Molecular basis and species specificity of high affinity binding of vasoactive intestinal polypeptide by the rat secretin receptor

The affinity and specificity of the binding interaction between ligands and their receptors are key for appropriate hormonal regulation of target tissues. However, it is now apparent that vasoactive intestinal polypeptide (VIP) binds to the rat secretin receptor with similar affinity to that for its natural ligand, secretin (Holtmann et al., 1995). In this report, we establish that this is not a characteristic of the human secretin receptor, and use rat-human secretin receptor chimeras, site mutants and truncated receptor constructs to establish the molecular basis for this unusual binding interaction. Of note, isolated N-terminal domains of the rat secretin and the VIP receptors are capable of high affinity binding of VIP. In the recently recognized secretin family of receptors, this domain has six conserved cysteine residues and disulfide bonds that are likely important to achieve the complex conformation critical for this binding. A single acidic residue (Asp98) present in the rat secretin receptor appears to be critical, because a site-mutant changing this to the polar, but uncharged residue present in that position in the human receptor (Asn) eliminates the high affinity binding of VIP. Of interest, a previously identified critical basic residue in VIP (Lys15) provides a candidate for charge-pairing with this residue, potentially aligning the peptide ligand in a nonproductive orientation within this receptor.     

Substitution of the human beta-spectrin promoter for the human agamma-globin promoter prevents silencing of a linked human beta-globin gene in transgenic mice

During development, changes occur in both the sites of erythropoiesis and the globin genes expressed at each developmental stage. Previous work has shown that high-level expression of human beta-like globin genes in transgenic mice requires the presence of the locus control region (LCR). Models of hemoglobin switching propose that the LCR and/or stage-specific elements interact with globin gene sequences to activate specific genes in erythroid cells. To test these models, we generated transgenic mice which contain the human Agamma-globin gene linked to a 576-bp fragment containing the human beta-spectrin promoter. In these mice, the beta-spectrin Agamma-globin (betasp/Agamma) transgene was expressed at high levels in erythroid cells throughout development. Transgenic mice containing a 40-kb cosmid construct with the micro-LCR, betasp/Agamma-, psibeta-, delta-, and beta-globin genes showed no developmental switching and expressed both human gamma- and beta-globin mRNAs in erythroid cells throughout development. Mice containing control cosmids with the Agamma-globin gene promoter showed developmental switching and expressed Agamma-globin mRNA in yolk sac and fetal liver erythroid cells and beta-globin mRNA in fetal liver and adult erythroid cells. Our results suggest that replacement of the gamma-globin promoter with the beta-spectrin promoter allows the expression of the beta-globin gene. We conclude that the gamma-globin promoter is necessary and sufficient to suppress the expression of the beta-globin gene in yolk sac erythroid cells.     

Treatment of spondylolysis with external electrical stimulation and bracing in adolescent athletes: a report of two cases

BACKGROUND: An epidemic of bilateral optic neuropathy is affecting large numbers of people aged between 10 and 40 in Dar es Salaam, the capital city of Tanzania. The disease is characterised by acute onset of bilateral visual impairment, bilateral impairment of colour vision, and a characteristic temporal pallor of the optic discs. The disease often occurs in association with peripheral neuropathy and sensorineural hearing loss. This report presents the first data on disease prevalence in adolescents, based on a rapid assessment of schoolchildren. METHODS: Three schools in Dar es Salaam were visited and all children aged between 10 and 16 were screened for the disease. RESULTS: The prevalence of bilateral optic neuropathy among the schoolchildren is estimated to be 1.0% (95% CI 0.5-1.4%). This suggests that 5000 children (95% CI 2600-7300) aged 10-16 in Dar es Salaam may have the disease. CONCLUSION: The results of this rapid assessment indicate this epidemic is a major public health problem. The prevalence of the disease in the community is likely to be far higher than found in this survey because children with the disease may have withdrawn from school. As the disease predominantly affects young adults, resulting in impaired vision and hearing, the economic and social consequences are enormous.     

The role of type III collagen in spontaneous cervical arterial dissections

OBJECTIVE: To determine the efficacy of lymphadenectomy after nephroureterectomy in patients with transitional cell carcinoma (TCC) of the upper urinary tract. PATIENTS AND METHODS: Between January 1986 and December 1995, 72 patients (mean age 67 years, range 45-82) underwent nephroureterectomy for primary TCC of the upper urinary tract. In 35 patients, a lymphadenectomy was also performed. The clinicopathological data were analysed retrospectively, focusing on the significance of lymphadenectomy. RESULTS: Lymph vessel invasion was found in 28 patients and its incidence was closely correlated with both tumour grade and pathological stage. Of the 35 patients who underwent lymphadenectomy, lymph node metastases were found in 13 patients, all of whom had lymph vessel invasion. There was no significant difference in the survival rate between patients with and without lymphadenectomy; however, among the 44 patients with no lymph vessel invasion, the survival rate of those with lymphadenectomy was significantly higher than in those without (P<0.05). CONCLUSION: Lymphadenectomy may provide a therapeutic advantage in patients with upper urinary tract TCC and no lymph vessel invasion. However, patients with lymph vessel invasion seem to have systemic disease; therefore, aggressive systemic adjuvant therapies rather than regional lymphadenectomy should be applied in these patients.     

Studies on the efficacy of hyperbaric rendering procedures in inactivating bovine spongiform encephalopathy (BSE) and scrapie agents

The efficacy of the procedures in use at the two rendering plants in the Netherlands was assessed on a laboratory-scale using procedures that simulated the pressure cooking part of the rendering process. A pool of bovine spongiform encephalopathy (BSE)-infected brainstem from the United Kingdom and a pool of scrapie-infected brainstem from Dutch sheep were used to spike the rendering materials. The mixtures were subjected to various time-temperature combinations of hyperbaric heat treatment related to the conditions used in Dutch rendering plants in the early 1990s, and to the combination of 20 minutes at 133 degrees C required by the EU Directive on rendering of 1996. The efficacy of the procedures in inactivating BSE or scrapie infectivity was measured by titrating the materials before and after heat treatment in inbred mice, by combined intracerebral and intraperitoneal inoculations at limiting dilutions. Two independent series of experiments were carried out. The design of the study allowed for minimum inactivations of up to 2.2 log (2.0 in the second series) to be measured in the diluted infective material and 3.1 log in the undiluted material. After 20 minutes at 133 degrees C there was a reduction of BSE infectivity of about 2.2 log in the first series (with some residual infectivity detected), and in the second series more than 2.0 log (with no residual infectivity detected). With undiluted brain material there was an inactivation of about 3.0 log (with some residual infectivity detected). With the same procedure, scrapie infectivity was reduced by more than 1.7 log in the first series and by more than 2.2 log in the second series. With undiluted brain material there was an inactivation of more than 3.1 log. In each case no residual scrapie infectivity was detected. The BSE agent consistently appeared to be more resistant to heat inactivation procedures than the scrapie agent, particularly at lower temperatures and shorter times.     

Klippel-Trenaunay-Weber syndrome with adrenal pseudocyst: characterization by blood pool and adrenocortical iodocholesterol scintigraphy

A 44-year-old woman with Klippel-Trenaunay-Weber syndrome (KTWS) was evaluated for an adrenal mass incidentally discovered on CT. An NP-59 scintigraph showed normal symmetric adrenal tracer uptake, and a Tc-99m labeled RBC scan showed no evidence for an adrenal hemangioma but did show characteristic dilated and tortuous vasculature at multiple other sites. The mass was removed and found to be an adrenal pseudocyst. The pseudocyst was believed to have arisen from a pre-existing, thrombosed and organized adrenal hemangioma. This case demonstrates the previously reported utility of RBC scintigraphy in the depiction of the vascular abnormalities in the diagnosis and treatment of patients with Klippel-Trenaunay-Weber syndrome, as well as the utility of NP-59 scintigraphy in evaluating patients with adrenal masses.     

Measurement of histamine release from human lung tissue ex vivo by microdialysis technique

OBJECTIVE AND DESIGN: Currently no method is available for measurement of mediator release from intact human lung. In this study, a microdialysis technique was used to measure histamine release from mast cells in human lung tissue ex vivo. MATERIAL: Microdialysis fibers of 216 microm were inserted into lung tissue and perfused with Krebs Ringer buffer at a rate of 3 microl/min. After a 15 min period of steady-state perfusion, anti-IgE and vehicle were injected into the lung tissue above individual fibers. Samples from each fibre were collected for 20 min at 2 min intervals. Histamine was assayed fluorometrically. RESULTS: Anti-IgE concentrations of 40-40,000 U/ml dose-dependently released histamine, significant histamine release being demonstrated with anti-IgE concentrations of 400 U/ml and greater. The kinetics of histamine release showed peak values 2-8 min after the injection. Great individual responses were observed but data could be reproduced within individual donors. Monocyte chemoattractant protein-1, a potent basophil secretagogue, did not induce histamine release in lung tissue which indicated mast cells to be the histamine source. Substance P did not release histamine in the lung tissue. CONCLUSIONS: The microdialysis technique allowed measurements of histamine release from mast cells in intact lung ex vivo. The method may prove useful since a number of experiments can be performed in a few hours in intact lung tissue without any dispersion or enzymatic treatment.     

Gastrointestinal tract symptoms and self-reported abuse: a population-based study

BACKGROUND/AIMS: A link between abuse and irritable bowel syndrome (IBS) has been reported in outpatients but remains controversial. No population-based studies have investigated this issue. The aim of this study was to determine the prevalence of abuse and its association with symptoms in a representative community sample. METHODS: An age- and sex-stratified random sample of residents of Olmsted County, Minnesota ranging in age from 30 to 49 years was mailed a valid self-report symptom questionnaire. Abuse was assessed by standard published criteria. RESULTS: Of the 919 responders (74%), the age-adjusted prevalence of any abuse was 41% in women and 11% in men, resulting in an age- and sex-adjusted prevalence of 26%. Symptoms of IBS, dyspepsia, and frequent heartburn were reported by 14%, 23%, and 12%, respectively. There was a significant association between IBS and sexual abuse, emotional or verbal abuse, and abuse in childhood and adulthood. Similarly, dyspepsia and heartburn were both significantly associated with abuse. In the population, 31% had visited a physician for gastrointestinal symptoms; the odds of visiting a physician were highest in those reporting abuse in adulthood and childhood. CONCLUSIONS: Self-reported abuse is common in middle-aged subjects; those who report abuse are more likely to have symptoms consistent with IBS, dyspepsia, or heartburn and to visit a physician for bowel symptoms.