The Scientific Life Of John Bahcall

This article follows the scientific life of John Norris Bahcall, including his tenacious pursuit of the solar neutrino problem, his contributions to our understanding of galaxies, quasars, and their emissions, and his leadership of and advocacy for astronomy and astrophysics.Comment: Prefactory for Annual Reviews of Nuclear and Particle Science; 23 pages, 6 figure

Pentosan polysulfate treatment preserves renal autoregulation in ANG II-infused hypertensive rats via normalization of P2X1 receptor activation

Inflammatory factors are elevated in animal and human subjects with hypertension and renal injury. We hypothesized that inflammation contributes to hypertension-induced renal injury by impairing autoregulation and microvascular reactivity to P2X1 receptor activation. Studies were conducted in vitro using the blood-perfused juxtamedullary nephron preparation. Rats receiving ANG II (60 ng/min) infusion were treated with the anti-inflammatory agent pentosan polysulfate (PPS) for 14 days. The magnitude and progression of hypertension were similar in ANG II and ANG II+PPS-treated rats (169 ± 5 vs. 172 ± 2 mmHg). Afferent arterioles from control rats exhibited normal autoregulatory behavior with diameter decreasing from 18.4 ± 1.6 to 11.4 ± 1.7 μm when perfusion pressure was increased from 70 to 160 mmHg. In contrast, pressure-mediated vasoconstriction was markedly attenuated in ANG II-treated rats, and diameter remained essentially unchanged over the range of perfusion pressures. However, ANG II-treated rats receiving PPS exhibited normal autoregulatory behavior compared with ANG II alone rats. Arteriolar reactivity to ATP and β,γ-methylene ATP was significantly reduced in ANG II hypertensive rats compared with controls. Interestingly, PPS treatment preserved normal reactivity to P2 and P2X1 receptor agonists despite the persistent hypertension. The maximal vasoconstriction was 79 ± 3 and 81 ± 2% of the control diameter for ATP and β,γ-methylene ATP, respectively, similar to responses in control rats. PPS treatment significantly reduced α-smooth muscle actin staining in afferent arterioles and plasma transforming growth factor-β1 concentration in ANG II-treated rats. In conclusion, PPS normalizes autoregulation without altering ANG II-induced hypertension, suggesting that inflammatory processes reduce P2X1 receptor reactivity and thereby impair autoregulatory behavior in ANG II hypertensive rats

Pentosan polysulfate inhibits atherosclerosis in Watanabe heritable hyperlipidemic rabbits: differential modulation of metalloproteinase-2 and -9

Pentosan polysulfate (PPS), a heparinoid compound essentially devoid of anticoagulant activity, modulates cell growth and decreases inflammation. We investigated the effect of PPS on the progression of established atherosclerosis in Watanabe heritable hyperlipidemic (WHHL) rabbits. After severe atherosclerosis developed on an atherogenic diet, WHHL rabbits were treated with oral PPS or tap water for 1 month. The aortic intima-to-media ratio and macrophage infiltration were reduced, plaque collagen content was increased, and plaque fibrous caps were preserved by PPS treatment. Plasma lipid levels and post-heparin hepatic lipase activity remained unchanged. However, net collagenolytic activity in aortic extracts was decreased, and the levels of matrix metalloproteinase (MMP)-2 and tissue inhibitor of metalloproteinase (TIMP) activity were increased by PPS. Moreover, PPS treatment decreased tumor necrosis factor α (TNFα)-stimulated proinflammatory responses, in particular activation of nuclear factor-κB and p38, and activation of MMPs in macrophages. In conclusion, oral PPS treatment prevents progression of established atherosclerosis in WHHL rabbits. This effect may be partially mediated by increased MMP-2 and TIMP activities in the aortic wall and reduced TNFα-stimulated inflammation and MMP activation in macrophages. Thus, PPS may be a useful agent in inhibiting the progression of atherosclerosis

Grassland cutting regimes affect soil properties, and consequently vegetation composition and belowground plant traits

<p>Machine mowing, mimicking the traditional hand mowing, is often used as a successful management tool to maintain grassland biodiversity, but few studies have investigated the long-term effects of traditional versus mechanical mowing of plant communities. Machine mowing as opposed to hand mowing causes soil compaction and reduction of soil aeration. In response, we expected strong effects on below-ground plant traits: root aerenchyma formation and superficial root growth, and no specific effects on aboveground traits. Effects were expected to be more pronounced in soils vulnerable to compaction.</p><p>We evaluated the changes in above- and belowground plant traits in a long-term (38-year) experiment with annual hand-mowing and machine-mowing management regimes on two different soil types: a coarse structured sandy soil and a finer structured sandy-organic soil</p><p>Only on the organic soil, long-term machine mowing leads to lower soil aeration (more compacted soil) and a marked change in the belowground trait distribution of the plant community. Here we find a higher cover of superficially rooting species and marginally significant lower cover of species without morphological adaptations to soil hypoxia, but no effect on species with a high capacity of forming aerenchyma.</p><p>Mowing with heavy machines on soils vulnerable to compaction affect the vegetation according to changes in soil physical conditions. This is reflected in a shift towards communities with greater proportion of superficially rooting species. Our results illustrate the sensitivity of grasslands to slight changes in the management regime.</p>