Biomedical subjects

H Liu

Publications and source records attributed to H Liu.

At least 1,153 records · Page 64Linked to original sources

PubMed1992

Effects of maternal marginal zinc deficiency on myelin protein profiles in the suckling rat and infant rhesus monkey.

In the current study, the effects of marginal Zn deficiency on myelin protein profiles in neonatal rats and rhesus monkeys were investigated. Following mating, rats were fed a Zn-adequate diet, ad libitum (50 micrograms Zn/g; 50 Zn AL), or a marginal Zn diet (10 micrograms Zn/g) from day 0 (10 Zn d0) or day 14 (10 Zn d14) of gestation to day 20 postnatal. An additional group of dams was restricted-fed the control diet to the food intake of the 10 Zn d0 group (50 Zn RF). Day 20 pup plasma and liver Zn concentrations in the 10 Zn groups were lower than in the 50 Zn groups. In a parallel experiment, rhesus monkeys were fed a Zn-adequate ad libitum diet (100 micrograms Zn/g) or a marginal Zn diet (4 micrograms Zn/g diet; MZD) throughout gestation and lactation. Day 30 monkey infant plasma and liver Zn levels were similar in the MZD and control groups. Rat brain and monkey brain cortex weights were similar among the dietary groups. The amount of myelin recovered (mg protein/g brain) from day 20 rat pups from the 10 Zn groups was lower than that recovered from the 50 Zn rat pups. Myelin recovery from the MZD and control monkey infants was similar. When myelin protein profiles were characterized, it was found that the percentages of high-molecular-weight (HMW) proteins and Wolfgram protein were higher, whereas the percentages of small and large basic proteins were lower in myelin from the 10 Zn d0 and 50 Zn RF pups compared to the distribution in the 50 Zn AL rat pups. Results for the 10 Zn d0 and 10 Zn d14 pups were similar for all of the parameters studied. The percentage of HMW proteins was higher and that of basic protein lower in myelin from MZD monkey infants compared to the percentage of these proteins in myelin from controls. Although the interpretation of the rat data is complicated because of the anorexia associated with Zn deficiency, the observed changes in monkey myelin protein profiles provide strong evidence that maternal Zn deficiency affects myelination in the offspring.

Animals↗

PubMed1992

Structural studies on metal-serum albumin. IV. The interaction of Zn(II), Cd(II) and Hg(II) with HSA and BSA.

There have been no detailed and reliable studies on the environment and configuration of Zn(II), Cd(II) and Hg(II) in the metal centers of human serum albumin and bovine serum albumin to date. In this paper the authentic evidence for the involvement of the cystinyl sulfur atoms in the ligation to the zinc group ions has been obtained from the X-ray photoelectron spectra. The belief that each of the zinc group ions possesses several similar binding sites in human- and bovine serum albumin and is bound to the deprotonated thiol group (-RS-) of the cysteinyl residues to form tetrahedral and linear metal centers has been further confirmed by the treatment of ligand to metal charge transfer data with Jorgensen's method. According to these results, we have inferred that these binding sites may be located at the seventeen disulfide bridges, most likely at the seven pairs of adjacent disulfide bridges between positions 75 and 567, in the serum albumins.

Animals↗

PubMed1992

Inhibition of insulin-like growth factor-I responses in MCF-7 cells by 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds.

Insulin-like growth factor-I (IGF-I) stimulated the growth and [3H]thymidine uptake in MCF-7 human breast cancer cells grown in serum- and growth factor-inactivated serum-containing media. Cotreatment of the cells with IGF-I plus 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in a significant decrease in mitogen-induced cell proliferation and [3H]thymidine uptake. Similar effects were observed for cells treated with 2,3,7,8-TCDD and IGF-I plus 17 beta-estradiol. The relative antimitogenic activities of 2,3,7,8-TCDD and related compounds followed the order 2,3,7,8-TCDD greater than 2,3,7,8-tetrachlorodibenzofuran (TCDF) greater than 1,2,7,8-TCDF greater than 1,3,7,8-TCDD which was similar to their aryl hydrocarbon (Ah) receptor binding affinities. The results showed that 2,3,7,8-TCDD did not alter the IGF-I receptor mRNA levels or the KD values for binding of [125I]IGF-I to the IGF-I receptor in MCF-7 cells. However, 2,3,7,8-TCDD significantly decreased the number of IGF-I-induced IGF-I receptor binding sites and this may play a role in the growth-inhibitory properties of 2,3,7,8-TCDD and related compounds and in the 'cross-talk' between the two endocrine-response pathways.

Benzofurans↗

PubMed1992

Optimized centrifugation for rapid elution of DNA from agarose gels.

A simple method has been developed for the isolation of DNA from agarose gels. Centrifugation in a low-cost device for 45 s at low speed provides a high yield of DNA suitable for further manipulation by restriction enzymes, T4 DNA ligase, Taq polymerase, Klenow fragment, and T4 polynucleotide kinase, and also for sequencing. In contrast, centrifugation for greater than 1 min leads to coelution of substances that inhibit DNA ligase.

Blotting, Southern↗

PubMed1992

Evolution of the mitochondrial cytochrome oxidase II gene among 10 orders of insects.

We examine the complete nucleotide sequences of the mitochondrial cytochrome oxidase II gene of 13 species of insects, representing 10 orders. The genes range from 673 to 690 bp in length, encoding 226 to 229 amino acids. Several insertion or deletion events, each involving one or two codons, can be observed. The 3' end of the gene is extremely variable in both length and sequence, making alignment of the ends unreliable. Using the first 639 nucleotide positions, for which unambiguous alignments could be obtained, we examine the neighbor-joining trees based on nucleotide divergences and based on conserved subsets of that data, including transversion and amino acid and second codon position divergences. Each of these subsets produces different trees, none of which can be easily reconciled with trees constructed using morphology and the fossil record. Bootstrap analysis using second codon positions strongly supports affinities between the order Blatteria (cockroaches) and the order Isoptera (termites) and between a wasp and the published honeybee sequence (Order Hymenoptera). The divergence of insect orders is very ancient and may have occurred too rapidly for easy resolution using mitochondrial protein sequences. Unambiguous resolution of insect orders will probably require analysis of many additional taxa, using the COII gene and other conserved sequences.

Amino Acid Sequence↗

PubMed1992

Characterization of TPM1 disrupted yeast cells indicates an involvement of tropomyosin in directed vesicular transport.

Disruption of the yeast tropomyosin gene TPM1 results in the apparent loss of actin cables from the cytoskeleton (Liu, H., and A. Bretscher. 1989. Cell. 57:233-242). Here we show that TPM1 disrupted cells grow slowly, show heterogeneity in cell size, have delocalized deposition of chitin, and mate poorly because of defects in both shmooing and cell fusion. The transit time of alpha-factor induced a-agglutinin secretion to the cell surface is longer than in isogenic wild-type strains, and some of the protein is mislocalized. Many of the TPM1-deleted cells contain abundant vesicles, similar in morphology to late secretory vesicles, but without an abnormal accumulation of intermediates in the delivery of either carboxypeptidase Y to the vacuole or invertase to the cell surface. Combinations of the TPM1 disruption with sec13 or sec18 mutations, which affect early steps in the secretory pathway, block vesicle accumulation, while combinations with sec1, sec4 or sec6 mutations, which affect a late step in the secretory pathway, have no effect on the vesicle accumulation. The phenotype of the TPM1 disrupted cells is very similar to that of a conditional mutation in the MYO2 gene, which encodes a myosin-like protein (Johnston, G. C., J. A. Prendergast, and R. A. Singer. 1991. J. Cell Biol. 113:539-551). The myo2-66 conditional mutation shows synthetic lethality with the TPM1 disruption, indicating that the MYO2 and TPM1 gene products may be involved in the same, or parallel function. We conclude that tropomyosin, and by inference actin cables, may facilitate directed vesicular transport of components to the correct location on the cell surface.

Chitin↗

PubMed1992

Construction of a GAL1-regulated yeast cDNA expression library and its application to the identification of genes whose overexpression causes lethality in yeast.

We have constructed a galactose-inducible expression library by cloning yeast cDNAs unidirectionally under control of the GAL1 promoter in a centromeric shuttle vector. Eleven independent libraries were made each with an average size of about 1 x 10(6) clones, about 50 times larger than the reported mRNA population in a yeast cell. From this library, LEU2 and HIS3 cDNAs were recovered at a frequency of about 1 in 10(4) and in 12 out of 13 cases these were expressed in a galactose-dependent manner. Sequence analysis of leu2 and his3 complementing cDNAs indicates that they contain all the coding sequence and much of the 5' untranslated region. To test the utility of the library for the identification of genes whose overexpression confers a specific phenotype, we screened 25,000 yeast transformants for lethality on galactose. Among 15 clones that showed galactose inducible lethality were cDNAs encoding structural proteins, including ACT1 (actin), TUB2 (beta-tubulin) and ABP1 (actin-binding protein 1), and genes in signal transduction pathways, including TPK1 (a cAMP-dependent protein kinase) and GLC7 (type 1 protein phosphatase). cDNAs overexpressing NHPB (nonhistone protein B) and NSR1 (nuclear sequence recognition protein) were also found to be lethal. Among these, ACT1 was isolated four times, and NSR1 three times. The useful features of this library for cDNA cloning in yeast by complementation, and for the identification of genes whose over-expression confers specific phenotypes, are discussed.

Base Sequence↗

PubMed1992

Clonal unresponsiveness results from an interaction between staphylococcal enterotoxin B and T cells expressing unexpected V beta elements.

The ability of staphylococcal toxins to stimulate large numbers of T cells has led to their designation as a superantigen. Previous studies have indicated that activation of T cells bearing particular V beta elements may be responsible for the toxic effects of these bacterial products. However, the widespread expression of functionally similar proteins by unrelated bacterial species suggests the possibility that these products may represent a successful microbial strategy for subversion of the host antibacterial response. We have examined the effects of the staphylococcal enterotoxin B (SEB) on T cell clones that express different V beta elements. We note that SEB stimulates clones bearing previously defined V beta elements to proliferate and to produce cytokines. In addition, we demonstrate that an interaction between SEB and the TCR of clones that express additional V beta elements, including V beta 2 and V beta 6, results in a sterile form of immunological activation. This activation phenotype is characterized by proliferation without detectable cytokine production and is followed by profound immunological unresponsiveness in vitro and in vivo. We propose that reduced levels of antibacterial responses resulting from this form of T cell unresponsiveness may account for the highly conserved expression of superantigens by diverse bacterial species.

Animals↗

PubMed1992

An efficient screen for peroxisome-deficient mutants of Pichia pastoris.

We describe a rapid and efficient screen for peroxisome-deficient (per) mutants in the yeast Pichia pastoris. The screen relies on the unusual ability of P. pastoris to grow on two carbon sources, methanol and oleic acid, both of which absolutely require peroxisomes to be metabolized. A collection of 280 methanol utilization-defective (Mut-) P. pastoris mutants was isolated, organized into 46 complementation groups, and tested for those that were also oleate-utilization defective (Out-) but still capable of growth on ethanol and glucose. Mutants in 10 groups met this phenotypic description, and 8 of these were observed by electron microscopy to be peroxisome deficient (Per-). In each per mutant, Mut-, Out-, and Per- phenotypes were tightly linked and therefore were most likely due to a mutation at a single locus. Subcellular fractionation experiments indicated that the peroxisomal marker enzyme catalase was mislocalized to the cytosol in both methanol- and oleate-induced cultures of the mutants. In contrast, alcohol oxidase, a peroxisomal methanol utilization pathway enzyme, was virtually absent from per mutant cells. The relative ease of per mutant isolation in P. pastoris, in conjunction with well-developed procedures for its molecular and genetic manipulation, makes this organism an attractive system for studies on peroxisome biogenesis.

Acyl-CoA Oxidase↗

PubMed1992

Acetylation of O-specific lipopolysaccharides from Shigella flexneri 3a and 2a occurs in Escherichia coli K-12 carrying cloned S. flexneri 3a and 2a rfb genes.

Most of the Shigella flexneri O-specific serotypes result from O-acetyl and/or glucosyl groups added to a common O-repeating unit of the lipopolysaccharide (LPS) molecule. The genes involved in acetylation and/or glucosylation of S. flexneri LPS are physically located on lysogenic bacteriophages, whereas the rfb cluster contains the biosynthesis genes for the common O-repeating unit (D.A.R. Simmons and E. Romanowska, J. Med. Microbiol. 23:289-302, 1987). Using a cosmid cloning strategy, we have cloned the rfb regions from S. flexneri 3a and 2a. Escherichia coli K-12 containing plasmids pYS1-5 (derived from S. flexneri 3a) and pEY5 (derived from S. flexneri 2a) expressed O-specific LPS which reacted immunologically with S. flexneri polyvalent O antiserum. However, O-specific LPS expressed in E. coli K-12 also reacted with group 6 antiserum, indicating the presence of O-acetyl groups attached to one of the rhamnose components of the O-repeating unit. This was confirmed by measuring the amounts of acetate released from purified LPS samples and also by the chemical removal of O-acetyl groups, which abolished group 6 reactivity. The O-acetylation phenotype was absent in an E. coli strain with an sbcB-his-rfb chromosomal deletion and could be restored upon conjugation of F' 129, which carries sequences corresponding to a portion of the deleted region. Our data demonstrate that E. coli K-12 strains possess a novel locus which directs the O acetylation of LPS and is located in the sbcB-rfb region of the chromosomal map.

Acetylation↗

PubMed1992

Is nasal airway size a marker for susceptibility toward clefting?

Johnston and Hunter (1989) reported that in monozygotic twins discordant for cleft lip +/- palate, the noncleft twins demonstrated what appeared to be a bimodal distribution of nasal cavity width. Two thirds showed reduced airway size and one third showed normal or slightly greater airway size. They suggested that the two-thirds group may represent reduced size of the medial nasal prominences and the other may represent underdevelopment of the maxillary prominence. We were particularly interested in the findings because the difference in distribution may represent differences in pathogenesis and therefore have etiologic significance. With this in mind we assessed nasal cross-sectional areas in 37 subjects with cleft lip or cleft lip +/- palate using the pressure-flow technique during breathing. A group of 72 noncleft individuals served as controls. As expected, the data revealed that subjects with clefts had a significantly reduced nasal airway (p = .0001). More important, the distribution of nasal airway size in the cleft group was similar to that reported by Johnston and Hunter (1989). This comparability suggests that it may be possible to assign most cleft lip +/- palate patients to a particular group. Since heredity may differ among the two groups (Chung et al., 1986), we may have a simple technique to assess the risk of occurrence for cleft lip +/- palate.

Adolescent↗

PubMed1992

Modified hemoglobin solution as possible perfusate relevant to organ transplantation.

A modified hemoglobin solution ( - conjugate solution, PHP solution) has very interesting characteristics such as oxygen-carrying property without corpuscular components. Experimental use of the PHP solution has shown promising possibilities as a perfusate relevant to organ transplantations. 1) Elongation of warm ischemic time in canine kidneys: Dogs survived even with the unilateral kidneys which had been exposed up to 4.5 hour warm ischemia and, thereafter, perfused with the PHP solution. 2) Elongation of perfusion preservation period of canine livers: Dogs survived with the transplanted livers which had been perfused for 48 hours with the PHP solution. 3) Successful perfusion of rat small intestine: Lewis rat intestines perfused and preserved for 12 hours with the PHP solution showed a higher survival rate compared with those with Collins or UW solution. 4) Removal of antibodies: By exchange transfusion with a total of 30-60 ml of the PHP solution, a Lewis rat hematocrit lowered to 5% while IgG went down to nil from 8970 mg/dl, IgA to 28 mg/dl from 118 mg/dl and IgM to 190 mg/dl from 897 mg/dl. This technique is expected to be applicable for removal of the naturally existing antibodies in xenotransplantation.

Animals↗

PubMed1992

Evaluation of a pyridoxylated hemoglobin polyoxyethylene conjugate solution as a perfusate for small intestine preservation.

A new type of artificial blood, pyridoxylated hemoglobin-polyoxyethylene conjugate (PHP) solution, (developed by PHP research group of the department of health and welfare of Japan, and produced by Ajinomoto Co., Inc. Tokyo) as an oxygen-carrying component, has been recently devised using hemoglobin obtained from hemolyzed human erythrocytes. Recently, the studies using this solution as a preservation solution were performed in some instances. To examine the mechanism of improved viability using this solution as a preservation solution, we developed a model of orthotopic small intestine transplantation (OIT) in the rat. As a baseline study, we compared parameters of viability of the grafts preserved in Collins and UW solution to those preserved in PHP solution including a survival rate, a serum level total protein and albumin, and a change in body weight after transplantation. In our study, the simple hypothermia storage together with intestinal perfusion preservation with PHP solution was performed. Animals were divided into 6, 12, and 24 hr preservation groups. All of the rats survived after 6 hr preservation following transplantation. However, in 12 hr storage, five of six rats in PHP solution preservation survived and recovery in body weight after grafting was better than those with Collins and UW solution. We conclude that the PHP solution is, therefore, considered to possibly be a more suitable perfusate for small intestine preservation than Collins and UW solution.

Adenosine↗

PubMed1992

Circulating endothelial cells in surgical patients.

The circulating endothelial cells (CEC) in healthy volunteers and surgical patients before and after operations were counted. The results showed that CEC counts of the patients were much higher than those of the volunteers. After operation, however, patients' CEC counts returned to control levels. It is suggested that detection of CEC may be useful for quantitatively evaluation of the injury to blood vessels in surgical patients. The operation may not only remove the source of injury, it also eliminates the injured microvascular bed which may be important to maintain homeostasis. Another possible interpretation of the results may be related to time lag and mental stress.

Blood Cell Count↗

PubMed1992

[An anatomic study of transpedicular posterior fixation of spine and its clinical application].

Intact anatomic specimens of spinal column from T8-L5 were obtained and the height and width of vertebral pedicles, the distance between the pedicle to the upper and lower borders of the vertebral body, the angle of inclination of the coronal surface of vertebral pedicles, and other parameters were measured. Simulating pedicle screw implant in operation, K-wires were inserted into the pedicles and after taking X-ray films the pedicles were sectioned transversely. A series of morphologic parameters of the pedicles were obtained. The distances between the two K-wires' entry and exit points, and between the two pedicles of the same or the adjacent vertebra were measured. The relationships of the sites of determining the pedicle screw site was evaluated also from roentgenograms. Twenty two patients of thoracolumbar fracture were treated. The vertebral body height, kyphotic deformity and the displacement were corrected obviously. After operation the neural functions from incomplete paraplegia were recovered. Several problems about the pedicle screw implant technique were discussed.

Adolescent↗

PubMed1992

Effect of dizocilpine maleate on cerebral anoxia and ischemic damage in rodents.

The Protective effects of dizocilpine maleate (DM) against anoxia in mice and ischemic damage in rats of 4-vessel occlusion (4-VO) were studied. DM 0.5 or 1.0 mg.kg-1 ip significantly prolonged the survival time of mice in closed containers. DM 0.5 and 1.0 mg.kg-1 ip 30 min prior to 4-VO obviously accelerated the electroencephalographic recovery, reduced the neuronal loss in the hippocampus, and increased the survival rate after 72-h reperfusion. These effects followed a dose-dependent manner. Our results indicate that selective non-competitive N-methyl-D-aspartate receptor blocker DM protects against anoxic and ischemic cerebral damage.

Animals↗

PubMed1992

[Grading of malignancy of thymomas by flow cytometry].

The nuclear DNA contents of paraffin embedded archival tissues from 33 cases of thymoma and carcinoma of the thymus were studied by flow cytometry (FCM). Twelve cases were ruled out because of coefficients of variance (CV) > 10.0, leaving 21 cases for analysis. Included were 9 cases of non-invasive thymomas and 12 cases of invasive thymomas and thymic carcinomas. Among non-invasive thymomas, the DNA content was diploid in 4 cases and aneuploid in 5 cases. The DNA content was aneuploid in all 12 cases of invasive thymomas and thymic carcinomas. Proliferative activity, determined by measuring S phase percentage and proliferative index, was significantly increased in invasive thymomas and thymic carcinomas as compared with the non-invasive ones. The average S phase percentage for invasive thymomas and thymic carcinomas was 29.17 +/- 6.91, and for non-invasive thymomas it was 15.86 +/- 3.17 (P < 0.001). The average proliferative indices in the invasive and non-invasive groups were 47.76 +/- 5.03 and 32.58 +/- 6.58, respectively (P < 0.001).

Adult↗

PubMed1992

Determination of free valproic acid: evaluation of the Centrifree system and comparison between high-performance liquid chromatography and enzyme immunoassay.

Valproic Acid (VPA) is an important drug for the treatment of several types of seizures because it has a wide spectrum of activity. Since VPA has an unusual nonlinear binding characteristic and a wide interindividual variation, monitoring of its free concentration can be helpful in patient management. The determination of unbound VPA is more difficult because an extra sample preparation step is needed and the concentration of free VPA is low. Free drug monitoring can assume a more important role if there is a refinement in the technology. A high-performance liquid chromatography (HPLC) method with isocratic elution has been established for the analysis of the 4-bromomethyl-7-methoxycoumarin (BrMMC) derivative of free VPA. This method has a better sensitivity, linearity, and precision than enzyme immunoassay (EIA). Ultrafiltration with the Centrifree system was evaluated for the sample preparation. The influence of centrifuge times, relative centrifugal forces, and the starting sample amounts on the final results of the ultrafiltration were investigated. There was a satisfactory correlation between the free VPA levels determined by the HPLC method and the concentrations obtained by EIA. The total and free VPA were determined on 100 samples from 36 patients. The total VPA levels were in a range of 25 to 208 micrograms/ml, free VPA concentrations ranged from 1.92 to 55.75 micrograms/ml with the free fractions from 7 to 37%.

Anticonvulsants↗