Autologous stem cell transplantation for malignancy: a systematic review of the literature.

A systematic review of the literature was undertaken to assess what published evidence is currently available to support the increasing use of autologous stem cell transplantation (ASCT), and to evaluate the published data with regard to the comparative cost of high-dose and conventional therapy. The review aimed to identify all published, randomized controlled trials (RCTs) comparing high-dose therapy (HDT) with ASCT versus conventional chemotherapy (CC) in acute lymphoblastic leukaemia, non-Hodgkin's lymphoma, Hodgkin's disease, multiple myeloma, and breast, lung, testicular and ovarian cancer. The review also aimed to identify all studies that had compared the cost of the two treatment strategies. Reports were identified by systematic searches of Cancerlit, Embase and Medline, and handsearching of several conference proceedings. Where possible, pooled odds ratios (ORs) were calculated according to the fixed-effect model. A total of 18 randomized trials were identified in acute lymphoblastic leukaemia, non-Hodgkin's lymphoma, Hodgkin's disease, multiple myeloma, and breast, lung and testicular cancer. Trials were generally small and no disease site had sufficient information to determine reliably whether high-dose therapy with autologous transplant is more effective than CC. Five studies were identified that compared the cost of the two treatments. These found the cost of HDT to be between one and four times higher than that of CC. Further randomized trials are required. Where appropriate, these should include economic assessment and assessments of long-term toxicity.

Effect of pH, phosphate, and ADP on relaxation of myocardium after photolysis of diazo 2.

The aim of this study was to examine the effect of the metabolites H+, ADP, and Pi on the rate of cardiac relaxation. We used guinea pig right ventricular trabeculae that had been chemically skinned, allowing the myofilaments to be studied in isolation. Laser-flash photolysis of the caged Ca2+ chelator diazo 2, causing a rapid fall in intracellular Ca2+, enabled investigation of relaxation independently of the rate of Ca2+ diffusion. On the photolysis of diazo 2, the trabeculae relaxed biphasically with exponential rate constants (k1 and k2) of 10.07 and 4.23 s-1, respectively, at 12 degrees C and 18.35 and 2.52 s-1, respectively, at a nominal 20 degrees C. Increasing the concentration of both protons (pH 7.2-6.8) and MgADP (0.5-3.4 mM) slowed the two phases of the relaxation transients. Raising the concentration of Pi from the control level of 1.36 mM to 15.2 mM increased the rate of both phases, with relaxation becoming monoexponential at 19.4 mM Pi (with a k of 20.31 s-1 at 12 degrees C). Cardiac muscle was compared with skeletal muscle under identical conditions; in cardiac muscle 19.4 mM Pi increased the rate of relaxation, whereas in skeletal muscle this concentration of Pi slowed relaxation. We conclude that the mechanism of relaxation differs between cardiac and skeletal muscle. This study is a direct demonstration of the effects of ATP metabolites on cardiac myofilament processes during relaxation.

Troponin I phosphorylation does not increase the rate of relaxation following laser flash photolysis of diazo-2 in guinea-pig skinned trabeculae.

In vivo, two effects of beta-adrenergic stimulation in cardiac muscle are phosphorylation of troponin I and an increase in relaxation rate. In vitro, cardiac TnI can be phosphorylated by protein kinase A (PKA). We have used the technique of laser flash photolysis of the calcium chelator diazo-2 to investigate the effect of phosphorylation of TnI on the relaxation rate of skinned trabeculae from the guinea-pig at 12 degrees C. The fibres were phosphorylated by PKA, and double exponential curve fits of the average relaxation transients showed no significant difference between the rate constants of the phosphorylated and control cases. We conclude that TnI phosphorylation has no effect on the rate of relaxation in skinned trabeculae from the guinea-pig following diazo-2 photolysis.

The thiadiazinone EMD 57033 speeds the activation of skinned cardiac muscle produced by the photolysis of nitr-5.

EMD 57033 is thought to produce its potentiating effect by increasing the apparent Ca2+ sensitivity of the myofilaments, possibly by altering the kinetics of actomyosin interaction. We have investigated the effect of 10 microM EMD 57033 upon activation speed, induced by flash photolysis of 2mM nitr-5 (caged Ca2+), in chemically skinned trabeculae from the guinea-pig at 12 degrees C. EMD 57033 increases the half time of activation from 238 +/- 18.5 msec (n = 6) to 132.1 +/- 34.0 msec (n = 8) (mean +/- s.e.m.) and suggests that this Ca2+ sensitiser has an important effect upon fapp, that is the transition from the non-force to force generating cross-bridge states.

The effect of EMD 57033, a novel cardiotonic agent, on the relaxation of skinned cardiac and skeletal muscle produced by photolysis of diazo-2, a caged calcium chelator.

EMD 57033 is thought to produce its potentiating effect by increasing the apparent calcium sensitivity of myofibrils. We have investigated the effect of 10 microM EMD 57033 on relaxation speed, induced by flash photolysis of 2mM diazo-2 (a caged Ca2+ chelator), in skinned semitendinosus frog muscle fibres and guinea-pig trabeculae. 10 microM EMD 57033 has no effect on the relaxation speed of semitendinosus fibres. In trabeculae, EMD 57033 slightly increases the relaxation speed slightly, in contrast to ADP which produces a slowing. 1mM ADP combined with 10 microM EMD 57033 slows relaxation but not to the degree seen with ADP alone. Like ADP, EMD 57033 increases the number of cross-bridges in the force producing state, but unlike ADP does not affect the transition rates involved in relaxation.

Barnacle muscle: Ca2+, activation and mechanics.

In this review, aspects of the ways in which Ca2+ is transported and regulated within muscle cells have been considered, with particular reference to crustacean muscle fibres. The large size of these fibres permits easy access to the internal environment of the cell, allowing it to be altered by microinjection or microperfusion. At rest, Ca2+ is not in equilibrium across the cell membrane, it enters the cell down a steep electrochemical gradient. The free [Ca2+] at rest is maintained at a value close to 200 nM by a combination of internal buffering systems, mainly the SR, mitochondria, and the fixed and diffusible Ca(2+)-binding proteins, as well as by an energy-dependent extrusion system operating across the external cell membrane. This system relies upon the inward movement of Na+ down its own electrochemical gradient to provide the energy for the extrusion of Ca2+ ions. As a result of electrical excitation, voltage-sensitive channels for Ca2+ are activated and permit Ca2+ to enter the cell more rapidly than at rest. It has been possible to determine both the amount of Ca2+ entering by this step, and what part this externally derived Ca2+ plays in the development of force as well as in the free Ca2+ change. The latter can be determined directly by Ca(2+)-sensitive indicators introduced into the cell sarcoplasm. A combination of techniques, allowing both the total and free Ca2+ changes to be assessed during electrical excitation, has provided valuable information as to how muscle cells buffer their Ca2+ in order to regulate the extent of the change in the free Ca2+ concentration. The data indicate that the entering Ca2+ can only make a small direct contribution to the force developed by the cell. The implication here is that the major source of Ca2+ for contraction must be derived from the internal Ca2+ storage sites within the SR system, a view reinforced by caged Ca2+ methods. The ability to measure the free Ca2+ concentration changes within a single cell during activation has also provided the opportunity to analyse, in detail, the likely relations between free Ca2+ and the process of force development in muscle. The fact that the free Ca2+ change precedes the development of force implies that there are delays in the mechanism, either at the site of Ca2+ attachment on the myofibril, or at some later stage in the process of force development that were not previously anticipated.(ABSTRACT TRUNCATED AT 400 WORDS)

Activation and relaxation mechanisms in single muscle fibres.

The effect of Ca2+ on the time course of force generation in frog skinned muscle fibres has been investigated using laser flash photolysis of the caged-calcium, either nitr-5 or DM-Nitrophen. Gradations in the rate and extent of contraction could be achieved by changing the energy of the laser pulse, which varied the amount of caged Ca2+ photolysed and hence the amount of calcium released. The half-time for force development at 12 degrees C was noticeably calcium-sensitive when small amounts of calcium were released (low energy pulses) but did not change appreciably for calcium releases which produced a final tension of more than 50% of the maximal tension at pCa 4.5. This result is unlikely to be due to calcium binding to the regulatory sites of troponin C when on the thin filament, as this process is considered rapid (kon 10(8) M-1 s-1, koff 100 s-1). Our experimental results show that force develops relatively rapidly at intermediate Ca2+ which produce only partial activation (i.e. 50% Pmax or greater). This would not be the case if the affinity of the regulatory sites changes slowly with crossbridge attachment. The kinetics of calcium exchange with the regulatory sites may be much more rapid than crossbridge cycling, so that if calcium binding to a particular functional unit induces crossbridge attachment and force production, the force producing state may be maintained long after calcium has dissociated from that particular functional unit. The relaxation of skinned muscle fibres has also been successfully studied following the rapid uptake of Ca2+ by a photolabile chelator Diazo-2, a photolabile derivative of BAPTA, which is rapidly (> 2000 s-1) converted from a chelator of low Ca2+ affinity (Kd 2.2 microM) to a high affinity chelator (Kd 0.073 microM). We have used single skinned muscle fibres from both frog (actin regulated) and scallop striated muscle (myosin regulated), to study the time course of muscle relaxation. This procedure has enabled us to examine the effects of the intracellular metabolites, ADP, Pi and H+ upon the rate of relaxation.(ABSTRACT TRUNCATED AT 400 WORDS)

Skeletal muscle relaxation with diazo-2: the effect of altered pH.

In a fatigued muscle fibre, the concentrations of ADP, Pi and H+ are all increased and relaxation is slowed. We have used the technique of laser flash photolysis of the caged calcium-chelator, diazo-2, to investigate the direct effect of changes in pH (pH 6.5, 7.0, 7.5) upon tension during relaxation of single chemically skinned fibres, when the effects of the sarcoplasmic reticulum are absent. The relaxation transients were closely fitted with 2 exponentials, a fast (42.3 +/- 1.4; pH 7.0) and a slow process (12.0 +/- 0.7; pH 7.0). The fast phase of relaxation was pH sensitive; lowering pH leading to a slowing of the rate of force decline and raising pH leading to an increase of the rate. The rate of the slow phase was unaltered by changing pH over the range investigated. Thus the slowing of relaxation in fatigued muscle may be due, in part, to the direct action of protons on the myofilaments independent of any effects upon the sarcoplasmic reticulum.