Biomedical subjects
J Robinson
Publications and source records attributed to J Robinson.
New mutations in the KVLQT1 potassium channel that cause long-QT syndrome.
BACKGROUND: Long-QT syndrome (LQTS) is an inherited cardiac arrhythmia that causes sudden death in young, otherwise healthy people. Four genes for LQTS have been mapped to chromosome 11p15.5 (LQT1), 7q35-36 (LQT2), 3p21-24 (LQT3), and 4q25-27 (LQT4). Genes responsible for LQT1, LQT2, and LQT3 have been identified as cardiac potassium channel genes (KVLQT1, HERG) and the cardiac sodium channel gene (SCN5A). METHODS AND RESULTS: After studying 115 families with LQTS, we used single-strand conformation polymorphism (SSCP) and DNA sequence analysis to identify mutations in the cardiac potassium channel gene, KVLQT1. Affected members of seven LQTS families were found to have new, previously unidentified mutations, including two identical missense mutations, four identical splicing mutations, and one 3-bp deletion. An identical splicing mutation was identified in affected members of four unrelated families (one Italian, one Irish, and two American), leading to an alternatively spliced form of KVLQT1. The 3-bp deletion arose de novo and occurs at an exon-intron boundary. This results in a single base deletion in the KVLQT1 cDNA sequence and alters splicing, leading to the truncation of KVLQT1 protein. CONCLUSIONS: We have identified LQTS-causing mutations of KVLQT1 in seven families. Five KVLQT1 mutations cause the truncation of KVLQT1 protein. These data further confirm that KVLQT1 mutations cause LQTS. The location and character of these mutations expand the types of mutation, confirm a mutational hot spot, and suggest that they act through a loss-of-function mechanism or a dominant-negative mechanism.
Influence of pregnancy on the risk for cardiac events in patients with hereditary long QT syndrome. LQTS Investigators.
BACKGROUND: The effects of pregnancy on women with the hereditary long QT syndrome are currently unknown. The appropriate medical management of pregnant patients with the long QT syndrome has not been established. METHODS AND RESULTS: The study was a retrospective analysis of the 422 women (111 probands affected with the long QT syndrome and 311 first-degree relatives) enrolled in the long QT syndrome registry who had one or more pregnancies. The first-degree relatives were classified as affected (QTc >0.47), borderline (QTc=0.45 to 0.47), and unaffected (QTc <0.45). Cardiac events were defined as the combined incidence of long QT syndrome-related death, aborted cardiac arrest, and syncope. The incidence of cardiac events was compared during equal prepregnancy, pregnancy, and postpartum intervals (40 weeks each). Multivariate logistic regression analysis was performed by use of a mixed-effects model to identify independent predictors of cardiac events among probands. The pregnancy and postpartum intervals were not associated with cardiac events among first-degree relatives. The postpartum interval was independently associated with cardiac events among probands (odds ratio [OR], 40.8; 95% confidence interval [CI], 3.1 to 540; P=.01); the pregnancy interval was not associated with cardiac events. Treatment with beta-adrenergic blockers was independently associated with a decrease in the risk for cardiac events among probands (OR, 0.023; 95% CI, 0.001 to 0.44; P=.01). CONCLUSIONS: The postpartum interval is associated with a significant increase in risk for cardiac events among probands with the long QT syndrome but not among first-degree relatives. Prophylactic treatment with beta-adrenergic blockers should be continued during the pregnancy and postpartum intervals in probands with the long QT syndrome.
Do pediatricians counsel families about sun protection?: a Massachusetts survey.
BACKGROUND: Pediatric visits during summer months may be especially opportune times for sun protection counseling for children and their parents. Few data exist on the extent of such counseling. OBJECTIVE: To begin to assess this, we surveyed practicing Massachusetts pediatricians to examine current attitudes and practices of sun protection counseling. DESIGN AND SETTING: Surveys mailed to Massachusetts pediatricians. RESULTS: We received surveys from 756 (60%) of 1263 eligible Massachusetts pediatricians. Almost 70% indicated that they recommended safe sun practices to more than 50% of their patients and their parents during the summer months. Counseling regarding seat belt use, bicycle helmet use, and smoking prevention were ranked higher in priority than sun protection counseling by pediatricians; nutritional guidelines were noted by pediatricians to be a parent's most frequent concern. Four variables were independently associated with a practitioner's providing safe sun recommendations to more than 50% of parents and children: (1) private setting and health maintenance organization practitioners as opposed to academic physicians, (2) high ranking of patients' safe sun knowledge, (3) high priorities of both parents and physicians for sun protection counseling and parental knowledge of safe sun practices relative to other recommendations, and (4) pediatrician interest in receiving instructional materials. CONCLUSIONS: For the most part, summer sun protection counseling among Massachusetts pediatricians seems well integrated into standard practice. Most pediatricians rated their confidence level as high for discussing sun protection and only a few cited inadequate training or poor reimbursement as barriers toward improved counseling. Small steps, such as providing more instructional materials to patients and using office-based reminder systems, may improve the quality of sun protection counseling practices. Incorporating sunburn prevention into the list of routinely recommended injury prevention guidelines for pediatricians should be considered.
Oesophageal, rectal, axillary, tympanic and pulmonary artery temperatures during cardiac surgery.
PURPOSE: The gradient between temperatures measured at different body sites is not constant; one factor which will change this gradient is rapid changes in body temperature. Measurement of this gradient was done in patients undergoing rapid changes in body temperature to establish the best site to measure temperature and to compare two brands of commercial tympanic thermometers. METHOD: A total of 228 sets of temperatures were measured from probes in the oesophagus, rectum, and axilla and from two brands of tympanic thermometer and compared with pulmonary artery (PA) temperature in 18 adults during cardiac surgery. RESULTS: Measurements from the oesophageal site was closest to PA readings (mean difference 0.0 +/- 0.5 degree C) compared with IVAC tympanic thermometer (mean difference -0.3 +/- 0.5 degree C), Genius tympanic thermometer (mean difference -0.4 +/- 0.5 degree C), axillary (mean difference 0.2 +/- 1.0 degrees C) and rectal (mean difference -0.4 +/- 1.0 degree C) readings. When data during cooling were analysed separately, all sites had similar gradients from PA except for rectal, which was larger. On rewarming, oesophageal readings were closest to PA readings; tympanic readings were closer to PA than were rectal or axillary readings. Readings from the two brands of tympanic thermometer were equivalent. CONCLUSION: Oesophageal temperature is more accurate and will reflect rapid changes in body temperature better than tympanic, axillary, or rectal temperature. When oesophageal temperature cannot be measured, tympanic temperature done by a trained operator should become the reading of choice.
Stress response dampening: effects of gender and family history of alcoholism and anxiety disorders.
One hundred and fifteen non-alcoholic social drinkers, ages 21-30 years, were selected on the basis of parental history of alcoholism and/or anxiety disorders to participate in a laboratory study of stress response dampening (SRD) effects of alcohol. The following four risk groups were identified based on the diagnoses of both parents: 1) alcoholism (ALC+), (2) alcoholism and anxiety disorder (ALCANX+), (3) anxiety (ANX+), and (4) no psychiatric diagnoses (FH-). Subjects were randomly assigned to receive a placebo or alcohol (0.85 g/kg) beverage, following which cardiovascular measures and self-reports of anxiety were monitored prior to, during and after a speech stressor. Women with a family history of alcoholism and women with a family history of anxiety disorders showed strong SRD effects of alcohol on heart rate and pulse transit time. Men with a family history of anxiety disorders showed evidence of increased subjective response to stress during the alcohol beverage condition. Finally, SRD effects of alcohol were not found for male subjects, and this was attributed to their heavier drinking histories and lower breath alcohol levels as compared to women. Implications of the SRD effects in women are discussed in the context of the comorbid association between alcoholism and anxiety disorders.
Recombinant human megakaryocyte growth and development factor attenuates postbypass thrombocytopenia.
BACKGROUND: Cardiopulmonary bypass contributes to platelet loss and dysfunction by exposure to shear stresses, foreign surfaces, and hypothermia. This study tested the hypothesis that pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) accelerates recovery of the platelet population after hypothermic extracorporeal circulation (HEC). METHODS: In a blinded study, subcutaneous injections of drug or placebo were given to dogs daily for 3 days preoperatively (day 0, 1, and 2) with no drug on day 3. On day 4, the animal was prepared for arteriovenous HEC. After heparinization, HEC was initiated at 30 to 40 mL x kg(-1) x min(-1). Hypothermic extracorporeal circulation (25 degrees C) was continued for 90 minutes. RESULTS: Preoperative platelet count (x10(3) platelets/microL) did not differ from predrug count in placebo (256+/-27 versus 255+/-20) or PEG-rHuMGDF (271+/-30 versus 291+/-38). During 60 minutes of HEC, the platelet count decreased to approximately 10% of baseline in placebo (29+/-5) and PEG-rHuMGDF (46+/-8), and recovered to approximately 70% of baseline after rewarming (90 minutes of HEC: placebo, 185+/-17, versus PEG-rHuMGDF, 169+/-22). After HEC, platelet count was greater in PEG-rHuMGDF-treated animals (p < 0.05) without altering function (aggregation responses). Within the first 6 hours after HEC, platelet count in PEG-rHuMGDF-treated animals was rising and increased to 260+/-29 (p < 0.01), but was unchanged in placebo animals (186+/-21). Thereafter, platelet count in placebo animals declined to a nadir of 124+/-15 (72 hours after HEC), whereas platelet count in PEG-rHuMGDF animals approximated the preoperative value (>200) at all times. CONCLUSIONS: Appropriately timed presurgical administration of PEG-rHuMGDF counteracts post-HEC relative thrombocytopenia without increasing platelet population and enhancing aggregation preoperatively or during extracorporeal circulation.
Effect of cryopreservation on Gal alpha 1-3Gal expression on adult porcine pancreatic islets.
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Smooth muscle dysfunction occurs independently of impaired endothelium-dependent dilation in adults at risk of atherosclerosis.
OBJECTIVES: We sought to assess smooth muscle function in adults at risk for atherosclerosis. BACKGROUND: Previous studies in subjects at risk for atherosclerosis have demonstrated arterial endothelial dysfunction, with reduced vasodilator responses after pharmacologic or physiologic stimulation of endothelial nitric oxide (NO). Most have also shown a slight but nonsignificant impairment of vasodilation in response to exogenous sources of NO, such as nitroglycerin (NTG). We hypothesized that NTG responses might be reduced in a large number of consecutively studied adults at risk for atherosclerosis, independent of any impaired endothelium-dependent responses, consistent with concomitant smooth muscle dysfunction. METHODS: Using high resolution ultrasound, the dilator response of the brachial artery to 400 microg of sublingual NTG was measured in 800 asymptomatic subjects. Subjects were also assessed for a history of vascular risk factors, blood pressure, total serum cholesterol and flow-mediated endothelium-dependent dilation (EDD). RESULTS: We studied 317 men and 483 women, 38 +/- 17 years old (mean +/- SD, range 15 to 76). The mean cholesterol level was 5.2 +/- 1.3 mmol/liter, and there were 126 smokers and ex-smokers (16 +/- 9 mean pack-years) and 105 diabetic subjects. On univariate analysis, a reduced vasodilator response to NTG was associated with high cholesterol, cigarette smoking, diabetes mellitus, increasing age, male gender, larger vessel size and reduced EDD (p < or = 0.01 for all). On multivariate analysis, diabetes, larger vessel size and reduced EDD were all independently associated with impaired NTG-related vasodilation (p < or = 0.001 for all). In the 574 nondiabetic subjects who had never smoked cigarettes, the independent relation between EDD and NTG responses was still observed (r = 0.24, p = 0.01). CONCLUSIONS: The vasodilator response to exogenous NO is impaired in asymptomatic subjects with reduced EDD, consistent with smooth muscle dysfunction in adults at risk for atherosclerosis.
A prospective clinical trial investigating the efficacy of a method of preparing subpopulations of antibody-free spermatozoa from the ejaculates of antibody-positive patients.
Couples undergoing in vitro fertilization treatment (IVF) were invited to take part in a controlled prospective clinical trial. The aim was to determine the effect on the fertilization rate of a technique devised to obtain an antibody-free preparation of spermatozoa from an antibody-positive ejaculate. Oocytes collected during IVF were allocated into one of two groups, ensuring that quality and maturity were comparable in each. One group, the control, was inseminated with Percoll-processed spermatozoa. The experimental group was inseminated with identical numbers of Percoll-processed spermatozoa which had been treated to obtain an antibody-free preparation. The treatment was found to have no beneficial effect on the fertilization rate at IVF. Laboratory studies were also performed on the ejaculates of antibody-positive volunteers to determine whether this treatment led to any effects, whether beneficial or detrimental, on sperm function. Membrane integrity was found to be unaffected, as was the percentage of spermatozoa undergoing the spontaneous acrosome reaction following overnight incubation. The percentage of spermatozoa undergoing the ionophore-induced acrosome reaction following treatment, however, was higher than that of the controls. The results of sperm-zona pellucida binding studies were equivocal. The findings indicated that the treatment procedure could not be justified for use in IVF, but may be beneficial for intrauterine insemination.
An evaluation of lectin-mediated magnetic bead cell sorting for the targeted separation of enteric bacteria.
Lectin-labelled magnetic beads were assessed and compared with antisera as an alternative approach for the targeted separation and isolation of enteric bacteria. Of the 16 lectins tested against a range of bacterial species, concanavalin A (conA) showed the greatest potential. Agglutination of bacterial cells in suspension using conA and methods for effective labelling of the magnetic beads with the lectin were optimized. ConA-labelled magnetic beads were compared with antibody-labelled beads for recovery of bacterial cells from pure or mixed laboratory cultures and from natural populations in river water. Recovered cell populations were free from environmental impurities and a high percentage of the culturable cells was extracted. Specific cell recovery was found to be variable, but the use of lectins offers some promise as an alternative cell discriminator.
An evaluation of services for women with long-term mental health problems.
This paper presents the results of an evaluation study of services for women with long-term mental health problems. The study, which was conducted in a long-term rehabilitation and community care service, examined the adequacy, accessibility, and responsiveness of services provided for women users; explored differences between the men and women using the service and those newly admitted to it; and explored the views and experiences of service providers and the women users themselves. The results of the study confirm and extend those of previous studies and suggest a number of service recommendations. The unevenness in attention to the needs of women across services needs to be addressed. Services should be more attractive to women. Agencies and facilities for women outside mental health services should be supported to ensure that they can accommodate women with long-term mental health problems, and the women themselves need to be offered the support necessary to ensure they have access to such facilities. Finally, efforts must be made to ensure that services both recognize the losses that women with long-term mental health problems have experienced and foster their continued hopes and aspirations for the future.
Embryo transfer--can we learn anything new from the observation of junctional zone contractions?
To assess whether embryo transfer can alter junctional zone contractility, we studied the effect of easy and difficult mock transfers in 14 oocyte donors during in-vitro fertilization (IVF) cycles. An Echovist bolus (30 microl) was used to represent embryos and transfer medium. An 'easy' transfer was judged to be an atraumatic insertion of the catheter without touching the uterine fundus. A 'difficult' embryo transfer was mimicked by deliberately touching the uterine fundus twice with the soft end of the cannula. Transvaginal scan images were recorded, digitized and converted into five times normal speed to allow us to evaluate junctional zone contractility. Easy mock embryo transfers did not change endometrial mechanical activity. Echovist remained in the upper part of the uterine cavity and was not dispersed after 45 min. A difficult procedure generated strong random waves in the fundal area and waves from fundus to cervix which relocated the Echovist in six out of seven cases. We observed movements of the transfer bolus from the upper part of the uterus towards the cervix (four cases) and into Fallopian tubes (two patients). Our study confirms that the mechanical activity of the uterus is capable of relocating intrauterine embryos and that this activity depends on physical stimulation. Junctional zone contractions can be implicated in cases of IVF/embryo transfer failure or ectopic gestation.
Fatal pneumococcal septicaemia in a coeliac patient.
A 78-year-old lady initially presented with painful hips, low back pain, lethargy and weight loss. She had a past history of osteomalacia. Investigations revealed evidence of malabsorption and jejunal biopsy revealed sub-total villous atrophy in keeping with coeliac disease. Peripheral blood film was within normal limits. She responded well clinically to a gluten-free diet and calcium and vitamin D supplementation. Four years after the initial diagnosis she presented acutely with vomiting, pleuritic chest pain, pyrexia and bronchospasm. Blood cultures confirmed the presence of Streptococcus pneumoniae and she was treated appropriately with ampicillin. Despite this she died shortly after admission. It is recognized that blood film examination alone cannot exclude hyposplenism complicating coeliac disease and it is presumed that this was the reason for the development of fatal pneumococcal septicaemia in this patient. Prophylactic vaccination may be appropriate in hyposplenism secondary to coeliac disease.
Recombinant mouse-human chimeric antibodies as calibrators in immunoassays that measure antibodies to Toxoplasma gondii.
In the present study, we examined the feasibility of using recombinant antibodies containing murine variable regions and human constant regions as calibrators or controls in immunoassays. As a model system, we chose the Abbott IMx Toxo immunoglobulin M (IgM) and Toxo IgG assays designed to detect antibodies to Toxoplasma gondii. Two mouse monoclonal antibodies were selected based on their reactivity to the T. gondii antigens P30 and P66. Heavy- and light-chain variable-region genes were cloned from both hybridomas and transferred into immunoglobulin expression vectors containing human kappa and IgG1 or IgM constant regions. The constructs were stably transfected into Sp2/0-Ag14 cells. In the IMx Toxo IgG assay, immunoreactivity of the anti-P30 chimeric IgG1 antibody paralleled that of the positive human plasma-derived assay calibrators. Signal generated with the anti-P66 chimeric IgG1 antibody was observed to plateau below the maximal reactivity observed for the assay calibrator. Examination of the IgM chimeric antibodies in the IMx Toxo IgM assay revealed that both the anti-P30 and anti-P66 antibodies matched the assay index calibrator manufactured with human Toxo IgM-positive plasma. When evaluated with patient samples, the correlation between results obtained with the chimeric antibody calibrators and the positive human plasma calibrators was > or =0.985. These data demonstrate that chimeric mouse-human antibodies are a viable alternative to high-titer positive human plasma for the manufacture of calibrators and controls for diagnostic assays.
Neutralization sensitivity of human immunodeficiency virus type 1 primary isolates to antibodies and CD4-based reagents is independent of coreceptor usage.
We have investigated whether the identity of the coreceptor (CCR5, CXCR4, or both) used by primary human immunodeficiency virus type 1 (HIV-1) isolates to enter CD4+ cells influences the sensitivity of these isolates to neutralization by monoclonal antibodies and CD4-based agents. Coreceptor usage was not an important determinant of neutralization titer for primary isolates in peripheral blood mononuclear cells. We also studied whether dualtropic primary isolates (able to use both CCR5 and CXCR4) were differentially sensitive to neutralization by the same antibodies when entering U87MG-CD4 cells stably expressing either CCR5 or CXCR4. Again, we found that the coreceptor used by a virus did not greatly affect its neutralization sensitivity. Similar results were obtained for CCR5- or CXCR4-expressing HOS cell lines engineered to express green fluorescent protein as a reporter of HIV-1 entry. Neutralizing antibodies are therefore unlikely to be the major selection pressure which drives the phenotypic evolution (change in coreceptor usage) of HIV-1 that can occur in vivo. In addition, the increase in neutralization sensitivity found when primary isolates adapt to growth in transformed cell lines in vitro has little to do with alterations in coreceptor usage.
CD4-Induced conformational changes in the human immunodeficiency virus type 1 gp120 glycoprotein: consequences for virus entry and neutralization.
Human immunodeficiency virus type 1 (HIV-1) entry into target cells involves sequential binding of the gp120 exterior envelope glycoprotein to CD4 and to specific chemokine receptors. Soluble CD4 (sCD4) is thought to mimic membrane-anchored CD4, and its binding alters the conformation of the HIV-1 envelope glycoproteins. Two cross-competing monoclonal antibodies, 17b and CG10, that recognize CD4-inducible gp120 epitopes and that block gp120-chemokine receptor binding were used to investigate the nature and functional significance of gp120 conformational changes initiated by CD4 binding. Envelope glycoproteins derived from both T-cell line-adapted and primary HIV-1 isolates exhibited increased binding of the 17b antibody in the presence of sCD4. CD4-induced exposure of the 17b epitope on the oligomeric envelope glycoprotein complex occurred over a wide range of temperatures and involved movement of the gp120 V1/V2 variable loops. Amino acid changes that reduced the efficiency of 17b epitope exposure following CD4 binding invariably compromised the ability of the HIV-1 envelope glycoproteins to form syncytia or to support virus entry. Comparison of the CD4 dependence and neutralization efficiencies of the 17b and CG10 antibodies suggested that the epitopes for these antibodies are minimally accessible following attachment of gp120 to cell surface CD4. These results underscore the functional importance of these CD4-induced changes in gp120 conformation and illustrate viral strategies for sequestering chemokine receptor-binding regions from the humoral immune response.