Cytomorphogenesis in cenocytic green algae. V. Segregative cell division and cortical microtubules in Dictyosphaeria cavernosa (Siphonocladales,Chlorophyceae)*

Disassembly and reassembly of cortical microtubules (MT) during and after segregative cell division (SCO) in Dictyosphaeria cavernosa (Forssk.) Børgesen were observed using fluorescence microscopy. Parallel cortical MT in a mother cell were intact just after the initiation of SCD, but soon circular, MT-free patches appeared. Protoplasmic contraction enlarged the patches, and in these areas, the protoplasm eventually became perforated. Long and undulating cortical MT were arranged densely in the reticulate protoplasm. During further protoplasmic contraction, cortical MT appeared to be random and decreased in density. Finally, short and random cortical MT were present in the segregated protoplasts. Parallel cortical MT reassembled in the expanding daughter cells. After the daughter cells came in contact with one another, a radial system of cortical MT was constructed at the side that faced the inside of the mother cell wall. A microtubule inhibitor (amiprophos methyl, APM) had no effect on SCO. Segregative cell division was not induced directly by mechanical wounding. A comparison between SCO and wound-induced protoplasmic contraction was made.     

Efficient method for the quantitation of urinary leukotriene E4: extraction using an Empore C18 disk cartridge

We describe here an efficient procedure for the precise quantitation of leukotriene E₄ (LTE₄) in a small volume of urine, which was achieved mainly by the use of an Empore extraction disk cartridge. After addition of [³H]LTE₄ to 2 ml of urine, an Empore C₁₈ cartridge was used for initial extraction of the urine, which resulted in the extraction of LTE₄ in a small volume of solvent. The eluate could then be injected onto a high-performance liquid chromatography column without further concentration. After separation by high-performance liquid chromatography, LTE₄ was extracted from the effluent using an Empore C₁₈ cartridge. The concentration of LTE₄ was subsequently quantified by enzyme immunoassay. LTE₄ can be recovered from urine with sufficient efficiency (69.9±4.7%, mean±S.D., n = 101). The coefficient of variation of the assay procedure was less than 10%. When urine was spiked with different amounts of LTE₄, the recovery of LTE₄ added to the urine specimen was less than 120%. The concentration of LTE₄ in urine from normal healthy subjects was 48.0±15.3 pg/mg creatinine (n = 15).     

Biosynthesis of a blood group H1 antigen by α1,2-fucosyltransferase in PC12 cells

We have examined the expression of GDP-fucose: glycosphingolipid fucosyltransferase activity in PC12 cells and PC12 sublines in relation to the neuronal differentiation induced by nerve growth factor (NGF) or dexamethasone. Transfer of fucose to paragloboside (nLc₄Cer) yielded a product which was determined to be a blood group H₁ antigen (Fuc1-2Gal1-4GlcNAc1-3Gal1-4Glc-Cer) by gas chromatography/mass spectrometry analysis and enzymatic hydrolysis, suggesting that PC12 cells have an 1,2-fucosyltransferase. Lactosylceramide was also fucosylated at a reduced rate. When the differentiation of PC12 cells and PC12 subline cells, PC12D and MR31, was induced by exposure to either NGF or dexamethasone, the fucosyltransferase activity for nLc₄Cer was found to decrease in both cell lines, suggesting the association with cell differentiation. This is the first report of the presence of an 1,2-fucosyltransferase in cultured neuronal cell lines which catalyses thein vitro biosynthesis from nLc₄Cer of a type-2 chain glycosphingolipid having the blood group H₁ determinant. The disaccharides, -lactose andN-acetyllactosamine, were also fucosylated by PC12 cell enzyme, although the specificity for the carbohydrate structure was different from that for glycosphingolipids.Abbreviations Glc d-glucose - Gal d-galactose - GlcNAc N-acetyl-d-glucosamine - Fuc l-fucose - Cer ceramide - nLc₄Cer neolactotetraosylceramide (paragloboside) - GDP guanosine diphosphate - CDP cytidine diphosphate - CTP cytidine triphosphate - NGF nerve growth factor - DX dexamethasone - GC/MS gas chromatography/mass spectrometry     

On the three visual pigments in the retina of the firefly squid,Watasenia scintillans

Summary The deep-sea bioluminescent squid, Watasenia scintillans, has three visual pigments: The major one (A1 pigment) is based on retinal and has _max = 484 nm, the second one (A2 pigment) is based on 3-dehydroretinal and has _max = 500 nm, and the third one (A4 pigment) is based on 4-hydroxyretinal and has _max = 470 nm. The distribution of these 3 visual pigments in the retina was studied by HPLC analysis of the retinals in retina slices obtained by microdissection. It was found that A1 pigment was not located in the specific region of the ventral retina receiving the down-welling light which contains very long photoreceptor cells, forming two strata. A2 and A4 pigment were found exclusively in the proximal pinkish stratum and in the distal yellowish stratum. The role of these pigments in the retina is hypothesized to involve spectral discrimination. The extraction and analysis of retinoids to determine the origin of 3-dehydroretinal and 4-hydroxyretinal in the mature squid showed only a trace amount of 4-hydroxyretinol in the eggs. Similar analysis of other cephalopods collected near Japan showed the absence of A2 or A4 pigment in their eyes.Abbreviations HPLC high-performance liquid chromatography - IS inner segment - OS outer segment