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Biomedical subjects

D S Fan

Publications and source records attributed to D S Fan.

53 records · Page 3Linked to original sources
PubMed1998

Short-term results of scleral intraocular lens fixation in children.

PURPOSE: To study the safety and efficacy of scleral intraocular lens (IOL) fixation in children. SETTING: A university practice. METHODS: This retrospective review evaluated the results and complications in 6 consecutive eyes of 3 children who had anterior vitrectomy, with or without lensectomy, and scleral IOL fixation to correct ectopia lentis or aphakia. RESULTS: At a mean follow-up of 17.3 months (range 13 to 21 months), all eyes had a stable and well-positioned posterior chamber IOL and good visual improvement. The only complication was asymptomatic pupillary capture of the IOL in 3 eyes. Reversal of the pupillary capture was achieved by pupil dilation with the patient in a supine position. CONCLUSIONS: The preliminary results of scleral IOL fixation in children are encouraging. The procedure's application in well-selected cases can be considered. However, its long-term safety and efficacy must be further assessed through studies with larger sample sizes and a longer follow-up.

Aphakia, Postcataract↗
PubMed1998

Effect of substance P on the short-circuit current of rat nasal mucosal epithelium.

Rats were sensitized by intranasal application of toluene diisocyanate as a nasal allergy model. By means of the Using chamber technique, rat nasal epithelial short-circuit current (Isc) was measured. Enhanced Isc of the rat nasal mucosa resulted from stimulation of substance P (SP) in a dose-dependent manner that could be inhibited by pretreatment with NK1 receptor antagonist CP-96345, the H1 receptor antagonist pyrilamine, the H2 receptor antagonist ranitidine, and the neurotoxin tetrodotoxin, respectively, to different extents. The results indicate that SP is able to cause ion secretion of the nasal mucosal epithelium, perhaps by activating mast cells to release histamine. These data suggest that mast cells and sensory nerves participate in the regulation of SP-induced ion secretion during nasal allergy.

Animals↗
PubMed1997

Ocular-hypertensive response to topical steroids in children.

OBJECTIVE: The purpose of the study is to investigate the rate and degree of ocular-hypertensive response to topical steroids in Chinese children. DESIGN: The study design was an institutional, randomized, clinical trial. PARTICIPANTS: A total of 19 consecutive patients were studied. INTERVENTION: Topical steroids were administered to Chinese children younger than 10 years of age who underwent bilateral strabismus surgery. One eye was randomized to receive topical 0.1% dexamethasone (DMS), whereas the fellow eye received 0.1% fluorometholone (FML) six times per day for up to 4 weeks. Intraocular pressure (IOP) was measured on the day before operation and at postoperative days 1, 3, 6, 10, 13, and 27, then every 2 weeks thereafter until the IOP fell to preoperative levels. Topical steroids would be stopped if IOP was 30.00 mmHg or greater. MAIN OUTCOME MEASURES: Peak IOP and maximal change of IOP from baseline were measured and categorized into low, intermediate, and high levels. Time to peak IOP also was studied. RESULTS: A total of 16 patients were included. The peak IOP for DMS-treated eyes was 30.66 +/- 8.35 mmHg (range, 13.00-48.00 mmHg), whereas that in FML-treated eyes was significantly lower at 20.66 +/- 6.03 mmHg (range, 11.30-36.30 mmHg) (P = 0.001). The maximal change in IOP ranged from -2.60 to +31.00 mmHg in DMS-treated eyes (mean, 15.48 +/- 8.71 mmHg), almost double that of FML-treated eyes (range, +1.00 to +17.00 mmHg; mean, 5.83 +/- 4.96 mmHg) (P = 0.001). When the ocular-hypertensive responses of both DMS and FML groups were categorized into three levels of severity, significant differences were found between the two treatment groups (P = 0.001). In the DMS group, nine patients (56.25%) were high responders and six patients (37.5%) were intermediate responders. In the FML group, only one patient (6.25%) was a high responder. CONCLUSIONS: The ocular-hypertensive response to topical DMS in children occurs more frequently, more severely, and more rapidly than that reported in adults. A total of 56% of the studied children, all younger than 10 years of age, were high responders to topical DMS. Of these, 89% attained their peak IOP within 8 days. Its use in children should best be avoided if possible. It would be desirable to monitor the IOP when it is being used. Conversely, FML produced a much less ocular-hypertensive effect and therefore poses an acceptable risk of clinically significant pressure elevation.

Administration, Topical↗
PubMed1997

The effect of the H2 antagonist cimetidine on the numbers of CD4+ and CD8+ cells in the nasal mucosa of patients with allergic rhinitis.

This paper reports the effects of the H2 antagonist cimetidine on the number of CD4+ and CD8+ cells in nasal mucosa and the IgE level of nasal secretions in patients with allergic rhinitis. The results showed the numbers of CD4+ cells were greater than the numbers of CD8+ cells in nasal mucosa, both in the patients with allergic rhinitis and normal subjects, but the ratio of CD4+:CD8+ cells was much higher in the patients with allergic rhinitis. After treatment with cimetidine locally for 4 weeks, the numbers of CD4+ cells fell and the numbers of CD8+ cells increased in the patients with allergic rhinitis. The high IgE level of nasal secretion of the patients with allergic rhinitis was much reduced after treatment with cimetidine. The results suggest that there are high numbers of CD4+ cells and lower numbers of CD8+ cells in the nasal mucosa and a high level of IgE in the nasal secretions of the patients with allergic rhinitis. Treatment with cimetidine locally may be of some value to relieve the clinical symptoms of allergic rhinitis.

Administration, Intranasal↗
PubMed1994

Myofibrillar Ca2+ sensitization predominantly enhances function and mechanical efficiency of stunned myocardium.

BACKGROUND: Myocardial stunning is characterized not only by a decreased regional postischemic function but also by a relatively high oxygen consumption (ie, decreased mechanical efficiency). Several lines of evidence suggest that the underlying mechanism may involve a decreased sensitivity of the myofibrils to calcium, but in vivo evidence is lacking. We therefore evaluated this hypothesis in vivo using EMD 60263, a calcium-sensitizing agent, which is devoid of any phosphodiesterase-inhibiting properties. METHODS AND RESULTS: We first established the effect of two consecutive doses of EMD 60263 (0.75 and 1.5 mg/kg i.v., n = 7), administered at 15-minute intervals, on segment length shortening (SLS), external work index (EW; the area inside the left ventricular pressure-segment length loop), myocardial oxygen consumption (MVO2), and mechanical efficiency (EW/MVO2) in anesthetized pigs with normal myocardium. After the highest dose of EMD 60263, SLS in the distribution area of the left anterior descending coronary artery (LADCA) increased from 13 +/- 1% at baseline to 17 +/- 1% (P < .05). However, EW, MVO2, and EW/MVO2 were not significantly affected (123 +/- 10%, 98 +/- 9%, and 85 +/- 13% of baseline, respectively). In 14 other anesthetized pigs, myocardial stunning was induced by two sequences of 10 minutes of LADCA occlusion and 30 minutes of myocardial reperfusion. After induction of stunning, the two doses of EMD 60263 (n = 7) or saline (3 and 6 mL, n = 7) were infused. In the distribution area of the LADCA, the stunning protocol caused decreases in SLS from 16 +/- 1% to 8 +/- 1% (P < .05) and in EW to 49 +/- 5% of baseline (P < .05), whereas MVO2 was only minimally affected (P > .05). Consequently, mechanical efficiency decreased to 59 +/- 8% of baseline (P < .05). Saline infusion did not affect any of these regional myocardial variables, but after administration of EMD 60263 SLS recovered dose-dependently to 15 +/- 2% after the highest dose of the drug. EW and mechanical efficiency also recovered dose-dependently to 89 +/- 4% (P < .05 versus stunning) and to 88 +/- 7% (NS versus baseline) of baseline, respectively. In the not-stunned segment, SLS increased from 15 +/- 2% (at baseline) to 18 +/- 2% (after the highest dose), and EW per beat was not changed significantly. An adrenergic mode of action of EMD 60263 was excluded by blocking the alpha- and beta-adrenergic receptors with phentolamine and propranolol, respectively, 15 minutes before administration of EMD 60263 (ie, 15 minutes into the second reperfusion period) in five additional experiments. In these experiments the EMD 60263-induced increases in SLS and EW were not attenuated. Because EMD 60263 decreased heart rate from 106 +/- 4 to 76 +/- 3 beats per minute (P < .05) in the animals with stunned myocardium, we performed five experiments with the specific negative chronotropic compound zatebradine (UL-FS 49, 0.1 to 0.5 mg/kg) to rule out bradycardia as a factor contributing to the effects of EMD 60263. These zatebradine doses lowered heart rate from 116 +/- 5 to 55 +/- 1 beats per minute (P < .05) but had no effect on SLS of stunned and not-stunned myocardium. CONCLUSIONS: Calcium sensitization affects function and mechanical efficiency of stunned myocardium more profoundly than of not-stunned myocardium, lending support to the hypothesis that Ca2+ desensitization of the myofibrils is involved in myocardial stunning.

Animals↗
PubMed1993

Reliability and accuracy of measurement of transductal gradient by Doppler ultrasound.

Simultaneous continuous wave Doppler echocardiography, aortic and pulmonary artery pressure measurements were performed during cardiac catheterization in 46 patients with patent ductus arteriosus. Doppler-derived systolic, mean and diastolic transductal gradients correlated well with those measured by catheterization, respectively (r = 0.972, SEE = 6.8 mmHg; r = 0.965, SEE = 5.4 mmHg; r = 0.939, SEE = 6.2 mmHg), and there were clinically acceptable agreements between the two technical measurements. It is concluded that Doppler echocardiography is a reliable and accurate technique for noninvasive estimation of transductal gradients.

Adolescent↗
PubMed1993

Quantification of left-side intracardiac pressures and gradients using mitral and aortic regurgitant velocities by simultaneous left and right catheterization and continuous-wave Doppler echocardiography.

Noninvasive determination of left-side intracardiac pressures is of clinical importance in many cardiac diseases. To test the reliability and accuracy of left-side intracardiac pressure measurements by continuous-wave Doppler echocardiography, using left-side valvular regurgitations, 47 patients with mitral regurgitation, with or without associated aortic regurgitation, underwent simultaneous Doppler and left and right catheterization. Doppler-derived left atrial and ventricular end-diastolic pressures were respectively estimated by subtracting mitral regurgitant gradient from systolic blood pressure and by diastolic blood pressure minus aortic regurgitant gradient. There were high correlations of mitral (r = 0.961) and aortic regurgitant gradients (r = 0.896) and of left atrial (r = 0.945) and ventricular end-diastolic pressures (r = 0.854) between noninvasive and invasive measurements. Also, agreement analyses showed that there was close agreement between the two technical measurements for each parameter. The present study concluded that continuous-wave Doppler echocardiography provides a reliable and accurate method for the noninvasive evaluation of left-side intracardiac pressures and gradients in patients with mitral and aortic regurgitations.

Adolescent↗
PubMed1992

[Noninvasive estimation of the pulmonary artery pressures in patent ductus arteriosus with continuous-wave Doppler echocardiography].

To develop a new method for noninvasive measuring of the pulmonary artery pressure (PAP) in patient ductus arteriosus (PDA), left and right heart catheterization (Cath) and continuous-wave Doppler echocardiography (CWD) were performed simultaneously in 30 cases with PDA. The results showed that there was high correlation of the systolic peak pressure gradient (delta pp), the end-diastolic pressure gradient (delta Pd) and the mean pressure gradient (delta Pm), across PDA measured with the two techniques (r = 0.99, 0.96 and 0.98, respectively). The CWD-derived pulmonary artery systolic (PASP), diastolic (PADP) and mean (PAMP) pressure, which were estimated by subtracting delta Pp, delta Pd and delta Pm from the brachial artery systolic, diastolic and mean pressure, correlated well with the corresponding PAP measured with Cath (r = 0.92, 0.89 and 0.94, respectively). It is concluded that CWD offers a reliable technique for estimating shunt pressure gradients and PAP in patients with PDA.

Adolescent↗
PubMed1989

[Pulsed Doppler echocardiographic findings in 100 normal Chinese fetuses].

To evaluate the feasibility and reliability of Doppler echocardiography in assessing fetal hemodynamics, pulsed Doppler echocardiography was performed in 100 normal Chinese fetuses and blood flow velocities through atrioventricular and semilunar valves were measured. The success rate in recording the maximal velocities were 76% for mitral flow, 86% for tricuspid flow, 94% for aortic flow and 49% for pulmonary flow. The flow velocities increased with fetal developments, and the increase became significant after 26 gestational weeks when the fetuses were in acceleration of growth. The maximal velocity (Vp) and velocity integral (VI) of flow through the tricuspid valve were significantly higher than those through mitral valve. Although there was no significant difference of Vp and VI in the flow between aortic and pulmonary valves, the ratio of acceleration time to ejection time (AT/ET) of flow through the pulmonary valve was significantly lower than that through the aortic valve.

Blood Flow Velocity↗
PubMedDate not supplied

Congenital hypertrophy of the retinal pigment epithelium and APC mutations in Chinese with familial adenomatous polyposis.

Mutations in the adenomatous polyposis coli gene (APC) often cause both congenital hypertrophy of the retinal pigment epithelium (CHRPE) and familial adenomatous polyposis (FAP). To investigate the relationship between APC mutations, CHRPE and FAP, all FAP patients at the Prince of Wales Hospital, Hong Kong, were asked to participate in a study. Ten Chinese patients from 6 kindreds and their family members volunteered, along with 12 healthy control subjects selected among hospital visitors and staff. All were examined for dilated fundus by indirect ophthalmoscopy. Mutations in APC coding exons were detected by sequencing. In one FAP patient, a novel A insertion at codon 1023 was detected. Three previously reported mutations were detected in 6 FAP patients: a deletion of ACAAA at codon 1061, and 2 truncating point substitutions at codons 216 and 283. In 3 FAP patients, no APC mutation was found, suggesting that mutations in APC coding regions are not the sole cause of FAP or CHRPE. A total of 64 CHRPE lesions were found in FAP patients and some relatives with and without APC mutations. Contrary to most reports, APC mutations before exon 9 did cause CHRPE lesions, albeit relatively few.

Adenomatous Polyposis Coli↗
PubMedDate not supplied

The electrophysiological study of differential diagnosis between amyotrophic lateral sclerosis and cervical spondylotic myelopathy.

Sternocleidomastoid muscle EMG (SCM-EMG) and dermatomal somatosensory evoked potential (DSSEP) were evaluated as diagnostic aids in differentiation between amyotrophic lateral sclerosis (ALS) and cervical spondylotic myelopathy (CSM) in this study. 104 inpatients were divided into three groups: those diagnosed clinically as either (A) ALS (36 cases), or (B) CSM (32 cases) and (C) those needed further investigation (36 cases). EMG of limb muscles and sternocleidomastoid of both sides in all, and of tongue muscles in 58/104 of three groups; DSSEP in 56/104 of all three groups; MRI/CTM in 12/36 of group A and all patients of group B and C. SCM-EMG abnormal in 34/36 of group A but normal in all 32 of group B. SCM-EMG also abnormal in 32/36 of group C and 8 of them showed postoperative aggravation. DSSEP normal in 12/12 of group A while abnormal in 19/20 of group B. DSSEP abnormal only in 6/24 of group C. MRI/CTM showed spinal compression in all cases presenting abnormal DSSEP and close correspondence between upper margins of pathological involvement as revealed using these two methods. Both SCM-EMG and DSSEP have proved to be valuable differential aids between ALS and CSM.

Adolescent↗