Immunoelectron microscopic localization of carcinoembryonic antigen in gastric adenocarcinoma cell lines

Fine structure of tuft cells of the main excretory duct epithelium in the rat submandibular gland

BACKGROUND

Tuft cells, which are characterized by long microvilli with prominent rootlets and by vesicular and tubular profiles, are present in the mucosal epithelium of a number of hollow organs, including the main excretory duct of the rat submandibular gland. Despite their widespread occurrence, little is known of their function.

METHODS

Main excretory ducts of the submandibular gland were obtained from 20 male Wistar rats and prepared for electron microscopic examination. Specimens also were subjected to various histochemical procedures, including HRP (horseradish peroxidase) uptake, the demonstration of catalase in peroxisomes, glycoconjugate cytochemistry, and ruthenium red staining.

RESULTS

The features of the tuft cells in the MED (main excretory duct) basically were similar to those described in other organs. However, for the first time it was observed that in the submicrovillus zone and intermicrovillus space, there were many membrane-bound electron-dense granules, which resemble the so-called glycocalyceal bodies found on the apical surface of normal and neoplastic intestinal-type epithelial cells. Hypolemmal nerve terminals were seen to be in contact with the basal portion of tuft cells. After injection of HRP, reaction products were observed on the luminal surface of the microvilli, but not within the vesicles. Vesicles and tubules in the supranuclear cytoplasm exhibited a positive cytochemical reaction for glycoconjugates. The surface coat of tuft cell microvilli was stained with ruthenium red, but the vesicles and tubules in the supranuclear cytoplasm remained unstained.

CONCLUSIONS

Our observations suggest that the tuft cells may engage in secretory activity in addition to reception.

Identification of carcinoembryonic antigen-producing cells circulating in the blood of patients with colorectal carcinoma by reverse transcriptase polymerase chain reaction

BACKGROUND

Application of the reverse transcriptase polymerase chain reaction (RT-PCR) to identification of circulating tumour cells in colorectal cancer.

AIMS

To assess whether circulating malignant cells in patients with colorectal liver metastasis could be identified by RT-PCR recognition of mRNA coding for the tumour marker carcinoembryonic antigen (CEA).

PATIENTS

A total of 31 with colorectal liver metastases and 22 no-cancer controls.

METHODS

Specific cDNA primers for CEA transcripts were used to apply RT-PCR to tissue biopsy specimens, colon carcinoma cell lines, and peripheral blood samples from patients with colorectal liver metastases. A strongly CEA-expressive HT115 colorectal carcinoma cell line was used to spike blood samples from no-cancer control subjects.

RESULTS

The limit for detection of CEA cDNA by Southern blotting using HT115 cells was 50 cells per 14 ml of spiked blood. There was a significant difference (p = 0.007) in RT-PCR positive expression between patients with liver metastasis (26/31) compared with controls (5/22). There was no significant relation between the prevalence of CEA cDNA amplification and serum CEA level or metastasis volume in patients with liver metastasis.

CONCLUSIONS

This is the first study to suggest that identification of circulating colorectal cancer cells using RT-PCR for detection of CEA cDNA is feasible.