Brain activity changes associated with pain perception variability.

Pain perception can be modulated by several factors. Phenomena like temporal summation leads to increased perceived pain, whereas behavioral conditioning can result in analgesic responses. Furthermore, during repeated, identical noxious stimuli, pain intensity can vary greatly in some individuals. Understanding these variations is important, given the increase in investigations that assume stable baseline pain for accurate response profiles, such as studies of analgesic mechanisms. We utilized functional magnetic resonance imaging to examine the differences in neural circuitry between individuals displaying consistent pain ratings and those who experienced variable pain during a series of identical noxious stimuli. We investigated 63 healthy participants: 31 were assigned to a "consistent" group, and 32 were assigned to a "variable" group dependent on pain rating variability. Variable pain ratings were associated with reduced signal intensity in the dorsolateral prefrontal cortex (dlPFC). Furthermore, the dlPFC connectivity with the primary somatosensory cortex and temperoparietal junction was significantly reduced in variable participants. Our results suggest that investigators should consider variability of baseline pain when investigating pain modulatory paradigms. Additionally, individuals with consistent and variable pain ratings differ in their dlPFC activity and connectivity with pain-sensitive regions during noxious stimulation, possibly reflecting the differences in attentional processing and catastrophizing during pain.

Facilitators and barriers to patient-centred goal-setting in rehabilitation: A scoping review.

OBJECTIVE: Identify, map, and synthesize existing reviews, to extract and analyse the most prominent barriers and facilitators to applying patient-centred goal-setting practice in rehabilitation using the Capability, Opportunity Motivation Behaviour (COM-B) model. DESIGN: Scoping review. DATA SOURCE: A primary search was conducted in MEDLINE, CINAHL, EMBASE, PsychInfo, and Cochrane. Citation chaining was employed. REVIEW METHODS: All types of review (systematic, scoping, and narrative) studies published up to June 14, 2022 that included physical and neurological rehabilitation, patient-centeredness, and goal-setting were reviewed. Studies were scrutinized for relevance, quality was not assessed. The most prominent barriers and facilitators were synthesized using thematic content analysis and mapped onto the COM-B model. RESULTS: Twenty-six review studies covering a range of conditions and settings, acute to community were included. Barrier and facilitators were identified at patient, provider, and organizational level. Barrier themes include provider's existing beliefs about goal-setting, lack of skills, and integration into clinical routines. Patient barriers related to capacity and opportunity to participate. Organizational barriers include lack of clinical guidelines, patient preparation, insufficient provider time, and high productivity expectations. Facilitators included goal-setting guidelines, training and education of providers and patients, revised clinical routines, performance monitoring, adequate time, and resources. CONCLUSION: Healthcare providers should be the primary target of intervention. A provider's motivation to change current practice is the most prominent barrier, followed closely by capacity and opportunity. Patients require information, training, and structured engagement opportunities. Organizations play a key role in creating the optimal environmental conditions to enable patient-centred goal-setting.

Improvements in pain, medication use and quality of life in onabotulinumtoxinA-resistant chronic migraine patients following erenumab treatment - real world outcomes.

BACKGROUND: The CGRP antagonists offer a novel therapeutic approach in migraine. Their utility in patients with severe forms of chronic migraine is a subject of particular interest. We present outcomes of 9 months of erenumab treatment in a cohort of patients with difficult-to-control chronic migraine, all of whom had prior unsatisfactory response to onabotulinumtoxinA. METHODS: We offered erenumab to 98 patients with a prior unsatisfactory response to onabotulinumtoxinA. Eighty of 98 had trialled greater occipital nerve injections (82%), 32/98 peripheral neurostimulation (33%) and 18/98 intravenous dihydroergotamine (18%). Thirty eight of 98 (39%) met the definition of triptan overuse and 43/98 (44%) analgesic overuse. All patients met the EHF criteria for 'resistant migraine'. Outcome measures (recorded monthly) included days with headache limiting activities of daily living ("red"), not limiting ("amber"), headache free ("green"), and requiring triptans or other analgesics. Quality of life scores - headache impact test 6 (HIT-6), patient health questionnaire 9 (PHQ-9) and pain disability index (PDI) - were also measured. RESULTS: Mean number of red days improved by - 6.4 days (SE 0.67, 95%CI - 7.7 to - 5.1, p=0.001) at 3 months; - 6.8 days (SE 0.96, 95%CI - 8.80 to - 4.9, p=0.001) at 6 months and - 6.5 days (SE 0.86, 95%CI - 8.3 to - 4.8, p=0.001) at 9 months. Repeated measures ANOVA confirmed improvements in the number of red (p=0.001), green (p=0.001), triptan (p=0.001) and painkiller days (p=0.001) as well as scores of the HIT-6 (p=0.001), PHQ-9 (p=0.001), and PDI (p=0.001) across the duration of study. CONCLUSION: We observed improvements in pain, medication use and quality of life in onabotulinumtoxinA-resistant chronic migraine patients following erenumab treatment.

Disseminated Saksenaea infection in an immunocompromised host associated with a good clinical outcome: a case report and review of the literature.

BACKGROUND: Saksenaea species (spp.) are uncommon causes of mucormycosis but are emerging pathogens mostly associated with trauma and soil contamination often in immunocompetent hosts. Due to lack of sporulation in the laboratory, diagnosis and susceptibility testing is difficult so optimal treatment regimens are unknown. CASE PRESENTATION: A 67 year-old man from the Northern Territory in Australia, with a history of eosinophilic granulomatosis with polyangiitis, developed disseminated Saksenaea infection after initially presenting with symptoms consistent with bacterial pyelonephritis. Despite a delay in diagnosis; with aggressive surgical management and dual therapy with amphotericin B and posaconazole, he survived. CONCLUSIONS: We describe an unusual case of disseminated infection with a favourable outcome to date.

Palladium-catalysed methoxycarbonylation of ethene with bidentate diphosphine ligands: a density functional theory study.

Catalytic methoxycarbonylation of ethene with a bidentate tertiary phosphine (DTBPX) and palladium has been explored at the B3PW91-D3/PCM level of density functional theory. Three different pathways for formation of methyl propanoate (MePro) have been studied, namely carbomethoxy (A), ketene (B) and hydride-hydroxyalkylpalladium pathways (C), the latter of which is favoured because it has the lowest overall kinetic barrier. After intermolecular methanolysis, a hydroxyalkylpalladium complex has been characterised on pathway C, which eventually leads to the low overall barrier to produce MePro. The possibility of copolymerisation leading to oligo-/polymers has also been considered. With a computed selectivity of >99% towards the formation of MePro and a reasonably low overall kinetic barrier of 23.0 kcal mol-1, pathway C appears to be the most plausible one. Consistent with experimental data, the overall barrier increases to 30.1 kcal mol-1 for a less bulky bidentate phosphine.

Patient preferences for topical treatment of actinic keratoses: a discrete-choice experiment.

BACKGROUND: The treatment of actinic keratosis (AK) is a potentially effective strategy for the prevention of cutaneous squamous cell carcinoma (cSCC). However, the patient perspective on potential benefits of AK treatment in terms of skin cancer reduction has received little attention to date. OBJECTIVES: (i) To investigate patient preferences for topical treatments for AK using a discrete-choice experiment (DCE); (ii) to evaluate patient willingness to trade between clinical benefit and medical burden. METHODS: The DCE was conducted as part of a study to establish the feasibility of a phase III randomized controlled trial evaluating the prevention of cSCC using currently available topical interventions. Preferences were elicited by asking patients to make a series of choices between treatment alternatives with different hypothetical combinations of attribute levels. Willingness to trade between treatment attributes was estimated using a flexible-choice model that allows for the heterogeneity of patient preferences. RESULTS: A total of 109 patients with AK completed the DCE. The majority of patients who expressed valid preferences were willing to accept some reduction in both prophylactic and cosmetic efficacy to reduce the burden of the treatment regimen, the severity of skin reaction and other adverse effects. Patients may reject treatment if the perceived therapeutic benefit is outweighed by the subjective burden of treatment. CONCLUSIONS: Evidence of significant variation in the perceived utility of treatments across patients highlights the importance of taking individual patient preferences into account to improve AK treatment acceptability and adherence.

Can We Do That Here? Establishing the Scope of Surgical Practice at a New Safety-Net Community Hospital Through a Transparent, Collaborative Review of Physician Privileges.

PROBLEM DEFINITION: Stewarding of physician privileges wisely is imperative, but no guidelines exist for how to incorporate system-level factors in privileging decisions. A newly opened, safety-net community hospital tailored the scope of surgical practice through review of physician privileges. Martin Luther King, Jr. Community Hospital is a public-private partnership, safety-net institution in South Los Angeles that opened in July 2015. It has 131 beds, including a 28-bed emergency department, a 20-bed ICU, and 5 operating rooms. Staff privileging decisions were initially based only on physicians' training and experience, but this resulted in several cases that tested the boundaries of what a small community hospital was prepared to handle. ITERATION AND PIVOTS: A collaborative, transparent process to review physician privileges was developed. This began with physician-only review of procedure lists, followed by a larger, multidisciplinary group to assess system-level factors. Specific questions were used to guide discussion, and unanimous approval from all stakeholders was required to include a procedure. An initial list of 558 procedures across 11 specialties was reduced to 321 (57.5%). No new cases that fall outside these new boundaries have arisen. KEY INSIGHTS: An inclusive process was crucial for obtaining buy-in and establishing cultural norms. Arranging transfer agreements remains a significant challenge. NEXT STEPS: Accumulation of institutional experience continues through regular performance reviews. As this hospital's capabilities mature, a blueprint has been established for expanding surgical scope of practice based explicitly on system-level factors.

Understanding a Hydroformylation Catalyst that Produces Branched Aldehydes from Alkyl Alkenes.

This paper reports experimental and computational studies on the mechanism of a rhodium-catalyzed hydroformylation that is selective for branched aldehyde products from unbiased alkene substrates. This highly unusual selectivity relies on a phospholane-phosphite ligand prosaically called BOBPHOS. Kinetic studies using in situ high pressure IR (HPIR) and the reaction progress kinetic analysis methodology suggested two steps in the catalytic cycle were involved as turnover determining. Negative order in CO and positive orders in alkene and H2 were found and the effect of hydrogen and carbon monoxide partial pressures on selectivity were measured. Labeling studies found rhodium hydride addition to the alkene to be largely irreversible. Detailed spectroscopic HPIR and NMR characterization of activated rhodium-hydrido dicarbonyl species were carried out. In the absence of H2, reaction of the rhodium-hydrido dicarbonyl with allylbenzene allowed further detailed spectroscopic characterization of four- and five-coordinate rhodium-acyl species. Under single-turnover conditions, the ratios of branched to linear acyl species were preserved in the final ratios of aldehyde products. Theoretical investigations uncovered unexpected stabilizing CH-π interactions between the ligand and substrate which influenced the high branched selectivity by causing potentially low energy pathways to become unproductive. Energy span and degree of TOF control analysis strongly support experimental observations and mechanistic rationale. A three-dimensional quadrant model was built to represent the structural origins of regio- and enantioselectivity.

The rise of methicillin resistant Staphylococcus aureus: now the dominant cause of skin and soft tissue infection in Central Australia.

This study aimed to examine the epidemiology and treatment outcomes of community-onset purulent staphylococcal skin and soft tissue infections (SSTI) in Central Australia. We performed a prospective observational study of patients hospitalised with community-onset purulent staphylococcal SSTI (n = 160). Indigenous patients accounted for 78% of cases. Patients were predominantly young adults; however, there were high rates of co-morbid disease. Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was the dominant phenotype, accounting for 60% of cases. Hospitalisation during the preceding 6 months, and haemodialysis dependence were significant predictors of CA-MRSA infection on univariate analysis. Clinical presentation and treatment outcomes were found to be comparable for methicillin-susceptible S. aureus (MSSA) and methicillin-resistant cases. All MRSA isolates were characterised as non-multi-resistant, with this term used interchangeably with CA-MRSA in this analysis. We did not find an association between receipt of an active antimicrobial agent within the first 48 h, and progression of infection; need for further surgical debridement; unplanned General Practitioner or hospital re-presentation; or need for further antibiotics. At least one adverse outcome was experienced by 39% of patients. Clindamycin resistance was common, while rates of trimethoprim-sulfamethoxazole resistance were low. This study suggested the possibility of healthcare-associated transmission of CA-MRSA. This is the first Australian report of CA-MRSA superseding MSSA as the cause of community onset staphylococcal SSTI.

Misremembering emotion: Inductive category effects for complex emotional stimuli.

Memories of objects are biased toward what is typical of the category to which they belong. Prior research on memory for emotional facial expressions has demonstrated a bias towards an emotional expression prototype (e.g., slightly happy faces are remembered as happier). We investigate an alternate source of bias in memory for emotional expressions - the central tendency bias. The central tendency bias skews reconstruction of a memory trace towards the center of the distribution for a particular attribute. This bias has been attributed to a Bayesian combination of an imprecise memory for a particular object with prior information about its category. Until now, studies examining the central tendency bias have focused on simple stimuli. We extend this work to socially relevant, complex, emotional facial expressions. We morphed facial expressions on a continuum from sad to happy. Different ranges of emotion were used in four experiments in which participants viewed individual expressions and, after a variable delay, reproduced each face by adjusting a morph to match it. Estimates were biased toward the center of the presented stimulus range, and the bias increased at longer memory delays, consistent with the Bayesian prediction that as trace memory loses precision, category knowledge is given more weight. The central tendency effect persisted within and across emotion categories (sad, neutral, and happy). This article expands the scope of work on inductive category effects to memory for complex, emotional stimuli.

Insights into structure and redox potential of lignin peroxidase from QM/MM calculations.

Redox potentials are computed for the active form (compound I) of lignin peroxidase (LiP) using a suitable QM/MM methodology (B3LYP/SDD/6-311G**//BP86/SVP:CHARMM). Allowing for dynamic conformational averaging, a potential of 0.67(33) V relative to ferrocenium/ferrocene is obtained for the active form with its oxoiron(iv) core. The computed redox potential is very sensitive to the charge distribution around the active site: protonation of titratable residues close to the metal center increases the redox potential, thereby rationalising the known pH dependence of LiP activity. A simple MM-charge deletion scheme is used to identify residues that are critical for the redox potential. Two mutant proteins are studied through homology modelling, E40Q and D183N, which are predicted to have an increased redox potential by 140 mV and 190 mV, respectively, relative to the wild type. These mutant proteins are thus promising targets for synthesis and further exploration toward a rational design of biocatalytic systems for oxidative degradation of lignin.

Meeting report: Emerging respiratory viral infections and nonhuman primate case reports.

A workshop on Emerging Respiratory Viral Infections and Spontaneous Diseases in nonhuman primates was sponsored by the concurrent Annual Meetings of the American College of Veterinary Pathologists and the American Society for Veterinary Clinical Pathology, held December 1-5, 2012, in Seattle, Washington. The session had platform presentations from Drs Karen Terio, Thijs Kuiken, Guy Boivin, and Robert Palermo that focused on naturally occurring influenza, human respiratory syncytial virus, and metapneumovirus in wild and zoo-housed great apes; the molecular biology and pathology of these viral respiratory diseases in nonhuman primate (NHP) models; and the therapeutic and vaccine approaches to prevention and control of these emerging respiratory viral infections. These formal presentations were followed by presentations of 14 unique case studies of rare or newly observed spontaneous lesions in NHPs (see online files for access to digital whole-slide images corresponding to each case report at http://scanscope.com/ACVP%20Slide%20Seminars/2012/Primate%20Pathology/view.apml). The session was attended by meeting participants that included students, pathology trainees, and experienced pathologists from academia and industry with an interest in respiratory and spontaneous diseases of NHPs.

Advancing NMR-based metabolomics using complete reduction to amplitude frequency table: Cultivar differentiation of black ripe table olives as a case study.

In NMR-based untargeted analysis, Fourier transformation is applied to the time-domain data to extract observables such as frequency and intensity. Despite its wide application, this approach has several limitations that can prevent NMR from reaching its highest potential. Here, we utilized Bayesian analysis through CRAFT as an alternative method, using California-style table olives as a model system. Our hypothesis was that the time-domain analysis through CRAFT will be as successful as the traditional approach. The results showed that CRAFT generated efficient unsupervised and supervised models in a robust, and rapid/automated manner. The duration of CRAFT analysis can be further reduced by using the first 14 k complex data points of the initial part of the FID, without affecting the performance of the untargeted analysis. For unsupervised analysis, CRAFT was generally more efficient, while for supervised analysis both approaches were effective. CRAFT can be also used for identifying marker compounds driving classifications.

Using the capability, opportunity, and motivation model of behaviour to assess provider perception of implementing solution-focused goal-setting in paediatric rehabilitation.

Adoption of family and child goal-setting in paediatric rehabilitation is important to positive long-term outcomes. Solution-focused coaching (SFC) has been identified as a promising approach to ensuring this type of goal-setting occurs, while the actual implementation of SFC by health care providers (HCPs) is low. This study utilized the capacity, opportunity, and motivation model of behaviour change (COM-B) to identify which strengths and difficulties health care providers (HCPs) perceived with respect to SFC goal-setting in paediatric rehabilitation. A self-report survey was developed and administered to HCPs at a paediatric rehabilitation hospital. Each survey question was based upon a COM-B sub-component. Demographic information was collected from HCPs, and descriptive statistics were used to rank perceived COM-B components from strongest to weakest. Results indicate HCPs view the provision of SFC goal-setting as an important practice, while they also perceive difficulties to actual delivery due to: lack of adequate individual skill, lack of experience with this type of goal-setting, and insufficient preparation for clients to engage in sharing their goals. HCPs also perceived lack of organizational processes to support the practice within their teams. Recommendations for intervention are provided.

SKIN REINNERVATION BY COLLATERAL SPROUTING FOLLOWING SPARED NERVE INJURY IN MICE.

Following peripheral nerve injury, denervated tissues can be reinnervated via regeneration of injured neurons or via collateral sprouting of neighboring uninjured afferents into the denervated territory. While there has been substantial focus on mechanisms underlying regeneration, collateral sprouting has received relatively less attention. In this study, we used immunohistochemistry and genetic neuronal labeling to define the subtype specificity of sprouting-mediated reinnervation of plantar hind paw skin in the mouse spared nerve injury (SNI) model, in which productive regeneration cannot occur. Following an initial loss of cutaneous afferents in the tibial nerve territory, we observed progressive centripetal reinnervation by multiple subtypes of neighboring uninjured fibers into denervated glabrous and hairy plantar skin. In addition to dermal reinnervation, CGRP-expressing peptidergic fibers slowly but continuously repopulated the denervated epidermis, Interestingly, GFRα2-expressing nonpeptidergic fibers exhibited a transient burst of epidermal reinnervation, followed by trend towards regression. Presumptive sympathetic nerve fibers also sprouted into the denervated territory, as did a population of myelinated TrkC lineage fibers, though the latter did so less efficiently. Conversely, rapidly adapting Aß fiber and C fiber low threshold mechanoreceptor (LTMR) subtypes failed to exhibit convincing collateral sprouting up to 8 weeks after nerve injury. Optogenetics and behavioral assays further demonstrated the functionality of collaterally sprouted fibers in hairy plantar skin with restoration of punctate mechanosensation without hypersensitivity. Our findings advance understanding of differential collateral sprouting among sensory neuron subpopulations and may guide strategies to promote the progression of sensory recovery or limit maladaptive sensory phenomena after peripheral nerve injury. Significance Statement: Following nerve injury, whereas one mechanism for tissue reinnervation is regeneration of injured neurons, another, less well studied mechanism is collateral sprouting of nearby uninjured neurons. In this study, we examined collateral sprouting in denervated mouse skin and showed that it involves some, but not all neuronal subtypes. Despite such heterogeneity, a significant degree of restoration of punctate mechanical sensitivity is achieved. These findings highlight the diversity of collateral sprouting among peripheral neuron subtypes and reveal important differences between pre- and post-denervation skin that might be appealing targets for therapeutic correction to enhance functional recovery from denervation and prevent unwanted sensory phenomena such as pain or numbness.

Memory for target height is scaled to observer height.

According to the embodied approach to visual perception, individuals scale the environment to their bodies. This approach highlights the central role of the body for immediate, situated action. The present experiments addressed whether body scaling--specifically, eye-height scaling--occurs in memory when action is not immediate. Participants viewed standard targets that were either the same height as, taller than, or shorter than themselves. Participants then viewed a comparison target and judged whether the comparison was taller or shorter than the standard target. Participants were most accurate when the standard target height matched their own heights, taking into account postural changes. Participants were biased to underestimate standard target height, in general, and to push standard target height away from their own heights. These results are consistent with the literature on eye-height scaling in visual perception and suggest that body scaling is not only a useful metric for perception and action, but is also preserved in memory.

A case of VIPoma.

This case report addresses the management of a pregnant woman in the peripartum period with a VIPoma. This rare and highly malignant neuroendocrine tumour secretes vasoactive intestinal peptide (VIP), a substance that may cause potentially life-threatening disruption to physiology. A 36-year-old woman presented for induction of labour with a three-year history of chronic diarrhoea, hypophosphataemia, palpitations and skin flushing. Raised VIP levels indicated presence of a VIPoma, however despite extensive investigation prior to pregnancy by neuroendocrine specialists, the tumour location remained unidentified. The patient delivered a healthy boy with the aid of forceps in theatre following an epidural top-up. Key features of management were a multidisciplinary approach, avoidance of triggers for VIP secretion, strict management of electrolytes and avoidance of severe changes in sympathetic tone during labour with epidural analgesia.

Development and clinical validation of multiplex TaqMan® assays for rapid diagnosis of viral gastroenteritis.

There is a need to provide rapid, sensitive, and often high throughput detection of pathogens in diagnostic virology. Viral gastroenteritis is a serious health issue often leading to hospitalization in the young, the immunocompromised and the elderly. The common causes of viral gastroenteritis include rotavirus, norovirus (genogroups I and II), astrovirus, and group F adenoviruses (serotypes 40 and 41). This article describes the work-up of two internally controlled multiplex, probe-based PCR assays and reports on the clinical validation over a 3-year period, March 2007 to February 2010. Multiplex assays were developed using a combination of TaqMan™ and minor groove binder (MGB™) hydrolysis probes. The assays were validated using a panel of 137 specimens, previously positive via a nested gel-based assay. The assays had improved sensitivity for adenovirus, rotavirus, and norovirus (97.3% vs. 86.1%, 100% vs. 87.8%, and 95.1% vs. 79.5%, respectively) and also more specific for targets adenovirus, rotavirus, and norovirus (99% vs. 95.2%, 100% vs. 93.6%, and 97.9% vs. 92.3%, respectively). For the specimens tested, both assays had equal sensitivity and specificity for astrovirus (100%). Overall the probe-based assays detected 16 more positive specimens than the nested gel-based assay. Post-introduction to the routine diagnostic service, a total of 9,846 specimens were processed with multiplex 1 and 2 (7,053 pediatric, 2,793 adult) over the 3-year study period. This clinically validated, probe-based multiplex testing algorithm allows highly sensitive and timely diagnosis of the four most prominent causes of viral gastroenteritis.

The flexible use of inductive and geometric spatial categories.

The present study examined the flexibility with which people can adopt different category schemes in the spatial domain. In a location memory task, participants viewed and estimated the locations of four kinds of objects that were spatially grouped by object identity. This identity-based arrangement was either congruent or incongruent with the perceptually based, geometric categories that have been reported in previous research. Four experiments examined the conditions under which these different category schemes are used to inform estimates of locations. The results showed that use of identity information depended on the number of objects to be remembered during a trial: When one or two objects were remembered at a time, only geometric categories affected estimates, but when four objects were to be remembered, both geometric categories and identity groupings affected estimates. As memory load increases, participants rely on additional sources to inform their estimates of location.

p53 in chronic myelogenous leukemia. Study of mechanisms of differential expression.

The p53 is a nuclear protein that is associated with normal cellular proliferation and can cooperate with Ha-ras in causing cellular transformation in vitro. Lineage association is known to exist between p53 expression and normal lymphopoiesis, but not myelopoiesis. We studied the expression of p53 using chronic myelogenous leukemia (CML) cell lines, somatic hybrids of these cells, and leukemic cells from CML patients. Lymphoid CML lines expressed both p53 mRNA and protein. We also analyzed p53 synthesis by two B-lymphoid lines from the same CML patient; cells of one line were derived from the neoplastic clone, cells of the other were derived from the normal clone. Both synthesized equal amounts of a phosphorylated p53 protein. None of the myeloid CML lines expressed detectable p53 protein and two of four expressed negligible p53 mRNA. Two other myeloid CML lines and myeloid cells from three of four patients expressed p53 mRNA. These findings suggest that expression of the gene is not regulated normally in CML. Several approaches were pursued to explore the differential expression of p53. Southern blot analyses showed no gross alterations in the p53 gene from cells of either the expressing or the nonexpressing lines. No difference in the pattern of demethylated CpG sites was noted in the region of the p53 gene in cells from K562 (myeloid p53 nonexpressor) and in BV173 (lymphoid p53 expressor). The sites of demethylation clustered in and around the p53 promoter in both cell lines. Somatic hybrids formed between a p53 mRNA nonexpressor myeloid line (K562) and the parental p53 expressor lymphoid lines (Daudi, PUT) produced p53 mRNA and protein, suggesting that p53 is a dominantly expressed protein and that lack of expression in myeloid cells is not mediated by a trans-acting negative regulatory protein. DNA transfection experiments performed using the indicator gene chloramphenicol acetyltransferase attached to promoter sequences of p53 showed that these constructs were equally activated in BV173 (p53 expressor) and K562 (p53 mRNA nonexpressor). The mechanism of p53 regulation in CML remains unclear.