Incorporating model quality information in climate change detection and attribution studies.

In a recent multimodel detection and attribution (D&A) study using the pooled results from 22 different climate models, the simulated "fingerprint" pattern of anthropogenically caused changes in water vapor was identifiable with high statistical confidence in satellite data. Each model received equal weight in the D&A analysis, despite large differences in the skill with which they simulate key aspects of observed climate. Here, we examine whether water vapor D&A results are sensitive to model quality. The "top 10" and "bottom 10" models are selected with three different sets of skill measures and two different ranking approaches. The entire D&A analysis is then repeated with each of these different sets of more or less skillful models. Our performance metrics include the ability to simulate the mean state, the annual cycle, and the variability associated with El Niño. We find that estimates of an anthropogenic water vapor fingerprint are insensitive to current model uncertainties, and are governed by basic physical processes that are well-represented in climate models. Because the fingerprint is both robust to current model uncertainties and dissimilar to the dominant noise patterns, our ability to identify an anthropogenic influence on observed multidecadal changes in water vapor is not affected by "screening" based on model quality.

Forced and unforced ocean temperature changes in Atlantic and Pacific tropical cyclogenesis regions.

Previous research has identified links between changes in sea surface temperature (SST) and hurricane intensity. We use climate models to study the possible causes of SST changes in Atlantic and Pacific tropical cyclogenesis regions. The observed SST increases in these regions range from 0.32 degrees C to 0.67 degrees C over the 20th century. The 22 climate models examined here suggest that century-timescale SST changes of this magnitude cannot be explained solely by unforced variability of the climate system. We employ model simulations of natural internal variability to make probabilistic estimates of the contribution of external forcing to observed SST changes. For the period 1906-2005, we find an 84% chance that external forcing explains at least 67% of observed SST increases in the two tropical cyclogenesis regions. Model "20th-century" simulations, with external forcing by combined anthropogenic and natural factors, are generally capable of replicating observed SST increases. In experiments in which forcing factors are varied individually rather than jointly, human-caused changes in greenhouse gases are the main driver of the 20th-century SST increases in both tropical cyclogenesis regions.

Simplified stepwise management of primary spontaneous pneumothorax: a pilot study.

In primary spontaneous pneumothorax (PSP) requiring intervention, removal of air from the pleural space can be achieved by manual needle aspiration or by pleural drainage after insertion of a chest tube. This study aimed to evaluate the efficacy and safety of a serial-steps approach with a single system (small-calibre catheter/Heimlich valve) in a homogeneous population of patients with a first episode of PSP. All patients had an 8.5 F distally multiperforated polyurethane pigtail catheter inserted via the anterior route, at the bedside without any guidance, using the Seldinger technique. A one-way Heimlich valve was connected to the catheter, allowing the air to flow spontaneously outwards for 24-48 h. Thereafter, if the lung failed to re-expand wall suction was applied. Patients with an air leak persisting for >4 days were referred for surgery. Primary end-points were success rates at 24 h and 1 week, and 1 yr recurrence-free survival. In total, 41 consecutive patients entered the study. They were typically thin, young, smoking males. No procedure-related complications were observed. The need for pain relief medication was minimal. Within the first 24 h, most of the patients were able to walk around and half of them were able to take a shower with their catheter in place. The 24-h and 1-week success rates were 61 and 85%, respectively, and the actuarial 1-yr recurrence rate was 24%. Four patients underwent surgical pleurodesis because of a persistent air leak. The length of stay when excluding the four surgical cases was 2.3+/-1.3 days. When 24-h and 1-week success rates and recurrence at 12 months were taken as end-points, the method described here is as effective as simple manual needle aspiration or a conventional chest tube thoracotomy. These results support further studies assessing this "one system, serial-steps approach" in an outpatient management algorithm.

Drier summers cancel out the CO2 uptake enhancement induced by warmer springs.

An increase in photosynthetic activity of the northern hemisphere terrestrial vegetation, as derived from satellite observations, has been reported in previous studies. The amplitude of the seasonal cycle of the annually detrended atmospheric CO(2) in the northern hemisphere (an indicator of biospheric activity) also increased during that period. We found, by analyzing the annually detrended CO(2) record by season, that early summer (June) CO(2) concentrations indeed decreased from 1985 to 1991, and they have continued to decrease from 1994 up to 2002. This decrease indicates accelerating springtime net CO(2) uptake. However, the CO(2) minimum concentration in late summer (an indicator of net growing-season uptake) showed no positive trend since 1994, indicating that lower net CO(2) uptake during summer cancelled out the enhanced uptake during spring. Using a recent satellite normalized difference vegetation index data set and climate data, we show that this lower summer uptake is probably the result of hotter and drier summers in both mid and high latitudes, demonstrating that a warming climate does not necessarily lead to higher CO(2) growing-season uptake, even in high-latitude ecosystems that are considered to be temperature limited.

Interactions of Bax and tBid with lipid monolayers.

The release of cytochrome c from mitochondria to the cytosol is a crucial step of apoptosis that involves interactions of Bax and tBid proteins with the mitochondrial membrane. We investigated Bax and tBid interactions with (i) phosphatidylcholine (PC) monolayer as the main component of the outer leaflet of the outer membrane, (ii) with phosphatidylethanolamine (PE) and phosphatidylserine (PS) that are present in the inner leaflet and (iii) with a mixed PC/PE/Cardiolipin (CL) monolayer of the contact sites between the outer and inner membranes. These interactions were studied by measuring the increase of the lipidic monolayer surface pressure induced by the proteins. Our measurements suggest that tBid interacts strongly with the POPC/DOPE/CL, whereas Bax interaction with this monolayer is about 12 times weaker. Both tBid and Bax interact moderately half as strongly with negatively charged DOPS and non-lamellar DOPE monolayers. TBid also slightly interacts with DOPC. Our results suggest that tBid but not Bax interacts with the PC-containing outer membrane. Subsequent insertion of these proteins may occur at the PC/PE/CL sites of contact between the outer and inner membranes. It was also shown that Bax and tBid being mixed in solution inhibit their insertion into POPC/DOPE/CL monolayer. The known 3-D structures of Bax and Bid allowed us to propose a structural interpretation of these experimental results.

A phase I pharmacokinetic and pharmacodynamic study of the DNA methyltransferase 1 inhibitor MG98 administered twice weekly.

BACKGROUND: Hypermethylation and inactivation of tumor suppressor genes by the enzyme DNA methyltransferase may lead to neoplastic transformation. MG98, a phosphorothioate antisense oligodeoxynucleotide that is a specific inhibitor of mRNA for human DNA methyltransferase 1 (DNMT1), was evaluated in a phase I study. PATIENTS AND METHODS: MG98 was given as a 2 h i.v. infusion twice weekly three weeks out of every four to patients with solid tumors. Pharmacokinetic evaluation was performed on days 1 and 15 of cycle 1 and mRNA expression of DNMT1 was measured in peripheral blood mononuclear cells (PBMCs). RESULTS: Nineteen patients were entered onto the study. A total of 74 cycles (range 1-18 cycles) were administered at dose levels from 40 to 480 mg/m(2). Dose limiting toxicity was seen in two of three patients at 480 mg/m(2) and consisted of a constellation of fever, chills, fatigue and, in one case, confusion beginning within 6 h after the first infusion. Other toxic effects included fatigue, anorexia, nausea, vomiting and diarrhea, reversible elevations in transaminases and partial thromboplastin time. Pharmacokinetic evaluation showed C(max) and AUC to be dose proportional with low inter- and intra-patient variability. No consistent changes in DNMT1 mRNA expression were noted in PBMCs. One partial response was documented in a patient with renal cell carcinoma treated at 80 mg/m(2). CONCLUSIONS: The recommended dose of MG98 was 360 mg/m(2) given by 2 h infusion twice a week for three weeks out of every four. Phase II trials using this dose and schedule are underway.

Management of facial paralysis resulting from temporal bone fractures: Our experience in 115 cases.

OBJECTIVE: The goal of this study was to review decision factors and overall results regarding surgical and nonsurgical management of post-traumatic facial nerve paralysis (FP). STUDY DESIGN: A retrospective study and literature review were performed. METHODS: Between 1984 and 1990, 115 cases of post-traumatic FP were handled. Patients were evaluated through clinical, audiologic, radiologic, and electromyogram assessment. Depending on examination results, patients were treated either medically or surgically through total facial nerve decompression. RESULTS: Forty-nine of the 50 medically treated patients experienced a normal or subnormal facial function recovery (grade I-II). Of the 65 (56.5%) surgically treated patients, 52 (80%) had immediate, 2 had delayed, and 11 (17%) had unknown delay-associated FP. The approaches chosen were middle fossa and transmastoid (75.3%), translabyrinthine (10.7%), or pure transmastoid according to facial nerve nonmotor branch evaluation, hearing, location of the fracture line, and the patient's general condition. Lesions were predominantly found in the geniculate ganglion area (66.2%). A nerve gap was found in only 13.8% of the cases. At 2 years after surgery, 93.8% had a grade I to III recovery. None had grade V or VI. CONCLUSION: The rarity of severe nerve lesions encountered in surgically treated patients raises the question of better selection of candidates for surgery. Surgery is clearly indicated when FP is total, is of immediate onset, and is associated with a bad prognosis electromyogram pattern. In other settings, decisions are to be made based on high-resolution CT data and electromyogram results, thanks to a clinical survey and second electromyogram evaluation.

Biphasic expression of rnrB in Dictyostelium discoideum suggests a direct relationship between cell cycle control and cell differentiation.

Cell differentiation in Dictyostelium is strongly affected by the cell cycle. Cell cycle control is well-understood in other systems, but this has had almost no impact on the study of Dictyostelium cell differentiation, in part because the cell cycle in Dictyostelium is unusual, lacking a G1 phase. Here we describe the cell-cycle regulated expression of rnrB, which codes for the small subunit of ribonucleotide reductase and is a marker of late G1 in many systems. There appear to be two expression peaks, one in mid-G2 and the other near the G2/M transition. Using Xgal/anti-BrdU double staining, we show that cells in asynchronously growing cultures express in both phases, with a gap between them during which the gene is transcriptionally silent. Cold-synchronized cells show exclusively G2/M expression, while mid-G2 expression is seen in high-density synchronized cells and can also be inferred in cells undergoing synchronization by either method. rnrB expression occurs in other systems shortly after cells pass a point (the "restriction point" or "start") at which they commit to complete their current cell cycle. We demonstrate a similar commitment point in Dictyostelium and show that this occurs shortly before the mid-G2 rnrB expression peak. The Dictyostelium cell cycle thus appears to include a well-defined though inconspicuous event, between early and mid-G2, with some features which are normally associated with the G1/S transition. Others have described a switch from stalk to spore differentiation preference at about this time. Since Dictyostelium cells switch back from spore to stalk preference approximately at the G2/M rnrB expression maximum, cell differentiation as well as rnrB expression may be regulated directly by fundamental cell cycle control processes.

Characterization of the human DNA methyltransferase splice variant Dnmt1b.

Tissue- and gene-specific patterns of cytosine-DNA methylation are characteristic features of vertebrate genomes. The generation and proper maintenance of DNA methylation patterns are essential for embryonic development, as demonstrated by the lethal phenotypes of mice with either a targeted disruption of Dnmt1, the gene responsible for the maintenance of DNA methylation, or targeted disruption of Dnmt3a or Dnmt3b, the genes involved in generation of newly formed methylation patterns. Recently, a novel mRNA, Dnmt1b, resulting from alternative splicing of Dnmt1 was identified (Hsu, D. W., Lin, M. J., Lee, T. L., Wen, S. C., Chen, X., and Shen, C. K., (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 9751-9756). The abundance of Dnmt1b mRNA was estimated by semiquantitative reverse transcription polymerase chain reaction and was suggested to encode a major C-5 DNA methyltransferase isoform. Here we report characterization of this novel DNA methyltransferase transcript, Dnmt1b, and its protein product in human cell lines and in freshly isolated human peripheral blood mononuclear cells. The abundance of Dnmt1b transcript, as determined by quantitative RNase protection analysis, was determined to range from 6% to 25% of Dnmt1 in human cells. Second generation antisense inhibitors targeted to the 5'- and 3'-ends of Dnmt1 inhibited the accumulation of both Dnmt1 and Dnmt1b in cells. Dnmt1b protein purified from a baculovirus expression system was demonstrated to be a functional DNA methyltransferase, and to have Michaelis constants for both DNA and S-adenosyl-L-methionine similar to baculovirus-expressed Dnmt1. However, antibodies raised against Dnmt1b epitopes demonstrated that Dnmt1b protein was present at approximately 2-5% of the level of Dnmt1 and therefore represents only a minor DNA methyltransferase isoform in human cells.

Circadian expression of the steroid 15 alpha-hydroxylase (Cyp2a4) and coumarin 7-hydroxylase (Cyp2a5) genes in mouse liver is regulated by the PAR leucine zipper transcription factor DBP.

To study the molecular mechanisms of circadian gene expression, we have sought to identify genes whose expression in mouse liver is regulated by the transcription factor DBP (albumin D-site-binding protein). This PAR basic leucine zipper protein accumulates according to a robust circadian rhythm in nuclei of hepatocytes and other cell types. Here, we report that the Cyp2a4 gene, encoding the cytochrome P450 steroid 15alpha-hydroxylase, is a novel circadian expression gene. This enzyme catalyzes one of the hydroxylation reactions leading to further metabolism of the sex hormones testosterone and estradiol in the liver. Accumulation of CYP2A4 mRNA in mouse liver displays circadian kinetics indistinguishable from those of the highly related CYP2A5 gene. Proteins encoded by both the Cyp2a4 and Cyp2a5 genes also display daily variation in accumulation, though this is more dramatic for CYP2A4 than for CYP2A5. Biochemical evidence, including in vitro DNase I footprinting on the Cyp2a4 and Cyp2a5 promoters and cotransfection experiments with the human hepatoma cell line HepG2, suggests that the Cyp2a4 and Cyp2a5 genes are indeed regulated by DBP. These conclusions are corroborated by genetic studies, in which the circadian amplitude of CYP2A4 and CYP2A5 mRNAs and protein expression in the liver was significantly impaired in a mutant mouse strain homozygous for a dbp null allele. These experiments strongly suggest that DBP is a major factor controlling circadian expression of the Cyp2a4 and Cyp2a5 genes in the mouse liver.

Supraomohyoid neck dissection in cancer of the oral cavity.

BACKGROUND: In oral cavity cancer, supraomohyoid neck dissection (SOHND) is becoming more popular for patients with N0 and N1 disease in the neck. The aim of this study was to assess the value of this surgical procedure. METHODS: The study included 237 previously untreated patients with oral cavity cancer. The neck treatment consisted of SOHND or functional neck dissection (FND). One hundred sixty patients underwent postoperative radiation therapy. Survival probabilities, neck recurrences, and distant metastases were analyzed according to the surgical procedure. RESULTS: For patients having undergone SOHND, the 5-year survival probabilities were 70.2% and 76.5% in N0 and N1 necks, respectively. The neck recurrence rate in SOHND was 2%. CONCLUSIONS: SOHND is an effective method of treatment for the clinically negative neck in patients with squamous cell carcinoma of the oral cavity. It also proves efficient, in conjunction with postoperative radiotherapy, for control of neck metastases in selected patients.

Identification of cis-regulating elements and trans-acting factors regulating the expression of the gene encoding the small subunit of ribonucleotide reductase in Dictyostelium discoideum.

We have examined the promoter of rnrB, the gene encoding the small subunit of ribonucleotide reductase of Dictyostelium discoideum, using lacZ as a reporter gene. Deletion analysis showed that expression of this gene in vegetative cells involves an A/T-rich element, whereas its expression in prespore cells during development requires a region encompassing two G/C-rich elements, designated box A and box B. Removal of boxes A and B results in very low level of activity. When either box A or box B is deleted, prestalk cells adjacent to the prespore zone also express beta-galactosidase. The behavior of these cis-regulatory elements implies that the mechanism regulating the prespore-specific expression of rnrB is different from that regulating other known prespore genes. We have used electrophoretic mobility shift assays to identify factors that interact with box A and box B. Box A interacts with a factor that is found in the nuclear fraction. While box B interacts with a factor that is present in the cytosolic fraction throughout growth and development, its presence in the nuclear fraction is developmentally regulated. Results from competition assays suggest that both box A and box B interact with transcriptional activators that have not been characterized previously.

Purification of a 58-kDa protein (ER58) from monkey liver microsomes and comparison with protein-disulfide isomerase.

A 58-kDa protein (ER58) was purified from monkey liver to apparent homogeneity. It accounts for more than 3% of microsomal proteins and is highly conserved among several mammalian species. The amino acid compositions of the N-terminal part and that of two internal peptide fragments present strong similarities with the sequence ascribed to phospholipase C-alpha. Numerous proteins exhibiting a high similarity with this sequence have been isolated by other investigators. Their biological function is controversial. Our purified protein is not active as a phosphatidylinositol-specific phospholipase C, protease or carnitine acyl transferase. Although less efficient than authentic protein-disulfide isomerase, ER58 catalyses the glutathione-dependent reduction of insulin and the reorganization of disulfide bonds of randomly oxidized (scrambled) ribonuclease in reducing conditions. In contrast, ER58 is devoid of oxidizing activity on thiol groups of reduced proteins. Many studies suggest that the proteins bearing the phospholipase C-alpha sequence could be considered as protein-disulfide isomerase isozymes. Our results indicate that ER58 is not totally similar to protein-disulfide isomerase in performing thiol :protein-disulfide oxidoreductase reactions and suggest that the two proteins may exert distinct cellular functions.

Effect of cell density and epidermal growth factor on the inducible expression of CYP3A and CYP1A genes in human hepatocytes in primary culture.

The influence of cell density and epidermal growth factor (EGF) on the expression and inducibility of cytochrome P450 (CYP) genes of the CYP3A and CYP1A families in adult human hepatocytes in primary culture has been evaluated. Only when cultured at subconfluence and in the presence of EGF did hepatocytes exhibit a proliferative response, assessed by measuring DNA synthesis and cyclin A accumulation. In the absence of EGF, the accumulation of CYP3A4 and CYP1A2 messenger RNAs (mRNAs) in response to their respective inducers (rifampicin and dioxin) was dramatically decreased in subconfluent culture with respect to confluent cultures. The presence of EGF only slightly decreased the accumulation of these mRNAs in both confluent and subconfluent cultures. The accumulation of CYP2D6 and CYP2E1 proteins, which are constitutively expressed in confluent cultures, and the production of fibrinogen and apolipoprotein (Apo) B100 exhibited similar behavior, while nicotinamide adenine dinucleotide phosphate cytochrome c reductase activity was affected neither by cell density nor by EGF. In contrast, the accumulation of CYP1A1 mRNA in response to dioxin was similar in confluent and subconfluent cultures, irrespective of the presence of EGF. Interestingly, CYP3A7, a gene that is preferentially expressed in the fetal liver, was expressed constitutively neither in confluent nor in subconfluent cultures, irrespective of the presence of EGF. It is concluded that the loss of cell-cell contacts rather than the proliferative status of cells per se is responsible for the dramatic decrease in the expression of CYP genes, normally expressed in the adult human liver.

Characterization of a dioxygenase from Trigonella foenum-graecum involved in 4-hydroxyisoleucine biosynthesis.

A study was made of the enzyme in fenugreek implicated in the biosynthesis of 4-hydroxyisoleucine, which is an unusual amino acid known for its insulin stimulating effect. 4-Hydroxyisoleucine was detected by HPLC following isoleucine incubation with a cell-free extract from etiolated 6-day-old fenugreek seedlings in the presence of various cofactors. The reaction showed that 4-hydroxyisoleucine formation is dependent on the presence of Fe2+, 2-oxoglutarate, ascorbate and oxygen. This suggests that a 2-oxoacid dependent dioxygenase plays a key role in this biosynthetic pathway.

[Infrahyoid musculocutaneous flaps: anatomical bases and indications in cervicofacial oncologic surgery]. / Le lambeau musculo-cutané infra-hyoïdien: bases anatomiques et indications en chirurgie carcinologique cervico-faciale.

The infrahyoïd myocutaneous flap has been described by Wang in 1986. Its use seems still limited, although its obvious interest in head and neck reconstructive surgery, especially in oropharyngeal area. Authors expound anatomic bases of this flap, and a 62 case's experience confirming its potential.

A prespore-specific gene of Dictyostelium discoideum encodes the small subunit of ribonucleotide reductase.

We have isolated the gene. rnrB, that encodes the ribonucleotide reductase small subunit of Dictyostelium discoideum. The deduced amino acid sequence of rnrB exhibits about 60% sequence identity with its homologues in other eukaryotes. As demonstrated by RNA blot analysis the rnrB transcript is detected in growing cells and decreases dramatically at the onset of development. The rnrB transcript reappears after the cells have formed multicellular aggregates. To further examine the pattern of expression, we have fused the rnrB promoter and part of its coding sequence to lacZ. The transgenic strain bearing such a reporter construct expresses the fusion gene with a biphasic profile, which is indistinguishable from that of the endogenous rnrB. The multicellular aggregates of Dictyostelium are differentiated along the anterior-posterior axis. Cells in the anterior give rise to the stalk of the fruiting body while cells in the posterior are precursors of spores. Results from histochemical staining show that beta-galactosidase activity is detected exclusively in the posterior two-thirds of the aggregates. These data suggest that rnrB is expressed in prespore cells during postaggregative development and in vegetative cells.

The fetal specific gene CYP3A7 is inducible by rifampicin in adult human hepatocytes in primary culture.

We investigated by RNase protection the differential expression of CYP3A4 and CYP3A7 mRNAs in fetal and adult human livers and in adult hepatocytes in primary culture. Our results show that CYP3A7 is expressed in the liver of 8 of 9 adult Caucasians examined, at an average level of 1.7% of the level found in a fetal liver. CYP3A4 mRNA appeared to be expressed in this fetal liver. In adult hepatocytes in primary culture, the constitutive level of CYP3A4 mRNA was low but detectable after 96 hours in untreated cells, but CYP3A7 mRNA remained undetectable. However, when the cells were treated for 48 hours with 25 microM rifampicin, both CYP3A4 and CYP3A7 mRNAs were strongly induced in the 3 and in 2 of 3 cultures examined, respectively. Using an isoelectric focusing immunoblotting the two proteins were resolved. Protein CYP3A4 was detectable in induced cells but CYP3A7 was not. These results show for the first time that CYP3A7 and CYP3A4 mRNAs, but not the proteins, are co-inducible by rifampicin in adult human hepatocytes in culture.

Oxidative metabolism of zolpidem by human liver cytochrome P450S.

The aim of this study was to identify the form(s) of cytochrome P450 (CYP) responsible for the biotransformation of zolpidem to its alcohol derivatives which, after rapid conversion to carboxylic acids, represents the main way of metabolism in humans. In human liver microsomes, zolpidem was converted to alcohol derivatives. Production of these correlated with the level of CYP3A4 and with cyclosporin oxidation and erythromycin N-demethylation activities, but not with the level of CYP1A2 nor with ethoxyresorufin O-deethylation or S-mephenytoin 4'-hydroxylation activities. Liver microsomes from CYP2D6-deficient patients exhibited normal activity. Production of alcohol derivatives was significantly inhibited by anti-CYP3A antibodies and by ketoconazole. Antibodies directed against other CYP forms (including CYP1A1, CYP1A2, CYP2A6, CYP2B4, and CYP2C8), and CYP-specific substrates or inhibitors (including propranolol, coumarin, mephenytoin, sulfaphenazole, quinidine, aniline, and lauric acid) produced a moderate or no inhibitory effect. cDNA-expressed CYP3A4 and CYP1A2 generated significant amounts of one of the alcohol derivatives, whereas CYP2D6 generated both of them in similar amounts. In human hepatocytes in primary culture, zolpidem was extensively and almost exclusively converted to one of the carboxylic acid derivatives, the main species identified in vivo. Treatment of cells with inducers of CYP1A (beta-naphthoflavone) and CYP3A (rifampicin and phenobarbital) greatly increased the rate of production of this metabolite. We conclude that the formation of alcohol derivatives of zolpidem is rate-limiting and principally mediated by CYP3A4. Both CYP1A2 and CYP2D6 participate in alcohol formation; but, because of their low relative level of expression in the human liver, their contribution is minor.

Luminescent visualization of low amounts of cytochrome P450 and hemoproteins by luminol in acrylamide gels.

In this paper we apply luminol (5-amino-2,3-dihydro-1,4-phthalazinedione), a light-emitting substrate, in conjunction with H2O2 to the luminescence labeling of hemoproteins. We describe in detail a photodetection device which permits an efficient recording of the light emitted by heme-containing proteins resolved in acrylamide gels. The sensitivity of this procedure, when compared to the classical 3,3'-5,5'-tetramethylbenzidine staining method, results in a 5- to 20-fold enhancement with standard hemoproteins (lactoperoxidase, catalase, cytochrome P450 2B4, horseradish peroxidase, hemoglobin, myoglobin, and cytochrome b5). The potential applications of this technique are illustrated by the detection of cytochrome P450 in microsomes from plant as well as from animal extrahepatic tissues which possess low amounts of this cytochrome.