The role of calmodulin in the regulation of (Mg2+ + Ca2+)-ATPase activity in erythrocyte membranes of cystic fibrosis patients and controls

(Mg²⁺ + Ca²⁺)-ATPase activity has been found to be significantly reduced in EDTA-washed erythrocyte membrane preparations from cystic fibrosis patients compared to aged-matched controls. Calmodulin was found to be present in erythrocytes from cystic fibrosis patients and characterized similarly to calmodulin isolated from control preparations. Calmodulin from control erythrocyte preparations stimulated the (Mg²⁺ + Ca²⁺)-ATPase activity of EDTA-washed erythrocyte membranes derived from cystic fibrosis patients to the same extent as those membranes derived from controls. Similarly, calmodulin obtained from erythrocytes of cystic fibrosis patients stimulated the (Mg²⁺ + Ca²⁺)-ATPase activity of control and cystic fibrosis erythrocyte membrane preparations to a similar extent. These results indicate that this decrease in (Mg²⁺ + Ca²⁺)-ATPase activity in erythrocytes from cystic fibrosis patients is not due to an alteration in the regulatory function of calmodulin.     

High specific activity ribulose 1,5-bisphosphate carboxylase-oxygenase from Nicotiana tabacum

Ribulose 1,5-bisphosphate carboxylase (EC.4.1.1.39) has been obtained from Nicotiana tabacum leaf homogenates with specific activites from 0.5 to 0.8 µmol CO₂ fixed (mg protein min)^-1. These activities are reconciled with much lower, previously reported activities. The results suggest that if the tobacco enzyme is assayed under optimum conditions there is little difference in the intrinsic specific activities of tobacco and spinach ribulose 1,5-bisphosphate carboxylase. Several factors affecting activity measurements were examined.     

Buffel Grass and fire in a Gidgee and Brigalow woodland: A case study from central Queensland

Summary The effects of a fire on plant community structure were examined in a remnant Gidgee (Acacia cambagei) and Brigalow (Acacia harpophylla) woodland infested with the naturalized exotic, Buffel Grass (Cenchrus ciliaris) in central Queensland. Fifteen months after the fire, burnt areas had about half the basal area of living trees and more than twice the cover of Buffel Grass and Parthenium Weed (Parthenium hysterophorus) as unburnt areas. This is consistent with the idea that Buffel Grass invasion, which increases ground fuel loads in Acacia woodlands, is facilitated by burning, producing positive feedback between Buffel Grass and fire. The result is accelerating remnant degradation, making the interaction between Buffel Grass and fire an important target for management measures. Fire‐breaks and fuel reduction strategies including periodic intense grazing and canopy enhancement have potential to reduce the impact of Buffel Grass invasion, but long‐term community survival will probably require effective control of Buffel Grass. The impact of weed invasion within remnant vegetation is clearly a complex issue but the simple ‘case study’ approach employed here can both increase and communicate understanding.     

Novel Plant-Microbe Rhizosphere Interaction Involving Streptomyces lydicus WYEC108 and the Pea Plant (Pisum sativum)

A previously undescribed plant-microbe interaction between a root-colonizing Streptomyces species, S. lydicus WYEC108, and the legume Pisum sativum is described. The interaction is potentially of great importance to the health and growth in nature of this nodulating legume. The root-colonizing soil actinomycete S. lydicus WYEC108 influences pea root nodulation by increasing root nodulation frequency, possibly at the level of infection by Rhizobium spp. S. lydicus also colonizes and then sporulates within the surface cell layers of the nodules. Colonization leads to an increase in the average size of the nodules that form and improves the vigor of bacteroids within the nodules by enhancing nodular assimilation of iron and possibly other soil nutrients. Bacteroid accumulation of the carbon storage polymer, poly-β-hydroxybutyrate, is reduced in colonized nodules. Root nodules of peas taken from agricultural fields in the Palouse hills of northern Idaho were also found to be colonized by actinomycete hyphae. We hypothesize that root and nodule colonization is one of several mechanisms by which Streptomyces acts as a naturally occurring plant growth-promoting bacterium in pea and possibly other leguminous plants.     

Observations on the Cytoplasmic Membranes of Testicular Cells,Examined by Phase Contrast and Electron Microscopy

In freshly isolated cells of the guinea pig germinal epithelium examined with phase contrast, dark contours are seen in the cytoplasm that appear to be optical sections of the cisternae of the endoplasmic reticulum. These increase in contrast, in number, and in linear extent with increasing time up to 4 hours after isolation of the cells from the testis. During this period, cisternae originally present in the cells are extended and new ones appear to be formed by coalescence of tubular and vesicular elements of the reticulum. The cisternae become associated in parallel array and ultimately form elaborate concentric systems resembling structures that have often been interpreted as intracellular "myelin figures." Until now our knowledge of the endoplasmic reticulum has been based largely upon electron micrographs. The observation that the cisternae are visible in certain cell types under phase contrast optics opens the way for experimental investigations on the behavior of this class of cytoplasmic membranes in living cells.     

Advertising Missionaries

Advertising Missionaries. 1996. 52 minutes, color. film by Chris Hilton and Gauthier Flounder. For more information please contact First Run/Icarus Films, 153 Waverly Place, New York, NY 10014.     

Morphometric Variation and Biogeography of Ogwa menzeli and Criconema sphagni

Morphometrics of Ogma menzeli from woodlands in the Adirondack Mountains of New York State and in Iowa were compared. Specimens from the Adirondacks were significantly greater in mean total body length, stylet length, the b, R, and RV values, body width, and esophagus length than specimens from Iowa. The V value was significantly greater in the Iowa than in the Adirondack specimens. The two populations are considered ecotypes of O. menzeli. Criconema sphagni morphometric measurements differed significantly for the RV value (negative) and V value (positive) relative to elevation in the Adirondacks. There was a positive regression correlation for the RV value of O. menzeli and elevation in the Adirondack Mountains.     

Photosynthetic glow peaks and their relationship with the free energy changes

This paper is concerned with relating thermoluminescence to the total free-energy change, G, involved in detrapping a particular electron-hole pair as a photosynthetic sample is warmed from an initial low temperature. It extends a mathematical discussion of four possible mechanisms introduced in an earlier paper [DeVault, Govindjee and Arnold, Proc Nat'l Acad Sci USA 80: 983–987 (1983)]; here, particular attention is paid to the dependence of the absolute temperature of the maximum of a glow-peak, T _m , on the total free-energy change, G. The conclusion from the cases studied is that T _m =G/(k _B W) where G is evaluated at T _m , W is a complicated function of temperature and of thermodynamic parameters in the steps of the mechanism, and k _B is the Boltzmann constant. If the rate limiting step in the mechanism of detrapping is not preceded by any step in which G is appreciably negative, W is likely to have a value of about 33 and T _m is approximately proportional to G. Otherwise W can become much smaller and more strongly dependent on temperature and T _m is no longer proportional to G. These conclusions are of significance in lending theoretical support to the practice of inferring redox midpoint potential changes from shifts in T _m .     

THE MECHANICAL HEART ON THE MEDICAL HORIZON

Progress in materials and design of a total artificial heart has lengthened survival times from 1(1/2) hours in 1958 to 3 months in 1974. During those years various limiting factors were found and analyzed. Remaining limitations encountered in a 3-month survivor were localized thrombosis within the blood chambers and infection along drive lines into the mediastinum.