癌基因ras对β-1,4-半乳糖基转移酶活性的调节

 研究癌基因ras对细胞表面的 β 1,4 半乳糖基转移酶活性的调节 构建Ha ras表达载体并转染NIH 3T3细胞株 ,测定细胞表面和细胞内 β 1,4 半乳糖基转移酶活性和其mRNA的水平 结果发现ras使NIH 3T3细胞表面的 β 1,4 半乳糖基转移酶活性降低 ,而高尔基体内的活性不变 此外用Northern印迹检测后发现 ,ras不能改变细胞内 β 1,4 半乳糖基转移酶的mRNA水平 这说明癌基因ras能够调节细胞表面β 1,4 半乳糖基转移酶活性 ,但不能改变其转录水平     

Reviews of publications

Book reviewed in this article:
The Voyage of Charles Darwin: His Autobiographical writings, selected and arranged by Christopher Railing.
Penguin Nature Guides: Fungi of Northern Europe, Vols I & II, by S. Nilsson &; O. Persson; illustrated by B. Mossberg
Penguin Nature Guides: Plant Communities, by Anned Biilow-Olsen, illustrated by Susanne Larsen; translated from the Danish by Joan Tate; edited and adapted by Francis Rose.
Penguin Nature Guides: Fishes of the British and Northern European Seas, by J. Moller Christensen; illustrated by Bente Nystrom; translated from the Danish by Gwynne Vevers; edited and adapted by Gwynne Vevers and Philip Orkin.
Birds of Wood, Park and Garden, text and illustrations by Lars Jonsson; translated from the Swedish by Roger Tanner
Birds of Sea and Coast, text and illustrations by Lars Jonsson; translated from the Swedish by Roger Tanner     

Comparison of the modes of action of a Vero toxin (a Shiga-like toxin) from Escherichia coli, of ricin, and of alpha-sarcin.

The modes of action of a Vero toxin (VT2 or Shiga-like toxin II) from Escherichia coli, of ricin, and of alpha-sarcin were compared. Elongation factor 1 (EF1) and GTP-dependent Phe-tRNA binding to ribosomes in the presence of poly(U) was inhibited by these three toxins, but EF1 and guanylyl (beta, gamma-methylene)-diphosphate-dependent Phe-tRNA binding was inhibited by alpha-sarcin only. EF1- and Phe-tRNA-dependent GTPase activity was inhibited by these toxins, but nonenzymatic binding of Phe-tRNA was not. The turnover rate of EF1 binding to ribosomes during Phe-tRNA binding was also decreased by these three toxins. The addition of EF1 recovered the inhibition of Phe-tRNA binding to ribosomes by VT2 and ricin but not by alpha-sarcin. The formation of and EF2- and GTP-dependent puromycin derivative of phenylalanine was inhibited slightly by the three toxins, indicating that translocation is not influenced significantly by them. EF2-dependent GTPase activity was stimulated by these toxins, and especially by VT2 and ricin. In contrast, the binding of EF2 to ribosomes was inhibited strongly by VT2 and ricin, and slightly by alpha-sarcin. The stimulation of EF2-dependent GTPase activity by the toxins may compensate for the decrease of EF2 binding to ribosomes which they caused during translocation. In total, these results indicate that VT2 and ricin inhibit protein synthesis through the disturbance of the turnover of EF1 binding to ribosomes during aminoacyl-tRNA binding to ribosomes, and that alpha-sarcin inhibits the synthesis through the inhibition of the binding of the complex of Phe-tRNA, EF1, and GTP to ribosomes.     

The effects of diphenyleneiodonium and of 2,4-dichlorodiphenyleneiodonium on mitochondrial reactions. Mechanism of the inhibition of oxygen uptake as a consequence of the catalysis of the chloride/hydroxyl-ion exchange.

1. Increasing the substrate concentration only decreased the inhibition of mitochondrial oxidations by diphenyleneiodonium or by 2,4-dichlorophenyleneiodonium by a small amount. 2. Diphenyleneiodonium and 2,4-dichlorodiphenyleneiodonium lowered the amounts of succinate, citrate and glutamate accumulated in the matrix of mitochondria in the presence of Cl-, but not in its absences. 2,4-Dichlorodiphenyleneiodonium decreased the accumulation of substrates by mitochondria oxidizing glycerol 3-phosphate. 3. Diphenyleneiodonium caused an alkalinization of the medium with an anaerobic suspension of mitochondria, which was only partly reversed by Triton X-100. 4. The rate of proton extrusion by mitochondria oxidizing succinate was not altered by diphenyleneiodonium or by 2,4-dichlorodiphenyleneiodium, although the rate of decay of proton pulses was increased. 5. 2,4-Dichlorodiphenyleneiodonium shifted the pH optimum for succinate oxidation by intact mitochondria from pH 7.2 to 8.0, whereas there was no effect on that of freeze-thawed mitochondria, which was pH 8.0. 6. The concentration of 2,4-dichlorophenyleneiodonium required to inhibit respiration by 50% is less the higher the absolute rate of oxygen uptake. 7. EDTA, but not EGTA [ethanedioxybis(ethylamine)-tetra-acetic acid] increased the inhibition of respiration by diphenyleneiodonium, 2,4-dichlorodiphenyleneiodonium and by tri-n-propyltin. 8. It is concluded that diphenyleneiodonium and 2,4-dichlorodiphenyleneiodonium limit respiration in Cl--containing medium by causing an acidification of the matrix, and that there are pH-sensitive sites in the respiratory chain between NADH and succinate, and between succinate and cytochrome c.     

Influence of the mechanism of transmission of the infective agent on the aetiological structure of leptospiral foci

It has been demonstrated that the differences observed in the aetiological structure of the individual foci of leptospirosis can be explained not only by the affinity of leptospiral serogroups to certain animal species, but also by different mechanisms of transmission of the causative agent of leptospiral infection which can be transferred both by sexual and alimentary routes (in water). It has been demonstrated that mostly one serotype of leptospires predominates in natural foci of leptospirosis, but several in anthropurgic ones. In the author's opinion, leptospiral infection in natural foci is mainly spread by the sexual route through the background species of animals--carriers of leptospirosis, and by the alimentary route in the anthropurgic foci. It is presumed that leptospires of the serogroups Javanica, Australis, Icterohaemorrhagiae, transmitted by the shrew-mice, hedgehogs and rats by the sexual route, are by their origin "ancient" serogroups of leptospires while the serogroups of leptospires isolated from domestic animals, showing predominantly the alimentary route of transmission of infection in the focus, are representatives of the "younger" forms of the evolutional development of leptospires.     

Reviews of publications

Book reviewed in this article:
Taxonomy of Economic Seaweeds: With reference to some Pacific and Caribbean Species, 2 edited by Isabella A. Abbott. La Jolla
Botanic Gardens and the World Conservation Strategy edited by D. Bramwell, O. Hamann, V. Heywood & H. Synge
Introduction to Ecological Biochemistry 3rd ed., by J. B. Harborne
A monographic study of the genus Rosularia (Crassulaceae) by Urs Eggli
The Photographic Guide to Identify Mediterranean Wild Flowers by Roger Phillips assisted by Martin Rix and Nicky Fox
The Photographic Guide to Identify Mediterranean Wild Flowers by Roger Phillips assisted by Martin Rix and Nicky Fox
Conserving the Wild Relatives of Crops by Erich Hoyt.
Somatic Cell Genetics of Woody Plants edited by M. R. Ahuja
Indian Journal of Natural Rubber Research
Dictionary of Weeds of Eastern Europe by G. Williams and K. Hunyadi
Nutrition of the Angiosperm Embryo by David R. Murray.
Plant Pigments edited by T. W. Goodwin.
Panbiogeography edited by R. Craw & G. Sermonti
Saxifrages of Europe: with notes on African, American and some Asiatic species by D. A. Webb & R. J. Gornall     

Regulation of ascorbic acid and of xylulose synthesis in rat-liver extracts. The effect of starvation on the enzymes of the glucuronic acid pathway

1. Control of enzyme formation has been examined in the pathways degrading mandelate and p-hydroxymandelate in Pseudomonas fluorescens. 2. The first three enzymes form a group which is common to both pathways and which is co-ordinately induced or repressed. The genes controlling these enzymes are assumed to form a ;regulon'. This group of enzymes is induced by mandelate or p-hydroxymandelate and repressed by benzoate and by p-hydroxybenzoate (the immediate end products resulting from the action of this group of enzymes). 3. Repression is independently exerted by end products of enzymes controlled by succeeding regulons, i.e. by catechol, by protocatechuate and finally by succinate and acetate. 4. The pattern is repeated further along the pathway, so that benzoate oxidase (controlled by the second regulon) is repressed by its immediate end product, catechol, and again by succinate and acetate. 5. Pyrocatechase, an enzyme controlled by the third regulon, is repressed by succinate and acetate. 6. There is a parallel system of multi-sensitive repression mechanisms controlling production of the enzymes that degrade the hydroxy compounds. Again, the enzymes of each regulon are repressed by the immediate end product of their action and by the end products of each succeeding group of enzymes. 7. Repressor activity appears to be exerted by compounds that are likely to occur as such in the external environment or that occur at points of convergence of the degradative pathways of the cell. 8. The net effect of this control system, involving both induction and end-product repression, appears to be that cells will not form inducible degradative enzymes if the end products are already being supplied from without or are being produced by degradation of some alternative source of carbon and energy.     

The stimulation by transmitter substances and putative transmitter substances of the net activity of phospholipase A2 of synaptic membranes of cortex of guinea-pig brain.

1. The distribution of the hydrolyses of phosphatidylcholine by phospholipase A2 and phospholipase A1, and the hydrolysis of lysophosphatidylcholine by lysophospholipase, in subcellular and subsynaptosomal fractions of cerebral cortices of guinea-pig brain, was determined. 2. Noradrenaline stimulated hydrolysis by phospholipase A2 in whole synaptosomes, synaptic membranes and fractions containing synaptic vesicles. 3. Stimulation of hydrolysis by phospholipase A2 in synaptic membranes by noradrenaline was enhanced by CaCl2, and by a mixture of ATP and MgCl2. The optimum concentration of CaCl2, in the presence of ATP and MgCl2, for stimulation by 10 muM-noradrenaline was in the range 1-10muM. The optimum concentration for ATP-2MgCl2 in the presence of 1 muM-CaCl2 was in the range 0.1-1mM. 4. Hydrolysis by phospholipase A2 of synaptic membranes was also stimulated by acetylcholine, carbamoylcholine, 5-hydroxytryptamine, dopamine (3,4-dihydroxyphenethylamine), histamine, psi-aminobutyric acid, glutamic acid and aspartic acid. With appropriate concentrations of cofactors, sigmoidal dose-response curves were obtained, half-maximum stimulations being obtained with concentrations of stimulant in the range 0.1-1muM. 5. Taurine also stimulated hydrolysis of phosphatidylcholine by phospholipase A2. There were only slight stimulations with methylamine, ethylenediamine or spermidine. No stimulation was obtained with glucagon.     

Reviews of Publications

Book reviewed in this article:
Flowers of the Himalaya , by Oleg Polunin and Adam Stainton.
A Guide to the Vegetation of Britain and Europe , by Oleg Polunin and Martin Walters.
The Experimental Biology of Bryophytes, edited by A. F. Dyer & J. G. Duckett.
A Birdwatcher's Miscellany, edited by Rob Hume.
The Moths and Butterjlies of Great Britain and Ireland, Volume 10, Noctuidae (Part II) and Agaristidae, edited by J. Heath.
Atlas of Butterjlies in Britain and Ireland, by J. Heath, E. Pollard & J. A. Thomas.
Colour Identification Guide to Butterjlies of the British Isles, revised edition by T. G. Howarth.
The World of Butterjlies, An Illustrated Encyclopaedia, by V. Sbordoni & S.Forestiero.
Colour Identijcation Guide to Moths of the British Isles, by Bernard Skinner.
The Biology of Buttegies, edited by R. I. Vane-Wright & P. R. Ackery.
Australian Grasses, by Nancy T. Burbidge, revised by Surrey W. L. Jacobs.
Collins Guide to Grasses, Sedges, Rushes and Ferns, by R. Fitter & A. Fitter. Collins.
Grasses of the Soviet Union, by N. N. Tsvelev, edited by A. A. Fedorov.
The European Garden Flora, Volume 2, Monocotyledons (Part ZZ), edited by S. M Walters et al.
Grasses, 3rd edition, by C. E. Hubbard, revised by J. C. E. Hubbard.     

Involvement of calmodulin in phagocytotic respiratory burst of leukocytes

The superoxide release of guinea pig exudate leukocytes induced by phagocytosis or by stimulation with cytochalasin D, digitonin or calcium ionophore A23187 was completely inhibited by the inhibitors of calmodulin-stimulated processes such as trifluoperazine at 10 μM. A particulate NADPH-dependent superoxide-forming enzyme from the cytochalasin D-stimulated cells was also inhibited by the inhibitors and by EGTA. The activation of heart phosphodiesterase by a boiled extract of the cells which was dependent on calcium ions and abolished by trifluoperazine was observed. These results suggest the presence of calmodulin in leukocytes and its possible role in the stimulation of the superoxide formation.     

Involvement of sulfhydryl groups in the activation mechanism of the ATPase activity of chloroplast coupling factor 1

Activation of the ATPase activity and the exposition of a new adenine nucleotide binding site of chloroplast coupling factor 1 (CF1) by dithioerythritol at 25 degrees C were reversed by oxidants. The ATPase activity elicited by heat (63 degrees C, 4 min) was slightly inhibited by oxidants and was partially additive with the activity induced by dithioerythritol. Titration of the thiols of CF1 and determination of their subunit distribution before and after activation by dithioerythritol show an increase of the free groups from 8 to 10 with the appearance of the 2 new thiols on the gamma subunit. These thiols were available to reagents in nondenatured enzyme and were reoxidized to a disulfide bond by iodosobenzoate or CuCl2. It is concluded that the mechanisms of CF1 activation by dithioerythritol and by heat are different and that the former involves a net reduction of a disulfide bond of the gamma subunit.     

Activation of Intracellular Proteinases of Yeast

The existence of the inactive precursors of yeast proteinases B and C was confirmed in the autolysate of baker’s yeast and they were named as pro-proteinases B and C, respectively. The active and inactive forms of proteinase C were two distinct proteins, separable by chromatographical procedures. The two precursors were markedly activated by incubation at pH 5 or by treatment with denaturing agents, e.g. urea, dioxane, acetone and certain alcohols.

These activations were also observed with extracts from acetone-dried cells and from mechanically destructed cells, but the activation of proteinase A was not demonstrated under any conditions tested. Therefore, it was assumed that most of proteinases B and C exist in vivo as inactive precursors, whereas proteinase A originally exists in an active form.

Pro-proteinase C, the latent form of yeast proteinase C, was partially purified from the autolysate of baker’s yeast. It was strongly activated by incubation at pH 5 or by treatment with urea or dioxane. The former activation was prevented by treatment to inactivate yeast proteinase A, which co-existed with the pro-enzyme in the present preparation, but was promoted by addition of purified proteinase A. Thus, it was confirmed that A could activate pro-proteinase C. Furthermore, it was found that activation could be caused by extremes in pH or by heating to 55~60°C, accompanied by the simultaneous destruction of the enzyme produced. Pro-proteinase C was stable over a range of pH 5 to 8 after 60 min incubation at 50°C.     

SV40 DNA transfection of cells in suspension: analysis of efficiency of transcription and translation of T-antigen

A modification of the Graham and Van der Eb (1974) DNA-calcium phosphate coprecipitation technique is shown to routinely transfect 15% of CV-1 cells with SV40 DNA. The transfection is done in suspension after detachment of cells by trypsin digestion. Transfection efficiency was measured by staining cells for the presence of SV40 T-antigen by indirect immunofluorescence and by assaying for the presence of SV40 early message by the Berk and Sharp (1978) technique.     

Effect of heparin on the extent of inhibition of thrombin by heparin cofactor.

A heparin preparation obtained by gel chromatography is compared to unfractionated heparin with respect to the effects of heparin on the reaction between thrombin and heparin cofactor. Whereas both preparations enhance the rate of inhibition of thrombin by heparin cofactor, the extent of inhibition is decreased by the unfractionated, but not by the fractionated heparin. The decreased extent of inhibition is accounted for by residua of unreacted and undegraded heparin cofactor and thrombin, as demonstrated by gel electrophoresis in dodecyl sulfate. However both heparin preparations enhance the rate of degradation by thrombin of the thrombin-heparin cofactor complex.     

Alteration of rheological properties of human erythrocytes by crosslinking of membrane proteins

The crosslinking of membrane proteins of human erythrocytes by diamide (diazene dicarboxylic acid bis(N,N-dimethylamide) ) was quantified by 4% polyacrylamide gel electrophoresis in 1% sodium dodecyl sulfate. The relation between the crosslinking of membrane proteins and erythrocyte functions (rheological and oxygen transporting) was quantitatively examined. (i) The crosslinking of membrane protein was induced by diamide, without changing the shape and the contents of intracellular organic phosphates (adenylates and 2,3-diphosphoglycerate). The intensity of spectrin 2 in SDS-polyacrylamide gel electrophoresis decreased proportionally to diamide concentration. The percentage decrease in spectrin 2 (using band 3 as an internal standard) was the most appropriate indicator for crosslinking ("% crosslinking'). (ii) The suspension viscosity of erythrocytes increased in proportion to the percentage of crosslinking, in the range of applied shear rates of 3.76-752 s-1. (iii) Erythrocyte deformability (measured by a high-shear rheoscope) was reduced by the crosslinking. The change was detectable even at 5% crosslinking. (iv) Rouleaux formation (measured by a television image analyzer combined with a low-shear rheoscope) was inhibited by the crosslinking. The inhibition was also sensitively detected at more than 5% crosslinking. (v) Hemoglobin in erythrocytes was chemically modified by higher dose of diamide (probably by the binding of diamide with sulfhydryl groups). Also the oxygen affinity of hemoglobin increased and the heme-heme interaction decreased. (vi) The reduction of the crosslinking of membrane proteins by dithiothreitol apparently reversed the intensity of spectrin bands in SDS-polyacrylamide gel electrophoresis and the erythrocyte functions (the suspension viscosity and the deformability), though not completely.     

Uptake and output of various forms of choline by organs of the conscious chronically catheterized sheep.

The net uptake and output of plasma unesterified choline, glycerophosphocholine, phosphocholine and lipid choline by organs of the conscious chronically catheterized sheep were measured. There was significant production of plasma unesterified choline by the upper- and lower-body regions and the alimentary tract and uptake by the liver, lungs and kidneys. The upper- and lower-body regions drained by the venae cavae provided the bulk (about 82%) of the total body venous return of plasma unesterified choline. Production of plasma unesterified choline by the alimentary tract was approximately balanced by the plasma unesterified choline taken up by the liver, and was almost equal to the amount of choline secreted in the bile. There was a considerable amount of glycerophosphocholine in the liver and there was production of plasma glycerophosphocholine by the liver and uptake by the lungs and kidneys. Glycerophosphocholine was higher in the plasma of sheep than in that of rats. Plasma phosphocholine was produced by the alimentary tract and kidneys. There was production of plasma lipid choline by the upper- and lower-body regions drained by the venae cavae. The results suggest that the sheep synthesizes substantial amounts of choline in ectrahepatic tissues and has the capacity for extensive retention and recycling of bile choline. These observations, coupled with a slow turnover of the endogenous choline body pool, explain the low requirement of sheep for dietary choline in contrast with non-ruminant species.     

The acetates of p-nitrophenyl alpha-L-arabinofuranoside--regioselective preparation by action of lipases

All possible di-O-acetates and mono-O-acetates of p-nitrophenyl alpha-L-arabinofuranoside were prepared by chemoenzymatic way using lipases. The 2,3-di-O-acetate was obtained in 90% yield by deacetylation of the primary acetyl group of per-O-acetylated p-nitrophenyl alpha-L-arabinofuranoside by Candida cylindracea lipase (CCL) or Candida rugosa lipase (LAY). The 2,5- and 3,5-di-O-acetates were obtained by acetylation of p-nitrophenyl alpha-L-arabinofuranoside by Pseudomonas cepacia lipase (LPS-30) in organic solvents. The 5-O-acetate was regioselectively synthesised in 95% yield by acetylation of p-nitrophenyl alpha-L-arabinofuranoside catalysed by porcine pancreas lipase. Finally, the 2- and 3-O-acetates of p-nitrophenyl alpha-L-arabinofuranoside were obtained in two steps. The enzymatic di-O-acetylation of p-nitrophenyl alpha-L-arabinofuranoside by LPS-30 was followed by enzymatic hydrolysis of the primary acetyl group by CCL or LAY.     

Time of onset of estrus in gilts

An experiment was conducted to determine when, during a 24-h period, gilts show the onset of behavioral estrus. Beginning on Day 16 of their first estrous cycle, 42 crossbred gilts were observed at 0600, 1200, 1800, and 2400 h for the onset of their second estrus. Fifty-five percent of the gilts had shown onset of estrus by 0600 h. None of the gilts showed the onset of estrus from 0600 to 1200 h, whereas 24% and 21% of the gilts had shown onset of estrus by 1800 and 2400 h, respectively. Chi-square analysis demonstrated that more (P < 0.025) gilts had shown onset of estrus by 0600 than by 1200, 1800, and 2400 h. When the data were combined for estrous checks by 0600 and 1800 h, 76% of the gilts had their onset of estrus by 0600 h as compared to 24% of the gilts by 1800 h (P < 0.005). In conclusion, more gilts had shown onset of estrus by 0600 h than at any other 6-h period.     

Contribution to knowledge of GABAergic innervation of the intermediate lobe of the hypophysis

Regulation of the synthesis and release of peptides by the melanotropic cells of the intermediate lobe of the murine hypophysis is mainly brought about by innervation of the lobe by dopaminergic and GABAergic fibres. The present work reports on a study of the distribution of nerve fibres inside the gland by immunocytochemical identification of the GABA contained in the axons.     

Mechanism of Action of Showdomycin

¹⁴C-Labelled showdomycin was rapidly taken up by Escherichia coli K-12 cells. The showdomycin uptake was highly temperature dependent, sensitive to azide and N-ethyl-maleimide, but was only partially inhibited by treatment with high concentration of iodoacetic acid.

The uptake of showdomycin was inhibited by a wide variety of nucleosides but not by purine and pyrimidine bases, nucleotides, ribose or ribose-5-phosphate. The inhibition of showdomycin uptake by adenosine was of a competitive type.

Since nucleosides inhibited the uptake of showdomycin but did not facilitate its efflux, they must play a role of inhibitors to the entry of the antibiotic into cells.

Removal of extracellular showdomycin by washing, or inhibition of its subsequent entry into cells by the addition of nucleosides or sulfhydryl compounds resulted in a rapid decrease in the intracellular level of the antibiotic during subsequent incubation.