Neutrophilic dermatosis in a patient with an IKZF1 variant and a review of monogenic autoinflammatory disorders presenting with neutrophilic dermatoses

Monogenic diseases of immune dysregulation should be considered in the evaluation of children presenting with recurrent neutrophilic dermatoses in association with systemic signs of inflammation, autoimmune disease, hematologic abnormalities, and opportunistic or recurrent infections. We report the case of a 2-year-old boy presenting with a neutrophilic dermatosis, found to have a novel likely pathogenic germline variant of the IKAROS Family Zinc Finger 1 (IKZF1) gene; the mutation likely results in a loss of function dimerization defective protein based on reports and studies of similar variants. IKZF1 variants could potentially lead to aberrant neutrophil chemotaxis and development of neutrophilic dermatoses. Long-term surveillance is required to monitor the development of hematologic malignancy, autoimmunity, immunodeficiency, and infection in patients with pathogenic IKZF1 germline variants.

Lupus anti-coagulant hypoprothrombinemia syndrome across different ages: a case report and review of the literature

Lupus anti-coagulant hypoprothrombinemia syndrome (LAHPS) is a rare condition that can be difficult to treat. It increases the risk of thrombosis and bleeding due to the presence of lupus anti-coagulant and factor II deficiency, respectively. There are a limited number of cases described in the literature. Herein we describe a case of LAHPS with bleeding symptoms as a first clinical manifestation of systemic lupus erythematosus (SLE) in an 8-year-old female. She has had multiple recurrences of her bleeding symptoms, requiring treatment with steroids, cyclophosphamide, mycophenolate mofetil, and rituximab. Her course was later complicated by development of arthritis and lupus nephritis. Her complicated course provides a new perspective on the clinical course and treatment of LAHPS. We also present a comprehensive literature review which demonstrates the difficulty in treating patients with LAHPS with underlying SLE and the variability of the clinical course and management of LAHPS depending on the age at presentation.

Updates and advances in pyruvate kinase deficiency

Mutations in the PKLR gene lead to pyruvate kinase (PK) deficiency, causing chronic hemolytic anemia secondary to reduced red cell energy, which is crucial for maintenance of the red cell membrane and function. Heterogeneous clinical manifestations can result in significant morbidity and reduced health-related quality of life. Treatment options have historically been limited to supportive care, including red cell transfusions and splenectomy. Current disease-modifying treatment considerations include an oral allosteric PK activator, mitapivat, which was recently approved for adults with PK deficiency, and gene therapy, which is currently undergoing clinical trials. Studies evaluating the role of PK activators in other congenital hemolytic anemias are ongoing. The long-term effect of treatment with disease-modifying therapy in PK deficiency will require continued evaluation.

Utilization of an ITP quality improvement pathway improves adherence to management guidelines

Despite availability of epidemiologic studies and national guidelines for the management of newly diagnosed pediatric immune thrombocytopenia (ITP), practice variation exists among and within hematology practices. We previously described the development of an ITP pathway guiding management based on bleeding symptoms. Over an 8-year period, integration of this iterative ITP pathway into management of newly diagnosed ITP increased observation rates in children with no or mild bleeding symptoms and improved consistency of laboratory evaluation and treatment strategies without increasing adverse outcomes. This quality improvement initiative has been sustainable, acceptable to providers, and increased adherence to guidelines.

Characteristics and outcomes of autoimmune hemolytic anemia after pediatric allogeneic stem cell transplant

BACKGROUND

Autoimmune hemolytic anemia (AIHA) after allogeneic hematopoietic stem cell transplant (HSCT) is a rare but complex and serious complication. Detailed descriptions of cases and management strategies are needed due to lack of prospective trials.

OBJECTIVES

Describe the incidence, clinical characteristics, and management of AIHA after HSCT in a pediatric cohort.

METHODS

This is a retrospective cohort study of 33 pediatric patients with AIHA after HSCT at an academic tertiary care center from 2003 to 2019.

RESULTS

The overall incidence of AIHA after allogeneic HSCT was 3.8% (33/868). AIHA was significantly more common after transplant for nonmalignant versus malignant diagnoses (7.0% [26/370] vs. 1.4% [7/498], p < .0001). AIHA developed at a median of 4.7 months (range 1.0-29.7) after transplant. Sixteen of 33 patients (48.5%) required new AIHA-directed pharmacologic therapy; 17 (51.5%) were managed on their current immunosuppression and supportive care. Patients managed without additional therapy were significantly older, more likely to have a malignant diagnosis, and tended to develop AIHA at an earlier time point after transplant. Patients received a median of two red blood cell transfusions within the first 2 weeks of diagnosis and a median of one AIHA-directed medication (range one to four), most commonly corticosteroids and rituximab.

CONCLUSIONS

AIHA after HSCT is rare but occurs more commonly in patients transplanted for nonmalignant diagnoses. While some pediatric patients who develop AIHA after transplant can be managed on current immunosuppression and supportive care, many require AIHA-directed therapy including second-line medications.

A Review of Venous Thromboembolism Risk Assessment and Prophylaxis in Plastic Surgery

BACKGROUND

Venous thromboembolism is a significant cause of postoperative death and morbidity. While prophylactic and treatment regimens exist, they usually come with some risk of clinically relevant bleeding and, thus, must be considered carefully for each individual patient.

METHODS

This special topic article represents a review of current evidence regarding venous thromboembolism risk, biology, and prevention in plastic surgery patients. The specific types and duration of available prophylaxis are also reviewed. The balance of venous thromboembolism risk must be weighed against the risk of hemorrhage.

RESULTS

Though alternatives exist, the most validated risk assessment tool is the 2005 modification of the Caprini Risk Assessment Model. Controversies remain regarding recommendations for outpatient and low risk cosmetic patients. The authors additionally make recommendations for high-risk patients regarding the use of tranexamic acid, estrogen therapy, anesthesia, and prophylaxis regimens.

CONCLUSION

Our profession has made great strides in understanding the science behind venous thromboembolism, risk stratification for patients, and prophylactic regimens; yet, continued studies and definitive data are needed.

Response to rituximab in children and adults with immune thrombocytopenia (ITP)

BACKGROUND

Rituximab is a monoclonal anti-CD20 antibody used as a second-line treatment for immune thrombocytopenia (ITP). As additional treatments for ITP emerge, identifying the most appropriate patients and optimal timing for rituximab are important but challenging without established predictors of response to therapy.

OBJECTIVES

The purpose of this study was to describe demographic, clinical, and laboratory characteristics of pediatric and adult patients with ITP to identify differences in evaluation before rituximab administration and correlates of platelet response.

METHODS

This is a retrospective cohort study describing the characteristics of patients with ITP treated with rituximab from 2010 to 2020 at two academic tertiary care centers.

RESULTS

A total of 64 patients met criteria for inclusion. Complete rituximab response (56%) was not significantly different between children (58%, n = 24) and adults (55%, n = 40). Response rate was similar in those with primary versus secondary ITP (53% vs 62%). Among patients treated with rituximab, Evans Syndrome was more common in children than adults (42% vs 18%). Immunologic labs assessed before rituximab varied by age and were more commonly evaluated in children (lymphocyte subsets 88% vs 22%). Immunologic markers, including antinuclear antibody, direct antiglobulin testing, immunoglobulin levels, and lymphocyte subsets, did not predict response to rituximab in pediatric or adult patients with ITP.

CONCLUSIONS

Pre-rituximab immunologic evaluation varied significantly between adults and children, which could represent institution-specific practice patterns or a more general practice difference. If the latter, underlying immunodeficiency in adults with ITP may be underrecognized. Standardized guidance for pre-rituximab immunologic evaluation is needed.

A Novel ALK Fusion in Pediatric Medullary Thyroid Carcinoma

Medullary thyroid carcinoma (MTC) is most commonly associated with RET gene mutations. ALK fusions have rarely been described, although not previously in pediatrics and not previously partnered with CCDC6 in MTC or any other cancer. A 10-year-old boy with progressive stridor was found to have metastatic MTC, including lung, lymph node, and adrenal metastases. Baseline calcitonin was 6703 pg/mL. While molecular testing was pending, he was treated empirically with the investigational selective RET inhibitor, LOXO-292, without improvement. Molecular testing revealed a novel CCDC6-ALK fusion. His therapy was changed to crizotinib and then to alectinib for improved tolerability. Calcitonin decreased to 663 pg/mL after 6 days of ALK inhibition. He remains on alectinib with ongoing response. A novel CCDC6-ALK fusion has now been implicated in a pediatric case of metastatic MTC. This fusion has profound clinical sensitivity to ALK inhibitors. This report expands the spectrum of ALK fusions seen in MTC, including the first pediatric case of ALK translocated MTC. This novel fusion with CCDC6 has not previously been reported in other human cancers. Given the dramatic response to ALK inhibition in this case, identifying patients with ALK fusion MTC has important therapeutic implications.

A 3-Week-Old With an Isolated "Blueberry Muffin" Rash

A 3-week-old boy, former 39-week term infant, presented to the emergency department with a rash. One week before presentation, he developed dark, purple papules on his forehead, which then spread to the abdomen and inguinal regions. Throughout this time, he was eating well, gaining weight, developing appropriately, and was afebrile without cough, congestion, or rhinorrhea. On presentation, the patient was well appearing with normal vital signs. His weight was 4.83 kg (86th percentile for age), his length was 56 cm (47th percentile for age), and his head circumference was 37 cm (62nd percentile for age). On skin examination, there were scattered purpuric papules and macules on the scalp, forehead, trunk, abdomen, and inguinal region. Initial laboratory studies were remarkable only for mild anemia. Our expert panel examines the case, offers a differential for a child with a "blueberry muffin" rash, and makes diagnostic considerations.

Factors impacting time to engraftment in patients with high-risk neuroblastoma following autologous stem cell transplant

e22008

Background: Neuroblastoma is the most common extra-cranial solid tumor of childhood, with overall survival for high-risk patients (HRNBL) near 50%. The outcomes of HRNBL have improved significantly with high dose chemotherapy followed by autologous stem cell rescue (ABMT). Data about factors influencing the rate of hematopoietic recovery following ABMT in HRNBL is lacking in the literature. Methods: This is a retrospective chart review of patients with HRNBL treated at Texas Children’s Hospital from October 2011 - November 2016. Neutrophil engraftment was considered the first of three consecutive days with post-transplant neutrophil count > 500 cells/uL. Red blood cell and platelet engraftment were considered at a hemoglobin > 8g/dL and platelets > 20,000/uL three days after the last transfusion. Race and conditioning regimen were analyzed using one-way ANOVA; amount of infused cells was analyzed using Pearson correlation coefficients; chemotherapy delay and bone marrow (BM) involvement after cycle 2 of induction chemotherapy were analyzed using independent sample t-tests. Results: The study included 17 males and 8 females with a median age at diagnosis of 3 years. 15 patients were Caucasian, 4 African-American, 5 Hispanic, and 1 Asian. The mean dose of infused CD34+ cells was 3.44x108cells/kg. 16 patients received conditioning therapy with carboplatin/etoposide/melphalan, 7 received busulfan/melphalan, and 2 received thiotepa/cyclophosphamide. Race was found to be significant for hemoglobin engraftment (p < 0.001). There were trends toward significance for conditioning regimen and neutrophil engraftment (p = 0.079), presence of delays in induction chemotherapy due to hematologic toxicity for platelet engraftment (p = 0.069) and BM involvement after cycle 2 of induction chemotherapy for hemoglobin engraftment (p = 0.12). Conclusions: Knowing the barriers for timely engraftment may help develop interventions for future patients. Race significantly impacted hemoglobin engraftment. Conditioning regimen, delays in induction chemotherapy, and BM involvement after cycle 2 of induction chemotherapy trended towards significance and need to be validated in a larger dataset.

Early feeding and neonatal hypoglycemia in infants of diabetic mothers

Objectives:

To examine the effects of early formula feeding or breast-feeding on hypoglycemia in infants born to 303 A1-A2 and 88 Class B-RF diabetics.

Methods:

Infants with hypoglycemia (blood glucose < 40 mg/dL) were breast-fed or formula-fed, and those with recurrences were given intravenous dextrose.

Results:

Of 293 infants admitted to the well-baby nursery, 87 (30%) had hypoglycemia, corrected by early feeding in 75 (86%), while 12 (14%) required intravenous dextrose. In all, 98 infants were admitted to the newborn intensive care unit for respiratory distress (40%), prematurity (33%) or prevention of hypoglycemia (27%). Although all newborn intensive care unit patients received intravenous dextrose, 22 (22%) had hypoglycemia. Of 109 hypoglycemia episodes, 89 (82%) were single low occurrences. At discharge, 56% of well-baby nursery and 43% of newborn intensive care unit infants initiated breast-feeding.

Conclusions:

Hypoglycemia among infants of diabetic mothers can be corrected by early breast-feeding or formula feeding.

Cyclic stretch reduces myofibrillar protein synthesis despite increases in FAK and anabolic signalling in L6 cells

Muscle protein synthesis is increased after exercise, but evidence is now accruing that during muscular activity it is suppressed. In life, muscles are subjected to shortening forces due to contraction, but may also be subject to stretching forces during lengthening. It would be biologically inefficient if contraction and stretch have different effects on muscle protein turnover, but little is known about the metabolic effects of stretch. To investigate this, we assessed myofibrillar and sarcoplasmic protein synthesis (MPS, SPS, respectively) by incorporation of [1-13C]proline (using gas chromatography-mass spectrometry) and anabolic signalling (by phospho-immunoblotting and kinase assays) in cultured L6 skeletal muscle cells during 30 min of cyclic stretch and over 30 min intervals for up to 120 min afterwards. SPS was unaffected, whereas MPS was suppressed by 40 +/- 0.03% during stretch, before returning to basal rates by 90-20 min afterwards. Paradoxically, stretch stimulated anabolic signalling with peak values after 2-30 min: e.g. focal adhesion kinase (FAK Tyr576/577; +28 +/- 6%), protein kinase B activity (Akt; +113 +/- 31%), p70S6K1 (ribosomal S6 kinase Thr389; 25 +/- 5%), 4E binding protein 1 (4EBP1 Thr37/46; 14 +/- 3%), eukaryotic elongation factor 2 (eEF2 Thr56; -47 +/- 4%), extracellular regulated protein kinase 1/2 (ERK1/2 Tyr202/204; +65% +/- 9%), eukaryotic initiation factor 2alpha (eIF2alpha Ser51; -20 +/- 5%, P < 0.05) and eukaryotic initiation factor 4E (eIF4E Ser209; +33 +/- 10%, P < 0.05). After stretch, except for Akt activity, stimulatory phosphorylations were sustained: e.g. FAK (+26 +/- 11%) for > or =30 min, eEF2 for > or =60 min (peak -45 +/- 4%), 4EBP1 for > or =90 min (+33 +/- 5%), and p70S6K1 remained elevated throughout (peak +64 +/- 7%). Adenosine monophosphate-activated protein kinase (AMPK) phosphorylation was unchanged throughout. We report for the first time that acute cyclic stretch specifically suppresses MPS, despite increases in activity/phosphorylation of elements thought to increase anabolism.

Study of Odours Coming Out of Polyurethane Flexible Foam Mattresses

Quality of life in Western populations is becoming an ever-growing concern. Higher demands are made in regard to for example comfort and safety. Low emissions of volatile organic compounds and odour criteria have become key performance requirements in most applications. To address this issue, the entire supply chain, from producers to end-users attempts to find ways and means to identify, understand and reduce unexpected emissions and odours.

Standard test methods have been developed for the evaluation of a wide range of product/materials emissions. A wide variety of experimental techniques as well as instrumental methods have been used for the sampling and the identification/quantification of volatile components emitted by materials. Work reported here includes the sensory and chemical evaluation of volatiles at low concentration levels (usually in the ppm or even the ppb range).

This paper describes the work conducted by EUROPUR (European Association of Flexible Polyurethane Foam Block Manufacturers) for the identification of odour emanating from PU samples. The data shown in this work gives some evidence for the potential contribution of very minor compounds emitted by PU samples to the odour. GC-MS-olfactometry was used to determine which components of the complex mixture of VOCs were primarily responsible for the perceived odour.

A Summary of Work Carried out by EUROPUR into Extractable Materials from Flexible Polyurethane Foam

The European polyurethane flexible slabstock manufacturing trade association, EUROPUR, has carried out extensive analytical work over recent years to determine if any extractable or volatile materials can be detected emanating from PU foam. Much of this work concerning aromatic amines and VOCs has already been published. This brief review summarises other work, which has been carried out during this research period.

Using a clinical pathway and education to reduce inappropriate prescribing of enoxaparin in patients with acute coronary syndromes: a controlled study

AIMS

To evaluate efficacy of a pathway-based quality improvement intervention on appropriate prescribing of the low molecular weight heparin, enoxaparin, in patients with varying risk categories of acute coronary syndrome (ACS).

METHODS

Rates of enoxaparin use retrospectively evaluated before and after pathway implementation at an intervention hospital were compared to concurrent control patients at a control hospital; both were community hospitals in south-east Queensland. The study population was a group of randomly selected patients (n = 439) admitted to study hospitals with a discharge diagnosis of chest pain, angina, or myocardial infarction, and stratified into high, intermediate, low-risk ACS or non-cardiac chest pain: 146 intervention patients (September-November 2003), 147 historical controls (August-December 2001) at the intervention hospital; 146 concurrent controls (September-November 2003) at the control hospital. Interventions were active implementation of a user-modified clinical pathway coupled with an iterative education programme to medical staff versus passive distribution of a similar pathway without user modification or targeted education. Outcome measures were rates of appropriate enoxaparin use in high-risk ACS patients and rates of inappropriate use in intermediate and low-risk patients.

RESULTS

Appropriate use of enoxaparin in high-risk ACS patients was above 90% in all patient groups. Inappropriate use of enoxaparin was significantly reduced as a result of pathway use in intermediate risk (9% intervention patients vs 75% historical controls vs 45% concurrent controls) and low-risk patients (9% vs 62% vs 41%; P < 0.001 for all comparisons). Pathway use was associated with a 3.5-fold (95% CI: 1.3-9.1; P = 0.012) increase in appropriate use of enoxaparin across all patient groups.

CONCLUSION

Active implementation of an acute chest pain pathway combined with continuous education reduced inappropriate use of enoxaparin in patients presenting with intermediate or low-risk ACS.

An Investigation into VOC Emissions from Polyurethane Flexible Foam Mattresses

Emissions of volatile species from flexible polyurethane foam mattresses were investigated by using large scale chamber tests designed to replicate the product use as mattress cores. Various trace impurities were identified and their concentrations were measured for input into a human health and toxicity risk assessment, which has concluded that none was injurious to health. The raw materials used to make the foam were analysed to identify the source of emanations and routes to their reduction or elimination. Several analytical artefacts were identified, and some recommendations made for their avoidance. Detailed product knowledge was essential to the reliable interpretation of analytical data. A quantitative risk assessment was carried out on each of the volatiles. No evidence of any human health risk was identified from the ‘worst-case’ exposure model employed

An Investigation into Claims that Toluene Diamine (TDA) is Present in Polyurethane Flexible Foams

Claims have been made in Scandinavia that polyurethane flexible foams can be a health hazard because they contain, or on ageing can form, traces of the carcinogenic substance 2,4-toluene diamine (TDA). A working group was set up to investigate these claims and some of their findings are reported here. Analytical protocols have been refined for the determination of TDA extractable into aqueous based media. Extensive testing has been carried out on many different kinds of polyurethane foam without any evidence being found for the presence of free TDA. These negative results apply to both fresh cured foam and foam treated to simulate heat ageing, autoclaving and use in humid conditions. The reason for the erroneous reporting of TDA in foams undoubtedly lies in the use of the wrong pretreatment of the extract or the use of inappropriate sample injection techniques. This could range from not filtering the extract, increasing the pH of the extract prior to either gc/ms or lc/ms detection, or using hot on-column injection gc techniques. The false reporting of TDA is demonstrated here.

Inhaled nitric oxide versus conventional therapy: effect on oxygenation in ARDS

A randomized, controlled clinical trial was performed with patients with acute respiratory distress syndrome (ARDS) to compare the effect of conventional therapy or inhaled nitric oxide (iNO) on oxygenation. Patients were randomized to either conventional therapy or conventional therapy plus iNO for 72 h. We tested the following hypotheses: (1) that iNO would improve oxygenation during the 72 h after randomization, as compared with conventional therapy; and (2) that iNO would increase the likelihood that patients would improve to the extent that the FI(O2) could be decreased by > or = 0.15 within 72 h after randomization. There were two major findings. First, That iNO as compared with conventional therapy increased Pa(O2)/FI(O2) at 1 h, 12 h, and possibly 24 h. Beyond 24 h, the two groups had an equivalent improvement in Pa(O2)/FI(O2). Second, that patients treated with iNO therapy were no more likely to improve so that they could be managed with a persistent decrease in FI(O2) > or = 0.15 during the 72 h following randomization (11 of 20 patients with iNO versus 9 of 20 patients with conventional therapy, p = 0.55). In patients with severe ARDS, our results indicate that iNO does not lead to a sustained improvement in oxygenation as compared with conventional therapy.

Investigation of the effects of platelet-activating factor (PAF) on ion transport and prostaglandin synthesis in human colonic mucosa in vitro

1 We have investigated the effects of platelet-activating factor (PAF), an endogenous mediator of inflammation, on ion transport and prostaglandin synthesis in the human isolated colon. 2 Application of PAF to the serosal surface of human colonic mucosa induced a marked, concentration-dependent increase in ion transport. Mucosal application was without effect. 3 The secretory response to PAF was significantly inhibited by prior application of a specific PAF receptor antagonist WEB 2170, indicating that the response is dependent on PAF receptor activation. 4 The response to PAF was attenuated by prior application of indomethacin or piroxicam, implicating products of the cyclo-oxygenase pathway in the response. 5 The response to PAF was attenuated by the loop diuretic bumetanide, indicating an involvement of chloride ion secretion in the response. 6 Addition of PAF to the serosal surface induced a significant increase in serosal prostaglandin E2 (PGE2), but not 6-oxo-PGF1alpha release. There was no effect on mucosal application of PAF. 7 In summary, we have shown that PAF is a potent secretagogue in isolated preparations of human colon and that the response is dependent on a specific PAF receptor, cyclo-oxygenase products and bumetanide-sensitive chloride ion transport.

Compartmentalisation and characteristics of a Ca2+-dependent phospholipase A2 in human colon mucosa

The biochemical properties of the phospholipase A2 (PLA2) found in the 100,000 x g centrifugate cytosol or particulate fractions of human colonic mucosa have been investigated using both deoxycholate-solubilized and Escherichia coli (E. coli) phospholipids as substrates. PLA2 activity was present in both subcellular fractions and the profiles of biochemical activites were similar. Activity in the particulate fraction was approximately twofold greater than the cytosol fraction when expressed on the basis of protein concentration. The PLA2 is Ca2+ dependent and using EGTA-regulated buffers cytosolic or particulate fraction activity was similar at both 10 microm or 10 mm Ca2+ concentrations. Using deoxycholate-phospholipid micelles as substrate a small but statistically significant twofold preference for glycero-phosphatidylcholine bearing sn-2-arachidonate compared with sn-2-oleate was seen, but this preference was not noted using arachidonate or oleate labelled E. coli membranes. Dithiothreitol (10 mM) reduced colon mucosal cytosol PLA2 activity significantly by 63.5 +/- 1.90% in cytosol and by 30.54 +/- 1.27% in microsomes using micelles as substrate or by 84.3 +/- 2.30% in cytosol and by 69.33 +/- 11.30% in microsomes using oleate-labelled E. coli as substrates. Warming at 57 degrees C reduced activity significantly by 35.0 +/- 5.80% in microsomes and by 40.0 +/- 7.08% in cytosol. Acid treatment increased PLA2 activity to 148 +/- 16.3% in microsomes and 145 +/- 18.6% in cytosol. When mucosal preparations were subjected to heparin-Sepharose chromatography, it bound tightly and eluted in the same position on a salt gradient as authentic human group II PLA2. Further purification by gel-permeation chromatography gave activity in the 14 kDa region of the elution profile. These features have many of the characteristics expected of a 14 kDa isoform of PLA2 but exhibit activity at concentrations of Ca2+ that are relevant in the intracellular environment and may participate in cellular lipid metabolism.

Characterization of muscarinic receptors mediating contractions of circular and longitudinal muscle of human isolated colon

1. The effects of seven muscarinic receptor antagonists were used to characterize the receptors which mediate carbachol-evoked contractions of intertaenial circular and taenial longitudinal muscle in human isolated colon. The effects of these antagonists were studied upon colon contractions induced by cumulatively added carbachol which had mean EC50 values of 11.7 +/- 2.3 microM (n = 8) and 12.6 +/- 2.3 microM (n = 8) respectively upon circular and longitudinal smooth muscle. 2. All antagonists displaced concentration-response curves to carbachol to the right in a parallel manner. The maximum concentration of each antagonist added (30 nM-10 microM) did not significantly suppress the maximum response. 3. In circular muscle, the M3 muscarinic receptor antagonists, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), hexahydrosiladiphenidol (HHSiD) and para-fluoro-hexahydrosiladiphenidol (p-F-HHSiD) inhibited responses with pA2 values of 9.41 +/- 0.23, 7.17 +/- 0.07, 6.94 +/- 0.18 respectively. The M2 muscarinic receptor antagonist, AF-DX 116, the M2/M4 muscarinic receptor antagonist, himbacine, and the M1 muscarinic receptor antagonist, pirenzepine, yielded pA2 values of 7.36 +/- 0.43, 7.47 +/- 0.14 and 7.23 +/- 0.48 respectively. The non-selective antagonist, atropine, had a pA2 of 8.72 +/- 0.28. 4. In longitudinal muscle 4-DAMP, HHSiD, p-F-HHSiD, AF-DX 116, himbacine and pirenzepine gave pA2 values of 9.09 +/- 0.16, 7.45 +/- 0.43, 7.44 +/- 0.21, 6.44 +/- 0.1, 7.54 +/- 0.40, 6.87 +/- 0.38 respectively. Atropine yielded a pA2 value of 8.60 +/- 0.08. 5. The pharmacological profile of antagonist affinities at the muscarinic receptor population responding to muscarinic agonist-evoked contraction is similar to that widely accepted as characterizing the activation of an M3 muscarinic receptor subtype, although pA2 values of some antagonists are lower than that seen in other investigations.

Biosynthesis of platelet-activating factor in normal and inflamed human colon mucosa: evidence for the involvement of the pathway of platelet-activating factor synthesis de novo in inflammatory bowel disease

1. Platelet-activating factor can be synthesized by two distinct biochemical pathways and is degraded by a number of enzymes, the first step of which is deacetylation by a specific acetyl hydrolase. 2. The biochemical pathway of platelet-activating factor synthesis de novo and the first step in platelet-activating factor degradation have been investigated for the first time in incubates of normal human colon mucosa and in inflamed mucosa from patients with inflammatory bowel disease. 3. In the presence of 100 mumol/l CDP-choline and 100 mumol/l hexadecyl acetyl glycerol, homogenates from inflamed mucosa synthesized significantly greater platelet-activating factor [851 +/- 574 pmol/mg of protein (mean +/- SEM) in 90 min incubation] than normal mucosa [105 +/- 61 pmol/mg of protein in 90 min incubation] (P < 0.05). 4. Under the same conditions of assay, the percentage turnover to inactive lyso-platelet-activating factor was similar in inflamed mucosa (35.5 +/- 9.4%) and normal mucosa (42.7 +/- 8.5%) in 90 min (P > 0.05). 5. The identity of platelet-activating factor was confirmed by HPLC, by its mobility on TLC and by the ability of WEB 2170, a selective platelet-activating factor receptor antagonist, to block its platelet-aggregatory action. 6. These findings confirm the presence of the pathway for the synthesis de novo of the potently proinflammatory platelet-activating factor in human colon mucosa in inflammatory bowel disease.

Differences in response to 5-HT4 receptor agonists and antagonists of the 5-HT4-like receptor in human colon circular smooth muscle

1. In isolated circular smooth muscle strips of human colon 5-hydroxytryptamine (5-HT) produced a concentration-related inhibition of spontaneous motility. 2. The azabicycloalkyl benzimidazolones, BIMU 8 and BIMU 1, which have 5-HT4 receptor stimulant properties, inhibited motility with EC50 values of 0.76 microM and 3.19 microM respectively and their Emax values were not significantly different from 5-HT (EC50, 0.13 microM). 3. The 5-HT4 receptor antagonist, DAU 6285 (1-10 microM), displaced the 5-HT concentration-response curve to the right in a parallel concentration-dependent manner without depressing the maximum. The Schild plot was linear and the slope did not differ significantly from unity giving a pA2 value of 6.32. 4. The high affinity selective 5-HT4 receptor antagonist, GR 113808, at a concentration of 3 nM displaced the 5-HT concentration-response curve in a parallel manner giving an apparent pKB estimate of 8.9 +/- 0.24. However, higher concentrations of 10-100 nM GR 113808 did not result in a further significant displacement of the 5-HT concentration-response curve and there was no suppression of Emax. 5. GR 113808 (10 nM) also caused a parallel displacement of the concentration-response curve to the 5-HT4 receptor agonist, 5-methoxytryptamine (5-MeOT) giving apparent pKB values ranging from 8.3-9.3. 6. GR 113808 (3-100 nM) failed to displace 5-HT or 5-MeOT concentration-response curves in tissue strips from 3 patients out of a total of 10 patients studied in whom the response to 5-HT and 5-MeOT was normal. 7. The 5-HT4 receptor antagonist, SDZ 205-557 (0.3-10 microM), had no significant effect on 5-HT-induced inhibition of spontaneous motility.8. The present results are discussed in the light of variability of response to GR 113808 and SDZ205-557 in other tissues.9. Overall, our data indicate that human colon circular smooth muscle can be regarded as a site in which 5-HT4-like receptors are present but it is as yet unclear whether these results are also an indication of receptor variation.

Characterization of the 5-hydroxytryptamine receptor type involved in inhibition of spontaneous activity of human isolated colonic circular muscle

1. Experiments were carried out to characterize pharmacologically the 5-hydroxytryptamine (5-HT) receptor types which mediate inhibition of spontaneous contractions of the intertaenial circular muscle in human isolated colon. 2. 5-HT caused a reproducible concentration-dependent inhibition of spontaneous contractions of the circular muscle of human colon in vitro with a mean EC50 value of 0.2 microM and 95% confidence limits of 0.1-0.5 microM. No evidence for a contractile action of 5-HT was found. Tetrodotoxin (TTX, 1.5 microM) caused a rightward shift of the concentration-response curve of 5-HT with a concentration-ratio of 2.9. 3. The inhibitory response to 5-HT was mimicked by several indoles with the rank order of potency 5-HT > 5-methoxytryptamine = alpha-methyl-5-HT > 5-carboxamidotryptamine >> 2-methyl-5-HT. 5-Hydroxyindalpine was inactive. 4. The substituted benzamides were agonists with the following rank order of potency, 5-HT > renzapride > zacopride > metoclopramide > cisapride. 5. The inhibitory responses to 5-HT were not inhibited by methysergide (10 microM) or methiothepin (1 microM), which are antagonists selective for 5-HT1-like and 5-HT2 receptors, nor by ondansetron (10 microM) which is an antagonist at 5-HT3 receptors. 6. The inhibitory responses induced by 5-HT and 5-methoxytryptamine were competitively antagonized by a weak 5-HT4 receptor antagonist, tropisetron, with pKB values of approximately 6. Tropisetron had no significant effect on the inhibitory response curve produced by isoprenaline (0.01-100 microM). 7. The pharmacological profile of the 5-HT-evoked relaxations of human colon circular muscle are consistent with activation of a 5-HT4-like receptor.

A randomized comparison of a bipolar steroid-eluting electrode and a bipolar microporous platinum electrode: implications for long-term programming

Differences in acute and chronic pacing thresholds were compared in patients receiving either the Medtronic Model 4004 steroid-eluting lead or the Medtronic Model 4012 microporous platinum lead. Patients (n = 35) were randomized at the time of implant to receive either a steroid-eluting (n = 17) or a microporous (n = 18) lead. Pacing thresholds were determined within 24 hours and at 2, 4, 6, 12, 24, and 52 weeks postimplant. By 2 weeks postimplant, pacing thresholds measured at 0.8, 1.6, 2.5, 3.3, and 4.2 V were significantly lower in the steroid lead group compared to the microporous lead group (P < 0.05). At 24 weeks, the voltage threshold at 0.3 msec was 0.8 V in 88% of patients with a steroid lead whereas this threshold was only observed in 33% of patients with the microporous lead (P < 0.01). At 52 weeks the pacing energy measured at 1.6 V, twice pulse duration threshold, was significantly lower in the steroid lead group (0.81 +/- 0.59 microJ) compared to the microporous lead group (1.25 +/- 0.60 microJ, P < 0.05). Thirteen patients in the steroid lead group and 9 patients in the microporous lead group have been programmed at a pulse amplitude of 1.6 V since the 24-week follow-up visit. These patients have been followed for a minimum of 6 months without documented failure to capture. This study shows that pacemaker/lead systems with stable chronic low thresholds can be safely programmed to low pulse amplitude settings. This practice will prolong the longevity of pulse generators.

Catabolism of platelet-activating factor by human colonic mucosa. Calcium dependence of the catabolizing enzymes

The catabolism of platelet-activating factor (PAF) and lyso PAF by a supernatant fraction of human colon mucosa homogenates has been studied in vitro. PAF is initially catabolized to lyso PAF by mucosal enzymes via removal of its acetyl group. Incubates in Ca(2+)-free Tris with EDTA showed that the acetyl hydrolase was Ca2+ independent. Addition of the hydrolase inhibitor, phenyl methyl sulphonyl fluoride, significantly reduced the catabolism of PAF. Lyso PAF was further catabolized in at least two ways. An acyl group was incorporated into the sn-2 position of lyso PAF to give 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine (alkyl acyl GPC); this step was Ca2+ independent as shown by omitting Ca2+ and adding EDTA to the incubate. Formation of alkyl acyl GPC was confirmed by HPLC. Alternatively, choline was removed from the head group of lyso PAF by a calcium-dependent lyso phospholipase D. Under the experimental conditions utilized a neutral lipid product was formed but significant amounts of the intermediate lysophosphatidic acid could not be detected. A substance with a chromatographic mobility of Rf = 0.8 on TLC plates having an intact phosphorylcholine head group was also formed but has not yet been identified. It is concluded that the human colon mucosa contains enzymes that actively catabolize pro-inflammatory PAF and lyso PAF.

Inhibition profiles of sodium cromoglycate and nedocromil sodium on mediator release from mast cells of human skin, lung, tonsil, adenoid and intestine

We have studied an aspect of the functional heterogeneity of human mast cells, namely responsiveness to the inhibitory effects of sodium cromoglycate and nedocromil sodium. The effects of these drugs were examined on the release of histamine and PGD2 from mast cells of human skin, lung, tonsils, adenoids and intestine. A high concentration, 1000 microM, of sodium cromoglycate was required to significantly inhibit histamine release from lung and tonsillar mast cells. Nedocromil sodium, 1000 microM, was more effective than sodium cromoglycate against histamine release from lung, tonsillar and adenoidal cells. Both compounds showed tachyphylaxis in lung and tonsillar mast cells but not in adenoidal and intestinal mast cells. In contrast, in intestinal mast cells, the effect of nedocromil sodium was weaker and more variable than sodium cromoglycate. Skin mast cells differed from mast cells of the other anatomical sites in being unresponsive to sodium cromoglycate and nedocromil sodium. Our results confirm that high concentrations of sodium cromoglycate and nedocromil sodium are required to achieve even modest inhibition of mediator release from human mast cells under in vitro conditions. Notwithstanding this, the results also indicate that differences exist among skin, lung, tonsillar, adenoidal and intestinal mast cells with respect to their sensitivity to sodium cromoglycate and nedocromil sodium, thus extending our knowledge of functional heterogeneity within the human mast cell populations.

The role of nitric oxide in mediating non-adrenergic non-cholinergic relaxation in longitudinal muscle of human taenia coli

Electrical field stimulation (EFS) of isolated longitudinal muscle of human taenia coli at 4Hz produced relaxation which was abolished by tetrodotoxin but not adrenergic and cholinergic blockade (NANC-relaxation). NG-nitro L-arginine (L-NOARG; 1-100 microM), an NO synthesis inhibitor, produced a concentration-dependent partial inhibition of the NANC response; 10 microM L-NOARG inhibited EFS-induced relaxation by 48.6 +/- 5.20% and 100 microM L-NOARG by 54.2 +/- 10.1%. L-Arginine (1mM), but not D-arginine (1mM) partially reversed the inhibitory effect and this was inversely proportional to the concentration of L-NOARG used. Cumulative administration of NO (acidified sodium nitrite solution; 1-100 microM) produced a concentration-dependent relaxation of the strips. L-NOARG (1 mM) did not affect either NO or isoprenaline-induced relaxations. These results provide the first preliminary evidence that NO is partially responsible for the NANC inhibitory transmission in the longitudinal muscle of the taenia coli of human colon.

Incorporation of fatty acids from fish oil and olive oil into colonic mucosal lipids and effects upon eicosanoid synthesis in inflammatory bowel disease

The incorporation of the fatty acids in fish and olive oil into the colonic mucosa of patients with inflammatory bowel disease was examined during 12 weeks' dietary supplementation with the oils, and the influence on colonic mucosal prostaglandin and thromboxane generation was measured. With a dietary supplement of 18 g fish oil daily, concentrations of the major polyunsaturated fatty acids in fish oil, eicosapentaenoic acid and docosahexaenoic acid, were significantly raised in mucosal lipids. The first time these were measured, after three weeks' supplementation, the mean increases in eicosapentaenoic and docosahexaenoic acid were seven fold and 1.5 fold respectively, and these increases were maintained during the 12 week study. Arachidonic acid values fell throughout the study and this reduction was significant at 12 weeks. Mucosal prostaglandin E2 (PGE2), thromboxane B2, and 6-keto prostaglandin F1 alpha synthesis were suppressed, and this reached significance (p less than 0.05) at three and 12 weeks for PGE2 and at 12 weeks for thromboxane B2. The predominant fatty acid in olive oil is oleic acid. Supplementation with 18 g/day resulted in a significant increase in oleic acid in colonic mucosa at 12 weeks (p less than 0.05) and a fall in stearic acid and docosahexaenoic acid; there was no significant change in eicosanoid synthesis. It is concluded that colonic lipids and prostaglandin and thromboxane synthesis can be readily altered by dietary supplementation with fish oil. The extent of incorporation of the fatty acids present in oils is dependent upon the individual fatty acid.

Effect of sucralfate and cimetidine on rheumatoid patients with active gastroduodenal lesions who are taking nonsteroidal anti-inflammatory drugs. A pilot study

In a pilot study, 26 rheumatoid arthritic patients taking continuous, stable dosage regimens of nonsteroidal anti-inflammatory drugs and with developed gastric and duodenal lesions were administered sucralfate 1 g four times per day (14 patients) or cimetidine 400 mg twice daily (12 patients) in a single-blind regimen for six weeks. Eleven of the patients given sucralfate and eight of the patients taking cimetidine had improved lesion scores. The lesion score of 10 of the 14 patients taking sucralfate and four of the 12 patients taking cimetidine improved by 50 percent or better (not significant). The antrum and body of the gastric mucosa and the mucosa of the duodenum synthesized prostanoids and thromboxane A2, and there was no significant difference in the synthesis of individual prostanoids at entry to the trial in the groups assigned to sucralfate or cimetidine. After six weeks of administration of sucralfate, prostaglandin E2 (PGE2) synthesis by the antrum and body, but not the duodenum, was significantly greater than observed in the biopsy specimens at entry despite continuation of non-steroidal anti-inflammatory drug therapy. After six weeks of cimetidine treatment, no change in PGE2 synthesis was noted in any biopsy specimens when compared with the synthesis at entry. No change in the synthesis of PGF2 alpha, 6-oxo-PGF1 alpha, or thromboxane B2 was noted in gastric or duodenal biopsy specimens in any treatment group. Sucralfate and cimetidine administration resulted in improved gastroduodenal lesion scores in rheumatoid arthritic patients continuing with nonsteroidal anti-inflammatory drug therapy.

The secretory characteristics of mast cells isolated from the human large intestinal mucosa and muscle

The use of a collagenase dispersion technique has allowed us to compare size, histamine content and the secretory characteristics of mast cells from the mucosal and muscle layers of the human large intestine. Mast cells from the mucosa, which constituted 1.8% of the total nucleated cells, contained approximately equal numbers of formalin-sensitive and -insensitive mast cells. Those dispersed from the muscle layer constituted 3.2% of the total nucleated cells and were almost all formalin insensitive. The cells from both layers were similar with respect to size and mean cell histamine content. Anti-IgE released up to 15.1% and 16.5% of total cell histamine in the mucosa and muscle, respectively, with similar concentration-response characteristics. The kinetics of anti-IgE-induced release, however, were different, mucosal mast cells releasing histamine 55 seconds (P less than 0.05) faster than cells dispersed from intestinal muscle. Cells from both layers also released histamine in response to A23187 in a similar concentration-related fashion. Neither mucosal or muscle mast cells released significant amounts of histamine in response to compound 48/80, substance P, morphine, poly-L-lysine or f-met-leu-phe. Our results show intestinal mast cells possess secretory characteristics similar to those of human lung, adenoids and tonsils, but are different from human skin mast cells. The absence of significant histamine release in response to basic secretagogues from either layer of the human intestine contrasts with studies in the rodent intestine. Furthermore it suggests that in human mast cells, histochemical properties, protease content and secretory characteristics may not be closely associated.

Effect of polyunsaturated fatty acids of the n-3 and n-6 series on lipid composition and eicosanoid synthesis of platelets and aorta and on immunological induction of atherosclerosis in rabbits

The effect of dietary fish oil (rich in n-3 polyunsaturated fatty acids (PUFA], corn oil (rich in n-6 PUFA) and coconut oil (low in n-3 and n-6 PUFA) on the induction of atherosclerosis by serum sickness in rabbits was investigated over a 12-month period. Dietary fish oil led to a significant increase in the level of eicosapentaenoic acid (EPA) in all platelet phospholipid fractions and to a significant reduction in the level of platelet phosphatidylethanolamine arachidonic acid (AA). In aortic total phospholipids, rabbits given fish oil showed a significant reduction in AA and a significant increase in EPA. Rabbits given fish oil showed significantly lower collagen-induced platelet thromboxane A2 release and aortic production of 6-keto-PGF1 alpha. Serum total immune complex levels and anti-horse serum IgG levels were not influenced by diet. There was a significant reduction in total aortic atherosclerosis in fish oil-fed animals compared with coconut oil fed animals.

Modification of upper gastrointestinal prostaglandin synthesis by dietary fatty acids

The effects of dietary oils on gastric, duodenal mucosa and liver were investigated in a rat model. Unsaturated fatty acid profiles and in vitro prostaglandin (PG) synthesis (PGE2, PGF2 alpha, 6-oxo-PGF1 alpha and thromboxane B2), were measured after 14 days of dietary oil supplements. There were no significant differences in prostanoid synthesis between rats fed coconut oil (high saturated fat content) and standard diet. After fish oil supplement, tissue eicosapentaenoic acid and docosahexaenoic acid levels were higher, arachidonic acid levels were lower, and prostanoid synthesis was reduced in both stomach and duodenum. After corn oil and evening primrose oil, linoleic acid levels were variably increased, but there were no significant differences in arachidonic acid or prostanoid synthesis. Dihomogamma-linolenic acid levels were slightly increased after evening primrose oil. Dietary incorporation of fatty acids into gastroduodenal tissue is not uniform. When incorporated, fatty acids can modify prostaglandin synthesis.

Increased arachidonic acid levels in phospholipids of human colonic mucosa in inflammatory bowel disease

1. Colonic mucosa from 19 patients with ulcerative colitis, eight with Crohn's disease and 14 controls were analysed for arachidonic acid (C20:4), linoleic acid (C18:2), oleic acid (C18:1), stearic acid (C18:0) and palmitic acid (C16:0). 2. Gas-liquid chromatography of lipid extracts showed that arachidonic acid was significantly higher in ulcerative colitis (19 +/- 4) and Crohn's disease (20 +/- 3) than in controls (13 +/- 5 micrograms/mg of protein) (means +/- SD). Neither the degree of inflammation nor treatment with sulphasalazine or prednisolone appeared to influence the fatty acid concentrations. 3. Seventy-five to ninety-five per cent of the arachidonic acid was found in the phospholipid fraction after separation by thin-layer chromatography. There were no significant changes in the concentrations of the other fatty acids measured, although oleic acid was lower in inflammatory bowel disease. The ratios of oleic acid to stearic acid and to palmitic acid were lower in inflammatory bowel disease. 4. The alteration in the fatty acid profile may partly explain the increased synthesis of eicosanoids in colonic mucosa in inflammatory bowel disease.

Effect of human chorionic gonadotrophin and indomethacin on ovulation, steroidogenesis and prostaglandin synthesis in preovulatory follicles of PMSG-primed immature rats

Immature rats were treated with PMSG followed 56 h later by 10 i.u. hCG. Follicles were removed at intervals after hCG injection. Transient increases in progesterone, testosterone and oestradiol synthesis were first evident 1 h after hCG, but values peaked at 3-5 h and returned to control levels by 10 h. Increased synthesis of PGE-2 and PGF-2 alpha was not evident until 3 h and peaked at more than 10 h after hCG. Ovulation began between 8 and 10 h after hCG and 83% of animals had ovulated within 12 h. Doses of 90 or 1800 micrograms indomethacin given together with hCG substantially inhibited ovulation and PG synthesis, but only the higher dose inhibited the hCG-induced elevation of progesterone and testosterone synthesis; hCG-induced oestradiol synthesis was not affected by either dose of indomethacin. We conclude that the peak of PG synthesis after hCG treatment related closely to the timing of ovulation; the steroidogenic response to hCG was not blocked by doses of indomethacin sufficient to inhibit synthesis of PGE-2 and PGF-2 alpha by more than 80%.

Kinetics of prostaglandin E2 and thromboxane A2 synthesis and suppression of PHA-stimulated peripheral blood mononuclear leucocytes

The immunomodulatory effects of thromboxane A2 and prostaglandin E2 on peripheral blood mononuclear leucocytes stimulated with PHA in vitro, and the relationship of this to the time-course of their synthesis in culture, were investigated using prostaglandin E2, a thromboxane A2 synthesis inhibitor (UK37248), a thromboxane A2 mimic (U46619) and a thromboxane A2 receptor blocker (EP045). The inhibitory effect of prostaglandin E2 on PHA-induced human peripheral blood mononuclear leucocyte proliferation diminishes if the addition of PGE2 is delayed. If added 4 hr after a maximum concentration of PHA (5 micrograms/ml), the effect of PGE2 was reduced by 60%. If a submaximal concentration of PHA (1 microgram/ml) was used, the effect of PGE2 was not reduced if added 4 hr later but fell by about 60% after 16 hr. UK37248 moderately inhibited PHA-induced activation while substantially inhibiting thromboxane A2 synthesis and simultaneously enhancing PGE2 synthesis. The enhanced accumulation of PGE2 occurs while sensitivity to PGE2 is dropping. U46619, exogenously applied as a thromboxane A2 mimic, inhibited PHA-induced activation at concentrations that did not significantly alter PGE2 synthesis. EP045, which may modulate the effects of endogenous thromboxane A2 by blocking receptors, did not alter PHA-induced activation. We conclude that thromboxane A2 may have a role in inhibiting PHA-induced activation on the basis of the effect of U46619. However, this study highlights difficulties in utilizing prostaglandin and thromboxane receptor and synthesis inhibitors to examine their endogenous role in the modulation of mitogen-induced activation in vitro. If sensitivity to the purported endogenous substance is limited to the early stages of culture and if only low levels are synthesized at this early stage, then blocking drugs would have little effect.

Stability of ascorbic acid and uptake of the vitamin by embryonic chick femurs during long-term culture

Ascorbic acid was added to organ cultures of 15-day-old embryonic chick femurs. The ascorbate that was taken up into the cultured tissue reached maximal concentrations after 1.5 h. The half-life of tissue ascorbate was 12-24 h, whereas the half-life of medium ascorbate was 1-2 h. 24 h after supplementing with ascorbate, the tissue concentrations were still 30-60-fold higher than the medium concentrations at that time. If no ascorbate was added to the culture medium, the tissue concentration declined over a period of days: after 6 days 2-7% of the pre-culture tissue concentrations were still present. Embryonic chick femurs in vitro are therefore shielded from massive fluctuations in the concentration of ascorbic acid in the medium, resulting from intermittent supplementation. Hence, feeding a culture with the vitamin once every 24 h is sufficient to ensure adequate levels in the tissue.

Ascorbic acid requirements for collagen synthesis (proline hydroxylation) during long-term culture of embryonic chick femurs

Although ascorbate is essential for collagen synthesis, especially the hydroxylation of prolyl residues, femurs from 15-day-old chick embryos could be cultured for at least 5 days without ascorbate additions to the medium before the hydroxylation of proline was significantly impaired. Only when the ascorbate concentration in the tissue was less than 6 micrograms/g wet weight (compared with 50-70 micrograms/g wet weight in fresh tissue), was hydroxyproline formation reduced by 75-85%. When sufficient ascorbate was present in the culture medium, the femurs accumulated and stored the vitamin at concentrations which were 5-10-fold above the threshold required for collagen synthesis. This may represent an adaptive mechanism to the instability of the vitamin. Above the minimum required level, synthesis of collagen was not quantitatively related to ascorbate concentration. To obtain comprehensive data on changes in collagen content and collagen synthesis during culture, total hydroxyproline was measured as well as [3H]proline uptake and the formation of [3H]hydroxyproline. These three parameters were assessed with a new combined assay, which was modified from existing methods, yet was more sensitive and less tedious.

Duodenal mucosa synthesis of prostaglandins in duodenal ulcer disease

Synthesis of prostaglandins (PGE2, PGI2 and PGF2 alpha) and thromboxane A2 was investigated in short term incubates of duodenal mucosa biopsies. Mucosa close to the ulcer site synthesised significantly less PGF2 alpha (p less than 0.001) and PGI2 (p less than 0.002) measured as its stable metabolite 6-oxo-PGF1 alpha than healthy mucosa from non-ulcer patients. In paired biopsies taken from the ulcer site and opposite the ulcer in the same patient PGF2 alpha and PGI2 syntheses were both significantly and similarly depressed when compared with normal mucosa. Synthesis of PGE2 and TxA2 (as its stable metabolite TxB2) was not different in any tissue. There is a defect in the ability of the human duodenal mucosa in duodenal ulcer disease to synthesise PGF2 alpha and PGI2; the defect is not limited to the ulcer site.