Surges of muscle sympathetic nerve activity during obstructive apnea are linked to hypoxemia

Obstructive sleep apnea (OSA) is associated with oscillations of arterial blood pressure (BP) that occur in phase with irregularities of respiration. To explore the role of the sympathetic nervous system in these responses, we studied muscle sympathetic nerve activity (MSNA; peroneal microneurography), an index of vasoconstrictor nerve traffic, and BP during awake regular breathing and during spontaneous apneas in patients with OSA. To determine the role of the arterial chemoreflex, we also examined the effects of 100% O2 (hyperoxia) on MSNA and BP. In awake regularly breathing patients with OSA (n = 12), resting MSNA was markedly higher than in an age-matched control population (n = 15) [41 +/- 23 (SD) vs. 24 +/- 17 bursts/min; P < 0.05] and was unchanged during hyperoxia (n = 9). Apneas during sleep (n = 8) were associated with surges in MSNA followed by transient rises in BP when breathing resumed. In contrast to room air apneas, hyperoxic apneas of similar duration were associated with attenuated MSNA responses (+82 +/- 84% vs. +5 +/- 25% compared with awake baseline; P < 0.05; n = 6), even though O2 did not affect sleep stage and the occurrence of arousal. Thus the BP oscillations that occur with apnea during sleep may in part be mediated by intermittent surges of sympathetic activity resulting in vasoconstriction. Because the MSNA responses to obstructive apnea are blunted during O2 administration, they appear to be linked to intermittent arterial hypoxemia and stimulation of arterial chemoreceptors.

Prevalence of diabetes and ethnic differences in cardiovascular risk factors. The 1992 Singapore National Health Survey

OBJECTIVE

The purpose of the 1992 Singapore National Health Survey was to determine the current distribution of major noncommunicable diseases and their risk factors, including the prevalence of diabetes and dyslipidemia, in Singapore.

RESEARCH DESIGN AND METHODS

A combination of disproportionate stratified sampling and systematic sampling were used to select the sample for the survey. The final number of respondents was 3,568, giving a response rate of 72.6%. All subjects fasted for 10 h and were given a 75-g glucose load, except those known to have diabetes. Blood was taken before and 2 h after the glucose load. Diagnosis of diabetes was based on 2-h glucose alone.

RESULTS

The age-standardized prevalence of diabetes in Singapore residents aged 18-69 years was 8.4%, with more than half (58.5%) previously undiagnosed. Prevalence of diabetes was high across all three ethnic groups. The prevalence of impaired glucose tolerance was 16.1%, that of hypertension was 6.5%, and 19.0% were regular smokers. The total cholesterol (mean +/- SD) of nondiabetic Singaporeans was 5.18 +/- 1.02 mmol/l; 47.9% had cholesterol > 5.2 mmol/l, while 15.4% had levels > 6.3 mmol/l. Mean LDL cholesterol was 3.31 +/- 0.89 mmol/l; HDL cholesterol was 1.30 +/- 0.32 mmol/l, and triglyceride was 1.23 +/- 0.82 mmol/l.

CONCLUSIONS

Prevalence of diabetes was high across all three ethnic groups. Ethnic differences in prevalence of diabetes, insulin resistance, central obesity, hypertension, smoking, and lipid profile could explain the differential coronary heart disease rates in the three major ethnic groups in Singapore.

Magnesium deficiency in patients on long-term diuretic therapy for heart failure

Magnesium levels in serum, erythrocytes, skeletal muscle, and bone were measured in 10 patients with valvular heart disease who had received diuretic therapy for heart failure for an average of 3.3 years. Five patients were found to have diminished values for skeletal muscle, indicating significant magnesium deficit. Values for erythrocytes were low in only two of the five patients, and none had low values for serum ultrafiltrate and bone: Magnesium replacement therapy restored skeletal muscle values to normal. Clinical features consistent with the presence of magnesium deficiency were found in all five magnesium-deficient patients. These features were, with few exceptions, corrected by magnesium replacement. The latter also corrected low skeletal muscle potassium values present in all five patients with low skeletal muscle magnesium, four of whom showed clinical features of digoxin poisoning before magnesium therapy was given. Concomitant secondary aldosteronism, inadequate dietary intake, and digoxin therapy had probably augmented the magnesium loss due to diuretic therapy.

Molecular characterization of human and bovine endothelin converting enzyme (ECE-1)

A membrane-bound protease activity that specifically converts Big endothelin-1 has been purified from bovine endothelial cells (FBHE). The enzyme was cleaved with trypsin and the peptide sequencing analysis confirmed it to be a zinc chelating metalloprotease containing the typical HEXXH (HELTH) motif. RT-PCR and cDNA screens were employed to isolate the complete cDNAs of the bovine and human enzymes. This human metalloprotease was expressed heterologously in cell culture and oocytes. The catalytic activity of the recombinant enzyme is the same as that determined for the natural enzyme. The data suggest that the characterized enzyme represents the functional human endothelin converting enzyme ECE-1.

Influence of hypoxia and of hypoxemia on the development of cardiac activity in zebrafish larvae

Cardiac activity and anaerobic metabolism were analyzed in zebrafish larvae raised under normoxia (PO(2) = 20 kPa) and under chronic hypoxia (PO(2) = 10 kPa) at three different temperatures (25, 28, and 31 degrees C). Heart rate increased with development and with temperature. Under normoxia, cardiac output increased significantly at high temperature (31 degrees C), but not at 28 or at 25 degrees C. Under chronic hypoxia, however, heart rate as well as cardiac output increased at all temperatures in larvae at about hatching time or shortly thereafter. Cardiac activity of larvae raised for 2 wk after fertilization with a reduced hemoglobin oxygen-carrying capacity in their blood (hypoxemia; due to the presence of CO or of phenylhydrazine in the incubation water) was not different from control animals. Whole body lactate content of these animals did not increase. Thus there was no indication of a stimulated anaerobic energy metabolism. The increase in cardiac activity observed during hypoxia suggests that at about hatching time receptors are present that sense hypoxic conditions, and this information can be used to induce a stimulation of convective oxygen transport to compensate for a reduction in bulk oxygen diffusion in the face of a reduced oxygen gradient between environmental water and tissues. Under normoxia, however, the PO(2) gradient between environmental water and tissues and diffusional oxygen transport assure sufficient oxygen supply even if hemoglobin oxygen transport in the blood is severely impaired. Thus, under normoxic conditions and with a normal metabolic rate of the tissues, convective oxygen transport is not required until approximately 2 wk after fertilization.

Urokinase-type and tissue-type plasminogen activators are essential for in vitro invasion of human melanoma cells

This study evaluates the contribution of two types of plasminogen activators (PAs; tissue-type PA (tPA) versus urokinase-type PA (uPA) toward the invasiveness of human melanoma cells in a novel in vitro assay. We identified two human melanoma cell lines, MelJuso and MeWo, expressing uPA or tPA as shown at mRNA, protein, and enzyme activity level. MelJuso cells produced uPA as well as plasminogen activator inhibitor-1 (PAI-1). The latter was, however, not sufficient to neutralize the cell-associated or secreted uPA activity. MeWo cells secreted tPA, but the enzyme was not found to be cell-associated. PAI-1 production by these cells was not detectable. Plasminogen activation and fibrinolytic capacity of both cell lines were reduced by anticatalytic monoclonal antibodies specific for the respective type of PA or by aprotinin. In a novel in vitro invasion assay, antibodies to PA as well as aprotinin decreased the invasiveness of both cell lines into a fibrin gel, Matrigel, or intact extracellular matrix. Our results confirm the importance of uPA-catalyzed plasminogen activation in tumor cell invasiveness. Furthermore, we provide evidence that tPA, beyond its key role in thrombolysis, can also be involved in in vitro invasion of human melanoma cells.

Identification of the structural requirements for mutagencitiy, by incorporating molecular flexibility and metabolic activation of chemicals. II. General Ames mutagenicity model

The tissue metabolic simulator (TIMES) modeling approach is a hybrid expert system that couples a metabolic simulator together with structure toxicity rules, underpinned by structural alerts, to predict interaction of chemicals or their metabolites with target macromolecules. Some of the structural alerts representing the reactivity pattern-causing effect could interact directly with the target whereas others necessitated a combination with two- or three-dimensional quantitative structure-activity relationship models describing the firing of the alerts from the rest of the molecules. Recently, TIMES has been used to model bacterial mutagenicity [Mekenyan, O., Dimitrov, S., Serafimova, R., Thompson, E., Kotov, S., Dimitrova, N., and Walker, J. (2004) Identification of the structural requirements for mutagenicity by incorporating molecular flexibility and metabolic activation of chemicals I: TA100 model. Chem. Res. Toxicol. 17 (6), 753-766]. The original model was derived for a single tester strain, Salmonella typhimurium (TA100), using the Ames test by the National Toxicology Program (NTP). The model correctly identified 82% of the primary acting mutagens, 94% of the nonmutagens, and 77% of the metabolically activated chemicals in a training set. The identified high correlation between activities across different strains changed the initial strategic direction to look at the other strains in the next modeling developments. In this respect, the focus of the present work was to build a general mutagenicity model predicting mutagenicity with respect to any of the Ames tester strains. The use of all reactivity alerts in the model was justified by their interaction mechanisms with DNA, found in the literature. The alerts identified for the current model were analyzed by comparison with other established alerts derived from human experts. In the new model, the original NTP training set with 1341 structures was expanded by 1626 proprietary chemicals provided by BASF AG. Eventually, the training set consisted of 435 chemicals, which are mutagenic as parents, 397 chemicals that are mutagenic after S9 metabolic activation, and 2012 nonmutagenic chemicals. The general mutagenicity model was found to have 82% sensitivity, 89% specificity, and 88% concordance for training set chemicals. The model applicability domain was introduced accounting for similarity (structural, mechanistic, etc.) between predicted chemicals and training set chemicals for which the model performs correctly.

Histone-gene reiteration in the genome of mouse

Histone messenger RNA labelled to high specific activity has been isolated and purified from the mouse tissue-culture cell line L929. It had an electrophoretic mobility equivalent to a mean molecular weight of 1.4 X 10(5). The synthesis of this RNA was suppressed, but apparently not completely so, by inhibition of cellular DNA synthesis to more than 95% by addition of cytosine arabinoside. The synthesis of other RNA species remained unaffected by this treatment. Poly(A)-containing mRNA, representing a 20% contaminant of the electrophoretically purified histone mRNA, was removed by poly(U)-Sepharose chromatography. Histone mRNA thus purified was hybridized to DNA fractions enriched for histone genes of the sea urchin Psammechinus miliaris by actinomycin/CsCl gradient centrifugation. The mRNA was eluted from the hybrids and challenged with mouse DNA in vast DNA excess conditions. A (cot1/2) of 360 mol s 1(-1) was obtained from the RNA trace curve, suggesting a 10-20-fold reiteration of the histone genes in the haploid genome. Thus histone genes in mouse are much less highly reiterated than in sea urchins, but nevertheless are present in considerable excess over the number theoretically necessary for histone synthesis during the S phase of the cell cycle.

Reiteration frequency of the histone genes in the genome of the amphibian, Xenopus laevis

Radioactive RNA was obtained from Xenopus laevis gastrula-stage embryos which had been labelled by microinjection of [3H]uridine. A 9-12-S RNA fraction was isolated by phenol extraction of whole embryos followed by sucrose gradient centrifugation of the RNA and polyacrylamide gel electrophoresis. This RNA was identified as histone mRNA on the basis of its chemical and physical properties. On polyacrylamide gels the labelled RNA could be subfractionated into different components with electrophoretic mobilities similar to those of histone mRNAs of the sea urchin. 9-12-S RNA lacked poly(A) sequences. In a protein synthesis system in vitro the RNA fraction directed the synthesis of the histones H4, H2A, H2B, H3 and, possibly, of H1 protein. The Xenopus gistone mRNA was challenged with Xenopus DNA under conditions of vast DNA excess. A cot1/2 of between 110 and 250 mol-s-1(-1) was obtained from the RNA trace curve, indicating that the histone genes were 20-50-fold reiterated in the haploid genome of the species. This value indicates that although amphibians have several embryological and morphological features in common with sea urchins, the reiteration frequency for Xenopus histone genes is closer to the value of 10-20 established for mammals than the value of 400-1000 determined for sea urchins.

Treatment of drug-induced toxic epidermal necrolysis (Lyell's syndrome) with intravenous human immunoglobulins

Toxic epidermal necrolysis (TEN) is a rare drug-induced life-threatening disease. Currently, the disease is only treated by supportive and antiseptic measures. Quite recently intravenous immunoglobulins (IG) were shown to be a promising TEN treatment. The rationale for their use is based on the fact that keratinocyte apoptosis in TEN involves the CD95 (APO-1/Fas) cell surface receptor-ligand system. We successfully treated a TEN patient with high dose of intravenous IG. The clinical recovery appeared exceptionally rapid. Immunohistochemistry showed that the IG action probably developed on the CD95 receptor-ligand system at the keratinocytes surface.

Prevalence of gestational thyrotoxicosis in Asian women evaluated in the 8th to 14th weeks of pregnancy: correlations with total and free beta human chorionic gonadotrophin

OBJECTIVES

The prevalence of gestational transient thyrotoxicosis (GTT) in Europeans evaluated during the 8th to 14th weeks of pregnancy is 2-3%. However, there is evidence that GTT may be more common in some Asian populations. The aims of this study were to evaluate the prevalence of thyroid hormone abnormalities in Asian women in their 8th to 14th weeks of pregnancy using highly sensitive free T4 and TSH assays and to correlate these with total and free beta-hCG levels.

DESIGN AND PATIENTS

One hundred and eighty-four consecutive unselected Asian (Singaporean) pregnant women seen at ante-natal clinics for the first time and who were in their 8th to 14th weeks of pregnancy were tested.

MEASUREMENTS

Serum free T4, free T3, TSH, total beta-hCG and free beta-HCG levels were measured on the Vitros ECi system (Johnson & Johnson Ortho-Clinical Diagnostics, Amersham, UK) which employs chemiluminescent immunochemical technology. This free T4 assay is free of biases related to serum binding capacity. The TSH assay used was a third generation assay. Thyrotrophin-receptor antibody (TRAb) levels were measured using LUMItest TRAK (BRAHMS Diagnostica, Berlin, Germany).

RESULTS

Two subjects (1.1%) were found to have Graves' disease. Elevated free T4, free T3, total T3 and suppressed TSH were seen in 14.8%, 3.3%, 26.4% and 33.0% of the remaining 182 pregnant women, respectively. Total and free beta-hCG correlated negatively with TSH (r = -0.30, P < 0.0001 and r = -0.29, P < 0.0001, respectively), positively with fT4 (r = 0.283, P < 0.001 and r = 0.253, P < 0.001) and fT3 (r = 0.273, P < 0.001 and r = 0.204, P < 0.01). 11.0% of cases had gestational thyrotoxicosis (GT) defined as elevated free T4 (> 19.1 pmol/l), suppressed TSH (< 0.36 mIU/l) and TRAb levels within the reference interval (0-0.9 U/l). The prevalence of GT was significantly higher in patients tested at 8-11 weeks compared to those evaluated at 12-14 weeks (14.4% vs. 4.7%, P < 0.05). Total beta-hCG (P = 0.0002), free beta-hCG (P < 0.0001) and free T4 (P = 0.02) levels were higher and TSH levels (P = 0.01) lower in patients tested at 8-11 weeks. Significant positive correlations between both total and free beta-hCG with free T4 were seen at 8-11 weeks but not in patients tested at 12 weeks or later. TT3 levels were similar in the two groups.

CONCLUSIONS

Using sensitive assays, the prevalence of gestational thyrotoxicosis in Asian women was found to be 11.0% and was significantly higher in subjects at 8-11 weeks of gestation than at 12-14 weeks. The positive correlation between hCG and free T4 seen in patients tested at 8-11 weeks was absent in patients tested at later stages of the first trimester. Future studies investigating the entity of gestational thyrotoxicosis, at least in Asian patients, should focus on patients at earlier stages of gestation than currently practised.

A fuzzy guided genetic algorithm for operon prediction

MOTIVATION

The operon structure of the prokaryotic genome is a critical input for the reconstruction of regulatory networks at the whole genome level. As experimental methods for the detection of operons are difficult and time-consuming, efforts are being put into developing computational methods that can use available biological information to predict operons.

METHOD

A genetic algorithm is developed to evolve a starting population of putative operon maps of the genome into progressively better predictions. Fuzzy scoring functions based on multiple criteria are used for assessing the 'fitness' of the newly evolved operon maps and guiding their evolution.

RESULTS

The algorithm organizes the whole genome into operons. The fuzzy guided genetic algorithm-based approach makes it possible to use diverse biological information like genome sequence data, functional annotations and conservation across multiple genomes, to guide the organization process. This approach does not require any prior training with experimental operons. The predictions from this algorithm for Escherchia coli K12 and Bacillus subtilis are evaluated against experimentally discovered operons for these organisms. The accuracy of the method is evaluated using an ROC (receiver operating characteristic) analysis. The area under the ROC curve is around 0.9, which indicates excellent accuracy.

CONTACT

roschen_csir@rediffmail.com.

Pain management in sickle cell disease

The unpredictable, recurrent, intense, and frequently persistent nature of pain associated with sickle cell disease poses a difficult challenge in terms of management. A wide variability exists in the way painful episodes are managed. Variations in practice reflect different views about the suitability of opioids, the efficacy of parenteral administration, and the risk of dependence on opioids. Consequently, the acute and chronic pain associated with sickle cell disease often is undertreated or inappropriately managed. Although medical staff fear that patients might abuse pain medication and become psychologically dependent, patients are more concerned about the side effects associated with analgesics. Some patients may persuade staff to give them more analgesics, engage in clock-watching, and request specific medications or dosages; these patients often are perceived as manipulative or demanding. However, these patients are knowledgeable about their medications and doses that have worked in the past. Requests for specific medications and dosages should not be interpreted as indications of drug-seeking behavior, but clinicians should communicate with these patients, make accurate assessments, and provide adequate doses of opioid analgesics. The American Pain Society recognized that the undertreatment of pain and inappropriate management of pain in sickle cell disease seem to be common. A Clinical Practice Guideline was developed to provide evidence-based recommendations that could potentially improve pain management. The purpose of this report is to describe the pharmacologic strategies used to manage pain associated with sickle cell disease, examine issues and challenges related to pain management as well as concerns and fears related to addiction, and explain the administration of opioids as recommended by the American Pain Society.

Poly(oxymethylene) dimethyl ether synthesis – a combined chemical equilibrium investigation towards an increasingly efficient and potentially sustainable synthetic route

Poly(oxymethylene) dimethyl ethers (denoted as OME) are potential sustainable energy carriers and platform chemicals.

Values for tissue magnesium as a guide in detecting magnesium deficiency

A large-scale survey of the normal magnesium content of various human tissues was carried out to facilitate clinical detection of magnesium deficiency, especially occult deficiency.A review of the literature favours the magnesium content of skeletal muscle as the most reliable index of the body's store of magnesium. There is a significant difference (P < 0.001) in both the serum and erythrocyte magnesium levels between normal pregnant women in the third trimester and the average normal population. The reason for this difference is discussed.

'M' cells in the follicle-associated epithelium of the human colon

The morphology of the epithelium overlying human colonic mucosal lymphoid follicles has been studied by electron microscopy. Epithelial crypts stop at the edge of the follicle and the centre is covered by a single layer of enterocytes. Numerous lymphocytes and, occasionally, other mononuclear cells, are associated with these enterocytes. The lymphocytes are situated in the intercellular spaces, invaginate the lateral cell wall and ultimately appear to be completely surrounded by the enterocyte. When the lymphocyte is near the centre of the enterocyte there is usually little change in enterocyte morphology, but when the lymphocyte is near the apical surface of the enterocyte, the latter closely resembles the membranous epithelial cells ('M' cells) of human small intestine. It is probable that, as with the 'M' cells in the small intestine, these colonic 'M' cells have an antigen sampling function. Their presence may explain the localization of the early lesions of some colonic inflammatory diseases, including Crohn's disease. They may also provide a portal of entry for some rectally-transmitted viral infections.

Pain in hospitalized children: pediatric nurses' beliefs and practices

A descriptive design was used to gather information regarding nurses' beliefs and documentation practices related to pain assessment and management in children. Pediatric nurses (n = 260) from eight hospital units completed a child and pain survey. Nurses' pain-related documentations on children (n = 153) were also examined. Results showed inconsistency between what nurses believe about pain assessment and management and their documentation of practice. Nurses believed that assessment is the first step toward alleviating pain in children. However, it was not evident in their documentations that nurses used developmentally appropriate tools for assessment or for evaluation of children's responses to pain management strategies.

Stress myocardial perfusion imaging for the evaluation and triage of chest pain in the emergency department: a randomized controlled trial

BACKGROUND

Patients with acute coronary syndrome (ACS) often present atypically. In a randomized controlled trial, we studied whether adding stress myocardial perfusion imaging (SMPI) to an evaluation strategy for emergency department (ED) patients presenting with chest pain more effectively identifies patients with ACS.

METHODS

Participants were randomized to standard ED chest pain protocol (clinical assessment) or standard protocol supplemented with SMPI results. During 6 hours of electrocardiogram (ECG) monitoring and serial cardiac markers (creatine kinase-MB isoenzyme, troponin), participants developing ST segment changes or elevated cardiac markers were admitted. Those with a negative observation period underwent SMPI (N = 1,004) or clinical assessment (N = 504) based on randomization, and admitted if their SMPI scan was abnormal or senior clinicians found a high or intermediate risk for ACS.

RESULTS

SMPI participants had a significantly lower admission rate than clinical assessment participants (10.16% vs 18.45%), with no significant between-group differences in risk of cardiac events (CEs) after 30 days (0.40% vs 0.79%) or 1 year (0.70% vs 0.99%).

CONCLUSIONS

When added to a standard triage strategy incorporating clinical evaluation, serial ECGs, and cardiac markers, SMPI improved clinical decision making for chest pain patients, significantly reducing the need for hospitalization without an increase in adverse CE rates at 30 days or 1 year.