[Blunt abdominal trauma in children and adolescents: treatment concepts in the acute phase]. / Stumpfes Bauchtrauma bei Kindern und Jugendlichen: Behandlungskonzepte in der Akutphase.

Fatal accidents due to blunt force trauma are the leading cause of death in children and adolescents [1]. Abdominal trauma is the third most common cause of death after traumatic brain injury and thoracic injuries [2]. Abdominal injury is seen in approximately 2-5% of children involved in accidents [3]. Blunt abdominal injuries are common sequelae of traffic accidents (for example as seat belt injury), falls, and sports accidents. Penetrating abdominal injuries are rare in central Europe. Spleen, liver, and kidney lacerations are the most common injuries after blunt abdominal trauma [4]. In most situations, nonoperative management (NOM) has become the gold standard with the surgeon leading the multidisciplinary treatment [5].

[Treatment principles and outcome after fractures of the lateral humeral condyle in children]. / Therapieprinzipien und Outcome nach Frakturen des Condylus radialis im Wachstumsalter.

BACKGROUND: Fractures of the lateral humeral condyle with displacement (>2 mm; <2 mm articular gap) require open reduction and stabilization. Non-displaced fractures should be treated conservatively; however, there are difficulties in the differentiation of complete (potentially unstable) an incomplete (stable) articular fractures. The aim of this study was to analyze the frequency of conservative and operative treatment approaches as well as the accuracy of treatment decisions based on fracture stability displayed on repetitive X­rays. MATERIAL AND METHODS: A retrospective data analysis of all lateral humeral condyles in children <16 years old treated between 2005 and 2014 was carried out. The patients were classified according to the fracture stability at the time of the incident (primarily stable or unstable) and after 4 days (secondarily stable or unstable) using conventional X­ray images. RESULTS: A total of 89 fractures of the lateral humeral condyle were treated (mean age 6.4 years, range 0.9-14 years). Of the fractures 52 (58%) were initially not displaced and 37 (42%) were initially displaced. The latter underwent open reduction and stabilization by osteosynthesis (primarily stable). Of the 52 initially not displaced fractures 35 remained stable and conservative treatment in a plaster cast was performed (primarily and secondarily stable). In 8 out of 52 cases a secondary displacement (>2 mm articular gap) occurred after an average of 6 days (range 3-10 days) and operative treatment was initiated (primarily stable and secondarily unstable). No follow-up x­ray could be performed in 2 of the 52 fractures and at the end of treatment the fractures healed with displacement (primarily stable and secondarily unstable). In 7 of the 52 fractures operative treatment was performed although no displacement (primarily stable) was initially documented (overtreatment). The outcome of the whole study cohort was comparable with that described in the literature. CONCLUSION: Treatment decisions in pediatric lateral humeral condyle fractures are based on the primary and secondary fracture stability as observed in staged follow-up radiographs. Stable fractures, whether complete or incomplete, healed with good results after conservative treatment and overtreatment could be avoided. Unstable fractures, whether primary or secondary during the course, need to be recognized as such and operative treatment with a stable osteosynthesis must be initiated.

[Strategies for paediatric spleen and liver injuries]. / Behandlungsstrategien bei Verletzungen von Milz und Leber im Kindesalter.

Traumatic injuries of the spleen and liver are typically caused by age-related falls or sports and traffic accidents. Today, the non-operative management for isolated injuries is established and evidence-based guidelines are available. The intact abdominal wall and the limited space within the peritoneum produce a compression which is the pathophysiological explanation for the limitation of the haemorrhage. Precondition for the non-operative therapy is the radiology-based classification of the injury (organ injury scale) and a haemodynamically stable patient. Haemodynamic stability is, if necessary maintained with blood transfusion, volume substitutes and the administration of catecholamines. In cases of hilar vascular injury and devascularisation or haemodynamic instability of the patient, despite utilisation of the measures mentioned above, urgent operative therapy needs to be performed. Organ sparing surgery is the therapy of choice for both liver and spleen. The spleen is required for the development of a competent immune system in the growing organism. Liver injuries can be further complicated by injury to the bile system, which might require operative reconstruction. If a patient suffers from multiple injuries and spleen or liver are involved, the decision on the management needs to be taken individually, no guidelines exist but the rate for operative therapy increases. Independent of the dimensions of injury, an experienced paediatric surgeon with his multidisciplinary team, considering the anatomic and age specific characteristics of a child, achieves the best therapeutic results.

[Growth behavior after fractures of the distal forearm: reasons for the high rate of overtreatment]. / Wachstumsverhalten nach Frakturen des distalen Unterarms: Gründe für die hohe Rate an Übertherapie.

BACKGROUND: The distal forearm fracture is the most common injury (40%) in pediatric traumatology. OBJECTIVES: The treatment of distal forearm fractures in the growth phase contains two contrasting phenomena which are incompatible with the patient's interests and are discussed in this article. METHODS: A selective literature search was carried out and selected cases are discussed. RESULTS: On the one hand there is a unique property of the juvenile skeleton with an enormous potential for spontaneous correction enabling conservative treatment for the majority of fractures. This generally leads to healing without functional or cosmetic defects, even in cases of some minor residual angulations. In contrast, high rates of overtreatment are observed, such as unnecessary or repetitive reductions and operative interventions, which are not only the result of ignorance of the growth prognosis and of correct conservative techniques but also of economic factors as a consequence of medical economization as well as positive experiences gained in adults but which cannot be transferred to children. The management of distal forearm fractures should be reserved for unstable fracture types especially in adolescent patients with limited age-dependent potential for spontaneous correction. Angulated fractures should be treated using cast wedging in order to reduce angulation to a reasonable extent. The most frequently occurring stable torus fractures require immobilization only for analgesic reasons. Intolerable angulations as well as completely dislocated fractures are treated by closed reduction and stabilized with a Kirschner wire osteosynthesis depending on age. CONCLUSION: Treatment of distal forearm fractures should be appropriate for children as well as highly efficient, by using a minimal amount of effort. Current forms of overtreatment have to be avoided because of moral and in particular economic reasons.

Pharmacological inhibition of beta-catenin in hepatoblastoma cells.

PURPOSE: The proto-oncogene beta-catenin is linked to an abnormal activation of the Wnt/beta-catenin-pathway and shows mutations in 50-90 % of hepatoblastoma (HB). Corresponding, the recently published murine orthotopic HB model differs from the former subcutaneous model by nuclear beta-catenin distribution. As the nuclear localization of beta-catenin is considered to reflect a more aggressive tumor growth, the influence of beta-catenin inhibition on cell viability and drug-efficiency in HB cells was analyzed. METHODS: Beta-catenin distribution in HB cells was analyzed by immunofluorescence. The influence of beta-catenin inhibitors Celecoxib, Etodolac, ICG001, and MET kinase inhibitor (SU11274) alone and in combination with cisplatin (CDDP) on HB cell lines (HuH6, HepT1) was evaluated by cell viability assays and BrdU incorporation. RESULTS: Celecoxib and ICG001 reduced dose-dependently HB cell viability and decreased nuclear beta-catenin in cultivated HB cells. Etodolac was without influence at concentrations up to 100 µM. Combinations of Celecoxib or ICG001 with MET kinase inhibitor or CDDP resulted in additive reduction of cell viability. CONCLUSION: Pharmaceutical beta-catenin inhibitors can modulate the nuclear localization of beta-catenin and reduce cell viability of HB cells in vitro. These promising effects might optimize the outcome of high-risk HB. The orthotopic HB model is a suitable basis for further in vivo studies.

[Diametaphyseal forearm fracture in childhood. Pitfalls and recommendations for treatment]. / Die diametaphysäre Unterarmfraktur im Kindesalter. Pitfalls und Empfehlungen in der Behandlung.

The optimal treatment for fractures in the diametaphyseal transition zone of the forearm is still a matter of debate. Stable fractures should be immobilized or treated by closed reduction when non-tolerably displaced. Unstable and displaced fractures can be treated by various operative techniques, which are all characterized by technical impracticability or disadvantages for the patient. In younger patients transepiphyseal intramedullary K-wire fixation represents a minimally invasive, quick and technically easy treatment option but requires additional immobilisation. In adolescent patients volar locking plate osteosynthesis constitutes an immobilisation-free treatment option, but is combined with high invasiveness. Percutaneous K-wire fixation and elastic stable intramedullary nailing may lead to poor results in the diametaphyseal region due to technical or biomechanical problems associated with the implant. The external fixator is indicated in some multifragmentary fractures. The choice of treatment option often results from an individual decision based on the patient's age, complexity and stability of the fracture and interest of the patient. The priority objective of all treatment modalities is a fully functional upper extremity, i.e. full range of motion.

Unstable diametaphyseal forearm fractures: transepiphyseal intramedullary Kirschner-wire fixation as a treatment option in children.

BACKGROUND: In unstable metaphyseal and diaphyseal forearm fractures the treatment of choice is percutaneous Kirschner wire (K-wire) fixation or elastic stable intramedullary nailing (ESIN), respectively. The optimal treatment for the diametaphyseal transition zone is still a matter of debate. METHODS: The diametaphyseal transition zone was defined as the square over the "physis of distal radius and ulna" minus the square of "physis of distal radius alone". Transepiphyseal intramedullary K-wire fixation was performed in unstable fractures affecting this transitional area. The operative, postoperative and functional outcomes were assessed and compared to previously treated patients who were treated using other techniques (plate, external fixator or ESIN). RESULTS: 10 patients received transepiphyseal intramedullary K-wire fixation. Additionally the ulna was stabilized by antegrade ESIN in 5 cases. Cast immobilization was performed for 39, sports restriction for 43 and metal removal was done after 50 days. No complications, bone malalignment, or functional deficits occurred (mean follow-up: 17 months). 13 patients were treated using alternative options. 3 patients had plates with cast immobilization for 26 days, sports restriction for 63 and metal removal after 287 days. 5 patients were treated by external fixation for 54 days. Their sports restriction was 73 days. The remaining 5 patients had ESIN. In 1 of these cases additional cast immobilization was necessary. Their sports restriction was 51 days and metal removal was done after 88 days. In 4 cases a malalignment >10° of the radius was documented, and 1 patient had a functional deficit of forearm pro-/supination. CONCLUSION: Transepiphyseal intramedullary K-wire fixation in unstable diametaphyseal forearm fractures is a minimally invasive, quick and technically easy treatment option but requires additional immobilization. Our data suggest that this technique offers advantages compared to alternative treatment options.

Neutrophil maturation and activation determine anatomic site of clearance from circulation.

The long-term disposition of circulating neutrophils and the site of disappearance from circulation remain unclear. We investigated neutrophil localization in mice using (111)In-labeled murine peripheral blood neutrophils, mature bone marrow neutrophils, and peritoneal exudate neutrophils to track in vivo localization of these different cell populations. Infused peripheral neutrophils were found to localize equally between liver and marrow sites by 4 h (31.2 +/- 1.9 vs. 31.9 +/- 1.8%), whereas exudate neutrophils predominantly localized to liver (42.0 +/- 1.1%) and marrow-derived neutrophils to the marrow (65.9 +/- 6.6%) where they were found to localize predominantly in the hematopoietic cords. Stimulation of marrow neutrophils before infusion caused a shift in localization from marrow to liver, and subsequent induction of an inflammatory site after infusion and marrow sequestration led to remobilization of infused marrow neutrophils but not of peripheral neutrophils. These results indicate that the marrow participates in removing neutrophils from circulation, with evidence supporting both storage and perhaps disposal functions. Furthermore, models for circulating neutrophil homeostasis should consider that the site of retention is governed by the maturation and activation states of the cell.

Motor cortex excitability in patients with focal epilepsy.

We studied the excitability of the motor cortex using, transcranial magnetic stimulation (TMS) in patients with temporal and extratemporal epilepsy. We applied single and paired-pulse TMS to 15 patients with temporal (n = 7), extratemporal (n = 6) and focal epilepsy lateralised to one hemisphere (n = 2). Patients had no antiepileptic drugs in the last 48 h and were seizure free for 4 h prior to testing. We determined the threshold for EMG responses at rest (RMT), the cortically evoked silent period (CSSP) and intracortical inhibition (ICI, intervals of 2-4 ms) and facilitation (ICF, 7-15 ms) and compared the results to those obtained in 17 normal controls. ICI and ICF was reduced in both hemispheres (P < 0.01. ANOVA) compared to the controls. In the hemisphere of seizure origin ('abnormal') there was a reduction of ICF (P < 0.01) and normal ICI, in the 'normal' hemisphere there was a reduced ICI (P < 0.01) and a slight reduction of ICF (P < 0.05). ICF on the 'abnormal' side was reduced (P < 0.05) compared to the 'normal' hemisphere. RMT was increased in two patients, but group comparison of RMT and CSSP showed no significant differences between patients and controls. The results suggest a remote effect of epileptic activity onto the motor cortex leading to an alteration of activity in local inhibitory circuits.

Synthesis and accumulation of a receptor regulatory protein associated with lipid droplet accumulation in 3T3-L1 cells.

Synthesis and accumulation of the recently identified prostaglandin F2alpha receptor regulatory protein (FPRP) was found to correlate closely with lipid droplet accumulation by 3T3-L1 preadipose cells. FPRP, a transmembrane glycoprotein, has been shown to regulate the binding of ligand to certain seven-transmembrane receptors. Anti-FPRP immunohistochemistry, Western blotting, and metabolic labeling/immunoprecipitation experiments demonstrated that FPRP was not detectable in undifferentiated 3T3-L1 cells. Interestingly, low levels of FPRP mRNA were detected in the undifferentiated 3T3-L1 cells. After induction of adipose differentiation, FPRP mRNA increased approximately 3 fold whereas FPRP synthesis increased approximately 50 fold. Differentiation induction with either dexamethasone/insulin/isobutylmethylxanthine or the thiazolidinedione derivative ADD 4743 were both effective at inducing FPRP accumulation and accumulation of lipid droplets. By co-immunohistochemical and lipid staining, greater than 99% of the cells accumulating lipid droplets possessed FPRP. FPRP mRNA and protein are also found in rat adipose tissue. Treatment of 3T3-L1 cells with an FPRP anti-sense oligonucleotide during differentiation decreased FPRP accumulation and resulted in a decrease in lipid droplets without altering the level of induction of a late marker of adipocyte differentiation, glycerol-3-phosphate dehydrogenase activity. Transient expression of an FPRP cDNA in undifferentiated 3T3-L1 cells was insufficient to induce lipid droplet accumulation.

Phlebotomy for pulmonary edema in dialysis patients.

STUDY OBJECTIVE: To assess the efficacy of phlebotomy in the treatment of pulmonary edema in hemodialysis patients. PROCEDURE: Maintenance hemodialysis patients presenting to the emergency room in respiratory distress from apparent pulmonary edema were assessed with regard to clinical response, change in blood pressure, change in hematocrit, and interval until the next hemodialysis treatment, RESULTS: Twenty-one patients underwent phlebotomy and seventeen improved markedly and did not require intubation or emergent dialysis. Hemodialysis was initiated 15.6 +/- 13.6 SD hours later. Four were able to have their treatment 24 or more hours later. Thirteen of 21 (62%) were hypertensive at the time of treatment and blood pressure tended to normalize in this subset. Four of 21 (19%) developed transient hypotension without permanent sequelae. Pre-mean hematocrit = 25.0 + 6.0 and post phlebotomy = 22.6 + 4.6 SD. All patients receiving phlebotomy survived to hospital discharge. CONCLUSION: Phlebotomy can often obviate the need for intubation or emergent dialysis in ESRD patients presenting with pulmonary edema.

Development of axonal arbors of layer 6 pyramidal neurons in ferret primary visual cortex.

We followed the development of axonal arbors of layer 6 pyramidal neurons in ferret striate cortex to determine whether early developing axon collaterals are formed specifically in the correct target layers from the outset or achieve their adult specificity by the elimination of initially exuberant projections. These neurons were chosen for study because they are amongst the first to be generated in the developing ferret's striate cortex, and, in mature animals, these cells have axonal arbors that are highly specific for layer 4 and to a lesser extent layers 2/3 but have few collateral branches in layer 5. The axonal arbors of individual layer 6 pyramidal neurons were reconstructed following labeling in living slices prepared from the striate cortex of ferrets aged 13-35 days postnatal (P13-35). At the earliest ages (P13-15), axonal arbors consisted of a simple axon extending from the base of the cell body into the subplate or white matter and usually forming a few collateral branches but never ascending into layer 5. By P19-20, about one-half of the cells had extended axon collaterals into layer 5 or higher, and these already appeared to branch preferentially in layer 4. All of the cells from older animals had substantial axonal arbors in layers 2-4. By P26-28, there were approximately ten times as many axonal branches in layer 4 as in layer 5. Between P26-28 and P35, there was no significant change in the number of branches in layer 5, but the numbers of both branches and of axon collateral terminations in layer 4 approximately doubled. Thus, the extent of axonal arborization in layer 4 increases dramatically between P13 and P35, and growth is highly specific for correct target layers, with few branches formed in layer 5.

Disruption of the vimentin intermediate filament system during adipose conversion of 3T3-L1 cells inhibits lipid droplet accumulation.

During the differentiation of 3T3-L1 pre-adipocytes, vimentin intermediate filaments are reorganized to form cage-like structures around the nascent lipid droplets. Initial studies with 3T3-L1 cells indicated that aggregation of vimentin filaments by nocodazole treatment during or shortly after induction of adipose conversion dramatically reduced the lipid droplet content of 3T3-L1 cells 96-120 hours after induction. Specific but transient disruption of vimentin following anti-IFA antibody injection also resulted in a decrease in lipid droplet formation in differentiating cells. To specifically and stably affect filament organization, 3T3-L1 cells lines were established by transfection with a glucocorticoid-regulatable, dominant negative mutant vimentin cDNA expression plasmid. Treatment of these cells (83 delta C) with dexamethasone resulted in expression of vimentin with a carboxyl-terminal deletion, which led to the disruption of the endogenous filament network. Induction of adipose conversion in 83 delta C cells lead to the formation of lipid droplets comparable to those seen in untransfected 3T3-L1 cells. Addition of dexamethasone during the adipose conversion of 83 delta C cells did not affect the induction of the marker enzyme glycerol-3-phosphate dehydrogenase or the incorporation of [14C]palmitate into triglycerides during a 10 minute pulse label. There was, however, a failure to form prominent lipid droplets and to accumulate [14C]palmitate-labeled triglycerides. Pulse-chase experiments indicated that the failure of these cells to accumulate triglyceride was associated with an increased rate of turnover. These studies indicate that vimentin filaments provide a function that influences lipid stability during adipose conversion of 3T3-L1 cells.

Variance cardiography for emergency department evaluation of chest pain patients.

OBJECTIVE: To determine the test performance of 24-lead variance cardiography (VC), an ECG technique that measures QRS morphologic variability, for ED evaluation of chest pain associated with coronary artery disease (CAD). METHODS: A prospective, single-blind study of VC was performed in a community teaching hospital ED. All chest pain patients (> 30 years of age) who, after initial emergency physician evaluation, were believed to have pain of potential cardiac etiology and were admitted to the hospital were eligible. Exclusion criteria included obvious noncardiac etiology for discomfort, bundle-branch block, atrial fibrillation, and incomplete subsequent cardiac evaluation. After initial evaluation and stabilization, VC was obtained. The numerical output of VC was a CAD index (CADI). Serum myoglobin and creatine kinase (CK)-MB levels were obtained at the time of presentation and after one, two, and six hours. Hospital records were reviewed to determine final diagnosis and in-hospital evaluation results. RESULTS: Fifty-two of 75 eligible patients had complete data. Final diagnoses were as follows: 27/52 (52%), noncardiac; 13/52 (25%), acute myocardial infarction (AMI); and 12/52 (23%), unstable angina due to CAD. Twenty-three percent (12/52) of the patients had CADIs < 75. Eleven of these were found to have noncardiac origins for their chest pain. The twelfth patient had a 12-lead ECG revealing AMI and had been given thrombolytic therapy with subsequent reperfusion prior to VC. Using a CADI < 75 as the cutoff for a negative study, VC alone had a negative predictive value of 92%, a sensitivity of 96%, a positive predictive value of 60%, and a specificity of 41%. CONCLUSION: A CADI < 75, in addition to clinical impression and initial ECG, may identify chest pain patients who do not have significant CAD. Further prospective assessment of VC is warranted.

Overexpression of potassium channel RNA: in vivo development rescues neurons from suppression of morphological differentiation in vitro.

Neuronal differentiation often proceeds differently in vitro than it does in vivo. Previous work demonstrated that overexpression of potassium channel RNA reduces the number of morphologically identifiable neurons that appear in cultures prepared from neural plate stage (17-1/2 hr) embryos (Jones and Ribera, 1994). Here, we report that morphological differentiation of neurons in situ is only slightly affected by overexpression of potassium channels. Endogenous factors appear to compensate for the effect of channel overexpression. Consistent with this view, when cultures are prepared from older neural tube embryos (22-24 hr), more neurons containing excess potassium channel RNA differentiate morphologically in vitro. Exposure in situ to a rapid intracellular calcium chelator, but not to tetrodotoxin, omega-conotoxin or a slow calcium chelator, prevents the compensation provided by extended development in vivo. Typically, RNA overexpression is limited to half of the embryo in order to provide an internal control. However, when potassium channel RNA is overexpressed throughout the embryo, few neurons differentiate morphologically in vitro, even if cultures are prepared from older neural tube embryos. Thus, recovery is possible if a minimum of 5 hr of further development in vivo is allowed under conditions in which rapid elevations of intracellular calcium are permitted and half of the nervous system has normal levels of potassium channel RNA. These results suggest that different or additional mechanisms operate in situ than in vitro to promote morphological differentiation of neurons.

The presence or absence of a vimentin-type intermediate filament network affects the shape of the nucleus in human SW-13 cells.

Human SW-13 cells express the intermediate filament protein vimentin in a mosaic pattern (Hedberg, K. K. and Chen, L. B. (1986). Exp. Cell Res. 163, 509-517). We have isolated SW-13 clones that do (vim+) or do not (vim-) synthesize vimentin as analyzed using anti-intermediate filament immunofluorescence, electron microscopy and two-dimensional gel analysis of detergent-extracted preparations. Vimentin is the only cytoplasmic intermediate filament protein present in the vim+ cells, and the vim- cells do not contain any detectable cytoplasmic intermediate filament system. The presence or absence of intermediate filaments did not observably affect the distribution of mitochondria, endoplasmic reticulum, microtubules or actin stress fibers when these structures were visualized by fluorescence microscopy. However, electron microscopy and anti-lamin A/C immunofluorescence studies showed that nuclear morphology in vim- cells was frequently characterized by large folds or invaginations, while vim+ cells had a more regular or smooth nuclear shape. When vim- cells were transfected with a mouse vimentin expression plasmid, the synthesis of a mouse vimentin filament network restored the smooth nuclear morphology characteristic of vim+ cells. Conversely, when vim+ cells were transfected with a carboxy-terminally truncated mutant vimentin, expression of the mutant protein disrupted the organization of the endogenous vimentin filaments and resulted in nuclei with a prominently invaginated morphology. These results indicated that in SW-13 cells the vimentin filament system affects the shape of the nucleus.

Influence of social partner on interactions of toddlers with disabilities: comparison of interactions with mothers and familiar playmates.

The social exchanges of young children with developmental disabilities over time with two different social partners and the nature of these exchanges were compared. Thirty-three toddlers with developmental disabilities were video-taped for 15 minutes with each partner at two different data points. Data were transcribed and coded using a modification of Vandell and Wilson's (1979) coding system. Results showed that more of the observation time was spent socially with mothers than with peers, and the number of turns per exchange was longer with mothers. In contrast, toddlers initiated more social exchanges with peers than with mothers. There were similarities in the content of the social exchanges with both partners. There were few changes over time, although exchanges consisted of more purely social behaviors at Time 2. Results were interpreted with respect to implications for early intervention.

Mast cell immunohistochemistry: non-immunological immunostaining mediated by non-specific F(ab')2-mast cell secretory granule interaction.

During investigations of murine and human mast cell immunoreactivity with potential anti-interleukin-4 antibodies, non-specific, non-immunological labelling of mouse and human mast cells became apparent. Non-specific, non-immunological labelling was identified by (i) immunolabelling of mast cells when using control isotype primary antibodies, (ii) ability of conjugated secondary antibodies to label mast cells without prior mast cell exposure to a primary antibody, (iii) extinction of the non-specific labelling and retention of specific labelling when the pH of the diluting and washing buffers is shifted from pH 7.2 to pH 6.0, and (iv) reduction/extinction of the labelling when the antibodies are pre-incubated with soluble heparin prior to immunostaining. The site of the reactivity on the electron microscope level was shown to be confined to the mast cell secretory granules. The results of this study support the hypothesis that non-specific labelling of mast cells results from an ionic interaction between the F(ab')2 segments of antibodies and the heparin constituent of the mast cell secretory granules. This study points out the necessity of stringent controls when using immunohistochemistry to determine mast cell reactivity to various antibodies.

Ultrastructural evidence for mast cell activation in a case of neurofibromatosis.

Neurofibromas contain fibroblasts and many mast cells, and recent hypotheses have linked fibrous tissue growth to activated mast cells. We describe the ultrastructure of mast cells and fibroblasts in a case of neurofibromatosis. Mast cells were numerous and showed extensive signs of activation. Mast cells were often intimately associated with fibroblasts, and mast cell granules could be seen inside fibroblasts ('transgranulation'). The fibroblasts were also activated. These results suggest that interactions between mast cells and fibroblasts may be important in the prominent collagen production that takes place in these tumors.