Plastic and Non-plastic Debris Ingestion in Three Gull Species Feeding in an Urban Landfill Environment.

Plastic debris is recognized as a widespread, common and problematic environmental pollutant. An important consequence of this pollution is the ingestion of plastic debris by wildlife. Assessing the degree to which different species ingest plastics, and the potential effects of these plastics on their health are important research needs for understanding the impacts of plastic pollution. We examined debris (plastic and other types) ingestion in three sympatric overwintering gull species (Herring gulls Larus smithsonianus, Great Black-backed Gulls Larus marinus, and Iceland Gulls Larus glaucoides) to understand how debris ingestion differs among species, age classes and sexes in gulls. We also assessed how plastic burdens were associated with body condition to investigate how gulls may be affected by debris ingestion. There were no differences among the species, age classes or sexes in the incidence of debris ingestion (plastic or otherwise), the mass or number of debris pieces ingested. We found no correlation between ingested plastics burdens and individual condition. Gulls ingested plastic debris, but also showed high levels of other debris types as well, including metal, glass and building materials, including a metal piece of debris found within an abscess in the stomach. Thus, when the health effects of debris ingestion on gulls, and other species that ingest debris, is of interest, either from a physical or chemical perspective, it may be necessary to consider all debris types and not just plastic burdens as is often currently done for seabirds.

Apoptosis inhibition of Atlantic salmon (Salmo salar) peritoneal macrophages by Piscirickettsia salmonis.

To improve the understanding of the piscirickettsiosis pathogenesis, the in vivo apoptosis modulation of peritoneal macrophages and lymphocytes was studied in juvenile Salmo salar intraperitoneally injected with Piscirickettsia salmonis. Five fish were sampled at post-exposure days 1, 5, 8 (preclinical), 20 (clinical) and 40 (post-clinical period of the disease), and the leucocytes of their coelomic washings were analysed by flow cytometry (using the JC-1 cationic dye), TUNEL and cytology to detect apoptotic cells. A selective and temporal pattern of apoptosis modulation by P. salmonis infection was observed. Apoptosis in lymphocytes was not affected, whereas it was inhibited in macrophages but only during the preclinical stage of the induced piscirickettsiosis. Hence, it is postulated that P. salmonis inhibits macrophage apoptosis at the beginning of the disease development to survive, multiply and probably be transported inside these phagocytes; once this process is complete, macrophage apoptosis is no longer inhibited, thus facilitating the exit of the bacteria from the infected cells for continuing their life cycle.

Cesarean delivery is not associated with decreased at-birth fracture rates in osteogenesis imperfecta.

PURPOSE: Osteogenesis imperfecta (OI) predisposes to recurrent fractures. Patients with the moderate to severe forms of OI present with antenatal fractures, and the mode of delivery that would be safest for the fetus is not known. METHODS: We conducted systematic analyses of the largest cohort of individuals with OI (n = 540) enrolled to date in the OI Linked Clinical Research Centers. Self-reported at-birth fracture rates were compared among individuals with OI types I, III, and IV. Multivariate analyses utilizing backward-elimination logistic regression model building were performed to assess the effect of multiple covariates, including method of delivery, on fracture-related outcomes. RESULTS: When accounting for other covariates, at-birth fracture rates did not differ based on whether delivery was by vaginal route or by cesarean delivery (CD). Increased birth weight conferred higher risk for fractures irrespective of the delivery method. In utero fracture, maternal history of OI, and breech presentation were strong predictors for choosing CD. CONCLUSION: Our study, the largest to analyze the effect of various factors on at-birth fracture rates in OI, shows that CD is not associated with decreased fracture rate. With the limitation that the fracture data were self-reported in this cohort, these results suggest that CD should be performed only for other maternal or fetal indications, not for the sole purpose of fracture prevention in OI.Genet Med 18 6, 570-576.

Effect of simvastatin on vascular tone in porcine coronary artery: Potential role of the mitochondria.

Statins induce acute vasorelaxation which may contribute to the overall benefits of statins in the treatment of cardiovascular disease. The mechanism underlying this relaxation is unknown. As statins have been shown to alter mitochondrial function, in this study we investigated the role of mitochondria in the relaxation to simvastatin. Relaxation of porcine coronary artery segments by statins was measured using isolated tissue baths. Mitochondrial activity was determined by measuring changes in rhodamine 123 fluorescence. Changes in intracellular calcium levels were determined in freshly isolated smooth muscle cells with Fluo-4 using standard epifluorescent imaging techniques. Simvastatin, but not pravastatin, produced a slow relaxation of the coronary artery, which was independent of the endothelium. The relaxation was attenuated by the mitochondrial complex I inhibitor rotenone (10µM) and the complex III inhibitor myxothiazol (10µM), or a combination of the two. The complex III inhibitor antimycin A (10µM) produced a similar time-dependent relaxation of the porcine coronary artery, which was attenuated by rotenone. Changes in rhodamine 123 fluorescence showed that simvastatin (10µM) depolarized the membrane potential of mitochondria in both isolated mitochondria and intact blood vessels. Simvastatin and antimycin A both inhibited calcium-induced contractions in isolated blood vessels and calcium influx in smooth muscle cells and this inhibition was prevented by rotenone. In conclusion, simvastatin produces an endothelium-independent relaxation of the porcine coronary artery which is dependent, in part, upon effects on the mitochondria. The effects on the mitochondria may lead to a reduction in calcium influx and hence relaxation of the blood vessel.

A cross-sectional multicenter study of osteogenesis imperfecta in North America - results from the linked clinical research centers.

Osteogenesis imperfecta (OI) is the most common skeletal dysplasia that predisposes to recurrent fractures and bone deformities. In spite of significant advances in understanding the genetic basis of OI, there have been no large-scale natural history studies. To better understand the natural history and improve the care of patients, a network of Linked Clinical Research Centers (LCRC) was established. Subjects with OI were enrolled in a longitudinal study, and in this report, we present cross-sectional data on the largest cohort of OI subjects (n = 544). OI type III subjects had higher prevalence of dentinogenesis imperfecta, severe scoliosis, and long bone deformities as compared to those with OI types I and IV. Whereas the mean lumbar spine area bone mineral density (LS aBMD) was low across all OI subtypes, those with more severe forms had lower bone mass. Molecular testing may help predict the subtype in type I collagen-related OI. Analysis of such well-collected and unbiased data in OI can not only help answering questions that are relevant to patient care but also foster hypothesis-driven research, especially in the context of 'phenotypic expansion' driven by next-generation sequencing.

A novel long-acting glucose-dependent insulinotropic peptide analogue: enhanced efficacy in normal and diabetic rodents.

AIM: Glucose-dependent insulinotropic peptide (GIP) is an incretin hormone that is released from intestinal K cells in response to nutrient ingestion. We aimed to investigate the therapeutic potential of the novel N- and C-terminally modified GIP analogue AC163794. METHODS: AC163794 was synthesized by solid-phase peptide synthesis. Design involved the substitution of the C-terminus tail region of the dipeptidyl peptidase IV (DPP-IV)-resistant GIP analogue [d-Ala(2) ]GIP(1-42) with the unique nine amino acid tail region of exenatide. The functional activity and binding of AC163794 to the GIP receptor were evaluated in RIN-m5F ß-cells. In vitro metabolic stability was tested in human plasma and kidney membrane preparations. Acute insulinotropic effects were investigated in isolated mouse islets and during an intravenous glucose tolerance test in normal and diabetic Zucker fatty diabetic (ZDF) rats. The biological actions of AC163794 were comprehensively assessed in normal, ob/ob and high-fat-fed streptozotocin (STZ)-induced diabetic mice. Acute glucoregulatory effects of AC163794 were tested in diet-induced obese mice treated subchronically with AC3174, the exendatide analogue [Leu(14) ] exenatide. Human GIP or [d-Ala(2) ]GIP(1-42) were used for comparison. RESULTS: AC163794 exhibited nanomolar functional GIP receptor potency in vitro similar to GIP and [d-Ala(2) ]GIP(1-42). AC163794 was metabolically more stable in vitro and displayed longer duration of insulinotropic action in vivo versus GIP and [d-Ala(2) ]GIP(1-42). In diabetic mice, AC163794 improved HbA1c through enhanced insulinotropic action, partial restoration of pancreatic insulin content and improved insulin sensitivity with no adverse effects on fat storage and metabolism. AC163794 provided additional baseline glucose-lowering when injected to mice treated with AC3174. CONCLUSIONS: These studies support the potential use of a novel GIP analogue AC163794 for the treatment of type 2 diabetes.

How often are late preterm births the result of non-evidence based practices: analysis from a retrospective cohort study at two tertiary referral centres in a nationalised healthcare system.

OBJECTIVE: To determine the proportion, characteristics, and predictors of late preterm birth (LPTB) in relation to evidence-based (EB) and non-evidence based (NEB) indications. DESIGN: Retrospective cohort study. SETTING: Two Canadian tertiary referral centres. POPULATION: All live singleton LPTBs over 1 year from 2010 to 2011, excluding major congenital anomalies. METHODS: Indications for LPTB were classified a priori as EB (i.e. based on practice guidelines or on evidence from randomised controlled trials) or NEB. Data were abstracted from maternal antenatal and labour records. Univariate analyses were completed using Fischer's exact, Pearson's chi-square, or analysis of variance (anova) F-tests. Logistic regression included gestation at birth, delivery provider, previous stillbirth, previous caesarean section, corticosteroid administration, and previous preterm birth as predictors for NEB LPTB. MAIN OUTCOME MEASURES: The proportion, characteristics, and predictors of women with NEB versus EB LPTBs. RESULTS: Of 524 LPTBs, 25.2% (n = 132) were NEB. Logistic regression revealed that NEB LPTBs were less likely if patients were delivered by their own doctor or their doctor's practice partner (OR 0.53, 95% CI 0.34-0.83). However, NEB LPTBs were more likely in women who had experienced a previous stillbirth (OR 2.57, 95% CI 1.20-5.49). CONCLUSIONS: Approximately one-quarter of LPTBs are NEB. Further research is needed to see if a review of the indications for LPTB, and subsequent reduction in NEB LPTBs, translates into improved neonatal outcomes and cost savings.

Evidence of exotoxin secretion of Piscirickettsia salmonis, the causative agent of piscirickettsiosis.

Piscirickettsia salmonis is the aetiological agent of piscirickettsiosis, a disease which affects a variety of teleost species and that is particularly severe in salmonid fish. Bacterial-free supernatants, obtained from cultures of three isolates of Piscirickettsia salmonis, were inoculated in Atlantic salmon, Salmo salar L., and in three continuous cell lines in an effort to determine the presence of secretion of extracellular products (ECPs) by this microorganism. Although steatosis was found in some liver samples, no mortalities or clinical signs occurred in the inoculated fish. Clear cytotoxicity was observed after inoculation in the cell lines CHSE-214 and ASK, derived from salmonid tissues, but not in MDBK, which is of mammalian origin. The degree of cytotoxicity of the ECPs was different among the P. salmonis isolates tested. The isolate that evidenced the highest cytotoxicity in its ECPs exhibited only an intermediate virulence level after challenging fish with bacterial suspensions of the three P. salmonis isolates. Almost complete inhibition of the cytotoxic activity of ECPs was seen after proteinase K treatment, indicating their peptidic nature, and a total preclusion of the cytotoxicity was shown after their incubation at 50 °C for 30 min. Results show that P. salmonis can produce ECPs and at least some of them are thermolabile exotoxins that probably play a role in the pathogenesis of piscirickettsiosis.

Suicide attempt by self-poisoning: characteristics of suicide attempters seen at the Emergency Room at the University Hospital of the West Indies.

OBJECTIVE: To document the characteristics of self-poisoning suicide attempters who were brought to the University Hospital of the West Indies (UHWI) Emergency Room and to outline the type of drug used in the attempt. METHOD: This was a retrospective study conducted over the period 2005-2009. Data were gathered from patients' case records, log books and the hospital records using a questionnaire developed for this study. The questionnaire examined demographics, parameters of the drug ingested, patient's disposition, and reasons for attempt, final outcome and the type of discharge of patients who reported to the UHWI Emergency Room due to a suicide attempt by self-poisoning. RESULTS: Over the five-year period, 127 cases of suicide attempt by self-poisoning were reported. Significantly more females than males presented to the hospital due to self-poisoning (3:1, chi2 = 33.37; p < 0.001). Of this amount, 96 cases (75.6%) were females and 31 (24.4%) were males. The age group most recorded was 16-30 years (70.8%). The most common reason for the suicide attempt was an interpersonal conflict (52%). The drug category most often used in self-poisoning was analgesics (52%) with acetaminophens being the most common (26.2%). CONCLUSION: These findings are consistent with global suicide trends and indicate an urgent need to develop and implement national preventative and treatment measures for groups known to be at risk of suicidal attempts.

Set up to 'fail'? Implementing contamination minimisation procedures and environmental monitoring in a Sexual Assault Referral Centre.

There are 47 Sexual Assault Referral Centres (SARCs) in the UK positioned regionally to provide specialist medical and forensic services to the victims of rape and sexual assault. The centres are managed and operated through multiagency agreements bringing together medical and forensic expertise to provide the necessary care for the victim and support the recovery of forensic evidence. A principal factor in preserving the evidence integrity and mitigating the risk of miscarriages of justice is reducing the risk from background DNA contamination to the samples and evidence recovered. This paper outlines a study reviewing the implementation of contamination reduction procedures at one SARC, providing a longitudinal examination of the outcomes of environmental monitoring procedures over a 12-month period. The outcomes show a myriad of factors affecting the process that need continual review and modification of the operating procedures to counteract these risks, as they arise. The Forensic Regulator's "Code of Practice for Forensic Medical Examinations - FSR-C-116", published in May 2020, provides an essential and useful mandate of activities, but this study shows further consideration is required in regard to SARC cleaning procedures and measuring the extent of background DNA contamination. Considerable investment, and further research is needed to implement new and more effective approaches within 'real-world' and local constraints.

Cytomegalovirus latency promotes cardiac lymphoid neogenesis and accelerated allograft rejection in CMV naïve recipients.

Human cytomegalovirus (HCMV) infection is associated with the acceleration of transplant vascular sclerosis (TVS) and chronic allograft rejection (CR). HCMV-negative recipients of latently HCMV infected donor grafts are at highest risk for developing CMV disease. Using a rat heart transplant CR model, we have previously shown that acute rat CMV (RCMV) infection following transplantation significantly accelerates both TVS and CR. Here, we report that RCMV-naïve recipients of heart allografts from latently RCMV-infected donors undergo acceleration of CR with similar kinetics as acutely infected recipients. In contrast to acutely infected recipients, treatment of recipients of latently infected donor hearts with ganciclovir did not prevent CR or TVS. We observed the formation of tertiary lymphoid structures (TLOs) containing macrophages and T cells in latently infected hearts prior to transplantation but not in uninfected rats. Moreover, pathway analysis of gene expression data from allografts from latently infected donors indicated an early and sustained production of TLO-associated genes compared to allografts from uninfected donors. We conclude that RCMV-induced TLO formation and alteration of donor tissue T cell profiles prior to transplantation in part mediate the ganciclovir-insensitive rejection of latently infected donor allografts transplanted into naïve recipients by providing a scaffold for immune activation.

Glucoregulatory effects and prolonged duration of action of davalintide: a novel amylinomimetic peptide.

AIMS: Davalintide is a second-generation amylinomimetic peptide possessing enhanced pharmacological properties over rat amylin to reduce food intake in preclinical models. The current experiments in rats describe additional glucoregulatory actions of davalintide consistent with amylin agonism, and explore the duration of action of these effects. METHODS: Subcutaneous (SC) injection of davalintide slowed gastric emptying with equal potency to amylin (ED50's = 2.3 and 4.1 µg/kg). This effect was maintained for 8 h with davalintide, but not amylin. Intraperitoneal injection of davalintide also reduced food intake with a potency similar to amylin (ED50's = 5.0 and 11.3 µg/kg). Consistent with amylin agonism, davalintide (10 µg/kg, SC) suppressed the plasma glucagon response over 90 min following an intravenous arginine bolus in anaesthetized rats. The elimination t(½) of davalintide (200 µg/kg, SC) was 26 min, similar to the t(½) of amylin, suggesting that pharmacokinetic-independent mechanisms contribute to davalintide's enhanced duration of action. Binding kinetic studies using ¹²5I davalintide revealed no appreciable dissociation from the amylin nucleus accumbens receptor after 7 h while ¹²5I rat amylin did dissociate from this receptor (K(off) = 0.013/min). Sustained SC infusion of davalintide (275 µg/kg/day) or amylin (300) decreased plasma glucose after an oral glucose challenge at 2 weeks (by 27 and 31%) and suppressed gastric emptying at 3 weeks (by 29 and 47%), demonstrating durable glucoregulatory actions of both peptides. CONCLUSIONS: These data show glucoregulatory properties of davalintide consistent with amylin agonism and suggest that slowed receptor dissociation plays a role in davalintide's prolonged pharmacodynamic actions.

Peptide-independent recognition by alloreactive cytotoxic T lymphocytes (CTL).

We have isolated several H-2K(b)-alloreactive cytotoxic T cell clones and analyzed their reactivity for several forms of H-2K(b). These cytotoxic T lymphocytes (CTL) were elicited by priming with a skin graft followed by in vitro stimulation using stimulator cells that express an H-2K(b) molecule unable to bind CD8. In contrast to most alloreactive T cells, these CTL were able to recognize H-2K(b) on the surface of the antigen processing defective cell lines RMA-S and T2. Furthermore, this reactivity was not increased by the addition of an extract containing peptides from C57BL/6 (H-2(b)) spleen cells, nor was the reactivity decreased by treating the target cells with acid to remove peptides bound to MHC molecules. The CTL were also capable of recognizing targets expressing the mutant H-2K(bm8) molecule. These findings suggested that the clones recognized determinants on H-2K(b) that were independent of peptide. Further evidence for this hypothesis was provided by experiments in which H-2K(b) produced in Drosophila melanogaster cells and immobilized on the surface of a tissue culture plate was able to stimulate hybridomas derived from these alloreactive T cells. Precursor frequency analysis demonstrated that skin graft priming, whether with skin expressing the wild-type or the mutant H-2K(b) molecule, is a strong stimulus to elicit peptide-independent CTL. Moreover, reconstitution experiments demonstrated that the peptide-independent CTL clones were capable of mediating rapid and complete rejection of H-2-incompatible skin grafts. These findings provide evidence that not all allorecognition is peptide dependent.

Davalintide (AC2307), a novel amylin-mimetic peptide: enhanced pharmacological properties over native amylin to reduce food intake and body weight.

OBJECTIVE: The current set of studies describe the in vivo metabolic actions of the novel amylin-mimetic peptide davalintide (AC2307) in rodents and compares these effects with those of the native peptide. RESEARCH DESIGN AND METHODS: The anti-obesity effects of davalintide were examined after intraperitoneal injection or sustained peripheral infusion through subcutaneously implanted osmotic pumps. The effect of davalintide on food intake after lesioning of the area postrema (AP) and neuronal activation as measured by c-Fos, were also investigated. RESULTS: Similar to amylin, davalintide bound with high affinity to amylin, calcitonin and calcitonin gene-related peptide receptors. Acutely, davalintide displayed greater suppression of dark-cycle feeding and an extended duration of action compared with amylin (23 versus 6 h). Davalintide had no effect on locomotor activity or kaolin consumption at doses that decreased food intake. Davalintide-induced weight loss through infusion was dose dependent, durable up to 8 weeks, fat-specific and lean-sparing, and was associated with a shift in food preference away from high-fat (palatable) chow. Metabolic rate was maintained during active weight loss. Both davalintide and amylin failed to suppress food intake after lesioning of the AP and activated similar brain nuclei, with davalintide displaying an extended duration of c-Fos expression compared with amylin (8 versus 2 h). CONCLUSION: Davalintide displayed enhanced in vivo metabolic activity over amylin while retaining the beneficial properties possessed by the native molecule. In vitro receptor binding, c-Fos expression and AP lesion studies suggest that the metabolic actions of davalintide and amylin occur through activation of similar neuronal pathways.

The prevalence and characterisation of TRAF3 and POT1 mutations in canine B-cell lymphoma.

The genetic and mutational basis of canine lymphoma remains poorly understood. Several genes, including TRAF3 and POT1, are mutated in canine B-cell lymphoma (cBCL), and are likely involved in the pathogenesis of this disease. The purpose of this study was to assess the prevalence of TRAF3 and POT1 mutations in a cohort of dogs with cBCL, compared to dogs with non-cBCL diseases (including four dogs with T-cell lymphoma [cTCL]). Forty-nine dogs were included (n = 24 cBCL; n = 25 non-cBCL). Eleven dogs had matched non-tumour DNA assessed to determine if mutations were germline or somatic. All dogs had TRAF3 and POT1 assessed by Sanger sequencing. The prevalence of deleterious TRAF3 and POT1 mutations in cBCL was 36% and 17%, respectively. A deleterious TRAF3 mutation was suspected to be germline in 1/5 cases with matched non-tumour DNA available for comparison. Deleterious mutations were not found in specimens from the non-cBCL group. Several synonymous variants were identified in both genes in cBCL and non-cBCL samples, which likely represent polymorphisms. These results indicate TRAF3 and POT1 mutations are common in cBCL. Deleterious TRAF3 and POT1 mutations were only identified in dogs with cBCL, and not in dogs with non-cBCL diseases, suggesting they are important in the pathogenesis of cBCL. Future studies to investigate the prognostic and therapeutic implications of these mutations are required.

The visualisation of fingermarks on Pangolin scales using gelatine lifters.

Recent media reports document the plight of the Pangolin and its current position as "the most trafficked mammal in the world". They are described by some as scaly anteaters as all species are covered in hard keratinous tissue in the form of overlapping scales acting as a "flexible dermal armour". It is estimated that between 2011 and 2013, 117,000-234,000 pangolins were slaughtered, but the seizures may only represent as little as 10% of the true volume of pangolins being illegally traded. In this paper, methods to visualise fingermarks on Pangolin scales using gelatine lifters is presented. The gelatine lifters provide an easy to use, inexpensive but effective method to help wildlife crime rangers across Africa and Asia to disrupt the trafficking. The gelatine lifting process visualised marks producing clear ridge detail on 52% of the Pangolin scales examined, with a further 30% showing the impression of a finger with limited ridge detail. The paper builds on an initial sociotechnical approach to establishing requirement, then it focuses on the methods and outcomes relating to lifting fingermarks off Pangolin scales using gelatine lifters, providing an evaluation of its use in practice.

Synaptic potentials in sympathetic ganglia: are they mediated by cyclic nucleotides?

The hypothesis that cyclic nucleotides are intracellular second messengers mediating the generation of synaptic potentials was studied in the sympathetic ganglia of the bullfrog. Synaptic potentials and the effect of administering cyclic nucleotides and agents which affect cyclic nucleotide metabolism were recorded by the sucrose gap technique. The administration of adenosine 3',5'-monophosphate (cyclic AMP), guanosine 3',5'-monophosphate (cyclic GMP), or several of their derivatives produced little or no change in membrane potential. Prostaglandin E1 did not block the generation of postsynaptic potentials. Theophylline produced membrane effects that were different from those associated with postsynaptic potential generation; it also reduced the slow excitatory postsynaptic potential (EPSP) and potentiated the slow inhibitory postsynaptic potential (IPSP). The administration of papaverine, however, reduced both the slow EPSP and the slow IPSP. Although synaptic stimulation increases both cyclic GMP and cyclic AMP in these neurons, these results raise the possibility that these cyclic nucleotides may have functionla roles other than mediation of synaptic potentials.

A developmentally modulated chromatin structure at the mouse immunoglobulin kappa 3' enhancer.

Transcription of the mouse immunoglobulin kappa gene is controlled by two enhancers: the intronic enhancer (Ei) that occurs between the joining (J kappa) and constant (C kappa) exons and the 3' enhancer (E3') located 8.5 kb downstream of the gene. To understand the role of E3' in the activation of the mouse immunoglobulin kappa gene, we studied its chromatin structure in cultured B-cell lines arrested at various stages of differentiation. We found that 120 bp of the enhancer's transcriptional core becomes DNase I hypersensitive early in B-cell development. Genomic footprinting of pro-B and pre-B cells localized this chromatin alteration to B-cell-specific protections at the region including the direct repeat (DR) and the sequence downstream of the DR (DS), the PU.1-NFEM-5 site, and the core's E-box motif, identifying bound transcription factors prior to kappa gene rearrangement. Early footprints were, however, not detected at downstream sites proposed to play a negative role in transcription. The early chromatin structure persisted through the mature B-cell stage but underwent a dramatic shift in plasma cells, correlating with the loss of guanosine protection within the DR-DS junction and the appearance of novel footprints at a GC-rich motif upstream and the NF-E1 (YY1/delta)-binding site downstream. Gel shift analysis demonstrated that the DR-DS junction is bound by a factor with properties similar to those of BSAP (B-cell-specific activator protein). These results reveal developmental-stage-specific changes in the composition of nuclear factors bound to E3', clarify the role of factors that bind constitutively in vitro, and point to the differentiation of mature B cells to plasma cells as an important transitional point in the function of this enhancer. The observed changes in nuclear factor composition were accompanied by the rearrangement of positioned nucleosomes that flank the core region, suggesting a role for both nuclear factors and chromatin structure in modulating kappa E3' function during B-cell development. The functional implications of the observed chromatin alterations are discussed in the context of recent studies on kappa E3' and the factors that bind to it.