Temperature Effect on the Photo-Accumulation and Phobic Response of Volvox aureus*

SYNOPSIS. The effect of temperature on photoaccumulation and photophobic response of Volvox aureus were studied. The algae exhibited positive photoaccumulation at room temperature and negative at low temperature. When stimulated with light of intermediate intensiy (～ 5 × 10³ lux), the phobic response of the algae consisted of a decrease in the frequency or the cessation of flagellar movement in the anterior cells. At room temperature, an increase in light intensity elicited the phobic response, whereas at low temperature a decrease in light intensity was the effective stimulus. The phobic response lasted only a few seconds. The positive and negative photoaccumulations of the algae could be explained by the brief cessation of flagellar movement in the anterior cells, elicited by an increase of stimulus light at room temperature or a decrease of stimulus at low temperature.     

Galvanic Stimulation of Volvox globator I. Electroosmotic Patterns Associated with the Ion Exchange Properties.

Application of direct electric potentials across immobilized Volvox globator colonies produced patterns in the ambient solution that were observable by dark field microscopy by the use of polystyrene spheres in the medium. Two large elliptical swirls occurred immediately adjacent to the colony nearest the anode. A clear area developed outwards from the cathodal side of the colony. Since similar patterns were obtained with live, dead, and deflagellated colonies, it was assumed that the phenomena were purely physical. The electric potential induced an electroosmosis in the glass stimulation chamber. Live or dead colonies, immobilized by being secured with a glass coverslip, experienced an anodal movement of water and associated polystyrene spheres. The electroosmosis gave rise to solution patterns which were shown not to be the result of hydrostatic pressure (turbulence) or thermal convection currents. When anion-exchange beads were substituted for colonies in the stimulation chamber, application of the electric potential produced a smooth laminar flow around the positively charged beads. Cation-exchange beads, on the other hand, produced 2 large anodal swirl patterns. Clearly, the colony surface behaved like a weakly charged cation exchanger. Other investigators have determined that the cell walls of pond water plants and algae are negatively charged and have ion-exchange abilities. The negatively charged Volvox cell wall caused an electroosmosis in the colony, in the cathodal direction. Previous explanations for the galvanotaxis of Volvox are not adequate because they do not take into account the negatively charged cell wall.     

Light-Induced Body Movement of Euglena gracilis Coupled to Flagellar Photophobic Responses by Mechanical Stimulation*†

SYNOPSIS. In low viscosity media, Euglena gracilis strain Z responds to a sudden change in light intensity by a cessation of forward movement, followed by a reorientation of the locomotor flagellum which results in turning of the cell around the lateral axis (photophobic response). At a viscosity interface between low [～ 1 cP (centipoise)] and high (4000 cP) media, the cells exhibit avoidance responses or become immobilized in the higher viscosity medium. Upon changing the light intensity, free swimming cells have photophobic responses, while immobilized ones undergo body contractions. For cells immersed in media of varying viscosity, the delay between light stimulation and body contraction (transduction time) is shortest at high viscosities. From 500 to 2000 cP, where the cells are capable of both movement and light-induced body contractions, there is a logarithmic dependence of the transduction time on the viscosity. The transduction time does not vary appreciably with the intensity of the primary light stimulus within a range of 0.14-1.13 kW/m².     

Galvanic Stimulation of Volvox globator II. Mechanism of Galvanic Response, an Effect of Calcium Displacement

Slight increases or decreases in calcium ions in solutions which supported the growth of Volvox globator colonies caused the colonies to fall to the bottoms of their containers. High speed cinematography (600 frames/sec) showed that the flagella beat normally (21/sec) in balanced electrolyte solutions which have calcium concentrations between 0.5 and 1.0 mM. When colonies were placed in 10.0 or 0.0 mM CaCl₂ solutions, flagellar beating disappeared within 1 hr. The cessation of flagellar beating was reversible when colonies were replaced in the balanced solution. The Volvox cell wall has been shown to be a fairly good cation-exchanger with calcium ions acting as the counterion to the fixed negative change. Colonies that were photopositive and gave a cathodal galvanotaxis responded to DC electrical potentials by producing solution patterns that were indicators of colony electronegativity. Colony resistance to electroosmotic flow was compared in potassium and calcium solutions. When colonies were placed in darkness for 24 hr and stimulated by DC electrical potentials, their cation-exchange properties became reduced and the cell walls appeared thinner. Application of a high DC electrical potential to dark-adapted colonies caused the colonies to shrink on their anode sides (anodal contraction). Other workers have found that the flagella on the anodal sides of dark-adapted colonies ceased beating during DC electrical stimulation. It is hypothesized that the electric current caused an increase of calcium ions on the anodal side of the colony that inhibited the flagellar mechanism of beating on that side. It is also hypothesized that the galvanotaxis associated with light-adapted (photopositive) colonies was due to calcium displacements in the colony cell walls that affected the flagellar beating on both sides of the colony.     

Growth-rate responses of Volvox aureus Ehrenb. (Chlorophyta,Volvocales) to variability in the physical environment

An analysis of the dynamic responses of a population of Volvox aureus to artificially-imposed alternations in mixing and stratification in a large limnetic enclosure (“Lund Tube” C, Blelham Tarn) is presented. The rates of population increase are shown to be regulated largely through the propagation of daughter colonies that are subsequently released into the medium. The efficiency of propagation is measured in terms of the numbers of developing daughter colonies in parent colonies at any time and the time required for their maturation prior to release. Efficiency of propagation increased when the vegetative population was unmixed and decreased when it was mixed through an optically-deeper water column. Self-regulation of vertical position in the depth profile also influences propagation and, hence, the rate of population increase.     

l-Phenylalanine Ammonia-lyase Activity in Robinia pseudoacacia Seedlings: I. Cyclic Phenomenon Activity during Continuous Light

Influences of light and darkness on l-phenylalanine ammonia-lyase activity of black locust (Robinia pseudoacacia) seedlings were studied. Light initiates both an increase in enzyme activity (or enzyme synthesis) and a subsequent decrease in activity. These dual influences of light create cyclic changes in l-phenylalanine ammonia lyase activity in continuous light. The cyclic changes in activity (during continued light) cannot be attributed to an endogenous rhythm and rather are related to the changes in balance between the enzyme activity and its inactivating system.     

Stimulation of Mitochondrial Calcium Uptake by Light during Growth of Corn Shoots

Ca²⁺ uptake in mitochondrial fractions, isolated on Percoll discontinuous density gradients, from light- and dark-grown corn (Zea mays L. var W64A × W182E) shoots was characterized by dual wavelength spectroscopy and the Ca²⁺-sensitive dye murexide. In light-grown seedlings, the rate of mitochondrial Ca²⁺ uptake was about 40 nanomoles per minute per milligram of mitochondrial protein. A portion of the Ca²⁺ uptake required an exogenous supply of ATP (65%) while the remaining 35% was the respiratory substrate-dependent reaction. Ruthenium red (2 micromolar) completely inhibited both ATP- and substrate-dependent reactions. There was no detectable Ca²⁺ efflux from the mitochondria with the inhibitor. When the mitochondrial fraction was prepared from the dark-grown shoots, the rate of uptake, in particular the ATP-dependent reaction, was greatly reduced. The dark treatment caused a reduction in mitochondrial Ca content which is largely due to the reduction of Ca associated with the mitochondrial membrane rather than to a reduction of Ca in the soluble matrix.     

Light Affects Flagellar Agglutinability in Chlamydomonas eugametos by Modification of the Agglutinin Molecules

The effect of light on the sexual competence of a light-sensitive mating type minus strain (mt⁻) of Chlamydomonas eugametos obtained by crossing a light-sensitive mating type plus strain (mt⁺) with a light-insensitive mt⁻ strain is described. As previously demonstrated for the mt⁺ parent, this study of one of the mt⁻ offspring shows that (a) a light-sensitive mechanism affects flagellar agglutinability in a rapid process that does not require protein synthesis; (b) only the activity of the flagellar agglutinins (glycoproteins responsible for agglutination) is susceptible to light while agglutinins on the cell body surface are not affected by light. We further demonstrate that (a) membrane vesicles naturally released from nonagglutinable dark gametes remain inactive. Extracts of these vesicles also remain inactive even though they contain agglutinin-like components; (b) inactive mt⁻ agglutinin is present in extracts of flagella from nonagglutinable dark gametes by comparison of its chromatographic, electrophoretic, and immunogenic properties with those of active agglutinin. When purified of all other flagellar proteins, it remains inactive; (c) a monoclonal antibody directed against the sexual agglutination site of the mt⁻ agglutintin discriminates between active and inactive agglutinins when present in a native state on the flagellar surface, but is unable to discriminate between them when they are denatured in sodium dodecyl sulfate-electrophoresis gels and blotted onto nitrocellulose. Taken collectively these observations suggest that light activation involves the chemical modification of the agglutinins in situ on the flagellar surface.     

Unusual Structures in the Flagellar Apparatus of a Strain of Trypanosoma cruzi*

Certain structures, associated with the flagellum, and which had hitherto been described as appearing occasionally in some species of trypanosomes, were found very frequently in epimastigote forms of strain F of Trypanosoma cruzi: (a) a group of tubular elements in an electron-dense mass enclosed within a swelling of the flagellar membrane as the flagellum emerges from its reservoir; (b) an expansion of the flagellar membrane at the point of the above swelling, which in cross-sections appears as a ring; and (c) an electron dense band in the body of the organism alongside the border of the flagellar pocket. The possible significance of these structures and the fact that so far they have been found only in one strain of T. cruzi are discussed.     

Phosphorylated Thiamine Derivatives and Cortical Activity in the Baboon Papio papio: Effect of Intermittent Light Stimulation

The effect of intermittent light stimulation (ILS) on the distribution of thiamine derivatives in three brain areas (occipital, motor, and premotor) was compared in photosensitive and nonphotosensitive baboons. ILS induces paroxysmal discharges in the motor and premotor areas of photosensitive animals only. In baboons submitted to ILS, thiamine triphosphate (TTP) decreases in both photosensitive and nonphotosensitive animals; thiamine monophosphate (TMP) increases in photosensitive animals, which present ILS-induced paroxysmal discharges, whereas it is unaffected in nonphotosensitive animals. The variations are the most significant in the occipital (visual) cortex. A consumption of TTP may result from electrical activity induced by light stimulation in the occipital area. No correlation between ILS-induced paroxysmal activity and a decrease in TTP contents was found. However, photosensitive animals are affected differently from nonphotosensitive animals, as their content of TMP in the cerebral cortex increases on stimulation. However, as long as the exact role of thiamine compounds in relation to membrane excitability in the nervous system remains unknown, it is impossible to conclude whether the differences observed in the metabolism of thiamine compounds are the cause or the consequence of the photosensitivity in the baboon Papio papio.     

Studies in the Mitosis of Euglena I. On the Chromosome Cycle of Euglena viridis Ehrbg.

The chromosome cycle in the vegetative division of Euglena viridis was investigated. The seeming chromatin granules in the interphase nucleus are in reality thread structures, paired and very loosely twisted. Each component of the paired threads is called a chromatid, and consists of a fine thread of even thickness, the chromonema.
In the prophase, linear contraction and thickening of the chromatids occurs by means of the spiralization of them. In the later prophase, the coiled chromonema splits into two finer strands which show the plectonemic spiral. At the metaphase, the chromosomes are arranged in the form of an equatorial ring, encircling the median portion of the elongated endosome. Nearly all of the chromosomes have a submedian or a sub-terminal and a few of them have a terminal kinetochore. In the early anaphase, separation of the sister chromosomes takes place beginning at the kinetochore. The spindle fibres in the metaphase and anaphase were not observed. The two stranded spiral in the chromosomes is separated into distinct components by the uncoiling in the later telophase, and they are transformed, in the interphase nucleus, into the paired chromatids.     

Activity catalase and superoxide dismutase of Staphylococcus aureus during its persistence in the body

The dynamics of the level of catalase and superoxidedismutase (SOD) expression by S. aureus isolated in persistent experimental kidney infection is described. A rise in the activity of the staphylococci under study during transition of the infectious process from the alteration to persistence stage. Changes in the expression of SOD and catalase were observed simultaneously with a decrease in hemolytic, fibrinolytic and protease activity, as well as in the presence of more pronounced clumping and an increase in the production of protein A, the antilysozyme and anticomplement activity of staphylococcal clones obtained from kidney tissue. The significance of all above-mentioned phenomena in the persistence of microorganisms is discussed.     

Action of the Organophosphorous Insecticide Parathion on the Free-Living Marine Dinoflagellate Prorocentrum micans Ehrbg.

Growth of cultures of the dinoflagellate Prorocentrum micans Ehrbg. was slowed by parathion >1 ppm. Parathion also decreased chlorophyll content and perturbed cellular ultrastructure, eliciting especially plastoglobuli in their chloroplasts. Toxicity of this organophosphorous insecticide is unlikely to be due to its anticholinesterase activity since P. micans appears not to contain cholinesterase. Fluorescence kinetics show that parathion affects the photosynthetic system, particularly photosystem II.