Phytochemical and Biological Activities in Limonium Species Collected in Different Biotopes of Tunisia

A particular interest is nowadays given to natural antioxidants occurring in foods which can reduce the risk of several diseases through their protective effect. The genus Limonium is widely distributed in different salt regions of Tunisia and known in traditional medicine for the presence of highly effective viral and bacterial replication inhibitors. Limonium leaves have possible beneficial effects on human health for their antioxidant activities and free radical scavenging abilities. To exploit the potential of plants from extreme environments as new sources of natural antioxidants, we studied the extracts from leaves of eight Limonium species growing in extreme environments in Tunisia. Antioxidant molecules (polyphenols, flavonoids, flavonols, ascorbate, tocopherols), in vitro (DPPH, ORAC) and ex vivo antioxidant potential on human erythrocytes, antioxidant enzymes activities (superoxide dismutase, peroxidases, glutathione reductase) were evaluated to identify the species with the best antioxidant capacity. The results showed variability among the species considered in function of the environmental conditions of their natural biotopes, as for the antioxidants measured. In particular, L. vulgare from Oued Rane biotope, characterized by dryness and high temperatures, was the species with the highest enzymatic activity and antioxidant capacity, making it interesting as possible edible halophyte plant or as food complement.     

Starch content and distribution in excised watermelon cotyledons treated with benzyladenine

We have examined the effect of benzyladenine (BA) on amyloplast number and distribution in semithin cross-sections of excised watermelon ( Citrullus vulgaris Schrad ., cv. Fairfax) cotyledons grown in the dark. The sections were stained with Lugol solution and observed with an immersion objective. In control cotyledons, amyloplasts were always more abundant and contain more starch grains than in BA-treated cotyledons. The higher starch content was correlated with a higher ratio between starch synthetase (EC 2.4.1.21) and amylase (EC 3.2.1.1) activities in the controls. In the central zone of the mesophyll, the amyloplasts contained more starch grains than in the abaxial and adaxial (palisade) zones. The average number of amyloplasts per cell was different in the three zones, and followed a different time course in control and treated cotyledons. BA decreased this number, particularly in the adaxial zones. Our data seem to indicate a different function of starch in the central and in adaxial zone of the mesophyll. In the central zone starch is probably used as a source of carbohydrates for export to the embryo axis, while in the adaxial zone, where the transformation from amyloplast to etioplast is particularly pronounced, starch may be a reserve for organelle differentiation. BA stimulates the utilization of starch for both functions.     

Nucleoprotein changes during male pronuclear development as determined by the ammoniacal silver reaction

Sperm nucleoprotein changes during male pronuclear development in fertilized sea urchin (Arbacia punctulata) eggs have been examined utilizing the ammoniacal silver reaction (ASR) at the light and electronic microscopic levels of observation. Previous studies and control preparations indicated that the ASR has an affinity for basic proteins, staining intensely those rich in arginine residues. Differences in the affinity of the paternally derived chromatin to the ASR prior to, during, and following pronuclear development were observed. Relative to the female pronucleus the unincorporated sperm nucleus was densely stained. Upon its entry into the egg the sperm nucleus showed a two-fold increase in staining, indicating an augmentation in the availability of reactive sites already present in the paternally derived chromatin or an accumulation of “new” reactive sites from the egg cytoplasm. With the dispersion of the sperm nucleus there was a progressive decrease in staining intensity of the paternally derived chromatin. Subsequent to pronuclear fusion the paternally derived chromatin, recognized by its relatively dense staining, was seen at one pole of the zygote nucleus. With time there was a gradual regression in the size and staining intensity of the paternally derived chromatin within the zygote nucleus. Changes in reactivity of sperm-derived chromatin are discussed in reference to previous studies of chromatin transitions at fertilization.     

Role of killer character in spontaneous fermentations from NW Spain: ecology,distribution and significance

Summary The presence of killer, resistant and sensitive populations of Saccharomyces cerevisiae along the successive stages of alcoholic fermentation in three vineyards from NW Spain was investigated. The global results showed that approximately 71% were killer-sensitive strains, 6.6% were killer-resistant, and 22.4% belonged to the k₂ killer type. However, there were important differences concerning the presence of the three phenotypes during successive stages of fermentation. Killer populations were isolated at the highest percentages in samples from must and from active alcoholic fermentations. Killer-resistant strains steadily increased during fermentation. Additionally, important differences in these populations were observed among the three vineyards. In this sense, the presence of killer populations was more important in samples from the vineyards with higher average pH values of the must. However, great differences in the distribution of killer phenotype between successive vintages (with the same initial pH of must) belonging to the same vineyard implies the presence of other factors effecting killer behaviour. Offprint requests to: T. G. Villa     

Sperm nuclear transformations consist of enlargement and condensation coordinate with stages of meiotic maturation in fertilized Spisula solidissima oocytes

Rates of sperm nuclear expansion were measured and correlated with processing of the maternal chromatin in synchronous populations of fertilized surf clam (Spisula solidissima) oocytes fixed at regular intervals following insemination and stained with the DNA fluorochrome Hoechst 33342. Sperm nuclei expanded in four distinct phases each temporally coordinate with events of meiotic maturation: germinal vesicle stage (phase A), germinal vesicle breakdown (phase B), polar body formation (phase C), and female pronuclear development (phase D). Sperm nuclei were essentially unchanged during phase A (rate = 0.1 micron2/min, enlarged during phases B (rate = 8.2 microns2/min) and D (rate = 6.2 microns2/min), and condensed during phase C (rate = -1.9 micron2/min). Sperm nuclear enlargement during phase D was significantly less in polyspermic and polygynic zygotes. The effects of various treatments (temperature, microtubule disruption, pH alterations, and metabolic and protein synthesis inhibitions) which perturbed sperm nuclear enlargement and meiotic processing of the maternal chromatin indicated that the two processes are coupled and may be linked by common regulatory agents.     

Genetic evidence of a new flocculation suppressor gene in Saccharomyces cerevisiae

Abstract The flocculation character in strain IM1-8b of Saccharomyces cerevisiae is controlled by a single and dominant gene shown to be allelic to FLO1 . Such a gene has been both mitotically and meiotically mapped on the right arm of chromosome I at 4.7 cM from PHO11 . The phenotype was suppressed by a single gene of wide distribution among non-flocculent strains (proposed as fsu3 ) that, however, was unable to suppress other FLO1 genes in other flocculent strains.