Long-term ototoxic effects of neomycin applied topically in the middle ear: a morphological study in the guinea pig

Neomycin was instilled daily, uni- or bilaterally, into the middle ear of guinea pigs for three months. The cochleae were examined, by light and electron microscopy, six months after the end of treatment. The organs of Corti of the treated ears were completely destroyed, and in the most advanced lesions, were substituted by a single layer of very thin flat cells. In the spiral ganglion only some glial cells and a few neurons could be observed. All surviving neurons were myelinated, and their ultrastructure was greatly altered, with disorganization of the rough endoplasmic reticulum and ribosomes. The basilar membrane almost disappeared, losing it amorphous and filamentous components. The spiral limbus and the stria vascularis were atrophic and were also covered, in the final stages, by flat elongated cells. In view of its morphological characteristics, this epithelium may arise from the displacement of the interdental cells and perhaps from the cochlear surface of Reissner's membrane.

Piperacillin and gentamicin as non toxic empirical therapy in pediatric patients with fever and neutropenia

To minimize renal and hematological toxicity during empirical antibiotic therapy for pediatric patients with fever and neutropenia, piperacillin and gentamicin combination therapy was evaluated. Twenty episodes of fever and neutropenia in pediatric patients (less than 20 years old) with malignancies were studied. Elligible patients were defined as having documented fever (temperature greater than 38.5 degrees C) and absolute neutrophil count less than 500/mm3. Antibiotics were continued until neutropenia resolved and clinical response was seen. No bleeding, renal, hematological or other adverse reactions were evident in the cases studied that could be attributed to antibiotic therapy. The organisms recovered were sensitive to one or both antibiotics. There was clinical improvement and bacteriological response in all cases.

The head-eye-body turning behavior induced by electrical or cholinergic stimulation of the pulvinar-lateralis posterior nucleus complex is not dependent on the catecholaminergic system

Two experimental designs were developed in cats in order to analyze the role of the catecholaminergic system in the turning response evoked by cholinergic or electrical stimulation of the pulvinar-lateralis posterior nucleus complex (P-LP). Twenty one adult cats were employed. In one series of experiments, nine cats had a cannula implanted in one P-LP, and through it, apomorphine alone or mixed with carbachol were microinjected. The behavior was observed and the EEG was recorded. In the second experimental design, a cannula and bipolar electrodes were implanted unilaterally in the P-LP of nine cats, and a series of electrical stimulations were performed before and after 6-OHDA administration into the P-LP, and apomorphine was injected parenterally in order to induce turning behavior. Finally three cats received 16 micrograms of 6 OHDA into the P-LP, through a Hamilton syringe and no electrodes or cannula were implanted, to study the histological damage. No evidence of involvement of the catecholaminergic system was found in either of these two experimental series. These results contrast with what has been found in the nigrostriatal dopaminergic system, where an imbalance in dopamine concentration induces turning behavior. High doses (16 micrograms) of 6-OHDA induced minimal damage in the P-LP.

TdT activity in acute myeloid leukemias defined by monoclonal antibodies

Blast cells from eight out of 71 patients diagnosed with acute myeloid leukemia (AML) by morphological, cytochemical, and immunological criteria showed TdT activity. Their distribution according to the FAB classification was one M1, one M2, one M4, two M5a, one M5b, one M6, and one undifferentiated case. The TdT+ AML cases did not show major clinical and hematological differences when compared with the classical TdT- AML patients. Other phenotypical aberrations in the expression of membrane antigens, apart from the presence of nuclear TdT, were not observed in these TdT+ cases after study with a large panel of monoclonal antibodies. A higher incidence of TdT+ cases was found among the monocytic variants of AML (M4 and M5)--four cases--than in the granulocytic variants (M1, M2, and M3)--2 cases. These TdT+ cases should be distinguished from mixed leukemias by double labeling techniques, assessing in the TdT+ AML the coexpression of TdT and myeloid markers in individual cells as shown in four of our cases.

Coexpression of T- and B-markers in a lymphoproliferative disorder

An atypical case of lymphoproliferative disorder in which T- and B-cell antigens were coexpressed in the neoplastic cells is described. The disease was characterised by hepatosplenomegaly, lymphadenopathy, a low WBC (5 X 10(9)/l) and bone marrow infiltration. The predominant cell population (greater than 70%) comprised lymphoid cells with a range of nuclear irregularities and included some blast cells. 90% of the peripheral blood lymphocytes showed a mature T-helper phenotype (E+, T11+, T3+, T4+, T8-, T6-, TdT-) with coexpression of the specific B-markers B1 and FMC7, in 90% and 50% of cells, respectively. HLA-DR antigens were present in 55% of cells while surface and cytoplasmic immunoglobulins (Ig) were detected in less than 10% of cells. Molecular investigations with appropriate probes showed evidence of T-cell receptor gene rearrangement but no rearrangement for the genes of the Ig-heavy and -light chains. Cytogenetic studies revealed a translocation t(10;19) (p12; q13) in all the metaphases analyzed. This case demonstrates that the study of neoplastic cells with a battery of monoclonal antibodies may disclose the existence of a hitherto unrecognised lymphoid cell population with atypical expression of B- and T-cell antigens. On the other hand, the presence of T-cell receptor gene rearrangement indicates that this is a T-cell disorder with the aberrant co-expression of specific B-cell markers.

The nature of blast cells in myelodysplastic syndromes evolving to acute leukaemia

The blast cells from nine patients with an overt acute leukaemia following a previous myelodysplastic syndrome (MDS) are analyzed with a panel of monoclonal antibodies as well as by morphological and cytochemical criteria. By integrating the results obtained with these three approaches the leukaemia in 6 patients was assessed as myeloid-granulocytic and/or monocytic-, in two as mixed- megakaryoblastic/myeloid- and in one as lymphoid. A good correlation between morphology, cytochemistry and immunological markers was observed in 7 out of the 9 cases. In three cases a noteworthy percentage of J5+ cells was detected. The exceptional finding of lymphoid as well as megakaryocytic and myeloid transformations suggests that the target cell for these leukaemias could be a pluripotent stem cell.