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1.
Arsenic, a known human carcinogen, was given to mice via drinking water as sodium arsenite at a dose 53.39, 133.47, 266.95 and 533.90 mol l for 35 days. A decrease in the activity of 17 HSD along with increase in LDH, GT activity were observed at 533.90 mol l. The observed sperm count, motility and morphological abnormalities in sperm were similar to control at lower dose levels. However at 533.90 mol l a significant decrease in sperm count and motility along with increase in abnormal sperm were noticed. Significant accumulation of arsenic in testes and accessory sex organs may be attributed to the arsenic binding to the tissues or greater cellular uptake. No effects were observed on indices studied for reproductive effects at 53.39 mol l arsenic close to which human being are exposed through drinking water under the present set of experimental conditions.  相似文献   

2.
Rapid multiplication of axillary meristems and direct shoot development occurred from nodal explants of mature Eucalyptus tereticornis Sm. with 5.3 M NAA, 1.1 M IAA and 4.4 M BA in Murashige-Skoog medium. Repeated subcultures of the second generation shoot cultures into low cytokinin-auxin containing media (0.44–0.88 M BA+0.1 M NAA) yielded axillary microshoots in large numbers. Half-strength MS liquid medium with 4.9 M IBA, 5.5 M IAA and 5.3 M NAA for four days, half-strength semi-solid hormonefree MS medium with charcoal, and MS liquid medium without charcoal and hormones, in sequence, induced rooting of shoots in the dark. This system is suitable for the mass propagation of this difficult-to-root eucalypt.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic acid - IBA -indole-3-butyric acid - 2-iP isopentyl adenine - Kn kinetin - MS Murashige-Skoog - NAA -naphthalene acetic acid - PVP polyvinylpyrrolidone  相似文献   

3.
Summary The total pigment and astaxanthin content ofPhaffia rhodozyma increased with increasing concentrations -pinene up to 500 l -pinene/l. Above this concentration the total pigment and astaxanthin content as well as the biomass production decreased. The addition of 500 l -pinene/l increased the total pigment content from 1652 g/g to 2201 g/g and the astaxanthin content from 1554 g/g to 1883 g/g. A sharp decrease in maximum specific growth rate occurred above 150 l -pinene/l.  相似文献   

4.
Reddell  Paul  Yun  Yang  Shipton  Warren A. 《Plant and Soil》1997,189(2):213-219
P requirements of Casuarina cunninghamiana seedlings inoculated with Frankia and reliant on symbiotic N2 fixation were compared with those of uninoculated seedlings grown with 4 levels of fertilizer N in a solution culture system.Growth responses to increasing P supply depended on the N treatment that had been imposed. At the two lowest levels of N supply (0 t M and 100 t M) growth was relatively poor and there was no response to increasing P supply above 10 t M and 50 t M P respectively. In contrast, inoculated seedlings and those with higher levels of combined N (500 t M and 1000 t M) had significantly greater shoot dry weights (except at 0.1 t M P), and they responded to increasing P supply to between 50 and 100 t M P. At each level of P supply, the dry weights of seedlings in these 3 N treatments were similar. Nitrogen concentrations in shoots of seedlings provided with fertilizer N decreased with increasing P supply to 50 t M and then remained unchanged. In contrast, N concentrations in shoots of inoculated seedlings increased with increasing P supply to 25 t M P. At the 2 highest levels of P supply, N concentrations in shoots of inoculated plants were significantly higher than those in seedlings provided with fertilizer N. In all N treatments, P concentrations in shoots increased with increasing P supply; concentrations were similar in inoculated seedlings and those with the 2 highest levels of fertilizer N across all levels of P supply.Alleviation of P deficiency in inoculated seedlings increased nodule number, nodule dry weight, N2 fixation g-1 nodule dry weight (nodule 'efficiency'), P concentration in nodules, proportion of total seedling biomass allocated to nodules and average nodule size. However, all these parameters reached their maximum values at levels of P supply at, or below, those required for maximum host-plant growth (50 to 100 t M P).The results indicate that the P requirement for host plant growth per se is similar to, or higher than, that required for symbiotic N2 fixation processes.  相似文献   

5.
Summary Size and shape of mitochondrial DNA molecules of Schizosaccharomyces pombe were analyzed by electron microscopy. Besides numerous linear molecules, circular molecules ranging from 0.83 m to 12.81 m were found. Depending on the method of preparation, both closed and open circular molecules were found. Most of the circular molecules could be assigned to five major size classes of 0.83±0.05 m, 1.7±0.05 m, 4.74±0.04 m, 5.74±0.04 m, and 8.32±0.07 m. Possible explanations for the different size classes of mitochondrial DNA molecules are discussed.  相似文献   

6.
Effects of Lead on Adenylate Cyclase Activity in Rat Cerebral Cortex   总被引:1,自引:0,他引:1  
Lead decreased in a dose dependent manner the basal AC activity in membranes of rat cerebral cortex (IC50 = 2.5 ± 0.1 M). In membranes preincubated under basal conditions, AC activity was stimulated by approximately two and fourfold by 10 M Gpp(NH)p or forskolin, respectively. Under basal conditions, lead (3 M) inhibited enzyme activity up to 50%, but was not able to inhibit the Gpp(NH)p- or the forskolin-stimulated AC activity. However, in membranes preincubated with Gpp(NH)p (10 M), lead (3 M) had no significant effect on enzyme activity, but it partly blocked the stimulation of AC activity elicited by forskolin (10 M). In membranes preincubated with 10 M lead, the addition of 10 M Gpp(NH)p or forskolin in the incubation medium did not stimulate AC activity. However, when added together in the incubation medium Gpp(NH)p + forskolin produced an increase in enzyme activity. In membranes preincubated with 10 M lead + 10 M Gpp(NH)p, Gpp(NH)p (10 M) or forskolin (10 M) added alone or in combination to the incubation medium did not stimulate AC activity. Moreover, under these latter conditions lead had no further effect on enzyme activity. These results indicate that lead may interact with G-proteins and with the catalytic subunit of cerebral cortical AC to produce inhibition of the enzyme activity.  相似文献   

7.
An electroporation procedure for the transformation of Pseudomonas oleovorans was developed using a model plasmid, pCN51. The optimal electrotransformation was achieved with cells harvested at 45 to 60 min of growth and concentrated to a cell density of 5 OD600nm, plasmid concentration of 6 g per 100 l of cell suspension, and a 0.1-cm gap-width cuvette. Electroporation was performed at the settings of 250 , 25F and 2.5 kV. Transformation yields in the order of 103 colony-forming-unit per electroporation sample were obtained. This is a first report of the electroporation of the commercially valuable bacterium Ps. oleovorans. © Rapid Science Ltd. 1998  相似文献   

8.
We have studied the mechanism of Ca current inactivation in the -cell line HIT-T15 by conventional and perforated patch recording techniques, using two pulse voltage protocols and a combination of current and tail current measurements. In 5 mM Ca, from a holding potential of - 80 mV, the maximum current showed a complex time course of inactivation: a relatively fast, double exponential inactivation (h1 12 ms and h2 60 ms) and a very slowly inactivating component ( > 1 s). The faster component (h1) was due to the voltage-dependent inactivation of a low-threshold-activated (LVA), T-type current, which deactivates more slowly ( 3–5 ms) than the other components ( 0.2–0.3 ms). The intermediate component (h2) was due to the Ca-dependent inactivation of a portion of the high-threshold-activated (HVA) current. A saturating dose of the dihydropyridine (DHP) nifedipine (10 M) did not affect the LVA current, but inhibited by 68 ± 5% the transient, Ca-sensitive portion of the HVA current and by 33 ± 12% the long lasting component. We suggest that three components of the calcium current can be resolved in HIT cells and the main target of DHPs is a HVA current, which inactivates faster than the DHP-resistant HVA component and does so primarily through calcium influx. Correspondence to: C. Marchetti  相似文献   

9.
Varying intracellular concentrations of zinc in laryngeal Hep-2 cells in relation to changing cultivation conditions in vitro were determined by atomic absorption spectrophotometry. Upon standard cultivation in DMEM with 10% serum, the mean concentration of zinc was determined at 0.88 ± 0.09 g/mg protein, with substantially decreased values in the cells exposed to a low-serum medium. Next, the study of the effects of a series of physiological and supraphysiological concentrations of ZnSO4 on laryngeal cells and their correlation with determined intracellular concentrations of zinc was performed. It was found that zinc concentrations above 100 M were toxic to Hep-2 cells, inducing cell death in the interval of 96 h as determined by videomicroscopy, selective nuclear staining, and immunofluorescence detection of caspase-3 and specific cytokeratin 18 fragment. Both types of cell death were observed, with apoptosis being induced at moderately toxic zinc concentration of 150 M and necrosis at higher zinc concentrations of 300 M and 750 M, respectively. Lower concentrations (1.5–100 M), on the other hand, did not produce any measurable changes in cell morphology and function in the same time interval. Zinc at concentration of 1.5 M was found to slightly enhance proliferation of Hep-2 cells up to the certain time point, which seemed to correlate with maximal tolerable momentary intracellular level of zinc. These results illustrate the importance of determining the intracellular levels of zinc when trying to characterize the effect of exogenous zinc on life and death of laryngeal cells.  相似文献   

10.
Maximum inhibition of Glycine max, cv. Essex seed germination occurred at 10 g/ml following 72 hr imbibition in constant light. Seeds imbided 108 hr in constant darkness at this concentration showed a 20% rise in germination over that of the control. Imbibition of G. max, cv. Williams seeds in either light or dark for 96 hr did not suppress germination. Imbibition of Essex seeds in either light or dark at 2.5 through 10 g/ml stimulated root elongation except for 10 g/ml at 96 hr (light). Maximum inhibition of Williams root elongation under constant light was at 48 and 72 hr with 10 g/ml. Statistically significant differences in cotyledon, leaf and stem lengths between non-treated (NT) and treated (T) seedlings were not found except for Williams stem length at 2.5 / ml. Root elongation was stimulated 1.2- and 1.1-folds, respectively, at 5.0 (Essex) and 2.5 (Williams) g/ml. Toxin at 2.5 through 10.0 g/ml did not markedly alter either cotyledon or leaf widths with the exception of Williams leaf width at 2.5 g/ml. Medium supplementation with 2.5 through 10.0 g/ml resulted in cotyledon, leaf and root weight enhancements for Essex seedlings. Stem weight was not markedly affected. An 18% rise in Williams cotyledon weight above that of the control was seen at 2.5 g/ml. Williams leaf weights were increased 1.75- and 1.25-folds, respectively, at 2.5 and 10.0 g/ml. Aflatoxin B1, at 2.5 g/ml promoted Williams stem and root elongation 1.20- and 1.09-folds, respectively. Most of the radioactivity from 65Zn-ZnCl2 recovered within organs was found within Essex roots for both T and NT seedlings. A higher amount of radioactivity was recovered within roots at each toxin concentration than was without toxin. However, this was not statistically significant. Significant differences in the distribution of radioactivity within roots between NT and T Williams seedlings were not observed. Generally, AFB1 failed to affect significantly these two varieties of soybeans based on the tests relating to germination, growth and radiolabel uptake.  相似文献   

11.
González  L.  Nekrassov  V.  Castell  A.  Sitges  M. 《Neurochemical research》1997,22(2):189-199
The effects of melittin at increasing concentrations on: [3H]GABA release from mouse brain synaptosomes; on the radioactivity released from [3H]arachidonic acid labeled synaptosomal membranes; on synaptosomes ultrastructure and on the leakage of the cytoplasmic marker, lactate-dehydrogenase (LDH) was investigated. Melittin 0.3, 1, 3, 7, and 10 M progressively increases [3H]GABA release, but the efficacy of melittin is decreased when the amount of tissue exposed to a constant concentration of the toxin increases. The release of [3H]GABA induced by melittin below 3 M is Ca2+ dependent, but not that induced by the higher concentrations. The Ca2+ dependent fraction of the [3H]GABA released by 0.3 M melittin is selectively inhibited by 10 M quinacrine and 1 M nordihydroguaiaretic acid (NDGA) and facilitated by 3 M indomethacin, whereas the Ca2+ independent fraction of the [3H]GABA released by melittin is not. In the presence of Ca2+, melittin 0.3, 1 and 10 M progressively increases [3H]arachidonic acid release over control release, but the effectiveness of melittin is also decreased as the amount of tissue increases. No apparent changes in synaptosomes ultrastructure are observed in 0.3 M treated synaptosomes, but a noticeable disorganization is produced in 10 M melittin-treated synaptosomes, independently on the presence of external Ca2+. LDH activity only increases over control activity in the supernatant solutions of 10 M melittin treated synaptosomes, also in a Ca2+ independent manner. Our interpretation of these results is that the Ca2+-dependent, pharmacologic sensitive component of melittin-induced release of [3H]GABA, unmasked when 0.3 M melittin was used, involves the activation of a Ca2+-dependent type of membrane PLA2. The Ca2+-independent release of [3H]GABA is in contrast, highly probable to be due to the membrane perturbation produced by complex melittin/lipid interactions.  相似文献   

12.
Summary A single injection of -interferon (-IFN) (30 000 units/mouse), a major biological modifier of natural killer (NK) cytolytic activity, strongly stimulated NK activity in normal mice, as expected, while the same treatment did not statistically alter the NK response in cyclophosphamide (CY)-suppressed animals.We investigated the possibility of thymosin 1 cooperating with -IFN in boosting NK activity in CY-suppressed animals.The results show that treatment with thymosin 1 (200 g/kg) for 4 days, followed by a single injection of -IFN 24 h before testing, strongly restored NK activity in CY-suppressed mice. Thymosin 1 was, moreover, able to accelerate the recovery rate of NK activity in bone marrow reconstituted murine chimeras.Taken together the data support the concept that the synergic effect between thymosin 1 and -IFN could be the result of effects on differentiation of the NK lineage at different levels.  相似文献   

13.
Zusammenfassung Die schwachelektrischen Mormyridae haben eine dreischichtige Epidermis, deren innere Schicht aus nur etwa 0,22 m dicken sechseckigen Zellen von ca. 60 m Durchmesser besteht. Die etwa 2 m dicken, linsenförmigen Kerne von 7,6 m Durchmesser liegen am Zellrand. Die Zellen sind zu Säulen aufgeschichtet. Ihr Rand ist ausgezackt und dort, wo er die Säulengrenze erreicht, auf etwa 0,34 m verdickt. In der Nähe der Säulengrenzen sind die Zellen über Desmosomen mit den Nachbarn in der eigenen und in der angrenzenden Säule verbunden. Diese Epidermisschicht ist auf die Körperpartien beschränkt, in denen auch Elektrorezeptoren ausgebildet sind.Die beiden anderen Epidermisschichten haben den üblichen Aufbau einer Fischepidermis, abgesehen vom Fehlen der Becherzellen.
Ultrastructure of the electroceptor epidermis of the Mormyridae (Teleostei, Pisces)
Summary The weakly electric fish of the family Mormyridae have a three layered epidermis, with a medium layer consisting of hexagonal cells of only 0.22 m in thickness and about 60 m in diameter. The lens-shaped nuclei are about 2 m thick and 7.6 m in diameter and are situated near the border of the cells. The cells are piled up to hexagonal columns. Their margin is serrate and where it reaches the boundary of the column, it has a thickness of about 0.34 m. Close to the boundaries of the columns, the cells are linked to their neighbours within the column and of the adjoining column by desmosomes. This layer of the epidermis is confined to those regions of the body surface which also contain electroreceptors.The other layers of the epidermis have a structure as usual in fish, except for the lack of goblet cells.
  相似文献   

14.
Scanning electron microscopical investigations of fractures and corrosion casts of the spiracles from femaleA. walkerae ticks revealed a four-part structure, consisting of spiracular plate, ostium and macula forming the external closure, followed by the subostial space and the vestibulum of regulable volume, as well as the atrial chamber as the innermost part from which the main tracheal trunks originate. On the average, the spiracular plate was 158 m long and 188 m at the broadest width. It consisted of a thin, highly perforated external and a thick internal layer, which enclosed the interpedicellar space with numerous stout pedicels. In its posterior region, the spiracular plate was covered by the macula, which was up to 80 m in length and 110 m in width. The interpedicellar cavity opened into the subostial space measuring 95.5 m in length and 159.6m in width, which proceeded into the 112-m long vestibulum. The roof of the vestibulum was flexible and could be everted and inverted. Inverted, the roof formed a quadratic bulge with numerous deep cuticular folds, which confined the lumen of the vestibulum either partially or completely. In corrosion casts, the roof was everted to a length of up to 89.3 m. In the posterior part of the vestibulum, as well as in the initial fourth of the artrial chamber, numerous anvil-, cone-or drop-like cuticular projections were arranged in wedge-like fashion. The atrial chamber was almost spherical with a diameter of 138.4 m. Five main tracheal trunks of different luminal diameter as well as numerous channels opened into the atrial chamber.  相似文献   

15.
In vitro regeneration of plants from immature leaflets of 3 day-old pea (Pisum sativum L. cv. Century) seedlings was studied under defined nutritional, hormonal and environmental conditions. Immature leaflets isolated from the second and third apical leaves of aseptically germinated seeds were cultured on MS medium containing vitamins as in B5 medium, 3% sucrose, 0.8% agar and supplemented with 0.1, 1, and 10 M concentrations of naphthaleneacetic acid (NAA) and 1 and 10 M levels of benzyladenine (BA) in various combinations. Shoot regeneration from the primary callus occurred within 45 to 90 days of culture in most of the hormone combinations. Although the number of calli producing shoots was maximal at 10 M levels of NAA and BA, multiple shoot regeneration was predominant at a combination of 0.1 M NAA and 10 M BA. Indoleacetic acid (IAA) and kinetin (K), both at 10 M, also induced shoot regeneration. No shoots were regenerated when 10 day-old leaflets were used as explants. Root production generally occurred on non-shoot regenerating calli. Roots were induced to differentiate by transferring the regenerated shoots onto half-strength B5 medium supplemented with 1 M NAA.NRCC # 19712Visiting Scientist, supported by a research fellowship from Consejo Nacional de Investigaciones Científicas y Técnicas (Rep. Argentina). Permanent address: Facultad de Ciencias Agrarias, IBONE, Casilla de Correos 209, Corrientes (3400), Argentina.  相似文献   

16.
-Glucuronidase from callus cultures of Scutellaria baicalensis Georgi was purified to apparent homogeneity by fractionated ammonium-sulfate precipitation and chromatography on diethylaminoethyl-cellulose, hydroxylapatite and baicalin-conjugated Sepharose 6B. A 650-fold purification was obtained by this purification system. When subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified protein migrated as a single band with a molecular mass of 55 kDa. We determined that the native enzyme has a molecular mass of 230 kDa using gel-filtration chromatography. These results suggested that the enzyme exists as a homotetramer composed of four identical 55-kDa subunits. The enzyme showed a broad pH optimum between 7.0 and 8.0. The K m values were 9 M, 10 M, 30 M and 40 M for luteolin 3 -O--d-glucuronide, baicalin, wogonin 7-O--d-glucoronide and oroxlin 7-O--d-glucuronide, respectively. The enzyme was most active with flavone 7-O--d-glucuronides.Abbreviations BA N6-benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - pI isoelectric point - R t retention time  相似文献   

17.
Picea glauca (white spruce) zygotic embryos and one-week-old-seedling epicotyl explants were placed on either Woody Plant Medium (WPM) or half-strength Schenk & Hildebrandt (1/2S&H) medium supplemented with varying levels of benzyladenine (BA) (0.1, 1.0, 10, 50, 100 M), zeatin (10, 50, 100 M) or thidiazuron (TDZ) (0.01, 0.1 M). In addition to differences in the number of buds induced at three months on the two media, buds induced on WPM were visually more uniform, less vitrified and elongated faster. On 1/2S&H supplemented with BA, maximum bud induction from embryos occurred on 1.0 M BA with 0.01 M TDZ with higher BA concentrations inhibitory to bud induction. In contrast, on WPM there was little difference in the number of buds induced from embryos placed on 10, 50 and 100 M BA with or without TDZ. One-week-old-seedling epicotyl explants required higher BA levels on 1/2S&H, as bud induction at three months was greatest at 10 M BA. On WPM, as with the embryos, there were only minor differences in the number of buds induced from epicotyl explants on the various BA levels. Zeatin was more effective at inducing buds than BA with both media. From embryos, bud induction was greatest on 50 or 100 M zeatin without TDZ and 50 or 100 M zeatin with or without TDZ on 1/2S&H and WPM respectively. From epicotyl explants on 1/2S&H, there was little difference in the number of buds induced with the zeatin concentrations used, while with WPM, 50 and 100 M zeatin induced the greatest number of buds. Interestingly, with BA, the epicotyl explants needed a higher level than the embryos for maximal response, while with zeatin, the level was the same for both embryos and epicotyl explants. Long-term (six month) survival was higher on WPM than with 1/2S&H. Additionally, embryos had a higher percentage of genotypes surviving at six-months when compared with epicotyl explants. For overall survival and development of the buds, 50 M zeatin with 0.01 M TDZ was the best treatment tested.Abbreviations BA benzyladenine, 1/2S&H-half-strength Schenk & Hildebrandt medium - TDZ thidiazuron - WPM woody plant medium  相似文献   

18.
Summary In a lactic acid fermentation by Streptococcus faecalis, the specific consumption rate of glucose (v) and the specific production rate of lactic acid () were represented by the following simple equations as functions of the specific growth rate (): 1/=(1/) + 1/ = (1/) + By use of data from a batch culture, these two equations were derived from enzyme kinetics of the product inhibition. These equations were successfully applied to the results of batch culture and chemostat culture. In addition, calculation of ATP yield by these equations agreed with the experimental results better than the conventional Leudeking-Piret type equation, which includes two terms associated with growth and not with growth. Correspondence to: H. Ohara  相似文献   

19.
Callus initiation from seedling explants of niger (Guizotia abyssinica Cass) cv. Ootacamund was found to be better on LS medium containing kinetin (1.4 M) plus 2,4-dichlorophenoxyacetic acid (9 M) than its analogues. Embryoids were induced directly from cotyledons on LS medium supplemented with 2,4,5-trichlorophenoxyacetic acid and 2,4,5-trichlorophenoxypropionic acid. When cotyledon-derived callus was subcultured onto medium with 10.7 M naphthalene-acetic acid and 2.3 M kinetin, embryogenesis was observed. Multiple shoots were obtained from cotyledonary explants in presence of MS medium containing 4.4 M benzyladenine and 11.4 M indoleacetic acid. Regenerated plants that were transferred to pots and grown to maturity were morphologically normal and fertile.Abbreviations NAA naphthaleneacetic acid - IAA indoleacetic acid - BA benzyladenine - GA3 gibberellic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - 2,4,5-T 2,4,5-trichlorophenoxypropionic acid - 2,4,5-TP 2,4,5-trichlorophenoxypropionic acid - ABA abscisic acid  相似文献   

20.
Callus growth and the production of anthocyanins were sustained on the salts and vitamins of Murashige and Skoog. Callus growth was stimulated at a concentration of 8–32 M -naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-d). Benzyladenine (BA) and zeatin at 8 M inhibited callus growth whereas isopentenyladenine (iP) stimulated callus growth. NAA repressed anthocyanin production with an increase in NAA from 8–32 M. Anthocyanin synthesis was promoted by an increase in 2,4-d from 0.5 to 2 M and decreased thereafter up to a concentration 32 M 2,4-d. A concentration of 8 M BA, thidiazuron and zeatin, respectively stimulated pigment production. Sucrose stimulated callus growth at 60 mM and pigment production at 120–360 mM.Abbreviations BA 6-benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - NAA -naphthaleneacetic acid - iP isopentenyladenine - TZ thidiazuron-N-phenyl-N-1,2,3-thiadiazol-5-yl-urea - Bu-HCl Butanol-2N HCl - BAW Butanol-acetic acid-water  相似文献   

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