Vascular distribution of nitric oxide synthase and vasodilation in the Australian lungfish, Neoceratodus forsteri

The presence of nitric oxide synthase (NOS) and role of nitric oxide (NO) in vascular regulation was investigated in the Australian lungfish, Neoceratodus forsteri. No evidence was found for NOS in the endothelium of large and small blood vessels following processing for NADPH-diaphorase histochemistry. However, both NADPH-diaphorase histochemistry and neural NOS immunohistochemistry demonstrated a sparse network of nitrergic nerves in the dorsal aorta, hepatic artery, and branchial arteries, but there were no nitrergic nerves in small blood vessels in tissues. In contrast, nitrergic nerves were found in non-vascular tissues of the lung, gut and kidney. Dual-wire myography was used to determine if NO signalling occurred in the branchial artery of N. forsteri. Both SNP and SIN-1 had no effect on the pre-constricted branchial artery, but the particulate guanylyl cyclase (GC) activator, C-type natriuretic peptide, always caused vasodilation. Nicotine mediated a dilation that was not inhibited by the soluble GC inhibitor, ODQ, or the NOS inhibitor, L-NNA, but was blocked by the cyclooxygenase inhibitor, indomethacin. These data suggest that NO control of the branchial artery is lacking, but that prostaglandins could be endothelial relaxing factors in the vasculature of lungfish.

The ß-amyloid peptide in Alzheimer's disease decreases adhesion of vascular muscle cells to the basement membrane

Cerebral amyloid angiopathy (CAA) is a major feature of Alzheimer's disease pathology. In CAA, degeneration of vascular smooth muscle cells (VSMCs) occurs close to regions of the basement membrane where the amyloid protein (Aβ) builds up. In this study, the possibility that Aβ disrupts adhesive interactions between VSMCs and the basement membrane was examined. VSMCs were cultured on a commercial basement membrane substrate (Matrigel). The presence of Aβ in the Matrigel decreased cell-substrate adhesion and cell viability. Full-length oligomeric Aβ was required for the effect, as N- and C-terminally truncated peptide analogues did not inhibit adhesion. Aβ that was fluorescently labelled at the N-terminus (fluo-Aβ) bound to Matrigel as well as to the basement membrane heparan sulfate proteoglycan (HSPG) perlecan and laminin. Adhesion of VSMCs to perlecan or laminin was decreased by Aβ. As perlecan influences VSMC viability through the extracellular signal-regulated kinase (ERK)1/2 signalling pathway, the effect of Aβ1–40 on ERK1/2 phosphorylation was examined. The level of phospho-ERK1/2 was decreased in cells following Aβ treatment. An inhibitor of ERK1/2 phosphorylation enhanced the effect of Aβ on cell adhesion. The studies suggest that Aβ can decrease VSMC viability by disrupting VSMC–extracellular matrix (ECM) adhesion.

Too little exercise and too much sitting : inactivity physiology and the need for new recommendations on sedentary behaviour

Moderate-to vigorous-intensity physical activity has an established preventive role in cardiovascular disease, type 2 diabetes, obesity, and some cancers. However, recent epidemiologic evidence suggests that sitting time has deleterious cardiovascular and metabolic effects that are independent of whether adults meet physical activity guidelines. Evidence from “inactivity physiology” laboratory studies has identified unique mechanisms that are distinct from the biologic bases of exercising. Opportunities for sedentary behaviors are ubiquitous and are likely to increase with further innovations in technologies. We present a compelling selection of emerging evidence on the deleterious effects of sedentary behavior, as it is underpinned by the unique physiology of inactivity. It is time to consider excessive sitting a serious health hazard, with the potential for ultimately giving consideration to the inclusion of too much sitting (or too few breaks from sitting) in physical activity and health guidelines.

Physiology and biochemistry of budburst in Vitis vinifera

Both the physiological and biochemical control of budburst in the grapevine, Vitis Vinifera L. were investigated. It was found that the accuracy of a predictive model for grapevine budburst based on ambient temperature was limited under the experimental conditions. There was a significant correlation of 4.7 ± 0.3 days between the days of maximal xylem exudation and budburst over the 3 years of investigation. The co-relationships between daily xylem exudate volume and a range of environmental parameters were considered. It was found that soil temperature was highly correlated against daily xylem exudation. Ambient temperature and soil moisture were significantly correlated with xylem exudation, however the coefficients of correlation were much lower than that of soil temperature. Rainfall showed only a very limited correlation with daily xylem exudate flow. Seasonal variations in the pH and the carbohydrate and inorganic nutrient concentrations of xylem exudate were investigated. Exudate carbohydrate concentrations fell from 660 µM before the day of maximal xylem exudation to zero levels within 4 weeks. Xylem exudate pH was found to consistently fall to a minimum at the time of maximal exudate flow. Exudate concentrations of the metallic cofactors Ca, K, Mg, Mn and Zn varied directly with daily exudate flow, suggesting some sort of flow-dependent mobilisation of these nutrients. A growth promontory oligosaccharide fraction was prepared by partial acid hydrolysis of grapevine primary cell wall material. This fraction significantly increased control growth of the Lemna minor L. bioassay over a limited ‘window’ of bioactivity. A growth inhibitory oligosaccharide fraction, similar in activity to abscisic acid was isolated from grapevine xylem exudate prior to budburst. The exudate concentration or efficacy of this substance declined after budburst such that there was no apparent growth inhibition. A model is proposed for grapevine budburst whereby an oligosaccharide growth inhibitor is gradually removed from the xylematic stream under the effects of soil temperature, allowing the surge of metabolic activity and vegetative growth that constitute budburst.

Cholesterol is necessary both for the toxic effect of Abeta peptides on vascular smooth muscle cells and for Abeta binding to vascular smooth muscle cell membranes

Accumulation of beta amyloid (Aβ) in the brain is central to the pathogenesis of Alzheimer's disease. Aβ can bind to membrane lipids and this binding may have detrimental effects on cell function. In this study, surface plasmon resonance technology was used to study Aβ binding to membranes. Aβ peptides bound to synthetic lipid mixtures and to an intact plasma membrane preparation isolated from vascular smooth muscle cells. Aβ peptides were also toxic to vascular smooth muscle cells. There was a good correlation between the toxic effect of Aβ peptides and their membrane binding. 'Ageing' the Aβ peptides by incubation for 5 days increased the proportion of oligomeric species, and also increased toxicity and the amount of binding to lipids. The toxicities of various Aβ analogs correlated with their lipid binding. Significantly, binding was influenced by the concentration of cholesterol in the lipid mixture. Reduction of cholesterol in vascular smooth muscle cells not only reduced the binding of Aβ to purified plasma membrane preparations but also reduced Aβ toxicity. The results support the view that Aβ toxicity is a direct consequence of binding to lipids in the membrane. Reduction of membrane cholesterol using cholesterol-lowering drugs may be of therapeutic benefit because it reduces Aβ-membrane binding.

Variations in vascular access flows in haemodialysis can depend on needle orientation

Introduction: While using the Transonic Qc[TM] machine to assess access flow in arteriovenous fistulae (AVF), we observed that when compared to antegrade arterial needle insertion, retrograde arterial needle insertion could regularly produce lower access flow measurements. This study sought to explore this phenomenon.

Method: 23 patients entered and 20 finished the study. Patient selection criteria included: functioning AVF and an adequate AVF length for either retrograde or antegrade arterial needle insertion. After ensuring stable and similar blood pressures, 3 flow measurements were taken during the first 2 hours on the same dialysis day of 3 consecutive weeks using antegrade needle insertion then were repeated on 3 further consecutive weeks using retrograde insertion.

Results: Overall, access flows measured with retrograde insertion were significantly lower by a mean difference of 107.15 ml/min (57-484 ml/min) than the flows measured with antegrade needle placement. In 5/20, 3 recorded minimal difference and 2 had a higher access flows during retrograde insertion. No recirculation was observed during either antegrade or retrograde needle insertion. The paired t-test showed that there was significant difference between the antegrade versus retrograde mean measurements (p = 0.005).

Conclusion: Although the sample size is small and the number of measurements limited, we conclude that access flows may be greater with an antegrade arterial orientation compared to flows recorded with a retrograde orientation. The phenomenon behind this conclusion is yet to be investigated. We suggest that when using the Transonic Qc[TM] access measurement device the arterial needle should always be in the same direction for each measurement for each individual patient.

Mechanism of nitric oxide regulation of vascular tone in the mesenteric arteries of the cane toad, Bufo marinus

Nitric oxide control of large systemic blood vessels of the cane toad, Bufo marinus is provided by nitrergic nerves. However, the involvement of nitrergic nerves in the regulation of small blood vessels has yet to be determined. This study investigated the nitric oxide (NO) control of the mesenteric arteries (MA) of B. marinus. Immunohistochemistry and NADPH-diaphorase histochemistry demonstrated a dense plexus of nitrergic nerves in the MA of B. marinus. MAs (~ 500–700µm in diameter) were mounted in a myograph and placed under an initial tension equivalent to their normal diameter. MAs were pre-constricted with the thromboxane A2 mimetic, U46619, prior to the addition of putative, vasodilatory chemicals. Acetylcholine caused a vasodilation that was endothelium-independent, because removal of the endothelium had no effect on the dilation. The response to acetylcholine was blocked by the NOS inhibitor, L-NNA, demonstrating that the effect was NO-dependent. Interestingly, nicotine also caused a dilation that was not affected by removal of the endothelium, but was significantly inhibited by L-NNA and the calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP(8–37). These findings indicate that the MA of B. marinus are controlled by NO released from nitrergic nerves. In addition, a component of the response to applied nicotine appears to be mediated CGRP, which is probably released from sensory nerves.

Mucosal vascular addressin cell adhesion molecule-1 is expressed outside the endothelial lineage on fibroblasts and melanoma cells

Mucosal vascular addressin cell adhesion molecule-1 (MAdCAM-1) is predominantly expressed on high endothelial venules in inflamed tissues where it assists with leucocyte extravasation. Here we report that MAdCAM-1 has the potential to be more widely expressed outside the endothelial cell lineage than previously appreciated. Thus, MAdCAM-1 RNA transcripts and cell-surface protein were expressed by NIH 3T3 fibroblasts following activation with tumour necrosis factor-alpha (TNF-alpha), and by freshly isolated and cultured primary mouse splenic and tail fibroblasts in the absence of TNF-alpha stimulation. They were constitutively expressed by B16F10 melanoma cells, and expression was enhanced by cell activation with TNF-alpha. Mucosal vascular addressin cell adhesion molecule-1 was expressed on the apical surface of isolated cells, but became predominantly localized to cell junctions in confluent cell monolayers, suggesting it may play a role in the homotypic aggregation of cells. Tumour necrosis factor-alpha enhanced the expression of a firefly luciferase reporter directed by the MAdCAM-1 promoter in NIH 3T3 and B16F10 cells. A DNA fragment extending from nt -1727 to -673 was sufficient to confer cell-type selective expression. Mucosal vascular addressin cell adhesion molecule-1 expressed by NIH 3T3 cells was biologically active, as it supported the adhesion of TK-1 T cells in an alpha4beta7-dependent fashion. The expression of MAdCAM-1 by fibroblasts, and melanomas suggests MAdCAM-1 may play a role in regulating host responses in the periphery, leucocyte transmigration across nonendothelial boundaries, or the homotypic interactions of some malignant melanomas.

Recent advances on the roles of NO in cancer and chronic inflammatory disorders

Nitric oxide (NO) is a short-life molecule produced by the enzyme known as the nitric oxide synthase (NOS), in a reaction that converts arginine and oxygen into citrulline and NO. There are three isoforms of the enzyme: neuronal NOS (nNOS, also called NOS1), inducible NOS (iNOS or NOS2), and endothelial NOS (eNOS or NOS3). It is now known that each of these isoforms may be expressed in a variety of tissues and cell types. This paper is a review of the current knowledge of various functions of NO in diseases. We discuss in more detail its role in Cancer, the role of NO in myocardial pathophysiology, in central nervous system (CNS) pathologies. Other diseases such as inflammation, asthma, in chronic liver diseases, inflammatory bowel disease (IBD), arthritis, are also discussed. This review also covers the role of NO in cardiovascular, central nervous, pancreas, lung, gut, kidney, myoskeletal and chronic liver diseases (CLD). The ubiquitous role that the simple gas nitric oxide plays in the body, from maintaining vascular homeostasis and fighting infections to acting as a neurotransmitter and its role in cancer, has spurred a lot of interest among researchers all over the world. Nitric oxide plays an important role in the physiologic modulation of coronary artery tone and myocardial function. Nitric oxide from iNOS appears to be a key mediator of such glial-induced neuronal death. The high sensitivity of neurons to NO is partly due to NO causing inhibition of respiration, rapid glutamate release from both astrocytes and neurons, and subsequent excitotoxic death of the neurons.

Vascular plant and small mammal communities over an elevational gradient

Plant species richness and plant and small mammal beta diversity decline over the elevational gradient in the Otway ranges. These patterns are influenced by climate, habitat and spatial structure. This highlights the need to preserve continuous habitat and understand the influence of climate, to conserve communities in the changing future.

Molecular physiology of water balance in the Spinifex hopping mouse

Many animals live in the deserts of Australia and survive without drinking water. This research examined desert adaptations in the Spinifex hopping mouse (Notomys alexis), and is the first study to demonstrate how many genes and exzymes in the kidney are controlled to maintain water balance in the absence of drinking water.

Study of the physiology and biochemistry of chlorophyllase in Zostera muelleri

Examines the biochemistry and physiology of chlorophyllase in the marine angiosperm Zostera muelleri. Enzyme activity was found to be highly correlated with chlorophyll synthesis in developing leaf tissue. This study provides evidence for the physiological role of chlorophyllase in chlorophyll degradation and provides insights into the senescence process in seagrass.