Anesthetic effects on pulmonary allergic responses in rats: changes in sensitivity to serotonin.

Subsequent to observations that pulmonary responses to antigen challenge are of different magnitudes in sensitized rats that are anesthetized with different drugs, we conducted studies to test whether the alterations in responses were due to changes in airway responsiveness to cholinergic or serotonergic challenge, opioid-receptor mediated events, or changes in mast cell mediator release. Immunoglobulin E-sensitized rats anesthetized with ketamine/urethan had larger changes in lung resistance and plasma histamine after pulmonary antigen challenge compared with rats anesthetized with fentanyl-droperidol. Blockade of opioid receptors with naloxone did not affect the responses. In unsensitized rats, airway responses to aerosolized methacholine were similar for the two anesthetics, indicating unchanged smooth muscle responsiveness; however, airway responses to intravenous serotonin were enhanced by ketamine and ablated by droperidol. We conclude that ketamine- and droperidol-induced alterations of pulmonary allergic responses are due to changes in sensitivity to serotonin and in mast cell mediator release. We speculate that mast cell mediator release may be modulated by a serotonin receptor-linked mechanism.     

Co-existence of immunoreactivity to anti-dopamine,anti-serotonin and anti-vasotocin in the cerebral giant neuron of the pond snail Lymnaea stagnalis

Summary Consecutive sections of certain neurons in the central ganglia of the pond snail Lymnaea stagnalis appear to be immunoreactive to anti-dopamine and anti-serotonin. The Cerebral Giant Neurons stain in addition with antivasotocin. The observations indicate the presence of two biogenic amines within the same neuron and in addition their co-existence with a biologically active peptide.     

Changes in gas exchange characteristics and water use efficiency of mangroves in response to salinity and vapour pressure deficit

Summary Measurements were made of the photosynthetic gas exchange properties and water use efficiency of 19 species of mangrove in 9 estuaries with different salinity and climatic regimes in north eastern Australia and Papua New Guinea. Stomatal conductance and CO₂ assimilation rates differed significantly between species at the same locality, with the salt-secreting species, Avicennia marina, consistently having the highest CO₂ assimilation rates and stomatal conductances. Proportional changes in stomatal conductance and CO₂ assimilation rate resulted in constant and similar intercellular CO₂ concentrations for leaves exposed to photon flux densities above 800 mol·m^-2·s^-1 in all species at a particular locality. In consequence, all species at the same locality had similar water use efficiencies. There were, however, significant differences in gas exchange properties between different localities. Stomatal conductance and CO₂ assimilation rate both decreased with increasing salinity and with increasing leaf to air vapour pressure deficit (VPD). Furthermore, the slope of the relationship between assimilation rate and stomatal conductance increased, while intercellular CO₂ concentration decreased, with increasing salinity and with decreasing ambient relative humidity. It is concluded from these results that the water use efficiency of mangroves increases with increasing environmental stress, in this case aridity, thereby maximising photosynthetic carbon fixation while minimising water loss.Contribution No. 459 from the Australian Institute of Marine Science     

Determination of carbon-reduction-cycle intermediates in leaves of Arbutus unedo L. suffering depressions in photosynthesis after application of abscisic acid or exposure to dry air

Gas exchange and contents of photosynthetic intermediates of leaves of Arbutus unedo L. were determined with the aim of recognizing the mechanisms of inhibition that were responsible for the midday depression of photosynthesis following exposure to dry air, and the decline in photosynthetic capacity following application of abscisic acid (ABA). Rapidly killed (<0.1 s) leaf samples were taken when gas analysis showed reduced CO₂ assimilation. Determination of the contents of 3-phosphoglyceric acid (PGA), ribulose 1,5-bisphosphate (RuBP), triose phosphates, fructose 1,6-bisphosphate and hexose phosphates in the samples showed that significant variation occurred only in the level of PGA. As a result, the ratio PGA/RuBP decreased with increasing inhibition of photosynthesis, particularly when application of ABA had been the cause. A comparison of metabolite patterns did not bring out qualitative differences that would have indicated that effects of ABA and of dry air had been caused by separate mechanisms. Depression of photosynthesis occurred in the presence of sufficient RuBP which indicated that the carboxylation reaction of the carbon-reduction-cycle was inhibited after application of ABA or exposure to dry air.Abbreviations and symbols ABA abscisic acid - C _a partial pressure of CO₂ in the ambient air - C _i partial pressure of CO₂ in the intercellular spaces - I quantum flux - PGA 3-phosphoglyceric acid - RuBP ribulose 1,5-bisphosphate - I _L leaf temperature - w water-vapor pressure difference between leaf and air     

Spontaneous abortion and confined chromosomal mosaicism

Summary Confined placental chorionic mosaicism is reported in 2% of viable pregnancies cytogenetically analyzed on chorionic villi samplings (CVS) at 9–12 weeks of gestation. In follow-up studies this mosaicism has been shown to be associated with increased frequency of second and third trimester pregnancy loss or intrauterine fetal growth retardation. We have studied 54 spontaneous abortions (SA) for the detection of confined placental mosaicism and found 11 of them to be mosaic. All mosaic cases were identified among first trimester spontaneous abortions, and the mosaicism was confined to specific placental or embryonic/fetal cell lineages. These results indicate that the previously reported mosaicism in SA represents both confined and generalized types of mosaicism and that its accepted frequency of 5%–10% in SA will likely be higher. Over the whole gestational period, the confined placental mosaicism is more common than the reported rate of 1%–2% seen in viable pregnancies at CVS, and a higher proportion of pregnancy complications than previously suspected may be associated with confined placental mosaicism.     

Mutational specificity of a proof-reading defective Escherichia coli dnaQ49 mutator

Summary The dnaQ (mutD) gene product which encodes the -subunit of the DNA polymerase III holoenzyme has a central role in controlling the fidelity of DNA replication because both mutD5 and dnaQ49 mutations severely decrease the 3–5 exonucleolytic editing capacity.It is shown in this paper that more than 95% of all anaQ49-induced base pair substitutions are transversions of the types G:C-T:A and A:T-T:A. Not only is this unusual mutational specificity precisely that observed recently for a number of potent carcinogens such as benzo(a) pyrene diolepoxide (BPDE) and aflatoxin B1 (AFB1), which are dependent on the SOS system to mutagenize bacteria, but it is also seen for the constitutively expressed SOS mutator activity in E. coli tif-1 strains as well as for the SOS mutator activity mediated gap filling of apurinic sites. Because the G:C-T:A and A:T-T:A transversions can either result from the insertion of an adenine across from apurinic sites or arise due to the incorporation of syn-adenine opposite a purine base, we postulate that the DNA polymerase III holoenzyme also has a reduced discrimination ability in a dnaQ49 background.The introduction of a lexA (Ind^-) allele, which prevents the expression of SOS functions, led to a significant reduction in the dnaQ49-caused mutator effect.Both, the mutational specificity observed and the partial lexA ⁺ dependence of the mutator effect provoke a reanalysis of the hypothesis that the DNA polymerase III holoenzyme can be converted into the postulated but until now unidentified SOS polymerase.     

Greater sensitivity to vanadate of rat renal relative to cardiac (Na++K+)-ATPase

Vanadate (VO₄^?3) produces a positive inotropic effect in rats and also promotes diuresis as well as natriuresis. Although the mechanism(s) of these effects is uncertain, in the kidney, VO₄^?3 may act through inhibition of (Na⁺+K⁺)-ATPase activity, whereas in the heart, other or additional mechanisms are likely. Under the assay conditions used in the present study, microsomal (Na⁺+K⁺)-ATPase activities from rat kidney cortex and medulla were inhibited to a greater extent than was left ventricular (Na⁺+K⁺)-ATPase activity over a range of VO₄^?3 concentrations. The apparent dissociation constant for left ventricular (Na⁺+K⁺)-ATPase (10.95 ± 1.26 × 10^?7M VO₄^?3) was significantly greater than that of (Na⁺+K⁺)-ATPase from the cortex (3.46±0.96×10^?7 M VO₄^?3) or the medulla (3.32±0.7×10^?7M VO₄^?3, N=6, P<.05) whereas there were no significant differences between the effects of VO₄^?3 on (Na⁺+K⁺)-ATPase from the cortex and medulla. The greater inhibition by VO₄, of (Na⁺+K⁺)-ATPase from the cortex relative to that of the left ventricle, occurred over a range of Na⁺ and K⁺ concentrations, and K⁺ enhanced the inhibition by VO₄^?3 to a greater extent for (Na⁺+K⁺)-ATPase from the cortex than the left ventricle. These results suggest that renal (Na⁺+K⁺)-ATPase is more sensitive than left ventricular (Na⁺+K⁺)-ATPase to inhibition by VO₄^?3 and would, therefore, be more likely to be modulated $\text{in}$$\text{vivo.}$