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The cytochrome P-450 is known to be a key enzymic component in steroid hydroxylation. Biochemically it is localized in adrenal cells, both in the mitochondrial and in the microsomal fractions. Owing to its characteristic light absorptivity, attempts were made at its localization and measurement in a microspectrophotometric system. Specific difference spectra were obtained in the cytoplasm of some cells from an adrenal cell suspension before and after saturation with carbon monoxide. Scanning at 450 nm showed slender absorption maxima after CO saturation randomly distributed in the cytoplasm. These may be attributed to mitochondria or larger cytoplasmic functional units including mitochondria.

Nucleic acids can be specifically localized at the electron microscope level by means of enzyme-gold complexes. Two enzymes RNAase A and DNAase I were labelled with colloidal gold, and the enzyme-gold complexes obtained applied on thin sections of glutaraldehyde-fixed and Epon-embedded tissues. Using RNAase-gold, the rough endoplasmic reticulum and the nucleolus of different cells appeared densely labelled. With the DNAase-gold the labelling was present over the euchromatin and the mitochondria. The quantitative evaluation, performed on different cellular compartments of the pancreatic acinar cells, confirmed the qualitative observations and ascertained the specificity of the labelling. The application of this technique, for the demonstration of nucleic acids in different tissues, is illustrated.

The argyrophilic proteins of the nucleolar organizer region (Ag-NOR proteins) were specifically localized at the optical level with a modified one-step silver technique performed at 20° C. This method was applied to various materials including cells in smears, chromosomes, semi-thin sections of plastic-embedded cells and sections of paraffin-embedded human pathological tissues. In order to improve the visualization of the silver deposits we tested various modes of imaging, including bright-field, Nomarski contrast, reflected light and combined Nomarski contrast with reflected light. The use of Nomarski contrast is useful to define precisely the phases of mitosis. The use of reflected light, which is based on the ability of silver to reflect incident light specifically, gives images with an improved resolution compared to bright-field.

In the field of the transplantation of organs, there is a great need for anin vitro test of viability which would confirm that the organ was capable of performing its normalin vivo functions. Such a test should ideally be simple, rapid and reproducible. Preliminary studies using the Haematoxylin-Basic Fuchsin-picric acid (HBFP) staining reaction to assess myocardial ischaemia in resuscitated and preserved hearts would suggest that this test meets many of the requirements of a viability assay. The test has been employed in hearts which have been in a state of anoxic arrest for 30 min and then resuscitated and preserved as an autoperfusing heart-lung preparation. The ‘positive’ response after 30 min anoxic arrest reverts to a ‘negative’ response after 2 h myocardial perfusion. In hearts which have been preserved as an autoperfusing heart-lung preparation with no interim period of anoxic arrest the HBFP stain response remains ‘negative’ throughout, confirming satisfactory myocardial perfusion.

Theoretical arguments are marshalled with experimental evidence to support claims made previously (Stoward & Burns, 1967, 1968) that at 60°C acetic anhydride in the presence of pyridine transforms C-terminal carboxyl groups of proteins to methyl ketones and converts side-chain carboxyl groups to acid anhydrides. On balance the experimental evidence also supports another claim, namely that the methyl ketones thus formed from C-terminal carboxyl groups may be demonstrated specificallyin situ by the intense fluorescence they emit after treatment successively with aqueous solutions of salicylhydrazide and zinc acetate. The experiments carried out included ones favouring the exclusive formation of acid anhydrides, blocking of possible anhydrides with aromatic amines or alcohols, hydrolysis of anhydrides with alkalis, and prior methylation of carboxyl groups.

CDw60 is a recently described T-cell antigen, which functionally delivers a costimulatory signal in T-cell activation. In addition, CDw60 has been regarded as a melanoma-associated antigen. To date, only limited information exists on the distribution of CDw60 in other normal and pathologically altered tissues in human. In the present study, the expression of CDw60 was analysed immunohistologically in a large panel of formalin-fixed and paraffin-embedded normal and pathological human tissues. The antigen was detected in several normal tissues, such as epithelia of the reproductive system, exocrine and endocrine glands, glial cells and neurons of the central and peripheral nervous systems, and lymphoid cells. These showed different subcellular distribution patterns, i.e. (1) cell surface labelling of peripheral lymphocytes and lymphocytes of the lymph node and thymus, (2) diffuse cytosolic staining in lymphocytes, subpial glial processes, and the outer plexiform layer of the retina, (3) granular cytoplasmic staining associated with the Golgi apparatus in epithelial cells of certain endocrine and exocrine glands, of the ductus epididymis and deferens, neurons of the peripheral and central nervous system, and lymphocytes and megakaryocytes of the bone marrow. In exocrine glands, e.g. of the prostate and uterine corpus, CDw60-positive Golgi fields were located in the juxtaluminal cell compartment, thus reflecting a polarized distribution. In some malignant tumours, the neoplastic cells contained CDw60-immunolabelled Golgi complexes, which were disorderly distributed throughout the cytoplasm, thus reflecting a loss of epithelial polarity. Only in mammary carcinomas was abnormal cell surface labelling detected. A putative de novo expression of CDw60 was observed in pleomorphic adenoma and mucoepidermoid carcinoma of the parotid gland, seminoma, embryonal and teratocarcinoma of the testis, small cell carcinoma of the lung, and malignant melanoma. These results define the CDw60 determinant as a broadly distributed antigen within a large panel of normal human tissues. The antigen is also detectable in some previously undescribed benign and malignant tumours, which may give importance to CDw60 as a possible diagnostic marker.