Obstetric anal sphincter injury by maternal origin and length of residence: a nationwide cohort study

OBJECTIVE

To estimate the association between maternal origin and obstetric anal sphincter injury (OASI), and assess if associations differed by length of residence.

DESIGN

Population-based cohort study.

SETTING

The Medical Birth Registry of Norway.

POPULATION

Primiparous women with vaginal livebirth of a singleton cephalic fetus between 2008 and 2017 (n = 188 658).

METHODS

Multivariable logistic regression models estimated adjusted odds ratios (aORs) for OASI with 95% CI by maternal region of origin and birthplace. We stratified models on length of residence and paternal birthplace.

MAIN OUTCOME MEASURES

OASI.

RESULTS

Overall, 6373 cases of OASI were identified (3.4% of total cohort). Women from South Asia were most likely to experience OASI (6.2%; aOR 2.24, 95% CI 1.87-2.69), followed by those from Southeast Asia, East Asia & the Pacific (5.7%; 1.59, 1.37-1.83) and Sub-Saharan Africa (5.2%; 1.85, 1.55-2.20), compared with women originating from Norway. Among women born in the same region, those with short length of residence in Norway (0-4 years), showed the highest odds of OASI. Migrant women across most regions of origin had the lowest risk of OASI if they had a Norwegian partner.

CONCLUSIONS

Primiparous women from Asian regions and Sub-Saharan Africa had up to two-fold risk of OASI, compared with women originating from Norway. Migrants with short residence and those with a foreign-born partner had higher risk of OASI, implying that some of the risk differential is due to sociocultural factors. Some migrants, especially new arrivals, may benefit from special attention during labour to reduce morbidity and achieve equitable outcomes.

TWEETABLE ABSTRACT

Anal sphincter injury during birth is more common among Asian and Sub-Saharan migrants and particularly among recent arrivals.

Patient characteristics, treatment patterns, and clinical outcomes among patients with previously treated recurrent or metastatic cervical cancer: A community oncology-based analysis

OBJECTIVE

There is no standard systemic treatment for recurrent or metastatic cervical cancer (r/mCC) after failure of first-line (1L) therapy. This study characterizes the patient experience, treatment patterns, and clinical outcomes of patients who initiated second-line (2L) therapy for r/mCC in a US community oncology setting.

METHODS

This is an observational study of cervical cancer patients who failed 1L systemic treatment for r/mCC and initiated 2L systemic therapy between 2014 and 2019 within the US Oncology Network (USON). USON's electronic health records were used to identify eligible patients and abstract data. Overall survival (OS), time to treatment discontinuation (TTD), and time to first subsequent treatment (TFST) were estimated using Kaplan-Meier methods.

RESULTS

A total of 130 patients were identified (mean age 53 years). Over 60% of patients had Eastern Cooperative Oncology Group score of 0-1. Cytotoxic monotherapy was the most frequently prescribed regimen (N = 60, 46%) in 2L, followed by combination therapies (N = 45, 35%), pembrolizumab monotherapy (N = 19, 15%), and bevacizumab monotherapy (N = 6, 5%). Median OS was 9.1 months (95% CI: 7.2-12.2) after initiation of 2L therapy. Median TTD was 2.8 months (95% CI: 2.5-3.3), and median TFST was 4.9 months (95% CI: 4.2-5.7). No significant difference in outcomes was found when stratified by 2L treatments.

CONCLUSIONS

The observed heterogeneity in 2L r/mCC therapy suggests no clear standard-of-care in this setting. Additionally, short duration of OS observed was consistent across 2L regimens. New, effective treatment options in this setting are needed.

Communication barriers in maternity care - a questionnaire study among migrants to Norway

Background

Sub-optimal maternity care among migrants has been reported in a number of European countries. Explanations are multifactorial; however, communication barriers have been suggested as a major factor. Our aim was to explore recent migrant women's reported need for interpreter, actual interpreter use and the understanding of information provided during maternity care in Norway.

Methods

As part of the multidisciplinary, mixed method MiPreg-project, we applied a quantitative questionnaire, using a modified version of Migrant Friendly Maternity Care Questionnaire. We included recently (≤ 5 years) migrated women born in low or middle-income countries giving birth in urban Oslo, Norway, during 2019. Face-to-face interviews in women's own language of choice were conducted postpartum.

Results

We included 401 women from 65 countries. The five most frequent languages spoken at home were English, Polish, Arabic, Urdu and Tigrinya. The Norwegian proficiency was low; 23% not at all, 39% with difficulty, 39% good. Two thirds of women would have understood the information during maternity care better in another language. Two out of five felt a need for interpreting services and of these 44% and 81% were not offered interpreter during pregnancy and birth, respectively. The woman's partner or other adult family member interpreted most frequently, followed by professional interpreter and healthcare professionals. The women themselves often felt they understood the information provided; 78% always, 20% sometimes and 2% rarely/never. Increased length of residency and higher education was associated with better understanding, also after adjusting for maternal age and immigrant status.

Discussions

Several communication barriers exist for recent migrant women, with possible consequences for quality of maternity care. Recommended standards for interpretation services were not followed. To address barriers, increased use of interpreter and multilingual antenatal courses could be effective.

Key messages

Low language proficiency and use of interpreter may contribute to disparities in maternity care for migrants. The unmet needs for interpretation services must be addressed with appropriate actions.

Cost effectiveness and impact on quality of life of abobotulinumtoxinA and onabotulinumtoxinA in the treatment of children with lower limb spasticity in Canada

Background: Injectable botulinum neurotoxins are a mainstay of treatment for pediatric spasticity. AbobotulinumtoxinA and onabotulinumtoxinA are both injectable toxin therapies used to treat pediatric lower limb (PLL) spasticity in Canada. The objective of this study was to assess the cost-effectiveness of abobotulinumtoxinA vs. onabotulinumtoxinA in the treatment of PLL spasticity in Canada.Methods: A probabilistic Markov cohort model with a 2-year time horizon was developed, with health states defined by response to therapy, as characterized by the goal attainment scale (GAS). Based on randomized controlled trial evidence, response to therapy was similar or higher for abobotulinumtoxinA relative to onabotulinumtoxinA; uncertainty was incorporated into model parameters, however, as the two therapies have not been compared head-to-head. Canadian resource use and cost data were incorporated.Results: In the base case, abobotulinumtoxinA generated 1.48 quality-adjusted life years over the model time horizon, compared to 1.47 for onabotulinumtoxinA. AbobotulinumtoxinA was associated with cost savings of $123 CAD, reflecting lower costs in both medication acquisition and health services. The estimated improvement to quality of life and reduced costs result in an estimate of economic dominance for abobotulinumtoxinA over onabotulinumtoxinA. This dominant result persisted across probabilistic and scenario analyses.Key points for decision makersBased on a review of available clinical evidence, abobotulinumtoxinA was found to have significant and/or numerical efficacy benefits to onabotulinumtoxinA on functional outcomes (Goal Attainment Scale) and tone (Modified Ashworth Scale) and in the treatment of pediatric lower limb spasticityIn this cost-effectiveness analysis, abobotulinumtoxinA was found to be associated with greater quality-adjusted life years and lower costs than onabotulinumtoxinA (economically dominant)A limitation of this analysis was the uncertainty around key parameters. Specifically, the lack of head-to-head comparison data for the two therapies, and variable data regarding likely onabotulinumtoxinA dosing in PLL in clinical practice. However, across a range of plausible scenarios, the economic dominant result remained.

Prevalence, Patterns, and Cost of Care for Children with Cerebral Palsy Enrolled in Medicaid Managed Care

BACKGROUND

In the United States, many children with cerebral palsy (CP) obtain health care coverage through managed Medicaid, but little is known about the current demographics or management of this high-need, complex population.

OBJECTIVE

To develop U.S. population-level information about the prevalence of CP, management patterns, and costs.

METHODS

Data (2013-2015) were analyzed from a managed Medicaid database with coverage of children and adolescents in 15 states. Analyses included demographic information and use of 10 prespecified CP management options often used to manage spasticity. Code-based algorithms were applied to indicate presence of spasticity and determine the likely ambulatory status.

RESULTS

In this claims analysis, the prevalence estimate of CP was 1.78 per 1,000 patients. Most (69.8%) children with CP had spasticity, of which 20.8% had hemiplegia, 15.6% diplegia, 32.9% quadriplegia, and 30.5% CP unspecified. Overall, 42.4% of children with CP were not treated with any of the 10 CP management options via Medicaid. Among treated children, the most common management options were physical therapy (37.1%), orthotics (29.9%), oral baclofen (13.5%) and botulinum toxins (9.4%). Overall annualized Medicaid costs were higher for children with CP versus children in the overall database population ($22,383 vs. $1,358). Within the CP population, costs were higher for those children who were likely nonambulatory than for those who were likely ambulatory ($43,687 vs. $10,368, respectively).

CONCLUSIONS

Most children with CP have spasticity, and the costs of care are high. This study highlights wide variation in the way CP is managed, with many young patients not receiving CP management options via Medicaid.

DISCLOSURES

This analysis was funded by Ipsen Biopharmaceuticals and conducted by Milliman. Pulgar and Bains were employees of Ipsen Biopharmaceuticals during the conduct of this study. Chambers is a consultant for OrthoPediatrics and an employee of the University of California. Pyenson and Ferro are employees of Milliman, as was Sawhney during the analysis. Gooch, Noritz, and Wright report no conflicts of interest. Part of this work was presented as a poster at TOXINS 2017: Basic Science and Clinical Aspects of Botulinum and Other Neurotoxins, held January 18-21, 2017, in Madrid, Spain.

A novel assay to diagnose hereditary angioedema utilizing inhibition of bradykinin-forming enzymes

BACKGROUND

Hereditary angioedema types I and II are caused by a functional deficiency of C1 inhibitor (C1-INH), leading to overproduction of bradykinin. The current functional diagnostic assays employ inhibition of activated C1s; however, an alternative, more physiologic method is desirable.

METHODS

ELISAs were developed using biotinylated activated factor XII (factor XIIa) or biotinylated kallikrein bound to avidin-coated plates. Incubation with plasma was followed by detection of bound C1-INH.

RESULTS

After standard curves were developed for quantification of C1-INH, serial dilutions of normal plasma were employed to validate the ability to detect known concentration of C1-INH in the plasma as a percent of normal. Hereditary angioedema (HAE) types I and II were then tested. The level of functional C1-INH in all HAE types I and II plasma tested was less than 40% of our normal control. This was evident regardless of whether we measured factor XIIa-C1-INH or kallikrein-C1-INH complexes, and the two assays were in close agreement. By contrast, testing the same samples utilizing the commercial method (complex ELISA, Quidel Corp.) revealed the levels of C1-INH between 0 and 57% of normal (mean, 38%), and 42 samples were considered equivocal (four controls and 38 patients).

CONCLUSIONS

Diagnosis of HAE types I and II can be ascertained by inhibition of enzymes of the bradykinin-forming cascade, namely factor XIIa and kallikrein. Either method yields functional C1-INH levels in patients with HAE (types I and II) that are clearly abnormal with less variance or uncertainty than the commercial method.

Probing the environment of neurotensin whilst bound to the neurotensin receptor by solid state NMR

A functionally active analogue of neurotensin, neurotensin(8-13), has been observed whilst bound to the agonist-binding site of the rat neurotensin receptor by nuclear magnetic resonance (NMR). Through the application of slow magic angle sample spinning and high-power proton decoupling, sufficient resolution and sensitivity were obtained in the carbon-13 spectrum to allow an assignment of many of the side chain resonances arising from uniformly carbon-13/nitrogen-15-labelled neurotensin(8-13) whilst bound to the neurotensin receptor. Significant perturbations in carbon-13 chemical shift were observed upon the binding of the neurotensin(8-13) to the receptor. Most importantly significant shifts were observed in both the carboxy terminus and tyrosine side chain of the neurotensin(8-13), suggesting that these sites are important in the interaction of the neurotensin with the agonist-binding site on the neurotensin receptor. Conversely, no perturbations were observed for the carbon-13 sites within the guanidinium groups of the arginine side chains, indicating little interaction with the receptor-binding site, or a shielding of the local environment by the surrounding nitrogen atoms. These NMR observations lend further support to previous structure-activity studies, site-directed mutagenesis and modelling studies of the agonist-binding site of the neurotensin receptor, from which the same specific residues for which NMR perturbations were observed are important for neurotensin receptor activation by neurotensin.

Effects of sevoflurane on dopamine, glutamate and aspartate release in an in vitro model of cerebral ischaemia

Release of excitatory amino acids and dopamine plays a central role in neuronal damage after cerebral ischaemia. In the present study, we used an in vitro model of ischaemia to investigate the effects of sevoflurane on dopamine, glutamate and aspartate efflux from rat corticostriatal slices. Slices were superfused with artificial cerebrospinal fluid at 34 degrees C and episodes of 'ischaemia' were mimicked by removal of oxygen and reduction in glucose concentration from 4 to 2 mmol litre(-1) for < or = 30 min. Dopamine efflux was monitored in situ by voltammetry while glutamate and aspartate concentrations in samples of the superfusate were measured by HPLC with fluorescence detection. Neurotransmitter outflow from slices was measured in the absence or presence of sevoflurane (4%). After induction of ischaemia in control slices, there was a mean (SEM) delay of 166 (7) s (n = 5) before sudden efflux of dopamine which reached a maximum extracellular concentration of 77.0 (15.2) micromol litre(-1). Sevoflurane (4%) reduced the rate of dopamine efflux during ischaemia (6.90 (1.5) and 4.73 (1.76) micromol litre(-1) s(-1) in controls and sevoflurane-treated slices, respectively; P<0.05), without affecting its onset or magnitude. Excitatory amino acid efflux was much slower. lschaemia-induced glutamate efflux had not reached maximum after 30 min of ischaemia. Basal (pre-ischaemic) glutamate and aspartate efflux per slice was 94.8 (24.8) and 69.3 (31.5) nmol litre(-1) superfusate (n = 4) and was not significantly reduced by 4% sevoflurane. lschaemia greatly increased glutamate and aspartate efflux (to a maximum of 919 (244)% and 974 (489)% of control, respectively). However, ischaemia-induced efflux of both glutamate and aspartate was significantly reduced by 4% sevoflurane (P < 0.001 for glutamate, P < 0.01 for aspartate). In summary, sevoflurane may owe part of its reported neuroprotective effect to a reduction of ischaemia-induced efflux of excitatory amino acids and, to a lesser extent, dopamine.

Imipramine and phenelzine decrease glutamate overflow in the prefrontal cortex--a possible mechanism of neuroprotection in major depression?

Antidepressant drugs have been used for decades, but the neurobiological substrate of their efficacy is not completely understood. Although these drugs have well-established effects on monoamines, evidence is emerging that they may also affect other neurotransmitter systems. It has been shown that treatment with a wide range of antidepressants changes the binding characteristics of the N-methyl-D-aspartate type of glutamate receptor. This change is delayed and occurs only in the cortex. The mechanism that triggers it is unknown. We hypothesized that N-methyl-D-aspartate receptor alterations may be due to changes in the dynamics of cortical excitatory amino acid release. Such changes are of particular interest in areas such as the prefrontal cortex, a region involved in stress responses and affected in major depression. We investigated the effects of two antidepressants with different modes of action, imipramine and phenelzine, on glutamate and aspartate outflow in rat prefrontal cortex and striatum. We showed that antidepressants significantly decreased stimulated glutamate outflow. The effect had a rapid onset, was sustained during chronic administration and was only seen in the prefrontal cortex. This change may initiate receptor alterations. Furthermore, if antidepressants can dampen states of hyperglutamatergic activity and the subsequent excitotoxicity, their chronic use may have a considerable neuroprotective potential in major depression.

A proteomic approach for the study of Saccharomyces cerevisiae cell wall biogenesis

In fungi, cell shape is determined by the presence of a rigid cell wall which separates the cell from the extracellular medium. This highly dynamic structure is essential for the maintenance of cell integrity and is involved in several phenomena such as flocculation, adherence and pathogenicity. The composition of the fungal cell wall is well known, but issues such as the assembly and remodeling of its components remain poorly understood. In an attempt to study the de novo construction of the yeast cell wall, we have undertaken a large-scale proteomic approach to analyze the proteins secreted by regenerating protoplasts. Upon incubation of protoplasts in regenerating conditions, numerous proteins are secreted into the culture medium. These presumably include proteins destined for the cell wall, comprising both structural proteins as well as enzymes involved in cell wall biogenesis. This work reports the establishment of a reference map of proteins secreted by regenerating protoplasts by means of two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and their identification by mass spectrometry. Thirty-two different proteins have been identified, including known cell wall proteins, glycolytic enzymes, heat shock proteins, and proteins involved in several other processes. Using this approach, novel proteins possibly involved in cell wall construction have also been identified. This reference map will allow comparative analyses to be carried out on a selected collection of mutants affected in the cell wall.

Termination of global warmth at the Palaeocene/Eocene boundary through productivity feedback

The onset of the Palaeocene/Eocene thermal maximum (about 55 Myr ago) was marked by global surface temperatures warming by 5-7 degrees C over approximately 30,000 yr (ref. 1), probably because of enhanced mantle outgassing and the pulsed release of approximately 1,500 gigatonnes of methane carbon from decomposing gas-hydrate reservoirs. The aftermath of this rapid, intense and global warming event may be the best example in the geological record of the response of the Earth to high atmospheric carbon dioxide concentrations and high temperatures. This response has been suggested to include an intensified flux of organic carbon from the ocean surface to the deep ocean and its subsequent burial through biogeochemical feedback mechanisms. Here we present firm evidence for this view from two ocean drilling cores, which record the largest accumulation rates of biogenic barium--indicative of export palaeoproductivity--at times of maximum global temperatures and peak excursion values of delta13C. The unusually rapid return of delta13C to values similar to those before the methane release and the apparent coupling of the accumulation rates of biogenic barium to temperature, suggests that the enhanced deposition of organic matter to the deep sea may have efficiently cooled this greenhouse climate by the rapid removal of excess carbon dioxide from the atmosphere.

Mechanisms of climate warming at the end of the paleocene

An abrupt episode of global warming marked the end of the Paleocene epoch. Oxygen and carbon isotope records from two widely separated sites support the notion that degassing of biogenic methane hydrate may have been an important factor in altering Earth's climate. The data show evidence for multiple injections of methane, separated by intervals in which the carbon cycle was in stasis. Correlations between the two sites suggest that even these small-scale events were global in nature.

Single amino acid substitutions disrupt tetramer formation in the dihydroneopterin aldolase enzyme of Pneumocystis carinii

In the opportunistic pathogen Pneumocystis carinii, dihydroneopterin aldolase function is expressed as the N-terminal portion of the multifunctional folic acid synthesis protein (Fas). This region encompasses two domains, FasA and FasB, which are 27% amino acid identical. FasA and FasB also share significant amino acid sequence similarity with bacterial dihydroneopterin aldolases. In the present study, this enzyme function has been overproduced as an independent monofunctional activity in Escherichia coli. Recombinant FasAB-Met23 (amino acids 23-290 of the predicted open reading frame) was purified and shown to contain dihydroneopterin aldolase activity. The native FasAB-Met23 is a tetramer of the 30-kDa subunit, demonstrating characteristics of an associating-dissociating equilibrium system in which only the multimeric form of the enzyme is active. Multiple sequence alignment of FasA and FasB with other dihydroneopterin aldolases highlights only three positions where the amino acid is invariable between all the predicted proteins. The role of these conserved amino acid residues in enzyme function was investigated using site-directed mutagenesis. Mutant FasAB-Met23 species were overproduced and purified to near homogeneity. Three FasA domain mutants and two FasB domain mutants had little or no detectable dihydroneopterin aldolase activity, implicating both FasA and FasB in the catalytic mechanism. We show that each mutant protein containing an inactivating amino acid substitution has lost its ability to form stable tetramers.

Conserved in vivo phosphorylation of calnexin at casein kinase II sites as well as a protein kinase C/proline-directed kinase site

Calnexin is a lectin-like chaperone of the endoplasmic reticulum (ER) that couples temporally and spatially N-linked oligosaccharide modifications with the productive folding of newly synthesized glycoproteins. Calnexin was originally identified as a major type I integral membrane protein substrate of kinase(s) associated with the ER. Casein kinase II (CK2) was subsequently identified as an ER-associated kinase responsible for the in vitro phosphorylation of calnexin in microsomes (Ou, W-J., Thomas, D. Y., Bell, A. W., and Bergeron, J. J. M. (1992) J. Biol. Chem. 267, 23789-23796). We now report on the in vivo sites of calnexin phosphorylation. After 32PO4 labeling of HepG2 and Madin-Darby canine kidney cells, immunoprecipitated calnexin was phosphorylated exclusively on serine residues. Using nonradiolabeled cells, we subjected calnexin immunoprecipitates to in gel tryptic digestion followed by nanoelectrospray mass spectrometry employing selective scans specific for detection of phosphorylated fragments. Mass analyses identified three phosphorylated sites in calnexin from either HepG2 or Madin-Darby canine kidney cells. The three sites were localized to the more carboxyl-terminal half of the cytosolic domain: S534DAE (CK2 motif), S544QEE (CK2 motif), and S563PR. We conclude that CK2 is a kinase that phosphorylates calnexin in vivo as well as in microsomes in vitro. Another yet to be identified kinase (protein kinase C and/or proline-directed kinase) is directed toward the most COOH-terminal serine residue. Elucidation of the signaling cascade responsible for calnexin phosphorylation at these sites in vivo may define a novel regulatory function for calnexin in cargo folding and transport to the ER exit sites.

Creating a supportive environment for Indo-Canadian women

For Indo-Canadian women, pregnancy and delivery can be very difficult because of the women's lack of knowledge of Western medical procedures and techniques. Young women who have recently immigrated are particularly likely to experience some trauma, for their lack of information is compounded by a lack of social support. Many of these young women have immigrated to enter into an arranged marriage, where the husband and his family are relative strangers. When the young woman becomes pregnant, she may experience considerable stress because of the adjustments she is required to make-to a new language, culture, husband and in-law family as well as to the physical changes associated with pregnancy. Her situation is also significantly affected by the traditional role of the young wife in Indian culture: As the junior woman in the family, she has the lowest status.

Restricted expression of a zinc finger protein in male germ cells

Zfp-37 is a zinc finger protein gene expressed in male germ cells. The cDNA detected two transcripts on Northern blots of testis RNA, with expression first detected at around day 19. To establish the pattern of expression of the protein we have raised antibodies to ZFP-37 and used them on thin sections of testis and on Western blots. On Western blots the antibody detected two proteins exclusively in testis extracts, confirming the previous mRNA expression data. A time-course study revealed that the larger of the two proteins appears at about day 22 but the smaller one is not detected until day 34. Analysis of the expression of these two proteins in purified germ cell preparations revealed that the smaller protein is only detectable in the elongating spermatids or residual bodies. Data from thin sections showed that most, but not all, of the protein recognized by the antibody is in the nucleus, a result further confirmed by Western blotting. These results are discussed in the light of the possible role of this protein in regulating spermatogenesis.

The mouse t-complex gene, Tcp-11, is under translational control

The mouse t-complex is known to harbour genes which affect male fertility. Tcp-11 is a t-complex gene which is only expressed in male germ cells and from its position is a candidate for a distorter, one of the two types of genetic element involved in transmission ratio distortion. Antibodies raised to TCP-11 protein made in E. Coli were used on thin sections of testis and shown to recognise late spermatids. On Western blots the antibodies bound to a 68-kD protein present in protein extracts from testis. No specific signal could be detected using the antibody on protein extracts from other mouse tissues. Following gentle lysis of the germ cells and fractionation on sucrose gradients, all the material recognised by the anti-Tcp-11 antibody was found to be soluble and unassociated with any membrane fraction or organelle. A comparison of the time course of expression of the Tcp-11 mRNA and the TCP-11 protein revealed that expression of this gene is under translational control.

Inverse relationship between cytochrome P-450 phosphorylation and complexation with cytochrome b5

Cytochrome P-450 LM2 purified from rabbit liver microsomes has been shown to be a substrate for cAMP-dependent protein kinase. Cytochrome b5, in contrast, was a very poor substrate for cAMP-dependent protein kinase, although it stimulated the activity of the kinase toward histone. When purified rabbit cytochrome b5 was mixed with purified LM2, phosphorylation of LM2 by cAMP-dependent protein kinase was inhibited approximately 80-90%. Recently, a functional covalent complex of cytochrome b5 and LM2 was prepared and purified to homogeneity (P.P. Tamburini and J.B. Schenkman (1987) Proc. Natl. Acad. Sci. USA 84, 11-15). When present as a covalent complex with cytochrome b5, the phosphorylation of LM2 in the complex by cAMP-dependent protein kinase was also inhibited about 80-90% relative to an equivalent amount of LM2 alone. On the other hand, when the LM2 was phosphorylated prior to interaction with cytochrome b5, the ability of the latter to perturb the spin equilibrium of LM2 and oxidation of p-nitroanisole by the LM2 was diminished to an extent comparable to the degree of phosphorylation. The results suggest either that the phosphorylation site on LM2 may be within the cytochrome b5 binding site or that phosphorylation and cytochrome b5 cause mutually exclusive conformational changes in LM2. In addition, eight different forms of cytochrome P-450 from the rat (RLM2, RLM3, fRLM4, RLM5, RLM5a, RLM5b, RLM6, and PBRLM5) were examined as potential substrates for cAMP-dependent protein kinase under the same conditions. Maximal phosphorylation of about 20 mol% was obtained with LM2, and about half as much with PBRLM5. The low extent of phosphorylation of LM2 was not due to the prior presence of phosphate on the enzyme since LM2, as isolated, contains less than 0.1 mol phosphate/mol of enzyme. The other forms of cytochrome P-450 tested showed little or no phosphorylation in vitro despite the presence of a cAMP-dependent protein kinase phosphorylation sequence on at least two of them.