An avidin-biotin alkaline-phosphatase (ABAP) staining method has been developed for the labeling of tissue sections and cell smears. The introduction of alkaline phosphatase as a marker enzyme through an avidin bridge results in excellent immunocytochemical labeling of different antigens using poly- and monoclonal antibodies. This technique avoids problems with endogenous peroxidase activity that sometimes occur using peroxidase staining procedures. The introduction of a preformed avidin-biotin alkaline-phosphatase complex (ABAPC) makes the presented technique as simple to handle as the widely used avidin biotin-peroxidase complex method (ABC). The ABAPC technique could be combined with other enzymatic labelings for double immunoenzymatic staining.

A pulmonary cancer of a 43 year-old-man was classified according to WHO-criteria as a poorly differentiated adenocarcinoma because of demonstration of mucinous substances in tumor cells and in rarely occurring acinar lumina. Immunohistochemical reactivity for several peptide hormones was detected in the predominant solid parts of the carcinoma. In many tumor cells an immunoreactivity to neurotensin, bombesin and — according to the elevated serum levels — to ACTH, CRF and calcitonin was found. Therefore the present lung cancer must be defined as a combined carcinoma composed of mucous producing and endocrine cell types. Because peptide hormone production is not restricted to the classical “neuro”-endocrine lung tumors, the histogenesis of this heterogeneous lung cancer is discussed.

A case of multiple, histologically in part differing gastric tumors and granulomatous inflammation in the upper gastrointestinal tract and terminal ileum in the same patient is presented. The differential diagnosis of granulomatous inflammation and a possible association between Crohn's disease and carcinoma is discussed.

In a human medullary carcinoma of thyroid gland containing calcitonin in light microscopic demonstration by the avidin biotin complex (ABC) method characteristic secretory granules were found electron microscopically in the cytoplasm of the tumour cells. They consisted in so-called type I granules (270±25 nm) and type II granules (135±17 nm). By the immuno gold staining (IGS) method the content of many secretory granules measuring 85–270 nm (152±18 nm) in diameter could be identified as calcitonin. These granules seemed to be predominantly of type II because of their nearly corresponding size and feature. The type I grnaules were less frequent in number and they showed no or little immunoreactivity. The results indicate that the IGS-method is practicable to demonstrate the ultrastructural localization of calcitonin and to identify clearly the nature of intracytoplasmic granules in electron microscopy.

In six cases of medullary carcinoma of the thyroid rather characteristic findings were seen in cytological specimens obtained by aspiration or imprint. The roundish-polygonal or spindle-shaped cells were predominantly disseminated, but occasionally arranged in small groups. The nuclei were frequently found in an excentric position; binuclear cells were sometimes encountered. In addition, five of the six cases showed intranuclear cytoplasmic inclusions which were also investigated by electron microscopy in specimens of two cases. Such inclusions in aspiration biopsies of the thyroid have so far been regarded, as characteristic for papillary carcinoma. In smears as well as in histological sections amyloid and calcitonin could be demonstrated by congo red staining and by immunocytochemistry, respectively. The cytomorphology of the tumor cells, their pattern of arrangement, and the peculiar nuclear inclusions make up a combination of findings that may justify the diagnosis of medullary carcinoma in aspiration biopsies. In smears the diagnosis can already be confirmed when (immuno-) cytochemical methods are applied to smear preparations.

The hemangioendothelioma of the thyroid gland is regarded as a special type of malignant goitre in view of its characteristic morphology and epidemiological behaviour. The histogenetic origin of these tumors (endothelial cells versus a special type of undifferentiated carcinoma of the thyroid) is still unresolved. By an immunoperoxidase method six hemangioendotheliomas were immunocytochemically investigated with an antibody to factor VIII-related antigen, a specific marker for endothelial cells and tumors thereof. In four of these tumors a strongly positive reaction was demonstrated, whereas control sections of undifferentiated and differentiated carcinomas, as well as two hemangioendotheliomas, remained negative. The demonstration of factor VIII-related antigen in four of six hemangioendotheliomas appears to offer evidence that most of these characteristic malignant tumors originate from endothelial cells or endothelial precursor cells. There is a histogenetic difference from true carcinomas originating from thyroid epithelial cells.

A monoclonal mouse antibody to human thyroglobulin was used in a modified biotin-peroxidase-complex method to demonstrate thyroglobulin in different tissues and tumors of the thyroid gland. Mouse ascites fluid containing monoclonal antibodies could be diluted up to 1∶1,600 for detection of thyroglobulin, whereas no staining was observed in a medullary carcinoma. Nonspecific background staining was negligible. These results demonstrate that monoclonal antibodies against thyroglobulin are suitable in the immunohistochemical localisation of thyroid hormones.

In the cytoplasm of hepatocytes of liver biopsy from a 30 year old man, there were proteinaceous inclusions which by use of the peroxidase-antiperoxidase method reacted strongly with antihuman-fibrinogen IgG, but gave a negative reaction with antihuman-alpha-1-antitrypsin IgG and with antihuman-albumin IgG. As shown in the electron microscope, these protein inclusions were composed of densely packed, irregularly arranged tubules of 40 nm diameter. Clinically, the patient and members of his family showed primary hypofibrinogenemia which on the basis of the morphological findings has to be interpreted as the consequence of a disturbance in the secretion of fibrinogen. Besides the well known alpha-1-antitrypsin deficiency, familial hypofibrinogenemia with hepatocellular fibrinogen storage appears to represent another example of a plasma deficiency due to failure of hepatic secretion.

The construction of a simple “incubatin chamber” is presented by which a homogeneous incubation of tissue sections with calculable amounts of immunoreagents is guaranteed. The incubation of large area sections, and parallel incubations of 10 slides are possible. As an example of application a case of alpha-1-antitrypsin deficiency in the liver is demonstrated.

The amount of autophagic vacuoles which, under certain presumptions, can be used as a measure of the intensity of cellular autophagy shows clear cut diurnal changes in untreated rats. Liver parenchymal cells, epithelial cells of proximal convoluted tubules of the kidney, and acinar cells of the exocrine pancreas were investigated. The rhythm is synchronous for these three cell types. The "maximum" was found during the light period, the "minimum" during the dark period. The quantitative findings are in keeping with the assumption that cellular organelles are destroyed exclusively by cellular autophagy. Different turnover rates of mitochondrial and peroxisomal constituents, as determined in biochemical experiments, are paralleled by different relative frequencies to which mitochondria and peroxisomes occur in autophagic vacuoles. In liver cells the physiological rhythm can be influenced by alteration of feeding conditions. It is inverted when a single daily meal is fed in the first half of the light period. In early starvation the level of the diurnal "maximum" of cellular autophagy continues for the first hours of the dark period until a slow decline takes place. Cellular autophagy is completely stopped for several days when rats are refed after starvation for 5 days.