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Biomedical subjects

L C Chen

Publications and source records attributed to L C Chen.

At least 217 records · Page 12Linked to original sources
PubMed1972

Permeability and selectivity of canine and human jejunum during cholera.

Increased permeability of the intestinal mucosa to small molecules and ions has previously been proposed as a mechanism causing the profuse diarrhoea characteristic of Asiatic cholera. A technique for measuring absorption rates of (14)C-urea and (3)H-arabinose has been employed to study jejunal permeability during experimental canine and naturally acquired human cholera. The ratio of the absorption rates of these two solutes of different size is an expression of intestinal membrane selectivity and permits calculation of an equivalent pore radius. No change of membrane selectivity was observed in canine loops after challenge with cholera toxin. During naturally acquired human cholera, jejunal pore size was not significantly different from that measured during convalescence. This method was demonstrated to be sensitive to changes induced by amphotericin B, an antibiotic known to alter membrane permeability and selectivity. These data are inconsistent with the hypothesis of increased intestinal permeability during cholera.

Amphotericin B↗
PubMed1972

Effect of spironolactone on stool electrolyte losses during human cholera.

This study demonstrated that endogenous aldosterone, as determined by its transient competitive block by spironolactone, caused significant sodium and chloride retention during naturally acquired cholera. This beneficial effect of the hormone is accompanied, however, by a deleterious depletion of potassium. In addition, it was found that stool rate significantly altered the sodium and potassium concentrations in cholera stool despite minimal or absent aldosterone activity.

Adult↗
PubMed1972

Properties of adenyl cyclase from human jejunal mucosa during naturally acquired cholera and convalescence.

The enterotoxin of Vibrio cholerae causes copious fluid production throughout the lenght of the small intestine. As this is thought to be mediated by stimulation of adenyl cyclase, a study has been made of the activity and properties of this enzyme in jejunal biopsy tissue taken from patients during the diarrheal phase of cholera and after recovery. Adenyl cyclase activity during cholera was increased more than twofold relative to the enzyme in convalescence. Under both conditions stimulation by prostaglandin E(1) (PGE(1)) and by fluoride was observed. The responsiveness to PGE(1) was not altered in cholera; the total activity of the fluoride-stimulated enzyme was similar, a finding that suggests cholera toxin stimulates pre-existing enzyme in the intestinal cell. The enzymes during cholera and convalescence were similar in all other properties examined. Optimal Mg(++) concentration was 10 mM; Mn(++) at 5 mM stimulated the enzyme but could not replace Mg(++) except in the presence of 10 mM fluoride. Calcium was markedly inhibitory at concentrations greater than 10(-4) M. The pH optimum was 7.5 and the Michaelis constant (K(m)) for ATP concentration approximated 10(-4) M. Thus the interaction of cholera toxin with human intestinal adenyl cyclase does not alter the basic properties of the enzyme. When biopsy specimens were maintained intact in oxygenated Ringer's solution at 0 degrees C, no loss of activity was observed at 1(1/2) and 3 hr. In contrast, when the cells were homogenized, rapid loss of activity, with a half-life of 90 min was seen even at 0 degrees C. Consequently for comparative assays of human jejunal adenyl cyclase, strict control of the experimental conditions is required. It was under such conditions that a twofold increase in basal adenyl cyclase activity during cholera was observed.

Adenosine Triphosphate↗
PubMedDate not supplied

The 5S rRNA and the rRNA intergenic spacer of the two varieties of Cryptococcus neoformans.

The intergenic spacers (IGS) separating the 23S-like and 16S-like rDNAs of the two varieties of the human pathogenic fungus Cryptococcus neoformans were amplified, cloned and sequenced. The C. neoformans var. neoformans IGS was 2421 nt with 5S rRNA at positions 1228-1345 3' of the 23S-like rRNA. The C. neoformans var. gattii IGS was 2480 nt with 5S rRNA at positions 1268-1385 3' of the 23S-like rRNA. For both varieties the 5S rDNA genes were in the same orientation as the 16S-5.8-23S genes and encode a 118 nt molecule of identical sequence. Phylogenetic comparison of C. neoformans 5S rDNA with that of other fungi placed this fungus in close relationship with other basidiomycetes including Tremella mesenterica, Bullera alba, and Cryptococcus laurentii. A secondary structure model for the deduced 5S rRNA was constructed by comparative sequence analysis. Polymerase chain reaction-amplified IGS of 12 C. neoformans var. neoformans strains revealed extensive size variation ranging from 100 to 300 nt. Size variation between strains in the length of the IGS may be useful for distinguishing strains. Structurally, the IGS were characterized by the presence of occasional short direct GC-rich 19-nt repeats. Overall IGS sequence identity between the C. neoformans varieties was only 78.5%, in sharp contrast to the identical or nearly identical sequences for the rDNA genes, and suggests rapid evolution for IGS sequences.

Base Sequence↗
PubMedDate not supplied

Physiological and histological alterations in the bronchial mucociliary clearance system of rabbits following intermittent oral or nasal inhalation of sulfuric acid mist.

Rabbits were exposed to submicometer sulfuric acid mist (H2SO4) for 1 h/d, 5 d/w for 4 wk, during which time mucociliary clearance was monitored by external in vivo measurements of tagged tracer aerosol retention. One group was exposed orally to 250 micrograms/m3, another to the same concentration via the nose, and a third to 500 micrograms/m3 also via nasal breathing. Clearance was accelerated on specific individual days during the course of the acid exposures, especially at 500 micrograms/m3. In all series, clearance was significantly faster, compared to preexposure controls, during a 2-wk follow-up period after acid exposures had ceased. At the end of this period, the rabbits were sacrificed, and histological sections were obtained from the tracheobronchial tree. Significantly increased epithelial thickness of small conducting airways, compared to sham exposure controls, occurred in rabbits exposed orally at 250 micrograms/m3 or nasally at 500 micrograms/m3, and additionally the lumen of the smallest airways of the former group was narrower than control. The number of airways containing epithelial secretory cells was also significantly greater in these acid exposure groups compared to sham controls. The only change in the rabbits exposed nasally at 250 micrograms/m3 was a significant increase in the number of airways with epithelial secretory cells in the smallest airway classification. The histological alterations provide a basis for observed changes in clearance, and are similar to those found in chronic bronchitis in humans and experimental animals. Differences in site and degree of histological response and degree of physiological change between the two groups exposed to identical acid concentrations appear to have been due to differences in exposure mode, with resultant effects on breathing pattern, aerosol size distribution, and concentration penetrating beyond the upper respiratory tract to specific lung sites.

Aerosols↗
PubMedDate not supplied

Alteration of pulmonary macrophage intracellular pH following inhalation exposure to sulfuric acid/ozone mixtures.

Recent studies have demonstrated that additive and synergistic effects on rabbit pulmonary macrophages (PM phi) function can occur after combined exposures to acid aerosols and ozone. This study investigated intracellular pH (pHi) homeostasis and H+ extrusion mechanisms of PM phi from rabbits exposed to sulfuric acid, ozone, and their mixtures. Animals were exposed for 3 h to 125 micrograms/m3 sulfuric acid, 0.1, 0.3, 0.6 ppm ozone, or combinations of acid with each concentration of ozone, and the pHi was determined by a fluorescent dye ratioing technique. Exposure to 125 micrograms/m3 acid reduced pHi and exposure to ozone resulted in a concentration-dependent reduction in pHi. Ozone generally tended to mitigate the effect of the acid aerosol on pHi. Other groups of rabbits were exposed to 50 micrograms/m3 sulfuric acid, 0.6 ppm ozone, or their mixture, for 3 h, and PM phi were again harvested. The pHi of PM phi following exposure to each of the pollutant atmospheres was not different from control. However, H+ extrusion with an imposed internal acid load was found to be significantly depressed following exposure to either sulfuric acid or ozone alone, while the mixture produced a significant interaction.

Administration, Inhalation↗
PubMedDate not supplied

Intractable wheezing and swallowing problem in an infant: report of one case.

A 9-month-old female infant with intractable wheezing and frequent aspiration pneumonia was poor response to the usual treatment for respiratory disease. The barium swallow test revealed barium aspirating into trachea directly. Because of the high-risk nature for aspiration in the swallowing disorder infant, a nasogastric tube feeding therapy was prescribed. Fortunately, her symptoms were greatly reduced. One month later, the clinical and roentgenographic findings strongly support a causal relationship between swallowing problem and wheezing. Therefore, swallowing problem should be considered when a young infant has refractory wheezing, even when there is no developmental problem.

Deglutition Disorders↗
PubMedDate not supplied

Diagnosis of anomalous innominate artery syndrome by spiral CT with 3D reconstruction of the airway: report of one case.

Stridor in infants is a symptom that indicates partial obstruction of the large airways. Vascular rings are an unusual cause of tracheal compression which can induce stridor in infants and children. We report a 4-month-old boy with recurrent wheezing and stridor for 2 months. Spiral computed tomography (CT) and three-dimensional (3D) reconstruction aided in the diagnosis of external compression on the trachea by an innominate artery. Successful relief of the airway's obstruction was achieved by aortopexy. Three months after surgery, he was symptom free without any medication.

Aorta, Thoracic↗
PubMedDate not supplied

Intraarticular triamcinolone hexacetonide injection in children with chronic arthritis: a survey of clinical practice.

To assess the efficacy of the intraarticular steroid(IAS) injection in the management of arthritis and the possible related complications in children with chronic arthritis. We evaluated 11 children of chronic arthritis (4 girls and 7 boys), age of onset ranged from 2-13.6 years, who had persistent arthritis treated with IAS from November 1994 to June 1997. The results of injections showed that the beneficial effect was noted within one day to 2 weeks without significant adverse reactions, remission exceeding 6 months was seen in 10 of 11 patients (in 14 of 18 joints). According to subgroups of chronic arthritis, the remission rate of IAS injection in children with pauciarticular arthritis reached 100%. A significant fall in C-reactive protein (CRP) between pre- and post-IAS injection (p = 0.03), but there were no differences in hemoglobin (Hb), white blood cells (WBCs), thrombocytes (Plts), erythrocyte sedimentation rate (ESR) and osteocalcin level. No injection-related complications were found. In conclusion, the IAS injection was an effective and safe treatment in children with chronic arthritis with no obvious complications especially in pauciarticular arthritis.

Adolescent↗
PubMedDate not supplied

Sequential changes to clinical parameters and adhesion molecules following intravenous pulse cyclophosphamide and methylprednisolone treatment of refractory juvenile idiopathic arthritis.

It is believed that the systemic subtype and the positive rheumatoid factor, polyarticular subtype of juvenile idiopathic arthritis (JIA) show the least favorable outcomes for therapy; patients with systemic JIA are often resistant to recommended therapeutic modalities. We report the sequential changes to clinical and laboratory findings from pulse therapy with monthly intravenous cyclophosphamide (0.5 g/m2 body surface area) administration combined with methylprednisolone (30 mg/kg; 1 gm maximum) for 6 months, following which the medication interval was elongated to 3 months for a total of from 7 to 12 courses. Among 4 children suffering from refractory systemic JIA, 3 demonstrated clinical improvement, 2 of whom achieved clinical remission. Furthermore, we also adminstered this therapy to a girl suffering from refractory polyarticular JIA, following which she revealed clinical remission subsequent to 9 courses of such therapy. From our experience, we suggest that patients afflicted with JIA that is unresponsive to traditional medication may experience benefit from this type of pulse therapy.

Adolescent↗