Lack of correlation between the rate of cholesterol biosynthesis and the activity of 3-hydroxy-3-methylgutaryl coenzyme A reductase in rats and in fibroblasts treated with ML-236B

The phospholipase-2 inhibitor, p-bromophenacyl bromide, has been shown to inhibit strongly the elongation of endogenous fatty acids in preparations of brain mitochondria and microsomes. On the other hand, it does not inhibit the elongation of added palmitic or linoleic acids. The implication is that the normal first step in alteration of membrane lipid fatty acids is their release to other membrane-bound enzyme systems by a membrane-bound phospholipase A.     

Factors controlling the in vitro growth pattern of human microvascular endothelial cells

Monolayer cultures of endothelial cells of human dermal microvascular origin were exposed to a variety of culture conditions and in vitro differentiation of the cells assessed by light and electron microscopic examination. Restoration of a cytologic and fine structural appearance which resembled most closely that present in vivo was possible by raising the intracellular cAMP level. These cells formed junctional complexes seen in uncontracted microvessels and specialized attachment sites at their basal cell membrane, contained a complex network of bundled micro- and intermediate filaments and numerous Weibel-Palade bodies and accumulated electron-opaque deposits between the cells and the culture dish surface.     

Immunoperoxidase staining of glial fibrillary acidic (GFA) protein polymerized in vitro: An ultramicroscopic study

The unlabeled antibody peroxidase-antiperoxidase (PAP) method of Sternberger et al. has been employed at the ultramicroscopic level to stain filaments polymerized in vitro from aqueous extracts of multiple sclerosis (MS) plaques. The filaments were heavily decorated with antiserum to the glial fibrillary acidic (GFA) protein but not stained with serum absorbed with GFA protein, preimmunization serum, or anti-rat brain tubulin antiserum. Reassembled rat brain tubulin was heavily stained with antiserum to tubulin but was not stained with antiserum to the GFA protein. The present study provides direct morphological evidence that filaments polymerized in vitro from extracts of MS plaques contain the GFA protein.     

Autumn migratory orientation and displacement responses of two willow warbler subspecies (Phylloscopus trochilus trochilus and P. t. acredula) in South Sweden

Topography and historical range expansion has formed a so-called migratory divide between two subspecies of willow warbler (Phylloscopus trochilus) in central Scandinavia. The autumn migratory directions of individuals assigned molecularly to both subspecies and possible hybrids were recorded using orientation cage experiments in southwest and southeast Sweden. We found pronounced differences in willow warblers’ orientation in respect to genotype. The mean directions registered in the control experiments were in accordance with the ringing recoveries and analyses of stable isotopes for Scandinavian willow warblers. With the same individuals we performed displacement experiments between both sites. They resulted in non-significant orientation, which could be explained by the intermediate distance of the displacement or reactions to housing, transportation and location. On a separate set of birds we tested whether stress following transportation could explain the disorientation and found that orientation before and after transport was unchanged. Experimental studies of effects of intermediate displacements across longitudes and studies of orientation of hybrid individuals in the zones of migratory divides are crucial for understanding the mechanisms underlying orientation behaviour. Our work further stresses the importance of knowing the migration genotype of a particular bird under study, in order to correctly evaluate expected migration routes.     

Haemosporidian infections in skylarks (<Emphasis Type="Italic">Alauda arvensis</Emphasis>): a comparative PCR-based and microscopy study on the parasite diversity and prevalence in southern Italy and the Netherlands

Changes in agricultural management have been identified as the most probable cause for the decline of Skylark (Alauda arvensis) populations in Europe. However, parasitic infections have not been considered as a possible factor influencing this process. Four hundred and thirty-four Skylarks from the Southern Italy and the Netherlands were screened for haemosporidian parasites (Haemosporida) using the microscopy and polymerase chain reaction (PCR)-based methods. The overall prevalence of infection was 19.5%; it was 41.8% in Italian birds and 8.3% in Dutch birds. The prevalence of Plasmodium spp. was 34.1% and 6.5% in Skylarks from Italy and Netherlands, respectively. Approximately 15% of all recorded haemosporidian infections were simultaneous infections both in Italian and Dutch populations. Six different mitochondrial cytochrome b (cyt b) lineages of Plasmodium spp. and three lineages of Haemoproteus tartakovskyi were found. The lineage SGS1 of Plasmodium relictum was the most prevalent at both study sites; it was recorded in 24.7% of birds in Italy and 5.5% in the Netherlands. The lineages SYAT05 of Plasmodium vaughani and GRW11 of P. relictum were also identified with a prevalence of <2% at both study sites. Two Plasmodium spp. lineages (SW2 and DELURB4) and three H. tartakovskyi lineages have been found only in Skylarks from Italy. Mitochondrial cyt b lineages SYAT05 are suggested for molecular identification of P. vaughani, a cosmopolitan malaria parasite of birds. This study reports the greatest overall prevalence of malaria infection in Skylarks during the last 100 years and shows that both Plasmodium and Haemoproteus spp. haemosporidian infections are expanding in Skylarks so it might contribute to a decrease of these bird populations in Europe.     

Histamine-modulated transdifferentiation of dermal microvascular endothelial cells.

Homeostatic and inflammatory functions of skin microvessels are tightly regulated by vasoactive amines. Following stimulation with histamine, dermal microvascular endothelial cells (MEC) undergo a rapid change in phenotype (transdifferentiation) and subsequently exhibit an enhanced rate of growth. To elucidate mechanisms regulating MEC transdifferentiation, this study investigated the functional relationships among vimentin, Ca2+, and protein kinase C (PKC) in histamine-modulated dermal MEC in vitro. Distribution of vimentin and PKC in foreskin-derived MEC cultivated in a modified Iscove's medium was assessed with immunocytochemistry. Calcium ion kinetics in histamine-treated MEC were analyzed using the Ca2+ probe Fluo-3 in conjunction with interactive laser cytometry. Histamine, acting through H-1 receptors, produces a rapid (less than 100 ms) and differential elevation of free calcium in each of three cytological compartments defined by the vimentin cytoskeleton in epithelial MEC. A distinctive compartmentalized and nonuniform distribution of PKC precisely coincides with that observed for free-Ca2+ released in response to histamine. The studies reveal that histamine modulation of the MEC phenotype is associated with a rapid patterned reorganization of the vimentin skeleton. It is hypothesized that histamine induces vimentin post-translational modifications by activating a spatially localized interaction among cytoplasmic free Ca2+, PKC, and the vimentin matrix. The results further suggest that vimentin, in addition to its structural role, may participate in signal transduction and gene regulation processes in effecting MEC transdifferentiation.