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Biomedical subjects

J M Yang

Publications and source records attributed to J M Yang.

At least 91 records · Page 5Linked to original sources
PubMed1998

Molecular cloning and analysis of transcription initiation in the Anagrapha falcifera multiple nucleocapsid polyhedrosis virus polyhedrin gene.

Using Autographa californica multiple nucleocapsid polyhedrosis virus (AcMNPV) polyhedrin to probe the Southern blots of Anagrapha falcifera multiple nucleocapsid polyedrosis virus (AfMNPV), we identified the location of the AfMNPV polyhedrin gene within the 7.2 kb EcoRI fragment. The 7.2 kb EcoRI fragment of AfMNPV was cloned and the nucleotide sequences of the polyhedrin coding region and its flanking regions were determined. Nucleotide sequence analysis indicated the presence of an open reading frame (ORF) of 735 nucleotides (nt) which could encode 245 amino acids with a predicted molecular mass of 29 kDa. The nucleotide sequences within the coding region of the AfMNPV polyhedrin shared 80% similarity with the polyhedrin gene from AcMNPV but were most closely related to Bombyx mori NPV with 92% sequence identity. The size of the AfMNPV polyhedrin mRNA, determined by the Northern blot analysis, was estimated to be 1200 nt. The consensus promoter sequence (ATAAG) for the baculovirus very late gene was also observed. Two degenerate poly(A) tailing signals were found immediately downstream of the translational stop codon. The transcription initiation site, mapped by primer extension analysis, was found to be at T located 24 nt upstream from the A of the translation initiation codon. This site is located 26 nt downstream from the second A of the consensus TAAG, the transcription initiation site of most other NPVs.

Amino Acid Sequence↗
PubMed1998

Characteristics of spontaneous Ca2+ oscillations in bovine aortic endothelial cells in Ca2+-free solution.

In nominally Ca2+-free solution, the incidence of spontaneous Ca2+ oscillations in the cultured bovine aortic endothelial (BAE) cells may occur during superfusion. Application of 3 microM ATP induced a single Ca2+ transient regardless of the prior absence or presence of spontaneous oscillations. The total mobilized [Ca2+] depends on the incidence of spontaneous oscillations and the length of exposure in Ca2+-free solution. The maximal rate of rise of the transient in cells induced by ATP immediately after an spontaneous spike was greater than that in cells without any spontaneous activity. But there was no difference in the recovery time constant. The sum of areas of spontaneous and ATP-induced transients in cells with spontaneous activity was not different from that of ATP-induced transient in cells without spontaneous activity. The results suggest that BAE cells, after growth to confluence, are subjected to spontaneous oscillations during superfusion in Ca2+-free solution. The release of internal Ca2+ in response to ATP is enhanced in cells with spontaneous oscillations. The content of ATP-sensitive stores continually decreased when cells were superfused with Ca2+-free solution, and most of the spontaneous release of Ca2+ was lost and not sequestrated back into ATP-sensitive stores.

Action Potentials↗
PubMed1998

The optx2 homeobox gene is expressed in early precursors of the eye and activates retina-specific genes.

Vertebrate eye development begins at the gastrula stage, when a region known as the eye field acquires the capacity to generate retina and lens. Optx2, a homeobox gene of the sine oculis-Six family, is selectively expressed in this early eye field and later in the lens placode and optic vesicle. The distal and ventral portion of the optic vesicle are fated to become the retina and optic nerve, whereas the dorsal portion eventually loses its neural characteristics and activates the synthesis of melanin, forming the retinal pigment epithelium. Optx2 expression is turned off in the future pigment epithelium but remains expressed in the proliferating neuroblasts and differentiating cells of the neural retina. When an Optx2-expressing plasmid is transfected into embryonic or mature chicken pigment epithelial cells, these cells adopt a neuronal morphology and express markers characteristic of developing neural retina and photoreceptors. One explanation of these results is that Optx2 functions as a determinant of retinal precursors and that it has induced the transdifferentiation of pigment epithelium into retinal neurons and photoreceptors. We also have isolated optix, a Drosophila gene that is the closest insect homologue of Optx2 and Six3. Optix is expressed during early development of the fly head and eye primordia.

Amino Acid Sequence↗
PubMed1998

Low oxygen tension induces positive inotropy and decreases a(i)Na in isolated guinea-pig cardiac ventricular papillary muscles.

Effects of low oxygen on contractile force, intracellular Na+ activity (aiNa), and action potential were simultaneously measured in isolated guinea-pig ventricular papillary muscles. Reduction of oxygen from control 488 to 150 mmHg biphasically increased and decreased the twitch tension, and decreased aiNa in muscles driven at 60 beats/min. The action potential duration (APD) was decreased but the maximum rate of upstroke (Vmax) was increased. In control, 1 microM epinephrine significantly increased the the action potential amplitude and twitch tension with decreases in the time to twitch peak (TTP), time for 50% relaxation (RT50), and aiNa. After exposure to low oxygen for 10 min, with twitch tension elevated and TTP and RT90 increased, 1 microM epinephrine significantly increased the twitch tension and Vmax, and decreased the APD and aiNa. Pretreatment with reserpine inhibited the twitch tension, both at control and in the presence of epinephrine. But changes of action potential and aiNa in response to low oxygen and epinephrine were similar to those in control. Our results indicate that the isolated guinea-pig ventricular muscle needs a high oxygen tension to maintain a normal contractile function. Reduction of oxygen deteriorates the electrical and mechanical activities, most likely, by a coaxial graded hypoxia. The decreased aiNa, not associated with endogenous catecholamines, suggests that the activity of the Na(+)-K+ pump can be maintained in the superficial muscle cells despite of core-central hypoxia.

Action Potentials↗
PubMed1998

The role of MAP4 expression in the sensitivity to paclitaxel and resistance to vinca alkaloids in p53 mutant cells.

Mutations in p53 change the sensitivity to cancer chemotherapeutic drugs. Whereas many drugs, including the vinca alkaloids, often become less effective when p53 is transcriptionally inactivated, several, most notably paclitaxel, may become more effective. In studying the underlying mechanism(s), we found that increased MAP4 expression, which occurs with transcriptionally silent p53, is associated with increased sensitivity to paclitaxel and decreased sensitivity to vinca alkaloids. Using murine fibroblasts transfected with MAP4, we directly demonstrated that the changes in drug sensitivity were associated with parallel alterations in drug-induced apoptosis and cell-cycle arrest. Immunofluorescent staining of the microtubule network revealed that cells with increased MAP4 expression displayed an increase in polymerized microtubules and an increased binding of fluorsceinated paclitaxel. Since MAP4 stabilizes polymerized microtubules, overexpression of this gene provides a plausible mechanism to explain the altered sensitivity to microtubule-active drugs in the presence of mutant p53.

3T3 Cells↗
PubMed1998

Phylogenetic analysis of the nef gene reveals a distinctive monophyletic clade in Korean HIV-1 cases.

To study the genetic variation of the HIV-1 strains prevalent in South Korea, we analyzed the nef sequences derived from 46 HIV-1-positive individuals living in various geographic regions in Korea. Phylogenetic analysis revealed four subtypes of HIV-1: A (3 patients), B (41 patients), D (1 patient), and a type that could not be clearly classified to any known subtype (1 patient). Thirty-five of the 41 Korean subtype B isolates formed a distinct monophyletic clade that is not related to any of the international sequences from the Los Alamos Database or GenBank as of June 1997. Indeed, the presence of unique conserved sequences was identified among the Korean isolates in this Korean subtype B group. The variations in the nucleotide sequences of a majority (32 of 35) subtype B samples within the Korean clade were 1.9% to 8.8%, and amino acid sequences varied from 3.9% to 15.5%. These results suggest that HIV-1 strains currently present in South Korea might have originated from a few sources or might be developing through a certain selective pressure. This is the first report on the molecular nature of the HIV-1 infection present in South Korea.

Adolescent↗
PubMed1998

Preparation and characterization of heparin-containing SBS-g-DMAEMA copolymer membrane.

The grafting of dimethyl amino ethyl methacrylate (DMAEMA) onto styrene-butadiene-styrene triblock copolymer (SBS) membrane was subsequently conducted by UV-radiation induced graft copolymerization without degassing to obtain the SBS-g-DMAEMA copolymer membrane. The substituted amino groups on the SBS-g-DMAEMA graft copolymer membrane were quaternized with iodomethane, and then the membrane was treated with heparin to prepare the heparin-containing SBS-g-DMAEMA copolymer membrane (SBS-g-DMAEMA-HEP). The graft copolymer membrane (SBS-g-DMAEMA) and the heparin-containing SBS-g-DMAEMA copolymer membrane (SBS-g-DMAEMA-HEP) were characterized by FTIR spectroscopy. The heparin content was determined by toluidine blue heparin assay. Contact angle, water content, and protein adsorption of fibrinogen and albumin experiments were also performed to evaluate the effect of graft amount and heparin content on the biocompatibility of SBS-g-DMAEMA and SBS-g-DMAEMA-HEP graft copolymer membranes. By using Kaelble's equation, the surface tension of SBS-g-DMAEMA and SBS-g-DMAEMA-HEP were determined. It was found that with increasing grafting amount and the heparin content, the surface tension and water content of SBS-g-DMAEMA membrane increased, whereas the contact angle decreased. The amount of the adsorption of albumin and fibrinogen decreased with increasing graft amount and heparin content. However, there was a minimum for adsorption of proteins in the SBS-g-DMAEMA and SBS-g-DMAEMA-HEP membranes.

Biocompatible Materials↗
PubMed1998

Study of polymerization of acrylic bone cement: effect of HEMA and EGDMA.

The polymerization reaction of standard surgical Simplex-P radiopaque bone cement was investigated by differential scanning calorimetry to determine the influence of hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) on the polymerization reaction. From the kinetic analysis, the polymerization reaction of the modified acrylic bone cement was found to be approximately a first-order reaction. The reaction rate constants (k) were determined. It was found that the effects of HEMA and EGDMA contents on the rate and the heat of polymerization can be explained by the frequency factor and the activation energy. An increase in HEMA content tends to result in an increase in the values of both frequency factor and activation energy, whereas an increase in EGDMA content tends to induce a decrease in the frequency factor and activation energy.

Bone Cements↗
PubMed1998

Measurement of pS2 protein in pancreatic cyst fluids. Evidence for a potential role of pS2 protein in the pathogenesis of mucinous cystic tumors.

CONCLUSION: Elevated levels of the growth factor pS2 protein in the cyst fluids of mucinous cystic tumors correlate with earlier observations using immunohistochemical techniques showing that pS2 protein is expressed by these tumors. The markedly elevated levels of pS2 protein compared to normal plasma values suggest that this growth factor may be important in the pathogenesis of pancreatic mucinous cystic tumors. BACKGROUND: Cystic lesions of the pancreas include inflammatory pseudocysts, serous cystadenomas, and mucinous cystic tumors, some of which are malignant. Previous studies using immunohistochemical techniques have shown that virtually all pancreatic mucinous tumors express pS2 protein. pS2 protein is a growth factor that is believed to be important in the normal process of inflammation and repair. We measured pS2 protein and other growth factors in pancreatic cyst fluids to assess their potential pathophysiologic and diagnostic significance. METHODS: Levels of pS2 protein were measured in 54 pancreatic cyst fluids by radioimmunoassay. The growth factors, epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and insulin-like growth factors I and II (IGF-I, IGF-II) were measured in 22 cyst fluids using commercial immunoassays. RESULTS: Mucinous cysts exhibited significantly higher levels of cyst fluid pS2 protein than nonmucinous lesions, including pseudocysts and serous cystadenomas (median: 78,303 pg/mL; range: 218-361,176 pg/mL vs median: 886 pg/mL; range: 0-14,206 pg/mL; p = 0.0001). The level of pS2 in mucinous tumors was markedly higher than plasma values (median: 392 pg/mL). Levels of pS2 protein in malignant mucinous lesions tended to be higher than those in benign mucinous cysts, but this difference was not statistically significant (median: 88,817 vs 64,350 pg/mL; p = 0.159). Levels of other growth factors, including EGF, TGF-alpha, IGF-I, and IGF-II, did not discriminate among the different cyst types, and the values were within normal plasma ranges.

Cyst Fluid↗
PubMed1998

Detection of chromosome 6 abnormalities in melanoma cell lines by chromosome arm painting probes.

Chromosome 6 abnormalities, particularly the deletion of 6q, are among the most frequent chromosomal changes in human malignant melanoma. In this study, chromosome 6 rearrangements in 21 melanoma cell lines were identified by fluorescence in situ hybridization (FISH) with the use of chromosome 6 arm specific painting probes (CAPs). Structural abnormalities of chromosome 6 were detectable in 18 of 21 (86%) cases, including the identification of structural abnormalities that were not detectable by routine G-banding analysis. The results of this study correlate the frequency of 6q alterations and demonstrate that FISH with CAPs can be of considerable use for rapid screening of specific chromosome abnormalities in melanoma.

Chromosome Aberrations↗
PubMed1998

Prediction of equilibrated postdialysis BUN by an artificial neural network in high-efficiency hemodialysis.

In urea kinetic modeling, postdialysis blood urea nitrogen (BUN) is usually underestimated with an overestimation of the Kt/V especially in high-efficiency hemodialysis (HD). Thus, an artificial neural network (ANN) was used to predict the equilibrated BUN (Ceq) and equilibrated Kt/V (eKt/V60) by using both predialysis, postdialysis, and low-flow postdialysis BUN. The results were compared to a Smye formula to predict Ceq and a Daugirdas' formula (eKt/V30) to predict eKt/V60. Seventy-four patients on high-efficiency or high-flux HD were recruited. Their mean urea rebound was 28.6+/-2%. Patients were divided into a "training" set (n = 40) and a validation set (n = 34) for the ANN. Their status was exchanged later, and the two results were pooled. In the prediction of Ceq, both Smye formula and low-flow ANN were equally highly accurate. In patients with a high urea rebound (>30%), although Smye formula lost its accuracy, low-flow ANN remained accurate. In the prediction of eKt/V60, both Daugirdas' formula and low-flow ANN were equally accurate, although the Smye formula was not so accurate. In patients with a high urea rebound, although both Smye and Daugirdas' formulas lost their accuracy, low-flow ANN remained accurate. We concluded that low-flow ANN can accurately predict both Ceq and eKt/V60 regardless of the degree of urea rebound.

Blood Urea Nitrogen↗
PubMed1998

Mutations in the 1A rod domain segment of the keratin 9 gene in epidermolytic palmoplantar keratoderma.

Palmoplantar keratodermas (PPK) constitute a heterogeneous group of diseases marked by the thickening of palms and soles of affected individuals. They are divided into autosomal dominant and autosomal recessive groups by the mode of transmission. The autosomal dominantly transmitted group is further divided into epidermolytic (EPPK, Voerner) and non-epidermolytic (NEPPK, Unna-Thost) types according to the histopathologic findings. Recent development of molecular approaches has confirmed that EPPK and NEPPK are caused by the mutations in keratin 9 and 1 genes, respectively. We have studied three families of EPPK to find the mutation in the keratin 9 gene. DNA sequence analyses revealed single base changes in sequences encoding the highly conserved 1A rod domain segment of the keratin 9 gene in two of the three families. These mutations caused Arg (CGG) to Glu (CAG; R162Q) and Arg (CGG) to Try (TGG; R162W) substitutions. The same arginine position has been mutated in the keratin 10 gene in epidermolytic hyperkeratosis, the keratin 14 gene in epidermolysis bullosa simplex, and the keratin 9 gene in hereditary EPPK in Western patients. In this study we show that unrelated Korean patients have similar mutations.

Arginine↗
PubMed1998

A glutamate to lysine mutation at the end of 2B rod domain of keratin 2e gene in ichthyosis bullosa of Siemens.

Ichthyosis bullosa of Siemens is a rare autosomal dominant skin disorder whose clinical findings are quite similar to those of epidermolytic hyperkeratosis. The differences between those two diseases include absence of erythroderma and different distributions in the skin in ichthyosis bullosa of Siemens. Recent studies have confirmed that ichthyosis bullosa of Siemens is caused by the mutation in the keratin 2e (K2e) gene, which is expressed in the upper spinous and granular layers. We have identified a sporadic case of ichthyosis bullosa of Siemens; based on diagnosis by histopathological findings, the K2e gene of the patient was analysed. Direct sequencing of PCR products revealed a single base change in sequences encoding the highly conserved end of the 2B rod domain segment of the K2e gene. This mutation results in substitution of the codon for glutamic acid by a codon for lysine in position 493 in K2e (E493K). Mutations of the K2e gene involving five different residue positions (Q187P, T485P, L490P, E493D, E493K and E494K) are known to cause ichthyosis bullosa of Siemens. Of these sites, E493, which is conserved in type I and type II keratin genes, is the most frequently altered amino acid in the K2e gene. These data together suggest that this codon constitutes a hot spot for mutations in the K2e gene.

Amino Acid Substitution↗
PubMed1998

Effects of prostaglandins on ethanol damage in primary cultured rat hepatocytes.

OBJECTIVES: Several reports demonstrated that ethanol administration impairs the DNA synthesis in rat hepatocytes. Also, it has been demonstrated that prostaglandin (PG) helps prevent membrane damage by hepatotoxic chemicals. In this study, the authors examined PG's effects on the toxicity of ethanol in the primary culture of rat regenerations. METHODS: We examined two kinds of parameters, i.e., DNA synthesis and lipid peroxidation in the primary culture of rat hepatocytes. Hepatocytes were isolated by the collagenase perfusion method. The rate of DNA synthesis was determined by pulse-labelling cultured cells with [3H]-thymidine. Incorporation of (3H)-thymidine was determined by liquid scintillation spectrophotometer. DNA content was measured by the fluorescence spectrophotometer. The lipid peroxidation was assayed with spectrophotometer. RESULTS: The results were as follows: 1) PG family (PGA1, PGD2, PGE1, PGE2, PGG2a, PGI2 & Thromboxane B2) stimulated the DNA synthesis of hepatocytes (especially PGD2 and PGE1), 2) ethanol decreased DNA synthesis by clear dose-dependent manner, 3) the combined treatment of PGD2 or PGE1, prevents the decreasing of DNA synthesis, which was induced by ethanol, 4) in ethanol treatment, lipid peroxidation was decreased significantly, but PGD2, PGE1 and PGA1 were not affected, and 5) PGD2, PGE1 and PGA1 decreased lipid peroxidation with ethanol, significantly. CONCLUSIONS: From these results, we concluded that PG could be useful for the treatment of degenerative liver disease and alcohol-induced liver disease in the assumption that further studies on the action mechanisms of PG will continue.

Animals↗
PubMed1998

A muscle-clamping system with an absorbable jaw clip to reduce suturing in strabismus surgery.

Most of the ocular complications of strabismus surgery are related to needle trauma during the suturing of muscles. The authors have developed a muscle-clamping system with an absorbable jaw clip to facilitate exact techniques of eye muscle surgery and to reduce the risk of complications. The absorbable jaw clip is composed of a lower fixing body with three jaws and an upper supporting body. The clip is used to tie an extraocular muscle (which is moved and reattached with the membrane) with a single scleral bite. Using the absorbable jaw clip, the authors performed superior rectus recession on 16 eyes of eight rabbits. The authors examined the conjunctival injection, muscle adhesion power, and light microscopic findings at 1, 2, 4, and 8 weeks postoperatively. The conjunctival injection diminished with time. Bond strengths ranged from 380 to 620 gram gravity, which is sufficient to withstand the normal pull of human extraocular muscles. Some inflammatory cells were found microscopically, and fibrosis increased with time. The muscle-clamping method with the newly invented clip was technically easy, fast, and exact, and it may reduce suturing and complications during strabismus surgery.

Animals↗
PubMed1998

The expression of drug resistance gene products during the progression of human prostate cancer.

Prostate cancer progresses from a localized disease to a widely disseminated malignancy. Each step along this progression pathway involves multiple genetic alterations that impart a survival advantage to the tumor cell over its normal counterparts and may confer resistance to therapy. Because metastatic prostate cancer is one of the most therapy-resistant human neoplasms, we studied the expression of certain molecular determinants of drug resistance in the context of tumor progression. Paraffin-embedded formalin-fixed resected prostates were chosen based on Gleason grade and surgical stage. Immunohistochemistry was used to detect the expression of multidrug resistance protein (MRP), topoisomerase II alpha, p53, glutathione S-transferase pi, Bcl-2, and P-glycoprotein in these specimens. We found that all of the proteins were expressed in resected prostate except for P-glycoprotein. The expression of MRP, topoisomerase II alpha, p53, and Bcl-2 increased with the Gleason grade. In addition, the expression of MRP, topoisomerase II alpha, and p53 increased with the surgical stage. In contrast, the glutathione S-transferase pi and Bcl-2 expression decreased with the increasing surgical stage. Stage was the strongest indicator of protein expression. These results suggest that drug resistance gene products are expressed in prostate cancer at the time of surgical resection. Thus, although the emergence of the "pan-resistance" phenotype in prostate cancer may partly be a function of the selection pressure exerted by therapeutic interventions, certain determinants of chemoresistance may be caused by genetic changes accompanying tumorigenesis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Impact of reverse end-diastolic flow velocity in umbilical artery on pregnancy outcome after the 28th gestational week.

BACKGROUND: The aim of this study was to discuss pregnancy outcome in chromosomally and structurally normal fetuses having reverse end-diastolic flow velocity (REDFV) on Doppler umbilical artery velocimetry (DUAV) in the third trimester. METHODS: DUAV was performed in the high risk pregnancy antepartum fetal surveillance. We excluded gestational age less than 28 weeks, multiple pregnancies, and chromosomal or congenital anomalies. Thirty cases were categorized as having REDFV The pregnancy outcome was investigated in these cases. RESULTS: There were three stillbirths and 12 neonatal deaths, resulting in a perinatal mortality rate of 50%. Twenty-eight patients (93.3%) had complications with preeclampsia (20 of severe degree and eight moderate). Cesarean section was performed on 24 patients (80%) due to acute fetal distress. The mean gestational age at delivery was 31.8+/-3.2 weeks. The mean diagnosis-to-delivery interval was 10+/-8.2 hours. The average birth weight was 970+/-270 gm, 28 (93.3%) were found to be below the 10th percentile of ideal birth weight. An umbilical artery pH less than 7.2 at delivery was found in 12 of 18 examined cases (66.7%). Twelve out of 15 placentae (80%) showed significant infarcts on pathological examination. All newborns (100%) needed admission to the neonatal intensive care unit. CONCLUSIONS: REDFV on DUAV represents an ominous and severe fetal condition with an adverse pregnancy outcome, especially in conditions associated with preeclampsia and/or intrauterine growth retardation. Intensive and frequent surveillance and aggressive management at the appropriate time would improve perinatal outcome.

Adult↗