The effect of light levels on daily patterns of chlorophyll fluorescence and organic acid accumulation in the tropical CAM treeClusia hilariana

Sandy plains are characteristic of the coastal region of Brazil. We investigated the diel patterns of changes in organic acid levels, leaf conductance and chlorophylla fluorescence for sun-exposed and shaded plants ofClusia hilariana, one of the dominant woody species in the sandy coastal plains of northern Rio de Janeiro state. Both exposed and shaded plants showed a typical CAM pattern with considerable diel oscillations in organic acid levels. The degradation of both malic and citric acids during the midday stomatal closure period could lead to potential CO₂ fixation rates of 28 mol m^-2 s^-1 in exposed leaves. Moreover, exposed leaves exhibited large increases in total non-photochemical quenching (q_N) accompanied by a substantial decrease in effective quantum yield during the course of the day. However, these potential high rates of CO₂ fixation and the increases inqn of exposed plants were not enough to maintain the primary electron acceptor of photosystem II (q_A) in a low reduction state, similar to that of shaded plants. As a result, there was a moderate increase in the reduction state of q_A throughout the day. Most of the decline in photochemical efficiency of exposed leaves ofC. hilariana was reversible, as evidenced by the high levels of pre-dawn potential quantum yields (F_v/F_m) and their rapid recovery after sunset. However, the depletion of the organic acid pool in the afternoon resulted in an accentuated subsequent drop in F_v/F_m, suggesting that prolonged periods of water stress accompanied by high irradiance levels may expose plants ofC. hilariana in unprotected habitats to the danger of photoinhibition.     

Specific induction of self-discrimination by follicle cells in Ciona intestinalis oocytes

Self-incompatibility, a mechanism that prevents self-fertilization in ascidians, is based on the ability of the oocyte vitelline coat to distinguish and accept only heterologous spermatozoa. In Ciona intestinalis self-discrimination is established during late oogenesis and is contributed or controlled by products of the overlying follicle cells. In this study we have further investigated the role of the follicle cells in the onset of self-discrimination by using in vitro maturation of ovarian oocytes deprived of the follicle cells and incubated with either autologous or heterologous follicle cells. Fertilization assays demonstrate that the action of the follicle cells is exerted even when they are detached from the vitelline coat and that only autologous follicle cells can promote the induction of self-sterility on the egg coat. Electron microscopy of the oocytes during maturation reveals that the switch from self-fertility to self-sterility is accompanied by the appearance of a thin electron-dense layer on the outer surface of the vitelline coat. We suggest that the formation of this layer is the result of the interaction between products of the follicle cells and the autologous vitelline coat.     

Cyclooxygenase and lipoxygenase metabolite generation in nasal polyps

A role of prostaglandins (PGs) and leukotrienes (LTs) in the pathogenesis of nasal polyps has been recently suggested. Cyclooxygenase (CO) products (thromboxane B₂, PGE₂ and 6-keto PGF₁ alpha) and lipoxygenase (LO) products (LTB₄ and LTC₄) were investigated by radioimmunoassay in polyps, hypertrophic turbinates and nasal mucosa from 14 patients with non-allergic (n = 6), allergic chronic rhinitis (n = 6) and aspirin-sensitive asthma (ASA) (n = 2), who underwent polypectomy. In all tissues CO metabolite levels were found higher than LO products (P < 0.01). Nasal polyps showed a significantly lower (P < 0.05) arachidonic acid (AA) metabolism in comparison to nasal mucosa. In polyps of allergic patients significantly higher LTB₄ levels (P < 0.001) and a tendency to produce higher amounts of CO products in comparison to non-allergic subjects were observed, whereas in turbinates of non-allergic patients LT levels were significantly higher in comparison to those of allergic ones (P < 0.01). In ASA patients a decreased ratio was found supporting the hypothesis of an imbalance of AA metabolism in this syndrome. These findings seem to indicate that the occurrence of nasal polyps may represent the result of different chronic inflammatory stimuli, regulated in part by AA metabolites.     

Skeletal troponin I as a marker of exercise-induced muscle damage

Sorichter, Stephan, Johannes Mair, Arnold Koller, WalterGebert, Daniel Rama, Charles Calzolari, Erika Artner-Dworzak, and BerndPuschendorf. Skeletal troponin I as a marker of exercise-inducedmuscle damage. J. Appl. Physiol.83(4): 1076-1082, 1997.The utility of skeletal troponin I (sTnI)as a plasma marker of skeletal muscle damage after exercise wascompared against creatine kinase (CK), myoglobin (Mb), and myosin heavychain (MHC) fragments. These markers were serially measured in normalphysical education teacher trainees after four different exerciseregimens: 20 min of level or downhill (16% decline) running(intensity: 70% maximal O₂uptake), high-force eccentric contractions (70 repetitions), orhigh-force isokinetic concentric contractions of the quadriceps group(40 repetitions). Eccentrically biased exercise (downhill running andeccentric contractions) promoted greater increases in all parameters.The highest plasma concentration were found after downhill running{median peaks: 309 U/l CK concentration ([CK])}, 466 µg/l Mb concentration([Mb]), 1,021 µU/l MHC concentration ([MHC]),and 27.3 µg/l sTnI concentration ([sTnI]). Level running produced a moderate response (median peaks: 178 U/l [CK],98 µg/l [Mb], 501 µU/l [MHC], and 6.6 µg/l [sTnI]), whereas the concentric contraction protocoldid not elicit significant changes in any of the markers assayed. sTnIincreased and peaked in parallel to CK and stayed elevated (>2.2µg/l) for at least 1-2 days after exercise. In contrast to MHC,sTnI is an initial, specific marker of exercise-induced muscle injury,which may be partly explained by their different intracellularcompartmentation with essentially no (MHC <0.1%) or a small solublepool (sTnI: median 3.4%).

     

Anti-Hepatitis A Virus Antibody Response Elicited in Mice by Different Forms of a Synthetic VP1 Peptide

Peptide VP1 (11-25) of the capsid of hepatitis A virus was synthesized by the Fmoc-polyamide solid phase method, and administered to mice in different forms: (1) free, (2) encapsulated in multilamellar liposomes, (3) coupled to keyhole limpet hemocyanin (KHL), and (4) incorporated into a tetrameric branched lysine core. The highest anti-VP1 peptide responses were generated by synthetic peptides entrapped into liposomes and coupled to KLH. No anti-HAV response was generated with the free peptide, while all the other forms induced both anti-HAV and HAV-neutralizing antibodies. Maximum neutralization indices were observed in ascites from mice treated with liposome-entrapped and KLH peptides.     

Composition and properties of Albizia lebbeck gum exudate

An analytical study has been made of six gum specimens from Albizia lebbeck, Leguminosae. Galactose, mannose, arabinose, glucuronic acid and its 4-O--metyl analogue are present in all the specimens studied. Rhamnose was not detected according to sugar analysis and spectral data. The absence of this sugar, the high acidity and the relatively low limit viscosity number contrast with the values reported previously for one African sample of A. lebbeck. The lead content is much higher than that recorded for other Albizia gums. ¹³C-NMR spectrum of this gum, in deuterium oxide, shows good resolution.     

Transferable clastogenic activity in plasma from patients with Fanconi anemia

The present study was conducted on 13 patients with Fanconi anemia, 25 parents and 12 siblings. The chromosomal instability characteristic of this congenital breakage syndrome was associated with the presence of transferable clastogenic material in the plasma, as also reported previously for ataxia telangiectasia and Bloom's syndrome. While all plasma ultrafiltrates from homozygotes had chromosome damaging properties, the clastogenic material had to be concentrated in most heterozygotes to reach detectable levels. The clastogenic effect was exerted via the intermediacy of superoxide radicals, since it was regularly inhibited by superoxide dismutase (SOD). This adds further evidence for a prooxidant state in this hereditary disease. The autosustained clastogenic activity possibly plays a role in the progressive impairment of blood cell-producing bone marrow and may predispose patients to develop cancer and leukemia. Prophylactic use of antioxidants may be recommended, using clastogenic plasma activity as a guide.     

Nodular pulmonary amyloidosis.

An elderly man had a 10-year history of multiple pulmonary nodules that he had refused to have investigated. He died of a ruptured abdominal aortic aneurysm. At autopsy the nodules were shown to consist of amyloid. There was no evidence of systemic amyloidosis.