Plantlet regeneration from mesophyll protoplasts ofBetula platyphylla var.japonica

Summary InBetula platyphylla var.japonica, colonies were induced efficiently from mesophyll protoplasts cultured in half strength MS (1/2MS) liquid medium containing 0.6 M mannitol, 0.09M sucrose and 1 M 4-PU and 1 M NAA at a cell density of 5 × 10⁴/ml. The colonies grew actively and developed into callus after 3 months of culture.Roots differentiated from the protoplast-derived white calluses cultured on the 1 /2MS solid media supplemented with 0.1–1 M 4-PU and 1 M NAA, and 10 M zeatin with no supplementation of NAA. Furthermore, the protoplast-derived green callus differentiated shoots with 1/2MS solid medium containing 1 M 4-PU or 10 M zeatin with no supplementation of NAA. When shoots obtained were cultured on the cytokinin-free MS solid medium with 2.5 M IBA and 0.1 M NAA, they rooted and developed into plantlets after one month of culture.The phenylurea-type cytokinin, 4-PU, was effective for plantlet regeneration from the mesophyll protoplasts ofB. platyphylla var.japonica. This suggests that there is potential for the use of 4-PU in the culture of protoplasts in many forest tree species.Abbreviations BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - FDA fluorescein diacetate - IBA indole-3-butyric acid - 2ip N ⁶-(2-isopentenyl)-adenine - NAA 1-naphthaleneacetic acid - 4-PU N-(2-chloro-4-pyridyl)-N–phenylurea - TDZ thidiazuron     

Photoreceptor membrane breakdown in the spider Dinopis: The fate of rhabdomere products

Summary Photoreceptor membrane breakdown at dawn in the posterior median eyes of the spider Dinopis is described. Coated and smooth vesicles are shed into the receptor cytoplasm and are assembled into multivesicular bodies of two kinds: (i) Coated vesicles form loosely-assembled multivesicular bodies (mvbs) whose bounding membranes are derived from endoplasmic reticulum. (ii) Smooth vesicles generated by the mass disintegration of membrane aggregate to yield tightly-assembled multivesicular bodies which are not membrane-bound. Both types are either lysed in the inter-rhabdomeral cytoplasm, or degrade via multi-lamellar bodies to residual bodies (rbs) while they are being transported to the intermediate segments. Two systems are associated with lysis. Nebenkerne produced by the rapid differentiation of GERL in the intermediate segments fuse with membrane-bound mvbs or rbs and may inject them with hydrolases. Partially-differentiated rigid tubules (Blest et al., 1978) travel to the receptive segments together with RER from the intermediate segments and also fuse with or engulf mvbs. Both systems may contain pro-enzymes which are activated at their target sites. No evidence of a close or necessary geometrical relationship between GERL and Golgi bodies has been seen, and there is no clear demarcation between RER, smooth ER and GERL which is entering into continuity with or engulfing mvbs. The implications of these findings for hypotheses about the origins of isolation membranes and autolytic systems in invertebrate systems are briefly discussed.The authors thank Professor D.T. Anderson, F.R.S., for our use of field facilities at the Crommelin Biological Field Station of Sydney University at Warrah, Pearl Beach, N.S.W., Andrew & Sally Austin and Sally Stowe for help in the field, and Joanne Maples for technical assistance. Professor T.H. Waterman and Dr. V.B. Meyer-Rochow kindly gave us access to certain of their results prior to publication. We are indebted to Rod Whitty and the Electron Microscopy Unit for advice and support throughout these studies     

Osmotic measurements on stomatal cells ofCommelina communis L.

Summary Observations of aperture changes as sucrose is added to the solution bathing epidermal strips ofCommelina communis L. allow calculation of the osmotic changes required to open or close the stomatal pore, for comparison with changes in potassium content. With isolated guard cells, in strips in which all cells other than guard cells have been killed, the internal osmotic changes required are 83 mosmol kg^–1 m^–1 below 10m aperture, 129 mosmol kg^–1 m^–1 in the range 10–15 m, and 180 mosmol kg^–1 m^–1 above 15 m. For opening against subsidiary cell turgor in addition to guard cell turgor, in intact strips with live subsidiary and epidermal cells, these figures should each be increased by about 33 mosmol kg^–1 m^–1. A change in subsidiary cell turgor is magnified in its effects on the water relations of the guard cell by a factor greater than 3.7 for equal changes in the water potential of the two cells, or greater than 4.7 at constant volume of the guard cell.     

The use of antimicrotubule herbicides for the production of doubled haploid plants from anther-derived maize callus

Summary Four antimicrotubule herbicides, amiprophosmethyl (APM), pronamide, oryzalin, and trifluralin, were evaluated for their ability to induce chromosome doubling in anther-derived, haploid maize callus. Effects of various herbicide treatments on the growth and regenerative capacity of callus along with the ploidy and seed set of regenerated plants were determined. Flow cytometric analysis was also used to measure changes in ploidy levels of callus cells following treatments. More than 50% of the cells were doubled in chromosome number after the haploid callus was treated with 5 or 10 M APM or 10 M pronamide for 3 days. A similar proportion of plants regenerated from the treated callus produced seed upon self-pollination. APM and pronamide did not inhibit callus growth at these concentrations and the treated callus retained a high plant regeneration capacity. Oryzalin very effectively induced chromosome doubling, but severely inhibited the growth of regenerable callus and plant regeneration. Trifluralin induced chromosome doubling in a small proportion of cells at lower concentrations (0.5 and 1 M), however, at a higher concentration (5 M) it inhibited callus growth and plant regeneration. The results indicate that APM and pronamide may be useful agents for inducing chromosome doubling of anther-derived maize haploid callus at very low concentrations.     

A new mechanism for transitory,local endocytosis in photoreceptors of a spider,Dinopis

Summary Intermediate segment outgrowths (ISOs) are transitory specialisations of the plasma membrane of intermediate segments of the posterior median photoreceptors of Dinopis. Local regions form outgrowths into the glial partitions separating the receptors and remain connected to their parent intermediate segments by narrow necks. ISOs, only a few m in diameter, are sites of intense endocytosis. Coated pits in their plasma membranes give rise to saccular internalisations. Unusual, slender, endocytotic tubules either pinch off coated vesicles, or become detached to yield a tubular detritus. Products of endocytosis are assembled to yield multivesicular and dense bodies, which are usually surrounded by smooth saccules derived from the endoplasmic reticulum of the intermediate segment. ISOs also contain arrays of tubules, thought to be stacks of haemocyanin molecules. There are usually at least 10 times the number of empty ISOs as full and active outgrowths. The number of active ISOs increases rapidly at dawn to peak at about 3 h after sunrise and then rapidly declines. The present sample suggests that the number of empty ISOs increases steadily throughout the day. Thus, ISOs turn over and are probably rapidly formed and short-lived. The contents of ISOs are observed to be evicted into the intermediate segments, where they presumably join the population of secondary lysosomes and are digested. The cyclical activity of ISOs is greatest after shedding of rhabdomeral membrane at dawn (Blest 1978). ISOs are thought to be concerned with the return to the receptors of a minor fraction of rhabdomeral material lost to extracellular space during shedding of the microvillar membrane.The authors thank Professor D.T. Anderson, F.R.S., for use of field facilities of the Crommelin Biological Field Station of Sydney University at Warrah, Pearl Beach, N.S.W., and Andrew and Sally Austin and Carolyn Lawson-Kerr for help in the field. We are indebted to Rod Whitty and the Electron Microscopy Unit for support during these studies, and to Gary Brown for preparing Figs. 1 and 16     

Photoreceptor membrane breakdown in the spider Dinopis: GERL differentiation in the receptors

Summary In the spider Dinopis, retinae of the posterior median eyes synthesise new photoreceptor membrane in bulk at dusk and destroy it at dawn (Blest, 1978). During the dawn period, there is a rapid, anticipatory differentiation of unusual organelles from the rough endoplasmic reticulum (RER) in the intermediate segments of the receptors. This system is classified as GERL. Its products appear to play a role in the autolysis of photoreceptor membrane. Consistent topographical relationship to Golgi bodies has not been determined. Circumscribed regions of RER whorls first reorganise to yield fenestrated profiles; these differentiate further to a number of structures by condensation and loss of ribosomes. Smooth tubular profiles are termed rigid tubules to indicate their probable homology with the rigid lamellae of vertebrate secretory cells. More complex smooth multilocular bodies are also produced. Evidence is discussed which implies that both rigid tubules and multilocular bodies give rise to condensing vacuoles. These, in turn, pinch off coated vesicles assembled as Nebenkerne. Some rigid tubules are transported to the interrhabdomeral cytoplasm of the receptive segments. At late stages of differentiation, rigid tubules, multilocular bodies and Nebenkerne give strong, positive responses to zinc iodide-osmium tetroxide (ZIO) treatment; early stages and both cis and trans Golgi components do not. GERL differentiation is independent of immediate illumination of the retina at dawn. It is suggested to mediate the lysis of membrane degradation products by the production of hydrolases.We thank Professor D.T. Anderson F.R.S. for our use of field facilities at the Crommelin Biological Field Station of Sydney University at Warrah, Pearl Beach, N.S.W., and Andrew and Sally Austin and Sally Stowe for help in the field. We are indebted to Rod Whitty and the Electron Microscopy Unit for advice and support throughout these studies     

Fumonisin and Beauvericin Induce Apoptosis in Turkey Peripheral Blood Lymphocytes

Fumonisins, a family of mycotoxins produced by Fusarium verticillioides (synonym Fusarium moniliforme Sheldon) and F. proliferatum, have been associated with various deleterious effects in different animal species. Serological, hematological and pathological effects and mortality have previously been observed in broiler chicks fed F. proliferatum culture material containing known concentrations of fumonisin, moniliformin and beauvericin. Turkey peripheral blood lymphocytes were exposed in vitro for 72 hours to fumonisin B₁(FB₁), fumonisin B₂(FB₂), hydrolyzed fumonisin B₁ (HFB₁), moniliformin and tricarballylic acid (TCA) (0.01-25 g/ml). A decrease in cell proliferation, as determined by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] bioassay, occurred in the order: FB₂ > FB₁ > HFB₁, with IC₅₀ = 0.6 M, 1 M and 10 M, respectively. Internucleosomal DNA fragmentation and morphological features characteristic of apoptosis were observed following exposure to fumonisin B₁ and beauvericin; cytoplasmic condensation and membrane blebbing were seen by light microscopy. Tricarballylic acid and moniliformin did not interfere with cell proliferation. Results suggested that fumonisin B₁ and beauvericin may affect immune functions by suppressing proliferation and inducing apoptosis of lymphocytes.     

In vitro propagation of Asparagus maritimus – A rare Mediterranean salt-resistant species

Asparagus maritimus L. Miller is a rare species growing of the Mediterranean region and is morphologically similar to A. officinalis. In order to establish an efficient in vitro propagation protocol, explants were excised from spear segments and cultured on Murashige and Skoog (1962) medium containing 3% sucrose and various concentrations of growth regulators. The best shoot initiation (3–4 per explant) was achieved on a medium containing 0.88 M N⁶-benzyladenine (BA), 0.93 M kinetin, 1.07 M -naphthaleneacetic acid (NAA) and 3.90 M ancymidol. Shoot initiation could also be achieved without ancymidol but the shoots were thinner and longer. A very high shoot multiplication rate was achieved on media supplemented with 3% sucrose, 1.07 M NAA, 0.93 M kinetin, 0.44 M BA and various concentrations of ancymidol. The lowest concentration of ancymidol (0.39 M) significantly promoted the highest shoot multiplication rate (11.9 shoots/crown). For root formation, media were supplemented with 6% sucrose, 1.07 M NAA and various concentrations of ancymidol. Rooting frequency increased with higher ancymidol concentration up to 5.07 M (82.0% rooting). The number of ex vitro shoots formed was strongly correlated (r=0.66) with the length of roots formed in vitro, which was the highest at a 1.95 M ancymidol.     

Initiation and propagation of Glycine max L. Merr.: Plants from tissue-cultured epicotyls

A successful technique for the initiation and proliferation of shoots from epicotyl tissue of soybean, Glycine max, has been developed and is described. Fertile plants were recovered. Seeds were germinated on Murashige and Skoog medium containing 5 M benzyladenine. Explanted epicotyl sections were induced to form callus and shoots on Schenk and Hildebrandt medium containing 5.2 mM monobasic ammonium phosphate, 74 M 3-aminopyridine, and 20 M kinetin for five weeks. Shoot proliferation was maintained on N6 medium containing 1.75 mM ammonium sulfate, 2.1 nM picloram, and 0.1 M benzyladenine. Shoots rooted on Gamborg's B5 medium without growth regulators. Shoot-forming cultures were maintained for 60 months. Although all varieties tested produced shoots, some variation in numbers of shoots obtained was observed.     

Five new species of Eimeria (Apicomplexa: Eimeriidae) from lizards

Five new species of Eimeria are described from lizards. Eimeria baltrocki n. sp. was found in the berber skink, Eumeces schneideri, from Egypt. The oöcysts are cylindroidal, averaging 38 × 18.3 m, with a single thick oöcyst wall. Most oöcysts possess a single polar granule; a micropyle and oöcyst residuum are absent. The sporocysts are ellipsoidal and average 11.5 × 8.1 m, each with a large, globular sporocyst residuum; the Stieda body is absent. Eimeria anolidis n. sp. is described form the common anole, Anolis carolinensis, from Florida, USA. The oöcysts are cylindroidal and average 31 × 15.8 m with a thick, single-layered oöcyst wall. Two polar granules are usually present; a micropyle and oöcyst residuum absent. The sporocysts are ellipsoidal and average 9.4 × 7.5 m with a globular sporocyst residuum; the Stieda body is absent. Eimeria guyanensis n. sp is recorded in the ameiva, Ameiva ameiva, from Guyana, South America. The oöcysts are spherical to subspherical, average 19.0 × 17.8 m and possess a thick, single-layered oöcyst wall. Numerous polar granules are present (n > 5); a micropyle and oöcyst residuum are absent. The sporocysts are spherical to subspherical, average 7.5 × 7.8 m and possess a compact globular sporocyst residuum; the Stieda body is absent. Eimeria phelsumae n. sp. was recovered from the giant day gecko, Phelsuma madagascariensis grandis, from Madagascar, which harboured a simultaneous infection of E. brygooi. The oöcysts measured 32 × 15 m and are cylindroidal without polar granules, a micropyle or oöcyst residuum, or a Steida body. The sporocysts are ellipsoidal and average 9.8 × 7 m, with a loosely clumped, granular sporocyst residuum; the Steida body is absent. Eimeria leiocephali n. sp. was discovered in the faeces of the ornate ground iguana, Leiocephalus barahonensis, from Haiti. The oöcysts are spherical to subspherical, 21 × 19 m, and contain a number of polar granules (n > 5); a micropyle and oöcyst residuum are absent. The sporocysts are spherical, 8 m in diameter and lack a sporocyst residuum. Eimeria turcicus and E. lineri were found in faeces of Hemidactylus turcicus turcicus from the host's country of origin, Turkey.     

The contribution of size-fractionated plankton to biomass and primary production of phytoplankton in saline–alkaline ponds

Primary productivity, biomass and chlorophyll-a of size fractionated phytoplankton (<0.22 m, <3 m, <8 m, <10 m, <40 m, <64 m, <112 m and <200 m) were estimated in 6 ponds and 5 experimental enclosures. The results showed that the planktonic algae less than 10 m are important in the biomass and production of phytoplankton in saline–alkaline ponds. The production of size fractionated phytoplankton corresponding to <112 m, <10 m and <3 m in saline–alkaline ponds were 10.5 ± 6.6 , 8.6 ± 5.4 and 0.33 ± 0.1 mgC l^–1 d^–1, respectively. Mean community respiration rate was 1.80 ± 0.73, 1.69 ± 0.90 and 1.38 ± 1.12 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) were 1.61, 8.30 and 0.33 mgC l^–1 d^–1, respectively. The ratio of those to the total phytoplankton production was 15%, 79% and 3%, respectively. The mean respiration rate of the different size groups was 0.11, 0.31 and 1.38 mgC l^–1 d^–1; the ratio of those to total respiration of phytoplankton was 6%, 17% and 77%, respectively. The production of size-fractionated phytoplankton corresponding to <200 m, <10 m and <3 m in enclosures was 2.19 ± 1.63, 2.08 ± 1.75 and 0.22 ± 0.08 mgC l^–1 d^-1, respectively. Mean community respiration rates were 1.25 ± 1.55, 1.17 ± 1.42 and 0.47 ± 0.32 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton was 0.11, 1.86 and 0.22 mgC l^–1 d^–1, respectively. The ratio of those to the total production of phytoplankton was 5%, 85% and 10%, respectively. The mean respiration rate of different size groups were 0.08, 0.72 and 0.46 mgC l^–1 d^–1, the ratio of those to total respiration of phytoplankton was 6%, 57% and 37%, respectively. The concentrations of chlorophyll-a of the phytoplankton in the corresponding size of micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) plankton in the experimental ponds were 19.3, 98.2 and 11. 9 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 15%, 76% and 9%, respectively. The concentrations of chlorophyll-a of phytoplankton micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton in enclosures were 1.7, 34.3 and 3.0 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 4%, 88% and 8%, respectively.     

Feeding in the rotifer Brachionus calyciflorus

Summary The laboratory feeding behavior of Brachionus calyciflorus varies depending upon the type of food cell available in suspension. When feeding on the yeast Rhodotorula glutinis, rotifers show a continuous increase in ingestion with increased cell density between 0.01 and 1000 g dry weight ml^-1. Effective clearance rates drop from ca. 50 l animal^-1 h^-1 to less than 0.5 l animal^-1 h^-1 over this food density range. When feeding on Englena gracilis, B. calyciflorus ingestion rates are constant between 1.0 and 100 g ml^-1 of available food, averaging close to 25 ng animal^-1 h^-1. The decrease in clearance rate is more striking than with R. glutinis, dropping from 45 l animal^-1 h^-1 at 0.1 g ml^-1 to 0.13 l animal^-1 h^-1 at 100 g ml^-1. Differences between the patterns obtained with the two food types indicate fundamental dissimilarities in the feeding behavior of this rotifer species when presented with these different foods.     

Quorum-sensing antagonist (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone influences siderophore biosynthesis in Pseudomonas putida and Pseudomonas aeruginosa

Siderophore synthesis of Pseudomonas putida F1 was found to be regulated by quorum sensing since normalized siderophore production (per cell) increased 4.2-fold with cell density after the cells entered middle exponential phase; similarly, normalized siderophore concentrations in Pseudomonas aeruginosa JB2 increased 28-fold, and a 5.5-fold increase was seen for P. aeruginosa PAO1. Further evidence of the link between quorum sensing and siderophore synthesis of P. putida F1 was that the quorum-sensing-disrupter (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) from the marine red alga Delisea pulchra was found to inhibit the formation of the siderophore produced by P. putida F1 in a concentration-dependent manner, with 57% siderophore synthesis repressed by 100 g/ml furanone. In contrast, this furanone did not affect the siderophore synthesis of Burkholderia cepacia G4 at 20–40 g/ml, and stimulated siderophore synthesis of P. aeruginosa JB2 2.5- to 3.7-fold at 20–100 g/ml. Similarly, 100 g/ml furanone stimulated siderophore synthesis in P. aeruginosa PAO1 about 3.5-fold. The furanone appears to interact with the quorum-sensing machinery of P. aeruginosa PAO1 since it stimulates less siderophore synthesis in the P. aeruginosa qscR quorum-sensing mutant (QscR is a negative regulator of LasI, an acylated homoserine lactone synthase).     

Micropropagation of Phytolacca dodecandra through shoot-tip and nodal cultures

A procedure for micropropagation of endod (Phytolacca dodecandra) is described. BA at 0.44 M produced 3.1 new shoots per expiant in six weeks using shoot tips. Nodal expiants, however, produced up to 4.7 shoots per explant on medium with 0.44 M BA and 0.27 M GA,. IBA at 0.49 M induced 90% rooting with minimal callus. Plantlets were successfully transferred to the greenhouse and some staminate clones produced flowers after six months.Abbreviations BA 6 benzylaminopurine - kinetin 6-furfurylaminopurine - 2iP N⁶-(2-isopentyl)adenine - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - GA₃ Gibberellic acid - IBA indole-3-butyric acid     

Effects of Lead on Adenylate Cyclase Activity in Rat Cerebral Cortex

Lead decreased in a dose dependent manner the basal AC activity in membranes of rat cerebral cortex (IC₅₀ = 2.5 ± 0.1 M). In membranes preincubated under basal conditions, AC activity was stimulated by approximately two and fourfold by 10 M Gpp(NH)p or forskolin, respectively. Under basal conditions, lead (3 M) inhibited enzyme activity up to 50%, but was not able to inhibit the Gpp(NH)p- or the forskolin-stimulated AC activity. However, in membranes preincubated with Gpp(NH)p (10 M), lead (3 M) had no significant effect on enzyme activity, but it partly blocked the stimulation of AC activity elicited by forskolin (10 M). In membranes preincubated with 10 M lead, the addition of 10 M Gpp(NH)p or forskolin in the incubation medium did not stimulate AC activity. However, when added together in the incubation medium Gpp(NH)p + forskolin produced an increase in enzyme activity. In membranes preincubated with 10 M lead + 10 M Gpp(NH)p, Gpp(NH)p (10 M) or forskolin (10 M) added alone or in combination to the incubation medium did not stimulate AC activity. Moreover, under these latter conditions lead had no further effect on enzyme activity. These results indicate that lead may interact with G-proteins and with the catalytic subunit of cerebral cortical AC to produce inhibition of the enzyme activity.     

Activity of dihydrofolate reductase in the mollicutesAcholeplasma laidlawii andMycoplasma gallisepticum and their susceptibility to antifolates

Mycoplasma gallisepticum andAcholeplasma laidlawii were found to possess dihydrofolate reductases exhibiting similar specific activities and kinetics, with values in the range of those reported for other microorganisms. The apparent Km values for dihydrofolate in enzymes ofM. gallisepticum andA. laidlawii are 7.95±0.13 and 7.50±0.11 M, and for NADPNH 8.46±0.25 and 9.32±0.18 M, respectively.M. gallisepticum is 3300-fold more resistant to methotrexate than isA. laidlawii; concentrations causing 50% inhibition were 200.00 and 0.06 M, respectively. This is in contrast to almost the same sensitivity to that drug exhibited by the dihydrofolate reductases of both microorganisms.M. gallisepticum is also 3600-fold more resistant to trimethoprim than isA. laidlawii, and the concentrations for 50% inhibition of growth were 1800.0 and 0.5 M, respectively. The high resistance was found to be due partially to a 130-fold lower affinity of the target enzyme for this antifolate, but another mechanism, presumably impaired transport, must also be involved. This is the first report of dihydrofolate reductase activity in Mollicutes.     

Control of yeast fed-batch process through regulation of extracellular ethanol concentration

At high growth rates, the biomass yield of bakers yeast (Saccharomyces cerevisiae) decreases due to the production of ethanol. For this reason, it is standard industrial practice to use a fed-batch process whereby the specific growth rate, , is fixed at a level below the point of ethanol production, i.e., _crit. Optimally, growth should be maintained at _crit, but in practice, this is difficult because _crit is dependent upon strain and culture conditions. In this work, growth was maintained at a point just above _crit by regulating ethanol concentration in the bioreactor. The models used for control design are shown, as are the experimental results obtained when this strategy was implemented. This technique should be applicable to all microorganisms that exhibit an overflow type metabolism.     

Influence of sarmesin on some dopamine-related types of behaviour

Summary The present study was undertaken to investigate the effects of sarmesin, an analogue of [Sar¹] angiotensin II (ANG II) where the tyrosine hydroxyl group in position 4 is methylated, on dopamine (DA)-related paradigms: locomotor and exploratory behaviour as well as apomorphine (3 mg/kg, ip)-induced stereotypy in rats. Sarmesin (0.5 and 1 g, icv) significantly decreased ambulation and rearing movements, and blocked the inhibitory effect of ANG II (0.1 g) on both types of activity. Sarmesin induced biphasic effects on apomorphine-induced stereotypy depending on the dose increase (0.5 and 5 g, icv) and decrease (10 g). Moreover, sarmesin (5 g) blocked the inhibitory effect of ANG II (2 g, icv) on apomorphine stereotypy. Taken together, these results suggest that sarmesin might interact with AT₁ and AT₂ receptor subtypes. The results further confirm the statement for ANG II-DA interaction in brain structures involved in these types of behaviour.     

Sisal plant regeneration via organogenesis

Callus was initiated from in vitro grown immature leaf and ex vitro grown mature leaf and rhizome explants of Agave sisalana Perr. ex. Engelm, on MS medium containing 2,4-D (9.05 M) and kinetin (4.6 M) or 2,4-D (9.05 M), kinetin (4.6 M) and CH (1000 mg l^–1) or mod. MS (NH₄NO₃, 1500 mg l^–1) containing 2,4-D (9.05 M) and kinetin (4.6 M). Light was essential for callus formation which, however, was different in three types of explants on three different media compositions. Increasing NH₄ ⁺had a negative impact while addition of CH had a positive impact on callus formation. Shoot regeneration from callus from CH-supplemented medium only was achieved for rhizome and immature leaf tissues. The highest rate of regeneration was obtained with BA (26.6 M) as the sole hormone. Shoot buds g^–1 callus varied according to BA concentrations. Shoot proliferation rate increased on half-strength MS medium containing BA (8.9 M). Microshoots developed on MS medium containing BA (2.22 M) and GA₃ (1.44 M) and finally rooted on MS medium containing IAA (11.42 M). Acclimatized rooted plantlets are growing satisfactorily in ex vitro. This is the first report on plant regeneration via organogenesis of A. sisalana.     

Effects of light on nitrate-limited Oscillatoria agardhii in chemostat cultures

The effects of the average light irradiance (I) on growth and nitrate uptake kinetics of the cyanobacterium Oscillatoria agardhii, in nitrate-limited chemostat cultures, were studied. Light was nonsaturating for I <9.4 Wm^–2, for all growth rates () studied. However, was throughout limited by the availability of nitrate. Under light-saturating conditions the kinetics of nitrate-limited growth could be adequately described by both the Monod and Droop equations. Under light-non-saturating conditions the internal nitrogen content (Q) was a function of both and I, for which new formulas were derived. The high uptake capacity (V _max) of nitrate-limited cells was independent of , but was significantly increased for cells growing at I <9.4 Wm^–2. The half-saturation constant for nitrate uptake (K _s ^u ) increased with increasing , but was independent of the prevailing light conditions. The effects of light during nitrate-limited growth were associated with the regulation in the nitrogen-containing pigments.The results reported herein have important consequences for the use of Q, K _s ^u and V _max values as indicators of nutrient-deficiency of natural populations.