Changes in the physico-chemical properties of synaptosomal membranes induced by phospholipase A2

Using fluorescent and EPR spin probing techniques, the changes in the physico-chemical properties of rat brain synaptosomal membranes induced by phospholipase A2 were studied. It was shown that treatment of synaptosomal membranes with phospholipase A2 leads to their depolarization, increases their surface negative potential and decreases the microviscosity of the membrane lipid bilayer. The observed changes in the physicochemical properties of synaptosomal membranes induced by phospholipase A2 are discussed in terms of a possible regulatory role of lipids in the transmembrane chemical signal transfer.     

Hyperglycaemia alters the physico-chemical properties of proteins in erythrocyte membranes of diabetic patients.

1. The dynamic properties of erythrocyte membranes in diabetic children and of control erythrocyte membranes subjected to in vitro glycation have been investigated by means of fluorescence quenching of membrane tryptophan residues and ESR spectroscopy. 2. The apparent distance separating the membrane protein tryptophan and the bound 1-anilino-8-naphthalenesulphonate (ANS) molecules was decreased in erythrocyte membranes from children with diabetes. This resulted in a significant increase of the maximum energy transfer efficiency in diabetic membranes. 3. The relevant alterations occurred in the above parameters due to the in vitro nonenzymatic glycosylation of control membranes. 4. These changes were accompanied by the decreased hw/hs parameter of MSL and the increased relative rotational correlation time (tau c) of ISL in diabetic membranes and in the membranes subjected to in vitro glycation. 5. The results suggest that the conformational changes in membrane proteins may occur at both the intrinsic and exposed thiol groups. 6. Both the in vivo and the in vitro data indicate that nonenzymatic glycosylation of membrane proteins may be the major factor attributable to the alterations in the dynamic properties of erythrocyte membrane in diabetic state.     

Immunohistochemical evidence for the heterogeneity of maternal and fetal vascular endothelial cells in human full-term placenta

The heterogeneity of endothelial cell surface antigen expression was studied in 5 human full-term placentae by means of indirect immunohistochemistry using 9 monoclonal antibodies and by staining with fluorescent-conjugated Ulex europaeus lectin, both of which are widely used endothelial cell markers. (1) A highly specific, homogeneous staining of fetal and maternal placental vessels of all sizes and anatomical regions was observed by the monoclonal antibodies PAL-E, QBEND10 and 1F10. These antibodies were even more specific than Ulex europaeus lectin, factor VIII antibody and von Willebrand factor antibody, which cross-reacted with some non-endothelial cells and structures. The reactivity of PAL-E, QBEND10 and 1F10 with residual surface cells of the basal plate strongly suggests an endothelial origin of these cells. (2) In contrast to other organs, PAL-E, QBEND10 and HM 15/3 strongly stained endothelial cells of the macrovascular system in the human placenta. This might indicate an organ-associated heterogeneity of fetal endothelial cells. (3) Monoclonal antibodies against receptors for transferrin and IgG (FcRII) labeled the endothelial cells of fetal placental vessels with increasing intensity distal to the insertion of the umbilical cord. The vessels of the umbilical cord itself were unreactive. This might suggest a heterogeneity of macro- and microvascular endothelial cells.     

The value of fluorescence markers in the distinction between maternal and fetal chromosomes.

Selected fluorescence markers of chromosomes were studied in 50 paired samples of cells obtained by culture of amniocentesis material and by culture of leukocytes from pregnant women. Comparative analyses showed that this method is of great value in disclosing admixture of maternal cells to material obtained by amniocentesis, as a minimum of 2 fluorescence marker differences between mother and fetus was found in the present material. The distribution of markers in mother/fetus pairs is in agreement with the assumption of genetic determination. Variation was observed between populations with respect to the frequency of the markers studied.     

Steadiness of oxygen tension in the fetal brain during changes in maternal oxygenation

In acute experiments on pregnant rats (86) and their fetuses (76) the authors studied oxygen tension in the brain of the developing organism. In inhalation PO2 in the brain of the fetus practically did not change.     

Analysis of early processes in wound-induced vascular regeneration using TED3 and ZeHB3 as molecular markers

Interruption of the vascular bundles of Zinnia internodes induced transdifferentiation of cells into tracheary elements (TEs) or sieve elements (SEs) within 4 d of wounding. The early stage of the regeneration processes was analyzed using two molecular marker genes, TED3 and ZeHB3, which are expressed specifically in TE precursor cells and immature phloem cells, respectively. An increase in the numbers of TED3 and ZeHB3 mRNA-expressing cells always preceded an increase in the numbers of TEs and SEs formed. The earliest sign of vascular differentiation was the appearance 24 h after wounding of a layer(s) of TED3 mRNA-expressing cells in the inter- and intrafascicular cambial-like regions along the severed vascular bundles. In contrast, the number of ZeHB3 mRNA-expressing cells decreased dramatically along the severed bundles 24 h after wounding, and increased again 36 h after wounding. These results clearly indicate that xylem and phloem differentiation are not synchronized during vascular regeneration. Treatment with 10(-3) M colchicine abolished the expression of ZeHB3 mRNA in pith parenchyma, but not TED3 mRNA; this suggests that cell division is a prerequisite for the transdifferentiation of pith parenchymal cells into immature phloem cells expressing ZeHB3. In contrast, transdifferentiation of pith parenchymal cells to TE precursor cells does not require preceding cell division. However, the inhibition of cell division prevented the formation of both radial files of TEs and the cambial-like layer(s) of TED3 mRNA-expressing cells, and, ultimately, vascular regeneration altogether. These results imply that wound-induced cambial-like activity in and between severed vascular bundles is essential for vascular regeneration.     

Analysis of the physico-chemical properties of fluorocarbon inducers of cytochrome P-450 in membranes of liver endoplasmic reticulum

Cytochrome P-450 induction in rat liver microsomes after intravenous injections of submicrone emulsions of nine perfluorochemicals (2 g of PFC per kg of body weight) was investigated. A comparison of physico-chemical properties of the fluorocarbons revealed that their activity as cytochrome P-450 inducers is determined by their solubility in H2O and lipids as well as by the pressure of their saturated vapours at 37 degrees C. The fluorocarbons capable of inducing cytochrome P-450 have a molecular mass of 400-550 Da. The presence of heteroatoms (N and O) and some structural peculiarities of the perfluorochemicals do not influence the ability of the fluorocarbons to induce cytochrome P-450.     

Serum prolactin level changes in the maternal and fetal circulation between the 28th-40th weeks of pregnancy

Serum prolactin concentration was determined in blood samples taken from the maternal cubital vein, the umbilical vein and artery between the 28th-40th weeks of pregnancy from 108 parturients, of whom 74 gave birth prematurely and 34 gave birth at term. Results indicated that during this period the prolactin level rose in the umbilical vein and artery but not in the maternal vein. Correlative analysis showed a significant positive correlation between gestational age and the serum prolactin concentration of umbilical arterial and venous blood, but no correlation was found in the case of maternal blood. During the 28th-32nd weeks the prolactin level of maternal blood was found to be higher than that of umbilical blood while during the 33rd-36th weeks and at the 40th week the prolactin level was higher in the umbilical vein and artery. No correlation was found between the prolactin concentration of maternal and umbilical blood. On the basis of these results the authors conclude that fetal prolactin concentration changes occur independently of the maternal organism and increases during the 28th-40th weeks of pregnancy.     

Effect of changes in the early maternal environment on predisposition to catalepsy in rats of different ages

Reciprocal cross-fostering of control Wistar and catalepsy-prone GC rat pups resulted in a decrease in duration of cataleptic reactions of GC rats estimated at the age of two weeks, one month, and six months and a tendency to its decrease in Wistar rats at the age of one month. In-fostering did not exert this effect.     

Ultrastructural changes in the erythrocyte plasma membranes of chickens in the early stages of interaction with the influenza virus

Using freeze-fracture method it is shown that at the early stages of interaction with chicken erythrocytes the influenza virus induces generalized changes in the physical state of erythrocyte plasma membranes resulted from local disturbances of the cell surface in adsorption sites of virions. Ultrastructural changes seen in the membranes reach their maximum 5 minutes after infection which corresponds to the moment of maximum pinocytotic cell activity in relation to the viruses.     

Contribution of electrodiffusion to the dynamics of electrically stimulated changes in mechanical properties of collagen membranes

We have studied the kinetics of oscillatory tensile forces in collagen membranes. These forces were generated by sinusoidal electric fields applied across the membrane. Both the magnitude and phase of the measured force changed with frequency over a three-decade range. The membrane-separated electrolyte baths had different ionic strength but identical non-isoelectric pH. Changes in intramembrane ionic strength due to the electric field were calculated over the same frequency range via an electrodiffusion model that was generalized to include convection and electrokinetic coupling. A comparison of the experimental and theoretical phases and amplitudes versus frequency suggests that electrodiffusion is the dominant rate-limiting process in this electromechanochemical transduction. These results are relevant to electrostatic interactions in connective tissues and to membrane-based filtration devices in which membrane permeability may be actively varied and controlled by an applied electric field.     

Can isoprenoids in leaves and roots of plants serve as biomarkers for past vegetation changes? A case study from the Ecuadorian Andes

Large-scale clear-cutting and burning caused the altitude of the natural upper forest line (UFL) in the Northern Ecuadorian Andes to decline to the point that its ‘natural’ position is now uncertain. To obtain a detailed reconstruction of the dynamics of the UFL over the last few thousand years, traditional proxies alone do not suffice. For instance, pollen analysis suffers from a low altitudinal resolution due to the large wind-blown component. In an attempt to find new, additional proxies to study past UFL dynamics in the Ecuadorian Andes, we investigated the occurrence of isoprenoids (diterpenes, phytosterols and pentacyclic triterpenoids) in the roots and leaves of 19 plant species responsible for the dominant biomass input in soil and peat records along altitudinal transects covering approximately 500 m above and below the current UFL in two locations in the Northern Ecuadorian Andes. Isoprenoids can serve as biomarker if they are uniquely present in a relevant plant species and preserved well enough in chronological order in suitable records. Such biomarkers could help establish past vegetation dynamics including the UFL position. For an isoprenoid to be a biomarker in soils normally it must be absent from the roots of a plant species as roots do not enter soils in chronological order. For peat deposits this criteria only needs to be met for the peat species themselves as only roots from peat species will be present. Two diterpenes, four phytosterols and six pentacyclic triterpenoids met the criteria for biomarker in peat records. Of these, one diterpene, two phytosterols and three pentacyclic triterpenoids also met the criteria for biomarker in soils. Samples from a soil under forest, a soil under the adjacent páramo and a nearby peat deposit, ¹⁴C dated at approximately 1500 cal. AD and 200 cal. AD, were tested for the presence of isoprenoids that meet the criteria for biomarker. Such isoprenoids were only found in the peat bog samples. However, we found that changes of number and concentrations of isoprenoids with depth might provide additional information related to past vegetation changes. In conclusion, isoprenoids show potential for use in a multi-proxy approach to reconstruct past UFL locations in the Northern Ecuadorian Andes and other ecosystems with similar vegetation and soils.