The unified neutral theory of biodiversity and biogeography provides a dynamic null hypothesis for the assembly of natural communities. It is also useful for understanding the influence of ...speciation, extinction, dispersal and ecological drift on patterns of relative species abundance, species-area relationships and phylogeny. Clark and McLachlan argue that neutral drift is inconsistent with the palaeorecord of stability in fossil pollen assemblages of the Holocene forests of southern Canada. We show here that their analysis is based on a partial misunderstanding of neutral theory and that their data alone cannot unambiguously test its validity.
Summary
1
The binding and functional properties of adenosine receptor ligands were compared in Chinese hamster ovary cells transfected with human adenosine A
3
receptors. Inhibition of
125
...I‐aminobenzyl‐5′‐
N
‐methylcarboamidoadenosine (
125
I‐AB‐MECA) binding by adenosine receptor ligands was examined in membrane preparations. Inhibition of forskolin‐induced cAMP accumulation by agonists was measured using a cAMP enzyme immunoassay.
2
The rank order of agonist potency for both assays was
N
6
‐(3‐iodobenzyl)‐adenosine‐5′‐
N
‐methyluronamide (IB‐MECA) > 5′‐
N
‐ethylcarboxamidoadenosine (NECA) > (−)‐
N
6
‐(
R
)‐phenylisopropyl adenosine (R‐PIA) > 4‐aminobenzyl‐5′‐
N
‐methylcarboxamidoadenosine (AB‐MECA) >
N
6
‐cyclopentyl adenosine (CPA) > adenosine. The radioligand binding rank order of antagonist potency was
N
‐9‐chloro‐2‐(2‐furanyl)1,2,4‐triazolo1,5‐cquinazolin‐5‐benzeneacetamide (MRS1220) > 1,3‐dipropyl‐8‐cyclopentylxanthine (DPCPX) > 8‐phenyltheophylline (8‐PT) > 8‐(
p
‐sulfophenyl)‐theophylline (8‐SPT). MRS1220 competitively inhibited the effect of IB‐MECA on cAMP production, with a
K
B
value of 0.35 n
m
. These data are characteristic of adenosine A
3
receptors.
3
The absence of Mg
2+
and presence of guanosine 5′‐(
γ
‐thio)triphosphate (GTP
γ
S) significantly reduced agonist binding inhibition potency, indicating binding to high‐ and low‐affinity states. The IB‐MECA, NECA and R‐PIA IC
50
values were greater for the cAMP assay than for radioligand binding, suggesting an efficient stimulus–response transduction pathway.
The binding and functional properties of adenosine receptor ligands were compared in Chinese hamster ovary cells transfected with human adenosine A(3) receptors. Inhibition of ...(125)I-aminobenzyl-5'-N-methylcarboamidoadenosine ((125)I-AB-MECA) binding by adenosine receptor ligands was examined in membrane preparations. Inhibition of forskolin-induced cAMP accumulation by agonists was measured using a cAMP enzyme immunoassay. The rank order of agonist potency for both assays was N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) > 5'-N-ethylcarboxamidoadenosine (NECA) > (-)-N(6)-(R)-phenylisopropyl adenosine (R-PIA) > 4-aminobenzyl-5'-N-methylcarboxamidoadenosine (AB-MECA) > N(6)-cyclopentyl adenosine (CPA) > adenosine. The radioligand binding rank order of antagonist potency was N-9-chloro-2-(2-furanyl)1,2,4-triazolo1,5-cquinazolin-5-benzeneacetamide (MRS1220) > 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) > 8-phenyltheophylline (8-PT) > 8-(p-sulfophenyl)-theophylline (8-SPT). MRS1220 competitively inhibited the effect of IB-MECA on cAMP production, with a K(B) value of 0.35 nm. These data are characteristic of adenosine A(3) receptors. The absence of Mg(2+) and presence of guanosine 5'-(gamma-thio)triphosphate (GTPgammaS) significantly reduced agonist binding inhibition potency, indicating binding to high- and low-affinity states. The IB-MECA, NECA and R-PIA IC(50) values were greater for the cAMP assay than for radioligand binding, suggesting an efficient stimulus-response transduction pathway.
1 The binding and functional properties of adenosine receptor ligands were compared in Chinese hamster ovary cells transfected with human adenosine A sub(3) receptors. Inhibition of ...super(125)I-aminobenzyl-5'-N-methylcarboamidoadenosine ( super(125)I-AB-MECA) binding by adenosine receptor ligands was examined in membrane preparations. Inhibition of forskolin-induced cAMP accumulation by agonists was measured using a cAMP enzyme immunoassay. 2 The rank order of agonist potency for both assays was N super(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) > 5'-N-ethylcarboxamidoadenosine (NECA) > (-)-N super(6)-(R)-phenylisopropyl adenosine (R-PIA) > 4-aminobenzyl-5'-N-methylcarboxamidoadenosine (AB-MECA) > N super(6)-cyclopentyl adenosine (CPA) > adenosine. The radioligand binding rank order of antagonist potency was N-9-chloro-2-(2-furanyl)1,2,4-triazolo1,5-cquinazolin-5-be nzeneacetamide (MRS1220) > 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) > 8-phenyltheophylline (8-PT) > 8-(p-sulfophenyl)-theophylline (8-SPT). MRS1220 competitively inhibited the effect of IB-MECA on cAMP production, with a K sub(B) value of 0.35 nm. These data are characteristic of adenosine A sub(3) receptors. 3 The absence of Mg super(2+) and presence of guanosine 5'-( gamma -thio)triphosphate (GTP gamma S) significantly reduced agonist binding inhibition potency, indicating binding to high- and low-affinity states. The IB-MECA, NECA and R-PIA IC sub(50) values were greater for the cAMP assay than for radioligand binding, suggesting an efficient stimulus-response transduction pathway.
Pressor Therapy in Critically III Patients Wohl, James S.; Clark, Terrence P.
Journal of veterinary emergency and critical care (San Antonio, Tex. : 2000),
March 2000, Volume:
10, Issue:
1
Journal Article
Peer reviewed
Summary
Vasopressors are agents that increase systemic vascular resistance by increasing vasoconstriction. Therapy with intravenous vasopressors may be required in critically ill patients when ...efforts to optimize cardiac output and blood pressure with intravascular fluid therapy fail. Increasing systemic vascular resistance can promote a favorable perfusion pressure gradient to vital organs in critically ill patients with severe, unresponsive vasodilation. Improperly administered, vasopressors may impede cardiac output and reduce oxygen transport to vital tissue sites. The understanding of systemic and regional effects of vasopressors is currently evolving. Recent literature of the commonly used agents is reviewed. Individual drugs, drug combinations, and potential new therapies are discussed. (Vet. Emerg. & Crit. Care, 10:19–33, 2000)
An outdoor CO sub(2) enrichment experiment was conducted in a loblolly pine (Pinus taeda) plantation in North Carolina. At the start of the experiment, trees were 16 yr old and not reproductively ...mature. After 3 yr of fumigation with CO sub(2) at a concentration of 200 mu l/l above ambient levels, trees were twice as likely to be reproductively mature and produced 3 times as many cones and seeds as control trees growing at ambient CO sub(2) concentrations. The CO sub(2)-fumigated trees began cone production at smaller stem diameters than the control trees. Implications for loblolly pine dispersal and recruitment patterns are discussed in the light of future increases in atmospheric CO sub(2) levels.
Andrew Hill Clark (1911-1975) was responsible for much of the recent rise of historical geography in North America. The focus on his research was the opening of New World lands by European peoples, ...and this North American experience is the subject of this collection of essays written by eight of Clark's students. They examine the role of a new physical and economic environment -- particularly abundant and cheap land -- in the settlement of New France, the cultural and physical problems that conditioned Russian America, the transformation of cultural regionalism in the eastern United States between the late colonial seaboard and the early republican interior, the changing economic geography of rice farming on the antebellum Southern seaboard, the interrelationships of the European and Indian economies in the pre-conquest fur trade of Canada, differential acculturation and ethnic territoriality among three immigrant groups in Kansas in the late nineteenth and early twentieth centuries, the development in England and the United States of similar social geographic images of the Victorian city, and the erosion of a sense of place and community by possessive individualism in eighteenth-century Pennsylvania. The essays are preceded by an appreciation of Clark as an historical geographer written by D.W. Meinig and are brought together in an epilogue by John Warkentin. The work is an unusually consistent Festchrift which should appeal to all interested in the patterns of North American settlement.
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