Conversion of a 24β-ethyl-25-methylene intermediate into poriferasterol by Trebouxia species

Clerosterol-[26-¹⁴C], a 24β-ethyl-25-methylene sterol [(24S)-24-ethylcholesta-5,25-dien-3β-ol], was incorporated into clionasterol and poriferasterol by cultures of the green algae Trebouxia sp. 213/3 and Trebouxia sp. 219/2. Degradation of the labelled poriferasterol showed that the ¹⁴C retained its identity and was not incorporated as a result of metabolism of the clerosterol-[26-¹⁴C] and randomisation of label. These results are consistent with the proposed production, and subsequent reduction, of a 24β-ethyl-25-methylene intermediate in 24β-ethyl sterol biosynthesis in algae of the order Chlorococcales.     

The growth and nutrient uptake of winter wheat

Summary Measurements with an ion selective electrode under winter wheat and in adjacent fallow soil, from April to July 1976, showed that nitrate concentrations were high in the 0–25 cm zone and correspondingly lower at 50 cm, because of the extreme drying conditions. Maximum differences in nitrate concentrations between cropped and fallow soil occurred at Feekes' stages 6, 10, and 11.1 indicating periods of maximum uptake by the crop (cf Ref.⁴).Dry matter weight of wheat, sampled biweekly, was maximum 15 days before maturity. The foliage senesced and lost weight from Feekes' stage 10.1 onwards. Nutrient concentrations in the foliage decreased from Feekes' stage 4, but N, P and Mg concentrations in the ears increased during Feekes' stage 11. N, P and Mg accumulated in the ears at the expense of the foliage during stage 11, maximum uptake occurring at stages 11.3, 11.1 and 11.2 respectively. In contrast, K and Ca uptake ceased at stages 10.1 and 10.5 respectively and then both were lost from the foliage in heavy showers.Rates of N uptake and soil nitrate depletion correlated significantly, enabling N uptake to be deduced approximately from thesein situ soil nitrate measurements.     

Characterization of messenger RNA for aldolase B in adult and fetal human liver

High molecular weight cellular RNA was isolated from adult and fetal human liver tissue by a procedure of ethanol precipitation in concentrated guanidine-HCl solutions. About 5 mg of RNA were obtained from one gram of liver. RNA was fractionated by sucrose gradient ultracentrifugation. Aldolase B neosynthesized in a reticulocyte lysate cell-free system under the direction of total or fractionated RNA was purified by immunoaffinity microchromatography. Messenger RNA specifying synthesis of aldolase B exhibited a sedimentation coefficient of 16 S both in adult and fetal liver. This enzyme represented 1.3 % of the total neosynthesized proteins in adult liver, 0.1 % in the liver of a 6-month-old fetus and less than 0.01 % in the liver of a 4.5 month-old fetus.     

Fusion of sphingomyelin vesicles induced by proteins from Taiwan cobra (Naja naja atra) venom. Interactions of zwitterionic phospholipids with cardiotoxin analogues

Egg sphingomyelin vesicles were used to assay aggregation/fusion activities of proteins from Taiwan (Naja naja atra) venom to avoid the problem of phospholipase A2 contamination during protein purification. It led to the identification of a new cardiotoxin (CTX) analogue protein (CTX V) with major aggregation/fusion, but few hemolysis, activities. On the contrary, cardiotoxin (CTX III) induced significant hemolysis of human red blood cells but exhibited few aggregation/fusion activities. To study the structure/activity relationship of these CTX-induced processes, the amino acid sequence of CTX V was determined and its aggregation/fusion activity was compared with that of CTX III by transmission electron microscopy, quasielastic laser light scattering, differential scanning calorimetry, and fluorescence spectroscopy. The results show that the CTX-induced fusion process at temperatures slightly above that of the gel to liquid-crystalline phase transition of sphingomyelin vesicles can ultimately convert small sonicated vesicles into large fused vesicles with sizes of 1-2 microns. The abilities of CTX V to induce the leakage of sphingomyelin vesicles content and to cause the fusion of vesicles are approximately 10-fold higher than those of CTX III. Based on the CTX structures determined in the present and other studies, it is suggested that the amino acid residue X within the well conserved sequence of -Cys-Pro-X-Gly-Lys-Gln-Leu-Cys- plays a role in the interaction of CTX with lipid molecules. The lipid phase transition could further enhance the protein-lipid interaction in the process leading to the fusion of vesicles.     

Experimental silver bioaccumulation in the polychaetePomatoceros triqueter (L.)

Summary The tubicolous polychaetePomatoceros triqueter was exposed for 6–7 weeks to 200 or 400 g · l^–1 silver introduced as the nitrate into sea water. Survival conditions and mortality were evaluated and silver bioaccumulation analysed by atomic absorption spectrometry. Characteristic morphological lesions were recognized. Histopathologic examination was performed on paraffin or semi-thin sections and at the ultrastructural level. Histochemical examination mainly concerned the metals, reducing groups and sulfur-containing proteins. Microanalytical study involved the use of a wavelength-dispersive X-ray spectrometry microprobe and ion microanalyzer, and the use of an energy-dispersive X-ray spectrometry microprobe at the ultrastructural level. Our results emphasize the role of the branchial crown for metal penetration. Its cuticle accumulates silver as a metal, in particulate form. The internal accumulation of mainly extracellular deposits concerns the basement membranes and connective tissue present in the axis of the branchial crown filaments, or surrounding the nephridial pouches and the gut sinus. The carrier role of the closed vascular system is suggested by ultrastructural observations. The silver route from transepithelial uptake to nephridial excretion involves at least two intracellular transits, plus the vascular mesothelium. Nephridia play a role in silver storage (lysosomes) and elimination (concretions). In all parts internal to the crown cuticle, silver is at least partly associated with protein SH-groups (metallothionein-like); deposits can be enriched with silver sulfide and metallic silver.     

Iodine intakes assessed by urinary iodine concentrations in healthy children aged ten months,two years,and four years

Urinary iodine excretion was assessed in 642 healthy children aged 10 mo (n=243), 2 yr (n=183), and 4 yr (n=216) living in the Paris area and originating from continental France (60.3%), North Africa (13.8%), the West Indies (9.1%), West Africa (8.3%), Southeast Asia (4.8%), and southern Europe (3.8%). Mild impairment of neurological (reflexes, tone, audiometry) and intellectual development (Brunet-Lézine scale) was assessed in relation to iodine status. Iodine excretions (median values) were 18.4, 11.9, and 10.9 μg/100 mL at 10 mo, 2 yr, and 4 yr, respectively, and risk of mild iodine deficiency (5–10 μg/100 mL) was 18.1%, 34.8%, and 38.3% for the same age groups. No relationship was found between anthropometry, global development quotient, and iodine status. High hearing thresholds were more commonly associated with lower iodine excretion, suggesting mild hearing defects. In spite of iodine prophylaxis, the risk of mild to moderate iodine deficiency still exists in France and in a number of European countries. Evaluation of neurological sequels of borderline iodine status is a major public health problem in European communities.     

Analysis of nuclear sugar-binding components in undifferentiated and in vitro differentiated human promyelocytic leukemia cells (HL60)

The nuclear sugar-binding components (i.e., lectinlike molecules) were analyzed using isolated and membrane-depleted nuclei after incubation in the presence of fluorescein-labeled neoglycoproteins. This analysis was performed before and during the in vitro differentiation of HL60 cells into monocytes by PMA treatment and into granulocytes by DMSO treatment. The nucleoli of undifferentiated and differentiated HL60 cells were not labeled, unlike the nucleoli of other mammalian cells studied so far. This peculiarity allowed us to quantitatively analyze by flow cytometry the changes in the lectin activity associated with the extranucleolar territories enriched in ribonucleoprotein complexes. The neoglycoprotein binding was found to be significantly lower in differentiated than in undifferentiated cells. The decrease in neoglycoprotein binding was observed within the first 24 h of DMSO or PMA treatment, just before the arrest of DNA synthesis. Taking into account that the granulocytic differentiation required 72 h of chemical treatment, the extra-nucleolar lectins might be involved in modulation of the DNA synthesis rather than in phenotypic differentiation. These data are discussed in an attempt to reconcile the association of lectins with RNP complexes and their possible involvement in modulation of HL60 cell proliferation.     

Reverse-phase high-pressure liquid chromatography of uridine diphosphate N-acetylmuramyl peptide precursors of bacterial cell wall peptidoglycan

A series of seven different UDP-N-acetylmuramyl peptide precursors of bacterial cell wall peptidoglycan was examined by reverse-phase high-pressure liquid chromatography. Mixtures of these compounds were successfully and rapidly analyzed by using a Waters μBondapak C₁₈ column as a stationary phase and isocratic elutions with 0.05 m ammonium phosphate or formate buffers of appopriate pH. Furthermore, their accurate quantitation could also be readily achieved by reverse-phase high-pressure liquid chromatography. All these techniques should be extremely useful for the purification of these compounds and for a wide range of biochemical studies concerning the cytoplasmic steps of the biosynthesis of peptidoglycan.     

Decreased heme content and cessation of cell growth in cultured chick embryo fibroblasts in the presence of horse serum: Stimulation of heme synthesis and cell growth by iron

A new spectrofluorometric method for heme quantitation in cultured fibroblasts is described. The method includes: (1) heme extraction by methanol/sulfuric acid, (2) partial purification of heme by a microchromatographic method, and (3) treatment of the purified heme by oxalic acid followed by fluorometric quantitation. Using this method, heme concentration was determined in chick embryo fibroblasts cultured in a medium supplemented with either 7% fetal bovine serum (FBS) or 10% horse serum (HS). In the presence of FBS, cultured cells actively divided and cells contained 34–55 pmol heme/mg protein. In contrast, cultures maintained in HS proliferated at a slower rate and contained 23–25 pmol heme/mg protein. The addition of 40 μM FeSO₄ to cultures maintained in the presence of HS stimulated cell proliferation, and the cellular heme concentration increased to 37–51 pmol/ mg protein. These findings suggest that the cessation of growth in the presence of HS may be due to decreased heme content in the cells and that the stimulation of cell growth by iron is mediated by its stimulation of heme synthesis.