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Biomedical subjects

R Wu

Publications and source records attributed to R Wu.

At least 253 records · Page 14Linked to original sources
PubMed1995

[Vibratory acoustic stimulation test in fetal hearing monitor].

In order to seek an antepartum diagnosis of hearing impairment in fetus, a vibratory acoustic stimulation test (VAST) was carried out with 57 women who were pregnant 27 weeks and an ABR test was carried out with their 57 newborn babies. The results showed: (1) On or after the 27th week the fetus would have the function of hearing. (2) The reliability of VAST was high (two positive rates were 87.7% and 89.5%) and the VAST was safe. (3) There was a correlation between fetal VAST and newborn ABR (P < 0.05). We consider that VAST is a simple, safe and effective measure for fetal hearing screening.

Acoustic Stimulation↗
PubMed1995

Heterocyclic amine mutagenicity/carcinogenicity: influence of repair, metabolism, and structure.

Cooking, heat processing, and pyrolysis of protein-rich foods induce the formation of structurally related heterocyclic aromatic amines that have been found to be mutagenic in bacteria, mammalian cells in culture and mice. All these compounds are potent mutagens and most are active below 1 ng/plate, in Ames/Salmonella tester strain TA1538 in the presence of S9 liver microsomal preparations from rat, mouse, or hamster. They are also potent in strains TA98, TA97, moderately active in TA1537, weakly active in TA100, and virtually inactive in TA1535 and TA102. Thus, they show powerful frameshift activity in reverting specific GC-rich sequences, but do not cause base substitution mutations or revert an AT-rich sequence. They are 100-fold less active in the uvrB+, repair-proficient strain TA1978, and in the case of 2-amino-3-methylimidazo [4,5-f] quinoline (IQ), cause insertions and large deletions not seen in TA1538.

Amines↗
PubMed1994

Functional dissection of a rice high-pI alpha-amylase gene promoter.

Deletion analysis has previously shown that a 260 bp fragment, located between positions -230 and +29 of the 5' end of a rice high-pI alpha--amylase gene, OSamy-c, is required for gibberellic acid (GA3)-dependent transcriptional activation. We have since established a quantitative transient assay based on expression of a luciferase reporter gene in rice aleurone cells and continued to characterize the OSamy-c promoter for GA3-dependent regulatory sequences. Using this method, we have shown that the DNA sequence between -158 and -46 (sequence I) is sufficient to confer GA3-responsive activation on OSamy-c. We have also shown that this sequence is capable of directing GA3-dependent expression from a heterologous minimal promoter. Our results also showed that sequence I confers GA3 regulatory control in an orientation-dependent manner and interacts with two further upstream DNA sequences, II and III, in a combination which mildly enhances the level of the GA3 response exhibited by sequence I. Thus, we propose that sequence I confers the fundamental GA3-responsive character on OSamy-c, and that regulatory proteins that bind sequences II and III interact with each other and with regulatory proteins that bind sequence I, effectively to modulate the GA3 response.

Base Sequence↗
PubMed1994

In vitro exposure of tracheobronchial epithelial cells and of tracheal explants to ozone.

An in vitro system for exposing respiratory epithelial cells or explant tissues to ozone has been developed and characterized. This system is designed to generate and monitor consistent, reproducible levels of ozone, over a range of concentrations, in a humidified atmosphere, and to allow an exposure time of 24 h or longer. Based on chemical analysis, highly reproducible concentrations of ozone are delivered throughout the chamber, with a coefficient of variation of < 5% between five replicate vials exposed to 0.5 ppm of ozone for 50 min. The viability of cultured human tracheobronchial epithelial cells, as measured by the ability to oxidize a vital dye, and of rat tracheal epithelium, as measured by total numbers of necrotic cells in tracheal explants, after ozone exposure was examined in this system. Responses of cultured cells to ozone exposure as measured by bioassay were consistent with the observed low level of variability of ozone concentration between replicate incubation dishes or vials. Responses of cultured cells to ozone were proportional to duration of exposure and inversely proportional to the volume of medium covering the cells. We conclude that this newly developed in vitro exposure system will allow relatively simple and convenient exposure of cultured cells or organs to ozone or other gaseous agents under highly controlled and reproducible conditions.

Air Pollution↗
PubMed1994

Purification and characterization of a novel form of brain L-glutamate decarboxylase. A Ca(2+)-dependent peripheral membrane protein.

L-Glutamic acid decarboxylase (GAD) catalyzes the one-step biosynthesis of gamma-aminobutyric acid (GABA), which is widely accepted as the major inhibitory neurotransmitter in the mammalian brain. In this paper, we report the identification and purification of a new and novel form of peripheral membrane GAD (MGAD) referred to as MGADIII, using a combination of chromatography on DE52, AcA 34, hydroxylapatite and Sephadex G-200, and native gel electrophoresis. The purified MGADIII migrated as a single protein band on a native 5-25% gradient polyacrylamide gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular mass of 118 +/- 6 and 60 +/- 4 kDa, respectively, suggesting that it is a homodimer of 60 kDa. MGADIII was established as a Ca(2+)-dependent peripheral membrane protein based on Triton X-114 phase partitioning assay, liposome binding experiment, and membrane extraction studies. Several lines of evidence are presented to show that the association of MGADIII with membranes occurs during depolarization of nerve terminal and that this is a reversible process. Based on these results and previous findings that GAD associates with synaptic vesicles and is regulated by phosphorylation, a model for regulation of GAD in the nerve terminal is proposed.

Animals↗
PubMed1994

A membrane form of brain L-glutamate decarboxylase: identification, isolation, and its relation to insulin-dependent mellitus.

A membrane form of L-glutamate decarboxylase (GAD) was identified and purified to apparent homogeneity from hog brain. The purified GAD was established as an integral membrane protein by phase-partitioning assay, charge-shift electrophoresis, and chromatography on a hydrophobic interaction column. This membrane GAD has a native molecular mass of 96 +/- 5 kDa and is a homodimer of 48 +/- 3-kDa subunits. Immunoprecipitation and immunoblotting tests revealed the presence of antibodies against this membrane GAD in sera from patients with insulin-dependent diabetes mellitus. Since this form of GAD appears to be an integral membrane protein and is presumed to have extracellular domains exposed, it seems reasonable to suggest that membrane GAD is more likely than soluble GAD to be involved in the pathogenesis of insulin-dependent diabetes and related autoimmune disorders such as stiff-man syndrome.

Animals↗
PubMed1994

TP53 mutations are frequent in malignant NF1 tumors.

Neurofibromatosis type I (NFI) is a common autosomal dominant disorder with an increased risk for developing benign and malignant tumors. The NFI gene has been cloned and maps to 17q11.2, and the gene product acts as a tumor suppressor gene. Here we analyzed the role of mutations in TP53 in four malignant NFI tumors. Mutations were found in 3 out of 4 tumors. One of these mutations is a common missense mutation in codon 278 in one of the previously identified hot spots for mutations. The two other are hitherto unreported mutations, including a splice mutation of exon 3 and a nonsense mutation in exon 4. In addition, these four tumors also showed loss of heterozygosity (LOH) for markers on chromosome 17 in the region of TP53. Malignant NFI tumors are initiated by a somatic inactivation of the second NFI allele. Tumor progression, however, occurs by accumulation of additional genetic abnormalities, such as homozygous inactivation of TP53, as demonstrated in this paper.

Base Sequence↗
PubMed1994

Transcribed repetitive DNA sequences in telomeric regions of rice (Oryza sativa).

We have isolated and characterized from rice three repetitive DNA sequences, Os48, Osc-567, and OsG3-430. Our results indicate that these repetitive sequences are highly transcribed, and transcripts complementary to both strands of the Os48 family of sequences account for up to 3% of the total cellular RNA. Pulsed-field gel electrophoresis, restriction mapping, and DNA sequence analyses have revealed a complex pattern of structural organization of the three families of repetitive sequences. Os48 and Osc-567 are organized in long tandem arrays, whereas copies of the OsG3-340 sequence are interspersed with other sequences including arrays of the Os48 and Osc567 families. Interestingly, the three families of repetitive sequences are closely linked not only to each other, but also to telomeric sequences of rice, suggesting that transcription of these repetitive sequences may occur in regions very close to telomeres in rice.

Base Sequence↗
PubMed1994

Control of keratin gene expression by vitamin A in tracheobronchial epithelial cells.

Vitamin A (retinol) treatment induces (and/or enhances) mucous cell differentiation and alters keratin gene expression in cultured airway epithelial cells of human and nonhuman primate origin. We observed that retinol greatly reduced the synthesis of keratins 5, 6, 14, 16, and 17, but slightly enhanced keratins 7, 8, 10, 13, 15, 18, and 19. These changes were also reflected at the mRNA level as demonstrated by cell-free translation and by cDNA cloning of human keratin genes based on differential hybridization. One of these cDNA clones, HT27, isolated from the cDNA library of human tracheobronchial epithelial cells and whose expression in cultured cells was greatly suppressed by retinol, had a nucleotide sequence identical to the C-terminus of keratin 16. The identity of this clone was further confirmed by Western blot analysis using an antibody specific to the 15-amino acid synthetic peptide and the C-terminal sequence. Using this cDNA clone and two known keratin clones, pKA1 (keratins 5 and 6) and pKB2 (keratin 14), we found the levels of these corresponding mRNAs in cultured cells to be reduced 10- to 25-fold after treatment of cells with vitamin A. The inhibition was time- and dose-dependent with respect to retinol and was sensitive to prior treatment with cycloheximide. However, nuclear run-on transcriptional assays revealed no significant reduction of the synthesis of these messages in retinol-treated cultures. Furthermore, no change in the half-life of these mRNAs was observed in cells after the retinol treatment. Based on these results, we conclude that vitamin A indirectly controls the synthesis of these keratins at the post-transcriptional level.

Amino Acid Sequence↗
PubMed1994

Expression of MUC2 gene is down-regulated by vitamin A at the transcriptional level in vitro in tracheobronchial epithelial cells.

The functional role of airway mucin in the respiratory system is well recognized. The isolation of mucin cDNA clones, MUC genes, introduces new information regarding the structure of the mucin core protein; however, the nature of the authentic core protein of airway mucin is still unresolved. In this communication, the effects of vitamin A on the regulation of MUC2 gene expression in primary tracheobronchial epithelial (TBE) cells of human and nonhuman primates were examined. Vitamin A has been recognized as one of the most important nutrients in the regulation of airway mucous cell differentiation. The expression of the MUC2 gene has been demonstrated in both rat and human tracheal tissues. The monkey cDNA clone MT80 was isolated from a cDNA library derived from vitamin A-depleted cultures of monkey TBE cells using a synthetic oligonucleotide probe corresponding to the 69 nucleotides of a tandemly repeated sequence in human MUC2 cDNA. DNA sequencing revealed a similar tandemly repeated sequence, except that 72 oligonucleotide repeats were observed in the monkey cDNA clone. Using the MT80 cDNA as a probe, the expression of the MUC2 gene was studied in vitro. The corresponding MUC2 message level in primary cultures of monkey TBE cells was down-regulated by vitamin A. This result was consistently demonstrated in primary human and hamster TBE cultures. The down-regulation was both time- and dosage-dependent on vitamin A. A nuclear run-on assay demonstrated a decrease in the transcriptional rate of the MUC2 gene in nuclei isolated from vitamin A-treated cultures. These results suggest that MUC2 gene expression in TBE cells is transcriptionally down-regulated by vitamin A.

Amino Acid Sequence↗
PubMed1994

Coordinated expression of a 45 kD protein and ozone toxicity in a human bronchial epithelial cell line.

The human bronchial epithelial cell line, BEAS-2B, which was immortalized by transformation with SV40 virus, when grown biphasically between 0.1 and 1.0 ppm of ozone and liquid medium showed increased release of Cr, decreased synthesis of various macromolecules, and decreased cell viability. Cell injury was a function of the concentration of ozone to which the cells were exposed. Furthermore, in proportion to the extent of cell injury, ozone exposure also induced and/or enhanced synthesis of a 45 kD protein but not any of the well-characterized heat shock proteins, e.g., HSP 70. Actinomycin D prevented enhanced synthesis of the 45 kD protein in cells exposed to ozone, suggesting transcriptional regulation of expression of the 45 kD protein. Enhanced synthesis of the 45 kD protein was not observed in cells treated with heat, cigarette smoke condensate, hydrogen peroxide, or bleomycin. High concentrations of glutathione added to the culture medium reduced ozone toxicity and ozone-enhanced synthesis of the 45 kD protein. These results suggest that ozone injury and enhanced expression of a gene encoding a 45 kD protein of as yet unknown function are coordinated in the SV40-immortalized bronchial epithelial cells.

Bleomycin↗
PubMed1994

The effect of luteinizing hormone-releasing hormone analog for central precocious puberty on growth hormone (GH) and GH-binding protein.

The pubertal growth spurt is characterized by a marked increase in the amplitude of GH secretory pulses. The high affinity GH-binding protein (GHBP) reportedly has an important role in enhancing the growth-promoting action of GH. Levels of GHBP are characteristic for an individual and increase only slightly as puberty progresses. It has been hypothesized that each individual adjusts GH production to a level appropriate for his GHBP environment. The withdrawal of gonadal steroids that occurs in children with central precocious puberty (CPP) treated with LH-releasing hormone agonist (LHRHa) therapy results in a decrease in growth velocity (GV) and GH secretion. This study was performed to determine the effect of treatment of CPP with the LHRHa leuprolide acetate for depot suspension on GH secretion and levels of GHBP. Six girls and one boy with CPP were studied before and 6 months after treatment was initiated. Within 6 months of initiation of therapy, there was a significant decline in GV, from 8.9 +/- 3.2 to 5.4 +/- 2.0 cm/yr (P < 0.05). Twelve-hour mean nocturnal GH levels decreased significantly from 8.6 +/- 3.5 to 5.1 +/- 2.3 micrograms/L (P < 0.05). This occurred via a decrease in the amplitude of GH pulses as the number of peaks remained 4.6 and 4.1/12 h. Individual levels of GHBP were variable and reflect the wide range of levels observed in normal children. Although GV and GH levels decreased substantially, mean GHBP levels remained unchanged at 139.9 +/- 46.0 and 152 +/- 39.8 pmol/L. In children with CPP, within 6 months of LHRHa therapy, the decrease in GV occurs via a decrease in nocturnal GH secretion as levels of GHBP remain unchanged. In children with CPP, the withdrawal of gonadal steroids may inhibit the child's ability to secrete the GH appropriate for his/her GH/GHBP milieu.

Body Mass Index↗
PubMed1994

Mutagenic activity of heterocyclic amines in cooked foods.

Mutagenic heterocyclic amines are generated in foods when they are cooked at temperatures over 150 degrees C. These compounds are present from 0.1 to 50 ppb, depending on the food and cooking conditions. These heterocyclic amines are not only present in cooked red meat, fish, and chicken, but are also present at lower levels in baked and fried foods derived from grain. Mutagenicity of fried beef hamburgers cooked at 230 degrees C is 800 +/- 37 TA98 revertants per gram cooked weight. We measured 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MelQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMelQx), and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) formation at this temperature and found 3.0 +/- 2.0, 1.0 +/- 0.18, and 0.06 +/- 0.03 ng/g, respectively. 2-amino-1-methyl-6-phenylimidaz[4,5-b]pyridine (PhIP) was found at a higher concentration of 9.6 ng/g. In our laboratory we have shown these heterocyclic amines are capable of producing both reverse and forward mutations in Salmonella bacteria and forward mutations in Chinese hamster ovary cells (CHO). We have also been able to show a statistically significant increase in mutations in the pancreas of the "mutamouse" following PhIP exposure. The pancreas also shows relatively high DNA binding compared to other organs in the mouse. The number and type of mutations depend on the repair capacity of the cells for both Salmonella and CHO. In Salmonella the mutations are primarily 2-base deletions when the cells lack uvrB repair, but mutations are more complex (larger deletions and insertions) but lower in frequency when repair is functional.(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗
PubMed1994

The ten point clock test: a quick screen and grading method for cognitive impairment in medical and surgical patients.

OBJECTIVE: The objective of this study was to evaluate the clinical utility of the ten point clock test in screening for and grading cognitive deficits in medical and surgical patients. METHOD: The setting was the hospital and clinics of Virginia Mason Medical Center, a tertiary referral center. Consecutive samples of hospitalized patients, and clinic outpatients--with and without a dementia--were administered the ten point clock test as well as a number of other neuropsychological tests and measures of cognitive impairment. RESULTS: Clock scores correlated with neuropsychological test scores and with the mini-mental state examination. They were stable from rater to rater, and from day to day in stable patients. The mean clock score of elderly outpatient controls was 8.5, significantly different from the mean of 5.5 scored by patients with a dementia. A cut off score of seven identified 76 percent of outpatients with dementia and 78 percent of elderly controls. Clock scores correlated well with nurses' ratings of their inpatients' cognitive deficits (Spearman's rs = -0.61). The test was easy to administer, even to hospitalized patients. CONCLUSIONS: The ten point clock test is reliable, valid, and useful as a quick screen and grading method for cognitive deficits in medical and surgical patients.

Adult↗
PubMed1994

A PCR differential screening method for rapid isolation of clones from a cDNA library.

We have developed a new two-step differential screening method that allows the rapid isolation of induced or suppressed pure gene clones from a lambda phage cDNA library. This method involves a primary differential screening step and a PCR differential screening step. From the primary screening step, impure pools of positive cDNA clones are obtained. Each pool of clones is then amplified directly by PCR using two primers flanking the cloning site in the vector. The PCR products are run on two duplicate agarose gels and blotted onto two filter strips. These two filters are then subjected to differential Southern hybridization with different cDNA probes. Each pure positive cDNA band on the gel is identified and selected for further subcloning. This method has three advantages over the traditional differential screening method. First, several rounds of plaque rescreening are replaced by a single PCR screening. Second, plaque hybridization is replaced by a more reliable and accurate PCR DNA Southern hybridization. Third, the time-consuming and tedious phage DNA isolation step is eliminated, and subcloning is facilitated by direct cloning of the pure PCR product to a plasmid vector. We have successfully used this method to isolate ozone-responsive genes from a cDNA library of monkey respiratory airways.

Animals↗