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Biomedical subjects

M Pla

Publications and source records attributed to M Pla.

At least 109 records · Page 6Linked to original sources
PubMed1983

[Histogenetic study and mixed lymphocyte reaction in 2 lines of chickens homozygotic for haplotypes B14 and B19].

The histocompatibility status of homozygous chicken for B14 and B19 haplotypes of Hy-line stock origin was compared by skin grafts and the mixed lymphocyte reaction. No differences in graft survival (33 days) could be recorded in H-B compatible grafts in either haplotype tested. Reciprocal allografts however (B14 in equilibrium B19) were rejected within 12 days in both haplotypes. A weak stimulation index (1.3-1.9) persisted in individuals serologically identical with respect to the H-B complex whereas a strong index of 10.4 was obtained in allogeneic lymphocyte cocultures.

Alleles↗
PubMed1982

Serological cross-reactivity between products of separate I regions.

A B10.S(7R) anti-B10.S(9R) serum (anti-IJEkCd) contained, as expected, antibodies specific for the I-E-subregion-encoded determinant Ia.7. However, tests on recombinant haplotypes demonstrated a series of unexpected weak extrareactions which could be interpreted to be directed against antigenic determinants encoded in the I-A subregion of the H-2 complex. The same type of extrareaction was observed in eluates from I-As, I-Ek cells coated with A.TH anti-A.TL (I-As, I-Ek anti-I-Ak, I-Ek) serum. This reactivity in serum and eluates could be interpreted as cross-reactivity between products of the I-E and I-A subregions.

Animals↗
PubMed1981

Inhibition of secondary mouse mixed lymphocyte reaction by anti-Ia sera.

Secondary mixed lymphocyte reaction (MLR-II) was studied in A.TH anti A.TL and A.TL anti-A.TH combinations in which stimulation was mainly due to H-21-region differences. In both cases of MLR-II was specifically inhibited by the responder anti-stimulator Ia serum. The level of inhibition was dependent on the ratio of the amount of immune serum to the number of stimulating cells. The inhibitory activity and Ia antibodies were specifically absorbed and eluted together. The results confirm that the lymphocyte-activating determinants of the MLR-II (1) are carried by the Ia molecules and (2) are identical to the serologically defined Ia determinants. - Anti-Ia sera directed against private and public specificities of the stimulating cell induced a higher level of inhibition than anti-Ia sera directed only against public specificities, indicating that both private and public Ia specificities are involved in re-stimulation during MLR-II. - These results, in connection with others, suggest that the receptor of the proliferating T cell recognizes the same Ia determinant as the combining site of the Ia-recognizing antibody.

Animals↗
PubMed1980

[Serological study of Ia antigens determined at the I-A and I-E sub-regions of the H-E complex in the H-2 complex of mice].

Immune serum B10.S (7R) anti-B10.S (9R)(anti I-JEkCd) contained as expected an anti-Ia7 antibody. A series of weaker but reproducible extra-reactions might recognize Ia3 specificity coded at the I-A subregion of the H-2 complex. Results with recombinant haplotypes confirmed this mapping. Such a reactivity could be interpreted as an interlocus cross-reaction (I-E/I-A) since the immunization was induced against an I-E subregion product. Another interpretation was possible: the immune serum would thus contain an antibody recognizing Ia7 (on the E alpha k Ia chain) and another antibody recognizing an antigenic determinant carried by the E beta k Ia chain. The latter antibody might recognize by cross-reaction as specificity carried by the A beta chain of various haplotypes (H-2b,k,q).

Animals↗
PubMed1979

[Stimulating determinants of the secondary mixed lymphocyte reaction (MLR-II)].

An anti-Ia immune serum (A . TL anti-A . TH) directed to the antigens of the stimulating cell, blocked the MLR-II. A significant correlation was observed between the anti-Ia reactivity of the immune serum, studied against a panel of eleven original H-2 haplotypes and the reactivity against the same panel of the in vitro primed responding cells (A . TL anti-A . TH). These results confirm the hypothesis that Ia antigens are the structures stimulating the MLR-II.

Animals↗
PubMed1979

H-2 restriction for lymphocyte homing into lymph nodes.

Migratory patterns into lymph nodes of labeled spleen lymphocytes, injected intravenously, showed considerable differences according to the genetic identity or disparity of donor and recipient mice. The use of mice carrying different H-2 haplotypes in the same B 10 background, or, conversely, the same H-2b haplotype in different backgrounds, showed that no homing was observed in the case of complete disparity at the H-2 complex, contrasting with optimal homing in the case of H-2 identity. Homing was not influenced by disparity at the genetic background. Irradiation of recipient mice did not change the results and suggested that no immunological host-vs.-graft reaction was involved in the H-2 restriction observed. The use of donor-recipient pairs carrying recombinant H-2 haplotypes showed that a single H-2 K and/or H-2 D identity allowed almost optimal homing. The results indirectly suggested that an immunological graft-vs.-host reaction was not involved in the phenomenon but rather a positive recognition of H-2 K or H-2 D identity between donor and recipient cells.

Animals↗
PubMedDate not supplied

Anti-MHC immunity detected prior to intentional alloimmunization. IV. Natural monoclonal H-2-specific antibodies.

Naturally occurring H-2-specific antibodies can be detected rather frequently in sera of non-alloimmunized mice by sufficiently sensitive techniques (Cerny-Provaznik et al., 1985a; Cerny-Provaznik & Ivanyi, 1985). In this report, we summarize our experiences with the preparation of monoclonal anit-H-2 antibodies obtained from hybridization experiments from non-alloimmunized mice. From a total of 30 spleen cell hybridization experiments, we could isolate only four anti-H-2 monoclonal antibodies (mAB). Two of the mAB are described in this report. Monoclonal antibody By-2 is anti-Kf and mAB By-3 is anti-Db, Ds. We investigated which conditions favour the isolation of monoclonal H-2-specific antibodies from non-alloimmunized mice. The presence of naturally occurring serum antibodies, the age of the spleen donor mouse or non-specific B cell stimulation were not critical for the isolation of natural anti-H-2 mAB. We hypothesise that the 'natural' H-2-specific antibodies represent compartments of the B cell repertoire which were triggered by modified or aberrant self-MHC expression.

Animals↗
PubMedDate not supplied

H-2 influence on the production of real but not of apparent H-2-specific antibodies induced by the association of syngeneic class I heavy chains with bovine beta 2-microglobulin.

Immunogenic properties of class I molecules resulting from the association of mouse class I heavy chains with a xenogeneic beta 2-microglobulin (beta 2-m) were investigated by studying the antibody response of mice of injections to syngeneic Con A lymphoblasts, induced in conditions allowing the replacement of endogenous beta 2-m by exogenously added bovine beta 2-m provided by fetal calf serum (FCS-Con A blasts). Lymphocytotoxic antibodies were regularly produced and according to their specificities they could be divided into two types: antibodies whose reactivity was (1) dependent on and (2) independent of the presence of bovine beta 2-m on target cells. Although both types displayed an H-2 dependent polymorphic reaction pattern, only antibodies recognizing class I molecules without bovine beta 2-m can be considered as real H-2-specific antibodies. The others are only apparent H-2-specific antibodies: their polymorphic reaction pattern is dependent both on the presence of bovine beta 2-m on the surface of target cells and on their H-2 haplotype. A comparison of the antibody response of mice with various H-2 haplotypes to injections of syngeneic FCS-Con A blasts showed no significant difference in the induction of bovine beta 2-m-dependent antibodies (apparent H-2-specific) among the mice from all strains tested (H-2b, H-2p, H-2q, and H-2s). Unexpectedly, for most strains more than 60% of the immunized mice produced also beta 2-m-independent antibodies (real H-2-specific), with the exception of H-2q mice, in which only 30% of sera were positive. The real H-2-specific antibody response is of two types: some mice (H-2p and H-2s) produced antibodies only reactive with allogeneic target cells whereas others (H-2b and H-2q) produced in addition antibodies that were reactive with syngeneic cells. Thus H-2 appears to play an important role in the induction and specificity of the lymphocytotoxic H-2-specific antibodies induced upon immunization with cells expressing syngeneic class I heavy chains associated with bovine beta 2-m.

Animals↗
PubMedDate not supplied

Physical aspects of a rotational total skin electron irradiation.

A technique for rotational total skin electron irradiation is presented in which the patient stands on a slowly rotating platform (SSD = 285 cm) in a large uniform linear accelerator electron field (Eo = 3.5 MeV). The beam is scattered by the transmission ionization chamber and by a special lead/aluminum scattering filter, and then degraded by a sheet of Lucite. A Farmer chamber is used as a patient dose monitor and a method for absolute dose calibration is presented. The field is uniform to within +/- 5% for dimensions of 180 X 40 cm2. The surface dose for rotational therapy is equal to 45% of the maximum dose in a stationary beam. The rotating beam exhibits a dose maximum on the surface, falls to 80% at 0.5 cm and has an x-ray contamination of approximately 4%. The surface dose rate is about 25 cGy/min for the rotating beam. The rotational beam percentage depth dose distributions, calculated using stationary beam information, agree well with measured data. The stationary beam exhibits a dose maximum at 4 mm in tissue, a surface dose of 93%, 80% dose at a depth of 1 cm, a practical range of 1.75 cm, and an x-ray contamination of 2.5%. The rotational total skin electron irradiation significantly reduces the patient treatment and setup time and solves the problem of beam matching, when compared to standard multiple-beam techniques.

Electrons↗
PubMedDate not supplied

Calculation of surface dose in rotational total skin electron irradiation.

A single-field rotational total skin electron irradiation technique has recently been developed at the McGill University for treatment of skin malignancies. The dose received by a given surface point during rotation in a uniform large electron field depends on the radius of rotation of the surface point, on the local radius of curvature of the contour in the vicinity of the point of interest, and on the shadows cast by limbs (arms upon trunk or head and neck, and legs upon each other). A method for calculating the surface dose distribution on a patient is presented accounting for the various parameters affecting the dose. A series of measurements were performed with polystyrene and a humanoid phantom, and an excellent agreement between measured and calculated dose distributions was obtained.

Electrons↗
PubMedDate not supplied

The influence of phantom size on output, peak scatter factor, and percentage depth dose in large-field photon irradiation.

Machine outputs, peak scatter factors, and central axis percentage depth dose distributions were measured for various phantom sizes in large radiation fields produced at extended distances by cobalt, 6-MV, and 10-MV photon beams. The results can be applied to practical total body irradiation procedures which usually involve treatment volumes smaller than the actual field sizes in order to provide a uniform total body exposure to radiation. Our study addresses the question of the appropriate phantom dimension to be used in the calibration of photon beams employed in total body irradiations. The measurements show that the machine outputs are only slightly dependent on phantom size; the percentage depth dose distributions, however, are strongly dependent on the phantom size, suggesting that machine data for total body irradiations should be measured in phantoms whose dimensions approximate the patient during the total body irradiation. Peak scatter factors measured in large-field/small-phantom configurations link up well with the published small-field/large-phantom data. The finite patient thickness lowers the dose to points close to the beam exit surface by a few percent, when compared to dose measured at the same depths in infinitely thick phantoms. The surface doses in large radiation fields are essentially independent of phantom cross sections and range from 40% for the 10-MV beam, to 65% for the 6-MV beam and 80% for the cobalt beam.

Cobalt Radioisotopes↗
PubMedDate not supplied

The influence of beam parameters on percentage depth dose in electron arc therapy.

The dependence of rotational or arc electron beam percentage depth doses on the depth of isocenter di and nominal beam field width w is presented. A characteristic angle beta, which uniquely depends on w and di, is defined and the dependence of the radial percentage depth doses on angle beta discussed. It is shown that the characteristic angle beta concept can be used in clinical situations to predict the shape of the percentage depth dose curve when w and di are known, or, more importantly, it can be used to determine the appropriate w when di and the percentage depth dose characteristics are known.

Electrons↗
PubMedDate not supplied

Electron dose rate and photon contamination in electron arc therapy.

The electron dose rate at the depth of dose maximum dmax and the photon contamination are discussed as a function of several parameters of the rotational electron beam. A pseudoarc technique with an angular increment of 10 degrees and a constant number of monitor units per each stationary electron field was used in our experiments. The electron dose rate is defined as the electron dose at a given point in phantom divided by the number of monitor units given for any one stationary electron beam. For a given depth of isocenter di the electron dose rates at dmax are linearly dependent on the nominal field width w, while for a given w the dose rates are inversely proportional to di. The dose rates for rotational electron beams with different di are related through the inverse square law provided that the two beams have (di,w) combinations which give the same characteristic angle beta. The photon dose at the isocenter depends on the arc angle alpha, field width w, and isocenter depth di. For constant w and di the photon dose at isocenter is proportional to alpha, for constant alpha and w it is proportional to di, and for constant alpha and di it is inversely proportional to w. The w and di dependence implies that for the same alpha the photon dose at the isocenter is inversely proportional to the electron dose rate at dmax.

Biometry↗
PubMedDate not supplied

[Myasthenia gravis].

The present review updates myasthenia gravis. Immunopathogenesis of this condition, the clinical picture and degrees of involvement according to Osserman's classification, diagnostic procedures currently available, medical treatment and repercussion on the patient who is going yo be thymectomized are discussed. We review the works of several authors as far as concern to the use of muscle relaxants in myasthenic patients, peroperative monitoring of neuromuscular blockade, anesthetic techniques to be used, analgesia and intensive care required during postoperative period.

Anesthesia↗