共查询到20条相似文献,搜索用时 15 毫秒
1.
In normalyears, eggs and prolarvae of the plaice (Pleuronectes platessa L.) in the southern North Sea develop within the temperature range 6.0–8.5 °C, although the water may at times be some degrees colder or warmer than this. The effect of temperature, t °C, on the embryonic development time, D days, has been investigated within the tolerated range 2.8–10.5 °C. Various models to express the observed curvilinear relationship between t and D have been considered, that giving the closest fit to the data being (t−t0)(D−D0) = k or . A method is given for the calculation of constants k, D0, and t0. The relationship may also be expressed by the equation D = a(t−t0)b where a and b are constants, but t0 must in this case be found by iteration. At investigated temperatures in the range 4.1–10.5 °C the smallest eggs in a batch from a single source hatched first. Within the tolerated range, hatching prolarvae were substantially smaller at 10.5 °C than at the other temperatures. During the period of prolarval yolk utilization, growth is slower at the high temperatures, so that median temperatures of 6.5–8.0 °C are most efficient in terms of the relationship between growth in length and yolk utilization. Toward the end of the yolk-sac phase, the rate of yolk utilization declines unless a suitable external food source (e.g., Artemia nauplii) is provided. 相似文献
2.
The influence of temperature on the rate of reduction of P-680+, the primary donor of Photosystem II, has been studied in the range 5–294 K, in chloroplasts and subchloroplasts particles. P-680 was oxidized by a short laser flash. Its oxidation state was followed by the absorption level at 820 nm, and its reduction attributed to two mechanisms: electron donation from electron donor D1 and electron return from the primary plastoquinone (back-reaction).Between 294 and approx. 200 K, the rate of the back-reaction, on a logarithmic scale, is a linear function of the reciprocal of the absolute temperature, corresponding to an activation energy between 3.3 and 3.7 kcal · mol?1, in all of the materials examined (chloroplasts treated at low pH or with Tris; particles prepared with digitonin). Between approx. 200 K and 5 K the rate of the back-reaction is temperature independent, with . In untreated chloroplasts we measured a of 1.7 ms for the back-reaction at 77 and 5 K.The rate of electron donation from the donor D1 has been measured in darkadapted Tris-treated chloroplasts, in the range 294–260 K. This rate is strongly affected by temperature. An activation energy of 11 kcal · mol?1 was determined for this reaction.In subchloroplast particles prepared with Triton X-100 the signals due to P-680 were contaminated by absorption changes due to the triplet state of chlorophyll a. This triplet state has been examined with pure chlorophyll a in Triton X-100. An Arrhenius plot of its rate of decay shows a temperature-dependent region (292–220 K) with an activation energy of 9 kcal · mol?1, and a temperature-independent region (below 200 K) with . 相似文献
3.
A novel high affinity dopaminergic ligand, N-(p-aminophenethyl)spiroperidol, has been synthesized and radioiodinated to a specific radioactivity of 2175 . Binding of this ligand to bovine anterior pituitary membranes is: (i) rapid (40–60 min to equilibrium at 25°C) and reversible t = 1 h at 25°C); (ii) saturable and of high affinity (KD ~ 20 pM) and (iii) displays a typical D2-dopaminergic specificity. The ligand, which identifies the same number of receptor sites as other tritiated antagonist ligands, can be used in different tissues and preparations to delineate the characteristics of the D2 receptor. Thus, this high affinity, high specific radioactivity ligand (N-(p-amino-m-[125I]iodophenethyl)spiroperidol) represents a tool which until now had not been available for the characterization of the D2-dopamine receptor. 相似文献
4.
Unidirectional fluxes of [14C]lactose by whole cells of Escherichia coli under highly energized and partially de-energized (in the presence of CN?) conditions are analyzed kinetically.When the cells are energized, the value for influx is internal concentration increment/s and is . At an external concentration of 0.61 mM the steady-state internal concentration is 0.25 M, reached after about 1h. The maximum steady-state concentration ratio is .The efflux process under these conditions is non-saturable, being linearly dependent upon internal concentration over the range 25–250 mM with a first-order rate constant of .The transport in the presence of CN? is active, with a maximum concentration ratio (internal concentration/external concentration) of 104, and the uptake is mimicked by anoxia (< 70 ppm O2).The effects of CN? are to lower the for influx and to change the efflux from a non-saturable to a saturable process with a value for (60 mM) intermediate between that for energized efflux () and influxe (0.3–0.6 mM), the latter value not changing appreciably. Partial de-energization thus affects both the influx and efflux processes. 相似文献
5.
6.
N. Vaysse J. Laval C. Senarens J.P. Esteve A. Ribet 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1982,720(4):378-383
Dispersed acini from dog pancreas were used to examine the ability of dopamine to increase cyclic AMP cellular content and the binding of [3H]dopamine. Cyclic AMP accumulation caused by dopamine was detected at 1·10?8 M and was half-maximal at . The increase at 1·10?5 M, (7.5-fold) was equal to the half-maximal increase caused by secretin at 1·10?9 M. Haloperidol, a dopaminergic receptor antagonist inhibited cyclic AMP accumulation caused by dopamine. The IC50 value for haloperidol, calculated from the inhibition of cyclic AMP increase caused by 1·10?5 M dopamine was . Haloperidol did not alter basal or secretin-stimulated cyclic AMP content. [3H]Dopamine binding was studied on the same batch of cells as cyclic AMP accumulation. At 37°C, it was rapid, reversible, saturable and stereospecific. The value for high affinity binding sites was and for low affinity binding sites. The concentration of drugs necessary to inhibit specific binding of dopamine by 50% was noradrenaline, 2·10/t-7 M epinine, fluphenazine, haloperidol, cis-flupenthixol, trans-flupenthixol, apomorphine, sulpiride, naloxone and isoproterenol. 相似文献
7.
Hans Berger Kathleen Kennedy 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,633(1):68-76
Bacteriophage φ6 has been studied by small-angle X-ray scattering, intensity-fluctuation spectroscopy, analytical ultracentrifugation, and spectroscopy. The sedimentation coefficient (s200, w) is 375 S, the diffusion coefficient (D200, w) is 2.66 · 10?8 cm2/s. Using the Svedberg equation and an estimate of the partial specific volume, the Mr is 1.49 ± 0.32 · 108.A simple model which describes φ6, is a central sphere consisting of RNA and protein of radius 330 Å and an outer shell of low electron density 40 Å thick. The RNA may form five concentric shells in the region 相似文献
8.
Immunity protein, an inhibitor of the ribonuclease activity of the protein antibiotic colicin E3, crystallizes in the orthorhombic space group C222 with cell dimensions and one molecule of Mr 9800 per asymmetric unit. The crystals are suitable for high resolution X-ray analysis. 相似文献
9.
J R Knox M L DeLucia N S Murthy J A Kelly P C Moews J M Frére J M Ghuysen 《Journal of molecular biology》1979,127(2):217-218
A pencillin-sensitive enzyme, the exocellular dd-carboxypeptidase-transpeptidase from Streptomyces R61, has been crystallized from polyethylene glycol (Mr = 6000 to 7500) solution at pH 7·6. X-ray examination of the orthorhombic crystals shows the space group is P212121, with unit cell dimensions . With four molecules of molecular weight 38,000, the ratio for the cell is 2·33. The crystals are stable to irradiation for 75 hours and are suitable for structure analysis to at least 2·4 Å resolution. The radius of gyration of the molecule in solution at pH 6.8 is 20.8 Å. 相似文献
10.
Determination of the rates of synthesis and degradation of vitamin D-dependent chick intestinal and renal calcium-binding proteins 总被引:1,自引:0,他引:1
Vitamin D3 and its biologically active metabolite 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] are shown to induce in the chick intestine and kidney the biosynthesis of a calcium binding protein (CaBP). In vitamin D3-replete chickens raised under adequate dietary calcium (Ca) and phosphorus (P) conditions, the steady-state level of intestinal CaBP (30–50 g/mg protein) is 5- to 20-fold greater than that of renal CaBP. Whereas dietary phosphorus restriction is known to elevate both intestinal and renal CaBP levels, dietary calcium restriction elevates only intestinal CaBP. The present study reports the rates of biosynthesis in vivo and in vitro, and of biodegradation in vivo, of both intestinal and renal CaBP after administration of vitamin D3 or 1,25(OH)2D3 to rachitic chicks. The apparent rate constant of degradation for intestinal CaBP was 0.024 h?1 () and that for renal CaBP was 0.019 h?1 () while total cellular soluble protein in the intestine and kidney had half-lives of 43 and 70 h, respectively. The time course of induction of the synthesis of CaBP was determined in intestine and kidney after administration of a physiological dose of 1,25(OH)2D3 to rachitic chicks. Intestinal CaBP synthesis was detectable by 3 hours, reached a maximal rate by 10 hours, and sharply decayed by 16–20 hours. The time course of induction of renal CaBP synthesis was very similar, although the rate of renal CaBP synthesis was readily detectable at the initial time of administration of 1,25(OH)2D3. The relative rates of synthesis of CaBP in the intestine and kidney under a variety of dietary Ca and P conditions in the vitamin D3-replete chick exactly paralleled the steady-state level of CaBP in these two tissues. These results are consistent with a model in which the steady-state levels of intestinal and renal CaBP are solely determined by their respective rates of biosynthesis; the CaBP biosynthetic capability, in turn, is regulated by the availability of 1,25(OH)2D3 to each target organ. 相似文献
11.
Patrick Van Roey Charles M. Weeks F.E. DeJarnette Terry A. Beerman Mary McHugh 《Journal of molecular biology》1981,153(1):183-185
Macromomycin (Mr 12,000) is the apoprotein of the antitumor drug auromomycin, which inhibits DNA synthesis by causing single-strand breaks in DNA. Two orthorhombic crystal forms of macromomycin have been observed. The platelike crystals of one form belong to space group P212121, with cell dimensions . The crystals of the second form are needle-shaped, and belong to space group P21212, with cell dimensions . At this point in time, the platelike crystals appear the most suitable for continued crystallographic studies. 相似文献
12.
The nematode Trichinella spiralis is rejected from the intestine at a time that is characteristic for each inbred strain of mouse. Previous work (R. G. Bell et al. 1982a) had empirically identified strong, intermediate, and weak phenotypes (NFR, , and mice, respectively) in mice infected with 400 muscle larvae. It is shown that this classification applies to another eight inbred strains: SWR, , , LP, —all intermediate, and , C57L, A, and Mus molossinus—all weak. This phenotypic classification consistently applies with infections of 400–800 muscle larvae. Below doses of 300 muscle larvae, the strain designation of phenotype does not consistently apply. By this it is meant that the relative rejection rate changes for certain strains so that eventually some strains that were strong (NFR) or intermediate (AKR) responders to 400 muscle larvae become weak responders to 50 muscle larvae. Other strains increase their relative rejection time (B10 · BR, B10 · Q) while many do not change (NFS, , , ). The phenomenon is most apparent in inbred parental strains rather than in F1 crosses, and it represents a phenotypic variation in rejection time that is dependent on dose. It is also demonstrated that time of rejection is directly proportional to dose in all inbred and F1 mouse strains that we have examined. Analysis of F1 crosses shows that most have the rejection time of the strongest responding parental line, suggesting simple genetic control of strong, intermediate, and weak responses. Two F1 crosses invalidated this theory. The (intermediate × intermediate) showed a strong response. The additive effects of parental rejection phenotype indicated that these lines could not be genetically identical for intermediate responsiveness. Similarly, the NFR (strong) × B10 · BR (weak) F1 showed intermediate rejection, indicating partial dominance of genes over the strong responder NFR strain. Neither the primary expulsion time phenotype, phenotypic variation to low doses, or the rejection characteristics of F1 crosses could be ascribed to genes linked to the major histocompatibility complex. 相似文献
13.
Properties of [3H]diazepam binding sites on rat blood platelets 总被引:8,自引:0,他引:8
Intact rat blood platelets are shown to possess benzodiazepine binding sites of the peripheral type, binding of [3H]diazepam being strongly inhibited by Ro5-4864 (Ki = 3.6 ± 0.5 nM) but only weakly inhibited by clonazepam (Ki = 35.1 ± 18.2 μM). Binding of [3H]diazepam is specific and saturable. Scatchard analysis reveals a single class of binding sites with KD = 14.7 ± 1.0 nM and Bmax = 564 ± 75 fmoles/108 platelets. The Hill coefficient is 0.94, indicating a lack of binding site heterogeneity or negative cooperativity. Binding reaches equiliibrium at 6 min, with k+1 = 2.9 × 107 M?1 min?1, and is rapidly reversible ( with K?1 = 0.315 min?1. KD derived from the rate constants agrees with that estimated by Scatchard analysis. KD of the crude membrane fraction of platelets is also close to that of intact platelets. Binding of [3H]diazepam is linear with platelet number (between 0.25–2 × 108 platelets), is temperature sensitive with maximum binding at 0°C, and has a broad optimal pH range between pH 5–9. 相似文献
14.
Rates of hemolysis of rabbit erythrocyte suspensions induced by P. parvum (prymnesin) have been measured colorimetrically at 25.5°C and pH 5.5. The data have been treated previously as consecutive first-order rate processes associated with the prolytic and lytic periods from which two specific rate constants have been obtained, k′ and kψ, respectively. These constants have been related to those obtained by a computer-generated fit of the rate data (absorbance At, as a function of time t) with the rate equation . Here Y equals At, X = time, t; D is equal to a spread factor, Ai ? A∞; C is the slope of the curve at the inflection point; B is the midpoint time value, i.e., the time at which ; E is termed the off-set constant and is equal to A∞. Of these constants, B is directly related to the length of the prolytic period, and C?1 is directly related to the specific first-order rate constant for hemolysis, kψ. 相似文献
15.
A.Scott Goustin 《Developmental biology》1981,87(1):163-175
This report presents an analysis of histone gene expression in the cleaving embryo of the sea urchin, Strongylocentrotus purpuratus, with emphasis on whether the regulatory site(s) in the pathway of gene expression change as development proceeds. The analysis focuses on the equation, , where = the absolute rate of histone synthesis; M = the mole quantity of histone messenger RNA; f = the fraction of histone mRNA in polysomes; n = the polysome size; and = the rate of elongation of nascent histone polypeptide chains. The embryo solves this rate equation differently at different times. Measurements were made (at 15°C) of absolute rates of histone synthesis (). The rate of histone synthesis increases at least 48-fold during the first 6 hr after fertilization from less than 0.5 to 24 pg embryo?1 hr?1; in the period from 6 to 12 hr, this rate rises to 182 pg embryo?1 hr?1, an additional 7.7-fold rise, resulting in an overall increase of 370-fold between the 1-cell and 200-cell stage. The fraction of newly synthesized (zygotic) histone messenger RNA that partitions into polysomes (fzygotic) has also been measured during the first 12 hr of development. This fraction increases from 0.2 in the 2-hr embryo to 0.8 in the 6-hr embryo (16-cell stage), increasing slowly thereafter to near unity by 12 hr. The size of histone-synthesizing polysomes (n) does not change substantially over the 12-hr interval, remaining constant at a weighted mean of 5 ribosomes per polysome (range 3 to 7). Utilizing the data on fzygotic and , the rate of elongation of nascent histone polypeptide chains () during the first 6 hr of development was estimated; remains constant at 1.11 codons per second. This calculated value is in fair agreement with a direct measurement of histone peptide elongation rate in the 12-hr embryo. It is proposed that histone gene expression in cleaving sea urchin embryos be divided into two phases, distinguished on the basis of their pivotal translational parameters: Phase I (0–6 hr), during which f is rate determining, and Phase II (6 hr on), during which M is the rate-determining parameter. 相似文献
16.
Kenneth H. Norwich 《Journal of theoretical biology》1982,95(2):399-407
Certain substances, when injected intravenously, are removed from the plasma in accordance with the simple power law, C = At?a. C is the concentration in plasma; A and a are constants. It is suggested that when a is of the order of 1·5, this power law may result from diffusion of the injected substance under conditions of spherical symmetry. It is shown for two such substances, that their diffusion coefficient in plasma, D, is given approximately by the expression , where ME is the effective diffusing mass. 相似文献
17.
Trichinella spiralis: genetic basis for differential expression of phase-specific intestinal immunity in inbred mice 总被引:2,自引:0,他引:2
Responsiveness of mouse strains after phase-specific immunization with Trichinella spiralis is compared. Two strains () showed strong overall responsiveness. The response type could be characterized in phase-specific terms as: strongly anti-adult, weakly to moderately anti-preadult, and strongly antifecundity. By comparison, congenic mice of the C57B1 background (B10·A, B10·D2, B10·S, B10·Q) displayed poor total responses that could be characterized as: weakly anti-adult, very weakly anti-preadult, weakly anti-fecundity after preadult immunization, and mixed (weak and strong) after adult immunization. The mouse appeared to be intermediate between the B10·BR and the strains in overall responsiveness. Genetic determinants of anti-preadult or anti-adult responses of strain mice were dominant over their B10 congenic counterparts as shown in F1, crosses of × B1O·BR mice. Since the (predominantly H-2q) and the (H-2S) are both strong responders, while the B10·Q(H-2q) and B10·S (H-2S) are weak, it is suggested that the major genes controlling anti-preadult and anti-adult responses are not linked to the major histocompatibility complex. However, variations in anti-adult immunity and anti-fecundity in the B10 congenic mice (B10·Q and B10·S are the strongest responders) suggest that minor genes linked to the MHC exert some control over these responses. Some evidence was obtained for gene complementation as the F1 cross of and mice responded more vigorously than the parental lines. We conclude that multiple genes determine anti-T. spiralis intestinal responses in mice. The major genes are unlinked to the major histocompatibility complex whereas several minor genes are linked. 相似文献
18.
The surface active properties and anti-bacterial activity of the compounds, trans-[Rh(L)4Cl2]Cl·nH2O
Thomas R Jack 《Journal of inorganic biochemistry》1980,12(3):187-199
The antibacterial activity and surfactant activity of the compounds trans-[Rh(L)4Cl2]Cl·nH2O increase in the order L = pyridine<4-methylpyridine<4-ethylpyridine<4-n-propylpyridine.As surfactants, the compounds are far more effective at reducing the interfacial tension, , than the surface tension, .The most effective and efficient surfactant in this series, trans-[Rh(4-n-propylpyridine)4Cl2]Cl·H2O, can cause the leakage of intracellular manganese ions from the gram-positive bacteria, Bacillus brevis ATCC 9999, at a concentration of 130 ppm but there is no observable effect on the retention of intracellular manganese ions at the minimum concentration required to prevent growth of this organism (~0.6 ppm at 23°C in nutrient broth).At 130 ppm, trans-[Rh(4-n-propylpyridine)4Cl2]Cl·H2O does not cause the loss of intracellular manganese ions from the gram-negative bacteria, Escherichia coli JS-1. In this case, a concentration of at least 63 ppm of this rhodium compound is required to prevent the growth of this organism in M9TUH medium at 35°C.On the basis of these results, it is suggested that gross membrane disruption effects caused by the surfactants trans-[Rh(L)4Cl2]Cl·nH2O are not directly responsible for their observed antibacterial action. 相似文献
19.
20.
L. Yeap Foo William T. Jones Lawrence J. Porter Vincent M. Williams 《Phytochemistry》1982,21(4):933-935
The structure of the condensed tannins of the most common fodder legumes is described. The number- (n) and weight-average (w ) MW of the polymers have been determined and most legume tannins have an approximately normal distribution of MWs with n values of 2000–4000. 相似文献