First report of metazoan parasites from the cichlid Pseudocrenilabrus philander and the cyprinid Enteromius paludinosus in a South African Ramsar wetland

Parasites of two small fish species from a Ramsar wetland in South Africa were studied in 2014–2015. The cichlid Pseudocrenilabrus philander (Weber, 1897) was parasitised by the copepod Lernaea cyprinacea Linnaeus, 1758, the monogenean Gyrodactylus thlapi Christison, Shinn & van As, 2005 and four gryporhynchid metacestode (Cyclophyllidea) species: Paradilepis scolecina (Rudolph, 1819), Paradilepis maleki Khalil, 1961, Neogryporhynchus lasiopeius Baer & Bona, 1960 and Valipora campylancristrota (Wedl, 1855). The cyprinid Enteromius paludinosus (syn. Barbus paludinosus) (Peters, 1852) was infected with the monogenean parasites Dogielius intorquens Crafford, Luus-Powell & Avenant-Oldewage, 2012, Dactylogyrus teresae Mashego, 1983, and three Dactylogyrus spp. These results represent several new locality as well as host records and further contribute information on the parasitic diversity in the Barberspan Ramsar wetland.     

Temporal synthesis and intranuclear accumulation of the nuclear acidic proteins during periods of chromatin reactivation in Physarum polycephalum

In the lower eukaryote Physarum polycephalum, depending upon the existing cell state (i.e., actively growing plasmodia or metabolically quiescent cysts), there is in the complement of acidic chromatin proteins certain “proliferation” or “nonproliferation” associated proteins. Nonproliferative microplasmodia can be induced to undergo a 12 hr period of physiological and metabolic reorganization resulting in mitosis, DNA synthesis, and the reestablishment of active synchronous growth. During the 12 hr period of chromatin reactivation the specific acidic proteins associated with inactive chromatin and nonproliferative cell states decrease in intranuclear concentration in a continuous and linear fashion. The specific proteins associated with metabolically active chromatin and proliferative cell states are synthesized preferentially at different times during the 12 hr transition period. While several of the proliferation-associated proteins increase continuously in intranuclear concentration during the reactivation period others show maximum increases in their intranuclear concentration during the 2 hr period just preceding mitosis and DNA synthesis. The changes which develop in the acidic chromatin and nucleolar proteins during the period of chromatin reactivation occur independent of and prior to DNA synthesis and mitosis. Incorporation studies using [¹⁴C]-glutamic acid have provided additional evidence for periods of pooled protein and delayed intranuclear binding. The relative specific activities of individual protein bands determined through gel radiography show temporal differences independent of intranuclear protein concentration.It has been estimated that the proteins which are synthesized and accumulate in the nucleus during periods of chromatin reactivation are present in intranuclear concentrations between 80,000 and 1,000,000 copies per nucleus.     

A photophysical model for diphenylhexatriene fluorescence decay in solvents and in phospholipid vesicles.

The fluorescence decay of 1,6-diphenyl-1,3,5-hexatriene (DPH) in pure solvents and in phospholipid vesicles has been measured using frequency domain fluorometry. Data analysis uses a model with two energetically close excited states. The model explains the high quantum yield and the double exponential decay of DPH observed in some pure solvents and in phospholipid vesicles. This model assumes that after excitation to a first excited state, there is a rapid interconversion to a lower excited state and that most of the emission occurs from this state. The interconversion rates between the two excited states determine the average lifetime. For DPH in solvents, we find that the interconversion rates are solvent and temperature dependent. For DPH in phospholipid vesicles, we find that the back reaction rate from excited state 2 to excited state 1 (R12) is what determines the fluorescence properties. The phospholipid phase transition affects only this back reaction rate. The model was analyzed globally for a range of solvents, temperatures and vesicle composition. Of the six parameters of the model, only two, the interconversion rates between the two excited states, varied in all different samples examined. For DPH in phospholipid vesicles, there is an additional feature of the model, which is related to the apparent distribution of the rate R12. Significantly better fits were obtained using a continuous lorentzian distribution of interconversion rates. The resulting lifetime distribution was asymmetric and showed a definite narrowing above the phase transition.     

Growth of Large Plasmodia of the Myxomycete Physarum polycephalum

A method has been developed for growing Physarum polycephalum plasmodia that are 8 to 10 times larger than those obtained in the petri dish cultures used by Nygaard, Guttes, and Rusch. In the large-scale procedure, plasmodia were grown in metal trays on a membrane supported by filter paper on stainless-steel screen. Plasmodia were started from a ring of inoculum to allow inward and outward migration and were incubated on a rocker so that nutrient medium would flow back and forth, wetting the undersurface of the plasmodium. Rocker and petri dish cultures had similar growth characteristics: (i) the interphase time between mitoses I and II and between II and III was about 8 hr; (ii) ribonucleic acid and protein increased essentially logarithmically throughout the cell cycle; and (iii) deoxyribonucleic acid increased only during early interphase and it doubled in approximately 3 hr after each mitosis. Rocker cultures were not as nearly synchronous as petri dish cultures and had a range in metaphase time (at mitosis III) within individual plasmodia of 15 to 45 min, as compared with 5 to 10 min in petri dish cultures.