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Biomedical subjects

Y S Lo

Publications and source records attributed to Y S Lo.

At least 19 recordsLinked to original sources
PubMed2001

Characterization of silane-modified immobilized gold colloids as a substrate for surface-enhanced Raman spectroscopy.

Immobilized gold colloid particles coated with a C-18 alkylsilane layer have been characterized as a substrate for surface-enhanced Raman scattering (SERS) studies of adsorption onto hydrophobic surfaces. Atomic force microscopy images, optical extinction spectra, and SERS measurements are reported as a function of accumulation of gold colloid on glass. As the metal particles become increasingly aggregated on the surface, the SERS enhancement increases until the plasmon resonance shifts to wavelengths longer than the excitation laser. The gold colloid substrates are stable and exhibit reproducible SERS enhancement. When octadecyltrimethoxysilane is self-assembled over the gold, the metal surface is protected from exposure to solution-phase species, as evidenced by the inhibition of chemisorption of a disulfide reagent to the overcoated gold surface. The results show that interactions with gold can be blocked by a silane layer so as not to significantly influence physisorption of molecules at the C-18/solution interface. The SERS enhancement from these C-18-overcoated gold substrates is reproducible for different films prepared from the same colloidal suspension; the substrates are also stable with time and upon exposure to laser irradiation.

Journal Article↗
PubMed2001

Solitary fibrous tumor of the liver.

Solitary fibrous tumor of the liver is a rare neoplasm. So far, 21 cases have been described in the English literature. We reported an additional case. Our patient, a 75-year-old man, suffered from abdominal fullness and body weight loss of 6 kg over 6 months, and chills and fever for 2 months. Hypoglycemia was noted at admission. Both abdominal sonography and CT showed a huge mass occupying the right lobe of liver. Liver biopsy showed fibrous tumor. Right lobectomy was performed and the tumor was resected. Pathological examination showed spindle-shaped and fibroblast-like cells within the collagenous stroma. On immunohistochemical stains, these spindle tumor cells showed CD34 positive reactivity. The post-operative course was uneventful and there was no more hypoglycemia. The patient recovered smoothly, regained his body weight, and was alive without evidence of disease recurrence at the last follow-up visit in November, 2000.

Aged↗
PubMed1998

Expression and activity of epidermal growth factor receptor in late fetal rat lung is cell- and sex-specific.

Epidermal growth factor (EGF) augments late fetal lung maturation by advancing the ontogeny of fetal lung development and by stimulating surfactant synthesis. Previous studies have indicated that fibroblastalveolar epithelial cell communications mediate surfactant synthesis in the fetal lung and EGF acts through such a mechanism. We investigated the hypothesis that is differential activity and expression of the epidermal growth factor receptor (EGF-R) in fetal lung fibroblasts during the canalicular stage of lung development mediates EGF effects. To test this hypothesis, we examined fetal rat lung fibroblasts (FLFs) and type II cells of late gestation (canalicular and saccular stages; 17-22 days) by EGF-R binding techniques, SDS-PAGE, and Western blot analysis. Specific EGF binding increased 181% in day 18 female FLFs, with male FLFs exhibiting a similar increase on day 19. In contrast, specific EGF binding was low in type II cells, did not increase during late gestation, and there were no sex-specific differences. SDS-PAGE and Western blot analysis revealed a predominant 170-kDa EGF-R band in fibroblasts that increased with gestation (peak = 19 days), and was stronger in females. Immunoprecipitation of EGF-treated cells demonstrated the tyrosine kinase activity of the identified receptor. In contrast, type II cells showed minimal signal that did not increase until day 21 of gestation. We also examined whole fetal lung sections by immunohistochemistry to determine cell-specific expression of the EGF-R in vivo. Immunohistochemistry revealed specific EGF-R staining in columnar and cuboidal epithelia of small conducting airways and in mesenchyme of epithelial-mesenchymal borders (including subepithelial mesenchyme). In contrast, alveolar epithelia showed minimal staining, while subalveolar mesenchyme EGF-R staining peaked at day 19 of gestation. We conclude that cell-specific and sex-specific differences in EGF-R binding and EGF-R immunolocalization appears in the fetal lung at a developmental stage that is critical for alveolar epithelial cell differentiation. The results suggest a role for EGF-R activation in late fetal alveolar epithelial cell maturation, which is mediated through mesenchymal-epithelial cell communication.

Animals↗
PubMed1998

Population heterogeneity of higher-plant mitochondria in structure and function.

Mitochondria of rapidly developing mungbean seedlings were fractionated into four populations: two density classes, each from a 1500S and a 150S pellet. Each of the four populations exhibited cytochrome c oxidase (COX) activity and contained mitochondrial DNA and cardiolipin; plastid and glyoxysome content were found to be relatively low. Five mitochondrial membrane proteins, COXII/III, ATPase alpha/beta and porin, and a matrix enzyme, manganese superoxide dismutase (MnSOD), were detected by immunoblots in all four populations. Another matrix enzyme, pyruvate dehydrogenase was detected only in the two respiratory-competent 1500S populations. The two 150S populations contained a previously unidentified organelle that lacked demonstrable respiratory capability. This organelle, which we have tentatively referred to as "slow-sedimenting (ss-) mitochondrion", was small in size (below light-optics resolution, 70-300nm, majority < or =200nm) and possessed a peculiar looking boundary membrane, ribosomes, and an occasional prominent electron-dense spot. Characteristically, ss-mitochondria were almost always in contact with a filament-aligned membrane-like structure of varying length. Cristae structure, while undetected in small ss-mitochondria, appeared in larger individuals. Typical mitochondria were found in the denser 1500S population, while the lighter 1500S population consisted of 300-800 nm mitochondria exhibiting a varying degree of size-dependent inner membrane folding. Using electron microscopy (EM) immunolocalization and serial sectioning, we have identified in situ organelles resembling in size and in fine structure the ss-mitochondria, which also exhibit a size-dependent folding of the inner membrane. These results suggest that small ss-mitochondria may undergo a progressive development in situ. Taken together, our findings demonstrate the existence of a pattern of structure-function-coordinated gross heterogeneity among mitochondria. This pattern of mitochondrial heterogeneity, characterized both in isolated mitochondria and in situ, implies that small ss-mitochondria may represent a type of "nascent mitochondria" derived from a yet unidentified mitochondria-propagation mode operating during rapid seedling growth. Mitochondrial division by binary fission, characterized by the appearance of dumbbell-shaped intermediates, was also detected.

Cardiolipins↗
PubMed1994

Characteristics and radiofrequency ablation therapy of intermediate septal accessory pathway.

Fourteen patients (5%) with an intermediate septal accessory pathway were identified among 283 consecutive patients with the Wolff-Parkinson-White syndrome who had electrophysiologic study and radiofrequency ablation therapy. Nine were women and 5 were men (mean age 33 +/- 13 years). The resting electrocardiogram showed ventricular preexcitation in 8 patients and normal PR interval in 6. Anterograde and retrograde mapping studies revealed that the accessory pathway was para-Hisian in 11 patients and paranodal in 3. The accessory pathway was successfully ablated in 10 patients (9 para-Hisian and 1 paranodal) and damaged in 1 (para-Hisian). Treatment of 3 patients was complicated by transient atrioventricular (AV) block, of 1 by intermittent second-degree AV block, and of another by permanent complete AV block requiring implantation of a permanent pacemaker. Six patients underwent a follow-up electrophysiologic study 84 +/- 55 days after ablation; none had induction of tachycardia even after isoproterenol infusion. It is concluded that radiofrequency ablation therapy for intermediate septal accessory pathway is feasible. However, the success rate is only modest (71%), whereas complications with heart block (36%) or complete right bundle branch block (29%) are high. Thus, the procedure should be reserved for patients with life-threatening or troublesome symptomatic tachyarrhythmias.

Adolescent↗
PubMed1994

Molecular characterization of glucose-6-phosphate dehydrogenase deficiency in Chinese infants with or without severe neonatal hyperbilirubinaemia.

To characterize mutations in the glucose-6-phosphate dehydrogenase (G6PD) gene in Chinese infants, we studied 213 G6PD-deficient infants without blood exchange transfusion (BET) therapy, and 34 patients who required BET therapy for their severe hyperbilirubinaemia after birth. Nine different point mutations were characterized in all infants. Of these mutations, the G to T substitution at cDNA nucleotide (nt) 1376, which accounts for the mutations in 131 (53.0%) neonates, followed by G to A substitution at nt 1388 in 18 (10.5%) infants, A to G substitution at nt 493 in 17 (6.9%) infants, A to G substitution at nt 95 in 10 (4.1%) infants, C to T substitution at nt 1024 in six (2.4%) infants, and G to T substitution at nt 392 in three (1.2%) infants, G to A substitution at nt 487 in two (0.8%) infants, C to T substitution at nt 1360 in two (0.8%) infants and C to T substitution at nt 592 in two (0.8%) infants. Mutations in 48 (19.5%) G6PD-deficient infants were not characterized. Most (64.7%) mutations in the G6PD-deficient infants who required BET therapy after birth result from a G to T substitution at nt 1376. The enzyme activity of G6PD deficient infants who required BET therapy is significantly lower than for those who did not, even in a group with the same variant (as in 1376 mutation). Severe neonatal jaundice requiring BET therapy can take place with the majority of variants encountered in this area.

Base Sequence↗
PubMed1993

[Congenital nasopharyngeal teratoma: report of a case and review of the literature].

Teratomas are the most common congenital tumors, but teratomas of the nasopharynx are rare and seen almost exclusively in infants, usually in neonates. An unusual case of a neonate with respiratory distress is presented and a nasopharyngeal mass protruding into the oral cavity. After successful removal of the mass, pathological examination revealed a mature teratoma. The management and differential diagnosis are discussed, accompanied by a review of the literature.

Female↗
PubMed1992

Synthesis and physicochemical properties of sulfamate derivatives as topical antiglaucoma agents.

Several imidazolylphenyl sulfamate and (imidazolylphenoxy)alkyl sulfamate derivatives were synthesized and evaluated as topically active carbonic anhydrase inhibitors. Water solubility, pKa, carbonic anhydrase inhibition, and partition coefficient for the compounds were measured. Sulfamic acid 2-[4-(1H-imidazol-1-yl)phenoxy]ethyl ester monohydrochloride (16) has the best combination of properties and showed excellent topical activity in lowering the intraocular pressure in New Zealand white rabbits.

Administration, Topical↗
PubMed1992

Physiological profiles of Hong Kong élite soccer players.

Most physiological profiles of élite soccer players originate from Western Europe and North America. Unfortunately, there is a scarcity of descriptive data on the physical characteristics of Asian soccer players. Therefore, the purpose of this study was to evaluate the physiological profiles of élite soccer players in Hong Kong. It was conducted in conjunction with the selection of the Hong Kong team before the 1990 Beijing Asian Games. In all, 24 professional soccer players were selected from a pool of 180 players as subjects for the study. The following means(s.d.) were observed: height 173.4(4.6) cm; weight 67.7(5.0) kg; body fat 7.3(3.0)%; forced vital capacity (FVC) 5.1(0.6) l; maximum oxygen uptake (VO2max) 59.1(4.9) ml kg-1 min-1; anaerobic threshold (AT 80.0(7.2)% of VO2max; alactic power index 13.5(2.4) W kg-1; lactic work index 298(27) J kg-1; peak isokinetic dominant knee extensor and flexor strengths 2.72(0.36) Nm kg-1 and 1.65(0.20) Nm kg-1. On average the physique of Hong Kong soccer players appeared to be smaller and lighter than those found in Europe, which may be one of the key factors that contribute to the lack of success of Hong Kong soccer teams in international competition.

Adult↗
PubMed1992

Quantitative measurement of muscle and subcutaneous fat thickness in newborn by real-time ultrasonography: a useful method for site and depth evaluation in vaccination.

In order to quantify muscle thickness and choose the appropriate site for intramuscular injection of vaccines in neonates, we used ultrasonography to measure muscle and subcutaneous fat thickness of anterolateral mid-thigh, upper outer quadrant of buttock and middle area of deltoid in fifty full term (group 1) and thirty low birth weight (group 2) infants. A Hitachi EUB40 real-time scanner and a 5 MHz transducer was used in the study. We delineated the normal distribution of muscle and subcutaneous fat thickness in mid-thigh, buttock and deltoid areas of full term and low birth weight infants. There was no significant difference between male and female infants in the two groups. Muscle and subcutaneous fat thickness in the thigh area was 11.8 +/- 1.9 mm and 3.8 +/- 0.4 mm, respectively, in group 1; 8.6 +/- 1.7 mm and 2.7 +/- 0.5 mm in group 2. Figures in the buttock area were 10. 1 +/- 1.5 mm and 3.7 +/- 0.5 mm in group 1, 6.9 +/- 1.2 mm and 2.7 +/- 0.7 mm in group 2; and in the deltoid area were 5.2 +/- 0.7 mm and 3.4 +/- 1.5 mm in group 1 and 3.8 +/- 0.8 mm and 2.3 +/- 0.6 mm in group 2. There was significant logarithmic correlation between muscle thickness and body weight (r = 0.6, 0.8, 0.6) and muscle thickness and body length (r = 0.4, 0.6, 0.6) in thigh, buttock and deltoid areas of the low birth weight infants. In contrast, there was significant logarithmic correlation only between buttock muscle and body weight (r = 0.5) in the full term infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1991

2-Phenyl-3H-imidazo[4,5-b]pyridine-3-acetamides as non-benzodiazepine anticonvulsants and anxiolytics.

A series of 2-phenyl-3H-imidazo[4,5-b]pyridine-3-acetamides were designed and synthesized as non-benzodiazepine anxiolytics based on a molecular disconnection of a typical 1,4-benzodiazepine (BZD). A number of these compounds showed submicromolar potency in a [3H]benzodiazepine binding assay in vitro and good potency in protecting rodents against pentylenetetrazole-induced seizures. Compound 84 appears to be a selective anticonvulsant (pentylenetetrazole) agent when tested against a profile of chemically and electrically induced seizures in mice. In addition, compound 148 appears to be a selective anxiolytic/hypnotic agent on the basis of biochemical and pharmacological characterization. It appears to be a full BZD agonist as assessed by GABA shift ratio and to be effective in punishment and nonpunishment animal models of anxiety. In addition, it shows a lower side-effect profile than diazepam as assessed by rotorod neurotoxicity and potentiation of ethanol-induced sleep time in mice. The chemistry and structure-activity relationships of this series is discussed.

Animals↗
PubMed1991

Protein Synthesis in Isolated Mitochondria of Rice (Oryza sativa L.) Seedlings.

For studies of in organello mitochondrial protein synthesis in rice, Oryza sativa L., conventional surface-sterilization procedures were demonstrated to be ineffective. Because of the over-whelmingly efficient [(35)S]methionine utilization by contaminating bacteria, even "essentially bacteria-free" rice mitochondria were shown to be unsuitable for the study of in organello protein synthesis. We developed a procedure to obtain a bacteria-free preparation of rice mitochondria. Such mitochondria favored a membrane-dependent ATP-generating system over an external ATP-generating system as the energy supplement for in organello protein synthesis. Two distinct classes of [(35)S]methionine-labeled, cycloheximide-insensitive products were detected: an electrophoretically unresolved population and a set of some 22 to 27 discrete polypeptide species, each with a characteristic electrophoretic mobility and relative abundance.

Journal Article↗
PubMed1990

Echocardiographic left ventricular hypertrophy in Chinese endurance athletes.

Most echocardiographic data on the athletic heart syndrome originate from the United States and Western Europe. There are no published data on echocardiographically documented left ventricular hypertrophy in Asian athletes. We investigated the echocardiographic changes which take place with endurance training by studying eight Hong Kong national cyclists. This study confirms that left ventricular hypertrophy and increased left ventricular end-diastolic dimensions are common findings in Chinese endurance athletes as in their Caucasian counterparts. Calculated left ventricular muscle mass exceeded the 95th percentile in seven of eight subjects.

Adult↗
PubMed1990

[Clinical studies of neonatal hyperbilirubinemia treated with blood exchange transfusion].

From April 1984 to November 1989, 194 cases of neonatal hyperbilirubinemia treated with blood exchange transfusions (BET) were studied. The patients included 127 male and 67 female neonates, with an age ranged from 13 hours to 16 days. The most common cause was idiopathic (52.6%), followed by G-6-PD deficiency (23.7%), and sepsis (12.9%). Most of the neonates received BET at the 4th day of birth (23.2%), but there were still 30 cases (15.5%) that received BET after 1 week of age. There were 17 cases (8.8%) with maximum serum bilirubin lower than 20 mg/dl before receiving BET, five of them were LBW infants; 11 cases (5.7%) were greater than 40 mg/dl. The mean of maximum serum bilirubin was 26.9 +/- 7.96 mg/dl. Most of the cases received BET once (145 cases) or twice (33 cases). There were two cases that received up to six BET's. One was G-6-PD deficiency and one idiopathic in etiology. No significant difference of BET frequency between sex or body weight (p greater than 0.05) was found. Newborns with higher serum bilirubin due to G-6-PD deficiency, received more BET (p less than 0.05). No significant differences of the pH value (7.33 +/- 0.08 vs 7.35 +/- 0.10) and bicarbonate values (21.20 +/- 3.99 vs 22.00 +/- 3.83 mM/L) occurred before and after blood exchange transfusion (p greater than 0.1). The serum calcium decreased significantly after BET (3.88 +/- 0.91 vs 3.15 +/- 6.97 mEq/L, p less than 0.05). There were 11 deaths in this series, the mortality rate was 5.7%. Three cases (1.5%) were dead within 6 hours after BET.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilirubin↗
PubMed1989

Angiographic coronary morphology in postinfarction angina.

To investigate the pathophysiologic relevance of angiographically irregular coronary stenoses in postinfarction angina (PIA), we analyzed the clinical course and coronary angiograms of 73 patients studied within 30 days of infarction. Coronary lesions were classified as smooth or irregular. Thirty-six patients had PIA (Group 1) and 37 had an uncomplicated course (Group 2). Irregular lesion(s) in patent infarct-related arteries were found in 77% of Group 1 vs. 24% of Group 2 patients (P less than 0.005). Irregular lesion(s) in any coronary artery were found in 58% of Group 1 versus 19% of Group 2 patients (P less than 0.002). Other univariate predictors of PIA included older age, hypertension, angina before myocardial infarct, lower peak creatine kinase, three-vessel disease, and higher modified Gensini score. Multivariate analysis ranked lesion irregularity as the strongest predictor of PIA. Our data suggests that ruptured atherosclerotic plaques may be important in the pathogenesis of PIA. It is possible that lesion irregularity is associated with an active process and/or a residual thrombus, which may be responsible for postinfarction angina.

Angina Pectoris↗