Mechanisms in bradykinin stimulated arachidonate release and synthesis of prostaglandin and platelet activating factor

Regulatory mechanisms in bradykinin (BK) activated release of arachidonate (ARA) and synthesis of prostaglandin (PG) and platelet activating factor (PAF) were studied in bovine pulmonary artery endothelial cells (BPAEC). A role for GTP binding protein (G-protein) in the binding of BK to the cells was determined. Guanosine 5-O- (thiotriphosphate), (GTPtauS), lowered the binding affinity for BK and increased the Kd for the binding from 0.45 to 1.99 nM. The Bmax remained unaltered at 2.25 x 10(-11) mole. Exposure of the cells to aluminium fluoride also reduced the affinity for BK. Bradykinin-induced release of ARA proved pertussis toxin (PTX) sensitive, with a maximum sensitivity at 10 ug/ml PTX. GTPtauS at 100 muM increased the release of arachidonate. The effect of GTPtauS and BK was additive at suboptimal doses of BK up to 0.5 nM but never exceeded the levels of maximal BK stimulation at 50 nM. PTX also inhibited the release of ARA induced by the calcium ionophore, A23187. Phorbol 12-myristate 13-acetate or more commonly known as tetradecanoyl phorbol acetate (TPA) itself had little effect on release by the intact cells. However, at 100 nM it augmented the BK activated release. This was downregulated by overnight exposure to TPA and correlated with down-regulation of protein kinase C (PKC) activity. The down-regulation only affected the augmentation of ARA release by TPA but not the original BK activated release. TPA displayed a similar, but more potent amplification of PAF synthesis in response to both BK or the calcium ionophore A23187. These results taken together point to the participation of G-protein in the binding of BK to BPAEC and its activation of ARA release. Possibly two types of G-protein are involved, one associated with the receptor, the other activated by Ca(2+) and perhaps associated with phospholipase A(2) (PLA(2)). Our results further suggest that a separate route of activation, probably also PLA(2) related, takes place through a PKC catalysed phosphorylation.     

Design of a system for the control of low dissolved oxygen concentrations: critical oxygen concentrations for Azotobacter vinelandii and Escherichia coli

The physiological activity of microorganisms in environments with low dissolved oxygen concentrations often differs from the metabolic activity of the same cells growing under fully aerobic or anaerobic conditions. This article describes a laboratory-scale system for the control of dissolved oxygen at low levels while maintaining other parameters, such as agitator speed, gas flowrate, position of sparger outlet, and temperature at fixed values. Thus, it is possible to attribute in dilute nonviscous fermentations all physiologic changes solely to changes in dissolved oxygen. Experiments were conducted with Azotobacter vinelandii and Escherichia coli. Critical oxygen concentrations for growth (that value of oxygen allowing growth at 97% of mu max) were measured as 0.35 +/- 0.03 mg/L for A. vinelandii and 0.12 +/- 0.03 mg/L for E. coli. These values are significantly different from the commonly quoted values for critical oxygen concentrations based on respiration rates. Because of the superior dissolved oxygen control system and an improved experimental protocol preventing CO2 limitation, we believe that the values reported in this work more closely represent reality.     

Effect of ultrasound treatment on the extraction of insulin

Insulin production requires a prolonged extraction process. An ultrasound method of insulin extraction was developed to increase efficiency. Application of ultrasound resulted in a significant increase in the extraction process as a result of pancreas tissue dispergation, destruction of the pancreas cells, intensive mixing, separation of particles, and increase in the interphase pancreas-extractive medium. Optimal technological parameters of insulin extraction were established: ultrasound frequency, 19.5 kHz, specific intensity of ultrasound, 3.3 W/cm(2); time of ultrasound exposure, 5-10 min; and influence of cavitation process. Effectiveness of insulin extraction depends on the properties of the extractive medium. Optimal conditions were pH, 1.6-1.7, concentration of alcohol, 75%, temperature of extractive mixture, 13-17 degrees C; ratio of ground pancreas to liquid extractive medium, 1 : 3.     

Hb疫苗无反应者的免疫效应研究

<正>乙型肝炎(HB)疫苗70年代后期引入美国,1982年正式批准使用。预料使用该疫苗将显著减少乙肝病毒(HBV)感染的发病率。慢性乙肝与原发性肝癌之关系目前已经证实,因而,广泛使用HB疫苗,尤其在亚洲和非洲地区,将显著减少这种恶性肿瘤的发生。     

Microtubule-associated protein MAP2 preferentially binds to a dA/dT sequence present in mouse satellite DNA

Microtubule-associated protein MAP2 binds to the Sau96.1 restriction monomer fragment of mouse satellite DNA. This fragment is also present in a lower proportion in bulk DNA. The digestion of MAP2-Sau96.1 fragment complex by DNase results in the protection of certain nucleotide sequences. The sequence poly(dA)4/poly(dT)4 is mainly protected against DNase digestion.     

Structural homology between different archaebacterial DNA-dependent RNA polymerases analyzed by immunological comparison of their components

The archaebacterial DNA-dependent RNA polymerases have a complex structure containing eight or more components. Immunochemical analysis shows an extensive homology between the components of the enzymes of nine different species. Two enzyme subtypes can be distinguished: that of the thermoacidophilic and/or sulfur-metabolizing archaebacteria with the composition BACDEFGHIJ and that of the methanogenic plus halophilic archaebacteria with the composition ABB'C(D).... Components B and B' of the latter subtype probably evolved by the division of the large component B of the BACD... type enzyme. The existence of the two subtypes corroborates the division of the archaebacteria into two phylogenetic main branches.     

Adenosine diphosphoglucose-starch glucosyltransferases from developing kernels of waxy maize

Two adenosine diphosphoglucose: α-1,4-glucan α-4-glucosyl-transferases were extracted from kernels of waxy maize harvested 22 days after pollination and separated by gradient elution from a diethylaminoethyl-cellulose column. Both fractions could utilize amylopectin, amylose, glycogen, maltotriose and maltose as primers. The rate of glucose transfer from adenosine diphosphoglucose to rabbit liver glycogen of fraction II was 78% of the rate of glucose transfer to amylopectin, but with fraction I the rate of transfer of glucose to rabbit liver glycogen was 380% of that observed to amylopectin. Glucan synthesis in the absence of added primer was found in fraction I in the presence of 0.5 m sodium citrate and bovine serum albumin. The unprimed product was a methanol-precipitable glucan with principally α-1,4 linkages and some α-1,6 linkages, and its iodine spectrum was similar to that of amylopectin.     

The Kok Effect in Chlamydomonas reinhardi

A Haxo-Blinks rate-measuring oxygen electrode together with a modulated light source gave an average current signal (change in net O₂ exchange) and a modulated current signal (photosynthetic O₂ evolution). Using this apparatus, net O₂ exchange and photosynthetic O₂ evolution at low intensities have been studied in the green alga, Chlamydomonas reinhardi. At both 645 nm and 695 nm, the curves of net O₂ exchange as a function of light intensity were steeper at lowest intensities than about compensation, indicative of the Kok effect. The effect was greater at 695 nm than at 645 nm. The corresponding curves of photosynthetic O₂ evolution, on the other hand, showed no Kok effect; here, the slope was lowest at lowest intensity. The absence of the Kok effect in O₂ evolution, together with its sensitivity to monofluoroacetic acid, show that it is due to an interaction of photosynthesis and respiration. The effect was exaggerated by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. In the presence of concentrations of this inhibitor sufficient to inhibit O₂ evolution completely, a light-induced change in net O₂ exchange remained. This was interpreted as a system I dependent depression of respiratory O₂ uptake. The Kok effect remained undiminished in concentrations of carbonyl cyanide m-chlorophenylhydrazone and 2,4-dinitrophenol which partially uncoupled either oxidative phosphorylation alone or both oxidative and photosynthetic phosphorylations. The above results can be explained within a model of the Kok effect in which O₂ uptake is depressed by diversion of reductant away from respiratory electron transport and into photosystem I. The same photodepression of O₂ uptake also appears to account for a transient in net O₂ exchange seen in several algae upon turning off the light.