CONTROL OF GERMINATION OF ALEXANDRIUM TAMARENSE (DINOPHYCEAE) CYSTS FROM THE LOWER ST. LAWRENCE ESTUARY (CANADA)

Cysts of the toxic dinoflagellate Alexandrium tamarense (Lebour) Balech 1992 from the lower St. Lawrence estuary were used in a test of the following hypotheses: (1) cyst germination is triggered by a change in temperature, and (2) germination rate varies throughout the year and is controlled by a circannual internal biological clock. Results show that cyst germination was not affected significantly by temperature of incubation over the range 1°–16° C, and light showed no significant stimulation of germination. This is supported by the lack of effect of cyst incubation conditions during evaluation of the seasonal changes in germination rate (two temperatures: 4° and 15° C, and two light conditions: darkness and 150 μmol photons·m^?2·s^?1). Thus, direct environmental control through short-term increases in temperature and exposure to light has no effect on the germination of the cysts tested. The rate of germination, observed monthly over a 16-month period, showed low germination (<20%) over most of the period tested, except for a maximum reaching more than 50% germination in August to October of the second year of the experiment. This pattern was observed for cysts both from monthly field collections and from laboratory-stored cysts kept under constant environmental conditions (4° C, in the dark). The peak in germination observed under constant environmental conditions (in the laboratory), the almost coincidental increase in cyst germination observed for the field-collected cysts, and the absence of effects of temperature and light during incubation could be explained either by a temperature-controlled cyst maturation period (the time-temperature hypothesis of Huber and Nipkow 1923) or by the presence of an internal biological clock. However, the large decline in the rate of germination 2 months after the maximum provides strong support for the biological clock hypothesis. The ca. 12-month maturation (dormancy) period observed for the laboratory-stored cysts is the longest reported for this species to our knowledge; this might be related to the low storage temperature (4° C), which is close to bottom temperatures generally encountered in this environment (0° to 6° C). Similar field and laboratory storage temperatures could explain the coincidental increase in germination rate in the fall of the second year if cyst maturation is controlled by temperature. A fraction of the laboratory-stored cysts did not follow a rhythmic pattern: A rather constant germination rate of about 20% was observed throughout the year. This continuous germination of likely mature cysts may supplement the local blooms of this toxic dinoflagellate, as these often occur earlier than peak germination observed in late summer. It seems that two cyst germination strategies are present in the St. Lawrence: continuous germination after cyst maturation, with temperature controlling the length of the maturation period, and germination controlled by a circannual internal rhythm.     

Immimocytological localization of a somatostatin-like substance in the brain of the giant slug,Limax maximus L.

Summary Immunocytological tests reveal the presence of a somatostatin-like substance in perikarya and axons in the brain of the giant slug Limax maximus L. Controls carried out on adjacent sections with absorbed antiserum or different antibodies raised against several biologically active peptides of vertebrates (ACTH-17-39, - and endorphin, - and MSH, methionin-enkephalin, TRH) demonstrate the specificity of the staining. However, some cells are both somatostatin- and FMRF-amide-positive. In the cerebral ganglia, the right Z-area cells, responsible for the synthesis of the maturation hormone (MH) are strongly somatostatin-positive. These results suggest a similarity between the MH and the somatostatin-like material contained in the Z-area cells. The simultaneous presence of two peptides in one and the same cell, the nature (elementary granules or soluble product) of the material, and its site of release are discussed.     

Optimization of culture medium for aroma production byCeratocystis fimbriata

Summary The fungusCeratocystis fimbriata is known to produce among others a banana-like aroma. With a fractional factorial experimental design a culture medium was optimized to produce characteristic volatile metabolites of this aroma. HPLC was used to separate and quantify some of the metabolites. This showed the influence of the composition of the basal culture medium. It is not yet possible to correlate these results with sensorial evaluation.     

Continuous Determination by a Chemiluminescent Method of Acetylcholine Release and Compartmentation in Torpedo Electric Organ Synaptosomes

Abstract: The detection of acetylcholine (ACh) with a chemiluminescent procedure enables one to follow continuously the release of transmitter from stimulated synaptosomes and to study the compartmentation of ACh in resting and active nerve terminals. A compartment of ACh liberated almost entirely by a single freezing and thawing could be directly measured and compared with a compartment of ACh resistant to several cycles of freezing and thawing but liberated by a detergent (60–70% of the total). It is the compartment liberated by freezing and thawing that is reduced when synaptosomes are stimulated. Up to half the total synaptosomal ACh content is readily releasable provided the calcium entry is maintained, or if a strong releasing agent such as the venom of Glycera convoluta is used. In addition, it is shown that synaptosomes contain only negligible amounts of choline, and that the proportion of the two ACh compartments is not influenced by changing extracellular calcium just before their determination.     

The genetic basis of C-glycosyl flavone B-ring modification in maize (Zea mays L.) silks.

Resistance to corn earworm (CEW) (Helicoverpa zea Boddie) has been attributed to high concentrations of C-glycosyl flavones and chlorogenic acid in maize (Zea mays L.) silks. The most common C-glycosyl flavones isolated from maize silks are maysin, apimaysin, and methoxymaysin, which are distinguished by their B-ring substitutions. For a better understanding of the genetic mechanisms underlying the synthesis of these compounds, we conducted a quantitative trait locus (QTL) study with two populations: (Tx501 x NC7A)F2 and (Tx501 x Mp708)F2. For chlorogenic acid, maysin, and methoxymaysin concentration, the major QTL for both populations was located on chromosome 4 near umc1963. For apimaysin, the major QTL in both populations was located at the position of the pr1 locus on chromosome 5. The QTL alleles on chromosome 4 that increased the synthesis of methoxymaysin significantly decreased the synthesis of maysin and chlorogenic acid. This decrease in maysin concentration was four-fold greater than the increase in methoxymaysin. Our results indicate that the QTL on chromosome 4, responsible for the increase in methoxymaysin synthesis, alters the dynamics of both the phenylpropanoid and flavonoid pathways.     

Calcium alginate immobilization of mammalian neurons: A potential tool to purify ligands of neuronal membrane proteins

Summary We report here improved immobilization conditions which permitted (i) to immobilize mouse neuroblastoma cells in calcium alginate beads, (ii) to test the functions of using patch clamp techniques and (iii) to quantitatively analyze ligand interactions with voltage-dependent sodium channels in neurons immobilized inside alginate beads. These results qualify this immobilization technique as a biotechnological tool to isolate and/or purify ligands of neuronal membrane proteins. A part of these results was presented at the International Symposium “Physiology of immobilized Cells” at Wageningnen, The Netherlands, December 10–13, 1989     

Biochemical research on oogenesis. Comparison between the proteins of the ribosomes and the proteins of the 42 S particles from small oocytes of Xenopus laevis

Previtellogenic oocytes of Xenopus laevis synthesize large amounts of 5 S RNA and transfer RNA, but very little, if any, 28 S and 18 S RNA. About half of the RNA of these oocytes is stored in nucleoprotein particles sedimenting at 42 S. These particles contain 5 S RNA, transfer RNA, and several proteins, the function of which remains so far unknown.The proteins of the 42 S particles were analyzed by two-dimensional electrophoresis on polyacrylamide gel. The resulting fingerprints displayed one major and two minor basic spots. None of these coincided with any of the 37 spots produced by the 60 S subunit of the ribosomes and with the 30 spots produced by the 40 S subunit. We conclude that no ribosomal component other than 5 S RNA is present in the 42 S particles.The fingerprints of 40 S and 60 S ribosomal proteins from X. laevis coincided almost completely with the corresponding fingerprints from the rat and the rabbit.     

Three new alkaloids from Buxus papillosa

Three new steroidal alkaloids have been obtained from Buxus papillosa Schneider. These are (?)-cyclobuxupaline-C (IV)(+)-cyclopapilosine-D (VII) and (+)-buxamine-C (IX). A known alkaloid also present is desoxy-16-buxidienine (X).