THE OCCURRENCE AND STRUCTURE OF FLAGELLAR SCALES IN SOME FRESHWATER CRYPTOPHYTES1

Flagellar scales were found in seven out of eleven fresh-water cryptophytes investigated by shadowing whole cells. All scales examined were 140 to 170 nm in diameter and had a basic seven-sided rosette pattern with delicate interlacing. The results of this study indicate that flagellar scales are common in cryptophytes .     

DESM1D ZYGOTES IN EAST TEXAS1

In an extensive survey for desmids in 217 lakes and ponds in 21 counties of east Texas, desmid zygotes were infrequently encountered. A list is given of zygotes of 22 species in 9 genera. Two zygotes previously unobserved are described and illustrated in photographs and camera lucida drawings .     

FLAVODOXIN EXPRESSION AS AN INDICATOR OF IRON LIMITATION IN MARINE DIATOMS1

We have prevously shown that a marine chlorophyte expressed flavodoxin under iron limitation but not under other nutrient stress conditions. Here we use polyclonal antiserum raised against the diatom Phaeodactylum tricornutum Bohlin to show that a similar response is observed in this species. Using our antibody, western blotting techniques, and standard colorimetric detection (4-chloro-1-naphthol), we can detect at least a 25–50-fold increase in flavodoxin in iron-depleted compared to iron-replete cells. In iron-limited batch cultures of P. tricornulum, flavodoxin accumulation was inversely proportional to growth rate and was not detectable in cultures containing initially more than 750 nm of iron. We demonstrated that the accumulation of flavodoxin under iron stress is widespread among marine diatoms and that it may be possible to use the presence or absence of flavodoxin in natural marine diatom assemblages to detect iron limitation. However, our polyclonal antisera appears to be specific for diatoms and did not cross-react with Synechococcus sp ., Micromonas pusilla ( Butcher) Manton et Parke , Dunaliella tertiolecta Butcher , Chlorella sp ., Emiliania huxleii ( Lohm.) Hay et Parke, or Isochrysis galbana Parke. A reverse bioassay experiment was conducted with natural phytoplankton assemblages containing mainly diatoms from Long Island Sound and in shelf waters near Cape Hatteras, two areas not suspected to be iron-limited. Although flavodoxin was not detected in situ in these areas, natural populations of diatoms driven into iron limitation expres.sed flavodoxin. Flavodoxin was detected in mats of the diatom Rhizosolenia castracanei Cleve collected from the Equatorial Pacific during a JGOFS cruise in 1992, consistent with the hypothesis that iron may be limiting in this high-nutrient, low-chlorophyll region .     

COMPARISON OF TOXINS IN THREE ISOLATES OF GONYAULAX TAMARENSIS (DINOPHYCEAE)1

Toxicity levels and profiles of three isolates of Gonyaulax tamarensis Lebour grown under the same conditions were compared. One isolate was collected from Ipswich, Massachusetts, during the massive red tide of 1972 along the New England coast. The other two isolates were obtained from Perch Pond (Falmouth, Massachusetts) and Mill Pond (Orleans, Massachusetts) located in the southwest and south of Cape Cod, Massachusetts, respectively. All the three cultures produced toxins with variation in their toxicity levels. Toxin contents were highest in the Ipswich isolate, followed in an order by Mill Pond and Perch Pond cultures. Morphological similarity existed between Ipswich and Mill Pond cells, whereas the Perch Pond cells possessed an additional ventral pore on the l' epithecal plate.     

GLIDING MOTILITY IN THE BLUE-GREEN ALGA OSCILLATORIA PRINCEPS1

Gliding is an active movement displayed by a microorganism in contact with a solid substrate where there is no evidence of a motility organelle or of a conformational change in the organism. Gliding may be accompanied by rotations, reversals, flectional activity, and mucilage sheath production, as well as linear translation. Previous explanations of the mechanism responsible did not consider all these aspects of behavior. The gliding behavior and ultrastructure of the blue-green alga Oscillatoria princeps Vaucher were examined. O. princeps has a maximum observed gliding rate of 11.1 μm/sec. The trichomes can glide in either longitudinal direction following rapid and occasionally frequent reversals. Right-handed trichome rotation was always observed, which means that any surface point on these trichomes traces a 60-deg right-handed helix. A mucilage sheath envelopes the moving trichomes. The rate of gliding was reduced by viscous substrates, extreme pH, lysozyme, DNP, and cyanide, while sustained darkness had no inhibitory effect. Ultrastructurally, the cell wall is composed of an L-1 layer which is 10 nm thick and often ill-defined. The L-2 layer which is outside this is 200 nm thick and participates in septum formation. The L-3 layer is outside the L-2 and is continuous over the trichome surface. The L-4 “membrane” lies outside the L-3 layer. Grazing surface sections and freeze-etch replicas show a parallel and tight array of 6–9 nm wide continuous fibrils in the cell wall on the surface of the distinctive L-2 layer. Isolated wall fragments were tightly coiled inside out with the fibrils on the inside. The angle of orientation for the fibrils was to the right in a helix with a pitch of 60 deg. O. animalis, a blue-green alga with a movement tracing a left-handed helix, showed a similar array of fibrils oriented in a left-handed helix with a pitch of 60 deg. It is proposed that gliding is produced by unidirectional waves of bending in the fibrils which, act against the sheath or substrate, tints displacing the trichome.     

STRONG PROBABILITY OF LETHAL TOXICITY IN THE BLUE-GREEN ALGA MICROCYSTIS VIRIDIS LEMMERMANN1

Lethal toxicity (intraperitoneal, mouse) was examined in relation to Species composition of samples containing bloom-forming Microcystis populations from natural waters and correlated with toxicity of laboratory strains of four Microcystis formas and species. Toxicity was not always associated with the presence of M. aeruginosa f . aeruginosa Elenkin. A sample with almost all cells of M. aeruginosa f . aeruginosa showed no toxicity, However samples comprised of a high percentage of M. viridis Lemmermann often showed lethal toxicity. Toxicity tests were done on culture strains M. aeruginosa f aeruginosa, M. aeruginosa f flos-aquae Elenkin , M. viridis and M. wesenbergii Kamárek. All five cultured strains of M. viridis were found to be toxic, while only one out of nine strains of M. aeruginosa f . aeruginosa was toxic. Six strains of M. wesenbergii showed no toxicity, It is recommended that attention should be paid to the occurrences and possibility of toxic bloom of M. viridis from the standpoint of water management and public health .     

INCORPORATION OF [14C]N-ACETYL NEURAMINIC ACID INTO BRAIN GLYCOPROTEINS AND GANGLIOSIDES IN VIVO1

—Intracerebrally administered [¹⁴C]N-acetyl neuraminic acid was incorporated into brain glycoproteins and gangliosides. Incorporation into both classes of compounds was markedly inhibited by acetoxycycloheximide but incorporation into the soluble glycoproteins of the nerve-ending fraction was inhibited least of all. In contrast to glucosamine and fucose, a relatively small proportion of the injected [¹⁴C]NANA was incorporated.     

Kinetics of NH4+ and K+ uptake by ectomycorrhizal fungi. Effect of NH4+ on K+ uptake

NH₄⁺ and K⁺ uptake experiments have been conducted with 3 ectomycorrhizal fungi, originating from Douglas fir (Pseudotsuga menziesii (Mirb.] Franco) stands. At concentrations up to 250 μM, uptake of both NH₄⁺ and K⁺ follow Michaelis-Menten kinetics. Laccaria bicolor (Maire) P. D. Orton, Lactarius rufus (Scop.) Fr. and Lactarius hepaticus Plowr. ap. Boud. exhibit K_m values for NH₄⁺ uptake of 6, 35, and 55 μM, respectively, and K_m values for K⁺ uptake of 24, 18, and 96 μM, respectively. Addition of 100 μM NH₄⁺ raises the K_m of K⁺ uptake by L. bicolor to 35 μM, while the V_max remains unchanged. It is argued that the increase of K_m is possibly caused by depolarization of the plasma membrane. It is not due to a competitive inhibition of K⁺ by NH₄⁺ since the apparent inhibitor constant is much higher than the K_m, for NH₄⁺ uptake. The possibility that NH₄⁺ and K⁺ are taken up by the same carrier can be excluded. The K_m, values for K⁺ uptake in the two other fungi are not significantly affected by 100 μM NH₄⁺. Except for a direct effect of NH₄⁺ on influx of K⁺ into the cells, there may also be an indirect effect after prolonged incubation of the cells in the presence of 100 μM NH₄⁺.     

Tyrosine Hydroxylase Phosphorylation in Bovine Adrenal Chromaffin Cells: The Role of Intracellular Ca2+ in the Histamine H1 Receptor-Stimulated Phosphorylation of Ser8, Ser19, Ser31, and Ser40

Abstract: Tyrosine hydroxylase (TOH), the rate-limiting enzyme in catecholamine biosynthesis, is regulated by phosphorylation. Activation of histaminergic H₁ receptors on cultured bovine adrenal chromaffin cells stimulated a rapid increase in TOH phosphorylation (within 5 s) that was sustained for at least 5 min. The initial increase in TOH phosphorylation (up to 1 min) was essentially unchanged by the removal of extracellular Ca²⁺. In contrast, the H₁-mediated response was abolished by preloading the cells with BAPTA acetoxymethyl ester (50 µ M ) and significantly reduced by prior exposure to caffeine (10 m M for 10 min) to deplete intracellular Ca²⁺. Trypticphosphopeptide analysis by HPLC revealed that the H₁ response in the presence or absence of extracellular Ca²⁺ resulted in a major increase in the phosphorylation of Ser¹⁹ with smaller increases in that of Ser⁴⁰ and Ser³¹. In contrast, although a brief stimulation with nicotine (30 µ M for 60 s) also resulted in a major increase in Ser¹⁹ phosphorylation, this response was abolished in the absence of extracellular Ca²⁺. These data indicate that the mobilization of intracellular Ca²⁺ plays a crucial role in supporting H₁-mediated TOH phosphorylation and may thus have a potentially important role in regulating catecholamine synthesis.