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C Martinez

Publications and source records attributed to C Martinez.

At least 235 records · Page 13Linked to original sources
PubMed1985

Secondary structure of the pore-forming colicin A and its C-terminal fragment. Experimental fact and structure prediction.

Conformational investigations, using circular dichroism, on the pore-forming protein, colicin A (Mr 60 000), and a C-terminal bromelain fragment (Mr 20 000) were undertaken to estimate their secondary structure and to search for pH-dependent conformational changes. Colicin A and the bromelain peptide are mainly alpha-helical with an enrichment of the alpha-helical content in the C-terminal domain carrying the ionophoric activity. The non-negligible beta-sheet structure in the C-terminal domain is unstable and is easily transformed into alpha-helix upon decreasing the polarity of the solvent. No evidence of pH-dependent conformational modification, correlated with modification of colicin A activity, could be obtained. The secondary structure estimated on the basis of experimental data favoured a model in which the pore is built of a minimal number of six transmembrane alpha-helical segments. Search for such segments in the amino acid sequence of the C-terminal domain of colicin A was carried out by combining secondary structure prediction methods with hydrophobicity and hydrophobic movement calculations. Similar calculations on the C-terminal domains of colicin E1 and IB indicate a common structure of the pores formed by colicin A, E1 and IB. Only two or three putative transmembrane segments could be selected in the sequences of colicin A, IB or E1. As a result, it is concluded that the channel is probably not built by a single colicin molecule but more likely by an oligomer.

Chemical Phenomena↗
PubMed1985

Interactions of small B lymphocytes with unprimed noncytolytic T cells: dissociation between "presentation" and growth induction.

The accessory cell requirements in lectin-dependent triggering and growth of unprimed Lyt-2-T lymphocytes were analyzed by quantitatively comparing the ability of small B cells and peritoneal macrophages to either induce reactivity to growth factors or support growth. Lightly or nonirradiated small B cells were 15 to 30-fold less efficient as compared to T cell-depleted peritoneal cell populations, in the support of the lectin-stimulated Lyt-2-T cell proliferation. In contrast, lightly irradiated small B lymphocytes were quantitatively as efficient as macrophages in mediating lectin-driven Lyt-2-T cell proliferation, if relevant supernatants were added into culture. Finally, supernatants derived from cultures where T-small B cell ratios were optimal for growth of responder Lyt-2-lymphocytes were two orders of magnitude less efficient than conditioned medium obtained from cultures containing optimal T-macrophage ratios, in their ability to support growth of activated T cells. We conclude from these experiments that: in contrast to cytolytic T cell precursors, lectin-dependent induction of unprimed Lyt-2- T lymphocytes requires accessory cells; small B cells and macrophages are equally competent in this respect; and growth support by small B cell populations is due to contamination by macrophages which are the only cell type performing this function. We therefore interpret reports on Lyt-2- T cell proliferation upon stimulation with high numbers of small B cells as a two-step process: "presentation" and induction of T cells which is essentially B cell dependent, and factor production ensured by contaminating macrophages.

Animals↗
PubMed1985

Odontoid fracture in a nine-month-old infant.

A type 2 odontoid fracture in a nine-month-old infant is presented. To the best of our knowledge, this case has the youngest reported patient with this type of injury having occurred by a mechanism other than direct trauma at birth. The purpose of this communication is to review odontoid fractures in the pediatric age group.

Axis, Cervical Vertebra↗
PubMed1985

Interleukin 2 promotes growth and cytolytic activity in human T3+4-8- thymocytes.

Human thymocytes bearing T3 but neither T4 nor T8 antigens (T3+4-8- cells) were obtained after negative selection of thymocytes, either fresh or cultured in medium containing recombinant interleukin 2 (IL-2), by treatment with Na1/34, OKT4A and B9.4 monoclonal antibodies (which recognize T6, T4, and T8 antigens, respectively) and complement. Quantitative flow cytometry showed a 98% pure population of T3+4-8- lymphocytes, which included proliferating cells. The growth and maturation requirements of these thymocytes were characterized and related to the T3-receptor complex and IL-2 pathways, thought to be used by mature lymphocytes. The results show that addition of recombinant IL-2 promotes, in a dose-dependent way, proliferation and acquisition of effector functions by cultured T3+4-8- thymocytes, the growth being inhibitable by monoclonal antibody 33B73 (anti-Tac). Furthermore, cytolytic activity of T3+4-8- cells induced by recombinant IL-2 is specifically blocked by monoclonal antibody OKT3, showing that it operates via the T3-receptor complex and does not require either T4 or T8 molecules. The finding of in vitro responsiveness to recombinant IL-2 in T3+4-8- thymocytes suggests a role of IL-2 in the growth and maturation of cells committed to the T-cell lineage, during intrathymic differentiation, prior to expression of T4 and T8 molecules.

Antibodies, Monoclonal↗
PubMed1984

Bovine skeletal muscle adenosine deaminase. Purification and some properties.

A low molecular weight form of adenosine deaminase from bovine skeletal muscle was purified about 930-fold. The enzyme had a mol. wt of 31,000, a Km value for adenosine of 2.37 X 10(-5) M and a pH optimum at 7.0. This enzyme is very resistant to heat inactivation and does not require metal activators or other dialysable cofactors. A possible role in the post-mortem metabolism of adenine nucleotide in skeletal muscle is discussed.

Adenosine Deaminase↗
PubMed1984

Internal complementarities in the immune system: regulation of the expression of helper T-cell idiotypes.

More than half of BALB/c helper T lymphocytes specific for 2,4,6-trinitrophenyl (TNP)-modified syngeneic spleen cells are inhibited in their proliferative responses to antigen-presenting cells and in their cooperation with B lymphocytes by monoclonal anti-idiotypic antibodies directed to a TNP-binding BALB/c myeloma protein (MOPC 460). This inhibition is specific for anti-TNP-self helper cells of BALB/c origin and is controlled by IgCh-linked genes, as it is not observed with CB.20 helper cells of the same specificity. In contrast, anti-TNP-self helper cells prepared from BALB/c mice that were chronically suppressed with anti-mu chain antibodies and possessed no B lymphocytes were not inhibited by anti-idiotypic antibodies. We conclude that the B-cell antibody repertoires contribute to the selection of the (idiotypic) T-helper-cell repertoires.

Animals↗
PubMed1984

The dilemma of mild hyperprolactinaemia.

Ninety-eight women with mild hyperprolactinaemia (less than 4N) were followed for a mean duration of 5.5 years. Where pregnancy was desired treatment with bromocriptine (+/- clomiphene) was effective in 87%. Following cessation of bromocriptine therapy almost one-third had a 'spontaneous' resolution of hyperprolactinaemia and resumed cyclical menstrual activity and fertility. Pituitary tumours were identified on coned-view assessment in 9% of patients at the time of presentation and a further 10% during follow-up. Although some of these latter tumours may have been diagnosed earlier had CAT scans been performed routinely in all hyperprolactinaemic patients, such a policy would be hard to justify for those with mild hyperprolactinaemia as the tumours were small, produced no harmful effects, and would almost certainly have responded to bromocriptine should this have been administered. All patients found to have pituitary tumours and given bromocriptine, showed no evidence of tumour progression subsequently, even where pregnancy occurred and the bromocriptine therapy was ceased. In addition, patients without pituitary tumours who were given bromocriptine to achieve pregnancy, were less likely to develop tumours during follow-up even when pregnancy had occurred. Bromocriptine therapy can thus be justified in mildly hyperprolactinaemic patients to reduce troublesome galactorrhoea, achieve pregnancy, improve the chance of 'spontaneous' resolution of the menstrual problem and infertility, control or reduce tumour growth where a pituitary tumour has been identified, and reduce the risk of tumour development in patients with normal radiographs at the time of presentation.

Bromocriptine↗
PubMed1984

T cell-dependent B cell activation.

T cell-dependent induction of small, resting B lymphocytes requires direct recognition of antigen and/or I-A/E molecules on the B cell surface by the inducing helper cell, and it does not require the participation of Ig receptors on the responding B cell. Triggering B cell receptors, therefore, are either the I-A/E molecules themselves, or other structures with complementarities on helper cell membranes that become available for productive interactions upon I-A/E recognition. It would appear that signal delivery by such triggering receptors can be regulated by a membrane complex of molecules, involving immunoglobulins, Class II MHC molecules and other classes of receptors, which in selective and distinct manners control the quantitative levels of expression and/or availability of the relevant structures. Classical in vivo observations and our in vitro experiments led us to conclude that induction of B cells does not occur upon binding of T cell-dependent antigens to Ig receptors and, consequently, that B lymphocyte activation by anti-receptor antibodies has no physiological counterpart. Induced B lymphocytes proliferate and mature to high rate secretion of antibodies under the influence of selective growth and maturation factors produced by helper cells which are MHC-unrelated, act polyclonally and have no influence in normal, resting cells. Specific ligand interactions with the membrane molecules participating of that functional complex may also regulate reactivity to either growth or maturation factors, and, thus, control clonal performances and the fate of activated cells.

Animals↗
PubMed1984

[Cutters and drillers: 2 different coal pneumoconioses?].

The radiographs of 393 coal-cutters (or hewers) and 187 drillers were read independently by two pneumoconiosis experts following the complete 12 grade classification (BIT 1980). The two groups were comparable for age, tobacco and alcohol consumption, and respiratory symptoms but the VEMS was lower in he drillers (p = 0.05). There were significant radiological differences between the groups as follows: with the coal-cutters predominantly type "p" opacities and Category 1; in the drillers "q" and "v" opacities and category 3 were most frequent, and there were a large number of pseudo-tumoral masses and signs of hyperinflation. The two groups have a quantitative and qualitative differences in exposure; it is necessary to interpret the results as two different types of pneumoconiosis, although there are intermediate types. The coal cutters have coal-workers pneumoconiosis in the strictest sense, while the drillers have silicosis with mixed dusts, the latter being more aggressive and incapacitating. One should take account of the two types in epidemiological evaluations in coal miners. It helps to explain certain contradictory results.

Coal Mining↗
PubMed1983

Activation of helper T cells for B lymphocytes in primary mixed lymphocyte cultures.

Normal B10.BR (H-2k, C57B1/6 background) spleen cells, enriched in primary mixed lymphocyte culture (MLC) for antigens of C3H/Tif mice (H-2k, C3H background), induced normal C3H/Tif but not B10.BR B lymphocytes to proliferate and produce Ig. In contrast, normal B10.BR spleen cells enriched in parallel B10.BR anti-C57B1/6 (H-2b) MLC were not able to activate either B10.BR or C57B1/6 B lymphocytes. However, normal B10.BR spleen cells depleted of Lyt2+ cells before initiation of the MLC, and subsequently enriched either for C3H/Tif or C57B1/6 antigens, activated B lymphocytes of the respective mouse strains specifically and equally well. These experiments show that primary MLC gives rise to effector T helper cells that, on recognition of specific alloantigens, activate normal B lymphocytes of the 'stimulator' strain. In response to major histocompatibility complex (MHC) alloantigens, this help is not revealed because of interference by Lyt 2+ lymphocytes. MHC-reactive T helper cells for B lymphocytes, however, participate in these reactions and constitute the predominant population in long-term cultures that are maintained by consecutive in vitro restimulations.

Animals↗
PubMed1983

Haematological and clinical data in 200 cases of thalassaemia trait in eastern Spain.

A total of 200 cases of thalassaemia trait, 102 of F thalassaemia and 98 of A2 thalassaemia were studied, evaluating haematometric, and morphological aspects of both groups. Significantly higher values were found in F thalassaemia for PCV, MCV and MCH, with 33.5% of women and 52% of men being found anaemic in F thalassaemia and 45% of women and 62% of men in A2 thalassaemia. Asthenia was usually present in A2 thalassaemia more so in women 50.9% as compared to 25% in man. Only 4% of F thalassaemia carriers were affected by asthenia. Cholecystectomy had been performed on 10% of the A2 thalassaemia group and on 5% of the F thalassaemia thamia group. Both groups show a high proportion of red cells with basophilic stippling (80%), the groups being morphologically indistinguishable. Intrafamilial segregation of Hb F values affected 22% of families carriers of F thalassaemia, whereas only 8% of families carriers of A2 thalassaemia showed segregation of HbA2 values. The values obtained in this study were compared with those of other authors.

Adolescent↗
PubMed1983

Natural history of patients with hyperprolactinaemia.

One hundred and nineteen women with sustained hyperprolactinaemia were followed for a mean duration of 5.5 years. Where pregnancy was desired, treatment with bromocriptine (+/- clomiphene) was effective in 86% of subjects. Following cessation of bromocriptine therapy one third of subjects whose initial serum prolactin (PRL) level was less than 4 times normal had a 'spontaneous' resolution of their hyperprolactinaemia and resumed cyclical menstrual activity and fertility. Subjects with higher PRL levels or those not treated with bromocriptine, did not show this beneficial effect. Pituitary or hypothalamic tumours were identified in 11% of subjects at the time of presentation and developed in a further 15.1% during follow-up. Most of these tumours were small, occurred more commonly when the PRL level was greater than 4 times normal, and were less likely to develop when treatment with bromocriptine had been administered. Bromocriptine therapy can thus be justified in hyperprolactinaemic subjects to reduce troublesome galactorrhoea, achieve pregnancy, improve the chance of a 'spontaneous' return of menstruation and fertility, control or reduce tumour growth where a pituitary tumour has been identified, and reduce the risk of tumour development in patients with normal plain X-rays of the pituitary fossa at the time of presentation.

Bromocriptine↗
PubMed1983

The pectoralis major myocutaneous flap: an angiographic study.

A new era in head and neck reconstruction has been opened with the use of myocutaneous flaps. The pectoralis major myocutaneous flap is considered the most reliable of its kind but flap failures still occur secondary to tension and infection. Our standard procedure has been to follow the acromioxiphoid line as a guide to the location of the blood supply of the pectoralis major muscle. We have noticed in the operating room and during cadaver dissection that the vascular supply is sometimes more laterally located than usually described. A review of the vascular supply of this anatomic area using angiographic studies of the subclavian and its branches is presented, with important findings critical to the surgical technique used to protect the flap's blood supply.

Adult↗
PubMed1981

Effect of anti-delta antibodies on clonal expansion and maturation of B lymphocytes.

The effect of a monoclonal anti-delta antibody on the in vitro B cell response to the B cell mitogen lipopolysaccharide (LPS) has been studied. Titration of anti-delta antibody in mass cultures stimulated by LPS resulted in a dose-dependent reduction of thymidine incorporation. IgM and IgG plaque forming cell (PFC) responses were poorly affected at high concentration, and slightly increased at low concentrations of anti-delta antibody. By limiting dilution analysis it was shown that anti-delta antibody inhibit 30-50% of LPS-reactive B cells to grow as IgM secreting clones, while increasing the average size of clones that grew in the presence of anti-delta as compared to control cultures. Anti-delta also results in increased frequencies of IgG secreting clones. By immunofluorescence it was possible to show the presence of a higher relative number of cells containing immunoglobulin as an effect of anti-delta antibodies. Observations made at early times of culture indicate that the cells that do not proliferate in the presence of anti-delta undergo an early maturation to secretion. Experiments performed on LPS blasts suggest that the effects of anti-delta on cell proliferation require the presence of antibodies at early times in the response, while the effects on maturation can be manifested during clonal development. The relevance of membrane IgD and of the IgM-to-IgD ratio in the maintenance versus exhaustion of the clone is discussed.

Animals↗
PubMed1981

[Effect of availability of computer tomography on activity in an emergency neuroradiological department (author's transl)].

Overall activity in an emergency neuroradiological department was altered when computed tomography facilities became available, as shown by comparative studies conducted during one year without and one year with the use of this investigational method. More examinations were conducted during the year the apparatus was available, and the diagnostic approach to patients with head or brain injuries was modified, computed tomography replacing the arteriography used as an initial examination during the first year. These findings can be related to the rapidity, safety, and diagnostic precision of computed tomography examinations.

Brain↗