Soil salinity is correlated with a decline in 13C discrimination in leaves of Atriplex species

Abstract A dune-swale-dune transect in north-eastern South Australia with a regular covering of saltbush (Atriplex vesicaria and Atriplex stipitata) was studied. The transect topography was surveyed, as were the Δ (discrimination against ¹³C in CO₂) of the saltbush plants, and the electrical conductivity and chloride profiles of the soil. Increasing soil salinity, surveyed as electromagnetic (EM) soil conductivity, correlated with a decrease in A composition in the leaves of the C4 Atriplex species. No such correlation occurred with the whole plant. Further, the Δ of foliage was more variable than the Δ of whole plants. The Δ of foliage was higher than that of corresponding stems. We suggest that soil conductivity measured in this way is a meaningful assessment of plant growth conditions, and that further study will demonstrate its scope for incorporation into field studies of native plants at a quantitative level.     

Sexually transmitted disease in a promiscuous insect, Adalia bipunctata

Abstract.

• 1 Sexually transmitted diseases (STDs) have rarely been reported in insects and other invertebrates. The majority of those reported involve organisms where sexual transmission is augmented by either vertical (i.e. inherited) transmission, or horizontal transmission, independent of host sexual activity.
• 2 We here demonstrate the existence of an STD in the coccinellid beetle Adalia bipunctata. This species bears a parasitic mite of the genus Coccipolipus. We show that, like many other podapolipid mites, this mite is transmitted between host individuals at a high rate during copulation. It also appears to be transmitted at a low rate between non-copulating individuals.
• 3 We show that infected female A.bipunctata produced eggs at a reduced rate, and that the eggs produced by infected females have highly decreased viability. However, no effect of infection upon host longevity was observed.
• 4 The results are discussed in relation to the incidences of sexually transmitted disease in invertebrates in general, the causes of disease symptoms, and the importance of this disease in the evolution of A.bipunctata.

     

THERAPEUTIC STRATEGIES FOR THE INHIBITION OF INDUCIBLE NITRIC OXIDE SYNTHASE—POTENTIAL FOR A NOVEL CLASS OF ANTI-INFLAMMATORY AGENTS

In recent years, NO, a gas previously considered a potentially toxic chemical, has become established as a diffusible universal messenger mediating cell—cell communication throughout the body. In mammals, NO is a recognized mediator of blood vessel relaxation that helps to maintain blood pressure. In the central nervous system NO acts as a non-conventional neurotransmitter and participates in the establishment of long-term plasticity required for memory formation. In addition, NO is responsible for some parts of the host response to sepsis and inflammation and contributes to certain disease states. A number of strategies have emerged with regard to a pharmacological control of pathological NO overproductions. This review will discuss these novel therapeutic approaches that may provide new means for clinical medicine.     

Macrophage Functional Heterogeneity in the <Emphasis Type="Italic">in vitro</Emphasis> Induced Immune Response

RNA from antigenically stimulated peritoneal macrophages is immunogenic in vitro^1–4. The studies of Fishman and Adler^5–6 suggest that the peritoneal macrophage population consists of at least three functionally distinct subpopulations. Although most peritoneal macrophages act as scavenger cells⁷, a second population—possibly less than one cell per 1,000—consists of cells that produce but do not necessarily secrete antibody^8,9 and respond to antigen by synthesizing informational RNA. On transfer to normal lymphoid cells, this RNA elicits IgM antibody with the allotypic specificity of the macrophage donor¹⁰. A third type of macrophage gives rise to the RNA-antigen complex responsible for the in vitro synthesis of IgG antibody with the allotypic specificity of the lymphocyte donor¹⁰.     

Potassium Transport Across the Membranes of Chara: I. THE RELATIONSHIP BETWEEN RADIOACTIVE TRACER INFLUX AND ELECTRICAL CONDUCTANCE

Smith, J. R., Smith, F. A. and Walker, N. A. 1987. Potassiumtransport across the membrane of Chara. I. The relationshipbetween radioactive tracer influx and electrical conductance.—J.exp. Bot. 38:731–751. The ⁴²K influx () and the electrical conductance (G_m) were measured simultaneously for the ‘membrane’of internodal cells of Chara australis as a function of theexternal [KCl] (K?. In bathing solutions of pH = 5?0, progressively increased from 20?5to 430?60 nmol m^–2 s^–1 and G_m increased from 0?36?0?02to 3?8?0?8 S m^–2 when K? was increased from 0?1 to 10mol m^–3. The resting membrane potential difference (p.d.)was approximately -135 mV for low K? and approached the expectedNernst equilibrium p.d. for K⁺ ions when K? > 1?0 mol m^–3.Measurements of ³⁶Cl influx suggested that the ⁴²K influx waspredominantly electrogenic. The equivalent Goldman permeabilityto K⁺ ions (P_k) was approximately 20–30 nm s^–1 anddid not vary significantly with increasing K?. The equivalentconductance attributable to the electrogenic transport of K⁺ ions was calculated from assuming passive, independent diffusionof K⁺ ions and the ratio was found to be typically close to one. It was also found that themagnitudes of and G_m measuredsimultaneously for each individual cell were also well correlatedfor K? 1?0 mol m^–3, and that the slope of the line ofbest fit was close to one. For each K? it was found that theconductance not attributable to K⁺ translocation and presumablyassociated primarily with the transport of protons or theirequivalents was typically 0?2–0?5 Sm^–2. For K? >1?0 mol m^–3 the results indicated that the transport ofK⁺ ions was essentially independent, i.e. there was no evidencefor flux interactions. The results also indicated that the equivalentconductance derived from the measured ⁴²K influx could usefullyindicate the fraction of the electrical conductance attributableto the translocation of K⁺ ions. Key words: Potassium, conductance, influx     

Chloride Transport in Chara: I. KINETICS AND CURRENT-VOLTAGE CURVES FOR A PROBABLE PROTON SYMPORT

Chara cells show an inward positive electric current acrossthe plasmalemma when exposed to Cl^– under voltage-clampconditions. The rapid rise of this current suggests that itis directly associated with the inward transport of Cl^–.The dependence of the current on Cl^– concentration showssaturation, the data fitting the Michaelis-Menten equation withV_m up to 100 nmol m^–2 s^–1 (for Cl^–starvedcells) with K_M 10–20 µM, and with some allowancefor an unstirred layer of water adjacent to the membrane. Theeffects on the current of clamp potential, illumination, withdrawalof alkali metal cations, and addition of amine were also investigated.These results suggest that the mechanism is the symport of 2H⁺ with each Cl^–, and that the actions of light, externalK⁺, and amine in stimulating Cl^–, influx are indirect.