Biomedical subjects

S C Lin

Publications and source records attributed to S C Lin.

At least 145 records · Page 8Linked to original sources

PubMed1994

The photodynamic occlusion of choroidal vessels using benzoporphyrin derivative.

We used benzoporphyrin derivative-monoacid (BPD-MA), a new photosensitizing agent, in photodynamic therapy (PDT) to occlude choroidal vessels in the rabbit. Using BPD-MA, seven dutch-belted rabbit eyes were photodynamically treated to achieve acute choroidal vessel closure. Fundoscopy, fluorescein angiography (FA), and histology were performed 1 hour, 1 day, 3 days, 7 days, 14 days, 21 days, and 28 days after PDT. On FA, PDT-treated spots remained nonperfused until day 3 when gradual reperfusion from the periphery began to appear. By day 28 the area of PDT appeared completely reperfused. Histology of lesions showed acute damage to choroidal vascular endothelial cells and retinal pigment epithelial (RPE) cells. Over subsequent days, recovery of RPE cells and regeneration of large choroidal vascular endothelial cells occurred. In addition, retinal degeneration occurred gradually over the 28 days of follow-up. Since current argon laser therapy of retinal neovascularization causes immediate retinal damage, the ability to occlude choroidal vessels without inducing acute thermal damage holds promise for treating clinical pathologic conditions that feature abnormal neovascularization, such as age-related macular degeneration and diabetic retinopathy.

Animals↗

PubMed1994

A strategy for precision of genotyping of Epstein-Barr virus by polymerase chain reaction: application for studying Hodgkin's lymphoma.

Previous studies on the genotyping of Epstein-Barr virus (EBV) have been based on the analysis of a single gene locus. The assignment of genotype of an isolate could easily be over-looked with this assay. Our strategy for precision of EBV genotyping has exploited the existence of two families of EBV strains (type A and B) that can be distinguished at three divergent gene loci (EBNA-2, EBNA-3C, and EBER). To precisely determine the genotype of EBV in Hodgkin's disease (HD), we designed primers and simultaneously analysed these three gene loci that distinguish type A and B viruses by the polymerase chain reaction (PCR) technique. The primers designed to amplify these three gene loci encompass either type-specific deletion sequences (EBNA-2 and EBNA-3C) or type-specific point mutations (EBER) that identify the virus strain based on the sizes of PCR-amplified products or the mobility shifts in single-strand conformation polymorphism (SSCP) analysis. The locations of point mutations were identified by direct sequencing of the PCR-amplified DNA. Fifteen EBV-infected cell lines were analysed and a good correlation between EBNA-2 and EBNA-3C typing results was found. In contrast, approximately 33% of the cell lines analysed maintained type A sequences in EBNA-2 and EBNA-3C genes while carrying type B sequences in the EBER region. Data obtained from analysis of cell lines served as a reference for studying HD samples. EBV DNA was detected in about 70% of HD. Among the EBV-positive samples, 56% were associated with type A virus, 13% with type B, and 31% with dual viral sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Viral↗

PubMed1994

[The analysis of plain film presentation and bone age of achondroplasia].

Achondroplasia is the most common type of inheritant dwarfism. The diagnosis is mainly depended on clinical and plain film presentation. This study mainly focus on the characteristic presentation of plain film in achomdroplasia. We try to find the most consistent presentation and explain it through the development and growth of bone. The presentation in our 16 cases is as follows: Metaphyseal flaring 100% (16/16), Concave backs of vertebral body 100% (4/4), Short & wide tubular bone of hand & foot 85% (12/24). Square iliac bone 78% (11/14), Flare anterior end of ribs 76% (10/13), Decrease interpeduncular distance of lower L-spines 64% (9/14), Proimal < distal tubular bone 33% (5/15). Disproportionately long fibular bone 8% (1/13). We also analyze the heritant characteristics and conclude that most of achondroplasia are caused by mutation. The heritant trait is only 6%. According to bone age study, we found high percentage (31%) of delayed bone maturation.

Achondroplasia↗

PubMed1993

Diagnostic accuracy of transesophageal echocardiography for detecting left atrial thrombi in patients with rheumatic heart disease having undergone mitral valve operations.

Transesophageal echocardiography (TEE) has emerged as an efficient method for detecting left atrial (LA) thrombi in recent years, but its accuracy has not been fully evaluated. A prospective clinicopathologic study in 213 consecutive patients with chronic rheumatic mitral valve disease over a period of 39 months was undertaken. All patients underwent open heart surgery within 3 days after the TEE study. The presence or absence of LA thrombi was confirmed at surgery by direct inspection of the left atrium and proven by histopathologic examination. Of the 213 patients, 147 had predominant mitral stenosis, and the remaining 66 patients had significant mitral regurgitation. Twenty-eight patients had LA thrombi by TEE criteria. These findings were all confirmed at surgicopathologic studies (specificity 100%). However, in 2 patients, LA thrombi were present but could not be detected by TEE (sensitivity 93.3%). Therefore, the positive predictive value was 100%, the negative predictive value was 98.9% and the diagnostic accuracy was 99.1%. No thrombi were found in patients with significant mitral regurgitation. The frequency of LA thrombi in patients with predominant mitral stenosis was 20% (30 of 147), and most of these patients had chronic atrial fibrillation (28 of 30, 93%). Only 16 patients (16 of 30, 53%) were found to have LA thrombi by transthoracic echocardiography. Furthermore, our data showed poor correlation between the echogenicity of LA thrombi and the degree of thrombus organization. Thus, TEE is excellent for detecting LA thrombi in patients with rheumatic heart disease severe enough to warrant mitral valve operations.

Adolescent↗

PubMed1993

Molecular basis of the little mouse phenotype and implications for cell type-specific growth.

The molecular basis for the little (lit) mouse phenotype, characterized by a hypoplastic anterior pituitary gland, is the mutation of a single nucleotide that alters Asp 60 to Gly in the growth hormone releasing factor receptor. Detailed analysis of the lit mouse anterior pituitary reveals spatially distinct proliferative zones of growth hormone-producing stem cells and mature somatotrophs, each regulated by a different trophic factor. This sequential growth factor requirement for a specific cell type may exemplify a common strategy for regulating cellular proliferation in other mammalian organs.

Amino Acid Sequence↗

PubMed1993

Precision of genotyping of Epstein-Barr virus by polymerase chain reaction using three gene loci (EBNA-2, EBNA-3C, and EBER): predominance of type A virus associated with Hodgkin's disease.

To precisely determine the genotype of Epstein-Barr virus (EBV) in Hodgkin's disease (HD), we simultaneously analyzed three divergent gene loci (EBNA-2, EBNA-3C, and EBER) that distinguish type A and B viruses. The primers designed to amplify these three gene loci encompass either type-specific deletion sequences (EBNA-2 and EBNA-3C) or type-specific point mutations (EBER) that identify the virus strain based on the sizes of the polymerase chain reaction (PCR)-amplified products or the mobility shifts in single-strand conformation polymorphism analysis. The locations of point mutations were identified by direct sequencing of the PCR-amplified DNA. We analyzed 15 EBV-infected cell lines and found a good correlation between EBNA-2 and EBNA-3C typing results. In contrast, approximately 33% of the cell lines analyzed maintained type A sequences in EBNA-2 and EBNA-3C genes while carrying type B sequences in the EBER region. Data obtained from analysis of cell lines served as a reference for studying HD samples. EBV DNA was detected in about 70% of HD. Among the EBV-positive samples, 56% were associated with type A virus, 13% with type B, and 31% with dual viral sequences. Thus, type A virus is predominant in HD. Based on the histology, the frequencies of EBV positivity were 83%, 71%, and 33% for mixed cellularity, nodular sclerosis, and lymphocyte predominance, respectively. The detection of high frequency of both type A and B sequences in HD may provide a lead in investigating the role of dual viral infection in EBV pathogenesis.

Antigens, Viral↗

PubMed1993

Thymosin beta 10 and thymosin beta 4 are both actin monomer sequestering proteins.

The beta-thymosins are a family of related peptides. Recently, thymosin beta 4 was identified as a significant actin monomer sequestering protein in cells. To determine if other beta-thymosins also bind actin, and how they may participate in the regulation of actin polymerization, we expressed thymosin beta 4 and its major homolog, thymosin beta 10, in bacteria and characterized their interactions with actin. Equilibrium sedimentation studies showed that thymosin beta 4 behaved as a monomeric protein in solution. Both beta-thymosins bound skeletal muscle actin and inhibited actin polymerization with similar Kd values (between 0.7-1 microM). They were not inhibited by polyphosphoinositides. Kinetic measurements showed that at high ratios of beta-thymosin to actin, beta-thymosin decreased the rate of barbed end filament growth. However, in spite of a close agreement between the kinetic and steady state Kd values, the rate of barbed end filament growth was slightly, but reproducibly, larger than expected, and this deviation was particularly noticeable at lower ratios of beta-thymosin to actin. We conclude that unlike profilin, beta-thymosins are primarily actin monomer sequestering proteins, although some aspects of their interactions with actin are still not completely understood.

Actins↗

PubMed1993

Monoclonal anti-CD44 antibody acts in synergy with anti-CD2 but inhibits anti-CD3 or T cell receptor-mediated signaling in murine T cell hybridomas.

We investigated the effects of anti-murine CD44 monoclonal antibodies on the activation of antigen-specific T cell hybridomas. Anti-murine CD44 antibodies by themselves did not induce the production of IL-2 by antigen-specific T cell hybridomas. However, anti-murine CD44 monoclonal antibodies were able to either inhibit or enhance the production of IL-2, depending on the other monoclonal antibodies used as comitogenic stimuli. When a T cell hybridoma was activated by antigen and antigen-presenting cells or anti-CD3 antibodies, addition of anti-CD44 antibodies inhibited IL-2 production. In contrast, monoclonal anti-CD44 antibodies acted in synergy with anti-human CD2 antibodies in stimulating a murine T cell hybridoma stably transfected with the human CD2 gene to produce IL-2. Therefore, cross-linking of surface CD44 is able to deliver either a positive or a negative signal in murine antigen-specific T cell hybridomas. One of the ligands for CD44 is hyaluronic acid. Hyaluronic acid in vitro significantly increased the activation of murine T cell hybridomas. Hyaluronic acid itself was mitogenic for T cell hybridomas. Therefore, in addition to being an adhesion molecule, CD44 functions as a signal-transducing molecule on murine T cell hybridomas.

Animals↗

PubMed1993

Coordinate regulation of Drosophila tropomyosin gene expression is controlled by multiple muscle-type-specific positive and negative enhancer elements.

Muscle development involves the coordinated regulation of transcription of muscle-type-specific genes and their encoded proteins during myogenesis. We show here that transcriptional regulation of the Drosophila tropomyosin I (TmI) gene during myogenesis is under the control of at least two muscle enhancer regions located within the first intron of the gene. Together these enhancer regions contain multiple muscle-type-specific positive and negative cis-acting elements which together contribute toward full expression of the gene. One of these enhancers is contained within a 355-bp fragment that is sufficient to direct high levels of temporally regulated expression from a heterologous promoter in all muscles of transgenic flies. Dissection of this enhancer region into smaller fragments has allowed us to identify a 91-bp enhancer fragment sufficient for directing expression in all somatic and visceral muscles of the larva and adult but not in the indirect flight muscles and tergal depressor of the trochanter or jump muscles of the adult. We also show that this somatic/visceral muscle element(s) can be repressed through an adjacent negative control region, suggesting that the regulation of expression in these muscles is under dual control during both phases of myogenesis. We propose a model in which transcriptional regulation of the Drosophila TmI gene is controlled by the cooperative interaction of multiple positive and negative cis-acting regulatory elements that control the temporal and muscle-type pattern of expression. The distribution of enhancer elements and their control of TmI gene expression are similar to those regulating transcription of the muscle promoter of the TmII gene and provide a framework for the coordinate expression of the two genes.

Animals↗

PubMed1993

Rapid and sensitive genotyping of Epstein-Barr virus using single-strand conformation polymorphism analysis of polymerase chain reaction products.

Two distinct wild-type Epstein-Barr virus (EBV) strains (A and B) that have significantly diverged at the two small RNA-encoding region (EBER) have been identified (Arrand et al., 1989). In order to test whether single-strand conformation polymorphism analysis (SSCP) would correlate with these sequence variations, we designed primer pairs specific for EBER-encoding regions for amplification of divergent sequences by polymerase chain reaction (PCR). The PCR-amplified products from six EBV-positive cell lines were analyzed by SSCP method, and the results were compared with the prototype strains B95-8 (type A) and AG876 (type B). Type-specific point mutations were detected as demonstrated by shifts in mobility due to conformational changes of DNA sequences. The locations of point mutations were identified by direct sequencing of the PCR amplified DNA. Of the three primer pairs designed, the pair that amplified a 190 bp fragment spanning six type-specific point mutations gave the best resolution in SSCP analysis. This pair is now preferred for initial genotyping of EBV-infected tumor biopsies. Thus, SSCP is a simple, fast and efficient technique for genotyping of EBV-associated diseases.

Antigens, Viral↗

PubMed1993

A tissue-specific enhancer confers Pit-1-dependent morphogen inducibility and autoregulation on the pit-1 gene.

Pit-1 is a tissue-specific POU domain factor obligatory for the appearance of three cell phenotypes in the anterior pituitary gland. Expression of the pit-1 gene requires the actions of a cell-specific 390-bp enhancer, located 10 kb 5' of the pit-1 transcription initiation site, within sequence that proves essential for effective pituitary targeting of transgene expression during murine development. The enhancer requires the concerted actions of a cell-specific cis-active element, Pit-1 autoregulatory sites, and atypical morphogen response elements. Pituitary ontogeny in the Pit-1-defective Snell dwarf mouse reveals that pit-1 autoregulation is not required for initial activation or continued expression during critical phases of Pit-1 target gene activation but, subsequently, is necessary for maintenance of pit-1 gene expression following birth. A potent 1,25-dihydroxyvitamin D3-responsive enhancer element defines a physiological site in which a single nucleotide alteration in the sequence of core binding motifs modulates the spacing rules for nuclear receptor response elements. Unexpectedly, the major retinoic acid response element is absolutely dependent on Pit-1 for retinoic acid receptor function. On this DNA element, Pit-1 appears to function as a coregulator of the retinoic acid receptor, suggesting an intriguing linkage between a cell-specific transcription factor and the actions of morphogen receptors that is likely to be prototypic of mechanisms by which other cell-specific transcription factors might confer morphogen receptor responsivity during mammalian organogenesis.

Animals↗

PubMed1993

Alterations in actin-binding beta-thymosin expression accompany neuronal differentiation and migration in rat cerebellum.

The beta 4- and beta 10-thymosins, recently identified as actin monomer-sequestering proteins, are developmentally regulated in brain. Using specific mRNA and protein probes, we have used in situ hybridization and immunohistochemical techniques to investigate the distribution of the beta-thymosin mRNAs and their proteins in developing rat cerebellum. Early in postnatal development, both beta-thymosin mRNAs were expressed at highest levels in the postmitotic, premigratory granule cells of the external granular layer; expression diminished as granule cells migrated to and differentiated within the developing internal granular layer. In addition, both beta-thymosin proteins were present in bundles of cerebellar afferent fibers in the white matter at this time. Throughout the maturation period, both proteins were present in elongating parallel fibers in the upper portion of the molecular layer. Later in cerebellar development, thymosin beta 4, but not thymosin beta 10, was expressed in Golgi epithelial cells and Bergmann processes. Thymosin beta 4 was expressed in a small population of cells with microglial morphology scattered throughout the gray and white matter. Thymosin beta 10 was detected in an even smaller population of glia. Expression of thymosin beta 4 and thymosin beta 10 in premigratory granule cells and in growing neuronal processes is consistent with the possibility that both beta-thymosins are involved in the dynamics of actin polymerization during migration and process extension of neurons.

Actins↗

PubMed1993

HLA-DR and DQ antigens in Chinese patients with Behçet's disease.

The frequencies of HLA-DR and DQ antigens in 24 Chinese patients with Behçet's disease (BD) were calculated and compared with those in 130 healthy control Chinese and those in 80 Chinese patients with recurrent oral ulcers (ROU). Although an increased trend of DRw6 and DRw8 antigens in patients with BD was noted, there was no significant difference in frequencies of HLA-DR and DQ antigens between patients with BD and healthy control subjects or patients with ROU after correction of P values (Pc > 0.05). Further analysis of our data of the phenotype frequencies of DRw6 and DRw8 antigens according to the subtypes of BD also showed the increased frequencies of DRw6 and DRw8 antigens in patients with mucocutaneous type of BD as compared with those in healthy control subjects. However, only the phenotype frequency of DRw8 antigen in patients with mucocutaneous type of BD was significantly higher than that in patients with ROU (P < 0.005, Pc < 0.05, relative risk = 17.7, and etiologic fraction = 0.30). This significant increase of the phenotype frequency suggests that the gene coding for HLA-DRw8 antigen in patients with ROU was only partially (30%) responsible for susceptibility to the mucocutaneous type of BD.

Adolescent↗

PubMed1993

EDAP piezoelectric shock wave lithotripsy for gallbladder stones.

EDAP piezoelectric shock wave lithotripsy combined with oral ursodeoxycolic acid dissolution of stones was used to treat 1055 patients with gallbladder stones. 926 of them (87.8%) were followed up for more than 1 year. The patients were divided into two groups: Group I, 637 patients with functioning gallbladders containing one radiolucent stone less than or equal to 20 mm in diameter or 2 to 3 stones each less than or equal to 12 mm, and Group II: 289 patients with stones exceeding the above criteria. The stone fragmentation rate was 96.2% and 94.1% respectively in Group I and in Group II. Gallbladder stones disappeared in 18.5%, 35.0%, 46.2% and 52.4% of the patients in Group I in 1, 3, 6, and 12 months after treatment and 7.3%, 11.4%, 20.1%, and 27.7% in Group II. The treatment was more effective for solitary stones less than or equal to 20 mm in diameter. No serious complications were noted. The midterm curative effect was satisfactory. Further study is required to raise the curative effect and prevent stone recurrence.

Adult↗

PubMed1992

Morphologic characterization and quantitative assessment of mitral regurgitation with ruptured chordae tendineae by transesophageal echocardiography.

To compare the accuracy of transesophageal echocardiography (TEE) with that of transthoracic echocardiography (TTE) in the detection of morphologic characteristics and in the quantitative assessment of the severity of mitral regurgitation with ruptured chordae tendineae, 40 patients with ruptured chordae tendineae (group 1) and 20 patients with moderate or severe mitral regurgitation due to other causes (group 2) were studied. All echocardiograms were recorded before cardiac surgery. Cardiac catheterization was performed in 55 patients (92%). TEE showed greater sensitivity and negative predictive value than TTE (100 vs 65%, and 100 vs 56%, respectively; p < 0.005) in the diagnosis of ruptured chordae tendineae. Visualization of the ruptured chordae (termed snake-tongue sign) was highly sensitive and specific (93 and 95%, respectively) for establishing the diagnosis of ruptured chordae tendineae. The severity of mitral regurgitation in group 1 patients evaluated by TTE color flow mapping was underestimated by 2 grades in 1 patient and by 1 grade in 6 patients, and overestimated by 1 grade in 1 patient, compared with left ventriculography. In contrast, by TEE color flow mapping it was underestimated by 1 grade in 1 and overestimated by 1 grade in 1 patient. TEE color flow mapping showed better correlation with angiography than did TTE color flow mapping (r = 0.82 vs r = 0.49).

Adult↗

PubMed1992

Reappraisal by transesophageal echocardiography of the significance of left atrial thrombi in the prediction of systemic arterial embolization in rheumatic mitral valve disease.

Systemic arterial embolization imparts a significant risk of serious complications throughout the lives of patients with rheumatic heart disease. Left atrial (LA) thrombi have been thought to be the major source of emboli. A transesophageal echocardiography (TEE) study of 260 consecutive patients with rheumatic mitral valve disease was performed during a period of 24 months, with particular reference to understanding the association between LA thrombi and embolic complications. Of these patients, 155 had predominant mitral stenosis, 24 had significant mitral regurgitation, and the remaining 81 with xenograft mitral valve replacement developed valvular dysfunction (25 resulted in predominant mitral stenosis and 56 in significant mitral regurgitation). LA thrombi were detected in 38 patients (group A) and absent in 222 (group B). Group A patients had a higher frequency of recent (less than or equal to 1 week before TEE study) and remote (greater than 1 week before) embolization than did group B patients (recent: 26.3 vs 5.4% [p less than 0.001]; remote: 18.4 vs 5.0% [p less than 0.01]). The frequency of atrial fibrillation was also greater in group A patients (100 vs 74.3%; p less than 0.001). The exclusion of patients with significant mitral regurgitation and sinus rhythm had no effect on the association between LA thrombi and evidence of previous embolization. It is concluded that TEE is a convenient diagnostic modality that can be used to identify a subset of patients with rheumatic mitral valve disease at high risk for systemic embolization. Consequently, preventive anticoagulation for possible embolic complications should be more vigorously adhered to in patients with rheumatic mitral valve disease and LA thrombi.

Echocardiography↗

PubMed1992

Prospective study of blood culture during transesophageal echocardiography.

To ascertain the incidence and significance of bacteremia associated with transesophageal echocardiography (TEE), 132 consecutive patients (aged 17 to 73 years) free of apparent infection who were undergoing 135 transesophageal echocardiographic procedures from October 1990 to August 1991, were prospectively studied. For each procedure, two sets of blood cultures were obtained for culture 30 to 60 minutes before TEE, immediately after, and 180 to 240 minutes after the procedure. For each blood culture, 10 ml of venous blood was evenly inoculated into aerobic and anaerobic culture bottles and inoculated for 7 days using a radiometric system. A throat swab was obtained immediately before each procedure. Three of 270 preprocedure blood cultures were positive for Bacillus cereus, Staphylococcus simulans, and Peptostreptococcus species, respectively. No blood culture was positive in the immediate postprocedure period. Two of 270 late blood samples grew Staphylococcus epidermidis in the same patient. Nevertheless, the microorganisms isolated from blood cultures were different from those isolated from the throat swab. No patients had fever or evidence of infective endocarditis after TEE during the follow-up period. It is concluded that the incidence of TEE-related bacteremia is extremely low, and a general recommendation for antibiotic prophylaxis during TEE is not warranted.

Adolescent↗

PubMed1992

Presence of anti-basal cell antibodies in oral lichen planus.

BACKGROUND: An autoimmune hypothesis for oral lichen planus (OLP) has been proposed, but no anti-basal cell antibodies (anti-BCA) have been found in the sera of patients with OLP. OBJECTIVE: Our purpose was to test whether the negative results of anti-BCA assays in sera have been due to the insensitivity of the substrates. Rat esophagus, monkey esophagus, as well as human oral mucosa and skin were used to detect anti-BCA in sera of OLP patients. METHODS: By indirect immunofluorescence technique, the rat esophagus was found to be the most sensitive substrate. Therefore it was used as the only substrate to test the presence of anti-epithelial cell antibodies (anti-ECA) in a large group of patients with OLP and other oral mucosal diseases or normal control subjects. RESULTS: The results showed that anti-ECA were detected in 54% (34 of 63) of patients with OLP, 71% (15 of 21) of patients with aphthous ulcers, 29% (6 of 21) of patients with oral carcinoma, 20% (2 of 10) of patients with traumatic ulcer, and 7% (1 of 15) of patients with periodontitis but none of the healthy control subjects (n = 41). The presence of anti-BCA in OLP patients' sera was persistent and lasted for a few months or years. There was a decrease in the serum anti-BCA titers in six of eight anti-BCA-positive OLP patients after topical application of triamcinolone. CONCLUSION: These anti-BCA that persist longer in OLP patients' sera may be autoantibodies that are raised against altered basal cell-specific antigens.

Adult↗