Potential Surface Studies of Open Shell Systems

The electronic structure of a large number of organic radicals was examined by using the developed unrestricted version of the semiempirical MIND0/3 method. A review of the obtained results is presented. The calculated heats of formation (/I.Hr) are generally in good agreement with available experimental data. The estimated /I.Hr values are usually too low - 40 kJ/mol. This is not a serious drawback and had to be expected from the single determinant approach. However, it only shifts the origin of the energy scale. The relative stabilities of radical isomers are in most cases predicted quite correctly. Theoretical interatomic distances are in reasonably good accordance with experiment. Particular emphasis is placed on the discussion of the reactivity of radicals and reaction paths. Theoretical results are here of utmost importance because the elementary reactionsteps in radical rearrangements are extremely difficult to access by conventional experimental techniques. An original procedure for searching and verifying local minima and saddle points on the energy hypersurfaces is discussed. This approach is applied on the series of w-alkenyl radicals and their routes of cyclisations were throughly investigated. It was found that the experimental findings can be rationalised by a simple orbital overlap model which on the other hand leads to a natural link to the allowed/forbidden concept. These findings are corroborated by the available pieces of experimental evidence. An important outcome of our analyses is, that unlike for closed shell systems, the activated complexes of forbidden reactions for doublet states can be successfully described by single configurations and should therefore be accessible by appropriate semiempirical treatments

Magnetic domain walls in constrained geometries

Magnetic domain walls have been studied in micrometer-sized Fe20Ni80 elements containing geometrical constrictions by spin-polarized scanning electron microscopy and numerical simulations. By controlling the constriction dimensions, the wall width can be tailored and the wall type modified. In particular, the width of a 180 degree Neel wall can be strongly reduced or increased by the constriction geometry compared with the wall in unconstrained systems.Comment: 4 pages, 6 figure

Immunohistochemical localization of pregnancy-associated plasma protein-A in the male genital tract

Pregnancy-associated plasma protein-A (PAPP-A) has been found in seminal fluid at concentrations 10-20 times higher than in plasma. This observation prompted us to undertake a morphological study of the male genital tract with the aid of the immunoperoxidase technique. Immunoreactive cells were found among the Leydig cell population, as well as among the epithelium of the rete testis, the head of the epididymis and the seminal vesicles. The relatively small number of weakly staining epithelial cells leaves open the question of whether PAPP-A is excreted by these cells or whether an active transfer mechanism-possibly in the seminal vesicles-is at work, the Leydig cells increasing the plasma concentration locally, by secretion of PAPP-A into the circulatio

CA 125 in seminal plasma: correlation with semen parameters

Ovarian cancer marker CA 125 was measured in human seminal plasma, and the concentrations ranged between 22 and 1149 U/ml, and between 39 and 4711 U/ejaculate. This very high patient-to-patient variability was in contrast to a much lower within-patient variability, which was comparable to that of other semen parameters. No significant differences in CA 125 concentration were found in seminal plasma from normospermic patients, patients with male factors, vasectomized men, and in aliquots of samples which led to a pregnancy, via artificial insemination or in-vitro fertilization. The seminal plasma CA 125 concentration was not correlated with sperm count, motility and morphology. In contrast, seminal plasma CA 125 concentrations correlated with the age of the patient (P < 0.001) and inversely with the volume of the ejaculate (P < 0.001). These correlations were independent of each other. CA 125 did not correlate with the prostatic marker zinc, but did do so with the seminal vesicle marker fructose and the epididymal marker carnitin

Integrins and adhesion molecules: Gelatinase and oncofetal fibronectin secretion is dependent on integrin expression on human cytotrophoblasts

Collagenolytic activity of cytotrophoblasts is stimulated by glycoproteins of the extracellular matrix and since this stimulation can possibly occur through integrins, we measured the gelatinolytic activity of villous and extravillous cytotrophoblasts according to the type of integrins expressed on these cells. Cytotrophoblasts were isolated from legal abortions, immunopurified with anti-CD45, separated according to their expression of histocompatibility-linked antigen (HLA)-G, α6 or α5 integrin subunits and cultured for 5 days on plastic or agarose. Fetal fibronectin, human chorionic gonadotrophin (HCG) and the gelatinolytic activity were measured in the culture supernatants. Following immunopurification with anti-CD45, the gelatinolytic activity of cytotrophoblasts was significantly higher than before, indicating that contaminating lymphomyeloid cells secreted gelatinolytic inhibitors. HLA-G positive cells secreted significantly more gelatinases than HLA-G negative cells but their HCG secretion was similar. Compared to α5 positive cells, α6 positive cytotrophoblasts secreted significantly more gelatinases, significantly less fibronectin but similar amounts of HCG. We conclude that during trophoblast invasion, extravillous cytotrophoblasts (HLA-G positive) expressing the α6 integrin subunit represent the invasive population of cells (high gelatinase and low fibronectin secretion). When expression of the α5 integrin subunit is turned on, their invasive behaviour ceases and they secrete low amounts of gelatinases and high concentrations of fibronecti

Gelatinase and oncofetal fibronectin secretion is dependent on integrin expression on human cytotrophoblasts

Collagenolytic activity of cytotrophoblasts is stimulated by glycoproteins of the extracellular matrix and since this stimulation can possibly occur through integrins, we measured the gelatinolytic activity of villous and extravillous cytotrophoblasts according to the type of integrins expressed on these cells. Cytotrophoblasts were isolated from legal abortions, immunopurified with anti-CD45, separated according to their expression of histocompatibiltty-linked antigen (HLA)-G, α6 or α5 integrin subunits and cultured for 5 days on plastic or agarose. Fetal fibronectin, human chorionic gonadotrophin (HCG) and the gelatinolytic activity were measured in the culture supernatants. Following immunopurrfication with anti-CD45, the gelatinolytic activity of cytotrophoblasts was significantly higher than before, indicating that contaminating lymphomyeloid cells secreted gelatinolytic inhibitors. HLA-G positive cells secreted significantly more gelatinases than HLA-G negative cells but their HCG secretion was similar. Compared to α5 positive cells, α6 positive cytotrophoblasts secreted significantly more gelatinases, significantly less fibronectin but similar amounts of HCG. We conclude that during trophoblast invasion, extravillous cytotrophoblasts (HLA-G positive) expressing the α6 integrin subunit represent the invasive population of cells (high gelatinase and low fibronectin secretion). When expression of the α5 integrin subunit is turned on, their invasive behaviour ceases and they secrete low amounts of gelatinases and high concentrations of fibronecti

Modulation of placental vascular endothelial growth factor by leptin and hCG

Vascular endothelial growth factor (VEGF) has been identified as an endothelium‐specific mitogen and inducer of angiogenesis and endothelial cell survival. Leptin and hCG have also been suggested as possible regulators of angiogenesis in various models. In‐vivo and in‐vitro assays revealed that leptin has an angiogenic activity and that the vascular endothelium is a target for leptin. Thus, we hypothesized that products of cytotrophoblastic cells may play a role in placental angiogenesis and we therefore investigated the effects of leptin and hCG on cytotrophoblast VEGF secretion. We incubated cytotrophoblastic cells (CTB) with recombinant human leptin (rhLept) (0-4 pg/ml) or hCG (0-30000 IU/ml) for 4 h. rhLept significantly stimulated hCG (P = 0.0045) and decreased VEGF release (P = 0.0008) by CTB in a concentration‐dependent manner. On the other hand, increasing concentrations of hCG (0-30000 IU/ml), induced a significant inhibition of leptin secretion (P = 0.0028) and a marked dose‐dependent stimulation of VEGF165 secretion (P 1000‐fold in basal trophoblastic VEGF secretion with physiological concentrations of hCG in vitro. An inhibitory effect of hCG on trophoblastic leptin secretion was also observed, suggesting that hCG might exert a possible negative feedback on trophoblastic release of leptin. We hypothesize that trophoblastic products such as hCG and leptin are probably involved in the control of VEGF secretion at the maternal-fetal interfac