Co-Creating Recommendations to Redesign and Promote Strength and Balance Service Provision.

Background: Awareness of physical activity guidelines are low, particularly the "forgotten guidelines" of strength and balance. Increasing awareness of guidelines, but also of appropriate local services that can be utilised, is an important step towards active ageing. Co-creation can inform tailored service provision to potentially increase uptake and adherence. The aim was to co-create recommendations to redesign and promote local leisure services, emphasising strength and balance activity provision. Method: Twenty-four ageing and older adults engaged in 10 co-creation workshops. Workshops consisted of interactive tasks, and fieldwork tasks were undertaken externally. Data were collected using field notes, worksheet tasks and facilitator reflections and were analysed using qualitative content analysis. Results: Retention and adherence rates were 92% and 85%. Co-creators cited group cohesion, scientific input from experts and perceived knowledge development as enjoyable elements of the process. Four key themes emerged from analysis: (1) localised strategies for awareness raising, (2) recruitment of volunteer champions to increase uptake and maintenance, (3) accessibility of activities, including what they are and when they are, and (4) evaluation of impact. Conclusion: This has been the first study, to our knowledge, to utilise co-creation for informed leisure service provision improvement. Future work should aim to implement these recommendations to ascertain what impact these themes might make.

Absence of human papillomavirus in esophageal carcinomas from southwestern Kenya.

Esophageal squamous cell cancer is highly prevalent in south-western Kenya. The role of human papillomavirus (HPV) in esophageal cancers from this region was evaluated. Biopsies of 29 esophageal squamous cell cancers were assayed for HPV DNA sequences by reverse line blot polymerase chain reaction, using 27 HPV type-specific probes. Viral sequences were found in none of the specimens. These results suggest the HPV is unlikely to be an etiologic factor for esophageal squamous cell cancers in this region.

Pharmacist involvement in primary care improves hypertensive patient clinical outcomes.

BACKGROUND: The practice of pharmaceutical care in primary care settings in Thailand is currently not generally accepted. OBJECTIVE: To evaluate the effect of pharmacist involvement in treatment with hypertensive patients in primary care settings. METHODS: The treatment objective was to stabilize the blood pressure (BP) of hypertensive patients in accordance with the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure guidelines. Patients were randomly assigned to a pharmacist-involved group (treatment) or a group with no pharmacist involvement (control). Pre- and post-test BPs, tablet counts, lifestyle modifications, and pharmacists' recommendations were recorded. The 6-month study was carried out in Mahasarakham University pharmacy and 2 primary care units. Patients were monitored monthly by reviewing their medications and supported by providing pharmaceutical care and counseling. RESULTS: From a total of 235 patients, the treatment group (n = 118) had a significant reduction in both systolic (S) and diastolic (D) BP compared with the 117 patients of the control group (p = 0.037, 0.027, respectively). The 158 patients (76 treatment, 82 control) with BPs >or=140/90 mm Hg at the beginning of the study showed significant BP reductions (p = 0.002 SBP, 0.008 DBP). The proportion of 158 patients whose BP became stabilized was higher in the treatment group (p = 0.017). The treatment group showed significantly better adherence (p = 0.014) and exercise control (p = 0.012) at the end of the study. Physicians accepted 42.72% of medication modifications and 5.34% of the suggestions for additional investigations. CONCLUSIONS: Hypertensive patients who received pharmacist input achieved a significantly greater benefit in BP reduction, BP control, and improvement in adherence rate and lifestyle modification.

Patterns of inflammation in mucosal biopsies of ulcerative colitis: perceived differences in pediatric populations are limited to children younger than 10 years.

The histologic criteria used to diagnose ulcerative colitis in colonic mucosal biopsies have been established for many years and include crypt architectural distortion, plasmacellular infiltrates, and neutrophils in the crypt epithelium and lumen. In several recent studies, it has been noted that colonic mucosal biopsies from children presenting with ulcerative colitis show fewer histologic abnormalities at initial presentation, especially less architectural distortion, than do biopsies from adults. In this study, colonic mucosal biopsies taken at the time of presentation of ulcerative colitis in 15 adults and 25 children were examined blindly by two pathologists. All biopsies were taken prior to the initiation of therapy. Twelve children were between 1 and 10 years of age, and 13 children were between the ages of 11 and 17 years. All patients had at least 1 year of follow-up, with clinical and pathologic confirmation of the diagnosis of ulcerative colitis. Five separate histologic features that are characteristic of ulcerative colitis were scored on mucosal biopsies. Children < or = 10 years of age had significantly less crypt branching, plasma cells in the lamina propria, cryptitis, crypt abscesses, and epithelial injury than adults (P values ranging from < 0.0001 to 0.0032). Children between the ages of 11 and 17 years had less cryptitis, crypt abscesses, and epithelial injury than adults (P values ranging from 0.0001 to 0.007) but similar degrees of crypt architectural distortion and plasma cell infiltrates. For all histologic features examined except epithelial injury, the significant findings were due to differences in biopsies taken proximal to the rectum. No significant differences in histology scores were found in rectal biopsies between any age group, except for epithelial injury, which was significantly less in children < or = 10 years. The findings show for the first time that the perceived differences between adults and children with ulcerative colitis are largely due to a decrease in histologic features of colitis in children less than 10 years of age. As children approach adulthood, the degree of inflammation and architectural distortion seen is similar to that found in adults. However, rectal biopsies show similar degrees of colitis in all age groups.

Selective T-cell subset ablation demonstrates a role for T1 and T2 cells in ongoing acute graft-versus-host disease: a model system for the reversal of disease.

Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality of allogeneic stem cell transplantation. Strategies to control GVHD while maintaining graft versus leukemia (GVL) include herpes simplex virus thymidine kinase (HSV-tk) gene transduction of donor T cells followed by treatment with ganciclovir (GCV). Alternatively, GVHD and GVL may be mediated by distinct processes. In this regard, whether cytokine polarization occurs and to what degrees various subsets of cytokine-producing T cells mediate GVHD or GVL has been an active area of research using cytokine or cytokine antibody infusion or genetically deficient mice. This study takes a different approach that allows simultaneous investigation into both the mechanisms underlying GVHD reactions and the efficacy of HSV-tk suicide gene-based T-cell deletion. A source of donor T cells, splenocytes from mice transgenic for HSV-tk controlled by elements of either the interleukin-2 (IL-2) or IL-4 promoters (IL-2-tk and IL-4-tk, respectively) was used, thus allowing investigation into the roles of T1 and T2 cells in ongoing GVHD reactions. To assess treatment rather than prevention of GVHD, GCV was started at peak disease. Remarkably, treatment at this late time point rescued mice from the clinical effects of GVHD caused by T cells expressing either transgene. Thus, both T1 and T2 cells play an important role in clinical GVHD in a minor histocompatibility antigen-mismatched setting. In addition, because clinical disease was reversible even at its maximum, these observations provide controlled evidence that this strategy of treating ongoing GVHD could be effective clinically.

Noise enhances modulation sensitivity in cochlear implant listeners: stochastic resonance in a prosthetic sensory system?

Cochlear implants restore auditory sensitivity to the profoundly hearing-impaired by means of electrical stimulation of residual auditory nerve fibers. Sensorineural hearing loss results in a loss of spontaneous activity among the remaining auditory neurons and is accompanied by a reduction in the normal stochastic nature of neural firing in response to electric stimulation. It has been hypothesized that the natural stochasticity of the neural response is important for auditory signal processing and that introducing some optimal amount of noise into the stimulus may improve auditory perception through the implant. In this article we show that, for soft but audible stimuli, an optimal amount of "prosthetic" noise significantly improves sensitivity to envelope modulation in cochlear implant listeners. A nonmonotonic function relates modulation sensitivity and noise level, suggesting the presence of stochastic resonance.

Reproducibility of the diagnosis of dysplasia in Barrett esophagus: a reaffirmation.

Morphologic assessment of dysplasia in Barrett esophagus, despite limitations, remains the basis of treatment. We rigorously tested modified 1988 criteria, assessing intraobserver and interobserver reproducibility. Participants submitted slides of Barrett mucosa negative (BE) and indefinite (IND) for dysplasia, with low-grade dysplasia (LGD) and high-grade dysplasia (HGD), and with carcinoma. Two hundred fifty slides were divided into 2 groups. The first 125 slides were reviewed, without knowledge of the prior diagnoses, on 2 occasions by 12 gastrointestinal pathologists without prior discussion of criteria. Results were analyzed by kappa statistics, which correct for agreement by chance. A consensus meeting was then held, establishing, by group review of the index 125 slides, the criteria outlined herein. The second 125-slide set was then reviewed twice by each of the same 12 pathologists, and follow-up kappa statistics were calculated. When statistical analysis was performed using 2 broad diagnostic categories (BE, IND, and LG v HG and carcinoma), intraobserver agreement was near perfect both before and after the consensus meeting (mean kappa = 0.82 and 0.80). Interobserver agreement was substantial (kappa = 0.66) and improved after the consensus meeting (kappa = 0.70; P =.02). When statistical analysis was performed using 4 clinically relevant separations (BE; IND and LGD; HGD; carcinoma), mean intraobserver kappa improved from 0.64 to 0.68 (both substantial) after the consensus meeting, and mean interobserver kappa improved from 0.43 to 0.46 (both moderate agreement). When statistical analysis was performed using 4 diagnostic categories that required distinction between LGD and IND (BE; IND; LGD; HGD and carcinoma), the pre-consensus meeting mean intraobserver kappa was 0.60 (substantial agreement), improving to 0.65 after the meeting (P <.05). Interobserver agreement was poorer, with premeeting and postmeeting mean values unchanged (kappa = 0.43 at both times). Interobserver agreement was substantial for HGD/carcinoma (kappa = 0.65), moderate to substantial for BE (kappa = 0.58), fair for LGD (kappa = 0.32), and slight for IND (kappa = 0.15). The intraobserver reproducibility for the diagnosis of dysplasia in BE was substantial. Interobserver reproducibility was substantial at the ends of the spectrum (BE and HG/carcinoma) but slight for IND. Both intraobserver and interobserver variation improved overall after the application of a modified grading system developed at a consensus conference but not in separation of BE, IND, and LGD. The criteria used by the group are presented. HUM PATHOL 32:368-978.

Dysplasia as a predictive marker for invasive carcinoma in Barrett esophagus: a follow-up study based on 138 cases from a diagnostic variability study.

The objective of endoscopic surveillance in Barrett esophagus (BE) is to assess the risk of subsequent development of invasive carcinoma. Criteria for morphologic evaluation of dysplasia, the presumed precursor lesion, have been established, although there are surprisingly few data in the literature correlating biopsy diagnosis of dysplasia with outcome. We collected follow-up information on 138 patients with BE whose initial endoscopic biopsy specimens had been selected for submission in an interobserver variability study performed by 12 pathologists with special interest in gastrointestinal pathology and reviewed blindly twice each by all the participants. Cases were scored as BE with no dysplasia, atypia indefinite for dysplasia (IND), low-grade dysplasia (LGD), high-grade dysplasia (HGD), intramucosal carcinoma, and frankly invasive carcinoma, thus generating 24 scores on each biopsy specimen. Clinical follow-up was obtained and correlated with both the submitting diagnoses and majority diagnoses. Kaplan-Meier statistics were used to compare both the submitting and majority diagnoses with outcome using detection or documentation of invasive carcinoma as the endpoint. Using the submitting diagnoses, no invasive carcinomas were detected in 44 cases diagnosed as BE (median follow-up, 38.5 months). Carcinomas were detected in 4 of 22 (18%) cases submitted as IND (median progression-free survival of 62 months), in 4 of 25 (15%) cases of LGD (median progression-free survival of 60 months), in 20 of 33 cases of HGD (median progression-free survival, 8 months), and all 13 (100%) cases submitted as adenocarcinoma. Grade on initial biopsy correlated significantly with progression to invasive carcinoma (log-rank P =.0001). Majority diagnosis was achieved in 99 of the cases. Using the majority diagnoses, no invasive carcinomas were found in 50 cases of BE (median follow-up, 48 months), and carcinomas were detected in 1 of 7 (14%) IND cases (80% progression-free survival at 2 months), 3 of 15 (20%) LGD (median progression-free survival, 60 months), 9 of 15 (60%) HGD (median progression-free survival, 7 months), and all 12 (100%) carcinoma. Initial grading again correlated significantly with progression to invasive carcinoma (log-rank P =.0001). However, there were 39 cases without a majority diagnosis. Among these, no carcinomas developed in 8 cases with an average score between BE and IND. Carcinomas were detected in 9 of 21 (43%) cases with an average score between IND and LGD, and 7 of 10 (70%) cases with an average score between LGD and HGD. There were ulcers in 8 of 39 cases (20%) of the "no-majority" group and in 13 of 99 (13%) of the majority cases. Of 21 total ulcerated cases, cancer was demonstrated in 15 (71%) of these on follow-up. These data support combining the IND and LGD categories for surveillance purposes. Cases without dysplasia may be followed up conservatively. The data obtained from submitted diagnoses as opposed to those from blind review suggest that knowledge of the clinical findings aids in diagnosis. The data also support the assertion that HGD is strongly associated with invasive carcinoma. Rebiopsy of ulcerated areas should be considered because they may harbor malignancy. Histologic grading of dysplasia using established criteria is a powerful prognosticator in BE. HUM PATHOL 32:379-388.

Morphology of isolated colonic crypts.

The traditional paradigm of colonic fluid and electrolyte transport includes a spatial separation of absorptive and secretory processes to surface and crypt cells, respectively. Recent studies of isolated microperfused colonic crypts revealed constitutive Na-dependent fluid absorption while secretion is regulated by one or more neurohumoral agonists. One obvious reason for the difference found in microdissected crypts is their separation from the lamina propria milieu. While it has been shown that isolated crypts are devoid of obvious lamina propria elements, including pericryptal fibroblasts, detailed morphologic information of the content of isolated crypts has been lacking. To characterize the morphology of the isolated crypt, we performed transmission electron microscopy (TEM) and immunofluorescence on microdissected and Ca2+ chelated crypts. Crypt cell type analysis was carried out separately on intact rat colon using light microscopy. TEM revealed a complete lack of either lamina propria cells or extracellular material in crypts isolated by either technique. TEM also revealed a subtle difference between the two isolation methods, with intact basal membranes in microdissected crypts but focal disruption of basal membranes in Ca2+- chelated crypts. Immunofluorescent stains for two basement membrane components (laminin and collagen type IV) revealed the presence of adherent basement membrane only on microdissected crypts; evidence that the plane of separation differs in these two preparations. Crypt cell type analysis on intact rat colon revealed an equal proportion of goblet cells in the right and left colon (approximately 50%) when measuring the middle 70% of the crypts - the area studied during crypt microperfusion. This morphologic analysis will increase our understanding of the observed physiology of isolated colonic crypts.

Granular cells as a marker of early amiodarone hepatotoxicity.

Hepatotoxicity due to chronic amiodarone (AD) use is well described. However, hepatitis occurring after acute administration of AD has only occasionally been reported and the pathologic findings in the liver in this condition have not been well characterized. We describe an idiosyncratic reaction, in a 40-year-old man after 6 weeks of oral AD therapy, consisting of acute hepatitis, which resolved after withdrawal of the drug. The liver biopsy showed clusters of cells with granular cytoplasm. These cells were characterized as macrophages, and phospholipid membranous inclusions were demonstrated ultrastructurally in the granular cells and in the hepatocytes. Pathologists and clinicians should be aware of this subtle histologic finding when looking for evidence to support AD hepatotoxicity.

Evidence for the neoplastic transformation of Von-Meyenburg complexes.

Von-Meyenburg complexes (VMC) are seen frequently in the liver and are largely considered to be innocuous, with only 11 cases reported in the literature of neoplastic transformation of VMCs. The authors report three cases of cholangiocarcinoma, each occurring in a background of fibrosis and nodularity that was reported initially as micronodular cirrhosis. Although the livers showed cirrhosis, the central veins were often preserved, and regenerative activity was patchy and focal. Histologic examination revealed many VMCs, and a gradual transition from VMCs to hyperplastic or adenomatous lesions and cholangiocarcinoma. The adenomatous lesions consisted of extensive replacement of the parenchyma by tumor-like nodules of ductular proliferations without obvious features of malignancy. All three patients were older than 60 years of age and had portal hypertension. Computed tomographic scans showed multiple, small renal cysts in one patient. Immunohistochemical staining showed positivity for epithelial membrane antigen, carcinoembryonic antigen, and keratins (AE1/AE3 and CAM5.2) in tumor cells, consistent with cholangiocarcinoma. The pattern of fibrosis and nodularity in these cases is not typical of either congenital hepatic fibrosis or usual cirrhosis. The authors propose that these patients represent another aspect in the spectrum of ductal plate malformations that may be modified by other factors such as alcohol, drugs, or infection. To their knowledge, neoplastic transformation of VMCs in the background of such changes has never been reported before.

The histologic spectrum and clinical outcome of refractory and unclassified sprue.

The vast majority of patients with celiac disease respond to a gluten-free diet; yet, a small number of refractory patients do not respond and have persistent malabsorption and residual mucosal abnormalities of the small intestine. The histologic features of refractory/unclassified sprue have been published as case reports, often without long-term follow up, and no clear histologic picture has emerged. We present the results of a long-term study of the clinical and histologic features of 10 patients with refractory/unclassified sprue. The histologic features of small bowel biopsies in this group of patients were compared with those of 10 patients with responsive celiac disease and with 10 patients without malabsorption who had normal duodenal biopsies. Five of the 10 refractory patients ultimately developed collagenous sprue as a distinct histologic marker of refractory disease. Additional distinctive findings found in small bowel biopsies in the refractory group were subcryptal chronic inflammation (10 of 10) and marked mucosal thinning in three patients. Other nonspecific findings included acute inflammation and gastric metaplasia. One patient with collagenous sprue developed a B-cell lymphoma of the ileum, and in general collagenous sprue was associated with a poor prognosis. Two of five patients died whereas two others require total parenteral nutrition for survival. Pathologists evaluating small bowel biopsies in the setting of malabsorption should be aware of the subtle histologic changes described here that may portend a refractory course.

Prevention of graft versus host disease by inactivation of host antigen-presenting cells.

Graft versus host disease, an alloimmune attack on host tissues mounted by donor T cells, is the most important toxicity of allogeneic bone marrow transplantation. The mechanism by which allogeneic T cells are initially stimulated is unknown. In a murine allogeneic bone marrow transplantation model it was found that, despite the presence of numerous donor antigen-presenting cells, only host-derived antigen-presenting cells initiated graft versus host disease. Thus, strategies for preventing graft versus host disease could be developed that are based on inactivating host antigen-presenting cells. Such strategies could expand the safety and application of allogeneic bone marrow transplantation in treatment of common genetic and neoplastic diseases.

Human allogeneic vascular rejection after arterial transplantation and peripheral lymphoid reconstitution in severe combined immunodeficient mice.

BACKGROUND: Interspecies differences create important shortcomings in existing animal models used to describe in vivo events responsible for allograft rejection. Alloimmune destruction of human dermal microvessels, histologically consistent with rejection, has been demonstrated in human skin-grafted severe combined immunodeficient (SCID) mice receiving allogeneic human peripheral blood mononuclear cells (PBMC). We have now documented human alloimmune injury in a vascularized, SCID-human arterial transplantation model. METHODS: Fresh human artery was used to replace the CB.17 SCID/beige mouse infrarenal aorta. Seven days later, 3x10(8) human PBMC were administered intraperitoneally, and lymphocyte engraftment was considered successful when circulating human CD3+ cells were later identified in peripheral blood. RESULTS: Forty-six of 49 (94%) mice undergoing transplantation survived, including 14 controls with arterial grafts receiving no PBMC. Twenty-eight of 32 mice demonstrated circulating human CD3+ cells, 14 days after PBMC administration. Animals were killed at 14, 21, or 28 days after receiving allogeneic PBMC, and arteries were recovered for histology and immunohistology. All 14 control mice had patent transplanted grafts with normal vascular histology and no lymphoid infiltration. Damage to transplanted arteries among lymphocyte-engrafted mice was apparent by 14 and 21 days in some animals, whereas 16 of 22 exhibited moderate to severe intimal, medial, and/or adventitial lymphocytic infiltration with intimal expansion by day 28. The infiltrate consisted of HLA-A, -B, -C+, and -DR+, human CD3+ cells, approximately equally distributed as CD4+ and CD8+ subsets. Some infiltrating lymphocytes were cytolytic cells as demonstrated by perforin staining. The endothelium of transplanted human arteries exhibited endothelialitis, and the endothelial cells stained intensely with anti-HLA-A, -B, -C and anti-HLA-DR antibodies. The expanded intima was predominantly smooth muscle cells, staining positively for smooth muscle alpha-actin, HLA-A, -B, -C and HLA-DR. Medial necrosis was not observed. CONCLUSION: The results provide evidence of alloimmune-mediated vascular rejection in this human arterial transplantation model.

Biliary tract obstruction secondary to mycosis fungoides: a case report.

Mycosis fungoides is a cutaneous T-cell lymphoma that can disseminate to multiple organs. We report a patient who presented with obstructive jaundice caused by isolated involvement of the extrahepatic biliary tree by mycosis fungoides. Initially, endoscopic examinations and biopsies of the biliary tree and liver failed to reveal a cause for the obstructive symptoms. Finally, surgical resection of the gallbladder and extrahepatic ducts was performed. Examination revealed a dense, mixed lymphocytic infiltrate with atypical cells within the mucosa. Gene rearrangement studies confirmed the presence of a monoclonal T-cell population. The pattern of the gene rearrangement in the biliary tree was identical to that found in a previous skin biopsy that showed mycosis fungoides. Although liver involvement by mycosis fungoides is not uncommon, disease isolated to the extrahepatic biliary tree has not previously been reported. This case should alert clinicians and pathologists to yet another cause of obstructive jaundice.

Effect of heparin on dextran sulfate sodium-induced colitis.

Heparin has been shown to ameliorate inflammatory bowel disease in several series. In addition to its anticoagulant properties, heparin has numerous other effects that may be beneficial in inflammatory bowel disease. Other sulfated polysaccharides, such as dextran sulfate, cause colitis in mice through unknown mechanisms. We postulate that dextran sulfate and heparin may act via similar pathways with opposite effects. To examine this thesis, the effect of heparin on dextran sulfate-induced colitis was studied. Swiss-Webster mice were given 5% dextran sulfate in their drinking water for five days to induce colitis. Heparin was given both therapeutically after the induction of colitis and prophylactically by subcutaneous injections, with saline injections given in controls. Histologic sections of colon were randomized and graded for colitis. Heparinized animals showed no significant difference in the pattern or severity of colitis when compared to control animals. It is concluded that heparin does not ameliorate the murine colitis induced by dextran sulfate in the doses given.

Perforin protects against autoimmunity in lupus-prone mice.

The roles of cytolytic regulatory mechanisms in the immune system of lupus-prone mice were examined in perforin-deficient animals bearing functional or defective (lpr) Fas Ag (CD95). Perforin-deficient Fas+ animals developed accelerated autoimmunity, characterized by increased hypergammaglobulinemia, autoantibody production, and immune deposit-related end-organ disease compared with perforin-intact counterparts. In comparison, perforin-deficient lpr animals had accelerated mortality compared with perforin-intact lpr mice, associated with the abnormal accumulation of CD3+CD4-CD8- alphabeta T cells in conjunction with unaltered hypergammaglobulinemia, autoantibody production, and immune complex renal disease. These results indicate that cytolytic lymphoid regulation plays critical roles in the immune homeostasis of lupus-prone animals, and identify perforin-mediated cytotoxicity as a specific mechanism in the regulation of systemic autoimmunity.

Computer model: investigating role of filopodia-based steering in experimental neurite galvanotropism.

Since early in this century developing axons and dendrites in culture have been reported to grow along electric field lines. It is only in the last score of years, however, that evidence suggests developing neurites actually orient in response to the electrical stimulus. We are interested in how an imposed electric field appears to speed neurite outgrowth in a field-related direction. We ask the question whether enhanced outgrowth in one direction results from streamlining outgrowth in that direction or from differentially catalysing the rate of outgrowth. Evidence for possible mechanisms of such neurite galvanotropism includes an electric field-dependent redistribution of filopodia, the finger-like structures that extend from the growing neurite tip. Using simple rules based on filopodia-mediated substrate sampling and orientation of extending neurites in vitro, we have built a computer model to test the streamlining theory. This in silico model of non-branching neurite outgrowth in two dimensions possesses the capacity to apportion its sampling efforts relative to a fixed reference representing the orientation of the field lines of a steady uniform electric field. Our model suggests that simple outgrowth patterns observed for experimental neurite galvanotropism-deflected and enhanced neurite growth toward the negative electrode and reduced neurite growth directed toward the positive electrode-may be simulated by tipping the balance of filopodia in the direction of the negative electrode. The existence of an analogous pattern-generating interaction between an applied electric field and extending neuronal processes would suggest a role for endogenous fields arising from naturally occurring potential gradients in developing organisms.