Biomedical subjects

Zvi Cohen

Publications and source records attributed to Zvi Cohen.

6 recordsLinked to original sources

PubMed2003

Detection and analysis of membrane interactions by a biomimetic colorimetric lipid/polydiacetylene assay.

We describe applications of a colorimetric assay based on supramolecular assemblies of lipid-polydiacetylene vesicles for analysis and screening of membrane interactions of lipophilic enzymes, peptides, and ions and for study of the effects of lipid composition upon membrane properties. The lipid-polymer aggregates undergo visible and quantifiable blue-to-red transitions following interfacial interactions and perturbation by varied biochemical processes. Specifically, we show that the colorimetric assay can be tuned for selective detection of enzymes reacting with different lipid species. The experiments also demonstrate that the lipid/polymer platform facilitates screening of peptide-membrane interactions in multicomponent mixtures. The colorimetric vesicles can incorporate lipid species from different cellular sources facilitating analysis of the contribution of molecular components to membrane properties and lipid interactions.

Acetylene↗

PubMed2003

Cortical index and size of hand bones: segregation analysis and linkage with the 11q12-13 segment.

BACKGROUND: Bone geometry (BG) and size (BS) are important factors in determining bone fragility. Previous studies have suggested that more than half of BG and BS variation is genetically determined. The possible chromosomal locations of genes involved in BS and BG determination have not been explored. We evaluated the extent and mode of inheritance of the radiographic hand BS index (BSI) and the metacarpal cortical index (MCI), and tested the hypothesis of linkage between these traits and the 11q 12-13 chromosomal region. MATERIAL/METHODS: Hand radiographs and blood samples were collected from 1190 individuals belonging to 349 Chuvasha nuclear families (Russian Federation). Segregation analysis was conducted on a total sample. Transmission disequilibrium testing (TDT) and model-based linkage analyses (MBLA) were performed on a sub-sample of 163 families. RESULTS: The hypothesis of a major gene effect was confirmed for both studied traits. The best-fitting models were Mendelian, with an additive type of inheritance. The inferred major gene explained 50% of the CI and 40% of the BSI variation. The TDT and MBLA results did not permit confirmation of hypotheses about linkage between hand BSI and the 11q 12-13 chromosomal region, but a possible linkage between CI and that region cannot be ruled out. CONCLUSIONS: We support the hypothesis of a major gene effect in the heritability of BSI and MCI. We provide suggestive evidence for possible linkage disequilibrium between MCI and the 11q12-13 chromosomal segment (marker D11S1983), but not for a linkage between BSI and this

Adolescent↗

PubMed2002

Biosynthesis of arachidonic acid in the oleaginous microalga Parietochloris incisa (Chlorophyceae): radiolabeling studies.

The fresh-water green alga Parietochloris incisa is the richest plant source of the PUFA arachidonic acid (20:4n-6, AA). To elucidate the biosynthesis of AA in this alga we labeled cultures of P. incisa with radioactive precursors. Pulse chase labeling with acetate resulted in its incorporation via the de novo biosynthesis pathway of FA. However, labeled acetate was also utilized for the elongation of C16 and C18 PUFA. Labeling with [1-14C]oleic acid has shown that the first steps of the lipid-linked FA desaturations utilize cytoplasmic lipids. PC and diacylglyceryltrimethylhomoserine are the major lipids involved as acyl carriers for the delta12 and delta6 desaturations of oleic acid, leading sequentially to linoleic and gamma-linolenic acids. The latter is released from its lipid carrier and elongated to 20:3n-6, which is reincorporated primarily into PE and PC and finally desaturated to AA. Galactolipids, mostly monogalctosyldiacyl-glycerol (MGDG), serve as substrates for the chloroplastic delta12 desaturase and, apparently, the omega3 desaturation, common to higher plants and many green algae. The predominant sequence desaturates the 18:1/16:0 molecular species of MGDG stepwise to the 18:3n-3/16:3n-3 molecular species similar to the prokaryotic pathway of higher plants and green algae.

Arachidonic Acid↗

PubMed2002

Accumulation of arachidonic acid-rich triacylglycerols in the microalga Parietochloris incisa (Trebuxiophyceae, Chlorophyta).

The freshwater green microalga Parietochloris incisa is the richest known plant source of the polyunsaturated fatty acid (PUFA), arachidonic acid (20:4omega6, AA). While many microalgae accumulate triacylglycerols (TAG) in the stationary phase or under certain stress conditions, these TAG are generally made of saturated and monounsaturated fatty acids. In contrast, most cellular AA of P. incisa resides in TAG. Using various inhibitors, we have attempted to find out if the induction of the biosynthesis of AA and the accumulation of TAG are codependent. Salicylhydroxamic acid (SHAM) affected a growth reduction that was accompanied with an increase in the content of TAG from 3.0 to 6.2% of dry weight. The proportion of 18:1 increased sharply in all lipids while that of 18:2 and its down stream products, 18:3omega6, 20:3omega6 and AA, decreased, indicating an inhibition of the Delta12 desaturation of 18:1. Treatment with the herbicide SAN 9785 significantly reduced the proportion of TAG. However, the proportion of AA in TAG, as well as in the polar lipids, increased. These findings indicate that while there is a preference for AA as a building block of TAG, the latter can be produced using other fatty acids, when the production of AA is inhibited. On the other hand, inhibiting TAG construction did not affect the production of AA. In order to elucidate the possible role of AA in TAG we have labeled exponential cultures of P. incisa kept at 25 degrees C with [1-14C]arachidonic acid and cultivated the cultures for another 12 h at 25, 12 or 4 degrees C. At the lower temperatures, labeled AA was transferred from TAG to polar lipids, indicating that TAG of P. incisa may have a role as a depot of AA that can be incorporated into the membranes, enabling the organism to quickly respond to low temperature-induced stress.

Arachidonic Acid↗

PubMed2002

Lipid and fatty acid composition of the green oleaginous alga Parietochloris incisa, the richest plant source of arachidonic acid.

We have hypothesized that among algae of alpine environment there could be strains particularly rich in long chain polyunsaturated fatty acids (LC-PUFA). Indeed, the chlorophyte (Trebuxiophyceae) Parietochloris incisa isolated from Mt. Tateyama, Japan, was found to be the richest plant source of the pharmaceutically valuable LC-PUFA, arachidonic acid (AA, 20:4omega6). The alga is also extremely rich in triacylglycerols (TAG), which reaches 43% (of total fatty acids) in the logarithmic phase and up to 77% in the stationary phase. In contrast to most algae whose TAG are made of mainly saturated and monounsaturated fatty acids, TAG of P. incisa are the major lipid class where AA is deposited, reaching up to 47% in the stationary phase. Except for the presence of AA, the PUFA composition of the chloroplastic lipids resembled that of green algae, consisting predominantly of C(16) and C(18) PUFAs. The composition of the extrachloroplastic lipids is rare, including phosphatidylcholine (PC), phosphatidylethanolamine (PE) as well as diacylglyceryltrimethylhomoserine (DGTS). PC and PE are particularly rich in AA and are also the major depots of the presumed precursors of AA, l8:3omega6 and 20:3omega6, respectively.

Arachidonic Acid↗

PubMedDate not supplied

Interrelationship between bone aging traits and basic anthropometric characteristics.

Using plain hand radiographs, the age dependence of various bone-aging traits (bone mineral density [BMD], cortical index [CI], osteoarthritis [OA], and osseographic [OSS] scores) was evaluated to test whether the correlation among these traits is an individual- or population-based phenomenon. In addition, the effect of anthropometric features on variation of bone-aging traits was estimated. The study included 1,295 individuals from Chuvasha, Russia, 18 to 89 years. BMD was measured from the compact compartment of the middle and distal phalanges of both 3(rd) fingers. The CI of the II-IV metacarpal bones and II-IV proximal phalanges was obtained. The development of OA was based on the standard Kellgren and Lawrence grading scheme for 28 hand joints. OSS score, a surrogate measure that takes into account different kinds of bone changes, was also obtained for each individual. Body weight and height, eight skinfold thicknesses on the trunk and extremities, and breadths of the long bones were measured. Sex-based univariate analyses and multivariate statistical analysis showed the following: 1) Age dependence was defined more strongly in "OA-linked" compared to "osteoporosis (OP)-linked" traits; 2) While "OP-linked" bone-aging traits correlated with age differently between sexes, "OA-linked" traits did not; 3) The strong interrelationship between OA-linked and OP-linked traits in both sexes became very weak and statistically insignificant (P > 0.10) after adjustment for age. Thus, OA and OP conditions in the same individual develop independently and probably reflect different underlying physiological mechanisms. 4) Anthropometric characteristics were significantly correlated with bone-aging traits, but correlations were low (r < 0.20). Thus, the contribution of anthropometric characteristics to the rate and pattern of bone aging of the hand was to relatively small.

Adolescent↗