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Biomedical subjects

W Qian

Publications and source records attributed to W Qian.

At least 127 records · Page 7Linked to original sources
PubMed1992

[Effects of substance P on the activities of oviductal isthmic smooth muscle in rabbits].

The effect of substance P (SP) on the activities of oviductal isthmic smooth muscle in rabbits was studied. Rabbits were divided into estrous, diestrous and ovariectomized groups. The results were as follows: (1) SP suppressed the activity of the oviductal isthmic smooth muscle in diestrous rabbit (P less than 0.05). (2) SP did not suppress the activities of the oviductal isthmic smooth muscles in estrous and ovariectomized rabbits (P greater than 0.05).

Animals↗
PubMed1991

Vibrational analysis of crystalline tri-L-alanine.

We have found that tri-L-alanine (Ala3) can crystallize in a parallel-chain beta structure in addition to the previously known antiparallel-chain beta structure. Although the chain conformations in each structure are essentially similar, the ir and Raman spectra are distinctively different. We have calculated the normal modes of each structure, and can account in significant detail for these differences. This demonstrates the essential validity of our empirically refined force fields, as well as showing that deeper insights into polypeptide and protein structure can be achieved through the rigorous analyses of normal mode calculations.

Amino Acid Sequence↗
PubMed1991

"Near miss" death in obstructive sleep apnea: a critical care syndrome.

OBJECTIVE: The objective of this study was to alert critical care physicians to the syndrome of obstructive sleep apnea with respiratory failure ("near miss" death) and to elucidate characteristics that might allow earlier recognition and treatment of such patients. DESIGN: We examined clinical and laboratory characteristics of eight patients with obstructive sleep apnea presenting to the ICU with respiratory failure. These characteristics were compared with those of eight stable apnea patients of similar severity but without a history of presentation with respiratory failure. SETTING: Medical ICU and pulmonary outpatient clinic at the Houston Veterans Administration Medical Center, a teaching hospital affiliated with Baylor College of Medicine. PATIENTS: Eight patients with obstructive sleep apnea who presented in, or developed, acute respiratory failure requiring tracheal intubation and mechanical ventilation were matched to eight stable obstructive sleep apnea outpatients from the chest clinic. MEASUREMENTS AND MAIN RESULTS: The records of these 16 patients were reviewed and multiple characteristics that might predict these obstructive sleep apnea patients prone to respiratory failure and death (called the "near miss" death group; n = 8) were examined. The mean age of the near miss group was 57 yrs. All eight patients presented with respiratory acidosis (mean pH 7.22), hypercarbia (mean PaCO2 82 torr [10.9 kPa]), and hypoxemia (mean PaO2 45 torr [6.0 kPa]). Six of the eight patients had concomitant chronic obstructive pulmonary disease as determined by clinical characteristics and spirometry. Predisposing factors included facial trauma, lower respiratory tract infections or bronchospasm, and use of pain medication. All but one of the near miss subjects had awake hypercarbia (mean PaCO2 49 torr [6.5 kPa]) and hypoxemia (mean PaO2 58 torr [7.7 kPa]) during periods of clinical stability while only two controls had concomitant chronic obstructive pulmonary disease and none had hypercarbia. The prevalence of a history of wheezing and prior hospitalization for "respiratory problems" were greater in the near miss group. Once cured of apnea, no patient presented with recurrence of respiratory failure in follow-up ranging from 6 to 80 months, and cor pulmonale recurred in only one patient during subsequent onset of central apneas. CONCLUSION: Patients with obstructive sleep apnea who have concomitant chronic obstructive pulmonary disease or hypercarbia and hypoxemia are more prone to develop severe respiratory failure and probable death than those patients with apnea alone. The current study shows that recurrent respiratory failure and presumably mortality from this acute complication can be reversed with effective treatment of the obstructive apnea.

Acute Disease↗
PubMed1991

Rate of oxyhemoglobin desaturation in obstructive versus nonobstructive apnea.

Preapneic thoracic gas volume (Vtg), arterial saturation (SaO2), and mixed venous oxygen saturation (SvO2), have been shown to influence the rate of SaO2 fall (dSaO2/dt) during apnea. We asked the following question: does tissue oxygen consumption (tVO2) affect the dSaO2/dt during apnea? We attempted to answer this question by comparing dSaO2/dt during obstructive apneas (high tVO2) with dSaO2/dt during nonobstructive apneas (low tVO2) in six adult baboons. Fiberoptic central venous and arterial catheters were used for continuous monitoring of SvO2, SaO2, and cardiac output. A sapphire-bearing turbine monitored minute ventilation and airflow cessation. A Respitrace and esophageal pressures were used to assess relative differences in Vtg. Obstructive apneas (30, 45, and 60-s) were created by clamping an indwelling cuffed endotracheal tube at end-expiration. Nonobstructive apneas were created by paralyzing the animals with atracurium and interrupting ventilation for periods equivalent to those of the obstructed apneas. The ventilator was adjusted to duplicate the respiratory rate, tidal volume, and relative Vtg of the spontaneously breathing animal. Mean tVO2 during spontaneous breathing was 110 ml/min (Fick method) and decreased to 90 ml/min during paralysis (p less than 0.05). The dSaO2/dt for the three apnea durations (mean, all animals), obstructive versus nonobstructed were: 0.85 and 0.74%/s (n = 6), 0.87 and 0.75%/s (n = 6), and 0.60 and 0.48%/s (n = 4), respectively. The dSaO2/dt was significantly lower during the nonobstructive apneas. We conclude that differences in VO2 during apnea may affect the dSaO2/dt and that for the same duration apnea, central apneas may show less desaturation than obstructive apneas where vigorous muscular efforts at overcoming obstruction are common.

Animals↗
PubMed1991

Evolution of nocturnal oxyhemoglobin desaturation in patients with chronic obstructive pulmonary disease and a daytime PaO2 above 60 mm Hg.

We studied 31 clinically stable chronic obstructive pulmonary disease (COPD) patients with a PaO2 greater than or equal to 60 mm Hg using polysomnographic sleep study at baseline (between 1983 and 1986) and at a mean follow-up time of 42.5 months to examine the evolution of rapid-eye-movement (REM) sleep nocturnal oxyhemoglobin desaturation (NOD). Arterial blood gases and spirometry measured at baseline and follow-up were compared with mean nocturnal SaO2 and to other REM sleep SaO2 parameters. We postulated that the onset of NOD would be seen most frequently in those patients with marked derangements of lung mechanics and greater longitudinal deterioration in arterial blood gases. Eight of the subjects developed REM-NOD on follow-up polysomnography. The appearance of REM-NOD was not related, or only minimally so, to initial PaO2, PaCO2, or mean nocturnal SaO2. Upon follow-up, however, the onset of NOD was always associated with deterioration of daytime PaO2 and PaCO2, mainly in those patients with the most severe baseline derangement of spirometry (lung mechanics). On the other hand, one group showed equivalent deterioration in daytime PaO2 and a stable PaCO2 but had less severely deranged baseline mechanics and demonstrated a fall in mean nocturnal SaO2 only. The findings in this latter group indicate that the development of NOD is not purely a result of decreasing daytime PaO2. We conclude that the onset of REM-NOD is mainly related to a severe derangement of lung mechanics with deterioration of resting awake gas exchange (progressive hypoxemia, hypercarbia, and worsening airflow).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Effect of cardiac output reduction on rate of desaturation in obstructive apnea.

The nadir of SaO2 during an obstructive apnea is dependent upon the apnea's duration and the rate of fall of saturation (dSaO2/dt). We postulated that a low Q, such as in patients with congestive heart failure with sleep apnea, or a reduction in Q, as seen in some humans during obstructive sleep apnea, might steepen dSaO2/dt. The mechanism postulated was lowering of SvO2 with increased pulmonary capillary blood oxygen uptake and faster depletion of alveolar oxygen. This study examines dSaO2/dt following the onset of apnea in eight spontaneously breathing adult baboons. Nonrepetitive obstructive apneas (30, 45, and 60 seconds) were created by clamping an indwelling cuffed endotracheal tube at the end of expiration. Following baseline measurements, the animals were given a bolus of a rapid-acting beta-adrenergic blocker followed by continuous infusion to reduce cardiac output and to limit the cardiovascular response to obstructive asphyxia. Fiberoptic catheters were used for continuous monitoring of SaO2, SvO2, and cardiac output. Esophageal pressure and relative thoracic gas volume (Respitrace) were monitored to insure equivalence of lung volume at the onset of apnea. Beta-adrenergic blockade reduced resting Q by a mean of 25 percent. The blocked vs unblocked dSaO2/dt was 0.73 vs 0.72 percent/s, 0.76 vs 0.73 percent/s, and 0.70 vs 0.71 percent/s for 30-second, 45-second, and 60-second apneas, respectively. Thus, mean dSaO2/dt for all durations of apneas was unaffected by beta-adrenergic blockade. We concluded that dSaO2/dt is not influenced by limited Q preceding or induced by obstructive asphyxia.

Adrenergic beta-Antagonists↗
PubMed1991

[Quantitative study of myocardial pathological lesions in rheumatic mitral valve disease: correlations with changes in cardiac function after valve replacement].

Pathological lesions of left ventricular myocardium from 21 patients with predominant mitral stenosis (MS) and from 16 patients with predominant mitral regurgitation (MI) were studied quantitatively by means of image analysis system and light microscopic examination. Their correlations with changes of cardiac function after mitral valve replacement were also studied. The results showed that the percentage of the area of interstitial fibrosis (F%), the shortest diameter of myocardial fiber (SDMF) and endocardial thickness (ET) increased, and the inner diameter-out diameter ratio of intramyocardial arteries (Di/Do) decreased in 37 patients in various degrees. F%, Di/Do, SDMF and ET correlated with delta EF, delta FS, delta ESVI, postoperative dosage of dopamine, and duration of assisted respiration analysed respectively by linear regression. Multiple myocardial pathological lesions correlated strongly with delta EF analysed by multiple linear regression with multiple correlation coefficient of 0.803 in MS group (P less than 0.01) and 0.763 in MI group (P less than 0.05). These data suggest that multiple evaluation of myocardial pathological lesions plays an important role in predicting prognosis of mitral valve replacement. After operation mean delta EF and delta FS decreased, dosage of dopamine and duration of assisted respiration increased when the patient had two or more following criteria: 1. F% greater than 31%, 2. Di/Do less than 0.400, 3. SDMF greater than 16 microns, 4. ET greater than 326 microns.

Adolescent↗
PubMedDate not supplied

Image segmentation in digital mammography: comparison of local thresholding and region growing algorithms.

Local thresholding and region-growing algorithms are developed and applied to digitized mammograms to quantify the parenchymal densities. The algorithms are first evaluated and optimized on phantom images reflecting varying image contrast, X-ray exposure conditions, and time-related changes. The difference between the segmentation results of the two techniques is less than 6% on the phantom images and 11% on the mammograms. The agreement between the computerized procedures and a manual one is in the range of 74-98%, depending on the breast parenchymal pattern and segmentation algorithm. The results show that computerized parenchymal classification of digitized mammograms is possible and independent of exposure.

Algorithms↗
PubMedDate not supplied

Digital mammography: M-channel quadrature mirror filters (QMFs) for microcalcification extraction.

Multiresolution methods are reported for feature extraction in breast cancer screening using digital mammography. The initial application is directed at the detection of microcalcification clusters (MCCs). Quadrature mirror filter (QMF) banks, using both two and three channel are proposed for the first time for both multiresolution decomposition and reconstruction. These filters are specifically tailored for automatic extraction of MCCs. The QMF multiresolution methods are compared to two channel tree structured wavelet transforms (TSWTs) methods previously reported. The QMF filters are preceded by an advanced tree structured nonlinear filter for noise suppression, prior to feature extraction, in order to minimize the false positive (FP) detection rate in digital mammography. The relative performance of these methods were evaluated using both simulated images and fifteen representative digitized mammograms containing biopsy proven microcalcification clusters. Similar high sensitivity (true positive (TP) detection rate (100%) and high specificity (0.6 average false positive (FP) MCC's/image) were observed, substantially better than more traditional approaches using single scale filters. The three channel QMF method, however, demonstrated better detail preservation of MCC's extracted compared to the two channel method. Detail preservation is important for the characterization of MCC's or individual microcalcifications in cancer screening.

Algorithms↗
PubMedDate not supplied

Nitric oxide in the nasal airway: a new dimension in otorhinolaryngology.

The discovery that the gas nitric oxide (NO) is an important signaling molecule in the cardiovascular system earned its Nobel prize in 1998. NO has since been found to play important roles in a variety of physiologic and pathophysiologic processes in the body including vasoregulation, hemostasis, neurotransmission, immune defense, and respiration. The surprisingly high concentrations of NO in the nasal airway and paranasal sinuses has important implications for the field of otorhinolaryngology. NO provides a first-line defense against micro-organisms through its antiviral and antimicrobial activity and by its upregulation of ciliary motility. Nasal treatments such as polypectomy, sinus surgery, removal of hypertrophic adenoids and tonsils, and treatment of allergic rhinitis may alter NO output and, therefore, the microbial colonization of the upper airways. Nasal surgery aimed at relieving nasal obstruction may do the same but would also be expected to improve pulmonary function in patients with asthma and upper airway obstruction. NO output rises in a number of conditions associated with chronic airway inflammation, but not all of them. Concentrations are increased in asthma, allergic rhinitis, and viral respiratory infections, but reduced in sinusitis, cystic fibrosis, primary ciliary dysfunction, chronic cough, and after exposure to tobacco and alcohol. Therefore, NO, similar to several other inflammatory mediators, probably subserves different functions as local conditions dictate. At present, it seems that the measurement of NO in the upper airway may prove valuable as a simple, noninvasive diagnostic marker of airway pathologies. The objective of this review is to highlight some aspects of the origin, physiology, and functions of upper airway NO, and to discuss the particular methodological problems that result from the complex anatomy.

Humans↗
PubMedDate not supplied

Universal opacity standard for Scheimpflug photography.

PURPOSE: To develop a universal standard for comparison of the results from different studies using Scheimpflug photography. MATERIAL AND METHOD: A suspension including polystyrene spheres was selected as the universal standard. The polystyrene suspension was diluted into 10 concentrations by adding spectroscopic quality water. An artificial eye chamber was designed to hold the diluted suspension for photography. Each concentration was photographed by both a Topcon SL-45 slit-lamp camera and a Nidek EAS-1000 system. The intensity of back-scattered light was analyzed statistically. RESULTS: The relationship between the concentration of the polystyrene suspension and the internal gray scale step within the Topcon SL-45 camera can be described by a second-order polynomial. The relationship between the concentration of the polystyrene suspension and the measurement of the Nidek EAS-1000 system can also be expressed by a second-order polynomial. The relationship between the Topcon SL-45 camera and the Nidek EAS-1000 system is linear. CONCLUSIONS: The results of lens nuclear opacity measured with different Scheimpflug cameras can be compared using the method established in the study. The linear relationship between the Topcon SL-45 and Nidek EAS-1000 systems can be used to convert measurements from one system to the other.

Anterior Chamber↗
PubMedDate not supplied

Nasal nitric oxide is not altered by topical anesthesia.

This prospective study was undertaken to determine whether topical nasal anesthetic agents affect nasal nitric oxide (NO) output in healthy adults. Seven volunteers (aged: 29-56 (40.6 +/- 10.7) years, six male), were recruited. A topical anesthetic (4% lidocaine or 0.5% tetracaine) was sprayed into the subject's right nostril while the left nostril served as a control. Unilateral nasal NO and nasal volume were measured before administration of the anesthetic and at 15 and 30 minutes after the administration. The mean (+/- SD) unilateral nasal NO output was 307 +/- 45.9 nL/minute from the right nostril (exposure side) before the topical application of lidocaine. At 30 minutes after topical application (n = 6), it was 295.5 +/- 41.5 in the right nostril and 297.5 +/- 39.8 in the left (control side). In the tetracaine group (n = 7), the mean (+/- SD) unilateral nasal NO output was 302 +/- 53.3 before the administration and 307 +/- 39.7 at 30 minutes after the administration in the right nostril. The mean NO output in the left nostril at 30 minutes after the administration was 297.7 +/- 40.75. In neither group was there any significant difference in nasal NO output between either the pre- and postlocal anesthetic application on the exposure side (Group 1, P = 0.76; group 2, P = 0.41) or the two nostrils after topical anesthesia application (group 1, P = 0.83; group 2, P = 0.62). Topical anesthesia with either lidocaine or tetracaine does not alter nasal NO output. NO measurement should not be affected in circumstances that require topical anesthesia of the nasal cavity.

Administration, Inhalation↗
PubMedDate not supplied

Nasal nitric oxide is independent of nasal cavity volume.

This study was performed to evaluate the relationship between nasal nitric oxide (NO) and changes in nasal cavity volume resulting from the topical application of xylometazoline and saline and between upright and supine posture. Nasal NO was measured using a fixed high flow technique that avoids contamination with lower airways NO. In nine healthy subjects nasal NO concentration was measured by a rapid response chemiluminescent analyzer. A tapered tube was inserted in one nostril, into which room air was insufflated to produce a constant flow of 100 mL/second; another tube was inserted into the opposite nostril for NO sampling (air exit side). Subjects were instructed to keep the vellum closed while NO was sampled through a sideport connected to the analyzer. Nasal cavity volume was measured by acoustic rhinometry from a segment of the acoustic pathway, 2 to 5 cm from the nostril. Nasal cavity volume and NO measurements were made at baseline, 15 minutes, and 60 minutes after intervention (administration of saline 0.9%, xylometazoline or posture changes on 3 consecutive days). Xylometazoline produced a significant increase in nasal cavity volume, together with a significant reduction in NO level at 15 and 60 minutes after intervention. In addition, the change from seated to supine position decreased the total nasal volume significantly, but without changes in nasal NO. No correlation was found between the magnitudes of changes in nasal NO and the changes in nasal volume. Topical application of xylomethazoline resulted in increased nasal cavity volume and reduced NO output. In contrast to previous published reports, a technique using high flow rate insufflation demonstrated an abscence of correlation between the magnitudes of changes in nasal NO and nasal cavity volume brought about by decongestant, saline, or posture.

Acoustic Stimulation↗
PubMedDate not supplied

Nasal nitric oxide: a comparison of measurement techniques.

Nasal nitric oxide measurement may be a surrogate marker of upper airway inflammation. There is, however, no standardized measurement technique; and this led us to examine measurement techniques for acceptability and reproducibility. In five subjects we examined the flow dependence of nasal NO. In 13 healthy volunteers, nasal NO was measured on-line by five methods: 1) Tidal nasal and oral breathing: NO sampling during exclusive nasal followed by exclusive oral tidal breathing; 2) Fixed flow exhalation: NO sampling during exclusive nasal followed by exclusive oral exhalation at 100 mL/second from total lung capacity; 3) Nasal-oral aspiration: air aspirated from the mouth via both nares at 100 mL/second with glottis closure; 4) Aspiration from one nares: air aspirated from one nares at 3.3 mL/second using nitric oxide analyzer sample line with velum closure; 5) Nasal Insufflation: NO sampled at one nares as air insufflated into the other nares at a flow of 100 mL/second with velum closure. Acceptability of all methods was assessed by subjects and technicians. Nasal NO concentration showed a significant inverse correlation with transnasal flow rate. All methods showed excellent reproducibility as assessed by the intraclass correlation coefficient except tidal breathing, which showed highly variable breath-to-breath NO levels, although mean breath values were reproducible. Mean nasal NO concentrations with methods 1, 2, 3, 4, and 5 were 32.1, 50.2, 62.8, 1381, and 60.0 ppb, respectively. Velum closure was not always achieved in methods 4 and 5, whereas methods 1 and 2 required separate nasal and oral procedures. Method 5 had reduced acceptability. NO concentrations were similar with methods that used the same airflow (2, 3, and 5). Nasal NO can be sampled in different ways with excellent reproducibility. In view of the flow dependence of nasal NO, it is vital to use a constant flow rate, and lower airway NO contribution must be excluded or subtracted. The fixed flow exhalation appears to be the preferred method as it is highly reproducible and acceptable.

Analysis of Variance↗
PubMedDate not supplied

Acoustic rhinometry: a study of transient and continuous noise techniques with nasal models.

The objective of this study is to compare the properties of two of the most frequently used acoustic rhinometers: the EcoVision (Hood Laboratories, USA) using the transient technique, and the Rhin2100 (RhinoMetrics, Denmark) using the continuous wide-band technique. In the wide-band rhinometer (Rhin2100), the transient analog signals of traditional rhinometers (EcoVision), are replaced by a digitally produced continuous wide-band noise signal. Tubular models and a plastic model produced by stereolithography (SLA), representing the true replicate of the nasal anatomy, were used to compare the accuracy of the two rhinometers. The effect of increasing angling (0-50 degrees) between the sound wave tube and the cavity was evaluated in a tubular model. The curves obtained with the two rhinometers showed close similarity, and the acoustically derived volumes correlated well with the volumes of tubular (% error < 4%) as well as the complex nasal model (% error < 10.5%). Both rhinometers underestimated the minimum cross-sectional area (MCA) of the complex nasal model (mean % error complex model: Rhin2100 = -7.6%, EcoVision = -13%). The effect of increasing the angle between the nose adapter and the tubular models was small for both rhinometers (CV < 3% for MCA and CV < 1% for volumes). The similar, and in general, high accuracy of the two rhinometers evaluated, particularly in the complicated geometry of the SLA model, is an indication of the reliability of both. The small effect of changing the angle between the nose adapter and the models was unexpected and very encouraging. Nevertheless, some minor differences in performance and capabilities of the two rhinometers might influence interpretation and comparison of results. Further comparisons in a clinical setting are under current investigation.

Acoustics↗