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31.
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The effects of iontophoretically applied human pancreatic growth hormone-releasing factor (hpGRF), peptide histidine isoleucine (PHI-27), and somatostatin (SS) on the extracellular activity of single cells in the hypothalamus, thalamus, and cortex of the rat brain were studied in urethane-anesthetized, male rats. Neurons with membrane sensitivity to hpGRF, PHI-27, and SS were present in each brain region. Although neurons excited by these peptides were encountered in thalamus and hypothalamus, depression of neuronal firing was the predominant response observed. Overall, the neurons responding to hpGRF also possessed membrane sensitivity to PHI-27, whereas, the hpGRF sensitive neurons appeared to be more divided as to their ability to respond to SS. The results clearly demonstrate that hpGRF and PHI-27 are capable of affecting the membrane excitability of neurons in several brain regions. The distribution of neurons sensitive to hpGRF suggests that hypothalamic GRF, in addition to its well documented role in the regulation of pituitary growth hormone secretion, may subserve other physiological events in the rat central nervous system as a neurotransmitter and/or neuromodulator. 相似文献
33.
Metabolism of pyrimidine bases and nucleosides in the coryneform bacteria Brevibacterium ammoniagenes and Micrococcus luteus. 下载免费PDF全文
The metabolism of exogenous pyrimidine bases and nucleosides was investigated in Brevibacterium ammoniagenes and Micrococcus luteus with fluorinated analogs and radioactive precursors. Salvage of thymine and thymidine was found in M. luteus, but not in B. ammoniagenes. Exogenous uracil or uracil nucleosides, but not cytosine or cytosine nucleosides, were nucleic acid precursors for both bacteria. By examining the possible nucleoside-metabolizing enzymes, it can be suggested that the pyrimidine salvage pathways in the coryneform bacteria are different from those of members of the family Enterobacteriaceae. 相似文献
34.
Contraction of rabbit skinned skeletal muscle fibers at low levels of magnesium adenosine triphosphate 总被引:5,自引:1,他引:4 下载免费PDF全文
The contractile properties of skinned single fibers from rabbit psoas muscle were investigated under conditions of low MgATP and no Ca2+ (i.e., less than 10(-8) M). At 1 microM MgATP, fibers shortened at a maximum velocity of 660 +/- 420 A/half sarcomere/s (n = 9), compared with 34,000 A/half sarcomere/s measured during maximum Ca2+-activation at 1 mM MgATP (Moss, R. L., 1982. J. Muscle Res. Cell. Motil ., 3:295-311). The observed dependence of Vmax on pMgATP between 7.0 and 5.3 was similar to that of actomyosin ATPase measured previously by Weber, A., R. Herz , and I. Reiss (1969, Biochemistry, 8:2266-2270). Isometric tension was found to vary with pMgATP in a manner much like that reported by Reuben , J. P., P. W. Brandt, M. Berman , and H. Grundfest (J. Gen. Physiol. 1971. 57:385-407). A simple cross-bridge model was developed to simulate contractile behaviour at both high and low levels of MgATP. It was found that the pMgATP dependence of Vmax and ATPase could be successfully modeled if the rate of detachment of the cross-bridge was made proportional to the concentration of MgATP. In the model, the similar dependence of Vmax and ATPase on pMgATP was derived from the fact that in this range of pMgATP every pass of a cross-bridge by an actin site resulted in an attachment-detachment cycle, and every such cycle caused hydrolysis of one molecule of ATP. 相似文献
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36.
Linkage of tyrosine hydroxylase to four other markers on the short arm of chromosome 11. 总被引:5,自引:2,他引:3 下载免费PDF全文
Tyrosine hydroxylase is the rate-limiting enzyme in catecholamine synthesis; the gene has previously been cloned and localised to the short arm of chromosome 11. Because of the interest in tyrosine hydroxylase as a candidate gene for manic-depressive psychosis and other affective disorders, we carried out family studies to determine the linkage of tyrosine hydroxylase with insulin, beta-globin, D11S12 and Harvey-ras 1, members of a linkage group which has previously been localised to 11p. Using DNA from the Centre d'Etude du Polymorphisme Humain (CEPH) and from two large British pedigrees, we show that tyrosine hydroxylase is closely linked to these four loci (z = 7.36, theta = 0.04 for linkage to insulin) and suggest a gene order based on multipoint mapping. 相似文献
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38.
Cynthia F. Moss Andrea Megela Simmons 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1986,159(2):257-266
Frequency selectivity of hearing was measured in the green treefrog, Hyla cinerea. A psychophysical technique based on reflex modification was used to obtain masked threshold estimates for pure tones (300-5,400 Hz) presented against two levels of broadband masking noise. A pure tone (S-1) presented 200 ms prior to a reflex-eliciting stimulus (S-2) inhibited the motor reflex response to S-2. The magnitude of this reflex modification effect varied systematically with the sound pressure level (SPL) of S-1, and threshold was defined as the SPL of S-1 at which the reflex modification effect disappeared. Masked thresholds were used to calculate critical ratios, an index of the auditory system's frequency selectivity. The frequency selectivity of the treefrog's hearing is greatest and critical ratios are lowest (22-24 dB) at about 900 and 3,000 Hz, the two spectral regions dominant in the male treefrog's species-specific advertisement call. These results suggest that the treefrog's auditory system may be specialized to reject noise at biologically-relevant frequencies. As in other vertebrates, critical ratios remain constant when background noise level is varied; however, the shape of the treefrog's critical ratio function across frequencies differs from the typical vertebrate function that increases with increasing frequency at a slope of about 3 dB/octave. Instead, the treefrog's critical ratio function resembles its pure tone audiogram. Although the shape of the treefrog's critical ratio function is atypical, the critical ratio values themselves are comparable to those of many other vertebrates in the same frequency range. Critical ratio values here measured behaviorally do not match critical ratio values previously measured physiologically in single eighth nerve fibers.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
39.
Selective regulation by pertussis toxin of insulin-induced activation of particulate cAMP phosphodiesterase activity in 3T3-L1 adipocytes 总被引:8,自引:0,他引:8
M L Elks P A Watkins V C Manganiello J Moss E Hewlett M Vaughan 《Biochemical and biophysical research communications》1983,116(2):593-598
Incubation of 3T3-L1 adipocytes with insulin or isoproterenol for 10 min increased particulate "low Km" cAMP phosphodiesterase activity by 42% and 50%, respectively. Pertussis toxin catalyzed the [32P]-ADP ribosylation of a 41,000 dalton protein in adipocyte particulate fractions; prior incubation of adipocytes with toxin markedly reduced incorporation of radiolabel. Exposure of adipocytes to pertussis toxin (0.3 microgram, 18 hr) increased glycerol production and inhibited activation of cAMP phosphodiesterase by insulin, but not by isoproterenol. These results suggest that pertussis toxin can interfere with receptor-mediated processes that stimulate cAMP hydrolysis as well as those that inhibit cAMP formation. 相似文献
40.
Exogenous gangliosides enhance the interaction of fibronectin with ganglioside-deficient cells 总被引:14,自引:0,他引:14
Kenneth M. Yamada David R. Critchley Peter H. Fishman Joel Moss 《Experimental cell research》1983,143(2):295-302
The major cell-surface glycoprotein fibronectin mediates a variety of cellular adhesive interactions that have been reported to be competitively inhibited by gangliosides. These effects suggest a possible function of gangliosides as receptors for fibronectin. To test this hypothesis more directly, we examined the interaction of endogenous fibronectin with a ganglioside-deficient cell line, NCTC 2071. These cells, which grow in serum-free medium, synthesized fibronectin. The fibronectin did not bind to these cells, but instead bound diffusely to the culture substratum. When the cells were cultured in medium containing ganglioside, the fibronectin became bound to the cell surface in fibrillar strands. The order of effectiveness of purified gangliosides was GT1b greater than GD1a greater than GM1 greater than GM2 greater than GM3. The effect with mixed gangliosides was accompanied by a restoration of cellular capacity to bind and to respond to cholera toxin. Treatment of the cells with several phospholipids did not alter fibronectin binding. Our results support the hypothesis that gangliosides can help mediate the binding of fibronectin to fibroblasts. 相似文献