Combined effects of vasoactive intestinal peptide and dopamine on adenylate cyclase in prolactin-secreting cells

VIP stimulates adenylate cyclase activity of male and female rat anterior pituitaries and human prolactinomas, while dopamine inhibits the enzyme activity of female rat pituitaries and prolactinomas. A dopamine inhibited cyclase can be detected also in male rats provided the enzyme activity is increased by VIP. The analysis of the dose-response curves for one agent (VIP or dopamine) in the absence or in the presence of the other indicates that the two agents exhibit a different pattern of interaction in the different systems. In fact, in female rat pituitaries and in human prolactinomas, the curves for dopamine±VIP and for VIP±dopamine were parallel, indicating that the two agents exherted their effects independently from one another. On the contrary, in male rat pituitaries, the curves were definitively non parallel, that is, the inhibitory effect of dopamine was greatly amplified by VIP. In no case was the apparent affinity (EC₅₀) of one agent modified by the presence of the other. It is concluded that two different modes of interaction between stimulatory and inhibitory neurohormones might exist at the level of adenylate cyclase from anterior pituitary cells.     

Effects of GTP on binding of (3H) glucagon to receptors in rat hepatic plasma membranes.

In this study, we report the preparation of [3H]glucagon and its characteristics of binding to receptors in the rat liver plasma membrane. Binding of the labeled hormone is optimal at pH 7.0. In the absence of GTP, [3H]glucagon binding to receptors is slow and the time of equilibration is inversely proportional to the hormone concentration. In the presence of GTP, equilibrium is reached within 30 s regardless of hormone levels, and the kinetics of binding are in accord with the kinetics of activation of adenylate cyclase by native glucagon in the presence of the nucleotide. Equilibrium binding measurements indicate that, in the absence of GTP, the binding isotherm is sigmoidal with an apparent Kd of 2 nM. The addition of GTP results in a complex binding isotherm with about 90% of the binding sites having a considerably lower apparent dissociation constant (greater than 10 nM) and a small population of sites having high affinity for the hormone. The binding properties of [3H]glucagon are compared with those of 125I-glucagon, and the implications of the actions of GTP on glucagon binding are discussed in relation to the overall regulation of adenylate cyclase by hormone and the nucleotide.     

Activation by bacterial lipopolysaccharide causes changes in the cytosolic free calcium concentration in single peritoneal macrophages

Variations in the cytosolic free Ca2+ concentration [( Ca2+]i) upon LPS exposure were studied in single rat peritoneal macrophages loaded with fura-2 under carefully controlled conditions. Of a total of 60 cells examined, 47% responded to LPS (1 microgram/ml) with an increase in [Ca2+]i. Macrophages were heterogeneous with regard to the LPS response, with individual cells exhibiting single rapid and transient increases in [Ca2+]i, multiple transients, or slower and more sustained variations. In 62% of the responding cells, a second exposure to LPS elicited a [Ca2+]i rise, although usually to a slightly lower peak value. Thus, rapid desensitization to LPS does not occur in the majority of these macrophages. EGTA did not abolish the response of those cells that exhibited a single rapid transient in [Ca2+]i, indicating that the source of the initial [Ca2+]i rise was the intracellular stores. There was no obvious correlation between the type of response to LPS and the initial morphologic features (rounded vs polarized) of the cells. Our present work shows unequivocally that LPS induces increases in macrophage [Ca2+]i and, thereby, lends substantial support to the hypothesis that [Ca2+]i is a second messenger in LPS-mediated activation of the macrophage.     

Modulation of microvascular growth and morphogenesis by reconstituted basement membrane gel in three-dimensional cultures of rat aorta: A comparative study of angiogenesis in Matrigel,collagen, fibrin,and plasma clot

Summary Rings of rat aorta cultured in Matrigel, a reconstituted gel composed of basement membrane molecules, gave rise to three-dimensional networks composed of solid cellular cords and occasional microvessels with slitlike lumina. Immunohistochemical and ultrastructural studies showed that the solid cords were composed of endothelial sprouts surrounded by nonendothelial mesenchymal cells. The angiogenic response of the aortic rings in Matrigel was compared to that obtained in interstitial collagen, fibrin, or plasma clot. Morphometric analysis demonstrated that the mean luminal area of the microvascular sprouts and channels was significantly smaller in Matrigel than in collagen, fibrin, or plasma clot. The percentage of patent microvessels in Matrigel was also markedly reduced. Autoradiographic studies of³H-thymidine-labeled cultures showed reduced DNA synthesis by developing microvessels in Matrigel. The overall number of solid endothelial cords and microvessels was lower in Matrigel than in fibrin or plasma clot. A mixed cell population isolated from Matrigel cultures formed a monolayer in collagen or fibrin-coated dishes but rapidly reorganized into a polygonal network when plated on Matrigel. The observation that gels composed of basement membrane molecules modulate the canalization, proliferation, and organization into networks of vasoformative endothelial cells in three-dimensional cultures supports the hypothesis that the basement membrane is a potent regulator of microvascular growth and morphogenesis. This work was supported by grants from the W. W. Smith Charitable Trust and grants CA14137 and HL43392 from the National Institutes of Health, Bethesda, MD.     

Species loss of stoneflies (Plecoptera) in the Czech Republic during the 20th century

1. Rapid expansion and intensification of anthropogenic activities in the 20th century has caused profound changes in freshwater assemblages. Unfortunately, knowledge of the extent and causes of species loss (SL) is limited due to the lack of reliable historical data. An unusual data set allows us to compare changes in the most sensitive of aquatic insect orders, the Plecoptera, at some 170 locations in the Czech Republic between two time periods, 1955–1960 and 2006–2010. Historical data (1890–1911) on assemblages of six lowland rivers allow us to infer even earlier changes. 2. Regional stonefly diversity decreased in the first half of the 20th century. Streams at lower altitudes lost a substantial number of species, which were never recovered. In the second half of the century, large‐scale anthropogenic pressure caused SL in all habitats, leading to a dissimilarity of contemporary and previous assemblages. The greatest changes were found at sites affected by organic pollution and a mixture of organic pollution and channelisation or impoundment. Colonisation of new habitats was observed in only three of the 80 species evaluated. 3. Species of moderate habitat specialisation and tolerance to organic pollution were most likely to be lost. Those with narrow specialisations in protected habitats were present in both historical and contemporary collections. 4. Contemporary assemblages are the consequence of more than a 100 years of anthropogenic impacts. In particular, streams at lower altitude and draining intensively exploited landscapes host a mere fragment of the original species complement. Most stonefly species are less frequently present than before, although their assemblages remain almost intact in near‐natural mountain streams. Our analyses demonstrate dramatic restriction of species ranges and, in some cases, apparent changes in altitudinal preference throughout the area.     

Measurement of Phospholipids May Improve Diagnostic Accuracy in Ovarian Cancer

Background

More than two-thirds of women who undergo surgery for suspected ovarian neoplasm do not have cancer. Our previous results suggest phospholipids as potential biomarkers of ovarian cancer. In this study, we measured the serum levels of multiple phospholipids among women undergoing surgery for suspected ovarian cancer to identify biomarkers that better predict whether an ovarian mass is malignant.

Methodology/Principal Findings

We obtained serum samples preoperatively from women with suspected ovarian cancer enrolled through a prospective, population-based rapid ascertainment system. Samples were analyzed from all women in whom a diagnosis of epithelial ovarian cancer (EOC) was confirmed and from benign disease cases randomly selected from the remaining (non-EOC) samples. We measured biologically relevant phospholipids using liquid chromatography/electrospray ionization mass spectrometry. We applied a powerful statistical and machine learning approach, Hybrid huberized support vector machine (HH-SVM) to prioritize phospholipids to enter the biomarker models, and used cross-validation to obtain conservative estimates of classification error rates.

Results

The HH-SVM model using the measurements of specific combinations of phospholipids supplements clinical CA125 measurement and improves diagnostic accuracy. Specifically, the measurement of phospholipids improved sensitivity (identification of cases with preoperative CA125 levels below 35) among two types of cases in which CA125 performance is historically poor - early stage cases and those of mucinous histology. Measurement of phospholipids improved the identification of early stage cases from 65% (based on CA125) to 82%, and mucinous cases from 44% to 88%.

Conclusions/Significance

Levels of specific serum phospholipids differ between women with ovarian cancer and those with benign conditions. If validated by independent studies in the future, these biomarkers may serve as an adjunct at the time of clinical presentation, to distinguish between women with ovarian cancer and those with benign conditions with shared symptoms and features.     

Re-Examination of Some Large Early Mesozoic Tetrapod Footprints from the African Collection of Paul Ellenberger

The Late Triassic—Early Jurassic ichnofauna described mainly by Paul Ellenberger from southern Africa (Lesotho) is a valuable window on first phases of dinosaur diversification. Unfortunately, the present taxonomic status of several forms from that ichnofauna is unclear. The revision of this material has been frequently invoked and partially done without reaching many definitive results. Due to the enormous amount of data, a global revision seems at present impossible and must be accomplished in smaller steps. A small number of Ellenberger's ichnogenera including Tetrasauropus, Pseudotetrasauropus, Pentasauropus, Paratetrasauropus, Sauropodopus and Deuterosauropodopus, which different authors have ascribed to basal sauropodomorphs, are here revised in a consistent manner and their attribution to osteological clades is considered. Tetrasauropus and Pseudotetrasauropus are here validated as the only ichnotaxa related to sauropodomorphs. Pentasauropus is retained as valid, and a therapsid trackmaker is suggested. Paratetrasauropus and Sauropodopus are also validated and ascribed to non-dinosaurian trackmakers, and Deuterosauropodopus is synonymized with Sauropodopus.