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Biomedical subjects

D Yang

Publications and source records attributed to D Yang.

At least 253 records · Page 14Linked to original sources
PubMed1998

Assay of low deuterium enrichment of water by isotopic exchange with [U-13C3]acetone and gas chromatography-mass spectrometry.

A sensitive assay of the 2H-enrichment of water based on the isotopic exchange between the hydrogens of water and of acetone in alkaline medium is described and validated. For low 2H-enrichments (0.008 to 0.5%), the sample is spiked with [U-13C3]acetone and NaOH. After exchange, 2H-enriched [U-13C3]acetone is extracted with chloroform and assayed by gas chromatography-mass spectrometry. With some instruments, ion-molecule reactions, resulting in increased baseline enrichment, are minimized by lowering the electron ionization energy from the usual 70 to 10 eV. The 2H-enrichment of water is amplified nearly sixfold in the M4/M3 ratio of [U-13C3]acetone. For high 2H-enrichments (0.25 to 100%), the use of unlabeled acetone suffices. After exchange, the mass isotopomer distribution of acetone is analyzed, yielding the 2H-enrichment of water. The assay with [U-13C3]acetone allows measuring the 2H-enrichment of water even in biological samples containing acetone. This technique is more rapid and economical than the classical isotope ratio mass spectrometric assay of the enrichment of hydrogen gas derived from the reduction of water.

Acetone↗
PubMed1998

No association of presenilin-1 intronic polymorphism and Alzheimer's disease in Australia.

We screened 703 Australian subjects for an intronic polymorphism in the presenilin-1 (PS-1) gene. PS-1 intronic allele 1 homozygosity was not associated with individuals with early- or late-onset sporadic Alzheimer's disease (EOAD or LOAD). Carriers for the PS-1 intronic allele 1 were also not associated with significantly increased risk for AD regardless of gender. Our results for the Australian population are consistent with those of recent reports for other populations and do not support the conclusion that the PS-1 intronic polymorphism is associated with AD.

Adult↗
PubMed1998

A study of protein side-chain dynamics from new 2H auto-correlation and 13C cross-correlation NMR experiments: application to the N-terminal SH3 domain from drk.

Two new NMR experiments are presented for measuring side-chain dynamics in proteins. The first method, requiring 15N, 13C, approximately 50% 2H-labeled protein, measures 2H T1 and T1p spin relaxation times at side-chain positions. A second experiment permits the straightforward measurement of 13C-1H dipole-dipole cross-correlation relaxation rates at 13C beta positions in 15N, 13C-labeled molecules. An excellent correlation is observed between order parameters, describing the amplitude of motion at these sites, obtained on the basis of 2H relaxation and dipole-dipole cross-correlation relaxation rates. Together these experiments provide a powerful approach for selecting appropriate motional models. The methods are applied to study the side-chain motional properties of the N-terminal SH3 domain from the signaling protein drk.

Animals↗
PubMed1998

Mitogen-activated protein kinase activation mediates PDGF-directed migration of RPE cells.

Growth factor-directed migration is a critical component of the wound healing response although little is known about the signaling pathways involved. We examined the effect of inhibiting the mitogen-activated protein kinase (MAPK) pathway on platelet-derived growth factor (PDGF) and fibronectin-induced cell migration of human retinal pigment epithelial (RPE) cells. Using transwell cell-culture chambers, the effect of PDGF-BB (10-50 ng/ml) and fibronectin on components of migration was measured with or without the MAPK pathway inhibitor PD98059 (10-30 microM) MAPK activation of serum-starved cells by PDGF-BB was demonstrated by an immunoprecipitation/kinase assay and by immunohistochemistry using antibody specific for phosphorylated MAPK. PDGF-BB (10 ng/ml) stimulated MAPK activity in RPE (10 min) and its nuclear localization (1 h). PD98059 inhibited the activation of MAPK by PDGF-BB or serum. PDGF-BB stimulated RPE chemokinesis, chemotaxis, and haptotaxis; chemokinesis was additively increased and chemotaxis synergistically increased by the presence of a fibronectin substratum. PD98059 potently inhibited fibronectin-induced haptotaxis and PDGF-BB-induced chemotaxis but inhibited chemokinesis only at higher PDGF-BB (50 ng/ml) concentrations in the presence of fibronectin substratum. These results demonstrate that MAPK is critically involved in multiple components of RPE migration in vitro and suggest the potential of targeting MAPK to inhibit RPE migration in vivo.

Becaplermin↗
PubMed1998

A gene encoding antigenic peptides of human squamous cell carcinoma recognized by cytotoxic T lymphocytes.

Except for melanomas, tumor antigens recognized by cytotoxic T lymphocytes (CTLs) are yet unidentified. We have identified a gene encoding antigenic peptides of human squamous cell carcinomas (SCCs) recognized by human histocompatibility leukocyte antigens (HLA)- A2601-restricted CTLs. This gene showed no similarity to known sequences, and encoded two (125- and 43-kilodalton [kD]) proteins. The 125-kD protein with the leucine zipper motif was expressed in the nucleus of the majority of proliferating cells tested, including normal and malignant cells. The 43-kD protein was expressed in the cytosol of most SCCs from various organs and half of lung adenocarcinomas, but was not expressed in other cancers nor in a panel of normal tissues. The three nonapeptides shared by the two proteins were recognized by the KE4 CTLs, and one of the peptides induced in vitro from peripheral blood mononuclear cells (PBMCs) the CTLs restricted to the autologous tumor cells. The 43-kD protein and this nonapeptide (KGSGKMKTE) may be useful for the specific immunotherapy of HLA-A2601(+) epithelial cancer patients.

Amino Acid Sequence↗
PubMed1998

Factor VII deficiency caused by a structural variant N57D of the first epidermal growth factor domain.

We have previously described a kindred with factor VII (FVII) deficiency whose members exhibited reduced procoagulant activity relative to FVII antigen concentration. In this report, the molecular genetic basis of the FVII defect has been determined to be a heterozygous substitution of Asp for Asn at position 57 in the first epidermal growth factor (EGF) domain. Recombinant FVII (N57D) cDNA was created by site-directed mutagenesis and transiently expressed in human 293 cells. The transfected cells synthesized an immunoprecipitable protein with an apparent molecular weight of 50 kD. Quantitation of expression by FVII enzyme-linked immunosorbent assay indicated that mutant protein yields were consistently low, typically 10% to 30% of wild-type FVII. FVII (N57D) protein did not accumulate intracellularly, and Northern blot analysis indicated equivalent FVII mRNA levels in 293 cells expressing either wild-type FVII or FVII (N57D). Secreted FVII (N57D) protein did not bind tissue factor, exhibited no procoagulant activity, and failed to bind a conformation-dependent monoclonal antibody specific for the first EGF domain of FVII. Molecular modeling of the first EGF domain of FVII predicted that the N57D amino acid substitution would disrupt tertiary bonding structure. We conclude that the N57D mutation affects folding of the first EGF domain of FVII resulting in decreased cellular secretion of a mutant FVII molecule, which is unable to bind tissue factor and is therefore biologically inactive.

Animals↗
PubMed1998

Bandwidth extension in noise spectroscopy.

Noise spectroscopy has previously been demonstrated to provide broad-bandwidth excitation with minimal applied RF field strengths. Nonetheless, its application to broadline solid-state NMR spectroscopy has appeared limited by the need to have unrealistically short probe- and receiver-recovery times after pulses. In this Communication, we explain theoretically and demonstrate experimentally that accurate lineshapes can be observed in 2H solid-state NMR spectroscopy even where the probe ringdown time greatly exceeds the required time between sampled data points. Moreover, accurate lineshapes can be observed to +/-125 kHz using RF fields as weak as a few hundred hertz.

Fourier Analysis↗
PubMed1998

The sartorius muscle: anatomic considerations for reconstructive surgeons.

To evaluate the sartorius muscle as an alternative donor site for functional transfer, the neurovascular anatomy of the muscle was studied in 42 human sartorius muscle specimens (22 fresh and 20 preserved). Eleven adult fresh cadavers were injected with a mixture of lead oxide, gelatin and water (200 ml/kg) through the common carotid and femoral arteries. The sartorius muscle with its neurovascular pedicles was dissected, and radiographed. The sartorius muscle was also dissected out in 10 preserved cadavers. The neurovascular anatomy was thus analyzed in 42 sartorius muscles. The results show that each nerve supplying the sartorius muscle is accompanied by one vascular pedicle, forming a neurovascular hilum. Within the muscle, most of the nerves and vessels divide early, and their branches run parallel to each other and to the muscle fibers. Many of the vessels anastomose with each other to form an intricate vascular network. We conclude that it is possible to subdivide the muscle into functional units to harvest a segmental muscle flap with a neurovascular pedicle for transfer.

Adult↗
PubMed1998

Extrahepatic and intrahepatic replication and expression of hepatitis C virus.

In order to determine the replication sites of hepatitis C virus, the in situ hybridization and immunohistochemical technique using digoxin-labeled 531 bp plus-strand and minus-strand HCVRNA probes were employed to detect HCVRNA in the liver tissues, bone marrow mononuclear cells and peripheral blood mononuclear cells (PBMCs) from the patients with chronic hepatitis C, and in HCV transfected COS cells. The results showed that both plus-strand and minus-strand HCVRNA were detected in 80% of liver tissues (4/5). Plus-strand HCVRNA could be detected in 90% of PBMCs and bone marrow mononuclear cells (18/20), minus-strand HCVRNA in 25% of PBMCs. In HCV transfected COS cells, plus-strand HCVRNA distributed evenly in 20% cellular nuclei and cytoplasms. No minus-strand HCVRNA was detected in the bone marrow mononuclear cells and HCV transfected COS cells. The positive signal appeared in more cells when the liver tissues, PBMCs and marrow mononuclear cells were hybridized by plus-strand probes than when hybridized by minus-strand probes. Our results suggested that the hepatocytic cytoplasms and PBMC cytoplasms were the replication sites of HCV, but the marrow mononuclear cells were not the replication sites of HCV although they were infected by HCV. HCV infection might be accounted for the pathogenesis of chronic hepatitis and relapse of hepatitis C after liver transplantation.

Animals↗
PubMed1998

Induction of virus-induced IDDM in virus resistant mice without lymphocyte maturation.

The role of lymphocytes in the pathogenesis of viral-induced insulin dependent diabetes mellitus (IDDM) is controversial. To better understand how a virus-induced IDDM depends on the infiltrating lymphocytes, encephalomyocarditis virus (EMCV) was inoculated intraperitoneally into three kinds of mice; virus-susceptible C57BL/6, virus-resistant 129/SV and recombination activity gene-2 (Rag2) knockout 129/SV mice. Pancreatic inflammation and beta cell necrosis were evaluated after EMCV, D variant (10(3) pfu/mouse) inoculation. On post-inoculation day 14, the lethal rates of C57BL/6, 129/SV and Rag2 knockout mice were 52, 10 and 100%, respectively. The blood glucose in Rag2KO mice on day 8 was significantly elevated as compared with 129SV mice (231 +/- 49 vs 169 +/- 32 mg/dl, P<0.05). In situ hybridization demonstrated the EMCV genome in the pancreas of Rag2 knockout and C57BL/6 mice, but not in 129/SV mice. Beta cell necrosis were more severe in Rag-2 knockout mice than in wild type 129/SV mice, but lymphocyte infiltration was less severe than C57BL/6. Pancreas in Rag2 knockout mice infected with virus were affected more severely than the virus-resistant strain of mice. Diabetogenic virus induced IDDM in virus-resistant mice without mature lymphocytes.

Animals↗
PubMed1998

SEK1/MKK4 is required for maintenance of a normal peripheral lymphoid compartment but not for lymphocyte development.

SAPK is a member of the group of evolutionary conserved stress-activated kinases that mediate control of cellular death and proliferation. In lymphocytes, the SAPK pathway has been implicated in signaling from antigen, costimulatory, and death receptors; SEK1, which directly activates SAPK, is required for early embryonic development and has also been reported to be essential for normal lymphocyte development. In contrast to the latter findings, we have used RAG-2-deficient blastocyst complementation to show that SEK1-deficient embryonic stem cells support unimpaired T and B lymphocyte development. Moreover, mature SEK1-deficient lymphocytes are capable of SAPK activation. Surprisingly, however, aging SEK1-deficient chimeric mice frequently develop lymphadenopathy and polyclonal B and T cell expansions. Thus, SEK1 is not required for lymphocyte development, but is required for maintaining peripheral lymphoid homeostasis.

Animals↗
PubMed1998

Interaction of viral proteins with host cell death machinery.

In recent years, intense research has been directed towards understanding molecular mechanisms involved in viral pathogenesis. It is now known that many viruses manipulate host defense mechanisms to prevent apoptosis in order to maximize viral replication. Towards the end of their replication cycle, certain viruses direct the synthesis of proteins that induce apoptosis or cell lysis thereby facilitating viral release from the cell. The present review summarizes the current understanding of interactions between viral proteins and the host cell death machinery.

Animals↗
PubMed1998

Prednisone and low-dose activated prothrombin complex concentrates for FVIII inhibitor in nonhaemophilic patients.

Eight nonhaemophilic patients with factor VIII (FVIII) inhibitors were reported. There was no difference in sex distribution. Median age at diagnosis was 62 years (ranging from 14 to 73 years). No associated disorders were revealed and all the patients were presented with severe muscular or arthral bleeding. Inhibitor titre was measured by the Bethesda method, which were 6.4, 126.0, 155.0, 4.8, 56.0, 13.5, 35.0 and 150.0 BU mL-1, respectively, at diagnosis. FVIII:C levels were less than 1 U dL-1 in seven patients and less than 2 U dL-1 in one patient. The median vWF:Ag level was 210% (ranging from 80% to 340%). All the patients had good response to activated prothrombin complex concentrates for acute bleeding episodes and prednisone for inhibitor elimination. Inhibitors completely eliminated in seven patients within a follow-up duration over 1 year, and one patient died of intracranial haemorrhage when her inhibitor titre decreased to 4.5 BU mL-1 and FVIII:C increased to 21 U dL-1.

Adolescent↗
PubMed1998

Vascular basis of the retroauricular flap.

The aims of this study were to investigate the vascular communication between the superficial temporal artery (STA) and the posterior auricular artery (PAA) and to determine the vascular territory of various retroauricular flaps for flap design. A series of eight adult fresh cadavers were perfused with a mixture of lead oxide, gelatin, and water through the common carotid and femoral arteries. The full thickness of scalp and facial skin was removed with the STA and the PAA. A radiograph was taken of each specimen. After the retroauricular flap with the PAA from the posterior auricular and mastoid regions was elevated, another radiograph was taken of the specimen. Our radiographic assessment revealed two patterns of vascular anastomosis between the STA and PAA. The auricular anastomoses were found at the upper portion of the posterior surface of the ear, where some reticular anastomoses occurred between auricular branches derived from the STA and the PAA. The scalp anastomoses were located in the scalp superior to the ear, where some reduced caliber choke anastomoses or true anastomoses existed between the parietal branch and the terminal branches of the PAA. The results of this study will be helpful for better understanding of the vascular communication between the STA and the PAA and the vascular territory of retroauricular flaps. Our findings will also provide anatomic information and guidance for the design of reliable flaps.

Adult↗
PubMed1998

Trapezius muscle: anatomic basis for flap design.

During the past two decades the vascular anatomy of the trapezius muscle has been the subject of several anatomic studies. The anatomy of the trapezius is variable and confusing, and this anatomic variability seems to be the basis for sometimes unpredictable clinical results of the trapezius muscle flap. The purpose of the present study was to provide a careful overview of the intra- and extramuscular anatomy of the trapezius. In a series of 10 fresh and 10 preserved cadaveric studies, the intra- and extramuscular anatomy of the trapezius as well as the intramuscular neurovascular anatomy were studied. It was found that there are two main patterns of vascular supply to the trapezius, and that the muscle is principally supplied by three vascular sources: the transverse cervical artery, the dorsal scapular artery, and the posterior intercostal arterial branches. Although this study of the vascular anatomy of the trapezius helps to clarify the cause of the occasional loss or partial loss of the trapezius muscle, it does not provide a means of preventing partial flap loss.

Aged↗
PubMed1998

Immunoreactive endothelin-1 and its receptors in human adrenal tissues.

To elucidate the pathophysiologic significance of endothelin-1 (ET-1) in adrenal and the mechanism for reduced responsiveness to exogenous ET-1 in aldosterone-producing adenoma (APA), we have investigated ET-1 receptors by radioligand binding assay (RBA) in human normal adrenal (NA), APA, idiopathic hyperaldosteronism (IHA), and pheochromocytoma (PHEO), immunoreactive (ir-) ET-1 content in NA, APA and PHEO by radioimmunoassay (RIA), and immunohistochemical staining of ET-1 with the peroxidase-anti-peroxidase (PAP) method in NA, APA, and PHEO. A single class of high-affinity binding sites for ET-1 was found in human NA and tumor tissues. Dissociation constant (Kd) values of ET-1 receptors were similar in NA, APA, and IHA, but maximal binding capacity (Bmax) of ET-1 receptors was lower in APA than in NA and IHA. Both Kd and Bmax in PHEO were higher than those in NA, APA, and IHA. Ir-ET-1 content in tumors of APA and PHEO were higher than in NA. Immunohistochemical staining was more intense in the tumor cells of APA and PHEO than in NA. These results suggest that the reduced response to exogenous ET-1 in APA could be related to downregulation of ET-1 receptors in the tumor. Increased ET-1 content and receptors may lead to hypersecretion of catecholamine in PHEO. ET-1 produced in normal and tumor adrenal tissues may regulate aldosterone and catecholamine secretion from adrenals in a paracrine/autocrine fashion.

Adrenal Gland Neoplasms↗
PubMed1998

Comparison of two different delay procedures in a rat skin flap model.

The overall objective of this study was to investigate how a strategic delay procedure could generate large flaps survival. On the basis of the vascular anatomy in 10 rats, a long three-territory skin flap spanning the length of the rat dorsum was designed. This flap was distally based on the deep circumflex iliac artery. The adjacent territories consisted of a large perforator of the posterior intercostal artery and the lateral thoracic artery in sequence. Two different vascular delay procedures were used and compared in nine animals. One dorsal midline incision was used to perform the two different delay procedures. The limited delay technique was performed by ligating a large cutaneous perforator of the posterior intercostal artery on one side of the rat. The extensive delay procedure was completed by ligating the cutaneous perforators of the posterior intercostal artery and the lateral thoracic artery on the other side of the rat. After a delay period of 10 days, the paired flaps were elevated, respectively, and sutured back in place. Seven days later, the area of viable skin flap was measured by the paper template technique. The animals were then killed, and the dorsal skin arteriograms were obtained by injecting a lead oxide mixture. Vascular changes of the paired flaps were assessed. In the extensive delay group, 100-percent survival was seen in four animals and distal partial necrosis was observed in five animals. The average survival area in the extensive delay group was 85.5 +/- 14.2 percent (mean +/- SD), whereas the flaps in limited delay group showed 100-percent survival in all animals (p < 0.05). In flaps that survived completely, the choke vessels among three vascular territories anastomosed throughout the flap. In the partially necrotic flaps, some choke and true anastomoses existed between the deep circumflex iliac and the posterior intercostal artery territories and the flap necrosis occurred in the third territory. This study suggests that the limited delay technique (ligation of one artery in the territory adjacent to the base of the flap) was the more effective delay procedure in the rat dorsal skin flap model.

Animals↗