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Biomedical subjects

J K Liu

Publications and source records attributed to J K Liu.

At least 73 records · Page 4Linked to original sources
PubMed1991

The effects of streptozotocin induced diabetes mellitus and fish oil compound on gene expression of atrial natriuretic peptide in rat.

1. Adult male Wistar rats were injected with streptozotocin (STZ: 55 mg/kg) for inducing diabetes. Then blood and atria for RNA extraction were withdrawn from rats treated 3 and 11 weeks previously with STZ respectively. Atrial total RNA were extracted with cold phenol method. The ANP mRNA contents were determined using Dot blot hybridization technique with alpha-32-P-labelled r-prepro ANP cDNA probe. 2. Plasma glucose was increased and plasma immunoreactive insulin was lowered in rats at 3 and 11 weeks after injection of STZ. ANP gene expression in diabetic rats was depressed. ANP mRNA contents in rats treated 3 and 11 weeks with STZ were 86.4% and 31.7% of that of control rats. 3. Three weeks after treatment of STZ, the rats were gastrically perfused with FOC (Fish Oil Compound) (0.355 ml/kg) once a day successively until 11 weeks. This treatment induces lower blood pressure in rats. ANP gene expression in FOC group was apparently recovered which had been decreased because of the effect of diabetes mellitus.

Animals↗
PubMed1991

Extracellular signals that regulate liver transcription factors during hepatic differentiation in vitro.

A complex cell culture environment has been shown to maintain the differentiated state of hepatocytes, yet the mechanisms by which environmental cues selectively maintain liver-specific gene transcription have been unknown. In this paper we show that the hepatic environment regulates the activities of at least three liver-enriched transcription factors, eE-TF, eG-TF/HNF3, and eH-TF, that activate the mouse serum albumin enhancer. eE-TF is a heat-stable factor that has a DNA-binding specificity similar to that of the liver transcription factor C/EBP, but is a distinct protein. eG-TF/HNF3 contributes to the liver-specific transcription of several other serum protein genes. eH-TF binds to a TGTTTGC sequence that occurs at regulatory sites of the albumin promoter, the hepatitis B virus enhancer, and other hepatic genes. eE-TF, eG-TF/HNF3, and eH-TF are regulated by different combinations of the following cell culture conditions: a hormonally defined serum-free medium; an extracellular matrix gel; and a transformation-competent simian virus 40 large T antigen. We propose a regulatory network model to explain how cues from the cell lineage and the extracellular environment coordinately help maintain the activities of transcription factors involved in hepatocyte differentiation.

Animals↗
PubMed1991

Effects of Guilingji on brain monoamines and their metabolites in mice.

Guillingji powder, a complex prescription of traditional Chinese medicines, has been pharmacologically shown to be a possible anti-aging agent, and also used for the treatment of male hypogonadism and female dysgenesis. Since the levels of numerous brain monoamines and their metabolites such as norepinephrine (NE), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT), and 5-hydroxyindole acetic acid (5-HIAA) have been correlated with aging, we examined the effects of Guilingji powder and its extract on such monoamines and metabolites in the cerebrum and the cerebellum of mice using HPLC-ECD. The results showed that dietary intake of Guilingji powder had the effect of increasing the NE level and the DOPAC/DA ratio, and decreasing the 5-HT level and 5-HT/NE ratio in the cerebrum. In the cerebellum, the powder did not produce any changes in the levels of the compounds investigated. The extract of Guilingji, on the other hand, not only increased the NE level and the DOPAC/DA ratio but also the 5-HIAA/5-HT ratio in the cerebrum. However, the extract did not decrease the 5-HT in the cerebrum, although it decreased the 5-HT/NE. Unlike the powder, the extract had an effect in the cerebellum, which increased the DOPAC/DA ratio. These results suggest that Guilingji may have the action of modulating the levels and the metabolism of monoamines.

Animals↗
PubMed1991

Tensile bond strength of reused orthodontic metal brackets.

Forty-five orthodontic brackets were used in this study on the bond strength of new and reused metal brackets using an Instron testing machine. First, new brackets were bonded to recently extracted human premolars and subjected to a bond strength test. After the test, the residual resin on 15 brackets each were removed by one of three methods, oven-treated, flame-treated and bur-treated. They were then rebonded to the cleansed tooth surface and again subjected to a bond strength test. The new brackets were found to have the greatest bond strength (13.71 +/- 2.95 kg) with the oven-treated brackets in second place (12.42 +/- 2.57 kg), followed by flame-treated (11.35 +/- 2.32 kg) and bur-treated (9.11 +/- 2.30 kg). The results were subjected to the Mann-Whitney U test. The differences in bond strength between the new and reused brackets were found to be statistically significant (p less than 0.05), except for the oven-treated group. The differences in bond strength between the reused brackets were also found to be statistically significant (p less than 0.05), with the exception of the comparison between the oven-treated and flame-treated groups.

Dental Bonding↗
PubMed1990

Site-directed mutagenesis reveals a liver transcription factor essential for the albumin transcriptional enhancer.

A method based on the polymerase chain reaction is described for constructing a clustered set of basepair changes, deletions, or insertions at any site on a DNA fragment. Advantages of the procedure are that virtually every product has the desired sequence alteration and that only a single round of polymerase chain reaction is required. We used this method to demonstrate that the binding of a specific liver nuclear protein, which we call eH-TF, is essential for the function of the enhancer of the mouse albumin gene. The eH-TF binding activity is hepatocyte-specific; it binds to a functional region of the albumin promoter and is distinct from other albumin promoter factors, and part of the eH-TF binding sequence, TGTTTGC, occurs in functional regulatory sites of other liver-specific genes.

Animals↗
PubMed1990

Analyses of surface membrane carbohydrates in parasitic flagellates of the order kinetoplastida using lectins.

Crithidia fasciculata, Leishmania donovani, Leishmania major, Leishmania mexicana amazonensis, Leishmania tropica, Leishmania tarentolae, Trypanosoma sp. from Formosan bats (Tb), Trypanosoma lewisi, Trypanosoma musculi, and different strains of Trypanosoma cruzi (Tc) were cultivated at 27 degrees C in a liquid culture medium. Flagellates harvested from log phase culture were analyzed for their lectin agglutinating characteristics with concanavalin A (Con A), Peanut agglutinin, Ricinus communis agglutinin 120, soybean agglutinin (SBA), Ulex europeus agglutinin (UEA) and wheat germ agglutinin (WGA). Results indicated that all these flagellates might have D-galactose and methyl- alpha-D-manopyranoside on their surface. The presence of L-Fucose, which complexes specifically with UEA, could not be demonstrated on the surface of these flagellates. Results from quantitative comparison of surface molecules of Tb and the Tulahuen strain of Tc suggested that Tb may have more WGA-binding molecules while Tc may have more ConA-binding molecules. Pretreatment of the flagellates with 0.05% trypsin at 37 degrees C for 30 minutes caused some reduction of agglutination titers. Cell agglutination with lectins was completely inhibited or reversed in the presence of the specific lectin-binding monosaccharides.

Agglutination↗
PubMed1989

Nutritional evaluation of blood meal and feather meal for turkeys.

Three samples each of commercial blood meal (BL) and feather meal (FEA) were obtained in Minnesota. True amino acid availability (TAAA) and TMEn contents were determined using Large White male turkeys at 8 wk of age. Average TMEn were 3,458 and 2,976 kcal/kg (DM basis) for BL and FEA, respectively. The TAAA of BL ranged from 86 to 91% for each of 15 amino acids except for isoleucine (74%) and cystine (79%). The TAAA of FEA ranged from 59 to 83%. The three feather meals averaged 72, 72, and 76% in amino acid availability. Two ring-dried blood meals averaged 86 and 82% and one spray dried blood meal averaged 91% in amino acid availability. A positive linear relationship was found between TMEII and TAAA of blood and feather meal samples, suggesting the possibility of approximating the estimation of one from the other in certain ingredients of high protein content.

Amino Acids↗
PubMed1989

Effects of sonication and growth temperature on the cytochrome oxidase activity of Bacillus species.

The cytochrome oxidase activity of Bacillus strains was analyzed quantitatively by colorimetric N, N, N', N'-tetramethyl-p-phenylene-diamine (TMPD) oxidase assay. Twenty six type strains were readily grouped, the oxidase positive, the oxidase negative, and the oxidase indeterminate groups. TMPD-dependent oxidase activities for whole cells and sonicated cells were compared. Spectral absorbance analyses of membrane fractions showed that all 26 Bacillus type strains contained the o-type cytochrome oxidase; 19 strains contained cytochrome a + a3 and among which 5 strains contained cytochromed. All of the 10 thermophilic Bacillus strains, which were predominantly oxidase positive, exhibited maximum oxidase activity when grown at optimum temperature (65 degrees C). The other three "caldo-active" thermophiles exhibited maximum oxidase activities when grown at their optimum temperatures, 70 degrees C to 80 degrees C. Mesophilic B. cereus and B. subtilis exhibited maximum oxidase activity in cells grown at 42 degrees C and 55 degrees C, respectively. In no case did growth temperature induce oxidase negative strains to exhibit an oxidase positive reaction, and vice versa.

Bacillus↗
PubMed1989

[A comparative study of EEG in patients with neurological and myxedematous cretinism].

A comparative study of EEG between neurological and myxedematous cretins was carried out in a total of 61 cases. The results were as follows: (1) The changes of EEG in myxedematous cretins appeared to be more obvious than those in neurological cretins; (2) The degree of mental retardation in cretins was not parallel to the degree of the abnormality of EEG; (3) with thyroid therapy, EEG in cretins was improved. The improvement rate in myxedematous cretins was higher than that in neurological cretins; (4) Brain CT scan was carried out in 50 cases of those cretins. It was found that the abnormality of certain intracerebral structure in myxedematous cretins appeared to be more obvious than that in neurological cretins. The change of EEG appeared in the same way as well. This is in contradiction to the traditional knowledge that the defect of neurological system in neurological cretinism was more severe than that in myxedematous cretinism. The current classification of cretins into neurological and myxedematous cretins does not reflect the changes of pathophysiology properly.

Adolescent↗
PubMed1988

The mouse albumin promoter and a distal upstream site are simultaneously DNase I hypersensitive in liver chromatin and bind similar liver-abundant factors in vitro.

In this paper we characterize the chromatin structure and nuclear proteins associated with different transcriptional states of the mouse serum albumin gene. We found the albumin gene to be transcribed in liver at rates 1000-fold or greater than in other tissues tested. We discovered seven DNase I hypersensitive sites encompassing the albumin gene only in liver chromatin, with strong hypersensitivity at the promoter and the enhancer, which is over 10 kb upstream. Using a gel retardation assay, we found a liver nuclear protein, or set of proteins, which binds specifically to DNA of a liver-specific hypersensitive site that maps 3.5 kb upstream, between the promoter and enhancer. Footprinting, heat insensitivity, and binding competition experiments indicate that the protein(s) have characteristics similar to a heat-stable, liver-abundant protein that binds to the albumin promoter and other enhancer and promoter sequences. Finally, we asked whether the liver-specific factors that cause DNase I hypersensitivity in vivo are present concurrently at the various sites in chromatin. We devised a simple new method to reveal that in liver, individual albumin genes are hypersensitive simultaneously at the promoter, the enhancer, and the -3.5-kb site. Thus, transcriptionally active albumin genes appear to contain tissue-abundant factors that are present at three widely spaced points in chromatin, yet at the same point in time. Similar factors binding simultaneously to at least two of these sites could create a specific structure in chromatin required for high-level albumin gene transcription.

Animals↗
PubMed1987

Quantitative and qualitative aspects of fish crop in relation to environmental quality.

The effects of environmental quality on the quantitative and qualitative aspects of fish crop are reviewed with reference to fisheries in rivers, lakes, reservoirs, and coastal waters ranging from the temperate zone to subtropical areas in mainland China. The mechanism of these effects is discussed, and the insidiousness of long-term exposure to low-concentration pollutants to fish stock is stressed. Regarding the assessment of the effect of pollution on fish, most of our information has been derived from laboratory studies, in which the antagonistic or synergistic action between multiple pollutants was scarcely taken into consideration. One has to be cautious when the results of laboratory experiments are extrapolated to the realistic natural environment. It is advocated that surveys and tests concerning the relation between environmental quality and fish life be made on natural waters in addition to laboratory studies, and the effects be elucidated at the individual level, population level, and the ecosystem level.

Animals↗
PubMed1984

Comparative Cytochrome Oxidase and Superoxide Dismutase Analyses on Strains of Azotobacter vinelandii and Other Related Free-Living Nitrogen-Fixing Bacteria.

Quantitative N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) oxidase and superoxide dismutase (SOD) analyses were performed on representative organisms of the family Azotobacteraceae. Azotobacter vinelandii, Azotobacter chroococcum, Azotobacter paspali, and Derxia gummosa exhibited high quantitative TMPD oxidase activities, and their extracts possessed very active and electrophoretically homogeneous (single gel band) Fe-type SODs. Azomonas macrocytogenes extracts had similar single Fe-type SODs, and their cells exhibited no TMPD-dependent cytochrome oxidase activity. Nitrogen-fixing cells of Beijerinckia indica, Beijerinckia derxii, and Beijerinckia mobilis exhibited minimal TMPD oxidation capabilities (rates equivalent to the TMPD autooxidation reaction), and these extracts also possessed very active SODs but only of the Mn metallotype.

Journal Article↗
PubMedDate not supplied

Improving cephalogram analysis through feature subimage extraction.

An MLP with a GA was proposed to extract feature subimages containing orthodontic landmarks. Simulated images and cephalograms were used to investigate its performance in comparison with the cross-correlation method. From the results of simulated image containing shapes with different geometrical conditions, it was shown that the fault tolerance of the MLP for rotation, scaling, brightness variety, and other anomalous deformations is good enough to overcome the clinical application problems. It was also shown that the stability, accuracy, and speed of this proposed algorithm are very promising. Moreover, the performance of the MLP can be significantly improved by collecting, more "representative" false patterns. The GA is a good approach to speed up the process of feature subimage extraction based on the fitness evaluated using the MLP.

Algorithms↗
PubMedDate not supplied

Association of functional malocclusion with temporomandibular disorders in orthodontic patients prior to treatment.

The purpose of this study was to investigate the role of functional malocclusion in temporomandibular disorders (TMD) in untreated orthodontic patients. A total of 508 orthodontic patients were enrolled. All patients were evaluated for the presence of various types of functional malocclusion and clinical signs of TMD before treatment. The chi-square test was used to evaluate the association of functional malocclusion and TMD. The frequencies of TMD were 44.2% in patients with retruded position (RP) interference and 38.1% in those without such interference (p > 0.05). The frequency of TMD in patients with protrusive interference was greater than those without (32.2% vs. 18.4%; p < 0.005). Patients with balancing interference had a significantly higher frequency of TMD than those without (49.2% vs. 23.9%; p < 0.0001). We thus conclude that patients with functional malocclusion of balancing or protrusive interference type have an increased risk for developing TMD.

Adolescent↗
PubMedDate not supplied

The prevalence of TMD in orthodontic patients prior to treatment at NCKUH in southern Taiwan. National Cheng Kung University Hospital.

Orthodontic treatment is considered one of the risk factors for temporomandibular disorders (TMD). However, TMD may occur before orthodontic treatment. The purpose of this study was to investigate the prevalence of TMD in orthodontic patients prior to treatment. The samples consisted of 508 patients (214 males and 294 females) at the National Cheng Kung University Hospital (NCKUH) in southern Taiwan. Ages ranged from 6 to 56 years. TMD signs were recorded by clinical examination prior to treatment. The overall prevalence of TMD was 26.6%. The prevalence was slightly higher in females (27.2%) than males (24.8%). However, the difference was not statistically significant. The prevalence of TMD in children (ages 6-17) and adults (ages 18-56) was 16.5% and 43.6%, respectively. The difference was statistically significant. Distribution of TMD signs was joint sounds (32.3%), muscle or joint pains (32.3%), muscle or joint pains (32.3%), mouth opening less than 35 mm (18%), combination of two signs (16.5%) and combination of three signs (0.8%).

Adolescent↗