磷脂模型膜的时间分辨纳秒荧光光谱的研究

叙述了用时间分辨率纳秒荧光技术研究大豆磷脂或合成磷脂模型膜（脂质体）的物理状态变化与荧光寿命以及时间分辨各向异性测量参数变化相关性的实验结果。用荧光探剂ＭＣ５４０标记模型膜的结果表明,荧光寿命（τ）的变化与脂质／探剂比例、磷脂组成、磷脂的极性头部、脂肪酸酰链长度等有关。用ＤＰＨ（１,６－ｄｉｐｈｅｎｙｌ－１,３,５－ｈｅｘａｔｒｉｅｎｅ）标记磷脂模型膜的时间分辨各向异性分析结果表明,序参数（Ｓ）、     

Kallikrein activation of a high molecular weight atrial peptide

Mammalian atrial extracts contain bioactive peptides that exert profound effects upon renal function and isolated smooth muscle preparations. Gel filtration chromatography of rat atrial extract separates the activity into two peaks having apparent molecular weights of 20,000 to 30,000 and less than 10,000. Mild proteolytic treatment (trypsin 1 U/ml) of the high molecular weight fraction enhances the smooth muscle relaxant activity of this fraction and concomitantly reduces the apparent molecular weight of this fraction to less than 10,000. In this report we show that urinary and submaxillary kallikrein enhances the activity of rat atrial extracts in a similar fashion. Pretreatment of the high molecular weight fraction with either kallikrein (1 microgram/ml) enhances the smooth muscle relaxant activity of this fraction. Similar treatment of the low molecular weight fraction had no effect. The enhancement of the bioactivity of the high molecular weight substance(s) by the kallikreins was abolished by aprotinin but was unaffected by soybean trypsin inhibitor. These results suggest that exogenous addition of tissue kallikrein activates a high molecular weight peptide by limited proteolysis. Analysis of the kallikrein-treated high molecular weight peptide fraction by gel filtration indicates that the biological activity comigrates with the low molecular weight peptides present in the original atrial extract.     

The effect of nitroimidazoles on glucose utilization and lactate accumulation in mouse brain

The radiation sensitizers misonidazole (MISO) and desmethylmisonidazole (DMM) can produce central and peripheral neuropathy in patients and laboratory animals. Behavioral and pathological investigations have indicated that in the central nervous system this primarily involves the cochlear and vestibular systems. Nitroimidazoles can also interfere with glycolysis in vitro under aerobic and anaerobic conditions. In the present work we have studied the effect of MISO or DMM on lactate production and glucose utilization in mouse brain. It is observed that these compounds result in a 25% inhibition of lactate production in brain slices relative to the control at a 10 mM level. Additionally, MISO (1.0 mg/g/day) or DMM (1.4 mg/g/day) were administered daily (oral) for 1, 4, 7, or 14 days to examine the effect of these two drugs on the regional glucose utilization in C3Hf mouse brain. Five microcuries of 2-deoxy[14C]glucose was given following the last drug dose and autoradiographs of serial brain sections were made and analyzed by a densitometer. Following a single dose of either MISO or DMM, no significant differences in glucose uptake were observed when compared with controls. However, following 4, 7, and 14 doses the rate of glucose utilization was significantly reduced in the intoxicated animals. Larger reductions were measured in specific regions including the posterior colliculus, cochlear nuclei, vestibular nuclei, and pons with increasing effects observed at later stages. These results share a degree of correspondence with the regional brain pathology produced by these nitroimidazoles.     

lac Operator nucleosomes. 2. lac Nucleosomes can change conformation to strengthen binding by lac repressor

We have shown previously that lac repressor binds specifically and quantitatively to lac operator restriction fragments which have been complexed with histones to form artificial nucleosomes (203 base pair restriction fragment) or core particles (144 base pair restriction fragment. We describe here a quantitative method for determining the equilibrium binding affinities of repressor for these lac reconstitutes. Quantitative analysis shows that the operator-histone reconstitutes may be grouped into two affinity classes: those with an affinity for repressor close to that of naked DNA and those with an affinity 2 or more orders of magnitude less than that of naked DNA. All particles in the lac nucleosome preparations bind repressor with high affinity, but the lac core particle preparations contain particles of both high and low affinities for repressor. Formaldehyde cross-linking causes all high-affinity species to suffer a 100-fold decrease in binding affinity. In contrast, there is no effect of cross-linking on species of low affinity. Therefore, the ability of a particle to be bound tightly by repressor depends on a property of the particle which is eliminated by cross-linking. Control experiments have shown that chemical damage to the operator does not accompany cross-linking. Therefore, the property sensitive to cross-linking must be the ability of the particle to change conformation. We infer that the particles of low native affinity, like cross-linked particles, are of low affinity because of an inability to facilitate repressor binding by means of this conformational change. Dimethyl suberimidate cross-linking experiments show that histone-histone cross-linking is sufficient to preclude high-affinity binding. Thus, the necessary conformational change involves a nucleosome histone core event. We find that the ability of a particle to undergo a repressor-induced facilitating conformational change appears to depend on the position of the operator along the DNA binding path of the nucleosome core. We present a general model which proposes that nucleosomes are divided into domains which function differentially to initiate conformational changes in response to physiological stimuli.     

Storage of marine fish erythrocytes in liquid nitrogen

The preservation of erythrocytes from cod ( Gadus morhua ), saithe ( Pollachius virens ) and mackerel ( Scomber scombrus ) at −196° C was studied using dimethyl sulphoxide (DMSO) as a cryoprotectant. Erythrocyte recoveries of greater than 90% were obtained from all species and cod erythrocytes were stored for eighteen months with insignificant lysis. Larger quantities of blood were stored by removal of plasma from citrated blood prior to the addition of DMSO solution, and by storage of pelleted frozen blood in aluminium canisters in liquid nitrogen. Maximum recoveries of washed intact erythrocytes required thawing of pellets in 125% DMSO solution and washing with buffer containing decreasing concentrations of DMSO. Washed erythrocytes kept at 4° for at least two days showed little haemolysis, were morphologically similar to fresh erythrocytes and equally susceptible to the δ-haemolysin of Staphylococcus aureus .     

Parasites,predators and other arthropods associated withMusca domestica and other flies breeding in bovine manure

The species of flies breeding in bovine manure, their parasites and predators as well as other associated arthropods in 3 localities in and near Bangalore are recoreded. The flies areMusca domestica L.,Musca pattoni Austen,Stomoxys calcitrans L.,Physiphora aenea F.,Physiphora demandata F.,Sargus metallinus F.,Sepsis thoracica R.-D.,Sepsis nitens Wiedemann,Sphaerocera scabricula Hal, andLeptocera (Coproica) hirtula Rondani. Four species of hymenopterous pupal parasites of these flies have been obtained:Spalangia cameroni Perkins from pupae ofM. domestica, M. pattoni, S. calcitrans, P. aenea andP. demandata; Spalangia endius Walker from pupae ofM. domestica, M. pattoni andS. calcitrans; Spalangia nigroaenea Curtis from pupae ofM. domestica andS. calcitrans; andDirhinus trichiophthalmus Masi from pupae ofSargus metallinus F. Percentage parasitism of fly puparia in field samples was noted. Four species ofHister andAleochara puberula Klug feeding on various immature stages ofM. domestica, 2 species of scarabaeid beetles, 2 species of ants and a pseudoscorpion were also found in the manure. The importance of biotic regulatory factors in the control of flies is discussed.

---

Résumé Dans 3 localités de Bangalore ou proches de cette ville, on a inventorié les espèces de mouches vivant dans le fumier de vache, leurs parasites et prédateurs ainsi que d'autres arthropodes associés. Les mouches récoltées sont:Musca domestica L.,Musca pattoni Austen,Stomoxys calcitrans L.,Physiphora aenea F.,Physiphora demandata F.,Sargus metallinus F.,Sepsis thoracica R-D.,Sepsis nitens Wiedemann,Sphaerocera scabricula Hal. etLeptocera (Coproica) hirtula Rondani. Quatre espèces d'hyménoptères parasites des pupes ont été obtenues de ces mouches:Spalangia cameroni Perkins deM. domestica, M. pattoni, S. calcitrans, P. aenea etP. demandata: Spalangia endius Walker deM. domestica, M. pattoni etS. calcitrans, P. aenea etP. demandata; Spalangia endius Walker trans; etDirhinus trichiophthalmus Masi deSargus metallinus F. On a noté le taux de parasitisme des nymphes dans les conditions naturelles. Quatre espèces deHister etAleochara puberula Klug s'attaquant aux divers stades non imaginaux deM. domestica, 2 espèces de scarabeides, 2 espèces de fourmis et un pseudoscorpion ont été également trouvés dans le fumier. L'importance de ces facteurs biotiques dans la régulation des populations de mouches est discutée.

---

---

Paper presented at the seminar on utilization of farm wastes for rural industrial growth, National Dairy Research Institute, Bangalore, 31 st December, 1975.

---

This paper is published with the permission of the Director-General, Indian Council of Medical Research, New Delhi     

壳聚糖固定化木瓜蛋白酶的研究

以壳聚糖为载体,成二醛为交联剂将木瓜蛋白酶固定化。5％戊二醛在4-6℃下处理载体5h,加酶液(3.5mg/mL蛋白,pH7.2)固定12h,活力回收达32％,作用于酪蛋白的半衰期为36天,其表观K_m(酪蛋白)值为0.075％(W/V),溶液酶的K_m值为0.086％;最适pH7.0～7.5,溶液酶为7.0～8.5。固定化酶在pH8.5以下,溶液酶在9.0以下活力稳定。固定化酶在45℃以下,溶液酶在75℃以下稳定。用6mol/L脲洗脱固定化酶4次(5.5h)活力仍有54.5％。用固定化酶处理啤酒浊度比对照下降了1.5-3.7倍,蛋白质含量下降了44％,冷藏(4℃)120天无冷混浊现象发生并保持了啤酒原有风味和理化性状。     

Halichondrin B and homohalichondrin B, marine natural products binding in the vinca domain of tubulin. Discovery of tubulin-based mechanism of action by analysis of differential cytotoxicity data

Data generated in the new National Cancer Institute drug evaluation program, which is based on inhibition of cell growth in 60 human tumor cell lines, were used to compare new compounds with agents of known mechanism of action in terms of their differential cytotoxicity. Two marine natural products, halichondrin B and homohalichondrin B, appeared repeatedly when the data base was probed with known antimitotic agents. We confirmed that both compounds were highly cytotoxic (IC50 values for L1210 murine leukemia cells of 0.3 and 1 nM, respectively), with accumulation of cells arrested in mitosis at toxic concentrations, that both inhibited the polymerization of purified tubulin, and that both inhibited microtubule assembly dependent on microtubule-associated proteins. Limited amounts of homohalichondrin B, the less active agent, were available, so only halichondrin B was studied in detail. Halichondrin B did not interfere with colchicine binding to tubulin, but it was a noncompetitive inhibitor of the binding of vinblastine to tubulin (apparent Ki, 5.0 microM). Halichondrin B was therefore compared with other agents which interfere with the binding of vinca alkaloids to tubulin (vinblastine, maytansine, dolastatin 10, phomopsin A, rhizoxin) in terms of its effects on tubulin polymerization, inhibition of GTP hydrolysis, inhibition of nucleotide exchange, and stabilization of tubulin, as well as the quantitative assessment of its effects on vinca alkaloid binding and inhibition of cell growth. Since halichondrin B was originally isolated from the same organism as the phosphatase inhibitor okadaic acid, and since it is about 50-fold more effective than okadaic acid as an inhibitor of L1210 cell growth, perturbations of cellular microtubules observed following treatment with okadaic acid should be interpreted cautiously.