Isolation of the Flagellar Swelling and Identification of Retinal in the Phototactic Flagellate, Ochromonas danica (Chrysophyceae)

Ochromonas danica, a freshwater, planktonic chrysophyte, is capable of sensing the light conditions of its environment. This biflagellate alga has a swelling near the base of the short flagellum and a chloroplastidic stigma in close association with it. A procedure is described for the isolation of this three dimensional flagellar swelling, the presumed photoreceptor. In contrast to an earlier method developed for the isolation of the paraflagellar swelling from Euglena gracilis, the protocol reported here for Ochromonas results in higher yields that should facilitate future biochemical investigations and could open avenues of investigation for the isolation and purification of the presumptive receptor protein. To verify the hypothesis that a rhodopsin-like protein might be present in this alga, we applied a standard extraction procedure successfully used in the identification of retinal. We here report the purification and identification of all-trans retinal in Ochromonas cells by column chromatography, HPLC and GC-MS. Since retinal is the chromophore of rhodopsin-like proteins, this finding may suggest that in these unicellular algae, too, a rhodopsin-like protein could be the photoreceptor pigment.     

The detection of plum pox virus in Prunus species by enzyme-linked immunosorbent assay (ELISA)

Plum pox virus (PPV) was detected by ELISA throughout the year in extracts of root, bark, fruit, flowers and leaves of Prunus species; extracts from healthy plants gave negligible background reactions. In the summer, ELISA values obtained with extracts from infected leaves were variable but samples extracted at 1:50 (w/v) could have been diluted a further five to 110 times before reaching the limit of detection. Using a single antiserum the virus was detected in several hundred trees, suggesting that there was little antigenic variation. PPV was unevenly distributed in leaves and shoots and commonly occurred in only a few branches of an infected tree although it was frequently present in suckers growing from the roots. Virus was detected in the only three trees known to be infected in random leaf samples taken from 530 1-yr-old trees, but some infected trees were missed in samples taken from older trees and from a 7-yr-old rootstock hedge. The main practical use of ELISA for PPV is therefore as a sensitive and highly reliable confirmatory test which greatly facilitates control of the disease by the prompt destruction of infected trees.     

Relationship Between the Increased Sensitivity of Heat Injured Clostridium perfringens Spores to Surface Active Antibiotics and to Sodium Chloride and Sodium Nitrite

Spores of Clostridium perfringens NCTC 8798 became increasingly sensitive to inhibition by sodium chloride, sodium nitrite and a mixture of polymyxin and neomycin when heated at 70–100°C. That the increased sensitivity to each agent was caused by the same cellular damage was suggested by: (1) the temperature coefficients for induction of cellular damage leading to increased sensitivity to all three agents were the same; (2) in the absence of the agents, the spores regained resistance to all three at about the same time and in each case in the presence of cell wall-, protein- and DNA-synthesis inhibitors; (3) combinations of the agents were generally no more inhibitory to the heated spores than were the individual agents.     

Rheumatic fever in Southern California; problems related to diagnosis

Rheumatic fever occurs in native of Southern California and is a cause of death. The incidence of streptococcosis in Los Angeles is approximately equal to that in three other major cities in the United States where rheumatic fever is known to occur commonly. Manifestations of rheumatic fever may range from mild to severe. It is suggested that a greater percentage of patients in Southern California have symptoms of rheumatic fever that are more mild. Differentiation between prolonged, uncomplicated streptococcosis and rheumatic fever is a major problem. The judicious use of a battery of tests, acute phase reactants, on the same blood sample will frequently help to establish the diagnosis in borderline situations so common to Southern California.     

Rapid changes in xanthophyll cycle-dependent energy dissipation and photosystem II efficiency in two vines, Stephania japonica and Smilax australis, growing in the understory of an open Eucalyptus forest

Leaves of Stephania japonica and Smilax australis were characterized in situ on the coast of north-eastern New South Wales, Australia, where they were growing naturally in three different light environments: deep shade, in the understory of an open Eucalyptus forest where they received frequent sunflecks of high intensity, and in an exposed site receiving full sunlight. In deep shade the xanthophyll cycle remained epoxidized during the day and the vast majority of absorbed light was utilized for photosynthesis. In the exposed site both deepoxidation and epoxidation of the xanthophyll cycle and changes in the level of xanthophyll-dependent thermal energy dissipation largely tracked the diurnal changes in photon flux density (PFD). In the understory the xanthophyll cycle became largely deepoxidized to zeaxanthin and antheraxanthin upon exposure of the leaves to the first high intensity sunfleck and this high level of deepoxidation was maintained throughout the day both during and between subsequent sunflecks. In contrast, thermal energy dissipation activity, and the efficiency of photosystem II, fluctuated rapidly in response to the changes in incident PFD. These findings suggest a fine level of control over the engagement of zeaxanthin and antheraxanthin in energy dissipation activity, presumably through rapid changes in thylakoid acidification, such that they became rapidly engaged for photoprotection during the sunflecks and rapidly disengaged upon return to low light when continued engagement might limit carbon gain.