Changes in protein phosphorylation during the cell cycle of Chinese hamster ovary cells

The phosphorylation patterns of proteins were examined during the cell cycle of Chinese hamster ovary cells. This was accomplished by labeling synchronized cells at various times with [32P]orthophosphate and separating the proteins by both isoelectric focusing and nonequilibrium pH gradient two-dimensional gel electrophoresis. The most dramatic changes occurred during late G2/M when approximately eight proteins (including vimentin, lamin B, and histones 1 and 3) showed increased phosphorylation. Ten other proteins appeared to be uniquely phosphorylated during late G2/M. Of these 10 proteins, seven were no longer phosphorylated shortly after mitosis. There is also at least one protein which showed a relative decrease in phosphorylation during late G2/M.     

Seasonal distribution of enteroviruses and adenoviruses in domestic sewage

A seasonal distribution of enteroviruses and adenoviruses in raw sewage effluents of Athens, Greece, was observed over a 15-month surveillance period. All 36 samples tested were positive for both virus groups. Adenovirus concentration levels ranged from 70 to 3200 cytopathic units per litre of sample, whereas the corresponding values for enteroviruses were 90-900 cytopathic units per litre. Peak values for adenoviruses were recorded during the months of April and June 1983, whereas for enteroviruses the peak was recorded in September 1983. All three types of poliovirus were present. Coxsackievirus types B-1, B-2, B-4, and B-5 and echovirus type 7 were also isolated. Adenovirus types 1, 2, 3, 5, 7, and 15 were detected as well.     

Furosemide-sensitive Na+-K+ cotransport and cellular metabolism in human erythrocytes

Metabolic depletion of human red cells with 2-deoxy-D-glucose in the presence of EGTA decreased ATP to about 4% of the initial value and increased total ouabain- and furosemide-resistant Na+ and K+ effluxes by 20% and 100%, respectively, and furosemide-sensitive Na+ and K+ effluxes by 100% and 60%, respectively. When ATP was restored, all the components of Na+ and K+ fluxes measured returned to baseline levels suggesting a metabolic dependence.     

The Role of Surface Water and Light on Differentiation in the Cellular Slime Molds

A key environmental factor in inducing final fruiting body differentiation in the migrating slugs of cellular slime molds is loss of contact with a surface film of water. If the slug tip reaches above the water film, fruiting tends to occur, but if it stays in contact with the surface water, continued migration is favored. Light is effective in promoting fruiting only if the phototactic slugs orient away from surface (as with overhead light) and therefore, only indirectly affects differentiation.     

Entamoeba histolytica: effect of growth conditions and bacterial associates on isoenzyme patterns and virulence

In xenic culture, isolates of Entamoeba histolytica from asymptomatic carriers are characterized, with rare exception, by possession of a nonpathogenic zymodeme. During the process of axenizing such an isolate, strain CDC:0784:4, a change in the pattern of the isoenzymes from nonpathogenic zymodeme I to pathogenic zymodeme II was observed 40 days after the amebae had been transferred from a medium for xenic cultivation to one used for axenic cultivation, but before axenization of the amebae had actually occurred. Axenization was accomplished by feeding the amebae lethally irradiated bacteria while suppressing and finally eradicating with antibiotics the bacterial flora accompanying the amebae in the original xenic culture. The change in zymodeme was accompanied by a change in virulence as evidenced by the ability of the amebae to produce hepatic abscesses in hamsters and to destroy monolayers of tissue culture cells. Two explanations are offered for the observed changes in zymodeme and virulence: a zymodeme is not a stable inherent property of the ameba. Alternatively, the original isolate consisted of two zymodeme populations and the conditions of growth selected for one or the other of the populations. In either case, our results suggest that the finding of a particular zymodeme in a culture of E. histolytica isolated from an asymptomatic carrier of the parasite cannot be used to predict a clinical condition or serve as a basis for the recommendation of therapy.     

The distribution and abundance of species of Danthonia DC on the New England Tablelands (Australia)

The distribution and percent frequency of the 13 species and one variety of Danthonia recorded on the New England Tablelands were examined in a survey of 110 predominantly pastoral sites. The relationships between site factors and the presence and percent frequency of the different Danthonia species were subjected to canonical correlation analysis. Individual species were found to have particular sets of environmental factors associated with their distribution and percent frequency; a fact not well recognized in the past. The most common factor associated with the abundance of Danthonia was either a long time since the last cultivation or no cultivation at all. Other factors such as altitude, drainage, soil parent material, soil texture and total soil phosphorus status were also of some importance. The six species most commonly recorded throughout the New England Tablelands were D. racemosa RBr, D. pilosa RBr, D. laevis J. Vickery, D. linkii Kunth., D. richardsonii Cashmore and D. tenuior (Steud.) Conert. Of these the first three are ecologically wide species. The first two can coexist with other naturalized species under grazing while D. laevis tends to disappear with disturbance. D. linkii and D. richardsonii require fairly narrow habitat conditions but these conditions and consequently these species are common. Both species respond positively to disturbance. Danthonia linkii increases with cultivation and D. richardsonii colonizes eroded soil surfaces. Danthonia tenuior has more restricted requirements and is not so frequent The other seven species and one variety did not occur often enough for detailed study and the occurrence of two of these species, D. carphoides and D. caespitosa must be considered as rare.     

Purine metabolic enzymes in lymphocytes. I. Adenosine deaminase and purine nucleoside phosphorylase activities in mouse lymphocyte subpopulations

The distribution of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) activities in lymphoid organs and lymphocyte subpopulations in mice, and the effect of phytohemagglutinin P (PHA-P) and concanavalin A (Con A) on the enzyme activities were studied. ADA activity was distributed equally in cells from all organs used and no mouse strain differences were observed. In contrast, PNP activity varied with the mouse strain, being highest in C57BL/6 mice and lowest in BALB/c mice, and with the organ in ICR mice, being high in peripheral blood lymphocytes and spleen lymphocytes, low in mesenteric lymph node cells and absent or very weak in thymus cells. T and B lymphocytes were prepared from spleen of ICR mice. High ADA activity was found in both T and B lymphocytes, whereas PNP activity in the T lymphocytes was about one-third of that in the B lymphocytes. PNP activity in thymus cells was increased to the normal level of T lymphocytes in the spleens by cultivation without stimulant. The development of PNP activity in thymus cells was partially inhibited by Con A but was not affected by PHA-P. ADA activity in thymus cells was enhanced by in vitro stimulation with PHA-P but not with Con A. In contrast, in spleen lymphocytes the development of ADA activity was enhanced by stimulation with PHA-P and Con A, and that of PNP activity was enhanced by PHA-P but not by Con A.     

Excitation of a magnetospheric MHD cavity by Kelvin-Helmholtz instability

The Kelvin-Helmholtz instability is investigated analytically by using a one-dimensional nonuniform model of the Earth’s magnetosphere and the adjacent solar wind region. Its properties are shown to be essentially governed by the presence of an MHD cavity that arises in the magnetosphere because of the non-uniformity of the latter and also because of the jump in the parameters of the medium at the magnetopause (the outer boundary of the magnetosphere). System oscillations constitute a discrete spectrum of eigenmodes, which are determined by the wave vector k _t along the tangential discontinuity and also by the mode number n = 0, 1, 2, …, playing the role of the wavenumber along a coordinate normal to the magnetopause. Analytic expressions are obtained for the frequency and instability growth rate of each eigenmode and for the functions describing its spatial structure. All these quantities depend parametrically on the solar wind velocity V _W , or more precisely, on the Doppler frequency shift ω _W = k _t · V _W . For each eigenmode, there is a lower instability threshold depending on the parameter ω _W and a sharp maximum in the growth rate at the eigenfrequency of the magnetospheric cavity. For ω _W values below the threshold, the properties of an eigenmode are highly sensitive to the type of solar wind nonuniformity. Three cases are considered: a uniform solar wind and solar winds in which the speed of sound increases or decreases away from the magnetopause.     

Isozymes of Ipomoea batatas catechol oxidase differ in catalase-like activity.

The amino acid sequences of two isozymes of catechol oxidase from sweet potatoes (Ipomoea batatas) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant catechol oxidases revealed about 80% equidistance between the two I. batatas catechol oxidases and approximately 40--60% to catechol oxidases of other plants. When H(2)O(2) was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.