Outcomes of adolescents with acute lymphoblastic leukaemia

INTRODUCTION

Compared with young children who have acute lymphoblastic leukaemia (ALL), adolescents with ALL have unfavourable disease profiles and worse survival. However, limited data are available regarding the characteristics and outcomes of adolescents with ALL who underwent treatment in clinical trials. The aim of this study was to investigate the causes of treatment failure in adolescents with ALL.

METHODS

We retrospectively analysed the outcomes of 711 children with ALL, aged 1-18 years, who were enrolled in five clinical trials of paediatric ALL treatment between 1993 and 2015.

RESULTS

Among the 711 children with ALL, 530 were young children (1-9 years at diagnosis) and 181 were adolescents (including 136 younger adolescents [10-14 years] and 45 older adolescents [15-18 years]). Compared with young children who had ALL, adolescents with ALL were less likely to have favourable genetic features and more likely to demonstrate poor early response to treatment. The 10-year overall survival and event-free survival rates were significantly lower among adolescents than among young children (77.9% vs 87.6%, P=0.0003; 69.7% vs 76.5%, P=0.0117). There were no significant differences in the 10-year cumulative incidence of relapse, but the 10-year cumulative incidence of treatment-related death (TRD) was significantly greater among adolescents (7.2%) than among young children (2.3%; P=0.002). Multivariable analysis showed that both younger and older adolescents (vs young children) had worse survival and greater incidence of TRD.

CONCLUSION

Adolescents with ALL had worse survival because they experienced a greater incidence of TRD. There is a need to investigate optimal treatment adjustments and novel targeted agents to achieve better survival rates (without excessive toxicity) among adolescents with ALL.

A177 AN UNUSUAL CULPRIT OF AN UPPER GASTROINTESTINAL BLEED IN A PAEDIATRIC PATIENT

Background

Leiomyomas are benign tumors originating from mesenchymal cells in the muscularis propria that present equally among the sexes usually as localized lesions after the fifth decade. Though rare, esophageal leiomyomas (EL) make up the majority of benign esophageal tumors and are typically located distally. Of all known cases, 2.6% are paediatric. In this population they are 1.71 times more common in females and are often diffuse. Most are slow growing and asymptomatic but when >5cm patients describe dysphagia, vomiting, pain, cough and anorexia. Gastric leiomyomas causing upper gastrointestinal bleeding (UGIB) in adults are reported.

Aims

To discuss a rare cause of UGIB in a child.

Methods

Case report.

Results

We present a 16-year-old Asian boy with no significant past medical history who was transferred to our institution for an UGIB following 3 days of dark black stools, 1 day of coffee ground emesis and pre-syncope. There was no history of non-steroidal anti-inflammatory use.

At presentation he was in shock and received fluid resuscitation and a pantoprazole infusion. His hemoglobin dropped to 81 from 150g/L and corrected with 2 units of packed red blood cells. He was pale, non-dysmorphic with no cutaneous lesions, abdomen was non-distended and non-tender with no masses or hepatosplenomegaly.

An abdominal ultrasound showed mild bowel wall thickening in the cecum and terminal ileum.

Emergent upper endoscopy identified an ulcerated sessile mass at the gastro-esophageal junction. Biopsies revealed polypoid inflamed gastric mucosa with a focal intestinal metaplasia, negative for malignancy.

Magnetic resonance scan characterized a 3.8x4.3x2.5cm lesion in the stomach cardia not extending beyond the serosa with suggested causes including EL and gastrointestinal stromal tumor (GIST).

Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) demonstrated a 2.8x1.8cm well circumscribed homogenous hypoechoic mass in the muscularis propria of the distal esophagus. Histopathology showed bland tumor cells with eosinophilic cytoplasm and nuclei that did not demonstrate atypia. Immunohistochemistry (IHC) stains were positive for smooth muscle actin and desmin. CD117, S-100 and DOG1 were negative. Findings were therefore in keeping with a leiomyoma and not a GIST.

He was referred to the Cancer Genetics clinic for consideration of hereditary leiomyomatosis renal cell cancer and General Surgery for resection.

Conclusions

This case highlights a rare cause of UGIB in a child. EL are scarcely found in children and at present there are no reports of EL causing UGIB. They can be associated with Alport Syndrome or Familial Leiomyomatosis. IHC is an essential diagnostic tool, enabling differentiation of EL from GIST which is important as the latter has malignant potential. EL can be monitored with endoscopy if small but are surgically resected if symptomatic, ulcerated, or growing.

Funding Agencies

None

Hepatic steatosis is highly prevalent across the paediatric age spectrum, including in pre-school age children

BACKGROUND

The prevalence of non-alcoholic fatty liver disease (NAFLD) in children is 8% in the general population, and 34% in the context of obesity. There is a paucity of data on the prevalence of hepatic steatosis in healthy children in Ontario.

AIMS

To determine the prevalence of hepatic steatosis using abdominal computed tomography (CT) scans in a cohort of previously healthy children across the paediatric age spectrum in Ontario, Canada, and to determine any association between measures of abdominal adiposity and hepatic steatosis.

METHODS

Retrospective review of the SickKids Trauma Database from 2004-2015. Previously healthy children ages 1-17 years having undergone an abdominal CT scan as a part of routine trauma assessment were included, and those with an intra-abdominal injury excluded. Steatosis was defined as a difference between liver and spleen attenuation ≤-25HU. The percentage of the total area occupied by abdominal subcutaneous adipose and visceral adipose tissue was measured. Anthropometrics and baseline demographics were collected.

RESULTS

A total of 503 (51% male) children with mean (±SD) age 9.5 ± 4.5 years and weight z-score of 0.37 ± 1.05 were studied. Seventy-seven (15%, 95% CI [12%-18%]) had hepatic steatosis; no differences found between sexes or across age quartiles. The abdominal subcutaneous adipose tissue area was greater in those with hepatic steatosis compared to those without (32% [22-42] vs 24% [17-36], P = 0.003). The visceral adipose tissue area was significantly greater in older children ≥9.8 years with hepatic steatosis (7.7% [5.1-10] vs 6.6% (4.9-8.5), P = 0.04).

CONCLUSION

Hepatic steatosis was highly prevalent in previously healthy children in Ontario, including children of pre-school age. We found an association between hepatic steatosis and abdominal subcutaneous adipose tissue, and in older children with visceral adipose tissue.

Chronic hepatitis B virus (HBV) infection in children: 25 years' experience

Whereas e-seroconversion represents the loss of hepatitis B e-antigen (HBeAg) followed by gain of antibody to HBeAg (anti-HBe), 'inactive chronic infection' extends this concept to include e-seroconversion with decreased serum viral load and biochemical remission. These events must be well-characterized before treatment outcomes can be evaluated. We examined the rates of e-seroconversion and achievement of inactive chronic infection among children with chronic HBV infection. Children who were HBsAg positive >6 months were identified retrospectively between 1983 and 2008 from the Hospital for Sick Children Liver Clinic. Inactive chronic infection was defined as loss of HBeAg, serum ALT ≤40 IU/mL, and HBV DNA <10(6 ) IU/mL. Both e-seroconversion and achievement of inactive chronic infection were characterized using survival analysis. The effect of transmission route, treatment, age at diagnosis, ethnicity, gender and baseline ALT on these rates was evaluated with univariate and multiple regression. Of 252 HBeAg-positive cases, 59.9% had HBV-infected mothers, 77% were Asian, and 33 received interferon-α. Untreated children were younger at last follow-up (mean 14.5 vs 17.6 years), had lower ALT (median 60 vs 116 IU/mL) and had shorter follow-up (6.6 vs 9.1 years, all P < 0.002) compared to treated children. Crude e-seroconversion rate was 41.7% over 0.5-19.1 years of follow-up, and this was not affected by transmission route (P = 0.93), gender (P = 0.62) nor treatment (P = 0.08). 49% achieved inactive chronic infection by age 19 years. Being non-Asian, age at diagnosis<3 years, and ALT ≥40 IU/mL were associated with a higher rate of e-seroconversion and achieving inactive chronic infection (P < 0.0001). Almost 50% of children achieved inactive chronic infection by early adulthood.

Decreased purinergic inhibition of synaptic activity in a mouse model of Niemann-Pick disease type C

Niemann-Pick disease type C (NPC) is a progressive neurodegenerative disorder characterized by accumulation of free cholesterol in lysosomes, mainly due to a mutation in the NPC1 gene. The pathophysiological basis of the neural disorders in NPC, however, is not well understood. We found that the hippocampal field excitatory postsynaptic potential (fEPSP) was enhanced in NPC1 mutant mice. A1-receptor antagonist or adenosine degrading enzyme enhanced the fEPSP in both types of mice, but had a much weaker effect in the mutant mice, suggesting less tonic inhibition of synaptic transmission by endogenous adenosine in the mutant. Further evidence showed impaired hippocampal long term potentiation (LTP) in mutant mice. Supplement of A1 agonist N6-Cyclopentyladenosine (CPA) partially rescued the impaired LTP in mutant mice. Moreover, adenosine release from hippocampal slices was significantly decreased in the mutant. The enhanced excitatory synaptic transmission and the decreased synaptic plasticity due to the decreased adenosine release in NPC brain may partially contribute to the neural disorders of NPC disease, such as seizures, neurodegeneration, and dementia.

Anti-neuroinflammatory and neurotrophic effects of combined therapy with annexin II and Reg-2 on injured spinal cord

The present study was designed to investigate the neuroprotective effects of Ca(2+)-dependent phospholipid-binding protein annexin II and a secreted protein Reg-2 (regeneration gene protein 2) in spinal cord injury (SCI) model produced by contusion SCI at T(9) using the weight drop method. The agents were delivered intrathecally with Alzet miniosmotic pumps. We found that annexin II and Reg-2 remarkably reduced neuronal death, attenuated tissue damage and alleviated detrimental inflammation in vivo; meanwhile, a significant increase in white matter sparing and myelination area was observed. The propriospinal axons and long-distance supraspinal pathways were protected by the treatments as revealed by retrograde tracing. Basso Beattie Bresnahan locomotor rating scores also revealed a measurable behavioral improvement. However, no evident behavioral improvements in locomotor performance were achieved by the combined treatment with annexin II and Reg-2, compared with the separate treatment with annexin II and Reg-2.

The changing face of hepatitis in boys with haemophilia associated with increased prevalence of obesity

Hepatitis in children with haemophilia was historically most often associated with transfusion-transmitted infections. However, with the use of recombinant clotting factor concentrates, acquisition of such infections has now become rare. We studied the profile of hepatitis in North-American children with haemophilia in the modern era of safe blood products and excess childhood obesity. A total of 173 boys (<18 years) registered in the Pediatric Comprehensive Care Haemophilia Program were included in this retrospective study. Hospital records were reviewed for baseline data, serial height and weight measurements and serial alanine aminotransferase (ALT) levels. A body mass index (BMI) ranking was available for 170 boys, of whom 25 (14.7%, 95% CI 9.7-20.9%) were obese. The rate of obesity was higher in severe haemophilic boys. Compared with the general childhood population, the rate of obesity trended towards being higher in young haemophilic boys (2-5 years), but was similar in other age groups. A persistently high ALT (≥80 U L(-1) ) was documented in 5 boys and was associated with obesity. Three boys had clinical and imaging studies compatible with non-alcoholic fatty liver disease (NAFLD). Overweight and obesity are common among haemophilic boys, especially those who are younger and with severe disease. In this large group of haemophilic boys, chronic viral hepatitis was rare and NAFLD was a more common cause of liver disease. Overweight and obese haemophilic boys should be evaluated for NAFLD and interventional programmes should be designed to reduce the potential complications associated with obesity.

Correlation between the distribution of SP and CGRP immunopositive neurons in dorsal root ganglia and the afferent sensation of preputial frenulum

The aim of this study was to explore the distribution of substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactive nerve terminals in the penis prepuce and the preputial frenulum. The possible correlation between SP- and CGRP-immunopositive neurons in dorsal root ganglia (DRG) and the afferent sensation of the penile preputial frenulum is also discussed. Immunohistochemistry showed SP- and CGRP-positive nerve terminals in the epidermal basal layer of the prepuce and frenulum in adult human males. The majority of the nerve terminals presented as bundles of different lengths and a few as enlarged nodosities. The density of SP- and CGRP-immunopositive nerve terminals in the preputial frenulum was significantly higher than those in the penis prepuce (P<0.01). Fluoro-Gold (FG) retrograde tracing method was used to trace the origin of nerve terminals in Sprague-Dawley rats. SP and CGRP immunofluorescence labeling was employed to detect the distribution of SP- and CGRP-immunoreactive neurons in DRG. FG retro-labeled neurons were localized in L(6) -DRG and S(1) -DRG. All the FG/SP and FG/CGRP double-labeled neurons were medium or small-sized. One-third of the FG-labeled neurons were SP-immunoreactive, and a half of them CGRP-immunoreactive in L(6) -DRG and S(1) -DRG, respectively. The FG/SP/CGRP-labeled neurons accounted for one fifth of the FG retro-labeled neurons. Taken together, these data suggest that the SP- and CGRP-immunopositive nerve fibers may participate in the transmission of afferent sensation in the preputial frenulum.

The neuroprotective effects of Reg-2 following spinal cord transection injury

This study was designed to elucidate the potential neuroprotective effects of Reg-2 (regeneration gene protein 2) in a rodent model of spinal cord transection injury at the ninth thoracic level. Reg-2 at 100 and 500 μg, recombinant rat ciliary neurotrophic factor, or vehicle were delivered intrathecally using Alzet miniosmotic pumps. We found that Reg-2 treatment significantly reduced neuronal death in the spinal cord. There was also an attenuation of inflammation at the injury site and an increase in white matter sparing and retained myelination. Retrograde tracing revealed that Reg-2 protected axons of long descending pathways at 6 weeks post-SCI, and the number of FluoroGold-labeled neurons in spinal and supraspinal regions was also significantly increased. Immunofluorescent staining confirmed that the spared white matter contained neurofilament-positive axons. Moreover, behavioral improvements were revealed by Basso Beattie Bresnahan locomotor rating scores and grid-walk analysis. These results suggest that Reg-2 might promote functional recovery by increasing axonal growth, inhibiting neuronal apoptosis, and attenuating spinal cord secondary injury after SCI.

Effects of Reg-2 on survival of spinal cord neurons in vitro

Regeneration gene protein 2 (Reg-2) is a small secreted protein expressed in motor and sensory neurons of spinal cord during developmental stages and following injury of peripheral nerves. Reg-2 appears to act as a neurotrophic factor and protects injured neurons from death during regeneration. To illustrate these potential protective effects in vitro, we investigated the blocking effects of Reg-2 antibodies on the survival of primary cultured spinal cord neurons and astrocytes, as well as on neurite outgrowth. In addition, the effects of Reg-2 in neuron injury models induced by peroxide and mitochondrial poisoning were assessed. Our results showed that Reg-2 antibody markedly reduced survival and neurite outgrowth from neurons, whereas astrocyte survival was unaffected. Addition of Reg-2 into the culture medium had no effect on neuron survival or neurite outgrowth. However, the addition of the Reg-2 into culture media after peroxide treatment or cellular hypoxia insult induced by mitochondrial poisoning can reduce lactate dehydrogenase release levels and cell death. Thus, the data suggests that Reg-2 is essential for the survival and neurite outgrowth of developing spinal cord neurons but not the survival of glial cells, and that Reg-2 plays protective effects on spinal cord neurons against injury in vitro.

Expression changes of transforming growth factor-beta1 and thrombospondin-1 in cavernous tissues of diabetic rats

OBJECTIVE

To assess transforming growth factor-beta1 (TGF-beta1) and thrombospondin-1 (TSP-1) expression in the cavernous tissue of rats with streptozotocin (STZ)-induced diabetes.

MATERIALS AND METHODS

Twenty male Sprague-Dawley rats were randomly divided into 2 groups: diabetics and controls. We injected STZ intraperitoneally to induce diabetes, and studied the alterations in TGF-beta1 and TSP-1 expression in the cavernous tissue of the 2 groups by immunohistochemistry and real-time quantitative reverse transcription polymerase chain reaction. HE staining was also applied to determine morphological changes. Weight, blood sugar and urine sugar were measured before and after model induction in both groups.

RESULTS

Expression of TGF-beta1 and TSP-1 increased significantly in the cavernous tissue of the diabetic rats compared to the control group.

CONCLUSIONS

TGF-beta1 and TSP-1 expression changes in cavernous tissues may play an important role in diabetic erectile dysfunction.

Pico-Salax versus polyethylene glycol for bowel cleanout before colonoscopy in children: a randomized controlled trial

BACKGROUND AND STUDY AIMS

Comparison of bowel preparation for colonoscopy in children with either Pico-Salax (sodium picosulphate with magnesium citrate) or polyethylene glycol with electrolyte solution (PEG-ELS).

PATIENTS AND METHODS

In this investigator-blinded, randomized controlled trial, 83 children (12.5 +/- 3.1 years) requiring elective colonoscopy at a referral hospital were randomly allocated to Pico-Salax (n = 43) or PEG-ELS (n = 40), and an intention-to treat analysis was applied. Pico-Salax was administered in two doses, one the evening before and one on the morning of the procedure. PEG-ELS was administered over 4 hours. Efficacy was scored using the Ottawa scale and other constructs. Tolerability and toxicity were measured by patient and nursing questionnaires and serum biochemistry.

RESULTS

35 of Pico-Salax patients (81 %) were satisfied or very satisfied with the cleanout, compared with 19 (48 %) in the PEG-ELS group (P = 0.001). No differences were found in bowel cleanout effectiveness, as judged by the Ottawa score (P = 0.24), completion rates (P = 0.69), colonoscopy duration (P = 0.59), need for enemas (P = 0.25), or physician's global impression (P = 0.7). Except for one case of mild dehydration in the Pico-Salax group, no clinically significant adverse events were recorded. Serum biochemistry results were similar between groups except for more hypermagnesemia associated with Pico-Salax and hypokalemia with PEG-ELS; neither was clinically significant.

CONCLUSION

Children tolerate Pico-Salax better than PEG-ELS for bowel cleanout before colonoscopy. This study did not demonstrate superiority of effectiveness or safety for either regimen.

Long-term follow-up of portal hypertension after liver transplantation in children

We aimed to describe the long-term changes in the imaging and clinical features of PHALT in children. A retrospective review was undertaken of consecutive children undergoing their first liver transplant between 1993 and 2003. Details of clinical progress and ultrasound imaging were recorded at one-yr post-transplantation and at last follow-up. Data were extracted on 83 children (median age at transplant 1.7 yr, range one month to 17.5 yr, 44 girls) who underwent 89 transplants. Four of these children died at a mean 5.6 yr (range 3.8-6.9 yr) after transplantation. Of the survivors, follow-up at one yr (n = 83) and at last follow-up (n = 71, median 4.3 yr post-transplant) revealed imaging evidence of splenomegaly in 46% and 44%, ascites in 6% and 4%, and portal systemic collaterals in 12% and 14%, respectively. Gastrointestinal hemorrhage associated with portal hypertension had occurred in no children at one yr and in four (6%) at latest follow-up. Features of portal hypertension on ultrasound scan are common in children before liver transplantation. An important minority of children will suffer clinically significant complications of PHALT during long-term follow-up, caused by both vascular and parenchymal disease.

[Substance P and/or calcitonin gene-related peptide immunoreactive neurons in dorsal root ganglia possibly involved in the transmission of nociception in rat penile frenulum]

OBJECTIVE

To study the relationship between substance P (SP) and/or calcitonin gene-related peptide (CGRP) immunoreactive neurons in dorsal root ganglia (DRG) and the transmission of nociception in the penile frenulum of rats.

METHODS

The fluoro-gold (FG) retrograde tracing method was used to trace the origin of nerve terminals in the penile frenulum of rats. And SP and/or CGRP immunofluorescence labeling was employed to detect the distribution of SP and/or CGRP immunoreactive neurons in DRG.

RESULTS

FG retrograde tracing showed that the FG retrolabeled neurons were localized in L6-DRG and S1-DRG. SP and/or CGRP immunofluorescence labeling indicated that a large number of DRG neurons were SP- and CGRP-immunoreactive, different in size, bright red and bright green respectively in color, and arranged in rows or spots among nerve bundles. All the FG/SP and FG/CGRP double-labeled neurons were medium or small-sized. One third of the FG-labeled neurons were SP-immunoreactive, and a half of them CGRP-immunoreactive in L6-DRG and S1-DRG respectively. The FG/SP/CGRP-labeled neurons accounted for one fifth of the FG retro labeled neurons.

CONCLUSION

SP- and CGRP-immunoreactive neurons in L6-DRG and SI-DRG of rats may be involved in the transmission of nociception in rat penile frenulum.

[Expression of RAG-1 in brain during mouse development]

OBJECTIVE

To investigate the expression of recombination activating gene-1 (RAG-1) and its localization in the mouse brain during the embryonic development.

METHODS

The brain tissues of E (embryonic day) 11, E13, E15, E17, E19, P0 (the birth day) and adult mice were taken, the total RNA of brains were extracted and the changes of RAG-1 expression were detected with the method of RT-PCR. The freeze sections of brain tissues from each group were stained with immunohistochemistry method.

RESULT

The expression of RAG-1 persisted from E11 to P0 brain and was steadily increased from E11 to E19; the results of RT-PCR were similar to that of immunohistochemistry. The positive-cells mainly appeared in the nucleus amygdalae, hypothalamus, thalamus and hippocampus at developmental stage. The expression began to appear in ventricular zone (VZ) and intermediate zone (IZ) of telecephalic vesicle, then gradually increased in subventricular zone (SVZ), corticle plate (CP) and subcorticle plate (SP).

CONCLUSION

The expression of RAG-1 in mouse embryonic brain tissue is higher than that in the adult mouse, which may be related to the process of neuron development.

Improved outcome of acute lymphoblastic leukaemia treated by delayed intensification in Hong Kong children: HKALL97 study

OBJECTIVE

To study the outcome of children with acute lymphoblastic leukaemia who were treated using a protocol including one or two delayed intensifications.

DESIGN

Prospective single-arm multicentre study.

SETTING

Five designated children cancer units of the Hospital Authority of Hong Kong.

PATIENTS

Children aged between 1 and 17.9 years with newly diagnosed acute lymphoblastic leukaemia seen from November 1997 to December 2002.

INTERVENTION

Chemotherapy was modified from a German Berlin-Frankfurt-Muenster 95 (BFM95) protocol that included a delayed intensification similar to the induction phase repeated 5 months after diagnosis. High-risk patients were given double delayed intensification.

MAIN OUTCOME MEASURES

Overall survival and event-free survival of the whole group and the three risk groups (standard-, intermediate-, and high-risk groups), and comparison with historical controls.

RESULTS

A total of 171 patients were recruited with a median age at diagnosis of 5.57 years (range, 1.15-17.85 years). The induction remission rate was 95.3% and non-leukaemia mortality during remission was 2.3%. At 4 years, the relapse rate of this (HKALL97) study was significantly lower than that of the HKALL93 study (15.7 vs 37.3%; P<0.001). The 4-year overall survival of HKALL97 and HKALL93 studies were 86.5% and 81.8%, respectively (P=0.51). The 4-year event-free survival for HKALL97 and HKALL93 studies were 79% and 65%, respectively (P=0.007). Nonetheless the difference of event-free survival was most remarkable in the intermediate-risk group: 75.6% and 53.1% for HKALL97 and HKALL93 studies, respectively (P=0.06).

CONCLUSION

A more intensive delayed consolidation phase improved the outcome for children with acute lymphoblastic leukaemia by reducing relapses at 4 years. The early treatment complications were manageable and non-leukaemia mortality during remission remained low.

Role of Imaging in Management of Hemophilic Patients

OBJECTIVE

The purpose of this study was to evaluate the role of symptomatology and conventional radiographic scoring in predicting synovial hypertrophy, which could affect the clinical management of hemophilic patients.

MATERIALS AND METHODS

Twenty males (mean age, 14.3 years old) with hemophilic arthropathy, including 34 symptomatic joints and 26 asymptomatic joints (16 knees, 20 ankles, and 24 elbows) had conventional radiographs of individual joints obtained that were rated according to the Arnold-Hilgartner stage and the Pettersson score. The patients also underwent MRI for the detection of synovial hypertrophy. The association of synovial hypertrophy and symptomatology was evaluated using the chi-square or Fisher's exact test. The best sensitivity, specificity, and positive and negative predictive values in detection of synovial hypertrophy using symptomatology and radiographic scoring were calculated.

RESULTS

A significant association was seen between symptomatology and synovial hypertrophy of the knee and ankle joints (p < 0.05). The sensitivity, specificity, and positive and negative predictive values of symptomatology in detection of synovial hypertrophy of the knee were 100%, 78%, 78%, and 100%, respectively, and for the ankle were 83%, 75%, 83%, and 75%, respectively. The Arnold-Hilgartner stage and Pettersson score of the radiograph had a significant association with synovial hypertrophy of the knee and ankle joints (p < 0.05). Arnold-Hilgartner staging provided a better prediction of synovial hypertrophy, with sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 100%, 100%, and 100% for knees and 82%, 100%, 100%, and 82% for ankles.

CONCLUSION

In hemophilic patients, the presence of symptomatology in the knee and ankle joints is associated with synovial hypertrophy, and scoring of the conventional radiographs using Arnold-Hilgartner staging is useful for the prediction of synovial hypertrophy.

Use of hair analysis in the diagnosis of heavy metal poisoning: report of three cases

We report three paediatric cases of suspected heavy metal poisoning that presented with non-specific symptoms. Hair samples of the three patients were sent overseas for analysis; results showed abnormal levels of many elements, including some heavy metals. A diagnosis of heavy metal poisoning was made and chelation therapy was offered to each patient. Blood levels for some heavy metals were subsequently checked and all were within the normal range. The original diagnosis of heavy metal poisoning was therefore not substantiated. The patients did not have a history of exposure to heavy metals or specific clinical features of heavy metal poisoning. The non-invasive nature of hair analysis is tempting, but the validity of such testing in diagnosing heavy metal poisoning is questionable.

Bone mineral assessment by dual energy X-ray absorptiometry in children with inflammatory bowel disease: evaluation by age or bone area

BACKGROUND

Abnormal linear growth and deficient bone mineral acquisition may coexist in children with inflammatory bowel disease (IBD). Traditionally, bone mineral assessment by dual energy x-ray absorptiometry (DXA) involves comparison to age- and gender-matched reference ranges, and these studies in children with IBD show a high prevalence of osteopenia.

AIMS

To compare the prevalence of osteopenia using two methods of interpretation; one adjusted for age and gender and the other adjusted for bone size and gender.

PATIENTS

Forty-seven patients with Crohn disease (CD) and 26 patients with ulcerative colitis (UC) with a median age of 13.5 years (range, 5.5-18.2 years) were evaluated.

METHODS

Lumbar spine (LS) and total body (TB) bone mineral content (BMC) were measured by DXA and converted to bone mineral density (BMD, g/cm) corresponding to BMC divided by the bone area. Age and gender-matched BMD standard deviation scores (SDS) were based on reference data providing age- and gender-matched BMC and bone area. These data also allowed calculation of percentage of predicted bone area for age and gender (ppBone Area) and percentage of predicted BMC for Bone Area (ppBMC).

RESULTS

Patients with CD were shorter than those with UC (median height, SDS, -0.9 v 0, P < 0.05). Median ppBone Area for LS and TB for the whole group was 85% (10th centile, 68; 90th centile 99) and 81% (10th centile 66; 90th centile, 97), respectively. The ppBone Area at both sites was directly related to height SDS and BMI SDS (r > 0.5; P < 0.005). Median BMD SDS for LS and TB was -1.6 (10th centile -3.6; 90th centile, -0.2) and -0.9 (10th centile, -2.4; 90th centile, 0.4), respectively. Median ppBMC for LS and TB was 98% (10th centile, 84%; 90th centile, 113%) and 101% (10th centile 94%; 90th centile, 107%), respectively. The ppBMC showed no relationship to ppBone Area (r = 0.1, NS). Failure to account for bone area led to a label of moderate or severe osteopenia in 65% of cases. After adjustment for bone area, the proportion of children with osteopenia fell to 22%.

CONCLUSIONS

The data suggest that children with IBD often have small bones for age because they have growth retardation. When DXA data are interpreted with adjustment for bone size, most children were found to have adequate bone mass. Correct interpretation of DXA is important for identifying children who may be at a real risk of osteoporosis.

Treatment of acute lymphoblastic leukemia in Hong Kong children: HKALL 93 study

A population-based multicentre study for childhood acute lymphoblastic leukemia (ALL) was conducted in Hong Kong from 1993 to 1997. One hundred and forty-five newly diagnosed ALL patients were treated by the HKALL 93 protocol. Patients were stratified into three risk groups according to age, presenting white cell count, immunophenotyping and cytogenetic study. The patients received the same induction and early and late intensification at week 5 and week 20. Fifty-eight standard risk (SR) patients received regular intrathecal methotrexate as CNS preventive therapy, while 49 intermediate risk (IR) patients received high dose intravenous methotrexate and regular intrathecal methotrexate. Thirty-eight high risk (HR) patients were treated with prophylactic cranial irradiation and an additional intensification block at week 35. The induction remission rate was 97.2% with 2% induction death. Two patients died during first complete remission. Relapse occurred in 20.7, 42.9 and 42.1% of SR, IR and HR patients respectively. By multivariate logistic regression, age> or =10 years and white cell count> or =100 x 10(9)/l were the two significant variables accounting for mortality. The 5-year overall and event-free survival of the whole group was 81.3 and 62.6% respectively. According to risk groups, the event-free survival was 79, 49 and 61% for SR, IR and HR patients respectively, while the overall survival was 96, 73 and 68% for SR, IR and HR patients respectively. In conclusion, the treatment protocol had low treatment-related mortality but was associated with a rather high relapse rate, especially in IR patients. Salvage therapy achieved sustained second remission in some patients. More intensive treatment especially a late intensification is required to improve the outcome.

Morbidity and mortality patterns of thalassaemia major patients in Hong Kong: retrospective study

OBJECTIVES

To study the morbidity and mortality patterns of transfusion-dependent thalassaemia major patients in Hong Kong, and compare the outcomes of these patients according to different periods of birth.

DESIGN

Retrospective study.

SETTING

Paediatric departments of three regional hospitals, Hong Kong.

SUBJECTS AND METHODS

Medical records of thalassaemia major patients were reviewed. Data gathered included demographic and survival data, complications of iron overload, repeated transfusion, and bone marrow transplantation; the probability of survival of three cohorts was also estimated.

RESULTS

Two hundred and thirty-two patients were studied at a median age of 15.5 years (range, 1.4-30.3 years). There were 60 patients born before 1980 (cohort 1), 117 patients born between 1980 and 1989 (cohort 2), and 55 patients born after 1989 (cohort 3). The median age of starting desferrioxamine was 8 years, 4 years, and 3 years for cohorts 1, 2, and 3, respectively. Cardiomyopathy, diabetes mellitus, and hypothyroidism occurred in 15.1%, 8.6%, and 6.9% of patients with thalassaemia major, respectively. The above complications developed in 5% to 12% of cohort 2 patients. Delayed puberty was present in 38.4% and hormonal replacement for gonadal failure was required in 29.7% of evaluable patients. Short stature was common and the median height standard deviation score was -1.63. Twenty patients had died, and cardiomyopathy was the leading cause of death, followed by complications of bone marrow transplantation. The probability of survival beyond the age of 20 years was 87.6%.

CONCLUSION

Despite the use of iron chelation in the past two decades, severe complications of iron overload still occurred even in those who started chelation therapy early. Cardiomyopathy was the leading cause of death, while endocrinopathies and short stature were common complications especially in teenagers and adults.

Analysis of 13C-mixed triacylglycerol in stool by bulk (EA-IRMS) and compound specific (GC/MS) methods

This paper was presented in poster form at the 17th International Congress of Nutrition, August 27-31, Vienna, Austria (Annals of Nutrition & Metabolism 2001; 45(Suppl.1):349). Some of the data were also presented in poster form at the British Society of Gastroenterology Meeting, March 18-21, Glasgow, UK (Gut 2001; 48(Suppl.1):A91). The 13C-mixed triacylglycerol (MTG) breath test is used to measure intraluminal fat digestion. In normal digestion, 20-40% of the ingested 13C label is recovered in breath CO2. We aimed to identify the proportions of ingested label excreted in stool, as well as breath following ingestion of 13C-MTG by children with impaired exocrine pancreatic function and healthy controls. 13C enrichment of breath samples was measured by continuous flow isotope ratio mass spectrometry (IRMS) and cumulative percent dose recovered (cPDR) in 10 h was calculated. Total 13C of a faecal fat extract from each stool was measured by elemental analyser-IRMS, and 13C enrichment and concentration of the TBDMS derivative of octanoic acid was measured by GC/MS after hydrolysis of the fat extract. Stool 5-day cPDR was calculated. Mean breath cPDR was 35%. Mean cPDR in stool by combustion-IRMS and GC/ MS, respectively, was 0.8% and 1.0%. Therefore, the remaining 64% of the 13C label must remain in the body and variability in breath cPDR is due to postabsorptive rather than predigestive factors.

Linear and knemometric growth in the early phase of rehabilitation from severe malnutrition

The relationship between ponderal, linear and lower leg growth in children recovering from severe malnutrition remains unclear. We report on the early growth of 141 severely malnourished Bangladeshi children aged 6 to 36 months of age who were followed for 90 d. Mean (sd) weight for height (WHZ) and height for age (HAZ) catch-up growth z scores over the 90 d were 1.6 (0.85) and 0.47 (0.325) respectively. Mean (sd) lower leg length growth was 10.35 (4.5) mm. Change in HAZ was significantly associated with initial WHZ, but linear growth occurred in the presence of severe wasting and no threshold WHZ score was identified. Lower leg length gain correlated throughout with ponderal indices but with change in HAZ score only after day 45. Only initial WHZ score and maternal height predicted for linear growth and only accounted for 20 % of total variance. We conclude that linear growth occurs early in severely malnourished children but that knemometry behaves as a ponderal index acutely.

Nutrition in inflammatory bowel disease

Recent developments concerning nutritional complications of inflammatory bowel disease include a better understanding of disease-associated anorexia and increasing recognition of the interaction of nutrition and cytokines in the pathogenesis of growth impairment of children. Decreased bone mineral density is a multifactorial complication and an increased focus of research. Enteral nutrition continues to play an important role in the therapy of Crohn's disease. The mechanisms whereby specific nutrients, such as n-3 fatty acids, antioxidants, and butyrate, ameliorate inflammation are being elucidated in in-vitro studies, but beneficial effects have yet to be translated into the clinical sphere.

Liver disease does not affect lipolysis as measured with the 13C-mixed triacylglycerol breath test in children with cystic fibrosis

BACKGROUND

Liver disease associated with cystic fibrosis may not only limit the solubilisation and absorption of the products of fat digestion, but also may depress the activity of pancreatic lipase. The purpose of this study was to measure the effect of liver disease on triacylglycerol lipolysis using the 13C-mixed triacylglycerol breath test.

METHODS

Forty children with cystic fibrosis took 13C-mixed triacylglycerol with a standard breakfast and the child's normal pancreatic enzyme replacement therapy. Breath samples were collected before and every 30 minutes after ingestion for 6 hours. The cumulative percentage dose of 13C recovered at 6 hours was calculated from sequential measurements of 13C enrichment of breath CO2, measured by isotope ratio mass spectrometry. Liver abnormalities and portal hypertension were defined by ultrasound scan and clinical examination.

RESULTS

Twenty-four children had liver abnormalities, including 5 with portal hypertension. No difference was found between cumulative percentage dose of 13C recovered at 6 hours in 16 children with no liver abnormality (mean, 21.4%+/-11.1%), 19 children with liver abnormalities (22.2%+/-10.0%) and 5 children with portal hypertension (20.9%+/-7.1%).

CONCLUSION

Intestinal lipolysis is not reduced in cystic fibrosis liver disease when measured using the 13C mixed triacylglycerol breath test. These findings affirm the test's use as an indirect measure of fat digestion that is not affected by inadequate intraluminal bile salts or liver disease.

The evolution of liver disease in cystic fibrosis

OBJECTIVES

To describe prospectively the evolution of liver abnormalities in cystic fibrosis (CF), and to assess their impact on nutritional status.

STUDY DESIGN

124 children (61 boys) with CF (median age, 5.4 years; range, 0.1-13.9) were followed longitudinally for a median of four years. Annual clinical examination, biochemistry, and ultrasound assessment were performed. Chrispin-Norman score, anthropometry, and bacterial colonisation of airway secretions were measured at each assessment.

RESULTS

At initial assessment, 45% of the patients had no liver abnormalities, 42% had biochemical abnormality, 35% ultrasound abnormality, and 6% had clinical abnormality of the liver. In this cross sectional analysis, abnormal biochemistry was present in 40% of children with ultrasound or clinical abnormalities, but when longitudinal follow up data were analysed, abnormal biochemistry preceded or coincided with abnormal ultrasound or clinical hepatosplenomegaly in three quarters of 53 children developing new abnormalities. Eighty four of 124 children (68%) showed ultrasound or clinical evidence of liver abnormality at some point during the four years of follow up. No association was found between liver disease and nutritional status.

CONCLUSIONS

Hepatic abnormality was common in this group of children with CF, was often predicted by intermittent biochemical abnormalities, and was not associated with deterioration in nutritional status.

Characterization of granular particles isolated from postsynaptic densities

We describe here the isolation and biochemical characterization of a population of protein aggregates from the postsynaptic density (PSD) prepared from pig cerebral cortex. The protein constituents of these aggregates are linked together primarily by disulfide bonds. Negative staining electron microscopy revealed that the isolated protein aggregates were granular objects with an average outside diameter of approximately 21 nm and with small protrusions on their surface. The major constituents of the isolated granular aggregates consist of tubulin and an unidentified protein of 70 kDa in size. Small amounts of the alpha subunit of calcium/calmodulin-dependent protein kinase II and subunits of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and NMDA subtypes of glutamate receptors were also detected by immunoblotting. Actin, however, was not found in these granular aggregates. We propose that these granular protein aggregates correspond to the approximately 20-nm-diameter granular particles of the PSD on the basis of their biochemical and morphological characteristics. The spatial arrangement of these granular aggregates relative to other components of the postsynaptic terminal is also postulated here.

Zinc and rehabilitation from severe protein-energy malnutrition: higher-dose regimens are associated with increased mortality

A randomized, double-blind trial was undertaken to measure the effects of zinc supplementation on catch-up growth in severe protein-energy malnutrition, with particular reference to linear growth. One hundred forty-one children between the ages of 6 mo and 3 y were enrolled after admission to a nutritional rehabilitation unit in Dhaka, Bangladesh, and randomly assigned to receive elemental zinc by mouth, 1.5 mg/kg for 15 d, 6.0 mg/kg for 15 d, or 6.0 mg/kg for 30 d, and thereafter they were followed for a total of 90 d. Anthropometric outcome measures included change in knee-heel length, midupper arm circumference, subscapular and triceps skinfold thicknesses, and change in height-for-age, weight-for-age, and weight-for-height z scores. Higher zinc doses were not associated with significant change in any anthropometric measurement, but mortality was significantly greater in children who received high-dose zinc (6.0 mg/kg) initially as opposed to those who received low-dose zinc supplementation (1.5 mg/kg) (Yates-corrected chi-square P value of 0.033 and a risk ratio of 4.53; 95% CI: 1.09 < risk ratio < 18.8). We conclude that there is no benefit to using high-dose zinc supplementation regimens and that they could contribute to increased mortality in severely malnourished children.

Ontogeny of hepatobiliary secretion: role of glutathione

The ontogeny of hepatic synthesis and biliary secretion of glutathione was characterized and correlated with hepatic gamma glutamyl transpeptidase, bile flow rate, biliary bile acids and amino acids in Sprague-Dawley rats at 18 days of gestation and postnatally at ages 7, 14, 21, 28 and 54 days. Bile was collected by bile duct cannulation under intraperitoneal anesthesia with nembutal/ketamine. Glutathione, gamma glutamyl transpeptidase and bile acids were analyzed enzymatically and amino acids by high-performance liquid chromatography using established methods. Hepatic glutathione was low in the fetus, but increased to approximate adult levels by 7 days postnatally (2.77 mumol/gm liver). Hepatic gamma glutamyl transpeptidase activity, high in the fetus, declined to adult levels by day 7 (0.03 mumol/mg protein). In contrast, significant efflux of glutathione and its constituent amino acids into bile did not occur until weaning (21 days of age). During weaning, there was a fivefold increase in the biliary glutathione and with a twofold increase in bile flow rate. Biliary bile acids concentration remained constant throughout development, with only a 30% to 50% increase in its secretion rate. The data suggest that the developmentally related increase in bile flow rate was principally a result of the increase in bile acid independent flow from 1.1 microliters/(min.100 gm body wt) in the suckling to 4.3 microliters/(min.100 gm body wt) in the post-weanling animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of nonabsorbable markers Poly R-478 and [14C]PEG-4,000 for use in developmental absorption studies

To determine the utility of Poly R-478, a stable, polymeric dye (MW, 40,000), as a nonabsorbable marker for studies in the developing small intestine, it was validated by comparison to carbon 14-labeled polyethylene glycol, MW 4,000 [( 14C]PEG-4,000) in rats from 14 to 40 days of age. The recovery and quantification of Poly R-478 from biological samples is simple and rapid compared to other nonradioactive nonabsorbable markers. In 40-day-old rats simultaneously given Poly R-478 and [14C]PEG, total recoveries were similar, the percentages of the Poly R-478 dose and the [14C]PEG dose recovered per segment were identical, and taurocholate absorption rates calculated using each marker were comparable. Recovery of Poly R-478 from flushed intestinal segments, determined by a one-step extraction, was equivalent to that of [14C]PEG in 40-day-old rats (96.5 +/- 3.7% versus 102.7 +/- 10.1%; NS) but was superior to that of [14C]PEG in 21-day-old rats (98.0 +/- 6.2% versus 63.4 +/- 5.5%; p less than 0.001) and 14-day-old rats (97.8 +/- 6.7% versus 56.7 +/- 12.6%; p less than 0.001). Within each age group, the distribution of Poly R-478 within the intestine was similar to that of [14C]PEG. In addition, total taurocholate absorption in the presence of Poly R-478 was comparable to that in the presence of [14C]PEG. Complete recovery of Poly R-478 from a suspension of liver particles and from mixtures with two commercial infant formulas was demonstrated in vitro, suggesting that Poly R-478 may be used when foods are present in the intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

A study on the vascular supply of the supraspinatus tendon

The vascular supply of the rotator cuff in 22 adult shoulders was studied by way of mixture infusion of gelatin and India ink and vascular cast, in combination with Scanning Electronic Microscopy of the vascular pattern in the supraspinatus tendon. It was found that the vessels of the supraspinatus tendon mainly derive from the anterior circumflex humeral and suprascapular arteries. Macroscopically, an avascular zone or critical zone could be seen on the surface of supraspinatus, and the mean distance of the external edge from the osteo-tendinous attachment was 7.8 mm. The area of the avascular zone increased with age.

Taurocholate transport by brush-border membrane vesicles from the developing rabbit ileum: structure/function relationships

To examine the ontogenesis of bile acid transport in the rabbit ileum, brush-border membrane vesicles (12- to 20-fold purified) were prepared from 14- to 49-day-old animals. Taurocholate uptake was characterized by the emergence of secondary active, Na(+)-dependent transport at the start of weaning (21 days). Transient intravesicular accumulation (overshoot) of taurocholate occurred at 5-10 s of incubation, and the overshoot maximum increased significantly from 21 days (349.2 +/- 22.4 nmol/mg protein) to 35 days (569.0 +/- 84.3 nmol/mg protein; p less than 0.001), without further increase at maturity (49 days, not equal to 607.6 +/- 136.7 nmol/mg protein). No significant taurocholate active uptake component was noted at 14 days; however, ileal vesicles from sucklings showed carrier-mediated, Na+ D-glucose cotransport. In greater than or equal to 35-day-old rabbits, osmolarity studies at 20 s of incubation showed that only approximately 12% of [14C]taurocholate uptake was secondary to bile acid-to-membrane binding. Conversely, at 20 min, greater than 95% of radiolabel incorporation represented solute bound to the external and/or internal membrane surface. Arrhenius plots establish brush-border membrane taurocholate uptake as an intrinsic, lipid-dependent process, with a slope discontinuity between 24 and 28 degrees C, similar to the membrane lipid thermotropic transition region. Steady-state fluorescence polarization studies (1,6-diphenyl-1,3,5-hexatriene) demonstrate a temporal association between the maturation of taurocholate uptake and age-related decreases in ileal brush-border membrane fluidity. These data indicate that maturation of bile acid secondary active transport in the rabbit ileum may be regulated, at least in part, by changes in brush-border membrane lipid dynamics.

Effects of ethinyl estradiol on intestinal membrane structure and function in the rabbit

Structural and functional properties of the small intestinal microvillus membrane were evaluated in the rabbit after administration of ethinyl estradiol, a synthetic estrogen with a demonstrated propensity to alter hepatic membrane lipid fluidity, and promote cholestasis. In the jejunum, no estrogen-induced changes in microvillus membrane total lipid, cholesterol or phospholipid content were observed. However, the ileal microvillus membrane in estradiol-treated animals demonstrates significant reductions vs. controls (per mg protein) in total lipid (0.55 milligrams vs. 0.89 milligrams) [corrected] and phospholipid (206.7 micrograms vs. 304.91 micrograms) (p less than 0.001) content, as well as modifications in specific phospholipid species. The increase in the ileal microvillus membrane cholesterol: phospholipid molar ratio (0.65 vs. 0.51, p less than 0.05) was associated with a significant decrease in membrane lipid fluidity reflected by an increase in fluorescence anisotropy measurements utilizing diphenyl hexatriene as the fluorophore (r at 25 degrees C = 0.306 vs. 0.282, p less than 0.05). Thermotropic lipid phase transitions, assessed by Arrhenius plots of both fluorescence data and ileal microvillus membrane p-nitrophenylphosphatase activity demonstrate that phase changes occur between and 24 and 28 degrees C in both treated and untreated groups. Within the temperature range studied (40-10 degrees C) no differences from control were observed in microvillus membrane alkaline phosphatase activity following estrogen treatment. These data therefore indicate that ethinyl estradiol-induced effects on microvillus membrane lipid composition and physical properties occur predominantly in the ileum and appear to be related, in part, to specific alterations in the availability of phospholipid following estrogen treatment.

Analysis of coronary flow fields in thoracotomized dogs

A nonlinear theory of pulsatile flow was used to investigate the detailed flow field in the left circumflex coronary artery of anesthetized open-chest dogs. Studies were carried out under a wide range of blood pressures and flow rates induced by intravenous infusions of dipyridamole. The results indicated that (1) the flow profiles, although less blunt than those in the descending aorta, are still nonparabolic, (2) the wall shear in the coronary arteries maintains a high value through diastole, and (3) during intravenous infusions of dipyridamole both coronary flow and wall shear increase. The peak value of the shear stress during these infusions, which reached 360 dynes/cm2, can approach the yield stress value of 400 dynes/cm2 reported by Fry for endothelial cells.

Nonlinear analysis of aortic flow in living dogs

A nonlinear theory which considered the convective accelerations of blood and the nonlinear elastic behavior and taper angle of the vascular wall was used to study the nature of blood flow in the descending thoracic aorta of living dogs under a wide range of pressures and flows. Velocity profiles, wall friction, and discharge waves were predicted from locally measured input data about the pressure-gradient wave and arterial distention. Precision pressure-gradient waves free of static errors were obtained through forward and backward pressure-gradient measurements, and the arterial pressure-radius relation was obtained through cinematography using a telephoto lens. The results indicated that a major part of the mean pressure gradient was balanced by convective accelerations; the theory, which took this factor into account, predicted the correct velocity distributions and flow waves. The results also showed that for high flow rates the magnitude of the peak wall-shear stress became comparable to the yield stress of the endothelial surface and that radial flows of significant magnitude existed with respect to the arterial wall.

Application of heated-film velocity and shear probes to hemodynamic studies

A constant-temperature heated-film anemometer system has been adapted for the detailed study of in-vivo aortic velocity fields. Two types of sensing probes were developed: a velocity probe and a velocity-gradient or fluid shear stress probe. These probes were evaluated for steady and pulsatile flow in rigid circular tubes using both a glycerin-water mixture and blood. Measurements using both devices agreed closely with the values predicted by well established theory. Moreover, the integrated velocity profiles that were measured correlated well with the simultaneously recorded flow values using orifice meter and electromagnetic flowmeter techniques. In-vivo studies were made along the thoracic aortas of anesthetized dogs and pigs. Velocity measurements along the aorta indicated that the velocity profiles are blunt. The flow-pulse forms obtained by the heated-film technique in vivo were also similar in magnitude and contour to those obtained simultaneously from an electromagnetic flowmeter. Fully developed turbulent flow was not observed; however, occasional "eddy" turbulence occurred in the aortic arch of dogs weighing less than 30 kg. Preliminary measurements indicate that peak wall-shear stresses reach values that are approximately one-third that of the endothelial yield stress.