A Gonzales

Imperial College London, Londinium, England, United Kingdom

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Publications (11)39.95 Total impact

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    ABSTRACT: We have compared polyethylene glycol-modified bovine hemoglobin (PEG-Hb; high O2 affinity, high viscosity, high oncotic pressure) and human hemoglobin cross-linked between the alpha-chains (alpha alpha-Hb; low O2 affinity, low viscosity, low oncotic pressure) with a non-O2-carrying plasma expander (pentastarch, high viscosity and oncotic pressure) after a 50% (by volume) exchange transfusion followed by a severe (60% of blood volume) hemorrhage. Mean arterial pressure and systemic vascular resistance rose significantly in the alpha alpha-Hb but not in the PEG-Hb animals. Two-hour survival was greater in the PEG-Hb animals (93%) than in control (35%), pentastarch (8%), or alpha alpha-Hb (6%) animals. In the PEG-Hb animals, there was no disturbance of acid-base balance, significantly less accumulation of lactic acid, and higher cardiac output than in the other groups. The data suggest that the rise in vascular resistance that follows alpha alpha-Hb exchange transfusion offsets the additional O2 transport provided by the cell-free hemoglobin. When resistance does not rise, as with PEG-Hb, even relatively small amounts of cell-free hemoglobin appear to be a very effective blood replacement.
    Journal of Applied Physiology 10/1998; 85(3):993-1003. · 3.48 Impact Factor
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    ABSTRACT: The enzyme heme oxygenase, which exists in inducible (HO-1) and constitutive (HO-2) isoforms, catalyzes the degradation of heme to biliverdin and CO in mammalian tissues. CO has been implicated in the control of vascular tone in a manner similar to that for NO. In the present study, we investigated the contribution of the heme oxygenase/CO pathway to the modulation of acute hypertensive responses in vivo induced by (1) alphaalphaHb, a chemically modified hemoglobin known to scavenge NO, and (2) NG-nitro-L-arginine methyl ester (L-NAME), a competitive NOS inhibitor. Experiments were carried out in conscious rats in which femoral arteries and veins were surgically catheterized 1 or 5 days before treatment with the vasoconstrictor agents. Intravenous infusion of alphaalphaHb (8% solution) or L-NAME (30 micromol/kg) [corrected] produced an acute and significant increase in mean arterial pressure (P<0.05) in rats at 5 days after catheter implantation. In contrast, no change in blood pressure was observed when alphaalphaHb or L-NAME was infused 1 day after the surgical intervention. The suppression of the hypertensive response observed at 1 day after surgery correlated with a significant (P<0.05) HO-1 expression in aorta, heart, and liver as well as increased aortic CO production and cGMP levels. At 1 day after surgery, pretreatment of animals with the heme oxygenase inhibitor zinc protoporphyrin IX (50 micromol/kg IP) markedly decreased aortic CO and cGMP levels and completely restored the vasoconstrictor effects of both alphaalphaHb and L-NAME. These results provide evidence for a crucial role of the heme oxygenase/CO pathway in the regulation of blood pressure under stress conditions in vivo.
    Circulation Research 09/1998; 83(5):568-77. · 11.86 Impact Factor
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    ABSTRACT: Changes in mean arterial pressure were monitored in rats following 50% isovolemic exchange transfusion with solutions of chemically modified hemoglobins. Blood pressure responses fall into three categories: 1) an immediate and sustained increase, 2) an immediate yet transient increase, or 3) no significant change either during or subsequent to exchange transfusion. The reactivities of these hemoglobins with nitric monoxide (.NO) were measured to test the hypothesis that different blood pressure responses to these solutions result from differences in .NO scavenging reactions. All hemoglobins studied exhibited a value of 30 microM-1 s-1 for both .NO bimolecular association rate constants and the rate constants for .NO-induced oxidation in vitro. Only the .NO dissociation rate constants and, thus, the equilibrium dissociation constants varied. Values of equilibrium dissociation constants ranged from 2 to 14 pM and varied inversely with vasopressor response. Hemoglobin solutions that exhibited either transient or no significant increase in blood pressure showed tighter .NO binding affinities than hemoglobin solutions that exhibited sustained increases. These results suggest that blood pressure increases observed upon exchange transfusion with cell-free hemoglobin solutions can not be the result of .NO scavenging reactions at the heme, but rather must be due to alternative physiologic mechanisms.
    Journal of Biological Chemistry 05/1998; 273(20):12128-34. · 4.65 Impact Factor
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    ABSTRACT: We have measured plasma volume and cardiac index in rats after 50% isovolemic exchange transfusion with human hemoglobin cross-linked between the alpha-chains with bis(3,5-dibromosalicyl)fumarate (alpha alpha Hb) and with bovine hemoglobin modified with polyethylene glycol (PEGHb). alpha alpha Hb and PEGHb differ in colloid osmotic pressure (23.4 and 118.0 Torr, respectively), oxygen affinity (oxygen half-saturation pressure of hemoglobin = 30.0 and 10.2 Torr, respectively), viscosity (1.00 and 3.39 cP, respectively), and molecular weight (64,400 and 105,000, respectively). Plasma volume was measured by Evans blue dye dilution modified for interference by plasma hemoglobin. Blood volumes in PEGHb-treated animals were significantly elevated (74.0 +/- 3.5 ml/kg) compared with animals treated with alpha alpha Hb (49.0 +/- 1.2 ml/kg) or Ringer lactate (48.0 +/- 2.0 ml/kg) or with controls (58.2 +/- 1.9 ml/kg). Heart rate reduction after alpha alpha Hb exchange is opposite to that expected with blood volume contraction, suggesting that alpha alpha Hb may have a direct myocardial depressant action. The apparently slow elimination of PEGHb during the 2 h after its injection is a consequence of plasma volume expansion: when absolute hemoglobin (concentration x plasma volume) is compared for PEGHb and alpha alpha Hb, no difference in their elimination rates is found. These studies emphasize the need to understand blood volume regulation when the effects of cell-free hemoglobin on hemodynamic measurements are evaluated.
    Journal of Applied Physiology 07/1997; 82(6):1995-2002. · 3.48 Impact Factor
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    ABSTRACT: Anesthesia may represent a considerable bias in experimental medicine, particularly in conditions of stress (such as hemorrhage). Sodium pentobarbital (PB), widely used for cardiovascular investigations, may impair oxygen delivery by hemodynamic and respiratory depression. The critical issue, however, is whether the microcirculation can still maintain tissue oxygenation during anesthesia. To answer this question, the authors studied the effect of PB anesthesia on subcutaneous microvascular oxygen delivery and interstitial oxygenation in Syrian golden hamsters. Sodium pentobarbital anesthesia was induced by intravenous injection (30 mg/kg body weight) and maintained by a 15-min infusion (2 mg.kg-1.min-1), with animals breathing spontaneously (PB-S) or ventilated with air (PB-V). Systemic parameters evaluated were mean arterial pressure (MAP), heart rate, cardiac index (CI), arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2), base excess, and pH. Microvascular and interstitial oxygen tension (PO2), vessel diameter, red blood cell velocity (vRBC), and blood flow (Qb) were measured in a dorsal skinfold preparation. Microcirculatory PO2 values were determined by phosphorescence decay. Sodium pentobarbital anesthesia significantly decreased CI, MAP, vRBC, and Qb. During PB infusion, PaO2 values were 56 +/- 12.8 mmHg (PB-S) and 115.9 +/- 14.6 mmHg (PB-V) compared with 69.4 +/- 18.2 mmHg and 61.4 +/- 12.6 mmHg at baseline. However, microvascular PO2 was reduced by 25-55% in both groups, resulting in an interstitial PO2 decrease from 23.9 +/- 5.6 mmHg (control) to 13.1 +/- 9.1 mmHg (PB-S) and 15.2 +/- 7 mmHg (PB-V). Microcirculatory PO2 values were restored 30 min after PB infusion, even though hemodynamic depression and a light anesthetic plane were maintained. Sodium pentobarbital anesthesia caused impairment of microvascular oxygen delivery and interstitial oxygenation, effects that were not prevented by mechanical ventilation. Although these effects were restricted to deep anesthetic planes, prolonged hemodynamic depression suggests that caution is warranted when using PB as an anesthetic in cardiovascular investigations.
    Anesthesiology 03/1997; 86(2):372-86. · 5.16 Impact Factor
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    ABSTRACT: Background: Anesthesia may represent a considerable bias in experimental medicine, particularly in conditions of stress (such as hemorrhage). Sodium pentobarbital (PB), widely used for cardiovascular investigations, may impair oxygen delivery by hemodynamic and respiratory depression. The critical issue, however, is whether the microcirculation can still maintain tissue oxygenation during anesthesia. To answer this question, the authors studied the effect of PB anesthesia on subcutaneous microvascular oxygen delivery and interstitial oxygenation in Syrian golden hamsters.
    Anesthesiology 01/1997; 86(2):372–386. · 5.16 Impact Factor
  • Shock. 01/1995; 4.
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    ABSTRACT: This report describes the tissue distribution and long-term (14-day) excretion of hemoglobin cross-linked between the alpha-chains (alpha alpha Hb) with carbon 14-labeled bis(3,5-dibromosalicyl)fumarate. Fully conscious, chronically cannulated rats (n = 40) were treated with a 50% isovolemic exchange transfusion (ET) with solutions of 14C-labeled alpha alpha Hb (8.0 gm/dl) and were then monitored for as long as 14 days. Thirteen tissue types were analyzed for radioactivity by liquid scintillation counting. The highest concentration of label was found in the kidney and in tissues of the reticuloendothelial system (i.e., spleen, bone marrow, and liver). The 14C-labeled alpha alpha Hb did not appear to cross the blood-brain barrier, because radioactivity in the brain was barely detectable. The dose of 14C-labeled alpha alpha Hb (2.4 gm Hb/kg) produced an initial plasma Hb level of 4.6 gm/dl, with a half-life in the plasma of 5.0 hours. The peak concentration in kidney, spleen, and liver occurred at 24 hours after ET, when at least 92% of the 14C-labeled alpha alpha Hb in plasma had been cleared. At 48 hours, red casts were seen in a tiny number of renal tubules in some rats. By 14 days, up to 64% of the injected radioactivity had been recovered in urine and about 10% was recovered in feces. Most excretion occurred 24 to 48 hours after ET. This study demonstrated that 2 weeks were required for the metabolic degradation and elimination of a large dose of alpha alpha Hb in rats.
    Journal of Laboratory and Clinical Medicine 06/1994; 123(5):701-11. · 2.62 Impact Factor
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    ABSTRACT: This report describes acute changes in systemic blood pressure and urine output observed after a 50-percent isovolemic exchange transfusion (ET) with diaspirin-crosslinked hemoglobin (alpha alpha Hb). Stroma-free Hb was crosslinked between the alpha chains by using a 14C-labeled diaspirin, bis(3,5-dibromosalicyl)fumarate. Forty conscious, chronically cannulated rats underwent ET with 14C-labeled alpha alpha Hb solution (8.0 g/dL [80 g/L]). This resulted in systemic hypertension for 3 to 4 hours after ET (mean arterial pressure rose from 120 to 145 torr at 1 to 2 hours after ET) and mild bradycardia for 2 to 3 hours (heart rate decreased from 420 to 335 beats/min [bpm] before stabilizing at 360 +/- 10 bpm). This was accompanied by significant diuresis immediately after ET (5- 6-fold increase in urine output, which normalized after 12 hours), and mild hemoglobinuria. The total amount of Hb recovered in the urine was < 5 percent of the injected dose. Reversed-phase high-performance liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed the presence of crosslinked alpha alpha Hb molecules in the urine. Renal excretion of radioactivity was significantly greater, with 20 percent of total radioactivity being eliminated within 24 hours. The plasma half-life for alpha alpha Hb was 5 hours (administered dose, 2.4 g Hb/kg body weight). Thus, infusion of alpha alpha Hb caused a transient systemic hypertension, and intramolecular crosslinking alone was not enough to exclude completely the filtration of alpha alpha Hb by the kidneys.
    Transfusion 09/1993; 33(9):701-8. · 3.53 Impact Factor
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    ABSTRACT: Stroma-free hemoglobin (SFHb) can be chemically modified to prolong the intravascular retention (prevent renal filtration), and to improve oxygen delivering capability for use as a red cell substitute. Hb derivatives radioactively tagged with tritium [3H] or 14C were used to study their metabolic fate following clearance from the circulation. Fully conscious, chronically cannulated rats were treated by exchange transfusion (ET). Hb solutions tested were: PLPHb (Hb monovalently reacted with pyridoxal 5'-phosphate); HbXL (Hb crosslinked beta-beta with 2-nor-2-formylpyridoxal 5'-phosphate, or with bis-pyridoxal tetraphosphate); alpha alpha Hb (Hb cross-linked between the alpha-chains using bis-3,5-dibromosalicyl fumarate); and polyHb (polymerized with glutaraldehyde or o-raffinose). Plasma retention (T1/2) was significantly affected by dose and the degree of cross-linking. Urine flow rates all increased transiently above normal. In rats treated with any 64 kDa interdimerically cross-linked Hb, mild hemoglobinuria was evident and kidney tissue had the highest label concentration at all time points (1, 5, 10, 24, 48 hr, 7 d, and 14 days post-ET). For polymerized Hb derivatives, the amount of radioactivity in urine and kidneys was inversely related to the MW of the polyHb molecules. In all rats, regardless of the Hb derivative tested, the majority of radioactivity (dpm's) was excreted in urine. About 75% of all renal excretion of radioactivity occurred from 12-60 hours post-ET. This provided evidence that catabolism of cross-linked Hb's began early, and that the kidneys are primarily responsible for excreting smaller degradation fragments.
    Biomaterials, artificial cells, and immobilization biotechnology: official journal of the International Society for Artificial Cells and Immobilization Biotechnology 02/1992; 20(2-4):737-45.
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    ABSTRACT: We have studied the plasma half-life (T 1/2), oxygen-binding affinity (P50), organ distribution, and excretion of the individual molecular weight (MW) components of human hemoglobin polymerized with periodate-oxidized, ring-opened raffinose (oR poly-Hb), following transfusion in the rat. The model was an isovolemic 50% exchange transfusion in the conscious, chronically catheterized rat. Total plasma Hb levels yielded a (T 1/2) of 10 to 11 hr for oR poly-Hb. The T 1/2 values of individual MW components of the poly-Hb as determined by size-exclusion HPLC were approximately: 4 hr for the monomeric fraction (Hb)1, 9 hr for the dimer (Hb)2, and 15 hr for the fraction representing trimers to nanomers (Hb)3-9. The P50 values of plasma samples containing oR poly-Hb (collected from 0-24 hr after exchange) remained unchanged at 28 +/- 3 mmHg. oR stabilized and polymerized Hb were not excreted via the kidneys. Hepatic and renal distribution as well as plasma and renal clearance were determined by liquid scintillation counting using individual tritium [3H] labelled MW components purified from [3H]-oR poly-Hb: (Hb)1/2, (Hb)1, (Hb)2, (Hb)3&4, and (Hb) greater than 9. In kidney, uptake (determined by the relative concentration of radioactivity) decreased with increasing MW of the labelled component. Conversely, in liver, uptake increased with increasing MW. Plasma and renal clearance results were consistent with those obtained by HPLC analysis. Hematocrit levels returned from a 20% post-transfusion level to normal pre-transfusion levels (44%) within 10 days after the exchange.
    Biomaterials, artificial cells, and immobilization biotechnology: official journal of the International Society for Artificial Cells and Immobilization Biotechnology 02/1992; 20(2-4):587-95.