脊髓苯环立啶受体的心血管效应与去甲肾上腺素能系统

本文应用受体阻断、高效液相,6-OHDA 化学损毁神经末梢和放射自显影等多学科技术方法,探讨脊髓苯环立啶受体的心血管效应与去甲肾上腺素能神经系统的关系。结果表明,哌唑嗪、育亨宾均可对抗 ith PCP 的降压和减慢心率作用,ith PCP 产生降压和减慢心率作用时,脊髓脑脊液内 MHPG 的含量升高;用6-OHDA 损毁脊髓 NA 能神经末梢后,ith PCP的降压和减慢心率作用大为减弱,脊髓 PCP 受体密度亦同时大为降低。可以认为,脊髓内有 PCP 受体分布于 NA 能神经末梢上,促进 NA 释放或抑制 NA 重摄取,可能是脊髓 PCP 受体产生心血管抑制效应的重要机理。     

Interactions of chiral molecules with an (r)-n-(3,5-dinitrobenzoyl) phenylglycine HPLC stationary phase

Forty different chiral molecules were studied by liquid chromatography with a Pirkle-type, (R)-N-(3,5-dinitrobenzoyl) phenylglycine (DNBPG), chiral stationary phase column. The dramatic effect of a small molecular change on chiral recognition was demonstrated using DL-amino acid derivatives. The inductive effect on chiral recognition was also studied using trifluoro-, trichloro-, dichloro-, monochloroacetyl, and acetyl derivatives of four different chiral amines. The study of the enantiomer separation of 11 different crown ethers of 2,2′-binaphthyldiyl showed that the rigidity of the chiral center can be an additional parameter in chiral recognition for the DNBPG phase but not for a β-cyclodextrin bonded chiral phase. It is apparent from this study that steric effects, inductive effects, and molecular rigidity play important roles in chiral recognition with DNBPG chiral stationary phases.     

Presynaptic regulation of dopaminergic transmission in the striatum

1. In vitro studies have indicated that several transmitters present in the striatum can regulate presynaptically the release of dopamine (DA) from nerve terminals of the nigrostriatal DA neurons. 2. The receptors involved in these local regulatory processes are located or not located on DA nerve terminals. 3. Recent in vivo investigations have demonstrated that the corticostriatal glutamatergic neurons facilitate presynaptically the release of DA and have allowed the analysis of the respective roles of presynaptic events and nerve activity in the control of DA transmission.     

Influence of exercise on cardiac and skeletal muscle myofibrillar proteins

The purpose of this study was to examine the Ca²⁺-Mg²⁺ myofibrillar ATPase and protein composition of cardiac and skeletal muscle following strenuous activity to voluntary exhaustion. Sprague-Dawley rats (200 g) were assigned to a control and exercised group, with the run group completing 25 m·min^–1 and 8% grade for 1 hour. Following activity, the myocardial Ca²⁺–Mg²⁺ myofibrillar ATPase activity -pCa relationship had undergone a rightward shift in the curve. Electrophoretic analysis revealed a change in the pattern of cardiac myofibrillar protein bands, particularly in the 38–42 Kdalton region. Enzymatic analysis of myofibrillar proteins from plantaris muscle, revealed no change in Ca²⁺ regulation following exercise. Electronmicrographic and electrophoretic analysis revealed extensively disrupted sarcomeric structure and a change in the ratio of several plantaris myofibrillar proteins. No difference was observed for myosin: Actin: tropomyosin ratios; however a dramatic reduction in 58 and 95 Kdalton proteins were evident. The results indicate that prolonged running is associated with similar responses in cardiac and skeletal muscle myofibrillar protein compositions. The abnormalities in myofibrillar ultrastructure may implicate force transmission failure as a factor in exercised-induced muscle damage and/or fatigue.     

The effects of cultural conditions on growth and secondary metabolism in Streptomyces thermoviolaceus

Abstract Granaticin, an isochromate quinone antibiotic is synthesized as a secondary metabolite by Streptomyces thermoviolaceus . Antibiotic productivity was investigated under a variety of cultural conditions, including complex and defined media, mesophilic and thermophilic temperatures and a variety of sole carbon sources. In a defined medium growth was supported, to varying extents, by different carbon sources and in most cases granaticin production was observed. Highest biomass and granaticin yields were obtained when cultures were grown in the presence of xylan, fructose, glutamate or proline as carbon source. Changes in pH during growth affected both the timing and extent of granaticin production.     

Carbon balance during CAM: an assessment of respiratory CO2 recycling in the epiphytic bromeliads Aechmea nudicaulis and Aechmea fendleri

Abstract The regulation of crassulacean acid metabolism (CAM) under controlled environmental conditions has been investigated for two tropical epiphytes, relating plant water and carbon balance to growth form and habitat preference under natural conditions. Aechmea fendleri is restricted to wet, upper montane regions of Trinidad, while A. nudicaulis has a wider distribution extending into more arid regions of the island. Morphological characteristics of these plants are related to habitat preference in terms of leaf succulence (0.44 and 0.94 kg m^?2 for the two species respectively) and a distinct layer of water storage parenchyma in A. nudicaulis In contrast, the thinner leaves of A. fendleri contain little water-storage parenchyma and less chlorenchyma per unit area, but the plants have a more open leaf rosette. The two species differ in expression of CAM, since the proportion of respiratory CO₂ recycled as part of CAM had been found to be much lower in A. fendleri This study compared the efficiency of water use and role of respiratory CO₂ recycling under two PAR regimes (300 and 120 μnol m^?2 s^?1) and three night temperatures (12, 18 and 25 °C). Dark CO₂ uptake rates for both species were comparable to plants in the field (maximum of 2.3 ± 0.2 μmol m^?2s^?1± SD, n= 3). Total net CO₂ uptake at night increased on leaf area basis with temperature for both species under higher PAR, although under the low PAR regime CO₂ uptake was maximal at 18 °C. Water-use efficiency (WUE) increased at 18 °C and 25 °C during dark CO₂ uptake (Phase I) and also during late afternoon photosynthesis (Phase IV) in both species. For A. fendleri, dawn to dusk changes in titrable acidity (ΔH ⁺) were similar under high and low PAR, although ΔH⁺ was correlated to night temperature and PAR in A. nudicaulis. The proportion of ΔH⁺ derived from respiratory CO₂ also varied with experimental conditions. Thus percentage recycling was lower in A. fendleri under high PAR (0–10%), but was only reduced at 18 °C under low PAR. Recycling by A. nudicaulis ranged from 32–42% under high PAR, but was also reduced to 6% under low PAR at 18 °C; at 12 °C and 25 °C, recycling was 37% and 52% respectively. Previous studies have suggested a relationship between the proportion of recycling and degree of water stress. This study indicated that CAM as a CO₂ concentrating mechanism regulates both water-use efficiency and plant carbon balance in these epiphytes, in response to PAR and night temperature. However, the precise relationship between respiratory processes and the balance between external and internal sources of CO₂ is as yet unresolved.     

A role for haemoglobin in all plant roots?

Abstract. We have found haemoglobin in plant roots whereas previously it has been recorded only in nitrogen fixing nodules of plants. Haemoglobin occurs not only in the roots of those plants that are capable of nodulation but also in the roots of species that are not known to nodulate. We suggest that a haemoglobin gene may be a component of the genome of all plants. The gene structure and sequence in two unrelated families of plants suggests that the plant haemoglobins have had a single origin and that this origin relates to the haemoglobin gene of the animal kingdom. At present we cannot completely rule out the possibility of a horizontal transfer of the gene from the animal kingdom to a progenitor of the dicotyledonous angiosperms but we favour a single origin of the gene from a progenitor organism to both the plant and animal kingdoms. We speculate about the possible functions of haemoglobin in plant roots and put the case that it is unlikely to have a function in facilitating oxygen diffusion. We suggest that haemoglobin may act as a signal molecule indicating oxygen deficit and the consequent need to shift plant metabolism from an oxidative to a fermentative pathway of energy generation.     

The major light-harvesting complex of Photosystem II: aspects of its molecular and cell biology

The light-harvesting complex of photosystem II (LHC II) contains one major (LHC IIb) and at least three minor chlorophyll-protein components. The apoproteins of LHC IIb (LHCP) are encoded by nuclear genes and synthesized in the cytoplasm as a higher molecular weight precursor(s) (pLHCP). Several genes coding for pLHCP have been cloned from various higher plant species. The expression of these genes is dependent upon a variety of factors such as light, the developmental stage of the plastids and the plant. After its synthesis in the cytoplasm, pLHCP is imported into plastids, inserted into thylakoids, processed to its mature form, and assembled into LHC IIb. The pathway of assembly of LHC IIb in the thylakoid membranes is currently being investigated in several laboratories. We present a model that gives some details of the steps in the assembly process. Many of the steps involved in the synthesis and assembly are dependent on light and the stage of plastid development.Abbreviations PS Photosystem - LHC II Light-harvesting complex of PS II - LHCP Apoproteins of LHC IIb - pLHCP Precursor of LHCP - PAGE Polyacrylamide gel electrophoresis     

Structure and function of ferredoxin-NADP+-oxidoreductase

The redox-enzyme ferredoxin-NADP-oxidoreductase has been shown to be activated by light and inactivated in the dark. This review will summarize recent data concerning the biochemical characterization of the enzyme compared to its in-vivo activation. Further-more the mechanism of this activation process is discussed as a conformational change caused by the light-driven proton gradient.Abbreviations cyt cytochrome - fd ferredoxin - FNR1 large form of ferredoxin-NADP-oxidoreductase - FNRox oxidized FNR - FNRred reduced FNR - FNRs small form of FNR - FNRsq FNR-semiquinone