The binding and processing of monoclonal human IgG1 by cells of a human macrophage-like cell line (U937)

The goal of these experiments was to assess the relationship between the binding and processing of IgG by Fc-receptor-bearing cells. Cells of the U937 human macrophage-like cell line were incubated with 125I- labeled monomers, dimers, oligomers (composed of 2-4 IgG1 subunits), and HP (heavy polymers composed of 5 or more subunits per polymer) of monoclonal human IgG1 in vitro. Binding was assessed by spinning cells through a layer of phthalate oils. Internalization of IgG1 was assessed by quantitating residual binding to cells after surface-bound IgG was removed by a brief treatment with a solution containing 0.25 M acetic acid and 0.5 M sodium chloride. Catabolism was assessed by measuring the release of radioactive fragments of IgG1, which were not precipitated by 10% trichloroacetic acid. Unstimulated U937 bound about 10,000 molecules per cell of IgG1 monomer, with an equilibrium binding constant (Ka) of 5 X 10(8) M-1. After stimulation with a conditioned medium in vitro, binding per cell was increased 3-7--fold, and the Ka was decreased 2-4--fold. Both unstimulated and stimulated cells internalized and catabolized labeled IgG1 HP, but stimulated cells internalized and digested much more IgG1 HP per cell than unstimulated cells. Both monomers and dimers of IgG1 were internalized and degraded very slowly by stimulated cells, even though both preparations readily bound to cells. In contrast, oligomers and (to an even greater extent) IgG1 HP were internalized and degraded much more rapidly. Internalization of IgG1 HP was markedly inhibited by incubation at 4 degrees C, but not by incubation with a variety of metabolic inhibitors. Catabolism was inhibited by chloroquine and monensin (inhibitors of lysosomal acidification) and by cytochalasin (an inhibitor of microfilament polymerization). Binding to the surface of cells was not markedly inhibited by any agent tested. The capacity of cells to bind labeled IgG1 was markedly reduced by prior incubation in the presence of unlabeled IgG1. This reduction was in part due to the steric blockade of receptors caused by the avid, but reversible, binding of IgG1. In addition, IgG1 oligomers or HP (but not IgG1 monomers or dimers) also caused an irreversible reduction in the number of Fc receptors by a process analogous to receptor down-regulation, as observed in other receptor--ligand systems.     

Possibility of selection against mtDNA mutations in tumors

Several studies of tumors have revealed substantial numbers of clonally expanded somatic mutations in mitochondrial DNA (mtDNA), not observed in adjacent intact tissues. These findings were interpreted as indicating the involvement of mtDNA mutations in tumorigenesis. Such comparisons, however, ignore an important confounding factor: the monoclonal origin of tumors as opposed to the highly polyclonal nature of normal tissues. Analysis of recently published data on the incidence of somatic mutations in nontumor monoclonal cells suggests that, contrary to the prevailing view, the process of tumorigenesis may be accompanied by active selection against detrimental mtDNA mutations.     

Surgical evaluation of candidates for donation. Selection of the kidney

Living donation for kidney transplantation is being promoted due to the shortage of organs, the improved outcomes of living donor transplants and the evolution of immunosuppression regimens. The process of organ donation from a living donor affects not only medical-surgical features but also emotional, social and economic. Using kidneys from living donors involves a great responsibility in evaluation and selection. Candidates for donation undergo an extensive set of examinations in order to optimize selection and to plan surgery. Radiological evaluation is one of the most important features of the evaluation process and selection of the kidney; it shows precisely the renal vascular anatomy, which is decisive in the choice of the kidney and helps to optimize the process and diminish risks and complications during extraction and/or tronsplantation. The advantages on imaging tests allow to evaluate potential donors in a safely, fast and almost noninvasive matter. The aim of the process is to select the kidney with less likelihood of failure due to technical reasons, and always leave the best kidney for the donor.     

Visual orienting response in goldfish: a multidisciplinary study

The neural basis underlying the orienting response has been thoroughly studied in frontal-eyed mammals. However, in non-mammalian species, including fish, it remains almost unknown. Therefore, we studied the contribution of the optic tectum and the mesencephalic reticular formation to the performance of the orienting response in goldfish, using behavioural, physiological, and anatomical tracer techniques. The appearance of a visual stimulus (a pellet of food) in the environment of a goldfish evoked a turn of the body to reorient the line of sight. Left-tectal lobe ablation abolished the orienting turn response towards the contralateral hemifield. Electrical microstimulation of the optic tectum suggested the presence of a motor map, which is in correspondence with the overlying visual representation, as previously reported in other vertebrates. The tracer biotin-dextran amine was injected into different functionally identified tectal zones. The results showed that rostral and caudal poles of the mesencephalic reticular formation receive outflow mainly from the rostral and caudal tectal poles, respectively. This suggests that the tectal wiring with downstream structures is site-dependent. Furthermore, the electrical activation of rostral and caudal mesencephalic reticular formation revealed a different contribution to vertical and horizontal orienting eye movements. We conclude that the basic neural system coding the orienting response appears early in phylogenesis, although some specific characteristics are selected by adaptive pressure.     

Hepatoid adenocarcinoma of the urinary bladder

Hepatoid adenocarcinoma is rare in the urinary bladder with only three well-illustrated previously reported cases. Pathological diagnosis is based on a combination of histological features resembling hepatocellular carcinoma and the positive immunostaining for alpha-fetoprotein. We present the clinicopathological features of four additional cases. The patients were males 66, 85, 61 and 68 years old. Hematuria was the initial symptom in all four patients. Two cases were treated by cystoprostatectomy and the remaining two by transurethral resection of the bladder. On histology, the cases showed a mixture of cells growing in a solid fashion and sheets or anastomosing trabeculae of hepatoid cells merging focally with a secondary glandular pattern of adenocarcinoma. Intracytoplasmic hyaline globules in all and bile production in three of the cases also supported the impression of hepatocytic differentiation. Immunoreactivity for alpha-fetoprotein, low molecular weight cytokeratin, alpha-1-antitrypsin, albumin, epithelial membrane antigen and a striking canalicular pattern when stained against polyclonal carcinoembryonic antigen (CEA), all indicate hepatocellular differentiation. The hepatic nature of the cells was further assessed by detecting the recently incorporated marker hepatocyte paraffin 1, by means of immunohistochemistry and albumin gene mRNA non-isotopic in situ hybridization, both of which had positive signals in all four cases. Three patients died 12, 14 and 19 months after diagnosis. The fourth patient was alive with disease at 26 months of follow-up. In conclusion, hepatoid adenocarcinoma seems to be an aggressive malignant neoplasm that is rare in the bladder whose correct diagnosis may need appropriate immunohistochemical and in situ hybridization means in addition to a complete patient clinical and pathological evaluation. The exact histogenesis and classification of these tumors remains to be established.     

Collagen remodelling in the guinea-pig uterine cervix at term is associated with a decrease in progesterone receptor expression

In human and guinea-pig parturition, progesterone withdrawal and estrogen action are not mediated by changes in their circulating levels. Instead, these events might be promoted by changes in the responsiveness of the uterus and cervix to progesterone and estrogen via changes in their receptors. In this study, the guinea-pig model was used to investigate whether high levels of progesterone and estrogen at term are associated with regional changes in PR and ERalpha levels in uterus and cervix. PR and ERalpha profiles were established in both subepithelium and the muscular layer of the cervix and the lower uterine horns during pregnancy, parturition and postpartum; while collagen remodelling was measured in the subepithelium. Our data showed that collagen remodelling involved in cervical ripening is temporally and spatially associated with a decrease in PR, whereas high expression of ERalpha is observed. This association was found in the subepithelium of the cervical tissue but not in the same region of the uterus. The muscular region of the cervix and uterus also present a transiently decreased expression of PR while ERalpha levels remain high. Thus, the present results indicate that, before parturition, diminished responsiveness of the cervix to progesterone might be caused by a decrease in PR levels and that this may be the mechanism of functional progesterone withdrawal. The guinea-pig was further validated as an animal model for human parturition studies.     

Development of a murine model of cerebral aspergillosis

Central nervous system (CNS) Aspergillus infection has a mortality rate in humans that approaches 95%. Because no animal models are available for studying this infection, we sought to develop a murine model of CNS aspergillosis. Inconsistent data were obtained for nonimmunosuppressed CD-1, C57BL/6, and DBA/2N mice after infection by midline intracranial injection of Aspergillus fumigatus. CD-1 mice given cyclophosphamide to produce immunosuppression had continuous pancytopenia. Dose-finding studies in CD-1 mice showed that infection with 5 x 106 conidia/mouse consistently caused 100% mortality by day 5-8; no mice died before day 3. Histologic examination of samples of brain tissue showed focal abscesses containing Aspergillus hyphae. Fungus burdens in brain were higher than those in other organs, although Aspergillus disseminated to the kidneys and the spleen. The model we established provides an opportunity to study immune responses to and therapeutic options for CNS disease in an immunologically defined, genetically manipulable, and inexpensive species.