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61.
Knut Pettersson Stefan Nilsson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1980,137(2):131-138
Summary Ventral (VAP) and dorsal (DAP) aortic blood pressure, heart rate (HR) and cardiac output (
) were recorded simultaneously in unanaesthetized Atlantic cod, and the effects of vasoactive drugs on the cardio-vascular parameters studied. Mean resting values for the parameters were VAP=4,39 kPa, DAP=2,49 kPa, HR=41 beats/min, and
= 29,1 ml/min×kg. Adrenaline constricted the systemic vasculature, dilated the branchial vasculature and caused a decrease of HR and
due to a cholinergic reflex. After atropine pre-treatment this reflex was abolished, and the effect of adrenaline on blood pressure enhanced. A small decrease in
persisted after atropine, presumably reflecting the effect of an increased end-systolic afterload.Phenylephrine produced a weak increase in systemic vascular resistance, while isoprenaline lowered both systemic and branchial vascular resistance. The effect of isoprenaline is probably mediated by beta adrenoceptors in both vascular beds, since propranolol antagonizes the effect.Acetylcholine in low doses produces a drop in
without affecting HR, while higher doses also stop the heart. There is no significant change in either branchial and systemic vascular resistance after acetylcholine.Abbreviations
VAP
mean ventral aortic blood pressure
-
DAP
mean dorsal aortic blood pressure
-
TBPD
trans-branchial blood pressure drop
-
HR
heart rate
-
SV
stroke volume
-
cardiac output (ventral aortic blood flow)
-
VR
g
branchial vascular resistance
-
VR
s
systemic vascular resistance 相似文献
62.
Sympathetic nervous control of blood flow in the gills of the Atlantic cod,Gadus morhua 总被引:1,自引:1,他引:0
Stefan Nilsson Knut Pettersson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1981,144(2):157-163
Summary The effects of sympathetic nerve stimulation, adrenaline and isoprenaline on the inflow pressure and efferent arterial and venous flow rates were studied in a cod gill preparation perfused at constant flow rate.The dominant effect of adrenaline was a reduced inflow pressure, accompanied by an increase in arterial flow and a decrease in venous flow. Isoprenaline also decreased the inflow pressure, but the changes in both outflow rates were small or absent.Sympathetic nerve stimulation gave arterial and venous flow changes comparable to the adrenaline effects, but the inflow pressure increased during nerve stimulation. Propranolol has little effect on the nerve responses, but phentolamine abolished or reversed the increase in inflow pressure, and also decreased or abolished the changes in outflow rates.The possible sites of action of the sympathetic fibres, and the distribution of adrenoceptors in the effector tissue is discussed. It is concluded that the main effect of sympathetic nerve stimulation is -adrenoceptor mediated, involving constriction of the arterio-venous pathway. The-adrenoceptor mediated control of total branchial vascular resistance may largely depend on circulating catecholamines. 相似文献
63.
A linear and a nonlinear transmission line model of the basilar membrane is described. The motion of the basilar membrane model has been simulated by numerical methods and compared with physiological data for several types of sound stimuli. It is shown that a linear model exhibits a frequency modulation in its impulse response that is in accordance with physiological data. The nonlinear model displays a sharpened frequency response for lower sound intensities. Futhermore, a nonlinear model explains why hearing damage imposed by short, high-intensity, sounds is extended to the low-frequency regions of the cochlea. 相似文献
64.
The use of a partition locus to increase stability of tryptophan-operon-bearing plasmids in Escherichia coli 总被引:6,自引:0,他引:6
The stability of different derivatives of plasmid vectors pBR322 and pACYC184 carrying the tryptophan operon of Escherichia coli was monitored in various media. It was found that in the absence of any special selective pressure, all plasmids were lost from the culture. The stability varied depending both on the orientation of the inserted tryptophan fragment and the growth media used. The pBR322::trp+ plasmids were lost at an average frequency of 0.3 to 0.8% per cell generation, while the pACYC184::trp+ plasmid was lost at a rate higher than 5%. In all cases the whole plasmid was lost at a rate higher than 5%. In all cases the whole plasmid was lost, indicating a high stability of the plasmid::cloned DNA as such. To increase the stability of the cloning vectors, the partition locus of plasmid pSC101 was added to both the pBR322::trp+ and pACYC184::trp+ plasmids. The addition of this gene increased the replicon stability at least 3- to 10-fold, with the pBR322::trp+-par+ plasmids being the most stable. Also in this case, the stability was dependent on the plasmid type and on the growth medium. In no case was there a discoordinate loss of the antibiotic-resistance and tryptophan genes from the vectors. 相似文献
65.
Mathias Uhlén Björn Nilsson Bengt Guss Martin Lindberg Sten Gatenbeck Lennart Philipson 《Gene》1983,23(3):369-378
Two plasmid vectors, containing the gene coding for staphylococcal protein A and adapted for gene fusion, have been constructed. These vectors will allow fusion of any gene to the protein A gene, thus giving hybrid proteins which can be purified, in a one-step procedure, by IgG affinity chromatography. As an example of the practical use of such vectors, the protein A gene has been fused to the lacZ gene of Escherichia coli. E. coli strains containing such plasmids produce hybrid proteins with both IgG binding and β-galactosidase activities. The hybrid protein(s) can be immobilized on IgG-Sepharose by its protein A moiety with high efficiency without losing its enzymatic activity and they can be eluted from the column by competitive elution with pure protein A. The fused protein(s) also binds to IgG-coated microtiter wells which means that the in vivo product can be used as an enzyme conjugate in ELISA tests. 相似文献
66.
Dieter Kabelitz Thomas H. Tötterman Magnus Gidlund Kenneth Nilsson Hans Wigzell 《Cellular immunology》1982,70(2):277-286
Stimulatory effects of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) on human T lymphocytes have been investigated. TPA was found to stimulate highly purified T cells (obtained by a three-step isolation procedure involving plastic adherence, nylon wool passage and Ig-anti-Ig column passage) in the absence of accessory cells (stimulation index of 5 to 10), whereas phytohemaglutinin (PHA) and concanavalin A (Con A) did not. This response was, however, increased by the addition of autologous adherent cells. Addition of TPA, but not adherent cells, induced T-cell proliferation in response to the nonmitogenic lectin, wheat germ agglutinin (WGA), while both adherent cells and TPA restored T-cell proliferation to mitogenic lectins such as PHA and Con A. Furthermore, TPA greatly increased the mixed-lymphocyte response of purified T cells to otherwise nonstimulating allogeneic cells such as T lymphocytes or tumor cells from some patients with chronic lymphocytic leukemia. These results suggest that TPA can directly act on human T cells to render them reactive to a variety of stimuli. 相似文献
67.
The Ca2(+)-and calmodulin-dependent protein kinase III, which specifically phosphorylates the eukaryotic elongation factor 2 (eEF-2), has been purified to apparent homogeneity from the post-ribosomal fraction of rabbit reticulocytes by an efficient four-step method. The method results in a more than 4000-fold purification of the enzyme. SDS-gel electrophoresis showed that the purified kinase contained only one polypeptide with the apparent molecular mass of 90 kDa. The kinase activity was associated with the 90-kDa protein as shown by analyzing the phosphorylating activity of SDS gel electrophoretically purified protein electroblotted to nitrocellulose membranes. The purified kinase was dependent on Ca2+, Mg2+ and calmodulin for activity. Kinetic analysis of the phosphorylation reaction indicates that the turnover number of the kinase was approximately 1 s-1. The Km for the two substrates ATP and eEF-2 was calculated to be approximately 100 microM and 10 microM, respectively. The activity of the kinase was competitively inhibited by cAMP. The inhibition constant Ki (0.5 mM) was found to be in the same order of magnitude as that calculated for the competitive product inhibition caused by ADP. GTP was ten-times less efficient as competitor, indicating that the kinase had a preference for adenosine nucleotides. Phosphorylation of eEF-2 did not interfere with the diphtheria-toxin-catalysed ADP-ribosylation of the factor nor did ADP-ribosylation inhibit phosphorylation. 相似文献
68.
69.
Treatment of reticulocyte polysomes with elongation factor eEF-2 and GTP led to an increased sensitivity of peptidyl-tRNA for puromycin as a result of the translocation from the ribosomal A-site to the P-site. Upon addition of an excess of the non-hydrolysable GTP analogue, GuoPP[CH2]P, the puromycin sensitivity decreased rapidly. The decrease in sensitivity required high concentrations of eEF-2 with half maximal effect at an eEF-2 concentration of around 1 microM. The data suggest either that peptidyl-tRNA had re-translocated back to the A-site due to the higher affinity of eEF-2 for the pre-translocation than for the post-translocation ribosome, or that the eEF-2-GuoPP[CH2]P complex blocks the peptidyl-transferase activity. 相似文献
70.
A preferential incorporation of dietary arachidonic acid (20:4, n-6) into chyle lipoprotein phospholipids, a relative resistance of 20:4 esters of chyle triacylglycerol (TG) to hydrolysis by lipoprotein lipase, a preferential utilization of 20:4 for phospholipid acylation, and a low rate of oxidation of 20:4 are factors that may contribute to the differences seen in the incorporation into tissue lipids between absorbed 20:4 and the predominant dietary 16-18 carbon fatty acids. In this study we fed [14C]20:4 and [3H]eicosapentaenoic acid (20:5, n-3) as free fatty acids in a fish oil emulsion to rats and analyzed the radioactivity in different tissue lipids after 1, 2, and 4 h. The purpose was to examine the degree of similarity in the fate of the two major eicosanoid precursors during the absorption of a fish oil meal. The recovery after 2 and 4 h of 14C exceeded that of 3H in lipids of small intestine, serum, liver, heart, kidneys, and spleen. The differences increased with time, e.g., the liver contained 9.7 (+/- 0.7)% 3H and 17.9 (+/- 1.4)% of the 14C (P less than 0.001), and the upper half of the small intestine 10.0 (+/- 0.8)% of the 3H and 22.8 (+/- 1.1)% of the 14C (P less than 0.001) after 4 h. The 14C and 3H radioactivity per g tissue after 4 h ranked as follows: liver and brown adipose tissue greater than kidneys greater than heart, lungs, spleen, and serum greater than colon greater than white adipose tissue and testes, the differences between tissues being up to 50-fold. There were up to fourfold variations in the 14C/3H ratios between tissues after 4 h, the highest value being observed in the heart and the lowest in white adipose tissue. Of the radioactivity retained in liver and intestine, more 14C and 3H was in phospholipids and less in triacylglycerol (TG), the differences being largest in the liver, e.g., after 4 h 57.6 (+/- 0.8)% of the 14C and 29.9 (+/- 0.9)% of the 3H (P less than 0.001) in the liver was in phosphatidylcholine (PC). In both intestine and liver the highest 14C/3H ratios were found in phosphatidylinositiol (PI). Also phosphatidylethanolamine (PE) contained more 14C than 3H but the quantitative differences were relatively small after 4 h. In heart the proportions of 3H and 14C found in PE and PI did not differ, whereas more of the 14C was in PC and more of the 3H was in cardiolipin and phosphatidylserine.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献