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81.
Stanley W. C.; Gertz E. W.; Wisneski J. A.; Neese R. A.; Morris D. L.; Brooks G. A. 《Journal of applied physiology》1986,60(4):1116-1120
Lactate metabolism was studied in six normal males using a primed continuous infusion of lactate tracer during continuous graded supine cycle ergometer exercise. Subjects exercised at 49, 98, 147, and 196 W for 6 min at each work load. Blood was sampled from the brachial artery, the iliac vein, and the brachial vein. Arteriovenous differences were determined for chemical lactate concentration and L-[1-14C]-lactate. Tracer-measured lactate extraction was determined from the decrease in lactate radioactivity per volume of blood perfusing the tissue bed. Net lactate release was determined from the change in lactate concentration across the tissue bed. Total lactate release was taken as the sum of tracer-measured lactate extraction and net (chemical) release. At rest the arms and legs showed tracer-measured lactate extraction, as determined from the isotope extraction, despite net chemical release. Exercise elicited an increase in both net lactate release and tracer-measured lactate extraction by the legs. For the legs the total lactate release (net lactate release + tracer-measured lactate extraction) was roughly equal to twice the net lactate release under all conditions. The tracer-measured lactate extraction by the exercising legs was positively correlated to arterial lactate concentration (r = 0.81, P less than 0.001) at the lower two power outputs. The arms showed net lactate extraction during exercise, which was correlated to the arterial concentration (r = 0.86). The results demonstrate that exercising skeletal muscle extracts a significant amount of lactate during net lactate release and that the working skeletal muscle appears to be a major site of blood lactate removal during exercise. 相似文献
82.
A subunit of choleragen and an erythrocyte ADP-ribosyltransferase catalyze the transfer of ADP-ribose from NAD to proteins and low molecular weight guanidino compounds such as arginine. These enzymes also catalyze the hydrolysis of NAD to nicotinamide and ADP-ribose. The kinetic mechanism for both transferases was investigated in the presence and absence of the product inhibitor nicotinamide by using agmatine as the acceptor molecule. To obtain accurate estimates of kinetic parameters, the transferase and glycohydrolase reactions were monitored simultaneously by using [adenine-2,8-3H]NAD and [carbonyl-14C]NAD as tracer compounds. Under optimal conditions for the transferase assay, NAD hydrolysis occurred at less than 5% of the Vmax for ADP-ribosylation; at subsaturating agmatine concentrations, the ratio of NAD hydrolysis to ADP-ribosylation was significantly higher. Binding of either NAD or agmatine resulted in a greater than 70% decrease in affinity for the second substrate. All data were consistent with a rapid equilibrium random sequential mechanism for both enzymes. 相似文献
83.
Synergism between hemopoietic growth factors (HGFs) detected by their effects on cells bearing receptors for a lineage specific HGF: assay of hemopoietin-1 总被引:24,自引:0,他引:24
The preceding paper describes a new approach to the detection and assay of growth factors for developmentally early multipotent hemopoietic cells (Bartelmez et al., J. Cell. Physiol., 1985). This approach, involving measurement of the increase in the number of receptors for the mononuclear phagocyte specific hemopoietic growth factor (HGF), colony stimulating factor-1 (CSF-1), in cultures of developmentally early murine cells incubated with putative HGFs, has been used to define and assay hemopoietin-1. Hemopoietin-1 (Mr approximately 20,000) is found in the medium derived from serum-free cultures of cells of the human urinary bladder carcinoma line 5637. In contrast to both hemopoietin-2 and CSF-1, which also stimulate an increase in CSF-1 receptor numbers in cultures of developmentally early hemopoietic cells, hemopoietin-1 alone has no detectable effect. However, hemopoietin-1 exhibits dramatic synergism with CSF-1. In the presence of CSF-1, hemopoietin-1 stimulates the proliferation of developmentally earlier cells than those that respond to either CSF-1 alone or hemopoietin-2 alone or their combination. These cells proliferate for at least 3 days with no alteration of the average CSF-1 receptor density. However, by 5 days of incubation, the progeny of developmentally early hemopoietic cells that have proliferated in response to hemopoietin-1 + CSF-1 exhibit an approximately tenfold increase in the average CSF-1 receptor density per cell, which immediately precedes their differentiation to adherent mononuclear phagocytes. As hemopoietin-1 does not possess colony stimulating or burst promoting activities for murine bone marrow cells, but acts on multipotent hemopoietic cells, the analysis of the mechanism of its synergistic effects with HGFs such as CSF-1 are of special relevance to the regulation of early events in hemopoiesis. 相似文献
84.
Stanley H. Faeth 《Oecologia》1985,68(1):34-40
Summary Patterns of herbivory over a two year period on Quercus emoryi (Fagaceae) were correlated with seasonal and yearly changes in tannin and protein content. Quantitative defense theory predicts that tannin and protein content in apparent plants should be negatively and positively correlated, respectively, with degree of herbivory. Most herbivory occurred early in the growing season, but the pattern varied between the two years. Tannin and protein content sometimes varied negatively and sometimes positively with degree of herbivory; they did not consistently covary with herbivory. Protein content was positively correlated with herbivory in 1981–1982 but not in 1982–1983. Condensed tannin content was negatively correlated with herbivory in 1981–1982 but not in 1982–1983. Hydrolysable tannin content was positively correlated with herbivory activity. Multiple regression analyses indicated these phytochemical variables explained either no significant variation in herbivory (1982–1983) or did so in a fashion opposite (1981–1982) to the predictions of the theory of quantitative defense.Feeding by oak insects was not solely a function of seasonal changes in quantitative defenses and nutrients. Obviously, population dynamics of the insects are sensitive to factors other than phytochemistry of the trees and I discuss other factors that can influence patterns of herbivory. 相似文献
85.
Summary The cell-body layer of the lamina ganglionaris of the housefly, Musca domestica, contains the perikarya of five types of monopolar interneuron (L1–L5) along with their enveloping neuroglia (Strausfeld 1971). We confirm previous reports (Trujillo-Cenóz 1965; Boschek 1971) that monopolar cell bodies in the lamina form three structural classes: Class I, Class II, and midget monopolar cells. Class-I cells (L1 and L2) have large (8–15 m) often crescentshaped cell bodies, much perinuclear cytoplasm and deep glial invaginations. Class-II cells (L3 and L4) have smaller perikarya (4–8 m) with little perinuclear cytoplasm and no glial invaginations. The midget monopolar cell (L5) resides at the base of the cell-body layer and has a cubshaped cell body. Though embedded within a reticulum of satellite glia, the L1–L4 monopolar perikarya and their immediately proximal neurites frequently appose each other directly. Typical arthropod (-type) gap junctions are routinely observed at these interfaces. These junctions can span up to 0.8 m with an intercellular space of 2–4 nm. The surrounding nonspecialized interspace is 12–20 nm. Freezefracture replicas of monopolar appositions confirm the presence of -type gap junctions, i.e., circular plaques (0.15–0.7 m diam.) of large (10–15 nm) E-face particles. Gap junctions are present between Class I somata and their proximal neurites, between Class I and Class II somata and proximal neurites, and between Class II somata. Intercartridge coupling may exist between such monopolar somata. The cell body and proximal neurite of L5 were not examined. We also find that Class I and Class II somata are extensively linked to their satellite glia via gap junctions. The gap width and nonjunctional interspace between neuron and glia are the same as those found between neurons. The particular arrangement and morphology of lamina monopolar neurons suggest that coupling or low resistance pathways between functionally distinct neurons and between neuron and glia are probably related to the metabolic requirements of the nuclear layer and may play a role in wide field signal averaging and light adaptation. 相似文献
86.
Abstract Oxic and sub-oxic N.-E. Atlantic sediments were examined for sulphate-reducing activity. Oxygen and/or nitrate reduction are probably the dominant mineralisation processes in the abyssal plain sediment studied. A low rate of sulphate reduction (0.1 nmol SO2− 4 /ml/day) was recorded in the surface 5 cm of the continental slope sediment, together with the presence of a range of sulphate-reducing bacteria (SRB). A higher activity of sulphate reduction (2.2 nmol SO2− 4 /ml/day) occurred in the continental shelf sediment which led to a small decrease in pore water sulphate and an increase in titration alkalinity. This sediment contained approx. 102 –103 acetate, lactate and propionate oxidising SRB/ml. No low- M r organic acids were detected in these sediments. However, amendment with 75 μM acetate stimulated sulphate-reducing activity in the shelf sediment. 相似文献
87.
Characterisation of DNA forms associated with cassava latent virus infection. 总被引:11,自引:7,他引:4
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In addition to the major encapsidated DNA species found in preparations of cassava latent virus (genomic DNAs 1 and 2) there are minor DNA populations of twice (dimeric) and approximately half genome length. Both minor species resemble the genomic DNAs in that they are composed of predominantly circular single-stranded DNA. All of these size groups have a corresponding covalently-closed circular double-stranded DNA form in infected tissue. Infectivity studies using cloned DNAs 1 and 2 show that dimeric DNA routinely appears, suggesting it to be an intermediate in the DNA replicative cycle that can be encapsidated at low efficiency. In contrast, half unit length DNA has not yet been detected after multiple passaging of virus derived from the cloned DNA inoculum. Half unit length DNAs appear to be derived exclusively from DNA 2 and consist of a population of molecules exhibiting a relatively specific deletion. As they have an inhibitory effect on virus multiplication, their encapsidated forms are analogous to defective interfering particles associated with other eukaryotic DNA containing viruses. Small primer molecules associated with the genomic single-stranded DNAs, as reported for another geminivirus, have not been detected in CLV. 相似文献
88.
Dr. William R. Usinger George C. Clark Ellen Gottschalk Stanley Holt Robert I. Mishell 《Current microbiology》1985,12(4):203-207
A Gram-negative, psychrophilic bacterium, designated GB-2, was isolated from fetal calf serum and analyzed for its morphological, physiological, and biochemical characteristics. Gliding motility, sensitivity to actinomycin D, the presence of the pigment flexirubin and cytochrome c, growth on a variety of carbohydrates, the production of acid fermentation products, and a 34.9 mol% guanine+cytosine (G+C) content of bacterial DNA indicate GB-2 to be a member either of the generaCytophaga orFlexibacter. Growth of GB-2 was optimized in a simple defined medium to facilitate isolation and characterization of bacterial products. Liquid growth of GB-2 resulted in the release of significant quantities of a macromolecule free of both endotoxin and protein into the growth supernatant, which activated the proliferation of murine lymphocytes. The relationship between this bacterium and its end-products to other species of theCytophaga/Flexibacter group is discussed. 相似文献
89.
Light regulation of extractable nitrate reductase (NR) activity of higher plants is complicated by: 1) involvement of several photoreceptors, 2) differences in the relative importance of the several photoreceptors among species and among developmental stages of the same species, 3) two types of effects – alteration of activity of existing NR and influences on de novo synthesis of NR, and 4) differing forms of NR within the same species. The interrelationships of all of these factors are not clear. It may be that each system will have to be understood separately before a general model can be developed. Immunochemical quantification of NR from systems exposed to varied light regimes may enhance our understanding of this area. Currently few general conclusions can be made; however, we think that the following statements are true or are usually true: (1) Phytochrome influences extractable NR activity by the low irradiance response and high irradiance response in etiolated tissues. (2) In de-etiolated tissues phytochrome can influence NR activity decay at the end of a light period by the low irradiance response. (3) The phytochrome equilibrium or the absolute level of Pfr influences extractable NR activity in green tissues under white light. (4) Blue light influences extractable NR activity through phytochrome and another, unknown, blue light-absorbing pigment. Flavins may be involved in vitro in reactivation of inactivated NR. (5) Photosynthesis does not directly influence the induction of the forms of NR that require substrate and light for induction. (6) In some tissues there appears to be a close link between nitrite-reducing and nitrate-reducing capabilities. (7) Much circumstantial evidence from kinetic and protein-synthesis-inhibitor studies and the only available immunochemical data indicate that light induces de novo synthesis of NR, resulting in increased extractable activity. 相似文献
90.
Katalin Rostas Prakash Rao Sista John Stanley Desh Pal S. Verma 《Molecular & general genetics : MGG》1984,197(2):230-235
Summary We report here successful mutagenesis with Transposon Tn5 of three slow-growing strains of Rhizobium japonicum USDA 122, 61A76, USDA 74 and one fast-growing strain, USDA 191. Strains were chosen as representatives of different DNA homology and serogroups of this divergent species, which effectively nodulate North American soybean cultivars. The source of Tn5 was the suicide plasmid pGS9, which possesses broad host range N-type transfer genes in a narrow host range p15A replicon. The selection of Tn5 mutants was facilitated by the expression of the Tn5 encoded streptomycin gene in R. japonicum. Kanamycin and streptomycin resistant colonies appeared from interspecific crosses with E. coli at optimal frequencies of 10-6 for R. japonicum USDA 61A76 and USDA 191 and 5x10-7 for R. japonicum USDA 122 and USDA 74. Altogether, 6550 Tn5 mutants were isolated in USDA 122 and 61A76, and a small number from USDA 74 and USDA 191. Colony hybridization showed that all tested mutants of 61A76 and USDA 122 contained Tn5. Physical analysis of total DNAs from representative numbers of USDA 122, 61A76 and USDA 191 mutants revealed that each of them carried one copy of the transposon integrated randomly in the genome. This was also true for most USDA 74 mutants. Screening of mutants for auxotrophy showed frequencies of 0.2% for USDA 122 and 0.08% for 61A76. Several symbiotically defective mutants were identified on plants, Glycine soja and G. max. 相似文献