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Biomedical subjects

L Yu

Publications and source records attributed to L Yu.

At least 217 records · Page 12Linked to original sources
PubMed1997

Proposal of invasiveness score to predict recurrence and survival after curative hepatic resection for hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most malignant human tumors and is associated with a high incidence of postoperative recurrence. There is no generally accepted definition for HCC invasiveness. Moreover, the predictive value of the pathologic factors that reflect HCC invasiveness was previously studied as separate events, with much controversy among different study groups. In this study, we proposed an invasiveness scoring system based on the relative importance of six criteria for HCC invasiveness: portal vein invasion, intrahepatic metastasis, hepatic vein invasion, serosal invasion, absence of tumor capsule, or presence of capsular invasion. METHODS: A total of 137 patients (111 male and 26 female) who underwent curative hepatectomy for HCC were included. Scoring of the six pathologic parameters was based on the clinical significance of each parameter as a single predictor for recurrence after curative resection. According to our scoring system, the patients were divided into three groups: low invasive HCC group A with a total invasiveness score 0 to 1, moderately invasive group B with a score of 2 to 4, and highly invasive group C with a total score of 5 or greater (5 to 11 points). RESULTS: Evaluation of the current scoring system showed a significant stepwise increase in the incidence of recurrence as the invasiveness score increased. Moreover, disease-free survival was significantly different among the three groups (log rank p < 0.0001). The 1-, 3-, 5-, and 8-year disease-free survival rates were 89%, 59%, 54%, and 54% in group A; 72%, 32%, 12%, and 10% in group B; and 54%, 19%, 7%, and 0 in group C, respectively. Multivariate analysis showed that the patients of groups B and C had a significantly worse prognosis compared with those of group A (p < 0.0001). CONCLUSIONS: The current scoring system can classify HCCs into three invasive categories and predict more accurately recurrence and disease-free survival after curative hepatectomy compared with any single invasive parameter previously proposed. Moreover, this system can be used as a therapeutic guide during and after the surgical decision making.

Adult↗
PubMed1997

Epstein-Barr virus BHRF1 prohibits the cells of nasopharyngeal carcinoma from apoptosis.

Epstein-Barr virus (EBV) is associated with nasopharyngeal carcinoma (NPC). The BHRF1 EBV protein is expressed at high levels in productively infected cells and certain latently infected cells. In order to investigate the effect of expression of BHRF1 on the biological behaviour of NPC cells, we constructed the BHRF1 high expression vector and transfected it into the NPC cell line, CNE2. Then, the alteration of proliferation and apoptotic rates in the cells were tested before and after camptothecin treatment. After treatment by camptothecin, BHRF1-CNE2 cells could constantly and slowly proliferate and its apoptotic rate was less than in control groups, and the number of cells in the G phase decreased and in the S phase increased. So, it suggests that BHRF1 expression can enhance the resistibility of CNE2 cells to DNA-damaging agents that cause apoptosis.

Antineoplastic Agents, Phytogenic↗
PubMed1997

Solution structure of an rRNA methyltransferase (ErmAM) that confers macrolide-lincosamide-streptogramin antibiotic resistance.

The Erm family of methyltransferases is responsible for the development of resistance to the macrolide-lincosamide-streptogramin type B (MLS) antibiotics. These enzymes methylate an adenine of 23S ribosomal RNA that prevents the MLS antibiotics from binding to the ribosome and exhibiting their antibacterial activity. Here we describe the three-dimensional structure of an Erm family member, ErmAM, as determined by NMR spectroscopy. The catalytic domain of ErmAM is structurally similar to that found in other methyltransferases and consists of a seven-stranded beta-sheet flanked by alpha-helices and a small two-stranded beta-sheet. In contrast to the catalytic domain, the substrate binding domain is different from other methyltransferases and adopts a novel fold that consists of four alpha-helices.

Amino Acid Sequence↗
PubMed1997

Identification of the polymorphically expressed CYP2C19 and the wild-type CYP2C9-ILE359 allele as low-Km catalysts of cyclophosphamide and ifosfamide activation.

Cyclophosphamide and ifosfamide are alkylating agent prodrugs that require activation by cytochrome P450 (CYP) to manifest their cancer chemotherapeutic activity. The present study investigates the activity of four individual human CYP2C enzymes and their allelic variants in cyclophosphamide and ifosfamide activation as an initial attempt to gain insight into the underlying basis for the large interpatient differences in the clinical pharmacokinetics and metabolism of these anticancer drugs. Recombinant CYP2C8, CYP2C19, two allelic variants of CYP2C18, and six variants of CYP2C9 expressed in a yeast cDNA expression system were each enzymatically active, as judged by the ability of the isolated microsomes to catalyse 7-ethoxycoumarin O-deethylation after reconstitution with purified NADPH-cytochrome P450 reductase and cytochrome b5. With cyclophosphamide as substrate, CYP2C19 had the lowest apparent Km, followed by CYP2C9, CYP2C18 and CYP2C8, whereas in the case of ifosfamide, the rank order was: Km CYP2C19 < CYP2C18 < CYP2C9 < CYP2C8. CYP2C18 had the highest in vitro intrinsic clearance/catalytic efficiency (apparent Vmax/Km) in cyclophosphamide and ifosfamide activation, followed by 2C19 > 2C9 approximately 2C8. Examination of a panel of CYP2C allelic variants revealed that CYP2C18-Thr385 had both a higher Vmax and a higher apparent Km toward cyclophosphamide than CYP2C18-Met385 with no difference in catalytic efficiency, whereas with ifosfamide the Thr385 allele exhibited a strikingly lower apparent Km resulting in a six-fold higher catalytic efficiency. In the case of CYP2C9, a Ile359 to Leu mutation associated with poor metabolism of the hypoglycemic drug tolbutamide decreased catalytic efficiency toward cyclophosphamide by increasing the apparent Km, whereas the same mutation reduced the efficiency of this P450 toward ifosfamide by decreasing the Vmax. Substitution of CYP2C9-Gly417 by Asp resulted in a two-fold lower catalytic efficiency for cyclophosphamide metabolism but a three-fold higher efficiency for ifosfamide metabolism. A His276 to Gly substitution resulted in an increase in both Vmax and apparent Km with no net change in catalytic efficiency for either oxazaphosphorine. Mutations at CYP2C9 residues 144 and 358 had little or no effect. Thus (a) wild type CYP2C19 and CYP2C9 are relatively low Km catalysts of cyclophosphamide and ifosfamide activation, and (b) all four human CYP2C enzymes activate these two anticancer prodrugs with varying efficiencies and with striking differences among naturally occurring allelic variants in the case of CYP2C9 and CYP2C18.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1997

Heterogeneity in androgen receptor levels and growth response to dihydrotestosterone in sublines derived from human hepatocellular carcinoma line (KYN-1).

Heterogeneity in the growth response to androgen and androgen receptor (AR) status in an AR-positive human hepatocellular carcinoma (HCC) line, KYN-1, was investigated in the present study. Seven sublines were obtained from KYN-1 by the limited dilution method. Four of them had no detectable amounts of AR and did not show any growth response to dihydrotestosterone (DHT) at the concentration up to 1000 nM, while the other three had varying amounts of both cytosolic and nucleosolic AR that were 5- to 7-fold higher than that of the parent cell. In the parent cell, the addition of DHT caused a modest but significant increase in the cell number (21%) in a 14-day culture. Such effect was increased by 2- to 7-fold in two AR-positive sublines. In addition, the sensitivity of the response in these two sublines was increased by up to 24-fold. The one remaining AR-positive subline did not show any growth response to DHT, although the behavior of its AR in sucrose gradient ultracentrifugation and Western blotting was the same as that of the other two sublines. These data clearly show that sublines derived from an established human HCC line have a broad heterogeneity in the growth response of HCC to androgen as well as in AR status and could be classified into three groups on the basis of the growth responsiveness to androgen and the AR expression.

Blotting, Western↗
PubMed1997

Structure-function analysis of the triphosphatase component of vaccinia virus mRNA capping enzyme.

The N-terminal 60 kDa (amino acids 1 to 545) of the D1 subunit of vaccinia virus mRNA capping enzyme is an autonomous bifunctional domain with triphosphatase and guanylyltransferase activities. We previously described two alanine cluster mutations, R77 to A (R77A)-K79A and E192A-E194A, which selectively inactivated the triphosphatase component. Here, we characterize the activities of 11 single alanine mutants-E37A, E39A, Q60A, E61A, T67A, T69A, K75A, R77A, K79A, E192A, and E194A-and a quadruple mutant in which four residues (R77, K79, E192, and E194) were replaced by alanine. We report that Glu-37, Glu-39, Arg-77, Glu-192, and Glu-194 are essential for gamma-phosphate cleavage. The five essential residues are conserved in the capping enzymes of Shope fibroma virus, molluscum contagiosum virus, and African swine fever virus. Probing the structure of D1(1-545) by limited V8 proteolysis suggested a bipartite subdomain structure. The essential residue Glu-192 is the principal site of V8 cleavage. Secondary cleavage by V8 occurs at the essential residue Glu-39. The triphosphatase-defective quadruple mutant transferred GMP to the triphosphate end of poly(A) to form a tetraphosphate cap structure, GppppA. We report that GppppA-capped RNA is a poor substrate for cap methylation by the vaccinia virus and Saccharomyces cerevisiae RNA (guanine-7) methyltransferases. The transcription termination factor activity of the D1-D12 capping enzyme heterodimer was not affected by mutations that abrogated ATPase activity. Thus, the capping enzyme is not responsible for the requirement for ATP hydrolysis during transcription termination.

Acid Anhydride Hydrolases↗
PubMed1997

Constitutive expression, not a particular primary sequence, is the important feature of the H3 replacement variant hv2 in Tetrahymena thermophila.

Although quantitatively minor replication-independent (replacement) histone variants have been found in a wide variety of organisms, their functions remain unknown. Like the H3.3 replacement variants of vertebrates, hv2, an H3 variant in the ciliated protozoan Tetrahymena thermophila, is synthesized and deposited in nuclei of nongrowing cells. Although hv2 is clearly an H3.3-like replacement variant by its expression, sequence analysis indicates that it evolved independently of the H3.3 variants of multicellular eukaryotes. This suggested that it is the constitutive synthesis, not the particular protein sequence, of these variants that is important in the function of H3 replacement variants. Here, we demonstrate that the gene (HHT3) encoding hv2 or either gene (HHT1 or HHT2) encoding the abundant major H3 can be completely knocked out in Tetrahymena. Surprisingly, when cells lacking hv2 are starved, a major histone H3 mRNA transcribed by the HHT2 gene, which is synthesized little, if at all, in wild-type nongrowing cells, is easily detectable. Both HHT2 and HHT3 knockout strains show no obvious defect during vegetative growth. In addition, a mutant with the double knockout of HHT1 and HHT3 is viable while the HHT2 HHT3 double-knockout mutant is not. These results argue strongly that cells require a constitutively expressed H3 gene but that the particular sequence being expressed is not critical.

Animals↗
PubMed1997

Evaluation of islet cell antigen (ICA) 512/IA-2 autoantibody radioassays using overlapping ICA512/IA-2 constructs.

Islet cell antigen (ICA) 512 also termed IA-2 is a novel autoantigen of type 1 diabetes, which has a tyrosine phosphatase-like domain. We have assessed autoantibody RIAs using a series of ICA512/IA-2 constructs to produce in vitro synthesized 35S-methionine-labeled proteins. Levels of ICA512/IA-2 (256-979, truncated aminoterminus) autoantibodies were strongly correlated with those of the full-length ICA512/IA-2 (1-979) autoantibodies (r = 0.96, P < 0.0001) and ICA512/IA-2 (687-979) autoantibodies (r = 0.98, P < 0.0001). RIAs using these 3 constructs had increased sensitivity relative to our initially reported ICA512 autoantibody RIA (amino acids 389-948, truncated carboxy- and aminoterminus). Only 2 of 38 sera examined in this study reacted with an aminoterminus ICA512/IA-2 (1-577) construct. The mean SD score (SD score = (index of unknown sample-mean index of controls)/SD of controls) using the ICA512/IA-2 (256-979) construct was significantly higher than the SD score obtained with other ICA512/IA-2 constructs (P < 0.001). Amongst patients with new-onset diabetes and prediabetic relatives, using RIAs for autoantibodies reacting with ICA512/IA-2 (256-979), insulin, and glutamic acid decarboxylase 65, 98% expressed one or more of these autoantibodies and 78% expressed two or more, whereas no control (n = 208) expressed more than a single autoantibody. A combined ICA512/IA-2 (256-979), glutamic acid decarboxylase 65 autoantibody RIA with differential autoantigen labeling (35S-methionine, 3H-leucine) has been developed that uses 96-well plate membrane filtration and Top Counter beta counting. Concordance between results of dual and single RIAs was greater than 90%. This simple combined autoantibody assay should facilitate large-scale autoantibody screening.

Adolescent↗
PubMed1997

Nephrotoxicity of amphotericin B is attenuated by solubilizing with lipid emulsion.

Nephrotoxicity is the major adverse effect of conventional amphotericin B (AMB/D), often limiting administration of full dosage. The new liposomal amphotericin B seems to be less toxic. The new liposomal amphotericin B seems to be less toxic. In this study, it is proposed that solubilizing the standard AMB/D preparation with 10% lipid emulsion will attenuate nephrotoxicity. Rats were injected with either AMB/D (Fungizone), AMB, AMB/D plus lipid emulsion (AMB/D/LE), or sodium deoxycholate (D). Renal function studies were performed on day 5. To assess a direct tubular toxic effect, isolated rat proximal tubule suspensions and inner medullary collecting duct cells in culture were exposed to AMB/D, AMB, AMB/D/LE, liposomal amphotericin B, and D for 60 min in normoxia. Lactate dehydrogenase (LDH) release was assessed as an index of cell injury. Creatinine clearance (ml/min per 100 g) averaged 0.79 +/- 0.04 in control rats, 0.29 +/- 0.09 in AMB rats (P < 0.001 versus control), 0.38 +/- 0.04 in AMB/D rats, 0.46 +/- 0.05 in D rats, and 0.78 +/- 0.03 in AMB/LE rats. Renal blood flow (ml/min per 100 g) was 3.45 +/- 0.31 in control, 1.29 +/- 0.28 in AMB, 1.42 +/- 0.23 in AMB/D, 3.03 +/- 0.39 in D, and 2.71 +/- 0.21 in AMB/D/LE rats. The fractional excretion of potassium (%) was 27.3 +/- 1.18 in control rats, 61.6 +/- 7.00 in AMB/D rats, 58.4 +/- 15.32 in AMB rats, and 37.9 +/- 2.06 in AMB/D/LE rats. LDH release (%) in proximal tubules incubated with AMB/D and D was 43.6 +/- 3.39 and 58.6 +/- 4.20, respectively. Addition of lipid emulsion decreased LDH release: 21.6 +/- 1.22 for AMB/D/LE and 26.4 +/- 3.03 for deoxycholate plus lipid emulsion. AMB did not demonstrate any toxic effect in proximal tubule suspensions. D was not toxic to inner medullary collecting duct cells at 0.16 mg/ml, whereas D at a higher dose and AMB induced a significant LDH release. Addition of lipid emulsion did not affect the antifungal activity as assessed by the Etest method. In conclusion, an alternative way of administering standard AMB with reduced nephrotoxicity is proposed.

Amphotericin B↗
PubMed1997

The role of late-onset autoimmune diabetes in white familial NIDDM pedigrees.

OBJECTIVE: To determine whether autoimmunity is a prominent feature of NIDDM among diabetic members in families with a strong history of NIDDM or in families with a mixture of NIDDM and IDDM. RESEARCH DESIGN AND METHODS: We determined GAD and islet cell (ICA512) autoantibodies from 215 NIDDM individuals and from 14 individuals with impaired glucose tolerance (IGT) of 68 families, including 1 family with maturity-onset diabetes of the young (MODY) and 3 families ascertained specifically for a mixture of NIDDM and IDDM. We tested 2 control populations: 50 unrelated spouses form Utah families, including 29 spouses with either IGT or NIDDM and 198 random nondiabetic white individuals from Colorado. RESULTS: We detected either GAD or ICA512 autoantibodies in 11 members of seven families and in one spouse used as a control subject. In two families, two affected individuals showed evidence of autoimmunity, but NIDDM individuals in each of the seven families showed no evidence of autoimmunity. Among the five families with both IDDM and NIDDM individuals (three families ascertained for a mixture and two families ascertained with an incidental IDDM child), antibodies were detected in members of only one family. Antibody-positive individuals were significantly younger at diabetes onset and had low waist-to-hip ratios, but were not more likely to be insulin treated. CONCLUSIONS: Autoimmunity is an important cause of apparent NIDDM, even among families with a strong history of NIDDM. However, autoimmunity among affected family members appeared to be a chance event and not the manifestation of a different genetic cause of diabetes.

Adult↗
PubMed1997

Role of nitric oxide in acute renal failure.

Nitric oxide synthase has been identified in several epithelial cells in the kidney, including proximal tubular cells, thick ascending limb, inner medullary collecting duct, and interstitial cells. Nitric oxide (NO) plays an important role in renal hemodynamics and sodium tubular transport. We have demonstrated that NO participates in hypoxia/reoxygenation (H/R) injury in isolated rat proximal tubules (PT) suspensions. In this in vitro model L-arginine addition enhanced H/R injury while L-NAME almost completely prevented injury. These effects were less intense in chronic supplemented rats with L-arginine and L-NAME, suggesting that NO synthase manipulation had interfered with PT susceptibility to H/R injury. In contrast, L-arginine protected IMCD cells in culture from hypercholesterolemic rats against hypoxia. Moreover, acute infusion of L-arginine before bilateral renal artery clamping was protective while L-arginine chronic administration and L-NAME were deleterious in this ARF model. The L-arginine protection was not observed in unilateral renal clamping plus contralateral nephrectomy in normal rats, but L-arginine was protective in hypercholesterolemic rats. Taken together, these results suggest that the net effect of NO stimulation is variable, and that it is the result of a balance between beneficial hemodynamic effects and cytotoxicity.

Acute Kidney Injury↗
PubMed1997

Anuric acute renal failure caused by dextran 40 administration.

Dextran 40 is largely used in clinical medicine as a plasma substitute because of its beneficial effects on the microcirculation and antithrombogenic properties. An unusual adverse reaction of dextran administration is oligoanuric acute renal failure. We report two cases of anuric ARF induced by dextran 40. Diuresis and renal function were quickly resumed after plasma-pheresis treatment. Renal biopsy revealed normal kidneys except for swelling and vacuolation of renal tubules suggestive of osmotic nephrosis.

Acute Kidney Injury↗
PubMed1997

[Construction of human genomic YAC clones with "terminal modification"].

A human YAC genomic pool with more than 4,000 clones was constructed by means of "terminal modification" of YAC vector and genomic inserts, as well as optimization of relevant experimental parameters. The transformation rate is approximately 400-500 transformants per microgram DNA. Preliminary characterization of randomly sampled clones demonstrates that YAC-specific inserts, in the average size of 450 kb and ranging 150-750 kb, were detected from 80% of the clones. The vector ligation experiment indicates the efficient reduction of "coligation" by terminal modification.

Chromosomes, Artificial, Yeast↗