New aspects of the photodegradation of iron(III) citrate: spectroscopic studies and plant-related factors.

Iron (Fe) is an essential cofactor for all livings. Although Fe membrane transport mechanisms often utilize FeII, uncoordinated or deliberated ferrous ions can initiate Fenton reactions. FeIII citrate complexes are among the most important complexed forms of FeIII especially in plants that, indeed, can undergo photoreduction. Since leaves as photosynthetic organs of higher plants are generally exposed to illumination in daytime, photoreaction of ferric species may have biological relevance in iron metabolism, the relevance of which is poorly understood. In present work FeIII citrate transformation during the photodegradation in solution and after foliar application on leaves was studied by Mössbauer analysis directly. To obtain irradiation time dependence of the speciation of iron in solutions, four model solutions of different pH values (1.5, 3.3, 5.5, and 7.0) with Fe to citrate molar ratio 1:1.1 were exposed to light. Highly acidic conditions led to a complete reduction of Fe together with the formation of FeII citrate and hexaaqua complexes in equal concentration. At higher pH, the only product of the photodegradation was FeII citrate, which was later reoxidized and polymerized, resulting in the formation of polynuclear stable ferric compound. To test biological relevance, leaves of cabbage were treated with FeIII citrate solution. X-ray fluorescence imaging indicated the accumulation of Fe in the treated leaf parts. Mössbauer analysis revealed the presence of several ferric species incorporated into the biological structure. The Fe speciation observed should be considered in biological systems where FeIII citrate has a ubiquitous role in Fe acquisition and homeostasis.

Evidence of human occupation in Mexico around the Last Glacial Maximum.

The initial colonization of the Americas remains a highly debated topic1, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico-which holds a key geographical position in the Americas-is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations2. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico3,4, the Chiapas Highlands5, Central Mexico6 and the Caribbean coast7-9 during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave-a high-altitude site in central-northern Mexico-that corroborate previous findings in the Americas10-17of cultural evidence that dates to the Last Glacial Maximum (26,500-19,000 years ago)18, and which push back dates for human dispersal to the region possibly as early as 33,000-31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research.

Brazilian montane rainforest expansion induced by Heinrich Stadial 1 event.

The origin of modern disjunct plant distributions in the Brazilian Highlands with strong floristic affinities to distant montane rainforests of isolated mountaintops in the northeast and northern Amazonia and the Guyana Shield remains unknown. We tested the hypothesis that these unexplained biogeographical patterns reflect former ecosystem rearrangements sustained by widespread plant migrations possibly due to climatic patterns that are very dissimilar from present-day conditions. To address this issue, we mapped the presence of the montane arboreal taxa Araucaria, Podocarpus, Drimys, Hedyosmum, Ilex, Myrsine, Symplocos, and Weinmannia, and cool-adapted plants in the families Myrtaceae, Ericaceae, and Arecaceae (palms) in 29 palynological records during Heinrich Stadial 1 Event, encompassing a latitudinal range of 30°S to 0°S. In addition, Principal Component Analysis and Species Distribution Modelling were used to represent past and modern habitat suitability for Podocarpus and Araucaria. The data reveals two long-distance patterns of plant migration connecting south/southeast to northeastern Brazil and Amazonia with a third short route extending from one of them. Their paleofloristic compositions suggest a climatic scenario of abundant rainfall and relative lower continental surface temperatures, possibly intensified by the effects of polar air incursions forming cold fronts into the Brazilian Highlands. Although these taxa are sensitive to changes in temperature, the combined pollen and speleothems proxy data indicate that this montane rainforest expansion during Heinrich Stadial 1 Event was triggered mainly by a less seasonal rainfall regime from the subtropics to the equatorial region.

New Holocene pollen records from the Brazilian Caatinga.

We present two pollen diagrams from the semi-arid Caatinga of the Catimbau National Park, in Pernambuco and from a Mauritia palm forest in the Caatinga/Cerrado ecotone of southern Piauí, NE Brazil, spanning the last 10,000 cal. yrs BP and the last 1,750 cal yrs BP, respectively. These two records contain a signature of the local vegetation and permit the correlation of the pollen signal with regional climatic changes. The Catimbau record shows Zizyphus sp., a typical Caatinga taxon, in all three pollen zones indicating regional Caatinga vegetation and the predominance of local arboreal taxa adapted to high humidity from 10,000 to ca. 6,000 cal. yrs BP with a gradual tendency towards drier conditions revealed by a deposition hiatus between 6,000 to ca. 2,000 cal. yrs BP. This abrupt loss of sediments in both localities is interpreted as a consequence of the establishment of modern semi-arid climates. The subsequent return of humidity is signaled by increased sedimentation rates and 14C date inversions in agreement with high precipitation, revealed by σ18O ratios in speleothems from NE Brazil. Modern sediments deposited in the last 500 years reflect local conditions with the maintenance of humidity by geological faulting and surfacing water tables.

Matrix metalloproteinases 2, 9, and 13, and tissue inhibitors of metalloproteinases 1 and 2 in experimental lung silicosis.

Exposure to silica induces granulomatous lung inflammation evolving to fibrosis through yet unclear pathogenic mechanisms. We examined the expression of extracellular matrix remodeling molecules: collagenase 3, gelatinases A and B, and TIMP-1 and TIMP-2 in experimental lung silicosis. Rats were instilled with 50 mg of silica and sacrificed after 15 and 60 d. At 60 d a significant increase in lung collagen content was found (170.2 +/- 34.4 versus 88.2 +/- 20.8 microgram/mg in controls, p = 0.01). Gelatin zymography of bronchoalveolar lavage fluid (BALF) from 15 and 60 d revealed bands of progelatinase A and progelatinase B, and lung tissue zymograms showed in addition, the active gelatinase A form at 15 d. By in situ hybridization and immunohistochemistry, early silicotic granulomas exhibited intense staining for all matrix metalloproteinases (MMPs) and TIMPs assayed. Labeling was restricted inside granulomas and surrounding areas. Late silicotic granulomas at 60 d showed lower MMP expression than did early lesions, and in highly fibrotic nodules scarce signal was usually found. TIMP-1 and TIMP-2 showed a moderate reduction in 60-d silicotic nodules. These findings suggest that an imbalance in the expression of MMPs and TIMPs may be implicated in extracellular matrix remodeling and basement membrane disruption during experimental lung silicosis.

Inflammatory cells and ferruginous bodies in bronchoalveolar lavage in urban dogs.

OBJECTIVE: To investigate whether high levels of atmospheric pollution modify the inflammatory cell count of the canine lung and to detect the presence of ferruginous bodies (FB) in the respiratory system. STUDY DESIGN: Bronchoalveolar lavage (BAL) was performed on dogs from four different areas of Mexico City and a rural area. With the BAL fluid recovered, total and differential cell counts were made, and ferruginous bodies were isolated by sodium hypochlorite digestion. They were counted by light microscopy and evaluated as a marker of exposure to particulate pollutants. RESULTS: There was no significant difference in the total cell count or in the macrophage number between the five groups. The neutrophil count was statistically higher in dogs from the southwest area as compared to the northeast and rural areas (P < .05). The lymphocyte count was significantly greater in the southwest, also. The northeast part of the city showed the highest number of FB in BAL fluids. CONCLUSION: The most polluted areas, in terms of particulate matter, were the northeast and the northwest; those are the locations of heavy industry. In contrast, in the southwest, where more inflammation was seen, the highest levels of ozone were registered during the year.

Effect of exposure of guinea pigs to cigarette smoke on elastolytic activity of pulmonary macrophages.

STUDY OBJECTIVE: To determine the effect of exposure to cigarette smoke on the elastolytic activity of guinea pigs' alveolar macrophages (AMs), and to compare elastolytic activity of AMs obtained by BAL with that of lung macrophages (LMs) obtained from minced lung tissue. METHODS: AMs were obtained by BAL from seven adult guinea pigs exposed to cigarette smoke for 5 d/wk during 6 weeks, as well as from age-matched control guinea pigs. From each animal, one lung was used to obtain LMs by mincing and teasing the lung, followed by enzymatic digestion and isolation of mononuclear cells by Hypaque-Ficoll separation. The other lung was inflated and fixed to quantitate emphysema by the destructive index (DI). Elastolytic activity (microgram of elastin degraded by 10(6) macrophages) was determined at 24, 48, and 72 h, by culturing AMs and LMs (1 x 10(6) cells in 1 mL of medium) in 3H-elastin-coated wells. RESULTS: In animals exposed to cigarette smoke, the total number of BAL cells (8.6+/-2.1 x 10(6)) and DI (21.8+/-8.1) were significantly higher than in nonexposed animals (6.4+/-1.8 x 10(6), p<0.05 for cells, and 12.1+/-4.1, p<0.01 for DI). Elastolytic activity of AMs from smoke-exposed guinea pigs was significantly higher at 24, 48, and 72 h than elastolytic activity of AMs from control animals (19.0+/-9.4 vs 10.0+/-5.3, p<0.05 at 72 h). Likewise, elastolytic activity of LMs was significantly higher in exposed than nonexposed guinea pigs (11.8+/-7.7 vs 7.4+/-5.0 at 72 h, p<0.05). Elastolytic activity of LMs was not significantly different from elastolytic activity of AMs, both in exposed guinea pigs (11.8+/-7.7 vs 19.0+/-9.4 at 72 h) and nonexposed animals (7.4+/-5.0 vs 10.0+/-5.3 at 72 h). CONCLUSIONS: These results indicate that elastolytic activity of both AMs and LMs of guinea pigs increases significantly after exposure to cigarette smoke and that AMs and LMs have similar elastolytic activities.

Tobacco smoke-induced lung emphysema in guinea pigs is associated with increased interstitial collagenase.

We examined the expression of interstitial collagenase and its enzymatic activity in lung damage induced by tobacco smoke. Guinea pigs were exposed to the smoke of 20 cigarettes per day from 1-8 wk. Age-matched guinea pigs were used as controls. At 6 and 8 wk of smoke exposure, lungs exhibited interstitial and peribronchiolar inflammation and moderate emphysematous changes. In situ hybridization of injured lungs revealed patchy expression of collagenase mRNA mainly in macrophages but also in alveolar epithelial and interstitial cells. Immunoreactive protein was detected in alveolar macrophages and in the alveolar walls and interstitium. Collagenolytic activity increased beginning in the 4th wk of exposure (0.7 +/- 0.43 micrograms collagen degraded/mg collagen incubated relative to 0.23 +/- 0.14 in controls; P < 0.05). At 6 and 8 wk, values were 0.85 +/- 0.34 and 0.98 +/- 0.33 compared with 0.25 +/- 0.11 and 0.26 +/- 13 in controls (P < 0.005 and 0.001). Collagen concentration decreased from 50.7 +/- 8.5 mg/g dry wt in control lungs to 40.2 +/- 5.0 and 42.9 +/- 6.0 at 6 and 8 wk of exposure, respectively (P < 0.05). These results strongly suggest that increased interstitial collagen degradation plays a role in the development of lung emphysema.

Thoracoabdominal wall repair with glutaraldehyde-preserved bovine pericardium.

Glutaraldehyde-preserved bovine pericardium (GPBP) is evaluated as a bioprosthesis for the reconstruction of surgical defects in the thoracoabdominal wall. The mechanical properties of bovine pericardium preserved at different concentrations of glutaraldehyde were studied. Samples preserved in 0.5% glutaraldehyde showed a significantly higher tensile strength (11.7 +/- 0.8 N/mm2) than samples preserved in 2.5, 5, or 10% (similar to pericardium preserved in normal saline). The percentage of elongation was significantly lower than samples preserved in 1, 2.5, and 5% glutaraldehyde. GPBP at 0.5% was used to repair experimentally induced defects of the abdominal wall (n = 9), chest wall (n = 6), diaphragm (n = 6), and sternum (n = 7). All animals presented adequate tolerance to the material used and no case of infection or rejection of the material was seen in any of the animals. Finally, 0.5% GPBP was used clinically in a series of 40 patients: postincisional abdominal hernia (n = 30), inguinal hernia (n = 8), diaphragmatic hernia (n = 1), and congenital pelvic defect with prolapse of abdominal organs (n = 1). Surgical use showed that GPBP was a very manageable material and long-term results were good in 37 patients with a mean follow up of 18 months (range 5-35 months). Six patients presented seroma formation (all abdominal hernia patients), three of which eventually developed infection and had the GPBP patch removed at 3, 5, and 7 months postoperatively. The rest of the patients presented good scar formation with adequate resistance at the area of implantation. GPBP is a biological material with sufficient resistance to be used surgically in the repair of thoracoabdominal defects. Ideal concentration of glutaraldehyde to be used in the preparation-preservation of the material is 0.5% since higher concentration negatively affect its tensile rupture strength and elongation.

[Repair of thoracoabdominal wall defects in dogs using a bovine pericardium bioprosthesis]. / Reparación de defectos de pared tóracoabdominal de perros con bioprótesis de pericardio bovino.

OBJECTIVES: To evaluate the in-vitro resistance of a pericardial tissue bioprothesis as well as its use for the reconstruction of surgical defects in the thoracoabdominal wall. MATERIALS AND METHODS: The prosthesis were preserved for 15 days in different concentrations of glutaraldehyde (0.5% to 10%). Normal saline and Hanks solution were used as controls. Tensile strength and percent elongation were measured using an Instrom 1011 automatic equipment; polypropilene (Marlex) and polyester (Mersilene) mesh samples were included. Also, the 0.5% glutaraldehyde-preserved pericardium was used to repair defects experimentally produced in the abdominal wall (n = 12), chest wall (n = 6), diaphragm (n = 6), and sternum (n = 7) of mongrel dogs. RESULTS: The samples preserved in 0.5% glutaraldehyde showed a significantly higher tensile strength (11.7 N/mm2, SEM = 0.8) than samples preserved in other concentrations as well as in the mesh samples. Percent elongation in 0.5% glutaraldehyde was 56% (SEM = 5.8) which was similar to the meshes' elongation but significantly lower than that seen for the 1%, 2.5% and 5% glutaraldehyde-preserved samples. The dogs showed good tolerance to the 0.5% preparation and the histopathology showed formation of a fibroblast layer with collagen deposits and development of scar tissue. There was no case of infection or rejection in the animals, and all the microbiological cultures of the preparations were negative. CONCLUSION: Pericardial bioprothesis is a resistant material which can be used surgically in the repair of thoracoabdominal defects.

Propranolol-induced hyperreactivity in guinea-pig lung parenchyma strips: possible role of histamine.

In vivo and in vitro studies have demonstrated that beta-adrenoceptor blockers enhance the airway smooth muscle contraction to antigen, but the mechanisms are not fully understood. In the present work, we corroborated that propranolol (3.9 x 10(-6) M, 30 min incubation) induces hyperreactivity to antigenic challenge (cumulative concentration-response curve to ovalbumin, 0.01 to 100 micrograms/ml) in lung parenchyma strips from sensitized guinea-pigs. This hyperreactivity was enhanced by indomethacin (3.2 x 10(-5) M) and was unaffected by the lipoxygenase/cyclooxygenase inhibitor phenidone (1 x 10(-4) M). However, the histamine H1 receptor antagonist pyrilamine (1 x 10(-6) M) reduced the potentiation effect of propranolol. These results suggest that bronchoconstrictor prostaglandins, thromboxane A2 and leukotrienes, are not involved in the propranolol-induced lung parenchyma strips hyperreactivity to antigen in vitro, and that histamine may account, at least in part, for such propranolol effect.

O3-induced airway hyperresponsiveness to noncholinergic system and other stimuli.

The effect of O3 exposure (3 ppm, 1 h) on the in vivo and in vitro airway responsiveness, as well as the changes in cell contents in bronchoalveolar lavage (BAL) fluid, were evaluated 16-18 h after O3 exposure in sensitized and nonsensitized male guinea pigs. The sensitization procedure was performed through repeated inhalation of ovalbumin for 3 wk. Increase in pulmonary insufflation pressure produced by the excitatory nonadrenergic noncholinergic (eNANC) system, histamine, and antigen were assessed in in vivo conditions, whereas airway responsiveness to histamine and substance P was evaluated in in vitro conditions by use of tracheal chains with or without epithelium and lung parenchymal strips. We found that O3 exposure 1) increased the neutrophil content in BAL fluids in both sensitized and nonsensitized guinea pigs, 2) caused hyperresponsiveness to eNANC stimulation in nonsensitized guinea pigs (although combination of sensitization and O3 exposure paradoxically abolished the hyperresponsiveness to eNANC stimulation), 3) increased the in vivo bronchoconstrictor responses to histamine and antigen, 4) caused hyperresponsiveness to substance P in nonsensitized tracheae with or without epithelium and in sensitized tracheae with epithelium, 5) did not modify the responsiveness to histamine in tracheae with or without epithelium (and in addition, epithelium removal caused hyperresponsiveness to histamine even in those tracheae exposed to O3), and 6) produced hyperresponsiveness to histamine in lung parenchymal strips either from sensitized or nonsensitized guinea pigs.

Pharmacological characterization of mediators and vagal influence in the acute allergic bronchoconstriction in guinea pigs.

The allergic bronchoconstriction in guinea pigs has been attributed mainly to the release of mast cell mediators. Histamine has been involved in the first minutes of the anaphylactic reaction and new-formed compounds in the subsequent response. In this asthma model the vagal influence has been sparsely investigated. In the present work we evaluated the pharmacological modification of the acute allergic bronchoconstrictor response in guinea pigs sensitized to ovalbumin through aerosol exposure. Pyrilamine (20 micrograms/kg), diethylcarbamazine (a lipoxygenase inhibitor, 10 mg/kg) and dexamethasone (4 mg/kg) each reduced the antigen-induced bronchoconstriction throughout the 30 min studied. Indomethacin (3.1 mg/kg) did not modify the response to the antigen. Atropine (2 mg/kg) plus bilateral vagotomy also diminished this response from 5 min onward. On the other hand, from 5 min ahead pyrilamine-resistant bronchoconstriction was partially inhibited by dexamethasone, and it was almost completely blocked during all of the response when atropine plus bilateral vagotomy were added to dexamethasone. Dipyridamole (an inhibitor of the adenosine uptake, 0.4 mg/kg) enhanced the bronchoconstriction, though this was significant only in the 2-5 min time-interval of the response. These results suggest that histamine and vagal influence play an important role in the whole response to antigen, that other mediators, probably leukotrienes, participate in this response from 5 min onward, and that adenosine could exert a potentiation effect on this response.