Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.     

Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea)

Summary

The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development.     

Comparative study of lipid composition and proliferative activity of rat cholangiocarcinoma RS1 and sarcoma M1 depending on the transplantation organ

The proliferative activity and lipid composition (phospholipids, gangliosides) were studied in rat cholangiocarcinoma RS1 and sarcoma M1 transplanted subcutaneously or intrahepatically. The mitotic index was higher in the tumors transplanted into the heterologous organ. The total phospholipid and sphingomyelin contents were higher in the tumors transplanted intrahepatically. GM3 and GD3 were the main gangliosides in both variants of each tumor. A significant amount of GM3 ganglioside lactone was found in the intrahepatic variants whereas it was absent in the subcutaneous tumors. Both the mitotic index and lipid composition of the tumors studied depended on their microenvironment.     

The changes in the sphingenine/sphinganine ratio in sphingolipids of transplantable rat tumors depends on a transplantation organ

The content of sphingenine (sphingosine) and sphinganine was determined in the total pool of sphingomyelin and ceramide in the rat tumors transplanted subcutaneously and intrahepatically. The sphingenine/sphinganine ratio in the subcutaneously transplanted sarcoma M1 and cholangiocellular carcinoma RS1 was lower than that in the sphingolipids of the intrahepatically transplanted tumors. However, the sphingenine/sphinganine ratio in the subcutaneously transplanted rat hepatoma 27 was higher than in the intrahepatically transplanted hepatoma. These observations indicate that the sphingenine/sphinganine ratio in sphingolipids of tumors depends on the tumor type and its cellular microenvironment.     

Inhibition of Gap Junction Intercellular Communications in Cell Culture by Polycyclic Aromatic Hydrocarbons (PAH) in the Absence of PAH Metabolism

We have studied the effect of polycyclic aromatic hydrocarbons (PAH) on gap junction intercellular communications (GJIC) in culture of hepatoma cells Hep G2 and G27. Carcinogenic PAH inhibited GJIC in both cultures in contrast to non-carcinogenic PAH. We showed that both constitutive and inducible expressions of mRNAs of Ah receptor and cytochrome P4501A1 (the main isoform involved in PAH metabolism) were absent in hepatoma G27 cells. We concluded that the initial, non-metabolized molecules of carcinogenic PAH are responsible for changes in GJIC through interaction with an unknown factor in the cellular membrane.     

Cytochrome P-450 Family 1 in Rat Embryo Cell Culture Immortalized by Rausher Leukemia Virus

We studied comparative expression and activity of cytochrome P450 family 1 (CYP1) isoforms in rat embryo cells, both primary and immortalized by Rausher leukemia virus (RLV). In RLV-infected embryonal cells compared with the initial ones the expression levels of CYP1A1 and 1B1 mRNAs and benzo[a]pyrene (BP) hydroxylase activity were higher, regardless of their treatment with the CYP1 inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin. The sensitivity to BP and 7,12-dimethylbenzo[a]anthracene was higher in the cells immortalized with RLV. The expression level of mRNAs of induction-mediating proteins aryl hydrocarbon receptor and aryl hydrocarbon receptor nuclear translocator was the same in both cell cultures tested. Higher sensitivity of cells immortalized with RLV compared with the initial embryo cells to transforming effect of BP, which was described previously, is possibly associated with elevated expression of CYP1 isoforms.