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Biomedical subjects

M Terzi

Publications and source records attributed to M Terzi.

At least 19 recordsLinked to original sources
PubMed2000

KDC1, a novel carrot root hair K+ channel. Cloning, characterization, and expression in mammalian cells.

Potassium is an essential nutrient which plays an important role in many aspects of plant growth and development. Plants have developed a number of highly specific mechanisms to take up potassium from the soil; these include the expression of K(+) transporters and potassium channels in root cells. Despite the fact that root epidermal and hair cells are in direct contact with the soil, the role of these tissues in K(+) uptake is not well understood. Here we report the molecular cloning and functional characterization of a novel potassium channel KDC1 which forms part of a new subfamily of plant K(in) channels. Kdc1 was isolated from carrot root RNA and in situ hybridization experiments show Kdc1 to be highly expressed in root hair cells. Expressing the KDC1 protein in Chinese hamster ovary cells identified it as a voltage and pH-dependent inwardly rectifying potassium channel. An electrophysiological analysis of carrot root hair protoplasts confirmed the biophysical properties of the Kdc1 gene product (KDC1) in the heterologous expression system. KDC1 thus represents a major K(+) uptake channel in carrot root hair cells.

Amino Acid Sequence↗
PubMed2000

Spontaneous and induced apoptosis in embryogenic cell cultures of carrot (Daucus carota L.) in different physiological states.

Programmed cell death (apoptosis) in plants - and plant cells in culture - has received much less attention than its animal counterpart. In the present work, using agents producing biotic or abiotic stress on cultivated cells from carrot - and, in a few experiments, Arabidopsis -, we show that DNA fragmentation, random or oligonucleosomal, can be induced by different treatments. Moreover, we demonstrate that the same cultures may or may not respond to the inducing signal according to their physiological state. In particular, stationary cells are more responsive to the inducing signal than actively proliferating ones, and cells growing in an unorganized way are more responsive than cells carrying out the embryogenic programme. Senescent cells in culture also appear to die by apoptosis, but healthy cells can also be induced to die apoptotically if exposed to the medium conditioned by senescent cells of the same or different species.

Apoptosis↗
PubMed2000

Identification and characterization of an 18-kilodalton, VAMP-like protein in suspension-cultured carrot cells.

Polyclonal antibodies raised against rat vesicle associated membrane protein-2 (VAMP-2) recognized, in carrot (Daucus carota) microsomes, two major polypeptides of 18 and 30 kD, respectively. A biochemical separation of intracellular membranes by a sucrose density gradient co-localized the two polypeptides as resident in light, dense microsomes, corresponding to the endoplasmic reticulum-enriched fractions. Purification of coated vesicles allowed us to distinguish the subcellular location of the 18-kD polypeptide from that of 30 kD. The 18-kD polypeptide is present in the non-clathrin-coated vesicle peak. Like other VAMPs, the carrot 18-kD polypeptide is proteolyzed by tetanus toxin after separation of coatomers. Amino acid sequence analysis of peptides obtained by digestion of the 18-kD carrot polypeptide with the endoproteinase Asp-N confirms it to be a member of the VAMP family, as is suggested by its molecular weight, vesicular localization, and toxin-induced cleavage.

Amino Acid Sequence↗
PubMed1999

Evidence suggesting protein tyrosine phosphorylation in plants depends on the developmental conditions.

Protein tyrosine phosphorylation plays a central role in a variety of signal transduction pathways regulating animal cell growth and differentiation, but its relevance and role in plants are controversial and still largely unknown. We report here that a large number of proteins from all plant subcellular fractions are recognized by recombinant, highly specific, anti-phosphotyrosine antibodies. Protein tyrosine phosphorylation patterns vary among different adult plant tissues or somatic embryo stages and somatic embryogenesis is blocked in vivo by a cell-permeable tyrosyl-phosphorylation inhibitor, demonstrating the involvement of protein tyrosine phosphorylation in control of specific steps in plant development.

Animals↗
PubMed1997

The secretory nature of the lesion of carrot cell variant ts11, rescuable by endochitinase.

The carrot cell variant ts11 is unable to form somatic embryos at the non-permissive temperature of 32 degrees C, but the block can be overcome by the addition of a 32-kDa acidic endochitinase to the medium. In this work we conducted a cyto-histological analysis of the blocked embryo forms. The morphology of the endomembrane system is altered; in particular, the ER is dilated and may show electron-dense precipitates and continuity with the plasma membrane. These morphological alterations do not occur in the presence of externally-added endochitinase. We also noticed modifications of the culture medium that are probably related to the morphological observations: the total amount of secreted proteins is reduced and pulse-chase experiments revealed that, compared with wild-type cells, the secretion of major polypeptides is reduced while new minor polypeptides are secreted. Western blot analysis revealed the presence of the binding protein BiP, a resident of the ER and of glutamine synthase, a cytosolic protein, in the medium of ts11 but not wild-type cells. These results indicate that ts11 is altered in the secretory pathway but do not clarify the role of endochitinase.

Cells, Cultured↗
PubMed1996

A protocol for obtaining embryogenic cell lines from Arabidopsis.

Embryogenic cell lines with lasting embryogenic potential can be obtained from somatic embryos induced directly from zygotic embryos of Arabidopsis thaliana, ecotype Columbia. The response to a critical concentration of auxin, which seems to be the all-important factor in the generation of embryogenic cell lines, is exhibited by somatic embryos but not by zygotic ones. The basis for this differential response remains obscure and will be discussed in relation to other systems.

Arabidopsis↗
PubMed1996

Anti-inflammatory activity of polyphosphazene-based naproxen slow-release systems.

A biocompatible and biodegradable polyphosphazene bearing phenylalanine ethyl ester, imidazole and chlorine (10.7:1:2.5 molar ratio) as substituents of the phosphorus atoms of the polymer backbone was studied for the preparation of polymeric naproxen slow-release systems. Discs 2.5 cm in diameter and 0.5 mm (thin) or 0.65 mm (thick), loaded, respectively, with 20 and 13.5% naproxen, showed different drug release kinetics, the thin matrices releasing naproxen at a faster rate and for a shorter time. In-vivo studies in rats demonstrated the pharmacological efficacy of these two different delivery systems in the inhibition of acute or chronic inflammatory diseases. Subcutaneous implantation of the thin matrices in rats was found to reduce carrageenan oedema induced both 1 h and 7 days after implantation. Rats implanted with thick matrices showed a reduction in chronic inflammation caused by adjuvant arthritis. Approximately 78% inhibition of arthritic oedema was found 28 days after subcutaneous administration of the matrices whereas 28.7% inhibition was found after daily oral administration of naproxen. Blood levels of naproxen in arthritic rats after matrix implantation showed the presence of drug up to day 28. These positive results have encouraged us to study a controlled-release system suitable for use in man.

Administration, Oral↗
PubMed1995

On the occurrence of somatic meiosis in embryogenic carrot cell cultures.

During the establishment of an embryogenic cell line from a carrot hypocotyl explant, processes closely resembling meiotic divisions are seen. A microdensitometric analysis revealed that the amount of cellular DNA diminished in the majority of cells to the haploid level. However, the diploid level was re-established in a matter of a few days. The genetic consequences of this segregation were studied by analyzing restriction fragment length polymorphisms (RFLP) and randomly amplified polymorphic DNAs (RAPD). The results showed that the great majority of embryos regenerated from segregants and that different segregants had different genetic constitutions.

Base Sequence↗
PubMed1995

Plasma concentrations and pharmacokinetic parameters of nitrofenac using a simple and sensitive HPLC method.

An accurate and sensitive HPLC method has been developed for the determination of nitrofenac, a new, original diclofenac derivate showing a good tolerability and a wide anti-inflammatory profile, diclofenac, and its metabolites in plasma. This method has been applied to evaluate the pharmacokinetic parameters of the drugs, using a noncompartmental model, after the oral administration of 5 mg/kg nitrofenac to rats. Nitrofenac and the internal standard flufenamic acid were dissolved in acetonitrile, and diclofenac was dissolved in methanol. The drugs were eluted from a 5 microns LC-8 column with a mobile phase consisting of acetonitrile/water (50/50 v/v) adjusted to pH 3.3 with glacial acetic acid, at a flow rate of 2 mL/min with UV detection at 280 nm for diclofenac and 275 nm for nitrofenac. The detection limit for the drugs in plasma was 25 ng/mL. The peak concentration of nitrofenac was reached 7 h after drug administration, while with diclofenac we observed three peaks at 2, 5, and 10 h; the mean residence time and the elimination rate constant for nitrofenac were 6.18 +/- 0.09 h and 0.37 +/- 0.03 h-1 respectively, while those for diclofenac were 12.24 +/- 0.11 h and 0.11 +/- 0.04 h-1. Under our conditions, the metabolism of nitrofenac produced 23% diclofenac and other metabolites: the plasma concentrations and kinetic characteristics of diclofenac are enough to induce an anti-inflammatory activity, while the clinical importance of the other metabolites remains to be elucidated.

Animals↗
PubMed1994

Selenium status, fatty acids, vitamins A and E, and aging: the Nove Study.

To investigate the relationships between aging and selenium status, vitamins A and E, and plasma and erythrocyte fatty acids, we studied 105 healthy subjects (53 women, 52 men) living in Nove, a village near Vicenza (Veneto Region, northern Italy). The subjects were distributed equally for age and sex into four groups: group 1, 20-39 y; group 2, 40-59 y; group 3, 60-75 y; and group 4, > 75 y. A careful selection of subjects to exclude those with chronic or acute diseases was obtained with the collaboration of the three general practitioners operating in Nove. Aging was associated with a progressive decrease in selenium status and in the ratio of plasma and erythrocyte polyunsaturated to saturated fatty acids (P:S). Stepwise multiple linear analysis revealed age, vitamin A, and n-6 polyunsaturated fatty acids (PUFAs) as useful predictors of a substantial proportion of the selenium variability (R = 0.618, R2 = 0.382; P < 0.001) and age and erythrocyte oleic acid as predictors of erythrocyte glutathione peroxidase variability (R = 0.413, R2 = 0.17; P < 0.001).

Adult↗
PubMed1992

A carrot somatic embryo mutant is rescued by chitinase.

At the nonpermissive temperature, somatic embryogenesis of the temperature-sensitive (ts) carrot cell mutant ts11 does not proceed beyond the globular stage. This developmental arrest can be lifted by the addition of proteins secreted by wild-type cells to the culture medium. From this mixture of secreted proteins, a 32-kD glycoprotein, designated extracellular protein 3 (EP3), that allows completion of somatic embryo development in ts11 at the nonpermissive temperature was purified. On the basis of peptide sequences and biochemical characterization, EP3 was identified as a glycosylated acidic endochitinase. The addition of the 32-kD endochitinase to ts11 embryo cultures at the nonpermissive temperature appeared to promote the formation of a correctly formed embryo protoderm. These results imply that a glycosylated acidic endochitinase has an important function in early plant somatic embryo development.

Amino Acid Sequence↗
PubMed1990

A carrot cell variant temperature sensitive for somatic embryogenesis reveals a defect in the glycosylation of extracellular proteins.

The temperature-sensitive carrot cell variant ts11c, arrested in somatic embryogenesis after the globular stage, was characterized. The sensitivity to a shift from 24 degrees C (permissive temperature) to 32 degrees C (non-permissive temperature) is greatest at the globular stage of embryogenesis, while cells proliferating in unorganized fashion and plantlets are not affected. Embryogenesis in ts11c is also arrested at the permissive temperature by replacement of conditioned culture medium with fresh medium. The timing of sensitivity of ts11c to medium replacement coincides with the sensitivity to temperature shift. Both sensitivities are recessive in somatic hybrids between ts11c and wild-type cells. Extracellular glycoproteins synthesized by ts11c at the non-permissive temperature contain much less fucose than those synthesized by the wild type. The glycoproteins synthesized by the variant under non-permissive conditions do not accumulate at the periphery of the embryo, as their wild-type counterparts do, but instead show a diffuse distribution throughout the embryo. The defect in ts11c can be fully complemented by the addition of extracellular wild-type proteins. A revertant of ts11c was isolated that simultaneously reacquired temperature insensitivity and normal glycosylation ability. Collectively, these observations indicate that ts11c is not able to perform proper glycosylation at the non-permissive temperature and suggest that the activity of certain extracellular proteins, essential for the transition of globular to heart stage somatic embryos, depends on the correct modification of their oligosaccharide side-chains.

Biological Transport↗
PubMed1980

Studies of mutagenicity on quiescent and proliferating hamster cell populations.

A few known mutagens were tested on proliferating hamster cells and on cells made quiescent by L-histidinol block. No differences were found in the effectiveness of two alkylating agents and a base analogue; whereas the carcinogen 4-nitroquinoline-1-oxide was more effective on quiescent than on proliferating cells. The implications of these data on the mechanism of action of mutagens are discussed.

4-Nitroquinoline-1-oxide↗
PubMed1974

Chromosomal variation and the origin of drug-resistant mutants in mammalian cell lines.

Drug-resistant mutants of somatic cell lines fall into two classes: one seems to correspond to classical gene mutation, the other is characterized, albeit transiently, by karyotypic instability, high reversion frequency, and low plating efficiency. An interpretation of the origin of these drug-resistant mutants is offered on the basis of chromosomal variation, which generates variation of the number of copies of each individual chromosome and, consequently, of gene dosage.

Alleles↗