Dynamic 13C NMR analysis of pyruvate and lactate oxidation in the in vivo canine myocardium: Evidence of reduced utilization with increased work

In this work, substrate selection was monitored in the left ventricle of the canine myocardium by following pyruvate and lactate oxidation under in vivo conditions at basal and elevated workloads. These studies were conducted in the open chest model using dynamic ¹³C NMR techniques in the presence and absence of dichloroacetic acid (DCA), a well-known activator of pyruvate dehydrogenase (PDH). Following the infusion of (3-¹³C) pyruvate or (3-¹³C) lactate into the left anterior descending artery, highly variable ¹³C enrichments of glutamate, alanine, aspartate, and citrate were noted under low (RPP <14,500 mmHg/min), intermediate (RPP = 15,000–25,000 mmHg/min), and high (RPP > 25,500 mmHg/min) rate pressure products (RPP). At low workloads, the myocardium typically oxidized the infused (3-¹³C) pyruvate or (3-¹³C) lactate and incorporated the labeled carbon into the glutamate pool as expected. However, in a few notable instances (n = 3), ¹³C-enriched pyruvate and lactate were unable to label the glutamate pool under in vivo conditions even at the lowest RPPs, indicating a lack of selection for these substrates by the tricarboxylic acid (TCA) cycle. Nonetheless, the levels of glutamate C4 enrichment observed at low workloads could usually be enhanced by infusion of DCA. Importantly, ¹³C NMR extract analysis revealed that (3-¹³C) pyruvate or (3-¹³C) lactate labeling of the glutamate pool was reduced (<20%) at high workloads in spite of increased DCA concentrations.     

Arteriovenous malformation with middle cranial fossa expansion a previously unrecorded association

Summary A large temporal arteriovenous malformation with expansion of the middle fossa is described. This previously unreported association is discussed in relation to the possible aetiology.     

Heterotopic ossification enveloping the sciatic nerve following posterior fracture-dislocation of the hip: a case report

Heterotopic ossification developing around the hip and enveloping the sciatic nerve is described in a patient who underwent open reduction and fixation of a large posterior acetabular fragment to decompress and suture the sciatic nerve. The postoperative treatment and a 2-year follow up are also described.     

Gilbert syndrome increasing unconjugated hyperbilirubinemia in a child with hereditary spherocytosis

Hemolytic anemia usually gives rise to only a modest elevation of serum bilirubin. Unconjugated hyperbilirubinemia of an extreme degree should raise suspicion of additional factors. We describe a 10-year-old child suffering from hereditary spherocytosis, who had unusually high levels of unconjugated serum bilirubin and was diagnosed to have Gilbert syndrome on the basis of genetic analysis.     

Metabolism of benzo[a]pyrene in human bronchoalveolar H358 cells using liquid chromatography-mass spectrometry

Benzo[ a]pyrene (B[ a]P), a representative polycyclic aromatic hydrocarbon (PAH), is metabolically activated by three enzymatic pathways: by peroxidases (e.g., cytochrome P450 peroxidase) to yield radical cations, by P4501A1/1B1 monooxygenation and epoxide hydrolase to yield diol epoxides, and by P4501A1/1B1 monooxygenation, epoxide hydrolase, and aldo-keto reductases (AKRs) to yield o-quinones. In humans, a major exposure site for environmental and tobacco smoke PAH is the lung; however, the profile of B[ a]P metabolites formed at this site has not been well characterized. In this study, human bronchoalveolar H358 cells were exposed to B[ a]P, and metabolites generated by peroxidase (B[ a]P-1,6- and B[ a]P-3,6-diones), from cytochrome P4501A1/1B1 monooxygenation [3-hydroxy-B[ a]P, B[ a]P-7,8- and 9,10- trans-dihydrodiols, and B[ a]P- r-7, t-8, t-9, c-10-tetrahydrotetrol (B[ a]P-tetraol-1)], and from AKRs (B[ a]P-7,8-dione) were detected and quantified by RP-HPLC, with in-line photo-diode array and radiometric detection, and identified by liquid chromatography-mass spectrometry (LC-MS). Progress curves showed a lag phase in the formation of 3-hydroxy-B[ a]P, B[ a]P-7,8- trans-dihydrodiol, B[ a]P-tetraol-1, and B[ a]P-7,8-dione over 24 h. Northern blot analysis showed that B[ a]P induced P4501B1 and AKR1C isoforms in H358 cells in a time-dependent manner, providing an explanation for the lag phase. Pretreatment of H358 cells with 10 nM 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) eliminated this lag phase but did not alter the levels of the individual metabolites observed, suggesting that both B[ a]P and TCDD induction ultimately yield the same B[ a]P metabolic profile. The one exception was B[ a]P-3,6-dione which was formed without a lag phase in the absence and presence of TCDD, suggesting that the peroxidase responsible for its formation was neither P4501A1 nor 1B1. Candidate peroxidases that remain include PGH synthases and uninduced P450 isoforms. This study shows that the P4501A1/1B1 and AKR pathways are inducible in human lung cells and that the peroxidase pathway was not. It also provides evidence that each of the pathways of PAH activation yields their distinctive metabolites in H358 human lung cells and that each pathway may contribute to the carcinogenic process.