The 'Prof. Dr. Rómulo Lambre' Collection: an Argentinian sample of modern skeletons.

This paper describes the 'Prof. Dr. Rómulo Lambre' skeletal collection. The Lambre Collection is housed in the School of Medical Sciences of the National University of La Plata and it consists of skeletal remains ceded by the Municipal Cemetery of La Plata. The collection has more than four hundred skeletons, with information on age, sex, nationality, date and cause of death. It was created for teaching and research purposes in compliance with current legislation, and its management meets guidelines specified in the Declaration of the Argentinian Association for Biological Anthropology on Research Ethics on Human Remains (2007).

A long term study of the desiccation resistance of Drosophila melanogaster and D. simulans from the Mexican nuclear power plant "Laguna Verde".

The generation of electricity through the use of radioactive material at the nuclear power plant is inevitably associated with the production of wastes, some of which have potential impact on the biosphere. The objective of the present investigation was to provide information for evaluating the presumed impact of the Mexican Nuclear Power Plant "Laguna Verde" on the natural populations. Two sibling species that live in the immediate vicinity, Drosophila melanogaster and D. simulans have been studied for several traits in a long term study. The present study describes results for the desiccation resistance (DR) trait obtained during the period from 1995 to 2002. Flies were collected at two sites, one near the reactors and another farther away. The data obtained confirmed that D. melanogaster had higher DR values than D. simulans at both sites. The analysis of the results obtained from both species of the site closer to the reactor indicated that the values of the DR in the operational stage did not change, compared with those in the preoperational stage previously analyzed. Therefore, the significant differences found between the monitored sites did not seem to be associated to the operation of the reactors.

Enzymatic debridement of corneal ulcers with fibrinolysin and desoxyribonuclease

1. Fibrinolysin and DNAase can effectively debride the necrotic tissue in artificially produced rabbit corneal ulcers without injuring the non-necrotic, viable portion of the cornea2. By comparing the treated and untreated bacterial and chemical corneal ulcers in rabbits, there was noted generally less inflammatory reaction and a faster and better healing in those where enzymatic debridement were done3. The basis for the clinical use of enzymatic debridement of corneal ulcers by fibrinolysin and DNAase has been amply demonstrated. (Summary and conclusions)

Ultrastructural study of fossil human tooth tissue

The preservation of fossil human soft tooth tissue from extinct populations which inhabited the northeast of Argentina (fourteenth and fifteenth centuries) is described. Studies were performed using both Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The preservation of the surface structure in Tomes fibrils and in odontoblastic processes was determined by SEM; whereas by TEM we could observe the dentin ducts occupied by acellular material, being the inner structure of the odontoblastic processes poorly preserved. It is suggested that such preservation is due to an "instantaneous phosphatization" occurring immediately after death as a result of the presence of calcium phosphate deposits

Ultrastructural study of fossil human tooth tissue

The preservation of fossil human soft tooth tissue from extinct populations which inhabited the northeast of Argentina (fourteenth and fifteenth centuries) is described. Studies were performed using both Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The preservation of the surface structure in Tomes fibrils and in odontoblastic processes was determined by SEM; whereas by TEM we could observe the dentin ducts occupied by acellular material, being the inner structure of the odontoblastic processes poorly preserved. It is suggested that such preservation is due to an "instantaneous phosphatization" occurring immediately after death as a result of the presence of calcium phosphate deposits

Ultrastructural study of fossil human tooth tissue.

The preservation of fossil human soft tooth tissue from extinct populations which inhabited the northeast of Argentina (fourteenth and fifteenth centuries) is described. Studies were performed using both Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The preservation of the surface structure in Tomes fibrils and in odontoblastic processes was determined by SEM; whereas by TEM we could observe the dentin ducts occupied by acellular material, being the inner structure of the odontoblastic processes poorly preserved. It is suggested that such preservation is due to an "instantaneous phosphatization" occurring immediately after death as a result of the presence of calcium phosphate deposits.

Ultrastructural study of fossil human tooth tissue.

The preservation of fossil human soft tooth tissue from extinct populations which inhabited the northeast of Argentina (fourteenth and fifteenth centuries) is described. Studies were performed using both Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The preservation of the surface structure in Tomes fibrils and in odontoblastic processes was determined by SEM; whereas by TEM we could observe the dentin ducts occupied by acellular material, being the inner structure of the odontoblastic processes poorly preserved. It is suggested that such preservation is due to an [quot ]instantaneous phosphatization[quot ] occurring immediately after death as a result of the presence of calcium phosphate deposits.

Hypoxia-inducible factor 1alpha (HIF-1alpha) is a non-heme iron protein. Implications for oxygen sensing.

The hypoxia-inducible factor 1 complex (HIF-1) is involved in the transcriptional activation of several genes, like erythropoietin and vascular endothelial growth factor, that are responsive to the lack of oxygen. The HIF-1 complex is composed of two b-HLH proteins: HIF-1beta that is constitutively expressed, and HIF-1alpha, that is present only in hypoxic cells. The HIF-1alpha subunit is continuously synthesized and degraded by the ubiquitin-proteasome under oxic conditions. Hypoxia, transition metals, iron chelators, and several antioxidants stabilize the HIF-1alpha protein, allowing the formation of the transcriptionally active HIF-1 complex. The mechanisms of oxygen sensing and the pathways leading to HIF-1alpha stabilization are unclear. Because the involvement of a heme protein oxygen sensor has been postulated, we tested the heme sensor hypothesis by using a luciferase-expressing cell line (B-1), that is highly responsive to hypoxia. Exposure of B-1 cells to carbon monoxide and heme synthesis inhibitors failed to show any effect on the hypoxia responsiveness of these cells, suggesting that heme proteins are not involved in hypoxia sensing. Measurement of iron in recombinantly expressed HIF-1alpha protein revealed that this protein binds iron in vivo. Iron binding was localized to a 129-amino acid peptide between sequences 529 and 658 of the HIF-1alpha protein. Although the exact structure of the iron center has not been yet defined, a 2:1 metal/protein molar ratio suggests a di-iron center, probably similar to the one found in hemerythrin. This finding is compatible with a model where redox reaction may occur directly in the iron center of the HIF-1alpha subunit, affecting its survival in oxic conditions.

Polycythemic responses to hypoxia: molecular and genetic mechanisms of chronic mountain sickness.

We examined erythropoietin (EPO) gene expression and EPO production during hypoxia in two Sprague-Dawley rat strains with divergent polycythemic responses to hypoxia. Hilltop (H) rats develop severe polycythemia, severe hypoxemia, and pulmonary artery hypertension. The H rats often die from a syndrome indistinguishable from chronic mountain sickness (CMS) in humans. Madison (M) rats develop polycythemia and pulmonary artery hypertension that is modest and suffer no excess mortality. We tested the hypothesis that these rat strains have different stimulus-response characteristics governing EPO production. Rats of each strain were exposed to hypoxia (0.5 atm, 73 Torr inspired PO2), and renal tissue EPO mRNA and EPO levels, plasma EPO, ventilation, arterial and renal venous blood gases, and indexes of renal function were measured at fixed times during a 30-day hypoxic exposure. During extended hypoxic exposure, H rats had significantly elevated renal EPO mRNA, renal EPO, and plasma EPO levels compared with M rats. Ventilatory responses and indexes of renal function were similar in the strains during the hypoxic exposure. H rats had greater arterial hypoxemia from the onset of hypoxia and more severe renal tissue hypoxemia and greater polycythemia after 14 days of hypoxic exposure. When EPO responses were expressed as functions of renal venous PO2, the two strains appeared to lie on the same dose-response curves, but the responses of H rats were shifted along the curve toward more hypoxic values. We conclude that H rats have significantly greater polycythemia secondary to poorer renal tissue oxygenation, but the stimulus-response characteristics governing EPO gene expression and EPO production do not seem to differ between M and H rats. Finally, the regulation of EPO levels during hypoxia occurs primarily at the transcriptional level.

Hypoxia-inducible factor 1alpha (HIF-1alpha) protein is rapidly degraded by the ubiquitin-proteasome system under normoxic conditions. Its stabilization by hypoxia depends on redox-induced changes.

The hypoxia-inducible factor 1 transcriptional activator complex (HIF-1) is involved in the activation of the erythropoietin and several other hypoxia-responsive genes. The HIF-1 complex is composed of two protein subunits: HIF-1beta/ARNT (aryl hydrocarbon receptor nuclear translocator), which is constitutively expressed, and HIF-1alpha, which is not present in normal cells but induced under hypoxic conditions. The HIF-1alpha subunit is continuously synthesized and degraded under normoxic conditions, while it accumulates rapidly following exposure to low oxygen tensions. The involvement of the ubiquitin-proteasome system in the proteolytic destruction of HIF-1 in normoxia was studied by the use of specific inhibitors of the proteasome system. Lactacystin and MG-132 were found to protect the degradation of the HIF-1 complex in cells transferred from hypoxia to normoxia. The same inhibitors were able to induce HIF-1 complex formation when added to normoxic cells. Final confirmation of the involvement of the ubiquitin-proteasome system in the regulated degradation of HIF-1alpha was obtained by the use of ts20TGR cells, which contain a temperature-sensitive mutant of E1, the ubiquitin-activating enzyme. Exposure of ts20 cells, under normoxic conditions, to the non-permissive temperature induced a rapid and progressive accumulation of HIF-1. The effect of proteasome inhibitors on the normoxic induction of HIF-1 binding activity was mimicked by the thiol reducing agent N-(2-mercaptopropionyl)-glycine and by the oxygen radical scavenger 2-acetamidoacrylic acid. Furthermore, N-(2-mercaptopropionyl)-glycine induced gene expression as measured by the stimulation of a HIF-1-luciferase expression vector and by the induction of erythropoietin mRNA in normoxic Hep 3B cells. These last findings strongly suggest that the hypoxia induced changes in HIF-1alpha stability and subsequent gene activation are mediated by redox-induced changes.

Absolute requirement of aryl hydrocarbon receptor nuclear translocator protein for gene activation by hypoxia.

Hypoxia-inducible factor 1 (HIF-1) is a DNA-binding heterodimeric protein complex originally described in the transcriptional activation of the erythropoietin gene by hypoxia. This protein complex is composed of two subunits, HIF-1alpha and -1beta (aryl hydrocarbon receptor nuclear translocator, ARNT). In this study, we used ARNT-deficient cells, derived from the mouse hepatoma cell line Hepa1c1c7, to further characterize HIF-1 complex formation and its relationship with gene activation by hypoxia and desferrioxamine (Df). Gel shift assays revealed that ARNT is absolutely required for the formation of the HIF-1 DNA-binding complex. Results from RNase protection assays and Northern blots showed that the lack of functional HIF-1 complex completely abrogated the response to hypoxia of vascular endothelial growth factor (VEGF) and the glycolytic enzymes aldolase A (ALDA) and phosphoglycerate kinase 1 (PGK-1), genes known to be upregulated by low oxygen tension. Desferrioxamine induction of VEGF and PGK-1 genes was reduced in the ARNT-deficient cells, but at difference with hypoxia, it was not completely suppressed. These results suggest that Df is able to activate gene transcription through HIF-1-independent mechanisms. Exposure to hypoxia or Df did not induce any changes in HIF-1alpha and -1beta mRNA levels, suggesting that posttranscriptional mechanisms are involved in HIF-1 complex activation.

Hypoxic stimulation of vascular endothelial growth factor expression in vitro and in vivo.

BACKGROUND: Vascular endothelial growth factor (VEGF) is a specific endothelial cell mitogen with potent angiogenic properties. In tumors, VEGF has been localized to the most necrotic and ischemic areas of the tissues, suggesting that local hypoxia is a potent inducer of VEGF production. Initial experiments in vitro confirmed the stimulatory effect of hypoxia on VEGF expression. The extent of this response and the mechanisms involved in oxygen sensing are poorly characterized. EXPERIMENTAL DESIGN: Confluent monolayers of malignant cell lines or primary cultures of fibroblast or endothelial cells were exposed to hypoxia or incubated with either cobalt chloride, a stimulator of erythropoietin gene expression, or sodium azide, an inhibitor of oxydative phosphorylation. VEGF expression was analyzed by Northern blot or RNase protection assays. The expression VEGF in vivo was studied in animals subjected to hypobaric hypoxia or functional anemia. RESULTS: Hypoxia greatly stimulated VEGF expression in tumor cell lines and primary fibroblast cultures. Endothelial cells, that expressed very low constitutive levels of VEGF, were resistant to hypoxic stimulation. RNase protection analysis showed that hypoxia primarily stimulated the induction of smaller and medium VEGF isoforms, i.e., the same ones expressed under normal conditions. The stimulatory effect of hypoxia on VEGF could be reproduced in vitro by cobalt chloride but not with sodium azide. In vivo, both hypoxia and anemia were found to be potent inducers of VEGF expression in several organs including heart, brain, liver, kidney, and muscle. As in vitro, cobalt was also found to be a potent stimulator of VEGF in vivo. CONCLUSIONS: Hypoxia is a potent inducer of VEGF expression in malignant as well as normal cultured cells. It is also a stimulator of VEGF expression in vivo. The VEGF gene appears to respond to hypoxia like the erythropoietin gene, and the mechanism of oxygen sensing probably is mediated by a heme-containing protein.