Search PubMed⌕ Search

Biomedical subjects

L Wu

Publications and source records attributed to L Wu.

At least 775 records · Page 43Linked to original sources
PubMed1988

Transcriptional activation by the pseudorabies virus immediate early protein requires the TATA box element in the adenovirus 2 E1B promoter.

The adenovirus E1A protein and immediately early (IE) protein of pseudorabies virus stimulate transcription from many promoters. It has been postulated that these proteins function via cellular intermediates. We analyzed the transcription of adenovirus E1B promoter mutants in response to the stimulatory effect of IE protein in comparison with E1A. Far upstream deletions and precise Sp1 and TATA box substitution mutations were examined. Only mutations affecting the TATA box element interfered with transactivation by IE protein. This result is similar to observations for E1A transactivation (L. Wu et al. Nature (London) 326, 512-515, 1987), suggesting that both E1A and IE proteins mediate transactivation of the E1B promoter through a common cellular intermediate which interacts with the TATA box.

Adenoviruses, Human↗
PubMed1988

Preparation of both DNA and RNA for hybridization analysis from limiting quantities of lymphoid cells.

This report describes a method for preparing both DNA and RNA simultaneously from as few as 5 X 10(5) lymphoid cells. The method is suitable for cultured cells or any tissue from which a cell suspension can be prepared and for the small samples of purified cells obtained by fluorescence activated cell sorting. Cells are lysed with Nonidet P-40 and the nuclear and cytoplasmic fractions separated by centrifugation. Nuclei are embedded in low-gelling-temperature agarose and the proteinase K and restriction enzyme digestions performed whilst the DNA is immobilized in this form. Total RNA is prepared from the cytoplasmic fraction. This method is simple but reliable and is therefore particularly useful for preparing and analyzing the DNA and RNA from multiple samples when material is limited.

Animals↗
PubMed1988

Molecular characterization of T-cell antigen receptor expression by subsets of CD4- CD8- murine thymocytes.

Precursors of all T-lineage cells are found in a population of thymocytes that lack the CD4 and CD8 surface glycoproteins. These "double-negative" thymocytes are markedly heterogeneous in their expression of other surface markers and include cells at various stages of development. In this study, CD4- CD8- adult murine thymocytes were separated into subsets based on the expression of the "heat stable antigen" (HSA) and of Ly 1 (CD5). The sorted subsets were analyzed directly (without prior expansion in culture) for T-cell antigen receptor (TcR) gene rearrangement and mRNA expression and for TcR and CD3 cell-surface protein expression. Very little surface CD3 or TcR expression was detected on the major HSA+ Ly 1low subset. However, the HSA+ Ly 1high, HSA- Ly 1high, and HSA- Ly 1low subsets all contained cells with surface expression of CD3 and TcR. In contrast to previous studies, we found no subset that exclusively expressed either the alpha beta or gamma delta heterodimer, although the ratio of alpha beta+ to gamma delta+ varied widely. Two of these three subsets (HSA- Ly 1low and HSA- Ly 1high) showed very high usage of V beta 8 gene products in the alpha beta heterodimer, but nevertheless included approximately equal to 15% non-V beta 8 alpha beta forms. All CD4- CD8- subsets were found to have extensively rearranged their TcR gamma genes and to express gamma mRNA. Expression of a high ratio of mature [1.3 kilobases (kb)] to truncated (1.0 kb) beta message and presence of alpha message was largely restricted to subsets with TcR alpha beta surface expression.

Animals↗
PubMed1988

Constraints on spacing between transcription factor binding sites in a simple adenovirus promoter.

The adenovirus 2 E1B transcription unit has an extremely simple promoter consisting of a TATA box and a closely situated GC box. The interaction between the TATA box and the GC box was analyzed using insertion mutations which expand the distance between the two elements. We observed that the E1B promoter has an unusually rigid architecture. When the GC box, which is a binding site for transcription factor Sp1, was separated further from the TATA box than in the wild-type promoter, in vivo transcription quickly diminished to a level comparable to the elimination of the Sp1 site. Yet all the insertion mutants bound Sp1 factor in vitro with an affinity approximately equal to that of the wild-type promoter. From these results, we argue that Sp1 binding alone is not sufficient to stimulate transcription. The increased distance might disrupt direct contacts between Sp1 and transcription factors bound at the TATA box, contacts required for transcription stimulation by Sp1. The insertion mutations do not interfere with the transcription activation process mediated by the adenovirus large E1A protein or the pseudorabies virus immediate early protein.

Adenoviridae↗
PubMed1988

Developmental status and reconstitution potential of subpopulations of murine thymocytes.

In this chapter we have summarized our view of the subsets of murine CD4- CD8- thymocytes which can be identified with a range of monoclonal antibodies. We have shown the division rate and turnover time of the main subsets and have listed what we know of the TcR gene rearrangement, and expression at the RNA and protein levels. We have been unable to completely segregate gamma delta-TcR-expressing cells from alpha beta-TcR-expressing cells by any of the markers we have used, although the proportions of the two receptor forms vary widely in the different subsets. Experiments involving intrathymic transfer of the CD4- CD8- subsets are described, which indicate that all the TcR- subsets of the CD4- CD8- thymocytes display some precursor activity and which suggest a progression of at least five stages through the TcR- subpopulations of CD4- CD8- cells. The earliest precursor is a Thy 1 low, HSA low, Pgp-1 high cell which has unrearranged C beta and is non-dividing and which closely resembles the bone marrow prothymocyte. The later precursors are Thy 1 high, HSA high, Pgp-1 low, have rearranged C beta and are rapidly dividing. We tentatively conclude that none of the TcR+ CD4- CD8- cells are precursors of the major thymocyte subsets or of typical peripheral T cells, and we have found no evidence so far of separate precursors for the different mature subsets of thymocytes or peripheral T cells.

Animals↗
PubMed1988

Inference of a molecular defect of apolipoprotein B in hypobetalipoproteinemia by linkage analysis in a large kindred.

Heterozygous hypobetalipoproteinemia is characterized by reduced plasma concentrations of LDL cholesterol, total triglycerides, and apo B to less than 50% of normal values. The molecular basis of this disorder remains unknown. The phenotype cosegregates with a DNA haplotype of the apo B gene in an Idaho pedigree, with a maximum decimal logarithm of the ratio (LOD) score of 7.56 at a recombination rate of zero. Individuals carrying this haplotype had total cholesterol levels of 96 mg/dl, LDL cholesterol levels of 37 mg/dl, triglycerides levels of 51 mg/dl, and apo B levels of 38 mg/dl. This study strongly suggests that apo B mutations underlie hypobetalipoproteinemia, and demonstrates the power of the candidate gene approach in linkage analysis for unraveling genetic determinants in metabolic disorders of undefined etiology.

Adolescent↗
PubMed1987

Preliminary evidence for genetic determination of intraerythrocytic sodium concentration in Utah pedigrees.

Intraerythrocytic sodium concentration has been reported to be increased in hypertensive individuals and some of their normotensive relatives. We investigated the "familiality" of this trait in 572 nonhypertensive subjects from 34 Utah kindreds. Most of these kindreds were selected because of a high incidence of hypertension, heart attack, or stroke. Intraerythrocytic sodium concentration was correlated with the sex of the subject and suprailiac skinfold thickness. Intraerythrocytic sodium concentration was adjusted by linear regression for these 2 factors. The residual values were positively correlated in parent-offspring pairs and among sibs, both those presumed to be living together and those presumed to be living apart. The spouse-spouse correlation was not significant. Pedigree analysis suggested a mixed major-gene/polygenic model of inheritance, but these data did not allow us to distinguish between dominant and recessive inheritance for the major gene component. Total heritability due to both major-gene and polygenic components was estimated to be 90-95%; the proportion of the total variance due to polygenes was estimated to be 60-75%. These results suggest that further study of the relationship between the inheritance of intraerythrocytic sodium and the pathophysiology of hypertension is warranted.

Epidemiologic Methods↗
PubMed1987

Major locus inheritance of apolipoprotein B in Utah pedigrees.

A major locus that determines levels of apolipoprotein B (apoB) was revealed by likelihood analysis on 331 members of 36 pedigrees. The major locus explained 43.2% of the observed variance, with the remainder attributed to random environmental factors. Estimated mean apoB levels (mg/dl) were 110.5 +/- 2.5, 141.9 +/- 4.4, and 208.1 +/- 11.5 for low homozygotes, heterozygotes, and high homozygotes, respectively. The corresponding genotypic frequencies were 0.718, 0.259, and 0.023. The apoB locus explained 13% and 14% of the variance in total and low-density-lipoprotein cholesterol levels, respectively. Persons with elevated apoB had normal to high levels of total serum cholesterol and triglyceride and low to normal levels of high-density lipoprotein and apolipoprotein A-I. Sixteen members of three of the pedigrees were heterozygous for familial hypercholesterolemia (FH). Their apoB levels were estimated as 35.72 +/- 7.16 mg/dl above the apoB genotypic means, assuming that the two loci act independently. Therefore, two major loci, the FH locus and the apoB locus, affect two levels, apoB and LDL cholesterol.

Apolipoprotein A-I↗
PubMed1987

Contribution of the urea appearance rate to diuretic-induced azotemia in the rat.

Studies were performed to evaluate the contribution of the urea appearance rate to the elevated plasma urea concentration found during diuretic-induced sodium depletion. Negative sodium balance of -1162 + 29 microEq/100 g body wt was induced over a four day period by the administration of furosemide, 20 to 30 mg/kg/d i.p., to rats ingesting a sodium free diet. When compared with sodium replete controls, sodium depletion significantly increased the plasma urea concentration (65.0 +/- 3.1 vs. 26.4 +/- 1.1 mg/dl) through both an increase in the urea appearance rate (160 +/- 5.2 vs. 125 +/- 3.5 mg/day/100 g body wt), and a decrease in the urea clearance rate (1.99 +/- 0.14 vs. 3.16 +/- 0.12 ml/min/kg). The urea appearance rate increased on the first day of diuretic administration, remained elevated three days after stopping diuretics, rapidly returned to control levels after sodium repletion, and was significantly correlated with the magnitude of sodium deficit. Similar results were obtained when diuretic-induced sodium depletion was produced in adrenalectomized animals. After four days of sodium depletion the plasma concentration was increased for some amino acids but not for the plasma total amino acid, nitrogen concentration. The results indicate that sodium depletion increases the urea appearance rate through a mechanism that is independent of adrenal function. Thirty to sixty percent of the elevation in plasma urea concentration that occurs in the rat during diuretic-induced sodium depletion can be accounted for by an enhanced urea appearance rate.

Adrenalectomy↗
PubMed1986

Methylenedioxymethamphetamine: a potentially neurotoxic amphetamine analogue.

The amphetamine analogue, methylenedioxymethamphetamine (MDMA) has received considerable attention recently as a novel and increasingly popular psychoactive agent. When administered acutely to rats in high doses, MDMA caused a selective and dramatic decrease in brain concentrations of serotonin and its metabolite, 5-hydroxyindoleacetic acid. The depletion of serotonin and its metabolite persisted for up to at least one week after a single injection of MDMA at approximately four to five times the acute dose reported for humans. These results are discussed in terms of the possible neurotoxic effects of MDMA.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

A DNA probe for the LDL receptor gene is tightly linked to hypercholesterolemia in a pedigree with early coronary disease.

A large, multigenerational family with dominantly inherited hypercholesterolemia was analyzed for genetic linkage between blood levels of low-density lipoprotein (LDL) cholesterol and the locus for the LDL receptor. A genetic marker was identified by restriction fragment length polymorphism (RFLP) in a cloned segment of the LDL receptor gene. We found no exceptions to segregation of the high-LDL cholesterol phenotype with a unique allele at the LDL receptor locus in this pedigree; tight linkage was indicated by a maximum lod score of 7.52 at theta = 0. Knowledge of the LDL receptor genotype will enable investigators to study variability of phenotypic expression in response to environmental influences or to different genetic determinants.

Cholesterol, LDL↗
PubMed1985

Relationship between the structure of chromosomal protein HMG1 and its accumulation in the cell nucleus.

When microinjected into the cytoplasm of cultured mammalian cells, non-histone chromosomal protein HMG1 migrates into the nucleus and binds to the chromatin. To define the features of the HMG1 molecule which are essential for this activity, fragments of HMG1 and chemically modified HMG1 molecules were injected into HeLa cells and the capacity of each of these probes to accumulate in the nucleus was measured by an autoradiographic technique. Fragments representing the C-terminal and central portions of HMG1 did not concentrate in the nucleus; a fragment which consisted of the N-terminal two-thirds of the molecule and which lacked the 41 consecutive aspartate and glutamate residues located near the C-terminal end of the molecule accumulated to about the same extent as intact HMG1. When the amino groups of HMG1 were chemically modified, there was a progressive loss in the ability of the protein to accumulate in the nucleus; derivatization of one-fourth of the total amino groups reduced the concentration of microinjected protein in the nucleus relative to that in the cytoplasm to one-half of the original value. In contrast, modification of one-fourth of the total carboxyl groups did not significantly affect the capacity of HMG1 to accumulate in the nucleus, although further modification resulted in decreased nuclear accumulation. Iodination of tyrosine residues was without effect and modification of the cysteine residues had only a modest effect on the ability of HMG1 to concentrate in the nucleus.

Amino Acids↗
PubMed1985

Binswanger's disease: progressive subcortical encephalopathy or multi-infarct dementia?

Since Binswanger's description of subcortical arteriosclerotic encephalopathy in 1894, numerous cases have been reported. Several authors doubt the validity of this malady, although the majority consider it to be a disease entity. We report seven cases with this type of pallor of myelin, only two of which are accompanied by a history of dementia. Among the seven cases, two had arteriosclerosis of penetrating arteries and arterioles in cerebral white matter. Electron microscopy showed splitting of myelin sheaths, probably the result of edema. In reviewing the blood supply of the cerebral white matter, we conclude that no pathological alterations of medullary branches of the cerebral arteries, the same vessels supplying the white matter, can give rise to such diffuse pallor of white matter and spare the arcuate fibres. This pallor can only be due to cerebral edema, most likely of hypoxic-ischemic, hypotensive, or acidotic origin. We also contend that arteriosclerosis can only cause dementia through multiple infarcts or lacunae, if it indeed leads to dementia.

Aged↗