Calcium and ATP regulation of the oscillatory torsional movement in a triton model of Physarum plasmodial strands.
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Adenosine Triphosphate↗
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Investigation of the role of the substrate metal ion in the yeast inorganic pyrophosphatase reaction.
The substrate activities of a series of tripositive metal ion-pyrophosphate complexes with yeast inorganic pyrophosphatase were examined. While the Michaelis constants for these complexes were shown to be between one and two orders of magnitude greater than that of the natural substrate, [Mg(H2O)4PPi]2-, the turnover numbers were in general comparable to that of [Mg(H2O)4PPi]2-. These data suggest that the nature of the metal ion cofactor effects substrate binding but in most cases not catalysis. Thus, the role of the metal ion in catalysis is probably restricted to that of an electron sink.
Cations↗
The quaternary structure of E. coli inorganic pyrophosphatase is not required for catalytic activity.
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Catalysis↗
Genitourinary calcification: an overview.
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Calcium↗
The medical and metabolic consequences of administration of sodium acetate.
1. The standard total parenteral nutrition, peritoneal dialysis, hemodialysis and many surgical fluids in use today contain 36 to 45 mM D,L-lactate or 2 to 140 mM acetate whereas the normal blood level of D-lactate is 0.02 mM L-lactate 0.5 to 5 mM and acetate 0.1 nM. The reasons for the continued use in patients of such unphysiological concentrations of these anions appear to be historic. 2. Administration of similar concentrations of these anions to the rat causes widespread metabolic disturbances which mimic many of the untoward complications associated with current parenteral and dialysis therapy. Understanding of the mechanisms attendant upon the metabolism of these anions may serve as a guide for designing improved parenteral fluids for human patients. 3. Elevation of blood D-lactate to 5 mM is associated with cerebral dysfunction in human patients. 4. Acetate stimulates the release of the inflammatory leukokine, interleukin-1 from human monocytes. Use of 35 to 45 mM acetate in peritoneal dialysis fluids led to peritoneal fibrosis. Patients exposed to acetate containing hemodialysis fluids have 12-fold elevation in their plasma interleukin-1 levels. 5. Administration of 20 mM sodium acetate to rats leads to a number of metabolic disturbances similar to those seen in human dialysis patients: (a) Acetate elevates blood glucose in the rat and may contribute to the exacerbation of the carbohydrate intolerance seen in uremic patients. (b) Acetate increases the levels of hepatic malonyl CoA, the rate controlling substrate of fatty acid synthesis and may exacerbate the hypertriglyceridemia characteristic of dialysis patients. (c) Acetate administration in the rat leads to a decrease in the cytosolic phosphorylation potential, reduction of the redox state of the free cytosolic NAD couple and paradoxical oxidation of the mitochondrial NAD couple in a pattern analogous to that produced by uncouplers of oxidative phosphorylation and may account in part for the elevation of temperature reported in patients undergoing hemodialysis with acetate. (d) Acetate administration in the rat leads to an increase in intracellular phosphorylated intermediates, adenine nucleotides, inorganic phosphate, inorganic pyrophosphate, calcium and magnesium. On cessation of acetate metabolism, the inorganic phosphate and calcium accumulated intracellularly leave the intracellular space. In patients undergoing hemodialysis, the blood phosphate returns to predialysis levels, within 6 hr after the completion of treatment, leaving significant numbers of patients with chronic hyperphosphatemia and the multiple complications attendant to that state.(ABSTRACT TRUNCATED AT 400 WORDS)
Acetates↗
Partial dissolution of struvite calculus with oral acetohydroxamic acid.
Most staghorn calculi occur in patients who have chronic urinary tract infections with urea-splitting organisms. Acetohydroxamic acid, an inhibitor of the bacterial urease enzyme, is currently undergoing clinical trials to determine whether or not it can prevent stone growth in patients at risk. We report on a patient whose stones grew while she was taking placebo and then decreased in size when she took the active drug.
Administration, Oral↗
Encrustation and stone formation: complication of indwelling ureteral stents.
Severe encrustation and stone formation on indwelling ureteral stents in 2 patients with a lithogenic history are reported. In both cases this complication occurred in the presence of sterile urine and treatment required pyelolithotomy in one and renal pelvic irrigation with urologic G solution in the other. Analyses of these stones revealed struvite and apatite, respectively. Dissolution of encrustations and stones via renal pelvic irrigation is suggested as a viable alternative to surgical intervention for this problem. A review of the literature shows a correlation between chronic stone formers and stent encrustation, rather than from bacteriuria alone. Long-term antibiotic suppression, more frequent followup with abdominal roentgenograms, and shorter periods of internal stenting are suggested for patients with a lithogenic history.
Adult↗
New location of milk-of-calcium.
A case of milk-of-calcium with an exceptional location is reported. The characteristics of milk-of-calcium are presented, with stasis and urinary tract infection being the most important etiologic factors in this case. Structurally the stones are formed by a central core of calcium phosphate surrounded by magnesium-ammonium phosphate (struvite).
Adult↗
Clinical experience with low dosage of propionohydroxamic acid (PHA) in infected renal stones.
The use of drugs inhibiting bacterial urease represents an interesting improvement in preventive treatment of renal infected stones. The low dose (120 mg/day) for one week followed by 60 mg/day of propionohydroxamic acid (PHA) has shown excellent anti-urease activity. The nearly normal absence of side effects also allows long-term administration.
Humans↗
Biochemical risk factors in patients with renal staghorn stone disease.
Thirty-three patients operated on for renal staghorn calculous disease were studied retrospectively with respect to urine and stone composition, bacteriuria, and abnormalities of the urinary tract. Calcium phosphate was the most common stone constituent, present in 30 of 31 concrements. Twenty-one of these stones also contained magnesium ammonium phosphate, despite the fact that only 10 patients had presented evidence of urinary tract infection during the initial period of the disease. Twenty-four-hour urine composition was normal in only 3 patients. In 59 per cent an increased CaOx risk index was observed suggesting that CaOx risk factors might contribute to the development of staghorn concrements. A metabolic evaluation of staghorn stone formers appears to be of importance for design of the postoperative treatment.
Adolescent↗
The unbreakable stone?
A case of a failed percutaneous ultrasonic lithotripsy is reported as an unusual occurrence.
Humans↗
Techniques in endoscopic lithotripsy using pulsed dye laser.
The pulsed dye laser represents a new tool in the treatment of ureteral calculi. Laser energy channeled through a delicate optical fiber is used to disimpact and fragment calculi. Standard ureteroscopic instruments including graspers, baskets and dilatation balloons can be used with the laser system. Interchangeable optical fibers ranging from 200 to 400 micrometers deliver up to 120 mJ of energy to the stone's surface. For two weeks in 1989 an endourology clinic was held in upper Egypt. Eighty patients ranging in age from nine years to sixty-seven years old were evaluated and treated endoscopically. Endoscopes ranging from 6.9F to 12.5F were used to deliver the optical fiber. All stones visualized endoscopically were fragmented. Greater than 60 percent of the stones fragmented were composed of pure calcium oxalate monohydrate. Schistosoma hematobium was endemic among our study group. Bilharzial strictures of the distal ureter were noted in 30 percent of these patients. Treatment of these strictures using both balloon dilatation and graduated Teflon dilators is reviewed. Techniques in treating different types of ureteral calculi were explored. Large calcium oxalate dihydrate stones were treated most efficiently with the 3-point fragmentation technique. The shear off-center technique was used for the calcium oxalate monohydrate calculi. Variations in total energy delivered and frequency of pulsation allowed for prompt stone disimpaction as well as prevention of retrograde fragment migration. Concurrent use of stone baskets and graspers with the pulsed dye laser was explored.
Adolescent↗
Simplified infusion method for 10% hemiacidrin irrigation of renal pelvis.
A variable pressure volumetric pump was used for 10% hemiacidrin irrigation of the renal pelvis in 7 renal units (6 patients) with struvite calculi after initial percutaneous debulking and extracorporeal shock-wave lithotripsy (ESWL). The pump provided a constant display of intrapelvic infusion pressure, and an alarm which signaled if a preset maximum infusion pressure was exceeded. Compared with standard open manometer monitoring of intrapelvic pressure, this closed system of irrigation eliminates the problems associated with time-consuming assembly and maintenance, irrigant spillage, and system contamination. At the completion of therapy, 5 renal units were completely stone-free while 2 had only minimal residual caliceal "dust." Complications were minor and few in number. We conclude that a variable pressure volumetric pump provides excellent clinical results and safely simplifies irrigation for percutaneous chemolysis of struvite calculi.
Citrates↗
Unscheduled DNA synthesis in rat pleural mesothelial cells treated with mineral fibres.
Unscheduled DNA synthesis (UDS) was studied in confluent rat pleural mesothelial cells (RPMCs) arrested in G0/G1 with hydroxyurea (HU) and treated with various fibre types, i.e., chrysotile, crocidolite or attapulgite. In addition, the effects of UV light and of benzo[a]pyrene were determined as references. Using autoradiography after [3H]thymidine incorporation ([3H]dThd), RPMCs treated with 4 micrograms/cm2 of chrysotile fibres exhibited a low but significant enhancement of net grains compared to untreated cells. Treatment with higher doses of chrysotile was not possible because of the impairment of microscopic observation due to the presence of the fibres. Using liquid scintillation counting, RPMCs treated with chrysotile or crocidolite showed a significant dose-dependent increase in [3H]dThd incorporation compared to untreated cells. In contrast, attapulgite did not enhance [3H]dThd incorporation compared to untreated cells. Treatment of RPMCs with 1, 2 or 4 micrograms/ml of benzo[a]pyrene resulted in a significant increase in [3H]dThd incorporation. In order to discount a possible role of S cells in the augmentation of [3H]dThd incorporation, despite the presence of 5 mM HU, S cells were counted by autoradiography. Results indicated that the percentage of S cells was similar in asbestos-treated and untreated cultures. Stimulation of the S phase also seems unlikely because treatment of RPMCs with asbestos fibres in the absence of HU resulted in a reduction of [3H]dThd incorporation attributed to an impairment of the S phase by the fibres. 1-4 micrograms/ml benzo[a]pyrene or 10-50 J/m2 UV light resulted in an approximate doubling of [3H]dThd incorporation. The effects of inhibitors of DNA repair were determined in chrysotile-treated RPMCs. [3H]dThd incorporation was inhibited by cytosine arabinoside and nalidixic acid. These results show that asbestos produces UDS in RPMCs.
Animals↗
Synaptic transmission in rat cardiac neurones.
Intracellular recordings of spontaneous synaptic activity and synaptic responses to fibre tract stimulation were taken from neurones of ganglia isolated from the left atrium and interatrial septum of the rat. In six out of 57 neurones studied, spontaneous fast excitatory postsynaptic potentials (EPSPs) were recorded. Single stimulation of fibre tracts approaching the ganglion resulted in an all-or-none response consisting of an EPSP, from which an action potential abruptly appeared. This response disappeared in Ca(2+)-free/high-Mg2+ solution, indicating that it was orthodromic in origin. EPSPs were markedly exaggerated and prolonged by neostigmine (1-5 microM). EPSPs produced by high-frequency (0.1-20 Hz) fibre tract stimulation were markedly attenuated when compared with responses to single fibre tract stimulation, although they usually remained suprathreshold for spike initiation. High concentrations of hexamethonium (1 mM) and d-tubocurarine (300 microM) failed to inhibit responses to single fibre tract stimulation, although they completely abolished responses to high-frequency stimulation. Responses to single fibre tract stimulation were abolished by trimetaphan (greater than or equal to 100 microM). No slow synaptic responses were detected during single or high-frequency fibre tract stimulation. All cardiac neurones that responded orthodromically were highly excitable: they had a short post-spike after-hyperpolarization (AHP) and responded with multiple firing to prolonged membrane depolarization. It is concluded that cardiac neurones, in the region of the heart studied here, receive single 'strong' cholinergic inputs from some fibre tracts approaching the ganglion that elicit EPSPs accompanied by spikes. EPSPs are rather resistant to ganglion-blocking agents and subject to frequency modulation.
Action Potentials↗
A molecular orbital study of a model of the Mg2+ coordination complex of the self splicing reaction of ribosomal RNA.
Recent discoveries have established the fact that RNA is capable of acting as an enzyme. In this study two different types of molecular orbital calculations, INDO and ab initio, were used in an attempt to assess the structural/functional role of the Mg2+ hydrated complex in ribozyme reactions. Preliminary studies indicate that the reaction is multistep and that the Mg2+ complex exerts a stabilizing effect on the intermediate or midpoint of the reaction.
Magnesium Compounds↗
The B-Z conformational transition and aggregation of poly[d(G-C)] induced by moderate concentrations of Mg(CIO4)2.
Mg(ClO4)2 induces the cooperative B-to-Z transition of poly[d(G-C)]; the salt concentration at the midpoint is 0.26 M. A comparison with previous data for NaCl, MgCl2 and NaClO4 (F.M. Pohl and T.M. Jovin, J. Mol. Biol. 67 (1972) 375) indicates that Mg(ClO4)2 is more effective than would be anticipated from the simple additive effects of the Mg2+ and ClO4- ions (the ionic strengths of the respective transition points are: NaCl, 2.4; MgCl2, 2.1; NaClO4, 1.8 and Mg(ClO4)2, 0.78). These results suggest the importance of specific interactions involving ClO4-, particularly in the presence of Mg2+. The B-Z transition of poly[d(G-C)] can be monitored spectroscopically via the large hyperchromic shift at 295 nm and the inversion in the CD spectrum. The reaction is fully reversible and can be fitted by a monoexponential function with half times varying between 8 and 150 min. The observed relaxation times are strongly dependent on the concentration of Mg(ClO4)2 with a distinct maximum at the transition point, in accordance with a concerted mechanism involving only the B and Z states. As the polymer assumes the Z conformation it progressively aggregates into a gel-like precipitate, which, however, redissolves rapidly upon lowering the salt concentration. The natural DNA from Micrococcus lysodeikticus which has a high GC content of 72% is also precipitated by Mg(ClO4)2 but we do not have direct spectroscopic evidence for the involvement of the Z conformation in this phenomenon. Neither calf thymus DNA (41% GC) nor poly[d(A-T)] (0% GC) aggregates under the same conditions.
Chlorates↗
The influence of internal stone structure upon the fracture behaviour of urinary calculi.
In vitro extracoporeal shock wave lithotripsy (ESWL) on different types of urinary calculi, in combination with microfocus x-ray and microphotography, illustrates the importance of the internal stone structure. Calculi with a rough surface layered structure (calcium oxalate monohydrate) and untextured calculi (cystine) are characterized by a low stone fragility, whereas coarse-grain calculi (calcium oxalate dihydrate, struvite), and calculi with a smooth surface layered structure (uric acid), are very fragile. Shell-like fragmentation in layered calculi, with smooth surface of the crystalline laminations, suggests that the stone matrix influenced the propagation of the shock wave energy inside the stone.
Calcium Oxalate↗