Transcellular transport of polymeric IgA in the rat hepatocyte: biochemical and morphological characterization of the transport pathway

Polymeric IgA (pIgA) is transported by liver parenchymal cells (hepatocytes) from blood to bile via a receptor-mediated process. We have studied the intracellular pathway taken by a TEPC15 mouse myeloma pIgA. When from 1 microgram to 1 mg 125I-pIgA was injected into the saphenous vein of a rat, 36% was transported as intact protein into the bile over a 3-h period. The concentration of transported 125I-pIgA was maximal in bile 30-60 min after injection, and approximately 80% of the total 125I-pIgA ultimately transported had been secreted into bile by 90 min. A horseradish peroxidase-pIgA conjugate (125I-pIgA-HRP) was transported to a similar extent and with kinetics similar to that of unconjugated 125I-pIgA and was therefore used to visualize the transport pathway. Peroxidase cytochemistry of livers fixed in situ 2.5 to 10 min after 125I-pIgA-HRP injection demonstrated a progressive redistribution of labeled structures from the sinusoidal area to intermediate and bile canalicular regions of the hepatocyte cytoplasm. Although conjugate-containing structures began accumulating in the bile canalicular region at these early times, no conjugate was present in bile until 20 min. From 7.5 to 45 min after injection approximately 30% of the labeled structures were in regions that contained Golgi complexes and lysosomes; however, we found no evidence that either organelle contained 125I-pIgA-HRP. At least 85% of all positive structures in the hepatocyte were vesicles of 110-160-nm median diameters, with the remaining structures accounted for by tubules and multivesicular bodies. Vesicles in the bile canalicular region tended to be larger than those in the sinusoidal region. Serial sectioning showed that the 125I-pIgA-HRP-containing structures were relatively simple (predominantly vesicular) and that extensive interconnections did not exist between structures in the sinusoidal and bile canalicular regions.     

Foliage sesquiterpenes of Dacrydium cupressinum: identification,variation and biosynthesis

The major sesquiterpenes in the foliage of Dacrydium cupressinum are α-longipinene, longifolene, longibornyl acetate, caryophyllene, caryophyllene oxide, humulene, α- and β-selinene, β- and δ-elemene, aromadendrene and the rare 9βH-caryophyllene. Sesquiterpene levels vary greatly from tree to tree. As this variation is largely independent of environmental factors, genetic control is proposed. Longifolene and α-longipinene levels are closely correlated, as are those of caryophyllene and humulene. The biosynthetic implications of these correlations are discussed.     

Detection of an antigenic cell wall layer inHistoplasma capsulatum

Histoplasma capsulatum yeast cells have been studied by immunoelectron microscopy using rabbit polyclonal antisera and a biotin-avidin-peroxidase detection system. An antigenic surface layer has been visualized in the cell wall of immunostained organisms. This layer was not seen in samples prepared by standard electron microscopic methods or in negative controls used with the immunocytochemical technique. Without immunostaining the cell wall ofHistoplasma appeared almost transparent. In contrast, after immunoperoxidase staining the cell wall was conspicuous, bounded by the darkly stained outer layer. This electron dense layer, appeared to be a reservoir of surface antigens that were recognized by anti-Histoplasma antibodies.Abbreviations CHHA Cystine-heart-hemoglobin agar - PBS phosphate buffered saline - Ig immunoglobulin - TBS Tris buffered saline - DAB 3,3-diaminobenzidine tetrachloride - FITC fluorescein isothiocyanate - M199 tissue culture medium 199, according to Morgan et al. (1950)     

A domain-specific marker for the hepatocyte plasma membrane. II. Ultrastructural localization of leucine aminopeptidase to the bile canalicular domain of isolated rat liver plasma membranes

Leucine aminopeptidase (LAP) is an integral membrane glycoprotein localized to the apical membrane domain of intestinal and kidney epithelial cells. By indirect immunofluorescence, we have shown that antibodies raised against rat intestinal LAP recognized a similar protein concentrated in the bile canalicular (BC) domain of the hepatocyte in situ (Roman, L.M., and A.L. Hubbard, 1983, J. Cell Biol., 96:1548-1558). We have extended this localization to the ultrastructural level. When a saponin-permeabilized, agarose-embedded plasma membrane (PM) fraction was incubated with affinity-purified anti-LAP, 85% of the protein A-gold particles associated with the three recognizable PM domains were present in the BC. The levels of labeling on the other two domains (sinusoidal and lateral) did not exceed that observed with nonimmune controls. The concentration of LAP in the BC domain in isolated PM sheets prompted us to use this antigen for the affinity isolation of BC membrane (Roman, L.M., and A.L. Hubbard, 1984, J. Cell Biol., 98:1497-1504, companion paper).     

Receptor-mediated endocytosis of epidermal growth factor by hepatocytes in the perfused rat liver: ligand and receptor dynamics

We have used biochemical and morphological techniques to demonstrate that hepatocytes in the perfused liver bind, internalize, and degrade substantial amounts of murine epidermal growth factor (EGF) via a receptor-mediated process. Before ligand exposure, about 300,000 high-affinity receptors were detectable per cell, displayed no latency, and co-distributed with conventional plasma membrane markers. Cytochemical localization using EGF coupled to horseradish peroxidase (EGF-HRP) revealed that the receptors were distributed along the entire sinusoidal and lateral surfaces of hepatocytes. When saturating concentrations of EGF were perfused through a liver at 35 degrees C, ligand clearance was biphasic with a rapid primary phase of 20,000 molecules/min per cell that dramatically changed at 15-20 min to a slower secondary phase of 2,500 molecules/min per cell. During the primary phase of uptake, approximately 250,000 molecules of EGF and 80% of the total functional receptors were internalized into endocytic vesicles which could be separated from enzyme markers for plasma membranes and lysosomes on sucrose gradients. The ligand pathway was visualized cytochemically 2-25 min after EGF-HRP internalization and a rapid transport from endosomes at the periphery to those in the Golgi apparatus-lysosome region was observed (t 1/2 approximately equal to 7 min). However, no 125I-EGF degradation was detected for at least 20 min. Within 30 min after EGF addition, a steady state was reached which lasted up to 4 h such that (a) the rate of EGF clearance equaled the rate of ligand degradation (2,500 molecules/min per cell); (b) a constant pool of undegraded ligand was maintained in endosomes; and (c) the number of accessible (i.e., cell surface) receptors remained constant at 20% of initial values. By 4 h hepatocytes had internalized and degraded 3 and 2.3 times more EGF, respectively, than the initial number of available receptors, even in the presence of cycloheximide and without substantial loss of receptors. All of these results suggest that EGF receptors are internalized and that their rate of recycling to the surface from intracellular sites is governed by the rate of entry of ligand and/or receptor into lysosomes.     

Augmentation of lung antineutrophil elastase capacity with recombinant human alpha-1-antitrypsin

To evaluate the potential use of recombinant DNA-produced alpha-1-antitrypsin (alpha-1-AT) to augment the lung antineutrophil elastase defenses in alpha-1-AT deficiency, we compared the kinetics of intravenously administered recombinant produced alpha-1-AT (r alpha-1-AT) and purified normal human plasma alpha-1-AT (p alpha-1-AT) in the blood and lung of rhesus monkeys. The r alpha-1-AT was produced in yeast transformed with an expressing plasmid containing a full-length human alpha-1-AT complementary deoxyribonucleic acid and purified to greater than 99% homogeneity. The r alpha-1-AT has a molecular weight of 45,000, no carbohydrates, and is identical in sequence to normal plasma alpha-1-AT except for an additional N-terminal acetylmethionine. Despite its lack of carbohydrates, the r alpha-1-AT inhibited human neutrophil elastase with an association rate constant similar to that of p alpha-1-AT. Rhesus monkeys were infused intravenously with 120 mg/kg of r alpha-1-AT (n = 13) or p alpha-1-AT (n = 12) and the serum, urine, and lung epithelial lining fluid (ELF) concentrations of these molecules quantified at various intervals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enumeration of chlorine-stressed organisms with acridine orange 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (AOINT)

Direct microscopic enumeration ofEnterobacter cloacae with the acridine orange 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride technique (AOINT) was compared with spread plate counts on nonselective media to establish the usefulness of the former technique in the enumeration of chlorine-stressed cells. Results indicate that the techniques are comparable when the organisms are not stressed. However, AOINT is more sensitive than are plate counts in the detection of chlorine-stressed cells.     

Genetic Analysis of Murine Arylsulfatase C and Steroid Sulfatase

SWR/J mice possess two- to threefold higher 4-methylumbelliferyl sulfate (4MUS), dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E1S) sulfatase activities in liver and kidney extracts than do A/J mice. These interstrain activity differences are maintained throughout the 6- to 45-day postnatal period. Characteristics of the hepatic activities of SWR/J mice suggest that all three activities reside in the same enzyme. Biochemical properties of the SWR/J and A/J enzyme were not significantly different. Expression of hepatic enzyme activity is subject to regulation by an autosomal locus possessing two alleles with additive effects. Postnuclear E1S- and DHEAS-sulfatase activities are primarily microsomal. Although postnuclear hepatic 4MUS-sulfatase activity is predominantly microsomal, renal activity is primarily nonmicrosomal. Only that portion of 4MUS-sulfatase occurring in cell membranes appears capable of hydrolyzing E1S and DHEAS. The hepatic- and renal-specific subcellular distributions of 4MUS-sulfatase activity may reflect tissue differences in enzyme processing. Renal 4MUS-sulfatase activity is also controlled by an autosomal gene with two alleles having additive effects. Positive correlation between hepatic and renal 4MUS-sulfatase activities indicates that both activities are most likely influenced by the same gene.