Evaluating the Correlation Between Anteroposterior Diameter, Body Surface Area, and Height for Liver Transplant Donors and Recipients.

Background: Small stature and female sex correlate to decreased deceased donor liver transplant (DDLT) access and higher waitlist mortality. However, efforts are being made to improve access and equity of allocation under the new continuous distribution (CD) system. Liver anteroposterior diameter (APD) is a method used by many centers to determine size compatibility for DDLT but is not recorded systematically, so it cannot be used for allocation algorithms. We therefore seek to correlate body surface area (BSA) and height to APD in donors and recipients and compare waitlist outcomes by these factors to support their use in the CD system. Methods: APD was measured from single-center DDLT recipients and donors with cross-sectional imaging. Linear, Pearson, and PhiK correlation coefficient were used to correlate BSA and height to APD. Competing risk analysis of waitlist outcomes was performed using United Network for Organ Sharing data. Results: For 143 pairs, donor BSA correlated better with APD than height (PhiK = 0.63 versus 0.20). For recipient all comers, neither BSA nor height were good correlates of APD, except in recipients without ascites, where BSA correlated well (PhiK = 0.63) but height did not. However, among female recipients, BSA, but not height, strongly correlated to APD regardless of ascites status (PhiK = 0.80 without, PhiK = 0.70 with). Among male recipients, BSA correlated to APD only in those without ascites (PhiK = 0.74). In multivariable models, both BSA and height were predictive of waitlist outcomes, with higher values being associated with increased access, decreased delisting for death/clinical deterioration, and decreased living donor transplant (model concordance 0.748 and 0.747, respectively). Conclusions: Taken together, BSA is a good surrogate for APD and can therefore be used in allocation decision making in the upcoming CD era to offset size and gender-based disparities among certain candidate populations.

Early allogeneic immune modulation after establishment of donor hematopoietic cell-induced mixed chimerism in a nonhuman primate kidney transplant model.

Background: Mixed lymphohematopoietic chimerism is a proven strategy for achieving operational transplant tolerance, though the underlying immunologic mechanisms are incompletely understood. Methods: A post-transplant, non-myeloablative, tomotherapy-based total lymphoid (TLI) irradiation protocol combined with anti-thymocyte globulin and T cell co-stimulatory blockade (belatacept) induction was applied to a 3-5 MHC antigen mismatched rhesus macaque kidney and hematopoietic cell transplant model. Mechanistic investigations of early (60 days post-transplant) allogeneic immune modulation induced by mixed chimerism were conducted. Results: Chimeric animals demonstrated expansion of circulating and graft-infiltrating CD4+CD25+Foxp3+ regulatory T cells (Tregs), as well as increased differentiation of allo-protective CD8+ T cell phenotypes compared to naïve and non-chimeric animals. In vitro mixed lymphocyte reaction (MLR) responses and donor-specific antibody production were suppressed in animals with mixed chimerism. PD-1 upregulation was observed among CD8+ T effector memory (CD28-CD95+) subsets in chimeric hosts only. PD-1 blockade in donor-specific functional assays augmented MLR and cytotoxic responses and was associated with increased intracellular granzyme B and extracellular IFN-γ production. Conclusions: These studies demonstrated that donor immune cell engraftment was associated with early immunomodulation via mechanisms of homeostatic expansion of Tregs and early PD-1 upregulation among CD8+ T effector memory cells. These responses may contribute to TLI-based mixed chimerism-induced allogenic tolerance.

Helical TomoTherapy Total Lymphoid Irradiation and Hematopoietic Cell Transplantation for Kidney Transplant Tolerance in Rhesus Macaques.

Development of a post-transplant kidney transplant tolerance induction protocol involving a novel total lymphoid irradiation (TLI) conditioning method in a rhesus macaque model is described. We examined the feasibility of acheiving tolerance to MHC 1-haplotype matched kidney transplants by establishing a mixed chimeric state with infusion of donor hematopoietic cells (HC) using TomoTherapy TLI. The chimeric state was hypothesized to permit the elimination of all immunosuppressive (IS) medications while preserving allograft function long-term without development of graft-versus-host-disease (GVHD) or rejection. An experimental group of 11 renal transplant recipients received the tolerance induction protocol and outcomes were compared to a control group (n = 7) that received the same conditioning but without donor HC infusion. Development of mixed chimerism and operational tolerance was accomplished in two recipients in the experimental group. Both recipients were withdrawn from all IS and continued to maintain normal renal allograft function for 4 years without rejection or GVHD. None of the animals in the control group achieved tolerance when IS was eliminated. This novel experimental model demonstrated the feasibility for inducing of long-term operational tolerance when mixed chimerism is achieved using a TLI post-transplant conditioning protocol in 1-haplotype matched non-human primate recipients of combined kidney and HC transplantation.

Extracellular Vesicle-associated GARP/TGFß:LAP Mediates "Infectious" Allo-tolerance.

Here we test the hypothesis that, like CD81-associated "latent" IL35, the transforming growth factor (TGF)ß:latency-associated peptide (LAP)/glycoprotein A repetitions predominant (GARP) complex was also tethered to small extracellular vesicles (sEVs), aka exosomes, produced by lymphocytes from allo-tolerized mice. Once these sEVs are taken up by conventional T cells, we also test whether TGFß could be activated suppressing the local immune response. Methods: C57BL/6 mice were tolerized by i.p. injection of CBA/J splenocytes followed by anti-CD40L/CD154 antibody treatment on days 0, 2, and 4. On day 35, spleen and lymph nodes were extracted and isolated lymphocytes were restimulated with sonicates of CBA splenocytes overnight. sEVs were extracted from culture supernatants by ultracentrifugation (100 000g) and assayed for (a) the presence of TGFß:LAP associated with tetraspanins CD81,CD63, and CD9 by enzyme-linked immunosorbent assay; (b) GARP, critical to membrane association of TGFß:LAP and to activation from its latent form, as well as various TGFß receptors; and (c) TGFß-dependent function in 1° and 2° immunosuppression of tetanus toxoid-immunized B6 splenocytes using trans-vivo delayed-type hypersensitivity assay. Results: After tolerization, CBA-restimulated lymphocytes secreted GARP/TGFß:LAP-coated extracellular vesicles. Like IL35 subunits, but unlike IL10, which was absent from ultracentrifuge pellets, GARP/TGFß:LAP was mainly associated with CD81+ exosomes. sEV-bound GARP/TGFß:LAP became active in both 1° and 2° immunosuppression, the latter requiring sEV uptake by "bystander" T cells and reexpression on the cell surface. Conclusions: Like other immune-suppressive components of the Treg exosome, which are produced in a latent form, exosomal GARP/TGFß:LAP produced by allo-specific regulatory T cells undergoes either immediate activation (1° suppression) or internalization by naive T cells, followed by surface reexpression and subsequent activation (2°), to become suppressive. Our results imply a membrane-associated form of TGFß:LAP that, like exosomal IL35, can target "bystander" lymphocytes. This new finding implicates exosomal TGFß:LAP along with Treg-derived GARP as part of the infectious tolerance network.

Blood products and liver transplantation: A strategy to balance optimal preparation with effective blood stewardship.

BACKGROUND: Unanticipated transfusion requirements during liver transplantation can delay lifesaving intraoperative resuscitation and strain blood bank resources. Risk-stratified preoperative blood preparation can mitigate these deleterious outcomes. STUDY DESIGN AND METHODS: A two-tiered blood preparation protocol for liver transplantation was retrospectively evaluated. Eleven binary variables served as criteria for high-risk (HR) allocation. Primary outcomes included red blood cell (RBC), plasma (FFP), and platelet (Plt) utilization. Secondary outcomes included product under- and overpreparation. Contingency tables for transfusion requirements above the population means were generated using 15 clinical variables. Modified protocols were developed and retrospectively optimized using the study population. RESULTS: Of 225 recipients, 102 received HR preoperative orders, which correlated to higher intraoperative transfusion requirements. However, univariate analysis identified only two statistical risk factors per product: Hgb ≤7.8 g/dl (p < .001) and MELD ≥38 (p = .035) for RBCs, Hgb ≤7.8 g/dl (p = .002) and acute alcoholic hepatitis (p = 0.015) for FFP, and Hgb ≤7.8 g/dl (p = .001) and normothermic liver preservation (p = .037) for Plts. Based on these findings, we developed modified protocols for individual products, which were evaluated retrospectively for their effectiveness at reducing under-preparatory events while limiting product overpreparation. Cohort statistics were used to define the preparation strategy for each protocol. Retrospective comparative analysis demonstrated the superiority of the modified protocols by improving the under-preparation rate from 24% to <10% for each product, which required a 1.56-fold and 1.44-fold increase in RBC and FFP overpreparation, respectively. Importantly, there was no difference in Plt overpreparation. DISCUSSION: We report translatable data-driven blood bank preparation protocols for liver transplantation.

Robust engraftment of fetal nonhuman primate CD34-positive cells in immune-deficient mice.

Nonhuman primates (NHPs) represent one of the most important models for preclinical studies of novel biomedical interventions. In contrast with small animal models, however, widespread utilization of NHPs is restricted by cost, logistics, and availability. Therefore, we sought to develop a translational primatized mouse model, akin to a humanized mouse, to allow for high-throughput in vivo experimentation leveraged to inform large animal immunology-based studies. We found that adult rhesus macaque mobilized blood (AMb) CD34+-enriched hematopoietic stem and progenitor cells (HSPCs) engrafted at low but persistent levels in immune-deficient mice harboring transgenes for human (NHP cross-reactive) GM-CSF and IL3, but did not in mice with wild-type murine cytokines lacking NHP cross-reactivity. To enhance engraftment, fetal liver-derived HSPCs were selected as the infusion product based on an increased CD34hi fraction compared with AMb and bone marrow. Coupled with cotransplantation of rhesus fetal thymic fragments beneath the mouse kidney capsule, fetal liver-derived HSPC infusion in cytokine-transgenic mice yielded robust multilineage lymphohematopoietic engraftment. The emergent immune system recapitulated that of the fetal monkey, with similar relative frequencies of lymphocyte, granulocyte, and monocyte subsets within the thymic, secondary lymphoid, and peripheral compartments. Importantly, while exhibiting a predominantly naïve phenotype, in vitro functional assays demonstrated robust cellular activation in response to nonspecific and allogenic stimuli. This primatized mouse represents a viable and translatable model for the study of hematopoietic stem cell physiology, immune development, and functional immunology in NHPs. Summary Sentence: Engraftment of rhesus macaque hematopoietic tissues in immune-deficient mice yields a robust BLT/NeoThy-type primatized mouse model for studying nonhuman primate hematopoiesis and immune function in vivo.

Cross-decoration of dendritic cells by non-inherited maternal antigen-containing extracellular vesicles: Potential mechanism for PD-L1-based tolerance in cord blood and organ transplantation.

Exposure to non-inherited maternal antigens (NIMA) during the fetal period induces lifelong split tolerance to grafts expressing these allo-antigens. In adult mice, the production of extracellular vesicles (EVs) from maternal microchimeric cells causes cross-decoration (XD) of offspring dendritic cells (DC) with NIMA and upregulation of PD-L1, contributing to NIMA tolerance. To see how this may apply to humans, we tested NIMA acquisition by fetal DCS in human cord blood. The average percentage of NIMA-XD among total DCs was 2.6% for myeloid and 4.5% for Plasmacytoid DC. These cells showed higher PD-L1 expression than their non-XD counterparts (mDC: p = .0016; pDC: p = .024). We detected CD9+ EVs bearing NIMA and PD-L1 in cord blood. To determine if this immune regulatory mechanism persists beyond the pregnancy, we analyzed NIMA-expressing kidney and liver transplant recipients. We found donor antigen XD DCs in peripheral blood and graft-infiltrating DCs. As in cord blood, the pattern of donor antigen expression was punctate, and PD-L1 expression was upregulated, likely due to both protein and miRNA acquired from EV. Our findings support a mechanism for split tolerance to NIMAs that develops during pregnancy and is recapitulated in adult transplant recipients.

Correlation of Time to Soft Tissue Coverage With Clinical Outcome in Lower Extremity Trauma in the Modern Era: A Single-Center Retrospective Review.

Background: Lower extremity salvage in the setting of severe trauma requires the consideration of multiple surgical specialties and treatment algorithms. We hypothesized that time to first ambulation, ambulation without an assistive device, chronic osteomyelitis, and delayed amputation were not affected by the time to soft tissue coverage in Gustilo IIIB and IIIC fractures at our institution. Methods: We evaluated all patients treated for open tibia fractures at our institution from 2007 to 2017. Patients requiring any form of soft tissue coverage to the lower extremity during their initial hospitalization and who had at least 30 days of follow-up from time of hospital discharge were included. Univariable and multivariable analysis was performed for all variables and outcomes of interest. Results: Of 575 patients included, 89 required soft tissue coverage. On multivariable analysis, the time to soft tissue coverage, length of negative pressure wound therapy treatment, and number of wound washouts were not found to be associated with development of chronic osteomyelitis, decreased 90-day return to any ambulation, decreased 180-day return to ambulation without assistive device, or delayed amputation. Conclusions: Time to soft tissue coverage in open tibia fractures did not affect time to first ambulation, ambulation without an assistive device, chronic osteomyelitis, or delayed amputation in this cohort. It remains difficult to definitively prove that time to soft tissue coverage meaningfully impacts lower extremity outcomes.

Donor-Recipient BSA Matching Is Prognostically Significant in Solitary and En Bloc Kidney Transplantation From Pediatric Circulatory Death Donors.

BACKGROUND: As the rate of early postoperative complications decline after transplant with pediatric donation after circulatory death (DCD) kidneys, attention has shifted to the long-term consequences of donor-recipient (D-R) size disparity given the pernicious systemic effects of inadequate functional nephron mass. METHODS: We conducted a retrospective cohort study using Organ Procurement and Transplantation Network data for all adult (aged ≥18 y) recipients of pediatric (aged 0-17 y) DCD kidneys in the United States from January 1, 2004 to March 10, 2020. RESULTS: DCD pediatric allografts transplanted between D-R pairs with a body surface area (BSA) ratio of 0.10-0.70 carried an increased risk of all-cause graft failure (relative risk [RR], 1.36; 95% confidence interval [CI], 1.10-1.69) and patient death (RR, 1.32; 95% CI, 1.01-1.73) when compared with pairings with a ratio of >0.91. Conversely, similar graft and patient survivals were demonstrated among the >0.70-0.91 and >0.91 cohorts. Furthermore, we found no difference in death-censored graft survival between all groups. Survival analysis revealed improved 10-y patient survival in recipients of en bloc allografts (P = 0.02) compared with recipients of single kidneys with D-R BSA ratios of 0.10-0.70. A similar survival advantage was demonstrated in recipients of solitary allografts with D-R BSA ratios >0.70 compared with the 0.10-0.70 cohort (P = 0.02). CONCLUSIONS: Inferior patient survival is likely associated with systemic sequelae of insufficient renal functional capacity in size-disparate DCD kidney recipients, which can be overcome by appropriate BSA matching or en bloc transplantation. We therefore suggest that in DCD kidney transplantation, D-R BSA ratios of 0.10-0.70 serve as criteria for en bloc allocation or alternative recipient selection to optimize the D-R BSA ratio to >0.70.

Livers From Pediatric Donation After Circulatory Death Donors Represent a Viable and Underutilized Source of Allograft.

Despite increased numbers of donation after circulatory death (DCD) donors, pediatric DCD livers are underused. To investigate possible reasons for this discrepancy, we conducted a retrospective cohort study using 2 data sets from the Organ Procurement and Transplantation Network for all deceased liver donors and for all recipients of DCD liver transplants from March 8, 1993, to June 30, 2018. Pediatric (0-12 years) and adolescent (13-17 years) DCD donors were compared with those aged 18-40 years. We found that pediatric DCD allografts are recovered at a significantly lower rate than from 18-to-40-year-old donors (27.3% versus 56.3%; P < 0.001). However, once recovered, these organs are transplanted at a similar rate to those from the 18-to-40-year-old donor cohort (74.7% versus 74.2%). Significantly more pediatric DCD livers (odds ratio [OR], 3.75; confidence interval [CI], 3.14-4.47) were not recovered compared with adult organs, which were most commonly not recovered due to organ quality (10.2% versus 7.1%; P < 0.001). The 10-year relative risks (RRs) for graft failure and patient death were similar between pediatric and adult DCD donors, with adolescent DCD livers demonstrating improved outcomes. DCD livers transplanted into pediatric donors were protective against graft failure (RR, 0.46; 95% confidence interval [CI], 0.21-0.99) and patient death (RR, 0.16; 95% CI, 0.04-0.69). In conclusion, despite lower rates of recovery, pediatric DCD livers represent a viable organ source for certain adults and children.

Evaluation of benazepril in cats with heart disease in a prospective, randomized, blinded, placebo-controlled clinical trial.

BACKGROUND: Heart disease is an important cause of morbidity and mortality in cats, but there is limited evidence of the benefit of any medication. HYPOTHESIS: The angiotensin-converting enzyme inhibitor benazepril would delay the time to treatment failure in cats with heart disease of various etiologies. ANIMALS: One hundred fifty-one client-owned cats. METHODS: Cats with heart disease, confirmed by echocardiography, with or without clinical signs of congestive heart failure, were recruited between 2002 and 2005 and randomized to benazepril or placebo in a prospective, multicenter, parallel-group, blinded clinical trial. Benazepril (0.5-1.0 mg/kg) or placebo was administered PO once daily for up to 2 years. The primary endpoint was treatment failure. Analyses were conducted separately for all-cause treatment failure (main analysis) and heart disease-related treatment failure (supportive analysis). RESULTS: No benefit of benazepril versus placebo was detected for time to all-cause treatment failure (P = .42) or time to treatment failure related to heart disease (P = .21). Hazard ratios (95% confidence interval [CI]) from multivariate analysis for benazepril compared with placebo were 1.00 (0.57-1.74) for all-cause failure, and 0.99 (0.50-1.94) for forward selection and 0.93 (0.48-1.81) for bidirectional selection models for heart disease-related failure. There were no significant differences between groups over time after administration of the test articles in left atrium diameter, left ventricle wall thickness, quality of life scores, adverse events, or plasma biochemistry or hematology variables. CONCLUSIONS AND CLINICAL RELEVANCE: Benazepril was tolerated well in cats with heart disease, but no evidence of benefit was detected.

Irradiated superficial femoral artery rupture after free flap: a case report and review of the literature.

Radical oncologic resection can result in large soft tissue defects with exposure of underlying vessels. Unless immediately covered with viable soft tissue, these vessels are vulnerable to desiccation from air exposure and mechanical trauma. Local radiation treatment also contributes to a decline in vessel wall strength. We present an index case of a patient with prolonged exposure of her femoral bone and superficial femoral artery after an initial failed reconstruction of a soft tissue sarcoma resection defect. We provided coverage using a free latissimus dorsi muscle flap. Two weeks after the initial free flap operation, the patient was readmitted to emergency service with profuse bleeding from beneath the free flap. Intraoperative inspection revealed a 2-cm defect of the irradiated superficial femoral artery. The defect was repaired with cryopreserved human arterial graft, and the flap was reset. This case highlights the importance of immediate coverage of soft tissue defects after oncologic resection. If any vessels are left exposed, they should be closely inspected before a delayed flap coverage to rule out future sources of bleeding that may jeopardize the outcomes of an otherwise successful free flap operation.

The key components of Schwann cell-like differentiation medium and their effects on gene expression pattern of adipose-derived stem cells.

BACKGROUND: Schwann cell-like cells differentiated from adipose-derived stem cells may have an important role in peripheral nerve regeneration. Herein, we document the individual effects of growth factors in Schwann cell-like differentiation medium. METHODS: There were 6 groups in the study. In the control group, we supplemented the rat adipose-derived stem cells with normal cell culture medium. In group 1, we fed the cells with Schwann cell-like differentiation medium (normal cell culture medium supplemented with platelet-derived growth factor, basic fibroblast growth factor, forskolin, and glial growth factor). In the other groups, we removed the components of the medium one at a time from the differentiation medium so that group 2 lacked glial growth factor, group 3 lacked forskolin, group 4 lacked basic fibroblast growth factor, and group 5 lacked platelet-derived growth factor. We examined the expression of the Schwann cell-specific genes with quantitative reverse transcription polymerase chain reaction and immunofluorescence staining in each group. RESULTS: Groups 3 and 4, lacking forskolin and basic fibroblast growth factor, respectively, had the highest expression levels of integrin-ß4, and p75. Group 1 showed a 3.2-fold increase in the expression of S100, but the expressions of integrin-ß4 and p75 were significantly lower compared to groups 3 and 4. Group 2 [glial growth factor (-)] did not express significant levels of Schwann cell-specific genes. The gene expression profile in group 4 most closely resembled Schwann cells. Immunofluorescence staining results were parallel with the quantitative real-time polymerase chain reaction results. CONCLUSIONS: Glial growth factor is a key component of Schwann cell-like differentiation medium.

The Effect of Chondroitin Sulphate and Hyaluronic Acid on Chondrocytes Cultured within a Fibrin-Alginate Hydrogel.

Osteoarthritis is a painful degenerative joint disease that could be better managed if tissue engineers can develop methods to create long-term engineered articular cartilage tissue substitutes. Many of the tissue engineered cartilage constructs currently available lack the chemical stimuli and cell-friendly environment that promote the matrix accumulation and cell proliferation needed for use in joint cartilage repair. The goal of this research was to test the efficacy of using a fibrin-alginate hydrogel containing hyaluronic acid (HA) and/or chondroitin sulphate (CS) supplements for chondrocyte culture. Neonatal porcine chondrocytes cultured in fibrin-alginate hydrogels retained their phenotype better than chondrocytes cultured in monolayer, as evidenced by analysis of their relative expression of type II versus type I collagen mRNA transcripts. HA or CS supplementation of the hydrogels increased matrix glycosaminoglycan (GAG) production during the first week of culture. However, the effects of these supplements on matrix accumulation were not additive and were no longer observed after two weeks of culture. Supplementation of the hydrogels with CS or a combination of both CS and HA increased the chondrocyte cell population after two weeks of culture. Statistical analysis indicated that the HA and CS treatment effects on chondrocyte numbers may be additive. This research suggests that supplementation with CS and/or HA has positive effects on cartilage matrix production and chondrocyte proliferation in three-dimensional (3D) fibrin-alginate hydrogels.

Notch-inducible hyperphosphorylated CREB and its ultradian oscillation in long-term memory formation.

Notch is a cell surface receptor that is known to regulate developmental processes by establishing physical contact between neighboring cells. Many recent studies show that it also plays an important role in the formation of long-term memory (LTM) in adults, implying that memory formation requires regulation at the level of cell-cell contacts among brain cells. Neither the target of Notch activity in LTM formation nor the underlying mechanism of regulation is known. We report here results of our studies in adult Drosophila melanogaster showing that Notch regulates dCrebB-17A, the CREB protein. CREB is a transcriptional factor that is pivotal for intrinsic and synaptic plasticity involved in LTM formation. Notch in conjunction with PKC activity upregulates the level of a hyperphosphorylated form of CREB (hyper-PO4 CREB) and triggers its ultradian oscillation, both of which are linked to LTM formation. One of the sites that is phosphorylated in hyper-PO4 CREB is serine 231, which is the functional equivalent of mammalian CREB serine 133, the phosphorylation of which is an important regulator of CREB functions. Our data suggest the model that Notch and PKC activities generate a cyclical accumulation of cytoplasmic hyper-PO4 CREB that is a precursor for generating the nuclear CREB isoforms. Cyclical accumulation of CREB might be important for repetitive aspects of LTM formation, such as memory consolidation. Because Notch, PKC, and CREB have been implicated in many neurodegenerative diseases (e.g., Alzheimer's disease), our data might also shed some light on memory loss and dementia.

Notch and PKC are involved in formation of the lateral region of the dorso-ventral axis in Drosophila embryos.

The Notch gene encodes an evolutionarily conserved cell surface receptor that generates regulatory signals based on interactions between neighboring cells. In Drosophila embryos it is normally expressed at a low level due to strong negative regulation. When this negative regulation is abrogated neurogenesis in the ventral region is suppressed, the development of lateral epidermis is severely disrupted, and the dorsal aminoserosa is expanded. Of these phenotypes only the anti-neurogenic phenotype could be linked to excess canonical Notch signaling. The other phenotypes were linked to high levels of Notch protein expression at the surface of cells in the lateral regions indicating that a non-canonical Notch signaling activity normally functions in these regions. Results of our studies reported here provide evidence. They show that Notch activities are inextricably linked to that of Pkc98E, the homolog of mammalian PKCδ. Notch and Pkc98E up-regulate the levels of the phosphorylated form of IκBCactus, a negative regulator of Toll signaling, and Mothers against dpp (MAD), an effector of Dpp signaling. Our data suggest that in the lateral regions of the Drosophila embryos Notch activity, in conjunction with Pkc98E activity, is used to form the slopes of the opposing gradients of Toll and Dpp signaling that specify cell fates along the dorso-ventral axis.

Histological changes in the external ear canal of dogs with otitis externa.

This study aimed to better characterise the gross anatomy of the normal ear canal, and to compare histological features of the normal ear canal to those affected by chronic otitis externa. In 40 normal ears from 20 dogs, the length of the annular and auricular cartilage was 1.2 +/- 0.2 and 4.1 +/- 0.9 cm, respectively; overall length of the external ear canal was 5.3 +/- 1.0 cm. The maximal internal diameter at the distal end of the external ear canal, the proximal opening of the auricular cartilage and the proximal end of the annular cartilage was 5.8 +/- 1.5, 0.7 +/- 0.2 and 0.5 +/- 0.1 cm, respectively. Body weight correlated positively with the overall length and diameter of the distal end of the ear canal (r = 0.78, P < 0.001; r = 0.42, P < 0.05). Morphometric evaluation was carried in 28 clinically healthy ears of 14 dogs, and 15 otitic ears of 13 dogs. Histological features of this integument revealed that the density and distribution of sebaceous and ceruminous gland tissue exhibits marked variation between individuals. Nevertheless, general patterns were observed; sebaceous tissue increases gradually from the proximal to the distal parts of the ear canal, whilst ceruminous gland tissue by contrast decreases. In otitic canine ears, the distribution of sebaceous and ceruminous glandular tissue was similar to normal ears but the glands became larger and hyperplastic (P < 0.05). Density of hair follicles was not different between healthy and otitic ears (P = 0.16), but the hair follicles became hyperplastic in otitic ears.