Characterization of a rotavirus rearranged gene 11 by gene reassortment

The effect of replacement of gene 11 of rotavirus SA-11 by a gene carrying a head to tail duplication obtained from a swine rotavirus strain was studied. The swine rotavirus strain with a duplicated gene (CC86) exhibits both a phenotype that allows to overgrow other viral strains when coinfected and an increased plaque size when plated in both CV-1 and MA-104 monkey kidney cells. Using reassortment methods the duplicated gene of the swine rotavirus was introduced into the SA-11 virus, replacing the regular gene 11. The reassorted strain was characterized to find out the origin of each of the other viral gene segments. Based on electrophoretic mobilities segments 1, 2, 3, 5, 7, 8 and 10 were identified as of SA-11. The SA-11 origin of the segments 4, 6 and 9 was confirmed by neutralization with polyclonal and monoclonal antibodies and by ELISA. The results suggest that the new reassortant virus was a monoreassortant carrying SA-11 genes except the duplicated gene originated from the swine virus CC86. The ability to in vivo replicate and to synthesize viral proteins was identical in the reassorted virus and the parental strains. Sequence analysis indicates that the new phenotype does not originate in the duplication of gene 11 but possibly from mutations in the coding region of NSP5 gene that may result in different phosphorylation patterns of the protein.     

Structure and function of a ganglioside receptor for porcine rotavirus

A ganglioside fraction isolated from pooled intestines from newborn to 4-week-old piglets, which we previously partially characterized and showed to specifically inhibit the binding of porcine rotavirus (OSU strain) to host cells (M. D. Rolsma, H. B. Gelberg, and M. S. Kuhlenschmidt, J. Virol. 68:258-268, 1994), was further purified and found to contain two major monosialogangliosides. Each ganglioside was purified to apparent homogeneity, and their carbohydrate structure was examined by high-pH anion-exchange chromatography coupled with pulsed amperometric detection and fast atom bombardment mass spectroscopy. Both gangliosides possessed a sialyllactose oligosaccharide moiety characteristic of GM3 gangliosides. Compositional analyses indicated that each ganglioside was composed of sialic acid, galactose, glucose, and sphingosine in approximately a 1:1:1:1 molar ratio. Each ganglioside differed, however, in the type of sialic acid residue it contained. An N-glycolylneuraminic acid (NeuGc) moiety was found in the more polar porcine GM3, whereas the less polar GM3 species contained N-acetylneuraminic acid (NeuAc). Both NeuGcGM3 and NeuAcGM3 displayed dose-dependent inhibition of virus binding to host cells. NeuGcGM3 was approximately two to three times more effective than NeuAcGM3 in blocking virus binding. Inhibition of binding occurred with as little as 400 pmol of NeuGcGM3/50 ng of virus (approximately 2 x 10(7) virions) and 2 x 10(6) cells/ml. Fifty percent inhibition of binding was achieved with 0.64 and 1.5 microM NeuGcGM3 and NeuAcGM3, respectively. The free oligosaccharides 3'- and 6'-sialyllactose inhibited binding 50% at millimolar concentrations, which were nearly 1,000 times the concentration of intact gangliosides required for the same degree of inhibition. Direct binding of infectious, triple-layer rotavirus particles, but not noninfectious, double-layered rotavirus particles, to NeuGcGM3 and NeuAcGM3 was demonstrated by using a thin-layer chromatographic overlay assay. NeuGcGM3 and NeuAcGM3 inhibited virus infectivity of MA-104 cells by 50% at concentrations of 3.97 and 9. 84 microM, respectively. NeuGcGM3 (700 nmol/g [dry weight] of intestine) was found to be the predominant enterocyte ganglioside (comprising 75% of the total lipid-bound sialic acid) in neonatal piglets, followed by NeuAcGM3 (200 nmol/g [dry weight] of intestine). NeuGcGM3 and NeuAcGM3 together comprised nearly 100% of the lipid-bound sialic acid in the neonatal intestine, but their quantities rapidly diminished during the first 5 weeks of life. These data support the hypothesis that porcine NeuGcGM3 and NeuAcGM3 are physiologically relevant receptors for porcine rotavirus (OSU strain). Further support for this hypothesis was obtained from virus binding studies using mutant or neuraminidase-treated cell lines. Lec-2 cells, a mutant clone of CHO cells characterized by a 90% reduction in sialyllation of its glycoconjugates, bound less than 5% of the virus compared to control cell binding. In contrast, Lec-1 cells, a mutant CHO clone characterized by a deficiency in glycosylation of N-linked oligosaccharides, still bound rotavirus. Furthermore, exogenous addition of NeuGcGM3 to the Lec-2 mutant cells restored their ability to bind rotavirus in amounts equivalent to that of their parent (CHO) cell line. In the virus-permissive MA-104 cell line, NeuGcGM3 was also able to partially restore rotavirus infectivity in neuraminidase-treated cells. These data suggest that gangliosides play a major role in recognition of host cells by porcine rotavirus (OSU strain).     

Clinical and biochemical studies in an American child with sialuria

Sialuria is a rare inborn error of sialic acid (NeuAc) metabolism resulting from failure of CMP-NeuAc to adequately feedback inhibit the rate-limiting enzyme in sialic acid synthesis, UDP N-acetylglucosamine (UDP-GlcNAc) 2-epimerase. We describe the fourth reported sialuria patient, T.W., whose clinical features include developmental delay, coarse facies, and massive urinary excretion of sialic acid. Biochemical studies of T.W. fibroblasts revealed a 200-fold increase in free NeuAc content compared with normal. Bound NeuAc was only slightly elevated. The free NeuAc was predominantly in the cytosol fraction of fibroblasts after differential centrifugation, with only 4% of the free NeuAc content in other (nuclear, granular, and microsomal) cellular compartments. CMP-NeuAc inhibited UDP-GlcNAc 2-epimerase by 80% in normal fibroblasts but inhibited the epimerase of T.W. (sialuria) cells by only 13%. Cytidine feeding of sialuria fibroblasts decreased the intracellular free NeuAc content by 47%; this was accompanied by a fourfold increase in CMP-NeuAc, which may be sufficient to feedback inhibit the mutant epimerase and reduce free NeuAc production. Cytoplasmic pH was determined by the pH sensitive fluorescent indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, pentaacetoxymethylester (BCECF/AM) using the H+ equilibration method. The intracellular pH of sialuria fibroblasts, 7.18 +/- 0.04, was not found to be significantly different from that of normal cells (7.19 +/- 0.08).     

Identification and characterization of S fimbria-binding sialoglycoproteins on brain microvascular endothelial cells

We have previously shown that S-fimbriated Escherichia coli binds brain microvascular endothelial cells (BMEC) via a lectin-like activity of SfaS adhesin specific for NeuAc alpha2,3-galactose; however, BMEC molecules bearing these epitopes have not been identified. In the present study, we showed that the expression of S fimbriae conferred a three-fold increase in adhesion of E. coli to cow, human, and rat BMEC but did not enhance E. coli adhesion to systemic vascular endothelial cells such as human umbilical vein endothelial cells and human aortic arterial endothelial cells. Two BMEC-binding molecules for S fimbriae were identified as 65 (major)- and 130 (minor)-kDa sialoglycoproteins by S fimbria immunoblotting and were purified from bovine BMEC by wheat germ agglutinin and Maackia amurensis lectin (specific to NeuAc alpha2,3-galactose) affinity chromatography. The 65-kDa BMEC glycoprotein showed effective inhibition of S fimbria-mediated binding of E. coli to BMEC. Polyclonal antibodies raised against the mixture of 65- and 130-kDa proteins reacted to 65-kDa protein present only on BMEC, not on systemic vascular endothelial cells. Immunoprecipitation of biotinylated BMEC membrane proteins and immunocytochemistry studies of BMEC with anti-S fimbria-binding protein antibodies revealed that the 65-kDa protein is a surface protein. The N-terminal amino acid sequence of 65- and 130-kDa proteins showed no significant sequence homology with any other known proteins. These findings suggest that 65- and 130-kDa proteins represent novel sialoglycoproteins involved in the binding of S-fimbriated E. coli to BMEC.     

IgM response to a human Pneumocystis carinii surface antigen in HIV-infected patients with pulmonary symptoms

A series of eight new N-hydroxy-N'-aminoguanidine (HAG) Schiff bases [ArCH = NNHC(= NH)NHOH.tosylate] was synthesized as potential antitumor agents through the inhibition of the enzyme ribonucleotide reductase (EC 1.17.4.1). Five of the HAG derivatives (LK02 through LK06) were designed to contain an orthohydroxy group on the phenyl ring of ArCH = to increase the stability of the Schiff base formed. In addition, two compounds with a substituted quinoline [LK10; ArCH = (4-hydroxy-7-trifluoromethylquinolin-3-yl)methylene] or isoquinoline (LK11; ArCH = (5-nitroisoquinolin-1-yl)methylene] moiety were synthesized through multiple-step reactions involving reduction and/or oxidation. The IC50 values of the newly synthesized HAG Schiff bases were determined against human leukemic CCRF-CEM/0 cells in culture. The IC50 values of two previously reported HAG derivatives [ATL25; ArCH = (5-nitro-isoquinolin-1-yl)methylene] and [LW02; ArCH = 2-hydroxy-3-allyl-benzylidene)] were also determined for the first time against CCRF-CEM/0 cells. Among the compounds tested, LK11 was found to be the most potent (IC50, 2.95 +/- 0.1 microM) and the 4-methoxy-2-hydroxyphenyl derivative (LK02) to be the least potent (IC50, 121 +/- 16 microM). LK11 was about 15-fold more potent against CCRF-CEM/0 cells compared to the parent compound hydroxyguanidine sulfate (IC50, 46 +/- 7.1 microM) and was about 32 times more potent than LK10 (IC50, 97.6 +/- 0.9 microM). LK11 in combination was incubated in sequence with cytarabine (ara-C) at various molar ratios against CCRF-CEM/0 cells for 48 hr. The results were analyzed using both the isobologram and the median-effect methods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fate of a terminal olefin with Drosophila microsomes and its inhibitory effects on some P-450 dependent activities

In vitro bioassays were used to analyze the metabolism of the 11-dodecenoic acid (11-DDNA) by microsomes prepared from Drosophila melanogaster RalDDTR strain. 11-DDNA is metabolized to 11,12-epoxylauric acid (epoxyLA) in a NADPH-dependent way. The microsomal production of epoxyLA reaches a plateau very quickly, suggesting the occurrence of an enzyme inactivation process. After incubation of microsomes with (1-14C)11-DDNA, three proteins of Mr approximately 50 kDa were labeled. 11-DDNA inhibits the microsomal metabolism of lauric acid and 7-ethoxycoumarin in a time and NADPH-dependent process. An inhibition of metabolites generated from DDT and testosterone was also obtained but at higher concentrations. These results are discussed according to the fact that RalDDTR is an insecticide resistant strain characterized as a high metabolizer of the insecticide DDT and also of lauric acid, testosterone, and ethoxycoumarin.     

Immune response associated with nonmelanoma skin cancer

The effect of antioxidants and reducing agents on glutamate-induced cytotoxicity was examined using PC12 cells. The antioxidants vitamin E, idebenone, and selegiline protected cells against the cytotoxicity observed 24 h after exposure to 0.5 or 10 mM glutamate, as determined by lactate dehydrogenase leakage, even when added 3 h after glutamate. The reducing agents, glutathione (GSH) and dithiothreitol (DTT), also provided protection against the cytotoxicity of glutamate. Preincubation of PC12 cells with the antioxidants mentioned above, or the incubation with those antioxidants after exposure to glutamate for 3 h, prevented the reduction of viability caused by glutamate. Cystine uptake was inhibited by exposure of cells to glutamate, as determined by L-[35S]-cystine uptake. Incubation of cells with 0.5 or 10 mM glutamate caused a marked decrease in cellular GSH levels, not prevented by antioxidants. The activity of GSSG reductase was decreased by glutamate and this inhibition was reverted in the presence of the reducing agents GSH and DTT. These results indicate that glutamate toxicity on PC12 cells results from the inhibition of cystine uptake with consequent GSH depletion and oxidative stress, suggesting that antioxidants may reduce the cellular damage in pathologic conditions associated with excessive glutamate release.     

Comparison of the genomic short regions of a vaccine strain (SA-2) and a virulent strain (CSW-1) of infectious laryngotracheitis virus (Gallid herpesvirus 1)

Restriction enzyme linkage maps were produced for the genomic short region of the virulent infectious laryngotracheitis virus (CSW-1 strain). After comparison with the equivalent restriction enzyme linkage maps for the infectious laryngotracheitis virus SA-2 strain (a vaccine strain), it was determined that the maps for the short regions of the two strains were identical, apart from a single section in each of the inverted terminal repeats. Each inverted terminal repeat of the SA-2 strain was discovered to contain 467 base pairs more DNA than the CSW-1 strain's inverted terminal repeats. This extra DNA was more precisely mapped entirely within the EcoRI fragments D and d of SA-2, which were found to form part of the SmaI fragments U and P of SA-2 and Q and b of SA-2 and to contain one SmaI restriction enzyme site.     

Polyanion inhibitors of HIV and other viruses. 7. Polyanionic compounds and polyzwitterionic compounds derived from cyclodextrins as inhibitors of HIV transmission

New polyanionic compounds were obtained from radical addition of thiomalic acid and mercaptopropionic acid onto perallylated cyclodextrins (CDs) under UV irradiation with a catalytic amount of alpha,alpha'-azobis(isobutyronitrile). All these polyanions, bearing 18-48 carboxylate groups, inhibited human immunodeficiency virus type 1 (HIV-1) strain IIIB replication in MT-4 cells at a 50% inhibitory concentration (IC50) of 0.1-2.9 microM, while not being toxic to the host cells at concentrations up to 62 microM. These compounds were also active against a clinical HIV-1 isolate (HE) at >/=4-fold higher concentrations. Only some compounds showed activity against the two HIV-2 strains (ROD and EHO) but at higher concentrations than those required to inhibit HIV-1 (IIIB and HE) replication. In addition, these compounds were not active against the M-tropic HIV-1 strain BaL but were active against simian immunodeficiency virus [SIV (MAC251)]. These compounds were also inhibitory to the replication of human cytomegalovirus at an IC50 of 1-10 microM, but not herpes simplex virus (type 1 and type 2) or other (picorna-, toga-, reo-, orthomyxo-, paramyxo-, bunya-, rhabdo-, and poxvirus) viruses. Radical addition on perallylated CDs of a protected cysteine gave polyzwitterionic compounds. None of these last compounds proved inhibitory to the replication of HIV-1, HIV-2, or any of the other viruses tested.     

Hemodynamic patterns and duration of post-dynamic exercise hypotension in hypertensive humans

It has been shown, that smoking results in a lower yield of surfactant associated phospholipids in bronchoalveolar lavage (BAL). Indirect evidence suggests impaired secretion. In the present study, we investigated the influence of cigarette smoke on surfactant secretion in cultured rat alveolar type II cells. Smoke exposure was achieved by bubbling the smoke of four cigarettes through Dulbecco's modified Eagle's medium (DMEM) which was adjusted to a reference absorption value of 1.36 at 320 nm. Cells were preincubated with various dilutions of cigarette smoke-treated medium for 30 min, and were then exposed to this medium for 2 h. After this time, secretion of 3H-choline-labelled phosphatidylcholine (PC) was measured as a marker of surfactant secretion. A 10 fold dilution of cigarette smoke-treated medium inhibited PC secretion stimulated by a combination of terbutaline, adenosine triphosphate and 12-O-tetradecanoylphorbol-13-acetate by over 50%, but did not alter basal secretion. Exposure to less concentrated cigarette smoke-treated medium resulted in less inhibition. Cellular injury was not observed with the concentrations of cigarette smoke-treated medium used in this study. The gas phase of cigarette smoke was not inhibitory at comparable concentrations. Longer exposure to cigarette smoke-treated medium resulted in increased inhibition of PC secretion. The cigarette smoke ingredients, nicotine and benzo[a]pyrene, failed to inhibit PC secretion. Secretion of type II cells exposed to cigarette smoke-treated medium at lower temperatures was not affected. Addition of antioxidants to medium and cells during the preincubation and secretion period did not alter cigarette smoke-treated medium-induced inhibition of stimulated PC secretion. These results demonstrate a direct inhibitory effect of cigarette smoke constituents on surfactant secretion in type II cells. Inhibition is mediated by compounds contained predominantly in the particulate phase of cigarette smoke. Inactivation of the inhibitory effect by lower temperatures suggests involvement of processes such as enzymatic bioactivation or active transport mechanisms.     

Activation of protein kinase C by intracellular free calcium in the motoneuron cell line NSC-19

Clotrimazole (CLT), a member of the antifungal imidazole family of compounds, has been found to inhibit both calcium (Ca2+)-activated 86Rb and potassium (K) fluxes of human red cells and to inhibit red cell binding of 125I-charybdotoxin (ChTX) [11]. We have now used patch-clamp techniques to demonstrate reversible inhibition of whole cell KCa2+ currents in murine erythroleukemia (MEL) cells by submicromolar concentrations of CLT. Inhibition was equivalent whether currents were elicited by bath application of the Ca2+ ionophore A23187 or by dialyzing cells with a pipette solution containing micromolar concentrations of free Ca2+. The extent of inhibition of whole cell MEL KCa2+ currents was voltage-dependent, decreasing with increasing test potential. We also determined the single channel basis of the CLT inhibition in MEL cells by demonstrating the inhibition of a calcium-activated, ChTX-sensitive K channel by CLT in outside-out patches. The channel was also blocked by the des-imidazolyl metabolite of CLT, 2-chlorophenyl-bisphenyl-methanol (MET II) [15], thus demonstrating that the imidazole ring is not required for the inhibitory action of CLT. Single KCa2+ channels were also evident in inside-out patches of MEL cells. Block of K current by CLT was not unique to MEL cells. CLT also inhibited a component of the whole cell K current in PC12 cells. Channel specificity of block by CLT was determined by examining its effects on other types of voltage-sensitive currents. CLT block showed the following rank order of potency: K currents in PC12 cells > Ca2+ currents in PC12 cells > Na currents in sympathetic neurons. These results demonstrate that direct inhibition of single KCa2+ by CLT can be dissociated from inhibition of cytochrome P-450 in MEL cells.     

Decreased CD11b expression, phagocytosis, and oxidative burst in urban particulate pollution-exposed human monocytes and alveolar macrophages

Elevated levels of air pollution particulates < or = 10 microm in diameter (PM10) have been associated with an increase in mortality and morbidity due to pulmonary complications, including pneumonia. Impairment of inflammatory and host defense functions of the alveolar macrophage (AM) may be a precipitating factor. The present study was undertaken to determine whether human AM and blood derived monocytes (MO) modulate the expression of receptors important for phagocytosis of opsonized microbes (CD11b, CD11c), gram-negative bacteria (CD14), extracellular matrix interaction (CD29), and immune responses (CD11a, CD54, HLA-DR) when exposed to particulates obtained from urban air (UAP). Furthermore, phagocytosis of and oxidant generation by opsonized yeast were investigated in particle-exposed cells. AM and MO exposed to UAP for 18 h expressed significantly lower levels of CD11b and CD29. CD14 expression was markedly decreased in MO but not in AM, and CD11c was reduced in AM but not in MO. CD11a, CD54, and HLA-DR were unaltered in both phagocyte populations. Decreased receptor expression was not dependent on particle load in the cells. Phagocytosis of Saccharomyces cerevisiae and the chemiluminescence response were also significantly inhibited by UAP. Time-course studies revealed that decreased oxidant generation was evident already at 3 h postexposure, while significant effects on phagocytosis and CD11b expression were found at 18 h. These data indicate that exposure to particulate pollution is likely to impair host defense functions of AM and MO, which are important in elimination of a variety of pathogens in the lung.     

Cyclic AMP-dependent modulation of vesicular monoamine transport in pheochromocytoma cells

Cyclic AMP (cAMP) is well known to enhance tyrosine hydroxylase activity in PC12 cells. We were able to demonstrate, however, that the cellular dopamine level in PC12 was lowered by dibutyryl cAMP. Furthermore, the decrease in the cellular level of dopamine was accompanied by about a 10-fold increase in the medium. The aim of this work was to elucidate the effect of cAMP on catecholamine transport. Dibutyryl cAMP did not induce exocytotic release of norepinephrine but rather inhibited its uptake. As with forskolin and cholera toxin, physiological signaling molecules such as vasoactive intestinal polypeptide (VIP) and AMP, for which PC12 cells are known to have receptors linked to activation of adenylate cyclase, also inhibited norepinephrine uptake. The inhibitory effects of dibutyryl cAMP, VIP, and AMP were dose dependent, and EC50 values were estimated to be 100 microM, 10 nM, and 1.0 microM, respectively. The inhibition profile of dibutyryl cAMP over the time course of norepinephrine uptake was biphasic: inhibition became clearly detectable after the cytosolic pool of norepinephrine had been saturated. This profile is similar to that of reserpine. Nomifensine, however, inhibited uptake at a rather constant rate throughout the entire time course. The ATP-dependent serotonin uptake by digitonin-permeabilized cells was lowered to approximately 50% that of the control by dibutyryl cAMP treatment before permeabilization, indicating inhibition of vesicular monoamine transport. This effect was also dependent on a dibutyryl cAMP concentration with an EC50 of < or = 100 microM.(ABSTRACT TRUNCATED AT 250 WORDS)     

Establishment of anti-idiotype monoclonal antibodies to human anti lung cancer monoclonal antibody (4G12)

The object of this study is to establish anti-idiotype (anti-ID) monoclonal antibodies (MoAbs) against a human MoAb (4G12) that highly reacts with lung squamous cell carcinomas. Two murine anti-ID MoAbs (2H1 and 2B12) were established by hybridoma technology. They showed specific reactivity with 4G12 but not with 3H12 human MoAb, human IgM and human IgG. These two MoAbs demonstrated more than 90% of binding inhibition of 4G12 to lung squamous cell cancer cell line (PC10). Moreover, cross inhibition test showed that 2H1 and 2B12 detect different idiotypes of 4G12 each other. Furthermore, specific reactivity of anti 2H1 and anti 2B12 sera to PC10 were observed by cell binding ELISA. These two anti-ID MoAbs had internal image of the original antigen.     

Acute stretching of peripheral nerves inhibits retrograde axonal transport

The conjugation of horseradish peroxidase with wheat germ agglutinin was used to identify the effect on retrograde axonal transport of stretching the rat sciatic nerve indirectly by 10% and 20% femoral lengthening with a unilateral external fixator. To investigate the relationship between retrograde axonal transport and blood flow in the stretched nerve, nerve blood flow in the sciatic nerve was measured by a hydrogen washout technique. At 11% strain (20% femoral lengthening), the numbers of horseradish peroxidase-labelled motor neuron cells and nerve blood flow had decreased by 43% and 50%, respectively. Histological examination demonstrated ischaemic changes, but not mechanical damage. However, at 6% strain (10% femoral lengthening) there were no significant abnormalities. These findings suggest that the inhibition of retrograde axonal transport can be induced by acute stretching of the peripheral nerve and that circulatory disturbance is the main cause of the inhibition of retrograde axonal transport at the low strain.     

Plasma containing artemether-pyrimethamine has ex vivo blood schizonticidal activity against Plasmodium falciparum

Four Eptesicus fuscus were trained in a range discrimination experiment to choose the closer of two phantom targets. Echo attenuation was roving between trials returning echoes ranging from -10 dB to -50 dB SPL (sound pressure level) relative to emission SPL. Discrimination thresholds were determined. After sufficient training, ranging performance was stable and about the same in the range between -20 dB and -50 dB with range difference thresholds around 300 microseconds. At -10 dB, performance was poor even after long training. After additional training at a constant relative echo SPL of -30 dB and a delay difference of 300 microseconds the performance measured with roving echo SPL improved at all relative echo SPL between -20 dB and -50 dB but not at -10 dB. The new experimental procedure improved the performance by additional learning, and the bats generalized over a wide range of relative echo SPL. Threshold improved to 100 microseconds when measured at a constant relative echo SPL of -30 dB, again indicating the influence of the experimental procedure. In correspondence to neurophysiological data the ranging performance deteriorates if the echo SPL is close to the emission SPL. Signal duration and emission SPL were variable during range discrimination.     

Inhibition of protein synthesis by zinc: comparison between protein synthesis and RNA synthesis

Inhalation of zinc fumes may lead to the acute respiratory distress syndrome. The mechanisms of pulmonary zinc toxicity are not yet understood. Therefore we investigated zinc-dependent depression of protein and RNA synthesis in rat and human lung cell lines. 1. After exposure to 120 or 150 micromol/l zinc, RNA synthesis as assessed by uridine incorporation decreased by 60-70% between 0 and 2 h exposition in rat alveolar type II cells (L2 cells) and human fibroblast-like cells (11Lu and 16Lu cells), and by 90% between 0 and 4 h in carcinoma-derived cells (A549 cells). 2. After 2 h exposure, L2, 11Lu, and 16Lu cells were half-maximally inhibited by 50 micromol/l zinc, whereas A549 cells were more resistant with half-maximal inhibition at 100 micromol/zinc. 3. Protein and RNA synthesis was inhibited in parallel in L2, 11Lu, and A549 cells as indicated by simultaneous determination of uridine and amino acid incorporation. In 16Lu cells, the decline in protein synthesis preceded RNA synthesis inhibition. Pretreatment with RNA synthesis inhibitors (amanitin or actinomycin D) had no effect on time curve and intensity of RNA synthesis inhibition. Taken together, our results indicate that the suppression of RNA and protein synthesis likely are independent phenomena, due to direct zinc effects on these biosynthetic pathways.     

SA-3对铜铋硫化矿分选分离的作用及机理研究

利用单矿物试验研究了SA-3对辉铋矿和黄铜矿浮选行为的影响,研究表明：SA-3对辉铋矿的抑制能力极弱;当SA-3用量为50mg／L时,黄铜矿受到强烈抑制．红外光谱分析表明：SA-3是一种包含-SH、-OH、-COOH的多官能团抑制剂,文中对SA-3在黄铜矿表面的作用进行了分析．