C. Elliott Bell

Human β-glucuronidase: In vivo clearance and in vitro uptake by a glycoprotein recognition system on reticuloendothelial cells

Abstract Previously reported studies demonstrated that infused human placental β-glucuronidase is rapidly cleared from rat plasma and localizes predominantly in rat liver. Prior treatment of the enzyme with sodium metaperiodate converted the enzyme to a very slow clearance form. This suggested that the clearance system recognized the carbohydrate structure of the glycoprotein hydrolase. This report defines the glycosyl specificity and the cell type(s) involved in the clearance process. Clearance of infused human β-glucuronidase was blocked by simultaneous infusion of glycoproteins which have mannose or N-acetylglucosamine in their exposed nonreducing position, or by some simple sugars (α-methylmannoside, mannose or L-fucose) which block clearance of these glycoproteins. Two immunohistochemical techniques demonstrated preferential localization of human β-glucuronidase in sinusoidal lining cells (nonparenchymal cells) in rat liver. Human placental β-glucuronidase was also taken up by isolated rat alveolar macrophages by the carbohydrate-mediated glycoprotein uptake system recently demonstrated in these cells. This isolated cell uptake system appears to have the same specificity as the system for plasma clearance of infused human placental β-glucuronidase in the intact rat. The combined data from in vivo clearance studies and from studies of enzyme uptake by isolated rat macrophages suggest that a mannose/N-acetylglucosamine-glycoprotein uptake system is expressed on fixed tissue macrophages in the rat, and that this system mediates plasma clearance of infused human placental β-glucuronidase.

Serum levels of CA-125 in patients with endometriosis: a preliminary report

Seven out of 8 patients with endometriosis demonstrated levels of CA-125 antigen above 35 U/ml. None of 15 patients with other benign gynecologic diagnoses demonstrated elevated levels. This antigen has been proposed as a tumor marker for epithelial carcinoma and other gynecologic neoplasms. However, it cannot be used to differentiate clinically between cancer and endometriosis.

Expression of endodermally derived and neural crest-derived differentiation antigens by human lung and colon tumors

Recent studies of the plasma membrane antigens of a human lung tumor (an oat cell carcinoma) indicated that the tumor expressed endodermally derived and neural crest‐derived differentiation antigens undetectable in normal respiratory epithelium, where the cell of origin of this histologic type of tumor is believed to reside. The present studies were designed to assess whether or not such differentiation antigens were regularly expressed by other oat cell carcinomas of the lung, by other lung tumor types, and by a nonlung tumor type. Rabbit antisera were prepared to the plasma membrane fractions of five different oat cell carcinomas, two adenocarcinomas, and two epidermoid carcinomas of the lung, and two adenocarcinomas of the colon. After absorption with normal lung and liver, the antisera were tested against the immunizing tumor and normal lung, colon, and peripheral nerve frozen section substrates by the indirect immunofluorescence method. The results indicated that the neural crest‐derived differentiation antigen(s) was expressed by all five oat cell carcinomas, but none of the other tumors studied except for one adeno‐carcinoma of the lung. The endodermally derived differentiation antigen(s) was expressed by all of the tumors studied except for one epidermoid carcinoma of the lung. It was concluded that expression of at least some differentiation antigens which are undetectable in normal respiratory epithelium occurs not infrequently among lung carcinomas. Furthermore, expression of the neural crest‐derived differentiation antigen(s) is highly associated with, but not absolutely restricted to, oat cell carcinoma of the lung.

A normal adult and fetal lung antigen present at different quantitative levels in different histologic types of human lung cancer.

Rabbits were immunized with extract of either an adenocarcinoma of the lung, or one of three oat cell carcinomas of the lung. Unabsorbed and variously absorbed antisera, and various extracts, were analyzed by double and radial immunodiffusion. The adenocarcinoma‐antisera identified an antigen subsequently quantitated at high concentration in seven adenocarcinomas of the lung, but at low concentration in five normal adult and four fetal lungs. Three of four epidermoid carcinomas of the lung contained the antigen at low concentration, however only trace amounts were detected in four of five oat cell carcinomas of the lung. The oat cell carcinoma‐antisera failed to identify a significant antigen. Quantitatively, the above antigen appeared to distinguish adenocarcinomas and to a lesser extent epidermoid carcinomas from oat cell carcinomas of the lung, and to be consistent with the concept that oat cell carcinomas arise from a different cell type than the other lung tumors.

Positive FTA-ABS Tests in Subjects with Corticosteroid-Induced Uveitis

Of 17 subjects who developed severe anterior nongranulomatous uveitis during or immediatelyy after testing with topical corticosteroid preparations, 14 (82%) had a positive fluorescent-treponemal-antibody absorption (FTA-ABS) test. No association was found between corticosteroid-induced uveitis and any specific HL-A locus.

Monoclonal antibodies to human neuron-specific enolase reveal heterogeneity of the enzyme in neurons of the central nervous system

Three monoclonal antibodies to human neuron-specific enolase (NSE) were used to survey the human brain and spinal cord for immunoreactivity. Two of the antibodies (EB and CF) recognized the same population of cells and cell processes. Reactivity was restricted to myelinated axons, basket cell bodies and processes, and a small population of pyramidal cell bodies in the visual cortex. The third antibody (AD) reacted with some, but not all, of the neuronal cell bodies in cerebral cortex, hippocampus, midbrain, and spinal cord. Many neurons did not react with any of the antibodies. The epitope recognized by AD was trypsin-sensitive, while those recognized by EB and CF were not. These studies suggest that NSE may have multiple conformational or structural forms which are segregated between the cell body and axon.

ENZYME THERAPY: EVIDENCE FOR TWO DISTINCT RECEPTORS THAT MEDIATE UPTAKE AND CLEARANCE OF HUMAN β-GLUCURONIDASE

Specific pinocytosis of lysosomal enzymes by fibroblasts, initially recognized by Neufeld and co-workers, displays the selectivity and saturability expected for a receptor-mediated process. We have used β-glucuronidase uptake by deficient fibroblasts to study this process. Previous studies indicated that β-glucuronidase exhibits charge heterogeneity and that “high-uptake” forms of the enzyme are more acidic than poorly pinocytosed low-uptake forms. More recently, competitive inhibition of the uptake process has been demonstrated by certain hexoses, hexose phosphates, and yeast mannans which contain phosphate. The inhibitor studies, plus the observation that alkaline phosphatase treatment destroys the high uptake capacity of human platelet β-glucuronidase, suggest a novel receptor on fibroblasts that recognizes hexose phosphate on glycoproteins.Low-uptake enzyme from placenta, though not recognized by fibroblasts, is cleared rapidly from rat plasma following infusion. Periodate treatment followed by borohydride reduction of the enzyme abolishes its rapid clearance. Clearance is inhibited by mannose terminal glycoproteins and free mannose. The enzyme localizes preferentially in hepatic Kupffer cells. Thus, Kupffer cells appear to have a receptor that recognizes mannosyl groups on low uptake enzyme that mediates its clearance. Identification of such cell-specific receptors is likely to be important to enzyme replacement therapy.