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91.
There is not yet a complete understanding of the functional interactions among various septal nuclei which regulate hippocampal function. Nevertheless, much has been learned histologically and biochemically about the major connections of the distinct areas of the septal complex and the chemical character of some of these pathways. The cholinergic septal-hippocampal pathway serves as a well defined link between these two important structures of the limbic system. Acetylcholine turnover rates in the hippocampus have been shown to increase or decrease proportionally to the activity of the cholinergic neurons originating in the septum. Moreover, these turnover rates have been shown to be modulated by intraseptal injections of agonists or antagonists of various neurotransmitters or neuromodulators which are stored in various cell groups located in the septum. By coupling this biochemical approach with techniques to study the receptor organization, greater detail concerning the transmitter and cotransmitter interactions among the various neuromodulators can be obtained. 相似文献
92.
A specific antiserum against met5-enkepha-lin-arg6-phe7 was raised and used to study the distribution and characterization of met5-enkephalin-arg6-phe7-like immunoreactive material in rat brains by radioimmunoassay and immunohistochemical procedures. The antiserum appears to be directed to the COOH-terminus of the peptide, as it fails to cross-react with met5-enkeph-alin, met3-enkephalin-arg6, met5-enkephalin-arg6-arg7, met6-enkephalin-lys6, and leu-enkephalin. However, it cross-reacts with phe-met-arg-phe by about 10% and with phe-met-arg-phe-NH2 to an insignificant degree. The highest content of met5-enkephalin-arg6-phe7 was found in the striatum, which contains a dense network of immunoreactive varicose fibers and terminals, as well as immunoreac tive cell bodies. The met5-enkephalin-arg6-phe7 in striatum can be released in a Ca2+-dependent manner by a depolarizing concentration of KC1, raising the possibility of a neu-roregulatory role for met5-enkephalin-arg6-phe7. Characterization of the immunoreactive material by gel filtration and high pressure liquid chromatography revealed the presence of multiple forms of immunoreactive material in some brain regions. 相似文献
93.
Fentanyl (FEN) and diprenorphine's (DIPR) potentials for analgesia and reinforcement were assayed using rats. Analgesia was measured by the classic tail-flick test. The test germane to opioid reinforcement involved measuring pressing rates for direct electrical stimulation of the lateral hypothalamus and ventral tegmental area. FEN, as does morphine and heroin, produced strong analgesia and enhanced pressing rates for brain stimulation. DIPR produced no analgesia and antagonized FEN's analgesia. DIPR, at doses antagonizing FEN's analgesia, enhanced pressing for brain stimulation. DIPR's enhancement of pressing was antagonized by naloxone (100 micrograms/kg). When FEN and DIPR were given concurrently, pressing for brain stimulation was not reduced and was greater than after FEN alone was given. These data support a conclusion that different types of receptors are associated with opioid analgesia and reinforcement. 相似文献
94.
Maria C. Olianas Pierluigi Onali Norton H. Neff Erminio Costa 《Journal of neurochemistry》1983,41(5):1364-1369
We investigated the effect of acetylcholine (ACh) on the activation of adenylate cyclase by dopamine (DA) in a lysed synaptosomal preparation from rat striatum. ACh reduced both basal and the DA-activated adenylate cyclase with an apparent IC50 of approximately 1 microM. From a kinetic analysis it appeared that ACh reduced the Vmax for activation by DA but not the activation constant for DA. For most preparations the Vmax was reduced by 30-40%. The presence of atropine did not affect the activation of the enzyme by DA but it blocked the inhibition by ACh. Following 6-hydroxydopamine lesion of the nigrostriatal pathway, the enzyme became supersensitive to activation by DA and also more sensitive to inhibition by ACh. Inhibition of adenylate cyclase by ACh appeared to be rather specific for activation by DA, as ACh had no effect on activation of adenylate cyclase by the adenosine analogue N6-(L-2-phenylisopropyl)adenosine. These results indicate that some striatal muscarinic and dopaminergic receptors are probably coupled to the same adenylate cyclase domain. Moreover, they suggest a biochemical model for the dynamic balance of cholinergic and dopaminergic neurons that innervate the striatum. 相似文献
95.
In cotton plants ( Gossypium hirsutum L. cv. B.J.A.) the temperature of the roots affected both root and shoot growth, as did the temperature of the shoot. Drought resistance increased when the temperature imposed on roots (27°C) was lower than that imposed on shoots (17°C); the result was a decrease in both transpiration and flow of root sap. Stomatal characteristics as measured by density, index and resistance, depended only on shoot temperature. Differences in drought resistance, depended only on shoot temperature. Differences in drought resistance seem to be a result of changes in transpiration flow modulated by the amount of absorbed water. 相似文献
96.
A review has been compiled illustrating the directions taken in examining the genotoxic effects of metals and their compounds centering only on those studies pertaining to effects of metals and their compounds on DNA structure and function, such as the induction of DNA strand breaks, production of DNA-protein crosslinks, induction of chromosomal aberrations, and sister chromatid exchanges. Although it is premature to declare a cause and effect relationship between the carcinogenic activity of metals and their ability to induce one or more lesions in DNA, strong evidence is emerging to suggest such a relationship. Low concentrations of metals induce the appearance of DNA lesions, such as strand breaks and crosslinks, or induce sister chromatid exchanges or DNA repair synthesis. Assays based upon these events constitute extremely sensitive probes for genotoxic effects of metals and their compounds. These effects of metals on DNA are consistent with the currently accepted mechanism of chemical carcinogenesis, allowing the acquisition and propagation of altered DNA function. The lack of complete information on the activity of metals in producing DNA lesions allow only preliminary conclusions to be drawn. Certain compounds containing potentially or actually carcinogenic elements, such as Ni, Be, As, Cr, Cd, and to a minor extent Pb, have yielded positive responses in one or more DNA lesion assays. At relatively nontoxic levels of Ni and Cr, considerable evidence suggests that multiple types of DNA lesions are induced. 相似文献
97.
On the active site of diamine oxidase: kinetic studies 总被引:1,自引:0,他引:1
98.
Abstract— Unilateral sympathetic decentralization of the superior cervical ganglion of rats was performed 3 days prior to the experiments. A two-compartment kinetic model was proposed to describe the effect of decentralization on (1) the uptake of a nonphysiological amino acid from plasma to the submaxillary gland and (2) the incorporation of a physiological amino acid from precursor pool into protein. The calculations based on the model showed that the fractional rate constant for efflux of the nonphysiological amino acid, α-[3-14 C] aminoisobutyric acid, was greater in the decentralized than in the normal gland. However, efflux rate was equal in the two glands because the extrapolated zero time value of the initial concentration was greater in the normal gland.
The labelled physiological amino acid, [14 C]leucine, was used in initial experiments to assess turnover rate of the gland proteins but it was rapidly metabolized to many other radioactive compounds. Therefore, arginine[14 C]guanido was employed-arginine being the only labelled amino acid found after injection. Since the steady state content of submaxillary gland proteins was not changed but the fractional rate constant of conversion of free arginine into protein (kp ) was greater in the decentralized gland (kp = 0-40 h_l ) than in the normal (kp = 0-27 h−1 ), we can conclude that decentralization increases protein turnover rate; thus, assuming that arginine[14 C]guanido is homogeneously distributed in the tissue pools of free arginine, the rate of protein turnover is greater in the sympathetically decentralized gland than in the normal. 相似文献
The labelled physiological amino acid, [
99.