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Biomedical subjects

L Wu

Publications and source records attributed to L Wu.

At least 649 records · Page 36Linked to original sources
PubMed1993

3'-end processing of the maize 27 kDa zein mRNA.

Cis-regulatory elements involved in the mRNA 3'-end processing of the 27 kDa zein gene have been investigated by deletion and site-directed mutagenesis analyses. In the 3' flanking region of the 27 kDa zein gene, several AATAAA-like sequences and a sequence resembling the mammalian GT-rich sequence are present around the polyadenylation sites. Among the multiple AATAAA-like sequences, the duplicated AATGAA motifs, located 30-40 bp upstream from the polyadenylation sites, have been shown to play roles as polyadenylation signals. Although either of the two AATGAA motifs can function as a polyadenylation signal in chimeric gene constructs, the one proximal to the polyadenylation sites is likely to be the functional polyadenylation signal in the 27 kDa zein gene. Deletion of the downstream GT-rich sequence as well as alteration of the sequence surrounding the poly-adenylation sites has little effect on the mRNA 3'-end processing. However, the sequence elements located upstream from the polyadenylation signals are essential for the mRNA 3'-end processing. Mutations in the AATGAA motifs or the upstream sequences reduced the level of a reporter gene expression. A model depicting the mechanism involved in the 3'-end processing of the 27 kDa zein mRNA is presented.

Base Sequence↗
PubMed1993

Segmentation in local hospital markets.

This study examines evidence of market segmentation on the basis of patients' insurance status, demographic characteristics, and medical condition in selected local markets in California in the years 1983 and 1989. Substantial differences exist in the probability patients may be admitted to particular hospitals based on insurance coverage, particularly Medicaid, and race. Segmentation based on insurance and race is related to hospital characteristics, but not the characteristics of the hospital's community. Medicaid patients are more likely to go to hospitals with lower costs and fewer service offerings. Privately insured patients go to hospitals offering more services, although cost concerns are increasing. Hispanic patients also go to low-cost hospitals, ceteris paribus. Results indicate little evidence of segmentation based on medical condition in either 1983 or 1989, suggesting that "centers of excellence" have yet to play an important role in patient choice of hospital. The authors found that distance matters, and that patients prefer nearby hospitals, moreso for some medical conditions than others, in ways consistent with economic theories of consumer choice.

California↗
PubMed1993

Osseous changes following placement of the transmandibular implant system in edentulous mandibles.

The transmandibular implant system is designed for the reconstruction and rehabilitation of the endentulous mandible utilizing an extraoral approach. Transmandibular implants were placed in 19 patients and mandibular bony changes were followed using standardized panoramic radiography. Eleven sites were identified on each postoperative radiograph and the percentage of radiographic enlargement was calculated for each site. The true bony changes were then computed for both short-term (9.4 months) and long-term (53.4 months) follow-up. Patients with an average mandibular height in the saddle areas of 3.5 to 8.9 mm showed bilateral bony regeneration in the saddle areas and over the most distal cortical screws of the implants. Most of these bony changes were seen in the first year, but continued beyond that time. Patients with residual bone height of 9.0 to 12.9 mm had little bone change, while patients with bone height of 13.0 to 20.5 mm demonstrated slight resorption. Theories for the observed changes are presented. The transmandibular implant is especially indicated for the severely atrophic mandible because its position within the mandible and the rigid box frame design of the implant promote bilateral bone regeneration distal to the framework of the implant.

Aged↗
PubMed1993

A G-protein beta-subunit is essential for Dictyostelium development.

Recent studies have demonstrated that G-protein-linked signal transduction pathways play a significant role in the developmental program of the simple eukaryotic organism Dictyostelium. We have reported previously the isolation of a G-protein beta-subunit and present here a more complete analysis of this gene. Low-stringency Southern blots and RFLP mapping studies suggest that the beta-subunit is a unique gene found on linkage group II. Its deduced amino acid sequence of 347 residues is approximately 60% identical to those of the human, Drosophila, and Caenorhabditis elegans beta-subunits. The carboxy-terminal 300 residues are about 70% identical; the amino-terminal 50 residues are quite divergent, containing only 10 identities. At all stages of growth and development, a single 1.9-kb beta-subunit mRNA is present at a high level, and a specific antibody detects a single 37-kD protein. We propose that G-protein heterotrimers are formed when this beta-subunit couples with each of the eight distinct G-protein alpha-subunits that are transiently expressed during development. Targeted disruption of the beta-subunit gene had no effect on the viability of haploid cells, but resulted in the inability of cells to aggregate.

Amino Acid Sequence↗
PubMed1993

Reconstitution of the Raf-1-MEK-ERK signal transduction pathway in vitro.

Raf-1 is a serine/threonine kinase which is essential in cell growth and differentiation. Tyrosine kinase oncogenes and receptors and p21ras can activate Raf-1, and recent studies have suggested that Raf-1 functions upstream of MEK (MAP/ERK kinase), which phosphorylates and activates ERK. To determine whether or not Raf-1 directly activates MEK, we developed an in vitro assay with purified recombinant proteins. Epitope-tagged versions of Raf-1 and MEK and kinase-inactive mutants of each protein were expressed in Sf9 cells, and ERK1 was purified as a glutathione S-transferase fusion protein from bacteria. Raf-1 purified from Sf9 cells which had been coinfected with v-src or v-ras was able to phosphorylate kinase-active and kinase-inactive MEK. A kinase-inactive version of Raf-1 purified from cells that had been coinfected with v-src or v-ras was not able to phosphorylate MEK. Raf-1 phosphorylation of MEK activated it, as judged by its ability to stimulate the phosphorylation of myelin basic protein by glutathione S-transferase-ERK1. We conclude that MEK is a direct substrate of Raf-1 and that the activation of MEK by Raf-1 is due to phosphorylation by Raf-1, which is sufficient for MEK activation. We also tested the ability of protein kinase C to activate Raf-1 and found that, although protein kinase C phosphorylation of Raf-1 was able to stimulate its autokinase activity, it did not stimulate its ability to phosphorylate MEK.

Animals↗
PubMed1993

Neural effects of parathyroid hormone: modulation of the calcium channel current and metabolism of monoamines in identified Helisoma snail neurons.

Neuronal effects of parathyroid hormone (PTH) have been reported in vertebrates. The effect of PTH on invertebrate central neurons within the buccal ganglion of Helisoma trivolvis snails was examined in the present study. By using a vibrating probe, PTH was found to induce a transient calcium-dependent inward current in intact buccal ganglia. Intracellular microelectrode recording revealed that PTH broadened the spontaneous action potential in buccal B5 neurons in situ. By using the whole-cell configuration of the patch-clamp technique, PTH was demonstrated to increase the N-like calcium channel currents in isolated B5 neurons in a concentration-dependent manner. This effect of PTH on the N-like calcium channel currents depended on the activation of a G protein insensitive to pertussis toxin, but was unlikely to be mediated by the cyclic AMP dependent protein kinase. Furthermore, the release of gamma-glutamyl conjugate of dopamine from buccal ganglia was selectively increased in the presence of PTH. These results represent the first demonstration that a vertebrate peptide hormone, PTH, selectively modulates the N-like voltage-dependent calcium channel currents in identified invertebrate neurons. Therefore, a novel role of PTH in the regulation of invertebrate central neural functions is indicated.

Action Potentials↗
PubMed1993

Cyclin A expression in normal and transformed alveolar epithelial cells.

The mature adult alveolar epithelial cell (AEC) is a highly differentiated phenotype that does not readily divide and exhibits numerous specialized functions. Yet, transformed AEC proliferate aggressively in certain forms of lung cancer. Normal AEC also proliferate but in a coordinated manner during embryonic growth and fetal development as well as during lung repair. Therefore, biochemical mechanisms regulating the cell cycle in AEC are clearly of fundamental significance for understanding lung development, lung injury, and cancer. Cyclin A is a protein that varies in abundance during the cell cycle and regulates critical transition points through its association with cyclin-dependent protein kinase subunits. We postulated that high expression of cyclin A might be associated with rapid proliferation in transformed AEC. We compared the expression of cyclin A mRNA and protein in primary cultures of fetal and adult rat AEC, in the E1A-T2 neonatal rat AEC, and in the malignant A549 human AEC. We used pharmacologic blockades with mimosine, aphidicolin, and nocodazole for cell cycle synchronization, which was verified by fluorescence-activated cell sorter (FACS) analysis of cellular DNA content. Transformed cells (A549 and E1A-T2) exhibited a much higher level of expression for both cyclin A mRNA and protein than did normal rat AEC. Induction of cyclin A mRNA expression in A549 human AEC and E1A-T2 rat AEC occurred in late G1, prior to the onset of S phase. Fetal and adult rat AEC and rat E1A-T2 AEC expressed two cyclin A mRNA transcripts, whereas human A549 cells in S phase and M phase expressed three cyclin A mRNA transcripts. We conclude that transformed AEC overexpress cyclin A in comparison with primary AEC cultures, while retaining cell cycle-dependent differences in cyclin A expression. We speculate that cyclin A expression is regulated both at the transcriptional and post-transcriptional levels, and that cyclin A may play a key role in the increased proliferation of transformed AEC that is associated with the pathogenesis of lung cancer.

Animals↗
PubMed1993

Fukuyama type congenital muscular dystrophy with central-temporal EEG foci (rolandic spikes).

Central-temporal EEG foci (rolandic spikes) in three patients who satisfied all the diagnostic criteria for Fukuyama type congenital muscular dystrophy (FCMD) are reported. Clinically one case remained silent and two cases were accompanied by epileptic seizures, characterized as follows: 1) partial seizures with elementary motor symptomatology; 2) brief and rare seizures, but occasionally with frequent or prolonged convulsions; 3) seizures were easily induced by defined precipitating factors such as fever; 4) seizures could be quickly controlled by routine antiepileptic treatment. Electroencephalographically, the appearance of repetitive stereotyped diphasic spikes over central and mid-temporal areas were quite similar to those described in rolandic epilepsy. We believe that the EEG findings in our cases corroborate the postulation that the prognosis is as good in these severely brain-damaged children as in normal children in terms of recovery from the epilepsy.

Brain↗
PubMed1993

[Quantitative perimetry for early diagnosis of open-angle glaucoma].

105 eyes were examined with the OCTUPUS 2000R automated perimeter. Of 19 glaucomatous eyes with abnormal visual fields by arc perimeter and campimeter, all showed field abnormalities by the quantitative perimetry, the defects being mostly of the mixed type (13/19), in the medium stage (10/19). Among 48 eyes of glaucoma or suspected glaucoma with normal visual fields by arc perimeter and campimeter, 33 showed field abnormalities by the quantitative perimetry, the defects being mostly of the mixed and diffuse type (29/33), in the early minor stage (23/33). The characteristic field defects were mostly sectorial and arcuate scotomata and some in the form of nasal steps. Among 38 normal eyes, minor local or diffuse field defects were found in 6 eyes.

Adult↗
PubMed1993

An immunologic study on age-related macular degeneration.

Forty-one patients with age-related macular degeneration (AMD) were detected for serum autoantibodies against normal human retinal protein by means of Western immunoblot analysis. Twenty-seven out of the 41 patients showed positive response, with a rate of 66 per cent. The positive rate of anti-retinal antibody in the AMD patients was significantly higher than that in normal controls (18%) and in patients with other retinal diseases (24%) (p < 0.0005). These antiretinal antibodies from the AMD patients partly reacted with the retinal protein of molecular weight between 28 and 32 Kd, partly with Mr of 38 to 42 Kd, 48 to 52 Kd, 62 to 65 Kd or 110 to 130 Kd. Of them, the antiretinal antibody against the protein with Mr of 28 to 32 Kd in the AMD patients was higher than in normal controls (p < 0.05). Two or more antibodies were found in the serum from AMD patients, showing a significant difference between the patients and the controls (p < 0.005). The results indicated that in the occurrence of AMD and/or during its developing process there were inflammation and immunological response, involving antibodies against retinal proteins of various molecular weight.

Aged↗
PubMed1993

The normal color vision evaluated with FM 100-hue test.

One hundred and twenty normal subjects (240 eyes) aged from 10 to 69 were tested with FM 100-hue test. They were divided into 6 groups according to their age. It was shown that there were no statistically significant difference in the total error score (TES) between the males and females or between the right and left eyes, but there existed some relationships between the TES and age. The total error score (TES) was the lowest in the 20-29 age group and increased gradually with aging. The analysis of the partial error score (PES) in each age group showed that the PES was the lowest in 20-29 age group and that the larger PES appeared around the axis of titan with age increasing.

Adolescent↗
PubMed1993

[The effect of acupuncture on plasticity of spinal Clarke's nucleus synaptic terminals].

Ten unilateral spared root cats with sectioned L1-S2 dorsal root ganglia, except L6, were used to explore the effect of acupuncture on plasticity of spinal Clarke's nucleus synaptic terminals. Five of the cats were needled on the operated hind limb for two courses (ten days as a course), and the other five were kept for control. Two pairs of acupoints located in the innervated area of L6 spinal nerve were used. The number of synaptic terminals per photo in neuropil of L3 Clarke's nucleus was compared directly, because there was no significant change in the area of Clarke's nucleus and its neuropil on the operated side of both groups. No significant difference was found in the number of three types of synaptic terminals between the unoperated sides of two groups, suggesting that acupuncture may not influence the contralateral side. In the control group, the number of giant axonal terminals from dorsal root of the operated side decreased to 75% of the unoperated side; however, in the experimental group, it recovered to contralateral or normal level of the operated side and was significantly higher than that of the control group's operated side, denoting that acupuncture may promote the plasticity such as collateral sprouting and synaptic reinnervation of coarse myelinated fibers from intact dorsal root, L6 mainly. The number of other two types of terminals from spinal interneurons showed no significant difference between the operated sides of two groups, indicating that acupuncture may not enhance the plasticity of nondorsal root nerve fibers.

Animals↗
PubMed1993

The natural history of dry type of age-related macular degeneration.

To study the natural history of dry type of age-related macular degeneration (AMD) and search for a sensitive method for detecting the development of the disease, the fundus fluorescein angiography, visual acuity, electroretinogram and FM 100-hue test were used to examine 75 eyes, 147 eyes, 73 eyes, and 94 eyes respectively. These examinations were taken at least twice during the follow-up periods. The average age was 63.2 years (50-80 years). The average follow-up was 29.8 months with a range of 3-74 months. It was shown tht there were not any statistically significant difference in the macular lesions and electroretinogram between the initial examinations and after follow-up (P > 0.05). 91.14% of the eyes maintained good visual acuity during the follow-up. Subretinal neovascularization developed only in one of the eyes. The total error score of FM 100-hue test had a statistically significant difference between the initial test and the test taken two years afterwards (P < 0.01). It was suggested that most of the dry type of AMD had a favorable prognosis and that color visual test was a sensitive method for monitoring the development of dry type of AMD.

Age Factors↗
PubMed1993

[The clinical use of steady-state flash visual evoked potentials].

The authors applied 30Hz flash stimuli to record steady-state flash visual evoked potentials (FVEP) and extracted the amplitudes and phases of the first and second harmonics as the characteristic value by discrete Fourier transform (DFT). 46 normal controls (89 eyes) and 78 patients (109 eyes) were detected and analysed by this method. The result showed that the characteristic values of the normal controls are significantly different in three age groups and showed the positive in 35 eyes with the optic never diseases (82.9%), 25 eyes with age-related macular degeneration (92%), and 9 eyes with retinal detachment involved macular (100%). It indicates the method is a sensitive index to evaluate the macular visual function. After preliminary observation, the visual acuities of postoperation were found above 0.4 in cataracts (28 eyes) or opacities (12 eyes) if preoperative FVEP were normal and non-complicated, or less than 0.4 if preoperative FVEP were abnormal. This suggests the method is one of the effective index to detect the postoperative vision of the media opacities. The advantages, disadvantages and the clinical applications were discussed.

Adolescent↗
PubMed1993

[Fast identification of Salmonella by chemiluminescent photographic detection].

Salmonella anatis was identified by the chemiluminescent photographic detection technique established in this lab. The horseradish peroxidase labelled antibody was incubated with the bacteria immobilized on nitrocellulose film; after washing, the film was contacted with a filter paper with absorbed chemiluminescence substrate solution. Twenty minutes of exposure of the chemiluminescence produced to X-ray film gave the positive results. As few as one hundred bacteria could be detected in about 2h. The tests showed that the specificity of the method is good.

Luminescent Measurements↗