the protein kinase inhibitor KT5926 on NGF-promoted responses in PC12 and PC12-C41 cells (a subclone of the parental cell line). Our findings reveal that this compound specifically and reversibly prevents the NGF-induced outgrowth and regeneration of neurites. In addition, neurites of NGF-pretreated cells cease further elongation upon exposure to KT5926. However, preexisting neurite networks in the cultures remain intact in the presence of the drug. The inhibition of neuritic growth appears to occur at least in part at the level of growth cones since KT5926 also causes these structures to collapse and inhibits NGF-promoted reactivation of NGF-deprived growth cones. Although KT5926 is an analogue of K-252a, which blocks all responses to NGF, it does not affect other NGF-elicited cellular responses examined, including NGF-dependent priming of cells, gp140prototrk autophosphorylation, immediate-early gene induction, and phosphorylation of several known cytoskeletal proteins (MAP 1.2/1B, chartin MAPs, and beta-tubulin). However, phosphate incorporation into a cytoskeletally localized 58 kDa phosphoprotein, designated pp58, is selectively reduced in KT5926-treated cultures (+/- NGF). Although KT5926 is an in vitro inhibitor of myosin light chain kinase and calmodulin-dependent protein kinase II, inhibition of these two kinase activities by ML-9 and KN-62, respectively, applied alone or together, does not mimic the effects of KT5926 on neurite growth and on pp58 phosphorylation. Taken together, our findings suggest that KT5926, via a previously unidentified protein kinase inhibitory activity, differentially interferes with NGF-promoted growth cone function and consequently affects neuritic outgrowth. This compound should therefore be a useful tool for dissecting the mechanism of NGF actions and affords a means to identify phosphoproteins that play specific roles in neurite growth/elongation.
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PMID:KT5926 selectively inhibits nerve growth factor-dependent neurite elongation. 818 31

The interaction of calf-thymus DNA with cobalt-hexammine and cobalt-pentammine cations was investigated, in aqueous solution at pH 6-7 with cation/DNA(phosphate) molar ratios r = 1/80, 1/40, 1/20, 1/10, 1/4, 1/2 and 1, using Fourier Transform infrared (FTIR) difference spectroscopy. Correlations between spectral changes, DNA condensation and helical stabilization due to the cation interaction as well as conformational features are established. At a very low cation concentration (r = 1/80), the binding of cobalt-hexammine cation with DNA is through the H-bond formation between cation NH3 groups and the PO2 groups of the backbone, resulting in duplex stability. As the cation concentration increases, hydrogen bonding expands towards guanine N-7 and O-6 atoms. At r > 1/20, DNA condensation occurs with major reduction in the intensity of several DNA in-plane vibrations and that of the phosphate group. The cobalt-pentammine cation binding is via the PO2 groups (directly) at very low metal cation concentration (r = 1/80) and the guanine N-7 and the O-6 groups (indirectly) at higher ratios. At r > 1/10, DNA condensation begins with some degree of direct cation-base binding. No major conformational changes from the B-family structure were observed before and after DNA collapse, in the presence of cobalt-ammine cations.
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PMID:The effects of cobalt-hexammine and cobalt-pentammine cations on the solution structure of calf-thymus DNA. DNA condensation and structural features studied by FTIR difference spectroscopy. 821 50


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