Jorge Ossa

Antitumor and Antiviral Activity of Colombian Medicinal Plant Extracts

Extracts of nine species of plants traditionally used in Colombia for the treatment of a variety of diseases were tested in vitro for their potential antitumor (cytotoxicity) and antiherpetic activity. MTT (Tetrazolium blue) and Neutral Red colorimetric assays were used to evaluate the reduction of viability of cell cultures in presence and absence of the extracts. MTT was also used to evaluate the effects of the extracts on the lytic activity of herpes simplex virus type 2 (HSV-2). The 50% cytotoxic concentration (CC50) and the 50% inhibitory concentration of the viral effect (EC50) for each extract were calculated by linear regression analysis. Extracts from Annona muricata, A. cherimolia and Rollinia membranacea, known for their cytotoxicity were used as positive controls. Likewise, acyclovir and heparin were used as positive controls of antiherpetic activity. Methanolic extract from Annona sp. on HEp-2 cells presented a CC50 value at 72 hr of 49.6x10(3)mg/ml. Neither of the other extracts examined showed a significant cytotoxicity. The aqueous extract from Beta vulgaris, the ethanol extract from Callisia grasilis and the methanol extract Annona sp. showed some antiherpetic activity with acceptable therapeutic indexes (the ratio of CC50 to EC50). These species are good candidates for further activity-monitored fractionation to identify active principles.

Presenilin-1–associated abnormalities in regional cerebral perfusion

Objective: To investigate the influence of the presenilin-1 gene (PS-1) mutation on regional cerebral perfusion, SPECT was evaluated in 57 individuals. The subjects were members of a large pedigree from Colombia, South America, many of whom carry a PS-1 mutation for early-onset AD. Methods: Members of this large kindred who were cognitively normal and did not carry the PS-1 mutation (n = 23) were compared with subjects who were carriers of the mutation but were asymptomatic (n = 18) and with individuals with the mutation and a clinical diagnosis of AD (n = 16). Cerebral perfusion was measured in each subject using hexamethylpropyleneamine oxime SPECT. The data were analyzed in two ways: 1) Mean cerebral perfusion in each of 4320 voxels in the brain was compared among the groups using t-tests (t-maps); and 2) each individual received a weighted score on 20 vectors (factors), based on a large normative sample (n = 200), using a method known as singular value decomposition (SVD). Results: Based on t-maps, subjects with the PS-1 mutation who were asymptomatic demonstrated reduced perfusion in comparison with the normal control subjects in the hippocampal complex, anterior and posterior cingulate, posterior parietal lobe, and anterior frontal lobe. The AD patients demonstrated decreased perfusion in the posterior parietal and superior frontal cortex in comparison with the normal control subjects. Discriminant function analysis of the vector scores derived from SVD (adjusted for age and gender) accurately discriminated 86% of the subjects in the three groups (p < 0.0005). Conclusion: Regional cerebral perfusion abnormalities based on SPECT are detectable before development of the clinical symptoms of AD in carriers of the PS-1 mutation.

E280A PS-1 mutation causes Alzheimer's disease but age of onset is not modified by ApoE alleles

A single base substitution of a glutamic acid to an alanine codon 280 was found in the presenilin‐1 (PS‐1) gene on chromosome 14 in affected individuals in each of seven Colombian early‐onset Alzheimers disease (AD) kindreds. The mutation segregated with disease in kindreds tested. In the largest kindred (C2), the maximum two‐point lod score between the mutation and AD was Z = 8.14 at θ = 0. The presence of a single mutation and the common geographic origin, with all families from the state of Antioquia, suggest a founder effect in this population. This finding is supported by the observation of a rare haplotype inherited with AD in all kindreds. These kindreds form the largest collection of AD cases with the same PS‐1 mutation and the same educational, environmental, and ethnic background in which to study the phenotypic effect of putative risk factors, such as the ϵ4 allele of apolipoprotein E (ApoE) or head trauma. Of the few AD cases having a history of head trauma, the age of onset was not lowered. No effect of ApoE genotype on the age of onset was detected. Previous investigations of the effect of ApoE genotype on the age of onset were confounded by small patient numbers, familial clustering of ApoE genotypes, and combining data from unrelated families with different mutations. Hum Mutat 10:186–195, 1997.

Heparin plus aspirin as a "single" therapy for recurrent spontaneous abortion associated with both allo- and autoimmunity.

PROBLEM: The aim of this study was to contribute to the study of the pathogenesis and the treatment of recurrent spontaneous abortion (RSA) associated with immune alterations.

The production of MLR-blocking factors after lymphocyte immunotherapy for RSA does not predict the outcome of pregnancy.

PROBLEM: The questions of whether production of mixed lymphocyte reaction‐blocking factors (MLR‐BFs) after immunotherapy with lymphocytes for recurrent spontaneous abortion (RSA) has prognostic value and whether cytotoxic antibodies are also involved were tested.

Is the immune system necessary for placental reproduction? A hypothesis on the mechanisms of alloimmunotherapy in recurrent spontaneous abortion.

Recurrent spontaneous abortion is being treated with alloimmunotherapy which consists of the inoculation of allogeneic mononuclear cells. However the mechanisms explaining the benefits of this therapy are not clear yet. Taking the immunotrophic hypothesis as the paradigm of the field of reproductive immunology, hereby we present a hypothesis to propose a role for the immune system in reproduction and at the same time to explain how alloimmunotherapy may work. We base our view on several facts: first, immunodeficient mice reproduce--albeit their progeny may not be as robust and numerous as that from normal individuals. Second, maternal lymphocytes cross the placenta and may induce graft versus host disease. Third, graft versus host disease in newborn F1 mice inoculated with paternal lymphocytes can be prevented by inoculation of the mother with the same paternal lymphocytes before and during pregnancy. We propose that: 1) the immune system by itself is not necessary for placental reproduction; 2) the immune system plays its major role in reproduction by counteracting the allogeneic response generated against the fetus; 3) recurrent spontaneous abortion represents a type of graft versus host disease induced by maternal cells infiltrating the fetus; and 4) alloimmunotherapy induces an antiidiotypic response necessary to counteract the graft versus host reaction in the fetus.

Bovine Fibroblasts Response to Foot-and-Mouth Disease Virus: Influence of Integrins and Soluble Factors in Resistance

Foot and mouth disease may be the most economically devastating animal disease nowadays. Blanco Orejinegro (BON) cattle are one of the native creole breeds from Colombia; this breed carries important genetic traits for survival and reproduction in the tropics showing in vitro and in vivo resistance to pathogens. Here we evaluate primary fibroblast cultures of BON cattle for their phenotypic resistence/susceptibility (R/S) polymorphism toward FMDV, and to determine whether a correlation exists between the R/S polymorphism and expression of integrin αV-β3, and/ or the antiviral activity in the supernatants of those cultures. Our data show that different R/S patterns to FMDV in vitro. Between 2% and 85% of the fibroblasts in the PCF-BON samples expressed integrin aV-b3. Interestingly, a correlation between R/S and expression of this receptor was observed for the A24 FMDV subtype. Highly resistant cultures showed a low level of integrin expression. Furthermore a correlation was observed between resistance and antiviral activity (AVA) of supernatants from infected samples. Supernatants with high AVA were always from very resistant samples for subtype A24, or from very resistant or resistant samples for subtype O1; supernatants with low AVA were from susceptible samples. In most samples, the factor in the supernatants responsible for AVA was not only resistant to heating, but AVA increases after heating. To our knowledge, this is the first report showing resistance to FMDV infection in vitro using primary cultures from bovines.

Commentary on Samuel Broder‘s, Stephen Hoffman's and Peter Hotez's article in EMBO reports, September 2002

Broder et al . recently published an article in EMBO reports about new cures for the health problems of the Third World. The subtitle was even more informative: the application of genomics to the diseases plaguing the developing world may have huge medical and economic benefits for those countries and might even prevent armed conflict. This is how we scientists are: candid! In summary, the authors of the above‐mentioned article predict that genomics will finally solve some of the major problems afflicting the so‐called ‘Third World countries’—from infectious diseases to social unrest—and put their economies on the right track… to what? Among the diseases listed as examples are many so‐called …