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Biomedical subjects

E Wang

Publications and source records attributed to E Wang.

At least 397 records · Page 22Linked to original sources
PubMed1988

Evidence that there is no direct correlation between alpha 2-adrenoceptor antagonism and inhibition of voltage-dependent sodium channels.

Electrophysiological and biochemical evidence suggests that the voltage-dependent sodium channel is the site of local anesthetic action, and that there is pharmacological similarity between alpha-adrenoceptors and Na+-channels. Yohimbine, a non-selective alpha 2-adrenoceptor antagonist, with a structure similar to that of cocaine affects the sodium channel by a mechanism different from that of other local anesthetics including cocaine. Some structural analogues of yohimbine -berbane compounds- were found to be potent and selective alpha 2-adrenoceptor antagonists. In this work the local anesthetic properties of two berbane compounds (6c and 6d (CH-38083) from the paper of Vizi, Toth, Somogyi, Szabo, Harsing and Szantay, 1987) were examined and compared to those of yohimbine in vitro on scorpion venom-enhanced specific binding of [3H]batrachotoxinin A 20-alpha-benzoate [( 3H]BTX-B) to the voltage-sensitive sodium channel and on the veratridine-induced depolarization measured by the uptake of [3H]trimethylphenylphosphonium ion [( 3H]TPMP+) in mouse brain cortex. Both of the compounds inhibited the [3H]BTX-B binding with an IC50 of (approximately) 150 microM, which is more than four orders of magnitude higher than the concentration required for antagonism of a presynaptic alpha 2-adrenoceptor (7 nM). They are 15 times less potent in inhibiting [3H]BTX-B binding and 2.5 times less potent in inhibiting veratridine-induced depolarization than yohimbine.

Adrenergic alpha-Antagonists↗
PubMed1988

Absence of three secreted proteins and presence of a 57-kDa protein related to irreversible arrest of cell growth.

Two subsets of proteins from the conditioned medium of normal human diploid fibroblasts were detected by NaDodSO4/polyacrylamide gel electrophoresis analysis; the presence of these subset is related to the nonproliferative state of in vitro aged cells. One subset consists of three proteins (molecular mass from 80 to 87 kDa) secreted by replicating cells in sparse cultures, as well as by quiescent cells in confluent or serum-starved cultures of young fibroblasts. These proteins disappear from the medium when cultures reach the state of senescence. The other subset consists of a single protein of 57 kDa, detected only in conditioned medium of senescent fibroblast cultures. The results suggest that when human fibroblasts reach senescence, they secrete the 57-kDa protein and concomitantly stop secreting the other three proteins normally found in the culture medium of young fibroblasts. Therefore, the alternative secretion of these protein subsets could specifically signify irreversible arrest of cell growth during in vitro cellular aging.

Cell Division↗
PubMed1988

Simian virus 40 (SV40) T antigen binds specifically to double-stranded DNA but not to single-stranded DNA or DNA/RNA hybrids containing the SV40 regulatory sequences.

Simian virus 40 T antigen has been shown previously to bind specifically with high affinity to sites within the regulatory region of double-stranded simian virus 40 DNA. Using competition filter binding and the DNA-binding immunoassay, we show that T antigen did not bind specifically to either early or late single-stranded DNA containing these binding sites. Moreover, T antigen did not bind these sequences present in single-stranded RNA, RNA/RNA duplexes, or RNA/DNA hybrids. T antigen did, however, bind as efficiently to single-stranded DNA-cellulose as to double-stranded DNA-cellulose. This binding was nonspecific because it was independent of the presence of T-antigen-binding sites. The implications of these observations are discussed.

Antigens, Polyomavirus Transforming↗
PubMed1988

Morphology of the fibrinogen exudate during evolution of a mycobacterial-induced murine eye granuloma.

The intent of this study was to visualize changes in the density and location of fibrinogen-related antigen (FRA) depositions within the murine vitreous space during the formation of a chronic mycobacterial-induced uveitis (CMIU) granuloma. Concurrent changes in cellular morphology of the granuloma were also examined. Fibrinogen derivatives within the exudates of granulomatous cell-mediated inflammations may induce physical induration and numerous other phlogistic effects. However, technical limitations of conventional FRA staining methods have tended to underestimate the extent of their presence within this category of inflammatory lesions. Conventional H and E sections of the CMIU granuloma confirmed the classic progression-early PMN influx, monocyte maturation and final macrophage and epithelioid cell dominance-described for such lesions. Avidin-biotin-complex staining utilizing a polyclonal mouse antifibrinogen then revealed a progressive increase in amorphous extracellular fibrinogen-FRA-positive staining material as the granuloma evolved. Thus, on day one the PMN influx showed no evidence of fibrinogen-FRA staining; at one week heavy staining was evident in the anterior chamber and in consolidated (i.e. macrophage) regions of the granuloma; at one month a heavy uniform staining appeared throughout the indurated granuloma where macrophages and epithelioid cells predominated. Patterns of heavy deposition on macrophage surfaces were suggested. The likelihood that bulky accumulations of FRA in mature granulomas are not solely fibrin, and may account for granulomatous induration and persistence, is discussed.

Animals↗
PubMed1987

Contact-inhibition-induced quiescent state is marked by intense nuclear expression of statin.

Statin, a nuclear protein of 57,000 daltons, is found in in vitro aged, nonproliferating human fibroblasts but not in their young, replicating counterparts or transformed derivatives; it is also found in the nuclei of young fibroblasts when their growth is arrested but rapidly disappears from the cells once the restriction to growth is removed. We reported earlier that as cells leave the quiescent state, the loss of statin from the nucleus precedes the initiation of DNA synthesis; here we report that in a confluent culture, as cells leave the traverse of the replicative cycle and assume the quiescent phenotype, statin is not expressed maximally until total contact inhibition of growth is achieved. This full manifestation of statin occurs in monolayer culture with cells forming the typical swirling pattern and fibronectin organized into large intercellular cables. The late expression of statin in cells approaching the quiescent state is also verified biochemically by immunoblotting assays. The present results, taken together with those reported earlier, indicate that the nuclear appearance of statin occurs only after the complete cessation of DNA synthesis and that the full manifestation of this protein can be used as a marker for the G0 quiescent state.

Cell Communication↗
PubMed1987

Hepatic function in rats after spaceflight: effects on lipids, glycogen, and enzymes.

The inclusion of rats aboard Spacelab 3 (SL-3) allowed analyses of liver lipids, glycogen, hepatic enzymes of cholesterol, glycerolipid and sphingolipid biosynthesis, and other enzyme activities. Glycogen content was markedly elevated in livers from the flight animals compared with controls. Cholesterol was 24% (P less than 0.04) lower in livers from the experimental groups, whereas blood cholesterol was 19% higher (P less than 0.05). The activity of 3-hydroxy-3-methylglutaryl-CoA reductase, the rate-limiting enzyme of steroid biosynthesis, was 80% lower (P less than 0.01). Total phospholipids and sphingolipid levels did not differ significantly. The specific activity of fatty acyl-CoA synthetase, which is responsible for activation of fatty acids, was 37% (P less than 0.05) higher in microsomes from the rats on SL-3; however, since these animals had 25% less microsomal protein (P less than 0.02), there was no difference per gram of liver. The initial enzymes of sphingolipid and glycerolipid biosynthesis were assayed; serine palmitoyltransferase was 40% lower (P less than 0.01), and glycerol 3-phosphate acyltransferase did not differ. Hepatic cytochrome P-450 content decreased by 50% after spaceflight. Enzymes that did not differ significantly between the two groups include cytochrome b5, glutathione S-transferase, tyrosine aminotransferase, aspartate aminotransferase, and cystathionase. These findings suggest that spaceflight alters hepatic metabolism of several classes of compounds.

Animals↗
PubMed1987

Extravascular plasminogen activator and inhibitor activities detected at the site of a chronic mycobacterial-induced inflammation.

Levels of extravascular tissue plasminogen activator activity (PA) and those of inhibitors of PA and of urokinase (UK) present within the anterior chamber of normal and inflamed feline eyes were assessed with the use of a direct PA assay of microsamples of aqueous humor. Purposes of the study were, first, to confirm prior indirect evidence that this extravascular space normally contains higher levels of uninhibited PA, but lower levels of inhibitor activity, than does plasma and, second, to determine patterns of change in these activities under in vivo conditions imposed by a chronic mycobacterial-induced uveitis (CMIU) disease model. The PA assay utilized a 125I-plasminogen substrate whose cleavage by PA contained in samples was both visualized during gel electrophoreis, and quantified by gamma counting. The results provided the first direct evidence that the higher fibrinolytic activity previously observed in normal aqueous in comparison with plasma is in fact associated with higher levels of available (uninhibited) PA (P less than 0.01) The data also indicated that normal aqueous contains a much higher level of PA inhibitor activity than previously suspected--roughly 40 times more than available PA levels. These normal values for PA and inhibitors occupied a relatively narrow, threefold range, in contrast to the wide scattering of individual values that appeared during 18-20 weeks of the chronic inflammation disease model. Despite this, however, the general pattern of observation for all individual eyes during CMIU was a significant increase in levels of both PA and inhibitors. The net effect of CMIU was thus to cause the 1:40 ratio noted above to be tilted more strongly in favor of inhibitor activity, ie, up to 1:80. Increases in local vasopermeability in this disease model were believed contributory to this change. However, local generations of PA and APA in vivo by inflammatory cells, especially monocyte-macrophages, must also be considered. Assays for UK inhibitor showed levels of activity and directions of change that closely followed those of PA inhibitor, which suggests the possibility that they may be identical. It is surmised that the above patterns, along with results of our prior studies, indicate an apparent need for a multistep, strict inhibitory control of plasmin generation and proteolysis in vivo within normal extravascular spaces such as the anterior chamber.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Transactivation of BKV and SV40 early promoters by BKV and SV40 T-antigens.

The early promoters of BKV and SV40 plasmids were transactivated in both BKV and SV40-transformed cells which failed to support replication of these plasmids. This suggests that the T-antigen of either virus can transactivate BKV and SV40 early promoters by either increasing the availability of cellular transcription factors or by directly interacting with specific sequences which comprise the transcriptional control region of the early promoters. We also observed that removal of 8-bp on the early side of T-antigen binding site I of BKV does not alter viral-plasmid replication.

Animals↗
PubMed1986

Biosynthesis of long-chain (sphingoid) bases from serine by LM cells. Evidence for introduction of the 4-trans-double bond after de novo biosynthesis of N-acylsphinganine(s).

The de novo biosynthesis of sphinganine and sphingosine was studied using LM cells incubated with [14C] serine in serum-free media. Most of the radiolabeled long-chain bases were initially found in dihydroceramides (as sphinganine) and the proportion appearing in complex sphingolipids (as sphingosine) increased over time. Since free long-chain bases were not detected (although formation of 3-ketosphinganine, the first condensation product of serine and palmitoyl-CoA, could be demonstrated in vitro), it appears that the first step is rate-limiting for dihydroceramide biosynthesis. The kinetics suggested that after N-acyl-sphinganines were formed they were dehydrogenated to N-acylsphingosines. No evidence was found for the formation in vivo or in vitro of the putative intermediates of the direct biosynthesis of sphingosine from sphinganine (i.e. 3-ketosphingosine and free sphingosine). The conversion of N-acylsphinganines to N-acyl-sphingosines was confirmed by incubating cells with [14C] serine followed by unlabeled serine, which resulted in a rapid increase in the sphingosine-to-sphinganine ratio in amide-linked sphingolipids during the chase. These findings are most consistent with a pathway for long-chain base biosynthesis in which N-acyl-sphinganines are first synthesized by LM cells and the 4-trans-double bond is added to this or subsequent products, as opposed to the most cited pathway wherein sphingosine is made directly from sphinganine.

Acylation↗
PubMed1986

Differences in the long chain (sphingoid) base composition of sphingomyelin from rats bearing Morris hepatoma 7777.

The long chain bases of sphingomyelin from Morris hepatoma 7777 and host and control livers were analyzed by capillary gas liquid chromatography. Sphingosine (18:1) was the major long chain base of control livers (66.5%) and hepatomas (65.6%), but hepatomas also had a high percentage (9.3 vs 4.4) of the 16:1 homolog. Host liver had the most unusual long chain base composition, with ca. equal 16:1 (24.4%) and 18:1 (21.4%) and high amounts of 20-carbon bases (9.2% 20:0 and 15.3% 20:1). These differences may be related to the aberrant fatty acid metabolism known to occur in tumor-bearing animals. Such large perturbations in the long chain base composition of hepatic sphingomyelin are unprecedented and could have a major impact on the properties of host membranes.

Animals↗
PubMed1986

The prediction and/or detection of ovulation by means of urinary steroid assays.

Twenty normally menstruating women volunteered for a study in which plasma samples were collected daily during an entire menstrual cycle. On the same days, samples of morning urine were also collected, as well as random samples of urine voided at the visit to the Outpatient Clinic. Progesterone (P), estradiol (E2) and lutropin (LH) were assayed in plasma, and pregnanediol-3-glucuronide (PdG), estrone-glucuronide (E1G), estriol-16-glucuronide (E3G), P, and E2 were measured in urine using radioimmunoassays. Progesterone in urine was assayed both with and without preceding chromatography. All urinary glucuronides and progesterone exhibited cyclic patterns similar to those of E2 or P in plasma. Seven-fold increases from early follicular to luteal phase values (for PdG and urinary P; the latter both with and without chromatography), or to peak levels (for E1G and E3G) were observed. The difference between the baseline and peak levels was less distinct (approximately 5-fold) for E2 in urine. The day-to-day coefficient of variation of early follicular phase values decreased from 40% to 25% by calculating the ratios of the glucuronides or P to creatinine (C). The peaks of estrogen glucuronides were delayed mostly by 1 day in comparison to the peaks of E2 in plasma. The urinary peaks of estrogens were in most cases more closely clustered around the day of the LH-peak when the measurements were corrected for C. For the determination of the first significant rise of steroid levels in a cycle, the calculation of a sustained rise (leading to a significant cumulative sum - CUSUM) was found superior when compared to other recommended indices, such as a 50% increase over the mean of 3 preceding values, or the increase over the baseline level plus 2 standard deviations. Sustained rises were calculated for all indices studied (including the ratio of urinary E1G to PdG). The ratio of E1G to C in morning urine gave consistently the most compact distribution of sustained rises. It is concluded that daily measurements of urinary PdG (or P) and E1G (or, possibly, E2) could substitute the serial assays of P and E2 in peripheral blood in the retrospective assessment of the ovarian functionn. The day-to-day variation can be significantly reduced, if results are expressed per concentration of C. For the prediction of ovulation or fertile period, the best index of urinary steroids appears to be the sustained rise in the ratio of E1G to C. However, this "best" method is still not good enough in terms of overall reliability and practicability.

Adult↗
PubMed1986

Disappearance of statin, a protein marker for non-proliferating and senescent cells, following serum-stimulated cell cycle entry.

Statin, a protein of 57,000 D, is present in the nuclei of quiescent or senescent fibroblasts (Wang, E, J cell biol 100 (1985) 545), but is absent in their young replicating counterparts. Immunohistochemical survey of a variety of tissues demonstrates that the presence of statin is a marker for cells that are no longer involved in proliferation, i.e. those cells that are terminally differentiated. Statin expression was examined by immunofluorescence microscopy in serum-starved cultures whose replication had been reinitiated by raising the serum concentration from 0.5 to 10%. Prior to serum addition, more than 85% of the cells stained positively for statin. After stimulation with serum, the expression of statin disappeared rapidly within the first 12-14 h. On the other hand, an increase in the level of DNA synthesis, signifying entry into S phase, was observed initially at 18 h after serum stimulation, and reached maximal levels 6 h later. Immunoprecipitation of statin derived from cells harvested at different intervals after serum stimulation revealed that the level of statin synthesis was reduced by 4 h and was hardly detectable at 8 h. These results demonstrate that the synthesis of statin occurs primarily when cells are in a quiescent state, and declines rapidly when cells are induced to proliferate; this decline precedes the transition from G1 to S phase.

Cell Cycle Proteins↗
PubMed1986

Activities of the hepatic enzymes of vitamin B6 metabolism for patients with cirrhosis.

Patients with cirrhosis and other hepatic diseases frequently exhibit lower concentrations of plasma pyridoxal 5'-phosphate (PLP), which is derived primarily from liver. To determine the biochemical basis for this abnormality, the enzymes of vitamin B6 metabolism--pyridoxal kinase, pyridoxine (pyridoxamine) 5'-phosphate oxidase, PLP phosphatase(s), and pyridoxal oxidase(s)--were analyzed in liver. The activities of the two biosynthetic enzymes, pyridoxal kinase and pyridoxine (pyridoxamine) 5'-phosphate oxidase were similar for both. The phosphatase activities were significantly higher (mean +/- SD of 9.55 +/- 8.03 versus 3.97 +/- 2.36 nmol X min X mg protein, p less than 0.05) for cirrhotics. Pyridoxal oxidase activities appeared slightly lower for cirrhotics. There was considerable variation in many indices of liver function, which suggests that the defects contributing to altered vitamin B6 metabolism may be complex and individualistic. These analyses have shown that cirrhotics are capable of apparently normal PLP synthesis and that increased hepatic dephosphorylation may be responsible for low levels of plasma PLP.

Adult↗
PubMed1986

Nucleotide pool in pho regulon mutants and alkaline phosphatase synthesis in Escherichia coli.

The intracellular nucleotide pool of Escherichia coli W3110 reproducibly changes from conditions of growth in phosphate excess to phosphate starvation, with at least two nucleotides appearing under starvation conditions and two nucleotides appearing only under excess phosphate conditions. Strains bearing a deletion of the phoA gene show the same pattern, indicating that dephosphorylation by alkaline phosphatase is not responsible for the changes. Strains with mutations in the phoU gene, which result in constitutive expression of the pho regulon, show the nucleotide pattern of phosphate-starved cells even during phosphate excess growth. These changes in nucleotides are therefore due to phoU mutation but not to alkaline phosphatase constitutivity. In fact, a phoR (phoR68) mutant strain has the patterns of the wild type in spite of being constitutive for alkaline phosphatase. That these nucleotides might be specific signals for pho regulon expression was supported by the fact that the two nucleotides appearing under phosphate starvation induced the synthesis of alkaline phosphatase in repressed permeabilized wild-type cells under conditions of phosphate excess.

Alkaline Phosphatase↗
PubMed1985

Increases in serum sphingomyelin by 17 beta-estradiol.

The effects of estrogens on plasma sphingomyelin and the hepatic activity of the initial enzyme of sphingomyelin synthesis were examined using immature chicks. After three days of 17 beta-estradiol administration, serum sphingomyelin, total phospholipids, and cholesterol doubled, and triacylglycerol levels increased 7.5 fold. The sphingomyelin content and percentage of total phospholipids of liver were unaffected by estrogen treatment. The specific activity of serine palmitoyltransferase (EC 2.3.1.50) was unchanged, but the total activity appeared slightly higher due to increased liver weights. The higher sphingomyelin may, therefore, be due less to increased levels of biosynthetic enzymes than to factors such as the substrate (i.e., fatty acid) supply or decreased clearance of plasma sphingomyelin. These results are similar to earlier findings with key enzymes of cholesterol and glycerolipid biosynthesis and suggest that the three lipid pathways may be coordinated during estrogen treatment and enhanced very-low density lipoprotein (VLDL) synthesis.

Acyltransferases↗