Biochemical properties of vascular endothelial cells

Present knowledge in the field of vascular endothelial cells is reviewed. The role of endothelial cells in the synthesis of matrix proteins and glycosaminoglycans is described. Endothelial cells play a considerable role in the processes of coagulation and fibrinolysis. They also interact with neurotransmitters and vasomotoric substances, and participate in inflammation and immunological responses. They procuce several different growth factors. Their role in lipoprotein metabolism is of special importance to research into atherosclerosis.     

Male accessory gland substances and the control of sexual receptivity in female Culex tarsalis

ABSTRACT. Homogenates of accessory glands from male Culex tarsalis Coquillet (Diptera; Culicidae) were fractionated using gel filtration column chromatography. A component of low molecular weight capable of suppressing female sexual receptivity was obtained and partially characterized. Proteins present in homogenates of isolated accessory glands formed aggregates with other proteins in extracts of whole mosquitoes. Consequently, previous reports of the molecular weight of biologically active components in homogenates from accessory glands from other mosquito species may be inaccurate.
When female Cx. tarsalis were mated with ³H-leucine labelled males. radioactivity could be found throughout the body of the female 24 h after mating. Autoradiography showed that the radioactivity was incorporated into the cells of various organs, and was not specifically localized in a particular target tissue. Approximately 30% of the total radioactivity transferred to the female was found in the head and thoracic regions, and proteins from the head had a specific activity twice that of the thoracic proteins. Bioassay of isolated body parts from mated and virgin females showed that injections of head tissues from mated females into virgin females suppressed sexual receptivity. These results suggest that the head is involved in the physiological mechanisms resulting in refractory mating behaviour.     

Präformierte chemische Abwehrstoffe in Pflanzen

Es gibt eine Reihe interessanter Ansätze über die mögliche Rolle präformierter chemischer Abwehrstoffe in Pflanzen. Eine abschließende Beurteilung der Rolle solcher Verbindungen bei der Resistenz gegenüber phytopathogenen Krankheitserregern ist im Augenblick aber noch nicht möglich. Die bisher erzielten Ergebnisse sollten jedoch zu weiterer Forschung ermutigen, um noch vorhandene Lücken zu schließen. Besonders dringlich wären Untersuchungen an Wirt-Parasit-Systemen, bei denen neben präformierten chemischen Abwehrstoffen auch gleichzeitig postinfektionell gebildete Verbindungen eine Rolle spielen könnten. Es ist zu erwarten, daß in vielen Fällen beide Abwehrsysteme — und vielleicht noch andere — erst in ihrem Zusammenwirken die Resistenzausprägung bewirken.     

Trace metals in Swedish natural fresh waters

Water samples were collected from unpolluted waters in southern and northern Sweden to show the range of natural trace metal concentrations. The results do not indicate any significant differences in metal levels between the two study areas. Negative correlations with pH exist for total concentrations of Cd, Pb, Al, Mn and Zn. The dissolved (dialysable) metal fractions also increase with increasing acidity. The concentration of humic substances influences the distribution of Fe, Mn, Al, Pb, Cr, Co and As, as shown by positive correlations with water colour.Increasing alkalinity has a limiting effect upon concentrations and annual fluctuations of Cd and Pb, and to some extent on Zn, in running waters.     

Evidence for erythrocyte membrane glycoproteins being carriers of blood-group P1 determinants

The contribution of different membrane constituents to the bloodgroup P₁ activity of human erythrocytes was investigated. Pronase digestion of native red cell stroma or partition between butanol and water had no serologically detectable effect, whereas pronase-treatment of previously butanol-extracted membranes liberated virtually all blood-group P₁ determinants from the ghosts. On Laemmli gels, all P₁ activity was found in the band 4.5 region. Thus it is concluded that, in addition to the well-documented P₁ glycolipid, also membrane glycoproteins are carriers of blood-group P₁ determinants.     

The role of C, N and P in dissolved and particulate organic matter as a nutrient source for phytoplankton growth, including toxic species

Phytoplankton have traditionally been regarded as strictly phototrophic, with a well defined position at the base of pelagic food webs. However, recently we have learned that the nutritional demands of a growing number of phytoplankton species can be met, at least partially, or under specific environmental conditions, through heterotrophy. Mixotrophy is the ability of an organism to be both phototrophic and heterotrophic, in the latter case utilizing either organic particles (phagotrophy) or dissolved organic substances (osmotrophy). This finding has direct implications for our view on algal survival strategies, particularly for harmful species, and energy- and nutrient flow in pelagic food webs. Mixotrophic species may outcompete strict autotrophs, e.g. in waters poor in inorganic nutrients or under low light. In the traditional view of the ‘microbial loop’ DOC is thought to be channeled from algal photosynthesis to bacteria and then up the food chain through heterotrophic flagellates, ciliates and mesozooplankton. Are mixotrophic phytoplankton that feed on bacteria also significantly contributing to this transport of photosynthetic carbon up the food chain? How can we estimate the fluxes of carbon and nutrients between different trophic levels in the plankton food web involving phagotrophic algae? These questions largely remain unanswered. In this review we treat evidence for both osmotrophy and phagotrophy in phytoplankton, especially toxic marine species, and some ecological implications of mixotrophy.     

Timing of female sexual unreceptivity and male adjustment of copulatory behaviour under competition risk in the wolf spider <Emphasis Type="Italic">Schizocosa malitiosa</Emphasis>

Males can change their copulatory or sperm transfer patterns in response to sperm competition risk. Schizocosa malitiosa performs long copulations, which include two consecutive patterns (Patterns 1 and 2). Virgin females are very sexually receptive, but mated females diminish their receptiveness. Female unreceptivity has been attributed to the action of receptivity-inhibiting substances, mainly transferred during Pattern 1. We tested: (1) if females who mated only with Pattern 1 were immediately unreceptive; (2) male and female behaviours when the copulating couple was exposed to another male. For (1), we interrupted mating when Pattern 1 finished and immediately exposed the female to a second male. For (2), we introduced a second male when the couple was starting (Ei) or finishing copulation (Li). Females were unreceptive immediately after finishing Pattern 1. Males from Ei and Li dismounted and approached the second males. Ei males diminished the frequencies of insertion after perceiving the presence of a second male and dismounted less frequently when copulating with heavy females. The study provides insights about the timing of sexual unreceptivity in S. malitiosa under possibilities of sperm competition, discussing male adjustment of copulatory behaviour in the presence of rival males. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The influence of ammoniates on 14CO2 assimilation in flax

A 1 μM solution of ammoniates [ZnCu(NH₃)_n]²⁺(CO₃)²⁻ was inserted into a cut shoot of flax with the transpiration stream of water. Analysis of the ¹⁴C content after ¹⁴CO₂ assimilation by the shoot showed that ammoniates increased radioactive label contents in the tissues (especially in the young leaves and stem). In the leaves the higher sucrose to hexoses ratio, an increased radioactivity of glycerate and malate and decreased incorporation of ¹⁴C into oligosaccharides and pigments were observed. These effects were more pronounced in the young leaves. Spraying of plants with 20 mM solution resulted in an increase of plant height and leaf number.