Biomedical subjects
Publications and source records attributed to J Marian.
Published evidence has not yielded clear guidelines about the best method of how to feed the preterm baby. Enteral feeding involves many potentially confounding interventions. Variations in nutritional practices are in part explained by difficulties in measuring outcome. Development and implementation of evidence-based nutrition practices led to improved nutrition outcomes.
We have investigated the phenotypic changes that take place during the process of neoplastic transformation in the thymocytes of C57BL/Ka mice infected by the radiation leukemia virus (RadLV). By the combined use of antibodies against the envelope glycoprotein gp70 of RadLV, the transformation-associated cell surface marker 1C11, and the CD3-T-cell receptor (TCR) complex, we found that in the RadLV-infected thymus, the earliest expression of viral gp70 is in 1C11hi cells; a small but significant percentage of these cells also express CD3. A first wave of viral replication, manifested by the expression of high levels of gp70 in thymocytes (over 70% positive), reaches a peak at 2 weeks; during this period, no significant changes are observed in the expression of 1C11 or CD3. The population of gp70+ cells is drastically reduced at 3 to 4 weeks after infection. However, a second cohort of gp70+ cells appears after 4 weeks, and these cells express high levels of 1C11 and TCR determinants as well. RadLV-induced lymphomas differ from normal thymocytes in their CD4 CD8 phenotype, with domination by one or more subsets. Characterization of TCR gene rearrangements in RadLV-induced lymphomas shows that most of these tumors are clonal or oligoclonal with respect to the J beta 2 TCR gene, while the J beta 1 TCR gene is rearranged in a minority (4 of 11) of lymphomas. TCR V beta repertoire analysis of 12 tumors reveals that 6 (50%) express exclusively the V beta 6 gene product, 2 (17%) are V beta 5+, and 1 (8%) each are V beta 8+ and V beta 9+. In normal C57BL/Ka mice, V beta 6 is expressed on 12%, V beta 5 is expressed on 9%, V beta 8 is expressed on 22%, and V beta 9 is expressed on 4% of TCRhi thymocytes. Thus, it appears that RadLV-induced thymic lymphomas are not randomly selected with respect to expressed TCR V beta type.
mAb 1C11 was raised against the cells of retrovirus-negative, radiation-induced thymomas of C57BL/Ka mice. MAb 1C11 binds to radiation- and RadLV-induced C57BL/Ka lymphomas, to lymphomas of other mouse strains and to B-lineage tumors. The 1C11 Ag is expressed on a subpopulation of normal thymocytes that is enriched in immature cells. After fractionated x-irradiation, this percentage increases gradually during the preleukemic period, hence mAb 1C11 appears to identify a transformation-related cell surface molecule. This conclusion is supported by experiments demonstrating that flow microfluorimetry-sorted, 1C11-expressing preleukemic thymocytes progress rapidly to full neoplasia following intrathymic injection, whereas nonexpressing cells do not. Most of day-14 fetal thymocytes are as strongly positive as thymic lymphomas for the 1C11 Ag whereas Ag-activated T cell lines express moderate levels. Multiparameter flow microfluorimetry analysis shows that 1C11 is expressed predominantly on CD3-/lo thymic blast cells of three phenotypically defined subsets: CD4-8-, CD4-8+, and CD4+8+, all of which contain thymic progenitors. By immunohistochemical staining, the Ag is also found in association with epithelial cells on a variety of normal, nonlymphoid tissue, but is not detectable on heart tissue. The 1C11 antibody immunoprecipitates a disulfide-linked heterodimeric protein of 85/37 kDa and the antigenic determinant is located on the H chain of the molecule. When analyzed by SDS-PAGE under nonreducing conditions, the molecule exists as a 130-kDa protein. Enzymatic digestion of the heterodimer indicates that the H chain, but not the L chain, has at least three N-linked glycosylation sites. We propose that this novel cell surface glycoprotein may be associated with processes of differentiation and lymphomagenesis.
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The subcellular localization of GnRH receptors in weanling rat anterior pituitary and ovarian tissue was determined by radioligand binding in biochemically defined fractions prepared by differential and density centrifugation. Morphological identification of membrane organelles or fragments, visualized by electron microscopy, confirmed the biochemical characterization. The greatest amount of specific ligand binding in both tissues was measured in the crude membrane fraction, while small amounts were detected in other fractions. The distribution of pituitary binding sites in sucrose gradient subfractionation of crude membranes correlated with the distribution of plasma membrane (assessed by 5'-nucleotidase activity and electron microscopy), but not that of secretory granules (identified by immunoreactive LH) or lysosomes (acid phosphatase activity). These data suggest that the GnRH-binding sites detected by radioligand binding assay in pituitaries of rats not previously exposed to GnRH are localized almost exclusively in the plasma membrane fraction.
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A bioactive, fluorescent derivative of gonadotropin-releasing hormone, < Glu-His-Trp-Ser-Tyr-D-Lys(N epsilon-tetramethylrhodamine)-Leu-Arg-Pro-Gly-NH2, was prepared. This peptide retained high-affinity binding (apparent dissociation constant, 3 nM) to the receptor for gonadotropin-releasing hormone and was utilized for microscopic visualization and localization of gonadotropin-releasing hormone receptors in cultured rat pituitary cells. The fluorescently labeled receptors were initially distributed uniformly on the cell surface and formed patches, which subsequently internalized (at 37 degrees C) into endocytic vesicles. These processes were dependent on specific binding sites for the rhodamine-labeled peptide to gonadotrope cells. Cluster formation and internalization were markedly reduced in the absence of Ca2+, which is required for gonadotropin secretion. It is possible that cluster formation, microaggregation, and internalization of gonadotropin-releasing hormone receptors may be important in eliciting biological effects or for the observed loss of tissue responsiveness after desensitization due to exposure to the homologous hormone.
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An in vivo preparation, in which a body plethysmograph was incorporated, was useful in monitoring the cardiopulmonary effects of pharmacological agents in the guinea pig and rabbit. Isoproterenol, given 30 seconds prior to histamine challenge, reproducibly blocked histamine-induced dynamic compliance decreases and increased heart in the artificially ventilated guinea pig. These effects were used to separate the activity of beta adrenergic blockers on airway and heart muscle. Dose-response data were obtained and ED50 values for pulmonary and cardiovascular blockade were compared. Relative potencies and cardioselectivity ratios for dichloroisoproterenol, practolol, dl-propranolol and d-propranolol were determined. Both practolol and dichloroisoproterenol were cardioselective; dl-propranolol was found to be the most potent. When a similar protocol was tried in the rabbit, isorpoterenol failed to antagonize either histamine or methacholine-induced airway constriction. This finding was supported in subsequent in vitro tests. Isoproterenol and epinephrine were ineffective in blocking methacholine-induced tracheal chain contractions and epinephrine did not significantly enhance adenylate cyclase activity. Our observations suggest rabbit airway smooth muscle is insensitive to beta adrenergic stimulants.
A technique to assess respiratory and cardiovascular effects of prostaglandins (PGs) in conscious guinea pigs was developed. Animals were placed in a plethysmograph and tidal volume, airflow, and heart rate were recorded. In addition, blood pressure and/or pleural pressure were obtained. Some experiments involved the use of a pulmonary calculator that processed the appropriate pulmonary signal and provided on-line readout of dynamic compliance and airway resistance. Aerosolized antagonists were evaluated for their ability to block responses to aerosolized histamine. We found the relative antagonistic potencies of PGE1, PGE2, isoproterenol, and salbutamol to be 5.5, 2.3, 1 and 0.2, respectively. Aerosolized PGE1 and PGE2 but not PGF2alpha given prior to histamine caused decreases in tidal volume, airflow and heart rate. These effects were not seen in animals that were prepared for measurements involving invasive surgical techniques. The aerosolized PGE2 induced tidal volume changes were not prevented by pretreatment with salbutamol, chlorpheniramine, atropine or hexamethonium, though the latter two drugs inhibited the fall in heart rate. We suggest that the bradycardia following aerosolized PGE2 administration may originate from airway irritant receptors. The results validate use of our methods for the assessment of responses to bronchoactive agents under physiological conditions.