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Biomedical subjects

J Yin

Publications and source records attributed to J Yin.

At least 91 records · Page 5Linked to original sources
PubMed1999

Low prevalence of the APC I1307K sequence in Jewish and non-Jewish patients with inflammatory bowel disease.

A germline sequence alteration at codon 1307 of the APC gene (I1307K) has been reported in 6-7% of the Ashkenazi Jewish population in the United States. This alteration is believed to predispose the APC gene to a secondary mutation at the same locus, resulting in an increased risk of colorectal carcinoma. There is an increased risk of colorectal carcinoma in patients with inflammatory bowel disease (IBD), a relatively large proportion of whom are Ashkenazi Jews. We therefore sought to determine whether the I1307K sequence variant occurred in the germline DNA of IBD patients. To our surprise, we found this sequence in only two of 267 patients with IBD (0.7%), occurring in only 1.5% of Jewish IBD patients. The I1307K sequence variant was not found in 67 patients with esophageal cancer, 53 patients with gastric carcinoma (13 MSI-H and 44 MSI-negative), or ten patients with sporadic MSI-H colon cancer. These findings suggest that the I1307K sequence is relatively rare in the germline of Jewish as well as non-Jewish IBD patients. It does not appear to contribute to the increased colorectal cancer risk present in these patients.

Colorectal Neoplasms↗
PubMed1999

Hypermethylation of the hMLH1 gene promoter in human gastric cancers with microsatellite instability.

Human gastric carcinoma shows a higher prevalence of microsatellite instability (MSI) than does any other type of sporadic human cancer. The reasons for this high frequency of MSI are not yet known. In contrast to endometrial and colorectal carcinoma, mutations of the DNA mismatch repair (MMR) genes hMLH1 or hMSH2 have not been described in gastric carcinoma. However, hypermethylation of the hMLH1 MMR gene promoter is quite common in MSI-positive endometrial and colorectal cancers. This hypermethylation has been associated with hMLH1 transcriptional blockade, which is reversible with demethylation, suggesting that an epigenetic mechanism underlies hMLH1 gene inactivation and MMR deficiency. Therefore, we studied the prevalence of hMLH1 promoter hypermethylation in a total of 65 gastric tumors: 18 with frequent MSI (MSI-H), 8 with infrequent MSI (MSI-L), and 39 that were MSI negative. We found a striking association between hMLH1 promoter hypermethylation and MSI; of 18 MSI-H tumors, 14 (77.8%) showed hypermethylation, whereas 6 of 8 MSI-L tumors (75%) were hypermethylated at hMLH1. In contrast, only 1 of 39 (2.6%) MSI-negative tumors demonstrated hMLH1 hypermethylation (P<0.0001 for MSI-H or MSI-L versus MSI-negative). Moreover, hypermethylated cancers demonstrated diminished expression of hMLH1 protein by both immunohistochemistry and Western blotting, whereas nonhypermethylated tumors expressed abundant hMLH1 protein. These data indicate that hypermethylation of hMLH1 is strongly associated with MSI in gastric cancers and suggest an epigenetic mechanism by which defective MMR occurs in this group of cancers.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Quantitative intracellular kinetics of HIV type 1.

Although our knowledge of HIV-1 growth, from a molecular mechanistic perspective, has rapidly increased, we do not yet know how the overall growth rate of HIV-1 depends on its constituent biochemical reactions. Such an understanding would be of fundamental importance and potentially useful for designing and evaluating anti-HIV strategies. As a first step toward addressing this need we formulate and implement here a global computer simulation for the intracellular growth of HIV-1 on a CD4+ T lymphocyte. Our simulation accounts for the kinetics of reverse transcription, integration of proviral DNA into the host genome, transcription, mRNA splicing and transport from the nucleus, translation, feedback of regulatory proteins to the nucleus, transport of viral proteins to the cell membrane, particle assembly, budding, and maturation. The simulation quantitatively captures the experimentally observed intracellular dynamics of viral DNA, mRNA, and proteins while employing no "fudge factors." Moreover, it provides an estimate of the intracellular growth rate of HIV-1 and enables evaluation of mono- and combined anti-HIV strategies.

CD4-Positive T-Lymphocytes↗
PubMed1999

ASP147 in the third transmembrane helix of the rat mu opioid receptor forms ion-pairing with morphine and naltrexone.

We tested the hypotheses that the carboxylate side chain of Asp147 of the mu opioid receptor interacts with the protonated nitrogen of naltrexone and morphine and that this interaction is important for pharmacological properties of the two compounds. Mutation of Asp147 to Ala or Asn substantially reduced the affinity of naltrexone and the affinity, potency and efficacy of morphine, while the Glu mutant had similar properties as the wildtype, indicating the significant role of the carboxylate group of Asp147 in receptor binding and activation. This role could be due to its direct interaction with ligands or involvement in interhelical interactions. The unprotonated analogs of naltrexone and morphine, cyclopropylcarbonyl noroxymorphone (CPCNOM) and N-formylnormorphine (NFNM), respectively, were used to discriminate between these mechanisms. CPCNOM was much less potent as an antagonist and had substantially lower affinity for the mu receptor than naltrexone. Similarly, NFNM was unable to activate the mu receptor and had much lower affinity than morphine. These results indicate the importance of the protonated nitrogen. Notably, the D147A and D147N mutations did not appreciably affect the binding affinities of CPCNOM and NFNM. In addition, the D147E mutant had similar affinities for CPCNOM and NFNM as the D147A and D147N mu receptors. Thus, the carboxylate group of Asp147 is not important for binding of the two unprotonated compounds. These results indicate that the carboxylate group of Asp147 of the mu receptor interacts directly with the protonated nitrogen of naltrexone and morphine and this interaction is important for binding and receptor activation.

Animals↗
PubMed1999

Determination of hexamethylene diisocyanate-based isocyanates in spray-painting operations. Part 2. Comparison of high performance liquid chromatography with capillary zone electrophoresis.

A capillary zone electrophoresis (CZE) approach was developed for the determination of hexamethylene diisocyanate (HDI) monomer and HDI-based oligomers. A comparison of CZE with high performance liquid chromatography (HPLC) indicates that the CZE separation completely isolates isocyanates from excess solvent, derivatizing reagent and pigment while offering a fivefold increase in sensitivity. The CZE approach allows for the quantification of HDI monomer and oligomer within a 1 min time window under the run conditions selected. For the determination of HDI-based oligomer, provided that the relative response with respect to HDI monomer is calculated, there is no significant difference (p < 0.05, n = 10) in the isocyanate air concentration when using either HPLC or CZE. The results are significant because they indicate that CZE has advantages for the determination of both HDI-based oligomer and HDI monomer generated during spray-painting operations.

Air Pollutants, Occupational↗
PubMed1999

[Characters of two gravity-related esterases in carrot callus cells].

On the basis of identification of two gravity-related esterases (grEST1 and grEST2) in carrot callus cells (Cai et al. 1998), we continued the study of the characteristics of these two esterases. They have the very special characteristic of SDS resistance. Their activities could be inhibited partially by deoxycholate. beta-Phenylpropionic acid, AgNO3 and CuSO4 had no inhibitory effect on their activities. The activities of grEST1 and grEST2 could be decreased by ascorbic acid and cysteine, and the influence by cysteine was particularly obvious. The molecular weights of grEST1 and grEST2 were shown to be near the ranges of 49-66 kD and 43-59 kD respectively by non-denaturing electrophoresis containing deoxycholate, Triton X-100 and SDS respectively, and the isoelectric points were approximately pH 5.4 and 4.9 respectively. Besides, grEST1 and grEST2 were found in the fraction precipitating at value between 30% and 40% saturation with (NH4)2SO4.

Copper Sulfate↗
PubMed1999

[Comparison of different alimentary reconstructions after total gastrectomy for cancer].

OBJECTIVE: To study the optimum reconstruction after total gastrectomy for malignant disease, especially the necessity of gastric substitute and duodenal passage. METHODS: Among 75 patients having total gastrectomy, five kinds of reconstruction were used: Braun, modified Braun (mBraun) I, II, III, and antigrade jejunal interposition (AJI). Postoperative complaints, body weight, food intake, serum nutritional parameters, complete blood count, half-emptying time of the gastric substitute, PNI, Visick index were evaluated. RESULTS: As compared with Braun group, the mBraun I and II groups showed less reflux esophagitis, higher nutritional parameters and PNI, while the operation time was similar. As compared with mBraun I and II groups, mBraun III and AJI groups showed better body weight, higher nutritional parameters, and PNI. CONCLUSIONS: It is essential to construct a gastric substitute and maintain the alimentary tract flowing through the duodenum after total gastrectomy for cancer, and the AJI may be a better choice in the operation of gastrectomy.

Adult↗
PubMed1999

[Secondary glaucoma after anterior chamber intraocular lens implantation].

OBJECTIVE: To investigate the intraocular pressure level, the change of anterior chamber angle and the occurrence of secondary glaucoma after anterior chamber intraocular lens (AC-IOL) implantation. METHODS: Sixty-two AC-IOL implanted eyes were followed up postoperatively for 3 months to 7 years (mean 31 months). The examination of anterior chamber angle was emphasized. The type of cataract mainly included senile and traumatic. The operation performed were lensectomy with anterior vitrectomy or extracapsular cataract extraction (ECCE) combined with primary or secondary AC-IOL implantation. RESULTS: The incidence of postoperative peripheral anterior synechia (PAS) of iris was 87.1% and that of the secondary glaucoma (mainly the angle-closure) was 11.3%. The incidence of the glaucoma after ECCE with primary or secondary implantation was 17.4%, while that after ECCE combined with anterior vitrectomy was 0%. CONCLUSION: The main causes of the secondary glaucoma are possibly the rupture of posterior capsule and vitreous loss during the surgery leading to postoperative severe uveitis and pupillary block. To prevent its occurrence, it is important to combine ECCE with anterior vitrectomy.

Adolescent↗
PubMed1999

[The reactions in ginseng cells induced by elicitor derived from digesting ginseng cell walls by cellulase].

After treatment of the elicitor derived from digesting ginseng cell walls by cellulase, the starch grains were degraded, and a large number of spherosomes were produced in Ginseng cells. In the mean time, the activity of amylase in the cells was increased and the activities of esterases in the cells were reduced; in addition, the content of soluble sugar and the content of lipoid were increased. These indicate that the emergency reactions and the adjustment of metabolism of lipoid were taken placed in the cells elicited. Besides, after the treatment with certain concentrations of elicitor, the content of ginseng saponin and the activity of phenylalanine ammonia lyase (PAL) were increased in ginseng cells. On the contrary, the activities of peroxidase (POD) and polyphenoloxidase (PPO) were reduced.

Amylases↗
PubMed1999

[Modification of N-terminal cDNA of hGM-CSF and high-expression in E. coli].

OBJECTIVE: N-terminal cDNA of human granulococyte-macrophage colony stimulating factor(GM-CSF) was designed to be modified and highly-expressed in E. coli. METHODS: A pair of oligo-nucleotide primers were used to modify the mature N-terminal cDNA sequence of hGM-CSF with the method of PCR. the modified cDNA of hGM-CSF was cloned into E. coli. expressive vector PBV220 and expressed in E. coli DH5 alpha strain, the biological activities of the recombinant protein was identified by means of cell colony formation and TF-1 cell growth assay in vitro. RESULTS: The expression level of modified hGM-CSF cDNA was higher than that of unmodified native type. SDS-PAGE revealed that expressed protein of hGM-CSF accounted for about 25% of total bacterial cell protein. The biological activity of recombinant protein was about 1.5 x 10(7) U/mg protein. The sequence of 1-16 amino acid of N-terminal of the recombinant protein was same with native hGM-CSF. CONCLUSIONS: Modification of the N-terminal cDNA of hGM-CSF could dramatically enhance the expression level in E. coli system.

Amino Acid Sequence↗
PubMed1999

[Spectrophotometric assay of polyethyene glycol in urine using ammonium ferrothiocyanate aqueous-chloroform system].

A spectrophotometric method for the quantitative determination of polyethylene glycol-600 (PEG-600) in urine is based on partitioning a chromophore present in ammonium ferrothiocyanate reagent into an aqueous phase and a chloroform phase in the presence of PEG. The method is simple and reproducible, and can detect PEG in a concentration of 0.25 g/L. It gives a linear response over a range of 0.25-2.5 g/L. The recovery of PEG-600 in urine is 107% and relative standard deviation is less than 5%.

Chloroform↗
PubMed1999

[Synthesis of methyl ester of aliphatic acid under irradiation of ultraviolet and mass spectra (MS) analysis].

A new method was introduced here to prepare methyl ester of aliphatic acid under irradiation of ultraviolet. Analysis was performed for the MS spectra of 19 products, by which Mclafferty rearrangements were discussed of methyl ester of aliphatic acid with two kinds of gamma-H in details. The regularity of Mclafferty rearrangement was established for the same kind of methyl ester with the increase of the carbon chain.

English Abstract↗
PubMed1998

Subsurface oxidation of polyethylene.

Since the 1960s ultrahigh molecular weight polyethylene has been a primary bearing material in orthopedic prostheses. Most polyethylene components have been sterilized by exposure to gamma radiation, but in the presence of oxygen this promotes degradation and correlates with component failure in the body. To better understand the mechanism of degradation, we measured oxidation profiles for components shelf aged 5.8 and 10.9 years. Microtomed sections from each component were analyzed for ketones, which are the primary oxidation products, by FTIR spectroscopy. Maximum ketone concentrations in both cases were found several millimeters below the surface. We propose a model to explain the profiles. Alkyl radicals, which are uniformly generated in the polyethylene during irradiation, react with peroxyl radicals, which are produced by alkyl radicals with oxygen to form ketones. At the component surface ketone levels are low because high oxygen concentrations deplete alkyl radicals, creating an excess of peroxyl radicals. In the bulk material ketones are low because low oxygen concentrations limit the formation of peroxyl radicals. However, just below the surface the concentrations of alkyl and peroxyl radicals balance, promoting ketone production. A computer simulation that accounts for the coupling of these reactions with the diffusion of oxygen shows a good agreement with the measured profiles.

Biocompatible Materials↗
PubMed1998

Sequence alterations of insulin-like growth factor binding protein 3 in neoplastic and normal gastrointestinal tissues.

Insulin-like growth factor binding protein 3 (IGFBP-3) is an important regulator of normal and malignant cell growth. It modulates the mitogenic effects of insulin-like growth factors (IGFs) by inhibiting growth through mechanisms both dependent on and independent of IGF binding. IGF-I and IGF-II levels are regulated by binding to the IGF-II receptor, which is inactivated by mutation in human gastrointestinal (GI) tumors. We have previously demonstrated elevated IGF-II ligand expression in IGF-II receptor-mutant GI tumors, implicating the IGF signaling system in GI tumorigenesis. Therefore, to investigate the potential involvement of IGFBP-3 in human GI carcinogenesis, direct DNA sequencing of exons 1-4 and intron-exon boundaries of the IGFBP-3 gene was performed in 10 colorectal cancers, 10 gastric cancers, and 10 esophageal cancers. Four distinct sequence alterations were identified: (a) in one gastric and one esophageal tumor, an A to C transversion occurred at nucleotide 5795 (CAC-->CCC), leading to a His-->Pro substitution at codon 179; (b) a second esophageal tumor had a C to T transition at nucleotide 8291 (ACC-->ATC), leading to a Thr-->Ile substitution at codon 277 of IGFBP-3; (c) one alteration comprised a G to C transversion in exon 1 at nucleotide 2132 (GGG-->GCG), leading to a Gly-->Ala substitution at codon 32 in two gastric cancers, seven esophageal cancers, and nine colon cancers; and (d) a C to G transversion located 17 nucleotides from the 3' splice site in intron 1 was observed in three colon cancers and four esophageal cancers. All of these DNA sequence alterations were present in matched normal DNA from the same subjects, which suggests that some or all of them may represent polymorphisms. However, we cannot exclude the possibility that the germ-line nonconservative amino acid substitutions predicted to occur as a result of these alterations result in subtle changes to IGFBP-3 protein function and a predisposition to developing GI malignancy.

Amino Acid Sequence↗
PubMed1998

Structural and kinetic evidence for strain in biological catalysis.

A classic hypothesis for enzyme catalysis is the induction of strain in the substrate. This notion was first expressed by Haldane with the lock and key analogy-"the key does not fit the lock perfectly but exercises a certain strain on it" (1). This mechanism has often been invoked to explain the catalytic efficiency of enzymes but has been difficult to establish conclusively (2-7). Here we describe X-ray crystallographic and mutational studies of an antibody metal chelatase which strongly support the notion that this antibody catalyzes metal ion insertion into the porphyrin ring by inducing strain. Analysis of the germline precursor suggests that this strain mechanism arose during the process of affinity maturation in response to a conformationally distorted N-alkylmesoporphyrin.

Amino Acid Sequence↗
PubMed1998

In situ PCR for in vivo detection of foreign genes transferred into rat brain.

Here we describe the use of in situ PCR to detect a viral transgene in rat brain. Previously, we have reported in vivo gene transfer by using a defective herpes simplex viral vector in mammalian brain (Kaplitt, M.G., Pfaus, J.G., Kleopoulos, S.P., Hanlon, B.A., Rabkin, S.D., Pfaff, D.W., Mol. Cell. Neurosci. 2 (1991) 320-330). For detection of the LacZ transgene, we have used histochemical staining for the protein product, beta-galactosidase, and in situ hybridization for its mRNA, but the DNA itself cannot be reliably detected with conventional methods. Therefore we have adapted the technique of in situ PCR, so that we may detect minute quantities of transgenic vector DNA following in vivo gene. The brain sections, prefixed, were treated with PBS-detergent before PCR amplification to increase permeability for peptides and oligonucleotides across cellular barriers in brain tissue. Pretreatment with detergent retained better brain morphology than the more widely used proteinase treatment. The PCR mixture containing dNTPs, primers, digoxigenin-dUTP (Dig-dUTP) and buffer was loaded onto each brain section. Slides containing brain sections were placed in an aluminum boat and then on the block of the thermal cycler. Temperature was brought to 82 degrees C before adding Taq polymerase ('hot start' method). Dig-labeled PCR amplified fragments were then detected by alkaline-phosphatase-linked anti-digoxigenin-antibody. Positive signals were seen within the nucleus of transduced neurons, indicating presence of viral DNA. Enhanced specificity was observed with the use of Dig-labeled primers which eliminates the possibility of non-specific viral DNA detection through primer-independent reactions. Overall, this technique can serve not only as an internal control for transgene presence during comparisons of experimental groups of animals, but may also have clinical applications including the detection of viral infection in human brain such as HIV in pathology specimens.

Animals↗
PubMed1998

Synthesis and immobilization of ceramide analogs on silica particles.

Ceramides are the major lipid components of the stratum corneum, the major permeability barrier of the skin. Here we report a chemical synthesis of ceramide analogs covalently bonded on the silica particles, that can be used to predict the skin permeability of chemicals via HPLC methods.

Ceramides↗