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Biomedical subjects

D Yang

Publications and source records attributed to D Yang.

At least 307 records · Page 17Linked to original sources
PubMed1997

Surgical closure of macular hole using an absorbable macular plug.

BACKGROUND: The surgical management of macular holes has been a subject of controversy in recent years. Various techniques such as vitrectomy, membrane peeling, and gas tamponade with or without transforming growth factor-beta 2, and recently the use of autologous platelets have produced closure rates from 58% to 96%, depending on the stage of the hole. METHODS: The authors present preliminary results in a study of 19 consecutive patients with stage 3 or stage 4 macular hole who underwent vitrectomy followed by placement of an absorbable partially cross-linked gelatin plug in the macular hole. The vitreous cavity was filled with a nonexpanding gas or air alone; the patient was instructed to maintain prone positioning for 2-3 days. RESULTS: Anatomic attachment of the edges of the macular hole was achieved in 19 out of 19 patients with a minimum follow-up period of 6 months (average 11.5 months). CONCLUSIONS: A cross-linked gelatin plug can effectively reattach the edges of macular holes of stages 3 and 4. Its use is recommended only in macular holes in high myopes with posterior staphyloma or recurrent macular hole.

Absorption↗
PubMed1997

Synthesis of isomers of 18F-labelled amino acid radiopharmaceutical: position 2- and 3-L-18F-alpha-methyltyrosine using a separation and purification system.

To diagnose cancers with radiolabelled amino acid using positron emission tomography, we have constructed a separation and purification system for the production of L-18F-alpha-methyltyrosine (L-18FAmT). This system could provide radioprotection and consistent production of L-18FAmT. L-18FAmT was synthesized and purified and the efficiency of the system was examined. The radiochemical yield of L-18FAmT was 20.3 +/- 5.1% (n = 5) based on the radioactivity trapped in the reaction vessel. The radiochemical purity was greater than 99.4 +/- 0.3% (n = 5). The radiochemical stability in phosphate-buffered saline and human plasma was examined and little decomposition was observed by HPLC analysis. Our results indicate that the separation and purification system gave simple and quick synthesis of L-18FAmT with a large reduction in radiation exposure and consistent production of L-18FAmT.

Amino Acids↗
PubMed1997

Acquired resistance to the anti-proliferative effect of interleukin-1 and interleukin-6 is a recessive phenotype in A375 human melanoma cells.

The proliferation of human melanoma cell line A375-6 is inhibited by several cytokines, including interleukin-1 (IL-1) and interleukin-6 (IL-6). However, during a long period of culture, the cells progressively acquire resistance to IL-1 irrespective of functional IL-1 receptor expression. These cells constitutively produce IL-1alpha and IL-6, and also acquire resistance to IL-6. In order to investigate the mechanism of the acquired resistance to these cytokines, we performed somatic cell hybridization experiments. Parental cells for the construction of hybrid cells were rendered G418- or hygromycin B-resistant by transfection with expression vectors containing drug-resistant genes. Hybridization was conducted using IL-1-resistant subclones A375-R8 and R19 and an IL-1 highly sensitive clone C2-1, which was originally resistant but became sensitive to IL-1 upon transfection with a human type I IL-1 receptor (IL-1R) expression plasmid. Cells produced by hybridization of resistant cells and C2-1 cells appeared to be sensitive to IL-1 and IL-6. In contrast, production of IL-1 was augmented in the hybrid cells. These results suggest that resistance to IL-1 and IL-6 is a recessive phenotype, while production of IL-1 is dominant in melanoma cells.

Cell Division↗
PubMed1997

Myocarditis as systemic disease: new perspectives on pathogenesis.

1. Myocarditis may be an early indicator of or may subsequently lead to dilated cardiomyopathy in humans. This hypothesis has evolved from research on viruses that induce myocarditis, wherein the coxsackie B group viruses (CVB) in the family Picornaviridae are the most common known viral infectants of heart muscle. 2. Many competing hypotheses exist as to the pathogenesis of CVB3-induced myocarditis, including direct virus-induced myocyte damage and immunopathological disease with autoimmune sequelae. Evidence to support the direct-damage and viral RNA-persistence hypothesis is derived from in situ hybridization and gene amplification studies. 3. Recent use of terminal deoxynucleotidyl transferase-mediated nick-end labelling indicates that this injury in target organs is largely non-apoptotic in nature. Most apoptotic bodies in cardiac tissue are derived from immune cells. 4. Beyond infection of heart muscle, CVB3 can also associate with, infect and persist in cells of immune origin. The CVB3 localizes to follicles in spleens and lymph nodes of the murine host and this particular localization may continue in mice susceptible to more aggressive myocarditis. Whether virus-immune cell association in these compartments is advantageous (or essential) to the host in the evolution of anti-viral immune responses or whether it is more advantageous to the virus in immunosuppression of the host is not known. 5. We suggest that CVB3 can directly perturb or alter the immune response, thereby delaying viral clearance from vulnerable systemic organs. Both host and viral genetic factors can influence susceptibility, persistence and disease progression. 6. Picornaviruses use a unique method for the initiation of translation, involving the internal binding of the ribosome on a sequence element of the 5' untranslated region, termed an internal ribosome entry site (IRES). 7. The IRES of CVB3 is located at approximately stem loops G, H and I, spanning nucloetides 530 and 630. Arrest of host translation is also a feature of picornavirus infection. Such regulation of host cell translation machinery no doubt fosters viral replication at the expense of the host cell. 8. Differences between cell types in the mechanisms, along with those at other key steps in the viral life cycle and in signalling via kinase pathways, may determine viral tropism and cellular destruction and the physiological outcome of neighbouring cells.

Animals↗
PubMed1997

Complement component 3 interactions with coxsackievirus B3 capsid proteins: innate immunity and the rapid formation of splenic antiviral germinal centers.

Innate immunity is central to the clearance of pathogens from hosts as well as to the definition of acquired immune responses (D. T. Fearon, and R. M. Locksley, Science 272:50-53, 1996). Coxsackievirus B3 (CVB3), a human cardiopathic virus, was evaluated for the ability to activate the alternative and classical pathway of complement. CVB3 proteins interact with complement component 3 (C3, a soluble protein effector of innate immunity) after either in vitro exposure to mouse serum or in vivo murine infection and activate the alternative pathway of complement. In addition, we demonstrate that viral antigen retention and localization in germinal centers is dependent on C3, while virus antigen retention in extrafollicular regions in the spleen is not. In vivo depletion of native C3 abolished the rapid formation of virus-specific germinal centers (by day 3 post-CVB3 infection) in the absence of serum anti-CVB3 antibodies. These studies demonstrate that innate immune mechanisms, such as C3 interaction with CVB3, are essential for splenic antiviral germinal center formation in naive (antigen nonsensitized) mice resistant (C57BL/6J strain) and susceptible (A/J strain) to CVB3-induced myocarditis.

Animals↗
PubMed1997

Fine-resolution analysis of products of intrachromosomal homeologous recombination in mammalian cells.

Mouse Ltk- cell lines that contained a herpes simplex virus type 1 (HSV-1) thymidine kinase (tk) gene with a 16-bp insertion mutation linked to either a defective HSV-2 tk gene or a hybrid tk sequence comprised of HSV-1 and HSV-2 tk sequences were constructed. HSV-1 and HSV-2 tk genes have 81% nucleotide identity and hence are homeologous. Correction of the insertion mutant HSV-1 tk gene via recombination with the hybrid tk sequence required an exchange between homeologous tk sequences, although recombination could initiate within a region of significant sequence identity. Seven cell lines containing linked HSV-1 and HSV-1-HSV-2 hybrid tk sequences gave rise to tk+ segregants at an average rate of 10(-8) events per cell division. DNA sequencing revealed that each recombinant from these lines displayed an apparent gene conversion which involved an accurate transfer of an uninterrupted block of information between homeologous tk sequences. Conversion tract lengths ranged from 35 to >330 bp. In contrast, cell lines containing linked HSV-1 and HSV-2 tk sequences with no significant stretches of sequence identity had an overall rate of homeologous recombination of <10(-9). One such cell line produced homeologous recombinants at a rate of 10(-8). Strikingly, all homeologous recombinants from this latter cell line were due to crossovers between the HSV-1 and HSV-2 tk genes. Our results, which provide the first detailed analysis of homeologous recombination within a mammalian genome, suggest that rearrangements in mammalian genomes are regulated by the degree of sequence divergence located at the site of recombination initiation.

Animals↗
PubMed1997

Mitogen-activated protein kinase activation is involved in platelet-derived growth factor-directed migration by vascular smooth muscle cells.

Migration of vascular smooth muscle cells (VSMCs) is a crucial response to vascular injury resulting in neointima formation and atherosclerosis. Platelet-derived growth factor (PDGF-BB) functions as a potent chemoattractant for VSMCs and enhances these pathologies in the vasculature. However, little is known about the intracellular pathways that mediate VSMC migration. In the present study, we investigated the role of mitogen-activated protein kinase (MAPK) activation in this function, since PDGF-BB as well as other growth factors activate this pathway. Using an in-gel kinase assay, we observed that PD 98059 an inhibitor of MEK that activates MAP kinase, inhibited PDGF-BB-induced activation of ERK-1 and ERK-2 in cultured rat aortic smooth muscle cells in a concentration-dependent manner. In contrast, PDGF-mediated activation of intracellular calcium release was not affected by PD 98059. The chemotactic response of both rat aortic smooth muscle cells (RASMCs) and human umbilical vein smooth muscle cells (HUSMCs) toward PDGF-BB (10 ng/mL) was significantly reduced by PD 98059 (10 mumol/L) to 41.7 +/- 7.1% in RASMCs (P < .01) and to 47.2 +/- 5.3% in HUSMCs (P < .01). Similar inhibition was seen at 30 mumol/L, less at 1 mumol/L. To further confirm the specificity of these results implicating the MAPK pathway, an antisense oligodeoxynucleotide (ODN) directed against the initiation translation site of rat ERK-1 and ERK-2 mRNA was used to suppress MAP kinase synthesis and function in rat VSMCs. Liposomal transfection with 0.4 mumol/L antisense ODN reduced ERK-1 and ERK-2 protein by 65% (P < .01) after 48 hours. The chemotactic response to PDGF-BB (10 ng/mL) was reduced by 75% (P < .01) in rat VSMCs transfected with the same antisense ODN concentration. Sense and scrambled control ODNs (0.4 mumol/L) did not affect ERK-1 and ERK-2 protein concentrations or chemotaxis of VSMCs induced by PDGF-BB. These experiments provide the first evidence that activation of MAPK is a critical event in PDGF-mediated signal transduction regulating VSMC migration.

Animals↗
PubMed1997

Effects of continuous infusion of endothelin-1 in pregnant sheep.

Plasma concentration of endothelin-1, a potent vasoconstrictor produced by the vascular endothelium, has been observed to be significantly increased in a number of pathophysiological states, including preeclampsia. In the present study we have evaluated the effects of elevated plasma endothelin-1 in pregnant sheep by continuous exogenous endothelin-1 administration. Nine pregnant ewes (110+/-5 days' gestation) were instrumented for measurements of maternal mean arterial pressure, renal blood flow, and uterine blood flow. After recovery, endothelin-1 was infused intravenously for 4 hours at a dose that was adjusted to raise mean arterial pressure by approximately 20 mm Hg by the end of the first hour (range 5 to 20 ng/kg per minute). Mean arterial pressure, renal blood flow, uterine blood flow, urinary protein excretion, hematocrit, and plasma endothelin-1 concentration were measured hourly, and renal and uterine vascular resistances were calculated. Endothelin-1 produced significant increases (% change from baseline at t=4 hours) in mean arterial pressure (45+/-8%), renal vascular resistance (353+/-66 %), and uterine vascular resistance (59+/-21%). Endothelin-1 also increased microvascular permeability both systemically and within the kidney, as suggested by marked increases in hematocrit (0.27+/-0.01 to 0.32+/-0.01) and urinary protein concentration (0.95+/-0.1 to 7.9+/-3.2 mg/mL per mg creatinine). There was a highly significant correlation (P<.0001) between plasma endothelin-1 and mean arterial pressure, renal vascular resistance, uterine vascular resistance, hematocrit, and urinary protein content in all sheep studied. In addition, plasma endothelin-1 corresponded well with the time course of the changes in cardiovascular parameters and urinary protein excretion observed. These results provide evidence to suggest that elevation of circulating endothelin-1 in pregnant sheep can produce cardiovascular and hemodynamic changes that in many ways resemble the human disease preeclampsia. This supports the hypothesis that endothelial cell damage and/or dysfunction that is associated with increased production of endothelin-1 could directly contribute to the progression of preeclampsia.

Animals↗
PubMed1997

Mutation of RET proto-oncogene in Japanese patients with multiple endocrine neoplasia type 2B and sporadic medullary thyroid carcinoma.

To determine whether patients with medullary thyroid carcinoma (MTC) develop other endocrine neoplasms or their relatives develop MTC, we investigated the mutations in the RET proto-oncogene in patients with multiple endocrine neoplasia type 2B (MEN 2B, N = 1) and sporadic MTC (N = 6). DNA from MTC tissue and the peripheral blood was screened by polymerase chain reaction single-strand conformational polymorphism (PCR-SSCP) analysis of exons 10 and 11. PCR products of exons 13 and 16 were also analyzed by AluI and FokI restriction enzyme digestion methods, respectively, and then sequenced. We did not find structural abnormalities in exon 10 or 11, or at codon 768 in exon 13, but a mutation at codon 918, ATG to ACG, was found in the peripheral blood and the MTC tissue from a patient with MEN 2B. The same mutation was also found in tumor tissue from 2 of 6 patients with sporadic MTC, but not in their peripheral blood.

Adult↗
PubMed1997

[Hepatocyte apoptosis in chronic viral hepatitis and its relationship with viral and Fas antigen expression].

To study the apoptosis of hepatocytes and its relationship with viral and Fas antigen expression in viral hepatitis, we detected apoptosis of liver cell and the expression of viral and Fas antigens in liver tissues of patients with chronic hepatitis B and/or C virus infection by using in situ end-labelling and immunohistochemical methods, respectively. 25 of 31 cases were detected end-labelling positive cells in their liver. The stained cells scattered in hepatic lobules, and also located in some necrosis areas and in bile duct epithelium. The apoptosis index was higher in patients with high histological active index (HAI) and in patients with viral antigen(s) positive in their liver than that in patients with low HAI and in patients without viral antigen, respectively. Apoptosis occurred in antigen positive and negative cells. There was no significant difference of apoptosis index between Fas antigen positive and negative group. These results indicated that both the infected and uninfected liver cells could occur apoptosis in patients with viral hepatitis. Further study on the mechanism of liver cell apoptosis is needed.

Adult↗
PubMed1997

[Gene expression of thyrotropin receptor, thyroid peroxidase and thyroglobulin in autoimmune thyroid disease].

To investigate the expression of thyrotropin (TSH) receptor gene in autoimmune thyroid disease and the relationship with expression of thyroid peroxidase (TPO) and thyroglobulin (TG) genes, we examined TSH receptor, TPO and TG gene expression levels in 10 human thyroid tissues by Northern blot analysis, including 7 Graves disease (GD), 2 Hashimoto disease (HT), and 1 normal thyroid tissue. The expression levels of TSH-R gene and TG/TPO gene were different between GD group and HT group. In GD group, TSH-R gene expression was closely correlated to the expression of TPO gene (r = 0.882; P < 0.01) and TG gene (r = 0.723; P < 0.05). The gene expression levels in GD were higher than those in HT and control. In HT group, TPO, TG gene expression levels were relatively lower while TSH-R gene expression levels were still in normal range. The difference in gene expression is possibly related to the types of autoimmune antibodies and various dripping rates.

Adult↗
PubMed1997

[Augmentation mammaplasty through the external oblique muscle route].

To reduce the rate of capsule contracture after implantation of the breast prosthesis, augmentation mammaplasty through an inframammary incision and the external oblique muscle has been performed in 96 cases since 1990. In 67 of 72 cases (93%), the cosmetic results are satisfactory with a natural contour and softness of the breast during the follow-up of more than 6 months. The capsule contracture rate is 2.8 percent. The advantage of the approach is the muscular coverage of almost the total surface of the implant that contributes to the excellent result and a low capsule contracture rate. This procedure can overcome the disadvantages of the transaxillary augmentation procedure, which is usually difficult in dissecting the origin of the pectoralis muscle at the sixth rib. This technique can also make the inframammary crease lower and improve moderate ptosis of the breast.

Adult↗
PubMed1997

[Nucleolar organizer regions enumeration in testicular teratoma].

To differenciate the benign and malignant testis teratoma. We investigated the value of AgNORs enumeration in 10 normal testis tissues, 6 benign teratomas and 7 malignant teratomas. The shape of the AgNORs in normal and benign teratoma was round, regular, with clear boundary and even size, setting in the center or the margin of the nucleus. In the malignant teratoma, the shape was irregular with unclear boundary and uneven size, setting in the near center or scattered in the nucleus. AgNORs enumeration: normal group: 1.56 +/- 0.17, benign teratoma: 2.40 +/- 0.26, malignant teratoma: 5.24 +/- 0.36. There was significant difference between the two groups (P < 0.01). The range of AgNORs enumeration in benign and malignant teratoma was separate. These results indicate that the mathod is helpful in differentiating benign and malignant testicular teratoma, and may provide an objective parameter.

Diagnosis, Differential↗
PubMed1997

[GS-MS analysis of essential oils from five species of Asarum].

This paper reports the result of GS-MS analysis of the essential oils from five species of Asarum, namely, A. heterotropoides var. mandshuricum (cultivated), A. sieboldii (cultivated), A. caudigerellum (from Sichuan), A. sieboldii(from Shandong) and A. sieboldii(wild). Ninety-two constituents were detected, of which 73 compounds were identified.

Drugs, Chinese Herbal↗
PubMed1997

[Isolation of coltivirus from mosquitoes in Beijing and it's biological characteristics].

Two strains (Beijing 95-70 and 95-75) of coltivirus were isolated from mosquitoes collected in Beijing during summer-autumn in 1994. The viruses caused cytopathogenic effect on C6/36 cells but not on BHK-21 and Vero cells, and were not lethal for new born mice and three week old mice. The isolates were resistant to 5'-IdU and ether, but sensitive to acid pH 3.0. There were 12 segments RNA shown by polyacrylamide gel electrophoresis (PAGE) and PAGE profile of the two isolates were similar (6-6). The PAGE profile was also similar to that of the TRT2 strain isolated in 1991, but there were at least 8 segments slightly different between the new isolates and TRT2 in band migration distance. Tissue culture cross-neutralization test showed that the new isolates were antigenically related to TRT2 strain identified as coltivirus. Growth curve of the two isolates on C6/36 cells showed that virus titer began to rise at the first day after infection and continued to increase up to 7.0 Log TCID50 per 0.1 ml and maintained a high level until the 21st day after infection. It seems that the virus may cause persistent infection on C6/36 cell.

Animals↗
PubMed1997

[Virological and clinical features of patients with sporadic hepatitis C].

In this study, the transmission route in 16 sporadic hepatitis C (SHC) patients was investigated. Three of them were surgeons who had often had occupational needlestick accidents, another 3 had close household contact with their spouses who had been diagnosed as chronic posttransfusion viral hepatitis C (PTHC), and the remaining 5 had potential parenteral exposure such as tooth extraction, injection or inoculation and so on. Five patients with SHC didn't have such history, their transmission route was not determined. Our result showed a lower viremia level in patients with SHC when compared to PTHC patients (the serum dilutions for HCV RNA detection was 10-100 times in the former and 100-10000 times in the latter. P<0.01). Only 1 patient with SHC was anti-HCV positive. Comparing to PTHC, the patients with SHC in our study had milder liver demage and lower ALT levels, and most of them (10/16) were symptomless.

Adult↗
PubMed1997

[High-resolution CT of otosclerosis].

High-resolution CT (HRCT) scans of thirty-two patients (60 ears) with the clinical diagnosis of fenestral otosclerosis were evaluated retrospectively. HRCT was performed with 1-mm-thick targeted sections and 1-mm (36 ears) or 0.5-mm (10 ears) intervals in the semiaxial projection. Seven patients (14 ears) underwent helical scanning with a 1-mm slice thickness and 1-mm/sec table speed. Forty-five ears (75%) were found to have one or more otospongiotic or otosclerotic foci on HRCT. In most instances (30 ears), the otospongiotic foci were found in the region of the fissula ante fenestram. No significant correlations between CT findings and air conduction threshold were observed. We found a significant relationship between lesions of the labrinthine capsule and sensorineural hearing loss. We conclude that HRCT is a valuable modality for diagnosing otosclerosis, especially when otospongiotic focus is detected.

Adolescent↗