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Biomedical subjects

W Rojas

Publications and source records attributed to W Rojas.

17 recordsLinked to original sources
PubMed2001

[Low-grade malignant peripheral nerve sheath tumor of the neck soft tissues].

BACKGROUND: Malignant Peripheral Nerve Sheath Tumours (MPNST) either grow sporadically, after radiation or chemotherapy respectively. In many cases they are associated with Neurofibromatosis I. Because of the multiform histologic picture they are often difficult to differentiate from other soft tissue tumours. PATIENT: We present the case of a sporadic MPNST which developed from the vagus nerve of a 39-year-old patient following radiation of the neck 7 years before. After complete excision there has been no recurrence up to now. RESULTS AND CONCLUSIONS: Sporadic MPNST of the head and neck are comparatively rare. With regard to the strong association with Neurofibromatosis I and the difficult differential diagnosis to other soft tissue tumours the emphasis should be put on excluding further manifestations of Neurofibromatosis I and of secondary tumours.

Adult↗
PubMed2001

Coupling between annual and ENSO timescales in the malaria-climate association in Colombia.

We present evidence that the El Niño phenomenon intensifies the annual cycle of malaria cases for Plasmodium vivax and Plasmodium falciparum in endemic areas of Colombia as a consequence of concomitant anomalies in the normal annual cycle of temperature and precipitation. We used simultaneous analyses of both variables at both timescales, as well as correlation and power spectral analyses of detailed spatial (municipal) and temporal (monthly) records. During "normal years," endemic malaria in rural Colombia exhibits a clear-cut "normal" annual cycle, which is tightly associated with prevalent climatic conditions, mainly mean temperature, precipitation, dew point, and river discharges. During historical El Niño events (interannual time scale), the timing of malaria outbreaks does not change from the annual cycle, but the number of cases intensifies. Such anomalies are associated with a consistent pattern of hydrological and climatic anomalies: increase in mean temperature, decrease in precipitation, increase in dew point, and decrease in river discharges, all of which favor malaria transmission. Such coupling explains why the effect appears stronger and more persistent during the second half of El Niño's year (0), and during the first half of the year (+1). We illustrate this finding with data for diverse localities in Buenaventura (on the Pacific coast) and Caucasia (along the Cauca river floodplain), but conclusions have been found valid for multiple localities throughout endemic regions of Colombia. The identified coupling between annual and interannual timescales in the climate-malaria system shed new light toward understanding the exact linkages between environmental, entomological, and epidemiological factors conductive to malaria outbreaks, and also imposes the coupling of those timescales in public health intervention programs.

Animals↗
PubMed2001

An integrated malaria control program with community participation on the Pacific Coast of Colombia.

The study focuses on integrated malaria control in 23 communities on the Pacific Coast of Colombia, with several elements of an ecosystem approach to human health, including malaria-related sociopolitical, ecological, and economic factors. The program fostered community participation. The program presented here had 2 components: implementation and research. The first was conducted in 23 communities, 21 of which lacked adequate health services in terms of education, community participation, prompt diagnosis and complete treatment, and vector control. Research focused on specific vector control measures and the current national health services decentralization process. The project: 1) created a malaria prevention culture in the community; 2) avoided deaths from malaria (no fatal cases in the 3-year period, compared to 5-8 deaths a year previously); 3) avoided cases of cerebral malaria (no cases, as compared to 90-110 per year previously); 4) reduced malaria incidence by 45.36%; 5) decreased length of sick leave from 7.52 to 3.7 days; 6) established a permanent network of microscope technicians and 2-way radio communications; 7) integrated work by local, regional, and outside institutions; 8) demonstrated efficacy of insecticide-impregnated bednets to reduce malaria transmission.

Ambulatory Care↗
PubMed2000

Expression of basic fibroblast growth factor protein and its down-regulation by interferons in head and neck cancer.

BACKGROUND: Angiogenesis is crucial for tumor growth and metastasis. In several tumors, microvascular density has been shown to correlate with metastasis and aggressiveness. Basic fibroblast growth factor (bFGF) has potent angiogenic activity and has been identified in a wide variety of malignancies including head and neck squamous cell carcinomas (HNSCC). Material and Methods Frozen sections of 50 HNSCC were immunostained for von Willebrand factor and bFGF. Microvessels were counted by light microscopy; bFGF expression was studied at the light and electron microscopic level. Laryngeal cancer cell line HlaC79 was incubated with interferon (IFN) alpha and beta. bFGF quantification was performed by ELISA, and antiproliferative effects were determined by BrdU assay. RESULTS: The mean number of blood vessels (77.5 +/- 23.7) is significantly increased in HNSCC compared with controls (17.1 +/- 5.9). bFGF protein expression was detected in all HNSCC but not in control tissue. An correlation between bFGF expression and mean number of microvessels was found (p <.001). However, no correlation between bFGF expression and the main clinicopathologic features was shown. The long-term exposure (144 hr) of HNSCC cells to noncytostatic concentrations of IFN alpha and beta (>10 U/mL) down-regulated the protein production of bFGF. CONCLUSION: bFGF expression and angiogenesis are enhanced in HNSCC. The higher microvessel density in HNSCC with strong bFGF expression supports the importance of bFGF for tumor angiogenesis. IFN alpha and beta treatment leads to a down-regulation of bFGF expression independent of their antiproliferative effects, suggesting that IFN treatment might result in a reduction of angiogenesis in HNSCC.

Adult↗
PubMed1997

Predicting high-risk years for malaria in Colombia using parameters of El Niño Southern Oscillation.

The interannual variation in malaria cases in Colombia between 1960 and 1992 shows a close association with a periodic climatic phenomenon known as El Niño Southern Oscillation (ENSO). Compared with other years, malaria cases increased by 17.3% during a Niño year and by 35.1% in the post-Niño year. The annual total number of malaria cases is also strongly correlated (r = 0.62, P < 0.001) with sea surface temperature (SST) anomalies in the eastern equatorial Pacific, a principal parameter of ENSO. The strong relation between malaria and ENSO in Colombia can be used to predict high and low-risk years for malaria with sufficient time to mobilize resources to reduce the impact of epidemics. In view of the current El Niño conditions, we anticipate an increase in malaria cases in Colombia in 1998. Further studies to elucidate the mechanisms which underlie the association are required. As Colombia has a wide range of climatic conditions, regional studies relating climate and vector ecology to malaria incidence may further improve an ENSO-based early warning system. Predicting malaria risk associated with ENSO and related climate variables may also serve as a short-term analogue for predicting longer-term effects posed by global climate change.

Colombia↗
PubMed1992

A new serotype of Bacillus thuringiensis from Colombia toxic to mosquito larvae.

During a survey conducted in Colombia a new isolate of Bacillus thuringiensis that showed toxicity toward Culex quinquefasciatus, Cx. pipiens, Aedes aegypti, and Anopheles stephensi larvae was isolated. Parasporal crystals were spherical in shape and showed a great degree of similarity with those produced by the reference strain of Bacillus thuringiensis subsp. israelensis. Supernatant fraction of the whole culture was not toxic, and heat-stable exotoxin production was negative. Catalase, urease, arginine dihydrolase, amylase, lecithinase, acetyl-methyl-carbinol, and gelatinase production were positive. Hemolysis on sheep blood agar was alpha-type. The isolate 163-131 showed natural resistance to azolocillin and was sensible to cephoperazone, cephalotin, nalidixic acid, and trimetoprin sulfametoxazole. Flagellar agglutination showed a specific H 30 antigen which allows individualization of this strain as a new serotype and the subspecies name of medellin is proposed.

Animals↗
PubMed1992

Strategies for malaria control in Colombia.

Attempts at malaria eradication this century have been highly effective but early successes have not been sustained. This has been ascribed to the lack of community involvement in these campaigns. Colombia has put huge effort into malaria control on a number of fronts, from vaccine development to the evaluation of the integrated use of more traditional methods. William Rojas, Fernando Peñaranda and Mouricio Echavarria describe a pilot programme for integrated malaria control in Colombia whose success they attribute to committed community participation.

Journal Article↗
PubMed1992

Effect of antibiotic treatment on mycelial growth of isolates of the mosquito pathogenic fungus Lagenidium giganteum (Oomycetes: Lagenidiales) from Australia, Colombia and United States.

Bacteria collected in mosquito breeding ponds were evaluated for resistance to streptomycin, chloramphenicol, penicillin and trimethoprim. Mycelial growth of Lagenidium giganteum isolates from Australia, United States and Colombia were evaluated in PYG media containing one antibiotic or a mixture of these compounds. Media containing chloramphenicol reduced mycelial growth of most of the isolates. The antibiotic mixtures and penicillin-streptomycin penicillin-trimethoprim did not significantly affect mycelial growth of the isolates; however, the later substantially reduced bacterial contamination.

Animals↗
PubMed1987

Reduction of malaria prevalence after introduction of Romanomermis culicivorax (Mermithidae: Nematoda) in larval Anopheles habitats in Colombia.

The worldwide resurgence of malaria has become a major public health problem. New methods of controlling the vectors of the disease are required, and we therefore studied the biological control of Anopheles albimanus by Romanomermis culicivorax in Colombia. The investigation was carried out in El Valle and Nuquí, two towns on the northern Pacific coast of the country. All of the mosquito larval habitats surrounding El Valle were seeded with the eggs and adults of R. culicivorax. The nematode established itself in the new habitat and recycled over 27 months. The larval population of A. albimanus, the only malarial vector detected in the two towns, decreased in El Valle. In contrast, no change in the larval populations of the vector was detected in ponds located near Nuquí, the untreated control town. A rapid and progressive decrease of the prevalence of malaria among schoolchildren in El Valle was observed during the 2-year evaluation period.

Animals↗
PubMedDate not supplied

Blood groups and malaria.

The possible relationship between erythrocyte antigens and the presence of malaria infection by P. vivax and P. falciparum was sought in four different ethnic groups of two departments of Colombia. Malaria infection by P. falciparum was found in 91.4% of malaria infected blacks. No significant differences were found between the presence of malaria infection and ABO antigens. In the other blood groups, it was observed that groups MNSs conferred black people a greater Rr for malaria by both species of Plasmodium and that Duffy-negative blacks and indians appeared to be resistant to P. vivax infection. A predominance of P. vivax infection was observed in Katio Indians while P. falciparum was predominant in Kuna Indians; the reason for this finding still needs to be explored.

Blood Group Antigens↗
PubMedDate not supplied

Transfer of toxin genes to alternate bacterial hosts for mosquito control.

Mosquitoes are vector of serious human and animal diseases, such as malaria, dengue, yellow fever, among others. The use of biological control agents has provide an environmentally safe and highly specific alternative to the use of chemical insecticides in the control of vector borne diseases. Bacillus thuringiensis and B. sphaericus produce toxic proteins to mosquito larvae. Great progress has been made on the biochemical and molecular characterization of such proteins and the genes encoding them. Nevertheless, the low residuality of these biological insecticides is one of the major drawbacks. This article present some interesting aspects of the mosquito larvae feeding habits and review the attempts that have been made to genetically engineer microorganisms that while are used by mosquito larvae as a food source should express the Bacillus toxin genes in order to improve the residuality and stability in the mosquito breeding ponds.

Animals↗