Specific detection of α-amylase activity in crude plant extracts after isoelectric focusing

A new method which utilizes Procion Red MX 2B amylopectin for the detection of α-amylase in crude plant extracts is described. The substrate is specific only against α-amylase hydrolysis and β-amylase does not attack it. Paper containing Procion Red MX 2B amylopectin applied to gels after isoelectric focusing reveals α-amylase isoenzymes as white bands. When this technique is used, heat-inactivation of β-amylase is not required.     

Diterpenoids from Caesalpinia pulcherrima

Three new furanoditerpenoids of the caesalpin-type have been isolated from the roots of Caesalpinia pulcherrima. The structures of these compounds, vouacapen-5α-ol, 6β-cinnamoyl-7β-hydroxy-vouacapen-5α-ol and 8,9,11,14-didehydrovouacapen-5α-ol, were elucidated through interpretation of their spectral data. Sitosterol was also obtained.     

Involvement of Both Inhibitory and Stimulatory Guanine Nucleotide Binding Proteins in the Expression of Chronic Opiate Regulation of Adenylate Cyclase Activity in NG108-15 Cells

Abstract: Chronic etorphine treatment of neuroblastoma × glioma NG108-15 cells results in both an increase in adenylate cyclase activity (upon addition of the opiate antagonist naloxone) as well as an homologous desensitization of the opiate receptor. The continued ability of opiate agonists to regulate adenylate cyclase activity following opiate receptor desensitization can be understood by proposing that the catalytic subunit of adenylate cyclase in NG108-15 cells is under tonic regulation by both guanine nucleotide regulatory (N_i) and stimulatory (N_s) components. Inactivation of N_i by pertussis toxin (PT) treatment resulted in elevated adenylate cyclase activities comparable to those observed in control cells following chronic opiate treatment. This increased enzymatic activity could not be further induced by PT treatment of cells exposed to opiate previously. In addition, procedures that prevented receptor-mediated activation of N_s, i.e., treatment with NaF or desensitization of the stimulatory receptors (prostaglandin E₁, adenosine) eliminated the increase in adenylate cyclase activity induced by naloxone following chronic opiate exposure. Hence, the increase in enzymatic activity observed following chronic opiate treatment may be due to a loss in tonic inhibitory regulation of adenylate cyclase mediated through N_i resulting in the unimpeded expression of N_s activity. This tonic inhibition of adenylate cyclase activity is one of the multiple mechanisms by which N_i regulates adenylate cyclase in this cell line.     

缺乏抗坏血酸对豚鼠胆固醇代谢的影响

边缘性缺乏抗坏血酸之豚鼠,于三周内其肝脏及小肠粘膜3-羟-3-甲基戊二酰辅酶A还原酶(HMGR)活力均下降到原有水平的50％,但肝脏胆固醇7α-羟化酶活力尚无显著性改变。坏血病豚鼠(三周内)上述几种酶活力都下降至原有水平的50％左右。豚鼠摄取抗坏血酸不足,其血清总胆固醇浓度显著增加,而血清高密度脂蛋自胆固醇浓度显著减少,其改变程度与抗坏血酸缺乏状况一致。     

In vitro induction and expression of interleukin 2 receptor in a clonal T helper cell differentiation model

Induction and expression of interleukin 2 (IL 2) receptor have been studied using a poly( Glu60 Ala30 Tyr10 ) (GAT)-specific T cell clone of mouse origin. This clone (52-3) has been characterized and it exhibits functional properties of T helper (TH) cells: it leads to a specific anti-DNP response in the presence of DNP-GAT and DNP-primed B cells and it secretes biological activities which can induce polyclonal B cell proliferation and IgM secretion. In vitro this clone mimics the activation stages of normal T lymphocytes and can be obtained under two states of differentiation. depending on the antigen-specific signal provided by antigen-presenting cells (APC). The expression of IL 2 receptor by this clone has been studied by (i) its response to IL 2, (ii) its capacity to absorb IL 2 bioactivity, and (iii) its reactivity with monoclonal antibody 7D4 specific for mouse IL 2 receptor. All the results indicate that the unstimulated state does not express the IL 2 receptor while the activated state does. Clone 52-3 has been compared with clone 14-1.6 that derives from a TH cell line and expresses the IL 2 receptor constitutively. 52-3 offers a good experimental model for studying in vitro, in a clonal TH cell population, the detailed mechanism of IL 2 receptor induction.     

Trihydroxytetraenes: A novel series of compounds formed from arachidonic acid in human leukocytes

Addition of 15L-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) to human leukocytes led to the formation of a novel series of compounds containing four conjugated double bonds. The yield of tetraenes was increased approx. 100-fold when ionophore A23187 (5 μM) was added simultaneously with 15-HPETE. The structure of the major tetraene was established by physical methods as well as by chemical degradation and found to be 5,6,15L-trihydroxy-7,9,11,13-eicosatetraenoic acid.     

The binding of monosaccharides to wheat germ agglutinin: fluorescence and NMR investigations

The synthesis of N-acetyl- and N-trifluoroacetyl-glucosaminides was reported. The interaction of these compounds with wheat germ agglutinin, a plant lectin specific for N-acetyl-glucosamine and sialic acid, was investigated by two complementary approaches: 1H and 19F NMR, and fluorescence spectroscopy. This last technique relies on the existence of a competitive equilibrium involving the protein, the ligand and O-(methylumbelliferyl)-N-acetyl-glucosaminide, a fluorescent saccharide. The binding constants and the chemical shifts in the complex were determined and were related to the protein structure.     

Chromophore structure in phytochrome intermediates and bleached forms of phytochrome

Phytochrome (120 kdalton or 60 kdalton) was isolated from etiolated seedlings of Avena sativa L. cv. Pirol (Baywa München). Irradiation with red light of the P_r form at −23°C in aqueous medium or at −40°C in 66% glycerol leads to the intermediate meta-Rb. Acidification of the glycerol solution at −40°C leads to the absorption of the 15(E) phytochrome chromophore (= P_fr chromophore). Subsequent irradiation transforms this into the 15(Z) chromophore (= P_r chromophore). The presence of the 15(E) chromophore was demonstrated by the same methods also in phytochrome bleached either as P_fr in the dark by 4 M urea, methanol, acetone, ethylene glycol, 8-anilinonaphthalene-1-sulfonate, or as P_r by irradiation with red light in the presence of the same agents. Phytochrome bleached by sodium dodecylsulfate or by dehydration was also investigated. It was concluded that bleached phytochrome contains the P_fr chromophore without specific interaction with the protein.     

Studies on the C-24 configurations of Δ7-sterols in theseeds of Cucurbita maxima

Uncertainties surrounding the structures of the Δ⁷-sterols in the seeds of Cucurbita maxima have been resolved. Seven components were found by TLC, GLC, HPLC, mass spectrometry and ¹H NMR. They were 24β-ethyl-5α-cholesta-7,22,25(27)-trien-3β-ol, 24β-ethyl-5α-cholesta-7,25(27)-dien-3gb-ol, avenasterol, spinasterol, 24-dihydrospinasterol, 24ζ-methyllathosterol and 25(27)-dehydrofungisterol. The ¹H NMR spectra indicated that the sterols with an ethyl substituent at C-24 occurred in the absence of their C-24 epimers. This seems to be the first instance of the detection of 25(27)-dehydrofungisterol in a higher plant.