Interlocality variation in speed of moult in the Citril Finch Serinus citrinella

The speed of avian moult has been related to body condition, and this to habitat quality. These facts suggest a relationship between habitat quality and moult speed. We looked for evidence of such a relationship in the Citril Finch Serinus citrinella in the Pyrenees, where, because of a Mediterranean influence, there is an important bioclimatic contrast between north- and south-facing slopes of the same mountain. This contrast strongly affects the general body condition of birds there (higher body mass, fat score and survival on north-facing slopes). Citril Finches in the higher quality area moulted more rapidly (measured as residual wing raggedness) than those in the lower quality area, the two sampling localities being only 5 km apart. As the birds initiated moult at the same time in the two locations, this difference in speed cannot have resulted from a differential effect of photoperiod. This stresses the importance of habitat selection, even at very small scales, for the completion of moult.     

Role of the reticuloendothelial system in the catabolism of low density lipoprotein in the rat

The role of the reticuloendothelial system (RES) in receptor-independent catabolism of human low density lipoprotein (h-LDL) was evaluated in the rat in vivo after blockade of its phagocytic activity with gadolinium chloride (GaCl3). After blockade of the RES with GaCl3, the recovery of [125I] h-LDL in the liver of 17 alpha-ethinyl oestradiol-treated rats (EE-rats), was decreased by 37 and 16%, 15 and 60 min after h-LDL injection, respectively. This decrease did not result in a decreased LDL degradation which represented 14 and 55% of the injected dose in the two groups of rats after 15 and 60 min respectively, both on GaCl3 and control rats. Contrasting with EE-rats, the catabolism of h-LDL in untreated rats is much slower and takes place essentially through a receptor-independent mechanism. Six hours after the injection of [125I] h-LDL, 64% of the dose was degraded. This proportion decreased to 45% after blockade of the RES phagocytic activity. This 30 percent difference represents the proportion of h-LDL catabolized by receptor-independent mechanisms present in the Küpffer and endothelial cells. We conclude from our study that in the normal rat, the parenchymal cells of the liver on the one hand and the Küpffer and endothelial cells on the other hand contribute 70 and 30% respectively to the receptor-independent catabolism of low density lipoproteins in vivo.     

Docosahexaenoate-containing phospholipids in sarcoplasmic reticulum and retinal photoreceptors. A proposal for a role in Ca2+-ATPase calcium transport

A critical review of the experimental literature concerning the metabolism of all-cis-4, 7, 10, 13, 16, 19-docosahexaenoate-containing phospholipids in muscle and retina suggests that it plays an essential role in maximizing the Ca²⁺/ATP stoichiometry of the Ca²⁺-ATPase of sarcoplasmic reticulum and retinal photoreceptor disks. Docosahexaenoate-phosphatidylcholine is proposed to participate in oligomerization of Ca²⁺-ATPase necessary for the establishment of a high Ca²⁺/ATP coupling ratio of the Ca²⁺ pump in these tissues. Possible tests of this hypothesis are presented.     

Human enzyme polymorphism in the Canary Islands. III. Tenerife Island population

We analyzed the genetic polymorphism of eight red cell enzymes in samples from different geographical areas of Tenerife and the Iberian peninsula. The gene frequency heterogeneity found within the Tenerife samples was at the same level as that of Tenerife-mainland comparisons. The presence of the Negroid G6PD A+ allele in the Tenerife samples is evidence of an African admixture with a mean estimation of 4.5%.     

Cytology and morphology of the amphiploid Hordeum chilense (4x) × Aegilops squarrosa (4x)

Summary The intergeneric amphiploid Hordeum chilense × Aegilops squarrosa has been synthesized. The amphiploid plants have the expected chromosome number of 28. The average meiotic chromosome pairing was 12.48 bivalents + 3.04 univalents. The morphology of the amphiploid resembles that of the Aegilops parent. Nucleoli from both H. chilense and A. squarrosa are expressed in the amphiploid. Neither chromosome instability nor homoeologous pairing was found. The amphiploid is fertile and vigorous.     

Subtelomeric expression regions of Borrelia hermsii linear plasmids are highly polymorphic

Borrelia hermsii, a relapsing fever agent, undergoes multiphasic antigenic variation to evade its host's immune response. Serotype specificity is determined by variable membrane lipoproteins, Vmps, which are expressed from genes located near the end of a linear plasmid. Using the polymerase chain reaction and primers representing the promoter of the active vmp and a conserved telomeric sequence, we characterized the subtelomeric expression regions of the 25 known serotypes of strain HS1. The distance from the promoter to the telomere fell into three size classes of approximately 1.0, 1.5, and 2.5 kilobases. In the sequenced serotypes the size differences were accounted for by variable lengths of the vmp genes and intervening sequences between 3' end of the vmp gene and the start of a downstream homology block. The degree of nucleotide identity between different vmp genes, or between the different 3' flanking DNA varied from 39-78%. Thus, there is length and sequence variability not only between vmp genes themselves but also between the 3' flanking regions of vmp genes.     

Transcriptional activation by heterodimers of the achaete-scute and daughterless gene products of Drosophila

The achaete-scute complex (AS-C) and the daughterless (da) genes encode helix-loop-helix proteins which have been shown to interact in vivo and to be required for neurogenesis. We show in vitro that heterodimers of three AS-C products with DA bind DNA strongly, whereas DA homodimers bind weakly and homo or heterocombinations of AS-C products not at all. Proteins unable to dimerize did not bind DNA. Target sequences for the heterodimers were found in the promoters of the hunchback and the achaete genes. Using sequences of the former we show that the DNA binding results obtained in vitro fully correlate with the ability of different combinations to activate the expression of a reporter gene in yeast. Embryos deficient for the lethal of scute gene fail to activate hunchback in some neural lineages in a pattern consistent with the lack of a member of a multigene family.