Purification and properties of L-asparaginase EC-2 from Escherichia coli 055:B5.

1. L-Asparaginase has been isolated from aerobically grown Escherichia coli 055:B5 and purified about 140-fold in a three-step procedure involving acidification to pH 4.5, ammonium sulphate fractionation and column chromatography on DEAE-Sephadex A-50. The activity of the preparation is 140 U/mg protein. 2. The enzyme acts within a broad pH range (pH 5-9) and is affected neither by PCMB, N-ethylmaleimide nor metal ions. 3. Molecular weight of the isolated asparaginase is 130 000.     

Precursors of cytoplasmic RNA in avian cell nucleus

In nucleus of chick embryo four pre-rRNA of molecular weight of 3.43, 2.93, 2.36 and 1.87 X 10(6) were found in addition to the heterogeneous population of "giant" RNA molecules larger than 4.5 X 10(6) daltons, partially polyadenylated, with few methyl groups and numerous double-stranded regions.     

Electron spin resonance and photoreaction of Mn(II) in lettuce chloroplasts.

Electron spin resonance (esr) of lettuce chloroplasts yields three types of signals: (i) a broad (~900 G) signal around g = 2.22 (apparently due to Cu²⁺ complexes); (ii) an Mn²⁺ spectrum around g = 2.003 consisting of six hyperfine lines (A = 94.5 G) of ~30 G width; and (iii) a sharp signal at g = 2.00 due to photosignals I and II. The present work is concerned with the Mn²⁺ signal and its relation to the photosynthetic process. Intensity measurements were performed by comparing the intensities of the Mn²⁺ signals of two identical chloroplast preparations, one of which was slightly acidified. The integrated intensity of the signal in the normal preparation was approximately one-fourth of that in the acidified sample, suggesting that only the?$\text{1}\text{2}\text{?}\text{1}\text{2}$ fine structure band is observed in untreated chloroplasts. This indicates that the manganese in the chloroplasts is bound in an asymmetric environment, apparently in protein complexes. The Mn²⁺ signal is light sensitive, decreasing on illumination and reappearing in the dark. Typical values for the half-lives of the light and dark processes in normal chloroplasts are 0.25 and 2.1s, respectively. The effect is interpreted in terms of the photooxidation of Mn²⁺ to higher oxidation states which are invisible to esr spectroscopy. In order to determine whether this process is related to photosynthesis the effect of certain reagents and treatments that are known to affect the photosynthetic system was studied. It was found that the oxygen evolution inhibitors 3-(3,4 dichlorophenyl)-1,1-dimethylurea (DCMU) and carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP) as well as the electron donors, phenylenediamine and sodium ascorbate, reduce or completely eliminate the light effect on the Mn²⁺ signal. Heat treatment and Tris washing caused deceleration of both the light and dark reactions. These effects indicate that the photooxidation of the Mn²⁺ is related to the photosynthetic cycle, the most probable site being the water splitting apparatus of photosystem II.     

Temperature-induced changes in lecithin model membranes detected by novel covalent spin-labelled phospholipids.

Several spin-labelled phospholipids carrying covalently bound 5-doxylstearic acid (2-(3-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl) were intercalated in liposomes of saturated and unsaturated lecithins. Temperature-induced changes of these liposomes, detected by the spin-labelled phospholipids, were found to be in agreement with the previously described transitions of hydrocarbon chains of host lecithins detected by different probes and different techniques, establishing that spin-labelled phosopholipids are sensitive probes for the detection of temperature-induced changes in lecithin model membranes. In addition to the detection of already-known transitions in lecithin liposomes, the coexistence of two distinctly different enviroments was observed above the characteristic transition temperature. This phenomenon was tentatively attributed to the influence of the lecithin polar group on the fluidity of fatty acyl chains near the polar group. Combined with other results from the literature, the coexistence of two environments could be associated with the coexistence of two conformational isomers of lecithin, differing in the orientation of the polar head group with respect to the plane of bilayer. These findings have been discussed in view of the present state of knowledge regarding temperature-induced changes in model membranes.     

Selective enzymatic radioactive and spin labelling of phospholipids in biological membranes: application to study of temperature-induced changes of microsomal phosphatidylinositols and mitochondrial polyglycerophosphatides.

A new method for the covalent radioactive and spin labelling of lipids within isolated biological membranes has been described in detail and applied to studies of temperature-induced changes of microsomal and mitochondrial membranes. The method is based on the enzymatic use of radioactive substrates carrying covalently bound doxyl derivatives of stearic acid in the biosynthesis of phospholipids in isolated membranes. Radioactive-and spin-labelled lipids bound to the microsomal and mitochondrial membranes were then used as internal probes in monitoring temperature-induced changes of these membranes. Since the analysis of isolated radioactive-and spin-labelled lipids revealed the exact composition of membrane-bound labelled lipids, specific temperature-induced changes were correlated with specific lipids of examined membranes. Phosphatidylinositol of microsomal membranes and polyglycerophosphatides (phosphatidyl-glycerol and cardiolipin) of mitochondrial and inner mitochondrial membranes were found to be involved in the apparent formation of lipid clusters at around 20-30 degrees C. Cardiolipin was found to be involved in the fluidization of inner mitochondrial membranes. These findings are discussed in view of the present state of knowledge of the organization of lipids in biological membranes.     

Decreased tuftsin concentrations in patients who have undergone splenectomy.

Serum tuftsin concentrations were measured, using a radioimmunoassay developed in Israel, in normal subjects and in patients who had undergone splenectomy. Concentrations in those who had undergone traumatic and elective splenectomy were much lower. The tuftsin concentration in 38 patients with Hodgkin''s disease who had undergone splenectomy during staging laparotomy was not significantly different from the mean concentration in other patients who had had elective splenectomy. In four patients who underwent splenectomy for non-malignant haematological disorders measurements made before and after operation showed that tuftsin concentrations fell significantly in the days after operation. The increased susceptibility to overwhelming infections of patients with Hodgkin''s disease and others who have undergone splenectomy may be related to the low tuftsin concentrations. As pre-splenectomy tuftsin concentrations in patients with Hodgkin''s disease were normal, the practice of performing staging laparotomy and splenectomy in patients with Hodgkin''s disease should perhaps be reconsidered.     

Age-related changes in the tissue content of total iodine, its hormonal and nonhormonal compounds and their metabolic course

By the spectrophotometric method the age changes of total iodine content, its hormonal and non-hormonal compounds in rats and men tissues (muscles, liver, kidney, heart, lungs, brain, spleen and blood) have been studied. It was established that the total iodine content decreased at the expense of the protein-bound iodine concentration and also of the butyl-alcohol extractable iodine. The exchange of thyroid hormones intensity lowered.     

Somatic embryogenesis and plant regeneration in an interspecific hybrid of Oryza

An embryogenic callus was obtained from immature panicle of an interspecific hybrid (Oryza sativa x O. latifolia) F₁. The medium consisted of HE salts supplemented with 2,4-D, NAA (each 2 mg/l), kinetin (3 mg/l), yeast extract (1360 mg/l) and casein hydrolyzate (300 mg/l). The callus was milk-white in colour compact and granulate in texture. Various developmental stage of embryoid, such as globular, heart-shape, scutellum-shape and mature embryoid were observed in an embryogenic callus. Plantlets were successfully regenerated from 1-month-old callus with more than 80% regenerational frequency in each subculture for 12 passages.