DISTRIBUTION OF THE XANTHOPHYLL LOROXANTHIN IN DESMIDS (CHAROPHYCEAE,CHLOROPHYTA)1

Forty-seven species of desmids, representing all four families, were examined for the presence of the xanthophyll loroxanthin by reverse-phase high-performance liquid chromatography. In the Desmidiaceae 28 of the 35 species examined possessed loroxanthin, and in the Mesotaeniaceae two of the six examined had loroxanthin present. All six species of the families Peniaceae and Closteriaceae examined possessed loroxanthin. Although the distribution of loroxanthin appears to be disjunct in the desmids and does not have strict taxonomic significance, it does follow a coherent pattern consistent with current ideas on desmid phylogeny. This pattern suggests that loroxanthin synthesis probably evolved once in the desmid lineage, with one or more subsequent reversals.     

DISJUNCT DISTRIBUTION OF THE XANTHOPHYLL LOROXANTHIN IN THE GREEN ALGAE (CHLOROPHYTA)1

Thirty-five green algal species, representing 17 orders in 5 classes, were examined for the presence of the xanthophyll loroxanthin by reversed-phase high-performance liquid chromatography. Of these, 16 possessed loroxanthin, including at least one member of each class of green algae. The distribution of loroxanthin as established by this and previous studies is disjunct within the Chlorophyta and does not appear to have any taxonomic significance. Most of the green algae examined possessed one or more xanthophyll pigments that have not been found in land plants.     

EXTRACELLULAR PEROXIDASE-MEDIATED OXYGEN CONSUMPTION IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)1

The unicellular green alga Chlamydomonas reinhardtii Dang. displays a high capacity for salicylhydroxamic acid (SHAM)—stimulated O₂ consumption, mediated by extracellular peroxidaie. Addition of exogenous NADH also resulted in stimulation of O₂ consumption. The SHAM-and NADH-stimulated peroxidase activity was partially sensitive to inhibition by exogenous superoxide dismutase, ascorbate, and gentisic acid. These compounds did not inhibit O₂ consumption in the absence of effectors. SHAM-and NADH-stimulated peroxidase activity also was sensitive to inhibition by cyanide, and cyanide titration curves indicated that O₂ consumption by peroxidase was more cyanide-sensitive than O₂ consumption by cytochrome oxidase. The differential sensitivity to cyanide was used to estimate partitioning of O₂ consumption between mitochondrial respiration and extracellular peroxidase. We suggest that, despite a large capacity for peroxidase-me-diated O₂ consumption, peroxidase did not consume O₂ at detectable rates in the absence of effectors. Therefore, in the absence of effectors, measured rates of O₂ consumption represented the rate of mitochondrial respiration .     

CA2+ BINDING PROTEIN CALRETICULIN IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA): BIOCHEMICAL CHARACTERIZATION, DIFFERENTIAL EXPRESSION DURING SEXUAL REPRODUCTION, AND PHYLOGENETIC ANALYSIS

The occurrence of calreticulin, the main Ca²⁺ binding protein in the endoplasmic reticulum of eukaryotic cells, was investigated in the unicellular green alga Chlamydomonas reinhardtii Dangeard. The biochemical characterization of a diethylaminoethyl purified extract highlighted the presence, on SDS-PAGE, of a 55-kDa protein that stained blue with the Stains All dye, a diagnostic feature of acidic Ca²⁺ binding proteins. Immunoblot analyses revealed a strong cross-reaction of the Chlamydomonas reinhardtii protein with antibodies to plant calreticulins and the endoplasmic reticulum retention signal HDEL. Furthermore, the 55-kDa protein bound [⁴⁵Ca²⁺] and had an acidic isoelectric point (pI = 4.9) but was neither glycosylated nor phosphorylated. N-terminal sequencing revealed strong amino acid sequence similarity to calreticulin from other sources. The presence of calreticulin in Chlamydomonas reinhardtii suggested that an endoplasmic reticulum Ca²⁺ buffering mechanism was present in this unicellular chlorophyte. The data suggest an early origin and high conservation of endoplasmic-reticulum-mediated Ca²⁺ functions in eukaryotes, whereby specific posttranslational modifications of the proteinhave been specifically acquired in different lineages of photosynthetic eukaryotes. Moreover, northern and western blot analysis experiments showed a regulation of calreticulin expression during Chlamydomonas sexual reproduction with a high abundance of calreticulin mRNA and protein in reproductive cells.     

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 .     

MITOSIS AND CYTOKINESIS IN ASTEROMONAS GRACILIS, A WALL-LESS GREEN MONAD1

Asteromonas gracilis Artari remains motile throughout cell division. Basal bodies separate and replicate at prophase. They are located lateral to the poles of the closed metaphase spindle. Kinetochores appear at late metaphase. Chromosomes move to the poles and extensions of the nuclear envelope develop into the pyrenoid at anaphase. The interzonal spindle disintegrates at telophase and a diffuse phycoplast is present. Cytokinesis proceeds rapidly from the anterior region of the cell. Newly formed daughter cells have four narrow-banded rootlets and both distal and proximal fibers connect the basal bodies. Features of cell division in Asteromonas are compared to those in other algae, particularly Dunaliella and Chlamydomonas.     

IDENTIFICATION OF A MYOSIN-LIKE PROTEIN IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)1

A myosin-like protein was identified in vegetative cells of the unicellular green alga Chlamydomonas reinhardtii Dangeard. Polyclonal antibodies affinity purified against the heavy chain of slime-mold myosin recognized a 180,000 M_r protein in western blots of total protein extracts from three different strains, including cyt-1, a cytokinesis-defective mutant. Immunoblots of isolated chloroplasts indicated that some of the cellular myosin fractionated with chloroplasts, whereas tubulin did not. Evidence for the presence of at least one myosin gene was obtained by probing Southern blots of genomic DNA with a myosin heavy-chain gene fragment isolated from the green alga Ernodesmis verticillata (Kützing) Børgesen. Collectively, the immunological and molecular data identify at least one myosin heavy-chain gene and a myosin-like protein in vegetative cells of the model organism Chlamydomonas.     

PHYSIOLOGICAL AND HERITABLE CHANGES IN CYCLIC AMP LEVELS ASSOCIATED WITH CHANGES IN FLAGELLAR FORMATION IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)1

Synchronously dividing cells of Chlamydomonas reinhardtii Dang. (Chlorophyta) produce a single peak of cyclic adenosine monophosphate (cAMP), about sevenfold above the basal level, at the time of onset of the flagellar shortening that precedes mitosis. Cultures of a spontaneous palmelloid variant (which forms flagella-less cell clusters) of C. reinhardtii produce up to 15 times more cAMP per gram fresh weight of cells than do cultures of normal C. reinhardtii. Revertants from the palmelloid phenotype to the normal phenotype exhibit the low levels of cAMP characteristic of normal C. reinhardtii. Thus, elevation of cAMP level and decreased ability to form or maintain flagella are closely related phenomena. We propose that flagellar assembly/disassembly is regulated by endogenous cAMP in C. reinhardtii.     

BIOCHEMICAL, PHYSIOLOGICAL, AND MOLECULAR ANALYSIS OF SEXUAL ISOLATION IN THE SPECIES COMPLEX CLOSTERIUM PERACEROSUM-STRIGOSUM-LITTORALE (CHLOROPHYTA)1

Closterium strains obtained from Japan ( NIES-64 and -65 ) and Nepal ( NIES-67 and -68 ) have been classified as the same taxonomic species; however, they are sexually isolated from each other. When NIES-64 and -65 cells were separately incubated in a medium in which both strains had previously been cultured together, release of protoplasts from both strains was observed. We suggest that factors responsible for the release of protoplasts from cells of both NIES-64 and -65 are produced in a mixed culture of these cells and function during conjugation. These factors, however, had no effect on the release of protoplasts from cells of strains NIFS-67 or -68. Alternatively, a protein that is responsible for the release of protoplasts from cells of NIES-68, called the protoplast-release-inducing protein ( PR-IP ), had no effect on the release of protoplasts from cells of strains NIES-64 or -65. When the media obtained from the culture of NIES-64 and -65 cells at various mixing ratios were analyzed by western blotting with antiserum to a 42-kDa subunit of PR-IP, no cross reaction was detected. In Southern hybridization analysis, no hybridizing band was observed when genomic DNAs of NIES-64 and -65 cells were probed with cDNAs encoding the two subunits of PR-IP. We suggest from these results that the factors responsible for the release of protoplasts from NIES-64 and -65 cells are not structurally similar to PR-IP. It is known that the release of PR-IP from NIES-67 cells can be induced by the action of another sex pheromone ( PR-IP inducer ) which is released by NIES-68 cells. In contrast, no protoplast-release-inducing activity was observed from either NIES-64 or -65 in a culture medium conditioned by opposite strains. We suggest that the conjugation systems employed by strains NIES-64/ NIES-65 and strains NIES-67 /NIES-68 differ, and we propose a possible mechanism of sexual isolation between these biological species .     

MORPHOLOGY AND PAEDOGAMOUS SEXUAL REPRODUCTION IN CHLOROGONIUM CAPILLATUM SP. NOV. (VOLVOCALES, CHLOROPHYTA)1

Morphology and sexual reproduction in Chlorogonium capillatum Nozaki, Watanabe & Aizawa sp. nov. (Volvocales, Chlorophyta) originating from Miyatoko Mire, Japan, were studied under controlled laboratory conditions. Vegetative cells of this new species were fusiform with blunt anterior and posterior ends, and they had a massive parietal chloroplast and numerous contractile vacuoles distributed throughout the protoplast. Several to many pyrenoids were randomly distributed in the chloroplast, but they disappeared under the light microscope when grown photoheterotrophically. During asexual reproduction, the first division took place transversely without a preceding rotation of the parental protoplast. In sexual reproduction, the parental protoplast divided successively to form 32 or 64 small, biflagellate isogametes. After gametogenesis, the gametes did not escape from the parental cell (gametangial) wall, within which pairs of the adjoining gametes fused to form quadriflagellate zygotes. Such zygotes were then released from the parental cell wall and developed into hypnozygotes, which at maturity developed numerous thin spines or hairs on the zygote wall. On zygote germination, four biflagellate germ cells were released from the zygote wall separately. This type of gametic union, paedogamy, has not previously been described in the green algae except for Chlorococcum echinozygotum Starr . Chlorogonium capillatum can be clearly distinguished from other described species of Chlorogonium by its numerous contractile vacuoles and blunt anterior and posterior ends in vegetative cells as well as by its unique sexual reproduction, in which paedogamous conjugation occurs, and numerous thin spines or hairs that develop on the hypnozygote walls .     

DETECTION OF CHLOROPHYLLS c1, c2 AND c3 IN PIGMENT EXTRACTS OF PRYMNESIUM PARWM (PRYMNESIOPHYCEAE)1

Three chlorophyll c-type pigments were separated by reversed-phase high Performance liquid chromatography and thin-layer chromatography from pigment extracts of the prymnesiophyte, Prymnesium parvum Carter. Based on spectral characteristics, retention times, and comparison with reference pigments isolated from the diatom Phaeodactylum tricornutum Bohlin, two of these pigments were identijied as chlorophyll c₁ and c₂. The other pigment was identified by its absorption spectrum and thin-layer chromatography retention times as the newly described chlorophyll c₃. However, in other prymnesiophytes so far examined, chlorophyll c₁ and chlorophyll c₃ were present with no chlorophyll c_l. The discovery of chlorophyll c₃ with chlorophyll c₁ and chlorophyll c₃ in Prymnesium parvum therefore represents the first report of this combination of pigments in prymnesiophytes.     

NOTE—THE STA-1 MUTATION PREVENTS ASSEMBLY OF STARCH GRANULES IN NITROGEN-STARVED CELLS AND SERVES AS A USEFUL MORPHOLOGICAL MARKER DURING SEXUAL REPRODUCTION IN CHLAMYDOMONAS MONOICA (CHLOROPHYCEAE)

Iodine staining of clones of nitrogen-starved Chlamydomonas cells was used to screen for mutants with altered levels or altered composition of storage starch. Mutations leading to defects in quantity or morphology of starch granules not only can provide information on storage starch biosynthesis and granule assembly but can also be used as morphological markers in genetic and cell biological studies. A mutant of Chlamydomonas monoica Strehlow devoid of starch granules was obtained following ultraviolet mutagenesis. Nitrogen-starved cells of the sta-1 strain lacked pyrenoidal starch granules and granules normally associated with thylakoid membranes. The mutant phenotype was the consequence of a single Mendelian mutation that appeared to affect granule assembly rather than starch biosynthesis per se and that had no effect on vegetative growth, sexual reproduction, or zygospore viability.     

PIGMENT COMPOSITION OF THE SCALY GREEN FLAGELLATE MESOSTIGMA VIRIDE (MICROMONADOPHYCEAE) IS SIMILAR TO THAT OF THE SIPHONOUS GREEN ALGA BRYOPIS PLUMOSA (ULVOPHYCEAE)1

Pigments were isolated from Mesostigma viride Lauterborn by reversed-phase high-performance liquid chromatography and compared to standards from Chlamydomonas reinhardtii Dang. and Bryopsis plumose (Huds.) Ag. M. viride possesses chlorophylls a and b, α and β-carotenes, and the xanthophylls siphonaxanthis, siphonein, neoxanthin, violaxanthin and echinenone. In addition, three unidentified xanthophylla were detected. Neither lutein nor zeaxanthin were detected. The pigment composition of M. viride was similar to that of B. plumosa which had chlorophylls a and b, ?- and α-carotenes, siphonaxanthin, siphonein, neoxanthin, violaxanthin, and two of the unidentified xanthophylls found in M. viride. The similarities in the pigments of Mesostigma and Bryopsis and other characters suggest that Mesostigma may be related to a flagellate ancestor of the Ulvophyceae.     

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.     

MICROALGAL LIGHT-HARVESTING IN EXTREME LOW-LIGHT ENVIRONMENTS IN MCMURDO SOUND, ANTARCTICA1

Microalgal pigment composition, photosynthetic characteristics, single-cell absorption efficiency (Qa_(λ)) spectra, and fluorescence-excitation (FE) spectra were determined for platelet ice and benthic communities underlying fast ice in Mc Murdo Sound, Antarctica, during austral spring 1988. Measurements of spectral irradiance (E_(λ)) and photosynthetically active radiation (PAR) as well as samples for particulate absorption measurements were taken directly under the congelation ice, within the platelet layer, as profiles vertically through the water column, and at the benihic surface. Light attenuation by.sea ice, algal pigments, and particulates reduced PAR reaching the platelet ice layer to 3%(9–33 fimol photons m-²-^?s-¹) of surface values and narrowed its spectral distribution to a band between 400 and 580 nm. Attenuation by the water column further reduced PAR reaching the sea floor (28–m depth) to 0.05% of surface levels (< 1 μmol photons m-² s-¹), with a spectral distribution dominated by 470–580–nm wavelengths. The photoadaptive index (I) for platelet ice algae (5.9–12.6 μmol photons m-^2.s-¹) was similar to ambient PAR, indicating that algae had acclimated to their light environment (i.e. the algae were light-replete). Maximum Qa_(λ) at the blue absorption peak (440 nm) was 0.63, and enhanced absorption was observed from 460–500 nm and was consistent with observed high cellular chlorophyll (chi) c:chl a and fucoxanthin: chl a molar ratios (0.4 and 1.2, respectively). Benthic algae were light-limited despite the maintenance of very low I_k values (4–11 μmol photons.m-^2.s-¹). Extremely high fucoxanthin: chi a ratios (1.6) in benthic algae produced enhanced green light absorption, resulting in a high degree of complementation between algal absorption and ambient spectral irradiance. Qa_(λ) values for benthic algae were maximal (0.9) between 400 and 510 nm but remained >0.35 even at absorption minima. Strong spectral flattening, a characteristic of intense pigment packaging, was also apparent in the Qa_(λ) spectra for benthic algae. FE and Qa_(λ) spectra were similar in shape for platelet ice algae, indicating that the efficiency at which absorbed energy was transferred to photosystem II (PSII) was independent of wavelength. Fluorescence emission by benthic algae was greatest for the 500–560–nm excitation wavelengths, suggesting that most energy absorbed by accessory pigments was transferred to PSII. These results suggest that under ice algae employ complementary pigmentation and maximize absorption efficiency as adaptive strategies to low-light stress. Regulating the distribution of absorbed energy between PSI and PSII may be an adaptive response to the restricted spectral distribution of irradiance.     

MOUSE NEUROBLASTOMA CELL ADENYLATE CYCLASE: REGULATION BY 2-CHLOROADENOSINE, PROSTAGLANDIN E1 AND THE CATIONS Mg2+, Ca2+ AND Mn

—Some basic kinetic properties of adenylate cyclase in cell free preparations of mouse neuroblastoma were investigated. Production of cAMP from ATP by the enzyme requires the presence of either Mg²⁺ or Mn²⁺ in addition to ATP. In the presence of Mg²⁺, the K_m for ATP is 120 ± 15 μM and the interaction of ATP and adenylate cyclase appears to be non-cooperative (Hill coefficient of 1). Magnesium ion concentrations in excess of the ATP concentration cause stimulation although similar excess concentrations of Mn²⁺ cause inhibition. Prostaglandin E₁ and 2-chloroadenosine activate the enzyme. The K_m of the cyclase for 2-chloroadenosine is 6 μm . Activation by 2-chloroadenosine leads to an increase in V_max but does not effect the K_m for ATP. At a fixed ATP concentration, the extent of activation caused by prostaglandin E₁ and 2-chloroadenosine is inversely related to the Mg²⁺ concentration. Calcium ion causes inhibition of adenylate cyclase from 0.1 to 4mM with a K_i of 5 ± 10^?4m . Ca²⁺ interaction with the enzyme in the absence or presence of either 2-chloroadenosine or prostaglandin E₁ appears cooperative (i.e. Hill coefficients of ?2). Ca²⁺ inhibition is non-competitive with respect to either ATP or 2-chloroadenosine but is progressively diminished by increasing Mn²⁺ concentrations. Divalent cation effects and activation by 2-chloroadenosine and prostaglandin E₁ of the neuroblastoma adenylate cyclase are compared with ion effects and hormone activation of the enzyme obtained from non-neuronal tissue.     

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 .     

BRAIN ACETYLCHOLINE AND CHOLINESTERASE: EFFECT OF PHENOTHIAZINES AND PHYSOSTIGMINE INTERACTION IN RATS1

Abstract— The effect of phenothiazines either alone or in combination with physostigmine on whole brain acetylcholine concn and cholinesterase activity has been investigated in male rats. Phenothiazines (chlorpromazine, trifluperazine and thioridazine) when injected alone had no significant effect on brain acetylcholine concentration. Pretreatment with chlorpromazine and thioridazine significantly enhanced the physostigmine-induced increase in brain acetylcholine concn and inhibition of cholinesterase activity. However, trifluperazine had no significant effect on the physostigmine-induced increase in brain acetylcholine concentration and inhibition of cholinesterase activity. The potentiation of the physostigmine-induced increase in brain acetylcholine concn by phenothiazines may be due to (1) increased acetylcholine turnover secondary to the blockade of dopamine receptors by neuroleptic drugs and.     

PHYSIOLOGICAL RESPONSES TO TEMPERATURE AND IRRADIANCE IN SPIROGYRA (ZYGNEMATALES, CHAROPHYCEAE)1

Spirogyra Link (1820) is an anabranched filamentous green alga that forms free-floating mats in shallow waters. It occurs widely in static waters such as ponds and ditches, sheltered littoral areas of lakes, and stow-flowing streams. Field observations of its seasonal distribution suggest that the 70-μm-wide filament form of Spirogyra should have a cool temperature and high irradiance optimum for net photosynthesis. Measurements of net photosynthesis and respiration were marie at 58 combinations of tight and temperature in a controlled environment facility. Optimum conditions were 25°C and 1500 μmol photons m⁻² s⁻¹, at which net photosynthesis averaged 75.7 mg O₂ gdm⁻¹ h⁻¹. Net photosynthesis was positive at temperatures from 5° to 35°C at most irradiances except at combinations of extremely low irradiances and high temperatures (7 and 23 μmol photons m⁻² s⁻¹ at 30°C and 7, 23, and 35 μmol photons m⁻² s⁻¹ at 35°C). Respiration rates increased with both temperature and prior irradiance. Light-enhanced respiration rates were significantly greater than dark respiration rates following irradiances of 750 μmol photons m⁻² s⁻¹ or greater. Polynomials were fitted to the data to generate response surfaces; such response surfaces can be used to represent net photosynthesis and respiration in ecological models. The data indicate that the alga can tolerate the cool water and high irradiances characteristic of early spring but cannot maintain positive net photosynthesis under conditions of high temperature and low light (e.g. when exposed to self-shading ).