Enhanced Phosphorylation of Tyrosine Hydroxylase at More Than One Site Is Induced by 56 mM K+ in Rat Pheochromocytoma PC 12 Cells in Culture

Incubation of rat pheochromocytoma PC12 cells with dibutyryl cyclic AMP or 56 mM K+ is associated with increased activity and enhanced phosphorylation of tyrosine hydroxylase in situ. Following incubation of the PC12 cells with 32Pi, rapid isolation of the tyrosine hydroxylase, and tryptic digestion of the enzyme, two distinct 32P-peptides can be identified after paper electrophoresis. 56 mM K+ increases 32Pi incorporation into both of these peptides, whereas dibutyryl cyclic AMP increases 32Pi incorporation into only one of these peptides. The rate of increase in the incorporation of 32Pi into these two peptides in cells treated with 56 mM K+ is similar. The phosphorylation of tyrosine hydroxylase in PC12 cells occurs exclusively on serine residues. These results suggest that tyrosine hydroxylase in PC12 cells is phosphorylated on serine residues at two or more distinct sites after 56 mM K+ -induced depolarization. Since only one of these sites is phosphorylated by cyclic AMP-dependent protein kinase, activation of tyrosine hydroxylase by 56 mM K+ may involve phosphorylation by multiple protein kinases in rat pheochromocytoma PC12 cells.     

(6R)-Tetrahydrobiopterin Increases the Activity of Tryptophan Hydroxylase in Rat Raphe Slices

The effects of (6R)- and (6S)-tetrahydrobiopterin (BPH4), tetrahydroneopterin, and 6-methyltetrahydropterin on the activity of tryptophan hydroxylase were investigated in rat raphe slices. The activity of tryptophan hydroxylase was estimated by measurement of 5-hydroxytryptophan (5-HTP) formation under inhibition of aromatic L-amino acid decarboxylase with use of HPLC-fluorometric detection. (6R)-BPH4 (the naturally occurring form) at 42 microM, tetrahydroneopterin at 50 microM, and 6-methyltetrahydropterin at 100 microM increased tryptophan hydroxylase activity to 350, 145, and 146% of control values, respectively. (6S)-BPH4, however, had no significant effects on tryptophan hydroxylase activity. These results suggest that tryptophan hydroxylase is subsaturating in vivo for the naturally occurring cofactor, (6R)-BPH4, and that the concentration of (6R)-BPH4 may play an important role for the regulation of tryptophan hydroxylase activity in vivo.     

Solubilization and Characterization of D2-Dopamine Receptors in an Estrone-Induced, Prolactin-Secreting Rat Pituitary Adenoma

D2-dopamine (3,4-dihydroxyphenylethylamine) receptors were successfully solubilized with 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate from an estrone-induced rat pituitary adenoma. Forty-five percent of initial protein and 48% of initial [3H]spiroperidol binding sites were solubilized. The high affinity as well as the stereoselectivity of the sites was preserved. The order of potency of dopaminergic agonists was found to be typical of D2 receptors. Target size analysis by radiation inactivation indicated a molecular weight of 143,000 +/- 3,000 and of 106,000 +/- 4,000 daltons for membrane-bound and solubilized receptors, respectively. This suggests the loss of a 37,000-dalton subunit during solubilization without significant modification of binding characteristics. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of receptor protein preparation photolabeled with N-(p-azido-m[125I]iodophenethyl)spiroperidol confirmed the existence of a 94,000-dalton peptide which probably constitutes the ligand binding site of the receptor. Thus, our data indicate that chronic estrogen treatment of rats, although inducing a pituitary adenoma, does not modify the pharmacological characteristics of D2 receptors. These data suggest therefore that these adenoma may represent an ideal source of material for further biochemical characterization of D2 receptors.     

夏季高温对水牛瘤胃代谢的影响

利用南京地区夏季炎热的自然条件,连续两年在高温季节(7—8月)进行实验。第一年(系列Ⅰ)的实验动物为四头装置瘤胃瘘管的空怀母水牛,研究高温初期(27.5～33.4℃)和持续高温期(28.0～35℃)对水牛瘤胃消化代谢的影响。第二年实验(系列Ⅱ)利用三头装置瘤胃瘘管的海仔母水牛重复高温(26～35.3℃)实验。 夏季高温期间,实验水牛的呼吸率、瘤胃温度和直肠温度升高,采食量减少,饮水量增加,瘤胃液流速减缓。高温初期出现瘤胃代谢升高[总挥发性脂肪酸(TVFA)和氨氮(NH_3-N)浓度及乙酸/丙酸(A/P)比率升高]。但在持续高温情况下,水牛的采食和瘤胃代谢均明显抑制。采取瘤胃内降温措施(投入冰袋)或冷水淋浴,均能迅速降低呼吸率、直肠和瘤胃温度,恢复采食和反刍,并缓解瘤胃代谢的抑制。提示动物机体参与调节瘤胃代谢的变化,并为改善水牛夏季的饲养管理提供生理学依据。     

神农香菊干花净油成分的研究

神农香菊全草提取的香浸膏香气浓郁独特,可用于调配多种高档化妆用香精,也可直接用于饮料中,在香精香料工业中具有较大的实用价值。本文首次报告了我们用毛细管气相色谱仪和色谱/质谱/计算机联用分析仪,对神农香菊干花净油成分进行分析的初步结果。鉴定出的已知成分包括脂肪族类,含氧或非含氧的单萜及倍半萜类化合物32个。     

营养膜无土栽培技术

前言营养膜技术(Nutrient Film Technique简称NFT)是国外广泛采用的一种特殊的无土栽培方法。它是将植物栽植在一个狭长的不透水的营养槽中,槽中有缓慢流动的营养液。植物根系的一部分浸没在营养液中,一部分露在空气中,植物从这种小环境中吸收水、营养物和氧气。由于这种方法采用很薄一层营养液在根际周围流动,裸露的根     

一种新病毒——兔出血症病毒的鉴定初报

从我国新发生的一种家兔急性败血性传染病死兔内脏抽提物中,观察到典型的病毒粒子,回归兔可引起典型发病,再从病死兔内脏回收到同样病毒,证明该病系病毒性传染病,暂定名为“兔病毒性出血症”,病原暂定为“兔出血症病毒”。经初步鉴定,认为本病毒可能是一种首次发现的新病毒,属双股RNA病毒。但从病毒大小和核酸节段看,又不同于呼肠病毒科。最终归属正在进一步研究。     

Use of diathermy for weeding heterogeneous tissue cultures

Summary Cultures generated from tissues consisting of multiple types of cells are often heterogeneous. Unless the cell type of interest has or can be given some selective growth advantage it may be overgrown by other cells. While developing techniques for the tissue culture of microvascular endothelial cells we evaluated an electrosurgical generator (diathermy) to selectively kill nonendothelail cells. Primary cell cultures were observed at ×100 magnification under phase contrast microscopy and a needle electrode apposed to the cell to be destroyed. A return electrode was constructed by placing a sterile clip in contact with the culture medium. The diathermy power setting controlled the area of lysis. Use of this technique allowed weeding of unwanted cells without damage to endothelial cells, which were able to grow to confluence in pure culture. Dr. Marks receives a Medical Postgraduate Research Scholarship from the National Health and Medical Research Council of Australia. Financial support was received from the Leo Leukaemia and Cancer Research Trust and the Scleroderma Association of New South Wales.     

Membrane and cytoplasmic resistivity properties of normal and sickle red blood cells

The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities. At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase. Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction of irreversibly sickled cells in the sample is discussed.     

Critical nuclear DNA size and distribution associated with S phase initiation

Using HeLa S-3 cells synchronized by selective detachment, in this paper we report a parallel study of nuclear morphology and autoradiography grain patterns between middle G₁ and middle S phases: Our results show two distinct [³H]-thymidine labeling patterns. The first “peripheral” labeling pattern has a characteristic nuclear size distribution, in contrast to the heterogeneous and varying size distributions of Feulgen-stained nuclei, and apparently is characteristic of very early S phase. The sizes of the second labeling pattern—homogeneous or inhomogeneous grain distribution throughout the nucleus—are equal or larger than the first and vary with S phase progression. Together, the corresponding nuclear sizes of the labeled nuclei represent the larger extreme of nuclear areas, and the labeling index closely parallels the fraction of nuclei with areas larger than the minimum size of the labeled nuclei. These results suggest a characteristic nuclear size (reflecting unique intranuclear DNA distribution) as a necessary, if not sufficient, requirement for S phase initiation. Parallel experimentation with rat liver cells—synchronized in vivo by partial hepatectomy and analyzed by thin section autoradiography—confirms the existence of a peripheral labeling pattern in both the very early part and the very late part of S phase, which reconciles our data with previous results and points to the fact that both initiation and termination sites for DNA replication are near the nuclear periphery.