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Biomedical subjects

M Y Chen

Publications and source records attributed to M Y Chen.

At least 145 records · Page 8Linked to original sources
PubMed1996

Concomitant human immunodeficiency virus infection and syphilitic meningitis.

Syphilis has once again become a public health issue with the advent of human immunodeficiency virus (HIV) infection. We report a 28-year-old Chinese man with recently acquired HIV infection together with early neurosyphilis. His presentation of acute mononucleosis-like syndrome, lymphadenopathy, aseptic meningitis, positive central nervous syndrome and reactive Venereal Disease Research Laboratory test in his cerebrospinal fluid helped to reach the diagnosis. Paired serum Western blot tests for HIV infection performed 1 month apart revealed either a new appearance or an increasing intensity of bands for p17, p24, p31, gp41, p52, p55, p68, gp120 and gp160 suggesting recently acquired HIV infection. The lymphadenopathy disappeared spontaneously and the neurosyphilis responded well to 14 days of penicillin G therapy. The Western blot pattern, clinical course, laboratory data, and therapeutic response indicated that the acute retroviral syndrome and early central nervous system involvement caused by Treponema pallidum occurred concomitantly.

Adult↗
PubMed1995

Characterization of subcutaneous microvascular blood flow during tilt table-induced neurally mediated syncope.

OBJECTIVES: This study aimed to characterize subcutaneous blood flow changes during neurally mediated syncope and to determine whether microvasculature oscillation (vasomotion) is characteristically altered in conjunction with syncopal events. BACKGROUND: Marked pallor is commonly associated with neurally mediated syncope. However, little attention has been paid to the evaluation of subcutaneous blood flow and vasomotion in this setting. METHODS: This study utilized laser Doppler flowmetry to assess changes in subcutaneous microvascular blood flow during head-up tilt table testing in 13 patients with syncope and 6 control subjects. Blood flow and vasomotion frequency were measured continuously before, during and after completion of 80 degrees head-up tilt testing (< or = 25-min duration). RESULTS: Among the 13 patients with syncope, tilt testing reproduced syncopal symptoms in 9 (tilt-positive group) but not in 4 (tilt-negative group). None of the six control subjects developed symptoms during testing. Baseline mean subcutaneous blood flow did not differ significantly among the three groups. However, during upright tilt, blood flow gradually diminished in the tilt-positive group, reaching a nadir of 0.8 +/- 0.33 ml/min per 100 g of tissue (mean +/- SD), but remained relatively constant in the tilt-negative group and control subjects. The difference in mean blood flow response to tilt was statistically significant when the tilt-positive group was compared with either the tilt-negative group or control subjects (p < 0.001). Similarly, baseline blood flow oscillation frequency did not differ significantly in the three subgroups (tilt-positive group 0.2 +/- 0.11 Hz; tilt-negative group 0.2 +/- 0.02 Hz; control subjects 0.2 +/- 0.11 Hz). Subsequently, during tilt testing only the tilt-positive group exhibited increased oscillation frequency; oscillation frequency remained essentially constant throughout the tilt test in the tilt-negative group and control subjects (p < 0.001, tilt-positive group vs. either the tilt-negative group or control subjects). CONCLUSIONS: These findings document an expected diminution of subcutaneous blood flow in association with neurally mediated syncope and indicate that characteristic changes in microvasculature oscillation frequency occur in conjunction with syncopal symptoms. To the extent that microvasculature vasomotion is influenced by neural control, the changes in vasomotion frequency are consistent with relative diminution of peripheral sympathetic neural influence during neurally mediated syncopal episodes.

Adolescent↗
PubMed1995

Comparison of patient reactions and diagnostic quality for hysterosalpingography using ionic and nonionic contrast media.

RATIONALE AND OBJECTIVES: We compared adverse reactions and image quality for hysterosalpingography (HSG) performed with ionic (diatrizoate meglumine combined with iodipamide meglumine [DM + IM]) and nonionic (iohexol) contrast media. METHODS: We performed a study of 95 patients who had HSG and were randomly selected to receive DM + IM or iohexol. Patients reported episodes of abdominal pain and other adverse reactions immediately and 24 hr after the procedure and categorized severity of symptoms on a subjective scale. Two radiologists evaluated image quality for diagnosis. RESULTS: Prevalence of abdominal pain and other reactions both immediately and 24 hr after HSG was lower in patients who received iohexol than in patients who received DM + IM. Moderate or severe abdominal pain was significantly lower in the iohexol group than in the DM + IM group (p < .05). Visualization of the uterine cavity and ampullary rugae was judged excellent with both contrast media (87% with iohexol and 92% with DM + IM). CONCLUSION: Iohexol and DM + IM are excellent contrast media for use during HSG; iohexol 300 may cause fewer episodes of more severe and prolonged abdominal pain.

Abdominal Pain↗
PubMed1995

Acoustic parameters of nasalized vowels in hearing-impaired and normal-hearing speakers.

One of the more prevalent abnormalities that contribute to reduced intelligibility in the speech of hearing-impaired speakers is inadvertent nasalization. Acoustic analysis of the speech of hearing-impaired children and nasalized vowels of normal-hearing adults indicate the presence of an extra pole-zero pair between the first and second formants and a reduced first-formant prominence. The difference between the amplitude of the first formant and the amplitude of the extra peak, A1-P1, was shown to be a promising measure that correlates with listener judgments of the degree of vowel nasality in utterances of hearing-impaired and normal-hearing children. To obtain further validation of these parameters as measures of nasality, A1 and P1 were systematically manipulated in synthetic utterances. The results of perceptual experiments with a number of synthesized words (of the form bVt) showed somewhat different relative importance of the two parameters, depending on the vowel. High correlation of A1-P1 with the average nasality perception judgments was found for each of the stimuli except those for which the first formant was very close to the extra peak frequency. A procedure was developed for correcting the value of A1-P1 to normalize for different vowels, based on the frequencies of the first two formants.

Adolescent↗
PubMed1995

Association of hiatal hernia and gastroesophageal reflux: correlation between presence and size of hiatal hernia and 24-hour pH monitoring of the esophagus.

OBJECTIVE: The relationship of hiatal hernia to gastroesophageal reflux disease remains controversial. Previous endoscopic and radiologic studies of hiatal hernia and reflux esophagitis have shown that hiatal hernia is a poor predictor of the presence of endoscopic esophagitis, especially for smaller hernias. Similar correlations with 24-hr pH monitoring have not been done. The purpose of this study was to determine if there is a correlation between the presence and size of hiatal hernias and gastroesophageal reflux using 24-hr pH monitoring as a measure of the degree of reflux. MATERIALS AND METHODS: We reviewed the barium esophagograms and the results of pH monitoring of the esophagus in 319 patients (161 women and 158 men; mean age, 51 years). The presence and size of hiatal hernia were determined from the radiographic examination; size was categorized as "minimal" or "larger" (> or = 2 cm axial length). An abnormal result of pH monitoring was defined as a pH less than 4 for 6% or more of the 24-hr observation time. RESULTS: Abnormal results of pH monitoring were found in 61 (31%) of 199 patients with hiatal hernia compared with 21 (18%) of 120 patients without hiatal hernia (p < .05). Abnormal findings of pH monitoring were present in 33 (35%) of 95 patients with a larger hiatal hernia versus 28 (27%) of 104 patients with a minimal hiatal hernia (p > .05); a significant difference (p < .05) was observed when patients without hiatal hernia were compared with those with a larger hiatal hernia. CONCLUSION: Most patients in this study had normal results of pH monitoring of the esophagus regardless of the presence or absence of hiatal hernia. However, patients with larger hiatal hernias were more likely to have abnormal findings on pH monitoring; hiatal hernias of minimal size were a poorer predictor of the presence of abnormal gastroesophageal reflux.

Esophagus↗
PubMed1995

Intramural pseudodiverticulosis of the esophagus detected on barium esophagograms: increased prevalence in patients with esophageal carcinoma.

OBJECTIVE: We tested the hypothesis that intramural pseudodiverticulosis of the esophagus is more prevalent in patients with esophageal carcinoma than in randomly selected patients who undergo esophagography for other indications. Such an association would prompt a careful search for carcinoma after esophageal intramural pseudodiverticulosis is found. MATERIALS AND METHODS: Single- and double-contrast esophagograms of 245 patients with esophageal carcinoma were retrospectively reviewed. A control group of 6400 esophagograms obtained for indications other than esophageal carcinoma was also reviewed. The statistical significance of the difference in prevalence of esophageal intramural pseudodiverticula between patients with esophageal carcinoma and the control group was tested using the chi-square test. The significance of difference between the number of esophageal intramural pseudodiverticula in patients with esophageal dilatation and the number in those without dilatation was tested using a small-sample nonparametric test. RESULTS: Intramural pseudodiverticulosis of the esophagus was found in 11 patients with esophageal carcinoma (4.5%) and in six control subjects (0.09%). Intramural pseudodiverticulosis of the esophagus was present opposite the tumor as well as both proximally and distally. The number of cases of intramural diverticulosis in patients with esophageal carcinoma and dilatation was not significantly higher than that in patients with carcinoma but without dilatation (p > .1) CONCLUSION: The prevalence of esophageal intramural pseudodiverticulosis is significantly higher in patients with esophageal carcinoma than in patients who underwent esophagography for other indications (p < .0002). This association implies increased risk of esophageal carcinoma in patients with intramural pseudodiverticulosis. Periodic surveillance of patients with intramural pseudodiverticulosis of the esophagus for esophageal carcinoma may be worthwhile.

Adult↗
PubMed1995

Assessment of heart wall motion: modified spatial modulation of magnetization for MR imaging.

This paper reports a new noninvasive method for detecting a regional myocardial infarction. The method consists of superimposing a magnetization grid onto different image planes of the human heart. In this study the spatial modulation of magnetization (SPAMM) in magnetic resonance imaging was modified to accommodate the use of a conventional clinical magnet. The percentages of circumferential shortening (PCS) and the percentages of wall thickening (PWT) during a cardiac cycle were estimated by measuring the amount of deformation of each grid from the end of the diastole to the end of the systole. A small data base was established on 10 subjects (6 normal volunteers and 4 patients). Patients with regional myocardial infarction, when monitored by the modified SPAMM investigation, showed smaller values of PCS and PWT in the areas where myocardial infarction was diagnosed by catheterization. The amount in decrement was directly proportional to the severity of the regional lesions.

Aged↗
PubMed1994

Serine 113 is the site of receptor-mediated phosphorylation of the Dictyostelium G protein alpha-subunit G alpha 2.

The G protein alpha-subunit G alpha 2 is essential to the developmental program of Dictyostelium. G alpha 2 is transiently phosphorylated on a serine residue(s) following stimulation with extracellular cAMP (Gundersen, R. E., and Devreotes, P.N. (1990) Science 248, 591-593). To aid in defining the function of alpha-subunit phosphorylation, we identified the site of G alpha 2 phosphorylation. Comparison of the isoelectric points (pI) of the phosphorylated and nonphosphorylated forms indicated that a single mole of phosphate is added to G alpha 2. Cleavage at tryptophan residues and immunoprecipitation with a specific peptide antibody localized the phosphorylated serine in the N-terminal 119 residues. Analysis of a series of G alpha 1 and G alpha 2 chimeras further confined the site between amino acids 33 and 215. Site-directed mutagenesis of serines between amino acids 33 and 119 produced two mutants that were not phosphorylated, S45A and S113A. Ser113 was identified as the site by sequential Edman degradation of 32P-radiolabeled G alpha 2 digested with endoproteinase Glu-C. We have expressed the G alpha 2 mutants S113A, S113I, S113T, and S113D in a G alpha 2 null cell line to examine the function of phosphorylation.

Amino Acid Sequence↗
PubMed1994

Correlation of lower esophageal mucosal ring and lower esophageal sphincter pressure.

We assessed the relationship of lower esophageal sphincter pressure (LESP) to presence and absence of lower esophageal mucosal ring (LEMR) in 66 patients to determine if the LEMR was more likely related to prolonged sphincter hypotension. This potential relationship is of interest because LEMR may be due to reflux esophagitis. Each patient had radiographic and manometric studies, and both examinations were done within one week of each other. The mean LESP in patients with LEMR was 23.8 mm Hg (range 4.2-64 mm Hg) compared to 28.7 mm Hg (range 8-59 mm Hg) in patients without LEMR; the difference was not statistically significant. Patients with LEMR were also divided into three subgroups according to the diameter of the rings (< or = 13 mm, 14-19 mm, > or = 20 mm). There was no significant relationship between the caliber of LEMR and LESP (P > 0.05). Presence of LEMR did not affect the amplitude or duration of primary esophageal peristalsis. These results do not support a relationship between LEMR and prolonged LESP hypotension or abnormal esophageal motility. However, other pathogenetic mechanisms involved in producing reflux esophagitis not related to prolonged sphincter hypotension were not studied.

Esophageal Motility Disorders↗
PubMed1994

Cytosolic acetylation of sulfamethazine decreases hepatic release of ketone bodies in vivo in fasting rats.

The effect of sulfamethazine (SMZ) on ketogenesis was studied in this report. SMZ, a sulfonamide metabolized by cytosolic acetylation in liver, was intraperitoneally injected (2 mmol/kg) to ketamine-anesthetized, overnight-fasted rats. Ketogenesis was measured by the Fick principle from the transhepatic (A-V) gradients of acetoacetate (AcAc) and D-beta-hydroxybutyrate (beta-OHB). Prior to SMZ injection, A-V gradient of ketone bodies (KB) (AcAc + beta-OHB) was -1.38 mM, indicating release from the liver. After SMZ injection, the release of KB decreased rapidly, maintaining at a level approximately 50% less than controls throughout the 2-h experimental period. Plasma concentrations of AcAc and beta-OHB also decreased. In contrast, plasma concentrations and trans-hepatic gradients of free fatty acids (FFA) were not significantly affected. Our results thus indicate that SMZ acetylation in liver mobilizes acetyl CoA from mitochondria. Decreased hepatic ketogenesis limits the availability of KB and may thus affect energy metabolism in the extrahepatic tissues. The incomplete inhibition on ketogenesis may indicate compartmentation of acetyl CoA in liver mitochondria.

3-Hydroxybutyric Acid↗
PubMed1994

Investigation of the interaction between the class I MHC-related Fc receptor and its immunoglobulin G ligand.

The neonatal Fc receptor (FcRn) is structurally similar to class I major histocompatibility molecules. FcRn transports maternal immunoglobulin G (IgG) from ingested milk into the blood. IgG is bound at the pH of milk (pH 6.0-6.5) in the gut and released at the pH of blood (pH 7.5). We find that alteration of a histidine pair within the alpha 3 domain of FcRn and of a nearby loop (the FcRn counterpart of the class I CD8-binding loop) affects the affinity for IgG. Inhibition studies suggest the involvement of the FcRn B2-microglobulin domain in IgG binding. Fragment B of protein A inhibits FcRn binding to IgG, localizing the binding site on Fc for FcRn to the CH2-CH3 domain interface. Three histidines present at the CH2-CH3 domain interface of Fc could be partially responsible for the pH-dependent interaction between FcRn and IgG.

Amino Acid Sequence↗
PubMed1994

A computer-aided walking rehabilitation robot.

Even with recent techniques, a significant number of patients with multiple injuries cannot be mobilized at an early stage despite the fixation of all fractures. Conventional mobilization aids are not able to provide the prescribed weight bearing needed in fractures, especially those involving both the lower limbs. Robotics is a current technology aimed at improving the quality of medical care. To this end, Takatoshi Ide developed the mobility rehabilitation robot, the REHABOT. This apparatus facilitates rehabilitation by providing secure postural support and prescribed weight bearing during ambulation. The REHABOT has been used for early mobilization and gait training of severely disabled patients at different hospitals in Japan during the last 6 years. In most of the cases, this training has resulted in earlier improvement of ambulatory capability. In this paper we report the use of this device for early ambulation in two patients with multiple fractures involving the extremities and the spine. Early mobilization was achieved by initially reducing the weight bearing to 30% of body weight followed by a gradual increase governed by patient tolerance. The average length of training for these two patients was 18 days. The average total distance was 5.5 km and total walking duration was 4.5 h. After the completion of the training both patients were able to walk independently.

Adult↗
PubMed1994

Cost-effective filming sequence for intravenous urography.

To define an intravenous urography (IVU) film sequence that maximizes sensitivity and minimizes filming costs, we evaluated the effect of omitting films from a standard IVU sequence. We reviewed 82 IVU series that demonstrated abnormalities. Each series comprised 11 films: preliminary abdominal radiograph and nephrotomogram, three 1-minute nephrotomograms, 5-minute abdominal film, 10-minute radiograph with abdominal compression, one frontal and two oblique 15-minute films, and postvoid film. Sensitivity was determined for each film. Eighty-two standard IVUs showed 120 abnormalities. Omitting any one film from the sequence decreased sensitivity by 0% to 12%. Omitting the preliminary film resulted in failure to detect 15 abnormalities (12%). Omitting any nephrotomogram, the 10-minute compression view, or either 15-minute oblique film did not decrease sensitivity. Omitting combinations of these films lowered overall sensitivity. The postvoid film was essential in only one case. We conclude that a sequence of nine radiographs decreases film and processing expenses by 18% without sacrificing sensitivity. Sequences with fewer films substantially reduce detection of common urinary tract abnormalities.

Cost-Benefit Analysis↗
PubMed1994

Globus pharyngeus: radiographic evaluation and 24-hour pH monitoring of the pharynx and esophagus in 22 patients.

PURPOSE: The authors correlated the radiographic evaluation and 24-hour pH monitoring of the pharynx and the esophagus in patients with globus pharyngeus. MATERIALS AND METHODS: Radiographic examination of the pharynx of 22 patients (13 women and nine men, aged 23-73 years [mean, 47 years]) included videofluoroscopy and static radiography. Twenty-four-hour double-probe pH monitoring of the pharynx (abnormal, pH < 4) and esophagus (abnormal, 6% or more total acid exposure) was performed in all patients. RESULTS: Radiographic results were normal in 17 patients; results were abnormal in five, with four having pharyngeal dysfunction and one showing a persistent cricopharyngeal impression. Zenker diverticulum was not seen. Results at pH monitoring of the pharynx and esophagus were normal in 20 and 18 of the 22 patients, respectively. In four of five patients with abnormal radiographic studies of the pharynx, results of pharyngeal pH monitoring were normal. CONCLUSION: Most patients with globus pharyngeus had normal results at pH monitoring and radiographic examination of the pharynx.

Adult↗
PubMed1994

The internationalization of the American Journal of Roentgenology: 1980-1992.

OBJECTIVE: The purpose of this study was to determine whether significant changes have occurred in the number of foreign articles published in the American Journal of Roentgenology since 1980. MATERIALS AND METHODS: A total of 3398 articles published in AJR during two 3-year periods (1980-1982 and 1990-1992) were classified by type, subject, radiologic technique, organ system, and national origin. Additionally, 2865 manuscripts submitted to AJR from 1990 to 1992 were analyzed to determine the probability of manuscript acceptance based on country of origin. RESULTS: From 1980 to 1992, 158 (10%) of 1610 articles published in AJR originated from institutions outside the United States. By 1990-1992, international articles accounted for 441 (25%) of 1788 published papers (p < .00001). Although the total number of published articles from most nations increased during the decade, Korea, Japan, and Germany made the largest advances. International contributions in the 1990s were most numerous in the following areas: adult radiology, abdominal/gastrointestinal imaging, pulmonary/thoracic imaging, sonography, and interventional radiology. Notwithstanding these trends, manuscripts submitted from international sources are somewhat less likely to be accepted for publication than those originating from the United States (acceptance rate for major papers 27% vs 33%, p = .01). CONCLUSION: The American Journal of Roentgenology is becoming increasingly internationalized, with Korea, Japan, and Germany making particularly striking advances in the past decade.

Bibliometrics↗
PubMed1994

The study of anticardiolipin antibodies and interleukin-6 in cerebrospinal fluid and blood of Chinese patients with systemic lupus erythematosus and central nervous system involvement.

Anticardiolipin (ACL) antibodies and interleukin-6 (IL-6) in cerebrospinal fluid (CSF) may be involved in the mechanism of lupus patients with central nervous system (CNS) involvement. ACL antibodies of 3 isotypes and IL-6 were measured in paired CSF and serum samples from 14 lupus patients with CNS involvement, 5 lupus patients without CNS involvement and 7 patients with non-inflammatory neurological diseases. ACL antibodies, IgG and IgM isotypes, and IL-6 were significantly increased in CSF from lupus patients with CNS involvement as compared with other 2 groups of patients. Both ACL antibodies and IL-6 decreased after neurological activity subsided. These results suggest increased ACL antibodies and IL-6 in CSF are involved in immune responses within CNS in lupus patients. Quantitation of CSF ACL antibodies may be helpful in evaluating neurological activity of lupus patients with CNS involvement.

Adolescent↗