Chronologic studies of the effects of a hypoproteinic diet followed by an equilibrated diet on delta-6 and delta-5 desaturations of linoleic acid in liver microsomes in the rat

A low protein diet affects amounts of linoleic and arachidonic acids in hepatic microsomal phospholipids of growing rats. Are the changes related to modifications in microsomal delta 6- and delta 5- linoleic acid desaturase activities? Two groups of Wistar rats weighing 80 +/- 5 g at the beginning of the experiment were used: Control group (T) was fed on a 16% gluten + 4% casein diet for 53 days; Experimental group (E) was fed on a 4% gluten + 1% casein diet for 26 days (MP) then Control diet for 27 days (RE). After 2, 14 and 26 days of MP and 2, 15 and 27 days of RE, rats of each group were sacrificed. Protein and water contents of liver, quantitative fatty acid, composition of total lipids in liver and hepatic microsomes were determined. delta 6- and delta 5- linoleic acid desaturase activities were estimated from incubation of liver microsomes with [1-14C] C 18: 2 n-6 or [2(14)C] C 20: 3 n-6 respectively. The low protein diet stops practically ponderal growth. The fatty-acid compositions of microsomal total lipids of E rats were affected in comparison with values of T rats. These modifications persist after 27 days of RE. The C 20: 4 n-6/C 18: 2 n-6 ratio in microsomal total lipids was slightly different between T and E rats but increased strongly during refeeding. Same modifications take place in the fatty-acid composition of hepatic total lipids. After two days of MP, delta 6- and delta 5- desaturase activities were depressed, phenomenon that not persist in the course of MP. These enzyme activities increase to higher values than those of the T after two days of RE.     

Phylogenetic diversification of immunoglobulin genes and the antibody repertoire

Immunoglobulins are encoded by a large multigene system that undergoes somatic rearrangement and additional genetic change during the development of immunoglobulin-producing cells. Inducible antibody and antibody-like responses are found in all vertebrates. However, immunoglobulin possessing disulfide-bonded heavy and light chains and domain-type organization has been described only in representatives of the jawed vertebrates. High degrees of nucleotide and predicted amino acid sequence identity are evident when the segmental elements that constitute the immunoglobulin gene loci in phylogenetically divergent vertebrates are compared. However, the organization of gene loci and the manner in which the independent elements recombine (and diversify) vary markedly among different taxa. One striking pattern of gene organization is the "cluster type" that appears to be restricted to the chondrichthyes (cartilaginous fishes) and limits segmental rearrangement to closely linked elements. This type of gene organization is associated with both heavy- and light-chain gene loci. In some cases, the clusters are "joined" or "partially joined" in the germ line, in effect predetermining or partially predetermining, respectively, the encoded specificities (the assumption being that these are expressed) of the individual loci. By relating the sequences of transcribed gene products to their respective germ-line genes, it is evident that, in some cases, joined-type genes are expressed. This raises a question about the existence and/or nature of allelic exclusion in these species. The extensive variation in gene organization found throughout the vertebrate species may relate directly to the role of intersegmental (V<==>D<==>J) distances in the commitment of the individual antibody-producing cell to a particular genetic specificity. Thus, the evolution of this locus, perhaps more so than that of others, may reflect the interrelationships between genetic organization and function.      

Elongation and desaturation of arachidonic and eicosapentaenoic acids in rat liver. Effect of clofibrate feeding.

The fatty acid elongation-desaturation ability of 5,8,11,14-eicosatetraenoic (20:4(n-6)) and 5,8,11,14,17-eicosapentaenoic (20:5(n-3)) acids was determined in both liver microsomal and light mitochondrial (rich in peroxisomes) fractions of untreated and clofibrate treated rats. The elongation and the subsequent desaturation steps were performed in the corresponding favorable media. 20:5(n-3) elongation was about 2-times more extensive than that of 20:4(n-6). Clofibrate feeding for 10 days resulted in a marked decrease in the elongation rate with the two substrates, while the delta 4 desaturation rate was increased. There were small differences in the elongation rate between the microsomal and light mitochondrial fractions, however, the relative delta 4 desaturation rate was higher in the light mitochondrial fraction than microsomes.     

What can we learn from noncoding regions of similarity between genomes?

Background  

In addition to known protein-coding genes, large amounts of apparently non-coding sequence are conserved between the human and mouse genomes. It seems reasonable to assume that these conserved regions are more likely to contain functional elements than less-conserved portions of the genome.     

Brain and hippocampus fatty acid composition in phospholipid classes of aged-relative cognitive deficit rats

The aim of this work was to study the composition of long chain fatty acids and the n-6 and n-3 fatty acid ratios in aged and young Wistar rats in brain and hippocampus, related to relative cognitive deficits. The aged animals showed cognitive deficits during acquisition of a memory task (delayed alternation). In brain, results showed a decrease in palmitoleic and palmitic acid percentages in all the studied phospholipid classes and in the phosphatidylserine and phosphatidylcholine classes, respectively, in old rats, compared to the young ones. There was also an increase in oleic and stearic acid amounts in the sphingomyelin, phosphatidylserine and phosphatidylinositol classes and in the phosphatidylserine and phosphatidylcholine classes, respectively. Arachidonic acid amount was decreased in old rats, compared to the young ones, in the phosphatidylserine and phosphatidylinositol classes. Total n-6 and n-3 fatty acid amounts were both decreased in all phospholipid classes, with a stable n-6/n-3 ratio. Our results confirm that arachidonic acid concentration is decreased in aged rats and that this reduction, more significant in phosphatidylserine and phosphatidylinositol classes, should be related to the fact that low concentrations of arachidonic acid are observed during activation of glutamate receptor.     

Fatty acid composition of brain hemispheres of spontaneously hypertensive rats suckled by female Wistar rats

Total lipid fatty acid composition was investigated in brain hemispheres of male Spontaneously Hypertensive Rats (SHR), compared with normotensive Wistar Kyoto rats (WKY) used as controls. Both strains were suckled by adoptive Wistar mothers, and then fed a standard diet after weaning. No difference was observed between the two hemispheres of WKY killed either at 10 or 30 days. In SHR killed at 10 days, the two hemispheres showed differences, SHR left hemispheres exhibiting greater fatty acid composition changes than those of WKY, phenomenon that toned down at 30 days. Hence, SHR pups showed a different total lipid fatty acid composition of their brain hemispheres when compared with their WKY controls, though the two strains received the same diet. Genetically programmed hypertension might be, directly or not, involved in these changes.