Collagen vitrigel membranes are transparent biomaterials characterized by a densely organized, fibrillar nanostructure that show promise in the treatment of corneal injury and disease. In this study, the influence of different type I collagen sources and processing techniques, including acid-solubilized collagen from bovine dermis (Bov), pepsin-solubilized collagen from human fibroblast cell culture (HuCC), and ficin-solubilized collagen from recombinant human collagen expressed in tobacco leaves (rH), on the properties of the vitrigel membranes was evaluated. Postvitrification carbodiimide crosslinking (CX) was also carried out on the vitrigels from each collagen source, forming crosslinked counterparts BovXL, HuCCXL, and rHXL, respectively. Collagen membrane ultrastructure and biomaterial properties were found to rely heavily on both collagen source and crosslinking. Bov and HuCC samples showed a random fibrillar organization of collagen, whereas rH vitrigels showed remarkable regional fibril alignment. After CX, light transmission was enhanced in all groups. Denaturation temperatures after CX increased in all membranes, of which the highest increase was seen in rH (14.71°C), suggesting improved thermal stability of the collagen fibrils in the membranes. Noncrosslinked rH vitrigels may be reinforced through CX to reach levels of mechanical strength and thermal stability comparable to Bov.
Aplastic anemia (AA) is a classic bone marrow failure syndrome simply defined as peripheral blood pancytopenia and a hypocelular bone marrow, yet the diagnosis must be made by excluding other causes of bone marrow failure. The incidence rate of AA reported by the International Aplastic Anemia and Agranulocytosis Study (IAAAS) in the 1980s was 2 cases per 1 million people. This disease is known to be caused by exposure to radiation, chemotherapy and some viral agents, yet most of the cases are idiopathic. Epstein Barr virus and non-A, non-B or non-C Hepatitis virus have classically been related to the development of some AA cases. Recently there have been some reports of AA following Parvovirus B19 (PvB19) infection. This virus, the only parvoviridae virus capable of infecting humans, attacks erythrocyte precursors attaching to the P antigen in their surface and requiring Beta1 integrin for viral entry. Although PvB19 seems to infect only erytroid precursors, it is widely recognized that the infection with this virus can cause not only anemia, but neutropenia and thrombocytopenia as well, producing aplastic crisis of varying intensity. A correlation has recently been found between PvB19 DNA in peripheral blood and AA in children. We pretend to corroborate this observation and include adult patients in order to improve our understanding of the relationship between PvB19 and AA. So far we have taken peripheral blood samples from 9 AA patients and 9 controls paired by age, sex and community; we plan to include 100 AA patients and their controls from several hospitals around Mexico. DNA was extracted using the PUREGENE DNA extraction kit (Gentra, Minneapolis MN). Nested PCR was performed using the sense primer (P1) 5-AATACACTGTGGTTTTATGGGCCG-3, antisense (P2) 5-CCATTGCTGGTTATAACCACAGGT-3 for the first round and the sense primer (P3) 5-AATGAAAACTTTCCATTTAATGATGTAG-3 and antisense primer (P4) 5-CTAAAATGGCTTTTGCAGCTTCTAC-3for the second round. A DNA sample from a patient with active infectious mononucleosis with positive IgG and IgM against PvB19 in serum was used as positive control. Two samples from the AA group (22%) and 1 from the control group (11%) have turned positive for PvB19 DNA. The reported incidence for the presence of this virusDNA in the peripheral blood of the population is 3%. We expect that, as the number of patients grows, the percentage of positive samples in the control group will decrease, while the percentage of positive samples in the AA group will rise or be sustained. Our partial results point towards a possible relationship between AA and the presence of PvB19 DNA in the peripheral blood cells. It is possible that this virus is one of many factors capable of precipitating the development of AA by limiting the bone marrows capacity to produce blood cells. We are in the process of gathering more samples to prove if a relationship really exists and, if so, future studies will likely shed light upon the mechanism by which PvB19 contributes to the development of AA and other marrow failure syndromes.
Although there have been extraordinary advances in leukemia therapy, there is still a large subset of cases in which complete remission or prolonged leukemia-free survival cannot be achieved. Some of this variability in results is thought to be related to the differences in the effect of chemotherapy drugs on different patients. In many cases, these differences may be associated with the presence of genetic alterations that produce defective drug-metabolizing enzymes, drug transporters or drug targets. One of these is the glutathione-S transferase (GST) gene, which is known to catalyze the conjugation of toxic compounds, such as aliphatic aromatic heterocyclic radicals and epoxides, among others, to glutathione. The enzymes encoded by this gene detoxify polycyclic aromatic hydrocarbons and conjugated isothiocyanates. Objective : Our aim is to evaluate the frequency of deletions in GSTT1 and GSTM1 of the GST gene in Mexican patients with de novo acute leukemia. Methods : Starting in July 2003 and up until now, have included 75 samples from as many patients diagnosed with de novo acute leukemia, regardless of age, sex, or leukemia type. After obtaining informed consent, we drew blood, purified DNA and performed PCR to look for deletions in the GST gene (variants GSTT1 and GSTM1). Results: We found GSTM1 positiveness in 54 samples (72%), of those, 24 (44.5%) were ALL and 30 (55.5%) AML. We had 18 samples (24%) positive for the GSTT1 deletion; of those, 10 (55.5%) were from patients with ALL and 8 (44.4%) from AML patients. Conclusions ; As far as we can tell this is the first report of the frequency of these genetic deletions in Mexican acute leukemia patients. Recently a Mexican group studying the possible association of GSTT1 to lung cancer found that among Mexican controls, the frequency of this deletion was around 4.5%. This result would appear to indicate, as has been done by some other authors, that regardless of the possibility of becoming a prognostic factor, at least some polymorphism of the GST gene could be related to the genesis of this disease.
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