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Biomedical subjects

Z F Xia

Publications and source records attributed to Z F Xia.

At least 19 recordsLinked to original sources
PubMed2001

Cardiac apoptosis in burned rats with delayed fluid resuscitation.

Clinical and experimental studies have shown that delayed fluid resuscitation postburn decreases heart function. We hypothesized that apoptosis occurs in the cardiomyocyte in this condition. To investigate this hypothesis, rats were burned, fluid resuscitation was delayed, and the integrity of cardiac genomic DNA in the burned rats was determined with an LM-PCR Ladder Assay kit. DNA fragmentation shown as DNA ladders on gels, the hallmark of apoptosis, was found in the heart tissue of these rats. In the early phase of delayed fluid resuscitation, the nuclear factor kappa B (NF-kappa B) was examined using an electrophoretic mobility shift assay and was found to be activated. In comparison with burned rats with immediate fluid resuscitation, nitric oxide levels in hearts from burned rats with delayed fluid resuscitation were significantly lower (P<0.01). These results suggest that apoptosis may be an important pathway for cardiac injury, which may result from the activation of NF-kappa B and decreased nitric oxide levels.

Animals↗
PubMed2001

Changes in cardiac contractile function and myocardial.

Cutaneous burn trauma causes cardiac contraction and relaxation defects, but the mechanism is unclear. Previous studies suggest that burn-related changes in myocyte handling of calcium may play an important role in postburn cardiac dysfunction. With the use of a high dissociation constant (K(d)) calcium indicator 1,2-bis(2-amino-5,6-difluorophenoxy)-ethane-N,N,N',N'-tetraacetic acid (TF-BAPTA) and (19)F NMR spectroscopy, this study examined the correlation between the changes in cytosolic free calcium concentration ([Ca(2+)](i)) and cardiac function after burn trauma. Sprague-Dawley rats were given scald burn (over 40% of the total body surface area) or sham burn. Twenty-four hours later, the hearts were excised and perfused by the Langendorff method with a modified phosphate-free Krebs-Henseleit bicarbonate buffer. Left ventricular (LV) developed pressure (LVDP), calculated from peak systolic LV pressure and LV end-diastolic pressure, was assessed through a catheter attached to an intraventricular balloon. At the same time, (31)P and (19)F NMR spectroscopy was performed before and after TF-BAPTA loading. LVDP measured in hearts from burned rats was <40% than that measured in hearts from sham burn rats (65 +/- 6 vs. 110 +/- 12 mmHg, P < 0.01); [Ca(2+)](i) was increased fourfold in hearts from the burned group compared with that measured in the sham burn group (0.807 +/- 0.192 vs. 3.891 +/- 0.929 microM). Loading TF-BAPTA in hearts transiently decreased LVDP by 15%. Phosphocreatine-to-P(i) ratio decreased, but ATP and intracellular pH remained unchanged by either TF-BAPTA loading or burn trauma. In conclusion, burn trauma impaired cardiac contractility, and this functional defect was paralleled by a significant rise in [Ca(2+)](i) in the heart.

Adenosine Triphosphate↗
PubMed1997

Relationship between energetic, ionic, and functional status in the perfused rat heart following thermal injury: a 31P and 23Na NMR study.

To test the hypothesis that energy deficits and intracellular ion derangements may be the cellular basis for intrinsic myocardial dysfunction in rats after burn trauma, we examined ATP metabolism, intracellular pH, sodium, and mechanical performance simultaneously in perfused beating hearts from sham burn or burned rats (43% TBSA, 3 degrees scald burn, resuscitated for 24 hr with lactated Ringer's solution, Parkland formula). Intracellular calcium was also measured in myocytes harvested from parallel groups of sham burn and burn resuscitated rats. Burn trauma caused a 46% decrease in left ventricular developed pressure, a 69% decrease in +dP/dtmax, and a 72% decrease in -dP/dtmax. Intracellular to external standard sodium ratio increased (+58%) from 0.318 +/- 0.027 to 0.500 +/- 0.048 (P < 0.05), and intracellular calcium increased (+67%) from 206 +/- 13 to 445 +/- 37 nM (P < 0.01). Burn hearts exhibited decreased functional response to isoproterenol challenge compared to sham burn controls, but energy metabolism was similar in all hearts, regardless of burn injury. Our data suggest that burn trauma alters intracellular cardiomyocyte calcium and sodium homeostasis, and ionic derangements are not related to either altered intracellular pH or high energy phosphate deficits.

Adrenergic beta-Agonists↗
PubMed1996

Effects of ischemia on intracellular sodium and phosphates in the in vivo rat liver.

Metabolic factors that influence the transition form reversible to irreversible ischemic injury were studied in the rat liver in vivo with 31P-nuclear magnetic resonance (NMR) spectroscopy. Hepatic ischemia for 15, 35, or 65 min was produced by occlusion of the hepatic artery and portal vein in rats. Ischemia caused a rapid decrease in the ATP concentration ([ATP])-to-P(i) concentration ratio and pH within 5 min, but there was little change in these variables detectable by 31P-NMR with longer periods of ischemia. After reperfusion, the [ATP] and P(i) concentration returned toward normal values in livers exposed to 15 or 35 min of ischemia, but 65 min of ischemia were associated with only modest recovery in [ATP], and the [ATP] later decreased. Because the 31P-NMR spectrum was similar after brief compared with prolonged ischemia, it appears that neither ATP depletion, P(i) accumulation, nor acidosis predicts metabolic recovery. Hepatic intracellular NA+ was also measured in separate groups of animals by 23Na-NMR in the presence of a shift agent, thulium (III) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis (methylene-phosphonate) (TmDOTP5-), and by atomic absorption spectroscopy. Under baseline conditions, the concentration of intracellular Na+ was 15.2 mM by atomic absorption spectroscopy and 16.5 mM by 23Na-NMR. Although the 31P-NMR spectrum responded very rapidly to the onset of ischemia, intracellular Na+ concentration measured by 23Na-NMR increased gradually but steadily at approximately 1.0 mM/min during early (up to 15 min) ischemia. These observations demonstrate that a rise in intracellular Na+ does occur early ischemia, that TmDOTP5- can be applied in vivo for analysis of intracellular Na+ in the ischemic liver, and that 31P-NMR spectroscopy is very sensitive to early ischemic injury.

Adenosine Triphosphate↗
PubMed1994

In vivo studies of cellular energy state, pH, and sodium in rat liver after thermal injury.

In vivo 31P- and 23Na-magnetic resonance spectroscopy was used to measure phosphorus metabolites, intracellular pH, cytosolic free Mg2+, and intracellular Na+ in the liver of rats 24 h after 40% total body surface area full-thickness burn injury. Studies were performed during infusion of thulium (III) 1,4,7,10-tetraazacyclododecane N,N',N",N"'-tetra(methylenephosphonate), which served as the Na+ shift agent. Compared with the sham-burn group, there was a significant increase in hepatic intracellular Na+ along with a decrease in intracellular pH and free Mg2+. The ratio of intra- to extra-cellular Na+ increased, indicating a decreased Na+ gradient that may determine the hepatic transmembrane potential difference. Hepatic beta-ATP/P(i) also significantly decreased, which suggests that either ATP utilization is significantly accelerated or ATP synthesis is inhibited after the thermal injury. Of the cations measured (Na+, Mg2+, H+), the change in intracellular Na+ was most dramatic. This study demonstrates that major burn injury may cause profound changes in hepatic bioenergetics and ionic metabolism 24 h after injury and that intracellular Na+ may be a sensitive indicator of hepatic dysfunction 24 h after injury. Because these animals tolerated the shift reagent, thulium (III) 1,4,7,10-tetraazacyclododecane N,N',N",N"'-tetra(methylenephosphonate), nuclear magnetic resonance spectroscopy may prove valuable in monitoring intracellular cations in the liver after major injury.

Animals↗
PubMed1993

Impact of exogenous insulinlike growth factor 1 on hepatic energy metabolism in burn injury.

BACKGROUND: Insulinlike growth factor 1 (IGF-1) has previously been demonstrated to improve the nutritional status of burned animals. The method by which it achieves this result has not yet been fully elucidated, but may be the result of alterations in hepatic metabolism. OBJECTIVE: To determine if IGF-1 is able to correct the burn-induced impairments in hepatic metabolic function. DESIGN: Seventy-two Sprague-Dawley rats were subjected to a sham burn (n = 24), or a 50% total body surface area scald burn (n = 48). Half the scald burn group received 3 micrograms/kg per day of IGF-1. The remainder received a placebo. The rats were sequentially assayed for multiple components of hepatic function. RESULTS: Insulinlike growth factor 1 corrected the burn-induced decrease in hepatic adenosine triphosphate concentration and prevented the burn-induced increase in hepatic ketone body levels. Insulinlike growth factor 1 was also able to prevent the burn-induced decrease in the hepatic acetoacetate-beta-hydroxybutyrate ratio. Since this ratio is directly proportional to mitochondrial redox potential this indicates that IGF-1 is also able to prevent the burn-induced impairment in hepatic redox potential. CONCLUSIONS: These data indicate that part of the previously demonstrated beneficial effect of IGF-1 in burn injury may be due to its ability to improve multiple components of hepatic metabolism.

Adenosine Triphosphate↗
PubMed1992

The effects of burn injury on the acute phase response.

The time course of changes in the levels of acute-phase-reactant (APR) mRNAs in different tissues of rats with a 10% or a 60% total-body-surface-area (TBSA) burn and the relationship between the induction of APRs and the host's tolerance to thermal injury were studied. The acute phase response in a LPS-induced inflammation model and a burn-plus-LPS model were compared. The results of this study indicated that (1) the major site of APR synthesis is the liver; (2) even a small surface burn injury can elicit a rapid acute phase response, but the intensity of APR expression increases with the severity of the burn; (3) the down regulation of albumin mRNA, which is characteristic of the acute phase response, does not occur even though transferrin (Trf) mRNA levels are significantly decreased; (4) the resistant strain of inbred rats showed higher levels of alpha 1-antitrypsin (AT) mRNA before and after burn injury, indicating its contribution to the host's tolerance to thermal injury; (5) the increases in alpha 1-acid glycoprotein (AGP) and AT expressions are limited in the burn-plus-LPS rat model compared with either the burn model or LPS-stimulated model alone.

Acute-Phase Proteins↗
PubMedDate not supplied

Reperfusion injury in burned rats after delayed fluid resuscitation.

Organ failure from ischemic injury is common in deaths that are due to burn when fluid resuscitation is not performed. Organ perfusion after a delay in resuscitation, however, may induce or even accelerate ischemic organ damage. To study this phenomenon, 40 rats were classified (n = 10) to serve as normal control, burn with no resuscitation, burn with early fluid resuscitation, and burn with delayed resuscitation groups. A modified Walker burn model was used to inflict 50% total body surface area scald burns on the rats. Cellular energy metabolism and tissue water content of several vital organs were measured at 8 hours after burn injury. Adenosine triphosphate, total adenine nucleotides, and energy charge in liver, heart, and kidney tissues were significantly lower (p less than 0.05) with delayed fluid resuscitation compared with early resuscitation. Furthermore, in heart and kidney tissues adenosine triphosphate, total adenine nucleotides, and energy charge were significantly lower in the delayed resuscitation group compared with the group that received no fluid resuscitation. This indicates that heart and kidney tissue are more viable at 8 hours after burn injury, with no fluid resuscitation compared with delayed resuscitation. Water content of lung and muscle tissue were significantly lower (p less than 0.05) in the burn group that received no fluid resuscitation compared with that in early and delayed resuscitation groups. Water content of muscle was significantly greater with delayed resuscitation compared with the early resuscitation group. Results indicate that delayed fluid resuscitation in cases of burn shock may disrupt the cellular energy metabolism in some vital organs and cause skeletal muscle edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMedDate not supplied

Efficacy of leupeptin, superoxide dismutase, and verapamil in modulating delayed reperfusion damage after burn injury.

Reperfusion damage has been identified as an important factor in multiorgan failure after severe burn injury. We wondered if leupeptin, a protease inhibitor, superoxide dismutase (SOD), a scavenger of free oxygen radicals, or verapamil, a calcium antagonist, would protect the cellular energy metabolism when they were given with fluid resuscitation that was delayed 6 hours after a severe burn injury. Fifty male rats weighing 280 to 300 gm received a 50% third-degree scald burn. Ten of these received fluid resuscitation at 30 minutes and 1 1/2 hours after injury, and 40 received delayed fluid resuscitation at 6 and 7 hours after injury. Thirty of these 40 rats were given leupeptin (n = 10), SOD (n = 10), or verapamil (n = 10). Heart, liver, and kidney tissue samples were obtained 8 hours after injury; adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate were measured; and the energy charge potential was calculated. Tissue water content (TWC) in lung and skeletal muscle was also determined. The adenine nucleotide pool and the energy charge potential in heart, liver, and kidney tissue were all significantly decreased (p < 0.01) in rats receiving delayed fluid resuscitation compared with those receiving early resuscitation. Leupeptin was effective in protecting the heart against reperfusion damage, and verapamil and leupeptin showed some efficacy in protecting kidney tissue. Liver tissue, however, showed no protective response with therapy. TWC was significantly decreased (p < 0.01) in skeletal muscle with SOD treatment, and though all treatments appeared to keep lung water content reduced, none was significant at p < 0.01. We thus conclude that both the decreases in heart and kidney adenine nucleotides and the increase in TWC that are caused by delayed fluid resuscitation can be attenuated with appropriate pharmacologic agents.

Adenine Nucleotides↗