The effect of dibutyryl cyclic AMP on the expression of actin isoforms in astroglia

Mammalian cells contain at least 8 actin isoforms. The functional significance and the mechanisms that regulate the expression of each actin isoform are not yet known. Using immunofluorescence staining, it was found that all astroglia in tissue culture express -actin isoform and about 86% of astroglia express -smooth muscle actin isoform. When astroglia were treated with dibutyryl cyclic AMP for 4,7,14 and 21 days, it was found that the number of the cells expressing -smooth muscle actin isoform progressively decreased, whereas, the number of the cells expressing -actin isoform remained constant. The western blot experiment showed that the amount of total -smooth muscle actin isoform (soluble and insoluble) and of the insoluble isoform expressed by astroglia treated with dibutyryl cAMP decreased whereas, the amount of total and insoluble -actin isoform expressed by the same cells did not show any significant changes. The cells treated with the cAMP failed to migrate and to close the area created by the scratch wound in monolayer culture. However, the non-treated cells migrated and closed the area created by the scratch after 3 days. This study shows that the astroglia have different mechanisms in regulating the expression of different actin isoforms and that the -sm actin isoform is important in migration of astroglia.     

Interaction of cycloalkanoprogesterones with mammalian progesterone receptor: binding of pregna-D'-pentaranes in the calf uterine cytosol

Pregna-D'-pentaranes (pentaranes) are modified progesterones with demonstrable progestational activity and contraceptive effect. We have examined the steroid binding characteristics of the two newly synthesized progesterone analogs, Pentarane A (16, 17-cyclohexanoprogesterone) and Pentarane B (6-methyl, 16, 17-cyclohexanoprogesterone), and studied the nature of their interaction with progesterone receptor (PR) from the chicken oviduct and the calf uterine cytosols. Pregna-D'-pentaranes exhibited no affinity for the chick PR but interacted with the calf uterine PR as did R5020. The pentaranes, however, bound PR less tightly. R5020- or pentarane-bound PR sedimented as an 8S moiety in 8–30% linear glycerol gradients. Thermal transformation of receptor resulted in the reduction of the 8S form, and caused an increase in the binding of R5020-and progesterone-bound PR complexes to DNA-cellulose. The pentarane-bound PR bound poorly, if at all, to DNA-cellulose. Our data suggest that pentaranes exhibit both similarities and differences with natural and synthetic progestins with respect to their interaction with calf uterine PR. The lack of pentarane binding to chicken PR is reminiscent of the general phenomenon that antiprogestins (RU486, ZK98299, and Org 31710 and Org 31806) do not interact with chicken PR. Pentaranes, therefore, represent unique steroid analogs to investigate the molecular mechanism of steroid hormone action.Abbreviations DMSO Dimethyl sulfoxide - DTT Dithiothreitol - E Estradiol - EDTA Ethylene-diaminetetraacetate - F Cortisol - IA Iodoacetamide - MER -mercaptoethanol - MTG Monothioglycerol - NEM N-ethylmaleimide - Org 31710 (6, 11, 17)-11-(4-dimethylaminophenyl)-6 methyl-4, 5-dihydro[estra-4, 9-diene-17, 2(3H')-furna]-3-one - Org 31806 (7, 11, 17)-11-(4-dimethyl-aminophenyl)-7 methyl-4, 5-dihydro[estra-4, 9-diene-17, 2(3H)-furan]-3-one - P Progesterone - Pentarane A 16, 17-cyclohexanoprogesterone - Pentarane B 6-methyl, 16, 17-cyclohexanoprogesterone - PMSF Phenylmethylsulfonyl Fluoride - PR Progesterone Receptor - R5020 17, 21-dimethylpregna-4, 9(10)-diene-3     

Solution conformations of proline rings in proteins studied by NMR spectroscopy

Summary Three different conformations of proline rings in a protein in solution, Up, Down and Twist, have been distinguished, and stereospecific assignments of the pyrrolidine -, - and -hydrogens have been made on the basis of ¹H-¹H vicinal coupling constant patterns and intraresidue NOEs. For all three conformations, interhydrogen distances in the pairs -³, ³-³, ²-², ²-², and ³-³ (2.3 Å) are shorter than those in the pairs -², ²-³, ³-², ²-³, and ³-² (2.7–3.0 Å), resulting in stronger NOESY cross peaks. For the Up conformation, the ³-² and ²-³ spin-spin coupling constants are small (<3 Hz), and weak cross peaks are obtained in a short-mixing-time (10 ms) TOCSY spectrum; all other vicinal coupling constants are in the range 5–12 Hz, and result in medium to strong TOCSY cross peaks. For the Down form, the -², ²-³, and ³-² vicinal coupling constants are small, leading to weak TOCSY cross peaks; all other couplings again are in the range 5–12 Hz, and result in medium to strong TOCSY cross peaks. In the case of a Twist conformation, dynamically averaged coupling constants are anticipated. The procedure has been applied to bovine pancreatic trypsin inhibitor and Cucurbita maxima trypsin inhibitor-V, and ring conformations of all prolines in the two proteins have been determined.     

Transforming growth factor ß1 acid interaction

Chick embryo skin fibroblasts release transforming growth factor ₁ that is able to modulate glycosaminoglycan synthesis and secretion. When incubated with individual classes of glycosaminoglycans, the factor's modulatory activity was altered. To determine whether direct interactions between transforming growth factor ₁ and glycosaminoglycans occur, we have assessed the activity of the growth factor after pre-incubation with single classes of glycosaminoglycans by assaying its inhibitory effect upon the proliferative response of thymocytes stimulated with interleukin-1. Untreated transforming growth factor ₁ suppressed the proliferative response of thymocytes to interleukin-1, as did transforming growth factor ₁ pre-incubated with sulphated glycosaminoglycans. By contrast, transforming growth factor ₁ lost its inhibitory capacity when preincubated with high molecular weight hyaluronic acid. Digestion of transforming growth factor ₁-hyaluronic acid complex with hyaluronidase released active transforming growth factor ₁. Trypsin degraded transforming growth factor ₁ alone, but did not degrade the transforming growth factor ₁-hyaluronic acid complex. These results suggest that hyaluronic acid interacts with transforming growth factor ₁, thus protecting the factor from tryptic degradation and may be a means of concentrating growth factor activity.     

Factors affecting the synthesis and distribution ofβ-lactamase inMycobacterium smegmatis SN2 cultures

A high level of extracellular -lactamase activity was detected in cultures ofMycobacterium smegmatis SN2. The extracellular distribution of the enzyme varied with growth conditions such as additional carbon source and pH of the medium. Addition of chloramphenicol tothe culture inhibited the increase in the extracellular -lactamase activity. Cell wall damage or autolysis may be responsible for the extracellular -lactamase activity.     

The genetics of phototaxis in Daphnia magna: Existence of three phenotypes for vertical migration among parthenogenetic females

Using a cloning technique, we revealed the existence of three phototactically distinct types in Daphnia magna, viz. negatives, positives, and gipsies. The latter migrate continuously between a low and a high light intensity. The expression of this behaviour is genetically determined, although positives and negatives can reversibly switch into gipsies.It is proposed that two opposite genotypes exist, with the gipsy behaviour epigenetically induced. All juveniles behave more or less uniformly, irrespective of their origin. The phototactic responses develop rather late during ontogenesis.     

Phylogenetic relationships of the stromateoid fishes (Perciformes)

The phylogenetic relationships of all 16 genera (plus Psenes pellucidus) of the suborder Stromateoidei were estimated cladistically based on 43 osteological, myological, and external characters. Thirty equally parsimonious trees were obtained. Based on the strict consensus tree, Centrolophidae was nonmonophyletic, Psenopsis being placed as a sister group of a clade comprising Amarsipus, Ariomma, nomeids, Tetragonurus, and stromateids. Schedophilus formed a sister group relationship with Seriolella. The relationships among the Centrolophus, Hyperoglyphe, Icichthys, Tubbia, Schedophilus+Seriolella clade, and Psenopsis+Amarsipus+Ariomma+nomeids+Tetragonurus+stromateids clade were unresolved. Amarsipus, which is unique within the suborder in lacking a pharyngeal sac, was nested within the stromateoid clade, being a sister group of the clade including Ariomma, nomeids, Tetragonurus, and stromateids. The absence of a pharyngeal sac in Amarsipus was interpreted as a reversal, its presence in the Stromateoidei therefore being considered as a synapomorphy. Ariomma was placed as the sister group of a clade comprising nomeids, Tetragonurus, and stromateids. Monophyly of the Nomeidae and Stromateidae were supported by 2 and 11 synapomorphies, respectively.     

Stochastic aggregative responses and spatial patterns of parasitism in patchy host-parasitoid interactions

Summary Assuming random search by parasitoids within host-containing patches, and a constant search rate, current host-parasitoid models suggest that positive searching time aggregation by parasitoids in patches of high host density should tend to produce spatially density dependent parasitism at the patch level. However, these models view the aggregative response as a deterministic process, ignoring variability in searching time (T _s) allocation among patches of equal host density, and it is not clear that stochastic analogues of these deterministic models would predict the same result.This question is examined by adding a stochastic aggregative response to the well-known random parasitoid equation, the deterministic equation on which most existing models have been based. Simulations, based on data collected in an earlier laboratory study, indicate that this stochastic model generates very different relationships between parasitoid searching behavior and spatial patterns of parasitism than are predicted using the deterministic approach. The stochastic model suggests that positive aggregative responses, in which patches of high host density receive larger allocations of searching time (on the average) than patches containing lower densities, may fail to produce spatially density dependent parasitism at the patch level if searching time allocation is also more variable at the higher densities. Similarly, a flat response, in which mean searching times do not vary among patches of different host density, may lead to density dependent, density independent, or inversely density dependent parasitism, depending on the variance of the searching time values among patches at different density levels. The different predictions generated by the deterministic and stochastic models can be explained on purely mathematical grounds.When models are written in units of total foraging time (T _TOT), different equations are usually required to describe the spatial features of host-parasitoid and predator-prey interactions. Because the model considered here is written in units of active searching time (T _s) it should, in cases in which the underlying assumptions hold, be capable of describing these different interactions in the framework of a single (unified) equation. This equation may also apply to some plant-herbivore systems and, to indicate its potential generality, might be referred to as a random forager equation.     

Identification of the LH and TSH-secreting cells in the pituitary gland of the rhesus monkey

Summary Pituitary glands from juvenile (pre-pubertal) and adult male and female rhesus monkeys were examined following immunocytochemical staining with antisera to the beta subunits of ovine luteinizing hormone (LH) and of human thyroid stimulating hormone (TSH). The LH antiserum reacts with a cell that is PAS-positive, occurs singly and is randomly distributed throughout the pars distalis. The diameter of these cells is approximately 11.5 m. They do not seem to vary in number in either juveniles (pre-pubertals) or adults, or in males or females. There appears to be fewer LH cells in the pituitary glands of pregnant and lactating females. In addition to staining cells in the pars distalis, the antiserum also reacts with a population of cells located in the pars tuberalis.The cells that stain with the anti-TSH serum are confined primarily to the pars distalis. They are approximately 15.8 m in diameter and are generally found in groups or clusters located in the anterior and medial regions of the gland. The TSH cells vary in number from one animal to another; however, this variability is unrelated to the age or the sex of the animals. No demonstrable changes occur in the number of TSH cells during pregnancy or lactation.Supported by NIH General Research Support Grant RR05654The author wishes to express appreciation to the Hormone Distribution Program of NIAMDD for the preparations of ovine FSH, TSH and human TSH, and to Drs. H. Papkoff for the ovine LH and LH, L. Reichert for the human FSH, J. Vaitukaitis for the anti-human TSH, and L.A. Sternberger for the PAP complex     

Glycosphingolipids of leukocytes are unbranched at the galactopyranosyl residue and contain fucosylα-1-3-N-acetylglucosamine structures

Glycolipids of peripheral leukocytes which had been used for the production of interferon were separated into oligoglycosylceramides, polyglycosylceramides and polyglycosylpeptides (erythroglycan). Neutral oligoglycosylceramides comprised glucosylceramide, galactosylceramide, lactosylceramide, lactotriaosylceramide, globotriaosylceramide andneolactotetraosylceramide. Globotetraosylceramide was not detected. Glycolipids which were more complex thanneolactotetraosylceramide belonged exclusively to theneolacto series of compounds and were essentially unbranched at galactopyranosyl residues. The polyglycosylceramide fraction contained a glycolipid with a probable structure Gal1-4(Fuc1-3) GlcNAc1-3Gal1-4GlcNAc1-3 Gal1-4GlcNAc1-3Gal1-4Glc1-1ceramide. Polyglycosylpeptides were found only in trace amounts and were also unbranched at galactopyranosyl residues. All glycoconjugates studies did not contain significant amounts of carbohydrate structures derived from ABH immunodominant groups.Nomenclature Gal1-4Gal1-4GlcCer Lactotrioasylcermide (LcOse₃Cer) - Gal1-4Gal1-4GlcCer globotriaosylceramide, (GbOse₄Cer) - GalNAc1-3Gal1-4 Gal1-4GlcCer globoside (globotetraosylceramide, GbOse₄Cer) - Gal1-4GlcNAc1-3Gal1-4GlcCer paragloboside (lacto-N-neo tetraosylceramide,nLcOse₄Cer)     

Detection and partial characterization of two antigenically distinct β-amylases in developing kernels of wheat

A -amylase (EC 3.2.1.2) was identified in the outer pericarp (P) of developing seeds of wheat (Triticum aestivum L.) and compared with the well known -amylase which is synthesized during seed development in the starchy endosperm (E). The enzyme P already exists in the tissues before anthesis and vanishes at the time when E starts to accumulate. The isoelectric-focusing patterns of P and E are very similar. The relative molecular weight (M_r) of P is slightly higher than that of E (66 and 64.5 kDa, respectively). Both P and E exhibit common epitopes in addition to epitopes specific for each of them. The two enzymes were identified in small amounts in the green tissues of the developing seeds (inner pericarp and testa). No antigenic difference was detected between P and the -amylases of roots and leaves.Abbreviations P pericarp -amylase - E endosperm -amylase - IS1 anti--amylase immune serum - IS2 anti- and anti- amylase immune serum - IS3 anti- amylase immune serum - IEF isoelectric focusing - IgG immunoglobulin G The authors thank Dr. P. Ziegler (Universität Bayreuth, FRG) for stimulating discussion and for useful suggestions during the writing of the text. The authors thank Miss C. Mayer for her skillful technical assistance.     

Adventitious shoot organogenesis and plant regeneration from cotyledons of Dalbergia sissoo Roxb., a timber yielding tree legume

A procedure is outlined to induce adventitious shoot organogenesis from semi-mature as well as mature cotyledons lacking the embryonic axis of Dalbergia sissoo Roxb., an economically important leguminous tree. Shoot buds were induced in the proximal region of the semi-mature cotyledons on Murashige and Skoog's (MS) medium supplemented with 4.44 M 6-benzyladenine (BA) and 0.26 M -naphthaleneacetic acid (NAA). These buds elongated into shoots following transfer to a similar medium containing half-strength macro-nutrients. Adventitious shoot bud formation was also induced in the mature cotyledons. However, unlike the semi-mature explants, the mature cotyledons exhibited shoot bud differentiation on MS medium containing 22.20 M BA without NAA. Pre-culture of mature cotyledons in liquid MS medium containing 8.88 M BA for a duration of 48 h improved shoot bud regeneration up to six-fold. Regenerated shoots, derived from semi-mature and mature cotyledons, rooted on half-strength MS medium containing 1.23 M and 4.92 M indole-3-butyric acid (IBA), respectively. Plantlets were acclimatized and established in soil.     

Comparative residual toxicities of pesticides to the predator Agistemus industani (Acari: Stigmaeidae) on citrus in Florida

Residual toxicities of registered and selected experimental pesticides used on citrus against Agistemus industani Gonzalez (Acari: Stigmaeidae) were compared. Pesticides considered highly toxic to A. industani were: abamectin 0.15 EC at 731ml/ha+FC 435-66 petroleum oil at 46.8l/ha, pyridaben 75WP at 469g/ha, ethion 4EC at 7.01l/ha+FC 435-66 petroleum oil at 46.8l/ha, propargite 6.55 EC at 3.51l/ha, chlorfenapyr 2SC at 1.46l/ha applied alone or in combination with FC 435-66 petroleum oil at 46.8l/ha, sulphur 80DF at 16.81kg/ha, dicofol 4EC at 7.01l/ha, fenbutatin oxide 50WP at 2.24kg/ha, benomyl 50WP at 2.24kg/ha, benomyl 50WP at 1.68kg/ha+ferbam 76 GF at 5.60kg/ha, ferbam 76GF at 11.21kg/ha, neem oil 90EC at 46.8l/ha, and copper hydroxide DF (40% metallic copper) at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha. Pesticides that were moderately to slightly toxic included: copper sulphate 98% at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha, fenbuconazole 2F at 280ml/ha+FC 435-66 petroleum oil at 46.8l/ha, FC 435-66 petroleum oil applied alone at 46.8l/ha or 23.4l/ha, and diflubenzuron 25WP at 1.40kg/ha. Pesticides that were non-toxic included: fenbuconazole 2F at 585ml/ha, malathion 57EC at 5.85l/ha, FC 435-66 petroleum oil at 46.8l/ha, carbaryl 80S at 3.36kg/ha, chlorpyrifos 4EC at 4.68l/ha, and formetanate 92SP at 1.12kg/ha. Understanding the toxic effects of field weathered pesticides against key predacious mite species is important for effective IPM. The results of this study provide a comparison of direct and indirect toxic effects of various pesticides to A. industani under field conditions.     

Studies of the action of ceramide-like substances (d- andl-PDMP) on sphingolipid glycosyltransferases and purified lactosylceramide synthase

We have studied the effects ofD-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP) and itsL-enantiomer on glycosphingolipids in cultured normal human kidney proximal tubular cells. We found thatD-PDMP exerted a concentration-dependent reduction in the metabolic labelling and cellular levels of glucosylceramide (GlcCer), lactosylceramide (LacCer), and the globo-series glycosphingolipids, GbOse₃Cer and GbOse₄Cer. It also directly inhibited the activity of UDP-glucose:ceramide 1 4-glucosyltransferase (GlcT-1) and UDP-galactose: GlcCer 1 4 galactosyltransferase (GalT-2). In contrast,L-PDMP had opposite effects on the metabolic labelling of GlcCer, LacCer, and GbOse₃Cer. The levels of GlcCer and LacCer were increased, while the labelling and level of GbOse₄Cer were strongly reduced. Purified GalT-2 from human kidney was inhibited byD-PDMP and stimulated byL-PDMP. It appears likely that the different glycosphingolipid glycosyltransferases possess similar binding sites for the ceramide moiety, which are blocked by binding toD-PDMP and, in the case of GbOse₄Cer synthase, byL-PDMP as well. The stimulatory effects ofL-PDMP on GlcCer and LacCer synthases may be the result of binding to a modulatory site on the glycosyltransferases; in intact cells, the enzyme-analog complex may afford protection against the normal catabolic inactivation of the enzymes.Abbreviations GalT-2 UDP-galactose:GlcCer -galactosyltransferase - GbOse₃Cer Gal1 4Gal1 GlcCer - GbOse₄Cer GalNAc1 3Gal1 4Gal1 GlcCer - GlcCer glucosylceramide - GlcT-1 UDP-glucose:ceramide -glucosyltransferase - GSLs glycosphingolipids - LacCer lactosylceramide - PDMP threo-1-phenyl-2-decanolyamino-3-morpholino-1-propanol     

Conservation status of parrot populations in an Atlantic rainforest area of southeastern Brazil

A census of four species of syntopic parrots was carried out using distance sampling methods on São Sebastião island, SE Brazil. Most of the 33593 ha island is covered by mature and secondary Atlantic rainforest. Almost 80% of these forests are within the Ilhabela Park. Although the species counted have marked differences in size and weight, density (individuals/km²) and estimated population size in 23500 ha of well-preserved forests were similar: Amazona farinosa (13.82±5.94; 3247±1395), Pionus maximiliani (15.79±7.04; 3712±1654), Brotogeris tirica (15.05±4.87; 3537±1143) and Pyrrhura frontalis (13.06±5.53; 3068±1298). Encounter rates of Forpus crassirostris and Pionopsitta pileata were very low, which suggests that there is only a small population of these species on the island. The São Sebastião forests still support healthy populations of parrots. Although woodpecker population estimates on the island are large enough to provide nesting sites for parrots, competition for holes with other secondary cavity nesters such as toucans, flycatchers and tytiras, and the selective cutting of dead trees for canoe construction, which is a common practice on the island, may limit hole availability for parrots.     

Intracellular sites of the synthesis of sweet potato mitochondrial F1ATPase subunits

Summary Five subunits (-, -, -, - and -subunits) of the six -and -subunits) in the F₁ portion (F₁ATPase) of sweet potato (Ipomoea batatas) mitochondrial adenosine triphosphatase were isolated by an electrophoretic method. The - and -subunits were not distinguishable immunologically but showed completely different tryptic peptide maps, indicating that they were different molecular species. In vitro protein synthesis with isolated sweet potato root mitochondria produced only the -subunit when analyzed with anti-sweet potato F₁ATPase antibody reacting with all the subunits except the -subunit. Sweet potato root poly(A)⁺RNA directed the synthesis of six polypeptides which were immunoprecipitated by the antibody: two of them immunologically related to the -subunit and the others to the - and -subunits. We conclude that the -subunit of the F₁ATPase is synthesized only in the mitochondria and the -, - and -subunits are in the cytoplasm.     

Organization of the nervous system of physonectid siphonophores

Summary An antiserum to the sequence Arg-Phe-amide (RFamide) was used to stain the nervous systems of various physonectid siphonophores. In the stem of Nanomia bijuga, this antiserum stained an ectodermal nerve net, which was interrupted, at regular intervals, by transverse collars of neurons. Injection of Lucifer yellow into the giant axon of the stem showed that this axon was dye-coupled to an ectodermal nerve net that resembled the RFamide-positive network. Ectodermal nets of neurons were also found in the pneumatophore, gastrozooids, tentacles and tentilla. At the junctions of the pneumatophore, the gastrozooids, the dactylozooids and the gonozooids with the stem, and at the junctions of tentacles and tentilla, collars or rings of neurons occurred. The stem was connected to the phyllozooids and nectophores by muscular lamellae, which were bordered by chains of neurons. At the margin of the nectophores, an immunoreactive nerve ring was found. Connected to this ring and located in theseitliche Zapfen (sidely-located patche), were two agglomerations of nerve cells. On the upper side of the bell margin, positioned at 90° relative to the seitliche Zapfen, a delta-shaped neuronal structure was found. This structure was connected to the nerve ring and was associated with a muscle, which ran a short distance along the exumbrellar surface.The nervous systems of Agalma elegans, Forskalia edwardsi, Forskalia leuckarti and Halistemma rubrum resembled that of Nanomia bijuga in all major respects.     

Sterol conjugates of two phenotypically different calli of Beta vulgaris

Steryl glycosides are the predominant form of sterol at 88% of the total sterol in non-betalain producing calli of Beta vulgaris. The total sterol decreases and sterol form shifts from steryl glycosides to 97% free sterol upon the transition of non-betalain to betalain producing calli. A substantial decrease in stigmasterol (24--ethylcholesta-5,22E-dien-3-ol) and sitosterol (24-ethylcholest-5-en-3-ol) levels is observed during this transition, and alters the ratio of ⁷:⁵ sterols. Spinasterol (24- ethyl-5-cholesta-7,22E-dien-3-ol) is the dominant sterol at 43% and 95% of the total sterol in non-betalain producing and betalain producing calli. The level of 22-dihydrospinasterol (24-ethyl-5-cholest-7-en-3-ol) is reduced in both calli to 3% from 25% in leaves. Lanosterol (4,4,14-trimethyl-cholesta-8(9),24-dien-3-ol) and cycloartenol (9,19-cyclopropyl-4,4,14-trimethyl-cholest-24-en-3-ol) were identified in betalain and nonbetalain producing callus respectively.     

Geochemical controls for Al, Fe, Mn, Cd, Cu, Pb, and Zn during experimental acidification and recovery of Little Rock Lake, WI, USA

Concentrations of Al, Fe, Mn, Cd, Cu, Pb, and Zn were measured in thereference and treatment basins of Little Rock Lake (Vilas County, Wisconsin), alow-alkalinity, seepage system (pH 6.1, alkalinity25eq/L) during six years of a whole-basinacidificationand the first four years of the lake's recovery. The treatment basin wasacidified with H₂SO₄ in three two-year steps to pH5.6, 5.1, and 4.7. By the end of year 4 of recovery, treatmentbasin pH increased to 5.3 as a result of internal alkalinity generation.During acidification, dissolved Mn and Fe (0.4mpore-size filters) increased at pH 5.6; dissolved Al, Cd, and Zn becameelevated at pH 5.1; and dissolved Pb at pH 4.7. Dissolved Cu remainedsimilar in both basins to pH 4.7. Al, Fe and Mn levels declinedsignificantly during the recovery period, approaching values at pH 5.3intermediate between the concentrations at pH 5.6 and 5.1 during acidification.Dissolved Al and Fe in the reference basin were near the equilibrium levels forsolubility of gibbsite (Al(OH)₃) and amorphousFe(OH)₃(s).The acidified basin was undersaturated relative to gibbsite, and dissolved Alwas limited by pH disequilibrium between the water column and sediments andpossibly by Al-DOC precipitation. Dissolved Fe apparently was controlled bysolubility of amorphous Fe(OH)₃(s) and Fe-DOC precipitation.Dissolved Mn levels in both basins were consistent with manganite[-MnOOH(s)] solubility. Elevated levels of Cd, Pb, and Zn in thetreatment basin during acidification probably resulted from less efficientscavenging of atmospherically-deposited Cd, Pb, and Zn by settling particles.     

Regulation of somatic embryogenesis in celery cell suspensions

Embryogenic suspension cultures of celery (Apium graveolens L.) were established from petiole and leaf callus. Suspensions were routinely subcultured in a maintenance medium (with 2.3 M 2,4-D and 0.88 M BA). Somatic embryogenesis occurred in this medium, but was considerably improved in a regeneration medium (2.3 M kinetin, without 2,4-D). Cultures thus maintained, contained embryogenic clumps, aggregated somatic embryos, and few free-floating singular somatic embryos. Addition of mannitol (3–4% w/v) prevented cell lysis, greatly increased the number of singular somatic embryos, improved their normal differentiation, and accelerated torpedo embryo development. Experiments to reveal the nature of the mannitol effect demonstrated that the decreased osmotic potential was an important factor, but not the only one: iso-molar solutions of sucrose alone were not as effective. The mannitol effect could be manifested after a short (2–3 days) exposure period, suggesting a trigger (induction) mechanism. Several pathways of somatic embryogenesis in celery and its regulation by subculturing, with the addition of mannitol, are outlined. Cultures thus maintained resulted in a high rate of normal somatic embryogenesis and production of normal transplantable celery plants.