Biomedical subjects

Wenjun Z Martini

Publications and source records attributed to Wenjun Z Martini.

11 recordsLinked to original sources

PubMed2006

Effects of hemorrhage and lactated Ringer's resuscitation on coagulation and fibrinogen metabolism in swine.

Hemorrhagic coagulopathy is a significant complication after traumatic injury, and much of the underlying mechanism remains unclear. We investigated the changes in fibrinogen metabolism and coagulation after a moderate hemorrhage and resuscitation. Pigs of either sex (weight, 40.9+/-0.8 kg) were anesthetized and instrumented with arterial and venous catheters and a thermodilution cardiac output catheter. Pigs were randomized into control (C; n=6), hemorrhage (H; n=6), and hemorrhage and resuscitation (H-LR; n=6) groups. Hemorrhage was induced by bleeding 35% of total blood volume for 30 min in H and H-LR groups. Resuscitation in H-LR group was performed using lactated Ringer's solution (LR) at 3 times the bled volume for 30 min. Fibrinogen metabolism was quantified using a primed constant infusion of 1-13C-phenylalanine (6 h) and d5-phenylalanine (4 h) and subsequent analysis by gas chromatograph-mass spectrometry, together with measurements of hemodynamics (hourly) and coagulation by thromboelastography (at baseline and 4 h after hemorrhage and resuscitation). Hemorrhage caused decreases in arterial pH and base excess, and an increase in arterial lactate content. Fluid resuscitation corrected these changes toward normal levels. Fibrinogen level was unchanged in C and decreased to 76%+/-4% in H and to 73%+/-3% in H-LR (both P<0.05, compared with baseline) after hemorrhage and resuscitation. Fibrinogen breakdown was increased from 3.0+/-0.4 mg kg-1 h-1 in C to 5.4+/-0.6 mg kg-1 h-1 in H and to 5.6+/-0.5 mg kg-1 h-1 in H-LR (both P<0.05, compared with control), but synthesis was unchanged. The clotting reaction time was unchanged in C and shortened to 93%+/-3% in H and to 91%+/-1% in H-LR (both P<0.05, compared with baseline). We conclude that hemorrhagic shock caused accelerated fibrinogen breakdown and coagulation. The LR resuscitation reduced tissue hypoxia indexes but did not affect the changes in fibrinogen metabolism and coagulation from hemorrhage. Thus, effective treatment of hemorrhage should include combining standard-of-care resuscitation with interventions to correct alterations in coagulation.

Animals↗

PubMed2006

Does bicarbonate correct coagulation function impaired by acidosis in swine?

BACKGROUND: Coagulopathy is an important contributor to morbidity and mortality in trauma patients. Acidosis contributes to coagulopathy. Acidosis can be neutralized with intravascular bicarbonate, but it is unclear if the coagulation defect is rapidly reversed. The effects of acidosis and bicarbonate neutralization on coagulation function were investigated in vivo. METHODS: Acidosis was induced in 12 pigs by infusing 0.2 mol/L HCl to pH 7.1. Pigs were then infused with either LR to maintain a pH of 7.1 (A-LR, n = 6) or 0.3 mol/L bicarbonate to a pH of 7.4 (A-Bi, n = 6). Blood samples were taken at baseline, 15 minutes after acidosis induction, and 15 minutes after bicarbonate neutralization. Coagulation function was assessed by prothrombin time (PT), partial thromboplastin time (PTT), thrombin generation, initial clot formation time (R), clotting rapidity (alpha), and clot strength (MA). RESULTS: Compared with baseline values, acidosis reduced fibrinogen concentration to 66% +/- 2% in A-LR and to 71% +/- 3% in A-Bi, and decreased platelet counts to 49% +/- 4% in A-LR and to 53% +/- 4% in A-Bi. Thrombin generation decreased to 60% +/- 4% in A-LR and to 53% +/- 7% in A-Bi. Acidosis prolonged PT and PTT about 20% and decreased alpha and MA. After pH neutralization, fibrinogen and platelet levels remained depleted and no reversal of acidosis-induced changes in thrombin generation, PT, PTT, alpha, and MA were observed. CONCLUSION: Acidosis impaired coagulation by depleting fibrinogen and platelets and by inhibiting clotting kinetics. The deficit associated with acidosis was not reversed with bicarbonate pH neutralization.

Acidosis↗

PubMed2005

Acute changes in fibrinogen metabolism and coagulation after hemorrhage in pigs.

Hemorrhagic coagulopathy is involved in the morbidity and mortality of trauma patients. Nonetheless, many aspects of the mechanisms underlying this disorder are poorly understood. We have therefore investigated changes in fibrinogen metabolism and coagulation function after a moderate hemorrhagic shock, using a new stable isotope approach. Twelve pigs were randomly divided into the control (C) and hemorrhage (H) groups. Hemorrhage was induced by bleeding 35% total blood volume over a 30-min period. A primed constant infusion of [1-(13)C]phenylalanine (Phe), d5-phenylalanine, and alpha-[1-(13)C]-ketoisocaproate (KIC) was given to quantify fibrinogen synthesis and breakdown, together with measurements of circulating liver enzyme activities and coagulation function. Mean arterial pressure was decreased by hemorrhage from 89 +/- 4 mmHg in C to 47 +/- 4 mmHg in H (P < 0.05), followed by a rebound to 68 +/- 5 mmHg afterward. Fibrinogen fractional synthesis rate increased from 2.7 +/- 0.2%/h in C to 4.2 +/- 0.4%/h in H by Phe (P < 0.05) and from 3.1 +/- 0.4%/h in C to 4.4 +/- 0.5%/h in H by KIC (P < 0.05). Fibrinogen fractional breakdown rate increased from 3.6 +/- 1.0%/h in C to 12.9 +/- 1.8%/h in H (P < 0.05). The absolute breakdown rate accelerated from 3.0 +/- 0.4 mg x kg(-1) x h(-1) in C to 5.4 +/- 0.6 mg x kg(-1) x h(-1) in H (P < 0.05), but the absolute synthesis rate remained unchanged. These metabolic changes were accompanied by a reduction in blood clotting time to 92.7 +/- 1.6% of the baseline value by hemorrhage (P < 0.05). No changes were found in liver enzyme activities. We conclude that the observed changes in coagulation after hemorrhagic shock are mechanistically related to the acute acceleration of fibrinogen degradation.

Amino Acids↗

PubMed2005

Independent contributions of hypothermia and acidosis to coagulopathy in swine.

BACKGROUND: Clinical coagulopathy occurs frequently in the presence of acidosis and hypothermia. The purpose of this study was to determine the relative contributions of acidosis and hypothermia to coagulopathy, as measured by current standard bedside and clinical laboratory analyses (i.e., bleeding time and prothrombin time). In addition, we investigated possible mechanisms of these effects using a modified prothrombin time test, thromboelastography, and thrombin kinetics analyses. An improved understanding of coagulopathy should facilitate hemorrhage control. METHODS: Twenty-four pigs were randomly allocated into normal (pH, 7.4; 39 degrees C), acidotic (pH, 7.1; 39 degrees C), hypothermic (pH, 7.4; 32 degrees C), and acidotic and hypothermic (pH, 7.1; 32 degrees C) combined groups. Acidosis was induced by the infusion of 0.2N hydrochloric acid in lactated Ringer's solution. Hypothermia was induced by using a blanket with circulating water at 4 degrees C. Development of a clinical coagulopathy was defined as a significant increase in splenic bleeding time. Measurements were compared before (pre) and 10 minutes after (post) the target condition was achieved. RESULTS: Acidosis, hypothermia, or both caused the development of coagulopathy, as indicated by 47%, 57%, and 72% increases in splenic bleeding time (p < 0.05, pre vs. post). Plasma fibrinogen concentration was decreased by 18% and 17% in the acidotic and combined groups, respectively, but not in the hypothermic group. Hypothermia caused a delay in the onset of thrombin generation, whereas acidosis primarily caused a decrease in thrombin generation rates. At 4 minutes' quench time, thrombin generation in the acidotic, hypothermic, and combined groups were 47.0%, 12.5%, and 5.7%, respectively, of the value in the control group. There were no changes in serum tumor necrosis factor-alpha and interleukin-6 in any group during the study. CONCLUSION: Acidosis and hypothermia cause a clinical coagulopathy with different thrombin generation kinetics. These results confirm the need to prevent or correct hypothermia and acidosis and indicate the need for improved techniques to monitor coagulopathy in the trauma population.

Acidosis↗

PubMed2004

Moderate severity heart failure does not involve a downregulation of myocardial fatty acid oxidation.

Recent human and animal studies have demonstrated that in severe end-stage heart failure (HF), the cardiac muscle switches to a more fetal metabolic phenotype, characterized by downregulation of free fatty acid (FFA) oxidation and an enhancement of glucose oxidation. The goal of this study was to examine myocardial substrate metabolism in a model of moderate coronary microembolization-induced HF. We hypothesized that during well-compensated HF, FFA oxidation would predominate as opposed to a more fetal metabolic phenotype of greater glucose oxidation. Cardiac substrate uptake and oxidation were measured in normal dogs (n = 8) and in dogs with microembolization-induced HF (n = 18, ejection fraction = 28%) by infusing three isotopic tracers ([9,10-(3)H]oleate, [U-(14)C]glucose, and [1-(13)C]lactate) in anesthetized open-chest animals. There were no differences in myocardial substrate metabolism between the two groups. The total activity of pyruvate dehydrogenase, the key enzyme regulating myocardial pyruvate oxidation (and hence glucose and lactate oxidation) was not affected by HF. We did not observe any difference in the activity of carnitine palmitoyl transferase I (CPT-I) and its sensitivity to inhibition by malonyl-CoA between groups; however, malonyl-CoA content was decreased by 22% with HF, suggesting less in vivo inhibition of CPT-I activity. The differences in malonyl-CoA content cannot be explained by changes in the Michaelis-Menten constant and maximal velocity for malonyl-CoA decarboxylase because neither were affected by HF. These results support the concept that there is no decrease in fatty acid oxidation during compensated HF and that the downregulation of fatty acid oxidation enzymes and the switch to carbohydrate oxidation observed in end-stage HF is only a late-stage phenomenon.

Animals↗

PubMed2004

Quantification of DNA synthesis from different pathways in cultured human fibroblasts and myocytes.

We have quantified DNA synthetic rates from different pathways in cultured cells using a new stable isotope technique. Human fibroblasts and myocytes were grown in culture media supplemented with [U-(13)C(6)]glucose and [(15)N]glycine. The cells were sampled daily from day 1 to day 5. A portion of the cells harvested at day 5 was subcultured for an additional 3 passages to reach isotopic plateau. In both cell types total DNA fractional synthetic rate (FSR) was found to agree closely with the rate of cell proliferation determined by cell counting (FSR = 0.94%. h(-1) v 0.92%. h(-1) for DNA synthesis and cell count, respectively, in myocytes and 0.85%. h(-1) v 0.91%. h(-1) for DNA synthesis and cell count, respectively, in fibroblasts). In fibroblasts the deoxyribonucleoside salvage pathway accounted for over 70% of total DNA synthesis. In myocytes the deoxyribonucleoside salvage pathway was minimal, whereas the de novo base synthesis pathway accounted for almost 80% of total DNA synthesis. We conclude that the contributions of various pathways to DNA synthesis are highly dependent on cell type. This new stable isotope technique can be modified for application in in vivo studies.

Carbon Isotopes↗

PubMed2004

The intracellular free amino acid pool represents tracer precursor enrichment for calculation of protein synthesis in cultured fibroblasts and myocytes.

We assessed the approach of using intracellular free amino acid enrichment as precursor enrichment for calculating the fractional synthetic rate of using the stable isotope tracer incorporation technique. We assumed that the true rate of protein synthesis was reflected by the rate of tracer incorporation over time divided by the plateau enrichment in protein. Isolated human fibroblasts and myocytes were cultured in medium supplemented with [(15)N]glycine, [(15)N]proline, and [d(5)]phenylalanine. Culture medium and cells were collected daily from d 1 to 5. A portion of cells harvested on d 5 was subcultured for an additional 3 passages to d 20. Protein enrichments in both cell types reached a plateau after 20 d of cell culture. In fibroblasts, the true protein synthesis rates were 0.74, 0.85, and 0.86%/h, using protein plateau enrichments of [(15)N]glycine, [(15)N]proline, and [d(5)]phenylalanine as precursor enrichments, respectively. When the corresponding intracellular free amino acid enrichments were used, protein synthesis rates were 0.76, 0.79, and 0.76%/h, respectively. Similarly, in myocytes, the true protein synthesis rates were 0.98 and 1.14%/h by protein plateau enrichments of [(15)N]glycine and [d(5)]phenylalanine, respectively. The synthesis rates were 0.94 and 1.01%/h by the corresponding intracellular enrichments, respectively. Extracellular amino acid enrichments resulted in underestimation of protein synthesis by a variable amount. We conclude that the intracellular free amino acid enrichment is an optimal surrogate for precursor enrichment to quantify protein synthesis.

Amino Acids↗

PubMed2004

Fractional synthesis rates of DNA and protein in rabbit skin are not correlated.

We developed a method for measurement of skin DNA synthesis, reflecting cell division, in conscious rabbits by infusing D-[U-(13)C(6)]glucose and L-[(15)N]glycine. Cutaneous protein synthesis was simultaneously measured by infusion of L-[ring-(2)H(5)]phenylalanine. Rabbits were fitted with jugular venous and carotid arterial catheters, and were studied during the infusion of an amino acid solution (10% Travasol). The fractional synthetic rate (FSR) of DNA from the de novo nucleotide synthesis pathway, a reflection of total cell division, was 3.26 +/- 0.59%/d in whole skin and 3.08 +/- 1.86%/d in dermis (P = 0.38). The de novo base synthesis pathway accounted for 76 and 60% of the total DNA FSR in whole skin and dermis, respectively; the contribution from the base salvage pathway was 24% in whole skin and 40% in dermis. The FSR of protein in whole skin was 5.35 +/- 4.42%/d, which was greater (P < 0.05) than that in dermis (2.91 +/- 2.52%/d). The FSRs of DNA and protein were not correlated (P = 0.33), indicating that cell division and protein synthesis are likely regulated by different mechanisms. This new approach enables investigations of metabolic disorders of skin diseases and regulation of skin wound healing by distinguishing the 2 principal components of skin metabolism, which are cell division and protein synthesis.

Amino Acids↗

PubMed2002

Quantitative assessment of anaplerosis from propionate in pig heart in vivo.

Normal cardiac metabolism requires continuous replenishment (anaplerosis) of catalytic intermediates of the citric acid cycle. Little is known about the quantitative aspects of propionate as a substrate of in vivo anaplerosis; therefore, we measured the rate of propionate entry into the citric acid cycle in hearts of anesthetized pigs. [U-(13)C(3)]propionate (0.25 mM) was infused in a coronary artery branch for 1 h via an extracorporeal perfusion circuit, and cardiac biopsies were analyzed for the mass isotopomer distribution of citric acid cycle intermediates. Infusion of propionate did not affect myocardial oxygen consumption, heart rate, or contractile function. In the infused territory, propionate infusion did not affect uptake of glucose and lactate but decreased free fatty acid uptake by one-half (P < 0.05). Propionate extraction and uptake were 57.4 +/- 3.3% and 0.078 +/- 0.009 micromol x min(-1) x g(-1). Anaplerosis from propionate, calculated from the mass isotopomer distribution of succinate, accounted for 8.9 +/- 1.3% of the citric acid cycle flux. Propioylcarnitine release accounted for only 0.033 +/- 0.002% of propionate uptake. Methylcitrate did not accumulate. Thus administration of a low concentration of propionate appears to be a convenient and safe way to boost anaplerosis in the heart.

Animals↗

PubMed2002

Assay of the concentration and (13)C isotopic enrichment of propionyl-CoA, methylmalonyl-CoA, and succinyl-CoA by gas chromatography-mass spectrometry.

We developed gas chromatography-mass spectrometry assays for the concentration and mass isotopomer distribution of propionyl-CoA, methylmalonyl-CoA, and succinyl-CoA in tissues. The assays involves perchloric acid extraction of the tissue, spiking the extract with [(2)H(5)]propionyl-CoA and [(2)H(4)]succinyl-CoA internal standards, and isolation of short-chain acyl-CoA fraction on an oligonucleotide purification cartridge. Propionyl-CoA is reacted with sarcosine and the formed N-propionylsarcosine is assayed as its pentafluorobenzyl derivative. Methylmalonyl-CoA and succinyl-CoA are hydrolyzed and the corresponding acids assayed as tert-butyl dimethylsilyl derivatives. The assay was applied to a study of [U-(13)C(3)]propionate metabolism in perfused rat livers. While propionyl-CoA is only M3 labeled, succinyl-CoA is M3, M2, and M1 labeled because of isotopic exchanges in the citric acid cycle. Methylmalonyl-CoA is M3 and M2 labeled, reflecting reversal of S-methylmalonyl-CoA mutase. Thus, our assays allow measuring the turnover of the coenzyme A derivatives involved in anaplerosis of the citric acid cycle via precursors of propionyl-CoA, i.e., propionate, odd-chain fatty acids, isoleucine, threonine, and valine.

Acyl Coenzyme A↗

PubMedDate not supplied

Dietary fat composition alters pulmonary function in pigs.

OBJECTIVES: We investigated the effect of various dietary fats on pulmonary surfactant composition and lung function changes that occur before and after endotoxin infusion in pigs. METHODS: Eighteen pigs were assigned to three groups (n = 6 per group) to receive a diet of protein (20% of calories), carbohydrate (20% of calories), and fat (40% of calories). In one group the fat content consisted entirely of palmitic acid. In the second group, fat came from Intralipid, which provided predominantly linoleic acid. The third group was fed fish oil. Pigs were maintained on these diets for 21 d before the experiment. Cardiovascular and pulmonary functions were determined on day 22. Pigs then were infused with endotoxin (80 mg. kg(-1). min(-1)) until the pulmonary arterial pressure reached a pressure similar to that found in trauma victims (45 to 50 mmHg). Cardiovascular and pulmonary function tests were then repeated, the animals killed, and the lungs removed for study. RESULTS: Compliance was reduced in the linoleate and fish-oil groups compared with the palmitate group before and after endotoxin. Compliance changes in pigs fed the linoleate and fish-oil diets were consistent with significant increases in lung wet:dry weight ratios, increased CO(2) retention, histologic evidence of vascular congestion, intra-alveolar edema, and alveolar septa thickening. Changes in surfactant phosphatidylcholine composition between groups were consistent with the notion that increased unsaturated fatty acids could affect surfactant function. CONCLUSIONS: We concluded that the common practice of providing calories in the form of polyunsaturated fatty acids to critically ill patients carries the risk of being detrimental to lung function.

Animals↗