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Biomedical subjects

Y J Lin

Publications and source records attributed to Y J Lin.

At least 73 records · Page 4Linked to original sources
PubMed1997

Left atrial spontaneous echo contrast in patients with permanent pacemakers.

OBJECTIVE: To determine the relations between left atrial appendage function, spontaneous echo contrast, and thromboembolism in patients with different modes of permanent pacemakers. PATIENTS AND METHODS: 88 patients with pacemaker implantation and 25 healthy controls in sinus rhythm had transoesophageal echocardiographic examination of the left atrial appendage. Left atrial size, appendage area, peak filling and emptying velocities of the atrial appendage, and the presence or absence of spontaneous echo contrast and thromboembolism were determined. The results in 63 patients with ventricular pacing (group 1, subdivided into subgroup 1A: 42 patients with sinus rhythm, and subgroup 1B: 21 patients with atrial fibrillation) were compared with those in 25 patients with synchronous pacing (group 2), and 25 normal control subjects (group 3). RESULTS: Patients with ventricular pacing had two distinct appendage flow patterns: well defined biphasic filling and emptying waves in subgroup 1A, and irregular very low filling and emptying waves in subgroup 1B. The ejection fraction of the left atrial appendage in subgroup 1A was significantly better than that in subgroup 1B (mean (SD) 40.6 (12.0)% v 7.6 (5.0)%, P < 0.0001). The spontaneous echo contrast was observed in 90% of subgroup 1B patients but in only 19% in subgroup 1A (P < 0.05) and was not found in groups 2 and 3 (P < 0.0001). There was a trend for increased prevalence of spontaneous echo contrast in subgroup 1A v group 2 (P = 0.053). Thrombi were detected in two cases, and cardiogenic embolism occurred in one case in subgroup 1B. All patients with spontaneous echo contrast had ventricular pacing. Multivariate analysis showed that atrial fibrillation was associated with occurrence of spontaneous echo contrast in patients with ventricular pacing (P = 0.005). CONCLUSIONS: The left atrial appendage ejection fraction was lower with ventricular pacing than with synchronous pacing. With ventricular pacing there was a trend towards increased prevalence of left atrial spontaneous echo contrast in patients in sinus rhythm, and a significantly increased prevalence in patients with atrial fibrillation.

Adult↗
PubMed1997

Cardiac output and mixed venous oxygen content measurements by a tracer bolus method: theory.

We present a bolus method of inert-gas delivery to the lungs that facilitates application of multiple inert gases and the multiple inert-gas-exchange technique (MIGET) model to noninvasive measurements of cardiac output (CO) and central mixed venous oxygen content Reduction in recirculation error is made possible by 1) replacement of sinusoidal input functions with impulse inputs and 2) replacement of steady-state analyses with transient analyses. Recirculation error reduction increases the inert-gas selection to include common gases without unusually high (and difficult to find) tissue-to-blood partition coefficients for maximizing the systemic filtering efficiency. This paper also presents a practical method for determining the recirculation contributions to inert expired profiles in animals and determining their specific contributions to errors in the calculations of CO and from simulations applied to published ventilation-perfusion ratio (V/Q) profiles. Recirculation errors from common gases were found to be reducible to the order of 5% or less for both CO and whereas simulation studies indicate that measurement bias contributions from recirculation, V/Q mismatch, and the V/Q extraction process can be limited to 15% for subjects with severe V/Q mismatch and high inspired oxygen fraction levels. These studies demonstrate a decreasing influence of V/Q mismatch on parameter extraction bias as the number of inert gases are increased. However, the influence of measurement uncertainty on parameter extraction error limits improvement to six gases.

Animals↗
PubMed1997

Intracellular pH regulation in cultured human pleural mesothelial cells.

The human pleural space is lined by a single layer of mesothelial cells, the intracellular pH (pH(i)) of which has never been investigated. In the present study, the intrinsic buffering power of H+ ions (beta(i)) and the pH(i) regulatory systems were investigated in primary cultures of human pleural mesothelial cells (PMCs) with microspectrofluorimetry. We found: (1) that at the resting pH(i), the beta(i) was low and increased as the pH(i) decreased; (2) that the pH(i) recovery was largely inhibited either with Na+-free medium or nominally HCO3 free medium containing ethyl-isopropyl amiloride (EIPA); (3) a 4-4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive, Na+/HCO3-dependent, but Cl(-)-independent acid extrusion mechanism in CO2/HCO3 buffer; and (4) that in the same buffer, a DIDS- sensitive but Na+-independent alkalosis was induced by intracellular Cl- depletion. We therefore conclude that at least three membrane pH(i) regulators are involved in regulating the pH(i) in PMCs, these being the EIPA-sensitive Na+-H+ exchanger; a novel electroneutral, DIDS-sensitive Na+-HCO3 cotransporter; and the DIDS-sensitive Cl(-)-HCO3 exchanger. Furthermore, under physiologic conditions, the Na+-HCO3 cotransporter plays a more important role in extrusion of excess intracellular H+ ions than does the Na+-H+ exchanger.

Amiloride↗
PubMed1997

Early postnatal dexamethasone therapy for the prevention of chronic lung disease in preterm infants with respiratory distress syndrome: a multicenter clinical trial.

OBJECTIVES: To study whether early postnatal (<12 hours) dexamethasone therapy reduces the incidence of chronic lung disease in preterm infants with respiratory distress syndrome. MATERIALS AND METHODS: A multicenter randomized, double-blind clinical trial was undertaken on 262 (saline placebo, 130; dexamethasone, 132) preterm infants (<2000 g) who had respiratory distress syndrome and required mechanical ventilation shortly after birth. The sample size was calculated based on the 50% reduction in the incidence of chronic lung disease when early dexamethasone is used, allowing a 5% chance of a type I error and a 10% chance of a type II error. For infants who received dexamethasone, the dosing schedules were: 0.25 mg/kg/dose every 12 hours intravenously on days 1 through 7; 0.12 mg/kg/dose every 12 hours intravenously on days 8 through 14; 0.05 mg/kg/dose every 12 hours intravenously on days 15 through 21; and 0. 02 mg/kg/dose every 12 hours intravenously on days 22 through 28. A standard protocol for respiratory care was followed by the participating hospitals. The protocol emphasized the criteria of initiation and weaning from mechanical ventilation. The diagnosis of chronic lung disease based on oxygen dependence and abnormal chest roentgenogram was made at 28 days of age. To assess the effect of dexamethasone on pulmonary inflammatory response, serial tracheal aspirates were assayed for cell counts, protein, leukotriene B4, and 6-keto prostaglandin F1alpha. All infants were observed for possible side effects, including hypertension, hyperglycemia, sepsis, intraventricular hemorrhage, retinopathy of prematurity, cardiomyopathy, and alterations in calcium homeostasis, protein metabolism, and somatic growth. RESULTS: Infants in the dexamethasone group had a significantly lower incidence of chronic lung disease than infants in the placebo group either judged at 28 postnatal days (21/132 vs 40/130) or at 36 postconceptional weeks (20/132 vs 37/130). More infants in the dexamethasone group than in the placebo group were extubated during the study. There was no difference between the groups in mortality (39/130 vs 44/132); however, a higher proportion of infants in the dexamethasone group died in the late study period, probably attributable to infection or sepsis. There was no difference between the groups in duration of oxygen therapy and hospitalization. Early postnatal use of dexamethasone was associated with a significant decrease in tracheal aspirate cell counts, protein, leukotriene B4, and 6-keto prostaglandin F1alpha, suggesting a suppression of pulmonary inflammatory response. Significantly more infants in the dexamethasone group than in the placebo group had either bacteremia or clinical sepsis (43/132 vs 27/130). Other immediate, but transient, side effects observed in the dexamethasone group are: an increase in blood glucose and blood pressure, cardiac hypertrophy, hyperparathyroidism, and a transient delay in the rate of growth. CONCLUSIONS: In preterm infants with severe respiratory distress syndrome requiring assisted ventilation shortly after birth, early postnatal dexamethasone therapy reduces the incidence of chronic lung disease, probably on the basis of decreasing the pulmonary inflammatory process during the early neonatal period. Infection or sepsis is the major side effect that may affect the immediate outcome. Other observable side effects are transient. In view of the significant side effects and the lack of overall improvement in outcome and mortality, and the lack of long term follow-up data, the routine use of early dexamethasone therapy is not yet recommended.

Chronic Disease↗
PubMed1997

Seroepidemiological study of measles after the 1992 nationwide MMR revaccination program in Taiwan.

The incidence of measles declined rapidly in Taiwan after the introduction of the measles vaccine into the routine immunization schedule in 1978. However, an epidemic still occurred every 3-5 years until recently. A nationwide measles-mumps-rubella (MMR) revaccination program for school and preschool children has been in place since 1992 to control the indigenous transmission of measles. In order to understand the current immune status after this recent nationwide revaccination program, we determined the presence of measles IgG antibodies by enzyme-linked immunosorbent assay (ELISA) in 1,281 blood samples from healthy persons aged from 2 months to above 30 years collected between 1993 and 1995, and also in another batch of 90 sera samples from children aged 2 years collected before 1992. The results showed that 1) the measles antibody seropositive rate (36.4%) was lowest in children aged 5-7 months and rose to an unexpectedly high level of 85.8% at the age of 12-14 months, 2) the seropositive rate rose further to between 85.9% and 95.1% after 2 years of age and remained high in adults and pregnant women, and 3) the seropositive rate of the 2-year-old children collected before 1992 was 61.4%, which was significantly lower than the rate of the same age group collected after the nationwide MMR revaccination program. We conclude that the national revaccination program has promoted effectively measles immunity in Taiwan. This immunity explains the rarity of reported measles cases since the last epidemic in 1989. This revaccination program should continue and be extended to all preschool children and young adults so that indigenous measles can be eliminated by the year 2000.

Adult↗
PubMed1997

Safety and immunogenicity of a conjugated Haemophilus influenzae type B polysaccharide-Neisseria meningitidis outer membrane protein vaccine.

This study was performed to determine the immunogenicity and safety of a conjugate Haemophilus influenzae type b (Hib) vaccine (PedvaxHIB:Merck Sharp & Dohme Inc, West Point, PA, USA) in Taiwanese children. There were two groups in this study. Group A included 56 infants at 2 months of age, who received an initial dose of Hib conjugate vaccine at age 2 months and 4 months. Another booster dose was given between 12 and 15 months of age. Group B included 58 children, aged 11 to 14 months, who were vaccinated at the time of enrollment and 2 months after the first vaccination. The results showed that this Hib conjugate vaccine was highly immunogenic with 100% and 86% of vaccinees in group A developing anti-Hib polyribosylribitol phosphate (PRP) antibody titers above 0.15 microgram/mL and 1 microgram/mL, respectively, after two vaccinations. A slightly better response rate was observed in group B, with 100% and 97% of vaccinees developing antibody titers above 0.15 microgram/mL and 1 microgram/ml, respectively, after two vaccinations. A significant booster effect was seen in group A; the proportion of subjects with antibody titers above 1 microgram/mL increased from 38% to 95%, and the geometric mean titer increased from 0.68 microgram/mL to 11.92 micrograms/mL. Adverse reactions were uncommon. Mild reactions consisted of low-grade fever and local discomfort. We conclude that the Hib conjugate vaccine is highly immunogenic and safe when given to Taiwanese children as young as 2 months of age.

Antibodies, Bacterial↗
PubMed1997

Phrenic nerve transfer in the repair of brachial plexus injuries: an animal model.

UNLABELLED: Ten young mongrel dogs underwent unilateral denervation of the brachial plexus. In six dogs, a 2-cm segment of phrenic nerve autograft was sutured to either the resected musculocutaneous nerve or the radial nerve. A hemoclip was applied to either musculocutaneous or radial nerve in the control groups. Five months postoperatively, the grafted musculocutaneous nerve demonstrated less fibrous tissue and less muscle atrophy of the biceps when compared to the control group with clipped nerve. In the group with the grafted radial nerve, the electromyographic findings of multiphasic action potential and muscle contraction from electric stimulation suggested reinnervation of the radial nerve. IN CONCLUSION: phrenic nerve transfer may be used to repair specific damages to nerve trunk with histological, electromyographic and clinical recovery.

Animals↗
PubMed1997

Endogenous regulation of angiogenesis in the rat aorta model. Role of vascular endothelial growth factor.

The purpose of this study was to investigate the role of vascular endothelial growth factor (VEGF) in the rat aorta model of angiogenesis. Freshly cut aortic rings generated microvascular outgrowths in serum-free collagen gel culture. Angiogenesis was reduced to 10% when the explants were embedded in collagen 10 to 14 days after excision from the animal. Immunochemical studies of conditioned medium demonstrated secretion of VEGF by the aortic cultures. Levels of VEGF decreased during the second week of culture when the explants became quiescent and microvessels stopped growing. Treatment of quiescent aortic rings with exogenous VEGF stimulated angiogenesis and restored microvascular growth to values observed in cultures of freshly cut explants. Reverse transcriptase polymerase chain reaction of vasoformative collagen gel cultures of rat aorta demonstrated the expression of the alternatively spliced isoforms VEGF165, VEGF189, and the high affinity VEGF receptor flk-1. Reverse transcriptase-polymerase chain reaction of rat aorta-derived cell strains confirmed the presence of VEGF165 and VEGF189 in endothelial cells, smooth muscle cells, and fibroblasts. The flk-1 receptor was expressed by endothelial cells but not by fibroblasts or smooth muscle cells, which is consistent with the endothelial target specificity of VEGF. The spontaneous angiogenic response of freshly cut aortic rings was inhibited by 70% with a neutralizing antibody against VEGF, whereas nonimmune IgG had no effect (P < 0.001). These findings provide evidence for a VEGF-mediated autocrine/paracrine regulation of angiogenesis in the rat aorta model.

Animals↗
PubMed1997

Heterochromatin (chromocentres) and regeneration of invertebrates and vertebrates: a correlation.

Previous investigations using several species of invertebrates have indicated a correlation between nuclear chromocentre content and the ability to regenerate. Such findings have resulted in the formulation of the hypothesis that the ability to regenerate may be dependent on cellular heterochromatin content. In order to test this concept further, a number of additional invertebrates were stained for heterochromatin (nuclear chromocentres). In accordance with the hypothesis, each species tested was found to contain numerous chromocentres. Many chromocentres were also found in cells of several vertebrates capable of partial regeneration, thereby extending the hypothesis to vertebrate regeneration. These findings provide additional supporting evidence for a correlation between cellular heterochromatin and the ability to regenerate.

Amphibians↗
PubMed1996

Cloning of the cDNA for the human NMDA receptor NR2C subunit and its expression in the central nervous system and periphery.

Several overlapping cDNA clones containing 3995 nucleotides of the human 2C NMDA receptor subunit (NR2C) were isolated from human hippocampal and cerebellar cDNA libraries. The nucleic acid sequence of the overlapping cDNA clones displays 85% identity to that of rat NR2C. The predicted protein sequence is 1233 amino acids long and has 88% identity to the amino acid sequence of the rat NR2C, Northern blot analysis has demonstrated a wide distribution pattern of the NR2C transcript in the brain. While the predominant expression is in the cerebellum, as observed in the rat, readily detectable levels are present in the hippocampus, amygdala, caudate nucleus, corpus callosum, subthalamic nuclei and thalamus. NR2C was also detected in the heart, skeletal muscle and pancreas. Distribution of the mouse NR2C NMDA receptor subunit homologue was investigated in mouse brain by in situ hybridization histochemistry using exonic genomic probes. Expression of the transcript was principally in the cerebellum, but is also detected in the hippocampus, dentate gyrus, thalamic and subthalamic nuclei, vestibular nuclei and olfactory bulb. These results demonstrate a widespread expression pattern of the NR2C gene, both in the CNS and in the periphery.

Amino Acid Sequence↗
PubMed1996

Left atrial spontaneous echo contrast in asymptomatic patients with a mechanical valve prosthesis.

BACKGROUND: Valve thromboembolism may be a fatal complication of mechanical valve prosthesis if detected late. Spontaneous echo contrast (SEC) is a well-documented prothrombotic phenomenon; here we report it in asymptomatic patients with a mechanical valve prosthesis. METHODS: Ninety-two asymptomatic patients with a mechanical valve prosthesis for underlying rheumatic heart disease underwent transesophageal echocardiography. Appendage area, peak filling and emptying velocities of the left atrial appendage, and the presence or absence of SEC and thrombi were determined. The results of 56 patients without SEC or thrombi (group I) were compared with those of 24 patients with SEC and no thrombi (group II) and 12 patients with thrombi (group III). RESULTS: Spontaneous echo contrast was present in 39% of the asymptomatic patients with a mechanical valve prosthesis. Although 12 patients had cardiac thrombi, including valve thrombi in 4, no patients presented symptoms. Anticoagulant therapy had no significant association with SEC and atrial thrombi. There was a significantly greater prevalence of atrial fibrillation and mitral prosthesis in groups II and III than in group I. Two patterns of left atrial appendage flow were identified: one was organized biphasic flow with peak filling velocities of 41.2 +/- 17.2 cm/s and emptying velocities of 40.5 +/- 17.5 cm/s. The other showed irregular, very low peak filling velocities (104 +/- 11.5 cm/s) and emptying velocities (12.3 +/- 13.1 cm/s). The former flow pattern was associated with sinus rhythm and the latter form was associated with atrial fibrillation. CONCLUSIONS: There was a relatively high prevalence of SEC and thrombi in patients with a mechanical valve prosthesis. Patients with a valve prosthesis may not have clinical symptoms. Anticoagulation intensity was not associated with the occurrence of SEC and thrombi. Patients with the mitral valve prosthesis and atrial fibrillation were identified as a high-risk of subgroup for the development of SEC and thrombi.

Adult↗
PubMed1996

The etiology of lung cancer in nonsmoking females in Harbin, China.

A case-control study of female lung adenocarcinoma in Harbin, China involving interviews with 120 cases of nonsmoking females, matched 1:1 with controls, showed that high coal use, indoor air pollution, exposure to coal dust, frequent frying and deep frying food, and a history of lung cancer in the family were statistically significant risk factors for female adenocarcinoma. High personal income, spacious living quarters, and frequent consumption of carrots were protective factors for adenocarcinoma.

Adult↗
PubMed1996

Primary hemangiopericytoma in the axis bone: case report and review of literature.

OBJECTIVE AND IMPORTANCE: To the best of our knowledge, this is the first reported case of primary hemangiopericytoma in the axis bone. With this report, we attempt to better characterize this uncommon lesion in the vertebral column. CLINICAL PRESENTATION: This report describes a case of primary heman-giopericytoma in the axis bone of a 16-year-old female patient who presented with acute torticollis. Her neurological status was unimpaired. A lateral radiograph of the cervical spine demonstrated an odontoid neck fracture and a C1-C2 rotatory deformity. The magnetic resonance imaging study showed a hypodense lesion with moderate enhancement on T1- and T2-weighted images on the dens and body of the axis with an odontoid neck fracture. Reviewing the literature, primary hemangiopericytoma in the spine is rare; 9 cases of hemangiopericytoma with vertebral bone involvement and 44 cases of this tumor with intraspinal meningeal involvement have been reported. INTERVENTION: The patient was treated with odontoidectomy via the transoral approach, along with posterior fixation using the Halifax clamp. She was followed up 17 months after surgery, and no evidence of tumor recurrence was found. CONCLUSION: The treatment for osseous hemangiopericytoma is still controversial. At present, adequate surgical removal with postoperative radio-therapy is recommended. In addition, although hemangiopericytoma is rare in the spine, it should be kept in mind in the differential diagnosis of spinal tumors.

Adolescent↗
PubMed1996

The 3' untranslated region of coronavirus RNA is required for subgenomic mRNA transcription from a defective interfering RNA.

The 3'-end of mouse hepatitis virus (MHV) genomic RNA contains a recognition sequence (55 nucleotides [nt]) required for minus-strand RNA synthesis. To determine whether the 3'-end sequence is also involved in subgenomic mRNA transcription, we have constructed MHV defective interfering (DI) RNAs which contain a chloramphenicol acetyltransferase (CAT) gene placed behind an intergenic sequence and a 3'-end sequence with various degrees of internal deletions. The DI RNAs were transfected into MHV-infected cells, and CAT activities, which represent subgenomic mRNA transcription from the intergenic site, were determined. The results demonstrated that the deletions of sequence upstream of the 350 nt at the 3'-end, which include the 3'-untranslated region (3'-UTR), of MHV genomic RNA did not affect subgenomic mRNA transcription. However, deletions that reduced the 3'-end sequences to 270 nt or less completely abolished the mRNA transcription despite the fact that all of these clones synthesized minus-strand RNAs. These results indicated that mRNA transcription from an intergenic site in the MHV DI RNA requires most of the 3'-UTR as a cis-acting signal, which likely exerts its effects during plus-strand RNA synthesis. A substitution of the corresponding bovine coronavirus sequence for the MHV sequence within nt 270 to 305 from the 3'-end abrogated the CAT gene expression, suggesting a very rigid sequence requirement in this region. The deletion of a putative pseudoknot structure within the 3'-UTR also abolished the CAT gene expression. These findings suggest that the 3'-UTR may interact with the other RNA regulatory elements to regulate mRNA transcription.

Animals↗
PubMed1996

Permeation and block of dopamine-modulated potassium channels on rat striatal neurons by cesium and barium ions.

1. In cell-attached patch-clamp recordings from freshly dissociated rat caudate-putamen neurons, an 85-pS inwardly rectifying K+ channel, which was previously found to be modulated by D2-like dopamine receptors, was blocked by externally applied BaCl2 or CsCl. 2. At concentrations between 100 and 500 microM, Ba2+ blockade was voltage dependent, with a greater block at hyperpolarized voltages, in a manner consistent with blockade of the channel pore. Single-channel currents were flickery, with intervening periods of more complete blockade, and block appeared to be time dependent, with an estimated electrical distance of 0.24 and an apparent dissociation constant of 205 microM at 0 mV. 3. At concentrations between 1 and 3 mM, Cs+ blockade was similarly voltage dependent, but without periods of longer blockade, with an electrical distance of 0.81 and an apparent dissociation constant of 625 microM at 0 mV. Cs+ could also permeate this channel at voltages near the K+ reversal potential. The current-voltage relationship displayed an anomalous negative slope conductance, in a manner inconsistent with a single-ion pore. 4. Smaller-conductance, dopamine-insensitive channels were blocked more potently by both Ba2+ and Cs+ than was the 85-pS channel, reflecting differences between inwardly rectifying K+ channels mediating resting conductance and those mediating dopamine receptor responses in striatal neurons.

Animals↗
PubMed1996

Exfoliation syndrome.

Increasing pathophysiologic evidence indicates that exfoliation syndrome, a systemic process involving various visceral organs, frequently manifests itself first in the eyes as exfoliation of the lens and glaucoma. Exfoliation syndrome occurs when several tissues synthesize an abnormal basement membrane protein. This protein may obstruct the trabecular meshwork in the eye and cause glaucoma. We present a case of exfoliation syndrome associated with angle-closure glaucoma in a 57-year-old male patient from Taiwan. After peripheral iridectomy and topical antiglaucoma medications, intraocular pressure in both eyes was well controlled in the range of 15 to 20 mmHg. The mechanism of the glaucomatous optic neuropathy in this patient was probably caused by chronic angle-closure glaucoma superimposed with the exfoliation syndrome.

Antihypertensive Agents↗