Acute Common Peroneal Nerve Decompression After Total Knee Arthroplasty.

Common peroneal nerve palsy (CPNP) after total knee arthroplasty has a reported incidence of 0.3% to 4% and can lead to foot drop, equinovarus deformity, and marked disability if not resolved. Patients typically present in the early postoperative period with weakness or inability to dorsiflex the ankle and decreased sensation of the dorsum of the foot. The authors report their experience, technique, and outcomes of acute peroneal decompression within the first 90 days postoperatively for 5 patients with this unique complication. Preoperatively, all patients had valgus deformity with intact dorsiflexion and sensation of the foot. The diagnosis of CPNP was made on postoperative day 0 or 1 in all cases. After diagnosis, patients were offered acute peroneal decompression and returned to the operating room electively. The surgical technique for dissection, release, and decompression of the nerve is described. At an average follow-up of 12 weeks (range, 6-16 weeks), all patients showed return of motor and sensory function, as tested by ankle dorsiflexion and dorsal foot sensation, with average motor strength of 4.6 of 5.3. Acute decompression of acute CPNP after total knee arthroplasty is a prudent treatment option that provides good functional results and rapid recovery. [Orthopedics. 2021;44(4):e556-e562.].

Presentation and outcome of COVID-19 in HIV patients with high viral loads and opportunistic infections: a case series.

Coronavirus disease 2019 (COVID-19) is especially severe in patients with underlying chronic conditions, with increased risk of mortality. There is concern that people living with HIV (PLWH), especially those with severe immunosuppression, and COVID-19 may have severe disease and a negative clinical outcome. Most studies on COVID-19 in PLWH are from Asia, Europe and America where population dynamics, antiretroviral treatment coverage and coexisting opportunistic infections may differ from that in sub-Saharan Africa. We report on the clinical profile and outcome of three cases of PLWH co-infected with SARS-CoV-2. They all presented with fever, cough and breathlessness and also had advanced HIV infection as evidenced by opportunistic infections, high HIV viral loads and low CD4 counts. The patients responded favourably to the standard of care and were discharged home. Our findings suggest that PLWH with advanced immunosuppression may not necessarily have an unfavourable disease course and outcome. However, case-controlled studies with a larger population size are needed to better understand the impact of COVID-19 in this patient population. FUNDING: Not declared.

Clinical characteristics of males with systemic lupus erythematosus (SLE) in an inception cohort of patients in Ghana.

BACKGROUND: Systemic Lupus Erythematosus (SLE) is said to be rare in Sub-Saharan Africa and even rarer in males worldwide. SLE is mostly considered a disease of women, though men may also be affected, and this may lead to a delay in diagnosis in men. The result is a greater burden of inflammation and subsequent organ damage over time. METHOD: Data from the medical records of 13 male patients diagnosed with SLE at the Rheumatology Clinic of Korle- Bu Teaching Hospital between January 2014 and January 2017 was retrospectively analyzed. RESULTS: A total of 13 male patients out of a total of 134 SLE patients were included in our analysis. The mean age was 30.62 ± SD 8.47 years (range of 17 to 46 years). All of them (100%) presented with constitutional features. The most common ACR criteria observed was 61.5 % rash, 54.5 % oral ulcers, 92.3% arthritis, 61.5 % serositis and 38.5% renal involvement, 46.2 % CNS involvement. Looking at their serological profile, 91.7 % had a positive antinuclear antibody (ANA). 33.3 % had positive anti-dsDNA and 58.3 % extractable nuclear antigens. The mean duration from onset of symptoms to diagnosis was 21.31 months. Five patients were diagnosed with lupus nephritis, all at the time of diagnosis. There were no mortalities. CONCLUSION: Male SLE patients in Ghana are comparable to other populations, with arthritis and constitutional features being predominant early features and lupus nephritis being the main early indicator of organ damage. This should warrant aggressive management in male patients. FUNDING: None declared.

Mid-Term Results of Modular Tapered Femoral Stems in Revision Total Hip Arthroplasty.

BACKGROUND: In revision total hip arthroplasty (THA), modular femoral components aid the surgeon in reconstructing joints compromised by loss of bone and soft-tissue integrity, providing customization to address bony deficits, deformity, limb length, and offset challenges. The purpose of this study was to review the survival and outcomes at minimum five-year follow up of patients who underwent revision THA at our center with a single modular femoral revision hip system offering a wide range of proximal body and distal stem geometries and sizing options. MATERIALS AND METHODS: A query of our practice arthroplasty registry revealed 66 consented patients (69 hips) who underwent revision THA using a modular femoral stem between December 2009 and July 2013 with minimum five-year follow up. There were 35 men (53%) and 31 women (47%). Mean age was 65.2 years (range, 36-87). Etiology for index revision was 32 aseptic loosening, 20 infection, nine periprosthetic fracture, three nonunion of internal fixation, three instability, one stem breakage, and one metal complication. RESULTS: Mean follow up was 6.3 years (range, 5-9). Harris Hip Scores improved from a mean of 45.4 preoperatively to 72.0 at most recent evaluations. There have been four re-revisions of the femoral stem: one infection, two periprosthetic femoral fracture, and one (proximal segment only) for instability. Radiographic assessment revealed satisfactory position, fixation, and alignment in all hips. Radiographic subsidence of 6-10mm occurred in four (none revised), and none had subsidence > 10mm. There were no modular junction failures. Kaplan-Meier survival to endpoint of femoral revision was 93.3% (95% CI ±3.3%) at 8.7 years. CONCLUSIONS: The minimum five-year results of this modular THA revision system are promising, with low rates of aseptic failure, minimal subsidence, and no modular junction failures. While there may be roles for the use of non-modular revision stems, the mid-term clinical results in this cohort of patients was found to be acceptable.

Community perceptions of a malaria vaccine in the Kintampo districts of Ghana.

BACKGROUND: Malaria remains the leading cause of morbidity and mortality in sub-Saharan Africa despite tools currently available for its control. Making malaria vaccine available for routine use will be a major hallmark, but its acceptance by community members and health professionals within the health system could pose considerable challenge as has been found with the introduction of polio vaccinations in parts of West Africa. Some of these challenges may not be expected since decisions people make are many a time driven by a complex myriad of perceptions. This paper reports knowledge and perceptions of community members in the Kintampo area of Ghana where malaria vaccine trials have been ongoing as part of the drive for the first-ever licensed malaria vaccine in the near future. METHODS: Both qualitative and quantitative methods were used in the data collection processes. Women and men whose children were or were not involved in the malaria vaccine trial were invited to participate in focus group discussions (FGDs). Respondents, made up of heads of religious groupings in the study area, health care providers, traditional healers and traditional birth attendants, were also invited to participate in in-depth interviews (IDIs). A cross-sectional survey was conducted in communities where the malaria vaccine trial (Mal 047RTS,S) was carried out. In total, 12 FGDs, 15 IDIs and 466 household head interviews were conducted. RESULTS: Knowledge about vaccines was widespread among participants. Respondents would like their children to be vaccinated against all childhood illnesses including malaria. Knowledge of the long existing routine vaccines was relatively high among respondents compared to hepatitis B and Haemophilus influenza type B vaccines that were introduced more recently in 2002. There was no clear religious belief or sociocultural practice that will serve as a possible barrier to the acceptance of a malaria vaccine. CONCLUSION: With the assumption that a malaria vaccine will be as efficacious as other EPI vaccines, community members in Central Ghana will accept and prefer malaria vaccine to malaria drugs as a malaria control tool. Beliefs and cultural practices as barriers to the acceptance of malaria vaccine were virtually unknown in the communities surveyed.

Soft-diet feeding decreases dopamine release and impairs aversion learning in Alzheimer model rats.

To examine the effects of soft-diet feeding on the dopaminergic system in a model rat for Alzheimer's disease (AD), we measured dopamine release in the hippocampus using a microdialysis approach and assessed learning ability and memory using step-through passive avoidance tests. Furthermore, we immunohistochemically examined the ventral tegmental area (VTA), which is the origin of hippocampal dopaminergic fibers using tyrosine hydroxylase (TH), a marker enzyme for the dopaminergic nervous system. Feeding a soft diet decreased dopamine release in the hippocampus and impaired learning ability and memory in AD model rats in comparison with rats fed a hard diet; however, TH-immunopositive profiles in the VTA seemed not to be notably different between rats fed a soft diet and those fed a hard diet. These observations suggest that soft-diet feeding enhances the impairment of learning ability and memory through the decline of dopamine release in the hippocampus in AD rats.

Genetic diversity and antigenic polymorphism in Plasmodium falciparum: extensive serological cross-reactivity between allelic variants of merozoite surface protein 2.

Diversity in the surface antigens of malaria parasites is generally assumed to be a mechanism for immune evasion, but there is little direct evidence that this leads to evasion of protective immunity. Here we show that alleles of the highly polymorphic merozoite surface protein 2 (MSP-2) can be grouped (within the known dimorphic families) into distinct serogroups; variants within a serogroup show extensive serological cross-reactivity. Cross-reactive epitopes are immunodominant, and responses to them may be boosted at the expense of responses to novel epitopes (original antigenic sin). The data imply that immune selection explains only some of the diversity in the msp-2 gene and that MSP-2 vaccines may need to include only a subset of the known variants in order to induce pan-reactive antibodies.

Induction of CYP2A5 by pyrazole and its derivatives in mouse primary hepatocytes.

Mouse liver CYP2A5 is induced by several structurally unrelated compounds. In intact mouse liver, pyrazole (PYR) and 4-hydroxypyrazole (4-OH) induce selectively the expression of CYP2A5 while expression of other CYPs is decreased. In this study we exposed mouse primary hepatocytes to PYR, 4-OH, 4-methylpyrazole (4Me; 0.1-20 mM) and 4-iodopyrazole (4-I; 0.1-5.0 mM). PYR and its derivatives increased coumarin 7-hydroxylase activity, with 4-1 and 4-OH being the strongest inducers, by 114-fold and 41-fold, respectively. However, only 4-1 treatment increased markedly the CYP2A5 protein content. CYP2B9/10-mediated pentoxyresorufin O-deethylase activity (PROD) was decreased by 80% by 4-Me and 4-1, and by 50% by 4-OH while PYR had no marked effect. PYR and 4-Me increased 2- to 3-fold the CYPA1/2-mediated ethoxyresorufin O-deethylase activity (EROD) while 4-OH and 4-1 had no marked effect on this enzyme. The time of exposure markedly affected the inducibility of 4-OH such that induction was 7-fold stronger when it was added to the incubation medium 24 h after the isolation of hepatocytes compared to exposure 3 h after their isolation. Cimetidine prevented the induction of coumarin 7-hydroxylase activity by PYR and 4-OH by 46 and 74%, respectively indicating that their effects on the expression of CYP2A5 are, at least partly, mediated via their metabolites. The data demonstrate that the regulation of CYP2A5 is different from other monooxygenases and that the effects of pyrazole and its derivatives are different in vivo and in vitro. Also, the timing of exposure markedly affects the inducibility of 4-OH in hepatocytes.

Distinct responses of mouse hepatic CYP enzymes to corn oil and peroxisome proliferators.

We studied the response of male DBA/2N mouse liver monooxygenases to acute (one-day) and subacute (7-day) exposure to clofibrate, gemfibrozil, and corn oil. The day following a single treatment with clofibrate (200 mg/kg), coumarin 7-hydroxylase (COH) activity decreased significantly (by 70%) with a concomitant decrease in the CYP2A4/5 protein and mRNA levels. The 7-day treatment schedule also decreased COH activity by only by 30%, though the levels of CYP2A4/5 protein and mRNA were still low. Treatment 1 and 7-day with clofibrate decreased 7-pentoxyresorufin O-dealkylase (PROD) activity by 40%. No changes were seen in testosterone 15 alpha-hydroxylase (T15 alpha OH) activity after 1 day of treatment with clofibrate but, after 7 days, it was decreased by 50%. Clofibrate treatment had no significant effects on testosterone 7 alpha-hydroxylase (T7 alpha OH), 7-ethoxyresorufin O-deethylase (EROD), or benzphetamine N-demethylase (BZDM) activities. Gemfibrozil (200 mg/kg) did not alter COH activity or CYP2A4/5 protein content after a single treatment, but a slight decrease was seen in the mRNA level. Treatment for 7 days significantly increased (2.5-fold) the activity and mRNA content but the amount of protein remained unchanged. Gemfibrozil enhanced (2-2.7-fold PROD and EROD (2-2.5-fold) activities by both treatments, whereas T15 alpha OH, T7 alpha OH, or BZDM activities were not significantly affected. Treatment with corn oil for 7 days significantly decreased (65%) COH activity and CYP2A4/5 protein and mRNA levels. PROD (55%) and T15 alpha OH (65%) activities were significantly decreased even after a single dose although injection for 7 days had no effect. Neither of the corn oil schedules had any marked effect on T7 alpha OH, EROD, or BZDM activities. These results demonstrate: 1. a decrease in the expression of CYP2A4/5 gene by clofibrate and corn oil; 2. substantial differences within the CYP2A subfamily in their responses to corn oil, clofibrate, and gemfibrozil; and 3. distinct responses of other xenobiotic metabolizing CYP subfamily enzymes to clofibrate and gemfibrozil.

CYP enzymes catalyze the formation of a terminal olefin from 2-ethylhexanoic acid in rat and human liver.

1. The metabolism of 2-ethylhexanoic acid (2-EHA) was studied in rat, mouse and human liver microsomes in vitro. The metabolites of 2-EHA were identified as methylated derivatives by gas chromatography-mass spectrometry. 2. 2-Ethyl-1,6-hexanedioic acid was the main metabolite produced in rat, mouse and human liver microsomes. Unsaturated 2-ethyl-5-hexenoic acid, a terminal olefin, was produced only in human liver microsomes and phenobarbital-induced rat liver microsomes. The cytochrome P450 (CYP) inhibitors metyrapone, SKF 525A, triacetyloleandomycin (TAO), quinidine and the cytochrome P450 reductase antibody abolished its formation both in rat and human microsomes. 3. The metabolites were analyzed also in vivo in urine of 2-EHA-exposed rats and in urine of sawmill workers exposed occupationally to 2-EHA. Both rat and human urine contained 2-ethyl-1,6-hexanedioic acid as the main metabolite and also 2-ethyl-5-hexenoic acid. Metyrapone, SKF 525A and TAO all decreased drastically the formation of 2-ethyl-5-hexenoic acid in the rat. 4. The data indicate that (1) several CYP families (CYP2A, CYP2B, CYP2D and CYP3A) could be responsible for the hepatic metabolism of 2-EHA, (2) the same metabolites were formed in rats and man and (3) an unsaturated terminal olefin, 2-ethyl-5-hexenoic acid is formed in the liver.

Regenerative changes in hepatic morphology and enhanced expression of CYP2B10 and CYP3A during daily administration of cocaine.

The effects of daily cocaine administration for up to 14 days were studied in terms of hepatic morphology and the expression of cytochrome P450 (CYP) enzymes in the mouse liver. Daily intraperitoneal doses of 60 mg/kg of cocaine for 3 days induced severe hepatocellular necrosis in the pericentral zone and decreased activities of CYP1A2, CYP2A4/5, and CYP2Cx. The microsomal CYP2B10 protein content was increased by about 2.5-fold, but 2B10-dependent 7-pentoxyresorufin O-dealkylase (PROD) activity was barely detectable. Five or seven daily cocaine doses caused prominent pericentral inflammation and a significant (up to 14-fold) increase in the microsomal protein content and PROD activity. An increase in microsomal CYP3A was also evident, but CYP2A5 and CYP1A2 still remained at a low level. Immunohistochemical examination showed that the relative induction of CYP2B10 and CYP3A after treatment with cocaine was strongest in perivenous hepatocytes. Immunoinhibition experiments showed that CYP2B10 accounted for catalysis of only 15% to 20% of the enhanced microsomal cocaine N-demethylase (CNDM) activity, which correlated well with immunoreactive 3A protein, and could be blocked 70% to 90% by triacetyloleandomycin. After 10 or 14 daily doses of cocaine, regenerative changes with hepatocyte ballooning were observed, coinciding with increases in CYP1A2, CYP2A4/5, and CYP3A. These results suggest the following: (1) cocaine enhances its own cytochrome P450-dependent metabolism; (2) increased production of norcocaine in microsomes is catalyzed mainly by CYP3A enzyme(s), whereas 2B10, although markedly increased by cocaine treatment, has only a minor role in cocaine hepatotoxicity; and (3) despite increased microsomal CNDM activity, cocaine-induced liver injury is reversible in mice.

Effects of simulated nuclear fuel particles on the histopathology and CYP enzymes in the rat lung and liver.

We studied both short-term (3 and 30 days) and long-term (3-24 months) effects of simulated nuclear fuel particles (neutron-activated UO2) on the rat lung and liver histopathology and cytochrome P450 (CYP) activities. In the short-term study, after a single intratracheal instillation with neutron-activated particles (administered activity 36 kBq), the lung histology revealed inflammation and a decrease in several lung testosterone hydroxylation levels. Liver exhibited normal histology but hepatic testosterone 7alpha-hydroxylase (T7alphaOH) was decreased by 30% at 3 days treatment with neutron-activated particles (9.3 kBq). At 30 days after treatment, hepatic T7alphaOH and testosterone 15alpha-hydroxylase activities were enhanced by 70 and 40%, respectively. At the long-term follow-up, benign and malignant lung tumors were observed but in the livers only slightly increased inflammation was found. At the 1.5-year follow-up (cumulated lung dose 0.4-0.66 Gy, 131 and 182 kBq), decreases in lung testosterone 6beta-hydroxylase (60%) and testosterone 6alpha-hydroxylase (30%) activities were found. In contrast to lungs, hepatic testosterone 16alpha-hydroxylase activity decreased by 60-75% with both nonactivated and neutron-activated particles. These findings indicate that when lung is exposed to nonactivated UO2 or beta-emitting UO2 particles they have differential effects on CYP enzymes in both the primary target organ (lung) and secondary tissue (liver).

Cytochrome P4502A5 expression and inducibility by phenobarbital is modulated by cAMP in mouse primary hepatocytes.

Factors involved in CYP2A5 expression were studied in mouse liver primary hepatocytes in culture. CYP2A5-mediated coumarin 7-hydroxylase (COH) activity was retained in simple culture conditions for at least 96 hours and the activity was inducible up to 33-fold by phenobarbital (PB). The constitutive activity and inducibility of COH was totally blocked by treatment of hepatocytes with actinomycin D, and short initial treatment with cycloheximide caused superinducibility when co-administered with PB. Treatment of hepatocytes with inhibitors of protein kinase C, tyrosine kinases and a generator of nitric oxide did not affect COH basal activity or inducibility. Administration of dibutyryl cAMP, forskolin, and 3-isobutyl-1-methylxanthine (IBMX) enhanced both basal and PB-induced COH activities and CYP2A5 mRNA levels, indicating that cAMP plays a major role in CYP2A5 expression.

Interindividual variability of coumarin 7-hydroxylation in healthy volunteers.

A test designed to estimate the extent and rate of formation of 7-hydroxycoumarin by measuring the urinary excretion of the metabolite in humans after administering 5 mg coumarin was developed. Coumarin was rapidly metabolized after oral administration and more than 95% of the 7OHC formed was excreted in 4 h. The total amount of 7OHC formed was 64 +/- 15% (mean +/- SD, variation 20-100%) of the dose given. The percentage of 7OHC excreted in 2 h, as compared with the 7OHC excretion in 4 h, was found to be a constant and stable individual characteristic for the rate of the formation of 7OHC ('2 h coumarin test'). In 110 volunteers, there was a great interindividual variability in the extent and rate of 7OHC formation. Four individuals had relatively 'slow' coumarin test values (50-60%), but much larger populations would be needed for the demonstration of polymorphism.

Regulation of the mouse liver cytochrome P450 2B subfamily by sex hormones and phenobarbital.

The sex-dependent expression and inducibility of the cytochrome P450 2B subfamily was studied in DBA/2 and Balb/c mice, and their F1 recombinants, at the mRNA, protein and activity levels. Analysis of poly(A)+ RNA with specific oligonucleotide probes directed to known mRNAs within the mouse 2B subfamily revealed that the levels of P450 2b-10 and 2b-9 mRNAs were co-regulated with two proteins (56 and 53 kDa) detected by a 2B-specific polyclonal antibody. Other mRNAs related to the 2B subfamily were barely or not at all detectable, and did not coincide with protein expression, suggesting that P450s 2b-9 and 2b-10 are the major 2B isoenzymes present in mouse liver. Specifically, castration of males increased the expression of 2b-9 and 2b-10 mRNAs and protein up to female levels, and testosterone administration to castrated mice reversed these changes. Ovariectomy of females appears to increase the expression of these P450s slightly. 2b-10, but not 2b-9, mRNA and protein were induced by phenobarbital. Based on immunoinhibition studies and the levels of these isoenzymes, P4502b-10 appears to be the major catalyst of 7-pentoxyresorufin O-dealkylation. Both P4502b-9 and P4502b-10 contribute up to 30% of the testosterone 16 alpha-hydroxylation, the balance being catalysed by P450s within the 2D subfamily. These experiments show that the female-predominant expression of the two mouse liver isoenzymes P4502b-9 and P4502b-10 is dependent on sex hormones. The fact that P4502b-9 does not respond to phenobarbital, while P4502b-10 is regulated by both phenobarbital and sex hormones, demonstrates the complexity of P450 expression even within one subfamily.

Inducibility of P450Coh by pyrazole and its derivatives.

Pyrazole and several of its derivatives increase the hepatic microsomal coumarin 7-hydroxylase to a variable extent. The strongest inducers are pyrazole itself and those derivatives which have a hydroxy group or a halogen at the 4-position of the molecule. The increase in coumarin 7-hydroxylase is due to an increase in the microsomal P450Coh and the corresponding mRNA. The increase of P450Coh by pyrazole and 4-hydroxypyrazole is selective because several other mono-oxygenase enzymes and the total P450 content are either not affected or even decreased. These include the testosterone 15 alpha-hydroxylase (P45015 alpha), a close structural analogue of P450Coh, which is induced only marginally by pyrazole and even decreased by 4-iodopyrazole, and P450ac which is decreased by pyrazole and 4-hydroxypyrazole. Introducing a methyl residue at the 4-position will alter the induction properties of the compound essentially bymaking it less selective for P450Coh. These results demonstrate the special selective action of pyrazole and some of its derivatives on the hepatic microsomal mono-oxygenase complex and the unique mode of regulation of the cytochrome P450Coh even within the same subfamily of cytochromes P450.

Preferential inhibition of mouse hepatic coumarin 7-hydroxylase by inhibitors of steroid metabolizing monooxygenases.

Etomidate, metomidate and metyrapone, all potent inhibitors of steroid metabolizing monooxygenases, inhibit preferentially coumarin 7-hydroxylase (COH) amongst several liver microsomal monooxygenase activities from control and pyrazole-treated D2 mice in vitro. SKF-525A, an inhibitor of phenobarbital-inducible monooxygenase activities has a much weaker effect on COH than the other three drugs, even though COH is a phenobarbital-inducible enzyme. Treatment of mice with eto- and metomidate decreases the microsomal COH also in vivo while the other activities remained unchanged (with the exception of 7-ethoxycoumarin O-deethylase (ECDE) in case of metomidate). Despite of the decrease in COH no parallel decrease in the amount of microsomal P450Coh (P450 isoenzyme highly active in the 7-hydroxylation of coumarin) could be found in dot immuno-binding analysis. These data suggest that among several liver microsomal P450 isoenzymes, metyrapone, eto- and metomidate interact preferentially with the P450Coh and that eto- and metomidate may alter selectively the catalytic properties of P450Coh leading to decreased enzyme activity. Two different Ks-values could be found for all three drug in their binding to microsomal cytochrome(s) P450. Based on substrate binding spectra, potassium ferricyanide treatment does not dissociate the complex between reduced P450 and metomidate and does it only partly for etomidate. Furthermore potassium ferricyanide treatment of microsomes does not increase COH after in vivo treatment of mice with eto- and metomidate. These data further suggest that the complex between P450Coh and eto- and metomidate may be particularly strong and independent from the redox state of the haem iron.

Hepatic mitochondrial coumarin 7-hydroxylase: comparison with the microsomal enzyme.

The specific activity of cytochrome P450-linked coumarin 7-hydroxylase (COH) of hepatic mitoplasts from DBA/2N mice is up to 55% as great as the microsomal activity. According to Western blot and immunodiffusion analysis and inhibition studies with anti-P450Coh and metyrapone, the mitoplastic P450Coh had the same molecular weight and immunochemical and catalytic properties as the corresponding microsomal enzyme. The inducibility of the two proteins by pyrazole and their genetic regulation, as studied with DBA/2N and AKR/J mice, appears to be similar. However, the mitochondrial electron transfer system was not able to support the COH activity of reconstituted microsomal P450Coh although the enzyme was fully active with the microsomal NADPH-cytochrome P450 reductase. This indicates some differences between the two proteins with respect to their interaction with the electron transfer system. This was confirmed by the ability of anti-adrenodoxin reductase antibody to effectively inhibit the mitoplastic COH but not the COH reconstituted with purified microsomal P450Coh and NADPH-P450 reductase. We have previously found that P450Coh does not react with anti-P450b or anti-P450c antibodies, which recognize respective isoforms in rat liver mitoplasts. While P450Coh from microsomes and mitoplasts possess a number of properties in common, the mitoplast P450Coh represents a new subspecies of mitochondrial P450. Some characteristics of mitoplast P450Coh may be the result of post-translational modifications necessary for processing and translocation into the mitochondria.

Mouse hepatic cytochrome P-450 isozyme induction by 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene, pyrazole, and phenobarbital.

The effects of 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) and pyrazole on mouse hepatic cytochrome P-450 isozyme expression were compared to the P-450 induction pattern elicited by phenobarbital. TCPOBOP and PB administration caused a similar induction profile by increasing microsomal protein and cytochrome P-450 content and the catalytic activities of several monooxygenases in DBA/2N and AKR/J mice. There were, however, several quantitative and some qualitative differences in the induction profile caused by phenobarbital and TCPOBOP. A few strain-related differences were also observed. Immunoblot analysis with polyclonal anti-coumarin hydroxylase (P-450Coh) antibody and epitope-specific monoclonal antibodies 1-7-1 and 2-66-3 showed that both phenobarbital and TCPOBOP increase the amount of P450IIB and P-450Coh. TCPOBOP caused a more pronounced increase in the amount of P-450IIB than phenobarbital, and TCPOBOP also caused an increase in the amount of P-450IA2. These data suggest that in the mouse, TCPOBOP increases mainly the expression of P-450 isozymes responsive to phenobarbital. The effects of pyrazole differed greatly from those caused by TCPOBOP and phenobarbital. In the DBA/2N mice, pyrazole increased coumarin 7-hydroxylation 9.4-fold, whereas in the AKR/J mice the activity was induced only to a level equivalent to the DBA/2N basal level. In immunoblot experiments with anti-P-450Coh antibody, the amount of P-450Coh was considerably higher in DBA/2N mice treated with phenobarbital, TCPOBOP, or pyrazole in comparison with the AKR/J mice, indicating a strain specificity in the inducibility of coumarin 7-hydroxylase by pyrazole.