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Biomedical subjects

F Ojeda

Publications and source records attributed to F Ojeda.

35 records · Page 2Linked to original sources
PubMed1982

Cytoplasmic requirements for the radio-induced modulation of IgG receptors on B-cells.

The effect of X-ray irradiation on IgG membrane receptors of B murine lymphocytes was studied. Cells were obtained from peripheral lymph nodes of RK mice and teased in Hank's solution. The cells were irradiated or kept as control samples, incubated at 37 degrees C, with or without drugs with known biochemical action at metabolic or structural levels, and labelled with fluorescein-conjugated anti-IgG antisera. The results show that X-ray irradiation results in a modulation of IgG receptor molecules on B-cells. The disappearance phase which takes only 10 min, is temperature dependent, and is prevented with metabolic inhibitors, microtubular disruptors, db-cAMP and local anesthetics. The re-appearance phase is also temperature dependent but apparently does not have either energy or cytoskeleton participation. The phenomenon is interpreted as partial and transient internalization of IgG molecules in the membrane.

2,4-Dinitrophenol↗
PubMed1981

Hodgkin's disease in childhood: therapy results in Argentina.

From 1940 to 1977, a total of 152 children aged 15 years or less with the histologic diagnosis of Hodgkin's disease were treated in Argentina. For analysis, these patients were placed into three periods which displayed the most outstanding changes in diagnostic workup and therapy. The periods are as follows: (1) 1940 to 1966 (43 children), (2) 1967 to 1972 (35 children), and (3) 1973 to 1977 (74 children). The patients were treated with extended field radiation therapy and followed by courses of cyclophosphamide-vinblastine-procarbazine-prednisone, with CCNU added (CCVPP) or not added (CVPP) in a randomized trial. The mean age of the whole group was 7.5 years (range 2 to 15 years) and there was a predominance of males (79%). Crude 6-year survival for the three periods were as follows: 1940 to 1966, 34%; 1967 to 1972, 50%; and 1973 to 1977, 79%. We conclude that (1) survival of Hodgkin's disease of childhood has shown a rather marked improvement during the last decade and this progress is probably due to the use of combined multidrug chemotherapy administered under collaborative controlled clinical trials; (2) preliminary evaluation of the results of CVPP and CCVPP therapy shows that the latter combination (CCVPP) neither increases the percent of patients achieving complete remission nor prolongs relapse-survival in Hodgkin's disease of childhood: and (3) all stages of childhood Hodgkin's disease can be successfully managed with multidrug chemotherapy alone.

Adolescent↗
PubMed1980

Modification of radiation response by agents that elevate the intracellular c-AMP level.

A study has been made of the effects of drugs known to elevate c-AMP level on radiation-induced damage in thymocytes. The test used was the ability of the cells to exclude dye, beta-receptor stimulation and phosphodiesterase inhibition were found to induce radioresistance. The possible importance of the plasma membrane in connection with cytoplasmic factors is briefly discussed.

Aminophylline↗
PubMed1977

[Radiation response of mitochondria in dependence on their metabolic status (author's transl)].

The influence of the metabolic status of mitochondria upon their radiation response was studied. It turned out that the reduction of pyridine nucleotides by addition of beta-hydroxybutyrate (BOH) and the decrease through respiration were distinctly impaired in mitochondria with a substrate deficit by an irradiation with 2.7 krd already. The evolution of the lesion depends on the incubation conditions following irradiation, a presence of BOH having protective effects. The general redox level seems to be essential for radiation response of mitochondria. An exit of NAD from mitochondria has proved to be the main cause for inhibition of the respiratory BOH-consumption.

Animals↗
PubMedDate not supplied

Radiation induced loss of anti-Ig binding ability of lymphocytes.

The effect of irradiation on the anti Ig binding ability of lymphocytes after irradiation was studied. Normal control and irradiated lymphoid cells were treated with rabbit anti mouse IgG fluorescein conjugated serum and the fluorescein positive cells compared. A reduction in the proportion of stained cells in the irradiated lymphocytes was found. It depends on the dose and on the incubation time at 37 degrees C after irradiation. The maximum effect was detected after 10 minutes of incubation, longer incubation is associated with a partial recovery of the stainability of the IgG receptors.

Animals↗
PubMedDate not supplied

Radiation-induced apoptosis in thymocytes: pH sensitization.

Thymocytes were used as a model system to study the effect of microenvironmental pH changes on the radiation-induced apoptosis. We found that the sensitivity of thymocytes toward radiation induced apoptosis is increased by increasing the pH of the incubation medium. The major sensitivity change occurs between pH 7 and 8. In a given cell suspension the results obtained where similar when the apoptosis evaluation was carried out either by counting the picnotic nuclei, or monitoring the fraction of apoptotic nuclei by flow cytometry; both methods show a radiosensitization when the pH value of incubation media rises from 7 to 8. These results may be important when "in vitro" experiments are performed with lymphoid cells, since changes in pH of the media may determine important changes in the results.

Animals↗
PubMedDate not supplied

[Infections caused by gram negative anaerobic bacteria and other associated bacterial strains].

Between November 1975--December 1977, in the Laboratory of Microbiology, National Institute of Nutrition, Mexico, 156 cultures for anaerobic bacteria were grown on 118 cases with a clinical picture suggestive of anaerobic infection. There were 42 positive cultures (26.9%) from which 18 (42.8%) grew a mixed flora (aerobicanaerobic). Those 42 cultures came from 35 patients (29.6%) and the 18 mixed cultures came from 18 cases (15.25% global and 51.42% of the cases with anaerobic flora). The highest positive marks were obtained from material provenient from the abdominal cavity, and lesser indexes were obtained from lungs, blood, bone and sinovial cavities. The overall mortality was registered in 24 cases (20.33%) but only in 6 cases (5.8% global and 25% of the total cases) a positive anaerobic culture was obtained. In these 6 cases the cause of death was secondary to the principal disease, and only in one case the patient died from septicemia. The diagnosis of anaerobic infection resides mainly in the clinical findings, secondly in a positive gram stain, and thirdly in the identification of the etiologic agent, that will aid in the choice of a more specific therapy, which must include a surgical excision of the affected tissues.

Anti-Bacterial Agents↗
PubMedDate not supplied

Dose rate dependence of radiation induced IgG membrane receptor alteration [1].

Mouse lymph node lymphocytes are irradiated at different dose rates and the B-cell receptors to anti IgG are tested. The expression of receptors is inhibited by irradiation. It is shown that the effectivity of irradiation increases with decreasing dose rate suggesting that membrane damage may be important for situations of chronic irradiation or implant radiotherapy.

Animals↗
PubMedDate not supplied

T gamma cell levels in mammary and cervical uterine cancer patients before and after local irradiation treatment.

Total T and T gamma cell populations were studied in patients suffering from mammary of cervical uterine cancer. The results show that for both groups of patients there were no changes in the total T cell counts when compared with controls: but T gamma subpopulation values were greatly increased in the cancer patient groups, irrespective of in the mammary cancer group, whether the tumor mass was present at the moment of evaluation or surgically removed. The percentage of T mu cells returned to normal level after local irradiation treatment in all cases studied. We speculate about the possible changes in lymphocyte migration as a consequence of irradiation which may affect cells in the blood stream.

Breast Neoplasms↗
PubMedDate not supplied

Proliferation and apoptosis in infection with infectious bursal disease virus: a flow cytometric study.

Programmed cell death, or apoptosis, is involved in the normal physiology of many immunocompetent organs, including lymphocytes of the bursa of Fabricius in chickens. Involvement of apoptosis has also been described in some viral diseases such as AIDS. The purpose of this work was to study the potential role of apoptosis in the pathogenesis of Gumboro disease in the bursa of Fabricius. Our results show that 1-3 days after infection of young chickens with infectious bursal disease virus, the number of apoptotic cells increases and cellularity and proliferation decrease. Because of the dynamic nature of bursal lymphocyte populations and the involvement of apoptosis in lymphocyte cell physiology, the increased level of cells undergoing apoptosis may be due to an impairment in the withdrawal of apoptotic cells. A concomitant increase in macrophages in infected bursae and a dramatic decrease in cellularity suggest that an increase in apoptosis may be an important cause of cell depletion.

Animals↗