Use of 125I-secretin to identify and characterize high-affinity secretin receptors on pancreatic acini

We prepared 125I-secretin and studied the kinetics, stoichiometry, and chemical specificity with which the labeled peptide binds to dispersed acini prepared from guinea pig pancreas. Iodinated secretin retained intrinsic biological activity in that it was as effective but 2.5-times less potent than native secretin in its ability to bind to pancreatic acini and to increase cellular cAMP. Scatchard analysis of binding of 125I-secretin indicated that each pancreatic acinar cell has approximately 93,000 binding sites, half of which are occupied by 11 nM iodinated secretin. Binding of 125I-secretin was rapid, reversible, saturable, specific, and temperature dependent. Binding of 125I-secretin was inhibited by secretin, vasoactive intestinal peptide, PHI, and Gila monster venom but not by glucagon, gastric inhibitory polypeptide, cholecystokinin, caerulein, gastrin, bovine pancreatic polypeptide, somatostatin, neurotensin, leucine-enkephalin, methionine-enkephalin, carbachol, bombesin, litorin, eledoisin, physalaemin, or substance P. With agonists (secretin, vasoactive intestinal peptide, PHI, or Gila monster venom), as well as antagonists (C-terminal fragments of secretin), there was a close correlation between their relative potencies for inhibiting binding of 125I-secretin and their relative potencies for increasing cAMP (agonists) or inhibiting the secretin-induced increase in cAMP (antagonists). For a given agonist, however, a 40-fold higher concentration was required for half-maximal inhibition of binding of 125I-secretin than was required to produce a half-maximal increase in cellular cAMP. Thus, maximal stimulation of cellular cAMP occurs when approximately one-third of the secretin receptors are occupied by an agonist.     

Extranodal posttransplant plasmacytic hyperplasia with subsequent posttransplant plasmacytic malignancy: six-year interval case report and review of the literature

Posttransplant lymphoproliferative disorders (PTLDs) represent a morphologic, immunophenotypic, and genotypic spectrum of disease. Most recently, Knowles et al divided PTLDs into 3 distinct categories: (1) plasmacytic hyperplasia, (2) polymorphic B-cell hyperplasia and polymorphic B-cell lymphoma, and (3) immunoblastic lymphoma and multiple myeloma. Although one form of PTLD may progress to another form, only 1 previous case has been reported in which multiple myeloma developed 14 months after an original diagnosis of plasmacytic hyperplasia. The type of solid organ transplant was not specified in that case. We report a post--cardiac transplant plasmacytic hyperplasia developing 7 years posttransplant. Six years subsequent to the plasmacytic hyperplasia, the patient developed a posttransplant plasmacytic malignancy, supported by morphology, flow cytometric immunophenotyping, and genotypic studies. Since we have no data to support disseminated bony disease or an abnormal serum protein, we have not used the term "multiple myeloma" for this case.     

Human immunodeficiency virus infections among civilian applicants for United States military service, October 1985 to March 1986. Demographic factors associated with seropositivity

During the six months from October 1985 through March 1986, blood samples from 306,061 civilian applicants for military service from the United States were tested for antibody to the human immunodeficiency virus (HIV). Four hundred sixty subjects were positive for the antibody as determined by Western (immune) blot reactivity. The mean prevalence of HIV infection in this population of teenagers and young adults was thus 1.50 per 1000. According to multivariate analysis, the following demographic factors were found to be significant independent predictors of a positive HIV-antibody test: age (adjusted odds ratio = 1.10 per year), black race (adjusted odds ratio = 2.04), male sex (adjusted odds ratio = 1.84), residence in a densely populated county (adjusted odds ratio = 1.05 per 1000 per square mile), and residence in a metropolitan area with a high incidence of the acquired immunodeficiency syndrome (adjusted odds ratio = 1.53). Antibody-positive applicants were identified in 43 of the 50 states. Counties with high prevalence rates for HIV (greater than 5 per 1000) were located in New York State (four counties), New Jersey (three counties), California (two counties), Maryland (two counties), and Texas, Colorado, and Washington, D.C.     

Flow of cells from polar to mural trophectoderm is polarized in the mouse blastocyst

During growth of the blastocyst there is a net flow of cells from the polar to the mural trophectoderm which is presumed to be radially symmetrical. However, such a pattern of cell movement is inconsistent with findings from a recent clonal analysis. To visualize the overall flow of cells directly, the polar trophectoderm of expanding blastocysts was labelled globally with fluorescent microspheres. Following further growth, the great majority of blastocysts that remained labelled throughout the polar trophectoderm exhibited a polarized rather than radial spread of label into the mural region. This was the case regardless of the labelling technique, whether the blastocysts were grown in utero or in vitro, or had the zona pellucida removed or left on. Intriguingly, where there were two foci of spread of label into the mural trophectoderm rather than one, these were diametrically opposite each other. In further experiments, fluorescent lineage labels were used to distinguish junctional trophectoderm cells with and without an extension onto the blastocoelic surface of the inner cell mass. The location of clones formed following further blastocyst growth provided no evidence that egress of cells from the polar trophectoderm is restricted circumferentially by the presence of junctional cells having an extension.     

Inhibition of TGF-beta modulates macrophages and vessel maturation in parallel to a lowering of interstitial fluid pressure in experimental carcinoma

A pathologically elevated interstitial fluid pressure (IFP) is a characteristic of both clinical and experimental carcinoma. The soluble TGF-beta receptor type II-murine Fc:IgG2A chimeric protein (Fc:TbetaRII) lowers IFP in the KAT-4 experimental model for anaplastic thyroid carcinoma. Analyses of messenger RNA (mRNA) expressions by Affymetrix microarrays and RNase protection assays, as well as of protein expressions identified tumor macrophages as targets for Fc:TbetaRII. Treatment with Fc:TbetaRII reduced albumin extravasation, increased coverage of alpha-smooth muscle actin-positive cells and reduced expression of NG2, a marker of activated pericytes, in KAT-4 carcinoma blood vessels. Specific inhibition of interleukin-1 (IL-1), a major cytokine produced by activated macrophages, lowered carcinoma IFP to a similar degree as Fc:TbetaRII but had no significant effect on the parameters of blood vessel maturation. Neither Fc:TbetaRII nor inhibition of IL-1 changed blood vessel density. Finally, pretreatment of KAT-4 carcinomas with Fc:TbetaRII increased the antitumor efficacy of doxorubicin. Our data emphasize a potential role of tumor macrophages in carcinoma physiology and identify these cells as potential stromal targets for treatment aimed to improve efficacy of chemotherapy.     

The 4p- syndrome—An autopsy study

The autopsy of an infant with the 4p- or Wolf-Hirschhorn syndrome revealed visceral abnormalities not previously described, i.e., agenesis of the gallbladder and spleen. The parent's chromosomes were normal.     

Absorption of amino acids and peptides from a complex mixture in the isolated small intestine of the rat.

Amino acid and peptide absorption from a pancreatic digest of casein at low concentration by an isolated preparation of perfused rat small intestine has been measured. 2. The rate of absorption of each amino acid (free or peptide-bound) is closely proportional to its concentration in the perfusate; this implies a constant Vmax/Km ration for all amino acids in the mixture. 3. There is a high correlation between the compositions of luminal perfusate and secretion into the tissue fluid (apart from the content of glutamic and aspartic acids and alanine). 4. The concentrations of each free amino acid are, on average, 9 times as great in secretion as in lumen; the total peptide-N concentration in secretion is approximately 4 times that in the lumen. 5. The rate of absorption of each free amino acid is highly negatively dependent on the rate of absorption of that amino acid in peptide-bound form, in addition to being positively dependent on the perfusate concentration of free amino acid. 6. While peptide-bound proline appears to be well absorbed, free proline liberated by hydrolysis appears to pass back into the lumen as well as into the tissue fluid. Substantial back flux of hydrolysis products may occur for all amino acids. 7. About one-third of the amino acids appearing in the secretion on the serosal surface are peptide-bound. 8. The rate of absorption of peptides appears to determine the rate of their hydrolysis which probably occurs mainly after entry into the mucosal cells.     

Complement fixing antibody responses to virus infection in children with acute lymphoblastic leukaemia.

Thirty children with acute lymphoblastic leukaemia (ALL) were studied and had a virus isolated. Only 50% produced a significant rise in complement fixing (CF) antibody titre compared to 100% of normal children. The failure to produce antibodies was unpredictable. CF antibodies are not a reliable guide to virus infections in children with ALL.     

Adherence and surface properties ofTritrichomonas mobilensis,an intestinal parasite of the squirrel monkey

Adherence properties of the potentially enteropathogenicTritrichomonas mobilensis were studied in vitro. Axenically cultivated trichomonads readily attached to isolated intestinal epithelial cells and mucus of the squirrel monkey. The kinetics and nature ofT. mobilensis cytadherence were microscopically evaluated in cell-suspension assay using Chinese hamster ovary (CHO) cells and in microplate hemagglutination assay with human erythrocytes. Adherence of the parasites to target cells was concentration- and time-dependent; it was inhibited by sialic acid (N-acetylneuraminic orN-glycolylneuraminic acid) and sialyllactose. Neither trypsinization of the flagellates nor their exposure to low temperature (4° C) affected their cytadherence capacities. The data indicate the presence of adhesin(s) with lectin properties onT. mobilensis. Aggulutination of live protozoa by animal and plant lectins with various carbohydrate-binding specificities as well as the occurrence of an electron-dense cell coat on plasma membrane suggest marked glycosylation of the parasite surface.