Occurrence of oscillations in ATP synthesis and hydrolysis in chromatophores of Rhodospirillum rubrum

The conditions under which an oscillatory behaviour is observed during net hydrolysis or synthesis of ATP in chromatophores of Rhodospirillum rubrum FR1 are described. In the case of ATPase the oscillations are observed at low temperature (ca. 11°C) in the dark after an initial transient behaviour. These oscillations are attenuated or disappear by the addition of an uncoupler.Oscillations are also observed during ATP synthesis. At 3°C the oscillations appear spontaneously if photophosphorylation is measured during a sufficiently long time. At 30°C the mere intercalation of a dark period also at 30°C is sufficient to trigger the oscillations in the following light period.Abbreviations Bchl Bacteriochlorophyll - FCCP carbonyl cyanide p-trifluoromethoxyphenyl hydrazone - PMS phenazine methosulfate - TMPD, N,N,N,N tetramethyl-1,4-phenylenediamine Dedicated to Prof. Dr. Gerhart Drews as a homage for his permanent example as hard worker and careful scientist and also for his remarkable human quality     

Clinical importance of circulating immune complexes in human acute lymphoblastic leukemia

Summary A total of 122 sera from acute lymphoblastic leukemia (ALL) patients were analyzed for circulating immune complexes (CIC) by two methods: the ¹²⁵I-C₁q binding assay and the polyethylene glycol precipitation test (PEG). The results were correlated with induction, remission and relapse stages of the disease. Using the first method the levels of CIC in induction were 15.18±9.15, with 19/29 positive cases (65.50%), P<0.001 compared with controls. In the remission phase the levels were 9.02±5.62, 11/45 (24.49%) nonsignificant P value, and in relapse they were 16.14±11.17 28/48 (58.33%) P<0.001. The PEG precipitation test results were: 0.33±0.10, 8/22 (36.36%); 0.24±0.11, 10/48 (20.83%) and 0.28±0.10, 6/28 (21.42%), respectively. Thus the values of CIC as measured by PEG in the three clinical of phases ALL did not differ significantly from controls. This contrasts with results obtained by the radioiodinated C₁q binding assay, where the incidence of positive values was significantly higher in induction and in relapse and lower in the remission phase. These observations were extended in sequential vertical studies performed in a group of patients. These results suggest that raised CIC detected by the ¹²⁵I-C₁q method may reflect a progressive state in ALL and that quantitation of these immune complexes may provide an adequate biochemical marker for prognosis.     

Differentiation of cotton fibers from single cells in suspension culture

Summary A cotton cell suspension culture has been developed that provides unique opportunities for plant biologists to investigate early developmental events regulating cotton fiber properties, plant cell elongation, and cell wall biogenesis. The suspension culture was derived from cells of cotton (Gossypium hirsutum L.) ovule callus. These cells undergo the stages of fiber development previously described for in vivo fiber development. Fibers range in length up to 11 mm and have secondary walls. Supported by the U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Laboratory, New Orleans, Louisiana, and Cotton Incorporated, Raleigh, North Carolina.     

Hemagglutination Inhibition with Arboviruses: Relationship Between Titers and Source of Erythrocytes

Antigens for Grand Arbaud, Hazara, and California arboviruses were able to agglutinate goose and either dog, hamster and guinea pig, or hamster red blood cells (RBC) to the same titer at the same pH; in hemagglutination-inhibition (HI) tests, titers for homologous and related sera were the same with these different types of RBC or occasionally one dilution higher with the mammalian cells. Antigens for St. Louis encephalitis and Eastern equine encephalitis viruses required use of lower antigen dilutions with human, guinea pig, and hamster RBC than with goose RBC. The results of comparative HI testing with these latter antigens and types of RBC indicate that HI titer is not directly related to the antigen dilution used with different types of RBC.     

The Kinetics of Ouabain Inhibition and the Partition of Rubidium Influx in Human Red Blood Cells

In the development of ouabain inhibition of rubidium influx in human red blood cells a time lag can be detected which is a function of at least three variables: the concentrations of external sodium, rubidium, and ouabain. The inhibition is antagonized by rubidium and favored by sodium. Similar considerations could be applied to the binding of ouabain to membrane sites. The total influx of rubidium as a function of external rubidium concentration can be separated into two components: (a) a linear uptake not affected by external sodium or ouabain and not requiring an energy supply, and (b) a saturable component. The latter component, on the basis of the different effects of the aforementioned factors, can be divided into three fractions. The first is ouabain-sensitive, inhibited by external sodium at low rubidium, and requires an energy supply; this represents about 70–80% of the total uptake and is related to the active sodium extrusion mechanism. The second is ouabain-insensitive, activated by external sodium over the entire range of rubidium concentrations studied, and dependent on internal ATP; this represents about 15% of the total influx; it could be coupled to an active sodium extrusion or belong to a rubidium-potassium exchange. The third, which can be called residual influx, is ouabain-insensitive, unaffected by external sodium, and independent of internal ATP; this represents about 10–20% of the total influx.     

Some properties of purified phospholipase D and especially the effect of amphipathic substances

1. The soluble phospholipase D of cabbage was purified by heat treatment, acetone precipitation and electrophoresis on a density gradient of aqueous glycerol. 2. The purified enzyme slowly attacked a lecithin suspension whereas ultrasonically treated lecithin was hydrolysed more rapidly. 3. Diethyl ether stimulated the hydrolysis of both the lecithin suspension and ultrasonically treated lecithin. 4. Ca²⁺ was essential for the hydrolysis (optimum about 0·04m); it could not be replaced by Mg²⁺ or cationic amphipathic substances. 5. The reaction had a sharp pH optimum at pH5·4, irrespective of the physical form of the lecithin substrate or the activator used. 6. Anionic amphipathic substances such as dodecyl sulphate, phosphatidic acid, triphosphoinositide and monocetyl phosphoric acid, were potent activators of the reaction: other acidic lipids were relatively inactive. 7. Cationic amphipathic substances inhibited the hydrolysis; however, they also reversed the inhibition caused by using an excess of anionic amphipathic substance as activator. 8. The activation produced by amphipathic substances could not be correlated with their effect on the ζ-potential or size of the substrate particles. 9. The addition of activating anionic amphipaths to lecithin induces the latter to adsorb enzyme from solution. In the absence of Ca²⁺ the enzyme is denatured on the highly negatively charged surface, but in the presence of Ca²⁺ (or Mg²⁺) it is protected from denaturation. It is suggested that this adsorption is an essential prerequisite for ready enzymic hydrolysis. 10. The hydrolysis of lecithin by the enzyme was strongly inhibited by protamine sulphate (0·1mg./ml.) and by choline and ethanolamine. 11. Ultrasonically treated phosphatidylethanolamine, or mixed particles of phosphatidylethanolamine plus dodecyl sulphate, were slowly attacked by the enzyme provided that Ca²⁺ was present.     

Receptor-Mediated Endocytosis of a Manganese Complex of Transferrin into Neuroblastoma (SHSY5Y) Cells in Culture

Abstract: Exposure to manganese compounds often occurs as the result of industrial production or mining. Although manganese appears in traces in animal and human tissue and is essential to certain biological processes, it is also toxic. In humans and animals, toxicity is mainly associated with the nervous system. The mechanism underlying behavioral and biochemical alterations observed after manganese intoxication is not fully understood. We have shown that the manganese present in serum after exposure to manganese oxide is bound to transferrin as trivalent manganic ion. In this study of manganese uptake and storage we used a clone of human neuroblastoma cells (SHSY5Y). These cells differentiate and express catechol-aminergic properties. Saturation binding analysis of the transferrin-manganese complex to the cells revealed a single class of binding sites, with an apparent K _D of 13 ± 1 n M and a density of 11, 000 ± 2, 000 binding sites per cell. The complex was internalized in a temperature-dependent way and reached saturation after 2 h when ∼2% of the added manganese had been internalized. About 80% of the internalized manganese was found in ferritin after 24 h of exposure. The results demonstrate that the transferrin receptor on SHSY5Y cells can bind and internalize a manganese-transferrin complex as efficiently as an iron-transferrin complex, although a saturation of the manganese uptake was achieved.     

Regional chromosomal assignment of the Kell blood group locus (KEL) to chromosome 7q33-q35 by fluorescence in situ hybridization: evidence for the polypeptide nature of antigenic variation

The gene encoding the Kell blood group polypeptide has been localized to chromosome 7q33-35 by in situ hybridization using a biotinylated 1.1-kb DNA fragment containing the 3 half of the human cDNA. This assignment is in accord with genetic localization using antigenic variation as a marker, and strongly suggests that Kell antigenic determinants are part of the polypeptide chain rather than the associated sugar molecules.     

A novel tomato spotted wilt virus isolate encoding a noncanonical NSm C118F substitution associated with Sw-5 tomato gene resistance breaking

The nonstructural protein NSm of tomato spotted wilt virus (TSWV) has been identified as the avirulence determinant of the tomato single dominant Sw-5 resistance gene. Although Sw-5 effectiveness has been shown for most TSWV isolates, the emergence of resistance-breaking (RB) isolates has been observed. It is strongly associated with two point mutations (C118Y or T120N) in the NSm viral protein. TSWV-like symptoms were observed in tomato crop cultivars (+Sw-5) in the Baja California peninsula, Mexico, and molecular methods confirmed the presence of TSWV. Sequence analysis of the NSm 118–120 motif and three-dimensional protein modelling exhibited a noncanonical C118F substitution in seven isolates, suggesting that this substitution could emulate the C118Y-related RB phenotype. Furthermore, phylogenetic and molecular analysis of the full-length genome (TSWV-MX) revealed its reassortment-related evolution and confirmed that putative RB-related features are restricted to the NSm protein. Biological and mutational NSm 118 residue assays in tomato (+Sw-5) confirmed the RB nature of TSWV-MX isolate, and the F118 residue plays a critical role in the RB phenotype. The discovery of a novel TSWV-RB Mexican isolate with the presence of C118F substitution highlights a not previously described viral adaptation in the genus Orthotospovirus, and hence, the necessity of further crop monitoring to alert the establishment of novel RB isolates in cultivated tomatoes.