AN ULTRASTRUCTURAL STUDY OF GAMETOGENESIS OF THE MARINE BIVALVE PINNA NOBILIS (LINNAEUS 1758)I. OOGENESIS

The ultrastructural stages of female gametogenesis are describedin a Mediterranean marine bivalve, Pinna nobiiis. Firstly, theprocess of oocyte formation is analysed and the formation ofthe yolk granules is discussed. Secondly the degeneration ofoocytes is described and seems to be most common in vitello-genicoocytes. The evolution of the oocyte reserves is particular;they form a dense globulose mass in the acinar lumen which willthen appear in the cytoplasm content of auxiliary cells. Duringearly stages of oogenesis the oocyte is completely surroundedby several layers of auxiliary cells. On formation of the viteliinecoat around the oocyte, the auxiliary cells are restricted tothe stalk and contact is maintained by desmosomes. Interdigitationphenomena are observed. The auxiliary cells appear to play anintegral role in development of the oocyte. Their functionsare the phagocytosis and intracellular digestion of productsoriginating from oocyte degeneration; this function can permita transfer of precursors necessary to vitellogenesis; they havealso a synthetic activity and they accumulate reserves in theircytoplasm, as glycogen and lipids, which can be employed byvitellogenic oocytes. (Received 2 November 1994; accepted 20 February 1995)     

The Effect of Red and Far-red Light on Subsequent Enzyme Activity in Arena Coleoptiles

The effect of red light (660 nm), far-red light (730 nm) and dark treatment on the subsequent enzyme activity in homogenates of Avena coleoptiles was investigated. The activities of succinic dehydrogenase (SDH), lactic dehydro-genase (LDH) and glucose-6-P dehydrogenase (GDH) were investigated. The activity of SDH was greatest in material receiving continuous darkness. LDH and GDH activity was stimulated by both light treatments compared with the dark values. Little or no difference in enzyme activity was found using either a single 15 min flash of light or continuous light for 24 h. Admixtures of extracts from dark treated and light treated material in a 1:1 ratio gave unexpected levels of enzyme activity. In all cases such admixtures gave much less than the anticipated enzyme activity.     

Expression of Polyoma-induced Transplantation Antigen in Hybrid Cell Lines

The polyoma-induced transplantation antigen is virus specific and its presence on polyoma transformed but not normal cells suggested that at least part of the polyoma genome is maintained in tumour cells. Studies reported here indicate that malignancy is not maintained solely by the presence of this transplantation antigen.     

Immunologic-mediated Protection of Trypanosoma congolense-Infected Mice by Polyribonucleotides

SYNOPSIS. When the synthetic polyribonucleotides polyinosinic acid-polycytidylic acid (poly I poly C) and polyadenylic acid-polyuridylic acid (poly A poly U) were tested against mice infected with varying numbers of Trypanosoma congolense the results varied with the method of passage of trypanosomes in mice. Thus, when 100 flagellates were passaged every 7th day and experiments were initiated with these trypanosomes from mice on the 7th day of their infection, the protective effects of poly I poly C and poly A poly U apparently varied independently of each other as assayed by the mean parasitemias and cumulative mortalities of infected mice. Poly I poly C-resistant and poly I poly C-susceptible variants (“R” and “S”, respectively) were isolated and maintained in mice by passage of 10⁶ trypanosomes every 4th day. Mice infected with these variants responded consistently to poly I poly C and poly A poly U injections in that mice infected with the “R” variant showed no response to either polyribonucleotide but those infected with the “S” variant consistently had a decrease in mean parasitemias and cumulative mortality when treated with poly I poly C, but not with poly A poly U. Using mice infected with the “S” variant, the protective effect of poly I poly C was dose-dependent and best protection was afforded when 1st injections of poly I poly C were given around the time of infection of the mice. The protective effects of the synthetic polyribonucleotides used in these experiments are probably due to their immunologic enhancing capacities and not to interferon. To support this, injections of Newcastle disease virus, a strong inducer of interferon in mice, did not protect against T. congolense in mice. It was not possible to determine whether serum from poly I poly C-treated mice had a greater neutralizing effect upon trypanosomes in vitro than serum from saline-treated mice since any effect of antibody was masked by a naturally occurring inhibitor in normal mouse serum which was reduced during infection. The protective effects of poly I poly C in T. congolense-infected mice were reversed by treatment with cyclophosphamide. This strong immunosuppressant, however, could not reverse the protective effects of poly I poly C against mice infected with Semliki Forest virus, strongly suggesting that the protective mechanisms stimulated by poly I poly C in these 2 infections were different. The response of mice infected with the “R” and “S” variants of T. congolense to synthetic polyribonucleotides is discussed in relation to antigenic variation of trypanosomes.     

Cryoprotectants for Crithidia fasciculata Stored at -20 C, with Notes on Trypanosoma gambiense and T. conorhini

SYNOPSIS. Cryoprotectants were tested in both complex and semidefined media for the trypanosomatid Crithidia fasciculata. Near log-phase or end-of-log-phase cultures were frozen for 24–48 hr at ∼ -20 C, then warmed in air to room temperature. Immediate motility was correlated with viability. The best protectant of the 83 tested was glycerol at ∼ 10% (w/v). Survival without cryoprotectant was rare. Outstanding cryoprotectants (perhaps also useful solvents for drugs poorly soluble in water) were: ethylene glycol; 2,2'-dioxyethanol (diethylene glycol); 1,2,4-butanetriol; 1,4-cyclohexanediol; dimethylsulfoxide; propylene glycol; and N -acetylethanolamine. Several sugars were active, e.g., D-arabinose, sucrose, and sorbitol. Trypanosomes tolerated cryoprotectants much less; tolerance was better in growth media than in suspension media. Trypanosoma gambiense was grown in blood-enriched media + 2-2.5% glycerol, suspended in 20% (w/v) glycerol. then frozen; this permitted 3-week survival. T. conorhini survived 4 weeks after growth in media containing glycerol 2.5%+ ethylene glycol 4%+ rutin 1.0 mg per 100 ml.     

Acriflavin-Induced Dyskinetoplastic Leishmania donovani Grown in Monkey Kidney Cell Culture

SYNOPSIS. Monkey kidney cells (LLC-MK₂) grown in flasks and on coverslips in Leighton tubes were used as host cells for the growth of the intracellular stage, Leishman-Donovan bodies (LDs), of Leishmania donovani obtained from hamster spleen. These parasitized cultures were then used to determine the ability of acriflavin to induce dyskinetoplastic LDs.
LD-infected cells were somewhat fewer in number than uninfected cells at all times except for the 1st day after infection. The parasites attained their maximum numbers on the 5th day after infection of the cultures having a 1.9-fold increase at that time.
When acriflavin was added to the cell culture medium (250 mμ/ml) the numbers of monkey kidney cells did not differ greatly from non-treated cultures until 6–7 days after treatment with acriflavin. Similarly, the numbers of LDs in acriflavin-treated cell cultures, altho somewhat below those of untreated cultures, did not differ greatly from them.
The combined effect of acriflavin and LDs reduced the numbers of monkey kidney cells in treated, LD-infected cell cultures more than either alone.
Dyskinetoplastic LDs appeared in considerable numbers in acriflavin-treated, LD-infected cell cultures. Dyskinetoplastic and normal LDs harvested from cell cultures were inoculated into NIH medium and incubated at 27 C for transformation into leptomonads. There was no indication that dyskinetoplastic LDs were capable of transforming into leptomonads.