Metabolism of 7,8-dihydrobenzo(a)pyrene by rat liver microsomal enzymes and mutagenicity of metabolites

7,8-Dihydrobenzo[a]pyrene (7,8-H2BaP) was metabolized by rat liver microsomes to form 7,8,9,10-tetrahydro-BaP trans-9,10-diol, 7,8,9,10-tetrahydro-BaP cis-9,10-diol, 7-hydroxy-7,8-H2BaP, 8-hydroxy-7,8-H2BaP, two phenolic products of 7,8-H2BaP [abbreviated as 7,8-H2BaP phenol 1 and phenol 2 according to their elution order on reversed-phase high-performance liquid chromatography (HPLC)], 4,5,7,8-tetrahydro-BaP trans-4,5-diol, BaP cis-7,8-dihydrodiol, BaP, and the metabolites known to be formed from the metabolism of BaP. Metabolites were isolated by reversed-phase and normal-phase HPLC and identified by ultraviolet-visible absorption and mass spectral analyses and by comparing their retention times with synthetic standards whenever available. The enantiomeric compositions of some mono-ol and diol metabolites were determined by chiral stationary phase HPLC. The optical purities of monool and diol metabolites formed were found to be dependent on the nature of cytochrome P-450 isozymes present in liver microsomes. Metabolites formed by liver microsomes from untreated, phenobarbital-treated, 3-methylcholanthrene-treated, and polychlorinated biphenyls (Aroclor 1254)-treated male Sprague-Dawley rats were quantified by using specifically tritium-labeled [10-3H]-7,8-H2BaP and liquid scintillation counting of fractions collected from reversed-phase HPLC. A portion (2-7% depending on the type of microsomes used) of the BaP found was formed nonenzymatically in microsomal metabolism of 7,8-H2BaP. The formations of other major metabolites were all cytochrome P-450 isozymes dependent since their formations were inhibited by carbon monoxide and were dependent on the presence of reduced nicotinamide adenine dinucleotide phosphate. Furthermore, the formations of tetrahydrodiols, monools, and phenols were not inhibited by the epoxide hydrolase inhibitor, 3,3,3-trichloropropylene 1,2-oxide. The relative mutagenic activities toward Salmonella typhimurium TA98 at 2 nmol of chemical per plate and 10 microliters of liver S9 fraction were: (+/-)BaP trans-7,8-dihydrodiol approximately equal to 7,8-H2BaP approximately equal to 7,8-H2BaP phenol 2 greater than (+/-)Bap cis-7,8-dihydrodiol greater than BaP approximately equal to 8-hydroxy-7,8-H2BaP greater than 7,8-H2BaP phenol 1 greater than 7-hydroxy-7,8-H2BaP. The results suggest that, in addition to the bay region 7,8,9,10-tetrahydro-BaP 9,10-epoxide, metabolic products formed by hydroxylations at the aliphatic and aromatic carbons of 7,8-H2BaP and their subsequent metabolism at the 9,10-double bond may also contribute to the carcinogenic activities of 7,8-H2BaP.     

Optimal vascular delay in cardiomyoplasty following latissimus dorsi muscle isolation in dogs.

BACKGROUND AND PURPOSE: Distal ischemia of the latissimus dorsi muscle (LDM) during cardiomyoplasty is a recognized complication that can reduce the muscle's function and mechanical effects. A 2-week vascular recovery period is recommended to allow revascularization and adhesion to the heart. It is not clear, however, that a 2-week vascular delay is optimal after LDM isolation. This study was designed to evaluate both the regional blood flow (RBF) in canine LDM flaps immediately after perforators were ligated, and the effect of 1-, 2-, and 3-week vascular delays on the regional perfusion of LDM flaps without electrical stimulation. MATERIALS AND METHODS: A catheter-access device connected to the left atrium was implanted in the left back subcutaneous layer in each of six adult mongrel dogs when the LDM was dissected. Five different colored microspheres were injected at five different time points: pre- and post-dissection, and after 1-, 2-, and 3-week vascular delays. At each time point, reference blood was withdrawn from the femoral artery at a fixed speed. The LDMs were removed post mortem for RBF determination. Both tissue and reference blood samples were spectrophotometrically processed to quantify the amount of dye. RESULTS: Proximal RBF did not decrease immediately after dissection when compared to the control (0.28 +/- 0.10 vs 0.26 +/- 0.05 mL.g-1.min-1, p > 0.05), but it decreased after a 1-week vascular delay (0.11 +/- 0.02 vs 0.26 +/- 0.05 mL.g-1.min-1, p < 0.01), and then returned to normal after a 3-week vascular delay (0.21 +/- 0.06 vs 0.26 +/- 0.05 mL.g-1.min-1, p > 0.05). RBF decreased immediately after dissection in the middle and distal segments, and did not return to the control value even after a 3-week vascular delay. CONCLUSION: RBF in the LDM was depressed by surgical dissection in this canine model. Without electrical stimulation, the middle and distal portions of the LDM remained compromised even after a 3-week vascular delay. The clinical effects of progressive programmed electrical stimulation of the LDM at different periods of vascular delay remain to be studied.     

Enhancement by tetraphenylborate of technetium-99m-MIBI uptake kinetics and accumulation in cultured chick myocardial cells

Myocellular uptake and retention of technetium-99m-hexakis (2-methoxyisobutylisonitrile) (Tc-MIBI), a lipophilic cationic myocardial perfusion and viability imaging agent, is dependent on both mitochondrial and plasma-membrane potentials. To test for enhancement of uptake kinetics by lipophilic anions, cultured chick heart cells were exposed to tetraphenylborate (TPB), which produced a concentration-dependent maximal 15-fold increase in Tc-MIBI uptake kinetics (at 3 x 10(-5) M) and enhanced peak accumulation of Tc-MIBI from 165.4 +/- 26.3 to 705.6 +/- 61.3 fmoles/mg protein.nMo (P less than 0.001). Carbonyl cyanide-m-chloro phenylhydrazone (CCCP; 10(-5) M), a mitochondrial uncoupler, rapidly depleted cellular content of Tc-MIBI in the presence of TPB (10(-5) M) from 300.0 +/- 30.0 to 42.5 +/- 1.9 fmole/mg protein.nMo (p less than 0.001). TPB enhanced both uptake rates and net accumulation of Tc-MIBI at all buffer Ko concentrations between 130 mM and 0.54 mM. Tc-MIBI influx rates allowed estimation of plasma-membrane potential as a function of Ko in the presence of valinomycin with a slope of -67 mV/decade (r = -0.99). The results further support a potential-dependent mechanism for cell uptake of Tc-MIBI and suggest a rational approach for increasing tissue extraction fraction in vivo.     

Arterialized tendocutaneous venous flap for dorsal finger reconstruction

We describe three cases of combined loss of skin and tendon on the dorsum of the finger that were reconstructed with venous flaps. The technique is feasible and offers a good treatment modality for the small but complex defect on the dorsum of the finger by a one-stage operation. © 1994 Wiley-Liss, Inc.     

Current perspectives on papillary carcinoma of the thyroid gland.

Papillary carcinoma is the most common of the carcinomas of the thyroid gland, but it is also the one with the best prognosis. At the present, diagnosis is best done by fine needle aspiration, and treatment by surgical resection. With recent advances in molecular and cellular biology, diagnosis and therapy in the future may depend on micromolecular technologies. The prognosis is promising for increased success in the treatment of papillary carcinoma.     

The Saturation Characteristics of Glucose Transport in Bovine Retinal Pigment Epithelium

Purpose: To study the saturation characteristics of the glucose transport across the bovine retinal pigment epithelium(RPE).Methods :The bovine RPE preparations were munted with a modified Ussing chamber. The L-[3H]-glucose and 3-0-methyl-D-[14C]-glucose fluxes across the RPE from the choroid to retina were studied at different glucose concentrations.Results: The glucose transport was found to be stereospecific, with 3-0-methyl-D-glucose (MDG) being transported about three times faster than L-glucose. The glucose transport showed typical saturation characteristics in Michaelis-Menten fashion. The Vmax and the Km of corrected MDG were 2452 nmol cm-2h-1 and 30.8 mM respectively. It was shown that the glucose transport system was saturated at 61.6 mM.Conclusions : The saturation characteristics of the corrected MDG flux suggested that the capacity of glucose transport through the bovine RPE is immense. Eye Science 1998; 14: 726 -729.     

A Clinico-Pathological Analysis of Seventeen Cases of Non-Hodgkin'S Lymphoma Involving the Orbit

Seventeen patients with non-Hodgkin's lymphoma involving the orbit were studied. There were 12 males and 5 females and their median age was 53 years. Three cases were classified as stage I, two as stage II and 12 as stage IV. the histology was small lymphocytic type in 4 of the 5 stage I and II cases, and immunophenotyping, confirming their B-cell origin, was performed in two of these cases. All stage I and II patients responded favourably to local radiotherapy alone. the 12 stage IV patients had a marked male predominance and more commonly an intermediate grade histology and T-immunophenotype. Several of the orbital lesions seemed to represent extension of nasal lymphomas. the stage IV patients had a poorer survival than the stage I and II patients but the difference was not statistically significant, probably due to the small number of patients.