Cardiovascular hemodynamics with increasing exercise intensities in postmenopausal women.

We sought to determine the cardiovascular responses to increasing exercise intensities in postmenopausal women with different physical activity levels and hormone replacement therapy (HRT) status. Forty-four women (11 sedentary, 19 physically active, 14 master athletes; 24 not on HRT, 20 on HRT) completed treadmill exercise at 40, 60, 80, and 100% of maximal oxygen consumption. Oxygen consumption, heart rate, blood pressure, and cardiac output, determined via acetylene rebreathing, were measured at each exercise intensity. HRT did not affect cardiovascular hemodynamics. Stroke volume (SV) decreased significantly between 40 and 100% of maximal oxygen consumption in all groups, and the decrease did not differ among groups. The greater oxygen consumption of the athletes at each intensity was due to their significantly greater cardiac output, which was the result of a significantly greater SV, compared with both of the less active groups. The athletes had significantly lower total peripheral resistance at each exercise intensity than did the two less active groups. There were no consistent significant hemodynamic differences between the physically active and sedentary women. These results indicate that SV decreases in postmenopausal women as exercise intensity increases to maximum, regardless of their habitual physical activity levels or HRT status.     

The use of clip cages to restrain insects reduces leaf expansion systemically in Rumex obtusifolius

Abstract. 1. Clip cages have been used widely by experimental ecologists to contain insects on plants.
2. Under controlled conditions, the effect of applying clip cages alone and clip cages and the chrysomelid beetle Gastrophysa viridula on systemic leaf expansion of Rumex obtusifolius was investigated. Treatments were applied to the fully expanded fourth leaf and expansion of leaf 8 was measured over a period of 22 days.
3. The application of clip cages reduced the rate at which leaf area increased and led to reductions in final leaf areas.
4. Clip cages have systemic effects on plant development and these effects are sustained even after the clip cage is removed. Investigators should take this into account in designing experiments.     

Aluminum,Fe, Ca,Mg, K,Mn, Cu,Zn and P in above- and belowground biomass. I.Abies amabilis andTsuga mertensiana

In a mature mixed subalpine stand ofTsuga mertensiana andAbies amabilis, significantly higher Al levels were found in foliage, branch and root tissues ofT. mertensiana.Tsuga mertensiana had significant increases in Al, Ca and Mn levels with increasing foliage age. In current foliage,T. mertensiana had lower levels of Ca, similar levels of Mg and P, and higher levels of Mn thanA. amabilis. Both tree species had Cu and Fe present at higher levels in branch than foliage tissues. Fine roots had the highest concentrations of Al, Fe and Cu but the lowest Ca and Mn concentrations of all tissues analyzed. In the roots of both species, phloem tissues always had significantly higher Al levels than xylem. Fine roots (< 1 and 1–2 mm) ofT. mertensiana had higher Al levels than were found inA. amabilis. Roots greater than 2 mm in diameter exhibited no significant differences in Al levels in phloem or xylem tissue betweenA. amabilis andT. mertensiana. The two species show a clear difference in their ability to accumulate specific elements from the soil.     

Proteolytic processing of foot-and-mouth disease virus polyproteins expressed in a cell-free system from clone-derived transcripts

All picornaviral genes are expressed as a single, large polyprotein, which is proteolytically processed into the system produces functional proteins, including viral protease 3C, which plays a major role in processing the precursor proteins. To study the function of the two putative proteases 3C and leader (L) in processing, we constructed several cDNA plasmids encoding various regions of the FMDV type A12 genome. These plasmids, containing FMDV cDNA segments under the control of the T7 promoter, were transcribed in vitro by using T7 RNA polymerase and then translated in rabbit reticulocyte lysates. The expressed FMDV gene products were identified by immunoprecipitation with specific antisera and analyzed by gel electrophoresis. The results demonstrate the following: (i) the leader protein, L, is processed from the structural protein precursor, P1, in the absence of any P2 or P3 region proteins; (ii) protein 2A remains associated with the structural protein precursor, P1, rather than the precursor, P2; (iii) the processing of the P1-2A/P2 junction is not catalyzed by 3C or L; (iv) the proteolytic processing of polyproteins from the structural P1 region (except VP4/VP2) and the nonstructural P2 and P3 region is catalyzed by 3C.     

Stopover and fat deposition by North American wood-warblers (Parulinae) following spring migration over the Gulf of Mexico

Summary Length of stopover and rate of weight gain (fat deposition) were studied in several species of passerine birds that stopped in southwestern Louisiana along the northern coast of the Gulf of Mexico after a trans-Gulf flight. Fatdepleted birds were more common among the birds that arrived at our study site in southwest Louisiana, though variability characterized our samples. Migrants that landed after encountering opposing winds or rain over the northern Gulf of Mexico were, on average, fatter than migrants that landed when weather was favorable for continued migration. Some of the variation in the energetic condition of arrivals may be explained by the location where migrants initiated crossings. Our simulation of flight over the Gulf of Mexico showed that with following winds a warbler can cross the Gulf of Mexico from Yucatan with fat reserves to spare, and stronger tailwinds make flights from as far south as Honduras energetically permissible. The length of stay after a trans-Gulf flight was related to the extent of fat-depletion upon arrival: lean birds stayed longer than fat migrants. Migrants stopped over for 1–7 days and replenished energy reserves at rates that varied from 0.19 g/d for Hooded Warblers (Wilsonia citrina) to 0.87 g/d for Ovenbirds (Seiurus aurocapillus). Within each species, most individuals gained weight at a rapid rate, though a few individuals lost or maintained weight during their stay.     

Calcium regulates inositol 1,3,4,5-tetrakisphosphate production in lysed thymocytes and in intact cells stimulated with concanavalin A.

Lysed mouse thymocytes release [3H]inositol 1,4,5 trisphosphate from [3H]inositol-labelled phosphatidyl inositol 4,5-bisphosphate in response to GTP gamma S, and rapidly phosphorylate [3H]inositol 1,4,5-trisphosphate to [3H]inositol 1,3,4,5-tetrakisphosphate. The rate of phosphorylation is increased approximately 7-fold when the free [Ca2+] in the lysate is increased from 0.1 to 1 microM, the range in which the cytosolic free [Ca2+] increases in intact thymocytes in response to the mitogen concanavalin A. Stimulation of the intact cells with concanavalin A also results in a rapid and sustained increase in the amount of inositol 1,3,4,5-tetrakisphosphate, and a much smaller transient increase in 1,4,5-trisphosphate. Lowering [Ca2+] in the medium from 0.4 mM to 0.1 microM before addition of concanavalin A reduces accumulation of inositol 1,3,4,5-tetrakisphosphate by at least 3-fold whereas the increase in inositol 1,4,5-trisphosphate is sustained rather than transient. The data imply that in normal medium the activity of the inositol 1,4,5-trisphosphate kinase increases substantially in response to the rise in cytosolic free [Ca2+] generated by concanavalin A, accounting for both the transient accumulation of inositol 1,4,5-trisphosphate and the sustained high levels of inositol 1,3,4,5-tetrakisphosphate. Inositol 1,3,4,5-tetrakisphosphate is a strong candidate for the second messenger for Ca2+ entry across the plasma membrane. This would imply that the inositol polyphosphates regulate both Ca2+ entry and intracellular Ca2+ release, with feedback control of the inositol polyphosphate levels by Ca2+.