Hemoglobin concentration, total hemoglobin mass and plasma volume in patients: implications for anemia

In practice, clinicians generally consider anemia (circulating hemoglobin concentration < 120 g.l-1 in non-pregnant females and < 130 g.l-1 in males) as due to impaired hemoglobin synthesis or increased erythrocyte loss or destruction. Rarely is a rise in plasma volume relative to circulating total hemoglobin mass considered as a cause. But does this matter? We explored this issue in patients, using the optimized carbon-monoxide rebreathing method to measure hemoglobin concentration and thereby calculate plasma volume in healthy volunteers, surgical patients, and those with inflammatory bowel disease, chronic liver disease or heart failure. We studied 109 participants. Hemoglobin mass correlated well with its concentration in the healthy, surgical and inflammatory bowel disease groups (r= 0.687-0.871, p< 0.001). However, they were poorly related in liver disease (r= 0.410, p= 0.11) and heart failure patients (r= 0.312, p= 0.16). Here, hemoglobin mass explained little of the variance in its concentration (adjusted R2= 0.109 and 0.052; p= 0.11 and 0.16), whilst plasma volume did (R2 change 0.724 and 0.805 in heart and liver disease respectively, p<0.0001). Exemplar patients with identical (normal or raised) total hemoglobin masses were diagnosed as profoundly anemic (or not) depending on differences in plasma volume that had not been measured or even considered as a cause. The traditional inference that anemia generally reflects hemoglobin deficiency may be misleading, potentially resulting in inappropriate tests and therapeutic interventions to address 'hemoglobin deficiency not plasma volume excess. Measurement of total hemoglobin mass and plasma volume is now simple, cheap and safe, and its more routine use advocated

A carbon monoxide ‘single breath’ method to measure total haemoglobin mass: a feasibility study

NEW FINDINGS: What is the central question of this study? Is it possible to modify the CO-rebreathing method to acquire reliable measurements of haemoglobin mass in ventilated patients? What is the main finding and its importance? A 'single breath' of carbon monoxide with a subsequent 30 sec breath hold provides almost as exact a measure of haemoglobin mass as the established optimized CO-rebreathing method when applied to healthy subjects. The modified method has now to be checked in ventilated patients before it can be used to quantify the contributions of blood loss and of dilution to the severity of anaemia. ABSTRACT: Anaemia is defined by the concentration of haemoglobin ([Hb]). However, this value is dependent upon both the total circulating haemoglobin mass (tHb-mass) and the plasma volume (PV) - neither of which are routinely measured. Carbon monoxide- (CO) rebreathing methods have been successfully used to determine both PV and tHb-mass in various populations. However, these methods are not yet suitable for ventilated patients. This study aimed to modify the CO-rebreathing procedure such that a single inhalation of a CO bolus would enable its use in ventilated patients. Eleven healthy volunteers performed four CO-rebreathing tests in a randomized order, inhaling an identical CO-volume. In two tests, CO was rebreathed for 2min (oCOR), and in the other two tests, a single inhalation of a CO bolus was conducted with a subsequent breath hold of 15sec (Procnew 15sec) or 30sec (Procnew 30sec). Subsequently, the CO volume in the exhaled air was continuously determined for 20 min. The amount of CO exhaled after 7min (after 20min) for oCOR was 3.1 ±0.3ml (5.9 ±1.1ml); for Procnew 15sec, 8.7 ±3.6ml (12.0 ±4.4ml); and for Procnew 30sec, 5.1 ±2.0ml (8.4 ±2.6ml)). tHb-mass determined by oCOR was 843 ±293g, from Procnew 15sec 821 ±288g (difference: p <0.05), and from Procnew 30sec 849 ±311g. Bland-Altman plots demonstrated slightly lower tHb-mass values for Procnew 15sec compared with oCOR (-21.8 ±15.3g) and similar values for Procnew 30sec. In healthy volunteers, a single inhalation of a CO bolus, preferably followed by a 30 sec breath hold, can be used to determine tHb-mass. These results must now be validated for ventilated patients. This article is protected by copyright. All rights reserved

Combined inhibition of DNA methylation and histone acetylation enhances gene re-expression and drug sensitivity in vivo

Histone deacetylation and DNA methylation have a central role in the control of gene expression in tumours, including transcriptional repression of tumour suppressor genes and genes involved in sensitivity to chemotherapy. Treatment of cisplatin-resistant cell lines with an inhibitor of DNA methyltransferases, 2-deoxy-5′azacytidine (decitabine), results in partial reversal of DNA methylation, re-expression of epigenetically silenced genes including hMLH1 and sensitisation to cisplatin both in vitro and in vivo. We have investigated whether the combination of decitabine and a clinically relevant inhibitor of histone deacetylase activity (belinostat, PXD101) can further increase the re-expression of genes epigenetically silenced by DNA methylation and enhance chemo-sensitisation in vivo at well-tolerated doses. The cisplatin-resistant human ovarian cell line A2780/cp70 has the hMLH1 gene methylated and is resistant to cisplatin both in vitro and when grown as a xenograft in mice. Treatment of A2780/cp70 with decitabine and belinostat results in a marked increase in expression of epigenetically silenced MLH1 and MAGE-A1 both in vitro and in vivo when compared with decitabine alone. The combination greatly enhanced the effects of decitabine alone on the cisplatin sensitivity of xenografts. As the dose of decitabine that can be given to patients and hence the maximum pharmacodynamic effect as a demethylating agent is limited by toxicity and eventual re-methylation of genes, we suggest that the combination of decitabine and belinostat could have a role in the efficacy of chemotherapy in tumours that have acquired drug resistance due to DNA methylation and gene silencing

The effect of distance on reaction time in aiming movements

Target distance affects movement duration in aiming tasks but its effect on reaction time (RT) is poorly documented. RT is a function of both preparation and initiation. Experiment 1 pre-cued movement (allowing advanced preparation) and found no influence of distance on RT. Thus, target distance does not affect initiation time. Experiment 2 removed pre-cue information and found that preparing a movement of increased distance lengthens RT. Experiment 3 explored movements to targets of cued size at non-cued distances and found size altered peak speed and movement duration but RT was influenced by distance alone. Thus, amplitude influences preparation time (for reasons other than altered duration) but not initiation time. We hypothesise that the RT distance effect might be due to the increased number of possible trajectories associated with further targets: a hypothesis that can be tested in future experiments

Total haemoglobin mass, but not haemoglobin concentration, is associated with preoperative cardiopulmonary exercise testing (CPET) derived oxygen consumption variables

BACKGROUND: Cardiopulmonary exercise testing (CPET) measures peak exertional oxygen consumption ( V˙O2peakV˙O2peak ) and that at the anaerobic threshold ( V˙O2V˙O2 at AT, i.e. the point at which anaerobic metabolism contributes substantially to overall metabolism). Lower values are associated with excess postoperative morbidity and mortality. A reduced haemoglobin concentration ([Hb]) results from a reduction in total haemoglobin mass (tHb-mass) or an increase in plasma volume. Thus, tHb-mass might be a more useful measure of oxygen-carrying capacity and might correlate better with CPET-derived fitness measures in preoperative patients than does circulating [Hb]. METHODS: Before major elective surgery, CPET was performed, and both tHb-mass (optimized carbon monoxide rebreathing method) and circulating [Hb] were determined. RESULTS: In 42 patients (83% male), [Hb] was unrelated to V˙O2V˙O2 at AT and V˙O2peakV˙O2peak (r=0.02, P=0.89 and r=0.04, P=0.80, respectively) and explained none of the variance in either measure. In contrast, tHb-mass was related to both (r=0.661, P<0.0001 and r=0.483, P=0.001 for V˙O2V˙O2 at AT and V˙O2peakV˙O2peak , respectively). The tHb-mass explained 44% of variance in V˙O2V˙O2 at AT (P<0.0001) and 23% in V˙O2peakV˙O2peak (P=0.001). CONCLUSIONS: In contrast to [Hb], tHb-mass is an important determinant of physical fitness before major elective surgery. Further studies should determine whether low tHb-mass is predictive of poor outcome and whether targeted increases in tHb-mass might thus improve outcome

Epigenetics as a mechanism driving polygenic clinical drug resistance

Aberrant methylation of CpG islands located at or near gene promoters is associated with inactivation of gene expression during tumour development. It is increasingly recognised that such epimutations may occur at a much higher frequency than gene mutation and therefore have a greater impact on selection of subpopulations of cells during tumour progression or acquisition of resistance to anticancer drugs. Although laboratory-based models of acquired resistance to anticancer agents tend to focus on specific genes or biochemical pathways, such 'one gene : one outcome' models may be an oversimplification of acquired resistance to treatment of cancer patients. Instead, clinical drug resistance may be due to changes in expression of a large number of genes that have a cumulative impact on chemosensitivity. Aberrant CpG island methylation of multiple genes occurring in a nonrandom manner during tumour development and during the acquisition of drug resistance provides a mechanism whereby expression of multiple genes could be affected simultaneously resulting in polygenic clinical drug resistance. If simultaneous epigenetic regulation of multiple genes is indeed a major driving force behind acquired resistance of patients' tumour to anticancer agents, this has important implications for biomarker studies of clinical outcome following chemotherapy and for clinical approaches designed to circumvent or modulate drug resistance

Influence of apical oxygen on the extent of in-plane exchange interaction in cuprate superconductors

In high Tc superconductors the magnetic and electronic properties are determined by the probability that valence electrons virtually jump from site to site in the CuO2 planes, a mechanism opposed by on-site Coulomb repulsion and favored by hopping integrals. The spatial extent of the latter is related to transport properties, including superconductivity, and to the dispersion relation of spin excitations (magnons). Here, for three antiferromagnetic parent compounds (single-layer Bi2Sr0.99La1.1CuO6+delta, double-layer Nd1.2Ba1.8Cu3O6 and infinite-layer CaCuO2) differing by the number of apical atoms, we compare the magnetic spectra measured by resonant inelastic x-ray scattering over a significant portion of the reciprocal space and with unprecedented accuracy. We observe that the absence of apical oxygens increases the in-plane hopping range and, in CaCuO2, it leads to a genuine 3D exchange-bond network. These results establish a corresponding relation between the exchange interactions and the crystal structure, and provide fresh insight into the materials dependence of the superconducting transition temperature.Comment: 9 pages, 4 figures, 1 Table, 42 reference

Does reductive metabolism predict response to tirapazamine (SR 4233) in human non-small-cell lung cancer cell lines?

The bioreductive drug tirapazamine (TPZ, SR 4233, WIN 59075) is a lead compound in a series of potent cytotoxins that selectively kill hypoxic rodent and human solid tumour cells in vitro and in vivo. Phases II and III trials have demonstrated its efficacy in combination with both fractionated radiotherapy and some chemotherapy. We have evaluated the generality of an enzyme-directed approach to TPZ toxicity by examining the importance of the one-electron reducing enzyme NADPH:cytochrome P450 reductase (P450R) in the metabolism and toxicity of this lead prodrug in a panel of seven human non-small-cell lung cancer cell lines. We relate our findings on TPZ sensitivity in these lung lines with our previously published results on TPZ sensitivity in six human breast cancer cell lines (Patterson et al (1995) Br J Cancer 72: 1144–1150) and with the sensitivity of all these cell types to eight unrelated cancer chemotherapeutic agents with diverse modes of action. Our results demonstrate that P450R plays a significant role in the activation of TPZ in this panel of lung lines, which is consistent with previous observations in a panel of breast cancer cell lines (Patterson et al (1995) Br J Cancer 72: 1144–1150; Patterson et al (1997) Br J Cancer 76: 1338–1347). However, in the lung lines it is likely that it is the inherent ability of these cells to respond to multiple forms of DNA damage, including that arising from P450R-dependent TPZ metabolism, that underlies the ultimate expression of toxicity. © 1999 Cancer Research Campaig

Altered expression of topoisomerase IIα contributes to cross-resistant to etoposide K562/MX2 cell line by aberrant methylation

KRN 8602 (MX2) is a novel morpholino anthracycline derivative having the chemical structure 3′-deamino-3′-morpholino-13-deoxo-10-hydroxycarminomycin hydrochloride. To investigate the mechanisms of resistance to MX2, we established an MX2-resistant phenotype (K562/MX2) of the human myelogeneous leukaemia cell line (K562/P), by continuously exposing a suspension culture to increasing concentrations of MX2. K562/MX2 cells were more resistant to MX2 than the parent cells, and also showed cross-resistance to etoposide and doxorubicin. Topoisomerase (Topo) IIα protein levels in K562/MX2 cells were lower of those in K562/P cells on immunoblot analysis and decreased expression of Topo IIα mRNA was seen in K562/MX2 cells. Topoisomerase II catalytic activity was also reduced in the nuclear extracts from K562/MX2 cells when compared with K562/P cells. Aberrant methylated CpG of Topo IIα gene was observed in K562/MX2 cells when compared with the parent line on methylation-specific restriction enzyme analysis. To overcome the drug resistance to MX2 and etoposide, we investigated treatment with 5-Aza-2′-deoxycytidine (5AZ), which is a demethylating agent, in K562/MX2 cells. 5-Aza-2′-deoxycytidine treatment increased Topo IIα mRNA expression in K562/MX2 cells, but not in K562/P cells, and increased the cytotoxicity of MX2 and etoposide. Methylated CpG was decreased in K562/MX2 cells after 5AZ treatment. We concluded that the mechanism of drug resistance to MX2 and etoposide in K562/MX2 cells might be the combination of decreased expression of Topo IIα gene and increased methylation, and that 5AZ could prove to be a novel treatment for etoposide-resistant cell lines, such as K562/MX2